1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1239 @c @cindex @code{--xdb}
1240 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1241 @c For information, see the file @file{xdb_trans.html}, which is usually
1242 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1245 @item -interpreter @var{interp}
1246 @cindex @code{--interpreter}
1247 Use the interpreter @var{interp} for interface with the controlling
1248 program or device. This option is meant to be set by programs which
1249 communicate with @value{GDBN} using it as a back end.
1250 @xref{Interpreters, , Command Interpreters}.
1252 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1253 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1254 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1255 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1256 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1257 @sc{gdb/mi} interfaces are no longer supported.
1260 @cindex @code{--write}
1261 Open the executable and core files for both reading and writing. This
1262 is equivalent to the @samp{set write on} command inside @value{GDBN}
1266 @cindex @code{--statistics}
1267 This option causes @value{GDBN} to print statistics about time and
1268 memory usage after it completes each command and returns to the prompt.
1271 @cindex @code{--version}
1272 This option causes @value{GDBN} to print its version number and
1273 no-warranty blurb, and exit.
1275 @item -configuration
1276 @cindex @code{--configuration}
1277 This option causes @value{GDBN} to print details about its build-time
1278 configuration parameters, and then exit. These details can be
1279 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1284 @subsection What @value{GDBN} Does During Startup
1285 @cindex @value{GDBN} startup
1287 Here's the description of what @value{GDBN} does during session startup:
1291 Sets up the command interpreter as specified by the command line
1292 (@pxref{Mode Options, interpreter}).
1296 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1297 used when building @value{GDBN}; @pxref{System-wide configuration,
1298 ,System-wide configuration and settings}) and executes all the commands in
1301 @anchor{Home Directory Init File}
1303 Reads the init file (if any) in your home directory@footnote{On
1304 DOS/Windows systems, the home directory is the one pointed to by the
1305 @code{HOME} environment variable.} and executes all the commands in
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1319 @anchor{Init File in the Current Directory during Startup}
1321 Reads and executes the commands from init file (if any) in the current
1322 working directory as long as @samp{set auto-load local-gdbinit} is set to
1323 @samp{on} (@pxref{Init File in the Current Directory}).
1324 This is only done if the current directory is
1325 different from your home directory. Thus, you can have more than one
1326 init file, one generic in your home directory, and another, specific
1327 to the program you are debugging, in the directory where you invoke
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 Init files use the same syntax as @dfn{command files} (@pxref{Command
1358 Files}) and are processed by @value{GDBN} in the same way. The init
1359 file in your home directory can set options (such as @samp{set
1360 complaints}) that affect subsequent processing of command line options
1361 and operands. Init files are not executed if you use the @samp{-nx}
1362 option (@pxref{Mode Options, ,Choosing Modes}).
1364 To display the list of init files loaded by gdb at startup, you
1365 can use @kbd{gdb --help}.
1367 @cindex init file name
1368 @cindex @file{.gdbinit}
1369 @cindex @file{gdb.ini}
1370 The @value{GDBN} init files are normally called @file{.gdbinit}.
1371 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1372 the limitations of file names imposed by DOS filesystems. The Windows
1373 port of @value{GDBN} uses the standard name, but if it finds a
1374 @file{gdb.ini} file in your home directory, it warns you about that
1375 and suggests to rename the file to the standard name.
1379 @section Quitting @value{GDBN}
1380 @cindex exiting @value{GDBN}
1381 @cindex leaving @value{GDBN}
1384 @kindex quit @r{[}@var{expression}@r{]}
1385 @kindex q @r{(@code{quit})}
1386 @item quit @r{[}@var{expression}@r{]}
1388 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1389 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1390 do not supply @var{expression}, @value{GDBN} will terminate normally;
1391 otherwise it will terminate using the result of @var{expression} as the
1396 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1397 terminates the action of any @value{GDBN} command that is in progress and
1398 returns to @value{GDBN} command level. It is safe to type the interrupt
1399 character at any time because @value{GDBN} does not allow it to take effect
1400 until a time when it is safe.
1402 If you have been using @value{GDBN} to control an attached process or
1403 device, you can release it with the @code{detach} command
1404 (@pxref{Attach, ,Debugging an Already-running Process}).
1406 @node Shell Commands
1407 @section Shell Commands
1409 If you need to execute occasional shell commands during your
1410 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1411 just use the @code{shell} command.
1416 @cindex shell escape
1417 @item shell @var{command-string}
1418 @itemx !@var{command-string}
1419 Invoke a standard shell to execute @var{command-string}.
1420 Note that no space is needed between @code{!} and @var{command-string}.
1421 If it exists, the environment variable @code{SHELL} determines which
1422 shell to run. Otherwise @value{GDBN} uses the default shell
1423 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1426 The utility @code{make} is often needed in development environments.
1427 You do not have to use the @code{shell} command for this purpose in
1432 @cindex calling make
1433 @item make @var{make-args}
1434 Execute the @code{make} program with the specified
1435 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1438 @node Logging Output
1439 @section Logging Output
1440 @cindex logging @value{GDBN} output
1441 @cindex save @value{GDBN} output to a file
1443 You may want to save the output of @value{GDBN} commands to a file.
1444 There are several commands to control @value{GDBN}'s logging.
1448 @item set logging on
1450 @item set logging off
1452 @cindex logging file name
1453 @item set logging file @var{file}
1454 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1455 @item set logging overwrite [on|off]
1456 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1457 you want @code{set logging on} to overwrite the logfile instead.
1458 @item set logging redirect [on|off]
1459 By default, @value{GDBN} output will go to both the terminal and the logfile.
1460 Set @code{redirect} if you want output to go only to the log file.
1461 @kindex show logging
1463 Show the current values of the logging settings.
1467 @chapter @value{GDBN} Commands
1469 You can abbreviate a @value{GDBN} command to the first few letters of the command
1470 name, if that abbreviation is unambiguous; and you can repeat certain
1471 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1472 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1473 show you the alternatives available, if there is more than one possibility).
1476 * Command Syntax:: How to give commands to @value{GDBN}
1477 * Completion:: Command completion
1478 * Help:: How to ask @value{GDBN} for help
1481 @node Command Syntax
1482 @section Command Syntax
1484 A @value{GDBN} command is a single line of input. There is no limit on
1485 how long it can be. It starts with a command name, which is followed by
1486 arguments whose meaning depends on the command name. For example, the
1487 command @code{step} accepts an argument which is the number of times to
1488 step, as in @samp{step 5}. You can also use the @code{step} command
1489 with no arguments. Some commands do not allow any arguments.
1491 @cindex abbreviation
1492 @value{GDBN} command names may always be truncated if that abbreviation is
1493 unambiguous. Other possible command abbreviations are listed in the
1494 documentation for individual commands. In some cases, even ambiguous
1495 abbreviations are allowed; for example, @code{s} is specially defined as
1496 equivalent to @code{step} even though there are other commands whose
1497 names start with @code{s}. You can test abbreviations by using them as
1498 arguments to the @code{help} command.
1500 @cindex repeating commands
1501 @kindex RET @r{(repeat last command)}
1502 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1503 repeat the previous command. Certain commands (for example, @code{run})
1504 will not repeat this way; these are commands whose unintentional
1505 repetition might cause trouble and which you are unlikely to want to
1506 repeat. User-defined commands can disable this feature; see
1507 @ref{Define, dont-repeat}.
1509 The @code{list} and @code{x} commands, when you repeat them with
1510 @key{RET}, construct new arguments rather than repeating
1511 exactly as typed. This permits easy scanning of source or memory.
1513 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1514 output, in a way similar to the common utility @code{more}
1515 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1516 @key{RET} too many in this situation, @value{GDBN} disables command
1517 repetition after any command that generates this sort of display.
1519 @kindex # @r{(a comment)}
1521 Any text from a @kbd{#} to the end of the line is a comment; it does
1522 nothing. This is useful mainly in command files (@pxref{Command
1523 Files,,Command Files}).
1525 @cindex repeating command sequences
1526 @kindex Ctrl-o @r{(operate-and-get-next)}
1527 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1528 commands. This command accepts the current line, like @key{RET}, and
1529 then fetches the next line relative to the current line from the history
1533 @section Command Completion
1536 @cindex word completion
1537 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1538 only one possibility; it can also show you what the valid possibilities
1539 are for the next word in a command, at any time. This works for @value{GDBN}
1540 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1542 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1543 of a word. If there is only one possibility, @value{GDBN} fills in the
1544 word, and waits for you to finish the command (or press @key{RET} to
1545 enter it). For example, if you type
1547 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1548 @c complete accuracy in these examples; space introduced for clarity.
1549 @c If texinfo enhancements make it unnecessary, it would be nice to
1550 @c replace " @key" by "@key" in the following...
1552 (@value{GDBP}) info bre @key{TAB}
1556 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1557 the only @code{info} subcommand beginning with @samp{bre}:
1560 (@value{GDBP}) info breakpoints
1564 You can either press @key{RET} at this point, to run the @code{info
1565 breakpoints} command, or backspace and enter something else, if
1566 @samp{breakpoints} does not look like the command you expected. (If you
1567 were sure you wanted @code{info breakpoints} in the first place, you
1568 might as well just type @key{RET} immediately after @samp{info bre},
1569 to exploit command abbreviations rather than command completion).
1571 If there is more than one possibility for the next word when you press
1572 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1573 characters and try again, or just press @key{TAB} a second time;
1574 @value{GDBN} displays all the possible completions for that word. For
1575 example, you might want to set a breakpoint on a subroutine whose name
1576 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1577 just sounds the bell. Typing @key{TAB} again displays all the
1578 function names in your program that begin with those characters, for
1582 (@value{GDBP}) b make_ @key{TAB}
1583 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1584 make_a_section_from_file make_environ
1585 make_abs_section make_function_type
1586 make_blockvector make_pointer_type
1587 make_cleanup make_reference_type
1588 make_command make_symbol_completion_list
1589 (@value{GDBP}) b make_
1593 After displaying the available possibilities, @value{GDBN} copies your
1594 partial input (@samp{b make_} in the example) so you can finish the
1597 If you just want to see the list of alternatives in the first place, you
1598 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1599 means @kbd{@key{META} ?}. You can type this either by holding down a
1600 key designated as the @key{META} shift on your keyboard (if there is
1601 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1603 If the number of possible completions is large, @value{GDBN} will
1604 print as much of the list as it has collected, as well as a message
1605 indicating that the list may be truncated.
1608 (@value{GDBP}) b m@key{TAB}@key{TAB}
1610 <... the rest of the possible completions ...>
1611 *** List may be truncated, max-completions reached. ***
1616 This behavior can be controlled with the following commands:
1619 @kindex set max-completions
1620 @item set max-completions @var{limit}
1621 @itemx set max-completions unlimited
1622 Set the maximum number of completion candidates. @value{GDBN} will
1623 stop looking for more completions once it collects this many candidates.
1624 This is useful when completing on things like function names as collecting
1625 all the possible candidates can be time consuming.
1626 The default value is 200. A value of zero disables tab-completion.
1627 Note that setting either no limit or a very large limit can make
1629 @kindex show max-completions
1630 @item show max-completions
1631 Show the maximum number of candidates that @value{GDBN} will collect and show
1635 @cindex quotes in commands
1636 @cindex completion of quoted strings
1637 Sometimes the string you need, while logically a ``word'', may contain
1638 parentheses or other characters that @value{GDBN} normally excludes from
1639 its notion of a word. To permit word completion to work in this
1640 situation, you may enclose words in @code{'} (single quote marks) in
1641 @value{GDBN} commands.
1643 The most likely situation where you might need this is in typing the
1644 name of a C@t{++} function. This is because C@t{++} allows function
1645 overloading (multiple definitions of the same function, distinguished
1646 by argument type). For example, when you want to set a breakpoint you
1647 may need to distinguish whether you mean the version of @code{name}
1648 that takes an @code{int} parameter, @code{name(int)}, or the version
1649 that takes a @code{float} parameter, @code{name(float)}. To use the
1650 word-completion facilities in this situation, type a single quote
1651 @code{'} at the beginning of the function name. This alerts
1652 @value{GDBN} that it may need to consider more information than usual
1653 when you press @key{TAB} or @kbd{M-?} to request word completion:
1656 (@value{GDBP}) b 'bubble( @kbd{M-?}
1657 bubble(double,double) bubble(int,int)
1658 (@value{GDBP}) b 'bubble(
1661 In some cases, @value{GDBN} can tell that completing a name requires using
1662 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1663 completing as much as it can) if you do not type the quote in the first
1667 (@value{GDBP}) b bub @key{TAB}
1668 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1669 (@value{GDBP}) b 'bubble(
1673 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1674 you have not yet started typing the argument list when you ask for
1675 completion on an overloaded symbol.
1677 For more information about overloaded functions, see @ref{C Plus Plus
1678 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1679 overload-resolution off} to disable overload resolution;
1680 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1682 @cindex completion of structure field names
1683 @cindex structure field name completion
1684 @cindex completion of union field names
1685 @cindex union field name completion
1686 When completing in an expression which looks up a field in a
1687 structure, @value{GDBN} also tries@footnote{The completer can be
1688 confused by certain kinds of invalid expressions. Also, it only
1689 examines the static type of the expression, not the dynamic type.} to
1690 limit completions to the field names available in the type of the
1694 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1695 magic to_fputs to_rewind
1696 to_data to_isatty to_write
1697 to_delete to_put to_write_async_safe
1702 This is because the @code{gdb_stdout} is a variable of the type
1703 @code{struct ui_file} that is defined in @value{GDBN} sources as
1710 ui_file_flush_ftype *to_flush;
1711 ui_file_write_ftype *to_write;
1712 ui_file_write_async_safe_ftype *to_write_async_safe;
1713 ui_file_fputs_ftype *to_fputs;
1714 ui_file_read_ftype *to_read;
1715 ui_file_delete_ftype *to_delete;
1716 ui_file_isatty_ftype *to_isatty;
1717 ui_file_rewind_ftype *to_rewind;
1718 ui_file_put_ftype *to_put;
1725 @section Getting Help
1726 @cindex online documentation
1729 You can always ask @value{GDBN} itself for information on its commands,
1730 using the command @code{help}.
1733 @kindex h @r{(@code{help})}
1736 You can use @code{help} (abbreviated @code{h}) with no arguments to
1737 display a short list of named classes of commands:
1741 List of classes of commands:
1743 aliases -- Aliases of other commands
1744 breakpoints -- Making program stop at certain points
1745 data -- Examining data
1746 files -- Specifying and examining files
1747 internals -- Maintenance commands
1748 obscure -- Obscure features
1749 running -- Running the program
1750 stack -- Examining the stack
1751 status -- Status inquiries
1752 support -- Support facilities
1753 tracepoints -- Tracing of program execution without
1754 stopping the program
1755 user-defined -- User-defined commands
1757 Type "help" followed by a class name for a list of
1758 commands in that class.
1759 Type "help" followed by command name for full
1761 Command name abbreviations are allowed if unambiguous.
1764 @c the above line break eliminates huge line overfull...
1766 @item help @var{class}
1767 Using one of the general help classes as an argument, you can get a
1768 list of the individual commands in that class. For example, here is the
1769 help display for the class @code{status}:
1772 (@value{GDBP}) help status
1777 @c Line break in "show" line falsifies real output, but needed
1778 @c to fit in smallbook page size.
1779 info -- Generic command for showing things
1780 about the program being debugged
1781 show -- Generic command for showing things
1784 Type "help" followed by command name for full
1786 Command name abbreviations are allowed if unambiguous.
1790 @item help @var{command}
1791 With a command name as @code{help} argument, @value{GDBN} displays a
1792 short paragraph on how to use that command.
1795 @item apropos @var{args}
1796 The @code{apropos} command searches through all of the @value{GDBN}
1797 commands, and their documentation, for the regular expression specified in
1798 @var{args}. It prints out all matches found. For example:
1809 alias -- Define a new command that is an alias of an existing command
1810 aliases -- Aliases of other commands
1811 d -- Delete some breakpoints or auto-display expressions
1812 del -- Delete some breakpoints or auto-display expressions
1813 delete -- Delete some breakpoints or auto-display expressions
1818 @item complete @var{args}
1819 The @code{complete @var{args}} command lists all the possible completions
1820 for the beginning of a command. Use @var{args} to specify the beginning of the
1821 command you want completed. For example:
1827 @noindent results in:
1838 @noindent This is intended for use by @sc{gnu} Emacs.
1841 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1842 and @code{show} to inquire about the state of your program, or the state
1843 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1844 manual introduces each of them in the appropriate context. The listings
1845 under @code{info} and under @code{show} in the Command, Variable, and
1846 Function Index point to all the sub-commands. @xref{Command and Variable
1852 @kindex i @r{(@code{info})}
1854 This command (abbreviated @code{i}) is for describing the state of your
1855 program. For example, you can show the arguments passed to a function
1856 with @code{info args}, list the registers currently in use with @code{info
1857 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1858 You can get a complete list of the @code{info} sub-commands with
1859 @w{@code{help info}}.
1863 You can assign the result of an expression to an environment variable with
1864 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1865 @code{set prompt $}.
1869 In contrast to @code{info}, @code{show} is for describing the state of
1870 @value{GDBN} itself.
1871 You can change most of the things you can @code{show}, by using the
1872 related command @code{set}; for example, you can control what number
1873 system is used for displays with @code{set radix}, or simply inquire
1874 which is currently in use with @code{show radix}.
1877 To display all the settable parameters and their current
1878 values, you can use @code{show} with no arguments; you may also use
1879 @code{info set}. Both commands produce the same display.
1880 @c FIXME: "info set" violates the rule that "info" is for state of
1881 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1882 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1886 Here are several miscellaneous @code{show} subcommands, all of which are
1887 exceptional in lacking corresponding @code{set} commands:
1890 @kindex show version
1891 @cindex @value{GDBN} version number
1893 Show what version of @value{GDBN} is running. You should include this
1894 information in @value{GDBN} bug-reports. If multiple versions of
1895 @value{GDBN} are in use at your site, you may need to determine which
1896 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1897 commands are introduced, and old ones may wither away. Also, many
1898 system vendors ship variant versions of @value{GDBN}, and there are
1899 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1900 The version number is the same as the one announced when you start
1903 @kindex show copying
1904 @kindex info copying
1905 @cindex display @value{GDBN} copyright
1908 Display information about permission for copying @value{GDBN}.
1910 @kindex show warranty
1911 @kindex info warranty
1913 @itemx info warranty
1914 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1915 if your version of @value{GDBN} comes with one.
1917 @kindex show configuration
1918 @item show configuration
1919 Display detailed information about the way @value{GDBN} was configured
1920 when it was built. This displays the optional arguments passed to the
1921 @file{configure} script and also configuration parameters detected
1922 automatically by @command{configure}. When reporting a @value{GDBN}
1923 bug (@pxref{GDB Bugs}), it is important to include this information in
1929 @chapter Running Programs Under @value{GDBN}
1931 When you run a program under @value{GDBN}, you must first generate
1932 debugging information when you compile it.
1934 You may start @value{GDBN} with its arguments, if any, in an environment
1935 of your choice. If you are doing native debugging, you may redirect
1936 your program's input and output, debug an already running process, or
1937 kill a child process.
1940 * Compilation:: Compiling for debugging
1941 * Starting:: Starting your program
1942 * Arguments:: Your program's arguments
1943 * Environment:: Your program's environment
1945 * Working Directory:: Your program's working directory
1946 * Input/Output:: Your program's input and output
1947 * Attach:: Debugging an already-running process
1948 * Kill Process:: Killing the child process
1950 * Inferiors and Programs:: Debugging multiple inferiors and programs
1951 * Threads:: Debugging programs with multiple threads
1952 * Forks:: Debugging forks
1953 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1957 @section Compiling for Debugging
1959 In order to debug a program effectively, you need to generate
1960 debugging information when you compile it. This debugging information
1961 is stored in the object file; it describes the data type of each
1962 variable or function and the correspondence between source line numbers
1963 and addresses in the executable code.
1965 To request debugging information, specify the @samp{-g} option when you run
1968 Programs that are to be shipped to your customers are compiled with
1969 optimizations, using the @samp{-O} compiler option. However, some
1970 compilers are unable to handle the @samp{-g} and @samp{-O} options
1971 together. Using those compilers, you cannot generate optimized
1972 executables containing debugging information.
1974 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1975 without @samp{-O}, making it possible to debug optimized code. We
1976 recommend that you @emph{always} use @samp{-g} whenever you compile a
1977 program. You may think your program is correct, but there is no sense
1978 in pushing your luck. For more information, see @ref{Optimized Code}.
1980 Older versions of the @sc{gnu} C compiler permitted a variant option
1981 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1982 format; if your @sc{gnu} C compiler has this option, do not use it.
1984 @value{GDBN} knows about preprocessor macros and can show you their
1985 expansion (@pxref{Macros}). Most compilers do not include information
1986 about preprocessor macros in the debugging information if you specify
1987 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1988 the @sc{gnu} C compiler, provides macro information if you are using
1989 the DWARF debugging format, and specify the option @option{-g3}.
1991 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1992 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1993 information on @value{NGCC} options affecting debug information.
1995 You will have the best debugging experience if you use the latest
1996 version of the DWARF debugging format that your compiler supports.
1997 DWARF is currently the most expressive and best supported debugging
1998 format in @value{GDBN}.
2002 @section Starting your Program
2008 @kindex r @r{(@code{run})}
2011 Use the @code{run} command to start your program under @value{GDBN}.
2012 You must first specify the program name with an argument to
2013 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2014 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2015 command (@pxref{Files, ,Commands to Specify Files}).
2019 If you are running your program in an execution environment that
2020 supports processes, @code{run} creates an inferior process and makes
2021 that process run your program. In some environments without processes,
2022 @code{run} jumps to the start of your program. Other targets,
2023 like @samp{remote}, are always running. If you get an error
2024 message like this one:
2027 The "remote" target does not support "run".
2028 Try "help target" or "continue".
2032 then use @code{continue} to run your program. You may need @code{load}
2033 first (@pxref{load}).
2035 The execution of a program is affected by certain information it
2036 receives from its superior. @value{GDBN} provides ways to specify this
2037 information, which you must do @emph{before} starting your program. (You
2038 can change it after starting your program, but such changes only affect
2039 your program the next time you start it.) This information may be
2040 divided into four categories:
2043 @item The @emph{arguments.}
2044 Specify the arguments to give your program as the arguments of the
2045 @code{run} command. If a shell is available on your target, the shell
2046 is used to pass the arguments, so that you may use normal conventions
2047 (such as wildcard expansion or variable substitution) in describing
2049 In Unix systems, you can control which shell is used with the
2050 @code{SHELL} environment variable. If you do not define @code{SHELL},
2051 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2052 use of any shell with the @code{set startup-with-shell} command (see
2055 @item The @emph{environment.}
2056 Your program normally inherits its environment from @value{GDBN}, but you can
2057 use the @value{GDBN} commands @code{set environment} and @code{unset
2058 environment} to change parts of the environment that affect
2059 your program. @xref{Environment, ,Your Program's Environment}.
2061 @item The @emph{working directory.}
2062 Your program inherits its working directory from @value{GDBN}. You can set
2063 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2064 @xref{Working Directory, ,Your Program's Working Directory}.
2066 @item The @emph{standard input and output.}
2067 Your program normally uses the same device for standard input and
2068 standard output as @value{GDBN} is using. You can redirect input and output
2069 in the @code{run} command line, or you can use the @code{tty} command to
2070 set a different device for your program.
2071 @xref{Input/Output, ,Your Program's Input and Output}.
2074 @emph{Warning:} While input and output redirection work, you cannot use
2075 pipes to pass the output of the program you are debugging to another
2076 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2080 When you issue the @code{run} command, your program begins to execute
2081 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2082 of how to arrange for your program to stop. Once your program has
2083 stopped, you may call functions in your program, using the @code{print}
2084 or @code{call} commands. @xref{Data, ,Examining Data}.
2086 If the modification time of your symbol file has changed since the last
2087 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2088 table, and reads it again. When it does this, @value{GDBN} tries to retain
2089 your current breakpoints.
2094 @cindex run to main procedure
2095 The name of the main procedure can vary from language to language.
2096 With C or C@t{++}, the main procedure name is always @code{main}, but
2097 other languages such as Ada do not require a specific name for their
2098 main procedure. The debugger provides a convenient way to start the
2099 execution of the program and to stop at the beginning of the main
2100 procedure, depending on the language used.
2102 The @samp{start} command does the equivalent of setting a temporary
2103 breakpoint at the beginning of the main procedure and then invoking
2104 the @samp{run} command.
2106 @cindex elaboration phase
2107 Some programs contain an @dfn{elaboration} phase where some startup code is
2108 executed before the main procedure is called. This depends on the
2109 languages used to write your program. In C@t{++}, for instance,
2110 constructors for static and global objects are executed before
2111 @code{main} is called. It is therefore possible that the debugger stops
2112 before reaching the main procedure. However, the temporary breakpoint
2113 will remain to halt execution.
2115 Specify the arguments to give to your program as arguments to the
2116 @samp{start} command. These arguments will be given verbatim to the
2117 underlying @samp{run} command. Note that the same arguments will be
2118 reused if no argument is provided during subsequent calls to
2119 @samp{start} or @samp{run}.
2121 It is sometimes necessary to debug the program during elaboration. In
2122 these cases, using the @code{start} command would stop the execution of
2123 your program too late, as the program would have already completed the
2124 elaboration phase. Under these circumstances, insert breakpoints in your
2125 elaboration code before running your program.
2127 @anchor{set exec-wrapper}
2128 @kindex set exec-wrapper
2129 @item set exec-wrapper @var{wrapper}
2130 @itemx show exec-wrapper
2131 @itemx unset exec-wrapper
2132 When @samp{exec-wrapper} is set, the specified wrapper is used to
2133 launch programs for debugging. @value{GDBN} starts your program
2134 with a shell command of the form @kbd{exec @var{wrapper}
2135 @var{program}}. Quoting is added to @var{program} and its
2136 arguments, but not to @var{wrapper}, so you should add quotes if
2137 appropriate for your shell. The wrapper runs until it executes
2138 your program, and then @value{GDBN} takes control.
2140 You can use any program that eventually calls @code{execve} with
2141 its arguments as a wrapper. Several standard Unix utilities do
2142 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2143 with @code{exec "$@@"} will also work.
2145 For example, you can use @code{env} to pass an environment variable to
2146 the debugged program, without setting the variable in your shell's
2150 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2154 This command is available when debugging locally on most targets, excluding
2155 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2157 @kindex set startup-with-shell
2158 @item set startup-with-shell
2159 @itemx set startup-with-shell on
2160 @itemx set startup-with-shell off
2161 @itemx show set startup-with-shell
2162 On Unix systems, by default, if a shell is available on your target,
2163 @value{GDBN}) uses it to start your program. Arguments of the
2164 @code{run} command are passed to the shell, which does variable
2165 substitution, expands wildcard characters and performs redirection of
2166 I/O. In some circumstances, it may be useful to disable such use of a
2167 shell, for example, when debugging the shell itself or diagnosing
2168 startup failures such as:
2172 Starting program: ./a.out
2173 During startup program terminated with signal SIGSEGV, Segmentation fault.
2177 which indicates the shell or the wrapper specified with
2178 @samp{exec-wrapper} crashed, not your program. Most often, this is
2179 caused by something odd in your shell's non-interactive mode
2180 initialization file---such as @file{.cshrc} for C-shell,
2181 $@file{.zshenv} for the Z shell, or the file specified in the
2182 @samp{BASH_ENV} environment variable for BASH.
2184 @anchor{set auto-connect-native-target}
2185 @kindex set auto-connect-native-target
2186 @item set auto-connect-native-target
2187 @itemx set auto-connect-native-target on
2188 @itemx set auto-connect-native-target off
2189 @itemx show auto-connect-native-target
2191 By default, if not connected to any target yet (e.g., with
2192 @code{target remote}), the @code{run} command starts your program as a
2193 native process under @value{GDBN}, on your local machine. If you're
2194 sure you don't want to debug programs on your local machine, you can
2195 tell @value{GDBN} to not connect to the native target automatically
2196 with the @code{set auto-connect-native-target off} command.
2198 If @code{on}, which is the default, and if @value{GDBN} is not
2199 connected to a target already, the @code{run} command automaticaly
2200 connects to the native target, if one is available.
2202 If @code{off}, and if @value{GDBN} is not connected to a target
2203 already, the @code{run} command fails with an error:
2207 Don't know how to run. Try "help target".
2210 If @value{GDBN} is already connected to a target, @value{GDBN} always
2211 uses it with the @code{run} command.
2213 In any case, you can explicitly connect to the native target with the
2214 @code{target native} command. For example,
2217 (@value{GDBP}) set auto-connect-native-target off
2219 Don't know how to run. Try "help target".
2220 (@value{GDBP}) target native
2222 Starting program: ./a.out
2223 [Inferior 1 (process 10421) exited normally]
2226 In case you connected explicitly to the @code{native} target,
2227 @value{GDBN} remains connected even if all inferiors exit, ready for
2228 the next @code{run} command. Use the @code{disconnect} command to
2231 Examples of other commands that likewise respect the
2232 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2233 proc}, @code{info os}.
2235 @kindex set disable-randomization
2236 @item set disable-randomization
2237 @itemx set disable-randomization on
2238 This option (enabled by default in @value{GDBN}) will turn off the native
2239 randomization of the virtual address space of the started program. This option
2240 is useful for multiple debugging sessions to make the execution better
2241 reproducible and memory addresses reusable across debugging sessions.
2243 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2244 On @sc{gnu}/Linux you can get the same behavior using
2247 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2250 @item set disable-randomization off
2251 Leave the behavior of the started executable unchanged. Some bugs rear their
2252 ugly heads only when the program is loaded at certain addresses. If your bug
2253 disappears when you run the program under @value{GDBN}, that might be because
2254 @value{GDBN} by default disables the address randomization on platforms, such
2255 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2256 disable-randomization off} to try to reproduce such elusive bugs.
2258 On targets where it is available, virtual address space randomization
2259 protects the programs against certain kinds of security attacks. In these
2260 cases the attacker needs to know the exact location of a concrete executable
2261 code. Randomizing its location makes it impossible to inject jumps misusing
2262 a code at its expected addresses.
2264 Prelinking shared libraries provides a startup performance advantage but it
2265 makes addresses in these libraries predictable for privileged processes by
2266 having just unprivileged access at the target system. Reading the shared
2267 library binary gives enough information for assembling the malicious code
2268 misusing it. Still even a prelinked shared library can get loaded at a new
2269 random address just requiring the regular relocation process during the
2270 startup. Shared libraries not already prelinked are always loaded at
2271 a randomly chosen address.
2273 Position independent executables (PIE) contain position independent code
2274 similar to the shared libraries and therefore such executables get loaded at
2275 a randomly chosen address upon startup. PIE executables always load even
2276 already prelinked shared libraries at a random address. You can build such
2277 executable using @command{gcc -fPIE -pie}.
2279 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2280 (as long as the randomization is enabled).
2282 @item show disable-randomization
2283 Show the current setting of the explicit disable of the native randomization of
2284 the virtual address space of the started program.
2289 @section Your Program's Arguments
2291 @cindex arguments (to your program)
2292 The arguments to your program can be specified by the arguments of the
2294 They are passed to a shell, which expands wildcard characters and
2295 performs redirection of I/O, and thence to your program. Your
2296 @code{SHELL} environment variable (if it exists) specifies what shell
2297 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2298 the default shell (@file{/bin/sh} on Unix).
2300 On non-Unix systems, the program is usually invoked directly by
2301 @value{GDBN}, which emulates I/O redirection via the appropriate system
2302 calls, and the wildcard characters are expanded by the startup code of
2303 the program, not by the shell.
2305 @code{run} with no arguments uses the same arguments used by the previous
2306 @code{run}, or those set by the @code{set args} command.
2311 Specify the arguments to be used the next time your program is run. If
2312 @code{set args} has no arguments, @code{run} executes your program
2313 with no arguments. Once you have run your program with arguments,
2314 using @code{set args} before the next @code{run} is the only way to run
2315 it again without arguments.
2319 Show the arguments to give your program when it is started.
2323 @section Your Program's Environment
2325 @cindex environment (of your program)
2326 The @dfn{environment} consists of a set of environment variables and
2327 their values. Environment variables conventionally record such things as
2328 your user name, your home directory, your terminal type, and your search
2329 path for programs to run. Usually you set up environment variables with
2330 the shell and they are inherited by all the other programs you run. When
2331 debugging, it can be useful to try running your program with a modified
2332 environment without having to start @value{GDBN} over again.
2336 @item path @var{directory}
2337 Add @var{directory} to the front of the @code{PATH} environment variable
2338 (the search path for executables) that will be passed to your program.
2339 The value of @code{PATH} used by @value{GDBN} does not change.
2340 You may specify several directory names, separated by whitespace or by a
2341 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2342 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2343 is moved to the front, so it is searched sooner.
2345 You can use the string @samp{$cwd} to refer to whatever is the current
2346 working directory at the time @value{GDBN} searches the path. If you
2347 use @samp{.} instead, it refers to the directory where you executed the
2348 @code{path} command. @value{GDBN} replaces @samp{.} in the
2349 @var{directory} argument (with the current path) before adding
2350 @var{directory} to the search path.
2351 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2352 @c document that, since repeating it would be a no-op.
2356 Display the list of search paths for executables (the @code{PATH}
2357 environment variable).
2359 @kindex show environment
2360 @item show environment @r{[}@var{varname}@r{]}
2361 Print the value of environment variable @var{varname} to be given to
2362 your program when it starts. If you do not supply @var{varname},
2363 print the names and values of all environment variables to be given to
2364 your program. You can abbreviate @code{environment} as @code{env}.
2366 @kindex set environment
2367 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2368 Set environment variable @var{varname} to @var{value}. The value
2369 changes for your program (and the shell @value{GDBN} uses to launch
2370 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2371 values of environment variables are just strings, and any
2372 interpretation is supplied by your program itself. The @var{value}
2373 parameter is optional; if it is eliminated, the variable is set to a
2375 @c "any string" here does not include leading, trailing
2376 @c blanks. Gnu asks: does anyone care?
2378 For example, this command:
2385 tells the debugged program, when subsequently run, that its user is named
2386 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2387 are not actually required.)
2389 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2390 which also inherits the environment set with @code{set environment}.
2391 If necessary, you can avoid that by using the @samp{env} program as a
2392 wrapper instead of using @code{set environment}. @xref{set
2393 exec-wrapper}, for an example doing just that.
2395 @kindex unset environment
2396 @item unset environment @var{varname}
2397 Remove variable @var{varname} from the environment to be passed to your
2398 program. This is different from @samp{set env @var{varname} =};
2399 @code{unset environment} removes the variable from the environment,
2400 rather than assigning it an empty value.
2403 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2404 the shell indicated by your @code{SHELL} environment variable if it
2405 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2406 names a shell that runs an initialization file when started
2407 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2408 for the Z shell, or the file specified in the @samp{BASH_ENV}
2409 environment variable for BASH---any variables you set in that file
2410 affect your program. You may wish to move setting of environment
2411 variables to files that are only run when you sign on, such as
2412 @file{.login} or @file{.profile}.
2414 @node Working Directory
2415 @section Your Program's Working Directory
2417 @cindex working directory (of your program)
2418 Each time you start your program with @code{run}, it inherits its
2419 working directory from the current working directory of @value{GDBN}.
2420 The @value{GDBN} working directory is initially whatever it inherited
2421 from its parent process (typically the shell), but you can specify a new
2422 working directory in @value{GDBN} with the @code{cd} command.
2424 The @value{GDBN} working directory also serves as a default for the commands
2425 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2430 @cindex change working directory
2431 @item cd @r{[}@var{directory}@r{]}
2432 Set the @value{GDBN} working directory to @var{directory}. If not
2433 given, @var{directory} uses @file{'~'}.
2437 Print the @value{GDBN} working directory.
2440 It is generally impossible to find the current working directory of
2441 the process being debugged (since a program can change its directory
2442 during its run). If you work on a system where @value{GDBN} is
2443 configured with the @file{/proc} support, you can use the @code{info
2444 proc} command (@pxref{SVR4 Process Information}) to find out the
2445 current working directory of the debuggee.
2448 @section Your Program's Input and Output
2453 By default, the program you run under @value{GDBN} does input and output to
2454 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2455 to its own terminal modes to interact with you, but it records the terminal
2456 modes your program was using and switches back to them when you continue
2457 running your program.
2460 @kindex info terminal
2462 Displays information recorded by @value{GDBN} about the terminal modes your
2466 You can redirect your program's input and/or output using shell
2467 redirection with the @code{run} command. For example,
2474 starts your program, diverting its output to the file @file{outfile}.
2477 @cindex controlling terminal
2478 Another way to specify where your program should do input and output is
2479 with the @code{tty} command. This command accepts a file name as
2480 argument, and causes this file to be the default for future @code{run}
2481 commands. It also resets the controlling terminal for the child
2482 process, for future @code{run} commands. For example,
2489 directs that processes started with subsequent @code{run} commands
2490 default to do input and output on the terminal @file{/dev/ttyb} and have
2491 that as their controlling terminal.
2493 An explicit redirection in @code{run} overrides the @code{tty} command's
2494 effect on the input/output device, but not its effect on the controlling
2497 When you use the @code{tty} command or redirect input in the @code{run}
2498 command, only the input @emph{for your program} is affected. The input
2499 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2500 for @code{set inferior-tty}.
2502 @cindex inferior tty
2503 @cindex set inferior controlling terminal
2504 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2505 display the name of the terminal that will be used for future runs of your
2509 @item set inferior-tty /dev/ttyb
2510 @kindex set inferior-tty
2511 Set the tty for the program being debugged to /dev/ttyb.
2513 @item show inferior-tty
2514 @kindex show inferior-tty
2515 Show the current tty for the program being debugged.
2519 @section Debugging an Already-running Process
2524 @item attach @var{process-id}
2525 This command attaches to a running process---one that was started
2526 outside @value{GDBN}. (@code{info files} shows your active
2527 targets.) The command takes as argument a process ID. The usual way to
2528 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2529 or with the @samp{jobs -l} shell command.
