1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. If it is @code{off}, then there is no
5840 locking and any thread may run at any time. If @code{on}, then only the
5841 current thread may run when the inferior is resumed. The @code{step}
5842 mode optimizes for single-stepping; it prevents other threads
5843 from preempting the current thread while you are stepping, so that
5844 the focus of debugging does not change unexpectedly.
5845 Other threads never get a chance to run when you step, and they are
5846 completely free to run when you use commands
5847 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5848 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5849 the current thread away from the thread that you are debugging.
5851 @item show scheduler-locking
5852 Display the current scheduler locking mode.
5855 @cindex resume threads of multiple processes simultaneously
5856 By default, when you issue one of the execution commands such as
5857 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5858 threads of the current inferior to run. For example, if @value{GDBN}
5859 is attached to two inferiors, each with two threads, the
5860 @code{continue} command resumes only the two threads of the current
5861 inferior. This is useful, for example, when you debug a program that
5862 forks and you want to hold the parent stopped (so that, for instance,
5863 it doesn't run to exit), while you debug the child. In other
5864 situations, you may not be interested in inspecting the current state
5865 of any of the processes @value{GDBN} is attached to, and you may want
5866 to resume them all until some breakpoint is hit. In the latter case,
5867 you can instruct @value{GDBN} to allow all threads of all the
5868 inferiors to run with the @w{@code{set schedule-multiple}} command.
5871 @kindex set schedule-multiple
5872 @item set schedule-multiple
5873 Set the mode for allowing threads of multiple processes to be resumed
5874 when an execution command is issued. When @code{on}, all threads of
5875 all processes are allowed to run. When @code{off}, only the threads
5876 of the current process are resumed. The default is @code{off}. The
5877 @code{scheduler-locking} mode takes precedence when set to @code{on},
5878 or while you are stepping and set to @code{step}.
5880 @item show schedule-multiple
5881 Display the current mode for resuming the execution of threads of
5886 @subsection Non-Stop Mode
5888 @cindex non-stop mode
5890 @c This section is really only a place-holder, and needs to be expanded
5891 @c with more details.
5893 For some multi-threaded targets, @value{GDBN} supports an optional
5894 mode of operation in which you can examine stopped program threads in
5895 the debugger while other threads continue to execute freely. This
5896 minimizes intrusion when debugging live systems, such as programs
5897 where some threads have real-time constraints or must continue to
5898 respond to external events. This is referred to as @dfn{non-stop} mode.
5900 In non-stop mode, when a thread stops to report a debugging event,
5901 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5902 threads as well, in contrast to the all-stop mode behavior. Additionally,
5903 execution commands such as @code{continue} and @code{step} apply by default
5904 only to the current thread in non-stop mode, rather than all threads as
5905 in all-stop mode. This allows you to control threads explicitly in
5906 ways that are not possible in all-stop mode --- for example, stepping
5907 one thread while allowing others to run freely, stepping
5908 one thread while holding all others stopped, or stepping several threads
5909 independently and simultaneously.
5911 To enter non-stop mode, use this sequence of commands before you run
5912 or attach to your program:
5915 # If using the CLI, pagination breaks non-stop.
5918 # Finally, turn it on!
5922 You can use these commands to manipulate the non-stop mode setting:
5925 @kindex set non-stop
5926 @item set non-stop on
5927 Enable selection of non-stop mode.
5928 @item set non-stop off
5929 Disable selection of non-stop mode.
5930 @kindex show non-stop
5932 Show the current non-stop enablement setting.
5935 Note these commands only reflect whether non-stop mode is enabled,
5936 not whether the currently-executing program is being run in non-stop mode.
5937 In particular, the @code{set non-stop} preference is only consulted when
5938 @value{GDBN} starts or connects to the target program, and it is generally
5939 not possible to switch modes once debugging has started. Furthermore,
5940 since not all targets support non-stop mode, even when you have enabled
5941 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5944 In non-stop mode, all execution commands apply only to the current thread
5945 by default. That is, @code{continue} only continues one thread.
5946 To continue all threads, issue @code{continue -a} or @code{c -a}.
5948 You can use @value{GDBN}'s background execution commands
5949 (@pxref{Background Execution}) to run some threads in the background
5950 while you continue to examine or step others from @value{GDBN}.
5951 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5952 always executed asynchronously in non-stop mode.
5954 Suspending execution is done with the @code{interrupt} command when
5955 running in the background, or @kbd{Ctrl-c} during foreground execution.
5956 In all-stop mode, this stops the whole process;
5957 but in non-stop mode the interrupt applies only to the current thread.
5958 To stop the whole program, use @code{interrupt -a}.
5960 Other execution commands do not currently support the @code{-a} option.
5962 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5963 that thread current, as it does in all-stop mode. This is because the
5964 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5965 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5966 changed to a different thread just as you entered a command to operate on the
5967 previously current thread.
5969 @node Background Execution
5970 @subsection Background Execution
5972 @cindex foreground execution
5973 @cindex background execution
5974 @cindex asynchronous execution
5975 @cindex execution, foreground, background and asynchronous
5977 @value{GDBN}'s execution commands have two variants: the normal
5978 foreground (synchronous) behavior, and a background
5979 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5980 the program to report that some thread has stopped before prompting for
5981 another command. In background execution, @value{GDBN} immediately gives
5982 a command prompt so that you can issue other commands while your program runs.
5984 If the target doesn't support async mode, @value{GDBN} issues an error
5985 message if you attempt to use the background execution commands.
5987 To specify background execution, add a @code{&} to the command. For example,
5988 the background form of the @code{continue} command is @code{continue&}, or
5989 just @code{c&}. The execution commands that accept background execution
5995 @xref{Starting, , Starting your Program}.
5999 @xref{Attach, , Debugging an Already-running Process}.
6003 @xref{Continuing and Stepping, step}.
6007 @xref{Continuing and Stepping, stepi}.
6011 @xref{Continuing and Stepping, next}.
6015 @xref{Continuing and Stepping, nexti}.
6019 @xref{Continuing and Stepping, continue}.
6023 @xref{Continuing and Stepping, finish}.
6027 @xref{Continuing and Stepping, until}.
6031 Background execution is especially useful in conjunction with non-stop
6032 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6033 However, you can also use these commands in the normal all-stop mode with
6034 the restriction that you cannot issue another execution command until the
6035 previous one finishes. Examples of commands that are valid in all-stop
6036 mode while the program is running include @code{help} and @code{info break}.
6038 You can interrupt your program while it is running in the background by
6039 using the @code{interrupt} command.
6046 Suspend execution of the running program. In all-stop mode,
6047 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6048 only the current thread. To stop the whole program in non-stop mode,
6049 use @code{interrupt -a}.
6052 @node Thread-Specific Breakpoints
6053 @subsection Thread-Specific Breakpoints
6055 When your program has multiple threads (@pxref{Threads,, Debugging
6056 Programs with Multiple Threads}), you can choose whether to set
6057 breakpoints on all threads, or on a particular thread.
6060 @cindex breakpoints and threads
6061 @cindex thread breakpoints
6062 @kindex break @dots{} thread @var{threadno}
6063 @item break @var{linespec} thread @var{threadno}
6064 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6065 @var{linespec} specifies source lines; there are several ways of
6066 writing them (@pxref{Specify Location}), but the effect is always to
6067 specify some source line.
6069 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6070 to specify that you only want @value{GDBN} to stop the program when a
6071 particular thread reaches this breakpoint. The @var{threadno} specifier
6072 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6073 in the first column of the @samp{info threads} display.
6075 If you do not specify @samp{thread @var{threadno}} when you set a
6076 breakpoint, the breakpoint applies to @emph{all} threads of your
6079 You can use the @code{thread} qualifier on conditional breakpoints as
6080 well; in this case, place @samp{thread @var{threadno}} before or
6081 after the breakpoint condition, like this:
6084 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6089 Thread-specific breakpoints are automatically deleted when
6090 @value{GDBN} detects the corresponding thread is no longer in the
6091 thread list. For example:
6095 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6098 There are several ways for a thread to disappear, such as a regular
6099 thread exit, but also when you detach from the process with the
6100 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6101 Process}), or if @value{GDBN} loses the remote connection
6102 (@pxref{Remote Debugging}), etc. Note that with some targets,
6103 @value{GDBN} is only able to detect a thread has exited when the user
6104 explictly asks for the thread list with the @code{info threads}
6107 @node Interrupted System Calls
6108 @subsection Interrupted System Calls
6110 @cindex thread breakpoints and system calls
6111 @cindex system calls and thread breakpoints
6112 @cindex premature return from system calls
6113 There is an unfortunate side effect when using @value{GDBN} to debug
6114 multi-threaded programs. If one thread stops for a
6115 breakpoint, or for some other reason, and another thread is blocked in a
6116 system call, then the system call may return prematurely. This is a
6117 consequence of the interaction between multiple threads and the signals
6118 that @value{GDBN} uses to implement breakpoints and other events that
6121 To handle this problem, your program should check the return value of
6122 each system call and react appropriately. This is good programming
6125 For example, do not write code like this:
6131 The call to @code{sleep} will return early if a different thread stops
6132 at a breakpoint or for some other reason.
6134 Instead, write this:
6139 unslept = sleep (unslept);
6142 A system call is allowed to return early, so the system is still
6143 conforming to its specification. But @value{GDBN} does cause your
6144 multi-threaded program to behave differently than it would without
6147 Also, @value{GDBN} uses internal breakpoints in the thread library to
6148 monitor certain events such as thread creation and thread destruction.
6149 When such an event happens, a system call in another thread may return
6150 prematurely, even though your program does not appear to stop.
6153 @subsection Observer Mode
6155 If you want to build on non-stop mode and observe program behavior
6156 without any chance of disruption by @value{GDBN}, you can set
6157 variables to disable all of the debugger's attempts to modify state,
6158 whether by writing memory, inserting breakpoints, etc. These operate
6159 at a low level, intercepting operations from all commands.
6161 When all of these are set to @code{off}, then @value{GDBN} is said to
6162 be @dfn{observer mode}. As a convenience, the variable
6163 @code{observer} can be set to disable these, plus enable non-stop
6166 Note that @value{GDBN} will not prevent you from making nonsensical
6167 combinations of these settings. For instance, if you have enabled
6168 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6169 then breakpoints that work by writing trap instructions into the code
6170 stream will still not be able to be placed.
6175 @item set observer on
6176 @itemx set observer off
6177 When set to @code{on}, this disables all the permission variables
6178 below (except for @code{insert-fast-tracepoints}), plus enables
6179 non-stop debugging. Setting this to @code{off} switches back to
6180 normal debugging, though remaining in non-stop mode.
6183 Show whether observer mode is on or off.
6185 @kindex may-write-registers
6186 @item set may-write-registers on
6187 @itemx set may-write-registers off
6188 This controls whether @value{GDBN} will attempt to alter the values of
6189 registers, such as with assignment expressions in @code{print}, or the
6190 @code{jump} command. It defaults to @code{on}.
6192 @item show may-write-registers
6193 Show the current permission to write registers.
6195 @kindex may-write-memory
6196 @item set may-write-memory on
6197 @itemx set may-write-memory off
6198 This controls whether @value{GDBN} will attempt to alter the contents
6199 of memory, such as with assignment expressions in @code{print}. It
6200 defaults to @code{on}.
6202 @item show may-write-memory
6203 Show the current permission to write memory.
6205 @kindex may-insert-breakpoints
6206 @item set may-insert-breakpoints on
6207 @itemx set may-insert-breakpoints off
6208 This controls whether @value{GDBN} will attempt to insert breakpoints.
6209 This affects all breakpoints, including internal breakpoints defined
6210 by @value{GDBN}. It defaults to @code{on}.
6212 @item show may-insert-breakpoints
6213 Show the current permission to insert breakpoints.
6215 @kindex may-insert-tracepoints
6216 @item set may-insert-tracepoints on
6217 @itemx set may-insert-tracepoints off
6218 This controls whether @value{GDBN} will attempt to insert (regular)
6219 tracepoints at the beginning of a tracing experiment. It affects only
6220 non-fast tracepoints, fast tracepoints being under the control of
6221 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6223 @item show may-insert-tracepoints
6224 Show the current permission to insert tracepoints.
6226 @kindex may-insert-fast-tracepoints
6227 @item set may-insert-fast-tracepoints on
6228 @itemx set may-insert-fast-tracepoints off
6229 This controls whether @value{GDBN} will attempt to insert fast
6230 tracepoints at the beginning of a tracing experiment. It affects only
6231 fast tracepoints, regular (non-fast) tracepoints being under the
6232 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6234 @item show may-insert-fast-tracepoints
6235 Show the current permission to insert fast tracepoints.
6237 @kindex may-interrupt
6238 @item set may-interrupt on
6239 @itemx set may-interrupt off
6240 This controls whether @value{GDBN} will attempt to interrupt or stop
6241 program execution. When this variable is @code{off}, the
6242 @code{interrupt} command will have no effect, nor will
6243 @kbd{Ctrl-c}. It defaults to @code{on}.
6245 @item show may-interrupt
6246 Show the current permission to interrupt or stop the program.
6250 @node Reverse Execution
6251 @chapter Running programs backward
6252 @cindex reverse execution
6253 @cindex running programs backward
6255 When you are debugging a program, it is not unusual to realize that
6256 you have gone too far, and some event of interest has already happened.
6257 If the target environment supports it, @value{GDBN} can allow you to
6258 ``rewind'' the program by running it backward.
6260 A target environment that supports reverse execution should be able
6261 to ``undo'' the changes in machine state that have taken place as the
6262 program was executing normally. Variables, registers etc.@: should
6263 revert to their previous values. Obviously this requires a great
6264 deal of sophistication on the part of the target environment; not
6265 all target environments can support reverse execution.
6267 When a program is executed in reverse, the instructions that
6268 have most recently been executed are ``un-executed'', in reverse
6269 order. The program counter runs backward, following the previous
6270 thread of execution in reverse. As each instruction is ``un-executed'',
6271 the values of memory and/or registers that were changed by that
6272 instruction are reverted to their previous states. After executing
6273 a piece of source code in reverse, all side effects of that code
6274 should be ``undone'', and all variables should be returned to their
6275 prior values@footnote{
6276 Note that some side effects are easier to undo than others. For instance,
6277 memory and registers are relatively easy, but device I/O is hard. Some
6278 targets may be able undo things like device I/O, and some may not.
6280 The contract between @value{GDBN} and the reverse executing target
6281 requires only that the target do something reasonable when
6282 @value{GDBN} tells it to execute backwards, and then report the
6283 results back to @value{GDBN}. Whatever the target reports back to
6284 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6285 assumes that the memory and registers that the target reports are in a
6286 consistant state, but @value{GDBN} accepts whatever it is given.
6289 If you are debugging in a target environment that supports
6290 reverse execution, @value{GDBN} provides the following commands.
6293 @kindex reverse-continue
6294 @kindex rc @r{(@code{reverse-continue})}
6295 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6296 @itemx rc @r{[}@var{ignore-count}@r{]}
6297 Beginning at the point where your program last stopped, start executing
6298 in reverse. Reverse execution will stop for breakpoints and synchronous
6299 exceptions (signals), just like normal execution. Behavior of
6300 asynchronous signals depends on the target environment.
6302 @kindex reverse-step
6303 @kindex rs @r{(@code{step})}
6304 @item reverse-step @r{[}@var{count}@r{]}
6305 Run the program backward until control reaches the start of a
6306 different source line; then stop it, and return control to @value{GDBN}.
6308 Like the @code{step} command, @code{reverse-step} will only stop
6309 at the beginning of a source line. It ``un-executes'' the previously
6310 executed source line. If the previous source line included calls to
6311 debuggable functions, @code{reverse-step} will step (backward) into
6312 the called function, stopping at the beginning of the @emph{last}
6313 statement in the called function (typically a return statement).
6315 Also, as with the @code{step} command, if non-debuggable functions are
6316 called, @code{reverse-step} will run thru them backward without stopping.
6318 @kindex reverse-stepi
6319 @kindex rsi @r{(@code{reverse-stepi})}
6320 @item reverse-stepi @r{[}@var{count}@r{]}
6321 Reverse-execute one machine instruction. Note that the instruction
6322 to be reverse-executed is @emph{not} the one pointed to by the program
6323 counter, but the instruction executed prior to that one. For instance,
6324 if the last instruction was a jump, @code{reverse-stepi} will take you
6325 back from the destination of the jump to the jump instruction itself.
6327 @kindex reverse-next
6328 @kindex rn @r{(@code{reverse-next})}
6329 @item reverse-next @r{[}@var{count}@r{]}
6330 Run backward to the beginning of the previous line executed in
6331 the current (innermost) stack frame. If the line contains function
6332 calls, they will be ``un-executed'' without stopping. Starting from
6333 the first line of a function, @code{reverse-next} will take you back
6334 to the caller of that function, @emph{before} the function was called,
6335 just as the normal @code{next} command would take you from the last
6336 line of a function back to its return to its caller
6337 @footnote{Unless the code is too heavily optimized.}.
6339 @kindex reverse-nexti
6340 @kindex rni @r{(@code{reverse-nexti})}
6341 @item reverse-nexti @r{[}@var{count}@r{]}
6342 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6343 in reverse, except that called functions are ``un-executed'' atomically.
6344 That is, if the previously executed instruction was a return from
6345 another function, @code{reverse-nexti} will continue to execute
6346 in reverse until the call to that function (from the current stack
6349 @kindex reverse-finish
6350 @item reverse-finish
6351 Just as the @code{finish} command takes you to the point where the
6352 current function returns, @code{reverse-finish} takes you to the point
6353 where it was called. Instead of ending up at the end of the current
6354 function invocation, you end up at the beginning.
6356 @kindex set exec-direction
6357 @item set exec-direction
6358 Set the direction of target execution.
6359 @item set exec-direction reverse
6360 @cindex execute forward or backward in time
6361 @value{GDBN} will perform all execution commands in reverse, until the
6362 exec-direction mode is changed to ``forward''. Affected commands include
6363 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6364 command cannot be used in reverse mode.
6365 @item set exec-direction forward
6366 @value{GDBN} will perform all execution commands in the normal fashion.
6367 This is the default.
6371 @node Process Record and Replay
6372 @chapter Recording Inferior's Execution and Replaying It
6373 @cindex process record and replay
6374 @cindex recording inferior's execution and replaying it
6376 On some platforms, @value{GDBN} provides a special @dfn{process record
6377 and replay} target that can record a log of the process execution, and
6378 replay it later with both forward and reverse execution commands.
6381 When this target is in use, if the execution log includes the record
6382 for the next instruction, @value{GDBN} will debug in @dfn{replay
6383 mode}. In the replay mode, the inferior does not really execute code
6384 instructions. Instead, all the events that normally happen during
6385 code execution are taken from the execution log. While code is not
6386 really executed in replay mode, the values of registers (including the
6387 program counter register) and the memory of the inferior are still
6388 changed as they normally would. Their contents are taken from the
6392 If the record for the next instruction is not in the execution log,
6393 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6394 inferior executes normally, and @value{GDBN} records the execution log
6397 The process record and replay target supports reverse execution
6398 (@pxref{Reverse Execution}), even if the platform on which the
6399 inferior runs does not. However, the reverse execution is limited in
6400 this case by the range of the instructions recorded in the execution
6401 log. In other words, reverse execution on platforms that don't
6402 support it directly can only be done in the replay mode.
6404 When debugging in the reverse direction, @value{GDBN} will work in
6405 replay mode as long as the execution log includes the record for the
6406 previous instruction; otherwise, it will work in record mode, if the
6407 platform supports reverse execution, or stop if not.
6409 For architecture environments that support process record and replay,
6410 @value{GDBN} provides the following commands:
6413 @kindex target record
6414 @kindex target record-full
6415 @kindex target record-btrace
6418 @kindex record btrace
6419 @kindex record btrace bts
6424 @kindex rec btrace bts
6426 @item record @var{method}
6427 This command starts the process record and replay target. The
6428 recording method can be specified as parameter. Without a parameter
6429 the command uses the @code{full} recording method. The following
6430 recording methods are available:
6434 Full record/replay recording using @value{GDBN}'s software record and
6435 replay implementation. This method allows replaying and reverse
6438 @item btrace @var{format}
6439 Hardware-supported instruction recording. This method does not record
6440 data. Further, the data is collected in a ring buffer so old data will
6441 be overwritten when the buffer is full. It allows limited replay and
6444 The recording format can be specified as parameter. Without a parameter
6445 the command chooses the recording format. The following recording
6446 formats are available:
6450 @cindex branch trace store
6451 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6452 this format, the processor stores a from/to record for each executed
6453 branch in the btrace ring buffer.
6456 Not all recording formats may be available on all processors.
6459 The process record and replay target can only debug a process that is
6460 already running. Therefore, you need first to start the process with
6461 the @kbd{run} or @kbd{start} commands, and then start the recording
6462 with the @kbd{record @var{method}} command.
6464 Both @code{record @var{method}} and @code{rec @var{method}} are
6465 aliases of @code{target record-@var{method}}.
6467 @cindex displaced stepping, and process record and replay
6468 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6469 will be automatically disabled when process record and replay target
6470 is started. That's because the process record and replay target
6471 doesn't support displaced stepping.
6473 @cindex non-stop mode, and process record and replay
6474 @cindex asynchronous execution, and process record and replay
6475 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6476 the asynchronous execution mode (@pxref{Background Execution}), not
6477 all recording methods are available. The @code{full} recording method
6478 does not support these two modes.
6483 Stop the process record and replay target. When process record and
6484 replay target stops, the entire execution log will be deleted and the
6485 inferior will either be terminated, or will remain in its final state.
6487 When you stop the process record and replay target in record mode (at
6488 the end of the execution log), the inferior will be stopped at the
6489 next instruction that would have been recorded. In other words, if
6490 you record for a while and then stop recording, the inferior process
6491 will be left in the same state as if the recording never happened.
6493 On the other hand, if the process record and replay target is stopped
6494 while in replay mode (that is, not at the end of the execution log,
6495 but at some earlier point), the inferior process will become ``live''
6496 at that earlier state, and it will then be possible to continue the
6497 usual ``live'' debugging of the process from that state.
6499 When the inferior process exits, or @value{GDBN} detaches from it,
6500 process record and replay target will automatically stop itself.
6504 Go to a specific location in the execution log. There are several
6505 ways to specify the location to go to:
6508 @item record goto begin
6509 @itemx record goto start
6510 Go to the beginning of the execution log.
6512 @item record goto end
6513 Go to the end of the execution log.
6515 @item record goto @var{n}
6516 Go to instruction number @var{n} in the execution log.
6520 @item record save @var{filename}
6521 Save the execution log to a file @file{@var{filename}}.
6522 Default filename is @file{gdb_record.@var{process_id}}, where
6523 @var{process_id} is the process ID of the inferior.
6525 This command may not be available for all recording methods.
6527 @kindex record restore
6528 @item record restore @var{filename}
6529 Restore the execution log from a file @file{@var{filename}}.
6530 File must have been created with @code{record save}.
6532 @kindex set record full
6533 @item set record full insn-number-max @var{limit}
6534 @itemx set record full insn-number-max unlimited
6535 Set the limit of instructions to be recorded for the @code{full}
6536 recording method. Default value is 200000.
6538 If @var{limit} is a positive number, then @value{GDBN} will start
6539 deleting instructions from the log once the number of the record
6540 instructions becomes greater than @var{limit}. For every new recorded
6541 instruction, @value{GDBN} will delete the earliest recorded
6542 instruction to keep the number of recorded instructions at the limit.
6543 (Since deleting recorded instructions loses information, @value{GDBN}
6544 lets you control what happens when the limit is reached, by means of
6545 the @code{stop-at-limit} option, described below.)
6547 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6548 delete recorded instructions from the execution log. The number of
6549 recorded instructions is limited only by the available memory.
6551 @kindex show record full
6552 @item show record full insn-number-max
6553 Show the limit of instructions to be recorded with the @code{full}
6556 @item set record full stop-at-limit
6557 Control the behavior of the @code{full} recording method when the
6558 number of recorded instructions reaches the limit. If ON (the
6559 default), @value{GDBN} will stop when the limit is reached for the
6560 first time and ask you whether you want to stop the inferior or
6561 continue running it and recording the execution log. If you decide
6562 to continue recording, each new recorded instruction will cause the
6563 oldest one to be deleted.
6565 If this option is OFF, @value{GDBN} will automatically delete the
6566 oldest record to make room for each new one, without asking.
6568 @item show record full stop-at-limit
6569 Show the current setting of @code{stop-at-limit}.
6571 @item set record full memory-query
6572 Control the behavior when @value{GDBN} is unable to record memory
6573 changes caused by an instruction for the @code{full} recording method.
6574 If ON, @value{GDBN} will query whether to stop the inferior in that
6577 If this option is OFF (the default), @value{GDBN} will automatically
6578 ignore the effect of such instructions on memory. Later, when
6579 @value{GDBN} replays this execution log, it will mark the log of this
6580 instruction as not accessible, and it will not affect the replay
6583 @item show record full memory-query
6584 Show the current setting of @code{memory-query}.
6586 @kindex set record btrace
6587 The @code{btrace} record target does not trace data. As a
6588 convenience, when replaying, @value{GDBN} reads read-only memory off
6589 the live program directly, assuming that the addresses of the
6590 read-only areas don't change. This for example makes it possible to
6591 disassemble code while replaying, but not to print variables.
6592 In some cases, being able to inspect variables might be useful.
6593 You can use the following command for that:
6595 @item set record btrace replay-memory-access
6596 Control the behavior of the @code{btrace} recording method when
6597 accessing memory during replay. If @code{read-only} (the default),
6598 @value{GDBN} will only allow accesses to read-only memory.
6599 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6600 and to read-write memory. Beware that the accessed memory corresponds
6601 to the live target and not necessarily to the current replay
6604 @kindex show record btrace
6605 @item show record btrace replay-memory-access
6606 Show the current setting of @code{replay-memory-access}.
6608 @kindex set record btrace bts
6609 @item set record btrace bts buffer-size @var{size}
6610 @itemx set record btrace bts buffer-size unlimited
6611 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6612 format. Default is 64KB.
6614 If @var{size} is a positive number, then @value{GDBN} will try to
6615 allocate a buffer of at least @var{size} bytes for each new thread
6616 that uses the btrace recording method and the @acronym{BTS} format.
6617 The actually obtained buffer size may differ from the requested
6618 @var{size}. Use the @code{info record} command to see the actual
6619 buffer size for each thread that uses the btrace recording method and
6620 the @acronym{BTS} format.
6622 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6623 allocate a buffer of 4MB.
6625 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6626 also need longer to process the branch trace data before it can be used.
6628 @item show record btrace bts buffer-size @var{size}
6629 Show the current setting of the requested ring buffer size for branch
6630 tracing in @acronym{BTS} format.
6634 Show various statistics about the recording depending on the recording
6639 For the @code{full} recording method, it shows the state of process
6640 record and its in-memory execution log buffer, including:
6644 Whether in record mode or replay mode.
6646 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6648 Highest recorded instruction number.
6650 Current instruction about to be replayed (if in replay mode).
6652 Number of instructions contained in the execution log.
6654 Maximum number of instructions that may be contained in the execution log.
6658 For the @code{btrace} recording method, it shows:
6664 Number of instructions that have been recorded.
6666 Number of blocks of sequential control-flow formed by the recorded
6669 Whether in record mode or replay mode.
6672 For the @code{bts} recording format, it also shows:
6675 Size of the perf ring buffer.
6679 @kindex record delete
6682 When record target runs in replay mode (``in the past''), delete the
6683 subsequent execution log and begin to record a new execution log starting
6684 from the current address. This means you will abandon the previously
6685 recorded ``future'' and begin recording a new ``future''.
6687 @kindex record instruction-history
6688 @kindex rec instruction-history
6689 @item record instruction-history
6690 Disassembles instructions from the recorded execution log. By
6691 default, ten instructions are disassembled. This can be changed using
6692 the @code{set record instruction-history-size} command. Instructions
6693 are printed in execution order. There are several ways to specify
6694 what part of the execution log to disassemble:
6697 @item record instruction-history @var{insn}
6698 Disassembles ten instructions starting from instruction number
6701 @item record instruction-history @var{insn}, +/-@var{n}
6702 Disassembles @var{n} instructions around instruction number
6703 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6704 @var{n} instructions after instruction number @var{insn}. If
6705 @var{n} is preceded with @code{-}, disassembles @var{n}
6706 instructions before instruction number @var{insn}.
6708 @item record instruction-history
6709 Disassembles ten more instructions after the last disassembly.
6711 @item record instruction-history -
6712 Disassembles ten more instructions before the last disassembly.
6714 @item record instruction-history @var{begin} @var{end}
6715 Disassembles instructions beginning with instruction number
6716 @var{begin} until instruction number @var{end}. The instruction
6717 number @var{end} is included.
6720 This command may not be available for all recording methods.
6723 @item set record instruction-history-size @var{size}
6724 @itemx set record instruction-history-size unlimited
6725 Define how many instructions to disassemble in the @code{record
6726 instruction-history} command. The default value is 10.
6727 A @var{size} of @code{unlimited} means unlimited instructions.
6730 @item show record instruction-history-size
6731 Show how many instructions to disassemble in the @code{record
6732 instruction-history} command.
6734 @kindex record function-call-history
6735 @kindex rec function-call-history
6736 @item record function-call-history
6737 Prints the execution history at function granularity. It prints one
6738 line for each sequence of instructions that belong to the same
6739 function giving the name of that function, the source lines
6740 for this instruction sequence (if the @code{/l} modifier is
6741 specified), and the instructions numbers that form the sequence (if
6742 the @code{/i} modifier is specified). The function names are indented
6743 to reflect the call stack depth if the @code{/c} modifier is
6744 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6748 (@value{GDBP}) @b{list 1, 10}
6759 (@value{GDBP}) @b{record function-call-history /ilc}
6760 1 bar inst 1,4 at foo.c:6,8
6761 2 foo inst 5,10 at foo.c:2,3
6762 3 bar inst 11,13 at foo.c:9,10
6765 By default, ten lines are printed. This can be changed using the
6766 @code{set record function-call-history-size} command. Functions are
6767 printed in execution order. There are several ways to specify what
6771 @item record function-call-history @var{func}
6772 Prints ten functions starting from function number @var{func}.
6774 @item record function-call-history @var{func}, +/-@var{n}
6775 Prints @var{n} functions around function number @var{func}. If
6776 @var{n} is preceded with @code{+}, prints @var{n} functions after
6777 function number @var{func}. If @var{n} is preceded with @code{-},
6778 prints @var{n} functions before function number @var{func}.
6780 @item record function-call-history
6781 Prints ten more functions after the last ten-line print.
6783 @item record function-call-history -
6784 Prints ten more functions before the last ten-line print.
6786 @item record function-call-history @var{begin} @var{end}
6787 Prints functions beginning with function number @var{begin} until
6788 function number @var{end}. The function number @var{end} is included.
6791 This command may not be available for all recording methods.
6793 @item set record function-call-history-size @var{size}
6794 @itemx set record function-call-history-size unlimited
6795 Define how many lines to print in the
6796 @code{record function-call-history} command. The default value is 10.
6797 A size of @code{unlimited} means unlimited lines.
6799 @item show record function-call-history-size
6800 Show how many lines to print in the
6801 @code{record function-call-history} command.
6806 @chapter Examining the Stack
6808 When your program has stopped, the first thing you need to know is where it
6809 stopped and how it got there.
6812 Each time your program performs a function call, information about the call
6814 That information includes the location of the call in your program,
6815 the arguments of the call,
6816 and the local variables of the function being called.
6817 The information is saved in a block of data called a @dfn{stack frame}.
6818 The stack frames are allocated in a region of memory called the @dfn{call
6821 When your program stops, the @value{GDBN} commands for examining the
6822 stack allow you to see all of this information.
6824 @cindex selected frame
6825 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6826 @value{GDBN} commands refer implicitly to the selected frame. In
6827 particular, whenever you ask @value{GDBN} for the value of a variable in
6828 your program, the value is found in the selected frame. There are
6829 special @value{GDBN} commands to select whichever frame you are
6830 interested in. @xref{Selection, ,Selecting a Frame}.
6832 When your program stops, @value{GDBN} automatically selects the
6833 currently executing frame and describes it briefly, similar to the
6834 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6837 * Frames:: Stack frames
6838 * Backtrace:: Backtraces
6839 * Frame Filter Management:: Managing frame filters
6840 * Selection:: Selecting a frame
6841 * Frame Info:: Information on a frame
6846 @section Stack Frames
6848 @cindex frame, definition
6850 The call stack is divided up into contiguous pieces called @dfn{stack
6851 frames}, or @dfn{frames} for short; each frame is the data associated
6852 with one call to one function. The frame contains the arguments given
6853 to the function, the function's local variables, and the address at
6854 which the function is executing.
6856 @cindex initial frame
6857 @cindex outermost frame
6858 @cindex innermost frame
6859 When your program is started, the stack has only one frame, that of the
6860 function @code{main}. This is called the @dfn{initial} frame or the
6861 @dfn{outermost} frame. Each time a function is called, a new frame is
6862 made. Each time a function returns, the frame for that function invocation
6863 is eliminated. If a function is recursive, there can be many frames for
6864 the same function. The frame for the function in which execution is
6865 actually occurring is called the @dfn{innermost} frame. This is the most
6866 recently created of all the stack frames that still exist.
6868 @cindex frame pointer
6869 Inside your program, stack frames are identified by their addresses. A
6870 stack frame consists of many bytes, each of which has its own address; each
6871 kind of computer has a convention for choosing one byte whose
6872 address serves as the address of the frame. Usually this address is kept
6873 in a register called the @dfn{frame pointer register}
6874 (@pxref{Registers, $fp}) while execution is going on in that frame.
6876 @cindex frame number
6877 @value{GDBN} assigns numbers to all existing stack frames, starting with
6878 zero for the innermost frame, one for the frame that called it,
6879 and so on upward. These numbers do not really exist in your program;
6880 they are assigned by @value{GDBN} to give you a way of designating stack
6881 frames in @value{GDBN} commands.
6883 @c The -fomit-frame-pointer below perennially causes hbox overflow
6884 @c underflow problems.
6885 @cindex frameless execution
6886 Some compilers provide a way to compile functions so that they operate
6887 without stack frames. (For example, the @value{NGCC} option
6889 @samp{-fomit-frame-pointer}
6891 generates functions without a frame.)
6892 This is occasionally done with heavily used library functions to save
6893 the frame setup time. @value{GDBN} has limited facilities for dealing
6894 with these function invocations. If the innermost function invocation
6895 has no stack frame, @value{GDBN} nevertheless regards it as though
6896 it had a separate frame, which is numbered zero as usual, allowing
6897 correct tracing of the function call chain. However, @value{GDBN} has
6898 no provision for frameless functions elsewhere in the stack.
6901 @kindex frame@r{, command}
6902 @cindex current stack frame
6903 @item frame @r{[}@var{framespec}@r{]}
6904 The @code{frame} command allows you to move from one stack frame to another,
6905 and to print the stack frame you select. The @var{framespec} may be either the
6906 address of the frame or the stack frame number. Without an argument,
6907 @code{frame} prints the current stack frame.
6909 @kindex select-frame
6910 @cindex selecting frame silently
6912 The @code{select-frame} command allows you to move from one stack frame
6913 to another without printing the frame. This is the silent version of
6921 @cindex call stack traces
6922 A backtrace is a summary of how your program got where it is. It shows one
6923 line per frame, for many frames, starting with the currently executing
6924 frame (frame zero), followed by its caller (frame one), and on up the
6927 @anchor{backtrace-command}
6930 @kindex bt @r{(@code{backtrace})}
6933 Print a backtrace of the entire stack: one line per frame for all
6934 frames in the stack.
6936 You can stop the backtrace at any time by typing the system interrupt
6937 character, normally @kbd{Ctrl-c}.
6939 @item backtrace @var{n}
6941 Similar, but print only the innermost @var{n} frames.
6943 @item backtrace -@var{n}
6945 Similar, but print only the outermost @var{n} frames.
6947 @item backtrace full
6949 @itemx bt full @var{n}
6950 @itemx bt full -@var{n}
6951 Print the values of the local variables also. As described above,
6952 @var{n} specifies the number of frames to print.
6954 @item backtrace no-filters
6955 @itemx bt no-filters
6956 @itemx bt no-filters @var{n}
6957 @itemx bt no-filters -@var{n}
6958 @itemx bt no-filters full
6959 @itemx bt no-filters full @var{n}
6960 @itemx bt no-filters full -@var{n}
6961 Do not run Python frame filters on this backtrace. @xref{Frame
6962 Filter API}, for more information. Additionally use @ref{disable
6963 frame-filter all} to turn off all frame filters. This is only
6964 relevant when @value{GDBN} has been configured with @code{Python}
6970 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6971 are additional aliases for @code{backtrace}.
6973 @cindex multiple threads, backtrace
6974 In a multi-threaded program, @value{GDBN} by default shows the
6975 backtrace only for the current thread. To display the backtrace for
6976 several or all of the threads, use the command @code{thread apply}
6977 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6978 apply all backtrace}, @value{GDBN} will display the backtrace for all
6979 the threads; this is handy when you debug a core dump of a
6980 multi-threaded program.
6982 Each line in the backtrace shows the frame number and the function name.
6983 The program counter value is also shown---unless you use @code{set
6984 print address off}. The backtrace also shows the source file name and
6985 line number, as well as the arguments to the function. The program
6986 counter value is omitted if it is at the beginning of the code for that
6989 Here is an example of a backtrace. It was made with the command
6990 @samp{bt 3}, so it shows the innermost three frames.
6994 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6996 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6997 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6999 (More stack frames follow...)
7004 The display for frame zero does not begin with a program counter
7005 value, indicating that your program has stopped at the beginning of the
7006 code for line @code{993} of @code{builtin.c}.
7009 The value of parameter @code{data} in frame 1 has been replaced by
7010 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7011 only if it is a scalar (integer, pointer, enumeration, etc). See command
7012 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7013 on how to configure the way function parameter values are printed.
7015 @cindex optimized out, in backtrace
7016 @cindex function call arguments, optimized out
7017 If your program was compiled with optimizations, some compilers will
7018 optimize away arguments passed to functions if those arguments are
7019 never used after the call. Such optimizations generate code that
7020 passes arguments through registers, but doesn't store those arguments
7021 in the stack frame. @value{GDBN} has no way of displaying such
7022 arguments in stack frames other than the innermost one. Here's what
7023 such a backtrace might look like:
7027 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7029 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7030 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7032 (More stack frames follow...)
7037 The values of arguments that were not saved in their stack frames are
7038 shown as @samp{<optimized out>}.
7040 If you need to display the values of such optimized-out arguments,
7041 either deduce that from other variables whose values depend on the one
7042 you are interested in, or recompile without optimizations.
7044 @cindex backtrace beyond @code{main} function
7045 @cindex program entry point
7046 @cindex startup code, and backtrace
7047 Most programs have a standard user entry point---a place where system
7048 libraries and startup code transition into user code. For C this is
7049 @code{main}@footnote{
7050 Note that embedded programs (the so-called ``free-standing''
7051 environment) are not required to have a @code{main} function as the
7052 entry point. They could even have multiple entry points.}.
7053 When @value{GDBN} finds the entry function in a backtrace
7054 it will terminate the backtrace, to avoid tracing into highly
7055 system-specific (and generally uninteresting) code.
7057 If you need to examine the startup code, or limit the number of levels
7058 in a backtrace, you can change this behavior:
7061 @item set backtrace past-main
7062 @itemx set backtrace past-main on
7063 @kindex set backtrace
7064 Backtraces will continue past the user entry point.
7066 @item set backtrace past-main off
7067 Backtraces will stop when they encounter the user entry point. This is the
7070 @item show backtrace past-main
7071 @kindex show backtrace
7072 Display the current user entry point backtrace policy.
7074 @item set backtrace past-entry
7075 @itemx set backtrace past-entry on
7076 Backtraces will continue past the internal entry point of an application.
7077 This entry point is encoded by the linker when the application is built,
7078 and is likely before the user entry point @code{main} (or equivalent) is called.
7080 @item set backtrace past-entry off
7081 Backtraces will stop when they encounter the internal entry point of an
7082 application. This is the default.
7084 @item show backtrace past-entry
7085 Display the current internal entry point backtrace policy.
7087 @item set backtrace limit @var{n}
7088 @itemx set backtrace limit 0
7089 @itemx set backtrace limit unlimited
7090 @cindex backtrace limit
7091 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7092 or zero means unlimited levels.
7094 @item show backtrace limit
7095 Display the current limit on backtrace levels.
7098 You can control how file names are displayed.
7101 @item set filename-display
7102 @itemx set filename-display relative
7103 @cindex filename-display
7104 Display file names relative to the compilation directory. This is the default.
7106 @item set filename-display basename
7107 Display only basename of a filename.
7109 @item set filename-display absolute
7110 Display an absolute filename.
7112 @item show filename-display
7113 Show the current way to display filenames.
7116 @node Frame Filter Management
7117 @section Management of Frame Filters.
7118 @cindex managing frame filters
7120 Frame filters are Python based utilities to manage and decorate the
7121 output of frames. @xref{Frame Filter API}, for further information.
7123 Managing frame filters is performed by several commands available
7124 within @value{GDBN}, detailed here.
7127 @kindex info frame-filter
7128 @item info frame-filter
7129 Print a list of installed frame filters from all dictionaries, showing
7130 their name, priority and enabled status.
7132 @kindex disable frame-filter
7133 @anchor{disable frame-filter all}
7134 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7135 Disable a frame filter in the dictionary matching
7136 @var{filter-dictionary} and @var{filter-name}. The
7137 @var{filter-dictionary} may be @code{all}, @code{global},
7138 @code{progspace}, or the name of the object file where the frame filter
7139 dictionary resides. When @code{all} is specified, all frame filters
7140 across all dictionaries are disabled. The @var{filter-name} is the name
7141 of the frame filter and is used when @code{all} is not the option for
7142 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7143 may be enabled again later.
7145 @kindex enable frame-filter
7146 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7147 Enable a frame filter in the dictionary matching
7148 @var{filter-dictionary} and @var{filter-name}. The
7149 @var{filter-dictionary} may be @code{all}, @code{global},
7150 @code{progspace} or the name of the object file where the frame filter
7151 dictionary resides. When @code{all} is specified, all frame filters across
7152 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7153 filter and is used when @code{all} is not the option for
7154 @var{filter-dictionary}.
7159 (gdb) info frame-filter
7161 global frame-filters:
7162 Priority Enabled Name
7163 1000 No PrimaryFunctionFilter
7166 progspace /build/test frame-filters:
7167 Priority Enabled Name
7168 100 Yes ProgspaceFilter
7170 objfile /build/test frame-filters:
7171 Priority Enabled Name
7172 999 Yes BuildProgra Filter
7174 (gdb) disable frame-filter /build/test BuildProgramFilter
7175 (gdb) info frame-filter
7177 global frame-filters:
7178 Priority Enabled Name
7179 1000 No PrimaryFunctionFilter
7182 progspace /build/test frame-filters:
7183 Priority Enabled Name
7184 100 Yes ProgspaceFilter
7186 objfile /build/test frame-filters:
7187 Priority Enabled Name
7188 999 No BuildProgramFilter
7190 (gdb) enable frame-filter global PrimaryFunctionFilter
7191 (gdb) info frame-filter
7193 global frame-filters:
7194 Priority Enabled Name
7195 1000 Yes PrimaryFunctionFilter
7198 progspace /build/test frame-filters:
7199 Priority Enabled Name
7200 100 Yes ProgspaceFilter
7202 objfile /build/test frame-filters:
7203 Priority Enabled Name
7204 999 No BuildProgramFilter
7207 @kindex set frame-filter priority
7208 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7209 Set the @var{priority} of a frame filter in the dictionary matching
7210 @var{filter-dictionary}, and the frame filter name matching
7211 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7212 @code{progspace} or the name of the object file where the frame filter
7213 dictionary resides. The @var{priority} is an integer.
7215 @kindex show frame-filter priority
7216 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7217 Show the @var{priority} of a frame filter in the dictionary matching
7218 @var{filter-dictionary}, and the frame filter name matching
7219 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7220 @code{progspace} or the name of the object file where the frame filter
7226 (gdb) info frame-filter
7228 global frame-filters:
7229 Priority Enabled Name
7230 1000 Yes PrimaryFunctionFilter
7233 progspace /build/test frame-filters:
7234 Priority Enabled Name
7235 100 Yes ProgspaceFilter
7237 objfile /build/test frame-filters:
7238 Priority Enabled Name
7239 999 No BuildProgramFilter
7241 (gdb) set frame-filter priority global Reverse 50
7242 (gdb) info frame-filter
7244 global frame-filters:
7245 Priority Enabled Name
7246 1000 Yes PrimaryFunctionFilter
7249 progspace /build/test frame-filters:
7250 Priority Enabled Name
7251 100 Yes ProgspaceFilter
7253 objfile /build/test frame-filters:
7254 Priority Enabled Name
7255 999 No BuildProgramFilter
7260 @section Selecting a Frame
7262 Most commands for examining the stack and other data in your program work on
7263 whichever stack frame is selected at the moment. Here are the commands for
7264 selecting a stack frame; all of them finish by printing a brief description
7265 of the stack frame just selected.
7268 @kindex frame@r{, selecting}
7269 @kindex f @r{(@code{frame})}
7272 Select frame number @var{n}. Recall that frame zero is the innermost
7273 (currently executing) frame, frame one is the frame that called the
7274 innermost one, and so on. The highest-numbered frame is the one for
7277 @item frame @var{addr}
7279 Select the frame at address @var{addr}. This is useful mainly if the
7280 chaining of stack frames has been damaged by a bug, making it
7281 impossible for @value{GDBN} to assign numbers properly to all frames. In
7282 addition, this can be useful when your program has multiple stacks and
7283 switches between them.
7285 On the SPARC architecture, @code{frame} needs two addresses to
7286 select an arbitrary frame: a frame pointer and a stack pointer.
7288 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7289 pointer and a program counter.
7291 On the 29k architecture, it needs three addresses: a register stack
7292 pointer, a program counter, and a memory stack pointer.
7296 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7297 numbers @var{n}, this advances toward the outermost frame, to higher
7298 frame numbers, to frames that have existed longer.
7301 @kindex do @r{(@code{down})}
7303 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7304 positive numbers @var{n}, this advances toward the innermost frame, to
7305 lower frame numbers, to frames that were created more recently.
7306 You may abbreviate @code{down} as @code{do}.
7309 All of these commands end by printing two lines of output describing the
7310 frame. The first line shows the frame number, the function name, the
7311 arguments, and the source file and line number of execution in that
7312 frame. The second line shows the text of that source line.
7320 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7322 10 read_input_file (argv[i]);
7326 After such a printout, the @code{list} command with no arguments
7327 prints ten lines centered on the point of execution in the frame.
7328 You can also edit the program at the point of execution with your favorite
7329 editing program by typing @code{edit}.
7330 @xref{List, ,Printing Source Lines},
7334 @kindex down-silently
7336 @item up-silently @var{n}
7337 @itemx down-silently @var{n}
7338 These two commands are variants of @code{up} and @code{down},
7339 respectively; they differ in that they do their work silently, without
7340 causing display of the new frame. They are intended primarily for use
7341 in @value{GDBN} command scripts, where the output might be unnecessary and
7346 @section Information About a Frame
7348 There are several other commands to print information about the selected
7354 When used without any argument, this command does not change which
7355 frame is selected, but prints a brief description of the currently
7356 selected stack frame. It can be abbreviated @code{f}. With an
7357 argument, this command is used to select a stack frame.
7358 @xref{Selection, ,Selecting a Frame}.
7361 @kindex info f @r{(@code{info frame})}
7364 This command prints a verbose description of the selected stack frame,
7369 the address of the frame
7371 the address of the next frame down (called by this frame)
7373 the address of the next frame up (caller of this frame)
7375 the language in which the source code corresponding to this frame is written
7377 the address of the frame's arguments
7379 the address of the frame's local variables
7381 the program counter saved in it (the address of execution in the caller frame)
7383 which registers were saved in the frame
7386 @noindent The verbose description is useful when
7387 something has gone wrong that has made the stack format fail to fit
7388 the usual conventions.
7390 @item info frame @var{addr}
7391 @itemx info f @var{addr}
7392 Print a verbose description of the frame at address @var{addr}, without
7393 selecting that frame. The selected frame remains unchanged by this
7394 command. This requires the same kind of address (more than one for some
7395 architectures) that you specify in the @code{frame} command.
7396 @xref{Selection, ,Selecting a Frame}.
7400 Print the arguments of the selected frame, each on a separate line.
7404 Print the local variables of the selected frame, each on a separate
7405 line. These are all variables (declared either static or automatic)
7406 accessible at the point of execution of the selected frame.
7412 @chapter Examining Source Files
7414 @value{GDBN} can print parts of your program's source, since the debugging
7415 information recorded in the program tells @value{GDBN} what source files were
7416 used to build it. When your program stops, @value{GDBN} spontaneously prints
7417 the line where it stopped. Likewise, when you select a stack frame
7418 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7419 execution in that frame has stopped. You can print other portions of
7420 source files by explicit command.
7422 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7423 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7424 @value{GDBN} under @sc{gnu} Emacs}.
7427 * List:: Printing source lines
7428 * Specify Location:: How to specify code locations
7429 * Edit:: Editing source files
7430 * Search:: Searching source files
7431 * Source Path:: Specifying source directories
7432 * Machine Code:: Source and machine code
7436 @section Printing Source Lines
7439 @kindex l @r{(@code{list})}
7440 To print lines from a source file, use the @code{list} command
7441 (abbreviated @code{l}). By default, ten lines are printed.
7442 There are several ways to specify what part of the file you want to
7443 print; see @ref{Specify Location}, for the full list.
7445 Here are the forms of the @code{list} command most commonly used:
7448 @item list @var{linenum}
7449 Print lines centered around line number @var{linenum} in the
7450 current source file.
7452 @item list @var{function}
7453 Print lines centered around the beginning of function
7457 Print more lines. If the last lines printed were printed with a
7458 @code{list} command, this prints lines following the last lines
7459 printed; however, if the last line printed was a solitary line printed
7460 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7461 Stack}), this prints lines centered around that line.
7464 Print lines just before the lines last printed.
7467 @cindex @code{list}, how many lines to display
7468 By default, @value{GDBN} prints ten source lines with any of these forms of
7469 the @code{list} command. You can change this using @code{set listsize}:
7472 @kindex set listsize
7473 @item set listsize @var{count}
7474 @itemx set listsize unlimited
7475 Make the @code{list} command display @var{count} source lines (unless
7476 the @code{list} argument explicitly specifies some other number).
7477 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7479 @kindex show listsize
7481 Display the number of lines that @code{list} prints.
7484 Repeating a @code{list} command with @key{RET} discards the argument,
7485 so it is equivalent to typing just @code{list}. This is more useful
7486 than listing the same lines again. An exception is made for an
7487 argument of @samp{-}; that argument is preserved in repetition so that
7488 each repetition moves up in the source file.
7490 In general, the @code{list} command expects you to supply zero, one or two
7491 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7492 of writing them (@pxref{Specify Location}), but the effect is always
7493 to specify some source line.
7495 Here is a complete description of the possible arguments for @code{list}:
7498 @item list @var{linespec}
7499 Print lines centered around the line specified by @var{linespec}.
7501 @item list @var{first},@var{last}
7502 Print lines from @var{first} to @var{last}. Both arguments are
7503 linespecs. When a @code{list} command has two linespecs, and the
7504 source file of the second linespec is omitted, this refers to
7505 the same source file as the first linespec.
7507 @item list ,@var{last}
7508 Print lines ending with @var{last}.
7510 @item list @var{first},
7511 Print lines starting with @var{first}.
7514 Print lines just after the lines last printed.
7517 Print lines just before the lines last printed.
7520 As described in the preceding table.
7523 @node Specify Location
7524 @section Specifying a Location
7525 @cindex specifying location
7528 Several @value{GDBN} commands accept arguments that specify a location
7529 of your program's code. Since @value{GDBN} is a source-level
7530 debugger, a location usually specifies some line in the source code;
7531 for that reason, locations are also known as @dfn{linespecs}.
7533 Here are all the different ways of specifying a code location that
7534 @value{GDBN} understands:
7538 Specifies the line number @var{linenum} of the current source file.
7541 @itemx +@var{offset}
7542 Specifies the line @var{offset} lines before or after the @dfn{current
7543 line}. For the @code{list} command, the current line is the last one
7544 printed; for the breakpoint commands, this is the line at which
7545 execution stopped in the currently selected @dfn{stack frame}
7546 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7547 used as the second of the two linespecs in a @code{list} command,
7548 this specifies the line @var{offset} lines up or down from the first
7551 @item @var{filename}:@var{linenum}
7552 Specifies the line @var{linenum} in the source file @var{filename}.
7553 If @var{filename} is a relative file name, then it will match any
7554 source file name with the same trailing components. For example, if
7555 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7556 name of @file{/build/trunk/gcc/expr.c}, but not
7557 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7559 @item @var{function}
7560 Specifies the line that begins the body of the function @var{function}.
7561 For example, in C, this is the line with the open brace.
7563 @item @var{function}:@var{label}
7564 Specifies the line where @var{label} appears in @var{function}.
7566 @item @var{filename}:@var{function}
7567 Specifies the line that begins the body of the function @var{function}
7568 in the file @var{filename}. You only need the file name with a
7569 function name to avoid ambiguity when there are identically named
7570 functions in different source files.
7573 Specifies the line at which the label named @var{label} appears.
7574 @value{GDBN} searches for the label in the function corresponding to
7575 the currently selected stack frame. If there is no current selected
7576 stack frame (for instance, if the inferior is not running), then
7577 @value{GDBN} will not search for a label.
7579 @item *@var{address}
7580 Specifies the program address @var{address}. For line-oriented
7581 commands, such as @code{list} and @code{edit}, this specifies a source
7582 line that contains @var{address}. For @code{break} and other
7583 breakpoint oriented commands, this can be used to set breakpoints in
7584 parts of your program which do not have debugging information or
7587 Here @var{address} may be any expression valid in the current working
7588 language (@pxref{Languages, working language}) that specifies a code
7589 address. In addition, as a convenience, @value{GDBN} extends the
7590 semantics of expressions used in locations to cover the situations
7591 that frequently happen during debugging. Here are the various forms
7595 @item @var{expression}
7596 Any expression valid in the current working language.
7598 @item @var{funcaddr}
7599 An address of a function or procedure derived from its name. In C,
7600 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7601 simply the function's name @var{function} (and actually a special case
7602 of a valid expression). In Pascal and Modula-2, this is
7603 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7604 (although the Pascal form also works).
7606 This form specifies the address of the function's first instruction,
7607 before the stack frame and arguments have been set up.
7609 @item '@var{filename}':@var{funcaddr}
7610 Like @var{funcaddr} above, but also specifies the name of the source
7611 file explicitly. This is useful if the name of the function does not
7612 specify the function unambiguously, e.g., if there are several
7613 functions with identical names in different source files.
7616 @cindex breakpoint at static probe point
7617 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7618 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7619 applications to embed static probes. @xref{Static Probe Points}, for more
7620 information on finding and using static probes. This form of linespec
7621 specifies the location of such a static probe.
7623 If @var{objfile} is given, only probes coming from that shared library
7624 or executable matching @var{objfile} as a regular expression are considered.
7625 If @var{provider} is given, then only probes from that provider are considered.
7626 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7627 each one of those probes.
7633 @section Editing Source Files
7634 @cindex editing source files
7637 @kindex e @r{(@code{edit})}
7638 To edit the lines in a source file, use the @code{edit} command.
7639 The editing program of your choice
7640 is invoked with the current line set to
7641 the active line in the program.
7642 Alternatively, there are several ways to specify what part of the file you
7643 want to print if you want to see other parts of the program:
7646 @item edit @var{location}
7647 Edit the source file specified by @code{location}. Editing starts at
7648 that @var{location}, e.g., at the specified source line of the
7649 specified file. @xref{Specify Location}, for all the possible forms
7650 of the @var{location} argument; here are the forms of the @code{edit}
7651 command most commonly used:
7654 @item edit @var{number}
7655 Edit the current source file with @var{number} as the active line number.
7657 @item edit @var{function}
7658 Edit the file containing @var{function} at the beginning of its definition.
7663 @subsection Choosing your Editor
7664 You can customize @value{GDBN} to use any editor you want
7666 The only restriction is that your editor (say @code{ex}), recognizes the
7667 following command-line syntax:
7669 ex +@var{number} file
7671 The optional numeric value +@var{number} specifies the number of the line in
7672 the file where to start editing.}.
7673 By default, it is @file{@value{EDITOR}}, but you can change this
7674 by setting the environment variable @code{EDITOR} before using
7675 @value{GDBN}. For example, to configure @value{GDBN} to use the
7676 @code{vi} editor, you could use these commands with the @code{sh} shell:
7682 or in the @code{csh} shell,
7684 setenv EDITOR /usr/bin/vi
7689 @section Searching Source Files
7690 @cindex searching source files
7692 There are two commands for searching through the current source file for a
7697 @kindex forward-search
7698 @kindex fo @r{(@code{forward-search})}
7699 @item forward-search @var{regexp}
7700 @itemx search @var{regexp}
7701 The command @samp{forward-search @var{regexp}} checks each line,
7702 starting with the one following the last line listed, for a match for
7703 @var{regexp}. It lists the line that is found. You can use the
7704 synonym @samp{search @var{regexp}} or abbreviate the command name as
7707 @kindex reverse-search
7708 @item reverse-search @var{regexp}
7709 The command @samp{reverse-search @var{regexp}} checks each line, starting
7710 with the one before the last line listed and going backward, for a match
7711 for @var{regexp}. It lists the line that is found. You can abbreviate
7712 this command as @code{rev}.
7716 @section Specifying Source Directories
7719 @cindex directories for source files
7720 Executable programs sometimes do not record the directories of the source
7721 files from which they were compiled, just the names. Even when they do,
7722 the directories could be moved between the compilation and your debugging
7723 session. @value{GDBN} has a list of directories to search for source files;
7724 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7725 it tries all the directories in the list, in the order they are present
7726 in the list, until it finds a file with the desired name.
7728 For example, suppose an executable references the file
7729 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7730 @file{/mnt/cross}. The file is first looked up literally; if this
7731 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7732 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7733 message is printed. @value{GDBN} does not look up the parts of the
7734 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7735 Likewise, the subdirectories of the source path are not searched: if
7736 the source path is @file{/mnt/cross}, and the binary refers to
7737 @file{foo.c}, @value{GDBN} would not find it under
7738 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7740 Plain file names, relative file names with leading directories, file
7741 names containing dots, etc.@: are all treated as described above; for
7742 instance, if the source path is @file{/mnt/cross}, and the source file
7743 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7744 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7745 that---@file{/mnt/cross/foo.c}.
7747 Note that the executable search path is @emph{not} used to locate the
7750 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7751 any information it has cached about where source files are found and where
7752 each line is in the file.
7756 When you start @value{GDBN}, its source path includes only @samp{cdir}
7757 and @samp{cwd}, in that order.
7758 To add other directories, use the @code{directory} command.
7760 The search path is used to find both program source files and @value{GDBN}
7761 script files (read using the @samp{-command} option and @samp{source} command).
7763 In addition to the source path, @value{GDBN} provides a set of commands
7764 that manage a list of source path substitution rules. A @dfn{substitution
7765 rule} specifies how to rewrite source directories stored in the program's
7766 debug information in case the sources were moved to a different
7767 directory between compilation and debugging. A rule is made of
7768 two strings, the first specifying what needs to be rewritten in
7769 the path, and the second specifying how it should be rewritten.
7770 In @ref{set substitute-path}, we name these two parts @var{from} and
7771 @var{to} respectively. @value{GDBN} does a simple string replacement
7772 of @var{from} with @var{to} at the start of the directory part of the
7773 source file name, and uses that result instead of the original file
7774 name to look up the sources.
7776 Using the previous example, suppose the @file{foo-1.0} tree has been
7777 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7778 @value{GDBN} to replace @file{/usr/src} in all source path names with
7779 @file{/mnt/cross}. The first lookup will then be
7780 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7781 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7782 substitution rule, use the @code{set substitute-path} command
7783 (@pxref{set substitute-path}).
7785 To avoid unexpected substitution results, a rule is applied only if the
7786 @var{from} part of the directory name ends at a directory separator.
7787 For instance, a rule substituting @file{/usr/source} into
7788 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7789 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7790 is applied only at the beginning of the directory name, this rule will
7791 not be applied to @file{/root/usr/source/baz.c} either.
7793 In many cases, you can achieve the same result using the @code{directory}
7794 command. However, @code{set substitute-path} can be more efficient in
7795 the case where the sources are organized in a complex tree with multiple
7796 subdirectories. With the @code{directory} command, you need to add each
7797 subdirectory of your project. If you moved the entire tree while
7798 preserving its internal organization, then @code{set substitute-path}
7799 allows you to direct the debugger to all the sources with one single
7802 @code{set substitute-path} is also more than just a shortcut command.
7803 The source path is only used if the file at the original location no
7804 longer exists. On the other hand, @code{set substitute-path} modifies
7805 the debugger behavior to look at the rewritten location instead. So, if
7806 for any reason a source file that is not relevant to your executable is
7807 located at the original location, a substitution rule is the only
7808 method available to point @value{GDBN} at the new location.
7810 @cindex @samp{--with-relocated-sources}
7811 @cindex default source path substitution
7812 You can configure a default source path substitution rule by
7813 configuring @value{GDBN} with the
7814 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7815 should be the name of a directory under @value{GDBN}'s configured
7816 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7817 directory names in debug information under @var{dir} will be adjusted
7818 automatically if the installed @value{GDBN} is moved to a new
7819 location. This is useful if @value{GDBN}, libraries or executables
7820 with debug information and corresponding source code are being moved
7824 @item directory @var{dirname} @dots{}
7825 @item dir @var{dirname} @dots{}
7826 Add directory @var{dirname} to the front of the source path. Several
7827 directory names may be given to this command, separated by @samp{:}
7828 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7829 part of absolute file names) or
7830 whitespace. You may specify a directory that is already in the source
7831 path; this moves it forward, so @value{GDBN} searches it sooner.
7835 @vindex $cdir@r{, convenience variable}
7836 @vindex $cwd@r{, convenience variable}
7837 @cindex compilation directory
7838 @cindex current directory
7839 @cindex working directory
7840 @cindex directory, current
7841 @cindex directory, compilation
7842 You can use the string @samp{$cdir} to refer to the compilation
7843 directory (if one is recorded), and @samp{$cwd} to refer to the current
7844 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7845 tracks the current working directory as it changes during your @value{GDBN}
7846 session, while the latter is immediately expanded to the current
7847 directory at the time you add an entry to the source path.
7850 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7852 @c RET-repeat for @code{directory} is explicitly disabled, but since
7853 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7855 @item set directories @var{path-list}
7856 @kindex set directories
7857 Set the source path to @var{path-list}.
7858 @samp{$cdir:$cwd} are added if missing.
7860 @item show directories
7861 @kindex show directories
7862 Print the source path: show which directories it contains.
7864 @anchor{set substitute-path}
7865 @item set substitute-path @var{from} @var{to}
7866 @kindex set substitute-path
7867 Define a source path substitution rule, and add it at the end of the
7868 current list of existing substitution rules. If a rule with the same
7869 @var{from} was already defined, then the old rule is also deleted.
7871 For example, if the file @file{/foo/bar/baz.c} was moved to
7872 @file{/mnt/cross/baz.c}, then the command
7875 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7879 will tell @value{GDBN} to replace @samp{/usr/src} with
7880 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7881 @file{baz.c} even though it was moved.
7883 In the case when more than one substitution rule have been defined,
7884 the rules are evaluated one by one in the order where they have been
7885 defined. The first one matching, if any, is selected to perform
7888 For instance, if we had entered the following commands:
7891 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7892 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7896 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7897 @file{/mnt/include/defs.h} by using the first rule. However, it would
7898 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7899 @file{/mnt/src/lib/foo.c}.
7902 @item unset substitute-path [path]
7903 @kindex unset substitute-path
7904 If a path is specified, search the current list of substitution rules
7905 for a rule that would rewrite that path. Delete that rule if found.
7906 A warning is emitted by the debugger if no rule could be found.
7908 If no path is specified, then all substitution rules are deleted.
7910 @item show substitute-path [path]
7911 @kindex show substitute-path
7912 If a path is specified, then print the source path substitution rule
7913 which would rewrite that path, if any.
7915 If no path is specified, then print all existing source path substitution
7920 If your source path is cluttered with directories that are no longer of
7921 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7922 versions of source. You can correct the situation as follows:
7926 Use @code{directory} with no argument to reset the source path to its default value.
7929 Use @code{directory} with suitable arguments to reinstall the
7930 directories you want in the source path. You can add all the
7931 directories in one command.
7935 @section Source and Machine Code
7936 @cindex source line and its code address
7938 You can use the command @code{info line} to map source lines to program
7939 addresses (and vice versa), and the command @code{disassemble} to display
7940 a range of addresses as machine instructions. You can use the command
7941 @code{set disassemble-next-line} to set whether to disassemble next
7942 source line when execution stops. When run under @sc{gnu} Emacs
7943 mode, the @code{info line} command causes the arrow to point to the
7944 line specified. Also, @code{info line} prints addresses in symbolic form as
7949 @item info line @var{linespec}
7950 Print the starting and ending addresses of the compiled code for
7951 source line @var{linespec}. You can specify source lines in any of
7952 the ways documented in @ref{Specify Location}.
7955 For example, we can use @code{info line} to discover the location of
7956 the object code for the first line of function
7957 @code{m4_changequote}:
7959 @c FIXME: I think this example should also show the addresses in
7960 @c symbolic form, as they usually would be displayed.
7962 (@value{GDBP}) info line m4_changequote
7963 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7967 @cindex code address and its source line
7968 We can also inquire (using @code{*@var{addr}} as the form for
7969 @var{linespec}) what source line covers a particular address:
7971 (@value{GDBP}) info line *0x63ff
7972 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7975 @cindex @code{$_} and @code{info line}
7976 @cindex @code{x} command, default address
7977 @kindex x@r{(examine), and} info line
7978 After @code{info line}, the default address for the @code{x} command
7979 is changed to the starting address of the line, so that @samp{x/i} is
7980 sufficient to begin examining the machine code (@pxref{Memory,
7981 ,Examining Memory}). Also, this address is saved as the value of the
7982 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7987 @cindex assembly instructions
7988 @cindex instructions, assembly
7989 @cindex machine instructions
7990 @cindex listing machine instructions
7992 @itemx disassemble /m
7993 @itemx disassemble /r
7994 This specialized command dumps a range of memory as machine
7995 instructions. It can also print mixed source+disassembly by specifying
7996 the @code{/m} modifier and print the raw instructions in hex as well as
7997 in symbolic form by specifying the @code{/r}.
7998 The default memory range is the function surrounding the
7999 program counter of the selected frame. A single argument to this
8000 command is a program counter value; @value{GDBN} dumps the function
8001 surrounding this value. When two arguments are given, they should
8002 be separated by a comma, possibly surrounded by whitespace. The
8003 arguments specify a range of addresses to dump, in one of two forms:
8006 @item @var{start},@var{end}
8007 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8008 @item @var{start},+@var{length}
8009 the addresses from @var{start} (inclusive) to
8010 @code{@var{start}+@var{length}} (exclusive).
8014 When 2 arguments are specified, the name of the function is also
8015 printed (since there could be several functions in the given range).
8017 The argument(s) can be any expression yielding a numeric value, such as
8018 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8020 If the range of memory being disassembled contains current program counter,
8021 the instruction at that location is shown with a @code{=>} marker.
8024 The following example shows the disassembly of a range of addresses of
8025 HP PA-RISC 2.0 code:
8028 (@value{GDBP}) disas 0x32c4, 0x32e4
8029 Dump of assembler code from 0x32c4 to 0x32e4:
8030 0x32c4 <main+204>: addil 0,dp
8031 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8032 0x32cc <main+212>: ldil 0x3000,r31
8033 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8034 0x32d4 <main+220>: ldo 0(r31),rp
8035 0x32d8 <main+224>: addil -0x800,dp
8036 0x32dc <main+228>: ldo 0x588(r1),r26
8037 0x32e0 <main+232>: ldil 0x3000,r31
8038 End of assembler dump.
8041 Here is an example showing mixed source+assembly for Intel x86, when the
8042 program is stopped just after function prologue:
8045 (@value{GDBP}) disas /m main
8046 Dump of assembler code for function main:
8048 0x08048330 <+0>: push %ebp
8049 0x08048331 <+1>: mov %esp,%ebp
8050 0x08048333 <+3>: sub $0x8,%esp
8051 0x08048336 <+6>: and $0xfffffff0,%esp
8052 0x08048339 <+9>: sub $0x10,%esp
8054 6 printf ("Hello.\n");
8055 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8056 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8060 0x08048348 <+24>: mov $0x0,%eax
8061 0x0804834d <+29>: leave
8062 0x0804834e <+30>: ret
8064 End of assembler dump.
8067 Here is another example showing raw instructions in hex for AMD x86-64,
8070 (gdb) disas /r 0x400281,+10
8071 Dump of assembler code from 0x400281 to 0x40028b:
8072 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8073 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8074 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8075 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8076 End of assembler dump.
8079 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8080 So, for example, if you want to disassemble function @code{bar}
8081 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8082 and not @samp{disassemble foo.c:bar}.
8084 Some architectures have more than one commonly-used set of instruction
8085 mnemonics or other syntax.
8087 For programs that were dynamically linked and use shared libraries,
8088 instructions that call functions or branch to locations in the shared
8089 libraries might show a seemingly bogus location---it's actually a
8090 location of the relocation table. On some architectures, @value{GDBN}
8091 might be able to resolve these to actual function names.
8094 @kindex set disassembly-flavor
8095 @cindex Intel disassembly flavor
8096 @cindex AT&T disassembly flavor
8097 @item set disassembly-flavor @var{instruction-set}
8098 Select the instruction set to use when disassembling the
8099 program via the @code{disassemble} or @code{x/i} commands.
8101 Currently this command is only defined for the Intel x86 family. You
8102 can set @var{instruction-set} to either @code{intel} or @code{att}.
8103 The default is @code{att}, the AT&T flavor used by default by Unix
8104 assemblers for x86-based targets.
8106 @kindex show disassembly-flavor
8107 @item show disassembly-flavor
8108 Show the current setting of the disassembly flavor.
8112 @kindex set disassemble-next-line
8113 @kindex show disassemble-next-line
8114 @item set disassemble-next-line
8115 @itemx show disassemble-next-line
8116 Control whether or not @value{GDBN} will disassemble the next source
8117 line or instruction when execution stops. If ON, @value{GDBN} will
8118 display disassembly of the next source line when execution of the
8119 program being debugged stops. This is @emph{in addition} to
8120 displaying the source line itself, which @value{GDBN} always does if
8121 possible. If the next source line cannot be displayed for some reason
8122 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8123 info in the debug info), @value{GDBN} will display disassembly of the
8124 next @emph{instruction} instead of showing the next source line. If
8125 AUTO, @value{GDBN} will display disassembly of next instruction only
8126 if the source line cannot be displayed. This setting causes
8127 @value{GDBN} to display some feedback when you step through a function
8128 with no line info or whose source file is unavailable. The default is
8129 OFF, which means never display the disassembly of the next line or
8135 @chapter Examining Data
8137 @cindex printing data
8138 @cindex examining data
8141 The usual way to examine data in your program is with the @code{print}
8142 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8143 evaluates and prints the value of an expression of the language your
8144 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8145 Different Languages}). It may also print the expression using a
8146 Python-based pretty-printer (@pxref{Pretty Printing}).
8149 @item print @var{expr}
8150 @itemx print /@var{f} @var{expr}
8151 @var{expr} is an expression (in the source language). By default the
8152 value of @var{expr} is printed in a format appropriate to its data type;
8153 you can choose a different format by specifying @samp{/@var{f}}, where
8154 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8158 @itemx print /@var{f}
8159 @cindex reprint the last value
8160 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8161 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8162 conveniently inspect the same value in an alternative format.
8165 A more low-level way of examining data is with the @code{x} command.
8166 It examines data in memory at a specified address and prints it in a
8167 specified format. @xref{Memory, ,Examining Memory}.
8169 If you are interested in information about types, or about how the
8170 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8171 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8174 @cindex exploring hierarchical data structures
8176 Another way of examining values of expressions and type information is
8177 through the Python extension command @code{explore} (available only if
8178 the @value{GDBN} build is configured with @code{--with-python}). It
8179 offers an interactive way to start at the highest level (or, the most
8180 abstract level) of the data type of an expression (or, the data type
8181 itself) and explore all the way down to leaf scalar values/fields
8182 embedded in the higher level data types.
8185 @item explore @var{arg}
8186 @var{arg} is either an expression (in the source language), or a type
8187 visible in the current context of the program being debugged.
8190 The working of the @code{explore} command can be illustrated with an
8191 example. If a data type @code{struct ComplexStruct} is defined in your
8201 struct ComplexStruct
8203 struct SimpleStruct *ss_p;
8209 followed by variable declarations as
8212 struct SimpleStruct ss = @{ 10, 1.11 @};
8213 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8217 then, the value of the variable @code{cs} can be explored using the
8218 @code{explore} command as follows.
8222 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8223 the following fields:
8225 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8226 arr = <Enter 1 to explore this field of type `int [10]'>
8228 Enter the field number of choice:
8232 Since the fields of @code{cs} are not scalar values, you are being
8233 prompted to chose the field you want to explore. Let's say you choose
8234 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8235 pointer, you will be asked if it is pointing to a single value. From
8236 the declaration of @code{cs} above, it is indeed pointing to a single
8237 value, hence you enter @code{y}. If you enter @code{n}, then you will
8238 be asked if it were pointing to an array of values, in which case this
8239 field will be explored as if it were an array.
8242 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8243 Continue exploring it as a pointer to a single value [y/n]: y
8244 The value of `*(cs.ss_p)' is a struct/class of type `struct
8245 SimpleStruct' with the following fields:
8247 i = 10 .. (Value of type `int')
8248 d = 1.1100000000000001 .. (Value of type `double')
8250 Press enter to return to parent value:
8254 If the field @code{arr} of @code{cs} was chosen for exploration by
8255 entering @code{1} earlier, then since it is as array, you will be
8256 prompted to enter the index of the element in the array that you want
8260 `cs.arr' is an array of `int'.
8261 Enter the index of the element you want to explore in `cs.arr': 5
8263 `(cs.arr)[5]' is a scalar value of type `int'.
8267 Press enter to return to parent value:
8270 In general, at any stage of exploration, you can go deeper towards the
8271 leaf values by responding to the prompts appropriately, or hit the
8272 return key to return to the enclosing data structure (the @i{higher}
8273 level data structure).
8275 Similar to exploring values, you can use the @code{explore} command to
8276 explore types. Instead of specifying a value (which is typically a
8277 variable name or an expression valid in the current context of the
8278 program being debugged), you specify a type name. If you consider the
8279 same example as above, your can explore the type
8280 @code{struct ComplexStruct} by passing the argument
8281 @code{struct ComplexStruct} to the @code{explore} command.
8284 (gdb) explore struct ComplexStruct
8288 By responding to the prompts appropriately in the subsequent interactive
8289 session, you can explore the type @code{struct ComplexStruct} in a
8290 manner similar to how the value @code{cs} was explored in the above
8293 The @code{explore} command also has two sub-commands,
8294 @code{explore value} and @code{explore type}. The former sub-command is
8295 a way to explicitly specify that value exploration of the argument is
8296 being invoked, while the latter is a way to explicitly specify that type
8297 exploration of the argument is being invoked.
8300 @item explore value @var{expr}
8301 @cindex explore value
8302 This sub-command of @code{explore} explores the value of the
8303 expression @var{expr} (if @var{expr} is an expression valid in the
8304 current context of the program being debugged). The behavior of this
8305 command is identical to that of the behavior of the @code{explore}
8306 command being passed the argument @var{expr}.
8308 @item explore type @var{arg}
8309 @cindex explore type
8310 This sub-command of @code{explore} explores the type of @var{arg} (if
8311 @var{arg} is a type visible in the current context of program being
8312 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8313 is an expression valid in the current context of the program being
8314 debugged). If @var{arg} is a type, then the behavior of this command is
8315 identical to that of the @code{explore} command being passed the
8316 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8317 this command will be identical to that of the @code{explore} command
8318 being passed the type of @var{arg} as the argument.
8322 * Expressions:: Expressions
8323 * Ambiguous Expressions:: Ambiguous Expressions
8324 * Variables:: Program variables
8325 * Arrays:: Artificial arrays
8326 * Output Formats:: Output formats
8327 * Memory:: Examining memory
8328 * Auto Display:: Automatic display
8329 * Print Settings:: Print settings
8330 * Pretty Printing:: Python pretty printing
8331 * Value History:: Value history
8332 * Convenience Vars:: Convenience variables
8333 * Convenience Funs:: Convenience functions
8334 * Registers:: Registers
8335 * Floating Point Hardware:: Floating point hardware
8336 * Vector Unit:: Vector Unit
8337 * OS Information:: Auxiliary data provided by operating system
8338 * Memory Region Attributes:: Memory region attributes
8339 * Dump/Restore Files:: Copy between memory and a file
8340 * Core File Generation:: Cause a program dump its core
8341 * Character Sets:: Debugging programs that use a different
8342 character set than GDB does
8343 * Caching Target Data:: Data caching for targets
8344 * Searching Memory:: Searching memory for a sequence of bytes
8348 @section Expressions
8351 @code{print} and many other @value{GDBN} commands accept an expression and
8352 compute its value. Any kind of constant, variable or operator defined
8353 by the programming language you are using is valid in an expression in
8354 @value{GDBN}. This includes conditional expressions, function calls,
8355 casts, and string constants. It also includes preprocessor macros, if
8356 you compiled your program to include this information; see
8359 @cindex arrays in expressions
8360 @value{GDBN} supports array constants in expressions input by
8361 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8362 you can use the command @code{print @{1, 2, 3@}} to create an array
8363 of three integers. If you pass an array to a function or assign it
8364 to a program variable, @value{GDBN} copies the array to memory that
8365 is @code{malloc}ed in the target program.
8367 Because C is so widespread, most of the expressions shown in examples in
8368 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8369 Languages}, for information on how to use expressions in other
8372 In this section, we discuss operators that you can use in @value{GDBN}
8373 expressions regardless of your programming language.
8375 @cindex casts, in expressions
8376 Casts are supported in all languages, not just in C, because it is so
8377 useful to cast a number into a pointer in order to examine a structure
8378 at that address in memory.
8379 @c FIXME: casts supported---Mod2 true?
8381 @value{GDBN} supports these operators, in addition to those common
8382 to programming languages:
8386 @samp{@@} is a binary operator for treating parts of memory as arrays.
8387 @xref{Arrays, ,Artificial Arrays}, for more information.
8390 @samp{::} allows you to specify a variable in terms of the file or
8391 function where it is defined. @xref{Variables, ,Program Variables}.
8393 @cindex @{@var{type}@}
8394 @cindex type casting memory
8395 @cindex memory, viewing as typed object
8396 @cindex casts, to view memory
8397 @item @{@var{type}@} @var{addr}
8398 Refers to an object of type @var{type} stored at address @var{addr} in
8399 memory. The address @var{addr} may be any expression whose value is
8400 an integer or pointer (but parentheses are required around binary
8401 operators, just as in a cast). This construct is allowed regardless
8402 of what kind of data is normally supposed to reside at @var{addr}.
8405 @node Ambiguous Expressions
8406 @section Ambiguous Expressions
8407 @cindex ambiguous expressions
8409 Expressions can sometimes contain some ambiguous elements. For instance,
8410 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8411 a single function name to be defined several times, for application in
8412 different contexts. This is called @dfn{overloading}. Another example
8413 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8414 templates and is typically instantiated several times, resulting in
8415 the same function name being defined in different contexts.
8417 In some cases and depending on the language, it is possible to adjust
8418 the expression to remove the ambiguity. For instance in C@t{++}, you
8419 can specify the signature of the function you want to break on, as in
8420 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8421 qualified name of your function often makes the expression unambiguous
8424 When an ambiguity that needs to be resolved is detected, the debugger
8425 has the capability to display a menu of numbered choices for each
8426 possibility, and then waits for the selection with the prompt @samp{>}.
8427 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8428 aborts the current command. If the command in which the expression was
8429 used allows more than one choice to be selected, the next option in the
8430 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8433 For example, the following session excerpt shows an attempt to set a
8434 breakpoint at the overloaded symbol @code{String::after}.
8435 We choose three particular definitions of that function name:
8437 @c FIXME! This is likely to change to show arg type lists, at least
8440 (@value{GDBP}) b String::after
8443 [2] file:String.cc; line number:867
8444 [3] file:String.cc; line number:860
8445 [4] file:String.cc; line number:875
8446 [5] file:String.cc; line number:853
8447 [6] file:String.cc; line number:846
8448 [7] file:String.cc; line number:735
8450 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8451 Breakpoint 2 at 0xb344: file String.cc, line 875.
8452 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8453 Multiple breakpoints were set.
8454 Use the "delete" command to delete unwanted
8461 @kindex set multiple-symbols
8462 @item set multiple-symbols @var{mode}
8463 @cindex multiple-symbols menu
8465 This option allows you to adjust the debugger behavior when an expression
8468 By default, @var{mode} is set to @code{all}. If the command with which
8469 the expression is used allows more than one choice, then @value{GDBN}
8470 automatically selects all possible choices. For instance, inserting
8471 a breakpoint on a function using an ambiguous name results in a breakpoint
8472 inserted on each possible match. However, if a unique choice must be made,
8473 then @value{GDBN} uses the menu to help you disambiguate the expression.
8474 For instance, printing the address of an overloaded function will result
8475 in the use of the menu.
8477 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8478 when an ambiguity is detected.
8480 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8481 an error due to the ambiguity and the command is aborted.
8483 @kindex show multiple-symbols
8484 @item show multiple-symbols
8485 Show the current value of the @code{multiple-symbols} setting.
8489 @section Program Variables
8491 The most common kind of expression to use is the name of a variable
8494 Variables in expressions are understood in the selected stack frame
8495 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8499 global (or file-static)
8506 visible according to the scope rules of the
8507 programming language from the point of execution in that frame
8510 @noindent This means that in the function
8525 you can examine and use the variable @code{a} whenever your program is
8526 executing within the function @code{foo}, but you can only use or
8527 examine the variable @code{b} while your program is executing inside
8528 the block where @code{b} is declared.
8530 @cindex variable name conflict
8531 There is an exception: you can refer to a variable or function whose
8532 scope is a single source file even if the current execution point is not
8533 in this file. But it is possible to have more than one such variable or
8534 function with the same name (in different source files). If that
8535 happens, referring to that name has unpredictable effects. If you wish,
8536 you can specify a static variable in a particular function or file by
8537 using the colon-colon (@code{::}) notation:
8539 @cindex colon-colon, context for variables/functions
8541 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8542 @cindex @code{::}, context for variables/functions
8545 @var{file}::@var{variable}
8546 @var{function}::@var{variable}
8550 Here @var{file} or @var{function} is the name of the context for the
8551 static @var{variable}. In the case of file names, you can use quotes to
8552 make sure @value{GDBN} parses the file name as a single word---for example,
8553 to print a global value of @code{x} defined in @file{f2.c}:
8556 (@value{GDBP}) p 'f2.c'::x
8559 The @code{::} notation is normally used for referring to
8560 static variables, since you typically disambiguate uses of local variables
8561 in functions by selecting the appropriate frame and using the
8562 simple name of the variable. However, you may also use this notation
8563 to refer to local variables in frames enclosing the selected frame:
8572 process (a); /* Stop here */
8583 For example, if there is a breakpoint at the commented line,
8584 here is what you might see
8585 when the program stops after executing the call @code{bar(0)}:
8590 (@value{GDBP}) p bar::a
8593 #2 0x080483d0 in foo (a=5) at foobar.c:12
8596 (@value{GDBP}) p bar::a
8600 @cindex C@t{++} scope resolution
8601 These uses of @samp{::} are very rarely in conflict with the very
8602 similar use of the same notation in C@t{++}. When they are in
8603 conflict, the C@t{++} meaning takes precedence; however, this can be
8604 overridden by quoting the file or function name with single quotes.
8606 For example, suppose the program is stopped in a method of a class
8607 that has a field named @code{includefile}, and there is also an
8608 include file named @file{includefile} that defines a variable,
8612 (@value{GDBP}) p includefile
8614 (@value{GDBP}) p includefile::some_global
8615 A syntax error in expression, near `'.
8616 (@value{GDBP}) p 'includefile'::some_global
8620 @cindex wrong values
8621 @cindex variable values, wrong
8622 @cindex function entry/exit, wrong values of variables
8623 @cindex optimized code, wrong values of variables
8625 @emph{Warning:} Occasionally, a local variable may appear to have the
8626 wrong value at certain points in a function---just after entry to a new
8627 scope, and just before exit.
8629 You may see this problem when you are stepping by machine instructions.
8630 This is because, on most machines, it takes more than one instruction to
8631 set up a stack frame (including local variable definitions); if you are
8632 stepping by machine instructions, variables may appear to have the wrong
8633 values until the stack frame is completely built. On exit, it usually
8634 also takes more than one machine instruction to destroy a stack frame;
8635 after you begin stepping through that group of instructions, local
8636 variable definitions may be gone.
8638 This may also happen when the compiler does significant optimizations.
8639 To be sure of always seeing accurate values, turn off all optimization
8642 @cindex ``No symbol "foo" in current context''
8643 Another possible effect of compiler optimizations is to optimize
8644 unused variables out of existence, or assign variables to registers (as
8645 opposed to memory addresses). Depending on the support for such cases
8646 offered by the debug info format used by the compiler, @value{GDBN}
8647 might not be able to display values for such local variables. If that
8648 happens, @value{GDBN} will print a message like this:
8651 No symbol "foo" in current context.
8654 To solve such problems, either recompile without optimizations, or use a
8655 different debug info format, if the compiler supports several such
8656 formats. @xref{Compilation}, for more information on choosing compiler
8657 options. @xref{C, ,C and C@t{++}}, for more information about debug
8658 info formats that are best suited to C@t{++} programs.
8660 If you ask to print an object whose contents are unknown to
8661 @value{GDBN}, e.g., because its data type is not completely specified
8662 by the debug information, @value{GDBN} will say @samp{<incomplete
8663 type>}. @xref{Symbols, incomplete type}, for more about this.
8665 If you append @kbd{@@entry} string to a function parameter name you get its
8666 value at the time the function got called. If the value is not available an
8667 error message is printed. Entry values are available only with some compilers.
8668 Entry values are normally also printed at the function parameter list according
8669 to @ref{set print entry-values}.
8672 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8678 (gdb) print i@@entry
8682 Strings are identified as arrays of @code{char} values without specified
8683 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8684 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8685 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8686 defines literal string type @code{"char"} as @code{char} without a sign.
8691 signed char var1[] = "A";
8694 You get during debugging
8699 $2 = @{65 'A', 0 '\0'@}
8703 @section Artificial Arrays
8705 @cindex artificial array
8707 @kindex @@@r{, referencing memory as an array}
8708 It is often useful to print out several successive objects of the
8709 same type in memory; a section of an array, or an array of
8710 dynamically determined size for which only a pointer exists in the
8713 You can do this by referring to a contiguous span of memory as an
8714 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8715 operand of @samp{@@} should be the first element of the desired array
8716 and be an individual object. The right operand should be the desired length
8717 of the array. The result is an array value whose elements are all of
8718 the type of the left argument. The first element is actually the left
8719 argument; the second element comes from bytes of memory immediately
8720 following those that hold the first element, and so on. Here is an
8721 example. If a program says
8724 int *array = (int *) malloc (len * sizeof (int));
8728 you can print the contents of @code{array} with
8734 The left operand of @samp{@@} must reside in memory. Array values made
8735 with @samp{@@} in this way behave just like other arrays in terms of
8736 subscripting, and are coerced to pointers when used in expressions.
8737 Artificial arrays most often appear in expressions via the value history
8738 (@pxref{Value History, ,Value History}), after printing one out.
8740 Another way to create an artificial array is to use a cast.
8741 This re-interprets a value as if it were an array.
8742 The value need not be in memory:
8744 (@value{GDBP}) p/x (short[2])0x12345678
8745 $1 = @{0x1234, 0x5678@}
8748 As a convenience, if you leave the array length out (as in
8749 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8750 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8752 (@value{GDBP}) p/x (short[])0x12345678
8753 $2 = @{0x1234, 0x5678@}
8756 Sometimes the artificial array mechanism is not quite enough; in
8757 moderately complex data structures, the elements of interest may not
8758 actually be adjacent---for example, if you are interested in the values
8759 of pointers in an array. One useful work-around in this situation is
8760 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8761 Variables}) as a counter in an expression that prints the first
8762 interesting value, and then repeat that expression via @key{RET}. For
8763 instance, suppose you have an array @code{dtab} of pointers to
8764 structures, and you are interested in the values of a field @code{fv}
8765 in each structure. Here is an example of what you might type:
8775 @node Output Formats
8776 @section Output Formats
8778 @cindex formatted output
8779 @cindex output formats
8780 By default, @value{GDBN} prints a value according to its data type. Sometimes
8781 this is not what you want. For example, you might want to print a number
8782 in hex, or a pointer in decimal. Or you might want to view data in memory
8783 at a certain address as a character string or as an instruction. To do
8784 these things, specify an @dfn{output format} when you print a value.
8786 The simplest use of output formats is to say how to print a value
8787 already computed. This is done by starting the arguments of the
8788 @code{print} command with a slash and a format letter. The format
8789 letters supported are:
8793 Regard the bits of the value as an integer, and print the integer in
8797 Print as integer in signed decimal.
8800 Print as integer in unsigned decimal.
8803 Print as integer in octal.
8806 Print as integer in binary. The letter @samp{t} stands for ``two''.
8807 @footnote{@samp{b} cannot be used because these format letters are also
8808 used with the @code{x} command, where @samp{b} stands for ``byte'';
8809 see @ref{Memory,,Examining Memory}.}
8812 @cindex unknown address, locating
8813 @cindex locate address
8814 Print as an address, both absolute in hexadecimal and as an offset from
8815 the nearest preceding symbol. You can use this format used to discover
8816 where (in what function) an unknown address is located:
8819 (@value{GDBP}) p/a 0x54320
8820 $3 = 0x54320 <_initialize_vx+396>
8824 The command @code{info symbol 0x54320} yields similar results.
8825 @xref{Symbols, info symbol}.
8828 Regard as an integer and print it as a character constant. This
8829 prints both the numerical value and its character representation. The
8830 character representation is replaced with the octal escape @samp{\nnn}
8831 for characters outside the 7-bit @sc{ascii} range.
8833 Without this format, @value{GDBN} displays @code{char},
8834 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8835 constants. Single-byte members of vectors are displayed as integer
8839 Regard the bits of the value as a floating point number and print
8840 using typical floating point syntax.
8843 @cindex printing strings
8844 @cindex printing byte arrays
8845 Regard as a string, if possible. With this format, pointers to single-byte
8846 data are displayed as null-terminated strings and arrays of single-byte data
8847 are displayed as fixed-length strings. Other values are displayed in their
8850 Without this format, @value{GDBN} displays pointers to and arrays of
8851 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8852 strings. Single-byte members of a vector are displayed as an integer
8856 Like @samp{x} formatting, the value is treated as an integer and
8857 printed as hexadecimal, but leading zeros are printed to pad the value
8858 to the size of the integer type.
8861 @cindex raw printing
8862 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8863 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8864 Printing}). This typically results in a higher-level display of the
8865 value's contents. The @samp{r} format bypasses any Python
8866 pretty-printer which might exist.
8869 For example, to print the program counter in hex (@pxref{Registers}), type
8876 Note that no space is required before the slash; this is because command
8877 names in @value{GDBN} cannot contain a slash.
8879 To reprint the last value in the value history with a different format,
8880 you can use the @code{print} command with just a format and no
8881 expression. For example, @samp{p/x} reprints the last value in hex.
8884 @section Examining Memory
8886 You can use the command @code{x} (for ``examine'') to examine memory in
8887 any of several formats, independently of your program's data types.
8889 @cindex examining memory
8891 @kindex x @r{(examine memory)}
8892 @item x/@var{nfu} @var{addr}
8895 Use the @code{x} command to examine memory.
8898 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8899 much memory to display and how to format it; @var{addr} is an
8900 expression giving the address where you want to start displaying memory.
8901 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8902 Several commands set convenient defaults for @var{addr}.
8905 @item @var{n}, the repeat count
8906 The repeat count is a decimal integer; the default is 1. It specifies
8907 how much memory (counting by units @var{u}) to display.
8908 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8911 @item @var{f}, the display format
8912 The display format is one of the formats used by @code{print}
8913 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8914 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8915 The default is @samp{x} (hexadecimal) initially. The default changes
8916 each time you use either @code{x} or @code{print}.
8918 @item @var{u}, the unit size
8919 The unit size is any of
8925 Halfwords (two bytes).
8927 Words (four bytes). This is the initial default.
8929 Giant words (eight bytes).
8932 Each time you specify a unit size with @code{x}, that size becomes the
8933 default unit the next time you use @code{x}. For the @samp{i} format,
8934 the unit size is ignored and is normally not written. For the @samp{s} format,
8935 the unit size defaults to @samp{b}, unless it is explicitly given.
8936 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8937 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8938 Note that the results depend on the programming language of the
8939 current compilation unit. If the language is C, the @samp{s}
8940 modifier will use the UTF-16 encoding while @samp{w} will use
8941 UTF-32. The encoding is set by the programming language and cannot
8944 @item @var{addr}, starting display address
8945 @var{addr} is the address where you want @value{GDBN} to begin displaying
8946 memory. The expression need not have a pointer value (though it may);
8947 it is always interpreted as an integer address of a byte of memory.
8948 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8949 @var{addr} is usually just after the last address examined---but several
8950 other commands also set the default address: @code{info breakpoints} (to
8951 the address of the last breakpoint listed), @code{info line} (to the
8952 starting address of a line), and @code{print} (if you use it to display
8953 a value from memory).
8956 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8957 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8958 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8959 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8960 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8962 Since the letters indicating unit sizes are all distinct from the
8963 letters specifying output formats, you do not have to remember whether
8964 unit size or format comes first; either order works. The output
8965 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8966 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8968 Even though the unit size @var{u} is ignored for the formats @samp{s}
8969 and @samp{i}, you might still want to use a count @var{n}; for example,
8970 @samp{3i} specifies that you want to see three machine instructions,
8971 including any operands. For convenience, especially when used with
8972 the @code{display} command, the @samp{i} format also prints branch delay
8973 slot instructions, if any, beyond the count specified, which immediately
8974 follow the last instruction that is within the count. The command
8975 @code{disassemble} gives an alternative way of inspecting machine
8976 instructions; see @ref{Machine Code,,Source and Machine Code}.
8978 All the defaults for the arguments to @code{x} are designed to make it
8979 easy to continue scanning memory with minimal specifications each time
8980 you use @code{x}. For example, after you have inspected three machine
8981 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8982 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8983 the repeat count @var{n} is used again; the other arguments default as
8984 for successive uses of @code{x}.
8986 When examining machine instructions, the instruction at current program
8987 counter is shown with a @code{=>} marker. For example:
8990 (@value{GDBP}) x/5i $pc-6
8991 0x804837f <main+11>: mov %esp,%ebp
8992 0x8048381 <main+13>: push %ecx
8993 0x8048382 <main+14>: sub $0x4,%esp
8994 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8995 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8998 @cindex @code{$_}, @code{$__}, and value history
8999 The addresses and contents printed by the @code{x} command are not saved
9000 in the value history because there is often too much of them and they
9001 would get in the way. Instead, @value{GDBN} makes these values available for
9002 subsequent use in expressions as values of the convenience variables
9003 @code{$_} and @code{$__}. After an @code{x} command, the last address
9004 examined is available for use in expressions in the convenience variable
9005 @code{$_}. The contents of that address, as examined, are available in
9006 the convenience variable @code{$__}.
9008 If the @code{x} command has a repeat count, the address and contents saved
9009 are from the last memory unit printed; this is not the same as the last
9010 address printed if several units were printed on the last line of output.
9012 @cindex remote memory comparison
9013 @cindex target memory comparison
9014 @cindex verify remote memory image
9015 @cindex verify target memory image
9016 When you are debugging a program running on a remote target machine
9017 (@pxref{Remote Debugging}), you may wish to verify the program's image
9018 in the remote machine's memory against the executable file you
9019 downloaded to the target. Or, on any target, you may want to check
9020 whether the program has corrupted its own read-only sections. The
9021 @code{compare-sections} command is provided for such situations.
9024 @kindex compare-sections
9025 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9026 Compare the data of a loadable section @var{section-name} in the
9027 executable file of the program being debugged with the same section in
9028 the target machine's memory, and report any mismatches. With no
9029 arguments, compares all loadable sections. With an argument of
9030 @code{-r}, compares all loadable read-only sections.
9032 Note: for remote targets, this command can be accelerated if the
9033 target supports computing the CRC checksum of a block of memory
9034 (@pxref{qCRC packet}).
9038 @section Automatic Display
9039 @cindex automatic display
9040 @cindex display of expressions
9042 If you find that you want to print the value of an expression frequently
9043 (to see how it changes), you might want to add it to the @dfn{automatic
9044 display list} so that @value{GDBN} prints its value each time your program stops.
9045 Each expression added to the list is given a number to identify it;
9046 to remove an expression from the list, you specify that number.
9047 The automatic display looks like this:
9051 3: bar[5] = (struct hack *) 0x3804
9055 This display shows item numbers, expressions and their current values. As with
9056 displays you request manually using @code{x} or @code{print}, you can
9057 specify the output format you prefer; in fact, @code{display} decides
9058 whether to use @code{print} or @code{x} depending your format
9059 specification---it uses @code{x} if you specify either the @samp{i}
9060 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9064 @item display @var{expr}
9065 Add the expression @var{expr} to the list of expressions to display
9066 each time your program stops. @xref{Expressions, ,Expressions}.
9068 @code{display} does not repeat if you press @key{RET} again after using it.
9070 @item display/@var{fmt} @var{expr}
9071 For @var{fmt} specifying only a display format and not a size or
9072 count, add the expression @var{expr} to the auto-display list but
9073 arrange to display it each time in the specified format @var{fmt}.
9074 @xref{Output Formats,,Output Formats}.
9076 @item display/@var{fmt} @var{addr}
9077 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9078 number of units, add the expression @var{addr} as a memory address to
9079 be examined each time your program stops. Examining means in effect
9080 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9083 For example, @samp{display/i $pc} can be helpful, to see the machine
9084 instruction about to be executed each time execution stops (@samp{$pc}
9085 is a common name for the program counter; @pxref{Registers, ,Registers}).
9088 @kindex delete display
9090 @item undisplay @var{dnums}@dots{}
9091 @itemx delete display @var{dnums}@dots{}
9092 Remove items from the list of expressions to display. Specify the
9093 numbers of the displays that you want affected with the command
9094 argument @var{dnums}. It can be a single display number, one of the
9095 numbers shown in the first field of the @samp{info display} display;
9096 or it could be a range of display numbers, as in @code{2-4}.
9098 @code{undisplay} does not repeat if you press @key{RET} after using it.
9099 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9101 @kindex disable display
9102 @item disable display @var{dnums}@dots{}
9103 Disable the display of item numbers @var{dnums}. A disabled display
9104 item is not printed automatically, but is not forgotten. It may be
9105 enabled again later. Specify the numbers of the displays that you
9106 want affected with the command argument @var{dnums}. It can be a
9107 single display number, one of the numbers shown in the first field of
9108 the @samp{info display} display; or it could be a range of display
9109 numbers, as in @code{2-4}.
9111 @kindex enable display
9112 @item enable display @var{dnums}@dots{}
9113 Enable display of item numbers @var{dnums}. It becomes effective once
9114 again in auto display of its expression, until you specify otherwise.
9115 Specify the numbers of the displays that you want affected with the
9116 command argument @var{dnums}. It can be a single display number, one
9117 of the numbers shown in the first field of the @samp{info display}
9118 display; or it could be a range of display numbers, as in @code{2-4}.
9121 Display the current values of the expressions on the list, just as is
9122 done when your program stops.
9124 @kindex info display
9126 Print the list of expressions previously set up to display
9127 automatically, each one with its item number, but without showing the
9128 values. This includes disabled expressions, which are marked as such.
9129 It also includes expressions which would not be displayed right now
9130 because they refer to automatic variables not currently available.
9133 @cindex display disabled out of scope
9134 If a display expression refers to local variables, then it does not make
9135 sense outside the lexical context for which it was set up. Such an
9136 expression is disabled when execution enters a context where one of its
9137 variables is not defined. For example, if you give the command
9138 @code{display last_char} while inside a function with an argument
9139 @code{last_char}, @value{GDBN} displays this argument while your program
9140 continues to stop inside that function. When it stops elsewhere---where
9141 there is no variable @code{last_char}---the display is disabled
9142 automatically. The next time your program stops where @code{last_char}
9143 is meaningful, you can enable the display expression once again.
9145 @node Print Settings
9146 @section Print Settings
9148 @cindex format options
9149 @cindex print settings
9150 @value{GDBN} provides the following ways to control how arrays, structures,
9151 and symbols are printed.
9154 These settings are useful for debugging programs in any language:
9158 @item set print address
9159 @itemx set print address on
9160 @cindex print/don't print memory addresses
9161 @value{GDBN} prints memory addresses showing the location of stack
9162 traces, structure values, pointer values, breakpoints, and so forth,
9163 even when it also displays the contents of those addresses. The default
9164 is @code{on}. For example, this is what a stack frame display looks like with
9165 @code{set print address on}:
9170 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9172 530 if (lquote != def_lquote)
9176 @item set print address off
9177 Do not print addresses when displaying their contents. For example,
9178 this is the same stack frame displayed with @code{set print address off}:
9182 (@value{GDBP}) set print addr off
9184 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9185 530 if (lquote != def_lquote)
9189 You can use @samp{set print address off} to eliminate all machine
9190 dependent displays from the @value{GDBN} interface. For example, with
9191 @code{print address off}, you should get the same text for backtraces on
9192 all machines---whether or not they involve pointer arguments.
9195 @item show print address
9196 Show whether or not addresses are to be printed.
9199 When @value{GDBN} prints a symbolic address, it normally prints the
9200 closest earlier symbol plus an offset. If that symbol does not uniquely
9201 identify the address (for example, it is a name whose scope is a single
9202 source file), you may need to clarify. One way to do this is with
9203 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9204 you can set @value{GDBN} to print the source file and line number when
9205 it prints a symbolic address:
9208 @item set print symbol-filename on
9209 @cindex source file and line of a symbol
9210 @cindex symbol, source file and line
9211 Tell @value{GDBN} to print the source file name and line number of a
9212 symbol in the symbolic form of an address.
9214 @item set print symbol-filename off
9215 Do not print source file name and line number of a symbol. This is the
9218 @item show print symbol-filename
9219 Show whether or not @value{GDBN} will print the source file name and
9220 line number of a symbol in the symbolic form of an address.
9223 Another situation where it is helpful to show symbol filenames and line
9224 numbers is when disassembling code; @value{GDBN} shows you the line
9225 number and source file that corresponds to each instruction.
9227 Also, you may wish to see the symbolic form only if the address being
9228 printed is reasonably close to the closest earlier symbol:
9231 @item set print max-symbolic-offset @var{max-offset}
9232 @itemx set print max-symbolic-offset unlimited
9233 @cindex maximum value for offset of closest symbol
9234 Tell @value{GDBN} to only display the symbolic form of an address if the
9235 offset between the closest earlier symbol and the address is less than
9236 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9237 to always print the symbolic form of an address if any symbol precedes
9238 it. Zero is equivalent to @code{unlimited}.
9240 @item show print max-symbolic-offset
9241 Ask how large the maximum offset is that @value{GDBN} prints in a
9245 @cindex wild pointer, interpreting
9246 @cindex pointer, finding referent
9247 If you have a pointer and you are not sure where it points, try
9248 @samp{set print symbol-filename on}. Then you can determine the name
9249 and source file location of the variable where it points, using
9250 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9251 For example, here @value{GDBN} shows that a variable @code{ptt} points
9252 at another variable @code{t}, defined in @file{hi2.c}:
9255 (@value{GDBP}) set print symbol-filename on
9256 (@value{GDBP}) p/a ptt
9257 $4 = 0xe008 <t in hi2.c>
9261 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9262 does not show the symbol name and filename of the referent, even with
9263 the appropriate @code{set print} options turned on.
9266 You can also enable @samp{/a}-like formatting all the time using
9267 @samp{set print symbol on}:
9270 @item set print symbol on
9271 Tell @value{GDBN} to print the symbol corresponding to an address, if
9274 @item set print symbol off
9275 Tell @value{GDBN} not to print the symbol corresponding to an
9276 address. In this mode, @value{GDBN} will still print the symbol
9277 corresponding to pointers to functions. This is the default.
9279 @item show print symbol
9280 Show whether @value{GDBN} will display the symbol corresponding to an
9284 Other settings control how different kinds of objects are printed:
9287 @item set print array
9288 @itemx set print array on
9289 @cindex pretty print arrays
9290 Pretty print arrays. This format is more convenient to read,
9291 but uses more space. The default is off.
9293 @item set print array off
9294 Return to compressed format for arrays.
9296 @item show print array
9297 Show whether compressed or pretty format is selected for displaying
9300 @cindex print array indexes
9301 @item set print array-indexes
9302 @itemx set print array-indexes on
9303 Print the index of each element when displaying arrays. May be more
9304 convenient to locate a given element in the array or quickly find the
9305 index of a given element in that printed array. The default is off.
9307 @item set print array-indexes off
9308 Stop printing element indexes when displaying arrays.
9310 @item show print array-indexes
9311 Show whether the index of each element is printed when displaying
9314 @item set print elements @var{number-of-elements}
9315 @itemx set print elements unlimited
9316 @cindex number of array elements to print
9317 @cindex limit on number of printed array elements
9318 Set a limit on how many elements of an array @value{GDBN} will print.
9319 If @value{GDBN} is printing a large array, it stops printing after it has
9320 printed the number of elements set by the @code{set print elements} command.
9321 This limit also applies to the display of strings.
9322 When @value{GDBN} starts, this limit is set to 200.
9323 Setting @var{number-of-elements} to @code{unlimited} or zero means
9324 that the number of elements to print is unlimited.
9326 @item show print elements
9327 Display the number of elements of a large array that @value{GDBN} will print.
9328 If the number is 0, then the printing is unlimited.
9330 @item set print frame-arguments @var{value}
9331 @kindex set print frame-arguments
9332 @cindex printing frame argument values
9333 @cindex print all frame argument values
9334 @cindex print frame argument values for scalars only
9335 @cindex do not print frame argument values
9336 This command allows to control how the values of arguments are printed
9337 when the debugger prints a frame (@pxref{Frames}). The possible
9342 The values of all arguments are printed.
9345 Print the value of an argument only if it is a scalar. The value of more
9346 complex arguments such as arrays, structures, unions, etc, is replaced
9347 by @code{@dots{}}. This is the default. Here is an example where
9348 only scalar arguments are shown:
9351 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9356 None of the argument values are printed. Instead, the value of each argument
9357 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9360 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9365 By default, only scalar arguments are printed. This command can be used
9366 to configure the debugger to print the value of all arguments, regardless
9367 of their type. However, it is often advantageous to not print the value
9368 of more complex parameters. For instance, it reduces the amount of
9369 information printed in each frame, making the backtrace more readable.
9370 Also, it improves performance when displaying Ada frames, because
9371 the computation of large arguments can sometimes be CPU-intensive,
9372 especially in large applications. Setting @code{print frame-arguments}
9373 to @code{scalars} (the default) or @code{none} avoids this computation,
9374 thus speeding up the display of each Ada frame.
9376 @item show print frame-arguments
9377 Show how the value of arguments should be displayed when printing a frame.
9379 @item set print raw frame-arguments on
9380 Print frame arguments in raw, non pretty-printed, form.
9382 @item set print raw frame-arguments off
9383 Print frame arguments in pretty-printed form, if there is a pretty-printer
9384 for the value (@pxref{Pretty Printing}),
9385 otherwise print the value in raw form.
9386 This is the default.
9388 @item show print raw frame-arguments
9389 Show whether to print frame arguments in raw form.
9391 @anchor{set print entry-values}
9392 @item set print entry-values @var{value}
9393 @kindex set print entry-values
9394 Set printing of frame argument values at function entry. In some cases
9395 @value{GDBN} can determine the value of function argument which was passed by
9396 the function caller, even if the value was modified inside the called function
9397 and therefore is different. With optimized code, the current value could be
9398 unavailable, but the entry value may still be known.
9400 The default value is @code{default} (see below for its description). Older
9401 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9402 this feature will behave in the @code{default} setting the same way as with the
9405 This functionality is currently supported only by DWARF 2 debugging format and
9406 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9407 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9410 The @var{value} parameter can be one of the following:
9414 Print only actual parameter values, never print values from function entry
9418 #0 different (val=6)
9419 #0 lost (val=<optimized out>)
9421 #0 invalid (val=<optimized out>)
9425 Print only parameter values from function entry point. The actual parameter
9426 values are never printed.
9428 #0 equal (val@@entry=5)
9429 #0 different (val@@entry=5)
9430 #0 lost (val@@entry=5)
9431 #0 born (val@@entry=<optimized out>)
9432 #0 invalid (val@@entry=<optimized out>)
9436 Print only parameter values from function entry point. If value from function
9437 entry point is not known while the actual value is known, print the actual
9438 value for such parameter.
9440 #0 equal (val@@entry=5)
9441 #0 different (val@@entry=5)
9442 #0 lost (val@@entry=5)
9444 #0 invalid (val@@entry=<optimized out>)
9448 Print actual parameter values. If actual parameter value is not known while
9449 value from function entry point is known, print the entry point value for such
9453 #0 different (val=6)
9454 #0 lost (val@@entry=5)
9456 #0 invalid (val=<optimized out>)
9460 Always print both the actual parameter value and its value from function entry
9461 point, even if values of one or both are not available due to compiler
9464 #0 equal (val=5, val@@entry=5)
9465 #0 different (val=6, val@@entry=5)
9466 #0 lost (val=<optimized out>, val@@entry=5)
9467 #0 born (val=10, val@@entry=<optimized out>)
9468 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9472 Print the actual parameter value if it is known and also its value from
9473 function entry point if it is known. If neither is known, print for the actual
9474 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9475 values are known and identical, print the shortened
9476 @code{param=param@@entry=VALUE} notation.
9478 #0 equal (val=val@@entry=5)
9479 #0 different (val=6, val@@entry=5)
9480 #0 lost (val@@entry=5)
9482 #0 invalid (val=<optimized out>)
9486 Always print the actual parameter value. Print also its value from function
9487 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9488 if both values are known and identical, print the shortened
9489 @code{param=param@@entry=VALUE} notation.
9491 #0 equal (val=val@@entry=5)
9492 #0 different (val=6, val@@entry=5)
9493 #0 lost (val=<optimized out>, val@@entry=5)
9495 #0 invalid (val=<optimized out>)
9499 For analysis messages on possible failures of frame argument values at function
9500 entry resolution see @ref{set debug entry-values}.
9502 @item show print entry-values
9503 Show the method being used for printing of frame argument values at function
9506 @item set print repeats @var{number-of-repeats}
9507 @itemx set print repeats unlimited
9508 @cindex repeated array elements
9509 Set the threshold for suppressing display of repeated array
9510 elements. When the number of consecutive identical elements of an
9511 array exceeds the threshold, @value{GDBN} prints the string
9512 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9513 identical repetitions, instead of displaying the identical elements
9514 themselves. Setting the threshold to @code{unlimited} or zero will
9515 cause all elements to be individually printed. The default threshold
9518 @item show print repeats
9519 Display the current threshold for printing repeated identical
9522 @item set print null-stop
9523 @cindex @sc{null} elements in arrays
9524 Cause @value{GDBN} to stop printing the characters of an array when the first
9525 @sc{null} is encountered. This is useful when large arrays actually
9526 contain only short strings.
9529 @item show print null-stop
9530 Show whether @value{GDBN} stops printing an array on the first
9531 @sc{null} character.
9533 @item set print pretty on
9534 @cindex print structures in indented form
9535 @cindex indentation in structure display
9536 Cause @value{GDBN} to print structures in an indented format with one member
9537 per line, like this:
9552 @item set print pretty off
9553 Cause @value{GDBN} to print structures in a compact format, like this:
9557 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9558 meat = 0x54 "Pork"@}
9563 This is the default format.
9565 @item show print pretty
9566 Show which format @value{GDBN} is using to print structures.
9568 @item set print sevenbit-strings on
9569 @cindex eight-bit characters in strings
9570 @cindex octal escapes in strings
9571 Print using only seven-bit characters; if this option is set,
9572 @value{GDBN} displays any eight-bit characters (in strings or
9573 character values) using the notation @code{\}@var{nnn}. This setting is
9574 best if you are working in English (@sc{ascii}) and you use the
9575 high-order bit of characters as a marker or ``meta'' bit.
9577 @item set print sevenbit-strings off
9578 Print full eight-bit characters. This allows the use of more
9579 international character sets, and is the default.
9581 @item show print sevenbit-strings
9582 Show whether or not @value{GDBN} is printing only seven-bit characters.
9584 @item set print union on
9585 @cindex unions in structures, printing
9586 Tell @value{GDBN} to print unions which are contained in structures
9587 and other unions. This is the default setting.
9589 @item set print union off
9590 Tell @value{GDBN} not to print unions which are contained in
9591 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9594 @item show print union
9595 Ask @value{GDBN} whether or not it will print unions which are contained in
9596 structures and other unions.
9598 For example, given the declarations
9601 typedef enum @{Tree, Bug@} Species;
9602 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9603 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9614 struct thing foo = @{Tree, @{Acorn@}@};
9618 with @code{set print union on} in effect @samp{p foo} would print
9621 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9625 and with @code{set print union off} in effect it would print
9628 $1 = @{it = Tree, form = @{...@}@}
9632 @code{set print union} affects programs written in C-like languages
9638 These settings are of interest when debugging C@t{++} programs:
9641 @cindex demangling C@t{++} names
9642 @item set print demangle
9643 @itemx set print demangle on
9644 Print C@t{++} names in their source form rather than in the encoded
9645 (``mangled'') form passed to the assembler and linker for type-safe
9646 linkage. The default is on.
9648 @item show print demangle
9649 Show whether C@t{++} names are printed in mangled or demangled form.
9651 @item set print asm-demangle
9652 @itemx set print asm-demangle on
9653 Print C@t{++} names in their source form rather than their mangled form, even
9654 in assembler code printouts such as instruction disassemblies.
9657 @item show print asm-demangle
9658 Show whether C@t{++} names in assembly listings are printed in mangled
9661 @cindex C@t{++} symbol decoding style
9662 @cindex symbol decoding style, C@t{++}
9663 @kindex set demangle-style
9664 @item set demangle-style @var{style}
9665 Choose among several encoding schemes used by different compilers to
9666 represent C@t{++} names. The choices for @var{style} are currently:
9670 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9671 This is the default.
9674 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9677 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9680 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9683 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9684 @strong{Warning:} this setting alone is not sufficient to allow
9685 debugging @code{cfront}-generated executables. @value{GDBN} would
9686 require further enhancement to permit that.
9689 If you omit @var{style}, you will see a list of possible formats.
9691 @item show demangle-style
9692 Display the encoding style currently in use for decoding C@t{++} symbols.
9694 @item set print object
9695 @itemx set print object on
9696 @cindex derived type of an object, printing
9697 @cindex display derived types
9698 When displaying a pointer to an object, identify the @emph{actual}
9699 (derived) type of the object rather than the @emph{declared} type, using
9700 the virtual function table. Note that the virtual function table is
9701 required---this feature can only work for objects that have run-time
9702 type identification; a single virtual method in the object's declared
9703 type is sufficient. Note that this setting is also taken into account when
9704 working with variable objects via MI (@pxref{GDB/MI}).
9706 @item set print object off
9707 Display only the declared type of objects, without reference to the
9708 virtual function table. This is the default setting.
9710 @item show print object
9711 Show whether actual, or declared, object types are displayed.
9713 @item set print static-members
9714 @itemx set print static-members on
9715 @cindex static members of C@t{++} objects
9716 Print static members when displaying a C@t{++} object. The default is on.
9718 @item set print static-members off
9719 Do not print static members when displaying a C@t{++} object.
9721 @item show print static-members
9722 Show whether C@t{++} static members are printed or not.
9724 @item set print pascal_static-members
9725 @itemx set print pascal_static-members on
9726 @cindex static members of Pascal objects
9727 @cindex Pascal objects, static members display
9728 Print static members when displaying a Pascal object. The default is on.
9730 @item set print pascal_static-members off
9731 Do not print static members when displaying a Pascal object.
9733 @item show print pascal_static-members
9734 Show whether Pascal static members are printed or not.
9736 @c These don't work with HP ANSI C++ yet.
9737 @item set print vtbl
9738 @itemx set print vtbl on
9739 @cindex pretty print C@t{++} virtual function tables
9740 @cindex virtual functions (C@t{++}) display
9741 @cindex VTBL display
9742 Pretty print C@t{++} virtual function tables. The default is off.
9743 (The @code{vtbl} commands do not work on programs compiled with the HP
9744 ANSI C@t{++} compiler (@code{aCC}).)
9746 @item set print vtbl off
9747 Do not pretty print C@t{++} virtual function tables.
9749 @item show print vtbl
9750 Show whether C@t{++} virtual function tables are pretty printed, or not.
9753 @node Pretty Printing
9754 @section Pretty Printing
9756 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9757 Python code. It greatly simplifies the display of complex objects. This
9758 mechanism works for both MI and the CLI.
9761 * Pretty-Printer Introduction:: Introduction to pretty-printers
9762 * Pretty-Printer Example:: An example pretty-printer
9763 * Pretty-Printer Commands:: Pretty-printer commands
9766 @node Pretty-Printer Introduction
9767 @subsection Pretty-Printer Introduction
9769 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9770 registered for the value. If there is then @value{GDBN} invokes the
9771 pretty-printer to print the value. Otherwise the value is printed normally.
9773 Pretty-printers are normally named. This makes them easy to manage.
9774 The @samp{info pretty-printer} command will list all the installed
9775 pretty-printers with their names.
9776 If a pretty-printer can handle multiple data types, then its
9777 @dfn{subprinters} are the printers for the individual data types.
9778 Each such subprinter has its own name.
9779 The format of the name is @var{printer-name};@var{subprinter-name}.
9781 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9782 Typically they are automatically loaded and registered when the corresponding
9783 debug information is loaded, thus making them available without having to
9784 do anything special.
9786 There are three places where a pretty-printer can be registered.
9790 Pretty-printers registered globally are available when debugging
9794 Pretty-printers registered with a program space are available only
9795 when debugging that program.
9796 @xref{Progspaces In Python}, for more details on program spaces in Python.
9799 Pretty-printers registered with an objfile are loaded and unloaded
9800 with the corresponding objfile (e.g., shared library).
9801 @xref{Objfiles In Python}, for more details on objfiles in Python.
9804 @xref{Selecting Pretty-Printers}, for further information on how
9805 pretty-printers are selected,
9807 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9810 @node Pretty-Printer Example
9811 @subsection Pretty-Printer Example
9813 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9816 (@value{GDBP}) print s
9818 static npos = 4294967295,
9820 <std::allocator<char>> = @{
9821 <__gnu_cxx::new_allocator<char>> = @{
9822 <No data fields>@}, <No data fields>
9824 members of std::basic_string<char, std::char_traits<char>,
9825 std::allocator<char> >::_Alloc_hider:
9826 _M_p = 0x804a014 "abcd"
9831 With a pretty-printer for @code{std::string} only the contents are printed:
9834 (@value{GDBP}) print s
9838 @node Pretty-Printer Commands
9839 @subsection Pretty-Printer Commands
9840 @cindex pretty-printer commands
9843 @kindex info pretty-printer
9844 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9845 Print the list of installed pretty-printers.
9846 This includes disabled pretty-printers, which are marked as such.
9848 @var{object-regexp} is a regular expression matching the objects
9849 whose pretty-printers to list.
9850 Objects can be @code{global}, the program space's file
9851 (@pxref{Progspaces In Python}),
9852 and the object files within that program space (@pxref{Objfiles In Python}).
9853 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9854 looks up a printer from these three objects.
9856 @var{name-regexp} is a regular expression matching the name of the printers
9859 @kindex disable pretty-printer
9860 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9861 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9862 A disabled pretty-printer is not forgotten, it may be enabled again later.
9864 @kindex enable pretty-printer
9865 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9866 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9871 Suppose we have three pretty-printers installed: one from library1.so
9872 named @code{foo} that prints objects of type @code{foo}, and
9873 another from library2.so named @code{bar} that prints two types of objects,
9874 @code{bar1} and @code{bar2}.
9877 (gdb) info pretty-printer
9884 (gdb) info pretty-printer library2
9889 (gdb) disable pretty-printer library1
9891 2 of 3 printers enabled
9892 (gdb) info pretty-printer
9899 (gdb) disable pretty-printer library2 bar:bar1
9901 1 of 3 printers enabled
9902 (gdb) info pretty-printer library2
9909 (gdb) disable pretty-printer library2 bar
9911 0 of 3 printers enabled
9912 (gdb) info pretty-printer library2
9921 Note that for @code{bar} the entire printer can be disabled,
9922 as can each individual subprinter.
9925 @section Value History
9927 @cindex value history
9928 @cindex history of values printed by @value{GDBN}
9929 Values printed by the @code{print} command are saved in the @value{GDBN}
9930 @dfn{value history}. This allows you to refer to them in other expressions.
9931 Values are kept until the symbol table is re-read or discarded
9932 (for example with the @code{file} or @code{symbol-file} commands).
