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 never get a chance to run when you step, and they are
5850 completely free to run when you use commands
5851 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5852 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5853 the current thread away from the thread that you are debugging.
5855 @item show scheduler-locking
5856 Display the current scheduler locking mode.
5859 @cindex resume threads of multiple processes simultaneously
5860 By default, when you issue one of the execution commands such as
5861 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5862 threads of the current inferior to run. For example, if @value{GDBN}
5863 is attached to two inferiors, each with two threads, the
5864 @code{continue} command resumes only the two threads of the current
5865 inferior. This is useful, for example, when you debug a program that
5866 forks and you want to hold the parent stopped (so that, for instance,
5867 it doesn't run to exit), while you debug the child. In other
5868 situations, you may not be interested in inspecting the current state
5869 of any of the processes @value{GDBN} is attached to, and you may want
5870 to resume them all until some breakpoint is hit. In the latter case,
5871 you can instruct @value{GDBN} to allow all threads of all the
5872 inferiors to run with the @w{@code{set schedule-multiple}} command.
5875 @kindex set schedule-multiple
5876 @item set schedule-multiple
5877 Set the mode for allowing threads of multiple processes to be resumed
5878 when an execution command is issued. When @code{on}, all threads of
5879 all processes are allowed to run. When @code{off}, only the threads
5880 of the current process are resumed. The default is @code{off}. The
5881 @code{scheduler-locking} mode takes precedence when set to @code{on},
5882 or while you are stepping and set to @code{step}.
5884 @item show schedule-multiple
5885 Display the current mode for resuming the execution of threads of
5890 @subsection Non-Stop Mode
5892 @cindex non-stop mode
5894 @c This section is really only a place-holder, and needs to be expanded
5895 @c with more details.
5897 For some multi-threaded targets, @value{GDBN} supports an optional
5898 mode of operation in which you can examine stopped program threads in
5899 the debugger while other threads continue to execute freely. This
5900 minimizes intrusion when debugging live systems, such as programs
5901 where some threads have real-time constraints or must continue to
5902 respond to external events. This is referred to as @dfn{non-stop} mode.
5904 In non-stop mode, when a thread stops to report a debugging event,
5905 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5906 threads as well, in contrast to the all-stop mode behavior. Additionally,
5907 execution commands such as @code{continue} and @code{step} apply by default
5908 only to the current thread in non-stop mode, rather than all threads as
5909 in all-stop mode. This allows you to control threads explicitly in
5910 ways that are not possible in all-stop mode --- for example, stepping
5911 one thread while allowing others to run freely, stepping
5912 one thread while holding all others stopped, or stepping several threads
5913 independently and simultaneously.
5915 To enter non-stop mode, use this sequence of commands before you run
5916 or attach to your program:
5919 # If using the CLI, pagination breaks non-stop.
5922 # Finally, turn it on!
5926 You can use these commands to manipulate the non-stop mode setting:
5929 @kindex set non-stop
5930 @item set non-stop on
5931 Enable selection of non-stop mode.
5932 @item set non-stop off
5933 Disable selection of non-stop mode.
5934 @kindex show non-stop
5936 Show the current non-stop enablement setting.
5939 Note these commands only reflect whether non-stop mode is enabled,
5940 not whether the currently-executing program is being run in non-stop mode.
5941 In particular, the @code{set non-stop} preference is only consulted when
5942 @value{GDBN} starts or connects to the target program, and it is generally
5943 not possible to switch modes once debugging has started. Furthermore,
5944 since not all targets support non-stop mode, even when you have enabled
5945 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5948 In non-stop mode, all execution commands apply only to the current thread
5949 by default. That is, @code{continue} only continues one thread.
5950 To continue all threads, issue @code{continue -a} or @code{c -a}.
5952 You can use @value{GDBN}'s background execution commands
5953 (@pxref{Background Execution}) to run some threads in the background
5954 while you continue to examine or step others from @value{GDBN}.
5955 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5956 always executed asynchronously in non-stop mode.
5958 Suspending execution is done with the @code{interrupt} command when
5959 running in the background, or @kbd{Ctrl-c} during foreground execution.
5960 In all-stop mode, this stops the whole process;
5961 but in non-stop mode the interrupt applies only to the current thread.
5962 To stop the whole program, use @code{interrupt -a}.
5964 Other execution commands do not currently support the @code{-a} option.
5966 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5967 that thread current, as it does in all-stop mode. This is because the
5968 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5969 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5970 changed to a different thread just as you entered a command to operate on the
5971 previously current thread.
5973 @node Background Execution
5974 @subsection Background Execution
5976 @cindex foreground execution
5977 @cindex background execution
5978 @cindex asynchronous execution
5979 @cindex execution, foreground, background and asynchronous
5981 @value{GDBN}'s execution commands have two variants: the normal
5982 foreground (synchronous) behavior, and a background
5983 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5984 the program to report that some thread has stopped before prompting for
5985 another command. In background execution, @value{GDBN} immediately gives
5986 a command prompt so that you can issue other commands while your program runs.
5988 If the target doesn't support async mode, @value{GDBN} issues an error
5989 message if you attempt to use the background execution commands.
5991 To specify background execution, add a @code{&} to the command. For example,
5992 the background form of the @code{continue} command is @code{continue&}, or
5993 just @code{c&}. The execution commands that accept background execution
5999 @xref{Starting, , Starting your Program}.
6003 @xref{Attach, , Debugging an Already-running Process}.
6007 @xref{Continuing and Stepping, step}.
6011 @xref{Continuing and Stepping, stepi}.
6015 @xref{Continuing and Stepping, next}.
6019 @xref{Continuing and Stepping, nexti}.
6023 @xref{Continuing and Stepping, continue}.
6027 @xref{Continuing and Stepping, finish}.
6031 @xref{Continuing and Stepping, until}.
6035 Background execution is especially useful in conjunction with non-stop
6036 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6037 However, you can also use these commands in the normal all-stop mode with
6038 the restriction that you cannot issue another execution command until the
6039 previous one finishes. Examples of commands that are valid in all-stop
6040 mode while the program is running include @code{help} and @code{info break}.
6042 You can interrupt your program while it is running in the background by
6043 using the @code{interrupt} command.
6050 Suspend execution of the running program. In all-stop mode,
6051 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6052 only the current thread. To stop the whole program in non-stop mode,
6053 use @code{interrupt -a}.
6056 @node Thread-Specific Breakpoints
6057 @subsection Thread-Specific Breakpoints
6059 When your program has multiple threads (@pxref{Threads,, Debugging
6060 Programs with Multiple Threads}), you can choose whether to set
6061 breakpoints on all threads, or on a particular thread.
6064 @cindex breakpoints and threads
6065 @cindex thread breakpoints
6066 @kindex break @dots{} thread @var{threadno}
6067 @item break @var{linespec} thread @var{threadno}
6068 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6069 @var{linespec} specifies source lines; there are several ways of
6070 writing them (@pxref{Specify Location}), but the effect is always to
6071 specify some source line.
6073 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6074 to specify that you only want @value{GDBN} to stop the program when a
6075 particular thread reaches this breakpoint. The @var{threadno} specifier
6076 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6077 in the first column of the @samp{info threads} display.
6079 If you do not specify @samp{thread @var{threadno}} when you set a
6080 breakpoint, the breakpoint applies to @emph{all} threads of your
6083 You can use the @code{thread} qualifier on conditional breakpoints as
6084 well; in this case, place @samp{thread @var{threadno}} before or
6085 after the breakpoint condition, like this:
6088 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6093 Thread-specific breakpoints are automatically deleted when
6094 @value{GDBN} detects the corresponding thread is no longer in the
6095 thread list. For example:
6099 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6102 There are several ways for a thread to disappear, such as a regular
6103 thread exit, but also when you detach from the process with the
6104 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6105 Process}), or if @value{GDBN} loses the remote connection
6106 (@pxref{Remote Debugging}), etc. Note that with some targets,
6107 @value{GDBN} is only able to detect a thread has exited when the user
6108 explictly asks for the thread list with the @code{info threads}
6111 @node Interrupted System Calls
6112 @subsection Interrupted System Calls
6114 @cindex thread breakpoints and system calls
6115 @cindex system calls and thread breakpoints
6116 @cindex premature return from system calls
6117 There is an unfortunate side effect when using @value{GDBN} to debug
6118 multi-threaded programs. If one thread stops for a
6119 breakpoint, or for some other reason, and another thread is blocked in a
6120 system call, then the system call may return prematurely. This is a
6121 consequence of the interaction between multiple threads and the signals
6122 that @value{GDBN} uses to implement breakpoints and other events that
6125 To handle this problem, your program should check the return value of
6126 each system call and react appropriately. This is good programming
6129 For example, do not write code like this:
6135 The call to @code{sleep} will return early if a different thread stops
6136 at a breakpoint or for some other reason.
6138 Instead, write this:
6143 unslept = sleep (unslept);
6146 A system call is allowed to return early, so the system is still
6147 conforming to its specification. But @value{GDBN} does cause your
6148 multi-threaded program to behave differently than it would without
6151 Also, @value{GDBN} uses internal breakpoints in the thread library to
6152 monitor certain events such as thread creation and thread destruction.
6153 When such an event happens, a system call in another thread may return
6154 prematurely, even though your program does not appear to stop.
6157 @subsection Observer Mode
6159 If you want to build on non-stop mode and observe program behavior
6160 without any chance of disruption by @value{GDBN}, you can set
6161 variables to disable all of the debugger's attempts to modify state,
6162 whether by writing memory, inserting breakpoints, etc. These operate
6163 at a low level, intercepting operations from all commands.
6165 When all of these are set to @code{off}, then @value{GDBN} is said to
6166 be @dfn{observer mode}. As a convenience, the variable
6167 @code{observer} can be set to disable these, plus enable non-stop
6170 Note that @value{GDBN} will not prevent you from making nonsensical
6171 combinations of these settings. For instance, if you have enabled
6172 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6173 then breakpoints that work by writing trap instructions into the code
6174 stream will still not be able to be placed.
6179 @item set observer on
6180 @itemx set observer off
6181 When set to @code{on}, this disables all the permission variables
6182 below (except for @code{insert-fast-tracepoints}), plus enables
6183 non-stop debugging. Setting this to @code{off} switches back to
6184 normal debugging, though remaining in non-stop mode.
6187 Show whether observer mode is on or off.
6189 @kindex may-write-registers
6190 @item set may-write-registers on
6191 @itemx set may-write-registers off
6192 This controls whether @value{GDBN} will attempt to alter the values of
6193 registers, such as with assignment expressions in @code{print}, or the
6194 @code{jump} command. It defaults to @code{on}.
6196 @item show may-write-registers
6197 Show the current permission to write registers.
6199 @kindex may-write-memory
6200 @item set may-write-memory on
6201 @itemx set may-write-memory off
6202 This controls whether @value{GDBN} will attempt to alter the contents
6203 of memory, such as with assignment expressions in @code{print}. It
6204 defaults to @code{on}.
6206 @item show may-write-memory
6207 Show the current permission to write memory.
6209 @kindex may-insert-breakpoints
6210 @item set may-insert-breakpoints on
6211 @itemx set may-insert-breakpoints off
6212 This controls whether @value{GDBN} will attempt to insert breakpoints.
6213 This affects all breakpoints, including internal breakpoints defined
6214 by @value{GDBN}. It defaults to @code{on}.
6216 @item show may-insert-breakpoints
6217 Show the current permission to insert breakpoints.
6219 @kindex may-insert-tracepoints
6220 @item set may-insert-tracepoints on
6221 @itemx set may-insert-tracepoints off
6222 This controls whether @value{GDBN} will attempt to insert (regular)
6223 tracepoints at the beginning of a tracing experiment. It affects only
6224 non-fast tracepoints, fast tracepoints being under the control of
6225 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6227 @item show may-insert-tracepoints
6228 Show the current permission to insert tracepoints.
6230 @kindex may-insert-fast-tracepoints
6231 @item set may-insert-fast-tracepoints on
6232 @itemx set may-insert-fast-tracepoints off
6233 This controls whether @value{GDBN} will attempt to insert fast
6234 tracepoints at the beginning of a tracing experiment. It affects only
6235 fast tracepoints, regular (non-fast) tracepoints being under the
6236 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6238 @item show may-insert-fast-tracepoints
6239 Show the current permission to insert fast tracepoints.
6241 @kindex may-interrupt
6242 @item set may-interrupt on
6243 @itemx set may-interrupt off
6244 This controls whether @value{GDBN} will attempt to interrupt or stop
6245 program execution. When this variable is @code{off}, the
6246 @code{interrupt} command will have no effect, nor will
6247 @kbd{Ctrl-c}. It defaults to @code{on}.
6249 @item show may-interrupt
6250 Show the current permission to interrupt or stop the program.
6254 @node Reverse Execution
6255 @chapter Running programs backward
6256 @cindex reverse execution
6257 @cindex running programs backward
6259 When you are debugging a program, it is not unusual to realize that
6260 you have gone too far, and some event of interest has already happened.
6261 If the target environment supports it, @value{GDBN} can allow you to
6262 ``rewind'' the program by running it backward.
6264 A target environment that supports reverse execution should be able
6265 to ``undo'' the changes in machine state that have taken place as the
6266 program was executing normally. Variables, registers etc.@: should
6267 revert to their previous values. Obviously this requires a great
6268 deal of sophistication on the part of the target environment; not
6269 all target environments can support reverse execution.
6271 When a program is executed in reverse, the instructions that
6272 have most recently been executed are ``un-executed'', in reverse
6273 order. The program counter runs backward, following the previous
6274 thread of execution in reverse. As each instruction is ``un-executed'',
6275 the values of memory and/or registers that were changed by that
6276 instruction are reverted to their previous states. After executing
6277 a piece of source code in reverse, all side effects of that code
6278 should be ``undone'', and all variables should be returned to their
6279 prior values@footnote{
6280 Note that some side effects are easier to undo than others. For instance,
6281 memory and registers are relatively easy, but device I/O is hard. Some
6282 targets may be able undo things like device I/O, and some may not.
6284 The contract between @value{GDBN} and the reverse executing target
6285 requires only that the target do something reasonable when
6286 @value{GDBN} tells it to execute backwards, and then report the
6287 results back to @value{GDBN}. Whatever the target reports back to
6288 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6289 assumes that the memory and registers that the target reports are in a
6290 consistant state, but @value{GDBN} accepts whatever it is given.
6293 If you are debugging in a target environment that supports
6294 reverse execution, @value{GDBN} provides the following commands.
6297 @kindex reverse-continue
6298 @kindex rc @r{(@code{reverse-continue})}
6299 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6300 @itemx rc @r{[}@var{ignore-count}@r{]}
6301 Beginning at the point where your program last stopped, start executing
6302 in reverse. Reverse execution will stop for breakpoints and synchronous
6303 exceptions (signals), just like normal execution. Behavior of
6304 asynchronous signals depends on the target environment.
6306 @kindex reverse-step
6307 @kindex rs @r{(@code{step})}
6308 @item reverse-step @r{[}@var{count}@r{]}
6309 Run the program backward until control reaches the start of a
6310 different source line; then stop it, and return control to @value{GDBN}.
6312 Like the @code{step} command, @code{reverse-step} will only stop
6313 at the beginning of a source line. It ``un-executes'' the previously
6314 executed source line. If the previous source line included calls to
6315 debuggable functions, @code{reverse-step} will step (backward) into
6316 the called function, stopping at the beginning of the @emph{last}
6317 statement in the called function (typically a return statement).
6319 Also, as with the @code{step} command, if non-debuggable functions are
6320 called, @code{reverse-step} will run thru them backward without stopping.
6322 @kindex reverse-stepi
6323 @kindex rsi @r{(@code{reverse-stepi})}
6324 @item reverse-stepi @r{[}@var{count}@r{]}
6325 Reverse-execute one machine instruction. Note that the instruction
6326 to be reverse-executed is @emph{not} the one pointed to by the program
6327 counter, but the instruction executed prior to that one. For instance,
6328 if the last instruction was a jump, @code{reverse-stepi} will take you
6329 back from the destination of the jump to the jump instruction itself.
6331 @kindex reverse-next
6332 @kindex rn @r{(@code{reverse-next})}
6333 @item reverse-next @r{[}@var{count}@r{]}
6334 Run backward to the beginning of the previous line executed in
6335 the current (innermost) stack frame. If the line contains function
6336 calls, they will be ``un-executed'' without stopping. Starting from
6337 the first line of a function, @code{reverse-next} will take you back
6338 to the caller of that function, @emph{before} the function was called,
6339 just as the normal @code{next} command would take you from the last
6340 line of a function back to its return to its caller
6341 @footnote{Unless the code is too heavily optimized.}.
6343 @kindex reverse-nexti
6344 @kindex rni @r{(@code{reverse-nexti})}
6345 @item reverse-nexti @r{[}@var{count}@r{]}
6346 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6347 in reverse, except that called functions are ``un-executed'' atomically.
6348 That is, if the previously executed instruction was a return from
6349 another function, @code{reverse-nexti} will continue to execute
6350 in reverse until the call to that function (from the current stack
6353 @kindex reverse-finish
6354 @item reverse-finish
6355 Just as the @code{finish} command takes you to the point where the
6356 current function returns, @code{reverse-finish} takes you to the point
6357 where it was called. Instead of ending up at the end of the current
6358 function invocation, you end up at the beginning.
6360 @kindex set exec-direction
6361 @item set exec-direction
6362 Set the direction of target execution.
6363 @item set exec-direction reverse
6364 @cindex execute forward or backward in time
6365 @value{GDBN} will perform all execution commands in reverse, until the
6366 exec-direction mode is changed to ``forward''. Affected commands include
6367 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6368 command cannot be used in reverse mode.
6369 @item set exec-direction forward
6370 @value{GDBN} will perform all execution commands in the normal fashion.
6371 This is the default.
6375 @node Process Record and Replay
6376 @chapter Recording Inferior's Execution and Replaying It
6377 @cindex process record and replay
6378 @cindex recording inferior's execution and replaying it
6380 On some platforms, @value{GDBN} provides a special @dfn{process record
6381 and replay} target that can record a log of the process execution, and
6382 replay it later with both forward and reverse execution commands.
6385 When this target is in use, if the execution log includes the record
6386 for the next instruction, @value{GDBN} will debug in @dfn{replay
6387 mode}. In the replay mode, the inferior does not really execute code
6388 instructions. Instead, all the events that normally happen during
6389 code execution are taken from the execution log. While code is not
6390 really executed in replay mode, the values of registers (including the
6391 program counter register) and the memory of the inferior are still
6392 changed as they normally would. Their contents are taken from the
6396 If the record for the next instruction is not in the execution log,
6397 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6398 inferior executes normally, and @value{GDBN} records the execution log
6401 The process record and replay target supports reverse execution
6402 (@pxref{Reverse Execution}), even if the platform on which the
6403 inferior runs does not. However, the reverse execution is limited in
6404 this case by the range of the instructions recorded in the execution
6405 log. In other words, reverse execution on platforms that don't
6406 support it directly can only be done in the replay mode.
6408 When debugging in the reverse direction, @value{GDBN} will work in
6409 replay mode as long as the execution log includes the record for the
6410 previous instruction; otherwise, it will work in record mode, if the
6411 platform supports reverse execution, or stop if not.
6413 For architecture environments that support process record and replay,
6414 @value{GDBN} provides the following commands:
6417 @kindex target record
6418 @kindex target record-full
6419 @kindex target record-btrace
6422 @kindex record btrace
6423 @kindex record btrace bts
6428 @kindex rec btrace bts
6430 @item record @var{method}
6431 This command starts the process record and replay target. The
6432 recording method can be specified as parameter. Without a parameter
6433 the command uses the @code{full} recording method. The following
6434 recording methods are available:
6438 Full record/replay recording using @value{GDBN}'s software record and
6439 replay implementation. This method allows replaying and reverse
6442 @item btrace @var{format}
6443 Hardware-supported instruction recording. This method does not record
6444 data. Further, the data is collected in a ring buffer so old data will
6445 be overwritten when the buffer is full. It allows limited replay and
6448 The recording format can be specified as parameter. Without a parameter
6449 the command chooses the recording format. The following recording
6450 formats are available:
6454 @cindex branch trace store
6455 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6456 this format, the processor stores a from/to record for each executed
6457 branch in the btrace ring buffer.
6460 Not all recording formats may be available on all processors.
6463 The process record and replay target can only debug a process that is
6464 already running. Therefore, you need first to start the process with
6465 the @kbd{run} or @kbd{start} commands, and then start the recording
6466 with the @kbd{record @var{method}} command.
6468 Both @code{record @var{method}} and @code{rec @var{method}} are
6469 aliases of @code{target record-@var{method}}.
6471 @cindex displaced stepping, and process record and replay
6472 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6473 will be automatically disabled when process record and replay target
6474 is started. That's because the process record and replay target
6475 doesn't support displaced stepping.
6477 @cindex non-stop mode, and process record and replay
6478 @cindex asynchronous execution, and process record and replay
6479 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6480 the asynchronous execution mode (@pxref{Background Execution}), not
6481 all recording methods are available. The @code{full} recording method
6482 does not support these two modes.
6487 Stop the process record and replay target. When process record and
6488 replay target stops, the entire execution log will be deleted and the
6489 inferior will either be terminated, or will remain in its final state.
6491 When you stop the process record and replay target in record mode (at
6492 the end of the execution log), the inferior will be stopped at the
6493 next instruction that would have been recorded. In other words, if
6494 you record for a while and then stop recording, the inferior process
6495 will be left in the same state as if the recording never happened.
6497 On the other hand, if the process record and replay target is stopped
6498 while in replay mode (that is, not at the end of the execution log,
6499 but at some earlier point), the inferior process will become ``live''
6500 at that earlier state, and it will then be possible to continue the
6501 usual ``live'' debugging of the process from that state.
6503 When the inferior process exits, or @value{GDBN} detaches from it,
6504 process record and replay target will automatically stop itself.
6508 Go to a specific location in the execution log. There are several
6509 ways to specify the location to go to:
6512 @item record goto begin
6513 @itemx record goto start
6514 Go to the beginning of the execution log.
6516 @item record goto end
6517 Go to the end of the execution log.
6519 @item record goto @var{n}
6520 Go to instruction number @var{n} in the execution log.
6524 @item record save @var{filename}
6525 Save the execution log to a file @file{@var{filename}}.
6526 Default filename is @file{gdb_record.@var{process_id}}, where
6527 @var{process_id} is the process ID of the inferior.
6529 This command may not be available for all recording methods.
6531 @kindex record restore
6532 @item record restore @var{filename}
6533 Restore the execution log from a file @file{@var{filename}}.
6534 File must have been created with @code{record save}.
6536 @kindex set record full
6537 @item set record full insn-number-max @var{limit}
6538 @itemx set record full insn-number-max unlimited
6539 Set the limit of instructions to be recorded for the @code{full}
6540 recording method. Default value is 200000.
6542 If @var{limit} is a positive number, then @value{GDBN} will start
6543 deleting instructions from the log once the number of the record
6544 instructions becomes greater than @var{limit}. For every new recorded
6545 instruction, @value{GDBN} will delete the earliest recorded
6546 instruction to keep the number of recorded instructions at the limit.
6547 (Since deleting recorded instructions loses information, @value{GDBN}
6548 lets you control what happens when the limit is reached, by means of
6549 the @code{stop-at-limit} option, described below.)
6551 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6552 delete recorded instructions from the execution log. The number of
6553 recorded instructions is limited only by the available memory.
6555 @kindex show record full
6556 @item show record full insn-number-max
6557 Show the limit of instructions to be recorded with the @code{full}
6560 @item set record full stop-at-limit
6561 Control the behavior of the @code{full} recording method when the
6562 number of recorded instructions reaches the limit. If ON (the
6563 default), @value{GDBN} will stop when the limit is reached for the
6564 first time and ask you whether you want to stop the inferior or
6565 continue running it and recording the execution log. If you decide
6566 to continue recording, each new recorded instruction will cause the
6567 oldest one to be deleted.
6569 If this option is OFF, @value{GDBN} will automatically delete the
6570 oldest record to make room for each new one, without asking.
6572 @item show record full stop-at-limit
6573 Show the current setting of @code{stop-at-limit}.
6575 @item set record full memory-query
6576 Control the behavior when @value{GDBN} is unable to record memory
6577 changes caused by an instruction for the @code{full} recording method.
6578 If ON, @value{GDBN} will query whether to stop the inferior in that
6581 If this option is OFF (the default), @value{GDBN} will automatically
6582 ignore the effect of such instructions on memory. Later, when
6583 @value{GDBN} replays this execution log, it will mark the log of this
6584 instruction as not accessible, and it will not affect the replay
6587 @item show record full memory-query
6588 Show the current setting of @code{memory-query}.
6590 @kindex set record btrace
6591 The @code{btrace} record target does not trace data. As a
6592 convenience, when replaying, @value{GDBN} reads read-only memory off
6593 the live program directly, assuming that the addresses of the
6594 read-only areas don't change. This for example makes it possible to
6595 disassemble code while replaying, but not to print variables.
6596 In some cases, being able to inspect variables might be useful.
6597 You can use the following command for that:
6599 @item set record btrace replay-memory-access
6600 Control the behavior of the @code{btrace} recording method when
6601 accessing memory during replay. If @code{read-only} (the default),
6602 @value{GDBN} will only allow accesses to read-only memory.
6603 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6604 and to read-write memory. Beware that the accessed memory corresponds
6605 to the live target and not necessarily to the current replay
6608 @kindex show record btrace
6609 @item show record btrace replay-memory-access
6610 Show the current setting of @code{replay-memory-access}.
6612 @kindex set record btrace bts
6613 @item set record btrace bts buffer-size @var{size}
6614 @itemx set record btrace bts buffer-size unlimited
6615 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6616 format. Default is 64KB.
6618 If @var{size} is a positive number, then @value{GDBN} will try to
6619 allocate a buffer of at least @var{size} bytes for each new thread
6620 that uses the btrace recording method and the @acronym{BTS} format.
6621 The actually obtained buffer size may differ from the requested
6622 @var{size}. Use the @code{info record} command to see the actual
6623 buffer size for each thread that uses the btrace recording method and
6624 the @acronym{BTS} format.
6626 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6627 allocate a buffer of 4MB.
6629 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6630 also need longer to process the branch trace data before it can be used.
6632 @item show record btrace bts buffer-size @var{size}
6633 Show the current setting of the requested ring buffer size for branch
6634 tracing in @acronym{BTS} format.
6638 Show various statistics about the recording depending on the recording
6643 For the @code{full} recording method, it shows the state of process
6644 record and its in-memory execution log buffer, including:
6648 Whether in record mode or replay mode.
6650 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6652 Highest recorded instruction number.
6654 Current instruction about to be replayed (if in replay mode).
6656 Number of instructions contained in the execution log.
6658 Maximum number of instructions that may be contained in the execution log.
6662 For the @code{btrace} recording method, it shows:
6668 Number of instructions that have been recorded.
6670 Number of blocks of sequential control-flow formed by the recorded
6673 Whether in record mode or replay mode.
6676 For the @code{bts} recording format, it also shows:
6679 Size of the perf ring buffer.
6683 @kindex record delete
6686 When record target runs in replay mode (``in the past''), delete the
6687 subsequent execution log and begin to record a new execution log starting
6688 from the current address. This means you will abandon the previously
6689 recorded ``future'' and begin recording a new ``future''.
6691 @kindex record instruction-history
6692 @kindex rec instruction-history
6693 @item record instruction-history
6694 Disassembles instructions from the recorded execution log. By
6695 default, ten instructions are disassembled. This can be changed using
6696 the @code{set record instruction-history-size} command. Instructions
6697 are printed in execution order. There are several ways to specify
6698 what part of the execution log to disassemble:
6701 @item record instruction-history @var{insn}
6702 Disassembles ten instructions starting from instruction number
6705 @item record instruction-history @var{insn}, +/-@var{n}
6706 Disassembles @var{n} instructions around instruction number
6707 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6708 @var{n} instructions after instruction number @var{insn}. If
6709 @var{n} is preceded with @code{-}, disassembles @var{n}
6710 instructions before instruction number @var{insn}.
6712 @item record instruction-history
6713 Disassembles ten more instructions after the last disassembly.
6715 @item record instruction-history -
6716 Disassembles ten more instructions before the last disassembly.
6718 @item record instruction-history @var{begin} @var{end}
6719 Disassembles instructions beginning with instruction number
6720 @var{begin} until instruction number @var{end}. The instruction
6721 number @var{end} is included.
6724 This command may not be available for all recording methods.
6727 @item set record instruction-history-size @var{size}
6728 @itemx set record instruction-history-size unlimited
6729 Define how many instructions to disassemble in the @code{record
6730 instruction-history} command. The default value is 10.
6731 A @var{size} of @code{unlimited} means unlimited instructions.
6734 @item show record instruction-history-size
6735 Show how many instructions to disassemble in the @code{record
6736 instruction-history} command.
6738 @kindex record function-call-history
6739 @kindex rec function-call-history
6740 @item record function-call-history
6741 Prints the execution history at function granularity. It prints one
6742 line for each sequence of instructions that belong to the same
6743 function giving the name of that function, the source lines
6744 for this instruction sequence (if the @code{/l} modifier is
6745 specified), and the instructions numbers that form the sequence (if
6746 the @code{/i} modifier is specified). The function names are indented
6747 to reflect the call stack depth if the @code{/c} modifier is
6748 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6752 (@value{GDBP}) @b{list 1, 10}
6763 (@value{GDBP}) @b{record function-call-history /ilc}
6764 1 bar inst 1,4 at foo.c:6,8
6765 2 foo inst 5,10 at foo.c:2,3
6766 3 bar inst 11,13 at foo.c:9,10
6769 By default, ten lines are printed. This can be changed using the
6770 @code{set record function-call-history-size} command. Functions are
6771 printed in execution order. There are several ways to specify what
6775 @item record function-call-history @var{func}
6776 Prints ten functions starting from function number @var{func}.
6778 @item record function-call-history @var{func}, +/-@var{n}
6779 Prints @var{n} functions around function number @var{func}. If
6780 @var{n} is preceded with @code{+}, prints @var{n} functions after
6781 function number @var{func}. If @var{n} is preceded with @code{-},
6782 prints @var{n} functions before function number @var{func}.
6784 @item record function-call-history
6785 Prints ten more functions after the last ten-line print.
6787 @item record function-call-history -
6788 Prints ten more functions before the last ten-line print.
6790 @item record function-call-history @var{begin} @var{end}
6791 Prints functions beginning with function number @var{begin} until
6792 function number @var{end}. The function number @var{end} is included.
6795 This command may not be available for all recording methods.
6797 @item set record function-call-history-size @var{size}
6798 @itemx set record function-call-history-size unlimited
6799 Define how many lines to print in the
6800 @code{record function-call-history} command. The default value is 10.
6801 A size of @code{unlimited} means unlimited lines.
6803 @item show record function-call-history-size
6804 Show how many lines to print in the
6805 @code{record function-call-history} command.
6810 @chapter Examining the Stack
6812 When your program has stopped, the first thing you need to know is where it
6813 stopped and how it got there.
6816 Each time your program performs a function call, information about the call
6818 That information includes the location of the call in your program,
6819 the arguments of the call,
6820 and the local variables of the function being called.
6821 The information is saved in a block of data called a @dfn{stack frame}.
6822 The stack frames are allocated in a region of memory called the @dfn{call
6825 When your program stops, the @value{GDBN} commands for examining the
6826 stack allow you to see all of this information.
6828 @cindex selected frame
6829 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6830 @value{GDBN} commands refer implicitly to the selected frame. In
6831 particular, whenever you ask @value{GDBN} for the value of a variable in
6832 your program, the value is found in the selected frame. There are
6833 special @value{GDBN} commands to select whichever frame you are
6834 interested in. @xref{Selection, ,Selecting a Frame}.
6836 When your program stops, @value{GDBN} automatically selects the
6837 currently executing frame and describes it briefly, similar to the
6838 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6841 * Frames:: Stack frames
6842 * Backtrace:: Backtraces
6843 * Frame Filter Management:: Managing frame filters
6844 * Selection:: Selecting a frame
6845 * Frame Info:: Information on a frame
6850 @section Stack Frames
6852 @cindex frame, definition
6854 The call stack is divided up into contiguous pieces called @dfn{stack
6855 frames}, or @dfn{frames} for short; each frame is the data associated
6856 with one call to one function. The frame contains the arguments given
6857 to the function, the function's local variables, and the address at
6858 which the function is executing.
6860 @cindex initial frame
6861 @cindex outermost frame
6862 @cindex innermost frame
6863 When your program is started, the stack has only one frame, that of the
6864 function @code{main}. This is called the @dfn{initial} frame or the
6865 @dfn{outermost} frame. Each time a function is called, a new frame is
6866 made. Each time a function returns, the frame for that function invocation
6867 is eliminated. If a function is recursive, there can be many frames for
6868 the same function. The frame for the function in which execution is
6869 actually occurring is called the @dfn{innermost} frame. This is the most
6870 recently created of all the stack frames that still exist.
6872 @cindex frame pointer
6873 Inside your program, stack frames are identified by their addresses. A
6874 stack frame consists of many bytes, each of which has its own address; each
6875 kind of computer has a convention for choosing one byte whose
6876 address serves as the address of the frame. Usually this address is kept
6877 in a register called the @dfn{frame pointer register}
6878 (@pxref{Registers, $fp}) while execution is going on in that frame.
6880 @cindex frame number
6881 @value{GDBN} assigns numbers to all existing stack frames, starting with
6882 zero for the innermost frame, one for the frame that called it,
6883 and so on upward. These numbers do not really exist in your program;
6884 they are assigned by @value{GDBN} to give you a way of designating stack
6885 frames in @value{GDBN} commands.
6887 @c The -fomit-frame-pointer below perennially causes hbox overflow
6888 @c underflow problems.
6889 @cindex frameless execution
6890 Some compilers provide a way to compile functions so that they operate
6891 without stack frames. (For example, the @value{NGCC} option
6893 @samp{-fomit-frame-pointer}
6895 generates functions without a frame.)
6896 This is occasionally done with heavily used library functions to save
6897 the frame setup time. @value{GDBN} has limited facilities for dealing
6898 with these function invocations. If the innermost function invocation
6899 has no stack frame, @value{GDBN} nevertheless regards it as though
6900 it had a separate frame, which is numbered zero as usual, allowing
6901 correct tracing of the function call chain. However, @value{GDBN} has
6902 no provision for frameless functions elsewhere in the stack.
6905 @kindex frame@r{, command}
6906 @cindex current stack frame
6907 @item frame @r{[}@var{framespec}@r{]}
6908 The @code{frame} command allows you to move from one stack frame to another,
6909 and to print the stack frame you select. The @var{framespec} may be either the
6910 address of the frame or the stack frame number. Without an argument,
6911 @code{frame} prints the current stack frame.
6913 @kindex select-frame
6914 @cindex selecting frame silently
6916 The @code{select-frame} command allows you to move from one stack frame
6917 to another without printing the frame. This is the silent version of
6925 @cindex call stack traces
6926 A backtrace is a summary of how your program got where it is. It shows one
6927 line per frame, for many frames, starting with the currently executing
6928 frame (frame zero), followed by its caller (frame one), and on up the
6931 @anchor{backtrace-command}
6934 @kindex bt @r{(@code{backtrace})}
6937 Print a backtrace of the entire stack: one line per frame for all
6938 frames in the stack.
6940 You can stop the backtrace at any time by typing the system interrupt
6941 character, normally @kbd{Ctrl-c}.
6943 @item backtrace @var{n}
6945 Similar, but print only the innermost @var{n} frames.
6947 @item backtrace -@var{n}
6949 Similar, but print only the outermost @var{n} frames.
6951 @item backtrace full
6953 @itemx bt full @var{n}
6954 @itemx bt full -@var{n}
6955 Print the values of the local variables also. As described above,
6956 @var{n} specifies the number of frames to print.
6958 @item backtrace no-filters
6959 @itemx bt no-filters
6960 @itemx bt no-filters @var{n}
6961 @itemx bt no-filters -@var{n}
6962 @itemx bt no-filters full
6963 @itemx bt no-filters full @var{n}
6964 @itemx bt no-filters full -@var{n}
6965 Do not run Python frame filters on this backtrace. @xref{Frame
6966 Filter API}, for more information. Additionally use @ref{disable
6967 frame-filter all} to turn off all frame filters. This is only
6968 relevant when @value{GDBN} has been configured with @code{Python}
6974 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6975 are additional aliases for @code{backtrace}.
6977 @cindex multiple threads, backtrace
6978 In a multi-threaded program, @value{GDBN} by default shows the
6979 backtrace only for the current thread. To display the backtrace for
6980 several or all of the threads, use the command @code{thread apply}
6981 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6982 apply all backtrace}, @value{GDBN} will display the backtrace for all
6983 the threads; this is handy when you debug a core dump of a
6984 multi-threaded program.
6986 Each line in the backtrace shows the frame number and the function name.
6987 The program counter value is also shown---unless you use @code{set
6988 print address off}. The backtrace also shows the source file name and
6989 line number, as well as the arguments to the function. The program
6990 counter value is omitted if it is at the beginning of the code for that
6993 Here is an example of a backtrace. It was made with the command
6994 @samp{bt 3}, so it shows the innermost three frames.
6998 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7000 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7001 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7003 (More stack frames follow...)
7008 The display for frame zero does not begin with a program counter
7009 value, indicating that your program has stopped at the beginning of the
7010 code for line @code{993} of @code{builtin.c}.
7013 The value of parameter @code{data} in frame 1 has been replaced by
7014 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7015 only if it is a scalar (integer, pointer, enumeration, etc). See command
7016 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7017 on how to configure the way function parameter values are printed.
7019 @cindex optimized out, in backtrace
7020 @cindex function call arguments, optimized out
7021 If your program was compiled with optimizations, some compilers will
7022 optimize away arguments passed to functions if those arguments are
7023 never used after the call. Such optimizations generate code that
7024 passes arguments through registers, but doesn't store those arguments
7025 in the stack frame. @value{GDBN} has no way of displaying such
7026 arguments in stack frames other than the innermost one. Here's what
7027 such a backtrace might look like:
7031 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7033 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7034 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7036 (More stack frames follow...)
7041 The values of arguments that were not saved in their stack frames are
7042 shown as @samp{<optimized out>}.
7044 If you need to display the values of such optimized-out arguments,
7045 either deduce that from other variables whose values depend on the one
7046 you are interested in, or recompile without optimizations.
7048 @cindex backtrace beyond @code{main} function
7049 @cindex program entry point
7050 @cindex startup code, and backtrace
7051 Most programs have a standard user entry point---a place where system
7052 libraries and startup code transition into user code. For C this is
7053 @code{main}@footnote{
7054 Note that embedded programs (the so-called ``free-standing''
7055 environment) are not required to have a @code{main} function as the
7056 entry point. They could even have multiple entry points.}.
7057 When @value{GDBN} finds the entry function in a backtrace
7058 it will terminate the backtrace, to avoid tracing into highly
7059 system-specific (and generally uninteresting) code.
7061 If you need to examine the startup code, or limit the number of levels
7062 in a backtrace, you can change this behavior:
7065 @item set backtrace past-main
7066 @itemx set backtrace past-main on
7067 @kindex set backtrace
7068 Backtraces will continue past the user entry point.
7070 @item set backtrace past-main off
7071 Backtraces will stop when they encounter the user entry point. This is the
7074 @item show backtrace past-main
7075 @kindex show backtrace
7076 Display the current user entry point backtrace policy.
7078 @item set backtrace past-entry
7079 @itemx set backtrace past-entry on
7080 Backtraces will continue past the internal entry point of an application.
7081 This entry point is encoded by the linker when the application is built,
7082 and is likely before the user entry point @code{main} (or equivalent) is called.
7084 @item set backtrace past-entry off
7085 Backtraces will stop when they encounter the internal entry point of an
7086 application. This is the default.
7088 @item show backtrace past-entry
7089 Display the current internal entry point backtrace policy.
7091 @item set backtrace limit @var{n}
7092 @itemx set backtrace limit 0
7093 @itemx set backtrace limit unlimited
7094 @cindex backtrace limit
7095 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7096 or zero means unlimited levels.
7098 @item show backtrace limit
7099 Display the current limit on backtrace levels.
7102 You can control how file names are displayed.
7105 @item set filename-display
7106 @itemx set filename-display relative
7107 @cindex filename-display
7108 Display file names relative to the compilation directory. This is the default.
7110 @item set filename-display basename
7111 Display only basename of a filename.
7113 @item set filename-display absolute
7114 Display an absolute filename.
7116 @item show filename-display
7117 Show the current way to display filenames.
7120 @node Frame Filter Management
7121 @section Management of Frame Filters.
7122 @cindex managing frame filters
7124 Frame filters are Python based utilities to manage and decorate the
7125 output of frames. @xref{Frame Filter API}, for further information.
7127 Managing frame filters is performed by several commands available
7128 within @value{GDBN}, detailed here.
7131 @kindex info frame-filter
7132 @item info frame-filter
7133 Print a list of installed frame filters from all dictionaries, showing
7134 their name, priority and enabled status.
7136 @kindex disable frame-filter
7137 @anchor{disable frame-filter all}
7138 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7139 Disable a frame filter in the dictionary matching
7140 @var{filter-dictionary} and @var{filter-name}. The
7141 @var{filter-dictionary} may be @code{all}, @code{global},
7142 @code{progspace}, or the name of the object file where the frame filter
7143 dictionary resides. When @code{all} is specified, all frame filters
7144 across all dictionaries are disabled. The @var{filter-name} is the name
7145 of the frame filter and is used when @code{all} is not the option for
7146 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7147 may be enabled again later.
7149 @kindex enable frame-filter
7150 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7151 Enable a frame filter in the dictionary matching
7152 @var{filter-dictionary} and @var{filter-name}. The
7153 @var{filter-dictionary} may be @code{all}, @code{global},
7154 @code{progspace} or the name of the object file where the frame filter
7155 dictionary resides. When @code{all} is specified, all frame filters across
7156 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7157 filter and is used when @code{all} is not the option for
7158 @var{filter-dictionary}.
7163 (gdb) info frame-filter
7165 global frame-filters:
7166 Priority Enabled Name
7167 1000 No PrimaryFunctionFilter
7170 progspace /build/test frame-filters:
7171 Priority Enabled Name
7172 100 Yes ProgspaceFilter
7174 objfile /build/test frame-filters:
7175 Priority Enabled Name
7176 999 Yes BuildProgra Filter
7178 (gdb) disable frame-filter /build/test BuildProgramFilter
7179 (gdb) info frame-filter
7181 global frame-filters:
7182 Priority Enabled Name
7183 1000 No PrimaryFunctionFilter
7186 progspace /build/test frame-filters:
7187 Priority Enabled Name
7188 100 Yes ProgspaceFilter
7190 objfile /build/test frame-filters:
7191 Priority Enabled Name
7192 999 No BuildProgramFilter
7194 (gdb) enable frame-filter global PrimaryFunctionFilter
7195 (gdb) info frame-filter
7197 global frame-filters:
7198 Priority Enabled Name
7199 1000 Yes PrimaryFunctionFilter
7202 progspace /build/test frame-filters:
7203 Priority Enabled Name
7204 100 Yes ProgspaceFilter
7206 objfile /build/test frame-filters:
7207 Priority Enabled Name
7208 999 No BuildProgramFilter
7211 @kindex set frame-filter priority
7212 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7213 Set the @var{priority} of a frame filter in the dictionary matching
7214 @var{filter-dictionary}, and the frame filter name matching
7215 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7216 @code{progspace} or the name of the object file where the frame filter
7217 dictionary resides. The @var{priority} is an integer.
7219 @kindex show frame-filter priority
7220 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7221 Show the @var{priority} of a frame filter in the dictionary matching
7222 @var{filter-dictionary}, and the frame filter name matching
7223 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7224 @code{progspace} or the name of the object file where the frame filter
7230 (gdb) info frame-filter
7232 global frame-filters:
7233 Priority Enabled Name
7234 1000 Yes PrimaryFunctionFilter
7237 progspace /build/test frame-filters:
7238 Priority Enabled Name
7239 100 Yes ProgspaceFilter
7241 objfile /build/test frame-filters:
7242 Priority Enabled Name
7243 999 No BuildProgramFilter
7245 (gdb) set frame-filter priority global Reverse 50
7246 (gdb) info frame-filter
7248 global frame-filters:
7249 Priority Enabled Name
7250 1000 Yes PrimaryFunctionFilter
7253 progspace /build/test frame-filters:
7254 Priority Enabled Name
7255 100 Yes ProgspaceFilter
7257 objfile /build/test frame-filters:
7258 Priority Enabled Name
7259 999 No BuildProgramFilter
7264 @section Selecting a Frame
7266 Most commands for examining the stack and other data in your program work on
7267 whichever stack frame is selected at the moment. Here are the commands for
7268 selecting a stack frame; all of them finish by printing a brief description
7269 of the stack frame just selected.
7272 @kindex frame@r{, selecting}
7273 @kindex f @r{(@code{frame})}
7276 Select frame number @var{n}. Recall that frame zero is the innermost
7277 (currently executing) frame, frame one is the frame that called the
7278 innermost one, and so on. The highest-numbered frame is the one for
7281 @item frame @var{addr}
7283 Select the frame at address @var{addr}. This is useful mainly if the
7284 chaining of stack frames has been damaged by a bug, making it
7285 impossible for @value{GDBN} to assign numbers properly to all frames. In
7286 addition, this can be useful when your program has multiple stacks and
7287 switches between them.
7289 On the SPARC architecture, @code{frame} needs two addresses to
7290 select an arbitrary frame: a frame pointer and a stack pointer.
7292 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7293 pointer and a program counter.
7295 On the 29k architecture, it needs three addresses: a register stack
7296 pointer, a program counter, and a memory stack pointer.
7300 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7301 numbers @var{n}, this advances toward the outermost frame, to higher
7302 frame numbers, to frames that have existed longer.
7305 @kindex do @r{(@code{down})}
7307 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7308 positive numbers @var{n}, this advances toward the innermost frame, to
7309 lower frame numbers, to frames that were created more recently.
7310 You may abbreviate @code{down} as @code{do}.
7313 All of these commands end by printing two lines of output describing the
7314 frame. The first line shows the frame number, the function name, the
7315 arguments, and the source file and line number of execution in that
7316 frame. The second line shows the text of that source line.
7324 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7326 10 read_input_file (argv[i]);
7330 After such a printout, the @code{list} command with no arguments
7331 prints ten lines centered on the point of execution in the frame.
7332 You can also edit the program at the point of execution with your favorite
7333 editing program by typing @code{edit}.
7334 @xref{List, ,Printing Source Lines},
7338 @kindex down-silently
7340 @item up-silently @var{n}
7341 @itemx down-silently @var{n}
7342 These two commands are variants of @code{up} and @code{down},
7343 respectively; they differ in that they do their work silently, without
7344 causing display of the new frame. They are intended primarily for use
7345 in @value{GDBN} command scripts, where the output might be unnecessary and
7350 @section Information About a Frame
7352 There are several other commands to print information about the selected
7358 When used without any argument, this command does not change which
7359 frame is selected, but prints a brief description of the currently
7360 selected stack frame. It can be abbreviated @code{f}. With an
7361 argument, this command is used to select a stack frame.
7362 @xref{Selection, ,Selecting a Frame}.
7365 @kindex info f @r{(@code{info frame})}
7368 This command prints a verbose description of the selected stack frame,
7373 the address of the frame
7375 the address of the next frame down (called by this frame)
7377 the address of the next frame up (caller of this frame)
7379 the language in which the source code corresponding to this frame is written
7381 the address of the frame's arguments
7383 the address of the frame's local variables
7385 the program counter saved in it (the address of execution in the caller frame)
7387 which registers were saved in the frame
7390 @noindent The verbose description is useful when
7391 something has gone wrong that has made the stack format fail to fit
7392 the usual conventions.
7394 @item info frame @var{addr}
7395 @itemx info f @var{addr}
7396 Print a verbose description of the frame at address @var{addr}, without
7397 selecting that frame. The selected frame remains unchanged by this
7398 command. This requires the same kind of address (more than one for some
7399 architectures) that you specify in the @code{frame} command.
7400 @xref{Selection, ,Selecting a Frame}.
7404 Print the arguments of the selected frame, each on a separate line.
7408 Print the local variables of the selected frame, each on a separate
7409 line. These are all variables (declared either static or automatic)
7410 accessible at the point of execution of the selected frame.
7416 @chapter Examining Source Files
7418 @value{GDBN} can print parts of your program's source, since the debugging
7419 information recorded in the program tells @value{GDBN} what source files were
7420 used to build it. When your program stops, @value{GDBN} spontaneously prints
7421 the line where it stopped. Likewise, when you select a stack frame
7422 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7423 execution in that frame has stopped. You can print other portions of
7424 source files by explicit command.
7426 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7427 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7428 @value{GDBN} under @sc{gnu} Emacs}.
7431 * List:: Printing source lines
7432 * Specify Location:: How to specify code locations
7433 * Edit:: Editing source files
7434 * Search:: Searching source files
7435 * Source Path:: Specifying source directories
7436 * Machine Code:: Source and machine code
7440 @section Printing Source Lines
7443 @kindex l @r{(@code{list})}
7444 To print lines from a source file, use the @code{list} command
7445 (abbreviated @code{l}). By default, ten lines are printed.
7446 There are several ways to specify what part of the file you want to
7447 print; see @ref{Specify Location}, for the full list.
7449 Here are the forms of the @code{list} command most commonly used:
7452 @item list @var{linenum}
7453 Print lines centered around line number @var{linenum} in the
7454 current source file.
7456 @item list @var{function}
7457 Print lines centered around the beginning of function
7461 Print more lines. If the last lines printed were printed with a
7462 @code{list} command, this prints lines following the last lines
7463 printed; however, if the last line printed was a solitary line printed
7464 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7465 Stack}), this prints lines centered around that line.
7468 Print lines just before the lines last printed.
7471 @cindex @code{list}, how many lines to display
7472 By default, @value{GDBN} prints ten source lines with any of these forms of
7473 the @code{list} command. You can change this using @code{set listsize}:
7476 @kindex set listsize
7477 @item set listsize @var{count}
7478 @itemx set listsize unlimited
7479 Make the @code{list} command display @var{count} source lines (unless
7480 the @code{list} argument explicitly specifies some other number).
7481 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7483 @kindex show listsize
7485 Display the number of lines that @code{list} prints.
7488 Repeating a @code{list} command with @key{RET} discards the argument,
7489 so it is equivalent to typing just @code{list}. This is more useful
7490 than listing the same lines again. An exception is made for an
7491 argument of @samp{-}; that argument is preserved in repetition so that
7492 each repetition moves up in the source file.
7494 In general, the @code{list} command expects you to supply zero, one or two
7495 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7496 of writing them (@pxref{Specify Location}), but the effect is always
7497 to specify some source line.
7499 Here is a complete description of the possible arguments for @code{list}:
7502 @item list @var{linespec}
7503 Print lines centered around the line specified by @var{linespec}.
7505 @item list @var{first},@var{last}
7506 Print lines from @var{first} to @var{last}. Both arguments are
7507 linespecs. When a @code{list} command has two linespecs, and the
7508 source file of the second linespec is omitted, this refers to
7509 the same source file as the first linespec.
7511 @item list ,@var{last}
7512 Print lines ending with @var{last}.
7514 @item list @var{first},
7515 Print lines starting with @var{first}.
7518 Print lines just after the lines last printed.
7521 Print lines just before the lines last printed.
7524 As described in the preceding table.
7527 @node Specify Location
7528 @section Specifying a Location
7529 @cindex specifying location
7532 Several @value{GDBN} commands accept arguments that specify a location
7533 of your program's code. Since @value{GDBN} is a source-level
7534 debugger, a location usually specifies some line in the source code;
7535 for that reason, locations are also known as @dfn{linespecs}.
7537 Here are all the different ways of specifying a code location that
7538 @value{GDBN} understands:
7542 Specifies the line number @var{linenum} of the current source file.
7545 @itemx +@var{offset}
7546 Specifies the line @var{offset} lines before or after the @dfn{current
7547 line}. For the @code{list} command, the current line is the last one
7548 printed; for the breakpoint commands, this is the line at which
7549 execution stopped in the currently selected @dfn{stack frame}
7550 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7551 used as the second of the two linespecs in a @code{list} command,
7552 this specifies the line @var{offset} lines up or down from the first
7555 @item @var{filename}:@var{linenum}
7556 Specifies the line @var{linenum} in the source file @var{filename}.
7557 If @var{filename} is a relative file name, then it will match any
7558 source file name with the same trailing components. For example, if
7559 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7560 name of @file{/build/trunk/gcc/expr.c}, but not
7561 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7563 @item @var{function}
7564 Specifies the line that begins the body of the function @var{function}.
7565 For example, in C, this is the line with the open brace.
7567 @item @var{function}:@var{label}
7568 Specifies the line where @var{label} appears in @var{function}.
7570 @item @var{filename}:@var{function}
7571 Specifies the line that begins the body of the function @var{function}
7572 in the file @var{filename}. You only need the file name with a
7573 function name to avoid ambiguity when there are identically named
7574 functions in different source files.
7577 Specifies the line at which the label named @var{label} appears.
7578 @value{GDBN} searches for the label in the function corresponding to
7579 the currently selected stack frame. If there is no current selected
7580 stack frame (for instance, if the inferior is not running), then
7581 @value{GDBN} will not search for a label.
7583 @item *@var{address}
7584 Specifies the program address @var{address}. For line-oriented
7585 commands, such as @code{list} and @code{edit}, this specifies a source
7586 line that contains @var{address}. For @code{break} and other
7587 breakpoint oriented commands, this can be used to set breakpoints in
7588 parts of your program which do not have debugging information or
7591 Here @var{address} may be any expression valid in the current working
7592 language (@pxref{Languages, working language}) that specifies a code
7593 address. In addition, as a convenience, @value{GDBN} extends the
7594 semantics of expressions used in locations to cover the situations
7595 that frequently happen during debugging. Here are the various forms
7599 @item @var{expression}
7600 Any expression valid in the current working language.
7602 @item @var{funcaddr}
7603 An address of a function or procedure derived from its name. In C,
7604 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7605 simply the function's name @var{function} (and actually a special case
7606 of a valid expression). In Pascal and Modula-2, this is
7607 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7608 (although the Pascal form also works).
7610 This form specifies the address of the function's first instruction,
7611 before the stack frame and arguments have been set up.
7613 @item '@var{filename}':@var{funcaddr}
7614 Like @var{funcaddr} above, but also specifies the name of the source
7615 file explicitly. This is useful if the name of the function does not
7616 specify the function unambiguously, e.g., if there are several
7617 functions with identical names in different source files.
7620 @cindex breakpoint at static probe point
7621 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7622 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7623 applications to embed static probes. @xref{Static Probe Points}, for more
7624 information on finding and using static probes. This form of linespec
7625 specifies the location of such a static probe.
7627 If @var{objfile} is given, only probes coming from that shared library
7628 or executable matching @var{objfile} as a regular expression are considered.
7629 If @var{provider} is given, then only probes from that provider are considered.
7630 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7631 each one of those probes.
7637 @section Editing Source Files
7638 @cindex editing source files
7641 @kindex e @r{(@code{edit})}
7642 To edit the lines in a source file, use the @code{edit} command.
7643 The editing program of your choice
7644 is invoked with the current line set to
7645 the active line in the program.
7646 Alternatively, there are several ways to specify what part of the file you
7647 want to print if you want to see other parts of the program:
7650 @item edit @var{location}
7651 Edit the source file specified by @code{location}. Editing starts at
7652 that @var{location}, e.g., at the specified source line of the
7653 specified file. @xref{Specify Location}, for all the possible forms
7654 of the @var{location} argument; here are the forms of the @code{edit}
7655 command most commonly used:
7658 @item edit @var{number}
7659 Edit the current source file with @var{number} as the active line number.
7661 @item edit @var{function}
7662 Edit the file containing @var{function} at the beginning of its definition.
7667 @subsection Choosing your Editor
7668 You can customize @value{GDBN} to use any editor you want
7670 The only restriction is that your editor (say @code{ex}), recognizes the
7671 following command-line syntax:
7673 ex +@var{number} file
7675 The optional numeric value +@var{number} specifies the number of the line in
7676 the file where to start editing.}.
7677 By default, it is @file{@value{EDITOR}}, but you can change this
7678 by setting the environment variable @code{EDITOR} before using
7679 @value{GDBN}. For example, to configure @value{GDBN} to use the
7680 @code{vi} editor, you could use these commands with the @code{sh} shell:
7686 or in the @code{csh} shell,
7688 setenv EDITOR /usr/bin/vi
7693 @section Searching Source Files
7694 @cindex searching source files
7696 There are two commands for searching through the current source file for a
7701 @kindex forward-search
7702 @kindex fo @r{(@code{forward-search})}
7703 @item forward-search @var{regexp}
7704 @itemx search @var{regexp}
7705 The command @samp{forward-search @var{regexp}} checks each line,
7706 starting with the one following the last line listed, for a match for
7707 @var{regexp}. It lists the line that is found. You can use the
7708 synonym @samp{search @var{regexp}} or abbreviate the command name as
7711 @kindex reverse-search
7712 @item reverse-search @var{regexp}
7713 The command @samp{reverse-search @var{regexp}} checks each line, starting
7714 with the one before the last line listed and going backward, for a match
7715 for @var{regexp}. It lists the line that is found. You can abbreviate
7716 this command as @code{rev}.
7720 @section Specifying Source Directories
7723 @cindex directories for source files
7724 Executable programs sometimes do not record the directories of the source
7725 files from which they were compiled, just the names. Even when they do,
7726 the directories could be moved between the compilation and your debugging
7727 session. @value{GDBN} has a list of directories to search for source files;
7728 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7729 it tries all the directories in the list, in the order they are present
7730 in the list, until it finds a file with the desired name.
7732 For example, suppose an executable references the file
7733 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7734 @file{/mnt/cross}. The file is first looked up literally; if this
7735 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7736 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7737 message is printed. @value{GDBN} does not look up the parts of the
7738 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7739 Likewise, the subdirectories of the source path are not searched: if
7740 the source path is @file{/mnt/cross}, and the binary refers to
7741 @file{foo.c}, @value{GDBN} would not find it under
7742 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7744 Plain file names, relative file names with leading directories, file
7745 names containing dots, etc.@: are all treated as described above; for
7746 instance, if the source path is @file{/mnt/cross}, and the source file
7747 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7748 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7749 that---@file{/mnt/cross/foo.c}.
7751 Note that the executable search path is @emph{not} used to locate the
7754 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7755 any information it has cached about where source files are found and where
7756 each line is in the file.
7760 When you start @value{GDBN}, its source path includes only @samp{cdir}
7761 and @samp{cwd}, in that order.
7762 To add other directories, use the @code{directory} command.
7764 The search path is used to find both program source files and @value{GDBN}
7765 script files (read using the @samp{-command} option and @samp{source} command).
7767 In addition to the source path, @value{GDBN} provides a set of commands
7768 that manage a list of source path substitution rules. A @dfn{substitution
7769 rule} specifies how to rewrite source directories stored in the program's
7770 debug information in case the sources were moved to a different
7771 directory between compilation and debugging. A rule is made of
7772 two strings, the first specifying what needs to be rewritten in
7773 the path, and the second specifying how it should be rewritten.
7774 In @ref{set substitute-path}, we name these two parts @var{from} and
7775 @var{to} respectively. @value{GDBN} does a simple string replacement
7776 of @var{from} with @var{to} at the start of the directory part of the
7777 source file name, and uses that result instead of the original file
7778 name to look up the sources.
7780 Using the previous example, suppose the @file{foo-1.0} tree has been
7781 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7782 @value{GDBN} to replace @file{/usr/src} in all source path names with
7783 @file{/mnt/cross}. The first lookup will then be
7784 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7785 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7786 substitution rule, use the @code{set substitute-path} command
7787 (@pxref{set substitute-path}).
7789 To avoid unexpected substitution results, a rule is applied only if the
7790 @var{from} part of the directory name ends at a directory separator.
7791 For instance, a rule substituting @file{/usr/source} into
7792 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7793 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7794 is applied only at the beginning of the directory name, this rule will
7795 not be applied to @file{/root/usr/source/baz.c} either.
7797 In many cases, you can achieve the same result using the @code{directory}
7798 command. However, @code{set substitute-path} can be more efficient in
7799 the case where the sources are organized in a complex tree with multiple
7800 subdirectories. With the @code{directory} command, you need to add each
7801 subdirectory of your project. If you moved the entire tree while
7802 preserving its internal organization, then @code{set substitute-path}
7803 allows you to direct the debugger to all the sources with one single
7806 @code{set substitute-path} is also more than just a shortcut command.
7807 The source path is only used if the file at the original location no
7808 longer exists. On the other hand, @code{set substitute-path} modifies
7809 the debugger behavior to look at the rewritten location instead. So, if
7810 for any reason a source file that is not relevant to your executable is
7811 located at the original location, a substitution rule is the only
7812 method available to point @value{GDBN} at the new location.
7814 @cindex @samp{--with-relocated-sources}
7815 @cindex default source path substitution
7816 You can configure a default source path substitution rule by
7817 configuring @value{GDBN} with the
7818 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7819 should be the name of a directory under @value{GDBN}'s configured
7820 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7821 directory names in debug information under @var{dir} will be adjusted
7822 automatically if the installed @value{GDBN} is moved to a new
7823 location. This is useful if @value{GDBN}, libraries or executables
7824 with debug information and corresponding source code are being moved
7828 @item directory @var{dirname} @dots{}
7829 @item dir @var{dirname} @dots{}
7830 Add directory @var{dirname} to the front of the source path. Several
7831 directory names may be given to this command, separated by @samp{:}
7832 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7833 part of absolute file names) or
7834 whitespace. You may specify a directory that is already in the source
7835 path; this moves it forward, so @value{GDBN} searches it sooner.
7839 @vindex $cdir@r{, convenience variable}
7840 @vindex $cwd@r{, convenience variable}
7841 @cindex compilation directory
7842 @cindex current directory
7843 @cindex working directory
7844 @cindex directory, current
7845 @cindex directory, compilation
7846 You can use the string @samp{$cdir} to refer to the compilation
7847 directory (if one is recorded), and @samp{$cwd} to refer to the current
7848 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7849 tracks the current working directory as it changes during your @value{GDBN}
7850 session, while the latter is immediately expanded to the current
7851 directory at the time you add an entry to the source path.
7854 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7856 @c RET-repeat for @code{directory} is explicitly disabled, but since
7857 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7859 @item set directories @var{path-list}
7860 @kindex set directories
7861 Set the source path to @var{path-list}.
7862 @samp{$cdir:$cwd} are added if missing.
7864 @item show directories
7865 @kindex show directories
7866 Print the source path: show which directories it contains.
7868 @anchor{set substitute-path}
7869 @item set substitute-path @var{from} @var{to}
7870 @kindex set substitute-path
7871 Define a source path substitution rule, and add it at the end of the
7872 current list of existing substitution rules. If a rule with the same
7873 @var{from} was already defined, then the old rule is also deleted.
7875 For example, if the file @file{/foo/bar/baz.c} was moved to
7876 @file{/mnt/cross/baz.c}, then the command
7879 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7883 will tell @value{GDBN} to replace @samp{/usr/src} with
7884 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7885 @file{baz.c} even though it was moved.
7887 In the case when more than one substitution rule have been defined,
7888 the rules are evaluated one by one in the order where they have been
7889 defined. The first one matching, if any, is selected to perform
7892 For instance, if we had entered the following commands:
7895 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7896 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7900 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7901 @file{/mnt/include/defs.h} by using the first rule. However, it would
7902 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7903 @file{/mnt/src/lib/foo.c}.
7906 @item unset substitute-path [path]
7907 @kindex unset substitute-path
7908 If a path is specified, search the current list of substitution rules
7909 for a rule that would rewrite that path. Delete that rule if found.
7910 A warning is emitted by the debugger if no rule could be found.
7912 If no path is specified, then all substitution rules are deleted.
7914 @item show substitute-path [path]
7915 @kindex show substitute-path
7916 If a path is specified, then print the source path substitution rule
7917 which would rewrite that path, if any.
7919 If no path is specified, then print all existing source path substitution
7924 If your source path is cluttered with directories that are no longer of
7925 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7926 versions of source. You can correct the situation as follows:
7930 Use @code{directory} with no argument to reset the source path to its default value.
7933 Use @code{directory} with suitable arguments to reinstall the
7934 directories you want in the source path. You can add all the
7935 directories in one command.
7939 @section Source and Machine Code
7940 @cindex source line and its code address
7942 You can use the command @code{info line} to map source lines to program
7943 addresses (and vice versa), and the command @code{disassemble} to display
7944 a range of addresses as machine instructions. You can use the command
7945 @code{set disassemble-next-line} to set whether to disassemble next
7946 source line when execution stops. When run under @sc{gnu} Emacs
7947 mode, the @code{info line} command causes the arrow to point to the
7948 line specified. Also, @code{info line} prints addresses in symbolic form as
7953 @item info line @var{linespec}
7954 Print the starting and ending addresses of the compiled code for
7955 source line @var{linespec}. You can specify source lines in any of
7956 the ways documented in @ref{Specify Location}.
7959 For example, we can use @code{info line} to discover the location of
7960 the object code for the first line of function
7961 @code{m4_changequote}:
7963 @c FIXME: I think this example should also show the addresses in
7964 @c symbolic form, as they usually would be displayed.
7966 (@value{GDBP}) info line m4_changequote
7967 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7971 @cindex code address and its source line
7972 We can also inquire (using @code{*@var{addr}} as the form for
7973 @var{linespec}) what source line covers a particular address:
7975 (@value{GDBP}) info line *0x63ff
7976 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7979 @cindex @code{$_} and @code{info line}
7980 @cindex @code{x} command, default address
7981 @kindex x@r{(examine), and} info line
7982 After @code{info line}, the default address for the @code{x} command
7983 is changed to the starting address of the line, so that @samp{x/i} is
7984 sufficient to begin examining the machine code (@pxref{Memory,
7985 ,Examining Memory}). Also, this address is saved as the value of the
7986 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7991 @cindex assembly instructions
7992 @cindex instructions, assembly
7993 @cindex machine instructions
7994 @cindex listing machine instructions
7996 @itemx disassemble /m
7997 @itemx disassemble /r
7998 This specialized command dumps a range of memory as machine
7999 instructions. It can also print mixed source+disassembly by specifying
8000 the @code{/m} modifier and print the raw instructions in hex as well as
8001 in symbolic form by specifying the @code{/r}.
8002 The default memory range is the function surrounding the
8003 program counter of the selected frame. A single argument to this
8004 command is a program counter value; @value{GDBN} dumps the function
8005 surrounding this value. When two arguments are given, they should
8006 be separated by a comma, possibly surrounded by whitespace. The
8007 arguments specify a range of addresses to dump, in one of two forms:
8010 @item @var{start},@var{end}
8011 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8012 @item @var{start},+@var{length}
8013 the addresses from @var{start} (inclusive) to
8014 @code{@var{start}+@var{length}} (exclusive).
8018 When 2 arguments are specified, the name of the function is also
8019 printed (since there could be several functions in the given range).
8021 The argument(s) can be any expression yielding a numeric value, such as
8022 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8024 If the range of memory being disassembled contains current program counter,
8025 the instruction at that location is shown with a @code{=>} marker.
8028 The following example shows the disassembly of a range of addresses of
8029 HP PA-RISC 2.0 code:
8032 (@value{GDBP}) disas 0x32c4, 0x32e4
8033 Dump of assembler code from 0x32c4 to 0x32e4:
8034 0x32c4 <main+204>: addil 0,dp
8035 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8036 0x32cc <main+212>: ldil 0x3000,r31
8037 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8038 0x32d4 <main+220>: ldo 0(r31),rp
8039 0x32d8 <main+224>: addil -0x800,dp
8040 0x32dc <main+228>: ldo 0x588(r1),r26
8041 0x32e0 <main+232>: ldil 0x3000,r31
8042 End of assembler dump.
8045 Here is an example showing mixed source+assembly for Intel x86, when the
8046 program is stopped just after function prologue:
8049 (@value{GDBP}) disas /m main
8050 Dump of assembler code for function main:
8052 0x08048330 <+0>: push %ebp
8053 0x08048331 <+1>: mov %esp,%ebp
8054 0x08048333 <+3>: sub $0x8,%esp
8055 0x08048336 <+6>: and $0xfffffff0,%esp
8056 0x08048339 <+9>: sub $0x10,%esp
8058 6 printf ("Hello.\n");
8059 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8060 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8064 0x08048348 <+24>: mov $0x0,%eax
8065 0x0804834d <+29>: leave
8066 0x0804834e <+30>: ret
8068 End of assembler dump.
8071 Here is another example showing raw instructions in hex for AMD x86-64,
8074 (gdb) disas /r 0x400281,+10
8075 Dump of assembler code from 0x400281 to 0x40028b:
8076 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8077 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8078 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8079 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8080 End of assembler dump.
8083 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8084 So, for example, if you want to disassemble function @code{bar}
8085 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8086 and not @samp{disassemble foo.c:bar}.
8088 Some architectures have more than one commonly-used set of instruction
8089 mnemonics or other syntax.
8091 For programs that were dynamically linked and use shared libraries,
8092 instructions that call functions or branch to locations in the shared
8093 libraries might show a seemingly bogus location---it's actually a
8094 location of the relocation table. On some architectures, @value{GDBN}
8095 might be able to resolve these to actual function names.
8098 @kindex set disassembly-flavor
8099 @cindex Intel disassembly flavor
8100 @cindex AT&T disassembly flavor
8101 @item set disassembly-flavor @var{instruction-set}
8102 Select the instruction set to use when disassembling the
8103 program via the @code{disassemble} or @code{x/i} commands.
8105 Currently this command is only defined for the Intel x86 family. You
8106 can set @var{instruction-set} to either @code{intel} or @code{att}.
8107 The default is @code{att}, the AT&T flavor used by default by Unix
8108 assemblers for x86-based targets.
8110 @kindex show disassembly-flavor
8111 @item show disassembly-flavor
8112 Show the current setting of the disassembly flavor.
8116 @kindex set disassemble-next-line
8117 @kindex show disassemble-next-line
8118 @item set disassemble-next-line
8119 @itemx show disassemble-next-line
8120 Control whether or not @value{GDBN} will disassemble the next source
8121 line or instruction when execution stops. If ON, @value{GDBN} will
8122 display disassembly of the next source line when execution of the
8123 program being debugged stops. This is @emph{in addition} to
8124 displaying the source line itself, which @value{GDBN} always does if
8125 possible. If the next source line cannot be displayed for some reason
8126 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8127 info in the debug info), @value{GDBN} will display disassembly of the
8128 next @emph{instruction} instead of showing the next source line. If
8129 AUTO, @value{GDBN} will display disassembly of next instruction only
8130 if the source line cannot be displayed. This setting causes
8131 @value{GDBN} to display some feedback when you step through a function
8132 with no line info or whose source file is unavailable. The default is
8133 OFF, which means never display the disassembly of the next line or
8139 @chapter Examining Data
8141 @cindex printing data
8142 @cindex examining data
8145 The usual way to examine data in your program is with the @code{print}
8146 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8147 evaluates and prints the value of an expression of the language your
8148 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8149 Different Languages}). It may also print the expression using a
8150 Python-based pretty-printer (@pxref{Pretty Printing}).
8153 @item print @var{expr}
8154 @itemx print /@var{f} @var{expr}
8155 @var{expr} is an expression (in the source language). By default the
8156 value of @var{expr} is printed in a format appropriate to its data type;
8157 you can choose a different format by specifying @samp{/@var{f}}, where
8158 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8162 @itemx print /@var{f}
8163 @cindex reprint the last value
8164 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8165 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8166 conveniently inspect the same value in an alternative format.
8169 A more low-level way of examining data is with the @code{x} command.
8170 It examines data in memory at a specified address and prints it in a
8171 specified format. @xref{Memory, ,Examining Memory}.
8173 If you are interested in information about types, or about how the
8174 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8175 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8178 @cindex exploring hierarchical data structures
8180 Another way of examining values of expressions and type information is
8181 through the Python extension command @code{explore} (available only if
8182 the @value{GDBN} build is configured with @code{--with-python}). It
8183 offers an interactive way to start at the highest level (or, the most
8184 abstract level) of the data type of an expression (or, the data type
8185 itself) and explore all the way down to leaf scalar values/fields
8186 embedded in the higher level data types.
8189 @item explore @var{arg}
8190 @var{arg} is either an expression (in the source language), or a type
8191 visible in the current context of the program being debugged.
8194 The working of the @code{explore} command can be illustrated with an
8195 example. If a data type @code{struct ComplexStruct} is defined in your
8205 struct ComplexStruct
8207 struct SimpleStruct *ss_p;
8213 followed by variable declarations as
8216 struct SimpleStruct ss = @{ 10, 1.11 @};
8217 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8221 then, the value of the variable @code{cs} can be explored using the
8222 @code{explore} command as follows.
8226 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8227 the following fields:
8229 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8230 arr = <Enter 1 to explore this field of type `int [10]'>
8232 Enter the field number of choice:
8236 Since the fields of @code{cs} are not scalar values, you are being
8237 prompted to chose the field you want to explore. Let's say you choose
8238 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8239 pointer, you will be asked if it is pointing to a single value. From
8240 the declaration of @code{cs} above, it is indeed pointing to a single
8241 value, hence you enter @code{y}. If you enter @code{n}, then you will
8242 be asked if it were pointing to an array of values, in which case this
8243 field will be explored as if it were an array.
8246 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8247 Continue exploring it as a pointer to a single value [y/n]: y
8248 The value of `*(cs.ss_p)' is a struct/class of type `struct
8249 SimpleStruct' with the following fields:
8251 i = 10 .. (Value of type `int')
8252 d = 1.1100000000000001 .. (Value of type `double')
8254 Press enter to return to parent value:
8258 If the field @code{arr} of @code{cs} was chosen for exploration by
8259 entering @code{1} earlier, then since it is as array, you will be
8260 prompted to enter the index of the element in the array that you want
8264 `cs.arr' is an array of `int'.
8265 Enter the index of the element you want to explore in `cs.arr': 5
8267 `(cs.arr)[5]' is a scalar value of type `int'.
8271 Press enter to return to parent value:
8274 In general, at any stage of exploration, you can go deeper towards the
8275 leaf values by responding to the prompts appropriately, or hit the
8276 return key to return to the enclosing data structure (the @i{higher}
8277 level data structure).
8279 Similar to exploring values, you can use the @code{explore} command to
8280 explore types. Instead of specifying a value (which is typically a
8281 variable name or an expression valid in the current context of the
8282 program being debugged), you specify a type name. If you consider the
8283 same example as above, your can explore the type
8284 @code{struct ComplexStruct} by passing the argument
8285 @code{struct ComplexStruct} to the @code{explore} command.
8288 (gdb) explore struct ComplexStruct
8292 By responding to the prompts appropriately in the subsequent interactive
8293 session, you can explore the type @code{struct ComplexStruct} in a
8294 manner similar to how the value @code{cs} was explored in the above
8297 The @code{explore} command also has two sub-commands,
8298 @code{explore value} and @code{explore type}. The former sub-command is
8299 a way to explicitly specify that value exploration of the argument is
8300 being invoked, while the latter is a way to explicitly specify that type
8301 exploration of the argument is being invoked.
8304 @item explore value @var{expr}
8305 @cindex explore value
8306 This sub-command of @code{explore} explores the value of the
8307 expression @var{expr} (if @var{expr} is an expression valid in the
8308 current context of the program being debugged). The behavior of this
8309 command is identical to that of the behavior of the @code{explore}
8310 command being passed the argument @var{expr}.
8312 @item explore type @var{arg}
8313 @cindex explore type
8314 This sub-command of @code{explore} explores the type of @var{arg} (if
8315 @var{arg} is a type visible in the current context of program being
8316 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8317 is an expression valid in the current context of the program being
8318 debugged). If @var{arg} is a type, then the behavior of this command is
8319 identical to that of the @code{explore} command being passed the
8320 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8321 this command will be identical to that of the @code{explore} command
8322 being passed the type of @var{arg} as the argument.
8326 * Expressions:: Expressions
8327 * Ambiguous Expressions:: Ambiguous Expressions
8328 * Variables:: Program variables
8329 * Arrays:: Artificial arrays
8330 * Output Formats:: Output formats
8331 * Memory:: Examining memory
8332 * Auto Display:: Automatic display
8333 * Print Settings:: Print settings
8334 * Pretty Printing:: Python pretty printing
8335 * Value History:: Value history
8336 * Convenience Vars:: Convenience variables
8337 * Convenience Funs:: Convenience functions
8338 * Registers:: Registers
8339 * Floating Point Hardware:: Floating point hardware
8340 * Vector Unit:: Vector Unit
8341 * OS Information:: Auxiliary data provided by operating system
8342 * Memory Region Attributes:: Memory region attributes
8343 * Dump/Restore Files:: Copy between memory and a file
8344 * Core File Generation:: Cause a program dump its core
8345 * Character Sets:: Debugging programs that use a different
8346 character set than GDB does
8347 * Caching Target Data:: Data caching for targets
8348 * Searching Memory:: Searching memory for a sequence of bytes
8352 @section Expressions
8355 @code{print} and many other @value{GDBN} commands accept an expression and
8356 compute its value. Any kind of constant, variable or operator defined
8357 by the programming language you are using is valid in an expression in
8358 @value{GDBN}. This includes conditional expressions, function calls,
8359 casts, and string constants. It also includes preprocessor macros, if
8360 you compiled your program to include this information; see
8363 @cindex arrays in expressions
8364 @value{GDBN} supports array constants in expressions input by
8365 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8366 you can use the command @code{print @{1, 2, 3@}} to create an array
8367 of three integers. If you pass an array to a function or assign it
8368 to a program variable, @value{GDBN} copies the array to memory that
8369 is @code{malloc}ed in the target program.
8371 Because C is so widespread, most of the expressions shown in examples in
8372 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8373 Languages}, for information on how to use expressions in other
8376 In this section, we discuss operators that you can use in @value{GDBN}
8377 expressions regardless of your programming language.
8379 @cindex casts, in expressions
8380 Casts are supported in all languages, not just in C, because it is so
8381 useful to cast a number into a pointer in order to examine a structure
8382 at that address in memory.
8383 @c FIXME: casts supported---Mod2 true?
8385 @value{GDBN} supports these operators, in addition to those common
8386 to programming languages:
8390 @samp{@@} is a binary operator for treating parts of memory as arrays.
8391 @xref{Arrays, ,Artificial Arrays}, for more information.
8394 @samp{::} allows you to specify a variable in terms of the file or
8395 function where it is defined. @xref{Variables, ,Program Variables}.
8397 @cindex @{@var{type}@}
8398 @cindex type casting memory
8399 @cindex memory, viewing as typed object
8400 @cindex casts, to view memory
8401 @item @{@var{type}@} @var{addr}
8402 Refers to an object of type @var{type} stored at address @var{addr} in
8403 memory. The address @var{addr} may be any expression whose value is
8404 an integer or pointer (but parentheses are required around binary
8405 operators, just as in a cast). This construct is allowed regardless
8406 of what kind of data is normally supposed to reside at @var{addr}.
8409 @node Ambiguous Expressions
8410 @section Ambiguous Expressions
8411 @cindex ambiguous expressions
8413 Expressions can sometimes contain some ambiguous elements. For instance,
8414 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8415 a single function name to be defined several times, for application in
8416 different contexts. This is called @dfn{overloading}. Another example
8417 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8418 templates and is typically instantiated several times, resulting in
8419 the same function name being defined in different contexts.
8421 In some cases and depending on the language, it is possible to adjust
8422 the expression to remove the ambiguity. For instance in C@t{++}, you
8423 can specify the signature of the function you want to break on, as in
8424 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8425 qualified name of your function often makes the expression unambiguous
8428 When an ambiguity that needs to be resolved is detected, the debugger
8429 has the capability to display a menu of numbered choices for each
8430 possibility, and then waits for the selection with the prompt @samp{>}.
8431 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8432 aborts the current command. If the command in which the expression was
8433 used allows more than one choice to be selected, the next option in the
8434 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8437 For example, the following session excerpt shows an attempt to set a
8438 breakpoint at the overloaded symbol @code{String::after}.
8439 We choose three particular definitions of that function name:
8441 @c FIXME! This is likely to change to show arg type lists, at least
8444 (@value{GDBP}) b String::after
8447 [2] file:String.cc; line number:867
8448 [3] file:String.cc; line number:860
8449 [4] file:String.cc; line number:875
8450 [5] file:String.cc; line number:853
8451 [6] file:String.cc; line number:846
8452 [7] file:String.cc; line number:735
8454 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8455 Breakpoint 2 at 0xb344: file String.cc, line 875.
8456 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8457 Multiple breakpoints were set.
8458 Use the "delete" command to delete unwanted
8465 @kindex set multiple-symbols
8466 @item set multiple-symbols @var{mode}
8467 @cindex multiple-symbols menu
8469 This option allows you to adjust the debugger behavior when an expression
8472 By default, @var{mode} is set to @code{all}. If the command with which
8473 the expression is used allows more than one choice, then @value{GDBN}
8474 automatically selects all possible choices. For instance, inserting
8475 a breakpoint on a function using an ambiguous name results in a breakpoint
8476 inserted on each possible match. However, if a unique choice must be made,
8477 then @value{GDBN} uses the menu to help you disambiguate the expression.
8478 For instance, printing the address of an overloaded function will result
8479 in the use of the menu.
8481 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8482 when an ambiguity is detected.
8484 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8485 an error due to the ambiguity and the command is aborted.
8487 @kindex show multiple-symbols
8488 @item show multiple-symbols
8489 Show the current value of the @code{multiple-symbols} setting.
8493 @section Program Variables
8495 The most common kind of expression to use is the name of a variable
8498 Variables in expressions are understood in the selected stack frame
8499 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8503 global (or file-static)
8510 visible according to the scope rules of the
8511 programming language from the point of execution in that frame
8514 @noindent This means that in the function
8529 you can examine and use the variable @code{a} whenever your program is
8530 executing within the function @code{foo}, but you can only use or
8531 examine the variable @code{b} while your program is executing inside
8532 the block where @code{b} is declared.
8534 @cindex variable name conflict
8535 There is an exception: you can refer to a variable or function whose
8536 scope is a single source file even if the current execution point is not
8537 in this file. But it is possible to have more than one such variable or
8538 function with the same name (in different source files). If that
8539 happens, referring to that name has unpredictable effects. If you wish,
8540 you can specify a static variable in a particular function or file by
8541 using the colon-colon (@code{::}) notation:
8543 @cindex colon-colon, context for variables/functions
8545 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8546 @cindex @code{::}, context for variables/functions
8549 @var{file}::@var{variable}
8550 @var{function}::@var{variable}
8554 Here @var{file} or @var{function} is the name of the context for the
8555 static @var{variable}. In the case of file names, you can use quotes to
8556 make sure @value{GDBN} parses the file name as a single word---for example,
8557 to print a global value of @code{x} defined in @file{f2.c}:
8560 (@value{GDBP}) p 'f2.c'::x
8563 The @code{::} notation is normally used for referring to
8564 static variables, since you typically disambiguate uses of local variables
8565 in functions by selecting the appropriate frame and using the
8566 simple name of the variable. However, you may also use this notation
8567 to refer to local variables in frames enclosing the selected frame:
8576 process (a); /* Stop here */
8587 For example, if there is a breakpoint at the commented line,
8588 here is what you might see
8589 when the program stops after executing the call @code{bar(0)}:
8594 (@value{GDBP}) p bar::a
8597 #2 0x080483d0 in foo (a=5) at foobar.c:12
8600 (@value{GDBP}) p bar::a
8604 @cindex C@t{++} scope resolution
8605 These uses of @samp{::} are very rarely in conflict with the very
8606 similar use of the same notation in C@t{++}. When they are in
8607 conflict, the C@t{++} meaning takes precedence; however, this can be
8608 overridden by quoting the file or function name with single quotes.
8610 For example, suppose the program is stopped in a method of a class
8611 that has a field named @code{includefile}, and there is also an
8612 include file named @file{includefile} that defines a variable,
8616 (@value{GDBP}) p includefile
8618 (@value{GDBP}) p includefile::some_global
8619 A syntax error in expression, near `'.
8620 (@value{GDBP}) p 'includefile'::some_global
8624 @cindex wrong values
8625 @cindex variable values, wrong
8626 @cindex function entry/exit, wrong values of variables
8627 @cindex optimized code, wrong values of variables
8629 @emph{Warning:} Occasionally, a local variable may appear to have the
8630 wrong value at certain points in a function---just after entry to a new
8631 scope, and just before exit.
8633 You may see this problem when you are stepping by machine instructions.
8634 This is because, on most machines, it takes more than one instruction to
8635 set up a stack frame (including local variable definitions); if you are
8636 stepping by machine instructions, variables may appear to have the wrong
8637 values until the stack frame is completely built. On exit, it usually
8638 also takes more than one machine instruction to destroy a stack frame;
8639 after you begin stepping through that group of instructions, local
8640 variable definitions may be gone.
8642 This may also happen when the compiler does significant optimizations.
8643 To be sure of always seeing accurate values, turn off all optimization
8646 @cindex ``No symbol "foo" in current context''
8647 Another possible effect of compiler optimizations is to optimize
8648 unused variables out of existence, or assign variables to registers (as
8649 opposed to memory addresses). Depending on the support for such cases
8650 offered by the debug info format used by the compiler, @value{GDBN}
8651 might not be able to display values for such local variables. If that
8652 happens, @value{GDBN} will print a message like this:
8655 No symbol "foo" in current context.
8658 To solve such problems, either recompile without optimizations, or use a
8659 different debug info format, if the compiler supports several such
8660 formats. @xref{Compilation}, for more information on choosing compiler
8661 options. @xref{C, ,C and C@t{++}}, for more information about debug
8662 info formats that are best suited to C@t{++} programs.
8664 If you ask to print an object whose contents are unknown to
8665 @value{GDBN}, e.g., because its data type is not completely specified
8666 by the debug information, @value{GDBN} will say @samp{<incomplete
8667 type>}. @xref{Symbols, incomplete type}, for more about this.
8669 If you append @kbd{@@entry} string to a function parameter name you get its
8670 value at the time the function got called. If the value is not available an
8671 error message is printed. Entry values are available only with some compilers.
8672 Entry values are normally also printed at the function parameter list according
8673 to @ref{set print entry-values}.
8676 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8682 (gdb) print i@@entry
8686 Strings are identified as arrays of @code{char} values without specified
8687 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8688 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8689 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8690 defines literal string type @code{"char"} as @code{char} without a sign.
8695 signed char var1[] = "A";
8698 You get during debugging
8703 $2 = @{65 'A', 0 '\0'@}
8707 @section Artificial Arrays
8709 @cindex artificial array
8711 @kindex @@@r{, referencing memory as an array}
8712 It is often useful to print out several successive objects of the
8713 same type in memory; a section of an array, or an array of
8714 dynamically determined size for which only a pointer exists in the
8717 You can do this by referring to a contiguous span of memory as an
8718 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8719 operand of @samp{@@} should be the first element of the desired array
8720 and be an individual object. The right operand should be the desired length
8721 of the array. The result is an array value whose elements are all of
8722 the type of the left argument. The first element is actually the left
8723 argument; the second element comes from bytes of memory immediately
8724 following those that hold the first element, and so on. Here is an
8725 example. If a program says
8728 int *array = (int *) malloc (len * sizeof (int));
8732 you can print the contents of @code{array} with
8738 The left operand of @samp{@@} must reside in memory. Array values made
8739 with @samp{@@} in this way behave just like other arrays in terms of
8740 subscripting, and are coerced to pointers when used in expressions.
8741 Artificial arrays most often appear in expressions via the value history
8742 (@pxref{Value History, ,Value History}), after printing one out.
8744 Another way to create an artificial array is to use a cast.
8745 This re-interprets a value as if it were an array.
8746 The value need not be in memory:
8748 (@value{GDBP}) p/x (short[2])0x12345678
8749 $1 = @{0x1234, 0x5678@}
8752 As a convenience, if you leave the array length out (as in
8753 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8754 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8756 (@value{GDBP}) p/x (short[])0x12345678
8757 $2 = @{0x1234, 0x5678@}
8760 Sometimes the artificial array mechanism is not quite enough; in
8761 moderately complex data structures, the elements of interest may not
8762 actually be adjacent---for example, if you are interested in the values
8763 of pointers in an array. One useful work-around in this situation is
8764 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8765 Variables}) as a counter in an expression that prints the first
8766 interesting value, and then repeat that expression via @key{RET}. For
8767 instance, suppose you have an array @code{dtab} of pointers to
8768 structures, and you are interested in the values of a field @code{fv}
8769 in each structure. Here is an example of what you might type:
8779 @node Output Formats
8780 @section Output Formats
8782 @cindex formatted output
8783 @cindex output formats
8784 By default, @value{GDBN} prints a value according to its data type. Sometimes
8785 this is not what you want. For example, you might want to print a number
8786 in hex, or a pointer in decimal. Or you might want to view data in memory
8787 at a certain address as a character string or as an instruction. To do
8788 these things, specify an @dfn{output format} when you print a value.
8790 The simplest use of output formats is to say how to print a value
8791 already computed. This is done by starting the arguments of the
8792 @code{print} command with a slash and a format letter. The format
8793 letters supported are:
8797 Regard the bits of the value as an integer, and print the integer in
8801 Print as integer in signed decimal.
8804 Print as integer in unsigned decimal.
8807 Print as integer in octal.
8810 Print as integer in binary. The letter @samp{t} stands for ``two''.
8811 @footnote{@samp{b} cannot be used because these format letters are also
8812 used with the @code{x} command, where @samp{b} stands for ``byte'';
8813 see @ref{Memory,,Examining Memory}.}
8816 @cindex unknown address, locating
8817 @cindex locate address
8818 Print as an address, both absolute in hexadecimal and as an offset from
8819 the nearest preceding symbol. You can use this format used to discover
8820 where (in what function) an unknown address is located:
8823 (@value{GDBP}) p/a 0x54320
8824 $3 = 0x54320 <_initialize_vx+396>
8828 The command @code{info symbol 0x54320} yields similar results.
8829 @xref{Symbols, info symbol}.
8832 Regard as an integer and print it as a character constant. This
8833 prints both the numerical value and its character representation. The
8834 character representation is replaced with the octal escape @samp{\nnn}
8835 for characters outside the 7-bit @sc{ascii} range.
8837 Without this format, @value{GDBN} displays @code{char},
8838 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8839 constants. Single-byte members of vectors are displayed as integer
8843 Regard the bits of the value as a floating point number and print
8844 using typical floating point syntax.
8847 @cindex printing strings
8848 @cindex printing byte arrays
8849 Regard as a string, if possible. With this format, pointers to single-byte
8850 data are displayed as null-terminated strings and arrays of single-byte data
8851 are displayed as fixed-length strings. Other values are displayed in their
8854 Without this format, @value{GDBN} displays pointers to and arrays of
8855 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8856 strings. Single-byte members of a vector are displayed as an integer
8860 Like @samp{x} formatting, the value is treated as an integer and
8861 printed as hexadecimal, but leading zeros are printed to pad the value
8862 to the size of the integer type.
8865 @cindex raw printing
8866 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8867 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8868 Printing}). This typically results in a higher-level display of the
8869 value's contents. The @samp{r} format bypasses any Python
8870 pretty-printer which might exist.
8873 For example, to print the program counter in hex (@pxref{Registers}), type
8880 Note that no space is required before the slash; this is because command
8881 names in @value{GDBN} cannot contain a slash.
8883 To reprint the last value in the value history with a different format,
8884 you can use the @code{print} command with just a format and no
8885 expression. For example, @samp{p/x} reprints the last value in hex.
8888 @section Examining Memory
8890 You can use the command @code{x} (for ``examine'') to examine memory in
8891 any of several formats, independently of your program's data types.
8893 @cindex examining memory
8895 @kindex x @r{(examine memory)}
8896 @item x/@var{nfu} @var{addr}
8899 Use the @code{x} command to examine memory.
8902 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8903 much memory to display and how to format it; @var{addr} is an
8904 expression giving the address where you want to start displaying memory.
8905 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8906 Several commands set convenient defaults for @var{addr}.
8909 @item @var{n}, the repeat count
8910 The repeat count is a decimal integer; the default is 1. It specifies
8911 how much memory (counting by units @var{u}) to display.
8912 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8915 @item @var{f}, the display format
8916 The display format is one of the formats used by @code{print}
8917 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8918 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8919 The default is @samp{x} (hexadecimal) initially. The default changes
8920 each time you use either @code{x} or @code{print}.
8922 @item @var{u}, the unit size
8923 The unit size is any of
8929 Halfwords (two bytes).
8931 Words (four bytes). This is the initial default.
8933 Giant words (eight bytes).
8936 Each time you specify a unit size with @code{x}, that size becomes the
8937 default unit the next time you use @code{x}. For the @samp{i} format,
8938 the unit size is ignored and is normally not written. For the @samp{s} format,
8939 the unit size defaults to @samp{b}, unless it is explicitly given.
8940 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8941 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8942 Note that the results depend on the programming language of the
8943 current compilation unit. If the language is C, the @samp{s}
8944 modifier will use the UTF-16 encoding while @samp{w} will use
8945 UTF-32. The encoding is set by the programming language and cannot
8948 @item @var{addr}, starting display address
8949 @var{addr} is the address where you want @value{GDBN} to begin displaying
8950 memory. The expression need not have a pointer value (though it may);
8951 it is always interpreted as an integer address of a byte of memory.
8952 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8953 @var{addr} is usually just after the last address examined---but several
8954 other commands also set the default address: @code{info breakpoints} (to
8955 the address of the last breakpoint listed), @code{info line} (to the
8956 starting address of a line), and @code{print} (if you use it to display
8957 a value from memory).
8960 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8961 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8962 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8963 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8964 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8966 Since the letters indicating unit sizes are all distinct from the
8967 letters specifying output formats, you do not have to remember whether
8968 unit size or format comes first; either order works. The output
8969 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8970 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8972 Even though the unit size @var{u} is ignored for the formats @samp{s}
8973 and @samp{i}, you might still want to use a count @var{n}; for example,
8974 @samp{3i} specifies that you want to see three machine instructions,
8975 including any operands. For convenience, especially when used with
8976 the @code{display} command, the @samp{i} format also prints branch delay
8977 slot instructions, if any, beyond the count specified, which immediately
8978 follow the last instruction that is within the count. The command
8979 @code{disassemble} gives an alternative way of inspecting machine
8980 instructions; see @ref{Machine Code,,Source and Machine Code}.
8982 All the defaults for the arguments to @code{x} are designed to make it
8983 easy to continue scanning memory with minimal specifications each time
8984 you use @code{x}. For example, after you have inspected three machine
8985 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8986 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8987 the repeat count @var{n} is used again; the other arguments default as
8988 for successive uses of @code{x}.
8990 When examining machine instructions, the instruction at current program
8991 counter is shown with a @code{=>} marker. For example:
8994 (@value{GDBP}) x/5i $pc-6
8995 0x804837f <main+11>: mov %esp,%ebp
8996 0x8048381 <main+13>: push %ecx
8997 0x8048382 <main+14>: sub $0x4,%esp
8998 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8999 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9002 @cindex @code{$_}, @code{$__}, and value history
9003 The addresses and contents printed by the @code{x} command are not saved
9004 in the value history because there is often too much of them and they
9005 would get in the way. Instead, @value{GDBN} makes these values available for
9006 subsequent use in expressions as values of the convenience variables
9007 @code{$_} and @code{$__}. After an @code{x} command, the last address
9008 examined is available for use in expressions in the convenience variable
9009 @code{$_}. The contents of that address, as examined, are available in
9010 the convenience variable @code{$__}.
9012 If the @code{x} command has a repeat count, the address and contents saved
9013 are from the last memory unit printed; this is not the same as the last
9014 address printed if several units were printed on the last line of output.
9016 @cindex remote memory comparison
9017 @cindex target memory comparison
9018 @cindex verify remote memory image
9019 @cindex verify target memory image
9020 When you are debugging a program running on a remote target machine
9021 (@pxref{Remote Debugging}), you may wish to verify the program's image
9022 in the remote machine's memory against the executable file you
9023 downloaded to the target. Or, on any target, you may want to check
9024 whether the program has corrupted its own read-only sections. The
9025 @code{compare-sections} command is provided for such situations.
9028 @kindex compare-sections
9029 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9030 Compare the data of a loadable section @var{section-name} in the
9031 executable file of the program being debugged with the same section in
9032 the target machine's memory, and report any mismatches. With no
9033 arguments, compares all loadable sections. With an argument of
9034 @code{-r}, compares all loadable read-only sections.
9036 Note: for remote targets, this command can be accelerated if the
9037 target supports computing the CRC checksum of a block of memory
9038 (@pxref{qCRC packet}).
9042 @section Automatic Display
9043 @cindex automatic display
9044 @cindex display of expressions
9046 If you find that you want to print the value of an expression frequently
9047 (to see how it changes), you might want to add it to the @dfn{automatic
9048 display list} so that @value{GDBN} prints its value each time your program stops.
9049 Each expression added to the list is given a number to identify it;
9050 to remove an expression from the list, you specify that number.
9051 The automatic display looks like this:
9055 3: bar[5] = (struct hack *) 0x3804
9059 This display shows item numbers, expressions and their current values. As with
9060 displays you request manually using @code{x} or @code{print}, you can
9061 specify the output format you prefer; in fact, @code{display} decides
9062 whether to use @code{print} or @code{x} depending your format
9063 specification---it uses @code{x} if you specify either the @samp{i}
9064 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9068 @item display @var{expr}
9069 Add the expression @var{expr} to the list of expressions to display
9070 each time your program stops. @xref{Expressions, ,Expressions}.
9072 @code{display} does not repeat if you press @key{RET} again after using it.
9074 @item display/@var{fmt} @var{expr}
9075 For @var{fmt} specifying only a display format and not a size or
9076 count, add the expression @var{expr} to the auto-display list but
9077 arrange to display it each time in the specified format @var{fmt}.
9078 @xref{Output Formats,,Output Formats}.
9080 @item display/@var{fmt} @var{addr}
9081 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9082 number of units, add the expression @var{addr} as a memory address to
9083 be examined each time your program stops. Examining means in effect
9084 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9087 For example, @samp{display/i $pc} can be helpful, to see the machine
9088 instruction about to be executed each time execution stops (@samp{$pc}
9089 is a common name for the program counter; @pxref{Registers, ,Registers}).
9092 @kindex delete display
9094 @item undisplay @var{dnums}@dots{}
9095 @itemx delete display @var{dnums}@dots{}
9096 Remove items from the list of expressions to display. Specify the
9097 numbers of the displays that you want affected with the command
9098 argument @var{dnums}. It can be a single display number, one of the
9099 numbers shown in the first field of the @samp{info display} display;
9100 or it could be a range of display numbers, as in @code{2-4}.
9102 @code{undisplay} does not repeat if you press @key{RET} after using it.
9103 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9105 @kindex disable display
9106 @item disable display @var{dnums}@dots{}
9107 Disable the display of item numbers @var{dnums}. A disabled display
9108 item is not printed automatically, but is not forgotten. It may be
9109 enabled again later. Specify the numbers of the displays that you
9110 want affected with the command argument @var{dnums}. It can be a
9111 single display number, one of the numbers shown in the first field of
9112 the @samp{info display} display; or it could be a range of display
9113 numbers, as in @code{2-4}.
9115 @kindex enable display
9116 @item enable display @var{dnums}@dots{}
9117 Enable display of item numbers @var{dnums}. It becomes effective once
9118 again in auto display of its expression, until you specify otherwise.
9119 Specify the numbers of the displays that you want affected with the
9120 command argument @var{dnums}. It can be a single display number, one
9121 of the numbers shown in the first field of the @samp{info display}
9122 display; or it could be a range of display numbers, as in @code{2-4}.
9125 Display the current values of the expressions on the list, just as is
9126 done when your program stops.
9128 @kindex info display
9130 Print the list of expressions previously set up to display
9131 automatically, each one with its item number, but without showing the
9132 values. This includes disabled expressions, which are marked as such.
9133 It also includes expressions which would not be displayed right now
9134 because they refer to automatic variables not currently available.
9137 @cindex display disabled out of scope
9138 If a display expression refers to local variables, then it does not make
9139 sense outside the lexical context for which it was set up. Such an
9140 expression is disabled when execution enters a context where one of its
9141 variables is not defined. For example, if you give the command
9142 @code{display last_char} while inside a function with an argument
9143 @code{last_char}, @value{GDBN} displays this argument while your program
9144 continues to stop inside that function. When it stops elsewhere---where
9145 there is no variable @code{last_char}---the display is disabled
9146 automatically. The next time your program stops where @code{last_char}
9147 is meaningful, you can enable the display expression once again.
9149 @node Print Settings
9150 @section Print Settings
9152 @cindex format options
9153 @cindex print settings
9154 @value{GDBN} provides the following ways to control how arrays, structures,
9155 and symbols are printed.
9158 These settings are useful for debugging programs in any language:
9162 @item set print address
9163 @itemx set print address on
9164 @cindex print/don't print memory addresses
9165 @value{GDBN} prints memory addresses showing the location of stack
9166 traces, structure values, pointer values, breakpoints, and so forth,
9167 even when it also displays the contents of those addresses. The default
9168 is @code{on}. For example, this is what a stack frame display looks like with
9169 @code{set print address on}:
9174 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9176 530 if (lquote != def_lquote)
9180 @item set print address off
9181 Do not print addresses when displaying their contents. For example,
9182 this is the same stack frame displayed with @code{set print address off}:
9186 (@value{GDBP}) set print addr off
9188 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9189 530 if (lquote != def_lquote)
9193 You can use @samp{set print address off} to eliminate all machine
9194 dependent displays from the @value{GDBN} interface. For example, with
9195 @code{print address off}, you should get the same text for backtraces on
9196 all machines---whether or not they involve pointer arguments.
9199 @item show print address
9200 Show whether or not addresses are to be printed.
9203 When @value{GDBN} prints a symbolic address, it normally prints the
9204 closest earlier symbol plus an offset. If that symbol does not uniquely
9205 identify the address (for example, it is a name whose scope is a single
9206 source file), you may need to clarify. One way to do this is with
9207 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9208 you can set @value{GDBN} to print the source file and line number when
9209 it prints a symbolic address:
9212 @item set print symbol-filename on
9213 @cindex source file and line of a symbol
9214 @cindex symbol, source file and line
9215 Tell @value{GDBN} to print the source file name and line number of a
9216 symbol in the symbolic form of an address.
9218 @item set print symbol-filename off
9219 Do not print source file name and line number of a symbol. This is the
9222 @item show print symbol-filename
9223 Show whether or not @value{GDBN} will print the source file name and
9224 line number of a symbol in the symbolic form of an address.
9227 Another situation where it is helpful to show symbol filenames and line
9228 numbers is when disassembling code; @value{GDBN} shows you the line
9229 number and source file that corresponds to each instruction.
9231 Also, you may wish to see the symbolic form only if the address being
9232 printed is reasonably close to the closest earlier symbol:
9235 @item set print max-symbolic-offset @var{max-offset}
9236 @itemx set print max-symbolic-offset unlimited
9237 @cindex maximum value for offset of closest symbol
9238 Tell @value{GDBN} to only display the symbolic form of an address if the
9239 offset between the closest earlier symbol and the address is less than
9240 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9241 to always print the symbolic form of an address if any symbol precedes
9242 it. Zero is equivalent to @code{unlimited}.
9244 @item show print max-symbolic-offset
9245 Ask how large the maximum offset is that @value{GDBN} prints in a
9249 @cindex wild pointer, interpreting
9250 @cindex pointer, finding referent
9251 If you have a pointer and you are not sure where it points, try
9252 @samp{set print symbol-filename on}. Then you can determine the name
9253 and source file location of the variable where it points, using
9254 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9255 For example, here @value{GDBN} shows that a variable @code{ptt} points
9256 at another variable @code{t}, defined in @file{hi2.c}:
9259 (@value{GDBP}) set print symbol-filename on
9260 (@value{GDBP}) p/a ptt
9261 $4 = 0xe008 <t in hi2.c>
9265 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9266 does not show the symbol name and filename of the referent, even with
9267 the appropriate @code{set print} options turned on.
9270 You can also enable @samp{/a}-like formatting all the time using
9271 @samp{set print symbol on}:
9274 @item set print symbol on
9275 Tell @value{GDBN} to print the symbol corresponding to an address, if
9278 @item set print symbol off
9279 Tell @value{GDBN} not to print the symbol corresponding to an
9280 address. In this mode, @value{GDBN} will still print the symbol
9281 corresponding to pointers to functions. This is the default.
9283 @item show print symbol
9284 Show whether @value{GDBN} will display the symbol corresponding to an
9288 Other settings control how different kinds of objects are printed:
9291 @item set print array
9292 @itemx set print array on
9293 @cindex pretty print arrays
9294 Pretty print arrays. This format is more convenient to read,
9295 but uses more space. The default is off.
9297 @item set print array off
9298 Return to compressed format for arrays.
9300 @item show print array
9301 Show whether compressed or pretty format is selected for displaying
9304 @cindex print array indexes
9305 @item set print array-indexes
9306 @itemx set print array-indexes on
9307 Print the index of each element when displaying arrays. May be more
9308 convenient to locate a given element in the array or quickly find the
9309 index of a given element in that printed array. The default is off.
9311 @item set print array-indexes off
9312 Stop printing element indexes when displaying arrays.
9314 @item show print array-indexes
9315 Show whether the index of each element is printed when displaying
9318 @item set print elements @var{number-of-elements}
9319 @itemx set print elements unlimited
9320 @cindex number of array elements to print
9321 @cindex limit on number of printed array elements
9322 Set a limit on how many elements of an array @value{GDBN} will print.
9323 If @value{GDBN} is printing a large array, it stops printing after it has
9324 printed the number of elements set by the @code{set print elements} command.
9325 This limit also applies to the display of strings.
9326 When @value{GDBN} starts, this limit is set to 200.
9327 Setting @var{number-of-elements} to @code{unlimited} or zero means
9328 that the number of elements to print is unlimited.
9330 @item show print elements
9331 Display the number of elements of a large array that @value{GDBN} will print.
9332 If the number is 0, then the printing is unlimited.
9334 @item set print frame-arguments @var{value}
9335 @kindex set print frame-arguments
9336 @cindex printing frame argument values
9337 @cindex print all frame argument values
9338 @cindex print frame argument values for scalars only
9339 @cindex do not print frame argument values
9340 This command allows to control how the values of arguments are printed
9341 when the debugger prints a frame (@pxref{Frames}). The possible
9346 The values of all arguments are printed.
9349 Print the value of an argument only if it is a scalar. The value of more
9350 complex arguments such as arrays, structures, unions, etc, is replaced
9351 by @code{@dots{}}. This is the default. Here is an example where
9352 only scalar arguments are shown:
9355 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9360 None of the argument values are printed. Instead, the value of each argument
9361 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9364 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9369 By default, only scalar arguments are printed. This command can be used
9370 to configure the debugger to print the value of all arguments, regardless
9371 of their type. However, it is often advantageous to not print the value
9372 of more complex parameters. For instance, it reduces the amount of
9373 information printed in each frame, making the backtrace more readable.
9374 Also, it improves performance when displaying Ada frames, because
9375 the computation of large arguments can sometimes be CPU-intensive,
9376 especially in large applications. Setting @code{print frame-arguments}
9377 to @code{scalars} (the default) or @code{none} avoids this computation,
9378 thus speeding up the display of each Ada frame.
9380 @item show print frame-arguments
9381 Show how the value of arguments should be displayed when printing a frame.
9383 @item set print raw frame-arguments on
9384 Print frame arguments in raw, non pretty-printed, form.
9386 @item set print raw frame-arguments off
9387 Print frame arguments in pretty-printed form, if there is a pretty-printer
9388 for the value (@pxref{Pretty Printing}),
9389 otherwise print the value in raw form.
9390 This is the default.
9392 @item show print raw frame-arguments
9393 Show whether to print frame arguments in raw form.
9395 @anchor{set print entry-values}
9396 @item set print entry-values @var{value}
9397 @kindex set print entry-values
9398 Set printing of frame argument values at function entry. In some cases
9399 @value{GDBN} can determine the value of function argument which was passed by
9400 the function caller, even if the value was modified inside the called function
9401 and therefore is different. With optimized code, the current value could be
9402 unavailable, but the entry value may still be known.
9404 The default value is @code{default} (see below for its description). Older
9405 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9406 this feature will behave in the @code{default} setting the same way as with the
9409 This functionality is currently supported only by DWARF 2 debugging format and
9410 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9411 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9414 The @var{value} parameter can be one of the following:
9418 Print only actual parameter values, never print values from function entry
9422 #0 different (val=6)
9423 #0 lost (val=<optimized out>)
9425 #0 invalid (val=<optimized out>)
9429 Print only parameter values from function entry point. The actual parameter
9430 values are never printed.
9432 #0 equal (val@@entry=5)
9433 #0 different (val@@entry=5)
9434 #0 lost (val@@entry=5)
9435 #0 born (val@@entry=<optimized out>)
9436 #0 invalid (val@@entry=<optimized out>)
9440 Print only parameter values from function entry point. If value from function
9441 entry point is not known while the actual value is known, print the actual
9442 value for such parameter.
9444 #0 equal (val@@entry=5)
9445 #0 different (val@@entry=5)
9446 #0 lost (val@@entry=5)
9448 #0 invalid (val@@entry=<optimized out>)
9452 Print actual parameter values. If actual parameter value is not known while
9453 value from function entry point is known, print the entry point value for such
9457 #0 different (val=6)
9458 #0 lost (val@@entry=5)
9460 #0 invalid (val=<optimized out>)
9464 Always print both the actual parameter value and its value from function entry
9465 point, even if values of one or both are not available due to compiler
9468 #0 equal (val=5, val@@entry=5)
9469 #0 different (val=6, val@@entry=5)
9470 #0 lost (val=<optimized out>, val@@entry=5)
9471 #0 born (val=10, val@@entry=<optimized out>)
9472 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9476 Print the actual parameter value if it is known and also its value from
9477 function entry point if it is known. If neither is known, print for the actual
9478 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9479 values are known and identical, print the shortened
9480 @code{param=param@@entry=VALUE} notation.
9482 #0 equal (val=val@@entry=5)
9483 #0 different (val=6, val@@entry=5)
9484 #0 lost (val@@entry=5)
9486 #0 invalid (val=<optimized out>)
9490 Always print the actual parameter value. Print also its value from function
9491 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9492 if both values are known and identical, print the shortened
9493 @code{param=param@@entry=VALUE} notation.
9495 #0 equal (val=val@@entry=5)
9496 #0 different (val=6, val@@entry=5)
9497 #0 lost (val=<optimized out>, val@@entry=5)
9499 #0 invalid (val=<optimized out>)
9503 For analysis messages on possible failures of frame argument values at function
9504 entry resolution see @ref{set debug entry-values}.
9506 @item show print entry-values
9507 Show the method being used for printing of frame argument values at function
9510 @item set print repeats @var{number-of-repeats}
9511 @itemx set print repeats unlimited
9512 @cindex repeated array elements
9513 Set the threshold for suppressing display of repeated array
9514 elements. When the number of consecutive identical elements of an
9515 array exceeds the threshold, @value{GDBN} prints the string
9516 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9517 identical repetitions, instead of displaying the identical elements
9518 themselves. Setting the threshold to @code{unlimited} or zero will
9519 cause all elements to be individually printed. The default threshold
9522 @item show print repeats
9523 Display the current threshold for printing repeated identical
9526 @item set print null-stop
9527 @cindex @sc{null} elements in arrays
9528 Cause @value{GDBN} to stop printing the characters of an array when the first
9529 @sc{null} is encountered. This is useful when large arrays actually
9530 contain only short strings.
9533 @item show print null-stop
9534 Show whether @value{GDBN} stops printing an array on the first
9535 @sc{null} character.
9537 @item set print pretty on
9538 @cindex print structures in indented form
9539 @cindex indentation in structure display
9540 Cause @value{GDBN} to print structures in an indented format with one member
9541 per line, like this:
9556 @item set print pretty off
9557 Cause @value{GDBN} to print structures in a compact format, like this:
9561 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9562 meat = 0x54 "Pork"@}
9567 This is the default format.
9569 @item show print pretty
9570 Show which format @value{GDBN} is using to print structures.
9572 @item set print sevenbit-strings on
9573 @cindex eight-bit characters in strings
9574 @cindex octal escapes in strings
9575 Print using only seven-bit characters; if this option is set,
9576 @value{GDBN} displays any eight-bit characters (in strings or
9577 character values) using the notation @code{\}@var{nnn}. This setting is
9578 best if you are working in English (@sc{ascii}) and you use the
9579 high-order bit of characters as a marker or ``meta'' bit.
9581 @item set print sevenbit-strings off
9582 Print full eight-bit characters. This allows the use of more
9583 international character sets, and is the default.
9585 @item show print sevenbit-strings
9586 Show whether or not @value{GDBN} is printing only seven-bit characters.
9588 @item set print union on
9589 @cindex unions in structures, printing
9590 Tell @value{GDBN} to print unions which are contained in structures
9591 and other unions. This is the default setting.
9593 @item set print union off
9594 Tell @value{GDBN} not to print unions which are contained in
9595 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9598 @item show print union
9599 Ask @value{GDBN} whether or not it will print unions which are contained in
9600 structures and other unions.
9602 For example, given the declarations
9605 typedef enum @{Tree, Bug@} Species;
9606 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9607 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9618 struct thing foo = @{Tree, @{Acorn@}@};
9622 with @code{set print union on} in effect @samp{p foo} would print
9625 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9629 and with @code{set print union off} in effect it would print
9632 $1 = @{it = Tree, form = @{...@}@}
9636 @code{set print union} affects programs written in C-like languages
9642 These settings are of interest when debugging C@t{++} programs:
9645 @cindex demangling C@t{++} names
9646 @item set print demangle
9647 @itemx set print demangle on
9648 Print C@t{++} names in their source form rather than in the encoded
9649 (``mangled'') form passed to the assembler and linker for type-safe
9650 linkage. The default is on.
9652 @item show print demangle
9653 Show whether C@t{++} names are printed in mangled or demangled form.
9655 @item set print asm-demangle
9656 @itemx set print asm-demangle on
9657 Print C@t{++} names in their source form rather than their mangled form, even
9658 in assembler code printouts such as instruction disassemblies.
9661 @item show print asm-demangle
9662 Show whether C@t{++} names in assembly listings are printed in mangled
9665 @cindex C@t{++} symbol decoding style
9666 @cindex symbol decoding style, C@t{++}
9667 @kindex set demangle-style
9668 @item set demangle-style @var{style}
9669 Choose among several encoding schemes used by different compilers to
9670 represent C@t{++} names. The choices for @var{style} are currently:
9674 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9675 This is the default.
9678 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9681 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9684 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9687 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9688 @strong{Warning:} this setting alone is not sufficient to allow
9689 debugging @code{cfront}-generated executables. @value{GDBN} would
9690 require further enhancement to permit that.
9693 If you omit @var{style}, you will see a list of possible formats.
9695 @item show demangle-style
9696 Display the encoding style currently in use for decoding C@t{++} symbols.
9698 @item set print object
9699 @itemx set print object on
9700 @cindex derived type of an object, printing
9701 @cindex display derived types
9702 When displaying a pointer to an object, identify the @emph{actual}
9703 (derived) type of the object rather than the @emph{declared} type, using
9704 the virtual function table. Note that the virtual function table is
9705 required---this feature can only work for objects that have run-time
9706 type identification; a single virtual method in the object's declared
9707 type is sufficient. Note that this setting is also taken into account when
9708 working with variable objects via MI (@pxref{GDB/MI}).
9710 @item set print object off
9711 Display only the declared type of objects, without reference to the
9712 virtual function table. This is the default setting.
9714 @item show print object
9715 Show whether actual, or declared, object types are displayed.
9717 @item set print static-members
9718 @itemx set print static-members on
9719 @cindex static members of C@t{++} objects
9720 Print static members when displaying a C@t{++} object. The default is on.
9722 @item set print static-members off
9723 Do not print static members when displaying a C@t{++} object.
9725 @item show print static-members
9726 Show whether C@t{++} static members are printed or not.
9728 @item set print pascal_static-members
9729 @itemx set print pascal_static-members on
9730 @cindex static members of Pascal objects
9731 @cindex Pascal objects, static members display
9732 Print static members when displaying a Pascal object. The default is on.
9734 @item set print pascal_static-members off
9735 Do not print static members when displaying a Pascal object.
9737 @item show print pascal_static-members
9738 Show whether Pascal static members are printed or not.
9740 @c These don't work with HP ANSI C++ yet.
9741 @item set print vtbl
9742 @itemx set print vtbl on
9743 @cindex pretty print C@t{++} virtual function tables
9744 @cindex virtual functions (C@t{++}) display
9745 @cindex VTBL display
9746 Pretty print C@t{++} virtual function tables. The default is off.
9747 (The @code{vtbl} commands do not work on programs compiled with the HP
9748 ANSI C@t{++} compiler (@code{aCC}).)
9750 @item set print vtbl off
9751 Do not pretty print C@t{++} virtual function tables.
9753 @item show print vtbl
9754 Show whether C@t{++} virtual function tables are pretty printed, or not.
9757 @node Pretty Printing
9758 @section Pretty Printing
9760 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9761 Python code. It greatly simplifies the display of complex objects. This
9762 mechanism works for both MI and the CLI.
9765 * Pretty-Printer Introduction:: Introduction to pretty-printers
9766 * Pretty-Printer Example:: An example pretty-printer
9767 * Pretty-Printer Commands:: Pretty-printer commands
9770 @node Pretty-Printer Introduction
9771 @subsection Pretty-Printer Introduction
9773 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9774 registered for the value. If there is then @value{GDBN} invokes the
9775 pretty-printer to print the value. Otherwise the value is printed normally.
9777 Pretty-printers are normally named. This makes them easy to manage.
9778 The @samp{info pretty-printer} command will list all the installed
9779 pretty-printers with their names.
9780 If a pretty-printer can handle multiple data types, then its
9781 @dfn{subprinters} are the printers for the individual data types.
9782 Each such subprinter has its own name.
9783 The format of the name is @var{printer-name};@var{subprinter-name}.
9785 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9786 Typically they are automatically loaded and registered when the corresponding
9787 debug information is loaded, thus making them available without having to
9788 do anything special.
9790 There are three places where a pretty-printer can be registered.
9794 Pretty-printers registered globally are available when debugging
9798 Pretty-printers registered with a program space are available only
9799 when debugging that program.
9800 @xref{Progspaces In Python}, for more details on program spaces in Python.
9803 Pretty-printers registered with an objfile are loaded and unloaded
9804 with the corresponding objfile (e.g., shared library).
9805 @xref{Objfiles In Python}, for more details on objfiles in Python.
9808 @xref{Selecting Pretty-Printers}, for further information on how
9809 pretty-printers are selected,
9811 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9814 @node Pretty-Printer Example
9815 @subsection Pretty-Printer Example
9817 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9820 (@value{GDBP}) print s
9822 static npos = 4294967295,
9824 <std::allocator<char>> = @{
9825 <__gnu_cxx::new_allocator<char>> = @{
9826 <No data fields>@}, <No data fields>
9828 members of std::basic_string<char, std::char_traits<char>,
9829 std::allocator<char> >::_Alloc_hider:
9830 _M_p = 0x804a014 "abcd"
9835 With a pretty-printer for @code{std::string} only the contents are printed:
9838 (@value{GDBP}) print s
9842 @node Pretty-Printer Commands
9843 @subsection Pretty-Printer Commands
9844 @cindex pretty-printer commands
9847 @kindex info pretty-printer
9848 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9849 Print the list of installed pretty-printers.
9850 This includes disabled pretty-printers, which are marked as such.
9852 @var{object-regexp} is a regular expression matching the objects
9853 whose pretty-printers to list.
9854 Objects can be @code{global}, the program space's file
9855 (@pxref{Progspaces In Python}),
9856 and the object files within that program space (@pxref{Objfiles In Python}).
9857 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9858 looks up a printer from these three objects.
9860 @var{name-regexp} is a regular expression matching the name of the printers
9863 @kindex disable pretty-printer
9864 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9865 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9866 A disabled pretty-printer is not forgotten, it may be enabled again later.
9868 @kindex enable pretty-printer
9869 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9870 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9875 Suppose we have three pretty-printers installed: one from library1.so
9876 named @code{foo} that prints objects of type @code{foo}, and
9877 another from library2.so named @code{bar} that prints two types of objects,
9878 @code{bar1} and @code{bar2}.
