1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1239 @c @cindex @code{--xdb}
1240 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1241 @c For information, see the file @file{xdb_trans.html}, which is usually
1242 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1245 @item -interpreter @var{interp}
1246 @cindex @code{--interpreter}
1247 Use the interpreter @var{interp} for interface with the controlling
1248 program or device. This option is meant to be set by programs which
1249 communicate with @value{GDBN} using it as a back end.
1250 @xref{Interpreters, , Command Interpreters}.
1252 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1253 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1254 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1255 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1256 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1257 @sc{gdb/mi} interfaces are no longer supported.
1260 @cindex @code{--write}
1261 Open the executable and core files for both reading and writing. This
1262 is equivalent to the @samp{set write on} command inside @value{GDBN}
1266 @cindex @code{--statistics}
1267 This option causes @value{GDBN} to print statistics about time and
1268 memory usage after it completes each command and returns to the prompt.
1271 @cindex @code{--version}
1272 This option causes @value{GDBN} to print its version number and
1273 no-warranty blurb, and exit.
1275 @item -configuration
1276 @cindex @code{--configuration}
1277 This option causes @value{GDBN} to print details about its build-time
1278 configuration parameters, and then exit. These details can be
1279 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1284 @subsection What @value{GDBN} Does During Startup
1285 @cindex @value{GDBN} startup
1287 Here's the description of what @value{GDBN} does during session startup:
1291 Sets up the command interpreter as specified by the command line
1292 (@pxref{Mode Options, interpreter}).
1296 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1297 used when building @value{GDBN}; @pxref{System-wide configuration,
1298 ,System-wide configuration and settings}) and executes all the commands in
1301 @anchor{Home Directory Init File}
1303 Reads the init file (if any) in your home directory@footnote{On
1304 DOS/Windows systems, the home directory is the one pointed to by the
1305 @code{HOME} environment variable.} and executes all the commands in
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1319 @anchor{Init File in the Current Directory during Startup}
1321 Reads and executes the commands from init file (if any) in the current
1322 working directory as long as @samp{set auto-load local-gdbinit} is set to
1323 @samp{on} (@pxref{Init File in the Current Directory}).
1324 This is only done if the current directory is
1325 different from your home directory. Thus, you can have more than one
1326 init file, one generic in your home directory, and another, specific
1327 to the program you are debugging, in the directory where you invoke
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 Init files use the same syntax as @dfn{command files} (@pxref{Command
1358 Files}) and are processed by @value{GDBN} in the same way. The init
1359 file in your home directory can set options (such as @samp{set
1360 complaints}) that affect subsequent processing of command line options
1361 and operands. Init files are not executed if you use the @samp{-nx}
1362 option (@pxref{Mode Options, ,Choosing Modes}).
1364 To display the list of init files loaded by gdb at startup, you
1365 can use @kbd{gdb --help}.
1367 @cindex init file name
1368 @cindex @file{.gdbinit}
1369 @cindex @file{gdb.ini}
1370 The @value{GDBN} init files are normally called @file{.gdbinit}.
1371 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1372 the limitations of file names imposed by DOS filesystems. The Windows
1373 port of @value{GDBN} uses the standard name, but if it finds a
1374 @file{gdb.ini} file in your home directory, it warns you about that
1375 and suggests to rename the file to the standard name.
1379 @section Quitting @value{GDBN}
1380 @cindex exiting @value{GDBN}
1381 @cindex leaving @value{GDBN}
1384 @kindex quit @r{[}@var{expression}@r{]}
1385 @kindex q @r{(@code{quit})}
1386 @item quit @r{[}@var{expression}@r{]}
1388 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1389 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1390 do not supply @var{expression}, @value{GDBN} will terminate normally;
1391 otherwise it will terminate using the result of @var{expression} as the
1396 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1397 terminates the action of any @value{GDBN} command that is in progress and
1398 returns to @value{GDBN} command level. It is safe to type the interrupt
1399 character at any time because @value{GDBN} does not allow it to take effect
1400 until a time when it is safe.
1402 If you have been using @value{GDBN} to control an attached process or
1403 device, you can release it with the @code{detach} command
1404 (@pxref{Attach, ,Debugging an Already-running Process}).
1406 @node Shell Commands
1407 @section Shell Commands
1409 If you need to execute occasional shell commands during your
1410 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1411 just use the @code{shell} command.
1416 @cindex shell escape
1417 @item shell @var{command-string}
1418 @itemx !@var{command-string}
1419 Invoke a standard shell to execute @var{command-string}.
1420 Note that no space is needed between @code{!} and @var{command-string}.
1421 If it exists, the environment variable @code{SHELL} determines which
1422 shell to run. Otherwise @value{GDBN} uses the default shell
1423 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1426 The utility @code{make} is often needed in development environments.
1427 You do not have to use the @code{shell} command for this purpose in
1432 @cindex calling make
1433 @item make @var{make-args}
1434 Execute the @code{make} program with the specified
1435 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1438 @node Logging Output
1439 @section Logging Output
1440 @cindex logging @value{GDBN} output
1441 @cindex save @value{GDBN} output to a file
1443 You may want to save the output of @value{GDBN} commands to a file.
1444 There are several commands to control @value{GDBN}'s logging.
1448 @item set logging on
1450 @item set logging off
1452 @cindex logging file name
1453 @item set logging file @var{file}
1454 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1455 @item set logging overwrite [on|off]
1456 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1457 you want @code{set logging on} to overwrite the logfile instead.
1458 @item set logging redirect [on|off]
1459 By default, @value{GDBN} output will go to both the terminal and the logfile.
1460 Set @code{redirect} if you want output to go only to the log file.
1461 @kindex show logging
1463 Show the current values of the logging settings.
1467 @chapter @value{GDBN} Commands
1469 You can abbreviate a @value{GDBN} command to the first few letters of the command
1470 name, if that abbreviation is unambiguous; and you can repeat certain
1471 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1472 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1473 show you the alternatives available, if there is more than one possibility).
1476 * Command Syntax:: How to give commands to @value{GDBN}
1477 * Completion:: Command completion
1478 * Help:: How to ask @value{GDBN} for help
1481 @node Command Syntax
1482 @section Command Syntax
1484 A @value{GDBN} command is a single line of input. There is no limit on
1485 how long it can be. It starts with a command name, which is followed by
1486 arguments whose meaning depends on the command name. For example, the
1487 command @code{step} accepts an argument which is the number of times to
1488 step, as in @samp{step 5}. You can also use the @code{step} command
1489 with no arguments. Some commands do not allow any arguments.
1491 @cindex abbreviation
1492 @value{GDBN} command names may always be truncated if that abbreviation is
1493 unambiguous. Other possible command abbreviations are listed in the
1494 documentation for individual commands. In some cases, even ambiguous
1495 abbreviations are allowed; for example, @code{s} is specially defined as
1496 equivalent to @code{step} even though there are other commands whose
1497 names start with @code{s}. You can test abbreviations by using them as
1498 arguments to the @code{help} command.
1500 @cindex repeating commands
1501 @kindex RET @r{(repeat last command)}
1502 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1503 repeat the previous command. Certain commands (for example, @code{run})
1504 will not repeat this way; these are commands whose unintentional
1505 repetition might cause trouble and which you are unlikely to want to
1506 repeat. User-defined commands can disable this feature; see
1507 @ref{Define, dont-repeat}.
1509 The @code{list} and @code{x} commands, when you repeat them with
1510 @key{RET}, construct new arguments rather than repeating
1511 exactly as typed. This permits easy scanning of source or memory.
1513 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1514 output, in a way similar to the common utility @code{more}
1515 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1516 @key{RET} too many in this situation, @value{GDBN} disables command
1517 repetition after any command that generates this sort of display.
1519 @kindex # @r{(a comment)}
1521 Any text from a @kbd{#} to the end of the line is a comment; it does
1522 nothing. This is useful mainly in command files (@pxref{Command
1523 Files,,Command Files}).
1525 @cindex repeating command sequences
1526 @kindex Ctrl-o @r{(operate-and-get-next)}
1527 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1528 commands. This command accepts the current line, like @key{RET}, and
1529 then fetches the next line relative to the current line from the history
1533 @section Command Completion
1536 @cindex word completion
1537 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1538 only one possibility; it can also show you what the valid possibilities
1539 are for the next word in a command, at any time. This works for @value{GDBN}
1540 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1542 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1543 of a word. If there is only one possibility, @value{GDBN} fills in the
1544 word, and waits for you to finish the command (or press @key{RET} to
1545 enter it). For example, if you type
1547 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1548 @c complete accuracy in these examples; space introduced for clarity.
1549 @c If texinfo enhancements make it unnecessary, it would be nice to
1550 @c replace " @key" by "@key" in the following...
1552 (@value{GDBP}) info bre @key{TAB}
1556 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1557 the only @code{info} subcommand beginning with @samp{bre}:
1560 (@value{GDBP}) info breakpoints
1564 You can either press @key{RET} at this point, to run the @code{info
1565 breakpoints} command, or backspace and enter something else, if
1566 @samp{breakpoints} does not look like the command you expected. (If you
1567 were sure you wanted @code{info breakpoints} in the first place, you
1568 might as well just type @key{RET} immediately after @samp{info bre},
1569 to exploit command abbreviations rather than command completion).
1571 If there is more than one possibility for the next word when you press
1572 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1573 characters and try again, or just press @key{TAB} a second time;
1574 @value{GDBN} displays all the possible completions for that word. For
1575 example, you might want to set a breakpoint on a subroutine whose name
1576 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1577 just sounds the bell. Typing @key{TAB} again displays all the
1578 function names in your program that begin with those characters, for
1582 (@value{GDBP}) b make_ @key{TAB}
1583 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1584 make_a_section_from_file make_environ
1585 make_abs_section make_function_type
1586 make_blockvector make_pointer_type
1587 make_cleanup make_reference_type
1588 make_command make_symbol_completion_list
1589 (@value{GDBP}) b make_
1593 After displaying the available possibilities, @value{GDBN} copies your
1594 partial input (@samp{b make_} in the example) so you can finish the
1597 If you just want to see the list of alternatives in the first place, you
1598 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1599 means @kbd{@key{META} ?}. You can type this either by holding down a
1600 key designated as the @key{META} shift on your keyboard (if there is
1601 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1603 @cindex quotes in commands
1604 @cindex completion of quoted strings
1605 Sometimes the string you need, while logically a ``word'', may contain
1606 parentheses or other characters that @value{GDBN} normally excludes from
1607 its notion of a word. To permit word completion to work in this
1608 situation, you may enclose words in @code{'} (single quote marks) in
1609 @value{GDBN} commands.
1611 The most likely situation where you might need this is in typing the
1612 name of a C@t{++} function. This is because C@t{++} allows function
1613 overloading (multiple definitions of the same function, distinguished
1614 by argument type). For example, when you want to set a breakpoint you
1615 may need to distinguish whether you mean the version of @code{name}
1616 that takes an @code{int} parameter, @code{name(int)}, or the version
1617 that takes a @code{float} parameter, @code{name(float)}. To use the
1618 word-completion facilities in this situation, type a single quote
1619 @code{'} at the beginning of the function name. This alerts
1620 @value{GDBN} that it may need to consider more information than usual
1621 when you press @key{TAB} or @kbd{M-?} to request word completion:
1624 (@value{GDBP}) b 'bubble( @kbd{M-?}
1625 bubble(double,double) bubble(int,int)
1626 (@value{GDBP}) b 'bubble(
1629 In some cases, @value{GDBN} can tell that completing a name requires using
1630 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1631 completing as much as it can) if you do not type the quote in the first
1635 (@value{GDBP}) b bub @key{TAB}
1636 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1637 (@value{GDBP}) b 'bubble(
1641 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1642 you have not yet started typing the argument list when you ask for
1643 completion on an overloaded symbol.
1645 For more information about overloaded functions, see @ref{C Plus Plus
1646 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1647 overload-resolution off} to disable overload resolution;
1648 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1650 @cindex completion of structure field names
1651 @cindex structure field name completion
1652 @cindex completion of union field names
1653 @cindex union field name completion
1654 When completing in an expression which looks up a field in a
1655 structure, @value{GDBN} also tries@footnote{The completer can be
1656 confused by certain kinds of invalid expressions. Also, it only
1657 examines the static type of the expression, not the dynamic type.} to
1658 limit completions to the field names available in the type of the
1662 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1663 magic to_fputs to_rewind
1664 to_data to_isatty to_write
1665 to_delete to_put to_write_async_safe
1670 This is because the @code{gdb_stdout} is a variable of the type
1671 @code{struct ui_file} that is defined in @value{GDBN} sources as
1678 ui_file_flush_ftype *to_flush;
1679 ui_file_write_ftype *to_write;
1680 ui_file_write_async_safe_ftype *to_write_async_safe;
1681 ui_file_fputs_ftype *to_fputs;
1682 ui_file_read_ftype *to_read;
1683 ui_file_delete_ftype *to_delete;
1684 ui_file_isatty_ftype *to_isatty;
1685 ui_file_rewind_ftype *to_rewind;
1686 ui_file_put_ftype *to_put;
1693 @section Getting Help
1694 @cindex online documentation
1697 You can always ask @value{GDBN} itself for information on its commands,
1698 using the command @code{help}.
1701 @kindex h @r{(@code{help})}
1704 You can use @code{help} (abbreviated @code{h}) with no arguments to
1705 display a short list of named classes of commands:
1709 List of classes of commands:
1711 aliases -- Aliases of other commands
1712 breakpoints -- Making program stop at certain points
1713 data -- Examining data
1714 files -- Specifying and examining files
1715 internals -- Maintenance commands
1716 obscure -- Obscure features
1717 running -- Running the program
1718 stack -- Examining the stack
1719 status -- Status inquiries
1720 support -- Support facilities
1721 tracepoints -- Tracing of program execution without
1722 stopping the program
1723 user-defined -- User-defined commands
1725 Type "help" followed by a class name for a list of
1726 commands in that class.
1727 Type "help" followed by command name for full
1729 Command name abbreviations are allowed if unambiguous.
1732 @c the above line break eliminates huge line overfull...
1734 @item help @var{class}
1735 Using one of the general help classes as an argument, you can get a
1736 list of the individual commands in that class. For example, here is the
1737 help display for the class @code{status}:
1740 (@value{GDBP}) help status
1745 @c Line break in "show" line falsifies real output, but needed
1746 @c to fit in smallbook page size.
1747 info -- Generic command for showing things
1748 about the program being debugged
1749 show -- Generic command for showing things
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1758 @item help @var{command}
1759 With a command name as @code{help} argument, @value{GDBN} displays a
1760 short paragraph on how to use that command.
1763 @item apropos @var{args}
1764 The @code{apropos} command searches through all of the @value{GDBN}
1765 commands, and their documentation, for the regular expression specified in
1766 @var{args}. It prints out all matches found. For example:
1777 alias -- Define a new command that is an alias of an existing command
1778 aliases -- Aliases of other commands
1779 d -- Delete some breakpoints or auto-display expressions
1780 del -- Delete some breakpoints or auto-display expressions
1781 delete -- Delete some breakpoints or auto-display expressions
1786 @item complete @var{args}
1787 The @code{complete @var{args}} command lists all the possible completions
1788 for the beginning of a command. Use @var{args} to specify the beginning of the
1789 command you want completed. For example:
1795 @noindent results in:
1806 @noindent This is intended for use by @sc{gnu} Emacs.
1809 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1810 and @code{show} to inquire about the state of your program, or the state
1811 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1812 manual introduces each of them in the appropriate context. The listings
1813 under @code{info} and under @code{show} in the Command, Variable, and
1814 Function Index point to all the sub-commands. @xref{Command and Variable
1820 @kindex i @r{(@code{info})}
1822 This command (abbreviated @code{i}) is for describing the state of your
1823 program. For example, you can show the arguments passed to a function
1824 with @code{info args}, list the registers currently in use with @code{info
1825 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1826 You can get a complete list of the @code{info} sub-commands with
1827 @w{@code{help info}}.
1831 You can assign the result of an expression to an environment variable with
1832 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1833 @code{set prompt $}.
1837 In contrast to @code{info}, @code{show} is for describing the state of
1838 @value{GDBN} itself.
1839 You can change most of the things you can @code{show}, by using the
1840 related command @code{set}; for example, you can control what number
1841 system is used for displays with @code{set radix}, or simply inquire
1842 which is currently in use with @code{show radix}.
1845 To display all the settable parameters and their current
1846 values, you can use @code{show} with no arguments; you may also use
1847 @code{info set}. Both commands produce the same display.
1848 @c FIXME: "info set" violates the rule that "info" is for state of
1849 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1850 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1854 Here are several miscellaneous @code{show} subcommands, all of which are
1855 exceptional in lacking corresponding @code{set} commands:
1858 @kindex show version
1859 @cindex @value{GDBN} version number
1861 Show what version of @value{GDBN} is running. You should include this
1862 information in @value{GDBN} bug-reports. If multiple versions of
1863 @value{GDBN} are in use at your site, you may need to determine which
1864 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1865 commands are introduced, and old ones may wither away. Also, many
1866 system vendors ship variant versions of @value{GDBN}, and there are
1867 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1868 The version number is the same as the one announced when you start
1871 @kindex show copying
1872 @kindex info copying
1873 @cindex display @value{GDBN} copyright
1876 Display information about permission for copying @value{GDBN}.
1878 @kindex show warranty
1879 @kindex info warranty
1881 @itemx info warranty
1882 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1883 if your version of @value{GDBN} comes with one.
1885 @kindex show configuration
1886 @item show configuration
1887 Display detailed information about the way @value{GDBN} was configured
1888 when it was built. This displays the optional arguments passed to the
1889 @file{configure} script and also configuration parameters detected
1890 automatically by @command{configure}. When reporting a @value{GDBN}
1891 bug (@pxref{GDB Bugs}), it is important to include this information in
1897 @chapter Running Programs Under @value{GDBN}
1899 When you run a program under @value{GDBN}, you must first generate
1900 debugging information when you compile it.
1902 You may start @value{GDBN} with its arguments, if any, in an environment
1903 of your choice. If you are doing native debugging, you may redirect
1904 your program's input and output, debug an already running process, or
1905 kill a child process.
1908 * Compilation:: Compiling for debugging
1909 * Starting:: Starting your program
1910 * Arguments:: Your program's arguments
1911 * Environment:: Your program's environment
1913 * Working Directory:: Your program's working directory
1914 * Input/Output:: Your program's input and output
1915 * Attach:: Debugging an already-running process
1916 * Kill Process:: Killing the child process
1918 * Inferiors and Programs:: Debugging multiple inferiors and programs
1919 * Threads:: Debugging programs with multiple threads
1920 * Forks:: Debugging forks
1921 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1925 @section Compiling for Debugging
1927 In order to debug a program effectively, you need to generate
1928 debugging information when you compile it. This debugging information
1929 is stored in the object file; it describes the data type of each
1930 variable or function and the correspondence between source line numbers
1931 and addresses in the executable code.
1933 To request debugging information, specify the @samp{-g} option when you run
1936 Programs that are to be shipped to your customers are compiled with
1937 optimizations, using the @samp{-O} compiler option. However, some
1938 compilers are unable to handle the @samp{-g} and @samp{-O} options
1939 together. Using those compilers, you cannot generate optimized
1940 executables containing debugging information.
1942 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1943 without @samp{-O}, making it possible to debug optimized code. We
1944 recommend that you @emph{always} use @samp{-g} whenever you compile a
1945 program. You may think your program is correct, but there is no sense
1946 in pushing your luck. For more information, see @ref{Optimized Code}.
1948 Older versions of the @sc{gnu} C compiler permitted a variant option
1949 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1950 format; if your @sc{gnu} C compiler has this option, do not use it.
1952 @value{GDBN} knows about preprocessor macros and can show you their
1953 expansion (@pxref{Macros}). Most compilers do not include information
1954 about preprocessor macros in the debugging information if you specify
1955 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1956 the @sc{gnu} C compiler, provides macro information if you are using
1957 the DWARF debugging format, and specify the option @option{-g3}.
1959 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1960 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1961 information on @value{NGCC} options affecting debug information.
1963 You will have the best debugging experience if you use the latest
1964 version of the DWARF debugging format that your compiler supports.
1965 DWARF is currently the most expressive and best supported debugging
1966 format in @value{GDBN}.
1970 @section Starting your Program
1976 @kindex r @r{(@code{run})}
1979 Use the @code{run} command to start your program under @value{GDBN}.
1980 You must first specify the program name with an argument to
1981 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1982 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
1983 command (@pxref{Files, ,Commands to Specify Files}).
1987 If you are running your program in an execution environment that
1988 supports processes, @code{run} creates an inferior process and makes
1989 that process run your program. In some environments without processes,
1990 @code{run} jumps to the start of your program. Other targets,
1991 like @samp{remote}, are always running. If you get an error
1992 message like this one:
1995 The "remote" target does not support "run".
1996 Try "help target" or "continue".
2000 then use @code{continue} to run your program. You may need @code{load}
2001 first (@pxref{load}).
2003 The execution of a program is affected by certain information it
2004 receives from its superior. @value{GDBN} provides ways to specify this
2005 information, which you must do @emph{before} starting your program. (You
2006 can change it after starting your program, but such changes only affect
2007 your program the next time you start it.) This information may be
2008 divided into four categories:
2011 @item The @emph{arguments.}
2012 Specify the arguments to give your program as the arguments of the
2013 @code{run} command. If a shell is available on your target, the shell
2014 is used to pass the arguments, so that you may use normal conventions
2015 (such as wildcard expansion or variable substitution) in describing
2017 In Unix systems, you can control which shell is used with the
2018 @code{SHELL} environment variable. If you do not define @code{SHELL},
2019 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2020 use of any shell with the @code{set startup-with-shell} command (see
2023 @item The @emph{environment.}
2024 Your program normally inherits its environment from @value{GDBN}, but you can
2025 use the @value{GDBN} commands @code{set environment} and @code{unset
2026 environment} to change parts of the environment that affect
2027 your program. @xref{Environment, ,Your Program's Environment}.
2029 @item The @emph{working directory.}
2030 Your program inherits its working directory from @value{GDBN}. You can set
2031 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2032 @xref{Working Directory, ,Your Program's Working Directory}.
2034 @item The @emph{standard input and output.}
2035 Your program normally uses the same device for standard input and
2036 standard output as @value{GDBN} is using. You can redirect input and output
2037 in the @code{run} command line, or you can use the @code{tty} command to
2038 set a different device for your program.
2039 @xref{Input/Output, ,Your Program's Input and Output}.
2042 @emph{Warning:} While input and output redirection work, you cannot use
2043 pipes to pass the output of the program you are debugging to another
2044 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2048 When you issue the @code{run} command, your program begins to execute
2049 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2050 of how to arrange for your program to stop. Once your program has
2051 stopped, you may call functions in your program, using the @code{print}
2052 or @code{call} commands. @xref{Data, ,Examining Data}.
2054 If the modification time of your symbol file has changed since the last
2055 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2056 table, and reads it again. When it does this, @value{GDBN} tries to retain
2057 your current breakpoints.
2062 @cindex run to main procedure
2063 The name of the main procedure can vary from language to language.
2064 With C or C@t{++}, the main procedure name is always @code{main}, but
2065 other languages such as Ada do not require a specific name for their
2066 main procedure. The debugger provides a convenient way to start the
2067 execution of the program and to stop at the beginning of the main
2068 procedure, depending on the language used.
2070 The @samp{start} command does the equivalent of setting a temporary
2071 breakpoint at the beginning of the main procedure and then invoking
2072 the @samp{run} command.
2074 @cindex elaboration phase
2075 Some programs contain an @dfn{elaboration} phase where some startup code is
2076 executed before the main procedure is called. This depends on the
2077 languages used to write your program. In C@t{++}, for instance,
2078 constructors for static and global objects are executed before
2079 @code{main} is called. It is therefore possible that the debugger stops
2080 before reaching the main procedure. However, the temporary breakpoint
2081 will remain to halt execution.
2083 Specify the arguments to give to your program as arguments to the
2084 @samp{start} command. These arguments will be given verbatim to the
2085 underlying @samp{run} command. Note that the same arguments will be
2086 reused if no argument is provided during subsequent calls to
2087 @samp{start} or @samp{run}.
2089 It is sometimes necessary to debug the program during elaboration. In
2090 these cases, using the @code{start} command would stop the execution of
2091 your program too late, as the program would have already completed the
2092 elaboration phase. Under these circumstances, insert breakpoints in your
2093 elaboration code before running your program.
2095 @anchor{set exec-wrapper}
2096 @kindex set exec-wrapper
2097 @item set exec-wrapper @var{wrapper}
2098 @itemx show exec-wrapper
2099 @itemx unset exec-wrapper
2100 When @samp{exec-wrapper} is set, the specified wrapper is used to
2101 launch programs for debugging. @value{GDBN} starts your program
2102 with a shell command of the form @kbd{exec @var{wrapper}
2103 @var{program}}. Quoting is added to @var{program} and its
2104 arguments, but not to @var{wrapper}, so you should add quotes if
2105 appropriate for your shell. The wrapper runs until it executes
2106 your program, and then @value{GDBN} takes control.
2108 You can use any program that eventually calls @code{execve} with
2109 its arguments as a wrapper. Several standard Unix utilities do
2110 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2111 with @code{exec "$@@"} will also work.
2113 For example, you can use @code{env} to pass an environment variable to
2114 the debugged program, without setting the variable in your shell's
2118 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2122 This command is available when debugging locally on most targets, excluding
2123 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2125 @kindex set startup-with-shell
2126 @item set startup-with-shell
2127 @itemx set startup-with-shell on
2128 @itemx set startup-with-shell off
2129 @itemx show set startup-with-shell
2130 On Unix systems, by default, if a shell is available on your target,
2131 @value{GDBN}) uses it to start your program. Arguments of the
2132 @code{run} command are passed to the shell, which does variable
2133 substitution, expands wildcard characters and performs redirection of
2134 I/O. In some circumstances, it may be useful to disable such use of a
2135 shell, for example, when debugging the shell itself or diagnosing
2136 startup failures such as:
2140 Starting program: ./a.out
2141 During startup program terminated with signal SIGSEGV, Segmentation fault.
2145 which indicates the shell or the wrapper specified with
2146 @samp{exec-wrapper} crashed, not your program. Most often, this is
2147 caused by something odd in your shell's non-interactive mode
2148 initialization file---such as @file{.cshrc} for C-shell,
2149 $@file{.zshenv} for the Z shell, or the file specified in the
2150 @samp{BASH_ENV} environment variable for BASH.
2152 @anchor{set auto-connect-native-target}
2153 @kindex set auto-connect-native-target
2154 @item set auto-connect-native-target
2155 @itemx set auto-connect-native-target on
2156 @itemx set auto-connect-native-target off
2157 @itemx show auto-connect-native-target
2159 By default, if not connected to any target yet (e.g., with
2160 @code{target remote}), the @code{run} command starts your program as a
2161 native process under @value{GDBN}, on your local machine. If you're
2162 sure you don't want to debug programs on your local machine, you can
2163 tell @value{GDBN} to not connect to the native target automatically
2164 with the @code{set auto-connect-native-target off} command.
2166 If @code{on}, which is the default, and if @value{GDBN} is not
2167 connected to a target already, the @code{run} command automaticaly
2168 connects to the native target, if one is available.
2170 If @code{off}, and if @value{GDBN} is not connected to a target
2171 already, the @code{run} command fails with an error:
2175 Don't know how to run. Try "help target".
2178 If @value{GDBN} is already connected to a target, @value{GDBN} always
2179 uses it with the @code{run} command.
2181 In any case, you can explicitly connect to the native target with the
2182 @code{target native} command. For example,
2185 (@value{GDBP}) set auto-connect-native-target off
2187 Don't know how to run. Try "help target".
2188 (@value{GDBP}) target native
2190 Starting program: ./a.out
2191 [Inferior 1 (process 10421) exited normally]
2194 In case you connected explicitly to the @code{native} target,
2195 @value{GDBN} remains connected even if all inferiors exit, ready for
2196 the next @code{run} command. Use the @code{disconnect} command to
2199 Examples of other commands that likewise respect the
2200 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2201 proc}, @code{info os}.
2203 @kindex set disable-randomization
2204 @item set disable-randomization
2205 @itemx set disable-randomization on
2206 This option (enabled by default in @value{GDBN}) will turn off the native
2207 randomization of the virtual address space of the started program. This option
2208 is useful for multiple debugging sessions to make the execution better
2209 reproducible and memory addresses reusable across debugging sessions.
2211 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2212 On @sc{gnu}/Linux you can get the same behavior using
2215 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2218 @item set disable-randomization off
2219 Leave the behavior of the started executable unchanged. Some bugs rear their
2220 ugly heads only when the program is loaded at certain addresses. If your bug
2221 disappears when you run the program under @value{GDBN}, that might be because
2222 @value{GDBN} by default disables the address randomization on platforms, such
2223 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2224 disable-randomization off} to try to reproduce such elusive bugs.
2226 On targets where it is available, virtual address space randomization
2227 protects the programs against certain kinds of security attacks. In these
2228 cases the attacker needs to know the exact location of a concrete executable
2229 code. Randomizing its location makes it impossible to inject jumps misusing
2230 a code at its expected addresses.
2232 Prelinking shared libraries provides a startup performance advantage but it
2233 makes addresses in these libraries predictable for privileged processes by
2234 having just unprivileged access at the target system. Reading the shared
2235 library binary gives enough information for assembling the malicious code
2236 misusing it. Still even a prelinked shared library can get loaded at a new
2237 random address just requiring the regular relocation process during the
2238 startup. Shared libraries not already prelinked are always loaded at
2239 a randomly chosen address.
2241 Position independent executables (PIE) contain position independent code
2242 similar to the shared libraries and therefore such executables get loaded at
2243 a randomly chosen address upon startup. PIE executables always load even
2244 already prelinked shared libraries at a random address. You can build such
2245 executable using @command{gcc -fPIE -pie}.
2247 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2248 (as long as the randomization is enabled).
2250 @item show disable-randomization
2251 Show the current setting of the explicit disable of the native randomization of
2252 the virtual address space of the started program.
2257 @section Your Program's Arguments
2259 @cindex arguments (to your program)
2260 The arguments to your program can be specified by the arguments of the
2262 They are passed to a shell, which expands wildcard characters and
2263 performs redirection of I/O, and thence to your program. Your
2264 @code{SHELL} environment variable (if it exists) specifies what shell
2265 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2266 the default shell (@file{/bin/sh} on Unix).
2268 On non-Unix systems, the program is usually invoked directly by
2269 @value{GDBN}, which emulates I/O redirection via the appropriate system
2270 calls, and the wildcard characters are expanded by the startup code of
2271 the program, not by the shell.
2273 @code{run} with no arguments uses the same arguments used by the previous
2274 @code{run}, or those set by the @code{set args} command.
2279 Specify the arguments to be used the next time your program is run. If
2280 @code{set args} has no arguments, @code{run} executes your program
2281 with no arguments. Once you have run your program with arguments,
2282 using @code{set args} before the next @code{run} is the only way to run
2283 it again without arguments.
2287 Show the arguments to give your program when it is started.
2291 @section Your Program's Environment
2293 @cindex environment (of your program)
2294 The @dfn{environment} consists of a set of environment variables and
2295 their values. Environment variables conventionally record such things as
2296 your user name, your home directory, your terminal type, and your search
2297 path for programs to run. Usually you set up environment variables with
2298 the shell and they are inherited by all the other programs you run. When
2299 debugging, it can be useful to try running your program with a modified
2300 environment without having to start @value{GDBN} over again.
2304 @item path @var{directory}
2305 Add @var{directory} to the front of the @code{PATH} environment variable
2306 (the search path for executables) that will be passed to your program.
2307 The value of @code{PATH} used by @value{GDBN} does not change.
2308 You may specify several directory names, separated by whitespace or by a
2309 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2310 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2311 is moved to the front, so it is searched sooner.
2313 You can use the string @samp{$cwd} to refer to whatever is the current
2314 working directory at the time @value{GDBN} searches the path. If you
2315 use @samp{.} instead, it refers to the directory where you executed the
2316 @code{path} command. @value{GDBN} replaces @samp{.} in the
2317 @var{directory} argument (with the current path) before adding
2318 @var{directory} to the search path.
2319 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2320 @c document that, since repeating it would be a no-op.
2324 Display the list of search paths for executables (the @code{PATH}
2325 environment variable).
2327 @kindex show environment
2328 @item show environment @r{[}@var{varname}@r{]}
2329 Print the value of environment variable @var{varname} to be given to
2330 your program when it starts. If you do not supply @var{varname},
2331 print the names and values of all environment variables to be given to
2332 your program. You can abbreviate @code{environment} as @code{env}.
2334 @kindex set environment
2335 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2336 Set environment variable @var{varname} to @var{value}. The value
2337 changes for your program (and the shell @value{GDBN} uses to launch
2338 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2339 values of environment variables are just strings, and any
2340 interpretation is supplied by your program itself. The @var{value}
2341 parameter is optional; if it is eliminated, the variable is set to a
2343 @c "any string" here does not include leading, trailing
2344 @c blanks. Gnu asks: does anyone care?
2346 For example, this command:
2353 tells the debugged program, when subsequently run, that its user is named
2354 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2355 are not actually required.)
2357 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2358 which also inherits the environment set with @code{set environment}.
2359 If necessary, you can avoid that by using the @samp{env} program as a
2360 wrapper instead of using @code{set environment}. @xref{set
2361 exec-wrapper}, for an example doing just that.
2363 @kindex unset environment
2364 @item unset environment @var{varname}
2365 Remove variable @var{varname} from the environment to be passed to your
2366 program. This is different from @samp{set env @var{varname} =};
2367 @code{unset environment} removes the variable from the environment,
2368 rather than assigning it an empty value.
2371 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2372 the shell indicated by your @code{SHELL} environment variable if it
2373 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2374 names a shell that runs an initialization file when started
2375 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2376 for the Z shell, or the file specified in the @samp{BASH_ENV}
2377 environment variable for BASH---any variables you set in that file
2378 affect your program. You may wish to move setting of environment
2379 variables to files that are only run when you sign on, such as
2380 @file{.login} or @file{.profile}.
2382 @node Working Directory
2383 @section Your Program's Working Directory
2385 @cindex working directory (of your program)
2386 Each time you start your program with @code{run}, it inherits its
2387 working directory from the current working directory of @value{GDBN}.
2388 The @value{GDBN} working directory is initially whatever it inherited
2389 from its parent process (typically the shell), but you can specify a new
2390 working directory in @value{GDBN} with the @code{cd} command.
2392 The @value{GDBN} working directory also serves as a default for the commands
2393 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2398 @cindex change working directory
2399 @item cd @r{[}@var{directory}@r{]}
2400 Set the @value{GDBN} working directory to @var{directory}. If not
2401 given, @var{directory} uses @file{'~'}.
2405 Print the @value{GDBN} working directory.
2408 It is generally impossible to find the current working directory of
2409 the process being debugged (since a program can change its directory
2410 during its run). If you work on a system where @value{GDBN} is
2411 configured with the @file{/proc} support, you can use the @code{info
2412 proc} command (@pxref{SVR4 Process Information}) to find out the
2413 current working directory of the debuggee.
2416 @section Your Program's Input and Output
2421 By default, the program you run under @value{GDBN} does input and output to
2422 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2423 to its own terminal modes to interact with you, but it records the terminal
2424 modes your program was using and switches back to them when you continue
2425 running your program.
2428 @kindex info terminal
2430 Displays information recorded by @value{GDBN} about the terminal modes your
2434 You can redirect your program's input and/or output using shell
2435 redirection with the @code{run} command. For example,
2442 starts your program, diverting its output to the file @file{outfile}.
2445 @cindex controlling terminal
2446 Another way to specify where your program should do input and output is
2447 with the @code{tty} command. This command accepts a file name as
2448 argument, and causes this file to be the default for future @code{run}
2449 commands. It also resets the controlling terminal for the child
2450 process, for future @code{run} commands. For example,
2457 directs that processes started with subsequent @code{run} commands
2458 default to do input and output on the terminal @file{/dev/ttyb} and have
2459 that as their controlling terminal.
2461 An explicit redirection in @code{run} overrides the @code{tty} command's
2462 effect on the input/output device, but not its effect on the controlling
2465 When you use the @code{tty} command or redirect input in the @code{run}
2466 command, only the input @emph{for your program} is affected. The input
2467 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2468 for @code{set inferior-tty}.
2470 @cindex inferior tty
2471 @cindex set inferior controlling terminal
2472 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2473 display the name of the terminal that will be used for future runs of your
2477 @item set inferior-tty /dev/ttyb
2478 @kindex set inferior-tty
2479 Set the tty for the program being debugged to /dev/ttyb.
2481 @item show inferior-tty
2482 @kindex show inferior-tty
2483 Show the current tty for the program being debugged.
2487 @section Debugging an Already-running Process
2492 @item attach @var{process-id}
2493 This command attaches to a running process---one that was started
2494 outside @value{GDBN}. (@code{info files} shows your active
2495 targets.) The command takes as argument a process ID. The usual way to
2496 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2497 or with the @samp{jobs -l} shell command.
2499 @code{attach} does not repeat if you press @key{RET} a second time after
2500 executing the command.
2503 To use @code{attach}, your program must be running in an environment
2504 which supports processes; for example, @code{attach} does not work for
2505 programs on bare-board targets that lack an operating system. You must
2506 also have permission to send the process a signal.
2508 When you use @code{attach}, the debugger finds the program running in
2509 the process first by looking in the current working directory, then (if
2510 the program is not found) by using the source file search path
2511 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2512 the @code{file} command to load the program. @xref{Files, ,Commands to
2515 The first thing @value{GDBN} does after arranging to debug the specified
2516 process is to stop it. You can examine and modify an attached process
2517 with all the @value{GDBN} commands that are ordinarily available when
2518 you start processes with @code{run}. You can insert breakpoints; you
2519 can step and continue; you can modify storage. If you would rather the
2520 process continue running, you may use the @code{continue} command after
2521 attaching @value{GDBN} to the process.
2526 When you have finished debugging the attached process, you can use the
2527 @code{detach} command to release it from @value{GDBN} control. Detaching
2528 the process continues its execution. After the @code{detach} command,
2529 that process and @value{GDBN} become completely independent once more, and you
2530 are ready to @code{attach} another process or start one with @code{run}.
2531 @code{detach} does not repeat if you press @key{RET} again after
2532 executing the command.
2535 If you exit @value{GDBN} while you have an attached process, you detach
2536 that process. If you use the @code{run} command, you kill that process.
2537 By default, @value{GDBN} asks for confirmation if you try to do either of these
2538 things; you can control whether or not you need to confirm by using the
2539 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2543 @section Killing the Child Process
2548 Kill the child process in which your program is running under @value{GDBN}.
2551 This command is useful if you wish to debug a core dump instead of a
2552 running process. @value{GDBN} ignores any core dump file while your program
2555 On some operating systems, a program cannot be executed outside @value{GDBN}
2556 while you have breakpoints set on it inside @value{GDBN}. You can use the
2557 @code{kill} command in this situation to permit running your program
2558 outside the debugger.
2560 The @code{kill} command is also useful if you wish to recompile and
2561 relink your program, since on many systems it is impossible to modify an
2562 executable file while it is running in a process. In this case, when you
2563 next type @code{run}, @value{GDBN} notices that the file has changed, and
2564 reads the symbol table again (while trying to preserve your current
2565 breakpoint settings).
2567 @node Inferiors and Programs
2568 @section Debugging Multiple Inferiors and Programs
2570 @value{GDBN} lets you run and debug multiple programs in a single
2571 session. In addition, @value{GDBN} on some systems may let you run
2572 several programs simultaneously (otherwise you have to exit from one
2573 before starting another). In the most general case, you can have
2574 multiple threads of execution in each of multiple processes, launched
2575 from multiple executables.
2578 @value{GDBN} represents the state of each program execution with an
2579 object called an @dfn{inferior}. An inferior typically corresponds to
2580 a process, but is more general and applies also to targets that do not
2581 have processes. Inferiors may be created before a process runs, and
2582 may be retained after a process exits. Inferiors have unique
2583 identifiers that are different from process ids. Usually each
2584 inferior will also have its own distinct address space, although some
2585 embedded targets may have several inferiors running in different parts
2586 of a single address space. Each inferior may in turn have multiple
2587 threads running in it.
2589 To find out what inferiors exist at any moment, use @w{@code{info
2593 @kindex info inferiors
2594 @item info inferiors
2595 Print a list of all inferiors currently being managed by @value{GDBN}.
2597 @value{GDBN} displays for each inferior (in this order):
2601 the inferior number assigned by @value{GDBN}
2604 the target system's inferior identifier
2607 the name of the executable the inferior is running.
2612 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2613 indicates the current inferior.
2617 @c end table here to get a little more width for example
2620 (@value{GDBP}) info inferiors
2621 Num Description Executable
2622 2 process 2307 hello
2623 * 1 process 3401 goodbye
2626 To switch focus between inferiors, use the @code{inferior} command:
2629 @kindex inferior @var{infno}
2630 @item inferior @var{infno}
2631 Make inferior number @var{infno} the current inferior. The argument
2632 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2633 in the first field of the @samp{info inferiors} display.
2637 You can get multiple executables into a debugging session via the
2638 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2639 systems @value{GDBN} can add inferiors to the debug session
2640 automatically by following calls to @code{fork} and @code{exec}. To
2641 remove inferiors from the debugging session use the
2642 @w{@code{remove-inferiors}} command.
2645 @kindex add-inferior
2646 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2647 Adds @var{n} inferiors to be run using @var{executable} as the
2648 executable; @var{n} defaults to 1. If no executable is specified,
2649 the inferiors begins empty, with no program. You can still assign or
2650 change the program assigned to the inferior at any time by using the
2651 @code{file} command with the executable name as its argument.
2653 @kindex clone-inferior
2654 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2655 Adds @var{n} inferiors ready to execute the same program as inferior
2656 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2657 number of the current inferior. This is a convenient command when you
2658 want to run another instance of the inferior you are debugging.
2661 (@value{GDBP}) info inferiors
2662 Num Description Executable
2663 * 1 process 29964 helloworld
2664 (@value{GDBP}) clone-inferior
2667 (@value{GDBP}) info inferiors
2668 Num Description Executable
2670 * 1 process 29964 helloworld
2673 You can now simply switch focus to inferior 2 and run it.
2675 @kindex remove-inferiors
2676 @item remove-inferiors @var{infno}@dots{}
2677 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2678 possible to remove an inferior that is running with this command. For
2679 those, use the @code{kill} or @code{detach} command first.
2683 To quit debugging one of the running inferiors that is not the current
2684 inferior, you can either detach from it by using the @w{@code{detach
2685 inferior}} command (allowing it to run independently), or kill it
2686 using the @w{@code{kill inferiors}} command:
2689 @kindex detach inferiors @var{infno}@dots{}
2690 @item detach inferior @var{infno}@dots{}
2691 Detach from the inferior or inferiors identified by @value{GDBN}
2692 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2693 still stays on the list of inferiors shown by @code{info inferiors},
2694 but its Description will show @samp{<null>}.
2696 @kindex kill inferiors @var{infno}@dots{}
2697 @item kill inferiors @var{infno}@dots{}
2698 Kill the inferior or inferiors identified by @value{GDBN} inferior
2699 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2700 stays on the list of inferiors shown by @code{info inferiors}, but its
2701 Description will show @samp{<null>}.
2704 After the successful completion of a command such as @code{detach},
2705 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2706 a normal process exit, the inferior is still valid and listed with
2707 @code{info inferiors}, ready to be restarted.
2710 To be notified when inferiors are started or exit under @value{GDBN}'s
2711 control use @w{@code{set print inferior-events}}:
2714 @kindex set print inferior-events
2715 @cindex print messages on inferior start and exit
2716 @item set print inferior-events
2717 @itemx set print inferior-events on
2718 @itemx set print inferior-events off
2719 The @code{set print inferior-events} command allows you to enable or
2720 disable printing of messages when @value{GDBN} notices that new
2721 inferiors have started or that inferiors have exited or have been
2722 detached. By default, these messages will not be printed.
2724 @kindex show print inferior-events
2725 @item show print inferior-events
2726 Show whether messages will be printed when @value{GDBN} detects that
2727 inferiors have started, exited or have been detached.
2730 Many commands will work the same with multiple programs as with a
2731 single program: e.g., @code{print myglobal} will simply display the
2732 value of @code{myglobal} in the current inferior.
2735 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2736 get more info about the relationship of inferiors, programs, address
2737 spaces in a debug session. You can do that with the @w{@code{maint
2738 info program-spaces}} command.
2741 @kindex maint info program-spaces
2742 @item maint info program-spaces
2743 Print a list of all program spaces currently being managed by
2746 @value{GDBN} displays for each program space (in this order):
2750 the program space number assigned by @value{GDBN}
2753 the name of the executable loaded into the program space, with e.g.,
2754 the @code{file} command.
2759 An asterisk @samp{*} preceding the @value{GDBN} program space number
2760 indicates the current program space.
2762 In addition, below each program space line, @value{GDBN} prints extra
2763 information that isn't suitable to display in tabular form. For
2764 example, the list of inferiors bound to the program space.
2767 (@value{GDBP}) maint info program-spaces
2770 Bound inferiors: ID 1 (process 21561)
2774 Here we can see that no inferior is running the program @code{hello},
2775 while @code{process 21561} is running the program @code{goodbye}. On
2776 some targets, it is possible that multiple inferiors are bound to the
2777 same program space. The most common example is that of debugging both
2778 the parent and child processes of a @code{vfork} call. For example,
2781 (@value{GDBP}) maint info program-spaces
2784 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2787 Here, both inferior 2 and inferior 1 are running in the same program
2788 space as a result of inferior 1 having executed a @code{vfork} call.
2792 @section Debugging Programs with Multiple Threads
2794 @cindex threads of execution
2795 @cindex multiple threads
2796 @cindex switching threads
2797 In some operating systems, such as HP-UX and Solaris, a single program
2798 may have more than one @dfn{thread} of execution. The precise semantics
2799 of threads differ from one operating system to another, but in general
2800 the threads of a single program are akin to multiple processes---except
2801 that they share one address space (that is, they can all examine and
2802 modify the same variables). On the other hand, each thread has its own
2803 registers and execution stack, and perhaps private memory.
2805 @value{GDBN} provides these facilities for debugging multi-thread
2809 @item automatic notification of new threads
2810 @item @samp{thread @var{threadno}}, a command to switch among threads
2811 @item @samp{info threads}, a command to inquire about existing threads
2812 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2813 a command to apply a command to a list of threads
2814 @item thread-specific breakpoints
2815 @item @samp{set print thread-events}, which controls printing of
2816 messages on thread start and exit.
2817 @item @samp{set libthread-db-search-path @var{path}}, which lets
2818 the user specify which @code{libthread_db} to use if the default choice
2819 isn't compatible with the program.
2823 @emph{Warning:} These facilities are not yet available on every
2824 @value{GDBN} configuration where the operating system supports threads.
2825 If your @value{GDBN} does not support threads, these commands have no
2826 effect. For example, a system without thread support shows no output
2827 from @samp{info threads}, and always rejects the @code{thread} command,
2831 (@value{GDBP}) info threads
2832 (@value{GDBP}) thread 1
2833 Thread ID 1 not known. Use the "info threads" command to
2834 see the IDs of currently known threads.
2836 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2837 @c doesn't support threads"?
2840 @cindex focus of debugging
2841 @cindex current thread
2842 The @value{GDBN} thread debugging facility allows you to observe all
2843 threads while your program runs---but whenever @value{GDBN} takes
2844 control, one thread in particular is always the focus of debugging.
2845 This thread is called the @dfn{current thread}. Debugging commands show
2846 program information from the perspective of the current thread.
2848 @cindex @code{New} @var{systag} message
2849 @cindex thread identifier (system)
2850 @c FIXME-implementors!! It would be more helpful if the [New...] message
2851 @c included GDB's numeric thread handle, so you could just go to that
2852 @c thread without first checking `info threads'.
2853 Whenever @value{GDBN} detects a new thread in your program, it displays
2854 the target system's identification for the thread with a message in the
2855 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2856 whose form varies depending on the particular system. For example, on
2857 @sc{gnu}/Linux, you might see
2860 [New Thread 0x41e02940 (LWP 25582)]
2864 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2865 the @var{systag} is simply something like @samp{process 368}, with no
2868 @c FIXME!! (1) Does the [New...] message appear even for the very first
2869 @c thread of a program, or does it only appear for the
2870 @c second---i.e.@: when it becomes obvious we have a multithread
2872 @c (2) *Is* there necessarily a first thread always? Or do some
2873 @c multithread systems permit starting a program with multiple
2874 @c threads ab initio?
2876 @cindex thread number
2877 @cindex thread identifier (GDB)
2878 For debugging purposes, @value{GDBN} associates its own thread
2879 number---always a single integer---with each thread in your program.
2882 @kindex info threads
2883 @item info threads @r{[}@var{id}@dots{}@r{]}
2884 Display a summary of all threads currently in your program. Optional
2885 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2886 means to print information only about the specified thread or threads.
2887 @value{GDBN} displays for each thread (in this order):
2891 the thread number assigned by @value{GDBN}
2894 the target system's thread identifier (@var{systag})
2897 the thread's name, if one is known. A thread can either be named by
2898 the user (see @code{thread name}, below), or, in some cases, by the
2902 the current stack frame summary for that thread
2906 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2907 indicates the current thread.
2911 @c end table here to get a little more width for example
2914 (@value{GDBP}) info threads
2916 3 process 35 thread 27 0x34e5 in sigpause ()
2917 2 process 35 thread 23 0x34e5 in sigpause ()
2918 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2922 On Solaris, you can display more information about user threads with a
2923 Solaris-specific command:
2926 @item maint info sol-threads
2927 @kindex maint info sol-threads
2928 @cindex thread info (Solaris)
2929 Display info on Solaris user threads.
2933 @kindex thread @var{threadno}
2934 @item thread @var{threadno}
2935 Make thread number @var{threadno} the current thread. The command
2936 argument @var{threadno} is the internal @value{GDBN} thread number, as
2937 shown in the first field of the @samp{info threads} display.
2938 @value{GDBN} responds by displaying the system identifier of the thread
2939 you selected, and its current stack frame summary:
2942 (@value{GDBP}) thread 2
2943 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2944 #0 some_function (ignore=0x0) at example.c:8
2945 8 printf ("hello\n");
2949 As with the @samp{[New @dots{}]} message, the form of the text after
2950 @samp{Switching to} depends on your system's conventions for identifying
2953 @vindex $_thread@r{, convenience variable}
2954 The debugger convenience variable @samp{$_thread} contains the number
2955 of the current thread. You may find this useful in writing breakpoint
2956 conditional expressions, command scripts, and so forth. See
2957 @xref{Convenience Vars,, Convenience Variables}, for general
2958 information on convenience variables.
2960 @kindex thread apply
2961 @cindex apply command to several threads
2962 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2963 The @code{thread apply} command allows you to apply the named
2964 @var{command} to one or more threads. Specify the numbers of the
2965 threads that you want affected with the command argument
2966 @var{threadno}. It can be a single thread number, one of the numbers
2967 shown in the first field of the @samp{info threads} display; or it
2968 could be a range of thread numbers, as in @code{2-4}. To apply
2969 a command to all threads in descending order, type @kbd{thread apply all
2970 @var{command}}. To apply a command to all threads in ascending order,
2971 type @kbd{thread apply all -ascending @var{command}}.
2975 @cindex name a thread
2976 @item thread name [@var{name}]
2977 This command assigns a name to the current thread. If no argument is
2978 given, any existing user-specified name is removed. The thread name
2979 appears in the @samp{info threads} display.
2981 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2982 determine the name of the thread as given by the OS. On these
2983 systems, a name specified with @samp{thread name} will override the
2984 system-give name, and removing the user-specified name will cause
2985 @value{GDBN} to once again display the system-specified name.
2988 @cindex search for a thread
2989 @item thread find [@var{regexp}]
2990 Search for and display thread ids whose name or @var{systag}
2991 matches the supplied regular expression.
2993 As well as being the complement to the @samp{thread name} command,
2994 this command also allows you to identify a thread by its target
2995 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2999 (@value{GDBN}) thread find 26688
3000 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3001 (@value{GDBN}) info thread 4
3003 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3006 @kindex set print thread-events
3007 @cindex print messages on thread start and exit
3008 @item set print thread-events
3009 @itemx set print thread-events on
3010 @itemx set print thread-events off
3011 The @code{set print thread-events} command allows you to enable or
3012 disable printing of messages when @value{GDBN} notices that new threads have
3013 started or that threads have exited. By default, these messages will
3014 be printed if detection of these events is supported by the target.
3015 Note that these messages cannot be disabled on all targets.
3017 @kindex show print thread-events
3018 @item show print thread-events
3019 Show whether messages will be printed when @value{GDBN} detects that threads
3020 have started and exited.
3023 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3024 more information about how @value{GDBN} behaves when you stop and start
3025 programs with multiple threads.
3027 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3028 watchpoints in programs with multiple threads.
3030 @anchor{set libthread-db-search-path}
3032 @kindex set libthread-db-search-path
3033 @cindex search path for @code{libthread_db}
3034 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3035 If this variable is set, @var{path} is a colon-separated list of
3036 directories @value{GDBN} will use to search for @code{libthread_db}.
3037 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3038 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3039 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3042 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3043 @code{libthread_db} library to obtain information about threads in the
3044 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3045 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3046 specific thread debugging library loading is enabled
3047 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3049 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3050 refers to the default system directories that are
3051 normally searched for loading shared libraries. The @samp{$sdir} entry
3052 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3053 (@pxref{libthread_db.so.1 file}).
3055 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3056 refers to the directory from which @code{libpthread}
3057 was loaded in the inferior process.
3059 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3060 @value{GDBN} attempts to initialize it with the current inferior process.
3061 If this initialization fails (which could happen because of a version
3062 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3063 will unload @code{libthread_db}, and continue with the next directory.
3064 If none of @code{libthread_db} libraries initialize successfully,
3065 @value{GDBN} will issue a warning and thread debugging will be disabled.
3067 Setting @code{libthread-db-search-path} is currently implemented
3068 only on some platforms.
3070 @kindex show libthread-db-search-path
3071 @item show libthread-db-search-path
3072 Display current libthread_db search path.
3074 @kindex set debug libthread-db
3075 @kindex show debug libthread-db
3076 @cindex debugging @code{libthread_db}
3077 @item set debug libthread-db
3078 @itemx show debug libthread-db
3079 Turns on or off display of @code{libthread_db}-related events.
3080 Use @code{1} to enable, @code{0} to disable.
3084 @section Debugging Forks
3086 @cindex fork, debugging programs which call
3087 @cindex multiple processes
3088 @cindex processes, multiple
3089 On most systems, @value{GDBN} has no special support for debugging
3090 programs which create additional processes using the @code{fork}
3091 function. When a program forks, @value{GDBN} will continue to debug the
3092 parent process and the child process will run unimpeded. If you have
3093 set a breakpoint in any code which the child then executes, the child
3094 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3095 will cause it to terminate.
3097 However, if you want to debug the child process there is a workaround
3098 which isn't too painful. Put a call to @code{sleep} in the code which
3099 the child process executes after the fork. It may be useful to sleep
3100 only if a certain environment variable is set, or a certain file exists,
3101 so that the delay need not occur when you don't want to run @value{GDBN}
3102 on the child. While the child is sleeping, use the @code{ps} program to
3103 get its process ID. Then tell @value{GDBN} (a new invocation of
3104 @value{GDBN} if you are also debugging the parent process) to attach to
3105 the child process (@pxref{Attach}). From that point on you can debug
3106 the child process just like any other process which you attached to.
3108 On some systems, @value{GDBN} provides support for debugging programs that
3109 create additional processes using the @code{fork} or @code{vfork} functions.
3110 Currently, the only platforms with this feature are HP-UX (11.x and later
3111 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3113 By default, when a program forks, @value{GDBN} will continue to debug
3114 the parent process and the child process will run unimpeded.
3116 If you want to follow the child process instead of the parent process,
3117 use the command @w{@code{set follow-fork-mode}}.
3120 @kindex set follow-fork-mode
3121 @item set follow-fork-mode @var{mode}
3122 Set the debugger response to a program call of @code{fork} or
3123 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3124 process. The @var{mode} argument can be:
3128 The original process is debugged after a fork. The child process runs
3129 unimpeded. This is the default.
3132 The new process is debugged after a fork. The parent process runs
3137 @kindex show follow-fork-mode
3138 @item show follow-fork-mode
3139 Display the current debugger response to a @code{fork} or @code{vfork} call.
3142 @cindex debugging multiple processes
3143 On Linux, if you want to debug both the parent and child processes, use the
3144 command @w{@code{set detach-on-fork}}.
3147 @kindex set detach-on-fork
3148 @item set detach-on-fork @var{mode}
3149 Tells gdb whether to detach one of the processes after a fork, or
3150 retain debugger control over them both.
3154 The child process (or parent process, depending on the value of
3155 @code{follow-fork-mode}) will be detached and allowed to run
3156 independently. This is the default.
3159 Both processes will be held under the control of @value{GDBN}.
3160 One process (child or parent, depending on the value of
3161 @code{follow-fork-mode}) is debugged as usual, while the other
3166 @kindex show detach-on-fork
3167 @item show detach-on-fork
3168 Show whether detach-on-fork mode is on/off.
3171 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3172 will retain control of all forked processes (including nested forks).
3173 You can list the forked processes under the control of @value{GDBN} by
3174 using the @w{@code{info inferiors}} command, and switch from one fork
3175 to another by using the @code{inferior} command (@pxref{Inferiors and
3176 Programs, ,Debugging Multiple Inferiors and Programs}).
3178 To quit debugging one of the forked processes, you can either detach
3179 from it by using the @w{@code{detach inferiors}} command (allowing it
3180 to run independently), or kill it using the @w{@code{kill inferiors}}
3181 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3184 If you ask to debug a child process and a @code{vfork} is followed by an
3185 @code{exec}, @value{GDBN} executes the new target up to the first
3186 breakpoint in the new target. If you have a breakpoint set on
3187 @code{main} in your original program, the breakpoint will also be set on
3188 the child process's @code{main}.
3190 On some systems, when a child process is spawned by @code{vfork}, you
3191 cannot debug the child or parent until an @code{exec} call completes.
3193 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3194 call executes, the new target restarts. To restart the parent
3195 process, use the @code{file} command with the parent executable name
3196 as its argument. By default, after an @code{exec} call executes,
3197 @value{GDBN} discards the symbols of the previous executable image.
3198 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3202 @kindex set follow-exec-mode
3203 @item set follow-exec-mode @var{mode}
3205 Set debugger response to a program call of @code{exec}. An
3206 @code{exec} call replaces the program image of a process.
3208 @code{follow-exec-mode} can be:
3212 @value{GDBN} creates a new inferior and rebinds the process to this
3213 new inferior. The program the process was running before the
3214 @code{exec} call can be restarted afterwards by restarting the
3220 (@value{GDBP}) info inferiors
3222 Id Description Executable
3225 process 12020 is executing new program: prog2
3226 Program exited normally.
3227 (@value{GDBP}) info inferiors
3228 Id Description Executable
3234 @value{GDBN} keeps the process bound to the same inferior. The new
3235 executable image replaces the previous executable loaded in the
3236 inferior. Restarting the inferior after the @code{exec} call, with
3237 e.g., the @code{run} command, restarts the executable the process was
3238 running after the @code{exec} call. This is the default mode.
3243 (@value{GDBP}) info inferiors
3244 Id Description Executable
3247 process 12020 is executing new program: prog2
3248 Program exited normally.
3249 (@value{GDBP}) info inferiors
3250 Id Description Executable
3257 You can use the @code{catch} command to make @value{GDBN} stop whenever
3258 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3259 Catchpoints, ,Setting Catchpoints}.
3261 @node Checkpoint/Restart
3262 @section Setting a @emph{Bookmark} to Return to Later
3267 @cindex snapshot of a process
3268 @cindex rewind program state
3270 On certain operating systems@footnote{Currently, only
3271 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3272 program's state, called a @dfn{checkpoint}, and come back to it
3275 Returning to a checkpoint effectively undoes everything that has
3276 happened in the program since the @code{checkpoint} was saved. This
3277 includes changes in memory, registers, and even (within some limits)
3278 system state. Effectively, it is like going back in time to the
3279 moment when the checkpoint was saved.
3281 Thus, if you're stepping thru a program and you think you're
3282 getting close to the point where things go wrong, you can save
3283 a checkpoint. Then, if you accidentally go too far and miss
3284 the critical statement, instead of having to restart your program
3285 from the beginning, you can just go back to the checkpoint and
3286 start again from there.
3288 This can be especially useful if it takes a lot of time or
3289 steps to reach the point where you think the bug occurs.
3291 To use the @code{checkpoint}/@code{restart} method of debugging:
3296 Save a snapshot of the debugged program's current execution state.
3297 The @code{checkpoint} command takes no arguments, but each checkpoint
3298 is assigned a small integer id, similar to a breakpoint id.
3300 @kindex info checkpoints
3301 @item info checkpoints
3302 List the checkpoints that have been saved in the current debugging
3303 session. For each checkpoint, the following information will be
3310 @item Source line, or label
3313 @kindex restart @var{checkpoint-id}
3314 @item restart @var{checkpoint-id}
3315 Restore the program state that was saved as checkpoint number
3316 @var{checkpoint-id}. All program variables, registers, stack frames
3317 etc.@: will be returned to the values that they had when the checkpoint
3318 was saved. In essence, gdb will ``wind back the clock'' to the point
3319 in time when the checkpoint was saved.
3321 Note that breakpoints, @value{GDBN} variables, command history etc.
3322 are not affected by restoring a checkpoint. In general, a checkpoint
3323 only restores things that reside in the program being debugged, not in
3326 @kindex delete checkpoint @var{checkpoint-id}
3327 @item delete checkpoint @var{checkpoint-id}
3328 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3332 Returning to a previously saved checkpoint will restore the user state
3333 of the program being debugged, plus a significant subset of the system
3334 (OS) state, including file pointers. It won't ``un-write'' data from
3335 a file, but it will rewind the file pointer to the previous location,
3336 so that the previously written data can be overwritten. For files
3337 opened in read mode, the pointer will also be restored so that the
3338 previously read data can be read again.
3340 Of course, characters that have been sent to a printer (or other
3341 external device) cannot be ``snatched back'', and characters received
3342 from eg.@: a serial device can be removed from internal program buffers,
3343 but they cannot be ``pushed back'' into the serial pipeline, ready to
3344 be received again. Similarly, the actual contents of files that have
3345 been changed cannot be restored (at this time).
3347 However, within those constraints, you actually can ``rewind'' your
3348 program to a previously saved point in time, and begin debugging it
3349 again --- and you can change the course of events so as to debug a
3350 different execution path this time.
3352 @cindex checkpoints and process id
3353 Finally, there is one bit of internal program state that will be
3354 different when you return to a checkpoint --- the program's process
3355 id. Each checkpoint will have a unique process id (or @var{pid}),
3356 and each will be different from the program's original @var{pid}.
3357 If your program has saved a local copy of its process id, this could
3358 potentially pose a problem.
3360 @subsection A Non-obvious Benefit of Using Checkpoints
3362 On some systems such as @sc{gnu}/Linux, address space randomization
3363 is performed on new processes for security reasons. This makes it
3364 difficult or impossible to set a breakpoint, or watchpoint, on an
3365 absolute address if you have to restart the program, since the
3366 absolute location of a symbol will change from one execution to the
3369 A checkpoint, however, is an @emph{identical} copy of a process.
3370 Therefore if you create a checkpoint at (eg.@:) the start of main,
3371 and simply return to that checkpoint instead of restarting the
3372 process, you can avoid the effects of address randomization and
3373 your symbols will all stay in the same place.
3376 @chapter Stopping and Continuing
3378 The principal purposes of using a debugger are so that you can stop your
3379 program before it terminates; or so that, if your program runs into
3380 trouble, you can investigate and find out why.
3382 Inside @value{GDBN}, your program may stop for any of several reasons,
3383 such as a signal, a breakpoint, or reaching a new line after a
3384 @value{GDBN} command such as @code{step}. You may then examine and
3385 change variables, set new breakpoints or remove old ones, and then
3386 continue execution. Usually, the messages shown by @value{GDBN} provide
3387 ample explanation of the status of your program---but you can also
3388 explicitly request this information at any time.
3391 @kindex info program
3393 Display information about the status of your program: whether it is
3394 running or not, what process it is, and why it stopped.
3398 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3399 * Continuing and Stepping:: Resuming execution
3400 * Skipping Over Functions and Files::
3401 Skipping over functions and files
3403 * Thread Stops:: Stopping and starting multi-thread programs
3407 @section Breakpoints, Watchpoints, and Catchpoints
3410 A @dfn{breakpoint} makes your program stop whenever a certain point in
3411 the program is reached. For each breakpoint, you can add conditions to
3412 control in finer detail whether your program stops. You can set
3413 breakpoints with the @code{break} command and its variants (@pxref{Set
3414 Breaks, ,Setting Breakpoints}), to specify the place where your program
3415 should stop by line number, function name or exact address in the
3418 On some systems, you can set breakpoints in shared libraries before
3419 the executable is run. There is a minor limitation on HP-UX systems:
3420 you must wait until the executable is run in order to set breakpoints
3421 in shared library routines that are not called directly by the program
3422 (for example, routines that are arguments in a @code{pthread_create}
3426 @cindex data breakpoints
3427 @cindex memory tracing
3428 @cindex breakpoint on memory address
3429 @cindex breakpoint on variable modification
3430 A @dfn{watchpoint} is a special breakpoint that stops your program
3431 when the value of an expression changes. The expression may be a value
3432 of a variable, or it could involve values of one or more variables
3433 combined by operators, such as @samp{a + b}. This is sometimes called
3434 @dfn{data breakpoints}. You must use a different command to set
3435 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3436 from that, you can manage a watchpoint like any other breakpoint: you
3437 enable, disable, and delete both breakpoints and watchpoints using the
3440 You can arrange to have values from your program displayed automatically
3441 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3445 @cindex breakpoint on events
3446 A @dfn{catchpoint} is another special breakpoint that stops your program
3447 when a certain kind of event occurs, such as the throwing of a C@t{++}
3448 exception or the loading of a library. As with watchpoints, you use a
3449 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3450 Catchpoints}), but aside from that, you can manage a catchpoint like any
3451 other breakpoint. (To stop when your program receives a signal, use the
3452 @code{handle} command; see @ref{Signals, ,Signals}.)
3454 @cindex breakpoint numbers
3455 @cindex numbers for breakpoints
3456 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3457 catchpoint when you create it; these numbers are successive integers
3458 starting with one. In many of the commands for controlling various
3459 features of breakpoints you use the breakpoint number to say which
3460 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3461 @dfn{disabled}; if disabled, it has no effect on your program until you
3464 @cindex breakpoint ranges
3465 @cindex ranges of breakpoints
3466 Some @value{GDBN} commands accept a range of breakpoints on which to
3467 operate. A breakpoint range is either a single breakpoint number, like
3468 @samp{5}, or two such numbers, in increasing order, separated by a
3469 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3470 all breakpoints in that range are operated on.
3473 * Set Breaks:: Setting breakpoints
3474 * Set Watchpoints:: Setting watchpoints
3475 * Set Catchpoints:: Setting catchpoints
3476 * Delete Breaks:: Deleting breakpoints
3477 * Disabling:: Disabling breakpoints
3478 * Conditions:: Break conditions
3479 * Break Commands:: Breakpoint command lists
3480 * Dynamic Printf:: Dynamic printf
3481 * Save Breakpoints:: How to save breakpoints in a file
3482 * Static Probe Points:: Listing static probe points
3483 * Error in Breakpoints:: ``Cannot insert breakpoints''
3484 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3488 @subsection Setting Breakpoints
3490 @c FIXME LMB what does GDB do if no code on line of breakpt?
3491 @c consider in particular declaration with/without initialization.
3493 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3496 @kindex b @r{(@code{break})}
3497 @vindex $bpnum@r{, convenience variable}
3498 @cindex latest breakpoint
3499 Breakpoints are set with the @code{break} command (abbreviated
3500 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3501 number of the breakpoint you've set most recently; see @ref{Convenience
3502 Vars,, Convenience Variables}, for a discussion of what you can do with
3503 convenience variables.
3506 @item break @var{location}
3507 Set a breakpoint at the given @var{location}, which can specify a
3508 function name, a line number, or an address of an instruction.
3509 (@xref{Specify Location}, for a list of all the possible ways to
3510 specify a @var{location}.) The breakpoint will stop your program just
3511 before it executes any of the code in the specified @var{location}.
3513 When using source languages that permit overloading of symbols, such as
3514 C@t{++}, a function name may refer to more than one possible place to break.
3515 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3518 It is also possible to insert a breakpoint that will stop the program
3519 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3520 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3523 When called without any arguments, @code{break} sets a breakpoint at
3524 the next instruction to be executed in the selected stack frame
3525 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3526 innermost, this makes your program stop as soon as control
3527 returns to that frame. This is similar to the effect of a
3528 @code{finish} command in the frame inside the selected frame---except
3529 that @code{finish} does not leave an active breakpoint. If you use
3530 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3531 the next time it reaches the current location; this may be useful
3534 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3535 least one instruction has been executed. If it did not do this, you
3536 would be unable to proceed past a breakpoint without first disabling the
3537 breakpoint. This rule applies whether or not the breakpoint already
3538 existed when your program stopped.
3540 @item break @dots{} if @var{cond}
3541 Set a breakpoint with condition @var{cond}; evaluate the expression
3542 @var{cond} each time the breakpoint is reached, and stop only if the
3543 value is nonzero---that is, if @var{cond} evaluates as true.
3544 @samp{@dots{}} stands for one of the possible arguments described
3545 above (or no argument) specifying where to break. @xref{Conditions,
3546 ,Break Conditions}, for more information on breakpoint conditions.
3549 @item tbreak @var{args}
3550 Set a breakpoint enabled only for one stop. The @var{args} are the
3551 same as for the @code{break} command, and the breakpoint is set in the same
3552 way, but the breakpoint is automatically deleted after the first time your
3553 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3556 @cindex hardware breakpoints
3557 @item hbreak @var{args}
3558 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3559 @code{break} command and the breakpoint is set in the same way, but the
3560 breakpoint requires hardware support and some target hardware may not
3561 have this support. The main purpose of this is EPROM/ROM code
3562 debugging, so you can set a breakpoint at an instruction without
3563 changing the instruction. This can be used with the new trap-generation
3564 provided by SPARClite DSU and most x86-based targets. These targets
3565 will generate traps when a program accesses some data or instruction
3566 address that is assigned to the debug registers. However the hardware
3567 breakpoint registers can take a limited number of breakpoints. For
3568 example, on the DSU, only two data breakpoints can be set at a time, and
3569 @value{GDBN} will reject this command if more than two are used. Delete
3570 or disable unused hardware breakpoints before setting new ones
3571 (@pxref{Disabling, ,Disabling Breakpoints}).
3572 @xref{Conditions, ,Break Conditions}.
3573 For remote targets, you can restrict the number of hardware
3574 breakpoints @value{GDBN} will use, see @ref{set remote
3575 hardware-breakpoint-limit}.
3578 @item thbreak @var{args}
3579 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3580 are the same as for the @code{hbreak} command and the breakpoint is set in
3581 the same way. However, like the @code{tbreak} command,
3582 the breakpoint is automatically deleted after the
3583 first time your program stops there. Also, like the @code{hbreak}
3584 command, the breakpoint requires hardware support and some target hardware
3585 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3586 See also @ref{Conditions, ,Break Conditions}.
3589 @cindex regular expression
3590 @cindex breakpoints at functions matching a regexp
3591 @cindex set breakpoints in many functions
3592 @item rbreak @var{regex}
3593 Set breakpoints on all functions matching the regular expression
3594 @var{regex}. This command sets an unconditional breakpoint on all
3595 matches, printing a list of all breakpoints it set. Once these
3596 breakpoints are set, they are treated just like the breakpoints set with
3597 the @code{break} command. You can delete them, disable them, or make
3598 them conditional the same way as any other breakpoint.
3600 The syntax of the regular expression is the standard one used with tools
3601 like @file{grep}. Note that this is different from the syntax used by
3602 shells, so for instance @code{foo*} matches all functions that include
3603 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3604 @code{.*} leading and trailing the regular expression you supply, so to
3605 match only functions that begin with @code{foo}, use @code{^foo}.
3607 @cindex non-member C@t{++} functions, set breakpoint in
3608 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3609 breakpoints on overloaded functions that are not members of any special
3612 @cindex set breakpoints on all functions
3613 The @code{rbreak} command can be used to set breakpoints in
3614 @strong{all} the functions in a program, like this:
3617 (@value{GDBP}) rbreak .
3620 @item rbreak @var{file}:@var{regex}
3621 If @code{rbreak} is called with a filename qualification, it limits
3622 the search for functions matching the given regular expression to the
3623 specified @var{file}. This can be used, for example, to set breakpoints on
3624 every function in a given file:
3627 (@value{GDBP}) rbreak file.c:.
3630 The colon separating the filename qualifier from the regex may
3631 optionally be surrounded by spaces.
3633 @kindex info breakpoints
3634 @cindex @code{$_} and @code{info breakpoints}
3635 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3636 @itemx info break @r{[}@var{n}@dots{}@r{]}
3637 Print a table of all breakpoints, watchpoints, and catchpoints set and
3638 not deleted. Optional argument @var{n} means print information only
3639 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3640 For each breakpoint, following columns are printed:
3643 @item Breakpoint Numbers
3645 Breakpoint, watchpoint, or catchpoint.
3647 Whether the breakpoint is marked to be disabled or deleted when hit.
3648 @item Enabled or Disabled
3649 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3650 that are not enabled.
3652 Where the breakpoint is in your program, as a memory address. For a
3653 pending breakpoint whose address is not yet known, this field will
3654 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3655 library that has the symbol or line referred by breakpoint is loaded.
3656 See below for details. A breakpoint with several locations will
3657 have @samp{<MULTIPLE>} in this field---see below for details.
3659 Where the breakpoint is in the source for your program, as a file and
3660 line number. For a pending breakpoint, the original string passed to
3661 the breakpoint command will be listed as it cannot be resolved until
3662 the appropriate shared library is loaded in the future.
3666 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3667 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3668 @value{GDBN} on the host's side. If it is ``target'', then the condition
3669 is evaluated by the target. The @code{info break} command shows
3670 the condition on the line following the affected breakpoint, together with
3671 its condition evaluation mode in between parentheses.
3673 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3674 allowed to have a condition specified for it. The condition is not parsed for
3675 validity until a shared library is loaded that allows the pending
3676 breakpoint to resolve to a valid location.
3679 @code{info break} with a breakpoint
3680 number @var{n} as argument lists only that breakpoint. The
3681 convenience variable @code{$_} and the default examining-address for
3682 the @code{x} command are set to the address of the last breakpoint
3683 listed (@pxref{Memory, ,Examining Memory}).
3686 @code{info break} displays a count of the number of times the breakpoint
3687 has been hit. This is especially useful in conjunction with the
3688 @code{ignore} command. You can ignore a large number of breakpoint
3689 hits, look at the breakpoint info to see how many times the breakpoint
3690 was hit, and then run again, ignoring one less than that number. This
3691 will get you quickly to the last hit of that breakpoint.
3694 For a breakpoints with an enable count (xref) greater than 1,
3695 @code{info break} also displays that count.
3699 @value{GDBN} allows you to set any number of breakpoints at the same place in
3700 your program. There is nothing silly or meaningless about this. When
3701 the breakpoints are conditional, this is even useful
3702 (@pxref{Conditions, ,Break Conditions}).
3704 @cindex multiple locations, breakpoints
3705 @cindex breakpoints, multiple locations
3706 It is possible that a breakpoint corresponds to several locations
3707 in your program. Examples of this situation are:
3711 Multiple functions in the program may have the same name.
3714 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3715 instances of the function body, used in different cases.
3718 For a C@t{++} template function, a given line in the function can
3719 correspond to any number of instantiations.
3722 For an inlined function, a given source line can correspond to
3723 several places where that function is inlined.
3726 In all those cases, @value{GDBN} will insert a breakpoint at all
3727 the relevant locations.
3729 A breakpoint with multiple locations is displayed in the breakpoint
3730 table using several rows---one header row, followed by one row for
3731 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3732 address column. The rows for individual locations contain the actual
3733 addresses for locations, and show the functions to which those
3734 locations belong. The number column for a location is of the form
3735 @var{breakpoint-number}.@var{location-number}.
3740 Num Type Disp Enb Address What
3741 1 breakpoint keep y <MULTIPLE>
3743 breakpoint already hit 1 time
3744 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3745 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3748 Each location can be individually enabled or disabled by passing
3749 @var{breakpoint-number}.@var{location-number} as argument to the
3750 @code{enable} and @code{disable} commands. Note that you cannot
3751 delete the individual locations from the list, you can only delete the
3752 entire list of locations that belong to their parent breakpoint (with
3753 the @kbd{delete @var{num}} command, where @var{num} is the number of
3754 the parent breakpoint, 1 in the above example). Disabling or enabling
3755 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3756 that belong to that breakpoint.
3758 @cindex pending breakpoints
3759 It's quite common to have a breakpoint inside a shared library.
3760 Shared libraries can be loaded and unloaded explicitly,
3761 and possibly repeatedly, as the program is executed. To support
3762 this use case, @value{GDBN} updates breakpoint locations whenever
3763 any shared library is loaded or unloaded. Typically, you would
3764 set a breakpoint in a shared library at the beginning of your
3765 debugging session, when the library is not loaded, and when the
3766 symbols from the library are not available. When you try to set
3767 breakpoint, @value{GDBN} will ask you if you want to set
3768 a so called @dfn{pending breakpoint}---breakpoint whose address
3769 is not yet resolved.
3771 After the program is run, whenever a new shared library is loaded,
3772 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3773 shared library contains the symbol or line referred to by some
3774 pending breakpoint, that breakpoint is resolved and becomes an
3775 ordinary breakpoint. When a library is unloaded, all breakpoints
3776 that refer to its symbols or source lines become pending again.
3778 This logic works for breakpoints with multiple locations, too. For
3779 example, if you have a breakpoint in a C@t{++} template function, and
3780 a newly loaded shared library has an instantiation of that template,
3781 a new location is added to the list of locations for the breakpoint.
3783 Except for having unresolved address, pending breakpoints do not
3784 differ from regular breakpoints. You can set conditions or commands,
3785 enable and disable them and perform other breakpoint operations.
3787 @value{GDBN} provides some additional commands for controlling what
3788 happens when the @samp{break} command cannot resolve breakpoint
3789 address specification to an address:
3791 @kindex set breakpoint pending
3792 @kindex show breakpoint pending
3794 @item set breakpoint pending auto
3795 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3796 location, it queries you whether a pending breakpoint should be created.
3798 @item set breakpoint pending on
3799 This indicates that an unrecognized breakpoint location should automatically
3800 result in a pending breakpoint being created.
3802 @item set breakpoint pending off
3803 This indicates that pending breakpoints are not to be created. Any
3804 unrecognized breakpoint location results in an error. This setting does
3805 not affect any pending breakpoints previously created.
3807 @item show breakpoint pending
3808 Show the current behavior setting for creating pending breakpoints.
3811 The settings above only affect the @code{break} command and its
3812 variants. Once breakpoint is set, it will be automatically updated
3813 as shared libraries are loaded and unloaded.
3815 @cindex automatic hardware breakpoints
3816 For some targets, @value{GDBN} can automatically decide if hardware or
3817 software breakpoints should be used, depending on whether the
3818 breakpoint address is read-only or read-write. This applies to
3819 breakpoints set with the @code{break} command as well as to internal
3820 breakpoints set by commands like @code{next} and @code{finish}. For
3821 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3824 You can control this automatic behaviour with the following commands::
3826 @kindex set breakpoint auto-hw
3827 @kindex show breakpoint auto-hw
3829 @item set breakpoint auto-hw on
3830 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3831 will try to use the target memory map to decide if software or hardware
3832 breakpoint must be used.
3834 @item set breakpoint auto-hw off
3835 This indicates @value{GDBN} should not automatically select breakpoint
3836 type. If the target provides a memory map, @value{GDBN} will warn when
3837 trying to set software breakpoint at a read-only address.
3840 @value{GDBN} normally implements breakpoints by replacing the program code
3841 at the breakpoint address with a special instruction, which, when
3842 executed, given control to the debugger. By default, the program
3843 code is so modified only when the program is resumed. As soon as
3844 the program stops, @value{GDBN} restores the original instructions. This
3845 behaviour guards against leaving breakpoints inserted in the
3846 target should gdb abrubptly disconnect. However, with slow remote
3847 targets, inserting and removing breakpoint can reduce the performance.
3848 This behavior can be controlled with the following commands::
3850 @kindex set breakpoint always-inserted
3851 @kindex show breakpoint always-inserted
3853 @item set breakpoint always-inserted off
3854 All breakpoints, including newly added by the user, are inserted in
3855 the target only when the target is resumed. All breakpoints are
3856 removed from the target when it stops. This is the default mode.
3858 @item set breakpoint always-inserted on
3859 Causes all breakpoints to be inserted in the target at all times. If
3860 the user adds a new breakpoint, or changes an existing breakpoint, the
3861 breakpoints in the target are updated immediately. A breakpoint is
3862 removed from the target only when breakpoint itself is deleted.
3865 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3866 when a breakpoint breaks. If the condition is true, then the process being
3867 debugged stops, otherwise the process is resumed.
3869 If the target supports evaluating conditions on its end, @value{GDBN} may
3870 download the breakpoint, together with its conditions, to it.
3872 This feature can be controlled via the following commands:
3874 @kindex set breakpoint condition-evaluation
3875 @kindex show breakpoint condition-evaluation
3877 @item set breakpoint condition-evaluation host
3878 This option commands @value{GDBN} to evaluate the breakpoint
3879 conditions on the host's side. Unconditional breakpoints are sent to
3880 the target which in turn receives the triggers and reports them back to GDB
3881 for condition evaluation. This is the standard evaluation mode.
3883 @item set breakpoint condition-evaluation target
3884 This option commands @value{GDBN} to download breakpoint conditions
3885 to the target at the moment of their insertion. The target
3886 is responsible for evaluating the conditional expression and reporting
3887 breakpoint stop events back to @value{GDBN} whenever the condition
3888 is true. Due to limitations of target-side evaluation, some conditions
3889 cannot be evaluated there, e.g., conditions that depend on local data
3890 that is only known to the host. Examples include
3891 conditional expressions involving convenience variables, complex types
3892 that cannot be handled by the agent expression parser and expressions
3893 that are too long to be sent over to the target, specially when the
3894 target is a remote system. In these cases, the conditions will be
3895 evaluated by @value{GDBN}.
3897 @item set breakpoint condition-evaluation auto
3898 This is the default mode. If the target supports evaluating breakpoint
3899 conditions on its end, @value{GDBN} will download breakpoint conditions to
3900 the target (limitations mentioned previously apply). If the target does
3901 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3902 to evaluating all these conditions on the host's side.
3906 @cindex negative breakpoint numbers
3907 @cindex internal @value{GDBN} breakpoints
3908 @value{GDBN} itself sometimes sets breakpoints in your program for
3909 special purposes, such as proper handling of @code{longjmp} (in C
3910 programs). These internal breakpoints are assigned negative numbers,
3911 starting with @code{-1}; @samp{info breakpoints} does not display them.
3912 You can see these breakpoints with the @value{GDBN} maintenance command
3913 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3916 @node Set Watchpoints
3917 @subsection Setting Watchpoints
3919 @cindex setting watchpoints
3920 You can use a watchpoint to stop execution whenever the value of an
3921 expression changes, without having to predict a particular place where
3922 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3923 The expression may be as simple as the value of a single variable, or
3924 as complex as many variables combined by operators. Examples include:
3928 A reference to the value of a single variable.
3931 An address cast to an appropriate data type. For example,
3932 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3933 address (assuming an @code{int} occupies 4 bytes).
3936 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3937 expression can use any operators valid in the program's native
3938 language (@pxref{Languages}).
3941 You can set a watchpoint on an expression even if the expression can
3942 not be evaluated yet. For instance, you can set a watchpoint on
3943 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3944 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3945 the expression produces a valid value. If the expression becomes
3946 valid in some other way than changing a variable (e.g.@: if the memory
3947 pointed to by @samp{*global_ptr} becomes readable as the result of a
3948 @code{malloc} call), @value{GDBN} may not stop until the next time
3949 the expression changes.
3951 @cindex software watchpoints
3952 @cindex hardware watchpoints
3953 Depending on your system, watchpoints may be implemented in software or
3954 hardware. @value{GDBN} does software watchpointing by single-stepping your
3955 program and testing the variable's value each time, which is hundreds of
3956 times slower than normal execution. (But this may still be worth it, to
3957 catch errors where you have no clue what part of your program is the
3960 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3961 x86-based targets, @value{GDBN} includes support for hardware
3962 watchpoints, which do not slow down the running of your program.
3966 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3967 Set a watchpoint for an expression. @value{GDBN} will break when the
3968 expression @var{expr} is written into by the program and its value
3969 changes. The simplest (and the most popular) use of this command is
3970 to watch the value of a single variable:
3973 (@value{GDBP}) watch foo
3976 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3977 argument, @value{GDBN} breaks only when the thread identified by
3978 @var{threadnum} changes the value of @var{expr}. If any other threads
3979 change the value of @var{expr}, @value{GDBN} will not break. Note
3980 that watchpoints restricted to a single thread in this way only work
3981 with Hardware Watchpoints.
3983 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3984 (see below). The @code{-location} argument tells @value{GDBN} to
3985 instead watch the memory referred to by @var{expr}. In this case,
3986 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3987 and watch the memory at that address. The type of the result is used
3988 to determine the size of the watched memory. If the expression's
3989 result does not have an address, then @value{GDBN} will print an
3992 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3993 of masked watchpoints, if the current architecture supports this
3994 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3995 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3996 to an address to watch. The mask specifies that some bits of an address
3997 (the bits which are reset in the mask) should be ignored when matching
3998 the address accessed by the inferior against the watchpoint address.
3999 Thus, a masked watchpoint watches many addresses simultaneously---those
4000 addresses whose unmasked bits are identical to the unmasked bits in the
4001 watchpoint address. The @code{mask} argument implies @code{-location}.
4005 (@value{GDBP}) watch foo mask 0xffff00ff
4006 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4010 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4011 Set a watchpoint that will break when the value of @var{expr} is read
4015 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4016 Set a watchpoint that will break when @var{expr} is either read from
4017 or written into by the program.
4019 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4020 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4021 This command prints a list of watchpoints, using the same format as
4022 @code{info break} (@pxref{Set Breaks}).
4025 If you watch for a change in a numerically entered address you need to
4026 dereference it, as the address itself is just a constant number which will
4027 never change. @value{GDBN} refuses to create a watchpoint that watches
4028 a never-changing value:
4031 (@value{GDBP}) watch 0x600850
4032 Cannot watch constant value 0x600850.
4033 (@value{GDBP}) watch *(int *) 0x600850
4034 Watchpoint 1: *(int *) 6293584
4037 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4038 watchpoints execute very quickly, and the debugger reports a change in
4039 value at the exact instruction where the change occurs. If @value{GDBN}
4040 cannot set a hardware watchpoint, it sets a software watchpoint, which
4041 executes more slowly and reports the change in value at the next
4042 @emph{statement}, not the instruction, after the change occurs.
4044 @cindex use only software watchpoints
4045 You can force @value{GDBN} to use only software watchpoints with the
4046 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4047 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4048 the underlying system supports them. (Note that hardware-assisted
4049 watchpoints that were set @emph{before} setting
4050 @code{can-use-hw-watchpoints} to zero will still use the hardware
4051 mechanism of watching expression values.)
4054 @item set can-use-hw-watchpoints
4055 @kindex set can-use-hw-watchpoints
4056 Set whether or not to use hardware watchpoints.
4058 @item show can-use-hw-watchpoints
4059 @kindex show can-use-hw-watchpoints
4060 Show the current mode of using hardware watchpoints.
4063 For remote targets, you can restrict the number of hardware
4064 watchpoints @value{GDBN} will use, see @ref{set remote
4065 hardware-breakpoint-limit}.
4067 When you issue the @code{watch} command, @value{GDBN} reports
4070 Hardware watchpoint @var{num}: @var{expr}
4074 if it was able to set a hardware watchpoint.
4076 Currently, the @code{awatch} and @code{rwatch} commands can only set
4077 hardware watchpoints, because accesses to data that don't change the
4078 value of the watched expression cannot be detected without examining
4079 every instruction as it is being executed, and @value{GDBN} does not do
4080 that currently. If @value{GDBN} finds that it is unable to set a
4081 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4082 will print a message like this:
4085 Expression cannot be implemented with read/access watchpoint.
4088 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4089 data type of the watched expression is wider than what a hardware
4090 watchpoint on the target machine can handle. For example, some systems
4091 can only watch regions that are up to 4 bytes wide; on such systems you
4092 cannot set hardware watchpoints for an expression that yields a
4093 double-precision floating-point number (which is typically 8 bytes
4094 wide). As a work-around, it might be possible to break the large region
4095 into a series of smaller ones and watch them with separate watchpoints.
4097 If you set too many hardware watchpoints, @value{GDBN} might be unable
4098 to insert all of them when you resume the execution of your program.
4099 Since the precise number of active watchpoints is unknown until such
4100 time as the program is about to be resumed, @value{GDBN} might not be
4101 able to warn you about this when you set the watchpoints, and the
4102 warning will be printed only when the program is resumed:
4105 Hardware watchpoint @var{num}: Could not insert watchpoint
4109 If this happens, delete or disable some of the watchpoints.
4111 Watching complex expressions that reference many variables can also
4112 exhaust the resources available for hardware-assisted watchpoints.
4113 That's because @value{GDBN} needs to watch every variable in the
4114 expression with separately allocated resources.
4116 If you call a function interactively using @code{print} or @code{call},
4117 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4118 kind of breakpoint or the call completes.
4120 @value{GDBN} automatically deletes watchpoints that watch local
4121 (automatic) variables, or expressions that involve such variables, when
4122 they go out of scope, that is, when the execution leaves the block in
4123 which these variables were defined. In particular, when the program
4124 being debugged terminates, @emph{all} local variables go out of scope,
4125 and so only watchpoints that watch global variables remain set. If you
4126 rerun the program, you will need to set all such watchpoints again. One
4127 way of doing that would be to set a code breakpoint at the entry to the
4128 @code{main} function and when it breaks, set all the watchpoints.
4130 @cindex watchpoints and threads
4131 @cindex threads and watchpoints
4132 In multi-threaded programs, watchpoints will detect changes to the
4133 watched expression from every thread.
4136 @emph{Warning:} In multi-threaded programs, software watchpoints
4137 have only limited usefulness. If @value{GDBN} creates a software
4138 watchpoint, it can only watch the value of an expression @emph{in a
4139 single thread}. If you are confident that the expression can only
4140 change due to the current thread's activity (and if you are also
4141 confident that no other thread can become current), then you can use
4142 software watchpoints as usual. However, @value{GDBN} may not notice
4143 when a non-current thread's activity changes the expression. (Hardware
4144 watchpoints, in contrast, watch an expression in all threads.)
4147 @xref{set remote hardware-watchpoint-limit}.
4149 @node Set Catchpoints
4150 @subsection Setting Catchpoints
4151 @cindex catchpoints, setting
4152 @cindex exception handlers
4153 @cindex event handling
4155 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4156 kinds of program events, such as C@t{++} exceptions or the loading of a
4157 shared library. Use the @code{catch} command to set a catchpoint.
4161 @item catch @var{event}
4162 Stop when @var{event} occurs. The @var{event} can be any of the following:
4165 @item throw @r{[}@var{regexp}@r{]}
4166 @itemx rethrow @r{[}@var{regexp}@r{]}
4167 @itemx catch @r{[}@var{regexp}@r{]}
4169 @kindex catch rethrow
4171 @cindex stop on C@t{++} exceptions
4172 The throwing, re-throwing, or catching of a C@t{++} exception.
4174 If @var{regexp} is given, then only exceptions whose type matches the
4175 regular expression will be caught.
4177 @vindex $_exception@r{, convenience variable}
4178 The convenience variable @code{$_exception} is available at an
4179 exception-related catchpoint, on some systems. This holds the
4180 exception being thrown.
4182 There are currently some limitations to C@t{++} exception handling in
4187 The support for these commands is system-dependent. Currently, only
4188 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4192 The regular expression feature and the @code{$_exception} convenience
4193 variable rely on the presence of some SDT probes in @code{libstdc++}.
4194 If these probes are not present, then these features cannot be used.
4195 These probes were first available in the GCC 4.8 release, but whether
4196 or not they are available in your GCC also depends on how it was
4200 The @code{$_exception} convenience variable is only valid at the
4201 instruction at which an exception-related catchpoint is set.
4204 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4205 location in the system library which implements runtime exception
4206 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4207 (@pxref{Selection}) to get to your code.
4210 If you call a function interactively, @value{GDBN} normally returns
4211 control to you when the function has finished executing. If the call
4212 raises an exception, however, the call may bypass the mechanism that
4213 returns control to you and cause your program either to abort or to
4214 simply continue running until it hits a breakpoint, catches a signal
4215 that @value{GDBN} is listening for, or exits. This is the case even if
4216 you set a catchpoint for the exception; catchpoints on exceptions are
4217 disabled within interactive calls. @xref{Calling}, for information on
4218 controlling this with @code{set unwind-on-terminating-exception}.
4221 You cannot raise an exception interactively.
4224 You cannot install an exception handler interactively.
4228 @kindex catch exception
4229 @cindex Ada exception catching
4230 @cindex catch Ada exceptions
4231 An Ada exception being raised. If an exception name is specified
4232 at the end of the command (eg @code{catch exception Program_Error}),
4233 the debugger will stop only when this specific exception is raised.
4234 Otherwise, the debugger stops execution when any Ada exception is raised.
4236 When inserting an exception catchpoint on a user-defined exception whose
4237 name is identical to one of the exceptions defined by the language, the
4238 fully qualified name must be used as the exception name. Otherwise,
4239 @value{GDBN} will assume that it should stop on the pre-defined exception
4240 rather than the user-defined one. For instance, assuming an exception
4241 called @code{Constraint_Error} is defined in package @code{Pck}, then
4242 the command to use to catch such exceptions is @kbd{catch exception
4243 Pck.Constraint_Error}.
4245 @item exception unhandled
4246 @kindex catch exception unhandled
4247 An exception that was raised but is not handled by the program.
4250 @kindex catch assert
4251 A failed Ada assertion.
4255 @cindex break on fork/exec
4256 A call to @code{exec}. This is currently only available for HP-UX
4260 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4261 @kindex catch syscall
4262 @cindex break on a system call.
4263 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4264 syscall is a mechanism for application programs to request a service
4265 from the operating system (OS) or one of the OS system services.
4266 @value{GDBN} can catch some or all of the syscalls issued by the
4267 debuggee, and show the related information for each syscall. If no
4268 argument is specified, calls to and returns from all system calls
4271 @var{name} can be any system call name that is valid for the
4272 underlying OS. Just what syscalls are valid depends on the OS. On
4273 GNU and Unix systems, you can find the full list of valid syscall
4274 names on @file{/usr/include/asm/unistd.h}.
4276 @c For MS-Windows, the syscall names and the corresponding numbers
4277 @c can be found, e.g., on this URL:
4278 @c http://www.metasploit.com/users/opcode/syscalls.html
4279 @c but we don't support Windows syscalls yet.
4281 Normally, @value{GDBN} knows in advance which syscalls are valid for
4282 each OS, so you can use the @value{GDBN} command-line completion
4283 facilities (@pxref{Completion,, command completion}) to list the
4286 You may also specify the system call numerically. A syscall's
4287 number is the value passed to the OS's syscall dispatcher to
4288 identify the requested service. When you specify the syscall by its
4289 name, @value{GDBN} uses its database of syscalls to convert the name
4290 into the corresponding numeric code, but using the number directly
4291 may be useful if @value{GDBN}'s database does not have the complete
4292 list of syscalls on your system (e.g., because @value{GDBN} lags
4293 behind the OS upgrades).
4295 The example below illustrates how this command works if you don't provide
4299 (@value{GDBP}) catch syscall
4300 Catchpoint 1 (syscall)
4302 Starting program: /tmp/catch-syscall
4304 Catchpoint 1 (call to syscall 'close'), \
4305 0xffffe424 in __kernel_vsyscall ()
4309 Catchpoint 1 (returned from syscall 'close'), \
4310 0xffffe424 in __kernel_vsyscall ()
4314 Here is an example of catching a system call by name:
4317 (@value{GDBP}) catch syscall chroot
4318 Catchpoint 1 (syscall 'chroot' [61])
4320 Starting program: /tmp/catch-syscall
4322 Catchpoint 1 (call to syscall 'chroot'), \
4323 0xffffe424 in __kernel_vsyscall ()
4327 Catchpoint 1 (returned from syscall 'chroot'), \
4328 0xffffe424 in __kernel_vsyscall ()
4332 An example of specifying a system call numerically. In the case
4333 below, the syscall number has a corresponding entry in the XML
4334 file, so @value{GDBN} finds its name and prints it:
4337 (@value{GDBP}) catch syscall 252
4338 Catchpoint 1 (syscall(s) 'exit_group')
4340 Starting program: /tmp/catch-syscall
4342 Catchpoint 1 (call to syscall 'exit_group'), \
4343 0xffffe424 in __kernel_vsyscall ()
4347 Program exited normally.
4351 However, there can be situations when there is no corresponding name
4352 in XML file for that syscall number. In this case, @value{GDBN} prints
4353 a warning message saying that it was not able to find the syscall name,
4354 but the catchpoint will be set anyway. See the example below:
4357 (@value{GDBP}) catch syscall 764
4358 warning: The number '764' does not represent a known syscall.
4359 Catchpoint 2 (syscall 764)
4363 If you configure @value{GDBN} using the @samp{--without-expat} option,
4364 it will not be able to display syscall names. Also, if your
4365 architecture does not have an XML file describing its system calls,
4366 you will not be able to see the syscall names. It is important to
4367 notice that these two features are used for accessing the syscall
4368 name database. In either case, you will see a warning like this:
4371 (@value{GDBP}) catch syscall
4372 warning: Could not open "syscalls/i386-linux.xml"
4373 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4374 GDB will not be able to display syscall names.
4375 Catchpoint 1 (syscall)
4379 Of course, the file name will change depending on your architecture and system.
4381 Still using the example above, you can also try to catch a syscall by its
4382 number. In this case, you would see something like:
4385 (@value{GDBP}) catch syscall 252
4386 Catchpoint 1 (syscall(s) 252)
4389 Again, in this case @value{GDBN} would not be able to display syscall's names.
4393 A call to @code{fork}. This is currently only available for HP-UX
4398 A call to @code{vfork}. This is currently only available for HP-UX
4401 @item load @r{[}regexp@r{]}
4402 @itemx unload @r{[}regexp@r{]}
4404 @kindex catch unload
4405 The loading or unloading of a shared library. If @var{regexp} is
4406 given, then the catchpoint will stop only if the regular expression
4407 matches one of the affected libraries.
4409 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4410 @kindex catch signal
4411 The delivery of a signal.
4413 With no arguments, this catchpoint will catch any signal that is not
4414 used internally by @value{GDBN}, specifically, all signals except
4415 @samp{SIGTRAP} and @samp{SIGINT}.
4417 With the argument @samp{all}, all signals, including those used by
4418 @value{GDBN}, will be caught. This argument cannot be used with other
4421 Otherwise, the arguments are a list of signal names as given to
4422 @code{handle} (@pxref{Signals}). Only signals specified in this list
4425 One reason that @code{catch signal} can be more useful than
4426 @code{handle} is that you can attach commands and conditions to the
4429 When a signal is caught by a catchpoint, the signal's @code{stop} and
4430 @code{print} settings, as specified by @code{handle}, are ignored.
4431 However, whether the signal is still delivered to the inferior depends
4432 on the @code{pass} setting; this can be changed in the catchpoint's
4437 @item tcatch @var{event}
4439 Set a catchpoint that is enabled only for one stop. The catchpoint is
4440 automatically deleted after the first time the event is caught.
4444 Use the @code{info break} command to list the current catchpoints.
4448 @subsection Deleting Breakpoints
4450 @cindex clearing breakpoints, watchpoints, catchpoints
4451 @cindex deleting breakpoints, watchpoints, catchpoints
4452 It is often necessary to eliminate a breakpoint, watchpoint, or
4453 catchpoint once it has done its job and you no longer want your program
4454 to stop there. This is called @dfn{deleting} the breakpoint. A
4455 breakpoint that has been deleted no longer exists; it is forgotten.
4457 With the @code{clear} command you can delete breakpoints according to
4458 where they are in your program. With the @code{delete} command you can
4459 delete individual breakpoints, watchpoints, or catchpoints by specifying
4460 their breakpoint numbers.
4462 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4463 automatically ignores breakpoints on the first instruction to be executed
4464 when you continue execution without changing the execution address.
4469 Delete any breakpoints at the next instruction to be executed in the
4470 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4471 the innermost frame is selected, this is a good way to delete a
4472 breakpoint where your program just stopped.
4474 @item clear @var{location}
4475 Delete any breakpoints set at the specified @var{location}.
4476 @xref{Specify Location}, for the various forms of @var{location}; the
4477 most useful ones are listed below:
4480 @item clear @var{function}
4481 @itemx clear @var{filename}:@var{function}
4482 Delete any breakpoints set at entry to the named @var{function}.
4484 @item clear @var{linenum}
4485 @itemx clear @var{filename}:@var{linenum}
4486 Delete any breakpoints set at or within the code of the specified
4487 @var{linenum} of the specified @var{filename}.
4490 @cindex delete breakpoints
4492 @kindex d @r{(@code{delete})}
4493 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4494 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4495 ranges specified as arguments. If no argument is specified, delete all
4496 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4497 confirm off}). You can abbreviate this command as @code{d}.
4501 @subsection Disabling Breakpoints
4503 @cindex enable/disable a breakpoint
4504 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4505 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4506 it had been deleted, but remembers the information on the breakpoint so
4507 that you can @dfn{enable} it again later.
4509 You disable and enable breakpoints, watchpoints, and catchpoints with
4510 the @code{enable} and @code{disable} commands, optionally specifying
4511 one or more breakpoint numbers as arguments. Use @code{info break} to
4512 print a list of all breakpoints, watchpoints, and catchpoints if you
4513 do not know which numbers to use.
4515 Disabling and enabling a breakpoint that has multiple locations
4516 affects all of its locations.
4518 A breakpoint, watchpoint, or catchpoint can have any of several
4519 different states of enablement:
4523 Enabled. The breakpoint stops your program. A breakpoint set
4524 with the @code{break} command starts out in this state.
4526 Disabled. The breakpoint has no effect on your program.
4528 Enabled once. The breakpoint stops your program, but then becomes
4531 Enabled for a count. The breakpoint stops your program for the next
4532 N times, then becomes disabled.
4534 Enabled for deletion. The breakpoint stops your program, but
4535 immediately after it does so it is deleted permanently. A breakpoint
4536 set with the @code{tbreak} command starts out in this state.
4539 You can use the following commands to enable or disable breakpoints,
4540 watchpoints, and catchpoints:
4544 @kindex dis @r{(@code{disable})}
4545 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4546 Disable the specified breakpoints---or all breakpoints, if none are
4547 listed. A disabled breakpoint has no effect but is not forgotten. All
4548 options such as ignore-counts, conditions and commands are remembered in
4549 case the breakpoint is enabled again later. You may abbreviate
4550 @code{disable} as @code{dis}.
4553 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4554 Enable the specified breakpoints (or all defined breakpoints). They
4555 become effective once again in stopping your program.
4557 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4558 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4559 of these breakpoints immediately after stopping your program.
4561 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4562 Enable the specified breakpoints temporarily. @value{GDBN} records
4563 @var{count} with each of the specified breakpoints, and decrements a
4564 breakpoint's count when it is hit. When any count reaches 0,
4565 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4566 count (@pxref{Conditions, ,Break Conditions}), that will be
4567 decremented to 0 before @var{count} is affected.
4569 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4570 Enable the specified breakpoints to work once, then die. @value{GDBN}
4571 deletes any of these breakpoints as soon as your program stops there.
4572 Breakpoints set by the @code{tbreak} command start out in this state.
4575 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4576 @c confusing: tbreak is also initially enabled.
4577 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4578 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4579 subsequently, they become disabled or enabled only when you use one of
4580 the commands above. (The command @code{until} can set and delete a
4581 breakpoint of its own, but it does not change the state of your other
4582 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4586 @subsection Break Conditions
4587 @cindex conditional breakpoints
4588 @cindex breakpoint conditions
4590 @c FIXME what is scope of break condition expr? Context where wanted?
4591 @c in particular for a watchpoint?
4592 The simplest sort of breakpoint breaks every time your program reaches a
4593 specified place. You can also specify a @dfn{condition} for a
4594 breakpoint. A condition is just a Boolean expression in your
4595 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4596 a condition evaluates the expression each time your program reaches it,
4597 and your program stops only if the condition is @emph{true}.
4599 This is the converse of using assertions for program validation; in that
4600 situation, you want to stop when the assertion is violated---that is,
4601 when the condition is false. In C, if you want to test an assertion expressed
4602 by the condition @var{assert}, you should set the condition
4603 @samp{! @var{assert}} on the appropriate breakpoint.
4605 Conditions are also accepted for watchpoints; you may not need them,
4606 since a watchpoint is inspecting the value of an expression anyhow---but
4607 it might be simpler, say, to just set a watchpoint on a variable name,
4608 and specify a condition that tests whether the new value is an interesting
4611 Break conditions can have side effects, and may even call functions in
4612 your program. This can be useful, for example, to activate functions
4613 that log program progress, or to use your own print functions to
4614 format special data structures. The effects are completely predictable
4615 unless there is another enabled breakpoint at the same address. (In
4616 that case, @value{GDBN} might see the other breakpoint first and stop your
4617 program without checking the condition of this one.) Note that
4618 breakpoint commands are usually more convenient and flexible than break
4620 purpose of performing side effects when a breakpoint is reached
4621 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4623 Breakpoint conditions can also be evaluated on the target's side if
4624 the target supports it. Instead of evaluating the conditions locally,
4625 @value{GDBN} encodes the expression into an agent expression
4626 (@pxref{Agent Expressions}) suitable for execution on the target,
4627 independently of @value{GDBN}. Global variables become raw memory
4628 locations, locals become stack accesses, and so forth.
4630 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4631 when its condition evaluates to true. This mechanism may provide faster
4632 response times depending on the performance characteristics of the target
4633 since it does not need to keep @value{GDBN} informed about
4634 every breakpoint trigger, even those with false conditions.
4636 Break conditions can be specified when a breakpoint is set, by using
4637 @samp{if} in the arguments to the @code{break} command. @xref{Set
4638 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4639 with the @code{condition} command.
4641 You can also use the @code{if} keyword with the @code{watch} command.
4642 The @code{catch} command does not recognize the @code{if} keyword;
4643 @code{condition} is the only way to impose a further condition on a
4648 @item condition @var{bnum} @var{expression}
4649 Specify @var{expression} as the break condition for breakpoint,
4650 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4651 breakpoint @var{bnum} stops your program only if the value of
4652 @var{expression} is true (nonzero, in C). When you use
4653 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4654 syntactic correctness, and to determine whether symbols in it have
4655 referents in the context of your breakpoint. If @var{expression} uses
4656 symbols not referenced in the context of the breakpoint, @value{GDBN}
4657 prints an error message:
4660 No symbol "foo" in current context.
4665 not actually evaluate @var{expression} at the time the @code{condition}
4666 command (or a command that sets a breakpoint with a condition, like
4667 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4669 @item condition @var{bnum}
4670 Remove the condition from breakpoint number @var{bnum}. It becomes
4671 an ordinary unconditional breakpoint.
4674 @cindex ignore count (of breakpoint)
4675 A special case of a breakpoint condition is to stop only when the
4676 breakpoint has been reached a certain number of times. This is so
4677 useful that there is a special way to do it, using the @dfn{ignore
4678 count} of the breakpoint. Every breakpoint has an ignore count, which
4679 is an integer. Most of the time, the ignore count is zero, and
4680 therefore has no effect. But if your program reaches a breakpoint whose
4681 ignore count is positive, then instead of stopping, it just decrements
4682 the ignore count by one and continues. As a result, if the ignore count
4683 value is @var{n}, the breakpoint does not stop the next @var{n} times
4684 your program reaches it.
4688 @item ignore @var{bnum} @var{count}
4689 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4690 The next @var{count} times the breakpoint is reached, your program's
4691 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4694 To make the breakpoint stop the next time it is reached, specify
4697 When you use @code{continue} to resume execution of your program from a
4698 breakpoint, you can specify an ignore count directly as an argument to
4699 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4700 Stepping,,Continuing and Stepping}.
4702 If a breakpoint has a positive ignore count and a condition, the
4703 condition is not checked. Once the ignore count reaches zero,
4704 @value{GDBN} resumes checking the condition.
4706 You could achieve the effect of the ignore count with a condition such
4707 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4708 is decremented each time. @xref{Convenience Vars, ,Convenience
4712 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4715 @node Break Commands
4716 @subsection Breakpoint Command Lists
4718 @cindex breakpoint commands
4719 You can give any breakpoint (or watchpoint or catchpoint) a series of
4720 commands to execute when your program stops due to that breakpoint. For
4721 example, you might want to print the values of certain expressions, or
4722 enable other breakpoints.
4726 @kindex end@r{ (breakpoint commands)}
4727 @item commands @r{[}@var{range}@dots{}@r{]}
4728 @itemx @dots{} @var{command-list} @dots{}
4730 Specify a list of commands for the given breakpoints. The commands
4731 themselves appear on the following lines. Type a line containing just
4732 @code{end} to terminate the commands.
4734 To remove all commands from a breakpoint, type @code{commands} and
4735 follow it immediately with @code{end}; that is, give no commands.
4737 With no argument, @code{commands} refers to the last breakpoint,
4738 watchpoint, or catchpoint set (not to the breakpoint most recently
4739 encountered). If the most recent breakpoints were set with a single
4740 command, then the @code{commands} will apply to all the breakpoints
4741 set by that command. This applies to breakpoints set by
4742 @code{rbreak}, and also applies when a single @code{break} command
4743 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4747 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4748 disabled within a @var{command-list}.
4750 You can use breakpoint commands to start your program up again. Simply
4751 use the @code{continue} command, or @code{step}, or any other command
4752 that resumes execution.
4754 Any other commands in the command list, after a command that resumes
4755 execution, are ignored. This is because any time you resume execution
4756 (even with a simple @code{next} or @code{step}), you may encounter
4757 another breakpoint---which could have its own command list, leading to
4758 ambiguities about which list to execute.
4761 If the first command you specify in a command list is @code{silent}, the
4762 usual message about stopping at a breakpoint is not printed. This may
4763 be desirable for breakpoints that are to print a specific message and
4764 then continue. If none of the remaining commands print anything, you
4765 see no sign that the breakpoint was reached. @code{silent} is
4766 meaningful only at the beginning of a breakpoint command list.
4768 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4769 print precisely controlled output, and are often useful in silent
4770 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4772 For example, here is how you could use breakpoint commands to print the
4773 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4779 printf "x is %d\n",x
4784 One application for breakpoint commands is to compensate for one bug so
4785 you can test for another. Put a breakpoint just after the erroneous line
4786 of code, give it a condition to detect the case in which something
4787 erroneous has been done, and give it commands to assign correct values
4788 to any variables that need them. End with the @code{continue} command
4789 so that your program does not stop, and start with the @code{silent}
4790 command so that no output is produced. Here is an example:
4801 @node Dynamic Printf
4802 @subsection Dynamic Printf
4804 @cindex dynamic printf
4806 The dynamic printf command @code{dprintf} combines a breakpoint with
4807 formatted printing of your program's data to give you the effect of
4808 inserting @code{printf} calls into your program on-the-fly, without
4809 having to recompile it.
4811 In its most basic form, the output goes to the GDB console. However,
4812 you can set the variable @code{dprintf-style} for alternate handling.
4813 For instance, you can ask to format the output by calling your
4814 program's @code{printf} function. This has the advantage that the
4815 characters go to the program's output device, so they can recorded in
4816 redirects to files and so forth.
4818 If you are doing remote debugging with a stub or agent, you can also
4819 ask to have the printf handled by the remote agent. In addition to
4820 ensuring that the output goes to the remote program's device along
4821 with any other output the program might produce, you can also ask that
4822 the dprintf remain active even after disconnecting from the remote
4823 target. Using the stub/agent is also more efficient, as it can do
4824 everything without needing to communicate with @value{GDBN}.
4828 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4829 Whenever execution reaches @var{location}, print the values of one or
4830 more @var{expressions} under the control of the string @var{template}.
4831 To print several values, separate them with commas.
4833 @item set dprintf-style @var{style}
4834 Set the dprintf output to be handled in one of several different
4835 styles enumerated below. A change of style affects all existing
4836 dynamic printfs immediately. (If you need individual control over the
4837 print commands, simply define normal breakpoints with
4838 explicitly-supplied command lists.)
4841 @kindex dprintf-style gdb
4842 Handle the output using the @value{GDBN} @code{printf} command.
4845 @kindex dprintf-style call
4846 Handle the output by calling a function in your program (normally
4850 @kindex dprintf-style agent
4851 Have the remote debugging agent (such as @code{gdbserver}) handle
4852 the output itself. This style is only available for agents that
4853 support running commands on the target.
4855 @item set dprintf-function @var{function}
4856 Set the function to call if the dprintf style is @code{call}. By
4857 default its value is @code{printf}. You may set it to any expression.
4858 that @value{GDBN} can evaluate to a function, as per the @code{call}
4861 @item set dprintf-channel @var{channel}
4862 Set a ``channel'' for dprintf. If set to a non-empty value,
4863 @value{GDBN} will evaluate it as an expression and pass the result as
4864 a first argument to the @code{dprintf-function}, in the manner of
4865 @code{fprintf} and similar functions. Otherwise, the dprintf format
4866 string will be the first argument, in the manner of @code{printf}.
4868 As an example, if you wanted @code{dprintf} output to go to a logfile
4869 that is a standard I/O stream assigned to the variable @code{mylog},
4870 you could do the following:
4873 (gdb) set dprintf-style call
4874 (gdb) set dprintf-function fprintf
4875 (gdb) set dprintf-channel mylog
4876 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4877 Dprintf 1 at 0x123456: file main.c, line 25.
4879 1 dprintf keep y 0x00123456 in main at main.c:25
4880 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4885 Note that the @code{info break} displays the dynamic printf commands
4886 as normal breakpoint commands; you can thus easily see the effect of
4887 the variable settings.
4889 @item set disconnected-dprintf on
4890 @itemx set disconnected-dprintf off
4891 @kindex set disconnected-dprintf
4892 Choose whether @code{dprintf} commands should continue to run if
4893 @value{GDBN} has disconnected from the target. This only applies
4894 if the @code{dprintf-style} is @code{agent}.
4896 @item show disconnected-dprintf off
4897 @kindex show disconnected-dprintf
4898 Show the current choice for disconnected @code{dprintf}.
4902 @value{GDBN} does not check the validity of function and channel,
4903 relying on you to supply values that are meaningful for the contexts
4904 in which they are being used. For instance, the function and channel
4905 may be the values of local variables, but if that is the case, then
4906 all enabled dynamic prints must be at locations within the scope of
4907 those locals. If evaluation fails, @value{GDBN} will report an error.
4909 @node Save Breakpoints
4910 @subsection How to save breakpoints to a file
4912 To save breakpoint definitions to a file use the @w{@code{save
4913 breakpoints}} command.
4916 @kindex save breakpoints
4917 @cindex save breakpoints to a file for future sessions
4918 @item save breakpoints [@var{filename}]
4919 This command saves all current breakpoint definitions together with
4920 their commands and ignore counts, into a file @file{@var{filename}}
4921 suitable for use in a later debugging session. This includes all
4922 types of breakpoints (breakpoints, watchpoints, catchpoints,
4923 tracepoints). To read the saved breakpoint definitions, use the
4924 @code{source} command (@pxref{Command Files}). Note that watchpoints
4925 with expressions involving local variables may fail to be recreated
4926 because it may not be possible to access the context where the
4927 watchpoint is valid anymore. Because the saved breakpoint definitions
4928 are simply a sequence of @value{GDBN} commands that recreate the
4929 breakpoints, you can edit the file in your favorite editing program,
4930 and remove the breakpoint definitions you're not interested in, or
4931 that can no longer be recreated.
4934 @node Static Probe Points
4935 @subsection Static Probe Points
4937 @cindex static probe point, SystemTap
4938 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4939 for Statically Defined Tracing, and the probes are designed to have a tiny
4940 runtime code and data footprint, and no dynamic relocations. They are
4941 usable from assembly, C and C@t{++} languages. See
4942 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4943 for a good reference on how the @acronym{SDT} probes are implemented.
4945 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4946 @acronym{SDT} probes are supported on ELF-compatible systems. See
4947 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4948 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4949 in your applications.
4951 @cindex semaphores on static probe points
4952 Some probes have an associated semaphore variable; for instance, this
4953 happens automatically if you defined your probe using a DTrace-style
4954 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4955 automatically enable it when you specify a breakpoint using the
4956 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4957 location by some other method (e.g., @code{break file:line}), then
4958 @value{GDBN} will not automatically set the semaphore.
4960 You can examine the available static static probes using @code{info
4961 probes}, with optional arguments:
4965 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4966 If given, @var{provider} is a regular expression used to match against provider
4967 names when selecting which probes to list. If omitted, probes by all
4968 probes from all providers are listed.
4970 If given, @var{name} is a regular expression to match against probe names
4971 when selecting which probes to list. If omitted, probe names are not
4972 considered when deciding whether to display them.
4974 If given, @var{objfile} is a regular expression used to select which
4975 object files (executable or shared libraries) to examine. If not
4976 given, all object files are considered.
4978 @item info probes all
4979 List the available static probes, from all types.
4982 @vindex $_probe_arg@r{, convenience variable}
4983 A probe may specify up to twelve arguments. These are available at the
4984 point at which the probe is defined---that is, when the current PC is
4985 at the probe's location. The arguments are available using the
4986 convenience variables (@pxref{Convenience Vars})
4987 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4988 an integer of the appropriate size; types are not preserved. The
4989 convenience variable @code{$_probe_argc} holds the number of arguments
4990 at the current probe point.
4992 These variables are always available, but attempts to access them at
4993 any location other than a probe point will cause @value{GDBN} to give
4997 @c @ifclear BARETARGET
4998 @node Error in Breakpoints
4999 @subsection ``Cannot insert breakpoints''
5001 If you request too many active hardware-assisted breakpoints and
5002 watchpoints, you will see this error message:
5004 @c FIXME: the precise wording of this message may change; the relevant
5005 @c source change is not committed yet (Sep 3, 1999).
5007 Stopped; cannot insert breakpoints.
5008 You may have requested too many hardware breakpoints and watchpoints.
5012 This message is printed when you attempt to resume the program, since
5013 only then @value{GDBN} knows exactly how many hardware breakpoints and
5014 watchpoints it needs to insert.
5016 When this message is printed, you need to disable or remove some of the
5017 hardware-assisted breakpoints and watchpoints, and then continue.
5019 @node Breakpoint-related Warnings
5020 @subsection ``Breakpoint address adjusted...''
5021 @cindex breakpoint address adjusted
5023 Some processor architectures place constraints on the addresses at
5024 which breakpoints may be placed. For architectures thus constrained,
5025 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5026 with the constraints dictated by the architecture.
5028 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5029 a VLIW architecture in which a number of RISC-like instructions may be
5030 bundled together for parallel execution. The FR-V architecture
5031 constrains the location of a breakpoint instruction within such a
5032 bundle to the instruction with the lowest address. @value{GDBN}
5033 honors this constraint by adjusting a breakpoint's address to the
5034 first in the bundle.
5036 It is not uncommon for optimized code to have bundles which contain
5037 instructions from different source statements, thus it may happen that
5038 a breakpoint's address will be adjusted from one source statement to
5039 another. Since this adjustment may significantly alter @value{GDBN}'s
5040 breakpoint related behavior from what the user expects, a warning is
5041 printed when the breakpoint is first set and also when the breakpoint
5044 A warning like the one below is printed when setting a breakpoint
5045 that's been subject to address adjustment:
5048 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5051 Such warnings are printed both for user settable and @value{GDBN}'s
5052 internal breakpoints. If you see one of these warnings, you should
5053 verify that a breakpoint set at the adjusted address will have the
5054 desired affect. If not, the breakpoint in question may be removed and
5055 other breakpoints may be set which will have the desired behavior.
5056 E.g., it may be sufficient to place the breakpoint at a later
5057 instruction. A conditional breakpoint may also be useful in some
5058 cases to prevent the breakpoint from triggering too often.
5060 @value{GDBN} will also issue a warning when stopping at one of these
5061 adjusted breakpoints:
5064 warning: Breakpoint 1 address previously adjusted from 0x00010414
5068 When this warning is encountered, it may be too late to take remedial
5069 action except in cases where the breakpoint is hit earlier or more
5070 frequently than expected.
5072 @node Continuing and Stepping
5073 @section Continuing and Stepping
5077 @cindex resuming execution
5078 @dfn{Continuing} means resuming program execution until your program
5079 completes normally. In contrast, @dfn{stepping} means executing just
5080 one more ``step'' of your program, where ``step'' may mean either one
5081 line of source code, or one machine instruction (depending on what
5082 particular command you use). Either when continuing or when stepping,
5083 your program may stop even sooner, due to a breakpoint or a signal. (If
5084 it stops due to a signal, you may want to use @code{handle}, or use
5085 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5086 or you may step into the signal's handler (@pxref{stepping and signal
5091 @kindex c @r{(@code{continue})}
5092 @kindex fg @r{(resume foreground execution)}
5093 @item continue @r{[}@var{ignore-count}@r{]}
5094 @itemx c @r{[}@var{ignore-count}@r{]}
5095 @itemx fg @r{[}@var{ignore-count}@r{]}
5096 Resume program execution, at the address where your program last stopped;
5097 any breakpoints set at that address are bypassed. The optional argument
5098 @var{ignore-count} allows you to specify a further number of times to
5099 ignore a breakpoint at this location; its effect is like that of
5100 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5102 The argument @var{ignore-count} is meaningful only when your program
5103 stopped due to a breakpoint. At other times, the argument to
5104 @code{continue} is ignored.
5106 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5107 debugged program is deemed to be the foreground program) are provided
5108 purely for convenience, and have exactly the same behavior as
5112 To resume execution at a different place, you can use @code{return}
5113 (@pxref{Returning, ,Returning from a Function}) to go back to the
5114 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5115 Different Address}) to go to an arbitrary location in your program.
5117 A typical technique for using stepping is to set a breakpoint
5118 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5119 beginning of the function or the section of your program where a problem
5120 is believed to lie, run your program until it stops at that breakpoint,
5121 and then step through the suspect area, examining the variables that are
5122 interesting, until you see the problem happen.
5126 @kindex s @r{(@code{step})}
5128 Continue running your program until control reaches a different source
5129 line, then stop it and return control to @value{GDBN}. This command is
5130 abbreviated @code{s}.
5133 @c "without debugging information" is imprecise; actually "without line
5134 @c numbers in the debugging information". (gcc -g1 has debugging info but
5135 @c not line numbers). But it seems complex to try to make that
5136 @c distinction here.
5137 @emph{Warning:} If you use the @code{step} command while control is
5138 within a function that was compiled without debugging information,
5139 execution proceeds until control reaches a function that does have
5140 debugging information. Likewise, it will not step into a function which
5141 is compiled without debugging information. To step through functions
5142 without debugging information, use the @code{stepi} command, described
5146 The @code{step} command only stops at the first instruction of a source
5147 line. This prevents the multiple stops that could otherwise occur in
5148 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5149 to stop if a function that has debugging information is called within
5150 the line. In other words, @code{step} @emph{steps inside} any functions
5151 called within the line.
5153 Also, the @code{step} command only enters a function if there is line
5154 number information for the function. Otherwise it acts like the
5155 @code{next} command. This avoids problems when using @code{cc -gl}
5156 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5157 was any debugging information about the routine.
5159 @item step @var{count}
5160 Continue running as in @code{step}, but do so @var{count} times. If a
5161 breakpoint is reached, or a signal not related to stepping occurs before
5162 @var{count} steps, stepping stops right away.
5165 @kindex n @r{(@code{next})}
5166 @item next @r{[}@var{count}@r{]}
5167 Continue to the next source line in the current (innermost) stack frame.
5168 This is similar to @code{step}, but function calls that appear within
5169 the line of code are executed without stopping. Execution stops when
5170 control reaches a different line of code at the original stack level
5171 that was executing when you gave the @code{next} command. This command
5172 is abbreviated @code{n}.
5174 An argument @var{count} is a repeat count, as for @code{step}.
5177 @c FIX ME!! Do we delete this, or is there a way it fits in with
5178 @c the following paragraph? --- Vctoria
5180 @c @code{next} within a function that lacks debugging information acts like
5181 @c @code{step}, but any function calls appearing within the code of the
5182 @c function are executed without stopping.
5184 The @code{next} command only stops at the first instruction of a
5185 source line. This prevents multiple stops that could otherwise occur in
5186 @code{switch} statements, @code{for} loops, etc.
5188 @kindex set step-mode
5190 @cindex functions without line info, and stepping
5191 @cindex stepping into functions with no line info
5192 @itemx set step-mode on
5193 The @code{set step-mode on} command causes the @code{step} command to
5194 stop at the first instruction of a function which contains no debug line
5195 information rather than stepping over it.
5197 This is useful in cases where you may be interested in inspecting the
5198 machine instructions of a function which has no symbolic info and do not
5199 want @value{GDBN} to automatically skip over this function.
5201 @item set step-mode off
5202 Causes the @code{step} command to step over any functions which contains no
5203 debug information. This is the default.
5205 @item show step-mode
5206 Show whether @value{GDBN} will stop in or step over functions without
5207 source line debug information.
5210 @kindex fin @r{(@code{finish})}
5212 Continue running until just after function in the selected stack frame
5213 returns. Print the returned value (if any). This command can be
5214 abbreviated as @code{fin}.
5216 Contrast this with the @code{return} command (@pxref{Returning,
5217 ,Returning from a Function}).
5220 @kindex u @r{(@code{until})}
5221 @cindex run until specified location
5224 Continue running until a source line past the current line, in the
5225 current stack frame, is reached. This command is used to avoid single
5226 stepping through a loop more than once. It is like the @code{next}
5227 command, except that when @code{until} encounters a jump, it
5228 automatically continues execution until the program counter is greater
5229 than the address of the jump.
5231 This means that when you reach the end of a loop after single stepping
5232 though it, @code{until} makes your program continue execution until it
5233 exits the loop. In contrast, a @code{next} command at the end of a loop
5234 simply steps back to the beginning of the loop, which forces you to step
5235 through the next iteration.
5237 @code{until} always stops your program if it attempts to exit the current
5240 @code{until} may produce somewhat counterintuitive results if the order
5241 of machine code does not match the order of the source lines. For
5242 example, in the following excerpt from a debugging session, the @code{f}
5243 (@code{frame}) command shows that execution is stopped at line
5244 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5248 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5250 (@value{GDBP}) until
5251 195 for ( ; argc > 0; NEXTARG) @{
5254 This happened because, for execution efficiency, the compiler had
5255 generated code for the loop closure test at the end, rather than the
5256 start, of the loop---even though the test in a C @code{for}-loop is
5257 written before the body of the loop. The @code{until} command appeared
5258 to step back to the beginning of the loop when it advanced to this
5259 expression; however, it has not really gone to an earlier
5260 statement---not in terms of the actual machine code.
5262 @code{until} with no argument works by means of single
5263 instruction stepping, and hence is slower than @code{until} with an
5266 @item until @var{location}
5267 @itemx u @var{location}
5268 Continue running your program until either the specified @var{location} is
5269 reached, or the current stack frame returns. The location is any of
5270 the forms described in @ref{Specify Location}.
5271 This form of the command uses temporary breakpoints, and
5272 hence is quicker than @code{until} without an argument. The specified
5273 location is actually reached only if it is in the current frame. This
5274 implies that @code{until} can be used to skip over recursive function
5275 invocations. For instance in the code below, if the current location is
5276 line @code{96}, issuing @code{until 99} will execute the program up to
5277 line @code{99} in the same invocation of factorial, i.e., after the inner
5278 invocations have returned.
5281 94 int factorial (int value)
5283 96 if (value > 1) @{
5284 97 value *= factorial (value - 1);
5291 @kindex advance @var{location}
5292 @item advance @var{location}
5293 Continue running the program up to the given @var{location}. An argument is
5294 required, which should be of one of the forms described in
5295 @ref{Specify Location}.
5296 Execution will also stop upon exit from the current stack
5297 frame. This command is similar to @code{until}, but @code{advance} will
5298 not skip over recursive function calls, and the target location doesn't
5299 have to be in the same frame as the current one.
5303 @kindex si @r{(@code{stepi})}
5305 @itemx stepi @var{arg}
5307 Execute one machine instruction, then stop and return to the debugger.
5309 It is often useful to do @samp{display/i $pc} when stepping by machine
5310 instructions. This makes @value{GDBN} automatically display the next
5311 instruction to be executed, each time your program stops. @xref{Auto
5312 Display,, Automatic Display}.
5314 An argument is a repeat count, as in @code{step}.
5318 @kindex ni @r{(@code{nexti})}
5320 @itemx nexti @var{arg}
5322 Execute one machine instruction, but if it is a function call,
5323 proceed until the function returns.
5325 An argument is a repeat count, as in @code{next}.
5329 @anchor{range stepping}
5330 @cindex range stepping
5331 @cindex target-assisted range stepping
5332 By default, and if available, @value{GDBN} makes use of
5333 target-assisted @dfn{range stepping}. In other words, whenever you
5334 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5335 tells the target to step the corresponding range of instruction
5336 addresses instead of issuing multiple single-steps. This speeds up
5337 line stepping, particularly for remote targets. Ideally, there should
5338 be no reason you would want to turn range stepping off. However, it's
5339 possible that a bug in the debug info, a bug in the remote stub (for
5340 remote targets), or even a bug in @value{GDBN} could make line
5341 stepping behave incorrectly when target-assisted range stepping is
5342 enabled. You can use the following command to turn off range stepping
5346 @kindex set range-stepping
5347 @kindex show range-stepping
5348 @item set range-stepping
5349 @itemx show range-stepping
5350 Control whether range stepping is enabled.
5352 If @code{on}, and the target supports it, @value{GDBN} tells the
5353 target to step a range of addresses itself, instead of issuing
5354 multiple single-steps. If @code{off}, @value{GDBN} always issues
5355 single-steps, even if range stepping is supported by the target. The
5356 default is @code{on}.
5360 @node Skipping Over Functions and Files
5361 @section Skipping Over Functions and Files
5362 @cindex skipping over functions and files
5364 The program you are debugging may contain some functions which are
5365 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5366 skip a function or all functions in a file when stepping.
5368 For example, consider the following C function:
5379 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5380 are not interested in stepping through @code{boring}. If you run @code{step}
5381 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5382 step over both @code{foo} and @code{boring}!
5384 One solution is to @code{step} into @code{boring} and use the @code{finish}
5385 command to immediately exit it. But this can become tedious if @code{boring}
5386 is called from many places.
5388 A more flexible solution is to execute @kbd{skip boring}. This instructs
5389 @value{GDBN} never to step into @code{boring}. Now when you execute
5390 @code{step} at line 103, you'll step over @code{boring} and directly into
5393 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5394 example, @code{skip file boring.c}.
5397 @kindex skip function
5398 @item skip @r{[}@var{linespec}@r{]}
5399 @itemx skip function @r{[}@var{linespec}@r{]}
5400 After running this command, the function named by @var{linespec} or the
5401 function containing the line named by @var{linespec} will be skipped over when
5402 stepping. @xref{Specify Location}.
5404 If you do not specify @var{linespec}, the function you're currently debugging
5407 (If you have a function called @code{file} that you want to skip, use
5408 @kbd{skip function file}.)
5411 @item skip file @r{[}@var{filename}@r{]}
5412 After running this command, any function whose source lives in @var{filename}
5413 will be skipped over when stepping.
5415 If you do not specify @var{filename}, functions whose source lives in the file
5416 you're currently debugging will be skipped.
5419 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5420 These are the commands for managing your list of skips:
5424 @item info skip @r{[}@var{range}@r{]}
5425 Print details about the specified skip(s). If @var{range} is not specified,
5426 print a table with details about all functions and files marked for skipping.
5427 @code{info skip} prints the following information about each skip:
5431 A number identifying this skip.
5433 The type of this skip, either @samp{function} or @samp{file}.
5434 @item Enabled or Disabled
5435 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5437 For function skips, this column indicates the address in memory of the function
5438 being skipped. If you've set a function skip on a function which has not yet
5439 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5440 which has the function is loaded, @code{info skip} will show the function's
5443 For file skips, this field contains the filename being skipped. For functions
5444 skips, this field contains the function name and its line number in the file
5445 where it is defined.
5449 @item skip delete @r{[}@var{range}@r{]}
5450 Delete the specified skip(s). If @var{range} is not specified, delete all
5454 @item skip enable @r{[}@var{range}@r{]}
5455 Enable the specified skip(s). If @var{range} is not specified, enable all
5458 @kindex skip disable
5459 @item skip disable @r{[}@var{range}@r{]}
5460 Disable the specified skip(s). If @var{range} is not specified, disable all
5469 A signal is an asynchronous event that can happen in a program. The
5470 operating system defines the possible kinds of signals, and gives each
5471 kind a name and a number. For example, in Unix @code{SIGINT} is the
5472 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5473 @code{SIGSEGV} is the signal a program gets from referencing a place in
5474 memory far away from all the areas in use; @code{SIGALRM} occurs when
5475 the alarm clock timer goes off (which happens only if your program has
5476 requested an alarm).
5478 @cindex fatal signals
5479 Some signals, including @code{SIGALRM}, are a normal part of the
5480 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5481 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5482 program has not specified in advance some other way to handle the signal.
5483 @code{SIGINT} does not indicate an error in your program, but it is normally
5484 fatal so it can carry out the purpose of the interrupt: to kill the program.
5486 @value{GDBN} has the ability to detect any occurrence of a signal in your
5487 program. You can tell @value{GDBN} in advance what to do for each kind of
5490 @cindex handling signals
5491 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5492 @code{SIGALRM} be silently passed to your program
5493 (so as not to interfere with their role in the program's functioning)
5494 but to stop your program immediately whenever an error signal happens.
5495 You can change these settings with the @code{handle} command.
5498 @kindex info signals
5502 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5503 handle each one. You can use this to see the signal numbers of all
5504 the defined types of signals.
5506 @item info signals @var{sig}
5507 Similar, but print information only about the specified signal number.
5509 @code{info handle} is an alias for @code{info signals}.
5511 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5512 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5513 for details about this command.
5516 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5517 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5518 can be the number of a signal or its name (with or without the
5519 @samp{SIG} at the beginning); a list of signal numbers of the form
5520 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5521 known signals. Optional arguments @var{keywords}, described below,
5522 say what change to make.
5526 The keywords allowed by the @code{handle} command can be abbreviated.
5527 Their full names are:
5531 @value{GDBN} should not stop your program when this signal happens. It may
5532 still print a message telling you that the signal has come in.
5535 @value{GDBN} should stop your program when this signal happens. This implies
5536 the @code{print} keyword as well.
5539 @value{GDBN} should print a message when this signal happens.
5542 @value{GDBN} should not mention the occurrence of the signal at all. This
5543 implies the @code{nostop} keyword as well.
5547 @value{GDBN} should allow your program to see this signal; your program
5548 can handle the signal, or else it may terminate if the signal is fatal
5549 and not handled. @code{pass} and @code{noignore} are synonyms.
5553 @value{GDBN} should not allow your program to see this signal.
5554 @code{nopass} and @code{ignore} are synonyms.
5558 When a signal stops your program, the signal is not visible to the
5560 continue. Your program sees the signal then, if @code{pass} is in
5561 effect for the signal in question @emph{at that time}. In other words,
5562 after @value{GDBN} reports a signal, you can use the @code{handle}
5563 command with @code{pass} or @code{nopass} to control whether your
5564 program sees that signal when you continue.
5566 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5567 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5568 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5571 You can also use the @code{signal} command to prevent your program from
5572 seeing a signal, or cause it to see a signal it normally would not see,
5573 or to give it any signal at any time. For example, if your program stopped
5574 due to some sort of memory reference error, you might store correct
5575 values into the erroneous variables and continue, hoping to see more
5576 execution; but your program would probably terminate immediately as
5577 a result of the fatal signal once it saw the signal. To prevent this,
5578 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5581 @cindex stepping and signal handlers
5582 @anchor{stepping and signal handlers}
5584 @value{GDBN} optimizes for stepping the mainline code. If a signal
5585 that has @code{handle nostop} and @code{handle pass} set arrives while
5586 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5587 in progress, @value{GDBN} lets the signal handler run and then resumes
5588 stepping the mainline code once the signal handler returns. In other
5589 words, @value{GDBN} steps over the signal handler. This prevents
5590 signals that you've specified as not interesting (with @code{handle
5591 nostop}) from changing the focus of debugging unexpectedly. Note that
5592 the signal handler itself may still hit a breakpoint, stop for another
5593 signal that has @code{handle stop} in effect, or for any other event
5594 that normally results in stopping the stepping command sooner. Also
5595 note that @value{GDBN} still informs you that the program received a
5596 signal if @code{handle print} is set.