9933 When the symbol table changes, the value history is discarded,
9934 since the values may contain pointers back to the types defined in the
9939 @cindex history number
9940 The values printed are given @dfn{history numbers} by which you can
9941 refer to them. These are successive integers starting with one.
9942 @code{print} shows you the history number assigned to a value by
9943 printing @samp{$@var{num} = } before the value; here @var{num} is the
9946 To refer to any previous value, use @samp{$} followed by the value's
9947 history number. The way @code{print} labels its output is designed to
9948 remind you of this. Just @code{$} refers to the most recent value in
9949 the history, and @code{$$} refers to the value before that.
9950 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9951 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9952 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9954 For example, suppose you have just printed a pointer to a structure and
9955 want to see the contents of the structure. It suffices to type
9961 If you have a chain of structures where the component @code{next} points
9962 to the next one, you can print the contents of the next one with this:
9969 You can print successive links in the chain by repeating this
9970 command---which you can do by just typing @key{RET}.
9972 Note that the history records values, not expressions. If the value of
9973 @code{x} is 4 and you type these commands:
9981 then the value recorded in the value history by the @code{print} command
9982 remains 4 even though the value of @code{x} has changed.
9987 Print the last ten values in the value history, with their item numbers.
9988 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9989 values} does not change the history.
9991 @item show values @var{n}
9992 Print ten history values centered on history item number @var{n}.
9995 Print ten history values just after the values last printed. If no more
9996 values are available, @code{show values +} produces no display.
9999 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10000 same effect as @samp{show values +}.
10002 @node Convenience Vars
10003 @section Convenience Variables
10005 @cindex convenience variables
10006 @cindex user-defined variables
10007 @value{GDBN} provides @dfn{convenience variables} that you can use within
10008 @value{GDBN} to hold on to a value and refer to it later. These variables
10009 exist entirely within @value{GDBN}; they are not part of your program, and
10010 setting a convenience variable has no direct effect on further execution
10011 of your program. That is why you can use them freely.
10013 Convenience variables are prefixed with @samp{$}. Any name preceded by
10014 @samp{$} can be used for a convenience variable, unless it is one of
10015 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10016 (Value history references, in contrast, are @emph{numbers} preceded
10017 by @samp{$}. @xref{Value History, ,Value History}.)
10019 You can save a value in a convenience variable with an assignment
10020 expression, just as you would set a variable in your program.
10024 set $foo = *object_ptr
10028 would save in @code{$foo} the value contained in the object pointed to by
10031 Using a convenience variable for the first time creates it, but its
10032 value is @code{void} until you assign a new value. You can alter the
10033 value with another assignment at any time.
10035 Convenience variables have no fixed types. You can assign a convenience
10036 variable any type of value, including structures and arrays, even if
10037 that variable already has a value of a different type. The convenience
10038 variable, when used as an expression, has the type of its current value.
10041 @kindex show convenience
10042 @cindex show all user variables and functions
10043 @item show convenience
10044 Print a list of convenience variables used so far, and their values,
10045 as well as a list of the convenience functions.
10046 Abbreviated @code{show conv}.
10048 @kindex init-if-undefined
10049 @cindex convenience variables, initializing
10050 @item init-if-undefined $@var{variable} = @var{expression}
10051 Set a convenience variable if it has not already been set. This is useful
10052 for user-defined commands that keep some state. It is similar, in concept,
10053 to using local static variables with initializers in C (except that
10054 convenience variables are global). It can also be used to allow users to
10055 override default values used in a command script.
10057 If the variable is already defined then the expression is not evaluated so
10058 any side-effects do not occur.
10061 One of the ways to use a convenience variable is as a counter to be
10062 incremented or a pointer to be advanced. For example, to print
10063 a field from successive elements of an array of structures:
10067 print bar[$i++]->contents
10071 Repeat that command by typing @key{RET}.
10073 Some convenience variables are created automatically by @value{GDBN} and given
10074 values likely to be useful.
10077 @vindex $_@r{, convenience variable}
10079 The variable @code{$_} is automatically set by the @code{x} command to
10080 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10081 commands which provide a default address for @code{x} to examine also
10082 set @code{$_} to that address; these commands include @code{info line}
10083 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10084 except when set by the @code{x} command, in which case it is a pointer
10085 to the type of @code{$__}.
10087 @vindex $__@r{, convenience variable}
10089 The variable @code{$__} is automatically set by the @code{x} command
10090 to the value found in the last address examined. Its type is chosen
10091 to match the format in which the data was printed.
10094 @vindex $_exitcode@r{, convenience variable}
10095 When the program being debugged terminates normally, @value{GDBN}
10096 automatically sets this variable to the exit code of the program, and
10097 resets @code{$_exitsignal} to @code{void}.
10100 @vindex $_exitsignal@r{, convenience variable}
10101 When the program being debugged dies due to an uncaught signal,
10102 @value{GDBN} automatically sets this variable to that signal's number,
10103 and resets @code{$_exitcode} to @code{void}.
10105 To distinguish between whether the program being debugged has exited
10106 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10107 @code{$_exitsignal} is not @code{void}), the convenience function
10108 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10109 Functions}). For example, considering the following source code:
10112 #include <signal.h>
10115 main (int argc, char *argv[])
10122 A valid way of telling whether the program being debugged has exited
10123 or signalled would be:
10126 (@value{GDBP}) define has_exited_or_signalled
10127 Type commands for definition of ``has_exited_or_signalled''.
10128 End with a line saying just ``end''.
10129 >if $_isvoid ($_exitsignal)
10130 >echo The program has exited\n
10132 >echo The program has signalled\n
10138 Program terminated with signal SIGALRM, Alarm clock.
10139 The program no longer exists.
10140 (@value{GDBP}) has_exited_or_signalled
10141 The program has signalled
10144 As can be seen, @value{GDBN} correctly informs that the program being
10145 debugged has signalled, since it calls @code{raise} and raises a
10146 @code{SIGALRM} signal. If the program being debugged had not called
10147 @code{raise}, then @value{GDBN} would report a normal exit:
10150 (@value{GDBP}) has_exited_or_signalled
10151 The program has exited
10155 The variable @code{$_exception} is set to the exception object being
10156 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10159 @itemx $_probe_arg0@dots{}$_probe_arg11
10160 Arguments to a static probe. @xref{Static Probe Points}.
10163 @vindex $_sdata@r{, inspect, convenience variable}
10164 The variable @code{$_sdata} contains extra collected static tracepoint
10165 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10166 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10167 if extra static tracepoint data has not been collected.
10170 @vindex $_siginfo@r{, convenience variable}
10171 The variable @code{$_siginfo} contains extra signal information
10172 (@pxref{extra signal information}). Note that @code{$_siginfo}
10173 could be empty, if the application has not yet received any signals.
10174 For example, it will be empty before you execute the @code{run} command.
10177 @vindex $_tlb@r{, convenience variable}
10178 The variable @code{$_tlb} is automatically set when debugging
10179 applications running on MS-Windows in native mode or connected to
10180 gdbserver that supports the @code{qGetTIBAddr} request.
10181 @xref{General Query Packets}.
10182 This variable contains the address of the thread information block.
10186 On HP-UX systems, if you refer to a function or variable name that
10187 begins with a dollar sign, @value{GDBN} searches for a user or system
10188 name first, before it searches for a convenience variable.
10190 @node Convenience Funs
10191 @section Convenience Functions
10193 @cindex convenience functions
10194 @value{GDBN} also supplies some @dfn{convenience functions}. These
10195 have a syntax similar to convenience variables. A convenience
10196 function can be used in an expression just like an ordinary function;
10197 however, a convenience function is implemented internally to
10200 These functions do not require @value{GDBN} to be configured with
10201 @code{Python} support, which means that they are always available.
10205 @item $_isvoid (@var{expr})
10206 @findex $_isvoid@r{, convenience function}
10207 Return one if the expression @var{expr} is @code{void}. Otherwise it
10210 A @code{void} expression is an expression where the type of the result
10211 is @code{void}. For example, you can examine a convenience variable
10212 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10216 (@value{GDBP}) print $_exitcode
10218 (@value{GDBP}) print $_isvoid ($_exitcode)
10221 Starting program: ./a.out
10222 [Inferior 1 (process 29572) exited normally]
10223 (@value{GDBP}) print $_exitcode
10225 (@value{GDBP}) print $_isvoid ($_exitcode)
10229 In the example above, we used @code{$_isvoid} to check whether
10230 @code{$_exitcode} is @code{void} before and after the execution of the
10231 program being debugged. Before the execution there is no exit code to
10232 be examined, therefore @code{$_exitcode} is @code{void}. After the
10233 execution the program being debugged returned zero, therefore
10234 @code{$_exitcode} is zero, which means that it is not @code{void}
10237 The @code{void} expression can also be a call of a function from the
10238 program being debugged. For example, given the following function:
10247 The result of calling it inside @value{GDBN} is @code{void}:
10250 (@value{GDBP}) print foo ()
10252 (@value{GDBP}) print $_isvoid (foo ())
10254 (@value{GDBP}) set $v = foo ()
10255 (@value{GDBP}) print $v
10257 (@value{GDBP}) print $_isvoid ($v)
10263 These functions require @value{GDBN} to be configured with
10264 @code{Python} support.
10268 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10269 @findex $_memeq@r{, convenience function}
10270 Returns one if the @var{length} bytes at the addresses given by
10271 @var{buf1} and @var{buf2} are equal.
10272 Otherwise it returns zero.
10274 @item $_regex(@var{str}, @var{regex})
10275 @findex $_regex@r{, convenience function}
10276 Returns one if the string @var{str} matches the regular expression
10277 @var{regex}. Otherwise it returns zero.
10278 The syntax of the regular expression is that specified by @code{Python}'s
10279 regular expression support.
10281 @item $_streq(@var{str1}, @var{str2})
10282 @findex $_streq@r{, convenience function}
10283 Returns one if the strings @var{str1} and @var{str2} are equal.
10284 Otherwise it returns zero.
10286 @item $_strlen(@var{str})
10287 @findex $_strlen@r{, convenience function}
10288 Returns the length of string @var{str}.
10290 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10291 @findex $_caller_is@r{, convenience function}
10292 Returns one if the calling function's name is equal to @var{name}.
10293 Otherwise it returns zero.
10295 If the optional argument @var{number_of_frames} is provided,
10296 it is the number of frames up in the stack to look.
10304 at testsuite/gdb.python/py-caller-is.c:21
10305 #1 0x00000000004005a0 in middle_func ()
10306 at testsuite/gdb.python/py-caller-is.c:27
10307 #2 0x00000000004005ab in top_func ()
10308 at testsuite/gdb.python/py-caller-is.c:33
10309 #3 0x00000000004005b6 in main ()
10310 at testsuite/gdb.python/py-caller-is.c:39
10311 (gdb) print $_caller_is ("middle_func")
10313 (gdb) print $_caller_is ("top_func", 2)
10317 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10318 @findex $_caller_matches@r{, convenience function}
10319 Returns one if the calling function's name matches the regular expression
10320 @var{regexp}. Otherwise it returns zero.
10322 If the optional argument @var{number_of_frames} is provided,
10323 it is the number of frames up in the stack to look.
10326 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10327 @findex $_any_caller_is@r{, convenience function}
10328 Returns one if any calling function's name is equal to @var{name}.
10329 Otherwise it returns zero.
10331 If the optional argument @var{number_of_frames} is provided,
10332 it is the number of frames up in the stack to look.
10335 This function differs from @code{$_caller_is} in that this function
10336 checks all stack frames from the immediate caller to the frame specified
10337 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10338 frame specified by @var{number_of_frames}.
10340 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10341 @findex $_any_caller_matches@r{, convenience function}
10342 Returns one if any calling function's name matches the regular expression
10343 @var{regexp}. Otherwise it returns zero.
10345 If the optional argument @var{number_of_frames} is provided,
10346 it is the number of frames up in the stack to look.
10349 This function differs from @code{$_caller_matches} in that this function
10350 checks all stack frames from the immediate caller to the frame specified
10351 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10352 frame specified by @var{number_of_frames}.
10356 @value{GDBN} provides the ability to list and get help on
10357 convenience functions.
10360 @item help function
10361 @kindex help function
10362 @cindex show all convenience functions
10363 Print a list of all convenience functions.
10370 You can refer to machine register contents, in expressions, as variables
10371 with names starting with @samp{$}. The names of registers are different
10372 for each machine; use @code{info registers} to see the names used on
10376 @kindex info registers
10377 @item info registers
10378 Print the names and values of all registers except floating-point
10379 and vector registers (in the selected stack frame).
10381 @kindex info all-registers
10382 @cindex floating point registers
10383 @item info all-registers
10384 Print the names and values of all registers, including floating-point
10385 and vector registers (in the selected stack frame).
10387 @item info registers @var{regname} @dots{}
10388 Print the @dfn{relativized} value of each specified register @var{regname}.
10389 As discussed in detail below, register values are normally relative to
10390 the selected stack frame. The @var{regname} may be any register name valid on
10391 the machine you are using, with or without the initial @samp{$}.
10394 @anchor{standard registers}
10395 @cindex stack pointer register
10396 @cindex program counter register
10397 @cindex process status register
10398 @cindex frame pointer register
10399 @cindex standard registers
10400 @value{GDBN} has four ``standard'' register names that are available (in
10401 expressions) on most machines---whenever they do not conflict with an
10402 architecture's canonical mnemonics for registers. The register names
10403 @code{$pc} and @code{$sp} are used for the program counter register and
10404 the stack pointer. @code{$fp} is used for a register that contains a
10405 pointer to the current stack frame, and @code{$ps} is used for a
10406 register that contains the processor status. For example,
10407 you could print the program counter in hex with
10414 or print the instruction to be executed next with
10421 or add four to the stack pointer@footnote{This is a way of removing
10422 one word from the stack, on machines where stacks grow downward in
10423 memory (most machines, nowadays). This assumes that the innermost
10424 stack frame is selected; setting @code{$sp} is not allowed when other
10425 stack frames are selected. To pop entire frames off the stack,
10426 regardless of machine architecture, use @code{return};
10427 see @ref{Returning, ,Returning from a Function}.} with
10433 Whenever possible, these four standard register names are available on
10434 your machine even though the machine has different canonical mnemonics,
10435 so long as there is no conflict. The @code{info registers} command
10436 shows the canonical names. For example, on the SPARC, @code{info
10437 registers} displays the processor status register as @code{$psr} but you
10438 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10439 is an alias for the @sc{eflags} register.
10441 @value{GDBN} always considers the contents of an ordinary register as an
10442 integer when the register is examined in this way. Some machines have
10443 special registers which can hold nothing but floating point; these
10444 registers are considered to have floating point values. There is no way
10445 to refer to the contents of an ordinary register as floating point value
10446 (although you can @emph{print} it as a floating point value with
10447 @samp{print/f $@var{regname}}).
10449 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10450 means that the data format in which the register contents are saved by
10451 the operating system is not the same one that your program normally
10452 sees. For example, the registers of the 68881 floating point
10453 coprocessor are always saved in ``extended'' (raw) format, but all C
10454 programs expect to work with ``double'' (virtual) format. In such
10455 cases, @value{GDBN} normally works with the virtual format only (the format
10456 that makes sense for your program), but the @code{info registers} command
10457 prints the data in both formats.
10459 @cindex SSE registers (x86)
10460 @cindex MMX registers (x86)
10461 Some machines have special registers whose contents can be interpreted
10462 in several different ways. For example, modern x86-based machines
10463 have SSE and MMX registers that can hold several values packed
10464 together in several different formats. @value{GDBN} refers to such
10465 registers in @code{struct} notation:
10468 (@value{GDBP}) print $xmm1
10470 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10471 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10472 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10473 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10474 v4_int32 = @{0, 20657912, 11, 13@},
10475 v2_int64 = @{88725056443645952, 55834574859@},
10476 uint128 = 0x0000000d0000000b013b36f800000000
10481 To set values of such registers, you need to tell @value{GDBN} which
10482 view of the register you wish to change, as if you were assigning
10483 value to a @code{struct} member:
10486 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10489 Normally, register values are relative to the selected stack frame
10490 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10491 value that the register would contain if all stack frames farther in
10492 were exited and their saved registers restored. In order to see the
10493 true contents of hardware registers, you must select the innermost
10494 frame (with @samp{frame 0}).
10496 @cindex caller-saved registers
10497 @cindex call-clobbered registers
10498 @cindex volatile registers
10499 @cindex <not saved> values
10500 Usually ABIs reserve some registers as not needed to be saved by the
10501 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10502 registers). It may therefore not be possible for @value{GDBN} to know
10503 the value a register had before the call (in other words, in the outer
10504 frame), if the register value has since been changed by the callee.
10505 @value{GDBN} tries to deduce where the inner frame saved
10506 (``callee-saved'') registers, from the debug info, unwind info, or the
10507 machine code generated by your compiler. If some register is not
10508 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10509 its own knowledge of the ABI, or because the debug/unwind info
10510 explicitly says the register's value is undefined), @value{GDBN}
10511 displays @w{@samp{<not saved>}} as the register's value. With targets
10512 that @value{GDBN} has no knowledge of the register saving convention,
10513 if a register was not saved by the callee, then its value and location
10514 in the outer frame are assumed to be the same of the inner frame.
10515 This is usually harmless, because if the register is call-clobbered,
10516 the caller either does not care what is in the register after the
10517 call, or has code to restore the value that it does care about. Note,
10518 however, that if you change such a register in the outer frame, you
10519 may also be affecting the inner frame. Also, the more ``outer'' the
10520 frame is you're looking at, the more likely a call-clobbered
10521 register's value is to be wrong, in the sense that it doesn't actually
10522 represent the value the register had just before the call.
10524 @node Floating Point Hardware
10525 @section Floating Point Hardware
10526 @cindex floating point
10528 Depending on the configuration, @value{GDBN} may be able to give
10529 you more information about the status of the floating point hardware.
10534 Display hardware-dependent information about the floating
10535 point unit. The exact contents and layout vary depending on the
10536 floating point chip. Currently, @samp{info float} is supported on
10537 the ARM and x86 machines.
10541 @section Vector Unit
10542 @cindex vector unit
10544 Depending on the configuration, @value{GDBN} may be able to give you
10545 more information about the status of the vector unit.
10548 @kindex info vector
10550 Display information about the vector unit. The exact contents and
10551 layout vary depending on the hardware.
10554 @node OS Information
10555 @section Operating System Auxiliary Information
10556 @cindex OS information
10558 @value{GDBN} provides interfaces to useful OS facilities that can help
10559 you debug your program.
10561 @cindex auxiliary vector
10562 @cindex vector, auxiliary
10563 Some operating systems supply an @dfn{auxiliary vector} to programs at
10564 startup. This is akin to the arguments and environment that you
10565 specify for a program, but contains a system-dependent variety of
10566 binary values that tell system libraries important details about the
10567 hardware, operating system, and process. Each value's purpose is
10568 identified by an integer tag; the meanings are well-known but system-specific.
10569 Depending on the configuration and operating system facilities,
10570 @value{GDBN} may be able to show you this information. For remote
10571 targets, this functionality may further depend on the remote stub's
10572 support of the @samp{qXfer:auxv:read} packet, see
10573 @ref{qXfer auxiliary vector read}.
10578 Display the auxiliary vector of the inferior, which can be either a
10579 live process or a core dump file. @value{GDBN} prints each tag value
10580 numerically, and also shows names and text descriptions for recognized
10581 tags. Some values in the vector are numbers, some bit masks, and some
10582 pointers to strings or other data. @value{GDBN} displays each value in the
10583 most appropriate form for a recognized tag, and in hexadecimal for
10584 an unrecognized tag.
10587 On some targets, @value{GDBN} can access operating system-specific
10588 information and show it to you. The types of information available
10589 will differ depending on the type of operating system running on the
10590 target. The mechanism used to fetch the data is described in
10591 @ref{Operating System Information}. For remote targets, this
10592 functionality depends on the remote stub's support of the
10593 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10597 @item info os @var{infotype}
10599 Display OS information of the requested type.
10601 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10603 @anchor{linux info os infotypes}
10605 @kindex info os cpus
10607 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10608 the available fields from /proc/cpuinfo. For each supported architecture
10609 different fields are available. Two common entries are processor which gives
10610 CPU number and bogomips; a system constant that is calculated during
10611 kernel initialization.
10613 @kindex info os files
10615 Display the list of open file descriptors on the target. For each
10616 file descriptor, @value{GDBN} prints the identifier of the process
10617 owning the descriptor, the command of the owning process, the value
10618 of the descriptor, and the target of the descriptor.
10620 @kindex info os modules
10622 Display the list of all loaded kernel modules on the target. For each
10623 module, @value{GDBN} prints the module name, the size of the module in
10624 bytes, the number of times the module is used, the dependencies of the
10625 module, the status of the module, and the address of the loaded module
10628 @kindex info os msg
10630 Display the list of all System V message queues on the target. For each
10631 message queue, @value{GDBN} prints the message queue key, the message
10632 queue identifier, the access permissions, the current number of bytes
10633 on the queue, the current number of messages on the queue, the processes
10634 that last sent and received a message on the queue, the user and group
10635 of the owner and creator of the message queue, the times at which a
10636 message was last sent and received on the queue, and the time at which
10637 the message queue was last changed.
10639 @kindex info os processes
10641 Display the list of processes on the target. For each process,
10642 @value{GDBN} prints the process identifier, the name of the user, the
10643 command corresponding to the process, and the list of processor cores
10644 that the process is currently running on. (To understand what these
10645 properties mean, for this and the following info types, please consult
10646 the general @sc{gnu}/Linux documentation.)
10648 @kindex info os procgroups
10650 Display the list of process groups on the target. For each process,
10651 @value{GDBN} prints the identifier of the process group that it belongs
10652 to, the command corresponding to the process group leader, the process
10653 identifier, and the command line of the process. The list is sorted
10654 first by the process group identifier, then by the process identifier,
10655 so that processes belonging to the same process group are grouped together
10656 and the process group leader is listed first.
10658 @kindex info os semaphores
10660 Display the list of all System V semaphore sets on the target. For each
10661 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10662 set identifier, the access permissions, the number of semaphores in the
10663 set, the user and group of the owner and creator of the semaphore set,
10664 and the times at which the semaphore set was operated upon and changed.
10666 @kindex info os shm
10668 Display the list of all System V shared-memory regions on the target.
10669 For each shared-memory region, @value{GDBN} prints the region key,
10670 the shared-memory identifier, the access permissions, the size of the
10671 region, the process that created the region, the process that last
10672 attached to or detached from the region, the current number of live
10673 attaches to the region, and the times at which the region was last
10674 attached to, detach from, and changed.
10676 @kindex info os sockets
10678 Display the list of Internet-domain sockets on the target. For each
10679 socket, @value{GDBN} prints the address and port of the local and
10680 remote endpoints, the current state of the connection, the creator of
10681 the socket, the IP address family of the socket, and the type of the
10684 @kindex info os threads
10686 Display the list of threads running on the target. For each thread,
10687 @value{GDBN} prints the identifier of the process that the thread
10688 belongs to, the command of the process, the thread identifier, and the
10689 processor core that it is currently running on. The main thread of a
10690 process is not listed.
10694 If @var{infotype} is omitted, then list the possible values for
10695 @var{infotype} and the kind of OS information available for each
10696 @var{infotype}. If the target does not return a list of possible
10697 types, this command will report an error.
10700 @node Memory Region Attributes
10701 @section Memory Region Attributes
10702 @cindex memory region attributes
10704 @dfn{Memory region attributes} allow you to describe special handling
10705 required by regions of your target's memory. @value{GDBN} uses
10706 attributes to determine whether to allow certain types of memory
10707 accesses; whether to use specific width accesses; and whether to cache
10708 target memory. By default the description of memory regions is
10709 fetched from the target (if the current target supports this), but the
10710 user can override the fetched regions.
10712 Defined memory regions can be individually enabled and disabled. When a
10713 memory region is disabled, @value{GDBN} uses the default attributes when
10714 accessing memory in that region. Similarly, if no memory regions have
10715 been defined, @value{GDBN} uses the default attributes when accessing
10718 When a memory region is defined, it is given a number to identify it;
10719 to enable, disable, or remove a memory region, you specify that number.
10723 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10724 Define a memory region bounded by @var{lower} and @var{upper} with
10725 attributes @var{attributes}@dots{}, and add it to the list of regions
10726 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10727 case: it is treated as the target's maximum memory address.
10728 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10731 Discard any user changes to the memory regions and use target-supplied
10732 regions, if available, or no regions if the target does not support.
10735 @item delete mem @var{nums}@dots{}
10736 Remove memory regions @var{nums}@dots{} from the list of regions
10737 monitored by @value{GDBN}.
10739 @kindex disable mem
10740 @item disable mem @var{nums}@dots{}
10741 Disable monitoring of memory regions @var{nums}@dots{}.
10742 A disabled memory region is not forgotten.
10743 It may be enabled again later.
10746 @item enable mem @var{nums}@dots{}
10747 Enable monitoring of memory regions @var{nums}@dots{}.
10751 Print a table of all defined memory regions, with the following columns
10755 @item Memory Region Number
10756 @item Enabled or Disabled.
10757 Enabled memory regions are marked with @samp{y}.
10758 Disabled memory regions are marked with @samp{n}.
10761 The address defining the inclusive lower bound of the memory region.
10764 The address defining the exclusive upper bound of the memory region.
10767 The list of attributes set for this memory region.
10772 @subsection Attributes
10774 @subsubsection Memory Access Mode
10775 The access mode attributes set whether @value{GDBN} may make read or
10776 write accesses to a memory region.
10778 While these attributes prevent @value{GDBN} from performing invalid
10779 memory accesses, they do nothing to prevent the target system, I/O DMA,
10780 etc.@: from accessing memory.
10784 Memory is read only.
10786 Memory is write only.
10788 Memory is read/write. This is the default.
10791 @subsubsection Memory Access Size
10792 The access size attribute tells @value{GDBN} to use specific sized
10793 accesses in the memory region. Often memory mapped device registers
10794 require specific sized accesses. If no access size attribute is
10795 specified, @value{GDBN} may use accesses of any size.
10799 Use 8 bit memory accesses.
10801 Use 16 bit memory accesses.
10803 Use 32 bit memory accesses.
10805 Use 64 bit memory accesses.
10808 @c @subsubsection Hardware/Software Breakpoints
10809 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10810 @c will use hardware or software breakpoints for the internal breakpoints
10811 @c used by the step, next, finish, until, etc. commands.
10815 @c Always use hardware breakpoints
10816 @c @item swbreak (default)
10819 @subsubsection Data Cache
10820 The data cache attributes set whether @value{GDBN} will cache target
10821 memory. While this generally improves performance by reducing debug
10822 protocol overhead, it can lead to incorrect results because @value{GDBN}
10823 does not know about volatile variables or memory mapped device
10828 Enable @value{GDBN} to cache target memory.
10830 Disable @value{GDBN} from caching target memory. This is the default.
10833 @subsection Memory Access Checking
10834 @value{GDBN} can be instructed to refuse accesses to memory that is
10835 not explicitly described. This can be useful if accessing such
10836 regions has undesired effects for a specific target, or to provide
10837 better error checking. The following commands control this behaviour.
10840 @kindex set mem inaccessible-by-default
10841 @item set mem inaccessible-by-default [on|off]
10842 If @code{on} is specified, make @value{GDBN} treat memory not
10843 explicitly described by the memory ranges as non-existent and refuse accesses
10844 to such memory. The checks are only performed if there's at least one
10845 memory range defined. If @code{off} is specified, make @value{GDBN}
10846 treat the memory not explicitly described by the memory ranges as RAM.
10847 The default value is @code{on}.
10848 @kindex show mem inaccessible-by-default
10849 @item show mem inaccessible-by-default
10850 Show the current handling of accesses to unknown memory.
10854 @c @subsubsection Memory Write Verification
10855 @c The memory write verification attributes set whether @value{GDBN}
10856 @c will re-reads data after each write to verify the write was successful.
10860 @c @item noverify (default)
10863 @node Dump/Restore Files
10864 @section Copy Between Memory and a File
10865 @cindex dump/restore files
10866 @cindex append data to a file
10867 @cindex dump data to a file
10868 @cindex restore data from a file
10870 You can use the commands @code{dump}, @code{append}, and
10871 @code{restore} to copy data between target memory and a file. The
10872 @code{dump} and @code{append} commands write data to a file, and the
10873 @code{restore} command reads data from a file back into the inferior's
10874 memory. Files may be in binary, Motorola S-record, Intel hex,
10875 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
10876 append to binary files, and cannot read from Verilog Hex files.
10881 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10882 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10883 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10884 or the value of @var{expr}, to @var{filename} in the given format.
10886 The @var{format} parameter may be any one of:
10893 Motorola S-record format.
10895 Tektronix Hex format.
10897 Verilog Hex format.
10900 @value{GDBN} uses the same definitions of these formats as the
10901 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10902 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10906 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10907 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10908 Append the contents of memory from @var{start_addr} to @var{end_addr},
10909 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10910 (@value{GDBN} can only append data to files in raw binary form.)
10913 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10914 Restore the contents of file @var{filename} into memory. The
10915 @code{restore} command can automatically recognize any known @sc{bfd}
10916 file format, except for raw binary. To restore a raw binary file you
10917 must specify the optional keyword @code{binary} after the filename.
10919 If @var{bias} is non-zero, its value will be added to the addresses
10920 contained in the file. Binary files always start at address zero, so
10921 they will be restored at address @var{bias}. Other bfd files have
10922 a built-in location; they will be restored at offset @var{bias}
10923 from that location.
10925 If @var{start} and/or @var{end} are non-zero, then only data between
10926 file offset @var{start} and file offset @var{end} will be restored.
10927 These offsets are relative to the addresses in the file, before
10928 the @var{bias} argument is applied.
10932 @node Core File Generation
10933 @section How to Produce a Core File from Your Program
10934 @cindex dump core from inferior
10936 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10937 image of a running process and its process status (register values
10938 etc.). Its primary use is post-mortem debugging of a program that
10939 crashed while it ran outside a debugger. A program that crashes
10940 automatically produces a core file, unless this feature is disabled by
10941 the user. @xref{Files}, for information on invoking @value{GDBN} in
10942 the post-mortem debugging mode.
10944 Occasionally, you may wish to produce a core file of the program you
10945 are debugging in order to preserve a snapshot of its state.
10946 @value{GDBN} has a special command for that.
10950 @kindex generate-core-file
10951 @item generate-core-file [@var{file}]
10952 @itemx gcore [@var{file}]
10953 Produce a core dump of the inferior process. The optional argument
10954 @var{file} specifies the file name where to put the core dump. If not
10955 specified, the file name defaults to @file{core.@var{pid}}, where
10956 @var{pid} is the inferior process ID.
10958 Note that this command is implemented only for some systems (as of
10959 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10961 On @sc{gnu}/Linux, this command can take into account the value of the
10962 file @file{/proc/@var{pid}/coredump_filter} when generating the core
10963 dump (@pxref{set use-coredump-filter}).
10965 @kindex set use-coredump-filter
10966 @anchor{set use-coredump-filter}
10967 @item set use-coredump-filter on
10968 @itemx set use-coredump-filter off
10969 Enable or disable the use of the file
10970 @file{/proc/@var{pid}/coredump_filter} when generating core dump
10971 files. This file is used by the Linux kernel to decide what types of
10972 memory mappings will be dumped or ignored when generating a core dump
10973 file. @var{pid} is the process ID of a currently running process.
10975 To make use of this feature, you have to write in the
10976 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
10977 which is a bit mask representing the memory mapping types. If a bit
10978 is set in the bit mask, then the memory mappings of the corresponding
10979 types will be dumped; otherwise, they will be ignored. This
10980 configuration is inherited by child processes. For more information
10981 about the bits that can be set in the
10982 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
10983 manpage of @code{core(5)}.
10985 By default, this option is @code{on}. If this option is turned
10986 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
10987 and instead uses the same default value as the Linux kernel in order
10988 to decide which pages will be dumped in the core dump file. This
10989 value is currently @code{0x33}, which means that bits @code{0}
10990 (anonymous private mappings), @code{1} (anonymous shared mappings),
10991 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
10992 This will cause these memory mappings to be dumped automatically.
10995 @node Character Sets
10996 @section Character Sets
10997 @cindex character sets
10999 @cindex translating between character sets
11000 @cindex host character set
11001 @cindex target character set
11003 If the program you are debugging uses a different character set to
11004 represent characters and strings than the one @value{GDBN} uses itself,
11005 @value{GDBN} can automatically translate between the character sets for
11006 you. The character set @value{GDBN} uses we call the @dfn{host
11007 character set}; the one the inferior program uses we call the
11008 @dfn{target character set}.
11010 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11011 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11012 remote protocol (@pxref{Remote Debugging}) to debug a program
11013 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11014 then the host character set is Latin-1, and the target character set is
11015 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11016 target-charset EBCDIC-US}, then @value{GDBN} translates between
11017 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11018 character and string literals in expressions.
11020 @value{GDBN} has no way to automatically recognize which character set
11021 the inferior program uses; you must tell it, using the @code{set
11022 target-charset} command, described below.
11024 Here are the commands for controlling @value{GDBN}'s character set
11028 @item set target-charset @var{charset}
11029 @kindex set target-charset
11030 Set the current target character set to @var{charset}. To display the
11031 list of supported target character sets, type
11032 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11034 @item set host-charset @var{charset}
11035 @kindex set host-charset
11036 Set the current host character set to @var{charset}.
11038 By default, @value{GDBN} uses a host character set appropriate to the
11039 system it is running on; you can override that default using the
11040 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11041 automatically determine the appropriate host character set. In this
11042 case, @value{GDBN} uses @samp{UTF-8}.
11044 @value{GDBN} can only use certain character sets as its host character
11045 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11046 @value{GDBN} will list the host character sets it supports.
11048 @item set charset @var{charset}
11049 @kindex set charset
11050 Set the current host and target character sets to @var{charset}. As
11051 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11052 @value{GDBN} will list the names of the character sets that can be used
11053 for both host and target.
11056 @kindex show charset
11057 Show the names of the current host and target character sets.
11059 @item show host-charset
11060 @kindex show host-charset
11061 Show the name of the current host character set.
11063 @item show target-charset
11064 @kindex show target-charset
11065 Show the name of the current target character set.
11067 @item set target-wide-charset @var{charset}
11068 @kindex set target-wide-charset
11069 Set the current target's wide character set to @var{charset}. This is
11070 the character set used by the target's @code{wchar_t} type. To
11071 display the list of supported wide character sets, type
11072 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11074 @item show target-wide-charset
11075 @kindex show target-wide-charset
11076 Show the name of the current target's wide character set.
11079 Here is an example of @value{GDBN}'s character set support in action.
11080 Assume that the following source code has been placed in the file
11081 @file{charset-test.c}:
11087 = @{72, 101, 108, 108, 111, 44, 32, 119,
11088 111, 114, 108, 100, 33, 10, 0@};
11089 char ibm1047_hello[]
11090 = @{200, 133, 147, 147, 150, 107, 64, 166,
11091 150, 153, 147, 132, 90, 37, 0@};
11095 printf ("Hello, world!\n");
11099 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11100 containing the string @samp{Hello, world!} followed by a newline,
11101 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11103 We compile the program, and invoke the debugger on it:
11106 $ gcc -g charset-test.c -o charset-test
11107 $ gdb -nw charset-test
11108 GNU gdb 2001-12-19-cvs
11109 Copyright 2001 Free Software Foundation, Inc.
11114 We can use the @code{show charset} command to see what character sets
11115 @value{GDBN} is currently using to interpret and display characters and
11119 (@value{GDBP}) show charset
11120 The current host and target character set is `ISO-8859-1'.
11124 For the sake of printing this manual, let's use @sc{ascii} as our
11125 initial character set:
11127 (@value{GDBP}) set charset ASCII
11128 (@value{GDBP}) show charset
11129 The current host and target character set is `ASCII'.
11133 Let's assume that @sc{ascii} is indeed the correct character set for our
11134 host system --- in other words, let's assume that if @value{GDBN} prints
11135 characters using the @sc{ascii} character set, our terminal will display
11136 them properly. Since our current target character set is also
11137 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11140 (@value{GDBP}) print ascii_hello
11141 $1 = 0x401698 "Hello, world!\n"
11142 (@value{GDBP}) print ascii_hello[0]
11147 @value{GDBN} uses the target character set for character and string
11148 literals you use in expressions:
11151 (@value{GDBP}) print '+'
11156 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11159 @value{GDBN} relies on the user to tell it which character set the
11160 target program uses. If we print @code{ibm1047_hello} while our target
11161 character set is still @sc{ascii}, we get jibberish:
11164 (@value{GDBP}) print ibm1047_hello
11165 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11166 (@value{GDBP}) print ibm1047_hello[0]
11171 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11172 @value{GDBN} tells us the character sets it supports:
11175 (@value{GDBP}) set target-charset
11176 ASCII EBCDIC-US IBM1047 ISO-8859-1
11177 (@value{GDBP}) set target-charset
11180 We can select @sc{ibm1047} as our target character set, and examine the
11181 program's strings again. Now the @sc{ascii} string is wrong, but
11182 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11183 target character set, @sc{ibm1047}, to the host character set,
11184 @sc{ascii}, and they display correctly:
11187 (@value{GDBP}) set target-charset IBM1047
11188 (@value{GDBP}) show charset
11189 The current host character set is `ASCII'.
11190 The current target character set is `IBM1047'.
11191 (@value{GDBP}) print ascii_hello
11192 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11193 (@value{GDBP}) print ascii_hello[0]
11195 (@value{GDBP}) print ibm1047_hello
11196 $8 = 0x4016a8 "Hello, world!\n"
11197 (@value{GDBP}) print ibm1047_hello[0]
11202 As above, @value{GDBN} uses the target character set for character and
11203 string literals you use in expressions:
11206 (@value{GDBP}) print '+'
11211 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11214 @node Caching Target Data
11215 @section Caching Data of Targets
11216 @cindex caching data of targets
11218 @value{GDBN} caches data exchanged between the debugger and a target.
11219 Each cache is associated with the address space of the inferior.
11220 @xref{Inferiors and Programs}, about inferior and address space.
11221 Such caching generally improves performance in remote debugging
11222 (@pxref{Remote Debugging}), because it reduces the overhead of the
11223 remote protocol by bundling memory reads and writes into large chunks.
11224 Unfortunately, simply caching everything would lead to incorrect results,
11225 since @value{GDBN} does not necessarily know anything about volatile
11226 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11227 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11229 Therefore, by default, @value{GDBN} only caches data
11230 known to be on the stack@footnote{In non-stop mode, it is moderately
11231 rare for a running thread to modify the stack of a stopped thread
11232 in a way that would interfere with a backtrace, and caching of
11233 stack reads provides a significant speed up of remote backtraces.} or
11234 in the code segment.
11235 Other regions of memory can be explicitly marked as
11236 cacheable; @pxref{Memory Region Attributes}.
11239 @kindex set remotecache
11240 @item set remotecache on
11241 @itemx set remotecache off
11242 This option no longer does anything; it exists for compatibility
11245 @kindex show remotecache
11246 @item show remotecache
11247 Show the current state of the obsolete remotecache flag.
11249 @kindex set stack-cache
11250 @item set stack-cache on
11251 @itemx set stack-cache off
11252 Enable or disable caching of stack accesses. When @code{on}, use
11253 caching. By default, this option is @code{on}.
11255 @kindex show stack-cache
11256 @item show stack-cache
11257 Show the current state of data caching for memory accesses.
11259 @kindex set code-cache
11260 @item set code-cache on
11261 @itemx set code-cache off
11262 Enable or disable caching of code segment accesses. When @code{on},
11263 use caching. By default, this option is @code{on}. This improves
11264 performance of disassembly in remote debugging.
11266 @kindex show code-cache
11267 @item show code-cache
11268 Show the current state of target memory cache for code segment
11271 @kindex info dcache
11272 @item info dcache @r{[}line@r{]}
11273 Print the information about the performance of data cache of the
11274 current inferior's address space. The information displayed
11275 includes the dcache width and depth, and for each cache line, its
11276 number, address, and how many times it was referenced. This
11277 command is useful for debugging the data cache operation.
11279 If a line number is specified, the contents of that line will be
11282 @item set dcache size @var{size}
11283 @cindex dcache size
11284 @kindex set dcache size
11285 Set maximum number of entries in dcache (dcache depth above).
11287 @item set dcache line-size @var{line-size}
11288 @cindex dcache line-size
11289 @kindex set dcache line-size
11290 Set number of bytes each dcache entry caches (dcache width above).
11291 Must be a power of 2.
11293 @item show dcache size
11294 @kindex show dcache size
11295 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11297 @item show dcache line-size
11298 @kindex show dcache line-size
11299 Show default size of dcache lines.
11303 @node Searching Memory
11304 @section Search Memory
11305 @cindex searching memory
11307 Memory can be searched for a particular sequence of bytes with the
11308 @code{find} command.
11312 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11313 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11314 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11315 etc. The search begins at address @var{start_addr} and continues for either
11316 @var{len} bytes or through to @var{end_addr} inclusive.
11319 @var{s} and @var{n} are optional parameters.
11320 They may be specified in either order, apart or together.
11323 @item @var{s}, search query size
11324 The size of each search query value.
11330 halfwords (two bytes)
11334 giant words (eight bytes)
11337 All values are interpreted in the current language.
11338 This means, for example, that if the current source language is C/C@t{++}
11339 then searching for the string ``hello'' includes the trailing '\0'.
11341 If the value size is not specified, it is taken from the
11342 value's type in the current language.
11343 This is useful when one wants to specify the search
11344 pattern as a mixture of types.
11345 Note that this means, for example, that in the case of C-like languages
11346 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11347 which is typically four bytes.
11349 @item @var{n}, maximum number of finds
11350 The maximum number of matches to print. The default is to print all finds.
11353 You can use strings as search values. Quote them with double-quotes
11355 The string value is copied into the search pattern byte by byte,
11356 regardless of the endianness of the target and the size specification.
11358 The address of each match found is printed as well as a count of the
11359 number of matches found.
11361 The address of the last value found is stored in convenience variable
11363 A count of the number of matches is stored in @samp{$numfound}.
11365 For example, if stopped at the @code{printf} in this function:
11371 static char hello[] = "hello-hello";
11372 static struct @{ char c; short s; int i; @}
11373 __attribute__ ((packed)) mixed
11374 = @{ 'c', 0x1234, 0x87654321 @};
11375 printf ("%s\n", hello);
11380 you get during debugging:
11383 (gdb) find &hello[0], +sizeof(hello), "hello"
11384 0x804956d <hello.1620+6>
11386 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11387 0x8049567 <hello.1620>
11388 0x804956d <hello.1620+6>
11390 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11391 0x8049567 <hello.1620>
11393 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11394 0x8049560 <mixed.1625>
11396 (gdb) print $numfound
11399 $2 = (void *) 0x8049560
11402 @node Optimized Code
11403 @chapter Debugging Optimized Code
11404 @cindex optimized code, debugging
11405 @cindex debugging optimized code
11407 Almost all compilers support optimization. With optimization
11408 disabled, the compiler generates assembly code that corresponds
11409 directly to your source code, in a simplistic way. As the compiler
11410 applies more powerful optimizations, the generated assembly code
11411 diverges from your original source code. With help from debugging
11412 information generated by the compiler, @value{GDBN} can map from
11413 the running program back to constructs from your original source.
11415 @value{GDBN} is more accurate with optimization disabled. If you
11416 can recompile without optimization, it is easier to follow the
11417 progress of your program during debugging. But, there are many cases
11418 where you may need to debug an optimized version.
11420 When you debug a program compiled with @samp{-g -O}, remember that the
11421 optimizer has rearranged your code; the debugger shows you what is
11422 really there. Do not be too surprised when the execution path does not
11423 exactly match your source file! An extreme example: if you define a
11424 variable, but never use it, @value{GDBN} never sees that
11425 variable---because the compiler optimizes it out of existence.
11427 Some things do not work as well with @samp{-g -O} as with just
11428 @samp{-g}, particularly on machines with instruction scheduling. If in
11429 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11430 please report it to us as a bug (including a test case!).
11431 @xref{Variables}, for more information about debugging optimized code.
11434 * Inline Functions:: How @value{GDBN} presents inlining
11435 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11438 @node Inline Functions
11439 @section Inline Functions
11440 @cindex inline functions, debugging
11442 @dfn{Inlining} is an optimization that inserts a copy of the function
11443 body directly at each call site, instead of jumping to a shared
11444 routine. @value{GDBN} displays inlined functions just like
11445 non-inlined functions. They appear in backtraces. You can view their
11446 arguments and local variables, step into them with @code{step}, skip
11447 them with @code{next}, and escape from them with @code{finish}.
11448 You can check whether a function was inlined by using the
11449 @code{info frame} command.
11451 For @value{GDBN} to support inlined functions, the compiler must
11452 record information about inlining in the debug information ---
11453 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11454 other compilers do also. @value{GDBN} only supports inlined functions
11455 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11456 do not emit two required attributes (@samp{DW_AT_call_file} and
11457 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11458 function calls with earlier versions of @value{NGCC}. It instead
11459 displays the arguments and local variables of inlined functions as
11460 local variables in the caller.
11462 The body of an inlined function is directly included at its call site;
11463 unlike a non-inlined function, there are no instructions devoted to
11464 the call. @value{GDBN} still pretends that the call site and the
11465 start of the inlined function are different instructions. Stepping to
11466 the call site shows the call site, and then stepping again shows
11467 the first line of the inlined function, even though no additional
11468 instructions are executed.
11470 This makes source-level debugging much clearer; you can see both the
11471 context of the call and then the effect of the call. Only stepping by
11472 a single instruction using @code{stepi} or @code{nexti} does not do
11473 this; single instruction steps always show the inlined body.
11475 There are some ways that @value{GDBN} does not pretend that inlined
11476 function calls are the same as normal calls:
11480 Setting breakpoints at the call site of an inlined function may not
11481 work, because the call site does not contain any code. @value{GDBN}
11482 may incorrectly move the breakpoint to the next line of the enclosing
11483 function, after the call. This limitation will be removed in a future
11484 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11485 or inside the inlined function instead.
11488 @value{GDBN} cannot locate the return value of inlined calls after
11489 using the @code{finish} command. This is a limitation of compiler-generated
11490 debugging information; after @code{finish}, you can step to the next line
11491 and print a variable where your program stored the return value.
11495 @node Tail Call Frames
11496 @section Tail Call Frames
11497 @cindex tail call frames, debugging
11499 Function @code{B} can call function @code{C} in its very last statement. In
11500 unoptimized compilation the call of @code{C} is immediately followed by return
11501 instruction at the end of @code{B} code. Optimizing compiler may replace the
11502 call and return in function @code{B} into one jump to function @code{C}
11503 instead. Such use of a jump instruction is called @dfn{tail call}.
11505 During execution of function @code{C}, there will be no indication in the
11506 function call stack frames that it was tail-called from @code{B}. If function
11507 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11508 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11509 some cases @value{GDBN} can determine that @code{C} was tail-called from
11510 @code{B}, and it will then create fictitious call frame for that, with the
11511 return address set up as if @code{B} called @code{C} normally.
11513 This functionality is currently supported only by DWARF 2 debugging format and
11514 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11515 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11518 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11519 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11523 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11525 Stack level 1, frame at 0x7fffffffda30:
11526 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11527 tail call frame, caller of frame at 0x7fffffffda30
11528 source language c++.
11529 Arglist at unknown address.
11530 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11533 The detection of all the possible code path executions can find them ambiguous.
11534 There is no execution history stored (possible @ref{Reverse Execution} is never
11535 used for this purpose) and the last known caller could have reached the known
11536 callee by multiple different jump sequences. In such case @value{GDBN} still
11537 tries to show at least all the unambiguous top tail callers and all the
11538 unambiguous bottom tail calees, if any.
11541 @anchor{set debug entry-values}
11542 @item set debug entry-values
11543 @kindex set debug entry-values
11544 When set to on, enables printing of analysis messages for both frame argument
11545 values at function entry and tail calls. It will show all the possible valid
11546 tail calls code paths it has considered. It will also print the intersection
11547 of them with the final unambiguous (possibly partial or even empty) code path
11550 @item show debug entry-values
11551 @kindex show debug entry-values
11552 Show the current state of analysis messages printing for both frame argument
11553 values at function entry and tail calls.
11556 The analysis messages for tail calls can for example show why the virtual tail
11557 call frame for function @code{c} has not been recognized (due to the indirect
11558 reference by variable @code{x}):
11561 static void __attribute__((noinline, noclone)) c (void);
11562 void (*x) (void) = c;
11563 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11564 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11565 int main (void) @{ x (); return 0; @}
11567 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11568 DW_TAG_GNU_call_site 0x40039a in main
11570 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11573 #1 0x000000000040039a in main () at t.c:5
11576 Another possibility is an ambiguous virtual tail call frames resolution:
11580 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11581 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11582 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11583 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11584 static void __attribute__((noinline, noclone)) b (void)
11585 @{ if (i) c (); else e (); @}
11586 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11587 int main (void) @{ a (); return 0; @}
11589 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11590 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11591 tailcall: reduced: 0x4004d2(a) |
11594 #1 0x00000000004004d2 in a () at t.c:8
11595 #2 0x0000000000400395 in main () at t.c:9
11598 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11599 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11601 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11602 @ifset HAVE_MAKEINFO_CLICK
11603 @set ARROW @click{}
11604 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11605 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11607 @ifclear HAVE_MAKEINFO_CLICK
11609 @set CALLSEQ1B @value{CALLSEQ1A}
11610 @set CALLSEQ2B @value{CALLSEQ2A}
11613 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11614 The code can have possible execution paths @value{CALLSEQ1B} or
11615 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11617 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11618 has found. It then finds another possible calling sequcen - that one is
11619 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11620 printed as the @code{reduced:} calling sequence. That one could have many
11621 futher @code{compare:} and @code{reduced:} statements as long as there remain
11622 any non-ambiguous sequence entries.
11624 For the frame of function @code{b} in both cases there are different possible
11625 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11626 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11627 therefore this one is displayed to the user while the ambiguous frames are
11630 There can be also reasons why printing of frame argument values at function
11635 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11636 static void __attribute__((noinline, noclone)) a (int i);
11637 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11638 static void __attribute__((noinline, noclone)) a (int i)
11639 @{ if (i) b (i - 1); else c (0); @}
11640 int main (void) @{ a (5); return 0; @}
11643 #0 c (i=i@@entry=0) at t.c:2
11644 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11645 function "a" at 0x400420 can call itself via tail calls
11646 i=<optimized out>) at t.c:6
11647 #2 0x000000000040036e in main () at t.c:7
11650 @value{GDBN} cannot find out from the inferior state if and how many times did
11651 function @code{a} call itself (via function @code{b}) as these calls would be
11652 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11653 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11654 prints @code{<optimized out>} instead.
11657 @chapter C Preprocessor Macros
11659 Some languages, such as C and C@t{++}, provide a way to define and invoke
11660 ``preprocessor macros'' which expand into strings of tokens.
11661 @value{GDBN} can evaluate expressions containing macro invocations, show
11662 the result of macro expansion, and show a macro's definition, including
11663 where it was defined.
11665 You may need to compile your program specially to provide @value{GDBN}
11666 with information about preprocessor macros. Most compilers do not
11667 include macros in their debugging information, even when you compile
11668 with the @option{-g} flag. @xref{Compilation}.
11670 A program may define a macro at one point, remove that definition later,
11671 and then provide a different definition after that. Thus, at different
11672 points in the program, a macro may have different definitions, or have
11673 no definition at all. If there is a current stack frame, @value{GDBN}
11674 uses the macros in scope at that frame's source code line. Otherwise,
11675 @value{GDBN} uses the macros in scope at the current listing location;
11678 Whenever @value{GDBN} evaluates an expression, it always expands any
11679 macro invocations present in the expression. @value{GDBN} also provides
11680 the following commands for working with macros explicitly.
11684 @kindex macro expand
11685 @cindex macro expansion, showing the results of preprocessor
11686 @cindex preprocessor macro expansion, showing the results of
11687 @cindex expanding preprocessor macros
11688 @item macro expand @var{expression}
11689 @itemx macro exp @var{expression}
11690 Show the results of expanding all preprocessor macro invocations in
11691 @var{expression}. Since @value{GDBN} simply expands macros, but does
11692 not parse the result, @var{expression} need not be a valid expression;
11693 it can be any string of tokens.
11696 @item macro expand-once @var{expression}
11697 @itemx macro exp1 @var{expression}
11698 @cindex expand macro once
11699 @i{(This command is not yet implemented.)} Show the results of
11700 expanding those preprocessor macro invocations that appear explicitly in
11701 @var{expression}. Macro invocations appearing in that expansion are
11702 left unchanged. This command allows you to see the effect of a
11703 particular macro more clearly, without being confused by further
11704 expansions. Since @value{GDBN} simply expands macros, but does not
11705 parse the result, @var{expression} need not be a valid expression; it
11706 can be any string of tokens.
11709 @cindex macro definition, showing
11710 @cindex definition of a macro, showing
11711 @cindex macros, from debug info
11712 @item info macro [-a|-all] [--] @var{macro}
11713 Show the current definition or all definitions of the named @var{macro},
11714 and describe the source location or compiler command-line where that
11715 definition was established. The optional double dash is to signify the end of
11716 argument processing and the beginning of @var{macro} for non C-like macros where
11717 the macro may begin with a hyphen.
11719 @kindex info macros
11720 @item info macros @var{linespec}
11721 Show all macro definitions that are in effect at the location specified
11722 by @var{linespec}, and describe the source location or compiler
11723 command-line where those definitions were established.
11725 @kindex macro define
11726 @cindex user-defined macros
11727 @cindex defining macros interactively
11728 @cindex macros, user-defined
11729 @item macro define @var{macro} @var{replacement-list}
11730 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11731 Introduce a definition for a preprocessor macro named @var{macro},
11732 invocations of which are replaced by the tokens given in
11733 @var{replacement-list}. The first form of this command defines an
11734 ``object-like'' macro, which takes no arguments; the second form
11735 defines a ``function-like'' macro, which takes the arguments given in
11738 A definition introduced by this command is in scope in every
11739 expression evaluated in @value{GDBN}, until it is removed with the
11740 @code{macro undef} command, described below. The definition overrides
11741 all definitions for @var{macro} present in the program being debugged,
11742 as well as any previous user-supplied definition.
11744 @kindex macro undef
11745 @item macro undef @var{macro}
11746 Remove any user-supplied definition for the macro named @var{macro}.
11747 This command only affects definitions provided with the @code{macro
11748 define} command, described above; it cannot remove definitions present
11749 in the program being debugged.
11753 List all the macros defined using the @code{macro define} command.
11756 @cindex macros, example of debugging with
11757 Here is a transcript showing the above commands in action. First, we
11758 show our source files:
11763 #include "sample.h"
11766 #define ADD(x) (M + x)
11771 printf ("Hello, world!\n");
11773 printf ("We're so creative.\n");
11775 printf ("Goodbye, world!\n");
11782 Now, we compile the program using the @sc{gnu} C compiler,
11783 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11784 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11785 and @option{-gdwarf-4}; we recommend always choosing the most recent
11786 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11787 includes information about preprocessor macros in the debugging
11791 $ gcc -gdwarf-2 -g3 sample.c -o sample
11795 Now, we start @value{GDBN} on our sample program:
11799 GNU gdb 2002-05-06-cvs
11800 Copyright 2002 Free Software Foundation, Inc.
11801 GDB is free software, @dots{}
11805 We can expand macros and examine their definitions, even when the
11806 program is not running. @value{GDBN} uses the current listing position
11807 to decide which macro definitions are in scope:
11810 (@value{GDBP}) list main
11813 5 #define ADD(x) (M + x)
11818 10 printf ("Hello, world!\n");
11820 12 printf ("We're so creative.\n");
11821 (@value{GDBP}) info macro ADD
11822 Defined at /home/jimb/gdb/macros/play/sample.c:5
11823 #define ADD(x) (M + x)
11824 (@value{GDBP}) info macro Q
11825 Defined at /home/jimb/gdb/macros/play/sample.h:1
11826 included at /home/jimb/gdb/macros/play/sample.c:2
11828 (@value{GDBP}) macro expand ADD(1)
11829 expands to: (42 + 1)
11830 (@value{GDBP}) macro expand-once ADD(1)
11831 expands to: once (M + 1)
11835 In the example above, note that @code{macro expand-once} expands only
11836 the macro invocation explicit in the original text --- the invocation of
11837 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11838 which was introduced by @code{ADD}.
11840 Once the program is running, @value{GDBN} uses the macro definitions in
11841 force at the source line of the current stack frame:
11844 (@value{GDBP}) break main
11845 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11847 Starting program: /home/jimb/gdb/macros/play/sample
11849 Breakpoint 1, main () at sample.c:10
11850 10 printf ("Hello, world!\n");
11854 At line 10, the definition of the macro @code{N} at line 9 is in force:
11857 (@value{GDBP}) info macro N
11858 Defined at /home/jimb/gdb/macros/play/sample.c:9
11860 (@value{GDBP}) macro expand N Q M
11861 expands to: 28 < 42
11862 (@value{GDBP}) print N Q M
11867 As we step over directives that remove @code{N}'s definition, and then
11868 give it a new definition, @value{GDBN} finds the definition (or lack
11869 thereof) in force at each point:
11872 (@value{GDBP}) next
11874 12 printf ("We're so creative.\n");
11875 (@value{GDBP}) info macro N
11876 The symbol `N' has no definition as a C/C++ preprocessor macro
11877 at /home/jimb/gdb/macros/play/sample.c:12
11878 (@value{GDBP}) next
11880 14 printf ("Goodbye, world!\n");
11881 (@value{GDBP}) info macro N
11882 Defined at /home/jimb/gdb/macros/play/sample.c:13
11884 (@value{GDBP}) macro expand N Q M
11885 expands to: 1729 < 42
11886 (@value{GDBP}) print N Q M
11891 In addition to source files, macros can be defined on the compilation command
11892 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11893 such a way, @value{GDBN} displays the location of their definition as line zero
11894 of the source file submitted to the compiler.
11897 (@value{GDBP}) info macro __STDC__
11898 Defined at /home/jimb/gdb/macros/play/sample.c:0
11905 @chapter Tracepoints
11906 @c This chapter is based on the documentation written by Michael
11907 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11909 @cindex tracepoints
11910 In some applications, it is not feasible for the debugger to interrupt
11911 the program's execution long enough for the developer to learn
11912 anything helpful about its behavior. If the program's correctness
11913 depends on its real-time behavior, delays introduced by a debugger
11914 might cause the program to change its behavior drastically, or perhaps
11915 fail, even when the code itself is correct. It is useful to be able
11916 to observe the program's behavior without interrupting it.
11918 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11919 specify locations in the program, called @dfn{tracepoints}, and
11920 arbitrary expressions to evaluate when those tracepoints are reached.
11921 Later, using the @code{tfind} command, you can examine the values
11922 those expressions had when the program hit the tracepoints. The
11923 expressions may also denote objects in memory---structures or arrays,
11924 for example---whose values @value{GDBN} should record; while visiting
11925 a particular tracepoint, you may inspect those objects as if they were
11926 in memory at that moment. However, because @value{GDBN} records these
11927 values without interacting with you, it can do so quickly and
11928 unobtrusively, hopefully not disturbing the program's behavior.
11930 The tracepoint facility is currently available only for remote
11931 targets. @xref{Targets}. In addition, your remote target must know
11932 how to collect trace data. This functionality is implemented in the
11933 remote stub; however, none of the stubs distributed with @value{GDBN}
11934 support tracepoints as of this writing. The format of the remote
11935 packets used to implement tracepoints are described in @ref{Tracepoint
11938 It is also possible to get trace data from a file, in a manner reminiscent
11939 of corefiles; you specify the filename, and use @code{tfind} to search
11940 through the file. @xref{Trace Files}, for more details.
11942 This chapter describes the tracepoint commands and features.
11945 * Set Tracepoints::
11946 * Analyze Collected Data::
11947 * Tracepoint Variables::
11951 @node Set Tracepoints
11952 @section Commands to Set Tracepoints
11954 Before running such a @dfn{trace experiment}, an arbitrary number of
11955 tracepoints can be set. A tracepoint is actually a special type of
11956 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11957 standard breakpoint commands. For instance, as with breakpoints,
11958 tracepoint numbers are successive integers starting from one, and many
11959 of the commands associated with tracepoints take the tracepoint number
11960 as their argument, to identify which tracepoint to work on.
11962 For each tracepoint, you can specify, in advance, some arbitrary set
11963 of data that you want the target to collect in the trace buffer when
11964 it hits that tracepoint. The collected data can include registers,
11965 local variables, or global data. Later, you can use @value{GDBN}
11966 commands to examine the values these data had at the time the
11967 tracepoint was hit.
11969 Tracepoints do not support every breakpoint feature. Ignore counts on
11970 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11971 commands when they are hit. Tracepoints may not be thread-specific
11974 @cindex fast tracepoints
11975 Some targets may support @dfn{fast tracepoints}, which are inserted in
11976 a different way (such as with a jump instead of a trap), that is
11977 faster but possibly restricted in where they may be installed.
11979 @cindex static tracepoints
11980 @cindex markers, static tracepoints
11981 @cindex probing markers, static tracepoints
11982 Regular and fast tracepoints are dynamic tracing facilities, meaning
11983 that they can be used to insert tracepoints at (almost) any location
11984 in the target. Some targets may also support controlling @dfn{static
11985 tracepoints} from @value{GDBN}. With static tracing, a set of
11986 instrumentation points, also known as @dfn{markers}, are embedded in
11987 the target program, and can be activated or deactivated by name or
11988 address. These are usually placed at locations which facilitate
11989 investigating what the target is actually doing. @value{GDBN}'s
11990 support for static tracing includes being able to list instrumentation
11991 points, and attach them with @value{GDBN} defined high level
11992 tracepoints that expose the whole range of convenience of
11993 @value{GDBN}'s tracepoints support. Namely, support for collecting
11994 registers values and values of global or local (to the instrumentation
11995 point) variables; tracepoint conditions and trace state variables.
11996 The act of installing a @value{GDBN} static tracepoint on an
11997 instrumentation point, or marker, is referred to as @dfn{probing} a
11998 static tracepoint marker.
12000 @code{gdbserver} supports tracepoints on some target systems.
12001 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12003 This section describes commands to set tracepoints and associated
12004 conditions and actions.
12007 * Create and Delete Tracepoints::
12008 * Enable and Disable Tracepoints::
12009 * Tracepoint Passcounts::
12010 * Tracepoint Conditions::
12011 * Trace State Variables::
12012 * Tracepoint Actions::
12013 * Listing Tracepoints::
12014 * Listing Static Tracepoint Markers::
12015 * Starting and Stopping Trace Experiments::
12016 * Tracepoint Restrictions::
12019 @node Create and Delete Tracepoints
12020 @subsection Create and Delete Tracepoints
12023 @cindex set tracepoint
12025 @item trace @var{location}
12026 The @code{trace} command is very similar to the @code{break} command.
12027 Its argument @var{location} can be a source line, a function name, or
12028 an address in the target program. @xref{Specify Location}. The
12029 @code{trace} command defines a tracepoint, which is a point in the
12030 target program where the debugger will briefly stop, collect some
12031 data, and then allow the program to continue. Setting a tracepoint or
12032 changing its actions takes effect immediately if the remote stub
12033 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12035 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12036 these changes don't take effect until the next @code{tstart}
12037 command, and once a trace experiment is running, further changes will
12038 not have any effect until the next trace experiment starts. In addition,
12039 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12040 address is not yet resolved. (This is similar to pending breakpoints.)
12041 Pending tracepoints are not downloaded to the target and not installed
12042 until they are resolved. The resolution of pending tracepoints requires
12043 @value{GDBN} support---when debugging with the remote target, and
12044 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12045 tracing}), pending tracepoints can not be resolved (and downloaded to
12046 the remote stub) while @value{GDBN} is disconnected.
12048 Here are some examples of using the @code{trace} command:
12051 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12053 (@value{GDBP}) @b{trace +2} // 2 lines forward
12055 (@value{GDBP}) @b{trace my_function} // first source line of function
12057 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12059 (@value{GDBP}) @b{trace *0x2117c4} // an address
12063 You can abbreviate @code{trace} as @code{tr}.
12065 @item trace @var{location} if @var{cond}
12066 Set a tracepoint with condition @var{cond}; evaluate the expression
12067 @var{cond} each time the tracepoint is reached, and collect data only
12068 if the value is nonzero---that is, if @var{cond} evaluates as true.
12069 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12070 information on tracepoint conditions.
12072 @item ftrace @var{location} [ if @var{cond} ]
12073 @cindex set fast tracepoint
12074 @cindex fast tracepoints, setting
12076 The @code{ftrace} command sets a fast tracepoint. For targets that
12077 support them, fast tracepoints will use a more efficient but possibly
12078 less general technique to trigger data collection, such as a jump
12079 instruction instead of a trap, or some sort of hardware support. It
12080 may not be possible to create a fast tracepoint at the desired
12081 location, in which case the command will exit with an explanatory
12084 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12087 On 32-bit x86-architecture systems, fast tracepoints normally need to
12088 be placed at an instruction that is 5 bytes or longer, but can be
12089 placed at 4-byte instructions if the low 64K of memory of the target
12090 program is available to install trampolines. Some Unix-type systems,
12091 such as @sc{gnu}/Linux, exclude low addresses from the program's
12092 address space; but for instance with the Linux kernel it is possible
12093 to let @value{GDBN} use this area by doing a @command{sysctl} command
12094 to set the @code{mmap_min_addr} kernel parameter, as in
12097 sudo sysctl -w vm.mmap_min_addr=32768
12101 which sets the low address to 32K, which leaves plenty of room for
12102 trampolines. The minimum address should be set to a page boundary.
12104 @item strace @var{location} [ if @var{cond} ]
12105 @cindex set static tracepoint
12106 @cindex static tracepoints, setting
12107 @cindex probe static tracepoint marker
12109 The @code{strace} command sets a static tracepoint. For targets that
12110 support it, setting a static tracepoint probes a static
12111 instrumentation point, or marker, found at @var{location}. It may not
12112 be possible to set a static tracepoint at the desired location, in
12113 which case the command will exit with an explanatory message.
12115 @value{GDBN} handles arguments to @code{strace} exactly as for
12116 @code{trace}, with the addition that the user can also specify
12117 @code{-m @var{marker}} as @var{location}. This probes the marker
12118 identified by the @var{marker} string identifier. This identifier
12119 depends on the static tracepoint backend library your program is
12120 using. You can find all the marker identifiers in the @samp{ID} field
12121 of the @code{info static-tracepoint-markers} command output.
12122 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12123 Markers}. For example, in the following small program using the UST
12129 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12134 the marker id is composed of joining the first two arguments to the
12135 @code{trace_mark} call with a slash, which translates to:
12138 (@value{GDBP}) info static-tracepoint-markers
12139 Cnt Enb ID Address What
12140 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12146 so you may probe the marker above with:
12149 (@value{GDBP}) strace -m ust/bar33
12152 Static tracepoints accept an extra collect action --- @code{collect
12153 $_sdata}. This collects arbitrary user data passed in the probe point
12154 call to the tracing library. In the UST example above, you'll see
12155 that the third argument to @code{trace_mark} is a printf-like format
12156 string. The user data is then the result of running that formating
12157 string against the following arguments. Note that @code{info
12158 static-tracepoint-markers} command output lists that format string in
12159 the @samp{Data:} field.
12161 You can inspect this data when analyzing the trace buffer, by printing
12162 the $_sdata variable like any other variable available to
12163 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12166 @cindex last tracepoint number
12167 @cindex recent tracepoint number
12168 @cindex tracepoint number
12169 The convenience variable @code{$tpnum} records the tracepoint number
12170 of the most recently set tracepoint.
12172 @kindex delete tracepoint
12173 @cindex tracepoint deletion
12174 @item delete tracepoint @r{[}@var{num}@r{]}
12175 Permanently delete one or more tracepoints. With no argument, the
12176 default is to delete all tracepoints. Note that the regular
12177 @code{delete} command can remove tracepoints also.
12182 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12184 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12188 You can abbreviate this command as @code{del tr}.
12191 @node Enable and Disable Tracepoints
12192 @subsection Enable and Disable Tracepoints
12194 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12197 @kindex disable tracepoint
12198 @item disable tracepoint @r{[}@var{num}@r{]}
12199 Disable tracepoint @var{num}, or all tracepoints if no argument
12200 @var{num} is given. A disabled tracepoint will have no effect during
12201 a trace experiment, but it is not forgotten. You can re-enable
12202 a disabled tracepoint using the @code{enable tracepoint} command.
12203 If the command is issued during a trace experiment and the debug target
12204 has support for disabling tracepoints during a trace experiment, then the
12205 change will be effective immediately. Otherwise, it will be applied to the
12206 next trace experiment.
12208 @kindex enable tracepoint
12209 @item enable tracepoint @r{[}@var{num}@r{]}
12210 Enable tracepoint @var{num}, or all tracepoints. If this command is
12211 issued during a trace experiment and the debug target supports enabling
12212 tracepoints during a trace experiment, then the enabled tracepoints will
12213 become effective immediately. Otherwise, they will become effective the
12214 next time a trace experiment is run.
12217 @node Tracepoint Passcounts
12218 @subsection Tracepoint Passcounts
12222 @cindex tracepoint pass count
12223 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12224 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12225 automatically stop a trace experiment. If a tracepoint's passcount is
12226 @var{n}, then the trace experiment will be automatically stopped on
12227 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12228 @var{num} is not specified, the @code{passcount} command sets the
12229 passcount of the most recently defined tracepoint. If no passcount is
12230 given, the trace experiment will run until stopped explicitly by the
12236 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12237 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12239 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12240 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12241 (@value{GDBP}) @b{trace foo}
12242 (@value{GDBP}) @b{pass 3}
12243 (@value{GDBP}) @b{trace bar}
12244 (@value{GDBP}) @b{pass 2}
12245 (@value{GDBP}) @b{trace baz}
12246 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12247 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12248 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12249 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12253 @node Tracepoint Conditions
12254 @subsection Tracepoint Conditions
12255 @cindex conditional tracepoints
12256 @cindex tracepoint conditions
12258 The simplest sort of tracepoint collects data every time your program
12259 reaches a specified place. You can also specify a @dfn{condition} for
12260 a tracepoint. A condition is just a Boolean expression in your
12261 programming language (@pxref{Expressions, ,Expressions}). A
12262 tracepoint with a condition evaluates the expression each time your
12263 program reaches it, and data collection happens only if the condition
12266 Tracepoint conditions can be specified when a tracepoint is set, by
12267 using @samp{if} in the arguments to the @code{trace} command.
12268 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12269 also be set or changed at any time with the @code{condition} command,
12270 just as with breakpoints.
12272 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12273 the conditional expression itself. Instead, @value{GDBN} encodes the
12274 expression into an agent expression (@pxref{Agent Expressions})
12275 suitable for execution on the target, independently of @value{GDBN}.
12276 Global variables become raw memory locations, locals become stack
12277 accesses, and so forth.
12279 For instance, suppose you have a function that is usually called
12280 frequently, but should not be called after an error has occurred. You
12281 could use the following tracepoint command to collect data about calls
12282 of that function that happen while the error code is propagating
12283 through the program; an unconditional tracepoint could end up
12284 collecting thousands of useless trace frames that you would have to
12288 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12291 @node Trace State Variables
12292 @subsection Trace State Variables
12293 @cindex trace state variables
12295 A @dfn{trace state variable} is a special type of variable that is
12296 created and managed by target-side code. The syntax is the same as
12297 that for GDB's convenience variables (a string prefixed with ``$''),
12298 but they are stored on the target. They must be created explicitly,
12299 using a @code{tvariable} command. They are always 64-bit signed
12302 Trace state variables are remembered by @value{GDBN}, and downloaded
12303 to the target along with tracepoint information when the trace
12304 experiment starts. There are no intrinsic limits on the number of
12305 trace state variables, beyond memory limitations of the target.
12307 @cindex convenience variables, and trace state variables
12308 Although trace state variables are managed by the target, you can use
12309 them in print commands and expressions as if they were convenience
12310 variables; @value{GDBN} will get the current value from the target
12311 while the trace experiment is running. Trace state variables share
12312 the same namespace as other ``$'' variables, which means that you
12313 cannot have trace state variables with names like @code{$23} or
12314 @code{$pc}, nor can you have a trace state variable and a convenience
12315 variable with the same name.
12319 @item tvariable $@var{name} [ = @var{expression} ]
12321 The @code{tvariable} command creates a new trace state variable named
12322 @code{$@var{name}}, and optionally gives it an initial value of
12323 @var{expression}. The @var{expression} is evaluated when this command is
12324 entered; the result will be converted to an integer if possible,
12325 otherwise @value{GDBN} will report an error. A subsequent
12326 @code{tvariable} command specifying the same name does not create a
12327 variable, but instead assigns the supplied initial value to the
12328 existing variable of that name, overwriting any previous initial
12329 value. The default initial value is 0.
12331 @item info tvariables
12332 @kindex info tvariables
12333 List all the trace state variables along with their initial values.
12334 Their current values may also be displayed, if the trace experiment is
12337 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12338 @kindex delete tvariable
12339 Delete the given trace state variables, or all of them if no arguments
12344 @node Tracepoint Actions
12345 @subsection Tracepoint Action Lists
12349 @cindex tracepoint actions
12350 @item actions @r{[}@var{num}@r{]}
12351 This command will prompt for a list of actions to be taken when the
12352 tracepoint is hit. If the tracepoint number @var{num} is not
12353 specified, this command sets the actions for the one that was most
12354 recently defined (so that you can define a tracepoint and then say
12355 @code{actions} without bothering about its number). You specify the
12356 actions themselves on the following lines, one action at a time, and
12357 terminate the actions list with a line containing just @code{end}. So
12358 far, the only defined actions are @code{collect}, @code{teval}, and
12359 @code{while-stepping}.
12361 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12362 Commands, ,Breakpoint Command Lists}), except that only the defined
12363 actions are allowed; any other @value{GDBN} command is rejected.
12365 @cindex remove actions from a tracepoint
12366 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12367 and follow it immediately with @samp{end}.
12370 (@value{GDBP}) @b{collect @var{data}} // collect some data
12372 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12374 (@value{GDBP}) @b{end} // signals the end of actions.
12377 In the following example, the action list begins with @code{collect}
12378 commands indicating the things to be collected when the tracepoint is
12379 hit. Then, in order to single-step and collect additional data
12380 following the tracepoint, a @code{while-stepping} command is used,
12381 followed by the list of things to be collected after each step in a
12382 sequence of single steps. The @code{while-stepping} command is
12383 terminated by its own separate @code{end} command. Lastly, the action
12384 list is terminated by an @code{end} command.
12387 (@value{GDBP}) @b{trace foo}
12388 (@value{GDBP}) @b{actions}
12389 Enter actions for tracepoint 1, one per line:
12392 > while-stepping 12
12393 > collect $pc, arr[i]
12398 @kindex collect @r{(tracepoints)}
12399 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12400 Collect values of the given expressions when the tracepoint is hit.
12401 This command accepts a comma-separated list of any valid expressions.
12402 In addition to global, static, or local variables, the following
12403 special arguments are supported:
12407 Collect all registers.
12410 Collect all function arguments.
12413 Collect all local variables.
12416 Collect the return address. This is helpful if you want to see more
12420 Collects the number of arguments from the static probe at which the
12421 tracepoint is located.
12422 @xref{Static Probe Points}.
12424 @item $_probe_arg@var{n}
12425 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12426 from the static probe at which the tracepoint is located.
12427 @xref{Static Probe Points}.
12430 @vindex $_sdata@r{, collect}
12431 Collect static tracepoint marker specific data. Only available for
12432 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12433 Lists}. On the UST static tracepoints library backend, an
12434 instrumentation point resembles a @code{printf} function call. The
12435 tracing library is able to collect user specified data formatted to a
12436 character string using the format provided by the programmer that
12437 instrumented the program. Other backends have similar mechanisms.
12438 Here's an example of a UST marker call:
12441 const char master_name[] = "$your_name";
12442 trace_mark(channel1, marker1, "hello %s", master_name)
12445 In this case, collecting @code{$_sdata} collects the string
12446 @samp{hello $yourname}. When analyzing the trace buffer, you can
12447 inspect @samp{$_sdata} like any other variable available to
12451 You can give several consecutive @code{collect} commands, each one
12452 with a single argument, or one @code{collect} command with several
12453 arguments separated by commas; the effect is the same.
12455 The optional @var{mods} changes the usual handling of the arguments.
12456 @code{s} requests that pointers to chars be handled as strings, in
12457 particular collecting the contents of the memory being pointed at, up
12458 to the first zero. The upper bound is by default the value of the
12459 @code{print elements} variable; if @code{s} is followed by a decimal
12460 number, that is the upper bound instead. So for instance
12461 @samp{collect/s25 mystr} collects as many as 25 characters at
12464 The command @code{info scope} (@pxref{Symbols, info scope}) is
12465 particularly useful for figuring out what data to collect.
12467 @kindex teval @r{(tracepoints)}
12468 @item teval @var{expr1}, @var{expr2}, @dots{}
12469 Evaluate the given expressions when the tracepoint is hit. This
12470 command accepts a comma-separated list of expressions. The results
12471 are discarded, so this is mainly useful for assigning values to trace
12472 state variables (@pxref{Trace State Variables}) without adding those
12473 values to the trace buffer, as would be the case if the @code{collect}
12476 @kindex while-stepping @r{(tracepoints)}
12477 @item while-stepping @var{n}
12478 Perform @var{n} single-step instruction traces after the tracepoint,
12479 collecting new data after each step. The @code{while-stepping}
12480 command is followed by the list of what to collect while stepping
12481 (followed by its own @code{end} command):
12484 > while-stepping 12
12485 > collect $regs, myglobal
12491 Note that @code{$pc} is not automatically collected by
12492 @code{while-stepping}; you need to explicitly collect that register if
12493 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12496 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12497 @kindex set default-collect
12498 @cindex default collection action
12499 This variable is a list of expressions to collect at each tracepoint
12500 hit. It is effectively an additional @code{collect} action prepended
12501 to every tracepoint action list. The expressions are parsed
12502 individually for each tracepoint, so for instance a variable named
12503 @code{xyz} may be interpreted as a global for one tracepoint, and a
12504 local for another, as appropriate to the tracepoint's location.
12506 @item show default-collect
12507 @kindex show default-collect
12508 Show the list of expressions that are collected by default at each
12513 @node Listing Tracepoints
12514 @subsection Listing Tracepoints
12517 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12518 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12519 @cindex information about tracepoints
12520 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12521 Display information about the tracepoint @var{num}. If you don't
12522 specify a tracepoint number, displays information about all the
12523 tracepoints defined so far. The format is similar to that used for
12524 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12525 command, simply restricting itself to tracepoints.
12527 A tracepoint's listing may include additional information specific to
12532 its passcount as given by the @code{passcount @var{n}} command
12535 the state about installed on target of each location
12539 (@value{GDBP}) @b{info trace}
12540 Num Type Disp Enb Address What
12541 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12543 collect globfoo, $regs
12548 2 tracepoint keep y <MULTIPLE>
12550 2.1 y 0x0804859c in func4 at change-loc.h:35
12551 installed on target
12552 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12553 installed on target
12554 2.3 y <PENDING> set_tracepoint
12555 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12556 not installed on target
12561 This command can be abbreviated @code{info tp}.
12564 @node Listing Static Tracepoint Markers
12565 @subsection Listing Static Tracepoint Markers
12568 @kindex info static-tracepoint-markers
12569 @cindex information about static tracepoint markers
12570 @item info static-tracepoint-markers
12571 Display information about all static tracepoint markers defined in the
12574 For each marker, the following columns are printed:
12578 An incrementing counter, output to help readability. This is not a
12581 The marker ID, as reported by the target.
12582 @item Enabled or Disabled
12583 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12584 that are not enabled.
12586 Where the marker is in your program, as a memory address.
12588 Where the marker is in the source for your program, as a file and line
12589 number. If the debug information included in the program does not
12590 allow @value{GDBN} to locate the source of the marker, this column
12591 will be left blank.
12595 In addition, the following information may be printed for each marker:
12599 User data passed to the tracing library by the marker call. In the
12600 UST backend, this is the format string passed as argument to the
12602 @item Static tracepoints probing the marker
12603 The list of static tracepoints attached to the marker.
12607 (@value{GDBP}) info static-tracepoint-markers
12608 Cnt ID Enb Address What
12609 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12610 Data: number1 %d number2 %d
12611 Probed by static tracepoints: #2
12612 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12618 @node Starting and Stopping Trace Experiments
12619 @subsection Starting and Stopping Trace Experiments
12622 @kindex tstart [ @var{notes} ]
12623 @cindex start a new trace experiment
12624 @cindex collected data discarded
12626 This command starts the trace experiment, and begins collecting data.
12627 It has the side effect of discarding all the data collected in the
12628 trace buffer during the previous trace experiment. If any arguments
12629 are supplied, they are taken as a note and stored with the trace
12630 experiment's state. The notes may be arbitrary text, and are
12631 especially useful with disconnected tracing in a multi-user context;
12632 the notes can explain what the trace is doing, supply user contact
12633 information, and so forth.
12635 @kindex tstop [ @var{notes} ]
12636 @cindex stop a running trace experiment
12638 This command stops the trace experiment. If any arguments are
12639 supplied, they are recorded with the experiment as a note. This is
12640 useful if you are stopping a trace started by someone else, for
12641 instance if the trace is interfering with the system's behavior and
12642 needs to be stopped quickly.
12644 @strong{Note}: a trace experiment and data collection may stop
12645 automatically if any tracepoint's passcount is reached
12646 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12649 @cindex status of trace data collection
12650 @cindex trace experiment, status of
12652 This command displays the status of the current trace data
12656 Here is an example of the commands we described so far:
12659 (@value{GDBP}) @b{trace gdb_c_test}
12660 (@value{GDBP}) @b{actions}
12661 Enter actions for tracepoint #1, one per line.
12662 > collect $regs,$locals,$args
12663 > while-stepping 11
12667 (@value{GDBP}) @b{tstart}
12668 [time passes @dots{}]
12669 (@value{GDBP}) @b{tstop}
12672 @anchor{disconnected tracing}
12673 @cindex disconnected tracing
12674 You can choose to continue running the trace experiment even if
12675 @value{GDBN} disconnects from the target, voluntarily or
12676 involuntarily. For commands such as @code{detach}, the debugger will
12677 ask what you want to do with the trace. But for unexpected
12678 terminations (@value{GDBN} crash, network outage), it would be
12679 unfortunate to lose hard-won trace data, so the variable
12680 @code{disconnected-tracing} lets you decide whether the trace should
12681 continue running without @value{GDBN}.
12684 @item set disconnected-tracing on
12685 @itemx set disconnected-tracing off
12686 @kindex set disconnected-tracing
12687 Choose whether a tracing run should continue to run if @value{GDBN}
12688 has disconnected from the target. Note that @code{detach} or
12689 @code{quit} will ask you directly what to do about a running trace no
12690 matter what this variable's setting, so the variable is mainly useful
12691 for handling unexpected situations, such as loss of the network.
12693 @item show disconnected-tracing
12694 @kindex show disconnected-tracing
12695 Show the current choice for disconnected tracing.
12699 When you reconnect to the target, the trace experiment may or may not
12700 still be running; it might have filled the trace buffer in the
12701 meantime, or stopped for one of the other reasons. If it is running,
12702 it will continue after reconnection.
12704 Upon reconnection, the target will upload information about the
12705 tracepoints in effect. @value{GDBN} will then compare that
12706 information to the set of tracepoints currently defined, and attempt
12707 to match them up, allowing for the possibility that the numbers may
12708 have changed due to creation and deletion in the meantime. If one of
12709 the target's tracepoints does not match any in @value{GDBN}, the
12710 debugger will create a new tracepoint, so that you have a number with
12711 which to specify that tracepoint. This matching-up process is
12712 necessarily heuristic, and it may result in useless tracepoints being
12713 created; you may simply delete them if they are of no use.
12715 @cindex circular trace buffer
12716 If your target agent supports a @dfn{circular trace buffer}, then you
12717 can run a trace experiment indefinitely without filling the trace
12718 buffer; when space runs out, the agent deletes already-collected trace
12719 frames, oldest first, until there is enough room to continue
12720 collecting. This is especially useful if your tracepoints are being
12721 hit too often, and your trace gets terminated prematurely because the
12722 buffer is full. To ask for a circular trace buffer, simply set
12723 @samp{circular-trace-buffer} to on. You can set this at any time,
12724 including during tracing; if the agent can do it, it will change
12725 buffer handling on the fly, otherwise it will not take effect until
12729 @item set circular-trace-buffer on
12730 @itemx set circular-trace-buffer off
12731 @kindex set circular-trace-buffer
12732 Choose whether a tracing run should use a linear or circular buffer
12733 for trace data. A linear buffer will not lose any trace data, but may
12734 fill up prematurely, while a circular buffer will discard old trace
12735 data, but it will have always room for the latest tracepoint hits.
12737 @item show circular-trace-buffer
12738 @kindex show circular-trace-buffer
12739 Show the current choice for the trace buffer. Note that this may not
12740 match the agent's current buffer handling, nor is it guaranteed to
12741 match the setting that might have been in effect during a past run,
12742 for instance if you are looking at frames from a trace file.
12747 @item set trace-buffer-size @var{n}
12748 @itemx set trace-buffer-size unlimited
12749 @kindex set trace-buffer-size
12750 Request that the target use a trace buffer of @var{n} bytes. Not all
12751 targets will honor the request; they may have a compiled-in size for
12752 the trace buffer, or some other limitation. Set to a value of
12753 @code{unlimited} or @code{-1} to let the target use whatever size it
12754 likes. This is also the default.
12756 @item show trace-buffer-size
12757 @kindex show trace-buffer-size
12758 Show the current requested size for the trace buffer. Note that this
12759 will only match the actual size if the target supports size-setting,
12760 and was able to handle the requested size. For instance, if the
12761 target can only change buffer size between runs, this variable will
12762 not reflect the change until the next run starts. Use @code{tstatus}
12763 to get a report of the actual buffer size.
12767 @item set trace-user @var{text}
12768 @kindex set trace-user
12770 @item show trace-user
12771 @kindex show trace-user
12773 @item set trace-notes @var{text}
12774 @kindex set trace-notes
12775 Set the trace run's notes.
12777 @item show trace-notes
12778 @kindex show trace-notes
12779 Show the trace run's notes.
12781 @item set trace-stop-notes @var{text}
12782 @kindex set trace-stop-notes
12783 Set the trace run's stop notes. The handling of the note is as for
12784 @code{tstop} arguments; the set command is convenient way to fix a
12785 stop note that is mistaken or incomplete.
12787 @item show trace-stop-notes
12788 @kindex show trace-stop-notes
12789 Show the trace run's stop notes.
12793 @node Tracepoint Restrictions
12794 @subsection Tracepoint Restrictions
12796 @cindex tracepoint restrictions
12797 There are a number of restrictions on the use of tracepoints. As
12798 described above, tracepoint data gathering occurs on the target
12799 without interaction from @value{GDBN}. Thus the full capabilities of
12800 the debugger are not available during data gathering, and then at data
12801 examination time, you will be limited by only having what was
12802 collected. The following items describe some common problems, but it
12803 is not exhaustive, and you may run into additional difficulties not
12809 Tracepoint expressions are intended to gather objects (lvalues). Thus
12810 the full flexibility of GDB's expression evaluator is not available.
12811 You cannot call functions, cast objects to aggregate types, access
12812 convenience variables or modify values (except by assignment to trace
12813 state variables). Some language features may implicitly call
12814 functions (for instance Objective-C fields with accessors), and therefore
12815 cannot be collected either.
12818 Collection of local variables, either individually or in bulk with
12819 @code{$locals} or @code{$args}, during @code{while-stepping} may
12820 behave erratically. The stepping action may enter a new scope (for
12821 instance by stepping into a function), or the location of the variable
12822 may change (for instance it is loaded into a register). The
12823 tracepoint data recorded uses the location information for the
12824 variables that is correct for the tracepoint location. When the
12825 tracepoint is created, it is not possible, in general, to determine
12826 where the steps of a @code{while-stepping} sequence will advance the
12827 program---particularly if a conditional branch is stepped.
12830 Collection of an incompletely-initialized or partially-destroyed object
12831 may result in something that @value{GDBN} cannot display, or displays
12832 in a misleading way.
12835 When @value{GDBN} displays a pointer to character it automatically
12836 dereferences the pointer to also display characters of the string
12837 being pointed to. However, collecting the pointer during tracing does
12838 not automatically collect the string. You need to explicitly
12839 dereference the pointer and provide size information if you want to
12840 collect not only the pointer, but the memory pointed to. For example,
12841 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12845 It is not possible to collect a complete stack backtrace at a
12846 tracepoint. Instead, you may collect the registers and a few hundred
12847 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12848 (adjust to use the name of the actual stack pointer register on your
12849 target architecture, and the amount of stack you wish to capture).
12850 Then the @code{backtrace} command will show a partial backtrace when
12851 using a trace frame. The number of stack frames that can be examined
12852 depends on the sizes of the frames in the collected stack. Note that
12853 if you ask for a block so large that it goes past the bottom of the
12854 stack, the target agent may report an error trying to read from an
12858 If you do not collect registers at a tracepoint, @value{GDBN} can
12859 infer that the value of @code{$pc} must be the same as the address of
12860 the tracepoint and use that when you are looking at a trace frame
12861 for that tracepoint. However, this cannot work if the tracepoint has
12862 multiple locations (for instance if it was set in a function that was
12863 inlined), or if it has a @code{while-stepping} loop. In those cases
12864 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12869 @node Analyze Collected Data
12870 @section Using the Collected Data
12872 After the tracepoint experiment ends, you use @value{GDBN} commands
12873 for examining the trace data. The basic idea is that each tracepoint
12874 collects a trace @dfn{snapshot} every time it is hit and another
12875 snapshot every time it single-steps. All these snapshots are
12876 consecutively numbered from zero and go into a buffer, and you can
12877 examine them later. The way you examine them is to @dfn{focus} on a
12878 specific trace snapshot. When the remote stub is focused on a trace
12879 snapshot, it will respond to all @value{GDBN} requests for memory and
12880 registers by reading from the buffer which belongs to that snapshot,
12881 rather than from @emph{real} memory or registers of the program being
12882 debugged. This means that @strong{all} @value{GDBN} commands
12883 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12884 behave as if we were currently debugging the program state as it was
12885 when the tracepoint occurred. Any requests for data that are not in
12886 the buffer will fail.
12889 * tfind:: How to select a trace snapshot
12890 * tdump:: How to display all data for a snapshot
12891 * save tracepoints:: How to save tracepoints for a future run
12895 @subsection @code{tfind @var{n}}
12898 @cindex select trace snapshot
12899 @cindex find trace snapshot
12900 The basic command for selecting a trace snapshot from the buffer is
12901 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12902 counting from zero. If no argument @var{n} is given, the next
12903 snapshot is selected.
12905 Here are the various forms of using the @code{tfind} command.
12909 Find the first snapshot in the buffer. This is a synonym for
12910 @code{tfind 0} (since 0 is the number of the first snapshot).
12913 Stop debugging trace snapshots, resume @emph{live} debugging.
12916 Same as @samp{tfind none}.
12919 No argument means find the next trace snapshot.
12922 Find the previous trace snapshot before the current one. This permits
12923 retracing earlier steps.
12925 @item tfind tracepoint @var{num}
12926 Find the next snapshot associated with tracepoint @var{num}. Search
12927 proceeds forward from the last examined trace snapshot. If no
12928 argument @var{num} is given, it means find the next snapshot collected
12929 for the same tracepoint as the current snapshot.
12931 @item tfind pc @var{addr}
12932 Find the next snapshot associated with the value @var{addr} of the
12933 program counter. Search proceeds forward from the last examined trace
12934 snapshot. If no argument @var{addr} is given, it means find the next
12935 snapshot with the same value of PC as the current snapshot.
12937 @item tfind outside @var{addr1}, @var{addr2}
12938 Find the next snapshot whose PC is outside the given range of
12939 addresses (exclusive).
12941 @item tfind range @var{addr1}, @var{addr2}
12942 Find the next snapshot whose PC is between @var{addr1} and
12943 @var{addr2} (inclusive).
12945 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12946 Find the next snapshot associated with the source line @var{n}. If
12947 the optional argument @var{file} is given, refer to line @var{n} in
12948 that source file. Search proceeds forward from the last examined
12949 trace snapshot. If no argument @var{n} is given, it means find the
12950 next line other than the one currently being examined; thus saying
12951 @code{tfind line} repeatedly can appear to have the same effect as
12952 stepping from line to line in a @emph{live} debugging session.
12955 The default arguments for the @code{tfind} commands are specifically
12956 designed to make it easy to scan through the trace buffer. For
12957 instance, @code{tfind} with no argument selects the next trace
12958 snapshot, and @code{tfind -} with no argument selects the previous
12959 trace snapshot. So, by giving one @code{tfind} command, and then
12960 simply hitting @key{RET} repeatedly you can examine all the trace
12961 snapshots in order. Or, by saying @code{tfind -} and then hitting
12962 @key{RET} repeatedly you can examine the snapshots in reverse order.
12963 The @code{tfind line} command with no argument selects the snapshot
12964 for the next source line executed. The @code{tfind pc} command with
12965 no argument selects the next snapshot with the same program counter
12966 (PC) as the current frame. The @code{tfind tracepoint} command with
12967 no argument selects the next trace snapshot collected by the same
12968 tracepoint as the current one.
12970 In addition to letting you scan through the trace buffer manually,
12971 these commands make it easy to construct @value{GDBN} scripts that
12972 scan through the trace buffer and print out whatever collected data
12973 you are interested in. Thus, if we want to examine the PC, FP, and SP
12974 registers from each trace frame in the buffer, we can say this:
12977 (@value{GDBP}) @b{tfind start}
12978 (@value{GDBP}) @b{while ($trace_frame != -1)}
12979 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12980 $trace_frame, $pc, $sp, $fp
12984 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12985 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12986 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12987 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12988 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12989 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12990 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12991 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12992 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12993 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12994 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12997 Or, if we want to examine the variable @code{X} at each source line in
13001 (@value{GDBP}) @b{tfind start}
13002 (@value{GDBP}) @b{while ($trace_frame != -1)}
13003 > printf "Frame %d, X == %d\n", $trace_frame, X
13013 @subsection @code{tdump}
13015 @cindex dump all data collected at tracepoint
13016 @cindex tracepoint data, display
13018 This command takes no arguments. It prints all the data collected at
13019 the current trace snapshot.
13022 (@value{GDBP}) @b{trace 444}
13023 (@value{GDBP}) @b{actions}
13024 Enter actions for tracepoint #2, one per line:
13025 > collect $regs, $locals, $args, gdb_long_test
13028 (@value{GDBP}) @b{tstart}
13030 (@value{GDBP}) @b{tfind line 444}
13031 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13033 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13035 (@value{GDBP}) @b{tdump}
13036 Data collected at tracepoint 2, trace frame 1:
13037 d0 0xc4aa0085 -995491707
13041 d4 0x71aea3d 119204413
13044 d7 0x380035 3670069
13045 a0 0x19e24a 1696330
13046 a1 0x3000668 50333288
13048 a3 0x322000 3284992
13049 a4 0x3000698 50333336
13050 a5 0x1ad3cc 1758156
13051 fp 0x30bf3c 0x30bf3c
13052 sp 0x30bf34 0x30bf34
13054 pc 0x20b2c8 0x20b2c8
13058 p = 0x20e5b4 "gdb-test"
13065 gdb_long_test = 17 '\021'
13070 @code{tdump} works by scanning the tracepoint's current collection
13071 actions and printing the value of each expression listed. So
13072 @code{tdump} can fail, if after a run, you change the tracepoint's
13073 actions to mention variables that were not collected during the run.
13075 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13076 uses the collected value of @code{$pc} to distinguish between trace
13077 frames that were collected at the tracepoint hit, and frames that were
13078 collected while stepping. This allows it to correctly choose whether
13079 to display the basic list of collections, or the collections from the
13080 body of the while-stepping loop. However, if @code{$pc} was not collected,
13081 then @code{tdump} will always attempt to dump using the basic collection
13082 list, and may fail if a while-stepping frame does not include all the
13083 same data that is collected at the tracepoint hit.
13084 @c This is getting pretty arcane, example would be good.
13086 @node save tracepoints
13087 @subsection @code{save tracepoints @var{filename}}
13088 @kindex save tracepoints
13089 @kindex save-tracepoints
13090 @cindex save tracepoints for future sessions
13092 This command saves all current tracepoint definitions together with
13093 their actions and passcounts, into a file @file{@var{filename}}
13094 suitable for use in a later debugging session. To read the saved
13095 tracepoint definitions, use the @code{source} command (@pxref{Command
13096 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13097 alias for @w{@code{save tracepoints}}
13099 @node Tracepoint Variables
13100 @section Convenience Variables for Tracepoints
13101 @cindex tracepoint variables
13102 @cindex convenience variables for tracepoints
13105 @vindex $trace_frame
13106 @item (int) $trace_frame
13107 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13108 snapshot is selected.
13110 @vindex $tracepoint
13111 @item (int) $tracepoint
13112 The tracepoint for the current trace snapshot.
13114 @vindex $trace_line
13115 @item (int) $trace_line
13116 The line number for the current trace snapshot.
13118 @vindex $trace_file
13119 @item (char []) $trace_file
13120 The source file for the current trace snapshot.
13122 @vindex $trace_func
13123 @item (char []) $trace_func
13124 The name of the function containing @code{$tracepoint}.
13127 Note: @code{$trace_file} is not suitable for use in @code{printf},
13128 use @code{output} instead.
13130 Here's a simple example of using these convenience variables for
13131 stepping through all the trace snapshots and printing some of their
13132 data. Note that these are not the same as trace state variables,
13133 which are managed by the target.
13136 (@value{GDBP}) @b{tfind start}
13138 (@value{GDBP}) @b{while $trace_frame != -1}
13139 > output $trace_file
13140 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13146 @section Using Trace Files
13147 @cindex trace files
13149 In some situations, the target running a trace experiment may no
13150 longer be available; perhaps it crashed, or the hardware was needed
13151 for a different activity. To handle these cases, you can arrange to
13152 dump the trace data into a file, and later use that file as a source
13153 of trace data, via the @code{target tfile} command.
13158 @item tsave [ -r ] @var{filename}
13159 @itemx tsave [-ctf] @var{dirname}
13160 Save the trace data to @var{filename}. By default, this command
13161 assumes that @var{filename} refers to the host filesystem, so if
13162 necessary @value{GDBN} will copy raw trace data up from the target and
13163 then save it. If the target supports it, you can also supply the
13164 optional argument @code{-r} (``remote'') to direct the target to save
13165 the data directly into @var{filename} in its own filesystem, which may be
13166 more efficient if the trace buffer is very large. (Note, however, that
13167 @code{target tfile} can only read from files accessible to the host.)
13168 By default, this command will save trace frame in tfile format.
13169 You can supply the optional argument @code{-ctf} to save date in CTF
13170 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13171 that can be shared by multiple debugging and tracing tools. Please go to
13172 @indicateurl{http://www.efficios.com/ctf} to get more information.
13174 @kindex target tfile
13178 @item target tfile @var{filename}
13179 @itemx target ctf @var{dirname}
13180 Use the file named @var{filename} or directory named @var{dirname} as
13181 a source of trace data. Commands that examine data work as they do with
13182 a live target, but it is not possible to run any new trace experiments.
13183 @code{tstatus} will report the state of the trace run at the moment
13184 the data was saved, as well as the current trace frame you are examining.
13185 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13189 (@value{GDBP}) target ctf ctf.ctf
13190 (@value{GDBP}) tfind
13191 Found trace frame 0, tracepoint 2
13192 39 ++a; /* set tracepoint 1 here */
13193 (@value{GDBP}) tdump
13194 Data collected at tracepoint 2, trace frame 0:
13198 c = @{"123", "456", "789", "123", "456", "789"@}
13199 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13207 @chapter Debugging Programs That Use Overlays
13210 If your program is too large to fit completely in your target system's
13211 memory, you can sometimes use @dfn{overlays} to work around this
13212 problem. @value{GDBN} provides some support for debugging programs that
13216 * How Overlays Work:: A general explanation of overlays.
13217 * Overlay Commands:: Managing overlays in @value{GDBN}.
13218 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13219 mapped by asking the inferior.
13220 * Overlay Sample Program:: A sample program using overlays.
13223 @node How Overlays Work
13224 @section How Overlays Work
13225 @cindex mapped overlays
13226 @cindex unmapped overlays
13227 @cindex load address, overlay's
13228 @cindex mapped address
13229 @cindex overlay area
13231 Suppose you have a computer whose instruction address space is only 64
13232 kilobytes long, but which has much more memory which can be accessed by
13233 other means: special instructions, segment registers, or memory
13234 management hardware, for example. Suppose further that you want to
13235 adapt a program which is larger than 64 kilobytes to run on this system.
13237 One solution is to identify modules of your program which are relatively
13238 independent, and need not call each other directly; call these modules
13239 @dfn{overlays}. Separate the overlays from the main program, and place
13240 their machine code in the larger memory. Place your main program in
13241 instruction memory, but leave at least enough space there to hold the
13242 largest overlay as well.
13244 Now, to call a function located in an overlay, you must first copy that
13245 overlay's machine code from the large memory into the space set aside
13246 for it in the instruction memory, and then jump to its entry point
13249 @c NB: In the below the mapped area's size is greater or equal to the
13250 @c size of all overlays. This is intentional to remind the developer
13251 @c that overlays don't necessarily need to be the same size.
13255 Data Instruction Larger
13256 Address Space Address Space Address Space
13257 +-----------+ +-----------+ +-----------+
13259 +-----------+ +-----------+ +-----------+<-- overlay 1
13260 | program | | main | .----| overlay 1 | load address
13261 | variables | | program | | +-----------+
13262 | and heap | | | | | |
13263 +-----------+ | | | +-----------+<-- overlay 2
13264 | | +-----------+ | | | load address
13265 +-----------+ | | | .-| overlay 2 |
13267 mapped --->+-----------+ | | +-----------+
13268 address | | | | | |
13269 | overlay | <-' | | |
13270 | area | <---' +-----------+<-- overlay 3
13271 | | <---. | | load address
13272 +-----------+ `--| overlay 3 |
13279 @anchor{A code overlay}A code overlay
13283 The diagram (@pxref{A code overlay}) shows a system with separate data
13284 and instruction address spaces. To map an overlay, the program copies
13285 its code from the larger address space to the instruction address space.
13286 Since the overlays shown here all use the same mapped address, only one
13287 may be mapped at a time. For a system with a single address space for
13288 data and instructions, the diagram would be similar, except that the
13289 program variables and heap would share an address space with the main
13290 program and the overlay area.
13292 An overlay loaded into instruction memory and ready for use is called a
13293 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13294 instruction memory. An overlay not present (or only partially present)
13295 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13296 is its address in the larger memory. The mapped address is also called
13297 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13298 called the @dfn{load memory address}, or @dfn{LMA}.
13300 Unfortunately, overlays are not a completely transparent way to adapt a
13301 program to limited instruction memory. They introduce a new set of
13302 global constraints you must keep in mind as you design your program:
13307 Before calling or returning to a function in an overlay, your program
13308 must make sure that overlay is actually mapped. Otherwise, the call or
13309 return will transfer control to the right address, but in the wrong
13310 overlay, and your program will probably crash.
13313 If the process of mapping an overlay is expensive on your system, you
13314 will need to choose your overlays carefully to minimize their effect on
13315 your program's performance.
13318 The executable file you load onto your system must contain each
13319 overlay's instructions, appearing at the overlay's load address, not its
13320 mapped address. However, each overlay's instructions must be relocated
13321 and its symbols defined as if the overlay were at its mapped address.
13322 You can use GNU linker scripts to specify different load and relocation
13323 addresses for pieces of your program; see @ref{Overlay Description,,,
13324 ld.info, Using ld: the GNU linker}.
13327 The procedure for loading executable files onto your system must be able
13328 to load their contents into the larger address space as well as the
13329 instruction and data spaces.
13333 The overlay system described above is rather simple, and could be
13334 improved in many ways:
13339 If your system has suitable bank switch registers or memory management
13340 hardware, you could use those facilities to make an overlay's load area
13341 contents simply appear at their mapped address in instruction space.
13342 This would probably be faster than copying the overlay to its mapped
13343 area in the usual way.
13346 If your overlays are small enough, you could set aside more than one
13347 overlay area, and have more than one overlay mapped at a time.
13350 You can use overlays to manage data, as well as instructions. In
13351 general, data overlays are even less transparent to your design than
13352 code overlays: whereas code overlays only require care when you call or
13353 return to functions, data overlays require care every time you access
13354 the data. Also, if you change the contents of a data overlay, you
13355 must copy its contents back out to its load address before you can copy a
13356 different data overlay into the same mapped area.
13361 @node Overlay Commands
13362 @section Overlay Commands
13364 To use @value{GDBN}'s overlay support, each overlay in your program must
13365 correspond to a separate section of the executable file. The section's
13366 virtual memory address and load memory address must be the overlay's
13367 mapped and load addresses. Identifying overlays with sections allows
13368 @value{GDBN} to determine the appropriate address of a function or
13369 variable, depending on whether the overlay is mapped or not.
13371 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13372 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13377 Disable @value{GDBN}'s overlay support. When overlay support is
13378 disabled, @value{GDBN} assumes that all functions and variables are
13379 always present at their mapped addresses. By default, @value{GDBN}'s
13380 overlay support is disabled.
13382 @item overlay manual
13383 @cindex manual overlay debugging
13384 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13385 relies on you to tell it which overlays are mapped, and which are not,
13386 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13387 commands described below.
13389 @item overlay map-overlay @var{overlay}
13390 @itemx overlay map @var{overlay}
13391 @cindex map an overlay
13392 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13393 be the name of the object file section containing the overlay. When an
13394 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13395 functions and variables at their mapped addresses. @value{GDBN} assumes
13396 that any other overlays whose mapped ranges overlap that of
13397 @var{overlay} are now unmapped.
13399 @item overlay unmap-overlay @var{overlay}
13400 @itemx overlay unmap @var{overlay}
13401 @cindex unmap an overlay
13402 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13403 must be the name of the object file section containing the overlay.
13404 When an overlay is unmapped, @value{GDBN} assumes it can find the
13405 overlay's functions and variables at their load addresses.
13408 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13409 consults a data structure the overlay manager maintains in the inferior
13410 to see which overlays are mapped. For details, see @ref{Automatic
13411 Overlay Debugging}.
13413 @item overlay load-target
13414 @itemx overlay load
13415 @cindex reloading the overlay table
13416 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13417 re-reads the table @value{GDBN} automatically each time the inferior
13418 stops, so this command should only be necessary if you have changed the
13419 overlay mapping yourself using @value{GDBN}. This command is only
13420 useful when using automatic overlay debugging.
13422 @item overlay list-overlays
13423 @itemx overlay list
13424 @cindex listing mapped overlays
13425 Display a list of the overlays currently mapped, along with their mapped
13426 addresses, load addresses, and sizes.
13430 Normally, when @value{GDBN} prints a code address, it includes the name
13431 of the function the address falls in:
13434 (@value{GDBP}) print main
13435 $3 = @{int ()@} 0x11a0 <main>
13438 When overlay debugging is enabled, @value{GDBN} recognizes code in
13439 unmapped overlays, and prints the names of unmapped functions with
13440 asterisks around them. For example, if @code{foo} is a function in an
13441 unmapped overlay, @value{GDBN} prints it this way:
13444 (@value{GDBP}) overlay list
13445 No sections are mapped.
13446 (@value{GDBP}) print foo
13447 $5 = @{int (int)@} 0x100000 <*foo*>
13450 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13454 (@value{GDBP}) overlay list
13455 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13456 mapped at 0x1016 - 0x104a
13457 (@value{GDBP}) print foo
13458 $6 = @{int (int)@} 0x1016 <foo>
13461 When overlay debugging is enabled, @value{GDBN} can find the correct
13462 address for functions and variables in an overlay, whether or not the
13463 overlay is mapped. This allows most @value{GDBN} commands, like
13464 @code{break} and @code{disassemble}, to work normally, even on unmapped
13465 code. However, @value{GDBN}'s breakpoint support has some limitations:
13469 @cindex breakpoints in overlays
13470 @cindex overlays, setting breakpoints in
13471 You can set breakpoints in functions in unmapped overlays, as long as
13472 @value{GDBN} can write to the overlay at its load address.
13474 @value{GDBN} can not set hardware or simulator-based breakpoints in
13475 unmapped overlays. However, if you set a breakpoint at the end of your
13476 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13477 you are using manual overlay management), @value{GDBN} will re-set its
13478 breakpoints properly.
13482 @node Automatic Overlay Debugging
13483 @section Automatic Overlay Debugging
13484 @cindex automatic overlay debugging
13486 @value{GDBN} can automatically track which overlays are mapped and which
13487 are not, given some simple co-operation from the overlay manager in the
13488 inferior. If you enable automatic overlay debugging with the
13489 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13490 looks in the inferior's memory for certain variables describing the
13491 current state of the overlays.
13493 Here are the variables your overlay manager must define to support
13494 @value{GDBN}'s automatic overlay debugging:
13498 @item @code{_ovly_table}:
13499 This variable must be an array of the following structures:
13504 /* The overlay's mapped address. */
13507 /* The size of the overlay, in bytes. */
13508 unsigned long size;
13510 /* The overlay's load address. */
13513 /* Non-zero if the overlay is currently mapped;
13515 unsigned long mapped;
13519 @item @code{_novlys}:
13520 This variable must be a four-byte signed integer, holding the total
13521 number of elements in @code{_ovly_table}.
13525 To decide whether a particular overlay is mapped or not, @value{GDBN}
13526 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13527 @code{lma} members equal the VMA and LMA of the overlay's section in the
13528 executable file. When @value{GDBN} finds a matching entry, it consults
13529 the entry's @code{mapped} member to determine whether the overlay is
13532 In addition, your overlay manager may define a function called
13533 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13534 will silently set a breakpoint there. If the overlay manager then
13535 calls this function whenever it has changed the overlay table, this
13536 will enable @value{GDBN} to accurately keep track of which overlays
13537 are in program memory, and update any breakpoints that may be set
13538 in overlays. This will allow breakpoints to work even if the
13539 overlays are kept in ROM or other non-writable memory while they
13540 are not being executed.
13542 @node Overlay Sample Program
13543 @section Overlay Sample Program
13544 @cindex overlay example program
13546 When linking a program which uses overlays, you must place the overlays
13547 at their load addresses, while relocating them to run at their mapped
13548 addresses. To do this, you must write a linker script (@pxref{Overlay
13549 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13550 since linker scripts are specific to a particular host system, target
13551 architecture, and target memory layout, this manual cannot provide
13552 portable sample code demonstrating @value{GDBN}'s overlay support.
13554 However, the @value{GDBN} source distribution does contain an overlaid
13555 program, with linker scripts for a few systems, as part of its test
13556 suite. The program consists of the following files from
13557 @file{gdb/testsuite/gdb.base}:
13561 The main program file.
13563 A simple overlay manager, used by @file{overlays.c}.
13568 Overlay modules, loaded and used by @file{overlays.c}.
13571 Linker scripts for linking the test program on the @code{d10v-elf}
13572 and @code{m32r-elf} targets.
13575 You can build the test program using the @code{d10v-elf} GCC
13576 cross-compiler like this:
13579 $ d10v-elf-gcc -g -c overlays.c
13580 $ d10v-elf-gcc -g -c ovlymgr.c
13581 $ d10v-elf-gcc -g -c foo.c
13582 $ d10v-elf-gcc -g -c bar.c
13583 $ d10v-elf-gcc -g -c baz.c
13584 $ d10v-elf-gcc -g -c grbx.c
13585 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13586 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13589 The build process is identical for any other architecture, except that
13590 you must substitute the appropriate compiler and linker script for the
13591 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13595 @chapter Using @value{GDBN} with Different Languages
13598 Although programming languages generally have common aspects, they are
13599 rarely expressed in the same manner. For instance, in ANSI C,
13600 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13601 Modula-2, it is accomplished by @code{p^}. Values can also be
13602 represented (and displayed) differently. Hex numbers in C appear as
13603 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13605 @cindex working language
13606 Language-specific information is built into @value{GDBN} for some languages,
13607 allowing you to express operations like the above in your program's
13608 native language, and allowing @value{GDBN} to output values in a manner
13609 consistent with the syntax of your program's native language. The
13610 language you use to build expressions is called the @dfn{working
13614 * Setting:: Switching between source languages
13615 * Show:: Displaying the language
13616 * Checks:: Type and range checks
13617 * Supported Languages:: Supported languages
13618 * Unsupported Languages:: Unsupported languages
13622 @section Switching Between Source Languages
13624 There are two ways to control the working language---either have @value{GDBN}
13625 set it automatically, or select it manually yourself. You can use the
13626 @code{set language} command for either purpose. On startup, @value{GDBN}
13627 defaults to setting the language automatically. The working language is
13628 used to determine how expressions you type are interpreted, how values
13631 In addition to the working language, every source file that
13632 @value{GDBN} knows about has its own working language. For some object
13633 file formats, the compiler might indicate which language a particular
13634 source file is in. However, most of the time @value{GDBN} infers the
13635 language from the name of the file. The language of a source file
13636 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13637 show each frame appropriately for its own language. There is no way to
13638 set the language of a source file from within @value{GDBN}, but you can
13639 set the language associated with a filename extension. @xref{Show, ,
13640 Displaying the Language}.
13642 This is most commonly a problem when you use a program, such
13643 as @code{cfront} or @code{f2c}, that generates C but is written in
13644 another language. In that case, make the
13645 program use @code{#line} directives in its C output; that way
13646 @value{GDBN} will know the correct language of the source code of the original
13647 program, and will display that source code, not the generated C code.
13650 * Filenames:: Filename extensions and languages.
13651 * Manually:: Setting the working language manually
13652 * Automatically:: Having @value{GDBN} infer the source language
13656 @subsection List of Filename Extensions and Languages
13658 If a source file name ends in one of the following extensions, then
13659 @value{GDBN} infers that its language is the one indicated.
13677 C@t{++} source file
13683 Objective-C source file
13687 Fortran source file
13690 Modula-2 source file
13694 Assembler source file. This actually behaves almost like C, but
13695 @value{GDBN} does not skip over function prologues when stepping.
13698 In addition, you may set the language associated with a filename
13699 extension. @xref{Show, , Displaying the Language}.
13702 @subsection Setting the Working Language
13704 If you allow @value{GDBN} to set the language automatically,
13705 expressions are interpreted the same way in your debugging session and
13708 @kindex set language
13709 If you wish, you may set the language manually. To do this, issue the
13710 command @samp{set language @var{lang}}, where @var{lang} is the name of
13711 a language, such as
13712 @code{c} or @code{modula-2}.
13713 For a list of the supported languages, type @samp{set language}.
13715 Setting the language manually prevents @value{GDBN} from updating the working
13716 language automatically. This can lead to confusion if you try
13717 to debug a program when the working language is not the same as the
13718 source language, when an expression is acceptable to both
13719 languages---but means different things. For instance, if the current
13720 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13728 might not have the effect you intended. In C, this means to add
13729 @code{b} and @code{c} and place the result in @code{a}. The result
13730 printed would be the value of @code{a}. In Modula-2, this means to compare
13731 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13733 @node Automatically
13734 @subsection Having @value{GDBN} Infer the Source Language
13736 To have @value{GDBN} set the working language automatically, use
13737 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13738 then infers the working language. That is, when your program stops in a
13739 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13740 working language to the language recorded for the function in that
13741 frame. If the language for a frame is unknown (that is, if the function
13742 or block corresponding to the frame was defined in a source file that
13743 does not have a recognized extension), the current working language is
13744 not changed, and @value{GDBN} issues a warning.
13746 This may not seem necessary for most programs, which are written
13747 entirely in one source language. However, program modules and libraries
13748 written in one source language can be used by a main program written in
13749 a different source language. Using @samp{set language auto} in this
13750 case frees you from having to set the working language manually.
13753 @section Displaying the Language
13755 The following commands help you find out which language is the
13756 working language, and also what language source files were written in.
13759 @item show language
13760 @anchor{show language}
13761 @kindex show language
13762 Display the current working language. This is the
13763 language you can use with commands such as @code{print} to
13764 build and compute expressions that may involve variables in your program.
13767 @kindex info frame@r{, show the source language}
13768 Display the source language for this frame. This language becomes the
13769 working language if you use an identifier from this frame.
13770 @xref{Frame Info, ,Information about a Frame}, to identify the other
13771 information listed here.
13774 @kindex info source@r{, show the source language}
13775 Display the source language of this source file.
13776 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13777 information listed here.
13780 In unusual circumstances, you may have source files with extensions
13781 not in the standard list. You can then set the extension associated
13782 with a language explicitly:
13785 @item set extension-language @var{ext} @var{language}
13786 @kindex set extension-language
13787 Tell @value{GDBN} that source files with extension @var{ext} are to be
13788 assumed as written in the source language @var{language}.
13790 @item info extensions
13791 @kindex info extensions
13792 List all the filename extensions and the associated languages.
13796 @section Type and Range Checking
13798 Some languages are designed to guard you against making seemingly common
13799 errors through a series of compile- and run-time checks. These include
13800 checking the type of arguments to functions and operators and making
13801 sure mathematical overflows are caught at run time. Checks such as
13802 these help to ensure a program's correctness once it has been compiled
13803 by eliminating type mismatches and providing active checks for range
13804 errors when your program is running.
13806 By default @value{GDBN} checks for these errors according to the
13807 rules of the current source language. Although @value{GDBN} does not check
13808 the statements in your program, it can check expressions entered directly
13809 into @value{GDBN} for evaluation via the @code{print} command, for example.
13812 * Type Checking:: An overview of type checking
13813 * Range Checking:: An overview of range checking
13816 @cindex type checking
13817 @cindex checks, type
13818 @node Type Checking
13819 @subsection An Overview of Type Checking
13821 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13822 arguments to operators and functions have to be of the correct type,
13823 otherwise an error occurs. These checks prevent type mismatch
13824 errors from ever causing any run-time problems. For example,
13827 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13829 (@value{GDBP}) print obj.my_method (0)
13832 (@value{GDBP}) print obj.my_method (0x1234)
13833 Cannot resolve method klass::my_method to any overloaded instance
13836 The second example fails because in C@t{++} the integer constant
13837 @samp{0x1234} is not type-compatible with the pointer parameter type.
13839 For the expressions you use in @value{GDBN} commands, you can tell
13840 @value{GDBN} to not enforce strict type checking or
13841 to treat any mismatches as errors and abandon the expression;
13842 When type checking is disabled, @value{GDBN} successfully evaluates
13843 expressions like the second example above.
13845 Even if type checking is off, there may be other reasons
13846 related to type that prevent @value{GDBN} from evaluating an expression.
13847 For instance, @value{GDBN} does not know how to add an @code{int} and
13848 a @code{struct foo}. These particular type errors have nothing to do
13849 with the language in use and usually arise from expressions which make
13850 little sense to evaluate anyway.
13852 @value{GDBN} provides some additional commands for controlling type checking:
13854 @kindex set check type
13855 @kindex show check type
13857 @item set check type on
13858 @itemx set check type off
13859 Set strict type checking on or off. If any type mismatches occur in
13860 evaluating an expression while type checking is on, @value{GDBN} prints a
13861 message and aborts evaluation of the expression.
13863 @item show check type
13864 Show the current setting of type checking and whether @value{GDBN}
13865 is enforcing strict type checking rules.
13868 @cindex range checking
13869 @cindex checks, range
13870 @node Range Checking
13871 @subsection An Overview of Range Checking
13873 In some languages (such as Modula-2), it is an error to exceed the
13874 bounds of a type; this is enforced with run-time checks. Such range
13875 checking is meant to ensure program correctness by making sure
13876 computations do not overflow, or indices on an array element access do
13877 not exceed the bounds of the array.
13879 For expressions you use in @value{GDBN} commands, you can tell
13880 @value{GDBN} to treat range errors in one of three ways: ignore them,
13881 always treat them as errors and abandon the expression, or issue
13882 warnings but evaluate the expression anyway.
13884 A range error can result from numerical overflow, from exceeding an
13885 array index bound, or when you type a constant that is not a member
13886 of any type. Some languages, however, do not treat overflows as an
13887 error. In many implementations of C, mathematical overflow causes the
13888 result to ``wrap around'' to lower values---for example, if @var{m} is
13889 the largest integer value, and @var{s} is the smallest, then
13892 @var{m} + 1 @result{} @var{s}
13895 This, too, is specific to individual languages, and in some cases
13896 specific to individual compilers or machines. @xref{Supported Languages, ,
13897 Supported Languages}, for further details on specific languages.
13899 @value{GDBN} provides some additional commands for controlling the range checker:
13901 @kindex set check range
13902 @kindex show check range
13904 @item set check range auto
13905 Set range checking on or off based on the current working language.
13906 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13909 @item set check range on
13910 @itemx set check range off
13911 Set range checking on or off, overriding the default setting for the
13912 current working language. A warning is issued if the setting does not
13913 match the language default. If a range error occurs and range checking is on,
13914 then a message is printed and evaluation of the expression is aborted.
13916 @item set check range warn
13917 Output messages when the @value{GDBN} range checker detects a range error,
13918 but attempt to evaluate the expression anyway. Evaluating the
13919 expression may still be impossible for other reasons, such as accessing
13920 memory that the process does not own (a typical example from many Unix
13924 Show the current setting of the range checker, and whether or not it is
13925 being set automatically by @value{GDBN}.
13928 @node Supported Languages
13929 @section Supported Languages
13931 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13932 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13933 @c This is false ...