2531 @code{attach} does not repeat if you press @key{RET} a second time after
2532 executing the command.
2535 To use @code{attach}, your program must be running in an environment
2536 which supports processes; for example, @code{attach} does not work for
2537 programs on bare-board targets that lack an operating system. You must
2538 also have permission to send the process a signal.
2540 When you use @code{attach}, the debugger finds the program running in
2541 the process first by looking in the current working directory, then (if
2542 the program is not found) by using the source file search path
2543 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2544 the @code{file} command to load the program. @xref{Files, ,Commands to
2547 The first thing @value{GDBN} does after arranging to debug the specified
2548 process is to stop it. You can examine and modify an attached process
2549 with all the @value{GDBN} commands that are ordinarily available when
2550 you start processes with @code{run}. You can insert breakpoints; you
2551 can step and continue; you can modify storage. If you would rather the
2552 process continue running, you may use the @code{continue} command after
2553 attaching @value{GDBN} to the process.
2558 When you have finished debugging the attached process, you can use the
2559 @code{detach} command to release it from @value{GDBN} control. Detaching
2560 the process continues its execution. After the @code{detach} command,
2561 that process and @value{GDBN} become completely independent once more, and you
2562 are ready to @code{attach} another process or start one with @code{run}.
2563 @code{detach} does not repeat if you press @key{RET} again after
2564 executing the command.
2567 If you exit @value{GDBN} while you have an attached process, you detach
2568 that process. If you use the @code{run} command, you kill that process.
2569 By default, @value{GDBN} asks for confirmation if you try to do either of these
2570 things; you can control whether or not you need to confirm by using the
2571 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2575 @section Killing the Child Process
2580 Kill the child process in which your program is running under @value{GDBN}.
2583 This command is useful if you wish to debug a core dump instead of a
2584 running process. @value{GDBN} ignores any core dump file while your program
2587 On some operating systems, a program cannot be executed outside @value{GDBN}
2588 while you have breakpoints set on it inside @value{GDBN}. You can use the
2589 @code{kill} command in this situation to permit running your program
2590 outside the debugger.
2592 The @code{kill} command is also useful if you wish to recompile and
2593 relink your program, since on many systems it is impossible to modify an
2594 executable file while it is running in a process. In this case, when you
2595 next type @code{run}, @value{GDBN} notices that the file has changed, and
2596 reads the symbol table again (while trying to preserve your current
2597 breakpoint settings).
2599 @node Inferiors and Programs
2600 @section Debugging Multiple Inferiors and Programs
2602 @value{GDBN} lets you run and debug multiple programs in a single
2603 session. In addition, @value{GDBN} on some systems may let you run
2604 several programs simultaneously (otherwise you have to exit from one
2605 before starting another). In the most general case, you can have
2606 multiple threads of execution in each of multiple processes, launched
2607 from multiple executables.
2610 @value{GDBN} represents the state of each program execution with an
2611 object called an @dfn{inferior}. An inferior typically corresponds to
2612 a process, but is more general and applies also to targets that do not
2613 have processes. Inferiors may be created before a process runs, and
2614 may be retained after a process exits. Inferiors have unique
2615 identifiers that are different from process ids. Usually each
2616 inferior will also have its own distinct address space, although some
2617 embedded targets may have several inferiors running in different parts
2618 of a single address space. Each inferior may in turn have multiple
2619 threads running in it.
2621 To find out what inferiors exist at any moment, use @w{@code{info
2625 @kindex info inferiors
2626 @item info inferiors
2627 Print a list of all inferiors currently being managed by @value{GDBN}.
2629 @value{GDBN} displays for each inferior (in this order):
2633 the inferior number assigned by @value{GDBN}
2636 the target system's inferior identifier
2639 the name of the executable the inferior is running.
2644 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2645 indicates the current inferior.
2649 @c end table here to get a little more width for example
2652 (@value{GDBP}) info inferiors
2653 Num Description Executable
2654 2 process 2307 hello
2655 * 1 process 3401 goodbye
2658 To switch focus between inferiors, use the @code{inferior} command:
2661 @kindex inferior @var{infno}
2662 @item inferior @var{infno}
2663 Make inferior number @var{infno} the current inferior. The argument
2664 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2665 in the first field of the @samp{info inferiors} display.
2669 You can get multiple executables into a debugging session via the
2670 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2671 systems @value{GDBN} can add inferiors to the debug session
2672 automatically by following calls to @code{fork} and @code{exec}. To
2673 remove inferiors from the debugging session use the
2674 @w{@code{remove-inferiors}} command.
2677 @kindex add-inferior
2678 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2679 Adds @var{n} inferiors to be run using @var{executable} as the
2680 executable; @var{n} defaults to 1. If no executable is specified,
2681 the inferiors begins empty, with no program. You can still assign or
2682 change the program assigned to the inferior at any time by using the
2683 @code{file} command with the executable name as its argument.
2685 @kindex clone-inferior
2686 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2687 Adds @var{n} inferiors ready to execute the same program as inferior
2688 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2689 number of the current inferior. This is a convenient command when you
2690 want to run another instance of the inferior you are debugging.
2693 (@value{GDBP}) info inferiors
2694 Num Description Executable
2695 * 1 process 29964 helloworld
2696 (@value{GDBP}) clone-inferior
2699 (@value{GDBP}) info inferiors
2700 Num Description Executable
2702 * 1 process 29964 helloworld
2705 You can now simply switch focus to inferior 2 and run it.
2707 @kindex remove-inferiors
2708 @item remove-inferiors @var{infno}@dots{}
2709 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2710 possible to remove an inferior that is running with this command. For
2711 those, use the @code{kill} or @code{detach} command first.
2715 To quit debugging one of the running inferiors that is not the current
2716 inferior, you can either detach from it by using the @w{@code{detach
2717 inferior}} command (allowing it to run independently), or kill it
2718 using the @w{@code{kill inferiors}} command:
2721 @kindex detach inferiors @var{infno}@dots{}
2722 @item detach inferior @var{infno}@dots{}
2723 Detach from the inferior or inferiors identified by @value{GDBN}
2724 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2725 still stays on the list of inferiors shown by @code{info inferiors},
2726 but its Description will show @samp{<null>}.
2728 @kindex kill inferiors @var{infno}@dots{}
2729 @item kill inferiors @var{infno}@dots{}
2730 Kill the inferior or inferiors identified by @value{GDBN} inferior
2731 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2732 stays on the list of inferiors shown by @code{info inferiors}, but its
2733 Description will show @samp{<null>}.
2736 After the successful completion of a command such as @code{detach},
2737 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2738 a normal process exit, the inferior is still valid and listed with
2739 @code{info inferiors}, ready to be restarted.
2742 To be notified when inferiors are started or exit under @value{GDBN}'s
2743 control use @w{@code{set print inferior-events}}:
2746 @kindex set print inferior-events
2747 @cindex print messages on inferior start and exit
2748 @item set print inferior-events
2749 @itemx set print inferior-events on
2750 @itemx set print inferior-events off
2751 The @code{set print inferior-events} command allows you to enable or
2752 disable printing of messages when @value{GDBN} notices that new
2753 inferiors have started or that inferiors have exited or have been
2754 detached. By default, these messages will not be printed.
2756 @kindex show print inferior-events
2757 @item show print inferior-events
2758 Show whether messages will be printed when @value{GDBN} detects that
2759 inferiors have started, exited or have been detached.
2762 Many commands will work the same with multiple programs as with a
2763 single program: e.g., @code{print myglobal} will simply display the
2764 value of @code{myglobal} in the current inferior.
2767 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2768 get more info about the relationship of inferiors, programs, address
2769 spaces in a debug session. You can do that with the @w{@code{maint
2770 info program-spaces}} command.
2773 @kindex maint info program-spaces
2774 @item maint info program-spaces
2775 Print a list of all program spaces currently being managed by
2778 @value{GDBN} displays for each program space (in this order):
2782 the program space number assigned by @value{GDBN}
2785 the name of the executable loaded into the program space, with e.g.,
2786 the @code{file} command.
2791 An asterisk @samp{*} preceding the @value{GDBN} program space number
2792 indicates the current program space.
2794 In addition, below each program space line, @value{GDBN} prints extra
2795 information that isn't suitable to display in tabular form. For
2796 example, the list of inferiors bound to the program space.
2799 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2806 Here we can see that no inferior is running the program @code{hello},
2807 while @code{process 21561} is running the program @code{goodbye}. On
2808 some targets, it is possible that multiple inferiors are bound to the
2809 same program space. The most common example is that of debugging both
2810 the parent and child processes of a @code{vfork} call. For example,
2813 (@value{GDBP}) maint info program-spaces
2816 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2819 Here, both inferior 2 and inferior 1 are running in the same program
2820 space as a result of inferior 1 having executed a @code{vfork} call.
2824 @section Debugging Programs with Multiple Threads
2826 @cindex threads of execution
2827 @cindex multiple threads
2828 @cindex switching threads
2829 In some operating systems, such as HP-UX and Solaris, a single program
2830 may have more than one @dfn{thread} of execution. The precise semantics
2831 of threads differ from one operating system to another, but in general
2832 the threads of a single program are akin to multiple processes---except
2833 that they share one address space (that is, they can all examine and
2834 modify the same variables). On the other hand, each thread has its own
2835 registers and execution stack, and perhaps private memory.
2837 @value{GDBN} provides these facilities for debugging multi-thread
2841 @item automatic notification of new threads
2842 @item @samp{thread @var{threadno}}, a command to switch among threads
2843 @item @samp{info threads}, a command to inquire about existing threads
2844 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2845 a command to apply a command to a list of threads
2846 @item thread-specific breakpoints
2847 @item @samp{set print thread-events}, which controls printing of
2848 messages on thread start and exit.
2849 @item @samp{set libthread-db-search-path @var{path}}, which lets
2850 the user specify which @code{libthread_db} to use if the default choice
2851 isn't compatible with the program.
2855 @emph{Warning:} These facilities are not yet available on every
2856 @value{GDBN} configuration where the operating system supports threads.
2857 If your @value{GDBN} does not support threads, these commands have no
2858 effect. For example, a system without thread support shows no output
2859 from @samp{info threads}, and always rejects the @code{thread} command,
2863 (@value{GDBP}) info threads
2864 (@value{GDBP}) thread 1
2865 Thread ID 1 not known. Use the "info threads" command to
2866 see the IDs of currently known threads.
2868 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2869 @c doesn't support threads"?
2872 @cindex focus of debugging
2873 @cindex current thread
2874 The @value{GDBN} thread debugging facility allows you to observe all
2875 threads while your program runs---but whenever @value{GDBN} takes
2876 control, one thread in particular is always the focus of debugging.
2877 This thread is called the @dfn{current thread}. Debugging commands show
2878 program information from the perspective of the current thread.
2880 @cindex @code{New} @var{systag} message
2881 @cindex thread identifier (system)
2882 @c FIXME-implementors!! It would be more helpful if the [New...] message
2883 @c included GDB's numeric thread handle, so you could just go to that
2884 @c thread without first checking `info threads'.
2885 Whenever @value{GDBN} detects a new thread in your program, it displays
2886 the target system's identification for the thread with a message in the
2887 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2888 whose form varies depending on the particular system. For example, on
2889 @sc{gnu}/Linux, you might see
2892 [New Thread 0x41e02940 (LWP 25582)]
2896 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2897 the @var{systag} is simply something like @samp{process 368}, with no
2900 @c FIXME!! (1) Does the [New...] message appear even for the very first
2901 @c thread of a program, or does it only appear for the
2902 @c second---i.e.@: when it becomes obvious we have a multithread
2904 @c (2) *Is* there necessarily a first thread always? Or do some
2905 @c multithread systems permit starting a program with multiple
2906 @c threads ab initio?
2908 @cindex thread number
2909 @cindex thread identifier (GDB)
2910 For debugging purposes, @value{GDBN} associates its own thread
2911 number---always a single integer---with each thread in your program.
2914 @kindex info threads
2915 @item info threads @r{[}@var{id}@dots{}@r{]}
2916 Display a summary of all threads currently in your program. Optional
2917 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2918 means to print information only about the specified thread or threads.
2919 @value{GDBN} displays for each thread (in this order):
2923 the thread number assigned by @value{GDBN}
2926 the target system's thread identifier (@var{systag})
2929 the thread's name, if one is known. A thread can either be named by
2930 the user (see @code{thread name}, below), or, in some cases, by the
2934 the current stack frame summary for that thread
2938 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2939 indicates the current thread.
2943 @c end table here to get a little more width for example
2946 (@value{GDBP}) info threads
2948 3 process 35 thread 27 0x34e5 in sigpause ()
2949 2 process 35 thread 23 0x34e5 in sigpause ()
2950 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2954 On Solaris, you can display more information about user threads with a
2955 Solaris-specific command:
2958 @item maint info sol-threads
2959 @kindex maint info sol-threads
2960 @cindex thread info (Solaris)
2961 Display info on Solaris user threads.
2965 @kindex thread @var{threadno}
2966 @item thread @var{threadno}
2967 Make thread number @var{threadno} the current thread. The command
2968 argument @var{threadno} is the internal @value{GDBN} thread number, as
2969 shown in the first field of the @samp{info threads} display.
2970 @value{GDBN} responds by displaying the system identifier of the thread
2971 you selected, and its current stack frame summary:
2974 (@value{GDBP}) thread 2
2975 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2976 #0 some_function (ignore=0x0) at example.c:8
2977 8 printf ("hello\n");
2981 As with the @samp{[New @dots{}]} message, the form of the text after
2982 @samp{Switching to} depends on your system's conventions for identifying
2985 @vindex $_thread@r{, convenience variable}
2986 The debugger convenience variable @samp{$_thread} contains the number
2987 of the current thread. You may find this useful in writing breakpoint
2988 conditional expressions, command scripts, and so forth. See
2989 @xref{Convenience Vars,, Convenience Variables}, for general
2990 information on convenience variables.
2992 @kindex thread apply
2993 @cindex apply command to several threads
2994 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2995 The @code{thread apply} command allows you to apply the named
2996 @var{command} to one or more threads. Specify the numbers of the
2997 threads that you want affected with the command argument
2998 @var{threadno}. It can be a single thread number, one of the numbers
2999 shown in the first field of the @samp{info threads} display; or it
3000 could be a range of thread numbers, as in @code{2-4}. To apply
3001 a command to all threads in descending order, type @kbd{thread apply all
3002 @var{command}}. To apply a command to all threads in ascending order,
3003 type @kbd{thread apply all -ascending @var{command}}.
3007 @cindex name a thread
3008 @item thread name [@var{name}]
3009 This command assigns a name to the current thread. If no argument is
3010 given, any existing user-specified name is removed. The thread name
3011 appears in the @samp{info threads} display.
3013 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3014 determine the name of the thread as given by the OS. On these
3015 systems, a name specified with @samp{thread name} will override the
3016 system-give name, and removing the user-specified name will cause
3017 @value{GDBN} to once again display the system-specified name.
3020 @cindex search for a thread
3021 @item thread find [@var{regexp}]
3022 Search for and display thread ids whose name or @var{systag}
3023 matches the supplied regular expression.
3025 As well as being the complement to the @samp{thread name} command,
3026 this command also allows you to identify a thread by its target
3027 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3031 (@value{GDBN}) thread find 26688
3032 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3033 (@value{GDBN}) info thread 4
3035 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3038 @kindex set print thread-events
3039 @cindex print messages on thread start and exit
3040 @item set print thread-events
3041 @itemx set print thread-events on
3042 @itemx set print thread-events off
3043 The @code{set print thread-events} command allows you to enable or
3044 disable printing of messages when @value{GDBN} notices that new threads have
3045 started or that threads have exited. By default, these messages will
3046 be printed if detection of these events is supported by the target.
3047 Note that these messages cannot be disabled on all targets.
3049 @kindex show print thread-events
3050 @item show print thread-events
3051 Show whether messages will be printed when @value{GDBN} detects that threads
3052 have started and exited.
3055 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3056 more information about how @value{GDBN} behaves when you stop and start
3057 programs with multiple threads.
3059 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3060 watchpoints in programs with multiple threads.
3062 @anchor{set libthread-db-search-path}
3064 @kindex set libthread-db-search-path
3065 @cindex search path for @code{libthread_db}
3066 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3067 If this variable is set, @var{path} is a colon-separated list of
3068 directories @value{GDBN} will use to search for @code{libthread_db}.
3069 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3070 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3071 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3074 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3075 @code{libthread_db} library to obtain information about threads in the
3076 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3077 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3078 specific thread debugging library loading is enabled
3079 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3081 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3082 refers to the default system directories that are
3083 normally searched for loading shared libraries. The @samp{$sdir} entry
3084 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3085 (@pxref{libthread_db.so.1 file}).
3087 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3088 refers to the directory from which @code{libpthread}
3089 was loaded in the inferior process.
3091 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3092 @value{GDBN} attempts to initialize it with the current inferior process.
3093 If this initialization fails (which could happen because of a version
3094 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3095 will unload @code{libthread_db}, and continue with the next directory.
3096 If none of @code{libthread_db} libraries initialize successfully,
3097 @value{GDBN} will issue a warning and thread debugging will be disabled.
3099 Setting @code{libthread-db-search-path} is currently implemented
3100 only on some platforms.
3102 @kindex show libthread-db-search-path
3103 @item show libthread-db-search-path
3104 Display current libthread_db search path.
3106 @kindex set debug libthread-db
3107 @kindex show debug libthread-db
3108 @cindex debugging @code{libthread_db}
3109 @item set debug libthread-db
3110 @itemx show debug libthread-db
3111 Turns on or off display of @code{libthread_db}-related events.
3112 Use @code{1} to enable, @code{0} to disable.
3116 @section Debugging Forks
3118 @cindex fork, debugging programs which call
3119 @cindex multiple processes
3120 @cindex processes, multiple
3121 On most systems, @value{GDBN} has no special support for debugging
3122 programs which create additional processes using the @code{fork}
3123 function. When a program forks, @value{GDBN} will continue to debug the
3124 parent process and the child process will run unimpeded. If you have
3125 set a breakpoint in any code which the child then executes, the child
3126 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3127 will cause it to terminate.
3129 However, if you want to debug the child process there is a workaround
3130 which isn't too painful. Put a call to @code{sleep} in the code which
3131 the child process executes after the fork. It may be useful to sleep
3132 only if a certain environment variable is set, or a certain file exists,
3133 so that the delay need not occur when you don't want to run @value{GDBN}
3134 on the child. While the child is sleeping, use the @code{ps} program to
3135 get its process ID. Then tell @value{GDBN} (a new invocation of
3136 @value{GDBN} if you are also debugging the parent process) to attach to
3137 the child process (@pxref{Attach}). From that point on you can debug
3138 the child process just like any other process which you attached to.
3140 On some systems, @value{GDBN} provides support for debugging programs that
3141 create additional processes using the @code{fork} or @code{vfork} functions.
3142 Currently, the only platforms with this feature are HP-UX (11.x and later
3143 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3145 By default, when a program forks, @value{GDBN} will continue to debug
3146 the parent process and the child process will run unimpeded.
3148 If you want to follow the child process instead of the parent process,
3149 use the command @w{@code{set follow-fork-mode}}.
3152 @kindex set follow-fork-mode
3153 @item set follow-fork-mode @var{mode}
3154 Set the debugger response to a program call of @code{fork} or
3155 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3156 process. The @var{mode} argument can be:
3160 The original process is debugged after a fork. The child process runs
3161 unimpeded. This is the default.
3164 The new process is debugged after a fork. The parent process runs
3169 @kindex show follow-fork-mode
3170 @item show follow-fork-mode
3171 Display the current debugger response to a @code{fork} or @code{vfork} call.
3174 @cindex debugging multiple processes
3175 On Linux, if you want to debug both the parent and child processes, use the
3176 command @w{@code{set detach-on-fork}}.
3179 @kindex set detach-on-fork
3180 @item set detach-on-fork @var{mode}
3181 Tells gdb whether to detach one of the processes after a fork, or
3182 retain debugger control over them both.
3186 The child process (or parent process, depending on the value of
3187 @code{follow-fork-mode}) will be detached and allowed to run
3188 independently. This is the default.
3191 Both processes will be held under the control of @value{GDBN}.
3192 One process (child or parent, depending on the value of
3193 @code{follow-fork-mode}) is debugged as usual, while the other
3198 @kindex show detach-on-fork
3199 @item show detach-on-fork
3200 Show whether detach-on-fork mode is on/off.
3203 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3204 will retain control of all forked processes (including nested forks).
3205 You can list the forked processes under the control of @value{GDBN} by
3206 using the @w{@code{info inferiors}} command, and switch from one fork
3207 to another by using the @code{inferior} command (@pxref{Inferiors and
3208 Programs, ,Debugging Multiple Inferiors and Programs}).
3210 To quit debugging one of the forked processes, you can either detach
3211 from it by using the @w{@code{detach inferiors}} command (allowing it
3212 to run independently), or kill it using the @w{@code{kill inferiors}}
3213 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3216 If you ask to debug a child process and a @code{vfork} is followed by an
3217 @code{exec}, @value{GDBN} executes the new target up to the first
3218 breakpoint in the new target. If you have a breakpoint set on
3219 @code{main} in your original program, the breakpoint will also be set on
3220 the child process's @code{main}.
3222 On some systems, when a child process is spawned by @code{vfork}, you
3223 cannot debug the child or parent until an @code{exec} call completes.
3225 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3226 call executes, the new target restarts. To restart the parent
3227 process, use the @code{file} command with the parent executable name
3228 as its argument. By default, after an @code{exec} call executes,
3229 @value{GDBN} discards the symbols of the previous executable image.
3230 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3234 @kindex set follow-exec-mode
3235 @item set follow-exec-mode @var{mode}
3237 Set debugger response to a program call of @code{exec}. An
3238 @code{exec} call replaces the program image of a process.
3240 @code{follow-exec-mode} can be:
3244 @value{GDBN} creates a new inferior and rebinds the process to this
3245 new inferior. The program the process was running before the
3246 @code{exec} call can be restarted afterwards by restarting the
3252 (@value{GDBP}) info inferiors
3254 Id Description Executable
3257 process 12020 is executing new program: prog2
3258 Program exited normally.
3259 (@value{GDBP}) info inferiors
3260 Id Description Executable
3266 @value{GDBN} keeps the process bound to the same inferior. The new
3267 executable image replaces the previous executable loaded in the
3268 inferior. Restarting the inferior after the @code{exec} call, with
3269 e.g., the @code{run} command, restarts the executable the process was
3270 running after the @code{exec} call. This is the default mode.
3275 (@value{GDBP}) info inferiors
3276 Id Description Executable
3279 process 12020 is executing new program: prog2
3280 Program exited normally.
3281 (@value{GDBP}) info inferiors
3282 Id Description Executable
3289 You can use the @code{catch} command to make @value{GDBN} stop whenever
3290 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3291 Catchpoints, ,Setting Catchpoints}.
3293 @node Checkpoint/Restart
3294 @section Setting a @emph{Bookmark} to Return to Later
3299 @cindex snapshot of a process
3300 @cindex rewind program state
3302 On certain operating systems@footnote{Currently, only
3303 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3304 program's state, called a @dfn{checkpoint}, and come back to it
3307 Returning to a checkpoint effectively undoes everything that has
3308 happened in the program since the @code{checkpoint} was saved. This
3309 includes changes in memory, registers, and even (within some limits)
3310 system state. Effectively, it is like going back in time to the
3311 moment when the checkpoint was saved.
3313 Thus, if you're stepping thru a program and you think you're
3314 getting close to the point where things go wrong, you can save
3315 a checkpoint. Then, if you accidentally go too far and miss
3316 the critical statement, instead of having to restart your program
3317 from the beginning, you can just go back to the checkpoint and
3318 start again from there.
3320 This can be especially useful if it takes a lot of time or
3321 steps to reach the point where you think the bug occurs.
3323 To use the @code{checkpoint}/@code{restart} method of debugging:
3328 Save a snapshot of the debugged program's current execution state.
3329 The @code{checkpoint} command takes no arguments, but each checkpoint
3330 is assigned a small integer id, similar to a breakpoint id.
3332 @kindex info checkpoints
3333 @item info checkpoints
3334 List the checkpoints that have been saved in the current debugging
3335 session. For each checkpoint, the following information will be
3342 @item Source line, or label
3345 @kindex restart @var{checkpoint-id}
3346 @item restart @var{checkpoint-id}
3347 Restore the program state that was saved as checkpoint number
3348 @var{checkpoint-id}. All program variables, registers, stack frames
3349 etc.@: will be returned to the values that they had when the checkpoint
3350 was saved. In essence, gdb will ``wind back the clock'' to the point
3351 in time when the checkpoint was saved.
3353 Note that breakpoints, @value{GDBN} variables, command history etc.
3354 are not affected by restoring a checkpoint. In general, a checkpoint
3355 only restores things that reside in the program being debugged, not in
3358 @kindex delete checkpoint @var{checkpoint-id}
3359 @item delete checkpoint @var{checkpoint-id}
3360 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3364 Returning to a previously saved checkpoint will restore the user state
3365 of the program being debugged, plus a significant subset of the system
3366 (OS) state, including file pointers. It won't ``un-write'' data from
3367 a file, but it will rewind the file pointer to the previous location,
3368 so that the previously written data can be overwritten. For files
3369 opened in read mode, the pointer will also be restored so that the
3370 previously read data can be read again.
3372 Of course, characters that have been sent to a printer (or other
3373 external device) cannot be ``snatched back'', and characters received
3374 from eg.@: a serial device can be removed from internal program buffers,
3375 but they cannot be ``pushed back'' into the serial pipeline, ready to
3376 be received again. Similarly, the actual contents of files that have
3377 been changed cannot be restored (at this time).
3379 However, within those constraints, you actually can ``rewind'' your
3380 program to a previously saved point in time, and begin debugging it
3381 again --- and you can change the course of events so as to debug a
3382 different execution path this time.
3384 @cindex checkpoints and process id
3385 Finally, there is one bit of internal program state that will be
3386 different when you return to a checkpoint --- the program's process
3387 id. Each checkpoint will have a unique process id (or @var{pid}),
3388 and each will be different from the program's original @var{pid}.
3389 If your program has saved a local copy of its process id, this could
3390 potentially pose a problem.
3392 @subsection A Non-obvious Benefit of Using Checkpoints
3394 On some systems such as @sc{gnu}/Linux, address space randomization
3395 is performed on new processes for security reasons. This makes it
3396 difficult or impossible to set a breakpoint, or watchpoint, on an
3397 absolute address if you have to restart the program, since the
3398 absolute location of a symbol will change from one execution to the
3401 A checkpoint, however, is an @emph{identical} copy of a process.
3402 Therefore if you create a checkpoint at (eg.@:) the start of main,
3403 and simply return to that checkpoint instead of restarting the
3404 process, you can avoid the effects of address randomization and
3405 your symbols will all stay in the same place.
3408 @chapter Stopping and Continuing
3410 The principal purposes of using a debugger are so that you can stop your
3411 program before it terminates; or so that, if your program runs into
3412 trouble, you can investigate and find out why.
3414 Inside @value{GDBN}, your program may stop for any of several reasons,
3415 such as a signal, a breakpoint, or reaching a new line after a
3416 @value{GDBN} command such as @code{step}. You may then examine and
3417 change variables, set new breakpoints or remove old ones, and then
3418 continue execution. Usually, the messages shown by @value{GDBN} provide
3419 ample explanation of the status of your program---but you can also
3420 explicitly request this information at any time.
3423 @kindex info program
3425 Display information about the status of your program: whether it is
3426 running or not, what process it is, and why it stopped.
3430 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3431 * Continuing and Stepping:: Resuming execution
3432 * Skipping Over Functions and Files::
3433 Skipping over functions and files
3435 * Thread Stops:: Stopping and starting multi-thread programs
3439 @section Breakpoints, Watchpoints, and Catchpoints
3442 A @dfn{breakpoint} makes your program stop whenever a certain point in
3443 the program is reached. For each breakpoint, you can add conditions to
3444 control in finer detail whether your program stops. You can set
3445 breakpoints with the @code{break} command and its variants (@pxref{Set
3446 Breaks, ,Setting Breakpoints}), to specify the place where your program
3447 should stop by line number, function name or exact address in the
3450 On some systems, you can set breakpoints in shared libraries before
3451 the executable is run. There is a minor limitation on HP-UX systems:
3452 you must wait until the executable is run in order to set breakpoints
3453 in shared library routines that are not called directly by the program
3454 (for example, routines that are arguments in a @code{pthread_create}
3458 @cindex data breakpoints
3459 @cindex memory tracing
3460 @cindex breakpoint on memory address
3461 @cindex breakpoint on variable modification
3462 A @dfn{watchpoint} is a special breakpoint that stops your program
3463 when the value of an expression changes. The expression may be a value
3464 of a variable, or it could involve values of one or more variables
3465 combined by operators, such as @samp{a + b}. This is sometimes called
3466 @dfn{data breakpoints}. You must use a different command to set
3467 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3468 from that, you can manage a watchpoint like any other breakpoint: you
3469 enable, disable, and delete both breakpoints and watchpoints using the
3472 You can arrange to have values from your program displayed automatically
3473 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3477 @cindex breakpoint on events
3478 A @dfn{catchpoint} is another special breakpoint that stops your program
3479 when a certain kind of event occurs, such as the throwing of a C@t{++}
3480 exception or the loading of a library. As with watchpoints, you use a
3481 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3482 Catchpoints}), but aside from that, you can manage a catchpoint like any
3483 other breakpoint. (To stop when your program receives a signal, use the
3484 @code{handle} command; see @ref{Signals, ,Signals}.)
3486 @cindex breakpoint numbers
3487 @cindex numbers for breakpoints
3488 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3489 catchpoint when you create it; these numbers are successive integers
3490 starting with one. In many of the commands for controlling various
3491 features of breakpoints you use the breakpoint number to say which
3492 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3493 @dfn{disabled}; if disabled, it has no effect on your program until you
3496 @cindex breakpoint ranges
3497 @cindex ranges of breakpoints
3498 Some @value{GDBN} commands accept a range of breakpoints on which to
3499 operate. A breakpoint range is either a single breakpoint number, like
3500 @samp{5}, or two such numbers, in increasing order, separated by a
3501 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3502 all breakpoints in that range are operated on.
3505 * Set Breaks:: Setting breakpoints
3506 * Set Watchpoints:: Setting watchpoints
3507 * Set Catchpoints:: Setting catchpoints
3508 * Delete Breaks:: Deleting breakpoints
3509 * Disabling:: Disabling breakpoints
3510 * Conditions:: Break conditions
3511 * Break Commands:: Breakpoint command lists
3512 * Dynamic Printf:: Dynamic printf
3513 * Save Breakpoints:: How to save breakpoints in a file
3514 * Static Probe Points:: Listing static probe points
3515 * Error in Breakpoints:: ``Cannot insert breakpoints''
3516 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3520 @subsection Setting Breakpoints
3522 @c FIXME LMB what does GDB do if no code on line of breakpt?
3523 @c consider in particular declaration with/without initialization.
3525 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3528 @kindex b @r{(@code{break})}
3529 @vindex $bpnum@r{, convenience variable}
3530 @cindex latest breakpoint
3531 Breakpoints are set with the @code{break} command (abbreviated
3532 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3533 number of the breakpoint you've set most recently; see @ref{Convenience
3534 Vars,, Convenience Variables}, for a discussion of what you can do with
3535 convenience variables.
3538 @item break @var{location}
3539 Set a breakpoint at the given @var{location}, which can specify a
3540 function name, a line number, or an address of an instruction.
3541 (@xref{Specify Location}, for a list of all the possible ways to
3542 specify a @var{location}.) The breakpoint will stop your program just
3543 before it executes any of the code in the specified @var{location}.
3545 When using source languages that permit overloading of symbols, such as
3546 C@t{++}, a function name may refer to more than one possible place to break.
3547 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3550 It is also possible to insert a breakpoint that will stop the program
3551 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3552 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3555 When called without any arguments, @code{break} sets a breakpoint at
3556 the next instruction to be executed in the selected stack frame
3557 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3558 innermost, this makes your program stop as soon as control
3559 returns to that frame. This is similar to the effect of a
3560 @code{finish} command in the frame inside the selected frame---except
3561 that @code{finish} does not leave an active breakpoint. If you use
3562 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3563 the next time it reaches the current location; this may be useful
3566 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3567 least one instruction has been executed. If it did not do this, you
3568 would be unable to proceed past a breakpoint without first disabling the
3569 breakpoint. This rule applies whether or not the breakpoint already
3570 existed when your program stopped.
3572 @item break @dots{} if @var{cond}
3573 Set a breakpoint with condition @var{cond}; evaluate the expression
3574 @var{cond} each time the breakpoint is reached, and stop only if the
3575 value is nonzero---that is, if @var{cond} evaluates as true.
3576 @samp{@dots{}} stands for one of the possible arguments described
3577 above (or no argument) specifying where to break. @xref{Conditions,
3578 ,Break Conditions}, for more information on breakpoint conditions.
3581 @item tbreak @var{args}
3582 Set a breakpoint enabled only for one stop. The @var{args} are the
3583 same as for the @code{break} command, and the breakpoint is set in the same
3584 way, but the breakpoint is automatically deleted after the first time your
3585 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3588 @cindex hardware breakpoints
3589 @item hbreak @var{args}
3590 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3591 @code{break} command and the breakpoint is set in the same way, but the
3592 breakpoint requires hardware support and some target hardware may not
3593 have this support. The main purpose of this is EPROM/ROM code
3594 debugging, so you can set a breakpoint at an instruction without
3595 changing the instruction. This can be used with the new trap-generation
3596 provided by SPARClite DSU and most x86-based targets. These targets
3597 will generate traps when a program accesses some data or instruction
3598 address that is assigned to the debug registers. However the hardware
3599 breakpoint registers can take a limited number of breakpoints. For
3600 example, on the DSU, only two data breakpoints can be set at a time, and
3601 @value{GDBN} will reject this command if more than two are used. Delete
3602 or disable unused hardware breakpoints before setting new ones
3603 (@pxref{Disabling, ,Disabling Breakpoints}).
3604 @xref{Conditions, ,Break Conditions}.
3605 For remote targets, you can restrict the number of hardware
3606 breakpoints @value{GDBN} will use, see @ref{set remote
3607 hardware-breakpoint-limit}.
3610 @item thbreak @var{args}
3611 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3612 are the same as for the @code{hbreak} command and the breakpoint is set in
3613 the same way. However, like the @code{tbreak} command,
3614 the breakpoint is automatically deleted after the
3615 first time your program stops there. Also, like the @code{hbreak}
3616 command, the breakpoint requires hardware support and some target hardware
3617 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3618 See also @ref{Conditions, ,Break Conditions}.
3621 @cindex regular expression
3622 @cindex breakpoints at functions matching a regexp
3623 @cindex set breakpoints in many functions
3624 @item rbreak @var{regex}
3625 Set breakpoints on all functions matching the regular expression
3626 @var{regex}. This command sets an unconditional breakpoint on all
3627 matches, printing a list of all breakpoints it set. Once these
3628 breakpoints are set, they are treated just like the breakpoints set with
3629 the @code{break} command. You can delete them, disable them, or make
3630 them conditional the same way as any other breakpoint.
3632 The syntax of the regular expression is the standard one used with tools
3633 like @file{grep}. Note that this is different from the syntax used by
3634 shells, so for instance @code{foo*} matches all functions that include
3635 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3636 @code{.*} leading and trailing the regular expression you supply, so to
3637 match only functions that begin with @code{foo}, use @code{^foo}.
3639 @cindex non-member C@t{++} functions, set breakpoint in
3640 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3641 breakpoints on overloaded functions that are not members of any special
3644 @cindex set breakpoints on all functions
3645 The @code{rbreak} command can be used to set breakpoints in
3646 @strong{all} the functions in a program, like this:
3649 (@value{GDBP}) rbreak .
3652 @item rbreak @var{file}:@var{regex}
3653 If @code{rbreak} is called with a filename qualification, it limits
3654 the search for functions matching the given regular expression to the
3655 specified @var{file}. This can be used, for example, to set breakpoints on
3656 every function in a given file:
3659 (@value{GDBP}) rbreak file.c:.
3662 The colon separating the filename qualifier from the regex may
3663 optionally be surrounded by spaces.
3665 @kindex info breakpoints
3666 @cindex @code{$_} and @code{info breakpoints}
3667 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3668 @itemx info break @r{[}@var{n}@dots{}@r{]}
3669 Print a table of all breakpoints, watchpoints, and catchpoints set and
3670 not deleted. Optional argument @var{n} means print information only
3671 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3672 For each breakpoint, following columns are printed:
3675 @item Breakpoint Numbers
3677 Breakpoint, watchpoint, or catchpoint.
3679 Whether the breakpoint is marked to be disabled or deleted when hit.
3680 @item Enabled or Disabled
3681 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3682 that are not enabled.
3684 Where the breakpoint is in your program, as a memory address. For a
3685 pending breakpoint whose address is not yet known, this field will
3686 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3687 library that has the symbol or line referred by breakpoint is loaded.
3688 See below for details. A breakpoint with several locations will
3689 have @samp{<MULTIPLE>} in this field---see below for details.
3691 Where the breakpoint is in the source for your program, as a file and
3692 line number. For a pending breakpoint, the original string passed to
3693 the breakpoint command will be listed as it cannot be resolved until
3694 the appropriate shared library is loaded in the future.
3698 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3699 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3700 @value{GDBN} on the host's side. If it is ``target'', then the condition
3701 is evaluated by the target. The @code{info break} command shows
3702 the condition on the line following the affected breakpoint, together with
3703 its condition evaluation mode in between parentheses.
3705 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3706 allowed to have a condition specified for it. The condition is not parsed for
3707 validity until a shared library is loaded that allows the pending
3708 breakpoint to resolve to a valid location.
3711 @code{info break} with a breakpoint
3712 number @var{n} as argument lists only that breakpoint. The
3713 convenience variable @code{$_} and the default examining-address for
3714 the @code{x} command are set to the address of the last breakpoint
3715 listed (@pxref{Memory, ,Examining Memory}).