5598 @anchor{stepping into signal handlers}
5600 If you set @code{handle pass} for a signal, and your program sets up a
5601 handler for it, then issuing a stepping command, such as @code{step}
5602 or @code{stepi}, when your program is stopped due to the signal will
5603 step @emph{into} the signal handler (if the target supports that).
5605 Likewise, if you use the @code{queue-signal} command to queue a signal
5606 to be delivered to the current thread when execution of the thread
5607 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5608 stepping command will step into the signal handler.
5610 Here's an example, using @code{stepi} to step to the first instruction
5611 of @code{SIGUSR1}'s handler:
5614 (@value{GDBP}) handle SIGUSR1
5615 Signal Stop Print Pass to program Description
5616 SIGUSR1 Yes Yes Yes User defined signal 1
5620 Program received signal SIGUSR1, User defined signal 1.
5621 main () sigusr1.c:28
5624 sigusr1_handler () at sigusr1.c:9
5628 The same, but using @code{queue-signal} instead of waiting for the
5629 program to receive the signal first:
5634 (@value{GDBP}) queue-signal SIGUSR1
5636 sigusr1_handler () at sigusr1.c:9
5641 @cindex extra signal information
5642 @anchor{extra signal information}
5644 On some targets, @value{GDBN} can inspect extra signal information
5645 associated with the intercepted signal, before it is actually
5646 delivered to the program being debugged. This information is exported
5647 by the convenience variable @code{$_siginfo}, and consists of data
5648 that is passed by the kernel to the signal handler at the time of the
5649 receipt of a signal. The data type of the information itself is
5650 target dependent. You can see the data type using the @code{ptype
5651 $_siginfo} command. On Unix systems, it typically corresponds to the
5652 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5655 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5656 referenced address that raised a segmentation fault.
5660 (@value{GDBP}) continue
5661 Program received signal SIGSEGV, Segmentation fault.
5662 0x0000000000400766 in main ()
5664 (@value{GDBP}) ptype $_siginfo
5671 struct @{...@} _kill;
5672 struct @{...@} _timer;
5674 struct @{...@} _sigchld;
5675 struct @{...@} _sigfault;
5676 struct @{...@} _sigpoll;
5679 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5683 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5684 $1 = (void *) 0x7ffff7ff7000
5688 Depending on target support, @code{$_siginfo} may also be writable.
5691 @section Stopping and Starting Multi-thread Programs
5693 @cindex stopped threads
5694 @cindex threads, stopped
5696 @cindex continuing threads
5697 @cindex threads, continuing
5699 @value{GDBN} supports debugging programs with multiple threads
5700 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5701 are two modes of controlling execution of your program within the
5702 debugger. In the default mode, referred to as @dfn{all-stop mode},
5703 when any thread in your program stops (for example, at a breakpoint
5704 or while being stepped), all other threads in the program are also stopped by
5705 @value{GDBN}. On some targets, @value{GDBN} also supports
5706 @dfn{non-stop mode}, in which other threads can continue to run freely while
5707 you examine the stopped thread in the debugger.
5710 * All-Stop Mode:: All threads stop when GDB takes control
5711 * Non-Stop Mode:: Other threads continue to execute
5712 * Background Execution:: Running your program asynchronously
5713 * Thread-Specific Breakpoints:: Controlling breakpoints
5714 * Interrupted System Calls:: GDB may interfere with system calls
5715 * Observer Mode:: GDB does not alter program behavior
5719 @subsection All-Stop Mode
5721 @cindex all-stop mode
5723 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5724 @emph{all} threads of execution stop, not just the current thread. This
5725 allows you to examine the overall state of the program, including
5726 switching between threads, without worrying that things may change
5729 Conversely, whenever you restart the program, @emph{all} threads start
5730 executing. @emph{This is true even when single-stepping} with commands
5731 like @code{step} or @code{next}.
5733 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5734 Since thread scheduling is up to your debugging target's operating
5735 system (not controlled by @value{GDBN}), other threads may
5736 execute more than one statement while the current thread completes a
5737 single step. Moreover, in general other threads stop in the middle of a
5738 statement, rather than at a clean statement boundary, when the program
5741 You might even find your program stopped in another thread after
5742 continuing or even single-stepping. This happens whenever some other
5743 thread runs into a breakpoint, a signal, or an exception before the
5744 first thread completes whatever you requested.
5746 @cindex automatic thread selection
5747 @cindex switching threads automatically
5748 @cindex threads, automatic switching
5749 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5750 signal, it automatically selects the thread where that breakpoint or
5751 signal happened. @value{GDBN} alerts you to the context switch with a
5752 message such as @samp{[Switching to Thread @var{n}]} to identify the
5755 On some OSes, you can modify @value{GDBN}'s default behavior by
5756 locking the OS scheduler to allow only a single thread to run.
5759 @item set scheduler-locking @var{mode}
5760 @cindex scheduler locking mode
5761 @cindex lock scheduler
5762 Set the scheduler locking mode. If it is @code{off}, then there is no
5763 locking and any thread may run at any time. If @code{on}, then only the
5764 current thread may run when the inferior is resumed. The @code{step}
5765 mode optimizes for single-stepping; it prevents other threads
5766 from preempting the current thread while you are stepping, so that
5767 the focus of debugging does not change unexpectedly.
5768 Other threads only rarely (or never) get a chance to run
5769 when you step. They are more likely to run when you @samp{next} over a
5770 function call, and they are completely free to run when you use commands
5771 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5772 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5773 the current thread away from the thread that you are debugging.
5775 @item show scheduler-locking
5776 Display the current scheduler locking mode.
5779 @cindex resume threads of multiple processes simultaneously
5780 By default, when you issue one of the execution commands such as
5781 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5782 threads of the current inferior to run. For example, if @value{GDBN}
5783 is attached to two inferiors, each with two threads, the
5784 @code{continue} command resumes only the two threads of the current
5785 inferior. This is useful, for example, when you debug a program that
5786 forks and you want to hold the parent stopped (so that, for instance,
5787 it doesn't run to exit), while you debug the child. In other
5788 situations, you may not be interested in inspecting the current state
5789 of any of the processes @value{GDBN} is attached to, and you may want
5790 to resume them all until some breakpoint is hit. In the latter case,
5791 you can instruct @value{GDBN} to allow all threads of all the
5792 inferiors to run with the @w{@code{set schedule-multiple}} command.
5795 @kindex set schedule-multiple
5796 @item set schedule-multiple
5797 Set the mode for allowing threads of multiple processes to be resumed
5798 when an execution command is issued. When @code{on}, all threads of
5799 all processes are allowed to run. When @code{off}, only the threads
5800 of the current process are resumed. The default is @code{off}. The
5801 @code{scheduler-locking} mode takes precedence when set to @code{on},
5802 or while you are stepping and set to @code{step}.
5804 @item show schedule-multiple
5805 Display the current mode for resuming the execution of threads of
5810 @subsection Non-Stop Mode
5812 @cindex non-stop mode
5814 @c This section is really only a place-holder, and needs to be expanded
5815 @c with more details.
5817 For some multi-threaded targets, @value{GDBN} supports an optional
5818 mode of operation in which you can examine stopped program threads in
5819 the debugger while other threads continue to execute freely. This
5820 minimizes intrusion when debugging live systems, such as programs
5821 where some threads have real-time constraints or must continue to
5822 respond to external events. This is referred to as @dfn{non-stop} mode.
5824 In non-stop mode, when a thread stops to report a debugging event,
5825 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5826 threads as well, in contrast to the all-stop mode behavior. Additionally,
5827 execution commands such as @code{continue} and @code{step} apply by default
5828 only to the current thread in non-stop mode, rather than all threads as
5829 in all-stop mode. This allows you to control threads explicitly in
5830 ways that are not possible in all-stop mode --- for example, stepping
5831 one thread while allowing others to run freely, stepping
5832 one thread while holding all others stopped, or stepping several threads
5833 independently and simultaneously.
5835 To enter non-stop mode, use this sequence of commands before you run
5836 or attach to your program:
5839 # If using the CLI, pagination breaks non-stop.
5842 # Finally, turn it on!
5846 You can use these commands to manipulate the non-stop mode setting:
5849 @kindex set non-stop
5850 @item set non-stop on
5851 Enable selection of non-stop mode.
5852 @item set non-stop off
5853 Disable selection of non-stop mode.
5854 @kindex show non-stop
5856 Show the current non-stop enablement setting.
5859 Note these commands only reflect whether non-stop mode is enabled,
5860 not whether the currently-executing program is being run in non-stop mode.
5861 In particular, the @code{set non-stop} preference is only consulted when
5862 @value{GDBN} starts or connects to the target program, and it is generally
5863 not possible to switch modes once debugging has started. Furthermore,
5864 since not all targets support non-stop mode, even when you have enabled
5865 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5868 In non-stop mode, all execution commands apply only to the current thread
5869 by default. That is, @code{continue} only continues one thread.
5870 To continue all threads, issue @code{continue -a} or @code{c -a}.
5872 You can use @value{GDBN}'s background execution commands
5873 (@pxref{Background Execution}) to run some threads in the background
5874 while you continue to examine or step others from @value{GDBN}.
5875 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5876 always executed asynchronously in non-stop mode.
5878 Suspending execution is done with the @code{interrupt} command when
5879 running in the background, or @kbd{Ctrl-c} during foreground execution.
5880 In all-stop mode, this stops the whole process;
5881 but in non-stop mode the interrupt applies only to the current thread.
5882 To stop the whole program, use @code{interrupt -a}.
5884 Other execution commands do not currently support the @code{-a} option.
5886 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5887 that thread current, as it does in all-stop mode. This is because the
5888 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5889 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5890 changed to a different thread just as you entered a command to operate on the
5891 previously current thread.
5893 @node Background Execution
5894 @subsection Background Execution
5896 @cindex foreground execution
5897 @cindex background execution
5898 @cindex asynchronous execution
5899 @cindex execution, foreground, background and asynchronous
5901 @value{GDBN}'s execution commands have two variants: the normal
5902 foreground (synchronous) behavior, and a background
5903 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5904 the program to report that some thread has stopped before prompting for
5905 another command. In background execution, @value{GDBN} immediately gives
5906 a command prompt so that you can issue other commands while your program runs.
5908 If the target doesn't support async mode, @value{GDBN} issues an error
5909 message if you attempt to use the background execution commands.
5911 To specify background execution, add a @code{&} to the command. For example,
5912 the background form of the @code{continue} command is @code{continue&}, or
5913 just @code{c&}. The execution commands that accept background execution
5919 @xref{Starting, , Starting your Program}.
5923 @xref{Attach, , Debugging an Already-running Process}.
5927 @xref{Continuing and Stepping, step}.
5931 @xref{Continuing and Stepping, stepi}.
5935 @xref{Continuing and Stepping, next}.
5939 @xref{Continuing and Stepping, nexti}.
5943 @xref{Continuing and Stepping, continue}.
5947 @xref{Continuing and Stepping, finish}.
5951 @xref{Continuing and Stepping, until}.
5955 Background execution is especially useful in conjunction with non-stop
5956 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5957 However, you can also use these commands in the normal all-stop mode with
5958 the restriction that you cannot issue another execution command until the
5959 previous one finishes. Examples of commands that are valid in all-stop
5960 mode while the program is running include @code{help} and @code{info break}.
5962 You can interrupt your program while it is running in the background by
5963 using the @code{interrupt} command.
5970 Suspend execution of the running program. In all-stop mode,
5971 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5972 only the current thread. To stop the whole program in non-stop mode,
5973 use @code{interrupt -a}.
5976 @node Thread-Specific Breakpoints
5977 @subsection Thread-Specific Breakpoints
5979 When your program has multiple threads (@pxref{Threads,, Debugging
5980 Programs with Multiple Threads}), you can choose whether to set
5981 breakpoints on all threads, or on a particular thread.
5984 @cindex breakpoints and threads
5985 @cindex thread breakpoints
5986 @kindex break @dots{} thread @var{threadno}
5987 @item break @var{linespec} thread @var{threadno}
5988 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5989 @var{linespec} specifies source lines; there are several ways of
5990 writing them (@pxref{Specify Location}), but the effect is always to
5991 specify some source line.
5993 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5994 to specify that you only want @value{GDBN} to stop the program when a
5995 particular thread reaches this breakpoint. The @var{threadno} specifier
5996 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
5997 in the first column of the @samp{info threads} display.
5999 If you do not specify @samp{thread @var{threadno}} when you set a
6000 breakpoint, the breakpoint applies to @emph{all} threads of your
6003 You can use the @code{thread} qualifier on conditional breakpoints as
6004 well; in this case, place @samp{thread @var{threadno}} before or
6005 after the breakpoint condition, like this:
6008 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6013 Thread-specific breakpoints are automatically deleted when
6014 @value{GDBN} detects the corresponding thread is no longer in the
6015 thread list. For example:
6019 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6022 There are several ways for a thread to disappear, such as a regular
6023 thread exit, but also when you detach from the process with the
6024 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6025 Process}), or if @value{GDBN} loses the remote connection
6026 (@pxref{Remote Debugging}), etc. Note that with some targets,
6027 @value{GDBN} is only able to detect a thread has exited when the user
6028 explictly asks for the thread list with the @code{info threads}
6031 @node Interrupted System Calls
6032 @subsection Interrupted System Calls
6034 @cindex thread breakpoints and system calls
6035 @cindex system calls and thread breakpoints
6036 @cindex premature return from system calls
6037 There is an unfortunate side effect when using @value{GDBN} to debug
6038 multi-threaded programs. If one thread stops for a
6039 breakpoint, or for some other reason, and another thread is blocked in a
6040 system call, then the system call may return prematurely. This is a
6041 consequence of the interaction between multiple threads and the signals
6042 that @value{GDBN} uses to implement breakpoints and other events that
6045 To handle this problem, your program should check the return value of
6046 each system call and react appropriately. This is good programming
6049 For example, do not write code like this:
6055 The call to @code{sleep} will return early if a different thread stops
6056 at a breakpoint or for some other reason.
6058 Instead, write this:
6063 unslept = sleep (unslept);
6066 A system call is allowed to return early, so the system is still
6067 conforming to its specification. But @value{GDBN} does cause your
6068 multi-threaded program to behave differently than it would without
6071 Also, @value{GDBN} uses internal breakpoints in the thread library to
6072 monitor certain events such as thread creation and thread destruction.
6073 When such an event happens, a system call in another thread may return
6074 prematurely, even though your program does not appear to stop.
6077 @subsection Observer Mode
6079 If you want to build on non-stop mode and observe program behavior
6080 without any chance of disruption by @value{GDBN}, you can set
6081 variables to disable all of the debugger's attempts to modify state,
6082 whether by writing memory, inserting breakpoints, etc. These operate
6083 at a low level, intercepting operations from all commands.
6085 When all of these are set to @code{off}, then @value{GDBN} is said to
6086 be @dfn{observer mode}. As a convenience, the variable
6087 @code{observer} can be set to disable these, plus enable non-stop
6090 Note that @value{GDBN} will not prevent you from making nonsensical
6091 combinations of these settings. For instance, if you have enabled
6092 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6093 then breakpoints that work by writing trap instructions into the code
6094 stream will still not be able to be placed.
6099 @item set observer on
6100 @itemx set observer off
6101 When set to @code{on}, this disables all the permission variables
6102 below (except for @code{insert-fast-tracepoints}), plus enables
6103 non-stop debugging. Setting this to @code{off} switches back to
6104 normal debugging, though remaining in non-stop mode.
6107 Show whether observer mode is on or off.
6109 @kindex may-write-registers
6110 @item set may-write-registers on
6111 @itemx set may-write-registers off
6112 This controls whether @value{GDBN} will attempt to alter the values of
6113 registers, such as with assignment expressions in @code{print}, or the
6114 @code{jump} command. It defaults to @code{on}.
6116 @item show may-write-registers
6117 Show the current permission to write registers.
6119 @kindex may-write-memory
6120 @item set may-write-memory on
6121 @itemx set may-write-memory off
6122 This controls whether @value{GDBN} will attempt to alter the contents
6123 of memory, such as with assignment expressions in @code{print}. It
6124 defaults to @code{on}.
6126 @item show may-write-memory
6127 Show the current permission to write memory.
6129 @kindex may-insert-breakpoints
6130 @item set may-insert-breakpoints on
6131 @itemx set may-insert-breakpoints off
6132 This controls whether @value{GDBN} will attempt to insert breakpoints.
6133 This affects all breakpoints, including internal breakpoints defined
6134 by @value{GDBN}. It defaults to @code{on}.
6136 @item show may-insert-breakpoints
6137 Show the current permission to insert breakpoints.
6139 @kindex may-insert-tracepoints
6140 @item set may-insert-tracepoints on
6141 @itemx set may-insert-tracepoints off
6142 This controls whether @value{GDBN} will attempt to insert (regular)
6143 tracepoints at the beginning of a tracing experiment. It affects only
6144 non-fast tracepoints, fast tracepoints being under the control of
6145 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6147 @item show may-insert-tracepoints
6148 Show the current permission to insert tracepoints.
6150 @kindex may-insert-fast-tracepoints
6151 @item set may-insert-fast-tracepoints on
6152 @itemx set may-insert-fast-tracepoints off
6153 This controls whether @value{GDBN} will attempt to insert fast
6154 tracepoints at the beginning of a tracing experiment. It affects only
6155 fast tracepoints, regular (non-fast) tracepoints being under the
6156 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6158 @item show may-insert-fast-tracepoints
6159 Show the current permission to insert fast tracepoints.
6161 @kindex may-interrupt
6162 @item set may-interrupt on
6163 @itemx set may-interrupt off
6164 This controls whether @value{GDBN} will attempt to interrupt or stop
6165 program execution. When this variable is @code{off}, the
6166 @code{interrupt} command will have no effect, nor will
6167 @kbd{Ctrl-c}. It defaults to @code{on}.
6169 @item show may-interrupt
6170 Show the current permission to interrupt or stop the program.
6174 @node Reverse Execution
6175 @chapter Running programs backward
6176 @cindex reverse execution
6177 @cindex running programs backward
6179 When you are debugging a program, it is not unusual to realize that
6180 you have gone too far, and some event of interest has already happened.
6181 If the target environment supports it, @value{GDBN} can allow you to
6182 ``rewind'' the program by running it backward.
6184 A target environment that supports reverse execution should be able
6185 to ``undo'' the changes in machine state that have taken place as the
6186 program was executing normally. Variables, registers etc.@: should
6187 revert to their previous values. Obviously this requires a great
6188 deal of sophistication on the part of the target environment; not
6189 all target environments can support reverse execution.
6191 When a program is executed in reverse, the instructions that
6192 have most recently been executed are ``un-executed'', in reverse
6193 order. The program counter runs backward, following the previous
6194 thread of execution in reverse. As each instruction is ``un-executed'',
6195 the values of memory and/or registers that were changed by that
6196 instruction are reverted to their previous states. After executing
6197 a piece of source code in reverse, all side effects of that code
6198 should be ``undone'', and all variables should be returned to their
6199 prior values@footnote{
6200 Note that some side effects are easier to undo than others. For instance,
6201 memory and registers are relatively easy, but device I/O is hard. Some
6202 targets may be able undo things like device I/O, and some may not.
6204 The contract between @value{GDBN} and the reverse executing target
6205 requires only that the target do something reasonable when
6206 @value{GDBN} tells it to execute backwards, and then report the
6207 results back to @value{GDBN}. Whatever the target reports back to
6208 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6209 assumes that the memory and registers that the target reports are in a
6210 consistant state, but @value{GDBN} accepts whatever it is given.
6213 If you are debugging in a target environment that supports
6214 reverse execution, @value{GDBN} provides the following commands.
6217 @kindex reverse-continue
6218 @kindex rc @r{(@code{reverse-continue})}
6219 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6220 @itemx rc @r{[}@var{ignore-count}@r{]}
6221 Beginning at the point where your program last stopped, start executing
6222 in reverse. Reverse execution will stop for breakpoints and synchronous
6223 exceptions (signals), just like normal execution. Behavior of
6224 asynchronous signals depends on the target environment.
6226 @kindex reverse-step
6227 @kindex rs @r{(@code{step})}
6228 @item reverse-step @r{[}@var{count}@r{]}
6229 Run the program backward until control reaches the start of a
6230 different source line; then stop it, and return control to @value{GDBN}.
6232 Like the @code{step} command, @code{reverse-step} will only stop
6233 at the beginning of a source line. It ``un-executes'' the previously
6234 executed source line. If the previous source line included calls to
6235 debuggable functions, @code{reverse-step} will step (backward) into
6236 the called function, stopping at the beginning of the @emph{last}
6237 statement in the called function (typically a return statement).
6239 Also, as with the @code{step} command, if non-debuggable functions are
6240 called, @code{reverse-step} will run thru them backward without stopping.
6242 @kindex reverse-stepi
6243 @kindex rsi @r{(@code{reverse-stepi})}
6244 @item reverse-stepi @r{[}@var{count}@r{]}
6245 Reverse-execute one machine instruction. Note that the instruction
6246 to be reverse-executed is @emph{not} the one pointed to by the program
6247 counter, but the instruction executed prior to that one. For instance,
6248 if the last instruction was a jump, @code{reverse-stepi} will take you
6249 back from the destination of the jump to the jump instruction itself.
6251 @kindex reverse-next
6252 @kindex rn @r{(@code{reverse-next})}
6253 @item reverse-next @r{[}@var{count}@r{]}
6254 Run backward to the beginning of the previous line executed in
6255 the current (innermost) stack frame. If the line contains function
6256 calls, they will be ``un-executed'' without stopping. Starting from
6257 the first line of a function, @code{reverse-next} will take you back
6258 to the caller of that function, @emph{before} the function was called,
6259 just as the normal @code{next} command would take you from the last
6260 line of a function back to its return to its caller
6261 @footnote{Unless the code is too heavily optimized.}.
6263 @kindex reverse-nexti
6264 @kindex rni @r{(@code{reverse-nexti})}
6265 @item reverse-nexti @r{[}@var{count}@r{]}
6266 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6267 in reverse, except that called functions are ``un-executed'' atomically.
6268 That is, if the previously executed instruction was a return from
6269 another function, @code{reverse-nexti} will continue to execute
6270 in reverse until the call to that function (from the current stack
6273 @kindex reverse-finish
6274 @item reverse-finish
6275 Just as the @code{finish} command takes you to the point where the
6276 current function returns, @code{reverse-finish} takes you to the point
6277 where it was called. Instead of ending up at the end of the current
6278 function invocation, you end up at the beginning.
6280 @kindex set exec-direction
6281 @item set exec-direction
6282 Set the direction of target execution.
6283 @item set exec-direction reverse
6284 @cindex execute forward or backward in time
6285 @value{GDBN} will perform all execution commands in reverse, until the
6286 exec-direction mode is changed to ``forward''. Affected commands include
6287 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6288 command cannot be used in reverse mode.
6289 @item set exec-direction forward
6290 @value{GDBN} will perform all execution commands in the normal fashion.
6291 This is the default.
6295 @node Process Record and Replay
6296 @chapter Recording Inferior's Execution and Replaying It
6297 @cindex process record and replay
6298 @cindex recording inferior's execution and replaying it
6300 On some platforms, @value{GDBN} provides a special @dfn{process record
6301 and replay} target that can record a log of the process execution, and
6302 replay it later with both forward and reverse execution commands.
6305 When this target is in use, if the execution log includes the record
6306 for the next instruction, @value{GDBN} will debug in @dfn{replay
6307 mode}. In the replay mode, the inferior does not really execute code
6308 instructions. Instead, all the events that normally happen during
6309 code execution are taken from the execution log. While code is not
6310 really executed in replay mode, the values of registers (including the
6311 program counter register) and the memory of the inferior are still
6312 changed as they normally would. Their contents are taken from the
6316 If the record for the next instruction is not in the execution log,
6317 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6318 inferior executes normally, and @value{GDBN} records the execution log
6321 The process record and replay target supports reverse execution
6322 (@pxref{Reverse Execution}), even if the platform on which the
6323 inferior runs does not. However, the reverse execution is limited in
6324 this case by the range of the instructions recorded in the execution
6325 log. In other words, reverse execution on platforms that don't
6326 support it directly can only be done in the replay mode.
6328 When debugging in the reverse direction, @value{GDBN} will work in
6329 replay mode as long as the execution log includes the record for the
6330 previous instruction; otherwise, it will work in record mode, if the
6331 platform supports reverse execution, or stop if not.
6333 For architecture environments that support process record and replay,
6334 @value{GDBN} provides the following commands:
6337 @kindex target record
6338 @kindex target record-full
6339 @kindex target record-btrace
6342 @kindex record btrace
6346 @item record @var{method}
6347 This command starts the process record and replay target. The
6348 recording method can be specified as parameter. Without a parameter
6349 the command uses the @code{full} recording method. The following
6350 recording methods are available:
6354 Full record/replay recording using @value{GDBN}'s software record and
6355 replay implementation. This method allows replaying and reverse
6359 Hardware-supported instruction recording. This method does not record
6360 data. Further, the data is collected in a ring buffer so old data will
6361 be overwritten when the buffer is full. It allows limited replay and
6364 This recording method may not be available on all processors.
6367 The process record and replay target can only debug a process that is
6368 already running. Therefore, you need first to start the process with
6369 the @kbd{run} or @kbd{start} commands, and then start the recording
6370 with the @kbd{record @var{method}} command.
6372 Both @code{record @var{method}} and @code{rec @var{method}} are
6373 aliases of @code{target record-@var{method}}.
6375 @cindex displaced stepping, and process record and replay
6376 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6377 will be automatically disabled when process record and replay target
6378 is started. That's because the process record and replay target
6379 doesn't support displaced stepping.
6381 @cindex non-stop mode, and process record and replay
6382 @cindex asynchronous execution, and process record and replay
6383 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6384 the asynchronous execution mode (@pxref{Background Execution}), not
6385 all recording methods are available. The @code{full} recording method
6386 does not support these two modes.
6391 Stop the process record and replay target. When process record and
6392 replay target stops, the entire execution log will be deleted and the
6393 inferior will either be terminated, or will remain in its final state.
6395 When you stop the process record and replay target in record mode (at
6396 the end of the execution log), the inferior will be stopped at the
6397 next instruction that would have been recorded. In other words, if
6398 you record for a while and then stop recording, the inferior process
6399 will be left in the same state as if the recording never happened.
6401 On the other hand, if the process record and replay target is stopped
6402 while in replay mode (that is, not at the end of the execution log,
6403 but at some earlier point), the inferior process will become ``live''
6404 at that earlier state, and it will then be possible to continue the
6405 usual ``live'' debugging of the process from that state.
6407 When the inferior process exits, or @value{GDBN} detaches from it,
6408 process record and replay target will automatically stop itself.
6412 Go to a specific location in the execution log. There are several
6413 ways to specify the location to go to:
6416 @item record goto begin
6417 @itemx record goto start
6418 Go to the beginning of the execution log.
6420 @item record goto end
6421 Go to the end of the execution log.
6423 @item record goto @var{n}
6424 Go to instruction number @var{n} in the execution log.
6428 @item record save @var{filename}
6429 Save the execution log to a file @file{@var{filename}}.
6430 Default filename is @file{gdb_record.@var{process_id}}, where
6431 @var{process_id} is the process ID of the inferior.
6433 This command may not be available for all recording methods.
6435 @kindex record restore
6436 @item record restore @var{filename}
6437 Restore the execution log from a file @file{@var{filename}}.
6438 File must have been created with @code{record save}.
6440 @kindex set record full
6441 @item set record full insn-number-max @var{limit}
6442 @itemx set record full insn-number-max unlimited
6443 Set the limit of instructions to be recorded for the @code{full}
6444 recording method. Default value is 200000.
6446 If @var{limit} is a positive number, then @value{GDBN} will start
6447 deleting instructions from the log once the number of the record
6448 instructions becomes greater than @var{limit}. For every new recorded
6449 instruction, @value{GDBN} will delete the earliest recorded
6450 instruction to keep the number of recorded instructions at the limit.
6451 (Since deleting recorded instructions loses information, @value{GDBN}
6452 lets you control what happens when the limit is reached, by means of
6453 the @code{stop-at-limit} option, described below.)
6455 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6456 delete recorded instructions from the execution log. The number of
6457 recorded instructions is limited only by the available memory.
6459 @kindex show record full
6460 @item show record full insn-number-max
6461 Show the limit of instructions to be recorded with the @code{full}
6464 @item set record full stop-at-limit
6465 Control the behavior of the @code{full} recording method when the
6466 number of recorded instructions reaches the limit. If ON (the
6467 default), @value{GDBN} will stop when the limit is reached for the
6468 first time and ask you whether you want to stop the inferior or
6469 continue running it and recording the execution log. If you decide
6470 to continue recording, each new recorded instruction will cause the
6471 oldest one to be deleted.
6473 If this option is OFF, @value{GDBN} will automatically delete the
6474 oldest record to make room for each new one, without asking.
6476 @item show record full stop-at-limit
6477 Show the current setting of @code{stop-at-limit}.
6479 @item set record full memory-query
6480 Control the behavior when @value{GDBN} is unable to record memory
6481 changes caused by an instruction for the @code{full} recording method.
6482 If ON, @value{GDBN} will query whether to stop the inferior in that
6485 If this option is OFF (the default), @value{GDBN} will automatically
6486 ignore the effect of such instructions on memory. Later, when
6487 @value{GDBN} replays this execution log, it will mark the log of this
6488 instruction as not accessible, and it will not affect the replay
6491 @item show record full memory-query
6492 Show the current setting of @code{memory-query}.
6494 @kindex set record btrace
6495 The @code{btrace} record target does not trace data. As a
6496 convenience, when replaying, @value{GDBN} reads read-only memory off
6497 the live program directly, assuming that the addresses of the
6498 read-only areas don't change. This for example makes it possible to
6499 disassemble code while replaying, but not to print variables.
6500 In some cases, being able to inspect variables might be useful.
6501 You can use the following command for that:
6503 @item set record btrace replay-memory-access
6504 Control the behavior of the @code{btrace} recording method when
6505 accessing memory during replay. If @code{read-only} (the default),
6506 @value{GDBN} will only allow accesses to read-only memory.
6507 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6508 and to read-write memory. Beware that the accessed memory corresponds
6509 to the live target and not necessarily to the current replay
6512 @kindex show record btrace
6513 @item show record btrace replay-memory-access
6514 Show the current setting of @code{replay-memory-access}.
6518 Show various statistics about the recording depending on the recording
6523 For the @code{full} recording method, it shows the state of process
6524 record and its in-memory execution log buffer, including:
6528 Whether in record mode or replay mode.
6530 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6532 Highest recorded instruction number.
6534 Current instruction about to be replayed (if in replay mode).
6536 Number of instructions contained in the execution log.
6538 Maximum number of instructions that may be contained in the execution log.
6542 For the @code{btrace} recording method, it shows the number of
6543 instructions that have been recorded and the number of blocks of
6544 sequential control-flow that is formed by the recorded instructions.
6547 @kindex record delete
6550 When record target runs in replay mode (``in the past''), delete the
6551 subsequent execution log and begin to record a new execution log starting
6552 from the current address. This means you will abandon the previously
6553 recorded ``future'' and begin recording a new ``future''.
6555 @kindex record instruction-history
6556 @kindex rec instruction-history
6557 @item record instruction-history
6558 Disassembles instructions from the recorded execution log. By
6559 default, ten instructions are disassembled. This can be changed using
6560 the @code{set record instruction-history-size} command. Instructions
6561 are printed in execution order. There are several ways to specify
6562 what part of the execution log to disassemble:
6565 @item record instruction-history @var{insn}
6566 Disassembles ten instructions starting from instruction number
6569 @item record instruction-history @var{insn}, +/-@var{n}
6570 Disassembles @var{n} instructions around instruction number
6571 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6572 @var{n} instructions after instruction number @var{insn}. If
6573 @var{n} is preceded with @code{-}, disassembles @var{n}
6574 instructions before instruction number @var{insn}.
6576 @item record instruction-history
6577 Disassembles ten more instructions after the last disassembly.
6579 @item record instruction-history -
6580 Disassembles ten more instructions before the last disassembly.
6582 @item record instruction-history @var{begin} @var{end}
6583 Disassembles instructions beginning with instruction number
6584 @var{begin} until instruction number @var{end}. The instruction
6585 number @var{end} is included.
6588 This command may not be available for all recording methods.
6591 @item set record instruction-history-size @var{size}
6592 @itemx set record instruction-history-size unlimited
6593 Define how many instructions to disassemble in the @code{record
6594 instruction-history} command. The default value is 10.
6595 A @var{size} of @code{unlimited} means unlimited instructions.
6598 @item show record instruction-history-size
6599 Show how many instructions to disassemble in the @code{record
6600 instruction-history} command.
6602 @kindex record function-call-history
6603 @kindex rec function-call-history
6604 @item record function-call-history
6605 Prints the execution history at function granularity. It prints one
6606 line for each sequence of instructions that belong to the same
6607 function giving the name of that function, the source lines
6608 for this instruction sequence (if the @code{/l} modifier is
6609 specified), and the instructions numbers that form the sequence (if
6610 the @code{/i} modifier is specified). The function names are indented
6611 to reflect the call stack depth if the @code{/c} modifier is
6612 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6616 (@value{GDBP}) @b{list 1, 10}
6627 (@value{GDBP}) @b{record function-call-history /ilc}
6628 1 bar inst 1,4 at foo.c:6,8
6629 2 foo inst 5,10 at foo.c:2,3
6630 3 bar inst 11,13 at foo.c:9,10
6633 By default, ten lines are printed. This can be changed using the
6634 @code{set record function-call-history-size} command. Functions are
6635 printed in execution order. There are several ways to specify what
6639 @item record function-call-history @var{func}
6640 Prints ten functions starting from function number @var{func}.
6642 @item record function-call-history @var{func}, +/-@var{n}
6643 Prints @var{n} functions around function number @var{func}. If
6644 @var{n} is preceded with @code{+}, prints @var{n} functions after
6645 function number @var{func}. If @var{n} is preceded with @code{-},
6646 prints @var{n} functions before function number @var{func}.
6648 @item record function-call-history
6649 Prints ten more functions after the last ten-line print.
6651 @item record function-call-history -
6652 Prints ten more functions before the last ten-line print.
6654 @item record function-call-history @var{begin} @var{end}
6655 Prints functions beginning with function number @var{begin} until
6656 function number @var{end}. The function number @var{end} is included.
6659 This command may not be available for all recording methods.
6661 @item set record function-call-history-size @var{size}
6662 @itemx set record function-call-history-size unlimited
6663 Define how many lines to print in the
6664 @code{record function-call-history} command. The default value is 10.
6665 A size of @code{unlimited} means unlimited lines.
6667 @item show record function-call-history-size
6668 Show how many lines to print in the
6669 @code{record function-call-history} command.
6674 @chapter Examining the Stack
6676 When your program has stopped, the first thing you need to know is where it
6677 stopped and how it got there.
6680 Each time your program performs a function call, information about the call
6682 That information includes the location of the call in your program,
6683 the arguments of the call,
6684 and the local variables of the function being called.
6685 The information is saved in a block of data called a @dfn{stack frame}.
6686 The stack frames are allocated in a region of memory called the @dfn{call
6689 When your program stops, the @value{GDBN} commands for examining the
6690 stack allow you to see all of this information.
6692 @cindex selected frame
6693 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6694 @value{GDBN} commands refer implicitly to the selected frame. In
6695 particular, whenever you ask @value{GDBN} for the value of a variable in
6696 your program, the value is found in the selected frame. There are
6697 special @value{GDBN} commands to select whichever frame you are
6698 interested in. @xref{Selection, ,Selecting a Frame}.
6700 When your program stops, @value{GDBN} automatically selects the
6701 currently executing frame and describes it briefly, similar to the
6702 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6705 * Frames:: Stack frames
6706 * Backtrace:: Backtraces
6707 * Frame Filter Management:: Managing frame filters
6708 * Selection:: Selecting a frame
6709 * Frame Info:: Information on a frame
6714 @section Stack Frames
6716 @cindex frame, definition
6718 The call stack is divided up into contiguous pieces called @dfn{stack
6719 frames}, or @dfn{frames} for short; each frame is the data associated
6720 with one call to one function. The frame contains the arguments given
6721 to the function, the function's local variables, and the address at
6722 which the function is executing.
6724 @cindex initial frame
6725 @cindex outermost frame
6726 @cindex innermost frame
6727 When your program is started, the stack has only one frame, that of the
6728 function @code{main}. This is called the @dfn{initial} frame or the
6729 @dfn{outermost} frame. Each time a function is called, a new frame is
6730 made. Each time a function returns, the frame for that function invocation
6731 is eliminated. If a function is recursive, there can be many frames for
6732 the same function. The frame for the function in which execution is
6733 actually occurring is called the @dfn{innermost} frame. This is the most
6734 recently created of all the stack frames that still exist.
6736 @cindex frame pointer
6737 Inside your program, stack frames are identified by their addresses. A
6738 stack frame consists of many bytes, each of which has its own address; each
6739 kind of computer has a convention for choosing one byte whose
6740 address serves as the address of the frame. Usually this address is kept
6741 in a register called the @dfn{frame pointer register}
6742 (@pxref{Registers, $fp}) while execution is going on in that frame.
6744 @cindex frame number
6745 @value{GDBN} assigns numbers to all existing stack frames, starting with
6746 zero for the innermost frame, one for the frame that called it,
6747 and so on upward. These numbers do not really exist in your program;
6748 they are assigned by @value{GDBN} to give you a way of designating stack
6749 frames in @value{GDBN} commands.
6751 @c The -fomit-frame-pointer below perennially causes hbox overflow
6752 @c underflow problems.
6753 @cindex frameless execution
6754 Some compilers provide a way to compile functions so that they operate
6755 without stack frames. (For example, the @value{NGCC} option
6757 @samp{-fomit-frame-pointer}
6759 generates functions without a frame.)
6760 This is occasionally done with heavily used library functions to save
6761 the frame setup time. @value{GDBN} has limited facilities for dealing
6762 with these function invocations. If the innermost function invocation
6763 has no stack frame, @value{GDBN} nevertheless regards it as though
6764 it had a separate frame, which is numbered zero as usual, allowing
6765 correct tracing of the function call chain. However, @value{GDBN} has
6766 no provision for frameless functions elsewhere in the stack.
6769 @kindex frame@r{, command}
6770 @cindex current stack frame
6771 @item frame @r{[}@var{framespec}@r{]}
6772 The @code{frame} command allows you to move from one stack frame to another,
6773 and to print the stack frame you select. The @var{framespec} may be either the
6774 address of the frame or the stack frame number. Without an argument,
6775 @code{frame} prints the current stack frame.
6777 @kindex select-frame
6778 @cindex selecting frame silently
6780 The @code{select-frame} command allows you to move from one stack frame
6781 to another without printing the frame. This is the silent version of
6789 @cindex call stack traces
6790 A backtrace is a summary of how your program got where it is. It shows one
6791 line per frame, for many frames, starting with the currently executing
6792 frame (frame zero), followed by its caller (frame one), and on up the
6795 @anchor{backtrace-command}
6798 @kindex bt @r{(@code{backtrace})}
6801 Print a backtrace of the entire stack: one line per frame for all
6802 frames in the stack.
6804 You can stop the backtrace at any time by typing the system interrupt
6805 character, normally @kbd{Ctrl-c}.
6807 @item backtrace @var{n}
6809 Similar, but print only the innermost @var{n} frames.
6811 @item backtrace -@var{n}
6813 Similar, but print only the outermost @var{n} frames.
6815 @item backtrace full
6817 @itemx bt full @var{n}
6818 @itemx bt full -@var{n}
6819 Print the values of the local variables also. As described above,
6820 @var{n} specifies the number of frames to print.
6822 @item backtrace no-filters
6823 @itemx bt no-filters
6824 @itemx bt no-filters @var{n}
6825 @itemx bt no-filters -@var{n}
6826 @itemx bt no-filters full
6827 @itemx bt no-filters full @var{n}
6828 @itemx bt no-filters full -@var{n}
6829 Do not run Python frame filters on this backtrace. @xref{Frame
6830 Filter API}, for more information. Additionally use @ref{disable
6831 frame-filter all} to turn off all frame filters. This is only
6832 relevant when @value{GDBN} has been configured with @code{Python}
6838 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6839 are additional aliases for @code{backtrace}.
6841 @cindex multiple threads, backtrace
6842 In a multi-threaded program, @value{GDBN} by default shows the
6843 backtrace only for the current thread. To display the backtrace for
6844 several or all of the threads, use the command @code{thread apply}
6845 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6846 apply all backtrace}, @value{GDBN} will display the backtrace for all
6847 the threads; this is handy when you debug a core dump of a
6848 multi-threaded program.
6850 Each line in the backtrace shows the frame number and the function name.
6851 The program counter value is also shown---unless you use @code{set
6852 print address off}. The backtrace also shows the source file name and
6853 line number, as well as the arguments to the function. The program
6854 counter value is omitted if it is at the beginning of the code for that
6857 Here is an example of a backtrace. It was made with the command
6858 @samp{bt 3}, so it shows the innermost three frames.
6862 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6864 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6865 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6867 (More stack frames follow...)
6872 The display for frame zero does not begin with a program counter
6873 value, indicating that your program has stopped at the beginning of the
6874 code for line @code{993} of @code{builtin.c}.
6877 The value of parameter @code{data} in frame 1 has been replaced by
6878 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6879 only if it is a scalar (integer, pointer, enumeration, etc). See command
6880 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6881 on how to configure the way function parameter values are printed.
6883 @cindex optimized out, in backtrace
6884 @cindex function call arguments, optimized out
6885 If your program was compiled with optimizations, some compilers will
6886 optimize away arguments passed to functions if those arguments are
6887 never used after the call. Such optimizations generate code that
6888 passes arguments through registers, but doesn't store those arguments
6889 in the stack frame. @value{GDBN} has no way of displaying such
6890 arguments in stack frames other than the innermost one. Here's what
6891 such a backtrace might look like:
6895 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6897 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6898 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6900 (More stack frames follow...)
6905 The values of arguments that were not saved in their stack frames are
6906 shown as @samp{<optimized out>}.
6908 If you need to display the values of such optimized-out arguments,
6909 either deduce that from other variables whose values depend on the one
6910 you are interested in, or recompile without optimizations.
6912 @cindex backtrace beyond @code{main} function
6913 @cindex program entry point
6914 @cindex startup code, and backtrace
6915 Most programs have a standard user entry point---a place where system
6916 libraries and startup code transition into user code. For C this is
6917 @code{main}@footnote{
6918 Note that embedded programs (the so-called ``free-standing''
6919 environment) are not required to have a @code{main} function as the
6920 entry point. They could even have multiple entry points.}.
6921 When @value{GDBN} finds the entry function in a backtrace
6922 it will terminate the backtrace, to avoid tracing into highly
6923 system-specific (and generally uninteresting) code.
6925 If you need to examine the startup code, or limit the number of levels
6926 in a backtrace, you can change this behavior:
6929 @item set backtrace past-main
6930 @itemx set backtrace past-main on
6931 @kindex set backtrace
6932 Backtraces will continue past the user entry point.
6934 @item set backtrace past-main off
6935 Backtraces will stop when they encounter the user entry point. This is the
6938 @item show backtrace past-main
6939 @kindex show backtrace
6940 Display the current user entry point backtrace policy.
6942 @item set backtrace past-entry
6943 @itemx set backtrace past-entry on
6944 Backtraces will continue past the internal entry point of an application.
6945 This entry point is encoded by the linker when the application is built,
6946 and is likely before the user entry point @code{main} (or equivalent) is called.
6948 @item set backtrace past-entry off
6949 Backtraces will stop when they encounter the internal entry point of an
6950 application. This is the default.
6952 @item show backtrace past-entry
6953 Display the current internal entry point backtrace policy.
6955 @item set backtrace limit @var{n}
6956 @itemx set backtrace limit 0
6957 @itemx set backtrace limit unlimited
6958 @cindex backtrace limit
6959 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6960 or zero means unlimited levels.
6962 @item show backtrace limit
6963 Display the current limit on backtrace levels.
6966 You can control how file names are displayed.
6969 @item set filename-display
6970 @itemx set filename-display relative
6971 @cindex filename-display
6972 Display file names relative to the compilation directory. This is the default.
6974 @item set filename-display basename
6975 Display only basename of a filename.
6977 @item set filename-display absolute
6978 Display an absolute filename.
6980 @item show filename-display
6981 Show the current way to display filenames.
6984 @node Frame Filter Management
6985 @section Management of Frame Filters.
6986 @cindex managing frame filters
6988 Frame filters are Python based utilities to manage and decorate the
6989 output of frames. @xref{Frame Filter API}, for further information.
6991 Managing frame filters is performed by several commands available
6992 within @value{GDBN}, detailed here.
6995 @kindex info frame-filter
6996 @item info frame-filter
6997 Print a list of installed frame filters from all dictionaries, showing
6998 their name, priority and enabled status.
7000 @kindex disable frame-filter
7001 @anchor{disable frame-filter all}
7002 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7003 Disable a frame filter in the dictionary matching
7004 @var{filter-dictionary} and @var{filter-name}. The
7005 @var{filter-dictionary} may be @code{all}, @code{global},
7006 @code{progspace}, or the name of the object file where the frame filter
7007 dictionary resides. When @code{all} is specified, all frame filters
7008 across all dictionaries are disabled. The @var{filter-name} is the name
7009 of the frame filter and is used when @code{all} is not the option for
7010 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7011 may be enabled again later.
7013 @kindex enable frame-filter
7014 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7015 Enable a frame filter in the dictionary matching
7016 @var{filter-dictionary} and @var{filter-name}. The
7017 @var{filter-dictionary} may be @code{all}, @code{global},
7018 @code{progspace} or the name of the object file where the frame filter
7019 dictionary resides. When @code{all} is specified, all frame filters across
7020 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7021 filter and is used when @code{all} is not the option for
7022 @var{filter-dictionary}.
7027 (gdb) info frame-filter
7029 global frame-filters:
7030 Priority Enabled Name
7031 1000 No PrimaryFunctionFilter
7034 progspace /build/test frame-filters:
7035 Priority Enabled Name
7036 100 Yes ProgspaceFilter
7038 objfile /build/test frame-filters:
7039 Priority Enabled Name
7040 999 Yes BuildProgra Filter
7042 (gdb) disable frame-filter /build/test BuildProgramFilter
7043 (gdb) info frame-filter
7045 global frame-filters:
7046 Priority Enabled Name
7047 1000 No PrimaryFunctionFilter
7050 progspace /build/test frame-filters:
7051 Priority Enabled Name
7052 100 Yes ProgspaceFilter
7054 objfile /build/test frame-filters:
7055 Priority Enabled Name
7056 999 No BuildProgramFilter
7058 (gdb) enable frame-filter global PrimaryFunctionFilter
7059 (gdb) info frame-filter
7061 global frame-filters:
7062 Priority Enabled Name
7063 1000 Yes PrimaryFunctionFilter
7066 progspace /build/test frame-filters:
7067 Priority Enabled Name
7068 100 Yes ProgspaceFilter
7070 objfile /build/test frame-filters:
7071 Priority Enabled Name
7072 999 No BuildProgramFilter
7075 @kindex set frame-filter priority
7076 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7077 Set the @var{priority} of a frame filter in the dictionary matching
7078 @var{filter-dictionary}, and the frame filter name matching
7079 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7080 @code{progspace} or the name of the object file where the frame filter
7081 dictionary resides. The @var{priority} is an integer.
7083 @kindex show frame-filter priority
7084 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7085 Show the @var{priority} of a frame filter in the dictionary matching
7086 @var{filter-dictionary}, and the frame filter name matching
7087 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7088 @code{progspace} or the name of the object file where the frame filter
7094 (gdb) info frame-filter
7096 global frame-filters:
7097 Priority Enabled Name
7098 1000 Yes PrimaryFunctionFilter
7101 progspace /build/test frame-filters:
7102 Priority Enabled Name
7103 100 Yes ProgspaceFilter
7105 objfile /build/test frame-filters:
7106 Priority Enabled Name
7107 999 No BuildProgramFilter
7109 (gdb) set frame-filter priority global Reverse 50
7110 (gdb) info frame-filter
7112 global frame-filters:
7113 Priority Enabled Name
7114 1000 Yes PrimaryFunctionFilter
7117 progspace /build/test frame-filters:
7118 Priority Enabled Name
7119 100 Yes ProgspaceFilter
7121 objfile /build/test frame-filters:
7122 Priority Enabled Name
7123 999 No BuildProgramFilter
7128 @section Selecting a Frame
7130 Most commands for examining the stack and other data in your program work on
7131 whichever stack frame is selected at the moment. Here are the commands for
7132 selecting a stack frame; all of them finish by printing a brief description
7133 of the stack frame just selected.
7136 @kindex frame@r{, selecting}
7137 @kindex f @r{(@code{frame})}
7140 Select frame number @var{n}. Recall that frame zero is the innermost
7141 (currently executing) frame, frame one is the frame that called the
7142 innermost one, and so on. The highest-numbered frame is the one for
7145 @item frame @var{addr}
7147 Select the frame at address @var{addr}. This is useful mainly if the
7148 chaining of stack frames has been damaged by a bug, making it
7149 impossible for @value{GDBN} to assign numbers properly to all frames. In
7150 addition, this can be useful when your program has multiple stacks and
7151 switches between them.
7153 On the SPARC architecture, @code{frame} needs two addresses to
7154 select an arbitrary frame: a frame pointer and a stack pointer.
7156 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7157 pointer and a program counter.
7159 On the 29k architecture, it needs three addresses: a register stack
7160 pointer, a program counter, and a memory stack pointer.
7164 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7165 numbers @var{n}, this advances toward the outermost frame, to higher
7166 frame numbers, to frames that have existed longer.
7169 @kindex do @r{(@code{down})}
7171 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7172 positive numbers @var{n}, this advances toward the innermost frame, to
7173 lower frame numbers, to frames that were created more recently.
7174 You may abbreviate @code{down} as @code{do}.
7177 All of these commands end by printing two lines of output describing the
7178 frame. The first line shows the frame number, the function name, the
7179 arguments, and the source file and line number of execution in that
7180 frame. The second line shows the text of that source line.
7188 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7190 10 read_input_file (argv[i]);
7194 After such a printout, the @code{list} command with no arguments
7195 prints ten lines centered on the point of execution in the frame.
7196 You can also edit the program at the point of execution with your favorite
7197 editing program by typing @code{edit}.
7198 @xref{List, ,Printing Source Lines},
7202 @kindex down-silently
7204 @item up-silently @var{n}
7205 @itemx down-silently @var{n}
7206 These two commands are variants of @code{up} and @code{down},
7207 respectively; they differ in that they do their work silently, without
7208 causing display of the new frame. They are intended primarily for use
7209 in @value{GDBN} command scripts, where the output might be unnecessary and
7214 @section Information About a Frame
7216 There are several other commands to print information about the selected
7222 When used without any argument, this command does not change which
7223 frame is selected, but prints a brief description of the currently
7224 selected stack frame. It can be abbreviated @code{f}. With an
7225 argument, this command is used to select a stack frame.
7226 @xref{Selection, ,Selecting a Frame}.
7229 @kindex info f @r{(@code{info frame})}
7232 This command prints a verbose description of the selected stack frame,
7237 the address of the frame
7239 the address of the next frame down (called by this frame)
7241 the address of the next frame up (caller of this frame)
7243 the language in which the source code corresponding to this frame is written
7245 the address of the frame's arguments
7247 the address of the frame's local variables
7249 the program counter saved in it (the address of execution in the caller frame)
7251 which registers were saved in the frame
7254 @noindent The verbose description is useful when
7255 something has gone wrong that has made the stack format fail to fit
7256 the usual conventions.
7258 @item info frame @var{addr}
7259 @itemx info f @var{addr}
7260 Print a verbose description of the frame at address @var{addr}, without
7261 selecting that frame. The selected frame remains unchanged by this
7262 command. This requires the same kind of address (more than one for some
7263 architectures) that you specify in the @code{frame} command.
7264 @xref{Selection, ,Selecting a Frame}.
7268 Print the arguments of the selected frame, each on a separate line.
7272 Print the local variables of the selected frame, each on a separate
7273 line. These are all variables (declared either static or automatic)
7274 accessible at the point of execution of the selected frame.
7280 @chapter Examining Source Files
7282 @value{GDBN} can print parts of your program's source, since the debugging
7283 information recorded in the program tells @value{GDBN} what source files were
7284 used to build it. When your program stops, @value{GDBN} spontaneously prints
7285 the line where it stopped. Likewise, when you select a stack frame
7286 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7287 execution in that frame has stopped. You can print other portions of
7288 source files by explicit command.
7290 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7291 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7292 @value{GDBN} under @sc{gnu} Emacs}.
7295 * List:: Printing source lines
7296 * Specify Location:: How to specify code locations
7297 * Edit:: Editing source files
7298 * Search:: Searching source files
7299 * Source Path:: Specifying source directories
7300 * Machine Code:: Source and machine code
7304 @section Printing Source Lines
7307 @kindex l @r{(@code{list})}
7308 To print lines from a source file, use the @code{list} command
7309 (abbreviated @code{l}). By default, ten lines are printed.
7310 There are several ways to specify what part of the file you want to
7311 print; see @ref{Specify Location}, for the full list.
7313 Here are the forms of the @code{list} command most commonly used:
7316 @item list @var{linenum}
7317 Print lines centered around line number @var{linenum} in the
7318 current source file.
7320 @item list @var{function}
7321 Print lines centered around the beginning of function
7325 Print more lines. If the last lines printed were printed with a
7326 @code{list} command, this prints lines following the last lines
7327 printed; however, if the last line printed was a solitary line printed
7328 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7329 Stack}), this prints lines centered around that line.
7332 Print lines just before the lines last printed.
7335 @cindex @code{list}, how many lines to display
7336 By default, @value{GDBN} prints ten source lines with any of these forms of
7337 the @code{list} command. You can change this using @code{set listsize}:
7340 @kindex set listsize
7341 @item set listsize @var{count}
7342 @itemx set listsize unlimited
7343 Make the @code{list} command display @var{count} source lines (unless
7344 the @code{list} argument explicitly specifies some other number).
7345 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7347 @kindex show listsize
7349 Display the number of lines that @code{list} prints.
7352 Repeating a @code{list} command with @key{RET} discards the argument,
7353 so it is equivalent to typing just @code{list}. This is more useful
7354 than listing the same lines again. An exception is made for an
7355 argument of @samp{-}; that argument is preserved in repetition so that
7356 each repetition moves up in the source file.
7358 In general, the @code{list} command expects you to supply zero, one or two
7359 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7360 of writing them (@pxref{Specify Location}), but the effect is always
7361 to specify some source line.
7363 Here is a complete description of the possible arguments for @code{list}:
7366 @item list @var{linespec}
7367 Print lines centered around the line specified by @var{linespec}.
7369 @item list @var{first},@var{last}
7370 Print lines from @var{first} to @var{last}. Both arguments are
7371 linespecs. When a @code{list} command has two linespecs, and the
7372 source file of the second linespec is omitted, this refers to
7373 the same source file as the first linespec.
7375 @item list ,@var{last}
7376 Print lines ending with @var{last}.
7378 @item list @var{first},
7379 Print lines starting with @var{first}.
7382 Print lines just after the lines last printed.
7385 Print lines just before the lines last printed.
7388 As described in the preceding table.
7391 @node Specify Location
7392 @section Specifying a Location
7393 @cindex specifying location
7396 Several @value{GDBN} commands accept arguments that specify a location
7397 of your program's code. Since @value{GDBN} is a source-level
7398 debugger, a location usually specifies some line in the source code;
7399 for that reason, locations are also known as @dfn{linespecs}.
7401 Here are all the different ways of specifying a code location that
7402 @value{GDBN} understands:
7406 Specifies the line number @var{linenum} of the current source file.
7409 @itemx +@var{offset}
7410 Specifies the line @var{offset} lines before or after the @dfn{current
7411 line}. For the @code{list} command, the current line is the last one
7412 printed; for the breakpoint commands, this is the line at which
7413 execution stopped in the currently selected @dfn{stack frame}
7414 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7415 used as the second of the two linespecs in a @code{list} command,
7416 this specifies the line @var{offset} lines up or down from the first
7419 @item @var{filename}:@var{linenum}
7420 Specifies the line @var{linenum} in the source file @var{filename}.
7421 If @var{filename} is a relative file name, then it will match any
7422 source file name with the same trailing components. For example, if
7423 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7424 name of @file{/build/trunk/gcc/expr.c}, but not
7425 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7427 @item @var{function}
7428 Specifies the line that begins the body of the function @var{function}.
7429 For example, in C, this is the line with the open brace.
7431 @item @var{function}:@var{label}
7432 Specifies the line where @var{label} appears in @var{function}.
7434 @item @var{filename}:@var{function}
7435 Specifies the line that begins the body of the function @var{function}
7436 in the file @var{filename}. You only need the file name with a
7437 function name to avoid ambiguity when there are identically named
7438 functions in different source files.
7441 Specifies the line at which the label named @var{label} appears.
7442 @value{GDBN} searches for the label in the function corresponding to
7443 the currently selected stack frame. If there is no current selected
7444 stack frame (for instance, if the inferior is not running), then
7445 @value{GDBN} will not search for a label.
7447 @item *@var{address}
7448 Specifies the program address @var{address}. For line-oriented
7449 commands, such as @code{list} and @code{edit}, this specifies a source
7450 line that contains @var{address}. For @code{break} and other
7451 breakpoint oriented commands, this can be used to set breakpoints in
7452 parts of your program which do not have debugging information or
7455 Here @var{address} may be any expression valid in the current working
7456 language (@pxref{Languages, working language}) that specifies a code
7457 address. In addition, as a convenience, @value{GDBN} extends the
7458 semantics of expressions used in locations to cover the situations
7459 that frequently happen during debugging. Here are the various forms
7463 @item @var{expression}
7464 Any expression valid in the current working language.
7466 @item @var{funcaddr}
7467 An address of a function or procedure derived from its name. In C,
7468 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7469 simply the function's name @var{function} (and actually a special case
7470 of a valid expression). In Pascal and Modula-2, this is
7471 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7472 (although the Pascal form also works).
7474 This form specifies the address of the function's first instruction,
7475 before the stack frame and arguments have been set up.
7477 @item '@var{filename}'::@var{funcaddr}
7478 Like @var{funcaddr} above, but also specifies the name of the source
7479 file explicitly. This is useful if the name of the function does not
7480 specify the function unambiguously, e.g., if there are several
7481 functions with identical names in different source files.
7484 @cindex breakpoint at static probe point
7485 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7486 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7487 applications to embed static probes. @xref{Static Probe Points}, for more
7488 information on finding and using static probes. This form of linespec
7489 specifies the location of such a static probe.
7491 If @var{objfile} is given, only probes coming from that shared library
7492 or executable matching @var{objfile} as a regular expression are considered.
7493 If @var{provider} is given, then only probes from that provider are considered.
7494 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7495 each one of those probes.
7501 @section Editing Source Files
7502 @cindex editing source files
7505 @kindex e @r{(@code{edit})}
7506 To edit the lines in a source file, use the @code{edit} command.
7507 The editing program of your choice
7508 is invoked with the current line set to
7509 the active line in the program.
7510 Alternatively, there are several ways to specify what part of the file you
7511 want to print if you want to see other parts of the program:
7514 @item edit @var{location}
7515 Edit the source file specified by @code{location}. Editing starts at
7516 that @var{location}, e.g., at the specified source line of the
7517 specified file. @xref{Specify Location}, for all the possible forms
7518 of the @var{location} argument; here are the forms of the @code{edit}
7519 command most commonly used:
7522 @item edit @var{number}
7523 Edit the current source file with @var{number} as the active line number.
7525 @item edit @var{function}
7526 Edit the file containing @var{function} at the beginning of its definition.
7531 @subsection Choosing your Editor
7532 You can customize @value{GDBN} to use any editor you want
7534 The only restriction is that your editor (say @code{ex}), recognizes the
7535 following command-line syntax:
7537 ex +@var{number} file
7539 The optional numeric value +@var{number} specifies the number of the line in
7540 the file where to start editing.}.
7541 By default, it is @file{@value{EDITOR}}, but you can change this
7542 by setting the environment variable @code{EDITOR} before using
7543 @value{GDBN}. For example, to configure @value{GDBN} to use the
7544 @code{vi} editor, you could use these commands with the @code{sh} shell:
7550 or in the @code{csh} shell,
7552 setenv EDITOR /usr/bin/vi
7557 @section Searching Source Files
7558 @cindex searching source files
7560 There are two commands for searching through the current source file for a
7565 @kindex forward-search
7566 @kindex fo @r{(@code{forward-search})}
7567 @item forward-search @var{regexp}
7568 @itemx search @var{regexp}
7569 The command @samp{forward-search @var{regexp}} checks each line,
7570 starting with the one following the last line listed, for a match for
7571 @var{regexp}. It lists the line that is found. You can use the
7572 synonym @samp{search @var{regexp}} or abbreviate the command name as
7575 @kindex reverse-search
7576 @item reverse-search @var{regexp}
7577 The command @samp{reverse-search @var{regexp}} checks each line, starting
7578 with the one before the last line listed and going backward, for a match
7579 for @var{regexp}. It lists the line that is found. You can abbreviate
7580 this command as @code{rev}.
7584 @section Specifying Source Directories
7587 @cindex directories for source files
7588 Executable programs sometimes do not record the directories of the source
7589 files from which they were compiled, just the names. Even when they do,
7590 the directories could be moved between the compilation and your debugging
7591 session. @value{GDBN} has a list of directories to search for source files;
7592 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7593 it tries all the directories in the list, in the order they are present
7594 in the list, until it finds a file with the desired name.
7596 For example, suppose an executable references the file
7597 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7598 @file{/mnt/cross}. The file is first looked up literally; if this
7599 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7600 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7601 message is printed. @value{GDBN} does not look up the parts of the
7602 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7603 Likewise, the subdirectories of the source path are not searched: if
7604 the source path is @file{/mnt/cross}, and the binary refers to
7605 @file{foo.c}, @value{GDBN} would not find it under
7606 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7608 Plain file names, relative file names with leading directories, file
7609 names containing dots, etc.@: are all treated as described above; for
7610 instance, if the source path is @file{/mnt/cross}, and the source file
7611 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7612 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7613 that---@file{/mnt/cross/foo.c}.
7615 Note that the executable search path is @emph{not} used to locate the
7618 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7619 any information it has cached about where source files are found and where
7620 each line is in the file.
7624 When you start @value{GDBN}, its source path includes only @samp{cdir}
7625 and @samp{cwd}, in that order.
7626 To add other directories, use the @code{directory} command.
7628 The search path is used to find both program source files and @value{GDBN}
7629 script files (read using the @samp{-command} option and @samp{source} command).
7631 In addition to the source path, @value{GDBN} provides a set of commands
7632 that manage a list of source path substitution rules. A @dfn{substitution
7633 rule} specifies how to rewrite source directories stored in the program's
7634 debug information in case the sources were moved to a different
7635 directory between compilation and debugging. A rule is made of
7636 two strings, the first specifying what needs to be rewritten in
7637 the path, and the second specifying how it should be rewritten.
7638 In @ref{set substitute-path}, we name these two parts @var{from} and
7639 @var{to} respectively. @value{GDBN} does a simple string replacement
7640 of @var{from} with @var{to} at the start of the directory part of the
7641 source file name, and uses that result instead of the original file
7642 name to look up the sources.
7644 Using the previous example, suppose the @file{foo-1.0} tree has been
7645 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7646 @value{GDBN} to replace @file{/usr/src} in all source path names with
7647 @file{/mnt/cross}. The first lookup will then be
7648 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7649 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7650 substitution rule, use the @code{set substitute-path} command
7651 (@pxref{set substitute-path}).
7653 To avoid unexpected substitution results, a rule is applied only if the
7654 @var{from} part of the directory name ends at a directory separator.
7655 For instance, a rule substituting @file{/usr/source} into
7656 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7657 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7658 is applied only at the beginning of the directory name, this rule will
7659 not be applied to @file{/root/usr/source/baz.c} either.
7661 In many cases, you can achieve the same result using the @code{directory}
7662 command. However, @code{set substitute-path} can be more efficient in
7663 the case where the sources are organized in a complex tree with multiple
7664 subdirectories. With the @code{directory} command, you need to add each
7665 subdirectory of your project. If you moved the entire tree while
7666 preserving its internal organization, then @code{set substitute-path}
7667 allows you to direct the debugger to all the sources with one single
7670 @code{set substitute-path} is also more than just a shortcut command.
7671 The source path is only used if the file at the original location no
7672 longer exists. On the other hand, @code{set substitute-path} modifies
7673 the debugger behavior to look at the rewritten location instead. So, if
7674 for any reason a source file that is not relevant to your executable is
7675 located at the original location, a substitution rule is the only
7676 method available to point @value{GDBN} at the new location.
7678 @cindex @samp{--with-relocated-sources}
7679 @cindex default source path substitution
7680 You can configure a default source path substitution rule by
7681 configuring @value{GDBN} with the
7682 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7683 should be the name of a directory under @value{GDBN}'s configured
7684 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7685 directory names in debug information under @var{dir} will be adjusted
7686 automatically if the installed @value{GDBN} is moved to a new
7687 location. This is useful if @value{GDBN}, libraries or executables
7688 with debug information and corresponding source code are being moved
7692 @item directory @var{dirname} @dots{}
7693 @item dir @var{dirname} @dots{}
7694 Add directory @var{dirname} to the front of the source path. Several
7695 directory names may be given to this command, separated by @samp{:}
7696 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7697 part of absolute file names) or
7698 whitespace. You may specify a directory that is already in the source
7699 path; this moves it forward, so @value{GDBN} searches it sooner.
7703 @vindex $cdir@r{, convenience variable}
7704 @vindex $cwd@r{, convenience variable}
7705 @cindex compilation directory
7706 @cindex current directory
7707 @cindex working directory
7708 @cindex directory, current
7709 @cindex directory, compilation
7710 You can use the string @samp{$cdir} to refer to the compilation
7711 directory (if one is recorded), and @samp{$cwd} to refer to the current
7712 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7713 tracks the current working directory as it changes during your @value{GDBN}
7714 session, while the latter is immediately expanded to the current
7715 directory at the time you add an entry to the source path.
7718 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7720 @c RET-repeat for @code{directory} is explicitly disabled, but since
7721 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7723 @item set directories @var{path-list}
7724 @kindex set directories
7725 Set the source path to @var{path-list}.
7726 @samp{$cdir:$cwd} are added if missing.
7728 @item show directories
7729 @kindex show directories
7730 Print the source path: show which directories it contains.
7732 @anchor{set substitute-path}
7733 @item set substitute-path @var{from} @var{to}
7734 @kindex set substitute-path
7735 Define a source path substitution rule, and add it at the end of the
7736 current list of existing substitution rules. If a rule with the same
7737 @var{from} was already defined, then the old rule is also deleted.
7739 For example, if the file @file{/foo/bar/baz.c} was moved to
7740 @file{/mnt/cross/baz.c}, then the command
7743 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7747 will tell @value{GDBN} to replace @samp{/usr/src} with
7748 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7749 @file{baz.c} even though it was moved.
7751 In the case when more than one substitution rule have been defined,
7752 the rules are evaluated one by one in the order where they have been
7753 defined. The first one matching, if any, is selected to perform
7756 For instance, if we had entered the following commands:
7759 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7760 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7764 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7765 @file{/mnt/include/defs.h} by using the first rule. However, it would
7766 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7767 @file{/mnt/src/lib/foo.c}.
7770 @item unset substitute-path [path]
7771 @kindex unset substitute-path
7772 If a path is specified, search the current list of substitution rules
7773 for a rule that would rewrite that path. Delete that rule if found.
7774 A warning is emitted by the debugger if no rule could be found.
7776 If no path is specified, then all substitution rules are deleted.
7778 @item show substitute-path [path]
7779 @kindex show substitute-path
7780 If a path is specified, then print the source path substitution rule
7781 which would rewrite that path, if any.
7783 If no path is specified, then print all existing source path substitution
7788 If your source path is cluttered with directories that are no longer of
7789 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7790 versions of source. You can correct the situation as follows:
7794 Use @code{directory} with no argument to reset the source path to its default value.
7797 Use @code{directory} with suitable arguments to reinstall the
7798 directories you want in the source path. You can add all the
7799 directories in one command.
7803 @section Source and Machine Code
7804 @cindex source line and its code address
7806 You can use the command @code{info line} to map source lines to program
7807 addresses (and vice versa), and the command @code{disassemble} to display
7808 a range of addresses as machine instructions. You can use the command
7809 @code{set disassemble-next-line} to set whether to disassemble next
7810 source line when execution stops. When run under @sc{gnu} Emacs
7811 mode, the @code{info line} command causes the arrow to point to the
7812 line specified. Also, @code{info line} prints addresses in symbolic form as
7817 @item info line @var{linespec}
7818 Print the starting and ending addresses of the compiled code for
7819 source line @var{linespec}. You can specify source lines in any of
7820 the ways documented in @ref{Specify Location}.
7823 For example, we can use @code{info line} to discover the location of
7824 the object code for the first line of function
7825 @code{m4_changequote}:
7827 @c FIXME: I think this example should also show the addresses in
7828 @c symbolic form, as they usually would be displayed.
7830 (@value{GDBP}) info line m4_changequote
7831 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7835 @cindex code address and its source line
7836 We can also inquire (using @code{*@var{addr}} as the form for
7837 @var{linespec}) what source line covers a particular address:
7839 (@value{GDBP}) info line *0x63ff
7840 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7843 @cindex @code{$_} and @code{info line}
7844 @cindex @code{x} command, default address
7845 @kindex x@r{(examine), and} info line
7846 After @code{info line}, the default address for the @code{x} command
7847 is changed to the starting address of the line, so that @samp{x/i} is
7848 sufficient to begin examining the machine code (@pxref{Memory,
7849 ,Examining Memory}). Also, this address is saved as the value of the
7850 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7855 @cindex assembly instructions
7856 @cindex instructions, assembly
7857 @cindex machine instructions
7858 @cindex listing machine instructions
7860 @itemx disassemble /m
7861 @itemx disassemble /r
7862 This specialized command dumps a range of memory as machine
7863 instructions. It can also print mixed source+disassembly by specifying
7864 the @code{/m} modifier and print the raw instructions in hex as well as
7865 in symbolic form by specifying the @code{/r}.
7866 The default memory range is the function surrounding the
7867 program counter of the selected frame. A single argument to this
7868 command is a program counter value; @value{GDBN} dumps the function
7869 surrounding this value. When two arguments are given, they should
7870 be separated by a comma, possibly surrounded by whitespace. The
7871 arguments specify a range of addresses to dump, in one of two forms:
7874 @item @var{start},@var{end}
7875 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7876 @item @var{start},+@var{length}
7877 the addresses from @var{start} (inclusive) to
7878 @code{@var{start}+@var{length}} (exclusive).
7882 When 2 arguments are specified, the name of the function is also
7883 printed (since there could be several functions in the given range).
7885 The argument(s) can be any expression yielding a numeric value, such as
7886 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7888 If the range of memory being disassembled contains current program counter,
7889 the instruction at that location is shown with a @code{=>} marker.
7892 The following example shows the disassembly of a range of addresses of
7893 HP PA-RISC 2.0 code:
7896 (@value{GDBP}) disas 0x32c4, 0x32e4
7897 Dump of assembler code from 0x32c4 to 0x32e4:
7898 0x32c4 <main+204>: addil 0,dp
7899 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7900 0x32cc <main+212>: ldil 0x3000,r31
7901 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7902 0x32d4 <main+220>: ldo 0(r31),rp
7903 0x32d8 <main+224>: addil -0x800,dp
7904 0x32dc <main+228>: ldo 0x588(r1),r26
7905 0x32e0 <main+232>: ldil 0x3000,r31
7906 End of assembler dump.
7909 Here is an example showing mixed source+assembly for Intel x86, when the
7910 program is stopped just after function prologue:
7913 (@value{GDBP}) disas /m main
7914 Dump of assembler code for function main:
7916 0x08048330 <+0>: push %ebp
7917 0x08048331 <+1>: mov %esp,%ebp
7918 0x08048333 <+3>: sub $0x8,%esp
7919 0x08048336 <+6>: and $0xfffffff0,%esp
7920 0x08048339 <+9>: sub $0x10,%esp
7922 6 printf ("Hello.\n");
7923 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7924 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7928 0x08048348 <+24>: mov $0x0,%eax
7929 0x0804834d <+29>: leave
7930 0x0804834e <+30>: ret
7932 End of assembler dump.
7935 Here is another example showing raw instructions in hex for AMD x86-64,
7938 (gdb) disas /r 0x400281,+10
7939 Dump of assembler code from 0x400281 to 0x40028b:
7940 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7941 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7942 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7943 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7944 End of assembler dump.
7947 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7948 So, for example, if you want to disassemble function @code{bar}
7949 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7950 and not @samp{disassemble foo.c:bar}.
7952 Some architectures have more than one commonly-used set of instruction
7953 mnemonics or other syntax.
7955 For programs that were dynamically linked and use shared libraries,
7956 instructions that call functions or branch to locations in the shared
7957 libraries might show a seemingly bogus location---it's actually a
7958 location of the relocation table. On some architectures, @value{GDBN}
7959 might be able to resolve these to actual function names.
7962 @kindex set disassembly-flavor
7963 @cindex Intel disassembly flavor
7964 @cindex AT&T disassembly flavor
7965 @item set disassembly-flavor @var{instruction-set}
7966 Select the instruction set to use when disassembling the
7967 program via the @code{disassemble} or @code{x/i} commands.
7969 Currently this command is only defined for the Intel x86 family. You
7970 can set @var{instruction-set} to either @code{intel} or @code{att}.
7971 The default is @code{att}, the AT&T flavor used by default by Unix
7972 assemblers for x86-based targets.
7974 @kindex show disassembly-flavor
7975 @item show disassembly-flavor
7976 Show the current setting of the disassembly flavor.
7980 @kindex set disassemble-next-line
7981 @kindex show disassemble-next-line
7982 @item set disassemble-next-line
7983 @itemx show disassemble-next-line
7984 Control whether or not @value{GDBN} will disassemble the next source
7985 line or instruction when execution stops. If ON, @value{GDBN} will
7986 display disassembly of the next source line when execution of the
7987 program being debugged stops. This is @emph{in addition} to
7988 displaying the source line itself, which @value{GDBN} always does if
7989 possible. If the next source line cannot be displayed for some reason
7990 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7991 info in the debug info), @value{GDBN} will display disassembly of the
7992 next @emph{instruction} instead of showing the next source line. If
7993 AUTO, @value{GDBN} will display disassembly of next instruction only
7994 if the source line cannot be displayed. This setting causes
7995 @value{GDBN} to display some feedback when you step through a function
7996 with no line info or whose source file is unavailable. The default is
7997 OFF, which means never display the disassembly of the next line or
8003 @chapter Examining Data
8005 @cindex printing data
8006 @cindex examining data
8009 The usual way to examine data in your program is with the @code{print}
8010 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8011 evaluates and prints the value of an expression of the language your
8012 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8013 Different Languages}). It may also print the expression using a
8014 Python-based pretty-printer (@pxref{Pretty Printing}).
8017 @item print @var{expr}
8018 @itemx print /@var{f} @var{expr}
8019 @var{expr} is an expression (in the source language). By default the
8020 value of @var{expr} is printed in a format appropriate to its data type;
8021 you can choose a different format by specifying @samp{/@var{f}}, where
8022 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8026 @itemx print /@var{f}
8027 @cindex reprint the last value
8028 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8029 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8030 conveniently inspect the same value in an alternative format.
8033 A more low-level way of examining data is with the @code{x} command.
8034 It examines data in memory at a specified address and prints it in a
8035 specified format. @xref{Memory, ,Examining Memory}.
8037 If you are interested in information about types, or about how the
8038 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8039 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8042 @cindex exploring hierarchical data structures
8044 Another way of examining values of expressions and type information is
8045 through the Python extension command @code{explore} (available only if
8046 the @value{GDBN} build is configured with @code{--with-python}). It
8047 offers an interactive way to start at the highest level (or, the most
8048 abstract level) of the data type of an expression (or, the data type
8049 itself) and explore all the way down to leaf scalar values/fields
8050 embedded in the higher level data types.
8053 @item explore @var{arg}
8054 @var{arg} is either an expression (in the source language), or a type
8055 visible in the current context of the program being debugged.
8058 The working of the @code{explore} command can be illustrated with an
8059 example. If a data type @code{struct ComplexStruct} is defined in your
8069 struct ComplexStruct
8071 struct SimpleStruct *ss_p;
8077 followed by variable declarations as
8080 struct SimpleStruct ss = @{ 10, 1.11 @};
8081 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8085 then, the value of the variable @code{cs} can be explored using the
8086 @code{explore} command as follows.
8090 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8091 the following fields:
8093 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8094 arr = <Enter 1 to explore this field of type `int [10]'>
8096 Enter the field number of choice:
8100 Since the fields of @code{cs} are not scalar values, you are being
8101 prompted to chose the field you want to explore. Let's say you choose
8102 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8103 pointer, you will be asked if it is pointing to a single value. From
8104 the declaration of @code{cs} above, it is indeed pointing to a single
8105 value, hence you enter @code{y}. If you enter @code{n}, then you will
8106 be asked if it were pointing to an array of values, in which case this
8107 field will be explored as if it were an array.
8110 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8111 Continue exploring it as a pointer to a single value [y/n]: y
8112 The value of `*(cs.ss_p)' is a struct/class of type `struct
8113 SimpleStruct' with the following fields:
8115 i = 10 .. (Value of type `int')
8116 d = 1.1100000000000001 .. (Value of type `double')
8118 Press enter to return to parent value:
8122 If the field @code{arr} of @code{cs} was chosen for exploration by
8123 entering @code{1} earlier, then since it is as array, you will be
8124 prompted to enter the index of the element in the array that you want
8128 `cs.arr' is an array of `int'.
8129 Enter the index of the element you want to explore in `cs.arr': 5
8131 `(cs.arr)[5]' is a scalar value of type `int'.
8135 Press enter to return to parent value:
8138 In general, at any stage of exploration, you can go deeper towards the
8139 leaf values by responding to the prompts appropriately, or hit the
8140 return key to return to the enclosing data structure (the @i{higher}
8141 level data structure).
8143 Similar to exploring values, you can use the @code{explore} command to
8144 explore types. Instead of specifying a value (which is typically a
8145 variable name or an expression valid in the current context of the
8146 program being debugged), you specify a type name. If you consider the
8147 same example as above, your can explore the type
8148 @code{struct ComplexStruct} by passing the argument
8149 @code{struct ComplexStruct} to the @code{explore} command.
8152 (gdb) explore struct ComplexStruct
8156 By responding to the prompts appropriately in the subsequent interactive
8157 session, you can explore the type @code{struct ComplexStruct} in a
8158 manner similar to how the value @code{cs} was explored in the above
8161 The @code{explore} command also has two sub-commands,
8162 @code{explore value} and @code{explore type}. The former sub-command is
8163 a way to explicitly specify that value exploration of the argument is
8164 being invoked, while the latter is a way to explicitly specify that type
8165 exploration of the argument is being invoked.
8168 @item explore value @var{expr}
8169 @cindex explore value
8170 This sub-command of @code{explore} explores the value of the
8171 expression @var{expr} (if @var{expr} is an expression valid in the
8172 current context of the program being debugged). The behavior of this
8173 command is identical to that of the behavior of the @code{explore}
8174 command being passed the argument @var{expr}.
8176 @item explore type @var{arg}
8177 @cindex explore type
8178 This sub-command of @code{explore} explores the type of @var{arg} (if
8179 @var{arg} is a type visible in the current context of program being
8180 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8181 is an expression valid in the current context of the program being
8182 debugged). If @var{arg} is a type, then the behavior of this command is
8183 identical to that of the @code{explore} command being passed the
8184 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8185 this command will be identical to that of the @code{explore} command
8186 being passed the type of @var{arg} as the argument.
8190 * Expressions:: Expressions
8191 * Ambiguous Expressions:: Ambiguous Expressions
8192 * Variables:: Program variables
8193 * Arrays:: Artificial arrays
8194 * Output Formats:: Output formats
8195 * Memory:: Examining memory
8196 * Auto Display:: Automatic display
8197 * Print Settings:: Print settings
8198 * Pretty Printing:: Python pretty printing
8199 * Value History:: Value history
8200 * Convenience Vars:: Convenience variables
8201 * Convenience Funs:: Convenience functions
8202 * Registers:: Registers
8203 * Floating Point Hardware:: Floating point hardware
8204 * Vector Unit:: Vector Unit
8205 * OS Information:: Auxiliary data provided by operating system
8206 * Memory Region Attributes:: Memory region attributes
8207 * Dump/Restore Files:: Copy between memory and a file
8208 * Core File Generation:: Cause a program dump its core
8209 * Character Sets:: Debugging programs that use a different
8210 character set than GDB does
8211 * Caching Target Data:: Data caching for targets
8212 * Searching Memory:: Searching memory for a sequence of bytes
8216 @section Expressions
8219 @code{print} and many other @value{GDBN} commands accept an expression and
8220 compute its value. Any kind of constant, variable or operator defined
8221 by the programming language you are using is valid in an expression in
8222 @value{GDBN}. This includes conditional expressions, function calls,
8223 casts, and string constants. It also includes preprocessor macros, if
8224 you compiled your program to include this information; see
8227 @cindex arrays in expressions
8228 @value{GDBN} supports array constants in expressions input by
8229 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8230 you can use the command @code{print @{1, 2, 3@}} to create an array
8231 of three integers. If you pass an array to a function or assign it
8232 to a program variable, @value{GDBN} copies the array to memory that
8233 is @code{malloc}ed in the target program.
8235 Because C is so widespread, most of the expressions shown in examples in
8236 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8237 Languages}, for information on how to use expressions in other
8240 In this section, we discuss operators that you can use in @value{GDBN}
8241 expressions regardless of your programming language.
8243 @cindex casts, in expressions
8244 Casts are supported in all languages, not just in C, because it is so
8245 useful to cast a number into a pointer in order to examine a structure
8246 at that address in memory.
8247 @c FIXME: casts supported---Mod2 true?
8249 @value{GDBN} supports these operators, in addition to those common
8250 to programming languages:
8254 @samp{@@} is a binary operator for treating parts of memory as arrays.
8255 @xref{Arrays, ,Artificial Arrays}, for more information.
8258 @samp{::} allows you to specify a variable in terms of the file or
8259 function where it is defined. @xref{Variables, ,Program Variables}.
8261 @cindex @{@var{type}@}
8262 @cindex type casting memory
8263 @cindex memory, viewing as typed object
8264 @cindex casts, to view memory
8265 @item @{@var{type}@} @var{addr}
8266 Refers to an object of type @var{type} stored at address @var{addr} in
8267 memory. The address @var{addr} may be any expression whose value is
8268 an integer or pointer (but parentheses are required around binary
8269 operators, just as in a cast). This construct is allowed regardless
8270 of what kind of data is normally supposed to reside at @var{addr}.
8273 @node Ambiguous Expressions
8274 @section Ambiguous Expressions
8275 @cindex ambiguous expressions
8277 Expressions can sometimes contain some ambiguous elements. For instance,
8278 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8279 a single function name to be defined several times, for application in
8280 different contexts. This is called @dfn{overloading}. Another example
8281 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8282 templates and is typically instantiated several times, resulting in
8283 the same function name being defined in different contexts.
8285 In some cases and depending on the language, it is possible to adjust
8286 the expression to remove the ambiguity. For instance in C@t{++}, you
8287 can specify the signature of the function you want to break on, as in
8288 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8289 qualified name of your function often makes the expression unambiguous
8292 When an ambiguity that needs to be resolved is detected, the debugger
8293 has the capability to display a menu of numbered choices for each
8294 possibility, and then waits for the selection with the prompt @samp{>}.
8295 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8296 aborts the current command. If the command in which the expression was
8297 used allows more than one choice to be selected, the next option in the
8298 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8301 For example, the following session excerpt shows an attempt to set a
8302 breakpoint at the overloaded symbol @code{String::after}.
8303 We choose three particular definitions of that function name:
8305 @c FIXME! This is likely to change to show arg type lists, at least
8308 (@value{GDBP}) b String::after
8311 [2] file:String.cc; line number:867
8312 [3] file:String.cc; line number:860
8313 [4] file:String.cc; line number:875
8314 [5] file:String.cc; line number:853
8315 [6] file:String.cc; line number:846
8316 [7] file:String.cc; line number:735
8318 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8319 Breakpoint 2 at 0xb344: file String.cc, line 875.
8320 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8321 Multiple breakpoints were set.
8322 Use the "delete" command to delete unwanted
8329 @kindex set multiple-symbols
8330 @item set multiple-symbols @var{mode}
8331 @cindex multiple-symbols menu
8333 This option allows you to adjust the debugger behavior when an expression
8336 By default, @var{mode} is set to @code{all}. If the command with which
8337 the expression is used allows more than one choice, then @value{GDBN}
8338 automatically selects all possible choices. For instance, inserting
8339 a breakpoint on a function using an ambiguous name results in a breakpoint
8340 inserted on each possible match. However, if a unique choice must be made,
8341 then @value{GDBN} uses the menu to help you disambiguate the expression.
8342 For instance, printing the address of an overloaded function will result
8343 in the use of the menu.
8345 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8346 when an ambiguity is detected.
8348 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8349 an error due to the ambiguity and the command is aborted.
8351 @kindex show multiple-symbols
8352 @item show multiple-symbols
8353 Show the current value of the @code{multiple-symbols} setting.
8357 @section Program Variables
8359 The most common kind of expression to use is the name of a variable
8362 Variables in expressions are understood in the selected stack frame
8363 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8367 global (or file-static)
8374 visible according to the scope rules of the
8375 programming language from the point of execution in that frame
8378 @noindent This means that in the function
8393 you can examine and use the variable @code{a} whenever your program is
8394 executing within the function @code{foo}, but you can only use or
8395 examine the variable @code{b} while your program is executing inside
8396 the block where @code{b} is declared.
8398 @cindex variable name conflict
8399 There is an exception: you can refer to a variable or function whose
8400 scope is a single source file even if the current execution point is not
8401 in this file. But it is possible to have more than one such variable or
8402 function with the same name (in different source files). If that
8403 happens, referring to that name has unpredictable effects. If you wish,
8404 you can specify a static variable in a particular function or file by
8405 using the colon-colon (@code{::}) notation:
8407 @cindex colon-colon, context for variables/functions
8409 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8410 @cindex @code{::}, context for variables/functions
8413 @var{file}::@var{variable}
8414 @var{function}::@var{variable}
8418 Here @var{file} or @var{function} is the name of the context for the
8419 static @var{variable}. In the case of file names, you can use quotes to
8420 make sure @value{GDBN} parses the file name as a single word---for example,
8421 to print a global value of @code{x} defined in @file{f2.c}:
8424 (@value{GDBP}) p 'f2.c'::x
8427 The @code{::} notation is normally used for referring to
8428 static variables, since you typically disambiguate uses of local variables
8429 in functions by selecting the appropriate frame and using the
8430 simple name of the variable. However, you may also use this notation
8431 to refer to local variables in frames enclosing the selected frame:
8440 process (a); /* Stop here */
8451 For example, if there is a breakpoint at the commented line,
8452 here is what you might see
8453 when the program stops after executing the call @code{bar(0)}:
8458 (@value{GDBP}) p bar::a
8461 #2 0x080483d0 in foo (a=5) at foobar.c:12
8464 (@value{GDBP}) p bar::a
8468 @cindex C@t{++} scope resolution
8469 These uses of @samp{::} are very rarely in conflict with the very
8470 similar use of the same notation in C@t{++}. When they are in
8471 conflict, the C@t{++} meaning takes precedence; however, this can be
8472 overridden by quoting the file or function name with single quotes.
8474 For example, suppose the program is stopped in a method of a class
8475 that has a field named @code{includefile}, and there is also an
8476 include file named @file{includefile} that defines a variable,
8480 (@value{GDBP}) p includefile
8482 (@value{GDBP}) p includefile::some_global
8483 A syntax error in expression, near `'.
8484 (@value{GDBP}) p 'includefile'::some_global
8488 @cindex wrong values
8489 @cindex variable values, wrong
8490 @cindex function entry/exit, wrong values of variables
8491 @cindex optimized code, wrong values of variables
8493 @emph{Warning:} Occasionally, a local variable may appear to have the
8494 wrong value at certain points in a function---just after entry to a new
8495 scope, and just before exit.
8497 You may see this problem when you are stepping by machine instructions.
8498 This is because, on most machines, it takes more than one instruction to
8499 set up a stack frame (including local variable definitions); if you are
8500 stepping by machine instructions, variables may appear to have the wrong
8501 values until the stack frame is completely built. On exit, it usually
8502 also takes more than one machine instruction to destroy a stack frame;
8503 after you begin stepping through that group of instructions, local
8504 variable definitions may be gone.
8506 This may also happen when the compiler does significant optimizations.
8507 To be sure of always seeing accurate values, turn off all optimization
8510 @cindex ``No symbol "foo" in current context''
8511 Another possible effect of compiler optimizations is to optimize
8512 unused variables out of existence, or assign variables to registers (as
8513 opposed to memory addresses). Depending on the support for such cases
8514 offered by the debug info format used by the compiler, @value{GDBN}
8515 might not be able to display values for such local variables. If that
8516 happens, @value{GDBN} will print a message like this:
8519 No symbol "foo" in current context.
8522 To solve such problems, either recompile without optimizations, or use a
8523 different debug info format, if the compiler supports several such
8524 formats. @xref{Compilation}, for more information on choosing compiler
8525 options. @xref{C, ,C and C@t{++}}, for more information about debug
8526 info formats that are best suited to C@t{++} programs.
8528 If you ask to print an object whose contents are unknown to
8529 @value{GDBN}, e.g., because its data type is not completely specified
8530 by the debug information, @value{GDBN} will say @samp{<incomplete
8531 type>}. @xref{Symbols, incomplete type}, for more about this.
8533 If you append @kbd{@@entry} string to a function parameter name you get its
8534 value at the time the function got called. If the value is not available an
8535 error message is printed. Entry values are available only with some compilers.
8536 Entry values are normally also printed at the function parameter list according
8537 to @ref{set print entry-values}.
8540 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8546 (gdb) print i@@entry
8550 Strings are identified as arrays of @code{char} values without specified
8551 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8552 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8553 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8554 defines literal string type @code{"char"} as @code{char} without a sign.
8559 signed char var1[] = "A";
8562 You get during debugging
8567 $2 = @{65 'A', 0 '\0'@}
8571 @section Artificial Arrays
8573 @cindex artificial array
8575 @kindex @@@r{, referencing memory as an array}
8576 It is often useful to print out several successive objects of the
8577 same type in memory; a section of an array, or an array of
8578 dynamically determined size for which only a pointer exists in the
8581 You can do this by referring to a contiguous span of memory as an
8582 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8583 operand of @samp{@@} should be the first element of the desired array
8584 and be an individual object. The right operand should be the desired length
8585 of the array. The result is an array value whose elements are all of
8586 the type of the left argument. The first element is actually the left
8587 argument; the second element comes from bytes of memory immediately
8588 following those that hold the first element, and so on. Here is an
8589 example. If a program says
8592 int *array = (int *) malloc (len * sizeof (int));
8596 you can print the contents of @code{array} with
8602 The left operand of @samp{@@} must reside in memory. Array values made
8603 with @samp{@@} in this way behave just like other arrays in terms of
8604 subscripting, and are coerced to pointers when used in expressions.
8605 Artificial arrays most often appear in expressions via the value history
8606 (@pxref{Value History, ,Value History}), after printing one out.
8608 Another way to create an artificial array is to use a cast.
8609 This re-interprets a value as if it were an array.
8610 The value need not be in memory:
8612 (@value{GDBP}) p/x (short[2])0x12345678
8613 $1 = @{0x1234, 0x5678@}
8616 As a convenience, if you leave the array length out (as in
8617 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8618 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8620 (@value{GDBP}) p/x (short[])0x12345678
8621 $2 = @{0x1234, 0x5678@}
8624 Sometimes the artificial array mechanism is not quite enough; in
8625 moderately complex data structures, the elements of interest may not
8626 actually be adjacent---for example, if you are interested in the values
8627 of pointers in an array. One useful work-around in this situation is
8628 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8629 Variables}) as a counter in an expression that prints the first
8630 interesting value, and then repeat that expression via @key{RET}. For
8631 instance, suppose you have an array @code{dtab} of pointers to
8632 structures, and you are interested in the values of a field @code{fv}
8633 in each structure. Here is an example of what you might type:
8643 @node Output Formats
8644 @section Output Formats
8646 @cindex formatted output
8647 @cindex output formats
8648 By default, @value{GDBN} prints a value according to its data type. Sometimes
8649 this is not what you want. For example, you might want to print a number
8650 in hex, or a pointer in decimal. Or you might want to view data in memory
8651 at a certain address as a character string or as an instruction. To do
8652 these things, specify an @dfn{output format} when you print a value.
8654 The simplest use of output formats is to say how to print a value
8655 already computed. This is done by starting the arguments of the
8656 @code{print} command with a slash and a format letter. The format
8657 letters supported are:
8661 Regard the bits of the value as an integer, and print the integer in
8665 Print as integer in signed decimal.
8668 Print as integer in unsigned decimal.
8671 Print as integer in octal.
8674 Print as integer in binary. The letter @samp{t} stands for ``two''.
8675 @footnote{@samp{b} cannot be used because these format letters are also
8676 used with the @code{x} command, where @samp{b} stands for ``byte'';
8677 see @ref{Memory,,Examining Memory}.}
8680 @cindex unknown address, locating
8681 @cindex locate address
8682 Print as an address, both absolute in hexadecimal and as an offset from
8683 the nearest preceding symbol. You can use this format used to discover
8684 where (in what function) an unknown address is located:
8687 (@value{GDBP}) p/a 0x54320
8688 $3 = 0x54320 <_initialize_vx+396>
8692 The command @code{info symbol 0x54320} yields similar results.
8693 @xref{Symbols, info symbol}.
8696 Regard as an integer and print it as a character constant. This
8697 prints both the numerical value and its character representation. The
8698 character representation is replaced with the octal escape @samp{\nnn}
8699 for characters outside the 7-bit @sc{ascii} range.
8701 Without this format, @value{GDBN} displays @code{char},
8702 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8703 constants. Single-byte members of vectors are displayed as integer
8707 Regard the bits of the value as a floating point number and print
8708 using typical floating point syntax.
8711 @cindex printing strings
8712 @cindex printing byte arrays
8713 Regard as a string, if possible. With this format, pointers to single-byte
8714 data are displayed as null-terminated strings and arrays of single-byte data
8715 are displayed as fixed-length strings. Other values are displayed in their
8718 Without this format, @value{GDBN} displays pointers to and arrays of
8719 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8720 strings. Single-byte members of a vector are displayed as an integer
8724 Like @samp{x} formatting, the value is treated as an integer and
8725 printed as hexadecimal, but leading zeros are printed to pad the value
8726 to the size of the integer type.
8729 @cindex raw printing
8730 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8731 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8732 Printing}). This typically results in a higher-level display of the
8733 value's contents. The @samp{r} format bypasses any Python
8734 pretty-printer which might exist.
8737 For example, to print the program counter in hex (@pxref{Registers}), type
8744 Note that no space is required before the slash; this is because command
8745 names in @value{GDBN} cannot contain a slash.
8747 To reprint the last value in the value history with a different format,
8748 you can use the @code{print} command with just a format and no
8749 expression. For example, @samp{p/x} reprints the last value in hex.
8752 @section Examining Memory
8754 You can use the command @code{x} (for ``examine'') to examine memory in
8755 any of several formats, independently of your program's data types.
8757 @cindex examining memory
8759 @kindex x @r{(examine memory)}
8760 @item x/@var{nfu} @var{addr}
8763 Use the @code{x} command to examine memory.
8766 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8767 much memory to display and how to format it; @var{addr} is an
8768 expression giving the address where you want to start displaying memory.
8769 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8770 Several commands set convenient defaults for @var{addr}.
8773 @item @var{n}, the repeat count
8774 The repeat count is a decimal integer; the default is 1. It specifies
8775 how much memory (counting by units @var{u}) to display.
8776 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8779 @item @var{f}, the display format
8780 The display format is one of the formats used by @code{print}
8781 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8782 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8783 The default is @samp{x} (hexadecimal) initially. The default changes
8784 each time you use either @code{x} or @code{print}.
8786 @item @var{u}, the unit size
8787 The unit size is any of
8793 Halfwords (two bytes).
8795 Words (four bytes). This is the initial default.
8797 Giant words (eight bytes).
8800 Each time you specify a unit size with @code{x}, that size becomes the
8801 default unit the next time you use @code{x}. For the @samp{i} format,
8802 the unit size is ignored and is normally not written. For the @samp{s} format,
8803 the unit size defaults to @samp{b}, unless it is explicitly given.
8804 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8805 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8806 Note that the results depend on the programming language of the
8807 current compilation unit. If the language is C, the @samp{s}
8808 modifier will use the UTF-16 encoding while @samp{w} will use
8809 UTF-32. The encoding is set by the programming language and cannot
8812 @item @var{addr}, starting display address
8813 @var{addr} is the address where you want @value{GDBN} to begin displaying
8814 memory. The expression need not have a pointer value (though it may);
8815 it is always interpreted as an integer address of a byte of memory.
8816 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8817 @var{addr} is usually just after the last address examined---but several
8818 other commands also set the default address: @code{info breakpoints} (to
8819 the address of the last breakpoint listed), @code{info line} (to the
8820 starting address of a line), and @code{print} (if you use it to display
8821 a value from memory).
8824 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8825 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8826 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8827 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8828 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8830 Since the letters indicating unit sizes are all distinct from the
8831 letters specifying output formats, you do not have to remember whether
8832 unit size or format comes first; either order works. The output
8833 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8834 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8836 Even though the unit size @var{u} is ignored for the formats @samp{s}
8837 and @samp{i}, you might still want to use a count @var{n}; for example,
8838 @samp{3i} specifies that you want to see three machine instructions,
8839 including any operands. For convenience, especially when used with
8840 the @code{display} command, the @samp{i} format also prints branch delay
8841 slot instructions, if any, beyond the count specified, which immediately
8842 follow the last instruction that is within the count. The command
8843 @code{disassemble} gives an alternative way of inspecting machine
8844 instructions; see @ref{Machine Code,,Source and Machine Code}.
8846 All the defaults for the arguments to @code{x} are designed to make it
8847 easy to continue scanning memory with minimal specifications each time
8848 you use @code{x}. For example, after you have inspected three machine
8849 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8850 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8851 the repeat count @var{n} is used again; the other arguments default as
8852 for successive uses of @code{x}.
8854 When examining machine instructions, the instruction at current program
8855 counter is shown with a @code{=>} marker. For example:
8858 (@value{GDBP}) x/5i $pc-6
8859 0x804837f <main+11>: mov %esp,%ebp
8860 0x8048381 <main+13>: push %ecx
8861 0x8048382 <main+14>: sub $0x4,%esp
8862 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8863 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8866 @cindex @code{$_}, @code{$__}, and value history
8867 The addresses and contents printed by the @code{x} command are not saved
8868 in the value history because there is often too much of them and they
8869 would get in the way. Instead, @value{GDBN} makes these values available for
8870 subsequent use in expressions as values of the convenience variables
8871 @code{$_} and @code{$__}. After an @code{x} command, the last address
8872 examined is available for use in expressions in the convenience variable
8873 @code{$_}. The contents of that address, as examined, are available in
8874 the convenience variable @code{$__}.
8876 If the @code{x} command has a repeat count, the address and contents saved
8877 are from the last memory unit printed; this is not the same as the last
8878 address printed if several units were printed on the last line of output.
8880 @cindex remote memory comparison
8881 @cindex target memory comparison
8882 @cindex verify remote memory image
8883 @cindex verify target memory image
8884 When you are debugging a program running on a remote target machine
8885 (@pxref{Remote Debugging}), you may wish to verify the program's image
8886 in the remote machine's memory against the executable file you
8887 downloaded to the target. Or, on any target, you may want to check
8888 whether the program has corrupted its own read-only sections. The
8889 @code{compare-sections} command is provided for such situations.
8892 @kindex compare-sections
8893 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8894 Compare the data of a loadable section @var{section-name} in the
8895 executable file of the program being debugged with the same section in
8896 the target machine's memory, and report any mismatches. With no
8897 arguments, compares all loadable sections. With an argument of
8898 @code{-r}, compares all loadable read-only sections.
8900 Note: for remote targets, this command can be accelerated if the
8901 target supports computing the CRC checksum of a block of memory
8902 (@pxref{qCRC packet}).
8906 @section Automatic Display
8907 @cindex automatic display
8908 @cindex display of expressions
8910 If you find that you want to print the value of an expression frequently
8911 (to see how it changes), you might want to add it to the @dfn{automatic
8912 display list} so that @value{GDBN} prints its value each time your program stops.
8913 Each expression added to the list is given a number to identify it;
8914 to remove an expression from the list, you specify that number.
8915 The automatic display looks like this:
8919 3: bar[5] = (struct hack *) 0x3804
8923 This display shows item numbers, expressions and their current values. As with
8924 displays you request manually using @code{x} or @code{print}, you can
8925 specify the output format you prefer; in fact, @code{display} decides
8926 whether to use @code{print} or @code{x} depending your format
8927 specification---it uses @code{x} if you specify either the @samp{i}
8928 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8932 @item display @var{expr}
8933 Add the expression @var{expr} to the list of expressions to display
8934 each time your program stops. @xref{Expressions, ,Expressions}.
8936 @code{display} does not repeat if you press @key{RET} again after using it.
8938 @item display/@var{fmt} @var{expr}
8939 For @var{fmt} specifying only a display format and not a size or
8940 count, add the expression @var{expr} to the auto-display list but
8941 arrange to display it each time in the specified format @var{fmt}.
8942 @xref{Output Formats,,Output Formats}.
8944 @item display/@var{fmt} @var{addr}
8945 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8946 number of units, add the expression @var{addr} as a memory address to
8947 be examined each time your program stops. Examining means in effect
8948 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8951 For example, @samp{display/i $pc} can be helpful, to see the machine
8952 instruction about to be executed each time execution stops (@samp{$pc}
8953 is a common name for the program counter; @pxref{Registers, ,Registers}).
8956 @kindex delete display
8958 @item undisplay @var{dnums}@dots{}
8959 @itemx delete display @var{dnums}@dots{}
8960 Remove items from the list of expressions to display. Specify the
8961 numbers of the displays that you want affected with the command
8962 argument @var{dnums}. It can be a single display number, one of the
8963 numbers shown in the first field of the @samp{info display} display;
8964 or it could be a range of display numbers, as in @code{2-4}.
8966 @code{undisplay} does not repeat if you press @key{RET} after using it.
8967 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8969 @kindex disable display
8970 @item disable display @var{dnums}@dots{}
8971 Disable the display of item numbers @var{dnums}. A disabled display
8972 item is not printed automatically, but is not forgotten. It may be
8973 enabled again later. Specify the numbers of the displays that you
8974 want affected with the command argument @var{dnums}. It can be a
8975 single display number, one of the numbers shown in the first field of
8976 the @samp{info display} display; or it could be a range of display
8977 numbers, as in @code{2-4}.
8979 @kindex enable display
8980 @item enable display @var{dnums}@dots{}
8981 Enable display of item numbers @var{dnums}. It becomes effective once
8982 again in auto display of its expression, until you specify otherwise.
8983 Specify the numbers of the displays that you want affected with the
8984 command argument @var{dnums}. It can be a single display number, one
8985 of the numbers shown in the first field of the @samp{info display}
8986 display; or it could be a range of display numbers, as in @code{2-4}.
8989 Display the current values of the expressions on the list, just as is
8990 done when your program stops.
8992 @kindex info display
8994 Print the list of expressions previously set up to display
8995 automatically, each one with its item number, but without showing the
8996 values. This includes disabled expressions, which are marked as such.
8997 It also includes expressions which would not be displayed right now
8998 because they refer to automatic variables not currently available.
9001 @cindex display disabled out of scope
9002 If a display expression refers to local variables, then it does not make
9003 sense outside the lexical context for which it was set up. Such an
9004 expression is disabled when execution enters a context where one of its
9005 variables is not defined. For example, if you give the command
9006 @code{display last_char} while inside a function with an argument
9007 @code{last_char}, @value{GDBN} displays this argument while your program
9008 continues to stop inside that function. When it stops elsewhere---where
9009 there is no variable @code{last_char}---the display is disabled
9010 automatically. The next time your program stops where @code{last_char}
9011 is meaningful, you can enable the display expression once again.
9013 @node Print Settings
9014 @section Print Settings
9016 @cindex format options
9017 @cindex print settings
9018 @value{GDBN} provides the following ways to control how arrays, structures,
9019 and symbols are printed.
9022 These settings are useful for debugging programs in any language:
9026 @item set print address
9027 @itemx set print address on
9028 @cindex print/don't print memory addresses
9029 @value{GDBN} prints memory addresses showing the location of stack
9030 traces, structure values, pointer values, breakpoints, and so forth,
9031 even when it also displays the contents of those addresses. The default
9032 is @code{on}. For example, this is what a stack frame display looks like with
9033 @code{set print address on}:
9038 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9040 530 if (lquote != def_lquote)
9044 @item set print address off
9045 Do not print addresses when displaying their contents. For example,
9046 this is the same stack frame displayed with @code{set print address off}:
9050 (@value{GDBP}) set print addr off
9052 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9053 530 if (lquote != def_lquote)
9057 You can use @samp{set print address off} to eliminate all machine
9058 dependent displays from the @value{GDBN} interface. For example, with
9059 @code{print address off}, you should get the same text for backtraces on
9060 all machines---whether or not they involve pointer arguments.
9063 @item show print address
9064 Show whether or not addresses are to be printed.
9067 When @value{GDBN} prints a symbolic address, it normally prints the
9068 closest earlier symbol plus an offset. If that symbol does not uniquely
9069 identify the address (for example, it is a name whose scope is a single
9070 source file), you may need to clarify. One way to do this is with
9071 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9072 you can set @value{GDBN} to print the source file and line number when
9073 it prints a symbolic address:
9076 @item set print symbol-filename on
9077 @cindex source file and line of a symbol
9078 @cindex symbol, source file and line
9079 Tell @value{GDBN} to print the source file name and line number of a
9080 symbol in the symbolic form of an address.
9082 @item set print symbol-filename off
9083 Do not print source file name and line number of a symbol. This is the
9086 @item show print symbol-filename
9087 Show whether or not @value{GDBN} will print the source file name and
9088 line number of a symbol in the symbolic form of an address.
9091 Another situation where it is helpful to show symbol filenames and line
9092 numbers is when disassembling code; @value{GDBN} shows you the line
9093 number and source file that corresponds to each instruction.
9095 Also, you may wish to see the symbolic form only if the address being
9096 printed is reasonably close to the closest earlier symbol:
9099 @item set print max-symbolic-offset @var{max-offset}
9100 @itemx set print max-symbolic-offset unlimited
9101 @cindex maximum value for offset of closest symbol
9102 Tell @value{GDBN} to only display the symbolic form of an address if the
9103 offset between the closest earlier symbol and the address is less than
9104 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9105 to always print the symbolic form of an address if any symbol precedes
9106 it. Zero is equivalent to @code{unlimited}.
9108 @item show print max-symbolic-offset
9109 Ask how large the maximum offset is that @value{GDBN} prints in a
9113 @cindex wild pointer, interpreting
9114 @cindex pointer, finding referent
9115 If you have a pointer and you are not sure where it points, try
9116 @samp{set print symbol-filename on}. Then you can determine the name
9117 and source file location of the variable where it points, using
9118 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9119 For example, here @value{GDBN} shows that a variable @code{ptt} points
9120 at another variable @code{t}, defined in @file{hi2.c}:
9123 (@value{GDBP}) set print symbol-filename on
9124 (@value{GDBP}) p/a ptt
9125 $4 = 0xe008 <t in hi2.c>
9129 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9130 does not show the symbol name and filename of the referent, even with
9131 the appropriate @code{set print} options turned on.
9134 You can also enable @samp{/a}-like formatting all the time using
9135 @samp{set print symbol on}:
9138 @item set print symbol on
9139 Tell @value{GDBN} to print the symbol corresponding to an address, if
9142 @item set print symbol off
9143 Tell @value{GDBN} not to print the symbol corresponding to an
9144 address. In this mode, @value{GDBN} will still print the symbol
9145 corresponding to pointers to functions. This is the default.
9147 @item show print symbol
9148 Show whether @value{GDBN} will display the symbol corresponding to an
9152 Other settings control how different kinds of objects are printed:
9155 @item set print array
9156 @itemx set print array on
9157 @cindex pretty print arrays
9158 Pretty print arrays. This format is more convenient to read,
9159 but uses more space. The default is off.
9161 @item set print array off
9162 Return to compressed format for arrays.
9164 @item show print array
9165 Show whether compressed or pretty format is selected for displaying
9168 @cindex print array indexes
9169 @item set print array-indexes
9170 @itemx set print array-indexes on
9171 Print the index of each element when displaying arrays. May be more
9172 convenient to locate a given element in the array or quickly find the
9173 index of a given element in that printed array. The default is off.
9175 @item set print array-indexes off
9176 Stop printing element indexes when displaying arrays.
9178 @item show print array-indexes
9179 Show whether the index of each element is printed when displaying
9182 @item set print elements @var{number-of-elements}
9183 @itemx set print elements unlimited
9184 @cindex number of array elements to print
9185 @cindex limit on number of printed array elements
9186 Set a limit on how many elements of an array @value{GDBN} will print.
9187 If @value{GDBN} is printing a large array, it stops printing after it has
9188 printed the number of elements set by the @code{set print elements} command.
9189 This limit also applies to the display of strings.
9190 When @value{GDBN} starts, this limit is set to 200.
9191 Setting @var{number-of-elements} to @code{unlimited} or zero means
9192 that the number of elements to print is unlimited.
9194 @item show print elements
9195 Display the number of elements of a large array that @value{GDBN} will print.
9196 If the number is 0, then the printing is unlimited.
9198 @item set print frame-arguments @var{value}
9199 @kindex set print frame-arguments
9200 @cindex printing frame argument values
9201 @cindex print all frame argument values
9202 @cindex print frame argument values for scalars only
9203 @cindex do not print frame argument values
9204 This command allows to control how the values of arguments are printed
9205 when the debugger prints a frame (@pxref{Frames}). The possible
9210 The values of all arguments are printed.
9213 Print the value of an argument only if it is a scalar. The value of more
9214 complex arguments such as arrays, structures, unions, etc, is replaced
9215 by @code{@dots{}}. This is the default. Here is an example where
9216 only scalar arguments are shown:
9219 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9224 None of the argument values are printed. Instead, the value of each argument
9225 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9228 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9233 By default, only scalar arguments are printed. This command can be used
9234 to configure the debugger to print the value of all arguments, regardless
9235 of their type. However, it is often advantageous to not print the value
9236 of more complex parameters. For instance, it reduces the amount of
9237 information printed in each frame, making the backtrace more readable.
9238 Also, it improves performance when displaying Ada frames, because
9239 the computation of large arguments can sometimes be CPU-intensive,
9240 especially in large applications. Setting @code{print frame-arguments}
9241 to @code{scalars} (the default) or @code{none} avoids this computation,
9242 thus speeding up the display of each Ada frame.
9244 @item show print frame-arguments
9245 Show how the value of arguments should be displayed when printing a frame.
9247 @item set print raw frame-arguments on
9248 Print frame arguments in raw, non pretty-printed, form.
9250 @item set print raw frame-arguments off
9251 Print frame arguments in pretty-printed form, if there is a pretty-printer
9252 for the value (@pxref{Pretty Printing}),
9253 otherwise print the value in raw form.
9254 This is the default.
9256 @item show print raw frame-arguments
9257 Show whether to print frame arguments in raw form.
9259 @anchor{set print entry-values}
9260 @item set print entry-values @var{value}
9261 @kindex set print entry-values
9262 Set printing of frame argument values at function entry. In some cases
9263 @value{GDBN} can determine the value of function argument which was passed by
9264 the function caller, even if the value was modified inside the called function
9265 and therefore is different. With optimized code, the current value could be
9266 unavailable, but the entry value may still be known.
9268 The default value is @code{default} (see below for its description). Older
9269 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9270 this feature will behave in the @code{default} setting the same way as with the
9273 This functionality is currently supported only by DWARF 2 debugging format and
9274 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9275 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9278 The @var{value} parameter can be one of the following:
9282 Print only actual parameter values, never print values from function entry
9286 #0 different (val=6)
9287 #0 lost (val=<optimized out>)
9289 #0 invalid (val=<optimized out>)
9293 Print only parameter values from function entry point. The actual parameter
9294 values are never printed.
9296 #0 equal (val@@entry=5)
9297 #0 different (val@@entry=5)
9298 #0 lost (val@@entry=5)
9299 #0 born (val@@entry=<optimized out>)
9300 #0 invalid (val@@entry=<optimized out>)
9304 Print only parameter values from function entry point. If value from function
9305 entry point is not known while the actual value is known, print the actual
9306 value for such parameter.
9308 #0 equal (val@@entry=5)
9309 #0 different (val@@entry=5)
9310 #0 lost (val@@entry=5)
9312 #0 invalid (val@@entry=<optimized out>)
9316 Print actual parameter values. If actual parameter value is not known while
9317 value from function entry point is known, print the entry point value for such
9321 #0 different (val=6)
9322 #0 lost (val@@entry=5)
9324 #0 invalid (val=<optimized out>)
9328 Always print both the actual parameter value and its value from function entry
9329 point, even if values of one or both are not available due to compiler
9332 #0 equal (val=5, val@@entry=5)
9333 #0 different (val=6, val@@entry=5)
9334 #0 lost (val=<optimized out>, val@@entry=5)
9335 #0 born (val=10, val@@entry=<optimized out>)
9336 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9340 Print the actual parameter value if it is known and also its value from
9341 function entry point if it is known. If neither is known, print for the actual
9342 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9343 values are known and identical, print the shortened
9344 @code{param=param@@entry=VALUE} notation.
9346 #0 equal (val=val@@entry=5)
9347 #0 different (val=6, val@@entry=5)
9348 #0 lost (val@@entry=5)
9350 #0 invalid (val=<optimized out>)
9354 Always print the actual parameter value. Print also its value from function
9355 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9356 if both values are known and identical, print the shortened
9357 @code{param=param@@entry=VALUE} notation.
9359 #0 equal (val=val@@entry=5)
9360 #0 different (val=6, val@@entry=5)
9361 #0 lost (val=<optimized out>, val@@entry=5)
9363 #0 invalid (val=<optimized out>)
9367 For analysis messages on possible failures of frame argument values at function
9368 entry resolution see @ref{set debug entry-values}.
9370 @item show print entry-values
9371 Show the method being used for printing of frame argument values at function
9374 @item set print repeats @var{number-of-repeats}
9375 @itemx set print repeats unlimited
9376 @cindex repeated array elements
9377 Set the threshold for suppressing display of repeated array
9378 elements. When the number of consecutive identical elements of an
9379 array exceeds the threshold, @value{GDBN} prints the string
9380 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9381 identical repetitions, instead of displaying the identical elements
9382 themselves. Setting the threshold to @code{unlimited} or zero will
9383 cause all elements to be individually printed. The default threshold
9386 @item show print repeats
9387 Display the current threshold for printing repeated identical
9390 @item set print null-stop
9391 @cindex @sc{null} elements in arrays
9392 Cause @value{GDBN} to stop printing the characters of an array when the first
9393 @sc{null} is encountered. This is useful when large arrays actually
9394 contain only short strings.
9397 @item show print null-stop
9398 Show whether @value{GDBN} stops printing an array on the first
9399 @sc{null} character.
9401 @item set print pretty on
9402 @cindex print structures in indented form
9403 @cindex indentation in structure display
9404 Cause @value{GDBN} to print structures in an indented format with one member
9405 per line, like this:
9420 @item set print pretty off
9421 Cause @value{GDBN} to print structures in a compact format, like this:
9425 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9426 meat = 0x54 "Pork"@}
9431 This is the default format.
9433 @item show print pretty
9434 Show which format @value{GDBN} is using to print structures.
9436 @item set print sevenbit-strings on
9437 @cindex eight-bit characters in strings
9438 @cindex octal escapes in strings
9439 Print using only seven-bit characters; if this option is set,
9440 @value{GDBN} displays any eight-bit characters (in strings or
9441 character values) using the notation @code{\}@var{nnn}. This setting is
9442 best if you are working in English (@sc{ascii}) and you use the
9443 high-order bit of characters as a marker or ``meta'' bit.
9445 @item set print sevenbit-strings off
9446 Print full eight-bit characters. This allows the use of more
9447 international character sets, and is the default.
9449 @item show print sevenbit-strings
9450 Show whether or not @value{GDBN} is printing only seven-bit characters.
9452 @item set print union on
9453 @cindex unions in structures, printing
9454 Tell @value{GDBN} to print unions which are contained in structures
9455 and other unions. This is the default setting.
9457 @item set print union off
9458 Tell @value{GDBN} not to print unions which are contained in
9459 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9462 @item show print union
9463 Ask @value{GDBN} whether or not it will print unions which are contained in
9464 structures and other unions.
9466 For example, given the declarations
9469 typedef enum @{Tree, Bug@} Species;
9470 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9471 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9482 struct thing foo = @{Tree, @{Acorn@}@};
9486 with @code{set print union on} in effect @samp{p foo} would print
9489 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9493 and with @code{set print union off} in effect it would print
9496 $1 = @{it = Tree, form = @{...@}@}
9500 @code{set print union} affects programs written in C-like languages
9506 These settings are of interest when debugging C@t{++} programs:
9509 @cindex demangling C@t{++} names
9510 @item set print demangle
9511 @itemx set print demangle on
9512 Print C@t{++} names in their source form rather than in the encoded
9513 (``mangled'') form passed to the assembler and linker for type-safe
9514 linkage. The default is on.
9516 @item show print demangle
9517 Show whether C@t{++} names are printed in mangled or demangled form.
9519 @item set print asm-demangle
9520 @itemx set print asm-demangle on
9521 Print C@t{++} names in their source form rather than their mangled form, even
9522 in assembler code printouts such as instruction disassemblies.
9525 @item show print asm-demangle
9526 Show whether C@t{++} names in assembly listings are printed in mangled
9529 @cindex C@t{++} symbol decoding style
9530 @cindex symbol decoding style, C@t{++}
9531 @kindex set demangle-style
9532 @item set demangle-style @var{style}
9533 Choose among several encoding schemes used by different compilers to
9534 represent C@t{++} names. The choices for @var{style} are currently:
9538 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9539 This is the default.
9542 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9545 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9548 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9551 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9552 @strong{Warning:} this setting alone is not sufficient to allow
9553 debugging @code{cfront}-generated executables. @value{GDBN} would
9554 require further enhancement to permit that.
9557 If you omit @var{style}, you will see a list of possible formats.
9559 @item show demangle-style
9560 Display the encoding style currently in use for decoding C@t{++} symbols.
9562 @item set print object
9563 @itemx set print object on
9564 @cindex derived type of an object, printing
9565 @cindex display derived types
9566 When displaying a pointer to an object, identify the @emph{actual}
9567 (derived) type of the object rather than the @emph{declared} type, using
9568 the virtual function table. Note that the virtual function table is
9569 required---this feature can only work for objects that have run-time
9570 type identification; a single virtual method in the object's declared
9571 type is sufficient. Note that this setting is also taken into account when
9572 working with variable objects via MI (@pxref{GDB/MI}).
9574 @item set print object off
9575 Display only the declared type of objects, without reference to the
9576 virtual function table. This is the default setting.
9578 @item show print object
9579 Show whether actual, or declared, object types are displayed.
9581 @item set print static-members
9582 @itemx set print static-members on
9583 @cindex static members of C@t{++} objects
9584 Print static members when displaying a C@t{++} object. The default is on.
9586 @item set print static-members off
9587 Do not print static members when displaying a C@t{++} object.
9589 @item show print static-members
9590 Show whether C@t{++} static members are printed or not.
9592 @item set print pascal_static-members
9593 @itemx set print pascal_static-members on
9594 @cindex static members of Pascal objects
9595 @cindex Pascal objects, static members display
9596 Print static members when displaying a Pascal object. The default is on.
9598 @item set print pascal_static-members off
9599 Do not print static members when displaying a Pascal object.
9601 @item show print pascal_static-members
9602 Show whether Pascal static members are printed or not.
9604 @c These don't work with HP ANSI C++ yet.
9605 @item set print vtbl
9606 @itemx set print vtbl on
9607 @cindex pretty print C@t{++} virtual function tables
9608 @cindex virtual functions (C@t{++}) display
9609 @cindex VTBL display
9610 Pretty print C@t{++} virtual function tables. The default is off.
9611 (The @code{vtbl} commands do not work on programs compiled with the HP
9612 ANSI C@t{++} compiler (@code{aCC}).)
9614 @item set print vtbl off
9615 Do not pretty print C@t{++} virtual function tables.
9617 @item show print vtbl
9618 Show whether C@t{++} virtual function tables are pretty printed, or not.
9621 @node Pretty Printing
9622 @section Pretty Printing
9624 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9625 Python code. It greatly simplifies the display of complex objects. This
9626 mechanism works for both MI and the CLI.
9629 * Pretty-Printer Introduction:: Introduction to pretty-printers
9630 * Pretty-Printer Example:: An example pretty-printer
9631 * Pretty-Printer Commands:: Pretty-printer commands
9634 @node Pretty-Printer Introduction
9635 @subsection Pretty-Printer Introduction
9637 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9638 registered for the value. If there is then @value{GDBN} invokes the
9639 pretty-printer to print the value. Otherwise the value is printed normally.
9641 Pretty-printers are normally named. This makes them easy to manage.
9642 The @samp{info pretty-printer} command will list all the installed
9643 pretty-printers with their names.
9644 If a pretty-printer can handle multiple data types, then its
9645 @dfn{subprinters} are the printers for the individual data types.
9646 Each such subprinter has its own name.
9647 The format of the name is @var{printer-name};@var{subprinter-name}.
9649 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9650 Typically they are automatically loaded and registered when the corresponding
9651 debug information is loaded, thus making them available without having to
9652 do anything special.
9654 There are three places where a pretty-printer can be registered.
9658 Pretty-printers registered globally are available when debugging
9662 Pretty-printers registered with a program space are available only
9663 when debugging that program.
9664 @xref{Progspaces In Python}, for more details on program spaces in Python.
9667 Pretty-printers registered with an objfile are loaded and unloaded
9668 with the corresponding objfile (e.g., shared library).
9669 @xref{Objfiles In Python}, for more details on objfiles in Python.
9672 @xref{Selecting Pretty-Printers}, for further information on how
9673 pretty-printers are selected,
9675 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9678 @node Pretty-Printer Example
9679 @subsection Pretty-Printer Example
9681 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9684 (@value{GDBP}) print s
9686 static npos = 4294967295,
9688 <std::allocator<char>> = @{
9689 <__gnu_cxx::new_allocator<char>> = @{
9690 <No data fields>@}, <No data fields>
9692 members of std::basic_string<char, std::char_traits<char>,
9693 std::allocator<char> >::_Alloc_hider:
9694 _M_p = 0x804a014 "abcd"
9699 With a pretty-printer for @code{std::string} only the contents are printed:
9702 (@value{GDBP}) print s
9706 @node Pretty-Printer Commands
9707 @subsection Pretty-Printer Commands
9708 @cindex pretty-printer commands
9711 @kindex info pretty-printer
9712 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9713 Print the list of installed pretty-printers.
9714 This includes disabled pretty-printers, which are marked as such.
9716 @var{object-regexp} is a regular expression matching the objects
9717 whose pretty-printers to list.
9718 Objects can be @code{global}, the program space's file
9719 (@pxref{Progspaces In Python}),
9720 and the object files within that program space (@pxref{Objfiles In Python}).
9721 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9722 looks up a printer from these three objects.
9724 @var{name-regexp} is a regular expression matching the name of the printers
9727 @kindex disable pretty-printer
9728 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9729 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9730 A disabled pretty-printer is not forgotten, it may be enabled again later.
9732 @kindex enable pretty-printer
9733 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9734 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9739 Suppose we have three pretty-printers installed: one from library1.so
9740 named @code{foo} that prints objects of type @code{foo}, and
9741 another from library2.so named @code{bar} that prints two types of objects,
9742 @code{bar1} and @code{bar2}.
9745 (gdb) info pretty-printer
9752 (gdb) info pretty-printer library2
9757 (gdb) disable pretty-printer library1
9759 2 of 3 printers enabled
9760 (gdb) info pretty-printer
9767 (gdb) disable pretty-printer library2 bar:bar1
9769 1 of 3 printers enabled
9770 (gdb) info pretty-printer library2
9777 (gdb) disable pretty-printer library2 bar
9779 0 of 3 printers enabled
9780 (gdb) info pretty-printer library2
9789 Note that for @code{bar} the entire printer can be disabled,
9790 as can each individual subprinter.
9793 @section Value History
9795 @cindex value history
9796 @cindex history of values printed by @value{GDBN}
9797 Values printed by the @code{print} command are saved in the @value{GDBN}
9798 @dfn{value history}. This allows you to refer to them in other expressions.
9799 Values are kept until the symbol table is re-read or discarded
9800 (for example with the @code{file} or @code{symbol-file} commands).
9801 When the symbol table changes, the value history is discarded,
9802 since the values may contain pointers back to the types defined in the
9807 @cindex history number
9808 The values printed are given @dfn{history numbers} by which you can
9809 refer to them. These are successive integers starting with one.
9810 @code{print} shows you the history number assigned to a value by
9811 printing @samp{$@var{num} = } before the value; here @var{num} is the
9814 To refer to any previous value, use @samp{$} followed by the value's
9815 history number. The way @code{print} labels its output is designed to
9816 remind you of this. Just @code{$} refers to the most recent value in
9817 the history, and @code{$$} refers to the value before that.
9818 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9819 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9820 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9822 For example, suppose you have just printed a pointer to a structure and
9823 want to see the contents of the structure. It suffices to type
9829 If you have a chain of structures where the component @code{next} points
9830 to the next one, you can print the contents of the next one with this:
9837 You can print successive links in the chain by repeating this
9838 command---which you can do by just typing @key{RET}.
9840 Note that the history records values, not expressions. If the value of
9841 @code{x} is 4 and you type these commands:
9849 then the value recorded in the value history by the @code{print} command
9850 remains 4 even though the value of @code{x} has changed.
9855 Print the last ten values in the value history, with their item numbers.
9856 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9857 values} does not change the history.
9859 @item show values @var{n}
9860 Print ten history values centered on history item number @var{n}.
9863 Print ten history values just after the values last printed. If no more
9864 values are available, @code{show values +} produces no display.
9867 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9868 same effect as @samp{show values +}.
9870 @node Convenience Vars
9871 @section Convenience Variables
9873 @cindex convenience variables
9874 @cindex user-defined variables
9875 @value{GDBN} provides @dfn{convenience variables} that you can use within
9876 @value{GDBN} to hold on to a value and refer to it later. These variables
9877 exist entirely within @value{GDBN}; they are not part of your program, and
9878 setting a convenience variable has no direct effect on further execution
9879 of your program. That is why you can use them freely.
9881 Convenience variables are prefixed with @samp{$}. Any name preceded by
9882 @samp{$} can be used for a convenience variable, unless it is one of
9883 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9884 (Value history references, in contrast, are @emph{numbers} preceded
9885 by @samp{$}. @xref{Value History, ,Value History}.)
9887 You can save a value in a convenience variable with an assignment
9888 expression, just as you would set a variable in your program.
9892 set $foo = *object_ptr
9896 would save in @code{$foo} the value contained in the object pointed to by
9899 Using a convenience variable for the first time creates it, but its
9900 value is @code{void} until you assign a new value. You can alter the
9901 value with another assignment at any time.
9903 Convenience variables have no fixed types. You can assign a convenience
9904 variable any type of value, including structures and arrays, even if
9905 that variable already has a value of a different type. The convenience
9906 variable, when used as an expression, has the type of its current value.
9909 @kindex show convenience
9910 @cindex show all user variables and functions
9911 @item show convenience
9912 Print a list of convenience variables used so far, and their values,
9913 as well as a list of the convenience functions.
9914 Abbreviated @code{show conv}.
9916 @kindex init-if-undefined
9917 @cindex convenience variables, initializing
9918 @item init-if-undefined $@var{variable} = @var{expression}
9919 Set a convenience variable if it has not already been set. This is useful
9920 for user-defined commands that keep some state. It is similar, in concept,
9921 to using local static variables with initializers in C (except that
9922 convenience variables are global). It can also be used to allow users to
9923 override default values used in a command script.
9925 If the variable is already defined then the expression is not evaluated so
9926 any side-effects do not occur.
9929 One of the ways to use a convenience variable is as a counter to be
9930 incremented or a pointer to be advanced. For example, to print
9931 a field from successive elements of an array of structures:
9935 print bar[$i++]->contents
9939 Repeat that command by typing @key{RET}.
9941 Some convenience variables are created automatically by @value{GDBN} and given
9942 values likely to be useful.
9945 @vindex $_@r{, convenience variable}
9947 The variable @code{$_} is automatically set by the @code{x} command to
9948 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9949 commands which provide a default address for @code{x} to examine also
9950 set @code{$_} to that address; these commands include @code{info line}
9951 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9952 except when set by the @code{x} command, in which case it is a pointer
9953 to the type of @code{$__}.
9955 @vindex $__@r{, convenience variable}
9957 The variable @code{$__} is automatically set by the @code{x} command
9958 to the value found in the last address examined. Its type is chosen
9959 to match the format in which the data was printed.
9962 @vindex $_exitcode@r{, convenience variable}
9963 When the program being debugged terminates normally, @value{GDBN}
9964 automatically sets this variable to the exit code of the program, and
9965 resets @code{$_exitsignal} to @code{void}.
9968 @vindex $_exitsignal@r{, convenience variable}
9969 When the program being debugged dies due to an uncaught signal,
9970 @value{GDBN} automatically sets this variable to that signal's number,
9971 and resets @code{$_exitcode} to @code{void}.
9973 To distinguish between whether the program being debugged has exited
9974 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9975 @code{$_exitsignal} is not @code{void}), the convenience function
9976 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9977 Functions}). For example, considering the following source code:
9983 main (int argc, char *argv[])
9990 A valid way of telling whether the program being debugged has exited
9991 or signalled would be:
9994 (@value{GDBP}) define has_exited_or_signalled
9995 Type commands for definition of ``has_exited_or_signalled''.
9996 End with a line saying just ``end''.
9997 >if $_isvoid ($_exitsignal)
9998 >echo The program has exited\n
10000 >echo The program has signalled\n
10006 Program terminated with signal SIGALRM, Alarm clock.
10007 The program no longer exists.
10008 (@value{GDBP}) has_exited_or_signalled
10009 The program has signalled
10012 As can be seen, @value{GDBN} correctly informs that the program being
10013 debugged has signalled, since it calls @code{raise} and raises a
10014 @code{SIGALRM} signal. If the program being debugged had not called
10015 @code{raise}, then @value{GDBN} would report a normal exit:
10018 (@value{GDBP}) has_exited_or_signalled
10019 The program has exited
10023 The variable @code{$_exception} is set to the exception object being
10024 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10027 @itemx $_probe_arg0@dots{}$_probe_arg11
10028 Arguments to a static probe. @xref{Static Probe Points}.
10031 @vindex $_sdata@r{, inspect, convenience variable}
10032 The variable @code{$_sdata} contains extra collected static tracepoint
10033 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10034 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10035 if extra static tracepoint data has not been collected.
10038 @vindex $_siginfo@r{, convenience variable}
10039 The variable @code{$_siginfo} contains extra signal information
10040 (@pxref{extra signal information}). Note that @code{$_siginfo}
10041 could be empty, if the application has not yet received any signals.
10042 For example, it will be empty before you execute the @code{run} command.
10045 @vindex $_tlb@r{, convenience variable}
10046 The variable @code{$_tlb} is automatically set when debugging
10047 applications running on MS-Windows in native mode or connected to
10048 gdbserver that supports the @code{qGetTIBAddr} request.
10049 @xref{General Query Packets}.
10050 This variable contains the address of the thread information block.
10054 On HP-UX systems, if you refer to a function or variable name that
10055 begins with a dollar sign, @value{GDBN} searches for a user or system
10056 name first, before it searches for a convenience variable.
10058 @node Convenience Funs
10059 @section Convenience Functions
10061 @cindex convenience functions
10062 @value{GDBN} also supplies some @dfn{convenience functions}. These
10063 have a syntax similar to convenience variables. A convenience
10064 function can be used in an expression just like an ordinary function;
10065 however, a convenience function is implemented internally to
10068 These functions do not require @value{GDBN} to be configured with
10069 @code{Python} support, which means that they are always available.
10073 @item $_isvoid (@var{expr})
10074 @findex $_isvoid@r{, convenience function}
10075 Return one if the expression @var{expr} is @code{void}. Otherwise it
10078 A @code{void} expression is an expression where the type of the result
10079 is @code{void}. For example, you can examine a convenience variable
10080 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10084 (@value{GDBP}) print $_exitcode
10086 (@value{GDBP}) print $_isvoid ($_exitcode)
10089 Starting program: ./a.out
10090 [Inferior 1 (process 29572) exited normally]
10091 (@value{GDBP}) print $_exitcode
10093 (@value{GDBP}) print $_isvoid ($_exitcode)
10097 In the example above, we used @code{$_isvoid} to check whether
10098 @code{$_exitcode} is @code{void} before and after the execution of the
10099 program being debugged. Before the execution there is no exit code to
10100 be examined, therefore @code{$_exitcode} is @code{void}. After the
10101 execution the program being debugged returned zero, therefore
10102 @code{$_exitcode} is zero, which means that it is not @code{void}
10105 The @code{void} expression can also be a call of a function from the
10106 program being debugged. For example, given the following function:
10115 The result of calling it inside @value{GDBN} is @code{void}:
10118 (@value{GDBP}) print foo ()
10120 (@value{GDBP}) print $_isvoid (foo ())
10122 (@value{GDBP}) set $v = foo ()
10123 (@value{GDBP}) print $v
10125 (@value{GDBP}) print $_isvoid ($v)
10131 These functions require @value{GDBN} to be configured with
10132 @code{Python} support.
10136 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10137 @findex $_memeq@r{, convenience function}
10138 Returns one if the @var{length} bytes at the addresses given by
10139 @var{buf1} and @var{buf2} are equal.
10140 Otherwise it returns zero.
10142 @item $_regex(@var{str}, @var{regex})
10143 @findex $_regex@r{, convenience function}
10144 Returns one if the string @var{str} matches the regular expression
10145 @var{regex}. Otherwise it returns zero.
10146 The syntax of the regular expression is that specified by @code{Python}'s
10147 regular expression support.
10149 @item $_streq(@var{str1}, @var{str2})
10150 @findex $_streq@r{, convenience function}
10151 Returns one if the strings @var{str1} and @var{str2} are equal.
10152 Otherwise it returns zero.
10154 @item $_strlen(@var{str})
10155 @findex $_strlen@r{, convenience function}
10156 Returns the length of string @var{str}.
10158 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10159 @findex $_caller_is@r{, convenience function}
10160 Returns one if the calling function's name is equal to @var{name}.
10161 Otherwise it returns zero.
10163 If the optional argument @var{number_of_frames} is provided,
10164 it is the number of frames up in the stack to look.
10172 at testsuite/gdb.python/py-caller-is.c:21
10173 #1 0x00000000004005a0 in middle_func ()
10174 at testsuite/gdb.python/py-caller-is.c:27
10175 #2 0x00000000004005ab in top_func ()
10176 at testsuite/gdb.python/py-caller-is.c:33
10177 #3 0x00000000004005b6 in main ()
10178 at testsuite/gdb.python/py-caller-is.c:39
10179 (gdb) print $_caller_is ("middle_func")
10181 (gdb) print $_caller_is ("top_func", 2)
10185 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10186 @findex $_caller_matches@r{, convenience function}
10187 Returns one if the calling function's name matches the regular expression
10188 @var{regexp}. Otherwise it returns zero.
10190 If the optional argument @var{number_of_frames} is provided,
10191 it is the number of frames up in the stack to look.
10194 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10195 @findex $_any_caller_is@r{, convenience function}
10196 Returns one if any calling function's name is equal to @var{name}.
10197 Otherwise it returns zero.
10199 If the optional argument @var{number_of_frames} is provided,
10200 it is the number of frames up in the stack to look.
10203 This function differs from @code{$_caller_is} in that this function
10204 checks all stack frames from the immediate caller to the frame specified
10205 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10206 frame specified by @var{number_of_frames}.
10208 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10209 @findex $_any_caller_matches@r{, convenience function}
10210 Returns one if any calling function's name matches the regular expression
10211 @var{regexp}. Otherwise it returns zero.
10213 If the optional argument @var{number_of_frames} is provided,
10214 it is the number of frames up in the stack to look.
10217 This function differs from @code{$_caller_matches} in that this function
10218 checks all stack frames from the immediate caller to the frame specified
10219 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10220 frame specified by @var{number_of_frames}.
10224 @value{GDBN} provides the ability to list and get help on
10225 convenience functions.