13934 Some @value{GDBN} features may be used in expressions regardless of the
13935 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13936 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13937 ,Expressions}) can be used with the constructs of any supported
13940 The following sections detail to what degree each source language is
13941 supported by @value{GDBN}. These sections are not meant to be language
13942 tutorials or references, but serve only as a reference guide to what the
13943 @value{GDBN} expression parser accepts, and what input and output
13944 formats should look like for different languages. There are many good
13945 books written on each of these languages; please look to these for a
13946 language reference or tutorial.
13949 * C:: C and C@t{++}
13952 * Objective-C:: Objective-C
13953 * OpenCL C:: OpenCL C
13954 * Fortran:: Fortran
13956 * Modula-2:: Modula-2
13961 @subsection C and C@t{++}
13963 @cindex C and C@t{++}
13964 @cindex expressions in C or C@t{++}
13966 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13967 to both languages. Whenever this is the case, we discuss those languages
13971 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13972 @cindex @sc{gnu} C@t{++}
13973 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13974 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13975 effectively, you must compile your C@t{++} programs with a supported
13976 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13977 compiler (@code{aCC}).
13980 * C Operators:: C and C@t{++} operators
13981 * C Constants:: C and C@t{++} constants
13982 * C Plus Plus Expressions:: C@t{++} expressions
13983 * C Defaults:: Default settings for C and C@t{++}
13984 * C Checks:: C and C@t{++} type and range checks
13985 * Debugging C:: @value{GDBN} and C
13986 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13987 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13991 @subsubsection C and C@t{++} Operators
13993 @cindex C and C@t{++} operators
13995 Operators must be defined on values of specific types. For instance,
13996 @code{+} is defined on numbers, but not on structures. Operators are
13997 often defined on groups of types.
13999 For the purposes of C and C@t{++}, the following definitions hold:
14004 @emph{Integral types} include @code{int} with any of its storage-class
14005 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14008 @emph{Floating-point types} include @code{float}, @code{double}, and
14009 @code{long double} (if supported by the target platform).
14012 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14015 @emph{Scalar types} include all of the above.
14020 The following operators are supported. They are listed here
14021 in order of increasing precedence:
14025 The comma or sequencing operator. Expressions in a comma-separated list
14026 are evaluated from left to right, with the result of the entire
14027 expression being the last expression evaluated.
14030 Assignment. The value of an assignment expression is the value
14031 assigned. Defined on scalar types.
14034 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14035 and translated to @w{@code{@var{a} = @var{a op b}}}.
14036 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14037 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14038 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14041 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14042 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14043 should be of an integral type.
14046 Logical @sc{or}. Defined on integral types.
14049 Logical @sc{and}. Defined on integral types.
14052 Bitwise @sc{or}. Defined on integral types.
14055 Bitwise exclusive-@sc{or}. Defined on integral types.
14058 Bitwise @sc{and}. Defined on integral types.
14061 Equality and inequality. Defined on scalar types. The value of these
14062 expressions is 0 for false and non-zero for true.
14064 @item <@r{, }>@r{, }<=@r{, }>=
14065 Less than, greater than, less than or equal, greater than or equal.
14066 Defined on scalar types. The value of these expressions is 0 for false
14067 and non-zero for true.
14070 left shift, and right shift. Defined on integral types.
14073 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14076 Addition and subtraction. Defined on integral types, floating-point types and
14079 @item *@r{, }/@r{, }%
14080 Multiplication, division, and modulus. Multiplication and division are
14081 defined on integral and floating-point types. Modulus is defined on
14085 Increment and decrement. When appearing before a variable, the
14086 operation is performed before the variable is used in an expression;
14087 when appearing after it, the variable's value is used before the
14088 operation takes place.
14091 Pointer dereferencing. Defined on pointer types. Same precedence as
14095 Address operator. Defined on variables. Same precedence as @code{++}.
14097 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14098 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14099 to examine the address
14100 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14104 Negative. Defined on integral and floating-point types. Same
14105 precedence as @code{++}.
14108 Logical negation. Defined on integral types. Same precedence as
14112 Bitwise complement operator. Defined on integral types. Same precedence as
14117 Structure member, and pointer-to-structure member. For convenience,
14118 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14119 pointer based on the stored type information.
14120 Defined on @code{struct} and @code{union} data.
14123 Dereferences of pointers to members.
14126 Array indexing. @code{@var{a}[@var{i}]} is defined as
14127 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14130 Function parameter list. Same precedence as @code{->}.
14133 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14134 and @code{class} types.
14137 Doubled colons also represent the @value{GDBN} scope operator
14138 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14142 If an operator is redefined in the user code, @value{GDBN} usually
14143 attempts to invoke the redefined version instead of using the operator's
14144 predefined meaning.
14147 @subsubsection C and C@t{++} Constants
14149 @cindex C and C@t{++} constants
14151 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14156 Integer constants are a sequence of digits. Octal constants are
14157 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14158 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14159 @samp{l}, specifying that the constant should be treated as a
14163 Floating point constants are a sequence of digits, followed by a decimal
14164 point, followed by a sequence of digits, and optionally followed by an
14165 exponent. An exponent is of the form:
14166 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14167 sequence of digits. The @samp{+} is optional for positive exponents.
14168 A floating-point constant may also end with a letter @samp{f} or
14169 @samp{F}, specifying that the constant should be treated as being of
14170 the @code{float} (as opposed to the default @code{double}) type; or with
14171 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14175 Enumerated constants consist of enumerated identifiers, or their
14176 integral equivalents.
14179 Character constants are a single character surrounded by single quotes
14180 (@code{'}), or a number---the ordinal value of the corresponding character
14181 (usually its @sc{ascii} value). Within quotes, the single character may
14182 be represented by a letter or by @dfn{escape sequences}, which are of
14183 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14184 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14185 @samp{@var{x}} is a predefined special character---for example,
14186 @samp{\n} for newline.
14188 Wide character constants can be written by prefixing a character
14189 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14190 form of @samp{x}. The target wide character set is used when
14191 computing the value of this constant (@pxref{Character Sets}).
14194 String constants are a sequence of character constants surrounded by
14195 double quotes (@code{"}). Any valid character constant (as described
14196 above) may appear. Double quotes within the string must be preceded by
14197 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14200 Wide string constants can be written by prefixing a string constant
14201 with @samp{L}, as in C. The target wide character set is used when
14202 computing the value of this constant (@pxref{Character Sets}).
14205 Pointer constants are an integral value. You can also write pointers
14206 to constants using the C operator @samp{&}.
14209 Array constants are comma-separated lists surrounded by braces @samp{@{}
14210 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14211 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14212 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14215 @node C Plus Plus Expressions
14216 @subsubsection C@t{++} Expressions
14218 @cindex expressions in C@t{++}
14219 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14221 @cindex debugging C@t{++} programs
14222 @cindex C@t{++} compilers
14223 @cindex debug formats and C@t{++}
14224 @cindex @value{NGCC} and C@t{++}
14226 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14227 the proper compiler and the proper debug format. Currently,
14228 @value{GDBN} works best when debugging C@t{++} code that is compiled
14229 with the most recent version of @value{NGCC} possible. The DWARF
14230 debugging format is preferred; @value{NGCC} defaults to this on most
14231 popular platforms. Other compilers and/or debug formats are likely to
14232 work badly or not at all when using @value{GDBN} to debug C@t{++}
14233 code. @xref{Compilation}.
14238 @cindex member functions
14240 Member function calls are allowed; you can use expressions like
14243 count = aml->GetOriginal(x, y)
14246 @vindex this@r{, inside C@t{++} member functions}
14247 @cindex namespace in C@t{++}
14249 While a member function is active (in the selected stack frame), your
14250 expressions have the same namespace available as the member function;
14251 that is, @value{GDBN} allows implicit references to the class instance
14252 pointer @code{this} following the same rules as C@t{++}. @code{using}
14253 declarations in the current scope are also respected by @value{GDBN}.
14255 @cindex call overloaded functions
14256 @cindex overloaded functions, calling
14257 @cindex type conversions in C@t{++}
14259 You can call overloaded functions; @value{GDBN} resolves the function
14260 call to the right definition, with some restrictions. @value{GDBN} does not
14261 perform overload resolution involving user-defined type conversions,
14262 calls to constructors, or instantiations of templates that do not exist
14263 in the program. It also cannot handle ellipsis argument lists or
14266 It does perform integral conversions and promotions, floating-point
14267 promotions, arithmetic conversions, pointer conversions, conversions of
14268 class objects to base classes, and standard conversions such as those of
14269 functions or arrays to pointers; it requires an exact match on the
14270 number of function arguments.
14272 Overload resolution is always performed, unless you have specified
14273 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14274 ,@value{GDBN} Features for C@t{++}}.
14276 You must specify @code{set overload-resolution off} in order to use an
14277 explicit function signature to call an overloaded function, as in
14279 p 'foo(char,int)'('x', 13)
14282 The @value{GDBN} command-completion facility can simplify this;
14283 see @ref{Completion, ,Command Completion}.
14285 @cindex reference declarations
14287 @value{GDBN} understands variables declared as C@t{++} references; you can use
14288 them in expressions just as you do in C@t{++} source---they are automatically
14291 In the parameter list shown when @value{GDBN} displays a frame, the values of
14292 reference variables are not displayed (unlike other variables); this
14293 avoids clutter, since references are often used for large structures.
14294 The @emph{address} of a reference variable is always shown, unless
14295 you have specified @samp{set print address off}.
14298 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14299 expressions can use it just as expressions in your program do. Since
14300 one scope may be defined in another, you can use @code{::} repeatedly if
14301 necessary, for example in an expression like
14302 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14303 resolving name scope by reference to source files, in both C and C@t{++}
14304 debugging (@pxref{Variables, ,Program Variables}).
14307 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14312 @subsubsection C and C@t{++} Defaults
14314 @cindex C and C@t{++} defaults
14316 If you allow @value{GDBN} to set range checking automatically, it
14317 defaults to @code{off} whenever the working language changes to
14318 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14319 selects the working language.
14321 If you allow @value{GDBN} to set the language automatically, it
14322 recognizes source files whose names end with @file{.c}, @file{.C}, or
14323 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14324 these files, it sets the working language to C or C@t{++}.
14325 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14326 for further details.
14329 @subsubsection C and C@t{++} Type and Range Checks
14331 @cindex C and C@t{++} checks
14333 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14334 checking is used. However, if you turn type checking off, @value{GDBN}
14335 will allow certain non-standard conversions, such as promoting integer
14336 constants to pointers.
14338 Range checking, if turned on, is done on mathematical operations. Array
14339 indices are not checked, since they are often used to index a pointer
14340 that is not itself an array.
14343 @subsubsection @value{GDBN} and C
14345 The @code{set print union} and @code{show print union} commands apply to
14346 the @code{union} type. When set to @samp{on}, any @code{union} that is
14347 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14348 appears as @samp{@{...@}}.
14350 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14351 with pointers and a memory allocation function. @xref{Expressions,
14354 @node Debugging C Plus Plus
14355 @subsubsection @value{GDBN} Features for C@t{++}
14357 @cindex commands for C@t{++}
14359 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14360 designed specifically for use with C@t{++}. Here is a summary:
14363 @cindex break in overloaded functions
14364 @item @r{breakpoint menus}
14365 When you want a breakpoint in a function whose name is overloaded,
14366 @value{GDBN} has the capability to display a menu of possible breakpoint
14367 locations to help you specify which function definition you want.
14368 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14370 @cindex overloading in C@t{++}
14371 @item rbreak @var{regex}
14372 Setting breakpoints using regular expressions is helpful for setting
14373 breakpoints on overloaded functions that are not members of any special
14375 @xref{Set Breaks, ,Setting Breakpoints}.
14377 @cindex C@t{++} exception handling
14379 @itemx catch rethrow
14381 Debug C@t{++} exception handling using these commands. @xref{Set
14382 Catchpoints, , Setting Catchpoints}.
14384 @cindex inheritance
14385 @item ptype @var{typename}
14386 Print inheritance relationships as well as other information for type
14388 @xref{Symbols, ,Examining the Symbol Table}.
14390 @item info vtbl @var{expression}.
14391 The @code{info vtbl} command can be used to display the virtual
14392 method tables of the object computed by @var{expression}. This shows
14393 one entry per virtual table; there may be multiple virtual tables when
14394 multiple inheritance is in use.
14396 @cindex C@t{++} demangling
14397 @item demangle @var{name}
14398 Demangle @var{name}.
14399 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14401 @cindex C@t{++} symbol display
14402 @item set print demangle
14403 @itemx show print demangle
14404 @itemx set print asm-demangle
14405 @itemx show print asm-demangle
14406 Control whether C@t{++} symbols display in their source form, both when
14407 displaying code as C@t{++} source and when displaying disassemblies.
14408 @xref{Print Settings, ,Print Settings}.
14410 @item set print object
14411 @itemx show print object
14412 Choose whether to print derived (actual) or declared types of objects.
14413 @xref{Print Settings, ,Print Settings}.
14415 @item set print vtbl
14416 @itemx show print vtbl
14417 Control the format for printing virtual function tables.
14418 @xref{Print Settings, ,Print Settings}.
14419 (The @code{vtbl} commands do not work on programs compiled with the HP
14420 ANSI C@t{++} compiler (@code{aCC}).)
14422 @kindex set overload-resolution
14423 @cindex overloaded functions, overload resolution
14424 @item set overload-resolution on
14425 Enable overload resolution for C@t{++} expression evaluation. The default
14426 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14427 and searches for a function whose signature matches the argument types,
14428 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14429 Expressions, ,C@t{++} Expressions}, for details).
14430 If it cannot find a match, it emits a message.
14432 @item set overload-resolution off
14433 Disable overload resolution for C@t{++} expression evaluation. For
14434 overloaded functions that are not class member functions, @value{GDBN}
14435 chooses the first function of the specified name that it finds in the
14436 symbol table, whether or not its arguments are of the correct type. For
14437 overloaded functions that are class member functions, @value{GDBN}
14438 searches for a function whose signature @emph{exactly} matches the
14441 @kindex show overload-resolution
14442 @item show overload-resolution
14443 Show the current setting of overload resolution.
14445 @item @r{Overloaded symbol names}
14446 You can specify a particular definition of an overloaded symbol, using
14447 the same notation that is used to declare such symbols in C@t{++}: type
14448 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14449 also use the @value{GDBN} command-line word completion facilities to list the
14450 available choices, or to finish the type list for you.
14451 @xref{Completion,, Command Completion}, for details on how to do this.
14454 @node Decimal Floating Point
14455 @subsubsection Decimal Floating Point format
14456 @cindex decimal floating point format
14458 @value{GDBN} can examine, set and perform computations with numbers in
14459 decimal floating point format, which in the C language correspond to the
14460 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14461 specified by the extension to support decimal floating-point arithmetic.
14463 There are two encodings in use, depending on the architecture: BID (Binary
14464 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14465 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14468 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14469 to manipulate decimal floating point numbers, it is not possible to convert
14470 (using a cast, for example) integers wider than 32-bit to decimal float.
14472 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14473 point computations, error checking in decimal float operations ignores
14474 underflow, overflow and divide by zero exceptions.
14476 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14477 to inspect @code{_Decimal128} values stored in floating point registers.
14478 See @ref{PowerPC,,PowerPC} for more details.
14484 @value{GDBN} can be used to debug programs written in D and compiled with
14485 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14486 specific feature --- dynamic arrays.
14491 @cindex Go (programming language)
14492 @value{GDBN} can be used to debug programs written in Go and compiled with
14493 @file{gccgo} or @file{6g} compilers.
14495 Here is a summary of the Go-specific features and restrictions:
14498 @cindex current Go package
14499 @item The current Go package
14500 The name of the current package does not need to be specified when
14501 specifying global variables and functions.
14503 For example, given the program:
14507 var myglob = "Shall we?"
14513 When stopped inside @code{main} either of these work:
14517 (gdb) p main.myglob
14520 @cindex builtin Go types
14521 @item Builtin Go types
14522 The @code{string} type is recognized by @value{GDBN} and is printed
14525 @cindex builtin Go functions
14526 @item Builtin Go functions
14527 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14528 function and handles it internally.
14530 @cindex restrictions on Go expressions
14531 @item Restrictions on Go expressions
14532 All Go operators are supported except @code{&^}.
14533 The Go @code{_} ``blank identifier'' is not supported.
14534 Automatic dereferencing of pointers is not supported.
14538 @subsection Objective-C
14540 @cindex Objective-C
14541 This section provides information about some commands and command
14542 options that are useful for debugging Objective-C code. See also
14543 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14544 few more commands specific to Objective-C support.
14547 * Method Names in Commands::
14548 * The Print Command with Objective-C::
14551 @node Method Names in Commands
14552 @subsubsection Method Names in Commands
14554 The following commands have been extended to accept Objective-C method
14555 names as line specifications:
14557 @kindex clear@r{, and Objective-C}
14558 @kindex break@r{, and Objective-C}
14559 @kindex info line@r{, and Objective-C}
14560 @kindex jump@r{, and Objective-C}
14561 @kindex list@r{, and Objective-C}
14565 @item @code{info line}
14570 A fully qualified Objective-C method name is specified as
14573 -[@var{Class} @var{methodName}]
14576 where the minus sign is used to indicate an instance method and a
14577 plus sign (not shown) is used to indicate a class method. The class
14578 name @var{Class} and method name @var{methodName} are enclosed in
14579 brackets, similar to the way messages are specified in Objective-C
14580 source code. For example, to set a breakpoint at the @code{create}
14581 instance method of class @code{Fruit} in the program currently being
14585 break -[Fruit create]
14588 To list ten program lines around the @code{initialize} class method,
14592 list +[NSText initialize]
14595 In the current version of @value{GDBN}, the plus or minus sign is
14596 required. In future versions of @value{GDBN}, the plus or minus
14597 sign will be optional, but you can use it to narrow the search. It
14598 is also possible to specify just a method name:
14604 You must specify the complete method name, including any colons. If
14605 your program's source files contain more than one @code{create} method,
14606 you'll be presented with a numbered list of classes that implement that
14607 method. Indicate your choice by number, or type @samp{0} to exit if
14610 As another example, to clear a breakpoint established at the
14611 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14614 clear -[NSWindow makeKeyAndOrderFront:]
14617 @node The Print Command with Objective-C
14618 @subsubsection The Print Command With Objective-C
14619 @cindex Objective-C, print objects
14620 @kindex print-object
14621 @kindex po @r{(@code{print-object})}
14623 The print command has also been extended to accept methods. For example:
14626 print -[@var{object} hash]
14629 @cindex print an Objective-C object description
14630 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14632 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14633 and print the result. Also, an additional command has been added,
14634 @code{print-object} or @code{po} for short, which is meant to print
14635 the description of an object. However, this command may only work
14636 with certain Objective-C libraries that have a particular hook
14637 function, @code{_NSPrintForDebugger}, defined.
14640 @subsection OpenCL C
14643 This section provides information about @value{GDBN}s OpenCL C support.
14646 * OpenCL C Datatypes::
14647 * OpenCL C Expressions::
14648 * OpenCL C Operators::
14651 @node OpenCL C Datatypes
14652 @subsubsection OpenCL C Datatypes
14654 @cindex OpenCL C Datatypes
14655 @value{GDBN} supports the builtin scalar and vector datatypes specified
14656 by OpenCL 1.1. In addition the half- and double-precision floating point
14657 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14658 extensions are also known to @value{GDBN}.
14660 @node OpenCL C Expressions
14661 @subsubsection OpenCL C Expressions
14663 @cindex OpenCL C Expressions
14664 @value{GDBN} supports accesses to vector components including the access as
14665 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14666 supported by @value{GDBN} can be used as well.
14668 @node OpenCL C Operators
14669 @subsubsection OpenCL C Operators
14671 @cindex OpenCL C Operators
14672 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14676 @subsection Fortran
14677 @cindex Fortran-specific support in @value{GDBN}
14679 @value{GDBN} can be used to debug programs written in Fortran, but it
14680 currently supports only the features of Fortran 77 language.
14682 @cindex trailing underscore, in Fortran symbols
14683 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14684 among them) append an underscore to the names of variables and
14685 functions. When you debug programs compiled by those compilers, you
14686 will need to refer to variables and functions with a trailing
14690 * Fortran Operators:: Fortran operators and expressions
14691 * Fortran Defaults:: Default settings for Fortran
14692 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14695 @node Fortran Operators
14696 @subsubsection Fortran Operators and Expressions
14698 @cindex Fortran operators and expressions
14700 Operators must be defined on values of specific types. For instance,
14701 @code{+} is defined on numbers, but not on characters or other non-
14702 arithmetic types. Operators are often defined on groups of types.
14706 The exponentiation operator. It raises the first operand to the power
14710 The range operator. Normally used in the form of array(low:high) to
14711 represent a section of array.
14714 The access component operator. Normally used to access elements in derived
14715 types. Also suitable for unions. As unions aren't part of regular Fortran,
14716 this can only happen when accessing a register that uses a gdbarch-defined
14720 @node Fortran Defaults
14721 @subsubsection Fortran Defaults
14723 @cindex Fortran Defaults
14725 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14726 default uses case-insensitive matches for Fortran symbols. You can
14727 change that with the @samp{set case-insensitive} command, see
14728 @ref{Symbols}, for the details.
14730 @node Special Fortran Commands
14731 @subsubsection Special Fortran Commands
14733 @cindex Special Fortran commands
14735 @value{GDBN} has some commands to support Fortran-specific features,
14736 such as displaying common blocks.
14739 @cindex @code{COMMON} blocks, Fortran
14740 @kindex info common
14741 @item info common @r{[}@var{common-name}@r{]}
14742 This command prints the values contained in the Fortran @code{COMMON}
14743 block whose name is @var{common-name}. With no argument, the names of
14744 all @code{COMMON} blocks visible at the current program location are
14751 @cindex Pascal support in @value{GDBN}, limitations
14752 Debugging Pascal programs which use sets, subranges, file variables, or
14753 nested functions does not currently work. @value{GDBN} does not support
14754 entering expressions, printing values, or similar features using Pascal
14757 The Pascal-specific command @code{set print pascal_static-members}
14758 controls whether static members of Pascal objects are displayed.
14759 @xref{Print Settings, pascal_static-members}.
14762 @subsection Modula-2
14764 @cindex Modula-2, @value{GDBN} support
14766 The extensions made to @value{GDBN} to support Modula-2 only support
14767 output from the @sc{gnu} Modula-2 compiler (which is currently being
14768 developed). Other Modula-2 compilers are not currently supported, and
14769 attempting to debug executables produced by them is most likely
14770 to give an error as @value{GDBN} reads in the executable's symbol
14773 @cindex expressions in Modula-2
14775 * M2 Operators:: Built-in operators
14776 * Built-In Func/Proc:: Built-in functions and procedures
14777 * M2 Constants:: Modula-2 constants
14778 * M2 Types:: Modula-2 types
14779 * M2 Defaults:: Default settings for Modula-2
14780 * Deviations:: Deviations from standard Modula-2
14781 * M2 Checks:: Modula-2 type and range checks
14782 * M2 Scope:: The scope operators @code{::} and @code{.}
14783 * GDB/M2:: @value{GDBN} and Modula-2
14787 @subsubsection Operators
14788 @cindex Modula-2 operators
14790 Operators must be defined on values of specific types. For instance,
14791 @code{+} is defined on numbers, but not on structures. Operators are
14792 often defined on groups of types. For the purposes of Modula-2, the
14793 following definitions hold:
14798 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14802 @emph{Character types} consist of @code{CHAR} and its subranges.
14805 @emph{Floating-point types} consist of @code{REAL}.
14808 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14812 @emph{Scalar types} consist of all of the above.
14815 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14818 @emph{Boolean types} consist of @code{BOOLEAN}.
14822 The following operators are supported, and appear in order of
14823 increasing precedence:
14827 Function argument or array index separator.
14830 Assignment. The value of @var{var} @code{:=} @var{value} is
14834 Less than, greater than on integral, floating-point, or enumerated
14838 Less than or equal to, greater than or equal to
14839 on integral, floating-point and enumerated types, or set inclusion on
14840 set types. Same precedence as @code{<}.
14842 @item =@r{, }<>@r{, }#
14843 Equality and two ways of expressing inequality, valid on scalar types.
14844 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14845 available for inequality, since @code{#} conflicts with the script
14849 Set membership. Defined on set types and the types of their members.
14850 Same precedence as @code{<}.
14853 Boolean disjunction. Defined on boolean types.
14856 Boolean conjunction. Defined on boolean types.
14859 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14862 Addition and subtraction on integral and floating-point types, or union
14863 and difference on set types.
14866 Multiplication on integral and floating-point types, or set intersection
14870 Division on floating-point types, or symmetric set difference on set
14871 types. Same precedence as @code{*}.
14874 Integer division and remainder. Defined on integral types. Same
14875 precedence as @code{*}.
14878 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14881 Pointer dereferencing. Defined on pointer types.
14884 Boolean negation. Defined on boolean types. Same precedence as
14888 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14889 precedence as @code{^}.
14892 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14895 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14899 @value{GDBN} and Modula-2 scope operators.
14903 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14904 treats the use of the operator @code{IN}, or the use of operators
14905 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14906 @code{<=}, and @code{>=} on sets as an error.
14910 @node Built-In Func/Proc
14911 @subsubsection Built-in Functions and Procedures
14912 @cindex Modula-2 built-ins
14914 Modula-2 also makes available several built-in procedures and functions.
14915 In describing these, the following metavariables are used:
14920 represents an @code{ARRAY} variable.
14923 represents a @code{CHAR} constant or variable.
14926 represents a variable or constant of integral type.
14929 represents an identifier that belongs to a set. Generally used in the
14930 same function with the metavariable @var{s}. The type of @var{s} should
14931 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14934 represents a variable or constant of integral or floating-point type.
14937 represents a variable or constant of floating-point type.
14943 represents a variable.
14946 represents a variable or constant of one of many types. See the
14947 explanation of the function for details.
14950 All Modula-2 built-in procedures also return a result, described below.
14954 Returns the absolute value of @var{n}.
14957 If @var{c} is a lower case letter, it returns its upper case
14958 equivalent, otherwise it returns its argument.
14961 Returns the character whose ordinal value is @var{i}.
14964 Decrements the value in the variable @var{v} by one. Returns the new value.
14966 @item DEC(@var{v},@var{i})
14967 Decrements the value in the variable @var{v} by @var{i}. Returns the
14970 @item EXCL(@var{m},@var{s})
14971 Removes the element @var{m} from the set @var{s}. Returns the new
14974 @item FLOAT(@var{i})
14975 Returns the floating point equivalent of the integer @var{i}.
14977 @item HIGH(@var{a})
14978 Returns the index of the last member of @var{a}.
14981 Increments the value in the variable @var{v} by one. Returns the new value.
14983 @item INC(@var{v},@var{i})
14984 Increments the value in the variable @var{v} by @var{i}. Returns the
14987 @item INCL(@var{m},@var{s})
14988 Adds the element @var{m} to the set @var{s} if it is not already
14989 there. Returns the new set.
14992 Returns the maximum value of the type @var{t}.
14995 Returns the minimum value of the type @var{t}.
14998 Returns boolean TRUE if @var{i} is an odd number.
15001 Returns the ordinal value of its argument. For example, the ordinal
15002 value of a character is its @sc{ascii} value (on machines supporting
15003 the @sc{ascii} character set). The argument @var{x} must be of an
15004 ordered type, which include integral, character and enumerated types.
15006 @item SIZE(@var{x})
15007 Returns the size of its argument. The argument @var{x} can be a
15008 variable or a type.
15010 @item TRUNC(@var{r})
15011 Returns the integral part of @var{r}.
15013 @item TSIZE(@var{x})
15014 Returns the size of its argument. The argument @var{x} can be a
15015 variable or a type.
15017 @item VAL(@var{t},@var{i})
15018 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15022 @emph{Warning:} Sets and their operations are not yet supported, so
15023 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15027 @cindex Modula-2 constants
15029 @subsubsection Constants
15031 @value{GDBN} allows you to express the constants of Modula-2 in the following
15037 Integer constants are simply a sequence of digits. When used in an
15038 expression, a constant is interpreted to be type-compatible with the
15039 rest of the expression. Hexadecimal integers are specified by a
15040 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15043 Floating point constants appear as a sequence of digits, followed by a
15044 decimal point and another sequence of digits. An optional exponent can
15045 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15046 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15047 digits of the floating point constant must be valid decimal (base 10)
15051 Character constants consist of a single character enclosed by a pair of
15052 like quotes, either single (@code{'}) or double (@code{"}). They may
15053 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15054 followed by a @samp{C}.
15057 String constants consist of a sequence of characters enclosed by a
15058 pair of like quotes, either single (@code{'}) or double (@code{"}).
15059 Escape sequences in the style of C are also allowed. @xref{C
15060 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15064 Enumerated constants consist of an enumerated identifier.
15067 Boolean constants consist of the identifiers @code{TRUE} and
15071 Pointer constants consist of integral values only.
15074 Set constants are not yet supported.
15078 @subsubsection Modula-2 Types
15079 @cindex Modula-2 types
15081 Currently @value{GDBN} can print the following data types in Modula-2
15082 syntax: array types, record types, set types, pointer types, procedure
15083 types, enumerated types, subrange types and base types. You can also
15084 print the contents of variables declared using these type.
15085 This section gives a number of simple source code examples together with
15086 sample @value{GDBN} sessions.
15088 The first example contains the following section of code:
15097 and you can request @value{GDBN} to interrogate the type and value of
15098 @code{r} and @code{s}.
15101 (@value{GDBP}) print s
15103 (@value{GDBP}) ptype s
15105 (@value{GDBP}) print r
15107 (@value{GDBP}) ptype r
15112 Likewise if your source code declares @code{s} as:
15116 s: SET ['A'..'Z'] ;
15120 then you may query the type of @code{s} by:
15123 (@value{GDBP}) ptype s
15124 type = SET ['A'..'Z']
15128 Note that at present you cannot interactively manipulate set
15129 expressions using the debugger.
15131 The following example shows how you might declare an array in Modula-2
15132 and how you can interact with @value{GDBN} to print its type and contents:
15136 s: ARRAY [-10..10] OF CHAR ;
15140 (@value{GDBP}) ptype s
15141 ARRAY [-10..10] OF CHAR
15144 Note that the array handling is not yet complete and although the type
15145 is printed correctly, expression handling still assumes that all
15146 arrays have a lower bound of zero and not @code{-10} as in the example
15149 Here are some more type related Modula-2 examples:
15153 colour = (blue, red, yellow, green) ;
15154 t = [blue..yellow] ;
15162 The @value{GDBN} interaction shows how you can query the data type
15163 and value of a variable.
15166 (@value{GDBP}) print s
15168 (@value{GDBP}) ptype t
15169 type = [blue..yellow]
15173 In this example a Modula-2 array is declared and its contents
15174 displayed. Observe that the contents are written in the same way as
15175 their @code{C} counterparts.
15179 s: ARRAY [1..5] OF CARDINAL ;
15185 (@value{GDBP}) print s
15186 $1 = @{1, 0, 0, 0, 0@}
15187 (@value{GDBP}) ptype s
15188 type = ARRAY [1..5] OF CARDINAL
15191 The Modula-2 language interface to @value{GDBN} also understands
15192 pointer types as shown in this example:
15196 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15203 and you can request that @value{GDBN} describes the type of @code{s}.
15206 (@value{GDBP}) ptype s
15207 type = POINTER TO ARRAY [1..5] OF CARDINAL
15210 @value{GDBN} handles compound types as we can see in this example.
15211 Here we combine array types, record types, pointer types and subrange
15222 myarray = ARRAY myrange OF CARDINAL ;
15223 myrange = [-2..2] ;
15225 s: POINTER TO ARRAY myrange OF foo ;
15229 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15233 (@value{GDBP}) ptype s
15234 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15237 f3 : ARRAY [-2..2] OF CARDINAL;
15242 @subsubsection Modula-2 Defaults
15243 @cindex Modula-2 defaults
15245 If type and range checking are set automatically by @value{GDBN}, they
15246 both default to @code{on} whenever the working language changes to
15247 Modula-2. This happens regardless of whether you or @value{GDBN}
15248 selected the working language.
15250 If you allow @value{GDBN} to set the language automatically, then entering
15251 code compiled from a file whose name ends with @file{.mod} sets the
15252 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15253 Infer the Source Language}, for further details.
15256 @subsubsection Deviations from Standard Modula-2
15257 @cindex Modula-2, deviations from
15259 A few changes have been made to make Modula-2 programs easier to debug.
15260 This is done primarily via loosening its type strictness:
15264 Unlike in standard Modula-2, pointer constants can be formed by
15265 integers. This allows you to modify pointer variables during
15266 debugging. (In standard Modula-2, the actual address contained in a
15267 pointer variable is hidden from you; it can only be modified
15268 through direct assignment to another pointer variable or expression that
15269 returned a pointer.)
15272 C escape sequences can be used in strings and characters to represent
15273 non-printable characters. @value{GDBN} prints out strings with these
15274 escape sequences embedded. Single non-printable characters are
15275 printed using the @samp{CHR(@var{nnn})} format.
15278 The assignment operator (@code{:=}) returns the value of its right-hand
15282 All built-in procedures both modify @emph{and} return their argument.
15286 @subsubsection Modula-2 Type and Range Checks
15287 @cindex Modula-2 checks
15290 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15293 @c FIXME remove warning when type/range checks added
15295 @value{GDBN} considers two Modula-2 variables type equivalent if:
15299 They are of types that have been declared equivalent via a @code{TYPE
15300 @var{t1} = @var{t2}} statement
15303 They have been declared on the same line. (Note: This is true of the
15304 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15307 As long as type checking is enabled, any attempt to combine variables
15308 whose types are not equivalent is an error.
15310 Range checking is done on all mathematical operations, assignment, array
15311 index bounds, and all built-in functions and procedures.
15314 @subsubsection The Scope Operators @code{::} and @code{.}
15316 @cindex @code{.}, Modula-2 scope operator
15317 @cindex colon, doubled as scope operator
15319 @vindex colon-colon@r{, in Modula-2}
15320 @c Info cannot handle :: but TeX can.
15323 @vindex ::@r{, in Modula-2}
15326 There are a few subtle differences between the Modula-2 scope operator
15327 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15332 @var{module} . @var{id}
15333 @var{scope} :: @var{id}
15337 where @var{scope} is the name of a module or a procedure,
15338 @var{module} the name of a module, and @var{id} is any declared
15339 identifier within your program, except another module.
15341 Using the @code{::} operator makes @value{GDBN} search the scope
15342 specified by @var{scope} for the identifier @var{id}. If it is not
15343 found in the specified scope, then @value{GDBN} searches all scopes
15344 enclosing the one specified by @var{scope}.
15346 Using the @code{.} operator makes @value{GDBN} search the current scope for
15347 the identifier specified by @var{id} that was imported from the
15348 definition module specified by @var{module}. With this operator, it is
15349 an error if the identifier @var{id} was not imported from definition
15350 module @var{module}, or if @var{id} is not an identifier in
15354 @subsubsection @value{GDBN} and Modula-2
15356 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15357 Five subcommands of @code{set print} and @code{show print} apply
15358 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15359 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15360 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15361 analogue in Modula-2.
15363 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15364 with any language, is not useful with Modula-2. Its
15365 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15366 created in Modula-2 as they can in C or C@t{++}. However, because an
15367 address can be specified by an integral constant, the construct
15368 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15370 @cindex @code{#} in Modula-2
15371 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15372 interpreted as the beginning of a comment. Use @code{<>} instead.
15378 The extensions made to @value{GDBN} for Ada only support
15379 output from the @sc{gnu} Ada (GNAT) compiler.
15380 Other Ada compilers are not currently supported, and
15381 attempting to debug executables produced by them is most likely
15385 @cindex expressions in Ada
15387 * Ada Mode Intro:: General remarks on the Ada syntax
15388 and semantics supported by Ada mode
15390 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15391 * Additions to Ada:: Extensions of the Ada expression syntax.
15392 * Stopping Before Main Program:: Debugging the program during elaboration.
15393 * Ada Exceptions:: Ada Exceptions
15394 * Ada Tasks:: Listing and setting breakpoints in tasks.
15395 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15396 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15398 * Ada Glitches:: Known peculiarities of Ada mode.
15401 @node Ada Mode Intro
15402 @subsubsection Introduction
15403 @cindex Ada mode, general
15405 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15406 syntax, with some extensions.
15407 The philosophy behind the design of this subset is
15411 That @value{GDBN} should provide basic literals and access to operations for
15412 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15413 leaving more sophisticated computations to subprograms written into the
15414 program (which therefore may be called from @value{GDBN}).
15417 That type safety and strict adherence to Ada language restrictions
15418 are not particularly important to the @value{GDBN} user.
15421 That brevity is important to the @value{GDBN} user.
15424 Thus, for brevity, the debugger acts as if all names declared in
15425 user-written packages are directly visible, even if they are not visible
15426 according to Ada rules, thus making it unnecessary to fully qualify most
15427 names with their packages, regardless of context. Where this causes
15428 ambiguity, @value{GDBN} asks the user's intent.
15430 The debugger will start in Ada mode if it detects an Ada main program.
15431 As for other languages, it will enter Ada mode when stopped in a program that
15432 was translated from an Ada source file.
15434 While in Ada mode, you may use `@t{--}' for comments. This is useful
15435 mostly for documenting command files. The standard @value{GDBN} comment
15436 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15437 middle (to allow based literals).
15439 The debugger supports limited overloading. Given a subprogram call in which
15440 the function symbol has multiple definitions, it will use the number of
15441 actual parameters and some information about their types to attempt to narrow
15442 the set of definitions. It also makes very limited use of context, preferring
15443 procedures to functions in the context of the @code{call} command, and
15444 functions to procedures elsewhere.
15446 @node Omissions from Ada
15447 @subsubsection Omissions from Ada
15448 @cindex Ada, omissions from
15450 Here are the notable omissions from the subset:
15454 Only a subset of the attributes are supported:
15458 @t{'First}, @t{'Last}, and @t{'Length}
15459 on array objects (not on types and subtypes).
15462 @t{'Min} and @t{'Max}.
15465 @t{'Pos} and @t{'Val}.
15471 @t{'Range} on array objects (not subtypes), but only as the right
15472 operand of the membership (@code{in}) operator.
15475 @t{'Access}, @t{'Unchecked_Access}, and
15476 @t{'Unrestricted_Access} (a GNAT extension).
15484 @code{Characters.Latin_1} are not available and
15485 concatenation is not implemented. Thus, escape characters in strings are
15486 not currently available.
15489 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15490 equality of representations. They will generally work correctly
15491 for strings and arrays whose elements have integer or enumeration types.
15492 They may not work correctly for arrays whose element
15493 types have user-defined equality, for arrays of real values
15494 (in particular, IEEE-conformant floating point, because of negative
15495 zeroes and NaNs), and for arrays whose elements contain unused bits with
15496 indeterminate values.
15499 The other component-by-component array operations (@code{and}, @code{or},
15500 @code{xor}, @code{not}, and relational tests other than equality)
15501 are not implemented.
15504 @cindex array aggregates (Ada)
15505 @cindex record aggregates (Ada)
15506 @cindex aggregates (Ada)
15507 There is limited support for array and record aggregates. They are
15508 permitted only on the right sides of assignments, as in these examples:
15511 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15512 (@value{GDBP}) set An_Array := (1, others => 0)
15513 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15514 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15515 (@value{GDBP}) set A_Record := (1, "Peter", True);
15516 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15520 discriminant's value by assigning an aggregate has an
15521 undefined effect if that discriminant is used within the record.
15522 However, you can first modify discriminants by directly assigning to
15523 them (which normally would not be allowed in Ada), and then performing an
15524 aggregate assignment. For example, given a variable @code{A_Rec}
15525 declared to have a type such as:
15528 type Rec (Len : Small_Integer := 0) is record
15530 Vals : IntArray (1 .. Len);
15534 you can assign a value with a different size of @code{Vals} with two
15538 (@value{GDBP}) set A_Rec.Len := 4
15539 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15542 As this example also illustrates, @value{GDBN} is very loose about the usual
15543 rules concerning aggregates. You may leave out some of the
15544 components of an array or record aggregate (such as the @code{Len}
15545 component in the assignment to @code{A_Rec} above); they will retain their
15546 original values upon assignment. You may freely use dynamic values as
15547 indices in component associations. You may even use overlapping or
15548 redundant component associations, although which component values are
15549 assigned in such cases is not defined.
15552 Calls to dispatching subprograms are not implemented.
15555 The overloading algorithm is much more limited (i.e., less selective)
15556 than that of real Ada. It makes only limited use of the context in
15557 which a subexpression appears to resolve its meaning, and it is much
15558 looser in its rules for allowing type matches. As a result, some
15559 function calls will be ambiguous, and the user will be asked to choose
15560 the proper resolution.
15563 The @code{new} operator is not implemented.
15566 Entry calls are not implemented.
15569 Aside from printing, arithmetic operations on the native VAX floating-point
15570 formats are not supported.
15573 It is not possible to slice a packed array.
15576 The names @code{True} and @code{False}, when not part of a qualified name,
15577 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15579 Should your program
15580 redefine these names in a package or procedure (at best a dubious practice),
15581 you will have to use fully qualified names to access their new definitions.
15584 @node Additions to Ada
15585 @subsubsection Additions to Ada
15586 @cindex Ada, deviations from
15588 As it does for other languages, @value{GDBN} makes certain generic
15589 extensions to Ada (@pxref{Expressions}):
15593 If the expression @var{E} is a variable residing in memory (typically
15594 a local variable or array element) and @var{N} is a positive integer,
15595 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15596 @var{N}-1 adjacent variables following it in memory as an array. In
15597 Ada, this operator is generally not necessary, since its prime use is
15598 in displaying parts of an array, and slicing will usually do this in
15599 Ada. However, there are occasional uses when debugging programs in
15600 which certain debugging information has been optimized away.
15603 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15604 appears in function or file @var{B}.'' When @var{B} is a file name,
15605 you must typically surround it in single quotes.
15608 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15609 @var{type} that appears at address @var{addr}.''
15612 A name starting with @samp{$} is a convenience variable
15613 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15616 In addition, @value{GDBN} provides a few other shortcuts and outright
15617 additions specific to Ada:
15621 The assignment statement is allowed as an expression, returning
15622 its right-hand operand as its value. Thus, you may enter
15625 (@value{GDBP}) set x := y + 3
15626 (@value{GDBP}) print A(tmp := y + 1)
15630 The semicolon is allowed as an ``operator,'' returning as its value
15631 the value of its right-hand operand.
15632 This allows, for example,
15633 complex conditional breaks:
15636 (@value{GDBP}) break f
15637 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15641 Rather than use catenation and symbolic character names to introduce special
15642 characters into strings, one may instead use a special bracket notation,
15643 which is also used to print strings. A sequence of characters of the form
15644 @samp{["@var{XX}"]} within a string or character literal denotes the
15645 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15646 sequence of characters @samp{["""]} also denotes a single quotation mark
15647 in strings. For example,
15649 "One line.["0a"]Next line.["0a"]"
15652 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15656 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15657 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15661 (@value{GDBP}) print 'max(x, y)
15665 When printing arrays, @value{GDBN} uses positional notation when the
15666 array has a lower bound of 1, and uses a modified named notation otherwise.
15667 For example, a one-dimensional array of three integers with a lower bound
15668 of 3 might print as
15675 That is, in contrast to valid Ada, only the first component has a @code{=>}
15679 You may abbreviate attributes in expressions with any unique,
15680 multi-character subsequence of
15681 their names (an exact match gets preference).
15682 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15683 in place of @t{a'length}.
15686 @cindex quoting Ada internal identifiers
15687 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15688 to lower case. The GNAT compiler uses upper-case characters for
15689 some of its internal identifiers, which are normally of no interest to users.
15690 For the rare occasions when you actually have to look at them,
15691 enclose them in angle brackets to avoid the lower-case mapping.
15694 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15698 Printing an object of class-wide type or dereferencing an
15699 access-to-class-wide value will display all the components of the object's
15700 specific type (as indicated by its run-time tag). Likewise, component
15701 selection on such a value will operate on the specific type of the
15706 @node Stopping Before Main Program
15707 @subsubsection Stopping at the Very Beginning
15709 @cindex breakpointing Ada elaboration code
15710 It is sometimes necessary to debug the program during elaboration, and
15711 before reaching the main procedure.
15712 As defined in the Ada Reference
15713 Manual, the elaboration code is invoked from a procedure called
15714 @code{adainit}. To run your program up to the beginning of
15715 elaboration, simply use the following two commands:
15716 @code{tbreak adainit} and @code{run}.
15718 @node Ada Exceptions
15719 @subsubsection Ada Exceptions
15721 A command is provided to list all Ada exceptions:
15724 @kindex info exceptions
15725 @item info exceptions
15726 @itemx info exceptions @var{regexp}
15727 The @code{info exceptions} command allows you to list all Ada exceptions
15728 defined within the program being debugged, as well as their addresses.
15729 With a regular expression, @var{regexp}, as argument, only those exceptions
15730 whose names match @var{regexp} are listed.
15733 Below is a small example, showing how the command can be used, first
15734 without argument, and next with a regular expression passed as an
15738 (@value{GDBP}) info exceptions
15739 All defined Ada exceptions:
15740 constraint_error: 0x613da0
15741 program_error: 0x613d20
15742 storage_error: 0x613ce0
15743 tasking_error: 0x613ca0
15744 const.aint_global_e: 0x613b00
15745 (@value{GDBP}) info exceptions const.aint
15746 All Ada exceptions matching regular expression "const.aint":
15747 constraint_error: 0x613da0
15748 const.aint_global_e: 0x613b00
15751 It is also possible to ask @value{GDBN} to stop your program's execution
15752 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15755 @subsubsection Extensions for Ada Tasks
15756 @cindex Ada, tasking
15758 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15759 @value{GDBN} provides the following task-related commands:
15764 This command shows a list of current Ada tasks, as in the following example:
15771 (@value{GDBP}) info tasks
15772 ID TID P-ID Pri State Name
15773 1 8088000 0 15 Child Activation Wait main_task
15774 2 80a4000 1 15 Accept Statement b
15775 3 809a800 1 15 Child Activation Wait a
15776 * 4 80ae800 3 15 Runnable c
15781 In this listing, the asterisk before the last task indicates it to be the
15782 task currently being inspected.
15786 Represents @value{GDBN}'s internal task number.
15792 The parent's task ID (@value{GDBN}'s internal task number).
15795 The base priority of the task.
15798 Current state of the task.
15802 The task has been created but has not been activated. It cannot be
15806 The task is not blocked for any reason known to Ada. (It may be waiting
15807 for a mutex, though.) It is conceptually "executing" in normal mode.
15810 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15811 that were waiting on terminate alternatives have been awakened and have
15812 terminated themselves.
15814 @item Child Activation Wait
15815 The task is waiting for created tasks to complete activation.
15817 @item Accept Statement
15818 The task is waiting on an accept or selective wait statement.
15820 @item Waiting on entry call
15821 The task is waiting on an entry call.
15823 @item Async Select Wait
15824 The task is waiting to start the abortable part of an asynchronous
15828 The task is waiting on a select statement with only a delay
15831 @item Child Termination Wait
15832 The task is sleeping having completed a master within itself, and is
15833 waiting for the tasks dependent on that master to become terminated or
15834 waiting on a terminate Phase.
15836 @item Wait Child in Term Alt
15837 The task is sleeping waiting for tasks on terminate alternatives to
15838 finish terminating.
15840 @item Accepting RV with @var{taskno}
15841 The task is accepting a rendez-vous with the task @var{taskno}.
15845 Name of the task in the program.
15849 @kindex info task @var{taskno}
15850 @item info task @var{taskno}
15851 This command shows detailled informations on the specified task, as in
15852 the following example:
15857 (@value{GDBP}) info tasks
15858 ID TID P-ID Pri State Name
15859 1 8077880 0 15 Child Activation Wait main_task
15860 * 2 807c468 1 15 Runnable task_1
15861 (@value{GDBP}) info task 2
15862 Ada Task: 0x807c468
15865 Parent: 1 (main_task)
15871 @kindex task@r{ (Ada)}
15872 @cindex current Ada task ID
15873 This command prints the ID of the current task.
15879 (@value{GDBP}) info tasks
15880 ID TID P-ID Pri State Name
15881 1 8077870 0 15 Child Activation Wait main_task
15882 * 2 807c458 1 15 Runnable t
15883 (@value{GDBP}) task
15884 [Current task is 2]
15887 @item task @var{taskno}
15888 @cindex Ada task switching
15889 This command is like the @code{thread @var{threadno}}
15890 command (@pxref{Threads}). It switches the context of debugging
15891 from the current task to the given task.
15897 (@value{GDBP}) info tasks
15898 ID TID P-ID Pri State Name
15899 1 8077870 0 15 Child Activation Wait main_task
15900 * 2 807c458 1 15 Runnable t
15901 (@value{GDBP}) task 1
15902 [Switching to task 1]
15903 #0 0x8067726 in pthread_cond_wait ()
15905 #0 0x8067726 in pthread_cond_wait ()
15906 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15907 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15908 #3 0x806153e in system.tasking.stages.activate_tasks ()
15909 #4 0x804aacc in un () at un.adb:5
15912 @item break @var{linespec} task @var{taskno}
15913 @itemx break @var{linespec} task @var{taskno} if @dots{}
15914 @cindex breakpoints and tasks, in Ada
15915 @cindex task breakpoints, in Ada
15916 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15917 These commands are like the @code{break @dots{} thread @dots{}}
15918 command (@pxref{Thread Stops}). The
15919 @var{linespec} argument specifies source lines, as described
15920 in @ref{Specify Location}.
15922 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15923 to specify that you only want @value{GDBN} to stop the program when a
15924 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15925 numeric task identifiers assigned by @value{GDBN}, shown in the first
15926 column of the @samp{info tasks} display.
15928 If you do not specify @samp{task @var{taskno}} when you set a
15929 breakpoint, the breakpoint applies to @emph{all} tasks of your
15932 You can use the @code{task} qualifier on conditional breakpoints as
15933 well; in this case, place @samp{task @var{taskno}} before the
15934 breakpoint condition (before the @code{if}).
15942 (@value{GDBP}) info tasks
15943 ID TID P-ID Pri State Name
15944 1 140022020 0 15 Child Activation Wait main_task
15945 2 140045060 1 15 Accept/Select Wait t2
15946 3 140044840 1 15 Runnable t1
15947 * 4 140056040 1 15 Runnable t3
15948 (@value{GDBP}) b 15 task 2
15949 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15950 (@value{GDBP}) cont
15955 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15957 (@value{GDBP}) info tasks
15958 ID TID P-ID Pri State Name
15959 1 140022020 0 15 Child Activation Wait main_task
15960 * 2 140045060 1 15 Runnable t2
15961 3 140044840 1 15 Runnable t1
15962 4 140056040 1 15 Delay Sleep t3
15966 @node Ada Tasks and Core Files
15967 @subsubsection Tasking Support when Debugging Core Files
15968 @cindex Ada tasking and core file debugging
15970 When inspecting a core file, as opposed to debugging a live program,
15971 tasking support may be limited or even unavailable, depending on
15972 the platform being used.
15973 For instance, on x86-linux, the list of tasks is available, but task
15974 switching is not supported.
15976 On certain platforms, the debugger needs to perform some
15977 memory writes in order to provide Ada tasking support. When inspecting
15978 a core file, this means that the core file must be opened with read-write
15979 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15980 Under these circumstances, you should make a backup copy of the core
15981 file before inspecting it with @value{GDBN}.
15983 @node Ravenscar Profile
15984 @subsubsection Tasking Support when using the Ravenscar Profile
15985 @cindex Ravenscar Profile
15987 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15988 specifically designed for systems with safety-critical real-time
15992 @kindex set ravenscar task-switching on
15993 @cindex task switching with program using Ravenscar Profile
15994 @item set ravenscar task-switching on
15995 Allows task switching when debugging a program that uses the Ravenscar
15996 Profile. This is the default.
15998 @kindex set ravenscar task-switching off
15999 @item set ravenscar task-switching off
16000 Turn off task switching when debugging a program that uses the Ravenscar
16001 Profile. This is mostly intended to disable the code that adds support
16002 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16003 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16004 To be effective, this command should be run before the program is started.
16006 @kindex show ravenscar task-switching
16007 @item show ravenscar task-switching
16008 Show whether it is possible to switch from task to task in a program
16009 using the Ravenscar Profile.
16014 @subsubsection Known Peculiarities of Ada Mode
16015 @cindex Ada, problems
16017 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16018 we know of several problems with and limitations of Ada mode in
16020 some of which will be fixed with planned future releases of the debugger
16021 and the GNU Ada compiler.
16025 Static constants that the compiler chooses not to materialize as objects in
16026 storage are invisible to the debugger.
16029 Named parameter associations in function argument lists are ignored (the
16030 argument lists are treated as positional).
16033 Many useful library packages are currently invisible to the debugger.
16036 Fixed-point arithmetic, conversions, input, and output is carried out using
16037 floating-point arithmetic, and may give results that only approximate those on
16041 The GNAT compiler never generates the prefix @code{Standard} for any of
16042 the standard symbols defined by the Ada language. @value{GDBN} knows about
16043 this: it will strip the prefix from names when you use it, and will never
16044 look for a name you have so qualified among local symbols, nor match against
16045 symbols in other packages or subprograms. If you have
16046 defined entities anywhere in your program other than parameters and
16047 local variables whose simple names match names in @code{Standard},
16048 GNAT's lack of qualification here can cause confusion. When this happens,
16049 you can usually resolve the confusion
16050 by qualifying the problematic names with package
16051 @code{Standard} explicitly.
16054 Older versions of the compiler sometimes generate erroneous debugging
16055 information, resulting in the debugger incorrectly printing the value
16056 of affected entities. In some cases, the debugger is able to work
16057 around an issue automatically. In other cases, the debugger is able
16058 to work around the issue, but the work-around has to be specifically
16061 @kindex set ada trust-PAD-over-XVS
16062 @kindex show ada trust-PAD-over-XVS
16065 @item set ada trust-PAD-over-XVS on
16066 Configure GDB to strictly follow the GNAT encoding when computing the
16067 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16068 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16069 a complete description of the encoding used by the GNAT compiler).
16070 This is the default.
16072 @item set ada trust-PAD-over-XVS off
16073 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16074 sometimes prints the wrong value for certain entities, changing @code{ada
16075 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16076 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16077 @code{off}, but this incurs a slight performance penalty, so it is
16078 recommended to leave this setting to @code{on} unless necessary.
16082 @cindex GNAT descriptive types
16083 @cindex GNAT encoding
16084 Internally, the debugger also relies on the compiler following a number
16085 of conventions known as the @samp{GNAT Encoding}, all documented in
16086 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16087 how the debugging information should be generated for certain types.
16088 In particular, this convention makes use of @dfn{descriptive types},
16089 which are artificial types generated purely to help the debugger.
16091 These encodings were defined at a time when the debugging information
16092 format used was not powerful enough to describe some of the more complex
16093 types available in Ada. Since DWARF allows us to express nearly all
16094 Ada features, the long-term goal is to slowly replace these descriptive
16095 types by their pure DWARF equivalent. To facilitate that transition,
16096 a new maintenance option is available to force the debugger to ignore
16097 those descriptive types. It allows the user to quickly evaluate how
16098 well @value{GDBN} works without them.
16102 @kindex maint ada set ignore-descriptive-types
16103 @item maintenance ada set ignore-descriptive-types [on|off]
16104 Control whether the debugger should ignore descriptive types.
16105 The default is not to ignore descriptives types (@code{off}).
16107 @kindex maint ada show ignore-descriptive-types
16108 @item maintenance ada show ignore-descriptive-types
16109 Show if descriptive types are ignored by @value{GDBN}.
16113 @node Unsupported Languages
16114 @section Unsupported Languages
16116 @cindex unsupported languages
16117 @cindex minimal language
16118 In addition to the other fully-supported programming languages,
16119 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16120 It does not represent a real programming language, but provides a set
16121 of capabilities close to what the C or assembly languages provide.
16122 This should allow most simple operations to be performed while debugging
16123 an application that uses a language currently not supported by @value{GDBN}.
16125 If the language is set to @code{auto}, @value{GDBN} will automatically
16126 select this language if the current frame corresponds to an unsupported
16130 @chapter Examining the Symbol Table
16132 The commands described in this chapter allow you to inquire about the
16133 symbols (names of variables, functions and types) defined in your
16134 program. This information is inherent in the text of your program and
16135 does not change as your program executes. @value{GDBN} finds it in your
16136 program's symbol table, in the file indicated when you started @value{GDBN}
16137 (@pxref{File Options, ,Choosing Files}), or by one of the
16138 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16140 @cindex symbol names
16141 @cindex names of symbols
16142 @cindex quoting names
16143 Occasionally, you may need to refer to symbols that contain unusual
16144 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16145 most frequent case is in referring to static variables in other
16146 source files (@pxref{Variables,,Program Variables}). File names
16147 are recorded in object files as debugging symbols, but @value{GDBN} would
16148 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16149 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16150 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16157 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16160 @cindex case-insensitive symbol names
16161 @cindex case sensitivity in symbol names
16162 @kindex set case-sensitive
16163 @item set case-sensitive on
16164 @itemx set case-sensitive off
16165 @itemx set case-sensitive auto
16166 Normally, when @value{GDBN} looks up symbols, it matches their names
16167 with case sensitivity determined by the current source language.
16168 Occasionally, you may wish to control that. The command @code{set
16169 case-sensitive} lets you do that by specifying @code{on} for
16170 case-sensitive matches or @code{off} for case-insensitive ones. If
16171 you specify @code{auto}, case sensitivity is reset to the default
16172 suitable for the source language. The default is case-sensitive
16173 matches for all languages except for Fortran, for which the default is
16174 case-insensitive matches.
16176 @kindex show case-sensitive
16177 @item show case-sensitive
16178 This command shows the current setting of case sensitivity for symbols
16181 @kindex set print type methods
16182 @item set print type methods
16183 @itemx set print type methods on
16184 @itemx set print type methods off
16185 Normally, when @value{GDBN} prints a class, it displays any methods
16186 declared in that class. You can control this behavior either by
16187 passing the appropriate flag to @code{ptype}, or using @command{set
16188 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16189 display the methods; this is the default. Specifying @code{off} will
16190 cause @value{GDBN} to omit the methods.
16192 @kindex show print type methods
16193 @item show print type methods
16194 This command shows the current setting of method display when printing
16197 @kindex set print type typedefs
16198 @item set print type typedefs
16199 @itemx set print type typedefs on
16200 @itemx set print type typedefs off
16202 Normally, when @value{GDBN} prints a class, it displays any typedefs
16203 defined in that class. You can control this behavior either by
16204 passing the appropriate flag to @code{ptype}, or using @command{set
16205 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16206 display the typedef definitions; this is the default. Specifying
16207 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16208 Note that this controls whether the typedef definition itself is
16209 printed, not whether typedef names are substituted when printing other
16212 @kindex show print type typedefs
16213 @item show print type typedefs
16214 This command shows the current setting of typedef display when
16217 @kindex info address
16218 @cindex address of a symbol
16219 @item info address @var{symbol}
16220 Describe where the data for @var{symbol} is stored. For a register
16221 variable, this says which register it is kept in. For a non-register
16222 local variable, this prints the stack-frame offset at which the variable
16225 Note the contrast with @samp{print &@var{symbol}}, which does not work
16226 at all for a register variable, and for a stack local variable prints
16227 the exact address of the current instantiation of the variable.
16229 @kindex info symbol
16230 @cindex symbol from address
16231 @cindex closest symbol and offset for an address
16232 @item info symbol @var{addr}
16233 Print the name of a symbol which is stored at the address @var{addr}.
16234 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16235 nearest symbol and an offset from it:
16238 (@value{GDBP}) info symbol 0x54320
16239 _initialize_vx + 396 in section .text
16243 This is the opposite of the @code{info address} command. You can use
16244 it to find out the name of a variable or a function given its address.
16246 For dynamically linked executables, the name of executable or shared
16247 library containing the symbol is also printed:
16250 (@value{GDBP}) info symbol 0x400225
16251 _start + 5 in section .text of /tmp/a.out
16252 (@value{GDBP}) info symbol 0x2aaaac2811cf
16253 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16258 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16259 Demangle @var{name}.
16260 If @var{language} is provided it is the name of the language to demangle
16261 @var{name} in. Otherwise @var{name} is demangled in the current language.
16263 The @samp{--} option specifies the end of options,
16264 and is useful when @var{name} begins with a dash.
16266 The parameter @code{demangle-style} specifies how to interpret the kind
16267 of mangling used. @xref{Print Settings}.
16270 @item whatis[/@var{flags}] [@var{arg}]
16271 Print the data type of @var{arg}, which can be either an expression
16272 or a name of a data type. With no argument, print the data type of
16273 @code{$}, the last value in the value history.
16275 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16276 is not actually evaluated, and any side-effecting operations (such as
16277 assignments or function calls) inside it do not take place.
16279 If @var{arg} is a variable or an expression, @code{whatis} prints its
16280 literal type as it is used in the source code. If the type was
16281 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16282 the data type underlying the @code{typedef}. If the type of the
16283 variable or the expression is a compound data type, such as
16284 @code{struct} or @code{class}, @code{whatis} never prints their
16285 fields or methods. It just prints the @code{struct}/@code{class}
16286 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16287 such a compound data type, use @code{ptype}.
16289 If @var{arg} is a type name that was defined using @code{typedef},
16290 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16291 Unrolling means that @code{whatis} will show the underlying type used
16292 in the @code{typedef} declaration of @var{arg}. However, if that
16293 underlying type is also a @code{typedef}, @code{whatis} will not
16296 For C code, the type names may also have the form @samp{class
16297 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16298 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16300 @var{flags} can be used to modify how the type is displayed.
16301 Available flags are:
16305 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16306 parameters and typedefs defined in a class when printing the class'
16307 members. The @code{/r} flag disables this.
16310 Do not print methods defined in the class.
16313 Print methods defined in the class. This is the default, but the flag
16314 exists in case you change the default with @command{set print type methods}.
16317 Do not print typedefs defined in the class. Note that this controls
16318 whether the typedef definition itself is printed, not whether typedef
16319 names are substituted when printing other types.
16322 Print typedefs defined in the class. This is the default, but the flag
16323 exists in case you change the default with @command{set print type typedefs}.
16327 @item ptype[/@var{flags}] [@var{arg}]
16328 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16329 detailed description of the type, instead of just the name of the type.
16330 @xref{Expressions, ,Expressions}.
16332 Contrary to @code{whatis}, @code{ptype} always unrolls any
16333 @code{typedef}s in its argument declaration, whether the argument is
16334 a variable, expression, or a data type. This means that @code{ptype}
16335 of a variable or an expression will not print literally its type as
16336 present in the source code---use @code{whatis} for that. @code{typedef}s at
16337 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16338 fields, methods and inner @code{class typedef}s of @code{struct}s,
16339 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16341 For example, for this variable declaration:
16344 typedef double real_t;
16345 struct complex @{ real_t real; double imag; @};
16346 typedef struct complex complex_t;
16348 real_t *real_pointer_var;
16352 the two commands give this output:
16356 (@value{GDBP}) whatis var
16358 (@value{GDBP}) ptype var
16359 type = struct complex @{
16363 (@value{GDBP}) whatis complex_t
16364 type = struct complex
16365 (@value{GDBP}) whatis struct complex
16366 type = struct complex
16367 (@value{GDBP}) ptype struct complex
16368 type = struct complex @{
16372 (@value{GDBP}) whatis real_pointer_var
16374 (@value{GDBP}) ptype real_pointer_var
16380 As with @code{whatis}, using @code{ptype} without an argument refers to
16381 the type of @code{$}, the last value in the value history.
16383 @cindex incomplete type
16384 Sometimes, programs use opaque data types or incomplete specifications
16385 of complex data structure. If the debug information included in the
16386 program does not allow @value{GDBN} to display a full declaration of
16387 the data type, it will say @samp{<incomplete type>}. For example,
16388 given these declarations:
16392 struct foo *fooptr;
16396 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16399 (@value{GDBP}) ptype foo
16400 $1 = <incomplete type>
16404 ``Incomplete type'' is C terminology for data types that are not
16405 completely specified.
16408 @item info types @var{regexp}
16410 Print a brief description of all types whose names match the regular
16411 expression @var{regexp} (or all types in your program, if you supply
16412 no argument). Each complete typename is matched as though it were a
16413 complete line; thus, @samp{i type value} gives information on all
16414 types in your program whose names include the string @code{value}, but
16415 @samp{i type ^value$} gives information only on types whose complete
16416 name is @code{value}.
16418 This command differs from @code{ptype} in two ways: first, like
16419 @code{whatis}, it does not print a detailed description; second, it
16420 lists all source files where a type is defined.
16422 @kindex info type-printers
16423 @item info type-printers
16424 Versions of @value{GDBN} that ship with Python scripting enabled may
16425 have ``type printers'' available. When using @command{ptype} or
16426 @command{whatis}, these printers are consulted when the name of a type
16427 is needed. @xref{Type Printing API}, for more information on writing
16430 @code{info type-printers} displays all the available type printers.
16432 @kindex enable type-printer
16433 @kindex disable type-printer
16434 @item enable type-printer @var{name}@dots{}
16435 @item disable type-printer @var{name}@dots{}
16436 These commands can be used to enable or disable type printers.
16439 @cindex local variables
16440 @item info scope @var{location}
16441 List all the variables local to a particular scope. This command
16442 accepts a @var{location} argument---a function name, a source line, or
16443 an address preceded by a @samp{*}, and prints all the variables local
16444 to the scope defined by that location. (@xref{Specify Location}, for
16445 details about supported forms of @var{location}.) For example:
16448 (@value{GDBP}) @b{info scope command_line_handler}
16449 Scope for command_line_handler:
16450 Symbol rl is an argument at stack/frame offset 8, length 4.
16451 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16452 Symbol linelength is in static storage at address 0x150a1c, length 4.
16453 Symbol p is a local variable in register $esi, length 4.
16454 Symbol p1 is a local variable in register $ebx, length 4.
16455 Symbol nline is a local variable in register $edx, length 4.
16456 Symbol repeat is a local variable at frame offset -8, length 4.
16460 This command is especially useful for determining what data to collect
16461 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16464 @kindex info source
16466 Show information about the current source file---that is, the source file for
16467 the function containing the current point of execution:
16470 the name of the source file, and the directory containing it,
16472 the directory it was compiled in,
16474 its length, in lines,
16476 which programming language it is written in,
16478 if the debug information provides it, the program that compiled the file
16479 (which may include, e.g., the compiler version and command line arguments),
16481 whether the executable includes debugging information for that file, and
16482 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16484 whether the debugging information includes information about
16485 preprocessor macros.
16489 @kindex info sources
16491 Print the names of all source files in your program for which there is
16492 debugging information, organized into two lists: files whose symbols
16493 have already been read, and files whose symbols will be read when needed.
16495 @kindex info functions
16496 @item info functions
16497 Print the names and data types of all defined functions.
16499 @item info functions @var{regexp}
16500 Print the names and data types of all defined functions
16501 whose names contain a match for regular expression @var{regexp}.
16502 Thus, @samp{info fun step} finds all functions whose names
16503 include @code{step}; @samp{info fun ^step} finds those whose names
16504 start with @code{step}. If a function name contains characters
16505 that conflict with the regular expression language (e.g.@:
16506 @samp{operator*()}), they may be quoted with a backslash.
16508 @kindex info variables
16509 @item info variables
16510 Print the names and data types of all variables that are defined
16511 outside of functions (i.e.@: excluding local variables).
16513 @item info variables @var{regexp}
16514 Print the names and data types of all variables (except for local
16515 variables) whose names contain a match for regular expression
16518 @kindex info classes
16519 @cindex Objective-C, classes and selectors
16521 @itemx info classes @var{regexp}
16522 Display all Objective-C classes in your program, or
16523 (with the @var{regexp} argument) all those matching a particular regular
16526 @kindex info selectors
16527 @item info selectors
16528 @itemx info selectors @var{regexp}
16529 Display all Objective-C selectors in your program, or
16530 (with the @var{regexp} argument) all those matching a particular regular
16534 This was never implemented.
16535 @kindex info methods
16537 @itemx info methods @var{regexp}
16538 The @code{info methods} command permits the user to examine all defined
16539 methods within C@t{++} program, or (with the @var{regexp} argument) a
16540 specific set of methods found in the various C@t{++} classes. Many
16541 C@t{++} classes provide a large number of methods. Thus, the output
16542 from the @code{ptype} command can be overwhelming and hard to use. The
16543 @code{info-methods} command filters the methods, printing only those
16544 which match the regular-expression @var{regexp}.
16547 @cindex opaque data types
16548 @kindex set opaque-type-resolution
16549 @item set opaque-type-resolution on
16550 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16551 declared as a pointer to a @code{struct}, @code{class}, or
16552 @code{union}---for example, @code{struct MyType *}---that is used in one
16553 source file although the full declaration of @code{struct MyType} is in
16554 another source file. The default is on.
16556 A change in the setting of this subcommand will not take effect until
16557 the next time symbols for a file are loaded.
16559 @item set opaque-type-resolution off
16560 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16561 is printed as follows:
16563 @{<no data fields>@}
16566 @kindex show opaque-type-resolution
16567 @item show opaque-type-resolution
16568 Show whether opaque types are resolved or not.
16570 @kindex set print symbol-loading
16571 @cindex print messages when symbols are loaded
16572 @item set print symbol-loading
16573 @itemx set print symbol-loading full
16574 @itemx set print symbol-loading brief
16575 @itemx set print symbol-loading off
16576 The @code{set print symbol-loading} command allows you to control the
16577 printing of messages when @value{GDBN} loads symbol information.
16578 By default a message is printed for the executable and one for each
16579 shared library, and normally this is what you want. However, when
16580 debugging apps with large numbers of shared libraries these messages
16582 When set to @code{brief} a message is printed for each executable,
16583 and when @value{GDBN} loads a collection of shared libraries at once
16584 it will only print one message regardless of the number of shared
16585 libraries. When set to @code{off} no messages are printed.
16587 @kindex show print symbol-loading
16588 @item show print symbol-loading
16589 Show whether messages will be printed when a @value{GDBN} command
16590 entered from the keyboard causes symbol information to be loaded.
16592 @kindex maint print symbols
16593 @cindex symbol dump
16594 @kindex maint print psymbols
16595 @cindex partial symbol dump
16596 @kindex maint print msymbols
16597 @cindex minimal symbol dump
16598 @item maint print symbols @var{filename}
16599 @itemx maint print psymbols @var{filename}
16600 @itemx maint print msymbols @var{filename}
16601 Write a dump of debugging symbol data into the file @var{filename}.
16602 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16603 symbols with debugging data are included. If you use @samp{maint print
16604 symbols}, @value{GDBN} includes all the symbols for which it has already
16605 collected full details: that is, @var{filename} reflects symbols for
16606 only those files whose symbols @value{GDBN} has read. You can use the
16607 command @code{info sources} to find out which files these are. If you
16608 use @samp{maint print psymbols} instead, the dump shows information about
16609 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16610 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16611 @samp{maint print msymbols} dumps just the minimal symbol information
16612 required for each object file from which @value{GDBN} has read some symbols.
16613 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16614 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16616 @kindex maint info symtabs
16617 @kindex maint info psymtabs
16618 @cindex listing @value{GDBN}'s internal symbol tables
16619 @cindex symbol tables, listing @value{GDBN}'s internal
16620 @cindex full symbol tables, listing @value{GDBN}'s internal
16621 @cindex partial symbol tables, listing @value{GDBN}'s internal
16622 @item maint info symtabs @r{[} @var{regexp} @r{]}
16623 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16625 List the @code{struct symtab} or @code{struct partial_symtab}
16626 structures whose names match @var{regexp}. If @var{regexp} is not
16627 given, list them all. The output includes expressions which you can
16628 copy into a @value{GDBN} debugging this one to examine a particular
16629 structure in more detail. For example:
16632 (@value{GDBP}) maint info psymtabs dwarf2read
16633 @{ objfile /home/gnu/build/gdb/gdb
16634 ((struct objfile *) 0x82e69d0)
16635 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16636 ((struct partial_symtab *) 0x8474b10)
16639 text addresses 0x814d3c8 -- 0x8158074
16640 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16641 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16642 dependencies (none)
16645 (@value{GDBP}) maint info symtabs
16649 We see that there is one partial symbol table whose filename contains
16650 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16651 and we see that @value{GDBN} has not read in any symtabs yet at all.
16652 If we set a breakpoint on a function, that will cause @value{GDBN} to
16653 read the symtab for the compilation unit containing that function:
16656 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16657 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16659 (@value{GDBP}) maint info symtabs
16660 @{ objfile /home/gnu/build/gdb/gdb
16661 ((struct objfile *) 0x82e69d0)
16662 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16663 ((struct symtab *) 0x86c1f38)
16666 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16667 linetable ((struct linetable *) 0x8370fa0)
16668 debugformat DWARF 2
16674 @kindex maint set symbol-cache-size
16675 @cindex symbol cache size
16676 @item maint set symbol-cache-size @var{size}
16677 Set the size of the symbol cache to @var{size}.
16678 The default size is intended to be good enough for debugging
16679 most applications. This option exists to allow for experimenting
16680 with different sizes.
16682 @kindex maint show symbol-cache-size
16683 @item maint show symbol-cache-size
16684 Show the size of the symbol cache.
16686 @kindex maint print symbol-cache
16687 @cindex symbol cache, printing its contents
16688 @item maint print symbol-cache
16689 Print the contents of the symbol cache.
16690 This is useful when debugging symbol cache issues.
16692 @kindex maint print symbol-cache-statistics
16693 @cindex symbol cache, printing usage statistics
16694 @item maint print symbol-cache-statistics
16695 Print symbol cache usage statistics.
16696 This helps determine how well the cache is being utilized.
16698 @kindex maint flush-symbol-cache
16699 @cindex symbol cache, flushing
16700 @item maint flush-symbol-cache
16701 Flush the contents of the symbol cache, all entries are removed.
16702 This command is useful when debugging the symbol cache.
16703 It is also useful when collecting performance data.
16708 @chapter Altering Execution
16710 Once you think you have found an error in your program, you might want to
16711 find out for certain whether correcting the apparent error would lead to
16712 correct results in the rest of the run. You can find the answer by
16713 experiment, using the @value{GDBN} features for altering execution of the
16716 For example, you can store new values into variables or memory
16717 locations, give your program a signal, restart it at a different
16718 address, or even return prematurely from a function.
16721 * Assignment:: Assignment to variables
16722 * Jumping:: Continuing at a different address
16723 * Signaling:: Giving your program a signal
16724 * Returning:: Returning from a function
16725 * Calling:: Calling your program's functions
16726 * Patching:: Patching your program
16727 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16731 @section Assignment to Variables
16734 @cindex setting variables
16735 To alter the value of a variable, evaluate an assignment expression.
16736 @xref{Expressions, ,Expressions}. For example,
16743 stores the value 4 into the variable @code{x}, and then prints the
16744 value of the assignment expression (which is 4).
16745 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16746 information on operators in supported languages.
16748 @kindex set variable
16749 @cindex variables, setting
16750 If you are not interested in seeing the value of the assignment, use the
16751 @code{set} command instead of the @code{print} command. @code{set} is
16752 really the same as @code{print} except that the expression's value is
16753 not printed and is not put in the value history (@pxref{Value History,
16754 ,Value History}). The expression is evaluated only for its effects.
16756 If the beginning of the argument string of the @code{set} command
16757 appears identical to a @code{set} subcommand, use the @code{set
16758 variable} command instead of just @code{set}. This command is identical
16759 to @code{set} except for its lack of subcommands. For example, if your
16760 program has a variable @code{width}, you get an error if you try to set
16761 a new value with just @samp{set width=13}, because @value{GDBN} has the
16762 command @code{set width}:
16765 (@value{GDBP}) whatis width
16767 (@value{GDBP}) p width
16769 (@value{GDBP}) set width=47
16770 Invalid syntax in expression.
16774 The invalid expression, of course, is @samp{=47}. In
16775 order to actually set the program's variable @code{width}, use
16778 (@value{GDBP}) set var width=47
16781 Because the @code{set} command has many subcommands that can conflict
16782 with the names of program variables, it is a good idea to use the
16783 @code{set variable} command instead of just @code{set}. For example, if
16784 your program has a variable @code{g}, you run into problems if you try
16785 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16786 the command @code{set gnutarget}, abbreviated @code{set g}:
16790 (@value{GDBP}) whatis g
16794 (@value{GDBP}) set g=4
16798 The program being debugged has been started already.
16799 Start it from the beginning? (y or n) y
16800 Starting program: /home/smith/cc_progs/a.out
16801 "/home/smith/cc_progs/a.out": can't open to read symbols:
16802 Invalid bfd target.
16803 (@value{GDBP}) show g
16804 The current BFD target is "=4".
16809 The program variable @code{g} did not change, and you silently set the
16810 @code{gnutarget} to an invalid value. In order to set the variable
16814 (@value{GDBP}) set var g=4
16817 @value{GDBN} allows more implicit conversions in assignments than C; you can
16818 freely store an integer value into a pointer variable or vice versa,
16819 and you can convert any structure to any other structure that is the
16820 same length or shorter.
16821 @comment FIXME: how do structs align/pad in these conversions?
16822 @comment /doc@cygnus.com 18dec1990
16824 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16825 construct to generate a value of specified type at a specified address
16826 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16827 to memory location @code{0x83040} as an integer (which implies a certain size
16828 and representation in memory), and
16831 set @{int@}0x83040 = 4
16835 stores the value 4 into that memory location.
16838 @section Continuing at a Different Address
16840 Ordinarily, when you continue your program, you do so at the place where
16841 it stopped, with the @code{continue} command. You can instead continue at
16842 an address of your own choosing, with the following commands:
16846 @kindex j @r{(@code{jump})}
16847 @item jump @var{linespec}
16848 @itemx j @var{linespec}
16849 @itemx jump @var{location}
16850 @itemx j @var{location}
16851 Resume execution at line @var{linespec} or at address given by
16852 @var{location}. Execution stops again immediately if there is a
16853 breakpoint there. @xref{Specify Location}, for a description of the
16854 different forms of @var{linespec} and @var{location}. It is common
16855 practice to use the @code{tbreak} command in conjunction with
16856 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16858 The @code{jump} command does not change the current stack frame, or
16859 the stack pointer, or the contents of any memory location or any
16860 register other than the program counter. If line @var{linespec} is in
16861 a different function from the one currently executing, the results may
16862 be bizarre if the two functions expect different patterns of arguments or
16863 of local variables. For this reason, the @code{jump} command requests
16864 confirmation if the specified line is not in the function currently
16865 executing. However, even bizarre results are predictable if you are
16866 well acquainted with the machine-language code of your program.
16869 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16870 On many systems, you can get much the same effect as the @code{jump}
16871 command by storing a new value into the register @code{$pc}. The
16872 difference is that this does not start your program running; it only
16873 changes the address of where it @emph{will} run when you continue. For
16881 makes the next @code{continue} command or stepping command execute at
16882 address @code{0x485}, rather than at the address where your program stopped.
16883 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16885 The most common occasion to use the @code{jump} command is to back
16886 up---perhaps with more breakpoints set---over a portion of a program
16887 that has already executed, in order to examine its execution in more
16892 @section Giving your Program a Signal
16893 @cindex deliver a signal to a program
16897 @item signal @var{signal}
16898 Resume execution where your program is stopped, but immediately give it the
16899 signal @var{signal}. The @var{signal} can be the name or the number of a
16900 signal. For example, on many systems @code{signal 2} and @code{signal
16901 SIGINT} are both ways of sending an interrupt signal.
16903 Alternatively, if @var{signal} is zero, continue execution without
16904 giving a signal. This is useful when your program stopped on account of
16905 a signal and would ordinarily see the signal when resumed with the
16906 @code{continue} command; @samp{signal 0} causes it to resume without a
16909 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16910 delivered to the currently selected thread, not the thread that last
16911 reported a stop. This includes the situation where a thread was
16912 stopped due to a signal. So if you want to continue execution
16913 suppressing the signal that stopped a thread, you should select that
16914 same thread before issuing the @samp{signal 0} command. If you issue
16915 the @samp{signal 0} command with another thread as the selected one,
16916 @value{GDBN} detects that and asks for confirmation.
16918 Invoking the @code{signal} command is not the same as invoking the
16919 @code{kill} utility from the shell. Sending a signal with @code{kill}
16920 causes @value{GDBN} to decide what to do with the signal depending on
16921 the signal handling tables (@pxref{Signals}). The @code{signal} command
16922 passes the signal directly to your program.
16924 @code{signal} does not repeat when you press @key{RET} a second time
16925 after executing the command.
16927 @kindex queue-signal
16928 @item queue-signal @var{signal}
16929 Queue @var{signal} to be delivered immediately to the current thread
16930 when execution of the thread resumes. The @var{signal} can be the name or
16931 the number of a signal. For example, on many systems @code{signal 2} and
16932 @code{signal SIGINT} are both ways of sending an interrupt signal.
16933 The handling of the signal must be set to pass the signal to the program,
16934 otherwise @value{GDBN} will report an error.
16935 You can control the handling of signals from @value{GDBN} with the
16936 @code{handle} command (@pxref{Signals}).
16938 Alternatively, if @var{signal} is zero, any currently queued signal
16939 for the current thread is discarded and when execution resumes no signal
16940 will be delivered. This is useful when your program stopped on account
16941 of a signal and would ordinarily see the signal when resumed with the
16942 @code{continue} command.
16944 This command differs from the @code{signal} command in that the signal
16945 is just queued, execution is not resumed. And @code{queue-signal} cannot
16946 be used to pass a signal whose handling state has been set to @code{nopass}
16951 @xref{stepping into signal handlers}, for information on how stepping
16952 commands behave when the thread has a signal queued.
16955 @section Returning from a Function
16958 @cindex returning from a function
16961 @itemx return @var{expression}
16962 You can cancel execution of a function call with the @code{return}
16963 command. If you give an
16964 @var{expression} argument, its value is used as the function's return
16968 When you use @code{return}, @value{GDBN} discards the selected stack frame
16969 (and all frames within it). You can think of this as making the
16970 discarded frame return prematurely. If you wish to specify a value to
16971 be returned, give that value as the argument to @code{return}.
16973 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16974 Frame}), and any other frames inside of it, leaving its caller as the
16975 innermost remaining frame. That frame becomes selected. The
16976 specified value is stored in the registers used for returning values
16979 The @code{return} command does not resume execution; it leaves the
16980 program stopped in the state that would exist if the function had just
16981 returned. In contrast, the @code{finish} command (@pxref{Continuing
16982 and Stepping, ,Continuing and Stepping}) resumes execution until the
16983 selected stack frame returns naturally.
16985 @value{GDBN} needs to know how the @var{expression} argument should be set for
16986 the inferior. The concrete registers assignment depends on the OS ABI and the
16987 type being returned by the selected stack frame. For example it is common for
16988 OS ABI to return floating point values in FPU registers while integer values in
16989 CPU registers. Still some ABIs return even floating point values in CPU
16990 registers. Larger integer widths (such as @code{long long int}) also have
16991 specific placement rules. @value{GDBN} already knows the OS ABI from its
16992 current target so it needs to find out also the type being returned to make the
16993 assignment into the right register(s).
16995 Normally, the selected stack frame has debug info. @value{GDBN} will always
16996 use the debug info instead of the implicit type of @var{expression} when the
16997 debug info is available. For example, if you type @kbd{return -1}, and the
16998 function in the current stack frame is declared to return a @code{long long
16999 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17000 into a @code{long long int}:
17003 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17005 (@value{GDBP}) return -1
17006 Make func return now? (y or n) y
17007 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17008 43 printf ("result=%lld\n", func ());
17012 However, if the selected stack frame does not have a debug info, e.g., if the
17013 function was compiled without debug info, @value{GDBN} has to find out the type
17014 to return from user. Specifying a different type by mistake may set the value
17015 in different inferior registers than the caller code expects. For example,
17016 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17017 of a @code{long long int} result for a debug info less function (on 32-bit
17018 architectures). Therefore the user is required to specify the return type by
17019 an appropriate cast explicitly:
17022 Breakpoint 2, 0x0040050b in func ()
17023 (@value{GDBP}) return -1
17024 Return value type not available for selected stack frame.
17025 Please use an explicit cast of the value to return.
17026 (@value{GDBP}) return (long long int) -1
17027 Make selected stack frame return now? (y or n) y
17028 #0 0x00400526 in main ()
17033 @section Calling Program Functions
17036 @cindex calling functions
17037 @cindex inferior functions, calling
17038 @item print @var{expr}
17039 Evaluate the expression @var{expr} and display the resulting value.
17040 The expression may include calls to functions in the program being
17044 @item call @var{expr}
17045 Evaluate the expression @var{expr} without displaying @code{void}
17048 You can use this variant of the @code{print} command if you want to
17049 execute a function from your program that does not return anything
17050 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17051 with @code{void} returned values that @value{GDBN} will otherwise
17052 print. If the result is not void, it is printed and saved in the
17056 It is possible for the function you call via the @code{print} or
17057 @code{call} command to generate a signal (e.g., if there's a bug in
17058 the function, or if you passed it incorrect arguments). What happens
17059 in that case is controlled by the @code{set unwindonsignal} command.
17061 Similarly, with a C@t{++} program it is possible for the function you
17062 call via the @code{print} or @code{call} command to generate an
17063 exception that is not handled due to the constraints of the dummy
17064 frame. In this case, any exception that is raised in the frame, but has
17065 an out-of-frame exception handler will not be found. GDB builds a
17066 dummy-frame for the inferior function call, and the unwinder cannot
17067 seek for exception handlers outside of this dummy-frame. What happens
17068 in that case is controlled by the
17069 @code{set unwind-on-terminating-exception} command.
17072 @item set unwindonsignal
17073 @kindex set unwindonsignal
17074 @cindex unwind stack in called functions
17075 @cindex call dummy stack unwinding
17076 Set unwinding of the stack if a signal is received while in a function
17077 that @value{GDBN} called in the program being debugged. If set to on,
17078 @value{GDBN} unwinds the stack it created for the call and restores
17079 the context to what it was before the call. If set to off (the
17080 default), @value{GDBN} stops in the frame where the signal was
17083 @item show unwindonsignal
17084 @kindex show unwindonsignal
17085 Show the current setting of stack unwinding in the functions called by
17088 @item set unwind-on-terminating-exception
17089 @kindex set unwind-on-terminating-exception
17090 @cindex unwind stack in called functions with unhandled exceptions
17091 @cindex call dummy stack unwinding on unhandled exception.
17092 Set unwinding of the stack if a C@t{++} exception is raised, but left
17093 unhandled while in a function that @value{GDBN} called in the program being
17094 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17095 it created for the call and restores the context to what it was before
17096 the call. If set to off, @value{GDBN} the exception is delivered to
17097 the default C@t{++} exception handler and the inferior terminated.
17099 @item show unwind-on-terminating-exception
17100 @kindex show unwind-on-terminating-exception
17101 Show the current setting of stack unwinding in the functions called by
17106 @cindex weak alias functions
17107 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17108 for another function. In such case, @value{GDBN} might not pick up
17109 the type information, including the types of the function arguments,
17110 which causes @value{GDBN} to call the inferior function incorrectly.
17111 As a result, the called function will function erroneously and may
17112 even crash. A solution to that is to use the name of the aliased
17116 @section Patching Programs
17118 @cindex patching binaries
17119 @cindex writing into executables
17120 @cindex writing into corefiles
17122 By default, @value{GDBN} opens the file containing your program's
17123 executable code (or the corefile) read-only. This prevents accidental
17124 alterations to machine code; but it also prevents you from intentionally
17125 patching your program's binary.
17127 If you'd like to be able to patch the binary, you can specify that
17128 explicitly with the @code{set write} command. For example, you might
17129 want to turn on internal debugging flags, or even to make emergency
17135 @itemx set write off
17136 If you specify @samp{set write on}, @value{GDBN} opens executable and
17137 core files for both reading and writing; if you specify @kbd{set write
17138 off} (the default), @value{GDBN} opens them read-only.
17140 If you have already loaded a file, you must load it again (using the
17141 @code{exec-file} or @code{core-file} command) after changing @code{set
17142 write}, for your new setting to take effect.
17146 Display whether executable files and core files are opened for writing
17147 as well as reading.
17150 @node Compiling and Injecting Code
17151 @section Compiling and injecting code in @value{GDBN}
17152 @cindex injecting code
17153 @cindex writing into executables
17154 @cindex compiling code
17156 @value{GDBN} supports on-demand compilation and code injection into
17157 programs running under @value{GDBN}. GCC 5.0 or higher built with
17158 @file{libcc1.so} must be installed for this functionality to be enabled.
17159 This functionality is implemented with the following commands.
17162 @kindex compile code
17163 @item compile code @var{source-code}
17164 @itemx compile code -raw @var{--} @var{source-code}
17165 Compile @var{source-code} with the compiler language found as the current
17166 language in @value{GDBN} (@pxref{Languages}). If compilation and
17167 injection is not supported with the current language specified in
17168 @value{GDBN}, or the compiler does not support this feature, an error
17169 message will be printed. If @var{source-code} compiles and links
17170 successfully, @value{GDBN} will load the object-code emitted,
17171 and execute it within the context of the currently selected inferior.
17172 It is important to note that the compiled code is executed immediately.
17173 After execution, the compiled code is removed from @value{GDBN} and any
17174 new types or variables you have defined will be deleted.
17176 The command allows you to specify @var{source-code} in two ways.
17177 The simplest method is to provide a single line of code to the command.
17181 compile code printf ("hello world\n");
17184 If you specify options on the command line as well as source code, they
17185 may conflict. The @samp{--} delimiter can be used to separate options
17186 from actual source code. E.g.:
17189 compile code -r -- printf ("hello world\n");
17192 Alternatively you can enter source code as multiple lines of text. To
17193 enter this mode, invoke the @samp{compile code} command without any text
17194 following the command. This will start the multiple-line editor and
17195 allow you to type as many lines of source code as required. When you
17196 have completed typing, enter @samp{end} on its own line to exit the
17201 >printf ("hello\n");
17202 >printf ("world\n");
17206 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17207 provided @var{source-code} in a callable scope. In this case, you must
17208 specify the entry point of the code by defining a function named
17209 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17210 inferior. Using @samp{-raw} option may be needed for example when
17211 @var{source-code} requires @samp{#include} lines which may conflict with
17212 inferior symbols otherwise.
17214 @kindex compile file
17215 @item compile file @var{filename}
17216 @itemx compile file -raw @var{filename}
17217 Like @code{compile code}, but take the source code from @var{filename}.
17220 compile file /home/user/example.c
17225 The process of compiling and injecting the code can be inspected using:
17228 @anchor{set debug compile}
17229 @item set debug compile
17230 @cindex compile command debugging info
17231 Turns on or off display of @value{GDBN} process of compiling and
17232 injecting the code. The default is off.
17234 @item show debug compile
17235 Displays the current state of displaying @value{GDBN} process of
17236 compiling and injecting the code.
17239 @subsection Compilation options for the @code{compile} command
17241 @value{GDBN} needs to specify the right compilation options for the code
17242 to be injected, in part to make its ABI compatible with the inferior
17243 and in part to make the injected code compatible with @value{GDBN}'s
17247 The options used, in increasing precedence:
17250 @item target architecture and OS options (@code{gdbarch})
17251 These options depend on target processor type and target operating
17252 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17253 (@code{-m64}) compilation option.
17255 @item compilation options recorded in the target
17256 @value{NGCC} (since version 4.7) stores the options used for compilation
17257 into @code{DW_AT_producer} part of DWARF debugging information according
17258 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17259 explicitly specify @code{-g} during inferior compilation otherwise
17260 @value{NGCC} produces no DWARF. This feature is only relevant for
17261 platforms where @code{-g} produces DWARF by default, otherwise one may
17262 try to enforce DWARF by using @code{-gdwarf-4}.
17264 @item compilation options set by @code{set compile-args}
17268 You can override compilation options using the following command:
17271 @item set compile-args
17272 @cindex compile command options override
17273 Set compilation options used for compiling and injecting code with the
17274 @code{compile} commands. These options override any conflicting ones
17275 from the target architecture and/or options stored during inferior
17278 @item show compile-args
17279 Displays the current state of compilation options override.
17280 This does not show all the options actually used during compilation,
17281 use @ref{set debug compile} for that.
17284 @subsection Caveats when using the @code{compile} command
17286 There are a few caveats to keep in mind when using the @code{compile}
17287 command. As the caveats are different per language, the table below
17288 highlights specific issues on a per language basis.
17291 @item C code examples and caveats
17292 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17293 attempt to compile the source code with a @samp{C} compiler. The source
17294 code provided to the @code{compile} command will have much the same
17295 access to variables and types as it normally would if it were part of
17296 the program currently being debugged in @value{GDBN}.
17298 Below is a sample program that forms the basis of the examples that
17299 follow. This program has been compiled and loaded into @value{GDBN},
17300 much like any other normal debugging session.
17303 void function1 (void)
17306 printf ("function 1\n");
17309 void function2 (void)
17324 For the purposes of the examples in this section, the program above has
17325 been compiled, loaded into @value{GDBN}, stopped at the function
17326 @code{main}, and @value{GDBN} is awaiting input from the user.
17328 To access variables and types for any program in @value{GDBN}, the
17329 program must be compiled and packaged with debug information. The
17330 @code{compile} command is not an exception to this rule. Without debug
17331 information, you can still use the @code{compile} command, but you will
17332 be very limited in what variables and types you can access.
17334 So with that in mind, the example above has been compiled with debug
17335 information enabled. The @code{compile} command will have access to
17336 all variables and types (except those that may have been optimized
17337 out). Currently, as @value{GDBN} has stopped the program in the
17338 @code{main} function, the @code{compile} command would have access to
17339 the variable @code{k}. You could invoke the @code{compile} command
17340 and type some source code to set the value of @code{k}. You can also
17341 read it, or do anything with that variable you would normally do in
17342 @code{C}. Be aware that changes to inferior variables in the
17343 @code{compile} command are persistent. In the following example:
17346 compile code k = 3;
17350 the variable @code{k} is now 3. It will retain that value until
17351 something else in the example program changes it, or another
17352 @code{compile} command changes it.
17354 Normal scope and access rules apply to source code compiled and
17355 injected by the @code{compile} command. In the example, the variables
17356 @code{j} and @code{k} are not accessible yet, because the program is
17357 currently stopped in the @code{main} function, where these variables
17358 are not in scope. Therefore, the following command
17361 compile code j = 3;
17365 will result in a compilation error message.
17367 Once the program is continued, execution will bring these variables in
17368 scope, and they will become accessible; then the code you specify via
17369 the @code{compile} command will be able to access them.
17371 You can create variables and types with the @code{compile} command as
17372 part of your source code. Variables and types that are created as part
17373 of the @code{compile} command are not visible to the rest of the program for
17374 the duration of its run. This example is valid:
17377 compile code int ff = 5; printf ("ff is %d\n", ff);
17380 However, if you were to type the following into @value{GDBN} after that
17381 command has completed:
17384 compile code printf ("ff is %d\n'', ff);
17388 a compiler error would be raised as the variable @code{ff} no longer
17389 exists. Object code generated and injected by the @code{compile}
17390 command is removed when its execution ends. Caution is advised
17391 when assigning to program variables values of variables created by the
17392 code submitted to the @code{compile} command. This example is valid:
17395 compile code int ff = 5; k = ff;
17398 The value of the variable @code{ff} is assigned to @code{k}. The variable
17399 @code{k} does not require the existence of @code{ff} to maintain the value
17400 it has been assigned. However, pointers require particular care in
17401 assignment. If the source code compiled with the @code{compile} command
17402 changed the address of a pointer in the example program, perhaps to a
17403 variable created in the @code{compile} command, that pointer would point
17404 to an invalid location when the command exits. The following example
17405 would likely cause issues with your debugged program:
17408 compile code int ff = 5; p = &ff;
17411 In this example, @code{p} would point to @code{ff} when the
17412 @code{compile} command is executing the source code provided to it.
17413 However, as variables in the (example) program persist with their
17414 assigned values, the variable @code{p} would point to an invalid
17415 location when the command exists. A general rule should be followed
17416 in that you should either assign @code{NULL} to any assigned pointers,
17417 or restore a valid location to the pointer before the command exits.
17419 Similar caution must be exercised with any structs, unions, and typedefs
17420 defined in @code{compile} command. Types defined in the @code{compile}
17421 command will no longer be available in the next @code{compile} command.
17422 Therefore, if you cast a variable to a type defined in the
17423 @code{compile} command, care must be taken to ensure that any future
17424 need to resolve the type can be achieved.
17427 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17428 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17429 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17430 Compilation failed.
17431 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17435 Variables that have been optimized away by the compiler are not
17436 accessible to the code submitted to the @code{compile} command.
17437 Access to those variables will generate a compiler error which @value{GDBN}
17438 will print to the console.
17441 @subsection Compiler search for the @code{compile} command
17443 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17444 may not be obvious for remote targets of different architecture than where
17445 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17446 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17447 command @code{set environment}). @xref{Environment}. @code{PATH} on
17448 @value{GDBN} host is searched for @value{NGCC} binary matching the
17449 target architecture and operating system.
17451 Specifically @code{PATH} is searched for binaries matching regular expression
17452 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17453 debugged. @var{arch} is processor name --- multiarch is supported, so for
17454 example both @code{i386} and @code{x86_64} targets look for pattern
17455 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17456 for pattern @code{s390x?}. @var{os} is currently supported only for
17457 pattern @code{linux(-gnu)?}.
17460 @chapter @value{GDBN} Files
17462 @value{GDBN} needs to know the file name of the program to be debugged,
17463 both in order to read its symbol table and in order to start your
17464 program. To debug a core dump of a previous run, you must also tell
17465 @value{GDBN} the name of the core dump file.
17468 * Files:: Commands to specify files
17469 * Separate Debug Files:: Debugging information in separate files
17470 * MiniDebugInfo:: Debugging information in a special section
17471 * Index Files:: Index files speed up GDB
17472 * Symbol Errors:: Errors reading symbol files
17473 * Data Files:: GDB data files
17477 @section Commands to Specify Files
17479 @cindex symbol table
17480 @cindex core dump file
17482 You may want to specify executable and core dump file names. The usual
17483 way to do this is at start-up time, using the arguments to
17484 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17485 Out of @value{GDBN}}).
17487 Occasionally it is necessary to change to a different file during a
17488 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17489 specify a file you want to use. Or you are debugging a remote target
17490 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17491 Program}). In these situations the @value{GDBN} commands to specify
17492 new files are useful.
17495 @cindex executable file
17497 @item file @var{filename}
17498 Use @var{filename} as the program to be debugged. It is read for its
17499 symbols and for the contents of pure memory. It is also the program
17500 executed when you use the @code{run} command. If you do not specify a
17501 directory and the file is not found in the @value{GDBN} working directory,
17502 @value{GDBN} uses the environment variable @code{PATH} as a list of
17503 directories to search, just as the shell does when looking for a program
17504 to run. You can change the value of this variable, for both @value{GDBN}
17505 and your program, using the @code{path} command.
17507 @cindex unlinked object files
17508 @cindex patching object files
17509 You can load unlinked object @file{.o} files into @value{GDBN} using
17510 the @code{file} command. You will not be able to ``run'' an object
17511 file, but you can disassemble functions and inspect variables. Also,
17512 if the underlying BFD functionality supports it, you could use
17513 @kbd{gdb -write} to patch object files using this technique. Note
17514 that @value{GDBN} can neither interpret nor modify relocations in this
17515 case, so branches and some initialized variables will appear to go to
17516 the wrong place. But this feature is still handy from time to time.
17519 @code{file} with no argument makes @value{GDBN} discard any information it
17520 has on both executable file and the symbol table.
17523 @item exec-file @r{[} @var{filename} @r{]}
17524 Specify that the program to be run (but not the symbol table) is found
17525 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17526 if necessary to locate your program. Omitting @var{filename} means to
17527 discard information on the executable file.
17529 @kindex symbol-file
17530 @item symbol-file @r{[} @var{filename} @r{]}
17531 Read symbol table information from file @var{filename}. @code{PATH} is
17532 searched when necessary. Use the @code{file} command to get both symbol
17533 table and program to run from the same file.
17535 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17536 program's symbol table.
17538 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17539 some breakpoints and auto-display expressions. This is because they may
17540 contain pointers to the internal data recording symbols and data types,
17541 which are part of the old symbol table data being discarded inside
17544 @code{symbol-file} does not repeat if you press @key{RET} again after
17547 When @value{GDBN} is configured for a particular environment, it
17548 understands debugging information in whatever format is the standard
17549 generated for that environment; you may use either a @sc{gnu} compiler, or
17550 other compilers that adhere to the local conventions.
17551 Best results are usually obtained from @sc{gnu} compilers; for example,
17552 using @code{@value{NGCC}} you can generate debugging information for
17555 For most kinds of object files, with the exception of old SVR3 systems
17556 using COFF, the @code{symbol-file} command does not normally read the
17557 symbol table in full right away. Instead, it scans the symbol table
17558 quickly to find which source files and which symbols are present. The
17559 details are read later, one source file at a time, as they are needed.
17561 The purpose of this two-stage reading strategy is to make @value{GDBN}
17562 start up faster. For the most part, it is invisible except for
17563 occasional pauses while the symbol table details for a particular source
17564 file are being read. (The @code{set verbose} command can turn these
17565 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17566 Warnings and Messages}.)
17568 We have not implemented the two-stage strategy for COFF yet. When the
17569 symbol table is stored in COFF format, @code{symbol-file} reads the
17570 symbol table data in full right away. Note that ``stabs-in-COFF''
17571 still does the two-stage strategy, since the debug info is actually
17575 @cindex reading symbols immediately
17576 @cindex symbols, reading immediately
17577 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17578 @itemx file @r{[} -readnow @r{]} @var{filename}
17579 You can override the @value{GDBN} two-stage strategy for reading symbol
17580 tables by using the @samp{-readnow} option with any of the commands that
17581 load symbol table information, if you want to be sure @value{GDBN} has the
17582 entire symbol table available.
17584 @c FIXME: for now no mention of directories, since this seems to be in
17585 @c flux. 13mar1992 status is that in theory GDB would look either in
17586 @c current dir or in same dir as myprog; but issues like competing
17587 @c GDB's, or clutter in system dirs, mean that in practice right now
17588 @c only current dir is used. FFish says maybe a special GDB hierarchy
17589 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17593 @item core-file @r{[}@var{filename}@r{]}
17595 Specify the whereabouts of a core dump file to be used as the ``contents
17596 of memory''. Traditionally, core files contain only some parts of the
17597 address space of the process that generated them; @value{GDBN} can access the
17598 executable file itself for other parts.
17600 @code{core-file} with no argument specifies that no core file is
17603 Note that the core file is ignored when your program is actually running
17604 under @value{GDBN}. So, if you have been running your program and you
17605 wish to debug a core file instead, you must kill the subprocess in which
17606 the program is running. To do this, use the @code{kill} command
17607 (@pxref{Kill Process, ,Killing the Child Process}).
17609 @kindex add-symbol-file
17610 @cindex dynamic linking
17611 @item add-symbol-file @var{filename} @var{address}
17612 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17613 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17614 The @code{add-symbol-file} command reads additional symbol table
17615 information from the file @var{filename}. You would use this command
17616 when @var{filename} has been dynamically loaded (by some other means)
17617 into the program that is running. The @var{address} should give the memory
17618 address at which the file has been loaded; @value{GDBN} cannot figure
17619 this out for itself. You can additionally specify an arbitrary number
17620 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17621 section name and base address for that section. You can specify any
17622 @var{address} as an expression.
17624 The symbol table of the file @var{filename} is added to the symbol table
17625 originally read with the @code{symbol-file} command. You can use the
17626 @code{add-symbol-file} command any number of times; the new symbol data
17627 thus read is kept in addition to the old.
17629 Changes can be reverted using the command @code{remove-symbol-file}.
17631 @cindex relocatable object files, reading symbols from
17632 @cindex object files, relocatable, reading symbols from
17633 @cindex reading symbols from relocatable object files
17634 @cindex symbols, reading from relocatable object files
17635 @cindex @file{.o} files, reading symbols from
17636 Although @var{filename} is typically a shared library file, an
17637 executable file, or some other object file which has been fully
17638 relocated for loading into a process, you can also load symbolic
17639 information from relocatable @file{.o} files, as long as:
17643 the file's symbolic information refers only to linker symbols defined in
17644 that file, not to symbols defined by other object files,
17646 every section the file's symbolic information refers to has actually
17647 been loaded into the inferior, as it appears in the file, and
17649 you can determine the address at which every section was loaded, and
17650 provide these to the @code{add-symbol-file} command.
17654 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17655 relocatable files into an already running program; such systems
17656 typically make the requirements above easy to meet. However, it's
17657 important to recognize that many native systems use complex link
17658 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17659 assembly, for example) that make the requirements difficult to meet. In
17660 general, one cannot assume that using @code{add-symbol-file} to read a
17661 relocatable object file's symbolic information will have the same effect
17662 as linking the relocatable object file into the program in the normal
17665 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17667 @kindex remove-symbol-file
17668 @item remove-symbol-file @var{filename}
17669 @item remove-symbol-file -a @var{address}
17670 Remove a symbol file added via the @code{add-symbol-file} command. The
17671 file to remove can be identified by its @var{filename} or by an @var{address}
17672 that lies within the boundaries of this symbol file in memory. Example:
17675 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17676 add symbol table from file "/home/user/gdb/mylib.so" at
17677 .text_addr = 0x7ffff7ff9480
17679 Reading symbols from /home/user/gdb/mylib.so...done.
17680 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17681 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17686 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17688 @kindex add-symbol-file-from-memory
17689 @cindex @code{syscall DSO}
17690 @cindex load symbols from memory
17691 @item add-symbol-file-from-memory @var{address}
17692 Load symbols from the given @var{address} in a dynamically loaded
17693 object file whose image is mapped directly into the inferior's memory.
17694 For example, the Linux kernel maps a @code{syscall DSO} into each
17695 process's address space; this DSO provides kernel-specific code for
17696 some system calls. The argument can be any expression whose
17697 evaluation yields the address of the file's shared object file header.
17698 For this command to work, you must have used @code{symbol-file} or
17699 @code{exec-file} commands in advance.
17702 @item section @var{section} @var{addr}
17703 The @code{section} command changes the base address of the named
17704 @var{section} of the exec file to @var{addr}. This can be used if the
17705 exec file does not contain section addresses, (such as in the
17706 @code{a.out} format), or when the addresses specified in the file
17707 itself are wrong. Each section must be changed separately. The
17708 @code{info files} command, described below, lists all the sections and
17712 @kindex info target
17715 @code{info files} and @code{info target} are synonymous; both print the
17716 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17717 including the names of the executable and core dump files currently in
17718 use by @value{GDBN}, and the files from which symbols were loaded. The
17719 command @code{help target} lists all possible targets rather than
17722 @kindex maint info sections
17723 @item maint info sections
17724 Another command that can give you extra information about program sections
17725 is @code{maint info sections}. In addition to the section information
17726 displayed by @code{info files}, this command displays the flags and file
17727 offset of each section in the executable and core dump files. In addition,
17728 @code{maint info sections} provides the following command options (which
17729 may be arbitrarily combined):
17733 Display sections for all loaded object files, including shared libraries.
17734 @item @var{sections}
17735 Display info only for named @var{sections}.
17736 @item @var{section-flags}
17737 Display info only for sections for which @var{section-flags} are true.
17738 The section flags that @value{GDBN} currently knows about are:
17741 Section will have space allocated in the process when loaded.
17742 Set for all sections except those containing debug information.
17744 Section will be loaded from the file into the child process memory.
17745 Set for pre-initialized code and data, clear for @code{.bss} sections.
17747 Section needs to be relocated before loading.
17749 Section cannot be modified by the child process.
17751 Section contains executable code only.
17753 Section contains data only (no executable code).
17755 Section will reside in ROM.
17757 Section contains data for constructor/destructor lists.
17759 Section is not empty.
17761 An instruction to the linker to not output the section.
17762 @item COFF_SHARED_LIBRARY
17763 A notification to the linker that the section contains
17764 COFF shared library information.
17766 Section contains common symbols.
17769 @kindex set trust-readonly-sections
17770 @cindex read-only sections
17771 @item set trust-readonly-sections on
17772 Tell @value{GDBN} that readonly sections in your object file
17773 really are read-only (i.e.@: that their contents will not change).
17774 In that case, @value{GDBN} can fetch values from these sections
17775 out of the object file, rather than from the target program.
17776 For some targets (notably embedded ones), this can be a significant
17777 enhancement to debugging performance.
17779 The default is off.
17781 @item set trust-readonly-sections off
17782 Tell @value{GDBN} not to trust readonly sections. This means that
17783 the contents of the section might change while the program is running,
17784 and must therefore be fetched from the target when needed.
17786 @item show trust-readonly-sections
17787 Show the current setting of trusting readonly sections.
17790 All file-specifying commands allow both absolute and relative file names
17791 as arguments. @value{GDBN} always converts the file name to an absolute file
17792 name and remembers it that way.
17794 @cindex shared libraries
17795 @anchor{Shared Libraries}
17796 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17797 and IBM RS/6000 AIX shared libraries.
17799 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17800 shared libraries. @xref{Expat}.
17802 @value{GDBN} automatically loads symbol definitions from shared libraries
17803 when you use the @code{run} command, or when you examine a core file.
17804 (Before you issue the @code{run} command, @value{GDBN} does not understand
17805 references to a function in a shared library, however---unless you are
17806 debugging a core file).
17808 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17809 automatically loads the symbols at the time of the @code{shl_load} call.
17811 @c FIXME: some @value{GDBN} release may permit some refs to undef
17812 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17813 @c FIXME...lib; check this from time to time when updating manual
17815 There are times, however, when you may wish to not automatically load
17816 symbol definitions from shared libraries, such as when they are
17817 particularly large or there are many of them.
17819 To control the automatic loading of shared library symbols, use the
17823 @kindex set auto-solib-add
17824 @item set auto-solib-add @var{mode}
17825 If @var{mode} is @code{on}, symbols from all shared object libraries
17826 will be loaded automatically when the inferior begins execution, you
17827 attach to an independently started inferior, or when the dynamic linker
17828 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17829 is @code{off}, symbols must be loaded manually, using the
17830 @code{sharedlibrary} command. The default value is @code{on}.
17832 @cindex memory used for symbol tables
17833 If your program uses lots of shared libraries with debug info that
17834 takes large amounts of memory, you can decrease the @value{GDBN}
17835 memory footprint by preventing it from automatically loading the
17836 symbols from shared libraries. To that end, type @kbd{set
17837 auto-solib-add off} before running the inferior, then load each
17838 library whose debug symbols you do need with @kbd{sharedlibrary
17839 @var{regexp}}, where @var{regexp} is a regular expression that matches
17840 the libraries whose symbols you want to be loaded.
17842 @kindex show auto-solib-add
17843 @item show auto-solib-add
17844 Display the current autoloading mode.
17847 @cindex load shared library
17848 To explicitly load shared library symbols, use the @code{sharedlibrary}
17852 @kindex info sharedlibrary
17854 @item info share @var{regex}
17855 @itemx info sharedlibrary @var{regex}
17856 Print the names of the shared libraries which are currently loaded
17857 that match @var{regex}. If @var{regex} is omitted then print
17858 all shared libraries that are loaded.
17861 @item info dll @var{regex}
17862 This is an alias of @code{info sharedlibrary}.
17864 @kindex sharedlibrary
17866 @item sharedlibrary @var{regex}
17867 @itemx share @var{regex}
17868 Load shared object library symbols for files matching a
17869 Unix regular expression.
17870 As with files loaded automatically, it only loads shared libraries
17871 required by your program for a core file or after typing @code{run}. If
17872 @var{regex} is omitted all shared libraries required by your program are
17875 @item nosharedlibrary
17876 @kindex nosharedlibrary
17877 @cindex unload symbols from shared libraries
17878 Unload all shared object library symbols. This discards all symbols
17879 that have been loaded from all shared libraries. Symbols from shared
17880 libraries that were loaded by explicit user requests are not
17884 Sometimes you may wish that @value{GDBN} stops and gives you control
17885 when any of shared library events happen. The best way to do this is
17886 to use @code{catch load} and @code{catch unload} (@pxref{Set
17889 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17890 command for this. This command exists for historical reasons. It is
17891 less useful than setting a catchpoint, because it does not allow for
17892 conditions or commands as a catchpoint does.
17895 @item set stop-on-solib-events
17896 @kindex set stop-on-solib-events
17897 This command controls whether @value{GDBN} should give you control
17898 when the dynamic linker notifies it about some shared library event.
17899 The most common event of interest is loading or unloading of a new
17902 @item show stop-on-solib-events
17903 @kindex show stop-on-solib-events
17904 Show whether @value{GDBN} stops and gives you control when shared
17905 library events happen.
17908 Shared libraries are also supported in many cross or remote debugging
17909 configurations. @value{GDBN} needs to have access to the target's libraries;
17910 this can be accomplished either by providing copies of the libraries
17911 on the host system, or by asking @value{GDBN} to automatically retrieve the
17912 libraries from the target. If copies of the target libraries are
17913 provided, they need to be the same as the target libraries, although the
17914 copies on the target can be stripped as long as the copies on the host are
17917 @cindex where to look for shared libraries
17918 For remote debugging, you need to tell @value{GDBN} where the target
17919 libraries are, so that it can load the correct copies---otherwise, it
17920 may try to load the host's libraries. @value{GDBN} has two variables
17921 to specify the search directories for target libraries.
17924 @cindex prefix for executable and shared library file names
17925 @cindex system root, alternate
17926 @kindex set solib-absolute-prefix
17927 @kindex set sysroot
17928 @item set sysroot @var{path}
17929 Use @var{path} as the system root for the program being debugged. Any
17930 absolute shared library paths will be prefixed with @var{path}; many
17931 runtime loaders store the absolute paths to the shared library in the
17932 target program's memory. When starting processes remotely, and when
17933 attaching to already-running processes (local or remote), their
17934 executable filenames will be prefixed with @var{path} if reported to
17935 @value{GDBN} as absolute by the operating system. If you use
17936 @code{set sysroot} to find executables and shared libraries, they need
17937 to be laid out in the same way that they are on the target, with
17938 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
17941 If @var{path} starts with the sequence @file{target:} and the target
17942 system is remote then @value{GDBN} will retrieve the target binaries
17943 from the remote system. This is only supported when using a remote
17944 target that supports the @code{remote get} command (@pxref{File
17945 Transfer,,Sending files to a remote system}). The part of @var{path}
17946 following the initial @file{target:} (if present) is used as system
17947 root prefix on the remote file system. If @var{path} starts with the
17948 sequence @file{remote:} this is converted to the sequence
17949 @file{target:} by @code{set sysroot}@footnote{Historically the
17950 functionality to retrieve binaries from the remote system was
17951 provided by prefixing @var{path} with @file{remote:}}. If you want
17952 to specify a local system root using a directory that happens to be
17953 named @file{target:} or @file{remote:}, you need to use some
17954 equivalent variant of the name like @file{./target:}.
17956 For targets with an MS-DOS based filesystem, such as MS-Windows and
17957 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17958 absolute file name with @var{path}. But first, on Unix hosts,
17959 @value{GDBN} converts all backslash directory separators into forward
17960 slashes, because the backslash is not a directory separator on Unix:
17963 c:\foo\bar.dll @result{} c:/foo/bar.dll
17966 Then, @value{GDBN} attempts prefixing the target file name with
17967 @var{path}, and looks for the resulting file name in the host file
17971 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17974 If that does not find the binary, @value{GDBN} tries removing
17975 the @samp{:} character from the drive spec, both for convenience, and,
17976 for the case of the host file system not supporting file names with
17980 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17983 This makes it possible to have a system root that mirrors a target
17984 with more than one drive. E.g., you may want to setup your local
17985 copies of the target system shared libraries like so (note @samp{c} vs
17989 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17990 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17991 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17995 and point the system root at @file{/path/to/sysroot}, so that
17996 @value{GDBN} can find the correct copies of both
17997 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17999 If that still does not find the binary, @value{GDBN} tries
18000 removing the whole drive spec from the target file name:
18003 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18006 This last lookup makes it possible to not care about the drive name,
18007 if you don't want or need to.
18009 The @code{set solib-absolute-prefix} command is an alias for @code{set
18012 @cindex default system root
18013 @cindex @samp{--with-sysroot}
18014 You can set the default system root by using the configure-time
18015 @samp{--with-sysroot} option. If the system root is inside
18016 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18017 @samp{--exec-prefix}), then the default system root will be updated
18018 automatically if the installed @value{GDBN} is moved to a new
18021 @kindex show sysroot
18023 Display the current executable and shared library prefix.
18025 @kindex set solib-search-path
18026 @item set solib-search-path @var{path}
18027 If this variable is set, @var{path} is a colon-separated list of
18028 directories to search for shared libraries. @samp{solib-search-path}
18029 is used after @samp{sysroot} fails to locate the library, or if the
18030 path to the library is relative instead of absolute. If you want to
18031 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18032 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18033 finding your host's libraries. @samp{sysroot} is preferred; setting
18034 it to a nonexistent directory may interfere with automatic loading
18035 of shared library symbols.
18037 @kindex show solib-search-path
18038 @item show solib-search-path
18039 Display the current shared library search path.
18041 @cindex DOS file-name semantics of file names.
18042 @kindex set target-file-system-kind (unix|dos-based|auto)
18043 @kindex show target-file-system-kind
18044 @item set target-file-system-kind @var{kind}
18045 Set assumed file system kind for target reported file names.
18047 Shared library file names as reported by the target system may not
18048 make sense as is on the system @value{GDBN} is running on. For
18049 example, when remote debugging a target that has MS-DOS based file
18050 system semantics, from a Unix host, the target may be reporting to
18051 @value{GDBN} a list of loaded shared libraries with file names such as
18052 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18053 drive letters, so the @samp{c:\} prefix is not normally understood as
18054 indicating an absolute file name, and neither is the backslash
18055 normally considered a directory separator character. In that case,
18056 the native file system would interpret this whole absolute file name
18057 as a relative file name with no directory components. This would make
18058 it impossible to point @value{GDBN} at a copy of the remote target's
18059 shared libraries on the host using @code{set sysroot}, and impractical
18060 with @code{set solib-search-path}. Setting
18061 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18062 to interpret such file names similarly to how the target would, and to
18063 map them to file names valid on @value{GDBN}'s native file system
18064 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18065 to one of the supported file system kinds. In that case, @value{GDBN}
18066 tries to determine the appropriate file system variant based on the
18067 current target's operating system (@pxref{ABI, ,Configuring the
18068 Current ABI}). The supported file system settings are:
18072 Instruct @value{GDBN} to assume the target file system is of Unix
18073 kind. Only file names starting the forward slash (@samp{/}) character
18074 are considered absolute, and the directory separator character is also
18078 Instruct @value{GDBN} to assume the target file system is DOS based.
18079 File names starting with either a forward slash, or a drive letter
18080 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18081 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18082 considered directory separators.
18085 Instruct @value{GDBN} to use the file system kind associated with the
18086 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18087 This is the default.
18091 @cindex file name canonicalization
18092 @cindex base name differences
18093 When processing file names provided by the user, @value{GDBN}
18094 frequently needs to compare them to the file names recorded in the
18095 program's debug info. Normally, @value{GDBN} compares just the
18096 @dfn{base names} of the files as strings, which is reasonably fast
18097 even for very large programs. (The base name of a file is the last
18098 portion of its name, after stripping all the leading directories.)
18099 This shortcut in comparison is based upon the assumption that files
18100 cannot have more than one base name. This is usually true, but
18101 references to files that use symlinks or similar filesystem
18102 facilities violate that assumption. If your program records files
18103 using such facilities, or if you provide file names to @value{GDBN}
18104 using symlinks etc., you can set @code{basenames-may-differ} to
18105 @code{true} to instruct @value{GDBN} to completely canonicalize each
18106 pair of file names it needs to compare. This will make file-name
18107 comparisons accurate, but at a price of a significant slowdown.
18110 @item set basenames-may-differ
18111 @kindex set basenames-may-differ
18112 Set whether a source file may have multiple base names.
18114 @item show basenames-may-differ
18115 @kindex show basenames-may-differ
18116 Show whether a source file may have multiple base names.
18119 @node Separate Debug Files
18120 @section Debugging Information in Separate Files
18121 @cindex separate debugging information files
18122 @cindex debugging information in separate files
18123 @cindex @file{.debug} subdirectories
18124 @cindex debugging information directory, global
18125 @cindex global debugging information directories
18126 @cindex build ID, and separate debugging files
18127 @cindex @file{.build-id} directory
18129 @value{GDBN} allows you to put a program's debugging information in a
18130 file separate from the executable itself, in a way that allows
18131 @value{GDBN} to find and load the debugging information automatically.
18132 Since debugging information can be very large---sometimes larger
18133 than the executable code itself---some systems distribute debugging
18134 information for their executables in separate files, which users can
18135 install only when they need to debug a problem.
18137 @value{GDBN} supports two ways of specifying the separate debug info
18142 The executable contains a @dfn{debug link} that specifies the name of
18143 the separate debug info file. The separate debug file's name is
18144 usually @file{@var{executable}.debug}, where @var{executable} is the
18145 name of the corresponding executable file without leading directories
18146 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18147 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18148 checksum for the debug file, which @value{GDBN} uses to validate that
18149 the executable and the debug file came from the same build.
18152 The executable contains a @dfn{build ID}, a unique bit string that is
18153 also present in the corresponding debug info file. (This is supported
18154 only on some operating systems, notably those which use the ELF format
18155 for binary files and the @sc{gnu} Binutils.) For more details about
18156 this feature, see the description of the @option{--build-id}
18157 command-line option in @ref{Options, , Command Line Options, ld.info,
18158 The GNU Linker}. The debug info file's name is not specified
18159 explicitly by the build ID, but can be computed from the build ID, see
18163 Depending on the way the debug info file is specified, @value{GDBN}
18164 uses two different methods of looking for the debug file:
18168 For the ``debug link'' method, @value{GDBN} looks up the named file in
18169 the directory of the executable file, then in a subdirectory of that
18170 directory named @file{.debug}, and finally under each one of the global debug
18171 directories, in a subdirectory whose name is identical to the leading
18172 directories of the executable's absolute file name.