9881 (gdb) info pretty-printer
9888 (gdb) info pretty-printer library2
9893 (gdb) disable pretty-printer library1
9895 2 of 3 printers enabled
9896 (gdb) info pretty-printer
9903 (gdb) disable pretty-printer library2 bar:bar1
9905 1 of 3 printers enabled
9906 (gdb) info pretty-printer library2
9913 (gdb) disable pretty-printer library2 bar
9915 0 of 3 printers enabled
9916 (gdb) info pretty-printer library2
9925 Note that for @code{bar} the entire printer can be disabled,
9926 as can each individual subprinter.
9929 @section Value History
9931 @cindex value history
9932 @cindex history of values printed by @value{GDBN}
9933 Values printed by the @code{print} command are saved in the @value{GDBN}
9934 @dfn{value history}. This allows you to refer to them in other expressions.
9935 Values are kept until the symbol table is re-read or discarded
9936 (for example with the @code{file} or @code{symbol-file} commands).
9937 When the symbol table changes, the value history is discarded,
9938 since the values may contain pointers back to the types defined in the
9943 @cindex history number
9944 The values printed are given @dfn{history numbers} by which you can
9945 refer to them. These are successive integers starting with one.
9946 @code{print} shows you the history number assigned to a value by
9947 printing @samp{$@var{num} = } before the value; here @var{num} is the
9950 To refer to any previous value, use @samp{$} followed by the value's
9951 history number. The way @code{print} labels its output is designed to
9952 remind you of this. Just @code{$} refers to the most recent value in
9953 the history, and @code{$$} refers to the value before that.
9954 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9955 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9956 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9958 For example, suppose you have just printed a pointer to a structure and
9959 want to see the contents of the structure. It suffices to type
9965 If you have a chain of structures where the component @code{next} points
9966 to the next one, you can print the contents of the next one with this:
9973 You can print successive links in the chain by repeating this
9974 command---which you can do by just typing @key{RET}.
9976 Note that the history records values, not expressions. If the value of
9977 @code{x} is 4 and you type these commands:
9985 then the value recorded in the value history by the @code{print} command
9986 remains 4 even though the value of @code{x} has changed.
9991 Print the last ten values in the value history, with their item numbers.
9992 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9993 values} does not change the history.
9995 @item show values @var{n}
9996 Print ten history values centered on history item number @var{n}.
9999 Print ten history values just after the values last printed. If no more
10000 values are available, @code{show values +} produces no display.
10003 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10004 same effect as @samp{show values +}.
10006 @node Convenience Vars
10007 @section Convenience Variables
10009 @cindex convenience variables
10010 @cindex user-defined variables
10011 @value{GDBN} provides @dfn{convenience variables} that you can use within
10012 @value{GDBN} to hold on to a value and refer to it later. These variables
10013 exist entirely within @value{GDBN}; they are not part of your program, and
10014 setting a convenience variable has no direct effect on further execution
10015 of your program. That is why you can use them freely.
10017 Convenience variables are prefixed with @samp{$}. Any name preceded by
10018 @samp{$} can be used for a convenience variable, unless it is one of
10019 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10020 (Value history references, in contrast, are @emph{numbers} preceded
10021 by @samp{$}. @xref{Value History, ,Value History}.)
10023 You can save a value in a convenience variable with an assignment
10024 expression, just as you would set a variable in your program.
10028 set $foo = *object_ptr
10032 would save in @code{$foo} the value contained in the object pointed to by
10035 Using a convenience variable for the first time creates it, but its
10036 value is @code{void} until you assign a new value. You can alter the
10037 value with another assignment at any time.
10039 Convenience variables have no fixed types. You can assign a convenience
10040 variable any type of value, including structures and arrays, even if
10041 that variable already has a value of a different type. The convenience
10042 variable, when used as an expression, has the type of its current value.
10045 @kindex show convenience
10046 @cindex show all user variables and functions
10047 @item show convenience
10048 Print a list of convenience variables used so far, and their values,
10049 as well as a list of the convenience functions.
10050 Abbreviated @code{show conv}.
10052 @kindex init-if-undefined
10053 @cindex convenience variables, initializing
10054 @item init-if-undefined $@var{variable} = @var{expression}
10055 Set a convenience variable if it has not already been set. This is useful
10056 for user-defined commands that keep some state. It is similar, in concept,
10057 to using local static variables with initializers in C (except that
10058 convenience variables are global). It can also be used to allow users to
10059 override default values used in a command script.
10061 If the variable is already defined then the expression is not evaluated so
10062 any side-effects do not occur.
10065 One of the ways to use a convenience variable is as a counter to be
10066 incremented or a pointer to be advanced. For example, to print
10067 a field from successive elements of an array of structures:
10071 print bar[$i++]->contents
10075 Repeat that command by typing @key{RET}.
10077 Some convenience variables are created automatically by @value{GDBN} and given
10078 values likely to be useful.
10081 @vindex $_@r{, convenience variable}
10083 The variable @code{$_} is automatically set by the @code{x} command to
10084 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10085 commands which provide a default address for @code{x} to examine also
10086 set @code{$_} to that address; these commands include @code{info line}
10087 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10088 except when set by the @code{x} command, in which case it is a pointer
10089 to the type of @code{$__}.
10091 @vindex $__@r{, convenience variable}
10093 The variable @code{$__} is automatically set by the @code{x} command
10094 to the value found in the last address examined. Its type is chosen
10095 to match the format in which the data was printed.
10098 @vindex $_exitcode@r{, convenience variable}
10099 When the program being debugged terminates normally, @value{GDBN}
10100 automatically sets this variable to the exit code of the program, and
10101 resets @code{$_exitsignal} to @code{void}.
10104 @vindex $_exitsignal@r{, convenience variable}
10105 When the program being debugged dies due to an uncaught signal,
10106 @value{GDBN} automatically sets this variable to that signal's number,
10107 and resets @code{$_exitcode} to @code{void}.
10109 To distinguish between whether the program being debugged has exited
10110 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10111 @code{$_exitsignal} is not @code{void}), the convenience function
10112 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10113 Functions}). For example, considering the following source code:
10116 #include <signal.h>
10119 main (int argc, char *argv[])
10126 A valid way of telling whether the program being debugged has exited
10127 or signalled would be:
10130 (@value{GDBP}) define has_exited_or_signalled
10131 Type commands for definition of ``has_exited_or_signalled''.
10132 End with a line saying just ``end''.
10133 >if $_isvoid ($_exitsignal)
10134 >echo The program has exited\n
10136 >echo The program has signalled\n
10142 Program terminated with signal SIGALRM, Alarm clock.
10143 The program no longer exists.
10144 (@value{GDBP}) has_exited_or_signalled
10145 The program has signalled
10148 As can be seen, @value{GDBN} correctly informs that the program being
10149 debugged has signalled, since it calls @code{raise} and raises a
10150 @code{SIGALRM} signal. If the program being debugged had not called
10151 @code{raise}, then @value{GDBN} would report a normal exit:
10154 (@value{GDBP}) has_exited_or_signalled
10155 The program has exited
10159 The variable @code{$_exception} is set to the exception object being
10160 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10163 @itemx $_probe_arg0@dots{}$_probe_arg11
10164 Arguments to a static probe. @xref{Static Probe Points}.
10167 @vindex $_sdata@r{, inspect, convenience variable}
10168 The variable @code{$_sdata} contains extra collected static tracepoint
10169 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10170 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10171 if extra static tracepoint data has not been collected.
10174 @vindex $_siginfo@r{, convenience variable}
10175 The variable @code{$_siginfo} contains extra signal information
10176 (@pxref{extra signal information}). Note that @code{$_siginfo}
10177 could be empty, if the application has not yet received any signals.
10178 For example, it will be empty before you execute the @code{run} command.
10181 @vindex $_tlb@r{, convenience variable}
10182 The variable @code{$_tlb} is automatically set when debugging
10183 applications running on MS-Windows in native mode or connected to
10184 gdbserver that supports the @code{qGetTIBAddr} request.
10185 @xref{General Query Packets}.
10186 This variable contains the address of the thread information block.
10190 On HP-UX systems, if you refer to a function or variable name that
10191 begins with a dollar sign, @value{GDBN} searches for a user or system
10192 name first, before it searches for a convenience variable.
10194 @node Convenience Funs
10195 @section Convenience Functions
10197 @cindex convenience functions
10198 @value{GDBN} also supplies some @dfn{convenience functions}. These
10199 have a syntax similar to convenience variables. A convenience
10200 function can be used in an expression just like an ordinary function;
10201 however, a convenience function is implemented internally to
10204 These functions do not require @value{GDBN} to be configured with
10205 @code{Python} support, which means that they are always available.
10209 @item $_isvoid (@var{expr})
10210 @findex $_isvoid@r{, convenience function}
10211 Return one if the expression @var{expr} is @code{void}. Otherwise it
10214 A @code{void} expression is an expression where the type of the result
10215 is @code{void}. For example, you can examine a convenience variable
10216 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10220 (@value{GDBP}) print $_exitcode
10222 (@value{GDBP}) print $_isvoid ($_exitcode)
10225 Starting program: ./a.out
10226 [Inferior 1 (process 29572) exited normally]
10227 (@value{GDBP}) print $_exitcode
10229 (@value{GDBP}) print $_isvoid ($_exitcode)
10233 In the example above, we used @code{$_isvoid} to check whether
10234 @code{$_exitcode} is @code{void} before and after the execution of the
10235 program being debugged. Before the execution there is no exit code to
10236 be examined, therefore @code{$_exitcode} is @code{void}. After the
10237 execution the program being debugged returned zero, therefore
10238 @code{$_exitcode} is zero, which means that it is not @code{void}
10241 The @code{void} expression can also be a call of a function from the
10242 program being debugged. For example, given the following function:
10251 The result of calling it inside @value{GDBN} is @code{void}:
10254 (@value{GDBP}) print foo ()
10256 (@value{GDBP}) print $_isvoid (foo ())
10258 (@value{GDBP}) set $v = foo ()
10259 (@value{GDBP}) print $v
10261 (@value{GDBP}) print $_isvoid ($v)
10267 These functions require @value{GDBN} to be configured with
10268 @code{Python} support.
10272 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10273 @findex $_memeq@r{, convenience function}
10274 Returns one if the @var{length} bytes at the addresses given by
10275 @var{buf1} and @var{buf2} are equal.
10276 Otherwise it returns zero.
10278 @item $_regex(@var{str}, @var{regex})
10279 @findex $_regex@r{, convenience function}
10280 Returns one if the string @var{str} matches the regular expression
10281 @var{regex}. Otherwise it returns zero.
10282 The syntax of the regular expression is that specified by @code{Python}'s
10283 regular expression support.
10285 @item $_streq(@var{str1}, @var{str2})
10286 @findex $_streq@r{, convenience function}
10287 Returns one if the strings @var{str1} and @var{str2} are equal.
10288 Otherwise it returns zero.
10290 @item $_strlen(@var{str})
10291 @findex $_strlen@r{, convenience function}
10292 Returns the length of string @var{str}.
10294 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10295 @findex $_caller_is@r{, convenience function}
10296 Returns one if the calling function's name is equal to @var{name}.
10297 Otherwise it returns zero.
10299 If the optional argument @var{number_of_frames} is provided,
10300 it is the number of frames up in the stack to look.
10308 at testsuite/gdb.python/py-caller-is.c:21
10309 #1 0x00000000004005a0 in middle_func ()
10310 at testsuite/gdb.python/py-caller-is.c:27
10311 #2 0x00000000004005ab in top_func ()
10312 at testsuite/gdb.python/py-caller-is.c:33
10313 #3 0x00000000004005b6 in main ()
10314 at testsuite/gdb.python/py-caller-is.c:39
10315 (gdb) print $_caller_is ("middle_func")
10317 (gdb) print $_caller_is ("top_func", 2)
10321 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10322 @findex $_caller_matches@r{, convenience function}
10323 Returns one if the calling function's name matches the regular expression
10324 @var{regexp}. Otherwise it returns zero.
10326 If the optional argument @var{number_of_frames} is provided,
10327 it is the number of frames up in the stack to look.
10330 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10331 @findex $_any_caller_is@r{, convenience function}
10332 Returns one if any calling function's name is equal to @var{name}.
10333 Otherwise it returns zero.
10335 If the optional argument @var{number_of_frames} is provided,
10336 it is the number of frames up in the stack to look.
10339 This function differs from @code{$_caller_is} in that this function
10340 checks all stack frames from the immediate caller to the frame specified
10341 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10342 frame specified by @var{number_of_frames}.
10344 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10345 @findex $_any_caller_matches@r{, convenience function}
10346 Returns one if any calling function's name matches the regular expression
10347 @var{regexp}. Otherwise it returns zero.
10349 If the optional argument @var{number_of_frames} is provided,
10350 it is the number of frames up in the stack to look.
10353 This function differs from @code{$_caller_matches} in that this function
10354 checks all stack frames from the immediate caller to the frame specified
10355 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10356 frame specified by @var{number_of_frames}.
10360 @value{GDBN} provides the ability to list and get help on
10361 convenience functions.
10364 @item help function
10365 @kindex help function
10366 @cindex show all convenience functions
10367 Print a list of all convenience functions.
10374 You can refer to machine register contents, in expressions, as variables
10375 with names starting with @samp{$}. The names of registers are different
10376 for each machine; use @code{info registers} to see the names used on
10380 @kindex info registers
10381 @item info registers
10382 Print the names and values of all registers except floating-point
10383 and vector registers (in the selected stack frame).
10385 @kindex info all-registers
10386 @cindex floating point registers
10387 @item info all-registers
10388 Print the names and values of all registers, including floating-point
10389 and vector registers (in the selected stack frame).
10391 @item info registers @var{regname} @dots{}
10392 Print the @dfn{relativized} value of each specified register @var{regname}.
10393 As discussed in detail below, register values are normally relative to
10394 the selected stack frame. The @var{regname} may be any register name valid on
10395 the machine you are using, with or without the initial @samp{$}.
10398 @anchor{standard registers}
10399 @cindex stack pointer register
10400 @cindex program counter register
10401 @cindex process status register
10402 @cindex frame pointer register
10403 @cindex standard registers
10404 @value{GDBN} has four ``standard'' register names that are available (in
10405 expressions) on most machines---whenever they do not conflict with an
10406 architecture's canonical mnemonics for registers. The register names
10407 @code{$pc} and @code{$sp} are used for the program counter register and
10408 the stack pointer. @code{$fp} is used for a register that contains a
10409 pointer to the current stack frame, and @code{$ps} is used for a
10410 register that contains the processor status. For example,
10411 you could print the program counter in hex with
10418 or print the instruction to be executed next with
10425 or add four to the stack pointer@footnote{This is a way of removing
10426 one word from the stack, on machines where stacks grow downward in
10427 memory (most machines, nowadays). This assumes that the innermost
10428 stack frame is selected; setting @code{$sp} is not allowed when other
10429 stack frames are selected. To pop entire frames off the stack,
10430 regardless of machine architecture, use @code{return};
10431 see @ref{Returning, ,Returning from a Function}.} with
10437 Whenever possible, these four standard register names are available on
10438 your machine even though the machine has different canonical mnemonics,
10439 so long as there is no conflict. The @code{info registers} command
10440 shows the canonical names. For example, on the SPARC, @code{info
10441 registers} displays the processor status register as @code{$psr} but you
10442 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10443 is an alias for the @sc{eflags} register.
10445 @value{GDBN} always considers the contents of an ordinary register as an
10446 integer when the register is examined in this way. Some machines have
10447 special registers which can hold nothing but floating point; these
10448 registers are considered to have floating point values. There is no way
10449 to refer to the contents of an ordinary register as floating point value
10450 (although you can @emph{print} it as a floating point value with
10451 @samp{print/f $@var{regname}}).
10453 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10454 means that the data format in which the register contents are saved by
10455 the operating system is not the same one that your program normally
10456 sees. For example, the registers of the 68881 floating point
10457 coprocessor are always saved in ``extended'' (raw) format, but all C
10458 programs expect to work with ``double'' (virtual) format. In such
10459 cases, @value{GDBN} normally works with the virtual format only (the format
10460 that makes sense for your program), but the @code{info registers} command
10461 prints the data in both formats.
10463 @cindex SSE registers (x86)
10464 @cindex MMX registers (x86)
10465 Some machines have special registers whose contents can be interpreted
10466 in several different ways. For example, modern x86-based machines
10467 have SSE and MMX registers that can hold several values packed
10468 together in several different formats. @value{GDBN} refers to such
10469 registers in @code{struct} notation:
10472 (@value{GDBP}) print $xmm1
10474 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10475 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10476 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10477 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10478 v4_int32 = @{0, 20657912, 11, 13@},
10479 v2_int64 = @{88725056443645952, 55834574859@},
10480 uint128 = 0x0000000d0000000b013b36f800000000
10485 To set values of such registers, you need to tell @value{GDBN} which
10486 view of the register you wish to change, as if you were assigning
10487 value to a @code{struct} member:
10490 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10493 Normally, register values are relative to the selected stack frame
10494 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10495 value that the register would contain if all stack frames farther in
10496 were exited and their saved registers restored. In order to see the
10497 true contents of hardware registers, you must select the innermost
10498 frame (with @samp{frame 0}).
10500 @cindex caller-saved registers
10501 @cindex call-clobbered registers
10502 @cindex volatile registers
10503 @cindex <not saved> values
10504 Usually ABIs reserve some registers as not needed to be saved by the
10505 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10506 registers). It may therefore not be possible for @value{GDBN} to know
10507 the value a register had before the call (in other words, in the outer
10508 frame), if the register value has since been changed by the callee.
10509 @value{GDBN} tries to deduce where the inner frame saved
10510 (``callee-saved'') registers, from the debug info, unwind info, or the
10511 machine code generated by your compiler. If some register is not
10512 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10513 its own knowledge of the ABI, or because the debug/unwind info
10514 explicitly says the register's value is undefined), @value{GDBN}
10515 displays @w{@samp{<not saved>}} as the register's value. With targets
10516 that @value{GDBN} has no knowledge of the register saving convention,
10517 if a register was not saved by the callee, then its value and location
10518 in the outer frame are assumed to be the same of the inner frame.
10519 This is usually harmless, because if the register is call-clobbered,
10520 the caller either does not care what is in the register after the
10521 call, or has code to restore the value that it does care about. Note,
10522 however, that if you change such a register in the outer frame, you
10523 may also be affecting the inner frame. Also, the more ``outer'' the
10524 frame is you're looking at, the more likely a call-clobbered
10525 register's value is to be wrong, in the sense that it doesn't actually
10526 represent the value the register had just before the call.
10528 @node Floating Point Hardware
10529 @section Floating Point Hardware
10530 @cindex floating point
10532 Depending on the configuration, @value{GDBN} may be able to give
10533 you more information about the status of the floating point hardware.
10538 Display hardware-dependent information about the floating
10539 point unit. The exact contents and layout vary depending on the
10540 floating point chip. Currently, @samp{info float} is supported on
10541 the ARM and x86 machines.
10545 @section Vector Unit
10546 @cindex vector unit
10548 Depending on the configuration, @value{GDBN} may be able to give you
10549 more information about the status of the vector unit.
10552 @kindex info vector
10554 Display information about the vector unit. The exact contents and
10555 layout vary depending on the hardware.
10558 @node OS Information
10559 @section Operating System Auxiliary Information
10560 @cindex OS information
10562 @value{GDBN} provides interfaces to useful OS facilities that can help
10563 you debug your program.
10565 @cindex auxiliary vector
10566 @cindex vector, auxiliary
10567 Some operating systems supply an @dfn{auxiliary vector} to programs at
10568 startup. This is akin to the arguments and environment that you
10569 specify for a program, but contains a system-dependent variety of
10570 binary values that tell system libraries important details about the
10571 hardware, operating system, and process. Each value's purpose is
10572 identified by an integer tag; the meanings are well-known but system-specific.
10573 Depending on the configuration and operating system facilities,
10574 @value{GDBN} may be able to show you this information. For remote
10575 targets, this functionality may further depend on the remote stub's
10576 support of the @samp{qXfer:auxv:read} packet, see
10577 @ref{qXfer auxiliary vector read}.
10582 Display the auxiliary vector of the inferior, which can be either a
10583 live process or a core dump file. @value{GDBN} prints each tag value
10584 numerically, and also shows names and text descriptions for recognized
10585 tags. Some values in the vector are numbers, some bit masks, and some
10586 pointers to strings or other data. @value{GDBN} displays each value in the
10587 most appropriate form for a recognized tag, and in hexadecimal for
10588 an unrecognized tag.
10591 On some targets, @value{GDBN} can access operating system-specific
10592 information and show it to you. The types of information available
10593 will differ depending on the type of operating system running on the
10594 target. The mechanism used to fetch the data is described in
10595 @ref{Operating System Information}. For remote targets, this
10596 functionality depends on the remote stub's support of the
10597 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10601 @item info os @var{infotype}
10603 Display OS information of the requested type.
10605 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10607 @anchor{linux info os infotypes}
10609 @kindex info os processes
10611 Display the list of processes on the target. For each process,
10612 @value{GDBN} prints the process identifier, the name of the user, the
10613 command corresponding to the process, and the list of processor cores
10614 that the process is currently running on. (To understand what these
10615 properties mean, for this and the following info types, please consult
10616 the general @sc{gnu}/Linux documentation.)
10618 @kindex info os procgroups
10620 Display the list of process groups on the target. For each process,
10621 @value{GDBN} prints the identifier of the process group that it belongs
10622 to, the command corresponding to the process group leader, the process
10623 identifier, and the command line of the process. The list is sorted
10624 first by the process group identifier, then by the process identifier,
10625 so that processes belonging to the same process group are grouped together
10626 and the process group leader is listed first.
10628 @kindex info os threads
10630 Display the list of threads running on the target. For each thread,
10631 @value{GDBN} prints the identifier of the process that the thread
10632 belongs to, the command of the process, the thread identifier, and the
10633 processor core that it is currently running on. The main thread of a
10634 process is not listed.
10636 @kindex info os files
10638 Display the list of open file descriptors on the target. For each
10639 file descriptor, @value{GDBN} prints the identifier of the process
10640 owning the descriptor, the command of the owning process, the value
10641 of the descriptor, and the target of the descriptor.
10643 @kindex info os sockets
10645 Display the list of Internet-domain sockets on the target. For each
10646 socket, @value{GDBN} prints the address and port of the local and
10647 remote endpoints, the current state of the connection, the creator of
10648 the socket, the IP address family of the socket, and the type of the
10651 @kindex info os shm
10653 Display the list of all System V shared-memory regions on the target.
10654 For each shared-memory region, @value{GDBN} prints the region key,
10655 the shared-memory identifier, the access permissions, the size of the
10656 region, the process that created the region, the process that last
10657 attached to or detached from the region, the current number of live
10658 attaches to the region, and the times at which the region was last
10659 attached to, detach from, and changed.
10661 @kindex info os semaphores
10663 Display the list of all System V semaphore sets on the target. For each
10664 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10665 set identifier, the access permissions, the number of semaphores in the
10666 set, the user and group of the owner and creator of the semaphore set,
10667 and the times at which the semaphore set was operated upon and changed.
10669 @kindex info os msg
10671 Display the list of all System V message queues on the target. For each
10672 message queue, @value{GDBN} prints the message queue key, the message
10673 queue identifier, the access permissions, the current number of bytes
10674 on the queue, the current number of messages on the queue, the processes
10675 that last sent and received a message on the queue, the user and group
10676 of the owner and creator of the message queue, the times at which a
10677 message was last sent and received on the queue, and the time at which
10678 the message queue was last changed.
10680 @kindex info os modules
10682 Display the list of all loaded kernel modules on the target. For each
10683 module, @value{GDBN} prints the module name, the size of the module in
10684 bytes, the number of times the module is used, the dependencies of the
10685 module, the status of the module, and the address of the loaded module
10690 If @var{infotype} is omitted, then list the possible values for
10691 @var{infotype} and the kind of OS information available for each
10692 @var{infotype}. If the target does not return a list of possible
10693 types, this command will report an error.
10696 @node Memory Region Attributes
10697 @section Memory Region Attributes
10698 @cindex memory region attributes
10700 @dfn{Memory region attributes} allow you to describe special handling
10701 required by regions of your target's memory. @value{GDBN} uses
10702 attributes to determine whether to allow certain types of memory
10703 accesses; whether to use specific width accesses; and whether to cache
10704 target memory. By default the description of memory regions is
10705 fetched from the target (if the current target supports this), but the
10706 user can override the fetched regions.
10708 Defined memory regions can be individually enabled and disabled. When a
10709 memory region is disabled, @value{GDBN} uses the default attributes when
10710 accessing memory in that region. Similarly, if no memory regions have
10711 been defined, @value{GDBN} uses the default attributes when accessing
10714 When a memory region is defined, it is given a number to identify it;
10715 to enable, disable, or remove a memory region, you specify that number.
10719 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10720 Define a memory region bounded by @var{lower} and @var{upper} with
10721 attributes @var{attributes}@dots{}, and add it to the list of regions
10722 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10723 case: it is treated as the target's maximum memory address.
10724 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10727 Discard any user changes to the memory regions and use target-supplied
10728 regions, if available, or no regions if the target does not support.
10731 @item delete mem @var{nums}@dots{}
10732 Remove memory regions @var{nums}@dots{} from the list of regions
10733 monitored by @value{GDBN}.
10735 @kindex disable mem
10736 @item disable mem @var{nums}@dots{}
10737 Disable monitoring of memory regions @var{nums}@dots{}.
10738 A disabled memory region is not forgotten.
10739 It may be enabled again later.
10742 @item enable mem @var{nums}@dots{}
10743 Enable monitoring of memory regions @var{nums}@dots{}.
10747 Print a table of all defined memory regions, with the following columns
10751 @item Memory Region Number
10752 @item Enabled or Disabled.
10753 Enabled memory regions are marked with @samp{y}.
10754 Disabled memory regions are marked with @samp{n}.
10757 The address defining the inclusive lower bound of the memory region.
10760 The address defining the exclusive upper bound of the memory region.
10763 The list of attributes set for this memory region.
10768 @subsection Attributes
10770 @subsubsection Memory Access Mode
10771 The access mode attributes set whether @value{GDBN} may make read or
10772 write accesses to a memory region.
10774 While these attributes prevent @value{GDBN} from performing invalid
10775 memory accesses, they do nothing to prevent the target system, I/O DMA,
10776 etc.@: from accessing memory.
10780 Memory is read only.
10782 Memory is write only.
10784 Memory is read/write. This is the default.
10787 @subsubsection Memory Access Size
10788 The access size attribute tells @value{GDBN} to use specific sized
10789 accesses in the memory region. Often memory mapped device registers
10790 require specific sized accesses. If no access size attribute is
10791 specified, @value{GDBN} may use accesses of any size.
10795 Use 8 bit memory accesses.
10797 Use 16 bit memory accesses.
10799 Use 32 bit memory accesses.
10801 Use 64 bit memory accesses.
10804 @c @subsubsection Hardware/Software Breakpoints
10805 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10806 @c will use hardware or software breakpoints for the internal breakpoints
10807 @c used by the step, next, finish, until, etc. commands.
10811 @c Always use hardware breakpoints
10812 @c @item swbreak (default)
10815 @subsubsection Data Cache
10816 The data cache attributes set whether @value{GDBN} will cache target
10817 memory. While this generally improves performance by reducing debug
10818 protocol overhead, it can lead to incorrect results because @value{GDBN}
10819 does not know about volatile variables or memory mapped device
10824 Enable @value{GDBN} to cache target memory.
10826 Disable @value{GDBN} from caching target memory. This is the default.
10829 @subsection Memory Access Checking
10830 @value{GDBN} can be instructed to refuse accesses to memory that is
10831 not explicitly described. This can be useful if accessing such
10832 regions has undesired effects for a specific target, or to provide
10833 better error checking. The following commands control this behaviour.
10836 @kindex set mem inaccessible-by-default
10837 @item set mem inaccessible-by-default [on|off]
10838 If @code{on} is specified, make @value{GDBN} treat memory not
10839 explicitly described by the memory ranges as non-existent and refuse accesses
10840 to such memory. The checks are only performed if there's at least one
10841 memory range defined. If @code{off} is specified, make @value{GDBN}
10842 treat the memory not explicitly described by the memory ranges as RAM.
10843 The default value is @code{on}.
10844 @kindex show mem inaccessible-by-default
10845 @item show mem inaccessible-by-default
10846 Show the current handling of accesses to unknown memory.
10850 @c @subsubsection Memory Write Verification
10851 @c The memory write verification attributes set whether @value{GDBN}
10852 @c will re-reads data after each write to verify the write was successful.
10856 @c @item noverify (default)
10859 @node Dump/Restore Files
10860 @section Copy Between Memory and a File
10861 @cindex dump/restore files
10862 @cindex append data to a file
10863 @cindex dump data to a file
10864 @cindex restore data from a file
10866 You can use the commands @code{dump}, @code{append}, and
10867 @code{restore} to copy data between target memory and a file. The
10868 @code{dump} and @code{append} commands write data to a file, and the
10869 @code{restore} command reads data from a file back into the inferior's
10870 memory. Files may be in binary, Motorola S-record, Intel hex, or
10871 Tektronix Hex format; however, @value{GDBN} can only append to binary
10877 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10878 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10879 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10880 or the value of @var{expr}, to @var{filename} in the given format.
10882 The @var{format} parameter may be any one of:
10889 Motorola S-record format.
10891 Tektronix Hex format.
10894 @value{GDBN} uses the same definitions of these formats as the
10895 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10896 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10900 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10901 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10902 Append the contents of memory from @var{start_addr} to @var{end_addr},
10903 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10904 (@value{GDBN} can only append data to files in raw binary form.)
10907 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10908 Restore the contents of file @var{filename} into memory. The
10909 @code{restore} command can automatically recognize any known @sc{bfd}
10910 file format, except for raw binary. To restore a raw binary file you
10911 must specify the optional keyword @code{binary} after the filename.
10913 If @var{bias} is non-zero, its value will be added to the addresses
10914 contained in the file. Binary files always start at address zero, so
10915 they will be restored at address @var{bias}. Other bfd files have
10916 a built-in location; they will be restored at offset @var{bias}
10917 from that location.
10919 If @var{start} and/or @var{end} are non-zero, then only data between
10920 file offset @var{start} and file offset @var{end} will be restored.
10921 These offsets are relative to the addresses in the file, before
10922 the @var{bias} argument is applied.
10926 @node Core File Generation
10927 @section How to Produce a Core File from Your Program
10928 @cindex dump core from inferior
10930 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10931 image of a running process and its process status (register values
10932 etc.). Its primary use is post-mortem debugging of a program that
10933 crashed while it ran outside a debugger. A program that crashes
10934 automatically produces a core file, unless this feature is disabled by
10935 the user. @xref{Files}, for information on invoking @value{GDBN} in
10936 the post-mortem debugging mode.
10938 Occasionally, you may wish to produce a core file of the program you
10939 are debugging in order to preserve a snapshot of its state.
10940 @value{GDBN} has a special command for that.
10944 @kindex generate-core-file
10945 @item generate-core-file [@var{file}]
10946 @itemx gcore [@var{file}]
10947 Produce a core dump of the inferior process. The optional argument
10948 @var{file} specifies the file name where to put the core dump. If not
10949 specified, the file name defaults to @file{core.@var{pid}}, where
10950 @var{pid} is the inferior process ID.
10952 Note that this command is implemented only for some systems (as of
10953 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10956 @node Character Sets
10957 @section Character Sets
10958 @cindex character sets
10960 @cindex translating between character sets
10961 @cindex host character set
10962 @cindex target character set
10964 If the program you are debugging uses a different character set to
10965 represent characters and strings than the one @value{GDBN} uses itself,
10966 @value{GDBN} can automatically translate between the character sets for
10967 you. The character set @value{GDBN} uses we call the @dfn{host
10968 character set}; the one the inferior program uses we call the
10969 @dfn{target character set}.
10971 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10972 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10973 remote protocol (@pxref{Remote Debugging}) to debug a program
10974 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10975 then the host character set is Latin-1, and the target character set is
10976 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10977 target-charset EBCDIC-US}, then @value{GDBN} translates between
10978 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10979 character and string literals in expressions.
10981 @value{GDBN} has no way to automatically recognize which character set
10982 the inferior program uses; you must tell it, using the @code{set
10983 target-charset} command, described below.
10985 Here are the commands for controlling @value{GDBN}'s character set
10989 @item set target-charset @var{charset}
10990 @kindex set target-charset
10991 Set the current target character set to @var{charset}. To display the
10992 list of supported target character sets, type
10993 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10995 @item set host-charset @var{charset}
10996 @kindex set host-charset
10997 Set the current host character set to @var{charset}.
10999 By default, @value{GDBN} uses a host character set appropriate to the
11000 system it is running on; you can override that default using the
11001 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11002 automatically determine the appropriate host character set. In this
11003 case, @value{GDBN} uses @samp{UTF-8}.
11005 @value{GDBN} can only use certain character sets as its host character
11006 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11007 @value{GDBN} will list the host character sets it supports.
11009 @item set charset @var{charset}
11010 @kindex set charset
11011 Set the current host and target character sets to @var{charset}. As
11012 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11013 @value{GDBN} will list the names of the character sets that can be used
11014 for both host and target.
11017 @kindex show charset
11018 Show the names of the current host and target character sets.
11020 @item show host-charset
11021 @kindex show host-charset
11022 Show the name of the current host character set.
11024 @item show target-charset
11025 @kindex show target-charset
11026 Show the name of the current target character set.
11028 @item set target-wide-charset @var{charset}
11029 @kindex set target-wide-charset
11030 Set the current target's wide character set to @var{charset}. This is
11031 the character set used by the target's @code{wchar_t} type. To
11032 display the list of supported wide character sets, type
11033 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11035 @item show target-wide-charset
11036 @kindex show target-wide-charset
11037 Show the name of the current target's wide character set.
11040 Here is an example of @value{GDBN}'s character set support in action.
11041 Assume that the following source code has been placed in the file
11042 @file{charset-test.c}:
11048 = @{72, 101, 108, 108, 111, 44, 32, 119,
11049 111, 114, 108, 100, 33, 10, 0@};
11050 char ibm1047_hello[]
11051 = @{200, 133, 147, 147, 150, 107, 64, 166,
11052 150, 153, 147, 132, 90, 37, 0@};
11056 printf ("Hello, world!\n");
11060 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11061 containing the string @samp{Hello, world!} followed by a newline,
11062 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11064 We compile the program, and invoke the debugger on it:
11067 $ gcc -g charset-test.c -o charset-test
11068 $ gdb -nw charset-test
11069 GNU gdb 2001-12-19-cvs
11070 Copyright 2001 Free Software Foundation, Inc.
11075 We can use the @code{show charset} command to see what character sets
11076 @value{GDBN} is currently using to interpret and display characters and
11080 (@value{GDBP}) show charset
11081 The current host and target character set is `ISO-8859-1'.
11085 For the sake of printing this manual, let's use @sc{ascii} as our
11086 initial character set:
11088 (@value{GDBP}) set charset ASCII
11089 (@value{GDBP}) show charset
11090 The current host and target character set is `ASCII'.
11094 Let's assume that @sc{ascii} is indeed the correct character set for our
11095 host system --- in other words, let's assume that if @value{GDBN} prints
11096 characters using the @sc{ascii} character set, our terminal will display
11097 them properly. Since our current target character set is also
11098 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11101 (@value{GDBP}) print ascii_hello
11102 $1 = 0x401698 "Hello, world!\n"
11103 (@value{GDBP}) print ascii_hello[0]
11108 @value{GDBN} uses the target character set for character and string
11109 literals you use in expressions:
11112 (@value{GDBP}) print '+'
11117 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11120 @value{GDBN} relies on the user to tell it which character set the
11121 target program uses. If we print @code{ibm1047_hello} while our target
11122 character set is still @sc{ascii}, we get jibberish:
11125 (@value{GDBP}) print ibm1047_hello
11126 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11127 (@value{GDBP}) print ibm1047_hello[0]
11132 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11133 @value{GDBN} tells us the character sets it supports:
11136 (@value{GDBP}) set target-charset
11137 ASCII EBCDIC-US IBM1047 ISO-8859-1
11138 (@value{GDBP}) set target-charset
11141 We can select @sc{ibm1047} as our target character set, and examine the
11142 program's strings again. Now the @sc{ascii} string is wrong, but
11143 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11144 target character set, @sc{ibm1047}, to the host character set,
11145 @sc{ascii}, and they display correctly:
11148 (@value{GDBP}) set target-charset IBM1047
11149 (@value{GDBP}) show charset
11150 The current host character set is `ASCII'.
11151 The current target character set is `IBM1047'.
11152 (@value{GDBP}) print ascii_hello
11153 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11154 (@value{GDBP}) print ascii_hello[0]
11156 (@value{GDBP}) print ibm1047_hello
11157 $8 = 0x4016a8 "Hello, world!\n"
11158 (@value{GDBP}) print ibm1047_hello[0]
11163 As above, @value{GDBN} uses the target character set for character and
11164 string literals you use in expressions:
11167 (@value{GDBP}) print '+'
11172 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11175 @node Caching Target Data
11176 @section Caching Data of Targets
11177 @cindex caching data of targets
11179 @value{GDBN} caches data exchanged between the debugger and a target.
11180 Each cache is associated with the address space of the inferior.
11181 @xref{Inferiors and Programs}, about inferior and address space.
11182 Such caching generally improves performance in remote debugging
11183 (@pxref{Remote Debugging}), because it reduces the overhead of the
11184 remote protocol by bundling memory reads and writes into large chunks.
11185 Unfortunately, simply caching everything would lead to incorrect results,
11186 since @value{GDBN} does not necessarily know anything about volatile
11187 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11188 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11190 Therefore, by default, @value{GDBN} only caches data
11191 known to be on the stack@footnote{In non-stop mode, it is moderately
11192 rare for a running thread to modify the stack of a stopped thread
11193 in a way that would interfere with a backtrace, and caching of
11194 stack reads provides a significant speed up of remote backtraces.} or
11195 in the code segment.
11196 Other regions of memory can be explicitly marked as
11197 cacheable; @pxref{Memory Region Attributes}.
11200 @kindex set remotecache
11201 @item set remotecache on
11202 @itemx set remotecache off
11203 This option no longer does anything; it exists for compatibility
11206 @kindex show remotecache
11207 @item show remotecache
11208 Show the current state of the obsolete remotecache flag.
11210 @kindex set stack-cache
11211 @item set stack-cache on
11212 @itemx set stack-cache off
11213 Enable or disable caching of stack accesses. When @code{on}, use
11214 caching. By default, this option is @code{on}.
11216 @kindex show stack-cache
11217 @item show stack-cache
11218 Show the current state of data caching for memory accesses.
11220 @kindex set code-cache
11221 @item set code-cache on
11222 @itemx set code-cache off
11223 Enable or disable caching of code segment accesses. When @code{on},
11224 use caching. By default, this option is @code{on}. This improves
11225 performance of disassembly in remote debugging.
11227 @kindex show code-cache
11228 @item show code-cache
11229 Show the current state of target memory cache for code segment
11232 @kindex info dcache
11233 @item info dcache @r{[}line@r{]}
11234 Print the information about the performance of data cache of the
11235 current inferior's address space. The information displayed
11236 includes the dcache width and depth, and for each cache line, its
11237 number, address, and how many times it was referenced. This
11238 command is useful for debugging the data cache operation.
11240 If a line number is specified, the contents of that line will be
11243 @item set dcache size @var{size}
11244 @cindex dcache size
11245 @kindex set dcache size
11246 Set maximum number of entries in dcache (dcache depth above).
11248 @item set dcache line-size @var{line-size}
11249 @cindex dcache line-size
11250 @kindex set dcache line-size
11251 Set number of bytes each dcache entry caches (dcache width above).
11252 Must be a power of 2.
11254 @item show dcache size
11255 @kindex show dcache size
11256 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11258 @item show dcache line-size
11259 @kindex show dcache line-size
11260 Show default size of dcache lines.
11264 @node Searching Memory
11265 @section Search Memory
11266 @cindex searching memory
11268 Memory can be searched for a particular sequence of bytes with the
11269 @code{find} command.
11273 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11274 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11275 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11276 etc. The search begins at address @var{start_addr} and continues for either
11277 @var{len} bytes or through to @var{end_addr} inclusive.
11280 @var{s} and @var{n} are optional parameters.
11281 They may be specified in either order, apart or together.
11284 @item @var{s}, search query size
11285 The size of each search query value.
11291 halfwords (two bytes)
11295 giant words (eight bytes)
11298 All values are interpreted in the current language.
11299 This means, for example, that if the current source language is C/C@t{++}
11300 then searching for the string ``hello'' includes the trailing '\0'.
11302 If the value size is not specified, it is taken from the
11303 value's type in the current language.
11304 This is useful when one wants to specify the search
11305 pattern as a mixture of types.
11306 Note that this means, for example, that in the case of C-like languages
11307 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11308 which is typically four bytes.
11310 @item @var{n}, maximum number of finds
11311 The maximum number of matches to print. The default is to print all finds.
11314 You can use strings as search values. Quote them with double-quotes
11316 The string value is copied into the search pattern byte by byte,
11317 regardless of the endianness of the target and the size specification.
11319 The address of each match found is printed as well as a count of the
11320 number of matches found.
11322 The address of the last value found is stored in convenience variable
11324 A count of the number of matches is stored in @samp{$numfound}.
11326 For example, if stopped at the @code{printf} in this function:
11332 static char hello[] = "hello-hello";
11333 static struct @{ char c; short s; int i; @}
11334 __attribute__ ((packed)) mixed
11335 = @{ 'c', 0x1234, 0x87654321 @};
11336 printf ("%s\n", hello);
11341 you get during debugging:
11344 (gdb) find &hello[0], +sizeof(hello), "hello"
11345 0x804956d <hello.1620+6>
11347 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11348 0x8049567 <hello.1620>
11349 0x804956d <hello.1620+6>
11351 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11352 0x8049567 <hello.1620>
11354 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11355 0x8049560 <mixed.1625>
11357 (gdb) print $numfound
11360 $2 = (void *) 0x8049560
11363 @node Optimized Code
11364 @chapter Debugging Optimized Code
11365 @cindex optimized code, debugging
11366 @cindex debugging optimized code
11368 Almost all compilers support optimization. With optimization
11369 disabled, the compiler generates assembly code that corresponds
11370 directly to your source code, in a simplistic way. As the compiler
11371 applies more powerful optimizations, the generated assembly code
11372 diverges from your original source code. With help from debugging
11373 information generated by the compiler, @value{GDBN} can map from
11374 the running program back to constructs from your original source.
11376 @value{GDBN} is more accurate with optimization disabled. If you
11377 can recompile without optimization, it is easier to follow the
11378 progress of your program during debugging. But, there are many cases
11379 where you may need to debug an optimized version.
11381 When you debug a program compiled with @samp{-g -O}, remember that the
11382 optimizer has rearranged your code; the debugger shows you what is
11383 really there. Do not be too surprised when the execution path does not
11384 exactly match your source file! An extreme example: if you define a
11385 variable, but never use it, @value{GDBN} never sees that
11386 variable---because the compiler optimizes it out of existence.
11388 Some things do not work as well with @samp{-g -O} as with just
11389 @samp{-g}, particularly on machines with instruction scheduling. If in
11390 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11391 please report it to us as a bug (including a test case!).
11392 @xref{Variables}, for more information about debugging optimized code.
11395 * Inline Functions:: How @value{GDBN} presents inlining
11396 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11399 @node Inline Functions
11400 @section Inline Functions
11401 @cindex inline functions, debugging
11403 @dfn{Inlining} is an optimization that inserts a copy of the function
11404 body directly at each call site, instead of jumping to a shared
11405 routine. @value{GDBN} displays inlined functions just like
11406 non-inlined functions. They appear in backtraces. You can view their
11407 arguments and local variables, step into them with @code{step}, skip
11408 them with @code{next}, and escape from them with @code{finish}.
11409 You can check whether a function was inlined by using the
11410 @code{info frame} command.
11412 For @value{GDBN} to support inlined functions, the compiler must
11413 record information about inlining in the debug information ---
11414 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11415 other compilers do also. @value{GDBN} only supports inlined functions
11416 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11417 do not emit two required attributes (@samp{DW_AT_call_file} and
11418 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11419 function calls with earlier versions of @value{NGCC}. It instead
11420 displays the arguments and local variables of inlined functions as
11421 local variables in the caller.
11423 The body of an inlined function is directly included at its call site;
11424 unlike a non-inlined function, there are no instructions devoted to
11425 the call. @value{GDBN} still pretends that the call site and the
11426 start of the inlined function are different instructions. Stepping to
11427 the call site shows the call site, and then stepping again shows
11428 the first line of the inlined function, even though no additional
11429 instructions are executed.
11431 This makes source-level debugging much clearer; you can see both the
11432 context of the call and then the effect of the call. Only stepping by
11433 a single instruction using @code{stepi} or @code{nexti} does not do
11434 this; single instruction steps always show the inlined body.
11436 There are some ways that @value{GDBN} does not pretend that inlined
11437 function calls are the same as normal calls:
11441 Setting breakpoints at the call site of an inlined function may not
11442 work, because the call site does not contain any code. @value{GDBN}
11443 may incorrectly move the breakpoint to the next line of the enclosing
11444 function, after the call. This limitation will be removed in a future
11445 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11446 or inside the inlined function instead.
11449 @value{GDBN} cannot locate the return value of inlined calls after
11450 using the @code{finish} command. This is a limitation of compiler-generated
11451 debugging information; after @code{finish}, you can step to the next line
11452 and print a variable where your program stored the return value.
11456 @node Tail Call Frames
11457 @section Tail Call Frames
11458 @cindex tail call frames, debugging
11460 Function @code{B} can call function @code{C} in its very last statement. In
11461 unoptimized compilation the call of @code{C} is immediately followed by return
11462 instruction at the end of @code{B} code. Optimizing compiler may replace the
11463 call and return in function @code{B} into one jump to function @code{C}
11464 instead. Such use of a jump instruction is called @dfn{tail call}.
11466 During execution of function @code{C}, there will be no indication in the
11467 function call stack frames that it was tail-called from @code{B}. If function
11468 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11469 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11470 some cases @value{GDBN} can determine that @code{C} was tail-called from
11471 @code{B}, and it will then create fictitious call frame for that, with the
11472 return address set up as if @code{B} called @code{C} normally.
11474 This functionality is currently supported only by DWARF 2 debugging format and
11475 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11476 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11479 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11480 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11484 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11486 Stack level 1, frame at 0x7fffffffda30:
11487 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11488 tail call frame, caller of frame at 0x7fffffffda30
11489 source language c++.
11490 Arglist at unknown address.
11491 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11494 The detection of all the possible code path executions can find them ambiguous.
11495 There is no execution history stored (possible @ref{Reverse Execution} is never
11496 used for this purpose) and the last known caller could have reached the known
11497 callee by multiple different jump sequences. In such case @value{GDBN} still
11498 tries to show at least all the unambiguous top tail callers and all the
11499 unambiguous bottom tail calees, if any.
11502 @anchor{set debug entry-values}
11503 @item set debug entry-values
11504 @kindex set debug entry-values
11505 When set to on, enables printing of analysis messages for both frame argument
11506 values at function entry and tail calls. It will show all the possible valid
11507 tail calls code paths it has considered. It will also print the intersection
11508 of them with the final unambiguous (possibly partial or even empty) code path
11511 @item show debug entry-values
11512 @kindex show debug entry-values
11513 Show the current state of analysis messages printing for both frame argument
11514 values at function entry and tail calls.
11517 The analysis messages for tail calls can for example show why the virtual tail
11518 call frame for function @code{c} has not been recognized (due to the indirect
11519 reference by variable @code{x}):
11522 static void __attribute__((noinline, noclone)) c (void);
11523 void (*x) (void) = c;
11524 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11525 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11526 int main (void) @{ x (); return 0; @}
11528 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11529 DW_TAG_GNU_call_site 0x40039a in main
11531 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11534 #1 0x000000000040039a in main () at t.c:5
11537 Another possibility is an ambiguous virtual tail call frames resolution:
11541 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11542 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11543 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11544 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11545 static void __attribute__((noinline, noclone)) b (void)
11546 @{ if (i) c (); else e (); @}
11547 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11548 int main (void) @{ a (); return 0; @}
11550 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11551 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11552 tailcall: reduced: 0x4004d2(a) |
11555 #1 0x00000000004004d2 in a () at t.c:8
11556 #2 0x0000000000400395 in main () at t.c:9
11559 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11560 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11562 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11563 @ifset HAVE_MAKEINFO_CLICK
11564 @set ARROW @click{}
11565 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11566 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11568 @ifclear HAVE_MAKEINFO_CLICK
11570 @set CALLSEQ1B @value{CALLSEQ1A}
11571 @set CALLSEQ2B @value{CALLSEQ2A}
11574 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11575 The code can have possible execution paths @value{CALLSEQ1B} or
11576 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11578 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11579 has found. It then finds another possible calling sequcen - that one is
11580 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11581 printed as the @code{reduced:} calling sequence. That one could have many
11582 futher @code{compare:} and @code{reduced:} statements as long as there remain
11583 any non-ambiguous sequence entries.
11585 For the frame of function @code{b} in both cases there are different possible
11586 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11587 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11588 therefore this one is displayed to the user while the ambiguous frames are
11591 There can be also reasons why printing of frame argument values at function
11596 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11597 static void __attribute__((noinline, noclone)) a (int i);
11598 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11599 static void __attribute__((noinline, noclone)) a (int i)
11600 @{ if (i) b (i - 1); else c (0); @}
11601 int main (void) @{ a (5); return 0; @}
11604 #0 c (i=i@@entry=0) at t.c:2
11605 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11606 function "a" at 0x400420 can call itself via tail calls
11607 i=<optimized out>) at t.c:6
11608 #2 0x000000000040036e in main () at t.c:7
11611 @value{GDBN} cannot find out from the inferior state if and how many times did
11612 function @code{a} call itself (via function @code{b}) as these calls would be
11613 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11614 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11615 prints @code{<optimized out>} instead.
11618 @chapter C Preprocessor Macros
11620 Some languages, such as C and C@t{++}, provide a way to define and invoke
11621 ``preprocessor macros'' which expand into strings of tokens.
11622 @value{GDBN} can evaluate expressions containing macro invocations, show
11623 the result of macro expansion, and show a macro's definition, including
11624 where it was defined.
11626 You may need to compile your program specially to provide @value{GDBN}
11627 with information about preprocessor macros. Most compilers do not
11628 include macros in their debugging information, even when you compile
11629 with the @option{-g} flag. @xref{Compilation}.
11631 A program may define a macro at one point, remove that definition later,
11632 and then provide a different definition after that. Thus, at different
11633 points in the program, a macro may have different definitions, or have
11634 no definition at all. If there is a current stack frame, @value{GDBN}
11635 uses the macros in scope at that frame's source code line. Otherwise,
11636 @value{GDBN} uses the macros in scope at the current listing location;
11639 Whenever @value{GDBN} evaluates an expression, it always expands any
11640 macro invocations present in the expression. @value{GDBN} also provides
11641 the following commands for working with macros explicitly.
11645 @kindex macro expand
11646 @cindex macro expansion, showing the results of preprocessor
11647 @cindex preprocessor macro expansion, showing the results of
11648 @cindex expanding preprocessor macros
11649 @item macro expand @var{expression}
11650 @itemx macro exp @var{expression}
11651 Show the results of expanding all preprocessor macro invocations in
11652 @var{expression}. Since @value{GDBN} simply expands macros, but does
11653 not parse the result, @var{expression} need not be a valid expression;
11654 it can be any string of tokens.
11657 @item macro expand-once @var{expression}
11658 @itemx macro exp1 @var{expression}
11659 @cindex expand macro once
11660 @i{(This command is not yet implemented.)} Show the results of
11661 expanding those preprocessor macro invocations that appear explicitly in
11662 @var{expression}. Macro invocations appearing in that expansion are
11663 left unchanged. This command allows you to see the effect of a
11664 particular macro more clearly, without being confused by further
11665 expansions. Since @value{GDBN} simply expands macros, but does not
11666 parse the result, @var{expression} need not be a valid expression; it
11667 can be any string of tokens.
11670 @cindex macro definition, showing
11671 @cindex definition of a macro, showing
11672 @cindex macros, from debug info
11673 @item info macro [-a|-all] [--] @var{macro}
11674 Show the current definition or all definitions of the named @var{macro},
11675 and describe the source location or compiler command-line where that
11676 definition was established. The optional double dash is to signify the end of
11677 argument processing and the beginning of @var{macro} for non C-like macros where
11678 the macro may begin with a hyphen.
11680 @kindex info macros
11681 @item info macros @var{linespec}
11682 Show all macro definitions that are in effect at the location specified
11683 by @var{linespec}, and describe the source location or compiler
11684 command-line where those definitions were established.
11686 @kindex macro define
11687 @cindex user-defined macros
11688 @cindex defining macros interactively
11689 @cindex macros, user-defined
11690 @item macro define @var{macro} @var{replacement-list}
11691 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11692 Introduce a definition for a preprocessor macro named @var{macro},
11693 invocations of which are replaced by the tokens given in
11694 @var{replacement-list}. The first form of this command defines an
11695 ``object-like'' macro, which takes no arguments; the second form
11696 defines a ``function-like'' macro, which takes the arguments given in
11699 A definition introduced by this command is in scope in every
11700 expression evaluated in @value{GDBN}, until it is removed with the
11701 @code{macro undef} command, described below. The definition overrides
11702 all definitions for @var{macro} present in the program being debugged,
11703 as well as any previous user-supplied definition.
11705 @kindex macro undef
11706 @item macro undef @var{macro}
11707 Remove any user-supplied definition for the macro named @var{macro}.
11708 This command only affects definitions provided with the @code{macro
11709 define} command, described above; it cannot remove definitions present
11710 in the program being debugged.
11714 List all the macros defined using the @code{macro define} command.
11717 @cindex macros, example of debugging with
11718 Here is a transcript showing the above commands in action. First, we
11719 show our source files:
11724 #include "sample.h"
11727 #define ADD(x) (M + x)
11732 printf ("Hello, world!\n");
11734 printf ("We're so creative.\n");
11736 printf ("Goodbye, world!\n");
11743 Now, we compile the program using the @sc{gnu} C compiler,
11744 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11745 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11746 and @option{-gdwarf-4}; we recommend always choosing the most recent
11747 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11748 includes information about preprocessor macros in the debugging
11752 $ gcc -gdwarf-2 -g3 sample.c -o sample
11756 Now, we start @value{GDBN} on our sample program:
11760 GNU gdb 2002-05-06-cvs
11761 Copyright 2002 Free Software Foundation, Inc.
11762 GDB is free software, @dots{}
11766 We can expand macros and examine their definitions, even when the
11767 program is not running. @value{GDBN} uses the current listing position
11768 to decide which macro definitions are in scope:
11771 (@value{GDBP}) list main
11774 5 #define ADD(x) (M + x)
11779 10 printf ("Hello, world!\n");
11781 12 printf ("We're so creative.\n");
11782 (@value{GDBP}) info macro ADD
11783 Defined at /home/jimb/gdb/macros/play/sample.c:5
11784 #define ADD(x) (M + x)
11785 (@value{GDBP}) info macro Q
11786 Defined at /home/jimb/gdb/macros/play/sample.h:1
11787 included at /home/jimb/gdb/macros/play/sample.c:2
11789 (@value{GDBP}) macro expand ADD(1)
11790 expands to: (42 + 1)
11791 (@value{GDBP}) macro expand-once ADD(1)
11792 expands to: once (M + 1)
11796 In the example above, note that @code{macro expand-once} expands only
11797 the macro invocation explicit in the original text --- the invocation of
11798 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11799 which was introduced by @code{ADD}.
11801 Once the program is running, @value{GDBN} uses the macro definitions in
11802 force at the source line of the current stack frame:
11805 (@value{GDBP}) break main
11806 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11808 Starting program: /home/jimb/gdb/macros/play/sample
11810 Breakpoint 1, main () at sample.c:10
11811 10 printf ("Hello, world!\n");
11815 At line 10, the definition of the macro @code{N} at line 9 is in force:
11818 (@value{GDBP}) info macro N
11819 Defined at /home/jimb/gdb/macros/play/sample.c:9
11821 (@value{GDBP}) macro expand N Q M
11822 expands to: 28 < 42
11823 (@value{GDBP}) print N Q M
11828 As we step over directives that remove @code{N}'s definition, and then
11829 give it a new definition, @value{GDBN} finds the definition (or lack
11830 thereof) in force at each point:
11833 (@value{GDBP}) next
11835 12 printf ("We're so creative.\n");
11836 (@value{GDBP}) info macro N
11837 The symbol `N' has no definition as a C/C++ preprocessor macro
11838 at /home/jimb/gdb/macros/play/sample.c:12
11839 (@value{GDBP}) next
11841 14 printf ("Goodbye, world!\n");
11842 (@value{GDBP}) info macro N
11843 Defined at /home/jimb/gdb/macros/play/sample.c:13
11845 (@value{GDBP}) macro expand N Q M
11846 expands to: 1729 < 42
11847 (@value{GDBP}) print N Q M
11852 In addition to source files, macros can be defined on the compilation command
11853 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11854 such a way, @value{GDBN} displays the location of their definition as line zero
11855 of the source file submitted to the compiler.
11858 (@value{GDBP}) info macro __STDC__
11859 Defined at /home/jimb/gdb/macros/play/sample.c:0
11866 @chapter Tracepoints
11867 @c This chapter is based on the documentation written by Michael
11868 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11870 @cindex tracepoints
11871 In some applications, it is not feasible for the debugger to interrupt
11872 the program's execution long enough for the developer to learn
11873 anything helpful about its behavior. If the program's correctness
11874 depends on its real-time behavior, delays introduced by a debugger
11875 might cause the program to change its behavior drastically, or perhaps
11876 fail, even when the code itself is correct. It is useful to be able
11877 to observe the program's behavior without interrupting it.
11879 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11880 specify locations in the program, called @dfn{tracepoints}, and
11881 arbitrary expressions to evaluate when those tracepoints are reached.
11882 Later, using the @code{tfind} command, you can examine the values
11883 those expressions had when the program hit the tracepoints. The
11884 expressions may also denote objects in memory---structures or arrays,
11885 for example---whose values @value{GDBN} should record; while visiting
11886 a particular tracepoint, you may inspect those objects as if they were
11887 in memory at that moment. However, because @value{GDBN} records these
11888 values without interacting with you, it can do so quickly and
11889 unobtrusively, hopefully not disturbing the program's behavior.
11891 The tracepoint facility is currently available only for remote
11892 targets. @xref{Targets}. In addition, your remote target must know
11893 how to collect trace data. This functionality is implemented in the
11894 remote stub; however, none of the stubs distributed with @value{GDBN}
11895 support tracepoints as of this writing. The format of the remote
11896 packets used to implement tracepoints are described in @ref{Tracepoint
11899 It is also possible to get trace data from a file, in a manner reminiscent
11900 of corefiles; you specify the filename, and use @code{tfind} to search
11901 through the file. @xref{Trace Files}, for more details.
11903 This chapter describes the tracepoint commands and features.
11906 * Set Tracepoints::
11907 * Analyze Collected Data::
11908 * Tracepoint Variables::
11912 @node Set Tracepoints
11913 @section Commands to Set Tracepoints
11915 Before running such a @dfn{trace experiment}, an arbitrary number of
11916 tracepoints can be set. A tracepoint is actually a special type of
11917 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11918 standard breakpoint commands. For instance, as with breakpoints,
11919 tracepoint numbers are successive integers starting from one, and many
11920 of the commands associated with tracepoints take the tracepoint number
11921 as their argument, to identify which tracepoint to work on.
11923 For each tracepoint, you can specify, in advance, some arbitrary set
11924 of data that you want the target to collect in the trace buffer when
11925 it hits that tracepoint. The collected data can include registers,
11926 local variables, or global data. Later, you can use @value{GDBN}
11927 commands to examine the values these data had at the time the
11928 tracepoint was hit.
11930 Tracepoints do not support every breakpoint feature. Ignore counts on
11931 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11932 commands when they are hit. Tracepoints may not be thread-specific
11935 @cindex fast tracepoints
11936 Some targets may support @dfn{fast tracepoints}, which are inserted in
11937 a different way (such as with a jump instead of a trap), that is
11938 faster but possibly restricted in where they may be installed.
11940 @cindex static tracepoints
11941 @cindex markers, static tracepoints
11942 @cindex probing markers, static tracepoints
11943 Regular and fast tracepoints are dynamic tracing facilities, meaning
11944 that they can be used to insert tracepoints at (almost) any location
11945 in the target. Some targets may also support controlling @dfn{static
11946 tracepoints} from @value{GDBN}. With static tracing, a set of
11947 instrumentation points, also known as @dfn{markers}, are embedded in
11948 the target program, and can be activated or deactivated by name or
11949 address. These are usually placed at locations which facilitate
11950 investigating what the target is actually doing. @value{GDBN}'s
11951 support for static tracing includes being able to list instrumentation
11952 points, and attach them with @value{GDBN} defined high level
11953 tracepoints that expose the whole range of convenience of
11954 @value{GDBN}'s tracepoints support. Namely, support for collecting
11955 registers values and values of global or local (to the instrumentation
11956 point) variables; tracepoint conditions and trace state variables.
11957 The act of installing a @value{GDBN} static tracepoint on an
11958 instrumentation point, or marker, is referred to as @dfn{probing} a
11959 static tracepoint marker.
11961 @code{gdbserver} supports tracepoints on some target systems.
11962 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11964 This section describes commands to set tracepoints and associated
11965 conditions and actions.
11968 * Create and Delete Tracepoints::
11969 * Enable and Disable Tracepoints::
11970 * Tracepoint Passcounts::
11971 * Tracepoint Conditions::
11972 * Trace State Variables::
11973 * Tracepoint Actions::
11974 * Listing Tracepoints::
11975 * Listing Static Tracepoint Markers::
11976 * Starting and Stopping Trace Experiments::
11977 * Tracepoint Restrictions::
11980 @node Create and Delete Tracepoints
11981 @subsection Create and Delete Tracepoints
11984 @cindex set tracepoint
11986 @item trace @var{location}
11987 The @code{trace} command is very similar to the @code{break} command.
11988 Its argument @var{location} can be a source line, a function name, or
11989 an address in the target program. @xref{Specify Location}. The
11990 @code{trace} command defines a tracepoint, which is a point in the
11991 target program where the debugger will briefly stop, collect some
11992 data, and then allow the program to continue. Setting a tracepoint or
11993 changing its actions takes effect immediately if the remote stub
11994 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11996 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11997 these changes don't take effect until the next @code{tstart}
11998 command, and once a trace experiment is running, further changes will
11999 not have any effect until the next trace experiment starts. In addition,
12000 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12001 address is not yet resolved. (This is similar to pending breakpoints.)
12002 Pending tracepoints are not downloaded to the target and not installed
12003 until they are resolved. The resolution of pending tracepoints requires
12004 @value{GDBN} support---when debugging with the remote target, and
12005 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12006 tracing}), pending tracepoints can not be resolved (and downloaded to
12007 the remote stub) while @value{GDBN} is disconnected.
12009 Here are some examples of using the @code{trace} command:
12012 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12014 (@value{GDBP}) @b{trace +2} // 2 lines forward
12016 (@value{GDBP}) @b{trace my_function} // first source line of function
12018 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12020 (@value{GDBP}) @b{trace *0x2117c4} // an address
12024 You can abbreviate @code{trace} as @code{tr}.
12026 @item trace @var{location} if @var{cond}
12027 Set a tracepoint with condition @var{cond}; evaluate the expression
12028 @var{cond} each time the tracepoint is reached, and collect data only
12029 if the value is nonzero---that is, if @var{cond} evaluates as true.
12030 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12031 information on tracepoint conditions.
12033 @item ftrace @var{location} [ if @var{cond} ]
12034 @cindex set fast tracepoint
12035 @cindex fast tracepoints, setting
12037 The @code{ftrace} command sets a fast tracepoint. For targets that
12038 support them, fast tracepoints will use a more efficient but possibly
12039 less general technique to trigger data collection, such as a jump
12040 instruction instead of a trap, or some sort of hardware support. It
12041 may not be possible to create a fast tracepoint at the desired
12042 location, in which case the command will exit with an explanatory
12045 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12048 On 32-bit x86-architecture systems, fast tracepoints normally need to
12049 be placed at an instruction that is 5 bytes or longer, but can be
12050 placed at 4-byte instructions if the low 64K of memory of the target
12051 program is available to install trampolines. Some Unix-type systems,
12052 such as @sc{gnu}/Linux, exclude low addresses from the program's
12053 address space; but for instance with the Linux kernel it is possible
12054 to let @value{GDBN} use this area by doing a @command{sysctl} command
12055 to set the @code{mmap_min_addr} kernel parameter, as in
12058 sudo sysctl -w vm.mmap_min_addr=32768
12062 which sets the low address to 32K, which leaves plenty of room for
12063 trampolines. The minimum address should be set to a page boundary.
12065 @item strace @var{location} [ if @var{cond} ]
12066 @cindex set static tracepoint
12067 @cindex static tracepoints, setting
12068 @cindex probe static tracepoint marker
12070 The @code{strace} command sets a static tracepoint. For targets that
12071 support it, setting a static tracepoint probes a static
12072 instrumentation point, or marker, found at @var{location}. It may not
12073 be possible to set a static tracepoint at the desired location, in
12074 which case the command will exit with an explanatory message.
12076 @value{GDBN} handles arguments to @code{strace} exactly as for
12077 @code{trace}, with the addition that the user can also specify
12078 @code{-m @var{marker}} as @var{location}. This probes the marker
12079 identified by the @var{marker} string identifier. This identifier
12080 depends on the static tracepoint backend library your program is
12081 using. You can find all the marker identifiers in the @samp{ID} field
12082 of the @code{info static-tracepoint-markers} command output.
12083 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12084 Markers}. For example, in the following small program using the UST
12090 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12095 the marker id is composed of joining the first two arguments to the
12096 @code{trace_mark} call with a slash, which translates to:
12099 (@value{GDBP}) info static-tracepoint-markers
12100 Cnt Enb ID Address What
12101 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12107 so you may probe the marker above with:
12110 (@value{GDBP}) strace -m ust/bar33
12113 Static tracepoints accept an extra collect action --- @code{collect
12114 $_sdata}. This collects arbitrary user data passed in the probe point
12115 call to the tracing library. In the UST example above, you'll see
12116 that the third argument to @code{trace_mark} is a printf-like format
12117 string. The user data is then the result of running that formating
12118 string against the following arguments. Note that @code{info
12119 static-tracepoint-markers} command output lists that format string in
12120 the @samp{Data:} field.
12122 You can inspect this data when analyzing the trace buffer, by printing
12123 the $_sdata variable like any other variable available to
12124 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12127 @cindex last tracepoint number
12128 @cindex recent tracepoint number
12129 @cindex tracepoint number
12130 The convenience variable @code{$tpnum} records the tracepoint number
12131 of the most recently set tracepoint.
12133 @kindex delete tracepoint
12134 @cindex tracepoint deletion
12135 @item delete tracepoint @r{[}@var{num}@r{]}
12136 Permanently delete one or more tracepoints. With no argument, the
12137 default is to delete all tracepoints. Note that the regular
12138 @code{delete} command can remove tracepoints also.
12143 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12145 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12149 You can abbreviate this command as @code{del tr}.
12152 @node Enable and Disable Tracepoints
12153 @subsection Enable and Disable Tracepoints
12155 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12158 @kindex disable tracepoint
12159 @item disable tracepoint @r{[}@var{num}@r{]}
12160 Disable tracepoint @var{num}, or all tracepoints if no argument
12161 @var{num} is given. A disabled tracepoint will have no effect during
12162 a trace experiment, but it is not forgotten. You can re-enable
12163 a disabled tracepoint using the @code{enable tracepoint} command.
12164 If the command is issued during a trace experiment and the debug target
12165 has support for disabling tracepoints during a trace experiment, then the
12166 change will be effective immediately. Otherwise, it will be applied to the
12167 next trace experiment.
12169 @kindex enable tracepoint
12170 @item enable tracepoint @r{[}@var{num}@r{]}
12171 Enable tracepoint @var{num}, or all tracepoints. If this command is
12172 issued during a trace experiment and the debug target supports enabling
12173 tracepoints during a trace experiment, then the enabled tracepoints will
12174 become effective immediately. Otherwise, they will become effective the
12175 next time a trace experiment is run.
12178 @node Tracepoint Passcounts
12179 @subsection Tracepoint Passcounts
12183 @cindex tracepoint pass count
12184 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12185 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12186 automatically stop a trace experiment. If a tracepoint's passcount is
12187 @var{n}, then the trace experiment will be automatically stopped on
12188 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12189 @var{num} is not specified, the @code{passcount} command sets the
12190 passcount of the most recently defined tracepoint. If no passcount is
12191 given, the trace experiment will run until stopped explicitly by the
12197 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12198 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12200 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12201 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12202 (@value{GDBP}) @b{trace foo}
12203 (@value{GDBP}) @b{pass 3}
12204 (@value{GDBP}) @b{trace bar}
12205 (@value{GDBP}) @b{pass 2}
12206 (@value{GDBP}) @b{trace baz}
12207 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12208 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12209 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12210 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12214 @node Tracepoint Conditions
12215 @subsection Tracepoint Conditions
12216 @cindex conditional tracepoints
12217 @cindex tracepoint conditions
12219 The simplest sort of tracepoint collects data every time your program
12220 reaches a specified place. You can also specify a @dfn{condition} for
12221 a tracepoint. A condition is just a Boolean expression in your
12222 programming language (@pxref{Expressions, ,Expressions}). A
12223 tracepoint with a condition evaluates the expression each time your
12224 program reaches it, and data collection happens only if the condition
12227 Tracepoint conditions can be specified when a tracepoint is set, by
12228 using @samp{if} in the arguments to the @code{trace} command.
12229 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12230 also be set or changed at any time with the @code{condition} command,
12231 just as with breakpoints.
12233 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12234 the conditional expression itself. Instead, @value{GDBN} encodes the
12235 expression into an agent expression (@pxref{Agent Expressions})
12236 suitable for execution on the target, independently of @value{GDBN}.
12237 Global variables become raw memory locations, locals become stack
12238 accesses, and so forth.
12240 For instance, suppose you have a function that is usually called
12241 frequently, but should not be called after an error has occurred. You
12242 could use the following tracepoint command to collect data about calls
12243 of that function that happen while the error code is propagating
12244 through the program; an unconditional tracepoint could end up
12245 collecting thousands of useless trace frames that you would have to
12249 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12252 @node Trace State Variables
12253 @subsection Trace State Variables
12254 @cindex trace state variables
12256 A @dfn{trace state variable} is a special type of variable that is
12257 created and managed by target-side code. The syntax is the same as
12258 that for GDB's convenience variables (a string prefixed with ``$''),
12259 but they are stored on the target. They must be created explicitly,
12260 using a @code{tvariable} command. They are always 64-bit signed
12263 Trace state variables are remembered by @value{GDBN}, and downloaded
12264 to the target along with tracepoint information when the trace
12265 experiment starts. There are no intrinsic limits on the number of
12266 trace state variables, beyond memory limitations of the target.
12268 @cindex convenience variables, and trace state variables
12269 Although trace state variables are managed by the target, you can use
12270 them in print commands and expressions as if they were convenience
12271 variables; @value{GDBN} will get the current value from the target
12272 while the trace experiment is running. Trace state variables share
12273 the same namespace as other ``$'' variables, which means that you
12274 cannot have trace state variables with names like @code{$23} or
12275 @code{$pc}, nor can you have a trace state variable and a convenience
12276 variable with the same name.
12280 @item tvariable $@var{name} [ = @var{expression} ]
12282 The @code{tvariable} command creates a new trace state variable named
12283 @code{$@var{name}}, and optionally gives it an initial value of
12284 @var{expression}. The @var{expression} is evaluated when this command is
12285 entered; the result will be converted to an integer if possible,
12286 otherwise @value{GDBN} will report an error. A subsequent
12287 @code{tvariable} command specifying the same name does not create a
12288 variable, but instead assigns the supplied initial value to the
12289 existing variable of that name, overwriting any previous initial
12290 value. The default initial value is 0.
12292 @item info tvariables
12293 @kindex info tvariables
12294 List all the trace state variables along with their initial values.
12295 Their current values may also be displayed, if the trace experiment is
12298 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12299 @kindex delete tvariable
12300 Delete the given trace state variables, or all of them if no arguments
12305 @node Tracepoint Actions
12306 @subsection Tracepoint Action Lists
12310 @cindex tracepoint actions
12311 @item actions @r{[}@var{num}@r{]}
12312 This command will prompt for a list of actions to be taken when the
12313 tracepoint is hit. If the tracepoint number @var{num} is not
12314 specified, this command sets the actions for the one that was most
12315 recently defined (so that you can define a tracepoint and then say
12316 @code{actions} without bothering about its number). You specify the
12317 actions themselves on the following lines, one action at a time, and
12318 terminate the actions list with a line containing just @code{end}. So
12319 far, the only defined actions are @code{collect}, @code{teval}, and
12320 @code{while-stepping}.
12322 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12323 Commands, ,Breakpoint Command Lists}), except that only the defined
12324 actions are allowed; any other @value{GDBN} command is rejected.
12326 @cindex remove actions from a tracepoint
12327 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12328 and follow it immediately with @samp{end}.
12331 (@value{GDBP}) @b{collect @var{data}} // collect some data
12333 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12335 (@value{GDBP}) @b{end} // signals the end of actions.
12338 In the following example, the action list begins with @code{collect}
12339 commands indicating the things to be collected when the tracepoint is
12340 hit. Then, in order to single-step and collect additional data
12341 following the tracepoint, a @code{while-stepping} command is used,
12342 followed by the list of things to be collected after each step in a
12343 sequence of single steps. The @code{while-stepping} command is
12344 terminated by its own separate @code{end} command. Lastly, the action
12345 list is terminated by an @code{end} command.
12348 (@value{GDBP}) @b{trace foo}
12349 (@value{GDBP}) @b{actions}
12350 Enter actions for tracepoint 1, one per line:
12353 > while-stepping 12
12354 > collect $pc, arr[i]
12359 @kindex collect @r{(tracepoints)}
12360 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12361 Collect values of the given expressions when the tracepoint is hit.
12362 This command accepts a comma-separated list of any valid expressions.
12363 In addition to global, static, or local variables, the following
12364 special arguments are supported:
12368 Collect all registers.
12371 Collect all function arguments.
12374 Collect all local variables.
12377 Collect the return address. This is helpful if you want to see more
12381 Collects the number of arguments from the static probe at which the
12382 tracepoint is located.
12383 @xref{Static Probe Points}.
12385 @item $_probe_arg@var{n}
12386 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12387 from the static probe at which the tracepoint is located.
12388 @xref{Static Probe Points}.
12391 @vindex $_sdata@r{, collect}
12392 Collect static tracepoint marker specific data. Only available for
12393 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12394 Lists}. On the UST static tracepoints library backend, an
12395 instrumentation point resembles a @code{printf} function call. The
12396 tracing library is able to collect user specified data formatted to a
12397 character string using the format provided by the programmer that
12398 instrumented the program. Other backends have similar mechanisms.
12399 Here's an example of a UST marker call:
12402 const char master_name[] = "$your_name";
12403 trace_mark(channel1, marker1, "hello %s", master_name)
12406 In this case, collecting @code{$_sdata} collects the string
12407 @samp{hello $yourname}. When analyzing the trace buffer, you can
12408 inspect @samp{$_sdata} like any other variable available to
12412 You can give several consecutive @code{collect} commands, each one
12413 with a single argument, or one @code{collect} command with several
12414 arguments separated by commas; the effect is the same.
12416 The optional @var{mods} changes the usual handling of the arguments.
12417 @code{s} requests that pointers to chars be handled as strings, in
12418 particular collecting the contents of the memory being pointed at, up
12419 to the first zero. The upper bound is by default the value of the
12420 @code{print elements} variable; if @code{s} is followed by a decimal
12421 number, that is the upper bound instead. So for instance
12422 @samp{collect/s25 mystr} collects as many as 25 characters at
12425 The command @code{info scope} (@pxref{Symbols, info scope}) is
12426 particularly useful for figuring out what data to collect.
12428 @kindex teval @r{(tracepoints)}
12429 @item teval @var{expr1}, @var{expr2}, @dots{}
12430 Evaluate the given expressions when the tracepoint is hit. This
12431 command accepts a comma-separated list of expressions. The results
12432 are discarded, so this is mainly useful for assigning values to trace
12433 state variables (@pxref{Trace State Variables}) without adding those
12434 values to the trace buffer, as would be the case if the @code{collect}
12437 @kindex while-stepping @r{(tracepoints)}
12438 @item while-stepping @var{n}
12439 Perform @var{n} single-step instruction traces after the tracepoint,
12440 collecting new data after each step. The @code{while-stepping}
12441 command is followed by the list of what to collect while stepping
12442 (followed by its own @code{end} command):
12445 > while-stepping 12
12446 > collect $regs, myglobal
12452 Note that @code{$pc} is not automatically collected by
12453 @code{while-stepping}; you need to explicitly collect that register if
12454 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12457 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12458 @kindex set default-collect
12459 @cindex default collection action
12460 This variable is a list of expressions to collect at each tracepoint
12461 hit. It is effectively an additional @code{collect} action prepended
12462 to every tracepoint action list. The expressions are parsed
12463 individually for each tracepoint, so for instance a variable named
12464 @code{xyz} may be interpreted as a global for one tracepoint, and a
12465 local for another, as appropriate to the tracepoint's location.
12467 @item show default-collect
12468 @kindex show default-collect
12469 Show the list of expressions that are collected by default at each
12474 @node Listing Tracepoints
12475 @subsection Listing Tracepoints
12478 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12479 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12480 @cindex information about tracepoints
12481 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12482 Display information about the tracepoint @var{num}. If you don't
12483 specify a tracepoint number, displays information about all the
12484 tracepoints defined so far. The format is similar to that used for
12485 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12486 command, simply restricting itself to tracepoints.
12488 A tracepoint's listing may include additional information specific to
12493 its passcount as given by the @code{passcount @var{n}} command
12496 the state about installed on target of each location
12500 (@value{GDBP}) @b{info trace}
12501 Num Type Disp Enb Address What
12502 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12504 collect globfoo, $regs
12509 2 tracepoint keep y <MULTIPLE>
12511 2.1 y 0x0804859c in func4 at change-loc.h:35
12512 installed on target
12513 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12514 installed on target
12515 2.3 y <PENDING> set_tracepoint
12516 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12517 not installed on target
12522 This command can be abbreviated @code{info tp}.
12525 @node Listing Static Tracepoint Markers
12526 @subsection Listing Static Tracepoint Markers
12529 @kindex info static-tracepoint-markers
12530 @cindex information about static tracepoint markers
12531 @item info static-tracepoint-markers
12532 Display information about all static tracepoint markers defined in the
12535 For each marker, the following columns are printed:
12539 An incrementing counter, output to help readability. This is not a
12542 The marker ID, as reported by the target.
12543 @item Enabled or Disabled
12544 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12545 that are not enabled.
12547 Where the marker is in your program, as a memory address.
12549 Where the marker is in the source for your program, as a file and line
12550 number. If the debug information included in the program does not
12551 allow @value{GDBN} to locate the source of the marker, this column
12552 will be left blank.
12556 In addition, the following information may be printed for each marker:
12560 User data passed to the tracing library by the marker call. In the
12561 UST backend, this is the format string passed as argument to the
12563 @item Static tracepoints probing the marker
12564 The list of static tracepoints attached to the marker.
12568 (@value{GDBP}) info static-tracepoint-markers
12569 Cnt ID Enb Address What
12570 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12571 Data: number1 %d number2 %d
12572 Probed by static tracepoints: #2
12573 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12579 @node Starting and Stopping Trace Experiments
12580 @subsection Starting and Stopping Trace Experiments
12583 @kindex tstart [ @var{notes} ]
12584 @cindex start a new trace experiment
12585 @cindex collected data discarded
12587 This command starts the trace experiment, and begins collecting data.
12588 It has the side effect of discarding all the data collected in the
12589 trace buffer during the previous trace experiment. If any arguments
12590 are supplied, they are taken as a note and stored with the trace
12591 experiment's state. The notes may be arbitrary text, and are
12592 especially useful with disconnected tracing in a multi-user context;
12593 the notes can explain what the trace is doing, supply user contact
12594 information, and so forth.
12596 @kindex tstop [ @var{notes} ]
12597 @cindex stop a running trace experiment
12599 This command stops the trace experiment. If any arguments are
12600 supplied, they are recorded with the experiment as a note. This is
12601 useful if you are stopping a trace started by someone else, for
12602 instance if the trace is interfering with the system's behavior and
12603 needs to be stopped quickly.
12605 @strong{Note}: a trace experiment and data collection may stop
12606 automatically if any tracepoint's passcount is reached
12607 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12610 @cindex status of trace data collection
12611 @cindex trace experiment, status of
12613 This command displays the status of the current trace data
12617 Here is an example of the commands we described so far:
12620 (@value{GDBP}) @b{trace gdb_c_test}
12621 (@value{GDBP}) @b{actions}
12622 Enter actions for tracepoint #1, one per line.
12623 > collect $regs,$locals,$args
12624 > while-stepping 11
12628 (@value{GDBP}) @b{tstart}
12629 [time passes @dots{}]
12630 (@value{GDBP}) @b{tstop}
12633 @anchor{disconnected tracing}
12634 @cindex disconnected tracing
12635 You can choose to continue running the trace experiment even if
12636 @value{GDBN} disconnects from the target, voluntarily or
12637 involuntarily. For commands such as @code{detach}, the debugger will
12638 ask what you want to do with the trace. But for unexpected
12639 terminations (@value{GDBN} crash, network outage), it would be
12640 unfortunate to lose hard-won trace data, so the variable
12641 @code{disconnected-tracing} lets you decide whether the trace should
12642 continue running without @value{GDBN}.
12645 @item set disconnected-tracing on
12646 @itemx set disconnected-tracing off
12647 @kindex set disconnected-tracing
12648 Choose whether a tracing run should continue to run if @value{GDBN}
12649 has disconnected from the target. Note that @code{detach} or
12650 @code{quit} will ask you directly what to do about a running trace no
12651 matter what this variable's setting, so the variable is mainly useful
12652 for handling unexpected situations, such as loss of the network.
12654 @item show disconnected-tracing
12655 @kindex show disconnected-tracing
12656 Show the current choice for disconnected tracing.
12660 When you reconnect to the target, the trace experiment may or may not
12661 still be running; it might have filled the trace buffer in the
12662 meantime, or stopped for one of the other reasons. If it is running,
12663 it will continue after reconnection.
12665 Upon reconnection, the target will upload information about the
12666 tracepoints in effect. @value{GDBN} will then compare that
12667 information to the set of tracepoints currently defined, and attempt
12668 to match them up, allowing for the possibility that the numbers may
12669 have changed due to creation and deletion in the meantime. If one of
12670 the target's tracepoints does not match any in @value{GDBN}, the
12671 debugger will create a new tracepoint, so that you have a number with
12672 which to specify that tracepoint. This matching-up process is
12673 necessarily heuristic, and it may result in useless tracepoints being
12674 created; you may simply delete them if they are of no use.
12676 @cindex circular trace buffer
12677 If your target agent supports a @dfn{circular trace buffer}, then you
12678 can run a trace experiment indefinitely without filling the trace
12679 buffer; when space runs out, the agent deletes already-collected trace
12680 frames, oldest first, until there is enough room to continue
12681 collecting. This is especially useful if your tracepoints are being
12682 hit too often, and your trace gets terminated prematurely because the
12683 buffer is full. To ask for a circular trace buffer, simply set
12684 @samp{circular-trace-buffer} to on. You can set this at any time,
12685 including during tracing; if the agent can do it, it will change
12686 buffer handling on the fly, otherwise it will not take effect until
12690 @item set circular-trace-buffer on
12691 @itemx set circular-trace-buffer off
12692 @kindex set circular-trace-buffer
12693 Choose whether a tracing run should use a linear or circular buffer
12694 for trace data. A linear buffer will not lose any trace data, but may
12695 fill up prematurely, while a circular buffer will discard old trace
12696 data, but it will have always room for the latest tracepoint hits.
12698 @item show circular-trace-buffer
12699 @kindex show circular-trace-buffer
12700 Show the current choice for the trace buffer. Note that this may not
12701 match the agent's current buffer handling, nor is it guaranteed to
12702 match the setting that might have been in effect during a past run,
12703 for instance if you are looking at frames from a trace file.
12708 @item set trace-buffer-size @var{n}
12709 @itemx set trace-buffer-size unlimited
12710 @kindex set trace-buffer-size
12711 Request that the target use a trace buffer of @var{n} bytes. Not all
12712 targets will honor the request; they may have a compiled-in size for
12713 the trace buffer, or some other limitation. Set to a value of
12714 @code{unlimited} or @code{-1} to let the target use whatever size it
12715 likes. This is also the default.
12717 @item show trace-buffer-size
12718 @kindex show trace-buffer-size
12719 Show the current requested size for the trace buffer. Note that this
12720 will only match the actual size if the target supports size-setting,
12721 and was able to handle the requested size. For instance, if the
12722 target can only change buffer size between runs, this variable will
12723 not reflect the change until the next run starts. Use @code{tstatus}
12724 to get a report of the actual buffer size.
12728 @item set trace-user @var{text}
12729 @kindex set trace-user
12731 @item show trace-user
12732 @kindex show trace-user
12734 @item set trace-notes @var{text}
12735 @kindex set trace-notes
12736 Set the trace run's notes.
12738 @item show trace-notes
12739 @kindex show trace-notes
12740 Show the trace run's notes.
12742 @item set trace-stop-notes @var{text}
12743 @kindex set trace-stop-notes
12744 Set the trace run's stop notes. The handling of the note is as for
12745 @code{tstop} arguments; the set command is convenient way to fix a
12746 stop note that is mistaken or incomplete.
12748 @item show trace-stop-notes
12749 @kindex show trace-stop-notes
12750 Show the trace run's stop notes.
12754 @node Tracepoint Restrictions
12755 @subsection Tracepoint Restrictions
12757 @cindex tracepoint restrictions
12758 There are a number of restrictions on the use of tracepoints. As
12759 described above, tracepoint data gathering occurs on the target
12760 without interaction from @value{GDBN}. Thus the full capabilities of
12761 the debugger are not available during data gathering, and then at data
12762 examination time, you will be limited by only having what was
12763 collected. The following items describe some common problems, but it
12764 is not exhaustive, and you may run into additional difficulties not
12770 Tracepoint expressions are intended to gather objects (lvalues). Thus
12771 the full flexibility of GDB's expression evaluator is not available.
12772 You cannot call functions, cast objects to aggregate types, access
12773 convenience variables or modify values (except by assignment to trace
12774 state variables). Some language features may implicitly call
12775 functions (for instance Objective-C fields with accessors), and therefore
12776 cannot be collected either.
12779 Collection of local variables, either individually or in bulk with
12780 @code{$locals} or @code{$args}, during @code{while-stepping} may
12781 behave erratically. The stepping action may enter a new scope (for
12782 instance by stepping into a function), or the location of the variable
12783 may change (for instance it is loaded into a register). The
12784 tracepoint data recorded uses the location information for the
12785 variables that is correct for the tracepoint location. When the
12786 tracepoint is created, it is not possible, in general, to determine
12787 where the steps of a @code{while-stepping} sequence will advance the
12788 program---particularly if a conditional branch is stepped.
12791 Collection of an incompletely-initialized or partially-destroyed object
12792 may result in something that @value{GDBN} cannot display, or displays
12793 in a misleading way.
12796 When @value{GDBN} displays a pointer to character it automatically
12797 dereferences the pointer to also display characters of the string
12798 being pointed to. However, collecting the pointer during tracing does
12799 not automatically collect the string. You need to explicitly
12800 dereference the pointer and provide size information if you want to
12801 collect not only the pointer, but the memory pointed to. For example,
12802 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12806 It is not possible to collect a complete stack backtrace at a
12807 tracepoint. Instead, you may collect the registers and a few hundred
12808 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12809 (adjust to use the name of the actual stack pointer register on your
12810 target architecture, and the amount of stack you wish to capture).
12811 Then the @code{backtrace} command will show a partial backtrace when
12812 using a trace frame. The number of stack frames that can be examined
12813 depends on the sizes of the frames in the collected stack. Note that
12814 if you ask for a block so large that it goes past the bottom of the
12815 stack, the target agent may report an error trying to read from an
12819 If you do not collect registers at a tracepoint, @value{GDBN} can
12820 infer that the value of @code{$pc} must be the same as the address of
12821 the tracepoint and use that when you are looking at a trace frame
12822 for that tracepoint. However, this cannot work if the tracepoint has
12823 multiple locations (for instance if it was set in a function that was
12824 inlined), or if it has a @code{while-stepping} loop. In those cases
12825 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12830 @node Analyze Collected Data
12831 @section Using the Collected Data
12833 After the tracepoint experiment ends, you use @value{GDBN} commands
12834 for examining the trace data. The basic idea is that each tracepoint
12835 collects a trace @dfn{snapshot} every time it is hit and another
12836 snapshot every time it single-steps. All these snapshots are
12837 consecutively numbered from zero and go into a buffer, and you can
12838 examine them later. The way you examine them is to @dfn{focus} on a
12839 specific trace snapshot. When the remote stub is focused on a trace
12840 snapshot, it will respond to all @value{GDBN} requests for memory and
12841 registers by reading from the buffer which belongs to that snapshot,
12842 rather than from @emph{real} memory or registers of the program being
12843 debugged. This means that @strong{all} @value{GDBN} commands
12844 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12845 behave as if we were currently debugging the program state as it was
12846 when the tracepoint occurred. Any requests for data that are not in
12847 the buffer will fail.
12850 * tfind:: How to select a trace snapshot
12851 * tdump:: How to display all data for a snapshot
12852 * save tracepoints:: How to save tracepoints for a future run
12856 @subsection @code{tfind @var{n}}
12859 @cindex select trace snapshot
12860 @cindex find trace snapshot
12861 The basic command for selecting a trace snapshot from the buffer is
12862 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12863 counting from zero. If no argument @var{n} is given, the next
12864 snapshot is selected.
12866 Here are the various forms of using the @code{tfind} command.
12870 Find the first snapshot in the buffer. This is a synonym for
12871 @code{tfind 0} (since 0 is the number of the first snapshot).
12874 Stop debugging trace snapshots, resume @emph{live} debugging.
12877 Same as @samp{tfind none}.
12880 No argument means find the next trace snapshot.
12883 Find the previous trace snapshot before the current one. This permits
12884 retracing earlier steps.
12886 @item tfind tracepoint @var{num}
12887 Find the next snapshot associated with tracepoint @var{num}. Search
12888 proceeds forward from the last examined trace snapshot. If no
12889 argument @var{num} is given, it means find the next snapshot collected
12890 for the same tracepoint as the current snapshot.
12892 @item tfind pc @var{addr}
12893 Find the next snapshot associated with the value @var{addr} of the
12894 program counter. Search proceeds forward from the last examined trace
12895 snapshot. If no argument @var{addr} is given, it means find the next
12896 snapshot with the same value of PC as the current snapshot.
12898 @item tfind outside @var{addr1}, @var{addr2}
12899 Find the next snapshot whose PC is outside the given range of
12900 addresses (exclusive).
12902 @item tfind range @var{addr1}, @var{addr2}
12903 Find the next snapshot whose PC is between @var{addr1} and
12904 @var{addr2} (inclusive).
12906 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12907 Find the next snapshot associated with the source line @var{n}. If
12908 the optional argument @var{file} is given, refer to line @var{n} in
12909 that source file. Search proceeds forward from the last examined
12910 trace snapshot. If no argument @var{n} is given, it means find the
12911 next line other than the one currently being examined; thus saying
12912 @code{tfind line} repeatedly can appear to have the same effect as
12913 stepping from line to line in a @emph{live} debugging session.
12916 The default arguments for the @code{tfind} commands are specifically
12917 designed to make it easy to scan through the trace buffer. For
12918 instance, @code{tfind} with no argument selects the next trace
12919 snapshot, and @code{tfind -} with no argument selects the previous
12920 trace snapshot. So, by giving one @code{tfind} command, and then
12921 simply hitting @key{RET} repeatedly you can examine all the trace
12922 snapshots in order. Or, by saying @code{tfind -} and then hitting
12923 @key{RET} repeatedly you can examine the snapshots in reverse order.
12924 The @code{tfind line} command with no argument selects the snapshot
12925 for the next source line executed. The @code{tfind pc} command with
12926 no argument selects the next snapshot with the same program counter
12927 (PC) as the current frame. The @code{tfind tracepoint} command with
12928 no argument selects the next trace snapshot collected by the same
12929 tracepoint as the current one.
12931 In addition to letting you scan through the trace buffer manually,
12932 these commands make it easy to construct @value{GDBN} scripts that
12933 scan through the trace buffer and print out whatever collected data
12934 you are interested in. Thus, if we want to examine the PC, FP, and SP
12935 registers from each trace frame in the buffer, we can say this:
12938 (@value{GDBP}) @b{tfind start}
12939 (@value{GDBP}) @b{while ($trace_frame != -1)}
12940 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12941 $trace_frame, $pc, $sp, $fp
12945 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12946 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12947 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12948 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12949 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12950 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12951 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12952 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12953 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12954 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12955 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12958 Or, if we want to examine the variable @code{X} at each source line in
12962 (@value{GDBP}) @b{tfind start}
12963 (@value{GDBP}) @b{while ($trace_frame != -1)}
12964 > printf "Frame %d, X == %d\n", $trace_frame, X
12974 @subsection @code{tdump}
12976 @cindex dump all data collected at tracepoint
12977 @cindex tracepoint data, display
12979 This command takes no arguments. It prints all the data collected at
12980 the current trace snapshot.
12983 (@value{GDBP}) @b{trace 444}
12984 (@value{GDBP}) @b{actions}
12985 Enter actions for tracepoint #2, one per line:
12986 > collect $regs, $locals, $args, gdb_long_test
12989 (@value{GDBP}) @b{tstart}
12991 (@value{GDBP}) @b{tfind line 444}
12992 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12994 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12996 (@value{GDBP}) @b{tdump}
12997 Data collected at tracepoint 2, trace frame 1:
12998 d0 0xc4aa0085 -995491707
13002 d4 0x71aea3d 119204413
13005 d7 0x380035 3670069
13006 a0 0x19e24a 1696330
13007 a1 0x3000668 50333288
13009 a3 0x322000 3284992
13010 a4 0x3000698 50333336
13011 a5 0x1ad3cc 1758156
13012 fp 0x30bf3c 0x30bf3c
13013 sp 0x30bf34 0x30bf34
13015 pc 0x20b2c8 0x20b2c8
13019 p = 0x20e5b4 "gdb-test"
13026 gdb_long_test = 17 '\021'
13031 @code{tdump} works by scanning the tracepoint's current collection
13032 actions and printing the value of each expression listed. So
13033 @code{tdump} can fail, if after a run, you change the tracepoint's
13034 actions to mention variables that were not collected during the run.
13036 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13037 uses the collected value of @code{$pc} to distinguish between trace
13038 frames that were collected at the tracepoint hit, and frames that were
13039 collected while stepping. This allows it to correctly choose whether
13040 to display the basic list of collections, or the collections from the
13041 body of the while-stepping loop. However, if @code{$pc} was not collected,
13042 then @code{tdump} will always attempt to dump using the basic collection
13043 list, and may fail if a while-stepping frame does not include all the
13044 same data that is collected at the tracepoint hit.
13045 @c This is getting pretty arcane, example would be good.
13047 @node save tracepoints
13048 @subsection @code{save tracepoints @var{filename}}
13049 @kindex save tracepoints
13050 @kindex save-tracepoints
13051 @cindex save tracepoints for future sessions
13053 This command saves all current tracepoint definitions together with
13054 their actions and passcounts, into a file @file{@var{filename}}
13055 suitable for use in a later debugging session. To read the saved
13056 tracepoint definitions, use the @code{source} command (@pxref{Command
13057 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13058 alias for @w{@code{save tracepoints}}
13060 @node Tracepoint Variables
13061 @section Convenience Variables for Tracepoints
13062 @cindex tracepoint variables
13063 @cindex convenience variables for tracepoints
13066 @vindex $trace_frame
13067 @item (int) $trace_frame
13068 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13069 snapshot is selected.
13071 @vindex $tracepoint
13072 @item (int) $tracepoint
13073 The tracepoint for the current trace snapshot.
13075 @vindex $trace_line
13076 @item (int) $trace_line
13077 The line number for the current trace snapshot.
13079 @vindex $trace_file
13080 @item (char []) $trace_file
13081 The source file for the current trace snapshot.
13083 @vindex $trace_func
13084 @item (char []) $trace_func
13085 The name of the function containing @code{$tracepoint}.
13088 Note: @code{$trace_file} is not suitable for use in @code{printf},
13089 use @code{output} instead.
13091 Here's a simple example of using these convenience variables for
13092 stepping through all the trace snapshots and printing some of their
13093 data. Note that these are not the same as trace state variables,
13094 which are managed by the target.
13097 (@value{GDBP}) @b{tfind start}
13099 (@value{GDBP}) @b{while $trace_frame != -1}
13100 > output $trace_file
13101 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13107 @section Using Trace Files
13108 @cindex trace files
13110 In some situations, the target running a trace experiment may no
13111 longer be available; perhaps it crashed, or the hardware was needed
13112 for a different activity. To handle these cases, you can arrange to
13113 dump the trace data into a file, and later use that file as a source
13114 of trace data, via the @code{target tfile} command.
13119 @item tsave [ -r ] @var{filename}
13120 @itemx tsave [-ctf] @var{dirname}
13121 Save the trace data to @var{filename}. By default, this command
13122 assumes that @var{filename} refers to the host filesystem, so if
13123 necessary @value{GDBN} will copy raw trace data up from the target and
13124 then save it. If the target supports it, you can also supply the
13125 optional argument @code{-r} (``remote'') to direct the target to save
13126 the data directly into @var{filename} in its own filesystem, which may be
13127 more efficient if the trace buffer is very large. (Note, however, that
13128 @code{target tfile} can only read from files accessible to the host.)
13129 By default, this command will save trace frame in tfile format.
13130 You can supply the optional argument @code{-ctf} to save date in CTF
13131 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13132 that can be shared by multiple debugging and tracing tools. Please go to
13133 @indicateurl{http://www.efficios.com/ctf} to get more information.
13135 @kindex target tfile
13139 @item target tfile @var{filename}
13140 @itemx target ctf @var{dirname}
13141 Use the file named @var{filename} or directory named @var{dirname} as
13142 a source of trace data. Commands that examine data work as they do with
13143 a live target, but it is not possible to run any new trace experiments.
13144 @code{tstatus} will report the state of the trace run at the moment
13145 the data was saved, as well as the current trace frame you are examining.
13146 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13150 (@value{GDBP}) target ctf ctf.ctf
13151 (@value{GDBP}) tfind
13152 Found trace frame 0, tracepoint 2
13153 39 ++a; /* set tracepoint 1 here */
13154 (@value{GDBP}) tdump
13155 Data collected at tracepoint 2, trace frame 0:
13159 c = @{"123", "456", "789", "123", "456", "789"@}
13160 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13168 @chapter Debugging Programs That Use Overlays
13171 If your program is too large to fit completely in your target system's
13172 memory, you can sometimes use @dfn{overlays} to work around this
13173 problem. @value{GDBN} provides some support for debugging programs that
13177 * How Overlays Work:: A general explanation of overlays.
13178 * Overlay Commands:: Managing overlays in @value{GDBN}.
13179 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13180 mapped by asking the inferior.
13181 * Overlay Sample Program:: A sample program using overlays.
13184 @node How Overlays Work
13185 @section How Overlays Work
13186 @cindex mapped overlays
13187 @cindex unmapped overlays
13188 @cindex load address, overlay's
13189 @cindex mapped address
13190 @cindex overlay area
13192 Suppose you have a computer whose instruction address space is only 64
13193 kilobytes long, but which has much more memory which can be accessed by
13194 other means: special instructions, segment registers, or memory
13195 management hardware, for example. Suppose further that you want to
13196 adapt a program which is larger than 64 kilobytes to run on this system.
13198 One solution is to identify modules of your program which are relatively
13199 independent, and need not call each other directly; call these modules
13200 @dfn{overlays}. Separate the overlays from the main program, and place
13201 their machine code in the larger memory. Place your main program in
13202 instruction memory, but leave at least enough space there to hold the
13203 largest overlay as well.
13205 Now, to call a function located in an overlay, you must first copy that
13206 overlay's machine code from the large memory into the space set aside
13207 for it in the instruction memory, and then jump to its entry point
13210 @c NB: In the below the mapped area's size is greater or equal to the
13211 @c size of all overlays. This is intentional to remind the developer
13212 @c that overlays don't necessarily need to be the same size.
13216 Data Instruction Larger
13217 Address Space Address Space Address Space
13218 +-----------+ +-----------+ +-----------+
13220 +-----------+ +-----------+ +-----------+<-- overlay 1
13221 | program | | main | .----| overlay 1 | load address
13222 | variables | | program | | +-----------+
13223 | and heap | | | | | |
13224 +-----------+ | | | +-----------+<-- overlay 2
13225 | | +-----------+ | | | load address
13226 +-----------+ | | | .-| overlay 2 |
13228 mapped --->+-----------+ | | +-----------+
13229 address | | | | | |
13230 | overlay | <-' | | |
13231 | area | <---' +-----------+<-- overlay 3
13232 | | <---. | | load address
13233 +-----------+ `--| overlay 3 |
13240 @anchor{A code overlay}A code overlay
13244 The diagram (@pxref{A code overlay}) shows a system with separate data
13245 and instruction address spaces. To map an overlay, the program copies
13246 its code from the larger address space to the instruction address space.
13247 Since the overlays shown here all use the same mapped address, only one
13248 may be mapped at a time. For a system with a single address space for
13249 data and instructions, the diagram would be similar, except that the
13250 program variables and heap would share an address space with the main
13251 program and the overlay area.
13253 An overlay loaded into instruction memory and ready for use is called a
13254 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13255 instruction memory. An overlay not present (or only partially present)
13256 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13257 is its address in the larger memory. The mapped address is also called
13258 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13259 called the @dfn{load memory address}, or @dfn{LMA}.
13261 Unfortunately, overlays are not a completely transparent way to adapt a
13262 program to limited instruction memory. They introduce a new set of
13263 global constraints you must keep in mind as you design your program:
13268 Before calling or returning to a function in an overlay, your program
13269 must make sure that overlay is actually mapped. Otherwise, the call or
13270 return will transfer control to the right address, but in the wrong
13271 overlay, and your program will probably crash.
13274 If the process of mapping an overlay is expensive on your system, you
13275 will need to choose your overlays carefully to minimize their effect on
13276 your program's performance.
13279 The executable file you load onto your system must contain each
13280 overlay's instructions, appearing at the overlay's load address, not its
13281 mapped address. However, each overlay's instructions must be relocated
13282 and its symbols defined as if the overlay were at its mapped address.
13283 You can use GNU linker scripts to specify different load and relocation
13284 addresses for pieces of your program; see @ref{Overlay Description,,,
13285 ld.info, Using ld: the GNU linker}.
13288 The procedure for loading executable files onto your system must be able
13289 to load their contents into the larger address space as well as the
13290 instruction and data spaces.
13294 The overlay system described above is rather simple, and could be
13295 improved in many ways:
13300 If your system has suitable bank switch registers or memory management
13301 hardware, you could use those facilities to make an overlay's load area
13302 contents simply appear at their mapped address in instruction space.
13303 This would probably be faster than copying the overlay to its mapped
13304 area in the usual way.
13307 If your overlays are small enough, you could set aside more than one
13308 overlay area, and have more than one overlay mapped at a time.
13311 You can use overlays to manage data, as well as instructions. In
13312 general, data overlays are even less transparent to your design than
13313 code overlays: whereas code overlays only require care when you call or
13314 return to functions, data overlays require care every time you access
13315 the data. Also, if you change the contents of a data overlay, you
13316 must copy its contents back out to its load address before you can copy a
13317 different data overlay into the same mapped area.
13322 @node Overlay Commands
13323 @section Overlay Commands
13325 To use @value{GDBN}'s overlay support, each overlay in your program must
13326 correspond to a separate section of the executable file. The section's
13327 virtual memory address and load memory address must be the overlay's
13328 mapped and load addresses. Identifying overlays with sections allows
13329 @value{GDBN} to determine the appropriate address of a function or
13330 variable, depending on whether the overlay is mapped or not.
13332 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13333 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13338 Disable @value{GDBN}'s overlay support. When overlay support is
13339 disabled, @value{GDBN} assumes that all functions and variables are
13340 always present at their mapped addresses. By default, @value{GDBN}'s
13341 overlay support is disabled.
13343 @item overlay manual
13344 @cindex manual overlay debugging
13345 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13346 relies on you to tell it which overlays are mapped, and which are not,
13347 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13348 commands described below.
13350 @item overlay map-overlay @var{overlay}
13351 @itemx overlay map @var{overlay}
13352 @cindex map an overlay
13353 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13354 be the name of the object file section containing the overlay. When an
13355 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13356 functions and variables at their mapped addresses. @value{GDBN} assumes
13357 that any other overlays whose mapped ranges overlap that of
13358 @var{overlay} are now unmapped.
13360 @item overlay unmap-overlay @var{overlay}
13361 @itemx overlay unmap @var{overlay}
13362 @cindex unmap an overlay
13363 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13364 must be the name of the object file section containing the overlay.
13365 When an overlay is unmapped, @value{GDBN} assumes it can find the
13366 overlay's functions and variables at their load addresses.
13369 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13370 consults a data structure the overlay manager maintains in the inferior
13371 to see which overlays are mapped. For details, see @ref{Automatic
13372 Overlay Debugging}.
13374 @item overlay load-target
13375 @itemx overlay load
13376 @cindex reloading the overlay table
13377 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13378 re-reads the table @value{GDBN} automatically each time the inferior
13379 stops, so this command should only be necessary if you have changed the
13380 overlay mapping yourself using @value{GDBN}. This command is only
13381 useful when using automatic overlay debugging.
13383 @item overlay list-overlays
13384 @itemx overlay list
13385 @cindex listing mapped overlays
13386 Display a list of the overlays currently mapped, along with their mapped
13387 addresses, load addresses, and sizes.
13391 Normally, when @value{GDBN} prints a code address, it includes the name
13392 of the function the address falls in:
13395 (@value{GDBP}) print main
13396 $3 = @{int ()@} 0x11a0 <main>
13399 When overlay debugging is enabled, @value{GDBN} recognizes code in
13400 unmapped overlays, and prints the names of unmapped functions with
13401 asterisks around them. For example, if @code{foo} is a function in an
13402 unmapped overlay, @value{GDBN} prints it this way:
13405 (@value{GDBP}) overlay list
13406 No sections are mapped.
13407 (@value{GDBP}) print foo
13408 $5 = @{int (int)@} 0x100000 <*foo*>
13411 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13415 (@value{GDBP}) overlay list
13416 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13417 mapped at 0x1016 - 0x104a
13418 (@value{GDBP}) print foo
13419 $6 = @{int (int)@} 0x1016 <foo>
13422 When overlay debugging is enabled, @value{GDBN} can find the correct
13423 address for functions and variables in an overlay, whether or not the
13424 overlay is mapped. This allows most @value{GDBN} commands, like
13425 @code{break} and @code{disassemble}, to work normally, even on unmapped
13426 code. However, @value{GDBN}'s breakpoint support has some limitations:
13430 @cindex breakpoints in overlays
13431 @cindex overlays, setting breakpoints in
13432 You can set breakpoints in functions in unmapped overlays, as long as
13433 @value{GDBN} can write to the overlay at its load address.
13435 @value{GDBN} can not set hardware or simulator-based breakpoints in
13436 unmapped overlays. However, if you set a breakpoint at the end of your
13437 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13438 you are using manual overlay management), @value{GDBN} will re-set its
13439 breakpoints properly.
13443 @node Automatic Overlay Debugging
13444 @section Automatic Overlay Debugging
13445 @cindex automatic overlay debugging
13447 @value{GDBN} can automatically track which overlays are mapped and which
13448 are not, given some simple co-operation from the overlay manager in the
13449 inferior. If you enable automatic overlay debugging with the
13450 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13451 looks in the inferior's memory for certain variables describing the
13452 current state of the overlays.
13454 Here are the variables your overlay manager must define to support
13455 @value{GDBN}'s automatic overlay debugging:
13459 @item @code{_ovly_table}:
13460 This variable must be an array of the following structures:
13465 /* The overlay's mapped address. */
13468 /* The size of the overlay, in bytes. */
13469 unsigned long size;
13471 /* The overlay's load address. */
13474 /* Non-zero if the overlay is currently mapped;
13476 unsigned long mapped;
13480 @item @code{_novlys}:
13481 This variable must be a four-byte signed integer, holding the total
13482 number of elements in @code{_ovly_table}.
13486 To decide whether a particular overlay is mapped or not, @value{GDBN}
13487 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13488 @code{lma} members equal the VMA and LMA of the overlay's section in the
13489 executable file. When @value{GDBN} finds a matching entry, it consults
13490 the entry's @code{mapped} member to determine whether the overlay is
13493 In addition, your overlay manager may define a function called
13494 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13495 will silently set a breakpoint there. If the overlay manager then
13496 calls this function whenever it has changed the overlay table, this
13497 will enable @value{GDBN} to accurately keep track of which overlays
13498 are in program memory, and update any breakpoints that may be set
13499 in overlays. This will allow breakpoints to work even if the
13500 overlays are kept in ROM or other non-writable memory while they
13501 are not being executed.
13503 @node Overlay Sample Program
13504 @section Overlay Sample Program
13505 @cindex overlay example program
13507 When linking a program which uses overlays, you must place the overlays
13508 at their load addresses, while relocating them to run at their mapped
13509 addresses. To do this, you must write a linker script (@pxref{Overlay
13510 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13511 since linker scripts are specific to a particular host system, target
13512 architecture, and target memory layout, this manual cannot provide
13513 portable sample code demonstrating @value{GDBN}'s overlay support.
13515 However, the @value{GDBN} source distribution does contain an overlaid
13516 program, with linker scripts for a few systems, as part of its test
13517 suite. The program consists of the following files from
13518 @file{gdb/testsuite/gdb.base}:
13522 The main program file.
13524 A simple overlay manager, used by @file{overlays.c}.
13529 Overlay modules, loaded and used by @file{overlays.c}.
13532 Linker scripts for linking the test program on the @code{d10v-elf}
13533 and @code{m32r-elf} targets.
13536 You can build the test program using the @code{d10v-elf} GCC
13537 cross-compiler like this:
13540 $ d10v-elf-gcc -g -c overlays.c
13541 $ d10v-elf-gcc -g -c ovlymgr.c
13542 $ d10v-elf-gcc -g -c foo.c
13543 $ d10v-elf-gcc -g -c bar.c
13544 $ d10v-elf-gcc -g -c baz.c
13545 $ d10v-elf-gcc -g -c grbx.c
13546 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13547 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13550 The build process is identical for any other architecture, except that
13551 you must substitute the appropriate compiler and linker script for the
13552 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13556 @chapter Using @value{GDBN} with Different Languages
13559 Although programming languages generally have common aspects, they are
13560 rarely expressed in the same manner. For instance, in ANSI C,
13561 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13562 Modula-2, it is accomplished by @code{p^}. Values can also be
13563 represented (and displayed) differently. Hex numbers in C appear as
13564 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13566 @cindex working language
13567 Language-specific information is built into @value{GDBN} for some languages,
13568 allowing you to express operations like the above in your program's
13569 native language, and allowing @value{GDBN} to output values in a manner
13570 consistent with the syntax of your program's native language. The
13571 language you use to build expressions is called the @dfn{working
13575 * Setting:: Switching between source languages
13576 * Show:: Displaying the language
13577 * Checks:: Type and range checks
13578 * Supported Languages:: Supported languages
13579 * Unsupported Languages:: Unsupported languages
13583 @section Switching Between Source Languages
13585 There are two ways to control the working language---either have @value{GDBN}
13586 set it automatically, or select it manually yourself. You can use the
13587 @code{set language} command for either purpose. On startup, @value{GDBN}
13588 defaults to setting the language automatically. The working language is
13589 used to determine how expressions you type are interpreted, how values
13592 In addition to the working language, every source file that
13593 @value{GDBN} knows about has its own working language. For some object
13594 file formats, the compiler might indicate which language a particular
13595 source file is in. However, most of the time @value{GDBN} infers the
13596 language from the name of the file. The language of a source file
13597 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13598 show each frame appropriately for its own language. There is no way to
13599 set the language of a source file from within @value{GDBN}, but you can
13600 set the language associated with a filename extension. @xref{Show, ,
13601 Displaying the Language}.
13603 This is most commonly a problem when you use a program, such
13604 as @code{cfront} or @code{f2c}, that generates C but is written in
13605 another language. In that case, make the
13606 program use @code{#line} directives in its C output; that way
13607 @value{GDBN} will know the correct language of the source code of the original
13608 program, and will display that source code, not the generated C code.
13611 * Filenames:: Filename extensions and languages.
13612 * Manually:: Setting the working language manually
13613 * Automatically:: Having @value{GDBN} infer the source language
13617 @subsection List of Filename Extensions and Languages
13619 If a source file name ends in one of the following extensions, then
13620 @value{GDBN} infers that its language is the one indicated.
13638 C@t{++} source file
13644 Objective-C source file
13648 Fortran source file
13651 Modula-2 source file
13655 Assembler source file. This actually behaves almost like C, but
13656 @value{GDBN} does not skip over function prologues when stepping.
13659 In addition, you may set the language associated with a filename
13660 extension. @xref{Show, , Displaying the Language}.
13663 @subsection Setting the Working Language
13665 If you allow @value{GDBN} to set the language automatically,
13666 expressions are interpreted the same way in your debugging session and
13669 @kindex set language
13670 If you wish, you may set the language manually. To do this, issue the
13671 command @samp{set language @var{lang}}, where @var{lang} is the name of
13672 a language, such as
13673 @code{c} or @code{modula-2}.
13674 For a list of the supported languages, type @samp{set language}.
13676 Setting the language manually prevents @value{GDBN} from updating the working
13677 language automatically. This can lead to confusion if you try
13678 to debug a program when the working language is not the same as the
13679 source language, when an expression is acceptable to both
13680 languages---but means different things. For instance, if the current
13681 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13689 might not have the effect you intended. In C, this means to add
13690 @code{b} and @code{c} and place the result in @code{a}. The result
13691 printed would be the value of @code{a}. In Modula-2, this means to compare
13692 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13694 @node Automatically
13695 @subsection Having @value{GDBN} Infer the Source Language
13697 To have @value{GDBN} set the working language automatically, use
13698 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13699 then infers the working language. That is, when your program stops in a
13700 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13701 working language to the language recorded for the function in that
13702 frame. If the language for a frame is unknown (that is, if the function
13703 or block corresponding to the frame was defined in a source file that
13704 does not have a recognized extension), the current working language is
13705 not changed, and @value{GDBN} issues a warning.
13707 This may not seem necessary for most programs, which are written
13708 entirely in one source language. However, program modules and libraries
13709 written in one source language can be used by a main program written in
13710 a different source language. Using @samp{set language auto} in this
13711 case frees you from having to set the working language manually.
13714 @section Displaying the Language
13716 The following commands help you find out which language is the
13717 working language, and also what language source files were written in.
13720 @item show language
13721 @anchor{show language}
13722 @kindex show language
13723 Display the current working language. This is the
13724 language you can use with commands such as @code{print} to
13725 build and compute expressions that may involve variables in your program.
13728 @kindex info frame@r{, show the source language}
13729 Display the source language for this frame. This language becomes the
13730 working language if you use an identifier from this frame.
13731 @xref{Frame Info, ,Information about a Frame}, to identify the other
13732 information listed here.
13735 @kindex info source@r{, show the source language}
13736 Display the source language of this source file.
13737 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13738 information listed here.
13741 In unusual circumstances, you may have source files with extensions
13742 not in the standard list. You can then set the extension associated
13743 with a language explicitly:
13746 @item set extension-language @var{ext} @var{language}
13747 @kindex set extension-language
13748 Tell @value{GDBN} that source files with extension @var{ext} are to be
13749 assumed as written in the source language @var{language}.
13751 @item info extensions
13752 @kindex info extensions
13753 List all the filename extensions and the associated languages.
13757 @section Type and Range Checking
13759 Some languages are designed to guard you against making seemingly common
13760 errors through a series of compile- and run-time checks. These include
13761 checking the type of arguments to functions and operators and making
13762 sure mathematical overflows are caught at run time. Checks such as
13763 these help to ensure a program's correctness once it has been compiled
13764 by eliminating type mismatches and providing active checks for range
13765 errors when your program is running.
13767 By default @value{GDBN} checks for these errors according to the
13768 rules of the current source language. Although @value{GDBN} does not check
13769 the statements in your program, it can check expressions entered directly
13770 into @value{GDBN} for evaluation via the @code{print} command, for example.
13773 * Type Checking:: An overview of type checking
13774 * Range Checking:: An overview of range checking
13777 @cindex type checking
13778 @cindex checks, type
13779 @node Type Checking
13780 @subsection An Overview of Type Checking
13782 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13783 arguments to operators and functions have to be of the correct type,
13784 otherwise an error occurs. These checks prevent type mismatch
13785 errors from ever causing any run-time problems. For example,
13788 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13790 (@value{GDBP}) print obj.my_method (0)
13793 (@value{GDBP}) print obj.my_method (0x1234)
13794 Cannot resolve method klass::my_method to any overloaded instance
13797 The second example fails because in C@t{++} the integer constant
13798 @samp{0x1234} is not type-compatible with the pointer parameter type.
13800 For the expressions you use in @value{GDBN} commands, you can tell
13801 @value{GDBN} to not enforce strict type checking or
13802 to treat any mismatches as errors and abandon the expression;
13803 When type checking is disabled, @value{GDBN} successfully evaluates
13804 expressions like the second example above.
13806 Even if type checking is off, there may be other reasons
13807 related to type that prevent @value{GDBN} from evaluating an expression.
13808 For instance, @value{GDBN} does not know how to add an @code{int} and
13809 a @code{struct foo}. These particular type errors have nothing to do
13810 with the language in use and usually arise from expressions which make
13811 little sense to evaluate anyway.
13813 @value{GDBN} provides some additional commands for controlling type checking:
13815 @kindex set check type
13816 @kindex show check type
13818 @item set check type on
13819 @itemx set check type off
13820 Set strict type checking on or off. If any type mismatches occur in
13821 evaluating an expression while type checking is on, @value{GDBN} prints a
13822 message and aborts evaluation of the expression.
13824 @item show check type
13825 Show the current setting of type checking and whether @value{GDBN}
13826 is enforcing strict type checking rules.
13829 @cindex range checking
13830 @cindex checks, range
13831 @node Range Checking
13832 @subsection An Overview of Range Checking
13834 In some languages (such as Modula-2), it is an error to exceed the
13835 bounds of a type; this is enforced with run-time checks. Such range
13836 checking is meant to ensure program correctness by making sure
13837 computations do not overflow, or indices on an array element access do
13838 not exceed the bounds of the array.
13840 For expressions you use in @value{GDBN} commands, you can tell
13841 @value{GDBN} to treat range errors in one of three ways: ignore them,
13842 always treat them as errors and abandon the expression, or issue
13843 warnings but evaluate the expression anyway.
13845 A range error can result from numerical overflow, from exceeding an
13846 array index bound, or when you type a constant that is not a member
13847 of any type. Some languages, however, do not treat overflows as an
13848 error. In many implementations of C, mathematical overflow causes the
13849 result to ``wrap around'' to lower values---for example, if @var{m} is
13850 the largest integer value, and @var{s} is the smallest, then
13853 @var{m} + 1 @result{} @var{s}
13856 This, too, is specific to individual languages, and in some cases
13857 specific to individual compilers or machines. @xref{Supported Languages, ,
13858 Supported Languages}, for further details on specific languages.
13860 @value{GDBN} provides some additional commands for controlling the range checker:
13862 @kindex set check range
13863 @kindex show check range
13865 @item set check range auto
13866 Set range checking on or off based on the current working language.
13867 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13870 @item set check range on
13871 @itemx set check range off
13872 Set range checking on or off, overriding the default setting for the
13873 current working language. A warning is issued if the setting does not
13874 match the language default. If a range error occurs and range checking is on,
13875 then a message is printed and evaluation of the expression is aborted.
13877 @item set check range warn
13878 Output messages when the @value{GDBN} range checker detects a range error,
13879 but attempt to evaluate the expression anyway. Evaluating the
13880 expression may still be impossible for other reasons, such as accessing
13881 memory that the process does not own (a typical example from many Unix
13885 Show the current setting of the range checker, and whether or not it is
13886 being set automatically by @value{GDBN}.