10228 @item help function
10229 @kindex help function
10230 @cindex show all convenience functions
10231 Print a list of all convenience functions.
10238 You can refer to machine register contents, in expressions, as variables
10239 with names starting with @samp{$}. The names of registers are different
10240 for each machine; use @code{info registers} to see the names used on
10244 @kindex info registers
10245 @item info registers
10246 Print the names and values of all registers except floating-point
10247 and vector registers (in the selected stack frame).
10249 @kindex info all-registers
10250 @cindex floating point registers
10251 @item info all-registers
10252 Print the names and values of all registers, including floating-point
10253 and vector registers (in the selected stack frame).
10255 @item info registers @var{regname} @dots{}
10256 Print the @dfn{relativized} value of each specified register @var{regname}.
10257 As discussed in detail below, register values are normally relative to
10258 the selected stack frame. The @var{regname} may be any register name valid on
10259 the machine you are using, with or without the initial @samp{$}.
10262 @anchor{standard registers}
10263 @cindex stack pointer register
10264 @cindex program counter register
10265 @cindex process status register
10266 @cindex frame pointer register
10267 @cindex standard registers
10268 @value{GDBN} has four ``standard'' register names that are available (in
10269 expressions) on most machines---whenever they do not conflict with an
10270 architecture's canonical mnemonics for registers. The register names
10271 @code{$pc} and @code{$sp} are used for the program counter register and
10272 the stack pointer. @code{$fp} is used for a register that contains a
10273 pointer to the current stack frame, and @code{$ps} is used for a
10274 register that contains the processor status. For example,
10275 you could print the program counter in hex with
10282 or print the instruction to be executed next with
10289 or add four to the stack pointer@footnote{This is a way of removing
10290 one word from the stack, on machines where stacks grow downward in
10291 memory (most machines, nowadays). This assumes that the innermost
10292 stack frame is selected; setting @code{$sp} is not allowed when other
10293 stack frames are selected. To pop entire frames off the stack,
10294 regardless of machine architecture, use @code{return};
10295 see @ref{Returning, ,Returning from a Function}.} with
10301 Whenever possible, these four standard register names are available on
10302 your machine even though the machine has different canonical mnemonics,
10303 so long as there is no conflict. The @code{info registers} command
10304 shows the canonical names. For example, on the SPARC, @code{info
10305 registers} displays the processor status register as @code{$psr} but you
10306 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10307 is an alias for the @sc{eflags} register.
10309 @value{GDBN} always considers the contents of an ordinary register as an
10310 integer when the register is examined in this way. Some machines have
10311 special registers which can hold nothing but floating point; these
10312 registers are considered to have floating point values. There is no way
10313 to refer to the contents of an ordinary register as floating point value
10314 (although you can @emph{print} it as a floating point value with
10315 @samp{print/f $@var{regname}}).
10317 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10318 means that the data format in which the register contents are saved by
10319 the operating system is not the same one that your program normally
10320 sees. For example, the registers of the 68881 floating point
10321 coprocessor are always saved in ``extended'' (raw) format, but all C
10322 programs expect to work with ``double'' (virtual) format. In such
10323 cases, @value{GDBN} normally works with the virtual format only (the format
10324 that makes sense for your program), but the @code{info registers} command
10325 prints the data in both formats.
10327 @cindex SSE registers (x86)
10328 @cindex MMX registers (x86)
10329 Some machines have special registers whose contents can be interpreted
10330 in several different ways. For example, modern x86-based machines
10331 have SSE and MMX registers that can hold several values packed
10332 together in several different formats. @value{GDBN} refers to such
10333 registers in @code{struct} notation:
10336 (@value{GDBP}) print $xmm1
10338 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10339 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10340 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10341 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10342 v4_int32 = @{0, 20657912, 11, 13@},
10343 v2_int64 = @{88725056443645952, 55834574859@},
10344 uint128 = 0x0000000d0000000b013b36f800000000
10349 To set values of such registers, you need to tell @value{GDBN} which
10350 view of the register you wish to change, as if you were assigning
10351 value to a @code{struct} member:
10354 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10357 Normally, register values are relative to the selected stack frame
10358 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10359 value that the register would contain if all stack frames farther in
10360 were exited and their saved registers restored. In order to see the
10361 true contents of hardware registers, you must select the innermost
10362 frame (with @samp{frame 0}).
10364 @cindex caller-saved registers
10365 @cindex call-clobbered registers
10366 @cindex volatile registers
10367 @cindex <not saved> values
10368 Usually ABIs reserve some registers as not needed to be saved by the
10369 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10370 registers). It may therefore not be possible for @value{GDBN} to know
10371 the value a register had before the call (in other words, in the outer
10372 frame), if the register value has since been changed by the callee.
10373 @value{GDBN} tries to deduce where the inner frame saved
10374 (``callee-saved'') registers, from the debug info, unwind info, or the
10375 machine code generated by your compiler. If some register is not
10376 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10377 its own knowledge of the ABI, or because the debug/unwind info
10378 explicitly says the register's value is undefined), @value{GDBN}
10379 displays @w{@samp{<not saved>}} as the register's value. With targets
10380 that @value{GDBN} has no knowledge of the register saving convention,
10381 if a register was not saved by the callee, then its value and location
10382 in the outer frame are assumed to be the same of the inner frame.
10383 This is usually harmless, because if the register is call-clobbered,
10384 the caller either does not care what is in the register after the
10385 call, or has code to restore the value that it does care about. Note,
10386 however, that if you change such a register in the outer frame, you
10387 may also be affecting the inner frame. Also, the more ``outer'' the
10388 frame is you're looking at, the more likely a call-clobbered
10389 register's value is to be wrong, in the sense that it doesn't actually
10390 represent the value the register had just before the call.
10392 @node Floating Point Hardware
10393 @section Floating Point Hardware
10394 @cindex floating point
10396 Depending on the configuration, @value{GDBN} may be able to give
10397 you more information about the status of the floating point hardware.
10402 Display hardware-dependent information about the floating
10403 point unit. The exact contents and layout vary depending on the
10404 floating point chip. Currently, @samp{info float} is supported on
10405 the ARM and x86 machines.
10409 @section Vector Unit
10410 @cindex vector unit
10412 Depending on the configuration, @value{GDBN} may be able to give you
10413 more information about the status of the vector unit.
10416 @kindex info vector
10418 Display information about the vector unit. The exact contents and
10419 layout vary depending on the hardware.
10422 @node OS Information
10423 @section Operating System Auxiliary Information
10424 @cindex OS information
10426 @value{GDBN} provides interfaces to useful OS facilities that can help
10427 you debug your program.
10429 @cindex auxiliary vector
10430 @cindex vector, auxiliary
10431 Some operating systems supply an @dfn{auxiliary vector} to programs at
10432 startup. This is akin to the arguments and environment that you
10433 specify for a program, but contains a system-dependent variety of
10434 binary values that tell system libraries important details about the
10435 hardware, operating system, and process. Each value's purpose is
10436 identified by an integer tag; the meanings are well-known but system-specific.
10437 Depending on the configuration and operating system facilities,
10438 @value{GDBN} may be able to show you this information. For remote
10439 targets, this functionality may further depend on the remote stub's
10440 support of the @samp{qXfer:auxv:read} packet, see
10441 @ref{qXfer auxiliary vector read}.
10446 Display the auxiliary vector of the inferior, which can be either a
10447 live process or a core dump file. @value{GDBN} prints each tag value
10448 numerically, and also shows names and text descriptions for recognized
10449 tags. Some values in the vector are numbers, some bit masks, and some
10450 pointers to strings or other data. @value{GDBN} displays each value in the
10451 most appropriate form for a recognized tag, and in hexadecimal for
10452 an unrecognized tag.
10455 On some targets, @value{GDBN} can access operating system-specific
10456 information and show it to you. The types of information available
10457 will differ depending on the type of operating system running on the
10458 target. The mechanism used to fetch the data is described in
10459 @ref{Operating System Information}. For remote targets, this
10460 functionality depends on the remote stub's support of the
10461 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10465 @item info os @var{infotype}
10467 Display OS information of the requested type.
10469 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10471 @anchor{linux info os infotypes}
10473 @kindex info os processes
10475 Display the list of processes on the target. For each process,
10476 @value{GDBN} prints the process identifier, the name of the user, the
10477 command corresponding to the process, and the list of processor cores
10478 that the process is currently running on. (To understand what these
10479 properties mean, for this and the following info types, please consult
10480 the general @sc{gnu}/Linux documentation.)
10482 @kindex info os procgroups
10484 Display the list of process groups on the target. For each process,
10485 @value{GDBN} prints the identifier of the process group that it belongs
10486 to, the command corresponding to the process group leader, the process
10487 identifier, and the command line of the process. The list is sorted
10488 first by the process group identifier, then by the process identifier,
10489 so that processes belonging to the same process group are grouped together
10490 and the process group leader is listed first.
10492 @kindex info os threads
10494 Display the list of threads running on the target. For each thread,
10495 @value{GDBN} prints the identifier of the process that the thread
10496 belongs to, the command of the process, the thread identifier, and the
10497 processor core that it is currently running on. The main thread of a
10498 process is not listed.
10500 @kindex info os files
10502 Display the list of open file descriptors on the target. For each
10503 file descriptor, @value{GDBN} prints the identifier of the process
10504 owning the descriptor, the command of the owning process, the value
10505 of the descriptor, and the target of the descriptor.
10507 @kindex info os sockets
10509 Display the list of Internet-domain sockets on the target. For each
10510 socket, @value{GDBN} prints the address and port of the local and
10511 remote endpoints, the current state of the connection, the creator of
10512 the socket, the IP address family of the socket, and the type of the
10515 @kindex info os shm
10517 Display the list of all System V shared-memory regions on the target.
10518 For each shared-memory region, @value{GDBN} prints the region key,
10519 the shared-memory identifier, the access permissions, the size of the
10520 region, the process that created the region, the process that last
10521 attached to or detached from the region, the current number of live
10522 attaches to the region, and the times at which the region was last
10523 attached to, detach from, and changed.
10525 @kindex info os semaphores
10527 Display the list of all System V semaphore sets on the target. For each
10528 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10529 set identifier, the access permissions, the number of semaphores in the
10530 set, the user and group of the owner and creator of the semaphore set,
10531 and the times at which the semaphore set was operated upon and changed.
10533 @kindex info os msg
10535 Display the list of all System V message queues on the target. For each
10536 message queue, @value{GDBN} prints the message queue key, the message
10537 queue identifier, the access permissions, the current number of bytes
10538 on the queue, the current number of messages on the queue, the processes
10539 that last sent and received a message on the queue, the user and group
10540 of the owner and creator of the message queue, the times at which a
10541 message was last sent and received on the queue, and the time at which
10542 the message queue was last changed.
10544 @kindex info os modules
10546 Display the list of all loaded kernel modules on the target. For each
10547 module, @value{GDBN} prints the module name, the size of the module in
10548 bytes, the number of times the module is used, the dependencies of the
10549 module, the status of the module, and the address of the loaded module
10554 If @var{infotype} is omitted, then list the possible values for
10555 @var{infotype} and the kind of OS information available for each
10556 @var{infotype}. If the target does not return a list of possible
10557 types, this command will report an error.
10560 @node Memory Region Attributes
10561 @section Memory Region Attributes
10562 @cindex memory region attributes
10564 @dfn{Memory region attributes} allow you to describe special handling
10565 required by regions of your target's memory. @value{GDBN} uses
10566 attributes to determine whether to allow certain types of memory
10567 accesses; whether to use specific width accesses; and whether to cache
10568 target memory. By default the description of memory regions is
10569 fetched from the target (if the current target supports this), but the
10570 user can override the fetched regions.
10572 Defined memory regions can be individually enabled and disabled. When a
10573 memory region is disabled, @value{GDBN} uses the default attributes when
10574 accessing memory in that region. Similarly, if no memory regions have
10575 been defined, @value{GDBN} uses the default attributes when accessing
10578 When a memory region is defined, it is given a number to identify it;
10579 to enable, disable, or remove a memory region, you specify that number.
10583 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10584 Define a memory region bounded by @var{lower} and @var{upper} with
10585 attributes @var{attributes}@dots{}, and add it to the list of regions
10586 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10587 case: it is treated as the target's maximum memory address.
10588 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10591 Discard any user changes to the memory regions and use target-supplied
10592 regions, if available, or no regions if the target does not support.
10595 @item delete mem @var{nums}@dots{}
10596 Remove memory regions @var{nums}@dots{} from the list of regions
10597 monitored by @value{GDBN}.
10599 @kindex disable mem
10600 @item disable mem @var{nums}@dots{}
10601 Disable monitoring of memory regions @var{nums}@dots{}.
10602 A disabled memory region is not forgotten.
10603 It may be enabled again later.
10606 @item enable mem @var{nums}@dots{}
10607 Enable monitoring of memory regions @var{nums}@dots{}.
10611 Print a table of all defined memory regions, with the following columns
10615 @item Memory Region Number
10616 @item Enabled or Disabled.
10617 Enabled memory regions are marked with @samp{y}.
10618 Disabled memory regions are marked with @samp{n}.
10621 The address defining the inclusive lower bound of the memory region.
10624 The address defining the exclusive upper bound of the memory region.
10627 The list of attributes set for this memory region.
10632 @subsection Attributes
10634 @subsubsection Memory Access Mode
10635 The access mode attributes set whether @value{GDBN} may make read or
10636 write accesses to a memory region.
10638 While these attributes prevent @value{GDBN} from performing invalid
10639 memory accesses, they do nothing to prevent the target system, I/O DMA,
10640 etc.@: from accessing memory.
10644 Memory is read only.
10646 Memory is write only.
10648 Memory is read/write. This is the default.
10651 @subsubsection Memory Access Size
10652 The access size attribute tells @value{GDBN} to use specific sized
10653 accesses in the memory region. Often memory mapped device registers
10654 require specific sized accesses. If no access size attribute is
10655 specified, @value{GDBN} may use accesses of any size.
10659 Use 8 bit memory accesses.
10661 Use 16 bit memory accesses.
10663 Use 32 bit memory accesses.
10665 Use 64 bit memory accesses.
10668 @c @subsubsection Hardware/Software Breakpoints
10669 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10670 @c will use hardware or software breakpoints for the internal breakpoints
10671 @c used by the step, next, finish, until, etc. commands.
10675 @c Always use hardware breakpoints
10676 @c @item swbreak (default)
10679 @subsubsection Data Cache
10680 The data cache attributes set whether @value{GDBN} will cache target
10681 memory. While this generally improves performance by reducing debug
10682 protocol overhead, it can lead to incorrect results because @value{GDBN}
10683 does not know about volatile variables or memory mapped device
10688 Enable @value{GDBN} to cache target memory.
10690 Disable @value{GDBN} from caching target memory. This is the default.
10693 @subsection Memory Access Checking
10694 @value{GDBN} can be instructed to refuse accesses to memory that is
10695 not explicitly described. This can be useful if accessing such
10696 regions has undesired effects for a specific target, or to provide
10697 better error checking. The following commands control this behaviour.
10700 @kindex set mem inaccessible-by-default
10701 @item set mem inaccessible-by-default [on|off]
10702 If @code{on} is specified, make @value{GDBN} treat memory not
10703 explicitly described by the memory ranges as non-existent and refuse accesses
10704 to such memory. The checks are only performed if there's at least one
10705 memory range defined. If @code{off} is specified, make @value{GDBN}
10706 treat the memory not explicitly described by the memory ranges as RAM.
10707 The default value is @code{on}.
10708 @kindex show mem inaccessible-by-default
10709 @item show mem inaccessible-by-default
10710 Show the current handling of accesses to unknown memory.
10714 @c @subsubsection Memory Write Verification
10715 @c The memory write verification attributes set whether @value{GDBN}
10716 @c will re-reads data after each write to verify the write was successful.
10720 @c @item noverify (default)
10723 @node Dump/Restore Files
10724 @section Copy Between Memory and a File
10725 @cindex dump/restore files
10726 @cindex append data to a file
10727 @cindex dump data to a file
10728 @cindex restore data from a file
10730 You can use the commands @code{dump}, @code{append}, and
10731 @code{restore} to copy data between target memory and a file. The
10732 @code{dump} and @code{append} commands write data to a file, and the
10733 @code{restore} command reads data from a file back into the inferior's
10734 memory. Files may be in binary, Motorola S-record, Intel hex, or
10735 Tektronix Hex format; however, @value{GDBN} can only append to binary
10741 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10742 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10743 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10744 or the value of @var{expr}, to @var{filename} in the given format.
10746 The @var{format} parameter may be any one of:
10753 Motorola S-record format.
10755 Tektronix Hex format.
10758 @value{GDBN} uses the same definitions of these formats as the
10759 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10760 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10764 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10765 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10766 Append the contents of memory from @var{start_addr} to @var{end_addr},
10767 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10768 (@value{GDBN} can only append data to files in raw binary form.)
10771 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10772 Restore the contents of file @var{filename} into memory. The
10773 @code{restore} command can automatically recognize any known @sc{bfd}
10774 file format, except for raw binary. To restore a raw binary file you
10775 must specify the optional keyword @code{binary} after the filename.
10777 If @var{bias} is non-zero, its value will be added to the addresses
10778 contained in the file. Binary files always start at address zero, so
10779 they will be restored at address @var{bias}. Other bfd files have
10780 a built-in location; they will be restored at offset @var{bias}
10781 from that location.
10783 If @var{start} and/or @var{end} are non-zero, then only data between
10784 file offset @var{start} and file offset @var{end} will be restored.
10785 These offsets are relative to the addresses in the file, before
10786 the @var{bias} argument is applied.
10790 @node Core File Generation
10791 @section How to Produce a Core File from Your Program
10792 @cindex dump core from inferior
10794 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10795 image of a running process and its process status (register values
10796 etc.). Its primary use is post-mortem debugging of a program that
10797 crashed while it ran outside a debugger. A program that crashes
10798 automatically produces a core file, unless this feature is disabled by
10799 the user. @xref{Files}, for information on invoking @value{GDBN} in
10800 the post-mortem debugging mode.
10802 Occasionally, you may wish to produce a core file of the program you
10803 are debugging in order to preserve a snapshot of its state.
10804 @value{GDBN} has a special command for that.
10808 @kindex generate-core-file
10809 @item generate-core-file [@var{file}]
10810 @itemx gcore [@var{file}]
10811 Produce a core dump of the inferior process. The optional argument
10812 @var{file} specifies the file name where to put the core dump. If not
10813 specified, the file name defaults to @file{core.@var{pid}}, where
10814 @var{pid} is the inferior process ID.
10816 Note that this command is implemented only for some systems (as of
10817 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10820 @node Character Sets
10821 @section Character Sets
10822 @cindex character sets
10824 @cindex translating between character sets
10825 @cindex host character set
10826 @cindex target character set
10828 If the program you are debugging uses a different character set to
10829 represent characters and strings than the one @value{GDBN} uses itself,
10830 @value{GDBN} can automatically translate between the character sets for
10831 you. The character set @value{GDBN} uses we call the @dfn{host
10832 character set}; the one the inferior program uses we call the
10833 @dfn{target character set}.
10835 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10836 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10837 remote protocol (@pxref{Remote Debugging}) to debug a program
10838 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10839 then the host character set is Latin-1, and the target character set is
10840 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10841 target-charset EBCDIC-US}, then @value{GDBN} translates between
10842 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10843 character and string literals in expressions.
10845 @value{GDBN} has no way to automatically recognize which character set
10846 the inferior program uses; you must tell it, using the @code{set
10847 target-charset} command, described below.
10849 Here are the commands for controlling @value{GDBN}'s character set
10853 @item set target-charset @var{charset}
10854 @kindex set target-charset
10855 Set the current target character set to @var{charset}. To display the
10856 list of supported target character sets, type
10857 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10859 @item set host-charset @var{charset}
10860 @kindex set host-charset
10861 Set the current host character set to @var{charset}.
10863 By default, @value{GDBN} uses a host character set appropriate to the
10864 system it is running on; you can override that default using the
10865 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10866 automatically determine the appropriate host character set. In this
10867 case, @value{GDBN} uses @samp{UTF-8}.
10869 @value{GDBN} can only use certain character sets as its host character
10870 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10871 @value{GDBN} will list the host character sets it supports.
10873 @item set charset @var{charset}
10874 @kindex set charset
10875 Set the current host and target character sets to @var{charset}. As
10876 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10877 @value{GDBN} will list the names of the character sets that can be used
10878 for both host and target.
10881 @kindex show charset
10882 Show the names of the current host and target character sets.
10884 @item show host-charset
10885 @kindex show host-charset
10886 Show the name of the current host character set.
10888 @item show target-charset
10889 @kindex show target-charset
10890 Show the name of the current target character set.
10892 @item set target-wide-charset @var{charset}
10893 @kindex set target-wide-charset
10894 Set the current target's wide character set to @var{charset}. This is
10895 the character set used by the target's @code{wchar_t} type. To
10896 display the list of supported wide character sets, type
10897 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10899 @item show target-wide-charset
10900 @kindex show target-wide-charset
10901 Show the name of the current target's wide character set.
10904 Here is an example of @value{GDBN}'s character set support in action.
10905 Assume that the following source code has been placed in the file
10906 @file{charset-test.c}:
10912 = @{72, 101, 108, 108, 111, 44, 32, 119,
10913 111, 114, 108, 100, 33, 10, 0@};
10914 char ibm1047_hello[]
10915 = @{200, 133, 147, 147, 150, 107, 64, 166,
10916 150, 153, 147, 132, 90, 37, 0@};
10920 printf ("Hello, world!\n");
10924 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10925 containing the string @samp{Hello, world!} followed by a newline,
10926 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10928 We compile the program, and invoke the debugger on it:
10931 $ gcc -g charset-test.c -o charset-test
10932 $ gdb -nw charset-test
10933 GNU gdb 2001-12-19-cvs
10934 Copyright 2001 Free Software Foundation, Inc.
10939 We can use the @code{show charset} command to see what character sets
10940 @value{GDBN} is currently using to interpret and display characters and
10944 (@value{GDBP}) show charset
10945 The current host and target character set is `ISO-8859-1'.
10949 For the sake of printing this manual, let's use @sc{ascii} as our
10950 initial character set:
10952 (@value{GDBP}) set charset ASCII
10953 (@value{GDBP}) show charset
10954 The current host and target character set is `ASCII'.
10958 Let's assume that @sc{ascii} is indeed the correct character set for our
10959 host system --- in other words, let's assume that if @value{GDBN} prints
10960 characters using the @sc{ascii} character set, our terminal will display
10961 them properly. Since our current target character set is also
10962 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10965 (@value{GDBP}) print ascii_hello
10966 $1 = 0x401698 "Hello, world!\n"
10967 (@value{GDBP}) print ascii_hello[0]
10972 @value{GDBN} uses the target character set for character and string
10973 literals you use in expressions:
10976 (@value{GDBP}) print '+'
10981 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10984 @value{GDBN} relies on the user to tell it which character set the
10985 target program uses. If we print @code{ibm1047_hello} while our target
10986 character set is still @sc{ascii}, we get jibberish:
10989 (@value{GDBP}) print ibm1047_hello
10990 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10991 (@value{GDBP}) print ibm1047_hello[0]
10996 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10997 @value{GDBN} tells us the character sets it supports:
11000 (@value{GDBP}) set target-charset
11001 ASCII EBCDIC-US IBM1047 ISO-8859-1
11002 (@value{GDBP}) set target-charset
11005 We can select @sc{ibm1047} as our target character set, and examine the
11006 program's strings again. Now the @sc{ascii} string is wrong, but
11007 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11008 target character set, @sc{ibm1047}, to the host character set,
11009 @sc{ascii}, and they display correctly:
11012 (@value{GDBP}) set target-charset IBM1047
11013 (@value{GDBP}) show charset
11014 The current host character set is `ASCII'.
11015 The current target character set is `IBM1047'.
11016 (@value{GDBP}) print ascii_hello
11017 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11018 (@value{GDBP}) print ascii_hello[0]
11020 (@value{GDBP}) print ibm1047_hello
11021 $8 = 0x4016a8 "Hello, world!\n"
11022 (@value{GDBP}) print ibm1047_hello[0]
11027 As above, @value{GDBN} uses the target character set for character and
11028 string literals you use in expressions:
11031 (@value{GDBP}) print '+'
11036 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11039 @node Caching Target Data
11040 @section Caching Data of Targets
11041 @cindex caching data of targets
11043 @value{GDBN} caches data exchanged between the debugger and a target.
11044 Each cache is associated with the address space of the inferior.
11045 @xref{Inferiors and Programs}, about inferior and address space.
11046 Such caching generally improves performance in remote debugging
11047 (@pxref{Remote Debugging}), because it reduces the overhead of the
11048 remote protocol by bundling memory reads and writes into large chunks.
11049 Unfortunately, simply caching everything would lead to incorrect results,
11050 since @value{GDBN} does not necessarily know anything about volatile
11051 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11052 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11054 Therefore, by default, @value{GDBN} only caches data
11055 known to be on the stack@footnote{In non-stop mode, it is moderately
11056 rare for a running thread to modify the stack of a stopped thread
11057 in a way that would interfere with a backtrace, and caching of
11058 stack reads provides a significant speed up of remote backtraces.} or
11059 in the code segment.
11060 Other regions of memory can be explicitly marked as
11061 cacheable; @pxref{Memory Region Attributes}.
11064 @kindex set remotecache
11065 @item set remotecache on
11066 @itemx set remotecache off
11067 This option no longer does anything; it exists for compatibility
11070 @kindex show remotecache
11071 @item show remotecache
11072 Show the current state of the obsolete remotecache flag.
11074 @kindex set stack-cache
11075 @item set stack-cache on
11076 @itemx set stack-cache off
11077 Enable or disable caching of stack accesses. When @code{on}, use
11078 caching. By default, this option is @code{on}.
11080 @kindex show stack-cache
11081 @item show stack-cache
11082 Show the current state of data caching for memory accesses.
11084 @kindex set code-cache
11085 @item set code-cache on
11086 @itemx set code-cache off
11087 Enable or disable caching of code segment accesses. When @code{on},
11088 use caching. By default, this option is @code{on}. This improves
11089 performance of disassembly in remote debugging.
11091 @kindex show code-cache
11092 @item show code-cache
11093 Show the current state of target memory cache for code segment
11096 @kindex info dcache
11097 @item info dcache @r{[}line@r{]}
11098 Print the information about the performance of data cache of the
11099 current inferior's address space. The information displayed
11100 includes the dcache width and depth, and for each cache line, its
11101 number, address, and how many times it was referenced. This
11102 command is useful for debugging the data cache operation.
11104 If a line number is specified, the contents of that line will be
11107 @item set dcache size @var{size}
11108 @cindex dcache size
11109 @kindex set dcache size
11110 Set maximum number of entries in dcache (dcache depth above).
11112 @item set dcache line-size @var{line-size}
11113 @cindex dcache line-size
11114 @kindex set dcache line-size
11115 Set number of bytes each dcache entry caches (dcache width above).
11116 Must be a power of 2.
11118 @item show dcache size
11119 @kindex show dcache size
11120 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11122 @item show dcache line-size
11123 @kindex show dcache line-size
11124 Show default size of dcache lines.
11128 @node Searching Memory
11129 @section Search Memory
11130 @cindex searching memory
11132 Memory can be searched for a particular sequence of bytes with the
11133 @code{find} command.
11137 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11138 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11139 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11140 etc. The search begins at address @var{start_addr} and continues for either
11141 @var{len} bytes or through to @var{end_addr} inclusive.
11144 @var{s} and @var{n} are optional parameters.
11145 They may be specified in either order, apart or together.
11148 @item @var{s}, search query size
11149 The size of each search query value.
11155 halfwords (two bytes)
11159 giant words (eight bytes)
11162 All values are interpreted in the current language.
11163 This means, for example, that if the current source language is C/C@t{++}
11164 then searching for the string ``hello'' includes the trailing '\0'.
11166 If the value size is not specified, it is taken from the
11167 value's type in the current language.
11168 This is useful when one wants to specify the search
11169 pattern as a mixture of types.
11170 Note that this means, for example, that in the case of C-like languages
11171 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11172 which is typically four bytes.
11174 @item @var{n}, maximum number of finds
11175 The maximum number of matches to print. The default is to print all finds.
11178 You can use strings as search values. Quote them with double-quotes
11180 The string value is copied into the search pattern byte by byte,
11181 regardless of the endianness of the target and the size specification.
11183 The address of each match found is printed as well as a count of the
11184 number of matches found.
11186 The address of the last value found is stored in convenience variable
11188 A count of the number of matches is stored in @samp{$numfound}.
11190 For example, if stopped at the @code{printf} in this function:
11196 static char hello[] = "hello-hello";
11197 static struct @{ char c; short s; int i; @}
11198 __attribute__ ((packed)) mixed
11199 = @{ 'c', 0x1234, 0x87654321 @};
11200 printf ("%s\n", hello);
11205 you get during debugging:
11208 (gdb) find &hello[0], +sizeof(hello), "hello"
11209 0x804956d <hello.1620+6>
11211 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11212 0x8049567 <hello.1620>
11213 0x804956d <hello.1620+6>
11215 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11216 0x8049567 <hello.1620>
11218 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11219 0x8049560 <mixed.1625>
11221 (gdb) print $numfound
11224 $2 = (void *) 0x8049560
11227 @node Optimized Code
11228 @chapter Debugging Optimized Code
11229 @cindex optimized code, debugging
11230 @cindex debugging optimized code
11232 Almost all compilers support optimization. With optimization
11233 disabled, the compiler generates assembly code that corresponds
11234 directly to your source code, in a simplistic way. As the compiler
11235 applies more powerful optimizations, the generated assembly code
11236 diverges from your original source code. With help from debugging
11237 information generated by the compiler, @value{GDBN} can map from
11238 the running program back to constructs from your original source.
11240 @value{GDBN} is more accurate with optimization disabled. If you
11241 can recompile without optimization, it is easier to follow the
11242 progress of your program during debugging. But, there are many cases
11243 where you may need to debug an optimized version.
11245 When you debug a program compiled with @samp{-g -O}, remember that the
11246 optimizer has rearranged your code; the debugger shows you what is
11247 really there. Do not be too surprised when the execution path does not
11248 exactly match your source file! An extreme example: if you define a
11249 variable, but never use it, @value{GDBN} never sees that
11250 variable---because the compiler optimizes it out of existence.
11252 Some things do not work as well with @samp{-g -O} as with just
11253 @samp{-g}, particularly on machines with instruction scheduling. If in
11254 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11255 please report it to us as a bug (including a test case!).
11256 @xref{Variables}, for more information about debugging optimized code.
11259 * Inline Functions:: How @value{GDBN} presents inlining
11260 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11263 @node Inline Functions
11264 @section Inline Functions
11265 @cindex inline functions, debugging
11267 @dfn{Inlining} is an optimization that inserts a copy of the function
11268 body directly at each call site, instead of jumping to a shared
11269 routine. @value{GDBN} displays inlined functions just like
11270 non-inlined functions. They appear in backtraces. You can view their
11271 arguments and local variables, step into them with @code{step}, skip
11272 them with @code{next}, and escape from them with @code{finish}.
11273 You can check whether a function was inlined by using the
11274 @code{info frame} command.
11276 For @value{GDBN} to support inlined functions, the compiler must
11277 record information about inlining in the debug information ---
11278 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11279 other compilers do also. @value{GDBN} only supports inlined functions
11280 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11281 do not emit two required attributes (@samp{DW_AT_call_file} and
11282 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11283 function calls with earlier versions of @value{NGCC}. It instead
11284 displays the arguments and local variables of inlined functions as
11285 local variables in the caller.
11287 The body of an inlined function is directly included at its call site;
11288 unlike a non-inlined function, there are no instructions devoted to
11289 the call. @value{GDBN} still pretends that the call site and the
11290 start of the inlined function are different instructions. Stepping to
11291 the call site shows the call site, and then stepping again shows
11292 the first line of the inlined function, even though no additional
11293 instructions are executed.
11295 This makes source-level debugging much clearer; you can see both the
11296 context of the call and then the effect of the call. Only stepping by
11297 a single instruction using @code{stepi} or @code{nexti} does not do
11298 this; single instruction steps always show the inlined body.
11300 There are some ways that @value{GDBN} does not pretend that inlined
11301 function calls are the same as normal calls:
11305 Setting breakpoints at the call site of an inlined function may not
11306 work, because the call site does not contain any code. @value{GDBN}
11307 may incorrectly move the breakpoint to the next line of the enclosing
11308 function, after the call. This limitation will be removed in a future
11309 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11310 or inside the inlined function instead.
11313 @value{GDBN} cannot locate the return value of inlined calls after
11314 using the @code{finish} command. This is a limitation of compiler-generated
11315 debugging information; after @code{finish}, you can step to the next line
11316 and print a variable where your program stored the return value.
11320 @node Tail Call Frames
11321 @section Tail Call Frames
11322 @cindex tail call frames, debugging
11324 Function @code{B} can call function @code{C} in its very last statement. In
11325 unoptimized compilation the call of @code{C} is immediately followed by return
11326 instruction at the end of @code{B} code. Optimizing compiler may replace the
11327 call and return in function @code{B} into one jump to function @code{C}
11328 instead. Such use of a jump instruction is called @dfn{tail call}.
11330 During execution of function @code{C}, there will be no indication in the
11331 function call stack frames that it was tail-called from @code{B}. If function
11332 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11333 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11334 some cases @value{GDBN} can determine that @code{C} was tail-called from
11335 @code{B}, and it will then create fictitious call frame for that, with the
11336 return address set up as if @code{B} called @code{C} normally.
11338 This functionality is currently supported only by DWARF 2 debugging format and
11339 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11340 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11343 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11344 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11348 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11350 Stack level 1, frame at 0x7fffffffda30:
11351 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11352 tail call frame, caller of frame at 0x7fffffffda30
11353 source language c++.
11354 Arglist at unknown address.
11355 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11358 The detection of all the possible code path executions can find them ambiguous.
11359 There is no execution history stored (possible @ref{Reverse Execution} is never
11360 used for this purpose) and the last known caller could have reached the known
11361 callee by multiple different jump sequences. In such case @value{GDBN} still
11362 tries to show at least all the unambiguous top tail callers and all the
11363 unambiguous bottom tail calees, if any.
11366 @anchor{set debug entry-values}
11367 @item set debug entry-values
11368 @kindex set debug entry-values
11369 When set to on, enables printing of analysis messages for both frame argument
11370 values at function entry and tail calls. It will show all the possible valid
11371 tail calls code paths it has considered. It will also print the intersection
11372 of them with the final unambiguous (possibly partial or even empty) code path
11375 @item show debug entry-values
11376 @kindex show debug entry-values
11377 Show the current state of analysis messages printing for both frame argument
11378 values at function entry and tail calls.
11381 The analysis messages for tail calls can for example show why the virtual tail
11382 call frame for function @code{c} has not been recognized (due to the indirect
11383 reference by variable @code{x}):
11386 static void __attribute__((noinline, noclone)) c (void);
11387 void (*x) (void) = c;
11388 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11389 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11390 int main (void) @{ x (); return 0; @}
11392 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11393 DW_TAG_GNU_call_site 0x40039a in main
11395 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11398 #1 0x000000000040039a in main () at t.c:5
11401 Another possibility is an ambiguous virtual tail call frames resolution:
11405 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11406 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11407 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11408 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11409 static void __attribute__((noinline, noclone)) b (void)
11410 @{ if (i) c (); else e (); @}
11411 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11412 int main (void) @{ a (); return 0; @}
11414 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11415 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11416 tailcall: reduced: 0x4004d2(a) |
11419 #1 0x00000000004004d2 in a () at t.c:8
11420 #2 0x0000000000400395 in main () at t.c:9
11423 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11424 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11426 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11427 @ifset HAVE_MAKEINFO_CLICK
11428 @set ARROW @click{}
11429 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11430 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11432 @ifclear HAVE_MAKEINFO_CLICK
11434 @set CALLSEQ1B @value{CALLSEQ1A}
11435 @set CALLSEQ2B @value{CALLSEQ2A}
11438 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11439 The code can have possible execution paths @value{CALLSEQ1B} or
11440 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11442 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11443 has found. It then finds another possible calling sequcen - that one is
11444 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11445 printed as the @code{reduced:} calling sequence. That one could have many
11446 futher @code{compare:} and @code{reduced:} statements as long as there remain
11447 any non-ambiguous sequence entries.
11449 For the frame of function @code{b} in both cases there are different possible
11450 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11451 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11452 therefore this one is displayed to the user while the ambiguous frames are
11455 There can be also reasons why printing of frame argument values at function
11460 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11461 static void __attribute__((noinline, noclone)) a (int i);
11462 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11463 static void __attribute__((noinline, noclone)) a (int i)
11464 @{ if (i) b (i - 1); else c (0); @}
11465 int main (void) @{ a (5); return 0; @}
11468 #0 c (i=i@@entry=0) at t.c:2
11469 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11470 function "a" at 0x400420 can call itself via tail calls
11471 i=<optimized out>) at t.c:6
11472 #2 0x000000000040036e in main () at t.c:7
11475 @value{GDBN} cannot find out from the inferior state if and how many times did
11476 function @code{a} call itself (via function @code{b}) as these calls would be
11477 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11478 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11479 prints @code{<optimized out>} instead.
11482 @chapter C Preprocessor Macros
11484 Some languages, such as C and C@t{++}, provide a way to define and invoke
11485 ``preprocessor macros'' which expand into strings of tokens.
11486 @value{GDBN} can evaluate expressions containing macro invocations, show
11487 the result of macro expansion, and show a macro's definition, including
11488 where it was defined.
11490 You may need to compile your program specially to provide @value{GDBN}
11491 with information about preprocessor macros. Most compilers do not
11492 include macros in their debugging information, even when you compile
11493 with the @option{-g} flag. @xref{Compilation}.
11495 A program may define a macro at one point, remove that definition later,
11496 and then provide a different definition after that. Thus, at different
11497 points in the program, a macro may have different definitions, or have
11498 no definition at all. If there is a current stack frame, @value{GDBN}
11499 uses the macros in scope at that frame's source code line. Otherwise,
11500 @value{GDBN} uses the macros in scope at the current listing location;
11503 Whenever @value{GDBN} evaluates an expression, it always expands any
11504 macro invocations present in the expression. @value{GDBN} also provides
11505 the following commands for working with macros explicitly.
11509 @kindex macro expand
11510 @cindex macro expansion, showing the results of preprocessor
11511 @cindex preprocessor macro expansion, showing the results of
11512 @cindex expanding preprocessor macros
11513 @item macro expand @var{expression}
11514 @itemx macro exp @var{expression}
11515 Show the results of expanding all preprocessor macro invocations in
11516 @var{expression}. Since @value{GDBN} simply expands macros, but does
11517 not parse the result, @var{expression} need not be a valid expression;
11518 it can be any string of tokens.
11521 @item macro expand-once @var{expression}
11522 @itemx macro exp1 @var{expression}
11523 @cindex expand macro once
11524 @i{(This command is not yet implemented.)} Show the results of
11525 expanding those preprocessor macro invocations that appear explicitly in
11526 @var{expression}. Macro invocations appearing in that expansion are
11527 left unchanged. This command allows you to see the effect of a
11528 particular macro more clearly, without being confused by further
11529 expansions. Since @value{GDBN} simply expands macros, but does not
11530 parse the result, @var{expression} need not be a valid expression; it
11531 can be any string of tokens.
11534 @cindex macro definition, showing
11535 @cindex definition of a macro, showing
11536 @cindex macros, from debug info
11537 @item info macro [-a|-all] [--] @var{macro}
11538 Show the current definition or all definitions of the named @var{macro},
11539 and describe the source location or compiler command-line where that
11540 definition was established. The optional double dash is to signify the end of
11541 argument processing and the beginning of @var{macro} for non C-like macros where
11542 the macro may begin with a hyphen.
11544 @kindex info macros
11545 @item info macros @var{linespec}
11546 Show all macro definitions that are in effect at the location specified
11547 by @var{linespec}, and describe the source location or compiler
11548 command-line where those definitions were established.
11550 @kindex macro define
11551 @cindex user-defined macros
11552 @cindex defining macros interactively
11553 @cindex macros, user-defined
11554 @item macro define @var{macro} @var{replacement-list}
11555 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11556 Introduce a definition for a preprocessor macro named @var{macro},
11557 invocations of which are replaced by the tokens given in
11558 @var{replacement-list}. The first form of this command defines an
11559 ``object-like'' macro, which takes no arguments; the second form
11560 defines a ``function-like'' macro, which takes the arguments given in
11563 A definition introduced by this command is in scope in every
11564 expression evaluated in @value{GDBN}, until it is removed with the
11565 @code{macro undef} command, described below. The definition overrides
11566 all definitions for @var{macro} present in the program being debugged,
11567 as well as any previous user-supplied definition.
11569 @kindex macro undef
11570 @item macro undef @var{macro}
11571 Remove any user-supplied definition for the macro named @var{macro}.
11572 This command only affects definitions provided with the @code{macro
11573 define} command, described above; it cannot remove definitions present
11574 in the program being debugged.
11578 List all the macros defined using the @code{macro define} command.
11581 @cindex macros, example of debugging with
11582 Here is a transcript showing the above commands in action. First, we
11583 show our source files:
11588 #include "sample.h"
11591 #define ADD(x) (M + x)
11596 printf ("Hello, world!\n");
11598 printf ("We're so creative.\n");
11600 printf ("Goodbye, world!\n");
11607 Now, we compile the program using the @sc{gnu} C compiler,
11608 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11609 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11610 and @option{-gdwarf-4}; we recommend always choosing the most recent
11611 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11612 includes information about preprocessor macros in the debugging
11616 $ gcc -gdwarf-2 -g3 sample.c -o sample
11620 Now, we start @value{GDBN} on our sample program:
11624 GNU gdb 2002-05-06-cvs
11625 Copyright 2002 Free Software Foundation, Inc.
11626 GDB is free software, @dots{}
11630 We can expand macros and examine their definitions, even when the
11631 program is not running. @value{GDBN} uses the current listing position
11632 to decide which macro definitions are in scope:
11635 (@value{GDBP}) list main
11638 5 #define ADD(x) (M + x)
11643 10 printf ("Hello, world!\n");
11645 12 printf ("We're so creative.\n");
11646 (@value{GDBP}) info macro ADD
11647 Defined at /home/jimb/gdb/macros/play/sample.c:5
11648 #define ADD(x) (M + x)
11649 (@value{GDBP}) info macro Q
11650 Defined at /home/jimb/gdb/macros/play/sample.h:1
11651 included at /home/jimb/gdb/macros/play/sample.c:2
11653 (@value{GDBP}) macro expand ADD(1)
11654 expands to: (42 + 1)
11655 (@value{GDBP}) macro expand-once ADD(1)
11656 expands to: once (M + 1)
11660 In the example above, note that @code{macro expand-once} expands only
11661 the macro invocation explicit in the original text --- the invocation of
11662 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11663 which was introduced by @code{ADD}.
11665 Once the program is running, @value{GDBN} uses the macro definitions in
11666 force at the source line of the current stack frame:
11669 (@value{GDBP}) break main
11670 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11672 Starting program: /home/jimb/gdb/macros/play/sample
11674 Breakpoint 1, main () at sample.c:10
11675 10 printf ("Hello, world!\n");
11679 At line 10, the definition of the macro @code{N} at line 9 is in force:
11682 (@value{GDBP}) info macro N
11683 Defined at /home/jimb/gdb/macros/play/sample.c:9
11685 (@value{GDBP}) macro expand N Q M
11686 expands to: 28 < 42
11687 (@value{GDBP}) print N Q M
11692 As we step over directives that remove @code{N}'s definition, and then
11693 give it a new definition, @value{GDBN} finds the definition (or lack
11694 thereof) in force at each point:
11697 (@value{GDBP}) next
11699 12 printf ("We're so creative.\n");
11700 (@value{GDBP}) info macro N
11701 The symbol `N' has no definition as a C/C++ preprocessor macro
11702 at /home/jimb/gdb/macros/play/sample.c:12
11703 (@value{GDBP}) next
11705 14 printf ("Goodbye, world!\n");
11706 (@value{GDBP}) info macro N
11707 Defined at /home/jimb/gdb/macros/play/sample.c:13
11709 (@value{GDBP}) macro expand N Q M
11710 expands to: 1729 < 42
11711 (@value{GDBP}) print N Q M
11716 In addition to source files, macros can be defined on the compilation command
11717 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11718 such a way, @value{GDBN} displays the location of their definition as line zero
11719 of the source file submitted to the compiler.
11722 (@value{GDBP}) info macro __STDC__
11723 Defined at /home/jimb/gdb/macros/play/sample.c:0
11730 @chapter Tracepoints
11731 @c This chapter is based on the documentation written by Michael
11732 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11734 @cindex tracepoints
11735 In some applications, it is not feasible for the debugger to interrupt
11736 the program's execution long enough for the developer to learn
11737 anything helpful about its behavior. If the program's correctness
11738 depends on its real-time behavior, delays introduced by a debugger
11739 might cause the program to change its behavior drastically, or perhaps
11740 fail, even when the code itself is correct. It is useful to be able
11741 to observe the program's behavior without interrupting it.
11743 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11744 specify locations in the program, called @dfn{tracepoints}, and
11745 arbitrary expressions to evaluate when those tracepoints are reached.
11746 Later, using the @code{tfind} command, you can examine the values
11747 those expressions had when the program hit the tracepoints. The
11748 expressions may also denote objects in memory---structures or arrays,
11749 for example---whose values @value{GDBN} should record; while visiting
11750 a particular tracepoint, you may inspect those objects as if they were
11751 in memory at that moment. However, because @value{GDBN} records these
11752 values without interacting with you, it can do so quickly and
11753 unobtrusively, hopefully not disturbing the program's behavior.
11755 The tracepoint facility is currently available only for remote
11756 targets. @xref{Targets}. In addition, your remote target must know
11757 how to collect trace data. This functionality is implemented in the
11758 remote stub; however, none of the stubs distributed with @value{GDBN}
11759 support tracepoints as of this writing. The format of the remote
11760 packets used to implement tracepoints are described in @ref{Tracepoint
11763 It is also possible to get trace data from a file, in a manner reminiscent
11764 of corefiles; you specify the filename, and use @code{tfind} to search
11765 through the file. @xref{Trace Files}, for more details.
11767 This chapter describes the tracepoint commands and features.
11770 * Set Tracepoints::
11771 * Analyze Collected Data::
11772 * Tracepoint Variables::
11776 @node Set Tracepoints
11777 @section Commands to Set Tracepoints
11779 Before running such a @dfn{trace experiment}, an arbitrary number of
11780 tracepoints can be set. A tracepoint is actually a special type of
11781 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11782 standard breakpoint commands. For instance, as with breakpoints,
11783 tracepoint numbers are successive integers starting from one, and many
11784 of the commands associated with tracepoints take the tracepoint number
11785 as their argument, to identify which tracepoint to work on.
11787 For each tracepoint, you can specify, in advance, some arbitrary set
11788 of data that you want the target to collect in the trace buffer when
11789 it hits that tracepoint. The collected data can include registers,
11790 local variables, or global data. Later, you can use @value{GDBN}
11791 commands to examine the values these data had at the time the
11792 tracepoint was hit.
11794 Tracepoints do not support every breakpoint feature. Ignore counts on
11795 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11796 commands when they are hit. Tracepoints may not be thread-specific
11799 @cindex fast tracepoints
11800 Some targets may support @dfn{fast tracepoints}, which are inserted in
11801 a different way (such as with a jump instead of a trap), that is
11802 faster but possibly restricted in where they may be installed.
11804 @cindex static tracepoints
11805 @cindex markers, static tracepoints
11806 @cindex probing markers, static tracepoints
11807 Regular and fast tracepoints are dynamic tracing facilities, meaning
11808 that they can be used to insert tracepoints at (almost) any location
11809 in the target. Some targets may also support controlling @dfn{static
11810 tracepoints} from @value{GDBN}. With static tracing, a set of
11811 instrumentation points, also known as @dfn{markers}, are embedded in
11812 the target program, and can be activated or deactivated by name or
11813 address. These are usually placed at locations which facilitate
11814 investigating what the target is actually doing. @value{GDBN}'s
11815 support for static tracing includes being able to list instrumentation
11816 points, and attach them with @value{GDBN} defined high level
11817 tracepoints that expose the whole range of convenience of
11818 @value{GDBN}'s tracepoints support. Namely, support for collecting
11819 registers values and values of global or local (to the instrumentation
11820 point) variables; tracepoint conditions and trace state variables.
11821 The act of installing a @value{GDBN} static tracepoint on an
11822 instrumentation point, or marker, is referred to as @dfn{probing} a
11823 static tracepoint marker.
11825 @code{gdbserver} supports tracepoints on some target systems.
11826 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11828 This section describes commands to set tracepoints and associated
11829 conditions and actions.
11832 * Create and Delete Tracepoints::
11833 * Enable and Disable Tracepoints::
11834 * Tracepoint Passcounts::
11835 * Tracepoint Conditions::
11836 * Trace State Variables::
11837 * Tracepoint Actions::
11838 * Listing Tracepoints::
11839 * Listing Static Tracepoint Markers::
11840 * Starting and Stopping Trace Experiments::
11841 * Tracepoint Restrictions::
11844 @node Create and Delete Tracepoints
11845 @subsection Create and Delete Tracepoints
11848 @cindex set tracepoint
11850 @item trace @var{location}
11851 The @code{trace} command is very similar to the @code{break} command.
11852 Its argument @var{location} can be a source line, a function name, or
11853 an address in the target program. @xref{Specify Location}. The
11854 @code{trace} command defines a tracepoint, which is a point in the
11855 target program where the debugger will briefly stop, collect some
11856 data, and then allow the program to continue. Setting a tracepoint or
11857 changing its actions takes effect immediately if the remote stub
11858 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11860 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11861 these changes don't take effect until the next @code{tstart}
11862 command, and once a trace experiment is running, further changes will
11863 not have any effect until the next trace experiment starts. In addition,
11864 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11865 address is not yet resolved. (This is similar to pending breakpoints.)
11866 Pending tracepoints are not downloaded to the target and not installed
11867 until they are resolved. The resolution of pending tracepoints requires
11868 @value{GDBN} support---when debugging with the remote target, and
11869 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11870 tracing}), pending tracepoints can not be resolved (and downloaded to
11871 the remote stub) while @value{GDBN} is disconnected.
11873 Here are some examples of using the @code{trace} command:
11876 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11878 (@value{GDBP}) @b{trace +2} // 2 lines forward
11880 (@value{GDBP}) @b{trace my_function} // first source line of function
11882 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11884 (@value{GDBP}) @b{trace *0x2117c4} // an address
11888 You can abbreviate @code{trace} as @code{tr}.
11890 @item trace @var{location} if @var{cond}
11891 Set a tracepoint with condition @var{cond}; evaluate the expression
11892 @var{cond} each time the tracepoint is reached, and collect data only
11893 if the value is nonzero---that is, if @var{cond} evaluates as true.
11894 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11895 information on tracepoint conditions.
11897 @item ftrace @var{location} [ if @var{cond} ]
11898 @cindex set fast tracepoint
11899 @cindex fast tracepoints, setting
11901 The @code{ftrace} command sets a fast tracepoint. For targets that
11902 support them, fast tracepoints will use a more efficient but possibly
11903 less general technique to trigger data collection, such as a jump
11904 instruction instead of a trap, or some sort of hardware support. It
11905 may not be possible to create a fast tracepoint at the desired
11906 location, in which case the command will exit with an explanatory
11909 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11912 On 32-bit x86-architecture systems, fast tracepoints normally need to
11913 be placed at an instruction that is 5 bytes or longer, but can be
11914 placed at 4-byte instructions if the low 64K of memory of the target
11915 program is available to install trampolines. Some Unix-type systems,
11916 such as @sc{gnu}/Linux, exclude low addresses from the program's
11917 address space; but for instance with the Linux kernel it is possible
11918 to let @value{GDBN} use this area by doing a @command{sysctl} command
11919 to set the @code{mmap_min_addr} kernel parameter, as in
11922 sudo sysctl -w vm.mmap_min_addr=32768
11926 which sets the low address to 32K, which leaves plenty of room for
11927 trampolines. The minimum address should be set to a page boundary.
11929 @item strace @var{location} [ if @var{cond} ]
11930 @cindex set static tracepoint
11931 @cindex static tracepoints, setting
11932 @cindex probe static tracepoint marker
11934 The @code{strace} command sets a static tracepoint. For targets that
11935 support it, setting a static tracepoint probes a static
11936 instrumentation point, or marker, found at @var{location}. It may not
11937 be possible to set a static tracepoint at the desired location, in
11938 which case the command will exit with an explanatory message.
11940 @value{GDBN} handles arguments to @code{strace} exactly as for
11941 @code{trace}, with the addition that the user can also specify
11942 @code{-m @var{marker}} as @var{location}. This probes the marker
11943 identified by the @var{marker} string identifier. This identifier
11944 depends on the static tracepoint backend library your program is
11945 using. You can find all the marker identifiers in the @samp{ID} field
11946 of the @code{info static-tracepoint-markers} command output.
11947 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11948 Markers}. For example, in the following small program using the UST
11954 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11959 the marker id is composed of joining the first two arguments to the
11960 @code{trace_mark} call with a slash, which translates to:
11963 (@value{GDBP}) info static-tracepoint-markers
11964 Cnt Enb ID Address What
11965 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11971 so you may probe the marker above with:
11974 (@value{GDBP}) strace -m ust/bar33
11977 Static tracepoints accept an extra collect action --- @code{collect
11978 $_sdata}. This collects arbitrary user data passed in the probe point
11979 call to the tracing library. In the UST example above, you'll see
11980 that the third argument to @code{trace_mark} is a printf-like format
11981 string. The user data is then the result of running that formating
11982 string against the following arguments. Note that @code{info
11983 static-tracepoint-markers} command output lists that format string in
11984 the @samp{Data:} field.
11986 You can inspect this data when analyzing the trace buffer, by printing
11987 the $_sdata variable like any other variable available to
11988 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11991 @cindex last tracepoint number
11992 @cindex recent tracepoint number
11993 @cindex tracepoint number
11994 The convenience variable @code{$tpnum} records the tracepoint number
11995 of the most recently set tracepoint.
11997 @kindex delete tracepoint
11998 @cindex tracepoint deletion
11999 @item delete tracepoint @r{[}@var{num}@r{]}
12000 Permanently delete one or more tracepoints. With no argument, the
12001 default is to delete all tracepoints. Note that the regular
12002 @code{delete} command can remove tracepoints also.
12007 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12009 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12013 You can abbreviate this command as @code{del tr}.
12016 @node Enable and Disable Tracepoints
12017 @subsection Enable and Disable Tracepoints
12019 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12022 @kindex disable tracepoint
12023 @item disable tracepoint @r{[}@var{num}@r{]}
12024 Disable tracepoint @var{num}, or all tracepoints if no argument
12025 @var{num} is given. A disabled tracepoint will have no effect during
12026 a trace experiment, but it is not forgotten. You can re-enable
12027 a disabled tracepoint using the @code{enable tracepoint} command.
12028 If the command is issued during a trace experiment and the debug target
12029 has support for disabling tracepoints during a trace experiment, then the
12030 change will be effective immediately. Otherwise, it will be applied to the
12031 next trace experiment.
12033 @kindex enable tracepoint
12034 @item enable tracepoint @r{[}@var{num}@r{]}
12035 Enable tracepoint @var{num}, or all tracepoints. If this command is
12036 issued during a trace experiment and the debug target supports enabling
12037 tracepoints during a trace experiment, then the enabled tracepoints will
12038 become effective immediately. Otherwise, they will become effective the
12039 next time a trace experiment is run.
12042 @node Tracepoint Passcounts
12043 @subsection Tracepoint Passcounts
12047 @cindex tracepoint pass count
12048 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12049 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12050 automatically stop a trace experiment. If a tracepoint's passcount is
12051 @var{n}, then the trace experiment will be automatically stopped on
12052 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12053 @var{num} is not specified, the @code{passcount} command sets the
12054 passcount of the most recently defined tracepoint. If no passcount is
12055 given, the trace experiment will run until stopped explicitly by the
12061 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12062 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12064 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12065 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12066 (@value{GDBP}) @b{trace foo}
12067 (@value{GDBP}) @b{pass 3}
12068 (@value{GDBP}) @b{trace bar}
12069 (@value{GDBP}) @b{pass 2}
12070 (@value{GDBP}) @b{trace baz}
12071 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12072 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12073 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12074 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12078 @node Tracepoint Conditions
12079 @subsection Tracepoint Conditions
12080 @cindex conditional tracepoints
12081 @cindex tracepoint conditions
12083 The simplest sort of tracepoint collects data every time your program
12084 reaches a specified place. You can also specify a @dfn{condition} for
12085 a tracepoint. A condition is just a Boolean expression in your
12086 programming language (@pxref{Expressions, ,Expressions}). A
12087 tracepoint with a condition evaluates the expression each time your
12088 program reaches it, and data collection happens only if the condition
12091 Tracepoint conditions can be specified when a tracepoint is set, by
12092 using @samp{if} in the arguments to the @code{trace} command.
12093 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12094 also be set or changed at any time with the @code{condition} command,
12095 just as with breakpoints.
12097 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12098 the conditional expression itself. Instead, @value{GDBN} encodes the
12099 expression into an agent expression (@pxref{Agent Expressions})
12100 suitable for execution on the target, independently of @value{GDBN}.
12101 Global variables become raw memory locations, locals become stack
12102 accesses, and so forth.
12104 For instance, suppose you have a function that is usually called
12105 frequently, but should not be called after an error has occurred. You
12106 could use the following tracepoint command to collect data about calls
12107 of that function that happen while the error code is propagating
12108 through the program; an unconditional tracepoint could end up
12109 collecting thousands of useless trace frames that you would have to
12113 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12116 @node Trace State Variables
12117 @subsection Trace State Variables
12118 @cindex trace state variables
12120 A @dfn{trace state variable} is a special type of variable that is
12121 created and managed by target-side code. The syntax is the same as
12122 that for GDB's convenience variables (a string prefixed with ``$''),
12123 but they are stored on the target. They must be created explicitly,
12124 using a @code{tvariable} command. They are always 64-bit signed
12127 Trace state variables are remembered by @value{GDBN}, and downloaded
12128 to the target along with tracepoint information when the trace
12129 experiment starts. There are no intrinsic limits on the number of
12130 trace state variables, beyond memory limitations of the target.
12132 @cindex convenience variables, and trace state variables
12133 Although trace state variables are managed by the target, you can use
12134 them in print commands and expressions as if they were convenience
12135 variables; @value{GDBN} will get the current value from the target
12136 while the trace experiment is running. Trace state variables share
12137 the same namespace as other ``$'' variables, which means that you
12138 cannot have trace state variables with names like @code{$23} or
12139 @code{$pc}, nor can you have a trace state variable and a convenience
12140 variable with the same name.
12144 @item tvariable $@var{name} [ = @var{expression} ]
12146 The @code{tvariable} command creates a new trace state variable named
12147 @code{$@var{name}}, and optionally gives it an initial value of
12148 @var{expression}. The @var{expression} is evaluated when this command is
12149 entered; the result will be converted to an integer if possible,
12150 otherwise @value{GDBN} will report an error. A subsequent
12151 @code{tvariable} command specifying the same name does not create a
12152 variable, but instead assigns the supplied initial value to the
12153 existing variable of that name, overwriting any previous initial
12154 value. The default initial value is 0.
12156 @item info tvariables
12157 @kindex info tvariables
12158 List all the trace state variables along with their initial values.
12159 Their current values may also be displayed, if the trace experiment is
12162 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12163 @kindex delete tvariable
12164 Delete the given trace state variables, or all of them if no arguments
12169 @node Tracepoint Actions
12170 @subsection Tracepoint Action Lists
12174 @cindex tracepoint actions
12175 @item actions @r{[}@var{num}@r{]}
12176 This command will prompt for a list of actions to be taken when the
12177 tracepoint is hit. If the tracepoint number @var{num} is not
12178 specified, this command sets the actions for the one that was most
12179 recently defined (so that you can define a tracepoint and then say
12180 @code{actions} without bothering about its number). You specify the
12181 actions themselves on the following lines, one action at a time, and
12182 terminate the actions list with a line containing just @code{end}. So
12183 far, the only defined actions are @code{collect}, @code{teval}, and
12184 @code{while-stepping}.
12186 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12187 Commands, ,Breakpoint Command Lists}), except that only the defined
12188 actions are allowed; any other @value{GDBN} command is rejected.
12190 @cindex remove actions from a tracepoint
12191 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12192 and follow it immediately with @samp{end}.
12195 (@value{GDBP}) @b{collect @var{data}} // collect some data
12197 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12199 (@value{GDBP}) @b{end} // signals the end of actions.
12202 In the following example, the action list begins with @code{collect}
12203 commands indicating the things to be collected when the tracepoint is
12204 hit. Then, in order to single-step and collect additional data
12205 following the tracepoint, a @code{while-stepping} command is used,
12206 followed by the list of things to be collected after each step in a
12207 sequence of single steps. The @code{while-stepping} command is
12208 terminated by its own separate @code{end} command. Lastly, the action
12209 list is terminated by an @code{end} command.
12212 (@value{GDBP}) @b{trace foo}
12213 (@value{GDBP}) @b{actions}
12214 Enter actions for tracepoint 1, one per line:
12217 > while-stepping 12
12218 > collect $pc, arr[i]
12223 @kindex collect @r{(tracepoints)}
12224 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12225 Collect values of the given expressions when the tracepoint is hit.
12226 This command accepts a comma-separated list of any valid expressions.
12227 In addition to global, static, or local variables, the following
12228 special arguments are supported:
12232 Collect all registers.
12235 Collect all function arguments.
12238 Collect all local variables.
12241 Collect the return address. This is helpful if you want to see more
12245 Collects the number of arguments from the static probe at which the
12246 tracepoint is located.
12247 @xref{Static Probe Points}.
12249 @item $_probe_arg@var{n}
12250 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12251 from the static probe at which the tracepoint is located.
12252 @xref{Static Probe Points}.
12255 @vindex $_sdata@r{, collect}
12256 Collect static tracepoint marker specific data. Only available for
12257 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12258 Lists}. On the UST static tracepoints library backend, an
12259 instrumentation point resembles a @code{printf} function call. The
12260 tracing library is able to collect user specified data formatted to a
12261 character string using the format provided by the programmer that
12262 instrumented the program. Other backends have similar mechanisms.
12263 Here's an example of a UST marker call:
12266 const char master_name[] = "$your_name";
12267 trace_mark(channel1, marker1, "hello %s", master_name)
12270 In this case, collecting @code{$_sdata} collects the string
12271 @samp{hello $yourname}. When analyzing the trace buffer, you can
12272 inspect @samp{$_sdata} like any other variable available to
12276 You can give several consecutive @code{collect} commands, each one
12277 with a single argument, or one @code{collect} command with several
12278 arguments separated by commas; the effect is the same.
12280 The optional @var{mods} changes the usual handling of the arguments.
12281 @code{s} requests that pointers to chars be handled as strings, in
12282 particular collecting the contents of the memory being pointed at, up
12283 to the first zero. The upper bound is by default the value of the
12284 @code{print elements} variable; if @code{s} is followed by a decimal
12285 number, that is the upper bound instead. So for instance
12286 @samp{collect/s25 mystr} collects as many as 25 characters at
12289 The command @code{info scope} (@pxref{Symbols, info scope}) is
12290 particularly useful for figuring out what data to collect.
12292 @kindex teval @r{(tracepoints)}
12293 @item teval @var{expr1}, @var{expr2}, @dots{}
12294 Evaluate the given expressions when the tracepoint is hit. This
12295 command accepts a comma-separated list of expressions. The results
12296 are discarded, so this is mainly useful for assigning values to trace
12297 state variables (@pxref{Trace State Variables}) without adding those
12298 values to the trace buffer, as would be the case if the @code{collect}
12301 @kindex while-stepping @r{(tracepoints)}
12302 @item while-stepping @var{n}
12303 Perform @var{n} single-step instruction traces after the tracepoint,
12304 collecting new data after each step. The @code{while-stepping}
12305 command is followed by the list of what to collect while stepping
12306 (followed by its own @code{end} command):
12309 > while-stepping 12
12310 > collect $regs, myglobal
12316 Note that @code{$pc} is not automatically collected by
12317 @code{while-stepping}; you need to explicitly collect that register if
12318 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12321 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12322 @kindex set default-collect
12323 @cindex default collection action
12324 This variable is a list of expressions to collect at each tracepoint
12325 hit. It is effectively an additional @code{collect} action prepended
12326 to every tracepoint action list. The expressions are parsed
12327 individually for each tracepoint, so for instance a variable named
12328 @code{xyz} may be interpreted as a global for one tracepoint, and a
12329 local for another, as appropriate to the tracepoint's location.
12331 @item show default-collect
12332 @kindex show default-collect
12333 Show the list of expressions that are collected by default at each
12338 @node Listing Tracepoints
12339 @subsection Listing Tracepoints
12342 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12343 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12344 @cindex information about tracepoints
12345 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12346 Display information about the tracepoint @var{num}. If you don't
12347 specify a tracepoint number, displays information about all the
12348 tracepoints defined so far. The format is similar to that used for
12349 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12350 command, simply restricting itself to tracepoints.
12352 A tracepoint's listing may include additional information specific to
12357 its passcount as given by the @code{passcount @var{n}} command
12360 the state about installed on target of each location
12364 (@value{GDBP}) @b{info trace}
12365 Num Type Disp Enb Address What
12366 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12368 collect globfoo, $regs
12373 2 tracepoint keep y <MULTIPLE>
12375 2.1 y 0x0804859c in func4 at change-loc.h:35
12376 installed on target
12377 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12378 installed on target
12379 2.3 y <PENDING> set_tracepoint
12380 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12381 not installed on target
12386 This command can be abbreviated @code{info tp}.
12389 @node Listing Static Tracepoint Markers
12390 @subsection Listing Static Tracepoint Markers
12393 @kindex info static-tracepoint-markers
12394 @cindex information about static tracepoint markers
12395 @item info static-tracepoint-markers
12396 Display information about all static tracepoint markers defined in the
12399 For each marker, the following columns are printed:
12403 An incrementing counter, output to help readability. This is not a
12406 The marker ID, as reported by the target.
12407 @item Enabled or Disabled
12408 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12409 that are not enabled.
12411 Where the marker is in your program, as a memory address.
12413 Where the marker is in the source for your program, as a file and line
12414 number. If the debug information included in the program does not
12415 allow @value{GDBN} to locate the source of the marker, this column
12416 will be left blank.
12420 In addition, the following information may be printed for each marker:
12424 User data passed to the tracing library by the marker call. In the
12425 UST backend, this is the format string passed as argument to the
12427 @item Static tracepoints probing the marker
12428 The list of static tracepoints attached to the marker.
12432 (@value{GDBP}) info static-tracepoint-markers
12433 Cnt ID Enb Address What
12434 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12435 Data: number1 %d number2 %d
12436 Probed by static tracepoints: #2
12437 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12443 @node Starting and Stopping Trace Experiments
12444 @subsection Starting and Stopping Trace Experiments
12447 @kindex tstart [ @var{notes} ]
12448 @cindex start a new trace experiment
12449 @cindex collected data discarded
12451 This command starts the trace experiment, and begins collecting data.
12452 It has the side effect of discarding all the data collected in the
12453 trace buffer during the previous trace experiment. If any arguments
12454 are supplied, they are taken as a note and stored with the trace
12455 experiment's state. The notes may be arbitrary text, and are
12456 especially useful with disconnected tracing in a multi-user context;
12457 the notes can explain what the trace is doing, supply user contact
12458 information, and so forth.
12460 @kindex tstop [ @var{notes} ]
12461 @cindex stop a running trace experiment
12463 This command stops the trace experiment. If any arguments are
12464 supplied, they are recorded with the experiment as a note. This is
12465 useful if you are stopping a trace started by someone else, for
12466 instance if the trace is interfering with the system's behavior and
12467 needs to be stopped quickly.
12469 @strong{Note}: a trace experiment and data collection may stop
12470 automatically if any tracepoint's passcount is reached
12471 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12474 @cindex status of trace data collection
12475 @cindex trace experiment, status of
12477 This command displays the status of the current trace data
12481 Here is an example of the commands we described so far:
12484 (@value{GDBP}) @b{trace gdb_c_test}
12485 (@value{GDBP}) @b{actions}
12486 Enter actions for tracepoint #1, one per line.
12487 > collect $regs,$locals,$args
12488 > while-stepping 11
12492 (@value{GDBP}) @b{tstart}
12493 [time passes @dots{}]
12494 (@value{GDBP}) @b{tstop}
12497 @anchor{disconnected tracing}
12498 @cindex disconnected tracing
12499 You can choose to continue running the trace experiment even if
12500 @value{GDBN} disconnects from the target, voluntarily or
12501 involuntarily. For commands such as @code{detach}, the debugger will
12502 ask what you want to do with the trace. But for unexpected
12503 terminations (@value{GDBN} crash, network outage), it would be
12504 unfortunate to lose hard-won trace data, so the variable
12505 @code{disconnected-tracing} lets you decide whether the trace should
12506 continue running without @value{GDBN}.
12509 @item set disconnected-tracing on
12510 @itemx set disconnected-tracing off
12511 @kindex set disconnected-tracing
12512 Choose whether a tracing run should continue to run if @value{GDBN}
12513 has disconnected from the target. Note that @code{detach} or
12514 @code{quit} will ask you directly what to do about a running trace no
12515 matter what this variable's setting, so the variable is mainly useful
12516 for handling unexpected situations, such as loss of the network.
12518 @item show disconnected-tracing
12519 @kindex show disconnected-tracing
12520 Show the current choice for disconnected tracing.
12524 When you reconnect to the target, the trace experiment may or may not
12525 still be running; it might have filled the trace buffer in the
12526 meantime, or stopped for one of the other reasons. If it is running,
12527 it will continue after reconnection.
12529 Upon reconnection, the target will upload information about the
12530 tracepoints in effect. @value{GDBN} will then compare that
12531 information to the set of tracepoints currently defined, and attempt
12532 to match them up, allowing for the possibility that the numbers may
12533 have changed due to creation and deletion in the meantime. If one of
12534 the target's tracepoints does not match any in @value{GDBN}, the
12535 debugger will create a new tracepoint, so that you have a number with
12536 which to specify that tracepoint. This matching-up process is
12537 necessarily heuristic, and it may result in useless tracepoints being
12538 created; you may simply delete them if they are of no use.
12540 @cindex circular trace buffer
12541 If your target agent supports a @dfn{circular trace buffer}, then you
12542 can run a trace experiment indefinitely without filling the trace
12543 buffer; when space runs out, the agent deletes already-collected trace
12544 frames, oldest first, until there is enough room to continue
12545 collecting. This is especially useful if your tracepoints are being
12546 hit too often, and your trace gets terminated prematurely because the
12547 buffer is full. To ask for a circular trace buffer, simply set
12548 @samp{circular-trace-buffer} to on. You can set this at any time,
12549 including during tracing; if the agent can do it, it will change
12550 buffer handling on the fly, otherwise it will not take effect until
12554 @item set circular-trace-buffer on
12555 @itemx set circular-trace-buffer off
12556 @kindex set circular-trace-buffer
12557 Choose whether a tracing run should use a linear or circular buffer
12558 for trace data. A linear buffer will not lose any trace data, but may
12559 fill up prematurely, while a circular buffer will discard old trace
12560 data, but it will have always room for the latest tracepoint hits.
12562 @item show circular-trace-buffer
12563 @kindex show circular-trace-buffer
12564 Show the current choice for the trace buffer. Note that this may not
12565 match the agent's current buffer handling, nor is it guaranteed to
12566 match the setting that might have been in effect during a past run,
12567 for instance if you are looking at frames from a trace file.
12572 @item set trace-buffer-size @var{n}
12573 @itemx set trace-buffer-size unlimited
12574 @kindex set trace-buffer-size
12575 Request that the target use a trace buffer of @var{n} bytes. Not all
12576 targets will honor the request; they may have a compiled-in size for
12577 the trace buffer, or some other limitation. Set to a value of
12578 @code{unlimited} or @code{-1} to let the target use whatever size it
12579 likes. This is also the default.
12581 @item show trace-buffer-size
12582 @kindex show trace-buffer-size
12583 Show the current requested size for the trace buffer. Note that this
12584 will only match the actual size if the target supports size-setting,
12585 and was able to handle the requested size. For instance, if the
12586 target can only change buffer size between runs, this variable will
12587 not reflect the change until the next run starts. Use @code{tstatus}
12588 to get a report of the actual buffer size.
12592 @item set trace-user @var{text}
12593 @kindex set trace-user
12595 @item show trace-user
12596 @kindex show trace-user
12598 @item set trace-notes @var{text}
12599 @kindex set trace-notes
12600 Set the trace run's notes.
12602 @item show trace-notes
12603 @kindex show trace-notes
12604 Show the trace run's notes.
12606 @item set trace-stop-notes @var{text}
12607 @kindex set trace-stop-notes
12608 Set the trace run's stop notes. The handling of the note is as for
12609 @code{tstop} arguments; the set command is convenient way to fix a
12610 stop note that is mistaken or incomplete.
12612 @item show trace-stop-notes
12613 @kindex show trace-stop-notes
12614 Show the trace run's stop notes.
12618 @node Tracepoint Restrictions
12619 @subsection Tracepoint Restrictions
12621 @cindex tracepoint restrictions
12622 There are a number of restrictions on the use of tracepoints. As
12623 described above, tracepoint data gathering occurs on the target
12624 without interaction from @value{GDBN}. Thus the full capabilities of
12625 the debugger are not available during data gathering, and then at data
12626 examination time, you will be limited by only having what was
12627 collected. The following items describe some common problems, but it
12628 is not exhaustive, and you may run into additional difficulties not
12634 Tracepoint expressions are intended to gather objects (lvalues). Thus
12635 the full flexibility of GDB's expression evaluator is not available.
12636 You cannot call functions, cast objects to aggregate types, access
12637 convenience variables or modify values (except by assignment to trace
12638 state variables). Some language features may implicitly call
12639 functions (for instance Objective-C fields with accessors), and therefore
12640 cannot be collected either.
12643 Collection of local variables, either individually or in bulk with
12644 @code{$locals} or @code{$args}, during @code{while-stepping} may
12645 behave erratically. The stepping action may enter a new scope (for
12646 instance by stepping into a function), or the location of the variable
12647 may change (for instance it is loaded into a register). The
12648 tracepoint data recorded uses the location information for the
12649 variables that is correct for the tracepoint location. When the
12650 tracepoint is created, it is not possible, in general, to determine
12651 where the steps of a @code{while-stepping} sequence will advance the
12652 program---particularly if a conditional branch is stepped.
12655 Collection of an incompletely-initialized or partially-destroyed object
12656 may result in something that @value{GDBN} cannot display, or displays
12657 in a misleading way.
12660 When @value{GDBN} displays a pointer to character it automatically
12661 dereferences the pointer to also display characters of the string
12662 being pointed to. However, collecting the pointer during tracing does
12663 not automatically collect the string. You need to explicitly
12664 dereference the pointer and provide size information if you want to
12665 collect not only the pointer, but the memory pointed to. For example,
12666 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12670 It is not possible to collect a complete stack backtrace at a
12671 tracepoint. Instead, you may collect the registers and a few hundred
12672 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12673 (adjust to use the name of the actual stack pointer register on your
12674 target architecture, and the amount of stack you wish to capture).
12675 Then the @code{backtrace} command will show a partial backtrace when
12676 using a trace frame. The number of stack frames that can be examined
12677 depends on the sizes of the frames in the collected stack. Note that
12678 if you ask for a block so large that it goes past the bottom of the
12679 stack, the target agent may report an error trying to read from an
12683 If you do not collect registers at a tracepoint, @value{GDBN} can
12684 infer that the value of @code{$pc} must be the same as the address of
12685 the tracepoint and use that when you are looking at a trace frame
12686 for that tracepoint. However, this cannot work if the tracepoint has
12687 multiple locations (for instance if it was set in a function that was
12688 inlined), or if it has a @code{while-stepping} loop. In those cases
12689 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12694 @node Analyze Collected Data
12695 @section Using the Collected Data
12697 After the tracepoint experiment ends, you use @value{GDBN} commands
12698 for examining the trace data. The basic idea is that each tracepoint
12699 collects a trace @dfn{snapshot} every time it is hit and another
12700 snapshot every time it single-steps. All these snapshots are
12701 consecutively numbered from zero and go into a buffer, and you can
12702 examine them later. The way you examine them is to @dfn{focus} on a
12703 specific trace snapshot. When the remote stub is focused on a trace
12704 snapshot, it will respond to all @value{GDBN} requests for memory and
12705 registers by reading from the buffer which belongs to that snapshot,
12706 rather than from @emph{real} memory or registers of the program being
12707 debugged. This means that @strong{all} @value{GDBN} commands
12708 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12709 behave as if we were currently debugging the program state as it was
12710 when the tracepoint occurred. Any requests for data that are not in
12711 the buffer will fail.
12714 * tfind:: How to select a trace snapshot
12715 * tdump:: How to display all data for a snapshot
12716 * save tracepoints:: How to save tracepoints for a future run
12720 @subsection @code{tfind @var{n}}
12723 @cindex select trace snapshot
12724 @cindex find trace snapshot
12725 The basic command for selecting a trace snapshot from the buffer is
12726 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12727 counting from zero. If no argument @var{n} is given, the next
12728 snapshot is selected.
12730 Here are the various forms of using the @code{tfind} command.
12734 Find the first snapshot in the buffer. This is a synonym for
12735 @code{tfind 0} (since 0 is the number of the first snapshot).
12738 Stop debugging trace snapshots, resume @emph{live} debugging.
12741 Same as @samp{tfind none}.
12744 No argument means find the next trace snapshot.
12747 Find the previous trace snapshot before the current one. This permits
12748 retracing earlier steps.
12750 @item tfind tracepoint @var{num}
12751 Find the next snapshot associated with tracepoint @var{num}. Search
12752 proceeds forward from the last examined trace snapshot. If no
12753 argument @var{num} is given, it means find the next snapshot collected
12754 for the same tracepoint as the current snapshot.
12756 @item tfind pc @var{addr}
12757 Find the next snapshot associated with the value @var{addr} of the
12758 program counter. Search proceeds forward from the last examined trace
12759 snapshot. If no argument @var{addr} is given, it means find the next
12760 snapshot with the same value of PC as the current snapshot.
12762 @item tfind outside @var{addr1}, @var{addr2}
12763 Find the next snapshot whose PC is outside the given range of
12764 addresses (exclusive).
12766 @item tfind range @var{addr1}, @var{addr2}
12767 Find the next snapshot whose PC is between @var{addr1} and
12768 @var{addr2} (inclusive).
12770 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12771 Find the next snapshot associated with the source line @var{n}. If
12772 the optional argument @var{file} is given, refer to line @var{n} in
12773 that source file. Search proceeds forward from the last examined
12774 trace snapshot. If no argument @var{n} is given, it means find the
12775 next line other than the one currently being examined; thus saying
12776 @code{tfind line} repeatedly can appear to have the same effect as
12777 stepping from line to line in a @emph{live} debugging session.
12780 The default arguments for the @code{tfind} commands are specifically
12781 designed to make it easy to scan through the trace buffer. For
12782 instance, @code{tfind} with no argument selects the next trace
12783 snapshot, and @code{tfind -} with no argument selects the previous
12784 trace snapshot. So, by giving one @code{tfind} command, and then
12785 simply hitting @key{RET} repeatedly you can examine all the trace
12786 snapshots in order. Or, by saying @code{tfind -} and then hitting
12787 @key{RET} repeatedly you can examine the snapshots in reverse order.
12788 The @code{tfind line} command with no argument selects the snapshot
12789 for the next source line executed. The @code{tfind pc} command with
12790 no argument selects the next snapshot with the same program counter
12791 (PC) as the current frame. The @code{tfind tracepoint} command with
12792 no argument selects the next trace snapshot collected by the same
12793 tracepoint as the current one.
12795 In addition to letting you scan through the trace buffer manually,
12796 these commands make it easy to construct @value{GDBN} scripts that
12797 scan through the trace buffer and print out whatever collected data
12798 you are interested in. Thus, if we want to examine the PC, FP, and SP
12799 registers from each trace frame in the buffer, we can say this:
12802 (@value{GDBP}) @b{tfind start}
12803 (@value{GDBP}) @b{while ($trace_frame != -1)}
12804 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12805 $trace_frame, $pc, $sp, $fp
12809 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12810 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12811 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12812 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12813 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12814 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12815 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12816 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12817 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12818 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12819 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12822 Or, if we want to examine the variable @code{X} at each source line in
12826 (@value{GDBP}) @b{tfind start}
12827 (@value{GDBP}) @b{while ($trace_frame != -1)}
12828 > printf "Frame %d, X == %d\n", $trace_frame, X
12838 @subsection @code{tdump}
12840 @cindex dump all data collected at tracepoint
12841 @cindex tracepoint data, display
12843 This command takes no arguments. It prints all the data collected at
12844 the current trace snapshot.
12847 (@value{GDBP}) @b{trace 444}
12848 (@value{GDBP}) @b{actions}
12849 Enter actions for tracepoint #2, one per line:
12850 > collect $regs, $locals, $args, gdb_long_test
12853 (@value{GDBP}) @b{tstart}
12855 (@value{GDBP}) @b{tfind line 444}
12856 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12858 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12860 (@value{GDBP}) @b{tdump}
12861 Data collected at tracepoint 2, trace frame 1:
12862 d0 0xc4aa0085 -995491707
12866 d4 0x71aea3d 119204413
12869 d7 0x380035 3670069
12870 a0 0x19e24a 1696330
12871 a1 0x3000668 50333288
12873 a3 0x322000 3284992
12874 a4 0x3000698 50333336
12875 a5 0x1ad3cc 1758156
12876 fp 0x30bf3c 0x30bf3c
12877 sp 0x30bf34 0x30bf34
12879 pc 0x20b2c8 0x20b2c8
12883 p = 0x20e5b4 "gdb-test"
12890 gdb_long_test = 17 '\021'
12895 @code{tdump} works by scanning the tracepoint's current collection
12896 actions and printing the value of each expression listed. So
12897 @code{tdump} can fail, if after a run, you change the tracepoint's
12898 actions to mention variables that were not collected during the run.
12900 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12901 uses the collected value of @code{$pc} to distinguish between trace
12902 frames that were collected at the tracepoint hit, and frames that were
12903 collected while stepping. This allows it to correctly choose whether
12904 to display the basic list of collections, or the collections from the
12905 body of the while-stepping loop. However, if @code{$pc} was not collected,
12906 then @code{tdump} will always attempt to dump using the basic collection
12907 list, and may fail if a while-stepping frame does not include all the
12908 same data that is collected at the tracepoint hit.
12909 @c This is getting pretty arcane, example would be good.
12911 @node save tracepoints
12912 @subsection @code{save tracepoints @var{filename}}
12913 @kindex save tracepoints
12914 @kindex save-tracepoints
12915 @cindex save tracepoints for future sessions
12917 This command saves all current tracepoint definitions together with
12918 their actions and passcounts, into a file @file{@var{filename}}
12919 suitable for use in a later debugging session. To read the saved
12920 tracepoint definitions, use the @code{source} command (@pxref{Command
12921 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12922 alias for @w{@code{save tracepoints}}
12924 @node Tracepoint Variables
12925 @section Convenience Variables for Tracepoints
12926 @cindex tracepoint variables
12927 @cindex convenience variables for tracepoints
12930 @vindex $trace_frame
12931 @item (int) $trace_frame
12932 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12933 snapshot is selected.
12935 @vindex $tracepoint
12936 @item (int) $tracepoint
12937 The tracepoint for the current trace snapshot.
12939 @vindex $trace_line
12940 @item (int) $trace_line
12941 The line number for the current trace snapshot.
12943 @vindex $trace_file
12944 @item (char []) $trace_file
12945 The source file for the current trace snapshot.
12947 @vindex $trace_func
12948 @item (char []) $trace_func
12949 The name of the function containing @code{$tracepoint}.
12952 Note: @code{$trace_file} is not suitable for use in @code{printf},
12953 use @code{output} instead.
12955 Here's a simple example of using these convenience variables for
12956 stepping through all the trace snapshots and printing some of their
12957 data. Note that these are not the same as trace state variables,
12958 which are managed by the target.
12961 (@value{GDBP}) @b{tfind start}
12963 (@value{GDBP}) @b{while $trace_frame != -1}
12964 > output $trace_file
12965 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12971 @section Using Trace Files
12972 @cindex trace files
12974 In some situations, the target running a trace experiment may no
12975 longer be available; perhaps it crashed, or the hardware was needed
12976 for a different activity. To handle these cases, you can arrange to
12977 dump the trace data into a file, and later use that file as a source
12978 of trace data, via the @code{target tfile} command.
12983 @item tsave [ -r ] @var{filename}
12984 @itemx tsave [-ctf] @var{dirname}
12985 Save the trace data to @var{filename}. By default, this command
12986 assumes that @var{filename} refers to the host filesystem, so if
12987 necessary @value{GDBN} will copy raw trace data up from the target and
12988 then save it. If the target supports it, you can also supply the
12989 optional argument @code{-r} (``remote'') to direct the target to save
12990 the data directly into @var{filename} in its own filesystem, which may be
12991 more efficient if the trace buffer is very large. (Note, however, that
12992 @code{target tfile} can only read from files accessible to the host.)
12993 By default, this command will save trace frame in tfile format.
12994 You can supply the optional argument @code{-ctf} to save date in CTF
12995 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12996 that can be shared by multiple debugging and tracing tools. Please go to
12997 @indicateurl{http://www.efficios.com/ctf} to get more information.
12999 @kindex target tfile
13003 @item target tfile @var{filename}
13004 @itemx target ctf @var{dirname}
13005 Use the file named @var{filename} or directory named @var{dirname} as
13006 a source of trace data. Commands that examine data work as they do with
13007 a live target, but it is not possible to run any new trace experiments.
13008 @code{tstatus} will report the state of the trace run at the moment
13009 the data was saved, as well as the current trace frame you are examining.
13010 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13014 (@value{GDBP}) target ctf ctf.ctf
13015 (@value{GDBP}) tfind
13016 Found trace frame 0, tracepoint 2
13017 39 ++a; /* set tracepoint 1 here */
13018 (@value{GDBP}) tdump
13019 Data collected at tracepoint 2, trace frame 0:
13023 c = @{"123", "456", "789", "123", "456", "789"@}
13024 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13032 @chapter Debugging Programs That Use Overlays
13035 If your program is too large to fit completely in your target system's
13036 memory, you can sometimes use @dfn{overlays} to work around this
13037 problem. @value{GDBN} provides some support for debugging programs that
13041 * How Overlays Work:: A general explanation of overlays.
13042 * Overlay Commands:: Managing overlays in @value{GDBN}.
13043 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13044 mapped by asking the inferior.
13045 * Overlay Sample Program:: A sample program using overlays.
13048 @node How Overlays Work
13049 @section How Overlays Work
13050 @cindex mapped overlays
13051 @cindex unmapped overlays
13052 @cindex load address, overlay's
13053 @cindex mapped address
13054 @cindex overlay area
13056 Suppose you have a computer whose instruction address space is only 64
13057 kilobytes long, but which has much more memory which can be accessed by
13058 other means: special instructions, segment registers, or memory
13059 management hardware, for example. Suppose further that you want to
13060 adapt a program which is larger than 64 kilobytes to run on this system.
13062 One solution is to identify modules of your program which are relatively
13063 independent, and need not call each other directly; call these modules
13064 @dfn{overlays}. Separate the overlays from the main program, and place
13065 their machine code in the larger memory. Place your main program in
13066 instruction memory, but leave at least enough space there to hold the
13067 largest overlay as well.
13069 Now, to call a function located in an overlay, you must first copy that
13070 overlay's machine code from the large memory into the space set aside
13071 for it in the instruction memory, and then jump to its entry point
13074 @c NB: In the below the mapped area's size is greater or equal to the
13075 @c size of all overlays. This is intentional to remind the developer
13076 @c that overlays don't necessarily need to be the same size.
13080 Data Instruction Larger
13081 Address Space Address Space Address Space
13082 +-----------+ +-----------+ +-----------+
13084 +-----------+ +-----------+ +-----------+<-- overlay 1
13085 | program | | main | .----| overlay 1 | load address
13086 | variables | | program | | +-----------+
13087 | and heap | | | | | |
13088 +-----------+ | | | +-----------+<-- overlay 2
13089 | | +-----------+ | | | load address
13090 +-----------+ | | | .-| overlay 2 |
13092 mapped --->+-----------+ | | +-----------+
13093 address | | | | | |
13094 | overlay | <-' | | |
13095 | area | <---' +-----------+<-- overlay 3
13096 | | <---. | | load address
13097 +-----------+ `--| overlay 3 |
13104 @anchor{A code overlay}A code overlay
13108 The diagram (@pxref{A code overlay}) shows a system with separate data
13109 and instruction address spaces. To map an overlay, the program copies
13110 its code from the larger address space to the instruction address space.
13111 Since the overlays shown here all use the same mapped address, only one
13112 may be mapped at a time. For a system with a single address space for
13113 data and instructions, the diagram would be similar, except that the
13114 program variables and heap would share an address space with the main
13115 program and the overlay area.
13117 An overlay loaded into instruction memory and ready for use is called a
13118 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13119 instruction memory. An overlay not present (or only partially present)
13120 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13121 is its address in the larger memory. The mapped address is also called
13122 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13123 called the @dfn{load memory address}, or @dfn{LMA}.
13125 Unfortunately, overlays are not a completely transparent way to adapt a
13126 program to limited instruction memory. They introduce a new set of
13127 global constraints you must keep in mind as you design your program:
13132 Before calling or returning to a function in an overlay, your program
13133 must make sure that overlay is actually mapped. Otherwise, the call or
13134 return will transfer control to the right address, but in the wrong
13135 overlay, and your program will probably crash.
13138 If the process of mapping an overlay is expensive on your system, you
13139 will need to choose your overlays carefully to minimize their effect on
13140 your program's performance.
13143 The executable file you load onto your system must contain each
13144 overlay's instructions, appearing at the overlay's load address, not its
13145 mapped address. However, each overlay's instructions must be relocated
13146 and its symbols defined as if the overlay were at its mapped address.
13147 You can use GNU linker scripts to specify different load and relocation
13148 addresses for pieces of your program; see @ref{Overlay Description,,,
13149 ld.info, Using ld: the GNU linker}.
13152 The procedure for loading executable files onto your system must be able
13153 to load their contents into the larger address space as well as the
13154 instruction and data spaces.
13158 The overlay system described above is rather simple, and could be
13159 improved in many ways:
13164 If your system has suitable bank switch registers or memory management
13165 hardware, you could use those facilities to make an overlay's load area
13166 contents simply appear at their mapped address in instruction space.
13167 This would probably be faster than copying the overlay to its mapped
13168 area in the usual way.
13171 If your overlays are small enough, you could set aside more than one
13172 overlay area, and have more than one overlay mapped at a time.
13175 You can use overlays to manage data, as well as instructions. In
13176 general, data overlays are even less transparent to your design than
13177 code overlays: whereas code overlays only require care when you call or
13178 return to functions, data overlays require care every time you access
13179 the data. Also, if you change the contents of a data overlay, you
13180 must copy its contents back out to its load address before you can copy a
13181 different data overlay into the same mapped area.
13186 @node Overlay Commands
13187 @section Overlay Commands
13189 To use @value{GDBN}'s overlay support, each overlay in your program must
13190 correspond to a separate section of the executable file. The section's
13191 virtual memory address and load memory address must be the overlay's
13192 mapped and load addresses. Identifying overlays with sections allows
13193 @value{GDBN} to determine the appropriate address of a function or
13194 variable, depending on whether the overlay is mapped or not.
13196 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13197 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13202 Disable @value{GDBN}'s overlay support. When overlay support is
13203 disabled, @value{GDBN} assumes that all functions and variables are
13204 always present at their mapped addresses. By default, @value{GDBN}'s
13205 overlay support is disabled.
13207 @item overlay manual
13208 @cindex manual overlay debugging
13209 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13210 relies on you to tell it which overlays are mapped, and which are not,
13211 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13212 commands described below.
13214 @item overlay map-overlay @var{overlay}
13215 @itemx overlay map @var{overlay}
13216 @cindex map an overlay
13217 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13218 be the name of the object file section containing the overlay. When an
13219 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13220 functions and variables at their mapped addresses. @value{GDBN} assumes
13221 that any other overlays whose mapped ranges overlap that of
13222 @var{overlay} are now unmapped.
13224 @item overlay unmap-overlay @var{overlay}
13225 @itemx overlay unmap @var{overlay}
13226 @cindex unmap an overlay
13227 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13228 must be the name of the object file section containing the overlay.
13229 When an overlay is unmapped, @value{GDBN} assumes it can find the
13230 overlay's functions and variables at their load addresses.
13233 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13234 consults a data structure the overlay manager maintains in the inferior
13235 to see which overlays are mapped. For details, see @ref{Automatic
13236 Overlay Debugging}.
13238 @item overlay load-target
13239 @itemx overlay load
13240 @cindex reloading the overlay table
13241 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13242 re-reads the table @value{GDBN} automatically each time the inferior
13243 stops, so this command should only be necessary if you have changed the
13244 overlay mapping yourself using @value{GDBN}. This command is only
13245 useful when using automatic overlay debugging.
13247 @item overlay list-overlays
13248 @itemx overlay list
13249 @cindex listing mapped overlays
13250 Display a list of the overlays currently mapped, along with their mapped
13251 addresses, load addresses, and sizes.
13255 Normally, when @value{GDBN} prints a code address, it includes the name
13256 of the function the address falls in:
13259 (@value{GDBP}) print main
13260 $3 = @{int ()@} 0x11a0 <main>
13263 When overlay debugging is enabled, @value{GDBN} recognizes code in
13264 unmapped overlays, and prints the names of unmapped functions with
13265 asterisks around them. For example, if @code{foo} is a function in an
13266 unmapped overlay, @value{GDBN} prints it this way:
13269 (@value{GDBP}) overlay list
13270 No sections are mapped.
13271 (@value{GDBP}) print foo
13272 $5 = @{int (int)@} 0x100000 <*foo*>
13275 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13279 (@value{GDBP}) overlay list
13280 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13281 mapped at 0x1016 - 0x104a
13282 (@value{GDBP}) print foo
13283 $6 = @{int (int)@} 0x1016 <foo>
13286 When overlay debugging is enabled, @value{GDBN} can find the correct
13287 address for functions and variables in an overlay, whether or not the
13288 overlay is mapped. This allows most @value{GDBN} commands, like
13289 @code{break} and @code{disassemble}, to work normally, even on unmapped
13290 code. However, @value{GDBN}'s breakpoint support has some limitations:
13294 @cindex breakpoints in overlays
13295 @cindex overlays, setting breakpoints in
13296 You can set breakpoints in functions in unmapped overlays, as long as
13297 @value{GDBN} can write to the overlay at its load address.
13299 @value{GDBN} can not set hardware or simulator-based breakpoints in
13300 unmapped overlays. However, if you set a breakpoint at the end of your
13301 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13302 you are using manual overlay management), @value{GDBN} will re-set its
13303 breakpoints properly.
13307 @node Automatic Overlay Debugging
13308 @section Automatic Overlay Debugging
13309 @cindex automatic overlay debugging
13311 @value{GDBN} can automatically track which overlays are mapped and which
13312 are not, given some simple co-operation from the overlay manager in the
13313 inferior. If you enable automatic overlay debugging with the
13314 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13315 looks in the inferior's memory for certain variables describing the
13316 current state of the overlays.
13318 Here are the variables your overlay manager must define to support
13319 @value{GDBN}'s automatic overlay debugging:
13323 @item @code{_ovly_table}:
13324 This variable must be an array of the following structures:
13329 /* The overlay's mapped address. */
13332 /* The size of the overlay, in bytes. */
13333 unsigned long size;
13335 /* The overlay's load address. */
13338 /* Non-zero if the overlay is currently mapped;
13340 unsigned long mapped;
13344 @item @code{_novlys}:
13345 This variable must be a four-byte signed integer, holding the total
13346 number of elements in @code{_ovly_table}.
13350 To decide whether a particular overlay is mapped or not, @value{GDBN}
13351 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13352 @code{lma} members equal the VMA and LMA of the overlay's section in the
13353 executable file. When @value{GDBN} finds a matching entry, it consults
13354 the entry's @code{mapped} member to determine whether the overlay is
13357 In addition, your overlay manager may define a function called
13358 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13359 will silently set a breakpoint there. If the overlay manager then
13360 calls this function whenever it has changed the overlay table, this
13361 will enable @value{GDBN} to accurately keep track of which overlays
13362 are in program memory, and update any breakpoints that may be set
13363 in overlays. This will allow breakpoints to work even if the
13364 overlays are kept in ROM or other non-writable memory while they
13365 are not being executed.
13367 @node Overlay Sample Program
13368 @section Overlay Sample Program
13369 @cindex overlay example program
13371 When linking a program which uses overlays, you must place the overlays
13372 at their load addresses, while relocating them to run at their mapped
13373 addresses. To do this, you must write a linker script (@pxref{Overlay
13374 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13375 since linker scripts are specific to a particular host system, target
13376 architecture, and target memory layout, this manual cannot provide
13377 portable sample code demonstrating @value{GDBN}'s overlay support.
13379 However, the @value{GDBN} source distribution does contain an overlaid
13380 program, with linker scripts for a few systems, as part of its test
13381 suite. The program consists of the following files from
13382 @file{gdb/testsuite/gdb.base}:
13386 The main program file.
13388 A simple overlay manager, used by @file{overlays.c}.
13393 Overlay modules, loaded and used by @file{overlays.c}.
13396 Linker scripts for linking the test program on the @code{d10v-elf}
13397 and @code{m32r-elf} targets.
13400 You can build the test program using the @code{d10v-elf} GCC
13401 cross-compiler like this:
13404 $ d10v-elf-gcc -g -c overlays.c
13405 $ d10v-elf-gcc -g -c ovlymgr.c
13406 $ d10v-elf-gcc -g -c foo.c
13407 $ d10v-elf-gcc -g -c bar.c
13408 $ d10v-elf-gcc -g -c baz.c
13409 $ d10v-elf-gcc -g -c grbx.c
13410 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13411 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13414 The build process is identical for any other architecture, except that
13415 you must substitute the appropriate compiler and linker script for the
13416 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13420 @chapter Using @value{GDBN} with Different Languages
13423 Although programming languages generally have common aspects, they are
13424 rarely expressed in the same manner. For instance, in ANSI C,
13425 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13426 Modula-2, it is accomplished by @code{p^}. Values can also be
13427 represented (and displayed) differently. Hex numbers in C appear as
13428 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13430 @cindex working language
13431 Language-specific information is built into @value{GDBN} for some languages,
13432 allowing you to express operations like the above in your program's
13433 native language, and allowing @value{GDBN} to output values in a manner
13434 consistent with the syntax of your program's native language. The
13435 language you use to build expressions is called the @dfn{working
13439 * Setting:: Switching between source languages
13440 * Show:: Displaying the language
13441 * Checks:: Type and range checks
13442 * Supported Languages:: Supported languages
13443 * Unsupported Languages:: Unsupported languages
13447 @section Switching Between Source Languages
13449 There are two ways to control the working language---either have @value{GDBN}
13450 set it automatically, or select it manually yourself. You can use the
13451 @code{set language} command for either purpose. On startup, @value{GDBN}
13452 defaults to setting the language automatically. The working language is
13453 used to determine how expressions you type are interpreted, how values
13456 In addition to the working language, every source file that
13457 @value{GDBN} knows about has its own working language. For some object
13458 file formats, the compiler might indicate which language a particular
13459 source file is in. However, most of the time @value{GDBN} infers the
13460 language from the name of the file. The language of a source file
13461 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13462 show each frame appropriately for its own language. There is no way to
13463 set the language of a source file from within @value{GDBN}, but you can
13464 set the language associated with a filename extension. @xref{Show, ,
13465 Displaying the Language}.
13467 This is most commonly a problem when you use a program, such
13468 as @code{cfront} or @code{f2c}, that generates C but is written in
13469 another language. In that case, make the
13470 program use @code{#line} directives in its C output; that way
13471 @value{GDBN} will know the correct language of the source code of the original
13472 program, and will display that source code, not the generated C code.
13475 * Filenames:: Filename extensions and languages.
13476 * Manually:: Setting the working language manually
13477 * Automatically:: Having @value{GDBN} infer the source language
13481 @subsection List of Filename Extensions and Languages
13483 If a source file name ends in one of the following extensions, then
13484 @value{GDBN} infers that its language is the one indicated.
13502 C@t{++} source file
13508 Objective-C source file
13512 Fortran source file
13515 Modula-2 source file
13519 Assembler source file. This actually behaves almost like C, but
13520 @value{GDBN} does not skip over function prologues when stepping.
13523 In addition, you may set the language associated with a filename
13524 extension. @xref{Show, , Displaying the Language}.
13527 @subsection Setting the Working Language
13529 If you allow @value{GDBN} to set the language automatically,
13530 expressions are interpreted the same way in your debugging session and
13533 @kindex set language
13534 If you wish, you may set the language manually. To do this, issue the
13535 command @samp{set language @var{lang}}, where @var{lang} is the name of
13536 a language, such as
13537 @code{c} or @code{modula-2}.
13538 For a list of the supported languages, type @samp{set language}.
13540 Setting the language manually prevents @value{GDBN} from updating the working
13541 language automatically. This can lead to confusion if you try
13542 to debug a program when the working language is not the same as the
13543 source language, when an expression is acceptable to both
13544 languages---but means different things. For instance, if the current
13545 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13553 might not have the effect you intended. In C, this means to add
13554 @code{b} and @code{c} and place the result in @code{a}. The result
13555 printed would be the value of @code{a}. In Modula-2, this means to compare
13556 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13558 @node Automatically
13559 @subsection Having @value{GDBN} Infer the Source Language
13561 To have @value{GDBN} set the working language automatically, use
13562 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13563 then infers the working language. That is, when your program stops in a
13564 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13565 working language to the language recorded for the function in that
13566 frame. If the language for a frame is unknown (that is, if the function
13567 or block corresponding to the frame was defined in a source file that
13568 does not have a recognized extension), the current working language is
13569 not changed, and @value{GDBN} issues a warning.
13571 This may not seem necessary for most programs, which are written
13572 entirely in one source language. However, program modules and libraries
13573 written in one source language can be used by a main program written in
13574 a different source language. Using @samp{set language auto} in this
13575 case frees you from having to set the working language manually.
13578 @section Displaying the Language
13580 The following commands help you find out which language is the
13581 working language, and also what language source files were written in.
13584 @item show language
13585 @anchor{show language}
13586 @kindex show language
13587 Display the current working language. This is the
13588 language you can use with commands such as @code{print} to
13589 build and compute expressions that may involve variables in your program.
13592 @kindex info frame@r{, show the source language}
13593 Display the source language for this frame. This language becomes the
13594 working language if you use an identifier from this frame.
13595 @xref{Frame Info, ,Information about a Frame}, to identify the other
13596 information listed here.
13599 @kindex info source@r{, show the source language}
13600 Display the source language of this source file.
13601 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13602 information listed here.
13605 In unusual circumstances, you may have source files with extensions
13606 not in the standard list. You can then set the extension associated
13607 with a language explicitly:
13610 @item set extension-language @var{ext} @var{language}
13611 @kindex set extension-language
13612 Tell @value{GDBN} that source files with extension @var{ext} are to be
13613 assumed as written in the source language @var{language}.
13615 @item info extensions
13616 @kindex info extensions
13617 List all the filename extensions and the associated languages.
13621 @section Type and Range Checking
13623 Some languages are designed to guard you against making seemingly common
13624 errors through a series of compile- and run-time checks. These include
13625 checking the type of arguments to functions and operators and making
13626 sure mathematical overflows are caught at run time. Checks such as
13627 these help to ensure a program's correctness once it has been compiled
13628 by eliminating type mismatches and providing active checks for range
13629 errors when your program is running.
13631 By default @value{GDBN} checks for these errors according to the
13632 rules of the current source language. Although @value{GDBN} does not check
13633 the statements in your program, it can check expressions entered directly
13634 into @value{GDBN} for evaluation via the @code{print} command, for example.
13637 * Type Checking:: An overview of type checking
13638 * Range Checking:: An overview of range checking
13641 @cindex type checking
13642 @cindex checks, type
13643 @node Type Checking
13644 @subsection An Overview of Type Checking
13646 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13647 arguments to operators and functions have to be of the correct type,
13648 otherwise an error occurs. These checks prevent type mismatch
13649 errors from ever causing any run-time problems. For example,
13652 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13654 (@value{GDBP}) print obj.my_method (0)
13657 (@value{GDBP}) print obj.my_method (0x1234)
13658 Cannot resolve method klass::my_method to any overloaded instance
13661 The second example fails because in C@t{++} the integer constant
13662 @samp{0x1234} is not type-compatible with the pointer parameter type.
13664 For the expressions you use in @value{GDBN} commands, you can tell
13665 @value{GDBN} to not enforce strict type checking or
13666 to treat any mismatches as errors and abandon the expression;
13667 When type checking is disabled, @value{GDBN} successfully evaluates
13668 expressions like the second example above.
13670 Even if type checking is off, there may be other reasons
13671 related to type that prevent @value{GDBN} from evaluating an expression.
13672 For instance, @value{GDBN} does not know how to add an @code{int} and
13673 a @code{struct foo}. These particular type errors have nothing to do
13674 with the language in use and usually arise from expressions which make
13675 little sense to evaluate anyway.
13677 @value{GDBN} provides some additional commands for controlling type checking:
13679 @kindex set check type
13680 @kindex show check type
13682 @item set check type on
13683 @itemx set check type off
13684 Set strict type checking on or off. If any type mismatches occur in
13685 evaluating an expression while type checking is on, @value{GDBN} prints a
13686 message and aborts evaluation of the expression.
13688 @item show check type
13689 Show the current setting of type checking and whether @value{GDBN}
13690 is enforcing strict type checking rules.
13693 @cindex range checking
13694 @cindex checks, range
13695 @node Range Checking
13696 @subsection An Overview of Range Checking
13698 In some languages (such as Modula-2), it is an error to exceed the
13699 bounds of a type; this is enforced with run-time checks. Such range
13700 checking is meant to ensure program correctness by making sure
13701 computations do not overflow, or indices on an array element access do
13702 not exceed the bounds of the array.
13704 For expressions you use in @value{GDBN} commands, you can tell
13705 @value{GDBN} to treat range errors in one of three ways: ignore them,
13706 always treat them as errors and abandon the expression, or issue
13707 warnings but evaluate the expression anyway.
13709 A range error can result from numerical overflow, from exceeding an
13710 array index bound, or when you type a constant that is not a member
13711 of any type. Some languages, however, do not treat overflows as an
13712 error. In many implementations of C, mathematical overflow causes the
13713 result to ``wrap around'' to lower values---for example, if @var{m} is
13714 the largest integer value, and @var{s} is the smallest, then
13717 @var{m} + 1 @result{} @var{s}
13720 This, too, is specific to individual languages, and in some cases
13721 specific to individual compilers or machines. @xref{Supported Languages, ,
13722 Supported Languages}, for further details on specific languages.
13724 @value{GDBN} provides some additional commands for controlling the range checker:
13726 @kindex set check range
13727 @kindex show check range
13729 @item set check range auto
13730 Set range checking on or off based on the current working language.
13731 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13734 @item set check range on
13735 @itemx set check range off
13736 Set range checking on or off, overriding the default setting for the
13737 current working language. A warning is issued if the setting does not
13738 match the language default. If a range error occurs and range checking is on,
13739 then a message is printed and evaluation of the expression is aborted.
13741 @item set check range warn
13742 Output messages when the @value{GDBN} range checker detects a range error,
13743 but attempt to evaluate the expression anyway. Evaluating the
13744 expression may still be impossible for other reasons, such as accessing
13745 memory that the process does not own (a typical example from many Unix
13749 Show the current setting of the range checker, and whether or not it is
13750 being set automatically by @value{GDBN}.
13753 @node Supported Languages
13754 @section Supported Languages
13756 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13757 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13758 @c This is false ...
13759 Some @value{GDBN} features may be used in expressions regardless of the
13760 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13761 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13762 ,Expressions}) can be used with the constructs of any supported
13765 The following sections detail to what degree each source language is
13766 supported by @value{GDBN}. These sections are not meant to be language
13767 tutorials or references, but serve only as a reference guide to what the
13768 @value{GDBN} expression parser accepts, and what input and output
13769 formats should look like for different languages. There are many good
13770 books written on each of these languages; please look to these for a
13771 language reference or tutorial.
13774 * C:: C and C@t{++}
13777 * Objective-C:: Objective-C
13778 * OpenCL C:: OpenCL C
13779 * Fortran:: Fortran
13781 * Modula-2:: Modula-2
13786 @subsection C and C@t{++}
13788 @cindex C and C@t{++}
13789 @cindex expressions in C or C@t{++}
13791 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13792 to both languages. Whenever this is the case, we discuss those languages
13796 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13797 @cindex @sc{gnu} C@t{++}
13798 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13799 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13800 effectively, you must compile your C@t{++} programs with a supported
13801 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13802 compiler (@code{aCC}).
13805 * C Operators:: C and C@t{++} operators
13806 * C Constants:: C and C@t{++} constants
13807 * C Plus Plus Expressions:: C@t{++} expressions
13808 * C Defaults:: Default settings for C and C@t{++}
13809 * C Checks:: C and C@t{++} type and range checks
13810 * Debugging C:: @value{GDBN} and C
13811 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13812 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13816 @subsubsection C and C@t{++} Operators
13818 @cindex C and C@t{++} operators
13820 Operators must be defined on values of specific types. For instance,
13821 @code{+} is defined on numbers, but not on structures. Operators are
13822 often defined on groups of types.
13824 For the purposes of C and C@t{++}, the following definitions hold:
13829 @emph{Integral types} include @code{int} with any of its storage-class
13830 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13833 @emph{Floating-point types} include @code{float}, @code{double}, and
13834 @code{long double} (if supported by the target platform).
13837 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13840 @emph{Scalar types} include all of the above.
13845 The following operators are supported. They are listed here
13846 in order of increasing precedence:
13850 The comma or sequencing operator. Expressions in a comma-separated list
13851 are evaluated from left to right, with the result of the entire
13852 expression being the last expression evaluated.
13855 Assignment. The value of an assignment expression is the value
13856 assigned. Defined on scalar types.
13859 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13860 and translated to @w{@code{@var{a} = @var{a op b}}}.
13861 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13862 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13863 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13866 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13867 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13868 should be of an integral type.
13871 Logical @sc{or}. Defined on integral types.
13874 Logical @sc{and}. Defined on integral types.
13877 Bitwise @sc{or}. Defined on integral types.
13880 Bitwise exclusive-@sc{or}. Defined on integral types.
13883 Bitwise @sc{and}. Defined on integral types.
13886 Equality and inequality. Defined on scalar types. The value of these
13887 expressions is 0 for false and non-zero for true.
13889 @item <@r{, }>@r{, }<=@r{, }>=
13890 Less than, greater than, less than or equal, greater than or equal.
13891 Defined on scalar types. The value of these expressions is 0 for false
13892 and non-zero for true.
13895 left shift, and right shift. Defined on integral types.
13898 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13901 Addition and subtraction. Defined on integral types, floating-point types and
13904 @item *@r{, }/@r{, }%
13905 Multiplication, division, and modulus. Multiplication and division are
13906 defined on integral and floating-point types. Modulus is defined on
13910 Increment and decrement. When appearing before a variable, the
13911 operation is performed before the variable is used in an expression;
13912 when appearing after it, the variable's value is used before the
13913 operation takes place.
13916 Pointer dereferencing. Defined on pointer types. Same precedence as
13920 Address operator. Defined on variables. Same precedence as @code{++}.
13922 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13923 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13924 to examine the address
13925 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13929 Negative. Defined on integral and floating-point types. Same
13930 precedence as @code{++}.
13933 Logical negation. Defined on integral types. Same precedence as
13937 Bitwise complement operator. Defined on integral types. Same precedence as
13942 Structure member, and pointer-to-structure member. For convenience,
13943 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13944 pointer based on the stored type information.
13945 Defined on @code{struct} and @code{union} data.
13948 Dereferences of pointers to members.
13951 Array indexing. @code{@var{a}[@var{i}]} is defined as
13952 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13955 Function parameter list. Same precedence as @code{->}.
13958 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13959 and @code{class} types.
13962 Doubled colons also represent the @value{GDBN} scope operator
13963 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13967 If an operator is redefined in the user code, @value{GDBN} usually
13968 attempts to invoke the redefined version instead of using the operator's
13969 predefined meaning.
13972 @subsubsection C and C@t{++} Constants
13974 @cindex C and C@t{++} constants
13976 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13981 Integer constants are a sequence of digits. Octal constants are
13982 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13983 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13984 @samp{l}, specifying that the constant should be treated as a
13988 Floating point constants are a sequence of digits, followed by a decimal
13989 point, followed by a sequence of digits, and optionally followed by an
13990 exponent. An exponent is of the form:
13991 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13992 sequence of digits. The @samp{+} is optional for positive exponents.
13993 A floating-point constant may also end with a letter @samp{f} or
13994 @samp{F}, specifying that the constant should be treated as being of
13995 the @code{float} (as opposed to the default @code{double}) type; or with
13996 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14000 Enumerated constants consist of enumerated identifiers, or their
14001 integral equivalents.
14004 Character constants are a single character surrounded by single quotes
14005 (@code{'}), or a number---the ordinal value of the corresponding character
14006 (usually its @sc{ascii} value). Within quotes, the single character may
14007 be represented by a letter or by @dfn{escape sequences}, which are of
14008 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14009 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14010 @samp{@var{x}} is a predefined special character---for example,
14011 @samp{\n} for newline.
14013 Wide character constants can be written by prefixing a character
14014 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14015 form of @samp{x}. The target wide character set is used when
14016 computing the value of this constant (@pxref{Character Sets}).
14019 String constants are a sequence of character constants surrounded by
14020 double quotes (@code{"}). Any valid character constant (as described
14021 above) may appear. Double quotes within the string must be preceded by
14022 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14025 Wide string constants can be written by prefixing a string constant
14026 with @samp{L}, as in C. The target wide character set is used when
14027 computing the value of this constant (@pxref{Character Sets}).
14030 Pointer constants are an integral value. You can also write pointers
14031 to constants using the C operator @samp{&}.
14034 Array constants are comma-separated lists surrounded by braces @samp{@{}
14035 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14036 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14037 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14040 @node C Plus Plus Expressions
14041 @subsubsection C@t{++} Expressions
14043 @cindex expressions in C@t{++}
14044 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14046 @cindex debugging C@t{++} programs
14047 @cindex C@t{++} compilers
14048 @cindex debug formats and C@t{++}
14049 @cindex @value{NGCC} and C@t{++}
14051 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14052 the proper compiler and the proper debug format. Currently,
14053 @value{GDBN} works best when debugging C@t{++} code that is compiled
14054 with the most recent version of @value{NGCC} possible. The DWARF
14055 debugging format is preferred; @value{NGCC} defaults to this on most
14056 popular platforms. Other compilers and/or debug formats are likely to
14057 work badly or not at all when using @value{GDBN} to debug C@t{++}
14058 code. @xref{Compilation}.
14063 @cindex member functions
14065 Member function calls are allowed; you can use expressions like
14068 count = aml->GetOriginal(x, y)
14071 @vindex this@r{, inside C@t{++} member functions}
14072 @cindex namespace in C@t{++}
14074 While a member function is active (in the selected stack frame), your
14075 expressions have the same namespace available as the member function;
14076 that is, @value{GDBN} allows implicit references to the class instance
14077 pointer @code{this} following the same rules as C@t{++}. @code{using}
14078 declarations in the current scope are also respected by @value{GDBN}.
14080 @cindex call overloaded functions
14081 @cindex overloaded functions, calling
14082 @cindex type conversions in C@t{++}
14084 You can call overloaded functions; @value{GDBN} resolves the function
14085 call to the right definition, with some restrictions. @value{GDBN} does not
14086 perform overload resolution involving user-defined type conversions,
14087 calls to constructors, or instantiations of templates that do not exist
14088 in the program. It also cannot handle ellipsis argument lists or
14091 It does perform integral conversions and promotions, floating-point
14092 promotions, arithmetic conversions, pointer conversions, conversions of
14093 class objects to base classes, and standard conversions such as those of
14094 functions or arrays to pointers; it requires an exact match on the
14095 number of function arguments.
14097 Overload resolution is always performed, unless you have specified
14098 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14099 ,@value{GDBN} Features for C@t{++}}.
14101 You must specify @code{set overload-resolution off} in order to use an
14102 explicit function signature to call an overloaded function, as in
14104 p 'foo(char,int)'('x', 13)
14107 The @value{GDBN} command-completion facility can simplify this;
14108 see @ref{Completion, ,Command Completion}.
14110 @cindex reference declarations
14112 @value{GDBN} understands variables declared as C@t{++} references; you can use
14113 them in expressions just as you do in C@t{++} source---they are automatically
14116 In the parameter list shown when @value{GDBN} displays a frame, the values of
14117 reference variables are not displayed (unlike other variables); this
14118 avoids clutter, since references are often used for large structures.
14119 The @emph{address} of a reference variable is always shown, unless
14120 you have specified @samp{set print address off}.
14123 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14124 expressions can use it just as expressions in your program do. Since
14125 one scope may be defined in another, you can use @code{::} repeatedly if
14126 necessary, for example in an expression like
14127 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14128 resolving name scope by reference to source files, in both C and C@t{++}
14129 debugging (@pxref{Variables, ,Program Variables}).
14132 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14137 @subsubsection C and C@t{++} Defaults
14139 @cindex C and C@t{++} defaults
14141 If you allow @value{GDBN} to set range checking automatically, it
14142 defaults to @code{off} whenever the working language changes to
14143 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14144 selects the working language.
14146 If you allow @value{GDBN} to set the language automatically, it
14147 recognizes source files whose names end with @file{.c}, @file{.C}, or
14148 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14149 these files, it sets the working language to C or C@t{++}.
14150 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14151 for further details.
14154 @subsubsection C and C@t{++} Type and Range Checks
14156 @cindex C and C@t{++} checks
14158 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14159 checking is used. However, if you turn type checking off, @value{GDBN}
14160 will allow certain non-standard conversions, such as promoting integer
14161 constants to pointers.
14163 Range checking, if turned on, is done on mathematical operations. Array
14164 indices are not checked, since they are often used to index a pointer
14165 that is not itself an array.
14168 @subsubsection @value{GDBN} and C
14170 The @code{set print union} and @code{show print union} commands apply to
14171 the @code{union} type. When set to @samp{on}, any @code{union} that is
14172 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14173 appears as @samp{@{...@}}.
14175 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14176 with pointers and a memory allocation function. @xref{Expressions,
14179 @node Debugging C Plus Plus
14180 @subsubsection @value{GDBN} Features for C@t{++}
14182 @cindex commands for C@t{++}
14184 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14185 designed specifically for use with C@t{++}. Here is a summary:
14188 @cindex break in overloaded functions
14189 @item @r{breakpoint menus}
14190 When you want a breakpoint in a function whose name is overloaded,
14191 @value{GDBN} has the capability to display a menu of possible breakpoint
14192 locations to help you specify which function definition you want.
14193 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14195 @cindex overloading in C@t{++}
14196 @item rbreak @var{regex}
14197 Setting breakpoints using regular expressions is helpful for setting
14198 breakpoints on overloaded functions that are not members of any special
14200 @xref{Set Breaks, ,Setting Breakpoints}.
14202 @cindex C@t{++} exception handling
14204 @itemx catch rethrow
14206 Debug C@t{++} exception handling using these commands. @xref{Set
14207 Catchpoints, , Setting Catchpoints}.
14209 @cindex inheritance
14210 @item ptype @var{typename}
14211 Print inheritance relationships as well as other information for type
14213 @xref{Symbols, ,Examining the Symbol Table}.
14215 @item info vtbl @var{expression}.
14216 The @code{info vtbl} command can be used to display the virtual
14217 method tables of the object computed by @var{expression}. This shows
14218 one entry per virtual table; there may be multiple virtual tables when
14219 multiple inheritance is in use.
14221 @cindex C@t{++} demangling
14222 @item demangle @var{name}
14223 Demangle @var{name}.
14224 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14226 @cindex C@t{++} symbol display
14227 @item set print demangle
14228 @itemx show print demangle
14229 @itemx set print asm-demangle
14230 @itemx show print asm-demangle
14231 Control whether C@t{++} symbols display in their source form, both when
14232 displaying code as C@t{++} source and when displaying disassemblies.
14233 @xref{Print Settings, ,Print Settings}.
14235 @item set print object
14236 @itemx show print object
14237 Choose whether to print derived (actual) or declared types of objects.
14238 @xref{Print Settings, ,Print Settings}.
14240 @item set print vtbl
14241 @itemx show print vtbl
14242 Control the format for printing virtual function tables.
14243 @xref{Print Settings, ,Print Settings}.
14244 (The @code{vtbl} commands do not work on programs compiled with the HP
14245 ANSI C@t{++} compiler (@code{aCC}).)
14247 @kindex set overload-resolution
14248 @cindex overloaded functions, overload resolution
14249 @item set overload-resolution on
14250 Enable overload resolution for C@t{++} expression evaluation. The default
14251 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14252 and searches for a function whose signature matches the argument types,
14253 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14254 Expressions, ,C@t{++} Expressions}, for details).
14255 If it cannot find a match, it emits a message.
14257 @item set overload-resolution off
14258 Disable overload resolution for C@t{++} expression evaluation. For
14259 overloaded functions that are not class member functions, @value{GDBN}
14260 chooses the first function of the specified name that it finds in the
14261 symbol table, whether or not its arguments are of the correct type. For
14262 overloaded functions that are class member functions, @value{GDBN}
14263 searches for a function whose signature @emph{exactly} matches the
14266 @kindex show overload-resolution
14267 @item show overload-resolution
14268 Show the current setting of overload resolution.
14270 @item @r{Overloaded symbol names}
14271 You can specify a particular definition of an overloaded symbol, using
14272 the same notation that is used to declare such symbols in C@t{++}: type
14273 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14274 also use the @value{GDBN} command-line word completion facilities to list the
14275 available choices, or to finish the type list for you.
14276 @xref{Completion,, Command Completion}, for details on how to do this.
14279 @node Decimal Floating Point
14280 @subsubsection Decimal Floating Point format
14281 @cindex decimal floating point format
14283 @value{GDBN} can examine, set and perform computations with numbers in
14284 decimal floating point format, which in the C language correspond to the
14285 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14286 specified by the extension to support decimal floating-point arithmetic.
14288 There are two encodings in use, depending on the architecture: BID (Binary
14289 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14290 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14293 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14294 to manipulate decimal floating point numbers, it is not possible to convert
14295 (using a cast, for example) integers wider than 32-bit to decimal float.
14297 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14298 point computations, error checking in decimal float operations ignores
14299 underflow, overflow and divide by zero exceptions.
14301 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14302 to inspect @code{_Decimal128} values stored in floating point registers.
14303 See @ref{PowerPC,,PowerPC} for more details.
14309 @value{GDBN} can be used to debug programs written in D and compiled with
14310 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14311 specific feature --- dynamic arrays.
14316 @cindex Go (programming language)
14317 @value{GDBN} can be used to debug programs written in Go and compiled with
14318 @file{gccgo} or @file{6g} compilers.
14320 Here is a summary of the Go-specific features and restrictions:
14323 @cindex current Go package
14324 @item The current Go package
14325 The name of the current package does not need to be specified when
14326 specifying global variables and functions.
14328 For example, given the program:
14332 var myglob = "Shall we?"
14338 When stopped inside @code{main} either of these work:
14342 (gdb) p main.myglob
14345 @cindex builtin Go types
14346 @item Builtin Go types
14347 The @code{string} type is recognized by @value{GDBN} and is printed
14350 @cindex builtin Go functions
14351 @item Builtin Go functions
14352 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14353 function and handles it internally.
14355 @cindex restrictions on Go expressions
14356 @item Restrictions on Go expressions
14357 All Go operators are supported except @code{&^}.
14358 The Go @code{_} ``blank identifier'' is not supported.
14359 Automatic dereferencing of pointers is not supported.
14363 @subsection Objective-C
14365 @cindex Objective-C
14366 This section provides information about some commands and command
14367 options that are useful for debugging Objective-C code. See also
14368 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14369 few more commands specific to Objective-C support.
14372 * Method Names in Commands::
14373 * The Print Command with Objective-C::
14376 @node Method Names in Commands
14377 @subsubsection Method Names in Commands
14379 The following commands have been extended to accept Objective-C method
14380 names as line specifications:
14382 @kindex clear@r{, and Objective-C}
14383 @kindex break@r{, and Objective-C}
14384 @kindex info line@r{, and Objective-C}
14385 @kindex jump@r{, and Objective-C}
14386 @kindex list@r{, and Objective-C}
14390 @item @code{info line}
14395 A fully qualified Objective-C method name is specified as
14398 -[@var{Class} @var{methodName}]
14401 where the minus sign is used to indicate an instance method and a
14402 plus sign (not shown) is used to indicate a class method. The class
14403 name @var{Class} and method name @var{methodName} are enclosed in
14404 brackets, similar to the way messages are specified in Objective-C
14405 source code. For example, to set a breakpoint at the @code{create}
14406 instance method of class @code{Fruit} in the program currently being
14410 break -[Fruit create]
14413 To list ten program lines around the @code{initialize} class method,
14417 list +[NSText initialize]
14420 In the current version of @value{GDBN}, the plus or minus sign is
14421 required. In future versions of @value{GDBN}, the plus or minus
14422 sign will be optional, but you can use it to narrow the search. It
14423 is also possible to specify just a method name:
14429 You must specify the complete method name, including any colons. If
14430 your program's source files contain more than one @code{create} method,
14431 you'll be presented with a numbered list of classes that implement that
14432 method. Indicate your choice by number, or type @samp{0} to exit if
14435 As another example, to clear a breakpoint established at the
14436 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14439 clear -[NSWindow makeKeyAndOrderFront:]
14442 @node The Print Command with Objective-C
14443 @subsubsection The Print Command With Objective-C
14444 @cindex Objective-C, print objects
14445 @kindex print-object
14446 @kindex po @r{(@code{print-object})}
14448 The print command has also been extended to accept methods. For example:
14451 print -[@var{object} hash]
14454 @cindex print an Objective-C object description
14455 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14457 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14458 and print the result. Also, an additional command has been added,
14459 @code{print-object} or @code{po} for short, which is meant to print
14460 the description of an object. However, this command may only work
14461 with certain Objective-C libraries that have a particular hook
14462 function, @code{_NSPrintForDebugger}, defined.
14465 @subsection OpenCL C
14468 This section provides information about @value{GDBN}s OpenCL C support.
14471 * OpenCL C Datatypes::
14472 * OpenCL C Expressions::
14473 * OpenCL C Operators::
14476 @node OpenCL C Datatypes
14477 @subsubsection OpenCL C Datatypes
14479 @cindex OpenCL C Datatypes
14480 @value{GDBN} supports the builtin scalar and vector datatypes specified
14481 by OpenCL 1.1. In addition the half- and double-precision floating point
14482 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14483 extensions are also known to @value{GDBN}.
14485 @node OpenCL C Expressions
14486 @subsubsection OpenCL C Expressions
14488 @cindex OpenCL C Expressions
14489 @value{GDBN} supports accesses to vector components including the access as
14490 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14491 supported by @value{GDBN} can be used as well.
14493 @node OpenCL C Operators
14494 @subsubsection OpenCL C Operators
14496 @cindex OpenCL C Operators
14497 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14501 @subsection Fortran
14502 @cindex Fortran-specific support in @value{GDBN}
14504 @value{GDBN} can be used to debug programs written in Fortran, but it
14505 currently supports only the features of Fortran 77 language.
14507 @cindex trailing underscore, in Fortran symbols
14508 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14509 among them) append an underscore to the names of variables and
14510 functions. When you debug programs compiled by those compilers, you
14511 will need to refer to variables and functions with a trailing
14515 * Fortran Operators:: Fortran operators and expressions
14516 * Fortran Defaults:: Default settings for Fortran
14517 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14520 @node Fortran Operators
14521 @subsubsection Fortran Operators and Expressions
14523 @cindex Fortran operators and expressions
14525 Operators must be defined on values of specific types. For instance,
14526 @code{+} is defined on numbers, but not on characters or other non-
14527 arithmetic types. Operators are often defined on groups of types.
14531 The exponentiation operator. It raises the first operand to the power
14535 The range operator. Normally used in the form of array(low:high) to
14536 represent a section of array.
14539 The access component operator. Normally used to access elements in derived
14540 types. Also suitable for unions. As unions aren't part of regular Fortran,
14541 this can only happen when accessing a register that uses a gdbarch-defined
14545 @node Fortran Defaults
14546 @subsubsection Fortran Defaults
14548 @cindex Fortran Defaults
14550 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14551 default uses case-insensitive matches for Fortran symbols. You can
14552 change that with the @samp{set case-insensitive} command, see
14553 @ref{Symbols}, for the details.
14555 @node Special Fortran Commands
14556 @subsubsection Special Fortran Commands
14558 @cindex Special Fortran commands
14560 @value{GDBN} has some commands to support Fortran-specific features,
14561 such as displaying common blocks.
14564 @cindex @code{COMMON} blocks, Fortran
14565 @kindex info common
14566 @item info common @r{[}@var{common-name}@r{]}
14567 This command prints the values contained in the Fortran @code{COMMON}
14568 block whose name is @var{common-name}. With no argument, the names of
14569 all @code{COMMON} blocks visible at the current program location are
14576 @cindex Pascal support in @value{GDBN}, limitations
14577 Debugging Pascal programs which use sets, subranges, file variables, or
14578 nested functions does not currently work. @value{GDBN} does not support
14579 entering expressions, printing values, or similar features using Pascal
14582 The Pascal-specific command @code{set print pascal_static-members}
14583 controls whether static members of Pascal objects are displayed.
14584 @xref{Print Settings, pascal_static-members}.
14587 @subsection Modula-2
14589 @cindex Modula-2, @value{GDBN} support
14591 The extensions made to @value{GDBN} to support Modula-2 only support
14592 output from the @sc{gnu} Modula-2 compiler (which is currently being
14593 developed). Other Modula-2 compilers are not currently supported, and
14594 attempting to debug executables produced by them is most likely
14595 to give an error as @value{GDBN} reads in the executable's symbol
14598 @cindex expressions in Modula-2
14600 * M2 Operators:: Built-in operators
14601 * Built-In Func/Proc:: Built-in functions and procedures
14602 * M2 Constants:: Modula-2 constants
14603 * M2 Types:: Modula-2 types
14604 * M2 Defaults:: Default settings for Modula-2
14605 * Deviations:: Deviations from standard Modula-2
14606 * M2 Checks:: Modula-2 type and range checks
14607 * M2 Scope:: The scope operators @code{::} and @code{.}
14608 * GDB/M2:: @value{GDBN} and Modula-2
14612 @subsubsection Operators
14613 @cindex Modula-2 operators
14615 Operators must be defined on values of specific types. For instance,
14616 @code{+} is defined on numbers, but not on structures. Operators are
14617 often defined on groups of types. For the purposes of Modula-2, the
14618 following definitions hold:
14623 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14627 @emph{Character types} consist of @code{CHAR} and its subranges.
14630 @emph{Floating-point types} consist of @code{REAL}.
14633 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14637 @emph{Scalar types} consist of all of the above.
14640 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14643 @emph{Boolean types} consist of @code{BOOLEAN}.
14647 The following operators are supported, and appear in order of
14648 increasing precedence:
14652 Function argument or array index separator.
14655 Assignment. The value of @var{var} @code{:=} @var{value} is
14659 Less than, greater than on integral, floating-point, or enumerated
14663 Less than or equal to, greater than or equal to
14664 on integral, floating-point and enumerated types, or set inclusion on
14665 set types. Same precedence as @code{<}.
14667 @item =@r{, }<>@r{, }#
14668 Equality and two ways of expressing inequality, valid on scalar types.
14669 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14670 available for inequality, since @code{#} conflicts with the script
14674 Set membership. Defined on set types and the types of their members.
14675 Same precedence as @code{<}.
14678 Boolean disjunction. Defined on boolean types.
14681 Boolean conjunction. Defined on boolean types.
14684 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14687 Addition and subtraction on integral and floating-point types, or union
14688 and difference on set types.
14691 Multiplication on integral and floating-point types, or set intersection
14695 Division on floating-point types, or symmetric set difference on set
14696 types. Same precedence as @code{*}.
14699 Integer division and remainder. Defined on integral types. Same
14700 precedence as @code{*}.
14703 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14706 Pointer dereferencing. Defined on pointer types.
14709 Boolean negation. Defined on boolean types. Same precedence as
14713 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14714 precedence as @code{^}.
14717 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14720 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14724 @value{GDBN} and Modula-2 scope operators.
14728 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14729 treats the use of the operator @code{IN}, or the use of operators
14730 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14731 @code{<=}, and @code{>=} on sets as an error.
14735 @node Built-In Func/Proc
14736 @subsubsection Built-in Functions and Procedures
14737 @cindex Modula-2 built-ins
14739 Modula-2 also makes available several built-in procedures and functions.
14740 In describing these, the following metavariables are used:
14745 represents an @code{ARRAY} variable.
14748 represents a @code{CHAR} constant or variable.
14751 represents a variable or constant of integral type.
14754 represents an identifier that belongs to a set. Generally used in the
14755 same function with the metavariable @var{s}. The type of @var{s} should
14756 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14759 represents a variable or constant of integral or floating-point type.
14762 represents a variable or constant of floating-point type.
14768 represents a variable.
14771 represents a variable or constant of one of many types. See the
14772 explanation of the function for details.
14775 All Modula-2 built-in procedures also return a result, described below.
14779 Returns the absolute value of @var{n}.
14782 If @var{c} is a lower case letter, it returns its upper case
14783 equivalent, otherwise it returns its argument.
14786 Returns the character whose ordinal value is @var{i}.
14789 Decrements the value in the variable @var{v} by one. Returns the new value.
14791 @item DEC(@var{v},@var{i})
14792 Decrements the value in the variable @var{v} by @var{i}. Returns the
14795 @item EXCL(@var{m},@var{s})
14796 Removes the element @var{m} from the set @var{s}. Returns the new
14799 @item FLOAT(@var{i})
14800 Returns the floating point equivalent of the integer @var{i}.
14802 @item HIGH(@var{a})
14803 Returns the index of the last member of @var{a}.
14806 Increments the value in the variable @var{v} by one. Returns the new value.
14808 @item INC(@var{v},@var{i})
14809 Increments the value in the variable @var{v} by @var{i}. Returns the
14812 @item INCL(@var{m},@var{s})
14813 Adds the element @var{m} to the set @var{s} if it is not already
14814 there. Returns the new set.
14817 Returns the maximum value of the type @var{t}.
14820 Returns the minimum value of the type @var{t}.
14823 Returns boolean TRUE if @var{i} is an odd number.
14826 Returns the ordinal value of its argument. For example, the ordinal
14827 value of a character is its @sc{ascii} value (on machines supporting
14828 the @sc{ascii} character set). The argument @var{x} must be of an
14829 ordered type, which include integral, character and enumerated types.
14831 @item SIZE(@var{x})
14832 Returns the size of its argument. The argument @var{x} can be a
14833 variable or a type.
14835 @item TRUNC(@var{r})
14836 Returns the integral part of @var{r}.
14838 @item TSIZE(@var{x})
14839 Returns the size of its argument. The argument @var{x} can be a
14840 variable or a type.
14842 @item VAL(@var{t},@var{i})
14843 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14847 @emph{Warning:} Sets and their operations are not yet supported, so
14848 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14852 @cindex Modula-2 constants
14854 @subsubsection Constants
14856 @value{GDBN} allows you to express the constants of Modula-2 in the following
14862 Integer constants are simply a sequence of digits. When used in an
14863 expression, a constant is interpreted to be type-compatible with the
14864 rest of the expression. Hexadecimal integers are specified by a
14865 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14868 Floating point constants appear as a sequence of digits, followed by a
14869 decimal point and another sequence of digits. An optional exponent can
14870 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14871 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14872 digits of the floating point constant must be valid decimal (base 10)
14876 Character constants consist of a single character enclosed by a pair of
14877 like quotes, either single (@code{'}) or double (@code{"}). They may
14878 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14879 followed by a @samp{C}.
14882 String constants consist of a sequence of characters enclosed by a
14883 pair of like quotes, either single (@code{'}) or double (@code{"}).
14884 Escape sequences in the style of C are also allowed. @xref{C
14885 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14889 Enumerated constants consist of an enumerated identifier.
14892 Boolean constants consist of the identifiers @code{TRUE} and
14896 Pointer constants consist of integral values only.
14899 Set constants are not yet supported.
14903 @subsubsection Modula-2 Types
14904 @cindex Modula-2 types
14906 Currently @value{GDBN} can print the following data types in Modula-2
14907 syntax: array types, record types, set types, pointer types, procedure
14908 types, enumerated types, subrange types and base types. You can also
14909 print the contents of variables declared using these type.
14910 This section gives a number of simple source code examples together with
14911 sample @value{GDBN} sessions.
14913 The first example contains the following section of code:
14922 and you can request @value{GDBN} to interrogate the type and value of
14923 @code{r} and @code{s}.