3718 @code{info break} displays a count of the number of times the breakpoint
3719 has been hit. This is especially useful in conjunction with the
3720 @code{ignore} command. You can ignore a large number of breakpoint
3721 hits, look at the breakpoint info to see how many times the breakpoint
3722 was hit, and then run again, ignoring one less than that number. This
3723 will get you quickly to the last hit of that breakpoint.
3726 For a breakpoints with an enable count (xref) greater than 1,
3727 @code{info break} also displays that count.
3731 @value{GDBN} allows you to set any number of breakpoints at the same place in
3732 your program. There is nothing silly or meaningless about this. When
3733 the breakpoints are conditional, this is even useful
3734 (@pxref{Conditions, ,Break Conditions}).
3736 @cindex multiple locations, breakpoints
3737 @cindex breakpoints, multiple locations
3738 It is possible that a breakpoint corresponds to several locations
3739 in your program. Examples of this situation are:
3743 Multiple functions in the program may have the same name.
3746 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3747 instances of the function body, used in different cases.
3750 For a C@t{++} template function, a given line in the function can
3751 correspond to any number of instantiations.
3754 For an inlined function, a given source line can correspond to
3755 several places where that function is inlined.
3758 In all those cases, @value{GDBN} will insert a breakpoint at all
3759 the relevant locations.
3761 A breakpoint with multiple locations is displayed in the breakpoint
3762 table using several rows---one header row, followed by one row for
3763 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3764 address column. The rows for individual locations contain the actual
3765 addresses for locations, and show the functions to which those
3766 locations belong. The number column for a location is of the form
3767 @var{breakpoint-number}.@var{location-number}.
3772 Num Type Disp Enb Address What
3773 1 breakpoint keep y <MULTIPLE>
3775 breakpoint already hit 1 time
3776 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3777 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3780 Each location can be individually enabled or disabled by passing
3781 @var{breakpoint-number}.@var{location-number} as argument to the
3782 @code{enable} and @code{disable} commands. Note that you cannot
3783 delete the individual locations from the list, you can only delete the
3784 entire list of locations that belong to their parent breakpoint (with
3785 the @kbd{delete @var{num}} command, where @var{num} is the number of
3786 the parent breakpoint, 1 in the above example). Disabling or enabling
3787 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3788 that belong to that breakpoint.
3790 @cindex pending breakpoints
3791 It's quite common to have a breakpoint inside a shared library.
3792 Shared libraries can be loaded and unloaded explicitly,
3793 and possibly repeatedly, as the program is executed. To support
3794 this use case, @value{GDBN} updates breakpoint locations whenever
3795 any shared library is loaded or unloaded. Typically, you would
3796 set a breakpoint in a shared library at the beginning of your
3797 debugging session, when the library is not loaded, and when the
3798 symbols from the library are not available. When you try to set
3799 breakpoint, @value{GDBN} will ask you if you want to set
3800 a so called @dfn{pending breakpoint}---breakpoint whose address
3801 is not yet resolved.
3803 After the program is run, whenever a new shared library is loaded,
3804 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3805 shared library contains the symbol or line referred to by some
3806 pending breakpoint, that breakpoint is resolved and becomes an
3807 ordinary breakpoint. When a library is unloaded, all breakpoints
3808 that refer to its symbols or source lines become pending again.
3810 This logic works for breakpoints with multiple locations, too. For
3811 example, if you have a breakpoint in a C@t{++} template function, and
3812 a newly loaded shared library has an instantiation of that template,
3813 a new location is added to the list of locations for the breakpoint.
3815 Except for having unresolved address, pending breakpoints do not
3816 differ from regular breakpoints. You can set conditions or commands,
3817 enable and disable them and perform other breakpoint operations.
3819 @value{GDBN} provides some additional commands for controlling what
3820 happens when the @samp{break} command cannot resolve breakpoint
3821 address specification to an address:
3823 @kindex set breakpoint pending
3824 @kindex show breakpoint pending
3826 @item set breakpoint pending auto
3827 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3828 location, it queries you whether a pending breakpoint should be created.
3830 @item set breakpoint pending on
3831 This indicates that an unrecognized breakpoint location should automatically
3832 result in a pending breakpoint being created.
3834 @item set breakpoint pending off
3835 This indicates that pending breakpoints are not to be created. Any
3836 unrecognized breakpoint location results in an error. This setting does
3837 not affect any pending breakpoints previously created.
3839 @item show breakpoint pending
3840 Show the current behavior setting for creating pending breakpoints.
3843 The settings above only affect the @code{break} command and its
3844 variants. Once breakpoint is set, it will be automatically updated
3845 as shared libraries are loaded and unloaded.
3847 @cindex automatic hardware breakpoints
3848 For some targets, @value{GDBN} can automatically decide if hardware or
3849 software breakpoints should be used, depending on whether the
3850 breakpoint address is read-only or read-write. This applies to
3851 breakpoints set with the @code{break} command as well as to internal
3852 breakpoints set by commands like @code{next} and @code{finish}. For
3853 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3856 You can control this automatic behaviour with the following commands::
3858 @kindex set breakpoint auto-hw
3859 @kindex show breakpoint auto-hw
3861 @item set breakpoint auto-hw on
3862 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3863 will try to use the target memory map to decide if software or hardware
3864 breakpoint must be used.
3866 @item set breakpoint auto-hw off
3867 This indicates @value{GDBN} should not automatically select breakpoint
3868 type. If the target provides a memory map, @value{GDBN} will warn when
3869 trying to set software breakpoint at a read-only address.
3872 @value{GDBN} normally implements breakpoints by replacing the program code
3873 at the breakpoint address with a special instruction, which, when
3874 executed, given control to the debugger. By default, the program
3875 code is so modified only when the program is resumed. As soon as
3876 the program stops, @value{GDBN} restores the original instructions. This
3877 behaviour guards against leaving breakpoints inserted in the
3878 target should gdb abrubptly disconnect. However, with slow remote
3879 targets, inserting and removing breakpoint can reduce the performance.
3880 This behavior can be controlled with the following commands::
3882 @kindex set breakpoint always-inserted
3883 @kindex show breakpoint always-inserted
3885 @item set breakpoint always-inserted off
3886 All breakpoints, including newly added by the user, are inserted in
3887 the target only when the target is resumed. All breakpoints are
3888 removed from the target when it stops. This is the default mode.
3890 @item set breakpoint always-inserted on
3891 Causes all breakpoints to be inserted in the target at all times. If
3892 the user adds a new breakpoint, or changes an existing breakpoint, the
3893 breakpoints in the target are updated immediately. A breakpoint is
3894 removed from the target only when breakpoint itself is deleted.
3897 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3898 when a breakpoint breaks. If the condition is true, then the process being
3899 debugged stops, otherwise the process is resumed.
3901 If the target supports evaluating conditions on its end, @value{GDBN} may
3902 download the breakpoint, together with its conditions, to it.
3904 This feature can be controlled via the following commands:
3906 @kindex set breakpoint condition-evaluation
3907 @kindex show breakpoint condition-evaluation
3909 @item set breakpoint condition-evaluation host
3910 This option commands @value{GDBN} to evaluate the breakpoint
3911 conditions on the host's side. Unconditional breakpoints are sent to
3912 the target which in turn receives the triggers and reports them back to GDB
3913 for condition evaluation. This is the standard evaluation mode.
3915 @item set breakpoint condition-evaluation target
3916 This option commands @value{GDBN} to download breakpoint conditions
3917 to the target at the moment of their insertion. The target
3918 is responsible for evaluating the conditional expression and reporting
3919 breakpoint stop events back to @value{GDBN} whenever the condition
3920 is true. Due to limitations of target-side evaluation, some conditions
3921 cannot be evaluated there, e.g., conditions that depend on local data
3922 that is only known to the host. Examples include
3923 conditional expressions involving convenience variables, complex types
3924 that cannot be handled by the agent expression parser and expressions
3925 that are too long to be sent over to the target, specially when the
3926 target is a remote system. In these cases, the conditions will be
3927 evaluated by @value{GDBN}.
3929 @item set breakpoint condition-evaluation auto
3930 This is the default mode. If the target supports evaluating breakpoint
3931 conditions on its end, @value{GDBN} will download breakpoint conditions to
3932 the target (limitations mentioned previously apply). If the target does
3933 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3934 to evaluating all these conditions on the host's side.
3938 @cindex negative breakpoint numbers
3939 @cindex internal @value{GDBN} breakpoints
3940 @value{GDBN} itself sometimes sets breakpoints in your program for
3941 special purposes, such as proper handling of @code{longjmp} (in C
3942 programs). These internal breakpoints are assigned negative numbers,
3943 starting with @code{-1}; @samp{info breakpoints} does not display them.
3944 You can see these breakpoints with the @value{GDBN} maintenance command
3945 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3948 @node Set Watchpoints
3949 @subsection Setting Watchpoints
3951 @cindex setting watchpoints
3952 You can use a watchpoint to stop execution whenever the value of an
3953 expression changes, without having to predict a particular place where
3954 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3955 The expression may be as simple as the value of a single variable, or
3956 as complex as many variables combined by operators. Examples include:
3960 A reference to the value of a single variable.
3963 An address cast to an appropriate data type. For example,
3964 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3965 address (assuming an @code{int} occupies 4 bytes).
3968 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3969 expression can use any operators valid in the program's native
3970 language (@pxref{Languages}).
3973 You can set a watchpoint on an expression even if the expression can
3974 not be evaluated yet. For instance, you can set a watchpoint on
3975 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3976 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3977 the expression produces a valid value. If the expression becomes
3978 valid in some other way than changing a variable (e.g.@: if the memory
3979 pointed to by @samp{*global_ptr} becomes readable as the result of a
3980 @code{malloc} call), @value{GDBN} may not stop until the next time
3981 the expression changes.
3983 @cindex software watchpoints
3984 @cindex hardware watchpoints
3985 Depending on your system, watchpoints may be implemented in software or
3986 hardware. @value{GDBN} does software watchpointing by single-stepping your
3987 program and testing the variable's value each time, which is hundreds of
3988 times slower than normal execution. (But this may still be worth it, to
3989 catch errors where you have no clue what part of your program is the
3992 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3993 x86-based targets, @value{GDBN} includes support for hardware
3994 watchpoints, which do not slow down the running of your program.
3998 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3999 Set a watchpoint for an expression. @value{GDBN} will break when the
4000 expression @var{expr} is written into by the program and its value
4001 changes. The simplest (and the most popular) use of this command is
4002 to watch the value of a single variable:
4005 (@value{GDBP}) watch foo
4008 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4009 argument, @value{GDBN} breaks only when the thread identified by
4010 @var{threadnum} changes the value of @var{expr}. If any other threads
4011 change the value of @var{expr}, @value{GDBN} will not break. Note
4012 that watchpoints restricted to a single thread in this way only work
4013 with Hardware Watchpoints.
4015 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4016 (see below). The @code{-location} argument tells @value{GDBN} to
4017 instead watch the memory referred to by @var{expr}. In this case,
4018 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4019 and watch the memory at that address. The type of the result is used
4020 to determine the size of the watched memory. If the expression's
4021 result does not have an address, then @value{GDBN} will print an
4024 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4025 of masked watchpoints, if the current architecture supports this
4026 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4027 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4028 to an address to watch. The mask specifies that some bits of an address
4029 (the bits which are reset in the mask) should be ignored when matching
4030 the address accessed by the inferior against the watchpoint address.
4031 Thus, a masked watchpoint watches many addresses simultaneously---those
4032 addresses whose unmasked bits are identical to the unmasked bits in the
4033 watchpoint address. The @code{mask} argument implies @code{-location}.
4037 (@value{GDBP}) watch foo mask 0xffff00ff
4038 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4042 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4043 Set a watchpoint that will break when the value of @var{expr} is read
4047 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4048 Set a watchpoint that will break when @var{expr} is either read from
4049 or written into by the program.
4051 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4052 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4053 This command prints a list of watchpoints, using the same format as
4054 @code{info break} (@pxref{Set Breaks}).
4057 If you watch for a change in a numerically entered address you need to
4058 dereference it, as the address itself is just a constant number which will
4059 never change. @value{GDBN} refuses to create a watchpoint that watches
4060 a never-changing value:
4063 (@value{GDBP}) watch 0x600850
4064 Cannot watch constant value 0x600850.
4065 (@value{GDBP}) watch *(int *) 0x600850
4066 Watchpoint 1: *(int *) 6293584
4069 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4070 watchpoints execute very quickly, and the debugger reports a change in
4071 value at the exact instruction where the change occurs. If @value{GDBN}
4072 cannot set a hardware watchpoint, it sets a software watchpoint, which
4073 executes more slowly and reports the change in value at the next
4074 @emph{statement}, not the instruction, after the change occurs.
4076 @cindex use only software watchpoints
4077 You can force @value{GDBN} to use only software watchpoints with the
4078 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4079 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4080 the underlying system supports them. (Note that hardware-assisted
4081 watchpoints that were set @emph{before} setting
4082 @code{can-use-hw-watchpoints} to zero will still use the hardware
4083 mechanism of watching expression values.)
4086 @item set can-use-hw-watchpoints
4087 @kindex set can-use-hw-watchpoints
4088 Set whether or not to use hardware watchpoints.
4090 @item show can-use-hw-watchpoints
4091 @kindex show can-use-hw-watchpoints
4092 Show the current mode of using hardware watchpoints.
4095 For remote targets, you can restrict the number of hardware
4096 watchpoints @value{GDBN} will use, see @ref{set remote
4097 hardware-breakpoint-limit}.
4099 When you issue the @code{watch} command, @value{GDBN} reports
4102 Hardware watchpoint @var{num}: @var{expr}
4106 if it was able to set a hardware watchpoint.
4108 Currently, the @code{awatch} and @code{rwatch} commands can only set
4109 hardware watchpoints, because accesses to data that don't change the
4110 value of the watched expression cannot be detected without examining
4111 every instruction as it is being executed, and @value{GDBN} does not do
4112 that currently. If @value{GDBN} finds that it is unable to set a
4113 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4114 will print a message like this:
4117 Expression cannot be implemented with read/access watchpoint.
4120 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4121 data type of the watched expression is wider than what a hardware
4122 watchpoint on the target machine can handle. For example, some systems
4123 can only watch regions that are up to 4 bytes wide; on such systems you
4124 cannot set hardware watchpoints for an expression that yields a
4125 double-precision floating-point number (which is typically 8 bytes
4126 wide). As a work-around, it might be possible to break the large region
4127 into a series of smaller ones and watch them with separate watchpoints.
4129 If you set too many hardware watchpoints, @value{GDBN} might be unable
4130 to insert all of them when you resume the execution of your program.
4131 Since the precise number of active watchpoints is unknown until such
4132 time as the program is about to be resumed, @value{GDBN} might not be
4133 able to warn you about this when you set the watchpoints, and the
4134 warning will be printed only when the program is resumed:
4137 Hardware watchpoint @var{num}: Could not insert watchpoint
4141 If this happens, delete or disable some of the watchpoints.
4143 Watching complex expressions that reference many variables can also
4144 exhaust the resources available for hardware-assisted watchpoints.
4145 That's because @value{GDBN} needs to watch every variable in the
4146 expression with separately allocated resources.
4148 If you call a function interactively using @code{print} or @code{call},
4149 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4150 kind of breakpoint or the call completes.
4152 @value{GDBN} automatically deletes watchpoints that watch local
4153 (automatic) variables, or expressions that involve such variables, when
4154 they go out of scope, that is, when the execution leaves the block in
4155 which these variables were defined. In particular, when the program
4156 being debugged terminates, @emph{all} local variables go out of scope,
4157 and so only watchpoints that watch global variables remain set. If you
4158 rerun the program, you will need to set all such watchpoints again. One
4159 way of doing that would be to set a code breakpoint at the entry to the
4160 @code{main} function and when it breaks, set all the watchpoints.
4162 @cindex watchpoints and threads
4163 @cindex threads and watchpoints
4164 In multi-threaded programs, watchpoints will detect changes to the
4165 watched expression from every thread.
4168 @emph{Warning:} In multi-threaded programs, software watchpoints
4169 have only limited usefulness. If @value{GDBN} creates a software
4170 watchpoint, it can only watch the value of an expression @emph{in a
4171 single thread}. If you are confident that the expression can only
4172 change due to the current thread's activity (and if you are also
4173 confident that no other thread can become current), then you can use
4174 software watchpoints as usual. However, @value{GDBN} may not notice
4175 when a non-current thread's activity changes the expression. (Hardware
4176 watchpoints, in contrast, watch an expression in all threads.)
4179 @xref{set remote hardware-watchpoint-limit}.
4181 @node Set Catchpoints
4182 @subsection Setting Catchpoints
4183 @cindex catchpoints, setting
4184 @cindex exception handlers
4185 @cindex event handling
4187 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4188 kinds of program events, such as C@t{++} exceptions or the loading of a
4189 shared library. Use the @code{catch} command to set a catchpoint.
4193 @item catch @var{event}
4194 Stop when @var{event} occurs. The @var{event} can be any of the following:
4197 @item throw @r{[}@var{regexp}@r{]}
4198 @itemx rethrow @r{[}@var{regexp}@r{]}
4199 @itemx catch @r{[}@var{regexp}@r{]}
4201 @kindex catch rethrow
4203 @cindex stop on C@t{++} exceptions
4204 The throwing, re-throwing, or catching of a C@t{++} exception.
4206 If @var{regexp} is given, then only exceptions whose type matches the
4207 regular expression will be caught.
4209 @vindex $_exception@r{, convenience variable}
4210 The convenience variable @code{$_exception} is available at an
4211 exception-related catchpoint, on some systems. This holds the
4212 exception being thrown.
4214 There are currently some limitations to C@t{++} exception handling in
4219 The support for these commands is system-dependent. Currently, only
4220 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4224 The regular expression feature and the @code{$_exception} convenience
4225 variable rely on the presence of some SDT probes in @code{libstdc++}.
4226 If these probes are not present, then these features cannot be used.
4227 These probes were first available in the GCC 4.8 release, but whether
4228 or not they are available in your GCC also depends on how it was
4232 The @code{$_exception} convenience variable is only valid at the
4233 instruction at which an exception-related catchpoint is set.
4236 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4237 location in the system library which implements runtime exception
4238 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4239 (@pxref{Selection}) to get to your code.
4242 If you call a function interactively, @value{GDBN} normally returns
4243 control to you when the function has finished executing. If the call
4244 raises an exception, however, the call may bypass the mechanism that
4245 returns control to you and cause your program either to abort or to
4246 simply continue running until it hits a breakpoint, catches a signal
4247 that @value{GDBN} is listening for, or exits. This is the case even if
4248 you set a catchpoint for the exception; catchpoints on exceptions are
4249 disabled within interactive calls. @xref{Calling}, for information on
4250 controlling this with @code{set unwind-on-terminating-exception}.
4253 You cannot raise an exception interactively.
4256 You cannot install an exception handler interactively.
4260 @kindex catch exception
4261 @cindex Ada exception catching
4262 @cindex catch Ada exceptions
4263 An Ada exception being raised. If an exception name is specified
4264 at the end of the command (eg @code{catch exception Program_Error}),
4265 the debugger will stop only when this specific exception is raised.
4266 Otherwise, the debugger stops execution when any Ada exception is raised.
4268 When inserting an exception catchpoint on a user-defined exception whose
4269 name is identical to one of the exceptions defined by the language, the
4270 fully qualified name must be used as the exception name. Otherwise,
4271 @value{GDBN} will assume that it should stop on the pre-defined exception
4272 rather than the user-defined one. For instance, assuming an exception
4273 called @code{Constraint_Error} is defined in package @code{Pck}, then
4274 the command to use to catch such exceptions is @kbd{catch exception
4275 Pck.Constraint_Error}.
4277 @item exception unhandled
4278 @kindex catch exception unhandled
4279 An exception that was raised but is not handled by the program.
4282 @kindex catch assert
4283 A failed Ada assertion.
4287 @cindex break on fork/exec
4288 A call to @code{exec}. This is currently only available for HP-UX
4292 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4293 @kindex catch syscall
4294 @cindex break on a system call.
4295 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4296 syscall is a mechanism for application programs to request a service
4297 from the operating system (OS) or one of the OS system services.
4298 @value{GDBN} can catch some or all of the syscalls issued by the
4299 debuggee, and show the related information for each syscall. If no
4300 argument is specified, calls to and returns from all system calls
4303 @var{name} can be any system call name that is valid for the
4304 underlying OS. Just what syscalls are valid depends on the OS. On
4305 GNU and Unix systems, you can find the full list of valid syscall
4306 names on @file{/usr/include/asm/unistd.h}.
4308 @c For MS-Windows, the syscall names and the corresponding numbers
4309 @c can be found, e.g., on this URL:
4310 @c http://www.metasploit.com/users/opcode/syscalls.html
4311 @c but we don't support Windows syscalls yet.
4313 Normally, @value{GDBN} knows in advance which syscalls are valid for
4314 each OS, so you can use the @value{GDBN} command-line completion
4315 facilities (@pxref{Completion,, command completion}) to list the
4318 You may also specify the system call numerically. A syscall's
4319 number is the value passed to the OS's syscall dispatcher to
4320 identify the requested service. When you specify the syscall by its
4321 name, @value{GDBN} uses its database of syscalls to convert the name
4322 into the corresponding numeric code, but using the number directly
4323 may be useful if @value{GDBN}'s database does not have the complete
4324 list of syscalls on your system (e.g., because @value{GDBN} lags
4325 behind the OS upgrades).
4327 The example below illustrates how this command works if you don't provide
4331 (@value{GDBP}) catch syscall
4332 Catchpoint 1 (syscall)
4334 Starting program: /tmp/catch-syscall
4336 Catchpoint 1 (call to syscall 'close'), \
4337 0xffffe424 in __kernel_vsyscall ()
4341 Catchpoint 1 (returned from syscall 'close'), \
4342 0xffffe424 in __kernel_vsyscall ()
4346 Here is an example of catching a system call by name:
4349 (@value{GDBP}) catch syscall chroot
4350 Catchpoint 1 (syscall 'chroot' [61])
4352 Starting program: /tmp/catch-syscall
4354 Catchpoint 1 (call to syscall 'chroot'), \
4355 0xffffe424 in __kernel_vsyscall ()
4359 Catchpoint 1 (returned from syscall 'chroot'), \
4360 0xffffe424 in __kernel_vsyscall ()
4364 An example of specifying a system call numerically. In the case
4365 below, the syscall number has a corresponding entry in the XML
4366 file, so @value{GDBN} finds its name and prints it:
4369 (@value{GDBP}) catch syscall 252
4370 Catchpoint 1 (syscall(s) 'exit_group')
4372 Starting program: /tmp/catch-syscall
4374 Catchpoint 1 (call to syscall 'exit_group'), \
4375 0xffffe424 in __kernel_vsyscall ()
4379 Program exited normally.
4383 However, there can be situations when there is no corresponding name
4384 in XML file for that syscall number. In this case, @value{GDBN} prints
4385 a warning message saying that it was not able to find the syscall name,
4386 but the catchpoint will be set anyway. See the example below:
4389 (@value{GDBP}) catch syscall 764
4390 warning: The number '764' does not represent a known syscall.
4391 Catchpoint 2 (syscall 764)
4395 If you configure @value{GDBN} using the @samp{--without-expat} option,
4396 it will not be able to display syscall names. Also, if your
4397 architecture does not have an XML file describing its system calls,
4398 you will not be able to see the syscall names. It is important to
4399 notice that these two features are used for accessing the syscall
4400 name database. In either case, you will see a warning like this:
4403 (@value{GDBP}) catch syscall
4404 warning: Could not open "syscalls/i386-linux.xml"
4405 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4406 GDB will not be able to display syscall names.
4407 Catchpoint 1 (syscall)
4411 Of course, the file name will change depending on your architecture and system.
4413 Still using the example above, you can also try to catch a syscall by its
4414 number. In this case, you would see something like:
4417 (@value{GDBP}) catch syscall 252
4418 Catchpoint 1 (syscall(s) 252)
4421 Again, in this case @value{GDBN} would not be able to display syscall's names.
4425 A call to @code{fork}. This is currently only available for HP-UX
4430 A call to @code{vfork}. This is currently only available for HP-UX
4433 @item load @r{[}regexp@r{]}
4434 @itemx unload @r{[}regexp@r{]}
4436 @kindex catch unload
4437 The loading or unloading of a shared library. If @var{regexp} is
4438 given, then the catchpoint will stop only if the regular expression
4439 matches one of the affected libraries.
4441 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4442 @kindex catch signal
4443 The delivery of a signal.
4445 With no arguments, this catchpoint will catch any signal that is not
4446 used internally by @value{GDBN}, specifically, all signals except
4447 @samp{SIGTRAP} and @samp{SIGINT}.
4449 With the argument @samp{all}, all signals, including those used by
4450 @value{GDBN}, will be caught. This argument cannot be used with other
4453 Otherwise, the arguments are a list of signal names as given to
4454 @code{handle} (@pxref{Signals}). Only signals specified in this list
4457 One reason that @code{catch signal} can be more useful than
4458 @code{handle} is that you can attach commands and conditions to the
4461 When a signal is caught by a catchpoint, the signal's @code{stop} and
4462 @code{print} settings, as specified by @code{handle}, are ignored.
4463 However, whether the signal is still delivered to the inferior depends
4464 on the @code{pass} setting; this can be changed in the catchpoint's
4469 @item tcatch @var{event}
4471 Set a catchpoint that is enabled only for one stop. The catchpoint is
4472 automatically deleted after the first time the event is caught.
4476 Use the @code{info break} command to list the current catchpoints.
4480 @subsection Deleting Breakpoints
4482 @cindex clearing breakpoints, watchpoints, catchpoints
4483 @cindex deleting breakpoints, watchpoints, catchpoints
4484 It is often necessary to eliminate a breakpoint, watchpoint, or
4485 catchpoint once it has done its job and you no longer want your program
4486 to stop there. This is called @dfn{deleting} the breakpoint. A
4487 breakpoint that has been deleted no longer exists; it is forgotten.
4489 With the @code{clear} command you can delete breakpoints according to
4490 where they are in your program. With the @code{delete} command you can
4491 delete individual breakpoints, watchpoints, or catchpoints by specifying
4492 their breakpoint numbers.
4494 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4495 automatically ignores breakpoints on the first instruction to be executed
4496 when you continue execution without changing the execution address.
4501 Delete any breakpoints at the next instruction to be executed in the
4502 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4503 the innermost frame is selected, this is a good way to delete a
4504 breakpoint where your program just stopped.
4506 @item clear @var{location}
4507 Delete any breakpoints set at the specified @var{location}.
4508 @xref{Specify Location}, for the various forms of @var{location}; the
4509 most useful ones are listed below:
4512 @item clear @var{function}
4513 @itemx clear @var{filename}:@var{function}
4514 Delete any breakpoints set at entry to the named @var{function}.
4516 @item clear @var{linenum}
4517 @itemx clear @var{filename}:@var{linenum}
4518 Delete any breakpoints set at or within the code of the specified
4519 @var{linenum} of the specified @var{filename}.
4522 @cindex delete breakpoints
4524 @kindex d @r{(@code{delete})}
4525 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4526 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4527 ranges specified as arguments. If no argument is specified, delete all
4528 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4529 confirm off}). You can abbreviate this command as @code{d}.
4533 @subsection Disabling Breakpoints
4535 @cindex enable/disable a breakpoint
4536 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4537 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4538 it had been deleted, but remembers the information on the breakpoint so
4539 that you can @dfn{enable} it again later.
4541 You disable and enable breakpoints, watchpoints, and catchpoints with
4542 the @code{enable} and @code{disable} commands, optionally specifying
4543 one or more breakpoint numbers as arguments. Use @code{info break} to
4544 print a list of all breakpoints, watchpoints, and catchpoints if you
4545 do not know which numbers to use.
4547 Disabling and enabling a breakpoint that has multiple locations
4548 affects all of its locations.
4550 A breakpoint, watchpoint, or catchpoint can have any of several
4551 different states of enablement:
4555 Enabled. The breakpoint stops your program. A breakpoint set
4556 with the @code{break} command starts out in this state.
4558 Disabled. The breakpoint has no effect on your program.
4560 Enabled once. The breakpoint stops your program, but then becomes
4563 Enabled for a count. The breakpoint stops your program for the next
4564 N times, then becomes disabled.
4566 Enabled for deletion. The breakpoint stops your program, but
4567 immediately after it does so it is deleted permanently. A breakpoint
4568 set with the @code{tbreak} command starts out in this state.
4571 You can use the following commands to enable or disable breakpoints,
4572 watchpoints, and catchpoints:
4576 @kindex dis @r{(@code{disable})}
4577 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4578 Disable the specified breakpoints---or all breakpoints, if none are
4579 listed. A disabled breakpoint has no effect but is not forgotten. All
4580 options such as ignore-counts, conditions and commands are remembered in
4581 case the breakpoint is enabled again later. You may abbreviate
4582 @code{disable} as @code{dis}.
4585 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4586 Enable the specified breakpoints (or all defined breakpoints). They
4587 become effective once again in stopping your program.
4589 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4591 of these breakpoints immediately after stopping your program.
4593 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4594 Enable the specified breakpoints temporarily. @value{GDBN} records
4595 @var{count} with each of the specified breakpoints, and decrements a
4596 breakpoint's count when it is hit. When any count reaches 0,
4597 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4598 count (@pxref{Conditions, ,Break Conditions}), that will be
4599 decremented to 0 before @var{count} is affected.
4601 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4602 Enable the specified breakpoints to work once, then die. @value{GDBN}
4603 deletes any of these breakpoints as soon as your program stops there.
4604 Breakpoints set by the @code{tbreak} command start out in this state.
4607 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4608 @c confusing: tbreak is also initially enabled.
4609 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4610 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4611 subsequently, they become disabled or enabled only when you use one of
4612 the commands above. (The command @code{until} can set and delete a
4613 breakpoint of its own, but it does not change the state of your other
4614 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4618 @subsection Break Conditions
4619 @cindex conditional breakpoints
4620 @cindex breakpoint conditions
4622 @c FIXME what is scope of break condition expr? Context where wanted?
4623 @c in particular for a watchpoint?
4624 The simplest sort of breakpoint breaks every time your program reaches a
4625 specified place. You can also specify a @dfn{condition} for a
4626 breakpoint. A condition is just a Boolean expression in your
4627 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4628 a condition evaluates the expression each time your program reaches it,
4629 and your program stops only if the condition is @emph{true}.
4631 This is the converse of using assertions for program validation; in that
4632 situation, you want to stop when the assertion is violated---that is,
4633 when the condition is false. In C, if you want to test an assertion expressed
4634 by the condition @var{assert}, you should set the condition
4635 @samp{! @var{assert}} on the appropriate breakpoint.
4637 Conditions are also accepted for watchpoints; you may not need them,
4638 since a watchpoint is inspecting the value of an expression anyhow---but
4639 it might be simpler, say, to just set a watchpoint on a variable name,
4640 and specify a condition that tests whether the new value is an interesting
4643 Break conditions can have side effects, and may even call functions in
4644 your program. This can be useful, for example, to activate functions
4645 that log program progress, or to use your own print functions to
4646 format special data structures. The effects are completely predictable
4647 unless there is another enabled breakpoint at the same address. (In
4648 that case, @value{GDBN} might see the other breakpoint first and stop your
4649 program without checking the condition of this one.) Note that
4650 breakpoint commands are usually more convenient and flexible than break
4652 purpose of performing side effects when a breakpoint is reached
4653 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4655 Breakpoint conditions can also be evaluated on the target's side if
4656 the target supports it. Instead of evaluating the conditions locally,
4657 @value{GDBN} encodes the expression into an agent expression
4658 (@pxref{Agent Expressions}) suitable for execution on the target,
4659 independently of @value{GDBN}. Global variables become raw memory
4660 locations, locals become stack accesses, and so forth.
4662 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4663 when its condition evaluates to true. This mechanism may provide faster
4664 response times depending on the performance characteristics of the target
4665 since it does not need to keep @value{GDBN} informed about
4666 every breakpoint trigger, even those with false conditions.
4668 Break conditions can be specified when a breakpoint is set, by using
4669 @samp{if} in the arguments to the @code{break} command. @xref{Set
4670 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4671 with the @code{condition} command.
4673 You can also use the @code{if} keyword with the @code{watch} command.
4674 The @code{catch} command does not recognize the @code{if} keyword;
4675 @code{condition} is the only way to impose a further condition on a
4680 @item condition @var{bnum} @var{expression}
4681 Specify @var{expression} as the break condition for breakpoint,
4682 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4683 breakpoint @var{bnum} stops your program only if the value of
4684 @var{expression} is true (nonzero, in C). When you use
4685 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4686 syntactic correctness, and to determine whether symbols in it have
4687 referents in the context of your breakpoint. If @var{expression} uses
4688 symbols not referenced in the context of the breakpoint, @value{GDBN}
4689 prints an error message:
4692 No symbol "foo" in current context.
4697 not actually evaluate @var{expression} at the time the @code{condition}
4698 command (or a command that sets a breakpoint with a condition, like
4699 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4701 @item condition @var{bnum}
4702 Remove the condition from breakpoint number @var{bnum}. It becomes
4703 an ordinary unconditional breakpoint.
4706 @cindex ignore count (of breakpoint)
4707 A special case of a breakpoint condition is to stop only when the
4708 breakpoint has been reached a certain number of times. This is so
4709 useful that there is a special way to do it, using the @dfn{ignore
4710 count} of the breakpoint. Every breakpoint has an ignore count, which
4711 is an integer. Most of the time, the ignore count is zero, and
4712 therefore has no effect. But if your program reaches a breakpoint whose
4713 ignore count is positive, then instead of stopping, it just decrements
4714 the ignore count by one and continues. As a result, if the ignore count
4715 value is @var{n}, the breakpoint does not stop the next @var{n} times
4716 your program reaches it.
4720 @item ignore @var{bnum} @var{count}
4721 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4722 The next @var{count} times the breakpoint is reached, your program's
4723 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4726 To make the breakpoint stop the next time it is reached, specify
4729 When you use @code{continue} to resume execution of your program from a
4730 breakpoint, you can specify an ignore count directly as an argument to
4731 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4732 Stepping,,Continuing and Stepping}.
4734 If a breakpoint has a positive ignore count and a condition, the
4735 condition is not checked. Once the ignore count reaches zero,
4736 @value{GDBN} resumes checking the condition.
4738 You could achieve the effect of the ignore count with a condition such
4739 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4740 is decremented each time. @xref{Convenience Vars, ,Convenience
4744 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4747 @node Break Commands
4748 @subsection Breakpoint Command Lists
4750 @cindex breakpoint commands
4751 You can give any breakpoint (or watchpoint or catchpoint) a series of
4752 commands to execute when your program stops due to that breakpoint. For
4753 example, you might want to print the values of certain expressions, or
4754 enable other breakpoints.
4758 @kindex end@r{ (breakpoint commands)}
4759 @item commands @r{[}@var{range}@dots{}@r{]}
4760 @itemx @dots{} @var{command-list} @dots{}
4762 Specify a list of commands for the given breakpoints. The commands
4763 themselves appear on the following lines. Type a line containing just
4764 @code{end} to terminate the commands.
4766 To remove all commands from a breakpoint, type @code{commands} and
4767 follow it immediately with @code{end}; that is, give no commands.
4769 With no argument, @code{commands} refers to the last breakpoint,
4770 watchpoint, or catchpoint set (not to the breakpoint most recently
4771 encountered). If the most recent breakpoints were set with a single
4772 command, then the @code{commands} will apply to all the breakpoints
4773 set by that command. This applies to breakpoints set by
4774 @code{rbreak}, and also applies when a single @code{break} command
4775 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4779 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4780 disabled within a @var{command-list}.
4782 You can use breakpoint commands to start your program up again. Simply
4783 use the @code{continue} command, or @code{step}, or any other command
4784 that resumes execution.
4786 Any other commands in the command list, after a command that resumes
4787 execution, are ignored. This is because any time you resume execution
4788 (even with a simple @code{next} or @code{step}), you may encounter
4789 another breakpoint---which could have its own command list, leading to
4790 ambiguities about which list to execute.
4793 If the first command you specify in a command list is @code{silent}, the
4794 usual message about stopping at a breakpoint is not printed. This may
4795 be desirable for breakpoints that are to print a specific message and
4796 then continue. If none of the remaining commands print anything, you
4797 see no sign that the breakpoint was reached. @code{silent} is
4798 meaningful only at the beginning of a breakpoint command list.
4800 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4801 print precisely controlled output, and are often useful in silent
4802 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4804 For example, here is how you could use breakpoint commands to print the
4805 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4811 printf "x is %d\n",x
4816 One application for breakpoint commands is to compensate for one bug so
4817 you can test for another. Put a breakpoint just after the erroneous line
4818 of code, give it a condition to detect the case in which something
4819 erroneous has been done, and give it commands to assign correct values
4820 to any variables that need them. End with the @code{continue} command
4821 so that your program does not stop, and start with the @code{silent}
4822 command so that no output is produced. Here is an example:
4833 @node Dynamic Printf
4834 @subsection Dynamic Printf
4836 @cindex dynamic printf
4838 The dynamic printf command @code{dprintf} combines a breakpoint with
4839 formatted printing of your program's data to give you the effect of
4840 inserting @code{printf} calls into your program on-the-fly, without
4841 having to recompile it.
4843 In its most basic form, the output goes to the GDB console. However,
4844 you can set the variable @code{dprintf-style} for alternate handling.
4845 For instance, you can ask to format the output by calling your
4846 program's @code{printf} function. This has the advantage that the
4847 characters go to the program's output device, so they can recorded in
4848 redirects to files and so forth.
4850 If you are doing remote debugging with a stub or agent, you can also
4851 ask to have the printf handled by the remote agent. In addition to
4852 ensuring that the output goes to the remote program's device along
4853 with any other output the program might produce, you can also ask that
4854 the dprintf remain active even after disconnecting from the remote
4855 target. Using the stub/agent is also more efficient, as it can do
4856 everything without needing to communicate with @value{GDBN}.
4860 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4861 Whenever execution reaches @var{location}, print the values of one or
4862 more @var{expressions} under the control of the string @var{template}.