18175 For the ``build ID'' method, @value{GDBN} looks in the
18176 @file{.build-id} subdirectory of each one of the global debug directories for
18177 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18178 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18179 are the rest of the bit string. (Real build ID strings are 32 or more
18180 hex characters, not 10.)
18183 So, for example, suppose you ask @value{GDBN} to debug
18184 @file{/usr/bin/ls}, which has a debug link that specifies the
18185 file @file{ls.debug}, and a build ID whose value in hex is
18186 @code{abcdef1234}. If the list of the global debug directories includes
18187 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18188 debug information files, in the indicated order:
18192 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18194 @file{/usr/bin/ls.debug}
18196 @file{/usr/bin/.debug/ls.debug}
18198 @file{/usr/lib/debug/usr/bin/ls.debug}.
18201 @anchor{debug-file-directory}
18202 Global debugging info directories default to what is set by @value{GDBN}
18203 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18204 you can also set the global debugging info directories, and view the list
18205 @value{GDBN} is currently using.
18209 @kindex set debug-file-directory
18210 @item set debug-file-directory @var{directories}
18211 Set the directories which @value{GDBN} searches for separate debugging
18212 information files to @var{directory}. Multiple path components can be set
18213 concatenating them by a path separator.
18215 @kindex show debug-file-directory
18216 @item show debug-file-directory
18217 Show the directories @value{GDBN} searches for separate debugging
18222 @cindex @code{.gnu_debuglink} sections
18223 @cindex debug link sections
18224 A debug link is a special section of the executable file named
18225 @code{.gnu_debuglink}. The section must contain:
18229 A filename, with any leading directory components removed, followed by
18232 zero to three bytes of padding, as needed to reach the next four-byte
18233 boundary within the section, and
18235 a four-byte CRC checksum, stored in the same endianness used for the
18236 executable file itself. The checksum is computed on the debugging
18237 information file's full contents by the function given below, passing
18238 zero as the @var{crc} argument.
18241 Any executable file format can carry a debug link, as long as it can
18242 contain a section named @code{.gnu_debuglink} with the contents
18245 @cindex @code{.note.gnu.build-id} sections
18246 @cindex build ID sections
18247 The build ID is a special section in the executable file (and in other
18248 ELF binary files that @value{GDBN} may consider). This section is
18249 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18250 It contains unique identification for the built files---the ID remains
18251 the same across multiple builds of the same build tree. The default
18252 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18253 content for the build ID string. The same section with an identical
18254 value is present in the original built binary with symbols, in its
18255 stripped variant, and in the separate debugging information file.
18257 The debugging information file itself should be an ordinary
18258 executable, containing a full set of linker symbols, sections, and
18259 debugging information. The sections of the debugging information file
18260 should have the same names, addresses, and sizes as the original file,
18261 but they need not contain any data---much like a @code{.bss} section
18262 in an ordinary executable.
18264 The @sc{gnu} binary utilities (Binutils) package includes the
18265 @samp{objcopy} utility that can produce
18266 the separated executable / debugging information file pairs using the
18267 following commands:
18270 @kbd{objcopy --only-keep-debug foo foo.debug}
18275 These commands remove the debugging
18276 information from the executable file @file{foo} and place it in the file
18277 @file{foo.debug}. You can use the first, second or both methods to link the
18282 The debug link method needs the following additional command to also leave
18283 behind a debug link in @file{foo}:
18286 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18289 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18290 a version of the @code{strip} command such that the command @kbd{strip foo -f
18291 foo.debug} has the same functionality as the two @code{objcopy} commands and
18292 the @code{ln -s} command above, together.
18295 Build ID gets embedded into the main executable using @code{ld --build-id} or
18296 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18297 compatibility fixes for debug files separation are present in @sc{gnu} binary
18298 utilities (Binutils) package since version 2.18.
18303 @cindex CRC algorithm definition
18304 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18305 IEEE 802.3 using the polynomial:
18307 @c TexInfo requires naked braces for multi-digit exponents for Tex
18308 @c output, but this causes HTML output to barf. HTML has to be set using
18309 @c raw commands. So we end up having to specify this equation in 2
18314 <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>
18315 + <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
18321 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18322 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18326 The function is computed byte at a time, taking the least
18327 significant bit of each byte first. The initial pattern
18328 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18329 the final result is inverted to ensure trailing zeros also affect the
18332 @emph{Note:} This is the same CRC polynomial as used in handling the
18333 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18334 However in the case of the Remote Serial Protocol, the CRC is computed
18335 @emph{most} significant bit first, and the result is not inverted, so
18336 trailing zeros have no effect on the CRC value.
18338 To complete the description, we show below the code of the function
18339 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18340 initially supplied @code{crc} argument means that an initial call to
18341 this function passing in zero will start computing the CRC using
18344 @kindex gnu_debuglink_crc32
18347 gnu_debuglink_crc32 (unsigned long crc,
18348 unsigned char *buf, size_t len)
18350 static const unsigned long crc32_table[256] =
18352 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18353 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18354 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18355 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18356 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18357 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18358 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18359 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18360 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18361 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18362 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18363 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18364 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18365 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18366 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18367 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18368 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18369 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18370 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18371 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18372 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18373 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18374 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18375 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18376 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18377 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18378 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18379 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18380 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18381 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18382 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18383 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18384 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18385 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18386 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18387 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18388 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18389 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18390 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18391 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18392 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18393 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18394 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18395 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18396 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18397 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18398 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18399 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18400 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18401 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18402 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18405 unsigned char *end;
18407 crc = ~crc & 0xffffffff;
18408 for (end = buf + len; buf < end; ++buf)
18409 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18410 return ~crc & 0xffffffff;
18415 This computation does not apply to the ``build ID'' method.
18417 @node MiniDebugInfo
18418 @section Debugging information in a special section
18419 @cindex separate debug sections
18420 @cindex @samp{.gnu_debugdata} section
18422 Some systems ship pre-built executables and libraries that have a
18423 special @samp{.gnu_debugdata} section. This feature is called
18424 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18425 is used to supply extra symbols for backtraces.
18427 The intent of this section is to provide extra minimal debugging
18428 information for use in simple backtraces. It is not intended to be a
18429 replacement for full separate debugging information (@pxref{Separate
18430 Debug Files}). The example below shows the intended use; however,
18431 @value{GDBN} does not currently put restrictions on what sort of
18432 debugging information might be included in the section.
18434 @value{GDBN} has support for this extension. If the section exists,
18435 then it is used provided that no other source of debugging information
18436 can be found, and that @value{GDBN} was configured with LZMA support.
18438 This section can be easily created using @command{objcopy} and other
18439 standard utilities:
18442 # Extract the dynamic symbols from the main binary, there is no need
18443 # to also have these in the normal symbol table.
18444 nm -D @var{binary} --format=posix --defined-only \
18445 | awk '@{ print $1 @}' | sort > dynsyms
18447 # Extract all the text (i.e. function) symbols from the debuginfo.
18448 # (Note that we actually also accept "D" symbols, for the benefit
18449 # of platforms like PowerPC64 that use function descriptors.)
18450 nm @var{binary} --format=posix --defined-only \
18451 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18454 # Keep all the function symbols not already in the dynamic symbol
18456 comm -13 dynsyms funcsyms > keep_symbols
18458 # Separate full debug info into debug binary.
18459 objcopy --only-keep-debug @var{binary} debug
18461 # Copy the full debuginfo, keeping only a minimal set of symbols and
18462 # removing some unnecessary sections.
18463 objcopy -S --remove-section .gdb_index --remove-section .comment \
18464 --keep-symbols=keep_symbols debug mini_debuginfo
18466 # Drop the full debug info from the original binary.
18467 strip --strip-all -R .comment @var{binary}
18469 # Inject the compressed data into the .gnu_debugdata section of the
18472 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18476 @section Index Files Speed Up @value{GDBN}
18477 @cindex index files
18478 @cindex @samp{.gdb_index} section
18480 When @value{GDBN} finds a symbol file, it scans the symbols in the
18481 file in order to construct an internal symbol table. This lets most
18482 @value{GDBN} operations work quickly---at the cost of a delay early
18483 on. For large programs, this delay can be quite lengthy, so
18484 @value{GDBN} provides a way to build an index, which speeds up
18487 The index is stored as a section in the symbol file. @value{GDBN} can
18488 write the index to a file, then you can put it into the symbol file
18489 using @command{objcopy}.
18491 To create an index file, use the @code{save gdb-index} command:
18494 @item save gdb-index @var{directory}
18495 @kindex save gdb-index
18496 Create an index file for each symbol file currently known by
18497 @value{GDBN}. Each file is named after its corresponding symbol file,
18498 with @samp{.gdb-index} appended, and is written into the given
18502 Once you have created an index file you can merge it into your symbol
18503 file, here named @file{symfile}, using @command{objcopy}:
18506 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18507 --set-section-flags .gdb_index=readonly symfile symfile
18510 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18511 sections that have been deprecated. Usually they are deprecated because
18512 they are missing a new feature or have performance issues.
18513 To tell @value{GDBN} to use a deprecated index section anyway
18514 specify @code{set use-deprecated-index-sections on}.
18515 The default is @code{off}.
18516 This can speed up startup, but may result in some functionality being lost.
18517 @xref{Index Section Format}.
18519 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18520 must be done before gdb reads the file. The following will not work:
18523 $ gdb -ex "set use-deprecated-index-sections on" <program>
18526 Instead you must do, for example,
18529 $ gdb -iex "set use-deprecated-index-sections on" <program>
18532 There are currently some limitation on indices. They only work when
18533 for DWARF debugging information, not stabs. And, they do not
18534 currently work for programs using Ada.
18536 @node Symbol Errors
18537 @section Errors Reading Symbol Files
18539 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18540 such as symbol types it does not recognize, or known bugs in compiler
18541 output. By default, @value{GDBN} does not notify you of such problems, since
18542 they are relatively common and primarily of interest to people
18543 debugging compilers. If you are interested in seeing information
18544 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18545 only one message about each such type of problem, no matter how many
18546 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18547 to see how many times the problems occur, with the @code{set
18548 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18551 The messages currently printed, and their meanings, include:
18554 @item inner block not inside outer block in @var{symbol}
18556 The symbol information shows where symbol scopes begin and end
18557 (such as at the start of a function or a block of statements). This
18558 error indicates that an inner scope block is not fully contained
18559 in its outer scope blocks.
18561 @value{GDBN} circumvents the problem by treating the inner block as if it had
18562 the same scope as the outer block. In the error message, @var{symbol}
18563 may be shown as ``@code{(don't know)}'' if the outer block is not a
18566 @item block at @var{address} out of order
18568 The symbol information for symbol scope blocks should occur in
18569 order of increasing addresses. This error indicates that it does not
18572 @value{GDBN} does not circumvent this problem, and has trouble
18573 locating symbols in the source file whose symbols it is reading. (You
18574 can often determine what source file is affected by specifying
18575 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18578 @item bad block start address patched
18580 The symbol information for a symbol scope block has a start address
18581 smaller than the address of the preceding source line. This is known
18582 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18584 @value{GDBN} circumvents the problem by treating the symbol scope block as
18585 starting on the previous source line.
18587 @item bad string table offset in symbol @var{n}
18590 Symbol number @var{n} contains a pointer into the string table which is
18591 larger than the size of the string table.
18593 @value{GDBN} circumvents the problem by considering the symbol to have the
18594 name @code{foo}, which may cause other problems if many symbols end up
18597 @item unknown symbol type @code{0x@var{nn}}
18599 The symbol information contains new data types that @value{GDBN} does
18600 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18601 uncomprehended information, in hexadecimal.
18603 @value{GDBN} circumvents the error by ignoring this symbol information.
18604 This usually allows you to debug your program, though certain symbols
18605 are not accessible. If you encounter such a problem and feel like
18606 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18607 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18608 and examine @code{*bufp} to see the symbol.
18610 @item stub type has NULL name
18612 @value{GDBN} could not find the full definition for a struct or class.
18614 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18615 The symbol information for a C@t{++} member function is missing some
18616 information that recent versions of the compiler should have output for
18619 @item info mismatch between compiler and debugger
18621 @value{GDBN} could not parse a type specification output by the compiler.
18626 @section GDB Data Files
18628 @cindex prefix for data files
18629 @value{GDBN} will sometimes read an auxiliary data file. These files
18630 are kept in a directory known as the @dfn{data directory}.
18632 You can set the data directory's name, and view the name @value{GDBN}
18633 is currently using.
18636 @kindex set data-directory
18637 @item set data-directory @var{directory}
18638 Set the directory which @value{GDBN} searches for auxiliary data files
18639 to @var{directory}.
18641 @kindex show data-directory
18642 @item show data-directory
18643 Show the directory @value{GDBN} searches for auxiliary data files.
18646 @cindex default data directory
18647 @cindex @samp{--with-gdb-datadir}
18648 You can set the default data directory by using the configure-time
18649 @samp{--with-gdb-datadir} option. If the data directory is inside
18650 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18651 @samp{--exec-prefix}), then the default data directory will be updated
18652 automatically if the installed @value{GDBN} is moved to a new
18655 The data directory may also be specified with the
18656 @code{--data-directory} command line option.
18657 @xref{Mode Options}.
18660 @chapter Specifying a Debugging Target
18662 @cindex debugging target
18663 A @dfn{target} is the execution environment occupied by your program.
18665 Often, @value{GDBN} runs in the same host environment as your program;
18666 in that case, the debugging target is specified as a side effect when
18667 you use the @code{file} or @code{core} commands. When you need more
18668 flexibility---for example, running @value{GDBN} on a physically separate
18669 host, or controlling a standalone system over a serial port or a
18670 realtime system over a TCP/IP connection---you can use the @code{target}
18671 command to specify one of the target types configured for @value{GDBN}
18672 (@pxref{Target Commands, ,Commands for Managing Targets}).
18674 @cindex target architecture
18675 It is possible to build @value{GDBN} for several different @dfn{target
18676 architectures}. When @value{GDBN} is built like that, you can choose
18677 one of the available architectures with the @kbd{set architecture}
18681 @kindex set architecture
18682 @kindex show architecture
18683 @item set architecture @var{arch}
18684 This command sets the current target architecture to @var{arch}. The
18685 value of @var{arch} can be @code{"auto"}, in addition to one of the
18686 supported architectures.
18688 @item show architecture
18689 Show the current target architecture.
18691 @item set processor
18693 @kindex set processor
18694 @kindex show processor
18695 These are alias commands for, respectively, @code{set architecture}
18696 and @code{show architecture}.
18700 * Active Targets:: Active targets
18701 * Target Commands:: Commands for managing targets
18702 * Byte Order:: Choosing target byte order
18705 @node Active Targets
18706 @section Active Targets
18708 @cindex stacking targets
18709 @cindex active targets
18710 @cindex multiple targets
18712 There are multiple classes of targets such as: processes, executable files or
18713 recording sessions. Core files belong to the process class, making core file
18714 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18715 on multiple active targets, one in each class. This allows you to (for
18716 example) start a process and inspect its activity, while still having access to
18717 the executable file after the process finishes. Or if you start process
18718 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18719 presented a virtual layer of the recording target, while the process target
18720 remains stopped at the chronologically last point of the process execution.
18722 Use the @code{core-file} and @code{exec-file} commands to select a new core
18723 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18724 specify as a target a process that is already running, use the @code{attach}
18725 command (@pxref{Attach, ,Debugging an Already-running Process}).
18727 @node Target Commands
18728 @section Commands for Managing Targets
18731 @item target @var{type} @var{parameters}
18732 Connects the @value{GDBN} host environment to a target machine or
18733 process. A target is typically a protocol for talking to debugging
18734 facilities. You use the argument @var{type} to specify the type or
18735 protocol of the target machine.
18737 Further @var{parameters} are interpreted by the target protocol, but
18738 typically include things like device names or host names to connect
18739 with, process numbers, and baud rates.
18741 The @code{target} command does not repeat if you press @key{RET} again
18742 after executing the command.
18744 @kindex help target
18746 Displays the names of all targets available. To display targets
18747 currently selected, use either @code{info target} or @code{info files}
18748 (@pxref{Files, ,Commands to Specify Files}).
18750 @item help target @var{name}
18751 Describe a particular target, including any parameters necessary to
18754 @kindex set gnutarget
18755 @item set gnutarget @var{args}
18756 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18757 knows whether it is reading an @dfn{executable},
18758 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18759 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18760 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18763 @emph{Warning:} To specify a file format with @code{set gnutarget},
18764 you must know the actual BFD name.
18768 @xref{Files, , Commands to Specify Files}.
18770 @kindex show gnutarget
18771 @item show gnutarget
18772 Use the @code{show gnutarget} command to display what file format
18773 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18774 @value{GDBN} will determine the file format for each file automatically,
18775 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18778 @cindex common targets
18779 Here are some common targets (available, or not, depending on the GDB
18784 @item target exec @var{program}
18785 @cindex executable file target
18786 An executable file. @samp{target exec @var{program}} is the same as
18787 @samp{exec-file @var{program}}.
18789 @item target core @var{filename}
18790 @cindex core dump file target
18791 A core dump file. @samp{target core @var{filename}} is the same as
18792 @samp{core-file @var{filename}}.
18794 @item target remote @var{medium}
18795 @cindex remote target
18796 A remote system connected to @value{GDBN} via a serial line or network
18797 connection. This command tells @value{GDBN} to use its own remote
18798 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18800 For example, if you have a board connected to @file{/dev/ttya} on the
18801 machine running @value{GDBN}, you could say:
18804 target remote /dev/ttya
18807 @code{target remote} supports the @code{load} command. This is only
18808 useful if you have some other way of getting the stub to the target
18809 system, and you can put it somewhere in memory where it won't get
18810 clobbered by the download.
18812 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18813 @cindex built-in simulator target
18814 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18822 works; however, you cannot assume that a specific memory map, device
18823 drivers, or even basic I/O is available, although some simulators do
18824 provide these. For info about any processor-specific simulator details,
18825 see the appropriate section in @ref{Embedded Processors, ,Embedded
18828 @item target native
18829 @cindex native target
18830 Setup for local/native process debugging. Useful to make the
18831 @code{run} command spawn native processes (likewise @code{attach},
18832 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18833 (@pxref{set auto-connect-native-target}).
18837 Different targets are available on different configurations of @value{GDBN};
18838 your configuration may have more or fewer targets.
18840 Many remote targets require you to download the executable's code once
18841 you've successfully established a connection. You may wish to control
18842 various aspects of this process.
18847 @kindex set hash@r{, for remote monitors}
18848 @cindex hash mark while downloading
18849 This command controls whether a hash mark @samp{#} is displayed while
18850 downloading a file to the remote monitor. If on, a hash mark is
18851 displayed after each S-record is successfully downloaded to the
18855 @kindex show hash@r{, for remote monitors}
18856 Show the current status of displaying the hash mark.
18858 @item set debug monitor
18859 @kindex set debug monitor
18860 @cindex display remote monitor communications
18861 Enable or disable display of communications messages between
18862 @value{GDBN} and the remote monitor.
18864 @item show debug monitor
18865 @kindex show debug monitor
18866 Show the current status of displaying communications between
18867 @value{GDBN} and the remote monitor.
18872 @kindex load @var{filename}
18873 @item load @var{filename}
18875 Depending on what remote debugging facilities are configured into
18876 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18877 is meant to make @var{filename} (an executable) available for debugging
18878 on the remote system---by downloading, or dynamic linking, for example.
18879 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18880 the @code{add-symbol-file} command.
18882 If your @value{GDBN} does not have a @code{load} command, attempting to
18883 execute it gets the error message ``@code{You can't do that when your
18884 target is @dots{}}''
18886 The file is loaded at whatever address is specified in the executable.
18887 For some object file formats, you can specify the load address when you
18888 link the program; for other formats, like a.out, the object file format
18889 specifies a fixed address.
18890 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18892 Depending on the remote side capabilities, @value{GDBN} may be able to
18893 load programs into flash memory.
18895 @code{load} does not repeat if you press @key{RET} again after using it.
18899 @section Choosing Target Byte Order
18901 @cindex choosing target byte order
18902 @cindex target byte order
18904 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18905 offer the ability to run either big-endian or little-endian byte
18906 orders. Usually the executable or symbol will include a bit to
18907 designate the endian-ness, and you will not need to worry about
18908 which to use. However, you may still find it useful to adjust
18909 @value{GDBN}'s idea of processor endian-ness manually.
18913 @item set endian big
18914 Instruct @value{GDBN} to assume the target is big-endian.
18916 @item set endian little
18917 Instruct @value{GDBN} to assume the target is little-endian.
18919 @item set endian auto
18920 Instruct @value{GDBN} to use the byte order associated with the
18924 Display @value{GDBN}'s current idea of the target byte order.
18928 Note that these commands merely adjust interpretation of symbolic
18929 data on the host, and that they have absolutely no effect on the
18933 @node Remote Debugging
18934 @chapter Debugging Remote Programs
18935 @cindex remote debugging
18937 If you are trying to debug a program running on a machine that cannot run
18938 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18939 For example, you might use remote debugging on an operating system kernel,
18940 or on a small system which does not have a general purpose operating system
18941 powerful enough to run a full-featured debugger.
18943 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18944 to make this work with particular debugging targets. In addition,
18945 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18946 but not specific to any particular target system) which you can use if you
18947 write the remote stubs---the code that runs on the remote system to
18948 communicate with @value{GDBN}.
18950 Other remote targets may be available in your
18951 configuration of @value{GDBN}; use @code{help target} to list them.
18954 * Connecting:: Connecting to a remote target
18955 * File Transfer:: Sending files to a remote system
18956 * Server:: Using the gdbserver program
18957 * Remote Configuration:: Remote configuration
18958 * Remote Stub:: Implementing a remote stub
18962 @section Connecting to a Remote Target
18964 @value{GDBN} needs an unstripped copy of your program to access symbol
18965 and debugging information. Some remote targets (@pxref{qXfer
18966 executable filename read}, and @pxref{Host I/O Packets}) allow
18967 @value{GDBN} to access program files over the same connection used to
18968 communicate with @value{GDBN}. With such a target, if the remote
18969 program is unstripped, the only command you need is @code{target
18970 remote}. Otherwise, start up @value{GDBN} using the name of the local
18971 unstripped copy of your program as the first argument, or use the
18972 @code{file} command.
18974 @cindex @code{target remote}
18975 @value{GDBN} can communicate with the target over a serial line, or
18976 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18977 each case, @value{GDBN} uses the same protocol for debugging your
18978 program; only the medium carrying the debugging packets varies. The
18979 @code{target remote} command establishes a connection to the target.
18980 Its arguments indicate which medium to use:
18984 @item target remote @var{serial-device}
18985 @cindex serial line, @code{target remote}
18986 Use @var{serial-device} to communicate with the target. For example,
18987 to use a serial line connected to the device named @file{/dev/ttyb}:
18990 target remote /dev/ttyb
18993 If you're using a serial line, you may want to give @value{GDBN} the
18994 @samp{--baud} option, or use the @code{set serial baud} command
18995 (@pxref{Remote Configuration, set serial baud}) before the
18996 @code{target} command.
18998 @item target remote @code{@var{host}:@var{port}}
18999 @itemx target remote @code{tcp:@var{host}:@var{port}}
19000 @cindex @acronym{TCP} port, @code{target remote}
19001 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19002 The @var{host} may be either a host name or a numeric @acronym{IP}
19003 address; @var{port} must be a decimal number. The @var{host} could be
19004 the target machine itself, if it is directly connected to the net, or
19005 it might be a terminal server which in turn has a serial line to the
19008 For example, to connect to port 2828 on a terminal server named
19012 target remote manyfarms:2828
19015 If your remote target is actually running on the same machine as your
19016 debugger session (e.g.@: a simulator for your target running on the
19017 same host), you can omit the hostname. For example, to connect to
19018 port 1234 on your local machine:
19021 target remote :1234
19025 Note that the colon is still required here.
19027 @item target remote @code{udp:@var{host}:@var{port}}
19028 @cindex @acronym{UDP} port, @code{target remote}
19029 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19030 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19033 target remote udp:manyfarms:2828
19036 When using a @acronym{UDP} connection for remote debugging, you should
19037 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19038 can silently drop packets on busy or unreliable networks, which will
19039 cause havoc with your debugging session.
19041 @item target remote | @var{command}
19042 @cindex pipe, @code{target remote} to
19043 Run @var{command} in the background and communicate with it using a
19044 pipe. The @var{command} is a shell command, to be parsed and expanded
19045 by the system's command shell, @code{/bin/sh}; it should expect remote
19046 protocol packets on its standard input, and send replies on its
19047 standard output. You could use this to run a stand-alone simulator
19048 that speaks the remote debugging protocol, to make net connections
19049 using programs like @code{ssh}, or for other similar tricks.
19051 If @var{command} closes its standard output (perhaps by exiting),
19052 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19053 program has already exited, this will have no effect.)
19057 Once the connection has been established, you can use all the usual
19058 commands to examine and change data. The remote program is already
19059 running; you can use @kbd{step} and @kbd{continue}, and you do not
19060 need to use @kbd{run}.
19062 @cindex interrupting remote programs
19063 @cindex remote programs, interrupting
19064 Whenever @value{GDBN} is waiting for the remote program, if you type the
19065 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19066 program. This may or may not succeed, depending in part on the hardware
19067 and the serial drivers the remote system uses. If you type the
19068 interrupt character once again, @value{GDBN} displays this prompt:
19071 Interrupted while waiting for the program.
19072 Give up (and stop debugging it)? (y or n)
19075 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19076 (If you decide you want to try again later, you can use @samp{target
19077 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19078 goes back to waiting.
19081 @kindex detach (remote)
19083 When you have finished debugging the remote program, you can use the
19084 @code{detach} command to release it from @value{GDBN} control.
19085 Detaching from the target normally resumes its execution, but the results
19086 will depend on your particular remote stub. After the @code{detach}
19087 command, @value{GDBN} is free to connect to another target.
19091 The @code{disconnect} command behaves like @code{detach}, except that
19092 the target is generally not resumed. It will wait for @value{GDBN}
19093 (this instance or another one) to connect and continue debugging. After
19094 the @code{disconnect} command, @value{GDBN} is again free to connect to
19097 @cindex send command to remote monitor
19098 @cindex extend @value{GDBN} for remote targets
19099 @cindex add new commands for external monitor
19101 @item monitor @var{cmd}
19102 This command allows you to send arbitrary commands directly to the
19103 remote monitor. Since @value{GDBN} doesn't care about the commands it
19104 sends like this, this command is the way to extend @value{GDBN}---you
19105 can add new commands that only the external monitor will understand
19109 @node File Transfer
19110 @section Sending files to a remote system
19111 @cindex remote target, file transfer
19112 @cindex file transfer
19113 @cindex sending files to remote systems
19115 Some remote targets offer the ability to transfer files over the same
19116 connection used to communicate with @value{GDBN}. This is convenient
19117 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19118 running @code{gdbserver} over a network interface. For other targets,
19119 e.g.@: embedded devices with only a single serial port, this may be
19120 the only way to upload or download files.
19122 Not all remote targets support these commands.
19126 @item remote put @var{hostfile} @var{targetfile}
19127 Copy file @var{hostfile} from the host system (the machine running
19128 @value{GDBN}) to @var{targetfile} on the target system.
19131 @item remote get @var{targetfile} @var{hostfile}
19132 Copy file @var{targetfile} from the target system to @var{hostfile}
19133 on the host system.
19135 @kindex remote delete
19136 @item remote delete @var{targetfile}
19137 Delete @var{targetfile} from the target system.
19142 @section Using the @code{gdbserver} Program
19145 @cindex remote connection without stubs
19146 @code{gdbserver} is a control program for Unix-like systems, which
19147 allows you to connect your program with a remote @value{GDBN} via
19148 @code{target remote}---but without linking in the usual debugging stub.
19150 @code{gdbserver} is not a complete replacement for the debugging stubs,
19151 because it requires essentially the same operating-system facilities
19152 that @value{GDBN} itself does. In fact, a system that can run
19153 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19154 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19155 because it is a much smaller program than @value{GDBN} itself. It is
19156 also easier to port than all of @value{GDBN}, so you may be able to get
19157 started more quickly on a new system by using @code{gdbserver}.
19158 Finally, if you develop code for real-time systems, you may find that
19159 the tradeoffs involved in real-time operation make it more convenient to
19160 do as much development work as possible on another system, for example
19161 by cross-compiling. You can use @code{gdbserver} to make a similar
19162 choice for debugging.
19164 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19165 or a TCP connection, using the standard @value{GDBN} remote serial
19169 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19170 Do not run @code{gdbserver} connected to any public network; a
19171 @value{GDBN} connection to @code{gdbserver} provides access to the
19172 target system with the same privileges as the user running
19176 @subsection Running @code{gdbserver}
19177 @cindex arguments, to @code{gdbserver}
19178 @cindex @code{gdbserver}, command-line arguments
19180 Run @code{gdbserver} on the target system. You need a copy of the
19181 program you want to debug, including any libraries it requires.
19182 @code{gdbserver} does not need your program's symbol table, so you can
19183 strip the program if necessary to save space. @value{GDBN} on the host
19184 system does all the symbol handling.
19186 To use the server, you must tell it how to communicate with @value{GDBN};
19187 the name of your program; and the arguments for your program. The usual
19191 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19194 @var{comm} is either a device name (to use a serial line), or a TCP
19195 hostname and portnumber, or @code{-} or @code{stdio} to use
19196 stdin/stdout of @code{gdbserver}.
19197 For example, to debug Emacs with the argument
19198 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19202 target> gdbserver /dev/com1 emacs foo.txt
19205 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19208 To use a TCP connection instead of a serial line:
19211 target> gdbserver host:2345 emacs foo.txt
19214 The only difference from the previous example is the first argument,
19215 specifying that you are communicating with the host @value{GDBN} via
19216 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19217 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19218 (Currently, the @samp{host} part is ignored.) You can choose any number
19219 you want for the port number as long as it does not conflict with any
19220 TCP ports already in use on the target system (for example, @code{23} is
19221 reserved for @code{telnet}).@footnote{If you choose a port number that
19222 conflicts with another service, @code{gdbserver} prints an error message
19223 and exits.} You must use the same port number with the host @value{GDBN}
19224 @code{target remote} command.
19226 The @code{stdio} connection is useful when starting @code{gdbserver}
19230 (gdb) target remote | ssh -T hostname gdbserver - hello
19233 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19234 and we don't want escape-character handling. Ssh does this by default when
19235 a command is provided, the flag is provided to make it explicit.
19236 You could elide it if you want to.
19238 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19239 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19240 display through a pipe connected to gdbserver.
19241 Both @code{stdout} and @code{stderr} use the same pipe.
19243 @subsubsection Attaching to a Running Program
19244 @cindex attach to a program, @code{gdbserver}
19245 @cindex @option{--attach}, @code{gdbserver} option
19247 On some targets, @code{gdbserver} can also attach to running programs.
19248 This is accomplished via the @code{--attach} argument. The syntax is:
19251 target> gdbserver --attach @var{comm} @var{pid}
19254 @var{pid} is the process ID of a currently running process. It isn't necessary
19255 to point @code{gdbserver} at a binary for the running process.
19258 You can debug processes by name instead of process ID if your target has the
19259 @code{pidof} utility:
19262 target> gdbserver --attach @var{comm} `pidof @var{program}`
19265 In case more than one copy of @var{program} is running, or @var{program}
19266 has multiple threads, most versions of @code{pidof} support the
19267 @code{-s} option to only return the first process ID.
19269 @subsubsection Multi-Process Mode for @code{gdbserver}
19270 @cindex @code{gdbserver}, multiple processes
19271 @cindex multiple processes with @code{gdbserver}
19273 When you connect to @code{gdbserver} using @code{target remote},
19274 @code{gdbserver} debugs the specified program only once. When the
19275 program exits, or you detach from it, @value{GDBN} closes the connection
19276 and @code{gdbserver} exits.
19278 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19279 enters multi-process mode. When the debugged program exits, or you
19280 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19281 though no program is running. The @code{run} and @code{attach}
19282 commands instruct @code{gdbserver} to run or attach to a new program.
19283 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19284 remote exec-file}) to select the program to run. Command line
19285 arguments are supported, except for wildcard expansion and I/O
19286 redirection (@pxref{Arguments}).
19288 @cindex @option{--multi}, @code{gdbserver} option
19289 To start @code{gdbserver} without supplying an initial command to run
19290 or process ID to attach, use the @option{--multi} command line option.
19291 Then you can connect using @kbd{target extended-remote} and start
19292 the program you want to debug.
19294 In multi-process mode @code{gdbserver} does not automatically exit unless you
19295 use the option @option{--once}. You can terminate it by using
19296 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19297 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19298 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19299 @option{--multi} option to @code{gdbserver} has no influence on that.
19301 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19303 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19305 @code{gdbserver} normally terminates after all of its debugged processes have
19306 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19307 extended-remote}, @code{gdbserver} stays running even with no processes left.
19308 @value{GDBN} normally terminates the spawned debugged process on its exit,
19309 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19310 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19311 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19312 stays running even in the @kbd{target remote} mode.
19314 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19315 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19316 completeness, at most one @value{GDBN} can be connected at a time.
19318 @cindex @option{--once}, @code{gdbserver} option
19319 By default, @code{gdbserver} keeps the listening TCP port open, so that
19320 subsequent connections are possible. However, if you start @code{gdbserver}
19321 with the @option{--once} option, it will stop listening for any further
19322 connection attempts after connecting to the first @value{GDBN} session. This
19323 means no further connections to @code{gdbserver} will be possible after the
19324 first one. It also means @code{gdbserver} will terminate after the first
19325 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19326 connections and even in the @kbd{target extended-remote} mode. The
19327 @option{--once} option allows reusing the same port number for connecting to
19328 multiple instances of @code{gdbserver} running on the same host, since each
19329 instance closes its port after the first connection.
19331 @anchor{Other Command-Line Arguments for gdbserver}
19332 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19334 @cindex @option{--debug}, @code{gdbserver} option
19335 The @option{--debug} option tells @code{gdbserver} to display extra
19336 status information about the debugging process.
19337 @cindex @option{--remote-debug}, @code{gdbserver} option
19338 The @option{--remote-debug} option tells @code{gdbserver} to display
19339 remote protocol debug output. These options are intended for
19340 @code{gdbserver} development and for bug reports to the developers.
19342 @cindex @option{--debug-format}, @code{gdbserver} option
19343 The @option{--debug-format=option1[,option2,...]} option tells
19344 @code{gdbserver} to include additional information in each output.
19345 Possible options are:
19349 Turn off all extra information in debugging output.
19351 Turn on all extra information in debugging output.
19353 Include a timestamp in each line of debugging output.
19356 Options are processed in order. Thus, for example, if @option{none}
19357 appears last then no additional information is added to debugging output.
19359 @cindex @option{--wrapper}, @code{gdbserver} option
19360 The @option{--wrapper} option specifies a wrapper to launch programs
19361 for debugging. The option should be followed by the name of the
19362 wrapper, then any command-line arguments to pass to the wrapper, then
19363 @kbd{--} indicating the end of the wrapper arguments.
19365 @code{gdbserver} runs the specified wrapper program with a combined
19366 command line including the wrapper arguments, then the name of the
19367 program to debug, then any arguments to the program. The wrapper
19368 runs until it executes your program, and then @value{GDBN} gains control.
19370 You can use any program that eventually calls @code{execve} with
19371 its arguments as a wrapper. Several standard Unix utilities do
19372 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19373 with @code{exec "$@@"} will also work.
19375 For example, you can use @code{env} to pass an environment variable to
19376 the debugged program, without setting the variable in @code{gdbserver}'s
19380 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19383 @subsection Connecting to @code{gdbserver}
19385 Run @value{GDBN} on the host system.
19387 First make sure you have the necessary symbol files. Load symbols for
19388 your application using the @code{file} command before you connect. Use
19389 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19390 was compiled with the correct sysroot using @code{--with-sysroot}).
19392 The symbol file and target libraries must exactly match the executable
19393 and libraries on the target, with one exception: the files on the host
19394 system should not be stripped, even if the files on the target system
19395 are. Mismatched or missing files will lead to confusing results
19396 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19397 files may also prevent @code{gdbserver} from debugging multi-threaded
19400 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19401 For TCP connections, you must start up @code{gdbserver} prior to using
19402 the @code{target remote} command. Otherwise you may get an error whose
19403 text depends on the host system, but which usually looks something like
19404 @samp{Connection refused}. Don't use the @code{load}
19405 command in @value{GDBN} when using @code{gdbserver}, since the program is
19406 already on the target.
19408 @subsection Monitor Commands for @code{gdbserver}
19409 @cindex monitor commands, for @code{gdbserver}
19410 @anchor{Monitor Commands for gdbserver}
19412 During a @value{GDBN} session using @code{gdbserver}, you can use the
19413 @code{monitor} command to send special requests to @code{gdbserver}.
19414 Here are the available commands.
19418 List the available monitor commands.
19420 @item monitor set debug 0
19421 @itemx monitor set debug 1
19422 Disable or enable general debugging messages.
19424 @item monitor set remote-debug 0
19425 @itemx monitor set remote-debug 1
19426 Disable or enable specific debugging messages associated with the remote
19427 protocol (@pxref{Remote Protocol}).
19429 @item monitor set debug-format option1@r{[},option2,...@r{]}
19430 Specify additional text to add to debugging messages.
19431 Possible options are:
19435 Turn off all extra information in debugging output.
19437 Turn on all extra information in debugging output.
19439 Include a timestamp in each line of debugging output.
19442 Options are processed in order. Thus, for example, if @option{none}
19443 appears last then no additional information is added to debugging output.
19445 @item monitor set libthread-db-search-path [PATH]
19446 @cindex gdbserver, search path for @code{libthread_db}
19447 When this command is issued, @var{path} is a colon-separated list of
19448 directories to search for @code{libthread_db} (@pxref{Threads,,set
19449 libthread-db-search-path}). If you omit @var{path},
19450 @samp{libthread-db-search-path} will be reset to its default value.
19452 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19453 not supported in @code{gdbserver}.
19456 Tell gdbserver to exit immediately. This command should be followed by
19457 @code{disconnect} to close the debugging session. @code{gdbserver} will
19458 detach from any attached processes and kill any processes it created.
19459 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19460 of a multi-process mode debug session.
19464 @subsection Tracepoints support in @code{gdbserver}
19465 @cindex tracepoints support in @code{gdbserver}
19467 On some targets, @code{gdbserver} supports tracepoints, fast
19468 tracepoints and static tracepoints.
19470 For fast or static tracepoints to work, a special library called the
19471 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19472 This library is built and distributed as an integral part of
19473 @code{gdbserver}. In addition, support for static tracepoints
19474 requires building the in-process agent library with static tracepoints
19475 support. At present, the UST (LTTng Userspace Tracer,
19476 @url{http://lttng.org/ust}) tracing engine is supported. This support
19477 is automatically available if UST development headers are found in the
19478 standard include path when @code{gdbserver} is built, or if
19479 @code{gdbserver} was explicitly configured using @option{--with-ust}
19480 to point at such headers. You can explicitly disable the support
19481 using @option{--with-ust=no}.
19483 There are several ways to load the in-process agent in your program:
19486 @item Specifying it as dependency at link time
19488 You can link your program dynamically with the in-process agent
19489 library. On most systems, this is accomplished by adding
19490 @code{-linproctrace} to the link command.
19492 @item Using the system's preloading mechanisms
19494 You can force loading the in-process agent at startup time by using
19495 your system's support for preloading shared libraries. Many Unixes
19496 support the concept of preloading user defined libraries. In most
19497 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19498 in the environment. See also the description of @code{gdbserver}'s
19499 @option{--wrapper} command line option.
19501 @item Using @value{GDBN} to force loading the agent at run time
19503 On some systems, you can force the inferior to load a shared library,
19504 by calling a dynamic loader function in the inferior that takes care
19505 of dynamically looking up and loading a shared library. On most Unix
19506 systems, the function is @code{dlopen}. You'll use the @code{call}
19507 command for that. For example:
19510 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19513 Note that on most Unix systems, for the @code{dlopen} function to be
19514 available, the program needs to be linked with @code{-ldl}.
19517 On systems that have a userspace dynamic loader, like most Unix
19518 systems, when you connect to @code{gdbserver} using @code{target
19519 remote}, you'll find that the program is stopped at the dynamic
19520 loader's entry point, and no shared library has been loaded in the
19521 program's address space yet, including the in-process agent. In that
19522 case, before being able to use any of the fast or static tracepoints
19523 features, you need to let the loader run and load the shared
19524 libraries. The simplest way to do that is to run the program to the
19525 main procedure. E.g., if debugging a C or C@t{++} program, start
19526 @code{gdbserver} like so:
19529 $ gdbserver :9999 myprogram
19532 Start GDB and connect to @code{gdbserver} like so, and run to main:
19536 (@value{GDBP}) target remote myhost:9999
19537 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19538 (@value{GDBP}) b main
19539 (@value{GDBP}) continue
19542 The in-process tracing agent library should now be loaded into the
19543 process; you can confirm it with the @code{info sharedlibrary}
19544 command, which will list @file{libinproctrace.so} as loaded in the
19545 process. You are now ready to install fast tracepoints, list static
19546 tracepoint markers, probe static tracepoints markers, and start
19549 @node Remote Configuration
19550 @section Remote Configuration
19553 @kindex show remote
19554 This section documents the configuration options available when
19555 debugging remote programs. For the options related to the File I/O
19556 extensions of the remote protocol, see @ref{system,
19557 system-call-allowed}.
19560 @item set remoteaddresssize @var{bits}
19561 @cindex address size for remote targets
19562 @cindex bits in remote address
19563 Set the maximum size of address in a memory packet to the specified
19564 number of bits. @value{GDBN} will mask off the address bits above
19565 that number, when it passes addresses to the remote target. The
19566 default value is the number of bits in the target's address.
19568 @item show remoteaddresssize
19569 Show the current value of remote address size in bits.
19571 @item set serial baud @var{n}
19572 @cindex baud rate for remote targets
19573 Set the baud rate for the remote serial I/O to @var{n} baud. The
19574 value is used to set the speed of the serial port used for debugging
19577 @item show serial baud
19578 Show the current speed of the remote connection.
19580 @item set serial parity @var{parity}
19581 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19582 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19584 @item show serial parity
19585 Show the current parity of the serial port.
19587 @item set remotebreak
19588 @cindex interrupt remote programs
19589 @cindex BREAK signal instead of Ctrl-C
19590 @anchor{set remotebreak}
19591 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19592 when you type @kbd{Ctrl-c} to interrupt the program running
19593 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19594 character instead. The default is off, since most remote systems
19595 expect to see @samp{Ctrl-C} as the interrupt signal.
19597 @item show remotebreak
19598 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19599 interrupt the remote program.
19601 @item set remoteflow on
19602 @itemx set remoteflow off
19603 @kindex set remoteflow
19604 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19605 on the serial port used to communicate to the remote target.
19607 @item show remoteflow
19608 @kindex show remoteflow
19609 Show the current setting of hardware flow control.
19611 @item set remotelogbase @var{base}
19612 Set the base (a.k.a.@: radix) of logging serial protocol
19613 communications to @var{base}. Supported values of @var{base} are:
19614 @code{ascii}, @code{octal}, and @code{hex}. The default is
19617 @item show remotelogbase
19618 Show the current setting of the radix for logging remote serial
19621 @item set remotelogfile @var{file}
19622 @cindex record serial communications on file
19623 Record remote serial communications on the named @var{file}. The
19624 default is not to record at all.
19626 @item show remotelogfile.
19627 Show the current setting of the file name on which to record the
19628 serial communications.
19630 @item set remotetimeout @var{num}
19631 @cindex timeout for serial communications
19632 @cindex remote timeout
19633 Set the timeout limit to wait for the remote target to respond to
19634 @var{num} seconds. The default is 2 seconds.
19636 @item show remotetimeout
19637 Show the current number of seconds to wait for the remote target
19640 @cindex limit hardware breakpoints and watchpoints
19641 @cindex remote target, limit break- and watchpoints
19642 @anchor{set remote hardware-watchpoint-limit}
19643 @anchor{set remote hardware-breakpoint-limit}
19644 @item set remote hardware-watchpoint-limit @var{limit}
19645 @itemx set remote hardware-breakpoint-limit @var{limit}
19646 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19647 watchpoints. A limit of -1, the default, is treated as unlimited.
19649 @cindex limit hardware watchpoints length
19650 @cindex remote target, limit watchpoints length
19651 @anchor{set remote hardware-watchpoint-length-limit}
19652 @item set remote hardware-watchpoint-length-limit @var{limit}
19653 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19654 a remote hardware watchpoint. A limit of -1, the default, is treated
19657 @item show remote hardware-watchpoint-length-limit
19658 Show the current limit (in bytes) of the maximum length of
19659 a remote hardware watchpoint.
19661 @item set remote exec-file @var{filename}
19662 @itemx show remote exec-file
19663 @anchor{set remote exec-file}
19664 @cindex executable file, for remote target
19665 Select the file used for @code{run} with @code{target
19666 extended-remote}. This should be set to a filename valid on the
19667 target system. If it is not set, the target will use a default
19668 filename (e.g.@: the last program run).
19670 @item set remote interrupt-sequence
19671 @cindex interrupt remote programs
19672 @cindex select Ctrl-C, BREAK or BREAK-g
19673 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19674 @samp{BREAK-g} as the
19675 sequence to the remote target in order to interrupt the execution.
19676 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19677 is high level of serial line for some certain time.
19678 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19679 It is @code{BREAK} signal followed by character @code{g}.
19681 @item show interrupt-sequence
19682 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19683 is sent by @value{GDBN} to interrupt the remote program.
19684 @code{BREAK-g} is BREAK signal followed by @code{g} and
19685 also known as Magic SysRq g.
19687 @item set remote interrupt-on-connect
19688 @cindex send interrupt-sequence on start
19689 Specify whether interrupt-sequence is sent to remote target when
19690 @value{GDBN} connects to it. This is mostly needed when you debug
19691 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19692 which is known as Magic SysRq g in order to connect @value{GDBN}.
19694 @item show interrupt-on-connect
19695 Show whether interrupt-sequence is sent
19696 to remote target when @value{GDBN} connects to it.
19700 @item set tcp auto-retry on
19701 @cindex auto-retry, for remote TCP target
19702 Enable auto-retry for remote TCP connections. This is useful if the remote
19703 debugging agent is launched in parallel with @value{GDBN}; there is a race
19704 condition because the agent may not become ready to accept the connection
19705 before @value{GDBN} attempts to connect. When auto-retry is
19706 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19707 to establish the connection using the timeout specified by
19708 @code{set tcp connect-timeout}.
19710 @item set tcp auto-retry off
19711 Do not auto-retry failed TCP connections.
19713 @item show tcp auto-retry
19714 Show the current auto-retry setting.
19716 @item set tcp connect-timeout @var{seconds}
19717 @itemx set tcp connect-timeout unlimited
19718 @cindex connection timeout, for remote TCP target
19719 @cindex timeout, for remote target connection
19720 Set the timeout for establishing a TCP connection to the remote target to
19721 @var{seconds}. The timeout affects both polling to retry failed connections
19722 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19723 that are merely slow to complete, and represents an approximate cumulative
19724 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19725 @value{GDBN} will keep attempting to establish a connection forever,
19726 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19728 @item show tcp connect-timeout
19729 Show the current connection timeout setting.
19732 @cindex remote packets, enabling and disabling
19733 The @value{GDBN} remote protocol autodetects the packets supported by
19734 your debugging stub. If you need to override the autodetection, you
19735 can use these commands to enable or disable individual packets. Each
19736 packet can be set to @samp{on} (the remote target supports this
19737 packet), @samp{off} (the remote target does not support this packet),
19738 or @samp{auto} (detect remote target support for this packet). They
19739 all default to @samp{auto}. For more information about each packet,
19740 see @ref{Remote Protocol}.
19742 During normal use, you should not have to use any of these commands.
19743 If you do, that may be a bug in your remote debugging stub, or a bug
19744 in @value{GDBN}. You may want to report the problem to the
19745 @value{GDBN} developers.
19747 For each packet @var{name}, the command to enable or disable the
19748 packet is @code{set remote @var{name}-packet}. The available settings
19751 @multitable @columnfractions 0.28 0.32 0.25
19754 @tab Related Features
19756 @item @code{fetch-register}
19758 @tab @code{info registers}
19760 @item @code{set-register}
19764 @item @code{binary-download}
19766 @tab @code{load}, @code{set}
19768 @item @code{read-aux-vector}
19769 @tab @code{qXfer:auxv:read}
19770 @tab @code{info auxv}
19772 @item @code{symbol-lookup}
19773 @tab @code{qSymbol}
19774 @tab Detecting multiple threads
19776 @item @code{attach}
19777 @tab @code{vAttach}
19780 @item @code{verbose-resume}
19782 @tab Stepping or resuming multiple threads
19788 @item @code{software-breakpoint}
19792 @item @code{hardware-breakpoint}
19796 @item @code{write-watchpoint}
19800 @item @code{read-watchpoint}
19804 @item @code{access-watchpoint}
19808 @item @code{pid-to-exec-file}
19809 @tab @code{qXfer:exec-file:read}
19810 @tab @code{attach}, @code{run}
19812 @item @code{target-features}
19813 @tab @code{qXfer:features:read}
19814 @tab @code{set architecture}
19816 @item @code{library-info}
19817 @tab @code{qXfer:libraries:read}
19818 @tab @code{info sharedlibrary}
19820 @item @code{memory-map}
19821 @tab @code{qXfer:memory-map:read}
19822 @tab @code{info mem}
19824 @item @code{read-sdata-object}
19825 @tab @code{qXfer:sdata:read}
19826 @tab @code{print $_sdata}
19828 @item @code{read-spu-object}
19829 @tab @code{qXfer:spu:read}
19830 @tab @code{info spu}
19832 @item @code{write-spu-object}
19833 @tab @code{qXfer:spu:write}
19834 @tab @code{info spu}
19836 @item @code{read-siginfo-object}
19837 @tab @code{qXfer:siginfo:read}
19838 @tab @code{print $_siginfo}
19840 @item @code{write-siginfo-object}
19841 @tab @code{qXfer:siginfo:write}
19842 @tab @code{set $_siginfo}
19844 @item @code{threads}
19845 @tab @code{qXfer:threads:read}
19846 @tab @code{info threads}
19848 @item @code{get-thread-local-@*storage-address}
19849 @tab @code{qGetTLSAddr}
19850 @tab Displaying @code{__thread} variables
19852 @item @code{get-thread-information-block-address}
19853 @tab @code{qGetTIBAddr}
19854 @tab Display MS-Windows Thread Information Block.
19856 @item @code{search-memory}
19857 @tab @code{qSearch:memory}
19860 @item @code{supported-packets}
19861 @tab @code{qSupported}
19862 @tab Remote communications parameters
19864 @item @code{pass-signals}
19865 @tab @code{QPassSignals}
19866 @tab @code{handle @var{signal}}
19868 @item @code{program-signals}
19869 @tab @code{QProgramSignals}
19870 @tab @code{handle @var{signal}}
19872 @item @code{hostio-close-packet}
19873 @tab @code{vFile:close}
19874 @tab @code{remote get}, @code{remote put}
19876 @item @code{hostio-open-packet}
19877 @tab @code{vFile:open}
19878 @tab @code{remote get}, @code{remote put}
19880 @item @code{hostio-pread-packet}
19881 @tab @code{vFile:pread}
19882 @tab @code{remote get}, @code{remote put}
19884 @item @code{hostio-pwrite-packet}
19885 @tab @code{vFile:pwrite}
19886 @tab @code{remote get}, @code{remote put}
19888 @item @code{hostio-unlink-packet}
19889 @tab @code{vFile:unlink}
19890 @tab @code{remote delete}
19892 @item @code{hostio-readlink-packet}
19893 @tab @code{vFile:readlink}
19896 @item @code{hostio-fstat-packet}
19897 @tab @code{vFile:fstat}
19900 @item @code{noack-packet}
19901 @tab @code{QStartNoAckMode}
19902 @tab Packet acknowledgment
19904 @item @code{osdata}
19905 @tab @code{qXfer:osdata:read}
19906 @tab @code{info os}
19908 @item @code{query-attached}
19909 @tab @code{qAttached}
19910 @tab Querying remote process attach state.
19912 @item @code{trace-buffer-size}
19913 @tab @code{QTBuffer:size}
19914 @tab @code{set trace-buffer-size}
19916 @item @code{trace-status}
19917 @tab @code{qTStatus}
19918 @tab @code{tstatus}
19920 @item @code{traceframe-info}
19921 @tab @code{qXfer:traceframe-info:read}
19922 @tab Traceframe info
19924 @item @code{install-in-trace}
19925 @tab @code{InstallInTrace}
19926 @tab Install tracepoint in tracing
19928 @item @code{disable-randomization}
19929 @tab @code{QDisableRandomization}
19930 @tab @code{set disable-randomization}
19932 @item @code{conditional-breakpoints-packet}
19933 @tab @code{Z0 and Z1}
19934 @tab @code{Support for target-side breakpoint condition evaluation}
19936 @item @code{swbreak-feature}
19937 @tab @code{swbreak stop reason}
19940 @item @code{hwbreak-feature}
19941 @tab @code{hwbreak stop reason}
19944 @item @code{fork-event-feature}
19945 @tab @code{fork stop reason}
19948 @item @code{vfork-event-feature}
19949 @tab @code{vfork stop reason}
19955 @section Implementing a Remote Stub
19957 @cindex debugging stub, example
19958 @cindex remote stub, example
19959 @cindex stub example, remote debugging
19960 The stub files provided with @value{GDBN} implement the target side of the
19961 communication protocol, and the @value{GDBN} side is implemented in the
19962 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19963 these subroutines to communicate, and ignore the details. (If you're
19964 implementing your own stub file, you can still ignore the details: start
19965 with one of the existing stub files. @file{sparc-stub.c} is the best
19966 organized, and therefore the easiest to read.)
19968 @cindex remote serial debugging, overview
19969 To debug a program running on another machine (the debugging
19970 @dfn{target} machine), you must first arrange for all the usual
19971 prerequisites for the program to run by itself. For example, for a C
19976 A startup routine to set up the C runtime environment; these usually
19977 have a name like @file{crt0}. The startup routine may be supplied by
19978 your hardware supplier, or you may have to write your own.
19981 A C subroutine library to support your program's
19982 subroutine calls, notably managing input and output.
19985 A way of getting your program to the other machine---for example, a
19986 download program. These are often supplied by the hardware
19987 manufacturer, but you may have to write your own from hardware
19991 The next step is to arrange for your program to use a serial port to
19992 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19993 machine). In general terms, the scheme looks like this:
19997 @value{GDBN} already understands how to use this protocol; when everything
19998 else is set up, you can simply use the @samp{target remote} command
19999 (@pxref{Targets,,Specifying a Debugging Target}).
20001 @item On the target,
20002 you must link with your program a few special-purpose subroutines that
20003 implement the @value{GDBN} remote serial protocol. The file containing these
20004 subroutines is called a @dfn{debugging stub}.
20006 On certain remote targets, you can use an auxiliary program
20007 @code{gdbserver} instead of linking a stub into your program.
20008 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20011 The debugging stub is specific to the architecture of the remote
20012 machine; for example, use @file{sparc-stub.c} to debug programs on
20015 @cindex remote serial stub list
20016 These working remote stubs are distributed with @value{GDBN}:
20021 @cindex @file{i386-stub.c}
20024 For Intel 386 and compatible architectures.
20027 @cindex @file{m68k-stub.c}
20028 @cindex Motorola 680x0
20030 For Motorola 680x0 architectures.
20033 @cindex @file{sh-stub.c}
20036 For Renesas SH architectures.
20039 @cindex @file{sparc-stub.c}
20041 For @sc{sparc} architectures.
20043 @item sparcl-stub.c
20044 @cindex @file{sparcl-stub.c}
20047 For Fujitsu @sc{sparclite} architectures.
20051 The @file{README} file in the @value{GDBN} distribution may list other
20052 recently added stubs.
20055 * Stub Contents:: What the stub can do for you
20056 * Bootstrapping:: What you must do for the stub
20057 * Debug Session:: Putting it all together
20060 @node Stub Contents
20061 @subsection What the Stub Can Do for You
20063 @cindex remote serial stub
20064 The debugging stub for your architecture supplies these three
20068 @item set_debug_traps
20069 @findex set_debug_traps
20070 @cindex remote serial stub, initialization
20071 This routine arranges for @code{handle_exception} to run when your
20072 program stops. You must call this subroutine explicitly in your
20073 program's startup code.
20075 @item handle_exception
20076 @findex handle_exception
20077 @cindex remote serial stub, main routine
20078 This is the central workhorse, but your program never calls it
20079 explicitly---the setup code arranges for @code{handle_exception} to
20080 run when a trap is triggered.
20082 @code{handle_exception} takes control when your program stops during
20083 execution (for example, on a breakpoint), and mediates communications
20084 with @value{GDBN} on the host machine. This is where the communications
20085 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20086 representative on the target machine. It begins by sending summary
20087 information on the state of your program, then continues to execute,
20088 retrieving and transmitting any information @value{GDBN} needs, until you
20089 execute a @value{GDBN} command that makes your program resume; at that point,
20090 @code{handle_exception} returns control to your own code on the target
20094 @cindex @code{breakpoint} subroutine, remote
20095 Use this auxiliary subroutine to make your program contain a
20096 breakpoint. Depending on the particular situation, this may be the only
20097 way for @value{GDBN} to get control. For instance, if your target
20098 machine has some sort of interrupt button, you won't need to call this;
20099 pressing the interrupt button transfers control to
20100 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20101 simply receiving characters on the serial port may also trigger a trap;
20102 again, in that situation, you don't need to call @code{breakpoint} from
20103 your own program---simply running @samp{target remote} from the host
20104 @value{GDBN} session gets control.
20106 Call @code{breakpoint} if none of these is true, or if you simply want
20107 to make certain your program stops at a predetermined point for the
20108 start of your debugging session.
20111 @node Bootstrapping
20112 @subsection What You Must Do for the Stub
20114 @cindex remote stub, support routines
20115 The debugging stubs that come with @value{GDBN} are set up for a particular
20116 chip architecture, but they have no information about the rest of your
20117 debugging target machine.
20119 First of all you need to tell the stub how to communicate with the
20123 @item int getDebugChar()
20124 @findex getDebugChar
20125 Write this subroutine to read a single character from the serial port.
20126 It may be identical to @code{getchar} for your target system; a
20127 different name is used to allow you to distinguish the two if you wish.
20129 @item void putDebugChar(int)
20130 @findex putDebugChar
20131 Write this subroutine to write a single character to the serial port.
20132 It may be identical to @code{putchar} for your target system; a
20133 different name is used to allow you to distinguish the two if you wish.
20136 @cindex control C, and remote debugging
20137 @cindex interrupting remote targets
20138 If you want @value{GDBN} to be able to stop your program while it is
20139 running, you need to use an interrupt-driven serial driver, and arrange
20140 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20141 character). That is the character which @value{GDBN} uses to tell the
20142 remote system to stop.
20144 Getting the debugging target to return the proper status to @value{GDBN}
20145 probably requires changes to the standard stub; one quick and dirty way
20146 is to just execute a breakpoint instruction (the ``dirty'' part is that
20147 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20149 Other routines you need to supply are:
20152 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20153 @findex exceptionHandler
20154 Write this function to install @var{exception_address} in the exception
20155 handling tables. You need to do this because the stub does not have any
20156 way of knowing what the exception handling tables on your target system
20157 are like (for example, the processor's table might be in @sc{rom},
20158 containing entries which point to a table in @sc{ram}).
20159 The @var{exception_number} specifies the exception which should be changed;
20160 its meaning is architecture-dependent (for example, different numbers
20161 might represent divide by zero, misaligned access, etc). When this
20162 exception occurs, control should be transferred directly to
20163 @var{exception_address}, and the processor state (stack, registers,
20164 and so on) should be just as it is when a processor exception occurs. So if
20165 you want to use a jump instruction to reach @var{exception_address}, it
20166 should be a simple jump, not a jump to subroutine.
20168 For the 386, @var{exception_address} should be installed as an interrupt
20169 gate so that interrupts are masked while the handler runs. The gate
20170 should be at privilege level 0 (the most privileged level). The
20171 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20172 help from @code{exceptionHandler}.
20174 @item void flush_i_cache()
20175 @findex flush_i_cache
20176 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20177 instruction cache, if any, on your target machine. If there is no
20178 instruction cache, this subroutine may be a no-op.
20180 On target machines that have instruction caches, @value{GDBN} requires this
20181 function to make certain that the state of your program is stable.
20185 You must also make sure this library routine is available:
20188 @item void *memset(void *, int, int)
20190 This is the standard library function @code{memset} that sets an area of
20191 memory to a known value. If you have one of the free versions of
20192 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20193 either obtain it from your hardware manufacturer, or write your own.
20196 If you do not use the GNU C compiler, you may need other standard
20197 library subroutines as well; this varies from one stub to another,
20198 but in general the stubs are likely to use any of the common library
20199 subroutines which @code{@value{NGCC}} generates as inline code.
20202 @node Debug Session
20203 @subsection Putting it All Together
20205 @cindex remote serial debugging summary
20206 In summary, when your program is ready to debug, you must follow these
20211 Make sure you have defined the supporting low-level routines
20212 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20214 @code{getDebugChar}, @code{putDebugChar},
20215 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20219 Insert these lines in your program's startup code, before the main
20220 procedure is called:
20227 On some machines, when a breakpoint trap is raised, the hardware
20228 automatically makes the PC point to the instruction after the
20229 breakpoint. If your machine doesn't do that, you may need to adjust
20230 @code{handle_exception} to arrange for it to return to the instruction
20231 after the breakpoint on this first invocation, so that your program
20232 doesn't keep hitting the initial breakpoint instead of making
20236 For the 680x0 stub only, you need to provide a variable called
20237 @code{exceptionHook}. Normally you just use:
20240 void (*exceptionHook)() = 0;
20244 but if before calling @code{set_debug_traps}, you set it to point to a
20245 function in your program, that function is called when
20246 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20247 error). The function indicated by @code{exceptionHook} is called with
20248 one parameter: an @code{int} which is the exception number.
20251 Compile and link together: your program, the @value{GDBN} debugging stub for
20252 your target architecture, and the supporting subroutines.
20255 Make sure you have a serial connection between your target machine and
20256 the @value{GDBN} host, and identify the serial port on the host.
20259 @c The "remote" target now provides a `load' command, so we should
20260 @c document that. FIXME.
20261 Download your program to your target machine (or get it there by
20262 whatever means the manufacturer provides), and start it.
20265 Start @value{GDBN} on the host, and connect to the target
20266 (@pxref{Connecting,,Connecting to a Remote Target}).
20270 @node Configurations
20271 @chapter Configuration-Specific Information
20273 While nearly all @value{GDBN} commands are available for all native and
20274 cross versions of the debugger, there are some exceptions. This chapter
20275 describes things that are only available in certain configurations.
20277 There are three major categories of configurations: native
20278 configurations, where the host and target are the same, embedded
20279 operating system configurations, which are usually the same for several
20280 different processor architectures, and bare embedded processors, which
20281 are quite different from each other.
20286 * Embedded Processors::
20293 This section describes details specific to particular native
20298 * BSD libkvm Interface:: Debugging BSD kernel memory images
20299 * SVR4 Process Information:: SVR4 process information
20300 * DJGPP Native:: Features specific to the DJGPP port
20301 * Cygwin Native:: Features specific to the Cygwin port
20302 * Hurd Native:: Features specific to @sc{gnu} Hurd
20303 * Darwin:: Features specific to Darwin
20309 On HP-UX systems, if you refer to a function or variable name that
20310 begins with a dollar sign, @value{GDBN} searches for a user or system
20311 name first, before it searches for a convenience variable.
20314 @node BSD libkvm Interface
20315 @subsection BSD libkvm Interface
20318 @cindex kernel memory image
20319 @cindex kernel crash dump
20321 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20322 interface that provides a uniform interface for accessing kernel virtual
20323 memory images, including live systems and crash dumps. @value{GDBN}
20324 uses this interface to allow you to debug live kernels and kernel crash
20325 dumps on many native BSD configurations. This is implemented as a
20326 special @code{kvm} debugging target. For debugging a live system, load
20327 the currently running kernel into @value{GDBN} and connect to the
20331 (@value{GDBP}) @b{target kvm}
20334 For debugging crash dumps, provide the file name of the crash dump as an
20338 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20341 Once connected to the @code{kvm} target, the following commands are
20347 Set current context from the @dfn{Process Control Block} (PCB) address.
20350 Set current context from proc address. This command isn't available on
20351 modern FreeBSD systems.
20354 @node SVR4 Process Information
20355 @subsection SVR4 Process Information
20357 @cindex examine process image
20358 @cindex process info via @file{/proc}
20360 Many versions of SVR4 and compatible systems provide a facility called
20361 @samp{/proc} that can be used to examine the image of a running
20362 process using file-system subroutines.
20364 If @value{GDBN} is configured for an operating system with this
20365 facility, the command @code{info proc} is available to report
20366 information about the process running your program, or about any
20367 process running on your system. This includes, as of this writing,
20368 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20370 This command may also work on core files that were created on a system
20371 that has the @samp{/proc} facility.
20377 @itemx info proc @var{process-id}
20378 Summarize available information about any running process. If a
20379 process ID is specified by @var{process-id}, display information about
20380 that process; otherwise display information about the program being
20381 debugged. The summary includes the debugged process ID, the command
20382 line used to invoke it, its current working directory, and its
20383 executable file's absolute file name.
20385 On some systems, @var{process-id} can be of the form
20386 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20387 within a process. If the optional @var{pid} part is missing, it means
20388 a thread from the process being debugged (the leading @samp{/} still
20389 needs to be present, or else @value{GDBN} will interpret the number as
20390 a process ID rather than a thread ID).
20392 @item info proc cmdline
20393 @cindex info proc cmdline
20394 Show the original command line of the process. This command is
20395 specific to @sc{gnu}/Linux.
20397 @item info proc cwd
20398 @cindex info proc cwd
20399 Show the current working directory of the process. This command is
20400 specific to @sc{gnu}/Linux.
20402 @item info proc exe
20403 @cindex info proc exe
20404 Show the name of executable of the process. This command is specific
20407 @item info proc mappings
20408 @cindex memory address space mappings
20409 Report the memory address space ranges accessible in the program, with
20410 information on whether the process has read, write, or execute access
20411 rights to each range. On @sc{gnu}/Linux systems, each memory range
20412 includes the object file which is mapped to that range, instead of the
20413 memory access rights to that range.
20415 @item info proc stat
20416 @itemx info proc status
20417 @cindex process detailed status information
20418 These subcommands are specific to @sc{gnu}/Linux systems. They show
20419 the process-related information, including the user ID and group ID;
20420 how many threads are there in the process; its virtual memory usage;
20421 the signals that are pending, blocked, and ignored; its TTY; its
20422 consumption of system and user time; its stack size; its @samp{nice}
20423 value; etc. For more information, see the @samp{proc} man page
20424 (type @kbd{man 5 proc} from your shell prompt).
20426 @item info proc all
20427 Show all the information about the process described under all of the
20428 above @code{info proc} subcommands.
20431 @comment These sub-options of 'info proc' were not included when
20432 @comment procfs.c was re-written. Keep their descriptions around
20433 @comment against the day when someone finds the time to put them back in.
20434 @kindex info proc times
20435 @item info proc times
20436 Starting time, user CPU time, and system CPU time for your program and
20439 @kindex info proc id
20441 Report on the process IDs related to your program: its own process ID,
20442 the ID of its parent, the process group ID, and the session ID.
20445 @item set procfs-trace
20446 @kindex set procfs-trace
20447 @cindex @code{procfs} API calls
20448 This command enables and disables tracing of @code{procfs} API calls.
20450 @item show procfs-trace
20451 @kindex show procfs-trace
20452 Show the current state of @code{procfs} API call tracing.
20454 @item set procfs-file @var{file}
20455 @kindex set procfs-file
20456 Tell @value{GDBN} to write @code{procfs} API trace to the named
20457 @var{file}. @value{GDBN} appends the trace info to the previous
20458 contents of the file. The default is to display the trace on the
20461 @item show procfs-file
20462 @kindex show procfs-file
20463 Show the file to which @code{procfs} API trace is written.
20465 @item proc-trace-entry
20466 @itemx proc-trace-exit
20467 @itemx proc-untrace-entry
20468 @itemx proc-untrace-exit
20469 @kindex proc-trace-entry
20470 @kindex proc-trace-exit
20471 @kindex proc-untrace-entry
20472 @kindex proc-untrace-exit
20473 These commands enable and disable tracing of entries into and exits
20474 from the @code{syscall} interface.
20477 @kindex info pidlist
20478 @cindex process list, QNX Neutrino
20479 For QNX Neutrino only, this command displays the list of all the
20480 processes and all the threads within each process.
20483 @kindex info meminfo
20484 @cindex mapinfo list, QNX Neutrino
20485 For QNX Neutrino only, this command displays the list of all mapinfos.
20489 @subsection Features for Debugging @sc{djgpp} Programs
20490 @cindex @sc{djgpp} debugging
20491 @cindex native @sc{djgpp} debugging
20492 @cindex MS-DOS-specific commands
20495 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20496 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20497 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20498 top of real-mode DOS systems and their emulations.
20500 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20501 defines a few commands specific to the @sc{djgpp} port. This
20502 subsection describes those commands.
20507 This is a prefix of @sc{djgpp}-specific commands which print
20508 information about the target system and important OS structures.
20511 @cindex MS-DOS system info
20512 @cindex free memory information (MS-DOS)
20513 @item info dos sysinfo
20514 This command displays assorted information about the underlying
20515 platform: the CPU type and features, the OS version and flavor, the
20516 DPMI version, and the available conventional and DPMI memory.
20521 @cindex segment descriptor tables
20522 @cindex descriptor tables display
20524 @itemx info dos ldt
20525 @itemx info dos idt
20526 These 3 commands display entries from, respectively, Global, Local,
20527 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20528 tables are data structures which store a descriptor for each segment
20529 that is currently in use. The segment's selector is an index into a
20530 descriptor table; the table entry for that index holds the
20531 descriptor's base address and limit, and its attributes and access
20534 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20535 segment (used for both data and the stack), and a DOS segment (which
20536 allows access to DOS/BIOS data structures and absolute addresses in
20537 conventional memory). However, the DPMI host will usually define
20538 additional segments in order to support the DPMI environment.
20540 @cindex garbled pointers
20541 These commands allow to display entries from the descriptor tables.
20542 Without an argument, all entries from the specified table are
20543 displayed. An argument, which should be an integer expression, means
20544 display a single entry whose index is given by the argument. For
20545 example, here's a convenient way to display information about the
20546 debugged program's data segment:
20549 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20550 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20554 This comes in handy when you want to see whether a pointer is outside
20555 the data segment's limit (i.e.@: @dfn{garbled}).
20557 @cindex page tables display (MS-DOS)
20559 @itemx info dos pte
20560 These two commands display entries from, respectively, the Page
20561 Directory and the Page Tables. Page Directories and Page Tables are
20562 data structures which control how virtual memory addresses are mapped
20563 into physical addresses. A Page Table includes an entry for every
20564 page of memory that is mapped into the program's address space; there
20565 may be several Page Tables, each one holding up to 4096 entries. A
20566 Page Directory has up to 4096 entries, one each for every Page Table
20567 that is currently in use.
20569 Without an argument, @kbd{info dos pde} displays the entire Page
20570 Directory, and @kbd{info dos pte} displays all the entries in all of
20571 the Page Tables. An argument, an integer expression, given to the
20572 @kbd{info dos pde} command means display only that entry from the Page
20573 Directory table. An argument given to the @kbd{info dos pte} command
20574 means display entries from a single Page Table, the one pointed to by
20575 the specified entry in the Page Directory.
20577 @cindex direct memory access (DMA) on MS-DOS
20578 These commands are useful when your program uses @dfn{DMA} (Direct
20579 Memory Access), which needs physical addresses to program the DMA
20582 These commands are supported only with some DPMI servers.
20584 @cindex physical address from linear address
20585 @item info dos address-pte @var{addr}
20586 This command displays the Page Table entry for a specified linear
20587 address. The argument @var{addr} is a linear address which should
20588 already have the appropriate segment's base address added to it,
20589 because this command accepts addresses which may belong to @emph{any}
20590 segment. For example, here's how to display the Page Table entry for
20591 the page where a variable @code{i} is stored:
20594 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20595 @exdent @code{Page Table entry for address 0x11a00d30:}
20596 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20600 This says that @code{i} is stored at offset @code{0xd30} from the page
20601 whose physical base address is @code{0x02698000}, and shows all the
20602 attributes of that page.
20604 Note that you must cast the addresses of variables to a @code{char *},
20605 since otherwise the value of @code{__djgpp_base_address}, the base
20606 address of all variables and functions in a @sc{djgpp} program, will
20607 be added using the rules of C pointer arithmetics: if @code{i} is
20608 declared an @code{int}, @value{GDBN} will add 4 times the value of
20609 @code{__djgpp_base_address} to the address of @code{i}.
20611 Here's another example, it displays the Page Table entry for the
20615 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20616 @exdent @code{Page Table entry for address 0x29110:}
20617 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20621 (The @code{+ 3} offset is because the transfer buffer's address is the
20622 3rd member of the @code{_go32_info_block} structure.) The output
20623 clearly shows that this DPMI server maps the addresses in conventional
20624 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20625 linear (@code{0x29110}) addresses are identical.
20627 This command is supported only with some DPMI servers.
20630 @cindex DOS serial data link, remote debugging
20631 In addition to native debugging, the DJGPP port supports remote
20632 debugging via a serial data link. The following commands are specific
20633 to remote serial debugging in the DJGPP port of @value{GDBN}.
20636 @kindex set com1base
20637 @kindex set com1irq
20638 @kindex set com2base
20639 @kindex set com2irq
20640 @kindex set com3base
20641 @kindex set com3irq
20642 @kindex set com4base
20643 @kindex set com4irq
20644 @item set com1base @var{addr}
20645 This command sets the base I/O port address of the @file{COM1} serial
20648 @item set com1irq @var{irq}
20649 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20650 for the @file{COM1} serial port.
20652 There are similar commands @samp{set com2base}, @samp{set com3irq},
20653 etc.@: for setting the port address and the @code{IRQ} lines for the
20656 @kindex show com1base
20657 @kindex show com1irq
20658 @kindex show com2base
20659 @kindex show com2irq
20660 @kindex show com3base
20661 @kindex show com3irq
20662 @kindex show com4base
20663 @kindex show com4irq
20664 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20665 display the current settings of the base address and the @code{IRQ}
20666 lines used by the COM ports.
20669 @kindex info serial
20670 @cindex DOS serial port status
20671 This command prints the status of the 4 DOS serial ports. For each
20672 port, it prints whether it's active or not, its I/O base address and
20673 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20674 counts of various errors encountered so far.
20678 @node Cygwin Native
20679 @subsection Features for Debugging MS Windows PE Executables
20680 @cindex MS Windows debugging
20681 @cindex native Cygwin debugging
20682 @cindex Cygwin-specific commands
20684 @value{GDBN} supports native debugging of MS Windows programs, including
20685 DLLs with and without symbolic debugging information.
20687 @cindex Ctrl-BREAK, MS-Windows
20688 @cindex interrupt debuggee on MS-Windows
20689 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20690 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20691 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20692 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20693 sequence, which can be used to interrupt the debuggee even if it
20696 There are various additional Cygwin-specific commands, described in
20697 this section. Working with DLLs that have no debugging symbols is
20698 described in @ref{Non-debug DLL Symbols}.
20703 This is a prefix of MS Windows-specific commands which print
20704 information about the target system and important OS structures.
20706 @item info w32 selector
20707 This command displays information returned by
20708 the Win32 API @code{GetThreadSelectorEntry} function.
20709 It takes an optional argument that is evaluated to
20710 a long value to give the information about this given selector.
20711 Without argument, this command displays information
20712 about the six segment registers.
20714 @item info w32 thread-information-block
20715 This command displays thread specific information stored in the
20716 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20717 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20719 @kindex set cygwin-exceptions
20720 @cindex debugging the Cygwin DLL
20721 @cindex Cygwin DLL, debugging
20722 @item set cygwin-exceptions @var{mode}
20723 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20724 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20725 @value{GDBN} will delay recognition of exceptions, and may ignore some
20726 exceptions which seem to be caused by internal Cygwin DLL
20727 ``bookkeeping''. This option is meant primarily for debugging the
20728 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20729 @value{GDBN} users with false @code{SIGSEGV} signals.
20731 @kindex show cygwin-exceptions
20732 @item show cygwin-exceptions
20733 Displays whether @value{GDBN} will break on exceptions that happen
20734 inside the Cygwin DLL itself.
20736 @kindex set new-console
20737 @item set new-console @var{mode}
20738 If @var{mode} is @code{on} the debuggee will
20739 be started in a new console on next start.
20740 If @var{mode} is @code{off}, the debuggee will
20741 be started in the same console as the debugger.
20743 @kindex show new-console
20744 @item show new-console
20745 Displays whether a new console is used
20746 when the debuggee is started.
20748 @kindex set new-group
20749 @item set new-group @var{mode}
20750 This boolean value controls whether the debuggee should
20751 start a new group or stay in the same group as the debugger.
20752 This affects the way the Windows OS handles
20755 @kindex show new-group
20756 @item show new-group
20757 Displays current value of new-group boolean.
20759 @kindex set debugevents
20760 @item set debugevents
20761 This boolean value adds debug output concerning kernel events related
20762 to the debuggee seen by the debugger. This includes events that
20763 signal thread and process creation and exit, DLL loading and
20764 unloading, console interrupts, and debugging messages produced by the
20765 Windows @code{OutputDebugString} API call.
20767 @kindex set debugexec
20768 @item set debugexec
20769 This boolean value adds debug output concerning execute events
20770 (such as resume thread) seen by the debugger.
20772 @kindex set debugexceptions
20773 @item set debugexceptions
20774 This boolean value adds debug output concerning exceptions in the
20775 debuggee seen by the debugger.
20777 @kindex set debugmemory
20778 @item set debugmemory
20779 This boolean value adds debug output concerning debuggee memory reads
20780 and writes by the debugger.
20784 This boolean values specifies whether the debuggee is called
20785 via a shell or directly (default value is on).
20789 Displays if the debuggee will be started with a shell.
20794 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20797 @node Non-debug DLL Symbols
20798 @subsubsection Support for DLLs without Debugging Symbols
20799 @cindex DLLs with no debugging symbols
20800 @cindex Minimal symbols and DLLs
20802 Very often on windows, some of the DLLs that your program relies on do
20803 not include symbolic debugging information (for example,
20804 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20805 symbols in a DLL, it relies on the minimal amount of symbolic
20806 information contained in the DLL's export table. This section
20807 describes working with such symbols, known internally to @value{GDBN} as
20808 ``minimal symbols''.
20810 Note that before the debugged program has started execution, no DLLs
20811 will have been loaded. The easiest way around this problem is simply to
20812 start the program --- either by setting a breakpoint or letting the
20813 program run once to completion.
20815 @subsubsection DLL Name Prefixes
20817 In keeping with the naming conventions used by the Microsoft debugging
20818 tools, DLL export symbols are made available with a prefix based on the
20819 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20820 also entered into the symbol table, so @code{CreateFileA} is often
20821 sufficient. In some cases there will be name clashes within a program
20822 (particularly if the executable itself includes full debugging symbols)
20823 necessitating the use of the fully qualified name when referring to the
20824 contents of the DLL. Use single-quotes around the name to avoid the
20825 exclamation mark (``!'') being interpreted as a language operator.
20827 Note that the internal name of the DLL may be all upper-case, even
20828 though the file name of the DLL is lower-case, or vice-versa. Since
20829 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20830 some confusion. If in doubt, try the @code{info functions} and
20831 @code{info variables} commands or even @code{maint print msymbols}
20832 (@pxref{Symbols}). Here's an example:
20835 (@value{GDBP}) info function CreateFileA
20836 All functions matching regular expression "CreateFileA":
20838 Non-debugging symbols:
20839 0x77e885f4 CreateFileA
20840 0x77e885f4 KERNEL32!CreateFileA
20844 (@value{GDBP}) info function !
20845 All functions matching regular expression "!":
20847 Non-debugging symbols:
20848 0x6100114c cygwin1!__assert
20849 0x61004034 cygwin1!_dll_crt0@@0
20850 0x61004240 cygwin1!dll_crt0(per_process *)
20854 @subsubsection Working with Minimal Symbols
20856 Symbols extracted from a DLL's export table do not contain very much
20857 type information. All that @value{GDBN} can do is guess whether a symbol
20858 refers to a function or variable depending on the linker section that
20859 contains the symbol. Also note that the actual contents of the memory
20860 contained in a DLL are not available unless the program is running. This
20861 means that you cannot examine the contents of a variable or disassemble
20862 a function within a DLL without a running program.
20864 Variables are generally treated as pointers and dereferenced
20865 automatically. For this reason, it is often necessary to prefix a
20866 variable name with the address-of operator (``&'') and provide explicit
20867 type information in the command. Here's an example of the type of
20871 (@value{GDBP}) print 'cygwin1!__argv'
20876 (@value{GDBP}) x 'cygwin1!__argv'
20877 0x10021610: "\230y\""
20880 And two possible solutions:
20883 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20884 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20888 (@value{GDBP}) x/2x &'cygwin1!__argv'
20889 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20890 (@value{GDBP}) x/x 0x10021608
20891 0x10021608: 0x0022fd98
20892 (@value{GDBP}) x/s 0x0022fd98
20893 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20896 Setting a break point within a DLL is possible even before the program
20897 starts execution. However, under these circumstances, @value{GDBN} can't
20898 examine the initial instructions of the function in order to skip the
20899 function's frame set-up code. You can work around this by using ``*&''
20900 to set the breakpoint at a raw memory address:
20903 (@value{GDBP}) break *&'python22!PyOS_Readline'
20904 Breakpoint 1 at 0x1e04eff0
20907 The author of these extensions is not entirely convinced that setting a
20908 break point within a shared DLL like @file{kernel32.dll} is completely
20912 @subsection Commands Specific to @sc{gnu} Hurd Systems
20913 @cindex @sc{gnu} Hurd debugging
20915 This subsection describes @value{GDBN} commands specific to the
20916 @sc{gnu} Hurd native debugging.
20921 @kindex set signals@r{, Hurd command}
20922 @kindex set sigs@r{, Hurd command}
20923 This command toggles the state of inferior signal interception by
20924 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20925 affected by this command. @code{sigs} is a shorthand alias for
20930 @kindex show signals@r{, Hurd command}
20931 @kindex show sigs@r{, Hurd command}
20932 Show the current state of intercepting inferior's signals.
20934 @item set signal-thread
20935 @itemx set sigthread
20936 @kindex set signal-thread
20937 @kindex set sigthread
20938 This command tells @value{GDBN} which thread is the @code{libc} signal
20939 thread. That thread is run when a signal is delivered to a running
20940 process. @code{set sigthread} is the shorthand alias of @code{set
20943 @item show signal-thread
20944 @itemx show sigthread
20945 @kindex show signal-thread
20946 @kindex show sigthread
20947 These two commands show which thread will run when the inferior is
20948 delivered a signal.
20951 @kindex set stopped@r{, Hurd command}
20952 This commands tells @value{GDBN} that the inferior process is stopped,
20953 as with the @code{SIGSTOP} signal. The stopped process can be
20954 continued by delivering a signal to it.
20957 @kindex show stopped@r{, Hurd command}
20958 This command shows whether @value{GDBN} thinks the debuggee is
20961 @item set exceptions
20962 @kindex set exceptions@r{, Hurd command}
20963 Use this command to turn off trapping of exceptions in the inferior.
20964 When exception trapping is off, neither breakpoints nor
20965 single-stepping will work. To restore the default, set exception
20968 @item show exceptions
20969 @kindex show exceptions@r{, Hurd command}
20970 Show the current state of trapping exceptions in the inferior.
20972 @item set task pause
20973 @kindex set task@r{, Hurd commands}
20974 @cindex task attributes (@sc{gnu} Hurd)
20975 @cindex pause current task (@sc{gnu} Hurd)
20976 This command toggles task suspension when @value{GDBN} has control.
20977 Setting it to on takes effect immediately, and the task is suspended
20978 whenever @value{GDBN} gets control. Setting it to off will take
20979 effect the next time the inferior is continued. If this option is set
20980 to off, you can use @code{set thread default pause on} or @code{set
20981 thread pause on} (see below) to pause individual threads.
20983 @item show task pause
20984 @kindex show task@r{, Hurd commands}
20985 Show the current state of task suspension.
20987 @item set task detach-suspend-count
20988 @cindex task suspend count
20989 @cindex detach from task, @sc{gnu} Hurd
20990 This command sets the suspend count the task will be left with when
20991 @value{GDBN} detaches from it.
20993 @item show task detach-suspend-count
20994 Show the suspend count the task will be left with when detaching.
20996 @item set task exception-port
20997 @itemx set task excp
20998 @cindex task exception port, @sc{gnu} Hurd
20999 This command sets the task exception port to which @value{GDBN} will
21000 forward exceptions. The argument should be the value of the @dfn{send
21001 rights} of the task. @code{set task excp} is a shorthand alias.
21003 @item set noninvasive
21004 @cindex noninvasive task options
21005 This command switches @value{GDBN} to a mode that is the least
21006 invasive as far as interfering with the inferior is concerned. This
21007 is the same as using @code{set task pause}, @code{set exceptions}, and
21008 @code{set signals} to values opposite to the defaults.
21010 @item info send-rights
21011 @itemx info receive-rights
21012 @itemx info port-rights
21013 @itemx info port-sets
21014 @itemx info dead-names
21017 @cindex send rights, @sc{gnu} Hurd
21018 @cindex receive rights, @sc{gnu} Hurd
21019 @cindex port rights, @sc{gnu} Hurd
21020 @cindex port sets, @sc{gnu} Hurd
21021 @cindex dead names, @sc{gnu} Hurd
21022 These commands display information about, respectively, send rights,
21023 receive rights, port rights, port sets, and dead names of a task.
21024 There are also shorthand aliases: @code{info ports} for @code{info
21025 port-rights} and @code{info psets} for @code{info port-sets}.
21027 @item set thread pause
21028 @kindex set thread@r{, Hurd command}
21029 @cindex thread properties, @sc{gnu} Hurd
21030 @cindex pause current thread (@sc{gnu} Hurd)
21031 This command toggles current thread suspension when @value{GDBN} has
21032 control. Setting it to on takes effect immediately, and the current
21033 thread is suspended whenever @value{GDBN} gets control. Setting it to
21034 off will take effect the next time the inferior is continued.
21035 Normally, this command has no effect, since when @value{GDBN} has
21036 control, the whole task is suspended. However, if you used @code{set
21037 task pause off} (see above), this command comes in handy to suspend
21038 only the current thread.
21040 @item show thread pause
21041 @kindex show thread@r{, Hurd command}
21042 This command shows the state of current thread suspension.
21044 @item set thread run
21045 This command sets whether the current thread is allowed to run.
21047 @item show thread run
21048 Show whether the current thread is allowed to run.
21050 @item set thread detach-suspend-count
21051 @cindex thread suspend count, @sc{gnu} Hurd
21052 @cindex detach from thread, @sc{gnu} Hurd
21053 This command sets the suspend count @value{GDBN} will leave on a
21054 thread when detaching. This number is relative to the suspend count
21055 found by @value{GDBN} when it notices the thread; use @code{set thread
21056 takeover-suspend-count} to force it to an absolute value.
21058 @item show thread detach-suspend-count
21059 Show the suspend count @value{GDBN} will leave on the thread when
21062 @item set thread exception-port
21063 @itemx set thread excp
21064 Set the thread exception port to which to forward exceptions. This
21065 overrides the port set by @code{set task exception-port} (see above).
21066 @code{set thread excp} is the shorthand alias.
21068 @item set thread takeover-suspend-count
21069 Normally, @value{GDBN}'s thread suspend counts are relative to the
21070 value @value{GDBN} finds when it notices each thread. This command
21071 changes the suspend counts to be absolute instead.
21073 @item set thread default
21074 @itemx show thread default
21075 @cindex thread default settings, @sc{gnu} Hurd
21076 Each of the above @code{set thread} commands has a @code{set thread
21077 default} counterpart (e.g., @code{set thread default pause}, @code{set
21078 thread default exception-port}, etc.). The @code{thread default}
21079 variety of commands sets the default thread properties for all
21080 threads; you can then change the properties of individual threads with
21081 the non-default commands.
21088 @value{GDBN} provides the following commands specific to the Darwin target:
21091 @item set debug darwin @var{num}
21092 @kindex set debug darwin
21093 When set to a non zero value, enables debugging messages specific to
21094 the Darwin support. Higher values produce more verbose output.
21096 @item show debug darwin
21097 @kindex show debug darwin
21098 Show the current state of Darwin messages.
21100 @item set debug mach-o @var{num}
21101 @kindex set debug mach-o
21102 When set to a non zero value, enables debugging messages while
21103 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21104 file format used on Darwin for object and executable files.) Higher
21105 values produce more verbose output. This is a command to diagnose
21106 problems internal to @value{GDBN} and should not be needed in normal
21109 @item show debug mach-o
21110 @kindex show debug mach-o
21111 Show the current state of Mach-O file messages.
21113 @item set mach-exceptions on
21114 @itemx set mach-exceptions off
21115 @kindex set mach-exceptions
21116 On Darwin, faults are first reported as a Mach exception and are then
21117 mapped to a Posix signal. Use this command to turn on trapping of
21118 Mach exceptions in the inferior. This might be sometimes useful to
21119 better understand the cause of a fault. The default is off.
21121 @item show mach-exceptions
21122 @kindex show mach-exceptions
21123 Show the current state of exceptions trapping.
21128 @section Embedded Operating Systems
21130 This section describes configurations involving the debugging of
21131 embedded operating systems that are available for several different
21134 @value{GDBN} includes the ability to debug programs running on
21135 various real-time operating systems.
21137 @node Embedded Processors
21138 @section Embedded Processors
21140 This section goes into details specific to particular embedded
21143 @cindex send command to simulator
21144 Whenever a specific embedded processor has a simulator, @value{GDBN}
21145 allows to send an arbitrary command to the simulator.
21148 @item sim @var{command}
21149 @kindex sim@r{, a command}
21150 Send an arbitrary @var{command} string to the simulator. Consult the
21151 documentation for the specific simulator in use for information about
21152 acceptable commands.
21158 * M32R/D:: Renesas M32R/D
21159 * M68K:: Motorola M68K
21160 * MicroBlaze:: Xilinx MicroBlaze
21161 * MIPS Embedded:: MIPS Embedded
21162 * PowerPC Embedded:: PowerPC Embedded
21163 * PA:: HP PA Embedded
21164 * Sparclet:: Tsqware Sparclet
21165 * Sparclite:: Fujitsu Sparclite
21166 * Z8000:: Zilog Z8000
21169 * Super-H:: Renesas Super-H
21178 @item target rdi @var{dev}
21179 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21180 use this target to communicate with both boards running the Angel
21181 monitor, or with the EmbeddedICE JTAG debug device.
21184 @item target rdp @var{dev}
21189 @value{GDBN} provides the following ARM-specific commands:
21192 @item set arm disassembler
21194 This commands selects from a list of disassembly styles. The
21195 @code{"std"} style is the standard style.
21197 @item show arm disassembler
21199 Show the current disassembly style.
21201 @item set arm apcs32
21202 @cindex ARM 32-bit mode
21203 This command toggles ARM operation mode between 32-bit and 26-bit.
21205 @item show arm apcs32
21206 Display the current usage of the ARM 32-bit mode.
21208 @item set arm fpu @var{fputype}
21209 This command sets the ARM floating-point unit (FPU) type. The
21210 argument @var{fputype} can be one of these:
21214 Determine the FPU type by querying the OS ABI.
21216 Software FPU, with mixed-endian doubles on little-endian ARM
21219 GCC-compiled FPA co-processor.
21221 Software FPU with pure-endian doubles.
21227 Show the current type of the FPU.
21230 This command forces @value{GDBN} to use the specified ABI.
21233 Show the currently used ABI.
21235 @item set arm fallback-mode (arm|thumb|auto)
21236 @value{GDBN} uses the symbol table, when available, to determine
21237 whether instructions are ARM or Thumb. This command controls
21238 @value{GDBN}'s default behavior when the symbol table is not
21239 available. The default is @samp{auto}, which causes @value{GDBN} to
21240 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21243 @item show arm fallback-mode
21244 Show the current fallback instruction mode.
21246 @item set arm force-mode (arm|thumb|auto)
21247 This command overrides use of the symbol table to determine whether
21248 instructions are ARM or Thumb. The default is @samp{auto}, which
21249 causes @value{GDBN} to use the symbol table and then the setting
21250 of @samp{set arm fallback-mode}.
21252 @item show arm force-mode
21253 Show the current forced instruction mode.
21255 @item set debug arm
21256 Toggle whether to display ARM-specific debugging messages from the ARM
21257 target support subsystem.
21259 @item show debug arm
21260 Show whether ARM-specific debugging messages are enabled.
21263 The following commands are available when an ARM target is debugged
21264 using the RDI interface:
21267 @item rdilogfile @r{[}@var{file}@r{]}
21269 @cindex ADP (Angel Debugger Protocol) logging
21270 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21271 With an argument, sets the log file to the specified @var{file}. With
21272 no argument, show the current log file name. The default log file is
21275 @item rdilogenable @r{[}@var{arg}@r{]}
21276 @kindex rdilogenable
21277 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21278 enables logging, with an argument 0 or @code{"no"} disables it. With
21279 no arguments displays the current setting. When logging is enabled,
21280 ADP packets exchanged between @value{GDBN} and the RDI target device
21281 are logged to a file.
21283 @item set rdiromatzero
21284 @kindex set rdiromatzero
21285 @cindex ROM at zero address, RDI
21286 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21287 vector catching is disabled, so that zero address can be used. If off
21288 (the default), vector catching is enabled. For this command to take
21289 effect, it needs to be invoked prior to the @code{target rdi} command.
21291 @item show rdiromatzero
21292 @kindex show rdiromatzero
21293 Show the current setting of ROM at zero address.
21295 @item set rdiheartbeat
21296 @kindex set rdiheartbeat
21297 @cindex RDI heartbeat
21298 Enable or disable RDI heartbeat packets. It is not recommended to
21299 turn on this option, since it confuses ARM and EPI JTAG interface, as
21300 well as the Angel monitor.
21302 @item show rdiheartbeat
21303 @kindex show rdiheartbeat
21304 Show the setting of RDI heartbeat packets.
21308 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21309 The @value{GDBN} ARM simulator accepts the following optional arguments.
21312 @item --swi-support=@var{type}
21313 Tell the simulator which SWI interfaces to support. The argument
21314 @var{type} may be a comma separated list of the following values.
21315 The default value is @code{all}.
21328 @subsection Renesas M32R/D and M32R/SDI
21331 @kindex target m32r
21332 @item target m32r @var{dev}
21333 Renesas M32R/D ROM monitor.
21335 @kindex target m32rsdi
21336 @item target m32rsdi @var{dev}
21337 Renesas M32R SDI server, connected via parallel port to the board.
21340 The following @value{GDBN} commands are specific to the M32R monitor:
21343 @item set download-path @var{path}
21344 @kindex set download-path
21345 @cindex find downloadable @sc{srec} files (M32R)
21346 Set the default path for finding downloadable @sc{srec} files.
21348 @item show download-path
21349 @kindex show download-path
21350 Show the default path for downloadable @sc{srec} files.
21352 @item set board-address @var{addr}
21353 @kindex set board-address
21354 @cindex M32-EVA target board address
21355 Set the IP address for the M32R-EVA target board.
21357 @item show board-address
21358 @kindex show board-address
21359 Show the current IP address of the target board.
21361 @item set server-address @var{addr}
21362 @kindex set server-address
21363 @cindex download server address (M32R)
21364 Set the IP address for the download server, which is the @value{GDBN}'s
21367 @item show server-address
21368 @kindex show server-address
21369 Display the IP address of the download server.
21371 @item upload @r{[}@var{file}@r{]}
21372 @kindex upload@r{, M32R}
21373 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21374 upload capability. If no @var{file} argument is given, the current
21375 executable file is uploaded.
21377 @item tload @r{[}@var{file}@r{]}
21378 @kindex tload@r{, M32R}
21379 Test the @code{upload} command.
21382 The following commands are available for M32R/SDI:
21387 @cindex reset SDI connection, M32R
21388 This command resets the SDI connection.
21392 This command shows the SDI connection status.
21395 @kindex debug_chaos
21396 @cindex M32R/Chaos debugging
21397 Instructs the remote that M32R/Chaos debugging is to be used.
21399 @item use_debug_dma
21400 @kindex use_debug_dma
21401 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21404 @kindex use_mon_code
21405 Instructs the remote to use the MON_CODE method of accessing memory.
21408 @kindex use_ib_break
21409 Instructs the remote to set breakpoints by IB break.
21411 @item use_dbt_break
21412 @kindex use_dbt_break
21413 Instructs the remote to set breakpoints by DBT.
21419 The Motorola m68k configuration includes ColdFire support, and a
21420 target command for the following ROM monitor.
21424 @kindex target dbug
21425 @item target dbug @var{dev}
21426 dBUG ROM monitor for Motorola ColdFire.
21431 @subsection MicroBlaze
21432 @cindex Xilinx MicroBlaze
21433 @cindex XMD, Xilinx Microprocessor Debugger
21435 The MicroBlaze is a soft-core processor supported on various Xilinx
21436 FPGAs, such as Spartan or Virtex series. Boards with these processors
21437 usually have JTAG ports which connect to a host system running the Xilinx
21438 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21439 This host system is used to download the configuration bitstream to
21440 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21441 communicates with the target board using the JTAG interface and
21442 presents a @code{gdbserver} interface to the board. By default
21443 @code{xmd} uses port @code{1234}. (While it is possible to change
21444 this default port, it requires the use of undocumented @code{xmd}
21445 commands. Contact Xilinx support if you need to do this.)
21447 Use these GDB commands to connect to the MicroBlaze target processor.
21450 @item target remote :1234
21451 Use this command to connect to the target if you are running @value{GDBN}
21452 on the same system as @code{xmd}.
21454 @item target remote @var{xmd-host}:1234
21455 Use this command to connect to the target if it is connected to @code{xmd}
21456 running on a different system named @var{xmd-host}.
21459 Use this command to download a program to the MicroBlaze target.
21461 @item set debug microblaze @var{n}
21462 Enable MicroBlaze-specific debugging messages if non-zero.
21464 @item show debug microblaze @var{n}
21465 Show MicroBlaze-specific debugging level.
21468 @node MIPS Embedded
21469 @subsection @acronym{MIPS} Embedded
21471 @cindex @acronym{MIPS} boards
21472 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21473 @acronym{MIPS} board attached to a serial line. This is available when
21474 you configure @value{GDBN} with @samp{--target=mips-elf}.
21477 Use these @value{GDBN} commands to specify the connection to your target board:
21480 @item target mips @var{port}
21481 @kindex target mips @var{port}
21482 To run a program on the board, start up @code{@value{GDBP}} with the
21483 name of your program as the argument. To connect to the board, use the
21484 command @samp{target mips @var{port}}, where @var{port} is the name of
21485 the serial port connected to the board. If the program has not already
21486 been downloaded to the board, you may use the @code{load} command to
21487 download it. You can then use all the usual @value{GDBN} commands.
21489 For example, this sequence connects to the target board through a serial
21490 port, and loads and runs a program called @var{prog} through the
21494 host$ @value{GDBP} @var{prog}
21495 @value{GDBN} is free software and @dots{}
21496 (@value{GDBP}) target mips /dev/ttyb
21497 (@value{GDBP}) load @var{prog}
21501 @item target mips @var{hostname}:@var{portnumber}
21502 On some @value{GDBN} host configurations, you can specify a TCP
21503 connection (for instance, to a serial line managed by a terminal
21504 concentrator) instead of a serial port, using the syntax
21505 @samp{@var{hostname}:@var{portnumber}}.
21507 @item target pmon @var{port}
21508 @kindex target pmon @var{port}
21511 @item target ddb @var{port}
21512 @kindex target ddb @var{port}
21513 NEC's DDB variant of PMON for Vr4300.
21515 @item target lsi @var{port}
21516 @kindex target lsi @var{port}
21517 LSI variant of PMON.
21519 @kindex target r3900
21520 @item target r3900 @var{dev}
21521 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21523 @kindex target array
21524 @item target array @var{dev}
21525 Array Tech LSI33K RAID controller board.
21531 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21534 @item set mipsfpu double
21535 @itemx set mipsfpu single
21536 @itemx set mipsfpu none
21537 @itemx set mipsfpu auto
21538 @itemx show mipsfpu
21539 @kindex set mipsfpu
21540 @kindex show mipsfpu
21541 @cindex @acronym{MIPS} remote floating point
21542 @cindex floating point, @acronym{MIPS} remote
21543 If your target board does not support the @acronym{MIPS} floating point
21544 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21545 need this, you may wish to put the command in your @value{GDBN} init
21546 file). This tells @value{GDBN} how to find the return value of
21547 functions which return floating point values. It also allows
21548 @value{GDBN} to avoid saving the floating point registers when calling
21549 functions on the board. If you are using a floating point coprocessor
21550 with only single precision floating point support, as on the @sc{r4650}
21551 processor, use the command @samp{set mipsfpu single}. The default
21552 double precision floating point coprocessor may be selected using
21553 @samp{set mipsfpu double}.
21555 In previous versions the only choices were double precision or no
21556 floating point, so @samp{set mipsfpu on} will select double precision
21557 and @samp{set mipsfpu off} will select no floating point.
21559 As usual, you can inquire about the @code{mipsfpu} variable with
21560 @samp{show mipsfpu}.
21562 @item set timeout @var{seconds}
21563 @itemx set retransmit-timeout @var{seconds}
21564 @itemx show timeout
21565 @itemx show retransmit-timeout
21566 @cindex @code{timeout}, @acronym{MIPS} protocol
21567 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21568 @kindex set timeout
21569 @kindex show timeout
21570 @kindex set retransmit-timeout
21571 @kindex show retransmit-timeout
21572 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21573 remote protocol, with the @code{set timeout @var{seconds}} command. The
21574 default is 5 seconds. Similarly, you can control the timeout used while
21575 waiting for an acknowledgment of a packet with the @code{set
21576 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21577 You can inspect both values with @code{show timeout} and @code{show
21578 retransmit-timeout}. (These commands are @emph{only} available when
21579 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21581 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21582 is waiting for your program to stop. In that case, @value{GDBN} waits
21583 forever because it has no way of knowing how long the program is going
21584 to run before stopping.
21586 @item set syn-garbage-limit @var{num}
21587 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21588 @cindex synchronize with remote @acronym{MIPS} target
21589 Limit the maximum number of characters @value{GDBN} should ignore when
21590 it tries to synchronize with the remote target. The default is 10
21591 characters. Setting the limit to -1 means there's no limit.
21593 @item show syn-garbage-limit
21594 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21595 Show the current limit on the number of characters to ignore when
21596 trying to synchronize with the remote system.
21598 @item set monitor-prompt @var{prompt}
21599 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21600 @cindex remote monitor prompt
21601 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21602 remote monitor. The default depends on the target:
21612 @item show monitor-prompt
21613 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21614 Show the current strings @value{GDBN} expects as the prompt from the
21617 @item set monitor-warnings
21618 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21619 Enable or disable monitor warnings about hardware breakpoints. This
21620 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21621 display warning messages whose codes are returned by the @code{lsi}
21622 PMON monitor for breakpoint commands.
21624 @item show monitor-warnings
21625 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21626 Show the current setting of printing monitor warnings.
21628 @item pmon @var{command}
21629 @kindex pmon@r{, @acronym{MIPS} remote}
21630 @cindex send PMON command
21631 This command allows sending an arbitrary @var{command} string to the
21632 monitor. The monitor must be in debug mode for this to work.
21635 @node PowerPC Embedded
21636 @subsection PowerPC Embedded
21638 @cindex DVC register
21639 @value{GDBN} supports using the DVC (Data Value Compare) register to
21640 implement in hardware simple hardware watchpoint conditions of the form:
21643 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21644 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21647 The DVC register will be automatically used when @value{GDBN} detects
21648 such pattern in a condition expression, and the created watchpoint uses one
21649 debug register (either the @code{exact-watchpoints} option is on and the
21650 variable is scalar, or the variable has a length of one byte). This feature
21651 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21654 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21655 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21656 in which case watchpoints using only one debug register are created when
21657 watching variables of scalar types.
21659 You can create an artificial array to watch an arbitrary memory
21660 region using one of the following commands (@pxref{Expressions}):
21663 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21664 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21667 PowerPC embedded processors support masked watchpoints. See the discussion
21668 about the @code{mask} argument in @ref{Set Watchpoints}.
21670 @cindex ranged breakpoint
21671 PowerPC embedded processors support hardware accelerated
21672 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21673 the inferior whenever it executes an instruction at any address within
21674 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21675 use the @code{break-range} command.
21677 @value{GDBN} provides the following PowerPC-specific commands:
21680 @kindex break-range
21681 @item break-range @var{start-location}, @var{end-location}
21682 Set a breakpoint for an address range given by
21683 @var{start-location} and @var{end-location}, which can specify a function name,
21684 a line number, an offset of lines from the current line or from the start
21685 location, or an address of an instruction (see @ref{Specify Location},
21686 for a list of all the possible ways to specify a @var{location}.)
21687 The breakpoint will stop execution of the inferior whenever it
21688 executes an instruction at any address within the specified range,
21689 (including @var{start-location} and @var{end-location}.)
21691 @kindex set powerpc
21692 @item set powerpc soft-float
21693 @itemx show powerpc soft-float
21694 Force @value{GDBN} to use (or not use) a software floating point calling
21695 convention. By default, @value{GDBN} selects the calling convention based
21696 on the selected architecture and the provided executable file.
21698 @item set powerpc vector-abi
21699 @itemx show powerpc vector-abi
21700 Force @value{GDBN} to use the specified calling convention for vector
21701 arguments and return values. The valid options are @samp{auto};
21702 @samp{generic}, to avoid vector registers even if they are present;
21703 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21704 registers. By default, @value{GDBN} selects the calling convention
21705 based on the selected architecture and the provided executable file.
21707 @item set powerpc exact-watchpoints
21708 @itemx show powerpc exact-watchpoints
21709 Allow @value{GDBN} to use only one debug register when watching a variable
21710 of scalar type, thus assuming that the variable is accessed through the
21711 address of its first byte.
21713 @kindex target dink32
21714 @item target dink32 @var{dev}
21715 DINK32 ROM monitor.
21717 @kindex target ppcbug
21718 @item target ppcbug @var{dev}
21719 @kindex target ppcbug1
21720 @item target ppcbug1 @var{dev}
21721 PPCBUG ROM monitor for PowerPC.
21724 @item target sds @var{dev}
21725 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21728 @cindex SDS protocol
21729 The following commands specific to the SDS protocol are supported
21733 @item set sdstimeout @var{nsec}
21734 @kindex set sdstimeout
21735 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21736 default is 2 seconds.
21738 @item show sdstimeout
21739 @kindex show sdstimeout
21740 Show the current value of the SDS timeout.
21742 @item sds @var{command}
21743 @kindex sds@r{, a command}
21744 Send the specified @var{command} string to the SDS monitor.
21749 @subsection HP PA Embedded
21753 @kindex target op50n
21754 @item target op50n @var{dev}
21755 OP50N monitor, running on an OKI HPPA board.
21757 @kindex target w89k
21758 @item target w89k @var{dev}
21759 W89K monitor, running on a Winbond HPPA board.
21764 @subsection Tsqware Sparclet
21768 @value{GDBN} enables developers to debug tasks running on
21769 Sparclet targets from a Unix host.
21770 @value{GDBN} uses code that runs on
21771 both the Unix host and on the Sparclet target. The program
21772 @code{@value{GDBP}} is installed and executed on the Unix host.
21775 @item remotetimeout @var{args}
21776 @kindex remotetimeout
21777 @value{GDBN} supports the option @code{remotetimeout}.
21778 This option is set by the user, and @var{args} represents the number of
21779 seconds @value{GDBN} waits for responses.
21782 @cindex compiling, on Sparclet
21783 When compiling for debugging, include the options @samp{-g} to get debug
21784 information and @samp{-Ttext} to relocate the program to where you wish to
21785 load it on the target. You may also want to add the options @samp{-n} or
21786 @samp{-N} in order to reduce the size of the sections. Example:
21789 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21792 You can use @code{objdump} to verify that the addresses are what you intended:
21795 sparclet-aout-objdump --headers --syms prog
21798 @cindex running, on Sparclet
21800 your Unix execution search path to find @value{GDBN}, you are ready to
21801 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21802 (or @code{sparclet-aout-gdb}, depending on your installation).
21804 @value{GDBN} comes up showing the prompt:
21811 * Sparclet File:: Setting the file to debug
21812 * Sparclet Connection:: Connecting to Sparclet
21813 * Sparclet Download:: Sparclet download
21814 * Sparclet Execution:: Running and debugging
21817 @node Sparclet File
21818 @subsubsection Setting File to Debug
21820 The @value{GDBN} command @code{file} lets you choose with program to debug.
21823 (gdbslet) file prog
21827 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21828 @value{GDBN} locates
21829 the file by searching the directories listed in the command search
21831 If the file was compiled with debug information (option @samp{-g}), source
21832 files will be searched as well.
21833 @value{GDBN} locates
21834 the source files by searching the directories listed in the directory search
21835 path (@pxref{Environment, ,Your Program's Environment}).
21837 to find a file, it displays a message such as:
21840 prog: No such file or directory.
21843 When this happens, add the appropriate directories to the search paths with
21844 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21845 @code{target} command again.
21847 @node Sparclet Connection
21848 @subsubsection Connecting to Sparclet
21850 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21851 To connect to a target on serial port ``@code{ttya}'', type:
21854 (gdbslet) target sparclet /dev/ttya
21855 Remote target sparclet connected to /dev/ttya
21856 main () at ../prog.c:3
21860 @value{GDBN} displays messages like these:
21866 @node Sparclet Download
21867 @subsubsection Sparclet Download
21869 @cindex download to Sparclet
21870 Once connected to the Sparclet target,
21871 you can use the @value{GDBN}
21872 @code{load} command to download the file from the host to the target.
21873 The file name and load offset should be given as arguments to the @code{load}
21875 Since the file format is aout, the program must be loaded to the starting
21876 address. You can use @code{objdump} to find out what this value is. The load
21877 offset is an offset which is added to the VMA (virtual memory address)
21878 of each of the file's sections.
21879 For instance, if the program
21880 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21881 and bss at 0x12010170, in @value{GDBN}, type:
21884 (gdbslet) load prog 0x12010000
21885 Loading section .text, size 0xdb0 vma 0x12010000
21888 If the code is loaded at a different address then what the program was linked
21889 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21890 to tell @value{GDBN} where to map the symbol table.
21892 @node Sparclet Execution
21893 @subsubsection Running and Debugging
21895 @cindex running and debugging Sparclet programs
21896 You can now begin debugging the task using @value{GDBN}'s execution control
21897 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21898 manual for the list of commands.
21902 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21904 Starting program: prog
21905 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21906 3 char *symarg = 0;
21908 4 char *execarg = "hello!";
21913 @subsection Fujitsu Sparclite
21917 @kindex target sparclite
21918 @item target sparclite @var{dev}
21919 Fujitsu sparclite boards, used only for the purpose of loading.
21920 You must use an additional command to debug the program.
21921 For example: target remote @var{dev} using @value{GDBN} standard
21927 @subsection Zilog Z8000
21930 @cindex simulator, Z8000
21931 @cindex Zilog Z8000 simulator
21933 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21936 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21937 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21938 segmented variant). The simulator recognizes which architecture is
21939 appropriate by inspecting the object code.
21942 @item target sim @var{args}
21944 @kindex target sim@r{, with Z8000}
21945 Debug programs on a simulated CPU. If the simulator supports setup
21946 options, specify them via @var{args}.
21950 After specifying this target, you can debug programs for the simulated
21951 CPU in the same style as programs for your host computer; use the
21952 @code{file} command to load a new program image, the @code{run} command
21953 to run your program, and so on.
21955 As well as making available all the usual machine registers
21956 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21957 additional items of information as specially named registers:
21962 Counts clock-ticks in the simulator.
21965 Counts instructions run in the simulator.
21968 Execution time in 60ths of a second.
21972 You can refer to these values in @value{GDBN} expressions with the usual
21973 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21974 conditional breakpoint that suspends only after at least 5000
21975 simulated clock ticks.
21978 @subsection Atmel AVR
21981 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21982 following AVR-specific commands:
21985 @item info io_registers
21986 @kindex info io_registers@r{, AVR}
21987 @cindex I/O registers (Atmel AVR)
21988 This command displays information about the AVR I/O registers. For
21989 each register, @value{GDBN} prints its number and value.
21996 When configured for debugging CRIS, @value{GDBN} provides the
21997 following CRIS-specific commands:
22000 @item set cris-version @var{ver}
22001 @cindex CRIS version
22002 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22003 The CRIS version affects register names and sizes. This command is useful in
22004 case autodetection of the CRIS version fails.
22006 @item show cris-version
22007 Show the current CRIS version.
22009 @item set cris-dwarf2-cfi
22010 @cindex DWARF-2 CFI and CRIS
22011 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22012 Change to @samp{off} when using @code{gcc-cris} whose version is below
22015 @item show cris-dwarf2-cfi
22016 Show the current state of using DWARF-2 CFI.
22018 @item set cris-mode @var{mode}
22020 Set the current CRIS mode to @var{mode}. It should only be changed when
22021 debugging in guru mode, in which case it should be set to
22022 @samp{guru} (the default is @samp{normal}).
22024 @item show cris-mode
22025 Show the current CRIS mode.
22029 @subsection Renesas Super-H
22032 For the Renesas Super-H processor, @value{GDBN} provides these
22036 @item set sh calling-convention @var{convention}
22037 @kindex set sh calling-convention
22038 Set the calling-convention used when calling functions from @value{GDBN}.
22039 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22040 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22041 convention. If the DWARF-2 information of the called function specifies
22042 that the function follows the Renesas calling convention, the function
22043 is called using the Renesas calling convention. If the calling convention
22044 is set to @samp{renesas}, the Renesas calling convention is always used,
22045 regardless of the DWARF-2 information. This can be used to override the
22046 default of @samp{gcc} if debug information is missing, or the compiler
22047 does not emit the DWARF-2 calling convention entry for a function.
22049 @item show sh calling-convention
22050 @kindex show sh calling-convention
22051 Show the current calling convention setting.
22056 @node Architectures
22057 @section Architectures
22059 This section describes characteristics of architectures that affect
22060 all uses of @value{GDBN} with the architecture, both native and cross.
22067 * HPPA:: HP PA architecture
22068 * SPU:: Cell Broadband Engine SPU architecture
22074 @subsection AArch64
22075 @cindex AArch64 support
22077 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22078 following special commands:
22081 @item set debug aarch64
22082 @kindex set debug aarch64
22083 This command determines whether AArch64 architecture-specific debugging
22084 messages are to be displayed.
22086 @item show debug aarch64
22087 Show whether AArch64 debugging messages are displayed.
22092 @subsection x86 Architecture-specific Issues
22095 @item set struct-convention @var{mode}
22096 @kindex set struct-convention
22097 @cindex struct return convention
22098 @cindex struct/union returned in registers
22099 Set the convention used by the inferior to return @code{struct}s and
22100 @code{union}s from functions to @var{mode}. Possible values of
22101 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22102 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22103 are returned on the stack, while @code{"reg"} means that a
22104 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22105 be returned in a register.
22107 @item show struct-convention
22108 @kindex show struct-convention
22109 Show the current setting of the convention to return @code{struct}s
22113 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22114 @cindex Intel(R) Memory Protection Extensions (MPX).
22116 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22117 @footnote{The register named with capital letters represent the architecture
22118 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22119 which are the lower bound and upper bound. Bounds are effective addresses or
22120 memory locations. The upper bounds are architecturally represented in 1's
22121 complement form. A bound having lower bound = 0, and upper bound = 0
22122 (1's complement of all bits set) will allow access to the entire address space.
22124 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22125 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22126 display the upper bound performing the complement of one operation on the
22127 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22128 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22129 can also be noted that the upper bounds are inclusive.
22131 As an example, assume that the register BND0 holds bounds for a pointer having
22132 access allowed for the range between 0x32 and 0x71. The values present on
22133 bnd0raw and bnd registers are presented as follows:
22136 bnd0raw = @{0x32, 0xffffffff8e@}
22137 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22140 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22141 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22142 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22143 Python, the display includes the memory size, in bits, accessible to
22149 See the following section.
22152 @subsection @acronym{MIPS}
22154 @cindex stack on Alpha
22155 @cindex stack on @acronym{MIPS}
22156 @cindex Alpha stack
22157 @cindex @acronym{MIPS} stack
22158 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22159 sometimes requires @value{GDBN} to search backward in the object code to
22160 find the beginning of a function.
22162 @cindex response time, @acronym{MIPS} debugging
22163 To improve response time (especially for embedded applications, where
22164 @value{GDBN} may be restricted to a slow serial line for this search)
22165 you may want to limit the size of this search, using one of these
22169 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22170 @item set heuristic-fence-post @var{limit}
22171 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22172 search for the beginning of a function. A value of @var{0} (the
22173 default) means there is no limit. However, except for @var{0}, the
22174 larger the limit the more bytes @code{heuristic-fence-post} must search
22175 and therefore the longer it takes to run. You should only need to use
22176 this command when debugging a stripped executable.
22178 @item show heuristic-fence-post
22179 Display the current limit.
22183 These commands are available @emph{only} when @value{GDBN} is configured
22184 for debugging programs on Alpha or @acronym{MIPS} processors.
22186 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22190 @item set mips abi @var{arg}
22191 @kindex set mips abi
22192 @cindex set ABI for @acronym{MIPS}
22193 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22194 values of @var{arg} are:
22198 The default ABI associated with the current binary (this is the
22208 @item show mips abi
22209 @kindex show mips abi
22210 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22212 @item set mips compression @var{arg}
22213 @kindex set mips compression
22214 @cindex code compression, @acronym{MIPS}
22215 Tell @value{GDBN} which @acronym{MIPS} compressed
22216 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22217 inferior. @value{GDBN} uses this for code disassembly and other
22218 internal interpretation purposes. This setting is only referred to
22219 when no executable has been associated with the debugging session or
22220 the executable does not provide information about the encoding it uses.
22221 Otherwise this setting is automatically updated from information
22222 provided by the executable.
22224 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22225 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22226 executables containing @acronym{MIPS16} code frequently are not
22227 identified as such.
22229 This setting is ``sticky''; that is, it retains its value across
22230 debugging sessions until reset either explicitly with this command or
22231 implicitly from an executable.
22233 The compiler and/or assembler typically add symbol table annotations to
22234 identify functions compiled for the @acronym{MIPS16} or
22235 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22236 are present, @value{GDBN} uses them in preference to the global
22237 compressed @acronym{ISA} encoding setting.
22239 @item show mips compression
22240 @kindex show mips compression
22241 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22242 @value{GDBN} to debug the inferior.
22245 @itemx show mipsfpu
22246 @xref{MIPS Embedded, set mipsfpu}.
22248 @item set mips mask-address @var{arg}
22249 @kindex set mips mask-address
22250 @cindex @acronym{MIPS} addresses, masking
22251 This command determines whether the most-significant 32 bits of 64-bit
22252 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22253 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22254 setting, which lets @value{GDBN} determine the correct value.
22256 @item show mips mask-address
22257 @kindex show mips mask-address
22258 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22261 @item set remote-mips64-transfers-32bit-regs
22262 @kindex set remote-mips64-transfers-32bit-regs
22263 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22264 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22265 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22266 and 64 bits for other registers, set this option to @samp{on}.
22268 @item show remote-mips64-transfers-32bit-regs
22269 @kindex show remote-mips64-transfers-32bit-regs
22270 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22272 @item set debug mips
22273 @kindex set debug mips
22274 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22275 target code in @value{GDBN}.
22277 @item show debug mips
22278 @kindex show debug mips
22279 Show the current setting of @acronym{MIPS} debugging messages.
22285 @cindex HPPA support
22287 When @value{GDBN} is debugging the HP PA architecture, it provides the
22288 following special commands:
22291 @item set debug hppa
22292 @kindex set debug hppa
22293 This command determines whether HPPA architecture-specific debugging
22294 messages are to be displayed.
22296 @item show debug hppa
22297 Show whether HPPA debugging messages are displayed.
22299 @item maint print unwind @var{address}
22300 @kindex maint print unwind@r{, HPPA}
22301 This command displays the contents of the unwind table entry at the
22302 given @var{address}.
22308 @subsection Cell Broadband Engine SPU architecture
22309 @cindex Cell Broadband Engine
22312 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22313 it provides the following special commands:
22316 @item info spu event
22318 Display SPU event facility status. Shows current event mask
22319 and pending event status.
22321 @item info spu signal
22322 Display SPU signal notification facility status. Shows pending
22323 signal-control word and signal notification mode of both signal
22324 notification channels.
22326 @item info spu mailbox
22327 Display SPU mailbox facility status. Shows all pending entries,
22328 in order of processing, in each of the SPU Write Outbound,
22329 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22332 Display MFC DMA status. Shows all pending commands in the MFC
22333 DMA queue. For each entry, opcode, tag, class IDs, effective
22334 and local store addresses and transfer size are shown.