14926 (@value{GDBP}) print s
14928 (@value{GDBP}) ptype s
14930 (@value{GDBP}) print r
14932 (@value{GDBP}) ptype r
14937 Likewise if your source code declares @code{s} as:
14941 s: SET ['A'..'Z'] ;
14945 then you may query the type of @code{s} by:
14948 (@value{GDBP}) ptype s
14949 type = SET ['A'..'Z']
14953 Note that at present you cannot interactively manipulate set
14954 expressions using the debugger.
14956 The following example shows how you might declare an array in Modula-2
14957 and how you can interact with @value{GDBN} to print its type and contents:
14961 s: ARRAY [-10..10] OF CHAR ;
14965 (@value{GDBP}) ptype s
14966 ARRAY [-10..10] OF CHAR
14969 Note that the array handling is not yet complete and although the type
14970 is printed correctly, expression handling still assumes that all
14971 arrays have a lower bound of zero and not @code{-10} as in the example
14974 Here are some more type related Modula-2 examples:
14978 colour = (blue, red, yellow, green) ;
14979 t = [blue..yellow] ;
14987 The @value{GDBN} interaction shows how you can query the data type
14988 and value of a variable.
14991 (@value{GDBP}) print s
14993 (@value{GDBP}) ptype t
14994 type = [blue..yellow]
14998 In this example a Modula-2 array is declared and its contents
14999 displayed. Observe that the contents are written in the same way as
15000 their @code{C} counterparts.
15004 s: ARRAY [1..5] OF CARDINAL ;
15010 (@value{GDBP}) print s
15011 $1 = @{1, 0, 0, 0, 0@}
15012 (@value{GDBP}) ptype s
15013 type = ARRAY [1..5] OF CARDINAL
15016 The Modula-2 language interface to @value{GDBN} also understands
15017 pointer types as shown in this example:
15021 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15028 and you can request that @value{GDBN} describes the type of @code{s}.
15031 (@value{GDBP}) ptype s
15032 type = POINTER TO ARRAY [1..5] OF CARDINAL
15035 @value{GDBN} handles compound types as we can see in this example.
15036 Here we combine array types, record types, pointer types and subrange
15047 myarray = ARRAY myrange OF CARDINAL ;
15048 myrange = [-2..2] ;
15050 s: POINTER TO ARRAY myrange OF foo ;
15054 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15058 (@value{GDBP}) ptype s
15059 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15062 f3 : ARRAY [-2..2] OF CARDINAL;
15067 @subsubsection Modula-2 Defaults
15068 @cindex Modula-2 defaults
15070 If type and range checking are set automatically by @value{GDBN}, they
15071 both default to @code{on} whenever the working language changes to
15072 Modula-2. This happens regardless of whether you or @value{GDBN}
15073 selected the working language.
15075 If you allow @value{GDBN} to set the language automatically, then entering
15076 code compiled from a file whose name ends with @file{.mod} sets the
15077 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15078 Infer the Source Language}, for further details.
15081 @subsubsection Deviations from Standard Modula-2
15082 @cindex Modula-2, deviations from
15084 A few changes have been made to make Modula-2 programs easier to debug.
15085 This is done primarily via loosening its type strictness:
15089 Unlike in standard Modula-2, pointer constants can be formed by
15090 integers. This allows you to modify pointer variables during
15091 debugging. (In standard Modula-2, the actual address contained in a
15092 pointer variable is hidden from you; it can only be modified
15093 through direct assignment to another pointer variable or expression that
15094 returned a pointer.)
15097 C escape sequences can be used in strings and characters to represent
15098 non-printable characters. @value{GDBN} prints out strings with these
15099 escape sequences embedded. Single non-printable characters are
15100 printed using the @samp{CHR(@var{nnn})} format.
15103 The assignment operator (@code{:=}) returns the value of its right-hand
15107 All built-in procedures both modify @emph{and} return their argument.
15111 @subsubsection Modula-2 Type and Range Checks
15112 @cindex Modula-2 checks
15115 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15118 @c FIXME remove warning when type/range checks added
15120 @value{GDBN} considers two Modula-2 variables type equivalent if:
15124 They are of types that have been declared equivalent via a @code{TYPE
15125 @var{t1} = @var{t2}} statement
15128 They have been declared on the same line. (Note: This is true of the
15129 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15132 As long as type checking is enabled, any attempt to combine variables
15133 whose types are not equivalent is an error.
15135 Range checking is done on all mathematical operations, assignment, array
15136 index bounds, and all built-in functions and procedures.
15139 @subsubsection The Scope Operators @code{::} and @code{.}
15141 @cindex @code{.}, Modula-2 scope operator
15142 @cindex colon, doubled as scope operator
15144 @vindex colon-colon@r{, in Modula-2}
15145 @c Info cannot handle :: but TeX can.
15148 @vindex ::@r{, in Modula-2}
15151 There are a few subtle differences between the Modula-2 scope operator
15152 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15157 @var{module} . @var{id}
15158 @var{scope} :: @var{id}
15162 where @var{scope} is the name of a module or a procedure,
15163 @var{module} the name of a module, and @var{id} is any declared
15164 identifier within your program, except another module.
15166 Using the @code{::} operator makes @value{GDBN} search the scope
15167 specified by @var{scope} for the identifier @var{id}. If it is not
15168 found in the specified scope, then @value{GDBN} searches all scopes
15169 enclosing the one specified by @var{scope}.
15171 Using the @code{.} operator makes @value{GDBN} search the current scope for
15172 the identifier specified by @var{id} that was imported from the
15173 definition module specified by @var{module}. With this operator, it is
15174 an error if the identifier @var{id} was not imported from definition
15175 module @var{module}, or if @var{id} is not an identifier in
15179 @subsubsection @value{GDBN} and Modula-2
15181 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15182 Five subcommands of @code{set print} and @code{show print} apply
15183 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15184 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15185 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15186 analogue in Modula-2.
15188 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15189 with any language, is not useful with Modula-2. Its
15190 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15191 created in Modula-2 as they can in C or C@t{++}. However, because an
15192 address can be specified by an integral constant, the construct
15193 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15195 @cindex @code{#} in Modula-2
15196 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15197 interpreted as the beginning of a comment. Use @code{<>} instead.
15203 The extensions made to @value{GDBN} for Ada only support
15204 output from the @sc{gnu} Ada (GNAT) compiler.
15205 Other Ada compilers are not currently supported, and
15206 attempting to debug executables produced by them is most likely
15210 @cindex expressions in Ada
15212 * Ada Mode Intro:: General remarks on the Ada syntax
15213 and semantics supported by Ada mode
15215 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15216 * Additions to Ada:: Extensions of the Ada expression syntax.
15217 * Stopping Before Main Program:: Debugging the program during elaboration.
15218 * Ada Exceptions:: Ada Exceptions
15219 * Ada Tasks:: Listing and setting breakpoints in tasks.
15220 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15221 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15223 * Ada Glitches:: Known peculiarities of Ada mode.
15226 @node Ada Mode Intro
15227 @subsubsection Introduction
15228 @cindex Ada mode, general
15230 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15231 syntax, with some extensions.
15232 The philosophy behind the design of this subset is
15236 That @value{GDBN} should provide basic literals and access to operations for
15237 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15238 leaving more sophisticated computations to subprograms written into the
15239 program (which therefore may be called from @value{GDBN}).
15242 That type safety and strict adherence to Ada language restrictions
15243 are not particularly important to the @value{GDBN} user.
15246 That brevity is important to the @value{GDBN} user.
15249 Thus, for brevity, the debugger acts as if all names declared in
15250 user-written packages are directly visible, even if they are not visible
15251 according to Ada rules, thus making it unnecessary to fully qualify most
15252 names with their packages, regardless of context. Where this causes
15253 ambiguity, @value{GDBN} asks the user's intent.
15255 The debugger will start in Ada mode if it detects an Ada main program.
15256 As for other languages, it will enter Ada mode when stopped in a program that
15257 was translated from an Ada source file.
15259 While in Ada mode, you may use `@t{--}' for comments. This is useful
15260 mostly for documenting command files. The standard @value{GDBN} comment
15261 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15262 middle (to allow based literals).
15264 The debugger supports limited overloading. Given a subprogram call in which
15265 the function symbol has multiple definitions, it will use the number of
15266 actual parameters and some information about their types to attempt to narrow
15267 the set of definitions. It also makes very limited use of context, preferring
15268 procedures to functions in the context of the @code{call} command, and
15269 functions to procedures elsewhere.
15271 @node Omissions from Ada
15272 @subsubsection Omissions from Ada
15273 @cindex Ada, omissions from
15275 Here are the notable omissions from the subset:
15279 Only a subset of the attributes are supported:
15283 @t{'First}, @t{'Last}, and @t{'Length}
15284 on array objects (not on types and subtypes).
15287 @t{'Min} and @t{'Max}.
15290 @t{'Pos} and @t{'Val}.
15296 @t{'Range} on array objects (not subtypes), but only as the right
15297 operand of the membership (@code{in}) operator.
15300 @t{'Access}, @t{'Unchecked_Access}, and
15301 @t{'Unrestricted_Access} (a GNAT extension).
15309 @code{Characters.Latin_1} are not available and
15310 concatenation is not implemented. Thus, escape characters in strings are
15311 not currently available.
15314 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15315 equality of representations. They will generally work correctly
15316 for strings and arrays whose elements have integer or enumeration types.
15317 They may not work correctly for arrays whose element
15318 types have user-defined equality, for arrays of real values
15319 (in particular, IEEE-conformant floating point, because of negative
15320 zeroes and NaNs), and for arrays whose elements contain unused bits with
15321 indeterminate values.
15324 The other component-by-component array operations (@code{and}, @code{or},
15325 @code{xor}, @code{not}, and relational tests other than equality)
15326 are not implemented.
15329 @cindex array aggregates (Ada)
15330 @cindex record aggregates (Ada)
15331 @cindex aggregates (Ada)
15332 There is limited support for array and record aggregates. They are
15333 permitted only on the right sides of assignments, as in these examples:
15336 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15337 (@value{GDBP}) set An_Array := (1, others => 0)
15338 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15339 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15340 (@value{GDBP}) set A_Record := (1, "Peter", True);
15341 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15345 discriminant's value by assigning an aggregate has an
15346 undefined effect if that discriminant is used within the record.
15347 However, you can first modify discriminants by directly assigning to
15348 them (which normally would not be allowed in Ada), and then performing an
15349 aggregate assignment. For example, given a variable @code{A_Rec}
15350 declared to have a type such as:
15353 type Rec (Len : Small_Integer := 0) is record
15355 Vals : IntArray (1 .. Len);
15359 you can assign a value with a different size of @code{Vals} with two
15363 (@value{GDBP}) set A_Rec.Len := 4
15364 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15367 As this example also illustrates, @value{GDBN} is very loose about the usual
15368 rules concerning aggregates. You may leave out some of the
15369 components of an array or record aggregate (such as the @code{Len}
15370 component in the assignment to @code{A_Rec} above); they will retain their
15371 original values upon assignment. You may freely use dynamic values as
15372 indices in component associations. You may even use overlapping or
15373 redundant component associations, although which component values are
15374 assigned in such cases is not defined.
15377 Calls to dispatching subprograms are not implemented.
15380 The overloading algorithm is much more limited (i.e., less selective)
15381 than that of real Ada. It makes only limited use of the context in
15382 which a subexpression appears to resolve its meaning, and it is much
15383 looser in its rules for allowing type matches. As a result, some
15384 function calls will be ambiguous, and the user will be asked to choose
15385 the proper resolution.
15388 The @code{new} operator is not implemented.
15391 Entry calls are not implemented.
15394 Aside from printing, arithmetic operations on the native VAX floating-point
15395 formats are not supported.
15398 It is not possible to slice a packed array.
15401 The names @code{True} and @code{False}, when not part of a qualified name,
15402 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15404 Should your program
15405 redefine these names in a package or procedure (at best a dubious practice),
15406 you will have to use fully qualified names to access their new definitions.
15409 @node Additions to Ada
15410 @subsubsection Additions to Ada
15411 @cindex Ada, deviations from
15413 As it does for other languages, @value{GDBN} makes certain generic
15414 extensions to Ada (@pxref{Expressions}):
15418 If the expression @var{E} is a variable residing in memory (typically
15419 a local variable or array element) and @var{N} is a positive integer,
15420 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15421 @var{N}-1 adjacent variables following it in memory as an array. In
15422 Ada, this operator is generally not necessary, since its prime use is
15423 in displaying parts of an array, and slicing will usually do this in
15424 Ada. However, there are occasional uses when debugging programs in
15425 which certain debugging information has been optimized away.
15428 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15429 appears in function or file @var{B}.'' When @var{B} is a file name,
15430 you must typically surround it in single quotes.
15433 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15434 @var{type} that appears at address @var{addr}.''
15437 A name starting with @samp{$} is a convenience variable
15438 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15441 In addition, @value{GDBN} provides a few other shortcuts and outright
15442 additions specific to Ada:
15446 The assignment statement is allowed as an expression, returning
15447 its right-hand operand as its value. Thus, you may enter
15450 (@value{GDBP}) set x := y + 3
15451 (@value{GDBP}) print A(tmp := y + 1)
15455 The semicolon is allowed as an ``operator,'' returning as its value
15456 the value of its right-hand operand.
15457 This allows, for example,
15458 complex conditional breaks:
15461 (@value{GDBP}) break f
15462 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15466 Rather than use catenation and symbolic character names to introduce special
15467 characters into strings, one may instead use a special bracket notation,
15468 which is also used to print strings. A sequence of characters of the form
15469 @samp{["@var{XX}"]} within a string or character literal denotes the
15470 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15471 sequence of characters @samp{["""]} also denotes a single quotation mark
15472 in strings. For example,
15474 "One line.["0a"]Next line.["0a"]"
15477 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15481 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15482 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15486 (@value{GDBP}) print 'max(x, y)
15490 When printing arrays, @value{GDBN} uses positional notation when the
15491 array has a lower bound of 1, and uses a modified named notation otherwise.
15492 For example, a one-dimensional array of three integers with a lower bound
15493 of 3 might print as
15500 That is, in contrast to valid Ada, only the first component has a @code{=>}
15504 You may abbreviate attributes in expressions with any unique,
15505 multi-character subsequence of
15506 their names (an exact match gets preference).
15507 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15508 in place of @t{a'length}.
15511 @cindex quoting Ada internal identifiers
15512 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15513 to lower case. The GNAT compiler uses upper-case characters for
15514 some of its internal identifiers, which are normally of no interest to users.
15515 For the rare occasions when you actually have to look at them,
15516 enclose them in angle brackets to avoid the lower-case mapping.
15519 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15523 Printing an object of class-wide type or dereferencing an
15524 access-to-class-wide value will display all the components of the object's
15525 specific type (as indicated by its run-time tag). Likewise, component
15526 selection on such a value will operate on the specific type of the
15531 @node Stopping Before Main Program
15532 @subsubsection Stopping at the Very Beginning
15534 @cindex breakpointing Ada elaboration code
15535 It is sometimes necessary to debug the program during elaboration, and
15536 before reaching the main procedure.
15537 As defined in the Ada Reference
15538 Manual, the elaboration code is invoked from a procedure called
15539 @code{adainit}. To run your program up to the beginning of
15540 elaboration, simply use the following two commands:
15541 @code{tbreak adainit} and @code{run}.
15543 @node Ada Exceptions
15544 @subsubsection Ada Exceptions
15546 A command is provided to list all Ada exceptions:
15549 @kindex info exceptions
15550 @item info exceptions
15551 @itemx info exceptions @var{regexp}
15552 The @code{info exceptions} command allows you to list all Ada exceptions
15553 defined within the program being debugged, as well as their addresses.
15554 With a regular expression, @var{regexp}, as argument, only those exceptions
15555 whose names match @var{regexp} are listed.
15558 Below is a small example, showing how the command can be used, first
15559 without argument, and next with a regular expression passed as an
15563 (@value{GDBP}) info exceptions
15564 All defined Ada exceptions:
15565 constraint_error: 0x613da0
15566 program_error: 0x613d20
15567 storage_error: 0x613ce0
15568 tasking_error: 0x613ca0
15569 const.aint_global_e: 0x613b00
15570 (@value{GDBP}) info exceptions const.aint
15571 All Ada exceptions matching regular expression "const.aint":
15572 constraint_error: 0x613da0
15573 const.aint_global_e: 0x613b00
15576 It is also possible to ask @value{GDBN} to stop your program's execution
15577 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15580 @subsubsection Extensions for Ada Tasks
15581 @cindex Ada, tasking
15583 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15584 @value{GDBN} provides the following task-related commands:
15589 This command shows a list of current Ada tasks, as in the following example:
15596 (@value{GDBP}) info tasks
15597 ID TID P-ID Pri State Name
15598 1 8088000 0 15 Child Activation Wait main_task
15599 2 80a4000 1 15 Accept Statement b
15600 3 809a800 1 15 Child Activation Wait a
15601 * 4 80ae800 3 15 Runnable c
15606 In this listing, the asterisk before the last task indicates it to be the
15607 task currently being inspected.
15611 Represents @value{GDBN}'s internal task number.
15617 The parent's task ID (@value{GDBN}'s internal task number).
15620 The base priority of the task.
15623 Current state of the task.
15627 The task has been created but has not been activated. It cannot be
15631 The task is not blocked for any reason known to Ada. (It may be waiting
15632 for a mutex, though.) It is conceptually "executing" in normal mode.
15635 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15636 that were waiting on terminate alternatives have been awakened and have
15637 terminated themselves.
15639 @item Child Activation Wait
15640 The task is waiting for created tasks to complete activation.
15642 @item Accept Statement
15643 The task is waiting on an accept or selective wait statement.
15645 @item Waiting on entry call
15646 The task is waiting on an entry call.
15648 @item Async Select Wait
15649 The task is waiting to start the abortable part of an asynchronous
15653 The task is waiting on a select statement with only a delay
15656 @item Child Termination Wait
15657 The task is sleeping having completed a master within itself, and is
15658 waiting for the tasks dependent on that master to become terminated or
15659 waiting on a terminate Phase.
15661 @item Wait Child in Term Alt
15662 The task is sleeping waiting for tasks on terminate alternatives to
15663 finish terminating.
15665 @item Accepting RV with @var{taskno}
15666 The task is accepting a rendez-vous with the task @var{taskno}.
15670 Name of the task in the program.
15674 @kindex info task @var{taskno}
15675 @item info task @var{taskno}
15676 This command shows detailled informations on the specified task, as in
15677 the following example:
15682 (@value{GDBP}) info tasks
15683 ID TID P-ID Pri State Name
15684 1 8077880 0 15 Child Activation Wait main_task
15685 * 2 807c468 1 15 Runnable task_1
15686 (@value{GDBP}) info task 2
15687 Ada Task: 0x807c468
15690 Parent: 1 (main_task)
15696 @kindex task@r{ (Ada)}
15697 @cindex current Ada task ID
15698 This command prints the ID of the current task.
15704 (@value{GDBP}) info tasks
15705 ID TID P-ID Pri State Name
15706 1 8077870 0 15 Child Activation Wait main_task
15707 * 2 807c458 1 15 Runnable t
15708 (@value{GDBP}) task
15709 [Current task is 2]
15712 @item task @var{taskno}
15713 @cindex Ada task switching
15714 This command is like the @code{thread @var{threadno}}
15715 command (@pxref{Threads}). It switches the context of debugging
15716 from the current task to the given task.
15722 (@value{GDBP}) info tasks
15723 ID TID P-ID Pri State Name
15724 1 8077870 0 15 Child Activation Wait main_task
15725 * 2 807c458 1 15 Runnable t
15726 (@value{GDBP}) task 1
15727 [Switching to task 1]
15728 #0 0x8067726 in pthread_cond_wait ()
15730 #0 0x8067726 in pthread_cond_wait ()
15731 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15732 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15733 #3 0x806153e in system.tasking.stages.activate_tasks ()
15734 #4 0x804aacc in un () at un.adb:5
15737 @item break @var{linespec} task @var{taskno}
15738 @itemx break @var{linespec} task @var{taskno} if @dots{}
15739 @cindex breakpoints and tasks, in Ada
15740 @cindex task breakpoints, in Ada
15741 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15742 These commands are like the @code{break @dots{} thread @dots{}}
15743 command (@pxref{Thread Stops}). The
15744 @var{linespec} argument specifies source lines, as described
15745 in @ref{Specify Location}.
15747 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15748 to specify that you only want @value{GDBN} to stop the program when a
15749 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15750 numeric task identifiers assigned by @value{GDBN}, shown in the first
15751 column of the @samp{info tasks} display.
15753 If you do not specify @samp{task @var{taskno}} when you set a
15754 breakpoint, the breakpoint applies to @emph{all} tasks of your
15757 You can use the @code{task} qualifier on conditional breakpoints as
15758 well; in this case, place @samp{task @var{taskno}} before the
15759 breakpoint condition (before the @code{if}).
15767 (@value{GDBP}) info tasks
15768 ID TID P-ID Pri State Name
15769 1 140022020 0 15 Child Activation Wait main_task
15770 2 140045060 1 15 Accept/Select Wait t2
15771 3 140044840 1 15 Runnable t1
15772 * 4 140056040 1 15 Runnable t3
15773 (@value{GDBP}) b 15 task 2
15774 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15775 (@value{GDBP}) cont
15780 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15782 (@value{GDBP}) info tasks
15783 ID TID P-ID Pri State Name
15784 1 140022020 0 15 Child Activation Wait main_task
15785 * 2 140045060 1 15 Runnable t2
15786 3 140044840 1 15 Runnable t1
15787 4 140056040 1 15 Delay Sleep t3
15791 @node Ada Tasks and Core Files
15792 @subsubsection Tasking Support when Debugging Core Files
15793 @cindex Ada tasking and core file debugging
15795 When inspecting a core file, as opposed to debugging a live program,
15796 tasking support may be limited or even unavailable, depending on
15797 the platform being used.
15798 For instance, on x86-linux, the list of tasks is available, but task
15799 switching is not supported.
15801 On certain platforms, the debugger needs to perform some
15802 memory writes in order to provide Ada tasking support. When inspecting
15803 a core file, this means that the core file must be opened with read-write
15804 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15805 Under these circumstances, you should make a backup copy of the core
15806 file before inspecting it with @value{GDBN}.
15808 @node Ravenscar Profile
15809 @subsubsection Tasking Support when using the Ravenscar Profile
15810 @cindex Ravenscar Profile
15812 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15813 specifically designed for systems with safety-critical real-time
15817 @kindex set ravenscar task-switching on
15818 @cindex task switching with program using Ravenscar Profile
15819 @item set ravenscar task-switching on
15820 Allows task switching when debugging a program that uses the Ravenscar
15821 Profile. This is the default.
15823 @kindex set ravenscar task-switching off
15824 @item set ravenscar task-switching off
15825 Turn off task switching when debugging a program that uses the Ravenscar
15826 Profile. This is mostly intended to disable the code that adds support
15827 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15828 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15829 To be effective, this command should be run before the program is started.
15831 @kindex show ravenscar task-switching
15832 @item show ravenscar task-switching
15833 Show whether it is possible to switch from task to task in a program
15834 using the Ravenscar Profile.
15839 @subsubsection Known Peculiarities of Ada Mode
15840 @cindex Ada, problems
15842 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15843 we know of several problems with and limitations of Ada mode in
15845 some of which will be fixed with planned future releases of the debugger
15846 and the GNU Ada compiler.
15850 Static constants that the compiler chooses not to materialize as objects in
15851 storage are invisible to the debugger.
15854 Named parameter associations in function argument lists are ignored (the
15855 argument lists are treated as positional).
15858 Many useful library packages are currently invisible to the debugger.
15861 Fixed-point arithmetic, conversions, input, and output is carried out using
15862 floating-point arithmetic, and may give results that only approximate those on
15866 The GNAT compiler never generates the prefix @code{Standard} for any of
15867 the standard symbols defined by the Ada language. @value{GDBN} knows about
15868 this: it will strip the prefix from names when you use it, and will never
15869 look for a name you have so qualified among local symbols, nor match against
15870 symbols in other packages or subprograms. If you have
15871 defined entities anywhere in your program other than parameters and
15872 local variables whose simple names match names in @code{Standard},
15873 GNAT's lack of qualification here can cause confusion. When this happens,
15874 you can usually resolve the confusion
15875 by qualifying the problematic names with package
15876 @code{Standard} explicitly.
15879 Older versions of the compiler sometimes generate erroneous debugging
15880 information, resulting in the debugger incorrectly printing the value
15881 of affected entities. In some cases, the debugger is able to work
15882 around an issue automatically. In other cases, the debugger is able
15883 to work around the issue, but the work-around has to be specifically
15886 @kindex set ada trust-PAD-over-XVS
15887 @kindex show ada trust-PAD-over-XVS
15890 @item set ada trust-PAD-over-XVS on
15891 Configure GDB to strictly follow the GNAT encoding when computing the
15892 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15893 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15894 a complete description of the encoding used by the GNAT compiler).
15895 This is the default.
15897 @item set ada trust-PAD-over-XVS off
15898 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15899 sometimes prints the wrong value for certain entities, changing @code{ada
15900 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15901 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15902 @code{off}, but this incurs a slight performance penalty, so it is
15903 recommended to leave this setting to @code{on} unless necessary.
15907 @cindex GNAT descriptive types
15908 @cindex GNAT encoding
15909 Internally, the debugger also relies on the compiler following a number
15910 of conventions known as the @samp{GNAT Encoding}, all documented in
15911 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15912 how the debugging information should be generated for certain types.
15913 In particular, this convention makes use of @dfn{descriptive types},
15914 which are artificial types generated purely to help the debugger.
15916 These encodings were defined at a time when the debugging information
15917 format used was not powerful enough to describe some of the more complex
15918 types available in Ada. Since DWARF allows us to express nearly all
15919 Ada features, the long-term goal is to slowly replace these descriptive
15920 types by their pure DWARF equivalent. To facilitate that transition,
15921 a new maintenance option is available to force the debugger to ignore
15922 those descriptive types. It allows the user to quickly evaluate how
15923 well @value{GDBN} works without them.
15927 @kindex maint ada set ignore-descriptive-types
15928 @item maintenance ada set ignore-descriptive-types [on|off]
15929 Control whether the debugger should ignore descriptive types.
15930 The default is not to ignore descriptives types (@code{off}).
15932 @kindex maint ada show ignore-descriptive-types
15933 @item maintenance ada show ignore-descriptive-types
15934 Show if descriptive types are ignored by @value{GDBN}.
15938 @node Unsupported Languages
15939 @section Unsupported Languages
15941 @cindex unsupported languages
15942 @cindex minimal language
15943 In addition to the other fully-supported programming languages,
15944 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15945 It does not represent a real programming language, but provides a set
15946 of capabilities close to what the C or assembly languages provide.
15947 This should allow most simple operations to be performed while debugging
15948 an application that uses a language currently not supported by @value{GDBN}.
15950 If the language is set to @code{auto}, @value{GDBN} will automatically
15951 select this language if the current frame corresponds to an unsupported
15955 @chapter Examining the Symbol Table
15957 The commands described in this chapter allow you to inquire about the
15958 symbols (names of variables, functions and types) defined in your
15959 program. This information is inherent in the text of your program and
15960 does not change as your program executes. @value{GDBN} finds it in your
15961 program's symbol table, in the file indicated when you started @value{GDBN}
15962 (@pxref{File Options, ,Choosing Files}), or by one of the
15963 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15965 @cindex symbol names
15966 @cindex names of symbols
15967 @cindex quoting names
15968 Occasionally, you may need to refer to symbols that contain unusual
15969 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15970 most frequent case is in referring to static variables in other
15971 source files (@pxref{Variables,,Program Variables}). File names
15972 are recorded in object files as debugging symbols, but @value{GDBN} would
15973 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15974 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15975 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15982 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15985 @cindex case-insensitive symbol names
15986 @cindex case sensitivity in symbol names
15987 @kindex set case-sensitive
15988 @item set case-sensitive on
15989 @itemx set case-sensitive off
15990 @itemx set case-sensitive auto
15991 Normally, when @value{GDBN} looks up symbols, it matches their names
15992 with case sensitivity determined by the current source language.
15993 Occasionally, you may wish to control that. The command @code{set
15994 case-sensitive} lets you do that by specifying @code{on} for
15995 case-sensitive matches or @code{off} for case-insensitive ones. If
15996 you specify @code{auto}, case sensitivity is reset to the default
15997 suitable for the source language. The default is case-sensitive
15998 matches for all languages except for Fortran, for which the default is
15999 case-insensitive matches.
16001 @kindex show case-sensitive
16002 @item show case-sensitive
16003 This command shows the current setting of case sensitivity for symbols
16006 @kindex set print type methods
16007 @item set print type methods
16008 @itemx set print type methods on
16009 @itemx set print type methods off
16010 Normally, when @value{GDBN} prints a class, it displays any methods
16011 declared in that class. You can control this behavior either by
16012 passing the appropriate flag to @code{ptype}, or using @command{set
16013 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16014 display the methods; this is the default. Specifying @code{off} will
16015 cause @value{GDBN} to omit the methods.
16017 @kindex show print type methods
16018 @item show print type methods
16019 This command shows the current setting of method display when printing
16022 @kindex set print type typedefs
16023 @item set print type typedefs
16024 @itemx set print type typedefs on
16025 @itemx set print type typedefs off
16027 Normally, when @value{GDBN} prints a class, it displays any typedefs
16028 defined in that class. You can control this behavior either by
16029 passing the appropriate flag to @code{ptype}, or using @command{set
16030 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16031 display the typedef definitions; this is the default. Specifying
16032 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16033 Note that this controls whether the typedef definition itself is
16034 printed, not whether typedef names are substituted when printing other
16037 @kindex show print type typedefs
16038 @item show print type typedefs
16039 This command shows the current setting of typedef display when
16042 @kindex info address
16043 @cindex address of a symbol
16044 @item info address @var{symbol}
16045 Describe where the data for @var{symbol} is stored. For a register
16046 variable, this says which register it is kept in. For a non-register
16047 local variable, this prints the stack-frame offset at which the variable
16050 Note the contrast with @samp{print &@var{symbol}}, which does not work
16051 at all for a register variable, and for a stack local variable prints
16052 the exact address of the current instantiation of the variable.
16054 @kindex info symbol
16055 @cindex symbol from address
16056 @cindex closest symbol and offset for an address
16057 @item info symbol @var{addr}
16058 Print the name of a symbol which is stored at the address @var{addr}.
16059 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16060 nearest symbol and an offset from it:
16063 (@value{GDBP}) info symbol 0x54320
16064 _initialize_vx + 396 in section .text
16068 This is the opposite of the @code{info address} command. You can use
16069 it to find out the name of a variable or a function given its address.
16071 For dynamically linked executables, the name of executable or shared
16072 library containing the symbol is also printed:
16075 (@value{GDBP}) info symbol 0x400225
16076 _start + 5 in section .text of /tmp/a.out
16077 (@value{GDBP}) info symbol 0x2aaaac2811cf
16078 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16083 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16084 Demangle @var{name}.
16085 If @var{language} is provided it is the name of the language to demangle
16086 @var{name} in. Otherwise @var{name} is demangled in the current language.
16088 The @samp{--} option specifies the end of options,
16089 and is useful when @var{name} begins with a dash.
16091 The parameter @code{demangle-style} specifies how to interpret the kind
16092 of mangling used. @xref{Print Settings}.
16095 @item whatis[/@var{flags}] [@var{arg}]
16096 Print the data type of @var{arg}, which can be either an expression
16097 or a name of a data type. With no argument, print the data type of
16098 @code{$}, the last value in the value history.
16100 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16101 is not actually evaluated, and any side-effecting operations (such as
16102 assignments or function calls) inside it do not take place.
16104 If @var{arg} is a variable or an expression, @code{whatis} prints its
16105 literal type as it is used in the source code. If the type was
16106 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16107 the data type underlying the @code{typedef}. If the type of the
16108 variable or the expression is a compound data type, such as
16109 @code{struct} or @code{class}, @code{whatis} never prints their
16110 fields or methods. It just prints the @code{struct}/@code{class}
16111 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16112 such a compound data type, use @code{ptype}.
16114 If @var{arg} is a type name that was defined using @code{typedef},
16115 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16116 Unrolling means that @code{whatis} will show the underlying type used
16117 in the @code{typedef} declaration of @var{arg}. However, if that
16118 underlying type is also a @code{typedef}, @code{whatis} will not
16121 For C code, the type names may also have the form @samp{class
16122 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16123 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16125 @var{flags} can be used to modify how the type is displayed.
16126 Available flags are:
16130 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16131 parameters and typedefs defined in a class when printing the class'
16132 members. The @code{/r} flag disables this.
16135 Do not print methods defined in the class.
16138 Print methods defined in the class. This is the default, but the flag
16139 exists in case you change the default with @command{set print type methods}.
16142 Do not print typedefs defined in the class. Note that this controls
16143 whether the typedef definition itself is printed, not whether typedef
16144 names are substituted when printing other types.
16147 Print typedefs defined in the class. This is the default, but the flag
16148 exists in case you change the default with @command{set print type typedefs}.
16152 @item ptype[/@var{flags}] [@var{arg}]
16153 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16154 detailed description of the type, instead of just the name of the type.
16155 @xref{Expressions, ,Expressions}.
16157 Contrary to @code{whatis}, @code{ptype} always unrolls any
16158 @code{typedef}s in its argument declaration, whether the argument is
16159 a variable, expression, or a data type. This means that @code{ptype}
16160 of a variable or an expression will not print literally its type as
16161 present in the source code---use @code{whatis} for that. @code{typedef}s at
16162 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16163 fields, methods and inner @code{class typedef}s of @code{struct}s,
16164 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16166 For example, for this variable declaration:
16169 typedef double real_t;
16170 struct complex @{ real_t real; double imag; @};
16171 typedef struct complex complex_t;
16173 real_t *real_pointer_var;
16177 the two commands give this output:
16181 (@value{GDBP}) whatis var
16183 (@value{GDBP}) ptype var
16184 type = struct complex @{
16188 (@value{GDBP}) whatis complex_t
16189 type = struct complex
16190 (@value{GDBP}) whatis struct complex
16191 type = struct complex
16192 (@value{GDBP}) ptype struct complex
16193 type = struct complex @{
16197 (@value{GDBP}) whatis real_pointer_var
16199 (@value{GDBP}) ptype real_pointer_var
16205 As with @code{whatis}, using @code{ptype} without an argument refers to
16206 the type of @code{$}, the last value in the value history.
16208 @cindex incomplete type
16209 Sometimes, programs use opaque data types or incomplete specifications
16210 of complex data structure. If the debug information included in the
16211 program does not allow @value{GDBN} to display a full declaration of
16212 the data type, it will say @samp{<incomplete type>}. For example,
16213 given these declarations:
16217 struct foo *fooptr;
16221 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16224 (@value{GDBP}) ptype foo
16225 $1 = <incomplete type>
16229 ``Incomplete type'' is C terminology for data types that are not
16230 completely specified.
16233 @item info types @var{regexp}
16235 Print a brief description of all types whose names match the regular
16236 expression @var{regexp} (or all types in your program, if you supply
16237 no argument). Each complete typename is matched as though it were a
16238 complete line; thus, @samp{i type value} gives information on all
16239 types in your program whose names include the string @code{value}, but
16240 @samp{i type ^value$} gives information only on types whose complete
16241 name is @code{value}.
16243 This command differs from @code{ptype} in two ways: first, like
16244 @code{whatis}, it does not print a detailed description; second, it
16245 lists all source files where a type is defined.
16247 @kindex info type-printers
16248 @item info type-printers
16249 Versions of @value{GDBN} that ship with Python scripting enabled may
16250 have ``type printers'' available. When using @command{ptype} or
16251 @command{whatis}, these printers are consulted when the name of a type
16252 is needed. @xref{Type Printing API}, for more information on writing
16255 @code{info type-printers} displays all the available type printers.
16257 @kindex enable type-printer
16258 @kindex disable type-printer
16259 @item enable type-printer @var{name}@dots{}
16260 @item disable type-printer @var{name}@dots{}
16261 These commands can be used to enable or disable type printers.
16264 @cindex local variables
16265 @item info scope @var{location}
16266 List all the variables local to a particular scope. This command
16267 accepts a @var{location} argument---a function name, a source line, or
16268 an address preceded by a @samp{*}, and prints all the variables local
16269 to the scope defined by that location. (@xref{Specify Location}, for
16270 details about supported forms of @var{location}.) For example:
16273 (@value{GDBP}) @b{info scope command_line_handler}
16274 Scope for command_line_handler:
16275 Symbol rl is an argument at stack/frame offset 8, length 4.
16276 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16277 Symbol linelength is in static storage at address 0x150a1c, length 4.
16278 Symbol p is a local variable in register $esi, length 4.
16279 Symbol p1 is a local variable in register $ebx, length 4.
16280 Symbol nline is a local variable in register $edx, length 4.
16281 Symbol repeat is a local variable at frame offset -8, length 4.
16285 This command is especially useful for determining what data to collect
16286 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16289 @kindex info source
16291 Show information about the current source file---that is, the source file for
16292 the function containing the current point of execution:
16295 the name of the source file, and the directory containing it,
16297 the directory it was compiled in,
16299 its length, in lines,
16301 which programming language it is written in,
16303 whether the executable includes debugging information for that file, and
16304 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16306 whether the debugging information includes information about
16307 preprocessor macros.
16311 @kindex info sources
16313 Print the names of all source files in your program for which there is
16314 debugging information, organized into two lists: files whose symbols
16315 have already been read, and files whose symbols will be read when needed.
16317 @kindex info functions
16318 @item info functions
16319 Print the names and data types of all defined functions.
16321 @item info functions @var{regexp}
16322 Print the names and data types of all defined functions
16323 whose names contain a match for regular expression @var{regexp}.
16324 Thus, @samp{info fun step} finds all functions whose names
16325 include @code{step}; @samp{info fun ^step} finds those whose names
16326 start with @code{step}. If a function name contains characters
16327 that conflict with the regular expression language (e.g.@:
16328 @samp{operator*()}), they may be quoted with a backslash.
16330 @kindex info variables
16331 @item info variables
16332 Print the names and data types of all variables that are defined
16333 outside of functions (i.e.@: excluding local variables).
16335 @item info variables @var{regexp}
16336 Print the names and data types of all variables (except for local
16337 variables) whose names contain a match for regular expression
16340 @kindex info classes
16341 @cindex Objective-C, classes and selectors
16343 @itemx info classes @var{regexp}
16344 Display all Objective-C classes in your program, or
16345 (with the @var{regexp} argument) all those matching a particular regular
16348 @kindex info selectors
16349 @item info selectors
16350 @itemx info selectors @var{regexp}
16351 Display all Objective-C selectors in your program, or
16352 (with the @var{regexp} argument) all those matching a particular regular
16356 This was never implemented.
16357 @kindex info methods
16359 @itemx info methods @var{regexp}
16360 The @code{info methods} command permits the user to examine all defined
16361 methods within C@t{++} program, or (with the @var{regexp} argument) a
16362 specific set of methods found in the various C@t{++} classes. Many
16363 C@t{++} classes provide a large number of methods. Thus, the output
16364 from the @code{ptype} command can be overwhelming and hard to use. The
16365 @code{info-methods} command filters the methods, printing only those
16366 which match the regular-expression @var{regexp}.
16369 @cindex opaque data types
16370 @kindex set opaque-type-resolution
16371 @item set opaque-type-resolution on
16372 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16373 declared as a pointer to a @code{struct}, @code{class}, or
16374 @code{union}---for example, @code{struct MyType *}---that is used in one
16375 source file although the full declaration of @code{struct MyType} is in
16376 another source file. The default is on.
16378 A change in the setting of this subcommand will not take effect until
16379 the next time symbols for a file are loaded.
16381 @item set opaque-type-resolution off
16382 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16383 is printed as follows:
16385 @{<no data fields>@}
16388 @kindex show opaque-type-resolution
16389 @item show opaque-type-resolution
16390 Show whether opaque types are resolved or not.
16392 @kindex set print symbol-loading
16393 @cindex print messages when symbols are loaded
16394 @item set print symbol-loading
16395 @itemx set print symbol-loading full
16396 @itemx set print symbol-loading brief
16397 @itemx set print symbol-loading off
16398 The @code{set print symbol-loading} command allows you to control the
16399 printing of messages when @value{GDBN} loads symbol information.
16400 By default a message is printed for the executable and one for each
16401 shared library, and normally this is what you want. However, when
16402 debugging apps with large numbers of shared libraries these messages
16404 When set to @code{brief} a message is printed for each executable,
16405 and when @value{GDBN} loads a collection of shared libraries at once
16406 it will only print one message regardless of the number of shared
16407 libraries. When set to @code{off} no messages are printed.
16409 @kindex show print symbol-loading
16410 @item show print symbol-loading
16411 Show whether messages will be printed when a @value{GDBN} command
16412 entered from the keyboard causes symbol information to be loaded.
16414 @kindex maint print symbols
16415 @cindex symbol dump
16416 @kindex maint print psymbols
16417 @cindex partial symbol dump
16418 @kindex maint print msymbols
16419 @cindex minimal symbol dump
16420 @item maint print symbols @var{filename}
16421 @itemx maint print psymbols @var{filename}
16422 @itemx maint print msymbols @var{filename}
16423 Write a dump of debugging symbol data into the file @var{filename}.
16424 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16425 symbols with debugging data are included. If you use @samp{maint print
16426 symbols}, @value{GDBN} includes all the symbols for which it has already
16427 collected full details: that is, @var{filename} reflects symbols for
16428 only those files whose symbols @value{GDBN} has read. You can use the
16429 command @code{info sources} to find out which files these are. If you
16430 use @samp{maint print psymbols} instead, the dump shows information about
16431 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16432 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16433 @samp{maint print msymbols} dumps just the minimal symbol information
16434 required for each object file from which @value{GDBN} has read some symbols.
16435 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16436 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16438 @kindex maint info symtabs
16439 @kindex maint info psymtabs
16440 @cindex listing @value{GDBN}'s internal symbol tables
16441 @cindex symbol tables, listing @value{GDBN}'s internal
16442 @cindex full symbol tables, listing @value{GDBN}'s internal
16443 @cindex partial symbol tables, listing @value{GDBN}'s internal
16444 @item maint info symtabs @r{[} @var{regexp} @r{]}
16445 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16447 List the @code{struct symtab} or @code{struct partial_symtab}
16448 structures whose names match @var{regexp}. If @var{regexp} is not
16449 given, list them all. The output includes expressions which you can
16450 copy into a @value{GDBN} debugging this one to examine a particular
16451 structure in more detail. For example:
16454 (@value{GDBP}) maint info psymtabs dwarf2read
16455 @{ objfile /home/gnu/build/gdb/gdb
16456 ((struct objfile *) 0x82e69d0)
16457 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16458 ((struct partial_symtab *) 0x8474b10)
16461 text addresses 0x814d3c8 -- 0x8158074
16462 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16463 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16464 dependencies (none)
16467 (@value{GDBP}) maint info symtabs
16471 We see that there is one partial symbol table whose filename contains
16472 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16473 and we see that @value{GDBN} has not read in any symtabs yet at all.
16474 If we set a breakpoint on a function, that will cause @value{GDBN} to
16475 read the symtab for the compilation unit containing that function:
16478 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16479 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16481 (@value{GDBP}) maint info symtabs
16482 @{ objfile /home/gnu/build/gdb/gdb
16483 ((struct objfile *) 0x82e69d0)
16484 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16485 ((struct symtab *) 0x86c1f38)
16488 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16489 linetable ((struct linetable *) 0x8370fa0)
16490 debugformat DWARF 2
16499 @chapter Altering Execution
16501 Once you think you have found an error in your program, you might want to
16502 find out for certain whether correcting the apparent error would lead to
16503 correct results in the rest of the run. You can find the answer by
16504 experiment, using the @value{GDBN} features for altering execution of the
16507 For example, you can store new values into variables or memory
16508 locations, give your program a signal, restart it at a different
16509 address, or even return prematurely from a function.
16512 * Assignment:: Assignment to variables
16513 * Jumping:: Continuing at a different address
16514 * Signaling:: Giving your program a signal
16515 * Returning:: Returning from a function
16516 * Calling:: Calling your program's functions
16517 * Patching:: Patching your program
16518 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16522 @section Assignment to Variables
16525 @cindex setting variables
16526 To alter the value of a variable, evaluate an assignment expression.
16527 @xref{Expressions, ,Expressions}. For example,
16534 stores the value 4 into the variable @code{x}, and then prints the
16535 value of the assignment expression (which is 4).
16536 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16537 information on operators in supported languages.
16539 @kindex set variable
16540 @cindex variables, setting
16541 If you are not interested in seeing the value of the assignment, use the
16542 @code{set} command instead of the @code{print} command. @code{set} is
16543 really the same as @code{print} except that the expression's value is
16544 not printed and is not put in the value history (@pxref{Value History,
16545 ,Value History}). The expression is evaluated only for its effects.
16547 If the beginning of the argument string of the @code{set} command
16548 appears identical to a @code{set} subcommand, use the @code{set
16549 variable} command instead of just @code{set}. This command is identical
16550 to @code{set} except for its lack of subcommands. For example, if your
16551 program has a variable @code{width}, you get an error if you try to set
16552 a new value with just @samp{set width=13}, because @value{GDBN} has the
16553 command @code{set width}:
16556 (@value{GDBP}) whatis width
16558 (@value{GDBP}) p width
16560 (@value{GDBP}) set width=47
16561 Invalid syntax in expression.
16565 The invalid expression, of course, is @samp{=47}. In
16566 order to actually set the program's variable @code{width}, use
16569 (@value{GDBP}) set var width=47
16572 Because the @code{set} command has many subcommands that can conflict
16573 with the names of program variables, it is a good idea to use the
16574 @code{set variable} command instead of just @code{set}. For example, if
16575 your program has a variable @code{g}, you run into problems if you try
16576 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16577 the command @code{set gnutarget}, abbreviated @code{set g}:
16581 (@value{GDBP}) whatis g
16585 (@value{GDBP}) set g=4
16589 The program being debugged has been started already.
16590 Start it from the beginning? (y or n) y
16591 Starting program: /home/smith/cc_progs/a.out
16592 "/home/smith/cc_progs/a.out": can't open to read symbols:
16593 Invalid bfd target.
16594 (@value{GDBP}) show g
16595 The current BFD target is "=4".
16600 The program variable @code{g} did not change, and you silently set the
16601 @code{gnutarget} to an invalid value. In order to set the variable
16605 (@value{GDBP}) set var g=4
16608 @value{GDBN} allows more implicit conversions in assignments than C; you can
16609 freely store an integer value into a pointer variable or vice versa,
16610 and you can convert any structure to any other structure that is the
16611 same length or shorter.
16612 @comment FIXME: how do structs align/pad in these conversions?
16613 @comment /doc@cygnus.com 18dec1990
16615 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16616 construct to generate a value of specified type at a specified address
16617 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16618 to memory location @code{0x83040} as an integer (which implies a certain size
16619 and representation in memory), and
16622 set @{int@}0x83040 = 4
16626 stores the value 4 into that memory location.
16629 @section Continuing at a Different Address
16631 Ordinarily, when you continue your program, you do so at the place where
16632 it stopped, with the @code{continue} command. You can instead continue at
16633 an address of your own choosing, with the following commands:
16637 @kindex j @r{(@code{jump})}
16638 @item jump @var{linespec}
16639 @itemx j @var{linespec}
16640 @itemx jump @var{location}
16641 @itemx j @var{location}
16642 Resume execution at line @var{linespec} or at address given by
16643 @var{location}. Execution stops again immediately if there is a
16644 breakpoint there. @xref{Specify Location}, for a description of the
16645 different forms of @var{linespec} and @var{location}. It is common
16646 practice to use the @code{tbreak} command in conjunction with
16647 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16649 The @code{jump} command does not change the current stack frame, or
16650 the stack pointer, or the contents of any memory location or any
16651 register other than the program counter. If line @var{linespec} is in
16652 a different function from the one currently executing, the results may
16653 be bizarre if the two functions expect different patterns of arguments or
16654 of local variables. For this reason, the @code{jump} command requests
16655 confirmation if the specified line is not in the function currently
16656 executing. However, even bizarre results are predictable if you are
16657 well acquainted with the machine-language code of your program.
16660 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16661 On many systems, you can get much the same effect as the @code{jump}
16662 command by storing a new value into the register @code{$pc}. The
16663 difference is that this does not start your program running; it only
16664 changes the address of where it @emph{will} run when you continue. For
16672 makes the next @code{continue} command or stepping command execute at
16673 address @code{0x485}, rather than at the address where your program stopped.
16674 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16676 The most common occasion to use the @code{jump} command is to back
16677 up---perhaps with more breakpoints set---over a portion of a program
16678 that has already executed, in order to examine its execution in more
16683 @section Giving your Program a Signal
16684 @cindex deliver a signal to a program
16688 @item signal @var{signal}
16689 Resume execution where your program is stopped, but immediately give it the
16690 signal @var{signal}. The @var{signal} can be the name or the number of a
16691 signal. For example, on many systems @code{signal 2} and @code{signal
16692 SIGINT} are both ways of sending an interrupt signal.
16694 Alternatively, if @var{signal} is zero, continue execution without
16695 giving a signal. This is useful when your program stopped on account of
16696 a signal and would ordinarily see the signal when resumed with the
16697 @code{continue} command; @samp{signal 0} causes it to resume without a
16700 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16701 delivered to the currently selected thread, not the thread that last
16702 reported a stop. This includes the situation where a thread was
16703 stopped due to a signal. So if you want to continue execution
16704 suppressing the signal that stopped a thread, you should select that
16705 same thread before issuing the @samp{signal 0} command. If you issue
16706 the @samp{signal 0} command with another thread as the selected one,
16707 @value{GDBN} detects that and asks for confirmation.
16709 Invoking the @code{signal} command is not the same as invoking the
16710 @code{kill} utility from the shell. Sending a signal with @code{kill}
16711 causes @value{GDBN} to decide what to do with the signal depending on
16712 the signal handling tables (@pxref{Signals}). The @code{signal} command
16713 passes the signal directly to your program.
16715 @code{signal} does not repeat when you press @key{RET} a second time
16716 after executing the command.
16718 @kindex queue-signal
16719 @item queue-signal @var{signal}
16720 Queue @var{signal} to be delivered immediately to the current thread
16721 when execution of the thread resumes. The @var{signal} can be the name or
16722 the number of a signal. For example, on many systems @code{signal 2} and
16723 @code{signal SIGINT} are both ways of sending an interrupt signal.
16724 The handling of the signal must be set to pass the signal to the program,
16725 otherwise @value{GDBN} will report an error.
16726 You can control the handling of signals from @value{GDBN} with the
16727 @code{handle} command (@pxref{Signals}).
16729 Alternatively, if @var{signal} is zero, any currently queued signal
16730 for the current thread is discarded and when execution resumes no signal
16731 will be delivered. This is useful when your program stopped on account
16732 of a signal and would ordinarily see the signal when resumed with the
16733 @code{continue} command.
16735 This command differs from the @code{signal} command in that the signal
16736 is just queued, execution is not resumed. And @code{queue-signal} cannot
16737 be used to pass a signal whose handling state has been set to @code{nopass}
16742 @xref{stepping into signal handlers}, for information on how stepping
16743 commands behave when the thread has a signal queued.
16746 @section Returning from a Function
16749 @cindex returning from a function
16752 @itemx return @var{expression}
16753 You can cancel execution of a function call with the @code{return}
16754 command. If you give an
16755 @var{expression} argument, its value is used as the function's return
16759 When you use @code{return}, @value{GDBN} discards the selected stack frame
16760 (and all frames within it). You can think of this as making the
16761 discarded frame return prematurely. If you wish to specify a value to
16762 be returned, give that value as the argument to @code{return}.
16764 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16765 Frame}), and any other frames inside of it, leaving its caller as the
16766 innermost remaining frame. That frame becomes selected. The
16767 specified value is stored in the registers used for returning values
16770 The @code{return} command does not resume execution; it leaves the
16771 program stopped in the state that would exist if the function had just
16772 returned. In contrast, the @code{finish} command (@pxref{Continuing
16773 and Stepping, ,Continuing and Stepping}) resumes execution until the
16774 selected stack frame returns naturally.
16776 @value{GDBN} needs to know how the @var{expression} argument should be set for
16777 the inferior. The concrete registers assignment depends on the OS ABI and the
16778 type being returned by the selected stack frame. For example it is common for
16779 OS ABI to return floating point values in FPU registers while integer values in
16780 CPU registers. Still some ABIs return even floating point values in CPU
16781 registers. Larger integer widths (such as @code{long long int}) also have
16782 specific placement rules. @value{GDBN} already knows the OS ABI from its
16783 current target so it needs to find out also the type being returned to make the
16784 assignment into the right register(s).
16786 Normally, the selected stack frame has debug info. @value{GDBN} will always
16787 use the debug info instead of the implicit type of @var{expression} when the
16788 debug info is available. For example, if you type @kbd{return -1}, and the
16789 function in the current stack frame is declared to return a @code{long long
16790 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16791 into a @code{long long int}:
16794 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16796 (@value{GDBP}) return -1
16797 Make func return now? (y or n) y
16798 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16799 43 printf ("result=%lld\n", func ());
16803 However, if the selected stack frame does not have a debug info, e.g., if the
16804 function was compiled without debug info, @value{GDBN} has to find out the type
16805 to return from user. Specifying a different type by mistake may set the value
16806 in different inferior registers than the caller code expects. For example,
16807 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16808 of a @code{long long int} result for a debug info less function (on 32-bit
16809 architectures). Therefore the user is required to specify the return type by
16810 an appropriate cast explicitly:
16813 Breakpoint 2, 0x0040050b in func ()
16814 (@value{GDBP}) return -1
16815 Return value type not available for selected stack frame.
16816 Please use an explicit cast of the value to return.
16817 (@value{GDBP}) return (long long int) -1
16818 Make selected stack frame return now? (y or n) y
16819 #0 0x00400526 in main ()
16824 @section Calling Program Functions
16827 @cindex calling functions
16828 @cindex inferior functions, calling
16829 @item print @var{expr}
16830 Evaluate the expression @var{expr} and display the resulting value.
16831 The expression may include calls to functions in the program being
16835 @item call @var{expr}
16836 Evaluate the expression @var{expr} without displaying @code{void}
16839 You can use this variant of the @code{print} command if you want to
16840 execute a function from your program that does not return anything
16841 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16842 with @code{void} returned values that @value{GDBN} will otherwise
16843 print. If the result is not void, it is printed and saved in the
16847 It is possible for the function you call via the @code{print} or
16848 @code{call} command to generate a signal (e.g., if there's a bug in
16849 the function, or if you passed it incorrect arguments). What happens
16850 in that case is controlled by the @code{set unwindonsignal} command.
16852 Similarly, with a C@t{++} program it is possible for the function you
16853 call via the @code{print} or @code{call} command to generate an
16854 exception that is not handled due to the constraints of the dummy
16855 frame. In this case, any exception that is raised in the frame, but has
16856 an out-of-frame exception handler will not be found. GDB builds a
16857 dummy-frame for the inferior function call, and the unwinder cannot
16858 seek for exception handlers outside of this dummy-frame. What happens
16859 in that case is controlled by the
16860 @code{set unwind-on-terminating-exception} command.
16863 @item set unwindonsignal
16864 @kindex set unwindonsignal
16865 @cindex unwind stack in called functions
16866 @cindex call dummy stack unwinding
16867 Set unwinding of the stack if a signal is received while in a function
16868 that @value{GDBN} called in the program being debugged. If set to on,
16869 @value{GDBN} unwinds the stack it created for the call and restores
16870 the context to what it was before the call. If set to off (the
16871 default), @value{GDBN} stops in the frame where the signal was
16874 @item show unwindonsignal
16875 @kindex show unwindonsignal
16876 Show the current setting of stack unwinding in the functions called by
16879 @item set unwind-on-terminating-exception
16880 @kindex set unwind-on-terminating-exception
16881 @cindex unwind stack in called functions with unhandled exceptions
16882 @cindex call dummy stack unwinding on unhandled exception.
16883 Set unwinding of the stack if a C@t{++} exception is raised, but left
16884 unhandled while in a function that @value{GDBN} called in the program being
16885 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16886 it created for the call and restores the context to what it was before
16887 the call. If set to off, @value{GDBN} the exception is delivered to
16888 the default C@t{++} exception handler and the inferior terminated.
16890 @item show unwind-on-terminating-exception
16891 @kindex show unwind-on-terminating-exception
16892 Show the current setting of stack unwinding in the functions called by
16897 @cindex weak alias functions
16898 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16899 for another function. In such case, @value{GDBN} might not pick up
16900 the type information, including the types of the function arguments,
16901 which causes @value{GDBN} to call the inferior function incorrectly.
16902 As a result, the called function will function erroneously and may
16903 even crash. A solution to that is to use the name of the aliased
16907 @section Patching Programs
16909 @cindex patching binaries
16910 @cindex writing into executables
16911 @cindex writing into corefiles
16913 By default, @value{GDBN} opens the file containing your program's
16914 executable code (or the corefile) read-only. This prevents accidental
16915 alterations to machine code; but it also prevents you from intentionally
16916 patching your program's binary.
16918 If you'd like to be able to patch the binary, you can specify that
16919 explicitly with the @code{set write} command. For example, you might
16920 want to turn on internal debugging flags, or even to make emergency
16926 @itemx set write off
16927 If you specify @samp{set write on}, @value{GDBN} opens executable and
16928 core files for both reading and writing; if you specify @kbd{set write
16929 off} (the default), @value{GDBN} opens them read-only.
16931 If you have already loaded a file, you must load it again (using the
16932 @code{exec-file} or @code{core-file} command) after changing @code{set
16933 write}, for your new setting to take effect.
16937 Display whether executable files and core files are opened for writing
16938 as well as reading.
16941 @node Compiling and Injecting Code
16942 @section Compiling and injecting code in @value{GDBN}
16943 @cindex injecting code
16944 @cindex writing into executables
16945 @cindex compiling code
16947 @value{GDBN} supports on-demand compilation and code injection into
16948 programs running under @value{GDBN}. GCC 5.0 or higher built with
16949 @file{libcc1.so} must be installed for this functionality to be enabled.
16950 This functionality is implemented with the following commands.
16953 @kindex compile code
16954 @item compile code @var{source-code}
16955 @itemx compile code -raw @var{--} @var{source-code}
16956 Compile @var{source-code} with the compiler language found as the current
16957 language in @value{GDBN} (@pxref{Languages}). If compilation and
16958 injection is not supported with the current language specified in
16959 @value{GDBN}, or the compiler does not support this feature, an error
16960 message will be printed. If @var{source-code} compiles and links
16961 successfully, @value{GDBN} will load the object-code emitted,
16962 and execute it within the context of the currently selected inferior.
16963 It is important to note that the compiled code is executed immediately.
16964 After execution, the compiled code is removed from @value{GDBN} and any
16965 new types or variables you have defined will be deleted.
16967 The command allows you to specify @var{source-code} in two ways.
16968 The simplest method is to provide a single line of code to the command.
16972 compile code printf ("hello world\n");
16975 If you specify options on the command line as well as source code, they
16976 may conflict. The @samp{--} delimiter can be used to separate options
16977 from actual source code. E.g.:
16980 compile code -r -- printf ("hello world\n");
16983 Alternatively you can enter source code as multiple lines of text. To
16984 enter this mode, invoke the @samp{compile code} command without any text
16985 following the command. This will start the multiple-line editor and
16986 allow you to type as many lines of source code as required. When you
16987 have completed typing, enter @samp{end} on its own line to exit the
16992 >printf ("hello\n");
16993 >printf ("world\n");
16997 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
16998 provided @var{source-code} in a callable scope. In this case, you must
16999 specify the entry point of the code by defining a function named
17000 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17001 inferior. Using @samp{-raw} option may be needed for example when
17002 @var{source-code} requires @samp{#include} lines which may conflict with
17003 inferior symbols otherwise.
17005 @kindex compile file
17006 @item compile file @var{filename}
17007 @itemx compile file -raw @var{filename}
17008 Like @code{compile code}, but take the source code from @var{filename}.
17011 compile file /home/user/example.c
17015 @subsection Caveats when using the @code{compile} command
17017 There are a few caveats to keep in mind when using the @code{compile}
17018 command. As the caveats are different per language, the table below
17019 highlights specific issues on a per language basis.
17022 @item C code examples and caveats
17023 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17024 attempt to compile the source code with a @samp{C} compiler. The source
17025 code provided to the @code{compile} command will have much the same
17026 access to variables and types as it normally would if it were part of
17027 the program currently being debugged in @value{GDBN}.
17029 Below is a sample program that forms the basis of the examples that
17030 follow. This program has been compiled and loaded into @value{GDBN},
17031 much like any other normal debugging session.
17034 void function1 (void)
17037 printf ("function 1\n");
17040 void function2 (void)
17055 For the purposes of the examples in this section, the program above has
17056 been compiled, loaded into @value{GDBN}, stopped at the function
17057 @code{main}, and @value{GDBN} is awaiting input from the user.
17059 To access variables and types for any program in @value{GDBN}, the
17060 program must be compiled and packaged with debug information. The
17061 @code{compile} command is not an exception to this rule. Without debug
17062 information, you can still use the @code{compile} command, but you will
17063 be very limited in what variables and types you can access.
17065 So with that in mind, the example above has been compiled with debug
17066 information enabled. The @code{compile} command will have access to
17067 all variables and types (except those that may have been optimized
17068 out). Currently, as @value{GDBN} has stopped the program in the
17069 @code{main} function, the @code{compile} command would have access to
17070 the variable @code{k}. You could invoke the @code{compile} command
17071 and type some source code to set the value of @code{k}. You can also
17072 read it, or do anything with that variable you would normally do in
17073 @code{C}. Be aware that changes to inferior variables in the
17074 @code{compile} command are persistent. In the following example:
17077 compile code k = 3;
17081 the variable @code{k} is now 3. It will retain that value until
17082 something else in the example program changes it, or another
17083 @code{compile} command changes it.
17085 Normal scope and access rules apply to source code compiled and
17086 injected by the @code{compile} command. In the example, the variables
17087 @code{j} and @code{k} are not accessible yet, because the program is
17088 currently stopped in the @code{main} function, where these variables
17089 are not in scope. Therefore, the following command
17092 compile code j = 3;
17096 will result in a compilation error message.
17098 Once the program is continued, execution will bring these variables in
17099 scope, and they will become accessible; then the code you specify via
17100 the @code{compile} command will be able to access them.
17102 You can create variables and types with the @code{compile} command as
17103 part of your source code. Variables and types that are created as part
17104 of the @code{compile} command are not visible to the rest of the program for
17105 the duration of its run. This example is valid:
17108 compile code int ff = 5; printf ("ff is %d\n", ff);
17111 However, if you were to type the following into @value{GDBN} after that
17112 command has completed:
17115 compile code printf ("ff is %d\n'', ff);
17119 a compiler error would be raised as the variable @code{ff} no longer
17120 exists. Object code generated and injected by the @code{compile}
17121 command is removed when its execution ends. Caution is advised
17122 when assigning to program variables values of variables created by the
17123 code submitted to the @code{compile} command. This example is valid:
17126 compile code int ff = 5; k = ff;
17129 The value of the variable @code{ff} is assigned to @code{k}. The variable
17130 @code{k} does not require the existence of @code{ff} to maintain the value
17131 it has been assigned. However, pointers require particular care in
17132 assignment. If the source code compiled with the @code{compile} command
17133 changed the address of a pointer in the example program, perhaps to a
17134 variable created in the @code{compile} command, that pointer would point
17135 to an invalid location when the command exits. The following example
17136 would likely cause issues with your debugged program:
17139 compile code int ff = 5; p = &ff;
17142 In this example, @code{p} would point to @code{ff} when the
17143 @code{compile} command is executing the source code provided to it.
17144 However, as variables in the (example) program persist with their
17145 assigned values, the variable @code{p} would point to an invalid
17146 location when the command exists. A general rule should be followed
17147 in that you should either assign @code{NULL} to any assigned pointers,
17148 or restore a valid location to the pointer before the command exits.
17150 Similar caution must be exercised with any structs, unions, and typedefs
17151 defined in @code{compile} command. Types defined in the @code{compile}
17152 command will no longer be available in the next @code{compile} command.
17153 Therefore, if you cast a variable to a type defined in the
17154 @code{compile} command, care must be taken to ensure that any future
17155 need to resolve the type can be achieved.
17158 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17159 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17160 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17161 Compilation failed.
17162 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17166 Variables that have been optimized away by the compiler are not
17167 accessible to the code submitted to the @code{compile} command.
17168 Access to those variables will generate a compiler error which @value{GDBN}
17169 will print to the console.
17173 @chapter @value{GDBN} Files
17175 @value{GDBN} needs to know the file name of the program to be debugged,
17176 both in order to read its symbol table and in order to start your
17177 program. To debug a core dump of a previous run, you must also tell
17178 @value{GDBN} the name of the core dump file.
17181 * Files:: Commands to specify files
17182 * Separate Debug Files:: Debugging information in separate files
17183 * MiniDebugInfo:: Debugging information in a special section
17184 * Index Files:: Index files speed up GDB
17185 * Symbol Errors:: Errors reading symbol files
17186 * Data Files:: GDB data files
17190 @section Commands to Specify Files
17192 @cindex symbol table
17193 @cindex core dump file
17195 You may want to specify executable and core dump file names. The usual
17196 way to do this is at start-up time, using the arguments to
17197 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17198 Out of @value{GDBN}}).
17200 Occasionally it is necessary to change to a different file during a
17201 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17202 specify a file you want to use. Or you are debugging a remote target
17203 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17204 Program}). In these situations the @value{GDBN} commands to specify
17205 new files are useful.
17208 @cindex executable file
17210 @item file @var{filename}
17211 Use @var{filename} as the program to be debugged. It is read for its
17212 symbols and for the contents of pure memory. It is also the program
17213 executed when you use the @code{run} command. If you do not specify a
17214 directory and the file is not found in the @value{GDBN} working directory,
17215 @value{GDBN} uses the environment variable @code{PATH} as a list of
17216 directories to search, just as the shell does when looking for a program
17217 to run. You can change the value of this variable, for both @value{GDBN}
17218 and your program, using the @code{path} command.
17220 @cindex unlinked object files
17221 @cindex patching object files
17222 You can load unlinked object @file{.o} files into @value{GDBN} using
17223 the @code{file} command. You will not be able to ``run'' an object
17224 file, but you can disassemble functions and inspect variables. Also,
17225 if the underlying BFD functionality supports it, you could use
17226 @kbd{gdb -write} to patch object files using this technique. Note
17227 that @value{GDBN} can neither interpret nor modify relocations in this
17228 case, so branches and some initialized variables will appear to go to
17229 the wrong place. But this feature is still handy from time to time.
17232 @code{file} with no argument makes @value{GDBN} discard any information it
17233 has on both executable file and the symbol table.
17236 @item exec-file @r{[} @var{filename} @r{]}
17237 Specify that the program to be run (but not the symbol table) is found
17238 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17239 if necessary to locate your program. Omitting @var{filename} means to
17240 discard information on the executable file.
17242 @kindex symbol-file
17243 @item symbol-file @r{[} @var{filename} @r{]}
17244 Read symbol table information from file @var{filename}. @code{PATH} is
17245 searched when necessary. Use the @code{file} command to get both symbol
17246 table and program to run from the same file.
17248 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17249 program's symbol table.
17251 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17252 some breakpoints and auto-display expressions. This is because they may
17253 contain pointers to the internal data recording symbols and data types,
17254 which are part of the old symbol table data being discarded inside
17257 @code{symbol-file} does not repeat if you press @key{RET} again after
17260 When @value{GDBN} is configured for a particular environment, it
17261 understands debugging information in whatever format is the standard
17262 generated for that environment; you may use either a @sc{gnu} compiler, or
17263 other compilers that adhere to the local conventions.
17264 Best results are usually obtained from @sc{gnu} compilers; for example,
17265 using @code{@value{NGCC}} you can generate debugging information for
17268 For most kinds of object files, with the exception of old SVR3 systems
17269 using COFF, the @code{symbol-file} command does not normally read the
17270 symbol table in full right away. Instead, it scans the symbol table
17271 quickly to find which source files and which symbols are present. The
17272 details are read later, one source file at a time, as they are needed.
17274 The purpose of this two-stage reading strategy is to make @value{GDBN}
17275 start up faster. For the most part, it is invisible except for
17276 occasional pauses while the symbol table details for a particular source
17277 file are being read. (The @code{set verbose} command can turn these
17278 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17279 Warnings and Messages}.)
17281 We have not implemented the two-stage strategy for COFF yet. When the
17282 symbol table is stored in COFF format, @code{symbol-file} reads the
17283 symbol table data in full right away. Note that ``stabs-in-COFF''
17284 still does the two-stage strategy, since the debug info is actually
17288 @cindex reading symbols immediately
17289 @cindex symbols, reading immediately
17290 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17291 @itemx file @r{[} -readnow @r{]} @var{filename}
17292 You can override the @value{GDBN} two-stage strategy for reading symbol
17293 tables by using the @samp{-readnow} option with any of the commands that
17294 load symbol table information, if you want to be sure @value{GDBN} has the
17295 entire symbol table available.
17297 @c FIXME: for now no mention of directories, since this seems to be in
17298 @c flux. 13mar1992 status is that in theory GDB would look either in
17299 @c current dir or in same dir as myprog; but issues like competing
17300 @c GDB's, or clutter in system dirs, mean that in practice right now
17301 @c only current dir is used. FFish says maybe a special GDB hierarchy
17302 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17306 @item core-file @r{[}@var{filename}@r{]}
17308 Specify the whereabouts of a core dump file to be used as the ``contents
17309 of memory''. Traditionally, core files contain only some parts of the
17310 address space of the process that generated them; @value{GDBN} can access the
17311 executable file itself for other parts.
17313 @code{core-file} with no argument specifies that no core file is
17316 Note that the core file is ignored when your program is actually running
17317 under @value{GDBN}. So, if you have been running your program and you
17318 wish to debug a core file instead, you must kill the subprocess in which
17319 the program is running. To do this, use the @code{kill} command
17320 (@pxref{Kill Process, ,Killing the Child Process}).
17322 @kindex add-symbol-file
17323 @cindex dynamic linking
17324 @item add-symbol-file @var{filename} @var{address}
17325 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17326 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17327 The @code{add-symbol-file} command reads additional symbol table
17328 information from the file @var{filename}. You would use this command
17329 when @var{filename} has been dynamically loaded (by some other means)
17330 into the program that is running. The @var{address} should give the memory
17331 address at which the file has been loaded; @value{GDBN} cannot figure
17332 this out for itself. You can additionally specify an arbitrary number
17333 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17334 section name and base address for that section. You can specify any
17335 @var{address} as an expression.
17337 The symbol table of the file @var{filename} is added to the symbol table
17338 originally read with the @code{symbol-file} command. You can use the
17339 @code{add-symbol-file} command any number of times; the new symbol data
17340 thus read is kept in addition to the old.
17342 Changes can be reverted using the command @code{remove-symbol-file}.
17344 @cindex relocatable object files, reading symbols from
17345 @cindex object files, relocatable, reading symbols from
17346 @cindex reading symbols from relocatable object files
17347 @cindex symbols, reading from relocatable object files
17348 @cindex @file{.o} files, reading symbols from
17349 Although @var{filename} is typically a shared library file, an
17350 executable file, or some other object file which has been fully
17351 relocated for loading into a process, you can also load symbolic
17352 information from relocatable @file{.o} files, as long as:
17356 the file's symbolic information refers only to linker symbols defined in
17357 that file, not to symbols defined by other object files,
17359 every section the file's symbolic information refers to has actually
17360 been loaded into the inferior, as it appears in the file, and
17362 you can determine the address at which every section was loaded, and
17363 provide these to the @code{add-symbol-file} command.
17367 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17368 relocatable files into an already running program; such systems
17369 typically make the requirements above easy to meet. However, it's
17370 important to recognize that many native systems use complex link
17371 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17372 assembly, for example) that make the requirements difficult to meet. In
17373 general, one cannot assume that using @code{add-symbol-file} to read a
17374 relocatable object file's symbolic information will have the same effect
17375 as linking the relocatable object file into the program in the normal
17378 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17380 @kindex remove-symbol-file
17381 @item remove-symbol-file @var{filename}
17382 @item remove-symbol-file -a @var{address}
17383 Remove a symbol file added via the @code{add-symbol-file} command. The
17384 file to remove can be identified by its @var{filename} or by an @var{address}
17385 that lies within the boundaries of this symbol file in memory. Example:
17388 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17389 add symbol table from file "/home/user/gdb/mylib.so" at
17390 .text_addr = 0x7ffff7ff9480
17392 Reading symbols from /home/user/gdb/mylib.so...done.
17393 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17394 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17399 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17401 @kindex add-symbol-file-from-memory
17402 @cindex @code{syscall DSO}
17403 @cindex load symbols from memory
17404 @item add-symbol-file-from-memory @var{address}
17405 Load symbols from the given @var{address} in a dynamically loaded
17406 object file whose image is mapped directly into the inferior's memory.
17407 For example, the Linux kernel maps a @code{syscall DSO} into each
17408 process's address space; this DSO provides kernel-specific code for
17409 some system calls. The argument can be any expression whose
17410 evaluation yields the address of the file's shared object file header.
17411 For this command to work, you must have used @code{symbol-file} or
17412 @code{exec-file} commands in advance.
17415 @item section @var{section} @var{addr}
17416 The @code{section} command changes the base address of the named
17417 @var{section} of the exec file to @var{addr}. This can be used if the
17418 exec file does not contain section addresses, (such as in the
17419 @code{a.out} format), or when the addresses specified in the file
17420 itself are wrong. Each section must be changed separately. The
17421 @code{info files} command, described below, lists all the sections and
17425 @kindex info target
17428 @code{info files} and @code{info target} are synonymous; both print the
17429 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17430 including the names of the executable and core dump files currently in
17431 use by @value{GDBN}, and the files from which symbols were loaded. The
17432 command @code{help target} lists all possible targets rather than
17435 @kindex maint info sections
17436 @item maint info sections
17437 Another command that can give you extra information about program sections
17438 is @code{maint info sections}. In addition to the section information
17439 displayed by @code{info files}, this command displays the flags and file
17440 offset of each section in the executable and core dump files. In addition,
17441 @code{maint info sections} provides the following command options (which
17442 may be arbitrarily combined):
17446 Display sections for all loaded object files, including shared libraries.
17447 @item @var{sections}
17448 Display info only for named @var{sections}.
17449 @item @var{section-flags}
17450 Display info only for sections for which @var{section-flags} are true.
17451 The section flags that @value{GDBN} currently knows about are:
17454 Section will have space allocated in the process when loaded.
17455 Set for all sections except those containing debug information.
17457 Section will be loaded from the file into the child process memory.
17458 Set for pre-initialized code and data, clear for @code{.bss} sections.
17460 Section needs to be relocated before loading.
17462 Section cannot be modified by the child process.
17464 Section contains executable code only.
17466 Section contains data only (no executable code).
17468 Section will reside in ROM.
17470 Section contains data for constructor/destructor lists.
17472 Section is not empty.
17474 An instruction to the linker to not output the section.
17475 @item COFF_SHARED_LIBRARY
17476 A notification to the linker that the section contains
17477 COFF shared library information.
17479 Section contains common symbols.
17482 @kindex set trust-readonly-sections
17483 @cindex read-only sections
17484 @item set trust-readonly-sections on
17485 Tell @value{GDBN} that readonly sections in your object file
17486 really are read-only (i.e.@: that their contents will not change).
17487 In that case, @value{GDBN} can fetch values from these sections
17488 out of the object file, rather than from the target program.
17489 For some targets (notably embedded ones), this can be a significant
17490 enhancement to debugging performance.
17492 The default is off.
17494 @item set trust-readonly-sections off
17495 Tell @value{GDBN} not to trust readonly sections. This means that
17496 the contents of the section might change while the program is running,
17497 and must therefore be fetched from the target when needed.
17499 @item show trust-readonly-sections
17500 Show the current setting of trusting readonly sections.
17503 All file-specifying commands allow both absolute and relative file names
17504 as arguments. @value{GDBN} always converts the file name to an absolute file
17505 name and remembers it that way.
17507 @cindex shared libraries
17508 @anchor{Shared Libraries}
17509 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17510 and IBM RS/6000 AIX shared libraries.
17512 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17513 shared libraries. @xref{Expat}.
17515 @value{GDBN} automatically loads symbol definitions from shared libraries
17516 when you use the @code{run} command, or when you examine a core file.
17517 (Before you issue the @code{run} command, @value{GDBN} does not understand
17518 references to a function in a shared library, however---unless you are
17519 debugging a core file).
17521 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17522 automatically loads the symbols at the time of the @code{shl_load} call.
17524 @c FIXME: some @value{GDBN} release may permit some refs to undef
17525 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17526 @c FIXME...lib; check this from time to time when updating manual
17528 There are times, however, when you may wish to not automatically load
17529 symbol definitions from shared libraries, such as when they are
17530 particularly large or there are many of them.
17532 To control the automatic loading of shared library symbols, use the
17536 @kindex set auto-solib-add
17537 @item set auto-solib-add @var{mode}
17538 If @var{mode} is @code{on}, symbols from all shared object libraries
17539 will be loaded automatically when the inferior begins execution, you
17540 attach to an independently started inferior, or when the dynamic linker
17541 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17542 is @code{off}, symbols must be loaded manually, using the
17543 @code{sharedlibrary} command. The default value is @code{on}.
17545 @cindex memory used for symbol tables
17546 If your program uses lots of shared libraries with debug info that
17547 takes large amounts of memory, you can decrease the @value{GDBN}
17548 memory footprint by preventing it from automatically loading the
17549 symbols from shared libraries. To that end, type @kbd{set
17550 auto-solib-add off} before running the inferior, then load each
17551 library whose debug symbols you do need with @kbd{sharedlibrary
17552 @var{regexp}}, where @var{regexp} is a regular expression that matches
17553 the libraries whose symbols you want to be loaded.
17555 @kindex show auto-solib-add
17556 @item show auto-solib-add
17557 Display the current autoloading mode.
17560 @cindex load shared library
17561 To explicitly load shared library symbols, use the @code{sharedlibrary}
17565 @kindex info sharedlibrary
17567 @item info share @var{regex}
17568 @itemx info sharedlibrary @var{regex}
17569 Print the names of the shared libraries which are currently loaded
17570 that match @var{regex}. If @var{regex} is omitted then print
17571 all shared libraries that are loaded.
17573 @kindex sharedlibrary
17575 @item sharedlibrary @var{regex}
17576 @itemx share @var{regex}
17577 Load shared object library symbols for files matching a
17578 Unix regular expression.
17579 As with files loaded automatically, it only loads shared libraries
17580 required by your program for a core file or after typing @code{run}. If
17581 @var{regex} is omitted all shared libraries required by your program are
17584 @item nosharedlibrary
17585 @kindex nosharedlibrary
17586 @cindex unload symbols from shared libraries
17587 Unload all shared object library symbols. This discards all symbols
17588 that have been loaded from all shared libraries. Symbols from shared
17589 libraries that were loaded by explicit user requests are not
17593 Sometimes you may wish that @value{GDBN} stops and gives you control
17594 when any of shared library events happen. The best way to do this is
17595 to use @code{catch load} and @code{catch unload} (@pxref{Set
17598 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17599 command for this. This command exists for historical reasons. It is
17600 less useful than setting a catchpoint, because it does not allow for
17601 conditions or commands as a catchpoint does.
17604 @item set stop-on-solib-events
17605 @kindex set stop-on-solib-events
17606 This command controls whether @value{GDBN} should give you control
17607 when the dynamic linker notifies it about some shared library event.
17608 The most common event of interest is loading or unloading of a new
17611 @item show stop-on-solib-events
17612 @kindex show stop-on-solib-events
17613 Show whether @value{GDBN} stops and gives you control when shared
17614 library events happen.
17617 Shared libraries are also supported in many cross or remote debugging
17618 configurations. @value{GDBN} needs to have access to the target's libraries;
17619 this can be accomplished either by providing copies of the libraries
17620 on the host system, or by asking @value{GDBN} to automatically retrieve the
17621 libraries from the target. If copies of the target libraries are
17622 provided, they need to be the same as the target libraries, although the
17623 copies on the target can be stripped as long as the copies on the host are
17626 @cindex where to look for shared libraries
17627 For remote debugging, you need to tell @value{GDBN} where the target
17628 libraries are, so that it can load the correct copies---otherwise, it
17629 may try to load the host's libraries. @value{GDBN} has two variables
17630 to specify the search directories for target libraries.
17633 @cindex prefix for shared library file names
17634 @cindex system root, alternate
17635 @kindex set solib-absolute-prefix
17636 @kindex set sysroot
17637 @item set sysroot @var{path}
17638 Use @var{path} as the system root for the program being debugged. Any
17639 absolute shared library paths will be prefixed with @var{path}; many
17640 runtime loaders store the absolute paths to the shared library in the
17641 target program's memory. If you use @code{set sysroot} to find shared
17642 libraries, they need to be laid out in the same way that they are on
17643 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17646 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17647 retrieve the target libraries from the remote system. This is only
17648 supported when using a remote target that supports the @code{remote get}
17649 command (@pxref{File Transfer,,Sending files to a remote system}).
17650 The part of @var{path} following the initial @file{remote:}
17651 (if present) is used as system root prefix on the remote file system.
17652 @footnote{If you want to specify a local system root using a directory
17653 that happens to be named @file{remote:}, you need to use some equivalent
17654 variant of the name like @file{./remote:}.}
17656 For targets with an MS-DOS based filesystem, such as MS-Windows and
17657 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17658 absolute file name with @var{path}. But first, on Unix hosts,
17659 @value{GDBN} converts all backslash directory separators into forward
17660 slashes, because the backslash is not a directory separator on Unix:
17663 c:\foo\bar.dll @result{} c:/foo/bar.dll
17666 Then, @value{GDBN} attempts prefixing the target file name with
17667 @var{path}, and looks for the resulting file name in the host file
17671 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17674 If that does not find the shared library, @value{GDBN} tries removing
17675 the @samp{:} character from the drive spec, both for convenience, and,
17676 for the case of the host file system not supporting file names with
17680 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17683 This makes it possible to have a system root that mirrors a target
17684 with more than one drive. E.g., you may want to setup your local
17685 copies of the target system shared libraries like so (note @samp{c} vs
17689 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17690 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17691 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17695 and point the system root at @file{/path/to/sysroot}, so that
17696 @value{GDBN} can find the correct copies of both
17697 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17699 If that still does not find the shared library, @value{GDBN} tries
17700 removing the whole drive spec from the target file name:
17703 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17706 This last lookup makes it possible to not care about the drive name,
17707 if you don't want or need to.
17709 The @code{set solib-absolute-prefix} command is an alias for @code{set
17712 @cindex default system root
17713 @cindex @samp{--with-sysroot}
17714 You can set the default system root by using the configure-time
17715 @samp{--with-sysroot} option. If the system root is inside
17716 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17717 @samp{--exec-prefix}), then the default system root will be updated
17718 automatically if the installed @value{GDBN} is moved to a new
17721 @kindex show sysroot
17723 Display the current shared library prefix.
17725 @kindex set solib-search-path
17726 @item set solib-search-path @var{path}
17727 If this variable is set, @var{path} is a colon-separated list of
17728 directories to search for shared libraries. @samp{solib-search-path}
17729 is used after @samp{sysroot} fails to locate the library, or if the
17730 path to the library is relative instead of absolute. If you want to
17731 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17732 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17733 finding your host's libraries. @samp{sysroot} is preferred; setting
17734 it to a nonexistent directory may interfere with automatic loading
17735 of shared library symbols.
17737 @kindex show solib-search-path
17738 @item show solib-search-path
17739 Display the current shared library search path.
17741 @cindex DOS file-name semantics of file names.
17742 @kindex set target-file-system-kind (unix|dos-based|auto)
17743 @kindex show target-file-system-kind
17744 @item set target-file-system-kind @var{kind}
17745 Set assumed file system kind for target reported file names.
17747 Shared library file names as reported by the target system may not
17748 make sense as is on the system @value{GDBN} is running on. For
17749 example, when remote debugging a target that has MS-DOS based file
17750 system semantics, from a Unix host, the target may be reporting to
17751 @value{GDBN} a list of loaded shared libraries with file names such as
17752 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17753 drive letters, so the @samp{c:\} prefix is not normally understood as
17754 indicating an absolute file name, and neither is the backslash
17755 normally considered a directory separator character. In that case,
17756 the native file system would interpret this whole absolute file name
17757 as a relative file name with no directory components. This would make
17758 it impossible to point @value{GDBN} at a copy of the remote target's
17759 shared libraries on the host using @code{set sysroot}, and impractical
17760 with @code{set solib-search-path}. Setting
17761 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17762 to interpret such file names similarly to how the target would, and to
17763 map them to file names valid on @value{GDBN}'s native file system
17764 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17765 to one of the supported file system kinds. In that case, @value{GDBN}
17766 tries to determine the appropriate file system variant based on the
17767 current target's operating system (@pxref{ABI, ,Configuring the
17768 Current ABI}). The supported file system settings are:
17772 Instruct @value{GDBN} to assume the target file system is of Unix
17773 kind. Only file names starting the forward slash (@samp{/}) character
17774 are considered absolute, and the directory separator character is also
17778 Instruct @value{GDBN} to assume the target file system is DOS based.
17779 File names starting with either a forward slash, or a drive letter
17780 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17781 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17782 considered directory separators.
17785 Instruct @value{GDBN} to use the file system kind associated with the
17786 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17787 This is the default.
17791 @cindex file name canonicalization
17792 @cindex base name differences
17793 When processing file names provided by the user, @value{GDBN}
17794 frequently needs to compare them to the file names recorded in the
17795 program's debug info. Normally, @value{GDBN} compares just the
17796 @dfn{base names} of the files as strings, which is reasonably fast
17797 even for very large programs. (The base name of a file is the last
17798 portion of its name, after stripping all the leading directories.)
17799 This shortcut in comparison is based upon the assumption that files
17800 cannot have more than one base name. This is usually true, but
17801 references to files that use symlinks or similar filesystem
17802 facilities violate that assumption. If your program records files
17803 using such facilities, or if you provide file names to @value{GDBN}
17804 using symlinks etc., you can set @code{basenames-may-differ} to
17805 @code{true} to instruct @value{GDBN} to completely canonicalize each
17806 pair of file names it needs to compare. This will make file-name
17807 comparisons accurate, but at a price of a significant slowdown.
17810 @item set basenames-may-differ
17811 @kindex set basenames-may-differ
17812 Set whether a source file may have multiple base names.
17814 @item show basenames-may-differ
17815 @kindex show basenames-may-differ
17816 Show whether a source file may have multiple base names.
17819 @node Separate Debug Files
17820 @section Debugging Information in Separate Files
17821 @cindex separate debugging information files
17822 @cindex debugging information in separate files
17823 @cindex @file{.debug} subdirectories
17824 @cindex debugging information directory, global
17825 @cindex global debugging information directories
17826 @cindex build ID, and separate debugging files
17827 @cindex @file{.build-id} directory
17829 @value{GDBN} allows you to put a program's debugging information in a
17830 file separate from the executable itself, in a way that allows
17831 @value{GDBN} to find and load the debugging information automatically.
17832 Since debugging information can be very large---sometimes larger
17833 than the executable code itself---some systems distribute debugging
17834 information for their executables in separate files, which users can
17835 install only when they need to debug a problem.
17837 @value{GDBN} supports two ways of specifying the separate debug info
17842 The executable contains a @dfn{debug link} that specifies the name of
17843 the separate debug info file. The separate debug file's name is
17844 usually @file{@var{executable}.debug}, where @var{executable} is the
17845 name of the corresponding executable file without leading directories
17846 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17847 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17848 checksum for the debug file, which @value{GDBN} uses to validate that
17849 the executable and the debug file came from the same build.
17852 The executable contains a @dfn{build ID}, a unique bit string that is
17853 also present in the corresponding debug info file. (This is supported
17854 only on some operating systems, notably those which use the ELF format
17855 for binary files and the @sc{gnu} Binutils.) For more details about
17856 this feature, see the description of the @option{--build-id}
17857 command-line option in @ref{Options, , Command Line Options, ld.info,
17858 The GNU Linker}. The debug info file's name is not specified
17859 explicitly by the build ID, but can be computed from the build ID, see
17863 Depending on the way the debug info file is specified, @value{GDBN}
17864 uses two different methods of looking for the debug file:
17868 For the ``debug link'' method, @value{GDBN} looks up the named file in
17869 the directory of the executable file, then in a subdirectory of that
17870 directory named @file{.debug}, and finally under each one of the global debug
17871 directories, in a subdirectory whose name is identical to the leading
17872 directories of the executable's absolute file name.
17875 For the ``build ID'' method, @value{GDBN} looks in the
17876 @file{.build-id} subdirectory of each one of the global debug directories for
17877 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17878 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17879 are the rest of the bit string. (Real build ID strings are 32 or more
17880 hex characters, not 10.)
17883 So, for example, suppose you ask @value{GDBN} to debug
17884 @file{/usr/bin/ls}, which has a debug link that specifies the
17885 file @file{ls.debug}, and a build ID whose value in hex is
17886 @code{abcdef1234}. If the list of the global debug directories includes
17887 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17888 debug information files, in the indicated order:
17892 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17894 @file{/usr/bin/ls.debug}
17896 @file{/usr/bin/.debug/ls.debug}
17898 @file{/usr/lib/debug/usr/bin/ls.debug}.
17901 @anchor{debug-file-directory}
17902 Global debugging info directories default to what is set by @value{GDBN}
17903 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17904 you can also set the global debugging info directories, and view the list
17905 @value{GDBN} is currently using.
17909 @kindex set debug-file-directory
17910 @item set debug-file-directory @var{directories}
17911 Set the directories which @value{GDBN} searches for separate debugging
17912 information files to @var{directory}. Multiple path components can be set
17913 concatenating them by a path separator.
17915 @kindex show debug-file-directory
17916 @item show debug-file-directory
17917 Show the directories @value{GDBN} searches for separate debugging
17922 @cindex @code{.gnu_debuglink} sections
17923 @cindex debug link sections
17924 A debug link is a special section of the executable file named
17925 @code{.gnu_debuglink}. The section must contain:
17929 A filename, with any leading directory components removed, followed by
17932 zero to three bytes of padding, as needed to reach the next four-byte
17933 boundary within the section, and
17935 a four-byte CRC checksum, stored in the same endianness used for the
17936 executable file itself. The checksum is computed on the debugging
17937 information file's full contents by the function given below, passing
17938 zero as the @var{crc} argument.
17941 Any executable file format can carry a debug link, as long as it can
17942 contain a section named @code{.gnu_debuglink} with the contents
17945 @cindex @code{.note.gnu.build-id} sections
17946 @cindex build ID sections
17947 The build ID is a special section in the executable file (and in other
17948 ELF binary files that @value{GDBN} may consider). This section is
17949 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17950 It contains unique identification for the built files---the ID remains
17951 the same across multiple builds of the same build tree. The default
17952 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17953 content for the build ID string. The same section with an identical
17954 value is present in the original built binary with symbols, in its
17955 stripped variant, and in the separate debugging information file.
17957 The debugging information file itself should be an ordinary
17958 executable, containing a full set of linker symbols, sections, and
17959 debugging information. The sections of the debugging information file
17960 should have the same names, addresses, and sizes as the original file,
17961 but they need not contain any data---much like a @code{.bss} section
17962 in an ordinary executable.
17964 The @sc{gnu} binary utilities (Binutils) package includes the
17965 @samp{objcopy} utility that can produce
17966 the separated executable / debugging information file pairs using the
17967 following commands:
17970 @kbd{objcopy --only-keep-debug foo foo.debug}
17975 These commands remove the debugging
17976 information from the executable file @file{foo} and place it in the file
17977 @file{foo.debug}. You can use the first, second or both methods to link the
17982 The debug link method needs the following additional command to also leave
17983 behind a debug link in @file{foo}:
17986 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17989 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17990 a version of the @code{strip} command such that the command @kbd{strip foo -f
17991 foo.debug} has the same functionality as the two @code{objcopy} commands and
17992 the @code{ln -s} command above, together.
17995 Build ID gets embedded into the main executable using @code{ld --build-id} or
17996 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17997 compatibility fixes for debug files separation are present in @sc{gnu} binary
17998 utilities (Binutils) package since version 2.18.
18003 @cindex CRC algorithm definition
18004 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18005 IEEE 802.3 using the polynomial:
18007 @c TexInfo requires naked braces for multi-digit exponents for Tex
18008 @c output, but this causes HTML output to barf. HTML has to be set using
18009 @c raw commands. So we end up having to specify this equation in 2
18014 <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>
18015 + <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
18021 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18022 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18026 The function is computed byte at a time, taking the least
18027 significant bit of each byte first. The initial pattern
18028 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18029 the final result is inverted to ensure trailing zeros also affect the
18032 @emph{Note:} This is the same CRC polynomial as used in handling the
18033 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18034 However in the case of the Remote Serial Protocol, the CRC is computed
18035 @emph{most} significant bit first, and the result is not inverted, so
18036 trailing zeros have no effect on the CRC value.
18038 To complete the description, we show below the code of the function
18039 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18040 initially supplied @code{crc} argument means that an initial call to
18041 this function passing in zero will start computing the CRC using
18044 @kindex gnu_debuglink_crc32
18047 gnu_debuglink_crc32 (unsigned long crc,
18048 unsigned char *buf, size_t len)
18050 static const unsigned long crc32_table[256] =
18052 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18053 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18054 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18055 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18056 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18057 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18058 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18059 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18060 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18061 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18062 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18063 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18064 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18065 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18066 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18067 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18068 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18069 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18070 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18071 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18072 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18073 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18074 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18075 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18076 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18077 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18078 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18079 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18080 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18081 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18082 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18083 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18084 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18085 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18086 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18087 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18088 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18089 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18090 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18091 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18092 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18093 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18094 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18095 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18096 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18097 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18098 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18099 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18100 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18101 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18102 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18105 unsigned char *end;
18107 crc = ~crc & 0xffffffff;
18108 for (end = buf + len; buf < end; ++buf)
18109 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18110 return ~crc & 0xffffffff;
18115 This computation does not apply to the ``build ID'' method.
18117 @node MiniDebugInfo
18118 @section Debugging information in a special section
18119 @cindex separate debug sections
18120 @cindex @samp{.gnu_debugdata} section
18122 Some systems ship pre-built executables and libraries that have a
18123 special @samp{.gnu_debugdata} section. This feature is called
18124 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18125 is used to supply extra symbols for backtraces.
18127 The intent of this section is to provide extra minimal debugging
18128 information for use in simple backtraces. It is not intended to be a
18129 replacement for full separate debugging information (@pxref{Separate
18130 Debug Files}). The example below shows the intended use; however,
18131 @value{GDBN} does not currently put restrictions on what sort of
18132 debugging information might be included in the section.
18134 @value{GDBN} has support for this extension. If the section exists,
18135 then it is used provided that no other source of debugging information
18136 can be found, and that @value{GDBN} was configured with LZMA support.
18138 This section can be easily created using @command{objcopy} and other
18139 standard utilities:
18142 # Extract the dynamic symbols from the main binary, there is no need
18143 # to also have these in the normal symbol table.
18144 nm -D @var{binary} --format=posix --defined-only \
18145 | awk '@{ print $1 @}' | sort > dynsyms
18147 # Extract all the text (i.e. function) symbols from the debuginfo.
18148 # (Note that we actually also accept "D" symbols, for the benefit
18149 # of platforms like PowerPC64 that use function descriptors.)
18150 nm @var{binary} --format=posix --defined-only \
18151 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18154 # Keep all the function symbols not already in the dynamic symbol
18156 comm -13 dynsyms funcsyms > keep_symbols
18158 # Separate full debug info into debug binary.
18159 objcopy --only-keep-debug @var{binary} debug
18161 # Copy the full debuginfo, keeping only a minimal set of symbols and
18162 # removing some unnecessary sections.
18163 objcopy -S --remove-section .gdb_index --remove-section .comment \
18164 --keep-symbols=keep_symbols debug mini_debuginfo
18166 # Drop the full debug info from the original binary.
18167 strip --strip-all -R .comment @var{binary}
18169 # Inject the compressed data into the .gnu_debugdata section of the
18172 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18176 @section Index Files Speed Up @value{GDBN}
18177 @cindex index files
18178 @cindex @samp{.gdb_index} section
18180 When @value{GDBN} finds a symbol file, it scans the symbols in the
18181 file in order to construct an internal symbol table. This lets most
18182 @value{GDBN} operations work quickly---at the cost of a delay early
18183 on. For large programs, this delay can be quite lengthy, so
18184 @value{GDBN} provides a way to build an index, which speeds up
18187 The index is stored as a section in the symbol file. @value{GDBN} can
18188 write the index to a file, then you can put it into the symbol file
18189 using @command{objcopy}.
18191 To create an index file, use the @code{save gdb-index} command:
18194 @item save gdb-index @var{directory}
18195 @kindex save gdb-index
18196 Create an index file for each symbol file currently known by
18197 @value{GDBN}. Each file is named after its corresponding symbol file,
18198 with @samp{.gdb-index} appended, and is written into the given
18202 Once you have created an index file you can merge it into your symbol
18203 file, here named @file{symfile}, using @command{objcopy}:
18206 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18207 --set-section-flags .gdb_index=readonly symfile symfile
18210 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18211 sections that have been deprecated. Usually they are deprecated because
18212 they are missing a new feature or have performance issues.
18213 To tell @value{GDBN} to use a deprecated index section anyway
18214 specify @code{set use-deprecated-index-sections on}.
18215 The default is @code{off}.
18216 This can speed up startup, but may result in some functionality being lost.
18217 @xref{Index Section Format}.
18219 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18220 must be done before gdb reads the file. The following will not work:
18223 $ gdb -ex "set use-deprecated-index-sections on" <program>
18226 Instead you must do, for example,
18229 $ gdb -iex "set use-deprecated-index-sections on" <program>
18232 There are currently some limitation on indices. They only work when
18233 for DWARF debugging information, not stabs. And, they do not
18234 currently work for programs using Ada.
18236 @node Symbol Errors
18237 @section Errors Reading Symbol Files
18239 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18240 such as symbol types it does not recognize, or known bugs in compiler
18241 output. By default, @value{GDBN} does not notify you of such problems, since
18242 they are relatively common and primarily of interest to people
18243 debugging compilers. If you are interested in seeing information
18244 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18245 only one message about each such type of problem, no matter how many
18246 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18247 to see how many times the problems occur, with the @code{set
18248 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18251 The messages currently printed, and their meanings, include:
18254 @item inner block not inside outer block in @var{symbol}
18256 The symbol information shows where symbol scopes begin and end
18257 (such as at the start of a function or a block of statements). This
18258 error indicates that an inner scope block is not fully contained
18259 in its outer scope blocks.
18261 @value{GDBN} circumvents the problem by treating the inner block as if it had
18262 the same scope as the outer block. In the error message, @var{symbol}
18263 may be shown as ``@code{(don't know)}'' if the outer block is not a
18266 @item block at @var{address} out of order
18268 The symbol information for symbol scope blocks should occur in
18269 order of increasing addresses. This error indicates that it does not
18272 @value{GDBN} does not circumvent this problem, and has trouble
18273 locating symbols in the source file whose symbols it is reading. (You
18274 can often determine what source file is affected by specifying
18275 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18278 @item bad block start address patched
18280 The symbol information for a symbol scope block has a start address
18281 smaller than the address of the preceding source line. This is known
18282 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18284 @value{GDBN} circumvents the problem by treating the symbol scope block as
18285 starting on the previous source line.
18287 @item bad string table offset in symbol @var{n}
18290 Symbol number @var{n} contains a pointer into the string table which is
18291 larger than the size of the string table.
18293 @value{GDBN} circumvents the problem by considering the symbol to have the
18294 name @code{foo}, which may cause other problems if many symbols end up
18297 @item unknown symbol type @code{0x@var{nn}}
18299 The symbol information contains new data types that @value{GDBN} does
18300 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18301 uncomprehended information, in hexadecimal.
18303 @value{GDBN} circumvents the error by ignoring this symbol information.
18304 This usually allows you to debug your program, though certain symbols
18305 are not accessible. If you encounter such a problem and feel like
18306 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18307 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18308 and examine @code{*bufp} to see the symbol.
18310 @item stub type has NULL name
18312 @value{GDBN} could not find the full definition for a struct or class.
18314 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18315 The symbol information for a C@t{++} member function is missing some
18316 information that recent versions of the compiler should have output for
18319 @item info mismatch between compiler and debugger
18321 @value{GDBN} could not parse a type specification output by the compiler.
18326 @section GDB Data Files
18328 @cindex prefix for data files
18329 @value{GDBN} will sometimes read an auxiliary data file. These files
18330 are kept in a directory known as the @dfn{data directory}.
18332 You can set the data directory's name, and view the name @value{GDBN}
18333 is currently using.
18336 @kindex set data-directory
18337 @item set data-directory @var{directory}
18338 Set the directory which @value{GDBN} searches for auxiliary data files
18339 to @var{directory}.
18341 @kindex show data-directory
18342 @item show data-directory
18343 Show the directory @value{GDBN} searches for auxiliary data files.
18346 @cindex default data directory
18347 @cindex @samp{--with-gdb-datadir}
18348 You can set the default data directory by using the configure-time
18349 @samp{--with-gdb-datadir} option. If the data directory is inside
18350 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18351 @samp{--exec-prefix}), then the default data directory will be updated
18352 automatically if the installed @value{GDBN} is moved to a new
18355 The data directory may also be specified with the
18356 @code{--data-directory} command line option.
18357 @xref{Mode Options}.
18360 @chapter Specifying a Debugging Target
18362 @cindex debugging target
18363 A @dfn{target} is the execution environment occupied by your program.
18365 Often, @value{GDBN} runs in the same host environment as your program;
18366 in that case, the debugging target is specified as a side effect when
18367 you use the @code{file} or @code{core} commands. When you need more
18368 flexibility---for example, running @value{GDBN} on a physically separate
18369 host, or controlling a standalone system over a serial port or a
18370 realtime system over a TCP/IP connection---you can use the @code{target}
18371 command to specify one of the target types configured for @value{GDBN}
18372 (@pxref{Target Commands, ,Commands for Managing Targets}).
18374 @cindex target architecture
18375 It is possible to build @value{GDBN} for several different @dfn{target
18376 architectures}. When @value{GDBN} is built like that, you can choose
18377 one of the available architectures with the @kbd{set architecture}
18381 @kindex set architecture
18382 @kindex show architecture
18383 @item set architecture @var{arch}
18384 This command sets the current target architecture to @var{arch}. The
18385 value of @var{arch} can be @code{"auto"}, in addition to one of the
18386 supported architectures.
18388 @item show architecture
18389 Show the current target architecture.
18391 @item set processor
18393 @kindex set processor
18394 @kindex show processor
18395 These are alias commands for, respectively, @code{set architecture}
18396 and @code{show architecture}.
18400 * Active Targets:: Active targets
18401 * Target Commands:: Commands for managing targets
18402 * Byte Order:: Choosing target byte order
18405 @node Active Targets
18406 @section Active Targets
18408 @cindex stacking targets
18409 @cindex active targets
18410 @cindex multiple targets
18412 There are multiple classes of targets such as: processes, executable files or
18413 recording sessions. Core files belong to the process class, making core file
18414 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18415 on multiple active targets, one in each class. This allows you to (for
18416 example) start a process and inspect its activity, while still having access to
18417 the executable file after the process finishes. Or if you start process
18418 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18419 presented a virtual layer of the recording target, while the process target
18420 remains stopped at the chronologically last point of the process execution.
18422 Use the @code{core-file} and @code{exec-file} commands to select a new core
18423 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18424 specify as a target a process that is already running, use the @code{attach}
18425 command (@pxref{Attach, ,Debugging an Already-running Process}).
18427 @node Target Commands
18428 @section Commands for Managing Targets
18431 @item target @var{type} @var{parameters}
18432 Connects the @value{GDBN} host environment to a target machine or
18433 process. A target is typically a protocol for talking to debugging
18434 facilities. You use the argument @var{type} to specify the type or
18435 protocol of the target machine.
18437 Further @var{parameters} are interpreted by the target protocol, but
18438 typically include things like device names or host names to connect
18439 with, process numbers, and baud rates.
18441 The @code{target} command does not repeat if you press @key{RET} again
18442 after executing the command.
18444 @kindex help target
18446 Displays the names of all targets available. To display targets
18447 currently selected, use either @code{info target} or @code{info files}
18448 (@pxref{Files, ,Commands to Specify Files}).
18450 @item help target @var{name}
18451 Describe a particular target, including any parameters necessary to
18454 @kindex set gnutarget
18455 @item set gnutarget @var{args}
18456 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18457 knows whether it is reading an @dfn{executable},
18458 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18459 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18460 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18463 @emph{Warning:} To specify a file format with @code{set gnutarget},
18464 you must know the actual BFD name.
18468 @xref{Files, , Commands to Specify Files}.
18470 @kindex show gnutarget
18471 @item show gnutarget
18472 Use the @code{show gnutarget} command to display what file format
18473 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18474 @value{GDBN} will determine the file format for each file automatically,
18475 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18478 @cindex common targets
18479 Here are some common targets (available, or not, depending on the GDB
18484 @item target exec @var{program}
18485 @cindex executable file target
18486 An executable file. @samp{target exec @var{program}} is the same as
18487 @samp{exec-file @var{program}}.
18489 @item target core @var{filename}
18490 @cindex core dump file target
18491 A core dump file. @samp{target core @var{filename}} is the same as
18492 @samp{core-file @var{filename}}.
18494 @item target remote @var{medium}
18495 @cindex remote target
18496 A remote system connected to @value{GDBN} via a serial line or network
18497 connection. This command tells @value{GDBN} to use its own remote
18498 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18500 For example, if you have a board connected to @file{/dev/ttya} on the
18501 machine running @value{GDBN}, you could say:
18504 target remote /dev/ttya
18507 @code{target remote} supports the @code{load} command. This is only
18508 useful if you have some other way of getting the stub to the target
18509 system, and you can put it somewhere in memory where it won't get
18510 clobbered by the download.
18512 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18513 @cindex built-in simulator target
18514 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18522 works; however, you cannot assume that a specific memory map, device
18523 drivers, or even basic I/O is available, although some simulators do
18524 provide these. For info about any processor-specific simulator details,
18525 see the appropriate section in @ref{Embedded Processors, ,Embedded
18528 @item target native
18529 @cindex native target
18530 Setup for local/native process debugging. Useful to make the
18531 @code{run} command spawn native processes (likewise @code{attach},
18532 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18533 (@pxref{set auto-connect-native-target}).
18537 Different targets are available on different configurations of @value{GDBN};
18538 your configuration may have more or fewer targets.
18540 Many remote targets require you to download the executable's code once
18541 you've successfully established a connection. You may wish to control
18542 various aspects of this process.
18547 @kindex set hash@r{, for remote monitors}
18548 @cindex hash mark while downloading
18549 This command controls whether a hash mark @samp{#} is displayed while
18550 downloading a file to the remote monitor. If on, a hash mark is
18551 displayed after each S-record is successfully downloaded to the
18555 @kindex show hash@r{, for remote monitors}
18556 Show the current status of displaying the hash mark.
18558 @item set debug monitor
18559 @kindex set debug monitor
18560 @cindex display remote monitor communications
18561 Enable or disable display of communications messages between
18562 @value{GDBN} and the remote monitor.
18564 @item show debug monitor
18565 @kindex show debug monitor
18566 Show the current status of displaying communications between
18567 @value{GDBN} and the remote monitor.
18572 @kindex load @var{filename}
18573 @item load @var{filename}
18575 Depending on what remote debugging facilities are configured into
18576 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18577 is meant to make @var{filename} (an executable) available for debugging
18578 on the remote system---by downloading, or dynamic linking, for example.
18579 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18580 the @code{add-symbol-file} command.
18582 If your @value{GDBN} does not have a @code{load} command, attempting to
18583 execute it gets the error message ``@code{You can't do that when your
18584 target is @dots{}}''
18586 The file is loaded at whatever address is specified in the executable.
18587 For some object file formats, you can specify the load address when you
18588 link the program; for other formats, like a.out, the object file format
18589 specifies a fixed address.
18590 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18592 Depending on the remote side capabilities, @value{GDBN} may be able to
18593 load programs into flash memory.
18595 @code{load} does not repeat if you press @key{RET} again after using it.
18599 @section Choosing Target Byte Order
18601 @cindex choosing target byte order
18602 @cindex target byte order
18604 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18605 offer the ability to run either big-endian or little-endian byte
18606 orders. Usually the executable or symbol will include a bit to
18607 designate the endian-ness, and you will not need to worry about
18608 which to use. However, you may still find it useful to adjust
18609 @value{GDBN}'s idea of processor endian-ness manually.
18613 @item set endian big
18614 Instruct @value{GDBN} to assume the target is big-endian.
18616 @item set endian little
18617 Instruct @value{GDBN} to assume the target is little-endian.
18619 @item set endian auto
18620 Instruct @value{GDBN} to use the byte order associated with the
18624 Display @value{GDBN}'s current idea of the target byte order.
18628 Note that these commands merely adjust interpretation of symbolic
18629 data on the host, and that they have absolutely no effect on the
18633 @node Remote Debugging
18634 @chapter Debugging Remote Programs
18635 @cindex remote debugging
18637 If you are trying to debug a program running on a machine that cannot run
18638 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18639 For example, you might use remote debugging on an operating system kernel,
18640 or on a small system which does not have a general purpose operating system
18641 powerful enough to run a full-featured debugger.
18643 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18644 to make this work with particular debugging targets. In addition,
18645 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18646 but not specific to any particular target system) which you can use if you
18647 write the remote stubs---the code that runs on the remote system to
18648 communicate with @value{GDBN}.
18650 Other remote targets may be available in your
18651 configuration of @value{GDBN}; use @code{help target} to list them.
18654 * Connecting:: Connecting to a remote target
18655 * File Transfer:: Sending files to a remote system
18656 * Server:: Using the gdbserver program
18657 * Remote Configuration:: Remote configuration
18658 * Remote Stub:: Implementing a remote stub
18662 @section Connecting to a Remote Target
18664 On the @value{GDBN} host machine, you will need an unstripped copy of
18665 your program, since @value{GDBN} needs symbol and debugging information.
18666 Start up @value{GDBN} as usual, using the name of the local copy of your
18667 program as the first argument.
18669 @cindex @code{target remote}
18670 @value{GDBN} can communicate with the target over a serial line, or
18671 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18672 each case, @value{GDBN} uses the same protocol for debugging your
18673 program; only the medium carrying the debugging packets varies. The
18674 @code{target remote} command establishes a connection to the target.
18675 Its arguments indicate which medium to use:
18679 @item target remote @var{serial-device}
18680 @cindex serial line, @code{target remote}
18681 Use @var{serial-device} to communicate with the target. For example,
18682 to use a serial line connected to the device named @file{/dev/ttyb}:
18685 target remote /dev/ttyb
18688 If you're using a serial line, you may want to give @value{GDBN} the
18689 @samp{--baud} option, or use the @code{set serial baud} command
18690 (@pxref{Remote Configuration, set serial baud}) before the
18691 @code{target} command.
18693 @item target remote @code{@var{host}:@var{port}}
18694 @itemx target remote @code{tcp:@var{host}:@var{port}}
18695 @cindex @acronym{TCP} port, @code{target remote}
18696 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18697 The @var{host} may be either a host name or a numeric @acronym{IP}
18698 address; @var{port} must be a decimal number. The @var{host} could be
18699 the target machine itself, if it is directly connected to the net, or
18700 it might be a terminal server which in turn has a serial line to the
18703 For example, to connect to port 2828 on a terminal server named
18707 target remote manyfarms:2828
18710 If your remote target is actually running on the same machine as your
18711 debugger session (e.g.@: a simulator for your target running on the
18712 same host), you can omit the hostname. For example, to connect to
18713 port 1234 on your local machine:
18716 target remote :1234
18720 Note that the colon is still required here.
18722 @item target remote @code{udp:@var{host}:@var{port}}
18723 @cindex @acronym{UDP} port, @code{target remote}
18724 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18725 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18728 target remote udp:manyfarms:2828
18731 When using a @acronym{UDP} connection for remote debugging, you should
18732 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18733 can silently drop packets on busy or unreliable networks, which will
18734 cause havoc with your debugging session.
18736 @item target remote | @var{command}
18737 @cindex pipe, @code{target remote} to
18738 Run @var{command} in the background and communicate with it using a
18739 pipe. The @var{command} is a shell command, to be parsed and expanded
18740 by the system's command shell, @code{/bin/sh}; it should expect remote
18741 protocol packets on its standard input, and send replies on its
18742 standard output. You could use this to run a stand-alone simulator
18743 that speaks the remote debugging protocol, to make net connections
18744 using programs like @code{ssh}, or for other similar tricks.
18746 If @var{command} closes its standard output (perhaps by exiting),
18747 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18748 program has already exited, this will have no effect.)
18752 Once the connection has been established, you can use all the usual
18753 commands to examine and change data. The remote program is already
18754 running; you can use @kbd{step} and @kbd{continue}, and you do not
18755 need to use @kbd{run}.
18757 @cindex interrupting remote programs
18758 @cindex remote programs, interrupting
18759 Whenever @value{GDBN} is waiting for the remote program, if you type the
18760 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18761 program. This may or may not succeed, depending in part on the hardware
18762 and the serial drivers the remote system uses. If you type the
18763 interrupt character once again, @value{GDBN} displays this prompt:
18766 Interrupted while waiting for the program.
18767 Give up (and stop debugging it)? (y or n)
18770 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18771 (If you decide you want to try again later, you can use @samp{target
18772 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18773 goes back to waiting.
18776 @kindex detach (remote)
18778 When you have finished debugging the remote program, you can use the
18779 @code{detach} command to release it from @value{GDBN} control.
18780 Detaching from the target normally resumes its execution, but the results
18781 will depend on your particular remote stub. After the @code{detach}
18782 command, @value{GDBN} is free to connect to another target.
18786 The @code{disconnect} command behaves like @code{detach}, except that
18787 the target is generally not resumed. It will wait for @value{GDBN}
18788 (this instance or another one) to connect and continue debugging. After
18789 the @code{disconnect} command, @value{GDBN} is again free to connect to
18792 @cindex send command to remote monitor
18793 @cindex extend @value{GDBN} for remote targets
18794 @cindex add new commands for external monitor
18796 @item monitor @var{cmd}
18797 This command allows you to send arbitrary commands directly to the
18798 remote monitor. Since @value{GDBN} doesn't care about the commands it
18799 sends like this, this command is the way to extend @value{GDBN}---you
18800 can add new commands that only the external monitor will understand
18804 @node File Transfer
18805 @section Sending files to a remote system
18806 @cindex remote target, file transfer
18807 @cindex file transfer
18808 @cindex sending files to remote systems
18810 Some remote targets offer the ability to transfer files over the same
18811 connection used to communicate with @value{GDBN}. This is convenient
18812 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18813 running @code{gdbserver} over a network interface. For other targets,
18814 e.g.@: embedded devices with only a single serial port, this may be
18815 the only way to upload or download files.
18817 Not all remote targets support these commands.
18821 @item remote put @var{hostfile} @var{targetfile}
18822 Copy file @var{hostfile} from the host system (the machine running
18823 @value{GDBN}) to @var{targetfile} on the target system.
18826 @item remote get @var{targetfile} @var{hostfile}
18827 Copy file @var{targetfile} from the target system to @var{hostfile}
18828 on the host system.
18830 @kindex remote delete
18831 @item remote delete @var{targetfile}
18832 Delete @var{targetfile} from the target system.
18837 @section Using the @code{gdbserver} Program
18840 @cindex remote connection without stubs
18841 @code{gdbserver} is a control program for Unix-like systems, which
18842 allows you to connect your program with a remote @value{GDBN} via
18843 @code{target remote}---but without linking in the usual debugging stub.
18845 @code{gdbserver} is not a complete replacement for the debugging stubs,
18846 because it requires essentially the same operating-system facilities
18847 that @value{GDBN} itself does. In fact, a system that can run
18848 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18849 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18850 because it is a much smaller program than @value{GDBN} itself. It is
18851 also easier to port than all of @value{GDBN}, so you may be able to get
18852 started more quickly on a new system by using @code{gdbserver}.
18853 Finally, if you develop code for real-time systems, you may find that
18854 the tradeoffs involved in real-time operation make it more convenient to
18855 do as much development work as possible on another system, for example
18856 by cross-compiling. You can use @code{gdbserver} to make a similar
18857 choice for debugging.
18859 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18860 or a TCP connection, using the standard @value{GDBN} remote serial
18864 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18865 Do not run @code{gdbserver} connected to any public network; a
18866 @value{GDBN} connection to @code{gdbserver} provides access to the
18867 target system with the same privileges as the user running
18871 @subsection Running @code{gdbserver}
18872 @cindex arguments, to @code{gdbserver}
18873 @cindex @code{gdbserver}, command-line arguments
18875 Run @code{gdbserver} on the target system. You need a copy of the
18876 program you want to debug, including any libraries it requires.
18877 @code{gdbserver} does not need your program's symbol table, so you can
18878 strip the program if necessary to save space. @value{GDBN} on the host
18879 system does all the symbol handling.
18881 To use the server, you must tell it how to communicate with @value{GDBN};
18882 the name of your program; and the arguments for your program. The usual
18886 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18889 @var{comm} is either a device name (to use a serial line), or a TCP
18890 hostname and portnumber, or @code{-} or @code{stdio} to use
18891 stdin/stdout of @code{gdbserver}.
18892 For example, to debug Emacs with the argument
18893 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18897 target> gdbserver /dev/com1 emacs foo.txt
18900 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18903 To use a TCP connection instead of a serial line:
18906 target> gdbserver host:2345 emacs foo.txt
18909 The only difference from the previous example is the first argument,
18910 specifying that you are communicating with the host @value{GDBN} via
18911 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18912 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18913 (Currently, the @samp{host} part is ignored.) You can choose any number
18914 you want for the port number as long as it does not conflict with any
18915 TCP ports already in use on the target system (for example, @code{23} is
18916 reserved for @code{telnet}).@footnote{If you choose a port number that
18917 conflicts with another service, @code{gdbserver} prints an error message
18918 and exits.} You must use the same port number with the host @value{GDBN}
18919 @code{target remote} command.
18921 The @code{stdio} connection is useful when starting @code{gdbserver}
18925 (gdb) target remote | ssh -T hostname gdbserver - hello
18928 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18929 and we don't want escape-character handling. Ssh does this by default when
18930 a command is provided, the flag is provided to make it explicit.
18931 You could elide it if you want to.
18933 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18934 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18935 display through a pipe connected to gdbserver.
18936 Both @code{stdout} and @code{stderr} use the same pipe.
18938 @subsubsection Attaching to a Running Program
18939 @cindex attach to a program, @code{gdbserver}
18940 @cindex @option{--attach}, @code{gdbserver} option
18942 On some targets, @code{gdbserver} can also attach to running programs.
18943 This is accomplished via the @code{--attach} argument. The syntax is:
18946 target> gdbserver --attach @var{comm} @var{pid}
18949 @var{pid} is the process ID of a currently running process. It isn't necessary
18950 to point @code{gdbserver} at a binary for the running process.
18953 You can debug processes by name instead of process ID if your target has the
18954 @code{pidof} utility:
18957 target> gdbserver --attach @var{comm} `pidof @var{program}`
18960 In case more than one copy of @var{program} is running, or @var{program}
18961 has multiple threads, most versions of @code{pidof} support the
18962 @code{-s} option to only return the first process ID.
18964 @subsubsection Multi-Process Mode for @code{gdbserver}
18965 @cindex @code{gdbserver}, multiple processes
18966 @cindex multiple processes with @code{gdbserver}
18968 When you connect to @code{gdbserver} using @code{target remote},
18969 @code{gdbserver} debugs the specified program only once. When the
18970 program exits, or you detach from it, @value{GDBN} closes the connection
18971 and @code{gdbserver} exits.
18973 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18974 enters multi-process mode. When the debugged program exits, or you
18975 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18976 though no program is running. The @code{run} and @code{attach}
18977 commands instruct @code{gdbserver} to run or attach to a new program.
18978 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18979 remote exec-file}) to select the program to run. Command line
18980 arguments are supported, except for wildcard expansion and I/O
18981 redirection (@pxref{Arguments}).
18983 @cindex @option{--multi}, @code{gdbserver} option
18984 To start @code{gdbserver} without supplying an initial command to run
18985 or process ID to attach, use the @option{--multi} command line option.
18986 Then you can connect using @kbd{target extended-remote} and start
18987 the program you want to debug.
18989 In multi-process mode @code{gdbserver} does not automatically exit unless you
18990 use the option @option{--once}. You can terminate it by using
18991 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18992 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18993 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18994 @option{--multi} option to @code{gdbserver} has no influence on that.
18996 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18998 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19000 @code{gdbserver} normally terminates after all of its debugged processes have
19001 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19002 extended-remote}, @code{gdbserver} stays running even with no processes left.
19003 @value{GDBN} normally terminates the spawned debugged process on its exit,
19004 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19005 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19006 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19007 stays running even in the @kbd{target remote} mode.
19009 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19010 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19011 completeness, at most one @value{GDBN} can be connected at a time.
19013 @cindex @option{--once}, @code{gdbserver} option
19014 By default, @code{gdbserver} keeps the listening TCP port open, so that
19015 subsequent connections are possible. However, if you start @code{gdbserver}
19016 with the @option{--once} option, it will stop listening for any further
19017 connection attempts after connecting to the first @value{GDBN} session. This
19018 means no further connections to @code{gdbserver} will be possible after the
19019 first one. It also means @code{gdbserver} will terminate after the first
19020 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19021 connections and even in the @kbd{target extended-remote} mode. The
19022 @option{--once} option allows reusing the same port number for connecting to
19023 multiple instances of @code{gdbserver} running on the same host, since each
19024 instance closes its port after the first connection.
19026 @anchor{Other Command-Line Arguments for gdbserver}
19027 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19029 @cindex @option{--debug}, @code{gdbserver} option
19030 The @option{--debug} option tells @code{gdbserver} to display extra
19031 status information about the debugging process.
19032 @cindex @option{--remote-debug}, @code{gdbserver} option
19033 The @option{--remote-debug} option tells @code{gdbserver} to display
19034 remote protocol debug output. These options are intended for
19035 @code{gdbserver} development and for bug reports to the developers.
19037 @cindex @option{--debug-format}, @code{gdbserver} option
19038 The @option{--debug-format=option1[,option2,...]} option tells
19039 @code{gdbserver} to include additional information in each output.
19040 Possible options are:
19044 Turn off all extra information in debugging output.
19046 Turn on all extra information in debugging output.
19048 Include a timestamp in each line of debugging output.
19051 Options are processed in order. Thus, for example, if @option{none}
19052 appears last then no additional information is added to debugging output.
19054 @cindex @option{--wrapper}, @code{gdbserver} option
19055 The @option{--wrapper} option specifies a wrapper to launch programs
19056 for debugging. The option should be followed by the name of the
19057 wrapper, then any command-line arguments to pass to the wrapper, then
19058 @kbd{--} indicating the end of the wrapper arguments.
19060 @code{gdbserver} runs the specified wrapper program with a combined
19061 command line including the wrapper arguments, then the name of the
19062 program to debug, then any arguments to the program. The wrapper
19063 runs until it executes your program, and then @value{GDBN} gains control.
19065 You can use any program that eventually calls @code{execve} with
19066 its arguments as a wrapper. Several standard Unix utilities do
19067 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19068 with @code{exec "$@@"} will also work.
19070 For example, you can use @code{env} to pass an environment variable to
19071 the debugged program, without setting the variable in @code{gdbserver}'s
19075 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19078 @subsection Connecting to @code{gdbserver}
19080 Run @value{GDBN} on the host system.
19082 First make sure you have the necessary symbol files. Load symbols for
19083 your application using the @code{file} command before you connect. Use
19084 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19085 was compiled with the correct sysroot using @code{--with-sysroot}).
19087 The symbol file and target libraries must exactly match the executable
19088 and libraries on the target, with one exception: the files on the host
19089 system should not be stripped, even if the files on the target system
19090 are. Mismatched or missing files will lead to confusing results
19091 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19092 files may also prevent @code{gdbserver} from debugging multi-threaded
19095 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19096 For TCP connections, you must start up @code{gdbserver} prior to using
19097 the @code{target remote} command. Otherwise you may get an error whose
19098 text depends on the host system, but which usually looks something like
19099 @samp{Connection refused}. Don't use the @code{load}
19100 command in @value{GDBN} when using @code{gdbserver}, since the program is
19101 already on the target.
19103 @subsection Monitor Commands for @code{gdbserver}
19104 @cindex monitor commands, for @code{gdbserver}
19105 @anchor{Monitor Commands for gdbserver}
19107 During a @value{GDBN} session using @code{gdbserver}, you can use the
19108 @code{monitor} command to send special requests to @code{gdbserver}.
19109 Here are the available commands.
19113 List the available monitor commands.
19115 @item monitor set debug 0
19116 @itemx monitor set debug 1
19117 Disable or enable general debugging messages.
19119 @item monitor set remote-debug 0
19120 @itemx monitor set remote-debug 1
19121 Disable or enable specific debugging messages associated with the remote
19122 protocol (@pxref{Remote Protocol}).
19124 @item monitor set debug-format option1@r{[},option2,...@r{]}
19125 Specify additional text to add to debugging messages.
19126 Possible options are:
19130 Turn off all extra information in debugging output.
19132 Turn on all extra information in debugging output.
19134 Include a timestamp in each line of debugging output.
19137 Options are processed in order. Thus, for example, if @option{none}
19138 appears last then no additional information is added to debugging output.
19140 @item monitor set libthread-db-search-path [PATH]
19141 @cindex gdbserver, search path for @code{libthread_db}
19142 When this command is issued, @var{path} is a colon-separated list of
19143 directories to search for @code{libthread_db} (@pxref{Threads,,set
19144 libthread-db-search-path}). If you omit @var{path},
19145 @samp{libthread-db-search-path} will be reset to its default value.
19147 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19148 not supported in @code{gdbserver}.
19151 Tell gdbserver to exit immediately. This command should be followed by
19152 @code{disconnect} to close the debugging session. @code{gdbserver} will
19153 detach from any attached processes and kill any processes it created.
19154 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19155 of a multi-process mode debug session.
19159 @subsection Tracepoints support in @code{gdbserver}
19160 @cindex tracepoints support in @code{gdbserver}
19162 On some targets, @code{gdbserver} supports tracepoints, fast
19163 tracepoints and static tracepoints.
19165 For fast or static tracepoints to work, a special library called the
19166 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19167 This library is built and distributed as an integral part of
19168 @code{gdbserver}. In addition, support for static tracepoints
19169 requires building the in-process agent library with static tracepoints
19170 support. At present, the UST (LTTng Userspace Tracer,
19171 @url{http://lttng.org/ust}) tracing engine is supported. This support
19172 is automatically available if UST development headers are found in the
19173 standard include path when @code{gdbserver} is built, or if
19174 @code{gdbserver} was explicitly configured using @option{--with-ust}
19175 to point at such headers. You can explicitly disable the support
19176 using @option{--with-ust=no}.
19178 There are several ways to load the in-process agent in your program:
19181 @item Specifying it as dependency at link time
19183 You can link your program dynamically with the in-process agent
19184 library. On most systems, this is accomplished by adding
19185 @code{-linproctrace} to the link command.
19187 @item Using the system's preloading mechanisms
19189 You can force loading the in-process agent at startup time by using
19190 your system's support for preloading shared libraries. Many Unixes
19191 support the concept of preloading user defined libraries. In most
19192 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19193 in the environment. See also the description of @code{gdbserver}'s
19194 @option{--wrapper} command line option.
19196 @item Using @value{GDBN} to force loading the agent at run time
19198 On some systems, you can force the inferior to load a shared library,
19199 by calling a dynamic loader function in the inferior that takes care
19200 of dynamically looking up and loading a shared library. On most Unix
19201 systems, the function is @code{dlopen}. You'll use the @code{call}
19202 command for that. For example:
19205 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19208 Note that on most Unix systems, for the @code{dlopen} function to be
19209 available, the program needs to be linked with @code{-ldl}.
19212 On systems that have a userspace dynamic loader, like most Unix
19213 systems, when you connect to @code{gdbserver} using @code{target
19214 remote}, you'll find that the program is stopped at the dynamic
19215 loader's entry point, and no shared library has been loaded in the
19216 program's address space yet, including the in-process agent. In that
19217 case, before being able to use any of the fast or static tracepoints
19218 features, you need to let the loader run and load the shared
19219 libraries. The simplest way to do that is to run the program to the
19220 main procedure. E.g., if debugging a C or C@t{++} program, start
19221 @code{gdbserver} like so:
19224 $ gdbserver :9999 myprogram
19227 Start GDB and connect to @code{gdbserver} like so, and run to main:
19231 (@value{GDBP}) target remote myhost:9999
19232 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19233 (@value{GDBP}) b main
19234 (@value{GDBP}) continue
19237 The in-process tracing agent library should now be loaded into the
19238 process; you can confirm it with the @code{info sharedlibrary}
19239 command, which will list @file{libinproctrace.so} as loaded in the
19240 process. You are now ready to install fast tracepoints, list static
19241 tracepoint markers, probe static tracepoints markers, and start
19244 @node Remote Configuration
19245 @section Remote Configuration
19248 @kindex show remote
19249 This section documents the configuration options available when
19250 debugging remote programs. For the options related to the File I/O
19251 extensions of the remote protocol, see @ref{system,
19252 system-call-allowed}.
19255 @item set remoteaddresssize @var{bits}
19256 @cindex address size for remote targets
19257 @cindex bits in remote address
19258 Set the maximum size of address in a memory packet to the specified
19259 number of bits. @value{GDBN} will mask off the address bits above
19260 that number, when it passes addresses to the remote target. The
19261 default value is the number of bits in the target's address.
19263 @item show remoteaddresssize
19264 Show the current value of remote address size in bits.
19266 @item set serial baud @var{n}
19267 @cindex baud rate for remote targets
19268 Set the baud rate for the remote serial I/O to @var{n} baud. The
19269 value is used to set the speed of the serial port used for debugging
19272 @item show serial baud
19273 Show the current speed of the remote connection.
19275 @item set remotebreak
19276 @cindex interrupt remote programs
19277 @cindex BREAK signal instead of Ctrl-C
19278 @anchor{set remotebreak}
19279 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19280 when you type @kbd{Ctrl-c} to interrupt the program running
19281 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19282 character instead. The default is off, since most remote systems
19283 expect to see @samp{Ctrl-C} as the interrupt signal.
19285 @item show remotebreak
19286 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19287 interrupt the remote program.
19289 @item set remoteflow on
19290 @itemx set remoteflow off
19291 @kindex set remoteflow
19292 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19293 on the serial port used to communicate to the remote target.
19295 @item show remoteflow
19296 @kindex show remoteflow
19297 Show the current setting of hardware flow control.
19299 @item set remotelogbase @var{base}
19300 Set the base (a.k.a.@: radix) of logging serial protocol
19301 communications to @var{base}. Supported values of @var{base} are:
19302 @code{ascii}, @code{octal}, and @code{hex}. The default is
19305 @item show remotelogbase
19306 Show the current setting of the radix for logging remote serial
19309 @item set remotelogfile @var{file}
19310 @cindex record serial communications on file
19311 Record remote serial communications on the named @var{file}. The
19312 default is not to record at all.
19314 @item show remotelogfile.
19315 Show the current setting of the file name on which to record the
19316 serial communications.
19318 @item set remotetimeout @var{num}
19319 @cindex timeout for serial communications
19320 @cindex remote timeout
19321 Set the timeout limit to wait for the remote target to respond to
19322 @var{num} seconds. The default is 2 seconds.
19324 @item show remotetimeout
19325 Show the current number of seconds to wait for the remote target
19328 @cindex limit hardware breakpoints and watchpoints
19329 @cindex remote target, limit break- and watchpoints
19330 @anchor{set remote hardware-watchpoint-limit}
19331 @anchor{set remote hardware-breakpoint-limit}
19332 @item set remote hardware-watchpoint-limit @var{limit}
19333 @itemx set remote hardware-breakpoint-limit @var{limit}
19334 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19335 watchpoints. A limit of -1, the default, is treated as unlimited.
19337 @cindex limit hardware watchpoints length
19338 @cindex remote target, limit watchpoints length
19339 @anchor{set remote hardware-watchpoint-length-limit}
19340 @item set remote hardware-watchpoint-length-limit @var{limit}
19341 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19342 a remote hardware watchpoint. A limit of -1, the default, is treated
19345 @item show remote hardware-watchpoint-length-limit
19346 Show the current limit (in bytes) of the maximum length of
19347 a remote hardware watchpoint.
19349 @item set remote exec-file @var{filename}
19350 @itemx show remote exec-file
19351 @anchor{set remote exec-file}
19352 @cindex executable file, for remote target
19353 Select the file used for @code{run} with @code{target
19354 extended-remote}. This should be set to a filename valid on the
19355 target system. If it is not set, the target will use a default
19356 filename (e.g.@: the last program run).
19358 @item set remote interrupt-sequence
19359 @cindex interrupt remote programs
19360 @cindex select Ctrl-C, BREAK or BREAK-g
19361 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19362 @samp{BREAK-g} as the
19363 sequence to the remote target in order to interrupt the execution.
19364 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19365 is high level of serial line for some certain time.
19366 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19367 It is @code{BREAK} signal followed by character @code{g}.
19369 @item show interrupt-sequence
19370 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19371 is sent by @value{GDBN} to interrupt the remote program.
19372 @code{BREAK-g} is BREAK signal followed by @code{g} and
19373 also known as Magic SysRq g.
19375 @item set remote interrupt-on-connect
19376 @cindex send interrupt-sequence on start
19377 Specify whether interrupt-sequence is sent to remote target when
19378 @value{GDBN} connects to it. This is mostly needed when you debug
19379 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19380 which is known as Magic SysRq g in order to connect @value{GDBN}.
19382 @item show interrupt-on-connect
19383 Show whether interrupt-sequence is sent
19384 to remote target when @value{GDBN} connects to it.
19388 @item set tcp auto-retry on
19389 @cindex auto-retry, for remote TCP target
19390 Enable auto-retry for remote TCP connections. This is useful if the remote
19391 debugging agent is launched in parallel with @value{GDBN}; there is a race
19392 condition because the agent may not become ready to accept the connection
19393 before @value{GDBN} attempts to connect. When auto-retry is
19394 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19395 to establish the connection using the timeout specified by
19396 @code{set tcp connect-timeout}.
19398 @item set tcp auto-retry off
19399 Do not auto-retry failed TCP connections.
19401 @item show tcp auto-retry
19402 Show the current auto-retry setting.
19404 @item set tcp connect-timeout @var{seconds}
19405 @itemx set tcp connect-timeout unlimited
19406 @cindex connection timeout, for remote TCP target
19407 @cindex timeout, for remote target connection
19408 Set the timeout for establishing a TCP connection to the remote target to
19409 @var{seconds}. The timeout affects both polling to retry failed connections
19410 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19411 that are merely slow to complete, and represents an approximate cumulative
19412 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19413 @value{GDBN} will keep attempting to establish a connection forever,
19414 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19416 @item show tcp connect-timeout
19417 Show the current connection timeout setting.
19420 @cindex remote packets, enabling and disabling
19421 The @value{GDBN} remote protocol autodetects the packets supported by
19422 your debugging stub. If you need to override the autodetection, you
19423 can use these commands to enable or disable individual packets. Each
19424 packet can be set to @samp{on} (the remote target supports this
19425 packet), @samp{off} (the remote target does not support this packet),
19426 or @samp{auto} (detect remote target support for this packet). They
19427 all default to @samp{auto}. For more information about each packet,
19428 see @ref{Remote Protocol}.
19430 During normal use, you should not have to use any of these commands.
19431 If you do, that may be a bug in your remote debugging stub, or a bug
19432 in @value{GDBN}. You may want to report the problem to the
19433 @value{GDBN} developers.
19435 For each packet @var{name}, the command to enable or disable the
19436 packet is @code{set remote @var{name}-packet}. The available settings
19439 @multitable @columnfractions 0.28 0.32 0.25
19442 @tab Related Features
19444 @item @code{fetch-register}
19446 @tab @code{info registers}
19448 @item @code{set-register}
19452 @item @code{binary-download}
19454 @tab @code{load}, @code{set}
19456 @item @code{read-aux-vector}
19457 @tab @code{qXfer:auxv:read}
19458 @tab @code{info auxv}
19460 @item @code{symbol-lookup}
19461 @tab @code{qSymbol}
19462 @tab Detecting multiple threads
19464 @item @code{attach}
19465 @tab @code{vAttach}
19468 @item @code{verbose-resume}
19470 @tab Stepping or resuming multiple threads
19476 @item @code{software-breakpoint}
19480 @item @code{hardware-breakpoint}
19484 @item @code{write-watchpoint}
19488 @item @code{read-watchpoint}
19492 @item @code{access-watchpoint}
19496 @item @code{target-features}
19497 @tab @code{qXfer:features:read}
19498 @tab @code{set architecture}
19500 @item @code{library-info}
19501 @tab @code{qXfer:libraries:read}
19502 @tab @code{info sharedlibrary}
19504 @item @code{memory-map}
19505 @tab @code{qXfer:memory-map:read}
19506 @tab @code{info mem}
19508 @item @code{read-sdata-object}
19509 @tab @code{qXfer:sdata:read}
19510 @tab @code{print $_sdata}
19512 @item @code{read-spu-object}
19513 @tab @code{qXfer:spu:read}
19514 @tab @code{info spu}
19516 @item @code{write-spu-object}
19517 @tab @code{qXfer:spu:write}
19518 @tab @code{info spu}
19520 @item @code{read-siginfo-object}
19521 @tab @code{qXfer:siginfo:read}
19522 @tab @code{print $_siginfo}
19524 @item @code{write-siginfo-object}
19525 @tab @code{qXfer:siginfo:write}
19526 @tab @code{set $_siginfo}
19528 @item @code{threads}
19529 @tab @code{qXfer:threads:read}
19530 @tab @code{info threads}
19532 @item @code{get-thread-local-@*storage-address}
19533 @tab @code{qGetTLSAddr}
19534 @tab Displaying @code{__thread} variables
19536 @item @code{get-thread-information-block-address}
19537 @tab @code{qGetTIBAddr}
19538 @tab Display MS-Windows Thread Information Block.