4863 To print several values, separate them with commas.
4865 @item set dprintf-style @var{style}
4866 Set the dprintf output to be handled in one of several different
4867 styles enumerated below. A change of style affects all existing
4868 dynamic printfs immediately. (If you need individual control over the
4869 print commands, simply define normal breakpoints with
4870 explicitly-supplied command lists.)
4873 @kindex dprintf-style gdb
4874 Handle the output using the @value{GDBN} @code{printf} command.
4877 @kindex dprintf-style call
4878 Handle the output by calling a function in your program (normally
4882 @kindex dprintf-style agent
4883 Have the remote debugging agent (such as @code{gdbserver}) handle
4884 the output itself. This style is only available for agents that
4885 support running commands on the target.
4887 @item set dprintf-function @var{function}
4888 Set the function to call if the dprintf style is @code{call}. By
4889 default its value is @code{printf}. You may set it to any expression.
4890 that @value{GDBN} can evaluate to a function, as per the @code{call}
4893 @item set dprintf-channel @var{channel}
4894 Set a ``channel'' for dprintf. If set to a non-empty value,
4895 @value{GDBN} will evaluate it as an expression and pass the result as
4896 a first argument to the @code{dprintf-function}, in the manner of
4897 @code{fprintf} and similar functions. Otherwise, the dprintf format
4898 string will be the first argument, in the manner of @code{printf}.
4900 As an example, if you wanted @code{dprintf} output to go to a logfile
4901 that is a standard I/O stream assigned to the variable @code{mylog},
4902 you could do the following:
4905 (gdb) set dprintf-style call
4906 (gdb) set dprintf-function fprintf
4907 (gdb) set dprintf-channel mylog
4908 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4909 Dprintf 1 at 0x123456: file main.c, line 25.
4911 1 dprintf keep y 0x00123456 in main at main.c:25
4912 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4917 Note that the @code{info break} displays the dynamic printf commands
4918 as normal breakpoint commands; you can thus easily see the effect of
4919 the variable settings.
4921 @item set disconnected-dprintf on
4922 @itemx set disconnected-dprintf off
4923 @kindex set disconnected-dprintf
4924 Choose whether @code{dprintf} commands should continue to run if
4925 @value{GDBN} has disconnected from the target. This only applies
4926 if the @code{dprintf-style} is @code{agent}.
4928 @item show disconnected-dprintf off
4929 @kindex show disconnected-dprintf
4930 Show the current choice for disconnected @code{dprintf}.
4934 @value{GDBN} does not check the validity of function and channel,
4935 relying on you to supply values that are meaningful for the contexts
4936 in which they are being used. For instance, the function and channel
4937 may be the values of local variables, but if that is the case, then
4938 all enabled dynamic prints must be at locations within the scope of
4939 those locals. If evaluation fails, @value{GDBN} will report an error.
4941 @node Save Breakpoints
4942 @subsection How to save breakpoints to a file
4944 To save breakpoint definitions to a file use the @w{@code{save
4945 breakpoints}} command.
4948 @kindex save breakpoints
4949 @cindex save breakpoints to a file for future sessions
4950 @item save breakpoints [@var{filename}]
4951 This command saves all current breakpoint definitions together with
4952 their commands and ignore counts, into a file @file{@var{filename}}
4953 suitable for use in a later debugging session. This includes all
4954 types of breakpoints (breakpoints, watchpoints, catchpoints,
4955 tracepoints). To read the saved breakpoint definitions, use the
4956 @code{source} command (@pxref{Command Files}). Note that watchpoints
4957 with expressions involving local variables may fail to be recreated
4958 because it may not be possible to access the context where the
4959 watchpoint is valid anymore. Because the saved breakpoint definitions
4960 are simply a sequence of @value{GDBN} commands that recreate the
4961 breakpoints, you can edit the file in your favorite editing program,
4962 and remove the breakpoint definitions you're not interested in, or
4963 that can no longer be recreated.
4966 @node Static Probe Points
4967 @subsection Static Probe Points
4969 @cindex static probe point, SystemTap
4970 @cindex static probe point, DTrace
4971 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4972 for Statically Defined Tracing, and the probes are designed to have a tiny
4973 runtime code and data footprint, and no dynamic relocations.
4975 Currently, the following types of probes are supported on
4976 ELF-compatible systems:
4980 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4981 @acronym{SDT} probes@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4983 for more information on how to add @code{SystemTap} @acronym{SDT}
4984 probes in your applications.}. @code{SystemTap} probes are usable
4985 from assembly, C and C@t{++} languages@footnote{See
4986 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4987 for a good reference on how the @acronym{SDT} probes are implemented.}.
4989 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4990 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4994 @cindex semaphores on static probe points
4995 Some @code{SystemTap} probes have an associated semaphore variable;
4996 for instance, this happens automatically if you defined your probe
4997 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4998 @value{GDBN} will automatically enable it when you specify a
4999 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5000 breakpoint at a probe's location by some other method (e.g.,
5001 @code{break file:line}), then @value{GDBN} will not automatically set
5002 the semaphore. @code{DTrace} probes do not support semaphores.
5004 You can examine the available static static probes using @code{info
5005 probes}, with optional arguments:
5009 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5010 If given, @var{type} is either @code{stap} for listing
5011 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5012 probes. If omitted all probes are listed regardless of their types.
5014 If given, @var{provider} is a regular expression used to match against provider
5015 names when selecting which probes to list. If omitted, probes by all
5016 probes from all providers are listed.
5018 If given, @var{name} is a regular expression to match against probe names
5019 when selecting which probes to list. If omitted, probe names are not
5020 considered when deciding whether to display them.
5022 If given, @var{objfile} is a regular expression used to select which
5023 object files (executable or shared libraries) to examine. If not
5024 given, all object files are considered.
5026 @item info probes all
5027 List the available static probes, from all types.
5030 @cindex enabling and disabling probes
5031 Some probe points can be enabled and/or disabled. The effect of
5032 enabling or disabling a probe depends on the type of probe being
5033 handled. Some @code{DTrace} probes can be enabled or
5034 disabled, but @code{SystemTap} probes cannot be disabled.
5036 You can enable (or disable) one or more probes using the following
5037 commands, with optional arguments:
5040 @kindex enable probes
5041 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5042 If given, @var{provider} is a regular expression used to match against
5043 provider names when selecting which probes to enable. If omitted,
5044 all probes from all providers are enabled.
5046 If given, @var{name} is a regular expression to match against probe
5047 names when selecting which probes to enable. If omitted, probe names
5048 are not considered when deciding whether to enable them.
5050 If given, @var{objfile} is a regular expression used to select which
5051 object files (executable or shared libraries) to examine. If not
5052 given, all object files are considered.
5054 @kindex disable probes
5055 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5056 See the @code{enable probes} command above for a description of the
5057 optional arguments accepted by this command.
5060 @vindex $_probe_arg@r{, convenience variable}
5061 A probe may specify up to twelve arguments. These are available at the
5062 point at which the probe is defined---that is, when the current PC is
5063 at the probe's location. The arguments are available using the
5064 convenience variables (@pxref{Convenience Vars})
5065 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5066 probes each probe argument is an integer of the appropriate size;
5067 types are not preserved. In @code{DTrace} probes types are preserved
5068 provided that they are recognized as such by @value{GDBN}; otherwise
5069 the value of the probe argument will be a long integer. The
5070 convenience variable @code{$_probe_argc} holds the number of arguments
5071 at the current probe point.
5073 These variables are always available, but attempts to access them at
5074 any location other than a probe point will cause @value{GDBN} to give
5078 @c @ifclear BARETARGET
5079 @node Error in Breakpoints
5080 @subsection ``Cannot insert breakpoints''
5082 If you request too many active hardware-assisted breakpoints and
5083 watchpoints, you will see this error message:
5085 @c FIXME: the precise wording of this message may change; the relevant
5086 @c source change is not committed yet (Sep 3, 1999).
5088 Stopped; cannot insert breakpoints.
5089 You may have requested too many hardware breakpoints and watchpoints.
5093 This message is printed when you attempt to resume the program, since
5094 only then @value{GDBN} knows exactly how many hardware breakpoints and
5095 watchpoints it needs to insert.
5097 When this message is printed, you need to disable or remove some of the
5098 hardware-assisted breakpoints and watchpoints, and then continue.
5100 @node Breakpoint-related Warnings
5101 @subsection ``Breakpoint address adjusted...''
5102 @cindex breakpoint address adjusted
5104 Some processor architectures place constraints on the addresses at
5105 which breakpoints may be placed. For architectures thus constrained,
5106 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5107 with the constraints dictated by the architecture.
5109 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5110 a VLIW architecture in which a number of RISC-like instructions may be
5111 bundled together for parallel execution. The FR-V architecture
5112 constrains the location of a breakpoint instruction within such a
5113 bundle to the instruction with the lowest address. @value{GDBN}
5114 honors this constraint by adjusting a breakpoint's address to the
5115 first in the bundle.
5117 It is not uncommon for optimized code to have bundles which contain
5118 instructions from different source statements, thus it may happen that
5119 a breakpoint's address will be adjusted from one source statement to
5120 another. Since this adjustment may significantly alter @value{GDBN}'s
5121 breakpoint related behavior from what the user expects, a warning is
5122 printed when the breakpoint is first set and also when the breakpoint
5125 A warning like the one below is printed when setting a breakpoint
5126 that's been subject to address adjustment:
5129 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5132 Such warnings are printed both for user settable and @value{GDBN}'s
5133 internal breakpoints. If you see one of these warnings, you should
5134 verify that a breakpoint set at the adjusted address will have the
5135 desired affect. If not, the breakpoint in question may be removed and
5136 other breakpoints may be set which will have the desired behavior.
5137 E.g., it may be sufficient to place the breakpoint at a later
5138 instruction. A conditional breakpoint may also be useful in some
5139 cases to prevent the breakpoint from triggering too often.
5141 @value{GDBN} will also issue a warning when stopping at one of these
5142 adjusted breakpoints:
5145 warning: Breakpoint 1 address previously adjusted from 0x00010414
5149 When this warning is encountered, it may be too late to take remedial
5150 action except in cases where the breakpoint is hit earlier or more
5151 frequently than expected.
5153 @node Continuing and Stepping
5154 @section Continuing and Stepping
5158 @cindex resuming execution
5159 @dfn{Continuing} means resuming program execution until your program
5160 completes normally. In contrast, @dfn{stepping} means executing just
5161 one more ``step'' of your program, where ``step'' may mean either one
5162 line of source code, or one machine instruction (depending on what
5163 particular command you use). Either when continuing or when stepping,
5164 your program may stop even sooner, due to a breakpoint or a signal. (If
5165 it stops due to a signal, you may want to use @code{handle}, or use
5166 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5167 or you may step into the signal's handler (@pxref{stepping and signal
5172 @kindex c @r{(@code{continue})}
5173 @kindex fg @r{(resume foreground execution)}
5174 @item continue @r{[}@var{ignore-count}@r{]}
5175 @itemx c @r{[}@var{ignore-count}@r{]}
5176 @itemx fg @r{[}@var{ignore-count}@r{]}
5177 Resume program execution, at the address where your program last stopped;
5178 any breakpoints set at that address are bypassed. The optional argument
5179 @var{ignore-count} allows you to specify a further number of times to
5180 ignore a breakpoint at this location; its effect is like that of
5181 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5183 The argument @var{ignore-count} is meaningful only when your program
5184 stopped due to a breakpoint. At other times, the argument to
5185 @code{continue} is ignored.
5187 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5188 debugged program is deemed to be the foreground program) are provided
5189 purely for convenience, and have exactly the same behavior as
5193 To resume execution at a different place, you can use @code{return}
5194 (@pxref{Returning, ,Returning from a Function}) to go back to the
5195 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5196 Different Address}) to go to an arbitrary location in your program.
5198 A typical technique for using stepping is to set a breakpoint
5199 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5200 beginning of the function or the section of your program where a problem
5201 is believed to lie, run your program until it stops at that breakpoint,
5202 and then step through the suspect area, examining the variables that are
5203 interesting, until you see the problem happen.
5207 @kindex s @r{(@code{step})}
5209 Continue running your program until control reaches a different source
5210 line, then stop it and return control to @value{GDBN}. This command is
5211 abbreviated @code{s}.
5214 @c "without debugging information" is imprecise; actually "without line
5215 @c numbers in the debugging information". (gcc -g1 has debugging info but
5216 @c not line numbers). But it seems complex to try to make that
5217 @c distinction here.
5218 @emph{Warning:} If you use the @code{step} command while control is
5219 within a function that was compiled without debugging information,
5220 execution proceeds until control reaches a function that does have
5221 debugging information. Likewise, it will not step into a function which
5222 is compiled without debugging information. To step through functions
5223 without debugging information, use the @code{stepi} command, described
5227 The @code{step} command only stops at the first instruction of a source
5228 line. This prevents the multiple stops that could otherwise occur in
5229 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5230 to stop if a function that has debugging information is called within
5231 the line. In other words, @code{step} @emph{steps inside} any functions
5232 called within the line.
5234 Also, the @code{step} command only enters a function if there is line
5235 number information for the function. Otherwise it acts like the
5236 @code{next} command. This avoids problems when using @code{cc -gl}
5237 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5238 was any debugging information about the routine.
5240 @item step @var{count}
5241 Continue running as in @code{step}, but do so @var{count} times. If a
5242 breakpoint is reached, or a signal not related to stepping occurs before
5243 @var{count} steps, stepping stops right away.
5246 @kindex n @r{(@code{next})}
5247 @item next @r{[}@var{count}@r{]}
5248 Continue to the next source line in the current (innermost) stack frame.
5249 This is similar to @code{step}, but function calls that appear within
5250 the line of code are executed without stopping. Execution stops when
5251 control reaches a different line of code at the original stack level
5252 that was executing when you gave the @code{next} command. This command
5253 is abbreviated @code{n}.
5255 An argument @var{count} is a repeat count, as for @code{step}.
5258 @c FIX ME!! Do we delete this, or is there a way it fits in with
5259 @c the following paragraph? --- Vctoria
5261 @c @code{next} within a function that lacks debugging information acts like
5262 @c @code{step}, but any function calls appearing within the code of the
5263 @c function are executed without stopping.
5265 The @code{next} command only stops at the first instruction of a
5266 source line. This prevents multiple stops that could otherwise occur in
5267 @code{switch} statements, @code{for} loops, etc.
5269 @kindex set step-mode
5271 @cindex functions without line info, and stepping
5272 @cindex stepping into functions with no line info
5273 @itemx set step-mode on
5274 The @code{set step-mode on} command causes the @code{step} command to
5275 stop at the first instruction of a function which contains no debug line
5276 information rather than stepping over it.
5278 This is useful in cases where you may be interested in inspecting the
5279 machine instructions of a function which has no symbolic info and do not
5280 want @value{GDBN} to automatically skip over this function.
5282 @item set step-mode off
5283 Causes the @code{step} command to step over any functions which contains no
5284 debug information. This is the default.
5286 @item show step-mode
5287 Show whether @value{GDBN} will stop in or step over functions without
5288 source line debug information.
5291 @kindex fin @r{(@code{finish})}
5293 Continue running until just after function in the selected stack frame
5294 returns. Print the returned value (if any). This command can be
5295 abbreviated as @code{fin}.
5297 Contrast this with the @code{return} command (@pxref{Returning,
5298 ,Returning from a Function}).
5301 @kindex u @r{(@code{until})}
5302 @cindex run until specified location
5305 Continue running until a source line past the current line, in the
5306 current stack frame, is reached. This command is used to avoid single
5307 stepping through a loop more than once. It is like the @code{next}
5308 command, except that when @code{until} encounters a jump, it
5309 automatically continues execution until the program counter is greater
5310 than the address of the jump.
5312 This means that when you reach the end of a loop after single stepping
5313 though it, @code{until} makes your program continue execution until it
5314 exits the loop. In contrast, a @code{next} command at the end of a loop
5315 simply steps back to the beginning of the loop, which forces you to step
5316 through the next iteration.
5318 @code{until} always stops your program if it attempts to exit the current
5321 @code{until} may produce somewhat counterintuitive results if the order
5322 of machine code does not match the order of the source lines. For
5323 example, in the following excerpt from a debugging session, the @code{f}
5324 (@code{frame}) command shows that execution is stopped at line
5325 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5329 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5331 (@value{GDBP}) until
5332 195 for ( ; argc > 0; NEXTARG) @{
5335 This happened because, for execution efficiency, the compiler had
5336 generated code for the loop closure test at the end, rather than the
5337 start, of the loop---even though the test in a C @code{for}-loop is
5338 written before the body of the loop. The @code{until} command appeared
5339 to step back to the beginning of the loop when it advanced to this
5340 expression; however, it has not really gone to an earlier
5341 statement---not in terms of the actual machine code.
5343 @code{until} with no argument works by means of single
5344 instruction stepping, and hence is slower than @code{until} with an
5347 @item until @var{location}
5348 @itemx u @var{location}
5349 Continue running your program until either the specified @var{location} is
5350 reached, or the current stack frame returns. The location is any of
5351 the forms described in @ref{Specify Location}.
5352 This form of the command uses temporary breakpoints, and
5353 hence is quicker than @code{until} without an argument. The specified
5354 location is actually reached only if it is in the current frame. This
5355 implies that @code{until} can be used to skip over recursive function
5356 invocations. For instance in the code below, if the current location is
5357 line @code{96}, issuing @code{until 99} will execute the program up to
5358 line @code{99} in the same invocation of factorial, i.e., after the inner
5359 invocations have returned.
5362 94 int factorial (int value)
5364 96 if (value > 1) @{
5365 97 value *= factorial (value - 1);
5372 @kindex advance @var{location}
5373 @item advance @var{location}
5374 Continue running the program up to the given @var{location}. An argument is
5375 required, which should be of one of the forms described in
5376 @ref{Specify Location}.
5377 Execution will also stop upon exit from the current stack
5378 frame. This command is similar to @code{until}, but @code{advance} will
5379 not skip over recursive function calls, and the target location doesn't
5380 have to be in the same frame as the current one.
5384 @kindex si @r{(@code{stepi})}
5386 @itemx stepi @var{arg}
5388 Execute one machine instruction, then stop and return to the debugger.
5390 It is often useful to do @samp{display/i $pc} when stepping by machine
5391 instructions. This makes @value{GDBN} automatically display the next
5392 instruction to be executed, each time your program stops. @xref{Auto
5393 Display,, Automatic Display}.
5395 An argument is a repeat count, as in @code{step}.
5399 @kindex ni @r{(@code{nexti})}
5401 @itemx nexti @var{arg}
5403 Execute one machine instruction, but if it is a function call,
5404 proceed until the function returns.
5406 An argument is a repeat count, as in @code{next}.
5410 @anchor{range stepping}
5411 @cindex range stepping
5412 @cindex target-assisted range stepping
5413 By default, and if available, @value{GDBN} makes use of
5414 target-assisted @dfn{range stepping}. In other words, whenever you
5415 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5416 tells the target to step the corresponding range of instruction
5417 addresses instead of issuing multiple single-steps. This speeds up
5418 line stepping, particularly for remote targets. Ideally, there should
5419 be no reason you would want to turn range stepping off. However, it's
5420 possible that a bug in the debug info, a bug in the remote stub (for
5421 remote targets), or even a bug in @value{GDBN} could make line
5422 stepping behave incorrectly when target-assisted range stepping is
5423 enabled. You can use the following command to turn off range stepping
5427 @kindex set range-stepping
5428 @kindex show range-stepping
5429 @item set range-stepping
5430 @itemx show range-stepping
5431 Control whether range stepping is enabled.
5433 If @code{on}, and the target supports it, @value{GDBN} tells the
5434 target to step a range of addresses itself, instead of issuing
5435 multiple single-steps. If @code{off}, @value{GDBN} always issues
5436 single-steps, even if range stepping is supported by the target. The
5437 default is @code{on}.
5441 @node Skipping Over Functions and Files
5442 @section Skipping Over Functions and Files
5443 @cindex skipping over functions and files
5445 The program you are debugging may contain some functions which are
5446 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5447 skip a function or all functions in a file when stepping.
5449 For example, consider the following C function:
5460 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5461 are not interested in stepping through @code{boring}. If you run @code{step}
5462 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5463 step over both @code{foo} and @code{boring}!
5465 One solution is to @code{step} into @code{boring} and use the @code{finish}
5466 command to immediately exit it. But this can become tedious if @code{boring}
5467 is called from many places.
5469 A more flexible solution is to execute @kbd{skip boring}. This instructs
5470 @value{GDBN} never to step into @code{boring}. Now when you execute
5471 @code{step} at line 103, you'll step over @code{boring} and directly into
5474 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5475 example, @code{skip file boring.c}.
5478 @kindex skip function
5479 @item skip @r{[}@var{linespec}@r{]}
5480 @itemx skip function @r{[}@var{linespec}@r{]}
5481 After running this command, the function named by @var{linespec} or the
5482 function containing the line named by @var{linespec} will be skipped over when
5483 stepping. @xref{Specify Location}.
5485 If you do not specify @var{linespec}, the function you're currently debugging
5488 (If you have a function called @code{file} that you want to skip, use
5489 @kbd{skip function file}.)
5492 @item skip file @r{[}@var{filename}@r{]}
5493 After running this command, any function whose source lives in @var{filename}
5494 will be skipped over when stepping.
5496 If you do not specify @var{filename}, functions whose source lives in the file
5497 you're currently debugging will be skipped.
5500 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5501 These are the commands for managing your list of skips:
5505 @item info skip @r{[}@var{range}@r{]}
5506 Print details about the specified skip(s). If @var{range} is not specified,
5507 print a table with details about all functions and files marked for skipping.
5508 @code{info skip} prints the following information about each skip:
5512 A number identifying this skip.
5514 The type of this skip, either @samp{function} or @samp{file}.
5515 @item Enabled or Disabled
5516 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5518 For function skips, this column indicates the address in memory of the function
5519 being skipped. If you've set a function skip on a function which has not yet
5520 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5521 which has the function is loaded, @code{info skip} will show the function's
5524 For file skips, this field contains the filename being skipped. For functions
5525 skips, this field contains the function name and its line number in the file
5526 where it is defined.
5530 @item skip delete @r{[}@var{range}@r{]}
5531 Delete the specified skip(s). If @var{range} is not specified, delete all
5535 @item skip enable @r{[}@var{range}@r{]}
5536 Enable the specified skip(s). If @var{range} is not specified, enable all
5539 @kindex skip disable
5540 @item skip disable @r{[}@var{range}@r{]}
5541 Disable the specified skip(s). If @var{range} is not specified, disable all
5550 A signal is an asynchronous event that can happen in a program. The
5551 operating system defines the possible kinds of signals, and gives each
5552 kind a name and a number. For example, in Unix @code{SIGINT} is the
5553 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5554 @code{SIGSEGV} is the signal a program gets from referencing a place in
5555 memory far away from all the areas in use; @code{SIGALRM} occurs when
5556 the alarm clock timer goes off (which happens only if your program has
5557 requested an alarm).
5559 @cindex fatal signals
5560 Some signals, including @code{SIGALRM}, are a normal part of the
5561 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5562 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5563 program has not specified in advance some other way to handle the signal.
5564 @code{SIGINT} does not indicate an error in your program, but it is normally
5565 fatal so it can carry out the purpose of the interrupt: to kill the program.
5567 @value{GDBN} has the ability to detect any occurrence of a signal in your
5568 program. You can tell @value{GDBN} in advance what to do for each kind of
5571 @cindex handling signals
5572 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5573 @code{SIGALRM} be silently passed to your program
5574 (so as not to interfere with their role in the program's functioning)
5575 but to stop your program immediately whenever an error signal happens.
5576 You can change these settings with the @code{handle} command.
5579 @kindex info signals
5583 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5584 handle each one. You can use this to see the signal numbers of all
5585 the defined types of signals.
5587 @item info signals @var{sig}
5588 Similar, but print information only about the specified signal number.
5590 @code{info handle} is an alias for @code{info signals}.
5592 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5593 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5594 for details about this command.
5597 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5598 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5599 can be the number of a signal or its name (with or without the
5600 @samp{SIG} at the beginning); a list of signal numbers of the form
5601 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5602 known signals. Optional arguments @var{keywords}, described below,
5603 say what change to make.
5607 The keywords allowed by the @code{handle} command can be abbreviated.
5608 Their full names are:
5612 @value{GDBN} should not stop your program when this signal happens. It may
5613 still print a message telling you that the signal has come in.
5616 @value{GDBN} should stop your program when this signal happens. This implies
5617 the @code{print} keyword as well.
5620 @value{GDBN} should print a message when this signal happens.
5623 @value{GDBN} should not mention the occurrence of the signal at all. This
5624 implies the @code{nostop} keyword as well.
5628 @value{GDBN} should allow your program to see this signal; your program
5629 can handle the signal, or else it may terminate if the signal is fatal
5630 and not handled. @code{pass} and @code{noignore} are synonyms.
5634 @value{GDBN} should not allow your program to see this signal.
5635 @code{nopass} and @code{ignore} are synonyms.
5639 When a signal stops your program, the signal is not visible to the
5641 continue. Your program sees the signal then, if @code{pass} is in
5642 effect for the signal in question @emph{at that time}. In other words,
5643 after @value{GDBN} reports a signal, you can use the @code{handle}
5644 command with @code{pass} or @code{nopass} to control whether your
5645 program sees that signal when you continue.
5647 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5648 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5649 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5652 You can also use the @code{signal} command to prevent your program from
5653 seeing a signal, or cause it to see a signal it normally would not see,
5654 or to give it any signal at any time. For example, if your program stopped
5655 due to some sort of memory reference error, you might store correct
5656 values into the erroneous variables and continue, hoping to see more
5657 execution; but your program would probably terminate immediately as
5658 a result of the fatal signal once it saw the signal. To prevent this,
5659 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5662 @cindex stepping and signal handlers
5663 @anchor{stepping and signal handlers}
5665 @value{GDBN} optimizes for stepping the mainline code. If a signal
5666 that has @code{handle nostop} and @code{handle pass} set arrives while
5667 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5668 in progress, @value{GDBN} lets the signal handler run and then resumes
5669 stepping the mainline code once the signal handler returns. In other
5670 words, @value{GDBN} steps over the signal handler. This prevents
5671 signals that you've specified as not interesting (with @code{handle
5672 nostop}) from changing the focus of debugging unexpectedly. Note that
5673 the signal handler itself may still hit a breakpoint, stop for another
5674 signal that has @code{handle stop} in effect, or for any other event
5675 that normally results in stopping the stepping command sooner. Also
5676 note that @value{GDBN} still informs you that the program received a
5677 signal if @code{handle print} is set.
5679 @anchor{stepping into signal handlers}
5681 If you set @code{handle pass} for a signal, and your program sets up a
5682 handler for it, then issuing a stepping command, such as @code{step}
5683 or @code{stepi}, when your program is stopped due to the signal will
5684 step @emph{into} the signal handler (if the target supports that).
5686 Likewise, if you use the @code{queue-signal} command to queue a signal
5687 to be delivered to the current thread when execution of the thread
5688 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5689 stepping command will step into the signal handler.
5691 Here's an example, using @code{stepi} to step to the first instruction
5692 of @code{SIGUSR1}'s handler:
5695 (@value{GDBP}) handle SIGUSR1
5696 Signal Stop Print Pass to program Description
5697 SIGUSR1 Yes Yes Yes User defined signal 1
5701 Program received signal SIGUSR1, User defined signal 1.
5702 main () sigusr1.c:28
5705 sigusr1_handler () at sigusr1.c:9
5709 The same, but using @code{queue-signal} instead of waiting for the
5710 program to receive the signal first:
5715 (@value{GDBP}) queue-signal SIGUSR1
5717 sigusr1_handler () at sigusr1.c:9
5722 @cindex extra signal information
5723 @anchor{extra signal information}
5725 On some targets, @value{GDBN} can inspect extra signal information
5726 associated with the intercepted signal, before it is actually
5727 delivered to the program being debugged. This information is exported
5728 by the convenience variable @code{$_siginfo}, and consists of data
5729 that is passed by the kernel to the signal handler at the time of the
5730 receipt of a signal. The data type of the information itself is
5731 target dependent. You can see the data type using the @code{ptype
5732 $_siginfo} command. On Unix systems, it typically corresponds to the
5733 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5736 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5737 referenced address that raised a segmentation fault.
5741 (@value{GDBP}) continue
5742 Program received signal SIGSEGV, Segmentation fault.
5743 0x0000000000400766 in main ()
5745 (@value{GDBP}) ptype $_siginfo
5752 struct @{...@} _kill;
5753 struct @{...@} _timer;
5755 struct @{...@} _sigchld;
5756 struct @{...@} _sigfault;
5757 struct @{...@} _sigpoll;
5760 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5764 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5765 $1 = (void *) 0x7ffff7ff7000
5769 Depending on target support, @code{$_siginfo} may also be writable.
5772 @section Stopping and Starting Multi-thread Programs
5774 @cindex stopped threads
5775 @cindex threads, stopped
5777 @cindex continuing threads
5778 @cindex threads, continuing
5780 @value{GDBN} supports debugging programs with multiple threads
5781 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5782 are two modes of controlling execution of your program within the
5783 debugger. In the default mode, referred to as @dfn{all-stop mode},
5784 when any thread in your program stops (for example, at a breakpoint
5785 or while being stepped), all other threads in the program are also stopped by
5786 @value{GDBN}. On some targets, @value{GDBN} also supports
5787 @dfn{non-stop mode}, in which other threads can continue to run freely while
5788 you examine the stopped thread in the debugger.
5791 * All-Stop Mode:: All threads stop when GDB takes control
5792 * Non-Stop Mode:: Other threads continue to execute
5793 * Background Execution:: Running your program asynchronously
5794 * Thread-Specific Breakpoints:: Controlling breakpoints
5795 * Interrupted System Calls:: GDB may interfere with system calls
5796 * Observer Mode:: GDB does not alter program behavior
5800 @subsection All-Stop Mode
5802 @cindex all-stop mode
5804 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5805 @emph{all} threads of execution stop, not just the current thread. This
5806 allows you to examine the overall state of the program, including
5807 switching between threads, without worrying that things may change
5810 Conversely, whenever you restart the program, @emph{all} threads start
5811 executing. @emph{This is true even when single-stepping} with commands
5812 like @code{step} or @code{next}.
5814 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5815 Since thread scheduling is up to your debugging target's operating
5816 system (not controlled by @value{GDBN}), other threads may
5817 execute more than one statement while the current thread completes a
5818 single step. Moreover, in general other threads stop in the middle of a
5819 statement, rather than at a clean statement boundary, when the program
5822 You might even find your program stopped in another thread after
5823 continuing or even single-stepping. This happens whenever some other
5824 thread runs into a breakpoint, a signal, or an exception before the
5825 first thread completes whatever you requested.
5827 @cindex automatic thread selection
5828 @cindex switching threads automatically
5829 @cindex threads, automatic switching
5830 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5831 signal, it automatically selects the thread where that breakpoint or
5832 signal happened. @value{GDBN} alerts you to the context switch with a
5833 message such as @samp{[Switching to Thread @var{n}]} to identify the
5836 On some OSes, you can modify @value{GDBN}'s default behavior by
5837 locking the OS scheduler to allow only a single thread to run.
5840 @item set scheduler-locking @var{mode}
5841 @cindex scheduler locking mode
5842 @cindex lock scheduler
5843 Set the scheduler locking mode. If it is @code{off}, then there is no
5844 locking and any thread may run at any time. If @code{on}, then only the
5845 current thread may run when the inferior is resumed. The @code{step}
5846 mode optimizes for single-stepping; it prevents other threads
5847 from preempting the current thread while you are stepping, so that
5848 the focus of debugging does not change unexpectedly.
5849 Other threads never get a chance to run when you step, and they are
5850 completely free to run when you use commands
5851 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5852 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5853 the current thread away from the thread that you are debugging.
5855 @item show scheduler-locking
5856 Display the current scheduler locking mode.
5859 @cindex resume threads of multiple processes simultaneously
5860 By default, when you issue one of the execution commands such as
5861 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5862 threads of the current inferior to run. For example, if @value{GDBN}
5863 is attached to two inferiors, each with two threads, the
5864 @code{continue} command resumes only the two threads of the current
5865 inferior. This is useful, for example, when you debug a program that
5866 forks and you want to hold the parent stopped (so that, for instance,
5867 it doesn't run to exit), while you debug the child. In other
5868 situations, you may not be interested in inspecting the current state
5869 of any of the processes @value{GDBN} is attached to, and you may want
5870 to resume them all until some breakpoint is hit. In the latter case,
5871 you can instruct @value{GDBN} to allow all threads of all the
5872 inferiors to run with the @w{@code{set schedule-multiple}} command.
5875 @kindex set schedule-multiple
5876 @item set schedule-multiple
5877 Set the mode for allowing threads of multiple processes to be resumed
5878 when an execution command is issued. When @code{on}, all threads of
5879 all processes are allowed to run. When @code{off}, only the threads
5880 of the current process are resumed. The default is @code{off}. The
5881 @code{scheduler-locking} mode takes precedence when set to @code{on},
5882 or while you are stepping and set to @code{step}.
5884 @item show schedule-multiple
5885 Display the current mode for resuming the execution of threads of
5890 @subsection Non-Stop Mode
5892 @cindex non-stop mode
5894 @c This section is really only a place-holder, and needs to be expanded
5895 @c with more details.
5897 For some multi-threaded targets, @value{GDBN} supports an optional
5898 mode of operation in which you can examine stopped program threads in
5899 the debugger while other threads continue to execute freely. This
5900 minimizes intrusion when debugging live systems, such as programs
5901 where some threads have real-time constraints or must continue to
5902 respond to external events. This is referred to as @dfn{non-stop} mode.
5904 In non-stop mode, when a thread stops to report a debugging event,
5905 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5906 threads as well, in contrast to the all-stop mode behavior. Additionally,
5907 execution commands such as @code{continue} and @code{step} apply by default
5908 only to the current thread in non-stop mode, rather than all threads as
5909 in all-stop mode. This allows you to control threads explicitly in
5910 ways that are not possible in all-stop mode --- for example, stepping
5911 one thread while allowing others to run freely, stepping
5912 one thread while holding all others stopped, or stepping several threads
5913 independently and simultaneously.
5915 To enter non-stop mode, use this sequence of commands before you run
5916 or attach to your program:
5919 # If using the CLI, pagination breaks non-stop.
5922 # Finally, turn it on!
5926 You can use these commands to manipulate the non-stop mode setting:
5929 @kindex set non-stop
5930 @item set non-stop on
5931 Enable selection of non-stop mode.
5932 @item set non-stop off
5933 Disable selection of non-stop mode.
5934 @kindex show non-stop
5936 Show the current non-stop enablement setting.
5939 Note these commands only reflect whether non-stop mode is enabled,
5940 not whether the currently-executing program is being run in non-stop mode.
5941 In particular, the @code{set non-stop} preference is only consulted when
5942 @value{GDBN} starts or connects to the target program, and it is generally
5943 not possible to switch modes once debugging has started. Furthermore,
5944 since not all targets support non-stop mode, even when you have enabled
5945 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5948 In non-stop mode, all execution commands apply only to the current thread
5949 by default. That is, @code{continue} only continues one thread.
5950 To continue all threads, issue @code{continue -a} or @code{c -a}.
5952 You can use @value{GDBN}'s background execution commands
5953 (@pxref{Background Execution}) to run some threads in the background
5954 while you continue to examine or step others from @value{GDBN}.
5955 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5956 always executed asynchronously in non-stop mode.
5958 Suspending execution is done with the @code{interrupt} command when
5959 running in the background, or @kbd{Ctrl-c} during foreground execution.
5960 In all-stop mode, this stops the whole process;
5961 but in non-stop mode the interrupt applies only to the current thread.
5962 To stop the whole program, use @code{interrupt -a}.
5964 Other execution commands do not currently support the @code{-a} option.
5966 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5967 that thread current, as it does in all-stop mode. This is because the
5968 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5969 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5970 changed to a different thread just as you entered a command to operate on the
5971 previously current thread.
5973 @node Background Execution
5974 @subsection Background Execution
5976 @cindex foreground execution
5977 @cindex background execution
5978 @cindex asynchronous execution
5979 @cindex execution, foreground, background and asynchronous
5981 @value{GDBN}'s execution commands have two variants: the normal
5982 foreground (synchronous) behavior, and a background
5983 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5984 the program to report that some thread has stopped before prompting for
5985 another command. In background execution, @value{GDBN} immediately gives
5986 a command prompt so that you can issue other commands while your program runs.
5988 If the target doesn't support async mode, @value{GDBN} issues an error
5989 message if you attempt to use the background execution commands.
5991 To specify background execution, add a @code{&} to the command. For example,
5992 the background form of the @code{continue} command is @code{continue&}, or
5993 just @code{c&}. The execution commands that accept background execution
5999 @xref{Starting, , Starting your Program}.
6003 @xref{Attach, , Debugging an Already-running Process}.
6007 @xref{Continuing and Stepping, step}.
6011 @xref{Continuing and Stepping, stepi}.
6015 @xref{Continuing and Stepping, next}.
6019 @xref{Continuing and Stepping, nexti}.
6023 @xref{Continuing and Stepping, continue}.
6027 @xref{Continuing and Stepping, finish}.
6031 @xref{Continuing and Stepping, until}.
6035 Background execution is especially useful in conjunction with non-stop
6036 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6037 However, you can also use these commands in the normal all-stop mode with
6038 the restriction that you cannot issue another execution command until the
6039 previous one finishes. Examples of commands that are valid in all-stop
6040 mode while the program is running include @code{help} and @code{info break}.
6042 You can interrupt your program while it is running in the background by
6043 using the @code{interrupt} command.
6050 Suspend execution of the running program. In all-stop mode,
6051 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6052 only the current thread. To stop the whole program in non-stop mode,
6053 use @code{interrupt -a}.
6056 @node Thread-Specific Breakpoints
6057 @subsection Thread-Specific Breakpoints
6059 When your program has multiple threads (@pxref{Threads,, Debugging
6060 Programs with Multiple Threads}), you can choose whether to set
6061 breakpoints on all threads, or on a particular thread.