22336 @item info spu proxydma
22337 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22338 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22339 and local store addresses and transfer size are shown.
22343 When @value{GDBN} is debugging a combined PowerPC/SPU application
22344 on the Cell Broadband Engine, it provides in addition the following
22348 @item set spu stop-on-load @var{arg}
22350 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22351 will give control to the user when a new SPE thread enters its @code{main}
22352 function. The default is @code{off}.
22354 @item show spu stop-on-load
22356 Show whether to stop for new SPE threads.
22358 @item set spu auto-flush-cache @var{arg}
22359 Set whether to automatically flush the software-managed cache. When set to
22360 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22361 cache to be flushed whenever SPE execution stops. This provides a consistent
22362 view of PowerPC memory that is accessed via the cache. If an application
22363 does not use the software-managed cache, this option has no effect.
22365 @item show spu auto-flush-cache
22366 Show whether to automatically flush the software-managed cache.
22371 @subsection PowerPC
22372 @cindex PowerPC architecture
22374 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22375 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22376 numbers stored in the floating point registers. These values must be stored
22377 in two consecutive registers, always starting at an even register like
22378 @code{f0} or @code{f2}.
22380 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22381 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22382 @code{f2} and @code{f3} for @code{$dl1} and so on.
22384 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22385 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22388 @subsection Nios II
22389 @cindex Nios II architecture
22391 When @value{GDBN} is debugging the Nios II architecture,
22392 it provides the following special commands:
22396 @item set debug nios2
22397 @kindex set debug nios2
22398 This command turns on and off debugging messages for the Nios II
22399 target code in @value{GDBN}.
22401 @item show debug nios2
22402 @kindex show debug nios2
22403 Show the current setting of Nios II debugging messages.
22406 @node Controlling GDB
22407 @chapter Controlling @value{GDBN}
22409 You can alter the way @value{GDBN} interacts with you by using the
22410 @code{set} command. For commands controlling how @value{GDBN} displays
22411 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22416 * Editing:: Command editing
22417 * Command History:: Command history
22418 * Screen Size:: Screen size
22419 * Numbers:: Numbers
22420 * ABI:: Configuring the current ABI
22421 * Auto-loading:: Automatically loading associated files
22422 * Messages/Warnings:: Optional warnings and messages
22423 * Debugging Output:: Optional messages about internal happenings
22424 * Other Misc Settings:: Other Miscellaneous Settings
22432 @value{GDBN} indicates its readiness to read a command by printing a string
22433 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22434 can change the prompt string with the @code{set prompt} command. For
22435 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22436 the prompt in one of the @value{GDBN} sessions so that you can always tell
22437 which one you are talking to.
22439 @emph{Note:} @code{set prompt} does not add a space for you after the
22440 prompt you set. This allows you to set a prompt which ends in a space
22441 or a prompt that does not.
22445 @item set prompt @var{newprompt}
22446 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22448 @kindex show prompt
22450 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22453 Versions of @value{GDBN} that ship with Python scripting enabled have
22454 prompt extensions. The commands for interacting with these extensions
22458 @kindex set extended-prompt
22459 @item set extended-prompt @var{prompt}
22460 Set an extended prompt that allows for substitutions.
22461 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22462 substitution. Any escape sequences specified as part of the prompt
22463 string are replaced with the corresponding strings each time the prompt
22469 set extended-prompt Current working directory: \w (gdb)
22472 Note that when an extended-prompt is set, it takes control of the
22473 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22475 @kindex show extended-prompt
22476 @item show extended-prompt
22477 Prints the extended prompt. Any escape sequences specified as part of
22478 the prompt string with @code{set extended-prompt}, are replaced with the
22479 corresponding strings each time the prompt is displayed.
22483 @section Command Editing
22485 @cindex command line editing
22487 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22488 @sc{gnu} library provides consistent behavior for programs which provide a
22489 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22490 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22491 substitution, and a storage and recall of command history across
22492 debugging sessions.
22494 You may control the behavior of command line editing in @value{GDBN} with the
22495 command @code{set}.
22498 @kindex set editing
22501 @itemx set editing on
22502 Enable command line editing (enabled by default).
22504 @item set editing off
22505 Disable command line editing.
22507 @kindex show editing
22509 Show whether command line editing is enabled.
22512 @ifset SYSTEM_READLINE
22513 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22515 @ifclear SYSTEM_READLINE
22516 @xref{Command Line Editing},
22518 for more details about the Readline
22519 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22520 encouraged to read that chapter.
22522 @node Command History
22523 @section Command History
22524 @cindex command history
22526 @value{GDBN} can keep track of the commands you type during your
22527 debugging sessions, so that you can be certain of precisely what
22528 happened. Use these commands to manage the @value{GDBN} command
22531 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22532 package, to provide the history facility.
22533 @ifset SYSTEM_READLINE
22534 @xref{Using History Interactively, , , history, GNU History Library},
22536 @ifclear SYSTEM_READLINE
22537 @xref{Using History Interactively},
22539 for the detailed description of the History library.
22541 To issue a command to @value{GDBN} without affecting certain aspects of
22542 the state which is seen by users, prefix it with @samp{server }
22543 (@pxref{Server Prefix}). This
22544 means that this command will not affect the command history, nor will it
22545 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22546 pressed on a line by itself.
22548 @cindex @code{server}, command prefix
22549 The server prefix does not affect the recording of values into the value
22550 history; to print a value without recording it into the value history,
22551 use the @code{output} command instead of the @code{print} command.
22553 Here is the description of @value{GDBN} commands related to command
22557 @cindex history substitution
22558 @cindex history file
22559 @kindex set history filename
22560 @cindex @env{GDBHISTFILE}, environment variable
22561 @item set history filename @var{fname}
22562 Set the name of the @value{GDBN} command history file to @var{fname}.
22563 This is the file where @value{GDBN} reads an initial command history
22564 list, and where it writes the command history from this session when it
22565 exits. You can access this list through history expansion or through
22566 the history command editing characters listed below. This file defaults
22567 to the value of the environment variable @code{GDBHISTFILE}, or to
22568 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22571 @cindex save command history
22572 @kindex set history save
22573 @item set history save
22574 @itemx set history save on
22575 Record command history in a file, whose name may be specified with the
22576 @code{set history filename} command. By default, this option is disabled.
22578 @item set history save off
22579 Stop recording command history in a file.
22581 @cindex history size
22582 @kindex set history size
22583 @cindex @env{HISTSIZE}, environment variable
22584 @item set history size @var{size}
22585 @itemx set history size unlimited
22586 Set the number of commands which @value{GDBN} keeps in its history list.
22587 This defaults to the value of the environment variable
22588 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22589 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22590 history list is unlimited.
22593 History expansion assigns special meaning to the character @kbd{!}.
22594 @ifset SYSTEM_READLINE
22595 @xref{Event Designators, , , history, GNU History Library},
22597 @ifclear SYSTEM_READLINE
22598 @xref{Event Designators},
22602 @cindex history expansion, turn on/off
22603 Since @kbd{!} is also the logical not operator in C, history expansion
22604 is off by default. If you decide to enable history expansion with the
22605 @code{set history expansion on} command, you may sometimes need to
22606 follow @kbd{!} (when it is used as logical not, in an expression) with
22607 a space or a tab to prevent it from being expanded. The readline
22608 history facilities do not attempt substitution on the strings
22609 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22611 The commands to control history expansion are:
22614 @item set history expansion on
22615 @itemx set history expansion
22616 @kindex set history expansion
22617 Enable history expansion. History expansion is off by default.
22619 @item set history expansion off
22620 Disable history expansion.
22623 @kindex show history
22625 @itemx show history filename
22626 @itemx show history save
22627 @itemx show history size
22628 @itemx show history expansion
22629 These commands display the state of the @value{GDBN} history parameters.
22630 @code{show history} by itself displays all four states.
22635 @kindex show commands
22636 @cindex show last commands
22637 @cindex display command history
22638 @item show commands
22639 Display the last ten commands in the command history.
22641 @item show commands @var{n}
22642 Print ten commands centered on command number @var{n}.
22644 @item show commands +
22645 Print ten commands just after the commands last printed.
22649 @section Screen Size
22650 @cindex size of screen
22651 @cindex screen size
22654 @cindex pauses in output
22656 Certain commands to @value{GDBN} may produce large amounts of
22657 information output to the screen. To help you read all of it,
22658 @value{GDBN} pauses and asks you for input at the end of each page of
22659 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22660 to discard the remaining output. Also, the screen width setting
22661 determines when to wrap lines of output. Depending on what is being
22662 printed, @value{GDBN} tries to break the line at a readable place,
22663 rather than simply letting it overflow onto the following line.
22665 Normally @value{GDBN} knows the size of the screen from the terminal
22666 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22667 together with the value of the @code{TERM} environment variable and the
22668 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22669 you can override it with the @code{set height} and @code{set
22676 @kindex show height
22677 @item set height @var{lpp}
22678 @itemx set height unlimited
22680 @itemx set width @var{cpl}
22681 @itemx set width unlimited
22683 These @code{set} commands specify a screen height of @var{lpp} lines and
22684 a screen width of @var{cpl} characters. The associated @code{show}
22685 commands display the current settings.
22687 If you specify a height of either @code{unlimited} or zero lines,
22688 @value{GDBN} does not pause during output no matter how long the
22689 output is. This is useful if output is to a file or to an editor
22692 Likewise, you can specify @samp{set width unlimited} or @samp{set
22693 width 0} to prevent @value{GDBN} from wrapping its output.
22695 @item set pagination on
22696 @itemx set pagination off
22697 @kindex set pagination
22698 Turn the output pagination on or off; the default is on. Turning
22699 pagination off is the alternative to @code{set height unlimited}. Note that
22700 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22701 Options, -batch}) also automatically disables pagination.
22703 @item show pagination
22704 @kindex show pagination
22705 Show the current pagination mode.
22710 @cindex number representation
22711 @cindex entering numbers
22713 You can always enter numbers in octal, decimal, or hexadecimal in
22714 @value{GDBN} by the usual conventions: octal numbers begin with
22715 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22716 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22717 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22718 10; likewise, the default display for numbers---when no particular
22719 format is specified---is base 10. You can change the default base for
22720 both input and output with the commands described below.
22723 @kindex set input-radix
22724 @item set input-radix @var{base}
22725 Set the default base for numeric input. Supported choices
22726 for @var{base} are decimal 8, 10, or 16. The base must itself be
22727 specified either unambiguously or using the current input radix; for
22731 set input-radix 012
22732 set input-radix 10.
22733 set input-radix 0xa
22737 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22738 leaves the input radix unchanged, no matter what it was, since
22739 @samp{10}, being without any leading or trailing signs of its base, is
22740 interpreted in the current radix. Thus, if the current radix is 16,
22741 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22744 @kindex set output-radix
22745 @item set output-radix @var{base}
22746 Set the default base for numeric display. Supported choices
22747 for @var{base} are decimal 8, 10, or 16. The base must itself be
22748 specified either unambiguously or using the current input radix.
22750 @kindex show input-radix
22751 @item show input-radix
22752 Display the current default base for numeric input.
22754 @kindex show output-radix
22755 @item show output-radix
22756 Display the current default base for numeric display.
22758 @item set radix @r{[}@var{base}@r{]}
22762 These commands set and show the default base for both input and output
22763 of numbers. @code{set radix} sets the radix of input and output to
22764 the same base; without an argument, it resets the radix back to its
22765 default value of 10.
22770 @section Configuring the Current ABI
22772 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22773 application automatically. However, sometimes you need to override its
22774 conclusions. Use these commands to manage @value{GDBN}'s view of the
22780 @cindex Newlib OS ABI and its influence on the longjmp handling
22782 One @value{GDBN} configuration can debug binaries for multiple operating
22783 system targets, either via remote debugging or native emulation.
22784 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22785 but you can override its conclusion using the @code{set osabi} command.
22786 One example where this is useful is in debugging of binaries which use
22787 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22788 not have the same identifying marks that the standard C library for your
22791 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22792 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22793 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22794 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22798 Show the OS ABI currently in use.
22801 With no argument, show the list of registered available OS ABI's.
22803 @item set osabi @var{abi}
22804 Set the current OS ABI to @var{abi}.
22807 @cindex float promotion
22809 Generally, the way that an argument of type @code{float} is passed to a
22810 function depends on whether the function is prototyped. For a prototyped
22811 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22812 according to the architecture's convention for @code{float}. For unprototyped
22813 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22814 @code{double} and then passed.
22816 Unfortunately, some forms of debug information do not reliably indicate whether
22817 a function is prototyped. If @value{GDBN} calls a function that is not marked
22818 as prototyped, it consults @kbd{set coerce-float-to-double}.
22821 @kindex set coerce-float-to-double
22822 @item set coerce-float-to-double
22823 @itemx set coerce-float-to-double on
22824 Arguments of type @code{float} will be promoted to @code{double} when passed
22825 to an unprototyped function. This is the default setting.
22827 @item set coerce-float-to-double off
22828 Arguments of type @code{float} will be passed directly to unprototyped
22831 @kindex show coerce-float-to-double
22832 @item show coerce-float-to-double
22833 Show the current setting of promoting @code{float} to @code{double}.
22837 @kindex show cp-abi
22838 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22839 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22840 used to build your application. @value{GDBN} only fully supports
22841 programs with a single C@t{++} ABI; if your program contains code using
22842 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22843 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22844 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22845 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22846 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22847 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22852 Show the C@t{++} ABI currently in use.
22855 With no argument, show the list of supported C@t{++} ABI's.
22857 @item set cp-abi @var{abi}
22858 @itemx set cp-abi auto
22859 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22863 @section Automatically loading associated files
22864 @cindex auto-loading
22866 @value{GDBN} sometimes reads files with commands and settings automatically,
22867 without being explicitly told so by the user. We call this feature
22868 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22869 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22870 results or introduce security risks (e.g., if the file comes from untrusted
22874 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22875 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22877 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22878 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22881 There are various kinds of files @value{GDBN} can automatically load.
22882 In addition to these files, @value{GDBN} supports auto-loading code written
22883 in various extension languages. @xref{Auto-loading extensions}.
22885 Note that loading of these associated files (including the local @file{.gdbinit}
22886 file) requires accordingly configured @code{auto-load safe-path}
22887 (@pxref{Auto-loading safe path}).
22889 For these reasons, @value{GDBN} includes commands and options to let you
22890 control when to auto-load files and which files should be auto-loaded.
22893 @anchor{set auto-load off}
22894 @kindex set auto-load off
22895 @item set auto-load off
22896 Globally disable loading of all auto-loaded files.
22897 You may want to use this command with the @samp{-iex} option
22898 (@pxref{Option -init-eval-command}) such as:
22900 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22903 Be aware that system init file (@pxref{System-wide configuration})
22904 and init files from your home directory (@pxref{Home Directory Init File})
22905 still get read (as they come from generally trusted directories).
22906 To prevent @value{GDBN} from auto-loading even those init files, use the
22907 @option{-nx} option (@pxref{Mode Options}), in addition to
22908 @code{set auto-load no}.
22910 @anchor{show auto-load}
22911 @kindex show auto-load
22912 @item show auto-load
22913 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22917 (gdb) show auto-load
22918 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22919 libthread-db: Auto-loading of inferior specific libthread_db is on.
22920 local-gdbinit: Auto-loading of .gdbinit script from current directory
22922 python-scripts: Auto-loading of Python scripts is on.
22923 safe-path: List of directories from which it is safe to auto-load files
22924 is $debugdir:$datadir/auto-load.
22925 scripts-directory: List of directories from which to load auto-loaded scripts
22926 is $debugdir:$datadir/auto-load.
22929 @anchor{info auto-load}
22930 @kindex info auto-load
22931 @item info auto-load
22932 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22936 (gdb) info auto-load
22939 Yes /home/user/gdb/gdb-gdb.gdb
22940 libthread-db: No auto-loaded libthread-db.
22941 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22945 Yes /home/user/gdb/gdb-gdb.py
22949 These are @value{GDBN} control commands for the auto-loading:
22951 @multitable @columnfractions .5 .5
22952 @item @xref{set auto-load off}.
22953 @tab Disable auto-loading globally.
22954 @item @xref{show auto-load}.
22955 @tab Show setting of all kinds of files.
22956 @item @xref{info auto-load}.
22957 @tab Show state of all kinds of files.
22958 @item @xref{set auto-load gdb-scripts}.
22959 @tab Control for @value{GDBN} command scripts.
22960 @item @xref{show auto-load gdb-scripts}.
22961 @tab Show setting of @value{GDBN} command scripts.
22962 @item @xref{info auto-load gdb-scripts}.
22963 @tab Show state of @value{GDBN} command scripts.
22964 @item @xref{set auto-load python-scripts}.
22965 @tab Control for @value{GDBN} Python scripts.
22966 @item @xref{show auto-load python-scripts}.
22967 @tab Show setting of @value{GDBN} Python scripts.
22968 @item @xref{info auto-load python-scripts}.
22969 @tab Show state of @value{GDBN} Python scripts.
22970 @item @xref{set auto-load guile-scripts}.
22971 @tab Control for @value{GDBN} Guile scripts.
22972 @item @xref{show auto-load guile-scripts}.
22973 @tab Show setting of @value{GDBN} Guile scripts.
22974 @item @xref{info auto-load guile-scripts}.
22975 @tab Show state of @value{GDBN} Guile scripts.
22976 @item @xref{set auto-load scripts-directory}.
22977 @tab Control for @value{GDBN} auto-loaded scripts location.
22978 @item @xref{show auto-load scripts-directory}.
22979 @tab Show @value{GDBN} auto-loaded scripts location.
22980 @item @xref{add-auto-load-scripts-directory}.
22981 @tab Add directory for auto-loaded scripts location list.
22982 @item @xref{set auto-load local-gdbinit}.
22983 @tab Control for init file in the current directory.
22984 @item @xref{show auto-load local-gdbinit}.
22985 @tab Show setting of init file in the current directory.
22986 @item @xref{info auto-load local-gdbinit}.
22987 @tab Show state of init file in the current directory.
22988 @item @xref{set auto-load libthread-db}.
22989 @tab Control for thread debugging library.
22990 @item @xref{show auto-load libthread-db}.
22991 @tab Show setting of thread debugging library.
22992 @item @xref{info auto-load libthread-db}.
22993 @tab Show state of thread debugging library.
22994 @item @xref{set auto-load safe-path}.
22995 @tab Control directories trusted for automatic loading.
22996 @item @xref{show auto-load safe-path}.
22997 @tab Show directories trusted for automatic loading.
22998 @item @xref{add-auto-load-safe-path}.
22999 @tab Add directory trusted for automatic loading.
23002 @node Init File in the Current Directory
23003 @subsection Automatically loading init file in the current directory
23004 @cindex auto-loading init file in the current directory
23006 By default, @value{GDBN} reads and executes the canned sequences of commands
23007 from init file (if any) in the current working directory,
23008 see @ref{Init File in the Current Directory during Startup}.
23010 Note that loading of this local @file{.gdbinit} file also requires accordingly
23011 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23014 @anchor{set auto-load local-gdbinit}
23015 @kindex set auto-load local-gdbinit
23016 @item set auto-load local-gdbinit [on|off]
23017 Enable or disable the auto-loading of canned sequences of commands
23018 (@pxref{Sequences}) found in init file in the current directory.
23020 @anchor{show auto-load local-gdbinit}
23021 @kindex show auto-load local-gdbinit
23022 @item show auto-load local-gdbinit
23023 Show whether auto-loading of canned sequences of commands from init file in the
23024 current directory is enabled or disabled.
23026 @anchor{info auto-load local-gdbinit}
23027 @kindex info auto-load local-gdbinit
23028 @item info auto-load local-gdbinit
23029 Print whether canned sequences of commands from init file in the
23030 current directory have been auto-loaded.
23033 @node libthread_db.so.1 file
23034 @subsection Automatically loading thread debugging library
23035 @cindex auto-loading libthread_db.so.1
23037 This feature is currently present only on @sc{gnu}/Linux native hosts.
23039 @value{GDBN} reads in some cases thread debugging library from places specific
23040 to the inferior (@pxref{set libthread-db-search-path}).
23042 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23043 without checking this @samp{set auto-load libthread-db} switch as system
23044 libraries have to be trusted in general. In all other cases of
23045 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23046 auto-load libthread-db} is enabled before trying to open such thread debugging
23049 Note that loading of this debugging library also requires accordingly configured
23050 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23053 @anchor{set auto-load libthread-db}
23054 @kindex set auto-load libthread-db
23055 @item set auto-load libthread-db [on|off]
23056 Enable or disable the auto-loading of inferior specific thread debugging library.
23058 @anchor{show auto-load libthread-db}
23059 @kindex show auto-load libthread-db
23060 @item show auto-load libthread-db
23061 Show whether auto-loading of inferior specific thread debugging library is
23062 enabled or disabled.
23064 @anchor{info auto-load libthread-db}
23065 @kindex info auto-load libthread-db
23066 @item info auto-load libthread-db
23067 Print the list of all loaded inferior specific thread debugging libraries and
23068 for each such library print list of inferior @var{pid}s using it.
23071 @node Auto-loading safe path
23072 @subsection Security restriction for auto-loading
23073 @cindex auto-loading safe-path
23075 As the files of inferior can come from untrusted source (such as submitted by
23076 an application user) @value{GDBN} does not always load any files automatically.
23077 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23078 directories trusted for loading files not explicitly requested by user.
23079 Each directory can also be a shell wildcard pattern.
23081 If the path is not set properly you will see a warning and the file will not
23086 Reading symbols from /home/user/gdb/gdb...done.
23087 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23088 declined by your `auto-load safe-path' set
23089 to "$debugdir:$datadir/auto-load".
23090 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23091 declined by your `auto-load safe-path' set
23092 to "$debugdir:$datadir/auto-load".
23096 To instruct @value{GDBN} to go ahead and use the init files anyway,
23097 invoke @value{GDBN} like this:
23100 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23103 The list of trusted directories is controlled by the following commands:
23106 @anchor{set auto-load safe-path}
23107 @kindex set auto-load safe-path
23108 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23109 Set the list of directories (and their subdirectories) trusted for automatic
23110 loading and execution of scripts. You can also enter a specific trusted file.
23111 Each directory can also be a shell wildcard pattern; wildcards do not match
23112 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23113 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23114 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23115 its default value as specified during @value{GDBN} compilation.
23117 The list of directories uses path separator (@samp{:} on GNU and Unix
23118 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23119 to the @env{PATH} environment variable.
23121 @anchor{show auto-load safe-path}
23122 @kindex show auto-load safe-path
23123 @item show auto-load safe-path
23124 Show the list of directories trusted for automatic loading and execution of
23127 @anchor{add-auto-load-safe-path}
23128 @kindex add-auto-load-safe-path
23129 @item add-auto-load-safe-path
23130 Add an entry (or list of entries) to the list of directories trusted for
23131 automatic loading and execution of scripts. Multiple entries may be delimited
23132 by the host platform path separator in use.
23135 This variable defaults to what @code{--with-auto-load-dir} has been configured
23136 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23137 substitution applies the same as for @ref{set auto-load scripts-directory}.
23138 The default @code{set auto-load safe-path} value can be also overriden by
23139 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23141 Setting this variable to @file{/} disables this security protection,
23142 corresponding @value{GDBN} configuration option is
23143 @option{--without-auto-load-safe-path}.
23144 This variable is supposed to be set to the system directories writable by the
23145 system superuser only. Users can add their source directories in init files in
23146 their home directories (@pxref{Home Directory Init File}). See also deprecated
23147 init file in the current directory
23148 (@pxref{Init File in the Current Directory during Startup}).
23150 To force @value{GDBN} to load the files it declined to load in the previous
23151 example, you could use one of the following ways:
23154 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23155 Specify this trusted directory (or a file) as additional component of the list.
23156 You have to specify also any existing directories displayed by
23157 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23159 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23160 Specify this directory as in the previous case but just for a single
23161 @value{GDBN} session.
23163 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23164 Disable auto-loading safety for a single @value{GDBN} session.
23165 This assumes all the files you debug during this @value{GDBN} session will come
23166 from trusted sources.
23168 @item @kbd{./configure --without-auto-load-safe-path}
23169 During compilation of @value{GDBN} you may disable any auto-loading safety.
23170 This assumes all the files you will ever debug with this @value{GDBN} come from
23174 On the other hand you can also explicitly forbid automatic files loading which
23175 also suppresses any such warning messages:
23178 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23179 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23181 @item @file{~/.gdbinit}: @samp{set auto-load no}
23182 Disable auto-loading globally for the user
23183 (@pxref{Home Directory Init File}). While it is improbable, you could also
23184 use system init file instead (@pxref{System-wide configuration}).
23187 This setting applies to the file names as entered by user. If no entry matches
23188 @value{GDBN} tries as a last resort to also resolve all the file names into
23189 their canonical form (typically resolving symbolic links) and compare the
23190 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23191 own before starting the comparison so a canonical form of directories is
23192 recommended to be entered.
23194 @node Auto-loading verbose mode
23195 @subsection Displaying files tried for auto-load
23196 @cindex auto-loading verbose mode
23198 For better visibility of all the file locations where you can place scripts to
23199 be auto-loaded with inferior --- or to protect yourself against accidental
23200 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23201 all the files attempted to be loaded. Both existing and non-existing files may
23204 For example the list of directories from which it is safe to auto-load files
23205 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23206 may not be too obvious while setting it up.
23209 (gdb) set debug auto-load on
23210 (gdb) file ~/src/t/true
23211 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23212 for objfile "/tmp/true".
23213 auto-load: Updating directories of "/usr:/opt".
23214 auto-load: Using directory "/usr".
23215 auto-load: Using directory "/opt".
23216 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23217 by your `auto-load safe-path' set to "/usr:/opt".
23221 @anchor{set debug auto-load}
23222 @kindex set debug auto-load
23223 @item set debug auto-load [on|off]
23224 Set whether to print the filenames attempted to be auto-loaded.
23226 @anchor{show debug auto-load}
23227 @kindex show debug auto-load
23228 @item show debug auto-load
23229 Show whether printing of the filenames attempted to be auto-loaded is turned
23233 @node Messages/Warnings
23234 @section Optional Warnings and Messages
23236 @cindex verbose operation
23237 @cindex optional warnings
23238 By default, @value{GDBN} is silent about its inner workings. If you are
23239 running on a slow machine, you may want to use the @code{set verbose}
23240 command. This makes @value{GDBN} tell you when it does a lengthy
23241 internal operation, so you will not think it has crashed.
23243 Currently, the messages controlled by @code{set verbose} are those
23244 which announce that the symbol table for a source file is being read;
23245 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23248 @kindex set verbose
23249 @item set verbose on
23250 Enables @value{GDBN} output of certain informational messages.
23252 @item set verbose off
23253 Disables @value{GDBN} output of certain informational messages.
23255 @kindex show verbose
23257 Displays whether @code{set verbose} is on or off.
23260 By default, if @value{GDBN} encounters bugs in the symbol table of an
23261 object file, it is silent; but if you are debugging a compiler, you may
23262 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23267 @kindex set complaints
23268 @item set complaints @var{limit}
23269 Permits @value{GDBN} to output @var{limit} complaints about each type of
23270 unusual symbols before becoming silent about the problem. Set
23271 @var{limit} to zero to suppress all complaints; set it to a large number
23272 to prevent complaints from being suppressed.
23274 @kindex show complaints
23275 @item show complaints
23276 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23280 @anchor{confirmation requests}
23281 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23282 lot of stupid questions to confirm certain commands. For example, if
23283 you try to run a program which is already running:
23287 The program being debugged has been started already.
23288 Start it from the beginning? (y or n)
23291 If you are willing to unflinchingly face the consequences of your own
23292 commands, you can disable this ``feature'':
23296 @kindex set confirm
23298 @cindex confirmation
23299 @cindex stupid questions
23300 @item set confirm off
23301 Disables confirmation requests. Note that running @value{GDBN} with
23302 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23303 automatically disables confirmation requests.
23305 @item set confirm on
23306 Enables confirmation requests (the default).
23308 @kindex show confirm
23310 Displays state of confirmation requests.
23314 @cindex command tracing
23315 If you need to debug user-defined commands or sourced files you may find it
23316 useful to enable @dfn{command tracing}. In this mode each command will be
23317 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23318 quantity denoting the call depth of each command.
23321 @kindex set trace-commands
23322 @cindex command scripts, debugging
23323 @item set trace-commands on
23324 Enable command tracing.
23325 @item set trace-commands off
23326 Disable command tracing.
23327 @item show trace-commands
23328 Display the current state of command tracing.
23331 @node Debugging Output
23332 @section Optional Messages about Internal Happenings
23333 @cindex optional debugging messages
23335 @value{GDBN} has commands that enable optional debugging messages from
23336 various @value{GDBN} subsystems; normally these commands are of
23337 interest to @value{GDBN} maintainers, or when reporting a bug. This
23338 section documents those commands.
23341 @kindex set exec-done-display
23342 @item set exec-done-display
23343 Turns on or off the notification of asynchronous commands'
23344 completion. When on, @value{GDBN} will print a message when an
23345 asynchronous command finishes its execution. The default is off.
23346 @kindex show exec-done-display
23347 @item show exec-done-display
23348 Displays the current setting of asynchronous command completion
23351 @cindex ARM AArch64
23352 @item set debug aarch64
23353 Turns on or off display of debugging messages related to ARM AArch64.
23354 The default is off.
23356 @item show debug aarch64
23357 Displays the current state of displaying debugging messages related to
23359 @cindex gdbarch debugging info
23360 @cindex architecture debugging info
23361 @item set debug arch
23362 Turns on or off display of gdbarch debugging info. The default is off
23363 @item show debug arch
23364 Displays the current state of displaying gdbarch debugging info.
23365 @item set debug aix-solib
23366 @cindex AIX shared library debugging
23367 Control display of debugging messages from the AIX shared library
23368 support module. The default is off.
23369 @item show debug aix-thread
23370 Show the current state of displaying AIX shared library debugging messages.
23371 @item set debug aix-thread
23372 @cindex AIX threads
23373 Display debugging messages about inner workings of the AIX thread
23375 @item show debug aix-thread
23376 Show the current state of AIX thread debugging info display.
23377 @item set debug check-physname
23379 Check the results of the ``physname'' computation. When reading DWARF
23380 debugging information for C@t{++}, @value{GDBN} attempts to compute
23381 each entity's name. @value{GDBN} can do this computation in two
23382 different ways, depending on exactly what information is present.
23383 When enabled, this setting causes @value{GDBN} to compute the names
23384 both ways and display any discrepancies.
23385 @item show debug check-physname
23386 Show the current state of ``physname'' checking.
23387 @item set debug coff-pe-read
23388 @cindex COFF/PE exported symbols
23389 Control display of debugging messages related to reading of COFF/PE
23390 exported symbols. The default is off.
23391 @item show debug coff-pe-read
23392 Displays the current state of displaying debugging messages related to
23393 reading of COFF/PE exported symbols.
23394 @item set debug dwarf2-die
23395 @cindex DWARF2 DIEs
23396 Dump DWARF2 DIEs after they are read in.
23397 The value is the number of nesting levels to print.
23398 A value of zero turns off the display.
23399 @item show debug dwarf2-die
23400 Show the current state of DWARF2 DIE debugging.
23401 @item set debug dwarf2-read
23402 @cindex DWARF2 Reading
23403 Turns on or off display of debugging messages related to reading
23404 DWARF debug info. The default is 0 (off).
23405 A value of 1 provides basic information.
23406 A value greater than 1 provides more verbose information.
23407 @item show debug dwarf2-read
23408 Show the current state of DWARF2 reader debugging.
23409 @item set debug displaced
23410 @cindex displaced stepping debugging info
23411 Turns on or off display of @value{GDBN} debugging info for the
23412 displaced stepping support. The default is off.
23413 @item show debug displaced
23414 Displays the current state of displaying @value{GDBN} debugging info
23415 related to displaced stepping.
23416 @item set debug event
23417 @cindex event debugging info
23418 Turns on or off display of @value{GDBN} event debugging info. The
23420 @item show debug event
23421 Displays the current state of displaying @value{GDBN} event debugging
23423 @item set debug expression
23424 @cindex expression debugging info
23425 Turns on or off display of debugging info about @value{GDBN}
23426 expression parsing. The default is off.
23427 @item show debug expression
23428 Displays the current state of displaying debugging info about
23429 @value{GDBN} expression parsing.
23430 @item set debug frame
23431 @cindex frame debugging info
23432 Turns on or off display of @value{GDBN} frame debugging info. The
23434 @item show debug frame
23435 Displays the current state of displaying @value{GDBN} frame debugging
23437 @item set debug gnu-nat
23438 @cindex @sc{gnu}/Hurd debug messages
23439 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23440 @item show debug gnu-nat
23441 Show the current state of @sc{gnu}/Hurd debugging messages.
23442 @item set debug infrun
23443 @cindex inferior debugging info
23444 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23445 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23446 for implementing operations such as single-stepping the inferior.
23447 @item show debug infrun
23448 Displays the current state of @value{GDBN} inferior debugging.
23449 @item set debug jit
23450 @cindex just-in-time compilation, debugging messages
23451 Turns on or off debugging messages from JIT debug support.
23452 @item show debug jit
23453 Displays the current state of @value{GDBN} JIT debugging.
23454 @item set debug lin-lwp
23455 @cindex @sc{gnu}/Linux LWP debug messages
23456 @cindex Linux lightweight processes
23457 Turns on or off debugging messages from the Linux LWP debug support.
23458 @item show debug lin-lwp
23459 Show the current state of Linux LWP debugging messages.
23460 @item set debug mach-o
23461 @cindex Mach-O symbols processing
23462 Control display of debugging messages related to Mach-O symbols
23463 processing. The default is off.
23464 @item show debug mach-o
23465 Displays the current state of displaying debugging messages related to
23466 reading of COFF/PE exported symbols.
23467 @item set debug notification
23468 @cindex remote async notification debugging info
23469 Turns on or off debugging messages about remote async notification.
23470 The default is off.
23471 @item show debug notification
23472 Displays the current state of remote async notification debugging messages.
23473 @item set debug observer
23474 @cindex observer debugging info
23475 Turns on or off display of @value{GDBN} observer debugging. This
23476 includes info such as the notification of observable events.
23477 @item show debug observer
23478 Displays the current state of observer debugging.
23479 @item set debug overload
23480 @cindex C@t{++} overload debugging info
23481 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23482 info. This includes info such as ranking of functions, etc. The default
23484 @item show debug overload
23485 Displays the current state of displaying @value{GDBN} C@t{++} overload
23487 @cindex expression parser, debugging info
23488 @cindex debug expression parser
23489 @item set debug parser
23490 Turns on or off the display of expression parser debugging output.
23491 Internally, this sets the @code{yydebug} variable in the expression
23492 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23493 details. The default is off.
23494 @item show debug parser
23495 Show the current state of expression parser debugging.
23496 @cindex packets, reporting on stdout
23497 @cindex serial connections, debugging
23498 @cindex debug remote protocol
23499 @cindex remote protocol debugging
23500 @cindex display remote packets
23501 @item set debug remote
23502 Turns on or off display of reports on all packets sent back and forth across
23503 the serial line to the remote machine. The info is printed on the
23504 @value{GDBN} standard output stream. The default is off.
23505 @item show debug remote
23506 Displays the state of display of remote packets.
23507 @item set debug serial
23508 Turns on or off display of @value{GDBN} serial debugging info. The
23510 @item show debug serial
23511 Displays the current state of displaying @value{GDBN} serial debugging
23513 @item set debug solib-frv
23514 @cindex FR-V shared-library debugging
23515 Turns on or off debugging messages for FR-V shared-library code.
23516 @item show debug solib-frv
23517 Display the current state of FR-V shared-library code debugging
23519 @item set debug symbol-lookup
23520 @cindex symbol lookup
23521 Turns on or off display of debugging messages related to symbol lookup.
23522 The default is 0 (off).
23523 A value of 1 provides basic information.
23524 A value greater than 1 provides more verbose information.
23525 @item show debug symbol-lookup
23526 Show the current state of symbol lookup debugging messages.
23527 @item set debug symfile
23528 @cindex symbol file functions
23529 Turns on or off display of debugging messages related to symbol file functions.
23530 The default is off. @xref{Files}.
23531 @item show debug symfile
23532 Show the current state of symbol file debugging messages.
23533 @item set debug symtab-create
23534 @cindex symbol table creation
23535 Turns on or off display of debugging messages related to symbol table creation.
23536 The default is 0 (off).
23537 A value of 1 provides basic information.
23538 A value greater than 1 provides more verbose information.
23539 @item show debug symtab-create
23540 Show the current state of symbol table creation debugging.
23541 @item set debug target
23542 @cindex target debugging info
23543 Turns on or off display of @value{GDBN} target debugging info. This info
23544 includes what is going on at the target level of GDB, as it happens. The
23545 default is 0. Set it to 1 to track events, and to 2 to also track the
23546 value of large memory transfers.
23547 @item show debug target
23548 Displays the current state of displaying @value{GDBN} target debugging
23550 @item set debug timestamp
23551 @cindex timestampping debugging info
23552 Turns on or off display of timestamps with @value{GDBN} debugging info.
23553 When enabled, seconds and microseconds are displayed before each debugging
23555 @item show debug timestamp
23556 Displays the current state of displaying timestamps with @value{GDBN}
23558 @item set debug varobj
23559 @cindex variable object debugging info
23560 Turns on or off display of @value{GDBN} variable object debugging
23561 info. The default is off.
23562 @item show debug varobj
23563 Displays the current state of displaying @value{GDBN} variable object
23565 @item set debug xml
23566 @cindex XML parser debugging
23567 Turns on or off debugging messages for built-in XML parsers.
23568 @item show debug xml
23569 Displays the current state of XML debugging messages.
23572 @node Other Misc Settings
23573 @section Other Miscellaneous Settings
23574 @cindex miscellaneous settings
23577 @kindex set interactive-mode
23578 @item set interactive-mode
23579 If @code{on}, forces @value{GDBN} to assume that GDB was started
23580 in a terminal. In practice, this means that @value{GDBN} should wait
23581 for the user to answer queries generated by commands entered at
23582 the command prompt. If @code{off}, forces @value{GDBN} to operate
23583 in the opposite mode, and it uses the default answers to all queries.
23584 If @code{auto} (the default), @value{GDBN} tries to determine whether
23585 its standard input is a terminal, and works in interactive-mode if it
23586 is, non-interactively otherwise.
23588 In the vast majority of cases, the debugger should be able to guess
23589 correctly which mode should be used. But this setting can be useful
23590 in certain specific cases, such as running a MinGW @value{GDBN}
23591 inside a cygwin window.
23593 @kindex show interactive-mode
23594 @item show interactive-mode
23595 Displays whether the debugger is operating in interactive mode or not.
23598 @node Extending GDB
23599 @chapter Extending @value{GDBN}
23600 @cindex extending GDB
23602 @value{GDBN} provides several mechanisms for extension.
23603 @value{GDBN} also provides the ability to automatically load
23604 extensions when it reads a file for debugging. This allows the
23605 user to automatically customize @value{GDBN} for the program
23609 * Sequences:: Canned Sequences of @value{GDBN} Commands
23610 * Python:: Extending @value{GDBN} using Python
23611 * Guile:: Extending @value{GDBN} using Guile
23612 * Auto-loading extensions:: Automatically loading extensions
23613 * Multiple Extension Languages:: Working with multiple extension languages
23614 * Aliases:: Creating new spellings of existing commands
23617 To facilitate the use of extension languages, @value{GDBN} is capable
23618 of evaluating the contents of a file. When doing so, @value{GDBN}
23619 can recognize which extension language is being used by looking at
23620 the filename extension. Files with an unrecognized filename extension
23621 are always treated as a @value{GDBN} Command Files.
23622 @xref{Command Files,, Command files}.
23624 You can control how @value{GDBN} evaluates these files with the following
23628 @kindex set script-extension
23629 @kindex show script-extension
23630 @item set script-extension off
23631 All scripts are always evaluated as @value{GDBN} Command Files.
23633 @item set script-extension soft
23634 The debugger determines the scripting language based on filename
23635 extension. If this scripting language is supported, @value{GDBN}
23636 evaluates the script using that language. Otherwise, it evaluates
23637 the file as a @value{GDBN} Command File.
23639 @item set script-extension strict
23640 The debugger determines the scripting language based on filename
23641 extension, and evaluates the script using that language. If the
23642 language is not supported, then the evaluation fails.
23644 @item show script-extension
23645 Display the current value of the @code{script-extension} option.
23650 @section Canned Sequences of Commands
23652 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23653 Command Lists}), @value{GDBN} provides two ways to store sequences of
23654 commands for execution as a unit: user-defined commands and command
23658 * Define:: How to define your own commands
23659 * Hooks:: Hooks for user-defined commands
23660 * Command Files:: How to write scripts of commands to be stored in a file
23661 * Output:: Commands for controlled output
23662 * Auto-loading sequences:: Controlling auto-loaded command files
23666 @subsection User-defined Commands
23668 @cindex user-defined command
23669 @cindex arguments, to user-defined commands
23670 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23671 which you assign a new name as a command. This is done with the
23672 @code{define} command. User commands may accept up to 10 arguments
23673 separated by whitespace. Arguments are accessed within the user command
23674 via @code{$arg0@dots{}$arg9}. A trivial example:
23678 print $arg0 + $arg1 + $arg2
23683 To execute the command use:
23690 This defines the command @code{adder}, which prints the sum of
23691 its three arguments. Note the arguments are text substitutions, so they may
23692 reference variables, use complex expressions, or even perform inferior
23695 @cindex argument count in user-defined commands
23696 @cindex how many arguments (user-defined commands)
23697 In addition, @code{$argc} may be used to find out how many arguments have
23698 been passed. This expands to a number in the range 0@dots{}10.
23703 print $arg0 + $arg1
23706 print $arg0 + $arg1 + $arg2
23714 @item define @var{commandname}
23715 Define a command named @var{commandname}. If there is already a command
23716 by that name, you are asked to confirm that you want to redefine it.
23717 The argument @var{commandname} may be a bare command name consisting of letters,
23718 numbers, dashes, and underscores. It may also start with any predefined
23719 prefix command. For example, @samp{define target my-target} creates
23720 a user-defined @samp{target my-target} command.
23722 The definition of the command is made up of other @value{GDBN} command lines,
23723 which are given following the @code{define} command. The end of these
23724 commands is marked by a line containing @code{end}.
23727 @kindex end@r{ (user-defined commands)}
23728 @item document @var{commandname}
23729 Document the user-defined command @var{commandname}, so that it can be
23730 accessed by @code{help}. The command @var{commandname} must already be
23731 defined. This command reads lines of documentation just as @code{define}
23732 reads the lines of the command definition, ending with @code{end}.
23733 After the @code{document} command is finished, @code{help} on command
23734 @var{commandname} displays the documentation you have written.
23736 You may use the @code{document} command again to change the
23737 documentation of a command. Redefining the command with @code{define}
23738 does not change the documentation.
23740 @kindex dont-repeat
23741 @cindex don't repeat command
23743 Used inside a user-defined command, this tells @value{GDBN} that this
23744 command should not be repeated when the user hits @key{RET}
23745 (@pxref{Command Syntax, repeat last command}).
23747 @kindex help user-defined
23748 @item help user-defined
23749 List all user-defined commands and all python commands defined in class
23750 COMAND_USER. The first line of the documentation or docstring is
23755 @itemx show user @var{commandname}
23756 Display the @value{GDBN} commands used to define @var{commandname} (but
23757 not its documentation). If no @var{commandname} is given, display the
23758 definitions for all user-defined commands.
23759 This does not work for user-defined python commands.
23761 @cindex infinite recursion in user-defined commands
23762 @kindex show max-user-call-depth
23763 @kindex set max-user-call-depth
23764 @item show max-user-call-depth
23765 @itemx set max-user-call-depth
23766 The value of @code{max-user-call-depth} controls how many recursion
23767 levels are allowed in user-defined commands before @value{GDBN} suspects an
23768 infinite recursion and aborts the command.
23769 This does not apply to user-defined python commands.
23772 In addition to the above commands, user-defined commands frequently
23773 use control flow commands, described in @ref{Command Files}.
23775 When user-defined commands are executed, the
23776 commands of the definition are not printed. An error in any command
23777 stops execution of the user-defined command.
23779 If used interactively, commands that would ask for confirmation proceed
23780 without asking when used inside a user-defined command. Many @value{GDBN}
23781 commands that normally print messages to say what they are doing omit the
23782 messages when used in a user-defined command.
23785 @subsection User-defined Command Hooks
23786 @cindex command hooks
23787 @cindex hooks, for commands
23788 @cindex hooks, pre-command
23791 You may define @dfn{hooks}, which are a special kind of user-defined
23792 command. Whenever you run the command @samp{foo}, if the user-defined
23793 command @samp{hook-foo} exists, it is executed (with no arguments)
23794 before that command.
23796 @cindex hooks, post-command
23798 A hook may also be defined which is run after the command you executed.
23799 Whenever you run the command @samp{foo}, if the user-defined command
23800 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23801 that command. Post-execution hooks may exist simultaneously with
23802 pre-execution hooks, for the same command.
23804 It is valid for a hook to call the command which it hooks. If this
23805 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23807 @c It would be nice if hookpost could be passed a parameter indicating
23808 @c if the command it hooks executed properly or not. FIXME!
23810 @kindex stop@r{, a pseudo-command}
23811 In addition, a pseudo-command, @samp{stop} exists. Defining
23812 (@samp{hook-stop}) makes the associated commands execute every time
23813 execution stops in your program: before breakpoint commands are run,
23814 displays are printed, or the stack frame is printed.
23816 For example, to ignore @code{SIGALRM} signals while
23817 single-stepping, but treat them normally during normal execution,
23822 handle SIGALRM nopass
23826 handle SIGALRM pass
23829 define hook-continue
23830 handle SIGALRM pass
23834 As a further example, to hook at the beginning and end of the @code{echo}
23835 command, and to add extra text to the beginning and end of the message,
23843 define hookpost-echo
23847 (@value{GDBP}) echo Hello World
23848 <<<---Hello World--->>>
23853 You can define a hook for any single-word command in @value{GDBN}, but
23854 not for command aliases; you should define a hook for the basic command
23855 name, e.g.@: @code{backtrace} rather than @code{bt}.
23856 @c FIXME! So how does Joe User discover whether a command is an alias
23858 You can hook a multi-word command by adding @code{hook-} or
23859 @code{hookpost-} to the last word of the command, e.g.@:
23860 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23862 If an error occurs during the execution of your hook, execution of
23863 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23864 (before the command that you actually typed had a chance to run).
23866 If you try to define a hook which does not match any known command, you
23867 get a warning from the @code{define} command.
23869 @node Command Files
23870 @subsection Command Files
23872 @cindex command files
23873 @cindex scripting commands
23874 A command file for @value{GDBN} is a text file made of lines that are
23875 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23876 also be included. An empty line in a command file does nothing; it
23877 does not mean to repeat the last command, as it would from the
23880 You can request the execution of a command file with the @code{source}
23881 command. Note that the @code{source} command is also used to evaluate
23882 scripts that are not Command Files. The exact behavior can be configured
23883 using the @code{script-extension} setting.
23884 @xref{Extending GDB,, Extending GDB}.
23888 @cindex execute commands from a file
23889 @item source [-s] [-v] @var{filename}
23890 Execute the command file @var{filename}.
23893 The lines in a command file are generally executed sequentially,
23894 unless the order of execution is changed by one of the
23895 @emph{flow-control commands} described below. The commands are not
23896 printed as they are executed. An error in any command terminates
23897 execution of the command file and control is returned to the console.
23899 @value{GDBN} first searches for @var{filename} in the current directory.
23900 If the file is not found there, and @var{filename} does not specify a
23901 directory, then @value{GDBN} also looks for the file on the source search path
23902 (specified with the @samp{directory} command);
23903 except that @file{$cdir} is not searched because the compilation directory
23904 is not relevant to scripts.
23906 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23907 on the search path even if @var{filename} specifies a directory.
23908 The search is done by appending @var{filename} to each element of the
23909 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23910 and the search path contains @file{/home/user} then @value{GDBN} will
23911 look for the script @file{/home/user/mylib/myscript}.
23912 The search is also done if @var{filename} is an absolute path.
23913 For example, if @var{filename} is @file{/tmp/myscript} and
23914 the search path contains @file{/home/user} then @value{GDBN} will
23915 look for the script @file{/home/user/tmp/myscript}.
23916 For DOS-like systems, if @var{filename} contains a drive specification,
23917 it is stripped before concatenation. For example, if @var{filename} is
23918 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23919 will look for the script @file{c:/tmp/myscript}.
23921 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23922 each command as it is executed. The option must be given before
23923 @var{filename}, and is interpreted as part of the filename anywhere else.
23925 Commands that would ask for confirmation if used interactively proceed
23926 without asking when used in a command file. Many @value{GDBN} commands that
23927 normally print messages to say what they are doing omit the messages
23928 when called from command files.
23930 @value{GDBN} also accepts command input from standard input. In this
23931 mode, normal output goes to standard output and error output goes to
23932 standard error. Errors in a command file supplied on standard input do
23933 not terminate execution of the command file---execution continues with
23937 gdb < cmds > log 2>&1
23940 (The syntax above will vary depending on the shell used.) This example
23941 will execute commands from the file @file{cmds}. All output and errors
23942 would be directed to @file{log}.
23944 Since commands stored on command files tend to be more general than
23945 commands typed interactively, they frequently need to deal with
23946 complicated situations, such as different or unexpected values of
23947 variables and symbols, changes in how the program being debugged is
23948 built, etc. @value{GDBN} provides a set of flow-control commands to
23949 deal with these complexities. Using these commands, you can write
23950 complex scripts that loop over data structures, execute commands
23951 conditionally, etc.
23958 This command allows to include in your script conditionally executed
23959 commands. The @code{if} command takes a single argument, which is an
23960 expression to evaluate. It is followed by a series of commands that
23961 are executed only if the expression is true (its value is nonzero).
23962 There can then optionally be an @code{else} line, followed by a series
23963 of commands that are only executed if the expression was false. The
23964 end of the list is marked by a line containing @code{end}.
23968 This command allows to write loops. Its syntax is similar to
23969 @code{if}: the command takes a single argument, which is an expression
23970 to evaluate, and must be followed by the commands to execute, one per
23971 line, terminated by an @code{end}. These commands are called the
23972 @dfn{body} of the loop. The commands in the body of @code{while} are
23973 executed repeatedly as long as the expression evaluates to true.
23977 This command exits the @code{while} loop in whose body it is included.
23978 Execution of the script continues after that @code{while}s @code{end}
23981 @kindex loop_continue
23982 @item loop_continue
23983 This command skips the execution of the rest of the body of commands
23984 in the @code{while} loop in whose body it is included. Execution
23985 branches to the beginning of the @code{while} loop, where it evaluates
23986 the controlling expression.
23988 @kindex end@r{ (if/else/while commands)}
23990 Terminate the block of commands that are the body of @code{if},
23991 @code{else}, or @code{while} flow-control commands.
23996 @subsection Commands for Controlled Output
23998 During the execution of a command file or a user-defined command, normal
23999 @value{GDBN} output is suppressed; the only output that appears is what is
24000 explicitly printed by the commands in the definition. This section
24001 describes three commands useful for generating exactly the output you
24006 @item echo @var{text}
24007 @c I do not consider backslash-space a standard C escape sequence
24008 @c because it is not in ANSI.
24009 Print @var{text}. Nonprinting characters can be included in
24010 @var{text} using C escape sequences, such as @samp{\n} to print a
24011 newline. @strong{No newline is printed unless you specify one.}
24012 In addition to the standard C escape sequences, a backslash followed
24013 by a space stands for a space. This is useful for displaying a
24014 string with spaces at the beginning or the end, since leading and
24015 trailing spaces are otherwise trimmed from all arguments.
24016 To print @samp{@w{ }and foo =@w{ }}, use the command
24017 @samp{echo \@w{ }and foo = \@w{ }}.
24019 A backslash at the end of @var{text} can be used, as in C, to continue
24020 the command onto subsequent lines. For example,
24023 echo This is some text\n\
24024 which is continued\n\
24025 onto several lines.\n
24028 produces the same output as
24031 echo This is some text\n
24032 echo which is continued\n
24033 echo onto several lines.\n
24037 @item output @var{expression}
24038 Print the value of @var{expression} and nothing but that value: no
24039 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24040 value history either. @xref{Expressions, ,Expressions}, for more information
24043 @item output/@var{fmt} @var{expression}
24044 Print the value of @var{expression} in format @var{fmt}. You can use
24045 the same formats as for @code{print}. @xref{Output Formats,,Output
24046 Formats}, for more information.
24049 @item printf @var{template}, @var{expressions}@dots{}
24050 Print the values of one or more @var{expressions} under the control of
24051 the string @var{template}. To print several values, make
24052 @var{expressions} be a comma-separated list of individual expressions,
24053 which may be either numbers or pointers. Their values are printed as
24054 specified by @var{template}, exactly as a C program would do by
24055 executing the code below:
24058 printf (@var{template}, @var{expressions}@dots{});
24061 As in @code{C} @code{printf}, ordinary characters in @var{template}
24062 are printed verbatim, while @dfn{conversion specification} introduced
24063 by the @samp{%} character cause subsequent @var{expressions} to be
24064 evaluated, their values converted and formatted according to type and
24065 style information encoded in the conversion specifications, and then
24068 For example, you can print two values in hex like this:
24071 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24074 @code{printf} supports all the standard @code{C} conversion
24075 specifications, including the flags and modifiers between the @samp{%}
24076 character and the conversion letter, with the following exceptions:
24080 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24083 The modifier @samp{*} is not supported for specifying precision or
24087 The @samp{'} flag (for separation of digits into groups according to
24088 @code{LC_NUMERIC'}) is not supported.
24091 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24095 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24098 The conversion letters @samp{a} and @samp{A} are not supported.
24102 Note that the @samp{ll} type modifier is supported only if the
24103 underlying @code{C} implementation used to build @value{GDBN} supports
24104 the @code{long long int} type, and the @samp{L} type modifier is
24105 supported only if @code{long double} type is available.
24107 As in @code{C}, @code{printf} supports simple backslash-escape
24108 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24109 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24110 single character. Octal and hexadecimal escape sequences are not
24113 Additionally, @code{printf} supports conversion specifications for DFP
24114 (@dfn{Decimal Floating Point}) types using the following length modifiers
24115 together with a floating point specifier.
24120 @samp{H} for printing @code{Decimal32} types.
24123 @samp{D} for printing @code{Decimal64} types.
24126 @samp{DD} for printing @code{Decimal128} types.
24129 If the underlying @code{C} implementation used to build @value{GDBN} has
24130 support for the three length modifiers for DFP types, other modifiers
24131 such as width and precision will also be available for @value{GDBN} to use.
24133 In case there is no such @code{C} support, no additional modifiers will be
24134 available and the value will be printed in the standard way.
24136 Here's an example of printing DFP types using the above conversion letters:
24138 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24142 @item eval @var{template}, @var{expressions}@dots{}
24143 Convert the values of one or more @var{expressions} under the control of
24144 the string @var{template} to a command line, and call it.
24148 @node Auto-loading sequences
24149 @subsection Controlling auto-loading native @value{GDBN} scripts
24150 @cindex native script auto-loading
24152 When a new object file is read (for example, due to the @code{file}
24153 command, or because the inferior has loaded a shared library),
24154 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24155 @xref{Auto-loading extensions}.
24157 Auto-loading can be enabled or disabled,
24158 and the list of auto-loaded scripts can be printed.
24161 @anchor{set auto-load gdb-scripts}
24162 @kindex set auto-load gdb-scripts
24163 @item set auto-load gdb-scripts [on|off]
24164 Enable or disable the auto-loading of canned sequences of commands scripts.
24166 @anchor{show auto-load gdb-scripts}
24167 @kindex show auto-load gdb-scripts
24168 @item show auto-load gdb-scripts
24169 Show whether auto-loading of canned sequences of commands scripts is enabled or
24172 @anchor{info auto-load gdb-scripts}
24173 @kindex info auto-load gdb-scripts
24174 @cindex print list of auto-loaded canned sequences of commands scripts
24175 @item info auto-load gdb-scripts [@var{regexp}]
24176 Print the list of all canned sequences of commands scripts that @value{GDBN}
24180 If @var{regexp} is supplied only canned sequences of commands scripts with
24181 matching names are printed.
24183 @c Python docs live in a separate file.
24184 @include python.texi
24186 @c Guile docs live in a separate file.
24187 @include guile.texi
24189 @node Auto-loading extensions
24190 @section Auto-loading extensions
24191 @cindex auto-loading extensions
24193 @value{GDBN} provides two mechanisms for automatically loading extensions
24194 when a new object file is read (for example, due to the @code{file}
24195 command, or because the inferior has loaded a shared library):
24196 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24197 section of modern file formats like ELF.
24200 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24201 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24202 * Which flavor to choose?::
24205 The auto-loading feature is useful for supplying application-specific
24206 debugging commands and features.
24208 Auto-loading can be enabled or disabled,
24209 and the list of auto-loaded scripts can be printed.
24210 See the @samp{auto-loading} section of each extension language
24211 for more information.
24212 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24213 For Python files see @ref{Python Auto-loading}.
24215 Note that loading of this script file also requires accordingly configured
24216 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24218 @node objfile-gdbdotext file
24219 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24220 @cindex @file{@var{objfile}-gdb.gdb}
24221 @cindex @file{@var{objfile}-gdb.py}
24222 @cindex @file{@var{objfile}-gdb.scm}
24224 When a new object file is read, @value{GDBN} looks for a file named
24225 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24226 where @var{objfile} is the object file's name and
24227 where @var{ext} is the file extension for the extension language:
24230 @item @file{@var{objfile}-gdb.gdb}
24231 GDB's own command language
24232 @item @file{@var{objfile}-gdb.py}
24234 @item @file{@var{objfile}-gdb.scm}
24238 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24239 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24240 components, and appending the @file{-gdb.@var{ext}} suffix.
24241 If this file exists and is readable, @value{GDBN} will evaluate it as a
24242 script in the specified extension language.
24244 If this file does not exist, then @value{GDBN} will look for
24245 @var{script-name} file in all of the directories as specified below.
24247 Note that loading of these files requires an accordingly configured
24248 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24250 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24251 scripts normally according to its @file{.exe} filename. But if no scripts are
24252 found @value{GDBN} also tries script filenames matching the object file without
24253 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24254 is attempted on any platform. This makes the script filenames compatible
24255 between Unix and MS-Windows hosts.
24258 @anchor{set auto-load scripts-directory}
24259 @kindex set auto-load scripts-directory
24260 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24261 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24262 may be delimited by the host platform path separator in use
24263 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24265 Each entry here needs to be covered also by the security setting
24266 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24268 @anchor{with-auto-load-dir}
24269 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24270 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24271 configuration option @option{--with-auto-load-dir}.
24273 Any reference to @file{$debugdir} will get replaced by
24274 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24275 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24276 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24277 @file{$datadir} must be placed as a directory component --- either alone or
24278 delimited by @file{/} or @file{\} directory separators, depending on the host
24281 The list of directories uses path separator (@samp{:} on GNU and Unix
24282 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24283 to the @env{PATH} environment variable.
24285 @anchor{show auto-load scripts-directory}
24286 @kindex show auto-load scripts-directory
24287 @item show auto-load scripts-directory
24288 Show @value{GDBN} auto-loaded scripts location.
24290 @anchor{add-auto-load-scripts-directory}
24291 @kindex add-auto-load-scripts-directory
24292 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24293 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24294 Multiple entries may be delimited by the host platform path separator in use.
24297 @value{GDBN} does not track which files it has already auto-loaded this way.
24298 @value{GDBN} will load the associated script every time the corresponding
24299 @var{objfile} is opened.
24300 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24301 is evaluated more than once.
24303 @node dotdebug_gdb_scripts section
24304 @subsection The @code{.debug_gdb_scripts} section
24305 @cindex @code{.debug_gdb_scripts} section
24307 For systems using file formats like ELF and COFF,
24308 when @value{GDBN} loads a new object file
24309 it will look for a special section named @code{.debug_gdb_scripts}.
24310 If this section exists, its contents is a list of null-terminated entries
24311 specifying scripts to load. Each entry begins with a non-null prefix byte that
24312 specifies the kind of entry, typically the extension language and whether the
24313 script is in a file or inlined in @code{.debug_gdb_scripts}.
24315 The following entries are supported:
24318 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24319 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24320 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24321 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24324 @subsubsection Script File Entries
24326 If the entry specifies a file, @value{GDBN} will look for the file first
24327 in the current directory and then along the source search path
24328 (@pxref{Source Path, ,Specifying Source Directories}),
24329 except that @file{$cdir} is not searched, since the compilation
24330 directory is not relevant to scripts.
24332 File entries can be placed in section @code{.debug_gdb_scripts} with,
24333 for example, this GCC macro for Python scripts.
24336 /* Note: The "MS" section flags are to remove duplicates. */
24337 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24339 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24340 .byte 1 /* Python */\n\
24341 .asciz \"" script_name "\"\n\
24347 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24348 Then one can reference the macro in a header or source file like this:
24351 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24354 The script name may include directories if desired.
24356 Note that loading of this script file also requires accordingly configured
24357 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24359 If the macro invocation is put in a header, any application or library
24360 using this header will get a reference to the specified script,
24361 and with the use of @code{"MS"} attributes on the section, the linker
24362 will remove duplicates.
24364 @subsubsection Script Text Entries
24366 Script text entries allow to put the executable script in the entry
24367 itself instead of loading it from a file.
24368 The first line of the entry, everything after the prefix byte and up to
24369 the first newline (@code{0xa}) character, is the script name, and must not
24370 contain any kind of space character, e.g., spaces or tabs.
24371 The rest of the entry, up to the trailing null byte, is the script to
24372 execute in the specified language. The name needs to be unique among
24373 all script names, as @value{GDBN} executes each script only once based
24376 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24380 #include "symcat.h"
24381 #include "gdb/section-scripts.h"
24383 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24384 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24385 ".ascii \"gdb.inlined-script\\n\"\n"
24386 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24387 ".ascii \" def __init__ (self):\\n\"\n"
24388 ".ascii \" super (test_cmd, self).__init__ ("
24389 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24390 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24391 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24392 ".ascii \"test_cmd ()\\n\"\n"
24398 Loading of inlined scripts requires a properly configured
24399 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24400 The path to specify in @code{auto-load safe-path} is the path of the file
24401 containing the @code{.debug_gdb_scripts} section.
24403 @node Which flavor to choose?
24404 @subsection Which flavor to choose?
24406 Given the multiple ways of auto-loading extensions, it might not always
24407 be clear which one to choose. This section provides some guidance.
24410 Benefits of the @file{-gdb.@var{ext}} way:
24414 Can be used with file formats that don't support multiple sections.
24417 Ease of finding scripts for public libraries.
24419 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24420 in the source search path.
24421 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24422 isn't a source directory in which to find the script.
24425 Doesn't require source code additions.
24429 Benefits of the @code{.debug_gdb_scripts} way:
24433 Works with static linking.
24435 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24436 trigger their loading. When an application is statically linked the only
24437 objfile available is the executable, and it is cumbersome to attach all the
24438 scripts from all the input libraries to the executable's
24439 @file{-gdb.@var{ext}} script.
24442 Works with classes that are entirely inlined.
24444 Some classes can be entirely inlined, and thus there may not be an associated
24445 shared library to attach a @file{-gdb.@var{ext}} script to.
24448 Scripts needn't be copied out of the source tree.
24450 In some circumstances, apps can be built out of large collections of internal
24451 libraries, and the build infrastructure necessary to install the
24452 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24453 cumbersome. It may be easier to specify the scripts in the
24454 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24455 top of the source tree to the source search path.
24458 @node Multiple Extension Languages
24459 @section Multiple Extension Languages
24461 The Guile and Python extension languages do not share any state,
24462 and generally do not interfere with each other.
24463 There are some things to be aware of, however.
24465 @subsection Python comes first
24467 Python was @value{GDBN}'s first extension language, and to avoid breaking
24468 existing behaviour Python comes first. This is generally solved by the
24469 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24470 extension languages, and when it makes a call to an extension language,
24471 (say to pretty-print a value), it tries each in turn until an extension
24472 language indicates it has performed the request (e.g., has returned the
24473 pretty-printed form of a value).
24474 This extends to errors while performing such requests: If an error happens
24475 while, for example, trying to pretty-print an object then the error is
24476 reported and any following extension languages are not tried.
24479 @section Creating new spellings of existing commands
24480 @cindex aliases for commands
24482 It is often useful to define alternate spellings of existing commands.
24483 For example, if a new @value{GDBN} command defined in Python has
24484 a long name to type, it is handy to have an abbreviated version of it
24485 that involves less typing.
24487 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24488 of the @samp{step} command even though it is otherwise an ambiguous
24489 abbreviation of other commands like @samp{set} and @samp{show}.
24491 Aliases are also used to provide shortened or more common versions
24492 of multi-word commands. For example, @value{GDBN} provides the
24493 @samp{tty} alias of the @samp{set inferior-tty} command.
24495 You can define a new alias with the @samp{alias} command.
24500 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24504 @var{ALIAS} specifies the name of the new alias.
24505 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24508 @var{COMMAND} specifies the name of an existing command
24509 that is being aliased.
24511 The @samp{-a} option specifies that the new alias is an abbreviation
24512 of the command. Abbreviations are not shown in command
24513 lists displayed by the @samp{help} command.
24515 The @samp{--} option specifies the end of options,
24516 and is useful when @var{ALIAS} begins with a dash.
24518 Here is a simple example showing how to make an abbreviation
24519 of a command so that there is less to type.
24520 Suppose you were tired of typing @samp{disas}, the current
24521 shortest unambiguous abbreviation of the @samp{disassemble} command
24522 and you wanted an even shorter version named @samp{di}.
24523 The following will accomplish this.
24526 (gdb) alias -a di = disas
24529 Note that aliases are different from user-defined commands.
24530 With a user-defined command, you also need to write documentation
24531 for it with the @samp{document} command.
24532 An alias automatically picks up the documentation of the existing command.
24534 Here is an example where we make @samp{elms} an abbreviation of
24535 @samp{elements} in the @samp{set print elements} command.
24536 This is to show that you can make an abbreviation of any part
24540 (gdb) alias -a set print elms = set print elements
24541 (gdb) alias -a show print elms = show print elements
24542 (gdb) set p elms 20
24544 Limit on string chars or array elements to print is 200.
24547 Note that if you are defining an alias of a @samp{set} command,
24548 and you want to have an alias for the corresponding @samp{show}
24549 command, then you need to define the latter separately.
24551 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24552 @var{ALIAS}, just as they are normally.
24555 (gdb) alias -a set pr elms = set p ele
24558 Finally, here is an example showing the creation of a one word
24559 alias for a more complex command.
24560 This creates alias @samp{spe} of the command @samp{set print elements}.
24563 (gdb) alias spe = set print elements
24568 @chapter Command Interpreters
24569 @cindex command interpreters
24571 @value{GDBN} supports multiple command interpreters, and some command
24572 infrastructure to allow users or user interface writers to switch
24573 between interpreters or run commands in other interpreters.
24575 @value{GDBN} currently supports two command interpreters, the console
24576 interpreter (sometimes called the command-line interpreter or @sc{cli})
24577 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24578 describes both of these interfaces in great detail.
24580 By default, @value{GDBN} will start with the console interpreter.
24581 However, the user may choose to start @value{GDBN} with another
24582 interpreter by specifying the @option{-i} or @option{--interpreter}
24583 startup options. Defined interpreters include:
24587 @cindex console interpreter
24588 The traditional console or command-line interpreter. This is the most often
24589 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24590 @value{GDBN} will use this interpreter.
24593 @cindex mi interpreter
24594 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24595 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24596 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24600 @cindex mi2 interpreter
24601 The current @sc{gdb/mi} interface.
24604 @cindex mi1 interpreter
24605 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24609 @cindex invoke another interpreter
24610 The interpreter being used by @value{GDBN} may not be dynamically
24611 switched at runtime. Although possible, this could lead to a very
24612 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24613 enters the command "interpreter-set console" in a console view,
24614 @value{GDBN} would switch to using the console interpreter, rendering
24615 the IDE inoperable!
24617 @kindex interpreter-exec
24618 Although you may only choose a single interpreter at startup, you may execute
24619 commands in any interpreter from the current interpreter using the appropriate
24620 command. If you are running the console interpreter, simply use the
24621 @code{interpreter-exec} command:
24624 interpreter-exec mi "-data-list-register-names"
24627 @sc{gdb/mi} has a similar command, although it is only available in versions of
24628 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24631 @chapter @value{GDBN} Text User Interface
24633 @cindex Text User Interface
24636 * TUI Overview:: TUI overview
24637 * TUI Keys:: TUI key bindings
24638 * TUI Single Key Mode:: TUI single key mode
24639 * TUI Commands:: TUI-specific commands
24640 * TUI Configuration:: TUI configuration variables
24643 The @value{GDBN} Text User Interface (TUI) is a terminal
24644 interface which uses the @code{curses} library to show the source
24645 file, the assembly output, the program registers and @value{GDBN}
24646 commands in separate text windows. The TUI mode is supported only
24647 on platforms where a suitable version of the @code{curses} library
24650 The TUI mode is enabled by default when you invoke @value{GDBN} as
24651 @samp{@value{GDBP} -tui}.
24652 You can also switch in and out of TUI mode while @value{GDBN} runs by
24653 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24654 @xref{TUI Keys, ,TUI Key Bindings}.
24657 @section TUI Overview
24659 In TUI mode, @value{GDBN} can display several text windows:
24663 This window is the @value{GDBN} command window with the @value{GDBN}
24664 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24665 managed using readline.
24668 The source window shows the source file of the program. The current
24669 line and active breakpoints are displayed in this window.
24672 The assembly window shows the disassembly output of the program.
24675 This window shows the processor registers. Registers are highlighted
24676 when their values change.
24679 The source and assembly windows show the current program position
24680 by highlighting the current line and marking it with a @samp{>} marker.
24681 Breakpoints are indicated with two markers. The first marker
24682 indicates the breakpoint type:
24686 Breakpoint which was hit at least once.
24689 Breakpoint which was never hit.
24692 Hardware breakpoint which was hit at least once.
24695 Hardware breakpoint which was never hit.
24698 The second marker indicates whether the breakpoint is enabled or not:
24702 Breakpoint is enabled.
24705 Breakpoint is disabled.
24708 The source, assembly and register windows are updated when the current
24709 thread changes, when the frame changes, or when the program counter
24712 These windows are not all visible at the same time. The command
24713 window is always visible. The others can be arranged in several
24724 source and assembly,
24727 source and registers, or
24730 assembly and registers.
24733 A status line above the command window shows the following information:
24737 Indicates the current @value{GDBN} target.
24738 (@pxref{Targets, ,Specifying a Debugging Target}).
24741 Gives the current process or thread number.
24742 When no process is being debugged, this field is set to @code{No process}.
24745 Gives the current function name for the selected frame.
24746 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24747 When there is no symbol corresponding to the current program counter,
24748 the string @code{??} is displayed.
24751 Indicates the current line number for the selected frame.
24752 When the current line number is not known, the string @code{??} is displayed.
24755 Indicates the current program counter address.
24759 @section TUI Key Bindings
24760 @cindex TUI key bindings
24762 The TUI installs several key bindings in the readline keymaps
24763 @ifset SYSTEM_READLINE
24764 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24766 @ifclear SYSTEM_READLINE
24767 (@pxref{Command Line Editing}).
24769 The following key bindings are installed for both TUI mode and the
24770 @value{GDBN} standard mode.
24779 Enter or leave the TUI mode. When leaving the TUI mode,
24780 the curses window management stops and @value{GDBN} operates using
24781 its standard mode, writing on the terminal directly. When reentering
24782 the TUI mode, control is given back to the curses windows.
24783 The screen is then refreshed.
24787 Use a TUI layout with only one window. The layout will
24788 either be @samp{source} or @samp{assembly}. When the TUI mode
24789 is not active, it will switch to the TUI mode.
24791 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24795 Use a TUI layout with at least two windows. When the current
24796 layout already has two windows, the next layout with two windows is used.
24797 When a new layout is chosen, one window will always be common to the
24798 previous layout and the new one.
24800 Think of it as the Emacs @kbd{C-x 2} binding.
24804 Change the active window. The TUI associates several key bindings
24805 (like scrolling and arrow keys) with the active window. This command
24806 gives the focus to the next TUI window.
24808 Think of it as the Emacs @kbd{C-x o} binding.
24812 Switch in and out of the TUI SingleKey mode that binds single
24813 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24816 The following key bindings only work in the TUI mode:
24821 Scroll the active window one page up.
24825 Scroll the active window one page down.
24829 Scroll the active window one line up.
24833 Scroll the active window one line down.
24837 Scroll the active window one column left.
24841 Scroll the active window one column right.
24845 Refresh the screen.
24848 Because the arrow keys scroll the active window in the TUI mode, they
24849 are not available for their normal use by readline unless the command
24850 window has the focus. When another window is active, you must use
24851 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24852 and @kbd{C-f} to control the command window.
24854 @node TUI Single Key Mode
24855 @section TUI Single Key Mode
24856 @cindex TUI single key mode
24858 The TUI also provides a @dfn{SingleKey} mode, which binds several
24859 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24860 switch into this mode, where the following key bindings are used:
24863 @kindex c @r{(SingleKey TUI key)}
24867 @kindex d @r{(SingleKey TUI key)}
24871 @kindex f @r{(SingleKey TUI key)}
24875 @kindex n @r{(SingleKey TUI key)}
24879 @kindex q @r{(SingleKey TUI key)}
24881 exit the SingleKey mode.
24883 @kindex r @r{(SingleKey TUI key)}
24887 @kindex s @r{(SingleKey TUI key)}
24891 @kindex u @r{(SingleKey TUI key)}
24895 @kindex v @r{(SingleKey TUI key)}
24899 @kindex w @r{(SingleKey TUI key)}
24904 Other keys temporarily switch to the @value{GDBN} command prompt.
24905 The key that was pressed is inserted in the editing buffer so that
24906 it is possible to type most @value{GDBN} commands without interaction
24907 with the TUI SingleKey mode. Once the command is entered the TUI
24908 SingleKey mode is restored. The only way to permanently leave
24909 this mode is by typing @kbd{q} or @kbd{C-x s}.
24913 @section TUI-specific Commands
24914 @cindex TUI commands
24916 The TUI has specific commands to control the text windows.
24917 These commands are always available, even when @value{GDBN} is not in
24918 the TUI mode. When @value{GDBN} is in the standard mode, most
24919 of these commands will automatically switch to the TUI mode.
24921 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24922 terminal, or @value{GDBN} has been started with the machine interface
24923 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24924 these commands will fail with an error, because it would not be
24925 possible or desirable to enable curses window management.
24930 List and give the size of all displayed windows.
24934 Display the next layout.
24937 Display the previous layout.
24940 Display the source window only.
24943 Display the assembly window only.
24946 Display the source and assembly window.
24949 Display the register window together with the source or assembly window.
24953 Make the next window active for scrolling.
24956 Make the previous window active for scrolling.
24959 Make the source window active for scrolling.
24962 Make the assembly window active for scrolling.
24965 Make the register window active for scrolling.
24968 Make the command window active for scrolling.
24972 Refresh the screen. This is similar to typing @kbd{C-L}.
24974 @item tui reg float
24976 Show the floating point registers in the register window.
24978 @item tui reg general
24979 Show the general registers in the register window.
24982 Show the next register group. The list of register groups as well as
24983 their order is target specific. The predefined register groups are the
24984 following: @code{general}, @code{float}, @code{system}, @code{vector},
24985 @code{all}, @code{save}, @code{restore}.
24987 @item tui reg system
24988 Show the system registers in the register window.
24992 Update the source window and the current execution point.
24994 @item winheight @var{name} +@var{count}
24995 @itemx winheight @var{name} -@var{count}
24997 Change the height of the window @var{name} by @var{count}
24998 lines. Positive counts increase the height, while negative counts
24999 decrease it. The @var{name} parameter can be one of @code{src} (the
25000 source window), @code{cmd} (the command window), @code{asm} (the
25001 disassembly window), or @code{regs} (the register display window).
25003 @item tabset @var{nchars}
25005 Set the width of tab stops to be @var{nchars} characters. This
25006 setting affects the display of TAB characters in the source and
25010 @node TUI Configuration
25011 @section TUI Configuration Variables
25012 @cindex TUI configuration variables
25014 Several configuration variables control the appearance of TUI windows.
25017 @item set tui border-kind @var{kind}
25018 @kindex set tui border-kind
25019 Select the border appearance for the source, assembly and register windows.
25020 The possible values are the following:
25023 Use a space character to draw the border.
25026 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25029 Use the Alternate Character Set to draw the border. The border is
25030 drawn using character line graphics if the terminal supports them.
25033 @item set tui border-mode @var{mode}
25034 @kindex set tui border-mode
25035 @itemx set tui active-border-mode @var{mode}
25036 @kindex set tui active-border-mode
25037 Select the display attributes for the borders of the inactive windows
25038 or the active window. The @var{mode} can be one of the following:
25041 Use normal attributes to display the border.
25047 Use reverse video mode.
25050 Use half bright mode.
25052 @item half-standout
25053 Use half bright and standout mode.
25056 Use extra bright or bold mode.
25058 @item bold-standout
25059 Use extra bright or bold and standout mode.
25064 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25067 @cindex @sc{gnu} Emacs
25068 A special interface allows you to use @sc{gnu} Emacs to view (and
25069 edit) the source files for the program you are debugging with
25072 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25073 executable file you want to debug as an argument. This command starts
25074 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25075 created Emacs buffer.
25076 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25078 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25083 All ``terminal'' input and output goes through an Emacs buffer, called
25086 This applies both to @value{GDBN} commands and their output, and to the input
25087 and output done by the program you are debugging.
25089 This is useful because it means that you can copy the text of previous
25090 commands and input them again; you can even use parts of the output
25093 All the facilities of Emacs' Shell mode are available for interacting
25094 with your program. In particular, you can send signals the usual
25095 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25099 @value{GDBN} displays source code through Emacs.
25101 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25102 source file for that frame and puts an arrow (@samp{=>}) at the
25103 left margin of the current line. Emacs uses a separate buffer for
25104 source display, and splits the screen to show both your @value{GDBN} session
25107 Explicit @value{GDBN} @code{list} or search commands still produce output as
25108 usual, but you probably have no reason to use them from Emacs.
25111 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25112 a graphical mode, enabled by default, which provides further buffers
25113 that can control the execution and describe the state of your program.
25114 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25116 If you specify an absolute file name when prompted for the @kbd{M-x
25117 gdb} argument, then Emacs sets your current working directory to where
25118 your program resides. If you only specify the file name, then Emacs
25119 sets your current working directory to the directory associated
25120 with the previous buffer. In this case, @value{GDBN} may find your
25121 program by searching your environment's @code{PATH} variable, but on
25122 some operating systems it might not find the source. So, although the
25123 @value{GDBN} input and output session proceeds normally, the auxiliary
25124 buffer does not display the current source and line of execution.
25126 The initial working directory of @value{GDBN} is printed on the top
25127 line of the GUD buffer and this serves as a default for the commands
25128 that specify files for @value{GDBN} to operate on. @xref{Files,
25129 ,Commands to Specify Files}.
25131 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25132 need to call @value{GDBN} by a different name (for example, if you
25133 keep several configurations around, with different names) you can
25134 customize the Emacs variable @code{gud-gdb-command-name} to run the
25137 In the GUD buffer, you can use these special Emacs commands in
25138 addition to the standard Shell mode commands:
25142 Describe the features of Emacs' GUD Mode.
25145 Execute to another source line, like the @value{GDBN} @code{step} command; also
25146 update the display window to show the current file and location.
25149 Execute to next source line in this function, skipping all function
25150 calls, like the @value{GDBN} @code{next} command. Then update the display window
25151 to show the current file and location.
25154 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25155 display window accordingly.
25158 Execute until exit from the selected stack frame, like the @value{GDBN}
25159 @code{finish} command.
25162 Continue execution of your program, like the @value{GDBN} @code{continue}
25166 Go up the number of frames indicated by the numeric argument
25167 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25168 like the @value{GDBN} @code{up} command.
25171 Go down the number of frames indicated by the numeric argument, like the
25172 @value{GDBN} @code{down} command.
25175 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25176 tells @value{GDBN} to set a breakpoint on the source line point is on.
25178 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25179 separate frame which shows a backtrace when the GUD buffer is current.
25180 Move point to any frame in the stack and type @key{RET} to make it
25181 become the current frame and display the associated source in the
25182 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25183 selected frame become the current one. In graphical mode, the
25184 speedbar displays watch expressions.
25186 If you accidentally delete the source-display buffer, an easy way to get
25187 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25188 request a frame display; when you run under Emacs, this recreates
25189 the source buffer if necessary to show you the context of the current
25192 The source files displayed in Emacs are in ordinary Emacs buffers
25193 which are visiting the source files in the usual way. You can edit
25194 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25195 communicates with Emacs in terms of line numbers. If you add or
25196 delete lines from the text, the line numbers that @value{GDBN} knows cease
25197 to correspond properly with the code.
25199 A more detailed description of Emacs' interaction with @value{GDBN} is
25200 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25204 @chapter The @sc{gdb/mi} Interface
25206 @unnumberedsec Function and Purpose
25208 @cindex @sc{gdb/mi}, its purpose
25209 @sc{gdb/mi} is a line based machine oriented text interface to
25210 @value{GDBN} and is activated by specifying using the
25211 @option{--interpreter} command line option (@pxref{Mode Options}). It
25212 is specifically intended to support the development of systems which
25213 use the debugger as just one small component of a larger system.
25215 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25216 in the form of a reference manual.
25218 Note that @sc{gdb/mi} is still under construction, so some of the
25219 features described below are incomplete and subject to change
25220 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25222 @unnumberedsec Notation and Terminology
25224 @cindex notational conventions, for @sc{gdb/mi}
25225 This chapter uses the following notation:
25229 @code{|} separates two alternatives.
25232 @code{[ @var{something} ]} indicates that @var{something} is optional:
25233 it may or may not be given.
25236 @code{( @var{group} )*} means that @var{group} inside the parentheses
25237 may repeat zero or more times.
25240 @code{( @var{group} )+} means that @var{group} inside the parentheses
25241 may repeat one or more times.
25244 @code{"@var{string}"} means a literal @var{string}.
25248 @heading Dependencies
25252 * GDB/MI General Design::
25253 * GDB/MI Command Syntax::
25254 * GDB/MI Compatibility with CLI::
25255 * GDB/MI Development and Front Ends::
25256 * GDB/MI Output Records::
25257 * GDB/MI Simple Examples::
25258 * GDB/MI Command Description Format::
25259 * GDB/MI Breakpoint Commands::
25260 * GDB/MI Catchpoint Commands::
25261 * GDB/MI Program Context::
25262 * GDB/MI Thread Commands::
25263 * GDB/MI Ada Tasking Commands::
25264 * GDB/MI Program Execution::
25265 * GDB/MI Stack Manipulation::
25266 * GDB/MI Variable Objects::
25267 * GDB/MI Data Manipulation::
25268 * GDB/MI Tracepoint Commands::
25269 * GDB/MI Symbol Query::
25270 * GDB/MI File Commands::
25272 * GDB/MI Kod Commands::
25273 * GDB/MI Memory Overlay Commands::
25274 * GDB/MI Signal Handling Commands::
25276 * GDB/MI Target Manipulation::
25277 * GDB/MI File Transfer Commands::
25278 * GDB/MI Ada Exceptions Commands::
25279 * GDB/MI Support Commands::
25280 * GDB/MI Miscellaneous Commands::
25283 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25284 @node GDB/MI General Design
25285 @section @sc{gdb/mi} General Design
25286 @cindex GDB/MI General Design
25288 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25289 parts---commands sent to @value{GDBN}, responses to those commands
25290 and notifications. Each command results in exactly one response,
25291 indicating either successful completion of the command, or an error.
25292 For the commands that do not resume the target, the response contains the
25293 requested information. For the commands that resume the target, the
25294 response only indicates whether the target was successfully resumed.
25295 Notifications is the mechanism for reporting changes in the state of the
25296 target, or in @value{GDBN} state, that cannot conveniently be associated with
25297 a command and reported as part of that command response.
25299 The important examples of notifications are:
25303 Exec notifications. These are used to report changes in
25304 target state---when a target is resumed, or stopped. It would not
25305 be feasible to include this information in response of resuming
25306 commands, because one resume commands can result in multiple events in
25307 different threads. Also, quite some time may pass before any event
25308 happens in the target, while a frontend needs to know whether the resuming
25309 command itself was successfully executed.
25312 Console output, and status notifications. Console output
25313 notifications are used to report output of CLI commands, as well as
25314 diagnostics for other commands. Status notifications are used to
25315 report the progress of a long-running operation. Naturally, including
25316 this information in command response would mean no output is produced
25317 until the command is finished, which is undesirable.
25320 General notifications. Commands may have various side effects on
25321 the @value{GDBN} or target state beyond their official purpose. For example,
25322 a command may change the selected thread. Although such changes can
25323 be included in command response, using notification allows for more
25324 orthogonal frontend design.
25328 There's no guarantee that whenever an MI command reports an error,
25329 @value{GDBN} or the target are in any specific state, and especially,
25330 the state is not reverted to the state before the MI command was
25331 processed. Therefore, whenever an MI command results in an error,
25332 we recommend that the frontend refreshes all the information shown in
25333 the user interface.
25337 * Context management::
25338 * Asynchronous and non-stop modes::
25342 @node Context management
25343 @subsection Context management
25345 @subsubsection Threads and Frames
25347 In most cases when @value{GDBN} accesses the target, this access is
25348 done in context of a specific thread and frame (@pxref{Frames}).
25349 Often, even when accessing global data, the target requires that a thread
25350 be specified. The CLI interface maintains the selected thread and frame,
25351 and supplies them to target on each command. This is convenient,
25352 because a command line user would not want to specify that information
25353 explicitly on each command, and because user interacts with
25354 @value{GDBN} via a single terminal, so no confusion is possible as
25355 to what thread and frame are the current ones.
25357 In the case of MI, the concept of selected thread and frame is less
25358 useful. First, a frontend can easily remember this information
25359 itself. Second, a graphical frontend can have more than one window,
25360 each one used for debugging a different thread, and the frontend might
25361 want to access additional threads for internal purposes. This
25362 increases the risk that by relying on implicitly selected thread, the
25363 frontend may be operating on a wrong one. Therefore, each MI command
25364 should explicitly specify which thread and frame to operate on. To
25365 make it possible, each MI command accepts the @samp{--thread} and
25366 @samp{--frame} options, the value to each is @value{GDBN} identifier
25367 for thread and frame to operate on.
25369 Usually, each top-level window in a frontend allows the user to select
25370 a thread and a frame, and remembers the user selection for further
25371 operations. However, in some cases @value{GDBN} may suggest that the
25372 current thread be changed. For example, when stopping on a breakpoint
25373 it is reasonable to switch to the thread where breakpoint is hit. For
25374 another example, if the user issues the CLI @samp{thread} command via
25375 the frontend, it is desirable to change the frontend's selected thread to the
25376 one specified by user. @value{GDBN} communicates the suggestion to
25377 change current thread using the @samp{=thread-selected} notification.
25378 No such notification is available for the selected frame at the moment.
25380 Note that historically, MI shares the selected thread with CLI, so
25381 frontends used the @code{-thread-select} to execute commands in the
25382 right context. However, getting this to work right is cumbersome. The
25383 simplest way is for frontend to emit @code{-thread-select} command
25384 before every command. This doubles the number of commands that need
25385 to be sent. The alternative approach is to suppress @code{-thread-select}
25386 if the selected thread in @value{GDBN} is supposed to be identical to the
25387 thread the frontend wants to operate on. However, getting this
25388 optimization right can be tricky. In particular, if the frontend
25389 sends several commands to @value{GDBN}, and one of the commands changes the
25390 selected thread, then the behaviour of subsequent commands will
25391 change. So, a frontend should either wait for response from such
25392 problematic commands, or explicitly add @code{-thread-select} for
25393 all subsequent commands. No frontend is known to do this exactly
25394 right, so it is suggested to just always pass the @samp{--thread} and
25395 @samp{--frame} options.
25397 @subsubsection Language
25399 The execution of several commands depends on which language is selected.
25400 By default, the current language (@pxref{show language}) is used.
25401 But for commands known to be language-sensitive, it is recommended
25402 to use the @samp{--language} option. This option takes one argument,
25403 which is the name of the language to use while executing the command.
25407 -data-evaluate-expression --language c "sizeof (void*)"
25412 The valid language names are the same names accepted by the
25413 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25414 @samp{local} or @samp{unknown}.
25416 @node Asynchronous and non-stop modes
25417 @subsection Asynchronous command execution and non-stop mode
25419 On some targets, @value{GDBN} is capable of processing MI commands
25420 even while the target is running. This is called @dfn{asynchronous
25421 command execution} (@pxref{Background Execution}). The frontend may
25422 specify a preferrence for asynchronous execution using the
25423 @code{-gdb-set mi-async 1} command, which should be emitted before
25424 either running the executable or attaching to the target. After the
25425 frontend has started the executable or attached to the target, it can
25426 find if asynchronous execution is enabled using the
25427 @code{-list-target-features} command.
25430 @item -gdb-set mi-async on
25431 @item -gdb-set mi-async off
25432 Set whether MI is in asynchronous mode.
25434 When @code{off}, which is the default, MI execution commands (e.g.,
25435 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25436 for the program to stop before processing further commands.
25438 When @code{on}, MI execution commands are background execution
25439 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25440 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25441 MI commands even while the target is running.
25443 @item -gdb-show mi-async
25444 Show whether MI asynchronous mode is enabled.
25447 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25448 @code{target-async} instead of @code{mi-async}, and it had the effect
25449 of both putting MI in asynchronous mode and making CLI background
25450 commands possible. CLI background commands are now always possible
25451 ``out of the box'' if the target supports them. The old spelling is
25452 kept as a deprecated alias for backwards compatibility.
25454 Even if @value{GDBN} can accept a command while target is running,
25455 many commands that access the target do not work when the target is
25456 running. Therefore, asynchronous command execution is most useful
25457 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25458 it is possible to examine the state of one thread, while other threads
25461 When a given thread is running, MI commands that try to access the
25462 target in the context of that thread may not work, or may work only on
25463 some targets. In particular, commands that try to operate on thread's
25464 stack will not work, on any target. Commands that read memory, or
25465 modify breakpoints, may work or not work, depending on the target. Note
25466 that even commands that operate on global state, such as @code{print},
25467 @code{set}, and breakpoint commands, still access the target in the
25468 context of a specific thread, so frontend should try to find a
25469 stopped thread and perform the operation on that thread (using the
25470 @samp{--thread} option).
25472 Which commands will work in the context of a running thread is
25473 highly target dependent. However, the two commands
25474 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25475 to find the state of a thread, will always work.
25477 @node Thread groups
25478 @subsection Thread groups
25479 @value{GDBN} may be used to debug several processes at the same time.
25480 On some platfroms, @value{GDBN} may support debugging of several
25481 hardware systems, each one having several cores with several different
25482 processes running on each core. This section describes the MI
25483 mechanism to support such debugging scenarios.
25485 The key observation is that regardless of the structure of the
25486 target, MI can have a global list of threads, because most commands that
25487 accept the @samp{--thread} option do not need to know what process that
25488 thread belongs to. Therefore, it is not necessary to introduce
25489 neither additional @samp{--process} option, nor an notion of the
25490 current process in the MI interface. The only strictly new feature
25491 that is required is the ability to find how the threads are grouped
25494 To allow the user to discover such grouping, and to support arbitrary
25495 hierarchy of machines/cores/processes, MI introduces the concept of a
25496 @dfn{thread group}. Thread group is a collection of threads and other
25497 thread groups. A thread group always has a string identifier, a type,
25498 and may have additional attributes specific to the type. A new
25499 command, @code{-list-thread-groups}, returns the list of top-level
25500 thread groups, which correspond to processes that @value{GDBN} is
25501 debugging at the moment. By passing an identifier of a thread group
25502 to the @code{-list-thread-groups} command, it is possible to obtain
25503 the members of specific thread group.
25505 To allow the user to easily discover processes, and other objects, he
25506 wishes to debug, a concept of @dfn{available thread group} is
25507 introduced. Available thread group is an thread group that
25508 @value{GDBN} is not debugging, but that can be attached to, using the
25509 @code{-target-attach} command. The list of available top-level thread
25510 groups can be obtained using @samp{-list-thread-groups --available}.
25511 In general, the content of a thread group may be only retrieved only
25512 after attaching to that thread group.
25514 Thread groups are related to inferiors (@pxref{Inferiors and
25515 Programs}). Each inferior corresponds to a thread group of a special
25516 type @samp{process}, and some additional operations are permitted on
25517 such thread groups.
25519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25520 @node GDB/MI Command Syntax
25521 @section @sc{gdb/mi} Command Syntax
25524 * GDB/MI Input Syntax::
25525 * GDB/MI Output Syntax::
25528 @node GDB/MI Input Syntax
25529 @subsection @sc{gdb/mi} Input Syntax
25531 @cindex input syntax for @sc{gdb/mi}
25532 @cindex @sc{gdb/mi}, input syntax
25534 @item @var{command} @expansion{}
25535 @code{@var{cli-command} | @var{mi-command}}
25537 @item @var{cli-command} @expansion{}
25538 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25539 @var{cli-command} is any existing @value{GDBN} CLI command.
25541 @item @var{mi-command} @expansion{}
25542 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25543 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25545 @item @var{token} @expansion{}
25546 "any sequence of digits"
25548 @item @var{option} @expansion{}
25549 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25551 @item @var{parameter} @expansion{}
25552 @code{@var{non-blank-sequence} | @var{c-string}}
25554 @item @var{operation} @expansion{}
25555 @emph{any of the operations described in this chapter}
25557 @item @var{non-blank-sequence} @expansion{}
25558 @emph{anything, provided it doesn't contain special characters such as
25559 "-", @var{nl}, """ and of course " "}
25561 @item @var{c-string} @expansion{}
25562 @code{""" @var{seven-bit-iso-c-string-content} """}
25564 @item @var{nl} @expansion{}
25573 The CLI commands are still handled by the @sc{mi} interpreter; their
25574 output is described below.
25577 The @code{@var{token}}, when present, is passed back when the command
25581 Some @sc{mi} commands accept optional arguments as part of the parameter
25582 list. Each option is identified by a leading @samp{-} (dash) and may be
25583 followed by an optional argument parameter. Options occur first in the
25584 parameter list and can be delimited from normal parameters using
25585 @samp{--} (this is useful when some parameters begin with a dash).
25592 We want easy access to the existing CLI syntax (for debugging).
25595 We want it to be easy to spot a @sc{mi} operation.
25598 @node GDB/MI Output Syntax
25599 @subsection @sc{gdb/mi} Output Syntax
25601 @cindex output syntax of @sc{gdb/mi}
25602 @cindex @sc{gdb/mi}, output syntax
25603 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25604 followed, optionally, by a single result record. This result record
25605 is for the most recent command. The sequence of output records is
25606 terminated by @samp{(gdb)}.
25608 If an input command was prefixed with a @code{@var{token}} then the
25609 corresponding output for that command will also be prefixed by that same
25613 @item @var{output} @expansion{}
25614 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25616 @item @var{result-record} @expansion{}
25617 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25619 @item @var{out-of-band-record} @expansion{}
25620 @code{@var{async-record} | @var{stream-record}}
25622 @item @var{async-record} @expansion{}
25623 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25625 @item @var{exec-async-output} @expansion{}
25626 @code{[ @var{token} ] "*" @var{async-output nl}}
25628 @item @var{status-async-output} @expansion{}
25629 @code{[ @var{token} ] "+" @var{async-output nl}}
25631 @item @var{notify-async-output} @expansion{}
25632 @code{[ @var{token} ] "=" @var{async-output nl}}
25634 @item @var{async-output} @expansion{}
25635 @code{@var{async-class} ( "," @var{result} )*}
25637 @item @var{result-class} @expansion{}
25638 @code{"done" | "running" | "connected" | "error" | "exit"}
25640 @item @var{async-class} @expansion{}
25641 @code{"stopped" | @var{others}} (where @var{others} will be added
25642 depending on the needs---this is still in development).
25644 @item @var{result} @expansion{}
25645 @code{ @var{variable} "=" @var{value}}
25647 @item @var{variable} @expansion{}
25648 @code{ @var{string} }
25650 @item @var{value} @expansion{}
25651 @code{ @var{const} | @var{tuple} | @var{list} }
25653 @item @var{const} @expansion{}
25654 @code{@var{c-string}}
25656 @item @var{tuple} @expansion{}
25657 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25659 @item @var{list} @expansion{}
25660 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25661 @var{result} ( "," @var{result} )* "]" }
25663 @item @var{stream-record} @expansion{}
25664 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25666 @item @var{console-stream-output} @expansion{}
25667 @code{"~" @var{c-string nl}}
25669 @item @var{target-stream-output} @expansion{}
25670 @code{"@@" @var{c-string nl}}
25672 @item @var{log-stream-output} @expansion{}
25673 @code{"&" @var{c-string nl}}
25675 @item @var{nl} @expansion{}
25678 @item @var{token} @expansion{}
25679 @emph{any sequence of digits}.
25687 All output sequences end in a single line containing a period.
25690 The @code{@var{token}} is from the corresponding request. Note that
25691 for all async output, while the token is allowed by the grammar and
25692 may be output by future versions of @value{GDBN} for select async
25693 output messages, it is generally omitted. Frontends should treat
25694 all async output as reporting general changes in the state of the
25695 target and there should be no need to associate async output to any
25699 @cindex status output in @sc{gdb/mi}
25700 @var{status-async-output} contains on-going status information about the
25701 progress of a slow operation. It can be discarded. All status output is
25702 prefixed by @samp{+}.
25705 @cindex async output in @sc{gdb/mi}
25706 @var{exec-async-output} contains asynchronous state change on the target
25707 (stopped, started, disappeared). All async output is prefixed by
25711 @cindex notify output in @sc{gdb/mi}
25712 @var{notify-async-output} contains supplementary information that the
25713 client should handle (e.g., a new breakpoint information). All notify
25714 output is prefixed by @samp{=}.
25717 @cindex console output in @sc{gdb/mi}
25718 @var{console-stream-output} is output that should be displayed as is in the
25719 console. It is the textual response to a CLI command. All the console
25720 output is prefixed by @samp{~}.
25723 @cindex target output in @sc{gdb/mi}
25724 @var{target-stream-output} is the output produced by the target program.
25725 All the target output is prefixed by @samp{@@}.
25728 @cindex log output in @sc{gdb/mi}
25729 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25730 instance messages that should be displayed as part of an error log. All
25731 the log output is prefixed by @samp{&}.
25734 @cindex list output in @sc{gdb/mi}
25735 New @sc{gdb/mi} commands should only output @var{lists} containing
25741 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25742 details about the various output records.
25744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25745 @node GDB/MI Compatibility with CLI
25746 @section @sc{gdb/mi} Compatibility with CLI
25748 @cindex compatibility, @sc{gdb/mi} and CLI
25749 @cindex @sc{gdb/mi}, compatibility with CLI
25751 For the developers convenience CLI commands can be entered directly,
25752 but there may be some unexpected behaviour. For example, commands
25753 that query the user will behave as if the user replied yes, breakpoint
25754 command lists are not executed and some CLI commands, such as
25755 @code{if}, @code{when} and @code{define}, prompt for further input with
25756 @samp{>}, which is not valid MI output.
25758 This feature may be removed at some stage in the future and it is
25759 recommended that front ends use the @code{-interpreter-exec} command
25760 (@pxref{-interpreter-exec}).
25762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25763 @node GDB/MI Development and Front Ends
25764 @section @sc{gdb/mi} Development and Front Ends
25765 @cindex @sc{gdb/mi} development
25767 The application which takes the MI output and presents the state of the
25768 program being debugged to the user is called a @dfn{front end}.
25770 Although @sc{gdb/mi} is still incomplete, it is currently being used
25771 by a variety of front ends to @value{GDBN}. This makes it difficult
25772 to introduce new functionality without breaking existing usage. This
25773 section tries to minimize the problems by describing how the protocol
25776 Some changes in MI need not break a carefully designed front end, and
25777 for these the MI version will remain unchanged. The following is a
25778 list of changes that may occur within one level, so front ends should
25779 parse MI output in a way that can handle them:
25783 New MI commands may be added.
25786 New fields may be added to the output of any MI command.
25789 The range of values for fields with specified values, e.g.,
25790 @code{in_scope} (@pxref{-var-update}) may be extended.
25792 @c The format of field's content e.g type prefix, may change so parse it
25793 @c at your own risk. Yes, in general?
25795 @c The order of fields may change? Shouldn't really matter but it might
25796 @c resolve inconsistencies.
25799 If the changes are likely to break front ends, the MI version level
25800 will be increased by one. This will allow the front end to parse the
25801 output according to the MI version. Apart from mi0, new versions of
25802 @value{GDBN} will not support old versions of MI and it will be the
25803 responsibility of the front end to work with the new one.
25805 @c Starting with mi3, add a new command -mi-version that prints the MI
25808 The best way to avoid unexpected changes in MI that might break your front
25809 end is to make your project known to @value{GDBN} developers and
25810 follow development on @email{gdb@@sourceware.org} and
25811 @email{gdb-patches@@sourceware.org}.
25812 @cindex mailing lists
25814 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25815 @node GDB/MI Output Records
25816 @section @sc{gdb/mi} Output Records
25819 * GDB/MI Result Records::
25820 * GDB/MI Stream Records::
25821 * GDB/MI Async Records::
25822 * GDB/MI Breakpoint Information::
25823 * GDB/MI Frame Information::
25824 * GDB/MI Thread Information::
25825 * GDB/MI Ada Exception Information::
25828 @node GDB/MI Result Records
25829 @subsection @sc{gdb/mi} Result Records
25831 @cindex result records in @sc{gdb/mi}
25832 @cindex @sc{gdb/mi}, result records
25833 In addition to a number of out-of-band notifications, the response to a
25834 @sc{gdb/mi} command includes one of the following result indications:
25838 @item "^done" [ "," @var{results} ]
25839 The synchronous operation was successful, @code{@var{results}} are the return
25844 This result record is equivalent to @samp{^done}. Historically, it
25845 was output instead of @samp{^done} if the command has resumed the
25846 target. This behaviour is maintained for backward compatibility, but
25847 all frontends should treat @samp{^done} and @samp{^running}
25848 identically and rely on the @samp{*running} output record to determine
25849 which threads are resumed.
25853 @value{GDBN} has connected to a remote target.
25855 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25857 The operation failed. The @code{msg=@var{c-string}} variable contains
25858 the corresponding error message.
25860 If present, the @code{code=@var{c-string}} variable provides an error
25861 code on which consumers can rely on to detect the corresponding
25862 error condition. At present, only one error code is defined:
25865 @item "undefined-command"
25866 Indicates that the command causing the error does not exist.
25871 @value{GDBN} has terminated.
25875 @node GDB/MI Stream Records
25876 @subsection @sc{gdb/mi} Stream Records
25878 @cindex @sc{gdb/mi}, stream records
25879 @cindex stream records in @sc{gdb/mi}
25880 @value{GDBN} internally maintains a number of output streams: the console, the
25881 target, and the log. The output intended for each of these streams is
25882 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25884 Each stream record begins with a unique @dfn{prefix character} which
25885 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25886 Syntax}). In addition to the prefix, each stream record contains a
25887 @code{@var{string-output}}. This is either raw text (with an implicit new
25888 line) or a quoted C string (which does not contain an implicit newline).
25891 @item "~" @var{string-output}
25892 The console output stream contains text that should be displayed in the
25893 CLI console window. It contains the textual responses to CLI commands.
25895 @item "@@" @var{string-output}
25896 The target output stream contains any textual output from the running
25897 target. This is only present when GDB's event loop is truly
25898 asynchronous, which is currently only the case for remote targets.
25900 @item "&" @var{string-output}
25901 The log stream contains debugging messages being produced by @value{GDBN}'s
25905 @node GDB/MI Async Records
25906 @subsection @sc{gdb/mi} Async Records
25908 @cindex async records in @sc{gdb/mi}
25909 @cindex @sc{gdb/mi}, async records
25910 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25911 additional changes that have occurred. Those changes can either be a
25912 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25913 target activity (e.g., target stopped).
25915 The following is the list of possible async records:
25919 @item *running,thread-id="@var{thread}"
25920 The target is now running. The @var{thread} field tells which
25921 specific thread is now running, and can be @samp{all} if all threads
25922 are running. The frontend should assume that no interaction with a
25923 running thread is possible after this notification is produced.
25924 The frontend should not assume that this notification is output
25925 only once for any command. @value{GDBN} may emit this notification
25926 several times, either for different threads, because it cannot resume
25927 all threads together, or even for a single thread, if the thread must
25928 be stepped though some code before letting it run freely.
25930 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25931 The target has stopped. The @var{reason} field can have one of the
25935 @item breakpoint-hit
25936 A breakpoint was reached.
25937 @item watchpoint-trigger
25938 A watchpoint was triggered.
25939 @item read-watchpoint-trigger
25940 A read watchpoint was triggered.
25941 @item access-watchpoint-trigger
25942 An access watchpoint was triggered.
25943 @item function-finished
25944 An -exec-finish or similar CLI command was accomplished.
25945 @item location-reached
25946 An -exec-until or similar CLI command was accomplished.
25947 @item watchpoint-scope
25948 A watchpoint has gone out of scope.
25949 @item end-stepping-range
25950 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25951 similar CLI command was accomplished.
25952 @item exited-signalled
25953 The inferior exited because of a signal.
25955 The inferior exited.
25956 @item exited-normally
25957 The inferior exited normally.
25958 @item signal-received
25959 A signal was received by the inferior.
25961 The inferior has stopped due to a library being loaded or unloaded.
25962 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25963 set or when a @code{catch load} or @code{catch unload} catchpoint is
25964 in use (@pxref{Set Catchpoints}).
25966 The inferior has forked. This is reported when @code{catch fork}
25967 (@pxref{Set Catchpoints}) has been used.
25969 The inferior has vforked. This is reported in when @code{catch vfork}
25970 (@pxref{Set Catchpoints}) has been used.
25971 @item syscall-entry
25972 The inferior entered a system call. This is reported when @code{catch
25973 syscall} (@pxref{Set Catchpoints}) has been used.
25974 @item syscall-return
25975 The inferior returned from a system call. This is reported when
25976 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25978 The inferior called @code{exec}. This is reported when @code{catch exec}
25979 (@pxref{Set Catchpoints}) has been used.
25982 The @var{id} field identifies the thread that directly caused the stop
25983 -- for example by hitting a breakpoint. Depending on whether all-stop
25984 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25985 stop all threads, or only the thread that directly triggered the stop.
25986 If all threads are stopped, the @var{stopped} field will have the
25987 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25988 field will be a list of thread identifiers. Presently, this list will
25989 always include a single thread, but frontend should be prepared to see
25990 several threads in the list. The @var{core} field reports the
25991 processor core on which the stop event has happened. This field may be absent
25992 if such information is not available.
25994 @item =thread-group-added,id="@var{id}"
25995 @itemx =thread-group-removed,id="@var{id}"
25996 A thread group was either added or removed. The @var{id} field
25997 contains the @value{GDBN} identifier of the thread group. When a thread
25998 group is added, it generally might not be associated with a running
25999 process. When a thread group is removed, its id becomes invalid and
26000 cannot be used in any way.
26002 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26003 A thread group became associated with a running program,
26004 either because the program was just started or the thread group
26005 was attached to a program. The @var{id} field contains the
26006 @value{GDBN} identifier of the thread group. The @var{pid} field
26007 contains process identifier, specific to the operating system.
26009 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26010 A thread group is no longer associated with a running program,
26011 either because the program has exited, or because it was detached
26012 from. The @var{id} field contains the @value{GDBN} identifier of the
26013 thread group. The @var{code} field is the exit code of the inferior; it exists
26014 only when the inferior exited with some code.
26016 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26017 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26018 A thread either was created, or has exited. The @var{id} field
26019 contains the @value{GDBN} identifier of the thread. The @var{gid}
26020 field identifies the thread group this thread belongs to.
26022 @item =thread-selected,id="@var{id}"
26023 Informs that the selected thread was changed as result of the last
26024 command. This notification is not emitted as result of @code{-thread-select}
26025 command but is emitted whenever an MI command that is not documented
26026 to change the selected thread actually changes it. In particular,
26027 invoking, directly or indirectly (via user-defined command), the CLI
26028 @code{thread} command, will generate this notification.
26030 We suggest that in response to this notification, front ends
26031 highlight the selected thread and cause subsequent commands to apply to
26034 @item =library-loaded,...
26035 Reports that a new library file was loaded by the program. This
26036 notification has 4 fields---@var{id}, @var{target-name},
26037 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26038 opaque identifier of the library. For remote debugging case,
26039 @var{target-name} and @var{host-name} fields give the name of the
26040 library file on the target, and on the host respectively. For native
26041 debugging, both those fields have the same value. The
26042 @var{symbols-loaded} field is emitted only for backward compatibility
26043 and should not be relied on to convey any useful information. The
26044 @var{thread-group} field, if present, specifies the id of the thread
26045 group in whose context the library was loaded. If the field is
26046 absent, it means the library was loaded in the context of all present
26049 @item =library-unloaded,...
26050 Reports that a library was unloaded by the program. This notification
26051 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26052 the same meaning as for the @code{=library-loaded} notification.
26053 The @var{thread-group} field, if present, specifies the id of the
26054 thread group in whose context the library was unloaded. If the field is
26055 absent, it means the library was unloaded in the context of all present
26058 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26059 @itemx =traceframe-changed,end
26060 Reports that the trace frame was changed and its new number is
26061 @var{tfnum}. The number of the tracepoint associated with this trace
26062 frame is @var{tpnum}.
26064 @item =tsv-created,name=@var{name},initial=@var{initial}
26065 Reports that the new trace state variable @var{name} is created with
26066 initial value @var{initial}.
26068 @item =tsv-deleted,name=@var{name}
26069 @itemx =tsv-deleted
26070 Reports that the trace state variable @var{name} is deleted or all
26071 trace state variables are deleted.
26073 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26074 Reports that the trace state variable @var{name} is modified with
26075 the initial value @var{initial}. The current value @var{current} of
26076 trace state variable is optional and is reported if the current
26077 value of trace state variable is known.
26079 @item =breakpoint-created,bkpt=@{...@}
26080 @itemx =breakpoint-modified,bkpt=@{...@}
26081 @itemx =breakpoint-deleted,id=@var{number}
26082 Reports that a breakpoint was created, modified, or deleted,
26083 respectively. Only user-visible breakpoints are reported to the MI
26086 The @var{bkpt} argument is of the same form as returned by the various
26087 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26088 @var{number} is the ordinal number of the breakpoint.
26090 Note that if a breakpoint is emitted in the result record of a
26091 command, then it will not also be emitted in an async record.
26093 @item =record-started,thread-group="@var{id}"
26094 @itemx =record-stopped,thread-group="@var{id}"
26095 Execution log recording was either started or stopped on an
26096 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26097 group corresponding to the affected inferior.
26099 @item =cmd-param-changed,param=@var{param},value=@var{value}
26100 Reports that a parameter of the command @code{set @var{param}} is
26101 changed to @var{value}. In the multi-word @code{set} command,
26102 the @var{param} is the whole parameter list to @code{set} command.
26103 For example, In command @code{set check type on}, @var{param}
26104 is @code{check type} and @var{value} is @code{on}.
26106 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26107 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26108 written in an inferior. The @var{id} is the identifier of the
26109 thread group corresponding to the affected inferior. The optional
26110 @code{type="code"} part is reported if the memory written to holds
26114 @node GDB/MI Breakpoint Information
26115 @subsection @sc{gdb/mi} Breakpoint Information
26117 When @value{GDBN} reports information about a breakpoint, a
26118 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26123 The breakpoint number. For a breakpoint that represents one location
26124 of a multi-location breakpoint, this will be a dotted pair, like
26128 The type of the breakpoint. For ordinary breakpoints this will be
26129 @samp{breakpoint}, but many values are possible.
26132 If the type of the breakpoint is @samp{catchpoint}, then this
26133 indicates the exact type of catchpoint.
26136 This is the breakpoint disposition---either @samp{del}, meaning that
26137 the breakpoint will be deleted at the next stop, or @samp{keep},
26138 meaning that the breakpoint will not be deleted.
26141 This indicates whether the breakpoint is enabled, in which case the
26142 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26143 Note that this is not the same as the field @code{enable}.
26146 The address of the breakpoint. This may be a hexidecimal number,
26147 giving the address; or the string @samp{<PENDING>}, for a pending
26148 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26149 multiple locations. This field will not be present if no address can
26150 be determined. For example, a watchpoint does not have an address.
26153 If known, the function in which the breakpoint appears.
26154 If not known, this field is not present.
26157 The name of the source file which contains this function, if known.
26158 If not known, this field is not present.
26161 The full file name of the source file which contains this function, if
26162 known. If not known, this field is not present.
26165 The line number at which this breakpoint appears, if known.
26166 If not known, this field is not present.
26169 If the source file is not known, this field may be provided. If
26170 provided, this holds the address of the breakpoint, possibly followed
26174 If this breakpoint is pending, this field is present and holds the
26175 text used to set the breakpoint, as entered by the user.
26178 Where this breakpoint's condition is evaluated, either @samp{host} or
26182 If this is a thread-specific breakpoint, then this identifies the
26183 thread in which the breakpoint can trigger.
26186 If this breakpoint is restricted to a particular Ada task, then this
26187 field will hold the task identifier.
26190 If the breakpoint is conditional, this is the condition expression.
26193 The ignore count of the breakpoint.
26196 The enable count of the breakpoint.
26198 @item traceframe-usage
26201 @item static-tracepoint-marker-string-id
26202 For a static tracepoint, the name of the static tracepoint marker.
26205 For a masked watchpoint, this is the mask.
26208 A tracepoint's pass count.
26210 @item original-location
26211 The location of the breakpoint as originally specified by the user.
26212 This field is optional.
26215 The number of times the breakpoint has been hit.
26218 This field is only given for tracepoints. This is either @samp{y},
26219 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26223 Some extra data, the exact contents of which are type-dependent.
26227 For example, here is what the output of @code{-break-insert}
26228 (@pxref{GDB/MI Breakpoint Commands}) might be:
26231 -> -break-insert main
26232 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26233 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26234 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26239 @node GDB/MI Frame Information
26240 @subsection @sc{gdb/mi} Frame Information
26242 Response from many MI commands includes an information about stack
26243 frame. This information is a tuple that may have the following
26248 The level of the stack frame. The innermost frame has the level of
26249 zero. This field is always present.
26252 The name of the function corresponding to the frame. This field may
26253 be absent if @value{GDBN} is unable to determine the function name.
26256 The code address for the frame. This field is always present.
26259 The name of the source files that correspond to the frame's code
26260 address. This field may be absent.
26263 The source line corresponding to the frames' code address. This field
26267 The name of the binary file (either executable or shared library) the
26268 corresponds to the frame's code address. This field may be absent.
26272 @node GDB/MI Thread Information
26273 @subsection @sc{gdb/mi} Thread Information
26275 Whenever @value{GDBN} has to report an information about a thread, it
26276 uses a tuple with the following fields:
26280 The numeric id assigned to the thread by @value{GDBN}. This field is
26284 Target-specific string identifying the thread. This field is always present.
26287 Additional information about the thread provided by the target.
26288 It is supposed to be human-readable and not interpreted by the
26289 frontend. This field is optional.
26292 Either @samp{stopped} or @samp{running}, depending on whether the
26293 thread is presently running. This field is always present.
26296 The value of this field is an integer number of the processor core the
26297 thread was last seen on. This field is optional.
26300 @node GDB/MI Ada Exception Information
26301 @subsection @sc{gdb/mi} Ada Exception Information
26303 Whenever a @code{*stopped} record is emitted because the program
26304 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26305 @value{GDBN} provides the name of the exception that was raised via
26306 the @code{exception-name} field.
26308 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26309 @node GDB/MI Simple Examples
26310 @section Simple Examples of @sc{gdb/mi} Interaction
26311 @cindex @sc{gdb/mi}, simple examples
26313 This subsection presents several simple examples of interaction using
26314 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26315 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26316 the output received from @sc{gdb/mi}.
26318 Note the line breaks shown in the examples are here only for
26319 readability, they don't appear in the real output.
26321 @subheading Setting a Breakpoint
26323 Setting a breakpoint generates synchronous output which contains detailed
26324 information of the breakpoint.
26327 -> -break-insert main
26328 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26329 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26330 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26335 @subheading Program Execution
26337 Program execution generates asynchronous records and MI gives the
26338 reason that execution stopped.
26344 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26345 frame=@{addr="0x08048564",func="main",
26346 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26347 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26352 <- *stopped,reason="exited-normally"
26356 @subheading Quitting @value{GDBN}
26358 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26366 Please note that @samp{^exit} is printed immediately, but it might
26367 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26368 performs necessary cleanups, including killing programs being debugged
26369 or disconnecting from debug hardware, so the frontend should wait till
26370 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26371 fails to exit in reasonable time.
26373 @subheading A Bad Command
26375 Here's what happens if you pass a non-existent command:
26379 <- ^error,msg="Undefined MI command: rubbish"
26384 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26385 @node GDB/MI Command Description Format
26386 @section @sc{gdb/mi} Command Description Format
26388 The remaining sections describe blocks of commands. Each block of
26389 commands is laid out in a fashion similar to this section.
26391 @subheading Motivation
26393 The motivation for this collection of commands.
26395 @subheading Introduction
26397 A brief introduction to this collection of commands as a whole.
26399 @subheading Commands
26401 For each command in the block, the following is described:
26403 @subsubheading Synopsis
26406 -command @var{args}@dots{}
26409 @subsubheading Result
26411 @subsubheading @value{GDBN} Command
26413 The corresponding @value{GDBN} CLI command(s), if any.
26415 @subsubheading Example
26417 Example(s) formatted for readability. Some of the described commands have
26418 not been implemented yet and these are labeled N.A.@: (not available).
26421 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26422 @node GDB/MI Breakpoint Commands
26423 @section @sc{gdb/mi} Breakpoint Commands
26425 @cindex breakpoint commands for @sc{gdb/mi}
26426 @cindex @sc{gdb/mi}, breakpoint commands
26427 This section documents @sc{gdb/mi} commands for manipulating
26430 @subheading The @code{-break-after} Command
26431 @findex -break-after
26433 @subsubheading Synopsis
26436 -break-after @var{number} @var{count}
26439 The breakpoint number @var{number} is not in effect until it has been
26440 hit @var{count} times. To see how this is reflected in the output of
26441 the @samp{-break-list} command, see the description of the
26442 @samp{-break-list} command below.
26444 @subsubheading @value{GDBN} Command
26446 The corresponding @value{GDBN} command is @samp{ignore}.
26448 @subsubheading Example
26453 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26454 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26455 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26463 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26464 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26465 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26466 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26467 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26468 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26469 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26470 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26471 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26472 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26477 @subheading The @code{-break-catch} Command
26478 @findex -break-catch
26481 @subheading The @code{-break-commands} Command
26482 @findex -break-commands
26484 @subsubheading Synopsis
26487 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26490 Specifies the CLI commands that should be executed when breakpoint
26491 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26492 are the commands. If no command is specified, any previously-set
26493 commands are cleared. @xref{Break Commands}. Typical use of this
26494 functionality is tracing a program, that is, printing of values of
26495 some variables whenever breakpoint is hit and then continuing.
26497 @subsubheading @value{GDBN} Command
26499 The corresponding @value{GDBN} command is @samp{commands}.
26501 @subsubheading Example
26506 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26507 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26508 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26511 -break-commands 1 "print v" "continue"
26516 @subheading The @code{-break-condition} Command
26517 @findex -break-condition
26519 @subsubheading Synopsis
26522 -break-condition @var{number} @var{expr}
26525 Breakpoint @var{number} will stop the program only if the condition in
26526 @var{expr} is true. The condition becomes part of the
26527 @samp{-break-list} output (see the description of the @samp{-break-list}
26530 @subsubheading @value{GDBN} Command
26532 The corresponding @value{GDBN} command is @samp{condition}.
26534 @subsubheading Example
26538 -break-condition 1 1
26542 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26543 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26544 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26545 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26546 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26547 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26548 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26549 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26550 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26551 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26555 @subheading The @code{-break-delete} Command
26556 @findex -break-delete
26558 @subsubheading Synopsis
26561 -break-delete ( @var{breakpoint} )+
26564 Delete the breakpoint(s) whose number(s) are specified in the argument
26565 list. This is obviously reflected in the breakpoint list.