19540 @item @code{search-memory}
19541 @tab @code{qSearch:memory}
19544 @item @code{supported-packets}
19545 @tab @code{qSupported}
19546 @tab Remote communications parameters
19548 @item @code{pass-signals}
19549 @tab @code{QPassSignals}
19550 @tab @code{handle @var{signal}}
19552 @item @code{program-signals}
19553 @tab @code{QProgramSignals}
19554 @tab @code{handle @var{signal}}
19556 @item @code{hostio-close-packet}
19557 @tab @code{vFile:close}
19558 @tab @code{remote get}, @code{remote put}
19560 @item @code{hostio-open-packet}
19561 @tab @code{vFile:open}
19562 @tab @code{remote get}, @code{remote put}
19564 @item @code{hostio-pread-packet}
19565 @tab @code{vFile:pread}
19566 @tab @code{remote get}, @code{remote put}
19568 @item @code{hostio-pwrite-packet}
19569 @tab @code{vFile:pwrite}
19570 @tab @code{remote get}, @code{remote put}
19572 @item @code{hostio-unlink-packet}
19573 @tab @code{vFile:unlink}
19574 @tab @code{remote delete}
19576 @item @code{hostio-readlink-packet}
19577 @tab @code{vFile:readlink}
19580 @item @code{noack-packet}
19581 @tab @code{QStartNoAckMode}
19582 @tab Packet acknowledgment
19584 @item @code{osdata}
19585 @tab @code{qXfer:osdata:read}
19586 @tab @code{info os}
19588 @item @code{query-attached}
19589 @tab @code{qAttached}
19590 @tab Querying remote process attach state.
19592 @item @code{trace-buffer-size}
19593 @tab @code{QTBuffer:size}
19594 @tab @code{set trace-buffer-size}
19596 @item @code{trace-status}
19597 @tab @code{qTStatus}
19598 @tab @code{tstatus}
19600 @item @code{traceframe-info}
19601 @tab @code{qXfer:traceframe-info:read}
19602 @tab Traceframe info
19604 @item @code{install-in-trace}
19605 @tab @code{InstallInTrace}
19606 @tab Install tracepoint in tracing
19608 @item @code{disable-randomization}
19609 @tab @code{QDisableRandomization}
19610 @tab @code{set disable-randomization}
19612 @item @code{conditional-breakpoints-packet}
19613 @tab @code{Z0 and Z1}
19614 @tab @code{Support for target-side breakpoint condition evaluation}
19618 @section Implementing a Remote Stub
19620 @cindex debugging stub, example
19621 @cindex remote stub, example
19622 @cindex stub example, remote debugging
19623 The stub files provided with @value{GDBN} implement the target side of the
19624 communication protocol, and the @value{GDBN} side is implemented in the
19625 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19626 these subroutines to communicate, and ignore the details. (If you're
19627 implementing your own stub file, you can still ignore the details: start
19628 with one of the existing stub files. @file{sparc-stub.c} is the best
19629 organized, and therefore the easiest to read.)
19631 @cindex remote serial debugging, overview
19632 To debug a program running on another machine (the debugging
19633 @dfn{target} machine), you must first arrange for all the usual
19634 prerequisites for the program to run by itself. For example, for a C
19639 A startup routine to set up the C runtime environment; these usually
19640 have a name like @file{crt0}. The startup routine may be supplied by
19641 your hardware supplier, or you may have to write your own.
19644 A C subroutine library to support your program's
19645 subroutine calls, notably managing input and output.
19648 A way of getting your program to the other machine---for example, a
19649 download program. These are often supplied by the hardware
19650 manufacturer, but you may have to write your own from hardware
19654 The next step is to arrange for your program to use a serial port to
19655 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19656 machine). In general terms, the scheme looks like this:
19660 @value{GDBN} already understands how to use this protocol; when everything
19661 else is set up, you can simply use the @samp{target remote} command
19662 (@pxref{Targets,,Specifying a Debugging Target}).
19664 @item On the target,
19665 you must link with your program a few special-purpose subroutines that
19666 implement the @value{GDBN} remote serial protocol. The file containing these
19667 subroutines is called a @dfn{debugging stub}.
19669 On certain remote targets, you can use an auxiliary program
19670 @code{gdbserver} instead of linking a stub into your program.
19671 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19674 The debugging stub is specific to the architecture of the remote
19675 machine; for example, use @file{sparc-stub.c} to debug programs on
19678 @cindex remote serial stub list
19679 These working remote stubs are distributed with @value{GDBN}:
19684 @cindex @file{i386-stub.c}
19687 For Intel 386 and compatible architectures.
19690 @cindex @file{m68k-stub.c}
19691 @cindex Motorola 680x0
19693 For Motorola 680x0 architectures.
19696 @cindex @file{sh-stub.c}
19699 For Renesas SH architectures.
19702 @cindex @file{sparc-stub.c}
19704 For @sc{sparc} architectures.
19706 @item sparcl-stub.c
19707 @cindex @file{sparcl-stub.c}
19710 For Fujitsu @sc{sparclite} architectures.
19714 The @file{README} file in the @value{GDBN} distribution may list other
19715 recently added stubs.
19718 * Stub Contents:: What the stub can do for you
19719 * Bootstrapping:: What you must do for the stub
19720 * Debug Session:: Putting it all together
19723 @node Stub Contents
19724 @subsection What the Stub Can Do for You
19726 @cindex remote serial stub
19727 The debugging stub for your architecture supplies these three
19731 @item set_debug_traps
19732 @findex set_debug_traps
19733 @cindex remote serial stub, initialization
19734 This routine arranges for @code{handle_exception} to run when your
19735 program stops. You must call this subroutine explicitly in your
19736 program's startup code.
19738 @item handle_exception
19739 @findex handle_exception
19740 @cindex remote serial stub, main routine
19741 This is the central workhorse, but your program never calls it
19742 explicitly---the setup code arranges for @code{handle_exception} to
19743 run when a trap is triggered.
19745 @code{handle_exception} takes control when your program stops during
19746 execution (for example, on a breakpoint), and mediates communications
19747 with @value{GDBN} on the host machine. This is where the communications
19748 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19749 representative on the target machine. It begins by sending summary
19750 information on the state of your program, then continues to execute,
19751 retrieving and transmitting any information @value{GDBN} needs, until you
19752 execute a @value{GDBN} command that makes your program resume; at that point,
19753 @code{handle_exception} returns control to your own code on the target
19757 @cindex @code{breakpoint} subroutine, remote
19758 Use this auxiliary subroutine to make your program contain a
19759 breakpoint. Depending on the particular situation, this may be the only
19760 way for @value{GDBN} to get control. For instance, if your target
19761 machine has some sort of interrupt button, you won't need to call this;
19762 pressing the interrupt button transfers control to
19763 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19764 simply receiving characters on the serial port may also trigger a trap;
19765 again, in that situation, you don't need to call @code{breakpoint} from
19766 your own program---simply running @samp{target remote} from the host
19767 @value{GDBN} session gets control.
19769 Call @code{breakpoint} if none of these is true, or if you simply want
19770 to make certain your program stops at a predetermined point for the
19771 start of your debugging session.
19774 @node Bootstrapping
19775 @subsection What You Must Do for the Stub
19777 @cindex remote stub, support routines
19778 The debugging stubs that come with @value{GDBN} are set up for a particular
19779 chip architecture, but they have no information about the rest of your
19780 debugging target machine.
19782 First of all you need to tell the stub how to communicate with the
19786 @item int getDebugChar()
19787 @findex getDebugChar
19788 Write this subroutine to read a single character from the serial port.
19789 It may be identical to @code{getchar} for your target system; a
19790 different name is used to allow you to distinguish the two if you wish.
19792 @item void putDebugChar(int)
19793 @findex putDebugChar
19794 Write this subroutine to write a single character to the serial port.
19795 It may be identical to @code{putchar} for your target system; a
19796 different name is used to allow you to distinguish the two if you wish.
19799 @cindex control C, and remote debugging
19800 @cindex interrupting remote targets
19801 If you want @value{GDBN} to be able to stop your program while it is
19802 running, you need to use an interrupt-driven serial driver, and arrange
19803 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19804 character). That is the character which @value{GDBN} uses to tell the
19805 remote system to stop.
19807 Getting the debugging target to return the proper status to @value{GDBN}
19808 probably requires changes to the standard stub; one quick and dirty way
19809 is to just execute a breakpoint instruction (the ``dirty'' part is that
19810 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19812 Other routines you need to supply are:
19815 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19816 @findex exceptionHandler
19817 Write this function to install @var{exception_address} in the exception
19818 handling tables. You need to do this because the stub does not have any
19819 way of knowing what the exception handling tables on your target system
19820 are like (for example, the processor's table might be in @sc{rom},
19821 containing entries which point to a table in @sc{ram}).
19822 The @var{exception_number} specifies the exception which should be changed;
19823 its meaning is architecture-dependent (for example, different numbers
19824 might represent divide by zero, misaligned access, etc). When this
19825 exception occurs, control should be transferred directly to
19826 @var{exception_address}, and the processor state (stack, registers,
19827 and so on) should be just as it is when a processor exception occurs. So if
19828 you want to use a jump instruction to reach @var{exception_address}, it
19829 should be a simple jump, not a jump to subroutine.
19831 For the 386, @var{exception_address} should be installed as an interrupt
19832 gate so that interrupts are masked while the handler runs. The gate
19833 should be at privilege level 0 (the most privileged level). The
19834 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19835 help from @code{exceptionHandler}.
19837 @item void flush_i_cache()
19838 @findex flush_i_cache
19839 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19840 instruction cache, if any, on your target machine. If there is no
19841 instruction cache, this subroutine may be a no-op.
19843 On target machines that have instruction caches, @value{GDBN} requires this
19844 function to make certain that the state of your program is stable.
19848 You must also make sure this library routine is available:
19851 @item void *memset(void *, int, int)
19853 This is the standard library function @code{memset} that sets an area of
19854 memory to a known value. If you have one of the free versions of
19855 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19856 either obtain it from your hardware manufacturer, or write your own.
19859 If you do not use the GNU C compiler, you may need other standard
19860 library subroutines as well; this varies from one stub to another,
19861 but in general the stubs are likely to use any of the common library
19862 subroutines which @code{@value{NGCC}} generates as inline code.
19865 @node Debug Session
19866 @subsection Putting it All Together
19868 @cindex remote serial debugging summary
19869 In summary, when your program is ready to debug, you must follow these
19874 Make sure you have defined the supporting low-level routines
19875 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19877 @code{getDebugChar}, @code{putDebugChar},
19878 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19882 Insert these lines in your program's startup code, before the main
19883 procedure is called:
19890 On some machines, when a breakpoint trap is raised, the hardware
19891 automatically makes the PC point to the instruction after the
19892 breakpoint. If your machine doesn't do that, you may need to adjust
19893 @code{handle_exception} to arrange for it to return to the instruction
19894 after the breakpoint on this first invocation, so that your program
19895 doesn't keep hitting the initial breakpoint instead of making
19899 For the 680x0 stub only, you need to provide a variable called
19900 @code{exceptionHook}. Normally you just use:
19903 void (*exceptionHook)() = 0;
19907 but if before calling @code{set_debug_traps}, you set it to point to a
19908 function in your program, that function is called when
19909 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19910 error). The function indicated by @code{exceptionHook} is called with
19911 one parameter: an @code{int} which is the exception number.
19914 Compile and link together: your program, the @value{GDBN} debugging stub for
19915 your target architecture, and the supporting subroutines.
19918 Make sure you have a serial connection between your target machine and
19919 the @value{GDBN} host, and identify the serial port on the host.
19922 @c The "remote" target now provides a `load' command, so we should
19923 @c document that. FIXME.
19924 Download your program to your target machine (or get it there by
19925 whatever means the manufacturer provides), and start it.
19928 Start @value{GDBN} on the host, and connect to the target
19929 (@pxref{Connecting,,Connecting to a Remote Target}).
19933 @node Configurations
19934 @chapter Configuration-Specific Information
19936 While nearly all @value{GDBN} commands are available for all native and
19937 cross versions of the debugger, there are some exceptions. This chapter
19938 describes things that are only available in certain configurations.
19940 There are three major categories of configurations: native
19941 configurations, where the host and target are the same, embedded
19942 operating system configurations, which are usually the same for several
19943 different processor architectures, and bare embedded processors, which
19944 are quite different from each other.
19949 * Embedded Processors::
19956 This section describes details specific to particular native
19961 * BSD libkvm Interface:: Debugging BSD kernel memory images
19962 * SVR4 Process Information:: SVR4 process information
19963 * DJGPP Native:: Features specific to the DJGPP port
19964 * Cygwin Native:: Features specific to the Cygwin port
19965 * Hurd Native:: Features specific to @sc{gnu} Hurd
19966 * Darwin:: Features specific to Darwin
19972 On HP-UX systems, if you refer to a function or variable name that
19973 begins with a dollar sign, @value{GDBN} searches for a user or system
19974 name first, before it searches for a convenience variable.
19977 @node BSD libkvm Interface
19978 @subsection BSD libkvm Interface
19981 @cindex kernel memory image
19982 @cindex kernel crash dump
19984 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19985 interface that provides a uniform interface for accessing kernel virtual
19986 memory images, including live systems and crash dumps. @value{GDBN}
19987 uses this interface to allow you to debug live kernels and kernel crash
19988 dumps on many native BSD configurations. This is implemented as a
19989 special @code{kvm} debugging target. For debugging a live system, load
19990 the currently running kernel into @value{GDBN} and connect to the
19994 (@value{GDBP}) @b{target kvm}
19997 For debugging crash dumps, provide the file name of the crash dump as an
20001 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20004 Once connected to the @code{kvm} target, the following commands are
20010 Set current context from the @dfn{Process Control Block} (PCB) address.
20013 Set current context from proc address. This command isn't available on
20014 modern FreeBSD systems.
20017 @node SVR4 Process Information
20018 @subsection SVR4 Process Information
20020 @cindex examine process image
20021 @cindex process info via @file{/proc}
20023 Many versions of SVR4 and compatible systems provide a facility called
20024 @samp{/proc} that can be used to examine the image of a running
20025 process using file-system subroutines.
20027 If @value{GDBN} is configured for an operating system with this
20028 facility, the command @code{info proc} is available to report
20029 information about the process running your program, or about any
20030 process running on your system. This includes, as of this writing,
20031 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20033 This command may also work on core files that were created on a system
20034 that has the @samp{/proc} facility.
20040 @itemx info proc @var{process-id}
20041 Summarize available information about any running process. If a
20042 process ID is specified by @var{process-id}, display information about
20043 that process; otherwise display information about the program being
20044 debugged. The summary includes the debugged process ID, the command
20045 line used to invoke it, its current working directory, and its
20046 executable file's absolute file name.
20048 On some systems, @var{process-id} can be of the form
20049 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20050 within a process. If the optional @var{pid} part is missing, it means
20051 a thread from the process being debugged (the leading @samp{/} still
20052 needs to be present, or else @value{GDBN} will interpret the number as
20053 a process ID rather than a thread ID).
20055 @item info proc cmdline
20056 @cindex info proc cmdline
20057 Show the original command line of the process. This command is
20058 specific to @sc{gnu}/Linux.
20060 @item info proc cwd
20061 @cindex info proc cwd
20062 Show the current working directory of the process. This command is
20063 specific to @sc{gnu}/Linux.
20065 @item info proc exe
20066 @cindex info proc exe
20067 Show the name of executable of the process. This command is specific
20070 @item info proc mappings
20071 @cindex memory address space mappings
20072 Report the memory address space ranges accessible in the program, with
20073 information on whether the process has read, write, or execute access
20074 rights to each range. On @sc{gnu}/Linux systems, each memory range
20075 includes the object file which is mapped to that range, instead of the
20076 memory access rights to that range.
20078 @item info proc stat
20079 @itemx info proc status
20080 @cindex process detailed status information
20081 These subcommands are specific to @sc{gnu}/Linux systems. They show
20082 the process-related information, including the user ID and group ID;
20083 how many threads are there in the process; its virtual memory usage;
20084 the signals that are pending, blocked, and ignored; its TTY; its
20085 consumption of system and user time; its stack size; its @samp{nice}
20086 value; etc. For more information, see the @samp{proc} man page
20087 (type @kbd{man 5 proc} from your shell prompt).
20089 @item info proc all
20090 Show all the information about the process described under all of the
20091 above @code{info proc} subcommands.
20094 @comment These sub-options of 'info proc' were not included when
20095 @comment procfs.c was re-written. Keep their descriptions around
20096 @comment against the day when someone finds the time to put them back in.
20097 @kindex info proc times
20098 @item info proc times
20099 Starting time, user CPU time, and system CPU time for your program and
20102 @kindex info proc id
20104 Report on the process IDs related to your program: its own process ID,
20105 the ID of its parent, the process group ID, and the session ID.
20108 @item set procfs-trace
20109 @kindex set procfs-trace
20110 @cindex @code{procfs} API calls
20111 This command enables and disables tracing of @code{procfs} API calls.
20113 @item show procfs-trace
20114 @kindex show procfs-trace
20115 Show the current state of @code{procfs} API call tracing.
20117 @item set procfs-file @var{file}
20118 @kindex set procfs-file
20119 Tell @value{GDBN} to write @code{procfs} API trace to the named
20120 @var{file}. @value{GDBN} appends the trace info to the previous
20121 contents of the file. The default is to display the trace on the
20124 @item show procfs-file
20125 @kindex show procfs-file
20126 Show the file to which @code{procfs} API trace is written.
20128 @item proc-trace-entry
20129 @itemx proc-trace-exit
20130 @itemx proc-untrace-entry
20131 @itemx proc-untrace-exit
20132 @kindex proc-trace-entry
20133 @kindex proc-trace-exit
20134 @kindex proc-untrace-entry
20135 @kindex proc-untrace-exit
20136 These commands enable and disable tracing of entries into and exits
20137 from the @code{syscall} interface.
20140 @kindex info pidlist
20141 @cindex process list, QNX Neutrino
20142 For QNX Neutrino only, this command displays the list of all the
20143 processes and all the threads within each process.
20146 @kindex info meminfo
20147 @cindex mapinfo list, QNX Neutrino
20148 For QNX Neutrino only, this command displays the list of all mapinfos.
20152 @subsection Features for Debugging @sc{djgpp} Programs
20153 @cindex @sc{djgpp} debugging
20154 @cindex native @sc{djgpp} debugging
20155 @cindex MS-DOS-specific commands
20158 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20159 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20160 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20161 top of real-mode DOS systems and their emulations.
20163 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20164 defines a few commands specific to the @sc{djgpp} port. This
20165 subsection describes those commands.
20170 This is a prefix of @sc{djgpp}-specific commands which print
20171 information about the target system and important OS structures.
20174 @cindex MS-DOS system info
20175 @cindex free memory information (MS-DOS)
20176 @item info dos sysinfo
20177 This command displays assorted information about the underlying
20178 platform: the CPU type and features, the OS version and flavor, the
20179 DPMI version, and the available conventional and DPMI memory.
20184 @cindex segment descriptor tables
20185 @cindex descriptor tables display
20187 @itemx info dos ldt
20188 @itemx info dos idt
20189 These 3 commands display entries from, respectively, Global, Local,
20190 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20191 tables are data structures which store a descriptor for each segment
20192 that is currently in use. The segment's selector is an index into a
20193 descriptor table; the table entry for that index holds the
20194 descriptor's base address and limit, and its attributes and access
20197 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20198 segment (used for both data and the stack), and a DOS segment (which
20199 allows access to DOS/BIOS data structures and absolute addresses in
20200 conventional memory). However, the DPMI host will usually define
20201 additional segments in order to support the DPMI environment.
20203 @cindex garbled pointers
20204 These commands allow to display entries from the descriptor tables.
20205 Without an argument, all entries from the specified table are
20206 displayed. An argument, which should be an integer expression, means
20207 display a single entry whose index is given by the argument. For
20208 example, here's a convenient way to display information about the
20209 debugged program's data segment:
20212 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20213 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20217 This comes in handy when you want to see whether a pointer is outside
20218 the data segment's limit (i.e.@: @dfn{garbled}).
20220 @cindex page tables display (MS-DOS)
20222 @itemx info dos pte
20223 These two commands display entries from, respectively, the Page
20224 Directory and the Page Tables. Page Directories and Page Tables are
20225 data structures which control how virtual memory addresses are mapped
20226 into physical addresses. A Page Table includes an entry for every
20227 page of memory that is mapped into the program's address space; there
20228 may be several Page Tables, each one holding up to 4096 entries. A
20229 Page Directory has up to 4096 entries, one each for every Page Table
20230 that is currently in use.
20232 Without an argument, @kbd{info dos pde} displays the entire Page
20233 Directory, and @kbd{info dos pte} displays all the entries in all of
20234 the Page Tables. An argument, an integer expression, given to the
20235 @kbd{info dos pde} command means display only that entry from the Page
20236 Directory table. An argument given to the @kbd{info dos pte} command
20237 means display entries from a single Page Table, the one pointed to by
20238 the specified entry in the Page Directory.
20240 @cindex direct memory access (DMA) on MS-DOS
20241 These commands are useful when your program uses @dfn{DMA} (Direct
20242 Memory Access), which needs physical addresses to program the DMA
20245 These commands are supported only with some DPMI servers.
20247 @cindex physical address from linear address
20248 @item info dos address-pte @var{addr}
20249 This command displays the Page Table entry for a specified linear
20250 address. The argument @var{addr} is a linear address which should
20251 already have the appropriate segment's base address added to it,
20252 because this command accepts addresses which may belong to @emph{any}
20253 segment. For example, here's how to display the Page Table entry for
20254 the page where a variable @code{i} is stored:
20257 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20258 @exdent @code{Page Table entry for address 0x11a00d30:}
20259 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20263 This says that @code{i} is stored at offset @code{0xd30} from the page
20264 whose physical base address is @code{0x02698000}, and shows all the
20265 attributes of that page.
20267 Note that you must cast the addresses of variables to a @code{char *},
20268 since otherwise the value of @code{__djgpp_base_address}, the base
20269 address of all variables and functions in a @sc{djgpp} program, will
20270 be added using the rules of C pointer arithmetics: if @code{i} is
20271 declared an @code{int}, @value{GDBN} will add 4 times the value of
20272 @code{__djgpp_base_address} to the address of @code{i}.
20274 Here's another example, it displays the Page Table entry for the
20278 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20279 @exdent @code{Page Table entry for address 0x29110:}
20280 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20284 (The @code{+ 3} offset is because the transfer buffer's address is the
20285 3rd member of the @code{_go32_info_block} structure.) The output
20286 clearly shows that this DPMI server maps the addresses in conventional
20287 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20288 linear (@code{0x29110}) addresses are identical.
20290 This command is supported only with some DPMI servers.
20293 @cindex DOS serial data link, remote debugging
20294 In addition to native debugging, the DJGPP port supports remote
20295 debugging via a serial data link. The following commands are specific
20296 to remote serial debugging in the DJGPP port of @value{GDBN}.
20299 @kindex set com1base
20300 @kindex set com1irq
20301 @kindex set com2base
20302 @kindex set com2irq
20303 @kindex set com3base
20304 @kindex set com3irq
20305 @kindex set com4base
20306 @kindex set com4irq
20307 @item set com1base @var{addr}
20308 This command sets the base I/O port address of the @file{COM1} serial
20311 @item set com1irq @var{irq}
20312 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20313 for the @file{COM1} serial port.
20315 There are similar commands @samp{set com2base}, @samp{set com3irq},
20316 etc.@: for setting the port address and the @code{IRQ} lines for the
20319 @kindex show com1base
20320 @kindex show com1irq
20321 @kindex show com2base
20322 @kindex show com2irq
20323 @kindex show com3base
20324 @kindex show com3irq
20325 @kindex show com4base
20326 @kindex show com4irq
20327 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20328 display the current settings of the base address and the @code{IRQ}
20329 lines used by the COM ports.
20332 @kindex info serial
20333 @cindex DOS serial port status
20334 This command prints the status of the 4 DOS serial ports. For each
20335 port, it prints whether it's active or not, its I/O base address and
20336 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20337 counts of various errors encountered so far.
20341 @node Cygwin Native
20342 @subsection Features for Debugging MS Windows PE Executables
20343 @cindex MS Windows debugging
20344 @cindex native Cygwin debugging
20345 @cindex Cygwin-specific commands
20347 @value{GDBN} supports native debugging of MS Windows programs, including
20348 DLLs with and without symbolic debugging information.
20350 @cindex Ctrl-BREAK, MS-Windows
20351 @cindex interrupt debuggee on MS-Windows
20352 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20353 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20354 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20355 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20356 sequence, which can be used to interrupt the debuggee even if it
20359 There are various additional Cygwin-specific commands, described in
20360 this section. Working with DLLs that have no debugging symbols is
20361 described in @ref{Non-debug DLL Symbols}.
20366 This is a prefix of MS Windows-specific commands which print
20367 information about the target system and important OS structures.
20369 @item info w32 selector
20370 This command displays information returned by
20371 the Win32 API @code{GetThreadSelectorEntry} function.
20372 It takes an optional argument that is evaluated to
20373 a long value to give the information about this given selector.
20374 Without argument, this command displays information
20375 about the six segment registers.
20377 @item info w32 thread-information-block
20378 This command displays thread specific information stored in the
20379 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20380 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20384 This is a Cygwin-specific alias of @code{info shared}.
20386 @kindex set cygwin-exceptions
20387 @cindex debugging the Cygwin DLL
20388 @cindex Cygwin DLL, debugging
20389 @item set cygwin-exceptions @var{mode}
20390 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20391 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20392 @value{GDBN} will delay recognition of exceptions, and may ignore some
20393 exceptions which seem to be caused by internal Cygwin DLL
20394 ``bookkeeping''. This option is meant primarily for debugging the
20395 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20396 @value{GDBN} users with false @code{SIGSEGV} signals.
20398 @kindex show cygwin-exceptions
20399 @item show cygwin-exceptions
20400 Displays whether @value{GDBN} will break on exceptions that happen
20401 inside the Cygwin DLL itself.
20403 @kindex set new-console
20404 @item set new-console @var{mode}
20405 If @var{mode} is @code{on} the debuggee will
20406 be started in a new console on next start.
20407 If @var{mode} is @code{off}, the debuggee will
20408 be started in the same console as the debugger.
20410 @kindex show new-console
20411 @item show new-console
20412 Displays whether a new console is used
20413 when the debuggee is started.
20415 @kindex set new-group
20416 @item set new-group @var{mode}
20417 This boolean value controls whether the debuggee should
20418 start a new group or stay in the same group as the debugger.
20419 This affects the way the Windows OS handles
20422 @kindex show new-group
20423 @item show new-group
20424 Displays current value of new-group boolean.
20426 @kindex set debugevents
20427 @item set debugevents
20428 This boolean value adds debug output concerning kernel events related
20429 to the debuggee seen by the debugger. This includes events that
20430 signal thread and process creation and exit, DLL loading and
20431 unloading, console interrupts, and debugging messages produced by the
20432 Windows @code{OutputDebugString} API call.
20434 @kindex set debugexec
20435 @item set debugexec
20436 This boolean value adds debug output concerning execute events
20437 (such as resume thread) seen by the debugger.
20439 @kindex set debugexceptions
20440 @item set debugexceptions
20441 This boolean value adds debug output concerning exceptions in the
20442 debuggee seen by the debugger.
20444 @kindex set debugmemory
20445 @item set debugmemory
20446 This boolean value adds debug output concerning debuggee memory reads
20447 and writes by the debugger.
20451 This boolean values specifies whether the debuggee is called
20452 via a shell or directly (default value is on).
20456 Displays if the debuggee will be started with a shell.
20461 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20464 @node Non-debug DLL Symbols
20465 @subsubsection Support for DLLs without Debugging Symbols
20466 @cindex DLLs with no debugging symbols
20467 @cindex Minimal symbols and DLLs
20469 Very often on windows, some of the DLLs that your program relies on do
20470 not include symbolic debugging information (for example,
20471 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20472 symbols in a DLL, it relies on the minimal amount of symbolic
20473 information contained in the DLL's export table. This section
20474 describes working with such symbols, known internally to @value{GDBN} as
20475 ``minimal symbols''.
20477 Note that before the debugged program has started execution, no DLLs
20478 will have been loaded. The easiest way around this problem is simply to
20479 start the program --- either by setting a breakpoint or letting the
20480 program run once to completion.
20482 @subsubsection DLL Name Prefixes
20484 In keeping with the naming conventions used by the Microsoft debugging
20485 tools, DLL export symbols are made available with a prefix based on the
20486 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20487 also entered into the symbol table, so @code{CreateFileA} is often
20488 sufficient. In some cases there will be name clashes within a program
20489 (particularly if the executable itself includes full debugging symbols)
20490 necessitating the use of the fully qualified name when referring to the
20491 contents of the DLL. Use single-quotes around the name to avoid the
20492 exclamation mark (``!'') being interpreted as a language operator.
20494 Note that the internal name of the DLL may be all upper-case, even
20495 though the file name of the DLL is lower-case, or vice-versa. Since
20496 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20497 some confusion. If in doubt, try the @code{info functions} and
20498 @code{info variables} commands or even @code{maint print msymbols}
20499 (@pxref{Symbols}). Here's an example:
20502 (@value{GDBP}) info function CreateFileA
20503 All functions matching regular expression "CreateFileA":
20505 Non-debugging symbols:
20506 0x77e885f4 CreateFileA
20507 0x77e885f4 KERNEL32!CreateFileA
20511 (@value{GDBP}) info function !
20512 All functions matching regular expression "!":
20514 Non-debugging symbols:
20515 0x6100114c cygwin1!__assert
20516 0x61004034 cygwin1!_dll_crt0@@0
20517 0x61004240 cygwin1!dll_crt0(per_process *)
20521 @subsubsection Working with Minimal Symbols
20523 Symbols extracted from a DLL's export table do not contain very much
20524 type information. All that @value{GDBN} can do is guess whether a symbol
20525 refers to a function or variable depending on the linker section that
20526 contains the symbol. Also note that the actual contents of the memory
20527 contained in a DLL are not available unless the program is running. This
20528 means that you cannot examine the contents of a variable or disassemble
20529 a function within a DLL without a running program.
20531 Variables are generally treated as pointers and dereferenced
20532 automatically. For this reason, it is often necessary to prefix a
20533 variable name with the address-of operator (``&'') and provide explicit
20534 type information in the command. Here's an example of the type of
20538 (@value{GDBP}) print 'cygwin1!__argv'
20543 (@value{GDBP}) x 'cygwin1!__argv'
20544 0x10021610: "\230y\""
20547 And two possible solutions:
20550 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20551 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20555 (@value{GDBP}) x/2x &'cygwin1!__argv'
20556 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20557 (@value{GDBP}) x/x 0x10021608
20558 0x10021608: 0x0022fd98
20559 (@value{GDBP}) x/s 0x0022fd98
20560 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20563 Setting a break point within a DLL is possible even before the program
20564 starts execution. However, under these circumstances, @value{GDBN} can't
20565 examine the initial instructions of the function in order to skip the
20566 function's frame set-up code. You can work around this by using ``*&''
20567 to set the breakpoint at a raw memory address:
20570 (@value{GDBP}) break *&'python22!PyOS_Readline'
20571 Breakpoint 1 at 0x1e04eff0
20574 The author of these extensions is not entirely convinced that setting a
20575 break point within a shared DLL like @file{kernel32.dll} is completely
20579 @subsection Commands Specific to @sc{gnu} Hurd Systems
20580 @cindex @sc{gnu} Hurd debugging
20582 This subsection describes @value{GDBN} commands specific to the
20583 @sc{gnu} Hurd native debugging.
20588 @kindex set signals@r{, Hurd command}
20589 @kindex set sigs@r{, Hurd command}
20590 This command toggles the state of inferior signal interception by
20591 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20592 affected by this command. @code{sigs} is a shorthand alias for
20597 @kindex show signals@r{, Hurd command}
20598 @kindex show sigs@r{, Hurd command}
20599 Show the current state of intercepting inferior's signals.
20601 @item set signal-thread
20602 @itemx set sigthread
20603 @kindex set signal-thread
20604 @kindex set sigthread
20605 This command tells @value{GDBN} which thread is the @code{libc} signal
20606 thread. That thread is run when a signal is delivered to a running
20607 process. @code{set sigthread} is the shorthand alias of @code{set
20610 @item show signal-thread
20611 @itemx show sigthread
20612 @kindex show signal-thread
20613 @kindex show sigthread
20614 These two commands show which thread will run when the inferior is
20615 delivered a signal.
20618 @kindex set stopped@r{, Hurd command}
20619 This commands tells @value{GDBN} that the inferior process is stopped,
20620 as with the @code{SIGSTOP} signal. The stopped process can be
20621 continued by delivering a signal to it.
20624 @kindex show stopped@r{, Hurd command}
20625 This command shows whether @value{GDBN} thinks the debuggee is
20628 @item set exceptions
20629 @kindex set exceptions@r{, Hurd command}
20630 Use this command to turn off trapping of exceptions in the inferior.
20631 When exception trapping is off, neither breakpoints nor
20632 single-stepping will work. To restore the default, set exception
20635 @item show exceptions
20636 @kindex show exceptions@r{, Hurd command}
20637 Show the current state of trapping exceptions in the inferior.
20639 @item set task pause
20640 @kindex set task@r{, Hurd commands}
20641 @cindex task attributes (@sc{gnu} Hurd)
20642 @cindex pause current task (@sc{gnu} Hurd)
20643 This command toggles task suspension when @value{GDBN} has control.
20644 Setting it to on takes effect immediately, and the task is suspended
20645 whenever @value{GDBN} gets control. Setting it to off will take
20646 effect the next time the inferior is continued. If this option is set
20647 to off, you can use @code{set thread default pause on} or @code{set
20648 thread pause on} (see below) to pause individual threads.
20650 @item show task pause
20651 @kindex show task@r{, Hurd commands}
20652 Show the current state of task suspension.
20654 @item set task detach-suspend-count
20655 @cindex task suspend count
20656 @cindex detach from task, @sc{gnu} Hurd
20657 This command sets the suspend count the task will be left with when
20658 @value{GDBN} detaches from it.
20660 @item show task detach-suspend-count
20661 Show the suspend count the task will be left with when detaching.
20663 @item set task exception-port
20664 @itemx set task excp
20665 @cindex task exception port, @sc{gnu} Hurd
20666 This command sets the task exception port to which @value{GDBN} will
20667 forward exceptions. The argument should be the value of the @dfn{send
20668 rights} of the task. @code{set task excp} is a shorthand alias.
20670 @item set noninvasive
20671 @cindex noninvasive task options
20672 This command switches @value{GDBN} to a mode that is the least
20673 invasive as far as interfering with the inferior is concerned. This
20674 is the same as using @code{set task pause}, @code{set exceptions}, and
20675 @code{set signals} to values opposite to the defaults.
20677 @item info send-rights
20678 @itemx info receive-rights
20679 @itemx info port-rights
20680 @itemx info port-sets
20681 @itemx info dead-names
20684 @cindex send rights, @sc{gnu} Hurd
20685 @cindex receive rights, @sc{gnu} Hurd
20686 @cindex port rights, @sc{gnu} Hurd
20687 @cindex port sets, @sc{gnu} Hurd
20688 @cindex dead names, @sc{gnu} Hurd
20689 These commands display information about, respectively, send rights,
20690 receive rights, port rights, port sets, and dead names of a task.
20691 There are also shorthand aliases: @code{info ports} for @code{info
20692 port-rights} and @code{info psets} for @code{info port-sets}.
20694 @item set thread pause
20695 @kindex set thread@r{, Hurd command}
20696 @cindex thread properties, @sc{gnu} Hurd
20697 @cindex pause current thread (@sc{gnu} Hurd)
20698 This command toggles current thread suspension when @value{GDBN} has
20699 control. Setting it to on takes effect immediately, and the current
20700 thread is suspended whenever @value{GDBN} gets control. Setting it to
20701 off will take effect the next time the inferior is continued.
20702 Normally, this command has no effect, since when @value{GDBN} has
20703 control, the whole task is suspended. However, if you used @code{set
20704 task pause off} (see above), this command comes in handy to suspend
20705 only the current thread.
20707 @item show thread pause
20708 @kindex show thread@r{, Hurd command}
20709 This command shows the state of current thread suspension.
20711 @item set thread run
20712 This command sets whether the current thread is allowed to run.
20714 @item show thread run
20715 Show whether the current thread is allowed to run.
20717 @item set thread detach-suspend-count
20718 @cindex thread suspend count, @sc{gnu} Hurd
20719 @cindex detach from thread, @sc{gnu} Hurd
20720 This command sets the suspend count @value{GDBN} will leave on a
20721 thread when detaching. This number is relative to the suspend count
20722 found by @value{GDBN} when it notices the thread; use @code{set thread
20723 takeover-suspend-count} to force it to an absolute value.
20725 @item show thread detach-suspend-count
20726 Show the suspend count @value{GDBN} will leave on the thread when
20729 @item set thread exception-port
20730 @itemx set thread excp
20731 Set the thread exception port to which to forward exceptions. This
20732 overrides the port set by @code{set task exception-port} (see above).
20733 @code{set thread excp} is the shorthand alias.
20735 @item set thread takeover-suspend-count
20736 Normally, @value{GDBN}'s thread suspend counts are relative to the
20737 value @value{GDBN} finds when it notices each thread. This command
20738 changes the suspend counts to be absolute instead.
20740 @item set thread default
20741 @itemx show thread default
20742 @cindex thread default settings, @sc{gnu} Hurd
20743 Each of the above @code{set thread} commands has a @code{set thread
20744 default} counterpart (e.g., @code{set thread default pause}, @code{set
20745 thread default exception-port}, etc.). The @code{thread default}
20746 variety of commands sets the default thread properties for all
20747 threads; you can then change the properties of individual threads with
20748 the non-default commands.
20755 @value{GDBN} provides the following commands specific to the Darwin target:
20758 @item set debug darwin @var{num}
20759 @kindex set debug darwin
20760 When set to a non zero value, enables debugging messages specific to
20761 the Darwin support. Higher values produce more verbose output.
20763 @item show debug darwin
20764 @kindex show debug darwin
20765 Show the current state of Darwin messages.
20767 @item set debug mach-o @var{num}
20768 @kindex set debug mach-o
20769 When set to a non zero value, enables debugging messages while
20770 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20771 file format used on Darwin for object and executable files.) Higher
20772 values produce more verbose output. This is a command to diagnose
20773 problems internal to @value{GDBN} and should not be needed in normal
20776 @item show debug mach-o
20777 @kindex show debug mach-o
20778 Show the current state of Mach-O file messages.
20780 @item set mach-exceptions on
20781 @itemx set mach-exceptions off
20782 @kindex set mach-exceptions
20783 On Darwin, faults are first reported as a Mach exception and are then
20784 mapped to a Posix signal. Use this command to turn on trapping of
20785 Mach exceptions in the inferior. This might be sometimes useful to
20786 better understand the cause of a fault. The default is off.
20788 @item show mach-exceptions
20789 @kindex show mach-exceptions
20790 Show the current state of exceptions trapping.
20795 @section Embedded Operating Systems
20797 This section describes configurations involving the debugging of
20798 embedded operating systems that are available for several different
20801 @value{GDBN} includes the ability to debug programs running on
20802 various real-time operating systems.
20804 @node Embedded Processors
20805 @section Embedded Processors
20807 This section goes into details specific to particular embedded
20810 @cindex send command to simulator
20811 Whenever a specific embedded processor has a simulator, @value{GDBN}
20812 allows to send an arbitrary command to the simulator.
20815 @item sim @var{command}
20816 @kindex sim@r{, a command}
20817 Send an arbitrary @var{command} string to the simulator. Consult the
20818 documentation for the specific simulator in use for information about
20819 acceptable commands.
20825 * M32R/D:: Renesas M32R/D
20826 * M68K:: Motorola M68K
20827 * MicroBlaze:: Xilinx MicroBlaze
20828 * MIPS Embedded:: MIPS Embedded
20829 * PowerPC Embedded:: PowerPC Embedded
20830 * PA:: HP PA Embedded
20831 * Sparclet:: Tsqware Sparclet
20832 * Sparclite:: Fujitsu Sparclite
20833 * Z8000:: Zilog Z8000
20836 * Super-H:: Renesas Super-H
20845 @item target rdi @var{dev}
20846 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20847 use this target to communicate with both boards running the Angel
20848 monitor, or with the EmbeddedICE JTAG debug device.
20851 @item target rdp @var{dev}
20856 @value{GDBN} provides the following ARM-specific commands:
20859 @item set arm disassembler
20861 This commands selects from a list of disassembly styles. The
20862 @code{"std"} style is the standard style.
20864 @item show arm disassembler
20866 Show the current disassembly style.
20868 @item set arm apcs32
20869 @cindex ARM 32-bit mode
20870 This command toggles ARM operation mode between 32-bit and 26-bit.
20872 @item show arm apcs32
20873 Display the current usage of the ARM 32-bit mode.
20875 @item set arm fpu @var{fputype}
20876 This command sets the ARM floating-point unit (FPU) type. The
20877 argument @var{fputype} can be one of these:
20881 Determine the FPU type by querying the OS ABI.
20883 Software FPU, with mixed-endian doubles on little-endian ARM
20886 GCC-compiled FPA co-processor.
20888 Software FPU with pure-endian doubles.
20894 Show the current type of the FPU.
20897 This command forces @value{GDBN} to use the specified ABI.
20900 Show the currently used ABI.
20902 @item set arm fallback-mode (arm|thumb|auto)
20903 @value{GDBN} uses the symbol table, when available, to determine
20904 whether instructions are ARM or Thumb. This command controls
20905 @value{GDBN}'s default behavior when the symbol table is not
20906 available. The default is @samp{auto}, which causes @value{GDBN} to
20907 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20910 @item show arm fallback-mode
20911 Show the current fallback instruction mode.
20913 @item set arm force-mode (arm|thumb|auto)
20914 This command overrides use of the symbol table to determine whether
20915 instructions are ARM or Thumb. The default is @samp{auto}, which
20916 causes @value{GDBN} to use the symbol table and then the setting
20917 of @samp{set arm fallback-mode}.
20919 @item show arm force-mode
20920 Show the current forced instruction mode.
20922 @item set debug arm
20923 Toggle whether to display ARM-specific debugging messages from the ARM
20924 target support subsystem.
20926 @item show debug arm
20927 Show whether ARM-specific debugging messages are enabled.
20930 The following commands are available when an ARM target is debugged
20931 using the RDI interface:
20934 @item rdilogfile @r{[}@var{file}@r{]}
20936 @cindex ADP (Angel Debugger Protocol) logging
20937 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20938 With an argument, sets the log file to the specified @var{file}. With
20939 no argument, show the current log file name. The default log file is
20942 @item rdilogenable @r{[}@var{arg}@r{]}
20943 @kindex rdilogenable
20944 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20945 enables logging, with an argument 0 or @code{"no"} disables it. With
20946 no arguments displays the current setting. When logging is enabled,
20947 ADP packets exchanged between @value{GDBN} and the RDI target device
20948 are logged to a file.
20950 @item set rdiromatzero
20951 @kindex set rdiromatzero
20952 @cindex ROM at zero address, RDI
20953 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20954 vector catching is disabled, so that zero address can be used. If off
20955 (the default), vector catching is enabled. For this command to take
20956 effect, it needs to be invoked prior to the @code{target rdi} command.
20958 @item show rdiromatzero
20959 @kindex show rdiromatzero
20960 Show the current setting of ROM at zero address.
20962 @item set rdiheartbeat
20963 @kindex set rdiheartbeat
20964 @cindex RDI heartbeat
20965 Enable or disable RDI heartbeat packets. It is not recommended to
20966 turn on this option, since it confuses ARM and EPI JTAG interface, as
20967 well as the Angel monitor.
20969 @item show rdiheartbeat
20970 @kindex show rdiheartbeat
20971 Show the setting of RDI heartbeat packets.
20975 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20976 The @value{GDBN} ARM simulator accepts the following optional arguments.
20979 @item --swi-support=@var{type}
20980 Tell the simulator which SWI interfaces to support. The argument
20981 @var{type} may be a comma separated list of the following values.
20982 The default value is @code{all}.
20995 @subsection Renesas M32R/D and M32R/SDI
20998 @kindex target m32r
20999 @item target m32r @var{dev}
21000 Renesas M32R/D ROM monitor.
21002 @kindex target m32rsdi
21003 @item target m32rsdi @var{dev}
21004 Renesas M32R SDI server, connected via parallel port to the board.
21007 The following @value{GDBN} commands are specific to the M32R monitor:
21010 @item set download-path @var{path}
21011 @kindex set download-path
21012 @cindex find downloadable @sc{srec} files (M32R)
21013 Set the default path for finding downloadable @sc{srec} files.
21015 @item show download-path
21016 @kindex show download-path
21017 Show the default path for downloadable @sc{srec} files.
21019 @item set board-address @var{addr}
21020 @kindex set board-address
21021 @cindex M32-EVA target board address
21022 Set the IP address for the M32R-EVA target board.
21024 @item show board-address
21025 @kindex show board-address
21026 Show the current IP address of the target board.
21028 @item set server-address @var{addr}
21029 @kindex set server-address
21030 @cindex download server address (M32R)
21031 Set the IP address for the download server, which is the @value{GDBN}'s
21034 @item show server-address
21035 @kindex show server-address
21036 Display the IP address of the download server.
21038 @item upload @r{[}@var{file}@r{]}
21039 @kindex upload@r{, M32R}
21040 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21041 upload capability. If no @var{file} argument is given, the current
21042 executable file is uploaded.
21044 @item tload @r{[}@var{file}@r{]}
21045 @kindex tload@r{, M32R}
21046 Test the @code{upload} command.
21049 The following commands are available for M32R/SDI:
21054 @cindex reset SDI connection, M32R
21055 This command resets the SDI connection.
21059 This command shows the SDI connection status.
21062 @kindex debug_chaos
21063 @cindex M32R/Chaos debugging
21064 Instructs the remote that M32R/Chaos debugging is to be used.
21066 @item use_debug_dma
21067 @kindex use_debug_dma
21068 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21071 @kindex use_mon_code
21072 Instructs the remote to use the MON_CODE method of accessing memory.
21075 @kindex use_ib_break
21076 Instructs the remote to set breakpoints by IB break.
21078 @item use_dbt_break
21079 @kindex use_dbt_break
21080 Instructs the remote to set breakpoints by DBT.
21086 The Motorola m68k configuration includes ColdFire support, and a
21087 target command for the following ROM monitor.
21091 @kindex target dbug
21092 @item target dbug @var{dev}
21093 dBUG ROM monitor for Motorola ColdFire.
21098 @subsection MicroBlaze
21099 @cindex Xilinx MicroBlaze
21100 @cindex XMD, Xilinx Microprocessor Debugger
21102 The MicroBlaze is a soft-core processor supported on various Xilinx
21103 FPGAs, such as Spartan or Virtex series. Boards with these processors
21104 usually have JTAG ports which connect to a host system running the Xilinx
21105 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21106 This host system is used to download the configuration bitstream to
21107 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21108 communicates with the target board using the JTAG interface and
21109 presents a @code{gdbserver} interface to the board. By default
21110 @code{xmd} uses port @code{1234}. (While it is possible to change
21111 this default port, it requires the use of undocumented @code{xmd}
21112 commands. Contact Xilinx support if you need to do this.)
21114 Use these GDB commands to connect to the MicroBlaze target processor.
21117 @item target remote :1234
21118 Use this command to connect to the target if you are running @value{GDBN}
21119 on the same system as @code{xmd}.
21121 @item target remote @var{xmd-host}:1234
21122 Use this command to connect to the target if it is connected to @code{xmd}
21123 running on a different system named @var{xmd-host}.
21126 Use this command to download a program to the MicroBlaze target.
21128 @item set debug microblaze @var{n}
21129 Enable MicroBlaze-specific debugging messages if non-zero.
21131 @item show debug microblaze @var{n}
21132 Show MicroBlaze-specific debugging level.
21135 @node MIPS Embedded
21136 @subsection @acronym{MIPS} Embedded
21138 @cindex @acronym{MIPS} boards
21139 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21140 @acronym{MIPS} board attached to a serial line. This is available when
21141 you configure @value{GDBN} with @samp{--target=mips-elf}.
21144 Use these @value{GDBN} commands to specify the connection to your target board:
21147 @item target mips @var{port}
21148 @kindex target mips @var{port}
21149 To run a program on the board, start up @code{@value{GDBP}} with the
21150 name of your program as the argument. To connect to the board, use the
21151 command @samp{target mips @var{port}}, where @var{port} is the name of
21152 the serial port connected to the board. If the program has not already
21153 been downloaded to the board, you may use the @code{load} command to
21154 download it. You can then use all the usual @value{GDBN} commands.
21156 For example, this sequence connects to the target board through a serial
21157 port, and loads and runs a program called @var{prog} through the
21161 host$ @value{GDBP} @var{prog}
21162 @value{GDBN} is free software and @dots{}
21163 (@value{GDBP}) target mips /dev/ttyb
21164 (@value{GDBP}) load @var{prog}
21168 @item target mips @var{hostname}:@var{portnumber}
21169 On some @value{GDBN} host configurations, you can specify a TCP
21170 connection (for instance, to a serial line managed by a terminal
21171 concentrator) instead of a serial port, using the syntax
21172 @samp{@var{hostname}:@var{portnumber}}.
21174 @item target pmon @var{port}
21175 @kindex target pmon @var{port}
21178 @item target ddb @var{port}
21179 @kindex target ddb @var{port}
21180 NEC's DDB variant of PMON for Vr4300.
21182 @item target lsi @var{port}
21183 @kindex target lsi @var{port}
21184 LSI variant of PMON.
21186 @kindex target r3900
21187 @item target r3900 @var{dev}
21188 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21190 @kindex target array
21191 @item target array @var{dev}
21192 Array Tech LSI33K RAID controller board.
21198 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21201 @item set mipsfpu double
21202 @itemx set mipsfpu single
21203 @itemx set mipsfpu none
21204 @itemx set mipsfpu auto
21205 @itemx show mipsfpu
21206 @kindex set mipsfpu
21207 @kindex show mipsfpu
21208 @cindex @acronym{MIPS} remote floating point
21209 @cindex floating point, @acronym{MIPS} remote
21210 If your target board does not support the @acronym{MIPS} floating point
21211 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21212 need this, you may wish to put the command in your @value{GDBN} init
21213 file). This tells @value{GDBN} how to find the return value of
21214 functions which return floating point values. It also allows
21215 @value{GDBN} to avoid saving the floating point registers when calling
21216 functions on the board. If you are using a floating point coprocessor
21217 with only single precision floating point support, as on the @sc{r4650}
21218 processor, use the command @samp{set mipsfpu single}. The default
21219 double precision floating point coprocessor may be selected using
21220 @samp{set mipsfpu double}.
21222 In previous versions the only choices were double precision or no
21223 floating point, so @samp{set mipsfpu on} will select double precision
21224 and @samp{set mipsfpu off} will select no floating point.
21226 As usual, you can inquire about the @code{mipsfpu} variable with
21227 @samp{show mipsfpu}.
21229 @item set timeout @var{seconds}
21230 @itemx set retransmit-timeout @var{seconds}
21231 @itemx show timeout
21232 @itemx show retransmit-timeout
21233 @cindex @code{timeout}, @acronym{MIPS} protocol
21234 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21235 @kindex set timeout
21236 @kindex show timeout
21237 @kindex set retransmit-timeout
21238 @kindex show retransmit-timeout
21239 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21240 remote protocol, with the @code{set timeout @var{seconds}} command. The
21241 default is 5 seconds. Similarly, you can control the timeout used while
21242 waiting for an acknowledgment of a packet with the @code{set
21243 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21244 You can inspect both values with @code{show timeout} and @code{show
21245 retransmit-timeout}. (These commands are @emph{only} available when
21246 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21248 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21249 is waiting for your program to stop. In that case, @value{GDBN} waits
21250 forever because it has no way of knowing how long the program is going
21251 to run before stopping.
21253 @item set syn-garbage-limit @var{num}
21254 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21255 @cindex synchronize with remote @acronym{MIPS} target
21256 Limit the maximum number of characters @value{GDBN} should ignore when
21257 it tries to synchronize with the remote target. The default is 10
21258 characters. Setting the limit to -1 means there's no limit.
21260 @item show syn-garbage-limit
21261 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21262 Show the current limit on the number of characters to ignore when
21263 trying to synchronize with the remote system.
21265 @item set monitor-prompt @var{prompt}
21266 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21267 @cindex remote monitor prompt
21268 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21269 remote monitor. The default depends on the target:
21279 @item show monitor-prompt
21280 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21281 Show the current strings @value{GDBN} expects as the prompt from the
21284 @item set monitor-warnings
21285 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21286 Enable or disable monitor warnings about hardware breakpoints. This
21287 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21288 display warning messages whose codes are returned by the @code{lsi}
21289 PMON monitor for breakpoint commands.
21291 @item show monitor-warnings
21292 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21293 Show the current setting of printing monitor warnings.
21295 @item pmon @var{command}
21296 @kindex pmon@r{, @acronym{MIPS} remote}
21297 @cindex send PMON command
21298 This command allows sending an arbitrary @var{command} string to the
21299 monitor. The monitor must be in debug mode for this to work.
21302 @node PowerPC Embedded
21303 @subsection PowerPC Embedded
21305 @cindex DVC register
21306 @value{GDBN} supports using the DVC (Data Value Compare) register to
21307 implement in hardware simple hardware watchpoint conditions of the form:
21310 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21311 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21314 The DVC register will be automatically used when @value{GDBN} detects
21315 such pattern in a condition expression, and the created watchpoint uses one
21316 debug register (either the @code{exact-watchpoints} option is on and the
21317 variable is scalar, or the variable has a length of one byte). This feature
21318 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21321 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21322 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21323 in which case watchpoints using only one debug register are created when
21324 watching variables of scalar types.
21326 You can create an artificial array to watch an arbitrary memory
21327 region using one of the following commands (@pxref{Expressions}):
21330 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21331 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21334 PowerPC embedded processors support masked watchpoints. See the discussion
21335 about the @code{mask} argument in @ref{Set Watchpoints}.
21337 @cindex ranged breakpoint
21338 PowerPC embedded processors support hardware accelerated
21339 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21340 the inferior whenever it executes an instruction at any address within
21341 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21342 use the @code{break-range} command.
21344 @value{GDBN} provides the following PowerPC-specific commands:
21347 @kindex break-range
21348 @item break-range @var{start-location}, @var{end-location}
21349 Set a breakpoint for an address range given by
21350 @var{start-location} and @var{end-location}, which can specify a function name,
21351 a line number, an offset of lines from the current line or from the start
21352 location, or an address of an instruction (see @ref{Specify Location},
21353 for a list of all the possible ways to specify a @var{location}.)
21354 The breakpoint will stop execution of the inferior whenever it
21355 executes an instruction at any address within the specified range,
21356 (including @var{start-location} and @var{end-location}.)
21358 @kindex set powerpc
21359 @item set powerpc soft-float
21360 @itemx show powerpc soft-float
21361 Force @value{GDBN} to use (or not use) a software floating point calling
21362 convention. By default, @value{GDBN} selects the calling convention based
21363 on the selected architecture and the provided executable file.
21365 @item set powerpc vector-abi
21366 @itemx show powerpc vector-abi
21367 Force @value{GDBN} to use the specified calling convention for vector
21368 arguments and return values. The valid options are @samp{auto};
21369 @samp{generic}, to avoid vector registers even if they are present;
21370 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21371 registers. By default, @value{GDBN} selects the calling convention
21372 based on the selected architecture and the provided executable file.
21374 @item set powerpc exact-watchpoints
21375 @itemx show powerpc exact-watchpoints
21376 Allow @value{GDBN} to use only one debug register when watching a variable
21377 of scalar type, thus assuming that the variable is accessed through the
21378 address of its first byte.
21380 @kindex target dink32
21381 @item target dink32 @var{dev}
21382 DINK32 ROM monitor.
21384 @kindex target ppcbug
21385 @item target ppcbug @var{dev}
21386 @kindex target ppcbug1
21387 @item target ppcbug1 @var{dev}
21388 PPCBUG ROM monitor for PowerPC.
21391 @item target sds @var{dev}
21392 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21395 @cindex SDS protocol
21396 The following commands specific to the SDS protocol are supported
21400 @item set sdstimeout @var{nsec}
21401 @kindex set sdstimeout
21402 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21403 default is 2 seconds.
21405 @item show sdstimeout
21406 @kindex show sdstimeout
21407 Show the current value of the SDS timeout.
21409 @item sds @var{command}
21410 @kindex sds@r{, a command}
21411 Send the specified @var{command} string to the SDS monitor.
21416 @subsection HP PA Embedded
21420 @kindex target op50n
21421 @item target op50n @var{dev}
21422 OP50N monitor, running on an OKI HPPA board.
21424 @kindex target w89k
21425 @item target w89k @var{dev}
21426 W89K monitor, running on a Winbond HPPA board.
21431 @subsection Tsqware Sparclet
21435 @value{GDBN} enables developers to debug tasks running on
21436 Sparclet targets from a Unix host.
21437 @value{GDBN} uses code that runs on
21438 both the Unix host and on the Sparclet target. The program
21439 @code{@value{GDBP}} is installed and executed on the Unix host.
21442 @item remotetimeout @var{args}
21443 @kindex remotetimeout
21444 @value{GDBN} supports the option @code{remotetimeout}.
21445 This option is set by the user, and @var{args} represents the number of
21446 seconds @value{GDBN} waits for responses.
21449 @cindex compiling, on Sparclet
21450 When compiling for debugging, include the options @samp{-g} to get debug
21451 information and @samp{-Ttext} to relocate the program to where you wish to
21452 load it on the target. You may also want to add the options @samp{-n} or
21453 @samp{-N} in order to reduce the size of the sections. Example:
21456 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21459 You can use @code{objdump} to verify that the addresses are what you intended:
21462 sparclet-aout-objdump --headers --syms prog
21465 @cindex running, on Sparclet
21467 your Unix execution search path to find @value{GDBN}, you are ready to
21468 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21469 (or @code{sparclet-aout-gdb}, depending on your installation).
21471 @value{GDBN} comes up showing the prompt:
21478 * Sparclet File:: Setting the file to debug
21479 * Sparclet Connection:: Connecting to Sparclet
21480 * Sparclet Download:: Sparclet download
21481 * Sparclet Execution:: Running and debugging
21484 @node Sparclet File
21485 @subsubsection Setting File to Debug
21487 The @value{GDBN} command @code{file} lets you choose with program to debug.
21490 (gdbslet) file prog
21494 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21495 @value{GDBN} locates
21496 the file by searching the directories listed in the command search
21498 If the file was compiled with debug information (option @samp{-g}), source
21499 files will be searched as well.
21500 @value{GDBN} locates
21501 the source files by searching the directories listed in the directory search
21502 path (@pxref{Environment, ,Your Program's Environment}).
21504 to find a file, it displays a message such as:
21507 prog: No such file or directory.
21510 When this happens, add the appropriate directories to the search paths with
21511 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21512 @code{target} command again.
21514 @node Sparclet Connection
21515 @subsubsection Connecting to Sparclet
21517 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21518 To connect to a target on serial port ``@code{ttya}'', type:
21521 (gdbslet) target sparclet /dev/ttya
21522 Remote target sparclet connected to /dev/ttya
21523 main () at ../prog.c:3
21527 @value{GDBN} displays messages like these:
21533 @node Sparclet Download
21534 @subsubsection Sparclet Download
21536 @cindex download to Sparclet
21537 Once connected to the Sparclet target,
21538 you can use the @value{GDBN}
21539 @code{load} command to download the file from the host to the target.
21540 The file name and load offset should be given as arguments to the @code{load}
21542 Since the file format is aout, the program must be loaded to the starting
21543 address. You can use @code{objdump} to find out what this value is. The load
21544 offset is an offset which is added to the VMA (virtual memory address)
21545 of each of the file's sections.
21546 For instance, if the program
21547 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21548 and bss at 0x12010170, in @value{GDBN}, type:
21551 (gdbslet) load prog 0x12010000
21552 Loading section .text, size 0xdb0 vma 0x12010000
21555 If the code is loaded at a different address then what the program was linked
21556 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21557 to tell @value{GDBN} where to map the symbol table.
21559 @node Sparclet Execution
21560 @subsubsection Running and Debugging
21562 @cindex running and debugging Sparclet programs
21563 You can now begin debugging the task using @value{GDBN}'s execution control
21564 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21565 manual for the list of commands.
21569 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21571 Starting program: prog
21572 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21573 3 char *symarg = 0;
21575 4 char *execarg = "hello!";
21580 @subsection Fujitsu Sparclite
21584 @kindex target sparclite
21585 @item target sparclite @var{dev}
21586 Fujitsu sparclite boards, used only for the purpose of loading.
21587 You must use an additional command to debug the program.
21588 For example: target remote @var{dev} using @value{GDBN} standard
21594 @subsection Zilog Z8000
21597 @cindex simulator, Z8000
21598 @cindex Zilog Z8000 simulator
21600 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21603 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21604 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21605 segmented variant). The simulator recognizes which architecture is
21606 appropriate by inspecting the object code.
21609 @item target sim @var{args}
21611 @kindex target sim@r{, with Z8000}
21612 Debug programs on a simulated CPU. If the simulator supports setup
21613 options, specify them via @var{args}.
21617 After specifying this target, you can debug programs for the simulated
21618 CPU in the same style as programs for your host computer; use the
21619 @code{file} command to load a new program image, the @code{run} command
21620 to run your program, and so on.
21622 As well as making available all the usual machine registers
21623 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21624 additional items of information as specially named registers:
21629 Counts clock-ticks in the simulator.
21632 Counts instructions run in the simulator.
21635 Execution time in 60ths of a second.
21639 You can refer to these values in @value{GDBN} expressions with the usual
21640 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21641 conditional breakpoint that suspends only after at least 5000
21642 simulated clock ticks.
21645 @subsection Atmel AVR
21648 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21649 following AVR-specific commands:
21652 @item info io_registers
21653 @kindex info io_registers@r{, AVR}
21654 @cindex I/O registers (Atmel AVR)
21655 This command displays information about the AVR I/O registers. For
21656 each register, @value{GDBN} prints its number and value.
21663 When configured for debugging CRIS, @value{GDBN} provides the
21664 following CRIS-specific commands:
21667 @item set cris-version @var{ver}
21668 @cindex CRIS version
21669 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21670 The CRIS version affects register names and sizes. This command is useful in
21671 case autodetection of the CRIS version fails.
21673 @item show cris-version
21674 Show the current CRIS version.
21676 @item set cris-dwarf2-cfi
21677 @cindex DWARF-2 CFI and CRIS
21678 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21679 Change to @samp{off} when using @code{gcc-cris} whose version is below
21682 @item show cris-dwarf2-cfi
21683 Show the current state of using DWARF-2 CFI.
21685 @item set cris-mode @var{mode}
21687 Set the current CRIS mode to @var{mode}. It should only be changed when
21688 debugging in guru mode, in which case it should be set to
21689 @samp{guru} (the default is @samp{normal}).
21691 @item show cris-mode
21692 Show the current CRIS mode.
21696 @subsection Renesas Super-H
21699 For the Renesas Super-H processor, @value{GDBN} provides these
21703 @item set sh calling-convention @var{convention}
21704 @kindex set sh calling-convention
21705 Set the calling-convention used when calling functions from @value{GDBN}.
21706 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21707 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21708 convention. If the DWARF-2 information of the called function specifies
21709 that the function follows the Renesas calling convention, the function
21710 is called using the Renesas calling convention. If the calling convention
21711 is set to @samp{renesas}, the Renesas calling convention is always used,
21712 regardless of the DWARF-2 information. This can be used to override the
21713 default of @samp{gcc} if debug information is missing, or the compiler
21714 does not emit the DWARF-2 calling convention entry for a function.
21716 @item show sh calling-convention
21717 @kindex show sh calling-convention
21718 Show the current calling convention setting.
21723 @node Architectures
21724 @section Architectures
21726 This section describes characteristics of architectures that affect
21727 all uses of @value{GDBN} with the architecture, both native and cross.
21734 * HPPA:: HP PA architecture
21735 * SPU:: Cell Broadband Engine SPU architecture
21741 @subsection AArch64
21742 @cindex AArch64 support
21744 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21745 following special commands:
21748 @item set debug aarch64
21749 @kindex set debug aarch64
21750 This command determines whether AArch64 architecture-specific debugging
21751 messages are to be displayed.
21753 @item show debug aarch64
21754 Show whether AArch64 debugging messages are displayed.
21759 @subsection x86 Architecture-specific Issues
21762 @item set struct-convention @var{mode}
21763 @kindex set struct-convention
21764 @cindex struct return convention
21765 @cindex struct/union returned in registers
21766 Set the convention used by the inferior to return @code{struct}s and
21767 @code{union}s from functions to @var{mode}. Possible values of
21768 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21769 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21770 are returned on the stack, while @code{"reg"} means that a
21771 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21772 be returned in a register.
21774 @item show struct-convention
21775 @kindex show struct-convention
21776 Show the current setting of the convention to return @code{struct}s
21780 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21781 @cindex Intel(R) Memory Protection Extensions (MPX).
21783 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21784 @footnote{The register named with capital letters represent the architecture
21785 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21786 which are the lower bound and upper bound. Bounds are effective addresses or
21787 memory locations. The upper bounds are architecturally represented in 1's
21788 complement form. A bound having lower bound = 0, and upper bound = 0
21789 (1's complement of all bits set) will allow access to the entire address space.
21791 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21792 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21793 display the upper bound performing the complement of one operation on the
21794 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21795 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21796 can also be noted that the upper bounds are inclusive.
21798 As an example, assume that the register BND0 holds bounds for a pointer having
21799 access allowed for the range between 0x32 and 0x71. The values present on
21800 bnd0raw and bnd registers are presented as follows:
21803 bnd0raw = @{0x32, 0xffffffff8e@}
21804 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21807 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21808 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21809 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21810 Python, the display includes the memory size, in bits, accessible to
21816 See the following section.
21819 @subsection @acronym{MIPS}
21821 @cindex stack on Alpha
21822 @cindex stack on @acronym{MIPS}
21823 @cindex Alpha stack
21824 @cindex @acronym{MIPS} stack
21825 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21826 sometimes requires @value{GDBN} to search backward in the object code to
21827 find the beginning of a function.
21829 @cindex response time, @acronym{MIPS} debugging
21830 To improve response time (especially for embedded applications, where
21831 @value{GDBN} may be restricted to a slow serial line for this search)
21832 you may want to limit the size of this search, using one of these
21836 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21837 @item set heuristic-fence-post @var{limit}
21838 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21839 search for the beginning of a function. A value of @var{0} (the
21840 default) means there is no limit. However, except for @var{0}, the
21841 larger the limit the more bytes @code{heuristic-fence-post} must search
21842 and therefore the longer it takes to run. You should only need to use
21843 this command when debugging a stripped executable.
21845 @item show heuristic-fence-post
21846 Display the current limit.
21850 These commands are available @emph{only} when @value{GDBN} is configured
21851 for debugging programs on Alpha or @acronym{MIPS} processors.
21853 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21857 @item set mips abi @var{arg}
21858 @kindex set mips abi
21859 @cindex set ABI for @acronym{MIPS}
21860 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21861 values of @var{arg} are:
21865 The default ABI associated with the current binary (this is the
21875 @item show mips abi
21876 @kindex show mips abi
21877 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21879 @item set mips compression @var{arg}
21880 @kindex set mips compression
21881 @cindex code compression, @acronym{MIPS}
21882 Tell @value{GDBN} which @acronym{MIPS} compressed
21883 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21884 inferior. @value{GDBN} uses this for code disassembly and other
21885 internal interpretation purposes. This setting is only referred to
21886 when no executable has been associated with the debugging session or
21887 the executable does not provide information about the encoding it uses.
21888 Otherwise this setting is automatically updated from information
21889 provided by the executable.
21891 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21892 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21893 executables containing @acronym{MIPS16} code frequently are not
21894 identified as such.
21896 This setting is ``sticky''; that is, it retains its value across
21897 debugging sessions until reset either explicitly with this command or
21898 implicitly from an executable.
21900 The compiler and/or assembler typically add symbol table annotations to
21901 identify functions compiled for the @acronym{MIPS16} or
21902 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21903 are present, @value{GDBN} uses them in preference to the global
21904 compressed @acronym{ISA} encoding setting.
21906 @item show mips compression
21907 @kindex show mips compression
21908 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21909 @value{GDBN} to debug the inferior.
21912 @itemx show mipsfpu
21913 @xref{MIPS Embedded, set mipsfpu}.
21915 @item set mips mask-address @var{arg}
21916 @kindex set mips mask-address
21917 @cindex @acronym{MIPS} addresses, masking
21918 This command determines whether the most-significant 32 bits of 64-bit
21919 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21920 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21921 setting, which lets @value{GDBN} determine the correct value.
21923 @item show mips mask-address
21924 @kindex show mips mask-address
21925 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21928 @item set remote-mips64-transfers-32bit-regs
21929 @kindex set remote-mips64-transfers-32bit-regs
21930 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21931 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21932 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21933 and 64 bits for other registers, set this option to @samp{on}.
21935 @item show remote-mips64-transfers-32bit-regs
21936 @kindex show remote-mips64-transfers-32bit-regs
21937 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21939 @item set debug mips
21940 @kindex set debug mips
21941 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21942 target code in @value{GDBN}.
21944 @item show debug mips
21945 @kindex show debug mips
21946 Show the current setting of @acronym{MIPS} debugging messages.
21952 @cindex HPPA support
21954 When @value{GDBN} is debugging the HP PA architecture, it provides the
21955 following special commands:
21958 @item set debug hppa
21959 @kindex set debug hppa
21960 This command determines whether HPPA architecture-specific debugging
21961 messages are to be displayed.
21963 @item show debug hppa
21964 Show whether HPPA debugging messages are displayed.
21966 @item maint print unwind @var{address}
21967 @kindex maint print unwind@r{, HPPA}
21968 This command displays the contents of the unwind table entry at the
21969 given @var{address}.
21975 @subsection Cell Broadband Engine SPU architecture
21976 @cindex Cell Broadband Engine
21979 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21980 it provides the following special commands:
21983 @item info spu event
21985 Display SPU event facility status. Shows current event mask
21986 and pending event status.
21988 @item info spu signal
21989 Display SPU signal notification facility status. Shows pending
21990 signal-control word and signal notification mode of both signal
21991 notification channels.
21993 @item info spu mailbox
21994 Display SPU mailbox facility status. Shows all pending entries,
21995 in order of processing, in each of the SPU Write Outbound,
21996 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21999 Display MFC DMA status. Shows all pending commands in the MFC
22000 DMA queue. For each entry, opcode, tag, class IDs, effective
22001 and local store addresses and transfer size are shown.
22003 @item info spu proxydma
22004 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22005 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22006 and local store addresses and transfer size are shown.
22010 When @value{GDBN} is debugging a combined PowerPC/SPU application
22011 on the Cell Broadband Engine, it provides in addition the following
22015 @item set spu stop-on-load @var{arg}
22017 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22018 will give control to the user when a new SPE thread enters its @code{main}
22019 function. The default is @code{off}.
22021 @item show spu stop-on-load
22023 Show whether to stop for new SPE threads.
22025 @item set spu auto-flush-cache @var{arg}
22026 Set whether to automatically flush the software-managed cache. When set to
22027 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22028 cache to be flushed whenever SPE execution stops. This provides a consistent
22029 view of PowerPC memory that is accessed via the cache. If an application
22030 does not use the software-managed cache, this option has no effect.
22032 @item show spu auto-flush-cache
22033 Show whether to automatically flush the software-managed cache.
22038 @subsection PowerPC
22039 @cindex PowerPC architecture
22041 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22042 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22043 numbers stored in the floating point registers. These values must be stored
22044 in two consecutive registers, always starting at an even register like
22045 @code{f0} or @code{f2}.
22047 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22048 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22049 @code{f2} and @code{f3} for @code{$dl1} and so on.
22051 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22052 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22055 @subsection Nios II
22056 @cindex Nios II architecture
22058 When @value{GDBN} is debugging the Nios II architecture,
22059 it provides the following special commands:
22063 @item set debug nios2
22064 @kindex set debug nios2
22065 This command turns on and off debugging messages for the Nios II
22066 target code in @value{GDBN}.
22068 @item show debug nios2
22069 @kindex show debug nios2
22070 Show the current setting of Nios II debugging messages.
22073 @node Controlling GDB
22074 @chapter Controlling @value{GDBN}
22076 You can alter the way @value{GDBN} interacts with you by using the
22077 @code{set} command. For commands controlling how @value{GDBN} displays
22078 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22083 * Editing:: Command editing
22084 * Command History:: Command history
22085 * Screen Size:: Screen size
22086 * Numbers:: Numbers
22087 * ABI:: Configuring the current ABI
22088 * Auto-loading:: Automatically loading associated files
22089 * Messages/Warnings:: Optional warnings and messages
22090 * Debugging Output:: Optional messages about internal happenings
22091 * Other Misc Settings:: Other Miscellaneous Settings
22099 @value{GDBN} indicates its readiness to read a command by printing a string
22100 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22101 can change the prompt string with the @code{set prompt} command. For
22102 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22103 the prompt in one of the @value{GDBN} sessions so that you can always tell
22104 which one you are talking to.
22106 @emph{Note:} @code{set prompt} does not add a space for you after the
22107 prompt you set. This allows you to set a prompt which ends in a space
22108 or a prompt that does not.
22112 @item set prompt @var{newprompt}
22113 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22115 @kindex show prompt
22117 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22120 Versions of @value{GDBN} that ship with Python scripting enabled have
22121 prompt extensions. The commands for interacting with these extensions
22125 @kindex set extended-prompt
22126 @item set extended-prompt @var{prompt}
22127 Set an extended prompt that allows for substitutions.
22128 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22129 substitution. Any escape sequences specified as part of the prompt
22130 string are replaced with the corresponding strings each time the prompt
22136 set extended-prompt Current working directory: \w (gdb)
22139 Note that when an extended-prompt is set, it takes control of the
22140 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22142 @kindex show extended-prompt
22143 @item show extended-prompt
22144 Prints the extended prompt. Any escape sequences specified as part of
22145 the prompt string with @code{set extended-prompt}, are replaced with the
22146 corresponding strings each time the prompt is displayed.
22150 @section Command Editing
22152 @cindex command line editing
22154 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22155 @sc{gnu} library provides consistent behavior for programs which provide a
22156 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22157 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22158 substitution, and a storage and recall of command history across
22159 debugging sessions.
22161 You may control the behavior of command line editing in @value{GDBN} with the
22162 command @code{set}.
22165 @kindex set editing
22168 @itemx set editing on
22169 Enable command line editing (enabled by default).
22171 @item set editing off
22172 Disable command line editing.
22174 @kindex show editing
22176 Show whether command line editing is enabled.
22179 @ifset SYSTEM_READLINE
22180 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22182 @ifclear SYSTEM_READLINE
22183 @xref{Command Line Editing},
22185 for more details about the Readline
22186 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22187 encouraged to read that chapter.
22189 @node Command History
22190 @section Command History
22191 @cindex command history
22193 @value{GDBN} can keep track of the commands you type during your
22194 debugging sessions, so that you can be certain of precisely what
22195 happened. Use these commands to manage the @value{GDBN} command
22198 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22199 package, to provide the history facility.
22200 @ifset SYSTEM_READLINE
22201 @xref{Using History Interactively, , , history, GNU History Library},
22203 @ifclear SYSTEM_READLINE
22204 @xref{Using History Interactively},
22206 for the detailed description of the History library.
22208 To issue a command to @value{GDBN} without affecting certain aspects of
22209 the state which is seen by users, prefix it with @samp{server }
22210 (@pxref{Server Prefix}). This
22211 means that this command will not affect the command history, nor will it
22212 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22213 pressed on a line by itself.
22215 @cindex @code{server}, command prefix
22216 The server prefix does not affect the recording of values into the value
22217 history; to print a value without recording it into the value history,
22218 use the @code{output} command instead of the @code{print} command.
22220 Here is the description of @value{GDBN} commands related to command
22224 @cindex history substitution
22225 @cindex history file
22226 @kindex set history filename
22227 @cindex @env{GDBHISTFILE}, environment variable
22228 @item set history filename @var{fname}
22229 Set the name of the @value{GDBN} command history file to @var{fname}.
22230 This is the file where @value{GDBN} reads an initial command history
22231 list, and where it writes the command history from this session when it
22232 exits. You can access this list through history expansion or through
22233 the history command editing characters listed below. This file defaults
22234 to the value of the environment variable @code{GDBHISTFILE}, or to
22235 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22238 @cindex save command history
22239 @kindex set history save
22240 @item set history save
22241 @itemx set history save on
22242 Record command history in a file, whose name may be specified with the
22243 @code{set history filename} command. By default, this option is disabled.
22245 @item set history save off
22246 Stop recording command history in a file.
22248 @cindex history size
22249 @kindex set history size
22250 @cindex @env{HISTSIZE}, environment variable
22251 @item set history size @var{size}
22252 @itemx set history size unlimited
22253 Set the number of commands which @value{GDBN} keeps in its history list.
22254 This defaults to the value of the environment variable
22255 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22256 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22257 history list is unlimited.
22260 History expansion assigns special meaning to the character @kbd{!}.
22261 @ifset SYSTEM_READLINE
22262 @xref{Event Designators, , , history, GNU History Library},
22264 @ifclear SYSTEM_READLINE
22265 @xref{Event Designators},
22269 @cindex history expansion, turn on/off
22270 Since @kbd{!} is also the logical not operator in C, history expansion
22271 is off by default. If you decide to enable history expansion with the
22272 @code{set history expansion on} command, you may sometimes need to
22273 follow @kbd{!} (when it is used as logical not, in an expression) with
22274 a space or a tab to prevent it from being expanded. The readline
22275 history facilities do not attempt substitution on the strings
22276 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22278 The commands to control history expansion are:
22281 @item set history expansion on
22282 @itemx set history expansion
22283 @kindex set history expansion
22284 Enable history expansion. History expansion is off by default.
22286 @item set history expansion off
22287 Disable history expansion.
22290 @kindex show history
22292 @itemx show history filename
22293 @itemx show history save
22294 @itemx show history size
22295 @itemx show history expansion
22296 These commands display the state of the @value{GDBN} history parameters.
22297 @code{show history} by itself displays all four states.
22302 @kindex show commands
22303 @cindex show last commands
22304 @cindex display command history
22305 @item show commands
22306 Display the last ten commands in the command history.
22308 @item show commands @var{n}
22309 Print ten commands centered on command number @var{n}.
22311 @item show commands +
22312 Print ten commands just after the commands last printed.
22316 @section Screen Size
22317 @cindex size of screen
22318 @cindex screen size
22321 @cindex pauses in output
22323 Certain commands to @value{GDBN} may produce large amounts of
22324 information output to the screen. To help you read all of it,
22325 @value{GDBN} pauses and asks you for input at the end of each page of
22326 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22327 to discard the remaining output. Also, the screen width setting
22328 determines when to wrap lines of output. Depending on what is being
22329 printed, @value{GDBN} tries to break the line at a readable place,
22330 rather than simply letting it overflow onto the following line.
22332 Normally @value{GDBN} knows the size of the screen from the terminal
22333 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22334 together with the value of the @code{TERM} environment variable and the
22335 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22336 you can override it with the @code{set height} and @code{set
22343 @kindex show height
22344 @item set height @var{lpp}
22345 @itemx set height unlimited
22347 @itemx set width @var{cpl}
22348 @itemx set width unlimited
22350 These @code{set} commands specify a screen height of @var{lpp} lines and
22351 a screen width of @var{cpl} characters. The associated @code{show}
22352 commands display the current settings.
22354 If you specify a height of either @code{unlimited} or zero lines,
22355 @value{GDBN} does not pause during output no matter how long the
22356 output is. This is useful if output is to a file or to an editor
22359 Likewise, you can specify @samp{set width unlimited} or @samp{set
22360 width 0} to prevent @value{GDBN} from wrapping its output.
22362 @item set pagination on
22363 @itemx set pagination off
22364 @kindex set pagination
22365 Turn the output pagination on or off; the default is on. Turning
22366 pagination off is the alternative to @code{set height unlimited}. Note that
22367 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22368 Options, -batch}) also automatically disables pagination.
22370 @item show pagination
22371 @kindex show pagination
22372 Show the current pagination mode.
22377 @cindex number representation
22378 @cindex entering numbers
22380 You can always enter numbers in octal, decimal, or hexadecimal in
22381 @value{GDBN} by the usual conventions: octal numbers begin with
22382 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22383 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22384 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22385 10; likewise, the default display for numbers---when no particular
22386 format is specified---is base 10. You can change the default base for
22387 both input and output with the commands described below.
22390 @kindex set input-radix
22391 @item set input-radix @var{base}
22392 Set the default base for numeric input. Supported choices
22393 for @var{base} are decimal 8, 10, or 16. The base must itself be
22394 specified either unambiguously or using the current input radix; for
22398 set input-radix 012
22399 set input-radix 10.
22400 set input-radix 0xa
22404 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22405 leaves the input radix unchanged, no matter what it was, since
22406 @samp{10}, being without any leading or trailing signs of its base, is
22407 interpreted in the current radix. Thus, if the current radix is 16,
22408 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22411 @kindex set output-radix
22412 @item set output-radix @var{base}
22413 Set the default base for numeric display. Supported choices
22414 for @var{base} are decimal 8, 10, or 16. The base must itself be
22415 specified either unambiguously or using the current input radix.
22417 @kindex show input-radix
22418 @item show input-radix
22419 Display the current default base for numeric input.
22421 @kindex show output-radix
22422 @item show output-radix
22423 Display the current default base for numeric display.
22425 @item set radix @r{[}@var{base}@r{]}
22429 These commands set and show the default base for both input and output
22430 of numbers. @code{set radix} sets the radix of input and output to
22431 the same base; without an argument, it resets the radix back to its
22432 default value of 10.
22437 @section Configuring the Current ABI
22439 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22440 application automatically. However, sometimes you need to override its
22441 conclusions. Use these commands to manage @value{GDBN}'s view of the
22447 @cindex Newlib OS ABI and its influence on the longjmp handling
22449 One @value{GDBN} configuration can debug binaries for multiple operating
22450 system targets, either via remote debugging or native emulation.
22451 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22452 but you can override its conclusion using the @code{set osabi} command.
22453 One example where this is useful is in debugging of binaries which use
22454 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22455 not have the same identifying marks that the standard C library for your
22458 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22459 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22460 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22461 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22465 Show the OS ABI currently in use.
22468 With no argument, show the list of registered available OS ABI's.
22470 @item set osabi @var{abi}
22471 Set the current OS ABI to @var{abi}.
22474 @cindex float promotion
22476 Generally, the way that an argument of type @code{float} is passed to a
22477 function depends on whether the function is prototyped. For a prototyped
22478 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22479 according to the architecture's convention for @code{float}. For unprototyped
22480 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22481 @code{double} and then passed.
22483 Unfortunately, some forms of debug information do not reliably indicate whether
22484 a function is prototyped. If @value{GDBN} calls a function that is not marked
22485 as prototyped, it consults @kbd{set coerce-float-to-double}.
22488 @kindex set coerce-float-to-double
22489 @item set coerce-float-to-double
22490 @itemx set coerce-float-to-double on
22491 Arguments of type @code{float} will be promoted to @code{double} when passed
22492 to an unprototyped function. This is the default setting.
22494 @item set coerce-float-to-double off
22495 Arguments of type @code{float} will be passed directly to unprototyped
22498 @kindex show coerce-float-to-double
22499 @item show coerce-float-to-double
22500 Show the current setting of promoting @code{float} to @code{double}.
22504 @kindex show cp-abi
22505 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22506 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22507 used to build your application. @value{GDBN} only fully supports
22508 programs with a single C@t{++} ABI; if your program contains code using
22509 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22510 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22511 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22512 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22513 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22514 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22519 Show the C@t{++} ABI currently in use.
22522 With no argument, show the list of supported C@t{++} ABI's.
22524 @item set cp-abi @var{abi}
22525 @itemx set cp-abi auto
22526 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22530 @section Automatically loading associated files
22531 @cindex auto-loading
22533 @value{GDBN} sometimes reads files with commands and settings automatically,
22534 without being explicitly told so by the user. We call this feature
22535 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22536 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22537 results or introduce security risks (e.g., if the file comes from untrusted
22541 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22542 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22544 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22545 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22548 There are various kinds of files @value{GDBN} can automatically load.
22549 In addition to these files, @value{GDBN} supports auto-loading code written
22550 in various extension languages. @xref{Auto-loading extensions}.
22552 Note that loading of these associated files (including the local @file{.gdbinit}
22553 file) requires accordingly configured @code{auto-load safe-path}
22554 (@pxref{Auto-loading safe path}).
22556 For these reasons, @value{GDBN} includes commands and options to let you
22557 control when to auto-load files and which files should be auto-loaded.
22560 @anchor{set auto-load off}
22561 @kindex set auto-load off
22562 @item set auto-load off
22563 Globally disable loading of all auto-loaded files.
22564 You may want to use this command with the @samp{-iex} option
22565 (@pxref{Option -init-eval-command}) such as:
22567 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22570 Be aware that system init file (@pxref{System-wide configuration})
22571 and init files from your home directory (@pxref{Home Directory Init File})
22572 still get read (as they come from generally trusted directories).
22573 To prevent @value{GDBN} from auto-loading even those init files, use the
22574 @option{-nx} option (@pxref{Mode Options}), in addition to
22575 @code{set auto-load no}.
22577 @anchor{show auto-load}
22578 @kindex show auto-load
22579 @item show auto-load
22580 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22584 (gdb) show auto-load
22585 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22586 libthread-db: Auto-loading of inferior specific libthread_db is on.
22587 local-gdbinit: Auto-loading of .gdbinit script from current directory
22589 python-scripts: Auto-loading of Python scripts is on.
22590 safe-path: List of directories from which it is safe to auto-load files
22591 is $debugdir:$datadir/auto-load.
22592 scripts-directory: List of directories from which to load auto-loaded scripts
22593 is $debugdir:$datadir/auto-load.
22596 @anchor{info auto-load}
22597 @kindex info auto-load
22598 @item info auto-load
22599 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22603 (gdb) info auto-load
22606 Yes /home/user/gdb/gdb-gdb.gdb
22607 libthread-db: No auto-loaded libthread-db.
22608 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22612 Yes /home/user/gdb/gdb-gdb.py
22616 These are @value{GDBN} control commands for the auto-loading:
22618 @multitable @columnfractions .5 .5
22619 @item @xref{set auto-load off}.
22620 @tab Disable auto-loading globally.
22621 @item @xref{show auto-load}.
22622 @tab Show setting of all kinds of files.
22623 @item @xref{info auto-load}.
22624 @tab Show state of all kinds of files.
22625 @item @xref{set auto-load gdb-scripts}.
22626 @tab Control for @value{GDBN} command scripts.
22627 @item @xref{show auto-load gdb-scripts}.
22628 @tab Show setting of @value{GDBN} command scripts.
22629 @item @xref{info auto-load gdb-scripts}.
22630 @tab Show state of @value{GDBN} command scripts.
22631 @item @xref{set auto-load python-scripts}.
22632 @tab Control for @value{GDBN} Python scripts.
22633 @item @xref{show auto-load python-scripts}.
22634 @tab Show setting of @value{GDBN} Python scripts.
22635 @item @xref{info auto-load python-scripts}.
22636 @tab Show state of @value{GDBN} Python scripts.
22637 @item @xref{set auto-load guile-scripts}.
22638 @tab Control for @value{GDBN} Guile scripts.
22639 @item @xref{show auto-load guile-scripts}.
22640 @tab Show setting of @value{GDBN} Guile scripts.
22641 @item @xref{info auto-load guile-scripts}.
22642 @tab Show state of @value{GDBN} Guile scripts.
22643 @item @xref{set auto-load scripts-directory}.
22644 @tab Control for @value{GDBN} auto-loaded scripts location.
22645 @item @xref{show auto-load scripts-directory}.
22646 @tab Show @value{GDBN} auto-loaded scripts location.
22647 @item @xref{add-auto-load-scripts-directory}.
22648 @tab Add directory for auto-loaded scripts location list.
22649 @item @xref{set auto-load local-gdbinit}.
22650 @tab Control for init file in the current directory.
22651 @item @xref{show auto-load local-gdbinit}.
22652 @tab Show setting of init file in the current directory.
22653 @item @xref{info auto-load local-gdbinit}.
22654 @tab Show state of init file in the current directory.
22655 @item @xref{set auto-load libthread-db}.
22656 @tab Control for thread debugging library.
22657 @item @xref{show auto-load libthread-db}.
22658 @tab Show setting of thread debugging library.
22659 @item @xref{info auto-load libthread-db}.
22660 @tab Show state of thread debugging library.
22661 @item @xref{set auto-load safe-path}.
22662 @tab Control directories trusted for automatic loading.
22663 @item @xref{show auto-load safe-path}.
22664 @tab Show directories trusted for automatic loading.
22665 @item @xref{add-auto-load-safe-path}.
22666 @tab Add directory trusted for automatic loading.
22669 @node Init File in the Current Directory
22670 @subsection Automatically loading init file in the current directory
22671 @cindex auto-loading init file in the current directory
22673 By default, @value{GDBN} reads and executes the canned sequences of commands
22674 from init file (if any) in the current working directory,
22675 see @ref{Init File in the Current Directory during Startup}.
22677 Note that loading of this local @file{.gdbinit} file also requires accordingly
22678 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22681 @anchor{set auto-load local-gdbinit}
22682 @kindex set auto-load local-gdbinit
22683 @item set auto-load local-gdbinit [on|off]
22684 Enable or disable the auto-loading of canned sequences of commands
22685 (@pxref{Sequences}) found in init file in the current directory.
22687 @anchor{show auto-load local-gdbinit}
22688 @kindex show auto-load local-gdbinit
22689 @item show auto-load local-gdbinit
22690 Show whether auto-loading of canned sequences of commands from init file in the
22691 current directory is enabled or disabled.
22693 @anchor{info auto-load local-gdbinit}
22694 @kindex info auto-load local-gdbinit
22695 @item info auto-load local-gdbinit
22696 Print whether canned sequences of commands from init file in the
22697 current directory have been auto-loaded.
22700 @node libthread_db.so.1 file
22701 @subsection Automatically loading thread debugging library
22702 @cindex auto-loading libthread_db.so.1
22704 This feature is currently present only on @sc{gnu}/Linux native hosts.
22706 @value{GDBN} reads in some cases thread debugging library from places specific
22707 to the inferior (@pxref{set libthread-db-search-path}).
22709 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22710 without checking this @samp{set auto-load libthread-db} switch as system
22711 libraries have to be trusted in general. In all other cases of
22712 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22713 auto-load libthread-db} is enabled before trying to open such thread debugging
22716 Note that loading of this debugging library also requires accordingly configured
22717 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22720 @anchor{set auto-load libthread-db}
22721 @kindex set auto-load libthread-db
22722 @item set auto-load libthread-db [on|off]
22723 Enable or disable the auto-loading of inferior specific thread debugging library.
22725 @anchor{show auto-load libthread-db}
22726 @kindex show auto-load libthread-db
22727 @item show auto-load libthread-db
22728 Show whether auto-loading of inferior specific thread debugging library is
22729 enabled or disabled.
22731 @anchor{info auto-load libthread-db}
22732 @kindex info auto-load libthread-db
22733 @item info auto-load libthread-db
22734 Print the list of all loaded inferior specific thread debugging libraries and
22735 for each such library print list of inferior @var{pid}s using it.
22738 @node Auto-loading safe path
22739 @subsection Security restriction for auto-loading
22740 @cindex auto-loading safe-path
22742 As the files of inferior can come from untrusted source (such as submitted by
22743 an application user) @value{GDBN} does not always load any files automatically.
22744 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22745 directories trusted for loading files not explicitly requested by user.
22746 Each directory can also be a shell wildcard pattern.
22748 If the path is not set properly you will see a warning and the file will not
22753 Reading symbols from /home/user/gdb/gdb...done.
22754 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22755 declined by your `auto-load safe-path' set
22756 to "$debugdir:$datadir/auto-load".
22757 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22758 declined by your `auto-load safe-path' set
22759 to "$debugdir:$datadir/auto-load".
22763 To instruct @value{GDBN} to go ahead and use the init files anyway,
22764 invoke @value{GDBN} like this:
22767 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22770 The list of trusted directories is controlled by the following commands:
22773 @anchor{set auto-load safe-path}
22774 @kindex set auto-load safe-path
22775 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22776 Set the list of directories (and their subdirectories) trusted for automatic
22777 loading and execution of scripts. You can also enter a specific trusted file.
22778 Each directory can also be a shell wildcard pattern; wildcards do not match
22779 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22780 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22781 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22782 its default value as specified during @value{GDBN} compilation.
22784 The list of directories uses path separator (@samp{:} on GNU and Unix
22785 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22786 to the @env{PATH} environment variable.
22788 @anchor{show auto-load safe-path}
22789 @kindex show auto-load safe-path
22790 @item show auto-load safe-path
22791 Show the list of directories trusted for automatic loading and execution of
22794 @anchor{add-auto-load-safe-path}
22795 @kindex add-auto-load-safe-path
22796 @item add-auto-load-safe-path
22797 Add an entry (or list of entries) to the list of directories trusted for
22798 automatic loading and execution of scripts. Multiple entries may be delimited
22799 by the host platform path separator in use.
22802 This variable defaults to what @code{--with-auto-load-dir} has been configured
22803 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22804 substitution applies the same as for @ref{set auto-load scripts-directory}.
22805 The default @code{set auto-load safe-path} value can be also overriden by
22806 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22808 Setting this variable to @file{/} disables this security protection,
22809 corresponding @value{GDBN} configuration option is
22810 @option{--without-auto-load-safe-path}.
22811 This variable is supposed to be set to the system directories writable by the
22812 system superuser only. Users can add their source directories in init files in
22813 their home directories (@pxref{Home Directory Init File}). See also deprecated
22814 init file in the current directory
22815 (@pxref{Init File in the Current Directory during Startup}).
22817 To force @value{GDBN} to load the files it declined to load in the previous
22818 example, you could use one of the following ways:
22821 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22822 Specify this trusted directory (or a file) as additional component of the list.
22823 You have to specify also any existing directories displayed by
22824 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22826 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22827 Specify this directory as in the previous case but just for a single
22828 @value{GDBN} session.
22830 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22831 Disable auto-loading safety for a single @value{GDBN} session.
22832 This assumes all the files you debug during this @value{GDBN} session will come
22833 from trusted sources.
22835 @item @kbd{./configure --without-auto-load-safe-path}
22836 During compilation of @value{GDBN} you may disable any auto-loading safety.
22837 This assumes all the files you will ever debug with this @value{GDBN} come from
22841 On the other hand you can also explicitly forbid automatic files loading which
22842 also suppresses any such warning messages:
22845 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22846 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22848 @item @file{~/.gdbinit}: @samp{set auto-load no}
22849 Disable auto-loading globally for the user
22850 (@pxref{Home Directory Init File}). While it is improbable, you could also
22851 use system init file instead (@pxref{System-wide configuration}).
22854 This setting applies to the file names as entered by user. If no entry matches
22855 @value{GDBN} tries as a last resort to also resolve all the file names into
22856 their canonical form (typically resolving symbolic links) and compare the
22857 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22858 own before starting the comparison so a canonical form of directories is
22859 recommended to be entered.
22861 @node Auto-loading verbose mode
22862 @subsection Displaying files tried for auto-load
22863 @cindex auto-loading verbose mode
22865 For better visibility of all the file locations where you can place scripts to
22866 be auto-loaded with inferior --- or to protect yourself against accidental
22867 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22868 all the files attempted to be loaded. Both existing and non-existing files may
22871 For example the list of directories from which it is safe to auto-load files
22872 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22873 may not be too obvious while setting it up.
22876 (gdb) set debug auto-load on
22877 (gdb) file ~/src/t/true
22878 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22879 for objfile "/tmp/true".
22880 auto-load: Updating directories of "/usr:/opt".
22881 auto-load: Using directory "/usr".
22882 auto-load: Using directory "/opt".
22883 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22884 by your `auto-load safe-path' set to "/usr:/opt".
22888 @anchor{set debug auto-load}
22889 @kindex set debug auto-load
22890 @item set debug auto-load [on|off]
22891 Set whether to print the filenames attempted to be auto-loaded.
22893 @anchor{show debug auto-load}
22894 @kindex show debug auto-load
22895 @item show debug auto-load
22896 Show whether printing of the filenames attempted to be auto-loaded is turned
22900 @node Messages/Warnings
22901 @section Optional Warnings and Messages
22903 @cindex verbose operation
22904 @cindex optional warnings
22905 By default, @value{GDBN} is silent about its inner workings. If you are
22906 running on a slow machine, you may want to use the @code{set verbose}
22907 command. This makes @value{GDBN} tell you when it does a lengthy
22908 internal operation, so you will not think it has crashed.
22910 Currently, the messages controlled by @code{set verbose} are those
22911 which announce that the symbol table for a source file is being read;
22912 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22915 @kindex set verbose
22916 @item set verbose on
22917 Enables @value{GDBN} output of certain informational messages.
22919 @item set verbose off
22920 Disables @value{GDBN} output of certain informational messages.
22922 @kindex show verbose
22924 Displays whether @code{set verbose} is on or off.
22927 By default, if @value{GDBN} encounters bugs in the symbol table of an
22928 object file, it is silent; but if you are debugging a compiler, you may
22929 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22934 @kindex set complaints
22935 @item set complaints @var{limit}
22936 Permits @value{GDBN} to output @var{limit} complaints about each type of
22937 unusual symbols before becoming silent about the problem. Set
22938 @var{limit} to zero to suppress all complaints; set it to a large number
22939 to prevent complaints from being suppressed.
22941 @kindex show complaints
22942 @item show complaints
22943 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22947 @anchor{confirmation requests}
22948 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22949 lot of stupid questions to confirm certain commands. For example, if
22950 you try to run a program which is already running:
22954 The program being debugged has been started already.
22955 Start it from the beginning? (y or n)
22958 If you are willing to unflinchingly face the consequences of your own
22959 commands, you can disable this ``feature'':
22963 @kindex set confirm
22965 @cindex confirmation
22966 @cindex stupid questions
22967 @item set confirm off
22968 Disables confirmation requests. Note that running @value{GDBN} with
22969 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22970 automatically disables confirmation requests.
22972 @item set confirm on
22973 Enables confirmation requests (the default).
22975 @kindex show confirm
22977 Displays state of confirmation requests.
22981 @cindex command tracing
22982 If you need to debug user-defined commands or sourced files you may find it
22983 useful to enable @dfn{command tracing}. In this mode each command will be
22984 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22985 quantity denoting the call depth of each command.
22988 @kindex set trace-commands
22989 @cindex command scripts, debugging
22990 @item set trace-commands on
22991 Enable command tracing.
22992 @item set trace-commands off
22993 Disable command tracing.
22994 @item show trace-commands
22995 Display the current state of command tracing.
22998 @node Debugging Output
22999 @section Optional Messages about Internal Happenings
23000 @cindex optional debugging messages
23002 @value{GDBN} has commands that enable optional debugging messages from
23003 various @value{GDBN} subsystems; normally these commands are of
23004 interest to @value{GDBN} maintainers, or when reporting a bug. This
23005 section documents those commands.
23008 @kindex set exec-done-display
23009 @item set exec-done-display
23010 Turns on or off the notification of asynchronous commands'
23011 completion. When on, @value{GDBN} will print a message when an
23012 asynchronous command finishes its execution. The default is off.
23013 @kindex show exec-done-display
23014 @item show exec-done-display
23015 Displays the current setting of asynchronous command completion
23018 @cindex ARM AArch64
23019 @item set debug aarch64
23020 Turns on or off display of debugging messages related to ARM AArch64.
23021 The default is off.
23023 @item show debug aarch64
23024 Displays the current state of displaying debugging messages related to
23026 @cindex gdbarch debugging info
23027 @cindex architecture debugging info
23028 @item set debug arch
23029 Turns on or off display of gdbarch debugging info. The default is off
23030 @item show debug arch
23031 Displays the current state of displaying gdbarch debugging info.
23032 @item set debug aix-solib
23033 @cindex AIX shared library debugging
23034 Control display of debugging messages from the AIX shared library
23035 support module. The default is off.
23036 @item show debug aix-thread
23037 Show the current state of displaying AIX shared library debugging messages.
23038 @item set debug aix-thread
23039 @cindex AIX threads
23040 Display debugging messages about inner workings of the AIX thread
23042 @item show debug aix-thread
23043 Show the current state of AIX thread debugging info display.
23044 @item set debug check-physname
23046 Check the results of the ``physname'' computation. When reading DWARF
23047 debugging information for C@t{++}, @value{GDBN} attempts to compute
23048 each entity's name. @value{GDBN} can do this computation in two
23049 different ways, depending on exactly what information is present.
23050 When enabled, this setting causes @value{GDBN} to compute the names
23051 both ways and display any discrepancies.
23052 @item show debug check-physname
23053 Show the current state of ``physname'' checking.
23054 @item set debug coff-pe-read
23055 @cindex COFF/PE exported symbols
23056 Control display of debugging messages related to reading of COFF/PE
23057 exported symbols. The default is off.
23058 @item show debug coff-pe-read
23059 Displays the current state of displaying debugging messages related to
23060 reading of COFF/PE exported symbols.
23061 @item set debug dwarf2-die
23062 @cindex DWARF2 DIEs
23063 Dump DWARF2 DIEs after they are read in.
23064 The value is the number of nesting levels to print.
23065 A value of zero turns off the display.
23066 @item show debug dwarf2-die
23067 Show the current state of DWARF2 DIE debugging.
23068 @item set debug dwarf2-read
23069 @cindex DWARF2 Reading
23070 Turns on or off display of debugging messages related to reading
23071 DWARF debug info. The default is 0 (off).
23072 A value of 1 provides basic information.
23073 A value greater than 1 provides more verbose information.
23074 @item show debug dwarf2-read
23075 Show the current state of DWARF2 reader debugging.
23076 @item set debug displaced
23077 @cindex displaced stepping debugging info
23078 Turns on or off display of @value{GDBN} debugging info for the
23079 displaced stepping support. The default is off.
23080 @item show debug displaced
23081 Displays the current state of displaying @value{GDBN} debugging info
23082 related to displaced stepping.
23083 @item set debug event
23084 @cindex event debugging info
23085 Turns on or off display of @value{GDBN} event debugging info. The
23087 @item show debug event
23088 Displays the current state of displaying @value{GDBN} event debugging
23090 @item set debug expression
23091 @cindex expression debugging info
23092 Turns on or off display of debugging info about @value{GDBN}
23093 expression parsing. The default is off.
23094 @item show debug expression
23095 Displays the current state of displaying debugging info about
23096 @value{GDBN} expression parsing.
23097 @item set debug frame
23098 @cindex frame debugging info
23099 Turns on or off display of @value{GDBN} frame debugging info. The
23101 @item show debug frame
23102 Displays the current state of displaying @value{GDBN} frame debugging
23104 @item set debug gnu-nat
23105 @cindex @sc{gnu}/Hurd debug messages
23106 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23107 @item show debug gnu-nat
23108 Show the current state of @sc{gnu}/Hurd debugging messages.
23109 @item set debug infrun
23110 @cindex inferior debugging info
23111 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23112 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23113 for implementing operations such as single-stepping the inferior.
23114 @item show debug infrun
23115 Displays the current state of @value{GDBN} inferior debugging.
23116 @item set debug jit
23117 @cindex just-in-time compilation, debugging messages
23118 Turns on or off debugging messages from JIT debug support.
23119 @item show debug jit
23120 Displays the current state of @value{GDBN} JIT debugging.
23121 @item set debug lin-lwp
23122 @cindex @sc{gnu}/Linux LWP debug messages
23123 @cindex Linux lightweight processes
23124 Turns on or off debugging messages from the Linux LWP debug support.
23125 @item show debug lin-lwp
23126 Show the current state of Linux LWP debugging messages.
23127 @item set debug mach-o
23128 @cindex Mach-O symbols processing
23129 Control display of debugging messages related to Mach-O symbols
23130 processing. The default is off.
23131 @item show debug mach-o
23132 Displays the current state of displaying debugging messages related to
23133 reading of COFF/PE exported symbols.
23134 @item set debug notification
23135 @cindex remote async notification debugging info
23136 Turns on or off debugging messages about remote async notification.
23137 The default is off.
23138 @item show debug notification
23139 Displays the current state of remote async notification debugging messages.
23140 @item set debug observer
23141 @cindex observer debugging info
23142 Turns on or off display of @value{GDBN} observer debugging. This
23143 includes info such as the notification of observable events.
23144 @item show debug observer
23145 Displays the current state of observer debugging.
23146 @item set debug overload
23147 @cindex C@t{++} overload debugging info
23148 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23149 info. This includes info such as ranking of functions, etc. The default
23151 @item show debug overload
23152 Displays the current state of displaying @value{GDBN} C@t{++} overload
23154 @cindex expression parser, debugging info
23155 @cindex debug expression parser
23156 @item set debug parser
23157 Turns on or off the display of expression parser debugging output.
23158 Internally, this sets the @code{yydebug} variable in the expression
23159 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23160 details. The default is off.
23161 @item show debug parser
23162 Show the current state of expression parser debugging.
23163 @cindex packets, reporting on stdout
23164 @cindex serial connections, debugging
23165 @cindex debug remote protocol
23166 @cindex remote protocol debugging
23167 @cindex display remote packets
23168 @item set debug remote
23169 Turns on or off display of reports on all packets sent back and forth across
23170 the serial line to the remote machine. The info is printed on the
23171 @value{GDBN} standard output stream. The default is off.
23172 @item show debug remote
23173 Displays the state of display of remote packets.
23174 @item set debug serial
23175 Turns on or off display of @value{GDBN} serial debugging info. The
23177 @item show debug serial
23178 Displays the current state of displaying @value{GDBN} serial debugging
23180 @item set debug solib-frv
23181 @cindex FR-V shared-library debugging
23182 Turns on or off debugging messages for FR-V shared-library code.
23183 @item show debug solib-frv
23184 Display the current state of FR-V shared-library code debugging
23186 @item set debug symbol-lookup
23187 @cindex symbol lookup
23188 Turns on or off display of debugging messages related to symbol lookup.
23189 The default is 0 (off).
23190 A value of 1 provides basic information.
23191 A value greater than 1 provides more verbose information.
23192 @item show debug symbol-lookup
23193 Show the current state of symbol lookup debugging messages.
23194 @item set debug symfile
23195 @cindex symbol file functions
23196 Turns on or off display of debugging messages related to symbol file functions.
23197 The default is off. @xref{Files}.
23198 @item show debug symfile
23199 Show the current state of symbol file debugging messages.
23200 @item set debug symtab-create
23201 @cindex symbol table creation
23202 Turns on or off display of debugging messages related to symbol table creation.
23203 The default is 0 (off).
23204 A value of 1 provides basic information.
23205 A value greater than 1 provides more verbose information.
23206 @item show debug symtab-create
23207 Show the current state of symbol table creation debugging.
23208 @item set debug target
23209 @cindex target debugging info
23210 Turns on or off display of @value{GDBN} target debugging info. This info
23211 includes what is going on at the target level of GDB, as it happens. The
23212 default is 0. Set it to 1 to track events, and to 2 to also track the
23213 value of large memory transfers.
23214 @item show debug target
23215 Displays the current state of displaying @value{GDBN} target debugging
23217 @item set debug timestamp
23218 @cindex timestampping debugging info
23219 Turns on or off display of timestamps with @value{GDBN} debugging info.
23220 When enabled, seconds and microseconds are displayed before each debugging
23222 @item show debug timestamp
23223 Displays the current state of displaying timestamps with @value{GDBN}
23225 @item set debug varobj
23226 @cindex variable object debugging info
23227 Turns on or off display of @value{GDBN} variable object debugging
23228 info. The default is off.
23229 @item show debug varobj
23230 Displays the current state of displaying @value{GDBN} variable object
23232 @item set debug xml
23233 @cindex XML parser debugging
23234 Turns on or off debugging messages for built-in XML parsers.
23235 @item show debug xml
23236 Displays the current state of XML debugging messages.
23239 @node Other Misc Settings
23240 @section Other Miscellaneous Settings
23241 @cindex miscellaneous settings
23244 @kindex set interactive-mode
23245 @item set interactive-mode
23246 If @code{on}, forces @value{GDBN} to assume that GDB was started
23247 in a terminal. In practice, this means that @value{GDBN} should wait
23248 for the user to answer queries generated by commands entered at
23249 the command prompt. If @code{off}, forces @value{GDBN} to operate
23250 in the opposite mode, and it uses the default answers to all queries.
23251 If @code{auto} (the default), @value{GDBN} tries to determine whether
23252 its standard input is a terminal, and works in interactive-mode if it
23253 is, non-interactively otherwise.
23255 In the vast majority of cases, the debugger should be able to guess
23256 correctly which mode should be used. But this setting can be useful
23257 in certain specific cases, such as running a MinGW @value{GDBN}
23258 inside a cygwin window.
23260 @kindex show interactive-mode
23261 @item show interactive-mode
23262 Displays whether the debugger is operating in interactive mode or not.
23265 @node Extending GDB
23266 @chapter Extending @value{GDBN}
23267 @cindex extending GDB
23269 @value{GDBN} provides several mechanisms for extension.
23270 @value{GDBN} also provides the ability to automatically load
23271 extensions when it reads a file for debugging. This allows the
23272 user to automatically customize @value{GDBN} for the program
23276 * Sequences:: Canned Sequences of @value{GDBN} Commands
23277 * Python:: Extending @value{GDBN} using Python
23278 * Guile:: Extending @value{GDBN} using Guile
23279 * Auto-loading extensions:: Automatically loading extensions
23280 * Multiple Extension Languages:: Working with multiple extension languages
23281 * Aliases:: Creating new spellings of existing commands
23284 To facilitate the use of extension languages, @value{GDBN} is capable
23285 of evaluating the contents of a file. When doing so, @value{GDBN}
23286 can recognize which extension language is being used by looking at
23287 the filename extension. Files with an unrecognized filename extension
23288 are always treated as a @value{GDBN} Command Files.
23289 @xref{Command Files,, Command files}.
23291 You can control how @value{GDBN} evaluates these files with the following
23295 @kindex set script-extension
23296 @kindex show script-extension
23297 @item set script-extension off
23298 All scripts are always evaluated as @value{GDBN} Command Files.
23300 @item set script-extension soft
23301 The debugger determines the scripting language based on filename
23302 extension. If this scripting language is supported, @value{GDBN}
23303 evaluates the script using that language. Otherwise, it evaluates
23304 the file as a @value{GDBN} Command File.
23306 @item set script-extension strict
23307 The debugger determines the scripting language based on filename
23308 extension, and evaluates the script using that language. If the
23309 language is not supported, then the evaluation fails.
23311 @item show script-extension
23312 Display the current value of the @code{script-extension} option.
23317 @section Canned Sequences of Commands
23319 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23320 Command Lists}), @value{GDBN} provides two ways to store sequences of
23321 commands for execution as a unit: user-defined commands and command
23325 * Define:: How to define your own commands
23326 * Hooks:: Hooks for user-defined commands
23327 * Command Files:: How to write scripts of commands to be stored in a file
23328 * Output:: Commands for controlled output
23329 * Auto-loading sequences:: Controlling auto-loaded command files
23333 @subsection User-defined Commands
23335 @cindex user-defined command
23336 @cindex arguments, to user-defined commands
23337 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23338 which you assign a new name as a command. This is done with the
23339 @code{define} command. User commands may accept up to 10 arguments
23340 separated by whitespace. Arguments are accessed within the user command
23341 via @code{$arg0@dots{}$arg9}. A trivial example:
23345 print $arg0 + $arg1 + $arg2
23350 To execute the command use:
23357 This defines the command @code{adder}, which prints the sum of
23358 its three arguments. Note the arguments are text substitutions, so they may
23359 reference variables, use complex expressions, or even perform inferior
23362 @cindex argument count in user-defined commands
23363 @cindex how many arguments (user-defined commands)
23364 In addition, @code{$argc} may be used to find out how many arguments have
23365 been passed. This expands to a number in the range 0@dots{}10.
23370 print $arg0 + $arg1
23373 print $arg0 + $arg1 + $arg2
23381 @item define @var{commandname}
23382 Define a command named @var{commandname}. If there is already a command
23383 by that name, you are asked to confirm that you want to redefine it.
23384 The argument @var{commandname} may be a bare command name consisting of letters,
23385 numbers, dashes, and underscores. It may also start with any predefined
23386 prefix command. For example, @samp{define target my-target} creates
23387 a user-defined @samp{target my-target} command.
23389 The definition of the command is made up of other @value{GDBN} command lines,
23390 which are given following the @code{define} command. The end of these
23391 commands is marked by a line containing @code{end}.
23394 @kindex end@r{ (user-defined commands)}
23395 @item document @var{commandname}
23396 Document the user-defined command @var{commandname}, so that it can be
23397 accessed by @code{help}. The command @var{commandname} must already be
23398 defined. This command reads lines of documentation just as @code{define}
23399 reads the lines of the command definition, ending with @code{end}.
23400 After the @code{document} command is finished, @code{help} on command
23401 @var{commandname} displays the documentation you have written.
23403 You may use the @code{document} command again to change the
23404 documentation of a command. Redefining the command with @code{define}
23405 does not change the documentation.
23407 @kindex dont-repeat
23408 @cindex don't repeat command
23410 Used inside a user-defined command, this tells @value{GDBN} that this
23411 command should not be repeated when the user hits @key{RET}
23412 (@pxref{Command Syntax, repeat last command}).
23414 @kindex help user-defined
23415 @item help user-defined
23416 List all user-defined commands and all python commands defined in class
23417 COMAND_USER. The first line of the documentation or docstring is
23422 @itemx show user @var{commandname}
23423 Display the @value{GDBN} commands used to define @var{commandname} (but
23424 not its documentation). If no @var{commandname} is given, display the
23425 definitions for all user-defined commands.
23426 This does not work for user-defined python commands.
23428 @cindex infinite recursion in user-defined commands
23429 @kindex show max-user-call-depth
23430 @kindex set max-user-call-depth
23431 @item show max-user-call-depth
23432 @itemx set max-user-call-depth
23433 The value of @code{max-user-call-depth} controls how many recursion
23434 levels are allowed in user-defined commands before @value{GDBN} suspects an
23435 infinite recursion and aborts the command.
23436 This does not apply to user-defined python commands.
23439 In addition to the above commands, user-defined commands frequently
23440 use control flow commands, described in @ref{Command Files}.
23442 When user-defined commands are executed, the
23443 commands of the definition are not printed. An error in any command
23444 stops execution of the user-defined command.
23446 If used interactively, commands that would ask for confirmation proceed
23447 without asking when used inside a user-defined command. Many @value{GDBN}
23448 commands that normally print messages to say what they are doing omit the
23449 messages when used in a user-defined command.
23452 @subsection User-defined Command Hooks
23453 @cindex command hooks
23454 @cindex hooks, for commands
23455 @cindex hooks, pre-command
23458 You may define @dfn{hooks}, which are a special kind of user-defined
23459 command. Whenever you run the command @samp{foo}, if the user-defined
23460 command @samp{hook-foo} exists, it is executed (with no arguments)
23461 before that command.
23463 @cindex hooks, post-command
23465 A hook may also be defined which is run after the command you executed.
23466 Whenever you run the command @samp{foo}, if the user-defined command
23467 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23468 that command. Post-execution hooks may exist simultaneously with
23469 pre-execution hooks, for the same command.
23471 It is valid for a hook to call the command which it hooks. If this
23472 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23474 @c It would be nice if hookpost could be passed a parameter indicating
23475 @c if the command it hooks executed properly or not. FIXME!
23477 @kindex stop@r{, a pseudo-command}
23478 In addition, a pseudo-command, @samp{stop} exists. Defining
23479 (@samp{hook-stop}) makes the associated commands execute every time
23480 execution stops in your program: before breakpoint commands are run,
23481 displays are printed, or the stack frame is printed.
23483 For example, to ignore @code{SIGALRM} signals while
23484 single-stepping, but treat them normally during normal execution,
23489 handle SIGALRM nopass
23493 handle SIGALRM pass
23496 define hook-continue
23497 handle SIGALRM pass
23501 As a further example, to hook at the beginning and end of the @code{echo}
23502 command, and to add extra text to the beginning and end of the message,
23510 define hookpost-echo
23514 (@value{GDBP}) echo Hello World
23515 <<<---Hello World--->>>
23520 You can define a hook for any single-word command in @value{GDBN}, but
23521 not for command aliases; you should define a hook for the basic command
23522 name, e.g.@: @code{backtrace} rather than @code{bt}.
23523 @c FIXME! So how does Joe User discover whether a command is an alias
23525 You can hook a multi-word command by adding @code{hook-} or
23526 @code{hookpost-} to the last word of the command, e.g.@:
23527 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23529 If an error occurs during the execution of your hook, execution of
23530 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23531 (before the command that you actually typed had a chance to run).
23533 If you try to define a hook which does not match any known command, you
23534 get a warning from the @code{define} command.
23536 @node Command Files
23537 @subsection Command Files
23539 @cindex command files
23540 @cindex scripting commands
23541 A command file for @value{GDBN} is a text file made of lines that are
23542 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23543 also be included. An empty line in a command file does nothing; it
23544 does not mean to repeat the last command, as it would from the
23547 You can request the execution of a command file with the @code{source}
23548 command. Note that the @code{source} command is also used to evaluate
23549 scripts that are not Command Files. The exact behavior can be configured
23550 using the @code{script-extension} setting.
23551 @xref{Extending GDB,, Extending GDB}.
23555 @cindex execute commands from a file
23556 @item source [-s] [-v] @var{filename}
23557 Execute the command file @var{filename}.
23560 The lines in a command file are generally executed sequentially,
23561 unless the order of execution is changed by one of the
23562 @emph{flow-control commands} described below. The commands are not
23563 printed as they are executed. An error in any command terminates
23564 execution of the command file and control is returned to the console.
23566 @value{GDBN} first searches for @var{filename} in the current directory.
23567 If the file is not found there, and @var{filename} does not specify a
23568 directory, then @value{GDBN} also looks for the file on the source search path
23569 (specified with the @samp{directory} command);
23570 except that @file{$cdir} is not searched because the compilation directory
23571 is not relevant to scripts.
23573 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23574 on the search path even if @var{filename} specifies a directory.
23575 The search is done by appending @var{filename} to each element of the
23576 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23577 and the search path contains @file{/home/user} then @value{GDBN} will
23578 look for the script @file{/home/user/mylib/myscript}.
23579 The search is also done if @var{filename} is an absolute path.
23580 For example, if @var{filename} is @file{/tmp/myscript} and
23581 the search path contains @file{/home/user} then @value{GDBN} will
23582 look for the script @file{/home/user/tmp/myscript}.
23583 For DOS-like systems, if @var{filename} contains a drive specification,
23584 it is stripped before concatenation. For example, if @var{filename} is
23585 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23586 will look for the script @file{c:/tmp/myscript}.
23588 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23589 each command as it is executed. The option must be given before
23590 @var{filename}, and is interpreted as part of the filename anywhere else.
23592 Commands that would ask for confirmation if used interactively proceed
23593 without asking when used in a command file. Many @value{GDBN} commands that
23594 normally print messages to say what they are doing omit the messages
23595 when called from command files.
23597 @value{GDBN} also accepts command input from standard input. In this
23598 mode, normal output goes to standard output and error output goes to
23599 standard error. Errors in a command file supplied on standard input do
23600 not terminate execution of the command file---execution continues with
23604 gdb < cmds > log 2>&1
23607 (The syntax above will vary depending on the shell used.) This example
23608 will execute commands from the file @file{cmds}. All output and errors
23609 would be directed to @file{log}.
23611 Since commands stored on command files tend to be more general than
23612 commands typed interactively, they frequently need to deal with
23613 complicated situations, such as different or unexpected values of
23614 variables and symbols, changes in how the program being debugged is
23615 built, etc. @value{GDBN} provides a set of flow-control commands to
23616 deal with these complexities. Using these commands, you can write
23617 complex scripts that loop over data structures, execute commands
23618 conditionally, etc.
23625 This command allows to include in your script conditionally executed
23626 commands. The @code{if} command takes a single argument, which is an
23627 expression to evaluate. It is followed by a series of commands that
23628 are executed only if the expression is true (its value is nonzero).
23629 There can then optionally be an @code{else} line, followed by a series
23630 of commands that are only executed if the expression was false. The
23631 end of the list is marked by a line containing @code{end}.
23635 This command allows to write loops. Its syntax is similar to
23636 @code{if}: the command takes a single argument, which is an expression
23637 to evaluate, and must be followed by the commands to execute, one per
23638 line, terminated by an @code{end}. These commands are called the
23639 @dfn{body} of the loop. The commands in the body of @code{while} are
23640 executed repeatedly as long as the expression evaluates to true.
23644 This command exits the @code{while} loop in whose body it is included.
23645 Execution of the script continues after that @code{while}s @code{end}
23648 @kindex loop_continue
23649 @item loop_continue
23650 This command skips the execution of the rest of the body of commands
23651 in the @code{while} loop in whose body it is included. Execution
23652 branches to the beginning of the @code{while} loop, where it evaluates
23653 the controlling expression.
23655 @kindex end@r{ (if/else/while commands)}
23657 Terminate the block of commands that are the body of @code{if},
23658 @code{else}, or @code{while} flow-control commands.
23663 @subsection Commands for Controlled Output
23665 During the execution of a command file or a user-defined command, normal
23666 @value{GDBN} output is suppressed; the only output that appears is what is
23667 explicitly printed by the commands in the definition. This section
23668 describes three commands useful for generating exactly the output you
23673 @item echo @var{text}
23674 @c I do not consider backslash-space a standard C escape sequence
23675 @c because it is not in ANSI.
23676 Print @var{text}. Nonprinting characters can be included in
23677 @var{text} using C escape sequences, such as @samp{\n} to print a
23678 newline. @strong{No newline is printed unless you specify one.}
23679 In addition to the standard C escape sequences, a backslash followed
23680 by a space stands for a space. This is useful for displaying a
23681 string with spaces at the beginning or the end, since leading and
23682 trailing spaces are otherwise trimmed from all arguments.
23683 To print @samp{@w{ }and foo =@w{ }}, use the command
23684 @samp{echo \@w{ }and foo = \@w{ }}.
23686 A backslash at the end of @var{text} can be used, as in C, to continue
23687 the command onto subsequent lines. For example,
23690 echo This is some text\n\
23691 which is continued\n\
23692 onto several lines.\n
23695 produces the same output as
23698 echo This is some text\n
23699 echo which is continued\n
23700 echo onto several lines.\n
23704 @item output @var{expression}
23705 Print the value of @var{expression} and nothing but that value: no
23706 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23707 value history either. @xref{Expressions, ,Expressions}, for more information
23710 @item output/@var{fmt} @var{expression}
23711 Print the value of @var{expression} in format @var{fmt}. You can use
23712 the same formats as for @code{print}. @xref{Output Formats,,Output
23713 Formats}, for more information.
23716 @item printf @var{template}, @var{expressions}@dots{}
23717 Print the values of one or more @var{expressions} under the control of
23718 the string @var{template}. To print several values, make
23719 @var{expressions} be a comma-separated list of individual expressions,
23720 which may be either numbers or pointers. Their values are printed as
23721 specified by @var{template}, exactly as a C program would do by
23722 executing the code below:
23725 printf (@var{template}, @var{expressions}@dots{});
23728 As in @code{C} @code{printf}, ordinary characters in @var{template}
23729 are printed verbatim, while @dfn{conversion specification} introduced
23730 by the @samp{%} character cause subsequent @var{expressions} to be
23731 evaluated, their values converted and formatted according to type and
23732 style information encoded in the conversion specifications, and then
23735 For example, you can print two values in hex like this:
23738 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23741 @code{printf} supports all the standard @code{C} conversion
23742 specifications, including the flags and modifiers between the @samp{%}
23743 character and the conversion letter, with the following exceptions:
23747 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23750 The modifier @samp{*} is not supported for specifying precision or
23754 The @samp{'} flag (for separation of digits into groups according to
23755 @code{LC_NUMERIC'}) is not supported.
23758 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23762 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23765 The conversion letters @samp{a} and @samp{A} are not supported.
23769 Note that the @samp{ll} type modifier is supported only if the
23770 underlying @code{C} implementation used to build @value{GDBN} supports
23771 the @code{long long int} type, and the @samp{L} type modifier is
23772 supported only if @code{long double} type is available.
23774 As in @code{C}, @code{printf} supports simple backslash-escape
23775 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23776 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23777 single character. Octal and hexadecimal escape sequences are not
23780 Additionally, @code{printf} supports conversion specifications for DFP
23781 (@dfn{Decimal Floating Point}) types using the following length modifiers
23782 together with a floating point specifier.
23787 @samp{H} for printing @code{Decimal32} types.
23790 @samp{D} for printing @code{Decimal64} types.
23793 @samp{DD} for printing @code{Decimal128} types.
23796 If the underlying @code{C} implementation used to build @value{GDBN} has
23797 support for the three length modifiers for DFP types, other modifiers
23798 such as width and precision will also be available for @value{GDBN} to use.
23800 In case there is no such @code{C} support, no additional modifiers will be
23801 available and the value will be printed in the standard way.
23803 Here's an example of printing DFP types using the above conversion letters:
23805 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23809 @item eval @var{template}, @var{expressions}@dots{}
23810 Convert the values of one or more @var{expressions} under the control of
23811 the string @var{template} to a command line, and call it.
23815 @node Auto-loading sequences
23816 @subsection Controlling auto-loading native @value{GDBN} scripts
23817 @cindex native script auto-loading
23819 When a new object file is read (for example, due to the @code{file}
23820 command, or because the inferior has loaded a shared library),
23821 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23822 @xref{Auto-loading extensions}.
23824 Auto-loading can be enabled or disabled,
23825 and the list of auto-loaded scripts can be printed.
23828 @anchor{set auto-load gdb-scripts}
23829 @kindex set auto-load gdb-scripts
23830 @item set auto-load gdb-scripts [on|off]
23831 Enable or disable the auto-loading of canned sequences of commands scripts.
23833 @anchor{show auto-load gdb-scripts}
23834 @kindex show auto-load gdb-scripts
23835 @item show auto-load gdb-scripts
23836 Show whether auto-loading of canned sequences of commands scripts is enabled or
23839 @anchor{info auto-load gdb-scripts}
23840 @kindex info auto-load gdb-scripts
23841 @cindex print list of auto-loaded canned sequences of commands scripts
23842 @item info auto-load gdb-scripts [@var{regexp}]
23843 Print the list of all canned sequences of commands scripts that @value{GDBN}
23847 If @var{regexp} is supplied only canned sequences of commands scripts with
23848 matching names are printed.
23850 @c Python docs live in a separate file.
23851 @include python.texi
23853 @c Guile docs live in a separate file.
23854 @include guile.texi
23856 @node Auto-loading extensions
23857 @section Auto-loading extensions
23858 @cindex auto-loading extensions
23860 @value{GDBN} provides two mechanisms for automatically loading extensions
23861 when a new object file is read (for example, due to the @code{file}
23862 command, or because the inferior has loaded a shared library):
23863 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23864 section of modern file formats like ELF.
23867 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23868 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23869 * Which flavor to choose?::
23872 The auto-loading feature is useful for supplying application-specific
23873 debugging commands and features.
23875 Auto-loading can be enabled or disabled,
23876 and the list of auto-loaded scripts can be printed.
23877 See the @samp{auto-loading} section of each extension language
23878 for more information.
23879 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23880 For Python files see @ref{Python Auto-loading}.
23882 Note that loading of this script file also requires accordingly configured
23883 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23885 @node objfile-gdbdotext file
23886 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23887 @cindex @file{@var{objfile}-gdb.gdb}
23888 @cindex @file{@var{objfile}-gdb.py}
23889 @cindex @file{@var{objfile}-gdb.scm}
23891 When a new object file is read, @value{GDBN} looks for a file named
23892 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23893 where @var{objfile} is the object file's name and
23894 where @var{ext} is the file extension for the extension language:
23897 @item @file{@var{objfile}-gdb.gdb}
23898 GDB's own command language
23899 @item @file{@var{objfile}-gdb.py}
23901 @item @file{@var{objfile}-gdb.scm}
23905 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23906 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23907 components, and appending the @file{-gdb.@var{ext}} suffix.
23908 If this file exists and is readable, @value{GDBN} will evaluate it as a
23909 script in the specified extension language.
23911 If this file does not exist, then @value{GDBN} will look for
23912 @var{script-name} file in all of the directories as specified below.
23914 Note that loading of these files requires an accordingly configured
23915 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23917 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23918 scripts normally according to its @file{.exe} filename. But if no scripts are
23919 found @value{GDBN} also tries script filenames matching the object file without
23920 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23921 is attempted on any platform. This makes the script filenames compatible
23922 between Unix and MS-Windows hosts.
23925 @anchor{set auto-load scripts-directory}
23926 @kindex set auto-load scripts-directory
23927 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23928 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23929 may be delimited by the host platform path separator in use
23930 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23932 Each entry here needs to be covered also by the security setting
23933 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23935 @anchor{with-auto-load-dir}
23936 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23937 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23938 configuration option @option{--with-auto-load-dir}.
23940 Any reference to @file{$debugdir} will get replaced by
23941 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23942 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23943 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23944 @file{$datadir} must be placed as a directory component --- either alone or
23945 delimited by @file{/} or @file{\} directory separators, depending on the host
23948 The list of directories uses path separator (@samp{:} on GNU and Unix
23949 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23950 to the @env{PATH} environment variable.
23952 @anchor{show auto-load scripts-directory}
23953 @kindex show auto-load scripts-directory
23954 @item show auto-load scripts-directory
23955 Show @value{GDBN} auto-loaded scripts location.
23957 @anchor{add-auto-load-scripts-directory}
23958 @kindex add-auto-load-scripts-directory
23959 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
23960 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
23961 Multiple entries may be delimited by the host platform path separator in use.
23964 @value{GDBN} does not track which files it has already auto-loaded this way.
23965 @value{GDBN} will load the associated script every time the corresponding
23966 @var{objfile} is opened.
23967 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23968 is evaluated more than once.
23970 @node dotdebug_gdb_scripts section
23971 @subsection The @code{.debug_gdb_scripts} section
23972 @cindex @code{.debug_gdb_scripts} section
23974 For systems using file formats like ELF and COFF,
23975 when @value{GDBN} loads a new object file
23976 it will look for a special section named @code{.debug_gdb_scripts}.
23977 If this section exists, its contents is a list of NUL-terminated names
23978 of scripts to load. Each entry begins with a non-NULL prefix byte that
23979 specifies the kind of entry, typically the extension language.
23981 @value{GDBN} will look for each specified script file first in the
23982 current directory and then along the source search path
23983 (@pxref{Source Path, ,Specifying Source Directories}),
23984 except that @file{$cdir} is not searched, since the compilation
23985 directory is not relevant to scripts.
23987 Entries can be placed in section @code{.debug_gdb_scripts} with,
23988 for example, this GCC macro for Python scripts.
23991 /* Note: The "MS" section flags are to remove duplicates. */
23992 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23994 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23995 .byte 1 /* Python */\n\
23996 .asciz \"" script_name "\"\n\
24002 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24003 Then one can reference the macro in a header or source file like this:
24006 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24009 The script name may include directories if desired.
24011 Note that loading of this script file also requires accordingly configured
24012 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24014 If the macro invocation is put in a header, any application or library
24015 using this header will get a reference to the specified script,
24016 and with the use of @code{"MS"} attributes on the section, the linker
24017 will remove duplicates.
24019 @node Which flavor to choose?
24020 @subsection Which flavor to choose?
24022 Given the multiple ways of auto-loading extensions, it might not always
24023 be clear which one to choose. This section provides some guidance.
24026 Benefits of the @file{-gdb.@var{ext}} way:
24030 Can be used with file formats that don't support multiple sections.
24033 Ease of finding scripts for public libraries.
24035 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24036 in the source search path.
24037 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24038 isn't a source directory in which to find the script.
24041 Doesn't require source code additions.
24045 Benefits of the @code{.debug_gdb_scripts} way:
24049 Works with static linking.
24051 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24052 trigger their loading. When an application is statically linked the only
24053 objfile available is the executable, and it is cumbersome to attach all the
24054 scripts from all the input libraries to the executable's
24055 @file{-gdb.@var{ext}} script.
24058 Works with classes that are entirely inlined.
24060 Some classes can be entirely inlined, and thus there may not be an associated
24061 shared library to attach a @file{-gdb.@var{ext}} script to.
24064 Scripts needn't be copied out of the source tree.
24066 In some circumstances, apps can be built out of large collections of internal
24067 libraries, and the build infrastructure necessary to install the
24068 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24069 cumbersome. It may be easier to specify the scripts in the
24070 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24071 top of the source tree to the source search path.
24074 @node Multiple Extension Languages
24075 @section Multiple Extension Languages
24077 The Guile and Python extension languages do not share any state,
24078 and generally do not interfere with each other.
24079 There are some things to be aware of, however.
24081 @subsection Python comes first
24083 Python was @value{GDBN}'s first extension language, and to avoid breaking
24084 existing behaviour Python comes first. This is generally solved by the
24085 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24086 extension languages, and when it makes a call to an extension language,
24087 (say to pretty-print a value), it tries each in turn until an extension
24088 language indicates it has performed the request (e.g., has returned the
24089 pretty-printed form of a value).
24090 This extends to errors while performing such requests: If an error happens
24091 while, for example, trying to pretty-print an object then the error is
24092 reported and any following extension languages are not tried.
24095 @section Creating new spellings of existing commands
24096 @cindex aliases for commands
24098 It is often useful to define alternate spellings of existing commands.
24099 For example, if a new @value{GDBN} command defined in Python has
24100 a long name to type, it is handy to have an abbreviated version of it
24101 that involves less typing.
24103 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24104 of the @samp{step} command even though it is otherwise an ambiguous
24105 abbreviation of other commands like @samp{set} and @samp{show}.
24107 Aliases are also used to provide shortened or more common versions
24108 of multi-word commands. For example, @value{GDBN} provides the
24109 @samp{tty} alias of the @samp{set inferior-tty} command.
24111 You can define a new alias with the @samp{alias} command.
24116 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24120 @var{ALIAS} specifies the name of the new alias.
24121 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24124 @var{COMMAND} specifies the name of an existing command
24125 that is being aliased.
24127 The @samp{-a} option specifies that the new alias is an abbreviation
24128 of the command. Abbreviations are not shown in command
24129 lists displayed by the @samp{help} command.
24131 The @samp{--} option specifies the end of options,
24132 and is useful when @var{ALIAS} begins with a dash.
24134 Here is a simple example showing how to make an abbreviation
24135 of a command so that there is less to type.
24136 Suppose you were tired of typing @samp{disas}, the current
24137 shortest unambiguous abbreviation of the @samp{disassemble} command
24138 and you wanted an even shorter version named @samp{di}.
24139 The following will accomplish this.
24142 (gdb) alias -a di = disas
24145 Note that aliases are different from user-defined commands.
24146 With a user-defined command, you also need to write documentation
24147 for it with the @samp{document} command.
24148 An alias automatically picks up the documentation of the existing command.
24150 Here is an example where we make @samp{elms} an abbreviation of
24151 @samp{elements} in the @samp{set print elements} command.
24152 This is to show that you can make an abbreviation of any part
24156 (gdb) alias -a set print elms = set print elements
24157 (gdb) alias -a show print elms = show print elements
24158 (gdb) set p elms 20
24160 Limit on string chars or array elements to print is 200.
24163 Note that if you are defining an alias of a @samp{set} command,
24164 and you want to have an alias for the corresponding @samp{show}
24165 command, then you need to define the latter separately.
24167 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24168 @var{ALIAS}, just as they are normally.
24171 (gdb) alias -a set pr elms = set p ele
24174 Finally, here is an example showing the creation of a one word
24175 alias for a more complex command.
24176 This creates alias @samp{spe} of the command @samp{set print elements}.
24179 (gdb) alias spe = set print elements
24184 @chapter Command Interpreters
24185 @cindex command interpreters
24187 @value{GDBN} supports multiple command interpreters, and some command
24188 infrastructure to allow users or user interface writers to switch
24189 between interpreters or run commands in other interpreters.
24191 @value{GDBN} currently supports two command interpreters, the console
24192 interpreter (sometimes called the command-line interpreter or @sc{cli})
24193 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24194 describes both of these interfaces in great detail.