6064 @cindex breakpoints and threads
6065 @cindex thread breakpoints
6066 @kindex break @dots{} thread @var{threadno}
6067 @item break @var{linespec} thread @var{threadno}
6068 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6069 @var{linespec} specifies source lines; there are several ways of
6070 writing them (@pxref{Specify Location}), but the effect is always to
6071 specify some source line.
6073 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6074 to specify that you only want @value{GDBN} to stop the program when a
6075 particular thread reaches this breakpoint. The @var{threadno} specifier
6076 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6077 in the first column of the @samp{info threads} display.
6079 If you do not specify @samp{thread @var{threadno}} when you set a
6080 breakpoint, the breakpoint applies to @emph{all} threads of your
6083 You can use the @code{thread} qualifier on conditional breakpoints as
6084 well; in this case, place @samp{thread @var{threadno}} before or
6085 after the breakpoint condition, like this:
6088 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6093 Thread-specific breakpoints are automatically deleted when
6094 @value{GDBN} detects the corresponding thread is no longer in the
6095 thread list. For example:
6099 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6102 There are several ways for a thread to disappear, such as a regular
6103 thread exit, but also when you detach from the process with the
6104 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6105 Process}), or if @value{GDBN} loses the remote connection
6106 (@pxref{Remote Debugging}), etc. Note that with some targets,
6107 @value{GDBN} is only able to detect a thread has exited when the user
6108 explictly asks for the thread list with the @code{info threads}
6111 @node Interrupted System Calls
6112 @subsection Interrupted System Calls
6114 @cindex thread breakpoints and system calls
6115 @cindex system calls and thread breakpoints
6116 @cindex premature return from system calls
6117 There is an unfortunate side effect when using @value{GDBN} to debug
6118 multi-threaded programs. If one thread stops for a
6119 breakpoint, or for some other reason, and another thread is blocked in a
6120 system call, then the system call may return prematurely. This is a
6121 consequence of the interaction between multiple threads and the signals
6122 that @value{GDBN} uses to implement breakpoints and other events that
6125 To handle this problem, your program should check the return value of
6126 each system call and react appropriately. This is good programming
6129 For example, do not write code like this:
6135 The call to @code{sleep} will return early if a different thread stops
6136 at a breakpoint or for some other reason.
6138 Instead, write this:
6143 unslept = sleep (unslept);
6146 A system call is allowed to return early, so the system is still
6147 conforming to its specification. But @value{GDBN} does cause your
6148 multi-threaded program to behave differently than it would without
6151 Also, @value{GDBN} uses internal breakpoints in the thread library to
6152 monitor certain events such as thread creation and thread destruction.
6153 When such an event happens, a system call in another thread may return
6154 prematurely, even though your program does not appear to stop.
6157 @subsection Observer Mode
6159 If you want to build on non-stop mode and observe program behavior
6160 without any chance of disruption by @value{GDBN}, you can set
6161 variables to disable all of the debugger's attempts to modify state,
6162 whether by writing memory, inserting breakpoints, etc. These operate
6163 at a low level, intercepting operations from all commands.
6165 When all of these are set to @code{off}, then @value{GDBN} is said to
6166 be @dfn{observer mode}. As a convenience, the variable
6167 @code{observer} can be set to disable these, plus enable non-stop
6170 Note that @value{GDBN} will not prevent you from making nonsensical
6171 combinations of these settings. For instance, if you have enabled
6172 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6173 then breakpoints that work by writing trap instructions into the code
6174 stream will still not be able to be placed.
6179 @item set observer on
6180 @itemx set observer off
6181 When set to @code{on}, this disables all the permission variables
6182 below (except for @code{insert-fast-tracepoints}), plus enables
6183 non-stop debugging. Setting this to @code{off} switches back to
6184 normal debugging, though remaining in non-stop mode.
6187 Show whether observer mode is on or off.
6189 @kindex may-write-registers
6190 @item set may-write-registers on
6191 @itemx set may-write-registers off
6192 This controls whether @value{GDBN} will attempt to alter the values of
6193 registers, such as with assignment expressions in @code{print}, or the
6194 @code{jump} command. It defaults to @code{on}.
6196 @item show may-write-registers
6197 Show the current permission to write registers.
6199 @kindex may-write-memory
6200 @item set may-write-memory on
6201 @itemx set may-write-memory off
6202 This controls whether @value{GDBN} will attempt to alter the contents
6203 of memory, such as with assignment expressions in @code{print}. It
6204 defaults to @code{on}.
6206 @item show may-write-memory
6207 Show the current permission to write memory.
6209 @kindex may-insert-breakpoints
6210 @item set may-insert-breakpoints on
6211 @itemx set may-insert-breakpoints off
6212 This controls whether @value{GDBN} will attempt to insert breakpoints.
6213 This affects all breakpoints, including internal breakpoints defined
6214 by @value{GDBN}. It defaults to @code{on}.
6216 @item show may-insert-breakpoints
6217 Show the current permission to insert breakpoints.
6219 @kindex may-insert-tracepoints
6220 @item set may-insert-tracepoints on
6221 @itemx set may-insert-tracepoints off
6222 This controls whether @value{GDBN} will attempt to insert (regular)
6223 tracepoints at the beginning of a tracing experiment. It affects only
6224 non-fast tracepoints, fast tracepoints being under the control of
6225 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6227 @item show may-insert-tracepoints
6228 Show the current permission to insert tracepoints.
6230 @kindex may-insert-fast-tracepoints
6231 @item set may-insert-fast-tracepoints on
6232 @itemx set may-insert-fast-tracepoints off
6233 This controls whether @value{GDBN} will attempt to insert fast
6234 tracepoints at the beginning of a tracing experiment. It affects only
6235 fast tracepoints, regular (non-fast) tracepoints being under the
6236 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6238 @item show may-insert-fast-tracepoints
6239 Show the current permission to insert fast tracepoints.
6241 @kindex may-interrupt
6242 @item set may-interrupt on
6243 @itemx set may-interrupt off
6244 This controls whether @value{GDBN} will attempt to interrupt or stop
6245 program execution. When this variable is @code{off}, the
6246 @code{interrupt} command will have no effect, nor will
6247 @kbd{Ctrl-c}. It defaults to @code{on}.
6249 @item show may-interrupt
6250 Show the current permission to interrupt or stop the program.
6254 @node Reverse Execution
6255 @chapter Running programs backward
6256 @cindex reverse execution
6257 @cindex running programs backward
6259 When you are debugging a program, it is not unusual to realize that
6260 you have gone too far, and some event of interest has already happened.
6261 If the target environment supports it, @value{GDBN} can allow you to
6262 ``rewind'' the program by running it backward.
6264 A target environment that supports reverse execution should be able
6265 to ``undo'' the changes in machine state that have taken place as the
6266 program was executing normally. Variables, registers etc.@: should
6267 revert to their previous values. Obviously this requires a great
6268 deal of sophistication on the part of the target environment; not
6269 all target environments can support reverse execution.
6271 When a program is executed in reverse, the instructions that
6272 have most recently been executed are ``un-executed'', in reverse
6273 order. The program counter runs backward, following the previous
6274 thread of execution in reverse. As each instruction is ``un-executed'',
6275 the values of memory and/or registers that were changed by that
6276 instruction are reverted to their previous states. After executing
6277 a piece of source code in reverse, all side effects of that code
6278 should be ``undone'', and all variables should be returned to their
6279 prior values@footnote{
6280 Note that some side effects are easier to undo than others. For instance,
6281 memory and registers are relatively easy, but device I/O is hard. Some
6282 targets may be able undo things like device I/O, and some may not.
6284 The contract between @value{GDBN} and the reverse executing target
6285 requires only that the target do something reasonable when
6286 @value{GDBN} tells it to execute backwards, and then report the
6287 results back to @value{GDBN}. Whatever the target reports back to
6288 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6289 assumes that the memory and registers that the target reports are in a
6290 consistant state, but @value{GDBN} accepts whatever it is given.
6293 If you are debugging in a target environment that supports
6294 reverse execution, @value{GDBN} provides the following commands.
6297 @kindex reverse-continue
6298 @kindex rc @r{(@code{reverse-continue})}
6299 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6300 @itemx rc @r{[}@var{ignore-count}@r{]}
6301 Beginning at the point where your program last stopped, start executing
6302 in reverse. Reverse execution will stop for breakpoints and synchronous
6303 exceptions (signals), just like normal execution. Behavior of
6304 asynchronous signals depends on the target environment.
6306 @kindex reverse-step
6307 @kindex rs @r{(@code{step})}
6308 @item reverse-step @r{[}@var{count}@r{]}
6309 Run the program backward until control reaches the start of a
6310 different source line; then stop it, and return control to @value{GDBN}.
6312 Like the @code{step} command, @code{reverse-step} will only stop
6313 at the beginning of a source line. It ``un-executes'' the previously
6314 executed source line. If the previous source line included calls to
6315 debuggable functions, @code{reverse-step} will step (backward) into
6316 the called function, stopping at the beginning of the @emph{last}
6317 statement in the called function (typically a return statement).
6319 Also, as with the @code{step} command, if non-debuggable functions are
6320 called, @code{reverse-step} will run thru them backward without stopping.
6322 @kindex reverse-stepi
6323 @kindex rsi @r{(@code{reverse-stepi})}
6324 @item reverse-stepi @r{[}@var{count}@r{]}
6325 Reverse-execute one machine instruction. Note that the instruction
6326 to be reverse-executed is @emph{not} the one pointed to by the program
6327 counter, but the instruction executed prior to that one. For instance,
6328 if the last instruction was a jump, @code{reverse-stepi} will take you
6329 back from the destination of the jump to the jump instruction itself.
6331 @kindex reverse-next
6332 @kindex rn @r{(@code{reverse-next})}
6333 @item reverse-next @r{[}@var{count}@r{]}
6334 Run backward to the beginning of the previous line executed in
6335 the current (innermost) stack frame. If the line contains function
6336 calls, they will be ``un-executed'' without stopping. Starting from
6337 the first line of a function, @code{reverse-next} will take you back
6338 to the caller of that function, @emph{before} the function was called,
6339 just as the normal @code{next} command would take you from the last
6340 line of a function back to its return to its caller
6341 @footnote{Unless the code is too heavily optimized.}.
6343 @kindex reverse-nexti
6344 @kindex rni @r{(@code{reverse-nexti})}
6345 @item reverse-nexti @r{[}@var{count}@r{]}
6346 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6347 in reverse, except that called functions are ``un-executed'' atomically.
6348 That is, if the previously executed instruction was a return from
6349 another function, @code{reverse-nexti} will continue to execute
6350 in reverse until the call to that function (from the current stack
6353 @kindex reverse-finish
6354 @item reverse-finish
6355 Just as the @code{finish} command takes you to the point where the
6356 current function returns, @code{reverse-finish} takes you to the point
6357 where it was called. Instead of ending up at the end of the current
6358 function invocation, you end up at the beginning.
6360 @kindex set exec-direction
6361 @item set exec-direction
6362 Set the direction of target execution.
6363 @item set exec-direction reverse
6364 @cindex execute forward or backward in time
6365 @value{GDBN} will perform all execution commands in reverse, until the
6366 exec-direction mode is changed to ``forward''. Affected commands include
6367 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6368 command cannot be used in reverse mode.
6369 @item set exec-direction forward
6370 @value{GDBN} will perform all execution commands in the normal fashion.
6371 This is the default.
6375 @node Process Record and Replay
6376 @chapter Recording Inferior's Execution and Replaying It
6377 @cindex process record and replay
6378 @cindex recording inferior's execution and replaying it
6380 On some platforms, @value{GDBN} provides a special @dfn{process record
6381 and replay} target that can record a log of the process execution, and
6382 replay it later with both forward and reverse execution commands.
6385 When this target is in use, if the execution log includes the record
6386 for the next instruction, @value{GDBN} will debug in @dfn{replay
6387 mode}. In the replay mode, the inferior does not really execute code
6388 instructions. Instead, all the events that normally happen during
6389 code execution are taken from the execution log. While code is not
6390 really executed in replay mode, the values of registers (including the
6391 program counter register) and the memory of the inferior are still
6392 changed as they normally would. Their contents are taken from the
6396 If the record for the next instruction is not in the execution log,
6397 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6398 inferior executes normally, and @value{GDBN} records the execution log
6401 The process record and replay target supports reverse execution
6402 (@pxref{Reverse Execution}), even if the platform on which the
6403 inferior runs does not. However, the reverse execution is limited in
6404 this case by the range of the instructions recorded in the execution
6405 log. In other words, reverse execution on platforms that don't
6406 support it directly can only be done in the replay mode.
6408 When debugging in the reverse direction, @value{GDBN} will work in
6409 replay mode as long as the execution log includes the record for the
6410 previous instruction; otherwise, it will work in record mode, if the
6411 platform supports reverse execution, or stop if not.
6413 For architecture environments that support process record and replay,
6414 @value{GDBN} provides the following commands:
6417 @kindex target record
6418 @kindex target record-full
6419 @kindex target record-btrace
6422 @kindex record btrace
6423 @kindex record btrace bts
6428 @kindex rec btrace bts
6430 @item record @var{method}
6431 This command starts the process record and replay target. The
6432 recording method can be specified as parameter. Without a parameter
6433 the command uses the @code{full} recording method. The following
6434 recording methods are available:
6438 Full record/replay recording using @value{GDBN}'s software record and
6439 replay implementation. This method allows replaying and reverse
6442 @item btrace @var{format}
6443 Hardware-supported instruction recording. This method does not record
6444 data. Further, the data is collected in a ring buffer so old data will
6445 be overwritten when the buffer is full. It allows limited replay and
6448 The recording format can be specified as parameter. Without a parameter
6449 the command chooses the recording format. The following recording
6450 formats are available:
6454 @cindex branch trace store
6455 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6456 this format, the processor stores a from/to record for each executed
6457 branch in the btrace ring buffer.
6460 Not all recording formats may be available on all processors.
6463 The process record and replay target can only debug a process that is
6464 already running. Therefore, you need first to start the process with
6465 the @kbd{run} or @kbd{start} commands, and then start the recording
6466 with the @kbd{record @var{method}} command.
6468 Both @code{record @var{method}} and @code{rec @var{method}} are
6469 aliases of @code{target record-@var{method}}.
6471 @cindex displaced stepping, and process record and replay
6472 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6473 will be automatically disabled when process record and replay target
6474 is started. That's because the process record and replay target
6475 doesn't support displaced stepping.
6477 @cindex non-stop mode, and process record and replay
6478 @cindex asynchronous execution, and process record and replay
6479 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6480 the asynchronous execution mode (@pxref{Background Execution}), not
6481 all recording methods are available. The @code{full} recording method
6482 does not support these two modes.
6487 Stop the process record and replay target. When process record and
6488 replay target stops, the entire execution log will be deleted and the
6489 inferior will either be terminated, or will remain in its final state.
6491 When you stop the process record and replay target in record mode (at
6492 the end of the execution log), the inferior will be stopped at the
6493 next instruction that would have been recorded. In other words, if
6494 you record for a while and then stop recording, the inferior process
6495 will be left in the same state as if the recording never happened.
6497 On the other hand, if the process record and replay target is stopped
6498 while in replay mode (that is, not at the end of the execution log,
6499 but at some earlier point), the inferior process will become ``live''
6500 at that earlier state, and it will then be possible to continue the
6501 usual ``live'' debugging of the process from that state.
6503 When the inferior process exits, or @value{GDBN} detaches from it,
6504 process record and replay target will automatically stop itself.
6508 Go to a specific location in the execution log. There are several
6509 ways to specify the location to go to:
6512 @item record goto begin
6513 @itemx record goto start
6514 Go to the beginning of the execution log.
6516 @item record goto end
6517 Go to the end of the execution log.
6519 @item record goto @var{n}
6520 Go to instruction number @var{n} in the execution log.
6524 @item record save @var{filename}
6525 Save the execution log to a file @file{@var{filename}}.
6526 Default filename is @file{gdb_record.@var{process_id}}, where
6527 @var{process_id} is the process ID of the inferior.
6529 This command may not be available for all recording methods.
6531 @kindex record restore
6532 @item record restore @var{filename}
6533 Restore the execution log from a file @file{@var{filename}}.
6534 File must have been created with @code{record save}.
6536 @kindex set record full
6537 @item set record full insn-number-max @var{limit}
6538 @itemx set record full insn-number-max unlimited
6539 Set the limit of instructions to be recorded for the @code{full}
6540 recording method. Default value is 200000.
6542 If @var{limit} is a positive number, then @value{GDBN} will start
6543 deleting instructions from the log once the number of the record
6544 instructions becomes greater than @var{limit}. For every new recorded
6545 instruction, @value{GDBN} will delete the earliest recorded
6546 instruction to keep the number of recorded instructions at the limit.
6547 (Since deleting recorded instructions loses information, @value{GDBN}
6548 lets you control what happens when the limit is reached, by means of
6549 the @code{stop-at-limit} option, described below.)
6551 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6552 delete recorded instructions from the execution log. The number of
6553 recorded instructions is limited only by the available memory.
6555 @kindex show record full
6556 @item show record full insn-number-max
6557 Show the limit of instructions to be recorded with the @code{full}
6560 @item set record full stop-at-limit
6561 Control the behavior of the @code{full} recording method when the
6562 number of recorded instructions reaches the limit. If ON (the
6563 default), @value{GDBN} will stop when the limit is reached for the
6564 first time and ask you whether you want to stop the inferior or
6565 continue running it and recording the execution log. If you decide
6566 to continue recording, each new recorded instruction will cause the
6567 oldest one to be deleted.
6569 If this option is OFF, @value{GDBN} will automatically delete the
6570 oldest record to make room for each new one, without asking.
6572 @item show record full stop-at-limit
6573 Show the current setting of @code{stop-at-limit}.
6575 @item set record full memory-query
6576 Control the behavior when @value{GDBN} is unable to record memory
6577 changes caused by an instruction for the @code{full} recording method.
6578 If ON, @value{GDBN} will query whether to stop the inferior in that
6581 If this option is OFF (the default), @value{GDBN} will automatically
6582 ignore the effect of such instructions on memory. Later, when
6583 @value{GDBN} replays this execution log, it will mark the log of this
6584 instruction as not accessible, and it will not affect the replay
6587 @item show record full memory-query
6588 Show the current setting of @code{memory-query}.
6590 @kindex set record btrace
6591 The @code{btrace} record target does not trace data. As a
6592 convenience, when replaying, @value{GDBN} reads read-only memory off
6593 the live program directly, assuming that the addresses of the
6594 read-only areas don't change. This for example makes it possible to
6595 disassemble code while replaying, but not to print variables.
6596 In some cases, being able to inspect variables might be useful.
6597 You can use the following command for that:
6599 @item set record btrace replay-memory-access
6600 Control the behavior of the @code{btrace} recording method when
6601 accessing memory during replay. If @code{read-only} (the default),
6602 @value{GDBN} will only allow accesses to read-only memory.
6603 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6604 and to read-write memory. Beware that the accessed memory corresponds
6605 to the live target and not necessarily to the current replay
6608 @kindex show record btrace
6609 @item show record btrace replay-memory-access
6610 Show the current setting of @code{replay-memory-access}.
6612 @kindex set record btrace bts
6613 @item set record btrace bts buffer-size @var{size}
6614 @itemx set record btrace bts buffer-size unlimited
6615 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6616 format. Default is 64KB.
6618 If @var{size} is a positive number, then @value{GDBN} will try to
6619 allocate a buffer of at least @var{size} bytes for each new thread
6620 that uses the btrace recording method and the @acronym{BTS} format.
6621 The actually obtained buffer size may differ from the requested
6622 @var{size}. Use the @code{info record} command to see the actual
6623 buffer size for each thread that uses the btrace recording method and
6624 the @acronym{BTS} format.
6626 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6627 allocate a buffer of 4MB.
6629 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6630 also need longer to process the branch trace data before it can be used.
6632 @item show record btrace bts buffer-size @var{size}
6633 Show the current setting of the requested ring buffer size for branch
6634 tracing in @acronym{BTS} format.
6638 Show various statistics about the recording depending on the recording
6643 For the @code{full} recording method, it shows the state of process
6644 record and its in-memory execution log buffer, including:
6648 Whether in record mode or replay mode.
6650 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6652 Highest recorded instruction number.
6654 Current instruction about to be replayed (if in replay mode).
6656 Number of instructions contained in the execution log.
6658 Maximum number of instructions that may be contained in the execution log.
6662 For the @code{btrace} recording method, it shows:
6668 Number of instructions that have been recorded.
6670 Number of blocks of sequential control-flow formed by the recorded
6673 Whether in record mode or replay mode.
6676 For the @code{bts} recording format, it also shows:
6679 Size of the perf ring buffer.
6683 @kindex record delete
6686 When record target runs in replay mode (``in the past''), delete the
6687 subsequent execution log and begin to record a new execution log starting
6688 from the current address. This means you will abandon the previously
6689 recorded ``future'' and begin recording a new ``future''.
6691 @kindex record instruction-history
6692 @kindex rec instruction-history
6693 @item record instruction-history
6694 Disassembles instructions from the recorded execution log. By
6695 default, ten instructions are disassembled. This can be changed using
6696 the @code{set record instruction-history-size} command. Instructions
6697 are printed in execution order. There are several ways to specify
6698 what part of the execution log to disassemble:
6701 @item record instruction-history @var{insn}
6702 Disassembles ten instructions starting from instruction number
6705 @item record instruction-history @var{insn}, +/-@var{n}
6706 Disassembles @var{n} instructions around instruction number
6707 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6708 @var{n} instructions after instruction number @var{insn}. If
6709 @var{n} is preceded with @code{-}, disassembles @var{n}
6710 instructions before instruction number @var{insn}.
6712 @item record instruction-history
6713 Disassembles ten more instructions after the last disassembly.
6715 @item record instruction-history -
6716 Disassembles ten more instructions before the last disassembly.
6718 @item record instruction-history @var{begin} @var{end}
6719 Disassembles instructions beginning with instruction number
6720 @var{begin} until instruction number @var{end}. The instruction
6721 number @var{end} is included.
6724 This command may not be available for all recording methods.
6727 @item set record instruction-history-size @var{size}
6728 @itemx set record instruction-history-size unlimited
6729 Define how many instructions to disassemble in the @code{record
6730 instruction-history} command. The default value is 10.
6731 A @var{size} of @code{unlimited} means unlimited instructions.
6734 @item show record instruction-history-size
6735 Show how many instructions to disassemble in the @code{record
6736 instruction-history} command.
6738 @kindex record function-call-history
6739 @kindex rec function-call-history
6740 @item record function-call-history
6741 Prints the execution history at function granularity. It prints one
6742 line for each sequence of instructions that belong to the same
6743 function giving the name of that function, the source lines
6744 for this instruction sequence (if the @code{/l} modifier is
6745 specified), and the instructions numbers that form the sequence (if
6746 the @code{/i} modifier is specified). The function names are indented
6747 to reflect the call stack depth if the @code{/c} modifier is
6748 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6752 (@value{GDBP}) @b{list 1, 10}
6763 (@value{GDBP}) @b{record function-call-history /ilc}
6764 1 bar inst 1,4 at foo.c:6,8
6765 2 foo inst 5,10 at foo.c:2,3
6766 3 bar inst 11,13 at foo.c:9,10
6769 By default, ten lines are printed. This can be changed using the
6770 @code{set record function-call-history-size} command. Functions are
6771 printed in execution order. There are several ways to specify what
6775 @item record function-call-history @var{func}
6776 Prints ten functions starting from function number @var{func}.
6778 @item record function-call-history @var{func}, +/-@var{n}
6779 Prints @var{n} functions around function number @var{func}. If
6780 @var{n} is preceded with @code{+}, prints @var{n} functions after
6781 function number @var{func}. If @var{n} is preceded with @code{-},
6782 prints @var{n} functions before function number @var{func}.
6784 @item record function-call-history
6785 Prints ten more functions after the last ten-line print.
6787 @item record function-call-history -
6788 Prints ten more functions before the last ten-line print.
6790 @item record function-call-history @var{begin} @var{end}
6791 Prints functions beginning with function number @var{begin} until
6792 function number @var{end}. The function number @var{end} is included.
6795 This command may not be available for all recording methods.
6797 @item set record function-call-history-size @var{size}
6798 @itemx set record function-call-history-size unlimited
6799 Define how many lines to print in the
6800 @code{record function-call-history} command. The default value is 10.
6801 A size of @code{unlimited} means unlimited lines.
6803 @item show record function-call-history-size
6804 Show how many lines to print in the
6805 @code{record function-call-history} command.
6810 @chapter Examining the Stack
6812 When your program has stopped, the first thing you need to know is where it
6813 stopped and how it got there.
6816 Each time your program performs a function call, information about the call
6818 That information includes the location of the call in your program,
6819 the arguments of the call,
6820 and the local variables of the function being called.
6821 The information is saved in a block of data called a @dfn{stack frame}.
6822 The stack frames are allocated in a region of memory called the @dfn{call
6825 When your program stops, the @value{GDBN} commands for examining the
6826 stack allow you to see all of this information.
6828 @cindex selected frame
6829 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6830 @value{GDBN} commands refer implicitly to the selected frame. In
6831 particular, whenever you ask @value{GDBN} for the value of a variable in
6832 your program, the value is found in the selected frame. There are
6833 special @value{GDBN} commands to select whichever frame you are
6834 interested in. @xref{Selection, ,Selecting a Frame}.
6836 When your program stops, @value{GDBN} automatically selects the
6837 currently executing frame and describes it briefly, similar to the
6838 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6841 * Frames:: Stack frames
6842 * Backtrace:: Backtraces
6843 * Frame Filter Management:: Managing frame filters
6844 * Selection:: Selecting a frame
6845 * Frame Info:: Information on a frame
6850 @section Stack Frames
6852 @cindex frame, definition
6854 The call stack is divided up into contiguous pieces called @dfn{stack
6855 frames}, or @dfn{frames} for short; each frame is the data associated
6856 with one call to one function. The frame contains the arguments given
6857 to the function, the function's local variables, and the address at
6858 which the function is executing.
6860 @cindex initial frame
6861 @cindex outermost frame
6862 @cindex innermost frame
6863 When your program is started, the stack has only one frame, that of the
6864 function @code{main}. This is called the @dfn{initial} frame or the
6865 @dfn{outermost} frame. Each time a function is called, a new frame is
6866 made. Each time a function returns, the frame for that function invocation
6867 is eliminated. If a function is recursive, there can be many frames for
6868 the same function. The frame for the function in which execution is
6869 actually occurring is called the @dfn{innermost} frame. This is the most
6870 recently created of all the stack frames that still exist.
6872 @cindex frame pointer
6873 Inside your program, stack frames are identified by their addresses. A
6874 stack frame consists of many bytes, each of which has its own address; each
6875 kind of computer has a convention for choosing one byte whose
6876 address serves as the address of the frame. Usually this address is kept
6877 in a register called the @dfn{frame pointer register}
6878 (@pxref{Registers, $fp}) while execution is going on in that frame.
6880 @cindex frame number
6881 @value{GDBN} assigns numbers to all existing stack frames, starting with
6882 zero for the innermost frame, one for the frame that called it,
6883 and so on upward. These numbers do not really exist in your program;
6884 they are assigned by @value{GDBN} to give you a way of designating stack
6885 frames in @value{GDBN} commands.
6887 @c The -fomit-frame-pointer below perennially causes hbox overflow
6888 @c underflow problems.
6889 @cindex frameless execution
6890 Some compilers provide a way to compile functions so that they operate
6891 without stack frames. (For example, the @value{NGCC} option
6893 @samp{-fomit-frame-pointer}
6895 generates functions without a frame.)
6896 This is occasionally done with heavily used library functions to save
6897 the frame setup time. @value{GDBN} has limited facilities for dealing
6898 with these function invocations. If the innermost function invocation
6899 has no stack frame, @value{GDBN} nevertheless regards it as though
6900 it had a separate frame, which is numbered zero as usual, allowing
6901 correct tracing of the function call chain. However, @value{GDBN} has
6902 no provision for frameless functions elsewhere in the stack.
6905 @kindex frame@r{, command}
6906 @cindex current stack frame
6907 @item frame @r{[}@var{framespec}@r{]}
6908 The @code{frame} command allows you to move from one stack frame to another,
6909 and to print the stack frame you select. The @var{framespec} may be either the
6910 address of the frame or the stack frame number. Without an argument,
6911 @code{frame} prints the current stack frame.
6913 @kindex select-frame
6914 @cindex selecting frame silently
6916 The @code{select-frame} command allows you to move from one stack frame
6917 to another without printing the frame. This is the silent version of
6925 @cindex call stack traces
6926 A backtrace is a summary of how your program got where it is. It shows one
6927 line per frame, for many frames, starting with the currently executing
6928 frame (frame zero), followed by its caller (frame one), and on up the
6931 @anchor{backtrace-command}
6934 @kindex bt @r{(@code{backtrace})}
6937 Print a backtrace of the entire stack: one line per frame for all
6938 frames in the stack.
6940 You can stop the backtrace at any time by typing the system interrupt
6941 character, normally @kbd{Ctrl-c}.
6943 @item backtrace @var{n}
6945 Similar, but print only the innermost @var{n} frames.
6947 @item backtrace -@var{n}
6949 Similar, but print only the outermost @var{n} frames.
6951 @item backtrace full
6953 @itemx bt full @var{n}
6954 @itemx bt full -@var{n}
6955 Print the values of the local variables also. As described above,
6956 @var{n} specifies the number of frames to print.
6958 @item backtrace no-filters
6959 @itemx bt no-filters
6960 @itemx bt no-filters @var{n}
6961 @itemx bt no-filters -@var{n}
6962 @itemx bt no-filters full
6963 @itemx bt no-filters full @var{n}
6964 @itemx bt no-filters full -@var{n}
6965 Do not run Python frame filters on this backtrace. @xref{Frame
6966 Filter API}, for more information. Additionally use @ref{disable
6967 frame-filter all} to turn off all frame filters. This is only
6968 relevant when @value{GDBN} has been configured with @code{Python}
6974 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6975 are additional aliases for @code{backtrace}.
6977 @cindex multiple threads, backtrace
6978 In a multi-threaded program, @value{GDBN} by default shows the
6979 backtrace only for the current thread. To display the backtrace for
6980 several or all of the threads, use the command @code{thread apply}
6981 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6982 apply all backtrace}, @value{GDBN} will display the backtrace for all
6983 the threads; this is handy when you debug a core dump of a
6984 multi-threaded program.
6986 Each line in the backtrace shows the frame number and the function name.
6987 The program counter value is also shown---unless you use @code{set
6988 print address off}. The backtrace also shows the source file name and
6989 line number, as well as the arguments to the function. The program
6990 counter value is omitted if it is at the beginning of the code for that
6993 Here is an example of a backtrace. It was made with the command
6994 @samp{bt 3}, so it shows the innermost three frames.
6998 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7000 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7001 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7003 (More stack frames follow...)
7008 The display for frame zero does not begin with a program counter
7009 value, indicating that your program has stopped at the beginning of the
7010 code for line @code{993} of @code{builtin.c}.
7013 The value of parameter @code{data} in frame 1 has been replaced by
7014 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7015 only if it is a scalar (integer, pointer, enumeration, etc). See command
7016 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7017 on how to configure the way function parameter values are printed.
7019 @cindex optimized out, in backtrace
7020 @cindex function call arguments, optimized out
7021 If your program was compiled with optimizations, some compilers will
7022 optimize away arguments passed to functions if those arguments are
7023 never used after the call. Such optimizations generate code that
7024 passes arguments through registers, but doesn't store those arguments
7025 in the stack frame. @value{GDBN} has no way of displaying such
7026 arguments in stack frames other than the innermost one. Here's what
7027 such a backtrace might look like:
7031 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7033 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7034 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7036 (More stack frames follow...)
7041 The values of arguments that were not saved in their stack frames are
7042 shown as @samp{<optimized out>}.
7044 If you need to display the values of such optimized-out arguments,
7045 either deduce that from other variables whose values depend on the one
7046 you are interested in, or recompile without optimizations.
7048 @cindex backtrace beyond @code{main} function
7049 @cindex program entry point
7050 @cindex startup code, and backtrace
7051 Most programs have a standard user entry point---a place where system
7052 libraries and startup code transition into user code. For C this is
7053 @code{main}@footnote{
7054 Note that embedded programs (the so-called ``free-standing''
7055 environment) are not required to have a @code{main} function as the
7056 entry point. They could even have multiple entry points.}.
7057 When @value{GDBN} finds the entry function in a backtrace
7058 it will terminate the backtrace, to avoid tracing into highly
7059 system-specific (and generally uninteresting) code.
7061 If you need to examine the startup code, or limit the number of levels
7062 in a backtrace, you can change this behavior:
7065 @item set backtrace past-main
7066 @itemx set backtrace past-main on
7067 @kindex set backtrace
7068 Backtraces will continue past the user entry point.
7070 @item set backtrace past-main off
7071 Backtraces will stop when they encounter the user entry point. This is the
7074 @item show backtrace past-main
7075 @kindex show backtrace
7076 Display the current user entry point backtrace policy.
7078 @item set backtrace past-entry
7079 @itemx set backtrace past-entry on
7080 Backtraces will continue past the internal entry point of an application.
7081 This entry point is encoded by the linker when the application is built,
7082 and is likely before the user entry point @code{main} (or equivalent) is called.
7084 @item set backtrace past-entry off
7085 Backtraces will stop when they encounter the internal entry point of an
7086 application. This is the default.
7088 @item show backtrace past-entry
7089 Display the current internal entry point backtrace policy.
7091 @item set backtrace limit @var{n}
7092 @itemx set backtrace limit 0
7093 @itemx set backtrace limit unlimited
7094 @cindex backtrace limit
7095 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7096 or zero means unlimited levels.
7098 @item show backtrace limit
7099 Display the current limit on backtrace levels.
7102 You can control how file names are displayed.
7105 @item set filename-display
7106 @itemx set filename-display relative
7107 @cindex filename-display
7108 Display file names relative to the compilation directory. This is the default.
7110 @item set filename-display basename
7111 Display only basename of a filename.
7113 @item set filename-display absolute
7114 Display an absolute filename.
7116 @item show filename-display
7117 Show the current way to display filenames.
7120 @node Frame Filter Management
7121 @section Management of Frame Filters.
7122 @cindex managing frame filters
7124 Frame filters are Python based utilities to manage and decorate the
7125 output of frames. @xref{Frame Filter API}, for further information.
7127 Managing frame filters is performed by several commands available
7128 within @value{GDBN}, detailed here.
7131 @kindex info frame-filter
7132 @item info frame-filter
7133 Print a list of installed frame filters from all dictionaries, showing
7134 their name, priority and enabled status.
7136 @kindex disable frame-filter
7137 @anchor{disable frame-filter all}
7138 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7139 Disable a frame filter in the dictionary matching
7140 @var{filter-dictionary} and @var{filter-name}. The
7141 @var{filter-dictionary} may be @code{all}, @code{global},
7142 @code{progspace}, or the name of the object file where the frame filter
7143 dictionary resides. When @code{all} is specified, all frame filters
7144 across all dictionaries are disabled. The @var{filter-name} is the name
7145 of the frame filter and is used when @code{all} is not the option for
7146 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7147 may be enabled again later.
7149 @kindex enable frame-filter
7150 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7151 Enable a frame filter in the dictionary matching
7152 @var{filter-dictionary} and @var{filter-name}. The
7153 @var{filter-dictionary} may be @code{all}, @code{global},
7154 @code{progspace} or the name of the object file where the frame filter
7155 dictionary resides. When @code{all} is specified, all frame filters across
7156 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7157 filter and is used when @code{all} is not the option for
7158 @var{filter-dictionary}.
7163 (gdb) info frame-filter
7165 global frame-filters:
7166 Priority Enabled Name
7167 1000 No PrimaryFunctionFilter
7170 progspace /build/test frame-filters:
7171 Priority Enabled Name
7172 100 Yes ProgspaceFilter
7174 objfile /build/test frame-filters:
7175 Priority Enabled Name
7176 999 Yes BuildProgra Filter
7178 (gdb) disable frame-filter /build/test BuildProgramFilter
7179 (gdb) info frame-filter
7181 global frame-filters:
7182 Priority Enabled Name
7183 1000 No PrimaryFunctionFilter
7186 progspace /build/test frame-filters:
7187 Priority Enabled Name
7188 100 Yes ProgspaceFilter
7190 objfile /build/test frame-filters:
7191 Priority Enabled Name
7192 999 No BuildProgramFilter
7194 (gdb) enable frame-filter global PrimaryFunctionFilter
7195 (gdb) info frame-filter
7197 global frame-filters:
7198 Priority Enabled Name
7199 1000 Yes PrimaryFunctionFilter
7202 progspace /build/test frame-filters:
7203 Priority Enabled Name
7204 100 Yes ProgspaceFilter
7206 objfile /build/test frame-filters:
7207 Priority Enabled Name
7208 999 No BuildProgramFilter
7211 @kindex set frame-filter priority
7212 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7213 Set the @var{priority} of a frame filter in the dictionary matching
7214 @var{filter-dictionary}, and the frame filter name matching
7215 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7216 @code{progspace} or the name of the object file where the frame filter
7217 dictionary resides. The @var{priority} is an integer.
7219 @kindex show frame-filter priority
7220 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7221 Show the @var{priority} of a frame filter in the dictionary matching
7222 @var{filter-dictionary}, and the frame filter name matching
7223 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7224 @code{progspace} or the name of the object file where the frame filter
7230 (gdb) info frame-filter
7232 global frame-filters:
7233 Priority Enabled Name
7234 1000 Yes PrimaryFunctionFilter
7237 progspace /build/test frame-filters:
7238 Priority Enabled Name
7239 100 Yes ProgspaceFilter
7241 objfile /build/test frame-filters:
7242 Priority Enabled Name
7243 999 No BuildProgramFilter
7245 (gdb) set frame-filter priority global Reverse 50
7246 (gdb) info frame-filter
7248 global frame-filters:
7249 Priority Enabled Name
7250 1000 Yes PrimaryFunctionFilter
7253 progspace /build/test frame-filters:
7254 Priority Enabled Name
7255 100 Yes ProgspaceFilter
7257 objfile /build/test frame-filters:
7258 Priority Enabled Name
7259 999 No BuildProgramFilter
7264 @section Selecting a Frame
7266 Most commands for examining the stack and other data in your program work on
7267 whichever stack frame is selected at the moment. Here are the commands for
7268 selecting a stack frame; all of them finish by printing a brief description
7269 of the stack frame just selected.