26567 @subsubheading @value{GDBN} Command
26569 The corresponding @value{GDBN} command is @samp{delete}.
26571 @subsubheading Example
26579 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26580 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26581 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26582 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26583 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26584 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26585 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26590 @subheading The @code{-break-disable} Command
26591 @findex -break-disable
26593 @subsubheading Synopsis
26596 -break-disable ( @var{breakpoint} )+
26599 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26600 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26602 @subsubheading @value{GDBN} Command
26604 The corresponding @value{GDBN} command is @samp{disable}.
26606 @subsubheading Example
26614 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26615 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26616 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26617 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26618 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26619 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26620 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26621 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26622 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26623 line="5",thread-groups=["i1"],times="0"@}]@}
26627 @subheading The @code{-break-enable} Command
26628 @findex -break-enable
26630 @subsubheading Synopsis
26633 -break-enable ( @var{breakpoint} )+
26636 Enable (previously disabled) @var{breakpoint}(s).
26638 @subsubheading @value{GDBN} Command
26640 The corresponding @value{GDBN} command is @samp{enable}.
26642 @subsubheading Example
26650 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26651 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26652 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26653 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26654 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26655 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26656 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26657 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26658 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26659 line="5",thread-groups=["i1"],times="0"@}]@}
26663 @subheading The @code{-break-info} Command
26664 @findex -break-info
26666 @subsubheading Synopsis
26669 -break-info @var{breakpoint}
26673 Get information about a single breakpoint.
26675 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26676 Information}, for details on the format of each breakpoint in the
26679 @subsubheading @value{GDBN} Command
26681 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26683 @subsubheading Example
26686 @subheading The @code{-break-insert} Command
26687 @findex -break-insert
26689 @subsubheading Synopsis
26692 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26693 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26694 [ -p @var{thread-id} ] [ @var{location} ]
26698 If specified, @var{location}, can be one of:
26705 @item filename:linenum
26706 @item filename:function
26710 The possible optional parameters of this command are:
26714 Insert a temporary breakpoint.
26716 Insert a hardware breakpoint.
26718 If @var{location} cannot be parsed (for example if it
26719 refers to unknown files or functions), create a pending
26720 breakpoint. Without this flag, @value{GDBN} will report
26721 an error, and won't create a breakpoint, if @var{location}
26724 Create a disabled breakpoint.
26726 Create a tracepoint. @xref{Tracepoints}. When this parameter
26727 is used together with @samp{-h}, a fast tracepoint is created.
26728 @item -c @var{condition}
26729 Make the breakpoint conditional on @var{condition}.
26730 @item -i @var{ignore-count}
26731 Initialize the @var{ignore-count}.
26732 @item -p @var{thread-id}
26733 Restrict the breakpoint to the specified @var{thread-id}.
26736 @subsubheading Result
26738 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26739 resulting breakpoint.
26741 Note: this format is open to change.
26742 @c An out-of-band breakpoint instead of part of the result?
26744 @subsubheading @value{GDBN} Command
26746 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26747 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26749 @subsubheading Example
26754 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26755 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26758 -break-insert -t foo
26759 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26760 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26764 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26765 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26766 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26767 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26768 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26769 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26770 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26771 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26772 addr="0x0001072c", func="main",file="recursive2.c",
26773 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26775 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26776 addr="0x00010774",func="foo",file="recursive2.c",
26777 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26780 @c -break-insert -r foo.*
26781 @c ~int foo(int, int);
26782 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26783 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26788 @subheading The @code{-dprintf-insert} Command
26789 @findex -dprintf-insert
26791 @subsubheading Synopsis
26794 -dprintf-insert [ -t ] [ -f ] [ -d ]
26795 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26796 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26801 If specified, @var{location}, can be one of:
26804 @item @var{function}
26807 @c @item @var{linenum}
26808 @item @var{filename}:@var{linenum}
26809 @item @var{filename}:function
26810 @item *@var{address}
26813 The possible optional parameters of this command are:
26817 Insert a temporary breakpoint.
26819 If @var{location} cannot be parsed (for example, if it
26820 refers to unknown files or functions), create a pending
26821 breakpoint. Without this flag, @value{GDBN} will report
26822 an error, and won't create a breakpoint, if @var{location}
26825 Create a disabled breakpoint.
26826 @item -c @var{condition}
26827 Make the breakpoint conditional on @var{condition}.
26828 @item -i @var{ignore-count}
26829 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26830 to @var{ignore-count}.
26831 @item -p @var{thread-id}
26832 Restrict the breakpoint to the specified @var{thread-id}.
26835 @subsubheading Result
26837 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26838 resulting breakpoint.
26840 @c An out-of-band breakpoint instead of part of the result?
26842 @subsubheading @value{GDBN} Command
26844 The corresponding @value{GDBN} command is @samp{dprintf}.
26846 @subsubheading Example
26850 4-dprintf-insert foo "At foo entry\n"
26851 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26852 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26853 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26854 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26855 original-location="foo"@}
26857 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26858 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26859 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26860 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26861 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26862 original-location="mi-dprintf.c:26"@}
26866 @subheading The @code{-break-list} Command
26867 @findex -break-list
26869 @subsubheading Synopsis
26875 Displays the list of inserted breakpoints, showing the following fields:
26879 number of the breakpoint
26881 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26883 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26886 is the breakpoint enabled or no: @samp{y} or @samp{n}
26888 memory location at which the breakpoint is set
26890 logical location of the breakpoint, expressed by function name, file
26892 @item Thread-groups
26893 list of thread groups to which this breakpoint applies
26895 number of times the breakpoint has been hit
26898 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26899 @code{body} field is an empty list.
26901 @subsubheading @value{GDBN} Command
26903 The corresponding @value{GDBN} command is @samp{info break}.
26905 @subsubheading Example
26910 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26911 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26912 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26913 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26914 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26915 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26916 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26917 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26918 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26920 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26921 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26922 line="13",thread-groups=["i1"],times="0"@}]@}
26926 Here's an example of the result when there are no breakpoints:
26931 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26932 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26933 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26934 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26935 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26936 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26937 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26942 @subheading The @code{-break-passcount} Command
26943 @findex -break-passcount
26945 @subsubheading Synopsis
26948 -break-passcount @var{tracepoint-number} @var{passcount}
26951 Set the passcount for tracepoint @var{tracepoint-number} to
26952 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26953 is not a tracepoint, error is emitted. This corresponds to CLI
26954 command @samp{passcount}.
26956 @subheading The @code{-break-watch} Command
26957 @findex -break-watch
26959 @subsubheading Synopsis
26962 -break-watch [ -a | -r ]
26965 Create a watchpoint. With the @samp{-a} option it will create an
26966 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26967 read from or on a write to the memory location. With the @samp{-r}
26968 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26969 trigger only when the memory location is accessed for reading. Without
26970 either of the options, the watchpoint created is a regular watchpoint,
26971 i.e., it will trigger when the memory location is accessed for writing.
26972 @xref{Set Watchpoints, , Setting Watchpoints}.
26974 Note that @samp{-break-list} will report a single list of watchpoints and
26975 breakpoints inserted.
26977 @subsubheading @value{GDBN} Command
26979 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26982 @subsubheading Example
26984 Setting a watchpoint on a variable in the @code{main} function:
26989 ^done,wpt=@{number="2",exp="x"@}
26994 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26995 value=@{old="-268439212",new="55"@},
26996 frame=@{func="main",args=[],file="recursive2.c",
26997 fullname="/home/foo/bar/recursive2.c",line="5"@}
27001 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27002 the program execution twice: first for the variable changing value, then
27003 for the watchpoint going out of scope.
27008 ^done,wpt=@{number="5",exp="C"@}
27013 *stopped,reason="watchpoint-trigger",
27014 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27015 frame=@{func="callee4",args=[],
27016 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27017 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27022 *stopped,reason="watchpoint-scope",wpnum="5",
27023 frame=@{func="callee3",args=[@{name="strarg",
27024 value="0x11940 \"A string argument.\""@}],
27025 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27026 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27030 Listing breakpoints and watchpoints, at different points in the program
27031 execution. Note that once the watchpoint goes out of scope, it is
27037 ^done,wpt=@{number="2",exp="C"@}
27040 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27041 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27042 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27043 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27044 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27045 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27046 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27047 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27048 addr="0x00010734",func="callee4",
27049 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27050 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27052 bkpt=@{number="2",type="watchpoint",disp="keep",
27053 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27058 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27059 value=@{old="-276895068",new="3"@},
27060 frame=@{func="callee4",args=[],
27061 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27062 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27065 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27066 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27067 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27068 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27069 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27070 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27071 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27072 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27073 addr="0x00010734",func="callee4",
27074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27075 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27077 bkpt=@{number="2",type="watchpoint",disp="keep",
27078 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27082 ^done,reason="watchpoint-scope",wpnum="2",
27083 frame=@{func="callee3",args=[@{name="strarg",
27084 value="0x11940 \"A string argument.\""@}],
27085 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27086 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27089 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27096 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27097 addr="0x00010734",func="callee4",
27098 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27099 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27100 thread-groups=["i1"],times="1"@}]@}
27105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27106 @node GDB/MI Catchpoint Commands
27107 @section @sc{gdb/mi} Catchpoint Commands
27109 This section documents @sc{gdb/mi} commands for manipulating
27113 * Shared Library GDB/MI Catchpoint Commands::
27114 * Ada Exception GDB/MI Catchpoint Commands::
27117 @node Shared Library GDB/MI Catchpoint Commands
27118 @subsection Shared Library @sc{gdb/mi} Catchpoints
27120 @subheading The @code{-catch-load} Command
27121 @findex -catch-load
27123 @subsubheading Synopsis
27126 -catch-load [ -t ] [ -d ] @var{regexp}
27129 Add a catchpoint for library load events. If the @samp{-t} option is used,
27130 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27131 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27132 in a disabled state. The @samp{regexp} argument is a regular
27133 expression used to match the name of the loaded library.
27136 @subsubheading @value{GDBN} Command
27138 The corresponding @value{GDBN} command is @samp{catch load}.
27140 @subsubheading Example
27143 -catch-load -t foo.so
27144 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27145 what="load of library matching foo.so",catch-type="load",times="0"@}
27150 @subheading The @code{-catch-unload} Command
27151 @findex -catch-unload
27153 @subsubheading Synopsis
27156 -catch-unload [ -t ] [ -d ] @var{regexp}
27159 Add a catchpoint for library unload events. If the @samp{-t} option is
27160 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27161 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27162 created in a disabled state. The @samp{regexp} argument is a regular
27163 expression used to match the name of the unloaded library.
27165 @subsubheading @value{GDBN} Command
27167 The corresponding @value{GDBN} command is @samp{catch unload}.
27169 @subsubheading Example
27172 -catch-unload -d bar.so
27173 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27174 what="load of library matching bar.so",catch-type="unload",times="0"@}
27178 @node Ada Exception GDB/MI Catchpoint Commands
27179 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27181 The following @sc{gdb/mi} commands can be used to create catchpoints
27182 that stop the execution when Ada exceptions are being raised.
27184 @subheading The @code{-catch-assert} Command
27185 @findex -catch-assert
27187 @subsubheading Synopsis
27190 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27193 Add a catchpoint for failed Ada assertions.
27195 The possible optional parameters for this command are:
27198 @item -c @var{condition}
27199 Make the catchpoint conditional on @var{condition}.
27201 Create a disabled catchpoint.
27203 Create a temporary catchpoint.
27206 @subsubheading @value{GDBN} Command
27208 The corresponding @value{GDBN} command is @samp{catch assert}.
27210 @subsubheading Example
27214 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27215 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27216 thread-groups=["i1"],times="0",
27217 original-location="__gnat_debug_raise_assert_failure"@}
27221 @subheading The @code{-catch-exception} Command
27222 @findex -catch-exception
27224 @subsubheading Synopsis
27227 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27231 Add a catchpoint stopping when Ada exceptions are raised.
27232 By default, the command stops the program when any Ada exception
27233 gets raised. But it is also possible, by using some of the
27234 optional parameters described below, to create more selective
27237 The possible optional parameters for this command are:
27240 @item -c @var{condition}
27241 Make the catchpoint conditional on @var{condition}.
27243 Create a disabled catchpoint.
27244 @item -e @var{exception-name}
27245 Only stop when @var{exception-name} is raised. This option cannot
27246 be used combined with @samp{-u}.
27248 Create a temporary catchpoint.
27250 Stop only when an unhandled exception gets raised. This option
27251 cannot be used combined with @samp{-e}.
27254 @subsubheading @value{GDBN} Command
27256 The corresponding @value{GDBN} commands are @samp{catch exception}
27257 and @samp{catch exception unhandled}.
27259 @subsubheading Example
27262 -catch-exception -e Program_Error
27263 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27264 enabled="y",addr="0x0000000000404874",
27265 what="`Program_Error' Ada exception", thread-groups=["i1"],
27266 times="0",original-location="__gnat_debug_raise_exception"@}
27270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27271 @node GDB/MI Program Context
27272 @section @sc{gdb/mi} Program Context
27274 @subheading The @code{-exec-arguments} Command
27275 @findex -exec-arguments
27278 @subsubheading Synopsis
27281 -exec-arguments @var{args}
27284 Set the inferior program arguments, to be used in the next
27287 @subsubheading @value{GDBN} Command
27289 The corresponding @value{GDBN} command is @samp{set args}.
27291 @subsubheading Example
27295 -exec-arguments -v word
27302 @subheading The @code{-exec-show-arguments} Command
27303 @findex -exec-show-arguments
27305 @subsubheading Synopsis
27308 -exec-show-arguments
27311 Print the arguments of the program.
27313 @subsubheading @value{GDBN} Command
27315 The corresponding @value{GDBN} command is @samp{show args}.
27317 @subsubheading Example
27322 @subheading The @code{-environment-cd} Command
27323 @findex -environment-cd
27325 @subsubheading Synopsis
27328 -environment-cd @var{pathdir}
27331 Set @value{GDBN}'s working directory.
27333 @subsubheading @value{GDBN} Command
27335 The corresponding @value{GDBN} command is @samp{cd}.
27337 @subsubheading Example
27341 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27347 @subheading The @code{-environment-directory} Command
27348 @findex -environment-directory
27350 @subsubheading Synopsis
27353 -environment-directory [ -r ] [ @var{pathdir} ]+
27356 Add directories @var{pathdir} to beginning of search path for source files.
27357 If the @samp{-r} option is used, the search path is reset to the default
27358 search path. If directories @var{pathdir} are supplied in addition to the
27359 @samp{-r} option, the search path is first reset and then addition
27361 Multiple directories may be specified, separated by blanks. Specifying
27362 multiple directories in a single command
27363 results in the directories added to the beginning of the
27364 search path in the same order they were presented in the command.
27365 If blanks are needed as
27366 part of a directory name, double-quotes should be used around
27367 the name. In the command output, the path will show up separated
27368 by the system directory-separator character. The directory-separator
27369 character must not be used
27370 in any directory name.
27371 If no directories are specified, the current search path is displayed.
27373 @subsubheading @value{GDBN} Command
27375 The corresponding @value{GDBN} command is @samp{dir}.
27377 @subsubheading Example
27381 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27382 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27384 -environment-directory ""
27385 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27387 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27388 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27390 -environment-directory -r
27391 ^done,source-path="$cdir:$cwd"
27396 @subheading The @code{-environment-path} Command
27397 @findex -environment-path
27399 @subsubheading Synopsis
27402 -environment-path [ -r ] [ @var{pathdir} ]+
27405 Add directories @var{pathdir} to beginning of search path for object files.
27406 If the @samp{-r} option is used, the search path is reset to the original
27407 search path that existed at gdb start-up. If directories @var{pathdir} are
27408 supplied in addition to the
27409 @samp{-r} option, the search path is first reset and then addition
27411 Multiple directories may be specified, separated by blanks. Specifying
27412 multiple directories in a single command
27413 results in the directories added to the beginning of the
27414 search path in the same order they were presented in the command.
27415 If blanks are needed as
27416 part of a directory name, double-quotes should be used around
27417 the name. In the command output, the path will show up separated
27418 by the system directory-separator character. The directory-separator
27419 character must not be used
27420 in any directory name.
27421 If no directories are specified, the current path is displayed.
27424 @subsubheading @value{GDBN} Command
27426 The corresponding @value{GDBN} command is @samp{path}.
27428 @subsubheading Example
27433 ^done,path="/usr/bin"
27435 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27436 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27438 -environment-path -r /usr/local/bin
27439 ^done,path="/usr/local/bin:/usr/bin"
27444 @subheading The @code{-environment-pwd} Command
27445 @findex -environment-pwd
27447 @subsubheading Synopsis
27453 Show the current working directory.
27455 @subsubheading @value{GDBN} Command
27457 The corresponding @value{GDBN} command is @samp{pwd}.
27459 @subsubheading Example
27464 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27469 @node GDB/MI Thread Commands
27470 @section @sc{gdb/mi} Thread Commands
27473 @subheading The @code{-thread-info} Command
27474 @findex -thread-info
27476 @subsubheading Synopsis
27479 -thread-info [ @var{thread-id} ]
27482 Reports information about either a specific thread, if
27483 the @var{thread-id} parameter is present, or about all
27484 threads. When printing information about all threads,
27485 also reports the current thread.
27487 @subsubheading @value{GDBN} Command
27489 The @samp{info thread} command prints the same information
27492 @subsubheading Result
27494 The result is a list of threads. The following attributes are
27495 defined for a given thread:
27499 This field exists only for the current thread. It has the value @samp{*}.
27502 The identifier that @value{GDBN} uses to refer to the thread.
27505 The identifier that the target uses to refer to the thread.
27508 Extra information about the thread, in a target-specific format. This
27512 The name of the thread. If the user specified a name using the
27513 @code{thread name} command, then this name is given. Otherwise, if
27514 @value{GDBN} can extract the thread name from the target, then that
27515 name is given. If @value{GDBN} cannot find the thread name, then this
27519 The stack frame currently executing in the thread.
27522 The thread's state. The @samp{state} field may have the following
27527 The thread is stopped. Frame information is available for stopped
27531 The thread is running. There's no frame information for running
27537 If @value{GDBN} can find the CPU core on which this thread is running,
27538 then this field is the core identifier. This field is optional.
27542 @subsubheading Example
27547 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27548 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27549 args=[]@},state="running"@},
27550 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27551 frame=@{level="0",addr="0x0804891f",func="foo",
27552 args=[@{name="i",value="10"@}],
27553 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27554 state="running"@}],
27555 current-thread-id="1"
27559 @subheading The @code{-thread-list-ids} Command
27560 @findex -thread-list-ids
27562 @subsubheading Synopsis
27568 Produces a list of the currently known @value{GDBN} thread ids. At the
27569 end of the list it also prints the total number of such threads.
27571 This command is retained for historical reasons, the
27572 @code{-thread-info} command should be used instead.
27574 @subsubheading @value{GDBN} Command
27576 Part of @samp{info threads} supplies the same information.
27578 @subsubheading Example
27583 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27584 current-thread-id="1",number-of-threads="3"
27589 @subheading The @code{-thread-select} Command
27590 @findex -thread-select
27592 @subsubheading Synopsis
27595 -thread-select @var{threadnum}
27598 Make @var{threadnum} the current thread. It prints the number of the new
27599 current thread, and the topmost frame for that thread.
27601 This command is deprecated in favor of explicitly using the
27602 @samp{--thread} option to each command.
27604 @subsubheading @value{GDBN} Command
27606 The corresponding @value{GDBN} command is @samp{thread}.
27608 @subsubheading Example
27615 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27616 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27620 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27621 number-of-threads="3"
27624 ^done,new-thread-id="3",
27625 frame=@{level="0",func="vprintf",
27626 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27627 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27632 @node GDB/MI Ada Tasking Commands
27633 @section @sc{gdb/mi} Ada Tasking Commands
27635 @subheading The @code{-ada-task-info} Command
27636 @findex -ada-task-info
27638 @subsubheading Synopsis
27641 -ada-task-info [ @var{task-id} ]
27644 Reports information about either a specific Ada task, if the
27645 @var{task-id} parameter is present, or about all Ada tasks.
27647 @subsubheading @value{GDBN} Command
27649 The @samp{info tasks} command prints the same information
27650 about all Ada tasks (@pxref{Ada Tasks}).
27652 @subsubheading Result
27654 The result is a table of Ada tasks. The following columns are
27655 defined for each Ada task:
27659 This field exists only for the current thread. It has the value @samp{*}.
27662 The identifier that @value{GDBN} uses to refer to the Ada task.
27665 The identifier that the target uses to refer to the Ada task.
27668 The identifier of the thread corresponding to the Ada task.
27670 This field should always exist, as Ada tasks are always implemented
27671 on top of a thread. But if @value{GDBN} cannot find this corresponding
27672 thread for any reason, the field is omitted.
27675 This field exists only when the task was created by another task.
27676 In this case, it provides the ID of the parent task.
27679 The base priority of the task.
27682 The current state of the task. For a detailed description of the
27683 possible states, see @ref{Ada Tasks}.
27686 The name of the task.
27690 @subsubheading Example
27694 ^done,tasks=@{nr_rows="3",nr_cols="8",
27695 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27696 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27697 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27698 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27699 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27700 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27701 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27702 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27703 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27704 state="Child Termination Wait",name="main_task"@}]@}
27708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27709 @node GDB/MI Program Execution
27710 @section @sc{gdb/mi} Program Execution
27712 These are the asynchronous commands which generate the out-of-band
27713 record @samp{*stopped}. Currently @value{GDBN} only really executes
27714 asynchronously with remote targets and this interaction is mimicked in
27717 @subheading The @code{-exec-continue} Command
27718 @findex -exec-continue
27720 @subsubheading Synopsis
27723 -exec-continue [--reverse] [--all|--thread-group N]
27726 Resumes the execution of the inferior program, which will continue
27727 to execute until it reaches a debugger stop event. If the
27728 @samp{--reverse} option is specified, execution resumes in reverse until
27729 it reaches a stop event. Stop events may include
27732 breakpoints or watchpoints
27734 signals or exceptions
27736 the end of the process (or its beginning under @samp{--reverse})
27738 the end or beginning of a replay log if one is being used.
27740 In all-stop mode (@pxref{All-Stop
27741 Mode}), may resume only one thread, or all threads, depending on the
27742 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27743 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27744 ignored in all-stop mode. If the @samp{--thread-group} options is
27745 specified, then all threads in that thread group are resumed.
27747 @subsubheading @value{GDBN} Command
27749 The corresponding @value{GDBN} corresponding is @samp{continue}.
27751 @subsubheading Example
27758 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27759 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27765 @subheading The @code{-exec-finish} Command
27766 @findex -exec-finish
27768 @subsubheading Synopsis
27771 -exec-finish [--reverse]
27774 Resumes the execution of the inferior program until the current
27775 function is exited. Displays the results returned by the function.
27776 If the @samp{--reverse} option is specified, resumes the reverse
27777 execution of the inferior program until the point where current
27778 function was called.
27780 @subsubheading @value{GDBN} Command
27782 The corresponding @value{GDBN} command is @samp{finish}.
27784 @subsubheading Example
27786 Function returning @code{void}.
27793 *stopped,reason="function-finished",frame=@{func="main",args=[],
27794 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27798 Function returning other than @code{void}. The name of the internal
27799 @value{GDBN} variable storing the result is printed, together with the
27806 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27807 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27808 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27809 gdb-result-var="$1",return-value="0"
27814 @subheading The @code{-exec-interrupt} Command
27815 @findex -exec-interrupt
27817 @subsubheading Synopsis
27820 -exec-interrupt [--all|--thread-group N]
27823 Interrupts the background execution of the target. Note how the token
27824 associated with the stop message is the one for the execution command
27825 that has been interrupted. The token for the interrupt itself only
27826 appears in the @samp{^done} output. If the user is trying to
27827 interrupt a non-running program, an error message will be printed.
27829 Note that when asynchronous execution is enabled, this command is
27830 asynchronous just like other execution commands. That is, first the
27831 @samp{^done} response will be printed, and the target stop will be
27832 reported after that using the @samp{*stopped} notification.
27834 In non-stop mode, only the context thread is interrupted by default.
27835 All threads (in all inferiors) will be interrupted if the
27836 @samp{--all} option is specified. If the @samp{--thread-group}
27837 option is specified, all threads in that group will be interrupted.
27839 @subsubheading @value{GDBN} Command
27841 The corresponding @value{GDBN} command is @samp{interrupt}.
27843 @subsubheading Example
27854 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27855 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27856 fullname="/home/foo/bar/try.c",line="13"@}
27861 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27865 @subheading The @code{-exec-jump} Command
27868 @subsubheading Synopsis
27871 -exec-jump @var{location}
27874 Resumes execution of the inferior program at the location specified by
27875 parameter. @xref{Specify Location}, for a description of the
27876 different forms of @var{location}.
27878 @subsubheading @value{GDBN} Command
27880 The corresponding @value{GDBN} command is @samp{jump}.
27882 @subsubheading Example
27885 -exec-jump foo.c:10
27886 *running,thread-id="all"
27891 @subheading The @code{-exec-next} Command
27894 @subsubheading Synopsis
27897 -exec-next [--reverse]
27900 Resumes execution of the inferior program, stopping when the beginning
27901 of the next source line is reached.
27903 If the @samp{--reverse} option is specified, resumes reverse execution
27904 of the inferior program, stopping at the beginning of the previous
27905 source line. If you issue this command on the first line of a
27906 function, it will take you back to the caller of that function, to the
27907 source line where the function was called.
27910 @subsubheading @value{GDBN} Command
27912 The corresponding @value{GDBN} command is @samp{next}.
27914 @subsubheading Example
27920 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27925 @subheading The @code{-exec-next-instruction} Command
27926 @findex -exec-next-instruction
27928 @subsubheading Synopsis
27931 -exec-next-instruction [--reverse]
27934 Executes one machine instruction. If the instruction is a function
27935 call, continues until the function returns. If the program stops at an
27936 instruction in the middle of a source line, the address will be
27939 If the @samp{--reverse} option is specified, resumes reverse execution
27940 of the inferior program, stopping at the previous instruction. If the
27941 previously executed instruction was a return from another function,
27942 it will continue to execute in reverse until the call to that function
27943 (from the current stack frame) is reached.
27945 @subsubheading @value{GDBN} Command
27947 The corresponding @value{GDBN} command is @samp{nexti}.
27949 @subsubheading Example
27953 -exec-next-instruction
27957 *stopped,reason="end-stepping-range",
27958 addr="0x000100d4",line="5",file="hello.c"
27963 @subheading The @code{-exec-return} Command
27964 @findex -exec-return
27966 @subsubheading Synopsis
27972 Makes current function return immediately. Doesn't execute the inferior.
27973 Displays the new current frame.
27975 @subsubheading @value{GDBN} Command
27977 The corresponding @value{GDBN} command is @samp{return}.
27979 @subsubheading Example
27983 200-break-insert callee4
27984 200^done,bkpt=@{number="1",addr="0x00010734",
27985 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27990 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27991 frame=@{func="callee4",args=[],
27992 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27993 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27999 111^done,frame=@{level="0",func="callee3",
28000 args=[@{name="strarg",
28001 value="0x11940 \"A string argument.\""@}],
28002 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28003 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28008 @subheading The @code{-exec-run} Command
28011 @subsubheading Synopsis
28014 -exec-run [ --all | --thread-group N ] [ --start ]
28017 Starts execution of the inferior from the beginning. The inferior
28018 executes until either a breakpoint is encountered or the program
28019 exits. In the latter case the output will include an exit code, if
28020 the program has exited exceptionally.
28022 When neither the @samp{--all} nor the @samp{--thread-group} option
28023 is specified, the current inferior is started. If the
28024 @samp{--thread-group} option is specified, it should refer to a thread
28025 group of type @samp{process}, and that thread group will be started.
28026 If the @samp{--all} option is specified, then all inferiors will be started.
28028 Using the @samp{--start} option instructs the debugger to stop
28029 the execution at the start of the inferior's main subprogram,
28030 following the same behavior as the @code{start} command
28031 (@pxref{Starting}).
28033 @subsubheading @value{GDBN} Command
28035 The corresponding @value{GDBN} command is @samp{run}.
28037 @subsubheading Examples
28042 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28047 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28048 frame=@{func="main",args=[],file="recursive2.c",
28049 fullname="/home/foo/bar/recursive2.c",line="4"@}
28054 Program exited normally:
28062 *stopped,reason="exited-normally"
28067 Program exited exceptionally:
28075 *stopped,reason="exited",exit-code="01"
28079 Another way the program can terminate is if it receives a signal such as
28080 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28084 *stopped,reason="exited-signalled",signal-name="SIGINT",
28085 signal-meaning="Interrupt"
28089 @c @subheading -exec-signal
28092 @subheading The @code{-exec-step} Command
28095 @subsubheading Synopsis
28098 -exec-step [--reverse]
28101 Resumes execution of the inferior program, stopping when the beginning
28102 of the next source line is reached, if the next source line is not a
28103 function call. If it is, stop at the first instruction of the called
28104 function. If the @samp{--reverse} option is specified, resumes reverse
28105 execution of the inferior program, stopping at the beginning of the
28106 previously executed source line.
28108 @subsubheading @value{GDBN} Command
28110 The corresponding @value{GDBN} command is @samp{step}.
28112 @subsubheading Example
28114 Stepping into a function:
28120 *stopped,reason="end-stepping-range",
28121 frame=@{func="foo",args=[@{name="a",value="10"@},
28122 @{name="b",value="0"@}],file="recursive2.c",
28123 fullname="/home/foo/bar/recursive2.c",line="11"@}
28133 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28138 @subheading The @code{-exec-step-instruction} Command
28139 @findex -exec-step-instruction
28141 @subsubheading Synopsis
28144 -exec-step-instruction [--reverse]
28147 Resumes the inferior which executes one machine instruction. If the
28148 @samp{--reverse} option is specified, resumes reverse execution of the
28149 inferior program, stopping at the previously executed instruction.
28150 The output, once @value{GDBN} has stopped, will vary depending on
28151 whether we have stopped in the middle of a source line or not. In the
28152 former case, the address at which the program stopped will be printed
28155 @subsubheading @value{GDBN} Command
28157 The corresponding @value{GDBN} command is @samp{stepi}.
28159 @subsubheading Example
28163 -exec-step-instruction
28167 *stopped,reason="end-stepping-range",
28168 frame=@{func="foo",args=[],file="try.c",
28169 fullname="/home/foo/bar/try.c",line="10"@}
28171 -exec-step-instruction
28175 *stopped,reason="end-stepping-range",
28176 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28177 fullname="/home/foo/bar/try.c",line="10"@}
28182 @subheading The @code{-exec-until} Command
28183 @findex -exec-until
28185 @subsubheading Synopsis
28188 -exec-until [ @var{location} ]
28191 Executes the inferior until the @var{location} specified in the
28192 argument is reached. If there is no argument, the inferior executes
28193 until a source line greater than the current one is reached. The
28194 reason for stopping in this case will be @samp{location-reached}.
28196 @subsubheading @value{GDBN} Command
28198 The corresponding @value{GDBN} command is @samp{until}.
28200 @subsubheading Example
28204 -exec-until recursive2.c:6
28208 *stopped,reason="location-reached",frame=@{func="main",args=[],
28209 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28214 @subheading -file-clear
28215 Is this going away????
28218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28219 @node GDB/MI Stack Manipulation
28220 @section @sc{gdb/mi} Stack Manipulation Commands
28222 @subheading The @code{-enable-frame-filters} Command
28223 @findex -enable-frame-filters
28226 -enable-frame-filters
28229 @value{GDBN} allows Python-based frame filters to affect the output of
28230 the MI commands relating to stack traces. As there is no way to
28231 implement this in a fully backward-compatible way, a front end must
28232 request that this functionality be enabled.
28234 Once enabled, this feature cannot be disabled.
28236 Note that if Python support has not been compiled into @value{GDBN},
28237 this command will still succeed (and do nothing).
28239 @subheading The @code{-stack-info-frame} Command
28240 @findex -stack-info-frame
28242 @subsubheading Synopsis
28248 Get info on the selected frame.
28250 @subsubheading @value{GDBN} Command
28252 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28253 (without arguments).
28255 @subsubheading Example
28260 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28261 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28262 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28266 @subheading The @code{-stack-info-depth} Command
28267 @findex -stack-info-depth
28269 @subsubheading Synopsis
28272 -stack-info-depth [ @var{max-depth} ]
28275 Return the depth of the stack. If the integer argument @var{max-depth}
28276 is specified, do not count beyond @var{max-depth} frames.
28278 @subsubheading @value{GDBN} Command
28280 There's no equivalent @value{GDBN} command.
28282 @subsubheading Example
28284 For a stack with frame levels 0 through 11:
28291 -stack-info-depth 4
28294 -stack-info-depth 12
28297 -stack-info-depth 11
28300 -stack-info-depth 13
28305 @anchor{-stack-list-arguments}
28306 @subheading The @code{-stack-list-arguments} Command
28307 @findex -stack-list-arguments
28309 @subsubheading Synopsis
28312 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28313 [ @var{low-frame} @var{high-frame} ]
28316 Display a list of the arguments for the frames between @var{low-frame}
28317 and @var{high-frame} (inclusive). If @var{low-frame} and
28318 @var{high-frame} are not provided, list the arguments for the whole
28319 call stack. If the two arguments are equal, show the single frame
28320 at the corresponding level. It is an error if @var{low-frame} is
28321 larger than the actual number of frames. On the other hand,
28322 @var{high-frame} may be larger than the actual number of frames, in
28323 which case only existing frames will be returned.
28325 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28326 the variables; if it is 1 or @code{--all-values}, print also their
28327 values; and if it is 2 or @code{--simple-values}, print the name,
28328 type and value for simple data types, and the name and type for arrays,
28329 structures and unions. If the option @code{--no-frame-filters} is
28330 supplied, then Python frame filters will not be executed.
28332 If the @code{--skip-unavailable} option is specified, arguments that
28333 are not available are not listed. Partially available arguments
28334 are still displayed, however.
28336 Use of this command to obtain arguments in a single frame is
28337 deprecated in favor of the @samp{-stack-list-variables} command.
28339 @subsubheading @value{GDBN} Command
28341 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28342 @samp{gdb_get_args} command which partially overlaps with the
28343 functionality of @samp{-stack-list-arguments}.
28345 @subsubheading Example
28352 frame=@{level="0",addr="0x00010734",func="callee4",
28353 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28354 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28355 frame=@{level="1",addr="0x0001076c",func="callee3",
28356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28358 frame=@{level="2",addr="0x0001078c",func="callee2",
28359 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28360 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28361 frame=@{level="3",addr="0x000107b4",func="callee1",
28362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28363 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28364 frame=@{level="4",addr="0x000107e0",func="main",
28365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28366 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28368 -stack-list-arguments 0
28371 frame=@{level="0",args=[]@},
28372 frame=@{level="1",args=[name="strarg"]@},
28373 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28374 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28375 frame=@{level="4",args=[]@}]
28377 -stack-list-arguments 1
28380 frame=@{level="0",args=[]@},
28382 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28383 frame=@{level="2",args=[
28384 @{name="intarg",value="2"@},
28385 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28386 @{frame=@{level="3",args=[
28387 @{name="intarg",value="2"@},
28388 @{name="strarg",value="0x11940 \"A string argument.\""@},
28389 @{name="fltarg",value="3.5"@}]@},
28390 frame=@{level="4",args=[]@}]
28392 -stack-list-arguments 0 2 2
28393 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28395 -stack-list-arguments 1 2 2
28396 ^done,stack-args=[frame=@{level="2",
28397 args=[@{name="intarg",value="2"@},
28398 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28402 @c @subheading -stack-list-exception-handlers
28405 @anchor{-stack-list-frames}
28406 @subheading The @code{-stack-list-frames} Command
28407 @findex -stack-list-frames
28409 @subsubheading Synopsis
28412 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28415 List the frames currently on the stack. For each frame it displays the
28420 The frame number, 0 being the topmost frame, i.e., the innermost function.
28422 The @code{$pc} value for that frame.
28426 File name of the source file where the function lives.
28427 @item @var{fullname}
28428 The full file name of the source file where the function lives.
28430 Line number corresponding to the @code{$pc}.
28432 The shared library where this function is defined. This is only given
28433 if the frame's function is not known.
28436 If invoked without arguments, this command prints a backtrace for the
28437 whole stack. If given two integer arguments, it shows the frames whose
28438 levels are between the two arguments (inclusive). If the two arguments
28439 are equal, it shows the single frame at the corresponding level. It is
28440 an error if @var{low-frame} is larger than the actual number of
28441 frames. On the other hand, @var{high-frame} may be larger than the
28442 actual number of frames, in which case only existing frames will be
28443 returned. If the option @code{--no-frame-filters} is supplied, then
28444 Python frame filters will not be executed.
28446 @subsubheading @value{GDBN} Command
28448 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28450 @subsubheading Example
28452 Full stack backtrace:
28458 [frame=@{level="0",addr="0x0001076c",func="foo",
28459 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28460 frame=@{level="1",addr="0x000107a4",func="foo",
28461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28462 frame=@{level="2",addr="0x000107a4",func="foo",
28463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28464 frame=@{level="3",addr="0x000107a4",func="foo",
28465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28466 frame=@{level="4",addr="0x000107a4",func="foo",
28467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28468 frame=@{level="5",addr="0x000107a4",func="foo",
28469 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28470 frame=@{level="6",addr="0x000107a4",func="foo",
28471 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28472 frame=@{level="7",addr="0x000107a4",func="foo",
28473 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28474 frame=@{level="8",addr="0x000107a4",func="foo",
28475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28476 frame=@{level="9",addr="0x000107a4",func="foo",
28477 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28478 frame=@{level="10",addr="0x000107a4",func="foo",
28479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28480 frame=@{level="11",addr="0x00010738",func="main",
28481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28485 Show frames between @var{low_frame} and @var{high_frame}:
28489 -stack-list-frames 3 5
28491 [frame=@{level="3",addr="0x000107a4",func="foo",
28492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28493 frame=@{level="4",addr="0x000107a4",func="foo",
28494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28495 frame=@{level="5",addr="0x000107a4",func="foo",
28496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28500 Show a single frame:
28504 -stack-list-frames 3 3
28506 [frame=@{level="3",addr="0x000107a4",func="foo",
28507 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28512 @subheading The @code{-stack-list-locals} Command
28513 @findex -stack-list-locals
28514 @anchor{-stack-list-locals}
28516 @subsubheading Synopsis
28519 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28522 Display the local variable names for the selected frame. If
28523 @var{print-values} is 0 or @code{--no-values}, print only the names of
28524 the variables; if it is 1 or @code{--all-values}, print also their
28525 values; and if it is 2 or @code{--simple-values}, print the name,
28526 type and value for simple data types, and the name and type for arrays,
28527 structures and unions. In this last case, a frontend can immediately
28528 display the value of simple data types and create variable objects for
28529 other data types when the user wishes to explore their values in
28530 more detail. If the option @code{--no-frame-filters} is supplied, then
28531 Python frame filters will not be executed.
28533 If the @code{--skip-unavailable} option is specified, local variables
28534 that are not available are not listed. Partially available local
28535 variables are still displayed, however.
28537 This command is deprecated in favor of the
28538 @samp{-stack-list-variables} command.
28540 @subsubheading @value{GDBN} Command
28542 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28544 @subsubheading Example
28548 -stack-list-locals 0
28549 ^done,locals=[name="A",name="B",name="C"]
28551 -stack-list-locals --all-values
28552 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28553 @{name="C",value="@{1, 2, 3@}"@}]
28554 -stack-list-locals --simple-values
28555 ^done,locals=[@{name="A",type="int",value="1"@},
28556 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28560 @anchor{-stack-list-variables}
28561 @subheading The @code{-stack-list-variables} Command
28562 @findex -stack-list-variables
28564 @subsubheading Synopsis
28567 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28570 Display the names of local variables and function arguments for the selected frame. If
28571 @var{print-values} is 0 or @code{--no-values}, print only the names of
28572 the variables; if it is 1 or @code{--all-values}, print also their
28573 values; and if it is 2 or @code{--simple-values}, print the name,
28574 type and value for simple data types, and the name and type for arrays,
28575 structures and unions. If the option @code{--no-frame-filters} is
28576 supplied, then Python frame filters will not be executed.
28578 If the @code{--skip-unavailable} option is specified, local variables
28579 and arguments that are not available are not listed. Partially
28580 available arguments and local variables are still displayed, however.
28582 @subsubheading Example
28586 -stack-list-variables --thread 1 --frame 0 --all-values
28587 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28592 @subheading The @code{-stack-select-frame} Command
28593 @findex -stack-select-frame
28595 @subsubheading Synopsis
28598 -stack-select-frame @var{framenum}
28601 Change the selected frame. Select a different frame @var{framenum} on
28604 This command in deprecated in favor of passing the @samp{--frame}
28605 option to every command.
28607 @subsubheading @value{GDBN} Command
28609 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28610 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28612 @subsubheading Example
28616 -stack-select-frame 2
28621 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28622 @node GDB/MI Variable Objects
28623 @section @sc{gdb/mi} Variable Objects
28627 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28629 For the implementation of a variable debugger window (locals, watched
28630 expressions, etc.), we are proposing the adaptation of the existing code
28631 used by @code{Insight}.
28633 The two main reasons for that are:
28637 It has been proven in practice (it is already on its second generation).
28640 It will shorten development time (needless to say how important it is
28644 The original interface was designed to be used by Tcl code, so it was
28645 slightly changed so it could be used through @sc{gdb/mi}. This section
28646 describes the @sc{gdb/mi} operations that will be available and gives some
28647 hints about their use.
28649 @emph{Note}: In addition to the set of operations described here, we
28650 expect the @sc{gui} implementation of a variable window to require, at
28651 least, the following operations:
28654 @item @code{-gdb-show} @code{output-radix}
28655 @item @code{-stack-list-arguments}
28656 @item @code{-stack-list-locals}
28657 @item @code{-stack-select-frame}
28662 @subheading Introduction to Variable Objects
28664 @cindex variable objects in @sc{gdb/mi}
28666 Variable objects are "object-oriented" MI interface for examining and
28667 changing values of expressions. Unlike some other MI interfaces that
28668 work with expressions, variable objects are specifically designed for
28669 simple and efficient presentation in the frontend. A variable object
28670 is identified by string name. When a variable object is created, the
28671 frontend specifies the expression for that variable object. The
28672 expression can be a simple variable, or it can be an arbitrary complex
28673 expression, and can even involve CPU registers. After creating a
28674 variable object, the frontend can invoke other variable object
28675 operations---for example to obtain or change the value of a variable
28676 object, or to change display format.
28678 Variable objects have hierarchical tree structure. Any variable object
28679 that corresponds to a composite type, such as structure in C, has
28680 a number of child variable objects, for example corresponding to each
28681 element of a structure. A child variable object can itself have
28682 children, recursively. Recursion ends when we reach
28683 leaf variable objects, which always have built-in types. Child variable
28684 objects are created only by explicit request, so if a frontend
28685 is not interested in the children of a particular variable object, no
28686 child will be created.
28688 For a leaf variable object it is possible to obtain its value as a
28689 string, or set the value from a string. String value can be also
28690 obtained for a non-leaf variable object, but it's generally a string
28691 that only indicates the type of the object, and does not list its
28692 contents. Assignment to a non-leaf variable object is not allowed.
28694 A frontend does not need to read the values of all variable objects each time
28695 the program stops. Instead, MI provides an update command that lists all
28696 variable objects whose values has changed since the last update
28697 operation. This considerably reduces the amount of data that must
28698 be transferred to the frontend. As noted above, children variable
28699 objects are created on demand, and only leaf variable objects have a
28700 real value. As result, gdb will read target memory only for leaf
28701 variables that frontend has created.
28703 The automatic update is not always desirable. For example, a frontend
28704 might want to keep a value of some expression for future reference,
28705 and never update it. For another example, fetching memory is
28706 relatively slow for embedded targets, so a frontend might want
28707 to disable automatic update for the variables that are either not
28708 visible on the screen, or ``closed''. This is possible using so
28709 called ``frozen variable objects''. Such variable objects are never
28710 implicitly updated.
28712 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28713 fixed variable object, the expression is parsed when the variable
28714 object is created, including associating identifiers to specific
28715 variables. The meaning of expression never changes. For a floating
28716 variable object the values of variables whose names appear in the
28717 expressions are re-evaluated every time in the context of the current
28718 frame. Consider this example:
28723 struct work_state state;
28730 If a fixed variable object for the @code{state} variable is created in
28731 this function, and we enter the recursive call, the variable
28732 object will report the value of @code{state} in the top-level
28733 @code{do_work} invocation. On the other hand, a floating variable
28734 object will report the value of @code{state} in the current frame.
28736 If an expression specified when creating a fixed variable object
28737 refers to a local variable, the variable object becomes bound to the
28738 thread and frame in which the variable object is created. When such
28739 variable object is updated, @value{GDBN} makes sure that the
28740 thread/frame combination the variable object is bound to still exists,
28741 and re-evaluates the variable object in context of that thread/frame.
28743 The following is the complete set of @sc{gdb/mi} operations defined to
28744 access this functionality:
28746 @multitable @columnfractions .4 .6
28747 @item @strong{Operation}
28748 @tab @strong{Description}
28750 @item @code{-enable-pretty-printing}
28751 @tab enable Python-based pretty-printing
28752 @item @code{-var-create}
28753 @tab create a variable object
28754 @item @code{-var-delete}
28755 @tab delete the variable object and/or its children
28756 @item @code{-var-set-format}
28757 @tab set the display format of this variable
28758 @item @code{-var-show-format}
28759 @tab show the display format of this variable
28760 @item @code{-var-info-num-children}
28761 @tab tells how many children this object has
28762 @item @code{-var-list-children}
28763 @tab return a list of the object's children
28764 @item @code{-var-info-type}
28765 @tab show the type of this variable object
28766 @item @code{-var-info-expression}
28767 @tab print parent-relative expression that this variable object represents
28768 @item @code{-var-info-path-expression}
28769 @tab print full expression that this variable object represents
28770 @item @code{-var-show-attributes}
28771 @tab is this variable editable? does it exist here?
28772 @item @code{-var-evaluate-expression}
28773 @tab get the value of this variable
28774 @item @code{-var-assign}
28775 @tab set the value of this variable
28776 @item @code{-var-update}
28777 @tab update the variable and its children
28778 @item @code{-var-set-frozen}
28779 @tab set frozeness attribute
28780 @item @code{-var-set-update-range}
28781 @tab set range of children to display on update
28784 In the next subsection we describe each operation in detail and suggest
28785 how it can be used.
28787 @subheading Description And Use of Operations on Variable Objects
28789 @subheading The @code{-enable-pretty-printing} Command
28790 @findex -enable-pretty-printing
28793 -enable-pretty-printing
28796 @value{GDBN} allows Python-based visualizers to affect the output of the
28797 MI variable object commands. However, because there was no way to
28798 implement this in a fully backward-compatible way, a front end must
28799 request that this functionality be enabled.
28801 Once enabled, this feature cannot be disabled.
28803 Note that if Python support has not been compiled into @value{GDBN},
28804 this command will still succeed (and do nothing).
28806 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28807 may work differently in future versions of @value{GDBN}.
28809 @subheading The @code{-var-create} Command
28810 @findex -var-create
28812 @subsubheading Synopsis
28815 -var-create @{@var{name} | "-"@}
28816 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28819 This operation creates a variable object, which allows the monitoring of
28820 a variable, the result of an expression, a memory cell or a CPU
28823 The @var{name} parameter is the string by which the object can be
28824 referenced. It must be unique. If @samp{-} is specified, the varobj
28825 system will generate a string ``varNNNNNN'' automatically. It will be
28826 unique provided that one does not specify @var{name} of that format.
28827 The command fails if a duplicate name is found.
28829 The frame under which the expression should be evaluated can be
28830 specified by @var{frame-addr}. A @samp{*} indicates that the current
28831 frame should be used. A @samp{@@} indicates that a floating variable
28832 object must be created.
28834 @var{expression} is any expression valid on the current language set (must not
28835 begin with a @samp{*}), or one of the following:
28839 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28842 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28845 @samp{$@var{regname}} --- a CPU register name
28848 @cindex dynamic varobj
28849 A varobj's contents may be provided by a Python-based pretty-printer. In this
28850 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28851 have slightly different semantics in some cases. If the
28852 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28853 will never create a dynamic varobj. This ensures backward
28854 compatibility for existing clients.
28856 @subsubheading Result
28858 This operation returns attributes of the newly-created varobj. These
28863 The name of the varobj.
28866 The number of children of the varobj. This number is not necessarily
28867 reliable for a dynamic varobj. Instead, you must examine the
28868 @samp{has_more} attribute.
28871 The varobj's scalar value. For a varobj whose type is some sort of
28872 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28873 will not be interesting.
28876 The varobj's type. This is a string representation of the type, as
28877 would be printed by the @value{GDBN} CLI. If @samp{print object}
28878 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28879 @emph{actual} (derived) type of the object is shown rather than the
28880 @emph{declared} one.
28883 If a variable object is bound to a specific thread, then this is the
28884 thread's identifier.
28887 For a dynamic varobj, this indicates whether there appear to be any
28888 children available. For a non-dynamic varobj, this will be 0.
28891 This attribute will be present and have the value @samp{1} if the
28892 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28893 then this attribute will not be present.
28896 A dynamic varobj can supply a display hint to the front end. The
28897 value comes directly from the Python pretty-printer object's
28898 @code{display_hint} method. @xref{Pretty Printing API}.
28901 Typical output will look like this:
28904 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28905 has_more="@var{has_more}"
28909 @subheading The @code{-var-delete} Command
28910 @findex -var-delete
28912 @subsubheading Synopsis
28915 -var-delete [ -c ] @var{name}
28918 Deletes a previously created variable object and all of its children.
28919 With the @samp{-c} option, just deletes the children.
28921 Returns an error if the object @var{name} is not found.
28924 @subheading The @code{-var-set-format} Command
28925 @findex -var-set-format
28927 @subsubheading Synopsis
28930 -var-set-format @var{name} @var{format-spec}
28933 Sets the output format for the value of the object @var{name} to be
28936 @anchor{-var-set-format}
28937 The syntax for the @var{format-spec} is as follows:
28940 @var{format-spec} @expansion{}
28941 @{binary | decimal | hexadecimal | octal | natural@}
28944 The natural format is the default format choosen automatically
28945 based on the variable type (like decimal for an @code{int}, hex
28946 for pointers, etc.).
28948 For a variable with children, the format is set only on the
28949 variable itself, and the children are not affected.
28951 @subheading The @code{-var-show-format} Command
28952 @findex -var-show-format
28954 @subsubheading Synopsis
28957 -var-show-format @var{name}
28960 Returns the format used to display the value of the object @var{name}.
28963 @var{format} @expansion{}
28968 @subheading The @code{-var-info-num-children} Command
28969 @findex -var-info-num-children
28971 @subsubheading Synopsis
28974 -var-info-num-children @var{name}
28977 Returns the number of children of a variable object @var{name}:
28983 Note that this number is not completely reliable for a dynamic varobj.
28984 It will return the current number of children, but more children may
28988 @subheading The @code{-var-list-children} Command
28989 @findex -var-list-children
28991 @subsubheading Synopsis
28994 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28996 @anchor{-var-list-children}
28998 Return a list of the children of the specified variable object and
28999 create variable objects for them, if they do not already exist. With
29000 a single argument or if @var{print-values} has a value of 0 or
29001 @code{--no-values}, print only the names of the variables; if
29002 @var{print-values} is 1 or @code{--all-values}, also print their
29003 values; and if it is 2 or @code{--simple-values} print the name and
29004 value for simple data types and just the name for arrays, structures
29007 @var{from} and @var{to}, if specified, indicate the range of children
29008 to report. If @var{from} or @var{to} is less than zero, the range is
29009 reset and all children will be reported. Otherwise, children starting
29010 at @var{from} (zero-based) and up to and excluding @var{to} will be
29013 If a child range is requested, it will only affect the current call to
29014 @code{-var-list-children}, but not future calls to @code{-var-update}.
29015 For this, you must instead use @code{-var-set-update-range}. The
29016 intent of this approach is to enable a front end to implement any
29017 update approach it likes; for example, scrolling a view may cause the
29018 front end to request more children with @code{-var-list-children}, and
29019 then the front end could call @code{-var-set-update-range} with a
29020 different range to ensure that future updates are restricted to just
29023 For each child the following results are returned:
29028 Name of the variable object created for this child.
29031 The expression to be shown to the user by the front end to designate this child.
29032 For example this may be the name of a structure member.
29034 For a dynamic varobj, this value cannot be used to form an
29035 expression. There is no way to do this at all with a dynamic varobj.
29037 For C/C@t{++} structures there are several pseudo children returned to
29038 designate access qualifiers. For these pseudo children @var{exp} is
29039 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29040 type and value are not present.
29042 A dynamic varobj will not report the access qualifying
29043 pseudo-children, regardless of the language. This information is not
29044 available at all with a dynamic varobj.
29047 Number of children this child has. For a dynamic varobj, this will be
29051 The type of the child. If @samp{print object}
29052 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29053 @emph{actual} (derived) type of the object is shown rather than the
29054 @emph{declared} one.
29057 If values were requested, this is the value.
29060 If this variable object is associated with a thread, this is the thread id.
29061 Otherwise this result is not present.
29064 If the variable object is frozen, this variable will be present with a value of 1.
29067 A dynamic varobj can supply a display hint to the front end. The
29068 value comes directly from the Python pretty-printer object's
29069 @code{display_hint} method. @xref{Pretty Printing API}.
29072 This attribute will be present and have the value @samp{1} if the
29073 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29074 then this attribute will not be present.
29078 The result may have its own attributes:
29082 A dynamic varobj can supply a display hint to the front end. The
29083 value comes directly from the Python pretty-printer object's
29084 @code{display_hint} method. @xref{Pretty Printing API}.
29087 This is an integer attribute which is nonzero if there are children
29088 remaining after the end of the selected range.
29091 @subsubheading Example
29095 -var-list-children n
29096 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29097 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29099 -var-list-children --all-values n
29100 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29101 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29105 @subheading The @code{-var-info-type} Command
29106 @findex -var-info-type
29108 @subsubheading Synopsis
29111 -var-info-type @var{name}
29114 Returns the type of the specified variable @var{name}. The type is
29115 returned as a string in the same format as it is output by the
29119 type=@var{typename}
29123 @subheading The @code{-var-info-expression} Command
29124 @findex -var-info-expression
29126 @subsubheading Synopsis
29129 -var-info-expression @var{name}
29132 Returns a string that is suitable for presenting this
29133 variable object in user interface. The string is generally
29134 not valid expression in the current language, and cannot be evaluated.
29136 For example, if @code{a} is an array, and variable object
29137 @code{A} was created for @code{a}, then we'll get this output:
29140 (gdb) -var-info-expression A.1
29141 ^done,lang="C",exp="1"
29145 Here, the value of @code{lang} is the language name, which can be
29146 found in @ref{Supported Languages}.
29148 Note that the output of the @code{-var-list-children} command also
29149 includes those expressions, so the @code{-var-info-expression} command
29152 @subheading The @code{-var-info-path-expression} Command
29153 @findex -var-info-path-expression
29155 @subsubheading Synopsis
29158 -var-info-path-expression @var{name}
29161 Returns an expression that can be evaluated in the current
29162 context and will yield the same value that a variable object has.
29163 Compare this with the @code{-var-info-expression} command, which
29164 result can be used only for UI presentation. Typical use of
29165 the @code{-var-info-path-expression} command is creating a
29166 watchpoint from a variable object.
29168 This command is currently not valid for children of a dynamic varobj,
29169 and will give an error when invoked on one.
29171 For example, suppose @code{C} is a C@t{++} class, derived from class
29172 @code{Base}, and that the @code{Base} class has a member called
29173 @code{m_size}. Assume a variable @code{c} is has the type of
29174 @code{C} and a variable object @code{C} was created for variable
29175 @code{c}. Then, we'll get this output:
29177 (gdb) -var-info-path-expression C.Base.public.m_size
29178 ^done,path_expr=((Base)c).m_size)
29181 @subheading The @code{-var-show-attributes} Command
29182 @findex -var-show-attributes
29184 @subsubheading Synopsis
29187 -var-show-attributes @var{name}
29190 List attributes of the specified variable object @var{name}:
29193 status=@var{attr} [ ( ,@var{attr} )* ]
29197 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29199 @subheading The @code{-var-evaluate-expression} Command
29200 @findex -var-evaluate-expression
29202 @subsubheading Synopsis
29205 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29208 Evaluates the expression that is represented by the specified variable
29209 object and returns its value as a string. The format of the string
29210 can be specified with the @samp{-f} option. The possible values of
29211 this option are the same as for @code{-var-set-format}
29212 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29213 the current display format will be used. The current display format
29214 can be changed using the @code{-var-set-format} command.
29220 Note that one must invoke @code{-var-list-children} for a variable
29221 before the value of a child variable can be evaluated.
29223 @subheading The @code{-var-assign} Command
29224 @findex -var-assign
29226 @subsubheading Synopsis
29229 -var-assign @var{name} @var{expression}
29232 Assigns the value of @var{expression} to the variable object specified
29233 by @var{name}. The object must be @samp{editable}. If the variable's
29234 value is altered by the assign, the variable will show up in any
29235 subsequent @code{-var-update} list.
29237 @subsubheading Example
29245 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29249 @subheading The @code{-var-update} Command
29250 @findex -var-update
29252 @subsubheading Synopsis
29255 -var-update [@var{print-values}] @{@var{name} | "*"@}
29258 Reevaluate the expressions corresponding to the variable object
29259 @var{name} and all its direct and indirect children, and return the
29260 list of variable objects whose values have changed; @var{name} must
29261 be a root variable object. Here, ``changed'' means that the result of
29262 @code{-var-evaluate-expression} before and after the
29263 @code{-var-update} is different. If @samp{*} is used as the variable
29264 object names, all existing variable objects are updated, except
29265 for frozen ones (@pxref{-var-set-frozen}). The option
29266 @var{print-values} determines whether both names and values, or just
29267 names are printed. The possible values of this option are the same
29268 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29269 recommended to use the @samp{--all-values} option, to reduce the
29270 number of MI commands needed on each program stop.
29272 With the @samp{*} parameter, if a variable object is bound to a
29273 currently running thread, it will not be updated, without any
29276 If @code{-var-set-update-range} was previously used on a varobj, then
29277 only the selected range of children will be reported.
29279 @code{-var-update} reports all the changed varobjs in a tuple named
29282 Each item in the change list is itself a tuple holding:
29286 The name of the varobj.
29289 If values were requested for this update, then this field will be
29290 present and will hold the value of the varobj.
29293 @anchor{-var-update}
29294 This field is a string which may take one of three values:
29298 The variable object's current value is valid.
29301 The variable object does not currently hold a valid value but it may
29302 hold one in the future if its associated expression comes back into
29306 The variable object no longer holds a valid value.
29307 This can occur when the executable file being debugged has changed,
29308 either through recompilation or by using the @value{GDBN} @code{file}
29309 command. The front end should normally choose to delete these variable
29313 In the future new values may be added to this list so the front should
29314 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29317 This is only present if the varobj is still valid. If the type
29318 changed, then this will be the string @samp{true}; otherwise it will
29321 When a varobj's type changes, its children are also likely to have
29322 become incorrect. Therefore, the varobj's children are automatically
29323 deleted when this attribute is @samp{true}. Also, the varobj's update
29324 range, when set using the @code{-var-set-update-range} command, is
29328 If the varobj's type changed, then this field will be present and will
29331 @item new_num_children
29332 For a dynamic varobj, if the number of children changed, or if the
29333 type changed, this will be the new number of children.
29335 The @samp{numchild} field in other varobj responses is generally not
29336 valid for a dynamic varobj -- it will show the number of children that
29337 @value{GDBN} knows about, but because dynamic varobjs lazily
29338 instantiate their children, this will not reflect the number of
29339 children which may be available.
29341 The @samp{new_num_children} attribute only reports changes to the
29342 number of children known by @value{GDBN}. This is the only way to
29343 detect whether an update has removed children (which necessarily can
29344 only happen at the end of the update range).
29347 The display hint, if any.
29350 This is an integer value, which will be 1 if there are more children
29351 available outside the varobj's update range.
29354 This attribute will be present and have the value @samp{1} if the
29355 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29356 then this attribute will not be present.
29359 If new children were added to a dynamic varobj within the selected
29360 update range (as set by @code{-var-set-update-range}), then they will
29361 be listed in this attribute.
29364 @subsubheading Example
29371 -var-update --all-values var1
29372 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29373 type_changed="false"@}]
29377 @subheading The @code{-var-set-frozen} Command
29378 @findex -var-set-frozen
29379 @anchor{-var-set-frozen}
29381 @subsubheading Synopsis
29384 -var-set-frozen @var{name} @var{flag}
29387 Set the frozenness flag on the variable object @var{name}. The
29388 @var{flag} parameter should be either @samp{1} to make the variable
29389 frozen or @samp{0} to make it unfrozen. If a variable object is
29390 frozen, then neither itself, nor any of its children, are
29391 implicitly updated by @code{-var-update} of
29392 a parent variable or by @code{-var-update *}. Only
29393 @code{-var-update} of the variable itself will update its value and
29394 values of its children. After a variable object is unfrozen, it is
29395 implicitly updated by all subsequent @code{-var-update} operations.
29396 Unfreezing a variable does not update it, only subsequent
29397 @code{-var-update} does.
29399 @subsubheading Example
29403 -var-set-frozen V 1
29408 @subheading The @code{-var-set-update-range} command
29409 @findex -var-set-update-range
29410 @anchor{-var-set-update-range}
29412 @subsubheading Synopsis
29415 -var-set-update-range @var{name} @var{from} @var{to}
29418 Set the range of children to be returned by future invocations of
29419 @code{-var-update}.
29421 @var{from} and @var{to} indicate the range of children to report. If
29422 @var{from} or @var{to} is less than zero, the range is reset and all
29423 children will be reported. Otherwise, children starting at @var{from}
29424 (zero-based) and up to and excluding @var{to} will be reported.
29426 @subsubheading Example
29430 -var-set-update-range V 1 2
29434 @subheading The @code{-var-set-visualizer} command
29435 @findex -var-set-visualizer
29436 @anchor{-var-set-visualizer}
29438 @subsubheading Synopsis
29441 -var-set-visualizer @var{name} @var{visualizer}
29444 Set a visualizer for the variable object @var{name}.
29446 @var{visualizer} is the visualizer to use. The special value
29447 @samp{None} means to disable any visualizer in use.
29449 If not @samp{None}, @var{visualizer} must be a Python expression.
29450 This expression must evaluate to a callable object which accepts a
29451 single argument. @value{GDBN} will call this object with the value of
29452 the varobj @var{name} as an argument (this is done so that the same
29453 Python pretty-printing code can be used for both the CLI and MI).
29454 When called, this object must return an object which conforms to the
29455 pretty-printing interface (@pxref{Pretty Printing API}).
29457 The pre-defined function @code{gdb.default_visualizer} may be used to
29458 select a visualizer by following the built-in process
29459 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29460 a varobj is created, and so ordinarily is not needed.
29462 This feature is only available if Python support is enabled. The MI
29463 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29464 can be used to check this.
29466 @subsubheading Example
29468 Resetting the visualizer:
29472 -var-set-visualizer V None
29476 Reselecting the default (type-based) visualizer:
29480 -var-set-visualizer V gdb.default_visualizer
29484 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29485 can be used to instantiate this class for a varobj:
29489 -var-set-visualizer V "lambda val: SomeClass()"
29493 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29494 @node GDB/MI Data Manipulation
29495 @section @sc{gdb/mi} Data Manipulation
29497 @cindex data manipulation, in @sc{gdb/mi}
29498 @cindex @sc{gdb/mi}, data manipulation
29499 This section describes the @sc{gdb/mi} commands that manipulate data:
29500 examine memory and registers, evaluate expressions, etc.
29502 @c REMOVED FROM THE INTERFACE.
29503 @c @subheading -data-assign
29504 @c Change the value of a program variable. Plenty of side effects.
29505 @c @subsubheading GDB Command
29507 @c @subsubheading Example
29510 @subheading The @code{-data-disassemble} Command
29511 @findex -data-disassemble
29513 @subsubheading Synopsis
29517 [ -s @var{start-addr} -e @var{end-addr} ]
29518 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29526 @item @var{start-addr}
29527 is the beginning address (or @code{$pc})
29528 @item @var{end-addr}
29530 @item @var{filename}
29531 is the name of the file to disassemble
29532 @item @var{linenum}
29533 is the line number to disassemble around
29535 is the number of disassembly lines to be produced. If it is -1,
29536 the whole function will be disassembled, in case no @var{end-addr} is
29537 specified. If @var{end-addr} is specified as a non-zero value, and
29538 @var{lines} is lower than the number of disassembly lines between
29539 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29540 displayed; if @var{lines} is higher than the number of lines between
29541 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29544 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29545 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29546 mixed source and disassembly with raw opcodes).
29549 @subsubheading Result
29551 The result of the @code{-data-disassemble} command will be a list named
29552 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29553 used with the @code{-data-disassemble} command.
29555 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29560 The address at which this instruction was disassembled.
29563 The name of the function this instruction is within.
29566 The decimal offset in bytes from the start of @samp{func-name}.
29569 The text disassembly for this @samp{address}.
29572 This field is only present for mode 2. This contains the raw opcode
29573 bytes for the @samp{inst} field.
29577 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29578 @samp{src_and_asm_line}, each of which has the following fields:
29582 The line number within @samp{file}.
29585 The file name from the compilation unit. This might be an absolute
29586 file name or a relative file name depending on the compile command
29590 Absolute file name of @samp{file}. It is converted to a canonical form
29591 using the source file search path
29592 (@pxref{Source Path, ,Specifying Source Directories})
29593 and after resolving all the symbolic links.
29595 If the source file is not found this field will contain the path as
29596 present in the debug information.
29598 @item line_asm_insn
29599 This is a list of tuples containing the disassembly for @samp{line} in
29600 @samp{file}. The fields of each tuple are the same as for
29601 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29602 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29607 Note that whatever included in the @samp{inst} field, is not
29608 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29611 @subsubheading @value{GDBN} Command
29613 The corresponding @value{GDBN} command is @samp{disassemble}.
29615 @subsubheading Example
29617 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29621 -data-disassemble -s $pc -e "$pc + 20" -- 0
29624 @{address="0x000107c0",func-name="main",offset="4",
29625 inst="mov 2, %o0"@},
29626 @{address="0x000107c4",func-name="main",offset="8",
29627 inst="sethi %hi(0x11800), %o2"@},
29628 @{address="0x000107c8",func-name="main",offset="12",
29629 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29630 @{address="0x000107cc",func-name="main",offset="16",
29631 inst="sethi %hi(0x11800), %o2"@},
29632 @{address="0x000107d0",func-name="main",offset="20",
29633 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29637 Disassemble the whole @code{main} function. Line 32 is part of
29641 -data-disassemble -f basics.c -l 32 -- 0
29643 @{address="0x000107bc",func-name="main",offset="0",
29644 inst="save %sp, -112, %sp"@},
29645 @{address="0x000107c0",func-name="main",offset="4",
29646 inst="mov 2, %o0"@},
29647 @{address="0x000107c4",func-name="main",offset="8",
29648 inst="sethi %hi(0x11800), %o2"@},
29650 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29651 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29655 Disassemble 3 instructions from the start of @code{main}:
29659 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29661 @{address="0x000107bc",func-name="main",offset="0",
29662 inst="save %sp, -112, %sp"@},
29663 @{address="0x000107c0",func-name="main",offset="4",
29664 inst="mov 2, %o0"@},
29665 @{address="0x000107c4",func-name="main",offset="8",
29666 inst="sethi %hi(0x11800), %o2"@}]
29670 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29674 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29676 src_and_asm_line=@{line="31",
29677 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29678 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29679 line_asm_insn=[@{address="0x000107bc",
29680 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29681 src_and_asm_line=@{line="32",
29682 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29683 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29684 line_asm_insn=[@{address="0x000107c0",
29685 func-name="main",offset="4",inst="mov 2, %o0"@},
29686 @{address="0x000107c4",func-name="main",offset="8",
29687 inst="sethi %hi(0x11800), %o2"@}]@}]
29692 @subheading The @code{-data-evaluate-expression} Command
29693 @findex -data-evaluate-expression
29695 @subsubheading Synopsis
29698 -data-evaluate-expression @var{expr}
29701 Evaluate @var{expr} as an expression. The expression could contain an
29702 inferior function call. The function call will execute synchronously.
29703 If the expression contains spaces, it must be enclosed in double quotes.
29705 @subsubheading @value{GDBN} Command
29707 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29708 @samp{call}. In @code{gdbtk} only, there's a corresponding
29709 @samp{gdb_eval} command.
29711 @subsubheading Example
29713 In the following example, the numbers that precede the commands are the
29714 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29715 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29719 211-data-evaluate-expression A
29722 311-data-evaluate-expression &A
29723 311^done,value="0xefffeb7c"
29725 411-data-evaluate-expression A+3
29728 511-data-evaluate-expression "A + 3"
29734 @subheading The @code{-data-list-changed-registers} Command
29735 @findex -data-list-changed-registers
29737 @subsubheading Synopsis
29740 -data-list-changed-registers
29743 Display a list of the registers that have changed.
29745 @subsubheading @value{GDBN} Command
29747 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29748 has the corresponding command @samp{gdb_changed_register_list}.
29750 @subsubheading Example
29752 On a PPC MBX board:
29760 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29761 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29764 -data-list-changed-registers
29765 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29766 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29767 "24","25","26","27","28","30","31","64","65","66","67","69"]
29772 @subheading The @code{-data-list-register-names} Command
29773 @findex -data-list-register-names
29775 @subsubheading Synopsis
29778 -data-list-register-names [ ( @var{regno} )+ ]
29781 Show a list of register names for the current target. If no arguments
29782 are given, it shows a list of the names of all the registers. If
29783 integer numbers are given as arguments, it will print a list of the
29784 names of the registers corresponding to the arguments. To ensure
29785 consistency between a register name and its number, the output list may
29786 include empty register names.
29788 @subsubheading @value{GDBN} Command
29790 @value{GDBN} does not have a command which corresponds to
29791 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29792 corresponding command @samp{gdb_regnames}.
29794 @subsubheading Example
29796 For the PPC MBX board:
29799 -data-list-register-names
29800 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29801 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29802 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29803 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29804 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29805 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29806 "", "pc","ps","cr","lr","ctr","xer"]
29808 -data-list-register-names 1 2 3
29809 ^done,register-names=["r1","r2","r3"]
29813 @subheading The @code{-data-list-register-values} Command
29814 @findex -data-list-register-values
29816 @subsubheading Synopsis
29819 -data-list-register-values
29820 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29823 Display the registers' contents. The format according to which the
29824 registers' contents are to be returned is given by @var{fmt}, followed
29825 by an optional list of numbers specifying the registers to display. A
29826 missing list of numbers indicates that the contents of all the
29827 registers must be returned. The @code{--skip-unavailable} option
29828 indicates that only the available registers are to be returned.
29830 Allowed formats for @var{fmt} are:
29847 @subsubheading @value{GDBN} Command
29849 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29850 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29852 @subsubheading Example
29854 For a PPC MBX board (note: line breaks are for readability only, they
29855 don't appear in the actual output):
29859 -data-list-register-values r 64 65
29860 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29861 @{number="65",value="0x00029002"@}]
29863 -data-list-register-values x
29864 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29865 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29866 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29867 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29868 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29869 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29870 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29871 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29872 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29873 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29874 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29875 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29876 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29877 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29878 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29879 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29880 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29881 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29882 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29883 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29884 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29885 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29886 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29887 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29888 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29889 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29890 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29891 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29892 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29893 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29894 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29895 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29896 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29897 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29898 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29899 @{number="69",value="0x20002b03"@}]
29904 @subheading The @code{-data-read-memory} Command
29905 @findex -data-read-memory
29907 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29909 @subsubheading Synopsis
29912 -data-read-memory [ -o @var{byte-offset} ]
29913 @var{address} @var{word-format} @var{word-size}
29914 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29921 @item @var{address}
29922 An expression specifying the address of the first memory word to be
29923 read. Complex expressions containing embedded white space should be
29924 quoted using the C convention.
29926 @item @var{word-format}
29927 The format to be used to print the memory words. The notation is the
29928 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29931 @item @var{word-size}
29932 The size of each memory word in bytes.
29934 @item @var{nr-rows}
29935 The number of rows in the output table.
29937 @item @var{nr-cols}
29938 The number of columns in the output table.
29941 If present, indicates that each row should include an @sc{ascii} dump. The
29942 value of @var{aschar} is used as a padding character when a byte is not a
29943 member of the printable @sc{ascii} character set (printable @sc{ascii}
29944 characters are those whose code is between 32 and 126, inclusively).
29946 @item @var{byte-offset}
29947 An offset to add to the @var{address} before fetching memory.
29950 This command displays memory contents as a table of @var{nr-rows} by
29951 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29952 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29953 (returned as @samp{total-bytes}). Should less than the requested number
29954 of bytes be returned by the target, the missing words are identified
29955 using @samp{N/A}. The number of bytes read from the target is returned
29956 in @samp{nr-bytes} and the starting address used to read memory in
29959 The address of the next/previous row or page is available in
29960 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29963 @subsubheading @value{GDBN} Command
29965 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29966 @samp{gdb_get_mem} memory read command.
29968 @subsubheading Example
29970 Read six bytes of memory starting at @code{bytes+6} but then offset by
29971 @code{-6} bytes. Format as three rows of two columns. One byte per
29972 word. Display each word in hex.
29976 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29977 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29978 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29979 prev-page="0x0000138a",memory=[
29980 @{addr="0x00001390",data=["0x00","0x01"]@},
29981 @{addr="0x00001392",data=["0x02","0x03"]@},
29982 @{addr="0x00001394",data=["0x04","0x05"]@}]
29986 Read two bytes of memory starting at address @code{shorts + 64} and
29987 display as a single word formatted in decimal.
29991 5-data-read-memory shorts+64 d 2 1 1
29992 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29993 next-row="0x00001512",prev-row="0x0000150e",
29994 next-page="0x00001512",prev-page="0x0000150e",memory=[
29995 @{addr="0x00001510",data=["128"]@}]
29999 Read thirty two bytes of memory starting at @code{bytes+16} and format
30000 as eight rows of four columns. Include a string encoding with @samp{x}
30001 used as the non-printable character.
30005 4-data-read-memory bytes+16 x 1 8 4 x
30006 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30007 next-row="0x000013c0",prev-row="0x0000139c",
30008 next-page="0x000013c0",prev-page="0x00001380",memory=[
30009 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30010 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30011 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30012 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30013 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30014 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30015 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30016 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30020 @subheading The @code{-data-read-memory-bytes} Command
30021 @findex -data-read-memory-bytes
30023 @subsubheading Synopsis
30026 -data-read-memory-bytes [ -o @var{byte-offset} ]
30027 @var{address} @var{count}
30034 @item @var{address}
30035 An expression specifying the address of the first memory word to be
30036 read. Complex expressions containing embedded white space should be
30037 quoted using the C convention.
30040 The number of bytes to read. This should be an integer literal.
30042 @item @var{byte-offset}
30043 The offsets in bytes relative to @var{address} at which to start
30044 reading. This should be an integer literal. This option is provided
30045 so that a frontend is not required to first evaluate address and then
30046 perform address arithmetics itself.
30050 This command attempts to read all accessible memory regions in the
30051 specified range. First, all regions marked as unreadable in the memory
30052 map (if one is defined) will be skipped. @xref{Memory Region
30053 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30054 regions. For each one, if reading full region results in an errors,
30055 @value{GDBN} will try to read a subset of the region.
30057 In general, every single byte in the region may be readable or not,
30058 and the only way to read every readable byte is to try a read at
30059 every address, which is not practical. Therefore, @value{GDBN} will
30060 attempt to read all accessible bytes at either beginning or the end
30061 of the region, using a binary division scheme. This heuristic works
30062 well for reading accross a memory map boundary. Note that if a region
30063 has a readable range that is neither at the beginning or the end,
30064 @value{GDBN} will not read it.
30066 The result record (@pxref{GDB/MI Result Records}) that is output of
30067 the command includes a field named @samp{memory} whose content is a
30068 list of tuples. Each tuple represent a successfully read memory block
30069 and has the following fields:
30073 The start address of the memory block, as hexadecimal literal.
30076 The end address of the memory block, as hexadecimal literal.
30079 The offset of the memory block, as hexadecimal literal, relative to
30080 the start address passed to @code{-data-read-memory-bytes}.
30083 The contents of the memory block, in hex.
30089 @subsubheading @value{GDBN} Command
30091 The corresponding @value{GDBN} command is @samp{x}.
30093 @subsubheading Example
30097 -data-read-memory-bytes &a 10
30098 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30100 contents="01000000020000000300"@}]
30105 @subheading The @code{-data-write-memory-bytes} Command
30106 @findex -data-write-memory-bytes
30108 @subsubheading Synopsis
30111 -data-write-memory-bytes @var{address} @var{contents}
30112 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30119 @item @var{address}
30120 An expression specifying the address of the first memory word to be
30121 written. Complex expressions containing embedded white space should be
30122 quoted using the C convention.
30124 @item @var{contents}
30125 The hex-encoded bytes to write.
30128 Optional argument indicating the number of bytes to be written. If @var{count}
30129 is greater than @var{contents}' length, @value{GDBN} will repeatedly
30130 write @var{contents} until it fills @var{count} bytes.
30134 @subsubheading @value{GDBN} Command
30136 There's no corresponding @value{GDBN} command.
30138 @subsubheading Example
30142 -data-write-memory-bytes &a "aabbccdd"
30149 -data-write-memory-bytes &a "aabbccdd" 16e
30154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30155 @node GDB/MI Tracepoint Commands
30156 @section @sc{gdb/mi} Tracepoint Commands
30158 The commands defined in this section implement MI support for
30159 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30161 @subheading The @code{-trace-find} Command
30162 @findex -trace-find
30164 @subsubheading Synopsis
30167 -trace-find @var{mode} [@var{parameters}@dots{}]
30170 Find a trace frame using criteria defined by @var{mode} and
30171 @var{parameters}. The following table lists permissible
30172 modes and their parameters. For details of operation, see @ref{tfind}.
30177 No parameters are required. Stops examining trace frames.
30180 An integer is required as parameter. Selects tracepoint frame with
30183 @item tracepoint-number
30184 An integer is required as parameter. Finds next
30185 trace frame that corresponds to tracepoint with the specified number.
30188 An address is required as parameter. Finds
30189 next trace frame that corresponds to any tracepoint at the specified
30192 @item pc-inside-range
30193 Two addresses are required as parameters. Finds next trace
30194 frame that corresponds to a tracepoint at an address inside the
30195 specified range. Both bounds are considered to be inside the range.
30197 @item pc-outside-range
30198 Two addresses are required as parameters. Finds
30199 next trace frame that corresponds to a tracepoint at an address outside
30200 the specified range. Both bounds are considered to be inside the range.
30203 Line specification is required as parameter. @xref{Specify Location}.
30204 Finds next trace frame that corresponds to a tracepoint at
30205 the specified location.
30209 If @samp{none} was passed as @var{mode}, the response does not
30210 have fields. Otherwise, the response may have the following fields:
30214 This field has either @samp{0} or @samp{1} as the value, depending
30215 on whether a matching tracepoint was found.
30218 The index of the found traceframe. This field is present iff
30219 the @samp{found} field has value of @samp{1}.
30222 The index of the found tracepoint. This field is present iff
30223 the @samp{found} field has value of @samp{1}.
30226 The information about the frame corresponding to the found trace
30227 frame. This field is present only if a trace frame was found.
30228 @xref{GDB/MI Frame Information}, for description of this field.
30232 @subsubheading @value{GDBN} Command
30234 The corresponding @value{GDBN} command is @samp{tfind}.
30236 @subheading -trace-define-variable
30237 @findex -trace-define-variable
30239 @subsubheading Synopsis
30242 -trace-define-variable @var{name} [ @var{value} ]
30245 Create trace variable @var{name} if it does not exist. If
30246 @var{value} is specified, sets the initial value of the specified
30247 trace variable to that value. Note that the @var{name} should start
30248 with the @samp{$} character.
30250 @subsubheading @value{GDBN} Command
30252 The corresponding @value{GDBN} command is @samp{tvariable}.
30254 @subheading The @code{-trace-frame-collected} Command
30255 @findex -trace-frame-collected
30257 @subsubheading Synopsis
30260 -trace-frame-collected
30261 [--var-print-values @var{var_pval}]
30262 [--comp-print-values @var{comp_pval}]
30263 [--registers-format @var{regformat}]
30264 [--memory-contents]
30267 This command returns the set of collected objects, register names,
30268 trace state variable names, memory ranges and computed expressions
30269 that have been collected at a particular trace frame. The optional
30270 parameters to the command affect the output format in different ways.
30271 See the output description table below for more details.
30273 The reported names can be used in the normal manner to create
30274 varobjs and inspect the objects themselves. The items returned by
30275 this command are categorized so that it is clear which is a variable,
30276 which is a register, which is a trace state variable, which is a
30277 memory range and which is a computed expression.
30279 For instance, if the actions were
30281 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30282 collect *(int*)0xaf02bef0@@40
30286 the object collected in its entirety would be @code{myVar}. The
30287 object @code{myArray} would be partially collected, because only the
30288 element at index @code{myIndex} would be collected. The remaining
30289 objects would be computed expressions.
30291 An example output would be:
30295 -trace-frame-collected
30297 explicit-variables=[@{name="myVar",value="1"@}],
30298 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30299 @{name="myObj.field",value="0"@},
30300 @{name="myPtr->field",value="1"@},
30301 @{name="myCount + 2",value="3"@},
30302 @{name="$tvar1 + 1",value="43970027"@}],
30303 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30304 @{number="1",value="0x0"@},
30305 @{number="2",value="0x4"@},
30307 @{number="125",value="0x0"@}],
30308 tvars=[@{name="$tvar1",current="43970026"@}],
30309 memory=[@{address="0x0000000000602264",length="4"@},
30310 @{address="0x0000000000615bc0",length="4"@}]
30317 @item explicit-variables
30318 The set of objects that have been collected in their entirety (as
30319 opposed to collecting just a few elements of an array or a few struct
30320 members). For each object, its name and value are printed.
30321 The @code{--var-print-values} option affects how or whether the value
30322 field is output. If @var{var_pval} is 0, then print only the names;
30323 if it is 1, print also their values; and if it is 2, print the name,
30324 type and value for simple data types, and the name and type for
30325 arrays, structures and unions.
30327 @item computed-expressions
30328 The set of computed expressions that have been collected at the
30329 current trace frame. The @code{--comp-print-values} option affects
30330 this set like the @code{--var-print-values} option affects the
30331 @code{explicit-variables} set. See above.
30334 The registers that have been collected at the current trace frame.
30335 For each register collected, the name and current value are returned.
30336 The value is formatted according to the @code{--registers-format}
30337 option. See the @command{-data-list-register-values} command for a
30338 list of the allowed formats. The default is @samp{x}.
30341 The trace state variables that have been collected at the current
30342 trace frame. For each trace state variable collected, the name and
30343 current value are returned.
30346 The set of memory ranges that have been collected at the current trace
30347 frame. Its content is a list of tuples. Each tuple represents a
30348 collected memory range and has the following fields:
30352 The start address of the memory range, as hexadecimal literal.
30355 The length of the memory range, as decimal literal.
30358 The contents of the memory block, in hex. This field is only present
30359 if the @code{--memory-contents} option is specified.
30365 @subsubheading @value{GDBN} Command
30367 There is no corresponding @value{GDBN} command.
30369 @subsubheading Example
30371 @subheading -trace-list-variables
30372 @findex -trace-list-variables
30374 @subsubheading Synopsis
30377 -trace-list-variables
30380 Return a table of all defined trace variables. Each element of the
30381 table has the following fields:
30385 The name of the trace variable. This field is always present.
30388 The initial value. This is a 64-bit signed integer. This
30389 field is always present.
30392 The value the trace variable has at the moment. This is a 64-bit
30393 signed integer. This field is absent iff current value is
30394 not defined, for example if the trace was never run, or is
30399 @subsubheading @value{GDBN} Command
30401 The corresponding @value{GDBN} command is @samp{tvariables}.
30403 @subsubheading Example
30407 -trace-list-variables
30408 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30409 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30410 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30411 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30412 body=[variable=@{name="$trace_timestamp",initial="0"@}
30413 variable=@{name="$foo",initial="10",current="15"@}]@}
30417 @subheading -trace-save
30418 @findex -trace-save
30420 @subsubheading Synopsis
30423 -trace-save [-r ] @var{filename}
30426 Saves the collected trace data to @var{filename}. Without the
30427 @samp{-r} option, the data is downloaded from the target and saved
30428 in a local file. With the @samp{-r} option the target is asked
30429 to perform the save.
30431 @subsubheading @value{GDBN} Command
30433 The corresponding @value{GDBN} command is @samp{tsave}.
30436 @subheading -trace-start
30437 @findex -trace-start
30439 @subsubheading Synopsis
30445 Starts a tracing experiments. The result of this command does not
30448 @subsubheading @value{GDBN} Command
30450 The corresponding @value{GDBN} command is @samp{tstart}.
30452 @subheading -trace-status
30453 @findex -trace-status
30455 @subsubheading Synopsis
30461 Obtains the status of a tracing experiment. The result may include
30462 the following fields:
30467 May have a value of either @samp{0}, when no tracing operations are
30468 supported, @samp{1}, when all tracing operations are supported, or
30469 @samp{file} when examining trace file. In the latter case, examining
30470 of trace frame is possible but new tracing experiement cannot be
30471 started. This field is always present.
30474 May have a value of either @samp{0} or @samp{1} depending on whether
30475 tracing experiement is in progress on target. This field is present
30476 if @samp{supported} field is not @samp{0}.
30479 Report the reason why the tracing was stopped last time. This field
30480 may be absent iff tracing was never stopped on target yet. The
30481 value of @samp{request} means the tracing was stopped as result of
30482 the @code{-trace-stop} command. The value of @samp{overflow} means
30483 the tracing buffer is full. The value of @samp{disconnection} means
30484 tracing was automatically stopped when @value{GDBN} has disconnected.
30485 The value of @samp{passcount} means tracing was stopped when a
30486 tracepoint was passed a maximal number of times for that tracepoint.
30487 This field is present if @samp{supported} field is not @samp{0}.
30489 @item stopping-tracepoint
30490 The number of tracepoint whose passcount as exceeded. This field is
30491 present iff the @samp{stop-reason} field has the value of
30495 @itemx frames-created
30496 The @samp{frames} field is a count of the total number of trace frames
30497 in the trace buffer, while @samp{frames-created} is the total created
30498 during the run, including ones that were discarded, such as when a
30499 circular trace buffer filled up. Both fields are optional.
30503 These fields tell the current size of the tracing buffer and the
30504 remaining space. These fields are optional.
30507 The value of the circular trace buffer flag. @code{1} means that the
30508 trace buffer is circular and old trace frames will be discarded if
30509 necessary to make room, @code{0} means that the trace buffer is linear
30513 The value of the disconnected tracing flag. @code{1} means that
30514 tracing will continue after @value{GDBN} disconnects, @code{0} means
30515 that the trace run will stop.
30518 The filename of the trace file being examined. This field is
30519 optional, and only present when examining a trace file.
30523 @subsubheading @value{GDBN} Command
30525 The corresponding @value{GDBN} command is @samp{tstatus}.
30527 @subheading -trace-stop
30528 @findex -trace-stop
30530 @subsubheading Synopsis
30536 Stops a tracing experiment. The result of this command has the same
30537 fields as @code{-trace-status}, except that the @samp{supported} and
30538 @samp{running} fields are not output.
30540 @subsubheading @value{GDBN} Command
30542 The corresponding @value{GDBN} command is @samp{tstop}.
30545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30546 @node GDB/MI Symbol Query
30547 @section @sc{gdb/mi} Symbol Query Commands
30551 @subheading The @code{-symbol-info-address} Command
30552 @findex -symbol-info-address
30554 @subsubheading Synopsis
30557 -symbol-info-address @var{symbol}
30560 Describe where @var{symbol} is stored.
30562 @subsubheading @value{GDBN} Command
30564 The corresponding @value{GDBN} command is @samp{info address}.
30566 @subsubheading Example
30570 @subheading The @code{-symbol-info-file} Command
30571 @findex -symbol-info-file
30573 @subsubheading Synopsis
30579 Show the file for the symbol.
30581 @subsubheading @value{GDBN} Command
30583 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30584 @samp{gdb_find_file}.
30586 @subsubheading Example
30590 @subheading The @code{-symbol-info-function} Command
30591 @findex -symbol-info-function
30593 @subsubheading Synopsis
30596 -symbol-info-function
30599 Show which function the symbol lives in.
30601 @subsubheading @value{GDBN} Command
30603 @samp{gdb_get_function} in @code{gdbtk}.
30605 @subsubheading Example
30609 @subheading The @code{-symbol-info-line} Command
30610 @findex -symbol-info-line
30612 @subsubheading Synopsis
30618 Show the core addresses of the code for a source line.
30620 @subsubheading @value{GDBN} Command
30622 The corresponding @value{GDBN} command is @samp{info line}.
30623 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30625 @subsubheading Example
30629 @subheading The @code{-symbol-info-symbol} Command
30630 @findex -symbol-info-symbol
30632 @subsubheading Synopsis
30635 -symbol-info-symbol @var{addr}
30638 Describe what symbol is at location @var{addr}.
30640 @subsubheading @value{GDBN} Command
30642 The corresponding @value{GDBN} command is @samp{info symbol}.
30644 @subsubheading Example
30648 @subheading The @code{-symbol-list-functions} Command
30649 @findex -symbol-list-functions
30651 @subsubheading Synopsis
30654 -symbol-list-functions
30657 List the functions in the executable.
30659 @subsubheading @value{GDBN} Command
30661 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30662 @samp{gdb_search} in @code{gdbtk}.
30664 @subsubheading Example
30669 @subheading The @code{-symbol-list-lines} Command
30670 @findex -symbol-list-lines
30672 @subsubheading Synopsis
30675 -symbol-list-lines @var{filename}
30678 Print the list of lines that contain code and their associated program
30679 addresses for the given source filename. The entries are sorted in
30680 ascending PC order.
30682 @subsubheading @value{GDBN} Command
30684 There is no corresponding @value{GDBN} command.
30686 @subsubheading Example
30689 -symbol-list-lines basics.c
30690 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30696 @subheading The @code{-symbol-list-types} Command
30697 @findex -symbol-list-types
30699 @subsubheading Synopsis
30705 List all the type names.
30707 @subsubheading @value{GDBN} Command
30709 The corresponding commands are @samp{info types} in @value{GDBN},
30710 @samp{gdb_search} in @code{gdbtk}.
30712 @subsubheading Example
30716 @subheading The @code{-symbol-list-variables} Command
30717 @findex -symbol-list-variables
30719 @subsubheading Synopsis
30722 -symbol-list-variables
30725 List all the global and static variable names.
30727 @subsubheading @value{GDBN} Command
30729 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30731 @subsubheading Example
30735 @subheading The @code{-symbol-locate} Command
30736 @findex -symbol-locate
30738 @subsubheading Synopsis
30744 @subsubheading @value{GDBN} Command
30746 @samp{gdb_loc} in @code{gdbtk}.
30748 @subsubheading Example
30752 @subheading The @code{-symbol-type} Command
30753 @findex -symbol-type
30755 @subsubheading Synopsis
30758 -symbol-type @var{variable}
30761 Show type of @var{variable}.
30763 @subsubheading @value{GDBN} Command
30765 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30766 @samp{gdb_obj_variable}.
30768 @subsubheading Example
30773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30774 @node GDB/MI File Commands
30775 @section @sc{gdb/mi} File Commands
30777 This section describes the GDB/MI commands to specify executable file names
30778 and to read in and obtain symbol table information.
30780 @subheading The @code{-file-exec-and-symbols} Command
30781 @findex -file-exec-and-symbols
30783 @subsubheading Synopsis
30786 -file-exec-and-symbols @var{file}
30789 Specify the executable file to be debugged. This file is the one from
30790 which the symbol table is also read. If no file is specified, the
30791 command clears the executable and symbol information. If breakpoints
30792 are set when using this command with no arguments, @value{GDBN} will produce
30793 error messages. Otherwise, no output is produced, except a completion
30796 @subsubheading @value{GDBN} Command
30798 The corresponding @value{GDBN} command is @samp{file}.
30800 @subsubheading Example
30804 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30810 @subheading The @code{-file-exec-file} Command
30811 @findex -file-exec-file
30813 @subsubheading Synopsis
30816 -file-exec-file @var{file}
30819 Specify the executable file to be debugged. Unlike
30820 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30821 from this file. If used without argument, @value{GDBN} clears the information
30822 about the executable file. No output is produced, except a completion
30825 @subsubheading @value{GDBN} Command
30827 The corresponding @value{GDBN} command is @samp{exec-file}.
30829 @subsubheading Example
30833 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30840 @subheading The @code{-file-list-exec-sections} Command
30841 @findex -file-list-exec-sections
30843 @subsubheading Synopsis
30846 -file-list-exec-sections
30849 List the sections of the current executable file.
30851 @subsubheading @value{GDBN} Command
30853 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30854 information as this command. @code{gdbtk} has a corresponding command
30855 @samp{gdb_load_info}.
30857 @subsubheading Example
30862 @subheading The @code{-file-list-exec-source-file} Command
30863 @findex -file-list-exec-source-file
30865 @subsubheading Synopsis
30868 -file-list-exec-source-file
30871 List the line number, the current source file, and the absolute path
30872 to the current source file for the current executable. The macro
30873 information field has a value of @samp{1} or @samp{0} depending on
30874 whether or not the file includes preprocessor macro information.
30876 @subsubheading @value{GDBN} Command
30878 The @value{GDBN} equivalent is @samp{info source}
30880 @subsubheading Example
30884 123-file-list-exec-source-file
30885 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30890 @subheading The @code{-file-list-exec-source-files} Command
30891 @findex -file-list-exec-source-files
30893 @subsubheading Synopsis
30896 -file-list-exec-source-files
30899 List the source files for the current executable.
30901 It will always output both the filename and fullname (absolute file
30902 name) of a source file.
30904 @subsubheading @value{GDBN} Command
30906 The @value{GDBN} equivalent is @samp{info sources}.
30907 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30909 @subsubheading Example
30912 -file-list-exec-source-files
30914 @{file=foo.c,fullname=/home/foo.c@},
30915 @{file=/home/bar.c,fullname=/home/bar.c@},
30916 @{file=gdb_could_not_find_fullpath.c@}]
30921 @subheading The @code{-file-list-shared-libraries} Command
30922 @findex -file-list-shared-libraries
30924 @subsubheading Synopsis
30927 -file-list-shared-libraries
30930 List the shared libraries in the program.
30932 @subsubheading @value{GDBN} Command
30934 The corresponding @value{GDBN} command is @samp{info shared}.
30936 @subsubheading Example
30940 @subheading The @code{-file-list-symbol-files} Command
30941 @findex -file-list-symbol-files
30943 @subsubheading Synopsis
30946 -file-list-symbol-files
30951 @subsubheading @value{GDBN} Command
30953 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30955 @subsubheading Example
30960 @subheading The @code{-file-symbol-file} Command
30961 @findex -file-symbol-file
30963 @subsubheading Synopsis
30966 -file-symbol-file @var{file}
30969 Read symbol table info from the specified @var{file} argument. When
30970 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30971 produced, except for a completion notification.
30973 @subsubheading @value{GDBN} Command
30975 The corresponding @value{GDBN} command is @samp{symbol-file}.
30977 @subsubheading Example
30981 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30988 @node GDB/MI Memory Overlay Commands
30989 @section @sc{gdb/mi} Memory Overlay Commands
30991 The memory overlay commands are not implemented.
30993 @c @subheading -overlay-auto
30995 @c @subheading -overlay-list-mapping-state
30997 @c @subheading -overlay-list-overlays
30999 @c @subheading -overlay-map
31001 @c @subheading -overlay-off
31003 @c @subheading -overlay-on
31005 @c @subheading -overlay-unmap
31007 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31008 @node GDB/MI Signal Handling Commands
31009 @section @sc{gdb/mi} Signal Handling Commands
31011 Signal handling commands are not implemented.
31013 @c @subheading -signal-handle
31015 @c @subheading -signal-list-handle-actions
31017 @c @subheading -signal-list-signal-types
31021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31022 @node GDB/MI Target Manipulation
31023 @section @sc{gdb/mi} Target Manipulation Commands
31026 @subheading The @code{-target-attach} Command
31027 @findex -target-attach
31029 @subsubheading Synopsis
31032 -target-attach @var{pid} | @var{gid} | @var{file}
31035 Attach to a process @var{pid} or a file @var{file} outside of
31036 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31037 group, the id previously returned by
31038 @samp{-list-thread-groups --available} must be used.
31040 @subsubheading @value{GDBN} Command
31042 The corresponding @value{GDBN} command is @samp{attach}.
31044 @subsubheading Example
31048 =thread-created,id="1"
31049 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31055 @subheading The @code{-target-compare-sections} Command
31056 @findex -target-compare-sections
31058 @subsubheading Synopsis
31061 -target-compare-sections [ @var{section} ]
31064 Compare data of section @var{section} on target to the exec file.
31065 Without the argument, all sections are compared.
31067 @subsubheading @value{GDBN} Command
31069 The @value{GDBN} equivalent is @samp{compare-sections}.
31071 @subsubheading Example
31076 @subheading The @code{-target-detach} Command
31077 @findex -target-detach
31079 @subsubheading Synopsis
31082 -target-detach [ @var{pid} | @var{gid} ]
31085 Detach from the remote target which normally resumes its execution.
31086 If either @var{pid} or @var{gid} is specified, detaches from either
31087 the specified process, or specified thread group. There's no output.
31089 @subsubheading @value{GDBN} Command
31091 The corresponding @value{GDBN} command is @samp{detach}.
31093 @subsubheading Example
31103 @subheading The @code{-target-disconnect} Command
31104 @findex -target-disconnect
31106 @subsubheading Synopsis
31112 Disconnect from the remote target. There's no output and the target is
31113 generally not resumed.
31115 @subsubheading @value{GDBN} Command
31117 The corresponding @value{GDBN} command is @samp{disconnect}.
31119 @subsubheading Example
31129 @subheading The @code{-target-download} Command
31130 @findex -target-download
31132 @subsubheading Synopsis
31138 Loads the executable onto the remote target.
31139 It prints out an update message every half second, which includes the fields:
31143 The name of the section.
31145 The size of what has been sent so far for that section.
31147 The size of the section.
31149 The total size of what was sent so far (the current and the previous sections).
31151 The size of the overall executable to download.
31155 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31156 @sc{gdb/mi} Output Syntax}).
31158 In addition, it prints the name and size of the sections, as they are
31159 downloaded. These messages include the following fields:
31163 The name of the section.
31165 The size of the section.
31167 The size of the overall executable to download.
31171 At the end, a summary is printed.
31173 @subsubheading @value{GDBN} Command
31175 The corresponding @value{GDBN} command is @samp{load}.
31177 @subsubheading Example
31179 Note: each status message appears on a single line. Here the messages
31180 have been broken down so that they can fit onto a page.
31185 +download,@{section=".text",section-size="6668",total-size="9880"@}
31186 +download,@{section=".text",section-sent="512",section-size="6668",
31187 total-sent="512",total-size="9880"@}
31188 +download,@{section=".text",section-sent="1024",section-size="6668",
31189 total-sent="1024",total-size="9880"@}
31190 +download,@{section=".text",section-sent="1536",section-size="6668",
31191 total-sent="1536",total-size="9880"@}
31192 +download,@{section=".text",section-sent="2048",section-size="6668",
31193 total-sent="2048",total-size="9880"@}
31194 +download,@{section=".text",section-sent="2560",section-size="6668",
31195 total-sent="2560",total-size="9880"@}
31196 +download,@{section=".text",section-sent="3072",section-size="6668",
31197 total-sent="3072",total-size="9880"@}
31198 +download,@{section=".text",section-sent="3584",section-size="6668",
31199 total-sent="3584",total-size="9880"@}
31200 +download,@{section=".text",section-sent="4096",section-size="6668",
31201 total-sent="4096",total-size="9880"@}
31202 +download,@{section=".text",section-sent="4608",section-size="6668",
31203 total-sent="4608",total-size="9880"@}
31204 +download,@{section=".text",section-sent="5120",section-size="6668",
31205 total-sent="5120",total-size="9880"@}
31206 +download,@{section=".text",section-sent="5632",section-size="6668",
31207 total-sent="5632",total-size="9880"@}
31208 +download,@{section=".text",section-sent="6144",section-size="6668",
31209 total-sent="6144",total-size="9880"@}
31210 +download,@{section=".text",section-sent="6656",section-size="6668",
31211 total-sent="6656",total-size="9880"@}
31212 +download,@{section=".init",section-size="28",total-size="9880"@}
31213 +download,@{section=".fini",section-size="28",total-size="9880"@}
31214 +download,@{section=".data",section-size="3156",total-size="9880"@}
31215 +download,@{section=".data",section-sent="512",section-size="3156",
31216 total-sent="7236",total-size="9880"@}
31217 +download,@{section=".data",section-sent="1024",section-size="3156",
31218 total-sent="7748",total-size="9880"@}
31219 +download,@{section=".data",section-sent="1536",section-size="3156",
31220 total-sent="8260",total-size="9880"@}
31221 +download,@{section=".data",section-sent="2048",section-size="3156",
31222 total-sent="8772",total-size="9880"@}
31223 +download,@{section=".data",section-sent="2560",section-size="3156",
31224 total-sent="9284",total-size="9880"@}
31225 +download,@{section=".data",section-sent="3072",section-size="3156",
31226 total-sent="9796",total-size="9880"@}
31227 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31234 @subheading The @code{-target-exec-status} Command
31235 @findex -target-exec-status
31237 @subsubheading Synopsis
31240 -target-exec-status
31243 Provide information on the state of the target (whether it is running or
31244 not, for instance).
31246 @subsubheading @value{GDBN} Command
31248 There's no equivalent @value{GDBN} command.
31250 @subsubheading Example
31254 @subheading The @code{-target-list-available-targets} Command
31255 @findex -target-list-available-targets
31257 @subsubheading Synopsis
31260 -target-list-available-targets
31263 List the possible targets to connect to.
31265 @subsubheading @value{GDBN} Command
31267 The corresponding @value{GDBN} command is @samp{help target}.
31269 @subsubheading Example
31273 @subheading The @code{-target-list-current-targets} Command
31274 @findex -target-list-current-targets
31276 @subsubheading Synopsis
31279 -target-list-current-targets
31282 Describe the current target.
31284 @subsubheading @value{GDBN} Command
31286 The corresponding information is printed by @samp{info file} (among
31289 @subsubheading Example
31293 @subheading The @code{-target-list-parameters} Command
31294 @findex -target-list-parameters
31296 @subsubheading Synopsis
31299 -target-list-parameters
31305 @subsubheading @value{GDBN} Command
31309 @subsubheading Example
31313 @subheading The @code{-target-select} Command
31314 @findex -target-select
31316 @subsubheading Synopsis
31319 -target-select @var{type} @var{parameters @dots{}}
31322 Connect @value{GDBN} to the remote target. This command takes two args:
31326 The type of target, for instance @samp{remote}, etc.
31327 @item @var{parameters}
31328 Device names, host names and the like. @xref{Target Commands, ,
31329 Commands for Managing Targets}, for more details.
31332 The output is a connection notification, followed by the address at
31333 which the target program is, in the following form:
31336 ^connected,addr="@var{address}",func="@var{function name}",
31337 args=[@var{arg list}]
31340 @subsubheading @value{GDBN} Command
31342 The corresponding @value{GDBN} command is @samp{target}.
31344 @subsubheading Example
31348 -target-select remote /dev/ttya
31349 ^connected,addr="0xfe00a300",func="??",args=[]
31353 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31354 @node GDB/MI File Transfer Commands
31355 @section @sc{gdb/mi} File Transfer Commands
31358 @subheading The @code{-target-file-put} Command
31359 @findex -target-file-put
31361 @subsubheading Synopsis
31364 -target-file-put @var{hostfile} @var{targetfile}
31367 Copy file @var{hostfile} from the host system (the machine running
31368 @value{GDBN}) to @var{targetfile} on the target system.
31370 @subsubheading @value{GDBN} Command
31372 The corresponding @value{GDBN} command is @samp{remote put}.
31374 @subsubheading Example
31378 -target-file-put localfile remotefile
31384 @subheading The @code{-target-file-get} Command
31385 @findex -target-file-get
31387 @subsubheading Synopsis
31390 -target-file-get @var{targetfile} @var{hostfile}
31393 Copy file @var{targetfile} from the target system to @var{hostfile}
31394 on the host system.
31396 @subsubheading @value{GDBN} Command
31398 The corresponding @value{GDBN} command is @samp{remote get}.
31400 @subsubheading Example
31404 -target-file-get remotefile localfile
31410 @subheading The @code{-target-file-delete} Command
31411 @findex -target-file-delete
31413 @subsubheading Synopsis
31416 -target-file-delete @var{targetfile}
31419 Delete @var{targetfile} from the target system.
31421 @subsubheading @value{GDBN} Command
31423 The corresponding @value{GDBN} command is @samp{remote delete}.
31425 @subsubheading Example
31429 -target-file-delete remotefile
31435 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31436 @node GDB/MI Ada Exceptions Commands
31437 @section Ada Exceptions @sc{gdb/mi} Commands
31439 @subheading The @code{-info-ada-exceptions} Command
31440 @findex -info-ada-exceptions
31442 @subsubheading Synopsis
31445 -info-ada-exceptions [ @var{regexp}]
31448 List all Ada exceptions defined within the program being debugged.
31449 With a regular expression @var{regexp}, only those exceptions whose
31450 names match @var{regexp} are listed.
31452 @subsubheading @value{GDBN} Command
31454 The corresponding @value{GDBN} command is @samp{info exceptions}.
31456 @subsubheading Result
31458 The result is a table of Ada exceptions. The following columns are
31459 defined for each exception:
31463 The name of the exception.
31466 The address of the exception.
31470 @subsubheading Example
31473 -info-ada-exceptions aint
31474 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31475 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31476 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31477 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31478 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31481 @subheading Catching Ada Exceptions
31483 The commands describing how to ask @value{GDBN} to stop when a program
31484 raises an exception are described at @ref{Ada Exception GDB/MI
31485 Catchpoint Commands}.
31488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31489 @node GDB/MI Support Commands
31490 @section @sc{gdb/mi} Support Commands
31492 Since new commands and features get regularly added to @sc{gdb/mi},
31493 some commands are available to help front-ends query the debugger
31494 about support for these capabilities. Similarly, it is also possible
31495 to query @value{GDBN} about target support of certain features.
31497 @subheading The @code{-info-gdb-mi-command} Command
31498 @cindex @code{-info-gdb-mi-command}
31499 @findex -info-gdb-mi-command
31501 @subsubheading Synopsis
31504 -info-gdb-mi-command @var{cmd_name}
31507 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31509 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31510 is technically not part of the command name (@pxref{GDB/MI Input
31511 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31512 for ease of use, this command also accepts the form with the leading
31515 @subsubheading @value{GDBN} Command
31517 There is no corresponding @value{GDBN} command.
31519 @subsubheading Result
31521 The result is a tuple. There is currently only one field:
31525 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31526 @code{"false"} otherwise.
31530 @subsubheading Example
31532 Here is an example where the @sc{gdb/mi} command does not exist:
31535 -info-gdb-mi-command unsupported-command
31536 ^done,command=@{exists="false"@}
31540 And here is an example where the @sc{gdb/mi} command is known
31544 -info-gdb-mi-command symbol-list-lines
31545 ^done,command=@{exists="true"@}
31548 @subheading The @code{-list-features} Command
31549 @findex -list-features
31550 @cindex supported @sc{gdb/mi} features, list
31552 Returns a list of particular features of the MI protocol that
31553 this version of gdb implements. A feature can be a command,
31554 or a new field in an output of some command, or even an
31555 important bugfix. While a frontend can sometimes detect presence
31556 of a feature at runtime, it is easier to perform detection at debugger
31559 The command returns a list of strings, with each string naming an
31560 available feature. Each returned string is just a name, it does not
31561 have any internal structure. The list of possible feature names
31567 (gdb) -list-features
31568 ^done,result=["feature1","feature2"]
31571 The current list of features is:
31574 @item frozen-varobjs
31575 Indicates support for the @code{-var-set-frozen} command, as well
31576 as possible presense of the @code{frozen} field in the output
31577 of @code{-varobj-create}.
31578 @item pending-breakpoints
31579 Indicates support for the @option{-f} option to the @code{-break-insert}
31582 Indicates Python scripting support, Python-based
31583 pretty-printing commands, and possible presence of the
31584 @samp{display_hint} field in the output of @code{-var-list-children}
31586 Indicates support for the @code{-thread-info} command.
31587 @item data-read-memory-bytes
31588 Indicates support for the @code{-data-read-memory-bytes} and the
31589 @code{-data-write-memory-bytes} commands.
31590 @item breakpoint-notifications
31591 Indicates that changes to breakpoints and breakpoints created via the
31592 CLI will be announced via async records.
31593 @item ada-task-info
31594 Indicates support for the @code{-ada-task-info} command.
31595 @item language-option
31596 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31597 option (@pxref{Context management}).
31598 @item info-gdb-mi-command
31599 Indicates support for the @code{-info-gdb-mi-command} command.
31600 @item undefined-command-error-code
31601 Indicates support for the "undefined-command" error code in error result
31602 records, produced when trying to execute an undefined @sc{gdb/mi} command
31603 (@pxref{GDB/MI Result Records}).
31604 @item exec-run-start-option
31605 Indicates that the @code{-exec-run} command supports the @option{--start}
31606 option (@pxref{GDB/MI Program Execution}).
31609 @subheading The @code{-list-target-features} Command
31610 @findex -list-target-features
31612 Returns a list of particular features that are supported by the
31613 target. Those features affect the permitted MI commands, but
31614 unlike the features reported by the @code{-list-features} command, the
31615 features depend on which target GDB is using at the moment. Whenever
31616 a target can change, due to commands such as @code{-target-select},
31617 @code{-target-attach} or @code{-exec-run}, the list of target features
31618 may change, and the frontend should obtain it again.
31622 (gdb) -list-target-features
31623 ^done,result=["async"]
31626 The current list of features is:
31630 Indicates that the target is capable of asynchronous command
31631 execution, which means that @value{GDBN} will accept further commands
31632 while the target is running.
31635 Indicates that the target is capable of reverse execution.
31636 @xref{Reverse Execution}, for more information.
31640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31641 @node GDB/MI Miscellaneous Commands
31642 @section Miscellaneous @sc{gdb/mi} Commands
31644 @c @subheading -gdb-complete
31646 @subheading The @code{-gdb-exit} Command
31649 @subsubheading Synopsis
31655 Exit @value{GDBN} immediately.
31657 @subsubheading @value{GDBN} Command
31659 Approximately corresponds to @samp{quit}.
31661 @subsubheading Example
31671 @subheading The @code{-exec-abort} Command
31672 @findex -exec-abort
31674 @subsubheading Synopsis
31680 Kill the inferior running program.
31682 @subsubheading @value{GDBN} Command
31684 The corresponding @value{GDBN} command is @samp{kill}.
31686 @subsubheading Example
31691 @subheading The @code{-gdb-set} Command
31694 @subsubheading Synopsis
31700 Set an internal @value{GDBN} variable.
31701 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31703 @subsubheading @value{GDBN} Command
31705 The corresponding @value{GDBN} command is @samp{set}.
31707 @subsubheading Example
31717 @subheading The @code{-gdb-show} Command
31720 @subsubheading Synopsis
31726 Show the current value of a @value{GDBN} variable.
31728 @subsubheading @value{GDBN} Command
31730 The corresponding @value{GDBN} command is @samp{show}.
31732 @subsubheading Example
31741 @c @subheading -gdb-source
31744 @subheading The @code{-gdb-version} Command
31745 @findex -gdb-version
31747 @subsubheading Synopsis
31753 Show version information for @value{GDBN}. Used mostly in testing.
31755 @subsubheading @value{GDBN} Command
31757 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31758 default shows this information when you start an interactive session.
31760 @subsubheading Example
31762 @c This example modifies the actual output from GDB to avoid overfull
31768 ~Copyright 2000 Free Software Foundation, Inc.
31769 ~GDB is free software, covered by the GNU General Public License, and
31770 ~you are welcome to change it and/or distribute copies of it under
31771 ~ certain conditions.
31772 ~Type "show copying" to see the conditions.
31773 ~There is absolutely no warranty for GDB. Type "show warranty" for
31775 ~This GDB was configured as
31776 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31781 @subheading The @code{-list-thread-groups} Command
31782 @findex -list-thread-groups
31784 @subheading Synopsis
31787 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31790 Lists thread groups (@pxref{Thread groups}). When a single thread
31791 group is passed as the argument, lists the children of that group.
31792 When several thread group are passed, lists information about those
31793 thread groups. Without any parameters, lists information about all
31794 top-level thread groups.
31796 Normally, thread groups that are being debugged are reported.
31797 With the @samp{--available} option, @value{GDBN} reports thread groups
31798 available on the target.
31800 The output of this command may have either a @samp{threads} result or
31801 a @samp{groups} result. The @samp{thread} result has a list of tuples
31802 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31803 Information}). The @samp{groups} result has a list of tuples as value,
31804 each tuple describing a thread group. If top-level groups are
31805 requested (that is, no parameter is passed), or when several groups
31806 are passed, the output always has a @samp{groups} result. The format
31807 of the @samp{group} result is described below.
31809 To reduce the number of roundtrips it's possible to list thread groups
31810 together with their children, by passing the @samp{--recurse} option
31811 and the recursion depth. Presently, only recursion depth of 1 is
31812 permitted. If this option is present, then every reported thread group
31813 will also include its children, either as @samp{group} or
31814 @samp{threads} field.
31816 In general, any combination of option and parameters is permitted, with
31817 the following caveats:
31821 When a single thread group is passed, the output will typically
31822 be the @samp{threads} result. Because threads may not contain
31823 anything, the @samp{recurse} option will be ignored.
31826 When the @samp{--available} option is passed, limited information may
31827 be available. In particular, the list of threads of a process might
31828 be inaccessible. Further, specifying specific thread groups might
31829 not give any performance advantage over listing all thread groups.
31830 The frontend should assume that @samp{-list-thread-groups --available}
31831 is always an expensive operation and cache the results.
31835 The @samp{groups} result is a list of tuples, where each tuple may
31836 have the following fields:
31840 Identifier of the thread group. This field is always present.
31841 The identifier is an opaque string; frontends should not try to
31842 convert it to an integer, even though it might look like one.
31845 The type of the thread group. At present, only @samp{process} is a
31849 The target-specific process identifier. This field is only present
31850 for thread groups of type @samp{process} and only if the process exists.
31853 The exit code of this group's last exited thread, formatted in octal.
31854 This field is only present for thread groups of type @samp{process} and
31855 only if the process is not running.
31858 The number of children this thread group has. This field may be
31859 absent for an available thread group.
31862 This field has a list of tuples as value, each tuple describing a
31863 thread. It may be present if the @samp{--recurse} option is
31864 specified, and it's actually possible to obtain the threads.
31867 This field is a list of integers, each identifying a core that one
31868 thread of the group is running on. This field may be absent if
31869 such information is not available.
31872 The name of the executable file that corresponds to this thread group.
31873 The field is only present for thread groups of type @samp{process},
31874 and only if there is a corresponding executable file.
31878 @subheading Example
31882 -list-thread-groups
31883 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31884 -list-thread-groups 17
31885 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31886 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31887 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31888 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31889 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31890 -list-thread-groups --available
31891 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31892 -list-thread-groups --available --recurse 1
31893 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31894 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31895 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31896 -list-thread-groups --available --recurse 1 17 18
31897 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31898 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31899 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31902 @subheading The @code{-info-os} Command
31905 @subsubheading Synopsis
31908 -info-os [ @var{type} ]
31911 If no argument is supplied, the command returns a table of available
31912 operating-system-specific information types. If one of these types is
31913 supplied as an argument @var{type}, then the command returns a table
31914 of data of that type.
31916 The types of information available depend on the target operating
31919 @subsubheading @value{GDBN} Command
31921 The corresponding @value{GDBN} command is @samp{info os}.
31923 @subsubheading Example
31925 When run on a @sc{gnu}/Linux system, the output will look something
31931 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31932 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31933 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31934 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31935 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31937 item=@{col0="files",col1="Listing of all file descriptors",
31938 col2="File descriptors"@},
31939 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31940 col2="Kernel modules"@},
31941 item=@{col0="msg",col1="Listing of all message queues",
31942 col2="Message queues"@},
31943 item=@{col0="processes",col1="Listing of all processes",
31944 col2="Processes"@},
31945 item=@{col0="procgroups",col1="Listing of all process groups",
31946 col2="Process groups"@},
31947 item=@{col0="semaphores",col1="Listing of all semaphores",
31948 col2="Semaphores"@},
31949 item=@{col0="shm",col1="Listing of all shared-memory regions",
31950 col2="Shared-memory regions"@},
31951 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31953 item=@{col0="threads",col1="Listing of all threads",
31957 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31958 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31959 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31960 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31961 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31962 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31963 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31964 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31966 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31967 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31971 (Note that the MI output here includes a @code{"Title"} column that
31972 does not appear in command-line @code{info os}; this column is useful
31973 for MI clients that want to enumerate the types of data, such as in a
31974 popup menu, but is needless clutter on the command line, and
31975 @code{info os} omits it.)
31977 @subheading The @code{-add-inferior} Command
31978 @findex -add-inferior
31980 @subheading Synopsis
31986 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31987 inferior is not associated with any executable. Such association may
31988 be established with the @samp{-file-exec-and-symbols} command
31989 (@pxref{GDB/MI File Commands}). The command response has a single
31990 field, @samp{inferior}, whose value is the identifier of the
31991 thread group corresponding to the new inferior.
31993 @subheading Example
31998 ^done,inferior="i3"
32001 @subheading The @code{-interpreter-exec} Command
32002 @findex -interpreter-exec
32004 @subheading Synopsis
32007 -interpreter-exec @var{interpreter} @var{command}
32009 @anchor{-interpreter-exec}
32011 Execute the specified @var{command} in the given @var{interpreter}.
32013 @subheading @value{GDBN} Command
32015 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32017 @subheading Example
32021 -interpreter-exec console "break main"
32022 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32023 &"During symbol reading, bad structure-type format.\n"
32024 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32029 @subheading The @code{-inferior-tty-set} Command
32030 @findex -inferior-tty-set
32032 @subheading Synopsis
32035 -inferior-tty-set /dev/pts/1
32038 Set terminal for future runs of the program being debugged.
32040 @subheading @value{GDBN} Command
32042 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32044 @subheading Example
32048 -inferior-tty-set /dev/pts/1
32053 @subheading The @code{-inferior-tty-show} Command
32054 @findex -inferior-tty-show
32056 @subheading Synopsis
32062 Show terminal for future runs of program being debugged.
32064 @subheading @value{GDBN} Command
32066 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32068 @subheading Example
32072 -inferior-tty-set /dev/pts/1
32076 ^done,inferior_tty_terminal="/dev/pts/1"
32080 @subheading The @code{-enable-timings} Command
32081 @findex -enable-timings
32083 @subheading Synopsis
32086 -enable-timings [yes | no]
32089 Toggle the printing of the wallclock, user and system times for an MI
32090 command as a field in its output. This command is to help frontend
32091 developers optimize the performance of their code. No argument is
32092 equivalent to @samp{yes}.
32094 @subheading @value{GDBN} Command
32098 @subheading Example
32106 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32107 addr="0x080484ed",func="main",file="myprog.c",
32108 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32110 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32118 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32119 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32120 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32121 fullname="/home/nickrob/myprog.c",line="73"@}
32126 @chapter @value{GDBN} Annotations
32128 This chapter describes annotations in @value{GDBN}. Annotations were
32129 designed to interface @value{GDBN} to graphical user interfaces or other
32130 similar programs which want to interact with @value{GDBN} at a
32131 relatively high level.
32133 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32137 This is Edition @value{EDITION}, @value{DATE}.
32141 * Annotations Overview:: What annotations are; the general syntax.
32142 * Server Prefix:: Issuing a command without affecting user state.
32143 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32144 * Errors:: Annotations for error messages.
32145 * Invalidation:: Some annotations describe things now invalid.
32146 * Annotations for Running::
32147 Whether the program is running, how it stopped, etc.
32148 * Source Annotations:: Annotations describing source code.
32151 @node Annotations Overview
32152 @section What is an Annotation?
32153 @cindex annotations
32155 Annotations start with a newline character, two @samp{control-z}
32156 characters, and the name of the annotation. If there is no additional
32157 information associated with this annotation, the name of the annotation
32158 is followed immediately by a newline. If there is additional
32159 information, the name of the annotation is followed by a space, the
32160 additional information, and a newline. The additional information
32161 cannot contain newline characters.
32163 Any output not beginning with a newline and two @samp{control-z}
32164 characters denotes literal output from @value{GDBN}. Currently there is
32165 no need for @value{GDBN} to output a newline followed by two
32166 @samp{control-z} characters, but if there was such a need, the
32167 annotations could be extended with an @samp{escape} annotation which
32168 means those three characters as output.
32170 The annotation @var{level}, which is specified using the
32171 @option{--annotate} command line option (@pxref{Mode Options}), controls
32172 how much information @value{GDBN} prints together with its prompt,
32173 values of expressions, source lines, and other types of output. Level 0
32174 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32175 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32176 for programs that control @value{GDBN}, and level 2 annotations have
32177 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32178 Interface, annotate, GDB's Obsolete Annotations}).
32181 @kindex set annotate
32182 @item set annotate @var{level}
32183 The @value{GDBN} command @code{set annotate} sets the level of
32184 annotations to the specified @var{level}.
32186 @item show annotate
32187 @kindex show annotate
32188 Show the current annotation level.
32191 This chapter describes level 3 annotations.
32193 A simple example of starting up @value{GDBN} with annotations is:
32196 $ @kbd{gdb --annotate=3}
32198 Copyright 2003 Free Software Foundation, Inc.
32199 GDB is free software, covered by the GNU General Public License,
32200 and you are welcome to change it and/or distribute copies of it
32201 under certain conditions.
32202 Type "show copying" to see the conditions.
32203 There is absolutely no warranty for GDB. Type "show warranty"
32205 This GDB was configured as "i386-pc-linux-gnu"
32216 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32217 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32218 denotes a @samp{control-z} character) are annotations; the rest is
32219 output from @value{GDBN}.
32221 @node Server Prefix
32222 @section The Server Prefix
32223 @cindex server prefix
32225 If you prefix a command with @samp{server } then it will not affect
32226 the command history, nor will it affect @value{GDBN}'s notion of which
32227 command to repeat if @key{RET} is pressed on a line by itself. This
32228 means that commands can be run behind a user's back by a front-end in
32229 a transparent manner.