24196 By default, @value{GDBN} will start with the console interpreter.
24197 However, the user may choose to start @value{GDBN} with another
24198 interpreter by specifying the @option{-i} or @option{--interpreter}
24199 startup options. Defined interpreters include:
24203 @cindex console interpreter
24204 The traditional console or command-line interpreter. This is the most often
24205 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24206 @value{GDBN} will use this interpreter.
24209 @cindex mi interpreter
24210 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24211 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24212 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24216 @cindex mi2 interpreter
24217 The current @sc{gdb/mi} interface.
24220 @cindex mi1 interpreter
24221 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24225 @cindex invoke another interpreter
24226 The interpreter being used by @value{GDBN} may not be dynamically
24227 switched at runtime. Although possible, this could lead to a very
24228 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24229 enters the command "interpreter-set console" in a console view,
24230 @value{GDBN} would switch to using the console interpreter, rendering
24231 the IDE inoperable!
24233 @kindex interpreter-exec
24234 Although you may only choose a single interpreter at startup, you may execute
24235 commands in any interpreter from the current interpreter using the appropriate
24236 command. If you are running the console interpreter, simply use the
24237 @code{interpreter-exec} command:
24240 interpreter-exec mi "-data-list-register-names"
24243 @sc{gdb/mi} has a similar command, although it is only available in versions of
24244 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24247 @chapter @value{GDBN} Text User Interface
24249 @cindex Text User Interface
24252 * TUI Overview:: TUI overview
24253 * TUI Keys:: TUI key bindings
24254 * TUI Single Key Mode:: TUI single key mode
24255 * TUI Commands:: TUI-specific commands
24256 * TUI Configuration:: TUI configuration variables
24259 The @value{GDBN} Text User Interface (TUI) is a terminal
24260 interface which uses the @code{curses} library to show the source
24261 file, the assembly output, the program registers and @value{GDBN}
24262 commands in separate text windows. The TUI mode is supported only
24263 on platforms where a suitable version of the @code{curses} library
24266 The TUI mode is enabled by default when you invoke @value{GDBN} as
24267 @samp{@value{GDBP} -tui}.
24268 You can also switch in and out of TUI mode while @value{GDBN} runs by
24269 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24270 @xref{TUI Keys, ,TUI Key Bindings}.
24273 @section TUI Overview
24275 In TUI mode, @value{GDBN} can display several text windows:
24279 This window is the @value{GDBN} command window with the @value{GDBN}
24280 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24281 managed using readline.
24284 The source window shows the source file of the program. The current
24285 line and active breakpoints are displayed in this window.
24288 The assembly window shows the disassembly output of the program.
24291 This window shows the processor registers. Registers are highlighted
24292 when their values change.
24295 The source and assembly windows show the current program position
24296 by highlighting the current line and marking it with a @samp{>} marker.
24297 Breakpoints are indicated with two markers. The first marker
24298 indicates the breakpoint type:
24302 Breakpoint which was hit at least once.
24305 Breakpoint which was never hit.
24308 Hardware breakpoint which was hit at least once.
24311 Hardware breakpoint which was never hit.
24314 The second marker indicates whether the breakpoint is enabled or not:
24318 Breakpoint is enabled.
24321 Breakpoint is disabled.
24324 The source, assembly and register windows are updated when the current
24325 thread changes, when the frame changes, or when the program counter
24328 These windows are not all visible at the same time. The command
24329 window is always visible. The others can be arranged in several
24340 source and assembly,
24343 source and registers, or
24346 assembly and registers.
24349 A status line above the command window shows the following information:
24353 Indicates the current @value{GDBN} target.
24354 (@pxref{Targets, ,Specifying a Debugging Target}).
24357 Gives the current process or thread number.
24358 When no process is being debugged, this field is set to @code{No process}.
24361 Gives the current function name for the selected frame.
24362 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24363 When there is no symbol corresponding to the current program counter,
24364 the string @code{??} is displayed.
24367 Indicates the current line number for the selected frame.
24368 When the current line number is not known, the string @code{??} is displayed.
24371 Indicates the current program counter address.
24375 @section TUI Key Bindings
24376 @cindex TUI key bindings
24378 The TUI installs several key bindings in the readline keymaps
24379 @ifset SYSTEM_READLINE
24380 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24382 @ifclear SYSTEM_READLINE
24383 (@pxref{Command Line Editing}).
24385 The following key bindings are installed for both TUI mode and the
24386 @value{GDBN} standard mode.
24395 Enter or leave the TUI mode. When leaving the TUI mode,
24396 the curses window management stops and @value{GDBN} operates using
24397 its standard mode, writing on the terminal directly. When reentering
24398 the TUI mode, control is given back to the curses windows.
24399 The screen is then refreshed.
24403 Use a TUI layout with only one window. The layout will
24404 either be @samp{source} or @samp{assembly}. When the TUI mode
24405 is not active, it will switch to the TUI mode.
24407 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24411 Use a TUI layout with at least two windows. When the current
24412 layout already has two windows, the next layout with two windows is used.
24413 When a new layout is chosen, one window will always be common to the
24414 previous layout and the new one.
24416 Think of it as the Emacs @kbd{C-x 2} binding.
24420 Change the active window. The TUI associates several key bindings
24421 (like scrolling and arrow keys) with the active window. This command
24422 gives the focus to the next TUI window.
24424 Think of it as the Emacs @kbd{C-x o} binding.
24428 Switch in and out of the TUI SingleKey mode that binds single
24429 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24432 The following key bindings only work in the TUI mode:
24437 Scroll the active window one page up.
24441 Scroll the active window one page down.
24445 Scroll the active window one line up.
24449 Scroll the active window one line down.
24453 Scroll the active window one column left.
24457 Scroll the active window one column right.
24461 Refresh the screen.
24464 Because the arrow keys scroll the active window in the TUI mode, they
24465 are not available for their normal use by readline unless the command
24466 window has the focus. When another window is active, you must use
24467 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24468 and @kbd{C-f} to control the command window.
24470 @node TUI Single Key Mode
24471 @section TUI Single Key Mode
24472 @cindex TUI single key mode
24474 The TUI also provides a @dfn{SingleKey} mode, which binds several
24475 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24476 switch into this mode, where the following key bindings are used:
24479 @kindex c @r{(SingleKey TUI key)}
24483 @kindex d @r{(SingleKey TUI key)}
24487 @kindex f @r{(SingleKey TUI key)}
24491 @kindex n @r{(SingleKey TUI key)}
24495 @kindex q @r{(SingleKey TUI key)}
24497 exit the SingleKey mode.
24499 @kindex r @r{(SingleKey TUI key)}
24503 @kindex s @r{(SingleKey TUI key)}
24507 @kindex u @r{(SingleKey TUI key)}
24511 @kindex v @r{(SingleKey TUI key)}
24515 @kindex w @r{(SingleKey TUI key)}
24520 Other keys temporarily switch to the @value{GDBN} command prompt.
24521 The key that was pressed is inserted in the editing buffer so that
24522 it is possible to type most @value{GDBN} commands without interaction
24523 with the TUI SingleKey mode. Once the command is entered the TUI
24524 SingleKey mode is restored. The only way to permanently leave
24525 this mode is by typing @kbd{q} or @kbd{C-x s}.
24529 @section TUI-specific Commands
24530 @cindex TUI commands
24532 The TUI has specific commands to control the text windows.
24533 These commands are always available, even when @value{GDBN} is not in
24534 the TUI mode. When @value{GDBN} is in the standard mode, most
24535 of these commands will automatically switch to the TUI mode.
24537 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24538 terminal, or @value{GDBN} has been started with the machine interface
24539 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24540 these commands will fail with an error, because it would not be
24541 possible or desirable to enable curses window management.
24546 List and give the size of all displayed windows.
24550 Display the next layout.
24553 Display the previous layout.
24556 Display the source window only.
24559 Display the assembly window only.
24562 Display the source and assembly window.
24565 Display the register window together with the source or assembly window.
24569 Make the next window active for scrolling.
24572 Make the previous window active for scrolling.
24575 Make the source window active for scrolling.
24578 Make the assembly window active for scrolling.
24581 Make the register window active for scrolling.
24584 Make the command window active for scrolling.
24588 Refresh the screen. This is similar to typing @kbd{C-L}.
24590 @item tui reg float
24592 Show the floating point registers in the register window.
24594 @item tui reg general
24595 Show the general registers in the register window.
24598 Show the next register group. The list of register groups as well as
24599 their order is target specific. The predefined register groups are the
24600 following: @code{general}, @code{float}, @code{system}, @code{vector},
24601 @code{all}, @code{save}, @code{restore}.
24603 @item tui reg system
24604 Show the system registers in the register window.
24608 Update the source window and the current execution point.
24610 @item winheight @var{name} +@var{count}
24611 @itemx winheight @var{name} -@var{count}
24613 Change the height of the window @var{name} by @var{count}
24614 lines. Positive counts increase the height, while negative counts
24615 decrease it. The @var{name} parameter can be one of @code{src} (the
24616 source window), @code{cmd} (the command window), @code{asm} (the
24617 disassembly window), or @code{regs} (the register display window).
24619 @item tabset @var{nchars}
24621 Set the width of tab stops to be @var{nchars} characters. This
24622 setting affects the display of TAB characters in the source and
24626 @node TUI Configuration
24627 @section TUI Configuration Variables
24628 @cindex TUI configuration variables
24630 Several configuration variables control the appearance of TUI windows.
24633 @item set tui border-kind @var{kind}
24634 @kindex set tui border-kind
24635 Select the border appearance for the source, assembly and register windows.
24636 The possible values are the following:
24639 Use a space character to draw the border.
24642 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24645 Use the Alternate Character Set to draw the border. The border is
24646 drawn using character line graphics if the terminal supports them.
24649 @item set tui border-mode @var{mode}
24650 @kindex set tui border-mode
24651 @itemx set tui active-border-mode @var{mode}
24652 @kindex set tui active-border-mode
24653 Select the display attributes for the borders of the inactive windows
24654 or the active window. The @var{mode} can be one of the following:
24657 Use normal attributes to display the border.
24663 Use reverse video mode.
24666 Use half bright mode.
24668 @item half-standout
24669 Use half bright and standout mode.
24672 Use extra bright or bold mode.
24674 @item bold-standout
24675 Use extra bright or bold and standout mode.
24680 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24683 @cindex @sc{gnu} Emacs
24684 A special interface allows you to use @sc{gnu} Emacs to view (and
24685 edit) the source files for the program you are debugging with
24688 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24689 executable file you want to debug as an argument. This command starts
24690 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24691 created Emacs buffer.
24692 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24694 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24699 All ``terminal'' input and output goes through an Emacs buffer, called
24702 This applies both to @value{GDBN} commands and their output, and to the input
24703 and output done by the program you are debugging.
24705 This is useful because it means that you can copy the text of previous
24706 commands and input them again; you can even use parts of the output
24709 All the facilities of Emacs' Shell mode are available for interacting
24710 with your program. In particular, you can send signals the usual
24711 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24715 @value{GDBN} displays source code through Emacs.
24717 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24718 source file for that frame and puts an arrow (@samp{=>}) at the
24719 left margin of the current line. Emacs uses a separate buffer for
24720 source display, and splits the screen to show both your @value{GDBN} session
24723 Explicit @value{GDBN} @code{list} or search commands still produce output as
24724 usual, but you probably have no reason to use them from Emacs.
24727 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24728 a graphical mode, enabled by default, which provides further buffers
24729 that can control the execution and describe the state of your program.
24730 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24732 If you specify an absolute file name when prompted for the @kbd{M-x
24733 gdb} argument, then Emacs sets your current working directory to where
24734 your program resides. If you only specify the file name, then Emacs
24735 sets your current working directory to the directory associated
24736 with the previous buffer. In this case, @value{GDBN} may find your
24737 program by searching your environment's @code{PATH} variable, but on
24738 some operating systems it might not find the source. So, although the
24739 @value{GDBN} input and output session proceeds normally, the auxiliary
24740 buffer does not display the current source and line of execution.
24742 The initial working directory of @value{GDBN} is printed on the top
24743 line of the GUD buffer and this serves as a default for the commands
24744 that specify files for @value{GDBN} to operate on. @xref{Files,
24745 ,Commands to Specify Files}.
24747 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24748 need to call @value{GDBN} by a different name (for example, if you
24749 keep several configurations around, with different names) you can
24750 customize the Emacs variable @code{gud-gdb-command-name} to run the
24753 In the GUD buffer, you can use these special Emacs commands in
24754 addition to the standard Shell mode commands:
24758 Describe the features of Emacs' GUD Mode.
24761 Execute to another source line, like the @value{GDBN} @code{step} command; also
24762 update the display window to show the current file and location.
24765 Execute to next source line in this function, skipping all function
24766 calls, like the @value{GDBN} @code{next} command. Then update the display window
24767 to show the current file and location.
24770 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24771 display window accordingly.
24774 Execute until exit from the selected stack frame, like the @value{GDBN}
24775 @code{finish} command.
24778 Continue execution of your program, like the @value{GDBN} @code{continue}
24782 Go up the number of frames indicated by the numeric argument
24783 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24784 like the @value{GDBN} @code{up} command.
24787 Go down the number of frames indicated by the numeric argument, like the
24788 @value{GDBN} @code{down} command.
24791 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24792 tells @value{GDBN} to set a breakpoint on the source line point is on.
24794 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24795 separate frame which shows a backtrace when the GUD buffer is current.
24796 Move point to any frame in the stack and type @key{RET} to make it
24797 become the current frame and display the associated source in the
24798 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24799 selected frame become the current one. In graphical mode, the
24800 speedbar displays watch expressions.
24802 If you accidentally delete the source-display buffer, an easy way to get
24803 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24804 request a frame display; when you run under Emacs, this recreates
24805 the source buffer if necessary to show you the context of the current
24808 The source files displayed in Emacs are in ordinary Emacs buffers
24809 which are visiting the source files in the usual way. You can edit
24810 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24811 communicates with Emacs in terms of line numbers. If you add or
24812 delete lines from the text, the line numbers that @value{GDBN} knows cease
24813 to correspond properly with the code.
24815 A more detailed description of Emacs' interaction with @value{GDBN} is
24816 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24820 @chapter The @sc{gdb/mi} Interface
24822 @unnumberedsec Function and Purpose
24824 @cindex @sc{gdb/mi}, its purpose
24825 @sc{gdb/mi} is a line based machine oriented text interface to
24826 @value{GDBN} and is activated by specifying using the
24827 @option{--interpreter} command line option (@pxref{Mode Options}). It
24828 is specifically intended to support the development of systems which
24829 use the debugger as just one small component of a larger system.
24831 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24832 in the form of a reference manual.
24834 Note that @sc{gdb/mi} is still under construction, so some of the
24835 features described below are incomplete and subject to change
24836 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24838 @unnumberedsec Notation and Terminology
24840 @cindex notational conventions, for @sc{gdb/mi}
24841 This chapter uses the following notation:
24845 @code{|} separates two alternatives.
24848 @code{[ @var{something} ]} indicates that @var{something} is optional:
24849 it may or may not be given.
24852 @code{( @var{group} )*} means that @var{group} inside the parentheses
24853 may repeat zero or more times.
24856 @code{( @var{group} )+} means that @var{group} inside the parentheses
24857 may repeat one or more times.
24860 @code{"@var{string}"} means a literal @var{string}.
24864 @heading Dependencies
24868 * GDB/MI General Design::
24869 * GDB/MI Command Syntax::
24870 * GDB/MI Compatibility with CLI::
24871 * GDB/MI Development and Front Ends::
24872 * GDB/MI Output Records::
24873 * GDB/MI Simple Examples::
24874 * GDB/MI Command Description Format::
24875 * GDB/MI Breakpoint Commands::
24876 * GDB/MI Catchpoint Commands::
24877 * GDB/MI Program Context::
24878 * GDB/MI Thread Commands::
24879 * GDB/MI Ada Tasking Commands::
24880 * GDB/MI Program Execution::
24881 * GDB/MI Stack Manipulation::
24882 * GDB/MI Variable Objects::
24883 * GDB/MI Data Manipulation::
24884 * GDB/MI Tracepoint Commands::
24885 * GDB/MI Symbol Query::
24886 * GDB/MI File Commands::
24888 * GDB/MI Kod Commands::
24889 * GDB/MI Memory Overlay Commands::
24890 * GDB/MI Signal Handling Commands::
24892 * GDB/MI Target Manipulation::
24893 * GDB/MI File Transfer Commands::
24894 * GDB/MI Ada Exceptions Commands::
24895 * GDB/MI Support Commands::
24896 * GDB/MI Miscellaneous Commands::
24899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24900 @node GDB/MI General Design
24901 @section @sc{gdb/mi} General Design
24902 @cindex GDB/MI General Design
24904 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24905 parts---commands sent to @value{GDBN}, responses to those commands
24906 and notifications. Each command results in exactly one response,
24907 indicating either successful completion of the command, or an error.
24908 For the commands that do not resume the target, the response contains the
24909 requested information. For the commands that resume the target, the
24910 response only indicates whether the target was successfully resumed.
24911 Notifications is the mechanism for reporting changes in the state of the
24912 target, or in @value{GDBN} state, that cannot conveniently be associated with
24913 a command and reported as part of that command response.
24915 The important examples of notifications are:
24919 Exec notifications. These are used to report changes in
24920 target state---when a target is resumed, or stopped. It would not
24921 be feasible to include this information in response of resuming
24922 commands, because one resume commands can result in multiple events in
24923 different threads. Also, quite some time may pass before any event
24924 happens in the target, while a frontend needs to know whether the resuming
24925 command itself was successfully executed.
24928 Console output, and status notifications. Console output
24929 notifications are used to report output of CLI commands, as well as
24930 diagnostics for other commands. Status notifications are used to
24931 report the progress of a long-running operation. Naturally, including
24932 this information in command response would mean no output is produced
24933 until the command is finished, which is undesirable.
24936 General notifications. Commands may have various side effects on
24937 the @value{GDBN} or target state beyond their official purpose. For example,
24938 a command may change the selected thread. Although such changes can
24939 be included in command response, using notification allows for more
24940 orthogonal frontend design.
24944 There's no guarantee that whenever an MI command reports an error,
24945 @value{GDBN} or the target are in any specific state, and especially,
24946 the state is not reverted to the state before the MI command was
24947 processed. Therefore, whenever an MI command results in an error,
24948 we recommend that the frontend refreshes all the information shown in
24949 the user interface.
24953 * Context management::
24954 * Asynchronous and non-stop modes::
24958 @node Context management
24959 @subsection Context management
24961 @subsubsection Threads and Frames
24963 In most cases when @value{GDBN} accesses the target, this access is
24964 done in context of a specific thread and frame (@pxref{Frames}).
24965 Often, even when accessing global data, the target requires that a thread
24966 be specified. The CLI interface maintains the selected thread and frame,
24967 and supplies them to target on each command. This is convenient,
24968 because a command line user would not want to specify that information
24969 explicitly on each command, and because user interacts with
24970 @value{GDBN} via a single terminal, so no confusion is possible as
24971 to what thread and frame are the current ones.
24973 In the case of MI, the concept of selected thread and frame is less
24974 useful. First, a frontend can easily remember this information
24975 itself. Second, a graphical frontend can have more than one window,
24976 each one used for debugging a different thread, and the frontend might
24977 want to access additional threads for internal purposes. This
24978 increases the risk that by relying on implicitly selected thread, the
24979 frontend may be operating on a wrong one. Therefore, each MI command
24980 should explicitly specify which thread and frame to operate on. To
24981 make it possible, each MI command accepts the @samp{--thread} and
24982 @samp{--frame} options, the value to each is @value{GDBN} identifier
24983 for thread and frame to operate on.
24985 Usually, each top-level window in a frontend allows the user to select
24986 a thread and a frame, and remembers the user selection for further
24987 operations. However, in some cases @value{GDBN} may suggest that the
24988 current thread be changed. For example, when stopping on a breakpoint
24989 it is reasonable to switch to the thread where breakpoint is hit. For
24990 another example, if the user issues the CLI @samp{thread} command via
24991 the frontend, it is desirable to change the frontend's selected thread to the
24992 one specified by user. @value{GDBN} communicates the suggestion to
24993 change current thread using the @samp{=thread-selected} notification.
24994 No such notification is available for the selected frame at the moment.
24996 Note that historically, MI shares the selected thread with CLI, so
24997 frontends used the @code{-thread-select} to execute commands in the
24998 right context. However, getting this to work right is cumbersome. The
24999 simplest way is for frontend to emit @code{-thread-select} command
25000 before every command. This doubles the number of commands that need
25001 to be sent. The alternative approach is to suppress @code{-thread-select}
25002 if the selected thread in @value{GDBN} is supposed to be identical to the
25003 thread the frontend wants to operate on. However, getting this
25004 optimization right can be tricky. In particular, if the frontend
25005 sends several commands to @value{GDBN}, and one of the commands changes the
25006 selected thread, then the behaviour of subsequent commands will
25007 change. So, a frontend should either wait for response from such
25008 problematic commands, or explicitly add @code{-thread-select} for
25009 all subsequent commands. No frontend is known to do this exactly
25010 right, so it is suggested to just always pass the @samp{--thread} and
25011 @samp{--frame} options.
25013 @subsubsection Language
25015 The execution of several commands depends on which language is selected.
25016 By default, the current language (@pxref{show language}) is used.
25017 But for commands known to be language-sensitive, it is recommended
25018 to use the @samp{--language} option. This option takes one argument,
25019 which is the name of the language to use while executing the command.
25023 -data-evaluate-expression --language c "sizeof (void*)"
25028 The valid language names are the same names accepted by the
25029 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25030 @samp{local} or @samp{unknown}.
25032 @node Asynchronous and non-stop modes
25033 @subsection Asynchronous command execution and non-stop mode
25035 On some targets, @value{GDBN} is capable of processing MI commands
25036 even while the target is running. This is called @dfn{asynchronous
25037 command execution} (@pxref{Background Execution}). The frontend may
25038 specify a preferrence for asynchronous execution using the
25039 @code{-gdb-set mi-async 1} command, which should be emitted before
25040 either running the executable or attaching to the target. After the
25041 frontend has started the executable or attached to the target, it can
25042 find if asynchronous execution is enabled using the
25043 @code{-list-target-features} command.
25046 @item -gdb-set mi-async on
25047 @item -gdb-set mi-async off
25048 Set whether MI is in asynchronous mode.
25050 When @code{off}, which is the default, MI execution commands (e.g.,
25051 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25052 for the program to stop before processing further commands.
25054 When @code{on}, MI execution commands are background execution
25055 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25056 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25057 MI commands even while the target is running.
25059 @item -gdb-show mi-async
25060 Show whether MI asynchronous mode is enabled.
25063 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25064 @code{target-async} instead of @code{mi-async}, and it had the effect
25065 of both putting MI in asynchronous mode and making CLI background
25066 commands possible. CLI background commands are now always possible
25067 ``out of the box'' if the target supports them. The old spelling is
25068 kept as a deprecated alias for backwards compatibility.
25070 Even if @value{GDBN} can accept a command while target is running,
25071 many commands that access the target do not work when the target is
25072 running. Therefore, asynchronous command execution is most useful
25073 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25074 it is possible to examine the state of one thread, while other threads
25077 When a given thread is running, MI commands that try to access the
25078 target in the context of that thread may not work, or may work only on
25079 some targets. In particular, commands that try to operate on thread's
25080 stack will not work, on any target. Commands that read memory, or
25081 modify breakpoints, may work or not work, depending on the target. Note
25082 that even commands that operate on global state, such as @code{print},
25083 @code{set}, and breakpoint commands, still access the target in the
25084 context of a specific thread, so frontend should try to find a
25085 stopped thread and perform the operation on that thread (using the
25086 @samp{--thread} option).
25088 Which commands will work in the context of a running thread is
25089 highly target dependent. However, the two commands
25090 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25091 to find the state of a thread, will always work.
25093 @node Thread groups
25094 @subsection Thread groups
25095 @value{GDBN} may be used to debug several processes at the same time.
25096 On some platfroms, @value{GDBN} may support debugging of several
25097 hardware systems, each one having several cores with several different
25098 processes running on each core. This section describes the MI
25099 mechanism to support such debugging scenarios.
25101 The key observation is that regardless of the structure of the
25102 target, MI can have a global list of threads, because most commands that
25103 accept the @samp{--thread} option do not need to know what process that
25104 thread belongs to. Therefore, it is not necessary to introduce
25105 neither additional @samp{--process} option, nor an notion of the
25106 current process in the MI interface. The only strictly new feature
25107 that is required is the ability to find how the threads are grouped
25110 To allow the user to discover such grouping, and to support arbitrary
25111 hierarchy of machines/cores/processes, MI introduces the concept of a
25112 @dfn{thread group}. Thread group is a collection of threads and other
25113 thread groups. A thread group always has a string identifier, a type,
25114 and may have additional attributes specific to the type. A new
25115 command, @code{-list-thread-groups}, returns the list of top-level
25116 thread groups, which correspond to processes that @value{GDBN} is
25117 debugging at the moment. By passing an identifier of a thread group
25118 to the @code{-list-thread-groups} command, it is possible to obtain
25119 the members of specific thread group.
25121 To allow the user to easily discover processes, and other objects, he
25122 wishes to debug, a concept of @dfn{available thread group} is
25123 introduced. Available thread group is an thread group that
25124 @value{GDBN} is not debugging, but that can be attached to, using the
25125 @code{-target-attach} command. The list of available top-level thread
25126 groups can be obtained using @samp{-list-thread-groups --available}.
25127 In general, the content of a thread group may be only retrieved only
25128 after attaching to that thread group.
25130 Thread groups are related to inferiors (@pxref{Inferiors and
25131 Programs}). Each inferior corresponds to a thread group of a special
25132 type @samp{process}, and some additional operations are permitted on
25133 such thread groups.
25135 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25136 @node GDB/MI Command Syntax
25137 @section @sc{gdb/mi} Command Syntax
25140 * GDB/MI Input Syntax::
25141 * GDB/MI Output Syntax::
25144 @node GDB/MI Input Syntax
25145 @subsection @sc{gdb/mi} Input Syntax
25147 @cindex input syntax for @sc{gdb/mi}
25148 @cindex @sc{gdb/mi}, input syntax
25150 @item @var{command} @expansion{}
25151 @code{@var{cli-command} | @var{mi-command}}
25153 @item @var{cli-command} @expansion{}
25154 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25155 @var{cli-command} is any existing @value{GDBN} CLI command.
25157 @item @var{mi-command} @expansion{}
25158 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25159 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25161 @item @var{token} @expansion{}
25162 "any sequence of digits"
25164 @item @var{option} @expansion{}
25165 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25167 @item @var{parameter} @expansion{}
25168 @code{@var{non-blank-sequence} | @var{c-string}}
25170 @item @var{operation} @expansion{}
25171 @emph{any of the operations described in this chapter}
25173 @item @var{non-blank-sequence} @expansion{}
25174 @emph{anything, provided it doesn't contain special characters such as
25175 "-", @var{nl}, """ and of course " "}
25177 @item @var{c-string} @expansion{}
25178 @code{""" @var{seven-bit-iso-c-string-content} """}
25180 @item @var{nl} @expansion{}
25189 The CLI commands are still handled by the @sc{mi} interpreter; their
25190 output is described below.
25193 The @code{@var{token}}, when present, is passed back when the command
25197 Some @sc{mi} commands accept optional arguments as part of the parameter
25198 list. Each option is identified by a leading @samp{-} (dash) and may be
25199 followed by an optional argument parameter. Options occur first in the
25200 parameter list and can be delimited from normal parameters using
25201 @samp{--} (this is useful when some parameters begin with a dash).
25208 We want easy access to the existing CLI syntax (for debugging).
25211 We want it to be easy to spot a @sc{mi} operation.
25214 @node GDB/MI Output Syntax
25215 @subsection @sc{gdb/mi} Output Syntax
25217 @cindex output syntax of @sc{gdb/mi}
25218 @cindex @sc{gdb/mi}, output syntax
25219 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25220 followed, optionally, by a single result record. This result record
25221 is for the most recent command. The sequence of output records is
25222 terminated by @samp{(gdb)}.
25224 If an input command was prefixed with a @code{@var{token}} then the
25225 corresponding output for that command will also be prefixed by that same
25229 @item @var{output} @expansion{}
25230 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25232 @item @var{result-record} @expansion{}
25233 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25235 @item @var{out-of-band-record} @expansion{}
25236 @code{@var{async-record} | @var{stream-record}}
25238 @item @var{async-record} @expansion{}
25239 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25241 @item @var{exec-async-output} @expansion{}
25242 @code{[ @var{token} ] "*" @var{async-output nl}}
25244 @item @var{status-async-output} @expansion{}
25245 @code{[ @var{token} ] "+" @var{async-output nl}}
25247 @item @var{notify-async-output} @expansion{}
25248 @code{[ @var{token} ] "=" @var{async-output nl}}
25250 @item @var{async-output} @expansion{}
25251 @code{@var{async-class} ( "," @var{result} )*}
25253 @item @var{result-class} @expansion{}
25254 @code{"done" | "running" | "connected" | "error" | "exit"}
25256 @item @var{async-class} @expansion{}
25257 @code{"stopped" | @var{others}} (where @var{others} will be added
25258 depending on the needs---this is still in development).
25260 @item @var{result} @expansion{}
25261 @code{ @var{variable} "=" @var{value}}
25263 @item @var{variable} @expansion{}
25264 @code{ @var{string} }
25266 @item @var{value} @expansion{}
25267 @code{ @var{const} | @var{tuple} | @var{list} }
25269 @item @var{const} @expansion{}
25270 @code{@var{c-string}}
25272 @item @var{tuple} @expansion{}
25273 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25275 @item @var{list} @expansion{}
25276 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25277 @var{result} ( "," @var{result} )* "]" }
25279 @item @var{stream-record} @expansion{}
25280 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25282 @item @var{console-stream-output} @expansion{}
25283 @code{"~" @var{c-string nl}}
25285 @item @var{target-stream-output} @expansion{}
25286 @code{"@@" @var{c-string nl}}
25288 @item @var{log-stream-output} @expansion{}
25289 @code{"&" @var{c-string nl}}
25291 @item @var{nl} @expansion{}
25294 @item @var{token} @expansion{}
25295 @emph{any sequence of digits}.
25303 All output sequences end in a single line containing a period.
25306 The @code{@var{token}} is from the corresponding request. Note that
25307 for all async output, while the token is allowed by the grammar and
25308 may be output by future versions of @value{GDBN} for select async
25309 output messages, it is generally omitted. Frontends should treat
25310 all async output as reporting general changes in the state of the
25311 target and there should be no need to associate async output to any
25315 @cindex status output in @sc{gdb/mi}
25316 @var{status-async-output} contains on-going status information about the
25317 progress of a slow operation. It can be discarded. All status output is
25318 prefixed by @samp{+}.
25321 @cindex async output in @sc{gdb/mi}
25322 @var{exec-async-output} contains asynchronous state change on the target
25323 (stopped, started, disappeared). All async output is prefixed by
25327 @cindex notify output in @sc{gdb/mi}
25328 @var{notify-async-output} contains supplementary information that the
25329 client should handle (e.g., a new breakpoint information). All notify
25330 output is prefixed by @samp{=}.
25333 @cindex console output in @sc{gdb/mi}
25334 @var{console-stream-output} is output that should be displayed as is in the
25335 console. It is the textual response to a CLI command. All the console
25336 output is prefixed by @samp{~}.
25339 @cindex target output in @sc{gdb/mi}
25340 @var{target-stream-output} is the output produced by the target program.
25341 All the target output is prefixed by @samp{@@}.
25344 @cindex log output in @sc{gdb/mi}
25345 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25346 instance messages that should be displayed as part of an error log. All
25347 the log output is prefixed by @samp{&}.
25350 @cindex list output in @sc{gdb/mi}
25351 New @sc{gdb/mi} commands should only output @var{lists} containing
25357 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25358 details about the various output records.
25360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25361 @node GDB/MI Compatibility with CLI
25362 @section @sc{gdb/mi} Compatibility with CLI
25364 @cindex compatibility, @sc{gdb/mi} and CLI
25365 @cindex @sc{gdb/mi}, compatibility with CLI
25367 For the developers convenience CLI commands can be entered directly,
25368 but there may be some unexpected behaviour. For example, commands
25369 that query the user will behave as if the user replied yes, breakpoint
25370 command lists are not executed and some CLI commands, such as
25371 @code{if}, @code{when} and @code{define}, prompt for further input with
25372 @samp{>}, which is not valid MI output.
25374 This feature may be removed at some stage in the future and it is
25375 recommended that front ends use the @code{-interpreter-exec} command
25376 (@pxref{-interpreter-exec}).
25378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25379 @node GDB/MI Development and Front Ends
25380 @section @sc{gdb/mi} Development and Front Ends
25381 @cindex @sc{gdb/mi} development
25383 The application which takes the MI output and presents the state of the
25384 program being debugged to the user is called a @dfn{front end}.
25386 Although @sc{gdb/mi} is still incomplete, it is currently being used
25387 by a variety of front ends to @value{GDBN}. This makes it difficult
25388 to introduce new functionality without breaking existing usage. This
25389 section tries to minimize the problems by describing how the protocol
25392 Some changes in MI need not break a carefully designed front end, and
25393 for these the MI version will remain unchanged. The following is a
25394 list of changes that may occur within one level, so front ends should
25395 parse MI output in a way that can handle them:
25399 New MI commands may be added.
25402 New fields may be added to the output of any MI command.
25405 The range of values for fields with specified values, e.g.,
25406 @code{in_scope} (@pxref{-var-update}) may be extended.
25408 @c The format of field's content e.g type prefix, may change so parse it
25409 @c at your own risk. Yes, in general?
25411 @c The order of fields may change? Shouldn't really matter but it might
25412 @c resolve inconsistencies.
25415 If the changes are likely to break front ends, the MI version level
25416 will be increased by one. This will allow the front end to parse the
25417 output according to the MI version. Apart from mi0, new versions of
25418 @value{GDBN} will not support old versions of MI and it will be the
25419 responsibility of the front end to work with the new one.
25421 @c Starting with mi3, add a new command -mi-version that prints the MI
25424 The best way to avoid unexpected changes in MI that might break your front
25425 end is to make your project known to @value{GDBN} developers and
25426 follow development on @email{gdb@@sourceware.org} and
25427 @email{gdb-patches@@sourceware.org}.
25428 @cindex mailing lists
25430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25431 @node GDB/MI Output Records
25432 @section @sc{gdb/mi} Output Records
25435 * GDB/MI Result Records::
25436 * GDB/MI Stream Records::
25437 * GDB/MI Async Records::
25438 * GDB/MI Breakpoint Information::
25439 * GDB/MI Frame Information::
25440 * GDB/MI Thread Information::
25441 * GDB/MI Ada Exception Information::
25444 @node GDB/MI Result Records
25445 @subsection @sc{gdb/mi} Result Records
25447 @cindex result records in @sc{gdb/mi}
25448 @cindex @sc{gdb/mi}, result records
25449 In addition to a number of out-of-band notifications, the response to a
25450 @sc{gdb/mi} command includes one of the following result indications:
25454 @item "^done" [ "," @var{results} ]
25455 The synchronous operation was successful, @code{@var{results}} are the return
25460 This result record is equivalent to @samp{^done}. Historically, it
25461 was output instead of @samp{^done} if the command has resumed the
25462 target. This behaviour is maintained for backward compatibility, but
25463 all frontends should treat @samp{^done} and @samp{^running}
25464 identically and rely on the @samp{*running} output record to determine
25465 which threads are resumed.
25469 @value{GDBN} has connected to a remote target.
25471 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25473 The operation failed. The @code{msg=@var{c-string}} variable contains
25474 the corresponding error message.
25476 If present, the @code{code=@var{c-string}} variable provides an error
25477 code on which consumers can rely on to detect the corresponding
25478 error condition. At present, only one error code is defined:
25481 @item "undefined-command"
25482 Indicates that the command causing the error does not exist.
25487 @value{GDBN} has terminated.
25491 @node GDB/MI Stream Records
25492 @subsection @sc{gdb/mi} Stream Records
25494 @cindex @sc{gdb/mi}, stream records
25495 @cindex stream records in @sc{gdb/mi}
25496 @value{GDBN} internally maintains a number of output streams: the console, the
25497 target, and the log. The output intended for each of these streams is
25498 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25500 Each stream record begins with a unique @dfn{prefix character} which
25501 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25502 Syntax}). In addition to the prefix, each stream record contains a
25503 @code{@var{string-output}}. This is either raw text (with an implicit new
25504 line) or a quoted C string (which does not contain an implicit newline).
25507 @item "~" @var{string-output}
25508 The console output stream contains text that should be displayed in the
25509 CLI console window. It contains the textual responses to CLI commands.
25511 @item "@@" @var{string-output}
25512 The target output stream contains any textual output from the running
25513 target. This is only present when GDB's event loop is truly
25514 asynchronous, which is currently only the case for remote targets.
25516 @item "&" @var{string-output}
25517 The log stream contains debugging messages being produced by @value{GDBN}'s
25521 @node GDB/MI Async Records
25522 @subsection @sc{gdb/mi} Async Records
25524 @cindex async records in @sc{gdb/mi}
25525 @cindex @sc{gdb/mi}, async records
25526 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25527 additional changes that have occurred. Those changes can either be a
25528 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25529 target activity (e.g., target stopped).
25531 The following is the list of possible async records:
25535 @item *running,thread-id="@var{thread}"
25536 The target is now running. The @var{thread} field tells which
25537 specific thread is now running, and can be @samp{all} if all threads
25538 are running. The frontend should assume that no interaction with a
25539 running thread is possible after this notification is produced.
25540 The frontend should not assume that this notification is output
25541 only once for any command. @value{GDBN} may emit this notification
25542 several times, either for different threads, because it cannot resume
25543 all threads together, or even for a single thread, if the thread must
25544 be stepped though some code before letting it run freely.
25546 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25547 The target has stopped. The @var{reason} field can have one of the
25551 @item breakpoint-hit
25552 A breakpoint was reached.
25553 @item watchpoint-trigger
25554 A watchpoint was triggered.
25555 @item read-watchpoint-trigger
25556 A read watchpoint was triggered.
25557 @item access-watchpoint-trigger
25558 An access watchpoint was triggered.
25559 @item function-finished
25560 An -exec-finish or similar CLI command was accomplished.
25561 @item location-reached
25562 An -exec-until or similar CLI command was accomplished.
25563 @item watchpoint-scope
25564 A watchpoint has gone out of scope.
25565 @item end-stepping-range
25566 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25567 similar CLI command was accomplished.
25568 @item exited-signalled
25569 The inferior exited because of a signal.
25571 The inferior exited.
25572 @item exited-normally
25573 The inferior exited normally.
25574 @item signal-received
25575 A signal was received by the inferior.
25577 The inferior has stopped due to a library being loaded or unloaded.
25578 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25579 set or when a @code{catch load} or @code{catch unload} catchpoint is
25580 in use (@pxref{Set Catchpoints}).
25582 The inferior has forked. This is reported when @code{catch fork}
25583 (@pxref{Set Catchpoints}) has been used.
25585 The inferior has vforked. This is reported in when @code{catch vfork}
25586 (@pxref{Set Catchpoints}) has been used.
25587 @item syscall-entry
25588 The inferior entered a system call. This is reported when @code{catch
25589 syscall} (@pxref{Set Catchpoints}) has been used.
25590 @item syscall-entry
25591 The inferior returned from a system call. This is reported when
25592 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25594 The inferior called @code{exec}. This is reported when @code{catch exec}
25595 (@pxref{Set Catchpoints}) has been used.
25598 The @var{id} field identifies the thread that directly caused the stop
25599 -- for example by hitting a breakpoint. Depending on whether all-stop
25600 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25601 stop all threads, or only the thread that directly triggered the stop.
25602 If all threads are stopped, the @var{stopped} field will have the
25603 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25604 field will be a list of thread identifiers. Presently, this list will
25605 always include a single thread, but frontend should be prepared to see
25606 several threads in the list. The @var{core} field reports the
25607 processor core on which the stop event has happened. This field may be absent
25608 if such information is not available.
25610 @item =thread-group-added,id="@var{id}"
25611 @itemx =thread-group-removed,id="@var{id}"
25612 A thread group was either added or removed. The @var{id} field
25613 contains the @value{GDBN} identifier of the thread group. When a thread
25614 group is added, it generally might not be associated with a running
25615 process. When a thread group is removed, its id becomes invalid and
25616 cannot be used in any way.
25618 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25619 A thread group became associated with a running program,
25620 either because the program was just started or the thread group
25621 was attached to a program. The @var{id} field contains the
25622 @value{GDBN} identifier of the thread group. The @var{pid} field
25623 contains process identifier, specific to the operating system.
25625 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25626 A thread group is no longer associated with a running program,
25627 either because the program has exited, or because it was detached
25628 from. The @var{id} field contains the @value{GDBN} identifier of the
25629 thread group. The @var{code} field is the exit code of the inferior; it exists
25630 only when the inferior exited with some code.
25632 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25633 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25634 A thread either was created, or has exited. The @var{id} field
25635 contains the @value{GDBN} identifier of the thread. The @var{gid}
25636 field identifies the thread group this thread belongs to.
25638 @item =thread-selected,id="@var{id}"
25639 Informs that the selected thread was changed as result of the last
25640 command. This notification is not emitted as result of @code{-thread-select}
25641 command but is emitted whenever an MI command that is not documented
25642 to change the selected thread actually changes it. In particular,
25643 invoking, directly or indirectly (via user-defined command), the CLI
25644 @code{thread} command, will generate this notification.
25646 We suggest that in response to this notification, front ends
25647 highlight the selected thread and cause subsequent commands to apply to
25650 @item =library-loaded,...
25651 Reports that a new library file was loaded by the program. This
25652 notification has 4 fields---@var{id}, @var{target-name},
25653 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25654 opaque identifier of the library. For remote debugging case,
25655 @var{target-name} and @var{host-name} fields give the name of the
25656 library file on the target, and on the host respectively. For native
25657 debugging, both those fields have the same value. The
25658 @var{symbols-loaded} field is emitted only for backward compatibility
25659 and should not be relied on to convey any useful information. The
25660 @var{thread-group} field, if present, specifies the id of the thread
25661 group in whose context the library was loaded. If the field is
25662 absent, it means the library was loaded in the context of all present
25665 @item =library-unloaded,...
25666 Reports that a library was unloaded by the program. This notification
25667 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25668 the same meaning as for the @code{=library-loaded} notification.
25669 The @var{thread-group} field, if present, specifies the id of the
25670 thread group in whose context the library was unloaded. If the field is
25671 absent, it means the library was unloaded in the context of all present
25674 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25675 @itemx =traceframe-changed,end
25676 Reports that the trace frame was changed and its new number is
25677 @var{tfnum}. The number of the tracepoint associated with this trace
25678 frame is @var{tpnum}.
25680 @item =tsv-created,name=@var{name},initial=@var{initial}
25681 Reports that the new trace state variable @var{name} is created with
25682 initial value @var{initial}.
25684 @item =tsv-deleted,name=@var{name}
25685 @itemx =tsv-deleted
25686 Reports that the trace state variable @var{name} is deleted or all
25687 trace state variables are deleted.
25689 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25690 Reports that the trace state variable @var{name} is modified with
25691 the initial value @var{initial}. The current value @var{current} of
25692 trace state variable is optional and is reported if the current
25693 value of trace state variable is known.
25695 @item =breakpoint-created,bkpt=@{...@}
25696 @itemx =breakpoint-modified,bkpt=@{...@}
25697 @itemx =breakpoint-deleted,id=@var{number}
25698 Reports that a breakpoint was created, modified, or deleted,
25699 respectively. Only user-visible breakpoints are reported to the MI
25702 The @var{bkpt} argument is of the same form as returned by the various
25703 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25704 @var{number} is the ordinal number of the breakpoint.
25706 Note that if a breakpoint is emitted in the result record of a
25707 command, then it will not also be emitted in an async record.
25709 @item =record-started,thread-group="@var{id}"
25710 @itemx =record-stopped,thread-group="@var{id}"
25711 Execution log recording was either started or stopped on an
25712 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25713 group corresponding to the affected inferior.
25715 @item =cmd-param-changed,param=@var{param},value=@var{value}
25716 Reports that a parameter of the command @code{set @var{param}} is
25717 changed to @var{value}. In the multi-word @code{set} command,
25718 the @var{param} is the whole parameter list to @code{set} command.
25719 For example, In command @code{set check type on}, @var{param}
25720 is @code{check type} and @var{value} is @code{on}.
25722 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25723 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25724 written in an inferior. The @var{id} is the identifier of the
25725 thread group corresponding to the affected inferior. The optional
25726 @code{type="code"} part is reported if the memory written to holds
25730 @node GDB/MI Breakpoint Information
25731 @subsection @sc{gdb/mi} Breakpoint Information
25733 When @value{GDBN} reports information about a breakpoint, a
25734 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25739 The breakpoint number. For a breakpoint that represents one location
25740 of a multi-location breakpoint, this will be a dotted pair, like
25744 The type of the breakpoint. For ordinary breakpoints this will be
25745 @samp{breakpoint}, but many values are possible.
25748 If the type of the breakpoint is @samp{catchpoint}, then this
25749 indicates the exact type of catchpoint.
25752 This is the breakpoint disposition---either @samp{del}, meaning that
25753 the breakpoint will be deleted at the next stop, or @samp{keep},
25754 meaning that the breakpoint will not be deleted.
25757 This indicates whether the breakpoint is enabled, in which case the
25758 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25759 Note that this is not the same as the field @code{enable}.
25762 The address of the breakpoint. This may be a hexidecimal number,
25763 giving the address; or the string @samp{<PENDING>}, for a pending
25764 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25765 multiple locations. This field will not be present if no address can
25766 be determined. For example, a watchpoint does not have an address.
25769 If known, the function in which the breakpoint appears.
25770 If not known, this field is not present.
25773 The name of the source file which contains this function, if known.
25774 If not known, this field is not present.
25777 The full file name of the source file which contains this function, if
25778 known. If not known, this field is not present.
25781 The line number at which this breakpoint appears, if known.
25782 If not known, this field is not present.
25785 If the source file is not known, this field may be provided. If
25786 provided, this holds the address of the breakpoint, possibly followed
25790 If this breakpoint is pending, this field is present and holds the
25791 text used to set the breakpoint, as entered by the user.
25794 Where this breakpoint's condition is evaluated, either @samp{host} or
25798 If this is a thread-specific breakpoint, then this identifies the
25799 thread in which the breakpoint can trigger.
25802 If this breakpoint is restricted to a particular Ada task, then this
25803 field will hold the task identifier.
25806 If the breakpoint is conditional, this is the condition expression.
25809 The ignore count of the breakpoint.
25812 The enable count of the breakpoint.
25814 @item traceframe-usage
25817 @item static-tracepoint-marker-string-id
25818 For a static tracepoint, the name of the static tracepoint marker.
25821 For a masked watchpoint, this is the mask.
25824 A tracepoint's pass count.
25826 @item original-location
25827 The location of the breakpoint as originally specified by the user.
25828 This field is optional.
25831 The number of times the breakpoint has been hit.
25834 This field is only given for tracepoints. This is either @samp{y},
25835 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25839 Some extra data, the exact contents of which are type-dependent.
25843 For example, here is what the output of @code{-break-insert}
25844 (@pxref{GDB/MI Breakpoint Commands}) might be:
25847 -> -break-insert main
25848 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25849 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25850 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25855 @node GDB/MI Frame Information
25856 @subsection @sc{gdb/mi} Frame Information
25858 Response from many MI commands includes an information about stack
25859 frame. This information is a tuple that may have the following
25864 The level of the stack frame. The innermost frame has the level of
25865 zero. This field is always present.
25868 The name of the function corresponding to the frame. This field may
25869 be absent if @value{GDBN} is unable to determine the function name.
25872 The code address for the frame. This field is always present.
25875 The name of the source files that correspond to the frame's code
25876 address. This field may be absent.
25879 The source line corresponding to the frames' code address. This field
25883 The name of the binary file (either executable or shared library) the
25884 corresponds to the frame's code address. This field may be absent.
25888 @node GDB/MI Thread Information
25889 @subsection @sc{gdb/mi} Thread Information
25891 Whenever @value{GDBN} has to report an information about a thread, it
25892 uses a tuple with the following fields:
25896 The numeric id assigned to the thread by @value{GDBN}. This field is
25900 Target-specific string identifying the thread. This field is always present.
25903 Additional information about the thread provided by the target.
25904 It is supposed to be human-readable and not interpreted by the
25905 frontend. This field is optional.
25908 Either @samp{stopped} or @samp{running}, depending on whether the
25909 thread is presently running. This field is always present.
25912 The value of this field is an integer number of the processor core the
25913 thread was last seen on. This field is optional.
25916 @node GDB/MI Ada Exception Information
25917 @subsection @sc{gdb/mi} Ada Exception Information
25919 Whenever a @code{*stopped} record is emitted because the program
25920 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25921 @value{GDBN} provides the name of the exception that was raised via
25922 the @code{exception-name} field.
25924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25925 @node GDB/MI Simple Examples
25926 @section Simple Examples of @sc{gdb/mi} Interaction
25927 @cindex @sc{gdb/mi}, simple examples
25929 This subsection presents several simple examples of interaction using
25930 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25931 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25932 the output received from @sc{gdb/mi}.
25934 Note the line breaks shown in the examples are here only for
25935 readability, they don't appear in the real output.
25937 @subheading Setting a Breakpoint
25939 Setting a breakpoint generates synchronous output which contains detailed
25940 information of the breakpoint.
25943 -> -break-insert main
25944 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25945 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25946 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25951 @subheading Program Execution
25953 Program execution generates asynchronous records and MI gives the
25954 reason that execution stopped.
25960 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25961 frame=@{addr="0x08048564",func="main",
25962 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25963 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25968 <- *stopped,reason="exited-normally"
25972 @subheading Quitting @value{GDBN}
25974 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25982 Please note that @samp{^exit} is printed immediately, but it might
25983 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25984 performs necessary cleanups, including killing programs being debugged
25985 or disconnecting from debug hardware, so the frontend should wait till
25986 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25987 fails to exit in reasonable time.
25989 @subheading A Bad Command
25991 Here's what happens if you pass a non-existent command:
25995 <- ^error,msg="Undefined MI command: rubbish"
26000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26001 @node GDB/MI Command Description Format
26002 @section @sc{gdb/mi} Command Description Format
26004 The remaining sections describe blocks of commands. Each block of
26005 commands is laid out in a fashion similar to this section.
26007 @subheading Motivation
26009 The motivation for this collection of commands.
26011 @subheading Introduction
26013 A brief introduction to this collection of commands as a whole.
26015 @subheading Commands
26017 For each command in the block, the following is described:
26019 @subsubheading Synopsis
26022 -command @var{args}@dots{}
26025 @subsubheading Result
26027 @subsubheading @value{GDBN} Command
26029 The corresponding @value{GDBN} CLI command(s), if any.
26031 @subsubheading Example
26033 Example(s) formatted for readability. Some of the described commands have
26034 not been implemented yet and these are labeled N.A.@: (not available).
26037 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26038 @node GDB/MI Breakpoint Commands
26039 @section @sc{gdb/mi} Breakpoint Commands
26041 @cindex breakpoint commands for @sc{gdb/mi}
26042 @cindex @sc{gdb/mi}, breakpoint commands
26043 This section documents @sc{gdb/mi} commands for manipulating
26046 @subheading The @code{-break-after} Command
26047 @findex -break-after
26049 @subsubheading Synopsis
26052 -break-after @var{number} @var{count}
26055 The breakpoint number @var{number} is not in effect until it has been
26056 hit @var{count} times. To see how this is reflected in the output of
26057 the @samp{-break-list} command, see the description of the
26058 @samp{-break-list} command below.
26060 @subsubheading @value{GDBN} Command
26062 The corresponding @value{GDBN} command is @samp{ignore}.
26064 @subsubheading Example
26069 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26070 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26071 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26079 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26080 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26081 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26082 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26083 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26084 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26085 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26086 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26087 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26088 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26093 @subheading The @code{-break-catch} Command
26094 @findex -break-catch
26097 @subheading The @code{-break-commands} Command
26098 @findex -break-commands
26100 @subsubheading Synopsis
26103 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26106 Specifies the CLI commands that should be executed when breakpoint
26107 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26108 are the commands. If no command is specified, any previously-set
26109 commands are cleared. @xref{Break Commands}. Typical use of this
26110 functionality is tracing a program, that is, printing of values of
26111 some variables whenever breakpoint is hit and then continuing.
26113 @subsubheading @value{GDBN} Command
26115 The corresponding @value{GDBN} command is @samp{commands}.
26117 @subsubheading Example
26122 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26123 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26124 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26127 -break-commands 1 "print v" "continue"
26132 @subheading The @code{-break-condition} Command
26133 @findex -break-condition
26135 @subsubheading Synopsis
26138 -break-condition @var{number} @var{expr}
26141 Breakpoint @var{number} will stop the program only if the condition in
26142 @var{expr} is true. The condition becomes part of the
26143 @samp{-break-list} output (see the description of the @samp{-break-list}
26146 @subsubheading @value{GDBN} Command
26148 The corresponding @value{GDBN} command is @samp{condition}.
26150 @subsubheading Example
26154 -break-condition 1 1
26158 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26159 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26160 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26161 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26162 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26163 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26164 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26165 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26166 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26167 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26171 @subheading The @code{-break-delete} Command
26172 @findex -break-delete
26174 @subsubheading Synopsis
26177 -break-delete ( @var{breakpoint} )+
26180 Delete the breakpoint(s) whose number(s) are specified in the argument
26181 list. This is obviously reflected in the breakpoint list.
26183 @subsubheading @value{GDBN} Command
26185 The corresponding @value{GDBN} command is @samp{delete}.
26187 @subsubheading Example
26195 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26196 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26197 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26198 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26199 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26200 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26201 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26206 @subheading The @code{-break-disable} Command
26207 @findex -break-disable
26209 @subsubheading Synopsis
26212 -break-disable ( @var{breakpoint} )+
26215 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26216 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26218 @subsubheading @value{GDBN} Command
26220 The corresponding @value{GDBN} command is @samp{disable}.
26222 @subsubheading Example
26230 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26231 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26232 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26233 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26234 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26235 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26236 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26237 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26238 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26239 line="5",thread-groups=["i1"],times="0"@}]@}
26243 @subheading The @code{-break-enable} Command
26244 @findex -break-enable
26246 @subsubheading Synopsis
26249 -break-enable ( @var{breakpoint} )+
26252 Enable (previously disabled) @var{breakpoint}(s).
26254 @subsubheading @value{GDBN} Command
26256 The corresponding @value{GDBN} command is @samp{enable}.
26258 @subsubheading Example
26266 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26267 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26268 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26269 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26270 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26271 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26272 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26273 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26274 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26275 line="5",thread-groups=["i1"],times="0"@}]@}
26279 @subheading The @code{-break-info} Command
26280 @findex -break-info
26282 @subsubheading Synopsis
26285 -break-info @var{breakpoint}
26289 Get information about a single breakpoint.
26291 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26292 Information}, for details on the format of each breakpoint in the
26295 @subsubheading @value{GDBN} Command
26297 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26299 @subsubheading Example
26302 @subheading The @code{-break-insert} Command
26303 @findex -break-insert
26305 @subsubheading Synopsis
26308 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26309 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26310 [ -p @var{thread-id} ] [ @var{location} ]
26314 If specified, @var{location}, can be one of:
26321 @item filename:linenum
26322 @item filename:function
26326 The possible optional parameters of this command are:
26330 Insert a temporary breakpoint.
26332 Insert a hardware breakpoint.
26334 If @var{location} cannot be parsed (for example if it
26335 refers to unknown files or functions), create a pending
26336 breakpoint. Without this flag, @value{GDBN} will report
26337 an error, and won't create a breakpoint, if @var{location}
26340 Create a disabled breakpoint.
26342 Create a tracepoint. @xref{Tracepoints}. When this parameter
26343 is used together with @samp{-h}, a fast tracepoint is created.
26344 @item -c @var{condition}
26345 Make the breakpoint conditional on @var{condition}.
26346 @item -i @var{ignore-count}
26347 Initialize the @var{ignore-count}.
26348 @item -p @var{thread-id}
26349 Restrict the breakpoint to the specified @var{thread-id}.
26352 @subsubheading Result
26354 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26355 resulting breakpoint.
26357 Note: this format is open to change.
26358 @c An out-of-band breakpoint instead of part of the result?
26360 @subsubheading @value{GDBN} Command
26362 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26363 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26365 @subsubheading Example
26370 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26371 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26374 -break-insert -t foo
26375 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26376 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26380 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26381 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26382 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26383 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26384 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26385 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26386 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26387 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26388 addr="0x0001072c", func="main",file="recursive2.c",
26389 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26391 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26392 addr="0x00010774",func="foo",file="recursive2.c",
26393 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26396 @c -break-insert -r foo.*
26397 @c ~int foo(int, int);
26398 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26399 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26404 @subheading The @code{-dprintf-insert} Command
26405 @findex -dprintf-insert
26407 @subsubheading Synopsis
26410 -dprintf-insert [ -t ] [ -f ] [ -d ]
26411 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26412 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26417 If specified, @var{location}, can be one of:
26420 @item @var{function}
26423 @c @item @var{linenum}
26424 @item @var{filename}:@var{linenum}
26425 @item @var{filename}:function
26426 @item *@var{address}
26429 The possible optional parameters of this command are:
26433 Insert a temporary breakpoint.
26435 If @var{location} cannot be parsed (for example, if it
26436 refers to unknown files or functions), create a pending
26437 breakpoint. Without this flag, @value{GDBN} will report
26438 an error, and won't create a breakpoint, if @var{location}
26441 Create a disabled breakpoint.
26442 @item -c @var{condition}
26443 Make the breakpoint conditional on @var{condition}.
26444 @item -i @var{ignore-count}
26445 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26446 to @var{ignore-count}.
26447 @item -p @var{thread-id}
26448 Restrict the breakpoint to the specified @var{thread-id}.
26451 @subsubheading Result
26453 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26454 resulting breakpoint.
26456 @c An out-of-band breakpoint instead of part of the result?
26458 @subsubheading @value{GDBN} Command
26460 The corresponding @value{GDBN} command is @samp{dprintf}.
26462 @subsubheading Example
26466 4-dprintf-insert foo "At foo entry\n"
26467 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26468 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26469 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26470 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26471 original-location="foo"@}
26473 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26474 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26475 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26476 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26477 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26478 original-location="mi-dprintf.c:26"@}
26482 @subheading The @code{-break-list} Command
26483 @findex -break-list
26485 @subsubheading Synopsis
26491 Displays the list of inserted breakpoints, showing the following fields:
26495 number of the breakpoint
26497 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26499 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26502 is the breakpoint enabled or no: @samp{y} or @samp{n}
26504 memory location at which the breakpoint is set
26506 logical location of the breakpoint, expressed by function name, file
26508 @item Thread-groups
26509 list of thread groups to which this breakpoint applies
26511 number of times the breakpoint has been hit
26514 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26515 @code{body} field is an empty list.
26517 @subsubheading @value{GDBN} Command
26519 The corresponding @value{GDBN} command is @samp{info break}.
26521 @subsubheading Example
26526 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26527 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26528 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26529 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26530 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26531 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26532 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26533 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26534 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26536 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26537 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26538 line="13",thread-groups=["i1"],times="0"@}]@}
26542 Here's an example of the result when there are no breakpoints:
26547 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26548 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26549 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26550 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26551 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26552 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26553 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26558 @subheading The @code{-break-passcount} Command
26559 @findex -break-passcount
26561 @subsubheading Synopsis
26564 -break-passcount @var{tracepoint-number} @var{passcount}
26567 Set the passcount for tracepoint @var{tracepoint-number} to
26568 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26569 is not a tracepoint, error is emitted. This corresponds to CLI
26570 command @samp{passcount}.
26572 @subheading The @code{-break-watch} Command
26573 @findex -break-watch
26575 @subsubheading Synopsis
26578 -break-watch [ -a | -r ]
26581 Create a watchpoint. With the @samp{-a} option it will create an
26582 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26583 read from or on a write to the memory location. With the @samp{-r}
26584 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26585 trigger only when the memory location is accessed for reading. Without
26586 either of the options, the watchpoint created is a regular watchpoint,
26587 i.e., it will trigger when the memory location is accessed for writing.
26588 @xref{Set Watchpoints, , Setting Watchpoints}.
26590 Note that @samp{-break-list} will report a single list of watchpoints and
26591 breakpoints inserted.
26593 @subsubheading @value{GDBN} Command
26595 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26598 @subsubheading Example
26600 Setting a watchpoint on a variable in the @code{main} function:
26605 ^done,wpt=@{number="2",exp="x"@}
26610 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26611 value=@{old="-268439212",new="55"@},
26612 frame=@{func="main",args=[],file="recursive2.c",
26613 fullname="/home/foo/bar/recursive2.c",line="5"@}
26617 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26618 the program execution twice: first for the variable changing value, then
26619 for the watchpoint going out of scope.
26624 ^done,wpt=@{number="5",exp="C"@}
26629 *stopped,reason="watchpoint-trigger",
26630 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26631 frame=@{func="callee4",args=[],
26632 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26633 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26638 *stopped,reason="watchpoint-scope",wpnum="5",
26639 frame=@{func="callee3",args=[@{name="strarg",
26640 value="0x11940 \"A string argument.\""@}],
26641 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26642 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26646 Listing breakpoints and watchpoints, at different points in the program
26647 execution. Note that once the watchpoint goes out of scope, it is
26653 ^done,wpt=@{number="2",exp="C"@}
26656 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26657 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26658 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26659 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26660 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26661 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26662 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26663 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26664 addr="0x00010734",func="callee4",
26665 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26666 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26668 bkpt=@{number="2",type="watchpoint",disp="keep",
26669 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26674 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26675 value=@{old="-276895068",new="3"@},
26676 frame=@{func="callee4",args=[],
26677 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26678 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26681 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26682 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26683 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26684 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26685 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26686 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26687 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26688 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26689 addr="0x00010734",func="callee4",
26690 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26691 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26693 bkpt=@{number="2",type="watchpoint",disp="keep",
26694 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26698 ^done,reason="watchpoint-scope",wpnum="2",
26699 frame=@{func="callee3",args=[@{name="strarg",
26700 value="0x11940 \"A string argument.\""@}],
26701 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26702 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26705 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26706 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26707 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26708 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26709 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26710 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26711 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26712 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26713 addr="0x00010734",func="callee4",
26714 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26715 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26716 thread-groups=["i1"],times="1"@}]@}
26721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26722 @node GDB/MI Catchpoint Commands
26723 @section @sc{gdb/mi} Catchpoint Commands
26725 This section documents @sc{gdb/mi} commands for manipulating
26729 * Shared Library GDB/MI Catchpoint Commands::
26730 * Ada Exception GDB/MI Catchpoint Commands::
26733 @node Shared Library GDB/MI Catchpoint Commands
26734 @subsection Shared Library @sc{gdb/mi} Catchpoints
26736 @subheading The @code{-catch-load} Command
26737 @findex -catch-load
26739 @subsubheading Synopsis
26742 -catch-load [ -t ] [ -d ] @var{regexp}
26745 Add a catchpoint for library load events. If the @samp{-t} option is used,
26746 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26747 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26748 in a disabled state. The @samp{regexp} argument is a regular
26749 expression used to match the name of the loaded library.
26752 @subsubheading @value{GDBN} Command
26754 The corresponding @value{GDBN} command is @samp{catch load}.
26756 @subsubheading Example
26759 -catch-load -t foo.so
26760 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26761 what="load of library matching foo.so",catch-type="load",times="0"@}
26766 @subheading The @code{-catch-unload} Command
26767 @findex -catch-unload
26769 @subsubheading Synopsis
26772 -catch-unload [ -t ] [ -d ] @var{regexp}
26775 Add a catchpoint for library unload events. If the @samp{-t} option is
26776 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26777 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26778 created in a disabled state. The @samp{regexp} argument is a regular
26779 expression used to match the name of the unloaded library.
26781 @subsubheading @value{GDBN} Command
26783 The corresponding @value{GDBN} command is @samp{catch unload}.
26785 @subsubheading Example
26788 -catch-unload -d bar.so
26789 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26790 what="load of library matching bar.so",catch-type="unload",times="0"@}
26794 @node Ada Exception GDB/MI Catchpoint Commands
26795 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26797 The following @sc{gdb/mi} commands can be used to create catchpoints
26798 that stop the execution when Ada exceptions are being raised.
26800 @subheading The @code{-catch-assert} Command
26801 @findex -catch-assert
26803 @subsubheading Synopsis
26806 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26809 Add a catchpoint for failed Ada assertions.
26811 The possible optional parameters for this command are:
26814 @item -c @var{condition}
26815 Make the catchpoint conditional on @var{condition}.
26817 Create a disabled catchpoint.
26819 Create a temporary catchpoint.
26822 @subsubheading @value{GDBN} Command
26824 The corresponding @value{GDBN} command is @samp{catch assert}.
26826 @subsubheading Example
26830 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26831 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26832 thread-groups=["i1"],times="0",
26833 original-location="__gnat_debug_raise_assert_failure"@}
26837 @subheading The @code{-catch-exception} Command
26838 @findex -catch-exception
26840 @subsubheading Synopsis
26843 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26847 Add a catchpoint stopping when Ada exceptions are raised.
26848 By default, the command stops the program when any Ada exception
26849 gets raised. But it is also possible, by using some of the
26850 optional parameters described below, to create more selective
26853 The possible optional parameters for this command are:
26856 @item -c @var{condition}
26857 Make the catchpoint conditional on @var{condition}.
26859 Create a disabled catchpoint.
26860 @item -e @var{exception-name}
26861 Only stop when @var{exception-name} is raised. This option cannot
26862 be used combined with @samp{-u}.
26864 Create a temporary catchpoint.
26866 Stop only when an unhandled exception gets raised. This option
26867 cannot be used combined with @samp{-e}.
26870 @subsubheading @value{GDBN} Command
26872 The corresponding @value{GDBN} commands are @samp{catch exception}
26873 and @samp{catch exception unhandled}.
26875 @subsubheading Example
26878 -catch-exception -e Program_Error
26879 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26880 enabled="y",addr="0x0000000000404874",
26881 what="`Program_Error' Ada exception", thread-groups=["i1"],
26882 times="0",original-location="__gnat_debug_raise_exception"@}
26886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26887 @node GDB/MI Program Context
26888 @section @sc{gdb/mi} Program Context
26890 @subheading The @code{-exec-arguments} Command
26891 @findex -exec-arguments
26894 @subsubheading Synopsis
26897 -exec-arguments @var{args}
26900 Set the inferior program arguments, to be used in the next
26903 @subsubheading @value{GDBN} Command
26905 The corresponding @value{GDBN} command is @samp{set args}.
26907 @subsubheading Example
26911 -exec-arguments -v word
26918 @subheading The @code{-exec-show-arguments} Command
26919 @findex -exec-show-arguments
26921 @subsubheading Synopsis
26924 -exec-show-arguments
26927 Print the arguments of the program.
26929 @subsubheading @value{GDBN} Command
26931 The corresponding @value{GDBN} command is @samp{show args}.
26933 @subsubheading Example
26938 @subheading The @code{-environment-cd} Command
26939 @findex -environment-cd
26941 @subsubheading Synopsis
26944 -environment-cd @var{pathdir}
26947 Set @value{GDBN}'s working directory.
26949 @subsubheading @value{GDBN} Command
26951 The corresponding @value{GDBN} command is @samp{cd}.
26953 @subsubheading Example
26957 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26963 @subheading The @code{-environment-directory} Command
26964 @findex -environment-directory
26966 @subsubheading Synopsis
26969 -environment-directory [ -r ] [ @var{pathdir} ]+
26972 Add directories @var{pathdir} to beginning of search path for source files.
26973 If the @samp{-r} option is used, the search path is reset to the default
26974 search path. If directories @var{pathdir} are supplied in addition to the
26975 @samp{-r} option, the search path is first reset and then addition
26977 Multiple directories may be specified, separated by blanks. Specifying
26978 multiple directories in a single command
26979 results in the directories added to the beginning of the
26980 search path in the same order they were presented in the command.
26981 If blanks are needed as
26982 part of a directory name, double-quotes should be used around
26983 the name. In the command output, the path will show up separated
26984 by the system directory-separator character. The directory-separator
26985 character must not be used
26986 in any directory name.
26987 If no directories are specified, the current search path is displayed.
26989 @subsubheading @value{GDBN} Command
26991 The corresponding @value{GDBN} command is @samp{dir}.
26993 @subsubheading Example
26997 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26998 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27000 -environment-directory ""
27001 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27003 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27004 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27006 -environment-directory -r
27007 ^done,source-path="$cdir:$cwd"
27012 @subheading The @code{-environment-path} Command
27013 @findex -environment-path
27015 @subsubheading Synopsis
27018 -environment-path [ -r ] [ @var{pathdir} ]+
27021 Add directories @var{pathdir} to beginning of search path for object files.
27022 If the @samp{-r} option is used, the search path is reset to the original
27023 search path that existed at gdb start-up. If directories @var{pathdir} are
27024 supplied in addition to the
27025 @samp{-r} option, the search path is first reset and then addition
27027 Multiple directories may be specified, separated by blanks. Specifying
27028 multiple directories in a single command
27029 results in the directories added to the beginning of the
27030 search path in the same order they were presented in the command.
27031 If blanks are needed as
27032 part of a directory name, double-quotes should be used around
27033 the name. In the command output, the path will show up separated
27034 by the system directory-separator character. The directory-separator
27035 character must not be used
27036 in any directory name.
27037 If no directories are specified, the current path is displayed.
27040 @subsubheading @value{GDBN} Command
27042 The corresponding @value{GDBN} command is @samp{path}.
27044 @subsubheading Example
27049 ^done,path="/usr/bin"
27051 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27052 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27054 -environment-path -r /usr/local/bin
27055 ^done,path="/usr/local/bin:/usr/bin"
27060 @subheading The @code{-environment-pwd} Command
27061 @findex -environment-pwd
27063 @subsubheading Synopsis
27069 Show the current working directory.
27071 @subsubheading @value{GDBN} Command
27073 The corresponding @value{GDBN} command is @samp{pwd}.
27075 @subsubheading Example
27080 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27085 @node GDB/MI Thread Commands
27086 @section @sc{gdb/mi} Thread Commands
27089 @subheading The @code{-thread-info} Command
27090 @findex -thread-info
27092 @subsubheading Synopsis
27095 -thread-info [ @var{thread-id} ]
27098 Reports information about either a specific thread, if
27099 the @var{thread-id} parameter is present, or about all
27100 threads. When printing information about all threads,
27101 also reports the current thread.
27103 @subsubheading @value{GDBN} Command
27105 The @samp{info thread} command prints the same information
27108 @subsubheading Result
27110 The result is a list of threads. The following attributes are
27111 defined for a given thread:
27115 This field exists only for the current thread. It has the value @samp{*}.
27118 The identifier that @value{GDBN} uses to refer to the thread.
27121 The identifier that the target uses to refer to the thread.
27124 Extra information about the thread, in a target-specific format. This
27128 The name of the thread. If the user specified a name using the
27129 @code{thread name} command, then this name is given. Otherwise, if
27130 @value{GDBN} can extract the thread name from the target, then that
27131 name is given. If @value{GDBN} cannot find the thread name, then this
27135 The stack frame currently executing in the thread.
27138 The thread's state. The @samp{state} field may have the following
27143 The thread is stopped. Frame information is available for stopped
27147 The thread is running. There's no frame information for running
27153 If @value{GDBN} can find the CPU core on which this thread is running,
27154 then this field is the core identifier. This field is optional.
27158 @subsubheading Example
27163 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27164 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27165 args=[]@},state="running"@},
27166 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27167 frame=@{level="0",addr="0x0804891f",func="foo",
27168 args=[@{name="i",value="10"@}],
27169 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27170 state="running"@}],
27171 current-thread-id="1"
27175 @subheading The @code{-thread-list-ids} Command
27176 @findex -thread-list-ids
27178 @subsubheading Synopsis
27184 Produces a list of the currently known @value{GDBN} thread ids. At the
27185 end of the list it also prints the total number of such threads.
27187 This command is retained for historical reasons, the
27188 @code{-thread-info} command should be used instead.
27190 @subsubheading @value{GDBN} Command
27192 Part of @samp{info threads} supplies the same information.
27194 @subsubheading Example
27199 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27200 current-thread-id="1",number-of-threads="3"
27205 @subheading The @code{-thread-select} Command
27206 @findex -thread-select
27208 @subsubheading Synopsis
27211 -thread-select @var{threadnum}
27214 Make @var{threadnum} the current thread. It prints the number of the new
27215 current thread, and the topmost frame for that thread.
27217 This command is deprecated in favor of explicitly using the
27218 @samp{--thread} option to each command.
27220 @subsubheading @value{GDBN} Command
27222 The corresponding @value{GDBN} command is @samp{thread}.
27224 @subsubheading Example
27231 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27232 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27236 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27237 number-of-threads="3"
27240 ^done,new-thread-id="3",
27241 frame=@{level="0",func="vprintf",
27242 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27243 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27247 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27248 @node GDB/MI Ada Tasking Commands
27249 @section @sc{gdb/mi} Ada Tasking Commands
27251 @subheading The @code{-ada-task-info} Command
27252 @findex -ada-task-info
27254 @subsubheading Synopsis
27257 -ada-task-info [ @var{task-id} ]
27260 Reports information about either a specific Ada task, if the
27261 @var{task-id} parameter is present, or about all Ada tasks.
27263 @subsubheading @value{GDBN} Command
27265 The @samp{info tasks} command prints the same information
27266 about all Ada tasks (@pxref{Ada Tasks}).
27268 @subsubheading Result
27270 The result is a table of Ada tasks. The following columns are
27271 defined for each Ada task:
27275 This field exists only for the current thread. It has the value @samp{*}.
27278 The identifier that @value{GDBN} uses to refer to the Ada task.
27281 The identifier that the target uses to refer to the Ada task.
27284 The identifier of the thread corresponding to the Ada task.
27286 This field should always exist, as Ada tasks are always implemented
27287 on top of a thread. But if @value{GDBN} cannot find this corresponding
27288 thread for any reason, the field is omitted.
27291 This field exists only when the task was created by another task.
27292 In this case, it provides the ID of the parent task.
27295 The base priority of the task.
27298 The current state of the task. For a detailed description of the
27299 possible states, see @ref{Ada Tasks}.
27302 The name of the task.
27306 @subsubheading Example
27310 ^done,tasks=@{nr_rows="3",nr_cols="8",
27311 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27312 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27313 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27314 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27315 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27316 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27317 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27318 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27319 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27320 state="Child Termination Wait",name="main_task"@}]@}
27324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27325 @node GDB/MI Program Execution
27326 @section @sc{gdb/mi} Program Execution
27328 These are the asynchronous commands which generate the out-of-band
27329 record @samp{*stopped}. Currently @value{GDBN} only really executes
27330 asynchronously with remote targets and this interaction is mimicked in
27333 @subheading The @code{-exec-continue} Command
27334 @findex -exec-continue
27336 @subsubheading Synopsis
27339 -exec-continue [--reverse] [--all|--thread-group N]
27342 Resumes the execution of the inferior program, which will continue
27343 to execute until it reaches a debugger stop event. If the
27344 @samp{--reverse} option is specified, execution resumes in reverse until
27345 it reaches a stop event. Stop events may include
27348 breakpoints or watchpoints
27350 signals or exceptions
27352 the end of the process (or its beginning under @samp{--reverse})
27354 the end or beginning of a replay log if one is being used.
27356 In all-stop mode (@pxref{All-Stop
27357 Mode}), may resume only one thread, or all threads, depending on the
27358 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27359 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27360 ignored in all-stop mode. If the @samp{--thread-group} options is
27361 specified, then all threads in that thread group are resumed.
27363 @subsubheading @value{GDBN} Command
27365 The corresponding @value{GDBN} corresponding is @samp{continue}.
27367 @subsubheading Example
27374 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27375 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27381 @subheading The @code{-exec-finish} Command
27382 @findex -exec-finish
27384 @subsubheading Synopsis
27387 -exec-finish [--reverse]
27390 Resumes the execution of the inferior program until the current
27391 function is exited. Displays the results returned by the function.
27392 If the @samp{--reverse} option is specified, resumes the reverse
27393 execution of the inferior program until the point where current
27394 function was called.
27396 @subsubheading @value{GDBN} Command
27398 The corresponding @value{GDBN} command is @samp{finish}.
27400 @subsubheading Example
27402 Function returning @code{void}.
27409 *stopped,reason="function-finished",frame=@{func="main",args=[],
27410 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27414 Function returning other than @code{void}. The name of the internal
27415 @value{GDBN} variable storing the result is printed, together with the
27422 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27423 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27424 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27425 gdb-result-var="$1",return-value="0"
27430 @subheading The @code{-exec-interrupt} Command
27431 @findex -exec-interrupt
27433 @subsubheading Synopsis
27436 -exec-interrupt [--all|--thread-group N]
27439 Interrupts the background execution of the target. Note how the token
27440 associated with the stop message is the one for the execution command
27441 that has been interrupted. The token for the interrupt itself only
27442 appears in the @samp{^done} output. If the user is trying to
27443 interrupt a non-running program, an error message will be printed.
27445 Note that when asynchronous execution is enabled, this command is
27446 asynchronous just like other execution commands. That is, first the
27447 @samp{^done} response will be printed, and the target stop will be
27448 reported after that using the @samp{*stopped} notification.
27450 In non-stop mode, only the context thread is interrupted by default.
27451 All threads (in all inferiors) will be interrupted if the
27452 @samp{--all} option is specified. If the @samp{--thread-group}
27453 option is specified, all threads in that group will be interrupted.
27455 @subsubheading @value{GDBN} Command
27457 The corresponding @value{GDBN} command is @samp{interrupt}.
27459 @subsubheading Example
27470 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27471 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27472 fullname="/home/foo/bar/try.c",line="13"@}
27477 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27481 @subheading The @code{-exec-jump} Command
27484 @subsubheading Synopsis
27487 -exec-jump @var{location}
27490 Resumes execution of the inferior program at the location specified by
27491 parameter. @xref{Specify Location}, for a description of the
27492 different forms of @var{location}.
27494 @subsubheading @value{GDBN} Command
27496 The corresponding @value{GDBN} command is @samp{jump}.
27498 @subsubheading Example
27501 -exec-jump foo.c:10
27502 *running,thread-id="all"
27507 @subheading The @code{-exec-next} Command
27510 @subsubheading Synopsis
27513 -exec-next [--reverse]
27516 Resumes execution of the inferior program, stopping when the beginning
27517 of the next source line is reached.
27519 If the @samp{--reverse} option is specified, resumes reverse execution
27520 of the inferior program, stopping at the beginning of the previous
27521 source line. If you issue this command on the first line of a
27522 function, it will take you back to the caller of that function, to the
27523 source line where the function was called.
27526 @subsubheading @value{GDBN} Command
27528 The corresponding @value{GDBN} command is @samp{next}.
27530 @subsubheading Example
27536 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27541 @subheading The @code{-exec-next-instruction} Command
27542 @findex -exec-next-instruction
27544 @subsubheading Synopsis
27547 -exec-next-instruction [--reverse]
27550 Executes one machine instruction. If the instruction is a function
27551 call, continues until the function returns. If the program stops at an
27552 instruction in the middle of a source line, the address will be
27555 If the @samp{--reverse} option is specified, resumes reverse execution
27556 of the inferior program, stopping at the previous instruction. If the
27557 previously executed instruction was a return from another function,
27558 it will continue to execute in reverse until the call to that function
27559 (from the current stack frame) is reached.
27561 @subsubheading @value{GDBN} Command
27563 The corresponding @value{GDBN} command is @samp{nexti}.
27565 @subsubheading Example
27569 -exec-next-instruction
27573 *stopped,reason="end-stepping-range",
27574 addr="0x000100d4",line="5",file="hello.c"
27579 @subheading The @code{-exec-return} Command
27580 @findex -exec-return
27582 @subsubheading Synopsis
27588 Makes current function return immediately. Doesn't execute the inferior.
27589 Displays the new current frame.
27591 @subsubheading @value{GDBN} Command
27593 The corresponding @value{GDBN} command is @samp{return}.
27595 @subsubheading Example
27599 200-break-insert callee4
27600 200^done,bkpt=@{number="1",addr="0x00010734",
27601 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27606 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27607 frame=@{func="callee4",args=[],
27608 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27609 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27615 111^done,frame=@{level="0",func="callee3",
27616 args=[@{name="strarg",
27617 value="0x11940 \"A string argument.\""@}],
27618 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27619 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27624 @subheading The @code{-exec-run} Command
27627 @subsubheading Synopsis
27630 -exec-run [ --all | --thread-group N ] [ --start ]
27633 Starts execution of the inferior from the beginning. The inferior
27634 executes until either a breakpoint is encountered or the program
27635 exits. In the latter case the output will include an exit code, if
27636 the program has exited exceptionally.
27638 When neither the @samp{--all} nor the @samp{--thread-group} option
27639 is specified, the current inferior is started. If the
27640 @samp{--thread-group} option is specified, it should refer to a thread
27641 group of type @samp{process}, and that thread group will be started.
27642 If the @samp{--all} option is specified, then all inferiors will be started.
27644 Using the @samp{--start} option instructs the debugger to stop
27645 the execution at the start of the inferior's main subprogram,
27646 following the same behavior as the @code{start} command
27647 (@pxref{Starting}).
27649 @subsubheading @value{GDBN} Command
27651 The corresponding @value{GDBN} command is @samp{run}.
27653 @subsubheading Examples
27658 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27663 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27664 frame=@{func="main",args=[],file="recursive2.c",
27665 fullname="/home/foo/bar/recursive2.c",line="4"@}
27670 Program exited normally:
27678 *stopped,reason="exited-normally"
27683 Program exited exceptionally:
27691 *stopped,reason="exited",exit-code="01"
27695 Another way the program can terminate is if it receives a signal such as
27696 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27700 *stopped,reason="exited-signalled",signal-name="SIGINT",
27701 signal-meaning="Interrupt"
27705 @c @subheading -exec-signal
27708 @subheading The @code{-exec-step} Command
27711 @subsubheading Synopsis
27714 -exec-step [--reverse]
27717 Resumes execution of the inferior program, stopping when the beginning
27718 of the next source line is reached, if the next source line is not a
27719 function call. If it is, stop at the first instruction of the called
27720 function. If the @samp{--reverse} option is specified, resumes reverse
27721 execution of the inferior program, stopping at the beginning of the
27722 previously executed source line.
27724 @subsubheading @value{GDBN} Command
27726 The corresponding @value{GDBN} command is @samp{step}.
27728 @subsubheading Example
27730 Stepping into a function:
27736 *stopped,reason="end-stepping-range",
27737 frame=@{func="foo",args=[@{name="a",value="10"@},
27738 @{name="b",value="0"@}],file="recursive2.c",
27739 fullname="/home/foo/bar/recursive2.c",line="11"@}
27749 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27754 @subheading The @code{-exec-step-instruction} Command
27755 @findex -exec-step-instruction
27757 @subsubheading Synopsis
27760 -exec-step-instruction [--reverse]
27763 Resumes the inferior which executes one machine instruction. If the
27764 @samp{--reverse} option is specified, resumes reverse execution of the
27765 inferior program, stopping at the previously executed instruction.
27766 The output, once @value{GDBN} has stopped, will vary depending on
27767 whether we have stopped in the middle of a source line or not. In the
27768 former case, the address at which the program stopped will be printed
27771 @subsubheading @value{GDBN} Command
27773 The corresponding @value{GDBN} command is @samp{stepi}.
27775 @subsubheading Example
27779 -exec-step-instruction
27783 *stopped,reason="end-stepping-range",
27784 frame=@{func="foo",args=[],file="try.c",
27785 fullname="/home/foo/bar/try.c",line="10"@}
27787 -exec-step-instruction
27791 *stopped,reason="end-stepping-range",
27792 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27793 fullname="/home/foo/bar/try.c",line="10"@}
27798 @subheading The @code{-exec-until} Command
27799 @findex -exec-until
27801 @subsubheading Synopsis
27804 -exec-until [ @var{location} ]
27807 Executes the inferior until the @var{location} specified in the
27808 argument is reached. If there is no argument, the inferior executes
27809 until a source line greater than the current one is reached. The
27810 reason for stopping in this case will be @samp{location-reached}.
27812 @subsubheading @value{GDBN} Command
27814 The corresponding @value{GDBN} command is @samp{until}.
27816 @subsubheading Example
27820 -exec-until recursive2.c:6
27824 *stopped,reason="location-reached",frame=@{func="main",args=[],
27825 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27830 @subheading -file-clear
27831 Is this going away????
27834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27835 @node GDB/MI Stack Manipulation
27836 @section @sc{gdb/mi} Stack Manipulation Commands
27838 @subheading The @code{-enable-frame-filters} Command
27839 @findex -enable-frame-filters
27842 -enable-frame-filters
27845 @value{GDBN} allows Python-based frame filters to affect the output of
27846 the MI commands relating to stack traces. As there is no way to
27847 implement this in a fully backward-compatible way, a front end must
27848 request that this functionality be enabled.
27850 Once enabled, this feature cannot be disabled.
27852 Note that if Python support has not been compiled into @value{GDBN},
27853 this command will still succeed (and do nothing).
27855 @subheading The @code{-stack-info-frame} Command
27856 @findex -stack-info-frame
27858 @subsubheading Synopsis
27864 Get info on the selected frame.
27866 @subsubheading @value{GDBN} Command
27868 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27869 (without arguments).
27871 @subsubheading Example
27876 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27878 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27882 @subheading The @code{-stack-info-depth} Command
27883 @findex -stack-info-depth
27885 @subsubheading Synopsis
27888 -stack-info-depth [ @var{max-depth} ]
27891 Return the depth of the stack. If the integer argument @var{max-depth}
27892 is specified, do not count beyond @var{max-depth} frames.
27894 @subsubheading @value{GDBN} Command
27896 There's no equivalent @value{GDBN} command.
27898 @subsubheading Example
27900 For a stack with frame levels 0 through 11:
27907 -stack-info-depth 4
27910 -stack-info-depth 12
27913 -stack-info-depth 11
27916 -stack-info-depth 13
27921 @anchor{-stack-list-arguments}
27922 @subheading The @code{-stack-list-arguments} Command
27923 @findex -stack-list-arguments
27925 @subsubheading Synopsis
27928 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27929 [ @var{low-frame} @var{high-frame} ]
27932 Display a list of the arguments for the frames between @var{low-frame}
27933 and @var{high-frame} (inclusive). If @var{low-frame} and
27934 @var{high-frame} are not provided, list the arguments for the whole
27935 call stack. If the two arguments are equal, show the single frame
27936 at the corresponding level. It is an error if @var{low-frame} is
27937 larger than the actual number of frames. On the other hand,
27938 @var{high-frame} may be larger than the actual number of frames, in
27939 which case only existing frames will be returned.
27941 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27942 the variables; if it is 1 or @code{--all-values}, print also their
27943 values; and if it is 2 or @code{--simple-values}, print the name,
27944 type and value for simple data types, and the name and type for arrays,
27945 structures and unions. If the option @code{--no-frame-filters} is
27946 supplied, then Python frame filters will not be executed.
27948 If the @code{--skip-unavailable} option is specified, arguments that
27949 are not available are not listed. Partially available arguments
27950 are still displayed, however.
27952 Use of this command to obtain arguments in a single frame is
27953 deprecated in favor of the @samp{-stack-list-variables} command.
27955 @subsubheading @value{GDBN} Command
27957 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27958 @samp{gdb_get_args} command which partially overlaps with the
27959 functionality of @samp{-stack-list-arguments}.
27961 @subsubheading Example
27968 frame=@{level="0",addr="0x00010734",func="callee4",
27969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27971 frame=@{level="1",addr="0x0001076c",func="callee3",
27972 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27973 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27974 frame=@{level="2",addr="0x0001078c",func="callee2",
27975 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27976 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27977 frame=@{level="3",addr="0x000107b4",func="callee1",
27978 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27979 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27980 frame=@{level="4",addr="0x000107e0",func="main",
27981 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27982 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27984 -stack-list-arguments 0
27987 frame=@{level="0",args=[]@},
27988 frame=@{level="1",args=[name="strarg"]@},
27989 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27990 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27991 frame=@{level="4",args=[]@}]
27993 -stack-list-arguments 1
27996 frame=@{level="0",args=[]@},
27998 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27999 frame=@{level="2",args=[
28000 @{name="intarg",value="2"@},
28001 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28002 @{frame=@{level="3",args=[
28003 @{name="intarg",value="2"@},
28004 @{name="strarg",value="0x11940 \"A string argument.\""@},
28005 @{name="fltarg",value="3.5"@}]@},
28006 frame=@{level="4",args=[]@}]
28008 -stack-list-arguments 0 2 2
28009 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28011 -stack-list-arguments 1 2 2
28012 ^done,stack-args=[frame=@{level="2",
28013 args=[@{name="intarg",value="2"@},
28014 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28018 @c @subheading -stack-list-exception-handlers
28021 @anchor{-stack-list-frames}
28022 @subheading The @code{-stack-list-frames} Command
28023 @findex -stack-list-frames
28025 @subsubheading Synopsis
28028 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28031 List the frames currently on the stack. For each frame it displays the
28036 The frame number, 0 being the topmost frame, i.e., the innermost function.
28038 The @code{$pc} value for that frame.
28042 File name of the source file where the function lives.
28043 @item @var{fullname}
28044 The full file name of the source file where the function lives.
28046 Line number corresponding to the @code{$pc}.
28048 The shared library where this function is defined. This is only given
28049 if the frame's function is not known.
28052 If invoked without arguments, this command prints a backtrace for the
28053 whole stack. If given two integer arguments, it shows the frames whose
28054 levels are between the two arguments (inclusive). If the two arguments
28055 are equal, it shows the single frame at the corresponding level. It is
28056 an error if @var{low-frame} is larger than the actual number of
28057 frames. On the other hand, @var{high-frame} may be larger than the
28058 actual number of frames, in which case only existing frames will be
28059 returned. If the option @code{--no-frame-filters} is supplied, then
28060 Python frame filters will not be executed.
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28066 @subsubheading Example
28068 Full stack backtrace:
28074 [frame=@{level="0",addr="0x0001076c",func="foo",
28075 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28076 frame=@{level="1",addr="0x000107a4",func="foo",
28077 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28078 frame=@{level="2",addr="0x000107a4",func="foo",
28079 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28080 frame=@{level="3",addr="0x000107a4",func="foo",
28081 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28082 frame=@{level="4",addr="0x000107a4",func="foo",
28083 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28084 frame=@{level="5",addr="0x000107a4",func="foo",
28085 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28086 frame=@{level="6",addr="0x000107a4",func="foo",
28087 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28088 frame=@{level="7",addr="0x000107a4",func="foo",
28089 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28090 frame=@{level="8",addr="0x000107a4",func="foo",
28091 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28092 frame=@{level="9",addr="0x000107a4",func="foo",
28093 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28094 frame=@{level="10",addr="0x000107a4",func="foo",
28095 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28096 frame=@{level="11",addr="0x00010738",func="main",
28097 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28101 Show frames between @var{low_frame} and @var{high_frame}:
28105 -stack-list-frames 3 5
28107 [frame=@{level="3",addr="0x000107a4",func="foo",
28108 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28109 frame=@{level="4",addr="0x000107a4",func="foo",
28110 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28111 frame=@{level="5",addr="0x000107a4",func="foo",
28112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28116 Show a single frame:
28120 -stack-list-frames 3 3
28122 [frame=@{level="3",addr="0x000107a4",func="foo",
28123 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28128 @subheading The @code{-stack-list-locals} Command
28129 @findex -stack-list-locals
28130 @anchor{-stack-list-locals}
28132 @subsubheading Synopsis
28135 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28138 Display the local variable names for the selected frame. If
28139 @var{print-values} is 0 or @code{--no-values}, print only the names of
28140 the variables; if it is 1 or @code{--all-values}, print also their
28141 values; and if it is 2 or @code{--simple-values}, print the name,
28142 type and value for simple data types, and the name and type for arrays,
28143 structures and unions. In this last case, a frontend can immediately
28144 display the value of simple data types and create variable objects for
28145 other data types when the user wishes to explore their values in
28146 more detail. If the option @code{--no-frame-filters} is supplied, then
28147 Python frame filters will not be executed.
28149 If the @code{--skip-unavailable} option is specified, local variables
28150 that are not available are not listed. Partially available local
28151 variables are still displayed, however.
28153 This command is deprecated in favor of the
28154 @samp{-stack-list-variables} command.
28156 @subsubheading @value{GDBN} Command
28158 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28160 @subsubheading Example
28164 -stack-list-locals 0
28165 ^done,locals=[name="A",name="B",name="C"]
28167 -stack-list-locals --all-values
28168 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28169 @{name="C",value="@{1, 2, 3@}"@}]
28170 -stack-list-locals --simple-values
28171 ^done,locals=[@{name="A",type="int",value="1"@},
28172 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28176 @anchor{-stack-list-variables}
28177 @subheading The @code{-stack-list-variables} Command
28178 @findex -stack-list-variables
28180 @subsubheading Synopsis
28183 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28186 Display the names of local variables and function arguments for the selected frame. If
28187 @var{print-values} is 0 or @code{--no-values}, print only the names of
28188 the variables; if it is 1 or @code{--all-values}, print also their
28189 values; and if it is 2 or @code{--simple-values}, print the name,
28190 type and value for simple data types, and the name and type for arrays,
28191 structures and unions. If the option @code{--no-frame-filters} is
28192 supplied, then Python frame filters will not be executed.
28194 If the @code{--skip-unavailable} option is specified, local variables
28195 and arguments that are not available are not listed. Partially
28196 available arguments and local variables are still displayed, however.
28198 @subsubheading Example
28202 -stack-list-variables --thread 1 --frame 0 --all-values
28203 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28208 @subheading The @code{-stack-select-frame} Command
28209 @findex -stack-select-frame
28211 @subsubheading Synopsis
28214 -stack-select-frame @var{framenum}
28217 Change the selected frame. Select a different frame @var{framenum} on
28220 This command in deprecated in favor of passing the @samp{--frame}
28221 option to every command.
28223 @subsubheading @value{GDBN} Command
28225 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28226 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28228 @subsubheading Example
28232 -stack-select-frame 2
28237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28238 @node GDB/MI Variable Objects
28239 @section @sc{gdb/mi} Variable Objects
28243 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28245 For the implementation of a variable debugger window (locals, watched
28246 expressions, etc.), we are proposing the adaptation of the existing code
28247 used by @code{Insight}.
28249 The two main reasons for that are:
28253 It has been proven in practice (it is already on its second generation).
28256 It will shorten development time (needless to say how important it is
28260 The original interface was designed to be used by Tcl code, so it was
28261 slightly changed so it could be used through @sc{gdb/mi}. This section
28262 describes the @sc{gdb/mi} operations that will be available and gives some
28263 hints about their use.
28265 @emph{Note}: In addition to the set of operations described here, we
28266 expect the @sc{gui} implementation of a variable window to require, at
28267 least, the following operations:
28270 @item @code{-gdb-show} @code{output-radix}
28271 @item @code{-stack-list-arguments}
28272 @item @code{-stack-list-locals}
28273 @item @code{-stack-select-frame}
28278 @subheading Introduction to Variable Objects
28280 @cindex variable objects in @sc{gdb/mi}
28282 Variable objects are "object-oriented" MI interface for examining and
28283 changing values of expressions. Unlike some other MI interfaces that
28284 work with expressions, variable objects are specifically designed for
28285 simple and efficient presentation in the frontend. A variable object
28286 is identified by string name. When a variable object is created, the
28287 frontend specifies the expression for that variable object. The
28288 expression can be a simple variable, or it can be an arbitrary complex
28289 expression, and can even involve CPU registers. After creating a
28290 variable object, the frontend can invoke other variable object
28291 operations---for example to obtain or change the value of a variable
28292 object, or to change display format.
28294 Variable objects have hierarchical tree structure. Any variable object
28295 that corresponds to a composite type, such as structure in C, has
28296 a number of child variable objects, for example corresponding to each
28297 element of a structure. A child variable object can itself have
28298 children, recursively. Recursion ends when we reach
28299 leaf variable objects, which always have built-in types. Child variable
28300 objects are created only by explicit request, so if a frontend
28301 is not interested in the children of a particular variable object, no
28302 child will be created.
28304 For a leaf variable object it is possible to obtain its value as a
28305 string, or set the value from a string. String value can be also
28306 obtained for a non-leaf variable object, but it's generally a string
28307 that only indicates the type of the object, and does not list its
28308 contents. Assignment to a non-leaf variable object is not allowed.
28310 A frontend does not need to read the values of all variable objects each time
28311 the program stops. Instead, MI provides an update command that lists all
28312 variable objects whose values has changed since the last update
28313 operation. This considerably reduces the amount of data that must
28314 be transferred to the frontend. As noted above, children variable
28315 objects are created on demand, and only leaf variable objects have a
28316 real value. As result, gdb will read target memory only for leaf
28317 variables that frontend has created.
28319 The automatic update is not always desirable. For example, a frontend
28320 might want to keep a value of some expression for future reference,
28321 and never update it. For another example, fetching memory is
28322 relatively slow for embedded targets, so a frontend might want
28323 to disable automatic update for the variables that are either not
28324 visible on the screen, or ``closed''. This is possible using so
28325 called ``frozen variable objects''. Such variable objects are never
28326 implicitly updated.
28328 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28329 fixed variable object, the expression is parsed when the variable
28330 object is created, including associating identifiers to specific
28331 variables. The meaning of expression never changes. For a floating
28332 variable object the values of variables whose names appear in the
28333 expressions are re-evaluated every time in the context of the current
28334 frame. Consider this example:
28339 struct work_state state;
28346 If a fixed variable object for the @code{state} variable is created in
28347 this function, and we enter the recursive call, the variable
28348 object will report the value of @code{state} in the top-level
28349 @code{do_work} invocation. On the other hand, a floating variable
28350 object will report the value of @code{state} in the current frame.
28352 If an expression specified when creating a fixed variable object
28353 refers to a local variable, the variable object becomes bound to the
28354 thread and frame in which the variable object is created. When such
28355 variable object is updated, @value{GDBN} makes sure that the
28356 thread/frame combination the variable object is bound to still exists,
28357 and re-evaluates the variable object in context of that thread/frame.
28359 The following is the complete set of @sc{gdb/mi} operations defined to
28360 access this functionality:
28362 @multitable @columnfractions .4 .6
28363 @item @strong{Operation}
28364 @tab @strong{Description}
28366 @item @code{-enable-pretty-printing}
28367 @tab enable Python-based pretty-printing
28368 @item @code{-var-create}
28369 @tab create a variable object
28370 @item @code{-var-delete}
28371 @tab delete the variable object and/or its children
28372 @item @code{-var-set-format}
28373 @tab set the display format of this variable
28374 @item @code{-var-show-format}
28375 @tab show the display format of this variable
28376 @item @code{-var-info-num-children}
28377 @tab tells how many children this object has
28378 @item @code{-var-list-children}
28379 @tab return a list of the object's children
28380 @item @code{-var-info-type}
28381 @tab show the type of this variable object
28382 @item @code{-var-info-expression}
28383 @tab print parent-relative expression that this variable object represents
28384 @item @code{-var-info-path-expression}
28385 @tab print full expression that this variable object represents
28386 @item @code{-var-show-attributes}
28387 @tab is this variable editable? does it exist here?
28388 @item @code{-var-evaluate-expression}
28389 @tab get the value of this variable
28390 @item @code{-var-assign}
28391 @tab set the value of this variable
28392 @item @code{-var-update}
28393 @tab update the variable and its children
28394 @item @code{-var-set-frozen}
28395 @tab set frozeness attribute
28396 @item @code{-var-set-update-range}
28397 @tab set range of children to display on update
28400 In the next subsection we describe each operation in detail and suggest
28401 how it can be used.
28403 @subheading Description And Use of Operations on Variable Objects
28405 @subheading The @code{-enable-pretty-printing} Command
28406 @findex -enable-pretty-printing
28409 -enable-pretty-printing
28412 @value{GDBN} allows Python-based visualizers to affect the output of the
28413 MI variable object commands. However, because there was no way to
28414 implement this in a fully backward-compatible way, a front end must
28415 request that this functionality be enabled.
28417 Once enabled, this feature cannot be disabled.
28419 Note that if Python support has not been compiled into @value{GDBN},
28420 this command will still succeed (and do nothing).
28422 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28423 may work differently in future versions of @value{GDBN}.
28425 @subheading The @code{-var-create} Command
28426 @findex -var-create
28428 @subsubheading Synopsis
28431 -var-create @{@var{name} | "-"@}
28432 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28435 This operation creates a variable object, which allows the monitoring of
28436 a variable, the result of an expression, a memory cell or a CPU
28439 The @var{name} parameter is the string by which the object can be
28440 referenced. It must be unique. If @samp{-} is specified, the varobj
28441 system will generate a string ``varNNNNNN'' automatically. It will be
28442 unique provided that one does not specify @var{name} of that format.
28443 The command fails if a duplicate name is found.
28445 The frame under which the expression should be evaluated can be
28446 specified by @var{frame-addr}. A @samp{*} indicates that the current
28447 frame should be used. A @samp{@@} indicates that a floating variable
28448 object must be created.
28450 @var{expression} is any expression valid on the current language set (must not
28451 begin with a @samp{*}), or one of the following:
28455 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28458 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28461 @samp{$@var{regname}} --- a CPU register name
28464 @cindex dynamic varobj
28465 A varobj's contents may be provided by a Python-based pretty-printer. In this
28466 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28467 have slightly different semantics in some cases. If the
28468 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28469 will never create a dynamic varobj. This ensures backward
28470 compatibility for existing clients.
28472 @subsubheading Result
28474 This operation returns attributes of the newly-created varobj. These
28479 The name of the varobj.
28482 The number of children of the varobj. This number is not necessarily
28483 reliable for a dynamic varobj. Instead, you must examine the
28484 @samp{has_more} attribute.
28487 The varobj's scalar value. For a varobj whose type is some sort of
28488 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28489 will not be interesting.
28492 The varobj's type. This is a string representation of the type, as
28493 would be printed by the @value{GDBN} CLI. If @samp{print object}
28494 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28495 @emph{actual} (derived) type of the object is shown rather than the
28496 @emph{declared} one.
28499 If a variable object is bound to a specific thread, then this is the
28500 thread's identifier.
28503 For a dynamic varobj, this indicates whether there appear to be any
28504 children available. For a non-dynamic varobj, this will be 0.
28507 This attribute will be present and have the value @samp{1} if the
28508 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28509 then this attribute will not be present.
28512 A dynamic varobj can supply a display hint to the front end. The
28513 value comes directly from the Python pretty-printer object's
28514 @code{display_hint} method. @xref{Pretty Printing API}.
28517 Typical output will look like this:
28520 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28521 has_more="@var{has_more}"
28525 @subheading The @code{-var-delete} Command
28526 @findex -var-delete
28528 @subsubheading Synopsis
28531 -var-delete [ -c ] @var{name}
28534 Deletes a previously created variable object and all of its children.
28535 With the @samp{-c} option, just deletes the children.
28537 Returns an error if the object @var{name} is not found.
28540 @subheading The @code{-var-set-format} Command
28541 @findex -var-set-format
28543 @subsubheading Synopsis
28546 -var-set-format @var{name} @var{format-spec}
28549 Sets the output format for the value of the object @var{name} to be
28552 @anchor{-var-set-format}
28553 The syntax for the @var{format-spec} is as follows:
28556 @var{format-spec} @expansion{}
28557 @{binary | decimal | hexadecimal | octal | natural@}
28560 The natural format is the default format choosen automatically
28561 based on the variable type (like decimal for an @code{int}, hex
28562 for pointers, etc.).
28564 For a variable with children, the format is set only on the
28565 variable itself, and the children are not affected.
28567 @subheading The @code{-var-show-format} Command
28568 @findex -var-show-format
28570 @subsubheading Synopsis
28573 -var-show-format @var{name}
28576 Returns the format used to display the value of the object @var{name}.
28579 @var{format} @expansion{}
28584 @subheading The @code{-var-info-num-children} Command
28585 @findex -var-info-num-children
28587 @subsubheading Synopsis
28590 -var-info-num-children @var{name}
28593 Returns the number of children of a variable object @var{name}:
28599 Note that this number is not completely reliable for a dynamic varobj.
28600 It will return the current number of children, but more children may
28604 @subheading The @code{-var-list-children} Command
28605 @findex -var-list-children
28607 @subsubheading Synopsis
28610 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28612 @anchor{-var-list-children}
28614 Return a list of the children of the specified variable object and
28615 create variable objects for them, if they do not already exist. With
28616 a single argument or if @var{print-values} has a value of 0 or
28617 @code{--no-values}, print only the names of the variables; if
28618 @var{print-values} is 1 or @code{--all-values}, also print their
28619 values; and if it is 2 or @code{--simple-values} print the name and
28620 value for simple data types and just the name for arrays, structures
28623 @var{from} and @var{to}, if specified, indicate the range of children
28624 to report. If @var{from} or @var{to} is less than zero, the range is
28625 reset and all children will be reported. Otherwise, children starting
28626 at @var{from} (zero-based) and up to and excluding @var{to} will be
28629 If a child range is requested, it will only affect the current call to
28630 @code{-var-list-children}, but not future calls to @code{-var-update}.
28631 For this, you must instead use @code{-var-set-update-range}. The
28632 intent of this approach is to enable a front end to implement any
28633 update approach it likes; for example, scrolling a view may cause the
28634 front end to request more children with @code{-var-list-children}, and
28635 then the front end could call @code{-var-set-update-range} with a
28636 different range to ensure that future updates are restricted to just
28639 For each child the following results are returned:
28644 Name of the variable object created for this child.
28647 The expression to be shown to the user by the front end to designate this child.
28648 For example this may be the name of a structure member.
28650 For a dynamic varobj, this value cannot be used to form an
28651 expression. There is no way to do this at all with a dynamic varobj.
28653 For C/C@t{++} structures there are several pseudo children returned to
28654 designate access qualifiers. For these pseudo children @var{exp} is
28655 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28656 type and value are not present.
28658 A dynamic varobj will not report the access qualifying
28659 pseudo-children, regardless of the language. This information is not
28660 available at all with a dynamic varobj.
28663 Number of children this child has. For a dynamic varobj, this will be
28667 The type of the child. If @samp{print object}
28668 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28669 @emph{actual} (derived) type of the object is shown rather than the
28670 @emph{declared} one.
28673 If values were requested, this is the value.
28676 If this variable object is associated with a thread, this is the thread id.
28677 Otherwise this result is not present.
28680 If the variable object is frozen, this variable will be present with a value of 1.
28683 A dynamic varobj can supply a display hint to the front end. The
28684 value comes directly from the Python pretty-printer object's
28685 @code{display_hint} method. @xref{Pretty Printing API}.
28688 This attribute will be present and have the value @samp{1} if the
28689 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28690 then this attribute will not be present.
28694 The result may have its own attributes:
28698 A dynamic varobj can supply a display hint to the front end. The
28699 value comes directly from the Python pretty-printer object's
28700 @code{display_hint} method. @xref{Pretty Printing API}.
28703 This is an integer attribute which is nonzero if there are children
28704 remaining after the end of the selected range.
28707 @subsubheading Example
28711 -var-list-children n
28712 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28713 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28715 -var-list-children --all-values n
28716 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28717 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28721 @subheading The @code{-var-info-type} Command
28722 @findex -var-info-type
28724 @subsubheading Synopsis
28727 -var-info-type @var{name}
28730 Returns the type of the specified variable @var{name}. The type is
28731 returned as a string in the same format as it is output by the
28735 type=@var{typename}
28739 @subheading The @code{-var-info-expression} Command
28740 @findex -var-info-expression
28742 @subsubheading Synopsis
28745 -var-info-expression @var{name}
28748 Returns a string that is suitable for presenting this
28749 variable object in user interface. The string is generally
28750 not valid expression in the current language, and cannot be evaluated.
28752 For example, if @code{a} is an array, and variable object
28753 @code{A} was created for @code{a}, then we'll get this output:
28756 (gdb) -var-info-expression A.1
28757 ^done,lang="C",exp="1"
28761 Here, the value of @code{lang} is the language name, which can be
28762 found in @ref{Supported Languages}.
28764 Note that the output of the @code{-var-list-children} command also
28765 includes those expressions, so the @code{-var-info-expression} command
28768 @subheading The @code{-var-info-path-expression} Command
28769 @findex -var-info-path-expression
28771 @subsubheading Synopsis
28774 -var-info-path-expression @var{name}
28777 Returns an expression that can be evaluated in the current
28778 context and will yield the same value that a variable object has.
28779 Compare this with the @code{-var-info-expression} command, which
28780 result can be used only for UI presentation. Typical use of
28781 the @code{-var-info-path-expression} command is creating a
28782 watchpoint from a variable object.
28784 This command is currently not valid for children of a dynamic varobj,
28785 and will give an error when invoked on one.
28787 For example, suppose @code{C} is a C@t{++} class, derived from class
28788 @code{Base}, and that the @code{Base} class has a member called
28789 @code{m_size}. Assume a variable @code{c} is has the type of
28790 @code{C} and a variable object @code{C} was created for variable
28791 @code{c}. Then, we'll get this output:
28793 (gdb) -var-info-path-expression C.Base.public.m_size
28794 ^done,path_expr=((Base)c).m_size)
28797 @subheading The @code{-var-show-attributes} Command
28798 @findex -var-show-attributes
28800 @subsubheading Synopsis
28803 -var-show-attributes @var{name}
28806 List attributes of the specified variable object @var{name}:
28809 status=@var{attr} [ ( ,@var{attr} )* ]
28813 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28815 @subheading The @code{-var-evaluate-expression} Command
28816 @findex -var-evaluate-expression
28818 @subsubheading Synopsis
28821 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28824 Evaluates the expression that is represented by the specified variable
28825 object and returns its value as a string. The format of the string
28826 can be specified with the @samp{-f} option. The possible values of
28827 this option are the same as for @code{-var-set-format}
28828 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28829 the current display format will be used. The current display format
28830 can be changed using the @code{-var-set-format} command.
28836 Note that one must invoke @code{-var-list-children} for a variable
28837 before the value of a child variable can be evaluated.
28839 @subheading The @code{-var-assign} Command
28840 @findex -var-assign
28842 @subsubheading Synopsis
28845 -var-assign @var{name} @var{expression}
28848 Assigns the value of @var{expression} to the variable object specified
28849 by @var{name}. The object must be @samp{editable}. If the variable's
28850 value is altered by the assign, the variable will show up in any
28851 subsequent @code{-var-update} list.
28853 @subsubheading Example
28861 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28865 @subheading The @code{-var-update} Command
28866 @findex -var-update
28868 @subsubheading Synopsis
28871 -var-update [@var{print-values}] @{@var{name} | "*"@}
28874 Reevaluate the expressions corresponding to the variable object
28875 @var{name} and all its direct and indirect children, and return the
28876 list of variable objects whose values have changed; @var{name} must
28877 be a root variable object. Here, ``changed'' means that the result of
28878 @code{-var-evaluate-expression} before and after the
28879 @code{-var-update} is different. If @samp{*} is used as the variable
28880 object names, all existing variable objects are updated, except
28881 for frozen ones (@pxref{-var-set-frozen}). The option
28882 @var{print-values} determines whether both names and values, or just
28883 names are printed. The possible values of this option are the same
28884 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28885 recommended to use the @samp{--all-values} option, to reduce the
28886 number of MI commands needed on each program stop.
28888 With the @samp{*} parameter, if a variable object is bound to a
28889 currently running thread, it will not be updated, without any
28892 If @code{-var-set-update-range} was previously used on a varobj, then
28893 only the selected range of children will be reported.
28895 @code{-var-update} reports all the changed varobjs in a tuple named
28898 Each item in the change list is itself a tuple holding:
28902 The name of the varobj.
28905 If values were requested for this update, then this field will be
28906 present and will hold the value of the varobj.
28909 @anchor{-var-update}
28910 This field is a string which may take one of three values:
28914 The variable object's current value is valid.
28917 The variable object does not currently hold a valid value but it may
28918 hold one in the future if its associated expression comes back into
28922 The variable object no longer holds a valid value.
28923 This can occur when the executable file being debugged has changed,
28924 either through recompilation or by using the @value{GDBN} @code{file}
28925 command. The front end should normally choose to delete these variable
28929 In the future new values may be added to this list so the front should
28930 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28933 This is only present if the varobj is still valid. If the type
28934 changed, then this will be the string @samp{true}; otherwise it will
28937 When a varobj's type changes, its children are also likely to have
28938 become incorrect. Therefore, the varobj's children are automatically
28939 deleted when this attribute is @samp{true}. Also, the varobj's update
28940 range, when set using the @code{-var-set-update-range} command, is
28944 If the varobj's type changed, then this field will be present and will
28947 @item new_num_children
28948 For a dynamic varobj, if the number of children changed, or if the
28949 type changed, this will be the new number of children.
28951 The @samp{numchild} field in other varobj responses is generally not
28952 valid for a dynamic varobj -- it will show the number of children that
28953 @value{GDBN} knows about, but because dynamic varobjs lazily
28954 instantiate their children, this will not reflect the number of
28955 children which may be available.
28957 The @samp{new_num_children} attribute only reports changes to the
28958 number of children known by @value{GDBN}. This is the only way to
28959 detect whether an update has removed children (which necessarily can
28960 only happen at the end of the update range).
28963 The display hint, if any.
28966 This is an integer value, which will be 1 if there are more children
28967 available outside the varobj's update range.
28970 This attribute will be present and have the value @samp{1} if the
28971 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28972 then this attribute will not be present.
28975 If new children were added to a dynamic varobj within the selected
28976 update range (as set by @code{-var-set-update-range}), then they will
28977 be listed in this attribute.
28980 @subsubheading Example
28987 -var-update --all-values var1
28988 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28989 type_changed="false"@}]
28993 @subheading The @code{-var-set-frozen} Command
28994 @findex -var-set-frozen
28995 @anchor{-var-set-frozen}
28997 @subsubheading Synopsis
29000 -var-set-frozen @var{name} @var{flag}
29003 Set the frozenness flag on the variable object @var{name}. The
29004 @var{flag} parameter should be either @samp{1} to make the variable
29005 frozen or @samp{0} to make it unfrozen. If a variable object is
29006 frozen, then neither itself, nor any of its children, are
29007 implicitly updated by @code{-var-update} of
29008 a parent variable or by @code{-var-update *}. Only
29009 @code{-var-update} of the variable itself will update its value and
29010 values of its children. After a variable object is unfrozen, it is
29011 implicitly updated by all subsequent @code{-var-update} operations.
29012 Unfreezing a variable does not update it, only subsequent
29013 @code{-var-update} does.
29015 @subsubheading Example
29019 -var-set-frozen V 1
29024 @subheading The @code{-var-set-update-range} command
29025 @findex -var-set-update-range
29026 @anchor{-var-set-update-range}
29028 @subsubheading Synopsis
29031 -var-set-update-range @var{name} @var{from} @var{to}
29034 Set the range of children to be returned by future invocations of
29035 @code{-var-update}.
29037 @var{from} and @var{to} indicate the range of children to report. If
29038 @var{from} or @var{to} is less than zero, the range is reset and all
29039 children will be reported. Otherwise, children starting at @var{from}
29040 (zero-based) and up to and excluding @var{to} will be reported.
29042 @subsubheading Example
29046 -var-set-update-range V 1 2
29050 @subheading The @code{-var-set-visualizer} command
29051 @findex -var-set-visualizer
29052 @anchor{-var-set-visualizer}
29054 @subsubheading Synopsis
29057 -var-set-visualizer @var{name} @var{visualizer}
29060 Set a visualizer for the variable object @var{name}.
29062 @var{visualizer} is the visualizer to use. The special value
29063 @samp{None} means to disable any visualizer in use.
29065 If not @samp{None}, @var{visualizer} must be a Python expression.
29066 This expression must evaluate to a callable object which accepts a
29067 single argument. @value{GDBN} will call this object with the value of
29068 the varobj @var{name} as an argument (this is done so that the same
29069 Python pretty-printing code can be used for both the CLI and MI).
29070 When called, this object must return an object which conforms to the
29071 pretty-printing interface (@pxref{Pretty Printing API}).
29073 The pre-defined function @code{gdb.default_visualizer} may be used to
29074 select a visualizer by following the built-in process
29075 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29076 a varobj is created, and so ordinarily is not needed.
29078 This feature is only available if Python support is enabled. The MI
29079 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29080 can be used to check this.
29082 @subsubheading Example
29084 Resetting the visualizer:
29088 -var-set-visualizer V None
29092 Reselecting the default (type-based) visualizer:
29096 -var-set-visualizer V gdb.default_visualizer
29100 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29101 can be used to instantiate this class for a varobj:
29105 -var-set-visualizer V "lambda val: SomeClass()"
29109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29110 @node GDB/MI Data Manipulation
29111 @section @sc{gdb/mi} Data Manipulation
29113 @cindex data manipulation, in @sc{gdb/mi}
29114 @cindex @sc{gdb/mi}, data manipulation
29115 This section describes the @sc{gdb/mi} commands that manipulate data:
29116 examine memory and registers, evaluate expressions, etc.
29118 @c REMOVED FROM THE INTERFACE.
29119 @c @subheading -data-assign
29120 @c Change the value of a program variable. Plenty of side effects.
29121 @c @subsubheading GDB Command
29123 @c @subsubheading Example
29126 @subheading The @code{-data-disassemble} Command
29127 @findex -data-disassemble
29129 @subsubheading Synopsis
29133 [ -s @var{start-addr} -e @var{end-addr} ]
29134 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29142 @item @var{start-addr}
29143 is the beginning address (or @code{$pc})
29144 @item @var{end-addr}
29146 @item @var{filename}
29147 is the name of the file to disassemble
29148 @item @var{linenum}
29149 is the line number to disassemble around
29151 is the number of disassembly lines to be produced. If it is -1,
29152 the whole function will be disassembled, in case no @var{end-addr} is
29153 specified. If @var{end-addr} is specified as a non-zero value, and
29154 @var{lines} is lower than the number of disassembly lines between
29155 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29156 displayed; if @var{lines} is higher than the number of lines between
29157 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29160 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29161 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29162 mixed source and disassembly with raw opcodes).
29165 @subsubheading Result
29167 The result of the @code{-data-disassemble} command will be a list named
29168 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29169 used with the @code{-data-disassemble} command.
29171 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29176 The address at which this instruction was disassembled.
29179 The name of the function this instruction is within.
29182 The decimal offset in bytes from the start of @samp{func-name}.
29185 The text disassembly for this @samp{address}.
29188 This field is only present for mode 2. This contains the raw opcode
29189 bytes for the @samp{inst} field.
29193 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29194 @samp{src_and_asm_line}, each of which has the following fields:
29198 The line number within @samp{file}.
29201 The file name from the compilation unit. This might be an absolute
29202 file name or a relative file name depending on the compile command
29206 Absolute file name of @samp{file}. It is converted to a canonical form
29207 using the source file search path
29208 (@pxref{Source Path, ,Specifying Source Directories})
29209 and after resolving all the symbolic links.
29211 If the source file is not found this field will contain the path as
29212 present in the debug information.
29214 @item line_asm_insn
29215 This is a list of tuples containing the disassembly for @samp{line} in
29216 @samp{file}. The fields of each tuple are the same as for
29217 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29218 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29223 Note that whatever included in the @samp{inst} field, is not
29224 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29227 @subsubheading @value{GDBN} Command
29229 The corresponding @value{GDBN} command is @samp{disassemble}.
29231 @subsubheading Example
29233 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29237 -data-disassemble -s $pc -e "$pc + 20" -- 0
29240 @{address="0x000107c0",func-name="main",offset="4",
29241 inst="mov 2, %o0"@},
29242 @{address="0x000107c4",func-name="main",offset="8",
29243 inst="sethi %hi(0x11800), %o2"@},
29244 @{address="0x000107c8",func-name="main",offset="12",
29245 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29246 @{address="0x000107cc",func-name="main",offset="16",
29247 inst="sethi %hi(0x11800), %o2"@},
29248 @{address="0x000107d0",func-name="main",offset="20",
29249 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29253 Disassemble the whole @code{main} function. Line 32 is part of
29257 -data-disassemble -f basics.c -l 32 -- 0
29259 @{address="0x000107bc",func-name="main",offset="0",
29260 inst="save %sp, -112, %sp"@},
29261 @{address="0x000107c0",func-name="main",offset="4",
29262 inst="mov 2, %o0"@},
29263 @{address="0x000107c4",func-name="main",offset="8",
29264 inst="sethi %hi(0x11800), %o2"@},
29266 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29267 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29271 Disassemble 3 instructions from the start of @code{main}:
29275 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29277 @{address="0x000107bc",func-name="main",offset="0",
29278 inst="save %sp, -112, %sp"@},
29279 @{address="0x000107c0",func-name="main",offset="4",
29280 inst="mov 2, %o0"@},
29281 @{address="0x000107c4",func-name="main",offset="8",
29282 inst="sethi %hi(0x11800), %o2"@}]
29286 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29290 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29292 src_and_asm_line=@{line="31",
29293 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29294 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29295 line_asm_insn=[@{address="0x000107bc",
29296 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29297 src_and_asm_line=@{line="32",
29298 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29299 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29300 line_asm_insn=[@{address="0x000107c0",
29301 func-name="main",offset="4",inst="mov 2, %o0"@},
29302 @{address="0x000107c4",func-name="main",offset="8",
29303 inst="sethi %hi(0x11800), %o2"@}]@}]
29308 @subheading The @code{-data-evaluate-expression} Command
29309 @findex -data-evaluate-expression
29311 @subsubheading Synopsis
29314 -data-evaluate-expression @var{expr}
29317 Evaluate @var{expr} as an expression. The expression could contain an
29318 inferior function call. The function call will execute synchronously.
29319 If the expression contains spaces, it must be enclosed in double quotes.
29321 @subsubheading @value{GDBN} Command
29323 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29324 @samp{call}. In @code{gdbtk} only, there's a corresponding
29325 @samp{gdb_eval} command.
29327 @subsubheading Example
29329 In the following example, the numbers that precede the commands are the
29330 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29331 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29335 211-data-evaluate-expression A
29338 311-data-evaluate-expression &A
29339 311^done,value="0xefffeb7c"
29341 411-data-evaluate-expression A+3
29344 511-data-evaluate-expression "A + 3"
29350 @subheading The @code{-data-list-changed-registers} Command
29351 @findex -data-list-changed-registers
29353 @subsubheading Synopsis
29356 -data-list-changed-registers
29359 Display a list of the registers that have changed.
29361 @subsubheading @value{GDBN} Command
29363 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29364 has the corresponding command @samp{gdb_changed_register_list}.
29366 @subsubheading Example
29368 On a PPC MBX board:
29376 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29377 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29380 -data-list-changed-registers
29381 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29382 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29383 "24","25","26","27","28","30","31","64","65","66","67","69"]
29388 @subheading The @code{-data-list-register-names} Command
29389 @findex -data-list-register-names
29391 @subsubheading Synopsis
29394 -data-list-register-names [ ( @var{regno} )+ ]
29397 Show a list of register names for the current target. If no arguments
29398 are given, it shows a list of the names of all the registers. If
29399 integer numbers are given as arguments, it will print a list of the
29400 names of the registers corresponding to the arguments. To ensure
29401 consistency between a register name and its number, the output list may
29402 include empty register names.
29404 @subsubheading @value{GDBN} Command
29406 @value{GDBN} does not have a command which corresponds to
29407 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29408 corresponding command @samp{gdb_regnames}.
29410 @subsubheading Example
29412 For the PPC MBX board:
29415 -data-list-register-names
29416 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29417 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29418 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29419 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29420 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29421 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29422 "", "pc","ps","cr","lr","ctr","xer"]
29424 -data-list-register-names 1 2 3
29425 ^done,register-names=["r1","r2","r3"]
29429 @subheading The @code{-data-list-register-values} Command
29430 @findex -data-list-register-values
29432 @subsubheading Synopsis
29435 -data-list-register-values
29436 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29439 Display the registers' contents. The format according to which the
29440 registers' contents are to be returned is given by @var{fmt}, followed
29441 by an optional list of numbers specifying the registers to display. A
29442 missing list of numbers indicates that the contents of all the
29443 registers must be returned. The @code{--skip-unavailable} option
29444 indicates that only the available registers are to be returned.
29446 Allowed formats for @var{fmt} are:
29463 @subsubheading @value{GDBN} Command
29465 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29466 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29468 @subsubheading Example
29470 For a PPC MBX board (note: line breaks are for readability only, they
29471 don't appear in the actual output):
29475 -data-list-register-values r 64 65
29476 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29477 @{number="65",value="0x00029002"@}]
29479 -data-list-register-values x
29480 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29481 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29482 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29483 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29484 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29485 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29486 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29487 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29488 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29489 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29490 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29491 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29492 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29493 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29494 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29495 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29496 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29497 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29498 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29499 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29500 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29501 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29502 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29503 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29504 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29505 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29506 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29507 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29508 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29509 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29510 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29511 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29512 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29513 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29514 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29515 @{number="69",value="0x20002b03"@}]
29520 @subheading The @code{-data-read-memory} Command
29521 @findex -data-read-memory
29523 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29525 @subsubheading Synopsis
29528 -data-read-memory [ -o @var{byte-offset} ]
29529 @var{address} @var{word-format} @var{word-size}
29530 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29537 @item @var{address}
29538 An expression specifying the address of the first memory word to be
29539 read. Complex expressions containing embedded white space should be
29540 quoted using the C convention.
29542 @item @var{word-format}
29543 The format to be used to print the memory words. The notation is the
29544 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29547 @item @var{word-size}
29548 The size of each memory word in bytes.
29550 @item @var{nr-rows}
29551 The number of rows in the output table.
29553 @item @var{nr-cols}
29554 The number of columns in the output table.
29557 If present, indicates that each row should include an @sc{ascii} dump. The
29558 value of @var{aschar} is used as a padding character when a byte is not a
29559 member of the printable @sc{ascii} character set (printable @sc{ascii}
29560 characters are those whose code is between 32 and 126, inclusively).
29562 @item @var{byte-offset}
29563 An offset to add to the @var{address} before fetching memory.
29566 This command displays memory contents as a table of @var{nr-rows} by
29567 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29568 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29569 (returned as @samp{total-bytes}). Should less than the requested number
29570 of bytes be returned by the target, the missing words are identified
29571 using @samp{N/A}. The number of bytes read from the target is returned
29572 in @samp{nr-bytes} and the starting address used to read memory in
29575 The address of the next/previous row or page is available in
29576 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29579 @subsubheading @value{GDBN} Command
29581 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29582 @samp{gdb_get_mem} memory read command.
29584 @subsubheading Example
29586 Read six bytes of memory starting at @code{bytes+6} but then offset by
29587 @code{-6} bytes. Format as three rows of two columns. One byte per
29588 word. Display each word in hex.
29592 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29593 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29594 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29595 prev-page="0x0000138a",memory=[
29596 @{addr="0x00001390",data=["0x00","0x01"]@},
29597 @{addr="0x00001392",data=["0x02","0x03"]@},
29598 @{addr="0x00001394",data=["0x04","0x05"]@}]
29602 Read two bytes of memory starting at address @code{shorts + 64} and
29603 display as a single word formatted in decimal.
29607 5-data-read-memory shorts+64 d 2 1 1
29608 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29609 next-row="0x00001512",prev-row="0x0000150e",
29610 next-page="0x00001512",prev-page="0x0000150e",memory=[
29611 @{addr="0x00001510",data=["128"]@}]
29615 Read thirty two bytes of memory starting at @code{bytes+16} and format
29616 as eight rows of four columns. Include a string encoding with @samp{x}
29617 used as the non-printable character.
29621 4-data-read-memory bytes+16 x 1 8 4 x
29622 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29623 next-row="0x000013c0",prev-row="0x0000139c",
29624 next-page="0x000013c0",prev-page="0x00001380",memory=[
29625 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29626 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29627 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29628 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29629 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29630 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29631 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29632 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29636 @subheading The @code{-data-read-memory-bytes} Command
29637 @findex -data-read-memory-bytes
29639 @subsubheading Synopsis
29642 -data-read-memory-bytes [ -o @var{byte-offset} ]
29643 @var{address} @var{count}
29650 @item @var{address}
29651 An expression specifying the address of the first memory word to be
29652 read. Complex expressions containing embedded white space should be
29653 quoted using the C convention.
29656 The number of bytes to read. This should be an integer literal.
29658 @item @var{byte-offset}
29659 The offsets in bytes relative to @var{address} at which to start
29660 reading. This should be an integer literal. This option is provided
29661 so that a frontend is not required to first evaluate address and then
29662 perform address arithmetics itself.
29666 This command attempts to read all accessible memory regions in the
29667 specified range. First, all regions marked as unreadable in the memory
29668 map (if one is defined) will be skipped. @xref{Memory Region
29669 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29670 regions. For each one, if reading full region results in an errors,
29671 @value{GDBN} will try to read a subset of the region.
29673 In general, every single byte in the region may be readable or not,
29674 and the only way to read every readable byte is to try a read at
29675 every address, which is not practical. Therefore, @value{GDBN} will
29676 attempt to read all accessible bytes at either beginning or the end
29677 of the region, using a binary division scheme. This heuristic works
29678 well for reading accross a memory map boundary. Note that if a region
29679 has a readable range that is neither at the beginning or the end,
29680 @value{GDBN} will not read it.
29682 The result record (@pxref{GDB/MI Result Records}) that is output of
29683 the command includes a field named @samp{memory} whose content is a
29684 list of tuples. Each tuple represent a successfully read memory block
29685 and has the following fields:
29689 The start address of the memory block, as hexadecimal literal.
29692 The end address of the memory block, as hexadecimal literal.
29695 The offset of the memory block, as hexadecimal literal, relative to
29696 the start address passed to @code{-data-read-memory-bytes}.
29699 The contents of the memory block, in hex.
29705 @subsubheading @value{GDBN} Command
29707 The corresponding @value{GDBN} command is @samp{x}.
29709 @subsubheading Example
29713 -data-read-memory-bytes &a 10
29714 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29716 contents="01000000020000000300"@}]
29721 @subheading The @code{-data-write-memory-bytes} Command
29722 @findex -data-write-memory-bytes
29724 @subsubheading Synopsis
29727 -data-write-memory-bytes @var{address} @var{contents}
29728 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29735 @item @var{address}
29736 An expression specifying the address of the first memory word to be
29737 read. Complex expressions containing embedded white space should be
29738 quoted using the C convention.
29740 @item @var{contents}
29741 The hex-encoded bytes to write.
29744 Optional argument indicating the number of bytes to be written. If @var{count}
29745 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29746 write @var{contents} until it fills @var{count} bytes.
29750 @subsubheading @value{GDBN} Command
29752 There's no corresponding @value{GDBN} command.
29754 @subsubheading Example
29758 -data-write-memory-bytes &a "aabbccdd"
29765 -data-write-memory-bytes &a "aabbccdd" 16e
29770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29771 @node GDB/MI Tracepoint Commands
29772 @section @sc{gdb/mi} Tracepoint Commands
29774 The commands defined in this section implement MI support for
29775 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29777 @subheading The @code{-trace-find} Command
29778 @findex -trace-find
29780 @subsubheading Synopsis
29783 -trace-find @var{mode} [@var{parameters}@dots{}]
29786 Find a trace frame using criteria defined by @var{mode} and
29787 @var{parameters}. The following table lists permissible
29788 modes and their parameters. For details of operation, see @ref{tfind}.
29793 No parameters are required. Stops examining trace frames.
29796 An integer is required as parameter. Selects tracepoint frame with
29799 @item tracepoint-number
29800 An integer is required as parameter. Finds next
29801 trace frame that corresponds to tracepoint with the specified number.
29804 An address is required as parameter. Finds
29805 next trace frame that corresponds to any tracepoint at the specified
29808 @item pc-inside-range
29809 Two addresses are required as parameters. Finds next trace
29810 frame that corresponds to a tracepoint at an address inside the
29811 specified range. Both bounds are considered to be inside the range.
29813 @item pc-outside-range
29814 Two addresses are required as parameters. Finds
29815 next trace frame that corresponds to a tracepoint at an address outside
29816 the specified range. Both bounds are considered to be inside the range.
29819 Line specification is required as parameter. @xref{Specify Location}.
29820 Finds next trace frame that corresponds to a tracepoint at
29821 the specified location.
29825 If @samp{none} was passed as @var{mode}, the response does not
29826 have fields. Otherwise, the response may have the following fields:
29830 This field has either @samp{0} or @samp{1} as the value, depending
29831 on whether a matching tracepoint was found.
29834 The index of the found traceframe. This field is present iff
29835 the @samp{found} field has value of @samp{1}.
29838 The index of the found tracepoint. This field is present iff
29839 the @samp{found} field has value of @samp{1}.
29842 The information about the frame corresponding to the found trace
29843 frame. This field is present only if a trace frame was found.
29844 @xref{GDB/MI Frame Information}, for description of this field.
29848 @subsubheading @value{GDBN} Command
29850 The corresponding @value{GDBN} command is @samp{tfind}.
29852 @subheading -trace-define-variable
29853 @findex -trace-define-variable
29855 @subsubheading Synopsis
29858 -trace-define-variable @var{name} [ @var{value} ]
29861 Create trace variable @var{name} if it does not exist. If
29862 @var{value} is specified, sets the initial value of the specified
29863 trace variable to that value. Note that the @var{name} should start
29864 with the @samp{$} character.
29866 @subsubheading @value{GDBN} Command
29868 The corresponding @value{GDBN} command is @samp{tvariable}.
29870 @subheading The @code{-trace-frame-collected} Command
29871 @findex -trace-frame-collected
29873 @subsubheading Synopsis
29876 -trace-frame-collected
29877 [--var-print-values @var{var_pval}]
29878 [--comp-print-values @var{comp_pval}]
29879 [--registers-format @var{regformat}]
29880 [--memory-contents]
29883 This command returns the set of collected objects, register names,
29884 trace state variable names, memory ranges and computed expressions
29885 that have been collected at a particular trace frame. The optional
29886 parameters to the command affect the output format in different ways.
29887 See the output description table below for more details.
29889 The reported names can be used in the normal manner to create
29890 varobjs and inspect the objects themselves. The items returned by
29891 this command are categorized so that it is clear which is a variable,
29892 which is a register, which is a trace state variable, which is a
29893 memory range and which is a computed expression.
29895 For instance, if the actions were
29897 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29898 collect *(int*)0xaf02bef0@@40
29902 the object collected in its entirety would be @code{myVar}. The
29903 object @code{myArray} would be partially collected, because only the
29904 element at index @code{myIndex} would be collected. The remaining
29905 objects would be computed expressions.
29907 An example output would be:
29911 -trace-frame-collected
29913 explicit-variables=[@{name="myVar",value="1"@}],
29914 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29915 @{name="myObj.field",value="0"@},
29916 @{name="myPtr->field",value="1"@},
29917 @{name="myCount + 2",value="3"@},
29918 @{name="$tvar1 + 1",value="43970027"@}],
29919 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29920 @{number="1",value="0x0"@},
29921 @{number="2",value="0x4"@},
29923 @{number="125",value="0x0"@}],
29924 tvars=[@{name="$tvar1",current="43970026"@}],
29925 memory=[@{address="0x0000000000602264",length="4"@},
29926 @{address="0x0000000000615bc0",length="4"@}]
29933 @item explicit-variables
29934 The set of objects that have been collected in their entirety (as
29935 opposed to collecting just a few elements of an array or a few struct
29936 members). For each object, its name and value are printed.
29937 The @code{--var-print-values} option affects how or whether the value
29938 field is output. If @var{var_pval} is 0, then print only the names;
29939 if it is 1, print also their values; and if it is 2, print the name,
29940 type and value for simple data types, and the name and type for
29941 arrays, structures and unions.
29943 @item computed-expressions
29944 The set of computed expressions that have been collected at the
29945 current trace frame. The @code{--comp-print-values} option affects
29946 this set like the @code{--var-print-values} option affects the
29947 @code{explicit-variables} set. See above.
29950 The registers that have been collected at the current trace frame.
29951 For each register collected, the name and current value are returned.
29952 The value is formatted according to the @code{--registers-format}
29953 option. See the @command{-data-list-register-values} command for a
29954 list of the allowed formats. The default is @samp{x}.
29957 The trace state variables that have been collected at the current
29958 trace frame. For each trace state variable collected, the name and
29959 current value are returned.
29962 The set of memory ranges that have been collected at the current trace
29963 frame. Its content is a list of tuples. Each tuple represents a
29964 collected memory range and has the following fields:
29968 The start address of the memory range, as hexadecimal literal.
29971 The length of the memory range, as decimal literal.
29974 The contents of the memory block, in hex. This field is only present
29975 if the @code{--memory-contents} option is specified.
29981 @subsubheading @value{GDBN} Command
29983 There is no corresponding @value{GDBN} command.
29985 @subsubheading Example
29987 @subheading -trace-list-variables
29988 @findex -trace-list-variables
29990 @subsubheading Synopsis
29993 -trace-list-variables
29996 Return a table of all defined trace variables. Each element of the
29997 table has the following fields:
30001 The name of the trace variable. This field is always present.
30004 The initial value. This is a 64-bit signed integer. This
30005 field is always present.