7272 @kindex frame@r{, selecting}
7273 @kindex f @r{(@code{frame})}
7276 Select frame number @var{n}. Recall that frame zero is the innermost
7277 (currently executing) frame, frame one is the frame that called the
7278 innermost one, and so on. The highest-numbered frame is the one for
7281 @item frame @var{addr}
7283 Select the frame at address @var{addr}. This is useful mainly if the
7284 chaining of stack frames has been damaged by a bug, making it
7285 impossible for @value{GDBN} to assign numbers properly to all frames. In
7286 addition, this can be useful when your program has multiple stacks and
7287 switches between them.
7289 On the SPARC architecture, @code{frame} needs two addresses to
7290 select an arbitrary frame: a frame pointer and a stack pointer.
7292 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7293 pointer and a program counter.
7295 On the 29k architecture, it needs three addresses: a register stack
7296 pointer, a program counter, and a memory stack pointer.
7300 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7301 numbers @var{n}, this advances toward the outermost frame, to higher
7302 frame numbers, to frames that have existed longer.
7305 @kindex do @r{(@code{down})}
7307 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7308 positive numbers @var{n}, this advances toward the innermost frame, to
7309 lower frame numbers, to frames that were created more recently.
7310 You may abbreviate @code{down} as @code{do}.
7313 All of these commands end by printing two lines of output describing the
7314 frame. The first line shows the frame number, the function name, the
7315 arguments, and the source file and line number of execution in that
7316 frame. The second line shows the text of that source line.
7324 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7326 10 read_input_file (argv[i]);
7330 After such a printout, the @code{list} command with no arguments
7331 prints ten lines centered on the point of execution in the frame.
7332 You can also edit the program at the point of execution with your favorite
7333 editing program by typing @code{edit}.
7334 @xref{List, ,Printing Source Lines},
7338 @kindex down-silently
7340 @item up-silently @var{n}
7341 @itemx down-silently @var{n}
7342 These two commands are variants of @code{up} and @code{down},
7343 respectively; they differ in that they do their work silently, without
7344 causing display of the new frame. They are intended primarily for use
7345 in @value{GDBN} command scripts, where the output might be unnecessary and
7350 @section Information About a Frame
7352 There are several other commands to print information about the selected
7358 When used without any argument, this command does not change which
7359 frame is selected, but prints a brief description of the currently
7360 selected stack frame. It can be abbreviated @code{f}. With an
7361 argument, this command is used to select a stack frame.
7362 @xref{Selection, ,Selecting a Frame}.
7365 @kindex info f @r{(@code{info frame})}
7368 This command prints a verbose description of the selected stack frame,
7373 the address of the frame
7375 the address of the next frame down (called by this frame)
7377 the address of the next frame up (caller of this frame)
7379 the language in which the source code corresponding to this frame is written
7381 the address of the frame's arguments
7383 the address of the frame's local variables
7385 the program counter saved in it (the address of execution in the caller frame)
7387 which registers were saved in the frame
7390 @noindent The verbose description is useful when
7391 something has gone wrong that has made the stack format fail to fit
7392 the usual conventions.
7394 @item info frame @var{addr}
7395 @itemx info f @var{addr}
7396 Print a verbose description of the frame at address @var{addr}, without
7397 selecting that frame. The selected frame remains unchanged by this
7398 command. This requires the same kind of address (more than one for some
7399 architectures) that you specify in the @code{frame} command.
7400 @xref{Selection, ,Selecting a Frame}.
7404 Print the arguments of the selected frame, each on a separate line.
7408 Print the local variables of the selected frame, each on a separate
7409 line. These are all variables (declared either static or automatic)
7410 accessible at the point of execution of the selected frame.
7416 @chapter Examining Source Files
7418 @value{GDBN} can print parts of your program's source, since the debugging
7419 information recorded in the program tells @value{GDBN} what source files were
7420 used to build it. When your program stops, @value{GDBN} spontaneously prints
7421 the line where it stopped. Likewise, when you select a stack frame
7422 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7423 execution in that frame has stopped. You can print other portions of
7424 source files by explicit command.
7426 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7427 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7428 @value{GDBN} under @sc{gnu} Emacs}.
7431 * List:: Printing source lines
7432 * Specify Location:: How to specify code locations
7433 * Edit:: Editing source files
7434 * Search:: Searching source files
7435 * Source Path:: Specifying source directories
7436 * Machine Code:: Source and machine code
7440 @section Printing Source Lines
7443 @kindex l @r{(@code{list})}
7444 To print lines from a source file, use the @code{list} command
7445 (abbreviated @code{l}). By default, ten lines are printed.
7446 There are several ways to specify what part of the file you want to
7447 print; see @ref{Specify Location}, for the full list.
7449 Here are the forms of the @code{list} command most commonly used:
7452 @item list @var{linenum}
7453 Print lines centered around line number @var{linenum} in the
7454 current source file.
7456 @item list @var{function}
7457 Print lines centered around the beginning of function
7461 Print more lines. If the last lines printed were printed with a
7462 @code{list} command, this prints lines following the last lines
7463 printed; however, if the last line printed was a solitary line printed
7464 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7465 Stack}), this prints lines centered around that line.
7468 Print lines just before the lines last printed.
7471 @cindex @code{list}, how many lines to display
7472 By default, @value{GDBN} prints ten source lines with any of these forms of
7473 the @code{list} command. You can change this using @code{set listsize}:
7476 @kindex set listsize
7477 @item set listsize @var{count}
7478 @itemx set listsize unlimited
7479 Make the @code{list} command display @var{count} source lines (unless
7480 the @code{list} argument explicitly specifies some other number).
7481 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7483 @kindex show listsize
7485 Display the number of lines that @code{list} prints.
7488 Repeating a @code{list} command with @key{RET} discards the argument,
7489 so it is equivalent to typing just @code{list}. This is more useful
7490 than listing the same lines again. An exception is made for an
7491 argument of @samp{-}; that argument is preserved in repetition so that
7492 each repetition moves up in the source file.
7494 In general, the @code{list} command expects you to supply zero, one or two
7495 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7496 of writing them (@pxref{Specify Location}), but the effect is always
7497 to specify some source line.
7499 Here is a complete description of the possible arguments for @code{list}:
7502 @item list @var{linespec}
7503 Print lines centered around the line specified by @var{linespec}.
7505 @item list @var{first},@var{last}
7506 Print lines from @var{first} to @var{last}. Both arguments are
7507 linespecs. When a @code{list} command has two linespecs, and the
7508 source file of the second linespec is omitted, this refers to
7509 the same source file as the first linespec.
7511 @item list ,@var{last}
7512 Print lines ending with @var{last}.
7514 @item list @var{first},
7515 Print lines starting with @var{first}.
7518 Print lines just after the lines last printed.
7521 Print lines just before the lines last printed.
7524 As described in the preceding table.
7527 @node Specify Location
7528 @section Specifying a Location
7529 @cindex specifying location
7532 Several @value{GDBN} commands accept arguments that specify a location
7533 of your program's code. Since @value{GDBN} is a source-level
7534 debugger, a location usually specifies some line in the source code;
7535 for that reason, locations are also known as @dfn{linespecs}.
7537 Here are all the different ways of specifying a code location that
7538 @value{GDBN} understands:
7542 Specifies the line number @var{linenum} of the current source file.
7545 @itemx +@var{offset}
7546 Specifies the line @var{offset} lines before or after the @dfn{current
7547 line}. For the @code{list} command, the current line is the last one
7548 printed; for the breakpoint commands, this is the line at which
7549 execution stopped in the currently selected @dfn{stack frame}
7550 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7551 used as the second of the two linespecs in a @code{list} command,
7552 this specifies the line @var{offset} lines up or down from the first
7555 @item @var{filename}:@var{linenum}
7556 Specifies the line @var{linenum} in the source file @var{filename}.
7557 If @var{filename} is a relative file name, then it will match any
7558 source file name with the same trailing components. For example, if
7559 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7560 name of @file{/build/trunk/gcc/expr.c}, but not
7561 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7563 @item @var{function}
7564 Specifies the line that begins the body of the function @var{function}.
7565 For example, in C, this is the line with the open brace.
7567 @item @var{function}:@var{label}
7568 Specifies the line where @var{label} appears in @var{function}.
7570 @item @var{filename}:@var{function}
7571 Specifies the line that begins the body of the function @var{function}
7572 in the file @var{filename}. You only need the file name with a
7573 function name to avoid ambiguity when there are identically named
7574 functions in different source files.
7577 Specifies the line at which the label named @var{label} appears.
7578 @value{GDBN} searches for the label in the function corresponding to
7579 the currently selected stack frame. If there is no current selected
7580 stack frame (for instance, if the inferior is not running), then
7581 @value{GDBN} will not search for a label.
7583 @item *@var{address}
7584 Specifies the program address @var{address}. For line-oriented
7585 commands, such as @code{list} and @code{edit}, this specifies a source
7586 line that contains @var{address}. For @code{break} and other
7587 breakpoint oriented commands, this can be used to set breakpoints in
7588 parts of your program which do not have debugging information or
7591 Here @var{address} may be any expression valid in the current working
7592 language (@pxref{Languages, working language}) that specifies a code
7593 address. In addition, as a convenience, @value{GDBN} extends the
7594 semantics of expressions used in locations to cover the situations
7595 that frequently happen during debugging. Here are the various forms
7599 @item @var{expression}
7600 Any expression valid in the current working language.
7602 @item @var{funcaddr}
7603 An address of a function or procedure derived from its name. In C,
7604 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7605 simply the function's name @var{function} (and actually a special case
7606 of a valid expression). In Pascal and Modula-2, this is
7607 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7608 (although the Pascal form also works).
7610 This form specifies the address of the function's first instruction,
7611 before the stack frame and arguments have been set up.
7613 @item '@var{filename}':@var{funcaddr}
7614 Like @var{funcaddr} above, but also specifies the name of the source
7615 file explicitly. This is useful if the name of the function does not
7616 specify the function unambiguously, e.g., if there are several
7617 functions with identical names in different source files.
7620 @cindex breakpoint at static probe point
7621 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7622 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7623 applications to embed static probes. @xref{Static Probe Points}, for more
7624 information on finding and using static probes. This form of linespec
7625 specifies the location of such a static probe.
7627 If @var{objfile} is given, only probes coming from that shared library
7628 or executable matching @var{objfile} as a regular expression are considered.
7629 If @var{provider} is given, then only probes from that provider are considered.
7630 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7631 each one of those probes.
7637 @section Editing Source Files
7638 @cindex editing source files
7641 @kindex e @r{(@code{edit})}
7642 To edit the lines in a source file, use the @code{edit} command.
7643 The editing program of your choice
7644 is invoked with the current line set to
7645 the active line in the program.
7646 Alternatively, there are several ways to specify what part of the file you
7647 want to print if you want to see other parts of the program:
7650 @item edit @var{location}
7651 Edit the source file specified by @code{location}. Editing starts at
7652 that @var{location}, e.g., at the specified source line of the
7653 specified file. @xref{Specify Location}, for all the possible forms
7654 of the @var{location} argument; here are the forms of the @code{edit}
7655 command most commonly used:
7658 @item edit @var{number}
7659 Edit the current source file with @var{number} as the active line number.
7661 @item edit @var{function}
7662 Edit the file containing @var{function} at the beginning of its definition.
7667 @subsection Choosing your Editor
7668 You can customize @value{GDBN} to use any editor you want
7670 The only restriction is that your editor (say @code{ex}), recognizes the
7671 following command-line syntax:
7673 ex +@var{number} file
7675 The optional numeric value +@var{number} specifies the number of the line in
7676 the file where to start editing.}.
7677 By default, it is @file{@value{EDITOR}}, but you can change this
7678 by setting the environment variable @code{EDITOR} before using
7679 @value{GDBN}. For example, to configure @value{GDBN} to use the
7680 @code{vi} editor, you could use these commands with the @code{sh} shell:
7686 or in the @code{csh} shell,
7688 setenv EDITOR /usr/bin/vi
7693 @section Searching Source Files
7694 @cindex searching source files
7696 There are two commands for searching through the current source file for a
7701 @kindex forward-search
7702 @kindex fo @r{(@code{forward-search})}
7703 @item forward-search @var{regexp}
7704 @itemx search @var{regexp}
7705 The command @samp{forward-search @var{regexp}} checks each line,
7706 starting with the one following the last line listed, for a match for
7707 @var{regexp}. It lists the line that is found. You can use the
7708 synonym @samp{search @var{regexp}} or abbreviate the command name as
7711 @kindex reverse-search
7712 @item reverse-search @var{regexp}
7713 The command @samp{reverse-search @var{regexp}} checks each line, starting
7714 with the one before the last line listed and going backward, for a match
7715 for @var{regexp}. It lists the line that is found. You can abbreviate
7716 this command as @code{rev}.
7720 @section Specifying Source Directories
7723 @cindex directories for source files
7724 Executable programs sometimes do not record the directories of the source
7725 files from which they were compiled, just the names. Even when they do,
7726 the directories could be moved between the compilation and your debugging
7727 session. @value{GDBN} has a list of directories to search for source files;
7728 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7729 it tries all the directories in the list, in the order they are present
7730 in the list, until it finds a file with the desired name.
7732 For example, suppose an executable references the file
7733 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7734 @file{/mnt/cross}. The file is first looked up literally; if this
7735 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7736 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7737 message is printed. @value{GDBN} does not look up the parts of the
7738 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7739 Likewise, the subdirectories of the source path are not searched: if
7740 the source path is @file{/mnt/cross}, and the binary refers to
7741 @file{foo.c}, @value{GDBN} would not find it under
7742 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7744 Plain file names, relative file names with leading directories, file
7745 names containing dots, etc.@: are all treated as described above; for
7746 instance, if the source path is @file{/mnt/cross}, and the source file
7747 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7748 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7749 that---@file{/mnt/cross/foo.c}.
7751 Note that the executable search path is @emph{not} used to locate the
7754 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7755 any information it has cached about where source files are found and where
7756 each line is in the file.
7760 When you start @value{GDBN}, its source path includes only @samp{cdir}
7761 and @samp{cwd}, in that order.
7762 To add other directories, use the @code{directory} command.
7764 The search path is used to find both program source files and @value{GDBN}
7765 script files (read using the @samp{-command} option and @samp{source} command).
7767 In addition to the source path, @value{GDBN} provides a set of commands
7768 that manage a list of source path substitution rules. A @dfn{substitution
7769 rule} specifies how to rewrite source directories stored in the program's
7770 debug information in case the sources were moved to a different
7771 directory between compilation and debugging. A rule is made of
7772 two strings, the first specifying what needs to be rewritten in
7773 the path, and the second specifying how it should be rewritten.
7774 In @ref{set substitute-path}, we name these two parts @var{from} and
7775 @var{to} respectively. @value{GDBN} does a simple string replacement
7776 of @var{from} with @var{to} at the start of the directory part of the
7777 source file name, and uses that result instead of the original file
7778 name to look up the sources.
7780 Using the previous example, suppose the @file{foo-1.0} tree has been
7781 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7782 @value{GDBN} to replace @file{/usr/src} in all source path names with
7783 @file{/mnt/cross}. The first lookup will then be
7784 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7785 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7786 substitution rule, use the @code{set substitute-path} command
7787 (@pxref{set substitute-path}).
7789 To avoid unexpected substitution results, a rule is applied only if the
7790 @var{from} part of the directory name ends at a directory separator.
7791 For instance, a rule substituting @file{/usr/source} into
7792 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7793 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7794 is applied only at the beginning of the directory name, this rule will
7795 not be applied to @file{/root/usr/source/baz.c} either.
7797 In many cases, you can achieve the same result using the @code{directory}
7798 command. However, @code{set substitute-path} can be more efficient in
7799 the case where the sources are organized in a complex tree with multiple
7800 subdirectories. With the @code{directory} command, you need to add each
7801 subdirectory of your project. If you moved the entire tree while
7802 preserving its internal organization, then @code{set substitute-path}
7803 allows you to direct the debugger to all the sources with one single
7806 @code{set substitute-path} is also more than just a shortcut command.
7807 The source path is only used if the file at the original location no
7808 longer exists. On the other hand, @code{set substitute-path} modifies
7809 the debugger behavior to look at the rewritten location instead. So, if
7810 for any reason a source file that is not relevant to your executable is
7811 located at the original location, a substitution rule is the only
7812 method available to point @value{GDBN} at the new location.
7814 @cindex @samp{--with-relocated-sources}
7815 @cindex default source path substitution
7816 You can configure a default source path substitution rule by
7817 configuring @value{GDBN} with the
7818 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7819 should be the name of a directory under @value{GDBN}'s configured
7820 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7821 directory names in debug information under @var{dir} will be adjusted
7822 automatically if the installed @value{GDBN} is moved to a new
7823 location. This is useful if @value{GDBN}, libraries or executables
7824 with debug information and corresponding source code are being moved
7828 @item directory @var{dirname} @dots{}
7829 @item dir @var{dirname} @dots{}
7830 Add directory @var{dirname} to the front of the source path. Several
7831 directory names may be given to this command, separated by @samp{:}
7832 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7833 part of absolute file names) or
7834 whitespace. You may specify a directory that is already in the source
7835 path; this moves it forward, so @value{GDBN} searches it sooner.
7839 @vindex $cdir@r{, convenience variable}
7840 @vindex $cwd@r{, convenience variable}
7841 @cindex compilation directory
7842 @cindex current directory
7843 @cindex working directory
7844 @cindex directory, current
7845 @cindex directory, compilation
7846 You can use the string @samp{$cdir} to refer to the compilation
7847 directory (if one is recorded), and @samp{$cwd} to refer to the current
7848 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7849 tracks the current working directory as it changes during your @value{GDBN}
7850 session, while the latter is immediately expanded to the current
7851 directory at the time you add an entry to the source path.
7854 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7856 @c RET-repeat for @code{directory} is explicitly disabled, but since
7857 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7859 @item set directories @var{path-list}
7860 @kindex set directories
7861 Set the source path to @var{path-list}.
7862 @samp{$cdir:$cwd} are added if missing.
7864 @item show directories
7865 @kindex show directories
7866 Print the source path: show which directories it contains.
7868 @anchor{set substitute-path}
7869 @item set substitute-path @var{from} @var{to}
7870 @kindex set substitute-path
7871 Define a source path substitution rule, and add it at the end of the
7872 current list of existing substitution rules. If a rule with the same
7873 @var{from} was already defined, then the old rule is also deleted.
7875 For example, if the file @file{/foo/bar/baz.c} was moved to
7876 @file{/mnt/cross/baz.c}, then the command
7879 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7883 will tell @value{GDBN} to replace @samp{/usr/src} with
7884 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7885 @file{baz.c} even though it was moved.
7887 In the case when more than one substitution rule have been defined,
7888 the rules are evaluated one by one in the order where they have been
7889 defined. The first one matching, if any, is selected to perform
7892 For instance, if we had entered the following commands:
7895 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7896 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7900 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7901 @file{/mnt/include/defs.h} by using the first rule. However, it would
7902 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7903 @file{/mnt/src/lib/foo.c}.
7906 @item unset substitute-path [path]
7907 @kindex unset substitute-path
7908 If a path is specified, search the current list of substitution rules
7909 for a rule that would rewrite that path. Delete that rule if found.
7910 A warning is emitted by the debugger if no rule could be found.
7912 If no path is specified, then all substitution rules are deleted.
7914 @item show substitute-path [path]
7915 @kindex show substitute-path
7916 If a path is specified, then print the source path substitution rule
7917 which would rewrite that path, if any.
7919 If no path is specified, then print all existing source path substitution
7924 If your source path is cluttered with directories that are no longer of
7925 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7926 versions of source. You can correct the situation as follows:
7930 Use @code{directory} with no argument to reset the source path to its default value.
7933 Use @code{directory} with suitable arguments to reinstall the
7934 directories you want in the source path. You can add all the
7935 directories in one command.
7939 @section Source and Machine Code
7940 @cindex source line and its code address
7942 You can use the command @code{info line} to map source lines to program
7943 addresses (and vice versa), and the command @code{disassemble} to display
7944 a range of addresses as machine instructions. You can use the command
7945 @code{set disassemble-next-line} to set whether to disassemble next
7946 source line when execution stops. When run under @sc{gnu} Emacs
7947 mode, the @code{info line} command causes the arrow to point to the
7948 line specified. Also, @code{info line} prints addresses in symbolic form as
7953 @item info line @var{linespec}
7954 Print the starting and ending addresses of the compiled code for
7955 source line @var{linespec}. You can specify source lines in any of
7956 the ways documented in @ref{Specify Location}.
7959 For example, we can use @code{info line} to discover the location of
7960 the object code for the first line of function
7961 @code{m4_changequote}:
7963 @c FIXME: I think this example should also show the addresses in
7964 @c symbolic form, as they usually would be displayed.
7966 (@value{GDBP}) info line m4_changequote
7967 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7971 @cindex code address and its source line
7972 We can also inquire (using @code{*@var{addr}} as the form for
7973 @var{linespec}) what source line covers a particular address:
7975 (@value{GDBP}) info line *0x63ff
7976 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7979 @cindex @code{$_} and @code{info line}
7980 @cindex @code{x} command, default address
7981 @kindex x@r{(examine), and} info line
7982 After @code{info line}, the default address for the @code{x} command
7983 is changed to the starting address of the line, so that @samp{x/i} is
7984 sufficient to begin examining the machine code (@pxref{Memory,
7985 ,Examining Memory}). Also, this address is saved as the value of the
7986 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7991 @cindex assembly instructions
7992 @cindex instructions, assembly
7993 @cindex machine instructions
7994 @cindex listing machine instructions
7996 @itemx disassemble /m
7997 @itemx disassemble /r
7998 This specialized command dumps a range of memory as machine
7999 instructions. It can also print mixed source+disassembly by specifying
8000 the @code{/m} modifier and print the raw instructions in hex as well as
8001 in symbolic form by specifying the @code{/r}.
8002 The default memory range is the function surrounding the
8003 program counter of the selected frame. A single argument to this
8004 command is a program counter value; @value{GDBN} dumps the function
8005 surrounding this value. When two arguments are given, they should
8006 be separated by a comma, possibly surrounded by whitespace. The
8007 arguments specify a range of addresses to dump, in one of two forms:
8010 @item @var{start},@var{end}
8011 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8012 @item @var{start},+@var{length}
8013 the addresses from @var{start} (inclusive) to
8014 @code{@var{start}+@var{length}} (exclusive).
8018 When 2 arguments are specified, the name of the function is also
8019 printed (since there could be several functions in the given range).
8021 The argument(s) can be any expression yielding a numeric value, such as
8022 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8024 If the range of memory being disassembled contains current program counter,
8025 the instruction at that location is shown with a @code{=>} marker.
8028 The following example shows the disassembly of a range of addresses of
8029 HP PA-RISC 2.0 code:
8032 (@value{GDBP}) disas 0x32c4, 0x32e4
8033 Dump of assembler code from 0x32c4 to 0x32e4:
8034 0x32c4 <main+204>: addil 0,dp
8035 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8036 0x32cc <main+212>: ldil 0x3000,r31
8037 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8038 0x32d4 <main+220>: ldo 0(r31),rp
8039 0x32d8 <main+224>: addil -0x800,dp
8040 0x32dc <main+228>: ldo 0x588(r1),r26
8041 0x32e0 <main+232>: ldil 0x3000,r31
8042 End of assembler dump.
8045 Here is an example showing mixed source+assembly for Intel x86, when the
8046 program is stopped just after function prologue:
8049 (@value{GDBP}) disas /m main
8050 Dump of assembler code for function main:
8052 0x08048330 <+0>: push %ebp
8053 0x08048331 <+1>: mov %esp,%ebp
8054 0x08048333 <+3>: sub $0x8,%esp
8055 0x08048336 <+6>: and $0xfffffff0,%esp
8056 0x08048339 <+9>: sub $0x10,%esp
8058 6 printf ("Hello.\n");
8059 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8060 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8064 0x08048348 <+24>: mov $0x0,%eax
8065 0x0804834d <+29>: leave
8066 0x0804834e <+30>: ret
8068 End of assembler dump.
8071 Here is another example showing raw instructions in hex for AMD x86-64,
8074 (gdb) disas /r 0x400281,+10
8075 Dump of assembler code from 0x400281 to 0x40028b:
8076 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8077 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8078 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8079 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8080 End of assembler dump.
8083 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8084 So, for example, if you want to disassemble function @code{bar}
8085 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8086 and not @samp{disassemble foo.c:bar}.
8088 Some architectures have more than one commonly-used set of instruction
8089 mnemonics or other syntax.
8091 For programs that were dynamically linked and use shared libraries,
8092 instructions that call functions or branch to locations in the shared
8093 libraries might show a seemingly bogus location---it's actually a
8094 location of the relocation table. On some architectures, @value{GDBN}
8095 might be able to resolve these to actual function names.
8098 @kindex set disassembly-flavor
8099 @cindex Intel disassembly flavor
8100 @cindex AT&T disassembly flavor
8101 @item set disassembly-flavor @var{instruction-set}
8102 Select the instruction set to use when disassembling the
8103 program via the @code{disassemble} or @code{x/i} commands.
8105 Currently this command is only defined for the Intel x86 family. You
8106 can set @var{instruction-set} to either @code{intel} or @code{att}.
8107 The default is @code{att}, the AT&T flavor used by default by Unix
8108 assemblers for x86-based targets.
8110 @kindex show disassembly-flavor
8111 @item show disassembly-flavor
8112 Show the current setting of the disassembly flavor.
8116 @kindex set disassemble-next-line
8117 @kindex show disassemble-next-line
8118 @item set disassemble-next-line
8119 @itemx show disassemble-next-line
8120 Control whether or not @value{GDBN} will disassemble the next source
8121 line or instruction when execution stops. If ON, @value{GDBN} will
8122 display disassembly of the next source line when execution of the
8123 program being debugged stops. This is @emph{in addition} to
8124 displaying the source line itself, which @value{GDBN} always does if
8125 possible. If the next source line cannot be displayed for some reason
8126 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8127 info in the debug info), @value{GDBN} will display disassembly of the
8128 next @emph{instruction} instead of showing the next source line. If
8129 AUTO, @value{GDBN} will display disassembly of next instruction only
8130 if the source line cannot be displayed. This setting causes
8131 @value{GDBN} to display some feedback when you step through a function
8132 with no line info or whose source file is unavailable. The default is
8133 OFF, which means never display the disassembly of the next line or
8139 @chapter Examining Data
8141 @cindex printing data
8142 @cindex examining data
8145 The usual way to examine data in your program is with the @code{print}
8146 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8147 evaluates and prints the value of an expression of the language your
8148 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8149 Different Languages}). It may also print the expression using a
8150 Python-based pretty-printer (@pxref{Pretty Printing}).
8153 @item print @var{expr}
8154 @itemx print /@var{f} @var{expr}
8155 @var{expr} is an expression (in the source language). By default the
8156 value of @var{expr} is printed in a format appropriate to its data type;
8157 you can choose a different format by specifying @samp{/@var{f}}, where
8158 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8162 @itemx print /@var{f}
8163 @cindex reprint the last value
8164 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8165 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8166 conveniently inspect the same value in an alternative format.
8169 A more low-level way of examining data is with the @code{x} command.
8170 It examines data in memory at a specified address and prints it in a
8171 specified format. @xref{Memory, ,Examining Memory}.
8173 If you are interested in information about types, or about how the
8174 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8175 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8178 @cindex exploring hierarchical data structures
8180 Another way of examining values of expressions and type information is
8181 through the Python extension command @code{explore} (available only if
8182 the @value{GDBN} build is configured with @code{--with-python}). It
8183 offers an interactive way to start at the highest level (or, the most
8184 abstract level) of the data type of an expression (or, the data type
8185 itself) and explore all the way down to leaf scalar values/fields
8186 embedded in the higher level data types.
8189 @item explore @var{arg}
8190 @var{arg} is either an expression (in the source language), or a type
8191 visible in the current context of the program being debugged.
8194 The working of the @code{explore} command can be illustrated with an
8195 example. If a data type @code{struct ComplexStruct} is defined in your
8205 struct ComplexStruct
8207 struct SimpleStruct *ss_p;
8213 followed by variable declarations as
8216 struct SimpleStruct ss = @{ 10, 1.11 @};
8217 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8221 then, the value of the variable @code{cs} can be explored using the
8222 @code{explore} command as follows.
8226 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8227 the following fields:
8229 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8230 arr = <Enter 1 to explore this field of type `int [10]'>
8232 Enter the field number of choice:
8236 Since the fields of @code{cs} are not scalar values, you are being
8237 prompted to chose the field you want to explore. Let's say you choose
8238 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8239 pointer, you will be asked if it is pointing to a single value. From
8240 the declaration of @code{cs} above, it is indeed pointing to a single
8241 value, hence you enter @code{y}. If you enter @code{n}, then you will
8242 be asked if it were pointing to an array of values, in which case this
8243 field will be explored as if it were an array.
8246 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8247 Continue exploring it as a pointer to a single value [y/n]: y
8248 The value of `*(cs.ss_p)' is a struct/class of type `struct
8249 SimpleStruct' with the following fields:
8251 i = 10 .. (Value of type `int')
8252 d = 1.1100000000000001 .. (Value of type `double')
8254 Press enter to return to parent value:
8258 If the field @code{arr} of @code{cs} was chosen for exploration by
8259 entering @code{1} earlier, then since it is as array, you will be
8260 prompted to enter the index of the element in the array that you want
8264 `cs.arr' is an array of `int'.
8265 Enter the index of the element you want to explore in `cs.arr': 5
8267 `(cs.arr)[5]' is a scalar value of type `int'.
8271 Press enter to return to parent value:
8274 In general, at any stage of exploration, you can go deeper towards the
8275 leaf values by responding to the prompts appropriately, or hit the
8276 return key to return to the enclosing data structure (the @i{higher}
8277 level data structure).
8279 Similar to exploring values, you can use the @code{explore} command to
8280 explore types. Instead of specifying a value (which is typically a
8281 variable name or an expression valid in the current context of the
8282 program being debugged), you specify a type name. If you consider the
8283 same example as above, your can explore the type
8284 @code{struct ComplexStruct} by passing the argument
8285 @code{struct ComplexStruct} to the @code{explore} command.
8288 (gdb) explore struct ComplexStruct
8292 By responding to the prompts appropriately in the subsequent interactive
8293 session, you can explore the type @code{struct ComplexStruct} in a
8294 manner similar to how the value @code{cs} was explored in the above
8297 The @code{explore} command also has two sub-commands,
8298 @code{explore value} and @code{explore type}. The former sub-command is
8299 a way to explicitly specify that value exploration of the argument is
8300 being invoked, while the latter is a way to explicitly specify that type
8301 exploration of the argument is being invoked.
8304 @item explore value @var{expr}
8305 @cindex explore value
8306 This sub-command of @code{explore} explores the value of the
8307 expression @var{expr} (if @var{expr} is an expression valid in the
8308 current context of the program being debugged). The behavior of this
8309 command is identical to that of the behavior of the @code{explore}
8310 command being passed the argument @var{expr}.
8312 @item explore type @var{arg}
8313 @cindex explore type
8314 This sub-command of @code{explore} explores the type of @var{arg} (if
8315 @var{arg} is a type visible in the current context of program being
8316 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8317 is an expression valid in the current context of the program being
8318 debugged). If @var{arg} is a type, then the behavior of this command is
8319 identical to that of the @code{explore} command being passed the
8320 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8321 this command will be identical to that of the @code{explore} command
8322 being passed the type of @var{arg} as the argument.
8326 * Expressions:: Expressions
8327 * Ambiguous Expressions:: Ambiguous Expressions
8328 * Variables:: Program variables
8329 * Arrays:: Artificial arrays
8330 * Output Formats:: Output formats
8331 * Memory:: Examining memory
8332 * Auto Display:: Automatic display
8333 * Print Settings:: Print settings
8334 * Pretty Printing:: Python pretty printing
8335 * Value History:: Value history
8336 * Convenience Vars:: Convenience variables
8337 * Convenience Funs:: Convenience functions
8338 * Registers:: Registers
8339 * Floating Point Hardware:: Floating point hardware
8340 * Vector Unit:: Vector Unit
8341 * OS Information:: Auxiliary data provided by operating system
8342 * Memory Region Attributes:: Memory region attributes
8343 * Dump/Restore Files:: Copy between memory and a file
8344 * Core File Generation:: Cause a program dump its core
8345 * Character Sets:: Debugging programs that use a different
8346 character set than GDB does
8347 * Caching Target Data:: Data caching for targets
8348 * Searching Memory:: Searching memory for a sequence of bytes
8352 @section Expressions
8355 @code{print} and many other @value{GDBN} commands accept an expression and
8356 compute its value. Any kind of constant, variable or operator defined
8357 by the programming language you are using is valid in an expression in
8358 @value{GDBN}. This includes conditional expressions, function calls,
8359 casts, and string constants. It also includes preprocessor macros, if
8360 you compiled your program to include this information; see
8363 @cindex arrays in expressions
8364 @value{GDBN} supports array constants in expressions input by
8365 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8366 you can use the command @code{print @{1, 2, 3@}} to create an array
8367 of three integers. If you pass an array to a function or assign it
8368 to a program variable, @value{GDBN} copies the array to memory that
8369 is @code{malloc}ed in the target program.
8371 Because C is so widespread, most of the expressions shown in examples in
8372 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8373 Languages}, for information on how to use expressions in other
8376 In this section, we discuss operators that you can use in @value{GDBN}
8377 expressions regardless of your programming language.
8379 @cindex casts, in expressions
8380 Casts are supported in all languages, not just in C, because it is so
8381 useful to cast a number into a pointer in order to examine a structure
8382 at that address in memory.
8383 @c FIXME: casts supported---Mod2 true?
8385 @value{GDBN} supports these operators, in addition to those common
8386 to programming languages:
8390 @samp{@@} is a binary operator for treating parts of memory as arrays.
8391 @xref{Arrays, ,Artificial Arrays}, for more information.
8394 @samp{::} allows you to specify a variable in terms of the file or
8395 function where it is defined. @xref{Variables, ,Program Variables}.
8397 @cindex @{@var{type}@}
8398 @cindex type casting memory
8399 @cindex memory, viewing as typed object
8400 @cindex casts, to view memory
8401 @item @{@var{type}@} @var{addr}
8402 Refers to an object of type @var{type} stored at address @var{addr} in
8403 memory. The address @var{addr} may be any expression whose value is
8404 an integer or pointer (but parentheses are required around binary
8405 operators, just as in a cast). This construct is allowed regardless
8406 of what kind of data is normally supposed to reside at @var{addr}.
8409 @node Ambiguous Expressions
8410 @section Ambiguous Expressions
8411 @cindex ambiguous expressions
8413 Expressions can sometimes contain some ambiguous elements. For instance,
8414 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8415 a single function name to be defined several times, for application in
8416 different contexts. This is called @dfn{overloading}. Another example
8417 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8418 templates and is typically instantiated several times, resulting in
8419 the same function name being defined in different contexts.
8421 In some cases and depending on the language, it is possible to adjust
8422 the expression to remove the ambiguity. For instance in C@t{++}, you
8423 can specify the signature of the function you want to break on, as in
8424 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8425 qualified name of your function often makes the expression unambiguous
8428 When an ambiguity that needs to be resolved is detected, the debugger
8429 has the capability to display a menu of numbered choices for each
8430 possibility, and then waits for the selection with the prompt @samp{>}.
8431 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8432 aborts the current command. If the command in which the expression was
8433 used allows more than one choice to be selected, the next option in the
8434 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8437 For example, the following session excerpt shows an attempt to set a
8438 breakpoint at the overloaded symbol @code{String::after}.
8439 We choose three particular definitions of that function name:
8441 @c FIXME! This is likely to change to show arg type lists, at least
8444 (@value{GDBP}) b String::after
8447 [2] file:String.cc; line number:867
8448 [3] file:String.cc; line number:860
8449 [4] file:String.cc; line number:875
8450 [5] file:String.cc; line number:853
8451 [6] file:String.cc; line number:846
8452 [7] file:String.cc; line number:735
8454 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8455 Breakpoint 2 at 0xb344: file String.cc, line 875.
8456 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8457 Multiple breakpoints were set.
8458 Use the "delete" command to delete unwanted
8465 @kindex set multiple-symbols
8466 @item set multiple-symbols @var{mode}
8467 @cindex multiple-symbols menu
8469 This option allows you to adjust the debugger behavior when an expression
8472 By default, @var{mode} is set to @code{all}. If the command with which
8473 the expression is used allows more than one choice, then @value{GDBN}
8474 automatically selects all possible choices. For instance, inserting
8475 a breakpoint on a function using an ambiguous name results in a breakpoint
8476 inserted on each possible match. However, if a unique choice must be made,
8477 then @value{GDBN} uses the menu to help you disambiguate the expression.
8478 For instance, printing the address of an overloaded function will result
8479 in the use of the menu.
8481 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8482 when an ambiguity is detected.
8484 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8485 an error due to the ambiguity and the command is aborted.
8487 @kindex show multiple-symbols
8488 @item show multiple-symbols
8489 Show the current value of the @code{multiple-symbols} setting.
8493 @section Program Variables
8495 The most common kind of expression to use is the name of a variable
8498 Variables in expressions are understood in the selected stack frame
8499 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8503 global (or file-static)
8510 visible according to the scope rules of the
8511 programming language from the point of execution in that frame
8514 @noindent This means that in the function
8529 you can examine and use the variable @code{a} whenever your program is
8530 executing within the function @code{foo}, but you can only use or
8531 examine the variable @code{b} while your program is executing inside
8532 the block where @code{b} is declared.