32231 The @code{server } prefix does not affect the recording of values into
32232 the value history; to print a value without recording it into the
32233 value history, use the @code{output} command instead of the
32234 @code{print} command.
32236 Using this prefix also disables confirmation requests
32237 (@pxref{confirmation requests}).
32240 @section Annotation for @value{GDBN} Input
32242 @cindex annotations for prompts
32243 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32244 to know when to send output, when the output from a given command is
32247 Different kinds of input each have a different @dfn{input type}. Each
32248 input type has three annotations: a @code{pre-} annotation, which
32249 denotes the beginning of any prompt which is being output, a plain
32250 annotation, which denotes the end of the prompt, and then a @code{post-}
32251 annotation which denotes the end of any echo which may (or may not) be
32252 associated with the input. For example, the @code{prompt} input type
32253 features the following annotations:
32261 The input types are
32264 @findex pre-prompt annotation
32265 @findex prompt annotation
32266 @findex post-prompt annotation
32268 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32270 @findex pre-commands annotation
32271 @findex commands annotation
32272 @findex post-commands annotation
32274 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32275 command. The annotations are repeated for each command which is input.
32277 @findex pre-overload-choice annotation
32278 @findex overload-choice annotation
32279 @findex post-overload-choice annotation
32280 @item overload-choice
32281 When @value{GDBN} wants the user to select between various overloaded functions.
32283 @findex pre-query annotation
32284 @findex query annotation
32285 @findex post-query annotation
32287 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32289 @findex pre-prompt-for-continue annotation
32290 @findex prompt-for-continue annotation
32291 @findex post-prompt-for-continue annotation
32292 @item prompt-for-continue
32293 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32294 expect this to work well; instead use @code{set height 0} to disable
32295 prompting. This is because the counting of lines is buggy in the
32296 presence of annotations.
32301 @cindex annotations for errors, warnings and interrupts
32303 @findex quit annotation
32308 This annotation occurs right before @value{GDBN} responds to an interrupt.
32310 @findex error annotation
32315 This annotation occurs right before @value{GDBN} responds to an error.
32317 Quit and error annotations indicate that any annotations which @value{GDBN} was
32318 in the middle of may end abruptly. For example, if a
32319 @code{value-history-begin} annotation is followed by a @code{error}, one
32320 cannot expect to receive the matching @code{value-history-end}. One
32321 cannot expect not to receive it either, however; an error annotation
32322 does not necessarily mean that @value{GDBN} is immediately returning all the way
32325 @findex error-begin annotation
32326 A quit or error annotation may be preceded by
32332 Any output between that and the quit or error annotation is the error
32335 Warning messages are not yet annotated.
32336 @c If we want to change that, need to fix warning(), type_error(),
32337 @c range_error(), and possibly other places.
32340 @section Invalidation Notices
32342 @cindex annotations for invalidation messages
32343 The following annotations say that certain pieces of state may have
32347 @findex frames-invalid annotation
32348 @item ^Z^Zframes-invalid
32350 The frames (for example, output from the @code{backtrace} command) may
32353 @findex breakpoints-invalid annotation
32354 @item ^Z^Zbreakpoints-invalid
32356 The breakpoints may have changed. For example, the user just added or
32357 deleted a breakpoint.
32360 @node Annotations for Running
32361 @section Running the Program
32362 @cindex annotations for running programs
32364 @findex starting annotation
32365 @findex stopping annotation
32366 When the program starts executing due to a @value{GDBN} command such as
32367 @code{step} or @code{continue},
32373 is output. When the program stops,
32379 is output. Before the @code{stopped} annotation, a variety of
32380 annotations describe how the program stopped.
32383 @findex exited annotation
32384 @item ^Z^Zexited @var{exit-status}
32385 The program exited, and @var{exit-status} is the exit status (zero for
32386 successful exit, otherwise nonzero).
32388 @findex signalled annotation
32389 @findex signal-name annotation
32390 @findex signal-name-end annotation
32391 @findex signal-string annotation
32392 @findex signal-string-end annotation
32393 @item ^Z^Zsignalled
32394 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32395 annotation continues:
32401 ^Z^Zsignal-name-end
32405 ^Z^Zsignal-string-end
32410 where @var{name} is the name of the signal, such as @code{SIGILL} or
32411 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32412 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32413 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32414 user's benefit and have no particular format.
32416 @findex signal annotation
32418 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32419 just saying that the program received the signal, not that it was
32420 terminated with it.
32422 @findex breakpoint annotation
32423 @item ^Z^Zbreakpoint @var{number}
32424 The program hit breakpoint number @var{number}.
32426 @findex watchpoint annotation
32427 @item ^Z^Zwatchpoint @var{number}
32428 The program hit watchpoint number @var{number}.
32431 @node Source Annotations
32432 @section Displaying Source
32433 @cindex annotations for source display
32435 @findex source annotation
32436 The following annotation is used instead of displaying source code:
32439 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32442 where @var{filename} is an absolute file name indicating which source
32443 file, @var{line} is the line number within that file (where 1 is the
32444 first line in the file), @var{character} is the character position
32445 within the file (where 0 is the first character in the file) (for most
32446 debug formats this will necessarily point to the beginning of a line),
32447 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32448 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32449 @var{addr} is the address in the target program associated with the
32450 source which is being displayed. The @var{addr} is in the form @samp{0x}
32451 followed by one or more lowercase hex digits (note that this does not
32452 depend on the language).
32454 @node JIT Interface
32455 @chapter JIT Compilation Interface
32456 @cindex just-in-time compilation
32457 @cindex JIT compilation interface
32459 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32460 interface. A JIT compiler is a program or library that generates native
32461 executable code at runtime and executes it, usually in order to achieve good
32462 performance while maintaining platform independence.
32464 Programs that use JIT compilation are normally difficult to debug because
32465 portions of their code are generated at runtime, instead of being loaded from
32466 object files, which is where @value{GDBN} normally finds the program's symbols
32467 and debug information. In order to debug programs that use JIT compilation,
32468 @value{GDBN} has an interface that allows the program to register in-memory
32469 symbol files with @value{GDBN} at runtime.
32471 If you are using @value{GDBN} to debug a program that uses this interface, then
32472 it should work transparently so long as you have not stripped the binary. If
32473 you are developing a JIT compiler, then the interface is documented in the rest
32474 of this chapter. At this time, the only known client of this interface is the
32477 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32478 JIT compiler communicates with @value{GDBN} by writing data into a global
32479 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32480 attaches, it reads a linked list of symbol files from the global variable to
32481 find existing code, and puts a breakpoint in the function so that it can find
32482 out about additional code.
32485 * Declarations:: Relevant C struct declarations
32486 * Registering Code:: Steps to register code
32487 * Unregistering Code:: Steps to unregister code
32488 * Custom Debug Info:: Emit debug information in a custom format
32492 @section JIT Declarations
32494 These are the relevant struct declarations that a C program should include to
32495 implement the interface:
32505 struct jit_code_entry
32507 struct jit_code_entry *next_entry;
32508 struct jit_code_entry *prev_entry;
32509 const char *symfile_addr;
32510 uint64_t symfile_size;
32513 struct jit_descriptor
32516 /* This type should be jit_actions_t, but we use uint32_t
32517 to be explicit about the bitwidth. */
32518 uint32_t action_flag;
32519 struct jit_code_entry *relevant_entry;
32520 struct jit_code_entry *first_entry;
32523 /* GDB puts a breakpoint in this function. */
32524 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32526 /* Make sure to specify the version statically, because the
32527 debugger may check the version before we can set it. */
32528 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32531 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32532 modifications to this global data properly, which can easily be done by putting
32533 a global mutex around modifications to these structures.
32535 @node Registering Code
32536 @section Registering Code
32538 To register code with @value{GDBN}, the JIT should follow this protocol:
32542 Generate an object file in memory with symbols and other desired debug
32543 information. The file must include the virtual addresses of the sections.
32546 Create a code entry for the file, which gives the start and size of the symbol
32550 Add it to the linked list in the JIT descriptor.
32553 Point the relevant_entry field of the descriptor at the entry.
32556 Set @code{action_flag} to @code{JIT_REGISTER} and call
32557 @code{__jit_debug_register_code}.
32560 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32561 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32562 new code. However, the linked list must still be maintained in order to allow
32563 @value{GDBN} to attach to a running process and still find the symbol files.
32565 @node Unregistering Code
32566 @section Unregistering Code
32568 If code is freed, then the JIT should use the following protocol:
32572 Remove the code entry corresponding to the code from the linked list.
32575 Point the @code{relevant_entry} field of the descriptor at the code entry.
32578 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32579 @code{__jit_debug_register_code}.
32582 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32583 and the JIT will leak the memory used for the associated symbol files.
32585 @node Custom Debug Info
32586 @section Custom Debug Info
32587 @cindex custom JIT debug info
32588 @cindex JIT debug info reader
32590 Generating debug information in platform-native file formats (like ELF
32591 or COFF) may be an overkill for JIT compilers; especially if all the
32592 debug info is used for is displaying a meaningful backtrace. The
32593 issue can be resolved by having the JIT writers decide on a debug info
32594 format and also provide a reader that parses the debug info generated
32595 by the JIT compiler. This section gives a brief overview on writing
32596 such a parser. More specific details can be found in the source file
32597 @file{gdb/jit-reader.in}, which is also installed as a header at
32598 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32600 The reader is implemented as a shared object (so this functionality is
32601 not available on platforms which don't allow loading shared objects at
32602 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32603 @code{jit-reader-unload} are provided, to be used to load and unload
32604 the readers from a preconfigured directory. Once loaded, the shared
32605 object is used the parse the debug information emitted by the JIT
32609 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32610 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32613 @node Using JIT Debug Info Readers
32614 @subsection Using JIT Debug Info Readers
32615 @kindex jit-reader-load
32616 @kindex jit-reader-unload
32618 Readers can be loaded and unloaded using the @code{jit-reader-load}
32619 and @code{jit-reader-unload} commands.
32622 @item jit-reader-load @var{reader}
32623 Load the JIT reader named @var{reader}, which is a shared
32624 object specified as either an absolute or a relative file name. In
32625 the latter case, @value{GDBN} will try to load the reader from a
32626 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32627 system (here @var{libdir} is the system library directory, often
32628 @file{/usr/local/lib}).
32630 Only one reader can be active at a time; trying to load a second
32631 reader when one is already loaded will result in @value{GDBN}
32632 reporting an error. A new JIT reader can be loaded by first unloading
32633 the current one using @code{jit-reader-unload} and then invoking
32634 @code{jit-reader-load}.
32636 @item jit-reader-unload
32637 Unload the currently loaded JIT reader.
32641 @node Writing JIT Debug Info Readers
32642 @subsection Writing JIT Debug Info Readers
32643 @cindex writing JIT debug info readers
32645 As mentioned, a reader is essentially a shared object conforming to a
32646 certain ABI. This ABI is described in @file{jit-reader.h}.
32648 @file{jit-reader.h} defines the structures, macros and functions
32649 required to write a reader. It is installed (along with
32650 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32651 the system include directory.
32653 Readers need to be released under a GPL compatible license. A reader
32654 can be declared as released under such a license by placing the macro
32655 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32657 The entry point for readers is the symbol @code{gdb_init_reader},
32658 which is expected to be a function with the prototype
32660 @findex gdb_init_reader
32662 extern struct gdb_reader_funcs *gdb_init_reader (void);
32665 @cindex @code{struct gdb_reader_funcs}
32667 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32668 functions. These functions are executed to read the debug info
32669 generated by the JIT compiler (@code{read}), to unwind stack frames
32670 (@code{unwind}) and to create canonical frame IDs
32671 (@code{get_Frame_id}). It also has a callback that is called when the
32672 reader is being unloaded (@code{destroy}). The struct looks like this
32675 struct gdb_reader_funcs
32677 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32678 int reader_version;
32680 /* For use by the reader. */
32683 gdb_read_debug_info *read;
32684 gdb_unwind_frame *unwind;
32685 gdb_get_frame_id *get_frame_id;
32686 gdb_destroy_reader *destroy;
32690 @cindex @code{struct gdb_symbol_callbacks}
32691 @cindex @code{struct gdb_unwind_callbacks}
32693 The callbacks are provided with another set of callbacks by
32694 @value{GDBN} to do their job. For @code{read}, these callbacks are
32695 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32696 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32697 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32698 files and new symbol tables inside those object files. @code{struct
32699 gdb_unwind_callbacks} has callbacks to read registers off the current
32700 frame and to write out the values of the registers in the previous
32701 frame. Both have a callback (@code{target_read}) to read bytes off the
32702 target's address space.
32704 @node In-Process Agent
32705 @chapter In-Process Agent
32706 @cindex debugging agent
32707 The traditional debugging model is conceptually low-speed, but works fine,
32708 because most bugs can be reproduced in debugging-mode execution. However,
32709 as multi-core or many-core processors are becoming mainstream, and
32710 multi-threaded programs become more and more popular, there should be more
32711 and more bugs that only manifest themselves at normal-mode execution, for
32712 example, thread races, because debugger's interference with the program's
32713 timing may conceal the bugs. On the other hand, in some applications,
32714 it is not feasible for the debugger to interrupt the program's execution
32715 long enough for the developer to learn anything helpful about its behavior.
32716 If the program's correctness depends on its real-time behavior, delays
32717 introduced by a debugger might cause the program to fail, even when the
32718 code itself is correct. It is useful to be able to observe the program's
32719 behavior without interrupting it.
32721 Therefore, traditional debugging model is too intrusive to reproduce
32722 some bugs. In order to reduce the interference with the program, we can
32723 reduce the number of operations performed by debugger. The
32724 @dfn{In-Process Agent}, a shared library, is running within the same
32725 process with inferior, and is able to perform some debugging operations
32726 itself. As a result, debugger is only involved when necessary, and
32727 performance of debugging can be improved accordingly. Note that
32728 interference with program can be reduced but can't be removed completely,
32729 because the in-process agent will still stop or slow down the program.
32731 The in-process agent can interpret and execute Agent Expressions
32732 (@pxref{Agent Expressions}) during performing debugging operations. The
32733 agent expressions can be used for different purposes, such as collecting
32734 data in tracepoints, and condition evaluation in breakpoints.
32736 @anchor{Control Agent}
32737 You can control whether the in-process agent is used as an aid for
32738 debugging with the following commands:
32741 @kindex set agent on
32743 Causes the in-process agent to perform some operations on behalf of the
32744 debugger. Just which operations requested by the user will be done
32745 by the in-process agent depends on the its capabilities. For example,
32746 if you request to evaluate breakpoint conditions in the in-process agent,
32747 and the in-process agent has such capability as well, then breakpoint
32748 conditions will be evaluated in the in-process agent.
32750 @kindex set agent off
32751 @item set agent off
32752 Disables execution of debugging operations by the in-process agent. All
32753 of the operations will be performed by @value{GDBN}.
32757 Display the current setting of execution of debugging operations by
32758 the in-process agent.
32762 * In-Process Agent Protocol::
32765 @node In-Process Agent Protocol
32766 @section In-Process Agent Protocol
32767 @cindex in-process agent protocol
32769 The in-process agent is able to communicate with both @value{GDBN} and
32770 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32771 used for communications between @value{GDBN} or GDBserver and the IPA.
32772 In general, @value{GDBN} or GDBserver sends commands
32773 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32774 in-process agent replies back with the return result of the command, or
32775 some other information. The data sent to in-process agent is composed
32776 of primitive data types, such as 4-byte or 8-byte type, and composite
32777 types, which are called objects (@pxref{IPA Protocol Objects}).
32780 * IPA Protocol Objects::
32781 * IPA Protocol Commands::
32784 @node IPA Protocol Objects
32785 @subsection IPA Protocol Objects
32786 @cindex ipa protocol objects
32788 The commands sent to and results received from agent may contain some
32789 complex data types called @dfn{objects}.
32791 The in-process agent is running on the same machine with @value{GDBN}
32792 or GDBserver, so it doesn't have to handle as much differences between
32793 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32794 However, there are still some differences of two ends in two processes:
32798 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32799 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32801 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32802 GDBserver is compiled with one, and in-process agent is compiled with
32806 Here are the IPA Protocol Objects:
32810 agent expression object. It represents an agent expression
32811 (@pxref{Agent Expressions}).
32812 @anchor{agent expression object}
32814 tracepoint action object. It represents a tracepoint action
32815 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32816 memory, static trace data and to evaluate expression.
32817 @anchor{tracepoint action object}
32819 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32820 @anchor{tracepoint object}
32824 The following table describes important attributes of each IPA protocol
32827 @multitable @columnfractions .30 .20 .50
32828 @headitem Name @tab Size @tab Description
32829 @item @emph{agent expression object} @tab @tab
32830 @item length @tab 4 @tab length of bytes code
32831 @item byte code @tab @var{length} @tab contents of byte code
32832 @item @emph{tracepoint action for collecting memory} @tab @tab
32833 @item 'M' @tab 1 @tab type of tracepoint action
32834 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32835 address of the lowest byte to collect, otherwise @var{addr} is the offset
32836 of @var{basereg} for memory collecting.
32837 @item len @tab 8 @tab length of memory for collecting
32838 @item basereg @tab 4 @tab the register number containing the starting
32839 memory address for collecting.
32840 @item @emph{tracepoint action for collecting registers} @tab @tab
32841 @item 'R' @tab 1 @tab type of tracepoint action
32842 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32843 @item 'L' @tab 1 @tab type of tracepoint action
32844 @item @emph{tracepoint action for expression evaluation} @tab @tab
32845 @item 'X' @tab 1 @tab type of tracepoint action
32846 @item agent expression @tab length of @tab @ref{agent expression object}
32847 @item @emph{tracepoint object} @tab @tab
32848 @item number @tab 4 @tab number of tracepoint
32849 @item address @tab 8 @tab address of tracepoint inserted on
32850 @item type @tab 4 @tab type of tracepoint
32851 @item enabled @tab 1 @tab enable or disable of tracepoint
32852 @item step_count @tab 8 @tab step
32853 @item pass_count @tab 8 @tab pass
32854 @item numactions @tab 4 @tab number of tracepoint actions
32855 @item hit count @tab 8 @tab hit count
32856 @item trace frame usage @tab 8 @tab trace frame usage
32857 @item compiled_cond @tab 8 @tab compiled condition
32858 @item orig_size @tab 8 @tab orig size
32859 @item condition @tab 4 if condition is NULL otherwise length of
32860 @ref{agent expression object}
32861 @tab zero if condition is NULL, otherwise is
32862 @ref{agent expression object}
32863 @item actions @tab variable
32864 @tab numactions number of @ref{tracepoint action object}
32867 @node IPA Protocol Commands
32868 @subsection IPA Protocol Commands
32869 @cindex ipa protocol commands
32871 The spaces in each command are delimiters to ease reading this commands
32872 specification. They don't exist in real commands.
32876 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32877 Installs a new fast tracepoint described by @var{tracepoint_object}
32878 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32879 head of @dfn{jumppad}, which is used to jump to data collection routine
32884 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32885 @var{target_address} is address of tracepoint in the inferior.
32886 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32887 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32888 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32889 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32896 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32897 is about to kill inferiors.
32905 @item probe_marker_at:@var{address}
32906 Asks in-process agent to probe the marker at @var{address}.
32913 @item unprobe_marker_at:@var{address}
32914 Asks in-process agent to unprobe the marker at @var{address}.
32918 @chapter Reporting Bugs in @value{GDBN}
32919 @cindex bugs in @value{GDBN}
32920 @cindex reporting bugs in @value{GDBN}
32922 Your bug reports play an essential role in making @value{GDBN} reliable.
32924 Reporting a bug may help you by bringing a solution to your problem, or it
32925 may not. But in any case the principal function of a bug report is to help
32926 the entire community by making the next version of @value{GDBN} work better. Bug
32927 reports are your contribution to the maintenance of @value{GDBN}.
32929 In order for a bug report to serve its purpose, you must include the
32930 information that enables us to fix the bug.
32933 * Bug Criteria:: Have you found a bug?
32934 * Bug Reporting:: How to report bugs
32938 @section Have You Found a Bug?
32939 @cindex bug criteria
32941 If you are not sure whether you have found a bug, here are some guidelines:
32944 @cindex fatal signal
32945 @cindex debugger crash
32946 @cindex crash of debugger
32948 If the debugger gets a fatal signal, for any input whatever, that is a
32949 @value{GDBN} bug. Reliable debuggers never crash.
32951 @cindex error on valid input
32953 If @value{GDBN} produces an error message for valid input, that is a
32954 bug. (Note that if you're cross debugging, the problem may also be
32955 somewhere in the connection to the target.)
32957 @cindex invalid input
32959 If @value{GDBN} does not produce an error message for invalid input,
32960 that is a bug. However, you should note that your idea of
32961 ``invalid input'' might be our idea of ``an extension'' or ``support
32962 for traditional practice''.
32965 If you are an experienced user of debugging tools, your suggestions
32966 for improvement of @value{GDBN} are welcome in any case.
32969 @node Bug Reporting
32970 @section How to Report Bugs
32971 @cindex bug reports
32972 @cindex @value{GDBN} bugs, reporting
32974 A number of companies and individuals offer support for @sc{gnu} products.
32975 If you obtained @value{GDBN} from a support organization, we recommend you
32976 contact that organization first.
32978 You can find contact information for many support companies and
32979 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32981 @c should add a web page ref...
32984 @ifset BUGURL_DEFAULT
32985 In any event, we also recommend that you submit bug reports for
32986 @value{GDBN}. The preferred method is to submit them directly using
32987 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32988 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32991 @strong{Do not send bug reports to @samp{info-gdb}, or to
32992 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32993 not want to receive bug reports. Those that do have arranged to receive
32996 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32997 serves as a repeater. The mailing list and the newsgroup carry exactly
32998 the same messages. Often people think of posting bug reports to the
32999 newsgroup instead of mailing them. This appears to work, but it has one
33000 problem which can be crucial: a newsgroup posting often lacks a mail
33001 path back to the sender. Thus, if we need to ask for more information,
33002 we may be unable to reach you. For this reason, it is better to send
33003 bug reports to the mailing list.
33005 @ifclear BUGURL_DEFAULT
33006 In any event, we also recommend that you submit bug reports for
33007 @value{GDBN} to @value{BUGURL}.
33011 The fundamental principle of reporting bugs usefully is this:
33012 @strong{report all the facts}. If you are not sure whether to state a
33013 fact or leave it out, state it!
33015 Often people omit facts because they think they know what causes the
33016 problem and assume that some details do not matter. Thus, you might
33017 assume that the name of the variable you use in an example does not matter.
33018 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33019 stray memory reference which happens to fetch from the location where that
33020 name is stored in memory; perhaps, if the name were different, the contents
33021 of that location would fool the debugger into doing the right thing despite
33022 the bug. Play it safe and give a specific, complete example. That is the
33023 easiest thing for you to do, and the most helpful.
33025 Keep in mind that the purpose of a bug report is to enable us to fix the
33026 bug. It may be that the bug has been reported previously, but neither
33027 you nor we can know that unless your bug report is complete and
33030 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33031 bell?'' Those bug reports are useless, and we urge everyone to
33032 @emph{refuse to respond to them} except to chide the sender to report
33035 To enable us to fix the bug, you should include all these things:
33039 The version of @value{GDBN}. @value{GDBN} announces it if you start
33040 with no arguments; you can also print it at any time using @code{show
33043 Without this, we will not know whether there is any point in looking for
33044 the bug in the current version of @value{GDBN}.
33047 The type of machine you are using, and the operating system name and
33051 The details of the @value{GDBN} build-time configuration.
33052 @value{GDBN} shows these details if you invoke it with the
33053 @option{--configuration} command-line option, or if you type
33054 @code{show configuration} at @value{GDBN}'s prompt.
33057 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33058 ``@value{GCC}--2.8.1''.
33061 What compiler (and its version) was used to compile the program you are
33062 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33063 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33064 to get this information; for other compilers, see the documentation for
33068 The command arguments you gave the compiler to compile your example and
33069 observe the bug. For example, did you use @samp{-O}? To guarantee
33070 you will not omit something important, list them all. A copy of the
33071 Makefile (or the output from make) is sufficient.
33073 If we were to try to guess the arguments, we would probably guess wrong
33074 and then we might not encounter the bug.
33077 A complete input script, and all necessary source files, that will
33081 A description of what behavior you observe that you believe is
33082 incorrect. For example, ``It gets a fatal signal.''
33084 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33085 will certainly notice it. But if the bug is incorrect output, we might
33086 not notice unless it is glaringly wrong. You might as well not give us
33087 a chance to make a mistake.
33089 Even if the problem you experience is a fatal signal, you should still
33090 say so explicitly. Suppose something strange is going on, such as, your
33091 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33092 the C library on your system. (This has happened!) Your copy might
33093 crash and ours would not. If you told us to expect a crash, then when
33094 ours fails to crash, we would know that the bug was not happening for
33095 us. If you had not told us to expect a crash, then we would not be able
33096 to draw any conclusion from our observations.
33099 @cindex recording a session script
33100 To collect all this information, you can use a session recording program
33101 such as @command{script}, which is available on many Unix systems.
33102 Just run your @value{GDBN} session inside @command{script} and then
33103 include the @file{typescript} file with your bug report.
33105 Another way to record a @value{GDBN} session is to run @value{GDBN}
33106 inside Emacs and then save the entire buffer to a file.
33109 If you wish to suggest changes to the @value{GDBN} source, send us context
33110 diffs. If you even discuss something in the @value{GDBN} source, refer to
33111 it by context, not by line number.
33113 The line numbers in our development sources will not match those in your
33114 sources. Your line numbers would convey no useful information to us.
33118 Here are some things that are not necessary:
33122 A description of the envelope of the bug.
33124 Often people who encounter a bug spend a lot of time investigating
33125 which changes to the input file will make the bug go away and which
33126 changes will not affect it.
33128 This is often time consuming and not very useful, because the way we
33129 will find the bug is by running a single example under the debugger
33130 with breakpoints, not by pure deduction from a series of examples.
33131 We recommend that you save your time for something else.
33133 Of course, if you can find a simpler example to report @emph{instead}
33134 of the original one, that is a convenience for us. Errors in the
33135 output will be easier to spot, running under the debugger will take
33136 less time, and so on.
33138 However, simplification is not vital; if you do not want to do this,
33139 report the bug anyway and send us the entire test case you used.
33142 A patch for the bug.
33144 A patch for the bug does help us if it is a good one. But do not omit
33145 the necessary information, such as the test case, on the assumption that
33146 a patch is all we need. We might see problems with your patch and decide
33147 to fix the problem another way, or we might not understand it at all.
33149 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33150 construct an example that will make the program follow a certain path
33151 through the code. If you do not send us the example, we will not be able
33152 to construct one, so we will not be able to verify that the bug is fixed.
33154 And if we cannot understand what bug you are trying to fix, or why your
33155 patch should be an improvement, we will not install it. A test case will
33156 help us to understand.
33159 A guess about what the bug is or what it depends on.
33161 Such guesses are usually wrong. Even we cannot guess right about such
33162 things without first using the debugger to find the facts.
33165 @c The readline documentation is distributed with the readline code
33166 @c and consists of the two following files:
33169 @c Use -I with makeinfo to point to the appropriate directory,
33170 @c environment var TEXINPUTS with TeX.
33171 @ifclear SYSTEM_READLINE
33172 @include rluser.texi
33173 @include hsuser.texi
33177 @appendix In Memoriam
33179 The @value{GDBN} project mourns the loss of the following long-time
33184 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33185 to Free Software in general. Outside of @value{GDBN}, he was known in
33186 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33188 @item Michael Snyder
33189 Michael was one of the Global Maintainers of the @value{GDBN} project,
33190 with contributions recorded as early as 1996, until 2011. In addition
33191 to his day to day participation, he was a large driving force behind
33192 adding Reverse Debugging to @value{GDBN}.
33195 Beyond their technical contributions to the project, they were also
33196 enjoyable members of the Free Software Community. We will miss them.
33198 @node Formatting Documentation
33199 @appendix Formatting Documentation
33201 @cindex @value{GDBN} reference card
33202 @cindex reference card
33203 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33204 for printing with PostScript or Ghostscript, in the @file{gdb}
33205 subdirectory of the main source directory@footnote{In
33206 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33207 release.}. If you can use PostScript or Ghostscript with your printer,
33208 you can print the reference card immediately with @file{refcard.ps}.
33210 The release also includes the source for the reference card. You
33211 can format it, using @TeX{}, by typing:
33217 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33218 mode on US ``letter'' size paper;
33219 that is, on a sheet 11 inches wide by 8.5 inches
33220 high. You will need to specify this form of printing as an option to
33221 your @sc{dvi} output program.
33223 @cindex documentation
33225 All the documentation for @value{GDBN} comes as part of the machine-readable
33226 distribution. The documentation is written in Texinfo format, which is
33227 a documentation system that uses a single source file to produce both
33228 on-line information and a printed manual. You can use one of the Info
33229 formatting commands to create the on-line version of the documentation
33230 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33232 @value{GDBN} includes an already formatted copy of the on-line Info
33233 version of this manual in the @file{gdb} subdirectory. The main Info
33234 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33235 subordinate files matching @samp{gdb.info*} in the same directory. If
33236 necessary, you can print out these files, or read them with any editor;
33237 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33238 Emacs or the standalone @code{info} program, available as part of the
33239 @sc{gnu} Texinfo distribution.
33241 If you want to format these Info files yourself, you need one of the
33242 Info formatting programs, such as @code{texinfo-format-buffer} or
33245 If you have @code{makeinfo} installed, and are in the top level
33246 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33247 version @value{GDBVN}), you can make the Info file by typing:
33254 If you want to typeset and print copies of this manual, you need @TeX{},
33255 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33256 Texinfo definitions file.
33258 @TeX{} is a typesetting program; it does not print files directly, but
33259 produces output files called @sc{dvi} files. To print a typeset
33260 document, you need a program to print @sc{dvi} files. If your system
33261 has @TeX{} installed, chances are it has such a program. The precise
33262 command to use depends on your system; @kbd{lpr -d} is common; another
33263 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33264 require a file name without any extension or a @samp{.dvi} extension.
33266 @TeX{} also requires a macro definitions file called
33267 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33268 written in Texinfo format. On its own, @TeX{} cannot either read or
33269 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33270 and is located in the @file{gdb-@var{version-number}/texinfo}
33273 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33274 typeset and print this manual. First switch to the @file{gdb}
33275 subdirectory of the main source directory (for example, to
33276 @file{gdb-@value{GDBVN}/gdb}) and type:
33282 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33284 @node Installing GDB
33285 @appendix Installing @value{GDBN}
33286 @cindex installation
33289 * Requirements:: Requirements for building @value{GDBN}
33290 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33291 * Separate Objdir:: Compiling @value{GDBN} in another directory
33292 * Config Names:: Specifying names for hosts and targets
33293 * Configure Options:: Summary of options for configure
33294 * System-wide configuration:: Having a system-wide init file
33298 @section Requirements for Building @value{GDBN}
33299 @cindex building @value{GDBN}, requirements for
33301 Building @value{GDBN} requires various tools and packages to be available.
33302 Other packages will be used only if they are found.
33304 @heading Tools/Packages Necessary for Building @value{GDBN}
33306 @item ISO C90 compiler
33307 @value{GDBN} is written in ISO C90. It should be buildable with any
33308 working C90 compiler, e.g.@: GCC.
33312 @heading Tools/Packages Optional for Building @value{GDBN}
33316 @value{GDBN} can use the Expat XML parsing library. This library may be
33317 included with your operating system distribution; if it is not, you
33318 can get the latest version from @url{http://expat.sourceforge.net}.
33319 The @file{configure} script will search for this library in several
33320 standard locations; if it is installed in an unusual path, you can
33321 use the @option{--with-libexpat-prefix} option to specify its location.
33327 Remote protocol memory maps (@pxref{Memory Map Format})
33329 Target descriptions (@pxref{Target Descriptions})
33331 Remote shared library lists (@xref{Library List Format},
33332 or alternatively @pxref{Library List Format for SVR4 Targets})
33334 MS-Windows shared libraries (@pxref{Shared Libraries})
33336 Traceframe info (@pxref{Traceframe Info Format})
33338 Branch trace (@pxref{Branch Trace Format},
33339 @pxref{Branch Trace Configuration Format})
33343 @cindex compressed debug sections
33344 @value{GDBN} will use the @samp{zlib} library, if available, to read
33345 compressed debug sections. Some linkers, such as GNU gold, are capable
33346 of producing binaries with compressed debug sections. If @value{GDBN}
33347 is compiled with @samp{zlib}, it will be able to read the debug
33348 information in such binaries.
33350 The @samp{zlib} library is likely included with your operating system
33351 distribution; if it is not, you can get the latest version from
33352 @url{http://zlib.net}.
33355 @value{GDBN}'s features related to character sets (@pxref{Character
33356 Sets}) require a functioning @code{iconv} implementation. If you are
33357 on a GNU system, then this is provided by the GNU C Library. Some
33358 other systems also provide a working @code{iconv}.
33360 If @value{GDBN} is using the @code{iconv} program which is installed
33361 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33362 This is done with @option{--with-iconv-bin} which specifies the
33363 directory that contains the @code{iconv} program.
33365 On systems without @code{iconv}, you can install GNU Libiconv. If you
33366 have previously installed Libiconv, you can use the
33367 @option{--with-libiconv-prefix} option to configure.
33369 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33370 arrange to build Libiconv if a directory named @file{libiconv} appears
33371 in the top-most source directory. If Libiconv is built this way, and
33372 if the operating system does not provide a suitable @code{iconv}
33373 implementation, then the just-built library will automatically be used
33374 by @value{GDBN}. One easy way to set this up is to download GNU
33375 Libiconv, unpack it, and then rename the directory holding the
33376 Libiconv source code to @samp{libiconv}.
33379 @node Running Configure
33380 @section Invoking the @value{GDBN} @file{configure} Script
33381 @cindex configuring @value{GDBN}
33382 @value{GDBN} comes with a @file{configure} script that automates the process
33383 of preparing @value{GDBN} for installation; you can then use @code{make} to
33384 build the @code{gdb} program.
33386 @c irrelevant in info file; it's as current as the code it lives with.
33387 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33388 look at the @file{README} file in the sources; we may have improved the
33389 installation procedures since publishing this manual.}
33392 The @value{GDBN} distribution includes all the source code you need for
33393 @value{GDBN} in a single directory, whose name is usually composed by
33394 appending the version number to @samp{gdb}.
33396 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33397 @file{gdb-@value{GDBVN}} directory. That directory contains:
33400 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33401 script for configuring @value{GDBN} and all its supporting libraries
33403 @item gdb-@value{GDBVN}/gdb
33404 the source specific to @value{GDBN} itself
33406 @item gdb-@value{GDBVN}/bfd
33407 source for the Binary File Descriptor library
33409 @item gdb-@value{GDBVN}/include
33410 @sc{gnu} include files
33412 @item gdb-@value{GDBVN}/libiberty
33413 source for the @samp{-liberty} free software library
33415 @item gdb-@value{GDBVN}/opcodes
33416 source for the library of opcode tables and disassemblers
33418 @item gdb-@value{GDBVN}/readline
33419 source for the @sc{gnu} command-line interface
33421 @item gdb-@value{GDBVN}/glob
33422 source for the @sc{gnu} filename pattern-matching subroutine
33424 @item gdb-@value{GDBVN}/mmalloc
33425 source for the @sc{gnu} memory-mapped malloc package
33428 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33429 from the @file{gdb-@var{version-number}} source directory, which in
33430 this example is the @file{gdb-@value{GDBVN}} directory.
33432 First switch to the @file{gdb-@var{version-number}} source directory
33433 if you are not already in it; then run @file{configure}. Pass the
33434 identifier for the platform on which @value{GDBN} will run as an
33440 cd gdb-@value{GDBVN}
33441 ./configure @var{host}
33446 where @var{host} is an identifier such as @samp{sun4} or
33447 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33448 (You can often leave off @var{host}; @file{configure} tries to guess the
33449 correct value by examining your system.)
33451 Running @samp{configure @var{host}} and then running @code{make} builds the
33452 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33453 libraries, then @code{gdb} itself. The configured source files, and the
33454 binaries, are left in the corresponding source directories.
33457 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33458 system does not recognize this automatically when you run a different
33459 shell, you may need to run @code{sh} on it explicitly:
33462 sh configure @var{host}
33465 If you run @file{configure} from a directory that contains source
33466 directories for multiple libraries or programs, such as the
33467 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33469 creates configuration files for every directory level underneath (unless
33470 you tell it not to, with the @samp{--norecursion} option).
33472 You should run the @file{configure} script from the top directory in the
33473 source tree, the @file{gdb-@var{version-number}} directory. If you run
33474 @file{configure} from one of the subdirectories, you will configure only
33475 that subdirectory. That is usually not what you want. In particular,
33476 if you run the first @file{configure} from the @file{gdb} subdirectory
33477 of the @file{gdb-@var{version-number}} directory, you will omit the
33478 configuration of @file{bfd}, @file{readline}, and other sibling
33479 directories of the @file{gdb} subdirectory. This leads to build errors
33480 about missing include files such as @file{bfd/bfd.h}.
33482 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33483 However, you should make sure that the shell on your path (named by
33484 the @samp{SHELL} environment variable) is publicly readable. Remember
33485 that @value{GDBN} uses the shell to start your program---some systems refuse to
33486 let @value{GDBN} debug child processes whose programs are not readable.
33488 @node Separate Objdir
33489 @section Compiling @value{GDBN} in Another Directory
33491 If you want to run @value{GDBN} versions for several host or target machines,
33492 you need a different @code{gdb} compiled for each combination of
33493 host and target. @file{configure} is designed to make this easy by
33494 allowing you to generate each configuration in a separate subdirectory,
33495 rather than in the source directory. If your @code{make} program
33496 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33497 @code{make} in each of these directories builds the @code{gdb}
33498 program specified there.
33500 To build @code{gdb} in a separate directory, run @file{configure}
33501 with the @samp{--srcdir} option to specify where to find the source.
33502 (You also need to specify a path to find @file{configure}
33503 itself from your working directory. If the path to @file{configure}
33504 would be the same as the argument to @samp{--srcdir}, you can leave out
33505 the @samp{--srcdir} option; it is assumed.)
33507 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33508 separate directory for a Sun 4 like this:
33512 cd gdb-@value{GDBVN}
33515 ../gdb-@value{GDBVN}/configure sun4
33520 When @file{configure} builds a configuration using a remote source
33521 directory, it creates a tree for the binaries with the same structure
33522 (and using the same names) as the tree under the source directory. In
33523 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33524 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33525 @file{gdb-sun4/gdb}.
33527 Make sure that your path to the @file{configure} script has just one
33528 instance of @file{gdb} in it. If your path to @file{configure} looks
33529 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33530 one subdirectory of @value{GDBN}, not the whole package. This leads to
33531 build errors about missing include files such as @file{bfd/bfd.h}.
33533 One popular reason to build several @value{GDBN} configurations in separate
33534 directories is to configure @value{GDBN} for cross-compiling (where
33535 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33536 programs that run on another machine---the @dfn{target}).
33537 You specify a cross-debugging target by
33538 giving the @samp{--target=@var{target}} option to @file{configure}.
33540 When you run @code{make} to build a program or library, you must run
33541 it in a configured directory---whatever directory you were in when you
33542 called @file{configure} (or one of its subdirectories).
33544 The @code{Makefile} that @file{configure} generates in each source
33545 directory also runs recursively. If you type @code{make} in a source
33546 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33547 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33548 will build all the required libraries, and then build GDB.
33550 When you have multiple hosts or targets configured in separate
33551 directories, you can run @code{make} on them in parallel (for example,
33552 if they are NFS-mounted on each of the hosts); they will not interfere
33556 @section Specifying Names for Hosts and Targets
33558 The specifications used for hosts and targets in the @file{configure}
33559 script are based on a three-part naming scheme, but some short predefined
33560 aliases are also supported. The full naming scheme encodes three pieces
33561 of information in the following pattern:
33564 @var{architecture}-@var{vendor}-@var{os}
33567 For example, you can use the alias @code{sun4} as a @var{host} argument,
33568 or as the value for @var{target} in a @code{--target=@var{target}}
33569 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33571 The @file{configure} script accompanying @value{GDBN} does not provide
33572 any query facility to list all supported host and target names or
33573 aliases. @file{configure} calls the Bourne shell script
33574 @code{config.sub} to map abbreviations to full names; you can read the
33575 script, if you wish, or you can use it to test your guesses on
33576 abbreviations---for example:
33579 % sh config.sub i386-linux
33581 % sh config.sub alpha-linux
33582 alpha-unknown-linux-gnu
33583 % sh config.sub hp9k700
33585 % sh config.sub sun4
33586 sparc-sun-sunos4.1.1
33587 % sh config.sub sun3
33588 m68k-sun-sunos4.1.1
33589 % sh config.sub i986v
33590 Invalid configuration `i986v': machine `i986v' not recognized
33594 @code{config.sub} is also distributed in the @value{GDBN} source
33595 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33597 @node Configure Options
33598 @section @file{configure} Options
33600 Here is a summary of the @file{configure} options and arguments that
33601 are most often useful for building @value{GDBN}. @file{configure} also has
33602 several other options not listed here. @inforef{What Configure
33603 Does,,configure.info}, for a full explanation of @file{configure}.
33606 configure @r{[}--help@r{]}
33607 @r{[}--prefix=@var{dir}@r{]}
33608 @r{[}--exec-prefix=@var{dir}@r{]}
33609 @r{[}--srcdir=@var{dirname}@r{]}
33610 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33611 @r{[}--target=@var{target}@r{]}
33616 You may introduce options with a single @samp{-} rather than
33617 @samp{--} if you prefer; but you may abbreviate option names if you use
33622 Display a quick summary of how to invoke @file{configure}.
33624 @item --prefix=@var{dir}
33625 Configure the source to install programs and files under directory
33628 @item --exec-prefix=@var{dir}
33629 Configure the source to install programs under directory
33632 @c avoid splitting the warning from the explanation:
33634 @item --srcdir=@var{dirname}
33635 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33636 @code{make} that implements the @code{VPATH} feature.}@*
33637 Use this option to make configurations in directories separate from the
33638 @value{GDBN} source directories. Among other things, you can use this to
33639 build (or maintain) several configurations simultaneously, in separate
33640 directories. @file{configure} writes configuration-specific files in
33641 the current directory, but arranges for them to use the source in the
33642 directory @var{dirname}. @file{configure} creates directories under
33643 the working directory in parallel to the source directories below
33646 @item --norecursion
33647 Configure only the directory level where @file{configure} is executed; do not
33648 propagate configuration to subdirectories.
33650 @item --target=@var{target}
33651 Configure @value{GDBN} for cross-debugging programs running on the specified
33652 @var{target}. Without this option, @value{GDBN} is configured to debug
33653 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33655 There is no convenient way to generate a list of all available targets.
33657 @item @var{host} @dots{}
33658 Configure @value{GDBN} to run on the specified @var{host}.
33660 There is no convenient way to generate a list of all available hosts.
33663 There are many other options available as well, but they are generally
33664 needed for special purposes only.
33666 @node System-wide configuration
33667 @section System-wide configuration and settings
33668 @cindex system-wide init file
33670 @value{GDBN} can be configured to have a system-wide init file;
33671 this file will be read and executed at startup (@pxref{Startup, , What
33672 @value{GDBN} does during startup}).
33674 Here is the corresponding configure option:
33677 @item --with-system-gdbinit=@var{file}
33678 Specify that the default location of the system-wide init file is
33682 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33683 it may be subject to relocation. Two possible cases:
33687 If the default location of this init file contains @file{$prefix},
33688 it will be subject to relocation. Suppose that the configure options
33689 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33690 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33691 init file is looked for as @file{$install/etc/gdbinit} instead of
33692 @file{$prefix/etc/gdbinit}.
33695 By contrast, if the default location does not contain the prefix,
33696 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33697 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33698 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33699 wherever @value{GDBN} is installed.
33702 If the configured location of the system-wide init file (as given by the
33703 @option{--with-system-gdbinit} option at configure time) is in the
33704 data-directory (as specified by @option{--with-gdb-datadir} at configure
33705 time) or in one of its subdirectories, then @value{GDBN} will look for the
33706 system-wide init file in the directory specified by the
33707 @option{--data-directory} command-line option.
33708 Note that the system-wide init file is only read once, during @value{GDBN}
33709 initialization. If the data-directory is changed after @value{GDBN} has
33710 started with the @code{set data-directory} command, the file will not be
33714 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33717 @node System-wide Configuration Scripts
33718 @subsection Installed System-wide Configuration Scripts
33719 @cindex system-wide configuration scripts
33721 The @file{system-gdbinit} directory, located inside the data-directory
33722 (as specified by @option{--with-gdb-datadir} at configure time) contains
33723 a number of scripts which can be used as system-wide init files. To
33724 automatically source those scripts at startup, @value{GDBN} should be
33725 configured with @option{--with-system-gdbinit}. Otherwise, any user
33726 should be able to source them by hand as needed.
33728 The following scripts are currently available:
33731 @item @file{elinos.py}
33733 @cindex ELinOS system-wide configuration script
33734 This script is useful when debugging a program on an ELinOS target.
33735 It takes advantage of the environment variables defined in a standard
33736 ELinOS environment in order to determine the location of the system
33737 shared libraries, and then sets the @samp{solib-absolute-prefix}
33738 and @samp{solib-search-path} variables appropriately.
33740 @item @file{wrs-linux.py}
33741 @pindex wrs-linux.py
33742 @cindex Wind River Linux system-wide configuration script
33743 This script is useful when debugging a program on a target running
33744 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33745 the host-side sysroot used by the target system.
33749 @node Maintenance Commands
33750 @appendix Maintenance Commands
33751 @cindex maintenance commands
33752 @cindex internal commands
33754 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33755 includes a number of commands intended for @value{GDBN} developers,
33756 that are not documented elsewhere in this manual. These commands are
33757 provided here for reference. (For commands that turn on debugging
33758 messages, see @ref{Debugging Output}.)
33761 @kindex maint agent
33762 @kindex maint agent-eval
33763 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33764 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33765 Translate the given @var{expression} into remote agent bytecodes.
33766 This command is useful for debugging the Agent Expression mechanism
33767 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33768 expression useful for data collection, such as by tracepoints, while
33769 @samp{maint agent-eval} produces an expression that evaluates directly
33770 to a result. For instance, a collection expression for @code{globa +
33771 globb} will include bytecodes to record four bytes of memory at each
33772 of the addresses of @code{globa} and @code{globb}, while discarding
33773 the result of the addition, while an evaluation expression will do the
33774 addition and return the sum.
33775 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33776 If not, generate remote agent bytecode for current frame PC address.
33778 @kindex maint agent-printf
33779 @item maint agent-printf @var{format},@var{expr},...
33780 Translate the given format string and list of argument expressions
33781 into remote agent bytecodes and display them as a disassembled list.
33782 This command is useful for debugging the agent version of dynamic
33783 printf (@pxref{Dynamic Printf}).
33785 @kindex maint info breakpoints
33786 @item @anchor{maint info breakpoints}maint info breakpoints
33787 Using the same format as @samp{info breakpoints}, display both the
33788 breakpoints you've set explicitly, and those @value{GDBN} is using for
33789 internal purposes. Internal breakpoints are shown with negative
33790 breakpoint numbers. The type column identifies what kind of breakpoint
33795 Normal, explicitly set breakpoint.
33798 Normal, explicitly set watchpoint.
33801 Internal breakpoint, used to handle correctly stepping through
33802 @code{longjmp} calls.
33804 @item longjmp resume
33805 Internal breakpoint at the target of a @code{longjmp}.
33808 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33811 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33814 Shared library events.
33818 @kindex maint info bfds
33819 @item maint info bfds
33820 This prints information about each @code{bfd} object that is known to
33821 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33823 @kindex set displaced-stepping
33824 @kindex show displaced-stepping
33825 @cindex displaced stepping support
33826 @cindex out-of-line single-stepping
33827 @item set displaced-stepping
33828 @itemx show displaced-stepping
33829 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33830 if the target supports it. Displaced stepping is a way to single-step
33831 over breakpoints without removing them from the inferior, by executing
33832 an out-of-line copy of the instruction that was originally at the
33833 breakpoint location. It is also known as out-of-line single-stepping.
33836 @item set displaced-stepping on
33837 If the target architecture supports it, @value{GDBN} will use
33838 displaced stepping to step over breakpoints.
33840 @item set displaced-stepping off
33841 @value{GDBN} will not use displaced stepping to step over breakpoints,
33842 even if such is supported by the target architecture.
33844 @cindex non-stop mode, and @samp{set displaced-stepping}
33845 @item set displaced-stepping auto
33846 This is the default mode. @value{GDBN} will use displaced stepping
33847 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33848 architecture supports displaced stepping.
33851 @kindex maint check-psymtabs
33852 @item maint check-psymtabs
33853 Check the consistency of currently expanded psymtabs versus symtabs.
33854 Use this to check, for example, whether a symbol is in one but not the other.
33856 @kindex maint check-symtabs
33857 @item maint check-symtabs
33858 Check the consistency of currently expanded symtabs.
33860 @kindex maint expand-symtabs
33861 @item maint expand-symtabs [@var{regexp}]
33862 Expand symbol tables.
33863 If @var{regexp} is specified, only expand symbol tables for file
33864 names matching @var{regexp}.
33866 @kindex maint set catch-demangler-crashes
33867 @kindex maint show catch-demangler-crashes
33868 @cindex demangler crashes
33869 @item maint set catch-demangler-crashes [on|off]
33870 @itemx maint show catch-demangler-crashes
33871 Control whether @value{GDBN} should attempt to catch crashes in the
33872 symbol name demangler. The default is to attempt to catch crashes.
33873 If enabled, the first time a crash is caught, a core file is created,
33874 the offending symbol is displayed and the user is presented with the
33875 option to terminate the current session.
33877 @kindex maint cplus first_component
33878 @item maint cplus first_component @var{name}
33879 Print the first C@t{++} class/namespace component of @var{name}.
33881 @kindex maint cplus namespace
33882 @item maint cplus namespace
33883 Print the list of possible C@t{++} namespaces.
33885 @kindex maint deprecate
33886 @kindex maint undeprecate
33887 @cindex deprecated commands
33888 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33889 @itemx maint undeprecate @var{command}
33890 Deprecate or undeprecate the named @var{command}. Deprecated commands
33891 cause @value{GDBN} to issue a warning when you use them. The optional
33892 argument @var{replacement} says which newer command should be used in
33893 favor of the deprecated one; if it is given, @value{GDBN} will mention
33894 the replacement as part of the warning.
33896 @kindex maint dump-me
33897 @item maint dump-me
33898 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33899 Cause a fatal signal in the debugger and force it to dump its core.
33900 This is supported only on systems which support aborting a program
33901 with the @code{SIGQUIT} signal.
33903 @kindex maint internal-error
33904 @kindex maint internal-warning
33905 @kindex maint demangler-warning
33906 @cindex demangler crashes
33907 @item maint internal-error @r{[}@var{message-text}@r{]}
33908 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33909 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33911 Cause @value{GDBN} to call the internal function @code{internal_error},
33912 @code{internal_warning} or @code{demangler_warning} and hence behave
33913 as though an internal problem has been detected. In addition to
33914 reporting the internal problem, these functions give the user the
33915 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33916 and @code{internal_warning}) create a core file of the current
33917 @value{GDBN} session.
33919 These commands take an optional parameter @var{message-text} that is
33920 used as the text of the error or warning message.
33922 Here's an example of using @code{internal-error}:
33925 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33926 @dots{}/maint.c:121: internal-error: testing, 1, 2
33927 A problem internal to GDB has been detected. Further
33928 debugging may prove unreliable.
33929 Quit this debugging session? (y or n) @kbd{n}
33930 Create a core file? (y or n) @kbd{n}
33934 @cindex @value{GDBN} internal error
33935 @cindex internal errors, control of @value{GDBN} behavior
33936 @cindex demangler crashes
33938 @kindex maint set internal-error
33939 @kindex maint show internal-error
33940 @kindex maint set internal-warning
33941 @kindex maint show internal-warning
33942 @kindex maint set demangler-warning
33943 @kindex maint show demangler-warning
33944 @item maint set internal-error @var{action} [ask|yes|no]
33945 @itemx maint show internal-error @var{action}
33946 @itemx maint set internal-warning @var{action} [ask|yes|no]
33947 @itemx maint show internal-warning @var{action}
33948 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33949 @itemx maint show demangler-warning @var{action}
33950 When @value{GDBN} reports an internal problem (error or warning) it
33951 gives the user the opportunity to both quit @value{GDBN} and create a
33952 core file of the current @value{GDBN} session. These commands let you
33953 override the default behaviour for each particular @var{action},
33954 described in the table below.
33958 You can specify that @value{GDBN} should always (yes) or never (no)
33959 quit. The default is to ask the user what to do.
33962 You can specify that @value{GDBN} should always (yes) or never (no)
33963 create a core file. The default is to ask the user what to do. Note
33964 that there is no @code{corefile} option for @code{demangler-warning}:
33965 demangler warnings always create a core file and this cannot be
33969 @kindex maint packet
33970 @item maint packet @var{text}
33971 If @value{GDBN} is talking to an inferior via the serial protocol,
33972 then this command sends the string @var{text} to the inferior, and
33973 displays the response packet. @value{GDBN} supplies the initial
33974 @samp{$} character, the terminating @samp{#} character, and the
33977 @kindex maint print architecture
33978 @item maint print architecture @r{[}@var{file}@r{]}
33979 Print the entire architecture configuration. The optional argument
33980 @var{file} names the file where the output goes.
33982 @kindex maint print c-tdesc
33983 @item maint print c-tdesc
33984 Print the current target description (@pxref{Target Descriptions}) as
33985 a C source file. The created source file can be used in @value{GDBN}
33986 when an XML parser is not available to parse the description.
33988 @kindex maint print dummy-frames
33989 @item maint print dummy-frames
33990 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33993 (@value{GDBP}) @kbd{b add}
33995 (@value{GDBP}) @kbd{print add(2,3)}
33996 Breakpoint 2, add (a=2, b=3) at @dots{}
33998 The program being debugged stopped while in a function called from GDB.
34000 (@value{GDBP}) @kbd{maint print dummy-frames}
34001 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34005 Takes an optional file parameter.
34007 @kindex maint print registers
34008 @kindex maint print raw-registers
34009 @kindex maint print cooked-registers
34010 @kindex maint print register-groups
34011 @kindex maint print remote-registers
34012 @item maint print registers @r{[}@var{file}@r{]}
34013 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34014 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34015 @itemx maint print register-groups @r{[}@var{file}@r{]}
34016 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34017 Print @value{GDBN}'s internal register data structures.
34019 The command @code{maint print raw-registers} includes the contents of
34020 the raw register cache; the command @code{maint print
34021 cooked-registers} includes the (cooked) value of all registers,
34022 including registers which aren't available on the target nor visible
34023 to user; the command @code{maint print register-groups} includes the
34024 groups that each register is a member of; and the command @code{maint
34025 print remote-registers} includes the remote target's register numbers
34026 and offsets in the `G' packets.
34028 These commands take an optional parameter, a file name to which to
34029 write the information.
34031 @kindex maint print reggroups
34032 @item maint print reggroups @r{[}@var{file}@r{]}
34033 Print @value{GDBN}'s internal register group data structures. The
34034 optional argument @var{file} tells to what file to write the
34037 The register groups info looks like this:
34040 (@value{GDBP}) @kbd{maint print reggroups}
34053 This command forces @value{GDBN} to flush its internal register cache.
34055 @kindex maint print objfiles
34056 @cindex info for known object files
34057 @item maint print objfiles @r{[}@var{regexp}@r{]}
34058 Print a dump of all known object files.
34059 If @var{regexp} is specified, only print object files whose names
34060 match @var{regexp}. For each object file, this command prints its name,
34061 address in memory, and all of its psymtabs and symtabs.
34063 @kindex maint print user-registers
34064 @cindex user registers
34065 @item maint print user-registers
34066 List all currently available @dfn{user registers}. User registers
34067 typically provide alternate names for actual hardware registers. They
34068 include the four ``standard'' registers @code{$fp}, @code{$pc},
34069 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34070 registers can be used in expressions in the same way as the canonical
34071 register names, but only the latter are listed by the @code{info
34072 registers} and @code{maint print registers} commands.
34074 @kindex maint print section-scripts
34075 @cindex info for known .debug_gdb_scripts-loaded scripts
34076 @item maint print section-scripts [@var{regexp}]
34077 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34078 If @var{regexp} is specified, only print scripts loaded by object files
34079 matching @var{regexp}.
34080 For each script, this command prints its name as specified in the objfile,
34081 and the full path if known.
34082 @xref{dotdebug_gdb_scripts section}.
34084 @kindex maint print statistics
34085 @cindex bcache statistics
34086 @item maint print statistics
34087 This command prints, for each object file in the program, various data
34088 about that object file followed by the byte cache (@dfn{bcache})
34089 statistics for the object file. The objfile data includes the number
34090 of minimal, partial, full, and stabs symbols, the number of types
34091 defined by the objfile, the number of as yet unexpanded psym tables,
34092 the number of line tables and string tables, and the amount of memory
34093 used by the various tables. The bcache statistics include the counts,
34094 sizes, and counts of duplicates of all and unique objects, max,
34095 average, and median entry size, total memory used and its overhead and
34096 savings, and various measures of the hash table size and chain
34099 @kindex maint print target-stack
34100 @cindex target stack description
34101 @item maint print target-stack
34102 A @dfn{target} is an interface between the debugger and a particular
34103 kind of file or process. Targets can be stacked in @dfn{strata},
34104 so that more than one target can potentially respond to a request.
34105 In particular, memory accesses will walk down the stack of targets
34106 until they find a target that is interested in handling that particular
34109 This command prints a short description of each layer that was pushed on
34110 the @dfn{target stack}, starting from the top layer down to the bottom one.
34112 @kindex maint print type
34113 @cindex type chain of a data type
34114 @item maint print type @var{expr}
34115 Print the type chain for a type specified by @var{expr}. The argument
34116 can be either a type name or a symbol. If it is a symbol, the type of
34117 that symbol is described. The type chain produced by this command is
34118 a recursive definition of the data type as stored in @value{GDBN}'s
34119 data structures, including its flags and contained types.
34121 @kindex maint set dwarf2 always-disassemble
34122 @kindex maint show dwarf2 always-disassemble
34123 @item maint set dwarf2 always-disassemble
34124 @item maint show dwarf2 always-disassemble
34125 Control the behavior of @code{info address} when using DWARF debugging
34128 The default is @code{off}, which means that @value{GDBN} should try to
34129 describe a variable's location in an easily readable format. When
34130 @code{on}, @value{GDBN} will instead display the DWARF location
34131 expression in an assembly-like format. Note that some locations are
34132 too complex for @value{GDBN} to describe simply; in this case you will
34133 always see the disassembly form.
34135 Here is an example of the resulting disassembly:
34138 (gdb) info addr argc
34139 Symbol "argc" is a complex DWARF expression:
34143 For more information on these expressions, see
34144 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34146 @kindex maint set dwarf2 max-cache-age
34147 @kindex maint show dwarf2 max-cache-age
34148 @item maint set dwarf2 max-cache-age
34149 @itemx maint show dwarf2 max-cache-age
34150 Control the DWARF 2 compilation unit cache.
34152 @cindex DWARF 2 compilation units cache
34153 In object files with inter-compilation-unit references, such as those
34154 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34155 reader needs to frequently refer to previously read compilation units.
34156 This setting controls how long a compilation unit will remain in the
34157 cache if it is not referenced. A higher limit means that cached
34158 compilation units will be stored in memory longer, and more total
34159 memory will be used. Setting it to zero disables caching, which will
34160 slow down @value{GDBN} startup, but reduce memory consumption.
34162 @kindex maint set profile
34163 @kindex maint show profile
34164 @cindex profiling GDB
34165 @item maint set profile
34166 @itemx maint show profile
34167 Control profiling of @value{GDBN}.
34169 Profiling will be disabled until you use the @samp{maint set profile}
34170 command to enable it. When you enable profiling, the system will begin
34171 collecting timing and execution count data; when you disable profiling or
34172 exit @value{GDBN}, the results will be written to a log file. Remember that
34173 if you use profiling, @value{GDBN} will overwrite the profiling log file
34174 (often called @file{gmon.out}). If you have a record of important profiling
34175 data in a @file{gmon.out} file, be sure to move it to a safe location.
34177 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34178 compiled with the @samp{-pg} compiler option.
34180 @kindex maint set show-debug-regs
34181 @kindex maint show show-debug-regs
34182 @cindex hardware debug registers
34183 @item maint set show-debug-regs
34184 @itemx maint show show-debug-regs
34185 Control whether to show variables that mirror the hardware debug
34186 registers. Use @code{on} to enable, @code{off} to disable. If
34187 enabled, the debug registers values are shown when @value{GDBN} inserts or
34188 removes a hardware breakpoint or watchpoint, and when the inferior
34189 triggers a hardware-assisted breakpoint or watchpoint.
34191 @kindex maint set show-all-tib
34192 @kindex maint show show-all-tib
34193 @item maint set show-all-tib
34194 @itemx maint show show-all-tib
34195 Control whether to show all non zero areas within a 1k block starting
34196 at thread local base, when using the @samp{info w32 thread-information-block}
34199 @kindex maint set target-async
34200 @kindex maint show target-async
34201 @item maint set target-async
34202 @itemx maint show target-async
34203 This controls whether @value{GDBN} targets operate in synchronous or
34204 asynchronous mode (@pxref{Background Execution}). Normally the
34205 default is asynchronous, if it is available; but this can be changed
34206 to more easily debug problems occurring only in synchronous mode.
34208 @kindex maint set per-command
34209 @kindex maint show per-command
34210 @item maint set per-command
34211 @itemx maint show per-command
34212 @cindex resources used by commands
34214 @value{GDBN} can display the resources used by each command.
34215 This is useful in debugging performance problems.
34218 @item maint set per-command space [on|off]
34219 @itemx maint show per-command space
34220 Enable or disable the printing of the memory used by GDB for each command.
34221 If enabled, @value{GDBN} will display how much memory each command
34222 took, following the command's own output.
34223 This can also be requested by invoking @value{GDBN} with the
34224 @option{--statistics} command-line switch (@pxref{Mode Options}).
34226 @item maint set per-command time [on|off]
34227 @itemx maint show per-command time
34228 Enable or disable the printing of the execution time of @value{GDBN}
34230 If enabled, @value{GDBN} will display how much time it
34231 took to execute each command, following the command's own output.
34232 Both CPU time and wallclock time are printed.
34233 Printing both is useful when trying to determine whether the cost is
34234 CPU or, e.g., disk/network latency.
34235 Note that the CPU time printed is for @value{GDBN} only, it does not include
34236 the execution time of the inferior because there's no mechanism currently
34237 to compute how much time was spent by @value{GDBN} and how much time was
34238 spent by the program been debugged.
34239 This can also be requested by invoking @value{GDBN} with the
34240 @option{--statistics} command-line switch (@pxref{Mode Options}).
34242 @item maint set per-command symtab [on|off]
34243 @itemx maint show per-command symtab
34244 Enable or disable the printing of basic symbol table statistics
34246 If enabled, @value{GDBN} will display the following information:
34250 number of symbol tables
34252 number of primary symbol tables
34254 number of blocks in the blockvector
34258 @kindex maint space
34259 @cindex memory used by commands
34260 @item maint space @var{value}
34261 An alias for @code{maint set per-command space}.
34262 A non-zero value enables it, zero disables it.
34265 @cindex time of command execution
34266 @item maint time @var{value}
34267 An alias for @code{maint set per-command time}.
34268 A non-zero value enables it, zero disables it.
34270 @kindex maint translate-address
34271 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34272 Find the symbol stored at the location specified by the address
34273 @var{addr} and an optional section name @var{section}. If found,
34274 @value{GDBN} prints the name of the closest symbol and an offset from
34275 the symbol's location to the specified address. This is similar to
34276 the @code{info address} command (@pxref{Symbols}), except that this
34277 command also allows to find symbols in other sections.
34279 If section was not specified, the section in which the symbol was found
34280 is also printed. For dynamically linked executables, the name of
34281 executable or shared library containing the symbol is printed as well.
34285 The following command is useful for non-interactive invocations of
34286 @value{GDBN}, such as in the test suite.
34289 @item set watchdog @var{nsec}
34290 @kindex set watchdog
34291 @cindex watchdog timer
34292 @cindex timeout for commands
34293 Set the maximum number of seconds @value{GDBN} will wait for the
34294 target operation to finish. If this time expires, @value{GDBN}
34295 reports and error and the command is aborted.
34297 @item show watchdog
34298 Show the current setting of the target wait timeout.
34301 @node Remote Protocol
34302 @appendix @value{GDBN} Remote Serial Protocol
34307 * Stop Reply Packets::
34308 * General Query Packets::
34309 * Architecture-Specific Protocol Details::
34310 * Tracepoint Packets::
34311 * Host I/O Packets::
34313 * Notification Packets::
34314 * Remote Non-Stop::
34315 * Packet Acknowledgment::
34317 * File-I/O Remote Protocol Extension::
34318 * Library List Format::
34319 * Library List Format for SVR4 Targets::
34320 * Memory Map Format::
34321 * Thread List Format::
34322 * Traceframe Info Format::
34323 * Branch Trace Format::
34324 * Branch Trace Configuration Format::
34330 There may be occasions when you need to know something about the
34331 protocol---for example, if there is only one serial port to your target
34332 machine, you might want your program to do something special if it
34333 recognizes a packet meant for @value{GDBN}.
34335 In the examples below, @samp{->} and @samp{<-} are used to indicate
34336 transmitted and received data, respectively.
34338 @cindex protocol, @value{GDBN} remote serial
34339 @cindex serial protocol, @value{GDBN} remote
34340 @cindex remote serial protocol
34341 All @value{GDBN} commands and responses (other than acknowledgments
34342 and notifications, see @ref{Notification Packets}) are sent as a
34343 @var{packet}. A @var{packet} is introduced with the character
34344 @samp{$}, the actual @var{packet-data}, and the terminating character
34345 @samp{#} followed by a two-digit @var{checksum}:
34348 @code{$}@var{packet-data}@code{#}@var{checksum}
34352 @cindex checksum, for @value{GDBN} remote
34354 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34355 characters between the leading @samp{$} and the trailing @samp{#} (an
34356 eight bit unsigned checksum).
34358 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34359 specification also included an optional two-digit @var{sequence-id}:
34362 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34365 @cindex sequence-id, for @value{GDBN} remote
34367 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34368 has never output @var{sequence-id}s. Stubs that handle packets added
34369 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34371 When either the host or the target machine receives a packet, the first
34372 response expected is an acknowledgment: either @samp{+} (to indicate
34373 the package was received correctly) or @samp{-} (to request
34377 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34382 The @samp{+}/@samp{-} acknowledgments can be disabled
34383 once a connection is established.
34384 @xref{Packet Acknowledgment}, for details.
34386 The host (@value{GDBN}) sends @var{command}s, and the target (the
34387 debugging stub incorporated in your program) sends a @var{response}. In
34388 the case of step and continue @var{command}s, the response is only sent
34389 when the operation has completed, and the target has again stopped all
34390 threads in all attached processes. This is the default all-stop mode
34391 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34392 execution mode; see @ref{Remote Non-Stop}, for details.
34394 @var{packet-data} consists of a sequence of characters with the
34395 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34398 @cindex remote protocol, field separator
34399 Fields within the packet should be separated using @samp{,} @samp{;} or
34400 @samp{:}. Except where otherwise noted all numbers are represented in
34401 @sc{hex} with leading zeros suppressed.
34403 Implementors should note that prior to @value{GDBN} 5.0, the character
34404 @samp{:} could not appear as the third character in a packet (as it
34405 would potentially conflict with the @var{sequence-id}).
34407 @cindex remote protocol, binary data
34408 @anchor{Binary Data}
34409 Binary data in most packets is encoded either as two hexadecimal
34410 digits per byte of binary data. This allowed the traditional remote
34411 protocol to work over connections which were only seven-bit clean.
34412 Some packets designed more recently assume an eight-bit clean
34413 connection, and use a more efficient encoding to send and receive
34416 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34417 as an escape character. Any escaped byte is transmitted as the escape
34418 character followed by the original character XORed with @code{0x20}.
34419 For example, the byte @code{0x7d} would be transmitted as the two
34420 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34421 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34422 @samp{@}}) must always be escaped. Responses sent by the stub
34423 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34424 is not interpreted as the start of a run-length encoded sequence
34427 Response @var{data} can be run-length encoded to save space.
34428 Run-length encoding replaces runs of identical characters with one
34429 instance of the repeated character, followed by a @samp{*} and a
34430 repeat count. The repeat count is itself sent encoded, to avoid
34431 binary characters in @var{data}: a value of @var{n} is sent as
34432 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34433 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34434 code 32) for a repeat count of 3. (This is because run-length
34435 encoding starts to win for counts 3 or more.) Thus, for example,
34436 @samp{0* } is a run-length encoding of ``0000'': the space character
34437 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34440 The printable characters @samp{#} and @samp{$} or with a numeric value
34441 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34442 seven repeats (@samp{$}) can be expanded using a repeat count of only
34443 five (@samp{"}). For example, @samp{00000000} can be encoded as
34446 The error response returned for some packets includes a two character
34447 error number. That number is not well defined.
34449 @cindex empty response, for unsupported packets
34450 For any @var{command} not supported by the stub, an empty response
34451 (@samp{$#00}) should be returned. That way it is possible to extend the
34452 protocol. A newer @value{GDBN} can tell if a packet is supported based
34455 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34456 commands for register access, and the @samp{m} and @samp{M} commands
34457 for memory access. Stubs that only control single-threaded targets
34458 can implement run control with the @samp{c} (continue), and @samp{s}
34459 (step) commands. Stubs that support multi-threading targets should
34460 support the @samp{vCont} command. All other commands are optional.
34465 The following table provides a complete list of all currently defined
34466 @var{command}s and their corresponding response @var{data}.
34467 @xref{File-I/O Remote Protocol Extension}, for details about the File
34468 I/O extension of the remote protocol.
34470 Each packet's description has a template showing the packet's overall
34471 syntax, followed by an explanation of the packet's meaning. We
34472 include spaces in some of the templates for clarity; these are not
34473 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34474 separate its components. For example, a template like @samp{foo
34475 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34476 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34477 @var{baz}. @value{GDBN} does not transmit a space character between the
34478 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34481 @cindex @var{thread-id}, in remote protocol
34482 @anchor{thread-id syntax}
34483 Several packets and replies include a @var{thread-id} field to identify
34484 a thread. Normally these are positive numbers with a target-specific
34485 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34486 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34489 In addition, the remote protocol supports a multiprocess feature in
34490 which the @var{thread-id} syntax is extended to optionally include both
34491 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34492 The @var{pid} (process) and @var{tid} (thread) components each have the
34493 format described above: a positive number with target-specific
34494 interpretation formatted as a big-endian hex string, literal @samp{-1}
34495 to indicate all processes or threads (respectively), or @samp{0} to
34496 indicate an arbitrary process or thread. Specifying just a process, as
34497 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34498 error to specify all processes but a specific thread, such as
34499 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34500 for those packets and replies explicitly documented to include a process
34501 ID, rather than a @var{thread-id}.
34503 The multiprocess @var{thread-id} syntax extensions are only used if both
34504 @value{GDBN} and the stub report support for the @samp{multiprocess}
34505 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34508 Note that all packet forms beginning with an upper- or lower-case
34509 letter, other than those described here, are reserved for future use.
34511 Here are the packet descriptions.
34516 @cindex @samp{!} packet
34517 @anchor{extended mode}
34518 Enable extended mode. In extended mode, the remote server is made
34519 persistent. The @samp{R} packet is used to restart the program being
34525 The remote target both supports and has enabled extended mode.
34529 @cindex @samp{?} packet
34531 Indicate the reason the target halted. The reply is the same as for
34532 step and continue. This packet has a special interpretation when the
34533 target is in non-stop mode; see @ref{Remote Non-Stop}.
34536 @xref{Stop Reply Packets}, for the reply specifications.
34538 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34539 @cindex @samp{A} packet
34540 Initialized @code{argv[]} array passed into program. @var{arglen}
34541 specifies the number of bytes in the hex encoded byte stream
34542 @var{arg}. See @code{gdbserver} for more details.
34547 The arguments were set.
34553 @cindex @samp{b} packet
34554 (Don't use this packet; its behavior is not well-defined.)
34555 Change the serial line speed to @var{baud}.
34557 JTC: @emph{When does the transport layer state change? When it's
34558 received, or after the ACK is transmitted. In either case, there are
34559 problems if the command or the acknowledgment packet is dropped.}
34561 Stan: @emph{If people really wanted to add something like this, and get
34562 it working for the first time, they ought to modify ser-unix.c to send
34563 some kind of out-of-band message to a specially-setup stub and have the
34564 switch happen "in between" packets, so that from remote protocol's point
34565 of view, nothing actually happened.}
34567 @item B @var{addr},@var{mode}
34568 @cindex @samp{B} packet
34569 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34570 breakpoint at @var{addr}.
34572 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34573 (@pxref{insert breakpoint or watchpoint packet}).
34575 @cindex @samp{bc} packet
34578 Backward continue. Execute the target system in reverse. No parameter.
34579 @xref{Reverse Execution}, for more information.
34582 @xref{Stop Reply Packets}, for the reply specifications.
34584 @cindex @samp{bs} packet
34587 Backward single step. Execute one instruction in reverse. No parameter.
34588 @xref{Reverse Execution}, for more information.
34591 @xref{Stop Reply Packets}, for the reply specifications.
34593 @item c @r{[}@var{addr}@r{]}
34594 @cindex @samp{c} packet
34595 Continue at @var{addr}, which is the address to resume. If @var{addr}
34596 is omitted, resume at current address.
34598 This packet is deprecated for multi-threading support. @xref{vCont
34602 @xref{Stop Reply Packets}, for the reply specifications.
34604 @item C @var{sig}@r{[};@var{addr}@r{]}
34605 @cindex @samp{C} packet
34606 Continue with signal @var{sig} (hex signal number). If
34607 @samp{;@var{addr}} is omitted, resume at same address.
34609 This packet is deprecated for multi-threading support. @xref{vCont
34613 @xref{Stop Reply Packets}, for the reply specifications.
34616 @cindex @samp{d} packet
34619 Don't use this packet; instead, define a general set packet
34620 (@pxref{General Query Packets}).
34624 @cindex @samp{D} packet
34625 The first form of the packet is used to detach @value{GDBN} from the
34626 remote system. It is sent to the remote target
34627 before @value{GDBN} disconnects via the @code{detach} command.
34629 The second form, including a process ID, is used when multiprocess
34630 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34631 detach only a specific process. The @var{pid} is specified as a
34632 big-endian hex string.
34642 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34643 @cindex @samp{F} packet
34644 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34645 This is part of the File-I/O protocol extension. @xref{File-I/O
34646 Remote Protocol Extension}, for the specification.
34649 @anchor{read registers packet}
34650 @cindex @samp{g} packet
34651 Read general registers.
34655 @item @var{XX@dots{}}
34656 Each byte of register data is described by two hex digits. The bytes
34657 with the register are transmitted in target byte order. The size of
34658 each register and their position within the @samp{g} packet are
34659 determined by the @value{GDBN} internal gdbarch functions
34660 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34661 specification of several standard @samp{g} packets is specified below.
34663 When reading registers from a trace frame (@pxref{Analyze Collected
34664 Data,,Using the Collected Data}), the stub may also return a string of
34665 literal @samp{x}'s in place of the register data digits, to indicate
34666 that the corresponding register has not been collected, thus its value
34667 is unavailable. For example, for an architecture with 4 registers of
34668 4 bytes each, the following reply indicates to @value{GDBN} that
34669 registers 0 and 2 have not been collected, while registers 1 and 3
34670 have been collected, and both have zero value:
34674 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34681 @item G @var{XX@dots{}}
34682 @cindex @samp{G} packet
34683 Write general registers. @xref{read registers packet}, for a
34684 description of the @var{XX@dots{}} data.
34694 @item H @var{op} @var{thread-id}
34695 @cindex @samp{H} packet
34696 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34697 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34698 should be @samp{c} for step and continue operations (note that this
34699 is deprecated, supporting the @samp{vCont} command is a better
34700 option), and @samp{g} for other operations. The thread designator
34701 @var{thread-id} has the format and interpretation described in
34702 @ref{thread-id syntax}.
34713 @c 'H': How restrictive (or permissive) is the thread model. If a
34714 @c thread is selected and stopped, are other threads allowed
34715 @c to continue to execute? As I mentioned above, I think the
34716 @c semantics of each command when a thread is selected must be
34717 @c described. For example:
34719 @c 'g': If the stub supports threads and a specific thread is
34720 @c selected, returns the register block from that thread;
34721 @c otherwise returns current registers.
34723 @c 'G' If the stub supports threads and a specific thread is
34724 @c selected, sets the registers of the register block of
34725 @c that thread; otherwise sets current registers.
34727 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34728 @anchor{cycle step packet}
34729 @cindex @samp{i} packet
34730 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34731 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34732 step starting at that address.
34735 @cindex @samp{I} packet
34736 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34740 @cindex @samp{k} packet
34743 The exact effect of this packet is not specified.
34745 For a bare-metal target, it may power cycle or reset the target
34746 system. For that reason, the @samp{k} packet has no reply.
34748 For a single-process target, it may kill that process if possible.
34750 A multiple-process target may choose to kill just one process, or all
34751 that are under @value{GDBN}'s control. For more precise control, use
34752 the vKill packet (@pxref{vKill packet}).
34754 If the target system immediately closes the connection in response to
34755 @samp{k}, @value{GDBN} does not consider the lack of packet
34756 acknowledgment to be an error, and assumes the kill was successful.
34758 If connected using @kbd{target extended-remote}, and the target does
34759 not close the connection in response to a kill request, @value{GDBN}
34760 probes the target state as if a new connection was opened
34761 (@pxref{? packet}).
34763 @item m @var{addr},@var{length}
34764 @cindex @samp{m} packet
34765 Read @var{length} bytes of memory starting at address @var{addr}.
34766 Note that @var{addr} may not be aligned to any particular boundary.
34768 The stub need not use any particular size or alignment when gathering
34769 data from memory for the response; even if @var{addr} is word-aligned
34770 and @var{length} is a multiple of the word size, the stub is free to
34771 use byte accesses, or not. For this reason, this packet may not be
34772 suitable for accessing memory-mapped I/O devices.
34773 @cindex alignment of remote memory accesses
34774 @cindex size of remote memory accesses
34775 @cindex memory, alignment and size of remote accesses
34779 @item @var{XX@dots{}}
34780 Memory contents; each byte is transmitted as a two-digit hexadecimal
34781 number. The reply may contain fewer bytes than requested if the
34782 server was able to read only part of the region of memory.
34787 @item M @var{addr},@var{length}:@var{XX@dots{}}
34788 @cindex @samp{M} packet
34789 Write @var{length} bytes of memory starting at address @var{addr}.
34790 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34791 hexadecimal number.
34798 for an error (this includes the case where only part of the data was
34803 @cindex @samp{p} packet
34804 Read the value of register @var{n}; @var{n} is in hex.
34805 @xref{read registers packet}, for a description of how the returned
34806 register value is encoded.
34810 @item @var{XX@dots{}}
34811 the register's value
34815 Indicating an unrecognized @var{query}.
34818 @item P @var{n@dots{}}=@var{r@dots{}}
34819 @anchor{write register packet}
34820 @cindex @samp{P} packet
34821 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34822 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34823 digits for each byte in the register (target byte order).
34833 @item q @var{name} @var{params}@dots{}
34834 @itemx Q @var{name} @var{params}@dots{}
34835 @cindex @samp{q} packet
34836 @cindex @samp{Q} packet
34837 General query (@samp{q}) and set (@samp{Q}). These packets are
34838 described fully in @ref{General Query Packets}.
34841 @cindex @samp{r} packet
34842 Reset the entire system.
34844 Don't use this packet; use the @samp{R} packet instead.
34847 @cindex @samp{R} packet
34848 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34849 This packet is only available in extended mode (@pxref{extended mode}).
34851 The @samp{R} packet has no reply.
34853 @item s @r{[}@var{addr}@r{]}
34854 @cindex @samp{s} packet
34855 Single step, resuming at @var{addr}. If
34856 @var{addr} is omitted, resume at same address.
34858 This packet is deprecated for multi-threading support. @xref{vCont
34862 @xref{Stop Reply Packets}, for the reply specifications.
34864 @item S @var{sig}@r{[};@var{addr}@r{]}
34865 @anchor{step with signal packet}
34866 @cindex @samp{S} packet
34867 Step with signal. This is analogous to the @samp{C} packet, but
34868 requests a single-step, rather than a normal resumption of execution.
34870 This packet is deprecated for multi-threading support. @xref{vCont
34874 @xref{Stop Reply Packets}, for the reply specifications.
34876 @item t @var{addr}:@var{PP},@var{MM}
34877 @cindex @samp{t} packet
34878 Search backwards starting at address @var{addr} for a match with pattern
34879 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34880 There must be at least 3 digits in @var{addr}.
34882 @item T @var{thread-id}
34883 @cindex @samp{T} packet
34884 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34889 thread is still alive
34895 Packets starting with @samp{v} are identified by a multi-letter name,
34896 up to the first @samp{;} or @samp{?} (or the end of the packet).
34898 @item vAttach;@var{pid}
34899 @cindex @samp{vAttach} packet
34900 Attach to a new process with the specified process ID @var{pid}.
34901 The process ID is a
34902 hexadecimal integer identifying the process. In all-stop mode, all
34903 threads in the attached process are stopped; in non-stop mode, it may be
34904 attached without being stopped if that is supported by the target.
34906 @c In non-stop mode, on a successful vAttach, the stub should set the
34907 @c current thread to a thread of the newly-attached process. After
34908 @c attaching, GDB queries for the attached process's thread ID with qC.
34909 @c Also note that, from a user perspective, whether or not the
34910 @c target is stopped on attach in non-stop mode depends on whether you
34911 @c use the foreground or background version of the attach command, not
34912 @c on what vAttach does; GDB does the right thing with respect to either
34913 @c stopping or restarting threads.
34915 This packet is only available in extended mode (@pxref{extended mode}).
34921 @item @r{Any stop packet}
34922 for success in all-stop mode (@pxref{Stop Reply Packets})
34924 for success in non-stop mode (@pxref{Remote Non-Stop})
34927 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34928 @cindex @samp{vCont} packet
34929 @anchor{vCont packet}
34930 Resume the inferior, specifying different actions for each thread.
34931 If an action is specified with no @var{thread-id}, then it is applied to any
34932 threads that don't have a specific action specified; if no default action is
34933 specified then other threads should remain stopped in all-stop mode and
34934 in their current state in non-stop mode.
34935 Specifying multiple
34936 default actions is an error; specifying no actions is also an error.
34937 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34939 Currently supported actions are:
34945 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34949 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34952 @item r @var{start},@var{end}
34953 Step once, and then keep stepping as long as the thread stops at
34954 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34955 The remote stub reports a stop reply when either the thread goes out
34956 of the range or is stopped due to an unrelated reason, such as hitting
34957 a breakpoint. @xref{range stepping}.
34959 If the range is empty (@var{start} == @var{end}), then the action
34960 becomes equivalent to the @samp{s} action. In other words,
34961 single-step once, and report the stop (even if the stepped instruction
34962 jumps to @var{start}).
34964 (A stop reply may be sent at any point even if the PC is still within
34965 the stepping range; for example, it is valid to implement this packet
34966 in a degenerate way as a single instruction step operation.)
34970 The optional argument @var{addr} normally associated with the
34971 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34972 not supported in @samp{vCont}.
34974 The @samp{t} action is only relevant in non-stop mode
34975 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34976 A stop reply should be generated for any affected thread not already stopped.
34977 When a thread is stopped by means of a @samp{t} action,
34978 the corresponding stop reply should indicate that the thread has stopped with
34979 signal @samp{0}, regardless of whether the target uses some other signal
34980 as an implementation detail.
34982 The stub must support @samp{vCont} if it reports support for
34983 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34984 this case @samp{vCont} actions can be specified to apply to all threads
34985 in a process by using the @samp{p@var{pid}.-1} form of the
34989 @xref{Stop Reply Packets}, for the reply specifications.
34992 @cindex @samp{vCont?} packet
34993 Request a list of actions supported by the @samp{vCont} packet.
34997 @item vCont@r{[};@var{action}@dots{}@r{]}
34998 The @samp{vCont} packet is supported. Each @var{action} is a supported
34999 command in the @samp{vCont} packet.
35001 The @samp{vCont} packet is not supported.
35004 @item vFile:@var{operation}:@var{parameter}@dots{}
35005 @cindex @samp{vFile} packet
35006 Perform a file operation on the target system. For details,
35007 see @ref{Host I/O Packets}.
35009 @item vFlashErase:@var{addr},@var{length}
35010 @cindex @samp{vFlashErase} packet
35011 Direct the stub to erase @var{length} bytes of flash starting at
35012 @var{addr}. The region may enclose any number of flash blocks, but
35013 its start and end must fall on block boundaries, as indicated by the
35014 flash block size appearing in the memory map (@pxref{Memory Map
35015 Format}). @value{GDBN} groups flash memory programming operations
35016 together, and sends a @samp{vFlashDone} request after each group; the
35017 stub is allowed to delay erase operation until the @samp{vFlashDone}
35018 packet is received.
35028 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35029 @cindex @samp{vFlashWrite} packet
35030 Direct the stub to write data to flash address @var{addr}. The data
35031 is passed in binary form using the same encoding as for the @samp{X}
35032 packet (@pxref{Binary Data}). The memory ranges specified by
35033 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35034 not overlap, and must appear in order of increasing addresses
35035 (although @samp{vFlashErase} packets for higher addresses may already
35036 have been received; the ordering is guaranteed only between
35037 @samp{vFlashWrite} packets). If a packet writes to an address that was
35038 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35039 target-specific method, the results are unpredictable.
35047 for vFlashWrite addressing non-flash memory
35053 @cindex @samp{vFlashDone} packet
35054 Indicate to the stub that flash programming operation is finished.
35055 The stub is permitted to delay or batch the effects of a group of
35056 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35057 @samp{vFlashDone} packet is received. The contents of the affected
35058 regions of flash memory are unpredictable until the @samp{vFlashDone}
35059 request is completed.
35061 @item vKill;@var{pid}
35062 @cindex @samp{vKill} packet
35063 @anchor{vKill packet}
35064 Kill the process with the specified process ID @var{pid}, which is a
35065 hexadecimal integer identifying the process. This packet is used in
35066 preference to @samp{k} when multiprocess protocol extensions are
35067 supported; see @ref{multiprocess extensions}.
35077 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35078 @cindex @samp{vRun} packet
35079 Run the program @var{filename}, passing it each @var{argument} on its
35080 command line. The file and arguments are hex-encoded strings. If
35081 @var{filename} is an empty string, the stub may use a default program
35082 (e.g.@: the last program run). The program is created in the stopped
35085 @c FIXME: What about non-stop mode?
35087 This packet is only available in extended mode (@pxref{extended mode}).
35093 @item @r{Any stop packet}
35094 for success (@pxref{Stop Reply Packets})
35098 @cindex @samp{vStopped} packet
35099 @xref{Notification Packets}.
35101 @item X @var{addr},@var{length}:@var{XX@dots{}}
35103 @cindex @samp{X} packet
35104 Write data to memory, where the data is transmitted in binary.
35105 Memory is specified by its address @var{addr} and number of bytes @var{length};
35106 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35116 @item z @var{type},@var{addr},@var{kind}
35117 @itemx Z @var{type},@var{addr},@var{kind}
35118 @anchor{insert breakpoint or watchpoint packet}
35119 @cindex @samp{z} packet
35120 @cindex @samp{Z} packets
35121 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35122 watchpoint starting at address @var{address} of kind @var{kind}.
35124 Each breakpoint and watchpoint packet @var{type} is documented
35127 @emph{Implementation notes: A remote target shall return an empty string
35128 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35129 remote target shall support either both or neither of a given
35130 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35131 avoid potential problems with duplicate packets, the operations should
35132 be implemented in an idempotent way.}
35134 @item z0,@var{addr},@var{kind}
35135 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35136 @cindex @samp{z0} packet
35137 @cindex @samp{Z0} packet
35138 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35139 @var{addr} of type @var{kind}.
35141 A memory breakpoint is implemented by replacing the instruction at
35142 @var{addr} with a software breakpoint or trap instruction. The
35143 @var{kind} is target-specific and typically indicates the size of
35144 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35145 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35146 architectures have additional meanings for @var{kind};
35147 @var{cond_list} is an optional list of conditional expressions in bytecode
35148 form that should be evaluated on the target's side. These are the
35149 conditions that should be taken into consideration when deciding if
35150 the breakpoint trigger should be reported back to @var{GDBN}.
35152 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35153 for how to best report a memory breakpoint event to @value{GDBN}.
35155 The @var{cond_list} parameter is comprised of a series of expressions,
35156 concatenated without separators. Each expression has the following form:
35160 @item X @var{len},@var{expr}
35161 @var{len} is the length of the bytecode expression and @var{expr} is the
35162 actual conditional expression in bytecode form.
35166 The optional @var{cmd_list} parameter introduces commands that may be
35167 run on the target, rather than being reported back to @value{GDBN}.
35168 The parameter starts with a numeric flag @var{persist}; if the flag is
35169 nonzero, then the breakpoint may remain active and the commands
35170 continue to be run even when @value{GDBN} disconnects from the target.
35171 Following this flag is a series of expressions concatenated with no
35172 separators. Each expression has the following form:
35176 @item X @var{len},@var{expr}
35177 @var{len} is the length of the bytecode expression and @var{expr} is the
35178 actual conditional expression in bytecode form.
35182 see @ref{Architecture-Specific Protocol Details}.
35184 @emph{Implementation note: It is possible for a target to copy or move
35185 code that contains memory breakpoints (e.g., when implementing
35186 overlays). The behavior of this packet, in the presence of such a
35187 target, is not defined.}
35199 @item z1,@var{addr},@var{kind}
35200 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35201 @cindex @samp{z1} packet
35202 @cindex @samp{Z1} packet
35203 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35204 address @var{addr}.
35206 A hardware breakpoint is implemented using a mechanism that is not
35207 dependant on being able to modify the target's memory. The @var{kind}
35208 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35210 @emph{Implementation note: A hardware breakpoint is not affected by code
35223 @item z2,@var{addr},@var{kind}
35224 @itemx Z2,@var{addr},@var{kind}
35225 @cindex @samp{z2} packet
35226 @cindex @samp{Z2} packet
35227 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35228 The number of bytes to watch is specified by @var{kind}.
35240 @item z3,@var{addr},@var{kind}
35241 @itemx Z3,@var{addr},@var{kind}
35242 @cindex @samp{z3} packet
35243 @cindex @samp{Z3} packet
35244 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35245 The number of bytes to watch is specified by @var{kind}.
35257 @item z4,@var{addr},@var{kind}
35258 @itemx Z4,@var{addr},@var{kind}
35259 @cindex @samp{z4} packet
35260 @cindex @samp{Z4} packet
35261 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35262 The number of bytes to watch is specified by @var{kind}.
35276 @node Stop Reply Packets
35277 @section Stop Reply Packets
35278 @cindex stop reply packets
35280 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35281 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35282 receive any of the below as a reply. Except for @samp{?}
35283 and @samp{vStopped}, that reply is only returned
35284 when the target halts. In the below the exact meaning of @dfn{signal
35285 number} is defined by the header @file{include/gdb/signals.h} in the
35286 @value{GDBN} source code.
35288 As in the description of request packets, we include spaces in the
35289 reply templates for clarity; these are not part of the reply packet's
35290 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35296 The program received signal number @var{AA} (a two-digit hexadecimal
35297 number). This is equivalent to a @samp{T} response with no
35298 @var{n}:@var{r} pairs.
35300 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35301 @cindex @samp{T} packet reply
35302 The program received signal number @var{AA} (a two-digit hexadecimal
35303 number). This is equivalent to an @samp{S} response, except that the
35304 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35305 and other information directly in the stop reply packet, reducing
35306 round-trip latency. Single-step and breakpoint traps are reported
35307 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35311 If @var{n} is a hexadecimal number, it is a register number, and the
35312 corresponding @var{r} gives that register's value. The data @var{r} is a
35313 series of bytes in target byte order, with each byte given by a
35314 two-digit hex number.
35317 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35318 the stopped thread, as specified in @ref{thread-id syntax}.
35321 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35322 the core on which the stop event was detected.
35325 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35326 specific event that stopped the target. The currently defined stop
35327 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35328 signal. At most one stop reason should be present.
35331 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35332 and go on to the next; this allows us to extend the protocol in the
35336 The currently defined stop reasons are:
35342 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35345 @cindex shared library events, remote reply
35347 The packet indicates that the loaded libraries have changed.
35348 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35349 list of loaded libraries. The @var{r} part is ignored.
35351 @cindex replay log events, remote reply
35353 The packet indicates that the target cannot continue replaying
35354 logged execution events, because it has reached the end (or the
35355 beginning when executing backward) of the log. The value of @var{r}
35356 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35357 for more information.
35360 @anchor{swbreak stop reason}
35361 The packet indicates a memory breakpoint instruction was executed,
35362 irrespective of whether it was @value{GDBN} that planted the
35363 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35364 part must be left empty.
35366 On some architectures, such as x86, at the architecture level, when a
35367 breakpoint instruction executes the program counter points at the
35368 breakpoint address plus an offset. On such targets, the stub is
35369 responsible for adjusting the PC to point back at the breakpoint
35372 This packet should not be sent by default; older @value{GDBN} versions
35373 did not support it. @value{GDBN} requests it, by supplying an
35374 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35375 remote stub must also supply the appropriate @samp{qSupported} feature
35376 indicating support.
35378 This packet is required for correct non-stop mode operation.
35381 The packet indicates the target stopped for a hardware breakpoint.
35382 The @var{r} part must be left empty.
35384 The same remarks about @samp{qSupported} and non-stop mode above
35387 @cindex fork events, remote reply
35389 The packet indicates that @code{fork} was called, and @var{r}
35390 is the thread ID of the new child process. Refer to
35391 @ref{thread-id syntax} for the format of the @var{thread-id}
35392 field. This packet is only applicable to targets that support
35395 This packet should not be sent by default; older @value{GDBN} versions
35396 did not support it. @value{GDBN} requests it, by supplying an
35397 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35398 remote stub must also supply the appropriate @samp{qSupported} feature
35399 indicating support.
35401 @cindex vfork events, remote reply
35403 The packet indicates that @code{vfork} was called, and @var{r}
35404 is the thread ID of the new child process. Refer to
35405 @ref{thread-id syntax} for the format of the @var{thread-id}
35406 field. This packet is only applicable to targets that support
35409 This packet should not be sent by default; older @value{GDBN} versions
35410 did not support it. @value{GDBN} requests it, by supplying an
35411 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35412 remote stub must also supply the appropriate @samp{qSupported} feature
35413 indicating support.
35415 @cindex vforkdone events, remote reply
35417 The packet indicates that a child process created by a vfork
35418 has either called @code{exec} or terminated, so that the
35419 address spaces of the parent and child process are no longer
35420 shared. The @var{r} part is ignored. This packet is only
35421 applicable to targets that support vforkdone events.
35423 This packet should not be sent by default; older @value{GDBN} versions
35424 did not support it. @value{GDBN} requests it, by supplying an
35425 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35426 remote stub must also supply the appropriate @samp{qSupported} feature
35427 indicating support.
35432 @itemx W @var{AA} ; process:@var{pid}
35433 The process exited, and @var{AA} is the exit status. This is only
35434 applicable to certain targets.
35436 The second form of the response, including the process ID of the exited
35437 process, can be used only when @value{GDBN} has reported support for
35438 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35439 The @var{pid} is formatted as a big-endian hex string.
35442 @itemx X @var{AA} ; process:@var{pid}
35443 The process terminated with signal @var{AA}.
35445 The second form of the response, including the process ID of the
35446 terminated process, can be used only when @value{GDBN} has reported
35447 support for multiprocess protocol extensions; see @ref{multiprocess
35448 extensions}. The @var{pid} is formatted as a big-endian hex string.
35450 @item O @var{XX}@dots{}
35451 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35452 written as the program's console output. This can happen at any time
35453 while the program is running and the debugger should continue to wait
35454 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35456 @item F @var{call-id},@var{parameter}@dots{}
35457 @var{call-id} is the identifier which says which host system call should
35458 be called. This is just the name of the function. Translation into the
35459 correct system call is only applicable as it's defined in @value{GDBN}.
35460 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35463 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35464 this very system call.
35466 The target replies with this packet when it expects @value{GDBN} to
35467 call a host system call on behalf of the target. @value{GDBN} replies
35468 with an appropriate @samp{F} packet and keeps up waiting for the next
35469 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35470 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35471 Protocol Extension}, for more details.
35475 @node General Query Packets
35476 @section General Query Packets
35477 @cindex remote query requests
35479 Packets starting with @samp{q} are @dfn{general query packets};
35480 packets starting with @samp{Q} are @dfn{general set packets}. General
35481 query and set packets are a semi-unified form for retrieving and
35482 sending information to and from the stub.
35484 The initial letter of a query or set packet is followed by a name
35485 indicating what sort of thing the packet applies to. For example,
35486 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35487 definitions with the stub. These packet names follow some
35492 The name must not contain commas, colons or semicolons.
35494 Most @value{GDBN} query and set packets have a leading upper case
35497 The names of custom vendor packets should use a company prefix, in
35498 lower case, followed by a period. For example, packets designed at
35499 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35500 foos) or @samp{Qacme.bar} (for setting bars).
35503 The name of a query or set packet should be separated from any
35504 parameters by a @samp{:}; the parameters themselves should be
35505 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35506 full packet name, and check for a separator or the end of the packet,
35507 in case two packet names share a common prefix. New packets should not begin
35508 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35509 packets predate these conventions, and have arguments without any terminator
35510 for the packet name; we suspect they are in widespread use in places that
35511 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35512 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35515 Like the descriptions of the other packets, each description here
35516 has a template showing the packet's overall syntax, followed by an
35517 explanation of the packet's meaning. We include spaces in some of the
35518 templates for clarity; these are not part of the packet's syntax. No
35519 @value{GDBN} packet uses spaces to separate its components.
35521 Here are the currently defined query and set packets:
35527 Turn on or off the agent as a helper to perform some debugging operations
35528 delegated from @value{GDBN} (@pxref{Control Agent}).
35530 @item QAllow:@var{op}:@var{val}@dots{}
35531 @cindex @samp{QAllow} packet
35532 Specify which operations @value{GDBN} expects to request of the
35533 target, as a semicolon-separated list of operation name and value
35534 pairs. Possible values for @var{op} include @samp{WriteReg},
35535 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35536 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35537 indicating that @value{GDBN} will not request the operation, or 1,
35538 indicating that it may. (The target can then use this to set up its
35539 own internals optimally, for instance if the debugger never expects to
35540 insert breakpoints, it may not need to install its own trap handler.)
35543 @cindex current thread, remote request
35544 @cindex @samp{qC} packet
35545 Return the current thread ID.
35549 @item QC @var{thread-id}
35550 Where @var{thread-id} is a thread ID as documented in
35551 @ref{thread-id syntax}.
35552 @item @r{(anything else)}
35553 Any other reply implies the old thread ID.
35556 @item qCRC:@var{addr},@var{length}
35557 @cindex CRC of memory block, remote request
35558 @cindex @samp{qCRC} packet
35559 @anchor{qCRC packet}
35560 Compute the CRC checksum of a block of memory using CRC-32 defined in
35561 IEEE 802.3. The CRC is computed byte at a time, taking the most
35562 significant bit of each byte first. The initial pattern code
35563 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35565 @emph{Note:} This is the same CRC used in validating separate debug
35566 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35567 Files}). However the algorithm is slightly different. When validating
35568 separate debug files, the CRC is computed taking the @emph{least}
35569 significant bit of each byte first, and the final result is inverted to
35570 detect trailing zeros.
35575 An error (such as memory fault)
35576 @item C @var{crc32}
35577 The specified memory region's checksum is @var{crc32}.
35580 @item QDisableRandomization:@var{value}
35581 @cindex disable address space randomization, remote request
35582 @cindex @samp{QDisableRandomization} packet
35583 Some target operating systems will randomize the virtual address space
35584 of the inferior process as a security feature, but provide a feature
35585 to disable such randomization, e.g.@: to allow for a more deterministic
35586 debugging experience. On such systems, this packet with a @var{value}
35587 of 1 directs the target to disable address space randomization for
35588 processes subsequently started via @samp{vRun} packets, while a packet
35589 with a @var{value} of 0 tells the target to enable address space
35592 This packet is only available in extended mode (@pxref{extended mode}).
35597 The request succeeded.
35600 An error occurred. The error number @var{nn} is given as hex digits.
35603 An empty reply indicates that @samp{QDisableRandomization} is not supported
35607 This packet is not probed by default; the remote stub must request it,
35608 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35609 This should only be done on targets that actually support disabling
35610 address space randomization.
35613 @itemx qsThreadInfo
35614 @cindex list active threads, remote request
35615 @cindex @samp{qfThreadInfo} packet
35616 @cindex @samp{qsThreadInfo} packet
35617 Obtain a list of all active thread IDs from the target (OS). Since there
35618 may be too many active threads to fit into one reply packet, this query
35619 works iteratively: it may require more than one query/reply sequence to
35620 obtain the entire list of threads. The first query of the sequence will
35621 be the @samp{qfThreadInfo} query; subsequent queries in the
35622 sequence will be the @samp{qsThreadInfo} query.
35624 NOTE: This packet replaces the @samp{qL} query (see below).
35628 @item m @var{thread-id}
35630 @item m @var{thread-id},@var{thread-id}@dots{}
35631 a comma-separated list of thread IDs
35633 (lower case letter @samp{L}) denotes end of list.
35636 In response to each query, the target will reply with a list of one or
35637 more thread IDs, separated by commas.
35638 @value{GDBN} will respond to each reply with a request for more thread
35639 ids (using the @samp{qs} form of the query), until the target responds
35640 with @samp{l} (lower-case ell, for @dfn{last}).
35641 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35644 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35645 initial connection with the remote target, and the very first thread ID
35646 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35647 message. Therefore, the stub should ensure that the first thread ID in
35648 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35650 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35651 @cindex get thread-local storage address, remote request
35652 @cindex @samp{qGetTLSAddr} packet
35653 Fetch the address associated with thread local storage specified
35654 by @var{thread-id}, @var{offset}, and @var{lm}.
35656 @var{thread-id} is the thread ID associated with the
35657 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35659 @var{offset} is the (big endian, hex encoded) offset associated with the
35660 thread local variable. (This offset is obtained from the debug
35661 information associated with the variable.)
35663 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35664 load module associated with the thread local storage. For example,
35665 a @sc{gnu}/Linux system will pass the link map address of the shared
35666 object associated with the thread local storage under consideration.
35667 Other operating environments may choose to represent the load module
35668 differently, so the precise meaning of this parameter will vary.
35672 @item @var{XX}@dots{}
35673 Hex encoded (big endian) bytes representing the address of the thread
35674 local storage requested.
35677 An error occurred. The error number @var{nn} is given as hex digits.
35680 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35683 @item qGetTIBAddr:@var{thread-id}
35684 @cindex get thread information block address
35685 @cindex @samp{qGetTIBAddr} packet
35686 Fetch address of the Windows OS specific Thread Information Block.
35688 @var{thread-id} is the thread ID associated with the thread.
35692 @item @var{XX}@dots{}
35693 Hex encoded (big endian) bytes representing the linear address of the
35694 thread information block.
35697 An error occured. This means that either the thread was not found, or the
35698 address could not be retrieved.
35701 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35704 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35705 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35706 digit) is one to indicate the first query and zero to indicate a
35707 subsequent query; @var{threadcount} (two hex digits) is the maximum
35708 number of threads the response packet can contain; and @var{nextthread}
35709 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35710 returned in the response as @var{argthread}.
35712 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35716 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35717 Where: @var{count} (two hex digits) is the number of threads being
35718 returned; @var{done} (one hex digit) is zero to indicate more threads
35719 and one indicates no further threads; @var{argthreadid} (eight hex
35720 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35721 is a sequence of thread IDs, @var{threadid} (eight hex
35722 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35726 @cindex section offsets, remote request
35727 @cindex @samp{qOffsets} packet
35728 Get section offsets that the target used when relocating the downloaded
35733 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35734 Relocate the @code{Text} section by @var{xxx} from its original address.
35735 Relocate the @code{Data} section by @var{yyy} from its original address.
35736 If the object file format provides segment information (e.g.@: @sc{elf}
35737 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35738 segments by the supplied offsets.
35740 @emph{Note: while a @code{Bss} offset may be included in the response,
35741 @value{GDBN} ignores this and instead applies the @code{Data} offset
35742 to the @code{Bss} section.}
35744 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35745 Relocate the first segment of the object file, which conventionally
35746 contains program code, to a starting address of @var{xxx}. If
35747 @samp{DataSeg} is specified, relocate the second segment, which
35748 conventionally contains modifiable data, to a starting address of
35749 @var{yyy}. @value{GDBN} will report an error if the object file
35750 does not contain segment information, or does not contain at least
35751 as many segments as mentioned in the reply. Extra segments are
35752 kept at fixed offsets relative to the last relocated segment.
35755 @item qP @var{mode} @var{thread-id}
35756 @cindex thread information, remote request
35757 @cindex @samp{qP} packet
35758 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35759 encoded 32 bit mode; @var{thread-id} is a thread ID
35760 (@pxref{thread-id syntax}).
35762 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35765 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35769 @cindex non-stop mode, remote request
35770 @cindex @samp{QNonStop} packet
35772 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35773 @xref{Remote Non-Stop}, for more information.
35778 The request succeeded.
35781 An error occurred. The error number @var{nn} is given as hex digits.
35784 An empty reply indicates that @samp{QNonStop} is not supported by
35788 This packet is not probed by default; the remote stub must request it,
35789 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35790 Use of this packet is controlled by the @code{set non-stop} command;
35791 @pxref{Non-Stop Mode}.
35793 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35794 @cindex pass signals to inferior, remote request
35795 @cindex @samp{QPassSignals} packet
35796 @anchor{QPassSignals}
35797 Each listed @var{signal} should be passed directly to the inferior process.
35798 Signals are numbered identically to continue packets and stop replies
35799 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35800 strictly greater than the previous item. These signals do not need to stop
35801 the inferior, or be reported to @value{GDBN}. All other signals should be
35802 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35803 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35804 new list. This packet improves performance when using @samp{handle
35805 @var{signal} nostop noprint pass}.
35810 The request succeeded.
35813 An error occurred. The error number @var{nn} is given as hex digits.
35816 An empty reply indicates that @samp{QPassSignals} is not supported by
35820 Use of this packet is controlled by the @code{set remote pass-signals}
35821 command (@pxref{Remote Configuration, set remote pass-signals}).
35822 This packet is not probed by default; the remote stub must request it,
35823 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35825 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35826 @cindex signals the inferior may see, remote request
35827 @cindex @samp{QProgramSignals} packet
35828 @anchor{QProgramSignals}
35829 Each listed @var{signal} may be delivered to the inferior process.
35830 Others should be silently discarded.
35832 In some cases, the remote stub may need to decide whether to deliver a
35833 signal to the program or not without @value{GDBN} involvement. One
35834 example of that is while detaching --- the program's threads may have
35835 stopped for signals that haven't yet had a chance of being reported to
35836 @value{GDBN}, and so the remote stub can use the signal list specified
35837 by this packet to know whether to deliver or ignore those pending
35840 This does not influence whether to deliver a signal as requested by a
35841 resumption packet (@pxref{vCont packet}).
35843 Signals are numbered identically to continue packets and stop replies
35844 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35845 strictly greater than the previous item. Multiple
35846 @samp{QProgramSignals} packets do not combine; any earlier
35847 @samp{QProgramSignals} list is completely replaced by the new list.
35852 The request succeeded.
35855 An error occurred. The error number @var{nn} is given as hex digits.
35858 An empty reply indicates that @samp{QProgramSignals} is not supported
35862 Use of this packet is controlled by the @code{set remote program-signals}
35863 command (@pxref{Remote Configuration, set remote program-signals}).
35864 This packet is not probed by default; the remote stub must request it,
35865 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35867 @item qRcmd,@var{command}
35868 @cindex execute remote command, remote request
35869 @cindex @samp{qRcmd} packet
35870 @var{command} (hex encoded) is passed to the local interpreter for
35871 execution. Invalid commands should be reported using the output
35872 string. Before the final result packet, the target may also respond
35873 with a number of intermediate @samp{O@var{output}} console output
35874 packets. @emph{Implementors should note that providing access to a
35875 stubs's interpreter may have security implications}.
35880 A command response with no output.
35882 A command response with the hex encoded output string @var{OUTPUT}.
35884 Indicate a badly formed request.
35886 An empty reply indicates that @samp{qRcmd} is not recognized.
35889 (Note that the @code{qRcmd} packet's name is separated from the
35890 command by a @samp{,}, not a @samp{:}, contrary to the naming
35891 conventions above. Please don't use this packet as a model for new
35894 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35895 @cindex searching memory, in remote debugging
35897 @cindex @samp{qSearch:memory} packet
35899 @cindex @samp{qSearch memory} packet
35900 @anchor{qSearch memory}
35901 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35902 Both @var{address} and @var{length} are encoded in hex;
35903 @var{search-pattern} is a sequence of bytes, also hex encoded.
35908 The pattern was not found.
35910 The pattern was found at @var{address}.
35912 A badly formed request or an error was encountered while searching memory.
35914 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35917 @item QStartNoAckMode
35918 @cindex @samp{QStartNoAckMode} packet
35919 @anchor{QStartNoAckMode}
35920 Request that the remote stub disable the normal @samp{+}/@samp{-}
35921 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35926 The stub has switched to no-acknowledgment mode.
35927 @value{GDBN} acknowledges this reponse,
35928 but neither the stub nor @value{GDBN} shall send or expect further
35929 @samp{+}/@samp{-} acknowledgments in the current connection.
35931 An empty reply indicates that the stub does not support no-acknowledgment mode.
35934 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35935 @cindex supported packets, remote query
35936 @cindex features of the remote protocol
35937 @cindex @samp{qSupported} packet
35938 @anchor{qSupported}
35939 Tell the remote stub about features supported by @value{GDBN}, and
35940 query the stub for features it supports. This packet allows
35941 @value{GDBN} and the remote stub to take advantage of each others'
35942 features. @samp{qSupported} also consolidates multiple feature probes
35943 at startup, to improve @value{GDBN} performance---a single larger
35944 packet performs better than multiple smaller probe packets on
35945 high-latency links. Some features may enable behavior which must not
35946 be on by default, e.g.@: because it would confuse older clients or
35947 stubs. Other features may describe packets which could be
35948 automatically probed for, but are not. These features must be
35949 reported before @value{GDBN} will use them. This ``default
35950 unsupported'' behavior is not appropriate for all packets, but it
35951 helps to keep the initial connection time under control with new
35952 versions of @value{GDBN} which support increasing numbers of packets.
35956 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35957 The stub supports or does not support each returned @var{stubfeature},
35958 depending on the form of each @var{stubfeature} (see below for the
35961 An empty reply indicates that @samp{qSupported} is not recognized,
35962 or that no features needed to be reported to @value{GDBN}.
35965 The allowed forms for each feature (either a @var{gdbfeature} in the
35966 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35970 @item @var{name}=@var{value}
35971 The remote protocol feature @var{name} is supported, and associated
35972 with the specified @var{value}. The format of @var{value} depends
35973 on the feature, but it must not include a semicolon.
35975 The remote protocol feature @var{name} is supported, and does not
35976 need an associated value.
35978 The remote protocol feature @var{name} is not supported.
35980 The remote protocol feature @var{name} may be supported, and
35981 @value{GDBN} should auto-detect support in some other way when it is
35982 needed. This form will not be used for @var{gdbfeature} notifications,
35983 but may be used for @var{stubfeature} responses.
35986 Whenever the stub receives a @samp{qSupported} request, the
35987 supplied set of @value{GDBN} features should override any previous
35988 request. This allows @value{GDBN} to put the stub in a known
35989 state, even if the stub had previously been communicating with
35990 a different version of @value{GDBN}.
35992 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35997 This feature indicates whether @value{GDBN} supports multiprocess
35998 extensions to the remote protocol. @value{GDBN} does not use such
35999 extensions unless the stub also reports that it supports them by
36000 including @samp{multiprocess+} in its @samp{qSupported} reply.
36001 @xref{multiprocess extensions}, for details.
36004 This feature indicates that @value{GDBN} supports the XML target
36005 description. If the stub sees @samp{xmlRegisters=} with target
36006 specific strings separated by a comma, it will report register
36010 This feature indicates whether @value{GDBN} supports the
36011 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36012 instruction reply packet}).
36015 This feature indicates whether @value{GDBN} supports the swbreak stop
36016 reason in stop replies. @xref{swbreak stop reason}, for details.
36019 This feature indicates whether @value{GDBN} supports the hwbreak stop
36020 reason in stop replies. @xref{swbreak stop reason}, for details.
36023 This feature indicates whether @value{GDBN} supports fork event
36024 extensions to the remote protocol. @value{GDBN} does not use such
36025 extensions unless the stub also reports that it supports them by
36026 including @samp{fork-events+} in its @samp{qSupported} reply.
36029 This feature indicates whether @value{GDBN} supports vfork event
36030 extensions to the remote protocol. @value{GDBN} does not use such
36031 extensions unless the stub also reports that it supports them by
36032 including @samp{vfork-events+} in its @samp{qSupported} reply.
36035 Stubs should ignore any unknown values for
36036 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36037 packet supports receiving packets of unlimited length (earlier
36038 versions of @value{GDBN} may reject overly long responses). Additional values
36039 for @var{gdbfeature} may be defined in the future to let the stub take
36040 advantage of new features in @value{GDBN}, e.g.@: incompatible
36041 improvements in the remote protocol---the @samp{multiprocess} feature is
36042 an example of such a feature. The stub's reply should be independent
36043 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36044 describes all the features it supports, and then the stub replies with
36045 all the features it supports.
36047 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36048 responses, as long as each response uses one of the standard forms.
36050 Some features are flags. A stub which supports a flag feature
36051 should respond with a @samp{+} form response. Other features
36052 require values, and the stub should respond with an @samp{=}
36055 Each feature has a default value, which @value{GDBN} will use if
36056 @samp{qSupported} is not available or if the feature is not mentioned
36057 in the @samp{qSupported} response. The default values are fixed; a
36058 stub is free to omit any feature responses that match the defaults.
36060 Not all features can be probed, but for those which can, the probing
36061 mechanism is useful: in some cases, a stub's internal
36062 architecture may not allow the protocol layer to know some information
36063 about the underlying target in advance. This is especially common in
36064 stubs which may be configured for multiple targets.
36066 These are the currently defined stub features and their properties:
36068 @multitable @columnfractions 0.35 0.2 0.12 0.2
36069 @c NOTE: The first row should be @headitem, but we do not yet require
36070 @c a new enough version of Texinfo (4.7) to use @headitem.
36072 @tab Value Required
36076 @item @samp{PacketSize}
36081 @item @samp{qXfer:auxv:read}
36086 @item @samp{qXfer:btrace:read}
36091 @item @samp{qXfer:btrace-conf:read}
36096 @item @samp{qXfer:exec-file:read}
36101 @item @samp{qXfer:features:read}
36106 @item @samp{qXfer:libraries:read}
36111 @item @samp{qXfer:libraries-svr4:read}
36116 @item @samp{augmented-libraries-svr4-read}
36121 @item @samp{qXfer:memory-map:read}
36126 @item @samp{qXfer:sdata:read}
36131 @item @samp{qXfer:spu:read}
36136 @item @samp{qXfer:spu:write}
36141 @item @samp{qXfer:siginfo:read}
36146 @item @samp{qXfer:siginfo:write}
36151 @item @samp{qXfer:threads:read}
36156 @item @samp{qXfer:traceframe-info:read}
36161 @item @samp{qXfer:uib:read}
36166 @item @samp{qXfer:fdpic:read}
36171 @item @samp{Qbtrace:off}
36176 @item @samp{Qbtrace:bts}
36181 @item @samp{Qbtrace-conf:bts:size}
36186 @item @samp{QNonStop}
36191 @item @samp{QPassSignals}
36196 @item @samp{QStartNoAckMode}
36201 @item @samp{multiprocess}
36206 @item @samp{ConditionalBreakpoints}
36211 @item @samp{ConditionalTracepoints}
36216 @item @samp{ReverseContinue}
36221 @item @samp{ReverseStep}
36226 @item @samp{TracepointSource}
36231 @item @samp{QAgent}
36236 @item @samp{QAllow}
36241 @item @samp{QDisableRandomization}
36246 @item @samp{EnableDisableTracepoints}
36251 @item @samp{QTBuffer:size}
36256 @item @samp{tracenz}
36261 @item @samp{BreakpointCommands}
36266 @item @samp{swbreak}
36271 @item @samp{hwbreak}
36276 @item @samp{fork-events}
36281 @item @samp{vfork-events}
36288 These are the currently defined stub features, in more detail:
36291 @cindex packet size, remote protocol
36292 @item PacketSize=@var{bytes}
36293 The remote stub can accept packets up to at least @var{bytes} in
36294 length. @value{GDBN} will send packets up to this size for bulk
36295 transfers, and will never send larger packets. This is a limit on the
36296 data characters in the packet, including the frame and checksum.
36297 There is no trailing NUL byte in a remote protocol packet; if the stub
36298 stores packets in a NUL-terminated format, it should allow an extra
36299 byte in its buffer for the NUL. If this stub feature is not supported,
36300 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36302 @item qXfer:auxv:read
36303 The remote stub understands the @samp{qXfer:auxv:read} packet
36304 (@pxref{qXfer auxiliary vector read}).
36306 @item qXfer:btrace:read
36307 The remote stub understands the @samp{qXfer:btrace:read}
36308 packet (@pxref{qXfer btrace read}).
36310 @item qXfer:btrace-conf:read
36311 The remote stub understands the @samp{qXfer:btrace-conf:read}
36312 packet (@pxref{qXfer btrace-conf read}).
36314 @item qXfer:exec-file:read
36315 The remote stub understands the @samp{qXfer:exec-file:read} packet
36316 (@pxref{qXfer executable filename read}).
36318 @item qXfer:features:read
36319 The remote stub understands the @samp{qXfer:features:read} packet
36320 (@pxref{qXfer target description read}).
36322 @item qXfer:libraries:read
36323 The remote stub understands the @samp{qXfer:libraries:read} packet
36324 (@pxref{qXfer library list read}).
36326 @item qXfer:libraries-svr4:read
36327 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36328 (@pxref{qXfer svr4 library list read}).
36330 @item augmented-libraries-svr4-read
36331 The remote stub understands the augmented form of the
36332 @samp{qXfer:libraries-svr4:read} packet
36333 (@pxref{qXfer svr4 library list read}).
36335 @item qXfer:memory-map:read
36336 The remote stub understands the @samp{qXfer:memory-map:read} packet
36337 (@pxref{qXfer memory map read}).
36339 @item qXfer:sdata:read
36340 The remote stub understands the @samp{qXfer:sdata:read} packet
36341 (@pxref{qXfer sdata read}).
36343 @item qXfer:spu:read
36344 The remote stub understands the @samp{qXfer:spu:read} packet
36345 (@pxref{qXfer spu read}).
36347 @item qXfer:spu:write
36348 The remote stub understands the @samp{qXfer:spu:write} packet
36349 (@pxref{qXfer spu write}).
36351 @item qXfer:siginfo:read
36352 The remote stub understands the @samp{qXfer:siginfo:read} packet
36353 (@pxref{qXfer siginfo read}).
36355 @item qXfer:siginfo:write
36356 The remote stub understands the @samp{qXfer:siginfo:write} packet
36357 (@pxref{qXfer siginfo write}).
36359 @item qXfer:threads:read
36360 The remote stub understands the @samp{qXfer:threads:read} packet
36361 (@pxref{qXfer threads read}).
36363 @item qXfer:traceframe-info:read
36364 The remote stub understands the @samp{qXfer:traceframe-info:read}
36365 packet (@pxref{qXfer traceframe info read}).
36367 @item qXfer:uib:read
36368 The remote stub understands the @samp{qXfer:uib:read}
36369 packet (@pxref{qXfer unwind info block}).
36371 @item qXfer:fdpic:read
36372 The remote stub understands the @samp{qXfer:fdpic:read}
36373 packet (@pxref{qXfer fdpic loadmap read}).
36376 The remote stub understands the @samp{QNonStop} packet
36377 (@pxref{QNonStop}).
36380 The remote stub understands the @samp{QPassSignals} packet
36381 (@pxref{QPassSignals}).
36383 @item QStartNoAckMode
36384 The remote stub understands the @samp{QStartNoAckMode} packet and
36385 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36388 @anchor{multiprocess extensions}
36389 @cindex multiprocess extensions, in remote protocol
36390 The remote stub understands the multiprocess extensions to the remote
36391 protocol syntax. The multiprocess extensions affect the syntax of
36392 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36393 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36394 replies. Note that reporting this feature indicates support for the
36395 syntactic extensions only, not that the stub necessarily supports
36396 debugging of more than one process at a time. The stub must not use
36397 multiprocess extensions in packet replies unless @value{GDBN} has also
36398 indicated it supports them in its @samp{qSupported} request.
36400 @item qXfer:osdata:read
36401 The remote stub understands the @samp{qXfer:osdata:read} packet
36402 ((@pxref{qXfer osdata read}).