13889 @node Supported Languages
13890 @section Supported Languages
13892 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13893 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13894 @c This is false ...
13895 Some @value{GDBN} features may be used in expressions regardless of the
13896 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13897 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13898 ,Expressions}) can be used with the constructs of any supported
13901 The following sections detail to what degree each source language is
13902 supported by @value{GDBN}. These sections are not meant to be language
13903 tutorials or references, but serve only as a reference guide to what the
13904 @value{GDBN} expression parser accepts, and what input and output
13905 formats should look like for different languages. There are many good
13906 books written on each of these languages; please look to these for a
13907 language reference or tutorial.
13910 * C:: C and C@t{++}
13913 * Objective-C:: Objective-C
13914 * OpenCL C:: OpenCL C
13915 * Fortran:: Fortran
13917 * Modula-2:: Modula-2
13922 @subsection C and C@t{++}
13924 @cindex C and C@t{++}
13925 @cindex expressions in C or C@t{++}
13927 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13928 to both languages. Whenever this is the case, we discuss those languages
13932 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13933 @cindex @sc{gnu} C@t{++}
13934 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13935 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13936 effectively, you must compile your C@t{++} programs with a supported
13937 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13938 compiler (@code{aCC}).
13941 * C Operators:: C and C@t{++} operators
13942 * C Constants:: C and C@t{++} constants
13943 * C Plus Plus Expressions:: C@t{++} expressions
13944 * C Defaults:: Default settings for C and C@t{++}
13945 * C Checks:: C and C@t{++} type and range checks
13946 * Debugging C:: @value{GDBN} and C
13947 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13948 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13952 @subsubsection C and C@t{++} Operators
13954 @cindex C and C@t{++} operators
13956 Operators must be defined on values of specific types. For instance,
13957 @code{+} is defined on numbers, but not on structures. Operators are
13958 often defined on groups of types.
13960 For the purposes of C and C@t{++}, the following definitions hold:
13965 @emph{Integral types} include @code{int} with any of its storage-class
13966 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13969 @emph{Floating-point types} include @code{float}, @code{double}, and
13970 @code{long double} (if supported by the target platform).
13973 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13976 @emph{Scalar types} include all of the above.
13981 The following operators are supported. They are listed here
13982 in order of increasing precedence:
13986 The comma or sequencing operator. Expressions in a comma-separated list
13987 are evaluated from left to right, with the result of the entire
13988 expression being the last expression evaluated.
13991 Assignment. The value of an assignment expression is the value
13992 assigned. Defined on scalar types.
13995 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13996 and translated to @w{@code{@var{a} = @var{a op b}}}.
13997 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13998 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13999 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14002 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14003 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14004 should be of an integral type.
14007 Logical @sc{or}. Defined on integral types.
14010 Logical @sc{and}. Defined on integral types.
14013 Bitwise @sc{or}. Defined on integral types.
14016 Bitwise exclusive-@sc{or}. Defined on integral types.
14019 Bitwise @sc{and}. Defined on integral types.
14022 Equality and inequality. Defined on scalar types. The value of these
14023 expressions is 0 for false and non-zero for true.
14025 @item <@r{, }>@r{, }<=@r{, }>=
14026 Less than, greater than, less than or equal, greater than or equal.
14027 Defined on scalar types. The value of these expressions is 0 for false
14028 and non-zero for true.
14031 left shift, and right shift. Defined on integral types.
14034 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14037 Addition and subtraction. Defined on integral types, floating-point types and
14040 @item *@r{, }/@r{, }%
14041 Multiplication, division, and modulus. Multiplication and division are
14042 defined on integral and floating-point types. Modulus is defined on
14046 Increment and decrement. When appearing before a variable, the
14047 operation is performed before the variable is used in an expression;
14048 when appearing after it, the variable's value is used before the
14049 operation takes place.
14052 Pointer dereferencing. Defined on pointer types. Same precedence as
14056 Address operator. Defined on variables. Same precedence as @code{++}.
14058 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14059 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14060 to examine the address
14061 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14065 Negative. Defined on integral and floating-point types. Same
14066 precedence as @code{++}.
14069 Logical negation. Defined on integral types. Same precedence as
14073 Bitwise complement operator. Defined on integral types. Same precedence as
14078 Structure member, and pointer-to-structure member. For convenience,
14079 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14080 pointer based on the stored type information.
14081 Defined on @code{struct} and @code{union} data.
14084 Dereferences of pointers to members.
14087 Array indexing. @code{@var{a}[@var{i}]} is defined as
14088 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14091 Function parameter list. Same precedence as @code{->}.
14094 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14095 and @code{class} types.
14098 Doubled colons also represent the @value{GDBN} scope operator
14099 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14103 If an operator is redefined in the user code, @value{GDBN} usually
14104 attempts to invoke the redefined version instead of using the operator's
14105 predefined meaning.
14108 @subsubsection C and C@t{++} Constants
14110 @cindex C and C@t{++} constants
14112 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14117 Integer constants are a sequence of digits. Octal constants are
14118 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14119 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14120 @samp{l}, specifying that the constant should be treated as a
14124 Floating point constants are a sequence of digits, followed by a decimal
14125 point, followed by a sequence of digits, and optionally followed by an
14126 exponent. An exponent is of the form:
14127 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14128 sequence of digits. The @samp{+} is optional for positive exponents.
14129 A floating-point constant may also end with a letter @samp{f} or
14130 @samp{F}, specifying that the constant should be treated as being of
14131 the @code{float} (as opposed to the default @code{double}) type; or with
14132 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14136 Enumerated constants consist of enumerated identifiers, or their
14137 integral equivalents.
14140 Character constants are a single character surrounded by single quotes
14141 (@code{'}), or a number---the ordinal value of the corresponding character
14142 (usually its @sc{ascii} value). Within quotes, the single character may
14143 be represented by a letter or by @dfn{escape sequences}, which are of
14144 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14145 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14146 @samp{@var{x}} is a predefined special character---for example,
14147 @samp{\n} for newline.
14149 Wide character constants can be written by prefixing a character
14150 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14151 form of @samp{x}. The target wide character set is used when
14152 computing the value of this constant (@pxref{Character Sets}).
14155 String constants are a sequence of character constants surrounded by
14156 double quotes (@code{"}). Any valid character constant (as described
14157 above) may appear. Double quotes within the string must be preceded by
14158 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14161 Wide string constants can be written by prefixing a string constant
14162 with @samp{L}, as in C. The target wide character set is used when
14163 computing the value of this constant (@pxref{Character Sets}).
14166 Pointer constants are an integral value. You can also write pointers
14167 to constants using the C operator @samp{&}.
14170 Array constants are comma-separated lists surrounded by braces @samp{@{}
14171 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14172 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14173 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14176 @node C Plus Plus Expressions
14177 @subsubsection C@t{++} Expressions
14179 @cindex expressions in C@t{++}
14180 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14182 @cindex debugging C@t{++} programs
14183 @cindex C@t{++} compilers
14184 @cindex debug formats and C@t{++}
14185 @cindex @value{NGCC} and C@t{++}
14187 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14188 the proper compiler and the proper debug format. Currently,
14189 @value{GDBN} works best when debugging C@t{++} code that is compiled
14190 with the most recent version of @value{NGCC} possible. The DWARF
14191 debugging format is preferred; @value{NGCC} defaults to this on most
14192 popular platforms. Other compilers and/or debug formats are likely to
14193 work badly or not at all when using @value{GDBN} to debug C@t{++}
14194 code. @xref{Compilation}.
14199 @cindex member functions
14201 Member function calls are allowed; you can use expressions like
14204 count = aml->GetOriginal(x, y)
14207 @vindex this@r{, inside C@t{++} member functions}
14208 @cindex namespace in C@t{++}
14210 While a member function is active (in the selected stack frame), your
14211 expressions have the same namespace available as the member function;
14212 that is, @value{GDBN} allows implicit references to the class instance
14213 pointer @code{this} following the same rules as C@t{++}. @code{using}
14214 declarations in the current scope are also respected by @value{GDBN}.
14216 @cindex call overloaded functions
14217 @cindex overloaded functions, calling
14218 @cindex type conversions in C@t{++}
14220 You can call overloaded functions; @value{GDBN} resolves the function
14221 call to the right definition, with some restrictions. @value{GDBN} does not
14222 perform overload resolution involving user-defined type conversions,
14223 calls to constructors, or instantiations of templates that do not exist
14224 in the program. It also cannot handle ellipsis argument lists or
14227 It does perform integral conversions and promotions, floating-point
14228 promotions, arithmetic conversions, pointer conversions, conversions of
14229 class objects to base classes, and standard conversions such as those of
14230 functions or arrays to pointers; it requires an exact match on the
14231 number of function arguments.
14233 Overload resolution is always performed, unless you have specified
14234 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14235 ,@value{GDBN} Features for C@t{++}}.
14237 You must specify @code{set overload-resolution off} in order to use an
14238 explicit function signature to call an overloaded function, as in
14240 p 'foo(char,int)'('x', 13)
14243 The @value{GDBN} command-completion facility can simplify this;
14244 see @ref{Completion, ,Command Completion}.
14246 @cindex reference declarations
14248 @value{GDBN} understands variables declared as C@t{++} references; you can use
14249 them in expressions just as you do in C@t{++} source---they are automatically
14252 In the parameter list shown when @value{GDBN} displays a frame, the values of
14253 reference variables are not displayed (unlike other variables); this
14254 avoids clutter, since references are often used for large structures.
14255 The @emph{address} of a reference variable is always shown, unless
14256 you have specified @samp{set print address off}.
14259 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14260 expressions can use it just as expressions in your program do. Since
14261 one scope may be defined in another, you can use @code{::} repeatedly if
14262 necessary, for example in an expression like
14263 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14264 resolving name scope by reference to source files, in both C and C@t{++}
14265 debugging (@pxref{Variables, ,Program Variables}).
14268 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14273 @subsubsection C and C@t{++} Defaults
14275 @cindex C and C@t{++} defaults
14277 If you allow @value{GDBN} to set range checking automatically, it
14278 defaults to @code{off} whenever the working language changes to
14279 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14280 selects the working language.
14282 If you allow @value{GDBN} to set the language automatically, it
14283 recognizes source files whose names end with @file{.c}, @file{.C}, or
14284 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14285 these files, it sets the working language to C or C@t{++}.
14286 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14287 for further details.
14290 @subsubsection C and C@t{++} Type and Range Checks
14292 @cindex C and C@t{++} checks
14294 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14295 checking is used. However, if you turn type checking off, @value{GDBN}
14296 will allow certain non-standard conversions, such as promoting integer
14297 constants to pointers.
14299 Range checking, if turned on, is done on mathematical operations. Array
14300 indices are not checked, since they are often used to index a pointer
14301 that is not itself an array.
14304 @subsubsection @value{GDBN} and C
14306 The @code{set print union} and @code{show print union} commands apply to
14307 the @code{union} type. When set to @samp{on}, any @code{union} that is
14308 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14309 appears as @samp{@{...@}}.
14311 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14312 with pointers and a memory allocation function. @xref{Expressions,
14315 @node Debugging C Plus Plus
14316 @subsubsection @value{GDBN} Features for C@t{++}
14318 @cindex commands for C@t{++}
14320 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14321 designed specifically for use with C@t{++}. Here is a summary:
14324 @cindex break in overloaded functions
14325 @item @r{breakpoint menus}
14326 When you want a breakpoint in a function whose name is overloaded,
14327 @value{GDBN} has the capability to display a menu of possible breakpoint
14328 locations to help you specify which function definition you want.
14329 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14331 @cindex overloading in C@t{++}
14332 @item rbreak @var{regex}
14333 Setting breakpoints using regular expressions is helpful for setting
14334 breakpoints on overloaded functions that are not members of any special
14336 @xref{Set Breaks, ,Setting Breakpoints}.
14338 @cindex C@t{++} exception handling
14340 @itemx catch rethrow
14342 Debug C@t{++} exception handling using these commands. @xref{Set
14343 Catchpoints, , Setting Catchpoints}.
14345 @cindex inheritance
14346 @item ptype @var{typename}
14347 Print inheritance relationships as well as other information for type
14349 @xref{Symbols, ,Examining the Symbol Table}.
14351 @item info vtbl @var{expression}.
14352 The @code{info vtbl} command can be used to display the virtual
14353 method tables of the object computed by @var{expression}. This shows
14354 one entry per virtual table; there may be multiple virtual tables when
14355 multiple inheritance is in use.
14357 @cindex C@t{++} demangling
14358 @item demangle @var{name}
14359 Demangle @var{name}.
14360 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14362 @cindex C@t{++} symbol display
14363 @item set print demangle
14364 @itemx show print demangle
14365 @itemx set print asm-demangle
14366 @itemx show print asm-demangle
14367 Control whether C@t{++} symbols display in their source form, both when
14368 displaying code as C@t{++} source and when displaying disassemblies.
14369 @xref{Print Settings, ,Print Settings}.
14371 @item set print object
14372 @itemx show print object
14373 Choose whether to print derived (actual) or declared types of objects.
14374 @xref{Print Settings, ,Print Settings}.
14376 @item set print vtbl
14377 @itemx show print vtbl
14378 Control the format for printing virtual function tables.
14379 @xref{Print Settings, ,Print Settings}.
14380 (The @code{vtbl} commands do not work on programs compiled with the HP
14381 ANSI C@t{++} compiler (@code{aCC}).)
14383 @kindex set overload-resolution
14384 @cindex overloaded functions, overload resolution
14385 @item set overload-resolution on
14386 Enable overload resolution for C@t{++} expression evaluation. The default
14387 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14388 and searches for a function whose signature matches the argument types,
14389 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14390 Expressions, ,C@t{++} Expressions}, for details).
14391 If it cannot find a match, it emits a message.
14393 @item set overload-resolution off
14394 Disable overload resolution for C@t{++} expression evaluation. For
14395 overloaded functions that are not class member functions, @value{GDBN}
14396 chooses the first function of the specified name that it finds in the
14397 symbol table, whether or not its arguments are of the correct type. For
14398 overloaded functions that are class member functions, @value{GDBN}
14399 searches for a function whose signature @emph{exactly} matches the
14402 @kindex show overload-resolution
14403 @item show overload-resolution
14404 Show the current setting of overload resolution.
14406 @item @r{Overloaded symbol names}
14407 You can specify a particular definition of an overloaded symbol, using
14408 the same notation that is used to declare such symbols in C@t{++}: type
14409 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14410 also use the @value{GDBN} command-line word completion facilities to list the
14411 available choices, or to finish the type list for you.
14412 @xref{Completion,, Command Completion}, for details on how to do this.
14415 @node Decimal Floating Point
14416 @subsubsection Decimal Floating Point format
14417 @cindex decimal floating point format
14419 @value{GDBN} can examine, set and perform computations with numbers in
14420 decimal floating point format, which in the C language correspond to the
14421 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14422 specified by the extension to support decimal floating-point arithmetic.
14424 There are two encodings in use, depending on the architecture: BID (Binary
14425 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14426 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14429 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14430 to manipulate decimal floating point numbers, it is not possible to convert
14431 (using a cast, for example) integers wider than 32-bit to decimal float.
14433 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14434 point computations, error checking in decimal float operations ignores
14435 underflow, overflow and divide by zero exceptions.
14437 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14438 to inspect @code{_Decimal128} values stored in floating point registers.
14439 See @ref{PowerPC,,PowerPC} for more details.
14445 @value{GDBN} can be used to debug programs written in D and compiled with
14446 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14447 specific feature --- dynamic arrays.
14452 @cindex Go (programming language)
14453 @value{GDBN} can be used to debug programs written in Go and compiled with
14454 @file{gccgo} or @file{6g} compilers.
14456 Here is a summary of the Go-specific features and restrictions:
14459 @cindex current Go package
14460 @item The current Go package
14461 The name of the current package does not need to be specified when
14462 specifying global variables and functions.
14464 For example, given the program:
14468 var myglob = "Shall we?"
14474 When stopped inside @code{main} either of these work:
14478 (gdb) p main.myglob
14481 @cindex builtin Go types
14482 @item Builtin Go types
14483 The @code{string} type is recognized by @value{GDBN} and is printed
14486 @cindex builtin Go functions
14487 @item Builtin Go functions
14488 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14489 function and handles it internally.
14491 @cindex restrictions on Go expressions
14492 @item Restrictions on Go expressions
14493 All Go operators are supported except @code{&^}.
14494 The Go @code{_} ``blank identifier'' is not supported.
14495 Automatic dereferencing of pointers is not supported.
14499 @subsection Objective-C
14501 @cindex Objective-C
14502 This section provides information about some commands and command
14503 options that are useful for debugging Objective-C code. See also
14504 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14505 few more commands specific to Objective-C support.
14508 * Method Names in Commands::
14509 * The Print Command with Objective-C::
14512 @node Method Names in Commands
14513 @subsubsection Method Names in Commands
14515 The following commands have been extended to accept Objective-C method
14516 names as line specifications:
14518 @kindex clear@r{, and Objective-C}
14519 @kindex break@r{, and Objective-C}
14520 @kindex info line@r{, and Objective-C}
14521 @kindex jump@r{, and Objective-C}
14522 @kindex list@r{, and Objective-C}
14526 @item @code{info line}
14531 A fully qualified Objective-C method name is specified as
14534 -[@var{Class} @var{methodName}]
14537 where the minus sign is used to indicate an instance method and a
14538 plus sign (not shown) is used to indicate a class method. The class
14539 name @var{Class} and method name @var{methodName} are enclosed in
14540 brackets, similar to the way messages are specified in Objective-C
14541 source code. For example, to set a breakpoint at the @code{create}
14542 instance method of class @code{Fruit} in the program currently being
14546 break -[Fruit create]
14549 To list ten program lines around the @code{initialize} class method,
14553 list +[NSText initialize]
14556 In the current version of @value{GDBN}, the plus or minus sign is
14557 required. In future versions of @value{GDBN}, the plus or minus
14558 sign will be optional, but you can use it to narrow the search. It
14559 is also possible to specify just a method name:
14565 You must specify the complete method name, including any colons. If
14566 your program's source files contain more than one @code{create} method,
14567 you'll be presented with a numbered list of classes that implement that
14568 method. Indicate your choice by number, or type @samp{0} to exit if
14571 As another example, to clear a breakpoint established at the
14572 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14575 clear -[NSWindow makeKeyAndOrderFront:]
14578 @node The Print Command with Objective-C
14579 @subsubsection The Print Command With Objective-C
14580 @cindex Objective-C, print objects
14581 @kindex print-object
14582 @kindex po @r{(@code{print-object})}
14584 The print command has also been extended to accept methods. For example:
14587 print -[@var{object} hash]
14590 @cindex print an Objective-C object description
14591 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14593 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14594 and print the result. Also, an additional command has been added,
14595 @code{print-object} or @code{po} for short, which is meant to print
14596 the description of an object. However, this command may only work
14597 with certain Objective-C libraries that have a particular hook
14598 function, @code{_NSPrintForDebugger}, defined.
14601 @subsection OpenCL C
14604 This section provides information about @value{GDBN}s OpenCL C support.
14607 * OpenCL C Datatypes::
14608 * OpenCL C Expressions::
14609 * OpenCL C Operators::
14612 @node OpenCL C Datatypes
14613 @subsubsection OpenCL C Datatypes
14615 @cindex OpenCL C Datatypes
14616 @value{GDBN} supports the builtin scalar and vector datatypes specified
14617 by OpenCL 1.1. In addition the half- and double-precision floating point
14618 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14619 extensions are also known to @value{GDBN}.
14621 @node OpenCL C Expressions
14622 @subsubsection OpenCL C Expressions
14624 @cindex OpenCL C Expressions
14625 @value{GDBN} supports accesses to vector components including the access as
14626 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14627 supported by @value{GDBN} can be used as well.
14629 @node OpenCL C Operators
14630 @subsubsection OpenCL C Operators
14632 @cindex OpenCL C Operators
14633 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14637 @subsection Fortran
14638 @cindex Fortran-specific support in @value{GDBN}
14640 @value{GDBN} can be used to debug programs written in Fortran, but it
14641 currently supports only the features of Fortran 77 language.
14643 @cindex trailing underscore, in Fortran symbols
14644 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14645 among them) append an underscore to the names of variables and
14646 functions. When you debug programs compiled by those compilers, you
14647 will need to refer to variables and functions with a trailing
14651 * Fortran Operators:: Fortran operators and expressions
14652 * Fortran Defaults:: Default settings for Fortran
14653 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14656 @node Fortran Operators
14657 @subsubsection Fortran Operators and Expressions
14659 @cindex Fortran operators and expressions
14661 Operators must be defined on values of specific types. For instance,
14662 @code{+} is defined on numbers, but not on characters or other non-
14663 arithmetic types. Operators are often defined on groups of types.
14667 The exponentiation operator. It raises the first operand to the power
14671 The range operator. Normally used in the form of array(low:high) to
14672 represent a section of array.
14675 The access component operator. Normally used to access elements in derived
14676 types. Also suitable for unions. As unions aren't part of regular Fortran,
14677 this can only happen when accessing a register that uses a gdbarch-defined
14681 @node Fortran Defaults
14682 @subsubsection Fortran Defaults
14684 @cindex Fortran Defaults
14686 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14687 default uses case-insensitive matches for Fortran symbols. You can
14688 change that with the @samp{set case-insensitive} command, see
14689 @ref{Symbols}, for the details.
14691 @node Special Fortran Commands
14692 @subsubsection Special Fortran Commands
14694 @cindex Special Fortran commands
14696 @value{GDBN} has some commands to support Fortran-specific features,
14697 such as displaying common blocks.
14700 @cindex @code{COMMON} blocks, Fortran
14701 @kindex info common
14702 @item info common @r{[}@var{common-name}@r{]}
14703 This command prints the values contained in the Fortran @code{COMMON}
14704 block whose name is @var{common-name}. With no argument, the names of
14705 all @code{COMMON} blocks visible at the current program location are
14712 @cindex Pascal support in @value{GDBN}, limitations
14713 Debugging Pascal programs which use sets, subranges, file variables, or
14714 nested functions does not currently work. @value{GDBN} does not support
14715 entering expressions, printing values, or similar features using Pascal
14718 The Pascal-specific command @code{set print pascal_static-members}
14719 controls whether static members of Pascal objects are displayed.
14720 @xref{Print Settings, pascal_static-members}.
14723 @subsection Modula-2
14725 @cindex Modula-2, @value{GDBN} support
14727 The extensions made to @value{GDBN} to support Modula-2 only support
14728 output from the @sc{gnu} Modula-2 compiler (which is currently being
14729 developed). Other Modula-2 compilers are not currently supported, and
14730 attempting to debug executables produced by them is most likely
14731 to give an error as @value{GDBN} reads in the executable's symbol
14734 @cindex expressions in Modula-2
14736 * M2 Operators:: Built-in operators
14737 * Built-In Func/Proc:: Built-in functions and procedures
14738 * M2 Constants:: Modula-2 constants
14739 * M2 Types:: Modula-2 types
14740 * M2 Defaults:: Default settings for Modula-2
14741 * Deviations:: Deviations from standard Modula-2
14742 * M2 Checks:: Modula-2 type and range checks
14743 * M2 Scope:: The scope operators @code{::} and @code{.}
14744 * GDB/M2:: @value{GDBN} and Modula-2
14748 @subsubsection Operators
14749 @cindex Modula-2 operators
14751 Operators must be defined on values of specific types. For instance,
14752 @code{+} is defined on numbers, but not on structures. Operators are
14753 often defined on groups of types. For the purposes of Modula-2, the
14754 following definitions hold:
14759 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14763 @emph{Character types} consist of @code{CHAR} and its subranges.
14766 @emph{Floating-point types} consist of @code{REAL}.
14769 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14773 @emph{Scalar types} consist of all of the above.
14776 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14779 @emph{Boolean types} consist of @code{BOOLEAN}.
14783 The following operators are supported, and appear in order of
14784 increasing precedence:
14788 Function argument or array index separator.
14791 Assignment. The value of @var{var} @code{:=} @var{value} is
14795 Less than, greater than on integral, floating-point, or enumerated
14799 Less than or equal to, greater than or equal to
14800 on integral, floating-point and enumerated types, or set inclusion on
14801 set types. Same precedence as @code{<}.
14803 @item =@r{, }<>@r{, }#
14804 Equality and two ways of expressing inequality, valid on scalar types.
14805 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14806 available for inequality, since @code{#} conflicts with the script
14810 Set membership. Defined on set types and the types of their members.
14811 Same precedence as @code{<}.
14814 Boolean disjunction. Defined on boolean types.
14817 Boolean conjunction. Defined on boolean types.
14820 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14823 Addition and subtraction on integral and floating-point types, or union
14824 and difference on set types.
14827 Multiplication on integral and floating-point types, or set intersection
14831 Division on floating-point types, or symmetric set difference on set
14832 types. Same precedence as @code{*}.
14835 Integer division and remainder. Defined on integral types. Same
14836 precedence as @code{*}.
14839 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14842 Pointer dereferencing. Defined on pointer types.
14845 Boolean negation. Defined on boolean types. Same precedence as
14849 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14850 precedence as @code{^}.
14853 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14856 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14860 @value{GDBN} and Modula-2 scope operators.
14864 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14865 treats the use of the operator @code{IN}, or the use of operators
14866 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14867 @code{<=}, and @code{>=} on sets as an error.
14871 @node Built-In Func/Proc
14872 @subsubsection Built-in Functions and Procedures
14873 @cindex Modula-2 built-ins
14875 Modula-2 also makes available several built-in procedures and functions.
14876 In describing these, the following metavariables are used:
14881 represents an @code{ARRAY} variable.
14884 represents a @code{CHAR} constant or variable.
14887 represents a variable or constant of integral type.
14890 represents an identifier that belongs to a set. Generally used in the
14891 same function with the metavariable @var{s}. The type of @var{s} should
14892 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14895 represents a variable or constant of integral or floating-point type.
14898 represents a variable or constant of floating-point type.
14904 represents a variable.
14907 represents a variable or constant of one of many types. See the
14908 explanation of the function for details.
14911 All Modula-2 built-in procedures also return a result, described below.
14915 Returns the absolute value of @var{n}.
14918 If @var{c} is a lower case letter, it returns its upper case
14919 equivalent, otherwise it returns its argument.
14922 Returns the character whose ordinal value is @var{i}.
14925 Decrements the value in the variable @var{v} by one. Returns the new value.
14927 @item DEC(@var{v},@var{i})
14928 Decrements the value in the variable @var{v} by @var{i}. Returns the
14931 @item EXCL(@var{m},@var{s})
14932 Removes the element @var{m} from the set @var{s}. Returns the new
14935 @item FLOAT(@var{i})
14936 Returns the floating point equivalent of the integer @var{i}.
14938 @item HIGH(@var{a})
14939 Returns the index of the last member of @var{a}.
14942 Increments the value in the variable @var{v} by one. Returns the new value.
14944 @item INC(@var{v},@var{i})
14945 Increments the value in the variable @var{v} by @var{i}. Returns the
14948 @item INCL(@var{m},@var{s})
14949 Adds the element @var{m} to the set @var{s} if it is not already
14950 there. Returns the new set.
14953 Returns the maximum value of the type @var{t}.
14956 Returns the minimum value of the type @var{t}.
14959 Returns boolean TRUE if @var{i} is an odd number.
14962 Returns the ordinal value of its argument. For example, the ordinal
14963 value of a character is its @sc{ascii} value (on machines supporting
14964 the @sc{ascii} character set). The argument @var{x} must be of an
14965 ordered type, which include integral, character and enumerated types.
14967 @item SIZE(@var{x})
14968 Returns the size of its argument. The argument @var{x} can be a
14969 variable or a type.
14971 @item TRUNC(@var{r})
14972 Returns the integral part of @var{r}.
14974 @item TSIZE(@var{x})
14975 Returns the size of its argument. The argument @var{x} can be a
14976 variable or a type.
14978 @item VAL(@var{t},@var{i})
14979 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14983 @emph{Warning:} Sets and their operations are not yet supported, so
14984 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14988 @cindex Modula-2 constants
14990 @subsubsection Constants
14992 @value{GDBN} allows you to express the constants of Modula-2 in the following
14998 Integer constants are simply a sequence of digits. When used in an
14999 expression, a constant is interpreted to be type-compatible with the
15000 rest of the expression. Hexadecimal integers are specified by a
15001 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15004 Floating point constants appear as a sequence of digits, followed by a
15005 decimal point and another sequence of digits. An optional exponent can
15006 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15007 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15008 digits of the floating point constant must be valid decimal (base 10)
15012 Character constants consist of a single character enclosed by a pair of
15013 like quotes, either single (@code{'}) or double (@code{"}). They may
15014 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15015 followed by a @samp{C}.
15018 String constants consist of a sequence of characters enclosed by a
15019 pair of like quotes, either single (@code{'}) or double (@code{"}).
15020 Escape sequences in the style of C are also allowed. @xref{C
15021 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15025 Enumerated constants consist of an enumerated identifier.
15028 Boolean constants consist of the identifiers @code{TRUE} and
15032 Pointer constants consist of integral values only.
15035 Set constants are not yet supported.
15039 @subsubsection Modula-2 Types
15040 @cindex Modula-2 types
15042 Currently @value{GDBN} can print the following data types in Modula-2
15043 syntax: array types, record types, set types, pointer types, procedure
15044 types, enumerated types, subrange types and base types. You can also
15045 print the contents of variables declared using these type.
15046 This section gives a number of simple source code examples together with
15047 sample @value{GDBN} sessions.
15049 The first example contains the following section of code:
15058 and you can request @value{GDBN} to interrogate the type and value of
15059 @code{r} and @code{s}.
15062 (@value{GDBP}) print s
15064 (@value{GDBP}) ptype s
15066 (@value{GDBP}) print r
15068 (@value{GDBP}) ptype r
15073 Likewise if your source code declares @code{s} as:
15077 s: SET ['A'..'Z'] ;
15081 then you may query the type of @code{s} by:
15084 (@value{GDBP}) ptype s
15085 type = SET ['A'..'Z']
15089 Note that at present you cannot interactively manipulate set
15090 expressions using the debugger.
15092 The following example shows how you might declare an array in Modula-2
15093 and how you can interact with @value{GDBN} to print its type and contents:
15097 s: ARRAY [-10..10] OF CHAR ;
15101 (@value{GDBP}) ptype s
15102 ARRAY [-10..10] OF CHAR
15105 Note that the array handling is not yet complete and although the type
15106 is printed correctly, expression handling still assumes that all
15107 arrays have a lower bound of zero and not @code{-10} as in the example
15110 Here are some more type related Modula-2 examples:
15114 colour = (blue, red, yellow, green) ;
15115 t = [blue..yellow] ;
15123 The @value{GDBN} interaction shows how you can query the data type
15124 and value of a variable.
15127 (@value{GDBP}) print s
15129 (@value{GDBP}) ptype t
15130 type = [blue..yellow]
15134 In this example a Modula-2 array is declared and its contents
15135 displayed. Observe that the contents are written in the same way as
15136 their @code{C} counterparts.
15140 s: ARRAY [1..5] OF CARDINAL ;
15146 (@value{GDBP}) print s
15147 $1 = @{1, 0, 0, 0, 0@}
15148 (@value{GDBP}) ptype s
15149 type = ARRAY [1..5] OF CARDINAL
15152 The Modula-2 language interface to @value{GDBN} also understands
15153 pointer types as shown in this example:
15157 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15164 and you can request that @value{GDBN} describes the type of @code{s}.
15167 (@value{GDBP}) ptype s
15168 type = POINTER TO ARRAY [1..5] OF CARDINAL
15171 @value{GDBN} handles compound types as we can see in this example.
15172 Here we combine array types, record types, pointer types and subrange
15183 myarray = ARRAY myrange OF CARDINAL ;
15184 myrange = [-2..2] ;
15186 s: POINTER TO ARRAY myrange OF foo ;
15190 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15194 (@value{GDBP}) ptype s
15195 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15198 f3 : ARRAY [-2..2] OF CARDINAL;
15203 @subsubsection Modula-2 Defaults
15204 @cindex Modula-2 defaults
15206 If type and range checking are set automatically by @value{GDBN}, they
15207 both default to @code{on} whenever the working language changes to
15208 Modula-2. This happens regardless of whether you or @value{GDBN}
15209 selected the working language.
15211 If you allow @value{GDBN} to set the language automatically, then entering
15212 code compiled from a file whose name ends with @file{.mod} sets the
15213 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15214 Infer the Source Language}, for further details.
15217 @subsubsection Deviations from Standard Modula-2
15218 @cindex Modula-2, deviations from
15220 A few changes have been made to make Modula-2 programs easier to debug.
15221 This is done primarily via loosening its type strictness:
15225 Unlike in standard Modula-2, pointer constants can be formed by
15226 integers. This allows you to modify pointer variables during
15227 debugging. (In standard Modula-2, the actual address contained in a
15228 pointer variable is hidden from you; it can only be modified
15229 through direct assignment to another pointer variable or expression that
15230 returned a pointer.)
15233 C escape sequences can be used in strings and characters to represent
15234 non-printable characters. @value{GDBN} prints out strings with these
15235 escape sequences embedded. Single non-printable characters are
15236 printed using the @samp{CHR(@var{nnn})} format.
15239 The assignment operator (@code{:=}) returns the value of its right-hand
15243 All built-in procedures both modify @emph{and} return their argument.
15247 @subsubsection Modula-2 Type and Range Checks
15248 @cindex Modula-2 checks
15251 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15254 @c FIXME remove warning when type/range checks added
15256 @value{GDBN} considers two Modula-2 variables type equivalent if:
15260 They are of types that have been declared equivalent via a @code{TYPE
15261 @var{t1} = @var{t2}} statement
15264 They have been declared on the same line. (Note: This is true of the
15265 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15268 As long as type checking is enabled, any attempt to combine variables
15269 whose types are not equivalent is an error.
15271 Range checking is done on all mathematical operations, assignment, array
15272 index bounds, and all built-in functions and procedures.
15275 @subsubsection The Scope Operators @code{::} and @code{.}
15277 @cindex @code{.}, Modula-2 scope operator
15278 @cindex colon, doubled as scope operator
15280 @vindex colon-colon@r{, in Modula-2}
15281 @c Info cannot handle :: but TeX can.
15284 @vindex ::@r{, in Modula-2}
15287 There are a few subtle differences between the Modula-2 scope operator
15288 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15293 @var{module} . @var{id}
15294 @var{scope} :: @var{id}
15298 where @var{scope} is the name of a module or a procedure,
15299 @var{module} the name of a module, and @var{id} is any declared
15300 identifier within your program, except another module.
15302 Using the @code{::} operator makes @value{GDBN} search the scope
15303 specified by @var{scope} for the identifier @var{id}. If it is not
15304 found in the specified scope, then @value{GDBN} searches all scopes
15305 enclosing the one specified by @var{scope}.
15307 Using the @code{.} operator makes @value{GDBN} search the current scope for
15308 the identifier specified by @var{id} that was imported from the
15309 definition module specified by @var{module}. With this operator, it is
15310 an error if the identifier @var{id} was not imported from definition
15311 module @var{module}, or if @var{id} is not an identifier in
15315 @subsubsection @value{GDBN} and Modula-2
15317 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15318 Five subcommands of @code{set print} and @code{show print} apply
15319 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15320 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15321 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15322 analogue in Modula-2.
15324 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15325 with any language, is not useful with Modula-2. Its
15326 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15327 created in Modula-2 as they can in C or C@t{++}. However, because an
15328 address can be specified by an integral constant, the construct
15329 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15331 @cindex @code{#} in Modula-2
15332 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15333 interpreted as the beginning of a comment. Use @code{<>} instead.
15339 The extensions made to @value{GDBN} for Ada only support
15340 output from the @sc{gnu} Ada (GNAT) compiler.
15341 Other Ada compilers are not currently supported, and
15342 attempting to debug executables produced by them is most likely
15346 @cindex expressions in Ada
15348 * Ada Mode Intro:: General remarks on the Ada syntax
15349 and semantics supported by Ada mode
15351 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15352 * Additions to Ada:: Extensions of the Ada expression syntax.
15353 * Stopping Before Main Program:: Debugging the program during elaboration.
15354 * Ada Exceptions:: Ada Exceptions
15355 * Ada Tasks:: Listing and setting breakpoints in tasks.
15356 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15357 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15359 * Ada Glitches:: Known peculiarities of Ada mode.
15362 @node Ada Mode Intro
15363 @subsubsection Introduction
15364 @cindex Ada mode, general
15366 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15367 syntax, with some extensions.
15368 The philosophy behind the design of this subset is
15372 That @value{GDBN} should provide basic literals and access to operations for
15373 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15374 leaving more sophisticated computations to subprograms written into the
15375 program (which therefore may be called from @value{GDBN}).
15378 That type safety and strict adherence to Ada language restrictions
15379 are not particularly important to the @value{GDBN} user.
15382 That brevity is important to the @value{GDBN} user.
15385 Thus, for brevity, the debugger acts as if all names declared in
15386 user-written packages are directly visible, even if they are not visible
15387 according to Ada rules, thus making it unnecessary to fully qualify most
15388 names with their packages, regardless of context. Where this causes
15389 ambiguity, @value{GDBN} asks the user's intent.
15391 The debugger will start in Ada mode if it detects an Ada main program.
15392 As for other languages, it will enter Ada mode when stopped in a program that
15393 was translated from an Ada source file.
15395 While in Ada mode, you may use `@t{--}' for comments. This is useful
15396 mostly for documenting command files. The standard @value{GDBN} comment
15397 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15398 middle (to allow based literals).
15400 The debugger supports limited overloading. Given a subprogram call in which
15401 the function symbol has multiple definitions, it will use the number of
15402 actual parameters and some information about their types to attempt to narrow
15403 the set of definitions. It also makes very limited use of context, preferring
15404 procedures to functions in the context of the @code{call} command, and
15405 functions to procedures elsewhere.
15407 @node Omissions from Ada
15408 @subsubsection Omissions from Ada
15409 @cindex Ada, omissions from
15411 Here are the notable omissions from the subset:
15415 Only a subset of the attributes are supported:
15419 @t{'First}, @t{'Last}, and @t{'Length}
15420 on array objects (not on types and subtypes).
15423 @t{'Min} and @t{'Max}.
15426 @t{'Pos} and @t{'Val}.
15432 @t{'Range} on array objects (not subtypes), but only as the right
15433 operand of the membership (@code{in}) operator.
15436 @t{'Access}, @t{'Unchecked_Access}, and
15437 @t{'Unrestricted_Access} (a GNAT extension).
15445 @code{Characters.Latin_1} are not available and
15446 concatenation is not implemented. Thus, escape characters in strings are
15447 not currently available.
15450 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15451 equality of representations. They will generally work correctly
15452 for strings and arrays whose elements have integer or enumeration types.
15453 They may not work correctly for arrays whose element
15454 types have user-defined equality, for arrays of real values
15455 (in particular, IEEE-conformant floating point, because of negative
15456 zeroes and NaNs), and for arrays whose elements contain unused bits with
15457 indeterminate values.
15460 The other component-by-component array operations (@code{and}, @code{or},
15461 @code{xor}, @code{not}, and relational tests other than equality)
15462 are not implemented.
15465 @cindex array aggregates (Ada)
15466 @cindex record aggregates (Ada)
15467 @cindex aggregates (Ada)
15468 There is limited support for array and record aggregates. They are
15469 permitted only on the right sides of assignments, as in these examples:
15472 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15473 (@value{GDBP}) set An_Array := (1, others => 0)
15474 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15475 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15476 (@value{GDBP}) set A_Record := (1, "Peter", True);
15477 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15481 discriminant's value by assigning an aggregate has an
15482 undefined effect if that discriminant is used within the record.
15483 However, you can first modify discriminants by directly assigning to
15484 them (which normally would not be allowed in Ada), and then performing an
15485 aggregate assignment. For example, given a variable @code{A_Rec}
15486 declared to have a type such as:
15489 type Rec (Len : Small_Integer := 0) is record
15491 Vals : IntArray (1 .. Len);
15495 you can assign a value with a different size of @code{Vals} with two
15499 (@value{GDBP}) set A_Rec.Len := 4
15500 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15503 As this example also illustrates, @value{GDBN} is very loose about the usual
15504 rules concerning aggregates. You may leave out some of the
15505 components of an array or record aggregate (such as the @code{Len}
15506 component in the assignment to @code{A_Rec} above); they will retain their
15507 original values upon assignment. You may freely use dynamic values as
15508 indices in component associations. You may even use overlapping or
15509 redundant component associations, although which component values are
15510 assigned in such cases is not defined.
15513 Calls to dispatching subprograms are not implemented.
15516 The overloading algorithm is much more limited (i.e., less selective)
15517 than that of real Ada. It makes only limited use of the context in
15518 which a subexpression appears to resolve its meaning, and it is much
15519 looser in its rules for allowing type matches. As a result, some
15520 function calls will be ambiguous, and the user will be asked to choose
15521 the proper resolution.
15524 The @code{new} operator is not implemented.
15527 Entry calls are not implemented.
15530 Aside from printing, arithmetic operations on the native VAX floating-point
15531 formats are not supported.
15534 It is not possible to slice a packed array.
15537 The names @code{True} and @code{False}, when not part of a qualified name,
15538 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15540 Should your program
15541 redefine these names in a package or procedure (at best a dubious practice),
15542 you will have to use fully qualified names to access their new definitions.
15545 @node Additions to Ada
15546 @subsubsection Additions to Ada
15547 @cindex Ada, deviations from
15549 As it does for other languages, @value{GDBN} makes certain generic
15550 extensions to Ada (@pxref{Expressions}):
15554 If the expression @var{E} is a variable residing in memory (typically
15555 a local variable or array element) and @var{N} is a positive integer,
15556 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15557 @var{N}-1 adjacent variables following it in memory as an array. In
15558 Ada, this operator is generally not necessary, since its prime use is
15559 in displaying parts of an array, and slicing will usually do this in
15560 Ada. However, there are occasional uses when debugging programs in
15561 which certain debugging information has been optimized away.
15564 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15565 appears in function or file @var{B}.'' When @var{B} is a file name,
15566 you must typically surround it in single quotes.
15569 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15570 @var{type} that appears at address @var{addr}.''
15573 A name starting with @samp{$} is a convenience variable
15574 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15577 In addition, @value{GDBN} provides a few other shortcuts and outright
15578 additions specific to Ada:
15582 The assignment statement is allowed as an expression, returning
15583 its right-hand operand as its value. Thus, you may enter
15586 (@value{GDBP}) set x := y + 3
15587 (@value{GDBP}) print A(tmp := y + 1)
15591 The semicolon is allowed as an ``operator,'' returning as its value
15592 the value of its right-hand operand.
15593 This allows, for example,
15594 complex conditional breaks:
15597 (@value{GDBP}) break f
15598 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15602 Rather than use catenation and symbolic character names to introduce special
15603 characters into strings, one may instead use a special bracket notation,
15604 which is also used to print strings. A sequence of characters of the form
15605 @samp{["@var{XX}"]} within a string or character literal denotes the
15606 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15607 sequence of characters @samp{["""]} also denotes a single quotation mark
15608 in strings. For example,
15610 "One line.["0a"]Next line.["0a"]"
15613 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15617 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15618 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15622 (@value{GDBP}) print 'max(x, y)
15626 When printing arrays, @value{GDBN} uses positional notation when the
15627 array has a lower bound of 1, and uses a modified named notation otherwise.
15628 For example, a one-dimensional array of three integers with a lower bound
15629 of 3 might print as
15636 That is, in contrast to valid Ada, only the first component has a @code{=>}
15640 You may abbreviate attributes in expressions with any unique,
15641 multi-character subsequence of
15642 their names (an exact match gets preference).
15643 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15644 in place of @t{a'length}.
15647 @cindex quoting Ada internal identifiers
15648 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15649 to lower case. The GNAT compiler uses upper-case characters for
15650 some of its internal identifiers, which are normally of no interest to users.
15651 For the rare occasions when you actually have to look at them,
15652 enclose them in angle brackets to avoid the lower-case mapping.
15655 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15659 Printing an object of class-wide type or dereferencing an
15660 access-to-class-wide value will display all the components of the object's
15661 specific type (as indicated by its run-time tag). Likewise, component
15662 selection on such a value will operate on the specific type of the
15667 @node Stopping Before Main Program
15668 @subsubsection Stopping at the Very Beginning
15670 @cindex breakpointing Ada elaboration code
15671 It is sometimes necessary to debug the program during elaboration, and
15672 before reaching the main procedure.
15673 As defined in the Ada Reference
15674 Manual, the elaboration code is invoked from a procedure called
15675 @code{adainit}. To run your program up to the beginning of
15676 elaboration, simply use the following two commands:
15677 @code{tbreak adainit} and @code{run}.
15679 @node Ada Exceptions
15680 @subsubsection Ada Exceptions
15682 A command is provided to list all Ada exceptions:
15685 @kindex info exceptions
15686 @item info exceptions
15687 @itemx info exceptions @var{regexp}
15688 The @code{info exceptions} command allows you to list all Ada exceptions
15689 defined within the program being debugged, as well as their addresses.
15690 With a regular expression, @var{regexp}, as argument, only those exceptions
15691 whose names match @var{regexp} are listed.
15694 Below is a small example, showing how the command can be used, first
15695 without argument, and next with a regular expression passed as an
15699 (@value{GDBP}) info exceptions
15700 All defined Ada exceptions:
15701 constraint_error: 0x613da0
15702 program_error: 0x613d20
15703 storage_error: 0x613ce0
15704 tasking_error: 0x613ca0
15705 const.aint_global_e: 0x613b00
15706 (@value{GDBP}) info exceptions const.aint
15707 All Ada exceptions matching regular expression "const.aint":
15708 constraint_error: 0x613da0
15709 const.aint_global_e: 0x613b00
15712 It is also possible to ask @value{GDBN} to stop your program's execution
15713 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15716 @subsubsection Extensions for Ada Tasks
15717 @cindex Ada, tasking
15719 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15720 @value{GDBN} provides the following task-related commands:
15725 This command shows a list of current Ada tasks, as in the following example:
15732 (@value{GDBP}) info tasks
15733 ID TID P-ID Pri State Name
15734 1 8088000 0 15 Child Activation Wait main_task
15735 2 80a4000 1 15 Accept Statement b
15736 3 809a800 1 15 Child Activation Wait a
15737 * 4 80ae800 3 15 Runnable c
15742 In this listing, the asterisk before the last task indicates it to be the
15743 task currently being inspected.
15747 Represents @value{GDBN}'s internal task number.
15753 The parent's task ID (@value{GDBN}'s internal task number).
15756 The base priority of the task.
15759 Current state of the task.
15763 The task has been created but has not been activated. It cannot be
15767 The task is not blocked for any reason known to Ada. (It may be waiting
15768 for a mutex, though.) It is conceptually "executing" in normal mode.
15771 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15772 that were waiting on terminate alternatives have been awakened and have
15773 terminated themselves.
15775 @item Child Activation Wait
15776 The task is waiting for created tasks to complete activation.
15778 @item Accept Statement
15779 The task is waiting on an accept or selective wait statement.
15781 @item Waiting on entry call
15782 The task is waiting on an entry call.
15784 @item Async Select Wait
15785 The task is waiting to start the abortable part of an asynchronous
15789 The task is waiting on a select statement with only a delay
15792 @item Child Termination Wait
15793 The task is sleeping having completed a master within itself, and is
15794 waiting for the tasks dependent on that master to become terminated or
15795 waiting on a terminate Phase.
15797 @item Wait Child in Term Alt
15798 The task is sleeping waiting for tasks on terminate alternatives to
15799 finish terminating.
15801 @item Accepting RV with @var{taskno}
15802 The task is accepting a rendez-vous with the task @var{taskno}.
15806 Name of the task in the program.
15810 @kindex info task @var{taskno}
15811 @item info task @var{taskno}
15812 This command shows detailled informations on the specified task, as in
15813 the following example:
15818 (@value{GDBP}) info tasks
15819 ID TID P-ID Pri State Name
15820 1 8077880 0 15 Child Activation Wait main_task
15821 * 2 807c468 1 15 Runnable task_1
15822 (@value{GDBP}) info task 2
15823 Ada Task: 0x807c468
15826 Parent: 1 (main_task)
15832 @kindex task@r{ (Ada)}
15833 @cindex current Ada task ID
15834 This command prints the ID of the current task.
15840 (@value{GDBP}) info tasks
15841 ID TID P-ID Pri State Name
15842 1 8077870 0 15 Child Activation Wait main_task
15843 * 2 807c458 1 15 Runnable t
15844 (@value{GDBP}) task
15845 [Current task is 2]
15848 @item task @var{taskno}
15849 @cindex Ada task switching
15850 This command is like the @code{thread @var{threadno}}
15851 command (@pxref{Threads}). It switches the context of debugging
15852 from the current task to the given task.
15858 (@value{GDBP}) info tasks
15859 ID TID P-ID Pri State Name
15860 1 8077870 0 15 Child Activation Wait main_task
15861 * 2 807c458 1 15 Runnable t
15862 (@value{GDBP}) task 1
15863 [Switching to task 1]
15864 #0 0x8067726 in pthread_cond_wait ()
15866 #0 0x8067726 in pthread_cond_wait ()
15867 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15868 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15869 #3 0x806153e in system.tasking.stages.activate_tasks ()
15870 #4 0x804aacc in un () at un.adb:5
15873 @item break @var{linespec} task @var{taskno}
15874 @itemx break @var{linespec} task @var{taskno} if @dots{}
15875 @cindex breakpoints and tasks, in Ada
15876 @cindex task breakpoints, in Ada
15877 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15878 These commands are like the @code{break @dots{} thread @dots{}}
15879 command (@pxref{Thread Stops}). The
15880 @var{linespec} argument specifies source lines, as described
15881 in @ref{Specify Location}.
15883 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15884 to specify that you only want @value{GDBN} to stop the program when a
15885 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15886 numeric task identifiers assigned by @value{GDBN}, shown in the first
15887 column of the @samp{info tasks} display.
15889 If you do not specify @samp{task @var{taskno}} when you set a
15890 breakpoint, the breakpoint applies to @emph{all} tasks of your
15893 You can use the @code{task} qualifier on conditional breakpoints as
15894 well; in this case, place @samp{task @var{taskno}} before the
15895 breakpoint condition (before the @code{if}).
15903 (@value{GDBP}) info tasks
15904 ID TID P-ID Pri State Name
15905 1 140022020 0 15 Child Activation Wait main_task
15906 2 140045060 1 15 Accept/Select Wait t2
15907 3 140044840 1 15 Runnable t1
15908 * 4 140056040 1 15 Runnable t3
15909 (@value{GDBP}) b 15 task 2
15910 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15911 (@value{GDBP}) cont
15916 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15918 (@value{GDBP}) info tasks
15919 ID TID P-ID Pri State Name
15920 1 140022020 0 15 Child Activation Wait main_task
15921 * 2 140045060 1 15 Runnable t2
15922 3 140044840 1 15 Runnable t1
15923 4 140056040 1 15 Delay Sleep t3
15927 @node Ada Tasks and Core Files
15928 @subsubsection Tasking Support when Debugging Core Files
15929 @cindex Ada tasking and core file debugging
15931 When inspecting a core file, as opposed to debugging a live program,
15932 tasking support may be limited or even unavailable, depending on
15933 the platform being used.
15934 For instance, on x86-linux, the list of tasks is available, but task
15935 switching is not supported.
15937 On certain platforms, the debugger needs to perform some
15938 memory writes in order to provide Ada tasking support. When inspecting
15939 a core file, this means that the core file must be opened with read-write
15940 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15941 Under these circumstances, you should make a backup copy of the core
15942 file before inspecting it with @value{GDBN}.
15944 @node Ravenscar Profile
15945 @subsubsection Tasking Support when using the Ravenscar Profile
15946 @cindex Ravenscar Profile
15948 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15949 specifically designed for systems with safety-critical real-time
15953 @kindex set ravenscar task-switching on
15954 @cindex task switching with program using Ravenscar Profile
15955 @item set ravenscar task-switching on
15956 Allows task switching when debugging a program that uses the Ravenscar
15957 Profile. This is the default.
15959 @kindex set ravenscar task-switching off
15960 @item set ravenscar task-switching off
15961 Turn off task switching when debugging a program that uses the Ravenscar
15962 Profile. This is mostly intended to disable the code that adds support
15963 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15964 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15965 To be effective, this command should be run before the program is started.
15967 @kindex show ravenscar task-switching
15968 @item show ravenscar task-switching
15969 Show whether it is possible to switch from task to task in a program
15970 using the Ravenscar Profile.
15975 @subsubsection Known Peculiarities of Ada Mode
15976 @cindex Ada, problems
15978 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15979 we know of several problems with and limitations of Ada mode in
15981 some of which will be fixed with planned future releases of the debugger
15982 and the GNU Ada compiler.
15986 Static constants that the compiler chooses not to materialize as objects in
15987 storage are invisible to the debugger.
15990 Named parameter associations in function argument lists are ignored (the
15991 argument lists are treated as positional).
15994 Many useful library packages are currently invisible to the debugger.
15997 Fixed-point arithmetic, conversions, input, and output is carried out using
15998 floating-point arithmetic, and may give results that only approximate those on
16002 The GNAT compiler never generates the prefix @code{Standard} for any of
16003 the standard symbols defined by the Ada language. @value{GDBN} knows about
16004 this: it will strip the prefix from names when you use it, and will never
16005 look for a name you have so qualified among local symbols, nor match against
16006 symbols in other packages or subprograms. If you have
16007 defined entities anywhere in your program other than parameters and
16008 local variables whose simple names match names in @code{Standard},
16009 GNAT's lack of qualification here can cause confusion. When this happens,
16010 you can usually resolve the confusion
16011 by qualifying the problematic names with package
16012 @code{Standard} explicitly.
16015 Older versions of the compiler sometimes generate erroneous debugging
16016 information, resulting in the debugger incorrectly printing the value
16017 of affected entities. In some cases, the debugger is able to work
16018 around an issue automatically. In other cases, the debugger is able
16019 to work around the issue, but the work-around has to be specifically
16022 @kindex set ada trust-PAD-over-XVS
16023 @kindex show ada trust-PAD-over-XVS
16026 @item set ada trust-PAD-over-XVS on
16027 Configure GDB to strictly follow the GNAT encoding when computing the
16028 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16029 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16030 a complete description of the encoding used by the GNAT compiler).
16031 This is the default.
16033 @item set ada trust-PAD-over-XVS off
16034 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16035 sometimes prints the wrong value for certain entities, changing @code{ada
16036 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16037 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16038 @code{off}, but this incurs a slight performance penalty, so it is
16039 recommended to leave this setting to @code{on} unless necessary.
16043 @cindex GNAT descriptive types
16044 @cindex GNAT encoding
16045 Internally, the debugger also relies on the compiler following a number
16046 of conventions known as the @samp{GNAT Encoding}, all documented in
16047 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16048 how the debugging information should be generated for certain types.
16049 In particular, this convention makes use of @dfn{descriptive types},
16050 which are artificial types generated purely to help the debugger.
16052 These encodings were defined at a time when the debugging information
16053 format used was not powerful enough to describe some of the more complex
16054 types available in Ada. Since DWARF allows us to express nearly all
16055 Ada features, the long-term goal is to slowly replace these descriptive
16056 types by their pure DWARF equivalent. To facilitate that transition,
16057 a new maintenance option is available to force the debugger to ignore
16058 those descriptive types. It allows the user to quickly evaluate how
16059 well @value{GDBN} works without them.
16063 @kindex maint ada set ignore-descriptive-types
16064 @item maintenance ada set ignore-descriptive-types [on|off]
16065 Control whether the debugger should ignore descriptive types.
16066 The default is not to ignore descriptives types (@code{off}).
16068 @kindex maint ada show ignore-descriptive-types
16069 @item maintenance ada show ignore-descriptive-types
16070 Show if descriptive types are ignored by @value{GDBN}.
16074 @node Unsupported Languages
16075 @section Unsupported Languages
16077 @cindex unsupported languages
16078 @cindex minimal language
16079 In addition to the other fully-supported programming languages,
16080 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16081 It does not represent a real programming language, but provides a set
16082 of capabilities close to what the C or assembly languages provide.
16083 This should allow most simple operations to be performed while debugging
16084 an application that uses a language currently not supported by @value{GDBN}.
16086 If the language is set to @code{auto}, @value{GDBN} will automatically
16087 select this language if the current frame corresponds to an unsupported
16091 @chapter Examining the Symbol Table
16093 The commands described in this chapter allow you to inquire about the
16094 symbols (names of variables, functions and types) defined in your
16095 program. This information is inherent in the text of your program and
16096 does not change as your program executes. @value{GDBN} finds it in your
16097 program's symbol table, in the file indicated when you started @value{GDBN}
16098 (@pxref{File Options, ,Choosing Files}), or by one of the
16099 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16101 @cindex symbol names
16102 @cindex names of symbols
16103 @cindex quoting names
16104 Occasionally, you may need to refer to symbols that contain unusual
16105 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16106 most frequent case is in referring to static variables in other
16107 source files (@pxref{Variables,,Program Variables}). File names
16108 are recorded in object files as debugging symbols, but @value{GDBN} would
16109 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16110 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16111 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16118 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16121 @cindex case-insensitive symbol names
16122 @cindex case sensitivity in symbol names
16123 @kindex set case-sensitive
16124 @item set case-sensitive on
16125 @itemx set case-sensitive off
16126 @itemx set case-sensitive auto
16127 Normally, when @value{GDBN} looks up symbols, it matches their names
16128 with case sensitivity determined by the current source language.
16129 Occasionally, you may wish to control that. The command @code{set
16130 case-sensitive} lets you do that by specifying @code{on} for
16131 case-sensitive matches or @code{off} for case-insensitive ones. If
16132 you specify @code{auto}, case sensitivity is reset to the default
16133 suitable for the source language. The default is case-sensitive
16134 matches for all languages except for Fortran, for which the default is
16135 case-insensitive matches.
16137 @kindex show case-sensitive
16138 @item show case-sensitive
16139 This command shows the current setting of case sensitivity for symbols
16142 @kindex set print type methods
16143 @item set print type methods
16144 @itemx set print type methods on
16145 @itemx set print type methods off
16146 Normally, when @value{GDBN} prints a class, it displays any methods
16147 declared in that class. You can control this behavior either by
16148 passing the appropriate flag to @code{ptype}, or using @command{set
16149 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16150 display the methods; this is the default. Specifying @code{off} will
16151 cause @value{GDBN} to omit the methods.
16153 @kindex show print type methods
16154 @item show print type methods
16155 This command shows the current setting of method display when printing
16158 @kindex set print type typedefs
16159 @item set print type typedefs
16160 @itemx set print type typedefs on
16161 @itemx set print type typedefs off
16163 Normally, when @value{GDBN} prints a class, it displays any typedefs
16164 defined in that class. You can control this behavior either by
16165 passing the appropriate flag to @code{ptype}, or using @command{set
16166 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16167 display the typedef definitions; this is the default. Specifying
16168 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16169 Note that this controls whether the typedef definition itself is
16170 printed, not whether typedef names are substituted when printing other
16173 @kindex show print type typedefs
16174 @item show print type typedefs
16175 This command shows the current setting of typedef display when
16178 @kindex info address
16179 @cindex address of a symbol
16180 @item info address @var{symbol}
16181 Describe where the data for @var{symbol} is stored. For a register
16182 variable, this says which register it is kept in. For a non-register
16183 local variable, this prints the stack-frame offset at which the variable
16186 Note the contrast with @samp{print &@var{symbol}}, which does not work
16187 at all for a register variable, and for a stack local variable prints
16188 the exact address of the current instantiation of the variable.
16190 @kindex info symbol
16191 @cindex symbol from address
16192 @cindex closest symbol and offset for an address
16193 @item info symbol @var{addr}
16194 Print the name of a symbol which is stored at the address @var{addr}.
16195 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16196 nearest symbol and an offset from it:
16199 (@value{GDBP}) info symbol 0x54320
16200 _initialize_vx + 396 in section .text
16204 This is the opposite of the @code{info address} command. You can use
16205 it to find out the name of a variable or a function given its address.
16207 For dynamically linked executables, the name of executable or shared
16208 library containing the symbol is also printed:
16211 (@value{GDBP}) info symbol 0x400225
16212 _start + 5 in section .text of /tmp/a.out
16213 (@value{GDBP}) info symbol 0x2aaaac2811cf
16214 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16219 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16220 Demangle @var{name}.
16221 If @var{language} is provided it is the name of the language to demangle
16222 @var{name} in. Otherwise @var{name} is demangled in the current language.
16224 The @samp{--} option specifies the end of options,
16225 and is useful when @var{name} begins with a dash.
16227 The parameter @code{demangle-style} specifies how to interpret the kind
16228 of mangling used. @xref{Print Settings}.
16231 @item whatis[/@var{flags}] [@var{arg}]
16232 Print the data type of @var{arg}, which can be either an expression
16233 or a name of a data type. With no argument, print the data type of
16234 @code{$}, the last value in the value history.
16236 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16237 is not actually evaluated, and any side-effecting operations (such as
16238 assignments or function calls) inside it do not take place.
16240 If @var{arg} is a variable or an expression, @code{whatis} prints its
16241 literal type as it is used in the source code. If the type was
16242 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16243 the data type underlying the @code{typedef}. If the type of the
16244 variable or the expression is a compound data type, such as
16245 @code{struct} or @code{class}, @code{whatis} never prints their
16246 fields or methods. It just prints the @code{struct}/@code{class}
16247 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16248 such a compound data type, use @code{ptype}.
16250 If @var{arg} is a type name that was defined using @code{typedef},
16251 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16252 Unrolling means that @code{whatis} will show the underlying type used
16253 in the @code{typedef} declaration of @var{arg}. However, if that
16254 underlying type is also a @code{typedef}, @code{whatis} will not
16257 For C code, the type names may also have the form @samp{class
16258 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16259 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16261 @var{flags} can be used to modify how the type is displayed.
16262 Available flags are:
16266 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16267 parameters and typedefs defined in a class when printing the class'
16268 members. The @code{/r} flag disables this.
16271 Do not print methods defined in the class.
16274 Print methods defined in the class. This is the default, but the flag
16275 exists in case you change the default with @command{set print type methods}.
16278 Do not print typedefs defined in the class. Note that this controls
16279 whether the typedef definition itself is printed, not whether typedef
16280 names are substituted when printing other types.
16283 Print typedefs defined in the class. This is the default, but the flag
16284 exists in case you change the default with @command{set print type typedefs}.
16288 @item ptype[/@var{flags}] [@var{arg}]
16289 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16290 detailed description of the type, instead of just the name of the type.
16291 @xref{Expressions, ,Expressions}.
16293 Contrary to @code{whatis}, @code{ptype} always unrolls any
16294 @code{typedef}s in its argument declaration, whether the argument is
16295 a variable, expression, or a data type. This means that @code{ptype}
16296 of a variable or an expression will not print literally its type as
16297 present in the source code---use @code{whatis} for that. @code{typedef}s at
16298 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16299 fields, methods and inner @code{class typedef}s of @code{struct}s,
16300 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16302 For example, for this variable declaration:
16305 typedef double real_t;
16306 struct complex @{ real_t real; double imag; @};
16307 typedef struct complex complex_t;
16309 real_t *real_pointer_var;
16313 the two commands give this output:
16317 (@value{GDBP}) whatis var
16319 (@value{GDBP}) ptype var
16320 type = struct complex @{
16324 (@value{GDBP}) whatis complex_t
16325 type = struct complex
16326 (@value{GDBP}) whatis struct complex
16327 type = struct complex
16328 (@value{GDBP}) ptype struct complex
16329 type = struct complex @{
16333 (@value{GDBP}) whatis real_pointer_var
16335 (@value{GDBP}) ptype real_pointer_var
16341 As with @code{whatis}, using @code{ptype} without an argument refers to
16342 the type of @code{$}, the last value in the value history.
16344 @cindex incomplete type
16345 Sometimes, programs use opaque data types or incomplete specifications
16346 of complex data structure. If the debug information included in the
16347 program does not allow @value{GDBN} to display a full declaration of
16348 the data type, it will say @samp{<incomplete type>}. For example,
16349 given these declarations:
16353 struct foo *fooptr;
16357 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16360 (@value{GDBP}) ptype foo
16361 $1 = <incomplete type>
16365 ``Incomplete type'' is C terminology for data types that are not
16366 completely specified.
16369 @item info types @var{regexp}
16371 Print a brief description of all types whose names match the regular
16372 expression @var{regexp} (or all types in your program, if you supply
16373 no argument). Each complete typename is matched as though it were a
16374 complete line; thus, @samp{i type value} gives information on all
16375 types in your program whose names include the string @code{value}, but
16376 @samp{i type ^value$} gives information only on types whose complete
16377 name is @code{value}.
16379 This command differs from @code{ptype} in two ways: first, like
16380 @code{whatis}, it does not print a detailed description; second, it
16381 lists all source files where a type is defined.
16383 @kindex info type-printers
16384 @item info type-printers
16385 Versions of @value{GDBN} that ship with Python scripting enabled may
16386 have ``type printers'' available. When using @command{ptype} or
16387 @command{whatis}, these printers are consulted when the name of a type
16388 is needed. @xref{Type Printing API}, for more information on writing
16391 @code{info type-printers} displays all the available type printers.
16393 @kindex enable type-printer
16394 @kindex disable type-printer
16395 @item enable type-printer @var{name}@dots{}
16396 @item disable type-printer @var{name}@dots{}
16397 These commands can be used to enable or disable type printers.
16400 @cindex local variables
16401 @item info scope @var{location}
16402 List all the variables local to a particular scope. This command
16403 accepts a @var{location} argument---a function name, a source line, or
16404 an address preceded by a @samp{*}, and prints all the variables local
16405 to the scope defined by that location. (@xref{Specify Location}, for
16406 details about supported forms of @var{location}.) For example:
16409 (@value{GDBP}) @b{info scope command_line_handler}
16410 Scope for command_line_handler:
16411 Symbol rl is an argument at stack/frame offset 8, length 4.
16412 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16413 Symbol linelength is in static storage at address 0x150a1c, length 4.
16414 Symbol p is a local variable in register $esi, length 4.
16415 Symbol p1 is a local variable in register $ebx, length 4.
16416 Symbol nline is a local variable in register $edx, length 4.
16417 Symbol repeat is a local variable at frame offset -8, length 4.
16421 This command is especially useful for determining what data to collect
16422 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16425 @kindex info source
16427 Show information about the current source file---that is, the source file for
16428 the function containing the current point of execution:
16431 the name of the source file, and the directory containing it,
16433 the directory it was compiled in,
16435 its length, in lines,
16437 which programming language it is written in,
16439 if the debug information provides it, the program that compiled the file
16440 (which may include, e.g., the compiler version and command line arguments),
16442 whether the executable includes debugging information for that file, and
16443 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16445 whether the debugging information includes information about
16446 preprocessor macros.
16450 @kindex info sources
16452 Print the names of all source files in your program for which there is
16453 debugging information, organized into two lists: files whose symbols
16454 have already been read, and files whose symbols will be read when needed.
16456 @kindex info functions
16457 @item info functions
16458 Print the names and data types of all defined functions.
16460 @item info functions @var{regexp}
16461 Print the names and data types of all defined functions
16462 whose names contain a match for regular expression @var{regexp}.
16463 Thus, @samp{info fun step} finds all functions whose names
16464 include @code{step}; @samp{info fun ^step} finds those whose names
16465 start with @code{step}. If a function name contains characters
16466 that conflict with the regular expression language (e.g.@:
16467 @samp{operator*()}), they may be quoted with a backslash.
16469 @kindex info variables
16470 @item info variables
16471 Print the names and data types of all variables that are defined
16472 outside of functions (i.e.@: excluding local variables).
16474 @item info variables @var{regexp}
16475 Print the names and data types of all variables (except for local
16476 variables) whose names contain a match for regular expression
16479 @kindex info classes
16480 @cindex Objective-C, classes and selectors
16482 @itemx info classes @var{regexp}
16483 Display all Objective-C classes in your program, or
16484 (with the @var{regexp} argument) all those matching a particular regular
16487 @kindex info selectors
16488 @item info selectors
16489 @itemx info selectors @var{regexp}
16490 Display all Objective-C selectors in your program, or
16491 (with the @var{regexp} argument) all those matching a particular regular
16495 This was never implemented.
16496 @kindex info methods
16498 @itemx info methods @var{regexp}
16499 The @code{info methods} command permits the user to examine all defined
16500 methods within C@t{++} program, or (with the @var{regexp} argument) a
16501 specific set of methods found in the various C@t{++} classes. Many
16502 C@t{++} classes provide a large number of methods. Thus, the output
16503 from the @code{ptype} command can be overwhelming and hard to use. The
16504 @code{info-methods} command filters the methods, printing only those
16505 which match the regular-expression @var{regexp}.
16508 @cindex opaque data types
16509 @kindex set opaque-type-resolution
16510 @item set opaque-type-resolution on
16511 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16512 declared as a pointer to a @code{struct}, @code{class}, or
16513 @code{union}---for example, @code{struct MyType *}---that is used in one
16514 source file although the full declaration of @code{struct MyType} is in
16515 another source file. The default is on.
16517 A change in the setting of this subcommand will not take effect until
16518 the next time symbols for a file are loaded.
16520 @item set opaque-type-resolution off
16521 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16522 is printed as follows:
16524 @{<no data fields>@}
16527 @kindex show opaque-type-resolution
16528 @item show opaque-type-resolution
16529 Show whether opaque types are resolved or not.
16531 @kindex set print symbol-loading
16532 @cindex print messages when symbols are loaded
16533 @item set print symbol-loading
16534 @itemx set print symbol-loading full
16535 @itemx set print symbol-loading brief
16536 @itemx set print symbol-loading off
16537 The @code{set print symbol-loading} command allows you to control the
16538 printing of messages when @value{GDBN} loads symbol information.
16539 By default a message is printed for the executable and one for each
16540 shared library, and normally this is what you want. However, when
16541 debugging apps with large numbers of shared libraries these messages
16543 When set to @code{brief} a message is printed for each executable,
16544 and when @value{GDBN} loads a collection of shared libraries at once
16545 it will only print one message regardless of the number of shared
16546 libraries. When set to @code{off} no messages are printed.
16548 @kindex show print symbol-loading
16549 @item show print symbol-loading
16550 Show whether messages will be printed when a @value{GDBN} command
16551 entered from the keyboard causes symbol information to be loaded.
16553 @kindex maint print symbols
16554 @cindex symbol dump
16555 @kindex maint print psymbols
16556 @cindex partial symbol dump
16557 @kindex maint print msymbols
16558 @cindex minimal symbol dump
16559 @item maint print symbols @var{filename}
16560 @itemx maint print psymbols @var{filename}
16561 @itemx maint print msymbols @var{filename}
16562 Write a dump of debugging symbol data into the file @var{filename}.
16563 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16564 symbols with debugging data are included. If you use @samp{maint print
16565 symbols}, @value{GDBN} includes all the symbols for which it has already
16566 collected full details: that is, @var{filename} reflects symbols for
16567 only those files whose symbols @value{GDBN} has read. You can use the
16568 command @code{info sources} to find out which files these are. If you
16569 use @samp{maint print psymbols} instead, the dump shows information about
16570 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16571 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16572 @samp{maint print msymbols} dumps just the minimal symbol information
16573 required for each object file from which @value{GDBN} has read some symbols.
16574 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16575 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16577 @kindex maint info symtabs
16578 @kindex maint info psymtabs
16579 @cindex listing @value{GDBN}'s internal symbol tables
16580 @cindex symbol tables, listing @value{GDBN}'s internal
16581 @cindex full symbol tables, listing @value{GDBN}'s internal
16582 @cindex partial symbol tables, listing @value{GDBN}'s internal
16583 @item maint info symtabs @r{[} @var{regexp} @r{]}
16584 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16586 List the @code{struct symtab} or @code{struct partial_symtab}
16587 structures whose names match @var{regexp}. If @var{regexp} is not
16588 given, list them all. The output includes expressions which you can
16589 copy into a @value{GDBN} debugging this one to examine a particular
16590 structure in more detail. For example:
16593 (@value{GDBP}) maint info psymtabs dwarf2read
16594 @{ objfile /home/gnu/build/gdb/gdb
16595 ((struct objfile *) 0x82e69d0)
16596 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16597 ((struct partial_symtab *) 0x8474b10)
16600 text addresses 0x814d3c8 -- 0x8158074
16601 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16602 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16603 dependencies (none)
16606 (@value{GDBP}) maint info symtabs
16610 We see that there is one partial symbol table whose filename contains
16611 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16612 and we see that @value{GDBN} has not read in any symtabs yet at all.
16613 If we set a breakpoint on a function, that will cause @value{GDBN} to
16614 read the symtab for the compilation unit containing that function:
16617 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16618 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16620 (@value{GDBP}) maint info symtabs
16621 @{ objfile /home/gnu/build/gdb/gdb
16622 ((struct objfile *) 0x82e69d0)
16623 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16624 ((struct symtab *) 0x86c1f38)
16627 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16628 linetable ((struct linetable *) 0x8370fa0)
16629 debugformat DWARF 2
16635 @kindex maint set symbol-cache-size
16636 @cindex symbol cache size
16637 @item maint set symbol-cache-size @var{size}
16638 Set the size of the symbol cache to @var{size}.
16639 The default size is intended to be good enough for debugging
16640 most applications. This option exists to allow for experimenting
16641 with different sizes.
16643 @kindex maint show symbol-cache-size
16644 @item maint show symbol-cache-size
16645 Show the size of the symbol cache.
16647 @kindex maint print symbol-cache
16648 @cindex symbol cache, printing its contents
16649 @item maint print symbol-cache
16650 Print the contents of the symbol cache.
16651 This is useful when debugging symbol cache issues.
16653 @kindex maint print symbol-cache-statistics
16654 @cindex symbol cache, printing usage statistics
16655 @item maint print symbol-cache-statistics
16656 Print symbol cache usage statistics.
16657 This helps determine how well the cache is being utilized.
16659 @kindex maint flush-symbol-cache
16660 @cindex symbol cache, flushing
16661 @item maint flush-symbol-cache
16662 Flush the contents of the symbol cache, all entries are removed.
16663 This command is useful when debugging the symbol cache.
16664 It is also useful when collecting performance data.
16669 @chapter Altering Execution
16671 Once you think you have found an error in your program, you might want to
16672 find out for certain whether correcting the apparent error would lead to
16673 correct results in the rest of the run. You can find the answer by
16674 experiment, using the @value{GDBN} features for altering execution of the
16677 For example, you can store new values into variables or memory
16678 locations, give your program a signal, restart it at a different
16679 address, or even return prematurely from a function.
16682 * Assignment:: Assignment to variables
16683 * Jumping:: Continuing at a different address
16684 * Signaling:: Giving your program a signal
16685 * Returning:: Returning from a function
16686 * Calling:: Calling your program's functions
16687 * Patching:: Patching your program
16688 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16692 @section Assignment to Variables
16695 @cindex setting variables
16696 To alter the value of a variable, evaluate an assignment expression.
16697 @xref{Expressions, ,Expressions}. For example,
16704 stores the value 4 into the variable @code{x}, and then prints the
16705 value of the assignment expression (which is 4).
16706 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16707 information on operators in supported languages.
16709 @kindex set variable
16710 @cindex variables, setting
16711 If you are not interested in seeing the value of the assignment, use the
16712 @code{set} command instead of the @code{print} command. @code{set} is
16713 really the same as @code{print} except that the expression's value is
16714 not printed and is not put in the value history (@pxref{Value History,
16715 ,Value History}). The expression is evaluated only for its effects.
16717 If the beginning of the argument string of the @code{set} command
16718 appears identical to a @code{set} subcommand, use the @code{set
16719 variable} command instead of just @code{set}. This command is identical
16720 to @code{set} except for its lack of subcommands. For example, if your
16721 program has a variable @code{width}, you get an error if you try to set
16722 a new value with just @samp{set width=13}, because @value{GDBN} has the
16723 command @code{set width}:
16726 (@value{GDBP}) whatis width
16728 (@value{GDBP}) p width
16730 (@value{GDBP}) set width=47
16731 Invalid syntax in expression.
16735 The invalid expression, of course, is @samp{=47}. In
16736 order to actually set the program's variable @code{width}, use
16739 (@value{GDBP}) set var width=47
16742 Because the @code{set} command has many subcommands that can conflict
16743 with the names of program variables, it is a good idea to use the
16744 @code{set variable} command instead of just @code{set}. For example, if
16745 your program has a variable @code{g}, you run into problems if you try
16746 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16747 the command @code{set gnutarget}, abbreviated @code{set g}:
16751 (@value{GDBP}) whatis g
16755 (@value{GDBP}) set g=4
16759 The program being debugged has been started already.
16760 Start it from the beginning? (y or n) y
16761 Starting program: /home/smith/cc_progs/a.out
16762 "/home/smith/cc_progs/a.out": can't open to read symbols:
16763 Invalid bfd target.
16764 (@value{GDBP}) show g
16765 The current BFD target is "=4".
16770 The program variable @code{g} did not change, and you silently set the
16771 @code{gnutarget} to an invalid value. In order to set the variable
16775 (@value{GDBP}) set var g=4
16778 @value{GDBN} allows more implicit conversions in assignments than C; you can
16779 freely store an integer value into a pointer variable or vice versa,
16780 and you can convert any structure to any other structure that is the
16781 same length or shorter.
16782 @comment FIXME: how do structs align/pad in these conversions?
16783 @comment /doc@cygnus.com 18dec1990
16785 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16786 construct to generate a value of specified type at a specified address
16787 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16788 to memory location @code{0x83040} as an integer (which implies a certain size
16789 and representation in memory), and
16792 set @{int@}0x83040 = 4
16796 stores the value 4 into that memory location.
16799 @section Continuing at a Different Address
16801 Ordinarily, when you continue your program, you do so at the place where
16802 it stopped, with the @code{continue} command. You can instead continue at
16803 an address of your own choosing, with the following commands:
16807 @kindex j @r{(@code{jump})}
16808 @item jump @var{linespec}
16809 @itemx j @var{linespec}
16810 @itemx jump @var{location}
16811 @itemx j @var{location}
16812 Resume execution at line @var{linespec} or at address given by
16813 @var{location}. Execution stops again immediately if there is a
16814 breakpoint there. @xref{Specify Location}, for a description of the
16815 different forms of @var{linespec} and @var{location}. It is common
16816 practice to use the @code{tbreak} command in conjunction with
16817 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16819 The @code{jump} command does not change the current stack frame, or
16820 the stack pointer, or the contents of any memory location or any
16821 register other than the program counter. If line @var{linespec} is in
16822 a different function from the one currently executing, the results may
16823 be bizarre if the two functions expect different patterns of arguments or
16824 of local variables. For this reason, the @code{jump} command requests
16825 confirmation if the specified line is not in the function currently
16826 executing. However, even bizarre results are predictable if you are
16827 well acquainted with the machine-language code of your program.
16830 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16831 On many systems, you can get much the same effect as the @code{jump}
16832 command by storing a new value into the register @code{$pc}. The
16833 difference is that this does not start your program running; it only
16834 changes the address of where it @emph{will} run when you continue. For
16842 makes the next @code{continue} command or stepping command execute at
16843 address @code{0x485}, rather than at the address where your program stopped.
16844 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16846 The most common occasion to use the @code{jump} command is to back
16847 up---perhaps with more breakpoints set---over a portion of a program
16848 that has already executed, in order to examine its execution in more
16853 @section Giving your Program a Signal
16854 @cindex deliver a signal to a program
16858 @item signal @var{signal}
16859 Resume execution where your program is stopped, but immediately give it the
16860 signal @var{signal}. The @var{signal} can be the name or the number of a
16861 signal. For example, on many systems @code{signal 2} and @code{signal
16862 SIGINT} are both ways of sending an interrupt signal.
16864 Alternatively, if @var{signal} is zero, continue execution without
16865 giving a signal. This is useful when your program stopped on account of
16866 a signal and would ordinarily see the signal when resumed with the
16867 @code{continue} command; @samp{signal 0} causes it to resume without a
16870 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16871 delivered to the currently selected thread, not the thread that last
16872 reported a stop. This includes the situation where a thread was
16873 stopped due to a signal. So if you want to continue execution
16874 suppressing the signal that stopped a thread, you should select that
16875 same thread before issuing the @samp{signal 0} command. If you issue
16876 the @samp{signal 0} command with another thread as the selected one,
16877 @value{GDBN} detects that and asks for confirmation.
16879 Invoking the @code{signal} command is not the same as invoking the
16880 @code{kill} utility from the shell. Sending a signal with @code{kill}
16881 causes @value{GDBN} to decide what to do with the signal depending on
16882 the signal handling tables (@pxref{Signals}). The @code{signal} command
16883 passes the signal directly to your program.
16885 @code{signal} does not repeat when you press @key{RET} a second time
16886 after executing the command.
16888 @kindex queue-signal
16889 @item queue-signal @var{signal}
16890 Queue @var{signal} to be delivered immediately to the current thread
16891 when execution of the thread resumes. The @var{signal} can be the name or
16892 the number of a signal. For example, on many systems @code{signal 2} and
16893 @code{signal SIGINT} are both ways of sending an interrupt signal.
16894 The handling of the signal must be set to pass the signal to the program,
16895 otherwise @value{GDBN} will report an error.
16896 You can control the handling of signals from @value{GDBN} with the
16897 @code{handle} command (@pxref{Signals}).
16899 Alternatively, if @var{signal} is zero, any currently queued signal
16900 for the current thread is discarded and when execution resumes no signal
16901 will be delivered. This is useful when your program stopped on account
16902 of a signal and would ordinarily see the signal when resumed with the
16903 @code{continue} command.
16905 This command differs from the @code{signal} command in that the signal
16906 is just queued, execution is not resumed. And @code{queue-signal} cannot
16907 be used to pass a signal whose handling state has been set to @code{nopass}
16912 @xref{stepping into signal handlers}, for information on how stepping
16913 commands behave when the thread has a signal queued.
16916 @section Returning from a Function
16919 @cindex returning from a function
16922 @itemx return @var{expression}
16923 You can cancel execution of a function call with the @code{return}
16924 command. If you give an
16925 @var{expression} argument, its value is used as the function's return
16929 When you use @code{return}, @value{GDBN} discards the selected stack frame
16930 (and all frames within it). You can think of this as making the
16931 discarded frame return prematurely. If you wish to specify a value to
16932 be returned, give that value as the argument to @code{return}.
16934 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16935 Frame}), and any other frames inside of it, leaving its caller as the
16936 innermost remaining frame. That frame becomes selected. The
16937 specified value is stored in the registers used for returning values
16940 The @code{return} command does not resume execution; it leaves the
16941 program stopped in the state that would exist if the function had just
16942 returned. In contrast, the @code{finish} command (@pxref{Continuing
16943 and Stepping, ,Continuing and Stepping}) resumes execution until the
16944 selected stack frame returns naturally.
16946 @value{GDBN} needs to know how the @var{expression} argument should be set for
16947 the inferior. The concrete registers assignment depends on the OS ABI and the
16948 type being returned by the selected stack frame. For example it is common for
16949 OS ABI to return floating point values in FPU registers while integer values in
16950 CPU registers. Still some ABIs return even floating point values in CPU
16951 registers. Larger integer widths (such as @code{long long int}) also have
16952 specific placement rules. @value{GDBN} already knows the OS ABI from its
16953 current target so it needs to find out also the type being returned to make the
16954 assignment into the right register(s).
16956 Normally, the selected stack frame has debug info. @value{GDBN} will always
16957 use the debug info instead of the implicit type of @var{expression} when the
16958 debug info is available. For example, if you type @kbd{return -1}, and the
16959 function in the current stack frame is declared to return a @code{long long
16960 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16961 into a @code{long long int}:
16964 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16966 (@value{GDBP}) return -1
16967 Make func return now? (y or n) y
16968 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16969 43 printf ("result=%lld\n", func ());
16973 However, if the selected stack frame does not have a debug info, e.g., if the
16974 function was compiled without debug info, @value{GDBN} has to find out the type
16975 to return from user. Specifying a different type by mistake may set the value
16976 in different inferior registers than the caller code expects. For example,
16977 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16978 of a @code{long long int} result for a debug info less function (on 32-bit
16979 architectures). Therefore the user is required to specify the return type by
16980 an appropriate cast explicitly:
16983 Breakpoint 2, 0x0040050b in func ()
16984 (@value{GDBP}) return -1
16985 Return value type not available for selected stack frame.
16986 Please use an explicit cast of the value to return.
16987 (@value{GDBP}) return (long long int) -1
16988 Make selected stack frame return now? (y or n) y
16989 #0 0x00400526 in main ()
16994 @section Calling Program Functions
16997 @cindex calling functions
16998 @cindex inferior functions, calling
16999 @item print @var{expr}
17000 Evaluate the expression @var{expr} and display the resulting value.
17001 The expression may include calls to functions in the program being
17005 @item call @var{expr}
17006 Evaluate the expression @var{expr} without displaying @code{void}
17009 You can use this variant of the @code{print} command if you want to
17010 execute a function from your program that does not return anything
17011 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17012 with @code{void} returned values that @value{GDBN} will otherwise
17013 print. If the result is not void, it is printed and saved in the
17017 It is possible for the function you call via the @code{print} or
17018 @code{call} command to generate a signal (e.g., if there's a bug in
17019 the function, or if you passed it incorrect arguments). What happens
17020 in that case is controlled by the @code{set unwindonsignal} command.
17022 Similarly, with a C@t{++} program it is possible for the function you
17023 call via the @code{print} or @code{call} command to generate an
17024 exception that is not handled due to the constraints of the dummy
17025 frame. In this case, any exception that is raised in the frame, but has
17026 an out-of-frame exception handler will not be found. GDB builds a
17027 dummy-frame for the inferior function call, and the unwinder cannot
17028 seek for exception handlers outside of this dummy-frame. What happens
17029 in that case is controlled by the
17030 @code{set unwind-on-terminating-exception} command.
17033 @item set unwindonsignal
17034 @kindex set unwindonsignal
17035 @cindex unwind stack in called functions
17036 @cindex call dummy stack unwinding
17037 Set unwinding of the stack if a signal is received while in a function
17038 that @value{GDBN} called in the program being debugged. If set to on,
17039 @value{GDBN} unwinds the stack it created for the call and restores
17040 the context to what it was before the call. If set to off (the
17041 default), @value{GDBN} stops in the frame where the signal was
17044 @item show unwindonsignal
17045 @kindex show unwindonsignal
17046 Show the current setting of stack unwinding in the functions called by
17049 @item set unwind-on-terminating-exception
17050 @kindex set unwind-on-terminating-exception
17051 @cindex unwind stack in called functions with unhandled exceptions
17052 @cindex call dummy stack unwinding on unhandled exception.
17053 Set unwinding of the stack if a C@t{++} exception is raised, but left
17054 unhandled while in a function that @value{GDBN} called in the program being
17055 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17056 it created for the call and restores the context to what it was before
17057 the call. If set to off, @value{GDBN} the exception is delivered to
17058 the default C@t{++} exception handler and the inferior terminated.
17060 @item show unwind-on-terminating-exception
17061 @kindex show unwind-on-terminating-exception
17062 Show the current setting of stack unwinding in the functions called by
17067 @cindex weak alias functions
17068 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17069 for another function. In such case, @value{GDBN} might not pick up
17070 the type information, including the types of the function arguments,
17071 which causes @value{GDBN} to call the inferior function incorrectly.
17072 As a result, the called function will function erroneously and may
17073 even crash. A solution to that is to use the name of the aliased
17077 @section Patching Programs
17079 @cindex patching binaries
17080 @cindex writing into executables
17081 @cindex writing into corefiles
17083 By default, @value{GDBN} opens the file containing your program's
17084 executable code (or the corefile) read-only. This prevents accidental
17085 alterations to machine code; but it also prevents you from intentionally
17086 patching your program's binary.
17088 If you'd like to be able to patch the binary, you can specify that
17089 explicitly with the @code{set write} command. For example, you might
17090 want to turn on internal debugging flags, or even to make emergency
17096 @itemx set write off
17097 If you specify @samp{set write on}, @value{GDBN} opens executable and
17098 core files for both reading and writing; if you specify @kbd{set write
17099 off} (the default), @value{GDBN} opens them read-only.
17101 If you have already loaded a file, you must load it again (using the
17102 @code{exec-file} or @code{core-file} command) after changing @code{set
17103 write}, for your new setting to take effect.
17107 Display whether executable files and core files are opened for writing
17108 as well as reading.
17111 @node Compiling and Injecting Code
17112 @section Compiling and injecting code in @value{GDBN}
17113 @cindex injecting code
17114 @cindex writing into executables
17115 @cindex compiling code
17117 @value{GDBN} supports on-demand compilation and code injection into
17118 programs running under @value{GDBN}. GCC 5.0 or higher built with
17119 @file{libcc1.so} must be installed for this functionality to be enabled.
17120 This functionality is implemented with the following commands.
17123 @kindex compile code
17124 @item compile code @var{source-code}
17125 @itemx compile code -raw @var{--} @var{source-code}
17126 Compile @var{source-code} with the compiler language found as the current
17127 language in @value{GDBN} (@pxref{Languages}). If compilation and
17128 injection is not supported with the current language specified in
17129 @value{GDBN}, or the compiler does not support this feature, an error
17130 message will be printed. If @var{source-code} compiles and links
17131 successfully, @value{GDBN} will load the object-code emitted,
17132 and execute it within the context of the currently selected inferior.
17133 It is important to note that the compiled code is executed immediately.
17134 After execution, the compiled code is removed from @value{GDBN} and any
17135 new types or variables you have defined will be deleted.
17137 The command allows you to specify @var{source-code} in two ways.
17138 The simplest method is to provide a single line of code to the command.
17142 compile code printf ("hello world\n");
17145 If you specify options on the command line as well as source code, they
17146 may conflict. The @samp{--} delimiter can be used to separate options
17147 from actual source code. E.g.:
17150 compile code -r -- printf ("hello world\n");
17153 Alternatively you can enter source code as multiple lines of text. To
17154 enter this mode, invoke the @samp{compile code} command without any text
17155 following the command. This will start the multiple-line editor and
17156 allow you to type as many lines of source code as required. When you
17157 have completed typing, enter @samp{end} on its own line to exit the
17162 >printf ("hello\n");
17163 >printf ("world\n");
17167 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17168 provided @var{source-code} in a callable scope. In this case, you must
17169 specify the entry point of the code by defining a function named
17170 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17171 inferior. Using @samp{-raw} option may be needed for example when
17172 @var{source-code} requires @samp{#include} lines which may conflict with
17173 inferior symbols otherwise.
17175 @kindex compile file
17176 @item compile file @var{filename}
17177 @itemx compile file -raw @var{filename}
17178 Like @code{compile code}, but take the source code from @var{filename}.
17181 compile file /home/user/example.c
17185 @subsection Caveats when using the @code{compile} command
17187 There are a few caveats to keep in mind when using the @code{compile}
17188 command. As the caveats are different per language, the table below
17189 highlights specific issues on a per language basis.
17192 @item C code examples and caveats
17193 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17194 attempt to compile the source code with a @samp{C} compiler. The source
17195 code provided to the @code{compile} command will have much the same
17196 access to variables and types as it normally would if it were part of
17197 the program currently being debugged in @value{GDBN}.
17199 Below is a sample program that forms the basis of the examples that
17200 follow. This program has been compiled and loaded into @value{GDBN},
17201 much like any other normal debugging session.
17204 void function1 (void)
17207 printf ("function 1\n");
17210 void function2 (void)
17225 For the purposes of the examples in this section, the program above has
17226 been compiled, loaded into @value{GDBN}, stopped at the function
17227 @code{main}, and @value{GDBN} is awaiting input from the user.
17229 To access variables and types for any program in @value{GDBN}, the
17230 program must be compiled and packaged with debug information. The
17231 @code{compile} command is not an exception to this rule. Without debug
17232 information, you can still use the @code{compile} command, but you will
17233 be very limited in what variables and types you can access.
17235 So with that in mind, the example above has been compiled with debug
17236 information enabled. The @code{compile} command will have access to
17237 all variables and types (except those that may have been optimized
17238 out). Currently, as @value{GDBN} has stopped the program in the
17239 @code{main} function, the @code{compile} command would have access to
17240 the variable @code{k}. You could invoke the @code{compile} command
17241 and type some source code to set the value of @code{k}. You can also
17242 read it, or do anything with that variable you would normally do in
17243 @code{C}. Be aware that changes to inferior variables in the
17244 @code{compile} command are persistent. In the following example:
17247 compile code k = 3;
17251 the variable @code{k} is now 3. It will retain that value until
17252 something else in the example program changes it, or another
17253 @code{compile} command changes it.
17255 Normal scope and access rules apply to source code compiled and
17256 injected by the @code{compile} command. In the example, the variables
17257 @code{j} and @code{k} are not accessible yet, because the program is
17258 currently stopped in the @code{main} function, where these variables
17259 are not in scope. Therefore, the following command
17262 compile code j = 3;
17266 will result in a compilation error message.
17268 Once the program is continued, execution will bring these variables in
17269 scope, and they will become accessible; then the code you specify via
17270 the @code{compile} command will be able to access them.
17272 You can create variables and types with the @code{compile} command as
17273 part of your source code. Variables and types that are created as part
17274 of the @code{compile} command are not visible to the rest of the program for
17275 the duration of its run. This example is valid:
17278 compile code int ff = 5; printf ("ff is %d\n", ff);
17281 However, if you were to type the following into @value{GDBN} after that
17282 command has completed:
17285 compile code printf ("ff is %d\n'', ff);
17289 a compiler error would be raised as the variable @code{ff} no longer
17290 exists. Object code generated and injected by the @code{compile}
17291 command is removed when its execution ends. Caution is advised
17292 when assigning to program variables values of variables created by the
17293 code submitted to the @code{compile} command. This example is valid:
17296 compile code int ff = 5; k = ff;
17299 The value of the variable @code{ff} is assigned to @code{k}. The variable
17300 @code{k} does not require the existence of @code{ff} to maintain the value
17301 it has been assigned. However, pointers require particular care in
17302 assignment. If the source code compiled with the @code{compile} command
17303 changed the address of a pointer in the example program, perhaps to a
17304 variable created in the @code{compile} command, that pointer would point
17305 to an invalid location when the command exits. The following example
17306 would likely cause issues with your debugged program:
17309 compile code int ff = 5; p = &ff;
17312 In this example, @code{p} would point to @code{ff} when the
17313 @code{compile} command is executing the source code provided to it.
17314 However, as variables in the (example) program persist with their
17315 assigned values, the variable @code{p} would point to an invalid
17316 location when the command exists. A general rule should be followed
17317 in that you should either assign @code{NULL} to any assigned pointers,
17318 or restore a valid location to the pointer before the command exits.
17320 Similar caution must be exercised with any structs, unions, and typedefs
17321 defined in @code{compile} command. Types defined in the @code{compile}
17322 command will no longer be available in the next @code{compile} command.
17323 Therefore, if you cast a variable to a type defined in the
17324 @code{compile} command, care must be taken to ensure that any future
17325 need to resolve the type can be achieved.
17328 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17329 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17330 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17331 Compilation failed.
17332 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17336 Variables that have been optimized away by the compiler are not
17337 accessible to the code submitted to the @code{compile} command.
17338 Access to those variables will generate a compiler error which @value{GDBN}
17339 will print to the console.
17343 @chapter @value{GDBN} Files
17345 @value{GDBN} needs to know the file name of the program to be debugged,
17346 both in order to read its symbol table and in order to start your
17347 program. To debug a core dump of a previous run, you must also tell
17348 @value{GDBN} the name of the core dump file.
17351 * Files:: Commands to specify files
17352 * Separate Debug Files:: Debugging information in separate files
17353 * MiniDebugInfo:: Debugging information in a special section
17354 * Index Files:: Index files speed up GDB
17355 * Symbol Errors:: Errors reading symbol files
17356 * Data Files:: GDB data files
17360 @section Commands to Specify Files
17362 @cindex symbol table
17363 @cindex core dump file
17365 You may want to specify executable and core dump file names. The usual
17366 way to do this is at start-up time, using the arguments to
17367 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17368 Out of @value{GDBN}}).
17370 Occasionally it is necessary to change to a different file during a
17371 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17372 specify a file you want to use. Or you are debugging a remote target
17373 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17374 Program}). In these situations the @value{GDBN} commands to specify
17375 new files are useful.
17378 @cindex executable file
17380 @item file @var{filename}
17381 Use @var{filename} as the program to be debugged. It is read for its
17382 symbols and for the contents of pure memory. It is also the program
17383 executed when you use the @code{run} command. If you do not specify a
17384 directory and the file is not found in the @value{GDBN} working directory,
17385 @value{GDBN} uses the environment variable @code{PATH} as a list of
17386 directories to search, just as the shell does when looking for a program
17387 to run. You can change the value of this variable, for both @value{GDBN}
17388 and your program, using the @code{path} command.
17390 @cindex unlinked object files
17391 @cindex patching object files
17392 You can load unlinked object @file{.o} files into @value{GDBN} using
17393 the @code{file} command. You will not be able to ``run'' an object
17394 file, but you can disassemble functions and inspect variables. Also,
17395 if the underlying BFD functionality supports it, you could use
17396 @kbd{gdb -write} to patch object files using this technique. Note
17397 that @value{GDBN} can neither interpret nor modify relocations in this
17398 case, so branches and some initialized variables will appear to go to
17399 the wrong place. But this feature is still handy from time to time.
17402 @code{file} with no argument makes @value{GDBN} discard any information it
17403 has on both executable file and the symbol table.
17406 @item exec-file @r{[} @var{filename} @r{]}
17407 Specify that the program to be run (but not the symbol table) is found
17408 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17409 if necessary to locate your program. Omitting @var{filename} means to
17410 discard information on the executable file.
17412 @kindex symbol-file
17413 @item symbol-file @r{[} @var{filename} @r{]}
17414 Read symbol table information from file @var{filename}. @code{PATH} is
17415 searched when necessary. Use the @code{file} command to get both symbol
17416 table and program to run from the same file.
17418 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17419 program's symbol table.
17421 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17422 some breakpoints and auto-display expressions. This is because they may
17423 contain pointers to the internal data recording symbols and data types,
17424 which are part of the old symbol table data being discarded inside
17427 @code{symbol-file} does not repeat if you press @key{RET} again after
17430 When @value{GDBN} is configured for a particular environment, it
17431 understands debugging information in whatever format is the standard
17432 generated for that environment; you may use either a @sc{gnu} compiler, or
17433 other compilers that adhere to the local conventions.
17434 Best results are usually obtained from @sc{gnu} compilers; for example,
17435 using @code{@value{NGCC}} you can generate debugging information for
17438 For most kinds of object files, with the exception of old SVR3 systems
17439 using COFF, the @code{symbol-file} command does not normally read the
17440 symbol table in full right away. Instead, it scans the symbol table
17441 quickly to find which source files and which symbols are present. The
17442 details are read later, one source file at a time, as they are needed.
17444 The purpose of this two-stage reading strategy is to make @value{GDBN}
17445 start up faster. For the most part, it is invisible except for
17446 occasional pauses while the symbol table details for a particular source
17447 file are being read. (The @code{set verbose} command can turn these
17448 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17449 Warnings and Messages}.)
17451 We have not implemented the two-stage strategy for COFF yet. When the
17452 symbol table is stored in COFF format, @code{symbol-file} reads the
17453 symbol table data in full right away. Note that ``stabs-in-COFF''
17454 still does the two-stage strategy, since the debug info is actually
17458 @cindex reading symbols immediately
17459 @cindex symbols, reading immediately
17460 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17461 @itemx file @r{[} -readnow @r{]} @var{filename}
17462 You can override the @value{GDBN} two-stage strategy for reading symbol
17463 tables by using the @samp{-readnow} option with any of the commands that
17464 load symbol table information, if you want to be sure @value{GDBN} has the
17465 entire symbol table available.
17467 @c FIXME: for now no mention of directories, since this seems to be in
17468 @c flux. 13mar1992 status is that in theory GDB would look either in
17469 @c current dir or in same dir as myprog; but issues like competing
17470 @c GDB's, or clutter in system dirs, mean that in practice right now
17471 @c only current dir is used. FFish says maybe a special GDB hierarchy
17472 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17476 @item core-file @r{[}@var{filename}@r{]}
17478 Specify the whereabouts of a core dump file to be used as the ``contents
17479 of memory''. Traditionally, core files contain only some parts of the
17480 address space of the process that generated them; @value{GDBN} can access the
17481 executable file itself for other parts.
17483 @code{core-file} with no argument specifies that no core file is
17486 Note that the core file is ignored when your program is actually running
17487 under @value{GDBN}. So, if you have been running your program and you
17488 wish to debug a core file instead, you must kill the subprocess in which
17489 the program is running. To do this, use the @code{kill} command
17490 (@pxref{Kill Process, ,Killing the Child Process}).
17492 @kindex add-symbol-file
17493 @cindex dynamic linking
17494 @item add-symbol-file @var{filename} @var{address}
17495 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17496 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17497 The @code{add-symbol-file} command reads additional symbol table
17498 information from the file @var{filename}. You would use this command
17499 when @var{filename} has been dynamically loaded (by some other means)
17500 into the program that is running. The @var{address} should give the memory
17501 address at which the file has been loaded; @value{GDBN} cannot figure
17502 this out for itself. You can additionally specify an arbitrary number
17503 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17504 section name and base address for that section. You can specify any
17505 @var{address} as an expression.
17507 The symbol table of the file @var{filename} is added to the symbol table
17508 originally read with the @code{symbol-file} command. You can use the
17509 @code{add-symbol-file} command any number of times; the new symbol data
17510 thus read is kept in addition to the old.
17512 Changes can be reverted using the command @code{remove-symbol-file}.
17514 @cindex relocatable object files, reading symbols from
17515 @cindex object files, relocatable, reading symbols from
17516 @cindex reading symbols from relocatable object files
17517 @cindex symbols, reading from relocatable object files
17518 @cindex @file{.o} files, reading symbols from
17519 Although @var{filename} is typically a shared library file, an
17520 executable file, or some other object file which has been fully
17521 relocated for loading into a process, you can also load symbolic
17522 information from relocatable @file{.o} files, as long as:
17526 the file's symbolic information refers only to linker symbols defined in
17527 that file, not to symbols defined by other object files,
17529 every section the file's symbolic information refers to has actually
17530 been loaded into the inferior, as it appears in the file, and
17532 you can determine the address at which every section was loaded, and
17533 provide these to the @code{add-symbol-file} command.
17537 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17538 relocatable files into an already running program; such systems
17539 typically make the requirements above easy to meet. However, it's
17540 important to recognize that many native systems use complex link
17541 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17542 assembly, for example) that make the requirements difficult to meet. In
17543 general, one cannot assume that using @code{add-symbol-file} to read a
17544 relocatable object file's symbolic information will have the same effect
17545 as linking the relocatable object file into the program in the normal
17548 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17550 @kindex remove-symbol-file
17551 @item remove-symbol-file @var{filename}
17552 @item remove-symbol-file -a @var{address}
17553 Remove a symbol file added via the @code{add-symbol-file} command. The
17554 file to remove can be identified by its @var{filename} or by an @var{address}
17555 that lies within the boundaries of this symbol file in memory. Example:
17558 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17559 add symbol table from file "/home/user/gdb/mylib.so" at
17560 .text_addr = 0x7ffff7ff9480
17562 Reading symbols from /home/user/gdb/mylib.so...done.
17563 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17564 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17569 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17571 @kindex add-symbol-file-from-memory
17572 @cindex @code{syscall DSO}
17573 @cindex load symbols from memory
17574 @item add-symbol-file-from-memory @var{address}
17575 Load symbols from the given @var{address} in a dynamically loaded
17576 object file whose image is mapped directly into the inferior's memory.
17577 For example, the Linux kernel maps a @code{syscall DSO} into each
17578 process's address space; this DSO provides kernel-specific code for
17579 some system calls. The argument can be any expression whose
17580 evaluation yields the address of the file's shared object file header.
17581 For this command to work, you must have used @code{symbol-file} or
17582 @code{exec-file} commands in advance.
17585 @item section @var{section} @var{addr}
17586 The @code{section} command changes the base address of the named
17587 @var{section} of the exec file to @var{addr}. This can be used if the
17588 exec file does not contain section addresses, (such as in the
17589 @code{a.out} format), or when the addresses specified in the file
17590 itself are wrong. Each section must be changed separately. The
17591 @code{info files} command, described below, lists all the sections and
17595 @kindex info target
17598 @code{info files} and @code{info target} are synonymous; both print the
17599 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17600 including the names of the executable and core dump files currently in
17601 use by @value{GDBN}, and the files from which symbols were loaded. The
17602 command @code{help target} lists all possible targets rather than
17605 @kindex maint info sections
17606 @item maint info sections
17607 Another command that can give you extra information about program sections
17608 is @code{maint info sections}. In addition to the section information
17609 displayed by @code{info files}, this command displays the flags and file
17610 offset of each section in the executable and core dump files. In addition,
17611 @code{maint info sections} provides the following command options (which
17612 may be arbitrarily combined):
17616 Display sections for all loaded object files, including shared libraries.
17617 @item @var{sections}
17618 Display info only for named @var{sections}.
17619 @item @var{section-flags}
17620 Display info only for sections for which @var{section-flags} are true.
17621 The section flags that @value{GDBN} currently knows about are:
17624 Section will have space allocated in the process when loaded.
17625 Set for all sections except those containing debug information.
17627 Section will be loaded from the file into the child process memory.
17628 Set for pre-initialized code and data, clear for @code{.bss} sections.
17630 Section needs to be relocated before loading.
17632 Section cannot be modified by the child process.
17634 Section contains executable code only.
17636 Section contains data only (no executable code).
17638 Section will reside in ROM.
17640 Section contains data for constructor/destructor lists.
17642 Section is not empty.
17644 An instruction to the linker to not output the section.
17645 @item COFF_SHARED_LIBRARY
17646 A notification to the linker that the section contains
17647 COFF shared library information.
17649 Section contains common symbols.
17652 @kindex set trust-readonly-sections
17653 @cindex read-only sections
17654 @item set trust-readonly-sections on
17655 Tell @value{GDBN} that readonly sections in your object file
17656 really are read-only (i.e.@: that their contents will not change).
17657 In that case, @value{GDBN} can fetch values from these sections
17658 out of the object file, rather than from the target program.
17659 For some targets (notably embedded ones), this can be a significant
17660 enhancement to debugging performance.
17662 The default is off.
17664 @item set trust-readonly-sections off
17665 Tell @value{GDBN} not to trust readonly sections. This means that
17666 the contents of the section might change while the program is running,
17667 and must therefore be fetched from the target when needed.
17669 @item show trust-readonly-sections
17670 Show the current setting of trusting readonly sections.
17673 All file-specifying commands allow both absolute and relative file names
17674 as arguments. @value{GDBN} always converts the file name to an absolute file
17675 name and remembers it that way.
17677 @cindex shared libraries
17678 @anchor{Shared Libraries}
17679 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17680 and IBM RS/6000 AIX shared libraries.
17682 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17683 shared libraries. @xref{Expat}.
17685 @value{GDBN} automatically loads symbol definitions from shared libraries
17686 when you use the @code{run} command, or when you examine a core file.
17687 (Before you issue the @code{run} command, @value{GDBN} does not understand
17688 references to a function in a shared library, however---unless you are
17689 debugging a core file).
17691 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17692 automatically loads the symbols at the time of the @code{shl_load} call.
17694 @c FIXME: some @value{GDBN} release may permit some refs to undef
17695 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17696 @c FIXME...lib; check this from time to time when updating manual
17698 There are times, however, when you may wish to not automatically load
17699 symbol definitions from shared libraries, such as when they are
17700 particularly large or there are many of them.
17702 To control the automatic loading of shared library symbols, use the
17706 @kindex set auto-solib-add
17707 @item set auto-solib-add @var{mode}
17708 If @var{mode} is @code{on}, symbols from all shared object libraries
17709 will be loaded automatically when the inferior begins execution, you
17710 attach to an independently started inferior, or when the dynamic linker
17711 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17712 is @code{off}, symbols must be loaded manually, using the
17713 @code{sharedlibrary} command. The default value is @code{on}.
17715 @cindex memory used for symbol tables
17716 If your program uses lots of shared libraries with debug info that
17717 takes large amounts of memory, you can decrease the @value{GDBN}
17718 memory footprint by preventing it from automatically loading the
17719 symbols from shared libraries. To that end, type @kbd{set
17720 auto-solib-add off} before running the inferior, then load each
17721 library whose debug symbols you do need with @kbd{sharedlibrary
17722 @var{regexp}}, where @var{regexp} is a regular expression that matches
17723 the libraries whose symbols you want to be loaded.
17725 @kindex show auto-solib-add
17726 @item show auto-solib-add
17727 Display the current autoloading mode.
17730 @cindex load shared library
17731 To explicitly load shared library symbols, use the @code{sharedlibrary}
17735 @kindex info sharedlibrary
17737 @item info share @var{regex}
17738 @itemx info sharedlibrary @var{regex}
17739 Print the names of the shared libraries which are currently loaded
17740 that match @var{regex}. If @var{regex} is omitted then print
17741 all shared libraries that are loaded.
17743 @kindex sharedlibrary
17745 @item sharedlibrary @var{regex}
17746 @itemx share @var{regex}
17747 Load shared object library symbols for files matching a
17748 Unix regular expression.
17749 As with files loaded automatically, it only loads shared libraries
17750 required by your program for a core file or after typing @code{run}. If
17751 @var{regex} is omitted all shared libraries required by your program are
17754 @item nosharedlibrary
17755 @kindex nosharedlibrary
17756 @cindex unload symbols from shared libraries
17757 Unload all shared object library symbols. This discards all symbols
17758 that have been loaded from all shared libraries. Symbols from shared
17759 libraries that were loaded by explicit user requests are not
17763 Sometimes you may wish that @value{GDBN} stops and gives you control
17764 when any of shared library events happen. The best way to do this is
17765 to use @code{catch load} and @code{catch unload} (@pxref{Set
17768 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17769 command for this. This command exists for historical reasons. It is
17770 less useful than setting a catchpoint, because it does not allow for
17771 conditions or commands as a catchpoint does.
17774 @item set stop-on-solib-events
17775 @kindex set stop-on-solib-events
17776 This command controls whether @value{GDBN} should give you control
17777 when the dynamic linker notifies it about some shared library event.
17778 The most common event of interest is loading or unloading of a new
17781 @item show stop-on-solib-events
17782 @kindex show stop-on-solib-events
17783 Show whether @value{GDBN} stops and gives you control when shared
17784 library events happen.
17787 Shared libraries are also supported in many cross or remote debugging
17788 configurations. @value{GDBN} needs to have access to the target's libraries;
17789 this can be accomplished either by providing copies of the libraries
17790 on the host system, or by asking @value{GDBN} to automatically retrieve the
17791 libraries from the target. If copies of the target libraries are
17792 provided, they need to be the same as the target libraries, although the
17793 copies on the target can be stripped as long as the copies on the host are
17796 @cindex where to look for shared libraries
17797 For remote debugging, you need to tell @value{GDBN} where the target
17798 libraries are, so that it can load the correct copies---otherwise, it
17799 may try to load the host's libraries. @value{GDBN} has two variables
17800 to specify the search directories for target libraries.
17803 @cindex prefix for shared library file names
17804 @cindex system root, alternate
17805 @kindex set solib-absolute-prefix
17806 @kindex set sysroot
17807 @item set sysroot @var{path}
17808 Use @var{path} as the system root for the program being debugged. Any
17809 absolute shared library paths will be prefixed with @var{path}; many
17810 runtime loaders store the absolute paths to the shared library in the
17811 target program's memory. If you use @code{set sysroot} to find shared
17812 libraries, they need to be laid out in the same way that they are on
17813 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17816 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17817 retrieve the target libraries from the remote system. This is only
17818 supported when using a remote target that supports the @code{remote get}
17819 command (@pxref{File Transfer,,Sending files to a remote system}).
17820 The part of @var{path} following the initial @file{remote:}
17821 (if present) is used as system root prefix on the remote file system.
17822 @footnote{If you want to specify a local system root using a directory
17823 that happens to be named @file{remote:}, you need to use some equivalent
17824 variant of the name like @file{./remote:}.}
17826 For targets with an MS-DOS based filesystem, such as MS-Windows and
17827 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17828 absolute file name with @var{path}. But first, on Unix hosts,
17829 @value{GDBN} converts all backslash directory separators into forward
17830 slashes, because the backslash is not a directory separator on Unix:
17833 c:\foo\bar.dll @result{} c:/foo/bar.dll
17836 Then, @value{GDBN} attempts prefixing the target file name with
17837 @var{path}, and looks for the resulting file name in the host file
17841 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17844 If that does not find the shared library, @value{GDBN} tries removing
17845 the @samp{:} character from the drive spec, both for convenience, and,
17846 for the case of the host file system not supporting file names with
17850 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17853 This makes it possible to have a system root that mirrors a target
17854 with more than one drive. E.g., you may want to setup your local
17855 copies of the target system shared libraries like so (note @samp{c} vs
17859 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17860 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17861 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17865 and point the system root at @file{/path/to/sysroot}, so that
17866 @value{GDBN} can find the correct copies of both
17867 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17869 If that still does not find the shared library, @value{GDBN} tries
17870 removing the whole drive spec from the target file name:
17873 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17876 This last lookup makes it possible to not care about the drive name,
17877 if you don't want or need to.
17879 The @code{set solib-absolute-prefix} command is an alias for @code{set
17882 @cindex default system root
17883 @cindex @samp{--with-sysroot}
17884 You can set the default system root by using the configure-time
17885 @samp{--with-sysroot} option. If the system root is inside
17886 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17887 @samp{--exec-prefix}), then the default system root will be updated
17888 automatically if the installed @value{GDBN} is moved to a new
17891 @kindex show sysroot
17893 Display the current shared library prefix.
17895 @kindex set solib-search-path
17896 @item set solib-search-path @var{path}
17897 If this variable is set, @var{path} is a colon-separated list of
17898 directories to search for shared libraries. @samp{solib-search-path}
17899 is used after @samp{sysroot} fails to locate the library, or if the
17900 path to the library is relative instead of absolute. If you want to
17901 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17902 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17903 finding your host's libraries. @samp{sysroot} is preferred; setting
17904 it to a nonexistent directory may interfere with automatic loading
17905 of shared library symbols.
17907 @kindex show solib-search-path
17908 @item show solib-search-path
17909 Display the current shared library search path.
17911 @cindex DOS file-name semantics of file names.
17912 @kindex set target-file-system-kind (unix|dos-based|auto)
17913 @kindex show target-file-system-kind
17914 @item set target-file-system-kind @var{kind}
17915 Set assumed file system kind for target reported file names.
17917 Shared library file names as reported by the target system may not
17918 make sense as is on the system @value{GDBN} is running on. For
17919 example, when remote debugging a target that has MS-DOS based file
17920 system semantics, from a Unix host, the target may be reporting to
17921 @value{GDBN} a list of loaded shared libraries with file names such as
17922 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17923 drive letters, so the @samp{c:\} prefix is not normally understood as
17924 indicating an absolute file name, and neither is the backslash
17925 normally considered a directory separator character. In that case,
17926 the native file system would interpret this whole absolute file name
17927 as a relative file name with no directory components. This would make
17928 it impossible to point @value{GDBN} at a copy of the remote target's
17929 shared libraries on the host using @code{set sysroot}, and impractical
17930 with @code{set solib-search-path}. Setting
17931 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17932 to interpret such file names similarly to how the target would, and to
17933 map them to file names valid on @value{GDBN}'s native file system
17934 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17935 to one of the supported file system kinds. In that case, @value{GDBN}
17936 tries to determine the appropriate file system variant based on the
17937 current target's operating system (@pxref{ABI, ,Configuring the
17938 Current ABI}). The supported file system settings are:
17942 Instruct @value{GDBN} to assume the target file system is of Unix
17943 kind. Only file names starting the forward slash (@samp{/}) character
17944 are considered absolute, and the directory separator character is also
17948 Instruct @value{GDBN} to assume the target file system is DOS based.
17949 File names starting with either a forward slash, or a drive letter
17950 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17951 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17952 considered directory separators.
17955 Instruct @value{GDBN} to use the file system kind associated with the
17956 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17957 This is the default.
17961 @cindex file name canonicalization
17962 @cindex base name differences
17963 When processing file names provided by the user, @value{GDBN}
17964 frequently needs to compare them to the file names recorded in the
17965 program's debug info. Normally, @value{GDBN} compares just the
17966 @dfn{base names} of the files as strings, which is reasonably fast
17967 even for very large programs. (The base name of a file is the last
17968 portion of its name, after stripping all the leading directories.)
17969 This shortcut in comparison is based upon the assumption that files
17970 cannot have more than one base name. This is usually true, but
17971 references to files that use symlinks or similar filesystem
17972 facilities violate that assumption. If your program records files
17973 using such facilities, or if you provide file names to @value{GDBN}
17974 using symlinks etc., you can set @code{basenames-may-differ} to
17975 @code{true} to instruct @value{GDBN} to completely canonicalize each
17976 pair of file names it needs to compare. This will make file-name
17977 comparisons accurate, but at a price of a significant slowdown.
17980 @item set basenames-may-differ
17981 @kindex set basenames-may-differ
17982 Set whether a source file may have multiple base names.
17984 @item show basenames-may-differ
17985 @kindex show basenames-may-differ
17986 Show whether a source file may have multiple base names.
17989 @node Separate Debug Files
17990 @section Debugging Information in Separate Files
17991 @cindex separate debugging information files
17992 @cindex debugging information in separate files
17993 @cindex @file{.debug} subdirectories
17994 @cindex debugging information directory, global
17995 @cindex global debugging information directories
17996 @cindex build ID, and separate debugging files
17997 @cindex @file{.build-id} directory
17999 @value{GDBN} allows you to put a program's debugging information in a
18000 file separate from the executable itself, in a way that allows
18001 @value{GDBN} to find and load the debugging information automatically.
18002 Since debugging information can be very large---sometimes larger
18003 than the executable code itself---some systems distribute debugging
18004 information for their executables in separate files, which users can
18005 install only when they need to debug a problem.
18007 @value{GDBN} supports two ways of specifying the separate debug info
18012 The executable contains a @dfn{debug link} that specifies the name of
18013 the separate debug info file. The separate debug file's name is
18014 usually @file{@var{executable}.debug}, where @var{executable} is the
18015 name of the corresponding executable file without leading directories
18016 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18017 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18018 checksum for the debug file, which @value{GDBN} uses to validate that
18019 the executable and the debug file came from the same build.
18022 The executable contains a @dfn{build ID}, a unique bit string that is
18023 also present in the corresponding debug info file. (This is supported
18024 only on some operating systems, notably those which use the ELF format
18025 for binary files and the @sc{gnu} Binutils.) For more details about
18026 this feature, see the description of the @option{--build-id}
18027 command-line option in @ref{Options, , Command Line Options, ld.info,
18028 The GNU Linker}. The debug info file's name is not specified
18029 explicitly by the build ID, but can be computed from the build ID, see
18033 Depending on the way the debug info file is specified, @value{GDBN}
18034 uses two different methods of looking for the debug file:
18038 For the ``debug link'' method, @value{GDBN} looks up the named file in
18039 the directory of the executable file, then in a subdirectory of that
18040 directory named @file{.debug}, and finally under each one of the global debug
18041 directories, in a subdirectory whose name is identical to the leading
18042 directories of the executable's absolute file name.
18045 For the ``build ID'' method, @value{GDBN} looks in the
18046 @file{.build-id} subdirectory of each one of the global debug directories for
18047 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18048 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18049 are the rest of the bit string. (Real build ID strings are 32 or more
18050 hex characters, not 10.)
18053 So, for example, suppose you ask @value{GDBN} to debug
18054 @file{/usr/bin/ls}, which has a debug link that specifies the
18055 file @file{ls.debug}, and a build ID whose value in hex is
18056 @code{abcdef1234}. If the list of the global debug directories includes
18057 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18058 debug information files, in the indicated order:
18062 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18064 @file{/usr/bin/ls.debug}
18066 @file{/usr/bin/.debug/ls.debug}
18068 @file{/usr/lib/debug/usr/bin/ls.debug}.
18071 @anchor{debug-file-directory}
18072 Global debugging info directories default to what is set by @value{GDBN}
18073 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18074 you can also set the global debugging info directories, and view the list
18075 @value{GDBN} is currently using.
18079 @kindex set debug-file-directory
18080 @item set debug-file-directory @var{directories}
18081 Set the directories which @value{GDBN} searches for separate debugging
18082 information files to @var{directory}. Multiple path components can be set
18083 concatenating them by a path separator.