30008 The value the trace variable has at the moment. This is a 64-bit
30009 signed integer. This field is absent iff current value is
30010 not defined, for example if the trace was never run, or is
30015 @subsubheading @value{GDBN} Command
30017 The corresponding @value{GDBN} command is @samp{tvariables}.
30019 @subsubheading Example
30023 -trace-list-variables
30024 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30025 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30026 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30027 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30028 body=[variable=@{name="$trace_timestamp",initial="0"@}
30029 variable=@{name="$foo",initial="10",current="15"@}]@}
30033 @subheading -trace-save
30034 @findex -trace-save
30036 @subsubheading Synopsis
30039 -trace-save [-r ] @var{filename}
30042 Saves the collected trace data to @var{filename}. Without the
30043 @samp{-r} option, the data is downloaded from the target and saved
30044 in a local file. With the @samp{-r} option the target is asked
30045 to perform the save.
30047 @subsubheading @value{GDBN} Command
30049 The corresponding @value{GDBN} command is @samp{tsave}.
30052 @subheading -trace-start
30053 @findex -trace-start
30055 @subsubheading Synopsis
30061 Starts a tracing experiments. The result of this command does not
30064 @subsubheading @value{GDBN} Command
30066 The corresponding @value{GDBN} command is @samp{tstart}.
30068 @subheading -trace-status
30069 @findex -trace-status
30071 @subsubheading Synopsis
30077 Obtains the status of a tracing experiment. The result may include
30078 the following fields:
30083 May have a value of either @samp{0}, when no tracing operations are
30084 supported, @samp{1}, when all tracing operations are supported, or
30085 @samp{file} when examining trace file. In the latter case, examining
30086 of trace frame is possible but new tracing experiement cannot be
30087 started. This field is always present.
30090 May have a value of either @samp{0} or @samp{1} depending on whether
30091 tracing experiement is in progress on target. This field is present
30092 if @samp{supported} field is not @samp{0}.
30095 Report the reason why the tracing was stopped last time. This field
30096 may be absent iff tracing was never stopped on target yet. The
30097 value of @samp{request} means the tracing was stopped as result of
30098 the @code{-trace-stop} command. The value of @samp{overflow} means
30099 the tracing buffer is full. The value of @samp{disconnection} means
30100 tracing was automatically stopped when @value{GDBN} has disconnected.
30101 The value of @samp{passcount} means tracing was stopped when a
30102 tracepoint was passed a maximal number of times for that tracepoint.
30103 This field is present if @samp{supported} field is not @samp{0}.
30105 @item stopping-tracepoint
30106 The number of tracepoint whose passcount as exceeded. This field is
30107 present iff the @samp{stop-reason} field has the value of
30111 @itemx frames-created
30112 The @samp{frames} field is a count of the total number of trace frames
30113 in the trace buffer, while @samp{frames-created} is the total created
30114 during the run, including ones that were discarded, such as when a
30115 circular trace buffer filled up. Both fields are optional.
30119 These fields tell the current size of the tracing buffer and the
30120 remaining space. These fields are optional.
30123 The value of the circular trace buffer flag. @code{1} means that the
30124 trace buffer is circular and old trace frames will be discarded if
30125 necessary to make room, @code{0} means that the trace buffer is linear
30129 The value of the disconnected tracing flag. @code{1} means that
30130 tracing will continue after @value{GDBN} disconnects, @code{0} means
30131 that the trace run will stop.
30134 The filename of the trace file being examined. This field is
30135 optional, and only present when examining a trace file.
30139 @subsubheading @value{GDBN} Command
30141 The corresponding @value{GDBN} command is @samp{tstatus}.
30143 @subheading -trace-stop
30144 @findex -trace-stop
30146 @subsubheading Synopsis
30152 Stops a tracing experiment. The result of this command has the same
30153 fields as @code{-trace-status}, except that the @samp{supported} and
30154 @samp{running} fields are not output.
30156 @subsubheading @value{GDBN} Command
30158 The corresponding @value{GDBN} command is @samp{tstop}.
30161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30162 @node GDB/MI Symbol Query
30163 @section @sc{gdb/mi} Symbol Query Commands
30167 @subheading The @code{-symbol-info-address} Command
30168 @findex -symbol-info-address
30170 @subsubheading Synopsis
30173 -symbol-info-address @var{symbol}
30176 Describe where @var{symbol} is stored.
30178 @subsubheading @value{GDBN} Command
30180 The corresponding @value{GDBN} command is @samp{info address}.
30182 @subsubheading Example
30186 @subheading The @code{-symbol-info-file} Command
30187 @findex -symbol-info-file
30189 @subsubheading Synopsis
30195 Show the file for the symbol.
30197 @subsubheading @value{GDBN} Command
30199 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30200 @samp{gdb_find_file}.
30202 @subsubheading Example
30206 @subheading The @code{-symbol-info-function} Command
30207 @findex -symbol-info-function
30209 @subsubheading Synopsis
30212 -symbol-info-function
30215 Show which function the symbol lives in.
30217 @subsubheading @value{GDBN} Command
30219 @samp{gdb_get_function} in @code{gdbtk}.
30221 @subsubheading Example
30225 @subheading The @code{-symbol-info-line} Command
30226 @findex -symbol-info-line
30228 @subsubheading Synopsis
30234 Show the core addresses of the code for a source line.
30236 @subsubheading @value{GDBN} Command
30238 The corresponding @value{GDBN} command is @samp{info line}.
30239 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30241 @subsubheading Example
30245 @subheading The @code{-symbol-info-symbol} Command
30246 @findex -symbol-info-symbol
30248 @subsubheading Synopsis
30251 -symbol-info-symbol @var{addr}
30254 Describe what symbol is at location @var{addr}.
30256 @subsubheading @value{GDBN} Command
30258 The corresponding @value{GDBN} command is @samp{info symbol}.
30260 @subsubheading Example
30264 @subheading The @code{-symbol-list-functions} Command
30265 @findex -symbol-list-functions
30267 @subsubheading Synopsis
30270 -symbol-list-functions
30273 List the functions in the executable.
30275 @subsubheading @value{GDBN} Command
30277 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30278 @samp{gdb_search} in @code{gdbtk}.
30280 @subsubheading Example
30285 @subheading The @code{-symbol-list-lines} Command
30286 @findex -symbol-list-lines
30288 @subsubheading Synopsis
30291 -symbol-list-lines @var{filename}
30294 Print the list of lines that contain code and their associated program
30295 addresses for the given source filename. The entries are sorted in
30296 ascending PC order.
30298 @subsubheading @value{GDBN} Command
30300 There is no corresponding @value{GDBN} command.
30302 @subsubheading Example
30305 -symbol-list-lines basics.c
30306 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30312 @subheading The @code{-symbol-list-types} Command
30313 @findex -symbol-list-types
30315 @subsubheading Synopsis
30321 List all the type names.
30323 @subsubheading @value{GDBN} Command
30325 The corresponding commands are @samp{info types} in @value{GDBN},
30326 @samp{gdb_search} in @code{gdbtk}.
30328 @subsubheading Example
30332 @subheading The @code{-symbol-list-variables} Command
30333 @findex -symbol-list-variables
30335 @subsubheading Synopsis
30338 -symbol-list-variables
30341 List all the global and static variable names.
30343 @subsubheading @value{GDBN} Command
30345 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30347 @subsubheading Example
30351 @subheading The @code{-symbol-locate} Command
30352 @findex -symbol-locate
30354 @subsubheading Synopsis
30360 @subsubheading @value{GDBN} Command
30362 @samp{gdb_loc} in @code{gdbtk}.
30364 @subsubheading Example
30368 @subheading The @code{-symbol-type} Command
30369 @findex -symbol-type
30371 @subsubheading Synopsis
30374 -symbol-type @var{variable}
30377 Show type of @var{variable}.
30379 @subsubheading @value{GDBN} Command
30381 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30382 @samp{gdb_obj_variable}.
30384 @subsubheading Example
30389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30390 @node GDB/MI File Commands
30391 @section @sc{gdb/mi} File Commands
30393 This section describes the GDB/MI commands to specify executable file names
30394 and to read in and obtain symbol table information.
30396 @subheading The @code{-file-exec-and-symbols} Command
30397 @findex -file-exec-and-symbols
30399 @subsubheading Synopsis
30402 -file-exec-and-symbols @var{file}
30405 Specify the executable file to be debugged. This file is the one from
30406 which the symbol table is also read. If no file is specified, the
30407 command clears the executable and symbol information. If breakpoints
30408 are set when using this command with no arguments, @value{GDBN} will produce
30409 error messages. Otherwise, no output is produced, except a completion
30412 @subsubheading @value{GDBN} Command
30414 The corresponding @value{GDBN} command is @samp{file}.
30416 @subsubheading Example
30420 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30426 @subheading The @code{-file-exec-file} Command
30427 @findex -file-exec-file
30429 @subsubheading Synopsis
30432 -file-exec-file @var{file}
30435 Specify the executable file to be debugged. Unlike
30436 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30437 from this file. If used without argument, @value{GDBN} clears the information
30438 about the executable file. No output is produced, except a completion
30441 @subsubheading @value{GDBN} Command
30443 The corresponding @value{GDBN} command is @samp{exec-file}.
30445 @subsubheading Example
30449 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30456 @subheading The @code{-file-list-exec-sections} Command
30457 @findex -file-list-exec-sections
30459 @subsubheading Synopsis
30462 -file-list-exec-sections
30465 List the sections of the current executable file.
30467 @subsubheading @value{GDBN} Command
30469 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30470 information as this command. @code{gdbtk} has a corresponding command
30471 @samp{gdb_load_info}.
30473 @subsubheading Example
30478 @subheading The @code{-file-list-exec-source-file} Command
30479 @findex -file-list-exec-source-file
30481 @subsubheading Synopsis
30484 -file-list-exec-source-file
30487 List the line number, the current source file, and the absolute path
30488 to the current source file for the current executable. The macro
30489 information field has a value of @samp{1} or @samp{0} depending on
30490 whether or not the file includes preprocessor macro information.
30492 @subsubheading @value{GDBN} Command
30494 The @value{GDBN} equivalent is @samp{info source}
30496 @subsubheading Example
30500 123-file-list-exec-source-file
30501 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30506 @subheading The @code{-file-list-exec-source-files} Command
30507 @findex -file-list-exec-source-files
30509 @subsubheading Synopsis
30512 -file-list-exec-source-files
30515 List the source files for the current executable.
30517 It will always output both the filename and fullname (absolute file
30518 name) of a source file.
30520 @subsubheading @value{GDBN} Command
30522 The @value{GDBN} equivalent is @samp{info sources}.
30523 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30525 @subsubheading Example
30528 -file-list-exec-source-files
30530 @{file=foo.c,fullname=/home/foo.c@},
30531 @{file=/home/bar.c,fullname=/home/bar.c@},
30532 @{file=gdb_could_not_find_fullpath.c@}]
30537 @subheading The @code{-file-list-shared-libraries} Command
30538 @findex -file-list-shared-libraries
30540 @subsubheading Synopsis
30543 -file-list-shared-libraries
30546 List the shared libraries in the program.
30548 @subsubheading @value{GDBN} Command
30550 The corresponding @value{GDBN} command is @samp{info shared}.
30552 @subsubheading Example
30556 @subheading The @code{-file-list-symbol-files} Command
30557 @findex -file-list-symbol-files
30559 @subsubheading Synopsis
30562 -file-list-symbol-files
30567 @subsubheading @value{GDBN} Command
30569 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30571 @subsubheading Example
30576 @subheading The @code{-file-symbol-file} Command
30577 @findex -file-symbol-file
30579 @subsubheading Synopsis
30582 -file-symbol-file @var{file}
30585 Read symbol table info from the specified @var{file} argument. When
30586 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30587 produced, except for a completion notification.
30589 @subsubheading @value{GDBN} Command
30591 The corresponding @value{GDBN} command is @samp{symbol-file}.
30593 @subsubheading Example
30597 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30604 @node GDB/MI Memory Overlay Commands
30605 @section @sc{gdb/mi} Memory Overlay Commands
30607 The memory overlay commands are not implemented.
30609 @c @subheading -overlay-auto
30611 @c @subheading -overlay-list-mapping-state
30613 @c @subheading -overlay-list-overlays
30615 @c @subheading -overlay-map
30617 @c @subheading -overlay-off
30619 @c @subheading -overlay-on
30621 @c @subheading -overlay-unmap
30623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30624 @node GDB/MI Signal Handling Commands
30625 @section @sc{gdb/mi} Signal Handling Commands
30627 Signal handling commands are not implemented.
30629 @c @subheading -signal-handle
30631 @c @subheading -signal-list-handle-actions
30633 @c @subheading -signal-list-signal-types
30637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30638 @node GDB/MI Target Manipulation
30639 @section @sc{gdb/mi} Target Manipulation Commands
30642 @subheading The @code{-target-attach} Command
30643 @findex -target-attach
30645 @subsubheading Synopsis
30648 -target-attach @var{pid} | @var{gid} | @var{file}
30651 Attach to a process @var{pid} or a file @var{file} outside of
30652 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30653 group, the id previously returned by
30654 @samp{-list-thread-groups --available} must be used.
30656 @subsubheading @value{GDBN} Command
30658 The corresponding @value{GDBN} command is @samp{attach}.
30660 @subsubheading Example
30664 =thread-created,id="1"
30665 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30671 @subheading The @code{-target-compare-sections} Command
30672 @findex -target-compare-sections
30674 @subsubheading Synopsis
30677 -target-compare-sections [ @var{section} ]
30680 Compare data of section @var{section} on target to the exec file.
30681 Without the argument, all sections are compared.
30683 @subsubheading @value{GDBN} Command
30685 The @value{GDBN} equivalent is @samp{compare-sections}.
30687 @subsubheading Example
30692 @subheading The @code{-target-detach} Command
30693 @findex -target-detach
30695 @subsubheading Synopsis
30698 -target-detach [ @var{pid} | @var{gid} ]
30701 Detach from the remote target which normally resumes its execution.
30702 If either @var{pid} or @var{gid} is specified, detaches from either
30703 the specified process, or specified thread group. There's no output.
30705 @subsubheading @value{GDBN} Command
30707 The corresponding @value{GDBN} command is @samp{detach}.
30709 @subsubheading Example
30719 @subheading The @code{-target-disconnect} Command
30720 @findex -target-disconnect
30722 @subsubheading Synopsis
30728 Disconnect from the remote target. There's no output and the target is
30729 generally not resumed.
30731 @subsubheading @value{GDBN} Command
30733 The corresponding @value{GDBN} command is @samp{disconnect}.
30735 @subsubheading Example
30745 @subheading The @code{-target-download} Command
30746 @findex -target-download
30748 @subsubheading Synopsis
30754 Loads the executable onto the remote target.
30755 It prints out an update message every half second, which includes the fields:
30759 The name of the section.
30761 The size of what has been sent so far for that section.
30763 The size of the section.
30765 The total size of what was sent so far (the current and the previous sections).
30767 The size of the overall executable to download.
30771 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30772 @sc{gdb/mi} Output Syntax}).
30774 In addition, it prints the name and size of the sections, as they are
30775 downloaded. These messages include the following fields:
30779 The name of the section.
30781 The size of the section.
30783 The size of the overall executable to download.
30787 At the end, a summary is printed.
30789 @subsubheading @value{GDBN} Command
30791 The corresponding @value{GDBN} command is @samp{load}.
30793 @subsubheading Example
30795 Note: each status message appears on a single line. Here the messages
30796 have been broken down so that they can fit onto a page.
30801 +download,@{section=".text",section-size="6668",total-size="9880"@}
30802 +download,@{section=".text",section-sent="512",section-size="6668",
30803 total-sent="512",total-size="9880"@}
30804 +download,@{section=".text",section-sent="1024",section-size="6668",
30805 total-sent="1024",total-size="9880"@}
30806 +download,@{section=".text",section-sent="1536",section-size="6668",
30807 total-sent="1536",total-size="9880"@}
30808 +download,@{section=".text",section-sent="2048",section-size="6668",
30809 total-sent="2048",total-size="9880"@}
30810 +download,@{section=".text",section-sent="2560",section-size="6668",
30811 total-sent="2560",total-size="9880"@}
30812 +download,@{section=".text",section-sent="3072",section-size="6668",
30813 total-sent="3072",total-size="9880"@}
30814 +download,@{section=".text",section-sent="3584",section-size="6668",
30815 total-sent="3584",total-size="9880"@}
30816 +download,@{section=".text",section-sent="4096",section-size="6668",
30817 total-sent="4096",total-size="9880"@}
30818 +download,@{section=".text",section-sent="4608",section-size="6668",
30819 total-sent="4608",total-size="9880"@}
30820 +download,@{section=".text",section-sent="5120",section-size="6668",
30821 total-sent="5120",total-size="9880"@}
30822 +download,@{section=".text",section-sent="5632",section-size="6668",
30823 total-sent="5632",total-size="9880"@}
30824 +download,@{section=".text",section-sent="6144",section-size="6668",
30825 total-sent="6144",total-size="9880"@}
30826 +download,@{section=".text",section-sent="6656",section-size="6668",
30827 total-sent="6656",total-size="9880"@}
30828 +download,@{section=".init",section-size="28",total-size="9880"@}
30829 +download,@{section=".fini",section-size="28",total-size="9880"@}
30830 +download,@{section=".data",section-size="3156",total-size="9880"@}
30831 +download,@{section=".data",section-sent="512",section-size="3156",
30832 total-sent="7236",total-size="9880"@}
30833 +download,@{section=".data",section-sent="1024",section-size="3156",
30834 total-sent="7748",total-size="9880"@}
30835 +download,@{section=".data",section-sent="1536",section-size="3156",
30836 total-sent="8260",total-size="9880"@}
30837 +download,@{section=".data",section-sent="2048",section-size="3156",
30838 total-sent="8772",total-size="9880"@}
30839 +download,@{section=".data",section-sent="2560",section-size="3156",
30840 total-sent="9284",total-size="9880"@}
30841 +download,@{section=".data",section-sent="3072",section-size="3156",
30842 total-sent="9796",total-size="9880"@}
30843 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30850 @subheading The @code{-target-exec-status} Command
30851 @findex -target-exec-status
30853 @subsubheading Synopsis
30856 -target-exec-status
30859 Provide information on the state of the target (whether it is running or
30860 not, for instance).
30862 @subsubheading @value{GDBN} Command
30864 There's no equivalent @value{GDBN} command.
30866 @subsubheading Example
30870 @subheading The @code{-target-list-available-targets} Command
30871 @findex -target-list-available-targets
30873 @subsubheading Synopsis
30876 -target-list-available-targets
30879 List the possible targets to connect to.
30881 @subsubheading @value{GDBN} Command
30883 The corresponding @value{GDBN} command is @samp{help target}.
30885 @subsubheading Example
30889 @subheading The @code{-target-list-current-targets} Command
30890 @findex -target-list-current-targets
30892 @subsubheading Synopsis
30895 -target-list-current-targets
30898 Describe the current target.
30900 @subsubheading @value{GDBN} Command
30902 The corresponding information is printed by @samp{info file} (among
30905 @subsubheading Example
30909 @subheading The @code{-target-list-parameters} Command
30910 @findex -target-list-parameters
30912 @subsubheading Synopsis
30915 -target-list-parameters
30921 @subsubheading @value{GDBN} Command
30925 @subsubheading Example
30929 @subheading The @code{-target-select} Command
30930 @findex -target-select
30932 @subsubheading Synopsis
30935 -target-select @var{type} @var{parameters @dots{}}
30938 Connect @value{GDBN} to the remote target. This command takes two args:
30942 The type of target, for instance @samp{remote}, etc.
30943 @item @var{parameters}
30944 Device names, host names and the like. @xref{Target Commands, ,
30945 Commands for Managing Targets}, for more details.
30948 The output is a connection notification, followed by the address at
30949 which the target program is, in the following form:
30952 ^connected,addr="@var{address}",func="@var{function name}",
30953 args=[@var{arg list}]
30956 @subsubheading @value{GDBN} Command
30958 The corresponding @value{GDBN} command is @samp{target}.
30960 @subsubheading Example
30964 -target-select remote /dev/ttya
30965 ^connected,addr="0xfe00a300",func="??",args=[]
30969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30970 @node GDB/MI File Transfer Commands
30971 @section @sc{gdb/mi} File Transfer Commands
30974 @subheading The @code{-target-file-put} Command
30975 @findex -target-file-put
30977 @subsubheading Synopsis
30980 -target-file-put @var{hostfile} @var{targetfile}
30983 Copy file @var{hostfile} from the host system (the machine running
30984 @value{GDBN}) to @var{targetfile} on the target system.
30986 @subsubheading @value{GDBN} Command
30988 The corresponding @value{GDBN} command is @samp{remote put}.
30990 @subsubheading Example
30994 -target-file-put localfile remotefile
31000 @subheading The @code{-target-file-get} Command
31001 @findex -target-file-get
31003 @subsubheading Synopsis
31006 -target-file-get @var{targetfile} @var{hostfile}
31009 Copy file @var{targetfile} from the target system to @var{hostfile}
31010 on the host system.
31012 @subsubheading @value{GDBN} Command
31014 The corresponding @value{GDBN} command is @samp{remote get}.
31016 @subsubheading Example
31020 -target-file-get remotefile localfile
31026 @subheading The @code{-target-file-delete} Command
31027 @findex -target-file-delete
31029 @subsubheading Synopsis
31032 -target-file-delete @var{targetfile}
31035 Delete @var{targetfile} from the target system.
31037 @subsubheading @value{GDBN} Command
31039 The corresponding @value{GDBN} command is @samp{remote delete}.
31041 @subsubheading Example
31045 -target-file-delete remotefile
31051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31052 @node GDB/MI Ada Exceptions Commands
31053 @section Ada Exceptions @sc{gdb/mi} Commands
31055 @subheading The @code{-info-ada-exceptions} Command
31056 @findex -info-ada-exceptions
31058 @subsubheading Synopsis
31061 -info-ada-exceptions [ @var{regexp}]
31064 List all Ada exceptions defined within the program being debugged.
31065 With a regular expression @var{regexp}, only those exceptions whose
31066 names match @var{regexp} are listed.
31068 @subsubheading @value{GDBN} Command
31070 The corresponding @value{GDBN} command is @samp{info exceptions}.
31072 @subsubheading Result
31074 The result is a table of Ada exceptions. The following columns are
31075 defined for each exception:
31079 The name of the exception.
31082 The address of the exception.
31086 @subsubheading Example
31089 -info-ada-exceptions aint
31090 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31091 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31092 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31093 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31094 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31097 @subheading Catching Ada Exceptions
31099 The commands describing how to ask @value{GDBN} to stop when a program
31100 raises an exception are described at @ref{Ada Exception GDB/MI
31101 Catchpoint Commands}.
31104 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31105 @node GDB/MI Support Commands
31106 @section @sc{gdb/mi} Support Commands
31108 Since new commands and features get regularly added to @sc{gdb/mi},
31109 some commands are available to help front-ends query the debugger
31110 about support for these capabilities. Similarly, it is also possible
31111 to query @value{GDBN} about target support of certain features.
31113 @subheading The @code{-info-gdb-mi-command} Command
31114 @cindex @code{-info-gdb-mi-command}
31115 @findex -info-gdb-mi-command
31117 @subsubheading Synopsis
31120 -info-gdb-mi-command @var{cmd_name}
31123 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31125 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31126 is technically not part of the command name (@pxref{GDB/MI Input
31127 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31128 for ease of use, this command also accepts the form with the leading
31131 @subsubheading @value{GDBN} Command
31133 There is no corresponding @value{GDBN} command.
31135 @subsubheading Result
31137 The result is a tuple. There is currently only one field:
31141 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31142 @code{"false"} otherwise.
31146 @subsubheading Example
31148 Here is an example where the @sc{gdb/mi} command does not exist:
31151 -info-gdb-mi-command unsupported-command
31152 ^done,command=@{exists="false"@}
31156 And here is an example where the @sc{gdb/mi} command is known
31160 -info-gdb-mi-command symbol-list-lines
31161 ^done,command=@{exists="true"@}
31164 @subheading The @code{-list-features} Command
31165 @findex -list-features
31166 @cindex supported @sc{gdb/mi} features, list
31168 Returns a list of particular features of the MI protocol that
31169 this version of gdb implements. A feature can be a command,
31170 or a new field in an output of some command, or even an
31171 important bugfix. While a frontend can sometimes detect presence
31172 of a feature at runtime, it is easier to perform detection at debugger
31175 The command returns a list of strings, with each string naming an
31176 available feature. Each returned string is just a name, it does not
31177 have any internal structure. The list of possible feature names
31183 (gdb) -list-features
31184 ^done,result=["feature1","feature2"]
31187 The current list of features is:
31190 @item frozen-varobjs
31191 Indicates support for the @code{-var-set-frozen} command, as well
31192 as possible presense of the @code{frozen} field in the output
31193 of @code{-varobj-create}.
31194 @item pending-breakpoints
31195 Indicates support for the @option{-f} option to the @code{-break-insert}
31198 Indicates Python scripting support, Python-based
31199 pretty-printing commands, and possible presence of the
31200 @samp{display_hint} field in the output of @code{-var-list-children}
31202 Indicates support for the @code{-thread-info} command.
31203 @item data-read-memory-bytes
31204 Indicates support for the @code{-data-read-memory-bytes} and the
31205 @code{-data-write-memory-bytes} commands.
31206 @item breakpoint-notifications
31207 Indicates that changes to breakpoints and breakpoints created via the
31208 CLI will be announced via async records.
31209 @item ada-task-info
31210 Indicates support for the @code{-ada-task-info} command.
31211 @item language-option
31212 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31213 option (@pxref{Context management}).
31214 @item info-gdb-mi-command
31215 Indicates support for the @code{-info-gdb-mi-command} command.
31216 @item undefined-command-error-code
31217 Indicates support for the "undefined-command" error code in error result
31218 records, produced when trying to execute an undefined @sc{gdb/mi} command
31219 (@pxref{GDB/MI Result Records}).
31220 @item exec-run-start-option
31221 Indicates that the @code{-exec-run} command supports the @option{--start}
31222 option (@pxref{GDB/MI Program Execution}).
31225 @subheading The @code{-list-target-features} Command
31226 @findex -list-target-features
31228 Returns a list of particular features that are supported by the
31229 target. Those features affect the permitted MI commands, but
31230 unlike the features reported by the @code{-list-features} command, the
31231 features depend on which target GDB is using at the moment. Whenever
31232 a target can change, due to commands such as @code{-target-select},
31233 @code{-target-attach} or @code{-exec-run}, the list of target features
31234 may change, and the frontend should obtain it again.
31238 (gdb) -list-target-features
31239 ^done,result=["async"]
31242 The current list of features is:
31246 Indicates that the target is capable of asynchronous command
31247 execution, which means that @value{GDBN} will accept further commands
31248 while the target is running.
31251 Indicates that the target is capable of reverse execution.
31252 @xref{Reverse Execution}, for more information.
31256 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31257 @node GDB/MI Miscellaneous Commands
31258 @section Miscellaneous @sc{gdb/mi} Commands
31260 @c @subheading -gdb-complete
31262 @subheading The @code{-gdb-exit} Command
31265 @subsubheading Synopsis
31271 Exit @value{GDBN} immediately.
31273 @subsubheading @value{GDBN} Command
31275 Approximately corresponds to @samp{quit}.
31277 @subsubheading Example
31287 @subheading The @code{-exec-abort} Command
31288 @findex -exec-abort
31290 @subsubheading Synopsis
31296 Kill the inferior running program.
31298 @subsubheading @value{GDBN} Command
31300 The corresponding @value{GDBN} command is @samp{kill}.
31302 @subsubheading Example
31307 @subheading The @code{-gdb-set} Command
31310 @subsubheading Synopsis
31316 Set an internal @value{GDBN} variable.
31317 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} command is @samp{set}.
31323 @subsubheading Example
31333 @subheading The @code{-gdb-show} Command
31336 @subsubheading Synopsis
31342 Show the current value of a @value{GDBN} variable.
31344 @subsubheading @value{GDBN} Command
31346 The corresponding @value{GDBN} command is @samp{show}.
31348 @subsubheading Example
31357 @c @subheading -gdb-source
31360 @subheading The @code{-gdb-version} Command
31361 @findex -gdb-version
31363 @subsubheading Synopsis
31369 Show version information for @value{GDBN}. Used mostly in testing.
31371 @subsubheading @value{GDBN} Command
31373 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31374 default shows this information when you start an interactive session.
31376 @subsubheading Example
31378 @c This example modifies the actual output from GDB to avoid overfull
31384 ~Copyright 2000 Free Software Foundation, Inc.
31385 ~GDB is free software, covered by the GNU General Public License, and
31386 ~you are welcome to change it and/or distribute copies of it under
31387 ~ certain conditions.
31388 ~Type "show copying" to see the conditions.
31389 ~There is absolutely no warranty for GDB. Type "show warranty" for
31391 ~This GDB was configured as
31392 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31397 @subheading The @code{-list-thread-groups} Command
31398 @findex -list-thread-groups
31400 @subheading Synopsis
31403 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31406 Lists thread groups (@pxref{Thread groups}). When a single thread
31407 group is passed as the argument, lists the children of that group.
31408 When several thread group are passed, lists information about those
31409 thread groups. Without any parameters, lists information about all
31410 top-level thread groups.
31412 Normally, thread groups that are being debugged are reported.
31413 With the @samp{--available} option, @value{GDBN} reports thread groups
31414 available on the target.
31416 The output of this command may have either a @samp{threads} result or
31417 a @samp{groups} result. The @samp{thread} result has a list of tuples
31418 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31419 Information}). The @samp{groups} result has a list of tuples as value,
31420 each tuple describing a thread group. If top-level groups are
31421 requested (that is, no parameter is passed), or when several groups
31422 are passed, the output always has a @samp{groups} result. The format
31423 of the @samp{group} result is described below.
31425 To reduce the number of roundtrips it's possible to list thread groups
31426 together with their children, by passing the @samp{--recurse} option
31427 and the recursion depth. Presently, only recursion depth of 1 is
31428 permitted. If this option is present, then every reported thread group
31429 will also include its children, either as @samp{group} or
31430 @samp{threads} field.
31432 In general, any combination of option and parameters is permitted, with
31433 the following caveats:
31437 When a single thread group is passed, the output will typically
31438 be the @samp{threads} result. Because threads may not contain
31439 anything, the @samp{recurse} option will be ignored.
31442 When the @samp{--available} option is passed, limited information may
31443 be available. In particular, the list of threads of a process might
31444 be inaccessible. Further, specifying specific thread groups might
31445 not give any performance advantage over listing all thread groups.
31446 The frontend should assume that @samp{-list-thread-groups --available}
31447 is always an expensive operation and cache the results.
31451 The @samp{groups} result is a list of tuples, where each tuple may
31452 have the following fields:
31456 Identifier of the thread group. This field is always present.
31457 The identifier is an opaque string; frontends should not try to
31458 convert it to an integer, even though it might look like one.
31461 The type of the thread group. At present, only @samp{process} is a
31465 The target-specific process identifier. This field is only present
31466 for thread groups of type @samp{process} and only if the process exists.
31469 The exit code of this group's last exited thread, formatted in octal.
31470 This field is only present for thread groups of type @samp{process} and
31471 only if the process is not running.
31474 The number of children this thread group has. This field may be
31475 absent for an available thread group.
31478 This field has a list of tuples as value, each tuple describing a
31479 thread. It may be present if the @samp{--recurse} option is
31480 specified, and it's actually possible to obtain the threads.
31483 This field is a list of integers, each identifying a core that one
31484 thread of the group is running on. This field may be absent if
31485 such information is not available.
31488 The name of the executable file that corresponds to this thread group.
31489 The field is only present for thread groups of type @samp{process},
31490 and only if there is a corresponding executable file.
31494 @subheading Example
31498 -list-thread-groups
31499 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31500 -list-thread-groups 17
31501 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31502 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31503 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31504 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31505 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31506 -list-thread-groups --available
31507 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31508 -list-thread-groups --available --recurse 1
31509 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31510 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31511 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31512 -list-thread-groups --available --recurse 1 17 18
31513 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31514 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31515 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31518 @subheading The @code{-info-os} Command
31521 @subsubheading Synopsis
31524 -info-os [ @var{type} ]
31527 If no argument is supplied, the command returns a table of available
31528 operating-system-specific information types. If one of these types is
31529 supplied as an argument @var{type}, then the command returns a table
31530 of data of that type.
31532 The types of information available depend on the target operating
31535 @subsubheading @value{GDBN} Command
31537 The corresponding @value{GDBN} command is @samp{info os}.
31539 @subsubheading Example
31541 When run on a @sc{gnu}/Linux system, the output will look something
31547 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31548 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31549 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31550 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31551 body=[item=@{col0="processes",col1="Listing of all processes",
31552 col2="Processes"@},
31553 item=@{col0="procgroups",col1="Listing of all process groups",
31554 col2="Process groups"@},
31555 item=@{col0="threads",col1="Listing of all threads",
31557 item=@{col0="files",col1="Listing of all file descriptors",
31558 col2="File descriptors"@},
31559 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31561 item=@{col0="shm",col1="Listing of all shared-memory regions",
31562 col2="Shared-memory regions"@},
31563 item=@{col0="semaphores",col1="Listing of all semaphores",
31564 col2="Semaphores"@},
31565 item=@{col0="msg",col1="Listing of all message queues",
31566 col2="Message queues"@},
31567 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31568 col2="Kernel modules"@}]@}
31571 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31572 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31573 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31574 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31575 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31576 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31577 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31578 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31580 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31581 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31585 (Note that the MI output here includes a @code{"Title"} column that
31586 does not appear in command-line @code{info os}; this column is useful
31587 for MI clients that want to enumerate the types of data, such as in a
31588 popup menu, but is needless clutter on the command line, and
31589 @code{info os} omits it.)
31591 @subheading The @code{-add-inferior} Command
31592 @findex -add-inferior
31594 @subheading Synopsis
31600 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31601 inferior is not associated with any executable. Such association may
31602 be established with the @samp{-file-exec-and-symbols} command
31603 (@pxref{GDB/MI File Commands}). The command response has a single
31604 field, @samp{inferior}, whose value is the identifier of the
31605 thread group corresponding to the new inferior.
31607 @subheading Example
31612 ^done,inferior="i3"
31615 @subheading The @code{-interpreter-exec} Command
31616 @findex -interpreter-exec
31618 @subheading Synopsis
31621 -interpreter-exec @var{interpreter} @var{command}
31623 @anchor{-interpreter-exec}
31625 Execute the specified @var{command} in the given @var{interpreter}.
31627 @subheading @value{GDBN} Command
31629 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31631 @subheading Example
31635 -interpreter-exec console "break main"
31636 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31637 &"During symbol reading, bad structure-type format.\n"
31638 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31643 @subheading The @code{-inferior-tty-set} Command
31644 @findex -inferior-tty-set
31646 @subheading Synopsis
31649 -inferior-tty-set /dev/pts/1
31652 Set terminal for future runs of the program being debugged.
31654 @subheading @value{GDBN} Command
31656 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31658 @subheading Example
31662 -inferior-tty-set /dev/pts/1
31667 @subheading The @code{-inferior-tty-show} Command
31668 @findex -inferior-tty-show
31670 @subheading Synopsis
31676 Show terminal for future runs of program being debugged.
31678 @subheading @value{GDBN} Command
31680 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31682 @subheading Example
31686 -inferior-tty-set /dev/pts/1
31690 ^done,inferior_tty_terminal="/dev/pts/1"
31694 @subheading The @code{-enable-timings} Command
31695 @findex -enable-timings
31697 @subheading Synopsis
31700 -enable-timings [yes | no]
31703 Toggle the printing of the wallclock, user and system times for an MI
31704 command as a field in its output. This command is to help frontend
31705 developers optimize the performance of their code. No argument is
31706 equivalent to @samp{yes}.
31708 @subheading @value{GDBN} Command
31712 @subheading Example
31720 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31721 addr="0x080484ed",func="main",file="myprog.c",
31722 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31724 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31732 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31733 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31734 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31735 fullname="/home/nickrob/myprog.c",line="73"@}
31740 @chapter @value{GDBN} Annotations
31742 This chapter describes annotations in @value{GDBN}. Annotations were
31743 designed to interface @value{GDBN} to graphical user interfaces or other
31744 similar programs which want to interact with @value{GDBN} at a
31745 relatively high level.
31747 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31751 This is Edition @value{EDITION}, @value{DATE}.
31755 * Annotations Overview:: What annotations are; the general syntax.
31756 * Server Prefix:: Issuing a command without affecting user state.
31757 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31758 * Errors:: Annotations for error messages.
31759 * Invalidation:: Some annotations describe things now invalid.
31760 * Annotations for Running::
31761 Whether the program is running, how it stopped, etc.
31762 * Source Annotations:: Annotations describing source code.
31765 @node Annotations Overview
31766 @section What is an Annotation?
31767 @cindex annotations
31769 Annotations start with a newline character, two @samp{control-z}
31770 characters, and the name of the annotation. If there is no additional
31771 information associated with this annotation, the name of the annotation
31772 is followed immediately by a newline. If there is additional
31773 information, the name of the annotation is followed by a space, the
31774 additional information, and a newline. The additional information
31775 cannot contain newline characters.
31777 Any output not beginning with a newline and two @samp{control-z}
31778 characters denotes literal output from @value{GDBN}. Currently there is
31779 no need for @value{GDBN} to output a newline followed by two
31780 @samp{control-z} characters, but if there was such a need, the
31781 annotations could be extended with an @samp{escape} annotation which
31782 means those three characters as output.
31784 The annotation @var{level}, which is specified using the
31785 @option{--annotate} command line option (@pxref{Mode Options}), controls
31786 how much information @value{GDBN} prints together with its prompt,
31787 values of expressions, source lines, and other types of output. Level 0
31788 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31789 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31790 for programs that control @value{GDBN}, and level 2 annotations have
31791 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31792 Interface, annotate, GDB's Obsolete Annotations}).
31795 @kindex set annotate
31796 @item set annotate @var{level}
31797 The @value{GDBN} command @code{set annotate} sets the level of
31798 annotations to the specified @var{level}.
31800 @item show annotate
31801 @kindex show annotate
31802 Show the current annotation level.
31805 This chapter describes level 3 annotations.
31807 A simple example of starting up @value{GDBN} with annotations is:
31810 $ @kbd{gdb --annotate=3}
31812 Copyright 2003 Free Software Foundation, Inc.
31813 GDB is free software, covered by the GNU General Public License,
31814 and you are welcome to change it and/or distribute copies of it
31815 under certain conditions.
31816 Type "show copying" to see the conditions.
31817 There is absolutely no warranty for GDB. Type "show warranty"
31819 This GDB was configured as "i386-pc-linux-gnu"
31830 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31831 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31832 denotes a @samp{control-z} character) are annotations; the rest is
31833 output from @value{GDBN}.
31835 @node Server Prefix
31836 @section The Server Prefix
31837 @cindex server prefix
31839 If you prefix a command with @samp{server } then it will not affect
31840 the command history, nor will it affect @value{GDBN}'s notion of which
31841 command to repeat if @key{RET} is pressed on a line by itself. This
31842 means that commands can be run behind a user's back by a front-end in
31843 a transparent manner.
31845 The @code{server } prefix does not affect the recording of values into
31846 the value history; to print a value without recording it into the
31847 value history, use the @code{output} command instead of the
31848 @code{print} command.
31850 Using this prefix also disables confirmation requests
31851 (@pxref{confirmation requests}).
31854 @section Annotation for @value{GDBN} Input
31856 @cindex annotations for prompts
31857 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31858 to know when to send output, when the output from a given command is
31861 Different kinds of input each have a different @dfn{input type}. Each
31862 input type has three annotations: a @code{pre-} annotation, which
31863 denotes the beginning of any prompt which is being output, a plain
31864 annotation, which denotes the end of the prompt, and then a @code{post-}
31865 annotation which denotes the end of any echo which may (or may not) be
31866 associated with the input. For example, the @code{prompt} input type
31867 features the following annotations:
31875 The input types are
31878 @findex pre-prompt annotation
31879 @findex prompt annotation
31880 @findex post-prompt annotation
31882 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31884 @findex pre-commands annotation
31885 @findex commands annotation
31886 @findex post-commands annotation
31888 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31889 command. The annotations are repeated for each command which is input.
31891 @findex pre-overload-choice annotation
31892 @findex overload-choice annotation
31893 @findex post-overload-choice annotation
31894 @item overload-choice
31895 When @value{GDBN} wants the user to select between various overloaded functions.
31897 @findex pre-query annotation
31898 @findex query annotation
31899 @findex post-query annotation
31901 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31903 @findex pre-prompt-for-continue annotation
31904 @findex prompt-for-continue annotation
31905 @findex post-prompt-for-continue annotation
31906 @item prompt-for-continue
31907 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31908 expect this to work well; instead use @code{set height 0} to disable
31909 prompting. This is because the counting of lines is buggy in the
31910 presence of annotations.
31915 @cindex annotations for errors, warnings and interrupts
31917 @findex quit annotation
31922 This annotation occurs right before @value{GDBN} responds to an interrupt.
31924 @findex error annotation
31929 This annotation occurs right before @value{GDBN} responds to an error.
31931 Quit and error annotations indicate that any annotations which @value{GDBN} was
31932 in the middle of may end abruptly. For example, if a
31933 @code{value-history-begin} annotation is followed by a @code{error}, one
31934 cannot expect to receive the matching @code{value-history-end}. One
31935 cannot expect not to receive it either, however; an error annotation
31936 does not necessarily mean that @value{GDBN} is immediately returning all the way
31939 @findex error-begin annotation
31940 A quit or error annotation may be preceded by
31946 Any output between that and the quit or error annotation is the error
31949 Warning messages are not yet annotated.
31950 @c If we want to change that, need to fix warning(), type_error(),
31951 @c range_error(), and possibly other places.
31954 @section Invalidation Notices
31956 @cindex annotations for invalidation messages
31957 The following annotations say that certain pieces of state may have
31961 @findex frames-invalid annotation
31962 @item ^Z^Zframes-invalid
31964 The frames (for example, output from the @code{backtrace} command) may
31967 @findex breakpoints-invalid annotation
31968 @item ^Z^Zbreakpoints-invalid
31970 The breakpoints may have changed. For example, the user just added or
31971 deleted a breakpoint.
31974 @node Annotations for Running
31975 @section Running the Program
31976 @cindex annotations for running programs
31978 @findex starting annotation
31979 @findex stopping annotation
31980 When the program starts executing due to a @value{GDBN} command such as
31981 @code{step} or @code{continue},
31987 is output. When the program stops,
31993 is output. Before the @code{stopped} annotation, a variety of
31994 annotations describe how the program stopped.
31997 @findex exited annotation
31998 @item ^Z^Zexited @var{exit-status}
31999 The program exited, and @var{exit-status} is the exit status (zero for
32000 successful exit, otherwise nonzero).
32002 @findex signalled annotation
32003 @findex signal-name annotation
32004 @findex signal-name-end annotation
32005 @findex signal-string annotation
32006 @findex signal-string-end annotation
32007 @item ^Z^Zsignalled
32008 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32009 annotation continues:
32015 ^Z^Zsignal-name-end
32019 ^Z^Zsignal-string-end
32024 where @var{name} is the name of the signal, such as @code{SIGILL} or
32025 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32026 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32027 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32028 user's benefit and have no particular format.
32030 @findex signal annotation
32032 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32033 just saying that the program received the signal, not that it was
32034 terminated with it.
32036 @findex breakpoint annotation
32037 @item ^Z^Zbreakpoint @var{number}
32038 The program hit breakpoint number @var{number}.
32040 @findex watchpoint annotation
32041 @item ^Z^Zwatchpoint @var{number}
32042 The program hit watchpoint number @var{number}.
32045 @node Source Annotations
32046 @section Displaying Source
32047 @cindex annotations for source display
32049 @findex source annotation
32050 The following annotation is used instead of displaying source code:
32053 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32056 where @var{filename} is an absolute file name indicating which source
32057 file, @var{line} is the line number within that file (where 1 is the
32058 first line in the file), @var{character} is the character position
32059 within the file (where 0 is the first character in the file) (for most
32060 debug formats this will necessarily point to the beginning of a line),
32061 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32062 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32063 @var{addr} is the address in the target program associated with the
32064 source which is being displayed. The @var{addr} is in the form @samp{0x}
32065 followed by one or more lowercase hex digits (note that this does not
32066 depend on the language).
32068 @node JIT Interface
32069 @chapter JIT Compilation Interface
32070 @cindex just-in-time compilation
32071 @cindex JIT compilation interface
32073 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32074 interface. A JIT compiler is a program or library that generates native
32075 executable code at runtime and executes it, usually in order to achieve good
32076 performance while maintaining platform independence.
32078 Programs that use JIT compilation are normally difficult to debug because
32079 portions of their code are generated at runtime, instead of being loaded from
32080 object files, which is where @value{GDBN} normally finds the program's symbols
32081 and debug information. In order to debug programs that use JIT compilation,
32082 @value{GDBN} has an interface that allows the program to register in-memory
32083 symbol files with @value{GDBN} at runtime.
32085 If you are using @value{GDBN} to debug a program that uses this interface, then
32086 it should work transparently so long as you have not stripped the binary. If
32087 you are developing a JIT compiler, then the interface is documented in the rest
32088 of this chapter. At this time, the only known client of this interface is the
32091 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32092 JIT compiler communicates with @value{GDBN} by writing data into a global
32093 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32094 attaches, it reads a linked list of symbol files from the global variable to
32095 find existing code, and puts a breakpoint in the function so that it can find
32096 out about additional code.
32099 * Declarations:: Relevant C struct declarations
32100 * Registering Code:: Steps to register code
32101 * Unregistering Code:: Steps to unregister code
32102 * Custom Debug Info:: Emit debug information in a custom format
32106 @section JIT Declarations
32108 These are the relevant struct declarations that a C program should include to
32109 implement the interface:
32119 struct jit_code_entry
32121 struct jit_code_entry *next_entry;
32122 struct jit_code_entry *prev_entry;
32123 const char *symfile_addr;
32124 uint64_t symfile_size;
32127 struct jit_descriptor
32130 /* This type should be jit_actions_t, but we use uint32_t
32131 to be explicit about the bitwidth. */
32132 uint32_t action_flag;
32133 struct jit_code_entry *relevant_entry;
32134 struct jit_code_entry *first_entry;
32137 /* GDB puts a breakpoint in this function. */
32138 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32140 /* Make sure to specify the version statically, because the
32141 debugger may check the version before we can set it. */
32142 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32145 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32146 modifications to this global data properly, which can easily be done by putting
32147 a global mutex around modifications to these structures.
32149 @node Registering Code
32150 @section Registering Code
32152 To register code with @value{GDBN}, the JIT should follow this protocol:
32156 Generate an object file in memory with symbols and other desired debug
32157 information. The file must include the virtual addresses of the sections.
32160 Create a code entry for the file, which gives the start and size of the symbol
32164 Add it to the linked list in the JIT descriptor.
32167 Point the relevant_entry field of the descriptor at the entry.
32170 Set @code{action_flag} to @code{JIT_REGISTER} and call
32171 @code{__jit_debug_register_code}.
32174 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32175 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32176 new code. However, the linked list must still be maintained in order to allow
32177 @value{GDBN} to attach to a running process and still find the symbol files.
32179 @node Unregistering Code
32180 @section Unregistering Code
32182 If code is freed, then the JIT should use the following protocol:
32186 Remove the code entry corresponding to the code from the linked list.
32189 Point the @code{relevant_entry} field of the descriptor at the code entry.
32192 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32193 @code{__jit_debug_register_code}.
32196 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32197 and the JIT will leak the memory used for the associated symbol files.
32199 @node Custom Debug Info
32200 @section Custom Debug Info
32201 @cindex custom JIT debug info
32202 @cindex JIT debug info reader
32204 Generating debug information in platform-native file formats (like ELF
32205 or COFF) may be an overkill for JIT compilers; especially if all the
32206 debug info is used for is displaying a meaningful backtrace. The
32207 issue can be resolved by having the JIT writers decide on a debug info
32208 format and also provide a reader that parses the debug info generated
32209 by the JIT compiler. This section gives a brief overview on writing
32210 such a parser. More specific details can be found in the source file
32211 @file{gdb/jit-reader.in}, which is also installed as a header at
32212 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32214 The reader is implemented as a shared object (so this functionality is
32215 not available on platforms which don't allow loading shared objects at
32216 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32217 @code{jit-reader-unload} are provided, to be used to load and unload
32218 the readers from a preconfigured directory. Once loaded, the shared
32219 object is used the parse the debug information emitted by the JIT
32223 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32224 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32227 @node Using JIT Debug Info Readers
32228 @subsection Using JIT Debug Info Readers
32229 @kindex jit-reader-load
32230 @kindex jit-reader-unload
32232 Readers can be loaded and unloaded using the @code{jit-reader-load}
32233 and @code{jit-reader-unload} commands.
32236 @item jit-reader-load @var{reader}
32237 Load the JIT reader named @var{reader}, which is a shared
32238 object specified as either an absolute or a relative file name. In
32239 the latter case, @value{GDBN} will try to load the reader from a
32240 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32241 system (here @var{libdir} is the system library directory, often
32242 @file{/usr/local/lib}).
32244 Only one reader can be active at a time; trying to load a second
32245 reader when one is already loaded will result in @value{GDBN}
32246 reporting an error. A new JIT reader can be loaded by first unloading
32247 the current one using @code{jit-reader-unload} and then invoking
32248 @code{jit-reader-load}.
32250 @item jit-reader-unload
32251 Unload the currently loaded JIT reader.
32255 @node Writing JIT Debug Info Readers
32256 @subsection Writing JIT Debug Info Readers
32257 @cindex writing JIT debug info readers
32259 As mentioned, a reader is essentially a shared object conforming to a
32260 certain ABI. This ABI is described in @file{jit-reader.h}.
32262 @file{jit-reader.h} defines the structures, macros and functions
32263 required to write a reader. It is installed (along with
32264 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32265 the system include directory.
32267 Readers need to be released under a GPL compatible license. A reader
32268 can be declared as released under such a license by placing the macro
32269 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32271 The entry point for readers is the symbol @code{gdb_init_reader},
32272 which is expected to be a function with the prototype
32274 @findex gdb_init_reader
32276 extern struct gdb_reader_funcs *gdb_init_reader (void);
32279 @cindex @code{struct gdb_reader_funcs}
32281 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32282 functions. These functions are executed to read the debug info
32283 generated by the JIT compiler (@code{read}), to unwind stack frames
32284 (@code{unwind}) and to create canonical frame IDs
32285 (@code{get_Frame_id}). It also has a callback that is called when the
32286 reader is being unloaded (@code{destroy}). The struct looks like this
32289 struct gdb_reader_funcs
32291 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32292 int reader_version;
32294 /* For use by the reader. */
32297 gdb_read_debug_info *read;
32298 gdb_unwind_frame *unwind;
32299 gdb_get_frame_id *get_frame_id;
32300 gdb_destroy_reader *destroy;
32304 @cindex @code{struct gdb_symbol_callbacks}
32305 @cindex @code{struct gdb_unwind_callbacks}
32307 The callbacks are provided with another set of callbacks by
32308 @value{GDBN} to do their job. For @code{read}, these callbacks are
32309 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32310 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32311 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32312 files and new symbol tables inside those object files. @code{struct
32313 gdb_unwind_callbacks} has callbacks to read registers off the current
32314 frame and to write out the values of the registers in the previous
32315 frame. Both have a callback (@code{target_read}) to read bytes off the
32316 target's address space.
32318 @node In-Process Agent
32319 @chapter In-Process Agent
32320 @cindex debugging agent
32321 The traditional debugging model is conceptually low-speed, but works fine,
32322 because most bugs can be reproduced in debugging-mode execution. However,
32323 as multi-core or many-core processors are becoming mainstream, and
32324 multi-threaded programs become more and more popular, there should be more
32325 and more bugs that only manifest themselves at normal-mode execution, for
32326 example, thread races, because debugger's interference with the program's
32327 timing may conceal the bugs. On the other hand, in some applications,
32328 it is not feasible for the debugger to interrupt the program's execution
32329 long enough for the developer to learn anything helpful about its behavior.
32330 If the program's correctness depends on its real-time behavior, delays
32331 introduced by a debugger might cause the program to fail, even when the
32332 code itself is correct. It is useful to be able to observe the program's
32333 behavior without interrupting it.
32335 Therefore, traditional debugging model is too intrusive to reproduce
32336 some bugs. In order to reduce the interference with the program, we can
32337 reduce the number of operations performed by debugger. The
32338 @dfn{In-Process Agent}, a shared library, is running within the same
32339 process with inferior, and is able to perform some debugging operations
32340 itself. As a result, debugger is only involved when necessary, and
32341 performance of debugging can be improved accordingly. Note that
32342 interference with program can be reduced but can't be removed completely,
32343 because the in-process agent will still stop or slow down the program.
32345 The in-process agent can interpret and execute Agent Expressions
32346 (@pxref{Agent Expressions}) during performing debugging operations. The
32347 agent expressions can be used for different purposes, such as collecting
32348 data in tracepoints, and condition evaluation in breakpoints.
32350 @anchor{Control Agent}
32351 You can control whether the in-process agent is used as an aid for
32352 debugging with the following commands:
32355 @kindex set agent on
32357 Causes the in-process agent to perform some operations on behalf of the
32358 debugger. Just which operations requested by the user will be done
32359 by the in-process agent depends on the its capabilities. For example,
32360 if you request to evaluate breakpoint conditions in the in-process agent,
32361 and the in-process agent has such capability as well, then breakpoint
32362 conditions will be evaluated in the in-process agent.
32364 @kindex set agent off
32365 @item set agent off
32366 Disables execution of debugging operations by the in-process agent. All
32367 of the operations will be performed by @value{GDBN}.
32371 Display the current setting of execution of debugging operations by
32372 the in-process agent.
32376 * In-Process Agent Protocol::
32379 @node In-Process Agent Protocol
32380 @section In-Process Agent Protocol
32381 @cindex in-process agent protocol
32383 The in-process agent is able to communicate with both @value{GDBN} and
32384 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32385 used for communications between @value{GDBN} or GDBserver and the IPA.
32386 In general, @value{GDBN} or GDBserver sends commands
32387 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32388 in-process agent replies back with the return result of the command, or
32389 some other information. The data sent to in-process agent is composed
32390 of primitive data types, such as 4-byte or 8-byte type, and composite
32391 types, which are called objects (@pxref{IPA Protocol Objects}).
32394 * IPA Protocol Objects::
32395 * IPA Protocol Commands::
32398 @node IPA Protocol Objects
32399 @subsection IPA Protocol Objects
32400 @cindex ipa protocol objects
32402 The commands sent to and results received from agent may contain some
32403 complex data types called @dfn{objects}.
32405 The in-process agent is running on the same machine with @value{GDBN}
32406 or GDBserver, so it doesn't have to handle as much differences between
32407 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32408 However, there are still some differences of two ends in two processes:
32412 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32413 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32415 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32416 GDBserver is compiled with one, and in-process agent is compiled with
32420 Here are the IPA Protocol Objects:
32424 agent expression object. It represents an agent expression
32425 (@pxref{Agent Expressions}).
32426 @anchor{agent expression object}
32428 tracepoint action object. It represents a tracepoint action
32429 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32430 memory, static trace data and to evaluate expression.
32431 @anchor{tracepoint action object}
32433 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32434 @anchor{tracepoint object}
32438 The following table describes important attributes of each IPA protocol
32441 @multitable @columnfractions .30 .20 .50
32442 @headitem Name @tab Size @tab Description
32443 @item @emph{agent expression object} @tab @tab
32444 @item length @tab 4 @tab length of bytes code
32445 @item byte code @tab @var{length} @tab contents of byte code
32446 @item @emph{tracepoint action for collecting memory} @tab @tab
32447 @item 'M' @tab 1 @tab type of tracepoint action
32448 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32449 address of the lowest byte to collect, otherwise @var{addr} is the offset
32450 of @var{basereg} for memory collecting.
32451 @item len @tab 8 @tab length of memory for collecting
32452 @item basereg @tab 4 @tab the register number containing the starting
32453 memory address for collecting.
32454 @item @emph{tracepoint action for collecting registers} @tab @tab
32455 @item 'R' @tab 1 @tab type of tracepoint action
32456 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32457 @item 'L' @tab 1 @tab type of tracepoint action
32458 @item @emph{tracepoint action for expression evaluation} @tab @tab
32459 @item 'X' @tab 1 @tab type of tracepoint action
32460 @item agent expression @tab length of @tab @ref{agent expression object}
32461 @item @emph{tracepoint object} @tab @tab
32462 @item number @tab 4 @tab number of tracepoint
32463 @item address @tab 8 @tab address of tracepoint inserted on
32464 @item type @tab 4 @tab type of tracepoint
32465 @item enabled @tab 1 @tab enable or disable of tracepoint
32466 @item step_count @tab 8 @tab step
32467 @item pass_count @tab 8 @tab pass
32468 @item numactions @tab 4 @tab number of tracepoint actions
32469 @item hit count @tab 8 @tab hit count
32470 @item trace frame usage @tab 8 @tab trace frame usage
32471 @item compiled_cond @tab 8 @tab compiled condition
32472 @item orig_size @tab 8 @tab orig size
32473 @item condition @tab 4 if condition is NULL otherwise length of
32474 @ref{agent expression object}
32475 @tab zero if condition is NULL, otherwise is
32476 @ref{agent expression object}
32477 @item actions @tab variable
32478 @tab numactions number of @ref{tracepoint action object}
32481 @node IPA Protocol Commands
32482 @subsection IPA Protocol Commands
32483 @cindex ipa protocol commands
32485 The spaces in each command are delimiters to ease reading this commands
32486 specification. They don't exist in real commands.
32490 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32491 Installs a new fast tracepoint described by @var{tracepoint_object}
32492 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32493 head of @dfn{jumppad}, which is used to jump to data collection routine
32498 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32499 @var{target_address} is address of tracepoint in the inferior.
32500 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32501 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32502 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32503 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32510 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32511 is about to kill inferiors.
32519 @item probe_marker_at:@var{address}
32520 Asks in-process agent to probe the marker at @var{address}.
32527 @item unprobe_marker_at:@var{address}
32528 Asks in-process agent to unprobe the marker at @var{address}.
32532 @chapter Reporting Bugs in @value{GDBN}
32533 @cindex bugs in @value{GDBN}
32534 @cindex reporting bugs in @value{GDBN}
32536 Your bug reports play an essential role in making @value{GDBN} reliable.
32538 Reporting a bug may help you by bringing a solution to your problem, or it
32539 may not. But in any case the principal function of a bug report is to help
32540 the entire community by making the next version of @value{GDBN} work better. Bug
32541 reports are your contribution to the maintenance of @value{GDBN}.
32543 In order for a bug report to serve its purpose, you must include the
32544 information that enables us to fix the bug.
32547 * Bug Criteria:: Have you found a bug?
32548 * Bug Reporting:: How to report bugs
32552 @section Have You Found a Bug?
32553 @cindex bug criteria
32555 If you are not sure whether you have found a bug, here are some guidelines:
32558 @cindex fatal signal
32559 @cindex debugger crash
32560 @cindex crash of debugger
32562 If the debugger gets a fatal signal, for any input whatever, that is a
32563 @value{GDBN} bug. Reliable debuggers never crash.
32565 @cindex error on valid input
32567 If @value{GDBN} produces an error message for valid input, that is a
32568 bug. (Note that if you're cross debugging, the problem may also be
32569 somewhere in the connection to the target.)
32571 @cindex invalid input
32573 If @value{GDBN} does not produce an error message for invalid input,
32574 that is a bug. However, you should note that your idea of
32575 ``invalid input'' might be our idea of ``an extension'' or ``support
32576 for traditional practice''.
32579 If you are an experienced user of debugging tools, your suggestions
32580 for improvement of @value{GDBN} are welcome in any case.
32583 @node Bug Reporting
32584 @section How to Report Bugs
32585 @cindex bug reports
32586 @cindex @value{GDBN} bugs, reporting
32588 A number of companies and individuals offer support for @sc{gnu} products.
32589 If you obtained @value{GDBN} from a support organization, we recommend you
32590 contact that organization first.
32592 You can find contact information for many support companies and
32593 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32595 @c should add a web page ref...
32598 @ifset BUGURL_DEFAULT
32599 In any event, we also recommend that you submit bug reports for
32600 @value{GDBN}. The preferred method is to submit them directly using
32601 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32602 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32605 @strong{Do not send bug reports to @samp{info-gdb}, or to
32606 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32607 not want to receive bug reports. Those that do have arranged to receive
32610 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32611 serves as a repeater. The mailing list and the newsgroup carry exactly
32612 the same messages. Often people think of posting bug reports to the
32613 newsgroup instead of mailing them. This appears to work, but it has one
32614 problem which can be crucial: a newsgroup posting often lacks a mail
32615 path back to the sender. Thus, if we need to ask for more information,
32616 we may be unable to reach you. For this reason, it is better to send
32617 bug reports to the mailing list.
32619 @ifclear BUGURL_DEFAULT
32620 In any event, we also recommend that you submit bug reports for
32621 @value{GDBN} to @value{BUGURL}.
32625 The fundamental principle of reporting bugs usefully is this:
32626 @strong{report all the facts}. If you are not sure whether to state a
32627 fact or leave it out, state it!
32629 Often people omit facts because they think they know what causes the
32630 problem and assume that some details do not matter. Thus, you might
32631 assume that the name of the variable you use in an example does not matter.
32632 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32633 stray memory reference which happens to fetch from the location where that
32634 name is stored in memory; perhaps, if the name were different, the contents
32635 of that location would fool the debugger into doing the right thing despite
32636 the bug. Play it safe and give a specific, complete example. That is the
32637 easiest thing for you to do, and the most helpful.
32639 Keep in mind that the purpose of a bug report is to enable us to fix the
32640 bug. It may be that the bug has been reported previously, but neither
32641 you nor we can know that unless your bug report is complete and
32644 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32645 bell?'' Those bug reports are useless, and we urge everyone to
32646 @emph{refuse to respond to them} except to chide the sender to report
32649 To enable us to fix the bug, you should include all these things:
32653 The version of @value{GDBN}. @value{GDBN} announces it if you start
32654 with no arguments; you can also print it at any time using @code{show
32657 Without this, we will not know whether there is any point in looking for
32658 the bug in the current version of @value{GDBN}.
32661 The type of machine you are using, and the operating system name and
32665 The details of the @value{GDBN} build-time configuration.
32666 @value{GDBN} shows these details if you invoke it with the
32667 @option{--configuration} command-line option, or if you type
32668 @code{show configuration} at @value{GDBN}'s prompt.
32671 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32672 ``@value{GCC}--2.8.1''.
32675 What compiler (and its version) was used to compile the program you are
32676 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32677 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32678 to get this information; for other compilers, see the documentation for
32682 The command arguments you gave the compiler to compile your example and
32683 observe the bug. For example, did you use @samp{-O}? To guarantee
32684 you will not omit something important, list them all. A copy of the
32685 Makefile (or the output from make) is sufficient.
32687 If we were to try to guess the arguments, we would probably guess wrong
32688 and then we might not encounter the bug.
32691 A complete input script, and all necessary source files, that will
32695 A description of what behavior you observe that you believe is
32696 incorrect. For example, ``It gets a fatal signal.''
32698 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32699 will certainly notice it. But if the bug is incorrect output, we might
32700 not notice unless it is glaringly wrong. You might as well not give us
32701 a chance to make a mistake.
32703 Even if the problem you experience is a fatal signal, you should still
32704 say so explicitly. Suppose something strange is going on, such as, your
32705 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32706 the C library on your system. (This has happened!) Your copy might
32707 crash and ours would not. If you told us to expect a crash, then when
32708 ours fails to crash, we would know that the bug was not happening for
32709 us. If you had not told us to expect a crash, then we would not be able
32710 to draw any conclusion from our observations.
32713 @cindex recording a session script
32714 To collect all this information, you can use a session recording program
32715 such as @command{script}, which is available on many Unix systems.
32716 Just run your @value{GDBN} session inside @command{script} and then
32717 include the @file{typescript} file with your bug report.
32719 Another way to record a @value{GDBN} session is to run @value{GDBN}
32720 inside Emacs and then save the entire buffer to a file.
32723 If you wish to suggest changes to the @value{GDBN} source, send us context
32724 diffs. If you even discuss something in the @value{GDBN} source, refer to
32725 it by context, not by line number.
32727 The line numbers in our development sources will not match those in your
32728 sources. Your line numbers would convey no useful information to us.
32732 Here are some things that are not necessary:
32736 A description of the envelope of the bug.
32738 Often people who encounter a bug spend a lot of time investigating
32739 which changes to the input file will make the bug go away and which
32740 changes will not affect it.
32742 This is often time consuming and not very useful, because the way we
32743 will find the bug is by running a single example under the debugger
32744 with breakpoints, not by pure deduction from a series of examples.
32745 We recommend that you save your time for something else.
32747 Of course, if you can find a simpler example to report @emph{instead}
32748 of the original one, that is a convenience for us. Errors in the
32749 output will be easier to spot, running under the debugger will take
32750 less time, and so on.
32752 However, simplification is not vital; if you do not want to do this,
32753 report the bug anyway and send us the entire test case you used.
32756 A patch for the bug.
32758 A patch for the bug does help us if it is a good one. But do not omit
32759 the necessary information, such as the test case, on the assumption that
32760 a patch is all we need. We might see problems with your patch and decide
32761 to fix the problem another way, or we might not understand it at all.
32763 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32764 construct an example that will make the program follow a certain path
32765 through the code. If you do not send us the example, we will not be able
32766 to construct one, so we will not be able to verify that the bug is fixed.
32768 And if we cannot understand what bug you are trying to fix, or why your
32769 patch should be an improvement, we will not install it. A test case will
32770 help us to understand.
32773 A guess about what the bug is or what it depends on.
32775 Such guesses are usually wrong. Even we cannot guess right about such
32776 things without first using the debugger to find the facts.
32779 @c The readline documentation is distributed with the readline code
32780 @c and consists of the two following files:
32783 @c Use -I with makeinfo to point to the appropriate directory,
32784 @c environment var TEXINPUTS with TeX.
32785 @ifclear SYSTEM_READLINE
32786 @include rluser.texi
32787 @include hsuser.texi
32791 @appendix In Memoriam
32793 The @value{GDBN} project mourns the loss of the following long-time
32798 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32799 to Free Software in general. Outside of @value{GDBN}, he was known in
32800 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32802 @item Michael Snyder
32803 Michael was one of the Global Maintainers of the @value{GDBN} project,
32804 with contributions recorded as early as 1996, until 2011. In addition
32805 to his day to day participation, he was a large driving force behind
32806 adding Reverse Debugging to @value{GDBN}.
32809 Beyond their technical contributions to the project, they were also
32810 enjoyable members of the Free Software Community. We will miss them.
32812 @node Formatting Documentation
32813 @appendix Formatting Documentation
32815 @cindex @value{GDBN} reference card
32816 @cindex reference card
32817 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32818 for printing with PostScript or Ghostscript, in the @file{gdb}
32819 subdirectory of the main source directory@footnote{In
32820 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32821 release.}. If you can use PostScript or Ghostscript with your printer,
32822 you can print the reference card immediately with @file{refcard.ps}.
32824 The release also includes the source for the reference card. You
32825 can format it, using @TeX{}, by typing:
32831 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32832 mode on US ``letter'' size paper;
32833 that is, on a sheet 11 inches wide by 8.5 inches
32834 high. You will need to specify this form of printing as an option to
32835 your @sc{dvi} output program.
32837 @cindex documentation
32839 All the documentation for @value{GDBN} comes as part of the machine-readable
32840 distribution. The documentation is written in Texinfo format, which is
32841 a documentation system that uses a single source file to produce both
32842 on-line information and a printed manual. You can use one of the Info
32843 formatting commands to create the on-line version of the documentation
32844 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32846 @value{GDBN} includes an already formatted copy of the on-line Info
32847 version of this manual in the @file{gdb} subdirectory. The main Info
32848 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32849 subordinate files matching @samp{gdb.info*} in the same directory. If
32850 necessary, you can print out these files, or read them with any editor;
32851 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32852 Emacs or the standalone @code{info} program, available as part of the
32853 @sc{gnu} Texinfo distribution.
32855 If you want to format these Info files yourself, you need one of the
32856 Info formatting programs, such as @code{texinfo-format-buffer} or
32859 If you have @code{makeinfo} installed, and are in the top level
32860 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32861 version @value{GDBVN}), you can make the Info file by typing:
32868 If you want to typeset and print copies of this manual, you need @TeX{},
32869 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32870 Texinfo definitions file.
32872 @TeX{} is a typesetting program; it does not print files directly, but
32873 produces output files called @sc{dvi} files. To print a typeset
32874 document, you need a program to print @sc{dvi} files. If your system
32875 has @TeX{} installed, chances are it has such a program. The precise
32876 command to use depends on your system; @kbd{lpr -d} is common; another
32877 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32878 require a file name without any extension or a @samp{.dvi} extension.
32880 @TeX{} also requires a macro definitions file called
32881 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32882 written in Texinfo format. On its own, @TeX{} cannot either read or
32883 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32884 and is located in the @file{gdb-@var{version-number}/texinfo}
32887 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32888 typeset and print this manual. First switch to the @file{gdb}
32889 subdirectory of the main source directory (for example, to
32890 @file{gdb-@value{GDBVN}/gdb}) and type:
32896 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32898 @node Installing GDB
32899 @appendix Installing @value{GDBN}
32900 @cindex installation
32903 * Requirements:: Requirements for building @value{GDBN}
32904 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32905 * Separate Objdir:: Compiling @value{GDBN} in another directory
32906 * Config Names:: Specifying names for hosts and targets
32907 * Configure Options:: Summary of options for configure
32908 * System-wide configuration:: Having a system-wide init file
32912 @section Requirements for Building @value{GDBN}
32913 @cindex building @value{GDBN}, requirements for
32915 Building @value{GDBN} requires various tools and packages to be available.
32916 Other packages will be used only if they are found.
32918 @heading Tools/Packages Necessary for Building @value{GDBN}
32920 @item ISO C90 compiler
32921 @value{GDBN} is written in ISO C90. It should be buildable with any
32922 working C90 compiler, e.g.@: GCC.
32926 @heading Tools/Packages Optional for Building @value{GDBN}
32930 @value{GDBN} can use the Expat XML parsing library. This library may be
32931 included with your operating system distribution; if it is not, you
32932 can get the latest version from @url{http://expat.sourceforge.net}.
32933 The @file{configure} script will search for this library in several
32934 standard locations; if it is installed in an unusual path, you can
32935 use the @option{--with-libexpat-prefix} option to specify its location.
32941 Remote protocol memory maps (@pxref{Memory Map Format})
32943 Target descriptions (@pxref{Target Descriptions})
32945 Remote shared library lists (@xref{Library List Format},
32946 or alternatively @pxref{Library List Format for SVR4 Targets})
32948 MS-Windows shared libraries (@pxref{Shared Libraries})
32950 Traceframe info (@pxref{Traceframe Info Format})
32952 Branch trace (@pxref{Branch Trace Format})
32956 @cindex compressed debug sections
32957 @value{GDBN} will use the @samp{zlib} library, if available, to read
32958 compressed debug sections. Some linkers, such as GNU gold, are capable
32959 of producing binaries with compressed debug sections. If @value{GDBN}
32960 is compiled with @samp{zlib}, it will be able to read the debug
32961 information in such binaries.
32963 The @samp{zlib} library is likely included with your operating system
32964 distribution; if it is not, you can get the latest version from
32965 @url{http://zlib.net}.
32968 @value{GDBN}'s features related to character sets (@pxref{Character
32969 Sets}) require a functioning @code{iconv} implementation. If you are
32970 on a GNU system, then this is provided by the GNU C Library. Some
32971 other systems also provide a working @code{iconv}.
32973 If @value{GDBN} is using the @code{iconv} program which is installed
32974 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32975 This is done with @option{--with-iconv-bin} which specifies the
32976 directory that contains the @code{iconv} program.
32978 On systems without @code{iconv}, you can install GNU Libiconv. If you
32979 have previously installed Libiconv, you can use the
32980 @option{--with-libiconv-prefix} option to configure.
32982 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32983 arrange to build Libiconv if a directory named @file{libiconv} appears
32984 in the top-most source directory. If Libiconv is built this way, and
32985 if the operating system does not provide a suitable @code{iconv}
32986 implementation, then the just-built library will automatically be used
32987 by @value{GDBN}. One easy way to set this up is to download GNU
32988 Libiconv, unpack it, and then rename the directory holding the
32989 Libiconv source code to @samp{libiconv}.
32992 @node Running Configure
32993 @section Invoking the @value{GDBN} @file{configure} Script
32994 @cindex configuring @value{GDBN}
32995 @value{GDBN} comes with a @file{configure} script that automates the process
32996 of preparing @value{GDBN} for installation; you can then use @code{make} to
32997 build the @code{gdb} program.
32999 @c irrelevant in info file; it's as current as the code it lives with.
33000 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33001 look at the @file{README} file in the sources; we may have improved the
33002 installation procedures since publishing this manual.}
33005 The @value{GDBN} distribution includes all the source code you need for
33006 @value{GDBN} in a single directory, whose name is usually composed by
33007 appending the version number to @samp{gdb}.
33009 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33010 @file{gdb-@value{GDBVN}} directory. That directory contains:
33013 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33014 script for configuring @value{GDBN} and all its supporting libraries
33016 @item gdb-@value{GDBVN}/gdb
33017 the source specific to @value{GDBN} itself
33019 @item gdb-@value{GDBVN}/bfd
33020 source for the Binary File Descriptor library
33022 @item gdb-@value{GDBVN}/include
33023 @sc{gnu} include files
33025 @item gdb-@value{GDBVN}/libiberty
33026 source for the @samp{-liberty} free software library
33028 @item gdb-@value{GDBVN}/opcodes
33029 source for the library of opcode tables and disassemblers
33031 @item gdb-@value{GDBVN}/readline
33032 source for the @sc{gnu} command-line interface
33034 @item gdb-@value{GDBVN}/glob
33035 source for the @sc{gnu} filename pattern-matching subroutine
33037 @item gdb-@value{GDBVN}/mmalloc
33038 source for the @sc{gnu} memory-mapped malloc package
33041 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33042 from the @file{gdb-@var{version-number}} source directory, which in
33043 this example is the @file{gdb-@value{GDBVN}} directory.
33045 First switch to the @file{gdb-@var{version-number}} source directory
33046 if you are not already in it; then run @file{configure}. Pass the
33047 identifier for the platform on which @value{GDBN} will run as an
33053 cd gdb-@value{GDBVN}
33054 ./configure @var{host}
33059 where @var{host} is an identifier such as @samp{sun4} or
33060 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33061 (You can often leave off @var{host}; @file{configure} tries to guess the
33062 correct value by examining your system.)
33064 Running @samp{configure @var{host}} and then running @code{make} builds the
33065 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33066 libraries, then @code{gdb} itself. The configured source files, and the
33067 binaries, are left in the corresponding source directories.
33070 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33071 system does not recognize this automatically when you run a different
33072 shell, you may need to run @code{sh} on it explicitly:
33075 sh configure @var{host}
33078 If you run @file{configure} from a directory that contains source
33079 directories for multiple libraries or programs, such as the
33080 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33082 creates configuration files for every directory level underneath (unless
33083 you tell it not to, with the @samp{--norecursion} option).
33085 You should run the @file{configure} script from the top directory in the
33086 source tree, the @file{gdb-@var{version-number}} directory. If you run
33087 @file{configure} from one of the subdirectories, you will configure only
33088 that subdirectory. That is usually not what you want. In particular,
33089 if you run the first @file{configure} from the @file{gdb} subdirectory
33090 of the @file{gdb-@var{version-number}} directory, you will omit the
33091 configuration of @file{bfd}, @file{readline}, and other sibling
33092 directories of the @file{gdb} subdirectory. This leads to build errors
33093 about missing include files such as @file{bfd/bfd.h}.
33095 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33096 However, you should make sure that the shell on your path (named by
33097 the @samp{SHELL} environment variable) is publicly readable. Remember
33098 that @value{GDBN} uses the shell to start your program---some systems refuse to
33099 let @value{GDBN} debug child processes whose programs are not readable.
33101 @node Separate Objdir
33102 @section Compiling @value{GDBN} in Another Directory
33104 If you want to run @value{GDBN} versions for several host or target machines,
33105 you need a different @code{gdb} compiled for each combination of
33106 host and target. @file{configure} is designed to make this easy by
33107 allowing you to generate each configuration in a separate subdirectory,
33108 rather than in the source directory. If your @code{make} program
33109 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33110 @code{make} in each of these directories builds the @code{gdb}
33111 program specified there.
33113 To build @code{gdb} in a separate directory, run @file{configure}
33114 with the @samp{--srcdir} option to specify where to find the source.
33115 (You also need to specify a path to find @file{configure}
33116 itself from your working directory. If the path to @file{configure}
33117 would be the same as the argument to @samp{--srcdir}, you can leave out
33118 the @samp{--srcdir} option; it is assumed.)
33120 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33121 separate directory for a Sun 4 like this:
33125 cd gdb-@value{GDBVN}
33128 ../gdb-@value{GDBVN}/configure sun4
33133 When @file{configure} builds a configuration using a remote source
33134 directory, it creates a tree for the binaries with the same structure
33135 (and using the same names) as the tree under the source directory. In
33136 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33137 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33138 @file{gdb-sun4/gdb}.
33140 Make sure that your path to the @file{configure} script has just one
33141 instance of @file{gdb} in it. If your path to @file{configure} looks
33142 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33143 one subdirectory of @value{GDBN}, not the whole package. This leads to
33144 build errors about missing include files such as @file{bfd/bfd.h}.
33146 One popular reason to build several @value{GDBN} configurations in separate
33147 directories is to configure @value{GDBN} for cross-compiling (where
33148 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33149 programs that run on another machine---the @dfn{target}).
33150 You specify a cross-debugging target by
33151 giving the @samp{--target=@var{target}} option to @file{configure}.
33153 When you run @code{make} to build a program or library, you must run
33154 it in a configured directory---whatever directory you were in when you
33155 called @file{configure} (or one of its subdirectories).
33157 The @code{Makefile} that @file{configure} generates in each source
33158 directory also runs recursively. If you type @code{make} in a source
33159 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33160 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33161 will build all the required libraries, and then build GDB.
33163 When you have multiple hosts or targets configured in separate
33164 directories, you can run @code{make} on them in parallel (for example,
33165 if they are NFS-mounted on each of the hosts); they will not interfere
33169 @section Specifying Names for Hosts and Targets
33171 The specifications used for hosts and targets in the @file{configure}
33172 script are based on a three-part naming scheme, but some short predefined
33173 aliases are also supported. The full naming scheme encodes three pieces
33174 of information in the following pattern:
33177 @var{architecture}-@var{vendor}-@var{os}
33180 For example, you can use the alias @code{sun4} as a @var{host} argument,
33181 or as the value for @var{target} in a @code{--target=@var{target}}
33182 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33184 The @file{configure} script accompanying @value{GDBN} does not provide
33185 any query facility to list all supported host and target names or
33186 aliases. @file{configure} calls the Bourne shell script
33187 @code{config.sub} to map abbreviations to full names; you can read the
33188 script, if you wish, or you can use it to test your guesses on
33189 abbreviations---for example:
33192 % sh config.sub i386-linux
33194 % sh config.sub alpha-linux
33195 alpha-unknown-linux-gnu
33196 % sh config.sub hp9k700
33198 % sh config.sub sun4
33199 sparc-sun-sunos4.1.1
33200 % sh config.sub sun3
33201 m68k-sun-sunos4.1.1
33202 % sh config.sub i986v
33203 Invalid configuration `i986v': machine `i986v' not recognized
33207 @code{config.sub} is also distributed in the @value{GDBN} source
33208 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33210 @node Configure Options
33211 @section @file{configure} Options
33213 Here is a summary of the @file{configure} options and arguments that
33214 are most often useful for building @value{GDBN}. @file{configure} also has
33215 several other options not listed here. @inforef{What Configure
33216 Does,,configure.info}, for a full explanation of @file{configure}.
33219 configure @r{[}--help@r{]}
33220 @r{[}--prefix=@var{dir}@r{]}
33221 @r{[}--exec-prefix=@var{dir}@r{]}
33222 @r{[}--srcdir=@var{dirname}@r{]}
33223 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33224 @r{[}--target=@var{target}@r{]}
33229 You may introduce options with a single @samp{-} rather than
33230 @samp{--} if you prefer; but you may abbreviate option names if you use
33235 Display a quick summary of how to invoke @file{configure}.
33237 @item --prefix=@var{dir}
33238 Configure the source to install programs and files under directory
33241 @item --exec-prefix=@var{dir}
33242 Configure the source to install programs under directory
33245 @c avoid splitting the warning from the explanation:
33247 @item --srcdir=@var{dirname}
33248 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33249 @code{make} that implements the @code{VPATH} feature.}@*
33250 Use this option to make configurations in directories separate from the
33251 @value{GDBN} source directories. Among other things, you can use this to
33252 build (or maintain) several configurations simultaneously, in separate
33253 directories. @file{configure} writes configuration-specific files in
33254 the current directory, but arranges for them to use the source in the
33255 directory @var{dirname}. @file{configure} creates directories under
33256 the working directory in parallel to the source directories below
33259 @item --norecursion
33260 Configure only the directory level where @file{configure} is executed; do not
33261 propagate configuration to subdirectories.
33263 @item --target=@var{target}
33264 Configure @value{GDBN} for cross-debugging programs running on the specified
33265 @var{target}. Without this option, @value{GDBN} is configured to debug
33266 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33268 There is no convenient way to generate a list of all available targets.
33270 @item @var{host} @dots{}
33271 Configure @value{GDBN} to run on the specified @var{host}.
33273 There is no convenient way to generate a list of all available hosts.
33276 There are many other options available as well, but they are generally
33277 needed for special purposes only.
33279 @node System-wide configuration
33280 @section System-wide configuration and settings
33281 @cindex system-wide init file
33283 @value{GDBN} can be configured to have a system-wide init file;
33284 this file will be read and executed at startup (@pxref{Startup, , What
33285 @value{GDBN} does during startup}).
33287 Here is the corresponding configure option:
33290 @item --with-system-gdbinit=@var{file}
33291 Specify that the default location of the system-wide init file is
33295 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33296 it may be subject to relocation. Two possible cases:
33300 If the default location of this init file contains @file{$prefix},
33301 it will be subject to relocation. Suppose that the configure options
33302 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33303 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33304 init file is looked for as @file{$install/etc/gdbinit} instead of
33305 @file{$prefix/etc/gdbinit}.
33308 By contrast, if the default location does not contain the prefix,
33309 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33310 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33311 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33312 wherever @value{GDBN} is installed.
33315 If the configured location of the system-wide init file (as given by the
33316 @option{--with-system-gdbinit} option at configure time) is in the
33317 data-directory (as specified by @option{--with-gdb-datadir} at configure
33318 time) or in one of its subdirectories, then @value{GDBN} will look for the
33319 system-wide init file in the directory specified by the
33320 @option{--data-directory} command-line option.
33321 Note that the system-wide init file is only read once, during @value{GDBN}
33322 initialization. If the data-directory is changed after @value{GDBN} has
33323 started with the @code{set data-directory} command, the file will not be
33327 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33330 @node System-wide Configuration Scripts
33331 @subsection Installed System-wide Configuration Scripts
33332 @cindex system-wide configuration scripts
33334 The @file{system-gdbinit} directory, located inside the data-directory
33335 (as specified by @option{--with-gdb-datadir} at configure time) contains
33336 a number of scripts which can be used as system-wide init files. To
33337 automatically source those scripts at startup, @value{GDBN} should be
33338 configured with @option{--with-system-gdbinit}. Otherwise, any user
33339 should be able to source them by hand as needed.
33341 The following scripts are currently available:
33344 @item @file{elinos.py}
33346 @cindex ELinOS system-wide configuration script
33347 This script is useful when debugging a program on an ELinOS target.
33348 It takes advantage of the environment variables defined in a standard
33349 ELinOS environment in order to determine the location of the system
33350 shared libraries, and then sets the @samp{solib-absolute-prefix}
33351 and @samp{solib-search-path} variables appropriately.
33353 @item @file{wrs-linux.py}
33354 @pindex wrs-linux.py
33355 @cindex Wind River Linux system-wide configuration script
33356 This script is useful when debugging a program on a target running
33357 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33358 the host-side sysroot used by the target system.
33362 @node Maintenance Commands
33363 @appendix Maintenance Commands
33364 @cindex maintenance commands
33365 @cindex internal commands
33367 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33368 includes a number of commands intended for @value{GDBN} developers,
33369 that are not documented elsewhere in this manual. These commands are
33370 provided here for reference. (For commands that turn on debugging
33371 messages, see @ref{Debugging Output}.)
33374 @kindex maint agent
33375 @kindex maint agent-eval
33376 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33377 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33378 Translate the given @var{expression} into remote agent bytecodes.
33379 This command is useful for debugging the Agent Expression mechanism
33380 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33381 expression useful for data collection, such as by tracepoints, while
33382 @samp{maint agent-eval} produces an expression that evaluates directly
33383 to a result. For instance, a collection expression for @code{globa +
33384 globb} will include bytecodes to record four bytes of memory at each
33385 of the addresses of @code{globa} and @code{globb}, while discarding
33386 the result of the addition, while an evaluation expression will do the
33387 addition and return the sum.
33388 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33389 If not, generate remote agent bytecode for current frame PC address.
33391 @kindex maint agent-printf
33392 @item maint agent-printf @var{format},@var{expr},...
33393 Translate the given format string and list of argument expressions
33394 into remote agent bytecodes and display them as a disassembled list.
33395 This command is useful for debugging the agent version of dynamic
33396 printf (@pxref{Dynamic Printf}).
33398 @kindex maint info breakpoints
33399 @item @anchor{maint info breakpoints}maint info breakpoints
33400 Using the same format as @samp{info breakpoints}, display both the
33401 breakpoints you've set explicitly, and those @value{GDBN} is using for
33402 internal purposes. Internal breakpoints are shown with negative
33403 breakpoint numbers. The type column identifies what kind of breakpoint
33408 Normal, explicitly set breakpoint.
33411 Normal, explicitly set watchpoint.
33414 Internal breakpoint, used to handle correctly stepping through
33415 @code{longjmp} calls.
33417 @item longjmp resume
33418 Internal breakpoint at the target of a @code{longjmp}.
33421 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33424 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33427 Shared library events.
33431 @kindex maint info bfds
33432 @item maint info bfds
33433 This prints information about each @code{bfd} object that is known to
33434 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33436 @kindex set displaced-stepping
33437 @kindex show displaced-stepping
33438 @cindex displaced stepping support
33439 @cindex out-of-line single-stepping
33440 @item set displaced-stepping
33441 @itemx show displaced-stepping
33442 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33443 if the target supports it. Displaced stepping is a way to single-step
33444 over breakpoints without removing them from the inferior, by executing
33445 an out-of-line copy of the instruction that was originally at the
33446 breakpoint location. It is also known as out-of-line single-stepping.
33449 @item set displaced-stepping on
33450 If the target architecture supports it, @value{GDBN} will use
33451 displaced stepping to step over breakpoints.
33453 @item set displaced-stepping off
33454 @value{GDBN} will not use displaced stepping to step over breakpoints,
33455 even if such is supported by the target architecture.
33457 @cindex non-stop mode, and @samp{set displaced-stepping}
33458 @item set displaced-stepping auto
33459 This is the default mode. @value{GDBN} will use displaced stepping
33460 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33461 architecture supports displaced stepping.
33464 @kindex maint check-psymtabs
33465 @item maint check-psymtabs
33466 Check the consistency of currently expanded psymtabs versus symtabs.
33467 Use this to check, for example, whether a symbol is in one but not the other.
33469 @kindex maint check-symtabs
33470 @item maint check-symtabs
33471 Check the consistency of currently expanded symtabs.
33473 @kindex maint expand-symtabs
33474 @item maint expand-symtabs [@var{regexp}]
33475 Expand symbol tables.
33476 If @var{regexp} is specified, only expand symbol tables for file
33477 names matching @var{regexp}.
33479 @kindex maint set catch-demangler-crashes
33480 @kindex maint show catch-demangler-crashes
33481 @cindex demangler crashes
33482 @item maint set catch-demangler-crashes [on|off]
33483 @itemx maint show catch-demangler-crashes
33484 Control whether @value{GDBN} should attempt to catch crashes in the
33485 symbol name demangler. The default is to attempt to catch crashes.
33486 If enabled, the first time a crash is caught, a core file is created,
33487 the offending symbol is displayed and the user is presented with the
33488 option to terminate the current session.
33490 @kindex maint cplus first_component
33491 @item maint cplus first_component @var{name}
33492 Print the first C@t{++} class/namespace component of @var{name}.
33494 @kindex maint cplus namespace
33495 @item maint cplus namespace
33496 Print the list of possible C@t{++} namespaces.
33498 @kindex maint deprecate
33499 @kindex maint undeprecate
33500 @cindex deprecated commands
33501 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33502 @itemx maint undeprecate @var{command}
33503 Deprecate or undeprecate the named @var{command}. Deprecated commands
33504 cause @value{GDBN} to issue a warning when you use them. The optional
33505 argument @var{replacement} says which newer command should be used in
33506 favor of the deprecated one; if it is given, @value{GDBN} will mention
33507 the replacement as part of the warning.
33509 @kindex maint dump-me
33510 @item maint dump-me
33511 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33512 Cause a fatal signal in the debugger and force it to dump its core.
33513 This is supported only on systems which support aborting a program
33514 with the @code{SIGQUIT} signal.
33516 @kindex maint internal-error
33517 @kindex maint internal-warning
33518 @kindex maint demangler-warning
33519 @cindex demangler crashes
33520 @item maint internal-error @r{[}@var{message-text}@r{]}
33521 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33522 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33524 Cause @value{GDBN} to call the internal function @code{internal_error},
33525 @code{internal_warning} or @code{demangler_warning} and hence behave
33526 as though an internal problam has been detected. In addition to
33527 reporting the internal problem, these functions give the user the
33528 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33529 and @code{internal_warning}) create a core file of the current
33530 @value{GDBN} session.
33532 These commands take an optional parameter @var{message-text} that is
33533 used as the text of the error or warning message.
33535 Here's an example of using @code{internal-error}:
33538 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33539 @dots{}/maint.c:121: internal-error: testing, 1, 2
33540 A problem internal to GDB has been detected. Further
33541 debugging may prove unreliable.
33542 Quit this debugging session? (y or n) @kbd{n}
33543 Create a core file? (y or n) @kbd{n}
33547 @cindex @value{GDBN} internal error
33548 @cindex internal errors, control of @value{GDBN} behavior
33549 @cindex demangler crashes
33551 @kindex maint set internal-error
33552 @kindex maint show internal-error
33553 @kindex maint set internal-warning
33554 @kindex maint show internal-warning
33555 @kindex maint set demangler-warning
33556 @kindex maint show demangler-warning
33557 @item maint set internal-error @var{action} [ask|yes|no]
33558 @itemx maint show internal-error @var{action}
33559 @itemx maint set internal-warning @var{action} [ask|yes|no]
33560 @itemx maint show internal-warning @var{action}
33561 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33562 @itemx maint show demangler-warning @var{action}
33563 When @value{GDBN} reports an internal problem (error or warning) it
33564 gives the user the opportunity to both quit @value{GDBN} and create a
33565 core file of the current @value{GDBN} session. These commands let you
33566 override the default behaviour for each particular @var{action},
33567 described in the table below.
33571 You can specify that @value{GDBN} should always (yes) or never (no)
33572 quit. The default is to ask the user what to do.
33575 You can specify that @value{GDBN} should always (yes) or never (no)
33576 create a core file. The default is to ask the user what to do. Note
33577 that there is no @code{corefile} option for @code{demangler-warning}:
33578 demangler warnings always create a core file and this cannot be
33582 @kindex maint packet
33583 @item maint packet @var{text}
33584 If @value{GDBN} is talking to an inferior via the serial protocol,
33585 then this command sends the string @var{text} to the inferior, and
33586 displays the response packet. @value{GDBN} supplies the initial
33587 @samp{$} character, the terminating @samp{#} character, and the
33590 @kindex maint print architecture
33591 @item maint print architecture @r{[}@var{file}@r{]}
33592 Print the entire architecture configuration. The optional argument
33593 @var{file} names the file where the output goes.
33595 @kindex maint print c-tdesc
33596 @item maint print c-tdesc
33597 Print the current target description (@pxref{Target Descriptions}) as
33598 a C source file. The created source file can be used in @value{GDBN}
33599 when an XML parser is not available to parse the description.
33601 @kindex maint print dummy-frames
33602 @item maint print dummy-frames
33603 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33606 (@value{GDBP}) @kbd{b add}
33608 (@value{GDBP}) @kbd{print add(2,3)}
33609 Breakpoint 2, add (a=2, b=3) at @dots{}
33611 The program being debugged stopped while in a function called from GDB.
33613 (@value{GDBP}) @kbd{maint print dummy-frames}
33614 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33618 Takes an optional file parameter.
33620 @kindex maint print registers
33621 @kindex maint print raw-registers
33622 @kindex maint print cooked-registers
33623 @kindex maint print register-groups
33624 @kindex maint print remote-registers
33625 @item maint print registers @r{[}@var{file}@r{]}
33626 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33627 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33628 @itemx maint print register-groups @r{[}@var{file}@r{]}
33629 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33630 Print @value{GDBN}'s internal register data structures.
33632 The command @code{maint print raw-registers} includes the contents of
33633 the raw register cache; the command @code{maint print
33634 cooked-registers} includes the (cooked) value of all registers,
33635 including registers which aren't available on the target nor visible
33636 to user; the command @code{maint print register-groups} includes the
33637 groups that each register is a member of; and the command @code{maint
33638 print remote-registers} includes the remote target's register numbers
33639 and offsets in the `G' packets.
33641 These commands take an optional parameter, a file name to which to
33642 write the information.
33644 @kindex maint print reggroups
33645 @item maint print reggroups @r{[}@var{file}@r{]}
33646 Print @value{GDBN}'s internal register group data structures. The
33647 optional argument @var{file} tells to what file to write the
33650 The register groups info looks like this:
33653 (@value{GDBP}) @kbd{maint print reggroups}
33666 This command forces @value{GDBN} to flush its internal register cache.
33668 @kindex maint print objfiles
33669 @cindex info for known object files
33670 @item maint print objfiles @r{[}@var{regexp}@r{]}
33671 Print a dump of all known object files.
33672 If @var{regexp} is specified, only print object files whose names
33673 match @var{regexp}. For each object file, this command prints its name,
33674 address in memory, and all of its psymtabs and symtabs.
33676 @kindex maint print user-registers
33677 @cindex user registers
33678 @item maint print user-registers
33679 List all currently available @dfn{user registers}. User registers
33680 typically provide alternate names for actual hardware registers. They
33681 include the four ``standard'' registers @code{$fp}, @code{$pc},
33682 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33683 registers can be used in expressions in the same way as the canonical
33684 register names, but only the latter are listed by the @code{info
33685 registers} and @code{maint print registers} commands.
33687 @kindex maint print section-scripts
33688 @cindex info for known .debug_gdb_scripts-loaded scripts
33689 @item maint print section-scripts [@var{regexp}]
33690 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33691 If @var{regexp} is specified, only print scripts loaded by object files
33692 matching @var{regexp}.
33693 For each script, this command prints its name as specified in the objfile,
33694 and the full path if known.
33695 @xref{dotdebug_gdb_scripts section}.
33697 @kindex maint print statistics
33698 @cindex bcache statistics
33699 @item maint print statistics
33700 This command prints, for each object file in the program, various data
33701 about that object file followed by the byte cache (@dfn{bcache})
33702 statistics for the object file. The objfile data includes the number
33703 of minimal, partial, full, and stabs symbols, the number of types
33704 defined by the objfile, the number of as yet unexpanded psym tables,
33705 the number of line tables and string tables, and the amount of memory
33706 used by the various tables. The bcache statistics include the counts,
33707 sizes, and counts of duplicates of all and unique objects, max,
33708 average, and median entry size, total memory used and its overhead and
33709 savings, and various measures of the hash table size and chain
33712 @kindex maint print target-stack
33713 @cindex target stack description
33714 @item maint print target-stack
33715 A @dfn{target} is an interface between the debugger and a particular
33716 kind of file or process. Targets can be stacked in @dfn{strata},
33717 so that more than one target can potentially respond to a request.
33718 In particular, memory accesses will walk down the stack of targets
33719 until they find a target that is interested in handling that particular
33722 This command prints a short description of each layer that was pushed on
33723 the @dfn{target stack}, starting from the top layer down to the bottom one.
33725 @kindex maint print type
33726 @cindex type chain of a data type
33727 @item maint print type @var{expr}
33728 Print the type chain for a type specified by @var{expr}. The argument
33729 can be either a type name or a symbol. If it is a symbol, the type of
33730 that symbol is described. The type chain produced by this command is
33731 a recursive definition of the data type as stored in @value{GDBN}'s
33732 data structures, including its flags and contained types.
33734 @kindex maint set dwarf2 always-disassemble
33735 @kindex maint show dwarf2 always-disassemble
33736 @item maint set dwarf2 always-disassemble
33737 @item maint show dwarf2 always-disassemble
33738 Control the behavior of @code{info address} when using DWARF debugging
33741 The default is @code{off}, which means that @value{GDBN} should try to
33742 describe a variable's location in an easily readable format. When
33743 @code{on}, @value{GDBN} will instead display the DWARF location
33744 expression in an assembly-like format. Note that some locations are
33745 too complex for @value{GDBN} to describe simply; in this case you will
33746 always see the disassembly form.
33748 Here is an example of the resulting disassembly:
33751 (gdb) info addr argc
33752 Symbol "argc" is a complex DWARF expression:
33756 For more information on these expressions, see
33757 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33759 @kindex maint set dwarf2 max-cache-age
33760 @kindex maint show dwarf2 max-cache-age
33761 @item maint set dwarf2 max-cache-age
33762 @itemx maint show dwarf2 max-cache-age
33763 Control the DWARF 2 compilation unit cache.
33765 @cindex DWARF 2 compilation units cache
33766 In object files with inter-compilation-unit references, such as those
33767 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33768 reader needs to frequently refer to previously read compilation units.
33769 This setting controls how long a compilation unit will remain in the
33770 cache if it is not referenced. A higher limit means that cached
33771 compilation units will be stored in memory longer, and more total
33772 memory will be used. Setting it to zero disables caching, which will
33773 slow down @value{GDBN} startup, but reduce memory consumption.
33775 @kindex maint set profile
33776 @kindex maint show profile
33777 @cindex profiling GDB
33778 @item maint set profile
33779 @itemx maint show profile
33780 Control profiling of @value{GDBN}.
33782 Profiling will be disabled until you use the @samp{maint set profile}
33783 command to enable it. When you enable profiling, the system will begin
33784 collecting timing and execution count data; when you disable profiling or
33785 exit @value{GDBN}, the results will be written to a log file. Remember that
33786 if you use profiling, @value{GDBN} will overwrite the profiling log file
33787 (often called @file{gmon.out}). If you have a record of important profiling
33788 data in a @file{gmon.out} file, be sure to move it to a safe location.
33790 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33791 compiled with the @samp{-pg} compiler option.
33793 @kindex maint set show-debug-regs
33794 @kindex maint show show-debug-regs
33795 @cindex hardware debug registers
33796 @item maint set show-debug-regs
33797 @itemx maint show show-debug-regs
33798 Control whether to show variables that mirror the hardware debug
33799 registers. Use @code{on} to enable, @code{off} to disable. If
33800 enabled, the debug registers values are shown when @value{GDBN} inserts or
33801 removes a hardware breakpoint or watchpoint, and when the inferior
33802 triggers a hardware-assisted breakpoint or watchpoint.
33804 @kindex maint set show-all-tib
33805 @kindex maint show show-all-tib
33806 @item maint set show-all-tib
33807 @itemx maint show show-all-tib
33808 Control whether to show all non zero areas within a 1k block starting
33809 at thread local base, when using the @samp{info w32 thread-information-block}
33812 @kindex maint set target-async
33813 @kindex maint show target-async
33814 @item maint set target-async
33815 @itemx maint show target-async
33816 This controls whether @value{GDBN} targets operate in synchronous or
33817 asynchronous mode (@pxref{Background Execution}). Normally the
33818 default is asynchronous, if it is available; but this can be changed
33819 to more easily debug problems occurring only in synchronous mode.
33821 @kindex maint set per-command
33822 @kindex maint show per-command
33823 @item maint set per-command
33824 @itemx maint show per-command
33825 @cindex resources used by commands
33827 @value{GDBN} can display the resources used by each command.
33828 This is useful in debugging performance problems.
33831 @item maint set per-command space [on|off]
33832 @itemx maint show per-command space
33833 Enable or disable the printing of the memory used by GDB for each command.
33834 If enabled, @value{GDBN} will display how much memory each command
33835 took, following the command's own output.
33836 This can also be requested by invoking @value{GDBN} with the
33837 @option{--statistics} command-line switch (@pxref{Mode Options}).
33839 @item maint set per-command time [on|off]
33840 @itemx maint show per-command time
33841 Enable or disable the printing of the execution time of @value{GDBN}
33843 If enabled, @value{GDBN} will display how much time it
33844 took to execute each command, following the command's own output.
33845 Both CPU time and wallclock time are printed.
33846 Printing both is useful when trying to determine whether the cost is
33847 CPU or, e.g., disk/network latency.
33848 Note that the CPU time printed is for @value{GDBN} only, it does not include
33849 the execution time of the inferior because there's no mechanism currently
33850 to compute how much time was spent by @value{GDBN} and how much time was
33851 spent by the program been debugged.
33852 This can also be requested by invoking @value{GDBN} with the
33853 @option{--statistics} command-line switch (@pxref{Mode Options}).
33855 @item maint set per-command symtab [on|off]
33856 @itemx maint show per-command symtab
33857 Enable or disable the printing of basic symbol table statistics
33859 If enabled, @value{GDBN} will display the following information:
33863 number of symbol tables
33865 number of primary symbol tables
33867 number of blocks in the blockvector
33871 @kindex maint space
33872 @cindex memory used by commands
33873 @item maint space @var{value}
33874 An alias for @code{maint set per-command space}.
33875 A non-zero value enables it, zero disables it.
33878 @cindex time of command execution
33879 @item maint time @var{value}
33880 An alias for @code{maint set per-command time}.
33881 A non-zero value enables it, zero disables it.
33883 @kindex maint translate-address
33884 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33885 Find the symbol stored at the location specified by the address
33886 @var{addr} and an optional section name @var{section}. If found,
33887 @value{GDBN} prints the name of the closest symbol and an offset from
33888 the symbol's location to the specified address. This is similar to
33889 the @code{info address} command (@pxref{Symbols}), except that this
33890 command also allows to find symbols in other sections.
33892 If section was not specified, the section in which the symbol was found
33893 is also printed. For dynamically linked executables, the name of
33894 executable or shared library containing the symbol is printed as well.
33898 The following command is useful for non-interactive invocations of
33899 @value{GDBN}, such as in the test suite.
33902 @item set watchdog @var{nsec}
33903 @kindex set watchdog
33904 @cindex watchdog timer
33905 @cindex timeout for commands
33906 Set the maximum number of seconds @value{GDBN} will wait for the
33907 target operation to finish. If this time expires, @value{GDBN}
33908 reports and error and the command is aborted.
33910 @item show watchdog
33911 Show the current setting of the target wait timeout.
33914 @node Remote Protocol
33915 @appendix @value{GDBN} Remote Serial Protocol
33920 * Stop Reply Packets::
33921 * General Query Packets::
33922 * Architecture-Specific Protocol Details::
33923 * Tracepoint Packets::
33924 * Host I/O Packets::
33926 * Notification Packets::
33927 * Remote Non-Stop::
33928 * Packet Acknowledgment::
33930 * File-I/O Remote Protocol Extension::
33931 * Library List Format::
33932 * Library List Format for SVR4 Targets::
33933 * Memory Map Format::
33934 * Thread List Format::
33935 * Traceframe Info Format::
33936 * Branch Trace Format::
33942 There may be occasions when you need to know something about the
33943 protocol---for example, if there is only one serial port to your target
33944 machine, you might want your program to do something special if it
33945 recognizes a packet meant for @value{GDBN}.
33947 In the examples below, @samp{->} and @samp{<-} are used to indicate
33948 transmitted and received data, respectively.
33950 @cindex protocol, @value{GDBN} remote serial
33951 @cindex serial protocol, @value{GDBN} remote
33952 @cindex remote serial protocol
33953 All @value{GDBN} commands and responses (other than acknowledgments
33954 and notifications, see @ref{Notification Packets}) are sent as a
33955 @var{packet}. A @var{packet} is introduced with the character
33956 @samp{$}, the actual @var{packet-data}, and the terminating character
33957 @samp{#} followed by a two-digit @var{checksum}:
33960 @code{$}@var{packet-data}@code{#}@var{checksum}
33964 @cindex checksum, for @value{GDBN} remote
33966 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33967 characters between the leading @samp{$} and the trailing @samp{#} (an
33968 eight bit unsigned checksum).
33970 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33971 specification also included an optional two-digit @var{sequence-id}:
33974 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33977 @cindex sequence-id, for @value{GDBN} remote
33979 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33980 has never output @var{sequence-id}s. Stubs that handle packets added
33981 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33983 When either the host or the target machine receives a packet, the first
33984 response expected is an acknowledgment: either @samp{+} (to indicate
33985 the package was received correctly) or @samp{-} (to request
33989 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33994 The @samp{+}/@samp{-} acknowledgments can be disabled
33995 once a connection is established.
33996 @xref{Packet Acknowledgment}, for details.
33998 The host (@value{GDBN}) sends @var{command}s, and the target (the
33999 debugging stub incorporated in your program) sends a @var{response}. In
34000 the case of step and continue @var{command}s, the response is only sent
34001 when the operation has completed, and the target has again stopped all
34002 threads in all attached processes. This is the default all-stop mode
34003 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34004 execution mode; see @ref{Remote Non-Stop}, for details.
34006 @var{packet-data} consists of a sequence of characters with the
34007 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34010 @cindex remote protocol, field separator
34011 Fields within the packet should be separated using @samp{,} @samp{;} or
34012 @samp{:}. Except where otherwise noted all numbers are represented in
34013 @sc{hex} with leading zeros suppressed.
34015 Implementors should note that prior to @value{GDBN} 5.0, the character
34016 @samp{:} could not appear as the third character in a packet (as it
34017 would potentially conflict with the @var{sequence-id}).
34019 @cindex remote protocol, binary data
34020 @anchor{Binary Data}
34021 Binary data in most packets is encoded either as two hexadecimal
34022 digits per byte of binary data. This allowed the traditional remote
34023 protocol to work over connections which were only seven-bit clean.
34024 Some packets designed more recently assume an eight-bit clean
34025 connection, and use a more efficient encoding to send and receive
34028 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34029 as an escape character. Any escaped byte is transmitted as the escape
34030 character followed by the original character XORed with @code{0x20}.
34031 For example, the byte @code{0x7d} would be transmitted as the two
34032 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34033 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34034 @samp{@}}) must always be escaped. Responses sent by the stub
34035 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34036 is not interpreted as the start of a run-length encoded sequence
34039 Response @var{data} can be run-length encoded to save space.
34040 Run-length encoding replaces runs of identical characters with one
34041 instance of the repeated character, followed by a @samp{*} and a
34042 repeat count. The repeat count is itself sent encoded, to avoid
34043 binary characters in @var{data}: a value of @var{n} is sent as
34044 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34045 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34046 code 32) for a repeat count of 3. (This is because run-length
34047 encoding starts to win for counts 3 or more.) Thus, for example,
34048 @samp{0* } is a run-length encoding of ``0000'': the space character
34049 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34052 The printable characters @samp{#} and @samp{$} or with a numeric value
34053 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34054 seven repeats (@samp{$}) can be expanded using a repeat count of only
34055 five (@samp{"}). For example, @samp{00000000} can be encoded as
34058 The error response returned for some packets includes a two character
34059 error number. That number is not well defined.
34061 @cindex empty response, for unsupported packets
34062 For any @var{command} not supported by the stub, an empty response
34063 (@samp{$#00}) should be returned. That way it is possible to extend the
34064 protocol. A newer @value{GDBN} can tell if a packet is supported based
34067 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34068 commands for register access, and the @samp{m} and @samp{M} commands
34069 for memory access. Stubs that only control single-threaded targets
34070 can implement run control with the @samp{c} (continue), and @samp{s}
34071 (step) commands. Stubs that support multi-threading targets should
34072 support the @samp{vCont} command. All other commands are optional.
34077 The following table provides a complete list of all currently defined
34078 @var{command}s and their corresponding response @var{data}.
34079 @xref{File-I/O Remote Protocol Extension}, for details about the File
34080 I/O extension of the remote protocol.
34082 Each packet's description has a template showing the packet's overall
34083 syntax, followed by an explanation of the packet's meaning. We
34084 include spaces in some of the templates for clarity; these are not
34085 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34086 separate its components. For example, a template like @samp{foo
34087 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34088 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34089 @var{baz}. @value{GDBN} does not transmit a space character between the
34090 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34093 @cindex @var{thread-id}, in remote protocol
34094 @anchor{thread-id syntax}
34095 Several packets and replies include a @var{thread-id} field to identify
34096 a thread. Normally these are positive numbers with a target-specific
34097 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34098 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34101 In addition, the remote protocol supports a multiprocess feature in
34102 which the @var{thread-id} syntax is extended to optionally include both
34103 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34104 The @var{pid} (process) and @var{tid} (thread) components each have the
34105 format described above: a positive number with target-specific
34106 interpretation formatted as a big-endian hex string, literal @samp{-1}
34107 to indicate all processes or threads (respectively), or @samp{0} to
34108 indicate an arbitrary process or thread. Specifying just a process, as
34109 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34110 error to specify all processes but a specific thread, such as
34111 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34112 for those packets and replies explicitly documented to include a process
34113 ID, rather than a @var{thread-id}.
34115 The multiprocess @var{thread-id} syntax extensions are only used if both
34116 @value{GDBN} and the stub report support for the @samp{multiprocess}
34117 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34120 Note that all packet forms beginning with an upper- or lower-case
34121 letter, other than those described here, are reserved for future use.
34123 Here are the packet descriptions.
34128 @cindex @samp{!} packet
34129 @anchor{extended mode}
34130 Enable extended mode. In extended mode, the remote server is made
34131 persistent. The @samp{R} packet is used to restart the program being
34137 The remote target both supports and has enabled extended mode.
34141 @cindex @samp{?} packet
34143 Indicate the reason the target halted. The reply is the same as for
34144 step and continue. This packet has a special interpretation when the
34145 target is in non-stop mode; see @ref{Remote Non-Stop}.
34148 @xref{Stop Reply Packets}, for the reply specifications.
34150 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34151 @cindex @samp{A} packet
34152 Initialized @code{argv[]} array passed into program. @var{arglen}
34153 specifies the number of bytes in the hex encoded byte stream
34154 @var{arg}. See @code{gdbserver} for more details.
34159 The arguments were set.
34165 @cindex @samp{b} packet
34166 (Don't use this packet; its behavior is not well-defined.)
34167 Change the serial line speed to @var{baud}.
34169 JTC: @emph{When does the transport layer state change? When it's
34170 received, or after the ACK is transmitted. In either case, there are
34171 problems if the command or the acknowledgment packet is dropped.}
34173 Stan: @emph{If people really wanted to add something like this, and get
34174 it working for the first time, they ought to modify ser-unix.c to send
34175 some kind of out-of-band message to a specially-setup stub and have the
34176 switch happen "in between" packets, so that from remote protocol's point
34177 of view, nothing actually happened.}
34179 @item B @var{addr},@var{mode}
34180 @cindex @samp{B} packet
34181 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34182 breakpoint at @var{addr}.
34184 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34185 (@pxref{insert breakpoint or watchpoint packet}).
34187 @cindex @samp{bc} packet
34190 Backward continue. Execute the target system in reverse. No parameter.
34191 @xref{Reverse Execution}, for more information.
34194 @xref{Stop Reply Packets}, for the reply specifications.
34196 @cindex @samp{bs} packet
34199 Backward single step. Execute one instruction in reverse. No parameter.
34200 @xref{Reverse Execution}, for more information.
34203 @xref{Stop Reply Packets}, for the reply specifications.
34205 @item c @r{[}@var{addr}@r{]}
34206 @cindex @samp{c} packet
34207 Continue at @var{addr}, which is the address to resume. If @var{addr}
34208 is omitted, resume at current address.
34210 This packet is deprecated for multi-threading support. @xref{vCont
34214 @xref{Stop Reply Packets}, for the reply specifications.
34216 @item C @var{sig}@r{[};@var{addr}@r{]}
34217 @cindex @samp{C} packet
34218 Continue with signal @var{sig} (hex signal number). If
34219 @samp{;@var{addr}} is omitted, resume at same address.
34221 This packet is deprecated for multi-threading support. @xref{vCont
34225 @xref{Stop Reply Packets}, for the reply specifications.
34228 @cindex @samp{d} packet
34231 Don't use this packet; instead, define a general set packet
34232 (@pxref{General Query Packets}).
34236 @cindex @samp{D} packet
34237 The first form of the packet is used to detach @value{GDBN} from the
34238 remote system. It is sent to the remote target
34239 before @value{GDBN} disconnects via the @code{detach} command.
34241 The second form, including a process ID, is used when multiprocess
34242 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34243 detach only a specific process. The @var{pid} is specified as a
34244 big-endian hex string.
34254 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34255 @cindex @samp{F} packet
34256 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34257 This is part of the File-I/O protocol extension. @xref{File-I/O
34258 Remote Protocol Extension}, for the specification.
34261 @anchor{read registers packet}
34262 @cindex @samp{g} packet
34263 Read general registers.
34267 @item @var{XX@dots{}}
34268 Each byte of register data is described by two hex digits. The bytes
34269 with the register are transmitted in target byte order. The size of
34270 each register and their position within the @samp{g} packet are
34271 determined by the @value{GDBN} internal gdbarch functions
34272 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34273 specification of several standard @samp{g} packets is specified below.
34275 When reading registers from a trace frame (@pxref{Analyze Collected
34276 Data,,Using the Collected Data}), the stub may also return a string of
34277 literal @samp{x}'s in place of the register data digits, to indicate
34278 that the corresponding register has not been collected, thus its value
34279 is unavailable. For example, for an architecture with 4 registers of
34280 4 bytes each, the following reply indicates to @value{GDBN} that
34281 registers 0 and 2 have not been collected, while registers 1 and 3
34282 have been collected, and both have zero value:
34286 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34293 @item G @var{XX@dots{}}
34294 @cindex @samp{G} packet
34295 Write general registers. @xref{read registers packet}, for a
34296 description of the @var{XX@dots{}} data.
34306 @item H @var{op} @var{thread-id}
34307 @cindex @samp{H} packet
34308 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34309 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34310 should be @samp{c} for step and continue operations (note that this
34311 is deprecated, supporting the @samp{vCont} command is a better
34312 option), and @samp{g} for other operations. The thread designator
34313 @var{thread-id} has the format and interpretation described in
34314 @ref{thread-id syntax}.
34325 @c 'H': How restrictive (or permissive) is the thread model. If a
34326 @c thread is selected and stopped, are other threads allowed
34327 @c to continue to execute? As I mentioned above, I think the
34328 @c semantics of each command when a thread is selected must be
34329 @c described. For example:
34331 @c 'g': If the stub supports threads and a specific thread is
34332 @c selected, returns the register block from that thread;
34333 @c otherwise returns current registers.
34335 @c 'G' If the stub supports threads and a specific thread is
34336 @c selected, sets the registers of the register block of
34337 @c that thread; otherwise sets current registers.
34339 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34340 @anchor{cycle step packet}
34341 @cindex @samp{i} packet
34342 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34343 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34344 step starting at that address.
34347 @cindex @samp{I} packet
34348 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34352 @cindex @samp{k} packet
34355 The exact effect of this packet is not specified.
34357 For a bare-metal target, it may power cycle or reset the target
34358 system. For that reason, the @samp{k} packet has no reply.
34360 For a single-process target, it may kill that process if possible.
34362 A multiple-process target may choose to kill just one process, or all
34363 that are under @value{GDBN}'s control. For more precise control, use
34364 the vKill packet (@pxref{vKill packet}).
34366 If the target system immediately closes the connection in response to
34367 @samp{k}, @value{GDBN} does not consider the lack of packet
34368 acknowledgment to be an error, and assumes the kill was successful.
34370 If connected using @kbd{target extended-remote}, and the target does
34371 not close the connection in response to a kill request, @value{GDBN}
34372 probes the target state as if a new connection was opened
34373 (@pxref{? packet}).
34375 @item m @var{addr},@var{length}
34376 @cindex @samp{m} packet
34377 Read @var{length} bytes of memory starting at address @var{addr}.
34378 Note that @var{addr} may not be aligned to any particular boundary.
34380 The stub need not use any particular size or alignment when gathering
34381 data from memory for the response; even if @var{addr} is word-aligned
34382 and @var{length} is a multiple of the word size, the stub is free to
34383 use byte accesses, or not. For this reason, this packet may not be
34384 suitable for accessing memory-mapped I/O devices.
34385 @cindex alignment of remote memory accesses
34386 @cindex size of remote memory accesses
34387 @cindex memory, alignment and size of remote accesses
34391 @item @var{XX@dots{}}
34392 Memory contents; each byte is transmitted as a two-digit hexadecimal
34393 number. The reply may contain fewer bytes than requested if the
34394 server was able to read only part of the region of memory.
34399 @item M @var{addr},@var{length}:@var{XX@dots{}}
34400 @cindex @samp{M} packet
34401 Write @var{length} bytes of memory starting at address @var{addr}.
34402 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34403 hexadecimal number.
34410 for an error (this includes the case where only part of the data was
34415 @cindex @samp{p} packet
34416 Read the value of register @var{n}; @var{n} is in hex.
34417 @xref{read registers packet}, for a description of how the returned
34418 register value is encoded.
34422 @item @var{XX@dots{}}
34423 the register's value
34427 Indicating an unrecognized @var{query}.
34430 @item P @var{n@dots{}}=@var{r@dots{}}
34431 @anchor{write register packet}
34432 @cindex @samp{P} packet
34433 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34434 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34435 digits for each byte in the register (target byte order).
34445 @item q @var{name} @var{params}@dots{}
34446 @itemx Q @var{name} @var{params}@dots{}
34447 @cindex @samp{q} packet
34448 @cindex @samp{Q} packet
34449 General query (@samp{q}) and set (@samp{Q}). These packets are
34450 described fully in @ref{General Query Packets}.
34453 @cindex @samp{r} packet
34454 Reset the entire system.
34456 Don't use this packet; use the @samp{R} packet instead.
34459 @cindex @samp{R} packet
34460 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34461 This packet is only available in extended mode (@pxref{extended mode}).
34463 The @samp{R} packet has no reply.
34465 @item s @r{[}@var{addr}@r{]}
34466 @cindex @samp{s} packet
34467 Single step, resuming at @var{addr}. If
34468 @var{addr} is omitted, resume at same address.
34470 This packet is deprecated for multi-threading support. @xref{vCont
34474 @xref{Stop Reply Packets}, for the reply specifications.
34476 @item S @var{sig}@r{[};@var{addr}@r{]}
34477 @anchor{step with signal packet}
34478 @cindex @samp{S} packet
34479 Step with signal. This is analogous to the @samp{C} packet, but
34480 requests a single-step, rather than a normal resumption of execution.
34482 This packet is deprecated for multi-threading support. @xref{vCont
34486 @xref{Stop Reply Packets}, for the reply specifications.
34488 @item t @var{addr}:@var{PP},@var{MM}
34489 @cindex @samp{t} packet
34490 Search backwards starting at address @var{addr} for a match with pattern
34491 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34492 There must be at least 3 digits in @var{addr}.
34494 @item T @var{thread-id}
34495 @cindex @samp{T} packet
34496 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34501 thread is still alive
34507 Packets starting with @samp{v} are identified by a multi-letter name,
34508 up to the first @samp{;} or @samp{?} (or the end of the packet).
34510 @item vAttach;@var{pid}
34511 @cindex @samp{vAttach} packet
34512 Attach to a new process with the specified process ID @var{pid}.
34513 The process ID is a
34514 hexadecimal integer identifying the process. In all-stop mode, all
34515 threads in the attached process are stopped; in non-stop mode, it may be
34516 attached without being stopped if that is supported by the target.
34518 @c In non-stop mode, on a successful vAttach, the stub should set the
34519 @c current thread to a thread of the newly-attached process. After
34520 @c attaching, GDB queries for the attached process's thread ID with qC.
34521 @c Also note that, from a user perspective, whether or not the
34522 @c target is stopped on attach in non-stop mode depends on whether you
34523 @c use the foreground or background version of the attach command, not
34524 @c on what vAttach does; GDB does the right thing with respect to either
34525 @c stopping or restarting threads.
34527 This packet is only available in extended mode (@pxref{extended mode}).
34533 @item @r{Any stop packet}
34534 for success in all-stop mode (@pxref{Stop Reply Packets})
34536 for success in non-stop mode (@pxref{Remote Non-Stop})
34539 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34540 @cindex @samp{vCont} packet
34541 @anchor{vCont packet}
34542 Resume the inferior, specifying different actions for each thread.
34543 If an action is specified with no @var{thread-id}, then it is applied to any
34544 threads that don't have a specific action specified; if no default action is
34545 specified then other threads should remain stopped in all-stop mode and
34546 in their current state in non-stop mode.
34547 Specifying multiple
34548 default actions is an error; specifying no actions is also an error.
34549 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34551 Currently supported actions are:
34557 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34561 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34564 @item r @var{start},@var{end}
34565 Step once, and then keep stepping as long as the thread stops at
34566 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34567 The remote stub reports a stop reply when either the thread goes out
34568 of the range or is stopped due to an unrelated reason, such as hitting
34569 a breakpoint. @xref{range stepping}.
34571 If the range is empty (@var{start} == @var{end}), then the action
34572 becomes equivalent to the @samp{s} action. In other words,
34573 single-step once, and report the stop (even if the stepped instruction
34574 jumps to @var{start}).
34576 (A stop reply may be sent at any point even if the PC is still within
34577 the stepping range; for example, it is valid to implement this packet
34578 in a degenerate way as a single instruction step operation.)
34582 The optional argument @var{addr} normally associated with the
34583 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34584 not supported in @samp{vCont}.
34586 The @samp{t} action is only relevant in non-stop mode
34587 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34588 A stop reply should be generated for any affected thread not already stopped.
34589 When a thread is stopped by means of a @samp{t} action,
34590 the corresponding stop reply should indicate that the thread has stopped with
34591 signal @samp{0}, regardless of whether the target uses some other signal
34592 as an implementation detail.
34594 The stub must support @samp{vCont} if it reports support for
34595 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34596 this case @samp{vCont} actions can be specified to apply to all threads
34597 in a process by using the @samp{p@var{pid}.-1} form of the
34601 @xref{Stop Reply Packets}, for the reply specifications.
34604 @cindex @samp{vCont?} packet
34605 Request a list of actions supported by the @samp{vCont} packet.
34609 @item vCont@r{[};@var{action}@dots{}@r{]}
34610 The @samp{vCont} packet is supported. Each @var{action} is a supported
34611 command in the @samp{vCont} packet.
34613 The @samp{vCont} packet is not supported.
34616 @item vFile:@var{operation}:@var{parameter}@dots{}
34617 @cindex @samp{vFile} packet
34618 Perform a file operation on the target system. For details,
34619 see @ref{Host I/O Packets}.
34621 @item vFlashErase:@var{addr},@var{length}
34622 @cindex @samp{vFlashErase} packet
34623 Direct the stub to erase @var{length} bytes of flash starting at
34624 @var{addr}. The region may enclose any number of flash blocks, but
34625 its start and end must fall on block boundaries, as indicated by the
34626 flash block size appearing in the memory map (@pxref{Memory Map
34627 Format}). @value{GDBN} groups flash memory programming operations
34628 together, and sends a @samp{vFlashDone} request after each group; the
34629 stub is allowed to delay erase operation until the @samp{vFlashDone}
34630 packet is received.
34640 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34641 @cindex @samp{vFlashWrite} packet
34642 Direct the stub to write data to flash address @var{addr}. The data
34643 is passed in binary form using the same encoding as for the @samp{X}
34644 packet (@pxref{Binary Data}). The memory ranges specified by
34645 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34646 not overlap, and must appear in order of increasing addresses
34647 (although @samp{vFlashErase} packets for higher addresses may already
34648 have been received; the ordering is guaranteed only between
34649 @samp{vFlashWrite} packets). If a packet writes to an address that was
34650 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34651 target-specific method, the results are unpredictable.
34659 for vFlashWrite addressing non-flash memory
34665 @cindex @samp{vFlashDone} packet
34666 Indicate to the stub that flash programming operation is finished.
34667 The stub is permitted to delay or batch the effects of a group of
34668 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34669 @samp{vFlashDone} packet is received. The contents of the affected
34670 regions of flash memory are unpredictable until the @samp{vFlashDone}
34671 request is completed.
34673 @item vKill;@var{pid}
34674 @cindex @samp{vKill} packet
34675 @anchor{vKill packet}
34676 Kill the process with the specified process ID @var{pid}, which is a
34677 hexadecimal integer identifying the process. This packet is used in
34678 preference to @samp{k} when multiprocess protocol extensions are
34679 supported; see @ref{multiprocess extensions}.
34689 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34690 @cindex @samp{vRun} packet
34691 Run the program @var{filename}, passing it each @var{argument} on its
34692 command line. The file and arguments are hex-encoded strings. If
34693 @var{filename} is an empty string, the stub may use a default program
34694 (e.g.@: the last program run). The program is created in the stopped
34697 @c FIXME: What about non-stop mode?
34699 This packet is only available in extended mode (@pxref{extended mode}).
34705 @item @r{Any stop packet}
34706 for success (@pxref{Stop Reply Packets})
34710 @cindex @samp{vStopped} packet
34711 @xref{Notification Packets}.
34713 @item X @var{addr},@var{length}:@var{XX@dots{}}
34715 @cindex @samp{X} packet
34716 Write data to memory, where the data is transmitted in binary.
34717 Memory is specified by its address @var{addr} and number of bytes @var{length};
34718 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34728 @item z @var{type},@var{addr},@var{kind}
34729 @itemx Z @var{type},@var{addr},@var{kind}
34730 @anchor{insert breakpoint or watchpoint packet}
34731 @cindex @samp{z} packet
34732 @cindex @samp{Z} packets
34733 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34734 watchpoint starting at address @var{address} of kind @var{kind}.
34736 Each breakpoint and watchpoint packet @var{type} is documented
34739 @emph{Implementation notes: A remote target shall return an empty string
34740 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34741 remote target shall support either both or neither of a given
34742 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34743 avoid potential problems with duplicate packets, the operations should
34744 be implemented in an idempotent way.}
34746 @item z0,@var{addr},@var{kind}
34747 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34748 @cindex @samp{z0} packet
34749 @cindex @samp{Z0} packet
34750 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34751 @var{addr} of type @var{kind}.
34753 A memory breakpoint is implemented by replacing the instruction at
34754 @var{addr} with a software breakpoint or trap instruction. The
34755 @var{kind} is target-specific and typically indicates the size of
34756 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34757 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34758 architectures have additional meanings for @var{kind};
34759 @var{cond_list} is an optional list of conditional expressions in bytecode
34760 form that should be evaluated on the target's side. These are the
34761 conditions that should be taken into consideration when deciding if
34762 the breakpoint trigger should be reported back to @var{GDBN}.
34764 The @var{cond_list} parameter is comprised of a series of expressions,
34765 concatenated without separators. Each expression has the following form:
34769 @item X @var{len},@var{expr}
34770 @var{len} is the length of the bytecode expression and @var{expr} is the
34771 actual conditional expression in bytecode form.
34775 The optional @var{cmd_list} parameter introduces commands that may be
34776 run on the target, rather than being reported back to @value{GDBN}.
34777 The parameter starts with a numeric flag @var{persist}; if the flag is
34778 nonzero, then the breakpoint may remain active and the commands
34779 continue to be run even when @value{GDBN} disconnects from the target.
34780 Following this flag is a series of expressions concatenated with no
34781 separators. Each expression has the following form:
34785 @item X @var{len},@var{expr}
34786 @var{len} is the length of the bytecode expression and @var{expr} is the
34787 actual conditional expression in bytecode form.
34791 see @ref{Architecture-Specific Protocol Details}.
34793 @emph{Implementation note: It is possible for a target to copy or move
34794 code that contains memory breakpoints (e.g., when implementing
34795 overlays). The behavior of this packet, in the presence of such a
34796 target, is not defined.}
34808 @item z1,@var{addr},@var{kind}
34809 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34810 @cindex @samp{z1} packet
34811 @cindex @samp{Z1} packet
34812 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34813 address @var{addr}.
34815 A hardware breakpoint is implemented using a mechanism that is not
34816 dependant on being able to modify the target's memory. The @var{kind}
34817 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34819 @emph{Implementation note: A hardware breakpoint is not affected by code
34832 @item z2,@var{addr},@var{kind}
34833 @itemx Z2,@var{addr},@var{kind}
34834 @cindex @samp{z2} packet
34835 @cindex @samp{Z2} packet
34836 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34837 The number of bytes to watch is specified by @var{kind}.
34849 @item z3,@var{addr},@var{kind}
34850 @itemx Z3,@var{addr},@var{kind}
34851 @cindex @samp{z3} packet
34852 @cindex @samp{Z3} packet
34853 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34854 The number of bytes to watch is specified by @var{kind}.
34866 @item z4,@var{addr},@var{kind}
34867 @itemx Z4,@var{addr},@var{kind}
34868 @cindex @samp{z4} packet
34869 @cindex @samp{Z4} packet
34870 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34871 The number of bytes to watch is specified by @var{kind}.
34885 @node Stop Reply Packets
34886 @section Stop Reply Packets
34887 @cindex stop reply packets
34889 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34890 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34891 receive any of the below as a reply. Except for @samp{?}
34892 and @samp{vStopped}, that reply is only returned
34893 when the target halts. In the below the exact meaning of @dfn{signal
34894 number} is defined by the header @file{include/gdb/signals.h} in the
34895 @value{GDBN} source code.
34897 As in the description of request packets, we include spaces in the
34898 reply templates for clarity; these are not part of the reply packet's
34899 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34905 The program received signal number @var{AA} (a two-digit hexadecimal
34906 number). This is equivalent to a @samp{T} response with no
34907 @var{n}:@var{r} pairs.
34909 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34910 @cindex @samp{T} packet reply
34911 The program received signal number @var{AA} (a two-digit hexadecimal
34912 number). This is equivalent to an @samp{S} response, except that the
34913 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34914 and other information directly in the stop reply packet, reducing
34915 round-trip latency. Single-step and breakpoint traps are reported
34916 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34920 If @var{n} is a hexadecimal number, it is a register number, and the
34921 corresponding @var{r} gives that register's value. The data @var{r} is a
34922 series of bytes in target byte order, with each byte given by a
34923 two-digit hex number.
34926 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34927 the stopped thread, as specified in @ref{thread-id syntax}.
34930 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34931 the core on which the stop event was detected.
34934 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34935 specific event that stopped the target. The currently defined stop
34936 reasons are listed below. The @var{aa} should be @samp{05}, the trap
34937 signal. At most one stop reason should be present.
34940 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34941 and go on to the next; this allows us to extend the protocol in the
34945 The currently defined stop reasons are:
34951 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34954 @cindex shared library events, remote reply
34956 The packet indicates that the loaded libraries have changed.
34957 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34958 list of loaded libraries. The @var{r} part is ignored.
34960 @cindex replay log events, remote reply
34962 The packet indicates that the target cannot continue replaying
34963 logged execution events, because it has reached the end (or the
34964 beginning when executing backward) of the log. The value of @var{r}
34965 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34966 for more information.
34970 @itemx W @var{AA} ; process:@var{pid}
34971 The process exited, and @var{AA} is the exit status. This is only
34972 applicable to certain targets.
34974 The second form of the response, including the process ID of the exited
34975 process, can be used only when @value{GDBN} has reported support for
34976 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34977 The @var{pid} is formatted as a big-endian hex string.
34980 @itemx X @var{AA} ; process:@var{pid}
34981 The process terminated with signal @var{AA}.
34983 The second form of the response, including the process ID of the
34984 terminated process, can be used only when @value{GDBN} has reported
34985 support for multiprocess protocol extensions; see @ref{multiprocess
34986 extensions}. The @var{pid} is formatted as a big-endian hex string.
34988 @item O @var{XX}@dots{}
34989 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34990 written as the program's console output. This can happen at any time
34991 while the program is running and the debugger should continue to wait
34992 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34994 @item F @var{call-id},@var{parameter}@dots{}
34995 @var{call-id} is the identifier which says which host system call should
34996 be called. This is just the name of the function. Translation into the
34997 correct system call is only applicable as it's defined in @value{GDBN}.
34998 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35001 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35002 this very system call.
35004 The target replies with this packet when it expects @value{GDBN} to
35005 call a host system call on behalf of the target. @value{GDBN} replies
35006 with an appropriate @samp{F} packet and keeps up waiting for the next
35007 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35008 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35009 Protocol Extension}, for more details.
35013 @node General Query Packets
35014 @section General Query Packets
35015 @cindex remote query requests
35017 Packets starting with @samp{q} are @dfn{general query packets};
35018 packets starting with @samp{Q} are @dfn{general set packets}. General
35019 query and set packets are a semi-unified form for retrieving and
35020 sending information to and from the stub.
35022 The initial letter of a query or set packet is followed by a name
35023 indicating what sort of thing the packet applies to. For example,
35024 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35025 definitions with the stub. These packet names follow some
35030 The name must not contain commas, colons or semicolons.
35032 Most @value{GDBN} query and set packets have a leading upper case
35035 The names of custom vendor packets should use a company prefix, in
35036 lower case, followed by a period. For example, packets designed at
35037 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35038 foos) or @samp{Qacme.bar} (for setting bars).
35041 The name of a query or set packet should be separated from any
35042 parameters by a @samp{:}; the parameters themselves should be
35043 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35044 full packet name, and check for a separator or the end of the packet,
35045 in case two packet names share a common prefix. New packets should not begin
35046 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35047 packets predate these conventions, and have arguments without any terminator
35048 for the packet name; we suspect they are in widespread use in places that
35049 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35050 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35053 Like the descriptions of the other packets, each description here
35054 has a template showing the packet's overall syntax, followed by an
35055 explanation of the packet's meaning. We include spaces in some of the
35056 templates for clarity; these are not part of the packet's syntax. No
35057 @value{GDBN} packet uses spaces to separate its components.
35059 Here are the currently defined query and set packets:
35065 Turn on or off the agent as a helper to perform some debugging operations
35066 delegated from @value{GDBN} (@pxref{Control Agent}).
35068 @item QAllow:@var{op}:@var{val}@dots{}
35069 @cindex @samp{QAllow} packet
35070 Specify which operations @value{GDBN} expects to request of the
35071 target, as a semicolon-separated list of operation name and value
35072 pairs. Possible values for @var{op} include @samp{WriteReg},
35073 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35074 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35075 indicating that @value{GDBN} will not request the operation, or 1,
35076 indicating that it may. (The target can then use this to set up its
35077 own internals optimally, for instance if the debugger never expects to
35078 insert breakpoints, it may not need to install its own trap handler.)
35081 @cindex current thread, remote request
35082 @cindex @samp{qC} packet
35083 Return the current thread ID.
35087 @item QC @var{thread-id}
35088 Where @var{thread-id} is a thread ID as documented in
35089 @ref{thread-id syntax}.
35090 @item @r{(anything else)}
35091 Any other reply implies the old thread ID.
35094 @item qCRC:@var{addr},@var{length}
35095 @cindex CRC of memory block, remote request
35096 @cindex @samp{qCRC} packet
35097 @anchor{qCRC packet}
35098 Compute the CRC checksum of a block of memory using CRC-32 defined in
35099 IEEE 802.3. The CRC is computed byte at a time, taking the most
35100 significant bit of each byte first. The initial pattern code
35101 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35103 @emph{Note:} This is the same CRC used in validating separate debug
35104 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35105 Files}). However the algorithm is slightly different. When validating
35106 separate debug files, the CRC is computed taking the @emph{least}
35107 significant bit of each byte first, and the final result is inverted to
35108 detect trailing zeros.
35113 An error (such as memory fault)
35114 @item C @var{crc32}
35115 The specified memory region's checksum is @var{crc32}.
35118 @item QDisableRandomization:@var{value}
35119 @cindex disable address space randomization, remote request
35120 @cindex @samp{QDisableRandomization} packet
35121 Some target operating systems will randomize the virtual address space
35122 of the inferior process as a security feature, but provide a feature
35123 to disable such randomization, e.g.@: to allow for a more deterministic
35124 debugging experience. On such systems, this packet with a @var{value}
35125 of 1 directs the target to disable address space randomization for
35126 processes subsequently started via @samp{vRun} packets, while a packet
35127 with a @var{value} of 0 tells the target to enable address space
35130 This packet is only available in extended mode (@pxref{extended mode}).
35135 The request succeeded.
35138 An error occurred. The error number @var{nn} is given as hex digits.
35141 An empty reply indicates that @samp{QDisableRandomization} is not supported
35145 This packet is not probed by default; the remote stub must request it,
35146 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35147 This should only be done on targets that actually support disabling
35148 address space randomization.