36404 @item ConditionalBreakpoints
36405 The target accepts and implements evaluation of conditional expressions
36406 defined for breakpoints. The target will only report breakpoint triggers
36407 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36409 @item ConditionalTracepoints
36410 The remote stub accepts and implements conditional expressions defined
36411 for tracepoints (@pxref{Tracepoint Conditions}).
36413 @item ReverseContinue
36414 The remote stub accepts and implements the reverse continue packet
36418 The remote stub accepts and implements the reverse step packet
36421 @item TracepointSource
36422 The remote stub understands the @samp{QTDPsrc} packet that supplies
36423 the source form of tracepoint definitions.
36426 The remote stub understands the @samp{QAgent} packet.
36429 The remote stub understands the @samp{QAllow} packet.
36431 @item QDisableRandomization
36432 The remote stub understands the @samp{QDisableRandomization} packet.
36434 @item StaticTracepoint
36435 @cindex static tracepoints, in remote protocol
36436 The remote stub supports static tracepoints.
36438 @item InstallInTrace
36439 @anchor{install tracepoint in tracing}
36440 The remote stub supports installing tracepoint in tracing.
36442 @item EnableDisableTracepoints
36443 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36444 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36445 to be enabled and disabled while a trace experiment is running.
36447 @item QTBuffer:size
36448 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36449 packet that allows to change the size of the trace buffer.
36452 @cindex string tracing, in remote protocol
36453 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36454 See @ref{Bytecode Descriptions} for details about the bytecode.
36456 @item BreakpointCommands
36457 @cindex breakpoint commands, in remote protocol
36458 The remote stub supports running a breakpoint's command list itself,
36459 rather than reporting the hit to @value{GDBN}.
36462 The remote stub understands the @samp{Qbtrace:off} packet.
36465 The remote stub understands the @samp{Qbtrace:bts} packet.
36467 @item Qbtrace-conf:bts:size
36468 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36471 The remote stub reports the @samp{swbreak} stop reason for memory
36475 The remote stub reports the @samp{hwbreak} stop reason for hardware
36479 The remote stub reports the @samp{fork} stop reason for fork events.
36482 The remote stub reports the @samp{vfork} stop reason for vfork events
36483 and vforkdone events.
36488 @cindex symbol lookup, remote request
36489 @cindex @samp{qSymbol} packet
36490 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36491 requests. Accept requests from the target for the values of symbols.
36496 The target does not need to look up any (more) symbols.
36497 @item qSymbol:@var{sym_name}
36498 The target requests the value of symbol @var{sym_name} (hex encoded).
36499 @value{GDBN} may provide the value by using the
36500 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36504 @item qSymbol:@var{sym_value}:@var{sym_name}
36505 Set the value of @var{sym_name} to @var{sym_value}.
36507 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36508 target has previously requested.
36510 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36511 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36517 The target does not need to look up any (more) symbols.
36518 @item qSymbol:@var{sym_name}
36519 The target requests the value of a new symbol @var{sym_name} (hex
36520 encoded). @value{GDBN} will continue to supply the values of symbols
36521 (if available), until the target ceases to request them.
36526 @itemx QTDisconnected
36533 @itemx qTMinFTPILen
36535 @xref{Tracepoint Packets}.
36537 @item qThreadExtraInfo,@var{thread-id}
36538 @cindex thread attributes info, remote request
36539 @cindex @samp{qThreadExtraInfo} packet
36540 Obtain from the target OS a printable string description of thread
36541 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36542 for the forms of @var{thread-id}. This
36543 string may contain anything that the target OS thinks is interesting
36544 for @value{GDBN} to tell the user about the thread. The string is
36545 displayed in @value{GDBN}'s @code{info threads} display. Some
36546 examples of possible thread extra info strings are @samp{Runnable}, or
36547 @samp{Blocked on Mutex}.
36551 @item @var{XX}@dots{}
36552 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36553 comprising the printable string containing the extra information about
36554 the thread's attributes.
36557 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36558 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36559 conventions above. Please don't use this packet as a model for new
36578 @xref{Tracepoint Packets}.
36580 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36581 @cindex read special object, remote request
36582 @cindex @samp{qXfer} packet
36583 @anchor{qXfer read}
36584 Read uninterpreted bytes from the target's special data area
36585 identified by the keyword @var{object}. Request @var{length} bytes
36586 starting at @var{offset} bytes into the data. The content and
36587 encoding of @var{annex} is specific to @var{object}; it can supply
36588 additional details about what data to access.
36590 Here are the specific requests of this form defined so far. All
36591 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36592 formats, listed below.
36595 @item qXfer:auxv:read::@var{offset},@var{length}
36596 @anchor{qXfer auxiliary vector read}
36597 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36598 auxiliary vector}. Note @var{annex} must be empty.
36600 This packet is not probed by default; the remote stub must request it,
36601 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36603 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36604 @anchor{qXfer btrace read}
36606 Return a description of the current branch trace.
36607 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36608 packet may have one of the following values:
36612 Returns all available branch trace.
36615 Returns all available branch trace if the branch trace changed since
36616 the last read request.
36619 Returns the new branch trace since the last read request. Adds a new
36620 block to the end of the trace that begins at zero and ends at the source
36621 location of the first branch in the trace buffer. This extra block is
36622 used to stitch traces together.
36624 If the trace buffer overflowed, returns an error indicating the overflow.
36627 This packet is not probed by default; the remote stub must request it
36628 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36630 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36631 @anchor{qXfer btrace-conf read}
36633 Return a description of the current branch trace configuration.
36634 @xref{Branch Trace Configuration Format}.
36636 This packet is not probed by default; the remote stub must request it
36637 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36639 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36640 @anchor{qXfer executable filename read}
36641 Return the full absolute name of the file that was executed to create
36642 a process running on the remote system. The annex specifies the
36643 numeric process ID of the process to query, encoded as a hexadecimal
36644 number. If the annex part is empty the remote stub should return the
36645 filename corresponding to the currently executing process.
36647 This packet is not probed by default; the remote stub must request it,
36648 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36650 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36651 @anchor{qXfer target description read}
36652 Access the @dfn{target description}. @xref{Target Descriptions}. The
36653 annex specifies which XML document to access. The main description is
36654 always loaded from the @samp{target.xml} annex.
36656 This packet is not probed by default; the remote stub must request it,
36657 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36659 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36660 @anchor{qXfer library list read}
36661 Access the target's list of loaded libraries. @xref{Library List Format}.
36662 The annex part of the generic @samp{qXfer} packet must be empty
36663 (@pxref{qXfer read}).
36665 Targets which maintain a list of libraries in the program's memory do
36666 not need to implement this packet; it is designed for platforms where
36667 the operating system manages the list of loaded libraries.
36669 This packet is not probed by default; the remote stub must request it,
36670 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36672 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36673 @anchor{qXfer svr4 library list read}
36674 Access the target's list of loaded libraries when the target is an SVR4
36675 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36676 of the generic @samp{qXfer} packet must be empty unless the remote
36677 stub indicated it supports the augmented form of this packet
36678 by supplying an appropriate @samp{qSupported} response
36679 (@pxref{qXfer read}, @ref{qSupported}).
36681 This packet is optional for better performance on SVR4 targets.
36682 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36684 This packet is not probed by default; the remote stub must request it,
36685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36687 If the remote stub indicates it supports the augmented form of this
36688 packet then the annex part of the generic @samp{qXfer} packet may
36689 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36690 arguments. The currently supported arguments are:
36693 @item start=@var{address}
36694 A hexadecimal number specifying the address of the @samp{struct
36695 link_map} to start reading the library list from. If unset or zero
36696 then the first @samp{struct link_map} in the library list will be
36697 chosen as the starting point.
36699 @item prev=@var{address}
36700 A hexadecimal number specifying the address of the @samp{struct
36701 link_map} immediately preceding the @samp{struct link_map}
36702 specified by the @samp{start} argument. If unset or zero then
36703 the remote stub will expect that no @samp{struct link_map}
36704 exists prior to the starting point.
36708 Arguments that are not understood by the remote stub will be silently
36711 @item qXfer:memory-map:read::@var{offset},@var{length}
36712 @anchor{qXfer memory map read}
36713 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36714 annex part of the generic @samp{qXfer} packet must be empty
36715 (@pxref{qXfer read}).
36717 This packet is not probed by default; the remote stub must request it,
36718 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36720 @item qXfer:sdata:read::@var{offset},@var{length}
36721 @anchor{qXfer sdata read}
36723 Read contents of the extra collected static tracepoint marker
36724 information. The annex part of the generic @samp{qXfer} packet must
36725 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36728 This packet is not probed by default; the remote stub must request it,
36729 by supplying an appropriate @samp{qSupported} response
36730 (@pxref{qSupported}).
36732 @item qXfer:siginfo:read::@var{offset},@var{length}
36733 @anchor{qXfer siginfo read}
36734 Read contents of the extra signal information on the target
36735 system. The annex part of the generic @samp{qXfer} packet must be
36736 empty (@pxref{qXfer read}).
36738 This packet is not probed by default; the remote stub must request it,
36739 by supplying an appropriate @samp{qSupported} response
36740 (@pxref{qSupported}).
36742 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36743 @anchor{qXfer spu read}
36744 Read contents of an @code{spufs} file on the target system. The
36745 annex specifies which file to read; it must be of the form
36746 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36747 in the target process, and @var{name} identifes the @code{spufs} file
36748 in that context to be accessed.
36750 This packet is not probed by default; the remote stub must request it,
36751 by supplying an appropriate @samp{qSupported} response
36752 (@pxref{qSupported}).
36754 @item qXfer:threads:read::@var{offset},@var{length}
36755 @anchor{qXfer threads read}
36756 Access the list of threads on target. @xref{Thread List Format}. The
36757 annex part of the generic @samp{qXfer} packet must be empty
36758 (@pxref{qXfer read}).
36760 This packet is not probed by default; the remote stub must request it,
36761 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36763 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36764 @anchor{qXfer traceframe info read}
36766 Return a description of the current traceframe's contents.
36767 @xref{Traceframe Info Format}. The annex part of the generic
36768 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36770 This packet is not probed by default; the remote stub must request it,
36771 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36773 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36774 @anchor{qXfer unwind info block}
36776 Return the unwind information block for @var{pc}. This packet is used
36777 on OpenVMS/ia64 to ask the kernel unwind information.
36779 This packet is not probed by default.
36781 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36782 @anchor{qXfer fdpic loadmap read}
36783 Read contents of @code{loadmap}s on the target system. The
36784 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36785 executable @code{loadmap} or interpreter @code{loadmap} to read.
36787 This packet is not probed by default; the remote stub must request it,
36788 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36790 @item qXfer:osdata:read::@var{offset},@var{length}
36791 @anchor{qXfer osdata read}
36792 Access the target's @dfn{operating system information}.
36793 @xref{Operating System Information}.
36800 Data @var{data} (@pxref{Binary Data}) has been read from the
36801 target. There may be more data at a higher address (although
36802 it is permitted to return @samp{m} even for the last valid
36803 block of data, as long as at least one byte of data was read).
36804 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36808 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36809 There is no more data to be read. It is possible for @var{data} to
36810 have fewer bytes than the @var{length} in the request.
36813 The @var{offset} in the request is at the end of the data.
36814 There is no more data to be read.
36817 The request was malformed, or @var{annex} was invalid.
36820 The offset was invalid, or there was an error encountered reading the data.
36821 The @var{nn} part is a hex-encoded @code{errno} value.
36824 An empty reply indicates the @var{object} string was not recognized by
36825 the stub, or that the object does not support reading.
36828 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36829 @cindex write data into object, remote request
36830 @anchor{qXfer write}
36831 Write uninterpreted bytes into the target's special data area
36832 identified by the keyword @var{object}, starting at @var{offset} bytes
36833 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36834 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36835 is specific to @var{object}; it can supply additional details about what data
36838 Here are the specific requests of this form defined so far. All
36839 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36840 formats, listed below.
36843 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36844 @anchor{qXfer siginfo write}
36845 Write @var{data} to the extra signal information on the target system.
36846 The annex part of the generic @samp{qXfer} packet must be
36847 empty (@pxref{qXfer write}).
36849 This packet is not probed by default; the remote stub must request it,
36850 by supplying an appropriate @samp{qSupported} response
36851 (@pxref{qSupported}).
36853 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36854 @anchor{qXfer spu write}
36855 Write @var{data} to an @code{spufs} file on the target system. The
36856 annex specifies which file to write; it must be of the form
36857 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36858 in the target process, and @var{name} identifes the @code{spufs} file
36859 in that context to be accessed.
36861 This packet is not probed by default; the remote stub must request it,
36862 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36868 @var{nn} (hex encoded) is the number of bytes written.
36869 This may be fewer bytes than supplied in the request.
36872 The request was malformed, or @var{annex} was invalid.
36875 The offset was invalid, or there was an error encountered writing the data.
36876 The @var{nn} part is a hex-encoded @code{errno} value.
36879 An empty reply indicates the @var{object} string was not
36880 recognized by the stub, or that the object does not support writing.
36883 @item qXfer:@var{object}:@var{operation}:@dots{}
36884 Requests of this form may be added in the future. When a stub does
36885 not recognize the @var{object} keyword, or its support for
36886 @var{object} does not recognize the @var{operation} keyword, the stub
36887 must respond with an empty packet.
36889 @item qAttached:@var{pid}
36890 @cindex query attached, remote request
36891 @cindex @samp{qAttached} packet
36892 Return an indication of whether the remote server attached to an
36893 existing process or created a new process. When the multiprocess
36894 protocol extensions are supported (@pxref{multiprocess extensions}),
36895 @var{pid} is an integer in hexadecimal format identifying the target
36896 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36897 the query packet will be simplified as @samp{qAttached}.
36899 This query is used, for example, to know whether the remote process
36900 should be detached or killed when a @value{GDBN} session is ended with
36901 the @code{quit} command.
36906 The remote server attached to an existing process.
36908 The remote server created a new process.
36910 A badly formed request or an error was encountered.
36914 Enable branch tracing for the current thread using bts tracing.
36919 Branch tracing has been enabled.
36921 A badly formed request or an error was encountered.
36925 Disable branch tracing for the current thread.
36930 Branch tracing has been disabled.
36932 A badly formed request or an error was encountered.
36935 @item Qbtrace-conf:bts:size=@var{value}
36936 Set the requested ring buffer size for new threads that use the
36937 btrace recording method in bts format.
36942 The ring buffer size has been set.
36944 A badly formed request or an error was encountered.
36949 @node Architecture-Specific Protocol Details
36950 @section Architecture-Specific Protocol Details
36952 This section describes how the remote protocol is applied to specific
36953 target architectures. Also see @ref{Standard Target Features}, for
36954 details of XML target descriptions for each architecture.
36957 * ARM-Specific Protocol Details::
36958 * MIPS-Specific Protocol Details::
36961 @node ARM-Specific Protocol Details
36962 @subsection @acronym{ARM}-specific Protocol Details
36965 * ARM Breakpoint Kinds::
36968 @node ARM Breakpoint Kinds
36969 @subsubsection @acronym{ARM} Breakpoint Kinds
36970 @cindex breakpoint kinds, @acronym{ARM}
36972 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36977 16-bit Thumb mode breakpoint.
36980 32-bit Thumb mode (Thumb-2) breakpoint.
36983 32-bit @acronym{ARM} mode breakpoint.
36987 @node MIPS-Specific Protocol Details
36988 @subsection @acronym{MIPS}-specific Protocol Details
36991 * MIPS Register packet Format::
36992 * MIPS Breakpoint Kinds::
36995 @node MIPS Register packet Format
36996 @subsubsection @acronym{MIPS} Register Packet Format
36997 @cindex register packet format, @acronym{MIPS}
36999 The following @code{g}/@code{G} packets have previously been defined.
37000 In the below, some thirty-two bit registers are transferred as
37001 sixty-four bits. Those registers should be zero/sign extended (which?)
37002 to fill the space allocated. Register bytes are transferred in target
37003 byte order. The two nibbles within a register byte are transferred
37004 most-significant -- least-significant.
37009 All registers are transferred as thirty-two bit quantities in the order:
37010 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37011 registers; fsr; fir; fp.
37014 All registers are transferred as sixty-four bit quantities (including
37015 thirty-two bit registers such as @code{sr}). The ordering is the same
37020 @node MIPS Breakpoint Kinds
37021 @subsubsection @acronym{MIPS} Breakpoint Kinds
37022 @cindex breakpoint kinds, @acronym{MIPS}
37024 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37029 16-bit @acronym{MIPS16} mode breakpoint.
37032 16-bit @acronym{microMIPS} mode breakpoint.
37035 32-bit standard @acronym{MIPS} mode breakpoint.
37038 32-bit @acronym{microMIPS} mode breakpoint.
37042 @node Tracepoint Packets
37043 @section Tracepoint Packets
37044 @cindex tracepoint packets
37045 @cindex packets, tracepoint
37047 Here we describe the packets @value{GDBN} uses to implement
37048 tracepoints (@pxref{Tracepoints}).
37052 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37053 @cindex @samp{QTDP} packet
37054 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37055 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37056 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37057 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37058 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37059 the number of bytes that the target should copy elsewhere to make room
37060 for the tracepoint. If an @samp{X} is present, it introduces a
37061 tracepoint condition, which consists of a hexadecimal length, followed
37062 by a comma and hex-encoded bytes, in a manner similar to action
37063 encodings as described below. If the trailing @samp{-} is present,
37064 further @samp{QTDP} packets will follow to specify this tracepoint's
37070 The packet was understood and carried out.
37072 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37074 The packet was not recognized.
37077 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37078 Define actions to be taken when a tracepoint is hit. The @var{n} and
37079 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37080 this tracepoint. This packet may only be sent immediately after
37081 another @samp{QTDP} packet that ended with a @samp{-}. If the
37082 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37083 specifying more actions for this tracepoint.
37085 In the series of action packets for a given tracepoint, at most one
37086 can have an @samp{S} before its first @var{action}. If such a packet
37087 is sent, it and the following packets define ``while-stepping''
37088 actions. Any prior packets define ordinary actions --- that is, those
37089 taken when the tracepoint is first hit. If no action packet has an
37090 @samp{S}, then all the packets in the series specify ordinary
37091 tracepoint actions.
37093 The @samp{@var{action}@dots{}} portion of the packet is a series of
37094 actions, concatenated without separators. Each action has one of the
37100 Collect the registers whose bits are set in @var{mask},
37101 a hexadecimal number whose @var{i}'th bit is set if register number
37102 @var{i} should be collected. (The least significant bit is numbered
37103 zero.) Note that @var{mask} may be any number of digits long; it may
37104 not fit in a 32-bit word.
37106 @item M @var{basereg},@var{offset},@var{len}
37107 Collect @var{len} bytes of memory starting at the address in register
37108 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37109 @samp{-1}, then the range has a fixed address: @var{offset} is the
37110 address of the lowest byte to collect. The @var{basereg},
37111 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37112 values (the @samp{-1} value for @var{basereg} is a special case).
37114 @item X @var{len},@var{expr}
37115 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37116 it directs. The agent expression @var{expr} is as described in
37117 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37118 two-digit hex number in the packet; @var{len} is the number of bytes
37119 in the expression (and thus one-half the number of hex digits in the
37124 Any number of actions may be packed together in a single @samp{QTDP}
37125 packet, as long as the packet does not exceed the maximum packet
37126 length (400 bytes, for many stubs). There may be only one @samp{R}
37127 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37128 actions. Any registers referred to by @samp{M} and @samp{X} actions
37129 must be collected by a preceding @samp{R} action. (The
37130 ``while-stepping'' actions are treated as if they were attached to a
37131 separate tracepoint, as far as these restrictions are concerned.)
37136 The packet was understood and carried out.
37138 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37140 The packet was not recognized.
37143 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37144 @cindex @samp{QTDPsrc} packet
37145 Specify a source string of tracepoint @var{n} at address @var{addr}.
37146 This is useful to get accurate reproduction of the tracepoints
37147 originally downloaded at the beginning of the trace run. The @var{type}
37148 is the name of the tracepoint part, such as @samp{cond} for the
37149 tracepoint's conditional expression (see below for a list of types), while
37150 @var{bytes} is the string, encoded in hexadecimal.
37152 @var{start} is the offset of the @var{bytes} within the overall source
37153 string, while @var{slen} is the total length of the source string.
37154 This is intended for handling source strings that are longer than will
37155 fit in a single packet.
37156 @c Add detailed example when this info is moved into a dedicated
37157 @c tracepoint descriptions section.
37159 The available string types are @samp{at} for the location,
37160 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37161 @value{GDBN} sends a separate packet for each command in the action
37162 list, in the same order in which the commands are stored in the list.
37164 The target does not need to do anything with source strings except
37165 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37168 Although this packet is optional, and @value{GDBN} will only send it
37169 if the target replies with @samp{TracepointSource} @xref{General
37170 Query Packets}, it makes both disconnected tracing and trace files
37171 much easier to use. Otherwise the user must be careful that the
37172 tracepoints in effect while looking at trace frames are identical to
37173 the ones in effect during the trace run; even a small discrepancy
37174 could cause @samp{tdump} not to work, or a particular trace frame not
37177 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37178 @cindex define trace state variable, remote request
37179 @cindex @samp{QTDV} packet
37180 Create a new trace state variable, number @var{n}, with an initial
37181 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37182 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37183 the option of not using this packet for initial values of zero; the
37184 target should simply create the trace state variables as they are
37185 mentioned in expressions. The value @var{builtin} should be 1 (one)
37186 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37187 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37188 @samp{qTsV} packet had it set. The contents of @var{name} is the
37189 hex-encoded name (without the leading @samp{$}) of the trace state
37192 @item QTFrame:@var{n}
37193 @cindex @samp{QTFrame} packet
37194 Select the @var{n}'th tracepoint frame from the buffer, and use the
37195 register and memory contents recorded there to answer subsequent
37196 request packets from @value{GDBN}.
37198 A successful reply from the stub indicates that the stub has found the
37199 requested frame. The response is a series of parts, concatenated
37200 without separators, describing the frame we selected. Each part has
37201 one of the following forms:
37205 The selected frame is number @var{n} in the trace frame buffer;
37206 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37207 was no frame matching the criteria in the request packet.
37210 The selected trace frame records a hit of tracepoint number @var{t};
37211 @var{t} is a hexadecimal number.
37215 @item QTFrame:pc:@var{addr}
37216 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37217 currently selected frame whose PC is @var{addr};
37218 @var{addr} is a hexadecimal number.
37220 @item QTFrame:tdp:@var{t}
37221 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37222 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37223 is a hexadecimal number.
37225 @item QTFrame:range:@var{start}:@var{end}
37226 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37227 currently selected frame whose PC is between @var{start} (inclusive)
37228 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37231 @item QTFrame:outside:@var{start}:@var{end}
37232 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37233 frame @emph{outside} the given range of addresses (exclusive).
37236 @cindex @samp{qTMinFTPILen} packet
37237 This packet requests the minimum length of instruction at which a fast
37238 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37239 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37240 it depends on the target system being able to create trampolines in
37241 the first 64K of memory, which might or might not be possible for that
37242 system. So the reply to this packet will be 4 if it is able to
37249 The minimum instruction length is currently unknown.
37251 The minimum instruction length is @var{length}, where @var{length}
37252 is a hexadecimal number greater or equal to 1. A reply
37253 of 1 means that a fast tracepoint may be placed on any instruction
37254 regardless of size.
37256 An error has occurred.
37258 An empty reply indicates that the request is not supported by the stub.
37262 @cindex @samp{QTStart} packet
37263 Begin the tracepoint experiment. Begin collecting data from
37264 tracepoint hits in the trace frame buffer. This packet supports the
37265 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37266 instruction reply packet}).
37269 @cindex @samp{QTStop} packet
37270 End the tracepoint experiment. Stop collecting trace frames.
37272 @item QTEnable:@var{n}:@var{addr}
37274 @cindex @samp{QTEnable} packet
37275 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37276 experiment. If the tracepoint was previously disabled, then collection
37277 of data from it will resume.
37279 @item QTDisable:@var{n}:@var{addr}
37281 @cindex @samp{QTDisable} packet
37282 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37283 experiment. No more data will be collected from the tracepoint unless
37284 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37287 @cindex @samp{QTinit} packet
37288 Clear the table of tracepoints, and empty the trace frame buffer.
37290 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37291 @cindex @samp{QTro} packet
37292 Establish the given ranges of memory as ``transparent''. The stub
37293 will answer requests for these ranges from memory's current contents,
37294 if they were not collected as part of the tracepoint hit.
37296 @value{GDBN} uses this to mark read-only regions of memory, like those
37297 containing program code. Since these areas never change, they should
37298 still have the same contents they did when the tracepoint was hit, so
37299 there's no reason for the stub to refuse to provide their contents.
37301 @item QTDisconnected:@var{value}
37302 @cindex @samp{QTDisconnected} packet
37303 Set the choice to what to do with the tracing run when @value{GDBN}
37304 disconnects from the target. A @var{value} of 1 directs the target to
37305 continue the tracing run, while 0 tells the target to stop tracing if
37306 @value{GDBN} is no longer in the picture.
37309 @cindex @samp{qTStatus} packet
37310 Ask the stub if there is a trace experiment running right now.
37312 The reply has the form:
37316 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37317 @var{running} is a single digit @code{1} if the trace is presently
37318 running, or @code{0} if not. It is followed by semicolon-separated
37319 optional fields that an agent may use to report additional status.
37323 If the trace is not running, the agent may report any of several
37324 explanations as one of the optional fields:
37329 No trace has been run yet.
37331 @item tstop[:@var{text}]:0
37332 The trace was stopped by a user-originated stop command. The optional
37333 @var{text} field is a user-supplied string supplied as part of the
37334 stop command (for instance, an explanation of why the trace was
37335 stopped manually). It is hex-encoded.
37338 The trace stopped because the trace buffer filled up.
37340 @item tdisconnected:0
37341 The trace stopped because @value{GDBN} disconnected from the target.
37343 @item tpasscount:@var{tpnum}
37344 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37346 @item terror:@var{text}:@var{tpnum}
37347 The trace stopped because tracepoint @var{tpnum} had an error. The
37348 string @var{text} is available to describe the nature of the error
37349 (for instance, a divide by zero in the condition expression); it
37353 The trace stopped for some other reason.
37357 Additional optional fields supply statistical and other information.
37358 Although not required, they are extremely useful for users monitoring
37359 the progress of a trace run. If a trace has stopped, and these
37360 numbers are reported, they must reflect the state of the just-stopped
37365 @item tframes:@var{n}
37366 The number of trace frames in the buffer.
37368 @item tcreated:@var{n}
37369 The total number of trace frames created during the run. This may
37370 be larger than the trace frame count, if the buffer is circular.
37372 @item tsize:@var{n}
37373 The total size of the trace buffer, in bytes.
37375 @item tfree:@var{n}
37376 The number of bytes still unused in the buffer.
37378 @item circular:@var{n}
37379 The value of the circular trace buffer flag. @code{1} means that the
37380 trace buffer is circular and old trace frames will be discarded if
37381 necessary to make room, @code{0} means that the trace buffer is linear
37384 @item disconn:@var{n}
37385 The value of the disconnected tracing flag. @code{1} means that
37386 tracing will continue after @value{GDBN} disconnects, @code{0} means
37387 that the trace run will stop.
37391 @item qTP:@var{tp}:@var{addr}
37392 @cindex tracepoint status, remote request
37393 @cindex @samp{qTP} packet
37394 Ask the stub for the current state of tracepoint number @var{tp} at
37395 address @var{addr}.
37399 @item V@var{hits}:@var{usage}
37400 The tracepoint has been hit @var{hits} times so far during the trace
37401 run, and accounts for @var{usage} in the trace buffer. Note that
37402 @code{while-stepping} steps are not counted as separate hits, but the
37403 steps' space consumption is added into the usage number.
37407 @item qTV:@var{var}
37408 @cindex trace state variable value, remote request
37409 @cindex @samp{qTV} packet
37410 Ask the stub for the value of the trace state variable number @var{var}.
37415 The value of the variable is @var{value}. This will be the current
37416 value of the variable if the user is examining a running target, or a
37417 saved value if the variable was collected in the trace frame that the
37418 user is looking at. Note that multiple requests may result in
37419 different reply values, such as when requesting values while the
37420 program is running.
37423 The value of the variable is unknown. This would occur, for example,
37424 if the user is examining a trace frame in which the requested variable
37429 @cindex @samp{qTfP} packet
37431 @cindex @samp{qTsP} packet
37432 These packets request data about tracepoints that are being used by
37433 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37434 of data, and multiple @code{qTsP} to get additional pieces. Replies
37435 to these packets generally take the form of the @code{QTDP} packets
37436 that define tracepoints. (FIXME add detailed syntax)
37439 @cindex @samp{qTfV} packet
37441 @cindex @samp{qTsV} packet
37442 These packets request data about trace state variables that are on the
37443 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37444 and multiple @code{qTsV} to get additional variables. Replies to
37445 these packets follow the syntax of the @code{QTDV} packets that define
37446 trace state variables.
37452 @cindex @samp{qTfSTM} packet
37453 @cindex @samp{qTsSTM} packet
37454 These packets request data about static tracepoint markers that exist
37455 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37456 first piece of data, and multiple @code{qTsSTM} to get additional
37457 pieces. Replies to these packets take the following form:
37461 @item m @var{address}:@var{id}:@var{extra}
37463 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37464 a comma-separated list of markers
37466 (lower case letter @samp{L}) denotes end of list.
37468 An error occurred. The error number @var{nn} is given as hex digits.
37470 An empty reply indicates that the request is not supported by the
37474 The @var{address} is encoded in hex;
37475 @var{id} and @var{extra} are strings encoded in hex.
37477 In response to each query, the target will reply with a list of one or
37478 more markers, separated by commas. @value{GDBN} will respond to each
37479 reply with a request for more markers (using the @samp{qs} form of the
37480 query), until the target responds with @samp{l} (lower-case ell, for
37483 @item qTSTMat:@var{address}
37485 @cindex @samp{qTSTMat} packet
37486 This packets requests data about static tracepoint markers in the
37487 target program at @var{address}. Replies to this packet follow the
37488 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37489 tracepoint markers.
37491 @item QTSave:@var{filename}
37492 @cindex @samp{QTSave} packet
37493 This packet directs the target to save trace data to the file name
37494 @var{filename} in the target's filesystem. The @var{filename} is encoded
37495 as a hex string; the interpretation of the file name (relative vs
37496 absolute, wild cards, etc) is up to the target.
37498 @item qTBuffer:@var{offset},@var{len}
37499 @cindex @samp{qTBuffer} packet
37500 Return up to @var{len} bytes of the current contents of trace buffer,
37501 starting at @var{offset}. The trace buffer is treated as if it were
37502 a contiguous collection of traceframes, as per the trace file format.
37503 The reply consists as many hex-encoded bytes as the target can deliver
37504 in a packet; it is not an error to return fewer than were asked for.
37505 A reply consisting of just @code{l} indicates that no bytes are
37508 @item QTBuffer:circular:@var{value}
37509 This packet directs the target to use a circular trace buffer if
37510 @var{value} is 1, or a linear buffer if the value is 0.
37512 @item QTBuffer:size:@var{size}
37513 @anchor{QTBuffer-size}
37514 @cindex @samp{QTBuffer size} packet
37515 This packet directs the target to make the trace buffer be of size
37516 @var{size} if possible. A value of @code{-1} tells the target to
37517 use whatever size it prefers.
37519 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37520 @cindex @samp{QTNotes} packet
37521 This packet adds optional textual notes to the trace run. Allowable
37522 types include @code{user}, @code{notes}, and @code{tstop}, the
37523 @var{text} fields are arbitrary strings, hex-encoded.
37527 @subsection Relocate instruction reply packet
37528 When installing fast tracepoints in memory, the target may need to
37529 relocate the instruction currently at the tracepoint address to a
37530 different address in memory. For most instructions, a simple copy is
37531 enough, but, for example, call instructions that implicitly push the
37532 return address on the stack, and relative branches or other
37533 PC-relative instructions require offset adjustment, so that the effect
37534 of executing the instruction at a different address is the same as if
37535 it had executed in the original location.
37537 In response to several of the tracepoint packets, the target may also
37538 respond with a number of intermediate @samp{qRelocInsn} request
37539 packets before the final result packet, to have @value{GDBN} handle
37540 this relocation operation. If a packet supports this mechanism, its
37541 documentation will explicitly say so. See for example the above
37542 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37543 format of the request is:
37546 @item qRelocInsn:@var{from};@var{to}
37548 This requests @value{GDBN} to copy instruction at address @var{from}
37549 to address @var{to}, possibly adjusted so that executing the
37550 instruction at @var{to} has the same effect as executing it at
37551 @var{from}. @value{GDBN} writes the adjusted instruction to target
37552 memory starting at @var{to}.
37557 @item qRelocInsn:@var{adjusted_size}
37558 Informs the stub the relocation is complete. The @var{adjusted_size} is
37559 the length in bytes of resulting relocated instruction sequence.
37561 A badly formed request was detected, or an error was encountered while
37562 relocating the instruction.
37565 @node Host I/O Packets
37566 @section Host I/O Packets
37567 @cindex Host I/O, remote protocol
37568 @cindex file transfer, remote protocol
37570 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37571 operations on the far side of a remote link. For example, Host I/O is
37572 used to upload and download files to a remote target with its own
37573 filesystem. Host I/O uses the same constant values and data structure
37574 layout as the target-initiated File-I/O protocol. However, the
37575 Host I/O packets are structured differently. The target-initiated
37576 protocol relies on target memory to store parameters and buffers.
37577 Host I/O requests are initiated by @value{GDBN}, and the
37578 target's memory is not involved. @xref{File-I/O Remote Protocol
37579 Extension}, for more details on the target-initiated protocol.
37581 The Host I/O request packets all encode a single operation along with
37582 its arguments. They have this format:
37586 @item vFile:@var{operation}: @var{parameter}@dots{}
37587 @var{operation} is the name of the particular request; the target
37588 should compare the entire packet name up to the second colon when checking
37589 for a supported operation. The format of @var{parameter} depends on
37590 the operation. Numbers are always passed in hexadecimal. Negative
37591 numbers have an explicit minus sign (i.e.@: two's complement is not
37592 used). Strings (e.g.@: filenames) are encoded as a series of
37593 hexadecimal bytes. The last argument to a system call may be a
37594 buffer of escaped binary data (@pxref{Binary Data}).
37598 The valid responses to Host I/O packets are:
37602 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37603 @var{result} is the integer value returned by this operation, usually
37604 non-negative for success and -1 for errors. If an error has occured,
37605 @var{errno} will be included in the result specifying a
37606 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37607 operations which return data, @var{attachment} supplies the data as a
37608 binary buffer. Binary buffers in response packets are escaped in the
37609 normal way (@pxref{Binary Data}). See the individual packet
37610 documentation for the interpretation of @var{result} and
37614 An empty response indicates that this operation is not recognized.
37618 These are the supported Host I/O operations:
37621 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37622 Open a file at @var{filename} and return a file descriptor for it, or
37623 return -1 if an error occurs. The @var{filename} is a string,
37624 @var{flags} is an integer indicating a mask of open flags
37625 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37626 of mode bits to use if the file is created (@pxref{mode_t Values}).
37627 @xref{open}, for details of the open flags and mode values.
37629 @item vFile:close: @var{fd}
37630 Close the open file corresponding to @var{fd} and return 0, or
37631 -1 if an error occurs.
37633 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37634 Read data from the open file corresponding to @var{fd}. Up to
37635 @var{count} bytes will be read from the file, starting at @var{offset}
37636 relative to the start of the file. The target may read fewer bytes;
37637 common reasons include packet size limits and an end-of-file
37638 condition. The number of bytes read is returned. Zero should only be
37639 returned for a successful read at the end of the file, or if
37640 @var{count} was zero.
37642 The data read should be returned as a binary attachment on success.
37643 If zero bytes were read, the response should include an empty binary
37644 attachment (i.e.@: a trailing semicolon). The return value is the
37645 number of target bytes read; the binary attachment may be longer if
37646 some characters were escaped.
37648 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37649 Write @var{data} (a binary buffer) to the open file corresponding
37650 to @var{fd}. Start the write at @var{offset} from the start of the
37651 file. Unlike many @code{write} system calls, there is no
37652 separate @var{count} argument; the length of @var{data} in the
37653 packet is used. @samp{vFile:write} returns the number of bytes written,
37654 which may be shorter than the length of @var{data}, or -1 if an
37657 @item vFile:fstat: @var{fd}
37658 Get information about the open file corresponding to @var{fd}.
37659 On success the information is returned as a binary attachment
37660 and the return value is the size of this attachment in bytes.
37661 If an error occurs the return value is -1. The format of the
37662 returned binary attachment is as described in @ref{struct stat}.
37664 @item vFile:unlink: @var{filename}
37665 Delete the file at @var{filename} on the target. Return 0,
37666 or -1 if an error occurs. The @var{filename} is a string.
37668 @item vFile:readlink: @var{filename}
37669 Read value of symbolic link @var{filename} on the target. Return
37670 the number of bytes read, or -1 if an error occurs.
37672 The data read should be returned as a binary attachment on success.
37673 If zero bytes were read, the response should include an empty binary
37674 attachment (i.e.@: a trailing semicolon). The return value is the
37675 number of target bytes read; the binary attachment may be longer if
37676 some characters were escaped.
37681 @section Interrupts
37682 @cindex interrupts (remote protocol)
37684 When a program on the remote target is running, @value{GDBN} may
37685 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37686 a @code{BREAK} followed by @code{g},
37687 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37689 The precise meaning of @code{BREAK} is defined by the transport
37690 mechanism and may, in fact, be undefined. @value{GDBN} does not
37691 currently define a @code{BREAK} mechanism for any of the network
37692 interfaces except for TCP, in which case @value{GDBN} sends the
37693 @code{telnet} BREAK sequence.
37695 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37696 transport mechanisms. It is represented by sending the single byte
37697 @code{0x03} without any of the usual packet overhead described in
37698 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37699 transmitted as part of a packet, it is considered to be packet data
37700 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37701 (@pxref{X packet}), used for binary downloads, may include an unescaped
37702 @code{0x03} as part of its packet.
37704 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37705 When Linux kernel receives this sequence from serial port,
37706 it stops execution and connects to gdb.
37708 Stubs are not required to recognize these interrupt mechanisms and the
37709 precise meaning associated with receipt of the interrupt is
37710 implementation defined. If the target supports debugging of multiple
37711 threads and/or processes, it should attempt to interrupt all
37712 currently-executing threads and processes.
37713 If the stub is successful at interrupting the
37714 running program, it should send one of the stop
37715 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37716 of successfully stopping the program in all-stop mode, and a stop reply
37717 for each stopped thread in non-stop mode.
37718 Interrupts received while the
37719 program is stopped are discarded.
37721 @node Notification Packets
37722 @section Notification Packets
37723 @cindex notification packets
37724 @cindex packets, notification
37726 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37727 packets that require no acknowledgment. Both the GDB and the stub
37728 may send notifications (although the only notifications defined at
37729 present are sent by the stub). Notifications carry information
37730 without incurring the round-trip latency of an acknowledgment, and so
37731 are useful for low-impact communications where occasional packet loss
37734 A notification packet has the form @samp{% @var{data} #
37735 @var{checksum}}, where @var{data} is the content of the notification,
37736 and @var{checksum} is a checksum of @var{data}, computed and formatted
37737 as for ordinary @value{GDBN} packets. A notification's @var{data}
37738 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37739 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37740 to acknowledge the notification's receipt or to report its corruption.
37742 Every notification's @var{data} begins with a name, which contains no
37743 colon characters, followed by a colon character.
37745 Recipients should silently ignore corrupted notifications and
37746 notifications they do not understand. Recipients should restart
37747 timeout periods on receipt of a well-formed notification, whether or
37748 not they understand it.
37750 Senders should only send the notifications described here when this
37751 protocol description specifies that they are permitted. In the
37752 future, we may extend the protocol to permit existing notifications in
37753 new contexts; this rule helps older senders avoid confusing newer
37756 (Older versions of @value{GDBN} ignore bytes received until they see
37757 the @samp{$} byte that begins an ordinary packet, so new stubs may
37758 transmit notifications without fear of confusing older clients. There
37759 are no notifications defined for @value{GDBN} to send at the moment, but we
37760 assume that most older stubs would ignore them, as well.)
37762 Each notification is comprised of three parts:
37764 @item @var{name}:@var{event}
37765 The notification packet is sent by the side that initiates the
37766 exchange (currently, only the stub does that), with @var{event}
37767 carrying the specific information about the notification, and
37768 @var{name} specifying the name of the notification.
37770 The acknowledge sent by the other side, usually @value{GDBN}, to
37771 acknowledge the exchange and request the event.
37774 The purpose of an asynchronous notification mechanism is to report to
37775 @value{GDBN} that something interesting happened in the remote stub.
37777 The remote stub may send notification @var{name}:@var{event}
37778 at any time, but @value{GDBN} acknowledges the notification when
37779 appropriate. The notification event is pending before @value{GDBN}
37780 acknowledges. Only one notification at a time may be pending; if
37781 additional events occur before @value{GDBN} has acknowledged the
37782 previous notification, they must be queued by the stub for later
37783 synchronous transmission in response to @var{ack} packets from
37784 @value{GDBN}. Because the notification mechanism is unreliable,
37785 the stub is permitted to resend a notification if it believes
37786 @value{GDBN} may not have received it.
37788 Specifically, notifications may appear when @value{GDBN} is not
37789 otherwise reading input from the stub, or when @value{GDBN} is
37790 expecting to read a normal synchronous response or a
37791 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37792 Notification packets are distinct from any other communication from
37793 the stub so there is no ambiguity.
37795 After receiving a notification, @value{GDBN} shall acknowledge it by
37796 sending a @var{ack} packet as a regular, synchronous request to the
37797 stub. Such acknowledgment is not required to happen immediately, as
37798 @value{GDBN} is permitted to send other, unrelated packets to the
37799 stub first, which the stub should process normally.
37801 Upon receiving a @var{ack} packet, if the stub has other queued
37802 events to report to @value{GDBN}, it shall respond by sending a
37803 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37804 packet to solicit further responses; again, it is permitted to send
37805 other, unrelated packets as well which the stub should process
37808 If the stub receives a @var{ack} packet and there are no additional
37809 @var{event} to report, the stub shall return an @samp{OK} response.
37810 At this point, @value{GDBN} has finished processing a notification
37811 and the stub has completed sending any queued events. @value{GDBN}
37812 won't accept any new notifications until the final @samp{OK} is
37813 received . If further notification events occur, the stub shall send
37814 a new notification, @value{GDBN} shall accept the notification, and
37815 the process shall be repeated.
37817 The process of asynchronous notification can be illustrated by the
37820 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37823 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37825 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37830 The following notifications are defined:
37831 @multitable @columnfractions 0.12 0.12 0.38 0.38
37840 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37841 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37842 for information on how these notifications are acknowledged by
37844 @tab Report an asynchronous stop event in non-stop mode.
37848 @node Remote Non-Stop
37849 @section Remote Protocol Support for Non-Stop Mode
37851 @value{GDBN}'s remote protocol supports non-stop debugging of
37852 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37853 supports non-stop mode, it should report that to @value{GDBN} by including
37854 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37856 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37857 establishing a new connection with the stub. Entering non-stop mode
37858 does not alter the state of any currently-running threads, but targets
37859 must stop all threads in any already-attached processes when entering
37860 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37861 probe the target state after a mode change.
37863 In non-stop mode, when an attached process encounters an event that
37864 would otherwise be reported with a stop reply, it uses the
37865 asynchronous notification mechanism (@pxref{Notification Packets}) to
37866 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37867 in all processes are stopped when a stop reply is sent, in non-stop
37868 mode only the thread reporting the stop event is stopped. That is,
37869 when reporting a @samp{S} or @samp{T} response to indicate completion
37870 of a step operation, hitting a breakpoint, or a fault, only the
37871 affected thread is stopped; any other still-running threads continue
37872 to run. When reporting a @samp{W} or @samp{X} response, all running
37873 threads belonging to other attached processes continue to run.
37875 In non-stop mode, the target shall respond to the @samp{?} packet as
37876 follows. First, any incomplete stop reply notification/@samp{vStopped}
37877 sequence in progress is abandoned. The target must begin a new
37878 sequence reporting stop events for all stopped threads, whether or not
37879 it has previously reported those events to @value{GDBN}. The first
37880 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37881 subsequent stop replies are sent as responses to @samp{vStopped} packets
37882 using the mechanism described above. The target must not send
37883 asynchronous stop reply notifications until the sequence is complete.
37884 If all threads are running when the target receives the @samp{?} packet,
37885 or if the target is not attached to any process, it shall respond
37888 If the stub supports non-stop mode, it should also support the
37889 @samp{swbreak} stop reason if software breakpoints are supported, and
37890 the @samp{hwbreak} stop reason if hardware breakpoints are supported
37891 (@pxref{swbreak stop reason}). This is because given the asynchronous
37892 nature of non-stop mode, between the time a thread hits a breakpoint
37893 and the time the event is finally processed by @value{GDBN}, the
37894 breakpoint may have already been removed from the target. Due to
37895 this, @value{GDBN} needs to be able to tell whether a trap stop was
37896 caused by a delayed breakpoint event, which should be ignored, as
37897 opposed to a random trap signal, which should be reported to the user.
37898 Note the @samp{swbreak} feature implies that the target is responsible
37899 for adjusting the PC when a software breakpoint triggers, if
37900 necessary, such as on the x86 architecture.
37902 @node Packet Acknowledgment
37903 @section Packet Acknowledgment
37905 @cindex acknowledgment, for @value{GDBN} remote
37906 @cindex packet acknowledgment, for @value{GDBN} remote
37907 By default, when either the host or the target machine receives a packet,
37908 the first response expected is an acknowledgment: either @samp{+} (to indicate
37909 the package was received correctly) or @samp{-} (to request retransmission).
37910 This mechanism allows the @value{GDBN} remote protocol to operate over
37911 unreliable transport mechanisms, such as a serial line.
37913 In cases where the transport mechanism is itself reliable (such as a pipe or
37914 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37915 It may be desirable to disable them in that case to reduce communication
37916 overhead, or for other reasons. This can be accomplished by means of the
37917 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37919 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37920 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37921 and response format still includes the normal checksum, as described in
37922 @ref{Overview}, but the checksum may be ignored by the receiver.
37924 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37925 no-acknowledgment mode, it should report that to @value{GDBN}
37926 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37927 @pxref{qSupported}.
37928 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37929 disabled via the @code{set remote noack-packet off} command
37930 (@pxref{Remote Configuration}),
37931 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37932 Only then may the stub actually turn off packet acknowledgments.
37933 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37934 response, which can be safely ignored by the stub.
37936 Note that @code{set remote noack-packet} command only affects negotiation
37937 between @value{GDBN} and the stub when subsequent connections are made;
37938 it does not affect the protocol acknowledgment state for any current
37940 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37941 new connection is established,
37942 there is also no protocol request to re-enable the acknowledgments
37943 for the current connection, once disabled.
37948 Example sequence of a target being re-started. Notice how the restart
37949 does not get any direct output:
37954 @emph{target restarts}
37957 <- @code{T001:1234123412341234}
37961 Example sequence of a target being stepped by a single instruction:
37964 -> @code{G1445@dots{}}
37969 <- @code{T001:1234123412341234}
37973 <- @code{1455@dots{}}
37977 @node File-I/O Remote Protocol Extension
37978 @section File-I/O Remote Protocol Extension
37979 @cindex File-I/O remote protocol extension
37982 * File-I/O Overview::
37983 * Protocol Basics::
37984 * The F Request Packet::
37985 * The F Reply Packet::
37986 * The Ctrl-C Message::
37988 * List of Supported Calls::
37989 * Protocol-specific Representation of Datatypes::
37991 * File-I/O Examples::
37994 @node File-I/O Overview
37995 @subsection File-I/O Overview
37996 @cindex file-i/o overview
37998 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37999 target to use the host's file system and console I/O to perform various
38000 system calls. System calls on the target system are translated into a
38001 remote protocol packet to the host system, which then performs the needed
38002 actions and returns a response packet to the target system.
38003 This simulates file system operations even on targets that lack file systems.
38005 The protocol is defined to be independent of both the host and target systems.
38006 It uses its own internal representation of datatypes and values. Both
38007 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38008 translating the system-dependent value representations into the internal
38009 protocol representations when data is transmitted.
38011 The communication is synchronous. A system call is possible only when
38012 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38013 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38014 the target is stopped to allow deterministic access to the target's
38015 memory. Therefore File-I/O is not interruptible by target signals. On
38016 the other hand, it is possible to interrupt File-I/O by a user interrupt
38017 (@samp{Ctrl-C}) within @value{GDBN}.
38019 The target's request to perform a host system call does not finish
38020 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38021 after finishing the system call, the target returns to continuing the
38022 previous activity (continue, step). No additional continue or step
38023 request from @value{GDBN} is required.
38026 (@value{GDBP}) continue
38027 <- target requests 'system call X'
38028 target is stopped, @value{GDBN} executes system call
38029 -> @value{GDBN} returns result
38030 ... target continues, @value{GDBN} returns to wait for the target
38031 <- target hits breakpoint and sends a Txx packet
38034 The protocol only supports I/O on the console and to regular files on
38035 the host file system. Character or block special devices, pipes,
38036 named pipes, sockets or any other communication method on the host
38037 system are not supported by this protocol.
38039 File I/O is not supported in non-stop mode.
38041 @node Protocol Basics
38042 @subsection Protocol Basics
38043 @cindex protocol basics, file-i/o
38045 The File-I/O protocol uses the @code{F} packet as the request as well
38046 as reply packet. Since a File-I/O system call can only occur when
38047 @value{GDBN} is waiting for a response from the continuing or stepping target,
38048 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38049 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38050 This @code{F} packet contains all information needed to allow @value{GDBN}
38051 to call the appropriate host system call:
38055 A unique identifier for the requested system call.
38058 All parameters to the system call. Pointers are given as addresses
38059 in the target memory address space. Pointers to strings are given as
38060 pointer/length pair. Numerical values are given as they are.
38061 Numerical control flags are given in a protocol-specific representation.
38065 At this point, @value{GDBN} has to perform the following actions.
38069 If the parameters include pointer values to data needed as input to a
38070 system call, @value{GDBN} requests this data from the target with a
38071 standard @code{m} packet request. This additional communication has to be
38072 expected by the target implementation and is handled as any other @code{m}
38076 @value{GDBN} translates all value from protocol representation to host
38077 representation as needed. Datatypes are coerced into the host types.
38080 @value{GDBN} calls the system call.
38083 It then coerces datatypes back to protocol representation.
38086 If the system call is expected to return data in buffer space specified
38087 by pointer parameters to the call, the data is transmitted to the
38088 target using a @code{M} or @code{X} packet. This packet has to be expected
38089 by the target implementation and is handled as any other @code{M} or @code{X}
38094 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38095 necessary information for the target to continue. This at least contains
38102 @code{errno}, if has been changed by the system call.
38109 After having done the needed type and value coercion, the target continues
38110 the latest continue or step action.
38112 @node The F Request Packet
38113 @subsection The @code{F} Request Packet
38114 @cindex file-i/o request packet
38115 @cindex @code{F} request packet
38117 The @code{F} request packet has the following format:
38120 @item F@var{call-id},@var{parameter@dots{}}
38122 @var{call-id} is the identifier to indicate the host system call to be called.
38123 This is just the name of the function.
38125 @var{parameter@dots{}} are the parameters to the system call.
38126 Parameters are hexadecimal integer values, either the actual values in case
38127 of scalar datatypes, pointers to target buffer space in case of compound
38128 datatypes and unspecified memory areas, or pointer/length pairs in case
38129 of string parameters. These are appended to the @var{call-id} as a
38130 comma-delimited list. All values are transmitted in ASCII
38131 string representation, pointer/length pairs separated by a slash.
38137 @node The F Reply Packet
38138 @subsection The @code{F} Reply Packet
38139 @cindex file-i/o reply packet
38140 @cindex @code{F} reply packet
38142 The @code{F} reply packet has the following format:
38146 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38148 @var{retcode} is the return code of the system call as hexadecimal value.
38150 @var{errno} is the @code{errno} set by the call, in protocol-specific
38152 This parameter can be omitted if the call was successful.
38154 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38155 case, @var{errno} must be sent as well, even if the call was successful.
38156 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38163 or, if the call was interrupted before the host call has been performed:
38170 assuming 4 is the protocol-specific representation of @code{EINTR}.
38175 @node The Ctrl-C Message
38176 @subsection The @samp{Ctrl-C} Message
38177 @cindex ctrl-c message, in file-i/o protocol
38179 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38180 reply packet (@pxref{The F Reply Packet}),
38181 the target should behave as if it had
38182 gotten a break message. The meaning for the target is ``system call
38183 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38184 (as with a break message) and return to @value{GDBN} with a @code{T02}
38187 It's important for the target to know in which
38188 state the system call was interrupted. There are two possible cases:
38192 The system call hasn't been performed on the host yet.
38195 The system call on the host has been finished.
38199 These two states can be distinguished by the target by the value of the
38200 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38201 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38202 on POSIX systems. In any other case, the target may presume that the
38203 system call has been finished --- successfully or not --- and should behave
38204 as if the break message arrived right after the system call.
38206 @value{GDBN} must behave reliably. If the system call has not been called
38207 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38208 @code{errno} in the packet. If the system call on the host has been finished
38209 before the user requests a break, the full action must be finished by
38210 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38211 The @code{F} packet may only be sent when either nothing has happened
38212 or the full action has been completed.
38215 @subsection Console I/O
38216 @cindex console i/o as part of file-i/o
38218 By default and if not explicitly closed by the target system, the file
38219 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38220 on the @value{GDBN} console is handled as any other file output operation
38221 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38222 by @value{GDBN} so that after the target read request from file descriptor
38223 0 all following typing is buffered until either one of the following
38228 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38230 system call is treated as finished.
38233 The user presses @key{RET}. This is treated as end of input with a trailing
38237 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38238 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38242 If the user has typed more characters than fit in the buffer given to
38243 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38244 either another @code{read(0, @dots{})} is requested by the target, or debugging
38245 is stopped at the user's request.
38248 @node List of Supported Calls
38249 @subsection List of Supported Calls
38250 @cindex list of supported file-i/o calls
38267 @unnumberedsubsubsec open
38268 @cindex open, file-i/o system call
38273 int open(const char *pathname, int flags);
38274 int open(const char *pathname, int flags, mode_t mode);
38278 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38281 @var{flags} is the bitwise @code{OR} of the following values:
38285 If the file does not exist it will be created. The host
38286 rules apply as far as file ownership and time stamps
38290 When used with @code{O_CREAT}, if the file already exists it is
38291 an error and open() fails.
38294 If the file already exists and the open mode allows
38295 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38296 truncated to zero length.
38299 The file is opened in append mode.
38302 The file is opened for reading only.
38305 The file is opened for writing only.
38308 The file is opened for reading and writing.
38312 Other bits are silently ignored.
38316 @var{mode} is the bitwise @code{OR} of the following values:
38320 User has read permission.
38323 User has write permission.
38326 Group has read permission.
38329 Group has write permission.
38332 Others have read permission.
38335 Others have write permission.
38339 Other bits are silently ignored.
38342 @item Return value:
38343 @code{open} returns the new file descriptor or -1 if an error
38350 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38353 @var{pathname} refers to a directory.
38356 The requested access is not allowed.
38359 @var{pathname} was too long.
38362 A directory component in @var{pathname} does not exist.
38365 @var{pathname} refers to a device, pipe, named pipe or socket.
38368 @var{pathname} refers to a file on a read-only filesystem and
38369 write access was requested.
38372 @var{pathname} is an invalid pointer value.
38375 No space on device to create the file.
38378 The process already has the maximum number of files open.
38381 The limit on the total number of files open on the system
38385 The call was interrupted by the user.
38391 @unnumberedsubsubsec close
38392 @cindex close, file-i/o system call
38401 @samp{Fclose,@var{fd}}
38403 @item Return value:
38404 @code{close} returns zero on success, or -1 if an error occurred.
38410 @var{fd} isn't a valid open file descriptor.
38413 The call was interrupted by the user.
38419 @unnumberedsubsubsec read
38420 @cindex read, file-i/o system call
38425 int read(int fd, void *buf, unsigned int count);
38429 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38431 @item Return value:
38432 On success, the number of bytes read is returned.
38433 Zero indicates end of file. If count is zero, read
38434 returns zero as well. On error, -1 is returned.
38440 @var{fd} is not a valid file descriptor or is not open for
38444 @var{bufptr} is an invalid pointer value.
38447 The call was interrupted by the user.
38453 @unnumberedsubsubsec write
38454 @cindex write, file-i/o system call
38459 int write(int fd, const void *buf, unsigned int count);
38463 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38465 @item Return value:
38466 On success, the number of bytes written are returned.
38467 Zero indicates nothing was written. On error, -1
38474 @var{fd} is not a valid file descriptor or is not open for
38478 @var{bufptr} is an invalid pointer value.
38481 An attempt was made to write a file that exceeds the
38482 host-specific maximum file size allowed.
38485 No space on device to write the data.
38488 The call was interrupted by the user.
38494 @unnumberedsubsubsec lseek
38495 @cindex lseek, file-i/o system call
38500 long lseek (int fd, long offset, int flag);
38504 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38506 @var{flag} is one of:
38510 The offset is set to @var{offset} bytes.
38513 The offset is set to its current location plus @var{offset}
38517 The offset is set to the size of the file plus @var{offset}
38521 @item Return value:
38522 On success, the resulting unsigned offset in bytes from
38523 the beginning of the file is returned. Otherwise, a
38524 value of -1 is returned.
38530 @var{fd} is not a valid open file descriptor.
38533 @var{fd} is associated with the @value{GDBN} console.
38536 @var{flag} is not a proper value.
38539 The call was interrupted by the user.
38545 @unnumberedsubsubsec rename
38546 @cindex rename, file-i/o system call
38551 int rename(const char *oldpath, const char *newpath);
38555 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38557 @item Return value:
38558 On success, zero is returned. On error, -1 is returned.
38564 @var{newpath} is an existing directory, but @var{oldpath} is not a
38568 @var{newpath} is a non-empty directory.
38571 @var{oldpath} or @var{newpath} is a directory that is in use by some
38575 An attempt was made to make a directory a subdirectory
38579 A component used as a directory in @var{oldpath} or new
38580 path is not a directory. Or @var{oldpath} is a directory
38581 and @var{newpath} exists but is not a directory.
38584 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38587 No access to the file or the path of the file.
38591 @var{oldpath} or @var{newpath} was too long.
38594 A directory component in @var{oldpath} or @var{newpath} does not exist.
38597 The file is on a read-only filesystem.
38600 The device containing the file has no room for the new
38604 The call was interrupted by the user.
38610 @unnumberedsubsubsec unlink
38611 @cindex unlink, file-i/o system call
38616 int unlink(const char *pathname);
38620 @samp{Funlink,@var{pathnameptr}/@var{len}}
38622 @item Return value:
38623 On success, zero is returned. On error, -1 is returned.
38629 No access to the file or the path of the file.
38632 The system does not allow unlinking of directories.
38635 The file @var{pathname} cannot be unlinked because it's
38636 being used by another process.
38639 @var{pathnameptr} is an invalid pointer value.
38642 @var{pathname} was too long.
38645 A directory component in @var{pathname} does not exist.
38648 A component of the path is not a directory.
38651 The file is on a read-only filesystem.
38654 The call was interrupted by the user.
38660 @unnumberedsubsubsec stat/fstat
38661 @cindex fstat, file-i/o system call
38662 @cindex stat, file-i/o system call
38667 int stat(const char *pathname, struct stat *buf);
38668 int fstat(int fd, struct stat *buf);
38672 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38673 @samp{Ffstat,@var{fd},@var{bufptr}}
38675 @item Return value:
38676 On success, zero is returned. On error, -1 is returned.
38682 @var{fd} is not a valid open file.
38685 A directory component in @var{pathname} does not exist or the
38686 path is an empty string.
38689 A component of the path is not a directory.
38692 @var{pathnameptr} is an invalid pointer value.
38695 No access to the file or the path of the file.
38698 @var{pathname} was too long.
38701 The call was interrupted by the user.
38707 @unnumberedsubsubsec gettimeofday
38708 @cindex gettimeofday, file-i/o system call
38713 int gettimeofday(struct timeval *tv, void *tz);
38717 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38719 @item Return value:
38720 On success, 0 is returned, -1 otherwise.
38726 @var{tz} is a non-NULL pointer.
38729 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38735 @unnumberedsubsubsec isatty
38736 @cindex isatty, file-i/o system call
38741 int isatty(int fd);
38745 @samp{Fisatty,@var{fd}}
38747 @item Return value:
38748 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38754 The call was interrupted by the user.
38759 Note that the @code{isatty} call is treated as a special case: it returns
38760 1 to the target if the file descriptor is attached
38761 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38762 would require implementing @code{ioctl} and would be more complex than
38767 @unnumberedsubsubsec system
38768 @cindex system, file-i/o system call
38773 int system(const char *command);
38777 @samp{Fsystem,@var{commandptr}/@var{len}}
38779 @item Return value:
38780 If @var{len} is zero, the return value indicates whether a shell is
38781 available. A zero return value indicates a shell is not available.
38782 For non-zero @var{len}, the value returned is -1 on error and the
38783 return status of the command otherwise. Only the exit status of the
38784 command is returned, which is extracted from the host's @code{system}
38785 return value by calling @code{WEXITSTATUS(retval)}. In case
38786 @file{/bin/sh} could not be executed, 127 is returned.
38792 The call was interrupted by the user.
38797 @value{GDBN} takes over the full task of calling the necessary host calls
38798 to perform the @code{system} call. The return value of @code{system} on
38799 the host is simplified before it's returned
38800 to the target. Any termination signal information from the child process
38801 is discarded, and the return value consists
38802 entirely of the exit status of the called command.
38804 Due to security concerns, the @code{system} call is by default refused
38805 by @value{GDBN}. The user has to allow this call explicitly with the
38806 @code{set remote system-call-allowed 1} command.
38809 @item set remote system-call-allowed
38810 @kindex set remote system-call-allowed
38811 Control whether to allow the @code{system} calls in the File I/O
38812 protocol for the remote target. The default is zero (disabled).
38814 @item show remote system-call-allowed
38815 @kindex show remote system-call-allowed
38816 Show whether the @code{system} calls are allowed in the File I/O
38820 @node Protocol-specific Representation of Datatypes
38821 @subsection Protocol-specific Representation of Datatypes
38822 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38825 * Integral Datatypes::
38827 * Memory Transfer::
38832 @node Integral Datatypes
38833 @unnumberedsubsubsec Integral Datatypes
38834 @cindex integral datatypes, in file-i/o protocol
38836 The integral datatypes used in the system calls are @code{int},
38837 @code{unsigned int}, @code{long}, @code{unsigned long},
38838 @code{mode_t}, and @code{time_t}.
38840 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38841 implemented as 32 bit values in this protocol.
38843 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38845 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38846 in @file{limits.h}) to allow range checking on host and target.
38848 @code{time_t} datatypes are defined as seconds since the Epoch.
38850 All integral datatypes transferred as part of a memory read or write of a
38851 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38854 @node Pointer Values
38855 @unnumberedsubsubsec Pointer Values
38856 @cindex pointer values, in file-i/o protocol
38858 Pointers to target data are transmitted as they are. An exception
38859 is made for pointers to buffers for which the length isn't
38860 transmitted as part of the function call, namely strings. Strings
38861 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38868 which is a pointer to data of length 18 bytes at position 0x1aaf.
38869 The length is defined as the full string length in bytes, including
38870 the trailing null byte. For example, the string @code{"hello world"}
38871 at address 0x123456 is transmitted as
38877 @node Memory Transfer
38878 @unnumberedsubsubsec Memory Transfer
38879 @cindex memory transfer, in file-i/o protocol
38881 Structured data which is transferred using a memory read or write (for
38882 example, a @code{struct stat}) is expected to be in a protocol-specific format
38883 with all scalar multibyte datatypes being big endian. Translation to
38884 this representation needs to be done both by the target before the @code{F}
38885 packet is sent, and by @value{GDBN} before
38886 it transfers memory to the target. Transferred pointers to structured
38887 data should point to the already-coerced data at any time.
38891 @unnumberedsubsubsec struct stat
38892 @cindex struct stat, in file-i/o protocol
38894 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38895 is defined as follows:
38899 unsigned int st_dev; /* device */
38900 unsigned int st_ino; /* inode */
38901 mode_t st_mode; /* protection */
38902 unsigned int st_nlink; /* number of hard links */
38903 unsigned int st_uid; /* user ID of owner */
38904 unsigned int st_gid; /* group ID of owner */
38905 unsigned int st_rdev; /* device type (if inode device) */
38906 unsigned long st_size; /* total size, in bytes */
38907 unsigned long st_blksize; /* blocksize for filesystem I/O */
38908 unsigned long st_blocks; /* number of blocks allocated */
38909 time_t st_atime; /* time of last access */
38910 time_t st_mtime; /* time of last modification */
38911 time_t st_ctime; /* time of last change */
38915 The integral datatypes conform to the definitions given in the
38916 appropriate section (see @ref{Integral Datatypes}, for details) so this
38917 structure is of size 64 bytes.
38919 The values of several fields have a restricted meaning and/or
38925 A value of 0 represents a file, 1 the console.
38928 No valid meaning for the target. Transmitted unchanged.
38931 Valid mode bits are described in @ref{Constants}. Any other
38932 bits have currently no meaning for the target.
38937 No valid meaning for the target. Transmitted unchanged.
38942 These values have a host and file system dependent
38943 accuracy. Especially on Windows hosts, the file system may not
38944 support exact timing values.
38947 The target gets a @code{struct stat} of the above representation and is
38948 responsible for coercing it to the target representation before
38951 Note that due to size differences between the host, target, and protocol
38952 representations of @code{struct stat} members, these members could eventually
38953 get truncated on the target.
38955 @node struct timeval
38956 @unnumberedsubsubsec struct timeval
38957 @cindex struct timeval, in file-i/o protocol
38959 The buffer of type @code{struct timeval} used by the File-I/O protocol
38960 is defined as follows:
38964 time_t tv_sec; /* second */
38965 long tv_usec; /* microsecond */
38969 The integral datatypes conform to the definitions given in the
38970 appropriate section (see @ref{Integral Datatypes}, for details) so this
38971 structure is of size 8 bytes.
38974 @subsection Constants
38975 @cindex constants, in file-i/o protocol
38977 The following values are used for the constants inside of the
38978 protocol. @value{GDBN} and target are responsible for translating these
38979 values before and after the call as needed.
38990 @unnumberedsubsubsec Open Flags
38991 @cindex open flags, in file-i/o protocol
38993 All values are given in hexadecimal representation.
39005 @node mode_t Values
39006 @unnumberedsubsubsec mode_t Values
39007 @cindex mode_t values, in file-i/o protocol
39009 All values are given in octal representation.
39026 @unnumberedsubsubsec Errno Values
39027 @cindex errno values, in file-i/o protocol
39029 All values are given in decimal representation.
39054 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39055 any error value not in the list of supported error numbers.
39058 @unnumberedsubsubsec Lseek Flags
39059 @cindex lseek flags, in file-i/o protocol
39068 @unnumberedsubsubsec Limits
39069 @cindex limits, in file-i/o protocol
39071 All values are given in decimal representation.
39074 INT_MIN -2147483648
39076 UINT_MAX 4294967295
39077 LONG_MIN -9223372036854775808
39078 LONG_MAX 9223372036854775807
39079 ULONG_MAX 18446744073709551615
39082 @node File-I/O Examples
39083 @subsection File-I/O Examples
39084 @cindex file-i/o examples
39086 Example sequence of a write call, file descriptor 3, buffer is at target
39087 address 0x1234, 6 bytes should be written:
39090 <- @code{Fwrite,3,1234,6}
39091 @emph{request memory read from target}
39094 @emph{return "6 bytes written"}
39098 Example sequence of a read call, file descriptor 3, buffer is at target
39099 address 0x1234, 6 bytes should be read:
39102 <- @code{Fread,3,1234,6}
39103 @emph{request memory write to target}
39104 -> @code{X1234,6:XXXXXX}
39105 @emph{return "6 bytes read"}
39109 Example sequence of a read call, call fails on the host due to invalid
39110 file descriptor (@code{EBADF}):
39113 <- @code{Fread,3,1234,6}
39117 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39121 <- @code{Fread,3,1234,6}
39126 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39130 <- @code{Fread,3,1234,6}
39131 -> @code{X1234,6:XXXXXX}
39135 @node Library List Format
39136 @section Library List Format
39137 @cindex library list format, remote protocol
39139 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39140 same process as your application to manage libraries. In this case,
39141 @value{GDBN} can use the loader's symbol table and normal memory
39142 operations to maintain a list of shared libraries. On other
39143 platforms, the operating system manages loaded libraries.
39144 @value{GDBN} can not retrieve the list of currently loaded libraries
39145 through memory operations, so it uses the @samp{qXfer:libraries:read}
39146 packet (@pxref{qXfer library list read}) instead. The remote stub
39147 queries the target's operating system and reports which libraries
39150 The @samp{qXfer:libraries:read} packet returns an XML document which
39151 lists loaded libraries and their offsets. Each library has an
39152 associated name and one or more segment or section base addresses,
39153 which report where the library was loaded in memory.
39155 For the common case of libraries that are fully linked binaries, the
39156 library should have a list of segments. If the target supports
39157 dynamic linking of a relocatable object file, its library XML element
39158 should instead include a list of allocated sections. The segment or
39159 section bases are start addresses, not relocation offsets; they do not
39160 depend on the library's link-time base addresses.
39162 @value{GDBN} must be linked with the Expat library to support XML
39163 library lists. @xref{Expat}.
39165 A simple memory map, with one loaded library relocated by a single
39166 offset, looks like this:
39170 <library name="/lib/libc.so.6">
39171 <segment address="0x10000000"/>
39176 Another simple memory map, with one loaded library with three
39177 allocated sections (.text, .data, .bss), looks like this:
39181 <library name="sharedlib.o">
39182 <section address="0x10000000"/>
39183 <section address="0x20000000"/>
39184 <section address="0x30000000"/>
39189 The format of a library list is described by this DTD:
39192 <!-- library-list: Root element with versioning -->
39193 <!ELEMENT library-list (library)*>
39194 <!ATTLIST library-list version CDATA #FIXED "1.0">
39195 <!ELEMENT library (segment*, section*)>
39196 <!ATTLIST library name CDATA #REQUIRED>
39197 <!ELEMENT segment EMPTY>
39198 <!ATTLIST segment address CDATA #REQUIRED>
39199 <!ELEMENT section EMPTY>
39200 <!ATTLIST section address CDATA #REQUIRED>
39203 In addition, segments and section descriptors cannot be mixed within a
39204 single library element, and you must supply at least one segment or
39205 section for each library.
39207 @node Library List Format for SVR4 Targets
39208 @section Library List Format for SVR4 Targets
39209 @cindex library list format, remote protocol
39211 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39212 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39213 shared libraries. Still a special library list provided by this packet is
39214 more efficient for the @value{GDBN} remote protocol.
39216 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39217 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39218 target, the following parameters are reported:
39222 @code{name}, the absolute file name from the @code{l_name} field of
39223 @code{struct link_map}.
39225 @code{lm} with address of @code{struct link_map} used for TLS
39226 (Thread Local Storage) access.
39228 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39229 @code{struct link_map}. For prelinked libraries this is not an absolute
39230 memory address. It is a displacement of absolute memory address against
39231 address the file was prelinked to during the library load.
39233 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39236 Additionally the single @code{main-lm} attribute specifies address of
39237 @code{struct link_map} used for the main executable. This parameter is used
39238 for TLS access and its presence is optional.
39240 @value{GDBN} must be linked with the Expat library to support XML
39241 SVR4 library lists. @xref{Expat}.
39243 A simple memory map, with two loaded libraries (which do not use prelink),
39247 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39248 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39250 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39252 </library-list-svr>
39255 The format of an SVR4 library list is described by this DTD:
39258 <!-- library-list-svr4: Root element with versioning -->
39259 <!ELEMENT library-list-svr4 (library)*>
39260 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39261 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39262 <!ELEMENT library EMPTY>
39263 <!ATTLIST library name CDATA #REQUIRED>
39264 <!ATTLIST library lm CDATA #REQUIRED>
39265 <!ATTLIST library l_addr CDATA #REQUIRED>
39266 <!ATTLIST library l_ld CDATA #REQUIRED>
39269 @node Memory Map Format
39270 @section Memory Map Format
39271 @cindex memory map format
39273 To be able to write into flash memory, @value{GDBN} needs to obtain a
39274 memory map from the target. This section describes the format of the
39277 The memory map is obtained using the @samp{qXfer:memory-map:read}
39278 (@pxref{qXfer memory map read}) packet and is an XML document that
39279 lists memory regions.
39281 @value{GDBN} must be linked with the Expat library to support XML
39282 memory maps. @xref{Expat}.
39284 The top-level structure of the document is shown below:
39287 <?xml version="1.0"?>
39288 <!DOCTYPE memory-map
39289 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39290 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39296 Each region can be either:
39301 A region of RAM starting at @var{addr} and extending for @var{length}
39305 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39310 A region of read-only memory:
39313 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39318 A region of flash memory, with erasure blocks @var{blocksize}
39322 <memory type="flash" start="@var{addr}" length="@var{length}">
39323 <property name="blocksize">@var{blocksize}</property>
39329 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39330 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39331 packets to write to addresses in such ranges.
39333 The formal DTD for memory map format is given below:
39336 <!-- ................................................... -->
39337 <!-- Memory Map XML DTD ................................ -->
39338 <!-- File: memory-map.dtd .............................. -->
39339 <!-- .................................... .............. -->
39340 <!-- memory-map.dtd -->
39341 <!-- memory-map: Root element with versioning -->
39342 <!ELEMENT memory-map (memory | property)>
39343 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39344 <!ELEMENT memory (property)>
39345 <!-- memory: Specifies a memory region,
39346 and its type, or device. -->
39347 <!ATTLIST memory type CDATA #REQUIRED
39348 start CDATA #REQUIRED
39349 length CDATA #REQUIRED
39350 device CDATA #IMPLIED>
39351 <!-- property: Generic attribute tag -->
39352 <!ELEMENT property (#PCDATA | property)*>
39353 <!ATTLIST property name CDATA #REQUIRED>
39356 @node Thread List Format
39357 @section Thread List Format
39358 @cindex thread list format
39360 To efficiently update the list of threads and their attributes,
39361 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39362 (@pxref{qXfer threads read}) and obtains the XML document with
39363 the following structure:
39366 <?xml version="1.0"?>
39368 <thread id="id" core="0">
39369 ... description ...
39374 Each @samp{thread} element must have the @samp{id} attribute that
39375 identifies the thread (@pxref{thread-id syntax}). The
39376 @samp{core} attribute, if present, specifies which processor core
39377 the thread was last executing on. The content of the of @samp{thread}
39378 element is interpreted as human-readable auxilliary information.
39380 @node Traceframe Info Format
39381 @section Traceframe Info Format
39382 @cindex traceframe info format
39384 To be able to know which objects in the inferior can be examined when
39385 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39386 memory ranges, registers and trace state variables that have been
39387 collected in a traceframe.
39389 This list is obtained using the @samp{qXfer:traceframe-info:read}
39390 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39392 @value{GDBN} must be linked with the Expat library to support XML
39393 traceframe info discovery. @xref{Expat}.
39395 The top-level structure of the document is shown below:
39398 <?xml version="1.0"?>
39399 <!DOCTYPE traceframe-info
39400 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39401 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39407 Each traceframe block can be either:
39412 A region of collected memory starting at @var{addr} and extending for
39413 @var{length} bytes from there:
39416 <memory start="@var{addr}" length="@var{length}"/>
39420 A block indicating trace state variable numbered @var{number} has been
39424 <tvar id="@var{number}"/>
39429 The formal DTD for the traceframe info format is given below:
39432 <!ELEMENT traceframe-info (memory | tvar)* >
39433 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39435 <!ELEMENT memory EMPTY>
39436 <!ATTLIST memory start CDATA #REQUIRED
39437 length CDATA #REQUIRED>
39439 <!ATTLIST tvar id CDATA #REQUIRED>
39442 @node Branch Trace Format
39443 @section Branch Trace Format
39444 @cindex branch trace format
39446 In order to display the branch trace of an inferior thread,
39447 @value{GDBN} needs to obtain the list of branches. This list is
39448 represented as list of sequential code blocks that are connected via
39449 branches. The code in each block has been executed sequentially.
39451 This list is obtained using the @samp{qXfer:btrace:read}
39452 (@pxref{qXfer btrace read}) packet and is an XML document.
39454 @value{GDBN} must be linked with the Expat library to support XML
39455 traceframe info discovery. @xref{Expat}.
39457 The top-level structure of the document is shown below:
39460 <?xml version="1.0"?>
39462 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39463 "http://sourceware.org/gdb/gdb-btrace.dtd">
39472 A block of sequentially executed instructions starting at @var{begin}
39473 and ending at @var{end}:
39476 <block begin="@var{begin}" end="@var{end}"/>
39481 The formal DTD for the branch trace format is given below:
39484 <!ELEMENT btrace (block)* >
39485 <!ATTLIST btrace version CDATA #FIXED "1.0">
39487 <!ELEMENT block EMPTY>
39488 <!ATTLIST block begin CDATA #REQUIRED
39489 end CDATA #REQUIRED>
39492 @node Branch Trace Configuration Format
39493 @section Branch Trace Configuration Format
39494 @cindex branch trace configuration format
39496 For each inferior thread, @value{GDBN} can obtain the branch trace
39497 configuration using the @samp{qXfer:btrace-conf:read}
39498 (@pxref{qXfer btrace-conf read}) packet.
39500 The configuration describes the branch trace format and configuration
39501 settings for that format. The following information is described:
39505 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39508 The size of the @acronym{BTS} ring buffer in bytes.
39512 @value{GDBN} must be linked with the Expat library to support XML
39513 branch trace configuration discovery. @xref{Expat}.
39515 The formal DTD for the branch trace configuration format is given below:
39518 <!ELEMENT btrace-conf (bts?)>
39519 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39521 <!ELEMENT bts EMPTY>
39522 <!ATTLIST bts size CDATA #IMPLIED>
39525 @include agentexpr.texi
39527 @node Target Descriptions
39528 @appendix Target Descriptions
39529 @cindex target descriptions
39531 One of the challenges of using @value{GDBN} to debug embedded systems
39532 is that there are so many minor variants of each processor
39533 architecture in use. It is common practice for vendors to start with
39534 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39535 and then make changes to adapt it to a particular market niche. Some
39536 architectures have hundreds of variants, available from dozens of
39537 vendors. This leads to a number of problems:
39541 With so many different customized processors, it is difficult for
39542 the @value{GDBN} maintainers to keep up with the changes.
39544 Since individual variants may have short lifetimes or limited
39545 audiences, it may not be worthwhile to carry information about every
39546 variant in the @value{GDBN} source tree.
39548 When @value{GDBN} does support the architecture of the embedded system
39549 at hand, the task of finding the correct architecture name to give the
39550 @command{set architecture} command can be error-prone.
39553 To address these problems, the @value{GDBN} remote protocol allows a
39554 target system to not only identify itself to @value{GDBN}, but to
39555 actually describe its own features. This lets @value{GDBN} support
39556 processor variants it has never seen before --- to the extent that the
39557 descriptions are accurate, and that @value{GDBN} understands them.
39559 @value{GDBN} must be linked with the Expat library to support XML
39560 target descriptions. @xref{Expat}.
39563 * Retrieving Descriptions:: How descriptions are fetched from a target.
39564 * Target Description Format:: The contents of a target description.
39565 * Predefined Target Types:: Standard types available for target
39567 * Standard Target Features:: Features @value{GDBN} knows about.
39570 @node Retrieving Descriptions
39571 @section Retrieving Descriptions
39573 Target descriptions can be read from the target automatically, or
39574 specified by the user manually. The default behavior is to read the
39575 description from the target. @value{GDBN} retrieves it via the remote
39576 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39577 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39578 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39579 XML document, of the form described in @ref{Target Description
39582 Alternatively, you can specify a file to read for the target description.
39583 If a file is set, the target will not be queried. The commands to
39584 specify a file are:
39587 @cindex set tdesc filename
39588 @item set tdesc filename @var{path}
39589 Read the target description from @var{path}.
39591 @cindex unset tdesc filename
39592 @item unset tdesc filename
39593 Do not read the XML target description from a file. @value{GDBN}
39594 will use the description supplied by the current target.
39596 @cindex show tdesc filename
39597 @item show tdesc filename
39598 Show the filename to read for a target description, if any.
39602 @node Target Description Format
39603 @section Target Description Format
39604 @cindex target descriptions, XML format
39606 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39607 document which complies with the Document Type Definition provided in
39608 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39609 means you can use generally available tools like @command{xmllint} to
39610 check that your feature descriptions are well-formed and valid.
39611 However, to help people unfamiliar with XML write descriptions for
39612 their targets, we also describe the grammar here.
39614 Target descriptions can identify the architecture of the remote target
39615 and (for some architectures) provide information about custom register
39616 sets. They can also identify the OS ABI of the remote target.
39617 @value{GDBN} can use this information to autoconfigure for your
39618 target, or to warn you if you connect to an unsupported target.
39620 Here is a simple target description:
39623 <target version="1.0">
39624 <architecture>i386:x86-64</architecture>
39629 This minimal description only says that the target uses
39630 the x86-64 architecture.
39632 A target description has the following overall form, with [ ] marking
39633 optional elements and @dots{} marking repeatable elements. The elements
39634 are explained further below.
39637 <?xml version="1.0"?>
39638 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39639 <target version="1.0">
39640 @r{[}@var{architecture}@r{]}
39641 @r{[}@var{osabi}@r{]}
39642 @r{[}@var{compatible}@r{]}
39643 @r{[}@var{feature}@dots{}@r{]}
39648 The description is generally insensitive to whitespace and line
39649 breaks, under the usual common-sense rules. The XML version
39650 declaration and document type declaration can generally be omitted
39651 (@value{GDBN} does not require them), but specifying them may be
39652 useful for XML validation tools. The @samp{version} attribute for
39653 @samp{<target>} may also be omitted, but we recommend
39654 including it; if future versions of @value{GDBN} use an incompatible
39655 revision of @file{gdb-target.dtd}, they will detect and report
39656 the version mismatch.
39658 @subsection Inclusion
39659 @cindex target descriptions, inclusion
39662 @cindex <xi:include>
39665 It can sometimes be valuable to split a target description up into
39666 several different annexes, either for organizational purposes, or to
39667 share files between different possible target descriptions. You can
39668 divide a description into multiple files by replacing any element of
39669 the target description with an inclusion directive of the form:
39672 <xi:include href="@var{document}"/>
39676 When @value{GDBN} encounters an element of this form, it will retrieve
39677 the named XML @var{document}, and replace the inclusion directive with
39678 the contents of that document. If the current description was read
39679 using @samp{qXfer}, then so will be the included document;
39680 @var{document} will be interpreted as the name of an annex. If the
39681 current description was read from a file, @value{GDBN} will look for
39682 @var{document} as a file in the same directory where it found the
39683 original description.
39685 @subsection Architecture
39686 @cindex <architecture>
39688 An @samp{<architecture>} element has this form:
39691 <architecture>@var{arch}</architecture>
39694 @var{arch} is one of the architectures from the set accepted by
39695 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39698 @cindex @code{<osabi>}
39700 This optional field was introduced in @value{GDBN} version 7.0.
39701 Previous versions of @value{GDBN} ignore it.
39703 An @samp{<osabi>} element has this form:
39706 <osabi>@var{abi-name}</osabi>
39709 @var{abi-name} is an OS ABI name from the same selection accepted by
39710 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39712 @subsection Compatible Architecture
39713 @cindex @code{<compatible>}
39715 This optional field was introduced in @value{GDBN} version 7.0.
39716 Previous versions of @value{GDBN} ignore it.
39718 A @samp{<compatible>} element has this form:
39721 <compatible>@var{arch}</compatible>
39724 @var{arch} is one of the architectures from the set accepted by
39725 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39727 A @samp{<compatible>} element is used to specify that the target
39728 is able to run binaries in some other than the main target architecture
39729 given by the @samp{<architecture>} element. For example, on the
39730 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39731 or @code{powerpc:common64}, but the system is able to run binaries
39732 in the @code{spu} architecture as well. The way to describe this
39733 capability with @samp{<compatible>} is as follows:
39736 <architecture>powerpc:common</architecture>
39737 <compatible>spu</compatible>
39740 @subsection Features
39743 Each @samp{<feature>} describes some logical portion of the target
39744 system. Features are currently used to describe available CPU
39745 registers and the types of their contents. A @samp{<feature>} element
39749 <feature name="@var{name}">
39750 @r{[}@var{type}@dots{}@r{]}
39756 Each feature's name should be unique within the description. The name
39757 of a feature does not matter unless @value{GDBN} has some special
39758 knowledge of the contents of that feature; if it does, the feature
39759 should have its standard name. @xref{Standard Target Features}.
39763 Any register's value is a collection of bits which @value{GDBN} must
39764 interpret. The default interpretation is a two's complement integer,
39765 but other types can be requested by name in the register description.
39766 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39767 Target Types}), and the description can define additional composite types.
39769 Each type element must have an @samp{id} attribute, which gives
39770 a unique (within the containing @samp{<feature>}) name to the type.
39771 Types must be defined before they are used.
39774 Some targets offer vector registers, which can be treated as arrays
39775 of scalar elements. These types are written as @samp{<vector>} elements,
39776 specifying the array element type, @var{type}, and the number of elements,
39780 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39784 If a register's value is usefully viewed in multiple ways, define it
39785 with a union type containing the useful representations. The
39786 @samp{<union>} element contains one or more @samp{<field>} elements,
39787 each of which has a @var{name} and a @var{type}:
39790 <union id="@var{id}">
39791 <field name="@var{name}" type="@var{type}"/>
39797 If a register's value is composed from several separate values, define
39798 it with a structure type. There are two forms of the @samp{<struct>}
39799 element; a @samp{<struct>} element must either contain only bitfields
39800 or contain no bitfields. If the structure contains only bitfields,
39801 its total size in bytes must be specified, each bitfield must have an
39802 explicit start and end, and bitfields are automatically assigned an
39803 integer type. The field's @var{start} should be less than or
39804 equal to its @var{end}, and zero represents the least significant bit.
39807 <struct id="@var{id}" size="@var{size}">
39808 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39813 If the structure contains no bitfields, then each field has an
39814 explicit type, and no implicit padding is added.
39817 <struct id="@var{id}">
39818 <field name="@var{name}" type="@var{type}"/>
39824 If a register's value is a series of single-bit flags, define it with
39825 a flags type. The @samp{<flags>} element has an explicit @var{size}
39826 and contains one or more @samp{<field>} elements. Each field has a
39827 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39831 <flags id="@var{id}" size="@var{size}">
39832 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39837 @subsection Registers
39840 Each register is represented as an element with this form:
39843 <reg name="@var{name}"
39844 bitsize="@var{size}"
39845 @r{[}regnum="@var{num}"@r{]}
39846 @r{[}save-restore="@var{save-restore}"@r{]}
39847 @r{[}type="@var{type}"@r{]}
39848 @r{[}group="@var{group}"@r{]}/>
39852 The components are as follows:
39857 The register's name; it must be unique within the target description.
39860 The register's size, in bits.
39863 The register's number. If omitted, a register's number is one greater
39864 than that of the previous register (either in the current feature or in
39865 a preceding feature); the first register in the target description
39866 defaults to zero. This register number is used to read or write
39867 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39868 packets, and registers appear in the @code{g} and @code{G} packets
39869 in order of increasing register number.
39872 Whether the register should be preserved across inferior function
39873 calls; this must be either @code{yes} or @code{no}. The default is
39874 @code{yes}, which is appropriate for most registers except for
39875 some system control registers; this is not related to the target's
39879 The type of the register. It may be a predefined type, a type
39880 defined in the current feature, or one of the special types @code{int}
39881 and @code{float}. @code{int} is an integer type of the correct size
39882 for @var{bitsize}, and @code{float} is a floating point type (in the
39883 architecture's normal floating point format) of the correct size for
39884 @var{bitsize}. The default is @code{int}.
39887 The register group to which this register belongs. It must
39888 be either @code{general}, @code{float}, or @code{vector}. If no
39889 @var{group} is specified, @value{GDBN} will not display the register
39890 in @code{info registers}.
39894 @node Predefined Target Types
39895 @section Predefined Target Types
39896 @cindex target descriptions, predefined types
39898 Type definitions in the self-description can build up composite types
39899 from basic building blocks, but can not define fundamental types. Instead,
39900 standard identifiers are provided by @value{GDBN} for the fundamental
39901 types. The currently supported types are:
39910 Signed integer types holding the specified number of bits.
39917 Unsigned integer types holding the specified number of bits.
39921 Pointers to unspecified code and data. The program counter and
39922 any dedicated return address register may be marked as code
39923 pointers; printing a code pointer converts it into a symbolic
39924 address. The stack pointer and any dedicated address registers
39925 may be marked as data pointers.
39928 Single precision IEEE floating point.
39931 Double precision IEEE floating point.
39934 The 12-byte extended precision format used by ARM FPA registers.
39937 The 10-byte extended precision format used by x87 registers.
39940 32bit @sc{eflags} register used by x86.
39943 32bit @sc{mxcsr} register used by x86.
39947 @node Standard Target Features
39948 @section Standard Target Features
39949 @cindex target descriptions, standard features
39951 A target description must contain either no registers or all the
39952 target's registers. If the description contains no registers, then
39953 @value{GDBN} will assume a default register layout, selected based on
39954 the architecture. If the description contains any registers, the
39955 default layout will not be used; the standard registers must be
39956 described in the target description, in such a way that @value{GDBN}
39957 can recognize them.
39959 This is accomplished by giving specific names to feature elements
39960 which contain standard registers. @value{GDBN} will look for features
39961 with those names and verify that they contain the expected registers;
39962 if any known feature is missing required registers, or if any required
39963 feature is missing, @value{GDBN} will reject the target
39964 description. You can add additional registers to any of the
39965 standard features --- @value{GDBN} will display them just as if
39966 they were added to an unrecognized feature.
39968 This section lists the known features and their expected contents.
39969 Sample XML documents for these features are included in the
39970 @value{GDBN} source tree, in the directory @file{gdb/features}.
39972 Names recognized by @value{GDBN} should include the name of the
39973 company or organization which selected the name, and the overall
39974 architecture to which the feature applies; so e.g.@: the feature
39975 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39977 The names of registers are not case sensitive for the purpose
39978 of recognizing standard features, but @value{GDBN} will only display
39979 registers using the capitalization used in the description.
39982 * AArch64 Features::
39985 * MicroBlaze Features::
39988 * Nios II Features::
39989 * PowerPC Features::
39990 * S/390 and System z Features::
39995 @node AArch64 Features
39996 @subsection AArch64 Features
39997 @cindex target descriptions, AArch64 features
39999 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40000 targets. It should contain registers @samp{x0} through @samp{x30},
40001 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40003 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40004 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40008 @subsection ARM Features
40009 @cindex target descriptions, ARM features
40011 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40013 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40014 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40016 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40017 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40018 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40021 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40022 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40024 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40025 it should contain at least registers @samp{wR0} through @samp{wR15} and
40026 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40027 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40029 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40030 should contain at least registers @samp{d0} through @samp{d15}. If
40031 they are present, @samp{d16} through @samp{d31} should also be included.
40032 @value{GDBN} will synthesize the single-precision registers from
40033 halves of the double-precision registers.
40035 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40036 need to contain registers; it instructs @value{GDBN} to display the
40037 VFP double-precision registers as vectors and to synthesize the
40038 quad-precision registers from pairs of double-precision registers.
40039 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40040 be present and include 32 double-precision registers.
40042 @node i386 Features
40043 @subsection i386 Features
40044 @cindex target descriptions, i386 features
40046 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40047 targets. It should describe the following registers:
40051 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40053 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40055 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40056 @samp{fs}, @samp{gs}
40058 @samp{st0} through @samp{st7}
40060 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40061 @samp{foseg}, @samp{fooff} and @samp{fop}
40064 The register sets may be different, depending on the target.
40066 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40067 describe registers:
40071 @samp{xmm0} through @samp{xmm7} for i386
40073 @samp{xmm0} through @samp{xmm15} for amd64
40078 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40079 @samp{org.gnu.gdb.i386.sse} feature. It should
40080 describe the upper 128 bits of @sc{ymm} registers:
40084 @samp{ymm0h} through @samp{ymm7h} for i386
40086 @samp{ymm0h} through @samp{ymm15h} for amd64
40089 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40090 Memory Protection Extension (MPX). It should describe the following registers:
40094 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40096 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40099 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40100 describe a single register, @samp{orig_eax}.
40102 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40103 @samp{org.gnu.gdb.i386.avx} feature. It should
40104 describe additional @sc{xmm} registers:
40108 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40111 It should describe the upper 128 bits of additional @sc{ymm} registers:
40115 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40119 describe the upper 256 bits of @sc{zmm} registers:
40123 @samp{zmm0h} through @samp{zmm7h} for i386.
40125 @samp{zmm0h} through @samp{zmm15h} for amd64.
40129 describe the additional @sc{zmm} registers:
40133 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40136 @node MicroBlaze Features
40137 @subsection MicroBlaze Features
40138 @cindex target descriptions, MicroBlaze features
40140 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40141 targets. It should contain registers @samp{r0} through @samp{r31},
40142 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40143 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40144 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40146 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40147 If present, it should contain registers @samp{rshr} and @samp{rslr}
40149 @node MIPS Features
40150 @subsection @acronym{MIPS} Features
40151 @cindex target descriptions, @acronym{MIPS} features
40153 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40154 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40155 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40158 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40159 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40160 registers. They may be 32-bit or 64-bit depending on the target.
40162 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40163 it may be optional in a future version of @value{GDBN}. It should
40164 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40165 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40167 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40168 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40169 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40170 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40172 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40173 contain a single register, @samp{restart}, which is used by the
40174 Linux kernel to control restartable syscalls.
40176 @node M68K Features
40177 @subsection M68K Features
40178 @cindex target descriptions, M68K features
40181 @item @samp{org.gnu.gdb.m68k.core}
40182 @itemx @samp{org.gnu.gdb.coldfire.core}
40183 @itemx @samp{org.gnu.gdb.fido.core}
40184 One of those features must be always present.
40185 The feature that is present determines which flavor of m68k is
40186 used. The feature that is present should contain registers
40187 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40188 @samp{sp}, @samp{ps} and @samp{pc}.
40190 @item @samp{org.gnu.gdb.coldfire.fp}
40191 This feature is optional. If present, it should contain registers
40192 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40196 @node Nios II Features
40197 @subsection Nios II Features
40198 @cindex target descriptions, Nios II features
40200 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40201 targets. It should contain the 32 core registers (@samp{zero},
40202 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40203 @samp{pc}, and the 16 control registers (@samp{status} through
40206 @node PowerPC Features
40207 @subsection PowerPC Features
40208 @cindex target descriptions, PowerPC features
40210 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40211 targets. It should contain registers @samp{r0} through @samp{r31},
40212 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40213 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40215 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40216 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40218 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40219 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40222 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40223 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40224 will combine these registers with the floating point registers
40225 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40226 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40227 through @samp{vs63}, the set of vector registers for POWER7.
40229 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40230 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40231 @samp{spefscr}. SPE targets should provide 32-bit registers in
40232 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40233 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40234 these to present registers @samp{ev0} through @samp{ev31} to the
40237 @node S/390 and System z Features
40238 @subsection S/390 and System z Features
40239 @cindex target descriptions, S/390 features
40240 @cindex target descriptions, System z features
40242 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40243 System z targets. It should contain the PSW and the 16 general
40244 registers. In particular, System z targets should provide the 64-bit
40245 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40246 S/390 targets should provide the 32-bit versions of these registers.
40247 A System z target that runs in 31-bit addressing mode should provide
40248 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40249 register's upper halves @samp{r0h} through @samp{r15h}, and their
40250 lower halves @samp{r0l} through @samp{r15l}.
40252 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40253 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40256 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40257 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40259 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40260 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40261 targets and 32-bit otherwise. In addition, the feature may contain
40262 the @samp{last_break} register, whose width depends on the addressing
40263 mode, as well as the @samp{system_call} register, which is always
40266 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40267 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40268 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40270 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40271 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40272 combined by @value{GDBN} with the floating point registers @samp{f0}
40273 through @samp{f15} to present the 128-bit wide vector registers
40274 @samp{v0} through @samp{v15}. In addition, this feature should
40275 contain the 128-bit wide vector registers @samp{v16} through
40278 @node TIC6x Features
40279 @subsection TMS320C6x Features
40280 @cindex target descriptions, TIC6x features
40281 @cindex target descriptions, TMS320C6x features
40282 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40283 targets. It should contain registers @samp{A0} through @samp{A15},
40284 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40286 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40287 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40288 through @samp{B31}.
40290 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40291 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40293 @node Operating System Information
40294 @appendix Operating System Information
40295 @cindex operating system information
40301 Users of @value{GDBN} often wish to obtain information about the state of
40302 the operating system running on the target---for example the list of
40303 processes, or the list of open files. This section describes the
40304 mechanism that makes it possible. This mechanism is similar to the
40305 target features mechanism (@pxref{Target Descriptions}), but focuses
40306 on a different aspect of target.
40308 Operating system information is retrived from the target via the
40309 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40310 read}). The object name in the request should be @samp{osdata}, and
40311 the @var{annex} identifies the data to be fetched.
40314 @appendixsection Process list
40315 @cindex operating system information, process list
40317 When requesting the process list, the @var{annex} field in the
40318 @samp{qXfer} request should be @samp{processes}. The returned data is
40319 an XML document. The formal syntax of this document is defined in
40320 @file{gdb/features/osdata.dtd}.
40322 An example document is:
40325 <?xml version="1.0"?>
40326 <!DOCTYPE target SYSTEM "osdata.dtd">
40327 <osdata type="processes">
40329 <column name="pid">1</column>
40330 <column name="user">root</column>
40331 <column name="command">/sbin/init</column>
40332 <column name="cores">1,2,3</column>
40337 Each item should include a column whose name is @samp{pid}. The value
40338 of that column should identify the process on the target. The
40339 @samp{user} and @samp{command} columns are optional, and will be
40340 displayed by @value{GDBN}. The @samp{cores} column, if present,
40341 should contain a comma-separated list of cores that this process
40342 is running on. Target may provide additional columns,
40343 which @value{GDBN} currently ignores.
40345 @node Trace File Format
40346 @appendix Trace File Format
40347 @cindex trace file format
40349 The trace file comes in three parts: a header, a textual description
40350 section, and a trace frame section with binary data.
40352 The header has the form @code{\x7fTRACE0\n}. The first byte is
40353 @code{0x7f} so as to indicate that the file contains binary data,
40354 while the @code{0} is a version number that may have different values
40357 The description section consists of multiple lines of @sc{ascii} text
40358 separated by newline characters (@code{0xa}). The lines may include a
40359 variety of optional descriptive or context-setting information, such
40360 as tracepoint definitions or register set size. @value{GDBN} will
40361 ignore any line that it does not recognize. An empty line marks the end
40364 @c FIXME add some specific types of data
40366 The trace frame section consists of a number of consecutive frames.
40367 Each frame begins with a two-byte tracepoint number, followed by a
40368 four-byte size giving the amount of data in the frame. The data in
40369 the frame consists of a number of blocks, each introduced by a
40370 character indicating its type (at least register, memory, and trace
40371 state variable). The data in this section is raw binary, not a
40372 hexadecimal or other encoding; its endianness matches the target's
40375 @c FIXME bi-arch may require endianness/arch info in description section
40378 @item R @var{bytes}
40379 Register block. The number and ordering of bytes matches that of a
40380 @code{g} packet in the remote protocol. Note that these are the
40381 actual bytes, in target order and @value{GDBN} register order, not a
40382 hexadecimal encoding.
40384 @item M @var{address} @var{length} @var{bytes}...
40385 Memory block. This is a contiguous block of memory, at the 8-byte
40386 address @var{address}, with a 2-byte length @var{length}, followed by
40387 @var{length} bytes.
40389 @item V @var{number} @var{value}
40390 Trace state variable block. This records the 8-byte signed value
40391 @var{value} of trace state variable numbered @var{number}.
40395 Future enhancements of the trace file format may include additional types
40398 @node Index Section Format
40399 @appendix @code{.gdb_index} section format
40400 @cindex .gdb_index section format
40401 @cindex index section format
40403 This section documents the index section that is created by @code{save
40404 gdb-index} (@pxref{Index Files}). The index section is
40405 DWARF-specific; some knowledge of DWARF is assumed in this
40408 The mapped index file format is designed to be directly
40409 @code{mmap}able on any architecture. In most cases, a datum is
40410 represented using a little-endian 32-bit integer value, called an
40411 @code{offset_type}. Big endian machines must byte-swap the values
40412 before using them. Exceptions to this rule are noted. The data is
40413 laid out such that alignment is always respected.
40415 A mapped index consists of several areas, laid out in order.
40419 The file header. This is a sequence of values, of @code{offset_type}
40420 unless otherwise noted:
40424 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40425 Version 4 uses a different hashing function from versions 5 and 6.
40426 Version 6 includes symbols for inlined functions, whereas versions 4
40427 and 5 do not. Version 7 adds attributes to the CU indices in the
40428 symbol table. Version 8 specifies that symbols from DWARF type units
40429 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40430 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40432 @value{GDBN} will only read version 4, 5, or 6 indices
40433 by specifying @code{set use-deprecated-index-sections on}.
40434 GDB has a workaround for potentially broken version 7 indices so it is
40435 currently not flagged as deprecated.
40438 The offset, from the start of the file, of the CU list.
40441 The offset, from the start of the file, of the types CU list. Note
40442 that this area can be empty, in which case this offset will be equal
40443 to the next offset.
40446 The offset, from the start of the file, of the address area.
40449 The offset, from the start of the file, of the symbol table.
40452 The offset, from the start of the file, of the constant pool.
40456 The CU list. This is a sequence of pairs of 64-bit little-endian
40457 values, sorted by the CU offset. The first element in each pair is
40458 the offset of a CU in the @code{.debug_info} section. The second
40459 element in each pair is the length of that CU. References to a CU
40460 elsewhere in the map are done using a CU index, which is just the
40461 0-based index into this table. Note that if there are type CUs, then
40462 conceptually CUs and type CUs form a single list for the purposes of
40466 The types CU list. This is a sequence of triplets of 64-bit
40467 little-endian values. In a triplet, the first value is the CU offset,
40468 the second value is the type offset in the CU, and the third value is
40469 the type signature. The types CU list is not sorted.
40472 The address area. The address area consists of a sequence of address
40473 entries. Each address entry has three elements:
40477 The low address. This is a 64-bit little-endian value.
40480 The high address. This is a 64-bit little-endian value. Like
40481 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40484 The CU index. This is an @code{offset_type} value.
40488 The symbol table. This is an open-addressed hash table. The size of
40489 the hash table is always a power of 2.
40491 Each slot in the hash table consists of a pair of @code{offset_type}
40492 values. The first value is the offset of the symbol's name in the
40493 constant pool. The second value is the offset of the CU vector in the
40496 If both values are 0, then this slot in the hash table is empty. This
40497 is ok because while 0 is a valid constant pool index, it cannot be a
40498 valid index for both a string and a CU vector.
40500 The hash value for a table entry is computed by applying an
40501 iterative hash function to the symbol's name. Starting with an
40502 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40503 the string is incorporated into the hash using the formula depending on the
40508 The formula is @code{r = r * 67 + c - 113}.
40510 @item Versions 5 to 7
40511 The formula is @code{r = r * 67 + tolower (c) - 113}.
40514 The terminating @samp{\0} is not incorporated into the hash.
40516 The step size used in the hash table is computed via
40517 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40518 value, and @samp{size} is the size of the hash table. The step size
40519 is used to find the next candidate slot when handling a hash
40522 The names of C@t{++} symbols in the hash table are canonicalized. We
40523 don't currently have a simple description of the canonicalization
40524 algorithm; if you intend to create new index sections, you must read
40528 The constant pool. This is simply a bunch of bytes. It is organized
40529 so that alignment is correct: CU vectors are stored first, followed by
40532 A CU vector in the constant pool is a sequence of @code{offset_type}
40533 values. The first value is the number of CU indices in the vector.
40534 Each subsequent value is the index and symbol attributes of a CU in
40535 the CU list. This element in the hash table is used to indicate which
40536 CUs define the symbol and how the symbol is used.
40537 See below for the format of each CU index+attributes entry.
40539 A string in the constant pool is zero-terminated.
40542 Attributes were added to CU index values in @code{.gdb_index} version 7.
40543 If a symbol has multiple uses within a CU then there is one
40544 CU index+attributes value for each use.
40546 The format of each CU index+attributes entry is as follows
40552 This is the index of the CU in the CU list.
40554 These bits are reserved for future purposes and must be zero.
40556 The kind of the symbol in the CU.
40560 This value is reserved and should not be used.
40561 By reserving zero the full @code{offset_type} value is backwards compatible
40562 with previous versions of the index.
40564 The symbol is a type.
40566 The symbol is a variable or an enum value.
40568 The symbol is a function.
40570 Any other kind of symbol.
40572 These values are reserved.
40576 This bit is zero if the value is global and one if it is static.
40578 The determination of whether a symbol is global or static is complicated.
40579 The authorative reference is the file @file{dwarf2read.c} in
40580 @value{GDBN} sources.
40584 This pseudo-code describes the computation of a symbol's kind and
40585 global/static attributes in the index.
40588 is_external = get_attribute (die, DW_AT_external);
40589 language = get_attribute (cu_die, DW_AT_language);
40592 case DW_TAG_typedef:
40593 case DW_TAG_base_type:
40594 case DW_TAG_subrange_type:
40598 case DW_TAG_enumerator:
40600 is_static = (language != CPLUS && language != JAVA);
40602 case DW_TAG_subprogram:
40604 is_static = ! (is_external || language == ADA);
40606 case DW_TAG_constant:
40608 is_static = ! is_external;
40610 case DW_TAG_variable:
40612 is_static = ! is_external;
40614 case DW_TAG_namespace:
40618 case DW_TAG_class_type:
40619 case DW_TAG_interface_type:
40620 case DW_TAG_structure_type:
40621 case DW_TAG_union_type:
40622 case DW_TAG_enumeration_type:
40624 is_static = (language != CPLUS && language != JAVA);
40632 @appendix Manual pages
40636 * gdb man:: The GNU Debugger man page
40637 * gdbserver man:: Remote Server for the GNU Debugger man page
40638 * gcore man:: Generate a core file of a running program
40639 * gdbinit man:: gdbinit scripts
40645 @c man title gdb The GNU Debugger
40647 @c man begin SYNOPSIS gdb
40648 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40649 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40650 [@option{-b}@w{ }@var{bps}]
40651 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40652 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40653 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40654 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40655 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40658 @c man begin DESCRIPTION gdb
40659 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40660 going on ``inside'' another program while it executes -- or what another
40661 program was doing at the moment it crashed.
40663 @value{GDBN} can do four main kinds of things (plus other things in support of
40664 these) to help you catch bugs in the act:
40668 Start your program, specifying anything that might affect its behavior.
40671 Make your program stop on specified conditions.
40674 Examine what has happened, when your program has stopped.
40677 Change things in your program, so you can experiment with correcting the
40678 effects of one bug and go on to learn about another.
40681 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40684 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40685 commands from the terminal until you tell it to exit with the @value{GDBN}
40686 command @code{quit}. You can get online help from @value{GDBN} itself
40687 by using the command @code{help}.
40689 You can run @code{gdb} with no arguments or options; but the most
40690 usual way to start @value{GDBN} is with one argument or two, specifying an
40691 executable program as the argument:
40697 You can also start with both an executable program and a core file specified:
40703 You can, instead, specify a process ID as a second argument, if you want
40704 to debug a running process:
40712 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40713 named @file{1234}; @value{GDBN} does check for a core file first).
40714 With option @option{-p} you can omit the @var{program} filename.
40716 Here are some of the most frequently needed @value{GDBN} commands:
40718 @c pod2man highlights the right hand side of the @item lines.
40720 @item break [@var{file}:]@var{functiop}
40721 Set a breakpoint at @var{function} (in @var{file}).
40723 @item run [@var{arglist}]
40724 Start your program (with @var{arglist}, if specified).
40727 Backtrace: display the program stack.
40729 @item print @var{expr}
40730 Display the value of an expression.
40733 Continue running your program (after stopping, e.g. at a breakpoint).
40736 Execute next program line (after stopping); step @emph{over} any
40737 function calls in the line.
40739 @item edit [@var{file}:]@var{function}
40740 look at the program line where it is presently stopped.
40742 @item list [@var{file}:]@var{function}
40743 type the text of the program in the vicinity of where it is presently stopped.
40746 Execute next program line (after stopping); step @emph{into} any
40747 function calls in the line.
40749 @item help [@var{name}]
40750 Show information about @value{GDBN} command @var{name}, or general information
40751 about using @value{GDBN}.
40754 Exit from @value{GDBN}.
40758 For full details on @value{GDBN},
40759 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40760 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40761 as the @code{gdb} entry in the @code{info} program.
40765 @c man begin OPTIONS gdb
40766 Any arguments other than options specify an executable
40767 file and core file (or process ID); that is, the first argument
40768 encountered with no
40769 associated option flag is equivalent to a @option{-se} option, and the second,
40770 if any, is equivalent to a @option{-c} option if it's the name of a file.
40772 both long and short forms; both are shown here. The long forms are also
40773 recognized if you truncate them, so long as enough of the option is
40774 present to be unambiguous. (If you prefer, you can flag option
40775 arguments with @option{+} rather than @option{-}, though we illustrate the
40776 more usual convention.)
40778 All the options and command line arguments you give are processed
40779 in sequential order. The order makes a difference when the @option{-x}
40785 List all options, with brief explanations.
40787 @item -symbols=@var{file}
40788 @itemx -s @var{file}
40789 Read symbol table from file @var{file}.
40792 Enable writing into executable and core files.
40794 @item -exec=@var{file}
40795 @itemx -e @var{file}
40796 Use file @var{file} as the executable file to execute when
40797 appropriate, and for examining pure data in conjunction with a core
40800 @item -se=@var{file}
40801 Read symbol table from file @var{file} and use it as the executable
40804 @item -core=@var{file}
40805 @itemx -c @var{file}
40806 Use file @var{file} as a core dump to examine.
40808 @item -command=@var{file}
40809 @itemx -x @var{file}
40810 Execute @value{GDBN} commands from file @var{file}.
40812 @item -ex @var{command}
40813 Execute given @value{GDBN} @var{command}.
40815 @item -directory=@var{directory}
40816 @itemx -d @var{directory}
40817 Add @var{directory} to the path to search for source files.
40820 Do not execute commands from @file{~/.gdbinit}.
40824 Do not execute commands from any @file{.gdbinit} initialization files.
40828 ``Quiet''. Do not print the introductory and copyright messages. These
40829 messages are also suppressed in batch mode.
40832 Run in batch mode. Exit with status @code{0} after processing all the command
40833 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40834 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40835 commands in the command files.
40837 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40838 download and run a program on another computer; in order to make this
40839 more useful, the message
40842 Program exited normally.
40846 (which is ordinarily issued whenever a program running under @value{GDBN} control
40847 terminates) is not issued when running in batch mode.
40849 @item -cd=@var{directory}
40850 Run @value{GDBN} using @var{directory} as its working directory,
40851 instead of the current directory.
40855 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40856 @value{GDBN} to output the full file name and line number in a standard,
40857 recognizable fashion each time a stack frame is displayed (which
40858 includes each time the program stops). This recognizable format looks
40859 like two @samp{\032} characters, followed by the file name, line number
40860 and character position separated by colons, and a newline. The
40861 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40862 characters as a signal to display the source code for the frame.
40865 Set the line speed (baud rate or bits per second) of any serial
40866 interface used by @value{GDBN} for remote debugging.
40868 @item -tty=@var{device}
40869 Run using @var{device} for your program's standard input and output.
40873 @c man begin SEEALSO gdb
40875 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40876 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40877 documentation are properly installed at your site, the command
40884 should give you access to the complete manual.
40886 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40887 Richard M. Stallman and Roland H. Pesch, July 1991.
40891 @node gdbserver man
40892 @heading gdbserver man
40894 @c man title gdbserver Remote Server for the GNU Debugger
40896 @c man begin SYNOPSIS gdbserver
40897 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40899 gdbserver --attach @var{comm} @var{pid}
40901 gdbserver --multi @var{comm}
40905 @c man begin DESCRIPTION gdbserver
40906 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40907 than the one which is running the program being debugged.
40910 @subheading Usage (server (target) side)
40913 Usage (server (target) side):
40916 First, you need to have a copy of the program you want to debug put onto
40917 the target system. The program can be stripped to save space if needed, as
40918 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40919 the @value{GDBN} running on the host system.
40921 To use the server, you log on to the target system, and run the @command{gdbserver}
40922 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40923 your program, and (c) its arguments. The general syntax is:
40926 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40929 For example, using a serial port, you might say:
40933 @c @file would wrap it as F</dev/com1>.
40934 target> gdbserver /dev/com1 emacs foo.txt
40937 target> gdbserver @file{/dev/com1} emacs foo.txt
40941 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40942 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40943 waits patiently for the host @value{GDBN} to communicate with it.
40945 To use a TCP connection, you could say:
40948 target> gdbserver host:2345 emacs foo.txt
40951 This says pretty much the same thing as the last example, except that we are
40952 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40953 that we are expecting to see a TCP connection from @code{host} to local TCP port
40954 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40955 want for the port number as long as it does not conflict with any existing TCP
40956 ports on the target system. This same port number must be used in the host
40957 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40958 you chose a port number that conflicts with another service, @command{gdbserver} will
40959 print an error message and exit.
40961 @command{gdbserver} can also attach to running programs.
40962 This is accomplished via the @option{--attach} argument. The syntax is:
40965 target> gdbserver --attach @var{comm} @var{pid}
40968 @var{pid} is the process ID of a currently running process. It isn't
40969 necessary to point @command{gdbserver} at a binary for the running process.
40971 To start @code{gdbserver} without supplying an initial command to run
40972 or process ID to attach, use the @option{--multi} command line option.
40973 In such case you should connect using @kbd{target extended-remote} to start
40974 the program you want to debug.
40977 target> gdbserver --multi @var{comm}
40981 @subheading Usage (host side)
40987 You need an unstripped copy of the target program on your host system, since
40988 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40989 would, with the target program as the first argument. (You may need to use the
40990 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40991 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40992 new command you need to know about is @code{target remote}
40993 (or @code{target extended-remote}). Its argument is either
40994 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40995 descriptor. For example:
40999 @c @file would wrap it as F</dev/ttyb>.
41000 (gdb) target remote /dev/ttyb
41003 (gdb) target remote @file{/dev/ttyb}
41008 communicates with the server via serial line @file{/dev/ttyb}, and:
41011 (gdb) target remote the-target:2345
41015 communicates via a TCP connection to port 2345 on host `the-target', where
41016 you previously started up @command{gdbserver} with the same port number. Note that for
41017 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41018 command, otherwise you may get an error that looks something like
41019 `Connection refused'.
41021 @command{gdbserver} can also debug multiple inferiors at once,
41024 the @value{GDBN} manual in node @code{Inferiors and Programs}
41025 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41028 @ref{Inferiors and Programs}.
41030 In such case use the @code{extended-remote} @value{GDBN} command variant:
41033 (gdb) target extended-remote the-target:2345
41036 The @command{gdbserver} option @option{--multi} may or may not be used in such
41040 @c man begin OPTIONS gdbserver
41041 There are three different modes for invoking @command{gdbserver}:
41046 Debug a specific program specified by its program name:
41049 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41052 The @var{comm} parameter specifies how should the server communicate
41053 with @value{GDBN}; it is either a device name (to use a serial line),
41054 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41055 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41056 debug in @var{prog}. Any remaining arguments will be passed to the
41057 program verbatim. When the program exits, @value{GDBN} will close the
41058 connection, and @code{gdbserver} will exit.
41061 Debug a specific program by specifying the process ID of a running
41065 gdbserver --attach @var{comm} @var{pid}
41068 The @var{comm} parameter is as described above. Supply the process ID
41069 of a running program in @var{pid}; @value{GDBN} will do everything
41070 else. Like with the previous mode, when the process @var{pid} exits,
41071 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41074 Multi-process mode -- debug more than one program/process:
41077 gdbserver --multi @var{comm}
41080 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41081 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41082 close the connection when a process being debugged exits, so you can
41083 debug several processes in the same session.
41086 In each of the modes you may specify these options:
41091 List all options, with brief explanations.
41094 This option causes @command{gdbserver} to print its version number and exit.
41097 @command{gdbserver} will attach to a running program. The syntax is:
41100 target> gdbserver --attach @var{comm} @var{pid}
41103 @var{pid} is the process ID of a currently running process. It isn't
41104 necessary to point @command{gdbserver} at a binary for the running process.
41107 To start @code{gdbserver} without supplying an initial command to run
41108 or process ID to attach, use this command line option.
41109 Then you can connect using @kbd{target extended-remote} and start
41110 the program you want to debug. The syntax is:
41113 target> gdbserver --multi @var{comm}
41117 Instruct @code{gdbserver} to display extra status information about the debugging
41119 This option is intended for @code{gdbserver} development and for bug reports to
41122 @item --remote-debug
41123 Instruct @code{gdbserver} to display remote protocol debug output.
41124 This option is intended for @code{gdbserver} development and for bug reports to
41127 @item --debug-format=option1@r{[},option2,...@r{]}
41128 Instruct @code{gdbserver} to include extra information in each line
41129 of debugging output.
41130 @xref{Other Command-Line Arguments for gdbserver}.
41133 Specify a wrapper to launch programs
41134 for debugging. The option should be followed by the name of the
41135 wrapper, then any command-line arguments to pass to the wrapper, then
41136 @kbd{--} indicating the end of the wrapper arguments.
41139 By default, @command{gdbserver} keeps the listening TCP port open, so that
41140 additional connections are possible. However, if you start @code{gdbserver}
41141 with the @option{--once} option, it will stop listening for any further
41142 connection attempts after connecting to the first @value{GDBN} session.
41144 @c --disable-packet is not documented for users.
41146 @c --disable-randomization and --no-disable-randomization are superseded by
41147 @c QDisableRandomization.
41152 @c man begin SEEALSO gdbserver
41154 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41155 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41156 documentation are properly installed at your site, the command
41162 should give you access to the complete manual.
41164 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41165 Richard M. Stallman and Roland H. Pesch, July 1991.
41172 @c man title gcore Generate a core file of a running program
41175 @c man begin SYNOPSIS gcore
41176 gcore [-o @var{filename}] @var{pid}
41180 @c man begin DESCRIPTION gcore
41181 Generate a core dump of a running program with process ID @var{pid}.
41182 Produced file is equivalent to a kernel produced core file as if the process
41183 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41184 limit). Unlike after a crash, after @command{gcore} the program remains
41185 running without any change.
41188 @c man begin OPTIONS gcore
41190 @item -o @var{filename}
41191 The optional argument
41192 @var{filename} specifies the file name where to put the core dump.
41193 If not specified, the file name defaults to @file{core.@var{pid}},
41194 where @var{pid} is the running program process ID.
41198 @c man begin SEEALSO gcore
41200 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41201 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41202 documentation are properly installed at your site, the command
41209 should give you access to the complete manual.
41211 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41212 Richard M. Stallman and Roland H. Pesch, July 1991.
41219 @c man title gdbinit GDB initialization scripts
41222 @c man begin SYNOPSIS gdbinit
41223 @ifset SYSTEM_GDBINIT
41224 @value{SYSTEM_GDBINIT}
41233 @c man begin DESCRIPTION gdbinit
41234 These files contain @value{GDBN} commands to automatically execute during
41235 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41238 the @value{GDBN} manual in node @code{Sequences}
41239 -- shell command @code{info -f gdb -n Sequences}.
41245 Please read more in
41247 the @value{GDBN} manual in node @code{Startup}
41248 -- shell command @code{info -f gdb -n Startup}.
41255 @ifset SYSTEM_GDBINIT
41256 @item @value{SYSTEM_GDBINIT}
41258 @ifclear SYSTEM_GDBINIT
41259 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41261 System-wide initialization file. It is executed unless user specified
41262 @value{GDBN} option @code{-nx} or @code{-n}.
41265 the @value{GDBN} manual in node @code{System-wide configuration}
41266 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41269 @ref{System-wide configuration}.
41273 User initialization file. It is executed unless user specified
41274 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41277 Initialization file for current directory. It may need to be enabled with
41278 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41281 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41282 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41285 @ref{Init File in the Current Directory}.
41290 @c man begin SEEALSO gdbinit
41292 gdb(1), @code{info -f gdb -n Startup}
41294 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41295 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41296 documentation are properly installed at your site, the command
41302 should give you access to the complete manual.
41304 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41305 Richard M. Stallman and Roland H. Pesch, July 1991.
41311 @node GNU Free Documentation License
41312 @appendix GNU Free Documentation License
41315 @node Concept Index
41316 @unnumbered Concept Index
41320 @node Command and Variable Index
41321 @unnumbered Command, Variable, and Function Index
41326 % I think something like @@colophon should be in texinfo. In the
41328 \long\def\colophon{\hbox to0pt{}\vfill
41329 \centerline{The body of this manual is set in}
41330 \centerline{\fontname\tenrm,}
41331 \centerline{with headings in {\bf\fontname\tenbf}}
41332 \centerline{and examples in {\tt\fontname\tentt}.}
41333 \centerline{{\it\fontname\tenit\/},}
41334 \centerline{{\bf\fontname\tenbf}, and}
41335 \centerline{{\sl\fontname\tensl\/}}
41336 \centerline{are used for emphasis.}\vfill}
41338 % Blame: doc@@cygnus.com, 1991.