18085 @kindex show debug-file-directory
18086 @item show debug-file-directory
18087 Show the directories @value{GDBN} searches for separate debugging
18092 @cindex @code{.gnu_debuglink} sections
18093 @cindex debug link sections
18094 A debug link is a special section of the executable file named
18095 @code{.gnu_debuglink}. The section must contain:
18099 A filename, with any leading directory components removed, followed by
18102 zero to three bytes of padding, as needed to reach the next four-byte
18103 boundary within the section, and
18105 a four-byte CRC checksum, stored in the same endianness used for the
18106 executable file itself. The checksum is computed on the debugging
18107 information file's full contents by the function given below, passing
18108 zero as the @var{crc} argument.
18111 Any executable file format can carry a debug link, as long as it can
18112 contain a section named @code{.gnu_debuglink} with the contents
18115 @cindex @code{.note.gnu.build-id} sections
18116 @cindex build ID sections
18117 The build ID is a special section in the executable file (and in other
18118 ELF binary files that @value{GDBN} may consider). This section is
18119 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18120 It contains unique identification for the built files---the ID remains
18121 the same across multiple builds of the same build tree. The default
18122 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18123 content for the build ID string. The same section with an identical
18124 value is present in the original built binary with symbols, in its
18125 stripped variant, and in the separate debugging information file.
18127 The debugging information file itself should be an ordinary
18128 executable, containing a full set of linker symbols, sections, and
18129 debugging information. The sections of the debugging information file
18130 should have the same names, addresses, and sizes as the original file,
18131 but they need not contain any data---much like a @code{.bss} section
18132 in an ordinary executable.
18134 The @sc{gnu} binary utilities (Binutils) package includes the
18135 @samp{objcopy} utility that can produce
18136 the separated executable / debugging information file pairs using the
18137 following commands:
18140 @kbd{objcopy --only-keep-debug foo foo.debug}
18145 These commands remove the debugging
18146 information from the executable file @file{foo} and place it in the file
18147 @file{foo.debug}. You can use the first, second or both methods to link the
18152 The debug link method needs the following additional command to also leave
18153 behind a debug link in @file{foo}:
18156 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18159 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18160 a version of the @code{strip} command such that the command @kbd{strip foo -f
18161 foo.debug} has the same functionality as the two @code{objcopy} commands and
18162 the @code{ln -s} command above, together.
18165 Build ID gets embedded into the main executable using @code{ld --build-id} or
18166 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18167 compatibility fixes for debug files separation are present in @sc{gnu} binary
18168 utilities (Binutils) package since version 2.18.
18173 @cindex CRC algorithm definition
18174 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18175 IEEE 802.3 using the polynomial:
18177 @c TexInfo requires naked braces for multi-digit exponents for Tex
18178 @c output, but this causes HTML output to barf. HTML has to be set using
18179 @c raw commands. So we end up having to specify this equation in 2
18184 <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>
18185 + <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
18191 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18192 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18196 The function is computed byte at a time, taking the least
18197 significant bit of each byte first. The initial pattern
18198 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18199 the final result is inverted to ensure trailing zeros also affect the
18202 @emph{Note:} This is the same CRC polynomial as used in handling the
18203 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18204 However in the case of the Remote Serial Protocol, the CRC is computed
18205 @emph{most} significant bit first, and the result is not inverted, so
18206 trailing zeros have no effect on the CRC value.
18208 To complete the description, we show below the code of the function
18209 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18210 initially supplied @code{crc} argument means that an initial call to
18211 this function passing in zero will start computing the CRC using
18214 @kindex gnu_debuglink_crc32
18217 gnu_debuglink_crc32 (unsigned long crc,
18218 unsigned char *buf, size_t len)
18220 static const unsigned long crc32_table[256] =
18222 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18223 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18224 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18225 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18226 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18227 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18228 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18229 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18230 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18231 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18232 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18233 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18234 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18235 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18236 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18237 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18238 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18239 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18240 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18241 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18242 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18243 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18244 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18245 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18246 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18247 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18248 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18249 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18250 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18251 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18252 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18253 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18254 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18255 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18256 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18257 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18258 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18259 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18260 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18261 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18262 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18263 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18264 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18265 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18266 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18267 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18268 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18269 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18270 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18271 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18272 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18275 unsigned char *end;
18277 crc = ~crc & 0xffffffff;
18278 for (end = buf + len; buf < end; ++buf)
18279 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18280 return ~crc & 0xffffffff;
18285 This computation does not apply to the ``build ID'' method.
18287 @node MiniDebugInfo
18288 @section Debugging information in a special section
18289 @cindex separate debug sections
18290 @cindex @samp{.gnu_debugdata} section
18292 Some systems ship pre-built executables and libraries that have a
18293 special @samp{.gnu_debugdata} section. This feature is called
18294 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18295 is used to supply extra symbols for backtraces.
18297 The intent of this section is to provide extra minimal debugging
18298 information for use in simple backtraces. It is not intended to be a
18299 replacement for full separate debugging information (@pxref{Separate
18300 Debug Files}). The example below shows the intended use; however,
18301 @value{GDBN} does not currently put restrictions on what sort of
18302 debugging information might be included in the section.
18304 @value{GDBN} has support for this extension. If the section exists,
18305 then it is used provided that no other source of debugging information
18306 can be found, and that @value{GDBN} was configured with LZMA support.
18308 This section can be easily created using @command{objcopy} and other
18309 standard utilities:
18312 # Extract the dynamic symbols from the main binary, there is no need
18313 # to also have these in the normal symbol table.
18314 nm -D @var{binary} --format=posix --defined-only \
18315 | awk '@{ print $1 @}' | sort > dynsyms
18317 # Extract all the text (i.e. function) symbols from the debuginfo.
18318 # (Note that we actually also accept "D" symbols, for the benefit
18319 # of platforms like PowerPC64 that use function descriptors.)
18320 nm @var{binary} --format=posix --defined-only \
18321 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18324 # Keep all the function symbols not already in the dynamic symbol
18326 comm -13 dynsyms funcsyms > keep_symbols
18328 # Separate full debug info into debug binary.
18329 objcopy --only-keep-debug @var{binary} debug
18331 # Copy the full debuginfo, keeping only a minimal set of symbols and
18332 # removing some unnecessary sections.
18333 objcopy -S --remove-section .gdb_index --remove-section .comment \
18334 --keep-symbols=keep_symbols debug mini_debuginfo
18336 # Drop the full debug info from the original binary.
18337 strip --strip-all -R .comment @var{binary}
18339 # Inject the compressed data into the .gnu_debugdata section of the
18342 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18346 @section Index Files Speed Up @value{GDBN}
18347 @cindex index files
18348 @cindex @samp{.gdb_index} section
18350 When @value{GDBN} finds a symbol file, it scans the symbols in the
18351 file in order to construct an internal symbol table. This lets most
18352 @value{GDBN} operations work quickly---at the cost of a delay early
18353 on. For large programs, this delay can be quite lengthy, so
18354 @value{GDBN} provides a way to build an index, which speeds up
18357 The index is stored as a section in the symbol file. @value{GDBN} can
18358 write the index to a file, then you can put it into the symbol file
18359 using @command{objcopy}.
18361 To create an index file, use the @code{save gdb-index} command:
18364 @item save gdb-index @var{directory}
18365 @kindex save gdb-index
18366 Create an index file for each symbol file currently known by
18367 @value{GDBN}. Each file is named after its corresponding symbol file,
18368 with @samp{.gdb-index} appended, and is written into the given
18372 Once you have created an index file you can merge it into your symbol
18373 file, here named @file{symfile}, using @command{objcopy}:
18376 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18377 --set-section-flags .gdb_index=readonly symfile symfile
18380 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18381 sections that have been deprecated. Usually they are deprecated because
18382 they are missing a new feature or have performance issues.
18383 To tell @value{GDBN} to use a deprecated index section anyway
18384 specify @code{set use-deprecated-index-sections on}.
18385 The default is @code{off}.
18386 This can speed up startup, but may result in some functionality being lost.
18387 @xref{Index Section Format}.
18389 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18390 must be done before gdb reads the file. The following will not work:
18393 $ gdb -ex "set use-deprecated-index-sections on" <program>
18396 Instead you must do, for example,
18399 $ gdb -iex "set use-deprecated-index-sections on" <program>
18402 There are currently some limitation on indices. They only work when
18403 for DWARF debugging information, not stabs. And, they do not
18404 currently work for programs using Ada.
18406 @node Symbol Errors
18407 @section Errors Reading Symbol Files
18409 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18410 such as symbol types it does not recognize, or known bugs in compiler
18411 output. By default, @value{GDBN} does not notify you of such problems, since
18412 they are relatively common and primarily of interest to people
18413 debugging compilers. If you are interested in seeing information
18414 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18415 only one message about each such type of problem, no matter how many
18416 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18417 to see how many times the problems occur, with the @code{set
18418 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18421 The messages currently printed, and their meanings, include:
18424 @item inner block not inside outer block in @var{symbol}
18426 The symbol information shows where symbol scopes begin and end
18427 (such as at the start of a function or a block of statements). This
18428 error indicates that an inner scope block is not fully contained
18429 in its outer scope blocks.
18431 @value{GDBN} circumvents the problem by treating the inner block as if it had
18432 the same scope as the outer block. In the error message, @var{symbol}
18433 may be shown as ``@code{(don't know)}'' if the outer block is not a
18436 @item block at @var{address} out of order
18438 The symbol information for symbol scope blocks should occur in
18439 order of increasing addresses. This error indicates that it does not
18442 @value{GDBN} does not circumvent this problem, and has trouble
18443 locating symbols in the source file whose symbols it is reading. (You
18444 can often determine what source file is affected by specifying
18445 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18448 @item bad block start address patched
18450 The symbol information for a symbol scope block has a start address
18451 smaller than the address of the preceding source line. This is known
18452 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18454 @value{GDBN} circumvents the problem by treating the symbol scope block as
18455 starting on the previous source line.
18457 @item bad string table offset in symbol @var{n}
18460 Symbol number @var{n} contains a pointer into the string table which is
18461 larger than the size of the string table.
18463 @value{GDBN} circumvents the problem by considering the symbol to have the
18464 name @code{foo}, which may cause other problems if many symbols end up
18467 @item unknown symbol type @code{0x@var{nn}}
18469 The symbol information contains new data types that @value{GDBN} does
18470 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18471 uncomprehended information, in hexadecimal.
18473 @value{GDBN} circumvents the error by ignoring this symbol information.
18474 This usually allows you to debug your program, though certain symbols
18475 are not accessible. If you encounter such a problem and feel like
18476 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18477 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18478 and examine @code{*bufp} to see the symbol.
18480 @item stub type has NULL name
18482 @value{GDBN} could not find the full definition for a struct or class.
18484 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18485 The symbol information for a C@t{++} member function is missing some
18486 information that recent versions of the compiler should have output for
18489 @item info mismatch between compiler and debugger
18491 @value{GDBN} could not parse a type specification output by the compiler.
18496 @section GDB Data Files
18498 @cindex prefix for data files
18499 @value{GDBN} will sometimes read an auxiliary data file. These files
18500 are kept in a directory known as the @dfn{data directory}.
18502 You can set the data directory's name, and view the name @value{GDBN}
18503 is currently using.
18506 @kindex set data-directory
18507 @item set data-directory @var{directory}
18508 Set the directory which @value{GDBN} searches for auxiliary data files
18509 to @var{directory}.
18511 @kindex show data-directory
18512 @item show data-directory
18513 Show the directory @value{GDBN} searches for auxiliary data files.
18516 @cindex default data directory
18517 @cindex @samp{--with-gdb-datadir}
18518 You can set the default data directory by using the configure-time
18519 @samp{--with-gdb-datadir} option. If the data directory is inside
18520 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18521 @samp{--exec-prefix}), then the default data directory will be updated
18522 automatically if the installed @value{GDBN} is moved to a new
18525 The data directory may also be specified with the
18526 @code{--data-directory} command line option.
18527 @xref{Mode Options}.
18530 @chapter Specifying a Debugging Target
18532 @cindex debugging target
18533 A @dfn{target} is the execution environment occupied by your program.
18535 Often, @value{GDBN} runs in the same host environment as your program;
18536 in that case, the debugging target is specified as a side effect when
18537 you use the @code{file} or @code{core} commands. When you need more
18538 flexibility---for example, running @value{GDBN} on a physically separate
18539 host, or controlling a standalone system over a serial port or a
18540 realtime system over a TCP/IP connection---you can use the @code{target}
18541 command to specify one of the target types configured for @value{GDBN}
18542 (@pxref{Target Commands, ,Commands for Managing Targets}).
18544 @cindex target architecture
18545 It is possible to build @value{GDBN} for several different @dfn{target
18546 architectures}. When @value{GDBN} is built like that, you can choose
18547 one of the available architectures with the @kbd{set architecture}
18551 @kindex set architecture
18552 @kindex show architecture
18553 @item set architecture @var{arch}
18554 This command sets the current target architecture to @var{arch}. The
18555 value of @var{arch} can be @code{"auto"}, in addition to one of the
18556 supported architectures.
18558 @item show architecture
18559 Show the current target architecture.
18561 @item set processor
18563 @kindex set processor
18564 @kindex show processor
18565 These are alias commands for, respectively, @code{set architecture}
18566 and @code{show architecture}.
18570 * Active Targets:: Active targets
18571 * Target Commands:: Commands for managing targets
18572 * Byte Order:: Choosing target byte order
18575 @node Active Targets
18576 @section Active Targets
18578 @cindex stacking targets
18579 @cindex active targets
18580 @cindex multiple targets
18582 There are multiple classes of targets such as: processes, executable files or
18583 recording sessions. Core files belong to the process class, making core file
18584 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18585 on multiple active targets, one in each class. This allows you to (for
18586 example) start a process and inspect its activity, while still having access to
18587 the executable file after the process finishes. Or if you start process
18588 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18589 presented a virtual layer of the recording target, while the process target
18590 remains stopped at the chronologically last point of the process execution.
18592 Use the @code{core-file} and @code{exec-file} commands to select a new core
18593 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18594 specify as a target a process that is already running, use the @code{attach}
18595 command (@pxref{Attach, ,Debugging an Already-running Process}).
18597 @node Target Commands
18598 @section Commands for Managing Targets
18601 @item target @var{type} @var{parameters}
18602 Connects the @value{GDBN} host environment to a target machine or
18603 process. A target is typically a protocol for talking to debugging
18604 facilities. You use the argument @var{type} to specify the type or
18605 protocol of the target machine.
18607 Further @var{parameters} are interpreted by the target protocol, but
18608 typically include things like device names or host names to connect
18609 with, process numbers, and baud rates.
18611 The @code{target} command does not repeat if you press @key{RET} again
18612 after executing the command.
18614 @kindex help target
18616 Displays the names of all targets available. To display targets
18617 currently selected, use either @code{info target} or @code{info files}
18618 (@pxref{Files, ,Commands to Specify Files}).
18620 @item help target @var{name}
18621 Describe a particular target, including any parameters necessary to
18624 @kindex set gnutarget
18625 @item set gnutarget @var{args}
18626 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18627 knows whether it is reading an @dfn{executable},
18628 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18629 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18630 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18633 @emph{Warning:} To specify a file format with @code{set gnutarget},
18634 you must know the actual BFD name.
18638 @xref{Files, , Commands to Specify Files}.
18640 @kindex show gnutarget
18641 @item show gnutarget
18642 Use the @code{show gnutarget} command to display what file format
18643 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18644 @value{GDBN} will determine the file format for each file automatically,
18645 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18648 @cindex common targets
18649 Here are some common targets (available, or not, depending on the GDB
18654 @item target exec @var{program}
18655 @cindex executable file target
18656 An executable file. @samp{target exec @var{program}} is the same as
18657 @samp{exec-file @var{program}}.
18659 @item target core @var{filename}
18660 @cindex core dump file target
18661 A core dump file. @samp{target core @var{filename}} is the same as
18662 @samp{core-file @var{filename}}.
18664 @item target remote @var{medium}
18665 @cindex remote target
18666 A remote system connected to @value{GDBN} via a serial line or network
18667 connection. This command tells @value{GDBN} to use its own remote
18668 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18670 For example, if you have a board connected to @file{/dev/ttya} on the
18671 machine running @value{GDBN}, you could say:
18674 target remote /dev/ttya
18677 @code{target remote} supports the @code{load} command. This is only
18678 useful if you have some other way of getting the stub to the target
18679 system, and you can put it somewhere in memory where it won't get
18680 clobbered by the download.
18682 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18683 @cindex built-in simulator target
18684 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18692 works; however, you cannot assume that a specific memory map, device
18693 drivers, or even basic I/O is available, although some simulators do
18694 provide these. For info about any processor-specific simulator details,
18695 see the appropriate section in @ref{Embedded Processors, ,Embedded
18698 @item target native
18699 @cindex native target
18700 Setup for local/native process debugging. Useful to make the
18701 @code{run} command spawn native processes (likewise @code{attach},
18702 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18703 (@pxref{set auto-connect-native-target}).
18707 Different targets are available on different configurations of @value{GDBN};
18708 your configuration may have more or fewer targets.
18710 Many remote targets require you to download the executable's code once
18711 you've successfully established a connection. You may wish to control
18712 various aspects of this process.
18717 @kindex set hash@r{, for remote monitors}
18718 @cindex hash mark while downloading
18719 This command controls whether a hash mark @samp{#} is displayed while
18720 downloading a file to the remote monitor. If on, a hash mark is
18721 displayed after each S-record is successfully downloaded to the
18725 @kindex show hash@r{, for remote monitors}
18726 Show the current status of displaying the hash mark.
18728 @item set debug monitor
18729 @kindex set debug monitor
18730 @cindex display remote monitor communications
18731 Enable or disable display of communications messages between
18732 @value{GDBN} and the remote monitor.
18734 @item show debug monitor
18735 @kindex show debug monitor
18736 Show the current status of displaying communications between
18737 @value{GDBN} and the remote monitor.
18742 @kindex load @var{filename}
18743 @item load @var{filename}
18745 Depending on what remote debugging facilities are configured into
18746 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18747 is meant to make @var{filename} (an executable) available for debugging
18748 on the remote system---by downloading, or dynamic linking, for example.
18749 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18750 the @code{add-symbol-file} command.
18752 If your @value{GDBN} does not have a @code{load} command, attempting to
18753 execute it gets the error message ``@code{You can't do that when your
18754 target is @dots{}}''
18756 The file is loaded at whatever address is specified in the executable.
18757 For some object file formats, you can specify the load address when you
18758 link the program; for other formats, like a.out, the object file format
18759 specifies a fixed address.
18760 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18762 Depending on the remote side capabilities, @value{GDBN} may be able to
18763 load programs into flash memory.
18765 @code{load} does not repeat if you press @key{RET} again after using it.
18769 @section Choosing Target Byte Order
18771 @cindex choosing target byte order
18772 @cindex target byte order
18774 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18775 offer the ability to run either big-endian or little-endian byte
18776 orders. Usually the executable or symbol will include a bit to
18777 designate the endian-ness, and you will not need to worry about
18778 which to use. However, you may still find it useful to adjust
18779 @value{GDBN}'s idea of processor endian-ness manually.
18783 @item set endian big
18784 Instruct @value{GDBN} to assume the target is big-endian.
18786 @item set endian little
18787 Instruct @value{GDBN} to assume the target is little-endian.
18789 @item set endian auto
18790 Instruct @value{GDBN} to use the byte order associated with the
18794 Display @value{GDBN}'s current idea of the target byte order.
18798 Note that these commands merely adjust interpretation of symbolic
18799 data on the host, and that they have absolutely no effect on the
18803 @node Remote Debugging
18804 @chapter Debugging Remote Programs
18805 @cindex remote debugging
18807 If you are trying to debug a program running on a machine that cannot run
18808 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18809 For example, you might use remote debugging on an operating system kernel,
18810 or on a small system which does not have a general purpose operating system
18811 powerful enough to run a full-featured debugger.
18813 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18814 to make this work with particular debugging targets. In addition,
18815 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18816 but not specific to any particular target system) which you can use if you
18817 write the remote stubs---the code that runs on the remote system to
18818 communicate with @value{GDBN}.
18820 Other remote targets may be available in your
18821 configuration of @value{GDBN}; use @code{help target} to list them.
18824 * Connecting:: Connecting to a remote target
18825 * File Transfer:: Sending files to a remote system
18826 * Server:: Using the gdbserver program
18827 * Remote Configuration:: Remote configuration
18828 * Remote Stub:: Implementing a remote stub
18832 @section Connecting to a Remote Target
18834 On the @value{GDBN} host machine, you will need an unstripped copy of
18835 your program, since @value{GDBN} needs symbol and debugging information.
18836 Start up @value{GDBN} as usual, using the name of the local copy of your
18837 program as the first argument.
18839 @cindex @code{target remote}
18840 @value{GDBN} can communicate with the target over a serial line, or
18841 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18842 each case, @value{GDBN} uses the same protocol for debugging your
18843 program; only the medium carrying the debugging packets varies. The
18844 @code{target remote} command establishes a connection to the target.
18845 Its arguments indicate which medium to use:
18849 @item target remote @var{serial-device}
18850 @cindex serial line, @code{target remote}
18851 Use @var{serial-device} to communicate with the target. For example,
18852 to use a serial line connected to the device named @file{/dev/ttyb}:
18855 target remote /dev/ttyb
18858 If you're using a serial line, you may want to give @value{GDBN} the
18859 @samp{--baud} option, or use the @code{set serial baud} command
18860 (@pxref{Remote Configuration, set serial baud}) before the
18861 @code{target} command.
18863 @item target remote @code{@var{host}:@var{port}}
18864 @itemx target remote @code{tcp:@var{host}:@var{port}}
18865 @cindex @acronym{TCP} port, @code{target remote}
18866 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18867 The @var{host} may be either a host name or a numeric @acronym{IP}
18868 address; @var{port} must be a decimal number. The @var{host} could be
18869 the target machine itself, if it is directly connected to the net, or
18870 it might be a terminal server which in turn has a serial line to the
18873 For example, to connect to port 2828 on a terminal server named
18877 target remote manyfarms:2828
18880 If your remote target is actually running on the same machine as your
18881 debugger session (e.g.@: a simulator for your target running on the
18882 same host), you can omit the hostname. For example, to connect to
18883 port 1234 on your local machine:
18886 target remote :1234
18890 Note that the colon is still required here.
18892 @item target remote @code{udp:@var{host}:@var{port}}
18893 @cindex @acronym{UDP} port, @code{target remote}
18894 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18895 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18898 target remote udp:manyfarms:2828
18901 When using a @acronym{UDP} connection for remote debugging, you should
18902 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18903 can silently drop packets on busy or unreliable networks, which will
18904 cause havoc with your debugging session.
18906 @item target remote | @var{command}
18907 @cindex pipe, @code{target remote} to
18908 Run @var{command} in the background and communicate with it using a
18909 pipe. The @var{command} is a shell command, to be parsed and expanded
18910 by the system's command shell, @code{/bin/sh}; it should expect remote
18911 protocol packets on its standard input, and send replies on its
18912 standard output. You could use this to run a stand-alone simulator
18913 that speaks the remote debugging protocol, to make net connections
18914 using programs like @code{ssh}, or for other similar tricks.
18916 If @var{command} closes its standard output (perhaps by exiting),
18917 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18918 program has already exited, this will have no effect.)
18922 Once the connection has been established, you can use all the usual
18923 commands to examine and change data. The remote program is already
18924 running; you can use @kbd{step} and @kbd{continue}, and you do not
18925 need to use @kbd{run}.
18927 @cindex interrupting remote programs
18928 @cindex remote programs, interrupting
18929 Whenever @value{GDBN} is waiting for the remote program, if you type the
18930 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18931 program. This may or may not succeed, depending in part on the hardware
18932 and the serial drivers the remote system uses. If you type the
18933 interrupt character once again, @value{GDBN} displays this prompt:
18936 Interrupted while waiting for the program.
18937 Give up (and stop debugging it)? (y or n)
18940 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18941 (If you decide you want to try again later, you can use @samp{target
18942 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18943 goes back to waiting.
18946 @kindex detach (remote)
18948 When you have finished debugging the remote program, you can use the
18949 @code{detach} command to release it from @value{GDBN} control.
18950 Detaching from the target normally resumes its execution, but the results
18951 will depend on your particular remote stub. After the @code{detach}
18952 command, @value{GDBN} is free to connect to another target.
18956 The @code{disconnect} command behaves like @code{detach}, except that
18957 the target is generally not resumed. It will wait for @value{GDBN}
18958 (this instance or another one) to connect and continue debugging. After
18959 the @code{disconnect} command, @value{GDBN} is again free to connect to
18962 @cindex send command to remote monitor
18963 @cindex extend @value{GDBN} for remote targets
18964 @cindex add new commands for external monitor
18966 @item monitor @var{cmd}
18967 This command allows you to send arbitrary commands directly to the
18968 remote monitor. Since @value{GDBN} doesn't care about the commands it
18969 sends like this, this command is the way to extend @value{GDBN}---you
18970 can add new commands that only the external monitor will understand
18974 @node File Transfer
18975 @section Sending files to a remote system
18976 @cindex remote target, file transfer
18977 @cindex file transfer
18978 @cindex sending files to remote systems
18980 Some remote targets offer the ability to transfer files over the same
18981 connection used to communicate with @value{GDBN}. This is convenient
18982 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18983 running @code{gdbserver} over a network interface. For other targets,
18984 e.g.@: embedded devices with only a single serial port, this may be
18985 the only way to upload or download files.
18987 Not all remote targets support these commands.
18991 @item remote put @var{hostfile} @var{targetfile}
18992 Copy file @var{hostfile} from the host system (the machine running
18993 @value{GDBN}) to @var{targetfile} on the target system.
18996 @item remote get @var{targetfile} @var{hostfile}
18997 Copy file @var{targetfile} from the target system to @var{hostfile}
18998 on the host system.
19000 @kindex remote delete
19001 @item remote delete @var{targetfile}
19002 Delete @var{targetfile} from the target system.
19007 @section Using the @code{gdbserver} Program
19010 @cindex remote connection without stubs
19011 @code{gdbserver} is a control program for Unix-like systems, which
19012 allows you to connect your program with a remote @value{GDBN} via
19013 @code{target remote}---but without linking in the usual debugging stub.
19015 @code{gdbserver} is not a complete replacement for the debugging stubs,
19016 because it requires essentially the same operating-system facilities
19017 that @value{GDBN} itself does. In fact, a system that can run
19018 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19019 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19020 because it is a much smaller program than @value{GDBN} itself. It is
19021 also easier to port than all of @value{GDBN}, so you may be able to get
19022 started more quickly on a new system by using @code{gdbserver}.
19023 Finally, if you develop code for real-time systems, you may find that
19024 the tradeoffs involved in real-time operation make it more convenient to
19025 do as much development work as possible on another system, for example
19026 by cross-compiling. You can use @code{gdbserver} to make a similar
19027 choice for debugging.
19029 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19030 or a TCP connection, using the standard @value{GDBN} remote serial
19034 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19035 Do not run @code{gdbserver} connected to any public network; a
19036 @value{GDBN} connection to @code{gdbserver} provides access to the
19037 target system with the same privileges as the user running
19041 @subsection Running @code{gdbserver}
19042 @cindex arguments, to @code{gdbserver}
19043 @cindex @code{gdbserver}, command-line arguments
19045 Run @code{gdbserver} on the target system. You need a copy of the
19046 program you want to debug, including any libraries it requires.
19047 @code{gdbserver} does not need your program's symbol table, so you can
19048 strip the program if necessary to save space. @value{GDBN} on the host
19049 system does all the symbol handling.
19051 To use the server, you must tell it how to communicate with @value{GDBN};
19052 the name of your program; and the arguments for your program. The usual
19056 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19059 @var{comm} is either a device name (to use a serial line), or a TCP
19060 hostname and portnumber, or @code{-} or @code{stdio} to use
19061 stdin/stdout of @code{gdbserver}.
19062 For example, to debug Emacs with the argument
19063 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19067 target> gdbserver /dev/com1 emacs foo.txt
19070 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19073 To use a TCP connection instead of a serial line:
19076 target> gdbserver host:2345 emacs foo.txt
19079 The only difference from the previous example is the first argument,
19080 specifying that you are communicating with the host @value{GDBN} via
19081 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19082 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19083 (Currently, the @samp{host} part is ignored.) You can choose any number
19084 you want for the port number as long as it does not conflict with any
19085 TCP ports already in use on the target system (for example, @code{23} is
19086 reserved for @code{telnet}).@footnote{If you choose a port number that
19087 conflicts with another service, @code{gdbserver} prints an error message
19088 and exits.} You must use the same port number with the host @value{GDBN}
19089 @code{target remote} command.
19091 The @code{stdio} connection is useful when starting @code{gdbserver}
19095 (gdb) target remote | ssh -T hostname gdbserver - hello
19098 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19099 and we don't want escape-character handling. Ssh does this by default when
19100 a command is provided, the flag is provided to make it explicit.
19101 You could elide it if you want to.
19103 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19104 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19105 display through a pipe connected to gdbserver.
19106 Both @code{stdout} and @code{stderr} use the same pipe.
19108 @subsubsection Attaching to a Running Program
19109 @cindex attach to a program, @code{gdbserver}
19110 @cindex @option{--attach}, @code{gdbserver} option
19112 On some targets, @code{gdbserver} can also attach to running programs.
19113 This is accomplished via the @code{--attach} argument. The syntax is:
19116 target> gdbserver --attach @var{comm} @var{pid}
19119 @var{pid} is the process ID of a currently running process. It isn't necessary
19120 to point @code{gdbserver} at a binary for the running process.
19123 You can debug processes by name instead of process ID if your target has the
19124 @code{pidof} utility:
19127 target> gdbserver --attach @var{comm} `pidof @var{program}`
19130 In case more than one copy of @var{program} is running, or @var{program}
19131 has multiple threads, most versions of @code{pidof} support the
19132 @code{-s} option to only return the first process ID.
19134 @subsubsection Multi-Process Mode for @code{gdbserver}
19135 @cindex @code{gdbserver}, multiple processes
19136 @cindex multiple processes with @code{gdbserver}
19138 When you connect to @code{gdbserver} using @code{target remote},
19139 @code{gdbserver} debugs the specified program only once. When the
19140 program exits, or you detach from it, @value{GDBN} closes the connection
19141 and @code{gdbserver} exits.
19143 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19144 enters multi-process mode. When the debugged program exits, or you
19145 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19146 though no program is running. The @code{run} and @code{attach}
19147 commands instruct @code{gdbserver} to run or attach to a new program.
19148 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19149 remote exec-file}) to select the program to run. Command line
19150 arguments are supported, except for wildcard expansion and I/O
19151 redirection (@pxref{Arguments}).
19153 @cindex @option{--multi}, @code{gdbserver} option
19154 To start @code{gdbserver} without supplying an initial command to run
19155 or process ID to attach, use the @option{--multi} command line option.
19156 Then you can connect using @kbd{target extended-remote} and start
19157 the program you want to debug.
19159 In multi-process mode @code{gdbserver} does not automatically exit unless you
19160 use the option @option{--once}. You can terminate it by using
19161 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19162 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19163 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19164 @option{--multi} option to @code{gdbserver} has no influence on that.
19166 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19168 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19170 @code{gdbserver} normally terminates after all of its debugged processes have
19171 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19172 extended-remote}, @code{gdbserver} stays running even with no processes left.
19173 @value{GDBN} normally terminates the spawned debugged process on its exit,
19174 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19175 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19176 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19177 stays running even in the @kbd{target remote} mode.
19179 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19180 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19181 completeness, at most one @value{GDBN} can be connected at a time.
19183 @cindex @option{--once}, @code{gdbserver} option
19184 By default, @code{gdbserver} keeps the listening TCP port open, so that
19185 subsequent connections are possible. However, if you start @code{gdbserver}
19186 with the @option{--once} option, it will stop listening for any further
19187 connection attempts after connecting to the first @value{GDBN} session. This
19188 means no further connections to @code{gdbserver} will be possible after the
19189 first one. It also means @code{gdbserver} will terminate after the first
19190 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19191 connections and even in the @kbd{target extended-remote} mode. The
19192 @option{--once} option allows reusing the same port number for connecting to
19193 multiple instances of @code{gdbserver} running on the same host, since each
19194 instance closes its port after the first connection.
19196 @anchor{Other Command-Line Arguments for gdbserver}
19197 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19199 @cindex @option{--debug}, @code{gdbserver} option
19200 The @option{--debug} option tells @code{gdbserver} to display extra
19201 status information about the debugging process.
19202 @cindex @option{--remote-debug}, @code{gdbserver} option
19203 The @option{--remote-debug} option tells @code{gdbserver} to display
19204 remote protocol debug output. These options are intended for
19205 @code{gdbserver} development and for bug reports to the developers.
19207 @cindex @option{--debug-format}, @code{gdbserver} option
19208 The @option{--debug-format=option1[,option2,...]} option tells
19209 @code{gdbserver} to include additional information in each output.
19210 Possible options are:
19214 Turn off all extra information in debugging output.
19216 Turn on all extra information in debugging output.
19218 Include a timestamp in each line of debugging output.
19221 Options are processed in order. Thus, for example, if @option{none}
19222 appears last then no additional information is added to debugging output.
19224 @cindex @option{--wrapper}, @code{gdbserver} option
19225 The @option{--wrapper} option specifies a wrapper to launch programs
19226 for debugging. The option should be followed by the name of the
19227 wrapper, then any command-line arguments to pass to the wrapper, then
19228 @kbd{--} indicating the end of the wrapper arguments.
19230 @code{gdbserver} runs the specified wrapper program with a combined
19231 command line including the wrapper arguments, then the name of the
19232 program to debug, then any arguments to the program. The wrapper
19233 runs until it executes your program, and then @value{GDBN} gains control.
19235 You can use any program that eventually calls @code{execve} with
19236 its arguments as a wrapper. Several standard Unix utilities do
19237 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19238 with @code{exec "$@@"} will also work.
19240 For example, you can use @code{env} to pass an environment variable to
19241 the debugged program, without setting the variable in @code{gdbserver}'s
19245 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19248 @subsection Connecting to @code{gdbserver}
19250 Run @value{GDBN} on the host system.
19252 First make sure you have the necessary symbol files. Load symbols for
19253 your application using the @code{file} command before you connect. Use
19254 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19255 was compiled with the correct sysroot using @code{--with-sysroot}).
19257 The symbol file and target libraries must exactly match the executable
19258 and libraries on the target, with one exception: the files on the host
19259 system should not be stripped, even if the files on the target system
19260 are. Mismatched or missing files will lead to confusing results
19261 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19262 files may also prevent @code{gdbserver} from debugging multi-threaded
19265 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19266 For TCP connections, you must start up @code{gdbserver} prior to using
19267 the @code{target remote} command. Otherwise you may get an error whose
19268 text depends on the host system, but which usually looks something like
19269 @samp{Connection refused}. Don't use the @code{load}
19270 command in @value{GDBN} when using @code{gdbserver}, since the program is
19271 already on the target.
19273 @subsection Monitor Commands for @code{gdbserver}
19274 @cindex monitor commands, for @code{gdbserver}
19275 @anchor{Monitor Commands for gdbserver}
19277 During a @value{GDBN} session using @code{gdbserver}, you can use the
19278 @code{monitor} command to send special requests to @code{gdbserver}.
19279 Here are the available commands.
19283 List the available monitor commands.
19285 @item monitor set debug 0
19286 @itemx monitor set debug 1
19287 Disable or enable general debugging messages.
19289 @item monitor set remote-debug 0
19290 @itemx monitor set remote-debug 1
19291 Disable or enable specific debugging messages associated with the remote
19292 protocol (@pxref{Remote Protocol}).
19294 @item monitor set debug-format option1@r{[},option2,...@r{]}
19295 Specify additional text to add to debugging messages.
19296 Possible options are:
19300 Turn off all extra information in debugging output.
19302 Turn on all extra information in debugging output.
19304 Include a timestamp in each line of debugging output.
19307 Options are processed in order. Thus, for example, if @option{none}
19308 appears last then no additional information is added to debugging output.
19310 @item monitor set libthread-db-search-path [PATH]
19311 @cindex gdbserver, search path for @code{libthread_db}
19312 When this command is issued, @var{path} is a colon-separated list of
19313 directories to search for @code{libthread_db} (@pxref{Threads,,set
19314 libthread-db-search-path}). If you omit @var{path},
19315 @samp{libthread-db-search-path} will be reset to its default value.
19317 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19318 not supported in @code{gdbserver}.
19321 Tell gdbserver to exit immediately. This command should be followed by
19322 @code{disconnect} to close the debugging session. @code{gdbserver} will
19323 detach from any attached processes and kill any processes it created.
19324 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19325 of a multi-process mode debug session.
19329 @subsection Tracepoints support in @code{gdbserver}
19330 @cindex tracepoints support in @code{gdbserver}
19332 On some targets, @code{gdbserver} supports tracepoints, fast
19333 tracepoints and static tracepoints.
19335 For fast or static tracepoints to work, a special library called the
19336 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19337 This library is built and distributed as an integral part of
19338 @code{gdbserver}. In addition, support for static tracepoints
19339 requires building the in-process agent library with static tracepoints
19340 support. At present, the UST (LTTng Userspace Tracer,
19341 @url{http://lttng.org/ust}) tracing engine is supported. This support
19342 is automatically available if UST development headers are found in the
19343 standard include path when @code{gdbserver} is built, or if
19344 @code{gdbserver} was explicitly configured using @option{--with-ust}
19345 to point at such headers. You can explicitly disable the support
19346 using @option{--with-ust=no}.
19348 There are several ways to load the in-process agent in your program:
19351 @item Specifying it as dependency at link time
19353 You can link your program dynamically with the in-process agent
19354 library. On most systems, this is accomplished by adding
19355 @code{-linproctrace} to the link command.
19357 @item Using the system's preloading mechanisms
19359 You can force loading the in-process agent at startup time by using
19360 your system's support for preloading shared libraries. Many Unixes
19361 support the concept of preloading user defined libraries. In most
19362 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19363 in the environment. See also the description of @code{gdbserver}'s
19364 @option{--wrapper} command line option.
19366 @item Using @value{GDBN} to force loading the agent at run time
19368 On some systems, you can force the inferior to load a shared library,
19369 by calling a dynamic loader function in the inferior that takes care
19370 of dynamically looking up and loading a shared library. On most Unix
19371 systems, the function is @code{dlopen}. You'll use the @code{call}
19372 command for that. For example:
19375 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19378 Note that on most Unix systems, for the @code{dlopen} function to be
19379 available, the program needs to be linked with @code{-ldl}.
19382 On systems that have a userspace dynamic loader, like most Unix
19383 systems, when you connect to @code{gdbserver} using @code{target
19384 remote}, you'll find that the program is stopped at the dynamic
19385 loader's entry point, and no shared library has been loaded in the
19386 program's address space yet, including the in-process agent. In that
19387 case, before being able to use any of the fast or static tracepoints
19388 features, you need to let the loader run and load the shared
19389 libraries. The simplest way to do that is to run the program to the
19390 main procedure. E.g., if debugging a C or C@t{++} program, start
19391 @code{gdbserver} like so:
19394 $ gdbserver :9999 myprogram
19397 Start GDB and connect to @code{gdbserver} like so, and run to main:
19401 (@value{GDBP}) target remote myhost:9999
19402 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19403 (@value{GDBP}) b main
19404 (@value{GDBP}) continue
19407 The in-process tracing agent library should now be loaded into the
19408 process; you can confirm it with the @code{info sharedlibrary}
19409 command, which will list @file{libinproctrace.so} as loaded in the
19410 process. You are now ready to install fast tracepoints, list static
19411 tracepoint markers, probe static tracepoints markers, and start
19414 @node Remote Configuration
19415 @section Remote Configuration
19418 @kindex show remote
19419 This section documents the configuration options available when
19420 debugging remote programs. For the options related to the File I/O
19421 extensions of the remote protocol, see @ref{system,
19422 system-call-allowed}.
19425 @item set remoteaddresssize @var{bits}
19426 @cindex address size for remote targets
19427 @cindex bits in remote address
19428 Set the maximum size of address in a memory packet to the specified
19429 number of bits. @value{GDBN} will mask off the address bits above
19430 that number, when it passes addresses to the remote target. The
19431 default value is the number of bits in the target's address.
19433 @item show remoteaddresssize
19434 Show the current value of remote address size in bits.
19436 @item set serial baud @var{n}
19437 @cindex baud rate for remote targets
19438 Set the baud rate for the remote serial I/O to @var{n} baud. The
19439 value is used to set the speed of the serial port used for debugging
19442 @item show serial baud
19443 Show the current speed of the remote connection.
19445 @item set serial parity @var{parity}
19446 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19447 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19449 @item show serial parity
19450 Show the current parity of the serial port.
19452 @item set remotebreak
19453 @cindex interrupt remote programs
19454 @cindex BREAK signal instead of Ctrl-C
19455 @anchor{set remotebreak}
19456 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19457 when you type @kbd{Ctrl-c} to interrupt the program running
19458 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19459 character instead. The default is off, since most remote systems
19460 expect to see @samp{Ctrl-C} as the interrupt signal.
19462 @item show remotebreak
19463 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19464 interrupt the remote program.
19466 @item set remoteflow on
19467 @itemx set remoteflow off
19468 @kindex set remoteflow
19469 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19470 on the serial port used to communicate to the remote target.
19472 @item show remoteflow
19473 @kindex show remoteflow
19474 Show the current setting of hardware flow control.
19476 @item set remotelogbase @var{base}
19477 Set the base (a.k.a.@: radix) of logging serial protocol
19478 communications to @var{base}. Supported values of @var{base} are:
19479 @code{ascii}, @code{octal}, and @code{hex}. The default is
19482 @item show remotelogbase
19483 Show the current setting of the radix for logging remote serial
19486 @item set remotelogfile @var{file}
19487 @cindex record serial communications on file
19488 Record remote serial communications on the named @var{file}. The
19489 default is not to record at all.
19491 @item show remotelogfile.
19492 Show the current setting of the file name on which to record the
19493 serial communications.
19495 @item set remotetimeout @var{num}
19496 @cindex timeout for serial communications
19497 @cindex remote timeout
19498 Set the timeout limit to wait for the remote target to respond to
19499 @var{num} seconds. The default is 2 seconds.
19501 @item show remotetimeout
19502 Show the current number of seconds to wait for the remote target
19505 @cindex limit hardware breakpoints and watchpoints
19506 @cindex remote target, limit break- and watchpoints
19507 @anchor{set remote hardware-watchpoint-limit}
19508 @anchor{set remote hardware-breakpoint-limit}
19509 @item set remote hardware-watchpoint-limit @var{limit}
19510 @itemx set remote hardware-breakpoint-limit @var{limit}
19511 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19512 watchpoints. A limit of -1, the default, is treated as unlimited.
19514 @cindex limit hardware watchpoints length
19515 @cindex remote target, limit watchpoints length
19516 @anchor{set remote hardware-watchpoint-length-limit}
19517 @item set remote hardware-watchpoint-length-limit @var{limit}
19518 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19519 a remote hardware watchpoint. A limit of -1, the default, is treated
19522 @item show remote hardware-watchpoint-length-limit
19523 Show the current limit (in bytes) of the maximum length of
19524 a remote hardware watchpoint.
19526 @item set remote exec-file @var{filename}
19527 @itemx show remote exec-file
19528 @anchor{set remote exec-file}
19529 @cindex executable file, for remote target
19530 Select the file used for @code{run} with @code{target
19531 extended-remote}. This should be set to a filename valid on the
19532 target system. If it is not set, the target will use a default
19533 filename (e.g.@: the last program run).
19535 @item set remote interrupt-sequence
19536 @cindex interrupt remote programs
19537 @cindex select Ctrl-C, BREAK or BREAK-g
19538 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19539 @samp{BREAK-g} as the
19540 sequence to the remote target in order to interrupt the execution.
19541 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19542 is high level of serial line for some certain time.
19543 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19544 It is @code{BREAK} signal followed by character @code{g}.
19546 @item show interrupt-sequence
19547 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19548 is sent by @value{GDBN} to interrupt the remote program.
19549 @code{BREAK-g} is BREAK signal followed by @code{g} and
19550 also known as Magic SysRq g.
19552 @item set remote interrupt-on-connect
19553 @cindex send interrupt-sequence on start
19554 Specify whether interrupt-sequence is sent to remote target when
19555 @value{GDBN} connects to it. This is mostly needed when you debug
19556 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19557 which is known as Magic SysRq g in order to connect @value{GDBN}.
19559 @item show interrupt-on-connect
19560 Show whether interrupt-sequence is sent
19561 to remote target when @value{GDBN} connects to it.
19565 @item set tcp auto-retry on
19566 @cindex auto-retry, for remote TCP target
19567 Enable auto-retry for remote TCP connections. This is useful if the remote
19568 debugging agent is launched in parallel with @value{GDBN}; there is a race
19569 condition because the agent may not become ready to accept the connection
19570 before @value{GDBN} attempts to connect. When auto-retry is
19571 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19572 to establish the connection using the timeout specified by
19573 @code{set tcp connect-timeout}.
19575 @item set tcp auto-retry off
19576 Do not auto-retry failed TCP connections.
19578 @item show tcp auto-retry
19579 Show the current auto-retry setting.
19581 @item set tcp connect-timeout @var{seconds}
19582 @itemx set tcp connect-timeout unlimited
19583 @cindex connection timeout, for remote TCP target
19584 @cindex timeout, for remote target connection
19585 Set the timeout for establishing a TCP connection to the remote target to
19586 @var{seconds}. The timeout affects both polling to retry failed connections
19587 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19588 that are merely slow to complete, and represents an approximate cumulative
19589 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19590 @value{GDBN} will keep attempting to establish a connection forever,
19591 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19593 @item show tcp connect-timeout
19594 Show the current connection timeout setting.
19597 @cindex remote packets, enabling and disabling
19598 The @value{GDBN} remote protocol autodetects the packets supported by
19599 your debugging stub. If you need to override the autodetection, you
19600 can use these commands to enable or disable individual packets. Each
19601 packet can be set to @samp{on} (the remote target supports this
19602 packet), @samp{off} (the remote target does not support this packet),
19603 or @samp{auto} (detect remote target support for this packet). They
19604 all default to @samp{auto}. For more information about each packet,
19605 see @ref{Remote Protocol}.
19607 During normal use, you should not have to use any of these commands.
19608 If you do, that may be a bug in your remote debugging stub, or a bug
19609 in @value{GDBN}. You may want to report the problem to the
19610 @value{GDBN} developers.
19612 For each packet @var{name}, the command to enable or disable the
19613 packet is @code{set remote @var{name}-packet}. The available settings
19616 @multitable @columnfractions 0.28 0.32 0.25
19619 @tab Related Features
19621 @item @code{fetch-register}
19623 @tab @code{info registers}
19625 @item @code{set-register}
19629 @item @code{binary-download}
19631 @tab @code{load}, @code{set}
19633 @item @code{read-aux-vector}
19634 @tab @code{qXfer:auxv:read}
19635 @tab @code{info auxv}
19637 @item @code{symbol-lookup}
19638 @tab @code{qSymbol}
19639 @tab Detecting multiple threads
19641 @item @code{attach}
19642 @tab @code{vAttach}
19645 @item @code{verbose-resume}
19647 @tab Stepping or resuming multiple threads
19653 @item @code{software-breakpoint}
19657 @item @code{hardware-breakpoint}
19661 @item @code{write-watchpoint}
19665 @item @code{read-watchpoint}
19669 @item @code{access-watchpoint}
19673 @item @code{target-features}
19674 @tab @code{qXfer:features:read}
19675 @tab @code{set architecture}
19677 @item @code{library-info}
19678 @tab @code{qXfer:libraries:read}
19679 @tab @code{info sharedlibrary}
19681 @item @code{memory-map}
19682 @tab @code{qXfer:memory-map:read}
19683 @tab @code{info mem}
19685 @item @code{read-sdata-object}
19686 @tab @code{qXfer:sdata:read}
19687 @tab @code{print $_sdata}
19689 @item @code{read-spu-object}
19690 @tab @code{qXfer:spu:read}
19691 @tab @code{info spu}
19693 @item @code{write-spu-object}
19694 @tab @code{qXfer:spu:write}
19695 @tab @code{info spu}
19697 @item @code{read-siginfo-object}
19698 @tab @code{qXfer:siginfo:read}
19699 @tab @code{print $_siginfo}
19701 @item @code{write-siginfo-object}
19702 @tab @code{qXfer:siginfo:write}
19703 @tab @code{set $_siginfo}
19705 @item @code{threads}
19706 @tab @code{qXfer:threads:read}
19707 @tab @code{info threads}
19709 @item @code{get-thread-local-@*storage-address}
19710 @tab @code{qGetTLSAddr}
19711 @tab Displaying @code{__thread} variables
19713 @item @code{get-thread-information-block-address}
19714 @tab @code{qGetTIBAddr}
19715 @tab Display MS-Windows Thread Information Block.
19717 @item @code{search-memory}
19718 @tab @code{qSearch:memory}
19721 @item @code{supported-packets}
19722 @tab @code{qSupported}
19723 @tab Remote communications parameters
19725 @item @code{pass-signals}
19726 @tab @code{QPassSignals}
19727 @tab @code{handle @var{signal}}
19729 @item @code{program-signals}
19730 @tab @code{QProgramSignals}
19731 @tab @code{handle @var{signal}}
19733 @item @code{hostio-close-packet}
19734 @tab @code{vFile:close}
19735 @tab @code{remote get}, @code{remote put}
19737 @item @code{hostio-open-packet}
19738 @tab @code{vFile:open}
19739 @tab @code{remote get}, @code{remote put}
19741 @item @code{hostio-pread-packet}
19742 @tab @code{vFile:pread}
19743 @tab @code{remote get}, @code{remote put}
19745 @item @code{hostio-pwrite-packet}
19746 @tab @code{vFile:pwrite}
19747 @tab @code{remote get}, @code{remote put}
19749 @item @code{hostio-unlink-packet}
19750 @tab @code{vFile:unlink}
19751 @tab @code{remote delete}
19753 @item @code{hostio-readlink-packet}
19754 @tab @code{vFile:readlink}
19757 @item @code{hostio-fstat-packet}
19758 @tab @code{vFile:fstat}
19761 @item @code{noack-packet}
19762 @tab @code{QStartNoAckMode}
19763 @tab Packet acknowledgment
19765 @item @code{osdata}
19766 @tab @code{qXfer:osdata:read}
19767 @tab @code{info os}
19769 @item @code{query-attached}
19770 @tab @code{qAttached}
19771 @tab Querying remote process attach state.
19773 @item @code{trace-buffer-size}
19774 @tab @code{QTBuffer:size}
19775 @tab @code{set trace-buffer-size}
19777 @item @code{trace-status}
19778 @tab @code{qTStatus}
19779 @tab @code{tstatus}
19781 @item @code{traceframe-info}
19782 @tab @code{qXfer:traceframe-info:read}
19783 @tab Traceframe info
19785 @item @code{install-in-trace}
19786 @tab @code{InstallInTrace}
19787 @tab Install tracepoint in tracing
19789 @item @code{disable-randomization}
19790 @tab @code{QDisableRandomization}
19791 @tab @code{set disable-randomization}
19793 @item @code{conditional-breakpoints-packet}
19794 @tab @code{Z0 and Z1}
19795 @tab @code{Support for target-side breakpoint condition evaluation}
19797 @item @code{swbreak-feature}
19798 @tab @code{swbreak stop reason}
19801 @item @code{hwbreak-feature}
19802 @tab @code{hwbreak stop reason}
19808 @section Implementing a Remote Stub
19810 @cindex debugging stub, example
19811 @cindex remote stub, example
19812 @cindex stub example, remote debugging
19813 The stub files provided with @value{GDBN} implement the target side of the
19814 communication protocol, and the @value{GDBN} side is implemented in the
19815 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19816 these subroutines to communicate, and ignore the details. (If you're
19817 implementing your own stub file, you can still ignore the details: start
19818 with one of the existing stub files. @file{sparc-stub.c} is the best
19819 organized, and therefore the easiest to read.)
19821 @cindex remote serial debugging, overview
19822 To debug a program running on another machine (the debugging
19823 @dfn{target} machine), you must first arrange for all the usual
19824 prerequisites for the program to run by itself. For example, for a C
19829 A startup routine to set up the C runtime environment; these usually
19830 have a name like @file{crt0}. The startup routine may be supplied by
19831 your hardware supplier, or you may have to write your own.
19834 A C subroutine library to support your program's
19835 subroutine calls, notably managing input and output.
19838 A way of getting your program to the other machine---for example, a
19839 download program. These are often supplied by the hardware
19840 manufacturer, but you may have to write your own from hardware
19844 The next step is to arrange for your program to use a serial port to
19845 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19846 machine). In general terms, the scheme looks like this:
19850 @value{GDBN} already understands how to use this protocol; when everything
19851 else is set up, you can simply use the @samp{target remote} command
19852 (@pxref{Targets,,Specifying a Debugging Target}).
19854 @item On the target,
19855 you must link with your program a few special-purpose subroutines that
19856 implement the @value{GDBN} remote serial protocol. The file containing these
19857 subroutines is called a @dfn{debugging stub}.
19859 On certain remote targets, you can use an auxiliary program
19860 @code{gdbserver} instead of linking a stub into your program.
19861 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19864 The debugging stub is specific to the architecture of the remote
19865 machine; for example, use @file{sparc-stub.c} to debug programs on
19868 @cindex remote serial stub list
19869 These working remote stubs are distributed with @value{GDBN}:
19874 @cindex @file{i386-stub.c}
19877 For Intel 386 and compatible architectures.
19880 @cindex @file{m68k-stub.c}
19881 @cindex Motorola 680x0
19883 For Motorola 680x0 architectures.
19886 @cindex @file{sh-stub.c}
19889 For Renesas SH architectures.
19892 @cindex @file{sparc-stub.c}
19894 For @sc{sparc} architectures.
19896 @item sparcl-stub.c
19897 @cindex @file{sparcl-stub.c}
19900 For Fujitsu @sc{sparclite} architectures.
19904 The @file{README} file in the @value{GDBN} distribution may list other
19905 recently added stubs.
19908 * Stub Contents:: What the stub can do for you
19909 * Bootstrapping:: What you must do for the stub
19910 * Debug Session:: Putting it all together
19913 @node Stub Contents
19914 @subsection What the Stub Can Do for You
19916 @cindex remote serial stub
19917 The debugging stub for your architecture supplies these three
19921 @item set_debug_traps
19922 @findex set_debug_traps
19923 @cindex remote serial stub, initialization
19924 This routine arranges for @code{handle_exception} to run when your
19925 program stops. You must call this subroutine explicitly in your
19926 program's startup code.
19928 @item handle_exception
19929 @findex handle_exception
19930 @cindex remote serial stub, main routine
19931 This is the central workhorse, but your program never calls it
19932 explicitly---the setup code arranges for @code{handle_exception} to
19933 run when a trap is triggered.
19935 @code{handle_exception} takes control when your program stops during
19936 execution (for example, on a breakpoint), and mediates communications
19937 with @value{GDBN} on the host machine. This is where the communications
19938 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19939 representative on the target machine. It begins by sending summary
19940 information on the state of your program, then continues to execute,
19941 retrieving and transmitting any information @value{GDBN} needs, until you
19942 execute a @value{GDBN} command that makes your program resume; at that point,
19943 @code{handle_exception} returns control to your own code on the target
19947 @cindex @code{breakpoint} subroutine, remote
19948 Use this auxiliary subroutine to make your program contain a
19949 breakpoint. Depending on the particular situation, this may be the only
19950 way for @value{GDBN} to get control. For instance, if your target
19951 machine has some sort of interrupt button, you won't need to call this;
19952 pressing the interrupt button transfers control to
19953 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19954 simply receiving characters on the serial port may also trigger a trap;
19955 again, in that situation, you don't need to call @code{breakpoint} from
19956 your own program---simply running @samp{target remote} from the host
19957 @value{GDBN} session gets control.
19959 Call @code{breakpoint} if none of these is true, or if you simply want
19960 to make certain your program stops at a predetermined point for the
19961 start of your debugging session.
19964 @node Bootstrapping
19965 @subsection What You Must Do for the Stub
19967 @cindex remote stub, support routines
19968 The debugging stubs that come with @value{GDBN} are set up for a particular
19969 chip architecture, but they have no information about the rest of your
19970 debugging target machine.
19972 First of all you need to tell the stub how to communicate with the
19976 @item int getDebugChar()
19977 @findex getDebugChar
19978 Write this subroutine to read a single character from the serial port.
19979 It may be identical to @code{getchar} for your target system; a
19980 different name is used to allow you to distinguish the two if you wish.
19982 @item void putDebugChar(int)
19983 @findex putDebugChar
19984 Write this subroutine to write a single character to the serial port.
19985 It may be identical to @code{putchar} for your target system; a
19986 different name is used to allow you to distinguish the two if you wish.
19989 @cindex control C, and remote debugging
19990 @cindex interrupting remote targets
19991 If you want @value{GDBN} to be able to stop your program while it is
19992 running, you need to use an interrupt-driven serial driver, and arrange
19993 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19994 character). That is the character which @value{GDBN} uses to tell the
19995 remote system to stop.
19997 Getting the debugging target to return the proper status to @value{GDBN}
19998 probably requires changes to the standard stub; one quick and dirty way
19999 is to just execute a breakpoint instruction (the ``dirty'' part is that
20000 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20002 Other routines you need to supply are:
20005 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20006 @findex exceptionHandler
20007 Write this function to install @var{exception_address} in the exception
20008 handling tables. You need to do this because the stub does not have any
20009 way of knowing what the exception handling tables on your target system
20010 are like (for example, the processor's table might be in @sc{rom},
20011 containing entries which point to a table in @sc{ram}).
20012 The @var{exception_number} specifies the exception which should be changed;
20013 its meaning is architecture-dependent (for example, different numbers
20014 might represent divide by zero, misaligned access, etc). When this
20015 exception occurs, control should be transferred directly to
20016 @var{exception_address}, and the processor state (stack, registers,
20017 and so on) should be just as it is when a processor exception occurs. So if
20018 you want to use a jump instruction to reach @var{exception_address}, it
20019 should be a simple jump, not a jump to subroutine.
20021 For the 386, @var{exception_address} should be installed as an interrupt
20022 gate so that interrupts are masked while the handler runs. The gate
20023 should be at privilege level 0 (the most privileged level). The
20024 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20025 help from @code{exceptionHandler}.
20027 @item void flush_i_cache()
20028 @findex flush_i_cache
20029 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20030 instruction cache, if any, on your target machine. If there is no
20031 instruction cache, this subroutine may be a no-op.
20033 On target machines that have instruction caches, @value{GDBN} requires this
20034 function to make certain that the state of your program is stable.
20038 You must also make sure this library routine is available:
20041 @item void *memset(void *, int, int)
20043 This is the standard library function @code{memset} that sets an area of
20044 memory to a known value. If you have one of the free versions of
20045 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20046 either obtain it from your hardware manufacturer, or write your own.
20049 If you do not use the GNU C compiler, you may need other standard
20050 library subroutines as well; this varies from one stub to another,
20051 but in general the stubs are likely to use any of the common library
20052 subroutines which @code{@value{NGCC}} generates as inline code.
20055 @node Debug Session
20056 @subsection Putting it All Together
20058 @cindex remote serial debugging summary
20059 In summary, when your program is ready to debug, you must follow these
20064 Make sure you have defined the supporting low-level routines
20065 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20067 @code{getDebugChar}, @code{putDebugChar},
20068 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20072 Insert these lines in your program's startup code, before the main
20073 procedure is called:
20080 On some machines, when a breakpoint trap is raised, the hardware
20081 automatically makes the PC point to the instruction after the
20082 breakpoint. If your machine doesn't do that, you may need to adjust
20083 @code{handle_exception} to arrange for it to return to the instruction
20084 after the breakpoint on this first invocation, so that your program
20085 doesn't keep hitting the initial breakpoint instead of making
20089 For the 680x0 stub only, you need to provide a variable called
20090 @code{exceptionHook}. Normally you just use:
20093 void (*exceptionHook)() = 0;
20097 but if before calling @code{set_debug_traps}, you set it to point to a
20098 function in your program, that function is called when
20099 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20100 error). The function indicated by @code{exceptionHook} is called with
20101 one parameter: an @code{int} which is the exception number.
20104 Compile and link together: your program, the @value{GDBN} debugging stub for
20105 your target architecture, and the supporting subroutines.
20108 Make sure you have a serial connection between your target machine and
20109 the @value{GDBN} host, and identify the serial port on the host.
20112 @c The "remote" target now provides a `load' command, so we should
20113 @c document that. FIXME.
20114 Download your program to your target machine (or get it there by
20115 whatever means the manufacturer provides), and start it.
20118 Start @value{GDBN} on the host, and connect to the target
20119 (@pxref{Connecting,,Connecting to a Remote Target}).
20123 @node Configurations
20124 @chapter Configuration-Specific Information
20126 While nearly all @value{GDBN} commands are available for all native and
20127 cross versions of the debugger, there are some exceptions. This chapter
20128 describes things that are only available in certain configurations.
20130 There are three major categories of configurations: native
20131 configurations, where the host and target are the same, embedded
20132 operating system configurations, which are usually the same for several
20133 different processor architectures, and bare embedded processors, which
20134 are quite different from each other.
20139 * Embedded Processors::
20146 This section describes details specific to particular native
20151 * BSD libkvm Interface:: Debugging BSD kernel memory images
20152 * SVR4 Process Information:: SVR4 process information
20153 * DJGPP Native:: Features specific to the DJGPP port
20154 * Cygwin Native:: Features specific to the Cygwin port
20155 * Hurd Native:: Features specific to @sc{gnu} Hurd
20156 * Darwin:: Features specific to Darwin
20162 On HP-UX systems, if you refer to a function or variable name that
20163 begins with a dollar sign, @value{GDBN} searches for a user or system
20164 name first, before it searches for a convenience variable.
20167 @node BSD libkvm Interface
20168 @subsection BSD libkvm Interface
20171 @cindex kernel memory image
20172 @cindex kernel crash dump
20174 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20175 interface that provides a uniform interface for accessing kernel virtual
20176 memory images, including live systems and crash dumps. @value{GDBN}
20177 uses this interface to allow you to debug live kernels and kernel crash
20178 dumps on many native BSD configurations. This is implemented as a
20179 special @code{kvm} debugging target. For debugging a live system, load
20180 the currently running kernel into @value{GDBN} and connect to the
20184 (@value{GDBP}) @b{target kvm}
20187 For debugging crash dumps, provide the file name of the crash dump as an
20191 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20194 Once connected to the @code{kvm} target, the following commands are
20200 Set current context from the @dfn{Process Control Block} (PCB) address.
20203 Set current context from proc address. This command isn't available on
20204 modern FreeBSD systems.
20207 @node SVR4 Process Information
20208 @subsection SVR4 Process Information
20210 @cindex examine process image
20211 @cindex process info via @file{/proc}
20213 Many versions of SVR4 and compatible systems provide a facility called
20214 @samp{/proc} that can be used to examine the image of a running
20215 process using file-system subroutines.
20217 If @value{GDBN} is configured for an operating system with this
20218 facility, the command @code{info proc} is available to report
20219 information about the process running your program, or about any
20220 process running on your system. This includes, as of this writing,
20221 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20223 This command may also work on core files that were created on a system
20224 that has the @samp{/proc} facility.
20230 @itemx info proc @var{process-id}
20231 Summarize available information about any running process. If a
20232 process ID is specified by @var{process-id}, display information about
20233 that process; otherwise display information about the program being
20234 debugged. The summary includes the debugged process ID, the command
20235 line used to invoke it, its current working directory, and its
20236 executable file's absolute file name.
20238 On some systems, @var{process-id} can be of the form
20239 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20240 within a process. If the optional @var{pid} part is missing, it means
20241 a thread from the process being debugged (the leading @samp{/} still
20242 needs to be present, or else @value{GDBN} will interpret the number as
20243 a process ID rather than a thread ID).
20245 @item info proc cmdline
20246 @cindex info proc cmdline
20247 Show the original command line of the process. This command is
20248 specific to @sc{gnu}/Linux.
20250 @item info proc cwd
20251 @cindex info proc cwd
20252 Show the current working directory of the process. This command is
20253 specific to @sc{gnu}/Linux.
20255 @item info proc exe
20256 @cindex info proc exe
20257 Show the name of executable of the process. This command is specific
20260 @item info proc mappings
20261 @cindex memory address space mappings
20262 Report the memory address space ranges accessible in the program, with
20263 information on whether the process has read, write, or execute access
20264 rights to each range. On @sc{gnu}/Linux systems, each memory range
20265 includes the object file which is mapped to that range, instead of the
20266 memory access rights to that range.
20268 @item info proc stat
20269 @itemx info proc status
20270 @cindex process detailed status information
20271 These subcommands are specific to @sc{gnu}/Linux systems. They show
20272 the process-related information, including the user ID and group ID;
20273 how many threads are there in the process; its virtual memory usage;
20274 the signals that are pending, blocked, and ignored; its TTY; its
20275 consumption of system and user time; its stack size; its @samp{nice}
20276 value; etc. For more information, see the @samp{proc} man page
20277 (type @kbd{man 5 proc} from your shell prompt).
20279 @item info proc all
20280 Show all the information about the process described under all of the
20281 above @code{info proc} subcommands.
20284 @comment These sub-options of 'info proc' were not included when
20285 @comment procfs.c was re-written. Keep their descriptions around
20286 @comment against the day when someone finds the time to put them back in.
20287 @kindex info proc times
20288 @item info proc times
20289 Starting time, user CPU time, and system CPU time for your program and
20292 @kindex info proc id
20294 Report on the process IDs related to your program: its own process ID,
20295 the ID of its parent, the process group ID, and the session ID.
20298 @item set procfs-trace
20299 @kindex set procfs-trace
20300 @cindex @code{procfs} API calls
20301 This command enables and disables tracing of @code{procfs} API calls.
20303 @item show procfs-trace
20304 @kindex show procfs-trace
20305 Show the current state of @code{procfs} API call tracing.
20307 @item set procfs-file @var{file}
20308 @kindex set procfs-file
20309 Tell @value{GDBN} to write @code{procfs} API trace to the named
20310 @var{file}. @value{GDBN} appends the trace info to the previous
20311 contents of the file. The default is to display the trace on the
20314 @item show procfs-file
20315 @kindex show procfs-file
20316 Show the file to which @code{procfs} API trace is written.
20318 @item proc-trace-entry
20319 @itemx proc-trace-exit
20320 @itemx proc-untrace-entry
20321 @itemx proc-untrace-exit
20322 @kindex proc-trace-entry
20323 @kindex proc-trace-exit
20324 @kindex proc-untrace-entry
20325 @kindex proc-untrace-exit
20326 These commands enable and disable tracing of entries into and exits
20327 from the @code{syscall} interface.
20330 @kindex info pidlist
20331 @cindex process list, QNX Neutrino
20332 For QNX Neutrino only, this command displays the list of all the
20333 processes and all the threads within each process.
20336 @kindex info meminfo
20337 @cindex mapinfo list, QNX Neutrino
20338 For QNX Neutrino only, this command displays the list of all mapinfos.
20342 @subsection Features for Debugging @sc{djgpp} Programs
20343 @cindex @sc{djgpp} debugging
20344 @cindex native @sc{djgpp} debugging
20345 @cindex MS-DOS-specific commands
20348 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20349 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20350 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20351 top of real-mode DOS systems and their emulations.
20353 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20354 defines a few commands specific to the @sc{djgpp} port. This
20355 subsection describes those commands.
20360 This is a prefix of @sc{djgpp}-specific commands which print
20361 information about the target system and important OS structures.
20364 @cindex MS-DOS system info
20365 @cindex free memory information (MS-DOS)
20366 @item info dos sysinfo
20367 This command displays assorted information about the underlying
20368 platform: the CPU type and features, the OS version and flavor, the
20369 DPMI version, and the available conventional and DPMI memory.
20374 @cindex segment descriptor tables
20375 @cindex descriptor tables display
20377 @itemx info dos ldt
20378 @itemx info dos idt
20379 These 3 commands display entries from, respectively, Global, Local,
20380 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20381 tables are data structures which store a descriptor for each segment
20382 that is currently in use. The segment's selector is an index into a
20383 descriptor table; the table entry for that index holds the
20384 descriptor's base address and limit, and its attributes and access
20387 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20388 segment (used for both data and the stack), and a DOS segment (which
20389 allows access to DOS/BIOS data structures and absolute addresses in
20390 conventional memory). However, the DPMI host will usually define
20391 additional segments in order to support the DPMI environment.
20393 @cindex garbled pointers
20394 These commands allow to display entries from the descriptor tables.
20395 Without an argument, all entries from the specified table are
20396 displayed. An argument, which should be an integer expression, means
20397 display a single entry whose index is given by the argument. For
20398 example, here's a convenient way to display information about the
20399 debugged program's data segment:
20402 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20403 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20407 This comes in handy when you want to see whether a pointer is outside
20408 the data segment's limit (i.e.@: @dfn{garbled}).
20410 @cindex page tables display (MS-DOS)
20412 @itemx info dos pte
20413 These two commands display entries from, respectively, the Page
20414 Directory and the Page Tables. Page Directories and Page Tables are
20415 data structures which control how virtual memory addresses are mapped
20416 into physical addresses. A Page Table includes an entry for every
20417 page of memory that is mapped into the program's address space; there
20418 may be several Page Tables, each one holding up to 4096 entries. A
20419 Page Directory has up to 4096 entries, one each for every Page Table
20420 that is currently in use.
20422 Without an argument, @kbd{info dos pde} displays the entire Page
20423 Directory, and @kbd{info dos pte} displays all the entries in all of
20424 the Page Tables. An argument, an integer expression, given to the
20425 @kbd{info dos pde} command means display only that entry from the Page
20426 Directory table. An argument given to the @kbd{info dos pte} command
20427 means display entries from a single Page Table, the one pointed to by
20428 the specified entry in the Page Directory.
20430 @cindex direct memory access (DMA) on MS-DOS
20431 These commands are useful when your program uses @dfn{DMA} (Direct
20432 Memory Access), which needs physical addresses to program the DMA
20435 These commands are supported only with some DPMI servers.
20437 @cindex physical address from linear address
20438 @item info dos address-pte @var{addr}
20439 This command displays the Page Table entry for a specified linear
20440 address. The argument @var{addr} is a linear address which should
20441 already have the appropriate segment's base address added to it,
20442 because this command accepts addresses which may belong to @emph{any}
20443 segment. For example, here's how to display the Page Table entry for
20444 the page where a variable @code{i} is stored:
20447 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20448 @exdent @code{Page Table entry for address 0x11a00d30:}
20449 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20453 This says that @code{i} is stored at offset @code{0xd30} from the page
20454 whose physical base address is @code{0x02698000}, and shows all the
20455 attributes of that page.
20457 Note that you must cast the addresses of variables to a @code{char *},
20458 since otherwise the value of @code{__djgpp_base_address}, the base
20459 address of all variables and functions in a @sc{djgpp} program, will
20460 be added using the rules of C pointer arithmetics: if @code{i} is
20461 declared an @code{int}, @value{GDBN} will add 4 times the value of
20462 @code{__djgpp_base_address} to the address of @code{i}.
20464 Here's another example, it displays the Page Table entry for the
20468 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20469 @exdent @code{Page Table entry for address 0x29110:}
20470 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20474 (The @code{+ 3} offset is because the transfer buffer's address is the
20475 3rd member of the @code{_go32_info_block} structure.) The output
20476 clearly shows that this DPMI server maps the addresses in conventional
20477 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20478 linear (@code{0x29110}) addresses are identical.
20480 This command is supported only with some DPMI servers.
20483 @cindex DOS serial data link, remote debugging
20484 In addition to native debugging, the DJGPP port supports remote
20485 debugging via a serial data link. The following commands are specific
20486 to remote serial debugging in the DJGPP port of @value{GDBN}.
20489 @kindex set com1base
20490 @kindex set com1irq
20491 @kindex set com2base
20492 @kindex set com2irq
20493 @kindex set com3base
20494 @kindex set com3irq
20495 @kindex set com4base
20496 @kindex set com4irq
20497 @item set com1base @var{addr}
20498 This command sets the base I/O port address of the @file{COM1} serial
20501 @item set com1irq @var{irq}
20502 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20503 for the @file{COM1} serial port.
20505 There are similar commands @samp{set com2base}, @samp{set com3irq},
20506 etc.@: for setting the port address and the @code{IRQ} lines for the
20509 @kindex show com1base
20510 @kindex show com1irq
20511 @kindex show com2base
20512 @kindex show com2irq
20513 @kindex show com3base
20514 @kindex show com3irq
20515 @kindex show com4base
20516 @kindex show com4irq
20517 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20518 display the current settings of the base address and the @code{IRQ}
20519 lines used by the COM ports.
20522 @kindex info serial
20523 @cindex DOS serial port status
20524 This command prints the status of the 4 DOS serial ports. For each
20525 port, it prints whether it's active or not, its I/O base address and
20526 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20527 counts of various errors encountered so far.
20531 @node Cygwin Native
20532 @subsection Features for Debugging MS Windows PE Executables
20533 @cindex MS Windows debugging
20534 @cindex native Cygwin debugging
20535 @cindex Cygwin-specific commands
20537 @value{GDBN} supports native debugging of MS Windows programs, including
20538 DLLs with and without symbolic debugging information.
20540 @cindex Ctrl-BREAK, MS-Windows
20541 @cindex interrupt debuggee on MS-Windows
20542 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20543 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20544 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20545 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20546 sequence, which can be used to interrupt the debuggee even if it
20549 There are various additional Cygwin-specific commands, described in
20550 this section. Working with DLLs that have no debugging symbols is
20551 described in @ref{Non-debug DLL Symbols}.
20556 This is a prefix of MS Windows-specific commands which print
20557 information about the target system and important OS structures.
20559 @item info w32 selector
20560 This command displays information returned by
20561 the Win32 API @code{GetThreadSelectorEntry} function.
20562 It takes an optional argument that is evaluated to
20563 a long value to give the information about this given selector.
20564 Without argument, this command displays information
20565 about the six segment registers.
20567 @item info w32 thread-information-block
20568 This command displays thread specific information stored in the
20569 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20570 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20574 This is a Cygwin-specific alias of @code{info shared}.
20576 @kindex set cygwin-exceptions
20577 @cindex debugging the Cygwin DLL
20578 @cindex Cygwin DLL, debugging
20579 @item set cygwin-exceptions @var{mode}
20580 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20581 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20582 @value{GDBN} will delay recognition of exceptions, and may ignore some
20583 exceptions which seem to be caused by internal Cygwin DLL
20584 ``bookkeeping''. This option is meant primarily for debugging the
20585 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20586 @value{GDBN} users with false @code{SIGSEGV} signals.
20588 @kindex show cygwin-exceptions
20589 @item show cygwin-exceptions
20590 Displays whether @value{GDBN} will break on exceptions that happen
20591 inside the Cygwin DLL itself.
20593 @kindex set new-console
20594 @item set new-console @var{mode}
20595 If @var{mode} is @code{on} the debuggee will
20596 be started in a new console on next start.
20597 If @var{mode} is @code{off}, the debuggee will
20598 be started in the same console as the debugger.
20600 @kindex show new-console
20601 @item show new-console
20602 Displays whether a new console is used
20603 when the debuggee is started.
20605 @kindex set new-group
20606 @item set new-group @var{mode}
20607 This boolean value controls whether the debuggee should
20608 start a new group or stay in the same group as the debugger.
20609 This affects the way the Windows OS handles
20612 @kindex show new-group
20613 @item show new-group
20614 Displays current value of new-group boolean.
20616 @kindex set debugevents
20617 @item set debugevents
20618 This boolean value adds debug output concerning kernel events related
20619 to the debuggee seen by the debugger. This includes events that
20620 signal thread and process creation and exit, DLL loading and
20621 unloading, console interrupts, and debugging messages produced by the
20622 Windows @code{OutputDebugString} API call.
20624 @kindex set debugexec
20625 @item set debugexec
20626 This boolean value adds debug output concerning execute events
20627 (such as resume thread) seen by the debugger.
20629 @kindex set debugexceptions
20630 @item set debugexceptions
20631 This boolean value adds debug output concerning exceptions in the
20632 debuggee seen by the debugger.
20634 @kindex set debugmemory
20635 @item set debugmemory
20636 This boolean value adds debug output concerning debuggee memory reads
20637 and writes by the debugger.
20641 This boolean values specifies whether the debuggee is called
20642 via a shell or directly (default value is on).
20646 Displays if the debuggee will be started with a shell.
20651 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20654 @node Non-debug DLL Symbols
20655 @subsubsection Support for DLLs without Debugging Symbols
20656 @cindex DLLs with no debugging symbols
20657 @cindex Minimal symbols and DLLs
20659 Very often on windows, some of the DLLs that your program relies on do
20660 not include symbolic debugging information (for example,
20661 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20662 symbols in a DLL, it relies on the minimal amount of symbolic
20663 information contained in the DLL's export table. This section
20664 describes working with such symbols, known internally to @value{GDBN} as
20665 ``minimal symbols''.
20667 Note that before the debugged program has started execution, no DLLs
20668 will have been loaded. The easiest way around this problem is simply to
20669 start the program --- either by setting a breakpoint or letting the
20670 program run once to completion.
20672 @subsubsection DLL Name Prefixes
20674 In keeping with the naming conventions used by the Microsoft debugging
20675 tools, DLL export symbols are made available with a prefix based on the
20676 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20677 also entered into the symbol table, so @code{CreateFileA} is often
20678 sufficient. In some cases there will be name clashes within a program
20679 (particularly if the executable itself includes full debugging symbols)
20680 necessitating the use of the fully qualified name when referring to the
20681 contents of the DLL. Use single-quotes around the name to avoid the
20682 exclamation mark (``!'') being interpreted as a language operator.
20684 Note that the internal name of the DLL may be all upper-case, even
20685 though the file name of the DLL is lower-case, or vice-versa. Since
20686 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20687 some confusion. If in doubt, try the @code{info functions} and
20688 @code{info variables} commands or even @code{maint print msymbols}
20689 (@pxref{Symbols}). Here's an example:
20692 (@value{GDBP}) info function CreateFileA
20693 All functions matching regular expression "CreateFileA":
20695 Non-debugging symbols:
20696 0x77e885f4 CreateFileA
20697 0x77e885f4 KERNEL32!CreateFileA
20701 (@value{GDBP}) info function !
20702 All functions matching regular expression "!":
20704 Non-debugging symbols:
20705 0x6100114c cygwin1!__assert
20706 0x61004034 cygwin1!_dll_crt0@@0
20707 0x61004240 cygwin1!dll_crt0(per_process *)
20711 @subsubsection Working with Minimal Symbols
20713 Symbols extracted from a DLL's export table do not contain very much
20714 type information. All that @value{GDBN} can do is guess whether a symbol
20715 refers to a function or variable depending on the linker section that
20716 contains the symbol. Also note that the actual contents of the memory
20717 contained in a DLL are not available unless the program is running. This
20718 means that you cannot examine the contents of a variable or disassemble
20719 a function within a DLL without a running program.
20721 Variables are generally treated as pointers and dereferenced
20722 automatically. For this reason, it is often necessary to prefix a
20723 variable name with the address-of operator (``&'') and provide explicit
20724 type information in the command. Here's an example of the type of
20728 (@value{GDBP}) print 'cygwin1!__argv'
20733 (@value{GDBP}) x 'cygwin1!__argv'
20734 0x10021610: "\230y\""
20737 And two possible solutions:
20740 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20741 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20745 (@value{GDBP}) x/2x &'cygwin1!__argv'
20746 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20747 (@value{GDBP}) x/x 0x10021608
20748 0x10021608: 0x0022fd98
20749 (@value{GDBP}) x/s 0x0022fd98
20750 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20753 Setting a break point within a DLL is possible even before the program
20754 starts execution. However, under these circumstances, @value{GDBN} can't
20755 examine the initial instructions of the function in order to skip the
20756 function's frame set-up code. You can work around this by using ``*&''
20757 to set the breakpoint at a raw memory address:
20760 (@value{GDBP}) break *&'python22!PyOS_Readline'
20761 Breakpoint 1 at 0x1e04eff0
20764 The author of these extensions is not entirely convinced that setting a
20765 break point within a shared DLL like @file{kernel32.dll} is completely
20769 @subsection Commands Specific to @sc{gnu} Hurd Systems
20770 @cindex @sc{gnu} Hurd debugging
20772 This subsection describes @value{GDBN} commands specific to the
20773 @sc{gnu} Hurd native debugging.
20778 @kindex set signals@r{, Hurd command}
20779 @kindex set sigs@r{, Hurd command}
20780 This command toggles the state of inferior signal interception by
20781 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20782 affected by this command. @code{sigs} is a shorthand alias for
20787 @kindex show signals@r{, Hurd command}
20788 @kindex show sigs@r{, Hurd command}
20789 Show the current state of intercepting inferior's signals.
20791 @item set signal-thread
20792 @itemx set sigthread
20793 @kindex set signal-thread
20794 @kindex set sigthread
20795 This command tells @value{GDBN} which thread is the @code{libc} signal
20796 thread. That thread is run when a signal is delivered to a running
20797 process. @code{set sigthread} is the shorthand alias of @code{set
20800 @item show signal-thread
20801 @itemx show sigthread
20802 @kindex show signal-thread
20803 @kindex show sigthread
20804 These two commands show which thread will run when the inferior is
20805 delivered a signal.
20808 @kindex set stopped@r{, Hurd command}
20809 This commands tells @value{GDBN} that the inferior process is stopped,
20810 as with the @code{SIGSTOP} signal. The stopped process can be
20811 continued by delivering a signal to it.
20814 @kindex show stopped@r{, Hurd command}
20815 This command shows whether @value{GDBN} thinks the debuggee is
20818 @item set exceptions
20819 @kindex set exceptions@r{, Hurd command}
20820 Use this command to turn off trapping of exceptions in the inferior.
20821 When exception trapping is off, neither breakpoints nor
20822 single-stepping will work. To restore the default, set exception
20825 @item show exceptions
20826 @kindex show exceptions@r{, Hurd command}
20827 Show the current state of trapping exceptions in the inferior.
20829 @item set task pause
20830 @kindex set task@r{, Hurd commands}
20831 @cindex task attributes (@sc{gnu} Hurd)
20832 @cindex pause current task (@sc{gnu} Hurd)
20833 This command toggles task suspension when @value{GDBN} has control.
20834 Setting it to on takes effect immediately, and the task is suspended
20835 whenever @value{GDBN} gets control. Setting it to off will take
20836 effect the next time the inferior is continued. If this option is set
20837 to off, you can use @code{set thread default pause on} or @code{set
20838 thread pause on} (see below) to pause individual threads.
20840 @item show task pause
20841 @kindex show task@r{, Hurd commands}
20842 Show the current state of task suspension.
20844 @item set task detach-suspend-count
20845 @cindex task suspend count
20846 @cindex detach from task, @sc{gnu} Hurd
20847 This command sets the suspend count the task will be left with when
20848 @value{GDBN} detaches from it.
20850 @item show task detach-suspend-count
20851 Show the suspend count the task will be left with when detaching.
20853 @item set task exception-port
20854 @itemx set task excp
20855 @cindex task exception port, @sc{gnu} Hurd
20856 This command sets the task exception port to which @value{GDBN} will
20857 forward exceptions. The argument should be the value of the @dfn{send
20858 rights} of the task. @code{set task excp} is a shorthand alias.
20860 @item set noninvasive
20861 @cindex noninvasive task options
20862 This command switches @value{GDBN} to a mode that is the least
20863 invasive as far as interfering with the inferior is concerned. This
20864 is the same as using @code{set task pause}, @code{set exceptions}, and
20865 @code{set signals} to values opposite to the defaults.
20867 @item info send-rights
20868 @itemx info receive-rights
20869 @itemx info port-rights
20870 @itemx info port-sets
20871 @itemx info dead-names
20874 @cindex send rights, @sc{gnu} Hurd
20875 @cindex receive rights, @sc{gnu} Hurd
20876 @cindex port rights, @sc{gnu} Hurd
20877 @cindex port sets, @sc{gnu} Hurd
20878 @cindex dead names, @sc{gnu} Hurd
20879 These commands display information about, respectively, send rights,
20880 receive rights, port rights, port sets, and dead names of a task.
20881 There are also shorthand aliases: @code{info ports} for @code{info
20882 port-rights} and @code{info psets} for @code{info port-sets}.
20884 @item set thread pause
20885 @kindex set thread@r{, Hurd command}
20886 @cindex thread properties, @sc{gnu} Hurd
20887 @cindex pause current thread (@sc{gnu} Hurd)
20888 This command toggles current thread suspension when @value{GDBN} has
20889 control. Setting it to on takes effect immediately, and the current
20890 thread is suspended whenever @value{GDBN} gets control. Setting it to
20891 off will take effect the next time the inferior is continued.
20892 Normally, this command has no effect, since when @value{GDBN} has
20893 control, the whole task is suspended. However, if you used @code{set
20894 task pause off} (see above), this command comes in handy to suspend
20895 only the current thread.
20897 @item show thread pause
20898 @kindex show thread@r{, Hurd command}
20899 This command shows the state of current thread suspension.
20901 @item set thread run
20902 This command sets whether the current thread is allowed to run.
20904 @item show thread run
20905 Show whether the current thread is allowed to run.
20907 @item set thread detach-suspend-count
20908 @cindex thread suspend count, @sc{gnu} Hurd
20909 @cindex detach from thread, @sc{gnu} Hurd
20910 This command sets the suspend count @value{GDBN} will leave on a
20911 thread when detaching. This number is relative to the suspend count
20912 found by @value{GDBN} when it notices the thread; use @code{set thread
20913 takeover-suspend-count} to force it to an absolute value.
20915 @item show thread detach-suspend-count
20916 Show the suspend count @value{GDBN} will leave on the thread when
20919 @item set thread exception-port
20920 @itemx set thread excp
20921 Set the thread exception port to which to forward exceptions. This
20922 overrides the port set by @code{set task exception-port} (see above).
20923 @code{set thread excp} is the shorthand alias.
20925 @item set thread takeover-suspend-count
20926 Normally, @value{GDBN}'s thread suspend counts are relative to the
20927 value @value{GDBN} finds when it notices each thread. This command
20928 changes the suspend counts to be absolute instead.
20930 @item set thread default
20931 @itemx show thread default
20932 @cindex thread default settings, @sc{gnu} Hurd
20933 Each of the above @code{set thread} commands has a @code{set thread
20934 default} counterpart (e.g., @code{set thread default pause}, @code{set
20935 thread default exception-port}, etc.). The @code{thread default}
20936 variety of commands sets the default thread properties for all
20937 threads; you can then change the properties of individual threads with
20938 the non-default commands.
20945 @value{GDBN} provides the following commands specific to the Darwin target:
20948 @item set debug darwin @var{num}
20949 @kindex set debug darwin
20950 When set to a non zero value, enables debugging messages specific to
20951 the Darwin support. Higher values produce more verbose output.
20953 @item show debug darwin
20954 @kindex show debug darwin
20955 Show the current state of Darwin messages.
20957 @item set debug mach-o @var{num}
20958 @kindex set debug mach-o
20959 When set to a non zero value, enables debugging messages while
20960 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20961 file format used on Darwin for object and executable files.) Higher
20962 values produce more verbose output. This is a command to diagnose
20963 problems internal to @value{GDBN} and should not be needed in normal
20966 @item show debug mach-o
20967 @kindex show debug mach-o
20968 Show the current state of Mach-O file messages.
20970 @item set mach-exceptions on
20971 @itemx set mach-exceptions off
20972 @kindex set mach-exceptions
20973 On Darwin, faults are first reported as a Mach exception and are then
20974 mapped to a Posix signal. Use this command to turn on trapping of
20975 Mach exceptions in the inferior. This might be sometimes useful to
20976 better understand the cause of a fault. The default is off.
20978 @item show mach-exceptions
20979 @kindex show mach-exceptions
20980 Show the current state of exceptions trapping.
20985 @section Embedded Operating Systems
20987 This section describes configurations involving the debugging of
20988 embedded operating systems that are available for several different
20991 @value{GDBN} includes the ability to debug programs running on
20992 various real-time operating systems.
20994 @node Embedded Processors
20995 @section Embedded Processors
20997 This section goes into details specific to particular embedded
21000 @cindex send command to simulator
21001 Whenever a specific embedded processor has a simulator, @value{GDBN}
21002 allows to send an arbitrary command to the simulator.
21005 @item sim @var{command}
21006 @kindex sim@r{, a command}
21007 Send an arbitrary @var{command} string to the simulator. Consult the
21008 documentation for the specific simulator in use for information about
21009 acceptable commands.
21015 * M32R/D:: Renesas M32R/D
21016 * M68K:: Motorola M68K
21017 * MicroBlaze:: Xilinx MicroBlaze
21018 * MIPS Embedded:: MIPS Embedded
21019 * PowerPC Embedded:: PowerPC Embedded
21020 * PA:: HP PA Embedded
21021 * Sparclet:: Tsqware Sparclet
21022 * Sparclite:: Fujitsu Sparclite
21023 * Z8000:: Zilog Z8000
21026 * Super-H:: Renesas Super-H
21035 @item target rdi @var{dev}
21036 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21037 use this target to communicate with both boards running the Angel
21038 monitor, or with the EmbeddedICE JTAG debug device.
21041 @item target rdp @var{dev}
21046 @value{GDBN} provides the following ARM-specific commands:
21049 @item set arm disassembler
21051 This commands selects from a list of disassembly styles. The
21052 @code{"std"} style is the standard style.
21054 @item show arm disassembler
21056 Show the current disassembly style.
21058 @item set arm apcs32
21059 @cindex ARM 32-bit mode
21060 This command toggles ARM operation mode between 32-bit and 26-bit.
21062 @item show arm apcs32
21063 Display the current usage of the ARM 32-bit mode.
21065 @item set arm fpu @var{fputype}
21066 This command sets the ARM floating-point unit (FPU) type. The
21067 argument @var{fputype} can be one of these:
21071 Determine the FPU type by querying the OS ABI.
21073 Software FPU, with mixed-endian doubles on little-endian ARM
21076 GCC-compiled FPA co-processor.
21078 Software FPU with pure-endian doubles.
21084 Show the current type of the FPU.
21087 This command forces @value{GDBN} to use the specified ABI.
21090 Show the currently used ABI.
21092 @item set arm fallback-mode (arm|thumb|auto)
21093 @value{GDBN} uses the symbol table, when available, to determine
21094 whether instructions are ARM or Thumb. This command controls
21095 @value{GDBN}'s default behavior when the symbol table is not
21096 available. The default is @samp{auto}, which causes @value{GDBN} to
21097 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21100 @item show arm fallback-mode
21101 Show the current fallback instruction mode.
21103 @item set arm force-mode (arm|thumb|auto)
21104 This command overrides use of the symbol table to determine whether
21105 instructions are ARM or Thumb. The default is @samp{auto}, which
21106 causes @value{GDBN} to use the symbol table and then the setting
21107 of @samp{set arm fallback-mode}.
21109 @item show arm force-mode
21110 Show the current forced instruction mode.
21112 @item set debug arm
21113 Toggle whether to display ARM-specific debugging messages from the ARM
21114 target support subsystem.
21116 @item show debug arm
21117 Show whether ARM-specific debugging messages are enabled.
21120 The following commands are available when an ARM target is debugged
21121 using the RDI interface:
21124 @item rdilogfile @r{[}@var{file}@r{]}
21126 @cindex ADP (Angel Debugger Protocol) logging
21127 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21128 With an argument, sets the log file to the specified @var{file}. With
21129 no argument, show the current log file name. The default log file is
21132 @item rdilogenable @r{[}@var{arg}@r{]}
21133 @kindex rdilogenable
21134 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21135 enables logging, with an argument 0 or @code{"no"} disables it. With
21136 no arguments displays the current setting. When logging is enabled,
21137 ADP packets exchanged between @value{GDBN} and the RDI target device
21138 are logged to a file.
21140 @item set rdiromatzero
21141 @kindex set rdiromatzero
21142 @cindex ROM at zero address, RDI
21143 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21144 vector catching is disabled, so that zero address can be used. If off
21145 (the default), vector catching is enabled. For this command to take
21146 effect, it needs to be invoked prior to the @code{target rdi} command.
21148 @item show rdiromatzero
21149 @kindex show rdiromatzero
21150 Show the current setting of ROM at zero address.
21152 @item set rdiheartbeat
21153 @kindex set rdiheartbeat
21154 @cindex RDI heartbeat
21155 Enable or disable RDI heartbeat packets. It is not recommended to
21156 turn on this option, since it confuses ARM and EPI JTAG interface, as
21157 well as the Angel monitor.
21159 @item show rdiheartbeat
21160 @kindex show rdiheartbeat
21161 Show the setting of RDI heartbeat packets.
21165 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21166 The @value{GDBN} ARM simulator accepts the following optional arguments.
21169 @item --swi-support=@var{type}
21170 Tell the simulator which SWI interfaces to support. The argument
21171 @var{type} may be a comma separated list of the following values.
21172 The default value is @code{all}.
21185 @subsection Renesas M32R/D and M32R/SDI
21188 @kindex target m32r
21189 @item target m32r @var{dev}
21190 Renesas M32R/D ROM monitor.
21192 @kindex target m32rsdi
21193 @item target m32rsdi @var{dev}
21194 Renesas M32R SDI server, connected via parallel port to the board.
21197 The following @value{GDBN} commands are specific to the M32R monitor:
21200 @item set download-path @var{path}
21201 @kindex set download-path
21202 @cindex find downloadable @sc{srec} files (M32R)
21203 Set the default path for finding downloadable @sc{srec} files.
21205 @item show download-path
21206 @kindex show download-path
21207 Show the default path for downloadable @sc{srec} files.
21209 @item set board-address @var{addr}
21210 @kindex set board-address
21211 @cindex M32-EVA target board address
21212 Set the IP address for the M32R-EVA target board.
21214 @item show board-address
21215 @kindex show board-address
21216 Show the current IP address of the target board.
21218 @item set server-address @var{addr}
21219 @kindex set server-address
21220 @cindex download server address (M32R)
21221 Set the IP address for the download server, which is the @value{GDBN}'s
21224 @item show server-address
21225 @kindex show server-address
21226 Display the IP address of the download server.
21228 @item upload @r{[}@var{file}@r{]}
21229 @kindex upload@r{, M32R}
21230 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21231 upload capability. If no @var{file} argument is given, the current
21232 executable file is uploaded.
21234 @item tload @r{[}@var{file}@r{]}
21235 @kindex tload@r{, M32R}
21236 Test the @code{upload} command.
21239 The following commands are available for M32R/SDI:
21244 @cindex reset SDI connection, M32R
21245 This command resets the SDI connection.
21249 This command shows the SDI connection status.
21252 @kindex debug_chaos
21253 @cindex M32R/Chaos debugging
21254 Instructs the remote that M32R/Chaos debugging is to be used.
21256 @item use_debug_dma
21257 @kindex use_debug_dma
21258 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21261 @kindex use_mon_code
21262 Instructs the remote to use the MON_CODE method of accessing memory.
21265 @kindex use_ib_break
21266 Instructs the remote to set breakpoints by IB break.
21268 @item use_dbt_break
21269 @kindex use_dbt_break
21270 Instructs the remote to set breakpoints by DBT.
21276 The Motorola m68k configuration includes ColdFire support, and a
21277 target command for the following ROM monitor.
21281 @kindex target dbug
21282 @item target dbug @var{dev}
21283 dBUG ROM monitor for Motorola ColdFire.
21288 @subsection MicroBlaze
21289 @cindex Xilinx MicroBlaze
21290 @cindex XMD, Xilinx Microprocessor Debugger
21292 The MicroBlaze is a soft-core processor supported on various Xilinx
21293 FPGAs, such as Spartan or Virtex series. Boards with these processors
21294 usually have JTAG ports which connect to a host system running the Xilinx
21295 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21296 This host system is used to download the configuration bitstream to
21297 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21298 communicates with the target board using the JTAG interface and
21299 presents a @code{gdbserver} interface to the board. By default
21300 @code{xmd} uses port @code{1234}. (While it is possible to change
21301 this default port, it requires the use of undocumented @code{xmd}
21302 commands. Contact Xilinx support if you need to do this.)
21304 Use these GDB commands to connect to the MicroBlaze target processor.
21307 @item target remote :1234
21308 Use this command to connect to the target if you are running @value{GDBN}
21309 on the same system as @code{xmd}.
21311 @item target remote @var{xmd-host}:1234
21312 Use this command to connect to the target if it is connected to @code{xmd}
21313 running on a different system named @var{xmd-host}.
21316 Use this command to download a program to the MicroBlaze target.
21318 @item set debug microblaze @var{n}
21319 Enable MicroBlaze-specific debugging messages if non-zero.
21321 @item show debug microblaze @var{n}
21322 Show MicroBlaze-specific debugging level.
21325 @node MIPS Embedded
21326 @subsection @acronym{MIPS} Embedded
21328 @cindex @acronym{MIPS} boards
21329 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21330 @acronym{MIPS} board attached to a serial line. This is available when
21331 you configure @value{GDBN} with @samp{--target=mips-elf}.
21334 Use these @value{GDBN} commands to specify the connection to your target board:
21337 @item target mips @var{port}
21338 @kindex target mips @var{port}
21339 To run a program on the board, start up @code{@value{GDBP}} with the
21340 name of your program as the argument. To connect to the board, use the
21341 command @samp{target mips @var{port}}, where @var{port} is the name of
21342 the serial port connected to the board. If the program has not already
21343 been downloaded to the board, you may use the @code{load} command to
21344 download it. You can then use all the usual @value{GDBN} commands.
21346 For example, this sequence connects to the target board through a serial
21347 port, and loads and runs a program called @var{prog} through the
21351 host$ @value{GDBP} @var{prog}
21352 @value{GDBN} is free software and @dots{}
21353 (@value{GDBP}) target mips /dev/ttyb
21354 (@value{GDBP}) load @var{prog}
21358 @item target mips @var{hostname}:@var{portnumber}
21359 On some @value{GDBN} host configurations, you can specify a TCP
21360 connection (for instance, to a serial line managed by a terminal
21361 concentrator) instead of a serial port, using the syntax
21362 @samp{@var{hostname}:@var{portnumber}}.
21364 @item target pmon @var{port}
21365 @kindex target pmon @var{port}
21368 @item target ddb @var{port}
21369 @kindex target ddb @var{port}
21370 NEC's DDB variant of PMON for Vr4300.
21372 @item target lsi @var{port}
21373 @kindex target lsi @var{port}
21374 LSI variant of PMON.
21376 @kindex target r3900
21377 @item target r3900 @var{dev}
21378 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21380 @kindex target array
21381 @item target array @var{dev}
21382 Array Tech LSI33K RAID controller board.
21388 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21391 @item set mipsfpu double
21392 @itemx set mipsfpu single
21393 @itemx set mipsfpu none
21394 @itemx set mipsfpu auto
21395 @itemx show mipsfpu
21396 @kindex set mipsfpu
21397 @kindex show mipsfpu
21398 @cindex @acronym{MIPS} remote floating point
21399 @cindex floating point, @acronym{MIPS} remote
21400 If your target board does not support the @acronym{MIPS} floating point
21401 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21402 need this, you may wish to put the command in your @value{GDBN} init
21403 file). This tells @value{GDBN} how to find the return value of
21404 functions which return floating point values. It also allows
21405 @value{GDBN} to avoid saving the floating point registers when calling
21406 functions on the board. If you are using a floating point coprocessor
21407 with only single precision floating point support, as on the @sc{r4650}
21408 processor, use the command @samp{set mipsfpu single}. The default
21409 double precision floating point coprocessor may be selected using
21410 @samp{set mipsfpu double}.
21412 In previous versions the only choices were double precision or no
21413 floating point, so @samp{set mipsfpu on} will select double precision
21414 and @samp{set mipsfpu off} will select no floating point.
21416 As usual, you can inquire about the @code{mipsfpu} variable with
21417 @samp{show mipsfpu}.
21419 @item set timeout @var{seconds}
21420 @itemx set retransmit-timeout @var{seconds}
21421 @itemx show timeout
21422 @itemx show retransmit-timeout
21423 @cindex @code{timeout}, @acronym{MIPS} protocol
21424 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21425 @kindex set timeout
21426 @kindex show timeout
21427 @kindex set retransmit-timeout
21428 @kindex show retransmit-timeout
21429 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21430 remote protocol, with the @code{set timeout @var{seconds}} command. The
21431 default is 5 seconds. Similarly, you can control the timeout used while
21432 waiting for an acknowledgment of a packet with the @code{set
21433 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21434 You can inspect both values with @code{show timeout} and @code{show
21435 retransmit-timeout}. (These commands are @emph{only} available when
21436 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21438 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21439 is waiting for your program to stop. In that case, @value{GDBN} waits
21440 forever because it has no way of knowing how long the program is going
21441 to run before stopping.
21443 @item set syn-garbage-limit @var{num}
21444 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21445 @cindex synchronize with remote @acronym{MIPS} target
21446 Limit the maximum number of characters @value{GDBN} should ignore when
21447 it tries to synchronize with the remote target. The default is 10
21448 characters. Setting the limit to -1 means there's no limit.
21450 @item show syn-garbage-limit
21451 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21452 Show the current limit on the number of characters to ignore when
21453 trying to synchronize with the remote system.
21455 @item set monitor-prompt @var{prompt}
21456 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21457 @cindex remote monitor prompt
21458 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21459 remote monitor. The default depends on the target:
21469 @item show monitor-prompt
21470 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21471 Show the current strings @value{GDBN} expects as the prompt from the
21474 @item set monitor-warnings
21475 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21476 Enable or disable monitor warnings about hardware breakpoints. This
21477 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21478 display warning messages whose codes are returned by the @code{lsi}
21479 PMON monitor for breakpoint commands.
21481 @item show monitor-warnings
21482 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21483 Show the current setting of printing monitor warnings.
21485 @item pmon @var{command}
21486 @kindex pmon@r{, @acronym{MIPS} remote}
21487 @cindex send PMON command
21488 This command allows sending an arbitrary @var{command} string to the
21489 monitor. The monitor must be in debug mode for this to work.
21492 @node PowerPC Embedded
21493 @subsection PowerPC Embedded
21495 @cindex DVC register
21496 @value{GDBN} supports using the DVC (Data Value Compare) register to
21497 implement in hardware simple hardware watchpoint conditions of the form:
21500 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21501 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21504 The DVC register will be automatically used when @value{GDBN} detects
21505 such pattern in a condition expression, and the created watchpoint uses one
21506 debug register (either the @code{exact-watchpoints} option is on and the
21507 variable is scalar, or the variable has a length of one byte). This feature
21508 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21511 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21512 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21513 in which case watchpoints using only one debug register are created when
21514 watching variables of scalar types.
21516 You can create an artificial array to watch an arbitrary memory
21517 region using one of the following commands (@pxref{Expressions}):
21520 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21521 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21524 PowerPC embedded processors support masked watchpoints. See the discussion
21525 about the @code{mask} argument in @ref{Set Watchpoints}.
21527 @cindex ranged breakpoint
21528 PowerPC embedded processors support hardware accelerated
21529 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21530 the inferior whenever it executes an instruction at any address within
21531 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21532 use the @code{break-range} command.
21534 @value{GDBN} provides the following PowerPC-specific commands:
21537 @kindex break-range
21538 @item break-range @var{start-location}, @var{end-location}
21539 Set a breakpoint for an address range given by
21540 @var{start-location} and @var{end-location}, which can specify a function name,
21541 a line number, an offset of lines from the current line or from the start
21542 location, or an address of an instruction (see @ref{Specify Location},
21543 for a list of all the possible ways to specify a @var{location}.)
21544 The breakpoint will stop execution of the inferior whenever it
21545 executes an instruction at any address within the specified range,
21546 (including @var{start-location} and @var{end-location}.)
21548 @kindex set powerpc
21549 @item set powerpc soft-float
21550 @itemx show powerpc soft-float
21551 Force @value{GDBN} to use (or not use) a software floating point calling
21552 convention. By default, @value{GDBN} selects the calling convention based
21553 on the selected architecture and the provided executable file.
21555 @item set powerpc vector-abi
21556 @itemx show powerpc vector-abi
21557 Force @value{GDBN} to use the specified calling convention for vector
21558 arguments and return values. The valid options are @samp{auto};
21559 @samp{generic}, to avoid vector registers even if they are present;
21560 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21561 registers. By default, @value{GDBN} selects the calling convention
21562 based on the selected architecture and the provided executable file.
21564 @item set powerpc exact-watchpoints
21565 @itemx show powerpc exact-watchpoints
21566 Allow @value{GDBN} to use only one debug register when watching a variable
21567 of scalar type, thus assuming that the variable is accessed through the
21568 address of its first byte.
21570 @kindex target dink32
21571 @item target dink32 @var{dev}
21572 DINK32 ROM monitor.
21574 @kindex target ppcbug
21575 @item target ppcbug @var{dev}
21576 @kindex target ppcbug1
21577 @item target ppcbug1 @var{dev}
21578 PPCBUG ROM monitor for PowerPC.
21581 @item target sds @var{dev}
21582 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21585 @cindex SDS protocol
21586 The following commands specific to the SDS protocol are supported
21590 @item set sdstimeout @var{nsec}
21591 @kindex set sdstimeout
21592 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21593 default is 2 seconds.
21595 @item show sdstimeout
21596 @kindex show sdstimeout
21597 Show the current value of the SDS timeout.
21599 @item sds @var{command}
21600 @kindex sds@r{, a command}
21601 Send the specified @var{command} string to the SDS monitor.
21606 @subsection HP PA Embedded
21610 @kindex target op50n
21611 @item target op50n @var{dev}
21612 OP50N monitor, running on an OKI HPPA board.
21614 @kindex target w89k
21615 @item target w89k @var{dev}
21616 W89K monitor, running on a Winbond HPPA board.
21621 @subsection Tsqware Sparclet
21625 @value{GDBN} enables developers to debug tasks running on
21626 Sparclet targets from a Unix host.
21627 @value{GDBN} uses code that runs on
21628 both the Unix host and on the Sparclet target. The program
21629 @code{@value{GDBP}} is installed and executed on the Unix host.
21632 @item remotetimeout @var{args}
21633 @kindex remotetimeout
21634 @value{GDBN} supports the option @code{remotetimeout}.
21635 This option is set by the user, and @var{args} represents the number of
21636 seconds @value{GDBN} waits for responses.
21639 @cindex compiling, on Sparclet
21640 When compiling for debugging, include the options @samp{-g} to get debug
21641 information and @samp{-Ttext} to relocate the program to where you wish to
21642 load it on the target. You may also want to add the options @samp{-n} or
21643 @samp{-N} in order to reduce the size of the sections. Example:
21646 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21649 You can use @code{objdump} to verify that the addresses are what you intended:
21652 sparclet-aout-objdump --headers --syms prog
21655 @cindex running, on Sparclet
21657 your Unix execution search path to find @value{GDBN}, you are ready to
21658 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21659 (or @code{sparclet-aout-gdb}, depending on your installation).
21661 @value{GDBN} comes up showing the prompt:
21668 * Sparclet File:: Setting the file to debug
21669 * Sparclet Connection:: Connecting to Sparclet
21670 * Sparclet Download:: Sparclet download
21671 * Sparclet Execution:: Running and debugging
21674 @node Sparclet File
21675 @subsubsection Setting File to Debug
21677 The @value{GDBN} command @code{file} lets you choose with program to debug.
21680 (gdbslet) file prog
21684 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21685 @value{GDBN} locates
21686 the file by searching the directories listed in the command search
21688 If the file was compiled with debug information (option @samp{-g}), source
21689 files will be searched as well.
21690 @value{GDBN} locates
21691 the source files by searching the directories listed in the directory search
21692 path (@pxref{Environment, ,Your Program's Environment}).
21694 to find a file, it displays a message such as:
21697 prog: No such file or directory.
21700 When this happens, add the appropriate directories to the search paths with
21701 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21702 @code{target} command again.
21704 @node Sparclet Connection
21705 @subsubsection Connecting to Sparclet
21707 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21708 To connect to a target on serial port ``@code{ttya}'', type:
21711 (gdbslet) target sparclet /dev/ttya
21712 Remote target sparclet connected to /dev/ttya
21713 main () at ../prog.c:3
21717 @value{GDBN} displays messages like these:
21723 @node Sparclet Download
21724 @subsubsection Sparclet Download
21726 @cindex download to Sparclet
21727 Once connected to the Sparclet target,
21728 you can use the @value{GDBN}
21729 @code{load} command to download the file from the host to the target.
21730 The file name and load offset should be given as arguments to the @code{load}
21732 Since the file format is aout, the program must be loaded to the starting
21733 address. You can use @code{objdump} to find out what this value is. The load
21734 offset is an offset which is added to the VMA (virtual memory address)
21735 of each of the file's sections.
21736 For instance, if the program
21737 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21738 and bss at 0x12010170, in @value{GDBN}, type:
21741 (gdbslet) load prog 0x12010000
21742 Loading section .text, size 0xdb0 vma 0x12010000
21745 If the code is loaded at a different address then what the program was linked
21746 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21747 to tell @value{GDBN} where to map the symbol table.
21749 @node Sparclet Execution
21750 @subsubsection Running and Debugging
21752 @cindex running and debugging Sparclet programs
21753 You can now begin debugging the task using @value{GDBN}'s execution control
21754 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21755 manual for the list of commands.
21759 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21761 Starting program: prog
21762 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21763 3 char *symarg = 0;
21765 4 char *execarg = "hello!";
21770 @subsection Fujitsu Sparclite
21774 @kindex target sparclite
21775 @item target sparclite @var{dev}
21776 Fujitsu sparclite boards, used only for the purpose of loading.
21777 You must use an additional command to debug the program.
21778 For example: target remote @var{dev} using @value{GDBN} standard
21784 @subsection Zilog Z8000
21787 @cindex simulator, Z8000
21788 @cindex Zilog Z8000 simulator
21790 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21793 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21794 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21795 segmented variant). The simulator recognizes which architecture is
21796 appropriate by inspecting the object code.
21799 @item target sim @var{args}
21801 @kindex target sim@r{, with Z8000}
21802 Debug programs on a simulated CPU. If the simulator supports setup
21803 options, specify them via @var{args}.
21807 After specifying this target, you can debug programs for the simulated
21808 CPU in the same style as programs for your host computer; use the
21809 @code{file} command to load a new program image, the @code{run} command
21810 to run your program, and so on.
21812 As well as making available all the usual machine registers
21813 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21814 additional items of information as specially named registers:
21819 Counts clock-ticks in the simulator.
21822 Counts instructions run in the simulator.
21825 Execution time in 60ths of a second.
21829 You can refer to these values in @value{GDBN} expressions with the usual
21830 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21831 conditional breakpoint that suspends only after at least 5000
21832 simulated clock ticks.
21835 @subsection Atmel AVR
21838 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21839 following AVR-specific commands:
21842 @item info io_registers
21843 @kindex info io_registers@r{, AVR}
21844 @cindex I/O registers (Atmel AVR)
21845 This command displays information about the AVR I/O registers. For
21846 each register, @value{GDBN} prints its number and value.
21853 When configured for debugging CRIS, @value{GDBN} provides the
21854 following CRIS-specific commands:
21857 @item set cris-version @var{ver}
21858 @cindex CRIS version
21859 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21860 The CRIS version affects register names and sizes. This command is useful in
21861 case autodetection of the CRIS version fails.
21863 @item show cris-version
21864 Show the current CRIS version.
21866 @item set cris-dwarf2-cfi
21867 @cindex DWARF-2 CFI and CRIS
21868 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21869 Change to @samp{off} when using @code{gcc-cris} whose version is below
21872 @item show cris-dwarf2-cfi
21873 Show the current state of using DWARF-2 CFI.
21875 @item set cris-mode @var{mode}
21877 Set the current CRIS mode to @var{mode}. It should only be changed when
21878 debugging in guru mode, in which case it should be set to
21879 @samp{guru} (the default is @samp{normal}).
21881 @item show cris-mode
21882 Show the current CRIS mode.
21886 @subsection Renesas Super-H
21889 For the Renesas Super-H processor, @value{GDBN} provides these
21893 @item set sh calling-convention @var{convention}
21894 @kindex set sh calling-convention
21895 Set the calling-convention used when calling functions from @value{GDBN}.
21896 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21897 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21898 convention. If the DWARF-2 information of the called function specifies
21899 that the function follows the Renesas calling convention, the function
21900 is called using the Renesas calling convention. If the calling convention
21901 is set to @samp{renesas}, the Renesas calling convention is always used,
21902 regardless of the DWARF-2 information. This can be used to override the
21903 default of @samp{gcc} if debug information is missing, or the compiler
21904 does not emit the DWARF-2 calling convention entry for a function.
21906 @item show sh calling-convention
21907 @kindex show sh calling-convention
21908 Show the current calling convention setting.
21913 @node Architectures
21914 @section Architectures
21916 This section describes characteristics of architectures that affect
21917 all uses of @value{GDBN} with the architecture, both native and cross.
21924 * HPPA:: HP PA architecture
21925 * SPU:: Cell Broadband Engine SPU architecture
21931 @subsection AArch64
21932 @cindex AArch64 support
21934 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21935 following special commands:
21938 @item set debug aarch64
21939 @kindex set debug aarch64
21940 This command determines whether AArch64 architecture-specific debugging
21941 messages are to be displayed.
21943 @item show debug aarch64
21944 Show whether AArch64 debugging messages are displayed.
21949 @subsection x86 Architecture-specific Issues
21952 @item set struct-convention @var{mode}
21953 @kindex set struct-convention
21954 @cindex struct return convention
21955 @cindex struct/union returned in registers
21956 Set the convention used by the inferior to return @code{struct}s and
21957 @code{union}s from functions to @var{mode}. Possible values of
21958 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21959 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21960 are returned on the stack, while @code{"reg"} means that a
21961 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21962 be returned in a register.
21964 @item show struct-convention
21965 @kindex show struct-convention
21966 Show the current setting of the convention to return @code{struct}s
21970 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21971 @cindex Intel(R) Memory Protection Extensions (MPX).
21973 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21974 @footnote{The register named with capital letters represent the architecture
21975 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21976 which are the lower bound and upper bound. Bounds are effective addresses or
21977 memory locations. The upper bounds are architecturally represented in 1's
21978 complement form. A bound having lower bound = 0, and upper bound = 0
21979 (1's complement of all bits set) will allow access to the entire address space.
21981 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21982 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21983 display the upper bound performing the complement of one operation on the
21984 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21985 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21986 can also be noted that the upper bounds are inclusive.
21988 As an example, assume that the register BND0 holds bounds for a pointer having
21989 access allowed for the range between 0x32 and 0x71. The values present on
21990 bnd0raw and bnd registers are presented as follows:
21993 bnd0raw = @{0x32, 0xffffffff8e@}
21994 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21997 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21998 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21999 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22000 Python, the display includes the memory size, in bits, accessible to
22006 See the following section.
22009 @subsection @acronym{MIPS}
22011 @cindex stack on Alpha
22012 @cindex stack on @acronym{MIPS}
22013 @cindex Alpha stack
22014 @cindex @acronym{MIPS} stack
22015 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22016 sometimes requires @value{GDBN} to search backward in the object code to
22017 find the beginning of a function.
22019 @cindex response time, @acronym{MIPS} debugging
22020 To improve response time (especially for embedded applications, where
22021 @value{GDBN} may be restricted to a slow serial line for this search)
22022 you may want to limit the size of this search, using one of these
22026 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22027 @item set heuristic-fence-post @var{limit}
22028 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22029 search for the beginning of a function. A value of @var{0} (the
22030 default) means there is no limit. However, except for @var{0}, the
22031 larger the limit the more bytes @code{heuristic-fence-post} must search
22032 and therefore the longer it takes to run. You should only need to use
22033 this command when debugging a stripped executable.
22035 @item show heuristic-fence-post
22036 Display the current limit.
22040 These commands are available @emph{only} when @value{GDBN} is configured
22041 for debugging programs on Alpha or @acronym{MIPS} processors.
22043 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22047 @item set mips abi @var{arg}
22048 @kindex set mips abi
22049 @cindex set ABI for @acronym{MIPS}
22050 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22051 values of @var{arg} are:
22055 The default ABI associated with the current binary (this is the
22065 @item show mips abi
22066 @kindex show mips abi
22067 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22069 @item set mips compression @var{arg}
22070 @kindex set mips compression
22071 @cindex code compression, @acronym{MIPS}
22072 Tell @value{GDBN} which @acronym{MIPS} compressed
22073 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22074 inferior. @value{GDBN} uses this for code disassembly and other
22075 internal interpretation purposes. This setting is only referred to
22076 when no executable has been associated with the debugging session or
22077 the executable does not provide information about the encoding it uses.
22078 Otherwise this setting is automatically updated from information
22079 provided by the executable.
22081 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22082 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22083 executables containing @acronym{MIPS16} code frequently are not
22084 identified as such.
22086 This setting is ``sticky''; that is, it retains its value across
22087 debugging sessions until reset either explicitly with this command or
22088 implicitly from an executable.
22090 The compiler and/or assembler typically add symbol table annotations to
22091 identify functions compiled for the @acronym{MIPS16} or
22092 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22093 are present, @value{GDBN} uses them in preference to the global
22094 compressed @acronym{ISA} encoding setting.
22096 @item show mips compression
22097 @kindex show mips compression
22098 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22099 @value{GDBN} to debug the inferior.
22102 @itemx show mipsfpu
22103 @xref{MIPS Embedded, set mipsfpu}.
22105 @item set mips mask-address @var{arg}
22106 @kindex set mips mask-address
22107 @cindex @acronym{MIPS} addresses, masking
22108 This command determines whether the most-significant 32 bits of 64-bit
22109 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22110 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22111 setting, which lets @value{GDBN} determine the correct value.
22113 @item show mips mask-address
22114 @kindex show mips mask-address
22115 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22118 @item set remote-mips64-transfers-32bit-regs
22119 @kindex set remote-mips64-transfers-32bit-regs
22120 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22121 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22122 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22123 and 64 bits for other registers, set this option to @samp{on}.
22125 @item show remote-mips64-transfers-32bit-regs
22126 @kindex show remote-mips64-transfers-32bit-regs
22127 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22129 @item set debug mips
22130 @kindex set debug mips
22131 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22132 target code in @value{GDBN}.
22134 @item show debug mips
22135 @kindex show debug mips
22136 Show the current setting of @acronym{MIPS} debugging messages.
22142 @cindex HPPA support
22144 When @value{GDBN} is debugging the HP PA architecture, it provides the
22145 following special commands:
22148 @item set debug hppa
22149 @kindex set debug hppa
22150 This command determines whether HPPA architecture-specific debugging
22151 messages are to be displayed.
22153 @item show debug hppa
22154 Show whether HPPA debugging messages are displayed.
22156 @item maint print unwind @var{address}
22157 @kindex maint print unwind@r{, HPPA}
22158 This command displays the contents of the unwind table entry at the
22159 given @var{address}.
22165 @subsection Cell Broadband Engine SPU architecture
22166 @cindex Cell Broadband Engine
22169 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22170 it provides the following special commands:
22173 @item info spu event
22175 Display SPU event facility status. Shows current event mask
22176 and pending event status.
22178 @item info spu signal
22179 Display SPU signal notification facility status. Shows pending
22180 signal-control word and signal notification mode of both signal
22181 notification channels.
22183 @item info spu mailbox
22184 Display SPU mailbox facility status. Shows all pending entries,
22185 in order of processing, in each of the SPU Write Outbound,
22186 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22189 Display MFC DMA status. Shows all pending commands in the MFC
22190 DMA queue. For each entry, opcode, tag, class IDs, effective
22191 and local store addresses and transfer size are shown.
22193 @item info spu proxydma
22194 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22195 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22196 and local store addresses and transfer size are shown.
22200 When @value{GDBN} is debugging a combined PowerPC/SPU application
22201 on the Cell Broadband Engine, it provides in addition the following
22205 @item set spu stop-on-load @var{arg}
22207 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22208 will give control to the user when a new SPE thread enters its @code{main}
22209 function. The default is @code{off}.
22211 @item show spu stop-on-load
22213 Show whether to stop for new SPE threads.
22215 @item set spu auto-flush-cache @var{arg}
22216 Set whether to automatically flush the software-managed cache. When set to
22217 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22218 cache to be flushed whenever SPE execution stops. This provides a consistent
22219 view of PowerPC memory that is accessed via the cache. If an application
22220 does not use the software-managed cache, this option has no effect.
22222 @item show spu auto-flush-cache
22223 Show whether to automatically flush the software-managed cache.
22228 @subsection PowerPC
22229 @cindex PowerPC architecture
22231 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22232 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22233 numbers stored in the floating point registers. These values must be stored
22234 in two consecutive registers, always starting at an even register like
22235 @code{f0} or @code{f2}.
22237 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22238 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22239 @code{f2} and @code{f3} for @code{$dl1} and so on.