8534 @cindex variable name conflict
8535 There is an exception: you can refer to a variable or function whose
8536 scope is a single source file even if the current execution point is not
8537 in this file. But it is possible to have more than one such variable or
8538 function with the same name (in different source files). If that
8539 happens, referring to that name has unpredictable effects. If you wish,
8540 you can specify a static variable in a particular function or file by
8541 using the colon-colon (@code{::}) notation:
8543 @cindex colon-colon, context for variables/functions
8545 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8546 @cindex @code{::}, context for variables/functions
8549 @var{file}::@var{variable}
8550 @var{function}::@var{variable}
8554 Here @var{file} or @var{function} is the name of the context for the
8555 static @var{variable}. In the case of file names, you can use quotes to
8556 make sure @value{GDBN} parses the file name as a single word---for example,
8557 to print a global value of @code{x} defined in @file{f2.c}:
8560 (@value{GDBP}) p 'f2.c'::x
8563 The @code{::} notation is normally used for referring to
8564 static variables, since you typically disambiguate uses of local variables
8565 in functions by selecting the appropriate frame and using the
8566 simple name of the variable. However, you may also use this notation
8567 to refer to local variables in frames enclosing the selected frame:
8576 process (a); /* Stop here */
8587 For example, if there is a breakpoint at the commented line,
8588 here is what you might see
8589 when the program stops after executing the call @code{bar(0)}:
8594 (@value{GDBP}) p bar::a
8597 #2 0x080483d0 in foo (a=5) at foobar.c:12
8600 (@value{GDBP}) p bar::a
8604 @cindex C@t{++} scope resolution
8605 These uses of @samp{::} are very rarely in conflict with the very
8606 similar use of the same notation in C@t{++}. When they are in
8607 conflict, the C@t{++} meaning takes precedence; however, this can be
8608 overridden by quoting the file or function name with single quotes.
8610 For example, suppose the program is stopped in a method of a class
8611 that has a field named @code{includefile}, and there is also an
8612 include file named @file{includefile} that defines a variable,
8616 (@value{GDBP}) p includefile
8618 (@value{GDBP}) p includefile::some_global
8619 A syntax error in expression, near `'.
8620 (@value{GDBP}) p 'includefile'::some_global
8624 @cindex wrong values
8625 @cindex variable values, wrong
8626 @cindex function entry/exit, wrong values of variables
8627 @cindex optimized code, wrong values of variables
8629 @emph{Warning:} Occasionally, a local variable may appear to have the
8630 wrong value at certain points in a function---just after entry to a new
8631 scope, and just before exit.
8633 You may see this problem when you are stepping by machine instructions.
8634 This is because, on most machines, it takes more than one instruction to
8635 set up a stack frame (including local variable definitions); if you are
8636 stepping by machine instructions, variables may appear to have the wrong
8637 values until the stack frame is completely built. On exit, it usually
8638 also takes more than one machine instruction to destroy a stack frame;
8639 after you begin stepping through that group of instructions, local
8640 variable definitions may be gone.
8642 This may also happen when the compiler does significant optimizations.
8643 To be sure of always seeing accurate values, turn off all optimization
8646 @cindex ``No symbol "foo" in current context''
8647 Another possible effect of compiler optimizations is to optimize
8648 unused variables out of existence, or assign variables to registers (as
8649 opposed to memory addresses). Depending on the support for such cases
8650 offered by the debug info format used by the compiler, @value{GDBN}
8651 might not be able to display values for such local variables. If that
8652 happens, @value{GDBN} will print a message like this:
8655 No symbol "foo" in current context.
8658 To solve such problems, either recompile without optimizations, or use a
8659 different debug info format, if the compiler supports several such
8660 formats. @xref{Compilation}, for more information on choosing compiler
8661 options. @xref{C, ,C and C@t{++}}, for more information about debug
8662 info formats that are best suited to C@t{++} programs.
8664 If you ask to print an object whose contents are unknown to
8665 @value{GDBN}, e.g., because its data type is not completely specified
8666 by the debug information, @value{GDBN} will say @samp{<incomplete
8667 type>}. @xref{Symbols, incomplete type}, for more about this.
8669 If you append @kbd{@@entry} string to a function parameter name you get its
8670 value at the time the function got called. If the value is not available an
8671 error message is printed. Entry values are available only with some compilers.
8672 Entry values are normally also printed at the function parameter list according
8673 to @ref{set print entry-values}.
8676 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8682 (gdb) print i@@entry
8686 Strings are identified as arrays of @code{char} values without specified
8687 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8688 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8689 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8690 defines literal string type @code{"char"} as @code{char} without a sign.
8695 signed char var1[] = "A";
8698 You get during debugging
8703 $2 = @{65 'A', 0 '\0'@}
8707 @section Artificial Arrays
8709 @cindex artificial array
8711 @kindex @@@r{, referencing memory as an array}
8712 It is often useful to print out several successive objects of the
8713 same type in memory; a section of an array, or an array of
8714 dynamically determined size for which only a pointer exists in the
8717 You can do this by referring to a contiguous span of memory as an
8718 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8719 operand of @samp{@@} should be the first element of the desired array
8720 and be an individual object. The right operand should be the desired length
8721 of the array. The result is an array value whose elements are all of
8722 the type of the left argument. The first element is actually the left
8723 argument; the second element comes from bytes of memory immediately
8724 following those that hold the first element, and so on. Here is an
8725 example. If a program says
8728 int *array = (int *) malloc (len * sizeof (int));
8732 you can print the contents of @code{array} with
8738 The left operand of @samp{@@} must reside in memory. Array values made
8739 with @samp{@@} in this way behave just like other arrays in terms of
8740 subscripting, and are coerced to pointers when used in expressions.
8741 Artificial arrays most often appear in expressions via the value history
8742 (@pxref{Value History, ,Value History}), after printing one out.
8744 Another way to create an artificial array is to use a cast.
8745 This re-interprets a value as if it were an array.
8746 The value need not be in memory:
8748 (@value{GDBP}) p/x (short[2])0x12345678
8749 $1 = @{0x1234, 0x5678@}
8752 As a convenience, if you leave the array length out (as in
8753 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8754 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8756 (@value{GDBP}) p/x (short[])0x12345678
8757 $2 = @{0x1234, 0x5678@}
8760 Sometimes the artificial array mechanism is not quite enough; in
8761 moderately complex data structures, the elements of interest may not
8762 actually be adjacent---for example, if you are interested in the values
8763 of pointers in an array. One useful work-around in this situation is
8764 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8765 Variables}) as a counter in an expression that prints the first
8766 interesting value, and then repeat that expression via @key{RET}. For
8767 instance, suppose you have an array @code{dtab} of pointers to
8768 structures, and you are interested in the values of a field @code{fv}
8769 in each structure. Here is an example of what you might type:
8779 @node Output Formats
8780 @section Output Formats
8782 @cindex formatted output
8783 @cindex output formats
8784 By default, @value{GDBN} prints a value according to its data type. Sometimes
8785 this is not what you want. For example, you might want to print a number
8786 in hex, or a pointer in decimal. Or you might want to view data in memory
8787 at a certain address as a character string or as an instruction. To do
8788 these things, specify an @dfn{output format} when you print a value.
8790 The simplest use of output formats is to say how to print a value
8791 already computed. This is done by starting the arguments of the
8792 @code{print} command with a slash and a format letter. The format
8793 letters supported are:
8797 Regard the bits of the value as an integer, and print the integer in
8801 Print as integer in signed decimal.
8804 Print as integer in unsigned decimal.
8807 Print as integer in octal.
8810 Print as integer in binary. The letter @samp{t} stands for ``two''.
8811 @footnote{@samp{b} cannot be used because these format letters are also
8812 used with the @code{x} command, where @samp{b} stands for ``byte'';
8813 see @ref{Memory,,Examining Memory}.}
8816 @cindex unknown address, locating
8817 @cindex locate address
8818 Print as an address, both absolute in hexadecimal and as an offset from
8819 the nearest preceding symbol. You can use this format used to discover
8820 where (in what function) an unknown address is located:
8823 (@value{GDBP}) p/a 0x54320
8824 $3 = 0x54320 <_initialize_vx+396>
8828 The command @code{info symbol 0x54320} yields similar results.
8829 @xref{Symbols, info symbol}.
8832 Regard as an integer and print it as a character constant. This
8833 prints both the numerical value and its character representation. The
8834 character representation is replaced with the octal escape @samp{\nnn}
8835 for characters outside the 7-bit @sc{ascii} range.
8837 Without this format, @value{GDBN} displays @code{char},
8838 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8839 constants. Single-byte members of vectors are displayed as integer
8843 Regard the bits of the value as a floating point number and print
8844 using typical floating point syntax.
8847 @cindex printing strings
8848 @cindex printing byte arrays
8849 Regard as a string, if possible. With this format, pointers to single-byte
8850 data are displayed as null-terminated strings and arrays of single-byte data
8851 are displayed as fixed-length strings. Other values are displayed in their
8854 Without this format, @value{GDBN} displays pointers to and arrays of
8855 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8856 strings. Single-byte members of a vector are displayed as an integer
8860 Like @samp{x} formatting, the value is treated as an integer and
8861 printed as hexadecimal, but leading zeros are printed to pad the value
8862 to the size of the integer type.
8865 @cindex raw printing
8866 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8867 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8868 Printing}). This typically results in a higher-level display of the
8869 value's contents. The @samp{r} format bypasses any Python
8870 pretty-printer which might exist.
8873 For example, to print the program counter in hex (@pxref{Registers}), type
8880 Note that no space is required before the slash; this is because command
8881 names in @value{GDBN} cannot contain a slash.
8883 To reprint the last value in the value history with a different format,
8884 you can use the @code{print} command with just a format and no
8885 expression. For example, @samp{p/x} reprints the last value in hex.
8888 @section Examining Memory
8890 You can use the command @code{x} (for ``examine'') to examine memory in
8891 any of several formats, independently of your program's data types.
8893 @cindex examining memory
8895 @kindex x @r{(examine memory)}
8896 @item x/@var{nfu} @var{addr}
8899 Use the @code{x} command to examine memory.
8902 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8903 much memory to display and how to format it; @var{addr} is an
8904 expression giving the address where you want to start displaying memory.
8905 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8906 Several commands set convenient defaults for @var{addr}.
8909 @item @var{n}, the repeat count
8910 The repeat count is a decimal integer; the default is 1. It specifies
8911 how much memory (counting by units @var{u}) to display.
8912 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8915 @item @var{f}, the display format
8916 The display format is one of the formats used by @code{print}
8917 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8918 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8919 The default is @samp{x} (hexadecimal) initially. The default changes
8920 each time you use either @code{x} or @code{print}.
8922 @item @var{u}, the unit size
8923 The unit size is any of
8929 Halfwords (two bytes).
8931 Words (four bytes). This is the initial default.
8933 Giant words (eight bytes).
8936 Each time you specify a unit size with @code{x}, that size becomes the
8937 default unit the next time you use @code{x}. For the @samp{i} format,
8938 the unit size is ignored and is normally not written. For the @samp{s} format,
8939 the unit size defaults to @samp{b}, unless it is explicitly given.
8940 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8941 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8942 Note that the results depend on the programming language of the
8943 current compilation unit. If the language is C, the @samp{s}
8944 modifier will use the UTF-16 encoding while @samp{w} will use
8945 UTF-32. The encoding is set by the programming language and cannot
8948 @item @var{addr}, starting display address
8949 @var{addr} is the address where you want @value{GDBN} to begin displaying
8950 memory. The expression need not have a pointer value (though it may);
8951 it is always interpreted as an integer address of a byte of memory.
8952 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8953 @var{addr} is usually just after the last address examined---but several
8954 other commands also set the default address: @code{info breakpoints} (to
8955 the address of the last breakpoint listed), @code{info line} (to the
8956 starting address of a line), and @code{print} (if you use it to display
8957 a value from memory).
8960 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8961 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8962 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8963 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8964 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8966 Since the letters indicating unit sizes are all distinct from the
8967 letters specifying output formats, you do not have to remember whether
8968 unit size or format comes first; either order works. The output
8969 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8970 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8972 Even though the unit size @var{u} is ignored for the formats @samp{s}
8973 and @samp{i}, you might still want to use a count @var{n}; for example,
8974 @samp{3i} specifies that you want to see three machine instructions,
8975 including any operands. For convenience, especially when used with
8976 the @code{display} command, the @samp{i} format also prints branch delay
8977 slot instructions, if any, beyond the count specified, which immediately
8978 follow the last instruction that is within the count. The command
8979 @code{disassemble} gives an alternative way of inspecting machine
8980 instructions; see @ref{Machine Code,,Source and Machine Code}.
8982 All the defaults for the arguments to @code{x} are designed to make it
8983 easy to continue scanning memory with minimal specifications each time
8984 you use @code{x}. For example, after you have inspected three machine
8985 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8986 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8987 the repeat count @var{n} is used again; the other arguments default as
8988 for successive uses of @code{x}.
8990 When examining machine instructions, the instruction at current program
8991 counter is shown with a @code{=>} marker. For example:
8994 (@value{GDBP}) x/5i $pc-6
8995 0x804837f <main+11>: mov %esp,%ebp
8996 0x8048381 <main+13>: push %ecx
8997 0x8048382 <main+14>: sub $0x4,%esp
8998 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8999 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9002 @cindex @code{$_}, @code{$__}, and value history
9003 The addresses and contents printed by the @code{x} command are not saved
9004 in the value history because there is often too much of them and they
9005 would get in the way. Instead, @value{GDBN} makes these values available for
9006 subsequent use in expressions as values of the convenience variables
9007 @code{$_} and @code{$__}. After an @code{x} command, the last address
9008 examined is available for use in expressions in the convenience variable
9009 @code{$_}. The contents of that address, as examined, are available in
9010 the convenience variable @code{$__}.
9012 If the @code{x} command has a repeat count, the address and contents saved
9013 are from the last memory unit printed; this is not the same as the last
9014 address printed if several units were printed on the last line of output.
9016 @cindex remote memory comparison
9017 @cindex target memory comparison
9018 @cindex verify remote memory image
9019 @cindex verify target memory image
9020 When you are debugging a program running on a remote target machine
9021 (@pxref{Remote Debugging}), you may wish to verify the program's image
9022 in the remote machine's memory against the executable file you
9023 downloaded to the target. Or, on any target, you may want to check
9024 whether the program has corrupted its own read-only sections. The
9025 @code{compare-sections} command is provided for such situations.
9028 @kindex compare-sections
9029 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9030 Compare the data of a loadable section @var{section-name} in the
9031 executable file of the program being debugged with the same section in
9032 the target machine's memory, and report any mismatches. With no
9033 arguments, compares all loadable sections. With an argument of
9034 @code{-r}, compares all loadable read-only sections.
9036 Note: for remote targets, this command can be accelerated if the
9037 target supports computing the CRC checksum of a block of memory
9038 (@pxref{qCRC packet}).
9042 @section Automatic Display
9043 @cindex automatic display
9044 @cindex display of expressions
9046 If you find that you want to print the value of an expression frequently
9047 (to see how it changes), you might want to add it to the @dfn{automatic
9048 display list} so that @value{GDBN} prints its value each time your program stops.
9049 Each expression added to the list is given a number to identify it;
9050 to remove an expression from the list, you specify that number.
9051 The automatic display looks like this:
9055 3: bar[5] = (struct hack *) 0x3804
9059 This display shows item numbers, expressions and their current values. As with
9060 displays you request manually using @code{x} or @code{print}, you can
9061 specify the output format you prefer; in fact, @code{display} decides
9062 whether to use @code{print} or @code{x} depending your format
9063 specification---it uses @code{x} if you specify either the @samp{i}
9064 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9068 @item display @var{expr}
9069 Add the expression @var{expr} to the list of expressions to display
9070 each time your program stops. @xref{Expressions, ,Expressions}.
9072 @code{display} does not repeat if you press @key{RET} again after using it.
9074 @item display/@var{fmt} @var{expr}
9075 For @var{fmt} specifying only a display format and not a size or
9076 count, add the expression @var{expr} to the auto-display list but
9077 arrange to display it each time in the specified format @var{fmt}.
9078 @xref{Output Formats,,Output Formats}.
9080 @item display/@var{fmt} @var{addr}
9081 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9082 number of units, add the expression @var{addr} as a memory address to
9083 be examined each time your program stops. Examining means in effect
9084 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9087 For example, @samp{display/i $pc} can be helpful, to see the machine
9088 instruction about to be executed each time execution stops (@samp{$pc}
9089 is a common name for the program counter; @pxref{Registers, ,Registers}).
9092 @kindex delete display
9094 @item undisplay @var{dnums}@dots{}
9095 @itemx delete display @var{dnums}@dots{}
9096 Remove items from the list of expressions to display. Specify the
9097 numbers of the displays that you want affected with the command
9098 argument @var{dnums}. It can be a single display number, one of the
9099 numbers shown in the first field of the @samp{info display} display;
9100 or it could be a range of display numbers, as in @code{2-4}.
9102 @code{undisplay} does not repeat if you press @key{RET} after using it.
9103 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9105 @kindex disable display
9106 @item disable display @var{dnums}@dots{}
9107 Disable the display of item numbers @var{dnums}. A disabled display
9108 item is not printed automatically, but is not forgotten. It may be
9109 enabled again later. Specify the numbers of the displays that you
9110 want affected with the command argument @var{dnums}. It can be a
9111 single display number, one of the numbers shown in the first field of
9112 the @samp{info display} display; or it could be a range of display
9113 numbers, as in @code{2-4}.
9115 @kindex enable display
9116 @item enable display @var{dnums}@dots{}
9117 Enable display of item numbers @var{dnums}. It becomes effective once
9118 again in auto display of its expression, until you specify otherwise.
9119 Specify the numbers of the displays that you want affected with the
9120 command argument @var{dnums}. It can be a single display number, one
9121 of the numbers shown in the first field of the @samp{info display}
9122 display; or it could be a range of display numbers, as in @code{2-4}.
9125 Display the current values of the expressions on the list, just as is
9126 done when your program stops.
9128 @kindex info display
9130 Print the list of expressions previously set up to display
9131 automatically, each one with its item number, but without showing the
9132 values. This includes disabled expressions, which are marked as such.
9133 It also includes expressions which would not be displayed right now
9134 because they refer to automatic variables not currently available.
9137 @cindex display disabled out of scope
9138 If a display expression refers to local variables, then it does not make
9139 sense outside the lexical context for which it was set up. Such an
9140 expression is disabled when execution enters a context where one of its
9141 variables is not defined. For example, if you give the command
9142 @code{display last_char} while inside a function with an argument
9143 @code{last_char}, @value{GDBN} displays this argument while your program
9144 continues to stop inside that function. When it stops elsewhere---where
9145 there is no variable @code{last_char}---the display is disabled
9146 automatically. The next time your program stops where @code{last_char}
9147 is meaningful, you can enable the display expression once again.
9149 @node Print Settings
9150 @section Print Settings
9152 @cindex format options
9153 @cindex print settings
9154 @value{GDBN} provides the following ways to control how arrays, structures,
9155 and symbols are printed.
9158 These settings are useful for debugging programs in any language:
9162 @item set print address
9163 @itemx set print address on
9164 @cindex print/don't print memory addresses
9165 @value{GDBN} prints memory addresses showing the location of stack
9166 traces, structure values, pointer values, breakpoints, and so forth,
9167 even when it also displays the contents of those addresses. The default
9168 is @code{on}. For example, this is what a stack frame display looks like with
9169 @code{set print address on}:
9174 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9176 530 if (lquote != def_lquote)
9180 @item set print address off
9181 Do not print addresses when displaying their contents. For example,
9182 this is the same stack frame displayed with @code{set print address off}:
9186 (@value{GDBP}) set print addr off
9188 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9189 530 if (lquote != def_lquote)
9193 You can use @samp{set print address off} to eliminate all machine
9194 dependent displays from the @value{GDBN} interface. For example, with
9195 @code{print address off}, you should get the same text for backtraces on
9196 all machines---whether or not they involve pointer arguments.
9199 @item show print address
9200 Show whether or not addresses are to be printed.
9203 When @value{GDBN} prints a symbolic address, it normally prints the
9204 closest earlier symbol plus an offset. If that symbol does not uniquely
9205 identify the address (for example, it is a name whose scope is a single
9206 source file), you may need to clarify. One way to do this is with
9207 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9208 you can set @value{GDBN} to print the source file and line number when
9209 it prints a symbolic address:
9212 @item set print symbol-filename on
9213 @cindex source file and line of a symbol
9214 @cindex symbol, source file and line
9215 Tell @value{GDBN} to print the source file name and line number of a
9216 symbol in the symbolic form of an address.
9218 @item set print symbol-filename off
9219 Do not print source file name and line number of a symbol. This is the
9222 @item show print symbol-filename
9223 Show whether or not @value{GDBN} will print the source file name and
9224 line number of a symbol in the symbolic form of an address.
9227 Another situation where it is helpful to show symbol filenames and line
9228 numbers is when disassembling code; @value{GDBN} shows you the line
9229 number and source file that corresponds to each instruction.
9231 Also, you may wish to see the symbolic form only if the address being
9232 printed is reasonably close to the closest earlier symbol:
9235 @item set print max-symbolic-offset @var{max-offset}
9236 @itemx set print max-symbolic-offset unlimited
9237 @cindex maximum value for offset of closest symbol
9238 Tell @value{GDBN} to only display the symbolic form of an address if the
9239 offset between the closest earlier symbol and the address is less than
9240 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9241 to always print the symbolic form of an address if any symbol precedes
9242 it. Zero is equivalent to @code{unlimited}.
9244 @item show print max-symbolic-offset
9245 Ask how large the maximum offset is that @value{GDBN} prints in a
9249 @cindex wild pointer, interpreting
9250 @cindex pointer, finding referent
9251 If you have a pointer and you are not sure where it points, try
9252 @samp{set print symbol-filename on}. Then you can determine the name
9253 and source file location of the variable where it points, using
9254 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9255 For example, here @value{GDBN} shows that a variable @code{ptt} points
9256 at another variable @code{t}, defined in @file{hi2.c}:
9259 (@value{GDBP}) set print symbol-filename on
9260 (@value{GDBP}) p/a ptt
9261 $4 = 0xe008 <t in hi2.c>
9265 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9266 does not show the symbol name and filename of the referent, even with
9267 the appropriate @code{set print} options turned on.
9270 You can also enable @samp{/a}-like formatting all the time using
9271 @samp{set print symbol on}:
9274 @item set print symbol on
9275 Tell @value{GDBN} to print the symbol corresponding to an address, if
9278 @item set print symbol off
9279 Tell @value{GDBN} not to print the symbol corresponding to an
9280 address. In this mode, @value{GDBN} will still print the symbol
9281 corresponding to pointers to functions. This is the default.
9283 @item show print symbol
9284 Show whether @value{GDBN} will display the symbol corresponding to an
9288 Other settings control how different kinds of objects are printed:
9291 @item set print array
9292 @itemx set print array on
9293 @cindex pretty print arrays
9294 Pretty print arrays. This format is more convenient to read,
9295 but uses more space. The default is off.
9297 @item set print array off
9298 Return to compressed format for arrays.
9300 @item show print array
9301 Show whether compressed or pretty format is selected for displaying
9304 @cindex print array indexes
9305 @item set print array-indexes
9306 @itemx set print array-indexes on
9307 Print the index of each element when displaying arrays. May be more
9308 convenient to locate a given element in the array or quickly find the
9309 index of a given element in that printed array. The default is off.
9311 @item set print array-indexes off
9312 Stop printing element indexes when displaying arrays.
9314 @item show print array-indexes
9315 Show whether the index of each element is printed when displaying
9318 @item set print elements @var{number-of-elements}
9319 @itemx set print elements unlimited
9320 @cindex number of array elements to print
9321 @cindex limit on number of printed array elements
9322 Set a limit on how many elements of an array @value{GDBN} will print.
9323 If @value{GDBN} is printing a large array, it stops printing after it has
9324 printed the number of elements set by the @code{set print elements} command.
9325 This limit also applies to the display of strings.
9326 When @value{GDBN} starts, this limit is set to 200.
9327 Setting @var{number-of-elements} to @code{unlimited} or zero means
9328 that the number of elements to print is unlimited.
9330 @item show print elements
9331 Display the number of elements of a large array that @value{GDBN} will print.
9332 If the number is 0, then the printing is unlimited.
9334 @item set print frame-arguments @var{value}
9335 @kindex set print frame-arguments
9336 @cindex printing frame argument values
9337 @cindex print all frame argument values
9338 @cindex print frame argument values for scalars only
9339 @cindex do not print frame argument values
9340 This command allows to control how the values of arguments are printed
9341 when the debugger prints a frame (@pxref{Frames}). The possible
9346 The values of all arguments are printed.
9349 Print the value of an argument only if it is a scalar. The value of more
9350 complex arguments such as arrays, structures, unions, etc, is replaced
9351 by @code{@dots{}}. This is the default. Here is an example where
9352 only scalar arguments are shown:
9355 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9360 None of the argument values are printed. Instead, the value of each argument
9361 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9364 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9369 By default, only scalar arguments are printed. This command can be used
9370 to configure the debugger to print the value of all arguments, regardless
9371 of their type. However, it is often advantageous to not print the value
9372 of more complex parameters. For instance, it reduces the amount of
9373 information printed in each frame, making the backtrace more readable.
9374 Also, it improves performance when displaying Ada frames, because
9375 the computation of large arguments can sometimes be CPU-intensive,
9376 especially in large applications. Setting @code{print frame-arguments}
9377 to @code{scalars} (the default) or @code{none} avoids this computation,
9378 thus speeding up the display of each Ada frame.
9380 @item show print frame-arguments
9381 Show how the value of arguments should be displayed when printing a frame.
9383 @item set print raw frame-arguments on
9384 Print frame arguments in raw, non pretty-printed, form.
9386 @item set print raw frame-arguments off
9387 Print frame arguments in pretty-printed form, if there is a pretty-printer
9388 for the value (@pxref{Pretty Printing}),
9389 otherwise print the value in raw form.
9390 This is the default.
9392 @item show print raw frame-arguments
9393 Show whether to print frame arguments in raw form.
9395 @anchor{set print entry-values}
9396 @item set print entry-values @var{value}
9397 @kindex set print entry-values
9398 Set printing of frame argument values at function entry. In some cases
9399 @value{GDBN} can determine the value of function argument which was passed by
9400 the function caller, even if the value was modified inside the called function
9401 and therefore is different. With optimized code, the current value could be
9402 unavailable, but the entry value may still be known.
9404 The default value is @code{default} (see below for its description). Older
9405 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9406 this feature will behave in the @code{default} setting the same way as with the
9409 This functionality is currently supported only by DWARF 2 debugging format and
9410 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9411 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9414 The @var{value} parameter can be one of the following:
9418 Print only actual parameter values, never print values from function entry
9422 #0 different (val=6)
9423 #0 lost (val=<optimized out>)
9425 #0 invalid (val=<optimized out>)
9429 Print only parameter values from function entry point. The actual parameter
9430 values are never printed.
9432 #0 equal (val@@entry=5)
9433 #0 different (val@@entry=5)
9434 #0 lost (val@@entry=5)
9435 #0 born (val@@entry=<optimized out>)
9436 #0 invalid (val@@entry=<optimized out>)
9440 Print only parameter values from function entry point. If value from function
9441 entry point is not known while the actual value is known, print the actual
9442 value for such parameter.
9444 #0 equal (val@@entry=5)
9445 #0 different (val@@entry=5)
9446 #0 lost (val@@entry=5)
9448 #0 invalid (val@@entry=<optimized out>)
9452 Print actual parameter values. If actual parameter value is not known while
9453 value from function entry point is known, print the entry point value for such
9457 #0 different (val=6)
9458 #0 lost (val@@entry=5)
9460 #0 invalid (val=<optimized out>)
9464 Always print both the actual parameter value and its value from function entry
9465 point, even if values of one or both are not available due to compiler
9468 #0 equal (val=5, val@@entry=5)
9469 #0 different (val=6, val@@entry=5)
9470 #0 lost (val=<optimized out>, val@@entry=5)
9471 #0 born (val=10, val@@entry=<optimized out>)
9472 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9476 Print the actual parameter value if it is known and also its value from
9477 function entry point if it is known. If neither is known, print for the actual
9478 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9479 values are known and identical, print the shortened
9480 @code{param=param@@entry=VALUE} notation.
9482 #0 equal (val=val@@entry=5)
9483 #0 different (val=6, val@@entry=5)
9484 #0 lost (val@@entry=5)
9486 #0 invalid (val=<optimized out>)
9490 Always print the actual parameter value. Print also its value from function
9491 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9492 if both values are known and identical, print the shortened
9493 @code{param=param@@entry=VALUE} notation.
9495 #0 equal (val=val@@entry=5)
9496 #0 different (val=6, val@@entry=5)
9497 #0 lost (val=<optimized out>, val@@entry=5)
9499 #0 invalid (val=<optimized out>)
9503 For analysis messages on possible failures of frame argument values at function
9504 entry resolution see @ref{set debug entry-values}.
9506 @item show print entry-values
9507 Show the method being used for printing of frame argument values at function
9510 @item set print repeats @var{number-of-repeats}
9511 @itemx set print repeats unlimited
9512 @cindex repeated array elements
9513 Set the threshold for suppressing display of repeated array
9514 elements. When the number of consecutive identical elements of an
9515 array exceeds the threshold, @value{GDBN} prints the string
9516 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9517 identical repetitions, instead of displaying the identical elements
9518 themselves. Setting the threshold to @code{unlimited} or zero will
9519 cause all elements to be individually printed. The default threshold
9522 @item show print repeats
9523 Display the current threshold for printing repeated identical
9526 @item set print null-stop
9527 @cindex @sc{null} elements in arrays
9528 Cause @value{GDBN} to stop printing the characters of an array when the first
9529 @sc{null} is encountered. This is useful when large arrays actually
9530 contain only short strings.
9533 @item show print null-stop
9534 Show whether @value{GDBN} stops printing an array on the first
9535 @sc{null} character.
9537 @item set print pretty on
9538 @cindex print structures in indented form
9539 @cindex indentation in structure display
9540 Cause @value{GDBN} to print structures in an indented format with one member
9541 per line, like this:
9556 @item set print pretty off
9557 Cause @value{GDBN} to print structures in a compact format, like this:
9561 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9562 meat = 0x54 "Pork"@}
9567 This is the default format.
9569 @item show print pretty
9570 Show which format @value{GDBN} is using to print structures.
9572 @item set print sevenbit-strings on
9573 @cindex eight-bit characters in strings
9574 @cindex octal escapes in strings
9575 Print using only seven-bit characters; if this option is set,
9576 @value{GDBN} displays any eight-bit characters (in strings or
9577 character values) using the notation @code{\}@var{nnn}. This setting is
9578 best if you are working in English (@sc{ascii}) and you use the
9579 high-order bit of characters as a marker or ``meta'' bit.
9581 @item set print sevenbit-strings off
9582 Print full eight-bit characters. This allows the use of more
9583 international character sets, and is the default.
9585 @item show print sevenbit-strings
9586 Show whether or not @value{GDBN} is printing only seven-bit characters.
9588 @item set print union on
9589 @cindex unions in structures, printing
9590 Tell @value{GDBN} to print unions which are contained in structures
9591 and other unions. This is the default setting.
9593 @item set print union off
9594 Tell @value{GDBN} not to print unions which are contained in
9595 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9598 @item show print union
9599 Ask @value{GDBN} whether or not it will print unions which are contained in
9600 structures and other unions.
9602 For example, given the declarations
9605 typedef enum @{Tree, Bug@} Species;
9606 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9607 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9618 struct thing foo = @{Tree, @{Acorn@}@};
9622 with @code{set print union on} in effect @samp{p foo} would print
9625 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9629 and with @code{set print union off} in effect it would print
9632 $1 = @{it = Tree, form = @{...@}@}
9636 @code{set print union} affects programs written in C-like languages
9642 These settings are of interest when debugging C@t{++} programs:
9645 @cindex demangling C@t{++} names
9646 @item set print demangle
9647 @itemx set print demangle on
9648 Print C@t{++} names in their source form rather than in the encoded
9649 (``mangled'') form passed to the assembler and linker for type-safe
9650 linkage. The default is on.
9652 @item show print demangle
9653 Show whether C@t{++} names are printed in mangled or demangled form.
9655 @item set print asm-demangle
9656 @itemx set print asm-demangle on
9657 Print C@t{++} names in their source form rather than their mangled form, even
9658 in assembler code printouts such as instruction disassemblies.
9661 @item show print asm-demangle
9662 Show whether C@t{++} names in assembly listings are printed in mangled
9665 @cindex C@t{++} symbol decoding style
9666 @cindex symbol decoding style, C@t{++}
9667 @kindex set demangle-style
9668 @item set demangle-style @var{style}
9669 Choose among several encoding schemes used by different compilers to
9670 represent C@t{++} names. The choices for @var{style} are currently:
9674 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9675 This is the default.
9678 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9681 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9684 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9687 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9688 @strong{Warning:} this setting alone is not sufficient to allow
9689 debugging @code{cfront}-generated executables. @value{GDBN} would
9690 require further enhancement to permit that.
9693 If you omit @var{style}, you will see a list of possible formats.
9695 @item show demangle-style
9696 Display the encoding style currently in use for decoding C@t{++} symbols.
9698 @item set print object
9699 @itemx set print object on
9700 @cindex derived type of an object, printing
9701 @cindex display derived types
9702 When displaying a pointer to an object, identify the @emph{actual}
9703 (derived) type of the object rather than the @emph{declared} type, using
9704 the virtual function table. Note that the virtual function table is
9705 required---this feature can only work for objects that have run-time
9706 type identification; a single virtual method in the object's declared
9707 type is sufficient. Note that this setting is also taken into account when
9708 working with variable objects via MI (@pxref{GDB/MI}).
9710 @item set print object off
9711 Display only the declared type of objects, without reference to the
9712 virtual function table. This is the default setting.
9714 @item show print object
9715 Show whether actual, or declared, object types are displayed.
9717 @item set print static-members
9718 @itemx set print static-members on
9719 @cindex static members of C@t{++} objects
9720 Print static members when displaying a C@t{++} object. The default is on.
9722 @item set print static-members off
9723 Do not print static members when displaying a C@t{++} object.
9725 @item show print static-members
9726 Show whether C@t{++} static members are printed or not.
9728 @item set print pascal_static-members
9729 @itemx set print pascal_static-members on
9730 @cindex static members of Pascal objects
9731 @cindex Pascal objects, static members display
9732 Print static members when displaying a Pascal object. The default is on.
9734 @item set print pascal_static-members off
9735 Do not print static members when displaying a Pascal object.
9737 @item show print pascal_static-members
9738 Show whether Pascal static members are printed or not.
9740 @c These don't work with HP ANSI C++ yet.
9741 @item set print vtbl
9742 @itemx set print vtbl on
9743 @cindex pretty print C@t{++} virtual function tables
9744 @cindex virtual functions (C@t{++}) display
9745 @cindex VTBL display
9746 Pretty print C@t{++} virtual function tables. The default is off.
9747 (The @code{vtbl} commands do not work on programs compiled with the HP
9748 ANSI C@t{++} compiler (@code{aCC}).)
9750 @item set print vtbl off
9751 Do not pretty print C@t{++} virtual function tables.
9753 @item show print vtbl
9754 Show whether C@t{++} virtual function tables are pretty printed, or not.
9757 @node Pretty Printing
9758 @section Pretty Printing
9760 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9761 Python code. It greatly simplifies the display of complex objects. This
9762 mechanism works for both MI and the CLI.
9765 * Pretty-Printer Introduction:: Introduction to pretty-printers
9766 * Pretty-Printer Example:: An example pretty-printer
9767 * Pretty-Printer Commands:: Pretty-printer commands
9770 @node Pretty-Printer Introduction
9771 @subsection Pretty-Printer Introduction
9773 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9774 registered for the value. If there is then @value{GDBN} invokes the
9775 pretty-printer to print the value. Otherwise the value is printed normally.
9777 Pretty-printers are normally named. This makes them easy to manage.
9778 The @samp{info pretty-printer} command will list all the installed
9779 pretty-printers with their names.
9780 If a pretty-printer can handle multiple data types, then its
9781 @dfn{subprinters} are the printers for the individual data types.
9782 Each such subprinter has its own name.
9783 The format of the name is @var{printer-name};@var{subprinter-name}.
9785 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9786 Typically they are automatically loaded and registered when the corresponding
9787 debug information is loaded, thus making them available without having to
9788 do anything special.
9790 There are three places where a pretty-printer can be registered.
9794 Pretty-printers registered globally are available when debugging
9798 Pretty-printers registered with a program space are available only
9799 when debugging that program.
9800 @xref{Progspaces In Python}, for more details on program spaces in Python.
9803 Pretty-printers registered with an objfile are loaded and unloaded
9804 with the corresponding objfile (e.g., shared library).
9805 @xref{Objfiles In Python}, for more details on objfiles in Python.
9808 @xref{Selecting Pretty-Printers}, for further information on how
9809 pretty-printers are selected,
9811 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9814 @node Pretty-Printer Example
9815 @subsection Pretty-Printer Example
9817 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9820 (@value{GDBP}) print s
9822 static npos = 4294967295,
9824 <std::allocator<char>> = @{
9825 <__gnu_cxx::new_allocator<char>> = @{
9826 <No data fields>@}, <No data fields>
9828 members of std::basic_string<char, std::char_traits<char>,
9829 std::allocator<char> >::_Alloc_hider:
9830 _M_p = 0x804a014 "abcd"
9835 With a pretty-printer for @code{std::string} only the contents are printed:
9838 (@value{GDBP}) print s
9842 @node Pretty-Printer Commands
9843 @subsection Pretty-Printer Commands
9844 @cindex pretty-printer commands
9847 @kindex info pretty-printer
9848 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9849 Print the list of installed pretty-printers.
9850 This includes disabled pretty-printers, which are marked as such.
9852 @var{object-regexp} is a regular expression matching the objects
9853 whose pretty-printers to list.
9854 Objects can be @code{global}, the program space's file
9855 (@pxref{Progspaces In Python}),
9856 and the object files within that program space (@pxref{Objfiles In Python}).
9857 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9858 looks up a printer from these three objects.