35151 @itemx qsThreadInfo
35152 @cindex list active threads, remote request
35153 @cindex @samp{qfThreadInfo} packet
35154 @cindex @samp{qsThreadInfo} packet
35155 Obtain a list of all active thread IDs from the target (OS). Since there
35156 may be too many active threads to fit into one reply packet, this query
35157 works iteratively: it may require more than one query/reply sequence to
35158 obtain the entire list of threads. The first query of the sequence will
35159 be the @samp{qfThreadInfo} query; subsequent queries in the
35160 sequence will be the @samp{qsThreadInfo} query.
35162 NOTE: This packet replaces the @samp{qL} query (see below).
35166 @item m @var{thread-id}
35168 @item m @var{thread-id},@var{thread-id}@dots{}
35169 a comma-separated list of thread IDs
35171 (lower case letter @samp{L}) denotes end of list.
35174 In response to each query, the target will reply with a list of one or
35175 more thread IDs, separated by commas.
35176 @value{GDBN} will respond to each reply with a request for more thread
35177 ids (using the @samp{qs} form of the query), until the target responds
35178 with @samp{l} (lower-case ell, for @dfn{last}).
35179 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35182 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35183 initial connection with the remote target, and the very first thread ID
35184 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35185 message. Therefore, the stub should ensure that the first thread ID in
35186 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35188 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35189 @cindex get thread-local storage address, remote request
35190 @cindex @samp{qGetTLSAddr} packet
35191 Fetch the address associated with thread local storage specified
35192 by @var{thread-id}, @var{offset}, and @var{lm}.
35194 @var{thread-id} is the thread ID associated with the
35195 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35197 @var{offset} is the (big endian, hex encoded) offset associated with the
35198 thread local variable. (This offset is obtained from the debug
35199 information associated with the variable.)
35201 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35202 load module associated with the thread local storage. For example,
35203 a @sc{gnu}/Linux system will pass the link map address of the shared
35204 object associated with the thread local storage under consideration.
35205 Other operating environments may choose to represent the load module
35206 differently, so the precise meaning of this parameter will vary.
35210 @item @var{XX}@dots{}
35211 Hex encoded (big endian) bytes representing the address of the thread
35212 local storage requested.
35215 An error occurred. The error number @var{nn} is given as hex digits.
35218 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35221 @item qGetTIBAddr:@var{thread-id}
35222 @cindex get thread information block address
35223 @cindex @samp{qGetTIBAddr} packet
35224 Fetch address of the Windows OS specific Thread Information Block.
35226 @var{thread-id} is the thread ID associated with the thread.
35230 @item @var{XX}@dots{}
35231 Hex encoded (big endian) bytes representing the linear address of the
35232 thread information block.
35235 An error occured. This means that either the thread was not found, or the
35236 address could not be retrieved.
35239 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35242 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35243 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35244 digit) is one to indicate the first query and zero to indicate a
35245 subsequent query; @var{threadcount} (two hex digits) is the maximum
35246 number of threads the response packet can contain; and @var{nextthread}
35247 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35248 returned in the response as @var{argthread}.
35250 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35254 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35255 Where: @var{count} (two hex digits) is the number of threads being
35256 returned; @var{done} (one hex digit) is zero to indicate more threads
35257 and one indicates no further threads; @var{argthreadid} (eight hex
35258 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35259 is a sequence of thread IDs, @var{threadid} (eight hex
35260 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35264 @cindex section offsets, remote request
35265 @cindex @samp{qOffsets} packet
35266 Get section offsets that the target used when relocating the downloaded
35271 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35272 Relocate the @code{Text} section by @var{xxx} from its original address.
35273 Relocate the @code{Data} section by @var{yyy} from its original address.
35274 If the object file format provides segment information (e.g.@: @sc{elf}
35275 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35276 segments by the supplied offsets.
35278 @emph{Note: while a @code{Bss} offset may be included in the response,
35279 @value{GDBN} ignores this and instead applies the @code{Data} offset
35280 to the @code{Bss} section.}
35282 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35283 Relocate the first segment of the object file, which conventionally
35284 contains program code, to a starting address of @var{xxx}. If
35285 @samp{DataSeg} is specified, relocate the second segment, which
35286 conventionally contains modifiable data, to a starting address of
35287 @var{yyy}. @value{GDBN} will report an error if the object file
35288 does not contain segment information, or does not contain at least
35289 as many segments as mentioned in the reply. Extra segments are
35290 kept at fixed offsets relative to the last relocated segment.
35293 @item qP @var{mode} @var{thread-id}
35294 @cindex thread information, remote request
35295 @cindex @samp{qP} packet
35296 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35297 encoded 32 bit mode; @var{thread-id} is a thread ID
35298 (@pxref{thread-id syntax}).
35300 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35303 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35307 @cindex non-stop mode, remote request
35308 @cindex @samp{QNonStop} packet
35310 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35311 @xref{Remote Non-Stop}, for more information.
35316 The request succeeded.
35319 An error occurred. The error number @var{nn} is given as hex digits.
35322 An empty reply indicates that @samp{QNonStop} is not supported by
35326 This packet is not probed by default; the remote stub must request it,
35327 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35328 Use of this packet is controlled by the @code{set non-stop} command;
35329 @pxref{Non-Stop Mode}.
35331 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35332 @cindex pass signals to inferior, remote request
35333 @cindex @samp{QPassSignals} packet
35334 @anchor{QPassSignals}
35335 Each listed @var{signal} should be passed directly to the inferior process.
35336 Signals are numbered identically to continue packets and stop replies
35337 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35338 strictly greater than the previous item. These signals do not need to stop
35339 the inferior, or be reported to @value{GDBN}. All other signals should be
35340 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35341 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35342 new list. This packet improves performance when using @samp{handle
35343 @var{signal} nostop noprint pass}.
35348 The request succeeded.
35351 An error occurred. The error number @var{nn} is given as hex digits.
35354 An empty reply indicates that @samp{QPassSignals} is not supported by
35358 Use of this packet is controlled by the @code{set remote pass-signals}
35359 command (@pxref{Remote Configuration, set remote pass-signals}).
35360 This packet is not probed by default; the remote stub must request it,
35361 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35363 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35364 @cindex signals the inferior may see, remote request
35365 @cindex @samp{QProgramSignals} packet
35366 @anchor{QProgramSignals}
35367 Each listed @var{signal} may be delivered to the inferior process.
35368 Others should be silently discarded.
35370 In some cases, the remote stub may need to decide whether to deliver a
35371 signal to the program or not without @value{GDBN} involvement. One
35372 example of that is while detaching --- the program's threads may have
35373 stopped for signals that haven't yet had a chance of being reported to
35374 @value{GDBN}, and so the remote stub can use the signal list specified
35375 by this packet to know whether to deliver or ignore those pending
35378 This does not influence whether to deliver a signal as requested by a
35379 resumption packet (@pxref{vCont packet}).
35381 Signals are numbered identically to continue packets and stop replies
35382 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35383 strictly greater than the previous item. Multiple
35384 @samp{QProgramSignals} packets do not combine; any earlier
35385 @samp{QProgramSignals} list is completely replaced by the new list.
35390 The request succeeded.
35393 An error occurred. The error number @var{nn} is given as hex digits.
35396 An empty reply indicates that @samp{QProgramSignals} is not supported
35400 Use of this packet is controlled by the @code{set remote program-signals}
35401 command (@pxref{Remote Configuration, set remote program-signals}).
35402 This packet is not probed by default; the remote stub must request it,
35403 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35405 @item qRcmd,@var{command}
35406 @cindex execute remote command, remote request
35407 @cindex @samp{qRcmd} packet
35408 @var{command} (hex encoded) is passed to the local interpreter for
35409 execution. Invalid commands should be reported using the output
35410 string. Before the final result packet, the target may also respond
35411 with a number of intermediate @samp{O@var{output}} console output
35412 packets. @emph{Implementors should note that providing access to a
35413 stubs's interpreter may have security implications}.
35418 A command response with no output.
35420 A command response with the hex encoded output string @var{OUTPUT}.
35422 Indicate a badly formed request.
35424 An empty reply indicates that @samp{qRcmd} is not recognized.
35427 (Note that the @code{qRcmd} packet's name is separated from the
35428 command by a @samp{,}, not a @samp{:}, contrary to the naming
35429 conventions above. Please don't use this packet as a model for new
35432 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35433 @cindex searching memory, in remote debugging
35435 @cindex @samp{qSearch:memory} packet
35437 @cindex @samp{qSearch memory} packet
35438 @anchor{qSearch memory}
35439 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35440 Both @var{address} and @var{length} are encoded in hex;
35441 @var{search-pattern} is a sequence of bytes, also hex encoded.
35446 The pattern was not found.
35448 The pattern was found at @var{address}.
35450 A badly formed request or an error was encountered while searching memory.
35452 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35455 @item QStartNoAckMode
35456 @cindex @samp{QStartNoAckMode} packet
35457 @anchor{QStartNoAckMode}
35458 Request that the remote stub disable the normal @samp{+}/@samp{-}
35459 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35464 The stub has switched to no-acknowledgment mode.
35465 @value{GDBN} acknowledges this reponse,
35466 but neither the stub nor @value{GDBN} shall send or expect further
35467 @samp{+}/@samp{-} acknowledgments in the current connection.
35469 An empty reply indicates that the stub does not support no-acknowledgment mode.
35472 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35473 @cindex supported packets, remote query
35474 @cindex features of the remote protocol
35475 @cindex @samp{qSupported} packet
35476 @anchor{qSupported}
35477 Tell the remote stub about features supported by @value{GDBN}, and
35478 query the stub for features it supports. This packet allows
35479 @value{GDBN} and the remote stub to take advantage of each others'
35480 features. @samp{qSupported} also consolidates multiple feature probes
35481 at startup, to improve @value{GDBN} performance---a single larger
35482 packet performs better than multiple smaller probe packets on
35483 high-latency links. Some features may enable behavior which must not
35484 be on by default, e.g.@: because it would confuse older clients or
35485 stubs. Other features may describe packets which could be
35486 automatically probed for, but are not. These features must be
35487 reported before @value{GDBN} will use them. This ``default
35488 unsupported'' behavior is not appropriate for all packets, but it
35489 helps to keep the initial connection time under control with new
35490 versions of @value{GDBN} which support increasing numbers of packets.
35494 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35495 The stub supports or does not support each returned @var{stubfeature},
35496 depending on the form of each @var{stubfeature} (see below for the
35499 An empty reply indicates that @samp{qSupported} is not recognized,
35500 or that no features needed to be reported to @value{GDBN}.
35503 The allowed forms for each feature (either a @var{gdbfeature} in the
35504 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35508 @item @var{name}=@var{value}
35509 The remote protocol feature @var{name} is supported, and associated
35510 with the specified @var{value}. The format of @var{value} depends
35511 on the feature, but it must not include a semicolon.
35513 The remote protocol feature @var{name} is supported, and does not
35514 need an associated value.
35516 The remote protocol feature @var{name} is not supported.
35518 The remote protocol feature @var{name} may be supported, and
35519 @value{GDBN} should auto-detect support in some other way when it is
35520 needed. This form will not be used for @var{gdbfeature} notifications,
35521 but may be used for @var{stubfeature} responses.
35524 Whenever the stub receives a @samp{qSupported} request, the
35525 supplied set of @value{GDBN} features should override any previous
35526 request. This allows @value{GDBN} to put the stub in a known
35527 state, even if the stub had previously been communicating with
35528 a different version of @value{GDBN}.
35530 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35535 This feature indicates whether @value{GDBN} supports multiprocess
35536 extensions to the remote protocol. @value{GDBN} does not use such
35537 extensions unless the stub also reports that it supports them by
35538 including @samp{multiprocess+} in its @samp{qSupported} reply.
35539 @xref{multiprocess extensions}, for details.
35542 This feature indicates that @value{GDBN} supports the XML target
35543 description. If the stub sees @samp{xmlRegisters=} with target
35544 specific strings separated by a comma, it will report register
35548 This feature indicates whether @value{GDBN} supports the
35549 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35550 instruction reply packet}).
35553 Stubs should ignore any unknown values for
35554 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35555 packet supports receiving packets of unlimited length (earlier
35556 versions of @value{GDBN} may reject overly long responses). Additional values
35557 for @var{gdbfeature} may be defined in the future to let the stub take
35558 advantage of new features in @value{GDBN}, e.g.@: incompatible
35559 improvements in the remote protocol---the @samp{multiprocess} feature is
35560 an example of such a feature. The stub's reply should be independent
35561 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35562 describes all the features it supports, and then the stub replies with
35563 all the features it supports.
35565 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35566 responses, as long as each response uses one of the standard forms.
35568 Some features are flags. A stub which supports a flag feature
35569 should respond with a @samp{+} form response. Other features
35570 require values, and the stub should respond with an @samp{=}
35573 Each feature has a default value, which @value{GDBN} will use if
35574 @samp{qSupported} is not available or if the feature is not mentioned
35575 in the @samp{qSupported} response. The default values are fixed; a
35576 stub is free to omit any feature responses that match the defaults.
35578 Not all features can be probed, but for those which can, the probing
35579 mechanism is useful: in some cases, a stub's internal
35580 architecture may not allow the protocol layer to know some information
35581 about the underlying target in advance. This is especially common in
35582 stubs which may be configured for multiple targets.
35584 These are the currently defined stub features and their properties:
35586 @multitable @columnfractions 0.35 0.2 0.12 0.2
35587 @c NOTE: The first row should be @headitem, but we do not yet require
35588 @c a new enough version of Texinfo (4.7) to use @headitem.
35590 @tab Value Required
35594 @item @samp{PacketSize}
35599 @item @samp{qXfer:auxv:read}
35604 @item @samp{qXfer:btrace:read}
35609 @item @samp{qXfer:features:read}
35614 @item @samp{qXfer:libraries:read}
35619 @item @samp{qXfer:libraries-svr4:read}
35624 @item @samp{augmented-libraries-svr4-read}
35629 @item @samp{qXfer:memory-map:read}
35634 @item @samp{qXfer:sdata:read}
35639 @item @samp{qXfer:spu:read}
35644 @item @samp{qXfer:spu:write}
35649 @item @samp{qXfer:siginfo:read}
35654 @item @samp{qXfer:siginfo:write}
35659 @item @samp{qXfer:threads:read}
35664 @item @samp{qXfer:traceframe-info:read}
35669 @item @samp{qXfer:uib:read}
35674 @item @samp{qXfer:fdpic:read}
35679 @item @samp{Qbtrace:off}
35684 @item @samp{Qbtrace:bts}
35689 @item @samp{QNonStop}
35694 @item @samp{QPassSignals}
35699 @item @samp{QStartNoAckMode}
35704 @item @samp{multiprocess}
35709 @item @samp{ConditionalBreakpoints}
35714 @item @samp{ConditionalTracepoints}
35719 @item @samp{ReverseContinue}
35724 @item @samp{ReverseStep}
35729 @item @samp{TracepointSource}
35734 @item @samp{QAgent}
35739 @item @samp{QAllow}
35744 @item @samp{QDisableRandomization}
35749 @item @samp{EnableDisableTracepoints}
35754 @item @samp{QTBuffer:size}
35759 @item @samp{tracenz}
35764 @item @samp{BreakpointCommands}
35771 These are the currently defined stub features, in more detail:
35774 @cindex packet size, remote protocol
35775 @item PacketSize=@var{bytes}
35776 The remote stub can accept packets up to at least @var{bytes} in
35777 length. @value{GDBN} will send packets up to this size for bulk
35778 transfers, and will never send larger packets. This is a limit on the
35779 data characters in the packet, including the frame and checksum.
35780 There is no trailing NUL byte in a remote protocol packet; if the stub
35781 stores packets in a NUL-terminated format, it should allow an extra
35782 byte in its buffer for the NUL. If this stub feature is not supported,
35783 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35785 @item qXfer:auxv:read
35786 The remote stub understands the @samp{qXfer:auxv:read} packet
35787 (@pxref{qXfer auxiliary vector read}).
35789 @item qXfer:btrace:read
35790 The remote stub understands the @samp{qXfer:btrace:read}
35791 packet (@pxref{qXfer btrace read}).
35793 @item qXfer:features:read
35794 The remote stub understands the @samp{qXfer:features:read} packet
35795 (@pxref{qXfer target description read}).
35797 @item qXfer:libraries:read
35798 The remote stub understands the @samp{qXfer:libraries:read} packet
35799 (@pxref{qXfer library list read}).
35801 @item qXfer:libraries-svr4:read
35802 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35803 (@pxref{qXfer svr4 library list read}).
35805 @item augmented-libraries-svr4-read
35806 The remote stub understands the augmented form of the
35807 @samp{qXfer:libraries-svr4:read} packet
35808 (@pxref{qXfer svr4 library list read}).
35810 @item qXfer:memory-map:read
35811 The remote stub understands the @samp{qXfer:memory-map:read} packet
35812 (@pxref{qXfer memory map read}).
35814 @item qXfer:sdata:read
35815 The remote stub understands the @samp{qXfer:sdata:read} packet
35816 (@pxref{qXfer sdata read}).
35818 @item qXfer:spu:read
35819 The remote stub understands the @samp{qXfer:spu:read} packet
35820 (@pxref{qXfer spu read}).
35822 @item qXfer:spu:write
35823 The remote stub understands the @samp{qXfer:spu:write} packet
35824 (@pxref{qXfer spu write}).
35826 @item qXfer:siginfo:read
35827 The remote stub understands the @samp{qXfer:siginfo:read} packet
35828 (@pxref{qXfer siginfo read}).
35830 @item qXfer:siginfo:write
35831 The remote stub understands the @samp{qXfer:siginfo:write} packet
35832 (@pxref{qXfer siginfo write}).
35834 @item qXfer:threads:read
35835 The remote stub understands the @samp{qXfer:threads:read} packet
35836 (@pxref{qXfer threads read}).
35838 @item qXfer:traceframe-info:read
35839 The remote stub understands the @samp{qXfer:traceframe-info:read}
35840 packet (@pxref{qXfer traceframe info read}).
35842 @item qXfer:uib:read
35843 The remote stub understands the @samp{qXfer:uib:read}
35844 packet (@pxref{qXfer unwind info block}).
35846 @item qXfer:fdpic:read
35847 The remote stub understands the @samp{qXfer:fdpic:read}
35848 packet (@pxref{qXfer fdpic loadmap read}).
35851 The remote stub understands the @samp{QNonStop} packet
35852 (@pxref{QNonStop}).
35855 The remote stub understands the @samp{QPassSignals} packet
35856 (@pxref{QPassSignals}).
35858 @item QStartNoAckMode
35859 The remote stub understands the @samp{QStartNoAckMode} packet and
35860 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35863 @anchor{multiprocess extensions}
35864 @cindex multiprocess extensions, in remote protocol
35865 The remote stub understands the multiprocess extensions to the remote
35866 protocol syntax. The multiprocess extensions affect the syntax of
35867 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35868 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35869 replies. Note that reporting this feature indicates support for the
35870 syntactic extensions only, not that the stub necessarily supports
35871 debugging of more than one process at a time. The stub must not use
35872 multiprocess extensions in packet replies unless @value{GDBN} has also
35873 indicated it supports them in its @samp{qSupported} request.
35875 @item qXfer:osdata:read
35876 The remote stub understands the @samp{qXfer:osdata:read} packet
35877 ((@pxref{qXfer osdata read}).
35879 @item ConditionalBreakpoints
35880 The target accepts and implements evaluation of conditional expressions
35881 defined for breakpoints. The target will only report breakpoint triggers
35882 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35884 @item ConditionalTracepoints
35885 The remote stub accepts and implements conditional expressions defined
35886 for tracepoints (@pxref{Tracepoint Conditions}).
35888 @item ReverseContinue
35889 The remote stub accepts and implements the reverse continue packet
35893 The remote stub accepts and implements the reverse step packet
35896 @item TracepointSource
35897 The remote stub understands the @samp{QTDPsrc} packet that supplies
35898 the source form of tracepoint definitions.
35901 The remote stub understands the @samp{QAgent} packet.
35904 The remote stub understands the @samp{QAllow} packet.
35906 @item QDisableRandomization
35907 The remote stub understands the @samp{QDisableRandomization} packet.
35909 @item StaticTracepoint
35910 @cindex static tracepoints, in remote protocol
35911 The remote stub supports static tracepoints.
35913 @item InstallInTrace
35914 @anchor{install tracepoint in tracing}
35915 The remote stub supports installing tracepoint in tracing.
35917 @item EnableDisableTracepoints
35918 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35919 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35920 to be enabled and disabled while a trace experiment is running.
35922 @item QTBuffer:size
35923 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35924 packet that allows to change the size of the trace buffer.
35927 @cindex string tracing, in remote protocol
35928 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35929 See @ref{Bytecode Descriptions} for details about the bytecode.
35931 @item BreakpointCommands
35932 @cindex breakpoint commands, in remote protocol
35933 The remote stub supports running a breakpoint's command list itself,
35934 rather than reporting the hit to @value{GDBN}.
35937 The remote stub understands the @samp{Qbtrace:off} packet.
35940 The remote stub understands the @samp{Qbtrace:bts} packet.
35945 @cindex symbol lookup, remote request
35946 @cindex @samp{qSymbol} packet
35947 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35948 requests. Accept requests from the target for the values of symbols.
35953 The target does not need to look up any (more) symbols.
35954 @item qSymbol:@var{sym_name}
35955 The target requests the value of symbol @var{sym_name} (hex encoded).
35956 @value{GDBN} may provide the value by using the
35957 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35961 @item qSymbol:@var{sym_value}:@var{sym_name}
35962 Set the value of @var{sym_name} to @var{sym_value}.
35964 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35965 target has previously requested.
35967 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35968 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35974 The target does not need to look up any (more) symbols.
35975 @item qSymbol:@var{sym_name}
35976 The target requests the value of a new symbol @var{sym_name} (hex
35977 encoded). @value{GDBN} will continue to supply the values of symbols
35978 (if available), until the target ceases to request them.
35983 @itemx QTDisconnected
35990 @itemx qTMinFTPILen
35992 @xref{Tracepoint Packets}.
35994 @item qThreadExtraInfo,@var{thread-id}
35995 @cindex thread attributes info, remote request
35996 @cindex @samp{qThreadExtraInfo} packet
35997 Obtain from the target OS a printable string description of thread
35998 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
35999 for the forms of @var{thread-id}. This
36000 string may contain anything that the target OS thinks is interesting
36001 for @value{GDBN} to tell the user about the thread. The string is
36002 displayed in @value{GDBN}'s @code{info threads} display. Some
36003 examples of possible thread extra info strings are @samp{Runnable}, or
36004 @samp{Blocked on Mutex}.
36008 @item @var{XX}@dots{}
36009 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36010 comprising the printable string containing the extra information about
36011 the thread's attributes.
36014 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36015 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36016 conventions above. Please don't use this packet as a model for new
36035 @xref{Tracepoint Packets}.
36037 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36038 @cindex read special object, remote request
36039 @cindex @samp{qXfer} packet
36040 @anchor{qXfer read}
36041 Read uninterpreted bytes from the target's special data area
36042 identified by the keyword @var{object}. Request @var{length} bytes
36043 starting at @var{offset} bytes into the data. The content and
36044 encoding of @var{annex} is specific to @var{object}; it can supply
36045 additional details about what data to access.
36047 Here are the specific requests of this form defined so far. All
36048 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36049 formats, listed below.
36052 @item qXfer:auxv:read::@var{offset},@var{length}
36053 @anchor{qXfer auxiliary vector read}
36054 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36055 auxiliary vector}. Note @var{annex} must be empty.
36057 This packet is not probed by default; the remote stub must request it,
36058 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36060 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36061 @anchor{qXfer btrace read}
36063 Return a description of the current branch trace.
36064 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36065 packet may have one of the following values:
36069 Returns all available branch trace.
36072 Returns all available branch trace if the branch trace changed since
36073 the last read request.
36076 Returns the new branch trace since the last read request. Adds a new
36077 block to the end of the trace that begins at zero and ends at the source
36078 location of the first branch in the trace buffer. This extra block is
36079 used to stitch traces together.
36081 If the trace buffer overflowed, returns an error indicating the overflow.
36084 This packet is not probed by default; the remote stub must request it
36085 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36087 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36088 @anchor{qXfer target description read}
36089 Access the @dfn{target description}. @xref{Target Descriptions}. The
36090 annex specifies which XML document to access. The main description is
36091 always loaded from the @samp{target.xml} annex.
36093 This packet is not probed by default; the remote stub must request it,
36094 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36096 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36097 @anchor{qXfer library list read}
36098 Access the target's list of loaded libraries. @xref{Library List Format}.
36099 The annex part of the generic @samp{qXfer} packet must be empty
36100 (@pxref{qXfer read}).
36102 Targets which maintain a list of libraries in the program's memory do
36103 not need to implement this packet; it is designed for platforms where
36104 the operating system manages the list of loaded libraries.
36106 This packet is not probed by default; the remote stub must request it,
36107 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36109 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36110 @anchor{qXfer svr4 library list read}
36111 Access the target's list of loaded libraries when the target is an SVR4
36112 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36113 of the generic @samp{qXfer} packet must be empty unless the remote
36114 stub indicated it supports the augmented form of this packet
36115 by supplying an appropriate @samp{qSupported} response
36116 (@pxref{qXfer read}, @ref{qSupported}).
36118 This packet is optional for better performance on SVR4 targets.
36119 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36121 This packet is not probed by default; the remote stub must request it,
36122 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36124 If the remote stub indicates it supports the augmented form of this
36125 packet then the annex part of the generic @samp{qXfer} packet may
36126 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36127 arguments. The currently supported arguments are:
36130 @item start=@var{address}
36131 A hexadecimal number specifying the address of the @samp{struct
36132 link_map} to start reading the library list from. If unset or zero
36133 then the first @samp{struct link_map} in the library list will be
36134 chosen as the starting point.
36136 @item prev=@var{address}
36137 A hexadecimal number specifying the address of the @samp{struct
36138 link_map} immediately preceding the @samp{struct link_map}
36139 specified by the @samp{start} argument. If unset or zero then
36140 the remote stub will expect that no @samp{struct link_map}
36141 exists prior to the starting point.
36145 Arguments that are not understood by the remote stub will be silently
36148 @item qXfer:memory-map:read::@var{offset},@var{length}
36149 @anchor{qXfer memory map read}
36150 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36151 annex part of the generic @samp{qXfer} packet must be empty
36152 (@pxref{qXfer read}).
36154 This packet is not probed by default; the remote stub must request it,
36155 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36157 @item qXfer:sdata:read::@var{offset},@var{length}
36158 @anchor{qXfer sdata read}
36160 Read contents of the extra collected static tracepoint marker
36161 information. The annex part of the generic @samp{qXfer} packet must
36162 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36165 This packet is not probed by default; the remote stub must request it,
36166 by supplying an appropriate @samp{qSupported} response
36167 (@pxref{qSupported}).
36169 @item qXfer:siginfo:read::@var{offset},@var{length}
36170 @anchor{qXfer siginfo read}
36171 Read contents of the extra signal information on the target
36172 system. The annex part of the generic @samp{qXfer} packet must be
36173 empty (@pxref{qXfer read}).
36175 This packet is not probed by default; the remote stub must request it,
36176 by supplying an appropriate @samp{qSupported} response
36177 (@pxref{qSupported}).
36179 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36180 @anchor{qXfer spu read}
36181 Read contents of an @code{spufs} file on the target system. The
36182 annex specifies which file to read; it must be of the form
36183 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36184 in the target process, and @var{name} identifes the @code{spufs} file
36185 in that context to be accessed.
36187 This packet is not probed by default; the remote stub must request it,
36188 by supplying an appropriate @samp{qSupported} response
36189 (@pxref{qSupported}).
36191 @item qXfer:threads:read::@var{offset},@var{length}
36192 @anchor{qXfer threads read}
36193 Access the list of threads on target. @xref{Thread List Format}. The
36194 annex part of the generic @samp{qXfer} packet must be empty
36195 (@pxref{qXfer read}).
36197 This packet is not probed by default; the remote stub must request it,
36198 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36200 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36201 @anchor{qXfer traceframe info read}
36203 Return a description of the current traceframe's contents.
36204 @xref{Traceframe Info Format}. The annex part of the generic
36205 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36207 This packet is not probed by default; the remote stub must request it,
36208 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36210 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36211 @anchor{qXfer unwind info block}
36213 Return the unwind information block for @var{pc}. This packet is used
36214 on OpenVMS/ia64 to ask the kernel unwind information.
36216 This packet is not probed by default.
36218 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36219 @anchor{qXfer fdpic loadmap read}
36220 Read contents of @code{loadmap}s on the target system. The
36221 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36222 executable @code{loadmap} or interpreter @code{loadmap} to read.
36224 This packet is not probed by default; the remote stub must request it,
36225 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36227 @item qXfer:osdata:read::@var{offset},@var{length}
36228 @anchor{qXfer osdata read}
36229 Access the target's @dfn{operating system information}.
36230 @xref{Operating System Information}.
36237 Data @var{data} (@pxref{Binary Data}) has been read from the
36238 target. There may be more data at a higher address (although
36239 it is permitted to return @samp{m} even for the last valid
36240 block of data, as long as at least one byte of data was read).
36241 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36245 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36246 There is no more data to be read. It is possible for @var{data} to
36247 have fewer bytes than the @var{length} in the request.
36250 The @var{offset} in the request is at the end of the data.
36251 There is no more data to be read.
36254 The request was malformed, or @var{annex} was invalid.
36257 The offset was invalid, or there was an error encountered reading the data.
36258 The @var{nn} part is a hex-encoded @code{errno} value.
36261 An empty reply indicates the @var{object} string was not recognized by
36262 the stub, or that the object does not support reading.
36265 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36266 @cindex write data into object, remote request
36267 @anchor{qXfer write}
36268 Write uninterpreted bytes into the target's special data area
36269 identified by the keyword @var{object}, starting at @var{offset} bytes
36270 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36271 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36272 is specific to @var{object}; it can supply additional details about what data
36275 Here are the specific requests of this form defined so far. All
36276 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36277 formats, listed below.
36280 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36281 @anchor{qXfer siginfo write}
36282 Write @var{data} to the extra signal information on the target system.
36283 The annex part of the generic @samp{qXfer} packet must be
36284 empty (@pxref{qXfer write}).
36286 This packet is not probed by default; the remote stub must request it,
36287 by supplying an appropriate @samp{qSupported} response
36288 (@pxref{qSupported}).
36290 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36291 @anchor{qXfer spu write}
36292 Write @var{data} to an @code{spufs} file on the target system. The
36293 annex specifies which file to write; it must be of the form
36294 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36295 in the target process, and @var{name} identifes the @code{spufs} file
36296 in that context to be accessed.
36298 This packet is not probed by default; the remote stub must request it,
36299 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36305 @var{nn} (hex encoded) is the number of bytes written.
36306 This may be fewer bytes than supplied in the request.
36309 The request was malformed, or @var{annex} was invalid.
36312 The offset was invalid, or there was an error encountered writing the data.
36313 The @var{nn} part is a hex-encoded @code{errno} value.
36316 An empty reply indicates the @var{object} string was not
36317 recognized by the stub, or that the object does not support writing.
36320 @item qXfer:@var{object}:@var{operation}:@dots{}
36321 Requests of this form may be added in the future. When a stub does
36322 not recognize the @var{object} keyword, or its support for
36323 @var{object} does not recognize the @var{operation} keyword, the stub
36324 must respond with an empty packet.
36326 @item qAttached:@var{pid}
36327 @cindex query attached, remote request
36328 @cindex @samp{qAttached} packet
36329 Return an indication of whether the remote server attached to an
36330 existing process or created a new process. When the multiprocess
36331 protocol extensions are supported (@pxref{multiprocess extensions}),
36332 @var{pid} is an integer in hexadecimal format identifying the target
36333 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36334 the query packet will be simplified as @samp{qAttached}.
36336 This query is used, for example, to know whether the remote process
36337 should be detached or killed when a @value{GDBN} session is ended with
36338 the @code{quit} command.
36343 The remote server attached to an existing process.
36345 The remote server created a new process.
36347 A badly formed request or an error was encountered.
36351 Enable branch tracing for the current thread using bts tracing.
36356 Branch tracing has been enabled.
36358 A badly formed request or an error was encountered.
36362 Disable branch tracing for the current thread.
36367 Branch tracing has been disabled.
36369 A badly formed request or an error was encountered.
36374 @node Architecture-Specific Protocol Details
36375 @section Architecture-Specific Protocol Details
36377 This section describes how the remote protocol is applied to specific
36378 target architectures. Also see @ref{Standard Target Features}, for
36379 details of XML target descriptions for each architecture.
36382 * ARM-Specific Protocol Details::
36383 * MIPS-Specific Protocol Details::
36386 @node ARM-Specific Protocol Details
36387 @subsection @acronym{ARM}-specific Protocol Details
36390 * ARM Breakpoint Kinds::
36393 @node ARM Breakpoint Kinds
36394 @subsubsection @acronym{ARM} Breakpoint Kinds
36395 @cindex breakpoint kinds, @acronym{ARM}
36397 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36402 16-bit Thumb mode breakpoint.
36405 32-bit Thumb mode (Thumb-2) breakpoint.
36408 32-bit @acronym{ARM} mode breakpoint.
36412 @node MIPS-Specific Protocol Details
36413 @subsection @acronym{MIPS}-specific Protocol Details
36416 * MIPS Register packet Format::
36417 * MIPS Breakpoint Kinds::
36420 @node MIPS Register packet Format
36421 @subsubsection @acronym{MIPS} Register Packet Format
36422 @cindex register packet format, @acronym{MIPS}
36424 The following @code{g}/@code{G} packets have previously been defined.
36425 In the below, some thirty-two bit registers are transferred as
36426 sixty-four bits. Those registers should be zero/sign extended (which?)
36427 to fill the space allocated. Register bytes are transferred in target
36428 byte order. The two nibbles within a register byte are transferred
36429 most-significant -- least-significant.
36434 All registers are transferred as thirty-two bit quantities in the order:
36435 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36436 registers; fsr; fir; fp.
36439 All registers are transferred as sixty-four bit quantities (including
36440 thirty-two bit registers such as @code{sr}). The ordering is the same
36445 @node MIPS Breakpoint Kinds
36446 @subsubsection @acronym{MIPS} Breakpoint Kinds
36447 @cindex breakpoint kinds, @acronym{MIPS}
36449 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36454 16-bit @acronym{MIPS16} mode breakpoint.
36457 16-bit @acronym{microMIPS} mode breakpoint.
36460 32-bit standard @acronym{MIPS} mode breakpoint.
36463 32-bit @acronym{microMIPS} mode breakpoint.
36467 @node Tracepoint Packets
36468 @section Tracepoint Packets
36469 @cindex tracepoint packets
36470 @cindex packets, tracepoint
36472 Here we describe the packets @value{GDBN} uses to implement
36473 tracepoints (@pxref{Tracepoints}).
36477 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36478 @cindex @samp{QTDP} packet
36479 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36480 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36481 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36482 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36483 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36484 the number of bytes that the target should copy elsewhere to make room
36485 for the tracepoint. If an @samp{X} is present, it introduces a
36486 tracepoint condition, which consists of a hexadecimal length, followed
36487 by a comma and hex-encoded bytes, in a manner similar to action
36488 encodings as described below. If the trailing @samp{-} is present,
36489 further @samp{QTDP} packets will follow to specify this tracepoint's
36495 The packet was understood and carried out.
36497 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36499 The packet was not recognized.
36502 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36503 Define actions to be taken when a tracepoint is hit. The @var{n} and
36504 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36505 this tracepoint. This packet may only be sent immediately after
36506 another @samp{QTDP} packet that ended with a @samp{-}. If the
36507 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36508 specifying more actions for this tracepoint.
36510 In the series of action packets for a given tracepoint, at most one
36511 can have an @samp{S} before its first @var{action}. If such a packet
36512 is sent, it and the following packets define ``while-stepping''
36513 actions. Any prior packets define ordinary actions --- that is, those
36514 taken when the tracepoint is first hit. If no action packet has an
36515 @samp{S}, then all the packets in the series specify ordinary
36516 tracepoint actions.
36518 The @samp{@var{action}@dots{}} portion of the packet is a series of
36519 actions, concatenated without separators. Each action has one of the
36525 Collect the registers whose bits are set in @var{mask},
36526 a hexadecimal number whose @var{i}'th bit is set if register number
36527 @var{i} should be collected. (The least significant bit is numbered
36528 zero.) Note that @var{mask} may be any number of digits long; it may
36529 not fit in a 32-bit word.
36531 @item M @var{basereg},@var{offset},@var{len}
36532 Collect @var{len} bytes of memory starting at the address in register
36533 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36534 @samp{-1}, then the range has a fixed address: @var{offset} is the
36535 address of the lowest byte to collect. The @var{basereg},
36536 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36537 values (the @samp{-1} value for @var{basereg} is a special case).
36539 @item X @var{len},@var{expr}
36540 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36541 it directs. The agent expression @var{expr} is as described in
36542 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36543 two-digit hex number in the packet; @var{len} is the number of bytes
36544 in the expression (and thus one-half the number of hex digits in the
36549 Any number of actions may be packed together in a single @samp{QTDP}
36550 packet, as long as the packet does not exceed the maximum packet
36551 length (400 bytes, for many stubs). There may be only one @samp{R}
36552 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36553 actions. Any registers referred to by @samp{M} and @samp{X} actions
36554 must be collected by a preceding @samp{R} action. (The
36555 ``while-stepping'' actions are treated as if they were attached to a
36556 separate tracepoint, as far as these restrictions are concerned.)
36561 The packet was understood and carried out.
36563 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36565 The packet was not recognized.
36568 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36569 @cindex @samp{QTDPsrc} packet
36570 Specify a source string of tracepoint @var{n} at address @var{addr}.
36571 This is useful to get accurate reproduction of the tracepoints
36572 originally downloaded at the beginning of the trace run. The @var{type}
36573 is the name of the tracepoint part, such as @samp{cond} for the
36574 tracepoint's conditional expression (see below for a list of types), while
36575 @var{bytes} is the string, encoded in hexadecimal.
36577 @var{start} is the offset of the @var{bytes} within the overall source
36578 string, while @var{slen} is the total length of the source string.
36579 This is intended for handling source strings that are longer than will
36580 fit in a single packet.
36581 @c Add detailed example when this info is moved into a dedicated
36582 @c tracepoint descriptions section.
36584 The available string types are @samp{at} for the location,
36585 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36586 @value{GDBN} sends a separate packet for each command in the action
36587 list, in the same order in which the commands are stored in the list.
36589 The target does not need to do anything with source strings except
36590 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36593 Although this packet is optional, and @value{GDBN} will only send it
36594 if the target replies with @samp{TracepointSource} @xref{General
36595 Query Packets}, it makes both disconnected tracing and trace files
36596 much easier to use. Otherwise the user must be careful that the
36597 tracepoints in effect while looking at trace frames are identical to
36598 the ones in effect during the trace run; even a small discrepancy
36599 could cause @samp{tdump} not to work, or a particular trace frame not
36602 @item QTDV:@var{n}:@var{value}
36603 @cindex define trace state variable, remote request
36604 @cindex @samp{QTDV} packet
36605 Create a new trace state variable, number @var{n}, with an initial
36606 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36607 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36608 the option of not using this packet for initial values of zero; the
36609 target should simply create the trace state variables as they are
36610 mentioned in expressions.
36612 @item QTFrame:@var{n}
36613 @cindex @samp{QTFrame} packet
36614 Select the @var{n}'th tracepoint frame from the buffer, and use the
36615 register and memory contents recorded there to answer subsequent
36616 request packets from @value{GDBN}.
36618 A successful reply from the stub indicates that the stub has found the
36619 requested frame. The response is a series of parts, concatenated
36620 without separators, describing the frame we selected. Each part has
36621 one of the following forms:
36625 The selected frame is number @var{n} in the trace frame buffer;
36626 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36627 was no frame matching the criteria in the request packet.
36630 The selected trace frame records a hit of tracepoint number @var{t};
36631 @var{t} is a hexadecimal number.
36635 @item QTFrame:pc:@var{addr}
36636 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36637 currently selected frame whose PC is @var{addr};
36638 @var{addr} is a hexadecimal number.
36640 @item QTFrame:tdp:@var{t}
36641 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36642 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36643 is a hexadecimal number.
36645 @item QTFrame:range:@var{start}:@var{end}
36646 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36647 currently selected frame whose PC is between @var{start} (inclusive)
36648 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36651 @item QTFrame:outside:@var{start}:@var{end}
36652 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36653 frame @emph{outside} the given range of addresses (exclusive).
36656 @cindex @samp{qTMinFTPILen} packet
36657 This packet requests the minimum length of instruction at which a fast
36658 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36659 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36660 it depends on the target system being able to create trampolines in
36661 the first 64K of memory, which might or might not be possible for that
36662 system. So the reply to this packet will be 4 if it is able to
36669 The minimum instruction length is currently unknown.
36671 The minimum instruction length is @var{length}, where @var{length}
36672 is a hexadecimal number greater or equal to 1. A reply
36673 of 1 means that a fast tracepoint may be placed on any instruction
36674 regardless of size.
36676 An error has occurred.
36678 An empty reply indicates that the request is not supported by the stub.
36682 @cindex @samp{QTStart} packet
36683 Begin the tracepoint experiment. Begin collecting data from
36684 tracepoint hits in the trace frame buffer. This packet supports the
36685 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36686 instruction reply packet}).
36689 @cindex @samp{QTStop} packet
36690 End the tracepoint experiment. Stop collecting trace frames.
36692 @item QTEnable:@var{n}:@var{addr}
36694 @cindex @samp{QTEnable} packet
36695 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36696 experiment. If the tracepoint was previously disabled, then collection
36697 of data from it will resume.
36699 @item QTDisable:@var{n}:@var{addr}
36701 @cindex @samp{QTDisable} packet
36702 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36703 experiment. No more data will be collected from the tracepoint unless
36704 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36707 @cindex @samp{QTinit} packet
36708 Clear the table of tracepoints, and empty the trace frame buffer.
36710 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36711 @cindex @samp{QTro} packet
36712 Establish the given ranges of memory as ``transparent''. The stub
36713 will answer requests for these ranges from memory's current contents,
36714 if they were not collected as part of the tracepoint hit.
36716 @value{GDBN} uses this to mark read-only regions of memory, like those
36717 containing program code. Since these areas never change, they should
36718 still have the same contents they did when the tracepoint was hit, so
36719 there's no reason for the stub to refuse to provide their contents.
36721 @item QTDisconnected:@var{value}
36722 @cindex @samp{QTDisconnected} packet
36723 Set the choice to what to do with the tracing run when @value{GDBN}
36724 disconnects from the target. A @var{value} of 1 directs the target to
36725 continue the tracing run, while 0 tells the target to stop tracing if
36726 @value{GDBN} is no longer in the picture.
36729 @cindex @samp{qTStatus} packet
36730 Ask the stub if there is a trace experiment running right now.
36732 The reply has the form:
36736 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36737 @var{running} is a single digit @code{1} if the trace is presently
36738 running, or @code{0} if not. It is followed by semicolon-separated
36739 optional fields that an agent may use to report additional status.
36743 If the trace is not running, the agent may report any of several
36744 explanations as one of the optional fields:
36749 No trace has been run yet.
36751 @item tstop[:@var{text}]:0
36752 The trace was stopped by a user-originated stop command. The optional
36753 @var{text} field is a user-supplied string supplied as part of the
36754 stop command (for instance, an explanation of why the trace was
36755 stopped manually). It is hex-encoded.
36758 The trace stopped because the trace buffer filled up.
36760 @item tdisconnected:0
36761 The trace stopped because @value{GDBN} disconnected from the target.
36763 @item tpasscount:@var{tpnum}
36764 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36766 @item terror:@var{text}:@var{tpnum}
36767 The trace stopped because tracepoint @var{tpnum} had an error. The
36768 string @var{text} is available to describe the nature of the error
36769 (for instance, a divide by zero in the condition expression); it
36773 The trace stopped for some other reason.
36777 Additional optional fields supply statistical and other information.
36778 Although not required, they are extremely useful for users monitoring
36779 the progress of a trace run. If a trace has stopped, and these
36780 numbers are reported, they must reflect the state of the just-stopped
36785 @item tframes:@var{n}
36786 The number of trace frames in the buffer.
36788 @item tcreated:@var{n}
36789 The total number of trace frames created during the run. This may
36790 be larger than the trace frame count, if the buffer is circular.
36792 @item tsize:@var{n}
36793 The total size of the trace buffer, in bytes.
36795 @item tfree:@var{n}
36796 The number of bytes still unused in the buffer.
36798 @item circular:@var{n}
36799 The value of the circular trace buffer flag. @code{1} means that the
36800 trace buffer is circular and old trace frames will be discarded if
36801 necessary to make room, @code{0} means that the trace buffer is linear
36804 @item disconn:@var{n}
36805 The value of the disconnected tracing flag. @code{1} means that
36806 tracing will continue after @value{GDBN} disconnects, @code{0} means
36807 that the trace run will stop.
36811 @item qTP:@var{tp}:@var{addr}
36812 @cindex tracepoint status, remote request
36813 @cindex @samp{qTP} packet
36814 Ask the stub for the current state of tracepoint number @var{tp} at
36815 address @var{addr}.
36819 @item V@var{hits}:@var{usage}
36820 The tracepoint has been hit @var{hits} times so far during the trace
36821 run, and accounts for @var{usage} in the trace buffer. Note that
36822 @code{while-stepping} steps are not counted as separate hits, but the
36823 steps' space consumption is added into the usage number.
36827 @item qTV:@var{var}
36828 @cindex trace state variable value, remote request
36829 @cindex @samp{qTV} packet
36830 Ask the stub for the value of the trace state variable number @var{var}.
36835 The value of the variable is @var{value}. This will be the current
36836 value of the variable if the user is examining a running target, or a
36837 saved value if the variable was collected in the trace frame that the
36838 user is looking at. Note that multiple requests may result in
36839 different reply values, such as when requesting values while the
36840 program is running.
36843 The value of the variable is unknown. This would occur, for example,
36844 if the user is examining a trace frame in which the requested variable
36849 @cindex @samp{qTfP} packet
36851 @cindex @samp{qTsP} packet
36852 These packets request data about tracepoints that are being used by
36853 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36854 of data, and multiple @code{qTsP} to get additional pieces. Replies
36855 to these packets generally take the form of the @code{QTDP} packets
36856 that define tracepoints. (FIXME add detailed syntax)
36859 @cindex @samp{qTfV} packet
36861 @cindex @samp{qTsV} packet
36862 These packets request data about trace state variables that are on the
36863 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36864 and multiple @code{qTsV} to get additional variables. Replies to
36865 these packets follow the syntax of the @code{QTDV} packets that define
36866 trace state variables.
36872 @cindex @samp{qTfSTM} packet
36873 @cindex @samp{qTsSTM} packet
36874 These packets request data about static tracepoint markers that exist
36875 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36876 first piece of data, and multiple @code{qTsSTM} to get additional
36877 pieces. Replies to these packets take the following form:
36881 @item m @var{address}:@var{id}:@var{extra}
36883 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36884 a comma-separated list of markers
36886 (lower case letter @samp{L}) denotes end of list.
36888 An error occurred. The error number @var{nn} is given as hex digits.
36890 An empty reply indicates that the request is not supported by the
36894 The @var{address} is encoded in hex;
36895 @var{id} and @var{extra} are strings encoded in hex.
36897 In response to each query, the target will reply with a list of one or
36898 more markers, separated by commas. @value{GDBN} will respond to each
36899 reply with a request for more markers (using the @samp{qs} form of the
36900 query), until the target responds with @samp{l} (lower-case ell, for
36903 @item qTSTMat:@var{address}
36905 @cindex @samp{qTSTMat} packet
36906 This packets requests data about static tracepoint markers in the
36907 target program at @var{address}. Replies to this packet follow the
36908 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36909 tracepoint markers.
36911 @item QTSave:@var{filename}
36912 @cindex @samp{QTSave} packet
36913 This packet directs the target to save trace data to the file name
36914 @var{filename} in the target's filesystem. The @var{filename} is encoded
36915 as a hex string; the interpretation of the file name (relative vs
36916 absolute, wild cards, etc) is up to the target.
36918 @item qTBuffer:@var{offset},@var{len}
36919 @cindex @samp{qTBuffer} packet
36920 Return up to @var{len} bytes of the current contents of trace buffer,
36921 starting at @var{offset}. The trace buffer is treated as if it were
36922 a contiguous collection of traceframes, as per the trace file format.
36923 The reply consists as many hex-encoded bytes as the target can deliver
36924 in a packet; it is not an error to return fewer than were asked for.
36925 A reply consisting of just @code{l} indicates that no bytes are
36928 @item QTBuffer:circular:@var{value}
36929 This packet directs the target to use a circular trace buffer if
36930 @var{value} is 1, or a linear buffer if the value is 0.
36932 @item QTBuffer:size:@var{size}
36933 @anchor{QTBuffer-size}
36934 @cindex @samp{QTBuffer size} packet
36935 This packet directs the target to make the trace buffer be of size
36936 @var{size} if possible. A value of @code{-1} tells the target to
36937 use whatever size it prefers.
36939 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36940 @cindex @samp{QTNotes} packet
36941 This packet adds optional textual notes to the trace run. Allowable
36942 types include @code{user}, @code{notes}, and @code{tstop}, the
36943 @var{text} fields are arbitrary strings, hex-encoded.
36947 @subsection Relocate instruction reply packet
36948 When installing fast tracepoints in memory, the target may need to
36949 relocate the instruction currently at the tracepoint address to a
36950 different address in memory. For most instructions, a simple copy is
36951 enough, but, for example, call instructions that implicitly push the
36952 return address on the stack, and relative branches or other
36953 PC-relative instructions require offset adjustment, so that the effect
36954 of executing the instruction at a different address is the same as if
36955 it had executed in the original location.
36957 In response to several of the tracepoint packets, the target may also
36958 respond with a number of intermediate @samp{qRelocInsn} request
36959 packets before the final result packet, to have @value{GDBN} handle
36960 this relocation operation. If a packet supports this mechanism, its
36961 documentation will explicitly say so. See for example the above
36962 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36963 format of the request is:
36966 @item qRelocInsn:@var{from};@var{to}
36968 This requests @value{GDBN} to copy instruction at address @var{from}
36969 to address @var{to}, possibly adjusted so that executing the
36970 instruction at @var{to} has the same effect as executing it at
36971 @var{from}. @value{GDBN} writes the adjusted instruction to target
36972 memory starting at @var{to}.
36977 @item qRelocInsn:@var{adjusted_size}
36978 Informs the stub the relocation is complete. The @var{adjusted_size} is
36979 the length in bytes of resulting relocated instruction sequence.
36981 A badly formed request was detected, or an error was encountered while
36982 relocating the instruction.
36985 @node Host I/O Packets
36986 @section Host I/O Packets
36987 @cindex Host I/O, remote protocol
36988 @cindex file transfer, remote protocol
36990 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36991 operations on the far side of a remote link. For example, Host I/O is
36992 used to upload and download files to a remote target with its own
36993 filesystem. Host I/O uses the same constant values and data structure
36994 layout as the target-initiated File-I/O protocol. However, the
36995 Host I/O packets are structured differently. The target-initiated
36996 protocol relies on target memory to store parameters and buffers.
36997 Host I/O requests are initiated by @value{GDBN}, and the
36998 target's memory is not involved. @xref{File-I/O Remote Protocol
36999 Extension}, for more details on the target-initiated protocol.
37001 The Host I/O request packets all encode a single operation along with
37002 its arguments. They have this format:
37006 @item vFile:@var{operation}: @var{parameter}@dots{}
37007 @var{operation} is the name of the particular request; the target
37008 should compare the entire packet name up to the second colon when checking
37009 for a supported operation. The format of @var{parameter} depends on
37010 the operation. Numbers are always passed in hexadecimal. Negative
37011 numbers have an explicit minus sign (i.e.@: two's complement is not
37012 used). Strings (e.g.@: filenames) are encoded as a series of
37013 hexadecimal bytes. The last argument to a system call may be a
37014 buffer of escaped binary data (@pxref{Binary Data}).
37018 The valid responses to Host I/O packets are:
37022 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37023 @var{result} is the integer value returned by this operation, usually
37024 non-negative for success and -1 for errors. If an error has occured,
37025 @var{errno} will be included in the result specifying a
37026 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37027 operations which return data, @var{attachment} supplies the data as a
37028 binary buffer. Binary buffers in response packets are escaped in the
37029 normal way (@pxref{Binary Data}). See the individual packet
37030 documentation for the interpretation of @var{result} and
37034 An empty response indicates that this operation is not recognized.
37038 These are the supported Host I/O operations:
37041 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37042 Open a file at @var{filename} and return a file descriptor for it, or
37043 return -1 if an error occurs. The @var{filename} is a string,
37044 @var{flags} is an integer indicating a mask of open flags
37045 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37046 of mode bits to use if the file is created (@pxref{mode_t Values}).
37047 @xref{open}, for details of the open flags and mode values.
37049 @item vFile:close: @var{fd}
37050 Close the open file corresponding to @var{fd} and return 0, or
37051 -1 if an error occurs.
37053 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37054 Read data from the open file corresponding to @var{fd}. Up to
37055 @var{count} bytes will be read from the file, starting at @var{offset}
37056 relative to the start of the file. The target may read fewer bytes;
37057 common reasons include packet size limits and an end-of-file
37058 condition. The number of bytes read is returned. Zero should only be
37059 returned for a successful read at the end of the file, or if
37060 @var{count} was zero.
37062 The data read should be returned as a binary attachment on success.
37063 If zero bytes were read, the response should include an empty binary
37064 attachment (i.e.@: a trailing semicolon). The return value is the
37065 number of target bytes read; the binary attachment may be longer if
37066 some characters were escaped.
37068 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37069 Write @var{data} (a binary buffer) to the open file corresponding
37070 to @var{fd}. Start the write at @var{offset} from the start of the
37071 file. Unlike many @code{write} system calls, there is no
37072 separate @var{count} argument; the length of @var{data} in the
37073 packet is used. @samp{vFile:write} returns the number of bytes written,
37074 which may be shorter than the length of @var{data}, or -1 if an
37077 @item vFile:unlink: @var{filename}
37078 Delete the file at @var{filename} on the target. Return 0,
37079 or -1 if an error occurs. The @var{filename} is a string.
37081 @item vFile:readlink: @var{filename}
37082 Read value of symbolic link @var{filename} on the target. Return
37083 the number of bytes read, or -1 if an error occurs.
37085 The data read should be returned as a binary attachment on success.
37086 If zero bytes were read, the response should include an empty binary
37087 attachment (i.e.@: a trailing semicolon). The return value is the
37088 number of target bytes read; the binary attachment may be longer if
37089 some characters were escaped.
37094 @section Interrupts
37095 @cindex interrupts (remote protocol)
37097 When a program on the remote target is running, @value{GDBN} may
37098 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37099 a @code{BREAK} followed by @code{g},
37100 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37102 The precise meaning of @code{BREAK} is defined by the transport
37103 mechanism and may, in fact, be undefined. @value{GDBN} does not
37104 currently define a @code{BREAK} mechanism for any of the network
37105 interfaces except for TCP, in which case @value{GDBN} sends the
37106 @code{telnet} BREAK sequence.
37108 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37109 transport mechanisms. It is represented by sending the single byte
37110 @code{0x03} without any of the usual packet overhead described in
37111 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37112 transmitted as part of a packet, it is considered to be packet data
37113 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37114 (@pxref{X packet}), used for binary downloads, may include an unescaped
37115 @code{0x03} as part of its packet.
37117 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37118 When Linux kernel receives this sequence from serial port,
37119 it stops execution and connects to gdb.
37121 Stubs are not required to recognize these interrupt mechanisms and the
37122 precise meaning associated with receipt of the interrupt is
37123 implementation defined. If the target supports debugging of multiple
37124 threads and/or processes, it should attempt to interrupt all
37125 currently-executing threads and processes.
37126 If the stub is successful at interrupting the
37127 running program, it should send one of the stop
37128 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37129 of successfully stopping the program in all-stop mode, and a stop reply
37130 for each stopped thread in non-stop mode.
37131 Interrupts received while the
37132 program is stopped are discarded.
37134 @node Notification Packets
37135 @section Notification Packets
37136 @cindex notification packets
37137 @cindex packets, notification
37139 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37140 packets that require no acknowledgment. Both the GDB and the stub
37141 may send notifications (although the only notifications defined at
37142 present are sent by the stub). Notifications carry information
37143 without incurring the round-trip latency of an acknowledgment, and so
37144 are useful for low-impact communications where occasional packet loss
37147 A notification packet has the form @samp{% @var{data} #
37148 @var{checksum}}, where @var{data} is the content of the notification,
37149 and @var{checksum} is a checksum of @var{data}, computed and formatted
37150 as for ordinary @value{GDBN} packets. A notification's @var{data}
37151 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37152 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37153 to acknowledge the notification's receipt or to report its corruption.
37155 Every notification's @var{data} begins with a name, which contains no
37156 colon characters, followed by a colon character.
37158 Recipients should silently ignore corrupted notifications and
37159 notifications they do not understand. Recipients should restart
37160 timeout periods on receipt of a well-formed notification, whether or
37161 not they understand it.
37163 Senders should only send the notifications described here when this
37164 protocol description specifies that they are permitted. In the
37165 future, we may extend the protocol to permit existing notifications in
37166 new contexts; this rule helps older senders avoid confusing newer
37169 (Older versions of @value{GDBN} ignore bytes received until they see
37170 the @samp{$} byte that begins an ordinary packet, so new stubs may
37171 transmit notifications without fear of confusing older clients. There
37172 are no notifications defined for @value{GDBN} to send at the moment, but we
37173 assume that most older stubs would ignore them, as well.)
37175 Each notification is comprised of three parts:
37177 @item @var{name}:@var{event}
37178 The notification packet is sent by the side that initiates the
37179 exchange (currently, only the stub does that), with @var{event}
37180 carrying the specific information about the notification, and
37181 @var{name} specifying the name of the notification.
37183 The acknowledge sent by the other side, usually @value{GDBN}, to
37184 acknowledge the exchange and request the event.
37187 The purpose of an asynchronous notification mechanism is to report to
37188 @value{GDBN} that something interesting happened in the remote stub.
37190 The remote stub may send notification @var{name}:@var{event}
37191 at any time, but @value{GDBN} acknowledges the notification when
37192 appropriate. The notification event is pending before @value{GDBN}
37193 acknowledges. Only one notification at a time may be pending; if
37194 additional events occur before @value{GDBN} has acknowledged the
37195 previous notification, they must be queued by the stub for later
37196 synchronous transmission in response to @var{ack} packets from
37197 @value{GDBN}. Because the notification mechanism is unreliable,
37198 the stub is permitted to resend a notification if it believes
37199 @value{GDBN} may not have received it.
37201 Specifically, notifications may appear when @value{GDBN} is not
37202 otherwise reading input from the stub, or when @value{GDBN} is
37203 expecting to read a normal synchronous response or a
37204 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37205 Notification packets are distinct from any other communication from
37206 the stub so there is no ambiguity.
37208 After receiving a notification, @value{GDBN} shall acknowledge it by
37209 sending a @var{ack} packet as a regular, synchronous request to the
37210 stub. Such acknowledgment is not required to happen immediately, as
37211 @value{GDBN} is permitted to send other, unrelated packets to the
37212 stub first, which the stub should process normally.
37214 Upon receiving a @var{ack} packet, if the stub has other queued
37215 events to report to @value{GDBN}, it shall respond by sending a
37216 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37217 packet to solicit further responses; again, it is permitted to send
37218 other, unrelated packets as well which the stub should process
37221 If the stub receives a @var{ack} packet and there are no additional
37222 @var{event} to report, the stub shall return an @samp{OK} response.
37223 At this point, @value{GDBN} has finished processing a notification
37224 and the stub has completed sending any queued events. @value{GDBN}
37225 won't accept any new notifications until the final @samp{OK} is
37226 received . If further notification events occur, the stub shall send
37227 a new notification, @value{GDBN} shall accept the notification, and
37228 the process shall be repeated.
37230 The process of asynchronous notification can be illustrated by the
37233 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37236 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37238 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37243 The following notifications are defined:
37244 @multitable @columnfractions 0.12 0.12 0.38 0.38
37253 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37254 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37255 for information on how these notifications are acknowledged by
37257 @tab Report an asynchronous stop event in non-stop mode.
37261 @node Remote Non-Stop
37262 @section Remote Protocol Support for Non-Stop Mode
37264 @value{GDBN}'s remote protocol supports non-stop debugging of
37265 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37266 supports non-stop mode, it should report that to @value{GDBN} by including
37267 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37269 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37270 establishing a new connection with the stub. Entering non-stop mode
37271 does not alter the state of any currently-running threads, but targets
37272 must stop all threads in any already-attached processes when entering
37273 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37274 probe the target state after a mode change.
37276 In non-stop mode, when an attached process encounters an event that
37277 would otherwise be reported with a stop reply, it uses the
37278 asynchronous notification mechanism (@pxref{Notification Packets}) to
37279 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37280 in all processes are stopped when a stop reply is sent, in non-stop
37281 mode only the thread reporting the stop event is stopped. That is,
37282 when reporting a @samp{S} or @samp{T} response to indicate completion
37283 of a step operation, hitting a breakpoint, or a fault, only the
37284 affected thread is stopped; any other still-running threads continue
37285 to run. When reporting a @samp{W} or @samp{X} response, all running
37286 threads belonging to other attached processes continue to run.
37288 In non-stop mode, the target shall respond to the @samp{?} packet as
37289 follows. First, any incomplete stop reply notification/@samp{vStopped}
37290 sequence in progress is abandoned. The target must begin a new
37291 sequence reporting stop events for all stopped threads, whether or not
37292 it has previously reported those events to @value{GDBN}. The first
37293 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37294 subsequent stop replies are sent as responses to @samp{vStopped} packets
37295 using the mechanism described above. The target must not send
37296 asynchronous stop reply notifications until the sequence is complete.
37297 If all threads are running when the target receives the @samp{?} packet,
37298 or if the target is not attached to any process, it shall respond
37301 @node Packet Acknowledgment
37302 @section Packet Acknowledgment
37304 @cindex acknowledgment, for @value{GDBN} remote
37305 @cindex packet acknowledgment, for @value{GDBN} remote
37306 By default, when either the host or the target machine receives a packet,
37307 the first response expected is an acknowledgment: either @samp{+} (to indicate
37308 the package was received correctly) or @samp{-} (to request retransmission).
37309 This mechanism allows the @value{GDBN} remote protocol to operate over
37310 unreliable transport mechanisms, such as a serial line.
37312 In cases where the transport mechanism is itself reliable (such as a pipe or
37313 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37314 It may be desirable to disable them in that case to reduce communication
37315 overhead, or for other reasons. This can be accomplished by means of the
37316 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37318 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37319 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37320 and response format still includes the normal checksum, as described in
37321 @ref{Overview}, but the checksum may be ignored by the receiver.
37323 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37324 no-acknowledgment mode, it should report that to @value{GDBN}
37325 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37326 @pxref{qSupported}.
37327 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37328 disabled via the @code{set remote noack-packet off} command
37329 (@pxref{Remote Configuration}),
37330 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37331 Only then may the stub actually turn off packet acknowledgments.
37332 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37333 response, which can be safely ignored by the stub.
37335 Note that @code{set remote noack-packet} command only affects negotiation
37336 between @value{GDBN} and the stub when subsequent connections are made;
37337 it does not affect the protocol acknowledgment state for any current
37339 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37340 new connection is established,
37341 there is also no protocol request to re-enable the acknowledgments
37342 for the current connection, once disabled.
37347 Example sequence of a target being re-started. Notice how the restart
37348 does not get any direct output:
37353 @emph{target restarts}
37356 <- @code{T001:1234123412341234}
37360 Example sequence of a target being stepped by a single instruction:
37363 -> @code{G1445@dots{}}
37368 <- @code{T001:1234123412341234}
37372 <- @code{1455@dots{}}
37376 @node File-I/O Remote Protocol Extension
37377 @section File-I/O Remote Protocol Extension
37378 @cindex File-I/O remote protocol extension
37381 * File-I/O Overview::
37382 * Protocol Basics::
37383 * The F Request Packet::
37384 * The F Reply Packet::
37385 * The Ctrl-C Message::
37387 * List of Supported Calls::
37388 * Protocol-specific Representation of Datatypes::
37390 * File-I/O Examples::
37393 @node File-I/O Overview
37394 @subsection File-I/O Overview
37395 @cindex file-i/o overview
37397 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37398 target to use the host's file system and console I/O to perform various
37399 system calls. System calls on the target system are translated into a
37400 remote protocol packet to the host system, which then performs the needed
37401 actions and returns a response packet to the target system.
37402 This simulates file system operations even on targets that lack file systems.
37404 The protocol is defined to be independent of both the host and target systems.
37405 It uses its own internal representation of datatypes and values. Both
37406 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37407 translating the system-dependent value representations into the internal
37408 protocol representations when data is transmitted.
37410 The communication is synchronous. A system call is possible only when
37411 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37412 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37413 the target is stopped to allow deterministic access to the target's
37414 memory. Therefore File-I/O is not interruptible by target signals. On
37415 the other hand, it is possible to interrupt File-I/O by a user interrupt
37416 (@samp{Ctrl-C}) within @value{GDBN}.
37418 The target's request to perform a host system call does not finish
37419 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37420 after finishing the system call, the target returns to continuing the
37421 previous activity (continue, step). No additional continue or step
37422 request from @value{GDBN} is required.
37425 (@value{GDBP}) continue
37426 <- target requests 'system call X'
37427 target is stopped, @value{GDBN} executes system call
37428 -> @value{GDBN} returns result
37429 ... target continues, @value{GDBN} returns to wait for the target
37430 <- target hits breakpoint and sends a Txx packet
37433 The protocol only supports I/O on the console and to regular files on
37434 the host file system. Character or block special devices, pipes,
37435 named pipes, sockets or any other communication method on the host
37436 system are not supported by this protocol.
37438 File I/O is not supported in non-stop mode.
37440 @node Protocol Basics
37441 @subsection Protocol Basics
37442 @cindex protocol basics, file-i/o
37444 The File-I/O protocol uses the @code{F} packet as the request as well
37445 as reply packet. Since a File-I/O system call can only occur when
37446 @value{GDBN} is waiting for a response from the continuing or stepping target,
37447 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37448 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37449 This @code{F} packet contains all information needed to allow @value{GDBN}
37450 to call the appropriate host system call:
37454 A unique identifier for the requested system call.
37457 All parameters to the system call. Pointers are given as addresses
37458 in the target memory address space. Pointers to strings are given as
37459 pointer/length pair. Numerical values are given as they are.
37460 Numerical control flags are given in a protocol-specific representation.
37464 At this point, @value{GDBN} has to perform the following actions.
37468 If the parameters include pointer values to data needed as input to a
37469 system call, @value{GDBN} requests this data from the target with a
37470 standard @code{m} packet request. This additional communication has to be
37471 expected by the target implementation and is handled as any other @code{m}
37475 @value{GDBN} translates all value from protocol representation to host
37476 representation as needed. Datatypes are coerced into the host types.
37479 @value{GDBN} calls the system call.
37482 It then coerces datatypes back to protocol representation.
37485 If the system call is expected to return data in buffer space specified
37486 by pointer parameters to the call, the data is transmitted to the
37487 target using a @code{M} or @code{X} packet. This packet has to be expected
37488 by the target implementation and is handled as any other @code{M} or @code{X}
37493 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37494 necessary information for the target to continue. This at least contains
37501 @code{errno}, if has been changed by the system call.
37508 After having done the needed type and value coercion, the target continues
37509 the latest continue or step action.
37511 @node The F Request Packet
37512 @subsection The @code{F} Request Packet
37513 @cindex file-i/o request packet
37514 @cindex @code{F} request packet
37516 The @code{F} request packet has the following format:
37519 @item F@var{call-id},@var{parameter@dots{}}
37521 @var{call-id} is the identifier to indicate the host system call to be called.
37522 This is just the name of the function.
37524 @var{parameter@dots{}} are the parameters to the system call.
37525 Parameters are hexadecimal integer values, either the actual values in case
37526 of scalar datatypes, pointers to target buffer space in case of compound
37527 datatypes and unspecified memory areas, or pointer/length pairs in case
37528 of string parameters. These are appended to the @var{call-id} as a
37529 comma-delimited list. All values are transmitted in ASCII
37530 string representation, pointer/length pairs separated by a slash.
37536 @node The F Reply Packet
37537 @subsection The @code{F} Reply Packet
37538 @cindex file-i/o reply packet
37539 @cindex @code{F} reply packet
37541 The @code{F} reply packet has the following format:
37545 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37547 @var{retcode} is the return code of the system call as hexadecimal value.
37549 @var{errno} is the @code{errno} set by the call, in protocol-specific
37551 This parameter can be omitted if the call was successful.
37553 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37554 case, @var{errno} must be sent as well, even if the call was successful.
37555 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37562 or, if the call was interrupted before the host call has been performed:
37569 assuming 4 is the protocol-specific representation of @code{EINTR}.
37574 @node The Ctrl-C Message
37575 @subsection The @samp{Ctrl-C} Message
37576 @cindex ctrl-c message, in file-i/o protocol
37578 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37579 reply packet (@pxref{The F Reply Packet}),
37580 the target should behave as if it had
37581 gotten a break message. The meaning for the target is ``system call
37582 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37583 (as with a break message) and return to @value{GDBN} with a @code{T02}
37586 It's important for the target to know in which
37587 state the system call was interrupted. There are two possible cases:
37591 The system call hasn't been performed on the host yet.
37594 The system call on the host has been finished.
37598 These two states can be distinguished by the target by the value of the
37599 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37600 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37601 on POSIX systems. In any other case, the target may presume that the
37602 system call has been finished --- successfully or not --- and should behave
37603 as if the break message arrived right after the system call.
37605 @value{GDBN} must behave reliably. If the system call has not been called
37606 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37607 @code{errno} in the packet. If the system call on the host has been finished
37608 before the user requests a break, the full action must be finished by
37609 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37610 The @code{F} packet may only be sent when either nothing has happened
37611 or the full action has been completed.
37614 @subsection Console I/O
37615 @cindex console i/o as part of file-i/o
37617 By default and if not explicitly closed by the target system, the file
37618 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37619 on the @value{GDBN} console is handled as any other file output operation
37620 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37621 by @value{GDBN} so that after the target read request from file descriptor
37622 0 all following typing is buffered until either one of the following
37627 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37629 system call is treated as finished.
37632 The user presses @key{RET}. This is treated as end of input with a trailing
37636 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37637 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37641 If the user has typed more characters than fit in the buffer given to
37642 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37643 either another @code{read(0, @dots{})} is requested by the target, or debugging
37644 is stopped at the user's request.
37647 @node List of Supported Calls
37648 @subsection List of Supported Calls
37649 @cindex list of supported file-i/o calls
37666 @unnumberedsubsubsec open
37667 @cindex open, file-i/o system call
37672 int open(const char *pathname, int flags);
37673 int open(const char *pathname, int flags, mode_t mode);
37677 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37680 @var{flags} is the bitwise @code{OR} of the following values:
37684 If the file does not exist it will be created. The host
37685 rules apply as far as file ownership and time stamps
37689 When used with @code{O_CREAT}, if the file already exists it is
37690 an error and open() fails.
37693 If the file already exists and the open mode allows
37694 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37695 truncated to zero length.
37698 The file is opened in append mode.
37701 The file is opened for reading only.
37704 The file is opened for writing only.
37707 The file is opened for reading and writing.
37711 Other bits are silently ignored.
37715 @var{mode} is the bitwise @code{OR} of the following values:
37719 User has read permission.
37722 User has write permission.
37725 Group has read permission.
37728 Group has write permission.
37731 Others have read permission.
37734 Others have write permission.
37738 Other bits are silently ignored.
37741 @item Return value:
37742 @code{open} returns the new file descriptor or -1 if an error
37749 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37752 @var{pathname} refers to a directory.
37755 The requested access is not allowed.
37758 @var{pathname} was too long.
37761 A directory component in @var{pathname} does not exist.
37764 @var{pathname} refers to a device, pipe, named pipe or socket.
37767 @var{pathname} refers to a file on a read-only filesystem and
37768 write access was requested.
37771 @var{pathname} is an invalid pointer value.
37774 No space on device to create the file.
37777 The process already has the maximum number of files open.
37780 The limit on the total number of files open on the system
37784 The call was interrupted by the user.
37790 @unnumberedsubsubsec close
37791 @cindex close, file-i/o system call
37800 @samp{Fclose,@var{fd}}
37802 @item Return value:
37803 @code{close} returns zero on success, or -1 if an error occurred.
37809 @var{fd} isn't a valid open file descriptor.
37812 The call was interrupted by the user.
37818 @unnumberedsubsubsec read
37819 @cindex read, file-i/o system call
37824 int read(int fd, void *buf, unsigned int count);
37828 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37830 @item Return value:
37831 On success, the number of bytes read is returned.
37832 Zero indicates end of file. If count is zero, read
37833 returns zero as well. On error, -1 is returned.
37839 @var{fd} is not a valid file descriptor or is not open for
37843 @var{bufptr} is an invalid pointer value.
37846 The call was interrupted by the user.
37852 @unnumberedsubsubsec write
37853 @cindex write, file-i/o system call
37858 int write(int fd, const void *buf, unsigned int count);
37862 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37864 @item Return value:
37865 On success, the number of bytes written are returned.
37866 Zero indicates nothing was written. On error, -1
37873 @var{fd} is not a valid file descriptor or is not open for
37877 @var{bufptr} is an invalid pointer value.
37880 An attempt was made to write a file that exceeds the
37881 host-specific maximum file size allowed.
37884 No space on device to write the data.
37887 The call was interrupted by the user.
37893 @unnumberedsubsubsec lseek
37894 @cindex lseek, file-i/o system call
37899 long lseek (int fd, long offset, int flag);
37903 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37905 @var{flag} is one of:
37909 The offset is set to @var{offset} bytes.
37912 The offset is set to its current location plus @var{offset}
37916 The offset is set to the size of the file plus @var{offset}
37920 @item Return value:
37921 On success, the resulting unsigned offset in bytes from
37922 the beginning of the file is returned. Otherwise, a
37923 value of -1 is returned.
37929 @var{fd} is not a valid open file descriptor.
37932 @var{fd} is associated with the @value{GDBN} console.
37935 @var{flag} is not a proper value.
37938 The call was interrupted by the user.
37944 @unnumberedsubsubsec rename
37945 @cindex rename, file-i/o system call
37950 int rename(const char *oldpath, const char *newpath);
37954 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37956 @item Return value:
37957 On success, zero is returned. On error, -1 is returned.
37963 @var{newpath} is an existing directory, but @var{oldpath} is not a
37967 @var{newpath} is a non-empty directory.
37970 @var{oldpath} or @var{newpath} is a directory that is in use by some
37974 An attempt was made to make a directory a subdirectory
37978 A component used as a directory in @var{oldpath} or new
37979 path is not a directory. Or @var{oldpath} is a directory
37980 and @var{newpath} exists but is not a directory.
37983 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37986 No access to the file or the path of the file.
37990 @var{oldpath} or @var{newpath} was too long.
37993 A directory component in @var{oldpath} or @var{newpath} does not exist.
37996 The file is on a read-only filesystem.
37999 The device containing the file has no room for the new
38003 The call was interrupted by the user.
38009 @unnumberedsubsubsec unlink
38010 @cindex unlink, file-i/o system call
38015 int unlink(const char *pathname);
38019 @samp{Funlink,@var{pathnameptr}/@var{len}}
38021 @item Return value:
38022 On success, zero is returned. On error, -1 is returned.
38028 No access to the file or the path of the file.
38031 The system does not allow unlinking of directories.
38034 The file @var{pathname} cannot be unlinked because it's
38035 being used by another process.
38038 @var{pathnameptr} is an invalid pointer value.
38041 @var{pathname} was too long.
38044 A directory component in @var{pathname} does not exist.
38047 A component of the path is not a directory.
38050 The file is on a read-only filesystem.
38053 The call was interrupted by the user.
38059 @unnumberedsubsubsec stat/fstat
38060 @cindex fstat, file-i/o system call
38061 @cindex stat, file-i/o system call
38066 int stat(const char *pathname, struct stat *buf);
38067 int fstat(int fd, struct stat *buf);
38071 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38072 @samp{Ffstat,@var{fd},@var{bufptr}}
38074 @item Return value:
38075 On success, zero is returned. On error, -1 is returned.
38081 @var{fd} is not a valid open file.
38084 A directory component in @var{pathname} does not exist or the
38085 path is an empty string.
38088 A component of the path is not a directory.
38091 @var{pathnameptr} is an invalid pointer value.
38094 No access to the file or the path of the file.
38097 @var{pathname} was too long.
38100 The call was interrupted by the user.
38106 @unnumberedsubsubsec gettimeofday
38107 @cindex gettimeofday, file-i/o system call
38112 int gettimeofday(struct timeval *tv, void *tz);
38116 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38118 @item Return value:
38119 On success, 0 is returned, -1 otherwise.
38125 @var{tz} is a non-NULL pointer.
38128 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38134 @unnumberedsubsubsec isatty
38135 @cindex isatty, file-i/o system call
38140 int isatty(int fd);
38144 @samp{Fisatty,@var{fd}}
38146 @item Return value:
38147 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38153 The call was interrupted by the user.
38158 Note that the @code{isatty} call is treated as a special case: it returns
38159 1 to the target if the file descriptor is attached
38160 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38161 would require implementing @code{ioctl} and would be more complex than
38166 @unnumberedsubsubsec system
38167 @cindex system, file-i/o system call
38172 int system(const char *command);
38176 @samp{Fsystem,@var{commandptr}/@var{len}}
38178 @item Return value:
38179 If @var{len} is zero, the return value indicates whether a shell is
38180 available. A zero return value indicates a shell is not available.
38181 For non-zero @var{len}, the value returned is -1 on error and the
38182 return status of the command otherwise. Only the exit status of the
38183 command is returned, which is extracted from the host's @code{system}
38184 return value by calling @code{WEXITSTATUS(retval)}. In case
38185 @file{/bin/sh} could not be executed, 127 is returned.
38191 The call was interrupted by the user.
38196 @value{GDBN} takes over the full task of calling the necessary host calls
38197 to perform the @code{system} call. The return value of @code{system} on
38198 the host is simplified before it's returned
38199 to the target. Any termination signal information from the child process
38200 is discarded, and the return value consists
38201 entirely of the exit status of the called command.
38203 Due to security concerns, the @code{system} call is by default refused
38204 by @value{GDBN}. The user has to allow this call explicitly with the
38205 @code{set remote system-call-allowed 1} command.
38208 @item set remote system-call-allowed
38209 @kindex set remote system-call-allowed
38210 Control whether to allow the @code{system} calls in the File I/O
38211 protocol for the remote target. The default is zero (disabled).
38213 @item show remote system-call-allowed
38214 @kindex show remote system-call-allowed
38215 Show whether the @code{system} calls are allowed in the File I/O
38219 @node Protocol-specific Representation of Datatypes
38220 @subsection Protocol-specific Representation of Datatypes
38221 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38224 * Integral Datatypes::
38226 * Memory Transfer::
38231 @node Integral Datatypes
38232 @unnumberedsubsubsec Integral Datatypes
38233 @cindex integral datatypes, in file-i/o protocol
38235 The integral datatypes used in the system calls are @code{int},
38236 @code{unsigned int}, @code{long}, @code{unsigned long},
38237 @code{mode_t}, and @code{time_t}.
38239 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38240 implemented as 32 bit values in this protocol.
38242 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38244 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38245 in @file{limits.h}) to allow range checking on host and target.
38247 @code{time_t} datatypes are defined as seconds since the Epoch.
38249 All integral datatypes transferred as part of a memory read or write of a
38250 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38253 @node Pointer Values
38254 @unnumberedsubsubsec Pointer Values
38255 @cindex pointer values, in file-i/o protocol
38257 Pointers to target data are transmitted as they are. An exception
38258 is made for pointers to buffers for which the length isn't
38259 transmitted as part of the function call, namely strings. Strings
38260 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38267 which is a pointer to data of length 18 bytes at position 0x1aaf.
38268 The length is defined as the full string length in bytes, including
38269 the trailing null byte. For example, the string @code{"hello world"}
38270 at address 0x123456 is transmitted as
38276 @node Memory Transfer
38277 @unnumberedsubsubsec Memory Transfer
38278 @cindex memory transfer, in file-i/o protocol
38280 Structured data which is transferred using a memory read or write (for
38281 example, a @code{struct stat}) is expected to be in a protocol-specific format
38282 with all scalar multibyte datatypes being big endian. Translation to
38283 this representation needs to be done both by the target before the @code{F}
38284 packet is sent, and by @value{GDBN} before
38285 it transfers memory to the target. Transferred pointers to structured
38286 data should point to the already-coerced data at any time.
38290 @unnumberedsubsubsec struct stat
38291 @cindex struct stat, in file-i/o protocol
38293 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38294 is defined as follows:
38298 unsigned int st_dev; /* device */
38299 unsigned int st_ino; /* inode */
38300 mode_t st_mode; /* protection */
38301 unsigned int st_nlink; /* number of hard links */
38302 unsigned int st_uid; /* user ID of owner */
38303 unsigned int st_gid; /* group ID of owner */
38304 unsigned int st_rdev; /* device type (if inode device) */
38305 unsigned long st_size; /* total size, in bytes */
38306 unsigned long st_blksize; /* blocksize for filesystem I/O */
38307 unsigned long st_blocks; /* number of blocks allocated */
38308 time_t st_atime; /* time of last access */
38309 time_t st_mtime; /* time of last modification */
38310 time_t st_ctime; /* time of last change */
38314 The integral datatypes conform to the definitions given in the
38315 appropriate section (see @ref{Integral Datatypes}, for details) so this
38316 structure is of size 64 bytes.
38318 The values of several fields have a restricted meaning and/or
38324 A value of 0 represents a file, 1 the console.
38327 No valid meaning for the target. Transmitted unchanged.
38330 Valid mode bits are described in @ref{Constants}. Any other
38331 bits have currently no meaning for the target.
38336 No valid meaning for the target. Transmitted unchanged.
38341 These values have a host and file system dependent
38342 accuracy. Especially on Windows hosts, the file system may not
38343 support exact timing values.
38346 The target gets a @code{struct stat} of the above representation and is
38347 responsible for coercing it to the target representation before
38350 Note that due to size differences between the host, target, and protocol
38351 representations of @code{struct stat} members, these members could eventually
38352 get truncated on the target.
38354 @node struct timeval
38355 @unnumberedsubsubsec struct timeval
38356 @cindex struct timeval, in file-i/o protocol
38358 The buffer of type @code{struct timeval} used by the File-I/O protocol
38359 is defined as follows:
38363 time_t tv_sec; /* second */
38364 long tv_usec; /* microsecond */
38368 The integral datatypes conform to the definitions given in the
38369 appropriate section (see @ref{Integral Datatypes}, for details) so this
38370 structure is of size 8 bytes.
38373 @subsection Constants
38374 @cindex constants, in file-i/o protocol
38376 The following values are used for the constants inside of the
38377 protocol. @value{GDBN} and target are responsible for translating these
38378 values before and after the call as needed.
38389 @unnumberedsubsubsec Open Flags
38390 @cindex open flags, in file-i/o protocol
38392 All values are given in hexadecimal representation.
38404 @node mode_t Values
38405 @unnumberedsubsubsec mode_t Values
38406 @cindex mode_t values, in file-i/o protocol
38408 All values are given in octal representation.
38425 @unnumberedsubsubsec Errno Values
38426 @cindex errno values, in file-i/o protocol
38428 All values are given in decimal representation.
38453 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38454 any error value not in the list of supported error numbers.
38457 @unnumberedsubsubsec Lseek Flags
38458 @cindex lseek flags, in file-i/o protocol
38467 @unnumberedsubsubsec Limits
38468 @cindex limits, in file-i/o protocol
38470 All values are given in decimal representation.
38473 INT_MIN -2147483648
38475 UINT_MAX 4294967295
38476 LONG_MIN -9223372036854775808
38477 LONG_MAX 9223372036854775807
38478 ULONG_MAX 18446744073709551615
38481 @node File-I/O Examples
38482 @subsection File-I/O Examples
38483 @cindex file-i/o examples
38485 Example sequence of a write call, file descriptor 3, buffer is at target
38486 address 0x1234, 6 bytes should be written:
38489 <- @code{Fwrite,3,1234,6}
38490 @emph{request memory read from target}
38493 @emph{return "6 bytes written"}
38497 Example sequence of a read call, file descriptor 3, buffer is at target
38498 address 0x1234, 6 bytes should be read:
38501 <- @code{Fread,3,1234,6}
38502 @emph{request memory write to target}
38503 -> @code{X1234,6:XXXXXX}
38504 @emph{return "6 bytes read"}
38508 Example sequence of a read call, call fails on the host due to invalid
38509 file descriptor (@code{EBADF}):
38512 <- @code{Fread,3,1234,6}
38516 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38520 <- @code{Fread,3,1234,6}
38525 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38529 <- @code{Fread,3,1234,6}
38530 -> @code{X1234,6:XXXXXX}
38534 @node Library List Format
38535 @section Library List Format
38536 @cindex library list format, remote protocol
38538 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38539 same process as your application to manage libraries. In this case,
38540 @value{GDBN} can use the loader's symbol table and normal memory
38541 operations to maintain a list of shared libraries. On other
38542 platforms, the operating system manages loaded libraries.
38543 @value{GDBN} can not retrieve the list of currently loaded libraries
38544 through memory operations, so it uses the @samp{qXfer:libraries:read}
38545 packet (@pxref{qXfer library list read}) instead. The remote stub
38546 queries the target's operating system and reports which libraries
38549 The @samp{qXfer:libraries:read} packet returns an XML document which
38550 lists loaded libraries and their offsets. Each library has an
38551 associated name and one or more segment or section base addresses,
38552 which report where the library was loaded in memory.
38554 For the common case of libraries that are fully linked binaries, the
38555 library should have a list of segments. If the target supports
38556 dynamic linking of a relocatable object file, its library XML element
38557 should instead include a list of allocated sections. The segment or
38558 section bases are start addresses, not relocation offsets; they do not
38559 depend on the library's link-time base addresses.
38561 @value{GDBN} must be linked with the Expat library to support XML
38562 library lists. @xref{Expat}.
38564 A simple memory map, with one loaded library relocated by a single
38565 offset, looks like this:
38569 <library name="/lib/libc.so.6">
38570 <segment address="0x10000000"/>
38575 Another simple memory map, with one loaded library with three
38576 allocated sections (.text, .data, .bss), looks like this:
38580 <library name="sharedlib.o">
38581 <section address="0x10000000"/>
38582 <section address="0x20000000"/>
38583 <section address="0x30000000"/>
38588 The format of a library list is described by this DTD:
38591 <!-- library-list: Root element with versioning -->
38592 <!ELEMENT library-list (library)*>
38593 <!ATTLIST library-list version CDATA #FIXED "1.0">
38594 <!ELEMENT library (segment*, section*)>
38595 <!ATTLIST library name CDATA #REQUIRED>
38596 <!ELEMENT segment EMPTY>
38597 <!ATTLIST segment address CDATA #REQUIRED>
38598 <!ELEMENT section EMPTY>
38599 <!ATTLIST section address CDATA #REQUIRED>
38602 In addition, segments and section descriptors cannot be mixed within a
38603 single library element, and you must supply at least one segment or
38604 section for each library.
38606 @node Library List Format for SVR4 Targets
38607 @section Library List Format for SVR4 Targets
38608 @cindex library list format, remote protocol
38610 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38611 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38612 shared libraries. Still a special library list provided by this packet is
38613 more efficient for the @value{GDBN} remote protocol.
38615 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38616 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38617 target, the following parameters are reported:
38621 @code{name}, the absolute file name from the @code{l_name} field of
38622 @code{struct link_map}.
38624 @code{lm} with address of @code{struct link_map} used for TLS
38625 (Thread Local Storage) access.
38627 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38628 @code{struct link_map}. For prelinked libraries this is not an absolute
38629 memory address. It is a displacement of absolute memory address against
38630 address the file was prelinked to during the library load.
38632 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38635 Additionally the single @code{main-lm} attribute specifies address of
38636 @code{struct link_map} used for the main executable. This parameter is used
38637 for TLS access and its presence is optional.
38639 @value{GDBN} must be linked with the Expat library to support XML
38640 SVR4 library lists. @xref{Expat}.
38642 A simple memory map, with two loaded libraries (which do not use prelink),
38646 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38647 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38649 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38651 </library-list-svr>
38654 The format of an SVR4 library list is described by this DTD:
38657 <!-- library-list-svr4: Root element with versioning -->
38658 <!ELEMENT library-list-svr4 (library)*>
38659 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38660 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38661 <!ELEMENT library EMPTY>
38662 <!ATTLIST library name CDATA #REQUIRED>
38663 <!ATTLIST library lm CDATA #REQUIRED>
38664 <!ATTLIST library l_addr CDATA #REQUIRED>
38665 <!ATTLIST library l_ld CDATA #REQUIRED>
38668 @node Memory Map Format
38669 @section Memory Map Format
38670 @cindex memory map format
38672 To be able to write into flash memory, @value{GDBN} needs to obtain a
38673 memory map from the target. This section describes the format of the
38676 The memory map is obtained using the @samp{qXfer:memory-map:read}
38677 (@pxref{qXfer memory map read}) packet and is an XML document that
38678 lists memory regions.
38680 @value{GDBN} must be linked with the Expat library to support XML
38681 memory maps. @xref{Expat}.
38683 The top-level structure of the document is shown below:
38686 <?xml version="1.0"?>
38687 <!DOCTYPE memory-map
38688 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38689 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38695 Each region can be either:
38700 A region of RAM starting at @var{addr} and extending for @var{length}
38704 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38709 A region of read-only memory:
38712 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38717 A region of flash memory, with erasure blocks @var{blocksize}
38721 <memory type="flash" start="@var{addr}" length="@var{length}">
38722 <property name="blocksize">@var{blocksize}</property>
38728 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38729 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38730 packets to write to addresses in such ranges.
38732 The formal DTD for memory map format is given below:
38735 <!-- ................................................... -->
38736 <!-- Memory Map XML DTD ................................ -->
38737 <!-- File: memory-map.dtd .............................. -->
38738 <!-- .................................... .............. -->
38739 <!-- memory-map.dtd -->
38740 <!-- memory-map: Root element with versioning -->
38741 <!ELEMENT memory-map (memory | property)>
38742 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38743 <!ELEMENT memory (property)>
38744 <!-- memory: Specifies a memory region,
38745 and its type, or device. -->
38746 <!ATTLIST memory type CDATA #REQUIRED
38747 start CDATA #REQUIRED
38748 length CDATA #REQUIRED
38749 device CDATA #IMPLIED>
38750 <!-- property: Generic attribute tag -->
38751 <!ELEMENT property (#PCDATA | property)*>
38752 <!ATTLIST property name CDATA #REQUIRED>
38755 @node Thread List Format
38756 @section Thread List Format
38757 @cindex thread list format
38759 To efficiently update the list of threads and their attributes,
38760 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38761 (@pxref{qXfer threads read}) and obtains the XML document with
38762 the following structure:
38765 <?xml version="1.0"?>
38767 <thread id="id" core="0">
38768 ... description ...
38773 Each @samp{thread} element must have the @samp{id} attribute that
38774 identifies the thread (@pxref{thread-id syntax}). The
38775 @samp{core} attribute, if present, specifies which processor core
38776 the thread was last executing on. The content of the of @samp{thread}
38777 element is interpreted as human-readable auxilliary information.
38779 @node Traceframe Info Format
38780 @section Traceframe Info Format
38781 @cindex traceframe info format
38783 To be able to know which objects in the inferior can be examined when
38784 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38785 memory ranges, registers and trace state variables that have been
38786 collected in a traceframe.
38788 This list is obtained using the @samp{qXfer:traceframe-info:read}
38789 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38791 @value{GDBN} must be linked with the Expat library to support XML
38792 traceframe info discovery. @xref{Expat}.
38794 The top-level structure of the document is shown below:
38797 <?xml version="1.0"?>
38798 <!DOCTYPE traceframe-info
38799 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38800 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38806 Each traceframe block can be either:
38811 A region of collected memory starting at @var{addr} and extending for
38812 @var{length} bytes from there:
38815 <memory start="@var{addr}" length="@var{length}"/>
38819 A block indicating trace state variable numbered @var{number} has been
38823 <tvar id="@var{number}"/>
38828 The formal DTD for the traceframe info format is given below:
38831 <!ELEMENT traceframe-info (memory | tvar)* >
38832 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38834 <!ELEMENT memory EMPTY>
38835 <!ATTLIST memory start CDATA #REQUIRED
38836 length CDATA #REQUIRED>
38838 <!ATTLIST tvar id CDATA #REQUIRED>
38841 @node Branch Trace Format
38842 @section Branch Trace Format
38843 @cindex branch trace format
38845 In order to display the branch trace of an inferior thread,
38846 @value{GDBN} needs to obtain the list of branches. This list is
38847 represented as list of sequential code blocks that are connected via
38848 branches. The code in each block has been executed sequentially.
38850 This list is obtained using the @samp{qXfer:btrace:read}
38851 (@pxref{qXfer btrace read}) packet and is an XML document.
38853 @value{GDBN} must be linked with the Expat library to support XML
38854 traceframe info discovery. @xref{Expat}.
38856 The top-level structure of the document is shown below:
38859 <?xml version="1.0"?>
38861 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38862 "http://sourceware.org/gdb/gdb-btrace.dtd">
38871 A block of sequentially executed instructions starting at @var{begin}
38872 and ending at @var{end}:
38875 <block begin="@var{begin}" end="@var{end}"/>
38880 The formal DTD for the branch trace format is given below:
38883 <!ELEMENT btrace (block)* >
38884 <!ATTLIST btrace version CDATA #FIXED "1.0">
38886 <!ELEMENT block EMPTY>
38887 <!ATTLIST block begin CDATA #REQUIRED
38888 end CDATA #REQUIRED>
38891 @include agentexpr.texi
38893 @node Target Descriptions
38894 @appendix Target Descriptions
38895 @cindex target descriptions
38897 One of the challenges of using @value{GDBN} to debug embedded systems
38898 is that there are so many minor variants of each processor
38899 architecture in use. It is common practice for vendors to start with
38900 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38901 and then make changes to adapt it to a particular market niche. Some
38902 architectures have hundreds of variants, available from dozens of
38903 vendors. This leads to a number of problems:
38907 With so many different customized processors, it is difficult for
38908 the @value{GDBN} maintainers to keep up with the changes.
38910 Since individual variants may have short lifetimes or limited
38911 audiences, it may not be worthwhile to carry information about every
38912 variant in the @value{GDBN} source tree.
38914 When @value{GDBN} does support the architecture of the embedded system
38915 at hand, the task of finding the correct architecture name to give the
38916 @command{set architecture} command can be error-prone.
38919 To address these problems, the @value{GDBN} remote protocol allows a
38920 target system to not only identify itself to @value{GDBN}, but to
38921 actually describe its own features. This lets @value{GDBN} support
38922 processor variants it has never seen before --- to the extent that the
38923 descriptions are accurate, and that @value{GDBN} understands them.
38925 @value{GDBN} must be linked with the Expat library to support XML
38926 target descriptions. @xref{Expat}.
38929 * Retrieving Descriptions:: How descriptions are fetched from a target.
38930 * Target Description Format:: The contents of a target description.
38931 * Predefined Target Types:: Standard types available for target
38933 * Standard Target Features:: Features @value{GDBN} knows about.
38936 @node Retrieving Descriptions
38937 @section Retrieving Descriptions
38939 Target descriptions can be read from the target automatically, or
38940 specified by the user manually. The default behavior is to read the
38941 description from the target. @value{GDBN} retrieves it via the remote
38942 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38943 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38944 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38945 XML document, of the form described in @ref{Target Description
38948 Alternatively, you can specify a file to read for the target description.
38949 If a file is set, the target will not be queried. The commands to
38950 specify a file are:
38953 @cindex set tdesc filename
38954 @item set tdesc filename @var{path}
38955 Read the target description from @var{path}.
38957 @cindex unset tdesc filename
38958 @item unset tdesc filename
38959 Do not read the XML target description from a file. @value{GDBN}
38960 will use the description supplied by the current target.
38962 @cindex show tdesc filename
38963 @item show tdesc filename
38964 Show the filename to read for a target description, if any.
38968 @node Target Description Format
38969 @section Target Description Format
38970 @cindex target descriptions, XML format
38972 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38973 document which complies with the Document Type Definition provided in
38974 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38975 means you can use generally available tools like @command{xmllint} to
38976 check that your feature descriptions are well-formed and valid.
38977 However, to help people unfamiliar with XML write descriptions for
38978 their targets, we also describe the grammar here.
38980 Target descriptions can identify the architecture of the remote target
38981 and (for some architectures) provide information about custom register
38982 sets. They can also identify the OS ABI of the remote target.
38983 @value{GDBN} can use this information to autoconfigure for your
38984 target, or to warn you if you connect to an unsupported target.
38986 Here is a simple target description:
38989 <target version="1.0">
38990 <architecture>i386:x86-64</architecture>
38995 This minimal description only says that the target uses
38996 the x86-64 architecture.
38998 A target description has the following overall form, with [ ] marking
38999 optional elements and @dots{} marking repeatable elements. The elements
39000 are explained further below.
39003 <?xml version="1.0"?>
39004 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39005 <target version="1.0">
39006 @r{[}@var{architecture}@r{]}
39007 @r{[}@var{osabi}@r{]}
39008 @r{[}@var{compatible}@r{]}
39009 @r{[}@var{feature}@dots{}@r{]}
39014 The description is generally insensitive to whitespace and line
39015 breaks, under the usual common-sense rules. The XML version
39016 declaration and document type declaration can generally be omitted
39017 (@value{GDBN} does not require them), but specifying them may be
39018 useful for XML validation tools. The @samp{version} attribute for
39019 @samp{<target>} may also be omitted, but we recommend
39020 including it; if future versions of @value{GDBN} use an incompatible
39021 revision of @file{gdb-target.dtd}, they will detect and report
39022 the version mismatch.
39024 @subsection Inclusion
39025 @cindex target descriptions, inclusion
39028 @cindex <xi:include>
39031 It can sometimes be valuable to split a target description up into
39032 several different annexes, either for organizational purposes, or to
39033 share files between different possible target descriptions. You can
39034 divide a description into multiple files by replacing any element of
39035 the target description with an inclusion directive of the form:
39038 <xi:include href="@var{document}"/>
39042 When @value{GDBN} encounters an element of this form, it will retrieve
39043 the named XML @var{document}, and replace the inclusion directive with
39044 the contents of that document. If the current description was read
39045 using @samp{qXfer}, then so will be the included document;
39046 @var{document} will be interpreted as the name of an annex. If the
39047 current description was read from a file, @value{GDBN} will look for
39048 @var{document} as a file in the same directory where it found the
39049 original description.
39051 @subsection Architecture
39052 @cindex <architecture>
39054 An @samp{<architecture>} element has this form:
39057 <architecture>@var{arch}</architecture>
39060 @var{arch} is one of the architectures from the set accepted by
39061 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39064 @cindex @code{<osabi>}
39066 This optional field was introduced in @value{GDBN} version 7.0.
39067 Previous versions of @value{GDBN} ignore it.
39069 An @samp{<osabi>} element has this form:
39072 <osabi>@var{abi-name}</osabi>
39075 @var{abi-name} is an OS ABI name from the same selection accepted by
39076 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39078 @subsection Compatible Architecture
39079 @cindex @code{<compatible>}
39081 This optional field was introduced in @value{GDBN} version 7.0.
39082 Previous versions of @value{GDBN} ignore it.
39084 A @samp{<compatible>} element has this form:
39087 <compatible>@var{arch}</compatible>
39090 @var{arch} is one of the architectures from the set accepted by
39091 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39093 A @samp{<compatible>} element is used to specify that the target
39094 is able to run binaries in some other than the main target architecture
39095 given by the @samp{<architecture>} element. For example, on the
39096 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39097 or @code{powerpc:common64}, but the system is able to run binaries
39098 in the @code{spu} architecture as well. The way to describe this
39099 capability with @samp{<compatible>} is as follows:
39102 <architecture>powerpc:common</architecture>
39103 <compatible>spu</compatible>
39106 @subsection Features
39109 Each @samp{<feature>} describes some logical portion of the target
39110 system. Features are currently used to describe available CPU
39111 registers and the types of their contents. A @samp{<feature>} element
39115 <feature name="@var{name}">
39116 @r{[}@var{type}@dots{}@r{]}
39122 Each feature's name should be unique within the description. The name
39123 of a feature does not matter unless @value{GDBN} has some special
39124 knowledge of the contents of that feature; if it does, the feature
39125 should have its standard name. @xref{Standard Target Features}.
39129 Any register's value is a collection of bits which @value{GDBN} must
39130 interpret. The default interpretation is a two's complement integer,
39131 but other types can be requested by name in the register description.
39132 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39133 Target Types}), and the description can define additional composite types.
39135 Each type element must have an @samp{id} attribute, which gives
39136 a unique (within the containing @samp{<feature>}) name to the type.
39137 Types must be defined before they are used.
39140 Some targets offer vector registers, which can be treated as arrays
39141 of scalar elements. These types are written as @samp{<vector>} elements,
39142 specifying the array element type, @var{type}, and the number of elements,
39146 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39150 If a register's value is usefully viewed in multiple ways, define it
39151 with a union type containing the useful representations. The
39152 @samp{<union>} element contains one or more @samp{<field>} elements,
39153 each of which has a @var{name} and a @var{type}:
39156 <union id="@var{id}">
39157 <field name="@var{name}" type="@var{type}"/>
39163 If a register's value is composed from several separate values, define
39164 it with a structure type. There are two forms of the @samp{<struct>}
39165 element; a @samp{<struct>} element must either contain only bitfields
39166 or contain no bitfields. If the structure contains only bitfields,
39167 its total size in bytes must be specified, each bitfield must have an
39168 explicit start and end, and bitfields are automatically assigned an
39169 integer type. The field's @var{start} should be less than or
39170 equal to its @var{end}, and zero represents the least significant bit.
39173 <struct id="@var{id}" size="@var{size}">
39174 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39179 If the structure contains no bitfields, then each field has an
39180 explicit type, and no implicit padding is added.
39183 <struct id="@var{id}">
39184 <field name="@var{name}" type="@var{type}"/>
39190 If a register's value is a series of single-bit flags, define it with
39191 a flags type. The @samp{<flags>} element has an explicit @var{size}
39192 and contains one or more @samp{<field>} elements. Each field has a
39193 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39197 <flags id="@var{id}" size="@var{size}">
39198 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39203 @subsection Registers
39206 Each register is represented as an element with this form:
39209 <reg name="@var{name}"
39210 bitsize="@var{size}"
39211 @r{[}regnum="@var{num}"@r{]}
39212 @r{[}save-restore="@var{save-restore}"@r{]}
39213 @r{[}type="@var{type}"@r{]}
39214 @r{[}group="@var{group}"@r{]}/>
39218 The components are as follows:
39223 The register's name; it must be unique within the target description.
39226 The register's size, in bits.
39229 The register's number. If omitted, a register's number is one greater
39230 than that of the previous register (either in the current feature or in
39231 a preceding feature); the first register in the target description
39232 defaults to zero. This register number is used to read or write
39233 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39234 packets, and registers appear in the @code{g} and @code{G} packets
39235 in order of increasing register number.
39238 Whether the register should be preserved across inferior function
39239 calls; this must be either @code{yes} or @code{no}. The default is
39240 @code{yes}, which is appropriate for most registers except for
39241 some system control registers; this is not related to the target's
39245 The type of the register. It may be a predefined type, a type
39246 defined in the current feature, or one of the special types @code{int}
39247 and @code{float}. @code{int} is an integer type of the correct size
39248 for @var{bitsize}, and @code{float} is a floating point type (in the
39249 architecture's normal floating point format) of the correct size for
39250 @var{bitsize}. The default is @code{int}.
39253 The register group to which this register belongs. It must
39254 be either @code{general}, @code{float}, or @code{vector}. If no
39255 @var{group} is specified, @value{GDBN} will not display the register
39256 in @code{info registers}.
39260 @node Predefined Target Types
39261 @section Predefined Target Types
39262 @cindex target descriptions, predefined types
39264 Type definitions in the self-description can build up composite types
39265 from basic building blocks, but can not define fundamental types. Instead,
39266 standard identifiers are provided by @value{GDBN} for the fundamental
39267 types. The currently supported types are:
39276 Signed integer types holding the specified number of bits.
39283 Unsigned integer types holding the specified number of bits.
39287 Pointers to unspecified code and data. The program counter and
39288 any dedicated return address register may be marked as code
39289 pointers; printing a code pointer converts it into a symbolic
39290 address. The stack pointer and any dedicated address registers
39291 may be marked as data pointers.
39294 Single precision IEEE floating point.
39297 Double precision IEEE floating point.
39300 The 12-byte extended precision format used by ARM FPA registers.
39303 The 10-byte extended precision format used by x87 registers.
39306 32bit @sc{eflags} register used by x86.
39309 32bit @sc{mxcsr} register used by x86.
39313 @node Standard Target Features
39314 @section Standard Target Features
39315 @cindex target descriptions, standard features
39317 A target description must contain either no registers or all the
39318 target's registers. If the description contains no registers, then
39319 @value{GDBN} will assume a default register layout, selected based on
39320 the architecture. If the description contains any registers, the
39321 default layout will not be used; the standard registers must be
39322 described in the target description, in such a way that @value{GDBN}
39323 can recognize them.
39325 This is accomplished by giving specific names to feature elements
39326 which contain standard registers. @value{GDBN} will look for features
39327 with those names and verify that they contain the expected registers;
39328 if any known feature is missing required registers, or if any required
39329 feature is missing, @value{GDBN} will reject the target
39330 description. You can add additional registers to any of the
39331 standard features --- @value{GDBN} will display them just as if
39332 they were added to an unrecognized feature.
39334 This section lists the known features and their expected contents.
39335 Sample XML documents for these features are included in the
39336 @value{GDBN} source tree, in the directory @file{gdb/features}.
39338 Names recognized by @value{GDBN} should include the name of the
39339 company or organization which selected the name, and the overall
39340 architecture to which the feature applies; so e.g.@: the feature
39341 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39343 The names of registers are not case sensitive for the purpose
39344 of recognizing standard features, but @value{GDBN} will only display
39345 registers using the capitalization used in the description.
39348 * AArch64 Features::
39351 * MicroBlaze Features::
39354 * Nios II Features::
39355 * PowerPC Features::
39356 * S/390 and System z Features::
39361 @node AArch64 Features
39362 @subsection AArch64 Features
39363 @cindex target descriptions, AArch64 features
39365 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39366 targets. It should contain registers @samp{x0} through @samp{x30},
39367 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39369 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39370 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39374 @subsection ARM Features
39375 @cindex target descriptions, ARM features
39377 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39379 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39380 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39382 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39383 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39384 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39387 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39388 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39390 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39391 it should contain at least registers @samp{wR0} through @samp{wR15} and
39392 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39393 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39395 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39396 should contain at least registers @samp{d0} through @samp{d15}. If
39397 they are present, @samp{d16} through @samp{d31} should also be included.
39398 @value{GDBN} will synthesize the single-precision registers from
39399 halves of the double-precision registers.
39401 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39402 need to contain registers; it instructs @value{GDBN} to display the
39403 VFP double-precision registers as vectors and to synthesize the
39404 quad-precision registers from pairs of double-precision registers.
39405 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39406 be present and include 32 double-precision registers.
39408 @node i386 Features
39409 @subsection i386 Features
39410 @cindex target descriptions, i386 features
39412 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39413 targets. It should describe the following registers:
39417 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39419 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39421 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39422 @samp{fs}, @samp{gs}
39424 @samp{st0} through @samp{st7}
39426 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39427 @samp{foseg}, @samp{fooff} and @samp{fop}
39430 The register sets may be different, depending on the target.
39432 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39433 describe registers:
39437 @samp{xmm0} through @samp{xmm7} for i386
39439 @samp{xmm0} through @samp{xmm15} for amd64
39444 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39445 @samp{org.gnu.gdb.i386.sse} feature. It should
39446 describe the upper 128 bits of @sc{ymm} registers:
39450 @samp{ymm0h} through @samp{ymm7h} for i386
39452 @samp{ymm0h} through @samp{ymm15h} for amd64
39455 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39456 Memory Protection Extension (MPX). It should describe the following registers:
39460 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39462 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39465 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39466 describe a single register, @samp{orig_eax}.
39468 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39469 @samp{org.gnu.gdb.i386.avx} feature. It should
39470 describe additional @sc{xmm} registers:
39474 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39477 It should describe the upper 128 bits of additional @sc{ymm} registers:
39481 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39485 describe the upper 256 bits of @sc{zmm} registers:
39489 @samp{zmm0h} through @samp{zmm7h} for i386.
39491 @samp{zmm0h} through @samp{zmm15h} for amd64.
39495 describe the additional @sc{zmm} registers:
39499 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39502 @node MicroBlaze Features
39503 @subsection MicroBlaze Features
39504 @cindex target descriptions, MicroBlaze features
39506 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39507 targets. It should contain registers @samp{r0} through @samp{r31},
39508 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39509 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39510 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39512 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39513 If present, it should contain registers @samp{rshr} and @samp{rslr}
39515 @node MIPS Features
39516 @subsection @acronym{MIPS} Features
39517 @cindex target descriptions, @acronym{MIPS} features
39519 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39520 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39521 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39524 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39525 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39526 registers. They may be 32-bit or 64-bit depending on the target.
39528 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39529 it may be optional in a future version of @value{GDBN}. It should
39530 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39531 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39533 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39534 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39535 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39536 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39538 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39539 contain a single register, @samp{restart}, which is used by the
39540 Linux kernel to control restartable syscalls.
39542 @node M68K Features
39543 @subsection M68K Features
39544 @cindex target descriptions, M68K features
39547 @item @samp{org.gnu.gdb.m68k.core}
39548 @itemx @samp{org.gnu.gdb.coldfire.core}
39549 @itemx @samp{org.gnu.gdb.fido.core}
39550 One of those features must be always present.
39551 The feature that is present determines which flavor of m68k is
39552 used. The feature that is present should contain registers
39553 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39554 @samp{sp}, @samp{ps} and @samp{pc}.
39556 @item @samp{org.gnu.gdb.coldfire.fp}
39557 This feature is optional. If present, it should contain registers
39558 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39562 @node Nios II Features
39563 @subsection Nios II Features
39564 @cindex target descriptions, Nios II features
39566 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39567 targets. It should contain the 32 core registers (@samp{zero},
39568 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39569 @samp{pc}, and the 16 control registers (@samp{status} through
39572 @node PowerPC Features
39573 @subsection PowerPC Features
39574 @cindex target descriptions, PowerPC features
39576 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39577 targets. It should contain registers @samp{r0} through @samp{r31},
39578 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39579 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39581 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39582 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39584 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39585 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39588 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39589 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39590 will combine these registers with the floating point registers
39591 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39592 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39593 through @samp{vs63}, the set of vector registers for POWER7.
39595 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39596 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39597 @samp{spefscr}. SPE targets should provide 32-bit registers in
39598 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39599 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39600 these to present registers @samp{ev0} through @samp{ev31} to the
39603 @node S/390 and System z Features
39604 @subsection S/390 and System z Features
39605 @cindex target descriptions, S/390 features
39606 @cindex target descriptions, System z features
39608 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39609 System z targets. It should contain the PSW and the 16 general
39610 registers. In particular, System z targets should provide the 64-bit
39611 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39612 S/390 targets should provide the 32-bit versions of these registers.
39613 A System z target that runs in 31-bit addressing mode should provide
39614 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39615 register's upper halves @samp{r0h} through @samp{r15h}, and their
39616 lower halves @samp{r0l} through @samp{r15l}.
39618 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39619 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39622 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39623 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39625 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39626 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39627 targets and 32-bit otherwise. In addition, the feature may contain
39628 the @samp{last_break} register, whose width depends on the addressing
39629 mode, as well as the @samp{system_call} register, which is always
39632 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39633 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39634 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39636 @node TIC6x Features
39637 @subsection TMS320C6x Features
39638 @cindex target descriptions, TIC6x features
39639 @cindex target descriptions, TMS320C6x features
39640 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39641 targets. It should contain registers @samp{A0} through @samp{A15},
39642 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39644 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39645 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39646 through @samp{B31}.
39648 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39649 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39651 @node Operating System Information
39652 @appendix Operating System Information
39653 @cindex operating system information
39659 Users of @value{GDBN} often wish to obtain information about the state of
39660 the operating system running on the target---for example the list of
39661 processes, or the list of open files. This section describes the
39662 mechanism that makes it possible. This mechanism is similar to the
39663 target features mechanism (@pxref{Target Descriptions}), but focuses
39664 on a different aspect of target.
39666 Operating system information is retrived from the target via the
39667 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39668 read}). The object name in the request should be @samp{osdata}, and
39669 the @var{annex} identifies the data to be fetched.
39672 @appendixsection Process list
39673 @cindex operating system information, process list
39675 When requesting the process list, the @var{annex} field in the
39676 @samp{qXfer} request should be @samp{processes}. The returned data is
39677 an XML document. The formal syntax of this document is defined in
39678 @file{gdb/features/osdata.dtd}.
39680 An example document is:
39683 <?xml version="1.0"?>
39684 <!DOCTYPE target SYSTEM "osdata.dtd">
39685 <osdata type="processes">
39687 <column name="pid">1</column>
39688 <column name="user">root</column>
39689 <column name="command">/sbin/init</column>
39690 <column name="cores">1,2,3</column>
39695 Each item should include a column whose name is @samp{pid}. The value
39696 of that column should identify the process on the target. The
39697 @samp{user} and @samp{command} columns are optional, and will be
39698 displayed by @value{GDBN}. The @samp{cores} column, if present,
39699 should contain a comma-separated list of cores that this process
39700 is running on. Target may provide additional columns,
39701 which @value{GDBN} currently ignores.
39703 @node Trace File Format
39704 @appendix Trace File Format
39705 @cindex trace file format
39707 The trace file comes in three parts: a header, a textual description
39708 section, and a trace frame section with binary data.
39710 The header has the form @code{\x7fTRACE0\n}. The first byte is
39711 @code{0x7f} so as to indicate that the file contains binary data,
39712 while the @code{0} is a version number that may have different values
39715 The description section consists of multiple lines of @sc{ascii} text
39716 separated by newline characters (@code{0xa}). The lines may include a
39717 variety of optional descriptive or context-setting information, such
39718 as tracepoint definitions or register set size. @value{GDBN} will
39719 ignore any line that it does not recognize. An empty line marks the end
39722 @c FIXME add some specific types of data
39724 The trace frame section consists of a number of consecutive frames.
39725 Each frame begins with a two-byte tracepoint number, followed by a
39726 four-byte size giving the amount of data in the frame. The data in
39727 the frame consists of a number of blocks, each introduced by a
39728 character indicating its type (at least register, memory, and trace
39729 state variable). The data in this section is raw binary, not a
39730 hexadecimal or other encoding; its endianness matches the target's
39733 @c FIXME bi-arch may require endianness/arch info in description section
39736 @item R @var{bytes}
39737 Register block. The number and ordering of bytes matches that of a
39738 @code{g} packet in the remote protocol. Note that these are the
39739 actual bytes, in target order and @value{GDBN} register order, not a
39740 hexadecimal encoding.
39742 @item M @var{address} @var{length} @var{bytes}...
39743 Memory block. This is a contiguous block of memory, at the 8-byte
39744 address @var{address}, with a 2-byte length @var{length}, followed by
39745 @var{length} bytes.
39747 @item V @var{number} @var{value}
39748 Trace state variable block. This records the 8-byte signed value
39749 @var{value} of trace state variable numbered @var{number}.
39753 Future enhancements of the trace file format may include additional types
39756 @node Index Section Format
39757 @appendix @code{.gdb_index} section format
39758 @cindex .gdb_index section format
39759 @cindex index section format
39761 This section documents the index section that is created by @code{save
39762 gdb-index} (@pxref{Index Files}). The index section is
39763 DWARF-specific; some knowledge of DWARF is assumed in this
39766 The mapped index file format is designed to be directly
39767 @code{mmap}able on any architecture. In most cases, a datum is
39768 represented using a little-endian 32-bit integer value, called an
39769 @code{offset_type}. Big endian machines must byte-swap the values
39770 before using them. Exceptions to this rule are noted. The data is
39771 laid out such that alignment is always respected.
39773 A mapped index consists of several areas, laid out in order.
39777 The file header. This is a sequence of values, of @code{offset_type}
39778 unless otherwise noted:
39782 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39783 Version 4 uses a different hashing function from versions 5 and 6.
39784 Version 6 includes symbols for inlined functions, whereas versions 4
39785 and 5 do not. Version 7 adds attributes to the CU indices in the
39786 symbol table. Version 8 specifies that symbols from DWARF type units
39787 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39788 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39790 @value{GDBN} will only read version 4, 5, or 6 indices
39791 by specifying @code{set use-deprecated-index-sections on}.
39792 GDB has a workaround for potentially broken version 7 indices so it is
39793 currently not flagged as deprecated.
39796 The offset, from the start of the file, of the CU list.
39799 The offset, from the start of the file, of the types CU list. Note
39800 that this area can be empty, in which case this offset will be equal
39801 to the next offset.
39804 The offset, from the start of the file, of the address area.
39807 The offset, from the start of the file, of the symbol table.
39810 The offset, from the start of the file, of the constant pool.
39814 The CU list. This is a sequence of pairs of 64-bit little-endian
39815 values, sorted by the CU offset. The first element in each pair is
39816 the offset of a CU in the @code{.debug_info} section. The second
39817 element in each pair is the length of that CU. References to a CU
39818 elsewhere in the map are done using a CU index, which is just the
39819 0-based index into this table. Note that if there are type CUs, then
39820 conceptually CUs and type CUs form a single list for the purposes of
39824 The types CU list. This is a sequence of triplets of 64-bit
39825 little-endian values. In a triplet, the first value is the CU offset,
39826 the second value is the type offset in the CU, and the third value is
39827 the type signature. The types CU list is not sorted.
39830 The address area. The address area consists of a sequence of address
39831 entries. Each address entry has three elements:
39835 The low address. This is a 64-bit little-endian value.
39838 The high address. This is a 64-bit little-endian value. Like
39839 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39842 The CU index. This is an @code{offset_type} value.
39846 The symbol table. This is an open-addressed hash table. The size of
39847 the hash table is always a power of 2.
39849 Each slot in the hash table consists of a pair of @code{offset_type}
39850 values. The first value is the offset of the symbol's name in the
39851 constant pool. The second value is the offset of the CU vector in the
39854 If both values are 0, then this slot in the hash table is empty. This
39855 is ok because while 0 is a valid constant pool index, it cannot be a
39856 valid index for both a string and a CU vector.
39858 The hash value for a table entry is computed by applying an
39859 iterative hash function to the symbol's name. Starting with an
39860 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39861 the string is incorporated into the hash using the formula depending on the
39866 The formula is @code{r = r * 67 + c - 113}.
39868 @item Versions 5 to 7
39869 The formula is @code{r = r * 67 + tolower (c) - 113}.
39872 The terminating @samp{\0} is not incorporated into the hash.
39874 The step size used in the hash table is computed via
39875 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39876 value, and @samp{size} is the size of the hash table. The step size
39877 is used to find the next candidate slot when handling a hash
39880 The names of C@t{++} symbols in the hash table are canonicalized. We
39881 don't currently have a simple description of the canonicalization
39882 algorithm; if you intend to create new index sections, you must read
39886 The constant pool. This is simply a bunch of bytes. It is organized
39887 so that alignment is correct: CU vectors are stored first, followed by
39890 A CU vector in the constant pool is a sequence of @code{offset_type}
39891 values. The first value is the number of CU indices in the vector.
39892 Each subsequent value is the index and symbol attributes of a CU in
39893 the CU list. This element in the hash table is used to indicate which
39894 CUs define the symbol and how the symbol is used.
39895 See below for the format of each CU index+attributes entry.
39897 A string in the constant pool is zero-terminated.
39900 Attributes were added to CU index values in @code{.gdb_index} version 7.
39901 If a symbol has multiple uses within a CU then there is one
39902 CU index+attributes value for each use.
39904 The format of each CU index+attributes entry is as follows
39910 This is the index of the CU in the CU list.
39912 These bits are reserved for future purposes and must be zero.
39914 The kind of the symbol in the CU.
39918 This value is reserved and should not be used.
39919 By reserving zero the full @code{offset_type} value is backwards compatible
39920 with previous versions of the index.
39922 The symbol is a type.
39924 The symbol is a variable or an enum value.
39926 The symbol is a function.
39928 Any other kind of symbol.
39930 These values are reserved.
39934 This bit is zero if the value is global and one if it is static.
39936 The determination of whether a symbol is global or static is complicated.
39937 The authorative reference is the file @file{dwarf2read.c} in
39938 @value{GDBN} sources.
39942 This pseudo-code describes the computation of a symbol's kind and
39943 global/static attributes in the index.
39946 is_external = get_attribute (die, DW_AT_external);
39947 language = get_attribute (cu_die, DW_AT_language);
39950 case DW_TAG_typedef:
39951 case DW_TAG_base_type:
39952 case DW_TAG_subrange_type:
39956 case DW_TAG_enumerator:
39958 is_static = (language != CPLUS && language != JAVA);
39960 case DW_TAG_subprogram:
39962 is_static = ! (is_external || language == ADA);
39964 case DW_TAG_constant:
39966 is_static = ! is_external;
39968 case DW_TAG_variable:
39970 is_static = ! is_external;
39972 case DW_TAG_namespace:
39976 case DW_TAG_class_type:
39977 case DW_TAG_interface_type:
39978 case DW_TAG_structure_type:
39979 case DW_TAG_union_type:
39980 case DW_TAG_enumeration_type:
39982 is_static = (language != CPLUS && language != JAVA);
39990 @appendix Manual pages
39994 * gdb man:: The GNU Debugger man page
39995 * gdbserver man:: Remote Server for the GNU Debugger man page
39996 * gcore man:: Generate a core file of a running program
39997 * gdbinit man:: gdbinit scripts
40003 @c man title gdb The GNU Debugger
40005 @c man begin SYNOPSIS gdb
40006 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40007 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40008 [@option{-b}@w{ }@var{bps}]
40009 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40010 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40011 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40012 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40013 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40016 @c man begin DESCRIPTION gdb
40017 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40018 going on ``inside'' another program while it executes -- or what another
40019 program was doing at the moment it crashed.
40021 @value{GDBN} can do four main kinds of things (plus other things in support of
40022 these) to help you catch bugs in the act:
40026 Start your program, specifying anything that might affect its behavior.
40029 Make your program stop on specified conditions.
40032 Examine what has happened, when your program has stopped.
40035 Change things in your program, so you can experiment with correcting the
40036 effects of one bug and go on to learn about another.
40039 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40042 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40043 commands from the terminal until you tell it to exit with the @value{GDBN}
40044 command @code{quit}. You can get online help from @value{GDBN} itself
40045 by using the command @code{help}.
40047 You can run @code{gdb} with no arguments or options; but the most
40048 usual way to start @value{GDBN} is with one argument or two, specifying an
40049 executable program as the argument:
40055 You can also start with both an executable program and a core file specified:
40061 You can, instead, specify a process ID as a second argument, if you want
40062 to debug a running process:
40070 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40071 named @file{1234}; @value{GDBN} does check for a core file first).
40072 With option @option{-p} you can omit the @var{program} filename.
40074 Here are some of the most frequently needed @value{GDBN} commands:
40076 @c pod2man highlights the right hand side of the @item lines.
40078 @item break [@var{file}:]@var{functiop}
40079 Set a breakpoint at @var{function} (in @var{file}).
40081 @item run [@var{arglist}]
40082 Start your program (with @var{arglist}, if specified).
40085 Backtrace: display the program stack.
40087 @item print @var{expr}
40088 Display the value of an expression.
40091 Continue running your program (after stopping, e.g. at a breakpoint).
40094 Execute next program line (after stopping); step @emph{over} any
40095 function calls in the line.
40097 @item edit [@var{file}:]@var{function}
40098 look at the program line where it is presently stopped.
40100 @item list [@var{file}:]@var{function}
40101 type the text of the program in the vicinity of where it is presently stopped.
40104 Execute next program line (after stopping); step @emph{into} any
40105 function calls in the line.
40107 @item help [@var{name}]
40108 Show information about @value{GDBN} command @var{name}, or general information
40109 about using @value{GDBN}.
40112 Exit from @value{GDBN}.
40116 For full details on @value{GDBN},
40117 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40118 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40119 as the @code{gdb} entry in the @code{info} program.
40123 @c man begin OPTIONS gdb
40124 Any arguments other than options specify an executable
40125 file and core file (or process ID); that is, the first argument
40126 encountered with no
40127 associated option flag is equivalent to a @option{-se} option, and the second,
40128 if any, is equivalent to a @option{-c} option if it's the name of a file.
40130 both long and short forms; both are shown here. The long forms are also
40131 recognized if you truncate them, so long as enough of the option is
40132 present to be unambiguous. (If you prefer, you can flag option
40133 arguments with @option{+} rather than @option{-}, though we illustrate the
40134 more usual convention.)
40136 All the options and command line arguments you give are processed
40137 in sequential order. The order makes a difference when the @option{-x}
40143 List all options, with brief explanations.
40145 @item -symbols=@var{file}
40146 @itemx -s @var{file}
40147 Read symbol table from file @var{file}.
40150 Enable writing into executable and core files.
40152 @item -exec=@var{file}
40153 @itemx -e @var{file}
40154 Use file @var{file} as the executable file to execute when
40155 appropriate, and for examining pure data in conjunction with a core
40158 @item -se=@var{file}
40159 Read symbol table from file @var{file} and use it as the executable
40162 @item -core=@var{file}
40163 @itemx -c @var{file}
40164 Use file @var{file} as a core dump to examine.
40166 @item -command=@var{file}
40167 @itemx -x @var{file}
40168 Execute @value{GDBN} commands from file @var{file}.
40170 @item -ex @var{command}
40171 Execute given @value{GDBN} @var{command}.
40173 @item -directory=@var{directory}
40174 @itemx -d @var{directory}
40175 Add @var{directory} to the path to search for source files.
40178 Do not execute commands from @file{~/.gdbinit}.
40182 Do not execute commands from any @file{.gdbinit} initialization files.
40186 ``Quiet''. Do not print the introductory and copyright messages. These
40187 messages are also suppressed in batch mode.
40190 Run in batch mode. Exit with status @code{0} after processing all the command
40191 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40192 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40193 commands in the command files.
40195 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40196 download and run a program on another computer; in order to make this
40197 more useful, the message
40200 Program exited normally.
40204 (which is ordinarily issued whenever a program running under @value{GDBN} control
40205 terminates) is not issued when running in batch mode.
40207 @item -cd=@var{directory}
40208 Run @value{GDBN} using @var{directory} as its working directory,
40209 instead of the current directory.
40213 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40214 @value{GDBN} to output the full file name and line number in a standard,
40215 recognizable fashion each time a stack frame is displayed (which
40216 includes each time the program stops). This recognizable format looks
40217 like two @samp{\032} characters, followed by the file name, line number
40218 and character position separated by colons, and a newline. The
40219 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40220 characters as a signal to display the source code for the frame.
40223 Set the line speed (baud rate or bits per second) of any serial
40224 interface used by @value{GDBN} for remote debugging.
40226 @item -tty=@var{device}
40227 Run using @var{device} for your program's standard input and output.
40231 @c man begin SEEALSO gdb
40233 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40234 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40235 documentation are properly installed at your site, the command
40242 should give you access to the complete manual.
40244 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40245 Richard M. Stallman and Roland H. Pesch, July 1991.
40249 @node gdbserver man
40250 @heading gdbserver man
40252 @c man title gdbserver Remote Server for the GNU Debugger
40254 @c man begin SYNOPSIS gdbserver
40255 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40257 gdbserver --attach @var{comm} @var{pid}
40259 gdbserver --multi @var{comm}
40263 @c man begin DESCRIPTION gdbserver
40264 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40265 than the one which is running the program being debugged.
40268 @subheading Usage (server (target) side)
40271 Usage (server (target) side):
40274 First, you need to have a copy of the program you want to debug put onto
40275 the target system. The program can be stripped to save space if needed, as
40276 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40277 the @value{GDBN} running on the host system.
40279 To use the server, you log on to the target system, and run the @command{gdbserver}
40280 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40281 your program, and (c) its arguments. The general syntax is:
40284 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40287 For example, using a serial port, you might say:
40291 @c @file would wrap it as F</dev/com1>.
40292 target> gdbserver /dev/com1 emacs foo.txt
40295 target> gdbserver @file{/dev/com1} emacs foo.txt
40299 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40300 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40301 waits patiently for the host @value{GDBN} to communicate with it.
40303 To use a TCP connection, you could say:
40306 target> gdbserver host:2345 emacs foo.txt
40309 This says pretty much the same thing as the last example, except that we are
40310 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40311 that we are expecting to see a TCP connection from @code{host} to local TCP port
40312 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40313 want for the port number as long as it does not conflict with any existing TCP
40314 ports on the target system. This same port number must be used in the host
40315 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40316 you chose a port number that conflicts with another service, @command{gdbserver} will
40317 print an error message and exit.
40319 @command{gdbserver} can also attach to running programs.
40320 This is accomplished via the @option{--attach} argument. The syntax is:
40323 target> gdbserver --attach @var{comm} @var{pid}
40326 @var{pid} is the process ID of a currently running process. It isn't
40327 necessary to point @command{gdbserver} at a binary for the running process.
40329 To start @code{gdbserver} without supplying an initial command to run
40330 or process ID to attach, use the @option{--multi} command line option.
40331 In such case you should connect using @kbd{target extended-remote} to start
40332 the program you want to debug.
40335 target> gdbserver --multi @var{comm}
40339 @subheading Usage (host side)
40345 You need an unstripped copy of the target program on your host system, since
40346 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40347 would, with the target program as the first argument. (You may need to use the
40348 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40349 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40350 new command you need to know about is @code{target remote}
40351 (or @code{target extended-remote}). Its argument is either
40352 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40353 descriptor. For example:
40357 @c @file would wrap it as F</dev/ttyb>.
40358 (gdb) target remote /dev/ttyb
40361 (gdb) target remote @file{/dev/ttyb}
40366 communicates with the server via serial line @file{/dev/ttyb}, and:
40369 (gdb) target remote the-target:2345
40373 communicates via a TCP connection to port 2345 on host `the-target', where
40374 you previously started up @command{gdbserver} with the same port number. Note that for
40375 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40376 command, otherwise you may get an error that looks something like
40377 `Connection refused'.
40379 @command{gdbserver} can also debug multiple inferiors at once,
40382 the @value{GDBN} manual in node @code{Inferiors and Programs}
40383 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40386 @ref{Inferiors and Programs}.
40388 In such case use the @code{extended-remote} @value{GDBN} command variant:
40391 (gdb) target extended-remote the-target:2345
40394 The @command{gdbserver} option @option{--multi} may or may not be used in such
40398 @c man begin OPTIONS gdbserver
40399 There are three different modes for invoking @command{gdbserver}:
40404 Debug a specific program specified by its program name:
40407 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40410 The @var{comm} parameter specifies how should the server communicate
40411 with @value{GDBN}; it is either a device name (to use a serial line),
40412 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40413 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40414 debug in @var{prog}. Any remaining arguments will be passed to the
40415 program verbatim. When the program exits, @value{GDBN} will close the
40416 connection, and @code{gdbserver} will exit.
40419 Debug a specific program by specifying the process ID of a running
40423 gdbserver --attach @var{comm} @var{pid}
40426 The @var{comm} parameter is as described above. Supply the process ID
40427 of a running program in @var{pid}; @value{GDBN} will do everything
40428 else. Like with the previous mode, when the process @var{pid} exits,
40429 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40432 Multi-process mode -- debug more than one program/process:
40435 gdbserver --multi @var{comm}
40438 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40439 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40440 close the connection when a process being debugged exits, so you can
40441 debug several processes in the same session.
40444 In each of the modes you may specify these options:
40449 List all options, with brief explanations.
40452 This option causes @command{gdbserver} to print its version number and exit.
40455 @command{gdbserver} will attach to a running program. The syntax is:
40458 target> gdbserver --attach @var{comm} @var{pid}
40461 @var{pid} is the process ID of a currently running process. It isn't
40462 necessary to point @command{gdbserver} at a binary for the running process.
40465 To start @code{gdbserver} without supplying an initial command to run
40466 or process ID to attach, use this command line option.
40467 Then you can connect using @kbd{target extended-remote} and start
40468 the program you want to debug. The syntax is:
40471 target> gdbserver --multi @var{comm}
40475 Instruct @code{gdbserver} to display extra status information about the debugging
40477 This option is intended for @code{gdbserver} development and for bug reports to
40480 @item --remote-debug
40481 Instruct @code{gdbserver} to display remote protocol debug output.
40482 This option is intended for @code{gdbserver} development and for bug reports to
40485 @item --debug-format=option1@r{[},option2,...@r{]}
40486 Instruct @code{gdbserver} to include extra information in each line
40487 of debugging output.
40488 @xref{Other Command-Line Arguments for gdbserver}.
40491 Specify a wrapper to launch programs
40492 for debugging. The option should be followed by the name of the
40493 wrapper, then any command-line arguments to pass to the wrapper, then
40494 @kbd{--} indicating the end of the wrapper arguments.
40497 By default, @command{gdbserver} keeps the listening TCP port open, so that
40498 additional connections are possible. However, if you start @code{gdbserver}
40499 with the @option{--once} option, it will stop listening for any further
40500 connection attempts after connecting to the first @value{GDBN} session.
40502 @c --disable-packet is not documented for users.
40504 @c --disable-randomization and --no-disable-randomization are superseded by
40505 @c QDisableRandomization.
40510 @c man begin SEEALSO gdbserver
40512 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40513 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40514 documentation are properly installed at your site, the command
40520 should give you access to the complete manual.
40522 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40523 Richard M. Stallman and Roland H. Pesch, July 1991.
40530 @c man title gcore Generate a core file of a running program
40533 @c man begin SYNOPSIS gcore
40534 gcore [-o @var{filename}] @var{pid}
40538 @c man begin DESCRIPTION gcore
40539 Generate a core dump of a running program with process ID @var{pid}.
40540 Produced file is equivalent to a kernel produced core file as if the process
40541 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40542 limit). Unlike after a crash, after @command{gcore} the program remains
40543 running without any change.
40546 @c man begin OPTIONS gcore
40548 @item -o @var{filename}
40549 The optional argument
40550 @var{filename} specifies the file name where to put the core dump.
40551 If not specified, the file name defaults to @file{core.@var{pid}},
40552 where @var{pid} is the running program process ID.
40556 @c man begin SEEALSO gcore
40558 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40559 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40560 documentation are properly installed at your site, the command
40567 should give you access to the complete manual.
40569 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40570 Richard M. Stallman and Roland H. Pesch, July 1991.
40577 @c man title gdbinit GDB initialization scripts
40580 @c man begin SYNOPSIS gdbinit
40581 @ifset SYSTEM_GDBINIT
40582 @value{SYSTEM_GDBINIT}
40591 @c man begin DESCRIPTION gdbinit
40592 These files contain @value{GDBN} commands to automatically execute during
40593 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40596 the @value{GDBN} manual in node @code{Sequences}
40597 -- shell command @code{info -f gdb -n Sequences}.
40603 Please read more in
40605 the @value{GDBN} manual in node @code{Startup}
40606 -- shell command @code{info -f gdb -n Startup}.
40613 @ifset SYSTEM_GDBINIT
40614 @item @value{SYSTEM_GDBINIT}
40616 @ifclear SYSTEM_GDBINIT
40617 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40619 System-wide initialization file. It is executed unless user specified
40620 @value{GDBN} option @code{-nx} or @code{-n}.
40623 the @value{GDBN} manual in node @code{System-wide configuration}
40624 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40627 @ref{System-wide configuration}.
40631 User initialization file. It is executed unless user specified
40632 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40635 Initialization file for current directory. It may need to be enabled with
40636 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40639 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40640 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40643 @ref{Init File in the Current Directory}.
40648 @c man begin SEEALSO gdbinit
40650 gdb(1), @code{info -f gdb -n Startup}
40652 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40653 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40654 documentation are properly installed at your site, the command
40660 should give you access to the complete manual.
40662 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40663 Richard M. Stallman and Roland H. Pesch, July 1991.
40669 @node GNU Free Documentation License
40670 @appendix GNU Free Documentation License
40673 @node Concept Index
40674 @unnumbered Concept Index
40678 @node Command and Variable Index
40679 @unnumbered Command, Variable, and Function Index
40684 % I think something like @@colophon should be in texinfo. In the
40686 \long\def\colophon{\hbox to0pt{}\vfill
40687 \centerline{The body of this manual is set in}
40688 \centerline{\fontname\tenrm,}
40689 \centerline{with headings in {\bf\fontname\tenbf}}
40690 \centerline{and examples in {\tt\fontname\tentt}.}
40691 \centerline{{\it\fontname\tenit\/},}
40692 \centerline{{\bf\fontname\tenbf}, and}
40693 \centerline{{\sl\fontname\tensl\/}}
40694 \centerline{are used for emphasis.}\vfill}
40696 % Blame: doc@@cygnus.com, 1991.