22241 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22242 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22245 @subsection Nios II
22246 @cindex Nios II architecture
22248 When @value{GDBN} is debugging the Nios II architecture,
22249 it provides the following special commands:
22253 @item set debug nios2
22254 @kindex set debug nios2
22255 This command turns on and off debugging messages for the Nios II
22256 target code in @value{GDBN}.
22258 @item show debug nios2
22259 @kindex show debug nios2
22260 Show the current setting of Nios II debugging messages.
22263 @node Controlling GDB
22264 @chapter Controlling @value{GDBN}
22266 You can alter the way @value{GDBN} interacts with you by using the
22267 @code{set} command. For commands controlling how @value{GDBN} displays
22268 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22273 * Editing:: Command editing
22274 * Command History:: Command history
22275 * Screen Size:: Screen size
22276 * Numbers:: Numbers
22277 * ABI:: Configuring the current ABI
22278 * Auto-loading:: Automatically loading associated files
22279 * Messages/Warnings:: Optional warnings and messages
22280 * Debugging Output:: Optional messages about internal happenings
22281 * Other Misc Settings:: Other Miscellaneous Settings
22289 @value{GDBN} indicates its readiness to read a command by printing a string
22290 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22291 can change the prompt string with the @code{set prompt} command. For
22292 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22293 the prompt in one of the @value{GDBN} sessions so that you can always tell
22294 which one you are talking to.
22296 @emph{Note:} @code{set prompt} does not add a space for you after the
22297 prompt you set. This allows you to set a prompt which ends in a space
22298 or a prompt that does not.
22302 @item set prompt @var{newprompt}
22303 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22305 @kindex show prompt
22307 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22310 Versions of @value{GDBN} that ship with Python scripting enabled have
22311 prompt extensions. The commands for interacting with these extensions
22315 @kindex set extended-prompt
22316 @item set extended-prompt @var{prompt}
22317 Set an extended prompt that allows for substitutions.
22318 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22319 substitution. Any escape sequences specified as part of the prompt
22320 string are replaced with the corresponding strings each time the prompt
22326 set extended-prompt Current working directory: \w (gdb)
22329 Note that when an extended-prompt is set, it takes control of the
22330 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22332 @kindex show extended-prompt
22333 @item show extended-prompt
22334 Prints the extended prompt. Any escape sequences specified as part of
22335 the prompt string with @code{set extended-prompt}, are replaced with the
22336 corresponding strings each time the prompt is displayed.
22340 @section Command Editing
22342 @cindex command line editing
22344 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22345 @sc{gnu} library provides consistent behavior for programs which provide a
22346 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22347 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22348 substitution, and a storage and recall of command history across
22349 debugging sessions.
22351 You may control the behavior of command line editing in @value{GDBN} with the
22352 command @code{set}.
22355 @kindex set editing
22358 @itemx set editing on
22359 Enable command line editing (enabled by default).
22361 @item set editing off
22362 Disable command line editing.
22364 @kindex show editing
22366 Show whether command line editing is enabled.
22369 @ifset SYSTEM_READLINE
22370 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22372 @ifclear SYSTEM_READLINE
22373 @xref{Command Line Editing},
22375 for more details about the Readline
22376 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22377 encouraged to read that chapter.
22379 @node Command History
22380 @section Command History
22381 @cindex command history
22383 @value{GDBN} can keep track of the commands you type during your
22384 debugging sessions, so that you can be certain of precisely what
22385 happened. Use these commands to manage the @value{GDBN} command
22388 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22389 package, to provide the history facility.
22390 @ifset SYSTEM_READLINE
22391 @xref{Using History Interactively, , , history, GNU History Library},
22393 @ifclear SYSTEM_READLINE
22394 @xref{Using History Interactively},
22396 for the detailed description of the History library.
22398 To issue a command to @value{GDBN} without affecting certain aspects of
22399 the state which is seen by users, prefix it with @samp{server }
22400 (@pxref{Server Prefix}). This
22401 means that this command will not affect the command history, nor will it
22402 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22403 pressed on a line by itself.
22405 @cindex @code{server}, command prefix
22406 The server prefix does not affect the recording of values into the value
22407 history; to print a value without recording it into the value history,
22408 use the @code{output} command instead of the @code{print} command.
22410 Here is the description of @value{GDBN} commands related to command
22414 @cindex history substitution
22415 @cindex history file
22416 @kindex set history filename
22417 @cindex @env{GDBHISTFILE}, environment variable
22418 @item set history filename @var{fname}
22419 Set the name of the @value{GDBN} command history file to @var{fname}.
22420 This is the file where @value{GDBN} reads an initial command history
22421 list, and where it writes the command history from this session when it
22422 exits. You can access this list through history expansion or through
22423 the history command editing characters listed below. This file defaults
22424 to the value of the environment variable @code{GDBHISTFILE}, or to
22425 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22428 @cindex save command history
22429 @kindex set history save
22430 @item set history save
22431 @itemx set history save on
22432 Record command history in a file, whose name may be specified with the
22433 @code{set history filename} command. By default, this option is disabled.
22435 @item set history save off
22436 Stop recording command history in a file.
22438 @cindex history size
22439 @kindex set history size
22440 @cindex @env{HISTSIZE}, environment variable
22441 @item set history size @var{size}
22442 @itemx set history size unlimited
22443 Set the number of commands which @value{GDBN} keeps in its history list.
22444 This defaults to the value of the environment variable
22445 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22446 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22447 history list is unlimited.
22450 History expansion assigns special meaning to the character @kbd{!}.
22451 @ifset SYSTEM_READLINE
22452 @xref{Event Designators, , , history, GNU History Library},
22454 @ifclear SYSTEM_READLINE
22455 @xref{Event Designators},
22459 @cindex history expansion, turn on/off
22460 Since @kbd{!} is also the logical not operator in C, history expansion
22461 is off by default. If you decide to enable history expansion with the
22462 @code{set history expansion on} command, you may sometimes need to
22463 follow @kbd{!} (when it is used as logical not, in an expression) with
22464 a space or a tab to prevent it from being expanded. The readline
22465 history facilities do not attempt substitution on the strings
22466 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22468 The commands to control history expansion are:
22471 @item set history expansion on
22472 @itemx set history expansion
22473 @kindex set history expansion
22474 Enable history expansion. History expansion is off by default.
22476 @item set history expansion off
22477 Disable history expansion.
22480 @kindex show history
22482 @itemx show history filename
22483 @itemx show history save
22484 @itemx show history size
22485 @itemx show history expansion
22486 These commands display the state of the @value{GDBN} history parameters.
22487 @code{show history} by itself displays all four states.
22492 @kindex show commands
22493 @cindex show last commands
22494 @cindex display command history
22495 @item show commands
22496 Display the last ten commands in the command history.
22498 @item show commands @var{n}
22499 Print ten commands centered on command number @var{n}.
22501 @item show commands +
22502 Print ten commands just after the commands last printed.
22506 @section Screen Size
22507 @cindex size of screen
22508 @cindex screen size
22511 @cindex pauses in output
22513 Certain commands to @value{GDBN} may produce large amounts of
22514 information output to the screen. To help you read all of it,
22515 @value{GDBN} pauses and asks you for input at the end of each page of
22516 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22517 to discard the remaining output. Also, the screen width setting
22518 determines when to wrap lines of output. Depending on what is being
22519 printed, @value{GDBN} tries to break the line at a readable place,
22520 rather than simply letting it overflow onto the following line.
22522 Normally @value{GDBN} knows the size of the screen from the terminal
22523 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22524 together with the value of the @code{TERM} environment variable and the
22525 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22526 you can override it with the @code{set height} and @code{set
22533 @kindex show height
22534 @item set height @var{lpp}
22535 @itemx set height unlimited
22537 @itemx set width @var{cpl}
22538 @itemx set width unlimited
22540 These @code{set} commands specify a screen height of @var{lpp} lines and
22541 a screen width of @var{cpl} characters. The associated @code{show}
22542 commands display the current settings.
22544 If you specify a height of either @code{unlimited} or zero lines,
22545 @value{GDBN} does not pause during output no matter how long the
22546 output is. This is useful if output is to a file or to an editor
22549 Likewise, you can specify @samp{set width unlimited} or @samp{set
22550 width 0} to prevent @value{GDBN} from wrapping its output.
22552 @item set pagination on
22553 @itemx set pagination off
22554 @kindex set pagination
22555 Turn the output pagination on or off; the default is on. Turning
22556 pagination off is the alternative to @code{set height unlimited}. Note that
22557 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22558 Options, -batch}) also automatically disables pagination.
22560 @item show pagination
22561 @kindex show pagination
22562 Show the current pagination mode.
22567 @cindex number representation
22568 @cindex entering numbers
22570 You can always enter numbers in octal, decimal, or hexadecimal in
22571 @value{GDBN} by the usual conventions: octal numbers begin with
22572 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22573 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22574 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22575 10; likewise, the default display for numbers---when no particular
22576 format is specified---is base 10. You can change the default base for
22577 both input and output with the commands described below.
22580 @kindex set input-radix
22581 @item set input-radix @var{base}
22582 Set the default base for numeric input. Supported choices
22583 for @var{base} are decimal 8, 10, or 16. The base must itself be
22584 specified either unambiguously or using the current input radix; for
22588 set input-radix 012
22589 set input-radix 10.
22590 set input-radix 0xa
22594 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22595 leaves the input radix unchanged, no matter what it was, since
22596 @samp{10}, being without any leading or trailing signs of its base, is
22597 interpreted in the current radix. Thus, if the current radix is 16,
22598 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22601 @kindex set output-radix
22602 @item set output-radix @var{base}
22603 Set the default base for numeric display. Supported choices
22604 for @var{base} are decimal 8, 10, or 16. The base must itself be
22605 specified either unambiguously or using the current input radix.
22607 @kindex show input-radix
22608 @item show input-radix
22609 Display the current default base for numeric input.
22611 @kindex show output-radix
22612 @item show output-radix
22613 Display the current default base for numeric display.
22615 @item set radix @r{[}@var{base}@r{]}
22619 These commands set and show the default base for both input and output
22620 of numbers. @code{set radix} sets the radix of input and output to
22621 the same base; without an argument, it resets the radix back to its
22622 default value of 10.
22627 @section Configuring the Current ABI
22629 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22630 application automatically. However, sometimes you need to override its
22631 conclusions. Use these commands to manage @value{GDBN}'s view of the
22637 @cindex Newlib OS ABI and its influence on the longjmp handling
22639 One @value{GDBN} configuration can debug binaries for multiple operating
22640 system targets, either via remote debugging or native emulation.
22641 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22642 but you can override its conclusion using the @code{set osabi} command.
22643 One example where this is useful is in debugging of binaries which use
22644 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22645 not have the same identifying marks that the standard C library for your
22648 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22649 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22650 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22651 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22655 Show the OS ABI currently in use.
22658 With no argument, show the list of registered available OS ABI's.
22660 @item set osabi @var{abi}
22661 Set the current OS ABI to @var{abi}.
22664 @cindex float promotion
22666 Generally, the way that an argument of type @code{float} is passed to a
22667 function depends on whether the function is prototyped. For a prototyped
22668 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22669 according to the architecture's convention for @code{float}. For unprototyped
22670 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22671 @code{double} and then passed.
22673 Unfortunately, some forms of debug information do not reliably indicate whether
22674 a function is prototyped. If @value{GDBN} calls a function that is not marked
22675 as prototyped, it consults @kbd{set coerce-float-to-double}.
22678 @kindex set coerce-float-to-double
22679 @item set coerce-float-to-double
22680 @itemx set coerce-float-to-double on
22681 Arguments of type @code{float} will be promoted to @code{double} when passed
22682 to an unprototyped function. This is the default setting.
22684 @item set coerce-float-to-double off
22685 Arguments of type @code{float} will be passed directly to unprototyped
22688 @kindex show coerce-float-to-double
22689 @item show coerce-float-to-double
22690 Show the current setting of promoting @code{float} to @code{double}.
22694 @kindex show cp-abi
22695 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22696 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22697 used to build your application. @value{GDBN} only fully supports
22698 programs with a single C@t{++} ABI; if your program contains code using
22699 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22700 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22701 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22702 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22703 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22704 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22709 Show the C@t{++} ABI currently in use.
22712 With no argument, show the list of supported C@t{++} ABI's.
22714 @item set cp-abi @var{abi}
22715 @itemx set cp-abi auto
22716 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22720 @section Automatically loading associated files
22721 @cindex auto-loading
22723 @value{GDBN} sometimes reads files with commands and settings automatically,
22724 without being explicitly told so by the user. We call this feature
22725 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22726 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22727 results or introduce security risks (e.g., if the file comes from untrusted
22731 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22732 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22734 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22735 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22738 There are various kinds of files @value{GDBN} can automatically load.
22739 In addition to these files, @value{GDBN} supports auto-loading code written
22740 in various extension languages. @xref{Auto-loading extensions}.
22742 Note that loading of these associated files (including the local @file{.gdbinit}
22743 file) requires accordingly configured @code{auto-load safe-path}
22744 (@pxref{Auto-loading safe path}).
22746 For these reasons, @value{GDBN} includes commands and options to let you
22747 control when to auto-load files and which files should be auto-loaded.
22750 @anchor{set auto-load off}
22751 @kindex set auto-load off
22752 @item set auto-load off
22753 Globally disable loading of all auto-loaded files.
22754 You may want to use this command with the @samp{-iex} option
22755 (@pxref{Option -init-eval-command}) such as:
22757 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22760 Be aware that system init file (@pxref{System-wide configuration})
22761 and init files from your home directory (@pxref{Home Directory Init File})
22762 still get read (as they come from generally trusted directories).
22763 To prevent @value{GDBN} from auto-loading even those init files, use the
22764 @option{-nx} option (@pxref{Mode Options}), in addition to
22765 @code{set auto-load no}.
22767 @anchor{show auto-load}
22768 @kindex show auto-load
22769 @item show auto-load
22770 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22774 (gdb) show auto-load
22775 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22776 libthread-db: Auto-loading of inferior specific libthread_db is on.
22777 local-gdbinit: Auto-loading of .gdbinit script from current directory
22779 python-scripts: Auto-loading of Python scripts is on.
22780 safe-path: List of directories from which it is safe to auto-load files
22781 is $debugdir:$datadir/auto-load.
22782 scripts-directory: List of directories from which to load auto-loaded scripts
22783 is $debugdir:$datadir/auto-load.
22786 @anchor{info auto-load}
22787 @kindex info auto-load
22788 @item info auto-load
22789 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22793 (gdb) info auto-load
22796 Yes /home/user/gdb/gdb-gdb.gdb
22797 libthread-db: No auto-loaded libthread-db.
22798 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22802 Yes /home/user/gdb/gdb-gdb.py
22806 These are @value{GDBN} control commands for the auto-loading:
22808 @multitable @columnfractions .5 .5
22809 @item @xref{set auto-load off}.
22810 @tab Disable auto-loading globally.
22811 @item @xref{show auto-load}.
22812 @tab Show setting of all kinds of files.
22813 @item @xref{info auto-load}.
22814 @tab Show state of all kinds of files.
22815 @item @xref{set auto-load gdb-scripts}.
22816 @tab Control for @value{GDBN} command scripts.
22817 @item @xref{show auto-load gdb-scripts}.
22818 @tab Show setting of @value{GDBN} command scripts.
22819 @item @xref{info auto-load gdb-scripts}.
22820 @tab Show state of @value{GDBN} command scripts.
22821 @item @xref{set auto-load python-scripts}.
22822 @tab Control for @value{GDBN} Python scripts.
22823 @item @xref{show auto-load python-scripts}.
22824 @tab Show setting of @value{GDBN} Python scripts.
22825 @item @xref{info auto-load python-scripts}.
22826 @tab Show state of @value{GDBN} Python scripts.
22827 @item @xref{set auto-load guile-scripts}.
22828 @tab Control for @value{GDBN} Guile scripts.
22829 @item @xref{show auto-load guile-scripts}.
22830 @tab Show setting of @value{GDBN} Guile scripts.
22831 @item @xref{info auto-load guile-scripts}.
22832 @tab Show state of @value{GDBN} Guile scripts.
22833 @item @xref{set auto-load scripts-directory}.
22834 @tab Control for @value{GDBN} auto-loaded scripts location.
22835 @item @xref{show auto-load scripts-directory}.
22836 @tab Show @value{GDBN} auto-loaded scripts location.
22837 @item @xref{add-auto-load-scripts-directory}.
22838 @tab Add directory for auto-loaded scripts location list.
22839 @item @xref{set auto-load local-gdbinit}.
22840 @tab Control for init file in the current directory.
22841 @item @xref{show auto-load local-gdbinit}.
22842 @tab Show setting of init file in the current directory.
22843 @item @xref{info auto-load local-gdbinit}.
22844 @tab Show state of init file in the current directory.
22845 @item @xref{set auto-load libthread-db}.
22846 @tab Control for thread debugging library.
22847 @item @xref{show auto-load libthread-db}.
22848 @tab Show setting of thread debugging library.
22849 @item @xref{info auto-load libthread-db}.
22850 @tab Show state of thread debugging library.
22851 @item @xref{set auto-load safe-path}.
22852 @tab Control directories trusted for automatic loading.
22853 @item @xref{show auto-load safe-path}.
22854 @tab Show directories trusted for automatic loading.
22855 @item @xref{add-auto-load-safe-path}.
22856 @tab Add directory trusted for automatic loading.
22859 @node Init File in the Current Directory
22860 @subsection Automatically loading init file in the current directory
22861 @cindex auto-loading init file in the current directory
22863 By default, @value{GDBN} reads and executes the canned sequences of commands
22864 from init file (if any) in the current working directory,
22865 see @ref{Init File in the Current Directory during Startup}.
22867 Note that loading of this local @file{.gdbinit} file also requires accordingly
22868 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22871 @anchor{set auto-load local-gdbinit}
22872 @kindex set auto-load local-gdbinit
22873 @item set auto-load local-gdbinit [on|off]
22874 Enable or disable the auto-loading of canned sequences of commands
22875 (@pxref{Sequences}) found in init file in the current directory.
22877 @anchor{show auto-load local-gdbinit}
22878 @kindex show auto-load local-gdbinit
22879 @item show auto-load local-gdbinit
22880 Show whether auto-loading of canned sequences of commands from init file in the
22881 current directory is enabled or disabled.
22883 @anchor{info auto-load local-gdbinit}
22884 @kindex info auto-load local-gdbinit
22885 @item info auto-load local-gdbinit
22886 Print whether canned sequences of commands from init file in the
22887 current directory have been auto-loaded.
22890 @node libthread_db.so.1 file
22891 @subsection Automatically loading thread debugging library
22892 @cindex auto-loading libthread_db.so.1
22894 This feature is currently present only on @sc{gnu}/Linux native hosts.
22896 @value{GDBN} reads in some cases thread debugging library from places specific
22897 to the inferior (@pxref{set libthread-db-search-path}).
22899 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22900 without checking this @samp{set auto-load libthread-db} switch as system
22901 libraries have to be trusted in general. In all other cases of
22902 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22903 auto-load libthread-db} is enabled before trying to open such thread debugging
22906 Note that loading of this debugging library also requires accordingly configured
22907 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22910 @anchor{set auto-load libthread-db}
22911 @kindex set auto-load libthread-db
22912 @item set auto-load libthread-db [on|off]
22913 Enable or disable the auto-loading of inferior specific thread debugging library.
22915 @anchor{show auto-load libthread-db}
22916 @kindex show auto-load libthread-db
22917 @item show auto-load libthread-db
22918 Show whether auto-loading of inferior specific thread debugging library is
22919 enabled or disabled.
22921 @anchor{info auto-load libthread-db}
22922 @kindex info auto-load libthread-db
22923 @item info auto-load libthread-db
22924 Print the list of all loaded inferior specific thread debugging libraries and
22925 for each such library print list of inferior @var{pid}s using it.
22928 @node Auto-loading safe path
22929 @subsection Security restriction for auto-loading
22930 @cindex auto-loading safe-path
22932 As the files of inferior can come from untrusted source (such as submitted by
22933 an application user) @value{GDBN} does not always load any files automatically.
22934 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22935 directories trusted for loading files not explicitly requested by user.
22936 Each directory can also be a shell wildcard pattern.
22938 If the path is not set properly you will see a warning and the file will not
22943 Reading symbols from /home/user/gdb/gdb...done.
22944 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22945 declined by your `auto-load safe-path' set
22946 to "$debugdir:$datadir/auto-load".
22947 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22948 declined by your `auto-load safe-path' set
22949 to "$debugdir:$datadir/auto-load".
22953 To instruct @value{GDBN} to go ahead and use the init files anyway,
22954 invoke @value{GDBN} like this:
22957 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22960 The list of trusted directories is controlled by the following commands:
22963 @anchor{set auto-load safe-path}
22964 @kindex set auto-load safe-path
22965 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22966 Set the list of directories (and their subdirectories) trusted for automatic
22967 loading and execution of scripts. You can also enter a specific trusted file.
22968 Each directory can also be a shell wildcard pattern; wildcards do not match
22969 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22970 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22971 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22972 its default value as specified during @value{GDBN} compilation.
22974 The list of directories uses path separator (@samp{:} on GNU and Unix
22975 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22976 to the @env{PATH} environment variable.
22978 @anchor{show auto-load safe-path}
22979 @kindex show auto-load safe-path
22980 @item show auto-load safe-path
22981 Show the list of directories trusted for automatic loading and execution of
22984 @anchor{add-auto-load-safe-path}
22985 @kindex add-auto-load-safe-path
22986 @item add-auto-load-safe-path
22987 Add an entry (or list of entries) to the list of directories trusted for
22988 automatic loading and execution of scripts. Multiple entries may be delimited
22989 by the host platform path separator in use.
22992 This variable defaults to what @code{--with-auto-load-dir} has been configured
22993 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22994 substitution applies the same as for @ref{set auto-load scripts-directory}.
22995 The default @code{set auto-load safe-path} value can be also overriden by
22996 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22998 Setting this variable to @file{/} disables this security protection,
22999 corresponding @value{GDBN} configuration option is
23000 @option{--without-auto-load-safe-path}.
23001 This variable is supposed to be set to the system directories writable by the
23002 system superuser only. Users can add their source directories in init files in
23003 their home directories (@pxref{Home Directory Init File}). See also deprecated
23004 init file in the current directory
23005 (@pxref{Init File in the Current Directory during Startup}).
23007 To force @value{GDBN} to load the files it declined to load in the previous
23008 example, you could use one of the following ways:
23011 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23012 Specify this trusted directory (or a file) as additional component of the list.
23013 You have to specify also any existing directories displayed by
23014 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23016 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23017 Specify this directory as in the previous case but just for a single
23018 @value{GDBN} session.
23020 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23021 Disable auto-loading safety for a single @value{GDBN} session.
23022 This assumes all the files you debug during this @value{GDBN} session will come
23023 from trusted sources.
23025 @item @kbd{./configure --without-auto-load-safe-path}
23026 During compilation of @value{GDBN} you may disable any auto-loading safety.
23027 This assumes all the files you will ever debug with this @value{GDBN} come from
23031 On the other hand you can also explicitly forbid automatic files loading which
23032 also suppresses any such warning messages:
23035 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23036 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23038 @item @file{~/.gdbinit}: @samp{set auto-load no}
23039 Disable auto-loading globally for the user
23040 (@pxref{Home Directory Init File}). While it is improbable, you could also
23041 use system init file instead (@pxref{System-wide configuration}).
23044 This setting applies to the file names as entered by user. If no entry matches
23045 @value{GDBN} tries as a last resort to also resolve all the file names into
23046 their canonical form (typically resolving symbolic links) and compare the
23047 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23048 own before starting the comparison so a canonical form of directories is
23049 recommended to be entered.
23051 @node Auto-loading verbose mode
23052 @subsection Displaying files tried for auto-load
23053 @cindex auto-loading verbose mode
23055 For better visibility of all the file locations where you can place scripts to
23056 be auto-loaded with inferior --- or to protect yourself against accidental
23057 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23058 all the files attempted to be loaded. Both existing and non-existing files may
23061 For example the list of directories from which it is safe to auto-load files
23062 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23063 may not be too obvious while setting it up.
23066 (gdb) set debug auto-load on
23067 (gdb) file ~/src/t/true
23068 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23069 for objfile "/tmp/true".
23070 auto-load: Updating directories of "/usr:/opt".
23071 auto-load: Using directory "/usr".
23072 auto-load: Using directory "/opt".
23073 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23074 by your `auto-load safe-path' set to "/usr:/opt".
23078 @anchor{set debug auto-load}
23079 @kindex set debug auto-load
23080 @item set debug auto-load [on|off]
23081 Set whether to print the filenames attempted to be auto-loaded.
23083 @anchor{show debug auto-load}
23084 @kindex show debug auto-load
23085 @item show debug auto-load
23086 Show whether printing of the filenames attempted to be auto-loaded is turned
23090 @node Messages/Warnings
23091 @section Optional Warnings and Messages
23093 @cindex verbose operation
23094 @cindex optional warnings
23095 By default, @value{GDBN} is silent about its inner workings. If you are
23096 running on a slow machine, you may want to use the @code{set verbose}
23097 command. This makes @value{GDBN} tell you when it does a lengthy
23098 internal operation, so you will not think it has crashed.
23100 Currently, the messages controlled by @code{set verbose} are those
23101 which announce that the symbol table for a source file is being read;
23102 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23105 @kindex set verbose
23106 @item set verbose on
23107 Enables @value{GDBN} output of certain informational messages.
23109 @item set verbose off
23110 Disables @value{GDBN} output of certain informational messages.
23112 @kindex show verbose
23114 Displays whether @code{set verbose} is on or off.
23117 By default, if @value{GDBN} encounters bugs in the symbol table of an
23118 object file, it is silent; but if you are debugging a compiler, you may
23119 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23124 @kindex set complaints
23125 @item set complaints @var{limit}
23126 Permits @value{GDBN} to output @var{limit} complaints about each type of
23127 unusual symbols before becoming silent about the problem. Set
23128 @var{limit} to zero to suppress all complaints; set it to a large number
23129 to prevent complaints from being suppressed.
23131 @kindex show complaints
23132 @item show complaints
23133 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23137 @anchor{confirmation requests}
23138 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23139 lot of stupid questions to confirm certain commands. For example, if
23140 you try to run a program which is already running:
23144 The program being debugged has been started already.
23145 Start it from the beginning? (y or n)
23148 If you are willing to unflinchingly face the consequences of your own
23149 commands, you can disable this ``feature'':
23153 @kindex set confirm
23155 @cindex confirmation
23156 @cindex stupid questions
23157 @item set confirm off
23158 Disables confirmation requests. Note that running @value{GDBN} with
23159 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23160 automatically disables confirmation requests.
23162 @item set confirm on
23163 Enables confirmation requests (the default).
23165 @kindex show confirm
23167 Displays state of confirmation requests.
23171 @cindex command tracing
23172 If you need to debug user-defined commands or sourced files you may find it
23173 useful to enable @dfn{command tracing}. In this mode each command will be
23174 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23175 quantity denoting the call depth of each command.
23178 @kindex set trace-commands
23179 @cindex command scripts, debugging
23180 @item set trace-commands on
23181 Enable command tracing.
23182 @item set trace-commands off
23183 Disable command tracing.
23184 @item show trace-commands
23185 Display the current state of command tracing.
23188 @node Debugging Output
23189 @section Optional Messages about Internal Happenings
23190 @cindex optional debugging messages
23192 @value{GDBN} has commands that enable optional debugging messages from
23193 various @value{GDBN} subsystems; normally these commands are of
23194 interest to @value{GDBN} maintainers, or when reporting a bug. This
23195 section documents those commands.
23198 @kindex set exec-done-display
23199 @item set exec-done-display
23200 Turns on or off the notification of asynchronous commands'
23201 completion. When on, @value{GDBN} will print a message when an
23202 asynchronous command finishes its execution. The default is off.
23203 @kindex show exec-done-display
23204 @item show exec-done-display
23205 Displays the current setting of asynchronous command completion
23208 @cindex ARM AArch64
23209 @item set debug aarch64
23210 Turns on or off display of debugging messages related to ARM AArch64.
23211 The default is off.
23213 @item show debug aarch64
23214 Displays the current state of displaying debugging messages related to
23216 @cindex gdbarch debugging info
23217 @cindex architecture debugging info
23218 @item set debug arch
23219 Turns on or off display of gdbarch debugging info. The default is off
23220 @item show debug arch
23221 Displays the current state of displaying gdbarch debugging info.
23222 @item set debug aix-solib
23223 @cindex AIX shared library debugging
23224 Control display of debugging messages from the AIX shared library
23225 support module. The default is off.
23226 @item show debug aix-thread
23227 Show the current state of displaying AIX shared library debugging messages.
23228 @item set debug aix-thread
23229 @cindex AIX threads
23230 Display debugging messages about inner workings of the AIX thread
23232 @item show debug aix-thread
23233 Show the current state of AIX thread debugging info display.
23234 @item set debug check-physname
23236 Check the results of the ``physname'' computation. When reading DWARF
23237 debugging information for C@t{++}, @value{GDBN} attempts to compute
23238 each entity's name. @value{GDBN} can do this computation in two
23239 different ways, depending on exactly what information is present.
23240 When enabled, this setting causes @value{GDBN} to compute the names
23241 both ways and display any discrepancies.
23242 @item show debug check-physname
23243 Show the current state of ``physname'' checking.
23244 @item set debug coff-pe-read
23245 @cindex COFF/PE exported symbols
23246 Control display of debugging messages related to reading of COFF/PE
23247 exported symbols. The default is off.
23248 @item show debug coff-pe-read
23249 Displays the current state of displaying debugging messages related to
23250 reading of COFF/PE exported symbols.
23251 @item set debug dwarf2-die
23252 @cindex DWARF2 DIEs
23253 Dump DWARF2 DIEs after they are read in.
23254 The value is the number of nesting levels to print.
23255 A value of zero turns off the display.
23256 @item show debug dwarf2-die
23257 Show the current state of DWARF2 DIE debugging.
23258 @item set debug dwarf2-read
23259 @cindex DWARF2 Reading
23260 Turns on or off display of debugging messages related to reading
23261 DWARF debug info. The default is 0 (off).
23262 A value of 1 provides basic information.
23263 A value greater than 1 provides more verbose information.
23264 @item show debug dwarf2-read
23265 Show the current state of DWARF2 reader debugging.
23266 @item set debug displaced
23267 @cindex displaced stepping debugging info
23268 Turns on or off display of @value{GDBN} debugging info for the
23269 displaced stepping support. The default is off.
23270 @item show debug displaced
23271 Displays the current state of displaying @value{GDBN} debugging info
23272 related to displaced stepping.
23273 @item set debug event
23274 @cindex event debugging info
23275 Turns on or off display of @value{GDBN} event debugging info. The
23277 @item show debug event
23278 Displays the current state of displaying @value{GDBN} event debugging
23280 @item set debug expression
23281 @cindex expression debugging info
23282 Turns on or off display of debugging info about @value{GDBN}
23283 expression parsing. The default is off.
23284 @item show debug expression
23285 Displays the current state of displaying debugging info about
23286 @value{GDBN} expression parsing.
23287 @item set debug frame
23288 @cindex frame debugging info
23289 Turns on or off display of @value{GDBN} frame debugging info. The
23291 @item show debug frame
23292 Displays the current state of displaying @value{GDBN} frame debugging
23294 @item set debug gnu-nat
23295 @cindex @sc{gnu}/Hurd debug messages
23296 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23297 @item show debug gnu-nat
23298 Show the current state of @sc{gnu}/Hurd debugging messages.
23299 @item set debug infrun
23300 @cindex inferior debugging info
23301 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23302 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23303 for implementing operations such as single-stepping the inferior.
23304 @item show debug infrun
23305 Displays the current state of @value{GDBN} inferior debugging.
23306 @item set debug jit
23307 @cindex just-in-time compilation, debugging messages
23308 Turns on or off debugging messages from JIT debug support.
23309 @item show debug jit
23310 Displays the current state of @value{GDBN} JIT debugging.
23311 @item set debug lin-lwp
23312 @cindex @sc{gnu}/Linux LWP debug messages
23313 @cindex Linux lightweight processes
23314 Turns on or off debugging messages from the Linux LWP debug support.
23315 @item show debug lin-lwp
23316 Show the current state of Linux LWP debugging messages.
23317 @item set debug mach-o
23318 @cindex Mach-O symbols processing
23319 Control display of debugging messages related to Mach-O symbols
23320 processing. The default is off.
23321 @item show debug mach-o
23322 Displays the current state of displaying debugging messages related to
23323 reading of COFF/PE exported symbols.
23324 @item set debug notification
23325 @cindex remote async notification debugging info
23326 Turns on or off debugging messages about remote async notification.
23327 The default is off.
23328 @item show debug notification
23329 Displays the current state of remote async notification debugging messages.
23330 @item set debug observer
23331 @cindex observer debugging info
23332 Turns on or off display of @value{GDBN} observer debugging. This
23333 includes info such as the notification of observable events.
23334 @item show debug observer
23335 Displays the current state of observer debugging.
23336 @item set debug overload
23337 @cindex C@t{++} overload debugging info
23338 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23339 info. This includes info such as ranking of functions, etc. The default
23341 @item show debug overload
23342 Displays the current state of displaying @value{GDBN} C@t{++} overload
23344 @cindex expression parser, debugging info
23345 @cindex debug expression parser
23346 @item set debug parser
23347 Turns on or off the display of expression parser debugging output.
23348 Internally, this sets the @code{yydebug} variable in the expression
23349 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23350 details. The default is off.
23351 @item show debug parser
23352 Show the current state of expression parser debugging.
23353 @cindex packets, reporting on stdout
23354 @cindex serial connections, debugging
23355 @cindex debug remote protocol
23356 @cindex remote protocol debugging
23357 @cindex display remote packets
23358 @item set debug remote
23359 Turns on or off display of reports on all packets sent back and forth across
23360 the serial line to the remote machine. The info is printed on the
23361 @value{GDBN} standard output stream. The default is off.
23362 @item show debug remote
23363 Displays the state of display of remote packets.
23364 @item set debug serial
23365 Turns on or off display of @value{GDBN} serial debugging info. The
23367 @item show debug serial
23368 Displays the current state of displaying @value{GDBN} serial debugging
23370 @item set debug solib-frv
23371 @cindex FR-V shared-library debugging
23372 Turns on or off debugging messages for FR-V shared-library code.
23373 @item show debug solib-frv
23374 Display the current state of FR-V shared-library code debugging
23376 @item set debug symbol-lookup
23377 @cindex symbol lookup
23378 Turns on or off display of debugging messages related to symbol lookup.
23379 The default is 0 (off).
23380 A value of 1 provides basic information.
23381 A value greater than 1 provides more verbose information.
23382 @item show debug symbol-lookup
23383 Show the current state of symbol lookup debugging messages.
23384 @item set debug symfile
23385 @cindex symbol file functions
23386 Turns on or off display of debugging messages related to symbol file functions.
23387 The default is off. @xref{Files}.
23388 @item show debug symfile
23389 Show the current state of symbol file debugging messages.
23390 @item set debug symtab-create
23391 @cindex symbol table creation
23392 Turns on or off display of debugging messages related to symbol table creation.
23393 The default is 0 (off).
23394 A value of 1 provides basic information.
23395 A value greater than 1 provides more verbose information.
23396 @item show debug symtab-create
23397 Show the current state of symbol table creation debugging.
23398 @item set debug target
23399 @cindex target debugging info
23400 Turns on or off display of @value{GDBN} target debugging info. This info
23401 includes what is going on at the target level of GDB, as it happens. The
23402 default is 0. Set it to 1 to track events, and to 2 to also track the
23403 value of large memory transfers.
23404 @item show debug target
23405 Displays the current state of displaying @value{GDBN} target debugging
23407 @item set debug timestamp
23408 @cindex timestampping debugging info
23409 Turns on or off display of timestamps with @value{GDBN} debugging info.
23410 When enabled, seconds and microseconds are displayed before each debugging
23412 @item show debug timestamp
23413 Displays the current state of displaying timestamps with @value{GDBN}
23415 @item set debug varobj
23416 @cindex variable object debugging info
23417 Turns on or off display of @value{GDBN} variable object debugging
23418 info. The default is off.
23419 @item show debug varobj
23420 Displays the current state of displaying @value{GDBN} variable object
23422 @item set debug xml
23423 @cindex XML parser debugging
23424 Turns on or off debugging messages for built-in XML parsers.
23425 @item show debug xml
23426 Displays the current state of XML debugging messages.
23429 @node Other Misc Settings
23430 @section Other Miscellaneous Settings
23431 @cindex miscellaneous settings
23434 @kindex set interactive-mode
23435 @item set interactive-mode
23436 If @code{on}, forces @value{GDBN} to assume that GDB was started
23437 in a terminal. In practice, this means that @value{GDBN} should wait
23438 for the user to answer queries generated by commands entered at
23439 the command prompt. If @code{off}, forces @value{GDBN} to operate
23440 in the opposite mode, and it uses the default answers to all queries.
23441 If @code{auto} (the default), @value{GDBN} tries to determine whether
23442 its standard input is a terminal, and works in interactive-mode if it
23443 is, non-interactively otherwise.
23445 In the vast majority of cases, the debugger should be able to guess
23446 correctly which mode should be used. But this setting can be useful
23447 in certain specific cases, such as running a MinGW @value{GDBN}
23448 inside a cygwin window.
23450 @kindex show interactive-mode
23451 @item show interactive-mode
23452 Displays whether the debugger is operating in interactive mode or not.
23455 @node Extending GDB
23456 @chapter Extending @value{GDBN}
23457 @cindex extending GDB
23459 @value{GDBN} provides several mechanisms for extension.
23460 @value{GDBN} also provides the ability to automatically load
23461 extensions when it reads a file for debugging. This allows the
23462 user to automatically customize @value{GDBN} for the program
23466 * Sequences:: Canned Sequences of @value{GDBN} Commands
23467 * Python:: Extending @value{GDBN} using Python
23468 * Guile:: Extending @value{GDBN} using Guile
23469 * Auto-loading extensions:: Automatically loading extensions
23470 * Multiple Extension Languages:: Working with multiple extension languages
23471 * Aliases:: Creating new spellings of existing commands
23474 To facilitate the use of extension languages, @value{GDBN} is capable
23475 of evaluating the contents of a file. When doing so, @value{GDBN}
23476 can recognize which extension language is being used by looking at
23477 the filename extension. Files with an unrecognized filename extension
23478 are always treated as a @value{GDBN} Command Files.
23479 @xref{Command Files,, Command files}.
23481 You can control how @value{GDBN} evaluates these files with the following
23485 @kindex set script-extension
23486 @kindex show script-extension
23487 @item set script-extension off
23488 All scripts are always evaluated as @value{GDBN} Command Files.
23490 @item set script-extension soft
23491 The debugger determines the scripting language based on filename
23492 extension. If this scripting language is supported, @value{GDBN}
23493 evaluates the script using that language. Otherwise, it evaluates
23494 the file as a @value{GDBN} Command File.
23496 @item set script-extension strict
23497 The debugger determines the scripting language based on filename
23498 extension, and evaluates the script using that language. If the
23499 language is not supported, then the evaluation fails.
23501 @item show script-extension
23502 Display the current value of the @code{script-extension} option.
23507 @section Canned Sequences of Commands
23509 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23510 Command Lists}), @value{GDBN} provides two ways to store sequences of
23511 commands for execution as a unit: user-defined commands and command
23515 * Define:: How to define your own commands
23516 * Hooks:: Hooks for user-defined commands
23517 * Command Files:: How to write scripts of commands to be stored in a file
23518 * Output:: Commands for controlled output
23519 * Auto-loading sequences:: Controlling auto-loaded command files
23523 @subsection User-defined Commands
23525 @cindex user-defined command
23526 @cindex arguments, to user-defined commands
23527 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23528 which you assign a new name as a command. This is done with the
23529 @code{define} command. User commands may accept up to 10 arguments
23530 separated by whitespace. Arguments are accessed within the user command
23531 via @code{$arg0@dots{}$arg9}. A trivial example:
23535 print $arg0 + $arg1 + $arg2
23540 To execute the command use:
23547 This defines the command @code{adder}, which prints the sum of
23548 its three arguments. Note the arguments are text substitutions, so they may
23549 reference variables, use complex expressions, or even perform inferior
23552 @cindex argument count in user-defined commands
23553 @cindex how many arguments (user-defined commands)
23554 In addition, @code{$argc} may be used to find out how many arguments have
23555 been passed. This expands to a number in the range 0@dots{}10.
23560 print $arg0 + $arg1
23563 print $arg0 + $arg1 + $arg2
23571 @item define @var{commandname}
23572 Define a command named @var{commandname}. If there is already a command
23573 by that name, you are asked to confirm that you want to redefine it.
23574 The argument @var{commandname} may be a bare command name consisting of letters,
23575 numbers, dashes, and underscores. It may also start with any predefined
23576 prefix command. For example, @samp{define target my-target} creates
23577 a user-defined @samp{target my-target} command.
23579 The definition of the command is made up of other @value{GDBN} command lines,
23580 which are given following the @code{define} command. The end of these
23581 commands is marked by a line containing @code{end}.
23584 @kindex end@r{ (user-defined commands)}
23585 @item document @var{commandname}
23586 Document the user-defined command @var{commandname}, so that it can be
23587 accessed by @code{help}. The command @var{commandname} must already be
23588 defined. This command reads lines of documentation just as @code{define}
23589 reads the lines of the command definition, ending with @code{end}.
23590 After the @code{document} command is finished, @code{help} on command
23591 @var{commandname} displays the documentation you have written.
23593 You may use the @code{document} command again to change the
23594 documentation of a command. Redefining the command with @code{define}
23595 does not change the documentation.
23597 @kindex dont-repeat
23598 @cindex don't repeat command
23600 Used inside a user-defined command, this tells @value{GDBN} that this
23601 command should not be repeated when the user hits @key{RET}
23602 (@pxref{Command Syntax, repeat last command}).
23604 @kindex help user-defined
23605 @item help user-defined
23606 List all user-defined commands and all python commands defined in class
23607 COMAND_USER. The first line of the documentation or docstring is
23612 @itemx show user @var{commandname}
23613 Display the @value{GDBN} commands used to define @var{commandname} (but
23614 not its documentation). If no @var{commandname} is given, display the
23615 definitions for all user-defined commands.
23616 This does not work for user-defined python commands.
23618 @cindex infinite recursion in user-defined commands
23619 @kindex show max-user-call-depth
23620 @kindex set max-user-call-depth
23621 @item show max-user-call-depth
23622 @itemx set max-user-call-depth
23623 The value of @code{max-user-call-depth} controls how many recursion
23624 levels are allowed in user-defined commands before @value{GDBN} suspects an
23625 infinite recursion and aborts the command.
23626 This does not apply to user-defined python commands.
23629 In addition to the above commands, user-defined commands frequently
23630 use control flow commands, described in @ref{Command Files}.
23632 When user-defined commands are executed, the
23633 commands of the definition are not printed. An error in any command
23634 stops execution of the user-defined command.
23636 If used interactively, commands that would ask for confirmation proceed
23637 without asking when used inside a user-defined command. Many @value{GDBN}
23638 commands that normally print messages to say what they are doing omit the
23639 messages when used in a user-defined command.
23642 @subsection User-defined Command Hooks
23643 @cindex command hooks
23644 @cindex hooks, for commands
23645 @cindex hooks, pre-command
23648 You may define @dfn{hooks}, which are a special kind of user-defined
23649 command. Whenever you run the command @samp{foo}, if the user-defined
23650 command @samp{hook-foo} exists, it is executed (with no arguments)
23651 before that command.
23653 @cindex hooks, post-command
23655 A hook may also be defined which is run after the command you executed.
23656 Whenever you run the command @samp{foo}, if the user-defined command
23657 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23658 that command. Post-execution hooks may exist simultaneously with
23659 pre-execution hooks, for the same command.
23661 It is valid for a hook to call the command which it hooks. If this
23662 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23664 @c It would be nice if hookpost could be passed a parameter indicating
23665 @c if the command it hooks executed properly or not. FIXME!
23667 @kindex stop@r{, a pseudo-command}
23668 In addition, a pseudo-command, @samp{stop} exists. Defining
23669 (@samp{hook-stop}) makes the associated commands execute every time
23670 execution stops in your program: before breakpoint commands are run,
23671 displays are printed, or the stack frame is printed.
23673 For example, to ignore @code{SIGALRM} signals while
23674 single-stepping, but treat them normally during normal execution,
23679 handle SIGALRM nopass
23683 handle SIGALRM pass
23686 define hook-continue
23687 handle SIGALRM pass
23691 As a further example, to hook at the beginning and end of the @code{echo}
23692 command, and to add extra text to the beginning and end of the message,
23700 define hookpost-echo
23704 (@value{GDBP}) echo Hello World
23705 <<<---Hello World--->>>
23710 You can define a hook for any single-word command in @value{GDBN}, but
23711 not for command aliases; you should define a hook for the basic command
23712 name, e.g.@: @code{backtrace} rather than @code{bt}.
23713 @c FIXME! So how does Joe User discover whether a command is an alias
23715 You can hook a multi-word command by adding @code{hook-} or
23716 @code{hookpost-} to the last word of the command, e.g.@:
23717 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23719 If an error occurs during the execution of your hook, execution of
23720 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23721 (before the command that you actually typed had a chance to run).
23723 If you try to define a hook which does not match any known command, you
23724 get a warning from the @code{define} command.
23726 @node Command Files
23727 @subsection Command Files
23729 @cindex command files
23730 @cindex scripting commands
23731 A command file for @value{GDBN} is a text file made of lines that are
23732 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23733 also be included. An empty line in a command file does nothing; it
23734 does not mean to repeat the last command, as it would from the
23737 You can request the execution of a command file with the @code{source}
23738 command. Note that the @code{source} command is also used to evaluate
23739 scripts that are not Command Files. The exact behavior can be configured
23740 using the @code{script-extension} setting.
23741 @xref{Extending GDB,, Extending GDB}.
23745 @cindex execute commands from a file
23746 @item source [-s] [-v] @var{filename}
23747 Execute the command file @var{filename}.
23750 The lines in a command file are generally executed sequentially,
23751 unless the order of execution is changed by one of the
23752 @emph{flow-control commands} described below. The commands are not
23753 printed as they are executed. An error in any command terminates
23754 execution of the command file and control is returned to the console.
23756 @value{GDBN} first searches for @var{filename} in the current directory.
23757 If the file is not found there, and @var{filename} does not specify a
23758 directory, then @value{GDBN} also looks for the file on the source search path
23759 (specified with the @samp{directory} command);
23760 except that @file{$cdir} is not searched because the compilation directory
23761 is not relevant to scripts.
23763 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23764 on the search path even if @var{filename} specifies a directory.
23765 The search is done by appending @var{filename} to each element of the
23766 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23767 and the search path contains @file{/home/user} then @value{GDBN} will
23768 look for the script @file{/home/user/mylib/myscript}.
23769 The search is also done if @var{filename} is an absolute path.
23770 For example, if @var{filename} is @file{/tmp/myscript} and
23771 the search path contains @file{/home/user} then @value{GDBN} will
23772 look for the script @file{/home/user/tmp/myscript}.
23773 For DOS-like systems, if @var{filename} contains a drive specification,
23774 it is stripped before concatenation. For example, if @var{filename} is
23775 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23776 will look for the script @file{c:/tmp/myscript}.
23778 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23779 each command as it is executed. The option must be given before
23780 @var{filename}, and is interpreted as part of the filename anywhere else.
23782 Commands that would ask for confirmation if used interactively proceed
23783 without asking when used in a command file. Many @value{GDBN} commands that
23784 normally print messages to say what they are doing omit the messages
23785 when called from command files.
23787 @value{GDBN} also accepts command input from standard input. In this
23788 mode, normal output goes to standard output and error output goes to
23789 standard error. Errors in a command file supplied on standard input do
23790 not terminate execution of the command file---execution continues with
23794 gdb < cmds > log 2>&1
23797 (The syntax above will vary depending on the shell used.) This example
23798 will execute commands from the file @file{cmds}. All output and errors
23799 would be directed to @file{log}.
23801 Since commands stored on command files tend to be more general than
23802 commands typed interactively, they frequently need to deal with
23803 complicated situations, such as different or unexpected values of
23804 variables and symbols, changes in how the program being debugged is
23805 built, etc. @value{GDBN} provides a set of flow-control commands to
23806 deal with these complexities. Using these commands, you can write
23807 complex scripts that loop over data structures, execute commands
23808 conditionally, etc.
23815 This command allows to include in your script conditionally executed
23816 commands. The @code{if} command takes a single argument, which is an
23817 expression to evaluate. It is followed by a series of commands that
23818 are executed only if the expression is true (its value is nonzero).
23819 There can then optionally be an @code{else} line, followed by a series
23820 of commands that are only executed if the expression was false. The
23821 end of the list is marked by a line containing @code{end}.
23825 This command allows to write loops. Its syntax is similar to
23826 @code{if}: the command takes a single argument, which is an expression
23827 to evaluate, and must be followed by the commands to execute, one per
23828 line, terminated by an @code{end}. These commands are called the
23829 @dfn{body} of the loop. The commands in the body of @code{while} are
23830 executed repeatedly as long as the expression evaluates to true.
23834 This command exits the @code{while} loop in whose body it is included.
23835 Execution of the script continues after that @code{while}s @code{end}
23838 @kindex loop_continue
23839 @item loop_continue
23840 This command skips the execution of the rest of the body of commands
23841 in the @code{while} loop in whose body it is included. Execution
23842 branches to the beginning of the @code{while} loop, where it evaluates
23843 the controlling expression.
23845 @kindex end@r{ (if/else/while commands)}
23847 Terminate the block of commands that are the body of @code{if},
23848 @code{else}, or @code{while} flow-control commands.
23853 @subsection Commands for Controlled Output
23855 During the execution of a command file or a user-defined command, normal
23856 @value{GDBN} output is suppressed; the only output that appears is what is
23857 explicitly printed by the commands in the definition. This section
23858 describes three commands useful for generating exactly the output you
23863 @item echo @var{text}
23864 @c I do not consider backslash-space a standard C escape sequence
23865 @c because it is not in ANSI.
23866 Print @var{text}. Nonprinting characters can be included in
23867 @var{text} using C escape sequences, such as @samp{\n} to print a
23868 newline. @strong{No newline is printed unless you specify one.}
23869 In addition to the standard C escape sequences, a backslash followed
23870 by a space stands for a space. This is useful for displaying a
23871 string with spaces at the beginning or the end, since leading and
23872 trailing spaces are otherwise trimmed from all arguments.
23873 To print @samp{@w{ }and foo =@w{ }}, use the command
23874 @samp{echo \@w{ }and foo = \@w{ }}.
23876 A backslash at the end of @var{text} can be used, as in C, to continue
23877 the command onto subsequent lines. For example,
23880 echo This is some text\n\
23881 which is continued\n\
23882 onto several lines.\n
23885 produces the same output as
23888 echo This is some text\n
23889 echo which is continued\n
23890 echo onto several lines.\n
23894 @item output @var{expression}
23895 Print the value of @var{expression} and nothing but that value: no
23896 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23897 value history either. @xref{Expressions, ,Expressions}, for more information
23900 @item output/@var{fmt} @var{expression}
23901 Print the value of @var{expression} in format @var{fmt}. You can use
23902 the same formats as for @code{print}. @xref{Output Formats,,Output
23903 Formats}, for more information.
23906 @item printf @var{template}, @var{expressions}@dots{}
23907 Print the values of one or more @var{expressions} under the control of
23908 the string @var{template}. To print several values, make
23909 @var{expressions} be a comma-separated list of individual expressions,
23910 which may be either numbers or pointers. Their values are printed as
23911 specified by @var{template}, exactly as a C program would do by
23912 executing the code below:
23915 printf (@var{template}, @var{expressions}@dots{});
23918 As in @code{C} @code{printf}, ordinary characters in @var{template}
23919 are printed verbatim, while @dfn{conversion specification} introduced
23920 by the @samp{%} character cause subsequent @var{expressions} to be
23921 evaluated, their values converted and formatted according to type and
23922 style information encoded in the conversion specifications, and then
23925 For example, you can print two values in hex like this:
23928 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23931 @code{printf} supports all the standard @code{C} conversion
23932 specifications, including the flags and modifiers between the @samp{%}
23933 character and the conversion letter, with the following exceptions:
23937 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23940 The modifier @samp{*} is not supported for specifying precision or
23944 The @samp{'} flag (for separation of digits into groups according to
23945 @code{LC_NUMERIC'}) is not supported.
23948 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23952 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23955 The conversion letters @samp{a} and @samp{A} are not supported.
23959 Note that the @samp{ll} type modifier is supported only if the
23960 underlying @code{C} implementation used to build @value{GDBN} supports
23961 the @code{long long int} type, and the @samp{L} type modifier is
23962 supported only if @code{long double} type is available.
23964 As in @code{C}, @code{printf} supports simple backslash-escape
23965 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23966 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23967 single character. Octal and hexadecimal escape sequences are not
23970 Additionally, @code{printf} supports conversion specifications for DFP
23971 (@dfn{Decimal Floating Point}) types using the following length modifiers
23972 together with a floating point specifier.
23977 @samp{H} for printing @code{Decimal32} types.
23980 @samp{D} for printing @code{Decimal64} types.
23983 @samp{DD} for printing @code{Decimal128} types.
23986 If the underlying @code{C} implementation used to build @value{GDBN} has
23987 support for the three length modifiers for DFP types, other modifiers
23988 such as width and precision will also be available for @value{GDBN} to use.
23990 In case there is no such @code{C} support, no additional modifiers will be
23991 available and the value will be printed in the standard way.
23993 Here's an example of printing DFP types using the above conversion letters:
23995 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23999 @item eval @var{template}, @var{expressions}@dots{}
24000 Convert the values of one or more @var{expressions} under the control of
24001 the string @var{template} to a command line, and call it.
24005 @node Auto-loading sequences
24006 @subsection Controlling auto-loading native @value{GDBN} scripts
24007 @cindex native script auto-loading
24009 When a new object file is read (for example, due to the @code{file}
24010 command, or because the inferior has loaded a shared library),
24011 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24012 @xref{Auto-loading extensions}.
24014 Auto-loading can be enabled or disabled,
24015 and the list of auto-loaded scripts can be printed.
24018 @anchor{set auto-load gdb-scripts}
24019 @kindex set auto-load gdb-scripts
24020 @item set auto-load gdb-scripts [on|off]
24021 Enable or disable the auto-loading of canned sequences of commands scripts.
24023 @anchor{show auto-load gdb-scripts}
24024 @kindex show auto-load gdb-scripts
24025 @item show auto-load gdb-scripts
24026 Show whether auto-loading of canned sequences of commands scripts is enabled or
24029 @anchor{info auto-load gdb-scripts}
24030 @kindex info auto-load gdb-scripts
24031 @cindex print list of auto-loaded canned sequences of commands scripts
24032 @item info auto-load gdb-scripts [@var{regexp}]
24033 Print the list of all canned sequences of commands scripts that @value{GDBN}
24037 If @var{regexp} is supplied only canned sequences of commands scripts with
24038 matching names are printed.
24040 @c Python docs live in a separate file.
24041 @include python.texi
24043 @c Guile docs live in a separate file.
24044 @include guile.texi
24046 @node Auto-loading extensions
24047 @section Auto-loading extensions
24048 @cindex auto-loading extensions
24050 @value{GDBN} provides two mechanisms for automatically loading extensions
24051 when a new object file is read (for example, due to the @code{file}
24052 command, or because the inferior has loaded a shared library):
24053 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24054 section of modern file formats like ELF.
24057 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24058 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24059 * Which flavor to choose?::
24062 The auto-loading feature is useful for supplying application-specific
24063 debugging commands and features.
24065 Auto-loading can be enabled or disabled,
24066 and the list of auto-loaded scripts can be printed.
24067 See the @samp{auto-loading} section of each extension language
24068 for more information.
24069 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24070 For Python files see @ref{Python Auto-loading}.
24072 Note that loading of this script file also requires accordingly configured
24073 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24075 @node objfile-gdbdotext file
24076 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24077 @cindex @file{@var{objfile}-gdb.gdb}
24078 @cindex @file{@var{objfile}-gdb.py}
24079 @cindex @file{@var{objfile}-gdb.scm}
24081 When a new object file is read, @value{GDBN} looks for a file named
24082 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24083 where @var{objfile} is the object file's name and
24084 where @var{ext} is the file extension for the extension language:
24087 @item @file{@var{objfile}-gdb.gdb}
24088 GDB's own command language
24089 @item @file{@var{objfile}-gdb.py}
24091 @item @file{@var{objfile}-gdb.scm}
24095 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24096 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24097 components, and appending the @file{-gdb.@var{ext}} suffix.
24098 If this file exists and is readable, @value{GDBN} will evaluate it as a
24099 script in the specified extension language.
24101 If this file does not exist, then @value{GDBN} will look for
24102 @var{script-name} file in all of the directories as specified below.
24104 Note that loading of these files requires an accordingly configured
24105 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24107 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24108 scripts normally according to its @file{.exe} filename. But if no scripts are
24109 found @value{GDBN} also tries script filenames matching the object file without
24110 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24111 is attempted on any platform. This makes the script filenames compatible
24112 between Unix and MS-Windows hosts.
24115 @anchor{set auto-load scripts-directory}
24116 @kindex set auto-load scripts-directory
24117 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24118 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24119 may be delimited by the host platform path separator in use
24120 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24122 Each entry here needs to be covered also by the security setting
24123 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24125 @anchor{with-auto-load-dir}
24126 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24127 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24128 configuration option @option{--with-auto-load-dir}.
24130 Any reference to @file{$debugdir} will get replaced by
24131 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24132 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24133 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24134 @file{$datadir} must be placed as a directory component --- either alone or
24135 delimited by @file{/} or @file{\} directory separators, depending on the host
24138 The list of directories uses path separator (@samp{:} on GNU and Unix
24139 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24140 to the @env{PATH} environment variable.
24142 @anchor{show auto-load scripts-directory}
24143 @kindex show auto-load scripts-directory
24144 @item show auto-load scripts-directory
24145 Show @value{GDBN} auto-loaded scripts location.
24147 @anchor{add-auto-load-scripts-directory}
24148 @kindex add-auto-load-scripts-directory
24149 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24150 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24151 Multiple entries may be delimited by the host platform path separator in use.
24154 @value{GDBN} does not track which files it has already auto-loaded this way.
24155 @value{GDBN} will load the associated script every time the corresponding
24156 @var{objfile} is opened.
24157 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24158 is evaluated more than once.
24160 @node dotdebug_gdb_scripts section
24161 @subsection The @code{.debug_gdb_scripts} section
24162 @cindex @code{.debug_gdb_scripts} section
24164 For systems using file formats like ELF and COFF,
24165 when @value{GDBN} loads a new object file
24166 it will look for a special section named @code{.debug_gdb_scripts}.
24167 If this section exists, its contents is a list of null-terminated entries
24168 specifying scripts to load. Each entry begins with a non-null prefix byte that
24169 specifies the kind of entry, typically the extension language and whether the
24170 script is in a file or inlined in @code{.debug_gdb_scripts}.
24172 The following entries are supported:
24175 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24176 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24177 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24178 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24181 @subsubsection Script File Entries
24183 If the entry specifies a file, @value{GDBN} will look for the file first
24184 in the current directory and then along the source search path
24185 (@pxref{Source Path, ,Specifying Source Directories}),
24186 except that @file{$cdir} is not searched, since the compilation
24187 directory is not relevant to scripts.
24189 File entries can be placed in section @code{.debug_gdb_scripts} with,
24190 for example, this GCC macro for Python scripts.
24193 /* Note: The "MS" section flags are to remove duplicates. */
24194 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24196 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24197 .byte 1 /* Python */\n\
24198 .asciz \"" script_name "\"\n\
24204 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24205 Then one can reference the macro in a header or source file like this:
24208 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24211 The script name may include directories if desired.
24213 Note that loading of this script file also requires accordingly configured
24214 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24216 If the macro invocation is put in a header, any application or library
24217 using this header will get a reference to the specified script,
24218 and with the use of @code{"MS"} attributes on the section, the linker
24219 will remove duplicates.
24221 @subsubsection Script Text Entries
24223 Script text entries allow to put the executable script in the entry
24224 itself instead of loading it from a file.
24225 The first line of the entry, everything after the prefix byte and up to
24226 the first newline (@code{0xa}) character, is the script name, and must not
24227 contain any kind of space character, e.g., spaces or tabs.
24228 The rest of the entry, up to the trailing null byte, is the script to
24229 execute in the specified language. The name needs to be unique among
24230 all script names, as @value{GDBN} executes each script only once based
24233 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24237 #include "symcat.h"
24238 #include "gdb/section-scripts.h"
24240 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24241 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24242 ".ascii \"gdb.inlined-script\\n\"\n"
24243 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24244 ".ascii \" def __init__ (self):\\n\"\n"
24245 ".ascii \" super (test_cmd, self).__init__ ("
24246 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24247 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24248 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24249 ".ascii \"test_cmd ()\\n\"\n"
24255 Loading of inlined scripts requires a properly configured
24256 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24257 The path to specify in @code{auto-load safe-path} is the path of the file
24258 containing the @code{.debug_gdb_scripts} section.
24260 @node Which flavor to choose?
24261 @subsection Which flavor to choose?
24263 Given the multiple ways of auto-loading extensions, it might not always
24264 be clear which one to choose. This section provides some guidance.
24267 Benefits of the @file{-gdb.@var{ext}} way:
24271 Can be used with file formats that don't support multiple sections.
24274 Ease of finding scripts for public libraries.
24276 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24277 in the source search path.
24278 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24279 isn't a source directory in which to find the script.
24282 Doesn't require source code additions.
24286 Benefits of the @code{.debug_gdb_scripts} way:
24290 Works with static linking.
24292 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24293 trigger their loading. When an application is statically linked the only
24294 objfile available is the executable, and it is cumbersome to attach all the
24295 scripts from all the input libraries to the executable's
24296 @file{-gdb.@var{ext}} script.
24299 Works with classes that are entirely inlined.
24301 Some classes can be entirely inlined, and thus there may not be an associated
24302 shared library to attach a @file{-gdb.@var{ext}} script to.
24305 Scripts needn't be copied out of the source tree.
24307 In some circumstances, apps can be built out of large collections of internal
24308 libraries, and the build infrastructure necessary to install the
24309 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24310 cumbersome. It may be easier to specify the scripts in the
24311 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24312 top of the source tree to the source search path.
24315 @node Multiple Extension Languages
24316 @section Multiple Extension Languages
24318 The Guile and Python extension languages do not share any state,
24319 and generally do not interfere with each other.
24320 There are some things to be aware of, however.
24322 @subsection Python comes first
24324 Python was @value{GDBN}'s first extension language, and to avoid breaking
24325 existing behaviour Python comes first. This is generally solved by the
24326 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24327 extension languages, and when it makes a call to an extension language,
24328 (say to pretty-print a value), it tries each in turn until an extension
24329 language indicates it has performed the request (e.g., has returned the
24330 pretty-printed form of a value).
24331 This extends to errors while performing such requests: If an error happens
24332 while, for example, trying to pretty-print an object then the error is
24333 reported and any following extension languages are not tried.
24336 @section Creating new spellings of existing commands
24337 @cindex aliases for commands
24339 It is often useful to define alternate spellings of existing commands.
24340 For example, if a new @value{GDBN} command defined in Python has
24341 a long name to type, it is handy to have an abbreviated version of it
24342 that involves less typing.
24344 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24345 of the @samp{step} command even though it is otherwise an ambiguous
24346 abbreviation of other commands like @samp{set} and @samp{show}.
24348 Aliases are also used to provide shortened or more common versions
24349 of multi-word commands. For example, @value{GDBN} provides the
24350 @samp{tty} alias of the @samp{set inferior-tty} command.
24352 You can define a new alias with the @samp{alias} command.
24357 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24361 @var{ALIAS} specifies the name of the new alias.
24362 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24365 @var{COMMAND} specifies the name of an existing command
24366 that is being aliased.
24368 The @samp{-a} option specifies that the new alias is an abbreviation
24369 of the command. Abbreviations are not shown in command
24370 lists displayed by the @samp{help} command.
24372 The @samp{--} option specifies the end of options,
24373 and is useful when @var{ALIAS} begins with a dash.
24375 Here is a simple example showing how to make an abbreviation
24376 of a command so that there is less to type.
24377 Suppose you were tired of typing @samp{disas}, the current
24378 shortest unambiguous abbreviation of the @samp{disassemble} command
24379 and you wanted an even shorter version named @samp{di}.
24380 The following will accomplish this.
24383 (gdb) alias -a di = disas
24386 Note that aliases are different from user-defined commands.
24387 With a user-defined command, you also need to write documentation
24388 for it with the @samp{document} command.
24389 An alias automatically picks up the documentation of the existing command.
24391 Here is an example where we make @samp{elms} an abbreviation of
24392 @samp{elements} in the @samp{set print elements} command.
24393 This is to show that you can make an abbreviation of any part
24397 (gdb) alias -a set print elms = set print elements
24398 (gdb) alias -a show print elms = show print elements
24399 (gdb) set p elms 20
24401 Limit on string chars or array elements to print is 200.
24404 Note that if you are defining an alias of a @samp{set} command,
24405 and you want to have an alias for the corresponding @samp{show}
24406 command, then you need to define the latter separately.
24408 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24409 @var{ALIAS}, just as they are normally.
24412 (gdb) alias -a set pr elms = set p ele
24415 Finally, here is an example showing the creation of a one word
24416 alias for a more complex command.
24417 This creates alias @samp{spe} of the command @samp{set print elements}.
24420 (gdb) alias spe = set print elements
24425 @chapter Command Interpreters
24426 @cindex command interpreters
24428 @value{GDBN} supports multiple command interpreters, and some command
24429 infrastructure to allow users or user interface writers to switch
24430 between interpreters or run commands in other interpreters.
24432 @value{GDBN} currently supports two command interpreters, the console
24433 interpreter (sometimes called the command-line interpreter or @sc{cli})
24434 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24435 describes both of these interfaces in great detail.
24437 By default, @value{GDBN} will start with the console interpreter.
24438 However, the user may choose to start @value{GDBN} with another
24439 interpreter by specifying the @option{-i} or @option{--interpreter}
24440 startup options. Defined interpreters include:
24444 @cindex console interpreter
24445 The traditional console or command-line interpreter. This is the most often
24446 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24447 @value{GDBN} will use this interpreter.
24450 @cindex mi interpreter
24451 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24452 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24453 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24457 @cindex mi2 interpreter
24458 The current @sc{gdb/mi} interface.
24461 @cindex mi1 interpreter
24462 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24466 @cindex invoke another interpreter
24467 The interpreter being used by @value{GDBN} may not be dynamically
24468 switched at runtime. Although possible, this could lead to a very
24469 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24470 enters the command "interpreter-set console" in a console view,
24471 @value{GDBN} would switch to using the console interpreter, rendering
24472 the IDE inoperable!
24474 @kindex interpreter-exec
24475 Although you may only choose a single interpreter at startup, you may execute
24476 commands in any interpreter from the current interpreter using the appropriate
24477 command. If you are running the console interpreter, simply use the
24478 @code{interpreter-exec} command:
24481 interpreter-exec mi "-data-list-register-names"
24484 @sc{gdb/mi} has a similar command, although it is only available in versions of
24485 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24488 @chapter @value{GDBN} Text User Interface
24490 @cindex Text User Interface
24493 * TUI Overview:: TUI overview
24494 * TUI Keys:: TUI key bindings
24495 * TUI Single Key Mode:: TUI single key mode
24496 * TUI Commands:: TUI-specific commands
24497 * TUI Configuration:: TUI configuration variables
24500 The @value{GDBN} Text User Interface (TUI) is a terminal
24501 interface which uses the @code{curses} library to show the source
24502 file, the assembly output, the program registers and @value{GDBN}
24503 commands in separate text windows. The TUI mode is supported only
24504 on platforms where a suitable version of the @code{curses} library
24507 The TUI mode is enabled by default when you invoke @value{GDBN} as
24508 @samp{@value{GDBP} -tui}.
24509 You can also switch in and out of TUI mode while @value{GDBN} runs by
24510 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24511 @xref{TUI Keys, ,TUI Key Bindings}.
24514 @section TUI Overview
24516 In TUI mode, @value{GDBN} can display several text windows:
24520 This window is the @value{GDBN} command window with the @value{GDBN}
24521 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24522 managed using readline.
24525 The source window shows the source file of the program. The current
24526 line and active breakpoints are displayed in this window.
24529 The assembly window shows the disassembly output of the program.
24532 This window shows the processor registers. Registers are highlighted
24533 when their values change.
24536 The source and assembly windows show the current program position
24537 by highlighting the current line and marking it with a @samp{>} marker.
24538 Breakpoints are indicated with two markers. The first marker
24539 indicates the breakpoint type:
24543 Breakpoint which was hit at least once.
24546 Breakpoint which was never hit.
24549 Hardware breakpoint which was hit at least once.
24552 Hardware breakpoint which was never hit.
24555 The second marker indicates whether the breakpoint is enabled or not:
24559 Breakpoint is enabled.
24562 Breakpoint is disabled.
24565 The source, assembly and register windows are updated when the current
24566 thread changes, when the frame changes, or when the program counter
24569 These windows are not all visible at the same time. The command
24570 window is always visible. The others can be arranged in several
24581 source and assembly,
24584 source and registers, or
24587 assembly and registers.
24590 A status line above the command window shows the following information:
24594 Indicates the current @value{GDBN} target.
24595 (@pxref{Targets, ,Specifying a Debugging Target}).
24598 Gives the current process or thread number.
24599 When no process is being debugged, this field is set to @code{No process}.
24602 Gives the current function name for the selected frame.
24603 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24604 When there is no symbol corresponding to the current program counter,
24605 the string @code{??} is displayed.
24608 Indicates the current line number for the selected frame.
24609 When the current line number is not known, the string @code{??} is displayed.
24612 Indicates the current program counter address.
24616 @section TUI Key Bindings
24617 @cindex TUI key bindings
24619 The TUI installs several key bindings in the readline keymaps
24620 @ifset SYSTEM_READLINE
24621 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24623 @ifclear SYSTEM_READLINE
24624 (@pxref{Command Line Editing}).
24626 The following key bindings are installed for both TUI mode and the
24627 @value{GDBN} standard mode.
24636 Enter or leave the TUI mode. When leaving the TUI mode,
24637 the curses window management stops and @value{GDBN} operates using
24638 its standard mode, writing on the terminal directly. When reentering
24639 the TUI mode, control is given back to the curses windows.
24640 The screen is then refreshed.
24644 Use a TUI layout with only one window. The layout will
24645 either be @samp{source} or @samp{assembly}. When the TUI mode
24646 is not active, it will switch to the TUI mode.
24648 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24652 Use a TUI layout with at least two windows. When the current
24653 layout already has two windows, the next layout with two windows is used.
24654 When a new layout is chosen, one window will always be common to the
24655 previous layout and the new one.
24657 Think of it as the Emacs @kbd{C-x 2} binding.
24661 Change the active window. The TUI associates several key bindings
24662 (like scrolling and arrow keys) with the active window. This command
24663 gives the focus to the next TUI window.
24665 Think of it as the Emacs @kbd{C-x o} binding.
24669 Switch in and out of the TUI SingleKey mode that binds single
24670 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24673 The following key bindings only work in the TUI mode:
24678 Scroll the active window one page up.
24682 Scroll the active window one page down.
24686 Scroll the active window one line up.
24690 Scroll the active window one line down.
24694 Scroll the active window one column left.
24698 Scroll the active window one column right.
24702 Refresh the screen.
24705 Because the arrow keys scroll the active window in the TUI mode, they
24706 are not available for their normal use by readline unless the command
24707 window has the focus. When another window is active, you must use
24708 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24709 and @kbd{C-f} to control the command window.
24711 @node TUI Single Key Mode
24712 @section TUI Single Key Mode
24713 @cindex TUI single key mode
24715 The TUI also provides a @dfn{SingleKey} mode, which binds several
24716 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24717 switch into this mode, where the following key bindings are used:
24720 @kindex c @r{(SingleKey TUI key)}
24724 @kindex d @r{(SingleKey TUI key)}
24728 @kindex f @r{(SingleKey TUI key)}
24732 @kindex n @r{(SingleKey TUI key)}
24736 @kindex q @r{(SingleKey TUI key)}
24738 exit the SingleKey mode.
24740 @kindex r @r{(SingleKey TUI key)}
24744 @kindex s @r{(SingleKey TUI key)}
24748 @kindex u @r{(SingleKey TUI key)}
24752 @kindex v @r{(SingleKey TUI key)}
24756 @kindex w @r{(SingleKey TUI key)}
24761 Other keys temporarily switch to the @value{GDBN} command prompt.
24762 The key that was pressed is inserted in the editing buffer so that
24763 it is possible to type most @value{GDBN} commands without interaction
24764 with the TUI SingleKey mode. Once the command is entered the TUI
24765 SingleKey mode is restored. The only way to permanently leave
24766 this mode is by typing @kbd{q} or @kbd{C-x s}.
24770 @section TUI-specific Commands
24771 @cindex TUI commands
24773 The TUI has specific commands to control the text windows.
24774 These commands are always available, even when @value{GDBN} is not in
24775 the TUI mode. When @value{GDBN} is in the standard mode, most
24776 of these commands will automatically switch to the TUI mode.
24778 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24779 terminal, or @value{GDBN} has been started with the machine interface
24780 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24781 these commands will fail with an error, because it would not be
24782 possible or desirable to enable curses window management.
24787 List and give the size of all displayed windows.
24791 Display the next layout.
24794 Display the previous layout.
24797 Display the source window only.
24800 Display the assembly window only.
24803 Display the source and assembly window.
24806 Display the register window together with the source or assembly window.
24810 Make the next window active for scrolling.
24813 Make the previous window active for scrolling.
24816 Make the source window active for scrolling.
24819 Make the assembly window active for scrolling.
24822 Make the register window active for scrolling.
24825 Make the command window active for scrolling.
24829 Refresh the screen. This is similar to typing @kbd{C-L}.
24831 @item tui reg float
24833 Show the floating point registers in the register window.
24835 @item tui reg general
24836 Show the general registers in the register window.
24839 Show the next register group. The list of register groups as well as
24840 their order is target specific. The predefined register groups are the
24841 following: @code{general}, @code{float}, @code{system}, @code{vector},
24842 @code{all}, @code{save}, @code{restore}.
24844 @item tui reg system
24845 Show the system registers in the register window.
24849 Update the source window and the current execution point.
24851 @item winheight @var{name} +@var{count}
24852 @itemx winheight @var{name} -@var{count}
24854 Change the height of the window @var{name} by @var{count}
24855 lines. Positive counts increase the height, while negative counts
24856 decrease it. The @var{name} parameter can be one of @code{src} (the
24857 source window), @code{cmd} (the command window), @code{asm} (the
24858 disassembly window), or @code{regs} (the register display window).
24860 @item tabset @var{nchars}
24862 Set the width of tab stops to be @var{nchars} characters. This
24863 setting affects the display of TAB characters in the source and
24867 @node TUI Configuration
24868 @section TUI Configuration Variables
24869 @cindex TUI configuration variables
24871 Several configuration variables control the appearance of TUI windows.
24874 @item set tui border-kind @var{kind}
24875 @kindex set tui border-kind
24876 Select the border appearance for the source, assembly and register windows.
24877 The possible values are the following:
24880 Use a space character to draw the border.
24883 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24886 Use the Alternate Character Set to draw the border. The border is
24887 drawn using character line graphics if the terminal supports them.
24890 @item set tui border-mode @var{mode}
24891 @kindex set tui border-mode
24892 @itemx set tui active-border-mode @var{mode}
24893 @kindex set tui active-border-mode
24894 Select the display attributes for the borders of the inactive windows
24895 or the active window. The @var{mode} can be one of the following:
24898 Use normal attributes to display the border.
24904 Use reverse video mode.
24907 Use half bright mode.
24909 @item half-standout
24910 Use half bright and standout mode.
24913 Use extra bright or bold mode.
24915 @item bold-standout
24916 Use extra bright or bold and standout mode.
24921 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24924 @cindex @sc{gnu} Emacs
24925 A special interface allows you to use @sc{gnu} Emacs to view (and
24926 edit) the source files for the program you are debugging with
24929 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24930 executable file you want to debug as an argument. This command starts
24931 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24932 created Emacs buffer.
24933 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24935 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24940 All ``terminal'' input and output goes through an Emacs buffer, called
24943 This applies both to @value{GDBN} commands and their output, and to the input
24944 and output done by the program you are debugging.
24946 This is useful because it means that you can copy the text of previous
24947 commands and input them again; you can even use parts of the output
24950 All the facilities of Emacs' Shell mode are available for interacting
24951 with your program. In particular, you can send signals the usual
24952 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24956 @value{GDBN} displays source code through Emacs.
24958 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24959 source file for that frame and puts an arrow (@samp{=>}) at the
24960 left margin of the current line. Emacs uses a separate buffer for
24961 source display, and splits the screen to show both your @value{GDBN} session
24964 Explicit @value{GDBN} @code{list} or search commands still produce output as
24965 usual, but you probably have no reason to use them from Emacs.
24968 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24969 a graphical mode, enabled by default, which provides further buffers
24970 that can control the execution and describe the state of your program.
24971 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24973 If you specify an absolute file name when prompted for the @kbd{M-x
24974 gdb} argument, then Emacs sets your current working directory to where
24975 your program resides. If you only specify the file name, then Emacs
24976 sets your current working directory to the directory associated
24977 with the previous buffer. In this case, @value{GDBN} may find your
24978 program by searching your environment's @code{PATH} variable, but on
24979 some operating systems it might not find the source. So, although the
24980 @value{GDBN} input and output session proceeds normally, the auxiliary
24981 buffer does not display the current source and line of execution.
24983 The initial working directory of @value{GDBN} is printed on the top
24984 line of the GUD buffer and this serves as a default for the commands
24985 that specify files for @value{GDBN} to operate on. @xref{Files,
24986 ,Commands to Specify Files}.
24988 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24989 need to call @value{GDBN} by a different name (for example, if you
24990 keep several configurations around, with different names) you can
24991 customize the Emacs variable @code{gud-gdb-command-name} to run the
24994 In the GUD buffer, you can use these special Emacs commands in
24995 addition to the standard Shell mode commands:
24999 Describe the features of Emacs' GUD Mode.
25002 Execute to another source line, like the @value{GDBN} @code{step} command; also
25003 update the display window to show the current file and location.
25006 Execute to next source line in this function, skipping all function
25007 calls, like the @value{GDBN} @code{next} command. Then update the display window
25008 to show the current file and location.
25011 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25012 display window accordingly.
25015 Execute until exit from the selected stack frame, like the @value{GDBN}
25016 @code{finish} command.
25019 Continue execution of your program, like the @value{GDBN} @code{continue}
25023 Go up the number of frames indicated by the numeric argument
25024 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25025 like the @value{GDBN} @code{up} command.
25028 Go down the number of frames indicated by the numeric argument, like the
25029 @value{GDBN} @code{down} command.
25032 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25033 tells @value{GDBN} to set a breakpoint on the source line point is on.
25035 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25036 separate frame which shows a backtrace when the GUD buffer is current.
25037 Move point to any frame in the stack and type @key{RET} to make it
25038 become the current frame and display the associated source in the
25039 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25040 selected frame become the current one. In graphical mode, the
25041 speedbar displays watch expressions.
25043 If you accidentally delete the source-display buffer, an easy way to get
25044 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25045 request a frame display; when you run under Emacs, this recreates
25046 the source buffer if necessary to show you the context of the current
25049 The source files displayed in Emacs are in ordinary Emacs buffers
25050 which are visiting the source files in the usual way. You can edit
25051 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25052 communicates with Emacs in terms of line numbers. If you add or
25053 delete lines from the text, the line numbers that @value{GDBN} knows cease
25054 to correspond properly with the code.
25056 A more detailed description of Emacs' interaction with @value{GDBN} is
25057 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25061 @chapter The @sc{gdb/mi} Interface
25063 @unnumberedsec Function and Purpose
25065 @cindex @sc{gdb/mi}, its purpose
25066 @sc{gdb/mi} is a line based machine oriented text interface to
25067 @value{GDBN} and is activated by specifying using the
25068 @option{--interpreter} command line option (@pxref{Mode Options}). It
25069 is specifically intended to support the development of systems which
25070 use the debugger as just one small component of a larger system.
25072 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25073 in the form of a reference manual.
25075 Note that @sc{gdb/mi} is still under construction, so some of the
25076 features described below are incomplete and subject to change
25077 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25079 @unnumberedsec Notation and Terminology
25081 @cindex notational conventions, for @sc{gdb/mi}
25082 This chapter uses the following notation:
25086 @code{|} separates two alternatives.
25089 @code{[ @var{something} ]} indicates that @var{something} is optional:
25090 it may or may not be given.
25093 @code{( @var{group} )*} means that @var{group} inside the parentheses
25094 may repeat zero or more times.
25097 @code{( @var{group} )+} means that @var{group} inside the parentheses
25098 may repeat one or more times.
25101 @code{"@var{string}"} means a literal @var{string}.
25105 @heading Dependencies
25109 * GDB/MI General Design::
25110 * GDB/MI Command Syntax::
25111 * GDB/MI Compatibility with CLI::
25112 * GDB/MI Development and Front Ends::
25113 * GDB/MI Output Records::
25114 * GDB/MI Simple Examples::
25115 * GDB/MI Command Description Format::
25116 * GDB/MI Breakpoint Commands::
25117 * GDB/MI Catchpoint Commands::
25118 * GDB/MI Program Context::
25119 * GDB/MI Thread Commands::
25120 * GDB/MI Ada Tasking Commands::
25121 * GDB/MI Program Execution::
25122 * GDB/MI Stack Manipulation::
25123 * GDB/MI Variable Objects::
25124 * GDB/MI Data Manipulation::
25125 * GDB/MI Tracepoint Commands::
25126 * GDB/MI Symbol Query::
25127 * GDB/MI File Commands::
25129 * GDB/MI Kod Commands::
25130 * GDB/MI Memory Overlay Commands::
25131 * GDB/MI Signal Handling Commands::
25133 * GDB/MI Target Manipulation::
25134 * GDB/MI File Transfer Commands::
25135 * GDB/MI Ada Exceptions Commands::
25136 * GDB/MI Support Commands::
25137 * GDB/MI Miscellaneous Commands::
25140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25141 @node GDB/MI General Design
25142 @section @sc{gdb/mi} General Design
25143 @cindex GDB/MI General Design
25145 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25146 parts---commands sent to @value{GDBN}, responses to those commands
25147 and notifications. Each command results in exactly one response,
25148 indicating either successful completion of the command, or an error.
25149 For the commands that do not resume the target, the response contains the
25150 requested information. For the commands that resume the target, the
25151 response only indicates whether the target was successfully resumed.
25152 Notifications is the mechanism for reporting changes in the state of the
25153 target, or in @value{GDBN} state, that cannot conveniently be associated with
25154 a command and reported as part of that command response.
25156 The important examples of notifications are:
25160 Exec notifications. These are used to report changes in
25161 target state---when a target is resumed, or stopped. It would not
25162 be feasible to include this information in response of resuming
25163 commands, because one resume commands can result in multiple events in
25164 different threads. Also, quite some time may pass before any event
25165 happens in the target, while a frontend needs to know whether the resuming
25166 command itself was successfully executed.
25169 Console output, and status notifications. Console output
25170 notifications are used to report output of CLI commands, as well as
25171 diagnostics for other commands. Status notifications are used to
25172 report the progress of a long-running operation. Naturally, including
25173 this information in command response would mean no output is produced
25174 until the command is finished, which is undesirable.
25177 General notifications. Commands may have various side effects on
25178 the @value{GDBN} or target state beyond their official purpose. For example,
25179 a command may change the selected thread. Although such changes can
25180 be included in command response, using notification allows for more
25181 orthogonal frontend design.
25185 There's no guarantee that whenever an MI command reports an error,
25186 @value{GDBN} or the target are in any specific state, and especially,
25187 the state is not reverted to the state before the MI command was
25188 processed. Therefore, whenever an MI command results in an error,
25189 we recommend that the frontend refreshes all the information shown in
25190 the user interface.
25194 * Context management::
25195 * Asynchronous and non-stop modes::
25199 @node Context management
25200 @subsection Context management
25202 @subsubsection Threads and Frames
25204 In most cases when @value{GDBN} accesses the target, this access is
25205 done in context of a specific thread and frame (@pxref{Frames}).
25206 Often, even when accessing global data, the target requires that a thread
25207 be specified. The CLI interface maintains the selected thread and frame,
25208 and supplies them to target on each command. This is convenient,
25209 because a command line user would not want to specify that information
25210 explicitly on each command, and because user interacts with
25211 @value{GDBN} via a single terminal, so no confusion is possible as
25212 to what thread and frame are the current ones.
25214 In the case of MI, the concept of selected thread and frame is less
25215 useful. First, a frontend can easily remember this information
25216 itself. Second, a graphical frontend can have more than one window,
25217 each one used for debugging a different thread, and the frontend might
25218 want to access additional threads for internal purposes. This
25219 increases the risk that by relying on implicitly selected thread, the
25220 frontend may be operating on a wrong one. Therefore, each MI command
25221 should explicitly specify which thread and frame to operate on. To
25222 make it possible, each MI command accepts the @samp{--thread} and
25223 @samp{--frame} options, the value to each is @value{GDBN} identifier
25224 for thread and frame to operate on.
25226 Usually, each top-level window in a frontend allows the user to select
25227 a thread and a frame, and remembers the user selection for further
25228 operations. However, in some cases @value{GDBN} may suggest that the
25229 current thread be changed. For example, when stopping on a breakpoint
25230 it is reasonable to switch to the thread where breakpoint is hit. For
25231 another example, if the user issues the CLI @samp{thread} command via
25232 the frontend, it is desirable to change the frontend's selected thread to the
25233 one specified by user. @value{GDBN} communicates the suggestion to
25234 change current thread using the @samp{=thread-selected} notification.
25235 No such notification is available for the selected frame at the moment.
25237 Note that historically, MI shares the selected thread with CLI, so
25238 frontends used the @code{-thread-select} to execute commands in the
25239 right context. However, getting this to work right is cumbersome. The
25240 simplest way is for frontend to emit @code{-thread-select} command
25241 before every command. This doubles the number of commands that need
25242 to be sent. The alternative approach is to suppress @code{-thread-select}
25243 if the selected thread in @value{GDBN} is supposed to be identical to the
25244 thread the frontend wants to operate on. However, getting this
25245 optimization right can be tricky. In particular, if the frontend
25246 sends several commands to @value{GDBN}, and one of the commands changes the
25247 selected thread, then the behaviour of subsequent commands will
25248 change. So, a frontend should either wait for response from such
25249 problematic commands, or explicitly add @code{-thread-select} for
25250 all subsequent commands. No frontend is known to do this exactly
25251 right, so it is suggested to just always pass the @samp{--thread} and
25252 @samp{--frame} options.
25254 @subsubsection Language
25256 The execution of several commands depends on which language is selected.
25257 By default, the current language (@pxref{show language}) is used.
25258 But for commands known to be language-sensitive, it is recommended
25259 to use the @samp{--language} option. This option takes one argument,
25260 which is the name of the language to use while executing the command.
25264 -data-evaluate-expression --language c "sizeof (void*)"
25269 The valid language names are the same names accepted by the
25270 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25271 @samp{local} or @samp{unknown}.
25273 @node Asynchronous and non-stop modes
25274 @subsection Asynchronous command execution and non-stop mode
25276 On some targets, @value{GDBN} is capable of processing MI commands
25277 even while the target is running. This is called @dfn{asynchronous
25278 command execution} (@pxref{Background Execution}). The frontend may
25279 specify a preferrence for asynchronous execution using the
25280 @code{-gdb-set mi-async 1} command, which should be emitted before
25281 either running the executable or attaching to the target. After the
25282 frontend has started the executable or attached to the target, it can
25283 find if asynchronous execution is enabled using the
25284 @code{-list-target-features} command.
25287 @item -gdb-set mi-async on
25288 @item -gdb-set mi-async off
25289 Set whether MI is in asynchronous mode.
25291 When @code{off}, which is the default, MI execution commands (e.g.,
25292 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25293 for the program to stop before processing further commands.
25295 When @code{on}, MI execution commands are background execution
25296 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25297 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25298 MI commands even while the target is running.
25300 @item -gdb-show mi-async
25301 Show whether MI asynchronous mode is enabled.
25304 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25305 @code{target-async} instead of @code{mi-async}, and it had the effect
25306 of both putting MI in asynchronous mode and making CLI background
25307 commands possible. CLI background commands are now always possible
25308 ``out of the box'' if the target supports them. The old spelling is
25309 kept as a deprecated alias for backwards compatibility.
25311 Even if @value{GDBN} can accept a command while target is running,
25312 many commands that access the target do not work when the target is
25313 running. Therefore, asynchronous command execution is most useful
25314 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25315 it is possible to examine the state of one thread, while other threads
25318 When a given thread is running, MI commands that try to access the
25319 target in the context of that thread may not work, or may work only on
25320 some targets. In particular, commands that try to operate on thread's
25321 stack will not work, on any target. Commands that read memory, or
25322 modify breakpoints, may work or not work, depending on the target. Note
25323 that even commands that operate on global state, such as @code{print},
25324 @code{set}, and breakpoint commands, still access the target in the
25325 context of a specific thread, so frontend should try to find a
25326 stopped thread and perform the operation on that thread (using the
25327 @samp{--thread} option).
25329 Which commands will work in the context of a running thread is
25330 highly target dependent. However, the two commands
25331 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25332 to find the state of a thread, will always work.
25334 @node Thread groups
25335 @subsection Thread groups
25336 @value{GDBN} may be used to debug several processes at the same time.
25337 On some platfroms, @value{GDBN} may support debugging of several
25338 hardware systems, each one having several cores with several different
25339 processes running on each core. This section describes the MI
25340 mechanism to support such debugging scenarios.
25342 The key observation is that regardless of the structure of the
25343 target, MI can have a global list of threads, because most commands that
25344 accept the @samp{--thread} option do not need to know what process that
25345 thread belongs to. Therefore, it is not necessary to introduce
25346 neither additional @samp{--process} option, nor an notion of the
25347 current process in the MI interface. The only strictly new feature
25348 that is required is the ability to find how the threads are grouped
25351 To allow the user to discover such grouping, and to support arbitrary
25352 hierarchy of machines/cores/processes, MI introduces the concept of a
25353 @dfn{thread group}. Thread group is a collection of threads and other
25354 thread groups. A thread group always has a string identifier, a type,
25355 and may have additional attributes specific to the type. A new
25356 command, @code{-list-thread-groups}, returns the list of top-level
25357 thread groups, which correspond to processes that @value{GDBN} is
25358 debugging at the moment. By passing an identifier of a thread group
25359 to the @code{-list-thread-groups} command, it is possible to obtain
25360 the members of specific thread group.
25362 To allow the user to easily discover processes, and other objects, he
25363 wishes to debug, a concept of @dfn{available thread group} is
25364 introduced. Available thread group is an thread group that
25365 @value{GDBN} is not debugging, but that can be attached to, using the
25366 @code{-target-attach} command. The list of available top-level thread
25367 groups can be obtained using @samp{-list-thread-groups --available}.
25368 In general, the content of a thread group may be only retrieved only
25369 after attaching to that thread group.
25371 Thread groups are related to inferiors (@pxref{Inferiors and
25372 Programs}). Each inferior corresponds to a thread group of a special
25373 type @samp{process}, and some additional operations are permitted on
25374 such thread groups.
25376 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25377 @node GDB/MI Command Syntax
25378 @section @sc{gdb/mi} Command Syntax
25381 * GDB/MI Input Syntax::
25382 * GDB/MI Output Syntax::
25385 @node GDB/MI Input Syntax
25386 @subsection @sc{gdb/mi} Input Syntax
25388 @cindex input syntax for @sc{gdb/mi}
25389 @cindex @sc{gdb/mi}, input syntax
25391 @item @var{command} @expansion{}
25392 @code{@var{cli-command} | @var{mi-command}}
25394 @item @var{cli-command} @expansion{}
25395 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25396 @var{cli-command} is any existing @value{GDBN} CLI command.
25398 @item @var{mi-command} @expansion{}
25399 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25400 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25402 @item @var{token} @expansion{}
25403 "any sequence of digits"
25405 @item @var{option} @expansion{}
25406 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25408 @item @var{parameter} @expansion{}
25409 @code{@var{non-blank-sequence} | @var{c-string}}
25411 @item @var{operation} @expansion{}
25412 @emph{any of the operations described in this chapter}
25414 @item @var{non-blank-sequence} @expansion{}
25415 @emph{anything, provided it doesn't contain special characters such as
25416 "-", @var{nl}, """ and of course " "}
25418 @item @var{c-string} @expansion{}
25419 @code{""" @var{seven-bit-iso-c-string-content} """}
25421 @item @var{nl} @expansion{}
25430 The CLI commands are still handled by the @sc{mi} interpreter; their
25431 output is described below.
25434 The @code{@var{token}}, when present, is passed back when the command
25438 Some @sc{mi} commands accept optional arguments as part of the parameter
25439 list. Each option is identified by a leading @samp{-} (dash) and may be
25440 followed by an optional argument parameter. Options occur first in the
25441 parameter list and can be delimited from normal parameters using
25442 @samp{--} (this is useful when some parameters begin with a dash).
25449 We want easy access to the existing CLI syntax (for debugging).
25452 We want it to be easy to spot a @sc{mi} operation.
25455 @node GDB/MI Output Syntax
25456 @subsection @sc{gdb/mi} Output Syntax
25458 @cindex output syntax of @sc{gdb/mi}
25459 @cindex @sc{gdb/mi}, output syntax
25460 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25461 followed, optionally, by a single result record. This result record
25462 is for the most recent command. The sequence of output records is
25463 terminated by @samp{(gdb)}.
25465 If an input command was prefixed with a @code{@var{token}} then the
25466 corresponding output for that command will also be prefixed by that same
25470 @item @var{output} @expansion{}
25471 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25473 @item @var{result-record} @expansion{}
25474 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25476 @item @var{out-of-band-record} @expansion{}
25477 @code{@var{async-record} | @var{stream-record}}
25479 @item @var{async-record} @expansion{}
25480 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25482 @item @var{exec-async-output} @expansion{}
25483 @code{[ @var{token} ] "*" @var{async-output nl}}
25485 @item @var{status-async-output} @expansion{}
25486 @code{[ @var{token} ] "+" @var{async-output nl}}
25488 @item @var{notify-async-output} @expansion{}
25489 @code{[ @var{token} ] "=" @var{async-output nl}}
25491 @item @var{async-output} @expansion{}
25492 @code{@var{async-class} ( "," @var{result} )*}
25494 @item @var{result-class} @expansion{}
25495 @code{"done" | "running" | "connected" | "error" | "exit"}
25497 @item @var{async-class} @expansion{}
25498 @code{"stopped" | @var{others}} (where @var{others} will be added
25499 depending on the needs---this is still in development).
25501 @item @var{result} @expansion{}
25502 @code{ @var{variable} "=" @var{value}}
25504 @item @var{variable} @expansion{}
25505 @code{ @var{string} }
25507 @item @var{value} @expansion{}
25508 @code{ @var{const} | @var{tuple} | @var{list} }
25510 @item @var{const} @expansion{}
25511 @code{@var{c-string}}
25513 @item @var{tuple} @expansion{}
25514 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25516 @item @var{list} @expansion{}
25517 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25518 @var{result} ( "," @var{result} )* "]" }
25520 @item @var{stream-record} @expansion{}
25521 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25523 @item @var{console-stream-output} @expansion{}
25524 @code{"~" @var{c-string nl}}
25526 @item @var{target-stream-output} @expansion{}
25527 @code{"@@" @var{c-string nl}}
25529 @item @var{log-stream-output} @expansion{}
25530 @code{"&" @var{c-string nl}}
25532 @item @var{nl} @expansion{}
25535 @item @var{token} @expansion{}
25536 @emph{any sequence of digits}.
25544 All output sequences end in a single line containing a period.
25547 The @code{@var{token}} is from the corresponding request. Note that
25548 for all async output, while the token is allowed by the grammar and
25549 may be output by future versions of @value{GDBN} for select async
25550 output messages, it is generally omitted. Frontends should treat
25551 all async output as reporting general changes in the state of the
25552 target and there should be no need to associate async output to any
25556 @cindex status output in @sc{gdb/mi}
25557 @var{status-async-output} contains on-going status information about the
25558 progress of a slow operation. It can be discarded. All status output is
25559 prefixed by @samp{+}.
25562 @cindex async output in @sc{gdb/mi}
25563 @var{exec-async-output} contains asynchronous state change on the target
25564 (stopped, started, disappeared). All async output is prefixed by
25568 @cindex notify output in @sc{gdb/mi}
25569 @var{notify-async-output} contains supplementary information that the
25570 client should handle (e.g., a new breakpoint information). All notify
25571 output is prefixed by @samp{=}.
25574 @cindex console output in @sc{gdb/mi}
25575 @var{console-stream-output} is output that should be displayed as is in the
25576 console. It is the textual response to a CLI command. All the console
25577 output is prefixed by @samp{~}.
25580 @cindex target output in @sc{gdb/mi}
25581 @var{target-stream-output} is the output produced by the target program.
25582 All the target output is prefixed by @samp{@@}.
25585 @cindex log output in @sc{gdb/mi}
25586 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25587 instance messages that should be displayed as part of an error log. All
25588 the log output is prefixed by @samp{&}.
25591 @cindex list output in @sc{gdb/mi}
25592 New @sc{gdb/mi} commands should only output @var{lists} containing
25598 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25599 details about the various output records.
25601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25602 @node GDB/MI Compatibility with CLI
25603 @section @sc{gdb/mi} Compatibility with CLI
25605 @cindex compatibility, @sc{gdb/mi} and CLI
25606 @cindex @sc{gdb/mi}, compatibility with CLI
25608 For the developers convenience CLI commands can be entered directly,
25609 but there may be some unexpected behaviour. For example, commands
25610 that query the user will behave as if the user replied yes, breakpoint
25611 command lists are not executed and some CLI commands, such as
25612 @code{if}, @code{when} and @code{define}, prompt for further input with
25613 @samp{>}, which is not valid MI output.
25615 This feature may be removed at some stage in the future and it is
25616 recommended that front ends use the @code{-interpreter-exec} command
25617 (@pxref{-interpreter-exec}).
25619 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25620 @node GDB/MI Development and Front Ends
25621 @section @sc{gdb/mi} Development and Front Ends
25622 @cindex @sc{gdb/mi} development
25624 The application which takes the MI output and presents the state of the
25625 program being debugged to the user is called a @dfn{front end}.
25627 Although @sc{gdb/mi} is still incomplete, it is currently being used
25628 by a variety of front ends to @value{GDBN}. This makes it difficult
25629 to introduce new functionality without breaking existing usage. This
25630 section tries to minimize the problems by describing how the protocol
25633 Some changes in MI need not break a carefully designed front end, and
25634 for these the MI version will remain unchanged. The following is a
25635 list of changes that may occur within one level, so front ends should
25636 parse MI output in a way that can handle them:
25640 New MI commands may be added.
25643 New fields may be added to the output of any MI command.
25646 The range of values for fields with specified values, e.g.,
25647 @code{in_scope} (@pxref{-var-update}) may be extended.
25649 @c The format of field's content e.g type prefix, may change so parse it
25650 @c at your own risk. Yes, in general?
25652 @c The order of fields may change? Shouldn't really matter but it might
25653 @c resolve inconsistencies.
25656 If the changes are likely to break front ends, the MI version level
25657 will be increased by one. This will allow the front end to parse the
25658 output according to the MI version. Apart from mi0, new versions of
25659 @value{GDBN} will not support old versions of MI and it will be the
25660 responsibility of the front end to work with the new one.
25662 @c Starting with mi3, add a new command -mi-version that prints the MI
25665 The best way to avoid unexpected changes in MI that might break your front
25666 end is to make your project known to @value{GDBN} developers and
25667 follow development on @email{gdb@@sourceware.org} and
25668 @email{gdb-patches@@sourceware.org}.
25669 @cindex mailing lists
25671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25672 @node GDB/MI Output Records
25673 @section @sc{gdb/mi} Output Records
25676 * GDB/MI Result Records::
25677 * GDB/MI Stream Records::
25678 * GDB/MI Async Records::
25679 * GDB/MI Breakpoint Information::
25680 * GDB/MI Frame Information::
25681 * GDB/MI Thread Information::
25682 * GDB/MI Ada Exception Information::
25685 @node GDB/MI Result Records
25686 @subsection @sc{gdb/mi} Result Records
25688 @cindex result records in @sc{gdb/mi}
25689 @cindex @sc{gdb/mi}, result records
25690 In addition to a number of out-of-band notifications, the response to a
25691 @sc{gdb/mi} command includes one of the following result indications:
25695 @item "^done" [ "," @var{results} ]
25696 The synchronous operation was successful, @code{@var{results}} are the return
25701 This result record is equivalent to @samp{^done}. Historically, it
25702 was output instead of @samp{^done} if the command has resumed the
25703 target. This behaviour is maintained for backward compatibility, but
25704 all frontends should treat @samp{^done} and @samp{^running}
25705 identically and rely on the @samp{*running} output record to determine
25706 which threads are resumed.
25710 @value{GDBN} has connected to a remote target.
25712 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25714 The operation failed. The @code{msg=@var{c-string}} variable contains
25715 the corresponding error message.
25717 If present, the @code{code=@var{c-string}} variable provides an error
25718 code on which consumers can rely on to detect the corresponding
25719 error condition. At present, only one error code is defined:
25722 @item "undefined-command"
25723 Indicates that the command causing the error does not exist.
25728 @value{GDBN} has terminated.
25732 @node GDB/MI Stream Records
25733 @subsection @sc{gdb/mi} Stream Records
25735 @cindex @sc{gdb/mi}, stream records
25736 @cindex stream records in @sc{gdb/mi}
25737 @value{GDBN} internally maintains a number of output streams: the console, the
25738 target, and the log. The output intended for each of these streams is
25739 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25741 Each stream record begins with a unique @dfn{prefix character} which
25742 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25743 Syntax}). In addition to the prefix, each stream record contains a
25744 @code{@var{string-output}}. This is either raw text (with an implicit new
25745 line) or a quoted C string (which does not contain an implicit newline).
25748 @item "~" @var{string-output}
25749 The console output stream contains text that should be displayed in the
25750 CLI console window. It contains the textual responses to CLI commands.
25752 @item "@@" @var{string-output}
25753 The target output stream contains any textual output from the running
25754 target. This is only present when GDB's event loop is truly
25755 asynchronous, which is currently only the case for remote targets.
25757 @item "&" @var{string-output}
25758 The log stream contains debugging messages being produced by @value{GDBN}'s
25762 @node GDB/MI Async Records
25763 @subsection @sc{gdb/mi} Async Records
25765 @cindex async records in @sc{gdb/mi}
25766 @cindex @sc{gdb/mi}, async records
25767 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25768 additional changes that have occurred. Those changes can either be a
25769 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25770 target activity (e.g., target stopped).
25772 The following is the list of possible async records:
25776 @item *running,thread-id="@var{thread}"
25777 The target is now running. The @var{thread} field tells which
25778 specific thread is now running, and can be @samp{all} if all threads
25779 are running. The frontend should assume that no interaction with a
25780 running thread is possible after this notification is produced.
25781 The frontend should not assume that this notification is output
25782 only once for any command. @value{GDBN} may emit this notification
25783 several times, either for different threads, because it cannot resume
25784 all threads together, or even for a single thread, if the thread must
25785 be stepped though some code before letting it run freely.
25787 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25788 The target has stopped. The @var{reason} field can have one of the
25792 @item breakpoint-hit
25793 A breakpoint was reached.
25794 @item watchpoint-trigger
25795 A watchpoint was triggered.
25796 @item read-watchpoint-trigger
25797 A read watchpoint was triggered.
25798 @item access-watchpoint-trigger
25799 An access watchpoint was triggered.
25800 @item function-finished
25801 An -exec-finish or similar CLI command was accomplished.
25802 @item location-reached
25803 An -exec-until or similar CLI command was accomplished.
25804 @item watchpoint-scope
25805 A watchpoint has gone out of scope.
25806 @item end-stepping-range
25807 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25808 similar CLI command was accomplished.
25809 @item exited-signalled
25810 The inferior exited because of a signal.
25812 The inferior exited.
25813 @item exited-normally
25814 The inferior exited normally.
25815 @item signal-received
25816 A signal was received by the inferior.
25818 The inferior has stopped due to a library being loaded or unloaded.
25819 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25820 set or when a @code{catch load} or @code{catch unload} catchpoint is
25821 in use (@pxref{Set Catchpoints}).
25823 The inferior has forked. This is reported when @code{catch fork}
25824 (@pxref{Set Catchpoints}) has been used.
25826 The inferior has vforked. This is reported in when @code{catch vfork}
25827 (@pxref{Set Catchpoints}) has been used.
25828 @item syscall-entry
25829 The inferior entered a system call. This is reported when @code{catch
25830 syscall} (@pxref{Set Catchpoints}) has been used.
25831 @item syscall-return
25832 The inferior returned from a system call. This is reported when
25833 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25835 The inferior called @code{exec}. This is reported when @code{catch exec}
25836 (@pxref{Set Catchpoints}) has been used.
25839 The @var{id} field identifies the thread that directly caused the stop
25840 -- for example by hitting a breakpoint. Depending on whether all-stop
25841 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25842 stop all threads, or only the thread that directly triggered the stop.
25843 If all threads are stopped, the @var{stopped} field will have the
25844 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25845 field will be a list of thread identifiers. Presently, this list will
25846 always include a single thread, but frontend should be prepared to see
25847 several threads in the list. The @var{core} field reports the
25848 processor core on which the stop event has happened. This field may be absent
25849 if such information is not available.
25851 @item =thread-group-added,id="@var{id}"
25852 @itemx =thread-group-removed,id="@var{id}"
25853 A thread group was either added or removed. The @var{id} field
25854 contains the @value{GDBN} identifier of the thread group. When a thread
25855 group is added, it generally might not be associated with a running
25856 process. When a thread group is removed, its id becomes invalid and
25857 cannot be used in any way.
25859 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25860 A thread group became associated with a running program,
25861 either because the program was just started or the thread group
25862 was attached to a program. The @var{id} field contains the
25863 @value{GDBN} identifier of the thread group. The @var{pid} field
25864 contains process identifier, specific to the operating system.
25866 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25867 A thread group is no longer associated with a running program,
25868 either because the program has exited, or because it was detached
25869 from. The @var{id} field contains the @value{GDBN} identifier of the
25870 thread group. The @var{code} field is the exit code of the inferior; it exists
25871 only when the inferior exited with some code.
25873 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25874 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25875 A thread either was created, or has exited. The @var{id} field
25876 contains the @value{GDBN} identifier of the thread. The @var{gid}
25877 field identifies the thread group this thread belongs to.
25879 @item =thread-selected,id="@var{id}"
25880 Informs that the selected thread was changed as result of the last
25881 command. This notification is not emitted as result of @code{-thread-select}
25882 command but is emitted whenever an MI command that is not documented
25883 to change the selected thread actually changes it. In particular,
25884 invoking, directly or indirectly (via user-defined command), the CLI
25885 @code{thread} command, will generate this notification.
25887 We suggest that in response to this notification, front ends
25888 highlight the selected thread and cause subsequent commands to apply to
25891 @item =library-loaded,...
25892 Reports that a new library file was loaded by the program. This
25893 notification has 4 fields---@var{id}, @var{target-name},
25894 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25895 opaque identifier of the library. For remote debugging case,
25896 @var{target-name} and @var{host-name} fields give the name of the
25897 library file on the target, and on the host respectively. For native
25898 debugging, both those fields have the same value. The
25899 @var{symbols-loaded} field is emitted only for backward compatibility
25900 and should not be relied on to convey any useful information. The
25901 @var{thread-group} field, if present, specifies the id of the thread
25902 group in whose context the library was loaded. If the field is
25903 absent, it means the library was loaded in the context of all present
25906 @item =library-unloaded,...
25907 Reports that a library was unloaded by the program. This notification
25908 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25909 the same meaning as for the @code{=library-loaded} notification.
25910 The @var{thread-group} field, if present, specifies the id of the
25911 thread group in whose context the library was unloaded. If the field is
25912 absent, it means the library was unloaded in the context of all present
25915 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25916 @itemx =traceframe-changed,end
25917 Reports that the trace frame was changed and its new number is
25918 @var{tfnum}. The number of the tracepoint associated with this trace
25919 frame is @var{tpnum}.
25921 @item =tsv-created,name=@var{name},initial=@var{initial}
25922 Reports that the new trace state variable @var{name} is created with
25923 initial value @var{initial}.
25925 @item =tsv-deleted,name=@var{name}
25926 @itemx =tsv-deleted
25927 Reports that the trace state variable @var{name} is deleted or all
25928 trace state variables are deleted.
25930 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25931 Reports that the trace state variable @var{name} is modified with
25932 the initial value @var{initial}. The current value @var{current} of
25933 trace state variable is optional and is reported if the current
25934 value of trace state variable is known.
25936 @item =breakpoint-created,bkpt=@{...@}
25937 @itemx =breakpoint-modified,bkpt=@{...@}
25938 @itemx =breakpoint-deleted,id=@var{number}
25939 Reports that a breakpoint was created, modified, or deleted,
25940 respectively. Only user-visible breakpoints are reported to the MI
25943 The @var{bkpt} argument is of the same form as returned by the various
25944 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25945 @var{number} is the ordinal number of the breakpoint.
25947 Note that if a breakpoint is emitted in the result record of a
25948 command, then it will not also be emitted in an async record.
25950 @item =record-started,thread-group="@var{id}"
25951 @itemx =record-stopped,thread-group="@var{id}"
25952 Execution log recording was either started or stopped on an
25953 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25954 group corresponding to the affected inferior.
25956 @item =cmd-param-changed,param=@var{param},value=@var{value}
25957 Reports that a parameter of the command @code{set @var{param}} is
25958 changed to @var{value}. In the multi-word @code{set} command,
25959 the @var{param} is the whole parameter list to @code{set} command.
25960 For example, In command @code{set check type on}, @var{param}
25961 is @code{check type} and @var{value} is @code{on}.
25963 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25964 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25965 written in an inferior. The @var{id} is the identifier of the
25966 thread group corresponding to the affected inferior. The optional
25967 @code{type="code"} part is reported if the memory written to holds
25971 @node GDB/MI Breakpoint Information
25972 @subsection @sc{gdb/mi} Breakpoint Information
25974 When @value{GDBN} reports information about a breakpoint, a
25975 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25980 The breakpoint number. For a breakpoint that represents one location
25981 of a multi-location breakpoint, this will be a dotted pair, like
25985 The type of the breakpoint. For ordinary breakpoints this will be
25986 @samp{breakpoint}, but many values are possible.
25989 If the type of the breakpoint is @samp{catchpoint}, then this
25990 indicates the exact type of catchpoint.
25993 This is the breakpoint disposition---either @samp{del}, meaning that
25994 the breakpoint will be deleted at the next stop, or @samp{keep},
25995 meaning that the breakpoint will not be deleted.
25998 This indicates whether the breakpoint is enabled, in which case the
25999 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26000 Note that this is not the same as the field @code{enable}.
26003 The address of the breakpoint. This may be a hexidecimal number,
26004 giving the address; or the string @samp{<PENDING>}, for a pending
26005 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26006 multiple locations. This field will not be present if no address can
26007 be determined. For example, a watchpoint does not have an address.
26010 If known, the function in which the breakpoint appears.
26011 If not known, this field is not present.
26014 The name of the source file which contains this function, if known.
26015 If not known, this field is not present.
26018 The full file name of the source file which contains this function, if
26019 known. If not known, this field is not present.
26022 The line number at which this breakpoint appears, if known.
26023 If not known, this field is not present.
26026 If the source file is not known, this field may be provided. If
26027 provided, this holds the address of the breakpoint, possibly followed
26031 If this breakpoint is pending, this field is present and holds the
26032 text used to set the breakpoint, as entered by the user.
26035 Where this breakpoint's condition is evaluated, either @samp{host} or
26039 If this is a thread-specific breakpoint, then this identifies the
26040 thread in which the breakpoint can trigger.
26043 If this breakpoint is restricted to a particular Ada task, then this
26044 field will hold the task identifier.
26047 If the breakpoint is conditional, this is the condition expression.
26050 The ignore count of the breakpoint.
26053 The enable count of the breakpoint.
26055 @item traceframe-usage
26058 @item static-tracepoint-marker-string-id
26059 For a static tracepoint, the name of the static tracepoint marker.
26062 For a masked watchpoint, this is the mask.
26065 A tracepoint's pass count.
26067 @item original-location
26068 The location of the breakpoint as originally specified by the user.
26069 This field is optional.
26072 The number of times the breakpoint has been hit.
26075 This field is only given for tracepoints. This is either @samp{y},
26076 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26080 Some extra data, the exact contents of which are type-dependent.
26084 For example, here is what the output of @code{-break-insert}
26085 (@pxref{GDB/MI Breakpoint Commands}) might be:
26088 -> -break-insert main
26089 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26090 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26091 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26096 @node GDB/MI Frame Information
26097 @subsection @sc{gdb/mi} Frame Information
26099 Response from many MI commands includes an information about stack
26100 frame. This information is a tuple that may have the following
26105 The level of the stack frame. The innermost frame has the level of
26106 zero. This field is always present.
26109 The name of the function corresponding to the frame. This field may
26110 be absent if @value{GDBN} is unable to determine the function name.
26113 The code address for the frame. This field is always present.
26116 The name of the source files that correspond to the frame's code
26117 address. This field may be absent.
26120 The source line corresponding to the frames' code address. This field
26124 The name of the binary file (either executable or shared library) the
26125 corresponds to the frame's code address. This field may be absent.
26129 @node GDB/MI Thread Information
26130 @subsection @sc{gdb/mi} Thread Information
26132 Whenever @value{GDBN} has to report an information about a thread, it
26133 uses a tuple with the following fields:
26137 The numeric id assigned to the thread by @value{GDBN}. This field is
26141 Target-specific string identifying the thread. This field is always present.
26144 Additional information about the thread provided by the target.
26145 It is supposed to be human-readable and not interpreted by the
26146 frontend. This field is optional.
26149 Either @samp{stopped} or @samp{running}, depending on whether the
26150 thread is presently running. This field is always present.
26153 The value of this field is an integer number of the processor core the
26154 thread was last seen on. This field is optional.
26157 @node GDB/MI Ada Exception Information
26158 @subsection @sc{gdb/mi} Ada Exception Information
26160 Whenever a @code{*stopped} record is emitted because the program
26161 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26162 @value{GDBN} provides the name of the exception that was raised via
26163 the @code{exception-name} field.
26165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26166 @node GDB/MI Simple Examples
26167 @section Simple Examples of @sc{gdb/mi} Interaction
26168 @cindex @sc{gdb/mi}, simple examples
26170 This subsection presents several simple examples of interaction using
26171 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26172 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26173 the output received from @sc{gdb/mi}.
26175 Note the line breaks shown in the examples are here only for
26176 readability, they don't appear in the real output.
26178 @subheading Setting a Breakpoint
26180 Setting a breakpoint generates synchronous output which contains detailed
26181 information of the breakpoint.
26184 -> -break-insert main
26185 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26186 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26187 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26192 @subheading Program Execution
26194 Program execution generates asynchronous records and MI gives the
26195 reason that execution stopped.
26201 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26202 frame=@{addr="0x08048564",func="main",
26203 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26204 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26209 <- *stopped,reason="exited-normally"
26213 @subheading Quitting @value{GDBN}
26215 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26223 Please note that @samp{^exit} is printed immediately, but it might
26224 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26225 performs necessary cleanups, including killing programs being debugged
26226 or disconnecting from debug hardware, so the frontend should wait till
26227 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26228 fails to exit in reasonable time.
26230 @subheading A Bad Command
26232 Here's what happens if you pass a non-existent command:
26236 <- ^error,msg="Undefined MI command: rubbish"
26241 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26242 @node GDB/MI Command Description Format
26243 @section @sc{gdb/mi} Command Description Format
26245 The remaining sections describe blocks of commands. Each block of
26246 commands is laid out in a fashion similar to this section.
26248 @subheading Motivation
26250 The motivation for this collection of commands.
26252 @subheading Introduction
26254 A brief introduction to this collection of commands as a whole.
26256 @subheading Commands
26258 For each command in the block, the following is described:
26260 @subsubheading Synopsis
26263 -command @var{args}@dots{}
26266 @subsubheading Result
26268 @subsubheading @value{GDBN} Command
26270 The corresponding @value{GDBN} CLI command(s), if any.
26272 @subsubheading Example
26274 Example(s) formatted for readability. Some of the described commands have
26275 not been implemented yet and these are labeled N.A.@: (not available).
26278 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26279 @node GDB/MI Breakpoint Commands
26280 @section @sc{gdb/mi} Breakpoint Commands
26282 @cindex breakpoint commands for @sc{gdb/mi}
26283 @cindex @sc{gdb/mi}, breakpoint commands
26284 This section documents @sc{gdb/mi} commands for manipulating
26287 @subheading The @code{-break-after} Command
26288 @findex -break-after
26290 @subsubheading Synopsis
26293 -break-after @var{number} @var{count}
26296 The breakpoint number @var{number} is not in effect until it has been
26297 hit @var{count} times. To see how this is reflected in the output of
26298 the @samp{-break-list} command, see the description of the
26299 @samp{-break-list} command below.
26301 @subsubheading @value{GDBN} Command
26303 The corresponding @value{GDBN} command is @samp{ignore}.
26305 @subsubheading Example
26310 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26311 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26312 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26320 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26321 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26322 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26323 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26324 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26325 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26326 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26327 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26328 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26329 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26334 @subheading The @code{-break-catch} Command
26335 @findex -break-catch
26338 @subheading The @code{-break-commands} Command
26339 @findex -break-commands
26341 @subsubheading Synopsis
26344 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26347 Specifies the CLI commands that should be executed when breakpoint
26348 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26349 are the commands. If no command is specified, any previously-set
26350 commands are cleared. @xref{Break Commands}. Typical use of this
26351 functionality is tracing a program, that is, printing of values of
26352 some variables whenever breakpoint is hit and then continuing.
26354 @subsubheading @value{GDBN} Command
26356 The corresponding @value{GDBN} command is @samp{commands}.
26358 @subsubheading Example
26363 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26364 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26365 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26368 -break-commands 1 "print v" "continue"
26373 @subheading The @code{-break-condition} Command
26374 @findex -break-condition
26376 @subsubheading Synopsis
26379 -break-condition @var{number} @var{expr}
26382 Breakpoint @var{number} will stop the program only if the condition in
26383 @var{expr} is true. The condition becomes part of the
26384 @samp{-break-list} output (see the description of the @samp{-break-list}
26387 @subsubheading @value{GDBN} Command
26389 The corresponding @value{GDBN} command is @samp{condition}.
26391 @subsubheading Example
26395 -break-condition 1 1
26399 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26400 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26401 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26402 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26403 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26404 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26405 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26406 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26407 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26408 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26412 @subheading The @code{-break-delete} Command
26413 @findex -break-delete
26415 @subsubheading Synopsis
26418 -break-delete ( @var{breakpoint} )+
26421 Delete the breakpoint(s) whose number(s) are specified in the argument
26422 list. This is obviously reflected in the breakpoint list.
26424 @subsubheading @value{GDBN} Command
26426 The corresponding @value{GDBN} command is @samp{delete}.
26428 @subsubheading Example
26436 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26437 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26438 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26439 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26440 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26441 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26442 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26447 @subheading The @code{-break-disable} Command
26448 @findex -break-disable
26450 @subsubheading Synopsis
26453 -break-disable ( @var{breakpoint} )+
26456 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26457 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26459 @subsubheading @value{GDBN} Command
26461 The corresponding @value{GDBN} command is @samp{disable}.
26463 @subsubheading Example
26471 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26478 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26479 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26480 line="5",thread-groups=["i1"],times="0"@}]@}
26484 @subheading The @code{-break-enable} Command
26485 @findex -break-enable
26487 @subsubheading Synopsis
26490 -break-enable ( @var{breakpoint} )+
26493 Enable (previously disabled) @var{breakpoint}(s).
26495 @subsubheading @value{GDBN} Command
26497 The corresponding @value{GDBN} command is @samp{enable}.
26499 @subsubheading Example
26507 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26508 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26509 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26510 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26511 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26512 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26513 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26514 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26515 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26516 line="5",thread-groups=["i1"],times="0"@}]@}
26520 @subheading The @code{-break-info} Command
26521 @findex -break-info
26523 @subsubheading Synopsis
26526 -break-info @var{breakpoint}
26530 Get information about a single breakpoint.
26532 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26533 Information}, for details on the format of each breakpoint in the
26536 @subsubheading @value{GDBN} Command
26538 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26540 @subsubheading Example
26543 @subheading The @code{-break-insert} Command
26544 @findex -break-insert
26546 @subsubheading Synopsis
26549 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26550 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26551 [ -p @var{thread-id} ] [ @var{location} ]
26555 If specified, @var{location}, can be one of:
26562 @item filename:linenum
26563 @item filename:function
26567 The possible optional parameters of this command are:
26571 Insert a temporary breakpoint.
26573 Insert a hardware breakpoint.
26575 If @var{location} cannot be parsed (for example if it
26576 refers to unknown files or functions), create a pending
26577 breakpoint. Without this flag, @value{GDBN} will report
26578 an error, and won't create a breakpoint, if @var{location}
26581 Create a disabled breakpoint.
26583 Create a tracepoint. @xref{Tracepoints}. When this parameter
26584 is used together with @samp{-h}, a fast tracepoint is created.
26585 @item -c @var{condition}
26586 Make the breakpoint conditional on @var{condition}.
26587 @item -i @var{ignore-count}
26588 Initialize the @var{ignore-count}.
26589 @item -p @var{thread-id}
26590 Restrict the breakpoint to the specified @var{thread-id}.
26593 @subsubheading Result
26595 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26596 resulting breakpoint.
26598 Note: this format is open to change.
26599 @c An out-of-band breakpoint instead of part of the result?
26601 @subsubheading @value{GDBN} Command
26603 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26604 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26606 @subsubheading Example
26611 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26612 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26615 -break-insert -t foo
26616 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26617 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26621 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26622 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26623 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26624 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26625 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26626 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26627 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26628 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26629 addr="0x0001072c", func="main",file="recursive2.c",
26630 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26632 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26633 addr="0x00010774",func="foo",file="recursive2.c",
26634 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26637 @c -break-insert -r foo.*
26638 @c ~int foo(int, int);
26639 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26640 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26645 @subheading The @code{-dprintf-insert} Command
26646 @findex -dprintf-insert
26648 @subsubheading Synopsis
26651 -dprintf-insert [ -t ] [ -f ] [ -d ]
26652 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26653 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26658 If specified, @var{location}, can be one of:
26661 @item @var{function}
26664 @c @item @var{linenum}
26665 @item @var{filename}:@var{linenum}
26666 @item @var{filename}:function
26667 @item *@var{address}
26670 The possible optional parameters of this command are:
26674 Insert a temporary breakpoint.
26676 If @var{location} cannot be parsed (for example, if it
26677 refers to unknown files or functions), create a pending
26678 breakpoint. Without this flag, @value{GDBN} will report
26679 an error, and won't create a breakpoint, if @var{location}
26682 Create a disabled breakpoint.
26683 @item -c @var{condition}
26684 Make the breakpoint conditional on @var{condition}.
26685 @item -i @var{ignore-count}
26686 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26687 to @var{ignore-count}.
26688 @item -p @var{thread-id}
26689 Restrict the breakpoint to the specified @var{thread-id}.
26692 @subsubheading Result
26694 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26695 resulting breakpoint.
26697 @c An out-of-band breakpoint instead of part of the result?
26699 @subsubheading @value{GDBN} Command
26701 The corresponding @value{GDBN} command is @samp{dprintf}.
26703 @subsubheading Example
26707 4-dprintf-insert foo "At foo entry\n"
26708 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26709 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26710 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26711 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26712 original-location="foo"@}
26714 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26715 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26716 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26717 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26718 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26719 original-location="mi-dprintf.c:26"@}
26723 @subheading The @code{-break-list} Command
26724 @findex -break-list
26726 @subsubheading Synopsis
26732 Displays the list of inserted breakpoints, showing the following fields:
26736 number of the breakpoint
26738 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26740 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26743 is the breakpoint enabled or no: @samp{y} or @samp{n}
26745 memory location at which the breakpoint is set
26747 logical location of the breakpoint, expressed by function name, file
26749 @item Thread-groups
26750 list of thread groups to which this breakpoint applies
26752 number of times the breakpoint has been hit
26755 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26756 @code{body} field is an empty list.
26758 @subsubheading @value{GDBN} Command
26760 The corresponding @value{GDBN} command is @samp{info break}.
26762 @subsubheading Example
26767 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26768 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26769 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26770 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26771 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26772 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26773 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26774 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26775 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26777 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26778 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26779 line="13",thread-groups=["i1"],times="0"@}]@}
26783 Here's an example of the result when there are no breakpoints:
26788 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26789 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26790 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26791 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26792 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26793 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26794 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26799 @subheading The @code{-break-passcount} Command
26800 @findex -break-passcount
26802 @subsubheading Synopsis
26805 -break-passcount @var{tracepoint-number} @var{passcount}
26808 Set the passcount for tracepoint @var{tracepoint-number} to
26809 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26810 is not a tracepoint, error is emitted. This corresponds to CLI
26811 command @samp{passcount}.
26813 @subheading The @code{-break-watch} Command
26814 @findex -break-watch
26816 @subsubheading Synopsis
26819 -break-watch [ -a | -r ]
26822 Create a watchpoint. With the @samp{-a} option it will create an
26823 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26824 read from or on a write to the memory location. With the @samp{-r}
26825 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26826 trigger only when the memory location is accessed for reading. Without
26827 either of the options, the watchpoint created is a regular watchpoint,
26828 i.e., it will trigger when the memory location is accessed for writing.
26829 @xref{Set Watchpoints, , Setting Watchpoints}.
26831 Note that @samp{-break-list} will report a single list of watchpoints and
26832 breakpoints inserted.
26834 @subsubheading @value{GDBN} Command
26836 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26839 @subsubheading Example
26841 Setting a watchpoint on a variable in the @code{main} function:
26846 ^done,wpt=@{number="2",exp="x"@}
26851 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26852 value=@{old="-268439212",new="55"@},
26853 frame=@{func="main",args=[],file="recursive2.c",
26854 fullname="/home/foo/bar/recursive2.c",line="5"@}
26858 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26859 the program execution twice: first for the variable changing value, then
26860 for the watchpoint going out of scope.
26865 ^done,wpt=@{number="5",exp="C"@}
26870 *stopped,reason="watchpoint-trigger",
26871 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26872 frame=@{func="callee4",args=[],
26873 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26874 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26879 *stopped,reason="watchpoint-scope",wpnum="5",
26880 frame=@{func="callee3",args=[@{name="strarg",
26881 value="0x11940 \"A string argument.\""@}],
26882 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26883 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26887 Listing breakpoints and watchpoints, at different points in the program
26888 execution. Note that once the watchpoint goes out of scope, it is
26894 ^done,wpt=@{number="2",exp="C"@}
26897 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26898 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26899 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26900 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26901 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26902 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26903 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26904 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26905 addr="0x00010734",func="callee4",
26906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26907 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26909 bkpt=@{number="2",type="watchpoint",disp="keep",
26910 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26915 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26916 value=@{old="-276895068",new="3"@},
26917 frame=@{func="callee4",args=[],
26918 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26919 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26922 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26929 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26930 addr="0x00010734",func="callee4",
26931 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26932 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26934 bkpt=@{number="2",type="watchpoint",disp="keep",
26935 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26939 ^done,reason="watchpoint-scope",wpnum="2",
26940 frame=@{func="callee3",args=[@{name="strarg",
26941 value="0x11940 \"A string argument.\""@}],
26942 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26943 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26946 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26947 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26948 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26949 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26950 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26951 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26952 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26953 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26954 addr="0x00010734",func="callee4",
26955 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26956 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26957 thread-groups=["i1"],times="1"@}]@}
26962 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26963 @node GDB/MI Catchpoint Commands
26964 @section @sc{gdb/mi} Catchpoint Commands
26966 This section documents @sc{gdb/mi} commands for manipulating
26970 * Shared Library GDB/MI Catchpoint Commands::
26971 * Ada Exception GDB/MI Catchpoint Commands::
26974 @node Shared Library GDB/MI Catchpoint Commands
26975 @subsection Shared Library @sc{gdb/mi} Catchpoints
26977 @subheading The @code{-catch-load} Command
26978 @findex -catch-load
26980 @subsubheading Synopsis
26983 -catch-load [ -t ] [ -d ] @var{regexp}
26986 Add a catchpoint for library load events. If the @samp{-t} option is used,
26987 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26988 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26989 in a disabled state. The @samp{regexp} argument is a regular
26990 expression used to match the name of the loaded library.
26993 @subsubheading @value{GDBN} Command
26995 The corresponding @value{GDBN} command is @samp{catch load}.
26997 @subsubheading Example
27000 -catch-load -t foo.so
27001 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27002 what="load of library matching foo.so",catch-type="load",times="0"@}
27007 @subheading The @code{-catch-unload} Command
27008 @findex -catch-unload
27010 @subsubheading Synopsis
27013 -catch-unload [ -t ] [ -d ] @var{regexp}
27016 Add a catchpoint for library unload events. If the @samp{-t} option is
27017 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27018 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27019 created in a disabled state. The @samp{regexp} argument is a regular
27020 expression used to match the name of the unloaded library.
27022 @subsubheading @value{GDBN} Command
27024 The corresponding @value{GDBN} command is @samp{catch unload}.
27026 @subsubheading Example
27029 -catch-unload -d bar.so
27030 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27031 what="load of library matching bar.so",catch-type="unload",times="0"@}
27035 @node Ada Exception GDB/MI Catchpoint Commands
27036 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27038 The following @sc{gdb/mi} commands can be used to create catchpoints
27039 that stop the execution when Ada exceptions are being raised.
27041 @subheading The @code{-catch-assert} Command
27042 @findex -catch-assert
27044 @subsubheading Synopsis
27047 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27050 Add a catchpoint for failed Ada assertions.
27052 The possible optional parameters for this command are:
27055 @item -c @var{condition}
27056 Make the catchpoint conditional on @var{condition}.
27058 Create a disabled catchpoint.
27060 Create a temporary catchpoint.
27063 @subsubheading @value{GDBN} Command
27065 The corresponding @value{GDBN} command is @samp{catch assert}.
27067 @subsubheading Example
27071 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27072 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27073 thread-groups=["i1"],times="0",
27074 original-location="__gnat_debug_raise_assert_failure"@}
27078 @subheading The @code{-catch-exception} Command
27079 @findex -catch-exception
27081 @subsubheading Synopsis
27084 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27088 Add a catchpoint stopping when Ada exceptions are raised.
27089 By default, the command stops the program when any Ada exception
27090 gets raised. But it is also possible, by using some of the
27091 optional parameters described below, to create more selective
27094 The possible optional parameters for this command are:
27097 @item -c @var{condition}
27098 Make the catchpoint conditional on @var{condition}.
27100 Create a disabled catchpoint.
27101 @item -e @var{exception-name}
27102 Only stop when @var{exception-name} is raised. This option cannot
27103 be used combined with @samp{-u}.
27105 Create a temporary catchpoint.
27107 Stop only when an unhandled exception gets raised. This option
27108 cannot be used combined with @samp{-e}.
27111 @subsubheading @value{GDBN} Command
27113 The corresponding @value{GDBN} commands are @samp{catch exception}
27114 and @samp{catch exception unhandled}.
27116 @subsubheading Example
27119 -catch-exception -e Program_Error
27120 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27121 enabled="y",addr="0x0000000000404874",
27122 what="`Program_Error' Ada exception", thread-groups=["i1"],
27123 times="0",original-location="__gnat_debug_raise_exception"@}
27127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27128 @node GDB/MI Program Context
27129 @section @sc{gdb/mi} Program Context
27131 @subheading The @code{-exec-arguments} Command
27132 @findex -exec-arguments
27135 @subsubheading Synopsis
27138 -exec-arguments @var{args}
27141 Set the inferior program arguments, to be used in the next
27144 @subsubheading @value{GDBN} Command
27146 The corresponding @value{GDBN} command is @samp{set args}.
27148 @subsubheading Example
27152 -exec-arguments -v word
27159 @subheading The @code{-exec-show-arguments} Command
27160 @findex -exec-show-arguments
27162 @subsubheading Synopsis
27165 -exec-show-arguments
27168 Print the arguments of the program.
27170 @subsubheading @value{GDBN} Command
27172 The corresponding @value{GDBN} command is @samp{show args}.
27174 @subsubheading Example
27179 @subheading The @code{-environment-cd} Command
27180 @findex -environment-cd
27182 @subsubheading Synopsis
27185 -environment-cd @var{pathdir}
27188 Set @value{GDBN}'s working directory.
27190 @subsubheading @value{GDBN} Command
27192 The corresponding @value{GDBN} command is @samp{cd}.
27194 @subsubheading Example
27198 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27204 @subheading The @code{-environment-directory} Command
27205 @findex -environment-directory
27207 @subsubheading Synopsis
27210 -environment-directory [ -r ] [ @var{pathdir} ]+
27213 Add directories @var{pathdir} to beginning of search path for source files.
27214 If the @samp{-r} option is used, the search path is reset to the default
27215 search path. If directories @var{pathdir} are supplied in addition to the
27216 @samp{-r} option, the search path is first reset and then addition
27218 Multiple directories may be specified, separated by blanks. Specifying
27219 multiple directories in a single command
27220 results in the directories added to the beginning of the
27221 search path in the same order they were presented in the command.
27222 If blanks are needed as
27223 part of a directory name, double-quotes should be used around
27224 the name. In the command output, the path will show up separated
27225 by the system directory-separator character. The directory-separator
27226 character must not be used
27227 in any directory name.
27228 If no directories are specified, the current search path is displayed.
27230 @subsubheading @value{GDBN} Command
27232 The corresponding @value{GDBN} command is @samp{dir}.
27234 @subsubheading Example
27238 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27239 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27241 -environment-directory ""
27242 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27244 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27245 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27247 -environment-directory -r
27248 ^done,source-path="$cdir:$cwd"
27253 @subheading The @code{-environment-path} Command
27254 @findex -environment-path
27256 @subsubheading Synopsis
27259 -environment-path [ -r ] [ @var{pathdir} ]+
27262 Add directories @var{pathdir} to beginning of search path for object files.
27263 If the @samp{-r} option is used, the search path is reset to the original
27264 search path that existed at gdb start-up. If directories @var{pathdir} are
27265 supplied in addition to the
27266 @samp{-r} option, the search path is first reset and then addition
27268 Multiple directories may be specified, separated by blanks. Specifying
27269 multiple directories in a single command
27270 results in the directories added to the beginning of the
27271 search path in the same order they were presented in the command.
27272 If blanks are needed as
27273 part of a directory name, double-quotes should be used around
27274 the name. In the command output, the path will show up separated
27275 by the system directory-separator character. The directory-separator
27276 character must not be used
27277 in any directory name.
27278 If no directories are specified, the current path is displayed.
27281 @subsubheading @value{GDBN} Command
27283 The corresponding @value{GDBN} command is @samp{path}.
27285 @subsubheading Example
27290 ^done,path="/usr/bin"
27292 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27293 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27295 -environment-path -r /usr/local/bin
27296 ^done,path="/usr/local/bin:/usr/bin"
27301 @subheading The @code{-environment-pwd} Command
27302 @findex -environment-pwd
27304 @subsubheading Synopsis
27310 Show the current working directory.
27312 @subsubheading @value{GDBN} Command
27314 The corresponding @value{GDBN} command is @samp{pwd}.
27316 @subsubheading Example
27321 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27325 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27326 @node GDB/MI Thread Commands
27327 @section @sc{gdb/mi} Thread Commands
27330 @subheading The @code{-thread-info} Command
27331 @findex -thread-info
27333 @subsubheading Synopsis
27336 -thread-info [ @var{thread-id} ]
27339 Reports information about either a specific thread, if
27340 the @var{thread-id} parameter is present, or about all
27341 threads. When printing information about all threads,
27342 also reports the current thread.
27344 @subsubheading @value{GDBN} Command
27346 The @samp{info thread} command prints the same information
27349 @subsubheading Result
27351 The result is a list of threads. The following attributes are
27352 defined for a given thread:
27356 This field exists only for the current thread. It has the value @samp{*}.
27359 The identifier that @value{GDBN} uses to refer to the thread.
27362 The identifier that the target uses to refer to the thread.
27365 Extra information about the thread, in a target-specific format. This
27369 The name of the thread. If the user specified a name using the
27370 @code{thread name} command, then this name is given. Otherwise, if
27371 @value{GDBN} can extract the thread name from the target, then that
27372 name is given. If @value{GDBN} cannot find the thread name, then this
27376 The stack frame currently executing in the thread.
27379 The thread's state. The @samp{state} field may have the following
27384 The thread is stopped. Frame information is available for stopped
27388 The thread is running. There's no frame information for running
27394 If @value{GDBN} can find the CPU core on which this thread is running,
27395 then this field is the core identifier. This field is optional.
27399 @subsubheading Example
27404 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27405 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27406 args=[]@},state="running"@},
27407 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27408 frame=@{level="0",addr="0x0804891f",func="foo",
27409 args=[@{name="i",value="10"@}],
27410 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27411 state="running"@}],
27412 current-thread-id="1"
27416 @subheading The @code{-thread-list-ids} Command
27417 @findex -thread-list-ids
27419 @subsubheading Synopsis
27425 Produces a list of the currently known @value{GDBN} thread ids. At the
27426 end of the list it also prints the total number of such threads.
27428 This command is retained for historical reasons, the
27429 @code{-thread-info} command should be used instead.
27431 @subsubheading @value{GDBN} Command
27433 Part of @samp{info threads} supplies the same information.
27435 @subsubheading Example
27440 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27441 current-thread-id="1",number-of-threads="3"
27446 @subheading The @code{-thread-select} Command
27447 @findex -thread-select
27449 @subsubheading Synopsis
27452 -thread-select @var{threadnum}
27455 Make @var{threadnum} the current thread. It prints the number of the new
27456 current thread, and the topmost frame for that thread.
27458 This command is deprecated in favor of explicitly using the
27459 @samp{--thread} option to each command.
27461 @subsubheading @value{GDBN} Command
27463 The corresponding @value{GDBN} command is @samp{thread}.
27465 @subsubheading Example
27472 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27473 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27477 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27478 number-of-threads="3"
27481 ^done,new-thread-id="3",
27482 frame=@{level="0",func="vprintf",
27483 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27484 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27489 @node GDB/MI Ada Tasking Commands
27490 @section @sc{gdb/mi} Ada Tasking Commands
27492 @subheading The @code{-ada-task-info} Command
27493 @findex -ada-task-info
27495 @subsubheading Synopsis
27498 -ada-task-info [ @var{task-id} ]
27501 Reports information about either a specific Ada task, if the
27502 @var{task-id} parameter is present, or about all Ada tasks.
27504 @subsubheading @value{GDBN} Command
27506 The @samp{info tasks} command prints the same information
27507 about all Ada tasks (@pxref{Ada Tasks}).
27509 @subsubheading Result
27511 The result is a table of Ada tasks. The following columns are
27512 defined for each Ada task:
27516 This field exists only for the current thread. It has the value @samp{*}.
27519 The identifier that @value{GDBN} uses to refer to the Ada task.
27522 The identifier that the target uses to refer to the Ada task.
27525 The identifier of the thread corresponding to the Ada task.
27527 This field should always exist, as Ada tasks are always implemented
27528 on top of a thread. But if @value{GDBN} cannot find this corresponding
27529 thread for any reason, the field is omitted.
27532 This field exists only when the task was created by another task.
27533 In this case, it provides the ID of the parent task.
27536 The base priority of the task.
27539 The current state of the task. For a detailed description of the
27540 possible states, see @ref{Ada Tasks}.
27543 The name of the task.
27547 @subsubheading Example
27551 ^done,tasks=@{nr_rows="3",nr_cols="8",
27552 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27553 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27554 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27555 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27556 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27557 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27558 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27559 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27560 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27561 state="Child Termination Wait",name="main_task"@}]@}
27565 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27566 @node GDB/MI Program Execution
27567 @section @sc{gdb/mi} Program Execution
27569 These are the asynchronous commands which generate the out-of-band
27570 record @samp{*stopped}. Currently @value{GDBN} only really executes
27571 asynchronously with remote targets and this interaction is mimicked in
27574 @subheading The @code{-exec-continue} Command
27575 @findex -exec-continue
27577 @subsubheading Synopsis
27580 -exec-continue [--reverse] [--all|--thread-group N]
27583 Resumes the execution of the inferior program, which will continue
27584 to execute until it reaches a debugger stop event. If the
27585 @samp{--reverse} option is specified, execution resumes in reverse until
27586 it reaches a stop event. Stop events may include
27589 breakpoints or watchpoints
27591 signals or exceptions
27593 the end of the process (or its beginning under @samp{--reverse})
27595 the end or beginning of a replay log if one is being used.
27597 In all-stop mode (@pxref{All-Stop
27598 Mode}), may resume only one thread, or all threads, depending on the
27599 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27600 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27601 ignored in all-stop mode. If the @samp{--thread-group} options is
27602 specified, then all threads in that thread group are resumed.
27604 @subsubheading @value{GDBN} Command
27606 The corresponding @value{GDBN} corresponding is @samp{continue}.
27608 @subsubheading Example
27615 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27616 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27622 @subheading The @code{-exec-finish} Command
27623 @findex -exec-finish
27625 @subsubheading Synopsis
27628 -exec-finish [--reverse]
27631 Resumes the execution of the inferior program until the current
27632 function is exited. Displays the results returned by the function.
27633 If the @samp{--reverse} option is specified, resumes the reverse
27634 execution of the inferior program until the point where current
27635 function was called.
27637 @subsubheading @value{GDBN} Command
27639 The corresponding @value{GDBN} command is @samp{finish}.
27641 @subsubheading Example
27643 Function returning @code{void}.
27650 *stopped,reason="function-finished",frame=@{func="main",args=[],
27651 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27655 Function returning other than @code{void}. The name of the internal
27656 @value{GDBN} variable storing the result is printed, together with the
27663 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27664 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27665 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27666 gdb-result-var="$1",return-value="0"
27671 @subheading The @code{-exec-interrupt} Command
27672 @findex -exec-interrupt
27674 @subsubheading Synopsis
27677 -exec-interrupt [--all|--thread-group N]
27680 Interrupts the background execution of the target. Note how the token
27681 associated with the stop message is the one for the execution command
27682 that has been interrupted. The token for the interrupt itself only
27683 appears in the @samp{^done} output. If the user is trying to
27684 interrupt a non-running program, an error message will be printed.
27686 Note that when asynchronous execution is enabled, this command is
27687 asynchronous just like other execution commands. That is, first the
27688 @samp{^done} response will be printed, and the target stop will be
27689 reported after that using the @samp{*stopped} notification.
27691 In non-stop mode, only the context thread is interrupted by default.
27692 All threads (in all inferiors) will be interrupted if the
27693 @samp{--all} option is specified. If the @samp{--thread-group}
27694 option is specified, all threads in that group will be interrupted.
27696 @subsubheading @value{GDBN} Command
27698 The corresponding @value{GDBN} command is @samp{interrupt}.
27700 @subsubheading Example
27711 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27712 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27713 fullname="/home/foo/bar/try.c",line="13"@}
27718 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27722 @subheading The @code{-exec-jump} Command
27725 @subsubheading Synopsis
27728 -exec-jump @var{location}
27731 Resumes execution of the inferior program at the location specified by
27732 parameter. @xref{Specify Location}, for a description of the
27733 different forms of @var{location}.
27735 @subsubheading @value{GDBN} Command
27737 The corresponding @value{GDBN} command is @samp{jump}.
27739 @subsubheading Example
27742 -exec-jump foo.c:10
27743 *running,thread-id="all"
27748 @subheading The @code{-exec-next} Command
27751 @subsubheading Synopsis
27754 -exec-next [--reverse]
27757 Resumes execution of the inferior program, stopping when the beginning
27758 of the next source line is reached.
27760 If the @samp{--reverse} option is specified, resumes reverse execution
27761 of the inferior program, stopping at the beginning of the previous
27762 source line. If you issue this command on the first line of a
27763 function, it will take you back to the caller of that function, to the
27764 source line where the function was called.
27767 @subsubheading @value{GDBN} Command
27769 The corresponding @value{GDBN} command is @samp{next}.
27771 @subsubheading Example
27777 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27782 @subheading The @code{-exec-next-instruction} Command
27783 @findex -exec-next-instruction
27785 @subsubheading Synopsis
27788 -exec-next-instruction [--reverse]
27791 Executes one machine instruction. If the instruction is a function
27792 call, continues until the function returns. If the program stops at an
27793 instruction in the middle of a source line, the address will be
27796 If the @samp{--reverse} option is specified, resumes reverse execution
27797 of the inferior program, stopping at the previous instruction. If the
27798 previously executed instruction was a return from another function,
27799 it will continue to execute in reverse until the call to that function
27800 (from the current stack frame) is reached.
27802 @subsubheading @value{GDBN} Command
27804 The corresponding @value{GDBN} command is @samp{nexti}.
27806 @subsubheading Example
27810 -exec-next-instruction
27814 *stopped,reason="end-stepping-range",
27815 addr="0x000100d4",line="5",file="hello.c"
27820 @subheading The @code{-exec-return} Command
27821 @findex -exec-return
27823 @subsubheading Synopsis
27829 Makes current function return immediately. Doesn't execute the inferior.
27830 Displays the new current frame.
27832 @subsubheading @value{GDBN} Command
27834 The corresponding @value{GDBN} command is @samp{return}.
27836 @subsubheading Example
27840 200-break-insert callee4
27841 200^done,bkpt=@{number="1",addr="0x00010734",
27842 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27847 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27848 frame=@{func="callee4",args=[],
27849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27850 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27856 111^done,frame=@{level="0",func="callee3",
27857 args=[@{name="strarg",
27858 value="0x11940 \"A string argument.\""@}],
27859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27865 @subheading The @code{-exec-run} Command
27868 @subsubheading Synopsis
27871 -exec-run [ --all | --thread-group N ] [ --start ]
27874 Starts execution of the inferior from the beginning. The inferior
27875 executes until either a breakpoint is encountered or the program
27876 exits. In the latter case the output will include an exit code, if
27877 the program has exited exceptionally.
27879 When neither the @samp{--all} nor the @samp{--thread-group} option
27880 is specified, the current inferior is started. If the
27881 @samp{--thread-group} option is specified, it should refer to a thread
27882 group of type @samp{process}, and that thread group will be started.
27883 If the @samp{--all} option is specified, then all inferiors will be started.
27885 Using the @samp{--start} option instructs the debugger to stop
27886 the execution at the start of the inferior's main subprogram,
27887 following the same behavior as the @code{start} command
27888 (@pxref{Starting}).
27890 @subsubheading @value{GDBN} Command
27892 The corresponding @value{GDBN} command is @samp{run}.
27894 @subsubheading Examples
27899 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27904 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27905 frame=@{func="main",args=[],file="recursive2.c",
27906 fullname="/home/foo/bar/recursive2.c",line="4"@}
27911 Program exited normally:
27919 *stopped,reason="exited-normally"
27924 Program exited exceptionally:
27932 *stopped,reason="exited",exit-code="01"
27936 Another way the program can terminate is if it receives a signal such as
27937 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27941 *stopped,reason="exited-signalled",signal-name="SIGINT",
27942 signal-meaning="Interrupt"
27946 @c @subheading -exec-signal
27949 @subheading The @code{-exec-step} Command
27952 @subsubheading Synopsis
27955 -exec-step [--reverse]
27958 Resumes execution of the inferior program, stopping when the beginning
27959 of the next source line is reached, if the next source line is not a
27960 function call. If it is, stop at the first instruction of the called
27961 function. If the @samp{--reverse} option is specified, resumes reverse
27962 execution of the inferior program, stopping at the beginning of the
27963 previously executed source line.
27965 @subsubheading @value{GDBN} Command
27967 The corresponding @value{GDBN} command is @samp{step}.
27969 @subsubheading Example
27971 Stepping into a function:
27977 *stopped,reason="end-stepping-range",
27978 frame=@{func="foo",args=[@{name="a",value="10"@},
27979 @{name="b",value="0"@}],file="recursive2.c",
27980 fullname="/home/foo/bar/recursive2.c",line="11"@}
27990 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27995 @subheading The @code{-exec-step-instruction} Command
27996 @findex -exec-step-instruction
27998 @subsubheading Synopsis
28001 -exec-step-instruction [--reverse]
28004 Resumes the inferior which executes one machine instruction. If the
28005 @samp{--reverse} option is specified, resumes reverse execution of the
28006 inferior program, stopping at the previously executed instruction.
28007 The output, once @value{GDBN} has stopped, will vary depending on
28008 whether we have stopped in the middle of a source line or not. In the
28009 former case, the address at which the program stopped will be printed
28012 @subsubheading @value{GDBN} Command
28014 The corresponding @value{GDBN} command is @samp{stepi}.
28016 @subsubheading Example
28020 -exec-step-instruction
28024 *stopped,reason="end-stepping-range",
28025 frame=@{func="foo",args=[],file="try.c",
28026 fullname="/home/foo/bar/try.c",line="10"@}
28028 -exec-step-instruction
28032 *stopped,reason="end-stepping-range",
28033 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28034 fullname="/home/foo/bar/try.c",line="10"@}
28039 @subheading The @code{-exec-until} Command
28040 @findex -exec-until
28042 @subsubheading Synopsis
28045 -exec-until [ @var{location} ]
28048 Executes the inferior until the @var{location} specified in the
28049 argument is reached. If there is no argument, the inferior executes
28050 until a source line greater than the current one is reached. The
28051 reason for stopping in this case will be @samp{location-reached}.
28053 @subsubheading @value{GDBN} Command
28055 The corresponding @value{GDBN} command is @samp{until}.
28057 @subsubheading Example
28061 -exec-until recursive2.c:6
28065 *stopped,reason="location-reached",frame=@{func="main",args=[],
28066 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28071 @subheading -file-clear
28072 Is this going away????
28075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28076 @node GDB/MI Stack Manipulation
28077 @section @sc{gdb/mi} Stack Manipulation Commands
28079 @subheading The @code{-enable-frame-filters} Command
28080 @findex -enable-frame-filters
28083 -enable-frame-filters
28086 @value{GDBN} allows Python-based frame filters to affect the output of
28087 the MI commands relating to stack traces. As there is no way to
28088 implement this in a fully backward-compatible way, a front end must
28089 request that this functionality be enabled.
28091 Once enabled, this feature cannot be disabled.
28093 Note that if Python support has not been compiled into @value{GDBN},
28094 this command will still succeed (and do nothing).
28096 @subheading The @code{-stack-info-frame} Command
28097 @findex -stack-info-frame
28099 @subsubheading Synopsis
28105 Get info on the selected frame.
28107 @subsubheading @value{GDBN} Command
28109 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28110 (without arguments).
28112 @subsubheading Example
28117 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28118 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28119 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28123 @subheading The @code{-stack-info-depth} Command
28124 @findex -stack-info-depth
28126 @subsubheading Synopsis
28129 -stack-info-depth [ @var{max-depth} ]
28132 Return the depth of the stack. If the integer argument @var{max-depth}
28133 is specified, do not count beyond @var{max-depth} frames.
28135 @subsubheading @value{GDBN} Command
28137 There's no equivalent @value{GDBN} command.
28139 @subsubheading Example
28141 For a stack with frame levels 0 through 11:
28148 -stack-info-depth 4
28151 -stack-info-depth 12
28154 -stack-info-depth 11
28157 -stack-info-depth 13
28162 @anchor{-stack-list-arguments}
28163 @subheading The @code{-stack-list-arguments} Command
28164 @findex -stack-list-arguments
28166 @subsubheading Synopsis
28169 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28170 [ @var{low-frame} @var{high-frame} ]
28173 Display a list of the arguments for the frames between @var{low-frame}
28174 and @var{high-frame} (inclusive). If @var{low-frame} and
28175 @var{high-frame} are not provided, list the arguments for the whole
28176 call stack. If the two arguments are equal, show the single frame
28177 at the corresponding level. It is an error if @var{low-frame} is
28178 larger than the actual number of frames. On the other hand,
28179 @var{high-frame} may be larger than the actual number of frames, in
28180 which case only existing frames will be returned.
28182 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28183 the variables; if it is 1 or @code{--all-values}, print also their
28184 values; and if it is 2 or @code{--simple-values}, print the name,
28185 type and value for simple data types, and the name and type for arrays,
28186 structures and unions. If the option @code{--no-frame-filters} is
28187 supplied, then Python frame filters will not be executed.
28189 If the @code{--skip-unavailable} option is specified, arguments that
28190 are not available are not listed. Partially available arguments
28191 are still displayed, however.
28193 Use of this command to obtain arguments in a single frame is
28194 deprecated in favor of the @samp{-stack-list-variables} command.
28196 @subsubheading @value{GDBN} Command
28198 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28199 @samp{gdb_get_args} command which partially overlaps with the
28200 functionality of @samp{-stack-list-arguments}.
28202 @subsubheading Example
28209 frame=@{level="0",addr="0x00010734",func="callee4",
28210 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28211 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28212 frame=@{level="1",addr="0x0001076c",func="callee3",
28213 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28214 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28215 frame=@{level="2",addr="0x0001078c",func="callee2",
28216 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28217 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28218 frame=@{level="3",addr="0x000107b4",func="callee1",
28219 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28220 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28221 frame=@{level="4",addr="0x000107e0",func="main",
28222 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28223 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28225 -stack-list-arguments 0
28228 frame=@{level="0",args=[]@},
28229 frame=@{level="1",args=[name="strarg"]@},
28230 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28231 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28232 frame=@{level="4",args=[]@}]
28234 -stack-list-arguments 1
28237 frame=@{level="0",args=[]@},
28239 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28240 frame=@{level="2",args=[
28241 @{name="intarg",value="2"@},
28242 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28243 @{frame=@{level="3",args=[
28244 @{name="intarg",value="2"@},
28245 @{name="strarg",value="0x11940 \"A string argument.\""@},
28246 @{name="fltarg",value="3.5"@}]@},
28247 frame=@{level="4",args=[]@}]
28249 -stack-list-arguments 0 2 2
28250 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28252 -stack-list-arguments 1 2 2
28253 ^done,stack-args=[frame=@{level="2",
28254 args=[@{name="intarg",value="2"@},
28255 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28259 @c @subheading -stack-list-exception-handlers
28262 @anchor{-stack-list-frames}
28263 @subheading The @code{-stack-list-frames} Command
28264 @findex -stack-list-frames
28266 @subsubheading Synopsis
28269 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28272 List the frames currently on the stack. For each frame it displays the
28277 The frame number, 0 being the topmost frame, i.e., the innermost function.
28279 The @code{$pc} value for that frame.
28283 File name of the source file where the function lives.
28284 @item @var{fullname}
28285 The full file name of the source file where the function lives.
28287 Line number corresponding to the @code{$pc}.
28289 The shared library where this function is defined. This is only given
28290 if the frame's function is not known.
28293 If invoked without arguments, this command prints a backtrace for the
28294 whole stack. If given two integer arguments, it shows the frames whose
28295 levels are between the two arguments (inclusive). If the two arguments
28296 are equal, it shows the single frame at the corresponding level. It is
28297 an error if @var{low-frame} is larger than the actual number of
28298 frames. On the other hand, @var{high-frame} may be larger than the
28299 actual number of frames, in which case only existing frames will be
28300 returned. If the option @code{--no-frame-filters} is supplied, then
28301 Python frame filters will not be executed.
28303 @subsubheading @value{GDBN} Command
28305 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28307 @subsubheading Example
28309 Full stack backtrace:
28315 [frame=@{level="0",addr="0x0001076c",func="foo",
28316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28317 frame=@{level="1",addr="0x000107a4",func="foo",
28318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28319 frame=@{level="2",addr="0x000107a4",func="foo",
28320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28321 frame=@{level="3",addr="0x000107a4",func="foo",
28322 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28323 frame=@{level="4",addr="0x000107a4",func="foo",
28324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28325 frame=@{level="5",addr="0x000107a4",func="foo",
28326 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28327 frame=@{level="6",addr="0x000107a4",func="foo",
28328 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28329 frame=@{level="7",addr="0x000107a4",func="foo",
28330 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28331 frame=@{level="8",addr="0x000107a4",func="foo",
28332 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28333 frame=@{level="9",addr="0x000107a4",func="foo",
28334 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28335 frame=@{level="10",addr="0x000107a4",func="foo",
28336 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28337 frame=@{level="11",addr="0x00010738",func="main",
28338 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28342 Show frames between @var{low_frame} and @var{high_frame}:
28346 -stack-list-frames 3 5
28348 [frame=@{level="3",addr="0x000107a4",func="foo",
28349 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28350 frame=@{level="4",addr="0x000107a4",func="foo",
28351 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28352 frame=@{level="5",addr="0x000107a4",func="foo",
28353 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28357 Show a single frame:
28361 -stack-list-frames 3 3
28363 [frame=@{level="3",addr="0x000107a4",func="foo",
28364 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28369 @subheading The @code{-stack-list-locals} Command
28370 @findex -stack-list-locals
28371 @anchor{-stack-list-locals}
28373 @subsubheading Synopsis
28376 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28379 Display the local variable names for the selected frame. If
28380 @var{print-values} is 0 or @code{--no-values}, print only the names of
28381 the variables; if it is 1 or @code{--all-values}, print also their
28382 values; and if it is 2 or @code{--simple-values}, print the name,
28383 type and value for simple data types, and the name and type for arrays,
28384 structures and unions. In this last case, a frontend can immediately
28385 display the value of simple data types and create variable objects for
28386 other data types when the user wishes to explore their values in
28387 more detail. If the option @code{--no-frame-filters} is supplied, then
28388 Python frame filters will not be executed.
28390 If the @code{--skip-unavailable} option is specified, local variables
28391 that are not available are not listed. Partially available local
28392 variables are still displayed, however.
28394 This command is deprecated in favor of the
28395 @samp{-stack-list-variables} command.
28397 @subsubheading @value{GDBN} Command
28399 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28401 @subsubheading Example
28405 -stack-list-locals 0
28406 ^done,locals=[name="A",name="B",name="C"]
28408 -stack-list-locals --all-values
28409 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28410 @{name="C",value="@{1, 2, 3@}"@}]
28411 -stack-list-locals --simple-values
28412 ^done,locals=[@{name="A",type="int",value="1"@},
28413 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28417 @anchor{-stack-list-variables}
28418 @subheading The @code{-stack-list-variables} Command
28419 @findex -stack-list-variables
28421 @subsubheading Synopsis
28424 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28427 Display the names of local variables and function arguments for the selected frame. If
28428 @var{print-values} is 0 or @code{--no-values}, print only the names of
28429 the variables; if it is 1 or @code{--all-values}, print also their
28430 values; and if it is 2 or @code{--simple-values}, print the name,
28431 type and value for simple data types, and the name and type for arrays,
28432 structures and unions. If the option @code{--no-frame-filters} is
28433 supplied, then Python frame filters will not be executed.
28435 If the @code{--skip-unavailable} option is specified, local variables
28436 and arguments that are not available are not listed. Partially
28437 available arguments and local variables are still displayed, however.
28439 @subsubheading Example
28443 -stack-list-variables --thread 1 --frame 0 --all-values
28444 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28449 @subheading The @code{-stack-select-frame} Command
28450 @findex -stack-select-frame
28452 @subsubheading Synopsis
28455 -stack-select-frame @var{framenum}
28458 Change the selected frame. Select a different frame @var{framenum} on
28461 This command in deprecated in favor of passing the @samp{--frame}
28462 option to every command.
28464 @subsubheading @value{GDBN} Command
28466 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28467 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28469 @subsubheading Example
28473 -stack-select-frame 2
28478 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28479 @node GDB/MI Variable Objects
28480 @section @sc{gdb/mi} Variable Objects
28484 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28486 For the implementation of a variable debugger window (locals, watched
28487 expressions, etc.), we are proposing the adaptation of the existing code
28488 used by @code{Insight}.
28490 The two main reasons for that are:
28494 It has been proven in practice (it is already on its second generation).
28497 It will shorten development time (needless to say how important it is
28501 The original interface was designed to be used by Tcl code, so it was
28502 slightly changed so it could be used through @sc{gdb/mi}. This section
28503 describes the @sc{gdb/mi} operations that will be available and gives some
28504 hints about their use.
28506 @emph{Note}: In addition to the set of operations described here, we
28507 expect the @sc{gui} implementation of a variable window to require, at
28508 least, the following operations:
28511 @item @code{-gdb-show} @code{output-radix}
28512 @item @code{-stack-list-arguments}
28513 @item @code{-stack-list-locals}
28514 @item @code{-stack-select-frame}
28519 @subheading Introduction to Variable Objects
28521 @cindex variable objects in @sc{gdb/mi}
28523 Variable objects are "object-oriented" MI interface for examining and
28524 changing values of expressions. Unlike some other MI interfaces that
28525 work with expressions, variable objects are specifically designed for
28526 simple and efficient presentation in the frontend. A variable object
28527 is identified by string name. When a variable object is created, the
28528 frontend specifies the expression for that variable object. The
28529 expression can be a simple variable, or it can be an arbitrary complex
28530 expression, and can even involve CPU registers. After creating a
28531 variable object, the frontend can invoke other variable object
28532 operations---for example to obtain or change the value of a variable
28533 object, or to change display format.
28535 Variable objects have hierarchical tree structure. Any variable object
28536 that corresponds to a composite type, such as structure in C, has
28537 a number of child variable objects, for example corresponding to each
28538 element of a structure. A child variable object can itself have
28539 children, recursively. Recursion ends when we reach
28540 leaf variable objects, which always have built-in types. Child variable
28541 objects are created only by explicit request, so if a frontend
28542 is not interested in the children of a particular variable object, no
28543 child will be created.
28545 For a leaf variable object it is possible to obtain its value as a
28546 string, or set the value from a string. String value can be also
28547 obtained for a non-leaf variable object, but it's generally a string
28548 that only indicates the type of the object, and does not list its
28549 contents. Assignment to a non-leaf variable object is not allowed.
28551 A frontend does not need to read the values of all variable objects each time
28552 the program stops. Instead, MI provides an update command that lists all
28553 variable objects whose values has changed since the last update
28554 operation. This considerably reduces the amount of data that must
28555 be transferred to the frontend. As noted above, children variable
28556 objects are created on demand, and only leaf variable objects have a
28557 real value. As result, gdb will read target memory only for leaf
28558 variables that frontend has created.
28560 The automatic update is not always desirable. For example, a frontend
28561 might want to keep a value of some expression for future reference,
28562 and never update it. For another example, fetching memory is
28563 relatively slow for embedded targets, so a frontend might want
28564 to disable automatic update for the variables that are either not
28565 visible on the screen, or ``closed''. This is possible using so
28566 called ``frozen variable objects''. Such variable objects are never
28567 implicitly updated.
28569 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28570 fixed variable object, the expression is parsed when the variable
28571 object is created, including associating identifiers to specific
28572 variables. The meaning of expression never changes. For a floating
28573 variable object the values of variables whose names appear in the
28574 expressions are re-evaluated every time in the context of the current
28575 frame. Consider this example:
28580 struct work_state state;
28587 If a fixed variable object for the @code{state} variable is created in
28588 this function, and we enter the recursive call, the variable
28589 object will report the value of @code{state} in the top-level
28590 @code{do_work} invocation. On the other hand, a floating variable
28591 object will report the value of @code{state} in the current frame.
28593 If an expression specified when creating a fixed variable object
28594 refers to a local variable, the variable object becomes bound to the
28595 thread and frame in which the variable object is created. When such
28596 variable object is updated, @value{GDBN} makes sure that the
28597 thread/frame combination the variable object is bound to still exists,
28598 and re-evaluates the variable object in context of that thread/frame.
28600 The following is the complete set of @sc{gdb/mi} operations defined to
28601 access this functionality:
28603 @multitable @columnfractions .4 .6
28604 @item @strong{Operation}
28605 @tab @strong{Description}
28607 @item @code{-enable-pretty-printing}
28608 @tab enable Python-based pretty-printing
28609 @item @code{-var-create}
28610 @tab create a variable object
28611 @item @code{-var-delete}
28612 @tab delete the variable object and/or its children
28613 @item @code{-var-set-format}
28614 @tab set the display format of this variable
28615 @item @code{-var-show-format}
28616 @tab show the display format of this variable
28617 @item @code{-var-info-num-children}
28618 @tab tells how many children this object has
28619 @item @code{-var-list-children}
28620 @tab return a list of the object's children
28621 @item @code{-var-info-type}
28622 @tab show the type of this variable object
28623 @item @code{-var-info-expression}
28624 @tab print parent-relative expression that this variable object represents
28625 @item @code{-var-info-path-expression}
28626 @tab print full expression that this variable object represents
28627 @item @code{-var-show-attributes}
28628 @tab is this variable editable? does it exist here?
28629 @item @code{-var-evaluate-expression}
28630 @tab get the value of this variable
28631 @item @code{-var-assign}
28632 @tab set the value of this variable
28633 @item @code{-var-update}
28634 @tab update the variable and its children
28635 @item @code{-var-set-frozen}
28636 @tab set frozeness attribute
28637 @item @code{-var-set-update-range}
28638 @tab set range of children to display on update
28641 In the next subsection we describe each operation in detail and suggest
28642 how it can be used.
28644 @subheading Description And Use of Operations on Variable Objects
28646 @subheading The @code{-enable-pretty-printing} Command
28647 @findex -enable-pretty-printing
28650 -enable-pretty-printing
28653 @value{GDBN} allows Python-based visualizers to affect the output of the
28654 MI variable object commands. However, because there was no way to
28655 implement this in a fully backward-compatible way, a front end must
28656 request that this functionality be enabled.
28658 Once enabled, this feature cannot be disabled.
28660 Note that if Python support has not been compiled into @value{GDBN},
28661 this command will still succeed (and do nothing).
28663 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28664 may work differently in future versions of @value{GDBN}.
28666 @subheading The @code{-var-create} Command
28667 @findex -var-create
28669 @subsubheading Synopsis
28672 -var-create @{@var{name} | "-"@}
28673 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28676 This operation creates a variable object, which allows the monitoring of
28677 a variable, the result of an expression, a memory cell or a CPU
28680 The @var{name} parameter is the string by which the object can be
28681 referenced. It must be unique. If @samp{-} is specified, the varobj
28682 system will generate a string ``varNNNNNN'' automatically. It will be
28683 unique provided that one does not specify @var{name} of that format.
28684 The command fails if a duplicate name is found.
28686 The frame under which the expression should be evaluated can be
28687 specified by @var{frame-addr}. A @samp{*} indicates that the current
28688 frame should be used. A @samp{@@} indicates that a floating variable
28689 object must be created.
28691 @var{expression} is any expression valid on the current language set (must not
28692 begin with a @samp{*}), or one of the following:
28696 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28699 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28702 @samp{$@var{regname}} --- a CPU register name
28705 @cindex dynamic varobj
28706 A varobj's contents may be provided by a Python-based pretty-printer. In this
28707 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28708 have slightly different semantics in some cases. If the
28709 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28710 will never create a dynamic varobj. This ensures backward
28711 compatibility for existing clients.
28713 @subsubheading Result
28715 This operation returns attributes of the newly-created varobj. These
28720 The name of the varobj.
28723 The number of children of the varobj. This number is not necessarily
28724 reliable for a dynamic varobj. Instead, you must examine the
28725 @samp{has_more} attribute.
28728 The varobj's scalar value. For a varobj whose type is some sort of
28729 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28730 will not be interesting.
28733 The varobj's type. This is a string representation of the type, as
28734 would be printed by the @value{GDBN} CLI. If @samp{print object}
28735 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28736 @emph{actual} (derived) type of the object is shown rather than the
28737 @emph{declared} one.
28740 If a variable object is bound to a specific thread, then this is the
28741 thread's identifier.
28744 For a dynamic varobj, this indicates whether there appear to be any
28745 children available. For a non-dynamic varobj, this will be 0.
28748 This attribute will be present and have the value @samp{1} if the
28749 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28750 then this attribute will not be present.
28753 A dynamic varobj can supply a display hint to the front end. The
28754 value comes directly from the Python pretty-printer object's
28755 @code{display_hint} method. @xref{Pretty Printing API}.
28758 Typical output will look like this:
28761 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28762 has_more="@var{has_more}"
28766 @subheading The @code{-var-delete} Command
28767 @findex -var-delete
28769 @subsubheading Synopsis
28772 -var-delete [ -c ] @var{name}
28775 Deletes a previously created variable object and all of its children.
28776 With the @samp{-c} option, just deletes the children.
28778 Returns an error if the object @var{name} is not found.
28781 @subheading The @code{-var-set-format} Command
28782 @findex -var-set-format
28784 @subsubheading Synopsis
28787 -var-set-format @var{name} @var{format-spec}
28790 Sets the output format for the value of the object @var{name} to be
28793 @anchor{-var-set-format}
28794 The syntax for the @var{format-spec} is as follows:
28797 @var{format-spec} @expansion{}
28798 @{binary | decimal | hexadecimal | octal | natural@}
28801 The natural format is the default format choosen automatically
28802 based on the variable type (like decimal for an @code{int}, hex
28803 for pointers, etc.).
28805 For a variable with children, the format is set only on the
28806 variable itself, and the children are not affected.
28808 @subheading The @code{-var-show-format} Command
28809 @findex -var-show-format
28811 @subsubheading Synopsis
28814 -var-show-format @var{name}
28817 Returns the format used to display the value of the object @var{name}.
28820 @var{format} @expansion{}
28825 @subheading The @code{-var-info-num-children} Command
28826 @findex -var-info-num-children
28828 @subsubheading Synopsis
28831 -var-info-num-children @var{name}
28834 Returns the number of children of a variable object @var{name}:
28840 Note that this number is not completely reliable for a dynamic varobj.
28841 It will return the current number of children, but more children may
28845 @subheading The @code{-var-list-children} Command
28846 @findex -var-list-children
28848 @subsubheading Synopsis
28851 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28853 @anchor{-var-list-children}
28855 Return a list of the children of the specified variable object and
28856 create variable objects for them, if they do not already exist. With
28857 a single argument or if @var{print-values} has a value of 0 or
28858 @code{--no-values}, print only the names of the variables; if
28859 @var{print-values} is 1 or @code{--all-values}, also print their
28860 values; and if it is 2 or @code{--simple-values} print the name and
28861 value for simple data types and just the name for arrays, structures
28864 @var{from} and @var{to}, if specified, indicate the range of children
28865 to report. If @var{from} or @var{to} is less than zero, the range is
28866 reset and all children will be reported. Otherwise, children starting
28867 at @var{from} (zero-based) and up to and excluding @var{to} will be
28870 If a child range is requested, it will only affect the current call to
28871 @code{-var-list-children}, but not future calls to @code{-var-update}.
28872 For this, you must instead use @code{-var-set-update-range}. The
28873 intent of this approach is to enable a front end to implement any
28874 update approach it likes; for example, scrolling a view may cause the
28875 front end to request more children with @code{-var-list-children}, and
28876 then the front end could call @code{-var-set-update-range} with a
28877 different range to ensure that future updates are restricted to just
28880 For each child the following results are returned:
28885 Name of the variable object created for this child.
28888 The expression to be shown to the user by the front end to designate this child.
28889 For example this may be the name of a structure member.
28891 For a dynamic varobj, this value cannot be used to form an
28892 expression. There is no way to do this at all with a dynamic varobj.
28894 For C/C@t{++} structures there are several pseudo children returned to
28895 designate access qualifiers. For these pseudo children @var{exp} is
28896 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28897 type and value are not present.
28899 A dynamic varobj will not report the access qualifying
28900 pseudo-children, regardless of the language. This information is not
28901 available at all with a dynamic varobj.
28904 Number of children this child has. For a dynamic varobj, this will be
28908 The type of the child. If @samp{print object}
28909 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28910 @emph{actual} (derived) type of the object is shown rather than the
28911 @emph{declared} one.
28914 If values were requested, this is the value.
28917 If this variable object is associated with a thread, this is the thread id.
28918 Otherwise this result is not present.
28921 If the variable object is frozen, this variable will be present with a value of 1.
28924 A dynamic varobj can supply a display hint to the front end. The
28925 value comes directly from the Python pretty-printer object's
28926 @code{display_hint} method. @xref{Pretty Printing API}.
28929 This attribute will be present and have the value @samp{1} if the
28930 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28931 then this attribute will not be present.
28935 The result may have its own attributes:
28939 A dynamic varobj can supply a display hint to the front end. The
28940 value comes directly from the Python pretty-printer object's
28941 @code{display_hint} method. @xref{Pretty Printing API}.
28944 This is an integer attribute which is nonzero if there are children
28945 remaining after the end of the selected range.
28948 @subsubheading Example
28952 -var-list-children n
28953 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28954 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28956 -var-list-children --all-values n
28957 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28958 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28962 @subheading The @code{-var-info-type} Command
28963 @findex -var-info-type
28965 @subsubheading Synopsis
28968 -var-info-type @var{name}
28971 Returns the type of the specified variable @var{name}. The type is
28972 returned as a string in the same format as it is output by the
28976 type=@var{typename}
28980 @subheading The @code{-var-info-expression} Command
28981 @findex -var-info-expression
28983 @subsubheading Synopsis
28986 -var-info-expression @var{name}
28989 Returns a string that is suitable for presenting this
28990 variable object in user interface. The string is generally
28991 not valid expression in the current language, and cannot be evaluated.
28993 For example, if @code{a} is an array, and variable object
28994 @code{A} was created for @code{a}, then we'll get this output:
28997 (gdb) -var-info-expression A.1
28998 ^done,lang="C",exp="1"
29002 Here, the value of @code{lang} is the language name, which can be
29003 found in @ref{Supported Languages}.
29005 Note that the output of the @code{-var-list-children} command also
29006 includes those expressions, so the @code{-var-info-expression} command
29009 @subheading The @code{-var-info-path-expression} Command
29010 @findex -var-info-path-expression
29012 @subsubheading Synopsis
29015 -var-info-path-expression @var{name}
29018 Returns an expression that can be evaluated in the current
29019 context and will yield the same value that a variable object has.
29020 Compare this with the @code{-var-info-expression} command, which
29021 result can be used only for UI presentation. Typical use of
29022 the @code{-var-info-path-expression} command is creating a
29023 watchpoint from a variable object.
29025 This command is currently not valid for children of a dynamic varobj,
29026 and will give an error when invoked on one.
29028 For example, suppose @code{C} is a C@t{++} class, derived from class
29029 @code{Base}, and that the @code{Base} class has a member called
29030 @code{m_size}. Assume a variable @code{c} is has the type of
29031 @code{C} and a variable object @code{C} was created for variable
29032 @code{c}. Then, we'll get this output:
29034 (gdb) -var-info-path-expression C.Base.public.m_size
29035 ^done,path_expr=((Base)c).m_size)
29038 @subheading The @code{-var-show-attributes} Command
29039 @findex -var-show-attributes
29041 @subsubheading Synopsis
29044 -var-show-attributes @var{name}
29047 List attributes of the specified variable object @var{name}:
29050 status=@var{attr} [ ( ,@var{attr} )* ]
29054 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29056 @subheading The @code{-var-evaluate-expression} Command
29057 @findex -var-evaluate-expression
29059 @subsubheading Synopsis
29062 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29065 Evaluates the expression that is represented by the specified variable
29066 object and returns its value as a string. The format of the string
29067 can be specified with the @samp{-f} option. The possible values of
29068 this option are the same as for @code{-var-set-format}
29069 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29070 the current display format will be used. The current display format
29071 can be changed using the @code{-var-set-format} command.
29077 Note that one must invoke @code{-var-list-children} for a variable
29078 before the value of a child variable can be evaluated.
29080 @subheading The @code{-var-assign} Command
29081 @findex -var-assign
29083 @subsubheading Synopsis
29086 -var-assign @var{name} @var{expression}
29089 Assigns the value of @var{expression} to the variable object specified
29090 by @var{name}. The object must be @samp{editable}. If the variable's
29091 value is altered by the assign, the variable will show up in any
29092 subsequent @code{-var-update} list.
29094 @subsubheading Example
29102 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29106 @subheading The @code{-var-update} Command
29107 @findex -var-update
29109 @subsubheading Synopsis
29112 -var-update [@var{print-values}] @{@var{name} | "*"@}
29115 Reevaluate the expressions corresponding to the variable object
29116 @var{name} and all its direct and indirect children, and return the
29117 list of variable objects whose values have changed; @var{name} must
29118 be a root variable object. Here, ``changed'' means that the result of
29119 @code{-var-evaluate-expression} before and after the
29120 @code{-var-update} is different. If @samp{*} is used as the variable
29121 object names, all existing variable objects are updated, except
29122 for frozen ones (@pxref{-var-set-frozen}). The option
29123 @var{print-values} determines whether both names and values, or just
29124 names are printed. The possible values of this option are the same
29125 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29126 recommended to use the @samp{--all-values} option, to reduce the
29127 number of MI commands needed on each program stop.
29129 With the @samp{*} parameter, if a variable object is bound to a
29130 currently running thread, it will not be updated, without any
29133 If @code{-var-set-update-range} was previously used on a varobj, then
29134 only the selected range of children will be reported.
29136 @code{-var-update} reports all the changed varobjs in a tuple named
29139 Each item in the change list is itself a tuple holding:
29143 The name of the varobj.
29146 If values were requested for this update, then this field will be
29147 present and will hold the value of the varobj.
29150 @anchor{-var-update}
29151 This field is a string which may take one of three values:
29155 The variable object's current value is valid.
29158 The variable object does not currently hold a valid value but it may
29159 hold one in the future if its associated expression comes back into
29163 The variable object no longer holds a valid value.
29164 This can occur when the executable file being debugged has changed,
29165 either through recompilation or by using the @value{GDBN} @code{file}
29166 command. The front end should normally choose to delete these variable
29170 In the future new values may be added to this list so the front should
29171 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29174 This is only present if the varobj is still valid. If the type
29175 changed, then this will be the string @samp{true}; otherwise it will
29178 When a varobj's type changes, its children are also likely to have
29179 become incorrect. Therefore, the varobj's children are automatically
29180 deleted when this attribute is @samp{true}. Also, the varobj's update
29181 range, when set using the @code{-var-set-update-range} command, is
29185 If the varobj's type changed, then this field will be present and will
29188 @item new_num_children
29189 For a dynamic varobj, if the number of children changed, or if the
29190 type changed, this will be the new number of children.
29192 The @samp{numchild} field in other varobj responses is generally not
29193 valid for a dynamic varobj -- it will show the number of children that
29194 @value{GDBN} knows about, but because dynamic varobjs lazily
29195 instantiate their children, this will not reflect the number of
29196 children which may be available.
29198 The @samp{new_num_children} attribute only reports changes to the
29199 number of children known by @value{GDBN}. This is the only way to
29200 detect whether an update has removed children (which necessarily can
29201 only happen at the end of the update range).
29204 The display hint, if any.
29207 This is an integer value, which will be 1 if there are more children
29208 available outside the varobj's update range.
29211 This attribute will be present and have the value @samp{1} if the
29212 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29213 then this attribute will not be present.
29216 If new children were added to a dynamic varobj within the selected
29217 update range (as set by @code{-var-set-update-range}), then they will
29218 be listed in this attribute.
29221 @subsubheading Example
29228 -var-update --all-values var1
29229 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29230 type_changed="false"@}]
29234 @subheading The @code{-var-set-frozen} Command
29235 @findex -var-set-frozen
29236 @anchor{-var-set-frozen}
29238 @subsubheading Synopsis
29241 -var-set-frozen @var{name} @var{flag}
29244 Set the frozenness flag on the variable object @var{name}. The
29245 @var{flag} parameter should be either @samp{1} to make the variable
29246 frozen or @samp{0} to make it unfrozen. If a variable object is
29247 frozen, then neither itself, nor any of its children, are
29248 implicitly updated by @code{-var-update} of
29249 a parent variable or by @code{-var-update *}. Only
29250 @code{-var-update} of the variable itself will update its value and
29251 values of its children. After a variable object is unfrozen, it is
29252 implicitly updated by all subsequent @code{-var-update} operations.
29253 Unfreezing a variable does not update it, only subsequent
29254 @code{-var-update} does.
29256 @subsubheading Example
29260 -var-set-frozen V 1
29265 @subheading The @code{-var-set-update-range} command
29266 @findex -var-set-update-range
29267 @anchor{-var-set-update-range}
29269 @subsubheading Synopsis
29272 -var-set-update-range @var{name} @var{from} @var{to}
29275 Set the range of children to be returned by future invocations of
29276 @code{-var-update}.
29278 @var{from} and @var{to} indicate the range of children to report. If
29279 @var{from} or @var{to} is less than zero, the range is reset and all
29280 children will be reported. Otherwise, children starting at @var{from}
29281 (zero-based) and up to and excluding @var{to} will be reported.
29283 @subsubheading Example
29287 -var-set-update-range V 1 2
29291 @subheading The @code{-var-set-visualizer} command
29292 @findex -var-set-visualizer
29293 @anchor{-var-set-visualizer}
29295 @subsubheading Synopsis
29298 -var-set-visualizer @var{name} @var{visualizer}
29301 Set a visualizer for the variable object @var{name}.
29303 @var{visualizer} is the visualizer to use. The special value
29304 @samp{None} means to disable any visualizer in use.
29306 If not @samp{None}, @var{visualizer} must be a Python expression.
29307 This expression must evaluate to a callable object which accepts a
29308 single argument. @value{GDBN} will call this object with the value of
29309 the varobj @var{name} as an argument (this is done so that the same
29310 Python pretty-printing code can be used for both the CLI and MI).
29311 When called, this object must return an object which conforms to the
29312 pretty-printing interface (@pxref{Pretty Printing API}).
29314 The pre-defined function @code{gdb.default_visualizer} may be used to
29315 select a visualizer by following the built-in process
29316 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29317 a varobj is created, and so ordinarily is not needed.
29319 This feature is only available if Python support is enabled. The MI
29320 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29321 can be used to check this.
29323 @subsubheading Example
29325 Resetting the visualizer:
29329 -var-set-visualizer V None
29333 Reselecting the default (type-based) visualizer:
29337 -var-set-visualizer V gdb.default_visualizer
29341 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29342 can be used to instantiate this class for a varobj:
29346 -var-set-visualizer V "lambda val: SomeClass()"
29350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29351 @node GDB/MI Data Manipulation
29352 @section @sc{gdb/mi} Data Manipulation
29354 @cindex data manipulation, in @sc{gdb/mi}
29355 @cindex @sc{gdb/mi}, data manipulation
29356 This section describes the @sc{gdb/mi} commands that manipulate data:
29357 examine memory and registers, evaluate expressions, etc.
29359 @c REMOVED FROM THE INTERFACE.
29360 @c @subheading -data-assign
29361 @c Change the value of a program variable. Plenty of side effects.
29362 @c @subsubheading GDB Command
29364 @c @subsubheading Example
29367 @subheading The @code{-data-disassemble} Command
29368 @findex -data-disassemble
29370 @subsubheading Synopsis
29374 [ -s @var{start-addr} -e @var{end-addr} ]
29375 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29383 @item @var{start-addr}
29384 is the beginning address (or @code{$pc})
29385 @item @var{end-addr}
29387 @item @var{filename}
29388 is the name of the file to disassemble
29389 @item @var{linenum}
29390 is the line number to disassemble around
29392 is the number of disassembly lines to be produced. If it is -1,
29393 the whole function will be disassembled, in case no @var{end-addr} is
29394 specified. If @var{end-addr} is specified as a non-zero value, and
29395 @var{lines} is lower than the number of disassembly lines between
29396 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29397 displayed; if @var{lines} is higher than the number of lines between
29398 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29401 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29402 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29403 mixed source and disassembly with raw opcodes).
29406 @subsubheading Result
29408 The result of the @code{-data-disassemble} command will be a list named
29409 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29410 used with the @code{-data-disassemble} command.
29412 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29417 The address at which this instruction was disassembled.
29420 The name of the function this instruction is within.
29423 The decimal offset in bytes from the start of @samp{func-name}.
29426 The text disassembly for this @samp{address}.
29429 This field is only present for mode 2. This contains the raw opcode
29430 bytes for the @samp{inst} field.
29434 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29435 @samp{src_and_asm_line}, each of which has the following fields:
29439 The line number within @samp{file}.
29442 The file name from the compilation unit. This might be an absolute
29443 file name or a relative file name depending on the compile command
29447 Absolute file name of @samp{file}. It is converted to a canonical form
29448 using the source file search path
29449 (@pxref{Source Path, ,Specifying Source Directories})
29450 and after resolving all the symbolic links.
29452 If the source file is not found this field will contain the path as
29453 present in the debug information.
29455 @item line_asm_insn
29456 This is a list of tuples containing the disassembly for @samp{line} in
29457 @samp{file}. The fields of each tuple are the same as for
29458 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29459 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29464 Note that whatever included in the @samp{inst} field, is not
29465 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29468 @subsubheading @value{GDBN} Command
29470 The corresponding @value{GDBN} command is @samp{disassemble}.
29472 @subsubheading Example
29474 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29478 -data-disassemble -s $pc -e "$pc + 20" -- 0
29481 @{address="0x000107c0",func-name="main",offset="4",
29482 inst="mov 2, %o0"@},
29483 @{address="0x000107c4",func-name="main",offset="8",
29484 inst="sethi %hi(0x11800), %o2"@},
29485 @{address="0x000107c8",func-name="main",offset="12",
29486 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29487 @{address="0x000107cc",func-name="main",offset="16",
29488 inst="sethi %hi(0x11800), %o2"@},
29489 @{address="0x000107d0",func-name="main",offset="20",
29490 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29494 Disassemble the whole @code{main} function. Line 32 is part of
29498 -data-disassemble -f basics.c -l 32 -- 0
29500 @{address="0x000107bc",func-name="main",offset="0",
29501 inst="save %sp, -112, %sp"@},
29502 @{address="0x000107c0",func-name="main",offset="4",
29503 inst="mov 2, %o0"@},
29504 @{address="0x000107c4",func-name="main",offset="8",
29505 inst="sethi %hi(0x11800), %o2"@},
29507 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29508 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29512 Disassemble 3 instructions from the start of @code{main}:
29516 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29518 @{address="0x000107bc",func-name="main",offset="0",
29519 inst="save %sp, -112, %sp"@},
29520 @{address="0x000107c0",func-name="main",offset="4",
29521 inst="mov 2, %o0"@},
29522 @{address="0x000107c4",func-name="main",offset="8",
29523 inst="sethi %hi(0x11800), %o2"@}]
29527 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29531 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29533 src_and_asm_line=@{line="31",
29534 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29535 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29536 line_asm_insn=[@{address="0x000107bc",
29537 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29538 src_and_asm_line=@{line="32",
29539 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29540 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29541 line_asm_insn=[@{address="0x000107c0",
29542 func-name="main",offset="4",inst="mov 2, %o0"@},
29543 @{address="0x000107c4",func-name="main",offset="8",
29544 inst="sethi %hi(0x11800), %o2"@}]@}]
29549 @subheading The @code{-data-evaluate-expression} Command
29550 @findex -data-evaluate-expression
29552 @subsubheading Synopsis
29555 -data-evaluate-expression @var{expr}
29558 Evaluate @var{expr} as an expression. The expression could contain an
29559 inferior function call. The function call will execute synchronously.
29560 If the expression contains spaces, it must be enclosed in double quotes.
29562 @subsubheading @value{GDBN} Command
29564 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29565 @samp{call}. In @code{gdbtk} only, there's a corresponding
29566 @samp{gdb_eval} command.
29568 @subsubheading Example
29570 In the following example, the numbers that precede the commands are the
29571 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29572 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29576 211-data-evaluate-expression A
29579 311-data-evaluate-expression &A
29580 311^done,value="0xefffeb7c"
29582 411-data-evaluate-expression A+3
29585 511-data-evaluate-expression "A + 3"
29591 @subheading The @code{-data-list-changed-registers} Command
29592 @findex -data-list-changed-registers
29594 @subsubheading Synopsis
29597 -data-list-changed-registers
29600 Display a list of the registers that have changed.
29602 @subsubheading @value{GDBN} Command
29604 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29605 has the corresponding command @samp{gdb_changed_register_list}.
29607 @subsubheading Example
29609 On a PPC MBX board:
29617 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29618 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29621 -data-list-changed-registers
29622 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29623 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29624 "24","25","26","27","28","30","31","64","65","66","67","69"]
29629 @subheading The @code{-data-list-register-names} Command
29630 @findex -data-list-register-names
29632 @subsubheading Synopsis
29635 -data-list-register-names [ ( @var{regno} )+ ]
29638 Show a list of register names for the current target. If no arguments
29639 are given, it shows a list of the names of all the registers. If
29640 integer numbers are given as arguments, it will print a list of the
29641 names of the registers corresponding to the arguments. To ensure
29642 consistency between a register name and its number, the output list may
29643 include empty register names.
29645 @subsubheading @value{GDBN} Command
29647 @value{GDBN} does not have a command which corresponds to
29648 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29649 corresponding command @samp{gdb_regnames}.
29651 @subsubheading Example
29653 For the PPC MBX board:
29656 -data-list-register-names
29657 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29658 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29659 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29660 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29661 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29662 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29663 "", "pc","ps","cr","lr","ctr","xer"]
29665 -data-list-register-names 1 2 3
29666 ^done,register-names=["r1","r2","r3"]
29670 @subheading The @code{-data-list-register-values} Command
29671 @findex -data-list-register-values
29673 @subsubheading Synopsis
29676 -data-list-register-values
29677 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29680 Display the registers' contents. The format according to which the
29681 registers' contents are to be returned is given by @var{fmt}, followed
29682 by an optional list of numbers specifying the registers to display. A
29683 missing list of numbers indicates that the contents of all the
29684 registers must be returned. The @code{--skip-unavailable} option
29685 indicates that only the available registers are to be returned.
29687 Allowed formats for @var{fmt} are:
29704 @subsubheading @value{GDBN} Command
29706 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29707 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29709 @subsubheading Example
29711 For a PPC MBX board (note: line breaks are for readability only, they
29712 don't appear in the actual output):
29716 -data-list-register-values r 64 65
29717 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29718 @{number="65",value="0x00029002"@}]
29720 -data-list-register-values x
29721 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29722 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29723 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29724 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29725 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29726 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29727 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29728 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29729 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29730 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29731 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29732 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29733 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29734 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29735 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29736 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29737 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29738 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29739 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29740 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29741 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29742 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29743 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29744 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29745 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29746 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29747 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29748 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29749 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29750 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29751 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29752 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29753 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29754 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29755 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29756 @{number="69",value="0x20002b03"@}]
29761 @subheading The @code{-data-read-memory} Command
29762 @findex -data-read-memory
29764 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29766 @subsubheading Synopsis
29769 -data-read-memory [ -o @var{byte-offset} ]
29770 @var{address} @var{word-format} @var{word-size}
29771 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29778 @item @var{address}
29779 An expression specifying the address of the first memory word to be
29780 read. Complex expressions containing embedded white space should be
29781 quoted using the C convention.
29783 @item @var{word-format}
29784 The format to be used to print the memory words. The notation is the
29785 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29788 @item @var{word-size}
29789 The size of each memory word in bytes.
29791 @item @var{nr-rows}
29792 The number of rows in the output table.
29794 @item @var{nr-cols}
29795 The number of columns in the output table.
29798 If present, indicates that each row should include an @sc{ascii} dump. The
29799 value of @var{aschar} is used as a padding character when a byte is not a
29800 member of the printable @sc{ascii} character set (printable @sc{ascii}
29801 characters are those whose code is between 32 and 126, inclusively).
29803 @item @var{byte-offset}
29804 An offset to add to the @var{address} before fetching memory.
29807 This command displays memory contents as a table of @var{nr-rows} by
29808 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29809 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29810 (returned as @samp{total-bytes}). Should less than the requested number
29811 of bytes be returned by the target, the missing words are identified
29812 using @samp{N/A}. The number of bytes read from the target is returned
29813 in @samp{nr-bytes} and the starting address used to read memory in
29816 The address of the next/previous row or page is available in
29817 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29820 @subsubheading @value{GDBN} Command
29822 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29823 @samp{gdb_get_mem} memory read command.
29825 @subsubheading Example
29827 Read six bytes of memory starting at @code{bytes+6} but then offset by
29828 @code{-6} bytes. Format as three rows of two columns. One byte per
29829 word. Display each word in hex.
29833 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29834 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29835 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29836 prev-page="0x0000138a",memory=[
29837 @{addr="0x00001390",data=["0x00","0x01"]@},
29838 @{addr="0x00001392",data=["0x02","0x03"]@},
29839 @{addr="0x00001394",data=["0x04","0x05"]@}]
29843 Read two bytes of memory starting at address @code{shorts + 64} and
29844 display as a single word formatted in decimal.
29848 5-data-read-memory shorts+64 d 2 1 1
29849 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29850 next-row="0x00001512",prev-row="0x0000150e",
29851 next-page="0x00001512",prev-page="0x0000150e",memory=[
29852 @{addr="0x00001510",data=["128"]@}]
29856 Read thirty two bytes of memory starting at @code{bytes+16} and format
29857 as eight rows of four columns. Include a string encoding with @samp{x}
29858 used as the non-printable character.
29862 4-data-read-memory bytes+16 x 1 8 4 x
29863 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29864 next-row="0x000013c0",prev-row="0x0000139c",
29865 next-page="0x000013c0",prev-page="0x00001380",memory=[
29866 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29867 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29868 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29869 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29870 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29871 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29872 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29873 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29877 @subheading The @code{-data-read-memory-bytes} Command
29878 @findex -data-read-memory-bytes
29880 @subsubheading Synopsis
29883 -data-read-memory-bytes [ -o @var{byte-offset} ]
29884 @var{address} @var{count}
29891 @item @var{address}
29892 An expression specifying the address of the first memory word to be
29893 read. Complex expressions containing embedded white space should be
29894 quoted using the C convention.
29897 The number of bytes to read. This should be an integer literal.
29899 @item @var{byte-offset}
29900 The offsets in bytes relative to @var{address} at which to start
29901 reading. This should be an integer literal. This option is provided
29902 so that a frontend is not required to first evaluate address and then
29903 perform address arithmetics itself.
29907 This command attempts to read all accessible memory regions in the
29908 specified range. First, all regions marked as unreadable in the memory
29909 map (if one is defined) will be skipped. @xref{Memory Region
29910 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29911 regions. For each one, if reading full region results in an errors,
29912 @value{GDBN} will try to read a subset of the region.
29914 In general, every single byte in the region may be readable or not,
29915 and the only way to read every readable byte is to try a read at
29916 every address, which is not practical. Therefore, @value{GDBN} will
29917 attempt to read all accessible bytes at either beginning or the end
29918 of the region, using a binary division scheme. This heuristic works
29919 well for reading accross a memory map boundary. Note that if a region
29920 has a readable range that is neither at the beginning or the end,
29921 @value{GDBN} will not read it.
29923 The result record (@pxref{GDB/MI Result Records}) that is output of
29924 the command includes a field named @samp{memory} whose content is a
29925 list of tuples. Each tuple represent a successfully read memory block
29926 and has the following fields:
29930 The start address of the memory block, as hexadecimal literal.
29933 The end address of the memory block, as hexadecimal literal.
29936 The offset of the memory block, as hexadecimal literal, relative to
29937 the start address passed to @code{-data-read-memory-bytes}.
29940 The contents of the memory block, in hex.
29946 @subsubheading @value{GDBN} Command
29948 The corresponding @value{GDBN} command is @samp{x}.
29950 @subsubheading Example
29954 -data-read-memory-bytes &a 10
29955 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29957 contents="01000000020000000300"@}]
29962 @subheading The @code{-data-write-memory-bytes} Command
29963 @findex -data-write-memory-bytes
29965 @subsubheading Synopsis
29968 -data-write-memory-bytes @var{address} @var{contents}
29969 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29976 @item @var{address}
29977 An expression specifying the address of the first memory word to be
29978 written. Complex expressions containing embedded white space should be
29979 quoted using the C convention.
29981 @item @var{contents}
29982 The hex-encoded bytes to write.
29985 Optional argument indicating the number of bytes to be written. If @var{count}
29986 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29987 write @var{contents} until it fills @var{count} bytes.
29991 @subsubheading @value{GDBN} Command
29993 There's no corresponding @value{GDBN} command.
29995 @subsubheading Example
29999 -data-write-memory-bytes &a "aabbccdd"
30006 -data-write-memory-bytes &a "aabbccdd" 16e
30011 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30012 @node GDB/MI Tracepoint Commands
30013 @section @sc{gdb/mi} Tracepoint Commands
30015 The commands defined in this section implement MI support for
30016 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30018 @subheading The @code{-trace-find} Command
30019 @findex -trace-find
30021 @subsubheading Synopsis
30024 -trace-find @var{mode} [@var{parameters}@dots{}]
30027 Find a trace frame using criteria defined by @var{mode} and
30028 @var{parameters}. The following table lists permissible
30029 modes and their parameters. For details of operation, see @ref{tfind}.
30034 No parameters are required. Stops examining trace frames.
30037 An integer is required as parameter. Selects tracepoint frame with
30040 @item tracepoint-number
30041 An integer is required as parameter. Finds next
30042 trace frame that corresponds to tracepoint with the specified number.
30045 An address is required as parameter. Finds
30046 next trace frame that corresponds to any tracepoint at the specified
30049 @item pc-inside-range
30050 Two addresses are required as parameters. Finds next trace
30051 frame that corresponds to a tracepoint at an address inside the
30052 specified range. Both bounds are considered to be inside the range.
30054 @item pc-outside-range
30055 Two addresses are required as parameters. Finds
30056 next trace frame that corresponds to a tracepoint at an address outside
30057 the specified range. Both bounds are considered to be inside the range.
30060 Line specification is required as parameter. @xref{Specify Location}.
30061 Finds next trace frame that corresponds to a tracepoint at
30062 the specified location.
30066 If @samp{none} was passed as @var{mode}, the response does not
30067 have fields. Otherwise, the response may have the following fields:
30071 This field has either @samp{0} or @samp{1} as the value, depending
30072 on whether a matching tracepoint was found.
30075 The index of the found traceframe. This field is present iff
30076 the @samp{found} field has value of @samp{1}.
30079 The index of the found tracepoint. This field is present iff
30080 the @samp{found} field has value of @samp{1}.
30083 The information about the frame corresponding to the found trace
30084 frame. This field is present only if a trace frame was found.
30085 @xref{GDB/MI Frame Information}, for description of this field.
30089 @subsubheading @value{GDBN} Command
30091 The corresponding @value{GDBN} command is @samp{tfind}.
30093 @subheading -trace-define-variable
30094 @findex -trace-define-variable
30096 @subsubheading Synopsis
30099 -trace-define-variable @var{name} [ @var{value} ]
30102 Create trace variable @var{name} if it does not exist. If
30103 @var{value} is specified, sets the initial value of the specified
30104 trace variable to that value. Note that the @var{name} should start
30105 with the @samp{$} character.
30107 @subsubheading @value{GDBN} Command
30109 The corresponding @value{GDBN} command is @samp{tvariable}.
30111 @subheading The @code{-trace-frame-collected} Command
30112 @findex -trace-frame-collected
30114 @subsubheading Synopsis
30117 -trace-frame-collected
30118 [--var-print-values @var{var_pval}]
30119 [--comp-print-values @var{comp_pval}]
30120 [--registers-format @var{regformat}]
30121 [--memory-contents]
30124 This command returns the set of collected objects, register names,
30125 trace state variable names, memory ranges and computed expressions
30126 that have been collected at a particular trace frame. The optional
30127 parameters to the command affect the output format in different ways.
30128 See the output description table below for more details.
30130 The reported names can be used in the normal manner to create
30131 varobjs and inspect the objects themselves. The items returned by
30132 this command are categorized so that it is clear which is a variable,
30133 which is a register, which is a trace state variable, which is a
30134 memory range and which is a computed expression.
30136 For instance, if the actions were
30138 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30139 collect *(int*)0xaf02bef0@@40
30143 the object collected in its entirety would be @code{myVar}. The
30144 object @code{myArray} would be partially collected, because only the
30145 element at index @code{myIndex} would be collected. The remaining
30146 objects would be computed expressions.
30148 An example output would be:
30152 -trace-frame-collected
30154 explicit-variables=[@{name="myVar",value="1"@}],
30155 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30156 @{name="myObj.field",value="0"@},
30157 @{name="myPtr->field",value="1"@},
30158 @{name="myCount + 2",value="3"@},
30159 @{name="$tvar1 + 1",value="43970027"@}],
30160 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30161 @{number="1",value="0x0"@},
30162 @{number="2",value="0x4"@},
30164 @{number="125",value="0x0"@}],
30165 tvars=[@{name="$tvar1",current="43970026"@}],
30166 memory=[@{address="0x0000000000602264",length="4"@},
30167 @{address="0x0000000000615bc0",length="4"@}]
30174 @item explicit-variables
30175 The set of objects that have been collected in their entirety (as
30176 opposed to collecting just a few elements of an array or a few struct
30177 members). For each object, its name and value are printed.
30178 The @code{--var-print-values} option affects how or whether the value
30179 field is output. If @var{var_pval} is 0, then print only the names;
30180 if it is 1, print also their values; and if it is 2, print the name,
30181 type and value for simple data types, and the name and type for
30182 arrays, structures and unions.
30184 @item computed-expressions
30185 The set of computed expressions that have been collected at the
30186 current trace frame. The @code{--comp-print-values} option affects
30187 this set like the @code{--var-print-values} option affects the
30188 @code{explicit-variables} set. See above.
30191 The registers that have been collected at the current trace frame.
30192 For each register collected, the name and current value are returned.
30193 The value is formatted according to the @code{--registers-format}
30194 option. See the @command{-data-list-register-values} command for a
30195 list of the allowed formats. The default is @samp{x}.
30198 The trace state variables that have been collected at the current
30199 trace frame. For each trace state variable collected, the name and
30200 current value are returned.
30203 The set of memory ranges that have been collected at the current trace
30204 frame. Its content is a list of tuples. Each tuple represents a
30205 collected memory range and has the following fields:
30209 The start address of the memory range, as hexadecimal literal.
30212 The length of the memory range, as decimal literal.
30215 The contents of the memory block, in hex. This field is only present
30216 if the @code{--memory-contents} option is specified.
30222 @subsubheading @value{GDBN} Command
30224 There is no corresponding @value{GDBN} command.
30226 @subsubheading Example
30228 @subheading -trace-list-variables
30229 @findex -trace-list-variables
30231 @subsubheading Synopsis
30234 -trace-list-variables
30237 Return a table of all defined trace variables. Each element of the
30238 table has the following fields:
30242 The name of the trace variable. This field is always present.
30245 The initial value. This is a 64-bit signed integer. This
30246 field is always present.
30249 The value the trace variable has at the moment. This is a 64-bit
30250 signed integer. This field is absent iff current value is
30251 not defined, for example if the trace was never run, or is
30256 @subsubheading @value{GDBN} Command
30258 The corresponding @value{GDBN} command is @samp{tvariables}.
30260 @subsubheading Example
30264 -trace-list-variables
30265 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30266 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30267 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30268 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30269 body=[variable=@{name="$trace_timestamp",initial="0"@}
30270 variable=@{name="$foo",initial="10",current="15"@}]@}
30274 @subheading -trace-save
30275 @findex -trace-save
30277 @subsubheading Synopsis
30280 -trace-save [-r ] @var{filename}
30283 Saves the collected trace data to @var{filename}. Without the
30284 @samp{-r} option, the data is downloaded from the target and saved
30285 in a local file. With the @samp{-r} option the target is asked
30286 to perform the save.
30288 @subsubheading @value{GDBN} Command
30290 The corresponding @value{GDBN} command is @samp{tsave}.
30293 @subheading -trace-start
30294 @findex -trace-start
30296 @subsubheading Synopsis
30302 Starts a tracing experiments. The result of this command does not
30305 @subsubheading @value{GDBN} Command
30307 The corresponding @value{GDBN} command is @samp{tstart}.
30309 @subheading -trace-status
30310 @findex -trace-status
30312 @subsubheading Synopsis
30318 Obtains the status of a tracing experiment. The result may include
30319 the following fields:
30324 May have a value of either @samp{0}, when no tracing operations are
30325 supported, @samp{1}, when all tracing operations are supported, or
30326 @samp{file} when examining trace file. In the latter case, examining
30327 of trace frame is possible but new tracing experiement cannot be
30328 started. This field is always present.
30331 May have a value of either @samp{0} or @samp{1} depending on whether
30332 tracing experiement is in progress on target. This field is present
30333 if @samp{supported} field is not @samp{0}.
30336 Report the reason why the tracing was stopped last time. This field
30337 may be absent iff tracing was never stopped on target yet. The
30338 value of @samp{request} means the tracing was stopped as result of
30339 the @code{-trace-stop} command. The value of @samp{overflow} means
30340 the tracing buffer is full. The value of @samp{disconnection} means
30341 tracing was automatically stopped when @value{GDBN} has disconnected.
30342 The value of @samp{passcount} means tracing was stopped when a
30343 tracepoint was passed a maximal number of times for that tracepoint.
30344 This field is present if @samp{supported} field is not @samp{0}.
30346 @item stopping-tracepoint
30347 The number of tracepoint whose passcount as exceeded. This field is
30348 present iff the @samp{stop-reason} field has the value of
30352 @itemx frames-created
30353 The @samp{frames} field is a count of the total number of trace frames
30354 in the trace buffer, while @samp{frames-created} is the total created
30355 during the run, including ones that were discarded, such as when a
30356 circular trace buffer filled up. Both fields are optional.
30360 These fields tell the current size of the tracing buffer and the
30361 remaining space. These fields are optional.
30364 The value of the circular trace buffer flag. @code{1} means that the
30365 trace buffer is circular and old trace frames will be discarded if
30366 necessary to make room, @code{0} means that the trace buffer is linear
30370 The value of the disconnected tracing flag. @code{1} means that
30371 tracing will continue after @value{GDBN} disconnects, @code{0} means
30372 that the trace run will stop.
30375 The filename of the trace file being examined. This field is
30376 optional, and only present when examining a trace file.
30380 @subsubheading @value{GDBN} Command
30382 The corresponding @value{GDBN} command is @samp{tstatus}.
30384 @subheading -trace-stop
30385 @findex -trace-stop
30387 @subsubheading Synopsis
30393 Stops a tracing experiment. The result of this command has the same
30394 fields as @code{-trace-status}, except that the @samp{supported} and
30395 @samp{running} fields are not output.
30397 @subsubheading @value{GDBN} Command
30399 The corresponding @value{GDBN} command is @samp{tstop}.
30402 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30403 @node GDB/MI Symbol Query
30404 @section @sc{gdb/mi} Symbol Query Commands
30408 @subheading The @code{-symbol-info-address} Command
30409 @findex -symbol-info-address
30411 @subsubheading Synopsis
30414 -symbol-info-address @var{symbol}
30417 Describe where @var{symbol} is stored.
30419 @subsubheading @value{GDBN} Command
30421 The corresponding @value{GDBN} command is @samp{info address}.
30423 @subsubheading Example
30427 @subheading The @code{-symbol-info-file} Command
30428 @findex -symbol-info-file
30430 @subsubheading Synopsis
30436 Show the file for the symbol.
30438 @subsubheading @value{GDBN} Command
30440 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30441 @samp{gdb_find_file}.
30443 @subsubheading Example
30447 @subheading The @code{-symbol-info-function} Command
30448 @findex -symbol-info-function
30450 @subsubheading Synopsis
30453 -symbol-info-function
30456 Show which function the symbol lives in.
30458 @subsubheading @value{GDBN} Command
30460 @samp{gdb_get_function} in @code{gdbtk}.
30462 @subsubheading Example
30466 @subheading The @code{-symbol-info-line} Command
30467 @findex -symbol-info-line
30469 @subsubheading Synopsis
30475 Show the core addresses of the code for a source line.
30477 @subsubheading @value{GDBN} Command
30479 The corresponding @value{GDBN} command is @samp{info line}.
30480 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30482 @subsubheading Example
30486 @subheading The @code{-symbol-info-symbol} Command
30487 @findex -symbol-info-symbol
30489 @subsubheading Synopsis
30492 -symbol-info-symbol @var{addr}
30495 Describe what symbol is at location @var{addr}.
30497 @subsubheading @value{GDBN} Command
30499 The corresponding @value{GDBN} command is @samp{info symbol}.
30501 @subsubheading Example
30505 @subheading The @code{-symbol-list-functions} Command
30506 @findex -symbol-list-functions
30508 @subsubheading Synopsis
30511 -symbol-list-functions
30514 List the functions in the executable.
30516 @subsubheading @value{GDBN} Command
30518 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30519 @samp{gdb_search} in @code{gdbtk}.
30521 @subsubheading Example
30526 @subheading The @code{-symbol-list-lines} Command
30527 @findex -symbol-list-lines
30529 @subsubheading Synopsis
30532 -symbol-list-lines @var{filename}
30535 Print the list of lines that contain code and their associated program
30536 addresses for the given source filename. The entries are sorted in
30537 ascending PC order.
30539 @subsubheading @value{GDBN} Command
30541 There is no corresponding @value{GDBN} command.
30543 @subsubheading Example
30546 -symbol-list-lines basics.c
30547 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30553 @subheading The @code{-symbol-list-types} Command
30554 @findex -symbol-list-types
30556 @subsubheading Synopsis
30562 List all the type names.
30564 @subsubheading @value{GDBN} Command
30566 The corresponding commands are @samp{info types} in @value{GDBN},
30567 @samp{gdb_search} in @code{gdbtk}.
30569 @subsubheading Example
30573 @subheading The @code{-symbol-list-variables} Command
30574 @findex -symbol-list-variables
30576 @subsubheading Synopsis
30579 -symbol-list-variables
30582 List all the global and static variable names.
30584 @subsubheading @value{GDBN} Command
30586 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30588 @subsubheading Example
30592 @subheading The @code{-symbol-locate} Command
30593 @findex -symbol-locate
30595 @subsubheading Synopsis
30601 @subsubheading @value{GDBN} Command
30603 @samp{gdb_loc} in @code{gdbtk}.
30605 @subsubheading Example
30609 @subheading The @code{-symbol-type} Command
30610 @findex -symbol-type
30612 @subsubheading Synopsis
30615 -symbol-type @var{variable}
30618 Show type of @var{variable}.
30620 @subsubheading @value{GDBN} Command
30622 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30623 @samp{gdb_obj_variable}.
30625 @subsubheading Example
30630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30631 @node GDB/MI File Commands
30632 @section @sc{gdb/mi} File Commands
30634 This section describes the GDB/MI commands to specify executable file names
30635 and to read in and obtain symbol table information.
30637 @subheading The @code{-file-exec-and-symbols} Command
30638 @findex -file-exec-and-symbols
30640 @subsubheading Synopsis
30643 -file-exec-and-symbols @var{file}
30646 Specify the executable file to be debugged. This file is the one from
30647 which the symbol table is also read. If no file is specified, the
30648 command clears the executable and symbol information. If breakpoints
30649 are set when using this command with no arguments, @value{GDBN} will produce
30650 error messages. Otherwise, no output is produced, except a completion
30653 @subsubheading @value{GDBN} Command
30655 The corresponding @value{GDBN} command is @samp{file}.
30657 @subsubheading Example
30661 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30667 @subheading The @code{-file-exec-file} Command
30668 @findex -file-exec-file
30670 @subsubheading Synopsis
30673 -file-exec-file @var{file}
30676 Specify the executable file to be debugged. Unlike
30677 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30678 from this file. If used without argument, @value{GDBN} clears the information
30679 about the executable file. No output is produced, except a completion
30682 @subsubheading @value{GDBN} Command
30684 The corresponding @value{GDBN} command is @samp{exec-file}.
30686 @subsubheading Example
30690 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30697 @subheading The @code{-file-list-exec-sections} Command
30698 @findex -file-list-exec-sections
30700 @subsubheading Synopsis
30703 -file-list-exec-sections
30706 List the sections of the current executable file.
30708 @subsubheading @value{GDBN} Command
30710 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30711 information as this command. @code{gdbtk} has a corresponding command
30712 @samp{gdb_load_info}.
30714 @subsubheading Example
30719 @subheading The @code{-file-list-exec-source-file} Command
30720 @findex -file-list-exec-source-file
30722 @subsubheading Synopsis
30725 -file-list-exec-source-file
30728 List the line number, the current source file, and the absolute path
30729 to the current source file for the current executable. The macro
30730 information field has a value of @samp{1} or @samp{0} depending on
30731 whether or not the file includes preprocessor macro information.
30733 @subsubheading @value{GDBN} Command
30735 The @value{GDBN} equivalent is @samp{info source}
30737 @subsubheading Example
30741 123-file-list-exec-source-file
30742 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30747 @subheading The @code{-file-list-exec-source-files} Command
30748 @findex -file-list-exec-source-files
30750 @subsubheading Synopsis
30753 -file-list-exec-source-files
30756 List the source files for the current executable.
30758 It will always output both the filename and fullname (absolute file
30759 name) of a source file.
30761 @subsubheading @value{GDBN} Command
30763 The @value{GDBN} equivalent is @samp{info sources}.
30764 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30766 @subsubheading Example
30769 -file-list-exec-source-files
30771 @{file=foo.c,fullname=/home/foo.c@},
30772 @{file=/home/bar.c,fullname=/home/bar.c@},
30773 @{file=gdb_could_not_find_fullpath.c@}]
30778 @subheading The @code{-file-list-shared-libraries} Command
30779 @findex -file-list-shared-libraries
30781 @subsubheading Synopsis
30784 -file-list-shared-libraries
30787 List the shared libraries in the program.
30789 @subsubheading @value{GDBN} Command
30791 The corresponding @value{GDBN} command is @samp{info shared}.
30793 @subsubheading Example
30797 @subheading The @code{-file-list-symbol-files} Command
30798 @findex -file-list-symbol-files
30800 @subsubheading Synopsis
30803 -file-list-symbol-files
30808 @subsubheading @value{GDBN} Command
30810 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30812 @subsubheading Example
30817 @subheading The @code{-file-symbol-file} Command
30818 @findex -file-symbol-file
30820 @subsubheading Synopsis
30823 -file-symbol-file @var{file}
30826 Read symbol table info from the specified @var{file} argument. When
30827 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30828 produced, except for a completion notification.
30830 @subsubheading @value{GDBN} Command
30832 The corresponding @value{GDBN} command is @samp{symbol-file}.
30834 @subsubheading Example
30838 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30844 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30845 @node GDB/MI Memory Overlay Commands
30846 @section @sc{gdb/mi} Memory Overlay Commands
30848 The memory overlay commands are not implemented.
30850 @c @subheading -overlay-auto
30852 @c @subheading -overlay-list-mapping-state
30854 @c @subheading -overlay-list-overlays
30856 @c @subheading -overlay-map
30858 @c @subheading -overlay-off
30860 @c @subheading -overlay-on
30862 @c @subheading -overlay-unmap
30864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30865 @node GDB/MI Signal Handling Commands
30866 @section @sc{gdb/mi} Signal Handling Commands
30868 Signal handling commands are not implemented.
30870 @c @subheading -signal-handle
30872 @c @subheading -signal-list-handle-actions
30874 @c @subheading -signal-list-signal-types
30878 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30879 @node GDB/MI Target Manipulation
30880 @section @sc{gdb/mi} Target Manipulation Commands
30883 @subheading The @code{-target-attach} Command
30884 @findex -target-attach
30886 @subsubheading Synopsis
30889 -target-attach @var{pid} | @var{gid} | @var{file}
30892 Attach to a process @var{pid} or a file @var{file} outside of
30893 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30894 group, the id previously returned by
30895 @samp{-list-thread-groups --available} must be used.
30897 @subsubheading @value{GDBN} Command
30899 The corresponding @value{GDBN} command is @samp{attach}.
30901 @subsubheading Example
30905 =thread-created,id="1"
30906 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30912 @subheading The @code{-target-compare-sections} Command
30913 @findex -target-compare-sections
30915 @subsubheading Synopsis
30918 -target-compare-sections [ @var{section} ]
30921 Compare data of section @var{section} on target to the exec file.
30922 Without the argument, all sections are compared.
30924 @subsubheading @value{GDBN} Command
30926 The @value{GDBN} equivalent is @samp{compare-sections}.
30928 @subsubheading Example
30933 @subheading The @code{-target-detach} Command
30934 @findex -target-detach
30936 @subsubheading Synopsis
30939 -target-detach [ @var{pid} | @var{gid} ]
30942 Detach from the remote target which normally resumes its execution.
30943 If either @var{pid} or @var{gid} is specified, detaches from either
30944 the specified process, or specified thread group. There's no output.
30946 @subsubheading @value{GDBN} Command
30948 The corresponding @value{GDBN} command is @samp{detach}.
30950 @subsubheading Example
30960 @subheading The @code{-target-disconnect} Command
30961 @findex -target-disconnect
30963 @subsubheading Synopsis
30969 Disconnect from the remote target. There's no output and the target is
30970 generally not resumed.
30972 @subsubheading @value{GDBN} Command
30974 The corresponding @value{GDBN} command is @samp{disconnect}.
30976 @subsubheading Example
30986 @subheading The @code{-target-download} Command
30987 @findex -target-download
30989 @subsubheading Synopsis
30995 Loads the executable onto the remote target.
30996 It prints out an update message every half second, which includes the fields:
31000 The name of the section.
31002 The size of what has been sent so far for that section.
31004 The size of the section.
31006 The total size of what was sent so far (the current and the previous sections).
31008 The size of the overall executable to download.
31012 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31013 @sc{gdb/mi} Output Syntax}).
31015 In addition, it prints the name and size of the sections, as they are
31016 downloaded. These messages include the following fields:
31020 The name of the section.
31022 The size of the section.
31024 The size of the overall executable to download.
31028 At the end, a summary is printed.
31030 @subsubheading @value{GDBN} Command
31032 The corresponding @value{GDBN} command is @samp{load}.
31034 @subsubheading Example
31036 Note: each status message appears on a single line. Here the messages
31037 have been broken down so that they can fit onto a page.
31042 +download,@{section=".text",section-size="6668",total-size="9880"@}
31043 +download,@{section=".text",section-sent="512",section-size="6668",
31044 total-sent="512",total-size="9880"@}
31045 +download,@{section=".text",section-sent="1024",section-size="6668",
31046 total-sent="1024",total-size="9880"@}
31047 +download,@{section=".text",section-sent="1536",section-size="6668",
31048 total-sent="1536",total-size="9880"@}
31049 +download,@{section=".text",section-sent="2048",section-size="6668",
31050 total-sent="2048",total-size="9880"@}
31051 +download,@{section=".text",section-sent="2560",section-size="6668",
31052 total-sent="2560",total-size="9880"@}
31053 +download,@{section=".text",section-sent="3072",section-size="6668",
31054 total-sent="3072",total-size="9880"@}
31055 +download,@{section=".text",section-sent="3584",section-size="6668",
31056 total-sent="3584",total-size="9880"@}
31057 +download,@{section=".text",section-sent="4096",section-size="6668",
31058 total-sent="4096",total-size="9880"@}
31059 +download,@{section=".text",section-sent="4608",section-size="6668",
31060 total-sent="4608",total-size="9880"@}
31061 +download,@{section=".text",section-sent="5120",section-size="6668",
31062 total-sent="5120",total-size="9880"@}
31063 +download,@{section=".text",section-sent="5632",section-size="6668",
31064 total-sent="5632",total-size="9880"@}
31065 +download,@{section=".text",section-sent="6144",section-size="6668",
31066 total-sent="6144",total-size="9880"@}
31067 +download,@{section=".text",section-sent="6656",section-size="6668",
31068 total-sent="6656",total-size="9880"@}
31069 +download,@{section=".init",section-size="28",total-size="9880"@}
31070 +download,@{section=".fini",section-size="28",total-size="9880"@}
31071 +download,@{section=".data",section-size="3156",total-size="9880"@}
31072 +download,@{section=".data",section-sent="512",section-size="3156",
31073 total-sent="7236",total-size="9880"@}
31074 +download,@{section=".data",section-sent="1024",section-size="3156",
31075 total-sent="7748",total-size="9880"@}
31076 +download,@{section=".data",section-sent="1536",section-size="3156",
31077 total-sent="8260",total-size="9880"@}
31078 +download,@{section=".data",section-sent="2048",section-size="3156",
31079 total-sent="8772",total-size="9880"@}
31080 +download,@{section=".data",section-sent="2560",section-size="3156",
31081 total-sent="9284",total-size="9880"@}
31082 +download,@{section=".data",section-sent="3072",section-size="3156",
31083 total-sent="9796",total-size="9880"@}
31084 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31091 @subheading The @code{-target-exec-status} Command
31092 @findex -target-exec-status
31094 @subsubheading Synopsis
31097 -target-exec-status
31100 Provide information on the state of the target (whether it is running or
31101 not, for instance).
31103 @subsubheading @value{GDBN} Command
31105 There's no equivalent @value{GDBN} command.
31107 @subsubheading Example
31111 @subheading The @code{-target-list-available-targets} Command
31112 @findex -target-list-available-targets
31114 @subsubheading Synopsis
31117 -target-list-available-targets
31120 List the possible targets to connect to.
31122 @subsubheading @value{GDBN} Command
31124 The corresponding @value{GDBN} command is @samp{help target}.
31126 @subsubheading Example
31130 @subheading The @code{-target-list-current-targets} Command
31131 @findex -target-list-current-targets
31133 @subsubheading Synopsis
31136 -target-list-current-targets
31139 Describe the current target.
31141 @subsubheading @value{GDBN} Command
31143 The corresponding information is printed by @samp{info file} (among
31146 @subsubheading Example
31150 @subheading The @code{-target-list-parameters} Command
31151 @findex -target-list-parameters
31153 @subsubheading Synopsis
31156 -target-list-parameters
31162 @subsubheading @value{GDBN} Command
31166 @subsubheading Example
31170 @subheading The @code{-target-select} Command
31171 @findex -target-select
31173 @subsubheading Synopsis
31176 -target-select @var{type} @var{parameters @dots{}}
31179 Connect @value{GDBN} to the remote target. This command takes two args:
31183 The type of target, for instance @samp{remote}, etc.
31184 @item @var{parameters}
31185 Device names, host names and the like. @xref{Target Commands, ,
31186 Commands for Managing Targets}, for more details.
31189 The output is a connection notification, followed by the address at
31190 which the target program is, in the following form:
31193 ^connected,addr="@var{address}",func="@var{function name}",
31194 args=[@var{arg list}]
31197 @subsubheading @value{GDBN} Command
31199 The corresponding @value{GDBN} command is @samp{target}.
31201 @subsubheading Example
31205 -target-select remote /dev/ttya
31206 ^connected,addr="0xfe00a300",func="??",args=[]
31210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31211 @node GDB/MI File Transfer Commands
31212 @section @sc{gdb/mi} File Transfer Commands
31215 @subheading The @code{-target-file-put} Command
31216 @findex -target-file-put
31218 @subsubheading Synopsis
31221 -target-file-put @var{hostfile} @var{targetfile}
31224 Copy file @var{hostfile} from the host system (the machine running
31225 @value{GDBN}) to @var{targetfile} on the target system.
31227 @subsubheading @value{GDBN} Command
31229 The corresponding @value{GDBN} command is @samp{remote put}.
31231 @subsubheading Example
31235 -target-file-put localfile remotefile
31241 @subheading The @code{-target-file-get} Command
31242 @findex -target-file-get
31244 @subsubheading Synopsis
31247 -target-file-get @var{targetfile} @var{hostfile}
31250 Copy file @var{targetfile} from the target system to @var{hostfile}
31251 on the host system.
31253 @subsubheading @value{GDBN} Command
31255 The corresponding @value{GDBN} command is @samp{remote get}.
31257 @subsubheading Example
31261 -target-file-get remotefile localfile
31267 @subheading The @code{-target-file-delete} Command
31268 @findex -target-file-delete
31270 @subsubheading Synopsis
31273 -target-file-delete @var{targetfile}
31276 Delete @var{targetfile} from the target system.
31278 @subsubheading @value{GDBN} Command
31280 The corresponding @value{GDBN} command is @samp{remote delete}.
31282 @subsubheading Example
31286 -target-file-delete remotefile
31292 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31293 @node GDB/MI Ada Exceptions Commands
31294 @section Ada Exceptions @sc{gdb/mi} Commands
31296 @subheading The @code{-info-ada-exceptions} Command
31297 @findex -info-ada-exceptions
31299 @subsubheading Synopsis
31302 -info-ada-exceptions [ @var{regexp}]
31305 List all Ada exceptions defined within the program being debugged.
31306 With a regular expression @var{regexp}, only those exceptions whose
31307 names match @var{regexp} are listed.
31309 @subsubheading @value{GDBN} Command
31311 The corresponding @value{GDBN} command is @samp{info exceptions}.
31313 @subsubheading Result
31315 The result is a table of Ada exceptions. The following columns are
31316 defined for each exception:
31320 The name of the exception.
31323 The address of the exception.
31327 @subsubheading Example
31330 -info-ada-exceptions aint
31331 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31332 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31333 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31334 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31335 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31338 @subheading Catching Ada Exceptions
31340 The commands describing how to ask @value{GDBN} to stop when a program
31341 raises an exception are described at @ref{Ada Exception GDB/MI
31342 Catchpoint Commands}.
31345 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31346 @node GDB/MI Support Commands
31347 @section @sc{gdb/mi} Support Commands
31349 Since new commands and features get regularly added to @sc{gdb/mi},
31350 some commands are available to help front-ends query the debugger
31351 about support for these capabilities. Similarly, it is also possible
31352 to query @value{GDBN} about target support of certain features.
31354 @subheading The @code{-info-gdb-mi-command} Command
31355 @cindex @code{-info-gdb-mi-command}
31356 @findex -info-gdb-mi-command
31358 @subsubheading Synopsis
31361 -info-gdb-mi-command @var{cmd_name}
31364 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31366 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31367 is technically not part of the command name (@pxref{GDB/MI Input
31368 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31369 for ease of use, this command also accepts the form with the leading
31372 @subsubheading @value{GDBN} Command
31374 There is no corresponding @value{GDBN} command.
31376 @subsubheading Result
31378 The result is a tuple. There is currently only one field:
31382 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31383 @code{"false"} otherwise.
31387 @subsubheading Example
31389 Here is an example where the @sc{gdb/mi} command does not exist:
31392 -info-gdb-mi-command unsupported-command
31393 ^done,command=@{exists="false"@}
31397 And here is an example where the @sc{gdb/mi} command is known
31401 -info-gdb-mi-command symbol-list-lines
31402 ^done,command=@{exists="true"@}
31405 @subheading The @code{-list-features} Command
31406 @findex -list-features
31407 @cindex supported @sc{gdb/mi} features, list
31409 Returns a list of particular features of the MI protocol that
31410 this version of gdb implements. A feature can be a command,
31411 or a new field in an output of some command, or even an
31412 important bugfix. While a frontend can sometimes detect presence
31413 of a feature at runtime, it is easier to perform detection at debugger
31416 The command returns a list of strings, with each string naming an
31417 available feature. Each returned string is just a name, it does not
31418 have any internal structure. The list of possible feature names
31424 (gdb) -list-features
31425 ^done,result=["feature1","feature2"]
31428 The current list of features is:
31431 @item frozen-varobjs
31432 Indicates support for the @code{-var-set-frozen} command, as well
31433 as possible presense of the @code{frozen} field in the output
31434 of @code{-varobj-create}.
31435 @item pending-breakpoints
31436 Indicates support for the @option{-f} option to the @code{-break-insert}
31439 Indicates Python scripting support, Python-based
31440 pretty-printing commands, and possible presence of the
31441 @samp{display_hint} field in the output of @code{-var-list-children}
31443 Indicates support for the @code{-thread-info} command.
31444 @item data-read-memory-bytes
31445 Indicates support for the @code{-data-read-memory-bytes} and the
31446 @code{-data-write-memory-bytes} commands.
31447 @item breakpoint-notifications
31448 Indicates that changes to breakpoints and breakpoints created via the
31449 CLI will be announced via async records.
31450 @item ada-task-info
31451 Indicates support for the @code{-ada-task-info} command.
31452 @item language-option
31453 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31454 option (@pxref{Context management}).
31455 @item info-gdb-mi-command
31456 Indicates support for the @code{-info-gdb-mi-command} command.
31457 @item undefined-command-error-code
31458 Indicates support for the "undefined-command" error code in error result
31459 records, produced when trying to execute an undefined @sc{gdb/mi} command
31460 (@pxref{GDB/MI Result Records}).
31461 @item exec-run-start-option
31462 Indicates that the @code{-exec-run} command supports the @option{--start}
31463 option (@pxref{GDB/MI Program Execution}).
31466 @subheading The @code{-list-target-features} Command
31467 @findex -list-target-features
31469 Returns a list of particular features that are supported by the
31470 target. Those features affect the permitted MI commands, but
31471 unlike the features reported by the @code{-list-features} command, the
31472 features depend on which target GDB is using at the moment. Whenever
31473 a target can change, due to commands such as @code{-target-select},
31474 @code{-target-attach} or @code{-exec-run}, the list of target features
31475 may change, and the frontend should obtain it again.
31479 (gdb) -list-target-features
31480 ^done,result=["async"]
31483 The current list of features is:
31487 Indicates that the target is capable of asynchronous command
31488 execution, which means that @value{GDBN} will accept further commands
31489 while the target is running.
31492 Indicates that the target is capable of reverse execution.
31493 @xref{Reverse Execution}, for more information.
31497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31498 @node GDB/MI Miscellaneous Commands
31499 @section Miscellaneous @sc{gdb/mi} Commands
31501 @c @subheading -gdb-complete
31503 @subheading The @code{-gdb-exit} Command
31506 @subsubheading Synopsis
31512 Exit @value{GDBN} immediately.
31514 @subsubheading @value{GDBN} Command
31516 Approximately corresponds to @samp{quit}.
31518 @subsubheading Example
31528 @subheading The @code{-exec-abort} Command
31529 @findex -exec-abort
31531 @subsubheading Synopsis
31537 Kill the inferior running program.
31539 @subsubheading @value{GDBN} Command
31541 The corresponding @value{GDBN} command is @samp{kill}.
31543 @subsubheading Example
31548 @subheading The @code{-gdb-set} Command
31551 @subsubheading Synopsis
31557 Set an internal @value{GDBN} variable.
31558 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31560 @subsubheading @value{GDBN} Command
31562 The corresponding @value{GDBN} command is @samp{set}.
31564 @subsubheading Example
31574 @subheading The @code{-gdb-show} Command
31577 @subsubheading Synopsis
31583 Show the current value of a @value{GDBN} variable.
31585 @subsubheading @value{GDBN} Command
31587 The corresponding @value{GDBN} command is @samp{show}.
31589 @subsubheading Example
31598 @c @subheading -gdb-source
31601 @subheading The @code{-gdb-version} Command
31602 @findex -gdb-version
31604 @subsubheading Synopsis
31610 Show version information for @value{GDBN}. Used mostly in testing.
31612 @subsubheading @value{GDBN} Command
31614 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31615 default shows this information when you start an interactive session.
31617 @subsubheading Example
31619 @c This example modifies the actual output from GDB to avoid overfull
31625 ~Copyright 2000 Free Software Foundation, Inc.
31626 ~GDB is free software, covered by the GNU General Public License, and
31627 ~you are welcome to change it and/or distribute copies of it under
31628 ~ certain conditions.
31629 ~Type "show copying" to see the conditions.
31630 ~There is absolutely no warranty for GDB. Type "show warranty" for
31632 ~This GDB was configured as
31633 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31638 @subheading The @code{-list-thread-groups} Command
31639 @findex -list-thread-groups
31641 @subheading Synopsis
31644 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31647 Lists thread groups (@pxref{Thread groups}). When a single thread
31648 group is passed as the argument, lists the children of that group.
31649 When several thread group are passed, lists information about those
31650 thread groups. Without any parameters, lists information about all
31651 top-level thread groups.
31653 Normally, thread groups that are being debugged are reported.
31654 With the @samp{--available} option, @value{GDBN} reports thread groups
31655 available on the target.
31657 The output of this command may have either a @samp{threads} result or
31658 a @samp{groups} result. The @samp{thread} result has a list of tuples
31659 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31660 Information}). The @samp{groups} result has a list of tuples as value,
31661 each tuple describing a thread group. If top-level groups are
31662 requested (that is, no parameter is passed), or when several groups
31663 are passed, the output always has a @samp{groups} result. The format
31664 of the @samp{group} result is described below.
31666 To reduce the number of roundtrips it's possible to list thread groups
31667 together with their children, by passing the @samp{--recurse} option
31668 and the recursion depth. Presently, only recursion depth of 1 is
31669 permitted. If this option is present, then every reported thread group
31670 will also include its children, either as @samp{group} or
31671 @samp{threads} field.
31673 In general, any combination of option and parameters is permitted, with
31674 the following caveats:
31678 When a single thread group is passed, the output will typically
31679 be the @samp{threads} result. Because threads may not contain
31680 anything, the @samp{recurse} option will be ignored.
31683 When the @samp{--available} option is passed, limited information may
31684 be available. In particular, the list of threads of a process might
31685 be inaccessible. Further, specifying specific thread groups might
31686 not give any performance advantage over listing all thread groups.
31687 The frontend should assume that @samp{-list-thread-groups --available}
31688 is always an expensive operation and cache the results.
31692 The @samp{groups} result is a list of tuples, where each tuple may
31693 have the following fields:
31697 Identifier of the thread group. This field is always present.
31698 The identifier is an opaque string; frontends should not try to
31699 convert it to an integer, even though it might look like one.
31702 The type of the thread group. At present, only @samp{process} is a
31706 The target-specific process identifier. This field is only present
31707 for thread groups of type @samp{process} and only if the process exists.
31710 The exit code of this group's last exited thread, formatted in octal.
31711 This field is only present for thread groups of type @samp{process} and
31712 only if the process is not running.
31715 The number of children this thread group has. This field may be
31716 absent for an available thread group.
31719 This field has a list of tuples as value, each tuple describing a
31720 thread. It may be present if the @samp{--recurse} option is
31721 specified, and it's actually possible to obtain the threads.
31724 This field is a list of integers, each identifying a core that one
31725 thread of the group is running on. This field may be absent if
31726 such information is not available.
31729 The name of the executable file that corresponds to this thread group.
31730 The field is only present for thread groups of type @samp{process},
31731 and only if there is a corresponding executable file.
31735 @subheading Example
31739 -list-thread-groups
31740 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31741 -list-thread-groups 17
31742 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31743 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31744 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31745 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31746 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31747 -list-thread-groups --available
31748 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31749 -list-thread-groups --available --recurse 1
31750 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31751 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31752 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31753 -list-thread-groups --available --recurse 1 17 18
31754 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31755 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31756 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31759 @subheading The @code{-info-os} Command
31762 @subsubheading Synopsis
31765 -info-os [ @var{type} ]
31768 If no argument is supplied, the command returns a table of available
31769 operating-system-specific information types. If one of these types is
31770 supplied as an argument @var{type}, then the command returns a table
31771 of data of that type.
31773 The types of information available depend on the target operating
31776 @subsubheading @value{GDBN} Command
31778 The corresponding @value{GDBN} command is @samp{info os}.
31780 @subsubheading Example
31782 When run on a @sc{gnu}/Linux system, the output will look something
31788 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31789 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31790 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31791 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31792 body=[item=@{col0="processes",col1="Listing of all processes",
31793 col2="Processes"@},
31794 item=@{col0="procgroups",col1="Listing of all process groups",
31795 col2="Process groups"@},
31796 item=@{col0="threads",col1="Listing of all threads",
31798 item=@{col0="files",col1="Listing of all file descriptors",
31799 col2="File descriptors"@},
31800 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31802 item=@{col0="shm",col1="Listing of all shared-memory regions",
31803 col2="Shared-memory regions"@},
31804 item=@{col0="semaphores",col1="Listing of all semaphores",
31805 col2="Semaphores"@},
31806 item=@{col0="msg",col1="Listing of all message queues",
31807 col2="Message queues"@},
31808 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31809 col2="Kernel modules"@}]@}
31812 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31813 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31814 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31815 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31816 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31817 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31818 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31819 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31821 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31822 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31826 (Note that the MI output here includes a @code{"Title"} column that
31827 does not appear in command-line @code{info os}; this column is useful
31828 for MI clients that want to enumerate the types of data, such as in a
31829 popup menu, but is needless clutter on the command line, and
31830 @code{info os} omits it.)
31832 @subheading The @code{-add-inferior} Command
31833 @findex -add-inferior
31835 @subheading Synopsis
31841 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31842 inferior is not associated with any executable. Such association may
31843 be established with the @samp{-file-exec-and-symbols} command
31844 (@pxref{GDB/MI File Commands}). The command response has a single
31845 field, @samp{inferior}, whose value is the identifier of the
31846 thread group corresponding to the new inferior.
31848 @subheading Example
31853 ^done,inferior="i3"
31856 @subheading The @code{-interpreter-exec} Command
31857 @findex -interpreter-exec
31859 @subheading Synopsis
31862 -interpreter-exec @var{interpreter} @var{command}
31864 @anchor{-interpreter-exec}
31866 Execute the specified @var{command} in the given @var{interpreter}.
31868 @subheading @value{GDBN} Command
31870 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31872 @subheading Example
31876 -interpreter-exec console "break main"
31877 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31878 &"During symbol reading, bad structure-type format.\n"
31879 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31884 @subheading The @code{-inferior-tty-set} Command
31885 @findex -inferior-tty-set
31887 @subheading Synopsis
31890 -inferior-tty-set /dev/pts/1
31893 Set terminal for future runs of the program being debugged.
31895 @subheading @value{GDBN} Command
31897 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31899 @subheading Example
31903 -inferior-tty-set /dev/pts/1
31908 @subheading The @code{-inferior-tty-show} Command
31909 @findex -inferior-tty-show
31911 @subheading Synopsis
31917 Show terminal for future runs of program being debugged.
31919 @subheading @value{GDBN} Command
31921 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31923 @subheading Example
31927 -inferior-tty-set /dev/pts/1
31931 ^done,inferior_tty_terminal="/dev/pts/1"
31935 @subheading The @code{-enable-timings} Command
31936 @findex -enable-timings
31938 @subheading Synopsis
31941 -enable-timings [yes | no]
31944 Toggle the printing of the wallclock, user and system times for an MI
31945 command as a field in its output. This command is to help frontend
31946 developers optimize the performance of their code. No argument is
31947 equivalent to @samp{yes}.
31949 @subheading @value{GDBN} Command
31953 @subheading Example
31961 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31962 addr="0x080484ed",func="main",file="myprog.c",
31963 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31965 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31973 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31974 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31975 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31976 fullname="/home/nickrob/myprog.c",line="73"@}
31981 @chapter @value{GDBN} Annotations
31983 This chapter describes annotations in @value{GDBN}. Annotations were
31984 designed to interface @value{GDBN} to graphical user interfaces or other
31985 similar programs which want to interact with @value{GDBN} at a
31986 relatively high level.
31988 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31992 This is Edition @value{EDITION}, @value{DATE}.
31996 * Annotations Overview:: What annotations are; the general syntax.
31997 * Server Prefix:: Issuing a command without affecting user state.
31998 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31999 * Errors:: Annotations for error messages.
32000 * Invalidation:: Some annotations describe things now invalid.
32001 * Annotations for Running::
32002 Whether the program is running, how it stopped, etc.
32003 * Source Annotations:: Annotations describing source code.
32006 @node Annotations Overview
32007 @section What is an Annotation?
32008 @cindex annotations
32010 Annotations start with a newline character, two @samp{control-z}
32011 characters, and the name of the annotation. If there is no additional
32012 information associated with this annotation, the name of the annotation
32013 is followed immediately by a newline. If there is additional
32014 information, the name of the annotation is followed by a space, the
32015 additional information, and a newline. The additional information
32016 cannot contain newline characters.
32018 Any output not beginning with a newline and two @samp{control-z}
32019 characters denotes literal output from @value{GDBN}. Currently there is
32020 no need for @value{GDBN} to output a newline followed by two
32021 @samp{control-z} characters, but if there was such a need, the
32022 annotations could be extended with an @samp{escape} annotation which
32023 means those three characters as output.
32025 The annotation @var{level}, which is specified using the
32026 @option{--annotate} command line option (@pxref{Mode Options}), controls
32027 how much information @value{GDBN} prints together with its prompt,
32028 values of expressions, source lines, and other types of output. Level 0
32029 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32030 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32031 for programs that control @value{GDBN}, and level 2 annotations have
32032 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32033 Interface, annotate, GDB's Obsolete Annotations}).
32036 @kindex set annotate
32037 @item set annotate @var{level}
32038 The @value{GDBN} command @code{set annotate} sets the level of
32039 annotations to the specified @var{level}.
32041 @item show annotate
32042 @kindex show annotate
32043 Show the current annotation level.
32046 This chapter describes level 3 annotations.
32048 A simple example of starting up @value{GDBN} with annotations is:
32051 $ @kbd{gdb --annotate=3}
32053 Copyright 2003 Free Software Foundation, Inc.
32054 GDB is free software, covered by the GNU General Public License,
32055 and you are welcome to change it and/or distribute copies of it
32056 under certain conditions.
32057 Type "show copying" to see the conditions.
32058 There is absolutely no warranty for GDB. Type "show warranty"
32060 This GDB was configured as "i386-pc-linux-gnu"
32071 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32072 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32073 denotes a @samp{control-z} character) are annotations; the rest is
32074 output from @value{GDBN}.
32076 @node Server Prefix
32077 @section The Server Prefix
32078 @cindex server prefix
32080 If you prefix a command with @samp{server } then it will not affect
32081 the command history, nor will it affect @value{GDBN}'s notion of which
32082 command to repeat if @key{RET} is pressed on a line by itself. This
32083 means that commands can be run behind a user's back by a front-end in
32084 a transparent manner.
32086 The @code{server } prefix does not affect the recording of values into
32087 the value history; to print a value without recording it into the
32088 value history, use the @code{output} command instead of the
32089 @code{print} command.
32091 Using this prefix also disables confirmation requests
32092 (@pxref{confirmation requests}).
32095 @section Annotation for @value{GDBN} Input
32097 @cindex annotations for prompts
32098 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32099 to know when to send output, when the output from a given command is
32102 Different kinds of input each have a different @dfn{input type}. Each
32103 input type has three annotations: a @code{pre-} annotation, which
32104 denotes the beginning of any prompt which is being output, a plain
32105 annotation, which denotes the end of the prompt, and then a @code{post-}
32106 annotation which denotes the end of any echo which may (or may not) be
32107 associated with the input. For example, the @code{prompt} input type
32108 features the following annotations:
32116 The input types are
32119 @findex pre-prompt annotation
32120 @findex prompt annotation
32121 @findex post-prompt annotation
32123 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32125 @findex pre-commands annotation
32126 @findex commands annotation
32127 @findex post-commands annotation
32129 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32130 command. The annotations are repeated for each command which is input.
32132 @findex pre-overload-choice annotation
32133 @findex overload-choice annotation
32134 @findex post-overload-choice annotation
32135 @item overload-choice
32136 When @value{GDBN} wants the user to select between various overloaded functions.
32138 @findex pre-query annotation
32139 @findex query annotation
32140 @findex post-query annotation
32142 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32144 @findex pre-prompt-for-continue annotation
32145 @findex prompt-for-continue annotation
32146 @findex post-prompt-for-continue annotation
32147 @item prompt-for-continue
32148 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32149 expect this to work well; instead use @code{set height 0} to disable
32150 prompting. This is because the counting of lines is buggy in the
32151 presence of annotations.
32156 @cindex annotations for errors, warnings and interrupts
32158 @findex quit annotation
32163 This annotation occurs right before @value{GDBN} responds to an interrupt.
32165 @findex error annotation
32170 This annotation occurs right before @value{GDBN} responds to an error.
32172 Quit and error annotations indicate that any annotations which @value{GDBN} was
32173 in the middle of may end abruptly. For example, if a
32174 @code{value-history-begin} annotation is followed by a @code{error}, one
32175 cannot expect to receive the matching @code{value-history-end}. One
32176 cannot expect not to receive it either, however; an error annotation
32177 does not necessarily mean that @value{GDBN} is immediately returning all the way
32180 @findex error-begin annotation
32181 A quit or error annotation may be preceded by
32187 Any output between that and the quit or error annotation is the error
32190 Warning messages are not yet annotated.
32191 @c If we want to change that, need to fix warning(), type_error(),
32192 @c range_error(), and possibly other places.
32195 @section Invalidation Notices
32197 @cindex annotations for invalidation messages
32198 The following annotations say that certain pieces of state may have
32202 @findex frames-invalid annotation
32203 @item ^Z^Zframes-invalid
32205 The frames (for example, output from the @code{backtrace} command) may
32208 @findex breakpoints-invalid annotation
32209 @item ^Z^Zbreakpoints-invalid
32211 The breakpoints may have changed. For example, the user just added or
32212 deleted a breakpoint.
32215 @node Annotations for Running
32216 @section Running the Program
32217 @cindex annotations for running programs
32219 @findex starting annotation
32220 @findex stopping annotation
32221 When the program starts executing due to a @value{GDBN} command such as
32222 @code{step} or @code{continue},
32228 is output. When the program stops,
32234 is output. Before the @code{stopped} annotation, a variety of
32235 annotations describe how the program stopped.
32238 @findex exited annotation
32239 @item ^Z^Zexited @var{exit-status}
32240 The program exited, and @var{exit-status} is the exit status (zero for
32241 successful exit, otherwise nonzero).
32243 @findex signalled annotation
32244 @findex signal-name annotation
32245 @findex signal-name-end annotation
32246 @findex signal-string annotation
32247 @findex signal-string-end annotation
32248 @item ^Z^Zsignalled
32249 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32250 annotation continues:
32256 ^Z^Zsignal-name-end
32260 ^Z^Zsignal-string-end
32265 where @var{name} is the name of the signal, such as @code{SIGILL} or
32266 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32267 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32268 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32269 user's benefit and have no particular format.
32271 @findex signal annotation
32273 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32274 just saying that the program received the signal, not that it was
32275 terminated with it.
32277 @findex breakpoint annotation
32278 @item ^Z^Zbreakpoint @var{number}
32279 The program hit breakpoint number @var{number}.
32281 @findex watchpoint annotation
32282 @item ^Z^Zwatchpoint @var{number}
32283 The program hit watchpoint number @var{number}.
32286 @node Source Annotations
32287 @section Displaying Source
32288 @cindex annotations for source display
32290 @findex source annotation
32291 The following annotation is used instead of displaying source code:
32294 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32297 where @var{filename} is an absolute file name indicating which source
32298 file, @var{line} is the line number within that file (where 1 is the
32299 first line in the file), @var{character} is the character position
32300 within the file (where 0 is the first character in the file) (for most
32301 debug formats this will necessarily point to the beginning of a line),
32302 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32303 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32304 @var{addr} is the address in the target program associated with the
32305 source which is being displayed. The @var{addr} is in the form @samp{0x}
32306 followed by one or more lowercase hex digits (note that this does not
32307 depend on the language).
32309 @node JIT Interface
32310 @chapter JIT Compilation Interface
32311 @cindex just-in-time compilation
32312 @cindex JIT compilation interface
32314 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32315 interface. A JIT compiler is a program or library that generates native
32316 executable code at runtime and executes it, usually in order to achieve good
32317 performance while maintaining platform independence.
32319 Programs that use JIT compilation are normally difficult to debug because
32320 portions of their code are generated at runtime, instead of being loaded from
32321 object files, which is where @value{GDBN} normally finds the program's symbols
32322 and debug information. In order to debug programs that use JIT compilation,
32323 @value{GDBN} has an interface that allows the program to register in-memory
32324 symbol files with @value{GDBN} at runtime.
32326 If you are using @value{GDBN} to debug a program that uses this interface, then
32327 it should work transparently so long as you have not stripped the binary. If
32328 you are developing a JIT compiler, then the interface is documented in the rest
32329 of this chapter. At this time, the only known client of this interface is the
32332 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32333 JIT compiler communicates with @value{GDBN} by writing data into a global
32334 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32335 attaches, it reads a linked list of symbol files from the global variable to
32336 find existing code, and puts a breakpoint in the function so that it can find
32337 out about additional code.
32340 * Declarations:: Relevant C struct declarations
32341 * Registering Code:: Steps to register code
32342 * Unregistering Code:: Steps to unregister code
32343 * Custom Debug Info:: Emit debug information in a custom format
32347 @section JIT Declarations
32349 These are the relevant struct declarations that a C program should include to
32350 implement the interface:
32360 struct jit_code_entry
32362 struct jit_code_entry *next_entry;
32363 struct jit_code_entry *prev_entry;
32364 const char *symfile_addr;
32365 uint64_t symfile_size;
32368 struct jit_descriptor
32371 /* This type should be jit_actions_t, but we use uint32_t
32372 to be explicit about the bitwidth. */
32373 uint32_t action_flag;
32374 struct jit_code_entry *relevant_entry;
32375 struct jit_code_entry *first_entry;
32378 /* GDB puts a breakpoint in this function. */
32379 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32381 /* Make sure to specify the version statically, because the
32382 debugger may check the version before we can set it. */
32383 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32386 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32387 modifications to this global data properly, which can easily be done by putting
32388 a global mutex around modifications to these structures.
32390 @node Registering Code
32391 @section Registering Code
32393 To register code with @value{GDBN}, the JIT should follow this protocol:
32397 Generate an object file in memory with symbols and other desired debug
32398 information. The file must include the virtual addresses of the sections.
32401 Create a code entry for the file, which gives the start and size of the symbol
32405 Add it to the linked list in the JIT descriptor.
32408 Point the relevant_entry field of the descriptor at the entry.
32411 Set @code{action_flag} to @code{JIT_REGISTER} and call
32412 @code{__jit_debug_register_code}.
32415 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32416 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32417 new code. However, the linked list must still be maintained in order to allow
32418 @value{GDBN} to attach to a running process and still find the symbol files.
32420 @node Unregistering Code
32421 @section Unregistering Code
32423 If code is freed, then the JIT should use the following protocol:
32427 Remove the code entry corresponding to the code from the linked list.
32430 Point the @code{relevant_entry} field of the descriptor at the code entry.
32433 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32434 @code{__jit_debug_register_code}.
32437 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32438 and the JIT will leak the memory used for the associated symbol files.
32440 @node Custom Debug Info
32441 @section Custom Debug Info
32442 @cindex custom JIT debug info
32443 @cindex JIT debug info reader
32445 Generating debug information in platform-native file formats (like ELF
32446 or COFF) may be an overkill for JIT compilers; especially if all the
32447 debug info is used for is displaying a meaningful backtrace. The
32448 issue can be resolved by having the JIT writers decide on a debug info
32449 format and also provide a reader that parses the debug info generated
32450 by the JIT compiler. This section gives a brief overview on writing
32451 such a parser. More specific details can be found in the source file
32452 @file{gdb/jit-reader.in}, which is also installed as a header at
32453 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32455 The reader is implemented as a shared object (so this functionality is
32456 not available on platforms which don't allow loading shared objects at
32457 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32458 @code{jit-reader-unload} are provided, to be used to load and unload
32459 the readers from a preconfigured directory. Once loaded, the shared
32460 object is used the parse the debug information emitted by the JIT
32464 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32465 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32468 @node Using JIT Debug Info Readers
32469 @subsection Using JIT Debug Info Readers
32470 @kindex jit-reader-load
32471 @kindex jit-reader-unload
32473 Readers can be loaded and unloaded using the @code{jit-reader-load}
32474 and @code{jit-reader-unload} commands.
32477 @item jit-reader-load @var{reader}
32478 Load the JIT reader named @var{reader}, which is a shared
32479 object specified as either an absolute or a relative file name. In
32480 the latter case, @value{GDBN} will try to load the reader from a
32481 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32482 system (here @var{libdir} is the system library directory, often
32483 @file{/usr/local/lib}).
32485 Only one reader can be active at a time; trying to load a second
32486 reader when one is already loaded will result in @value{GDBN}
32487 reporting an error. A new JIT reader can be loaded by first unloading
32488 the current one using @code{jit-reader-unload} and then invoking
32489 @code{jit-reader-load}.
32491 @item jit-reader-unload
32492 Unload the currently loaded JIT reader.
32496 @node Writing JIT Debug Info Readers
32497 @subsection Writing JIT Debug Info Readers
32498 @cindex writing JIT debug info readers
32500 As mentioned, a reader is essentially a shared object conforming to a
32501 certain ABI. This ABI is described in @file{jit-reader.h}.
32503 @file{jit-reader.h} defines the structures, macros and functions
32504 required to write a reader. It is installed (along with
32505 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32506 the system include directory.
32508 Readers need to be released under a GPL compatible license. A reader
32509 can be declared as released under such a license by placing the macro
32510 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32512 The entry point for readers is the symbol @code{gdb_init_reader},
32513 which is expected to be a function with the prototype
32515 @findex gdb_init_reader
32517 extern struct gdb_reader_funcs *gdb_init_reader (void);
32520 @cindex @code{struct gdb_reader_funcs}
32522 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32523 functions. These functions are executed to read the debug info
32524 generated by the JIT compiler (@code{read}), to unwind stack frames
32525 (@code{unwind}) and to create canonical frame IDs
32526 (@code{get_Frame_id}). It also has a callback that is called when the
32527 reader is being unloaded (@code{destroy}). The struct looks like this
32530 struct gdb_reader_funcs
32532 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32533 int reader_version;
32535 /* For use by the reader. */
32538 gdb_read_debug_info *read;
32539 gdb_unwind_frame *unwind;
32540 gdb_get_frame_id *get_frame_id;
32541 gdb_destroy_reader *destroy;
32545 @cindex @code{struct gdb_symbol_callbacks}
32546 @cindex @code{struct gdb_unwind_callbacks}
32548 The callbacks are provided with another set of callbacks by
32549 @value{GDBN} to do their job. For @code{read}, these callbacks are
32550 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32551 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32552 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32553 files and new symbol tables inside those object files. @code{struct
32554 gdb_unwind_callbacks} has callbacks to read registers off the current
32555 frame and to write out the values of the registers in the previous
32556 frame. Both have a callback (@code{target_read}) to read bytes off the
32557 target's address space.
32559 @node In-Process Agent
32560 @chapter In-Process Agent
32561 @cindex debugging agent
32562 The traditional debugging model is conceptually low-speed, but works fine,
32563 because most bugs can be reproduced in debugging-mode execution. However,
32564 as multi-core or many-core processors are becoming mainstream, and
32565 multi-threaded programs become more and more popular, there should be more
32566 and more bugs that only manifest themselves at normal-mode execution, for
32567 example, thread races, because debugger's interference with the program's
32568 timing may conceal the bugs. On the other hand, in some applications,
32569 it is not feasible for the debugger to interrupt the program's execution
32570 long enough for the developer to learn anything helpful about its behavior.
32571 If the program's correctness depends on its real-time behavior, delays
32572 introduced by a debugger might cause the program to fail, even when the
32573 code itself is correct. It is useful to be able to observe the program's
32574 behavior without interrupting it.
32576 Therefore, traditional debugging model is too intrusive to reproduce
32577 some bugs. In order to reduce the interference with the program, we can
32578 reduce the number of operations performed by debugger. The
32579 @dfn{In-Process Agent}, a shared library, is running within the same
32580 process with inferior, and is able to perform some debugging operations
32581 itself. As a result, debugger is only involved when necessary, and
32582 performance of debugging can be improved accordingly. Note that
32583 interference with program can be reduced but can't be removed completely,
32584 because the in-process agent will still stop or slow down the program.
32586 The in-process agent can interpret and execute Agent Expressions
32587 (@pxref{Agent Expressions}) during performing debugging operations. The
32588 agent expressions can be used for different purposes, such as collecting
32589 data in tracepoints, and condition evaluation in breakpoints.
32591 @anchor{Control Agent}
32592 You can control whether the in-process agent is used as an aid for
32593 debugging with the following commands:
32596 @kindex set agent on
32598 Causes the in-process agent to perform some operations on behalf of the
32599 debugger. Just which operations requested by the user will be done
32600 by the in-process agent depends on the its capabilities. For example,
32601 if you request to evaluate breakpoint conditions in the in-process agent,
32602 and the in-process agent has such capability as well, then breakpoint
32603 conditions will be evaluated in the in-process agent.
32605 @kindex set agent off
32606 @item set agent off
32607 Disables execution of debugging operations by the in-process agent. All
32608 of the operations will be performed by @value{GDBN}.
32612 Display the current setting of execution of debugging operations by
32613 the in-process agent.
32617 * In-Process Agent Protocol::
32620 @node In-Process Agent Protocol
32621 @section In-Process Agent Protocol
32622 @cindex in-process agent protocol
32624 The in-process agent is able to communicate with both @value{GDBN} and
32625 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32626 used for communications between @value{GDBN} or GDBserver and the IPA.
32627 In general, @value{GDBN} or GDBserver sends commands
32628 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32629 in-process agent replies back with the return result of the command, or
32630 some other information. The data sent to in-process agent is composed
32631 of primitive data types, such as 4-byte or 8-byte type, and composite
32632 types, which are called objects (@pxref{IPA Protocol Objects}).
32635 * IPA Protocol Objects::
32636 * IPA Protocol Commands::
32639 @node IPA Protocol Objects
32640 @subsection IPA Protocol Objects
32641 @cindex ipa protocol objects
32643 The commands sent to and results received from agent may contain some
32644 complex data types called @dfn{objects}.
32646 The in-process agent is running on the same machine with @value{GDBN}
32647 or GDBserver, so it doesn't have to handle as much differences between
32648 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32649 However, there are still some differences of two ends in two processes:
32653 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32654 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32656 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32657 GDBserver is compiled with one, and in-process agent is compiled with
32661 Here are the IPA Protocol Objects:
32665 agent expression object. It represents an agent expression
32666 (@pxref{Agent Expressions}).
32667 @anchor{agent expression object}
32669 tracepoint action object. It represents a tracepoint action
32670 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32671 memory, static trace data and to evaluate expression.
32672 @anchor{tracepoint action object}
32674 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32675 @anchor{tracepoint object}
32679 The following table describes important attributes of each IPA protocol
32682 @multitable @columnfractions .30 .20 .50
32683 @headitem Name @tab Size @tab Description
32684 @item @emph{agent expression object} @tab @tab
32685 @item length @tab 4 @tab length of bytes code
32686 @item byte code @tab @var{length} @tab contents of byte code
32687 @item @emph{tracepoint action for collecting memory} @tab @tab
32688 @item 'M' @tab 1 @tab type of tracepoint action
32689 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32690 address of the lowest byte to collect, otherwise @var{addr} is the offset
32691 of @var{basereg} for memory collecting.
32692 @item len @tab 8 @tab length of memory for collecting
32693 @item basereg @tab 4 @tab the register number containing the starting
32694 memory address for collecting.
32695 @item @emph{tracepoint action for collecting registers} @tab @tab
32696 @item 'R' @tab 1 @tab type of tracepoint action
32697 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32698 @item 'L' @tab 1 @tab type of tracepoint action
32699 @item @emph{tracepoint action for expression evaluation} @tab @tab
32700 @item 'X' @tab 1 @tab type of tracepoint action
32701 @item agent expression @tab length of @tab @ref{agent expression object}
32702 @item @emph{tracepoint object} @tab @tab
32703 @item number @tab 4 @tab number of tracepoint
32704 @item address @tab 8 @tab address of tracepoint inserted on
32705 @item type @tab 4 @tab type of tracepoint
32706 @item enabled @tab 1 @tab enable or disable of tracepoint
32707 @item step_count @tab 8 @tab step
32708 @item pass_count @tab 8 @tab pass
32709 @item numactions @tab 4 @tab number of tracepoint actions
32710 @item hit count @tab 8 @tab hit count
32711 @item trace frame usage @tab 8 @tab trace frame usage
32712 @item compiled_cond @tab 8 @tab compiled condition
32713 @item orig_size @tab 8 @tab orig size
32714 @item condition @tab 4 if condition is NULL otherwise length of
32715 @ref{agent expression object}
32716 @tab zero if condition is NULL, otherwise is
32717 @ref{agent expression object}
32718 @item actions @tab variable
32719 @tab numactions number of @ref{tracepoint action object}
32722 @node IPA Protocol Commands
32723 @subsection IPA Protocol Commands
32724 @cindex ipa protocol commands
32726 The spaces in each command are delimiters to ease reading this commands
32727 specification. They don't exist in real commands.
32731 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32732 Installs a new fast tracepoint described by @var{tracepoint_object}
32733 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32734 head of @dfn{jumppad}, which is used to jump to data collection routine
32739 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32740 @var{target_address} is address of tracepoint in the inferior.
32741 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32742 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32743 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32744 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32751 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32752 is about to kill inferiors.
32760 @item probe_marker_at:@var{address}
32761 Asks in-process agent to probe the marker at @var{address}.
32768 @item unprobe_marker_at:@var{address}
32769 Asks in-process agent to unprobe the marker at @var{address}.
32773 @chapter Reporting Bugs in @value{GDBN}
32774 @cindex bugs in @value{GDBN}
32775 @cindex reporting bugs in @value{GDBN}
32777 Your bug reports play an essential role in making @value{GDBN} reliable.
32779 Reporting a bug may help you by bringing a solution to your problem, or it
32780 may not. But in any case the principal function of a bug report is to help
32781 the entire community by making the next version of @value{GDBN} work better. Bug
32782 reports are your contribution to the maintenance of @value{GDBN}.
32784 In order for a bug report to serve its purpose, you must include the
32785 information that enables us to fix the bug.
32788 * Bug Criteria:: Have you found a bug?
32789 * Bug Reporting:: How to report bugs
32793 @section Have You Found a Bug?
32794 @cindex bug criteria
32796 If you are not sure whether you have found a bug, here are some guidelines:
32799 @cindex fatal signal
32800 @cindex debugger crash
32801 @cindex crash of debugger
32803 If the debugger gets a fatal signal, for any input whatever, that is a
32804 @value{GDBN} bug. Reliable debuggers never crash.
32806 @cindex error on valid input
32808 If @value{GDBN} produces an error message for valid input, that is a
32809 bug. (Note that if you're cross debugging, the problem may also be
32810 somewhere in the connection to the target.)
32812 @cindex invalid input
32814 If @value{GDBN} does not produce an error message for invalid input,
32815 that is a bug. However, you should note that your idea of
32816 ``invalid input'' might be our idea of ``an extension'' or ``support
32817 for traditional practice''.
32820 If you are an experienced user of debugging tools, your suggestions
32821 for improvement of @value{GDBN} are welcome in any case.
32824 @node Bug Reporting
32825 @section How to Report Bugs
32826 @cindex bug reports
32827 @cindex @value{GDBN} bugs, reporting
32829 A number of companies and individuals offer support for @sc{gnu} products.
32830 If you obtained @value{GDBN} from a support organization, we recommend you
32831 contact that organization first.
32833 You can find contact information for many support companies and
32834 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32836 @c should add a web page ref...
32839 @ifset BUGURL_DEFAULT
32840 In any event, we also recommend that you submit bug reports for
32841 @value{GDBN}. The preferred method is to submit them directly using
32842 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32843 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32846 @strong{Do not send bug reports to @samp{info-gdb}, or to
32847 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32848 not want to receive bug reports. Those that do have arranged to receive
32851 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32852 serves as a repeater. The mailing list and the newsgroup carry exactly
32853 the same messages. Often people think of posting bug reports to the
32854 newsgroup instead of mailing them. This appears to work, but it has one
32855 problem which can be crucial: a newsgroup posting often lacks a mail
32856 path back to the sender. Thus, if we need to ask for more information,
32857 we may be unable to reach you. For this reason, it is better to send
32858 bug reports to the mailing list.
32860 @ifclear BUGURL_DEFAULT
32861 In any event, we also recommend that you submit bug reports for
32862 @value{GDBN} to @value{BUGURL}.
32866 The fundamental principle of reporting bugs usefully is this:
32867 @strong{report all the facts}. If you are not sure whether to state a
32868 fact or leave it out, state it!
32870 Often people omit facts because they think they know what causes the
32871 problem and assume that some details do not matter. Thus, you might
32872 assume that the name of the variable you use in an example does not matter.
32873 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32874 stray memory reference which happens to fetch from the location where that
32875 name is stored in memory; perhaps, if the name were different, the contents
32876 of that location would fool the debugger into doing the right thing despite
32877 the bug. Play it safe and give a specific, complete example. That is the
32878 easiest thing for you to do, and the most helpful.
32880 Keep in mind that the purpose of a bug report is to enable us to fix the
32881 bug. It may be that the bug has been reported previously, but neither
32882 you nor we can know that unless your bug report is complete and
32885 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32886 bell?'' Those bug reports are useless, and we urge everyone to
32887 @emph{refuse to respond to them} except to chide the sender to report
32890 To enable us to fix the bug, you should include all these things:
32894 The version of @value{GDBN}. @value{GDBN} announces it if you start
32895 with no arguments; you can also print it at any time using @code{show
32898 Without this, we will not know whether there is any point in looking for
32899 the bug in the current version of @value{GDBN}.
32902 The type of machine you are using, and the operating system name and
32906 The details of the @value{GDBN} build-time configuration.
32907 @value{GDBN} shows these details if you invoke it with the
32908 @option{--configuration} command-line option, or if you type
32909 @code{show configuration} at @value{GDBN}'s prompt.
32912 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32913 ``@value{GCC}--2.8.1''.
32916 What compiler (and its version) was used to compile the program you are
32917 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32918 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32919 to get this information; for other compilers, see the documentation for
32923 The command arguments you gave the compiler to compile your example and
32924 observe the bug. For example, did you use @samp{-O}? To guarantee
32925 you will not omit something important, list them all. A copy of the
32926 Makefile (or the output from make) is sufficient.
32928 If we were to try to guess the arguments, we would probably guess wrong
32929 and then we might not encounter the bug.
32932 A complete input script, and all necessary source files, that will
32936 A description of what behavior you observe that you believe is
32937 incorrect. For example, ``It gets a fatal signal.''
32939 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32940 will certainly notice it. But if the bug is incorrect output, we might
32941 not notice unless it is glaringly wrong. You might as well not give us
32942 a chance to make a mistake.
32944 Even if the problem you experience is a fatal signal, you should still
32945 say so explicitly. Suppose something strange is going on, such as, your
32946 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32947 the C library on your system. (This has happened!) Your copy might
32948 crash and ours would not. If you told us to expect a crash, then when
32949 ours fails to crash, we would know that the bug was not happening for
32950 us. If you had not told us to expect a crash, then we would not be able
32951 to draw any conclusion from our observations.
32954 @cindex recording a session script
32955 To collect all this information, you can use a session recording program
32956 such as @command{script}, which is available on many Unix systems.
32957 Just run your @value{GDBN} session inside @command{script} and then
32958 include the @file{typescript} file with your bug report.
32960 Another way to record a @value{GDBN} session is to run @value{GDBN}
32961 inside Emacs and then save the entire buffer to a file.
32964 If you wish to suggest changes to the @value{GDBN} source, send us context
32965 diffs. If you even discuss something in the @value{GDBN} source, refer to
32966 it by context, not by line number.
32968 The line numbers in our development sources will not match those in your
32969 sources. Your line numbers would convey no useful information to us.
32973 Here are some things that are not necessary:
32977 A description of the envelope of the bug.
32979 Often people who encounter a bug spend a lot of time investigating
32980 which changes to the input file will make the bug go away and which
32981 changes will not affect it.
32983 This is often time consuming and not very useful, because the way we
32984 will find the bug is by running a single example under the debugger
32985 with breakpoints, not by pure deduction from a series of examples.
32986 We recommend that you save your time for something else.
32988 Of course, if you can find a simpler example to report @emph{instead}
32989 of the original one, that is a convenience for us. Errors in the
32990 output will be easier to spot, running under the debugger will take
32991 less time, and so on.
32993 However, simplification is not vital; if you do not want to do this,
32994 report the bug anyway and send us the entire test case you used.
32997 A patch for the bug.
32999 A patch for the bug does help us if it is a good one. But do not omit
33000 the necessary information, such as the test case, on the assumption that
33001 a patch is all we need. We might see problems with your patch and decide
33002 to fix the problem another way, or we might not understand it at all.
33004 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33005 construct an example that will make the program follow a certain path
33006 through the code. If you do not send us the example, we will not be able
33007 to construct one, so we will not be able to verify that the bug is fixed.
33009 And if we cannot understand what bug you are trying to fix, or why your
33010 patch should be an improvement, we will not install it. A test case will
33011 help us to understand.
33014 A guess about what the bug is or what it depends on.
33016 Such guesses are usually wrong. Even we cannot guess right about such
33017 things without first using the debugger to find the facts.
33020 @c The readline documentation is distributed with the readline code
33021 @c and consists of the two following files:
33024 @c Use -I with makeinfo to point to the appropriate directory,
33025 @c environment var TEXINPUTS with TeX.
33026 @ifclear SYSTEM_READLINE
33027 @include rluser.texi
33028 @include hsuser.texi
33032 @appendix In Memoriam
33034 The @value{GDBN} project mourns the loss of the following long-time
33039 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33040 to Free Software in general. Outside of @value{GDBN}, he was known in
33041 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33043 @item Michael Snyder
33044 Michael was one of the Global Maintainers of the @value{GDBN} project,
33045 with contributions recorded as early as 1996, until 2011. In addition
33046 to his day to day participation, he was a large driving force behind
33047 adding Reverse Debugging to @value{GDBN}.
33050 Beyond their technical contributions to the project, they were also
33051 enjoyable members of the Free Software Community. We will miss them.
33053 @node Formatting Documentation
33054 @appendix Formatting Documentation
33056 @cindex @value{GDBN} reference card
33057 @cindex reference card
33058 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33059 for printing with PostScript or Ghostscript, in the @file{gdb}
33060 subdirectory of the main source directory@footnote{In
33061 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33062 release.}. If you can use PostScript or Ghostscript with your printer,
33063 you can print the reference card immediately with @file{refcard.ps}.
33065 The release also includes the source for the reference card. You
33066 can format it, using @TeX{}, by typing:
33072 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33073 mode on US ``letter'' size paper;
33074 that is, on a sheet 11 inches wide by 8.5 inches
33075 high. You will need to specify this form of printing as an option to
33076 your @sc{dvi} output program.
33078 @cindex documentation
33080 All the documentation for @value{GDBN} comes as part of the machine-readable
33081 distribution. The documentation is written in Texinfo format, which is
33082 a documentation system that uses a single source file to produce both
33083 on-line information and a printed manual. You can use one of the Info
33084 formatting commands to create the on-line version of the documentation
33085 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33087 @value{GDBN} includes an already formatted copy of the on-line Info
33088 version of this manual in the @file{gdb} subdirectory. The main Info
33089 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33090 subordinate files matching @samp{gdb.info*} in the same directory. If
33091 necessary, you can print out these files, or read them with any editor;
33092 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33093 Emacs or the standalone @code{info} program, available as part of the
33094 @sc{gnu} Texinfo distribution.
33096 If you want to format these Info files yourself, you need one of the
33097 Info formatting programs, such as @code{texinfo-format-buffer} or
33100 If you have @code{makeinfo} installed, and are in the top level
33101 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33102 version @value{GDBVN}), you can make the Info file by typing:
33109 If you want to typeset and print copies of this manual, you need @TeX{},
33110 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33111 Texinfo definitions file.
33113 @TeX{} is a typesetting program; it does not print files directly, but
33114 produces output files called @sc{dvi} files. To print a typeset
33115 document, you need a program to print @sc{dvi} files. If your system
33116 has @TeX{} installed, chances are it has such a program. The precise
33117 command to use depends on your system; @kbd{lpr -d} is common; another
33118 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33119 require a file name without any extension or a @samp{.dvi} extension.
33121 @TeX{} also requires a macro definitions file called
33122 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33123 written in Texinfo format. On its own, @TeX{} cannot either read or
33124 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33125 and is located in the @file{gdb-@var{version-number}/texinfo}
33128 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33129 typeset and print this manual. First switch to the @file{gdb}
33130 subdirectory of the main source directory (for example, to
33131 @file{gdb-@value{GDBVN}/gdb}) and type:
33137 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33139 @node Installing GDB
33140 @appendix Installing @value{GDBN}
33141 @cindex installation
33144 * Requirements:: Requirements for building @value{GDBN}
33145 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33146 * Separate Objdir:: Compiling @value{GDBN} in another directory
33147 * Config Names:: Specifying names for hosts and targets
33148 * Configure Options:: Summary of options for configure
33149 * System-wide configuration:: Having a system-wide init file
33153 @section Requirements for Building @value{GDBN}
33154 @cindex building @value{GDBN}, requirements for
33156 Building @value{GDBN} requires various tools and packages to be available.
33157 Other packages will be used only if they are found.
33159 @heading Tools/Packages Necessary for Building @value{GDBN}
33161 @item ISO C90 compiler
33162 @value{GDBN} is written in ISO C90. It should be buildable with any
33163 working C90 compiler, e.g.@: GCC.
33167 @heading Tools/Packages Optional for Building @value{GDBN}
33171 @value{GDBN} can use the Expat XML parsing library. This library may be
33172 included with your operating system distribution; if it is not, you
33173 can get the latest version from @url{http://expat.sourceforge.net}.
33174 The @file{configure} script will search for this library in several
33175 standard locations; if it is installed in an unusual path, you can
33176 use the @option{--with-libexpat-prefix} option to specify its location.
33182 Remote protocol memory maps (@pxref{Memory Map Format})
33184 Target descriptions (@pxref{Target Descriptions})
33186 Remote shared library lists (@xref{Library List Format},
33187 or alternatively @pxref{Library List Format for SVR4 Targets})
33189 MS-Windows shared libraries (@pxref{Shared Libraries})
33191 Traceframe info (@pxref{Traceframe Info Format})
33193 Branch trace (@pxref{Branch Trace Format},
33194 @pxref{Branch Trace Configuration Format})
33198 @cindex compressed debug sections
33199 @value{GDBN} will use the @samp{zlib} library, if available, to read
33200 compressed debug sections. Some linkers, such as GNU gold, are capable
33201 of producing binaries with compressed debug sections. If @value{GDBN}
33202 is compiled with @samp{zlib}, it will be able to read the debug
33203 information in such binaries.
33205 The @samp{zlib} library is likely included with your operating system
33206 distribution; if it is not, you can get the latest version from
33207 @url{http://zlib.net}.
33210 @value{GDBN}'s features related to character sets (@pxref{Character
33211 Sets}) require a functioning @code{iconv} implementation. If you are
33212 on a GNU system, then this is provided by the GNU C Library. Some
33213 other systems also provide a working @code{iconv}.
33215 If @value{GDBN} is using the @code{iconv} program which is installed
33216 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33217 This is done with @option{--with-iconv-bin} which specifies the
33218 directory that contains the @code{iconv} program.
33220 On systems without @code{iconv}, you can install GNU Libiconv. If you
33221 have previously installed Libiconv, you can use the
33222 @option{--with-libiconv-prefix} option to configure.
33224 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33225 arrange to build Libiconv if a directory named @file{libiconv} appears
33226 in the top-most source directory. If Libiconv is built this way, and
33227 if the operating system does not provide a suitable @code{iconv}
33228 implementation, then the just-built library will automatically be used
33229 by @value{GDBN}. One easy way to set this up is to download GNU
33230 Libiconv, unpack it, and then rename the directory holding the
33231 Libiconv source code to @samp{libiconv}.
33234 @node Running Configure
33235 @section Invoking the @value{GDBN} @file{configure} Script
33236 @cindex configuring @value{GDBN}
33237 @value{GDBN} comes with a @file{configure} script that automates the process
33238 of preparing @value{GDBN} for installation; you can then use @code{make} to
33239 build the @code{gdb} program.
33241 @c irrelevant in info file; it's as current as the code it lives with.
33242 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33243 look at the @file{README} file in the sources; we may have improved the
33244 installation procedures since publishing this manual.}
33247 The @value{GDBN} distribution includes all the source code you need for
33248 @value{GDBN} in a single directory, whose name is usually composed by
33249 appending the version number to @samp{gdb}.
33251 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33252 @file{gdb-@value{GDBVN}} directory. That directory contains:
33255 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33256 script for configuring @value{GDBN} and all its supporting libraries
33258 @item gdb-@value{GDBVN}/gdb
33259 the source specific to @value{GDBN} itself
33261 @item gdb-@value{GDBVN}/bfd
33262 source for the Binary File Descriptor library
33264 @item gdb-@value{GDBVN}/include
33265 @sc{gnu} include files
33267 @item gdb-@value{GDBVN}/libiberty
33268 source for the @samp{-liberty} free software library
33270 @item gdb-@value{GDBVN}/opcodes
33271 source for the library of opcode tables and disassemblers
33273 @item gdb-@value{GDBVN}/readline
33274 source for the @sc{gnu} command-line interface
33276 @item gdb-@value{GDBVN}/glob
33277 source for the @sc{gnu} filename pattern-matching subroutine
33279 @item gdb-@value{GDBVN}/mmalloc
33280 source for the @sc{gnu} memory-mapped malloc package
33283 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33284 from the @file{gdb-@var{version-number}} source directory, which in
33285 this example is the @file{gdb-@value{GDBVN}} directory.
33287 First switch to the @file{gdb-@var{version-number}} source directory
33288 if you are not already in it; then run @file{configure}. Pass the
33289 identifier for the platform on which @value{GDBN} will run as an
33295 cd gdb-@value{GDBVN}
33296 ./configure @var{host}
33301 where @var{host} is an identifier such as @samp{sun4} or
33302 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33303 (You can often leave off @var{host}; @file{configure} tries to guess the
33304 correct value by examining your system.)
33306 Running @samp{configure @var{host}} and then running @code{make} builds the
33307 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33308 libraries, then @code{gdb} itself. The configured source files, and the
33309 binaries, are left in the corresponding source directories.
33312 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33313 system does not recognize this automatically when you run a different
33314 shell, you may need to run @code{sh} on it explicitly:
33317 sh configure @var{host}
33320 If you run @file{configure} from a directory that contains source
33321 directories for multiple libraries or programs, such as the
33322 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33324 creates configuration files for every directory level underneath (unless
33325 you tell it not to, with the @samp{--norecursion} option).
33327 You should run the @file{configure} script from the top directory in the
33328 source tree, the @file{gdb-@var{version-number}} directory. If you run
33329 @file{configure} from one of the subdirectories, you will configure only
33330 that subdirectory. That is usually not what you want. In particular,
33331 if you run the first @file{configure} from the @file{gdb} subdirectory
33332 of the @file{gdb-@var{version-number}} directory, you will omit the
33333 configuration of @file{bfd}, @file{readline}, and other sibling
33334 directories of the @file{gdb} subdirectory. This leads to build errors
33335 about missing include files such as @file{bfd/bfd.h}.
33337 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33338 However, you should make sure that the shell on your path (named by
33339 the @samp{SHELL} environment variable) is publicly readable. Remember
33340 that @value{GDBN} uses the shell to start your program---some systems refuse to
33341 let @value{GDBN} debug child processes whose programs are not readable.
33343 @node Separate Objdir
33344 @section Compiling @value{GDBN} in Another Directory
33346 If you want to run @value{GDBN} versions for several host or target machines,
33347 you need a different @code{gdb} compiled for each combination of
33348 host and target. @file{configure} is designed to make this easy by
33349 allowing you to generate each configuration in a separate subdirectory,
33350 rather than in the source directory. If your @code{make} program
33351 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33352 @code{make} in each of these directories builds the @code{gdb}
33353 program specified there.
33355 To build @code{gdb} in a separate directory, run @file{configure}
33356 with the @samp{--srcdir} option to specify where to find the source.
33357 (You also need to specify a path to find @file{configure}
33358 itself from your working directory. If the path to @file{configure}
33359 would be the same as the argument to @samp{--srcdir}, you can leave out
33360 the @samp{--srcdir} option; it is assumed.)
33362 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33363 separate directory for a Sun 4 like this:
33367 cd gdb-@value{GDBVN}
33370 ../gdb-@value{GDBVN}/configure sun4
33375 When @file{configure} builds a configuration using a remote source
33376 directory, it creates a tree for the binaries with the same structure
33377 (and using the same names) as the tree under the source directory. In
33378 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33379 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33380 @file{gdb-sun4/gdb}.
33382 Make sure that your path to the @file{configure} script has just one
33383 instance of @file{gdb} in it. If your path to @file{configure} looks
33384 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33385 one subdirectory of @value{GDBN}, not the whole package. This leads to
33386 build errors about missing include files such as @file{bfd/bfd.h}.
33388 One popular reason to build several @value{GDBN} configurations in separate
33389 directories is to configure @value{GDBN} for cross-compiling (where
33390 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33391 programs that run on another machine---the @dfn{target}).
33392 You specify a cross-debugging target by
33393 giving the @samp{--target=@var{target}} option to @file{configure}.
33395 When you run @code{make} to build a program or library, you must run
33396 it in a configured directory---whatever directory you were in when you
33397 called @file{configure} (or one of its subdirectories).
33399 The @code{Makefile} that @file{configure} generates in each source
33400 directory also runs recursively. If you type @code{make} in a source
33401 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33402 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33403 will build all the required libraries, and then build GDB.
33405 When you have multiple hosts or targets configured in separate
33406 directories, you can run @code{make} on them in parallel (for example,
33407 if they are NFS-mounted on each of the hosts); they will not interfere
33411 @section Specifying Names for Hosts and Targets
33413 The specifications used for hosts and targets in the @file{configure}
33414 script are based on a three-part naming scheme, but some short predefined
33415 aliases are also supported. The full naming scheme encodes three pieces
33416 of information in the following pattern:
33419 @var{architecture}-@var{vendor}-@var{os}
33422 For example, you can use the alias @code{sun4} as a @var{host} argument,
33423 or as the value for @var{target} in a @code{--target=@var{target}}
33424 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33426 The @file{configure} script accompanying @value{GDBN} does not provide
33427 any query facility to list all supported host and target names or
33428 aliases. @file{configure} calls the Bourne shell script
33429 @code{config.sub} to map abbreviations to full names; you can read the
33430 script, if you wish, or you can use it to test your guesses on
33431 abbreviations---for example:
33434 % sh config.sub i386-linux
33436 % sh config.sub alpha-linux
33437 alpha-unknown-linux-gnu
33438 % sh config.sub hp9k700
33440 % sh config.sub sun4
33441 sparc-sun-sunos4.1.1
33442 % sh config.sub sun3
33443 m68k-sun-sunos4.1.1
33444 % sh config.sub i986v
33445 Invalid configuration `i986v': machine `i986v' not recognized
33449 @code{config.sub} is also distributed in the @value{GDBN} source
33450 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33452 @node Configure Options
33453 @section @file{configure} Options
33455 Here is a summary of the @file{configure} options and arguments that
33456 are most often useful for building @value{GDBN}. @file{configure} also has
33457 several other options not listed here. @inforef{What Configure
33458 Does,,configure.info}, for a full explanation of @file{configure}.
33461 configure @r{[}--help@r{]}
33462 @r{[}--prefix=@var{dir}@r{]}
33463 @r{[}--exec-prefix=@var{dir}@r{]}
33464 @r{[}--srcdir=@var{dirname}@r{]}
33465 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33466 @r{[}--target=@var{target}@r{]}
33471 You may introduce options with a single @samp{-} rather than
33472 @samp{--} if you prefer; but you may abbreviate option names if you use
33477 Display a quick summary of how to invoke @file{configure}.
33479 @item --prefix=@var{dir}
33480 Configure the source to install programs and files under directory
33483 @item --exec-prefix=@var{dir}
33484 Configure the source to install programs under directory
33487 @c avoid splitting the warning from the explanation:
33489 @item --srcdir=@var{dirname}
33490 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33491 @code{make} that implements the @code{VPATH} feature.}@*
33492 Use this option to make configurations in directories separate from the
33493 @value{GDBN} source directories. Among other things, you can use this to
33494 build (or maintain) several configurations simultaneously, in separate
33495 directories. @file{configure} writes configuration-specific files in
33496 the current directory, but arranges for them to use the source in the
33497 directory @var{dirname}. @file{configure} creates directories under
33498 the working directory in parallel to the source directories below
33501 @item --norecursion
33502 Configure only the directory level where @file{configure} is executed; do not
33503 propagate configuration to subdirectories.
33505 @item --target=@var{target}
33506 Configure @value{GDBN} for cross-debugging programs running on the specified
33507 @var{target}. Without this option, @value{GDBN} is configured to debug
33508 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33510 There is no convenient way to generate a list of all available targets.
33512 @item @var{host} @dots{}
33513 Configure @value{GDBN} to run on the specified @var{host}.
33515 There is no convenient way to generate a list of all available hosts.
33518 There are many other options available as well, but they are generally
33519 needed for special purposes only.
33521 @node System-wide configuration
33522 @section System-wide configuration and settings
33523 @cindex system-wide init file
33525 @value{GDBN} can be configured to have a system-wide init file;
33526 this file will be read and executed at startup (@pxref{Startup, , What
33527 @value{GDBN} does during startup}).
33529 Here is the corresponding configure option:
33532 @item --with-system-gdbinit=@var{file}
33533 Specify that the default location of the system-wide init file is
33537 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33538 it may be subject to relocation. Two possible cases:
33542 If the default location of this init file contains @file{$prefix},
33543 it will be subject to relocation. Suppose that the configure options
33544 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33545 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33546 init file is looked for as @file{$install/etc/gdbinit} instead of
33547 @file{$prefix/etc/gdbinit}.
33550 By contrast, if the default location does not contain the prefix,
33551 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33552 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33553 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33554 wherever @value{GDBN} is installed.
33557 If the configured location of the system-wide init file (as given by the
33558 @option{--with-system-gdbinit} option at configure time) is in the
33559 data-directory (as specified by @option{--with-gdb-datadir} at configure
33560 time) or in one of its subdirectories, then @value{GDBN} will look for the
33561 system-wide init file in the directory specified by the
33562 @option{--data-directory} command-line option.
33563 Note that the system-wide init file is only read once, during @value{GDBN}
33564 initialization. If the data-directory is changed after @value{GDBN} has
33565 started with the @code{set data-directory} command, the file will not be
33569 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33572 @node System-wide Configuration Scripts
33573 @subsection Installed System-wide Configuration Scripts
33574 @cindex system-wide configuration scripts
33576 The @file{system-gdbinit} directory, located inside the data-directory
33577 (as specified by @option{--with-gdb-datadir} at configure time) contains
33578 a number of scripts which can be used as system-wide init files. To
33579 automatically source those scripts at startup, @value{GDBN} should be
33580 configured with @option{--with-system-gdbinit}. Otherwise, any user
33581 should be able to source them by hand as needed.
33583 The following scripts are currently available:
33586 @item @file{elinos.py}
33588 @cindex ELinOS system-wide configuration script
33589 This script is useful when debugging a program on an ELinOS target.
33590 It takes advantage of the environment variables defined in a standard
33591 ELinOS environment in order to determine the location of the system
33592 shared libraries, and then sets the @samp{solib-absolute-prefix}
33593 and @samp{solib-search-path} variables appropriately.
33595 @item @file{wrs-linux.py}
33596 @pindex wrs-linux.py
33597 @cindex Wind River Linux system-wide configuration script
33598 This script is useful when debugging a program on a target running
33599 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33600 the host-side sysroot used by the target system.
33604 @node Maintenance Commands
33605 @appendix Maintenance Commands
33606 @cindex maintenance commands
33607 @cindex internal commands
33609 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33610 includes a number of commands intended for @value{GDBN} developers,
33611 that are not documented elsewhere in this manual. These commands are
33612 provided here for reference. (For commands that turn on debugging
33613 messages, see @ref{Debugging Output}.)
33616 @kindex maint agent
33617 @kindex maint agent-eval
33618 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33619 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33620 Translate the given @var{expression} into remote agent bytecodes.
33621 This command is useful for debugging the Agent Expression mechanism
33622 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33623 expression useful for data collection, such as by tracepoints, while
33624 @samp{maint agent-eval} produces an expression that evaluates directly
33625 to a result. For instance, a collection expression for @code{globa +
33626 globb} will include bytecodes to record four bytes of memory at each
33627 of the addresses of @code{globa} and @code{globb}, while discarding
33628 the result of the addition, while an evaluation expression will do the
33629 addition and return the sum.
33630 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33631 If not, generate remote agent bytecode for current frame PC address.
33633 @kindex maint agent-printf
33634 @item maint agent-printf @var{format},@var{expr},...
33635 Translate the given format string and list of argument expressions
33636 into remote agent bytecodes and display them as a disassembled list.
33637 This command is useful for debugging the agent version of dynamic
33638 printf (@pxref{Dynamic Printf}).
33640 @kindex maint info breakpoints
33641 @item @anchor{maint info breakpoints}maint info breakpoints
33642 Using the same format as @samp{info breakpoints}, display both the
33643 breakpoints you've set explicitly, and those @value{GDBN} is using for
33644 internal purposes. Internal breakpoints are shown with negative
33645 breakpoint numbers. The type column identifies what kind of breakpoint
33650 Normal, explicitly set breakpoint.
33653 Normal, explicitly set watchpoint.
33656 Internal breakpoint, used to handle correctly stepping through
33657 @code{longjmp} calls.
33659 @item longjmp resume
33660 Internal breakpoint at the target of a @code{longjmp}.
33663 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33666 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33669 Shared library events.
33673 @kindex maint info bfds
33674 @item maint info bfds
33675 This prints information about each @code{bfd} object that is known to
33676 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33678 @kindex set displaced-stepping
33679 @kindex show displaced-stepping
33680 @cindex displaced stepping support
33681 @cindex out-of-line single-stepping
33682 @item set displaced-stepping
33683 @itemx show displaced-stepping
33684 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33685 if the target supports it. Displaced stepping is a way to single-step
33686 over breakpoints without removing them from the inferior, by executing
33687 an out-of-line copy of the instruction that was originally at the
33688 breakpoint location. It is also known as out-of-line single-stepping.
33691 @item set displaced-stepping on
33692 If the target architecture supports it, @value{GDBN} will use
33693 displaced stepping to step over breakpoints.
33695 @item set displaced-stepping off
33696 @value{GDBN} will not use displaced stepping to step over breakpoints,
33697 even if such is supported by the target architecture.
33699 @cindex non-stop mode, and @samp{set displaced-stepping}
33700 @item set displaced-stepping auto
33701 This is the default mode. @value{GDBN} will use displaced stepping
33702 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33703 architecture supports displaced stepping.
33706 @kindex maint check-psymtabs
33707 @item maint check-psymtabs
33708 Check the consistency of currently expanded psymtabs versus symtabs.
33709 Use this to check, for example, whether a symbol is in one but not the other.
33711 @kindex maint check-symtabs
33712 @item maint check-symtabs
33713 Check the consistency of currently expanded symtabs.
33715 @kindex maint expand-symtabs
33716 @item maint expand-symtabs [@var{regexp}]
33717 Expand symbol tables.
33718 If @var{regexp} is specified, only expand symbol tables for file
33719 names matching @var{regexp}.
33721 @kindex maint set catch-demangler-crashes
33722 @kindex maint show catch-demangler-crashes
33723 @cindex demangler crashes
33724 @item maint set catch-demangler-crashes [on|off]
33725 @itemx maint show catch-demangler-crashes
33726 Control whether @value{GDBN} should attempt to catch crashes in the
33727 symbol name demangler. The default is to attempt to catch crashes.
33728 If enabled, the first time a crash is caught, a core file is created,
33729 the offending symbol is displayed and the user is presented with the
33730 option to terminate the current session.
33732 @kindex maint cplus first_component
33733 @item maint cplus first_component @var{name}
33734 Print the first C@t{++} class/namespace component of @var{name}.
33736 @kindex maint cplus namespace
33737 @item maint cplus namespace
33738 Print the list of possible C@t{++} namespaces.
33740 @kindex maint deprecate
33741 @kindex maint undeprecate
33742 @cindex deprecated commands
33743 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33744 @itemx maint undeprecate @var{command}
33745 Deprecate or undeprecate the named @var{command}. Deprecated commands
33746 cause @value{GDBN} to issue a warning when you use them. The optional
33747 argument @var{replacement} says which newer command should be used in
33748 favor of the deprecated one; if it is given, @value{GDBN} will mention
33749 the replacement as part of the warning.
33751 @kindex maint dump-me
33752 @item maint dump-me
33753 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33754 Cause a fatal signal in the debugger and force it to dump its core.
33755 This is supported only on systems which support aborting a program
33756 with the @code{SIGQUIT} signal.
33758 @kindex maint internal-error
33759 @kindex maint internal-warning
33760 @kindex maint demangler-warning
33761 @cindex demangler crashes
33762 @item maint internal-error @r{[}@var{message-text}@r{]}
33763 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33764 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33766 Cause @value{GDBN} to call the internal function @code{internal_error},
33767 @code{internal_warning} or @code{demangler_warning} and hence behave
33768 as though an internal problem has been detected. In addition to
33769 reporting the internal problem, these functions give the user the
33770 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33771 and @code{internal_warning}) create a core file of the current
33772 @value{GDBN} session.
33774 These commands take an optional parameter @var{message-text} that is
33775 used as the text of the error or warning message.
33777 Here's an example of using @code{internal-error}:
33780 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33781 @dots{}/maint.c:121: internal-error: testing, 1, 2
33782 A problem internal to GDB has been detected. Further
33783 debugging may prove unreliable.
33784 Quit this debugging session? (y or n) @kbd{n}
33785 Create a core file? (y or n) @kbd{n}
33789 @cindex @value{GDBN} internal error
33790 @cindex internal errors, control of @value{GDBN} behavior
33791 @cindex demangler crashes
33793 @kindex maint set internal-error
33794 @kindex maint show internal-error
33795 @kindex maint set internal-warning
33796 @kindex maint show internal-warning
33797 @kindex maint set demangler-warning
33798 @kindex maint show demangler-warning
33799 @item maint set internal-error @var{action} [ask|yes|no]
33800 @itemx maint show internal-error @var{action}
33801 @itemx maint set internal-warning @var{action} [ask|yes|no]
33802 @itemx maint show internal-warning @var{action}
33803 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33804 @itemx maint show demangler-warning @var{action}
33805 When @value{GDBN} reports an internal problem (error or warning) it
33806 gives the user the opportunity to both quit @value{GDBN} and create a
33807 core file of the current @value{GDBN} session. These commands let you
33808 override the default behaviour for each particular @var{action},
33809 described in the table below.
33813 You can specify that @value{GDBN} should always (yes) or never (no)
33814 quit. The default is to ask the user what to do.
33817 You can specify that @value{GDBN} should always (yes) or never (no)
33818 create a core file. The default is to ask the user what to do. Note
33819 that there is no @code{corefile} option for @code{demangler-warning}:
33820 demangler warnings always create a core file and this cannot be
33824 @kindex maint packet
33825 @item maint packet @var{text}
33826 If @value{GDBN} is talking to an inferior via the serial protocol,
33827 then this command sends the string @var{text} to the inferior, and
33828 displays the response packet. @value{GDBN} supplies the initial
33829 @samp{$} character, the terminating @samp{#} character, and the
33832 @kindex maint print architecture
33833 @item maint print architecture @r{[}@var{file}@r{]}
33834 Print the entire architecture configuration. The optional argument
33835 @var{file} names the file where the output goes.
33837 @kindex maint print c-tdesc
33838 @item maint print c-tdesc
33839 Print the current target description (@pxref{Target Descriptions}) as
33840 a C source file. The created source file can be used in @value{GDBN}
33841 when an XML parser is not available to parse the description.
33843 @kindex maint print dummy-frames
33844 @item maint print dummy-frames
33845 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33848 (@value{GDBP}) @kbd{b add}
33850 (@value{GDBP}) @kbd{print add(2,3)}
33851 Breakpoint 2, add (a=2, b=3) at @dots{}
33853 The program being debugged stopped while in a function called from GDB.
33855 (@value{GDBP}) @kbd{maint print dummy-frames}
33856 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33860 Takes an optional file parameter.
33862 @kindex maint print registers
33863 @kindex maint print raw-registers
33864 @kindex maint print cooked-registers
33865 @kindex maint print register-groups
33866 @kindex maint print remote-registers
33867 @item maint print registers @r{[}@var{file}@r{]}
33868 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33869 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33870 @itemx maint print register-groups @r{[}@var{file}@r{]}
33871 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33872 Print @value{GDBN}'s internal register data structures.
33874 The command @code{maint print raw-registers} includes the contents of
33875 the raw register cache; the command @code{maint print
33876 cooked-registers} includes the (cooked) value of all registers,
33877 including registers which aren't available on the target nor visible
33878 to user; the command @code{maint print register-groups} includes the
33879 groups that each register is a member of; and the command @code{maint
33880 print remote-registers} includes the remote target's register numbers
33881 and offsets in the `G' packets.
33883 These commands take an optional parameter, a file name to which to
33884 write the information.
33886 @kindex maint print reggroups
33887 @item maint print reggroups @r{[}@var{file}@r{]}
33888 Print @value{GDBN}'s internal register group data structures. The
33889 optional argument @var{file} tells to what file to write the
33892 The register groups info looks like this:
33895 (@value{GDBP}) @kbd{maint print reggroups}
33908 This command forces @value{GDBN} to flush its internal register cache.
33910 @kindex maint print objfiles
33911 @cindex info for known object files
33912 @item maint print objfiles @r{[}@var{regexp}@r{]}
33913 Print a dump of all known object files.
33914 If @var{regexp} is specified, only print object files whose names
33915 match @var{regexp}. For each object file, this command prints its name,
33916 address in memory, and all of its psymtabs and symtabs.
33918 @kindex maint print user-registers
33919 @cindex user registers
33920 @item maint print user-registers
33921 List all currently available @dfn{user registers}. User registers
33922 typically provide alternate names for actual hardware registers. They
33923 include the four ``standard'' registers @code{$fp}, @code{$pc},
33924 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33925 registers can be used in expressions in the same way as the canonical
33926 register names, but only the latter are listed by the @code{info
33927 registers} and @code{maint print registers} commands.
33929 @kindex maint print section-scripts
33930 @cindex info for known .debug_gdb_scripts-loaded scripts
33931 @item maint print section-scripts [@var{regexp}]
33932 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33933 If @var{regexp} is specified, only print scripts loaded by object files
33934 matching @var{regexp}.
33935 For each script, this command prints its name as specified in the objfile,
33936 and the full path if known.
33937 @xref{dotdebug_gdb_scripts section}.
33939 @kindex maint print statistics
33940 @cindex bcache statistics
33941 @item maint print statistics
33942 This command prints, for each object file in the program, various data
33943 about that object file followed by the byte cache (@dfn{bcache})
33944 statistics for the object file. The objfile data includes the number
33945 of minimal, partial, full, and stabs symbols, the number of types
33946 defined by the objfile, the number of as yet unexpanded psym tables,
33947 the number of line tables and string tables, and the amount of memory
33948 used by the various tables. The bcache statistics include the counts,
33949 sizes, and counts of duplicates of all and unique objects, max,
33950 average, and median entry size, total memory used and its overhead and
33951 savings, and various measures of the hash table size and chain
33954 @kindex maint print target-stack
33955 @cindex target stack description
33956 @item maint print target-stack
33957 A @dfn{target} is an interface between the debugger and a particular
33958 kind of file or process. Targets can be stacked in @dfn{strata},
33959 so that more than one target can potentially respond to a request.
33960 In particular, memory accesses will walk down the stack of targets
33961 until they find a target that is interested in handling that particular
33964 This command prints a short description of each layer that was pushed on
33965 the @dfn{target stack}, starting from the top layer down to the bottom one.
33967 @kindex maint print type
33968 @cindex type chain of a data type
33969 @item maint print type @var{expr}
33970 Print the type chain for a type specified by @var{expr}. The argument
33971 can be either a type name or a symbol. If it is a symbol, the type of
33972 that symbol is described. The type chain produced by this command is
33973 a recursive definition of the data type as stored in @value{GDBN}'s
33974 data structures, including its flags and contained types.
33976 @kindex maint set dwarf2 always-disassemble
33977 @kindex maint show dwarf2 always-disassemble
33978 @item maint set dwarf2 always-disassemble
33979 @item maint show dwarf2 always-disassemble
33980 Control the behavior of @code{info address} when using DWARF debugging
33983 The default is @code{off}, which means that @value{GDBN} should try to
33984 describe a variable's location in an easily readable format. When
33985 @code{on}, @value{GDBN} will instead display the DWARF location
33986 expression in an assembly-like format. Note that some locations are
33987 too complex for @value{GDBN} to describe simply; in this case you will
33988 always see the disassembly form.
33990 Here is an example of the resulting disassembly:
33993 (gdb) info addr argc
33994 Symbol "argc" is a complex DWARF expression:
33998 For more information on these expressions, see
33999 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34001 @kindex maint set dwarf2 max-cache-age
34002 @kindex maint show dwarf2 max-cache-age
34003 @item maint set dwarf2 max-cache-age
34004 @itemx maint show dwarf2 max-cache-age
34005 Control the DWARF 2 compilation unit cache.
34007 @cindex DWARF 2 compilation units cache
34008 In object files with inter-compilation-unit references, such as those
34009 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34010 reader needs to frequently refer to previously read compilation units.
34011 This setting controls how long a compilation unit will remain in the
34012 cache if it is not referenced. A higher limit means that cached
34013 compilation units will be stored in memory longer, and more total
34014 memory will be used. Setting it to zero disables caching, which will
34015 slow down @value{GDBN} startup, but reduce memory consumption.
34017 @kindex maint set profile
34018 @kindex maint show profile
34019 @cindex profiling GDB
34020 @item maint set profile
34021 @itemx maint show profile
34022 Control profiling of @value{GDBN}.
34024 Profiling will be disabled until you use the @samp{maint set profile}
34025 command to enable it. When you enable profiling, the system will begin
34026 collecting timing and execution count data; when you disable profiling or
34027 exit @value{GDBN}, the results will be written to a log file. Remember that
34028 if you use profiling, @value{GDBN} will overwrite the profiling log file
34029 (often called @file{gmon.out}). If you have a record of important profiling
34030 data in a @file{gmon.out} file, be sure to move it to a safe location.
34032 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34033 compiled with the @samp{-pg} compiler option.
34035 @kindex maint set show-debug-regs
34036 @kindex maint show show-debug-regs
34037 @cindex hardware debug registers
34038 @item maint set show-debug-regs
34039 @itemx maint show show-debug-regs
34040 Control whether to show variables that mirror the hardware debug
34041 registers. Use @code{on} to enable, @code{off} to disable. If
34042 enabled, the debug registers values are shown when @value{GDBN} inserts or
34043 removes a hardware breakpoint or watchpoint, and when the inferior
34044 triggers a hardware-assisted breakpoint or watchpoint.
34046 @kindex maint set show-all-tib
34047 @kindex maint show show-all-tib
34048 @item maint set show-all-tib
34049 @itemx maint show show-all-tib
34050 Control whether to show all non zero areas within a 1k block starting
34051 at thread local base, when using the @samp{info w32 thread-information-block}
34054 @kindex maint set target-async
34055 @kindex maint show target-async
34056 @item maint set target-async
34057 @itemx maint show target-async
34058 This controls whether @value{GDBN} targets operate in synchronous or
34059 asynchronous mode (@pxref{Background Execution}). Normally the
34060 default is asynchronous, if it is available; but this can be changed
34061 to more easily debug problems occurring only in synchronous mode.
34063 @kindex maint set per-command
34064 @kindex maint show per-command
34065 @item maint set per-command
34066 @itemx maint show per-command
34067 @cindex resources used by commands
34069 @value{GDBN} can display the resources used by each command.
34070 This is useful in debugging performance problems.
34073 @item maint set per-command space [on|off]
34074 @itemx maint show per-command space
34075 Enable or disable the printing of the memory used by GDB for each command.
34076 If enabled, @value{GDBN} will display how much memory each command
34077 took, following the command's own output.
34078 This can also be requested by invoking @value{GDBN} with the
34079 @option{--statistics} command-line switch (@pxref{Mode Options}).
34081 @item maint set per-command time [on|off]
34082 @itemx maint show per-command time
34083 Enable or disable the printing of the execution time of @value{GDBN}
34085 If enabled, @value{GDBN} will display how much time it
34086 took to execute each command, following the command's own output.
34087 Both CPU time and wallclock time are printed.
34088 Printing both is useful when trying to determine whether the cost is
34089 CPU or, e.g., disk/network latency.
34090 Note that the CPU time printed is for @value{GDBN} only, it does not include
34091 the execution time of the inferior because there's no mechanism currently
34092 to compute how much time was spent by @value{GDBN} and how much time was
34093 spent by the program been debugged.
34094 This can also be requested by invoking @value{GDBN} with the
34095 @option{--statistics} command-line switch (@pxref{Mode Options}).
34097 @item maint set per-command symtab [on|off]
34098 @itemx maint show per-command symtab
34099 Enable or disable the printing of basic symbol table statistics
34101 If enabled, @value{GDBN} will display the following information:
34105 number of symbol tables
34107 number of primary symbol tables
34109 number of blocks in the blockvector
34113 @kindex maint space
34114 @cindex memory used by commands
34115 @item maint space @var{value}
34116 An alias for @code{maint set per-command space}.
34117 A non-zero value enables it, zero disables it.
34120 @cindex time of command execution
34121 @item maint time @var{value}
34122 An alias for @code{maint set per-command time}.
34123 A non-zero value enables it, zero disables it.
34125 @kindex maint translate-address
34126 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34127 Find the symbol stored at the location specified by the address
34128 @var{addr} and an optional section name @var{section}. If found,
34129 @value{GDBN} prints the name of the closest symbol and an offset from
34130 the symbol's location to the specified address. This is similar to
34131 the @code{info address} command (@pxref{Symbols}), except that this
34132 command also allows to find symbols in other sections.
34134 If section was not specified, the section in which the symbol was found
34135 is also printed. For dynamically linked executables, the name of
34136 executable or shared library containing the symbol is printed as well.
34140 The following command is useful for non-interactive invocations of
34141 @value{GDBN}, such as in the test suite.
34144 @item set watchdog @var{nsec}
34145 @kindex set watchdog
34146 @cindex watchdog timer
34147 @cindex timeout for commands
34148 Set the maximum number of seconds @value{GDBN} will wait for the
34149 target operation to finish. If this time expires, @value{GDBN}
34150 reports and error and the command is aborted.
34152 @item show watchdog
34153 Show the current setting of the target wait timeout.
34156 @node Remote Protocol
34157 @appendix @value{GDBN} Remote Serial Protocol
34162 * Stop Reply Packets::
34163 * General Query Packets::
34164 * Architecture-Specific Protocol Details::
34165 * Tracepoint Packets::
34166 * Host I/O Packets::
34168 * Notification Packets::
34169 * Remote Non-Stop::
34170 * Packet Acknowledgment::
34172 * File-I/O Remote Protocol Extension::
34173 * Library List Format::
34174 * Library List Format for SVR4 Targets::
34175 * Memory Map Format::
34176 * Thread List Format::
34177 * Traceframe Info Format::
34178 * Branch Trace Format::
34179 * Branch Trace Configuration Format::
34185 There may be occasions when you need to know something about the
34186 protocol---for example, if there is only one serial port to your target
34187 machine, you might want your program to do something special if it
34188 recognizes a packet meant for @value{GDBN}.
34190 In the examples below, @samp{->} and @samp{<-} are used to indicate
34191 transmitted and received data, respectively.
34193 @cindex protocol, @value{GDBN} remote serial
34194 @cindex serial protocol, @value{GDBN} remote
34195 @cindex remote serial protocol
34196 All @value{GDBN} commands and responses (other than acknowledgments
34197 and notifications, see @ref{Notification Packets}) are sent as a
34198 @var{packet}. A @var{packet} is introduced with the character
34199 @samp{$}, the actual @var{packet-data}, and the terminating character
34200 @samp{#} followed by a two-digit @var{checksum}:
34203 @code{$}@var{packet-data}@code{#}@var{checksum}
34207 @cindex checksum, for @value{GDBN} remote
34209 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34210 characters between the leading @samp{$} and the trailing @samp{#} (an
34211 eight bit unsigned checksum).
34213 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34214 specification also included an optional two-digit @var{sequence-id}:
34217 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34220 @cindex sequence-id, for @value{GDBN} remote
34222 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34223 has never output @var{sequence-id}s. Stubs that handle packets added
34224 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34226 When either the host or the target machine receives a packet, the first
34227 response expected is an acknowledgment: either @samp{+} (to indicate
34228 the package was received correctly) or @samp{-} (to request
34232 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34237 The @samp{+}/@samp{-} acknowledgments can be disabled
34238 once a connection is established.
34239 @xref{Packet Acknowledgment}, for details.
34241 The host (@value{GDBN}) sends @var{command}s, and the target (the
34242 debugging stub incorporated in your program) sends a @var{response}. In
34243 the case of step and continue @var{command}s, the response is only sent
34244 when the operation has completed, and the target has again stopped all
34245 threads in all attached processes. This is the default all-stop mode
34246 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34247 execution mode; see @ref{Remote Non-Stop}, for details.
34249 @var{packet-data} consists of a sequence of characters with the
34250 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34253 @cindex remote protocol, field separator
34254 Fields within the packet should be separated using @samp{,} @samp{;} or
34255 @samp{:}. Except where otherwise noted all numbers are represented in
34256 @sc{hex} with leading zeros suppressed.
34258 Implementors should note that prior to @value{GDBN} 5.0, the character
34259 @samp{:} could not appear as the third character in a packet (as it
34260 would potentially conflict with the @var{sequence-id}).
34262 @cindex remote protocol, binary data
34263 @anchor{Binary Data}
34264 Binary data in most packets is encoded either as two hexadecimal
34265 digits per byte of binary data. This allowed the traditional remote
34266 protocol to work over connections which were only seven-bit clean.
34267 Some packets designed more recently assume an eight-bit clean
34268 connection, and use a more efficient encoding to send and receive
34271 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34272 as an escape character. Any escaped byte is transmitted as the escape
34273 character followed by the original character XORed with @code{0x20}.
34274 For example, the byte @code{0x7d} would be transmitted as the two
34275 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34276 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34277 @samp{@}}) must always be escaped. Responses sent by the stub
34278 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34279 is not interpreted as the start of a run-length encoded sequence
34282 Response @var{data} can be run-length encoded to save space.
34283 Run-length encoding replaces runs of identical characters with one
34284 instance of the repeated character, followed by a @samp{*} and a
34285 repeat count. The repeat count is itself sent encoded, to avoid
34286 binary characters in @var{data}: a value of @var{n} is sent as
34287 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34288 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34289 code 32) for a repeat count of 3. (This is because run-length
34290 encoding starts to win for counts 3 or more.) Thus, for example,
34291 @samp{0* } is a run-length encoding of ``0000'': the space character
34292 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34295 The printable characters @samp{#} and @samp{$} or with a numeric value
34296 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34297 seven repeats (@samp{$}) can be expanded using a repeat count of only
34298 five (@samp{"}). For example, @samp{00000000} can be encoded as
34301 The error response returned for some packets includes a two character
34302 error number. That number is not well defined.
34304 @cindex empty response, for unsupported packets
34305 For any @var{command} not supported by the stub, an empty response
34306 (@samp{$#00}) should be returned. That way it is possible to extend the
34307 protocol. A newer @value{GDBN} can tell if a packet is supported based
34310 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34311 commands for register access, and the @samp{m} and @samp{M} commands
34312 for memory access. Stubs that only control single-threaded targets
34313 can implement run control with the @samp{c} (continue), and @samp{s}
34314 (step) commands. Stubs that support multi-threading targets should
34315 support the @samp{vCont} command. All other commands are optional.
34320 The following table provides a complete list of all currently defined
34321 @var{command}s and their corresponding response @var{data}.
34322 @xref{File-I/O Remote Protocol Extension}, for details about the File
34323 I/O extension of the remote protocol.
34325 Each packet's description has a template showing the packet's overall
34326 syntax, followed by an explanation of the packet's meaning. We
34327 include spaces in some of the templates for clarity; these are not
34328 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34329 separate its components. For example, a template like @samp{foo
34330 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34331 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34332 @var{baz}. @value{GDBN} does not transmit a space character between the
34333 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34336 @cindex @var{thread-id}, in remote protocol
34337 @anchor{thread-id syntax}
34338 Several packets and replies include a @var{thread-id} field to identify
34339 a thread. Normally these are positive numbers with a target-specific
34340 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34341 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34344 In addition, the remote protocol supports a multiprocess feature in
34345 which the @var{thread-id} syntax is extended to optionally include both
34346 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34347 The @var{pid} (process) and @var{tid} (thread) components each have the
34348 format described above: a positive number with target-specific
34349 interpretation formatted as a big-endian hex string, literal @samp{-1}
34350 to indicate all processes or threads (respectively), or @samp{0} to
34351 indicate an arbitrary process or thread. Specifying just a process, as
34352 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34353 error to specify all processes but a specific thread, such as
34354 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34355 for those packets and replies explicitly documented to include a process
34356 ID, rather than a @var{thread-id}.
34358 The multiprocess @var{thread-id} syntax extensions are only used if both
34359 @value{GDBN} and the stub report support for the @samp{multiprocess}
34360 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34363 Note that all packet forms beginning with an upper- or lower-case
34364 letter, other than those described here, are reserved for future use.
34366 Here are the packet descriptions.
34371 @cindex @samp{!} packet
34372 @anchor{extended mode}
34373 Enable extended mode. In extended mode, the remote server is made
34374 persistent. The @samp{R} packet is used to restart the program being
34380 The remote target both supports and has enabled extended mode.
34384 @cindex @samp{?} packet
34386 Indicate the reason the target halted. The reply is the same as for
34387 step and continue. This packet has a special interpretation when the
34388 target is in non-stop mode; see @ref{Remote Non-Stop}.
34391 @xref{Stop Reply Packets}, for the reply specifications.
34393 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34394 @cindex @samp{A} packet
34395 Initialized @code{argv[]} array passed into program. @var{arglen}
34396 specifies the number of bytes in the hex encoded byte stream
34397 @var{arg}. See @code{gdbserver} for more details.
34402 The arguments were set.
34408 @cindex @samp{b} packet
34409 (Don't use this packet; its behavior is not well-defined.)
34410 Change the serial line speed to @var{baud}.
34412 JTC: @emph{When does the transport layer state change? When it's
34413 received, or after the ACK is transmitted. In either case, there are
34414 problems if the command or the acknowledgment packet is dropped.}
34416 Stan: @emph{If people really wanted to add something like this, and get
34417 it working for the first time, they ought to modify ser-unix.c to send
34418 some kind of out-of-band message to a specially-setup stub and have the
34419 switch happen "in between" packets, so that from remote protocol's point
34420 of view, nothing actually happened.}
34422 @item B @var{addr},@var{mode}
34423 @cindex @samp{B} packet
34424 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34425 breakpoint at @var{addr}.
34427 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34428 (@pxref{insert breakpoint or watchpoint packet}).
34430 @cindex @samp{bc} packet
34433 Backward continue. Execute the target system in reverse. No parameter.
34434 @xref{Reverse Execution}, for more information.
34437 @xref{Stop Reply Packets}, for the reply specifications.
34439 @cindex @samp{bs} packet
34442 Backward single step. Execute one instruction in reverse. No parameter.
34443 @xref{Reverse Execution}, for more information.
34446 @xref{Stop Reply Packets}, for the reply specifications.
34448 @item c @r{[}@var{addr}@r{]}
34449 @cindex @samp{c} packet
34450 Continue at @var{addr}, which is the address to resume. If @var{addr}
34451 is omitted, resume at current address.
34453 This packet is deprecated for multi-threading support. @xref{vCont
34457 @xref{Stop Reply Packets}, for the reply specifications.
34459 @item C @var{sig}@r{[};@var{addr}@r{]}
34460 @cindex @samp{C} packet
34461 Continue with signal @var{sig} (hex signal number). If
34462 @samp{;@var{addr}} is omitted, resume at same address.
34464 This packet is deprecated for multi-threading support. @xref{vCont
34468 @xref{Stop Reply Packets}, for the reply specifications.
34471 @cindex @samp{d} packet
34474 Don't use this packet; instead, define a general set packet
34475 (@pxref{General Query Packets}).
34479 @cindex @samp{D} packet
34480 The first form of the packet is used to detach @value{GDBN} from the
34481 remote system. It is sent to the remote target
34482 before @value{GDBN} disconnects via the @code{detach} command.
34484 The second form, including a process ID, is used when multiprocess
34485 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34486 detach only a specific process. The @var{pid} is specified as a
34487 big-endian hex string.
34497 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34498 @cindex @samp{F} packet
34499 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34500 This is part of the File-I/O protocol extension. @xref{File-I/O
34501 Remote Protocol Extension}, for the specification.
34504 @anchor{read registers packet}
34505 @cindex @samp{g} packet
34506 Read general registers.
34510 @item @var{XX@dots{}}
34511 Each byte of register data is described by two hex digits. The bytes
34512 with the register are transmitted in target byte order. The size of
34513 each register and their position within the @samp{g} packet are
34514 determined by the @value{GDBN} internal gdbarch functions
34515 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34516 specification of several standard @samp{g} packets is specified below.
34518 When reading registers from a trace frame (@pxref{Analyze Collected
34519 Data,,Using the Collected Data}), the stub may also return a string of
34520 literal @samp{x}'s in place of the register data digits, to indicate
34521 that the corresponding register has not been collected, thus its value
34522 is unavailable. For example, for an architecture with 4 registers of
34523 4 bytes each, the following reply indicates to @value{GDBN} that
34524 registers 0 and 2 have not been collected, while registers 1 and 3
34525 have been collected, and both have zero value:
34529 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34536 @item G @var{XX@dots{}}
34537 @cindex @samp{G} packet
34538 Write general registers. @xref{read registers packet}, for a
34539 description of the @var{XX@dots{}} data.
34549 @item H @var{op} @var{thread-id}
34550 @cindex @samp{H} packet
34551 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34552 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34553 should be @samp{c} for step and continue operations (note that this
34554 is deprecated, supporting the @samp{vCont} command is a better
34555 option), and @samp{g} for other operations. The thread designator
34556 @var{thread-id} has the format and interpretation described in
34557 @ref{thread-id syntax}.
34568 @c 'H': How restrictive (or permissive) is the thread model. If a
34569 @c thread is selected and stopped, are other threads allowed
34570 @c to continue to execute? As I mentioned above, I think the
34571 @c semantics of each command when a thread is selected must be
34572 @c described. For example:
34574 @c 'g': If the stub supports threads and a specific thread is
34575 @c selected, returns the register block from that thread;
34576 @c otherwise returns current registers.
34578 @c 'G' If the stub supports threads and a specific thread is
34579 @c selected, sets the registers of the register block of
34580 @c that thread; otherwise sets current registers.
34582 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34583 @anchor{cycle step packet}
34584 @cindex @samp{i} packet
34585 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34586 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34587 step starting at that address.
34590 @cindex @samp{I} packet
34591 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34595 @cindex @samp{k} packet
34598 The exact effect of this packet is not specified.
34600 For a bare-metal target, it may power cycle or reset the target
34601 system. For that reason, the @samp{k} packet has no reply.
34603 For a single-process target, it may kill that process if possible.
34605 A multiple-process target may choose to kill just one process, or all
34606 that are under @value{GDBN}'s control. For more precise control, use
34607 the vKill packet (@pxref{vKill packet}).
34609 If the target system immediately closes the connection in response to
34610 @samp{k}, @value{GDBN} does not consider the lack of packet
34611 acknowledgment to be an error, and assumes the kill was successful.
34613 If connected using @kbd{target extended-remote}, and the target does
34614 not close the connection in response to a kill request, @value{GDBN}
34615 probes the target state as if a new connection was opened
34616 (@pxref{? packet}).
34618 @item m @var{addr},@var{length}
34619 @cindex @samp{m} packet
34620 Read @var{length} bytes of memory starting at address @var{addr}.
34621 Note that @var{addr} may not be aligned to any particular boundary.
34623 The stub need not use any particular size or alignment when gathering
34624 data from memory for the response; even if @var{addr} is word-aligned
34625 and @var{length} is a multiple of the word size, the stub is free to
34626 use byte accesses, or not. For this reason, this packet may not be
34627 suitable for accessing memory-mapped I/O devices.
34628 @cindex alignment of remote memory accesses
34629 @cindex size of remote memory accesses
34630 @cindex memory, alignment and size of remote accesses
34634 @item @var{XX@dots{}}
34635 Memory contents; each byte is transmitted as a two-digit hexadecimal
34636 number. The reply may contain fewer bytes than requested if the
34637 server was able to read only part of the region of memory.
34642 @item M @var{addr},@var{length}:@var{XX@dots{}}
34643 @cindex @samp{M} packet
34644 Write @var{length} bytes of memory starting at address @var{addr}.
34645 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34646 hexadecimal number.
34653 for an error (this includes the case where only part of the data was
34658 @cindex @samp{p} packet
34659 Read the value of register @var{n}; @var{n} is in hex.
34660 @xref{read registers packet}, for a description of how the returned
34661 register value is encoded.
34665 @item @var{XX@dots{}}
34666 the register's value
34670 Indicating an unrecognized @var{query}.
34673 @item P @var{n@dots{}}=@var{r@dots{}}
34674 @anchor{write register packet}
34675 @cindex @samp{P} packet
34676 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34677 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34678 digits for each byte in the register (target byte order).
34688 @item q @var{name} @var{params}@dots{}
34689 @itemx Q @var{name} @var{params}@dots{}
34690 @cindex @samp{q} packet
34691 @cindex @samp{Q} packet
34692 General query (@samp{q}) and set (@samp{Q}). These packets are
34693 described fully in @ref{General Query Packets}.
34696 @cindex @samp{r} packet
34697 Reset the entire system.
34699 Don't use this packet; use the @samp{R} packet instead.
34702 @cindex @samp{R} packet
34703 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34704 This packet is only available in extended mode (@pxref{extended mode}).
34706 The @samp{R} packet has no reply.
34708 @item s @r{[}@var{addr}@r{]}
34709 @cindex @samp{s} packet
34710 Single step, resuming at @var{addr}. If
34711 @var{addr} is omitted, resume at same address.
34713 This packet is deprecated for multi-threading support. @xref{vCont
34717 @xref{Stop Reply Packets}, for the reply specifications.
34719 @item S @var{sig}@r{[};@var{addr}@r{]}
34720 @anchor{step with signal packet}
34721 @cindex @samp{S} packet
34722 Step with signal. This is analogous to the @samp{C} packet, but
34723 requests a single-step, rather than a normal resumption of execution.
34725 This packet is deprecated for multi-threading support. @xref{vCont
34729 @xref{Stop Reply Packets}, for the reply specifications.
34731 @item t @var{addr}:@var{PP},@var{MM}
34732 @cindex @samp{t} packet
34733 Search backwards starting at address @var{addr} for a match with pattern
34734 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34735 There must be at least 3 digits in @var{addr}.
34737 @item T @var{thread-id}
34738 @cindex @samp{T} packet
34739 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34744 thread is still alive
34750 Packets starting with @samp{v} are identified by a multi-letter name,
34751 up to the first @samp{;} or @samp{?} (or the end of the packet).
34753 @item vAttach;@var{pid}
34754 @cindex @samp{vAttach} packet
34755 Attach to a new process with the specified process ID @var{pid}.
34756 The process ID is a
34757 hexadecimal integer identifying the process. In all-stop mode, all
34758 threads in the attached process are stopped; in non-stop mode, it may be
34759 attached without being stopped if that is supported by the target.
34761 @c In non-stop mode, on a successful vAttach, the stub should set the
34762 @c current thread to a thread of the newly-attached process. After
34763 @c attaching, GDB queries for the attached process's thread ID with qC.
34764 @c Also note that, from a user perspective, whether or not the
34765 @c target is stopped on attach in non-stop mode depends on whether you
34766 @c use the foreground or background version of the attach command, not
34767 @c on what vAttach does; GDB does the right thing with respect to either
34768 @c stopping or restarting threads.
34770 This packet is only available in extended mode (@pxref{extended mode}).
34776 @item @r{Any stop packet}
34777 for success in all-stop mode (@pxref{Stop Reply Packets})
34779 for success in non-stop mode (@pxref{Remote Non-Stop})
34782 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34783 @cindex @samp{vCont} packet
34784 @anchor{vCont packet}
34785 Resume the inferior, specifying different actions for each thread.
34786 If an action is specified with no @var{thread-id}, then it is applied to any
34787 threads that don't have a specific action specified; if no default action is
34788 specified then other threads should remain stopped in all-stop mode and
34789 in their current state in non-stop mode.
34790 Specifying multiple
34791 default actions is an error; specifying no actions is also an error.
34792 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34794 Currently supported actions are:
34800 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34804 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34807 @item r @var{start},@var{end}
34808 Step once, and then keep stepping as long as the thread stops at
34809 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34810 The remote stub reports a stop reply when either the thread goes out
34811 of the range or is stopped due to an unrelated reason, such as hitting
34812 a breakpoint. @xref{range stepping}.
34814 If the range is empty (@var{start} == @var{end}), then the action
34815 becomes equivalent to the @samp{s} action. In other words,
34816 single-step once, and report the stop (even if the stepped instruction
34817 jumps to @var{start}).
34819 (A stop reply may be sent at any point even if the PC is still within
34820 the stepping range; for example, it is valid to implement this packet
34821 in a degenerate way as a single instruction step operation.)
34825 The optional argument @var{addr} normally associated with the
34826 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34827 not supported in @samp{vCont}.
34829 The @samp{t} action is only relevant in non-stop mode
34830 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34831 A stop reply should be generated for any affected thread not already stopped.
34832 When a thread is stopped by means of a @samp{t} action,
34833 the corresponding stop reply should indicate that the thread has stopped with
34834 signal @samp{0}, regardless of whether the target uses some other signal
34835 as an implementation detail.
34837 The stub must support @samp{vCont} if it reports support for
34838 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34839 this case @samp{vCont} actions can be specified to apply to all threads
34840 in a process by using the @samp{p@var{pid}.-1} form of the
34844 @xref{Stop Reply Packets}, for the reply specifications.
34847 @cindex @samp{vCont?} packet
34848 Request a list of actions supported by the @samp{vCont} packet.
34852 @item vCont@r{[};@var{action}@dots{}@r{]}
34853 The @samp{vCont} packet is supported. Each @var{action} is a supported
34854 command in the @samp{vCont} packet.
34856 The @samp{vCont} packet is not supported.
34859 @item vFile:@var{operation}:@var{parameter}@dots{}
34860 @cindex @samp{vFile} packet
34861 Perform a file operation on the target system. For details,
34862 see @ref{Host I/O Packets}.
34864 @item vFlashErase:@var{addr},@var{length}
34865 @cindex @samp{vFlashErase} packet
34866 Direct the stub to erase @var{length} bytes of flash starting at
34867 @var{addr}. The region may enclose any number of flash blocks, but
34868 its start and end must fall on block boundaries, as indicated by the
34869 flash block size appearing in the memory map (@pxref{Memory Map
34870 Format}). @value{GDBN} groups flash memory programming operations
34871 together, and sends a @samp{vFlashDone} request after each group; the
34872 stub is allowed to delay erase operation until the @samp{vFlashDone}
34873 packet is received.
34883 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34884 @cindex @samp{vFlashWrite} packet
34885 Direct the stub to write data to flash address @var{addr}. The data
34886 is passed in binary form using the same encoding as for the @samp{X}
34887 packet (@pxref{Binary Data}). The memory ranges specified by
34888 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34889 not overlap, and must appear in order of increasing addresses
34890 (although @samp{vFlashErase} packets for higher addresses may already
34891 have been received; the ordering is guaranteed only between
34892 @samp{vFlashWrite} packets). If a packet writes to an address that was
34893 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34894 target-specific method, the results are unpredictable.
34902 for vFlashWrite addressing non-flash memory
34908 @cindex @samp{vFlashDone} packet
34909 Indicate to the stub that flash programming operation is finished.
34910 The stub is permitted to delay or batch the effects of a group of
34911 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34912 @samp{vFlashDone} packet is received. The contents of the affected
34913 regions of flash memory are unpredictable until the @samp{vFlashDone}
34914 request is completed.
34916 @item vKill;@var{pid}
34917 @cindex @samp{vKill} packet
34918 @anchor{vKill packet}
34919 Kill the process with the specified process ID @var{pid}, which is a
34920 hexadecimal integer identifying the process. This packet is used in
34921 preference to @samp{k} when multiprocess protocol extensions are
34922 supported; see @ref{multiprocess extensions}.
34932 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34933 @cindex @samp{vRun} packet
34934 Run the program @var{filename}, passing it each @var{argument} on its
34935 command line. The file and arguments are hex-encoded strings. If
34936 @var{filename} is an empty string, the stub may use a default program
34937 (e.g.@: the last program run). The program is created in the stopped
34940 @c FIXME: What about non-stop mode?
34942 This packet is only available in extended mode (@pxref{extended mode}).
34948 @item @r{Any stop packet}
34949 for success (@pxref{Stop Reply Packets})
34953 @cindex @samp{vStopped} packet
34954 @xref{Notification Packets}.
34956 @item X @var{addr},@var{length}:@var{XX@dots{}}
34958 @cindex @samp{X} packet
34959 Write data to memory, where the data is transmitted in binary.
34960 Memory is specified by its address @var{addr} and number of bytes @var{length};
34961 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34971 @item z @var{type},@var{addr},@var{kind}
34972 @itemx Z @var{type},@var{addr},@var{kind}
34973 @anchor{insert breakpoint or watchpoint packet}
34974 @cindex @samp{z} packet
34975 @cindex @samp{Z} packets
34976 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34977 watchpoint starting at address @var{address} of kind @var{kind}.
34979 Each breakpoint and watchpoint packet @var{type} is documented
34982 @emph{Implementation notes: A remote target shall return an empty string
34983 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34984 remote target shall support either both or neither of a given
34985 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34986 avoid potential problems with duplicate packets, the operations should
34987 be implemented in an idempotent way.}
34989 @item z0,@var{addr},@var{kind}
34990 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34991 @cindex @samp{z0} packet
34992 @cindex @samp{Z0} packet
34993 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34994 @var{addr} of type @var{kind}.
34996 A memory breakpoint is implemented by replacing the instruction at
34997 @var{addr} with a software breakpoint or trap instruction. The
34998 @var{kind} is target-specific and typically indicates the size of
34999 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35000 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35001 architectures have additional meanings for @var{kind};
35002 @var{cond_list} is an optional list of conditional expressions in bytecode
35003 form that should be evaluated on the target's side. These are the
35004 conditions that should be taken into consideration when deciding if
35005 the breakpoint trigger should be reported back to @var{GDBN}.
35007 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35008 for how to best report a memory breakpoint event to @value{GDBN}.
35010 The @var{cond_list} parameter is comprised of a series of expressions,
35011 concatenated without separators. Each expression has the following form:
35015 @item X @var{len},@var{expr}
35016 @var{len} is the length of the bytecode expression and @var{expr} is the
35017 actual conditional expression in bytecode form.
35021 The optional @var{cmd_list} parameter introduces commands that may be
35022 run on the target, rather than being reported back to @value{GDBN}.
35023 The parameter starts with a numeric flag @var{persist}; if the flag is
35024 nonzero, then the breakpoint may remain active and the commands
35025 continue to be run even when @value{GDBN} disconnects from the target.
35026 Following this flag is a series of expressions concatenated with no
35027 separators. Each expression has the following form:
35031 @item X @var{len},@var{expr}
35032 @var{len} is the length of the bytecode expression and @var{expr} is the
35033 actual conditional expression in bytecode form.
35037 see @ref{Architecture-Specific Protocol Details}.
35039 @emph{Implementation note: It is possible for a target to copy or move
35040 code that contains memory breakpoints (e.g., when implementing
35041 overlays). The behavior of this packet, in the presence of such a
35042 target, is not defined.}
35054 @item z1,@var{addr},@var{kind}
35055 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35056 @cindex @samp{z1} packet
35057 @cindex @samp{Z1} packet
35058 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35059 address @var{addr}.
35061 A hardware breakpoint is implemented using a mechanism that is not
35062 dependant on being able to modify the target's memory. The @var{kind}
35063 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35065 @emph{Implementation note: A hardware breakpoint is not affected by code
35078 @item z2,@var{addr},@var{kind}
35079 @itemx Z2,@var{addr},@var{kind}
35080 @cindex @samp{z2} packet
35081 @cindex @samp{Z2} packet
35082 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35083 The number of bytes to watch is specified by @var{kind}.
35095 @item z3,@var{addr},@var{kind}
35096 @itemx Z3,@var{addr},@var{kind}
35097 @cindex @samp{z3} packet
35098 @cindex @samp{Z3} packet
35099 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35100 The number of bytes to watch is specified by @var{kind}.
35112 @item z4,@var{addr},@var{kind}
35113 @itemx Z4,@var{addr},@var{kind}
35114 @cindex @samp{z4} packet
35115 @cindex @samp{Z4} packet
35116 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35117 The number of bytes to watch is specified by @var{kind}.
35131 @node Stop Reply Packets
35132 @section Stop Reply Packets
35133 @cindex stop reply packets
35135 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35136 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35137 receive any of the below as a reply. Except for @samp{?}
35138 and @samp{vStopped}, that reply is only returned
35139 when the target halts. In the below the exact meaning of @dfn{signal
35140 number} is defined by the header @file{include/gdb/signals.h} in the
35141 @value{GDBN} source code.
35143 As in the description of request packets, we include spaces in the
35144 reply templates for clarity; these are not part of the reply packet's
35145 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35151 The program received signal number @var{AA} (a two-digit hexadecimal
35152 number). This is equivalent to a @samp{T} response with no
35153 @var{n}:@var{r} pairs.
35155 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35156 @cindex @samp{T} packet reply
35157 The program received signal number @var{AA} (a two-digit hexadecimal
35158 number). This is equivalent to an @samp{S} response, except that the
35159 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35160 and other information directly in the stop reply packet, reducing
35161 round-trip latency. Single-step and breakpoint traps are reported
35162 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35166 If @var{n} is a hexadecimal number, it is a register number, and the
35167 corresponding @var{r} gives that register's value. The data @var{r} is a
35168 series of bytes in target byte order, with each byte given by a
35169 two-digit hex number.
35172 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35173 the stopped thread, as specified in @ref{thread-id syntax}.
35176 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35177 the core on which the stop event was detected.
35180 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35181 specific event that stopped the target. The currently defined stop
35182 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35183 signal. At most one stop reason should be present.
35186 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35187 and go on to the next; this allows us to extend the protocol in the
35191 The currently defined stop reasons are:
35197 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35200 @cindex shared library events, remote reply
35202 The packet indicates that the loaded libraries have changed.
35203 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35204 list of loaded libraries. The @var{r} part is ignored.
35206 @cindex replay log events, remote reply
35208 The packet indicates that the target cannot continue replaying
35209 logged execution events, because it has reached the end (or the
35210 beginning when executing backward) of the log. The value of @var{r}
35211 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35212 for more information.
35215 @anchor{swbreak stop reason}
35216 The packet indicates a memory breakpoint instruction was executed,
35217 irrespective of whether it was @value{GDBN} that planted the
35218 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35219 part must be left empty.
35221 On some architectures, such as x86, at the architecture level, when a
35222 breakpoint instruction executes the program counter points at the
35223 breakpoint address plus an offset. On such targets, the stub is
35224 responsible for adjusting the PC to point back at the breakpoint
35227 This packet should not be sent by default; older @value{GDBN} versions
35228 did not support it. @value{GDBN} requests it, by supplying an
35229 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35230 remote stub must also supply the appropriate @samp{qSupported} feature
35231 indicating support.
35233 This packet is required for correct non-stop mode operation.
35236 The packet indicates the target stopped for a hardware breakpoint.
35237 The @var{r} part must be left empty.
35239 The same remarks about @samp{qSupported} and non-stop mode above
35244 @itemx W @var{AA} ; process:@var{pid}
35245 The process exited, and @var{AA} is the exit status. This is only
35246 applicable to certain targets.
35248 The second form of the response, including the process ID of the exited
35249 process, can be used only when @value{GDBN} has reported support for
35250 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35251 The @var{pid} is formatted as a big-endian hex string.
35254 @itemx X @var{AA} ; process:@var{pid}
35255 The process terminated with signal @var{AA}.
35257 The second form of the response, including the process ID of the
35258 terminated process, can be used only when @value{GDBN} has reported
35259 support for multiprocess protocol extensions; see @ref{multiprocess
35260 extensions}. The @var{pid} is formatted as a big-endian hex string.
35262 @item O @var{XX}@dots{}
35263 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35264 written as the program's console output. This can happen at any time
35265 while the program is running and the debugger should continue to wait
35266 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35268 @item F @var{call-id},@var{parameter}@dots{}
35269 @var{call-id} is the identifier which says which host system call should
35270 be called. This is just the name of the function. Translation into the
35271 correct system call is only applicable as it's defined in @value{GDBN}.
35272 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35275 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35276 this very system call.
35278 The target replies with this packet when it expects @value{GDBN} to
35279 call a host system call on behalf of the target. @value{GDBN} replies
35280 with an appropriate @samp{F} packet and keeps up waiting for the next
35281 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35282 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35283 Protocol Extension}, for more details.
35287 @node General Query Packets
35288 @section General Query Packets
35289 @cindex remote query requests
35291 Packets starting with @samp{q} are @dfn{general query packets};
35292 packets starting with @samp{Q} are @dfn{general set packets}. General
35293 query and set packets are a semi-unified form for retrieving and
35294 sending information to and from the stub.
35296 The initial letter of a query or set packet is followed by a name
35297 indicating what sort of thing the packet applies to. For example,
35298 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35299 definitions with the stub. These packet names follow some
35304 The name must not contain commas, colons or semicolons.
35306 Most @value{GDBN} query and set packets have a leading upper case
35309 The names of custom vendor packets should use a company prefix, in
35310 lower case, followed by a period. For example, packets designed at
35311 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35312 foos) or @samp{Qacme.bar} (for setting bars).
35315 The name of a query or set packet should be separated from any
35316 parameters by a @samp{:}; the parameters themselves should be
35317 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35318 full packet name, and check for a separator or the end of the packet,
35319 in case two packet names share a common prefix. New packets should not begin
35320 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35321 packets predate these conventions, and have arguments without any terminator
35322 for the packet name; we suspect they are in widespread use in places that
35323 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35324 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35327 Like the descriptions of the other packets, each description here
35328 has a template showing the packet's overall syntax, followed by an
35329 explanation of the packet's meaning. We include spaces in some of the
35330 templates for clarity; these are not part of the packet's syntax. No
35331 @value{GDBN} packet uses spaces to separate its components.
35333 Here are the currently defined query and set packets:
35339 Turn on or off the agent as a helper to perform some debugging operations
35340 delegated from @value{GDBN} (@pxref{Control Agent}).
35342 @item QAllow:@var{op}:@var{val}@dots{}
35343 @cindex @samp{QAllow} packet
35344 Specify which operations @value{GDBN} expects to request of the
35345 target, as a semicolon-separated list of operation name and value
35346 pairs. Possible values for @var{op} include @samp{WriteReg},
35347 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35348 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35349 indicating that @value{GDBN} will not request the operation, or 1,
35350 indicating that it may. (The target can then use this to set up its
35351 own internals optimally, for instance if the debugger never expects to
35352 insert breakpoints, it may not need to install its own trap handler.)
35355 @cindex current thread, remote request
35356 @cindex @samp{qC} packet
35357 Return the current thread ID.
35361 @item QC @var{thread-id}
35362 Where @var{thread-id} is a thread ID as documented in
35363 @ref{thread-id syntax}.
35364 @item @r{(anything else)}
35365 Any other reply implies the old thread ID.
35368 @item qCRC:@var{addr},@var{length}
35369 @cindex CRC of memory block, remote request
35370 @cindex @samp{qCRC} packet
35371 @anchor{qCRC packet}
35372 Compute the CRC checksum of a block of memory using CRC-32 defined in
35373 IEEE 802.3. The CRC is computed byte at a time, taking the most
35374 significant bit of each byte first. The initial pattern code
35375 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35377 @emph{Note:} This is the same CRC used in validating separate debug
35378 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35379 Files}). However the algorithm is slightly different. When validating
35380 separate debug files, the CRC is computed taking the @emph{least}
35381 significant bit of each byte first, and the final result is inverted to
35382 detect trailing zeros.
35387 An error (such as memory fault)
35388 @item C @var{crc32}
35389 The specified memory region's checksum is @var{crc32}.
35392 @item QDisableRandomization:@var{value}
35393 @cindex disable address space randomization, remote request
35394 @cindex @samp{QDisableRandomization} packet
35395 Some target operating systems will randomize the virtual address space
35396 of the inferior process as a security feature, but provide a feature
35397 to disable such randomization, e.g.@: to allow for a more deterministic
35398 debugging experience. On such systems, this packet with a @var{value}
35399 of 1 directs the target to disable address space randomization for
35400 processes subsequently started via @samp{vRun} packets, while a packet
35401 with a @var{value} of 0 tells the target to enable address space
35404 This packet is only available in extended mode (@pxref{extended mode}).
35409 The request succeeded.
35412 An error occurred. The error number @var{nn} is given as hex digits.
35415 An empty reply indicates that @samp{QDisableRandomization} is not supported
35419 This packet is not probed by default; the remote stub must request it,
35420 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35421 This should only be done on targets that actually support disabling
35422 address space randomization.
35425 @itemx qsThreadInfo
35426 @cindex list active threads, remote request
35427 @cindex @samp{qfThreadInfo} packet
35428 @cindex @samp{qsThreadInfo} packet
35429 Obtain a list of all active thread IDs from the target (OS). Since there
35430 may be too many active threads to fit into one reply packet, this query
35431 works iteratively: it may require more than one query/reply sequence to
35432 obtain the entire list of threads. The first query of the sequence will
35433 be the @samp{qfThreadInfo} query; subsequent queries in the
35434 sequence will be the @samp{qsThreadInfo} query.
35436 NOTE: This packet replaces the @samp{qL} query (see below).
35440 @item m @var{thread-id}
35442 @item m @var{thread-id},@var{thread-id}@dots{}
35443 a comma-separated list of thread IDs
35445 (lower case letter @samp{L}) denotes end of list.
35448 In response to each query, the target will reply with a list of one or
35449 more thread IDs, separated by commas.
35450 @value{GDBN} will respond to each reply with a request for more thread
35451 ids (using the @samp{qs} form of the query), until the target responds
35452 with @samp{l} (lower-case ell, for @dfn{last}).
35453 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35456 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35457 initial connection with the remote target, and the very first thread ID
35458 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35459 message. Therefore, the stub should ensure that the first thread ID in
35460 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35462 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35463 @cindex get thread-local storage address, remote request
35464 @cindex @samp{qGetTLSAddr} packet
35465 Fetch the address associated with thread local storage specified
35466 by @var{thread-id}, @var{offset}, and @var{lm}.
35468 @var{thread-id} is the thread ID associated with the
35469 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35471 @var{offset} is the (big endian, hex encoded) offset associated with the
35472 thread local variable. (This offset is obtained from the debug
35473 information associated with the variable.)
35475 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35476 load module associated with the thread local storage. For example,
35477 a @sc{gnu}/Linux system will pass the link map address of the shared
35478 object associated with the thread local storage under consideration.
35479 Other operating environments may choose to represent the load module
35480 differently, so the precise meaning of this parameter will vary.
35484 @item @var{XX}@dots{}
35485 Hex encoded (big endian) bytes representing the address of the thread
35486 local storage requested.
35489 An error occurred. The error number @var{nn} is given as hex digits.
35492 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35495 @item qGetTIBAddr:@var{thread-id}
35496 @cindex get thread information block address
35497 @cindex @samp{qGetTIBAddr} packet
35498 Fetch address of the Windows OS specific Thread Information Block.
35500 @var{thread-id} is the thread ID associated with the thread.
35504 @item @var{XX}@dots{}
35505 Hex encoded (big endian) bytes representing the linear address of the
35506 thread information block.
35509 An error occured. This means that either the thread was not found, or the
35510 address could not be retrieved.
35513 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35516 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35517 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35518 digit) is one to indicate the first query and zero to indicate a
35519 subsequent query; @var{threadcount} (two hex digits) is the maximum
35520 number of threads the response packet can contain; and @var{nextthread}
35521 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35522 returned in the response as @var{argthread}.
35524 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35528 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35529 Where: @var{count} (two hex digits) is the number of threads being
35530 returned; @var{done} (one hex digit) is zero to indicate more threads
35531 and one indicates no further threads; @var{argthreadid} (eight hex
35532 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35533 is a sequence of thread IDs, @var{threadid} (eight hex
35534 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35538 @cindex section offsets, remote request
35539 @cindex @samp{qOffsets} packet
35540 Get section offsets that the target used when relocating the downloaded
35545 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35546 Relocate the @code{Text} section by @var{xxx} from its original address.
35547 Relocate the @code{Data} section by @var{yyy} from its original address.
35548 If the object file format provides segment information (e.g.@: @sc{elf}
35549 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35550 segments by the supplied offsets.
35552 @emph{Note: while a @code{Bss} offset may be included in the response,
35553 @value{GDBN} ignores this and instead applies the @code{Data} offset
35554 to the @code{Bss} section.}
35556 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35557 Relocate the first segment of the object file, which conventionally
35558 contains program code, to a starting address of @var{xxx}. If
35559 @samp{DataSeg} is specified, relocate the second segment, which
35560 conventionally contains modifiable data, to a starting address of
35561 @var{yyy}. @value{GDBN} will report an error if the object file
35562 does not contain segment information, or does not contain at least
35563 as many segments as mentioned in the reply. Extra segments are
35564 kept at fixed offsets relative to the last relocated segment.
35567 @item qP @var{mode} @var{thread-id}
35568 @cindex thread information, remote request
35569 @cindex @samp{qP} packet
35570 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35571 encoded 32 bit mode; @var{thread-id} is a thread ID
35572 (@pxref{thread-id syntax}).
35574 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35577 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35581 @cindex non-stop mode, remote request
35582 @cindex @samp{QNonStop} packet
35584 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35585 @xref{Remote Non-Stop}, for more information.
35590 The request succeeded.
35593 An error occurred. The error number @var{nn} is given as hex digits.
35596 An empty reply indicates that @samp{QNonStop} is not supported by
35600 This packet is not probed by default; the remote stub must request it,
35601 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35602 Use of this packet is controlled by the @code{set non-stop} command;
35603 @pxref{Non-Stop Mode}.
35605 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35606 @cindex pass signals to inferior, remote request
35607 @cindex @samp{QPassSignals} packet
35608 @anchor{QPassSignals}
35609 Each listed @var{signal} should be passed directly to the inferior process.
35610 Signals are numbered identically to continue packets and stop replies
35611 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35612 strictly greater than the previous item. These signals do not need to stop
35613 the inferior, or be reported to @value{GDBN}. All other signals should be
35614 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35615 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35616 new list. This packet improves performance when using @samp{handle
35617 @var{signal} nostop noprint pass}.
35622 The request succeeded.
35625 An error occurred. The error number @var{nn} is given as hex digits.
35628 An empty reply indicates that @samp{QPassSignals} is not supported by
35632 Use of this packet is controlled by the @code{set remote pass-signals}
35633 command (@pxref{Remote Configuration, set remote pass-signals}).
35634 This packet is not probed by default; the remote stub must request it,
35635 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35637 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35638 @cindex signals the inferior may see, remote request
35639 @cindex @samp{QProgramSignals} packet
35640 @anchor{QProgramSignals}
35641 Each listed @var{signal} may be delivered to the inferior process.
35642 Others should be silently discarded.
35644 In some cases, the remote stub may need to decide whether to deliver a
35645 signal to the program or not without @value{GDBN} involvement. One
35646 example of that is while detaching --- the program's threads may have
35647 stopped for signals that haven't yet had a chance of being reported to
35648 @value{GDBN}, and so the remote stub can use the signal list specified
35649 by this packet to know whether to deliver or ignore those pending
35652 This does not influence whether to deliver a signal as requested by a
35653 resumption packet (@pxref{vCont packet}).
35655 Signals are numbered identically to continue packets and stop replies
35656 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35657 strictly greater than the previous item. Multiple
35658 @samp{QProgramSignals} packets do not combine; any earlier
35659 @samp{QProgramSignals} list is completely replaced by the new list.
35664 The request succeeded.
35667 An error occurred. The error number @var{nn} is given as hex digits.
35670 An empty reply indicates that @samp{QProgramSignals} is not supported
35674 Use of this packet is controlled by the @code{set remote program-signals}
35675 command (@pxref{Remote Configuration, set remote program-signals}).
35676 This packet is not probed by default; the remote stub must request it,
35677 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35679 @item qRcmd,@var{command}
35680 @cindex execute remote command, remote request
35681 @cindex @samp{qRcmd} packet
35682 @var{command} (hex encoded) is passed to the local interpreter for
35683 execution. Invalid commands should be reported using the output
35684 string. Before the final result packet, the target may also respond
35685 with a number of intermediate @samp{O@var{output}} console output
35686 packets. @emph{Implementors should note that providing access to a
35687 stubs's interpreter may have security implications}.
35692 A command response with no output.
35694 A command response with the hex encoded output string @var{OUTPUT}.
35696 Indicate a badly formed request.
35698 An empty reply indicates that @samp{qRcmd} is not recognized.
35701 (Note that the @code{qRcmd} packet's name is separated from the
35702 command by a @samp{,}, not a @samp{:}, contrary to the naming
35703 conventions above. Please don't use this packet as a model for new
35706 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35707 @cindex searching memory, in remote debugging
35709 @cindex @samp{qSearch:memory} packet
35711 @cindex @samp{qSearch memory} packet
35712 @anchor{qSearch memory}
35713 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35714 Both @var{address} and @var{length} are encoded in hex;
35715 @var{search-pattern} is a sequence of bytes, also hex encoded.
35720 The pattern was not found.
35722 The pattern was found at @var{address}.
35724 A badly formed request or an error was encountered while searching memory.
35726 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35729 @item QStartNoAckMode
35730 @cindex @samp{QStartNoAckMode} packet
35731 @anchor{QStartNoAckMode}
35732 Request that the remote stub disable the normal @samp{+}/@samp{-}
35733 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35738 The stub has switched to no-acknowledgment mode.
35739 @value{GDBN} acknowledges this reponse,
35740 but neither the stub nor @value{GDBN} shall send or expect further
35741 @samp{+}/@samp{-} acknowledgments in the current connection.
35743 An empty reply indicates that the stub does not support no-acknowledgment mode.
35746 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35747 @cindex supported packets, remote query
35748 @cindex features of the remote protocol
35749 @cindex @samp{qSupported} packet
35750 @anchor{qSupported}
35751 Tell the remote stub about features supported by @value{GDBN}, and
35752 query the stub for features it supports. This packet allows
35753 @value{GDBN} and the remote stub to take advantage of each others'
35754 features. @samp{qSupported} also consolidates multiple feature probes
35755 at startup, to improve @value{GDBN} performance---a single larger
35756 packet performs better than multiple smaller probe packets on
35757 high-latency links. Some features may enable behavior which must not
35758 be on by default, e.g.@: because it would confuse older clients or
35759 stubs. Other features may describe packets which could be
35760 automatically probed for, but are not. These features must be
35761 reported before @value{GDBN} will use them. This ``default
35762 unsupported'' behavior is not appropriate for all packets, but it
35763 helps to keep the initial connection time under control with new
35764 versions of @value{GDBN} which support increasing numbers of packets.
35768 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35769 The stub supports or does not support each returned @var{stubfeature},
35770 depending on the form of each @var{stubfeature} (see below for the
35773 An empty reply indicates that @samp{qSupported} is not recognized,
35774 or that no features needed to be reported to @value{GDBN}.
35777 The allowed forms for each feature (either a @var{gdbfeature} in the
35778 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35782 @item @var{name}=@var{value}
35783 The remote protocol feature @var{name} is supported, and associated
35784 with the specified @var{value}. The format of @var{value} depends
35785 on the feature, but it must not include a semicolon.
35787 The remote protocol feature @var{name} is supported, and does not
35788 need an associated value.
35790 The remote protocol feature @var{name} is not supported.
35792 The remote protocol feature @var{name} may be supported, and
35793 @value{GDBN} should auto-detect support in some other way when it is
35794 needed. This form will not be used for @var{gdbfeature} notifications,
35795 but may be used for @var{stubfeature} responses.
35798 Whenever the stub receives a @samp{qSupported} request, the
35799 supplied set of @value{GDBN} features should override any previous
35800 request. This allows @value{GDBN} to put the stub in a known
35801 state, even if the stub had previously been communicating with
35802 a different version of @value{GDBN}.
35804 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35809 This feature indicates whether @value{GDBN} supports multiprocess
35810 extensions to the remote protocol. @value{GDBN} does not use such
35811 extensions unless the stub also reports that it supports them by
35812 including @samp{multiprocess+} in its @samp{qSupported} reply.
35813 @xref{multiprocess extensions}, for details.
35816 This feature indicates that @value{GDBN} supports the XML target
35817 description. If the stub sees @samp{xmlRegisters=} with target
35818 specific strings separated by a comma, it will report register
35822 This feature indicates whether @value{GDBN} supports the
35823 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35824 instruction reply packet}).
35827 This feature indicates whether @value{GDBN} supports the swbreak stop
35828 reason in stop replies. @xref{swbreak stop reason}, for details.
35831 This feature indicates whether @value{GDBN} supports the hwbreak stop
35832 reason in stop replies. @xref{swbreak stop reason}, for details.
35835 Stubs should ignore any unknown values for
35836 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35837 packet supports receiving packets of unlimited length (earlier
35838 versions of @value{GDBN} may reject overly long responses). Additional values
35839 for @var{gdbfeature} may be defined in the future to let the stub take
35840 advantage of new features in @value{GDBN}, e.g.@: incompatible
35841 improvements in the remote protocol---the @samp{multiprocess} feature is
35842 an example of such a feature. The stub's reply should be independent
35843 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35844 describes all the features it supports, and then the stub replies with
35845 all the features it supports.
35847 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35848 responses, as long as each response uses one of the standard forms.
35850 Some features are flags. A stub which supports a flag feature
35851 should respond with a @samp{+} form response. Other features
35852 require values, and the stub should respond with an @samp{=}
35855 Each feature has a default value, which @value{GDBN} will use if
35856 @samp{qSupported} is not available or if the feature is not mentioned
35857 in the @samp{qSupported} response. The default values are fixed; a
35858 stub is free to omit any feature responses that match the defaults.
35860 Not all features can be probed, but for those which can, the probing
35861 mechanism is useful: in some cases, a stub's internal
35862 architecture may not allow the protocol layer to know some information
35863 about the underlying target in advance. This is especially common in
35864 stubs which may be configured for multiple targets.
35866 These are the currently defined stub features and their properties:
35868 @multitable @columnfractions 0.35 0.2 0.12 0.2
35869 @c NOTE: The first row should be @headitem, but we do not yet require
35870 @c a new enough version of Texinfo (4.7) to use @headitem.
35872 @tab Value Required
35876 @item @samp{PacketSize}
35881 @item @samp{qXfer:auxv:read}
35886 @item @samp{qXfer:btrace:read}
35891 @item @samp{qXfer:btrace-conf:read}
35896 @item @samp{qXfer:features:read}
35901 @item @samp{qXfer:libraries:read}
35906 @item @samp{qXfer:libraries-svr4:read}
35911 @item @samp{augmented-libraries-svr4-read}
35916 @item @samp{qXfer:memory-map:read}
35921 @item @samp{qXfer:sdata:read}
35926 @item @samp{qXfer:spu:read}
35931 @item @samp{qXfer:spu:write}
35936 @item @samp{qXfer:siginfo:read}
35941 @item @samp{qXfer:siginfo:write}
35946 @item @samp{qXfer:threads:read}
35951 @item @samp{qXfer:traceframe-info:read}
35956 @item @samp{qXfer:uib:read}
35961 @item @samp{qXfer:fdpic:read}
35966 @item @samp{Qbtrace:off}
35971 @item @samp{Qbtrace:bts}
35976 @item @samp{Qbtrace-conf:bts:size}
35981 @item @samp{QNonStop}
35986 @item @samp{QPassSignals}
35991 @item @samp{QStartNoAckMode}
35996 @item @samp{multiprocess}
36001 @item @samp{ConditionalBreakpoints}
36006 @item @samp{ConditionalTracepoints}
36011 @item @samp{ReverseContinue}
36016 @item @samp{ReverseStep}
36021 @item @samp{TracepointSource}
36026 @item @samp{QAgent}
36031 @item @samp{QAllow}
36036 @item @samp{QDisableRandomization}
36041 @item @samp{EnableDisableTracepoints}
36046 @item @samp{QTBuffer:size}
36051 @item @samp{tracenz}
36056 @item @samp{BreakpointCommands}
36061 @item @samp{swbreak}
36066 @item @samp{hwbreak}
36073 These are the currently defined stub features, in more detail:
36076 @cindex packet size, remote protocol
36077 @item PacketSize=@var{bytes}
36078 The remote stub can accept packets up to at least @var{bytes} in
36079 length. @value{GDBN} will send packets up to this size for bulk
36080 transfers, and will never send larger packets. This is a limit on the
36081 data characters in the packet, including the frame and checksum.
36082 There is no trailing NUL byte in a remote protocol packet; if the stub
36083 stores packets in a NUL-terminated format, it should allow an extra
36084 byte in its buffer for the NUL. If this stub feature is not supported,
36085 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36087 @item qXfer:auxv:read
36088 The remote stub understands the @samp{qXfer:auxv:read} packet
36089 (@pxref{qXfer auxiliary vector read}).
36091 @item qXfer:btrace:read
36092 The remote stub understands the @samp{qXfer:btrace:read}
36093 packet (@pxref{qXfer btrace read}).
36095 @item qXfer:btrace-conf:read
36096 The remote stub understands the @samp{qXfer:btrace-conf:read}
36097 packet (@pxref{qXfer btrace-conf read}).
36099 @item qXfer:features:read
36100 The remote stub understands the @samp{qXfer:features:read} packet
36101 (@pxref{qXfer target description read}).
36103 @item qXfer:libraries:read
36104 The remote stub understands the @samp{qXfer:libraries:read} packet
36105 (@pxref{qXfer library list read}).
36107 @item qXfer:libraries-svr4:read
36108 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36109 (@pxref{qXfer svr4 library list read}).
36111 @item augmented-libraries-svr4-read
36112 The remote stub understands the augmented form of the
36113 @samp{qXfer:libraries-svr4:read} packet
36114 (@pxref{qXfer svr4 library list read}).
36116 @item qXfer:memory-map:read
36117 The remote stub understands the @samp{qXfer:memory-map:read} packet
36118 (@pxref{qXfer memory map read}).
36120 @item qXfer:sdata:read
36121 The remote stub understands the @samp{qXfer:sdata:read} packet
36122 (@pxref{qXfer sdata read}).
36124 @item qXfer:spu:read
36125 The remote stub understands the @samp{qXfer:spu:read} packet
36126 (@pxref{qXfer spu read}).
36128 @item qXfer:spu:write
36129 The remote stub understands the @samp{qXfer:spu:write} packet
36130 (@pxref{qXfer spu write}).
36132 @item qXfer:siginfo:read
36133 The remote stub understands the @samp{qXfer:siginfo:read} packet
36134 (@pxref{qXfer siginfo read}).
36136 @item qXfer:siginfo:write
36137 The remote stub understands the @samp{qXfer:siginfo:write} packet
36138 (@pxref{qXfer siginfo write}).
36140 @item qXfer:threads:read
36141 The remote stub understands the @samp{qXfer:threads:read} packet
36142 (@pxref{qXfer threads read}).
36144 @item qXfer:traceframe-info:read
36145 The remote stub understands the @samp{qXfer:traceframe-info:read}
36146 packet (@pxref{qXfer traceframe info read}).
36148 @item qXfer:uib:read
36149 The remote stub understands the @samp{qXfer:uib:read}
36150 packet (@pxref{qXfer unwind info block}).
36152 @item qXfer:fdpic:read
36153 The remote stub understands the @samp{qXfer:fdpic:read}
36154 packet (@pxref{qXfer fdpic loadmap read}).
36157 The remote stub understands the @samp{QNonStop} packet
36158 (@pxref{QNonStop}).
36161 The remote stub understands the @samp{QPassSignals} packet
36162 (@pxref{QPassSignals}).
36164 @item QStartNoAckMode
36165 The remote stub understands the @samp{QStartNoAckMode} packet and
36166 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36169 @anchor{multiprocess extensions}
36170 @cindex multiprocess extensions, in remote protocol
36171 The remote stub understands the multiprocess extensions to the remote
36172 protocol syntax. The multiprocess extensions affect the syntax of
36173 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36174 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36175 replies. Note that reporting this feature indicates support for the
36176 syntactic extensions only, not that the stub necessarily supports
36177 debugging of more than one process at a time. The stub must not use
36178 multiprocess extensions in packet replies unless @value{GDBN} has also
36179 indicated it supports them in its @samp{qSupported} request.
36181 @item qXfer:osdata:read
36182 The remote stub understands the @samp{qXfer:osdata:read} packet
36183 ((@pxref{qXfer osdata read}).
36185 @item ConditionalBreakpoints
36186 The target accepts and implements evaluation of conditional expressions
36187 defined for breakpoints. The target will only report breakpoint triggers
36188 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36190 @item ConditionalTracepoints
36191 The remote stub accepts and implements conditional expressions defined
36192 for tracepoints (@pxref{Tracepoint Conditions}).
36194 @item ReverseContinue
36195 The remote stub accepts and implements the reverse continue packet
36199 The remote stub accepts and implements the reverse step packet
36202 @item TracepointSource
36203 The remote stub understands the @samp{QTDPsrc} packet that supplies
36204 the source form of tracepoint definitions.
36207 The remote stub understands the @samp{QAgent} packet.
36210 The remote stub understands the @samp{QAllow} packet.
36212 @item QDisableRandomization
36213 The remote stub understands the @samp{QDisableRandomization} packet.
36215 @item StaticTracepoint
36216 @cindex static tracepoints, in remote protocol
36217 The remote stub supports static tracepoints.
36219 @item InstallInTrace
36220 @anchor{install tracepoint in tracing}
36221 The remote stub supports installing tracepoint in tracing.
36223 @item EnableDisableTracepoints
36224 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36225 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36226 to be enabled and disabled while a trace experiment is running.
36228 @item QTBuffer:size
36229 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36230 packet that allows to change the size of the trace buffer.
36233 @cindex string tracing, in remote protocol
36234 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36235 See @ref{Bytecode Descriptions} for details about the bytecode.
36237 @item BreakpointCommands
36238 @cindex breakpoint commands, in remote protocol
36239 The remote stub supports running a breakpoint's command list itself,
36240 rather than reporting the hit to @value{GDBN}.
36243 The remote stub understands the @samp{Qbtrace:off} packet.
36246 The remote stub understands the @samp{Qbtrace:bts} packet.
36248 @item Qbtrace-conf:bts:size
36249 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36252 The remote stub reports the @samp{swbreak} stop reason for memory
36256 The remote stub reports the @samp{hwbreak} stop reason for hardware
36262 @cindex symbol lookup, remote request
36263 @cindex @samp{qSymbol} packet
36264 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36265 requests. Accept requests from the target for the values of symbols.
36270 The target does not need to look up any (more) symbols.
36271 @item qSymbol:@var{sym_name}
36272 The target requests the value of symbol @var{sym_name} (hex encoded).
36273 @value{GDBN} may provide the value by using the
36274 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36278 @item qSymbol:@var{sym_value}:@var{sym_name}
36279 Set the value of @var{sym_name} to @var{sym_value}.
36281 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36282 target has previously requested.
36284 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36285 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36291 The target does not need to look up any (more) symbols.
36292 @item qSymbol:@var{sym_name}
36293 The target requests the value of a new symbol @var{sym_name} (hex
36294 encoded). @value{GDBN} will continue to supply the values of symbols
36295 (if available), until the target ceases to request them.
36300 @itemx QTDisconnected
36307 @itemx qTMinFTPILen
36309 @xref{Tracepoint Packets}.
36311 @item qThreadExtraInfo,@var{thread-id}
36312 @cindex thread attributes info, remote request
36313 @cindex @samp{qThreadExtraInfo} packet
36314 Obtain from the target OS a printable string description of thread
36315 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36316 for the forms of @var{thread-id}. This
36317 string may contain anything that the target OS thinks is interesting
36318 for @value{GDBN} to tell the user about the thread. The string is
36319 displayed in @value{GDBN}'s @code{info threads} display. Some
36320 examples of possible thread extra info strings are @samp{Runnable}, or
36321 @samp{Blocked on Mutex}.
36325 @item @var{XX}@dots{}
36326 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36327 comprising the printable string containing the extra information about
36328 the thread's attributes.
36331 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36332 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36333 conventions above. Please don't use this packet as a model for new
36352 @xref{Tracepoint Packets}.
36354 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36355 @cindex read special object, remote request
36356 @cindex @samp{qXfer} packet
36357 @anchor{qXfer read}
36358 Read uninterpreted bytes from the target's special data area
36359 identified by the keyword @var{object}. Request @var{length} bytes
36360 starting at @var{offset} bytes into the data. The content and
36361 encoding of @var{annex} is specific to @var{object}; it can supply
36362 additional details about what data to access.
36364 Here are the specific requests of this form defined so far. All
36365 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36366 formats, listed below.
36369 @item qXfer:auxv:read::@var{offset},@var{length}
36370 @anchor{qXfer auxiliary vector read}
36371 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36372 auxiliary vector}. Note @var{annex} must be empty.
36374 This packet is not probed by default; the remote stub must request it,
36375 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36377 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36378 @anchor{qXfer btrace read}
36380 Return a description of the current branch trace.
36381 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36382 packet may have one of the following values:
36386 Returns all available branch trace.
36389 Returns all available branch trace if the branch trace changed since
36390 the last read request.
36393 Returns the new branch trace since the last read request. Adds a new
36394 block to the end of the trace that begins at zero and ends at the source
36395 location of the first branch in the trace buffer. This extra block is
36396 used to stitch traces together.
36398 If the trace buffer overflowed, returns an error indicating the overflow.
36401 This packet is not probed by default; the remote stub must request it
36402 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36404 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36405 @anchor{qXfer btrace-conf read}
36407 Return a description of the current branch trace configuration.
36408 @xref{Branch Trace Configuration Format}.
36410 This packet is not probed by default; the remote stub must request it
36411 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36413 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36414 @anchor{qXfer target description read}
36415 Access the @dfn{target description}. @xref{Target Descriptions}. The
36416 annex specifies which XML document to access. The main description is
36417 always loaded from the @samp{target.xml} annex.
36419 This packet is not probed by default; the remote stub must request it,
36420 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36422 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36423 @anchor{qXfer library list read}
36424 Access the target's list of loaded libraries. @xref{Library List Format}.
36425 The annex part of the generic @samp{qXfer} packet must be empty
36426 (@pxref{qXfer read}).
36428 Targets which maintain a list of libraries in the program's memory do
36429 not need to implement this packet; it is designed for platforms where
36430 the operating system manages the list of loaded libraries.
36432 This packet is not probed by default; the remote stub must request it,
36433 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36435 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36436 @anchor{qXfer svr4 library list read}
36437 Access the target's list of loaded libraries when the target is an SVR4
36438 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36439 of the generic @samp{qXfer} packet must be empty unless the remote
36440 stub indicated it supports the augmented form of this packet
36441 by supplying an appropriate @samp{qSupported} response
36442 (@pxref{qXfer read}, @ref{qSupported}).
36444 This packet is optional for better performance on SVR4 targets.
36445 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36447 This packet is not probed by default; the remote stub must request it,
36448 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36450 If the remote stub indicates it supports the augmented form of this
36451 packet then the annex part of the generic @samp{qXfer} packet may
36452 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36453 arguments. The currently supported arguments are:
36456 @item start=@var{address}
36457 A hexadecimal number specifying the address of the @samp{struct
36458 link_map} to start reading the library list from. If unset or zero
36459 then the first @samp{struct link_map} in the library list will be
36460 chosen as the starting point.
36462 @item prev=@var{address}
36463 A hexadecimal number specifying the address of the @samp{struct
36464 link_map} immediately preceding the @samp{struct link_map}
36465 specified by the @samp{start} argument. If unset or zero then
36466 the remote stub will expect that no @samp{struct link_map}
36467 exists prior to the starting point.
36471 Arguments that are not understood by the remote stub will be silently
36474 @item qXfer:memory-map:read::@var{offset},@var{length}
36475 @anchor{qXfer memory map read}
36476 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36477 annex part of the generic @samp{qXfer} packet must be empty
36478 (@pxref{qXfer read}).
36480 This packet is not probed by default; the remote stub must request it,
36481 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36483 @item qXfer:sdata:read::@var{offset},@var{length}
36484 @anchor{qXfer sdata read}
36486 Read contents of the extra collected static tracepoint marker
36487 information. The annex part of the generic @samp{qXfer} packet must
36488 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
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:siginfo:read::@var{offset},@var{length}
36496 @anchor{qXfer siginfo read}
36497 Read contents of the extra signal information on the target
36498 system. The annex part of the generic @samp{qXfer} packet must be
36499 empty (@pxref{qXfer read}).
36501 This packet is not probed by default; the remote stub must request it,
36502 by supplying an appropriate @samp{qSupported} response
36503 (@pxref{qSupported}).
36505 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36506 @anchor{qXfer spu read}
36507 Read contents of an @code{spufs} file on the target system. The
36508 annex specifies which file to read; it must be of the form
36509 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36510 in the target process, and @var{name} identifes the @code{spufs} file
36511 in that context to be accessed.
36513 This packet is not probed by default; the remote stub must request it,
36514 by supplying an appropriate @samp{qSupported} response
36515 (@pxref{qSupported}).
36517 @item qXfer:threads:read::@var{offset},@var{length}
36518 @anchor{qXfer threads read}
36519 Access the list of threads on target. @xref{Thread List Format}. The
36520 annex part of the generic @samp{qXfer} packet must be empty
36521 (@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:traceframe-info:read::@var{offset},@var{length}
36527 @anchor{qXfer traceframe info read}
36529 Return a description of the current traceframe's contents.
36530 @xref{Traceframe Info Format}. The annex part of the generic
36531 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36533 This packet is not probed by default; the remote stub must request it,
36534 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36536 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36537 @anchor{qXfer unwind info block}
36539 Return the unwind information block for @var{pc}. This packet is used
36540 on OpenVMS/ia64 to ask the kernel unwind information.
36542 This packet is not probed by default.
36544 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36545 @anchor{qXfer fdpic loadmap read}
36546 Read contents of @code{loadmap}s on the target system. The
36547 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36548 executable @code{loadmap} or interpreter @code{loadmap} to read.
36550 This packet is not probed by default; the remote stub must request it,
36551 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36553 @item qXfer:osdata:read::@var{offset},@var{length}
36554 @anchor{qXfer osdata read}
36555 Access the target's @dfn{operating system information}.
36556 @xref{Operating System Information}.
36563 Data @var{data} (@pxref{Binary Data}) has been read from the
36564 target. There may be more data at a higher address (although
36565 it is permitted to return @samp{m} even for the last valid
36566 block of data, as long as at least one byte of data was read).
36567 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36571 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36572 There is no more data to be read. It is possible for @var{data} to
36573 have fewer bytes than the @var{length} in the request.
36576 The @var{offset} in the request is at the end of the data.
36577 There is no more data to be read.
36580 The request was malformed, or @var{annex} was invalid.
36583 The offset was invalid, or there was an error encountered reading the data.
36584 The @var{nn} part is a hex-encoded @code{errno} value.
36587 An empty reply indicates the @var{object} string was not recognized by
36588 the stub, or that the object does not support reading.
36591 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36592 @cindex write data into object, remote request
36593 @anchor{qXfer write}
36594 Write uninterpreted bytes into the target's special data area
36595 identified by the keyword @var{object}, starting at @var{offset} bytes
36596 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36597 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36598 is specific to @var{object}; it can supply additional details about what data
36601 Here are the specific requests of this form defined so far. All
36602 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36603 formats, listed below.
36606 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36607 @anchor{qXfer siginfo write}
36608 Write @var{data} to the extra signal information on the target system.
36609 The annex part of the generic @samp{qXfer} packet must be
36610 empty (@pxref{qXfer write}).
36612 This packet is not probed by default; the remote stub must request it,
36613 by supplying an appropriate @samp{qSupported} response
36614 (@pxref{qSupported}).
36616 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36617 @anchor{qXfer spu write}
36618 Write @var{data} to an @code{spufs} file on the target system. The
36619 annex specifies which file to write; it must be of the form
36620 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36621 in the target process, and @var{name} identifes the @code{spufs} file
36622 in that context to be accessed.
36624 This packet is not probed by default; the remote stub must request it,
36625 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36631 @var{nn} (hex encoded) is the number of bytes written.
36632 This may be fewer bytes than supplied in the request.
36635 The request was malformed, or @var{annex} was invalid.
36638 The offset was invalid, or there was an error encountered writing the data.
36639 The @var{nn} part is a hex-encoded @code{errno} value.
36642 An empty reply indicates the @var{object} string was not
36643 recognized by the stub, or that the object does not support writing.
36646 @item qXfer:@var{object}:@var{operation}:@dots{}
36647 Requests of this form may be added in the future. When a stub does
36648 not recognize the @var{object} keyword, or its support for
36649 @var{object} does not recognize the @var{operation} keyword, the stub
36650 must respond with an empty packet.
36652 @item qAttached:@var{pid}
36653 @cindex query attached, remote request
36654 @cindex @samp{qAttached} packet
36655 Return an indication of whether the remote server attached to an
36656 existing process or created a new process. When the multiprocess
36657 protocol extensions are supported (@pxref{multiprocess extensions}),
36658 @var{pid} is an integer in hexadecimal format identifying the target
36659 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36660 the query packet will be simplified as @samp{qAttached}.
36662 This query is used, for example, to know whether the remote process
36663 should be detached or killed when a @value{GDBN} session is ended with
36664 the @code{quit} command.
36669 The remote server attached to an existing process.
36671 The remote server created a new process.
36673 A badly formed request or an error was encountered.
36677 Enable branch tracing for the current thread using bts tracing.
36682 Branch tracing has been enabled.
36684 A badly formed request or an error was encountered.
36688 Disable branch tracing for the current thread.
36693 Branch tracing has been disabled.
36695 A badly formed request or an error was encountered.
36698 @item Qbtrace-conf:bts:size=@var{value}
36699 Set the requested ring buffer size for new threads that use the
36700 btrace recording method in bts format.
36705 The ring buffer size has been set.
36707 A badly formed request or an error was encountered.
36712 @node Architecture-Specific Protocol Details
36713 @section Architecture-Specific Protocol Details
36715 This section describes how the remote protocol is applied to specific
36716 target architectures. Also see @ref{Standard Target Features}, for
36717 details of XML target descriptions for each architecture.
36720 * ARM-Specific Protocol Details::
36721 * MIPS-Specific Protocol Details::
36724 @node ARM-Specific Protocol Details
36725 @subsection @acronym{ARM}-specific Protocol Details
36728 * ARM Breakpoint Kinds::
36731 @node ARM Breakpoint Kinds
36732 @subsubsection @acronym{ARM} Breakpoint Kinds
36733 @cindex breakpoint kinds, @acronym{ARM}
36735 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36740 16-bit Thumb mode breakpoint.
36743 32-bit Thumb mode (Thumb-2) breakpoint.
36746 32-bit @acronym{ARM} mode breakpoint.
36750 @node MIPS-Specific Protocol Details
36751 @subsection @acronym{MIPS}-specific Protocol Details
36754 * MIPS Register packet Format::
36755 * MIPS Breakpoint Kinds::
36758 @node MIPS Register packet Format
36759 @subsubsection @acronym{MIPS} Register Packet Format
36760 @cindex register packet format, @acronym{MIPS}
36762 The following @code{g}/@code{G} packets have previously been defined.
36763 In the below, some thirty-two bit registers are transferred as
36764 sixty-four bits. Those registers should be zero/sign extended (which?)
36765 to fill the space allocated. Register bytes are transferred in target
36766 byte order. The two nibbles within a register byte are transferred
36767 most-significant -- least-significant.
36772 All registers are transferred as thirty-two bit quantities in the order:
36773 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36774 registers; fsr; fir; fp.
36777 All registers are transferred as sixty-four bit quantities (including
36778 thirty-two bit registers such as @code{sr}). The ordering is the same
36783 @node MIPS Breakpoint Kinds
36784 @subsubsection @acronym{MIPS} Breakpoint Kinds
36785 @cindex breakpoint kinds, @acronym{MIPS}
36787 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36792 16-bit @acronym{MIPS16} mode breakpoint.
36795 16-bit @acronym{microMIPS} mode breakpoint.
36798 32-bit standard @acronym{MIPS} mode breakpoint.
36801 32-bit @acronym{microMIPS} mode breakpoint.
36805 @node Tracepoint Packets
36806 @section Tracepoint Packets
36807 @cindex tracepoint packets
36808 @cindex packets, tracepoint
36810 Here we describe the packets @value{GDBN} uses to implement
36811 tracepoints (@pxref{Tracepoints}).
36815 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36816 @cindex @samp{QTDP} packet
36817 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36818 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36819 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36820 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36821 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36822 the number of bytes that the target should copy elsewhere to make room
36823 for the tracepoint. If an @samp{X} is present, it introduces a
36824 tracepoint condition, which consists of a hexadecimal length, followed
36825 by a comma and hex-encoded bytes, in a manner similar to action
36826 encodings as described below. If the trailing @samp{-} is present,
36827 further @samp{QTDP} packets will follow to specify this tracepoint's
36833 The packet was understood and carried out.
36835 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36837 The packet was not recognized.
36840 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36841 Define actions to be taken when a tracepoint is hit. The @var{n} and
36842 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36843 this tracepoint. This packet may only be sent immediately after
36844 another @samp{QTDP} packet that ended with a @samp{-}. If the
36845 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36846 specifying more actions for this tracepoint.
36848 In the series of action packets for a given tracepoint, at most one
36849 can have an @samp{S} before its first @var{action}. If such a packet
36850 is sent, it and the following packets define ``while-stepping''
36851 actions. Any prior packets define ordinary actions --- that is, those
36852 taken when the tracepoint is first hit. If no action packet has an
36853 @samp{S}, then all the packets in the series specify ordinary
36854 tracepoint actions.
36856 The @samp{@var{action}@dots{}} portion of the packet is a series of
36857 actions, concatenated without separators. Each action has one of the
36863 Collect the registers whose bits are set in @var{mask},
36864 a hexadecimal number whose @var{i}'th bit is set if register number
36865 @var{i} should be collected. (The least significant bit is numbered
36866 zero.) Note that @var{mask} may be any number of digits long; it may
36867 not fit in a 32-bit word.
36869 @item M @var{basereg},@var{offset},@var{len}
36870 Collect @var{len} bytes of memory starting at the address in register
36871 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36872 @samp{-1}, then the range has a fixed address: @var{offset} is the
36873 address of the lowest byte to collect. The @var{basereg},
36874 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36875 values (the @samp{-1} value for @var{basereg} is a special case).
36877 @item X @var{len},@var{expr}
36878 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36879 it directs. The agent expression @var{expr} is as described in
36880 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36881 two-digit hex number in the packet; @var{len} is the number of bytes
36882 in the expression (and thus one-half the number of hex digits in the
36887 Any number of actions may be packed together in a single @samp{QTDP}
36888 packet, as long as the packet does not exceed the maximum packet
36889 length (400 bytes, for many stubs). There may be only one @samp{R}
36890 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36891 actions. Any registers referred to by @samp{M} and @samp{X} actions
36892 must be collected by a preceding @samp{R} action. (The
36893 ``while-stepping'' actions are treated as if they were attached to a
36894 separate tracepoint, as far as these restrictions are concerned.)
36899 The packet was understood and carried out.
36901 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36903 The packet was not recognized.
36906 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36907 @cindex @samp{QTDPsrc} packet
36908 Specify a source string of tracepoint @var{n} at address @var{addr}.
36909 This is useful to get accurate reproduction of the tracepoints
36910 originally downloaded at the beginning of the trace run. The @var{type}
36911 is the name of the tracepoint part, such as @samp{cond} for the
36912 tracepoint's conditional expression (see below for a list of types), while
36913 @var{bytes} is the string, encoded in hexadecimal.
36915 @var{start} is the offset of the @var{bytes} within the overall source
36916 string, while @var{slen} is the total length of the source string.
36917 This is intended for handling source strings that are longer than will
36918 fit in a single packet.
36919 @c Add detailed example when this info is moved into a dedicated
36920 @c tracepoint descriptions section.
36922 The available string types are @samp{at} for the location,
36923 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36924 @value{GDBN} sends a separate packet for each command in the action
36925 list, in the same order in which the commands are stored in the list.
36927 The target does not need to do anything with source strings except
36928 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36931 Although this packet is optional, and @value{GDBN} will only send it
36932 if the target replies with @samp{TracepointSource} @xref{General
36933 Query Packets}, it makes both disconnected tracing and trace files
36934 much easier to use. Otherwise the user must be careful that the
36935 tracepoints in effect while looking at trace frames are identical to
36936 the ones in effect during the trace run; even a small discrepancy
36937 could cause @samp{tdump} not to work, or a particular trace frame not
36940 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
36941 @cindex define trace state variable, remote request
36942 @cindex @samp{QTDV} packet
36943 Create a new trace state variable, number @var{n}, with an initial
36944 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36945 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36946 the option of not using this packet for initial values of zero; the
36947 target should simply create the trace state variables as they are
36948 mentioned in expressions. The value @var{builtin} should be 1 (one)
36949 if the trace state variable is builtin and 0 (zero) if it is not builtin.
36950 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
36951 @samp{qTsV} packet had it set. The contents of @var{name} is the
36952 hex-encoded name (without the leading @samp{$}) of the trace state
36955 @item QTFrame:@var{n}
36956 @cindex @samp{QTFrame} packet
36957 Select the @var{n}'th tracepoint frame from the buffer, and use the
36958 register and memory contents recorded there to answer subsequent
36959 request packets from @value{GDBN}.
36961 A successful reply from the stub indicates that the stub has found the
36962 requested frame. The response is a series of parts, concatenated
36963 without separators, describing the frame we selected. Each part has
36964 one of the following forms:
36968 The selected frame is number @var{n} in the trace frame buffer;
36969 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36970 was no frame matching the criteria in the request packet.
36973 The selected trace frame records a hit of tracepoint number @var{t};
36974 @var{t} is a hexadecimal number.
36978 @item QTFrame:pc:@var{addr}
36979 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36980 currently selected frame whose PC is @var{addr};
36981 @var{addr} is a hexadecimal number.
36983 @item QTFrame:tdp:@var{t}
36984 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36985 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36986 is a hexadecimal number.
36988 @item QTFrame:range:@var{start}:@var{end}
36989 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36990 currently selected frame whose PC is between @var{start} (inclusive)
36991 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36994 @item QTFrame:outside:@var{start}:@var{end}
36995 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36996 frame @emph{outside} the given range of addresses (exclusive).
36999 @cindex @samp{qTMinFTPILen} packet
37000 This packet requests the minimum length of instruction at which a fast
37001 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37002 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37003 it depends on the target system being able to create trampolines in
37004 the first 64K of memory, which might or might not be possible for that
37005 system. So the reply to this packet will be 4 if it is able to
37012 The minimum instruction length is currently unknown.
37014 The minimum instruction length is @var{length}, where @var{length}
37015 is a hexadecimal number greater or equal to 1. A reply
37016 of 1 means that a fast tracepoint may be placed on any instruction
37017 regardless of size.
37019 An error has occurred.
37021 An empty reply indicates that the request is not supported by the stub.
37025 @cindex @samp{QTStart} packet
37026 Begin the tracepoint experiment. Begin collecting data from
37027 tracepoint hits in the trace frame buffer. This packet supports the
37028 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37029 instruction reply packet}).
37032 @cindex @samp{QTStop} packet
37033 End the tracepoint experiment. Stop collecting trace frames.
37035 @item QTEnable:@var{n}:@var{addr}
37037 @cindex @samp{QTEnable} packet
37038 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37039 experiment. If the tracepoint was previously disabled, then collection
37040 of data from it will resume.
37042 @item QTDisable:@var{n}:@var{addr}
37044 @cindex @samp{QTDisable} packet
37045 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37046 experiment. No more data will be collected from the tracepoint unless
37047 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37050 @cindex @samp{QTinit} packet
37051 Clear the table of tracepoints, and empty the trace frame buffer.
37053 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37054 @cindex @samp{QTro} packet
37055 Establish the given ranges of memory as ``transparent''. The stub
37056 will answer requests for these ranges from memory's current contents,
37057 if they were not collected as part of the tracepoint hit.
37059 @value{GDBN} uses this to mark read-only regions of memory, like those
37060 containing program code. Since these areas never change, they should
37061 still have the same contents they did when the tracepoint was hit, so
37062 there's no reason for the stub to refuse to provide their contents.
37064 @item QTDisconnected:@var{value}
37065 @cindex @samp{QTDisconnected} packet
37066 Set the choice to what to do with the tracing run when @value{GDBN}
37067 disconnects from the target. A @var{value} of 1 directs the target to
37068 continue the tracing run, while 0 tells the target to stop tracing if
37069 @value{GDBN} is no longer in the picture.
37072 @cindex @samp{qTStatus} packet
37073 Ask the stub if there is a trace experiment running right now.
37075 The reply has the form:
37079 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37080 @var{running} is a single digit @code{1} if the trace is presently
37081 running, or @code{0} if not. It is followed by semicolon-separated
37082 optional fields that an agent may use to report additional status.
37086 If the trace is not running, the agent may report any of several
37087 explanations as one of the optional fields:
37092 No trace has been run yet.
37094 @item tstop[:@var{text}]:0
37095 The trace was stopped by a user-originated stop command. The optional
37096 @var{text} field is a user-supplied string supplied as part of the
37097 stop command (for instance, an explanation of why the trace was
37098 stopped manually). It is hex-encoded.
37101 The trace stopped because the trace buffer filled up.
37103 @item tdisconnected:0
37104 The trace stopped because @value{GDBN} disconnected from the target.
37106 @item tpasscount:@var{tpnum}
37107 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37109 @item terror:@var{text}:@var{tpnum}
37110 The trace stopped because tracepoint @var{tpnum} had an error. The
37111 string @var{text} is available to describe the nature of the error
37112 (for instance, a divide by zero in the condition expression); it
37116 The trace stopped for some other reason.
37120 Additional optional fields supply statistical and other information.
37121 Although not required, they are extremely useful for users monitoring
37122 the progress of a trace run. If a trace has stopped, and these
37123 numbers are reported, they must reflect the state of the just-stopped
37128 @item tframes:@var{n}
37129 The number of trace frames in the buffer.
37131 @item tcreated:@var{n}
37132 The total number of trace frames created during the run. This may
37133 be larger than the trace frame count, if the buffer is circular.
37135 @item tsize:@var{n}
37136 The total size of the trace buffer, in bytes.
37138 @item tfree:@var{n}
37139 The number of bytes still unused in the buffer.
37141 @item circular:@var{n}
37142 The value of the circular trace buffer flag. @code{1} means that the
37143 trace buffer is circular and old trace frames will be discarded if
37144 necessary to make room, @code{0} means that the trace buffer is linear
37147 @item disconn:@var{n}
37148 The value of the disconnected tracing flag. @code{1} means that
37149 tracing will continue after @value{GDBN} disconnects, @code{0} means
37150 that the trace run will stop.
37154 @item qTP:@var{tp}:@var{addr}
37155 @cindex tracepoint status, remote request
37156 @cindex @samp{qTP} packet
37157 Ask the stub for the current state of tracepoint number @var{tp} at
37158 address @var{addr}.
37162 @item V@var{hits}:@var{usage}
37163 The tracepoint has been hit @var{hits} times so far during the trace
37164 run, and accounts for @var{usage} in the trace buffer. Note that
37165 @code{while-stepping} steps are not counted as separate hits, but the
37166 steps' space consumption is added into the usage number.
37170 @item qTV:@var{var}
37171 @cindex trace state variable value, remote request
37172 @cindex @samp{qTV} packet
37173 Ask the stub for the value of the trace state variable number @var{var}.
37178 The value of the variable is @var{value}. This will be the current
37179 value of the variable if the user is examining a running target, or a
37180 saved value if the variable was collected in the trace frame that the
37181 user is looking at. Note that multiple requests may result in
37182 different reply values, such as when requesting values while the
37183 program is running.
37186 The value of the variable is unknown. This would occur, for example,
37187 if the user is examining a trace frame in which the requested variable
37192 @cindex @samp{qTfP} packet
37194 @cindex @samp{qTsP} packet
37195 These packets request data about tracepoints that are being used by
37196 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37197 of data, and multiple @code{qTsP} to get additional pieces. Replies
37198 to these packets generally take the form of the @code{QTDP} packets
37199 that define tracepoints. (FIXME add detailed syntax)
37202 @cindex @samp{qTfV} packet
37204 @cindex @samp{qTsV} packet
37205 These packets request data about trace state variables that are on the
37206 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37207 and multiple @code{qTsV} to get additional variables. Replies to
37208 these packets follow the syntax of the @code{QTDV} packets that define
37209 trace state variables.
37215 @cindex @samp{qTfSTM} packet
37216 @cindex @samp{qTsSTM} packet
37217 These packets request data about static tracepoint markers that exist
37218 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37219 first piece of data, and multiple @code{qTsSTM} to get additional
37220 pieces. Replies to these packets take the following form:
37224 @item m @var{address}:@var{id}:@var{extra}
37226 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37227 a comma-separated list of markers
37229 (lower case letter @samp{L}) denotes end of list.
37231 An error occurred. The error number @var{nn} is given as hex digits.
37233 An empty reply indicates that the request is not supported by the
37237 The @var{address} is encoded in hex;
37238 @var{id} and @var{extra} are strings encoded in hex.
37240 In response to each query, the target will reply with a list of one or
37241 more markers, separated by commas. @value{GDBN} will respond to each
37242 reply with a request for more markers (using the @samp{qs} form of the
37243 query), until the target responds with @samp{l} (lower-case ell, for
37246 @item qTSTMat:@var{address}
37248 @cindex @samp{qTSTMat} packet
37249 This packets requests data about static tracepoint markers in the
37250 target program at @var{address}. Replies to this packet follow the
37251 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37252 tracepoint markers.
37254 @item QTSave:@var{filename}
37255 @cindex @samp{QTSave} packet
37256 This packet directs the target to save trace data to the file name
37257 @var{filename} in the target's filesystem. The @var{filename} is encoded
37258 as a hex string; the interpretation of the file name (relative vs
37259 absolute, wild cards, etc) is up to the target.
37261 @item qTBuffer:@var{offset},@var{len}
37262 @cindex @samp{qTBuffer} packet
37263 Return up to @var{len} bytes of the current contents of trace buffer,
37264 starting at @var{offset}. The trace buffer is treated as if it were
37265 a contiguous collection of traceframes, as per the trace file format.
37266 The reply consists as many hex-encoded bytes as the target can deliver
37267 in a packet; it is not an error to return fewer than were asked for.
37268 A reply consisting of just @code{l} indicates that no bytes are
37271 @item QTBuffer:circular:@var{value}
37272 This packet directs the target to use a circular trace buffer if
37273 @var{value} is 1, or a linear buffer if the value is 0.
37275 @item QTBuffer:size:@var{size}
37276 @anchor{QTBuffer-size}
37277 @cindex @samp{QTBuffer size} packet
37278 This packet directs the target to make the trace buffer be of size
37279 @var{size} if possible. A value of @code{-1} tells the target to
37280 use whatever size it prefers.
37282 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37283 @cindex @samp{QTNotes} packet
37284 This packet adds optional textual notes to the trace run. Allowable
37285 types include @code{user}, @code{notes}, and @code{tstop}, the
37286 @var{text} fields are arbitrary strings, hex-encoded.
37290 @subsection Relocate instruction reply packet
37291 When installing fast tracepoints in memory, the target may need to
37292 relocate the instruction currently at the tracepoint address to a
37293 different address in memory. For most instructions, a simple copy is
37294 enough, but, for example, call instructions that implicitly push the
37295 return address on the stack, and relative branches or other
37296 PC-relative instructions require offset adjustment, so that the effect
37297 of executing the instruction at a different address is the same as if
37298 it had executed in the original location.
37300 In response to several of the tracepoint packets, the target may also
37301 respond with a number of intermediate @samp{qRelocInsn} request
37302 packets before the final result packet, to have @value{GDBN} handle
37303 this relocation operation. If a packet supports this mechanism, its
37304 documentation will explicitly say so. See for example the above
37305 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37306 format of the request is:
37309 @item qRelocInsn:@var{from};@var{to}
37311 This requests @value{GDBN} to copy instruction at address @var{from}
37312 to address @var{to}, possibly adjusted so that executing the
37313 instruction at @var{to} has the same effect as executing it at
37314 @var{from}. @value{GDBN} writes the adjusted instruction to target
37315 memory starting at @var{to}.
37320 @item qRelocInsn:@var{adjusted_size}
37321 Informs the stub the relocation is complete. The @var{adjusted_size} is
37322 the length in bytes of resulting relocated instruction sequence.
37324 A badly formed request was detected, or an error was encountered while
37325 relocating the instruction.
37328 @node Host I/O Packets
37329 @section Host I/O Packets
37330 @cindex Host I/O, remote protocol
37331 @cindex file transfer, remote protocol
37333 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37334 operations on the far side of a remote link. For example, Host I/O is
37335 used to upload and download files to a remote target with its own
37336 filesystem. Host I/O uses the same constant values and data structure
37337 layout as the target-initiated File-I/O protocol. However, the
37338 Host I/O packets are structured differently. The target-initiated
37339 protocol relies on target memory to store parameters and buffers.
37340 Host I/O requests are initiated by @value{GDBN}, and the
37341 target's memory is not involved. @xref{File-I/O Remote Protocol
37342 Extension}, for more details on the target-initiated protocol.
37344 The Host I/O request packets all encode a single operation along with
37345 its arguments. They have this format:
37349 @item vFile:@var{operation}: @var{parameter}@dots{}
37350 @var{operation} is the name of the particular request; the target
37351 should compare the entire packet name up to the second colon when checking
37352 for a supported operation. The format of @var{parameter} depends on
37353 the operation. Numbers are always passed in hexadecimal. Negative
37354 numbers have an explicit minus sign (i.e.@: two's complement is not
37355 used). Strings (e.g.@: filenames) are encoded as a series of
37356 hexadecimal bytes. The last argument to a system call may be a
37357 buffer of escaped binary data (@pxref{Binary Data}).
37361 The valid responses to Host I/O packets are:
37365 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37366 @var{result} is the integer value returned by this operation, usually
37367 non-negative for success and -1 for errors. If an error has occured,
37368 @var{errno} will be included in the result specifying a
37369 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37370 operations which return data, @var{attachment} supplies the data as a
37371 binary buffer. Binary buffers in response packets are escaped in the
37372 normal way (@pxref{Binary Data}). See the individual packet
37373 documentation for the interpretation of @var{result} and
37377 An empty response indicates that this operation is not recognized.
37381 These are the supported Host I/O operations:
37384 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37385 Open a file at @var{filename} and return a file descriptor for it, or
37386 return -1 if an error occurs. The @var{filename} is a string,
37387 @var{flags} is an integer indicating a mask of open flags
37388 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37389 of mode bits to use if the file is created (@pxref{mode_t Values}).
37390 @xref{open}, for details of the open flags and mode values.
37392 @item vFile:close: @var{fd}
37393 Close the open file corresponding to @var{fd} and return 0, or
37394 -1 if an error occurs.
37396 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37397 Read data from the open file corresponding to @var{fd}. Up to
37398 @var{count} bytes will be read from the file, starting at @var{offset}
37399 relative to the start of the file. The target may read fewer bytes;
37400 common reasons include packet size limits and an end-of-file
37401 condition. The number of bytes read is returned. Zero should only be
37402 returned for a successful read at the end of the file, or if
37403 @var{count} was zero.
37405 The data read should be returned as a binary attachment on success.
37406 If zero bytes were read, the response should include an empty binary
37407 attachment (i.e.@: a trailing semicolon). The return value is the
37408 number of target bytes read; the binary attachment may be longer if
37409 some characters were escaped.
37411 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37412 Write @var{data} (a binary buffer) to the open file corresponding
37413 to @var{fd}. Start the write at @var{offset} from the start of the
37414 file. Unlike many @code{write} system calls, there is no
37415 separate @var{count} argument; the length of @var{data} in the
37416 packet is used. @samp{vFile:write} returns the number of bytes written,
37417 which may be shorter than the length of @var{data}, or -1 if an
37420 @item vFile:fstat: @var{fd}
37421 Get information about the open file corresponding to @var{fd}.
37422 On success the information is returned as a binary attachment
37423 and the return value is the size of this attachment in bytes.
37424 If an error occurs the return value is -1. The format of the
37425 returned binary attachment is as described in @ref{struct stat}.
37427 @item vFile:unlink: @var{filename}
37428 Delete the file at @var{filename} on the target. Return 0,
37429 or -1 if an error occurs. The @var{filename} is a string.
37431 @item vFile:readlink: @var{filename}
37432 Read value of symbolic link @var{filename} on the target. Return
37433 the number of bytes read, or -1 if an error occurs.
37435 The data read should be returned as a binary attachment on success.
37436 If zero bytes were read, the response should include an empty binary
37437 attachment (i.e.@: a trailing semicolon). The return value is the
37438 number of target bytes read; the binary attachment may be longer if
37439 some characters were escaped.
37444 @section Interrupts
37445 @cindex interrupts (remote protocol)
37447 When a program on the remote target is running, @value{GDBN} may
37448 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37449 a @code{BREAK} followed by @code{g},
37450 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37452 The precise meaning of @code{BREAK} is defined by the transport
37453 mechanism and may, in fact, be undefined. @value{GDBN} does not
37454 currently define a @code{BREAK} mechanism for any of the network
37455 interfaces except for TCP, in which case @value{GDBN} sends the
37456 @code{telnet} BREAK sequence.
37458 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37459 transport mechanisms. It is represented by sending the single byte
37460 @code{0x03} without any of the usual packet overhead described in
37461 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37462 transmitted as part of a packet, it is considered to be packet data
37463 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37464 (@pxref{X packet}), used for binary downloads, may include an unescaped
37465 @code{0x03} as part of its packet.
37467 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37468 When Linux kernel receives this sequence from serial port,
37469 it stops execution and connects to gdb.
37471 Stubs are not required to recognize these interrupt mechanisms and the
37472 precise meaning associated with receipt of the interrupt is
37473 implementation defined. If the target supports debugging of multiple
37474 threads and/or processes, it should attempt to interrupt all
37475 currently-executing threads and processes.
37476 If the stub is successful at interrupting the
37477 running program, it should send one of the stop
37478 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37479 of successfully stopping the program in all-stop mode, and a stop reply
37480 for each stopped thread in non-stop mode.
37481 Interrupts received while the
37482 program is stopped are discarded.
37484 @node Notification Packets
37485 @section Notification Packets
37486 @cindex notification packets
37487 @cindex packets, notification
37489 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37490 packets that require no acknowledgment. Both the GDB and the stub
37491 may send notifications (although the only notifications defined at
37492 present are sent by the stub). Notifications carry information
37493 without incurring the round-trip latency of an acknowledgment, and so
37494 are useful for low-impact communications where occasional packet loss
37497 A notification packet has the form @samp{% @var{data} #
37498 @var{checksum}}, where @var{data} is the content of the notification,
37499 and @var{checksum} is a checksum of @var{data}, computed and formatted
37500 as for ordinary @value{GDBN} packets. A notification's @var{data}
37501 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37502 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37503 to acknowledge the notification's receipt or to report its corruption.
37505 Every notification's @var{data} begins with a name, which contains no
37506 colon characters, followed by a colon character.
37508 Recipients should silently ignore corrupted notifications and
37509 notifications they do not understand. Recipients should restart
37510 timeout periods on receipt of a well-formed notification, whether or
37511 not they understand it.
37513 Senders should only send the notifications described here when this
37514 protocol description specifies that they are permitted. In the
37515 future, we may extend the protocol to permit existing notifications in
37516 new contexts; this rule helps older senders avoid confusing newer
37519 (Older versions of @value{GDBN} ignore bytes received until they see
37520 the @samp{$} byte that begins an ordinary packet, so new stubs may
37521 transmit notifications without fear of confusing older clients. There
37522 are no notifications defined for @value{GDBN} to send at the moment, but we
37523 assume that most older stubs would ignore them, as well.)
37525 Each notification is comprised of three parts:
37527 @item @var{name}:@var{event}
37528 The notification packet is sent by the side that initiates the
37529 exchange (currently, only the stub does that), with @var{event}
37530 carrying the specific information about the notification, and
37531 @var{name} specifying the name of the notification.
37533 The acknowledge sent by the other side, usually @value{GDBN}, to
37534 acknowledge the exchange and request the event.
37537 The purpose of an asynchronous notification mechanism is to report to
37538 @value{GDBN} that something interesting happened in the remote stub.
37540 The remote stub may send notification @var{name}:@var{event}
37541 at any time, but @value{GDBN} acknowledges the notification when
37542 appropriate. The notification event is pending before @value{GDBN}
37543 acknowledges. Only one notification at a time may be pending; if
37544 additional events occur before @value{GDBN} has acknowledged the
37545 previous notification, they must be queued by the stub for later
37546 synchronous transmission in response to @var{ack} packets from
37547 @value{GDBN}. Because the notification mechanism is unreliable,
37548 the stub is permitted to resend a notification if it believes
37549 @value{GDBN} may not have received it.
37551 Specifically, notifications may appear when @value{GDBN} is not
37552 otherwise reading input from the stub, or when @value{GDBN} is
37553 expecting to read a normal synchronous response or a
37554 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37555 Notification packets are distinct from any other communication from
37556 the stub so there is no ambiguity.
37558 After receiving a notification, @value{GDBN} shall acknowledge it by
37559 sending a @var{ack} packet as a regular, synchronous request to the
37560 stub. Such acknowledgment is not required to happen immediately, as
37561 @value{GDBN} is permitted to send other, unrelated packets to the
37562 stub first, which the stub should process normally.
37564 Upon receiving a @var{ack} packet, if the stub has other queued
37565 events to report to @value{GDBN}, it shall respond by sending a
37566 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37567 packet to solicit further responses; again, it is permitted to send
37568 other, unrelated packets as well which the stub should process
37571 If the stub receives a @var{ack} packet and there are no additional
37572 @var{event} to report, the stub shall return an @samp{OK} response.
37573 At this point, @value{GDBN} has finished processing a notification
37574 and the stub has completed sending any queued events. @value{GDBN}
37575 won't accept any new notifications until the final @samp{OK} is
37576 received . If further notification events occur, the stub shall send
37577 a new notification, @value{GDBN} shall accept the notification, and
37578 the process shall be repeated.
37580 The process of asynchronous notification can be illustrated by the
37583 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37586 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37588 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37593 The following notifications are defined:
37594 @multitable @columnfractions 0.12 0.12 0.38 0.38
37603 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37604 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37605 for information on how these notifications are acknowledged by
37607 @tab Report an asynchronous stop event in non-stop mode.
37611 @node Remote Non-Stop
37612 @section Remote Protocol Support for Non-Stop Mode
37614 @value{GDBN}'s remote protocol supports non-stop debugging of
37615 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37616 supports non-stop mode, it should report that to @value{GDBN} by including
37617 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37619 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37620 establishing a new connection with the stub. Entering non-stop mode
37621 does not alter the state of any currently-running threads, but targets
37622 must stop all threads in any already-attached processes when entering
37623 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37624 probe the target state after a mode change.
37626 In non-stop mode, when an attached process encounters an event that
37627 would otherwise be reported with a stop reply, it uses the
37628 asynchronous notification mechanism (@pxref{Notification Packets}) to
37629 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37630 in all processes are stopped when a stop reply is sent, in non-stop
37631 mode only the thread reporting the stop event is stopped. That is,
37632 when reporting a @samp{S} or @samp{T} response to indicate completion
37633 of a step operation, hitting a breakpoint, or a fault, only the
37634 affected thread is stopped; any other still-running threads continue
37635 to run. When reporting a @samp{W} or @samp{X} response, all running
37636 threads belonging to other attached processes continue to run.
37638 In non-stop mode, the target shall respond to the @samp{?} packet as
37639 follows. First, any incomplete stop reply notification/@samp{vStopped}
37640 sequence in progress is abandoned. The target must begin a new
37641 sequence reporting stop events for all stopped threads, whether or not
37642 it has previously reported those events to @value{GDBN}. The first
37643 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37644 subsequent stop replies are sent as responses to @samp{vStopped} packets
37645 using the mechanism described above. The target must not send
37646 asynchronous stop reply notifications until the sequence is complete.
37647 If all threads are running when the target receives the @samp{?} packet,
37648 or if the target is not attached to any process, it shall respond
37651 If the stub supports non-stop mode, it should also support the
37652 @samp{swbreak} stop reason if software breakpoints are supported, and
37653 the @samp{hwbreak} stop reason if hardware breakpoints are supported
37654 (@pxref{swbreak stop reason}). This is because given the asynchronous
37655 nature of non-stop mode, between the time a thread hits a breakpoint
37656 and the time the event is finally processed by @value{GDBN}, the
37657 breakpoint may have already been removed from the target. Due to
37658 this, @value{GDBN} needs to be able to tell whether a trap stop was
37659 caused by a delayed breakpoint event, which should be ignored, as
37660 opposed to a random trap signal, which should be reported to the user.
37661 Note the @samp{swbreak} feature implies that the target is responsible
37662 for adjusting the PC when a software breakpoint triggers, if
37663 necessary, such as on the x86 architecture.
37665 @node Packet Acknowledgment
37666 @section Packet Acknowledgment
37668 @cindex acknowledgment, for @value{GDBN} remote
37669 @cindex packet acknowledgment, for @value{GDBN} remote
37670 By default, when either the host or the target machine receives a packet,
37671 the first response expected is an acknowledgment: either @samp{+} (to indicate
37672 the package was received correctly) or @samp{-} (to request retransmission).
37673 This mechanism allows the @value{GDBN} remote protocol to operate over
37674 unreliable transport mechanisms, such as a serial line.
37676 In cases where the transport mechanism is itself reliable (such as a pipe or
37677 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37678 It may be desirable to disable them in that case to reduce communication
37679 overhead, or for other reasons. This can be accomplished by means of the
37680 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37682 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37683 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37684 and response format still includes the normal checksum, as described in
37685 @ref{Overview}, but the checksum may be ignored by the receiver.
37687 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37688 no-acknowledgment mode, it should report that to @value{GDBN}
37689 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37690 @pxref{qSupported}.
37691 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37692 disabled via the @code{set remote noack-packet off} command
37693 (@pxref{Remote Configuration}),
37694 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37695 Only then may the stub actually turn off packet acknowledgments.
37696 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37697 response, which can be safely ignored by the stub.
37699 Note that @code{set remote noack-packet} command only affects negotiation
37700 between @value{GDBN} and the stub when subsequent connections are made;
37701 it does not affect the protocol acknowledgment state for any current
37703 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37704 new connection is established,
37705 there is also no protocol request to re-enable the acknowledgments
37706 for the current connection, once disabled.
37711 Example sequence of a target being re-started. Notice how the restart
37712 does not get any direct output:
37717 @emph{target restarts}
37720 <- @code{T001:1234123412341234}
37724 Example sequence of a target being stepped by a single instruction:
37727 -> @code{G1445@dots{}}
37732 <- @code{T001:1234123412341234}
37736 <- @code{1455@dots{}}
37740 @node File-I/O Remote Protocol Extension
37741 @section File-I/O Remote Protocol Extension
37742 @cindex File-I/O remote protocol extension
37745 * File-I/O Overview::
37746 * Protocol Basics::
37747 * The F Request Packet::
37748 * The F Reply Packet::
37749 * The Ctrl-C Message::
37751 * List of Supported Calls::
37752 * Protocol-specific Representation of Datatypes::
37754 * File-I/O Examples::
37757 @node File-I/O Overview
37758 @subsection File-I/O Overview
37759 @cindex file-i/o overview
37761 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37762 target to use the host's file system and console I/O to perform various
37763 system calls. System calls on the target system are translated into a
37764 remote protocol packet to the host system, which then performs the needed
37765 actions and returns a response packet to the target system.
37766 This simulates file system operations even on targets that lack file systems.
37768 The protocol is defined to be independent of both the host and target systems.
37769 It uses its own internal representation of datatypes and values. Both
37770 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37771 translating the system-dependent value representations into the internal
37772 protocol representations when data is transmitted.
37774 The communication is synchronous. A system call is possible only when
37775 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37776 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37777 the target is stopped to allow deterministic access to the target's
37778 memory. Therefore File-I/O is not interruptible by target signals. On
37779 the other hand, it is possible to interrupt File-I/O by a user interrupt
37780 (@samp{Ctrl-C}) within @value{GDBN}.
37782 The target's request to perform a host system call does not finish
37783 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37784 after finishing the system call, the target returns to continuing the
37785 previous activity (continue, step). No additional continue or step
37786 request from @value{GDBN} is required.
37789 (@value{GDBP}) continue
37790 <- target requests 'system call X'
37791 target is stopped, @value{GDBN} executes system call
37792 -> @value{GDBN} returns result
37793 ... target continues, @value{GDBN} returns to wait for the target
37794 <- target hits breakpoint and sends a Txx packet
37797 The protocol only supports I/O on the console and to regular files on
37798 the host file system. Character or block special devices, pipes,
37799 named pipes, sockets or any other communication method on the host
37800 system are not supported by this protocol.
37802 File I/O is not supported in non-stop mode.
37804 @node Protocol Basics
37805 @subsection Protocol Basics
37806 @cindex protocol basics, file-i/o
37808 The File-I/O protocol uses the @code{F} packet as the request as well
37809 as reply packet. Since a File-I/O system call can only occur when
37810 @value{GDBN} is waiting for a response from the continuing or stepping target,
37811 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37812 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37813 This @code{F} packet contains all information needed to allow @value{GDBN}
37814 to call the appropriate host system call:
37818 A unique identifier for the requested system call.
37821 All parameters to the system call. Pointers are given as addresses
37822 in the target memory address space. Pointers to strings are given as
37823 pointer/length pair. Numerical values are given as they are.
37824 Numerical control flags are given in a protocol-specific representation.
37828 At this point, @value{GDBN} has to perform the following actions.
37832 If the parameters include pointer values to data needed as input to a
37833 system call, @value{GDBN} requests this data from the target with a
37834 standard @code{m} packet request. This additional communication has to be
37835 expected by the target implementation and is handled as any other @code{m}
37839 @value{GDBN} translates all value from protocol representation to host
37840 representation as needed. Datatypes are coerced into the host types.
37843 @value{GDBN} calls the system call.
37846 It then coerces datatypes back to protocol representation.
37849 If the system call is expected to return data in buffer space specified
37850 by pointer parameters to the call, the data is transmitted to the
37851 target using a @code{M} or @code{X} packet. This packet has to be expected
37852 by the target implementation and is handled as any other @code{M} or @code{X}
37857 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37858 necessary information for the target to continue. This at least contains
37865 @code{errno}, if has been changed by the system call.
37872 After having done the needed type and value coercion, the target continues
37873 the latest continue or step action.
37875 @node The F Request Packet
37876 @subsection The @code{F} Request Packet
37877 @cindex file-i/o request packet
37878 @cindex @code{F} request packet
37880 The @code{F} request packet has the following format:
37883 @item F@var{call-id},@var{parameter@dots{}}
37885 @var{call-id} is the identifier to indicate the host system call to be called.
37886 This is just the name of the function.
37888 @var{parameter@dots{}} are the parameters to the system call.
37889 Parameters are hexadecimal integer values, either the actual values in case
37890 of scalar datatypes, pointers to target buffer space in case of compound
37891 datatypes and unspecified memory areas, or pointer/length pairs in case
37892 of string parameters. These are appended to the @var{call-id} as a
37893 comma-delimited list. All values are transmitted in ASCII
37894 string representation, pointer/length pairs separated by a slash.
37900 @node The F Reply Packet
37901 @subsection The @code{F} Reply Packet
37902 @cindex file-i/o reply packet
37903 @cindex @code{F} reply packet
37905 The @code{F} reply packet has the following format:
37909 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37911 @var{retcode} is the return code of the system call as hexadecimal value.
37913 @var{errno} is the @code{errno} set by the call, in protocol-specific
37915 This parameter can be omitted if the call was successful.
37917 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37918 case, @var{errno} must be sent as well, even if the call was successful.
37919 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37926 or, if the call was interrupted before the host call has been performed:
37933 assuming 4 is the protocol-specific representation of @code{EINTR}.
37938 @node The Ctrl-C Message
37939 @subsection The @samp{Ctrl-C} Message
37940 @cindex ctrl-c message, in file-i/o protocol
37942 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37943 reply packet (@pxref{The F Reply Packet}),
37944 the target should behave as if it had
37945 gotten a break message. The meaning for the target is ``system call
37946 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37947 (as with a break message) and return to @value{GDBN} with a @code{T02}
37950 It's important for the target to know in which
37951 state the system call was interrupted. There are two possible cases:
37955 The system call hasn't been performed on the host yet.
37958 The system call on the host has been finished.
37962 These two states can be distinguished by the target by the value of the
37963 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37964 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37965 on POSIX systems. In any other case, the target may presume that the
37966 system call has been finished --- successfully or not --- and should behave
37967 as if the break message arrived right after the system call.
37969 @value{GDBN} must behave reliably. If the system call has not been called
37970 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37971 @code{errno} in the packet. If the system call on the host has been finished
37972 before the user requests a break, the full action must be finished by
37973 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37974 The @code{F} packet may only be sent when either nothing has happened
37975 or the full action has been completed.
37978 @subsection Console I/O
37979 @cindex console i/o as part of file-i/o
37981 By default and if not explicitly closed by the target system, the file
37982 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37983 on the @value{GDBN} console is handled as any other file output operation
37984 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37985 by @value{GDBN} so that after the target read request from file descriptor
37986 0 all following typing is buffered until either one of the following
37991 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37993 system call is treated as finished.
37996 The user presses @key{RET}. This is treated as end of input with a trailing
38000 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38001 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38005 If the user has typed more characters than fit in the buffer given to
38006 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38007 either another @code{read(0, @dots{})} is requested by the target, or debugging
38008 is stopped at the user's request.
38011 @node List of Supported Calls
38012 @subsection List of Supported Calls
38013 @cindex list of supported file-i/o calls
38030 @unnumberedsubsubsec open
38031 @cindex open, file-i/o system call
38036 int open(const char *pathname, int flags);
38037 int open(const char *pathname, int flags, mode_t mode);
38041 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38044 @var{flags} is the bitwise @code{OR} of the following values:
38048 If the file does not exist it will be created. The host
38049 rules apply as far as file ownership and time stamps
38053 When used with @code{O_CREAT}, if the file already exists it is
38054 an error and open() fails.
38057 If the file already exists and the open mode allows
38058 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38059 truncated to zero length.
38062 The file is opened in append mode.
38065 The file is opened for reading only.
38068 The file is opened for writing only.
38071 The file is opened for reading and writing.
38075 Other bits are silently ignored.
38079 @var{mode} is the bitwise @code{OR} of the following values:
38083 User has read permission.
38086 User has write permission.
38089 Group has read permission.
38092 Group has write permission.
38095 Others have read permission.
38098 Others have write permission.
38102 Other bits are silently ignored.
38105 @item Return value:
38106 @code{open} returns the new file descriptor or -1 if an error
38113 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38116 @var{pathname} refers to a directory.
38119 The requested access is not allowed.
38122 @var{pathname} was too long.
38125 A directory component in @var{pathname} does not exist.
38128 @var{pathname} refers to a device, pipe, named pipe or socket.
38131 @var{pathname} refers to a file on a read-only filesystem and
38132 write access was requested.
38135 @var{pathname} is an invalid pointer value.
38138 No space on device to create the file.
38141 The process already has the maximum number of files open.
38144 The limit on the total number of files open on the system
38148 The call was interrupted by the user.
38154 @unnumberedsubsubsec close
38155 @cindex close, file-i/o system call
38164 @samp{Fclose,@var{fd}}
38166 @item Return value:
38167 @code{close} returns zero on success, or -1 if an error occurred.
38173 @var{fd} isn't a valid open file descriptor.
38176 The call was interrupted by the user.
38182 @unnumberedsubsubsec read
38183 @cindex read, file-i/o system call
38188 int read(int fd, void *buf, unsigned int count);
38192 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38194 @item Return value:
38195 On success, the number of bytes read is returned.
38196 Zero indicates end of file. If count is zero, read
38197 returns zero as well. On error, -1 is returned.
38203 @var{fd} is not a valid file descriptor or is not open for
38207 @var{bufptr} is an invalid pointer value.
38210 The call was interrupted by the user.
38216 @unnumberedsubsubsec write
38217 @cindex write, file-i/o system call
38222 int write(int fd, const void *buf, unsigned int count);
38226 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38228 @item Return value:
38229 On success, the number of bytes written are returned.
38230 Zero indicates nothing was written. On error, -1
38237 @var{fd} is not a valid file descriptor or is not open for
38241 @var{bufptr} is an invalid pointer value.
38244 An attempt was made to write a file that exceeds the
38245 host-specific maximum file size allowed.
38248 No space on device to write the data.
38251 The call was interrupted by the user.
38257 @unnumberedsubsubsec lseek
38258 @cindex lseek, file-i/o system call
38263 long lseek (int fd, long offset, int flag);
38267 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38269 @var{flag} is one of:
38273 The offset is set to @var{offset} bytes.
38276 The offset is set to its current location plus @var{offset}
38280 The offset is set to the size of the file plus @var{offset}
38284 @item Return value:
38285 On success, the resulting unsigned offset in bytes from
38286 the beginning of the file is returned. Otherwise, a
38287 value of -1 is returned.
38293 @var{fd} is not a valid open file descriptor.
38296 @var{fd} is associated with the @value{GDBN} console.
38299 @var{flag} is not a proper value.
38302 The call was interrupted by the user.
38308 @unnumberedsubsubsec rename
38309 @cindex rename, file-i/o system call
38314 int rename(const char *oldpath, const char *newpath);
38318 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38320 @item Return value:
38321 On success, zero is returned. On error, -1 is returned.
38327 @var{newpath} is an existing directory, but @var{oldpath} is not a
38331 @var{newpath} is a non-empty directory.
38334 @var{oldpath} or @var{newpath} is a directory that is in use by some
38338 An attempt was made to make a directory a subdirectory
38342 A component used as a directory in @var{oldpath} or new
38343 path is not a directory. Or @var{oldpath} is a directory
38344 and @var{newpath} exists but is not a directory.
38347 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38350 No access to the file or the path of the file.
38354 @var{oldpath} or @var{newpath} was too long.
38357 A directory component in @var{oldpath} or @var{newpath} does not exist.
38360 The file is on a read-only filesystem.
38363 The device containing the file has no room for the new
38367 The call was interrupted by the user.
38373 @unnumberedsubsubsec unlink
38374 @cindex unlink, file-i/o system call
38379 int unlink(const char *pathname);
38383 @samp{Funlink,@var{pathnameptr}/@var{len}}
38385 @item Return value:
38386 On success, zero is returned. On error, -1 is returned.
38392 No access to the file or the path of the file.
38395 The system does not allow unlinking of directories.
38398 The file @var{pathname} cannot be unlinked because it's
38399 being used by another process.
38402 @var{pathnameptr} is an invalid pointer value.
38405 @var{pathname} was too long.
38408 A directory component in @var{pathname} does not exist.
38411 A component of the path is not a directory.
38414 The file is on a read-only filesystem.
38417 The call was interrupted by the user.
38423 @unnumberedsubsubsec stat/fstat
38424 @cindex fstat, file-i/o system call
38425 @cindex stat, file-i/o system call
38430 int stat(const char *pathname, struct stat *buf);
38431 int fstat(int fd, struct stat *buf);
38435 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38436 @samp{Ffstat,@var{fd},@var{bufptr}}
38438 @item Return value:
38439 On success, zero is returned. On error, -1 is returned.
38445 @var{fd} is not a valid open file.
38448 A directory component in @var{pathname} does not exist or the
38449 path is an empty string.
38452 A component of the path is not a directory.
38455 @var{pathnameptr} is an invalid pointer value.
38458 No access to the file or the path of the file.
38461 @var{pathname} was too long.
38464 The call was interrupted by the user.
38470 @unnumberedsubsubsec gettimeofday
38471 @cindex gettimeofday, file-i/o system call
38476 int gettimeofday(struct timeval *tv, void *tz);
38480 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38482 @item Return value:
38483 On success, 0 is returned, -1 otherwise.
38489 @var{tz} is a non-NULL pointer.
38492 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38498 @unnumberedsubsubsec isatty
38499 @cindex isatty, file-i/o system call
38504 int isatty(int fd);
38508 @samp{Fisatty,@var{fd}}
38510 @item Return value:
38511 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38517 The call was interrupted by the user.
38522 Note that the @code{isatty} call is treated as a special case: it returns
38523 1 to the target if the file descriptor is attached
38524 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38525 would require implementing @code{ioctl} and would be more complex than
38530 @unnumberedsubsubsec system
38531 @cindex system, file-i/o system call
38536 int system(const char *command);
38540 @samp{Fsystem,@var{commandptr}/@var{len}}
38542 @item Return value:
38543 If @var{len} is zero, the return value indicates whether a shell is
38544 available. A zero return value indicates a shell is not available.
38545 For non-zero @var{len}, the value returned is -1 on error and the
38546 return status of the command otherwise. Only the exit status of the
38547 command is returned, which is extracted from the host's @code{system}
38548 return value by calling @code{WEXITSTATUS(retval)}. In case
38549 @file{/bin/sh} could not be executed, 127 is returned.
38555 The call was interrupted by the user.
38560 @value{GDBN} takes over the full task of calling the necessary host calls
38561 to perform the @code{system} call. The return value of @code{system} on
38562 the host is simplified before it's returned
38563 to the target. Any termination signal information from the child process
38564 is discarded, and the return value consists
38565 entirely of the exit status of the called command.
38567 Due to security concerns, the @code{system} call is by default refused
38568 by @value{GDBN}. The user has to allow this call explicitly with the
38569 @code{set remote system-call-allowed 1} command.
38572 @item set remote system-call-allowed
38573 @kindex set remote system-call-allowed
38574 Control whether to allow the @code{system} calls in the File I/O
38575 protocol for the remote target. The default is zero (disabled).
38577 @item show remote system-call-allowed
38578 @kindex show remote system-call-allowed
38579 Show whether the @code{system} calls are allowed in the File I/O
38583 @node Protocol-specific Representation of Datatypes
38584 @subsection Protocol-specific Representation of Datatypes
38585 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38588 * Integral Datatypes::
38590 * Memory Transfer::
38595 @node Integral Datatypes
38596 @unnumberedsubsubsec Integral Datatypes
38597 @cindex integral datatypes, in file-i/o protocol
38599 The integral datatypes used in the system calls are @code{int},
38600 @code{unsigned int}, @code{long}, @code{unsigned long},
38601 @code{mode_t}, and @code{time_t}.
38603 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38604 implemented as 32 bit values in this protocol.
38606 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38608 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38609 in @file{limits.h}) to allow range checking on host and target.
38611 @code{time_t} datatypes are defined as seconds since the Epoch.
38613 All integral datatypes transferred as part of a memory read or write of a
38614 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38617 @node Pointer Values
38618 @unnumberedsubsubsec Pointer Values
38619 @cindex pointer values, in file-i/o protocol
38621 Pointers to target data are transmitted as they are. An exception
38622 is made for pointers to buffers for which the length isn't
38623 transmitted as part of the function call, namely strings. Strings
38624 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38631 which is a pointer to data of length 18 bytes at position 0x1aaf.
38632 The length is defined as the full string length in bytes, including
38633 the trailing null byte. For example, the string @code{"hello world"}
38634 at address 0x123456 is transmitted as
38640 @node Memory Transfer
38641 @unnumberedsubsubsec Memory Transfer
38642 @cindex memory transfer, in file-i/o protocol
38644 Structured data which is transferred using a memory read or write (for
38645 example, a @code{struct stat}) is expected to be in a protocol-specific format
38646 with all scalar multibyte datatypes being big endian. Translation to
38647 this representation needs to be done both by the target before the @code{F}
38648 packet is sent, and by @value{GDBN} before
38649 it transfers memory to the target. Transferred pointers to structured
38650 data should point to the already-coerced data at any time.
38654 @unnumberedsubsubsec struct stat
38655 @cindex struct stat, in file-i/o protocol
38657 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38658 is defined as follows:
38662 unsigned int st_dev; /* device */
38663 unsigned int st_ino; /* inode */
38664 mode_t st_mode; /* protection */
38665 unsigned int st_nlink; /* number of hard links */
38666 unsigned int st_uid; /* user ID of owner */
38667 unsigned int st_gid; /* group ID of owner */
38668 unsigned int st_rdev; /* device type (if inode device) */
38669 unsigned long st_size; /* total size, in bytes */
38670 unsigned long st_blksize; /* blocksize for filesystem I/O */
38671 unsigned long st_blocks; /* number of blocks allocated */
38672 time_t st_atime; /* time of last access */
38673 time_t st_mtime; /* time of last modification */
38674 time_t st_ctime; /* time of last change */
38678 The integral datatypes conform to the definitions given in the
38679 appropriate section (see @ref{Integral Datatypes}, for details) so this
38680 structure is of size 64 bytes.
38682 The values of several fields have a restricted meaning and/or
38688 A value of 0 represents a file, 1 the console.
38691 No valid meaning for the target. Transmitted unchanged.
38694 Valid mode bits are described in @ref{Constants}. Any other
38695 bits have currently no meaning for the target.
38700 No valid meaning for the target. Transmitted unchanged.
38705 These values have a host and file system dependent
38706 accuracy. Especially on Windows hosts, the file system may not
38707 support exact timing values.
38710 The target gets a @code{struct stat} of the above representation and is
38711 responsible for coercing it to the target representation before
38714 Note that due to size differences between the host, target, and protocol
38715 representations of @code{struct stat} members, these members could eventually
38716 get truncated on the target.
38718 @node struct timeval
38719 @unnumberedsubsubsec struct timeval
38720 @cindex struct timeval, in file-i/o protocol
38722 The buffer of type @code{struct timeval} used by the File-I/O protocol
38723 is defined as follows:
38727 time_t tv_sec; /* second */
38728 long tv_usec; /* microsecond */
38732 The integral datatypes conform to the definitions given in the
38733 appropriate section (see @ref{Integral Datatypes}, for details) so this
38734 structure is of size 8 bytes.
38737 @subsection Constants
38738 @cindex constants, in file-i/o protocol
38740 The following values are used for the constants inside of the
38741 protocol. @value{GDBN} and target are responsible for translating these
38742 values before and after the call as needed.
38753 @unnumberedsubsubsec Open Flags
38754 @cindex open flags, in file-i/o protocol
38756 All values are given in hexadecimal representation.
38768 @node mode_t Values
38769 @unnumberedsubsubsec mode_t Values
38770 @cindex mode_t values, in file-i/o protocol
38772 All values are given in octal representation.
38789 @unnumberedsubsubsec Errno Values
38790 @cindex errno values, in file-i/o protocol
38792 All values are given in decimal representation.
38817 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38818 any error value not in the list of supported error numbers.
38821 @unnumberedsubsubsec Lseek Flags
38822 @cindex lseek flags, in file-i/o protocol
38831 @unnumberedsubsubsec Limits
38832 @cindex limits, in file-i/o protocol
38834 All values are given in decimal representation.
38837 INT_MIN -2147483648
38839 UINT_MAX 4294967295
38840 LONG_MIN -9223372036854775808
38841 LONG_MAX 9223372036854775807
38842 ULONG_MAX 18446744073709551615
38845 @node File-I/O Examples
38846 @subsection File-I/O Examples
38847 @cindex file-i/o examples
38849 Example sequence of a write call, file descriptor 3, buffer is at target
38850 address 0x1234, 6 bytes should be written:
38853 <- @code{Fwrite,3,1234,6}
38854 @emph{request memory read from target}
38857 @emph{return "6 bytes written"}
38861 Example sequence of a read call, file descriptor 3, buffer is at target
38862 address 0x1234, 6 bytes should be read:
38865 <- @code{Fread,3,1234,6}
38866 @emph{request memory write to target}
38867 -> @code{X1234,6:XXXXXX}
38868 @emph{return "6 bytes read"}
38872 Example sequence of a read call, call fails on the host due to invalid
38873 file descriptor (@code{EBADF}):
38876 <- @code{Fread,3,1234,6}
38880 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38884 <- @code{Fread,3,1234,6}
38889 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38893 <- @code{Fread,3,1234,6}
38894 -> @code{X1234,6:XXXXXX}
38898 @node Library List Format
38899 @section Library List Format
38900 @cindex library list format, remote protocol
38902 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38903 same process as your application to manage libraries. In this case,
38904 @value{GDBN} can use the loader's symbol table and normal memory
38905 operations to maintain a list of shared libraries. On other
38906 platforms, the operating system manages loaded libraries.
38907 @value{GDBN} can not retrieve the list of currently loaded libraries
38908 through memory operations, so it uses the @samp{qXfer:libraries:read}
38909 packet (@pxref{qXfer library list read}) instead. The remote stub
38910 queries the target's operating system and reports which libraries
38913 The @samp{qXfer:libraries:read} packet returns an XML document which
38914 lists loaded libraries and their offsets. Each library has an
38915 associated name and one or more segment or section base addresses,
38916 which report where the library was loaded in memory.
38918 For the common case of libraries that are fully linked binaries, the
38919 library should have a list of segments. If the target supports
38920 dynamic linking of a relocatable object file, its library XML element
38921 should instead include a list of allocated sections. The segment or
38922 section bases are start addresses, not relocation offsets; they do not
38923 depend on the library's link-time base addresses.
38925 @value{GDBN} must be linked with the Expat library to support XML
38926 library lists. @xref{Expat}.
38928 A simple memory map, with one loaded library relocated by a single
38929 offset, looks like this:
38933 <library name="/lib/libc.so.6">
38934 <segment address="0x10000000"/>
38939 Another simple memory map, with one loaded library with three
38940 allocated sections (.text, .data, .bss), looks like this:
38944 <library name="sharedlib.o">
38945 <section address="0x10000000"/>
38946 <section address="0x20000000"/>
38947 <section address="0x30000000"/>
38952 The format of a library list is described by this DTD:
38955 <!-- library-list: Root element with versioning -->
38956 <!ELEMENT library-list (library)*>
38957 <!ATTLIST library-list version CDATA #FIXED "1.0">
38958 <!ELEMENT library (segment*, section*)>
38959 <!ATTLIST library name CDATA #REQUIRED>
38960 <!ELEMENT segment EMPTY>
38961 <!ATTLIST segment address CDATA #REQUIRED>
38962 <!ELEMENT section EMPTY>
38963 <!ATTLIST section address CDATA #REQUIRED>
38966 In addition, segments and section descriptors cannot be mixed within a
38967 single library element, and you must supply at least one segment or
38968 section for each library.
38970 @node Library List Format for SVR4 Targets
38971 @section Library List Format for SVR4 Targets
38972 @cindex library list format, remote protocol
38974 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38975 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38976 shared libraries. Still a special library list provided by this packet is
38977 more efficient for the @value{GDBN} remote protocol.
38979 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38980 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38981 target, the following parameters are reported:
38985 @code{name}, the absolute file name from the @code{l_name} field of
38986 @code{struct link_map}.
38988 @code{lm} with address of @code{struct link_map} used for TLS
38989 (Thread Local Storage) access.
38991 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38992 @code{struct link_map}. For prelinked libraries this is not an absolute
38993 memory address. It is a displacement of absolute memory address against
38994 address the file was prelinked to during the library load.
38996 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38999 Additionally the single @code{main-lm} attribute specifies address of
39000 @code{struct link_map} used for the main executable. This parameter is used
39001 for TLS access and its presence is optional.
39003 @value{GDBN} must be linked with the Expat library to support XML
39004 SVR4 library lists. @xref{Expat}.
39006 A simple memory map, with two loaded libraries (which do not use prelink),
39010 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39011 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39013 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39015 </library-list-svr>
39018 The format of an SVR4 library list is described by this DTD:
39021 <!-- library-list-svr4: Root element with versioning -->
39022 <!ELEMENT library-list-svr4 (library)*>
39023 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39024 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39025 <!ELEMENT library EMPTY>
39026 <!ATTLIST library name CDATA #REQUIRED>
39027 <!ATTLIST library lm CDATA #REQUIRED>
39028 <!ATTLIST library l_addr CDATA #REQUIRED>
39029 <!ATTLIST library l_ld CDATA #REQUIRED>
39032 @node Memory Map Format
39033 @section Memory Map Format
39034 @cindex memory map format
39036 To be able to write into flash memory, @value{GDBN} needs to obtain a
39037 memory map from the target. This section describes the format of the
39040 The memory map is obtained using the @samp{qXfer:memory-map:read}
39041 (@pxref{qXfer memory map read}) packet and is an XML document that
39042 lists memory regions.
39044 @value{GDBN} must be linked with the Expat library to support XML
39045 memory maps. @xref{Expat}.
39047 The top-level structure of the document is shown below:
39050 <?xml version="1.0"?>
39051 <!DOCTYPE memory-map
39052 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39053 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39059 Each region can be either:
39064 A region of RAM starting at @var{addr} and extending for @var{length}
39068 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39073 A region of read-only memory:
39076 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39081 A region of flash memory, with erasure blocks @var{blocksize}
39085 <memory type="flash" start="@var{addr}" length="@var{length}">
39086 <property name="blocksize">@var{blocksize}</property>
39092 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39093 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39094 packets to write to addresses in such ranges.
39096 The formal DTD for memory map format is given below:
39099 <!-- ................................................... -->
39100 <!-- Memory Map XML DTD ................................ -->
39101 <!-- File: memory-map.dtd .............................. -->
39102 <!-- .................................... .............. -->
39103 <!-- memory-map.dtd -->
39104 <!-- memory-map: Root element with versioning -->
39105 <!ELEMENT memory-map (memory | property)>
39106 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39107 <!ELEMENT memory (property)>
39108 <!-- memory: Specifies a memory region,
39109 and its type, or device. -->
39110 <!ATTLIST memory type CDATA #REQUIRED
39111 start CDATA #REQUIRED
39112 length CDATA #REQUIRED
39113 device CDATA #IMPLIED>
39114 <!-- property: Generic attribute tag -->
39115 <!ELEMENT property (#PCDATA | property)*>
39116 <!ATTLIST property name CDATA #REQUIRED>
39119 @node Thread List Format
39120 @section Thread List Format
39121 @cindex thread list format
39123 To efficiently update the list of threads and their attributes,
39124 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39125 (@pxref{qXfer threads read}) and obtains the XML document with
39126 the following structure:
39129 <?xml version="1.0"?>
39131 <thread id="id" core="0">
39132 ... description ...
39137 Each @samp{thread} element must have the @samp{id} attribute that
39138 identifies the thread (@pxref{thread-id syntax}). The
39139 @samp{core} attribute, if present, specifies which processor core
39140 the thread was last executing on. The content of the of @samp{thread}
39141 element is interpreted as human-readable auxilliary information.
39143 @node Traceframe Info Format
39144 @section Traceframe Info Format
39145 @cindex traceframe info format
39147 To be able to know which objects in the inferior can be examined when
39148 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39149 memory ranges, registers and trace state variables that have been
39150 collected in a traceframe.
39152 This list is obtained using the @samp{qXfer:traceframe-info:read}
39153 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39155 @value{GDBN} must be linked with the Expat library to support XML
39156 traceframe info discovery. @xref{Expat}.
39158 The top-level structure of the document is shown below:
39161 <?xml version="1.0"?>
39162 <!DOCTYPE traceframe-info
39163 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39164 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39170 Each traceframe block can be either:
39175 A region of collected memory starting at @var{addr} and extending for
39176 @var{length} bytes from there:
39179 <memory start="@var{addr}" length="@var{length}"/>
39183 A block indicating trace state variable numbered @var{number} has been
39187 <tvar id="@var{number}"/>
39192 The formal DTD for the traceframe info format is given below:
39195 <!ELEMENT traceframe-info (memory | tvar)* >
39196 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39198 <!ELEMENT memory EMPTY>
39199 <!ATTLIST memory start CDATA #REQUIRED
39200 length CDATA #REQUIRED>
39202 <!ATTLIST tvar id CDATA #REQUIRED>
39205 @node Branch Trace Format
39206 @section Branch Trace Format
39207 @cindex branch trace format
39209 In order to display the branch trace of an inferior thread,
39210 @value{GDBN} needs to obtain the list of branches. This list is
39211 represented as list of sequential code blocks that are connected via
39212 branches. The code in each block has been executed sequentially.
39214 This list is obtained using the @samp{qXfer:btrace:read}
39215 (@pxref{qXfer btrace read}) packet and is an XML document.
39217 @value{GDBN} must be linked with the Expat library to support XML
39218 traceframe info discovery. @xref{Expat}.
39220 The top-level structure of the document is shown below:
39223 <?xml version="1.0"?>
39225 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39226 "http://sourceware.org/gdb/gdb-btrace.dtd">
39235 A block of sequentially executed instructions starting at @var{begin}
39236 and ending at @var{end}:
39239 <block begin="@var{begin}" end="@var{end}"/>
39244 The formal DTD for the branch trace format is given below:
39247 <!ELEMENT btrace (block)* >
39248 <!ATTLIST btrace version CDATA #FIXED "1.0">
39250 <!ELEMENT block EMPTY>
39251 <!ATTLIST block begin CDATA #REQUIRED
39252 end CDATA #REQUIRED>
39255 @node Branch Trace Configuration Format
39256 @section Branch Trace Configuration Format
39257 @cindex branch trace configuration format
39259 For each inferior thread, @value{GDBN} can obtain the branch trace
39260 configuration using the @samp{qXfer:btrace-conf:read}
39261 (@pxref{qXfer btrace-conf read}) packet.
39263 The configuration describes the branch trace format and configuration
39264 settings for that format. The following information is described:
39268 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39271 The size of the @acronym{BTS} ring buffer in bytes.
39275 @value{GDBN} must be linked with the Expat library to support XML
39276 branch trace configuration discovery. @xref{Expat}.
39278 The formal DTD for the branch trace configuration format is given below:
39281 <!ELEMENT btrace-conf (bts?)>
39282 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39284 <!ELEMENT bts EMPTY>
39285 <!ATTLIST bts size CDATA #IMPLIED>
39288 @include agentexpr.texi
39290 @node Target Descriptions
39291 @appendix Target Descriptions
39292 @cindex target descriptions
39294 One of the challenges of using @value{GDBN} to debug embedded systems
39295 is that there are so many minor variants of each processor
39296 architecture in use. It is common practice for vendors to start with
39297 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39298 and then make changes to adapt it to a particular market niche. Some
39299 architectures have hundreds of variants, available from dozens of
39300 vendors. This leads to a number of problems:
39304 With so many different customized processors, it is difficult for
39305 the @value{GDBN} maintainers to keep up with the changes.
39307 Since individual variants may have short lifetimes or limited
39308 audiences, it may not be worthwhile to carry information about every
39309 variant in the @value{GDBN} source tree.
39311 When @value{GDBN} does support the architecture of the embedded system
39312 at hand, the task of finding the correct architecture name to give the
39313 @command{set architecture} command can be error-prone.
39316 To address these problems, the @value{GDBN} remote protocol allows a
39317 target system to not only identify itself to @value{GDBN}, but to
39318 actually describe its own features. This lets @value{GDBN} support
39319 processor variants it has never seen before --- to the extent that the
39320 descriptions are accurate, and that @value{GDBN} understands them.
39322 @value{GDBN} must be linked with the Expat library to support XML
39323 target descriptions. @xref{Expat}.
39326 * Retrieving Descriptions:: How descriptions are fetched from a target.
39327 * Target Description Format:: The contents of a target description.
39328 * Predefined Target Types:: Standard types available for target
39330 * Standard Target Features:: Features @value{GDBN} knows about.
39333 @node Retrieving Descriptions
39334 @section Retrieving Descriptions
39336 Target descriptions can be read from the target automatically, or
39337 specified by the user manually. The default behavior is to read the
39338 description from the target. @value{GDBN} retrieves it via the remote
39339 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39340 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39341 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39342 XML document, of the form described in @ref{Target Description
39345 Alternatively, you can specify a file to read for the target description.
39346 If a file is set, the target will not be queried. The commands to
39347 specify a file are:
39350 @cindex set tdesc filename
39351 @item set tdesc filename @var{path}
39352 Read the target description from @var{path}.
39354 @cindex unset tdesc filename
39355 @item unset tdesc filename
39356 Do not read the XML target description from a file. @value{GDBN}
39357 will use the description supplied by the current target.
39359 @cindex show tdesc filename
39360 @item show tdesc filename
39361 Show the filename to read for a target description, if any.
39365 @node Target Description Format
39366 @section Target Description Format
39367 @cindex target descriptions, XML format
39369 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39370 document which complies with the Document Type Definition provided in
39371 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39372 means you can use generally available tools like @command{xmllint} to
39373 check that your feature descriptions are well-formed and valid.
39374 However, to help people unfamiliar with XML write descriptions for
39375 their targets, we also describe the grammar here.
39377 Target descriptions can identify the architecture of the remote target
39378 and (for some architectures) provide information about custom register
39379 sets. They can also identify the OS ABI of the remote target.
39380 @value{GDBN} can use this information to autoconfigure for your
39381 target, or to warn you if you connect to an unsupported target.
39383 Here is a simple target description:
39386 <target version="1.0">
39387 <architecture>i386:x86-64</architecture>
39392 This minimal description only says that the target uses
39393 the x86-64 architecture.
39395 A target description has the following overall form, with [ ] marking
39396 optional elements and @dots{} marking repeatable elements. The elements
39397 are explained further below.
39400 <?xml version="1.0"?>
39401 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39402 <target version="1.0">
39403 @r{[}@var{architecture}@r{]}
39404 @r{[}@var{osabi}@r{]}
39405 @r{[}@var{compatible}@r{]}
39406 @r{[}@var{feature}@dots{}@r{]}
39411 The description is generally insensitive to whitespace and line
39412 breaks, under the usual common-sense rules. The XML version
39413 declaration and document type declaration can generally be omitted
39414 (@value{GDBN} does not require them), but specifying them may be
39415 useful for XML validation tools. The @samp{version} attribute for
39416 @samp{<target>} may also be omitted, but we recommend
39417 including it; if future versions of @value{GDBN} use an incompatible
39418 revision of @file{gdb-target.dtd}, they will detect and report
39419 the version mismatch.
39421 @subsection Inclusion
39422 @cindex target descriptions, inclusion
39425 @cindex <xi:include>
39428 It can sometimes be valuable to split a target description up into
39429 several different annexes, either for organizational purposes, or to
39430 share files between different possible target descriptions. You can
39431 divide a description into multiple files by replacing any element of
39432 the target description with an inclusion directive of the form:
39435 <xi:include href="@var{document}"/>
39439 When @value{GDBN} encounters an element of this form, it will retrieve
39440 the named XML @var{document}, and replace the inclusion directive with
39441 the contents of that document. If the current description was read
39442 using @samp{qXfer}, then so will be the included document;
39443 @var{document} will be interpreted as the name of an annex. If the
39444 current description was read from a file, @value{GDBN} will look for
39445 @var{document} as a file in the same directory where it found the
39446 original description.
39448 @subsection Architecture
39449 @cindex <architecture>
39451 An @samp{<architecture>} element has this form:
39454 <architecture>@var{arch}</architecture>
39457 @var{arch} is one of the architectures from the set accepted by
39458 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39461 @cindex @code{<osabi>}
39463 This optional field was introduced in @value{GDBN} version 7.0.
39464 Previous versions of @value{GDBN} ignore it.
39466 An @samp{<osabi>} element has this form:
39469 <osabi>@var{abi-name}</osabi>
39472 @var{abi-name} is an OS ABI name from the same selection accepted by
39473 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39475 @subsection Compatible Architecture
39476 @cindex @code{<compatible>}
39478 This optional field was introduced in @value{GDBN} version 7.0.
39479 Previous versions of @value{GDBN} ignore it.
39481 A @samp{<compatible>} element has this form:
39484 <compatible>@var{arch}</compatible>
39487 @var{arch} is one of the architectures from the set accepted by
39488 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39490 A @samp{<compatible>} element is used to specify that the target
39491 is able to run binaries in some other than the main target architecture
39492 given by the @samp{<architecture>} element. For example, on the
39493 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39494 or @code{powerpc:common64}, but the system is able to run binaries
39495 in the @code{spu} architecture as well. The way to describe this
39496 capability with @samp{<compatible>} is as follows:
39499 <architecture>powerpc:common</architecture>
39500 <compatible>spu</compatible>
39503 @subsection Features
39506 Each @samp{<feature>} describes some logical portion of the target
39507 system. Features are currently used to describe available CPU
39508 registers and the types of their contents. A @samp{<feature>} element
39512 <feature name="@var{name}">
39513 @r{[}@var{type}@dots{}@r{]}
39519 Each feature's name should be unique within the description. The name
39520 of a feature does not matter unless @value{GDBN} has some special
39521 knowledge of the contents of that feature; if it does, the feature
39522 should have its standard name. @xref{Standard Target Features}.
39526 Any register's value is a collection of bits which @value{GDBN} must
39527 interpret. The default interpretation is a two's complement integer,
39528 but other types can be requested by name in the register description.
39529 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39530 Target Types}), and the description can define additional composite types.
39532 Each type element must have an @samp{id} attribute, which gives
39533 a unique (within the containing @samp{<feature>}) name to the type.
39534 Types must be defined before they are used.
39537 Some targets offer vector registers, which can be treated as arrays
39538 of scalar elements. These types are written as @samp{<vector>} elements,
39539 specifying the array element type, @var{type}, and the number of elements,
39543 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39547 If a register's value is usefully viewed in multiple ways, define it
39548 with a union type containing the useful representations. The
39549 @samp{<union>} element contains one or more @samp{<field>} elements,
39550 each of which has a @var{name} and a @var{type}:
39553 <union id="@var{id}">
39554 <field name="@var{name}" type="@var{type}"/>
39560 If a register's value is composed from several separate values, define
39561 it with a structure type. There are two forms of the @samp{<struct>}
39562 element; a @samp{<struct>} element must either contain only bitfields
39563 or contain no bitfields. If the structure contains only bitfields,
39564 its total size in bytes must be specified, each bitfield must have an
39565 explicit start and end, and bitfields are automatically assigned an
39566 integer type. The field's @var{start} should be less than or
39567 equal to its @var{end}, and zero represents the least significant bit.
39570 <struct id="@var{id}" size="@var{size}">
39571 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39576 If the structure contains no bitfields, then each field has an
39577 explicit type, and no implicit padding is added.
39580 <struct id="@var{id}">
39581 <field name="@var{name}" type="@var{type}"/>
39587 If a register's value is a series of single-bit flags, define it with
39588 a flags type. The @samp{<flags>} element has an explicit @var{size}
39589 and contains one or more @samp{<field>} elements. Each field has a
39590 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39594 <flags id="@var{id}" size="@var{size}">
39595 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39600 @subsection Registers
39603 Each register is represented as an element with this form:
39606 <reg name="@var{name}"
39607 bitsize="@var{size}"
39608 @r{[}regnum="@var{num}"@r{]}
39609 @r{[}save-restore="@var{save-restore}"@r{]}
39610 @r{[}type="@var{type}"@r{]}
39611 @r{[}group="@var{group}"@r{]}/>
39615 The components are as follows:
39620 The register's name; it must be unique within the target description.
39623 The register's size, in bits.
39626 The register's number. If omitted, a register's number is one greater
39627 than that of the previous register (either in the current feature or in
39628 a preceding feature); the first register in the target description
39629 defaults to zero. This register number is used to read or write
39630 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39631 packets, and registers appear in the @code{g} and @code{G} packets
39632 in order of increasing register number.
39635 Whether the register should be preserved across inferior function
39636 calls; this must be either @code{yes} or @code{no}. The default is
39637 @code{yes}, which is appropriate for most registers except for
39638 some system control registers; this is not related to the target's
39642 The type of the register. It may be a predefined type, a type
39643 defined in the current feature, or one of the special types @code{int}
39644 and @code{float}. @code{int} is an integer type of the correct size
39645 for @var{bitsize}, and @code{float} is a floating point type (in the
39646 architecture's normal floating point format) of the correct size for
39647 @var{bitsize}. The default is @code{int}.
39650 The register group to which this register belongs. It must
39651 be either @code{general}, @code{float}, or @code{vector}. If no
39652 @var{group} is specified, @value{GDBN} will not display the register
39653 in @code{info registers}.
39657 @node Predefined Target Types
39658 @section Predefined Target Types
39659 @cindex target descriptions, predefined types
39661 Type definitions in the self-description can build up composite types
39662 from basic building blocks, but can not define fundamental types. Instead,
39663 standard identifiers are provided by @value{GDBN} for the fundamental
39664 types. The currently supported types are:
39673 Signed integer types holding the specified number of bits.
39680 Unsigned integer types holding the specified number of bits.
39684 Pointers to unspecified code and data. The program counter and
39685 any dedicated return address register may be marked as code
39686 pointers; printing a code pointer converts it into a symbolic
39687 address. The stack pointer and any dedicated address registers
39688 may be marked as data pointers.
39691 Single precision IEEE floating point.
39694 Double precision IEEE floating point.
39697 The 12-byte extended precision format used by ARM FPA registers.
39700 The 10-byte extended precision format used by x87 registers.
39703 32bit @sc{eflags} register used by x86.
39706 32bit @sc{mxcsr} register used by x86.
39710 @node Standard Target Features
39711 @section Standard Target Features
39712 @cindex target descriptions, standard features
39714 A target description must contain either no registers or all the
39715 target's registers. If the description contains no registers, then
39716 @value{GDBN} will assume a default register layout, selected based on
39717 the architecture. If the description contains any registers, the
39718 default layout will not be used; the standard registers must be
39719 described in the target description, in such a way that @value{GDBN}
39720 can recognize them.
39722 This is accomplished by giving specific names to feature elements
39723 which contain standard registers. @value{GDBN} will look for features
39724 with those names and verify that they contain the expected registers;
39725 if any known feature is missing required registers, or if any required
39726 feature is missing, @value{GDBN} will reject the target
39727 description. You can add additional registers to any of the
39728 standard features --- @value{GDBN} will display them just as if
39729 they were added to an unrecognized feature.
39731 This section lists the known features and their expected contents.
39732 Sample XML documents for these features are included in the
39733 @value{GDBN} source tree, in the directory @file{gdb/features}.
39735 Names recognized by @value{GDBN} should include the name of the
39736 company or organization which selected the name, and the overall
39737 architecture to which the feature applies; so e.g.@: the feature
39738 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39740 The names of registers are not case sensitive for the purpose
39741 of recognizing standard features, but @value{GDBN} will only display
39742 registers using the capitalization used in the description.
39745 * AArch64 Features::
39748 * MicroBlaze Features::
39751 * Nios II Features::
39752 * PowerPC Features::
39753 * S/390 and System z Features::
39758 @node AArch64 Features
39759 @subsection AArch64 Features
39760 @cindex target descriptions, AArch64 features
39762 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39763 targets. It should contain registers @samp{x0} through @samp{x30},
39764 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39766 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39767 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39771 @subsection ARM Features
39772 @cindex target descriptions, ARM features
39774 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39776 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39777 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39779 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39780 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39781 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39784 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39785 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39787 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39788 it should contain at least registers @samp{wR0} through @samp{wR15} and
39789 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39790 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39792 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39793 should contain at least registers @samp{d0} through @samp{d15}. If
39794 they are present, @samp{d16} through @samp{d31} should also be included.
39795 @value{GDBN} will synthesize the single-precision registers from
39796 halves of the double-precision registers.
39798 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39799 need to contain registers; it instructs @value{GDBN} to display the
39800 VFP double-precision registers as vectors and to synthesize the
39801 quad-precision registers from pairs of double-precision registers.
39802 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39803 be present and include 32 double-precision registers.
39805 @node i386 Features
39806 @subsection i386 Features
39807 @cindex target descriptions, i386 features
39809 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39810 targets. It should describe the following registers:
39814 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39816 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39818 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39819 @samp{fs}, @samp{gs}
39821 @samp{st0} through @samp{st7}
39823 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39824 @samp{foseg}, @samp{fooff} and @samp{fop}
39827 The register sets may be different, depending on the target.
39829 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39830 describe registers:
39834 @samp{xmm0} through @samp{xmm7} for i386
39836 @samp{xmm0} through @samp{xmm15} for amd64
39841 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39842 @samp{org.gnu.gdb.i386.sse} feature. It should
39843 describe the upper 128 bits of @sc{ymm} registers:
39847 @samp{ymm0h} through @samp{ymm7h} for i386
39849 @samp{ymm0h} through @samp{ymm15h} for amd64
39852 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39853 Memory Protection Extension (MPX). It should describe the following registers:
39857 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39859 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39862 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39863 describe a single register, @samp{orig_eax}.
39865 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39866 @samp{org.gnu.gdb.i386.avx} feature. It should
39867 describe additional @sc{xmm} registers:
39871 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39874 It should describe the upper 128 bits of additional @sc{ymm} registers:
39878 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39882 describe the upper 256 bits of @sc{zmm} registers:
39886 @samp{zmm0h} through @samp{zmm7h} for i386.
39888 @samp{zmm0h} through @samp{zmm15h} for amd64.
39892 describe the additional @sc{zmm} registers:
39896 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39899 @node MicroBlaze Features
39900 @subsection MicroBlaze Features
39901 @cindex target descriptions, MicroBlaze features
39903 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39904 targets. It should contain registers @samp{r0} through @samp{r31},
39905 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39906 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39907 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39909 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39910 If present, it should contain registers @samp{rshr} and @samp{rslr}
39912 @node MIPS Features
39913 @subsection @acronym{MIPS} Features
39914 @cindex target descriptions, @acronym{MIPS} features
39916 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39917 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39918 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39921 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39922 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39923 registers. They may be 32-bit or 64-bit depending on the target.
39925 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39926 it may be optional in a future version of @value{GDBN}. It should
39927 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39928 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39930 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39931 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39932 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39933 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39935 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39936 contain a single register, @samp{restart}, which is used by the
39937 Linux kernel to control restartable syscalls.
39939 @node M68K Features
39940 @subsection M68K Features
39941 @cindex target descriptions, M68K features
39944 @item @samp{org.gnu.gdb.m68k.core}
39945 @itemx @samp{org.gnu.gdb.coldfire.core}
39946 @itemx @samp{org.gnu.gdb.fido.core}
39947 One of those features must be always present.
39948 The feature that is present determines which flavor of m68k is
39949 used. The feature that is present should contain registers
39950 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39951 @samp{sp}, @samp{ps} and @samp{pc}.
39953 @item @samp{org.gnu.gdb.coldfire.fp}
39954 This feature is optional. If present, it should contain registers
39955 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39959 @node Nios II Features
39960 @subsection Nios II Features
39961 @cindex target descriptions, Nios II features
39963 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39964 targets. It should contain the 32 core registers (@samp{zero},
39965 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39966 @samp{pc}, and the 16 control registers (@samp{status} through
39969 @node PowerPC Features
39970 @subsection PowerPC Features
39971 @cindex target descriptions, PowerPC features
39973 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39974 targets. It should contain registers @samp{r0} through @samp{r31},
39975 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39976 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39978 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39979 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39981 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39982 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39985 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39986 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39987 will combine these registers with the floating point registers
39988 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39989 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39990 through @samp{vs63}, the set of vector registers for POWER7.
39992 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39993 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39994 @samp{spefscr}. SPE targets should provide 32-bit registers in
39995 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39996 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39997 these to present registers @samp{ev0} through @samp{ev31} to the
40000 @node S/390 and System z Features
40001 @subsection S/390 and System z Features
40002 @cindex target descriptions, S/390 features
40003 @cindex target descriptions, System z features
40005 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40006 System z targets. It should contain the PSW and the 16 general
40007 registers. In particular, System z targets should provide the 64-bit
40008 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40009 S/390 targets should provide the 32-bit versions of these registers.
40010 A System z target that runs in 31-bit addressing mode should provide
40011 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40012 register's upper halves @samp{r0h} through @samp{r15h}, and their
40013 lower halves @samp{r0l} through @samp{r15l}.
40015 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40016 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40019 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40020 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40022 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40023 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40024 targets and 32-bit otherwise. In addition, the feature may contain
40025 the @samp{last_break} register, whose width depends on the addressing
40026 mode, as well as the @samp{system_call} register, which is always
40029 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40030 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40031 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40033 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40034 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40035 combined by @value{GDBN} with the floating point registers @samp{f0}
40036 through @samp{f15} to present the 128-bit wide vector registers
40037 @samp{v0} through @samp{v15}. In addition, this feature should
40038 contain the 128-bit wide vector registers @samp{v16} through
40041 @node TIC6x Features
40042 @subsection TMS320C6x Features
40043 @cindex target descriptions, TIC6x features
40044 @cindex target descriptions, TMS320C6x features
40045 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40046 targets. It should contain registers @samp{A0} through @samp{A15},
40047 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40049 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40050 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40051 through @samp{B31}.
40053 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40054 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40056 @node Operating System Information
40057 @appendix Operating System Information
40058 @cindex operating system information
40064 Users of @value{GDBN} often wish to obtain information about the state of
40065 the operating system running on the target---for example the list of
40066 processes, or the list of open files. This section describes the
40067 mechanism that makes it possible. This mechanism is similar to the
40068 target features mechanism (@pxref{Target Descriptions}), but focuses
40069 on a different aspect of target.
40071 Operating system information is retrived from the target via the
40072 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40073 read}). The object name in the request should be @samp{osdata}, and
40074 the @var{annex} identifies the data to be fetched.
40077 @appendixsection Process list
40078 @cindex operating system information, process list
40080 When requesting the process list, the @var{annex} field in the
40081 @samp{qXfer} request should be @samp{processes}. The returned data is
40082 an XML document. The formal syntax of this document is defined in
40083 @file{gdb/features/osdata.dtd}.
40085 An example document is:
40088 <?xml version="1.0"?>
40089 <!DOCTYPE target SYSTEM "osdata.dtd">
40090 <osdata type="processes">
40092 <column name="pid">1</column>
40093 <column name="user">root</column>
40094 <column name="command">/sbin/init</column>
40095 <column name="cores">1,2,3</column>
40100 Each item should include a column whose name is @samp{pid}. The value
40101 of that column should identify the process on the target. The
40102 @samp{user} and @samp{command} columns are optional, and will be
40103 displayed by @value{GDBN}. The @samp{cores} column, if present,
40104 should contain a comma-separated list of cores that this process
40105 is running on. Target may provide additional columns,
40106 which @value{GDBN} currently ignores.
40108 @node Trace File Format
40109 @appendix Trace File Format
40110 @cindex trace file format
40112 The trace file comes in three parts: a header, a textual description
40113 section, and a trace frame section with binary data.
40115 The header has the form @code{\x7fTRACE0\n}. The first byte is
40116 @code{0x7f} so as to indicate that the file contains binary data,
40117 while the @code{0} is a version number that may have different values
40120 The description section consists of multiple lines of @sc{ascii} text
40121 separated by newline characters (@code{0xa}). The lines may include a
40122 variety of optional descriptive or context-setting information, such
40123 as tracepoint definitions or register set size. @value{GDBN} will
40124 ignore any line that it does not recognize. An empty line marks the end
40127 @c FIXME add some specific types of data
40129 The trace frame section consists of a number of consecutive frames.
40130 Each frame begins with a two-byte tracepoint number, followed by a
40131 four-byte size giving the amount of data in the frame. The data in
40132 the frame consists of a number of blocks, each introduced by a
40133 character indicating its type (at least register, memory, and trace
40134 state variable). The data in this section is raw binary, not a
40135 hexadecimal or other encoding; its endianness matches the target's
40138 @c FIXME bi-arch may require endianness/arch info in description section
40141 @item R @var{bytes}
40142 Register block. The number and ordering of bytes matches that of a
40143 @code{g} packet in the remote protocol. Note that these are the
40144 actual bytes, in target order and @value{GDBN} register order, not a
40145 hexadecimal encoding.
40147 @item M @var{address} @var{length} @var{bytes}...
40148 Memory block. This is a contiguous block of memory, at the 8-byte
40149 address @var{address}, with a 2-byte length @var{length}, followed by
40150 @var{length} bytes.
40152 @item V @var{number} @var{value}
40153 Trace state variable block. This records the 8-byte signed value
40154 @var{value} of trace state variable numbered @var{number}.
40158 Future enhancements of the trace file format may include additional types
40161 @node Index Section Format
40162 @appendix @code{.gdb_index} section format
40163 @cindex .gdb_index section format
40164 @cindex index section format
40166 This section documents the index section that is created by @code{save
40167 gdb-index} (@pxref{Index Files}). The index section is
40168 DWARF-specific; some knowledge of DWARF is assumed in this
40171 The mapped index file format is designed to be directly
40172 @code{mmap}able on any architecture. In most cases, a datum is
40173 represented using a little-endian 32-bit integer value, called an
40174 @code{offset_type}. Big endian machines must byte-swap the values
40175 before using them. Exceptions to this rule are noted. The data is
40176 laid out such that alignment is always respected.
40178 A mapped index consists of several areas, laid out in order.
40182 The file header. This is a sequence of values, of @code{offset_type}
40183 unless otherwise noted:
40187 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40188 Version 4 uses a different hashing function from versions 5 and 6.
40189 Version 6 includes symbols for inlined functions, whereas versions 4
40190 and 5 do not. Version 7 adds attributes to the CU indices in the
40191 symbol table. Version 8 specifies that symbols from DWARF type units
40192 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40193 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40195 @value{GDBN} will only read version 4, 5, or 6 indices
40196 by specifying @code{set use-deprecated-index-sections on}.
40197 GDB has a workaround for potentially broken version 7 indices so it is
40198 currently not flagged as deprecated.
40201 The offset, from the start of the file, of the CU list.
40204 The offset, from the start of the file, of the types CU list. Note
40205 that this area can be empty, in which case this offset will be equal
40206 to the next offset.
40209 The offset, from the start of the file, of the address area.
40212 The offset, from the start of the file, of the symbol table.
40215 The offset, from the start of the file, of the constant pool.
40219 The CU list. This is a sequence of pairs of 64-bit little-endian
40220 values, sorted by the CU offset. The first element in each pair is
40221 the offset of a CU in the @code{.debug_info} section. The second
40222 element in each pair is the length of that CU. References to a CU
40223 elsewhere in the map are done using a CU index, which is just the
40224 0-based index into this table. Note that if there are type CUs, then
40225 conceptually CUs and type CUs form a single list for the purposes of
40229 The types CU list. This is a sequence of triplets of 64-bit
40230 little-endian values. In a triplet, the first value is the CU offset,
40231 the second value is the type offset in the CU, and the third value is
40232 the type signature. The types CU list is not sorted.
40235 The address area. The address area consists of a sequence of address
40236 entries. Each address entry has three elements:
40240 The low address. This is a 64-bit little-endian value.
40243 The high address. This is a 64-bit little-endian value. Like
40244 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40247 The CU index. This is an @code{offset_type} value.
40251 The symbol table. This is an open-addressed hash table. The size of
40252 the hash table is always a power of 2.
40254 Each slot in the hash table consists of a pair of @code{offset_type}
40255 values. The first value is the offset of the symbol's name in the
40256 constant pool. The second value is the offset of the CU vector in the
40259 If both values are 0, then this slot in the hash table is empty. This
40260 is ok because while 0 is a valid constant pool index, it cannot be a
40261 valid index for both a string and a CU vector.
40263 The hash value for a table entry is computed by applying an
40264 iterative hash function to the symbol's name. Starting with an
40265 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40266 the string is incorporated into the hash using the formula depending on the
40271 The formula is @code{r = r * 67 + c - 113}.
40273 @item Versions 5 to 7
40274 The formula is @code{r = r * 67 + tolower (c) - 113}.
40277 The terminating @samp{\0} is not incorporated into the hash.
40279 The step size used in the hash table is computed via
40280 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40281 value, and @samp{size} is the size of the hash table. The step size
40282 is used to find the next candidate slot when handling a hash
40285 The names of C@t{++} symbols in the hash table are canonicalized. We
40286 don't currently have a simple description of the canonicalization
40287 algorithm; if you intend to create new index sections, you must read
40291 The constant pool. This is simply a bunch of bytes. It is organized
40292 so that alignment is correct: CU vectors are stored first, followed by
40295 A CU vector in the constant pool is a sequence of @code{offset_type}
40296 values. The first value is the number of CU indices in the vector.
40297 Each subsequent value is the index and symbol attributes of a CU in
40298 the CU list. This element in the hash table is used to indicate which
40299 CUs define the symbol and how the symbol is used.
40300 See below for the format of each CU index+attributes entry.
40302 A string in the constant pool is zero-terminated.
40305 Attributes were added to CU index values in @code{.gdb_index} version 7.
40306 If a symbol has multiple uses within a CU then there is one
40307 CU index+attributes value for each use.
40309 The format of each CU index+attributes entry is as follows
40315 This is the index of the CU in the CU list.
40317 These bits are reserved for future purposes and must be zero.
40319 The kind of the symbol in the CU.
40323 This value is reserved and should not be used.
40324 By reserving zero the full @code{offset_type} value is backwards compatible
40325 with previous versions of the index.
40327 The symbol is a type.
40329 The symbol is a variable or an enum value.
40331 The symbol is a function.
40333 Any other kind of symbol.
40335 These values are reserved.
40339 This bit is zero if the value is global and one if it is static.
40341 The determination of whether a symbol is global or static is complicated.
40342 The authorative reference is the file @file{dwarf2read.c} in
40343 @value{GDBN} sources.
40347 This pseudo-code describes the computation of a symbol's kind and
40348 global/static attributes in the index.
40351 is_external = get_attribute (die, DW_AT_external);
40352 language = get_attribute (cu_die, DW_AT_language);
40355 case DW_TAG_typedef:
40356 case DW_TAG_base_type:
40357 case DW_TAG_subrange_type:
40361 case DW_TAG_enumerator:
40363 is_static = (language != CPLUS && language != JAVA);
40365 case DW_TAG_subprogram:
40367 is_static = ! (is_external || language == ADA);
40369 case DW_TAG_constant:
40371 is_static = ! is_external;
40373 case DW_TAG_variable:
40375 is_static = ! is_external;
40377 case DW_TAG_namespace:
40381 case DW_TAG_class_type:
40382 case DW_TAG_interface_type:
40383 case DW_TAG_structure_type:
40384 case DW_TAG_union_type:
40385 case DW_TAG_enumeration_type:
40387 is_static = (language != CPLUS && language != JAVA);
40395 @appendix Manual pages
40399 * gdb man:: The GNU Debugger man page
40400 * gdbserver man:: Remote Server for the GNU Debugger man page
40401 * gcore man:: Generate a core file of a running program
40402 * gdbinit man:: gdbinit scripts
40408 @c man title gdb The GNU Debugger
40410 @c man begin SYNOPSIS gdb
40411 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40412 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40413 [@option{-b}@w{ }@var{bps}]
40414 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40415 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40416 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40417 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40418 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40421 @c man begin DESCRIPTION gdb
40422 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40423 going on ``inside'' another program while it executes -- or what another
40424 program was doing at the moment it crashed.
40426 @value{GDBN} can do four main kinds of things (plus other things in support of
40427 these) to help you catch bugs in the act:
40431 Start your program, specifying anything that might affect its behavior.
40434 Make your program stop on specified conditions.
40437 Examine what has happened, when your program has stopped.
40440 Change things in your program, so you can experiment with correcting the
40441 effects of one bug and go on to learn about another.
40444 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40447 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40448 commands from the terminal until you tell it to exit with the @value{GDBN}
40449 command @code{quit}. You can get online help from @value{GDBN} itself
40450 by using the command @code{help}.
40452 You can run @code{gdb} with no arguments or options; but the most
40453 usual way to start @value{GDBN} is with one argument or two, specifying an
40454 executable program as the argument:
40460 You can also start with both an executable program and a core file specified:
40466 You can, instead, specify a process ID as a second argument, if you want
40467 to debug a running process:
40475 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40476 named @file{1234}; @value{GDBN} does check for a core file first).
40477 With option @option{-p} you can omit the @var{program} filename.
40479 Here are some of the most frequently needed @value{GDBN} commands:
40481 @c pod2man highlights the right hand side of the @item lines.
40483 @item break [@var{file}:]@var{functiop}
40484 Set a breakpoint at @var{function} (in @var{file}).
40486 @item run [@var{arglist}]
40487 Start your program (with @var{arglist}, if specified).
40490 Backtrace: display the program stack.
40492 @item print @var{expr}
40493 Display the value of an expression.
40496 Continue running your program (after stopping, e.g. at a breakpoint).
40499 Execute next program line (after stopping); step @emph{over} any
40500 function calls in the line.
40502 @item edit [@var{file}:]@var{function}
40503 look at the program line where it is presently stopped.
40505 @item list [@var{file}:]@var{function}
40506 type the text of the program in the vicinity of where it is presently stopped.
40509 Execute next program line (after stopping); step @emph{into} any
40510 function calls in the line.
40512 @item help [@var{name}]
40513 Show information about @value{GDBN} command @var{name}, or general information
40514 about using @value{GDBN}.
40517 Exit from @value{GDBN}.
40521 For full details on @value{GDBN},
40522 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40523 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40524 as the @code{gdb} entry in the @code{info} program.
40528 @c man begin OPTIONS gdb
40529 Any arguments other than options specify an executable
40530 file and core file (or process ID); that is, the first argument
40531 encountered with no
40532 associated option flag is equivalent to a @option{-se} option, and the second,
40533 if any, is equivalent to a @option{-c} option if it's the name of a file.
40535 both long and short forms; both are shown here. The long forms are also
40536 recognized if you truncate them, so long as enough of the option is
40537 present to be unambiguous. (If you prefer, you can flag option
40538 arguments with @option{+} rather than @option{-}, though we illustrate the
40539 more usual convention.)
40541 All the options and command line arguments you give are processed
40542 in sequential order. The order makes a difference when the @option{-x}
40548 List all options, with brief explanations.
40550 @item -symbols=@var{file}
40551 @itemx -s @var{file}
40552 Read symbol table from file @var{file}.
40555 Enable writing into executable and core files.
40557 @item -exec=@var{file}
40558 @itemx -e @var{file}
40559 Use file @var{file} as the executable file to execute when
40560 appropriate, and for examining pure data in conjunction with a core
40563 @item -se=@var{file}
40564 Read symbol table from file @var{file} and use it as the executable
40567 @item -core=@var{file}
40568 @itemx -c @var{file}
40569 Use file @var{file} as a core dump to examine.
40571 @item -command=@var{file}
40572 @itemx -x @var{file}
40573 Execute @value{GDBN} commands from file @var{file}.
40575 @item -ex @var{command}
40576 Execute given @value{GDBN} @var{command}.
40578 @item -directory=@var{directory}
40579 @itemx -d @var{directory}
40580 Add @var{directory} to the path to search for source files.
40583 Do not execute commands from @file{~/.gdbinit}.
40587 Do not execute commands from any @file{.gdbinit} initialization files.
40591 ``Quiet''. Do not print the introductory and copyright messages. These
40592 messages are also suppressed in batch mode.
40595 Run in batch mode. Exit with status @code{0} after processing all the command
40596 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40597 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40598 commands in the command files.
40600 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40601 download and run a program on another computer; in order to make this
40602 more useful, the message
40605 Program exited normally.
40609 (which is ordinarily issued whenever a program running under @value{GDBN} control
40610 terminates) is not issued when running in batch mode.
40612 @item -cd=@var{directory}
40613 Run @value{GDBN} using @var{directory} as its working directory,
40614 instead of the current directory.
40618 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40619 @value{GDBN} to output the full file name and line number in a standard,
40620 recognizable fashion each time a stack frame is displayed (which
40621 includes each time the program stops). This recognizable format looks
40622 like two @samp{\032} characters, followed by the file name, line number
40623 and character position separated by colons, and a newline. The
40624 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40625 characters as a signal to display the source code for the frame.
40628 Set the line speed (baud rate or bits per second) of any serial
40629 interface used by @value{GDBN} for remote debugging.
40631 @item -tty=@var{device}
40632 Run using @var{device} for your program's standard input and output.
40636 @c man begin SEEALSO gdb
40638 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40639 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40640 documentation are properly installed at your site, the command
40647 should give you access to the complete manual.
40649 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40650 Richard M. Stallman and Roland H. Pesch, July 1991.
40654 @node gdbserver man
40655 @heading gdbserver man
40657 @c man title gdbserver Remote Server for the GNU Debugger
40659 @c man begin SYNOPSIS gdbserver
40660 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40662 gdbserver --attach @var{comm} @var{pid}
40664 gdbserver --multi @var{comm}
40668 @c man begin DESCRIPTION gdbserver
40669 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40670 than the one which is running the program being debugged.
40673 @subheading Usage (server (target) side)
40676 Usage (server (target) side):
40679 First, you need to have a copy of the program you want to debug put onto
40680 the target system. The program can be stripped to save space if needed, as
40681 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40682 the @value{GDBN} running on the host system.
40684 To use the server, you log on to the target system, and run the @command{gdbserver}
40685 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40686 your program, and (c) its arguments. The general syntax is:
40689 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40692 For example, using a serial port, you might say:
40696 @c @file would wrap it as F</dev/com1>.
40697 target> gdbserver /dev/com1 emacs foo.txt
40700 target> gdbserver @file{/dev/com1} emacs foo.txt
40704 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40705 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40706 waits patiently for the host @value{GDBN} to communicate with it.
40708 To use a TCP connection, you could say:
40711 target> gdbserver host:2345 emacs foo.txt
40714 This says pretty much the same thing as the last example, except that we are
40715 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40716 that we are expecting to see a TCP connection from @code{host} to local TCP port
40717 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40718 want for the port number as long as it does not conflict with any existing TCP
40719 ports on the target system. This same port number must be used in the host
40720 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40721 you chose a port number that conflicts with another service, @command{gdbserver} will
40722 print an error message and exit.
40724 @command{gdbserver} can also attach to running programs.
40725 This is accomplished via the @option{--attach} argument. The syntax is:
40728 target> gdbserver --attach @var{comm} @var{pid}
40731 @var{pid} is the process ID of a currently running process. It isn't
40732 necessary to point @command{gdbserver} at a binary for the running process.
40734 To start @code{gdbserver} without supplying an initial command to run
40735 or process ID to attach, use the @option{--multi} command line option.
40736 In such case you should connect using @kbd{target extended-remote} to start
40737 the program you want to debug.
40740 target> gdbserver --multi @var{comm}
40744 @subheading Usage (host side)
40750 You need an unstripped copy of the target program on your host system, since
40751 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40752 would, with the target program as the first argument. (You may need to use the
40753 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40754 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40755 new command you need to know about is @code{target remote}
40756 (or @code{target extended-remote}). Its argument is either
40757 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40758 descriptor. For example:
40762 @c @file would wrap it as F</dev/ttyb>.
40763 (gdb) target remote /dev/ttyb
40766 (gdb) target remote @file{/dev/ttyb}
40771 communicates with the server via serial line @file{/dev/ttyb}, and:
40774 (gdb) target remote the-target:2345
40778 communicates via a TCP connection to port 2345 on host `the-target', where
40779 you previously started up @command{gdbserver} with the same port number. Note that for
40780 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40781 command, otherwise you may get an error that looks something like
40782 `Connection refused'.
40784 @command{gdbserver} can also debug multiple inferiors at once,
40787 the @value{GDBN} manual in node @code{Inferiors and Programs}
40788 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40791 @ref{Inferiors and Programs}.
40793 In such case use the @code{extended-remote} @value{GDBN} command variant:
40796 (gdb) target extended-remote the-target:2345
40799 The @command{gdbserver} option @option{--multi} may or may not be used in such
40803 @c man begin OPTIONS gdbserver
40804 There are three different modes for invoking @command{gdbserver}:
40809 Debug a specific program specified by its program name:
40812 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40815 The @var{comm} parameter specifies how should the server communicate
40816 with @value{GDBN}; it is either a device name (to use a serial line),
40817 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40818 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40819 debug in @var{prog}. Any remaining arguments will be passed to the
40820 program verbatim. When the program exits, @value{GDBN} will close the
40821 connection, and @code{gdbserver} will exit.
40824 Debug a specific program by specifying the process ID of a running
40828 gdbserver --attach @var{comm} @var{pid}
40831 The @var{comm} parameter is as described above. Supply the process ID
40832 of a running program in @var{pid}; @value{GDBN} will do everything
40833 else. Like with the previous mode, when the process @var{pid} exits,
40834 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40837 Multi-process mode -- debug more than one program/process:
40840 gdbserver --multi @var{comm}
40843 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40844 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40845 close the connection when a process being debugged exits, so you can
40846 debug several processes in the same session.
40849 In each of the modes you may specify these options:
40854 List all options, with brief explanations.
40857 This option causes @command{gdbserver} to print its version number and exit.
40860 @command{gdbserver} will attach to a running program. The syntax is:
40863 target> gdbserver --attach @var{comm} @var{pid}
40866 @var{pid} is the process ID of a currently running process. It isn't
40867 necessary to point @command{gdbserver} at a binary for the running process.
40870 To start @code{gdbserver} without supplying an initial command to run
40871 or process ID to attach, use this command line option.
40872 Then you can connect using @kbd{target extended-remote} and start
40873 the program you want to debug. The syntax is:
40876 target> gdbserver --multi @var{comm}
40880 Instruct @code{gdbserver} to display extra status information about the debugging
40882 This option is intended for @code{gdbserver} development and for bug reports to
40885 @item --remote-debug
40886 Instruct @code{gdbserver} to display remote protocol debug output.
40887 This option is intended for @code{gdbserver} development and for bug reports to
40890 @item --debug-format=option1@r{[},option2,...@r{]}
40891 Instruct @code{gdbserver} to include extra information in each line
40892 of debugging output.
40893 @xref{Other Command-Line Arguments for gdbserver}.
40896 Specify a wrapper to launch programs
40897 for debugging. The option should be followed by the name of the
40898 wrapper, then any command-line arguments to pass to the wrapper, then
40899 @kbd{--} indicating the end of the wrapper arguments.
40902 By default, @command{gdbserver} keeps the listening TCP port open, so that
40903 additional connections are possible. However, if you start @code{gdbserver}
40904 with the @option{--once} option, it will stop listening for any further
40905 connection attempts after connecting to the first @value{GDBN} session.
40907 @c --disable-packet is not documented for users.
40909 @c --disable-randomization and --no-disable-randomization are superseded by
40910 @c QDisableRandomization.
40915 @c man begin SEEALSO gdbserver
40917 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40918 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40919 documentation are properly installed at your site, the command
40925 should give you access to the complete manual.
40927 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40928 Richard M. Stallman and Roland H. Pesch, July 1991.
40935 @c man title gcore Generate a core file of a running program
40938 @c man begin SYNOPSIS gcore
40939 gcore [-o @var{filename}] @var{pid}
40943 @c man begin DESCRIPTION gcore
40944 Generate a core dump of a running program with process ID @var{pid}.
40945 Produced file is equivalent to a kernel produced core file as if the process
40946 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40947 limit). Unlike after a crash, after @command{gcore} the program remains
40948 running without any change.
40951 @c man begin OPTIONS gcore
40953 @item -o @var{filename}
40954 The optional argument
40955 @var{filename} specifies the file name where to put the core dump.
40956 If not specified, the file name defaults to @file{core.@var{pid}},
40957 where @var{pid} is the running program process ID.
40961 @c man begin SEEALSO gcore
40963 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40964 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40965 documentation are properly installed at your site, the command
40972 should give you access to the complete manual.
40974 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40975 Richard M. Stallman and Roland H. Pesch, July 1991.
40982 @c man title gdbinit GDB initialization scripts
40985 @c man begin SYNOPSIS gdbinit
40986 @ifset SYSTEM_GDBINIT
40987 @value{SYSTEM_GDBINIT}
40996 @c man begin DESCRIPTION gdbinit
40997 These files contain @value{GDBN} commands to automatically execute during
40998 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41001 the @value{GDBN} manual in node @code{Sequences}
41002 -- shell command @code{info -f gdb -n Sequences}.
41008 Please read more in
41010 the @value{GDBN} manual in node @code{Startup}
41011 -- shell command @code{info -f gdb -n Startup}.
41018 @ifset SYSTEM_GDBINIT
41019 @item @value{SYSTEM_GDBINIT}
41021 @ifclear SYSTEM_GDBINIT
41022 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41024 System-wide initialization file. It is executed unless user specified
41025 @value{GDBN} option @code{-nx} or @code{-n}.
41028 the @value{GDBN} manual in node @code{System-wide configuration}
41029 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41032 @ref{System-wide configuration}.
41036 User initialization file. It is executed unless user specified
41037 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41040 Initialization file for current directory. It may need to be enabled with
41041 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41044 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41045 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41048 @ref{Init File in the Current Directory}.
41053 @c man begin SEEALSO gdbinit
41055 gdb(1), @code{info -f gdb -n Startup}
41057 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41058 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41059 documentation are properly installed at your site, the command
41065 should give you access to the complete manual.
41067 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41068 Richard M. Stallman and Roland H. Pesch, July 1991.
41074 @node GNU Free Documentation License
41075 @appendix GNU Free Documentation License
41078 @node Concept Index
41079 @unnumbered Concept Index
41083 @node Command and Variable Index
41084 @unnumbered Command, Variable, and Function Index
41089 % I think something like @@colophon should be in texinfo. In the
41091 \long\def\colophon{\hbox to0pt{}\vfill
41092 \centerline{The body of this manual is set in}
41093 \centerline{\fontname\tenrm,}
41094 \centerline{with headings in {\bf\fontname\tenbf}}
41095 \centerline{and examples in {\tt\fontname\tentt}.}
41096 \centerline{{\it\fontname\tenit\/},}
41097 \centerline{{\bf\fontname\tenbf}, and}
41098 \centerline{{\sl\fontname\tensl\/}}
41099 \centerline{are used for emphasis.}\vfill}
41101 % Blame: doc@@cygnus.com, 1991.