9860 @var{name-regexp} is a regular expression matching the name of the printers
9863 @kindex disable pretty-printer
9864 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9865 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9866 A disabled pretty-printer is not forgotten, it may be enabled again later.
9868 @kindex enable pretty-printer
9869 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9870 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9875 Suppose we have three pretty-printers installed: one from library1.so
9876 named @code{foo} that prints objects of type @code{foo}, and
9877 another from library2.so named @code{bar} that prints two types of objects,
9878 @code{bar1} and @code{bar2}.
9881 (gdb) info pretty-printer
9888 (gdb) info pretty-printer library2
9893 (gdb) disable pretty-printer library1
9895 2 of 3 printers enabled
9896 (gdb) info pretty-printer
9903 (gdb) disable pretty-printer library2 bar:bar1
9905 1 of 3 printers enabled
9906 (gdb) info pretty-printer library2
9913 (gdb) disable pretty-printer library2 bar
9915 0 of 3 printers enabled
9916 (gdb) info pretty-printer library2
9925 Note that for @code{bar} the entire printer can be disabled,
9926 as can each individual subprinter.
9929 @section Value History
9931 @cindex value history
9932 @cindex history of values printed by @value{GDBN}
9933 Values printed by the @code{print} command are saved in the @value{GDBN}
9934 @dfn{value history}. This allows you to refer to them in other expressions.
9935 Values are kept until the symbol table is re-read or discarded
9936 (for example with the @code{file} or @code{symbol-file} commands).
9937 When the symbol table changes, the value history is discarded,
9938 since the values may contain pointers back to the types defined in the
9943 @cindex history number
9944 The values printed are given @dfn{history numbers} by which you can
9945 refer to them. These are successive integers starting with one.
9946 @code{print} shows you the history number assigned to a value by
9947 printing @samp{$@var{num} = } before the value; here @var{num} is the
9950 To refer to any previous value, use @samp{$} followed by the value's
9951 history number. The way @code{print} labels its output is designed to
9952 remind you of this. Just @code{$} refers to the most recent value in
9953 the history, and @code{$$} refers to the value before that.
9954 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9955 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9956 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9958 For example, suppose you have just printed a pointer to a structure and
9959 want to see the contents of the structure. It suffices to type
9965 If you have a chain of structures where the component @code{next} points
9966 to the next one, you can print the contents of the next one with this:
9973 You can print successive links in the chain by repeating this
9974 command---which you can do by just typing @key{RET}.
9976 Note that the history records values, not expressions. If the value of
9977 @code{x} is 4 and you type these commands:
9985 then the value recorded in the value history by the @code{print} command
9986 remains 4 even though the value of @code{x} has changed.
9991 Print the last ten values in the value history, with their item numbers.
9992 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9993 values} does not change the history.
9995 @item show values @var{n}
9996 Print ten history values centered on history item number @var{n}.
9999 Print ten history values just after the values last printed. If no more
10000 values are available, @code{show values +} produces no display.
10003 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10004 same effect as @samp{show values +}.
10006 @node Convenience Vars
10007 @section Convenience Variables
10009 @cindex convenience variables
10010 @cindex user-defined variables
10011 @value{GDBN} provides @dfn{convenience variables} that you can use within
10012 @value{GDBN} to hold on to a value and refer to it later. These variables
10013 exist entirely within @value{GDBN}; they are not part of your program, and
10014 setting a convenience variable has no direct effect on further execution
10015 of your program. That is why you can use them freely.
10017 Convenience variables are prefixed with @samp{$}. Any name preceded by
10018 @samp{$} can be used for a convenience variable, unless it is one of
10019 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10020 (Value history references, in contrast, are @emph{numbers} preceded
10021 by @samp{$}. @xref{Value History, ,Value History}.)
10023 You can save a value in a convenience variable with an assignment
10024 expression, just as you would set a variable in your program.
10028 set $foo = *object_ptr
10032 would save in @code{$foo} the value contained in the object pointed to by
10035 Using a convenience variable for the first time creates it, but its
10036 value is @code{void} until you assign a new value. You can alter the
10037 value with another assignment at any time.
10039 Convenience variables have no fixed types. You can assign a convenience
10040 variable any type of value, including structures and arrays, even if
10041 that variable already has a value of a different type. The convenience
10042 variable, when used as an expression, has the type of its current value.
10045 @kindex show convenience
10046 @cindex show all user variables and functions
10047 @item show convenience
10048 Print a list of convenience variables used so far, and their values,
10049 as well as a list of the convenience functions.
10050 Abbreviated @code{show conv}.
10052 @kindex init-if-undefined
10053 @cindex convenience variables, initializing
10054 @item init-if-undefined $@var{variable} = @var{expression}
10055 Set a convenience variable if it has not already been set. This is useful
10056 for user-defined commands that keep some state. It is similar, in concept,
10057 to using local static variables with initializers in C (except that
10058 convenience variables are global). It can also be used to allow users to
10059 override default values used in a command script.
10061 If the variable is already defined then the expression is not evaluated so
10062 any side-effects do not occur.
10065 One of the ways to use a convenience variable is as a counter to be
10066 incremented or a pointer to be advanced. For example, to print
10067 a field from successive elements of an array of structures:
10071 print bar[$i++]->contents
10075 Repeat that command by typing @key{RET}.
10077 Some convenience variables are created automatically by @value{GDBN} and given
10078 values likely to be useful.
10081 @vindex $_@r{, convenience variable}
10083 The variable @code{$_} is automatically set by the @code{x} command to
10084 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10085 commands which provide a default address for @code{x} to examine also
10086 set @code{$_} to that address; these commands include @code{info line}
10087 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10088 except when set by the @code{x} command, in which case it is a pointer
10089 to the type of @code{$__}.
10091 @vindex $__@r{, convenience variable}
10093 The variable @code{$__} is automatically set by the @code{x} command
10094 to the value found in the last address examined. Its type is chosen
10095 to match the format in which the data was printed.
10098 @vindex $_exitcode@r{, convenience variable}
10099 When the program being debugged terminates normally, @value{GDBN}
10100 automatically sets this variable to the exit code of the program, and
10101 resets @code{$_exitsignal} to @code{void}.
10104 @vindex $_exitsignal@r{, convenience variable}
10105 When the program being debugged dies due to an uncaught signal,
10106 @value{GDBN} automatically sets this variable to that signal's number,
10107 and resets @code{$_exitcode} to @code{void}.
10109 To distinguish between whether the program being debugged has exited
10110 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10111 @code{$_exitsignal} is not @code{void}), the convenience function
10112 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10113 Functions}). For example, considering the following source code:
10116 #include <signal.h>
10119 main (int argc, char *argv[])
10126 A valid way of telling whether the program being debugged has exited
10127 or signalled would be:
10130 (@value{GDBP}) define has_exited_or_signalled
10131 Type commands for definition of ``has_exited_or_signalled''.
10132 End with a line saying just ``end''.
10133 >if $_isvoid ($_exitsignal)
10134 >echo The program has exited\n
10136 >echo The program has signalled\n
10142 Program terminated with signal SIGALRM, Alarm clock.
10143 The program no longer exists.
10144 (@value{GDBP}) has_exited_or_signalled
10145 The program has signalled
10148 As can be seen, @value{GDBN} correctly informs that the program being
10149 debugged has signalled, since it calls @code{raise} and raises a
10150 @code{SIGALRM} signal. If the program being debugged had not called
10151 @code{raise}, then @value{GDBN} would report a normal exit:
10154 (@value{GDBP}) has_exited_or_signalled
10155 The program has exited
10159 The variable @code{$_exception} is set to the exception object being
10160 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10163 @itemx $_probe_arg0@dots{}$_probe_arg11
10164 Arguments to a static probe. @xref{Static Probe Points}.
10167 @vindex $_sdata@r{, inspect, convenience variable}
10168 The variable @code{$_sdata} contains extra collected static tracepoint
10169 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10170 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10171 if extra static tracepoint data has not been collected.
10174 @vindex $_siginfo@r{, convenience variable}
10175 The variable @code{$_siginfo} contains extra signal information
10176 (@pxref{extra signal information}). Note that @code{$_siginfo}
10177 could be empty, if the application has not yet received any signals.
10178 For example, it will be empty before you execute the @code{run} command.
10181 @vindex $_tlb@r{, convenience variable}
10182 The variable @code{$_tlb} is automatically set when debugging
10183 applications running on MS-Windows in native mode or connected to
10184 gdbserver that supports the @code{qGetTIBAddr} request.
10185 @xref{General Query Packets}.
10186 This variable contains the address of the thread information block.
10190 On HP-UX systems, if you refer to a function or variable name that
10191 begins with a dollar sign, @value{GDBN} searches for a user or system
10192 name first, before it searches for a convenience variable.
10194 @node Convenience Funs
10195 @section Convenience Functions
10197 @cindex convenience functions
10198 @value{GDBN} also supplies some @dfn{convenience functions}. These
10199 have a syntax similar to convenience variables. A convenience
10200 function can be used in an expression just like an ordinary function;
10201 however, a convenience function is implemented internally to
10204 These functions do not require @value{GDBN} to be configured with
10205 @code{Python} support, which means that they are always available.
10209 @item $_isvoid (@var{expr})
10210 @findex $_isvoid@r{, convenience function}
10211 Return one if the expression @var{expr} is @code{void}. Otherwise it
10214 A @code{void} expression is an expression where the type of the result
10215 is @code{void}. For example, you can examine a convenience variable
10216 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10220 (@value{GDBP}) print $_exitcode
10222 (@value{GDBP}) print $_isvoid ($_exitcode)
10225 Starting program: ./a.out
10226 [Inferior 1 (process 29572) exited normally]
10227 (@value{GDBP}) print $_exitcode
10229 (@value{GDBP}) print $_isvoid ($_exitcode)
10233 In the example above, we used @code{$_isvoid} to check whether
10234 @code{$_exitcode} is @code{void} before and after the execution of the
10235 program being debugged. Before the execution there is no exit code to
10236 be examined, therefore @code{$_exitcode} is @code{void}. After the
10237 execution the program being debugged returned zero, therefore
10238 @code{$_exitcode} is zero, which means that it is not @code{void}
10241 The @code{void} expression can also be a call of a function from the
10242 program being debugged. For example, given the following function:
10251 The result of calling it inside @value{GDBN} is @code{void}:
10254 (@value{GDBP}) print foo ()
10256 (@value{GDBP}) print $_isvoid (foo ())
10258 (@value{GDBP}) set $v = foo ()
10259 (@value{GDBP}) print $v
10261 (@value{GDBP}) print $_isvoid ($v)
10267 These functions require @value{GDBN} to be configured with
10268 @code{Python} support.
10272 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10273 @findex $_memeq@r{, convenience function}
10274 Returns one if the @var{length} bytes at the addresses given by
10275 @var{buf1} and @var{buf2} are equal.
10276 Otherwise it returns zero.
10278 @item $_regex(@var{str}, @var{regex})
10279 @findex $_regex@r{, convenience function}
10280 Returns one if the string @var{str} matches the regular expression
10281 @var{regex}. Otherwise it returns zero.
10282 The syntax of the regular expression is that specified by @code{Python}'s
10283 regular expression support.
10285 @item $_streq(@var{str1}, @var{str2})
10286 @findex $_streq@r{, convenience function}
10287 Returns one if the strings @var{str1} and @var{str2} are equal.
10288 Otherwise it returns zero.
10290 @item $_strlen(@var{str})
10291 @findex $_strlen@r{, convenience function}
10292 Returns the length of string @var{str}.
10294 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10295 @findex $_caller_is@r{, convenience function}
10296 Returns one if the calling function's name is equal to @var{name}.
10297 Otherwise it returns zero.
10299 If the optional argument @var{number_of_frames} is provided,
10300 it is the number of frames up in the stack to look.
10308 at testsuite/gdb.python/py-caller-is.c:21
10309 #1 0x00000000004005a0 in middle_func ()
10310 at testsuite/gdb.python/py-caller-is.c:27
10311 #2 0x00000000004005ab in top_func ()
10312 at testsuite/gdb.python/py-caller-is.c:33
10313 #3 0x00000000004005b6 in main ()
10314 at testsuite/gdb.python/py-caller-is.c:39
10315 (gdb) print $_caller_is ("middle_func")
10317 (gdb) print $_caller_is ("top_func", 2)
10321 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10322 @findex $_caller_matches@r{, convenience function}
10323 Returns one if the calling function's name matches the regular expression
10324 @var{regexp}. Otherwise it returns zero.
10326 If the optional argument @var{number_of_frames} is provided,
10327 it is the number of frames up in the stack to look.
10330 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10331 @findex $_any_caller_is@r{, convenience function}
10332 Returns one if any calling function's name is equal to @var{name}.
10333 Otherwise it returns zero.
10335 If the optional argument @var{number_of_frames} is provided,
10336 it is the number of frames up in the stack to look.
10339 This function differs from @code{$_caller_is} in that this function
10340 checks all stack frames from the immediate caller to the frame specified
10341 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10342 frame specified by @var{number_of_frames}.
10344 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10345 @findex $_any_caller_matches@r{, convenience function}
10346 Returns one if any calling function's name matches the regular expression
10347 @var{regexp}. Otherwise it returns zero.
10349 If the optional argument @var{number_of_frames} is provided,
10350 it is the number of frames up in the stack to look.
10353 This function differs from @code{$_caller_matches} in that this function
10354 checks all stack frames from the immediate caller to the frame specified
10355 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10356 frame specified by @var{number_of_frames}.
10360 @value{GDBN} provides the ability to list and get help on
10361 convenience functions.
10364 @item help function
10365 @kindex help function
10366 @cindex show all convenience functions
10367 Print a list of all convenience functions.
10374 You can refer to machine register contents, in expressions, as variables
10375 with names starting with @samp{$}. The names of registers are different
10376 for each machine; use @code{info registers} to see the names used on
10380 @kindex info registers
10381 @item info registers
10382 Print the names and values of all registers except floating-point
10383 and vector registers (in the selected stack frame).
10385 @kindex info all-registers
10386 @cindex floating point registers
10387 @item info all-registers
10388 Print the names and values of all registers, including floating-point
10389 and vector registers (in the selected stack frame).
10391 @item info registers @var{regname} @dots{}
10392 Print the @dfn{relativized} value of each specified register @var{regname}.
10393 As discussed in detail below, register values are normally relative to
10394 the selected stack frame. The @var{regname} may be any register name valid on
10395 the machine you are using, with or without the initial @samp{$}.
10398 @anchor{standard registers}
10399 @cindex stack pointer register
10400 @cindex program counter register
10401 @cindex process status register
10402 @cindex frame pointer register
10403 @cindex standard registers
10404 @value{GDBN} has four ``standard'' register names that are available (in
10405 expressions) on most machines---whenever they do not conflict with an
10406 architecture's canonical mnemonics for registers. The register names
10407 @code{$pc} and @code{$sp} are used for the program counter register and
10408 the stack pointer. @code{$fp} is used for a register that contains a
10409 pointer to the current stack frame, and @code{$ps} is used for a
10410 register that contains the processor status. For example,
10411 you could print the program counter in hex with
10418 or print the instruction to be executed next with
10425 or add four to the stack pointer@footnote{This is a way of removing
10426 one word from the stack, on machines where stacks grow downward in
10427 memory (most machines, nowadays). This assumes that the innermost
10428 stack frame is selected; setting @code{$sp} is not allowed when other
10429 stack frames are selected. To pop entire frames off the stack,
10430 regardless of machine architecture, use @code{return};
10431 see @ref{Returning, ,Returning from a Function}.} with
10437 Whenever possible, these four standard register names are available on
10438 your machine even though the machine has different canonical mnemonics,
10439 so long as there is no conflict. The @code{info registers} command
10440 shows the canonical names. For example, on the SPARC, @code{info
10441 registers} displays the processor status register as @code{$psr} but you
10442 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10443 is an alias for the @sc{eflags} register.
10445 @value{GDBN} always considers the contents of an ordinary register as an
10446 integer when the register is examined in this way. Some machines have
10447 special registers which can hold nothing but floating point; these
10448 registers are considered to have floating point values. There is no way
10449 to refer to the contents of an ordinary register as floating point value
10450 (although you can @emph{print} it as a floating point value with
10451 @samp{print/f $@var{regname}}).
10453 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10454 means that the data format in which the register contents are saved by
10455 the operating system is not the same one that your program normally
10456 sees. For example, the registers of the 68881 floating point
10457 coprocessor are always saved in ``extended'' (raw) format, but all C
10458 programs expect to work with ``double'' (virtual) format. In such
10459 cases, @value{GDBN} normally works with the virtual format only (the format
10460 that makes sense for your program), but the @code{info registers} command
10461 prints the data in both formats.
10463 @cindex SSE registers (x86)
10464 @cindex MMX registers (x86)
10465 Some machines have special registers whose contents can be interpreted
10466 in several different ways. For example, modern x86-based machines
10467 have SSE and MMX registers that can hold several values packed
10468 together in several different formats. @value{GDBN} refers to such
10469 registers in @code{struct} notation:
10472 (@value{GDBP}) print $xmm1
10474 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10475 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10476 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10477 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10478 v4_int32 = @{0, 20657912, 11, 13@},
10479 v2_int64 = @{88725056443645952, 55834574859@},
10480 uint128 = 0x0000000d0000000b013b36f800000000
10485 To set values of such registers, you need to tell @value{GDBN} which
10486 view of the register you wish to change, as if you were assigning
10487 value to a @code{struct} member:
10490 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10493 Normally, register values are relative to the selected stack frame
10494 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10495 value that the register would contain if all stack frames farther in
10496 were exited and their saved registers restored. In order to see the
10497 true contents of hardware registers, you must select the innermost
10498 frame (with @samp{frame 0}).
10500 @cindex caller-saved registers
10501 @cindex call-clobbered registers
10502 @cindex volatile registers
10503 @cindex <not saved> values
10504 Usually ABIs reserve some registers as not needed to be saved by the
10505 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10506 registers). It may therefore not be possible for @value{GDBN} to know
10507 the value a register had before the call (in other words, in the outer
10508 frame), if the register value has since been changed by the callee.
10509 @value{GDBN} tries to deduce where the inner frame saved
10510 (``callee-saved'') registers, from the debug info, unwind info, or the
10511 machine code generated by your compiler. If some register is not
10512 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10513 its own knowledge of the ABI, or because the debug/unwind info
10514 explicitly says the register's value is undefined), @value{GDBN}
10515 displays @w{@samp{<not saved>}} as the register's value. With targets
10516 that @value{GDBN} has no knowledge of the register saving convention,
10517 if a register was not saved by the callee, then its value and location
10518 in the outer frame are assumed to be the same of the inner frame.
10519 This is usually harmless, because if the register is call-clobbered,
10520 the caller either does not care what is in the register after the
10521 call, or has code to restore the value that it does care about. Note,
10522 however, that if you change such a register in the outer frame, you
10523 may also be affecting the inner frame. Also, the more ``outer'' the
10524 frame is you're looking at, the more likely a call-clobbered
10525 register's value is to be wrong, in the sense that it doesn't actually
10526 represent the value the register had just before the call.
10528 @node Floating Point Hardware
10529 @section Floating Point Hardware
10530 @cindex floating point
10532 Depending on the configuration, @value{GDBN} may be able to give
10533 you more information about the status of the floating point hardware.
10538 Display hardware-dependent information about the floating
10539 point unit. The exact contents and layout vary depending on the
10540 floating point chip. Currently, @samp{info float} is supported on
10541 the ARM and x86 machines.
10545 @section Vector Unit
10546 @cindex vector unit
10548 Depending on the configuration, @value{GDBN} may be able to give you
10549 more information about the status of the vector unit.
10552 @kindex info vector
10554 Display information about the vector unit. The exact contents and
10555 layout vary depending on the hardware.
10558 @node OS Information
10559 @section Operating System Auxiliary Information
10560 @cindex OS information
10562 @value{GDBN} provides interfaces to useful OS facilities that can help
10563 you debug your program.
10565 @cindex auxiliary vector
10566 @cindex vector, auxiliary
10567 Some operating systems supply an @dfn{auxiliary vector} to programs at
10568 startup. This is akin to the arguments and environment that you
10569 specify for a program, but contains a system-dependent variety of
10570 binary values that tell system libraries important details about the
10571 hardware, operating system, and process. Each value's purpose is
10572 identified by an integer tag; the meanings are well-known but system-specific.
10573 Depending on the configuration and operating system facilities,
10574 @value{GDBN} may be able to show you this information. For remote
10575 targets, this functionality may further depend on the remote stub's
10576 support of the @samp{qXfer:auxv:read} packet, see
10577 @ref{qXfer auxiliary vector read}.
10582 Display the auxiliary vector of the inferior, which can be either a
10583 live process or a core dump file. @value{GDBN} prints each tag value
10584 numerically, and also shows names and text descriptions for recognized
10585 tags. Some values in the vector are numbers, some bit masks, and some
10586 pointers to strings or other data. @value{GDBN} displays each value in the
10587 most appropriate form for a recognized tag, and in hexadecimal for
10588 an unrecognized tag.
10591 On some targets, @value{GDBN} can access operating system-specific
10592 information and show it to you. The types of information available
10593 will differ depending on the type of operating system running on the
10594 target. The mechanism used to fetch the data is described in
10595 @ref{Operating System Information}. For remote targets, this
10596 functionality depends on the remote stub's support of the
10597 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10601 @item info os @var{infotype}
10603 Display OS information of the requested type.
10605 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10607 @anchor{linux info os infotypes}
10609 @kindex info os cpus
10611 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10612 the available fields from /proc/cpuinfo. For each supported architecture
10613 different fields are available. Two common entries are processor which gives
10614 CPU number and bogomips; a system constant that is calculated during
10615 kernel initialization.
10617 @kindex info os files
10619 Display the list of open file descriptors on the target. For each
10620 file descriptor, @value{GDBN} prints the identifier of the process
10621 owning the descriptor, the command of the owning process, the value
10622 of the descriptor, and the target of the descriptor.
10624 @kindex info os modules
10626 Display the list of all loaded kernel modules on the target. For each
10627 module, @value{GDBN} prints the module name, the size of the module in
10628 bytes, the number of times the module is used, the dependencies of the
10629 module, the status of the module, and the address of the loaded module
10632 @kindex info os msg
10634 Display the list of all System V message queues on the target. For each
10635 message queue, @value{GDBN} prints the message queue key, the message
10636 queue identifier, the access permissions, the current number of bytes
10637 on the queue, the current number of messages on the queue, the processes
10638 that last sent and received a message on the queue, the user and group
10639 of the owner and creator of the message queue, the times at which a
10640 message was last sent and received on the queue, and the time at which
10641 the message queue was last changed.
10643 @kindex info os processes
10645 Display the list of processes on the target. For each process,
10646 @value{GDBN} prints the process identifier, the name of the user, the
10647 command corresponding to the process, and the list of processor cores
10648 that the process is currently running on. (To understand what these
10649 properties mean, for this and the following info types, please consult
10650 the general @sc{gnu}/Linux documentation.)
10652 @kindex info os procgroups
10654 Display the list of process groups on the target. For each process,
10655 @value{GDBN} prints the identifier of the process group that it belongs
10656 to, the command corresponding to the process group leader, the process
10657 identifier, and the command line of the process. The list is sorted
10658 first by the process group identifier, then by the process identifier,
10659 so that processes belonging to the same process group are grouped together
10660 and the process group leader is listed first.
10662 @kindex info os semaphores
10664 Display the list of all System V semaphore sets on the target. For each
10665 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10666 set identifier, the access permissions, the number of semaphores in the
10667 set, the user and group of the owner and creator of the semaphore set,
10668 and the times at which the semaphore set was operated upon and changed.
10670 @kindex info os shm
10672 Display the list of all System V shared-memory regions on the target.
10673 For each shared-memory region, @value{GDBN} prints the region key,
10674 the shared-memory identifier, the access permissions, the size of the
10675 region, the process that created the region, the process that last
10676 attached to or detached from the region, the current number of live
10677 attaches to the region, and the times at which the region was last
10678 attached to, detach from, and changed.
10680 @kindex info os sockets
10682 Display the list of Internet-domain sockets on the target. For each
10683 socket, @value{GDBN} prints the address and port of the local and
10684 remote endpoints, the current state of the connection, the creator of
10685 the socket, the IP address family of the socket, and the type of the
10688 @kindex info os threads
10690 Display the list of threads running on the target. For each thread,
10691 @value{GDBN} prints the identifier of the process that the thread
10692 belongs to, the command of the process, the thread identifier, and the
10693 processor core that it is currently running on. The main thread of a
10694 process is not listed.
10698 If @var{infotype} is omitted, then list the possible values for
10699 @var{infotype} and the kind of OS information available for each
10700 @var{infotype}. If the target does not return a list of possible
10701 types, this command will report an error.
10704 @node Memory Region Attributes
10705 @section Memory Region Attributes
10706 @cindex memory region attributes
10708 @dfn{Memory region attributes} allow you to describe special handling
10709 required by regions of your target's memory. @value{GDBN} uses
10710 attributes to determine whether to allow certain types of memory
10711 accesses; whether to use specific width accesses; and whether to cache
10712 target memory. By default the description of memory regions is
10713 fetched from the target (if the current target supports this), but the
10714 user can override the fetched regions.
10716 Defined memory regions can be individually enabled and disabled. When a
10717 memory region is disabled, @value{GDBN} uses the default attributes when
10718 accessing memory in that region. Similarly, if no memory regions have
10719 been defined, @value{GDBN} uses the default attributes when accessing
10722 When a memory region is defined, it is given a number to identify it;
10723 to enable, disable, or remove a memory region, you specify that number.
10727 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10728 Define a memory region bounded by @var{lower} and @var{upper} with
10729 attributes @var{attributes}@dots{}, and add it to the list of regions
10730 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10731 case: it is treated as the target's maximum memory address.
10732 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10735 Discard any user changes to the memory regions and use target-supplied
10736 regions, if available, or no regions if the target does not support.
10739 @item delete mem @var{nums}@dots{}
10740 Remove memory regions @var{nums}@dots{} from the list of regions
10741 monitored by @value{GDBN}.
10743 @kindex disable mem
10744 @item disable mem @var{nums}@dots{}
10745 Disable monitoring of memory regions @var{nums}@dots{}.
10746 A disabled memory region is not forgotten.
10747 It may be enabled again later.
10750 @item enable mem @var{nums}@dots{}
10751 Enable monitoring of memory regions @var{nums}@dots{}.
10755 Print a table of all defined memory regions, with the following columns
10759 @item Memory Region Number
10760 @item Enabled or Disabled.
10761 Enabled memory regions are marked with @samp{y}.
10762 Disabled memory regions are marked with @samp{n}.
10765 The address defining the inclusive lower bound of the memory region.
10768 The address defining the exclusive upper bound of the memory region.
10771 The list of attributes set for this memory region.
10776 @subsection Attributes
10778 @subsubsection Memory Access Mode
10779 The access mode attributes set whether @value{GDBN} may make read or
10780 write accesses to a memory region.
10782 While these attributes prevent @value{GDBN} from performing invalid
10783 memory accesses, they do nothing to prevent the target system, I/O DMA,
10784 etc.@: from accessing memory.
10788 Memory is read only.
10790 Memory is write only.
10792 Memory is read/write. This is the default.
10795 @subsubsection Memory Access Size
10796 The access size attribute tells @value{GDBN} to use specific sized
10797 accesses in the memory region. Often memory mapped device registers
10798 require specific sized accesses. If no access size attribute is
10799 specified, @value{GDBN} may use accesses of any size.
10803 Use 8 bit memory accesses.
10805 Use 16 bit memory accesses.
10807 Use 32 bit memory accesses.
10809 Use 64 bit memory accesses.
10812 @c @subsubsection Hardware/Software Breakpoints
10813 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10814 @c will use hardware or software breakpoints for the internal breakpoints
10815 @c used by the step, next, finish, until, etc. commands.
10819 @c Always use hardware breakpoints
10820 @c @item swbreak (default)
10823 @subsubsection Data Cache
10824 The data cache attributes set whether @value{GDBN} will cache target
10825 memory. While this generally improves performance by reducing debug
10826 protocol overhead, it can lead to incorrect results because @value{GDBN}
10827 does not know about volatile variables or memory mapped device
10832 Enable @value{GDBN} to cache target memory.
10834 Disable @value{GDBN} from caching target memory. This is the default.
10837 @subsection Memory Access Checking
10838 @value{GDBN} can be instructed to refuse accesses to memory that is
10839 not explicitly described. This can be useful if accessing such
10840 regions has undesired effects for a specific target, or to provide
10841 better error checking. The following commands control this behaviour.
10844 @kindex set mem inaccessible-by-default
10845 @item set mem inaccessible-by-default [on|off]
10846 If @code{on} is specified, make @value{GDBN} treat memory not
10847 explicitly described by the memory ranges as non-existent and refuse accesses
10848 to such memory. The checks are only performed if there's at least one
10849 memory range defined. If @code{off} is specified, make @value{GDBN}
10850 treat the memory not explicitly described by the memory ranges as RAM.
10851 The default value is @code{on}.
10852 @kindex show mem inaccessible-by-default
10853 @item show mem inaccessible-by-default
10854 Show the current handling of accesses to unknown memory.
10858 @c @subsubsection Memory Write Verification
10859 @c The memory write verification attributes set whether @value{GDBN}
10860 @c will re-reads data after each write to verify the write was successful.
10864 @c @item noverify (default)
10867 @node Dump/Restore Files
10868 @section Copy Between Memory and a File
10869 @cindex dump/restore files
10870 @cindex append data to a file
10871 @cindex dump data to a file
10872 @cindex restore data from a file
10874 You can use the commands @code{dump}, @code{append}, and
10875 @code{restore} to copy data between target memory and a file. The
10876 @code{dump} and @code{append} commands write data to a file, and the
10877 @code{restore} command reads data from a file back into the inferior's
10878 memory. Files may be in binary, Motorola S-record, Intel hex, or
10879 Tektronix Hex format; however, @value{GDBN} can only append to binary
10885 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10886 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10887 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10888 or the value of @var{expr}, to @var{filename} in the given format.
10890 The @var{format} parameter may be any one of:
10897 Motorola S-record format.
10899 Tektronix Hex format.
10902 @value{GDBN} uses the same definitions of these formats as the
10903 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10904 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10908 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10909 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10910 Append the contents of memory from @var{start_addr} to @var{end_addr},
10911 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10912 (@value{GDBN} can only append data to files in raw binary form.)
10915 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10916 Restore the contents of file @var{filename} into memory. The
10917 @code{restore} command can automatically recognize any known @sc{bfd}
10918 file format, except for raw binary. To restore a raw binary file you
10919 must specify the optional keyword @code{binary} after the filename.
10921 If @var{bias} is non-zero, its value will be added to the addresses
10922 contained in the file. Binary files always start at address zero, so
10923 they will be restored at address @var{bias}. Other bfd files have
10924 a built-in location; they will be restored at offset @var{bias}
10925 from that location.
10927 If @var{start} and/or @var{end} are non-zero, then only data between
10928 file offset @var{start} and file offset @var{end} will be restored.
10929 These offsets are relative to the addresses in the file, before
10930 the @var{bias} argument is applied.
10934 @node Core File Generation
10935 @section How to Produce a Core File from Your Program
10936 @cindex dump core from inferior
10938 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10939 image of a running process and its process status (register values
10940 etc.). Its primary use is post-mortem debugging of a program that
10941 crashed while it ran outside a debugger. A program that crashes
10942 automatically produces a core file, unless this feature is disabled by
10943 the user. @xref{Files}, for information on invoking @value{GDBN} in
10944 the post-mortem debugging mode.
10946 Occasionally, you may wish to produce a core file of the program you
10947 are debugging in order to preserve a snapshot of its state.
10948 @value{GDBN} has a special command for that.
10952 @kindex generate-core-file
10953 @item generate-core-file [@var{file}]
10954 @itemx gcore [@var{file}]
10955 Produce a core dump of the inferior process. The optional argument
10956 @var{file} specifies the file name where to put the core dump. If not
10957 specified, the file name defaults to @file{core.@var{pid}}, where
10958 @var{pid} is the inferior process ID.
10960 Note that this command is implemented only for some systems (as of
10961 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10963 On @sc{gnu}/Linux, this command can take into account the value of the
10964 file @file{/proc/@var{pid}/coredump_filter} when generating the core
10965 dump (@pxref{set use-coredump-filter}).
10967 @kindex set use-coredump-filter
10968 @anchor{set use-coredump-filter}
10969 @item set use-coredump-filter on
10970 @itemx set use-coredump-filter off
10971 Enable or disable the use of the file
10972 @file{/proc/@var{pid}/coredump_filter} when generating core dump
10973 files. This file is used by the Linux kernel to decide what types of
10974 memory mappings will be dumped or ignored when generating a core dump
10975 file. @var{pid} is the process ID of a currently running process.
10977 To make use of this feature, you have to write in the
10978 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
10979 which is a bit mask representing the memory mapping types. If a bit
10980 is set in the bit mask, then the memory mappings of the corresponding
10981 types will be dumped; otherwise, they will be ignored. This
10982 configuration is inherited by child processes. For more information
10983 about the bits that can be set in the
10984 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
10985 manpage of @code{core(5)}.
10987 By default, this option is @code{on}. If this option is turned
10988 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
10989 and instead uses the same default value as the Linux kernel in order
10990 to decide which pages will be dumped in the core dump file. This
10991 value is currently @code{0x33}, which means that bits @code{0}
10992 (anonymous private mappings), @code{1} (anonymous shared mappings),
10993 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
10994 This will cause these memory mappings to be dumped automatically.
10997 @node Character Sets
10998 @section Character Sets
10999 @cindex character sets
11001 @cindex translating between character sets
11002 @cindex host character set
11003 @cindex target character set
11005 If the program you are debugging uses a different character set to
11006 represent characters and strings than the one @value{GDBN} uses itself,
11007 @value{GDBN} can automatically translate between the character sets for
11008 you. The character set @value{GDBN} uses we call the @dfn{host
11009 character set}; the one the inferior program uses we call the
11010 @dfn{target character set}.
11012 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11013 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11014 remote protocol (@pxref{Remote Debugging}) to debug a program
11015 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11016 then the host character set is Latin-1, and the target character set is
11017 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11018 target-charset EBCDIC-US}, then @value{GDBN} translates between
11019 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11020 character and string literals in expressions.
11022 @value{GDBN} has no way to automatically recognize which character set
11023 the inferior program uses; you must tell it, using the @code{set
11024 target-charset} command, described below.
11026 Here are the commands for controlling @value{GDBN}'s character set
11030 @item set target-charset @var{charset}
11031 @kindex set target-charset
11032 Set the current target character set to @var{charset}. To display the
11033 list of supported target character sets, type
11034 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11036 @item set host-charset @var{charset}
11037 @kindex set host-charset
11038 Set the current host character set to @var{charset}.
11040 By default, @value{GDBN} uses a host character set appropriate to the
11041 system it is running on; you can override that default using the
11042 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11043 automatically determine the appropriate host character set. In this
11044 case, @value{GDBN} uses @samp{UTF-8}.
11046 @value{GDBN} can only use certain character sets as its host character
11047 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11048 @value{GDBN} will list the host character sets it supports.
11050 @item set charset @var{charset}
11051 @kindex set charset
11052 Set the current host and target character sets to @var{charset}. As
11053 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11054 @value{GDBN} will list the names of the character sets that can be used
11055 for both host and target.
11058 @kindex show charset
11059 Show the names of the current host and target character sets.
11061 @item show host-charset
11062 @kindex show host-charset
11063 Show the name of the current host character set.
11065 @item show target-charset
11066 @kindex show target-charset
11067 Show the name of the current target character set.
11069 @item set target-wide-charset @var{charset}
11070 @kindex set target-wide-charset
11071 Set the current target's wide character set to @var{charset}. This is
11072 the character set used by the target's @code{wchar_t} type. To
11073 display the list of supported wide character sets, type
11074 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11076 @item show target-wide-charset
11077 @kindex show target-wide-charset
11078 Show the name of the current target's wide character set.
11081 Here is an example of @value{GDBN}'s character set support in action.
11082 Assume that the following source code has been placed in the file
11083 @file{charset-test.c}:
11089 = @{72, 101, 108, 108, 111, 44, 32, 119,
11090 111, 114, 108, 100, 33, 10, 0@};
11091 char ibm1047_hello[]
11092 = @{200, 133, 147, 147, 150, 107, 64, 166,
11093 150, 153, 147, 132, 90, 37, 0@};
11097 printf ("Hello, world!\n");
11101 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11102 containing the string @samp{Hello, world!} followed by a newline,
11103 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11105 We compile the program, and invoke the debugger on it:
11108 $ gcc -g charset-test.c -o charset-test
11109 $ gdb -nw charset-test
11110 GNU gdb 2001-12-19-cvs
11111 Copyright 2001 Free Software Foundation, Inc.
11116 We can use the @code{show charset} command to see what character sets
11117 @value{GDBN} is currently using to interpret and display characters and
11121 (@value{GDBP}) show charset
11122 The current host and target character set is `ISO-8859-1'.
11126 For the sake of printing this manual, let's use @sc{ascii} as our
11127 initial character set:
11129 (@value{GDBP}) set charset ASCII
11130 (@value{GDBP}) show charset
11131 The current host and target character set is `ASCII'.
11135 Let's assume that @sc{ascii} is indeed the correct character set for our
11136 host system --- in other words, let's assume that if @value{GDBN} prints
11137 characters using the @sc{ascii} character set, our terminal will display
11138 them properly. Since our current target character set is also
11139 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11142 (@value{GDBP}) print ascii_hello
11143 $1 = 0x401698 "Hello, world!\n"
11144 (@value{GDBP}) print ascii_hello[0]
11149 @value{GDBN} uses the target character set for character and string
11150 literals you use in expressions:
11153 (@value{GDBP}) print '+'
11158 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11161 @value{GDBN} relies on the user to tell it which character set the
11162 target program uses. If we print @code{ibm1047_hello} while our target
11163 character set is still @sc{ascii}, we get jibberish:
11166 (@value{GDBP}) print ibm1047_hello
11167 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11168 (@value{GDBP}) print ibm1047_hello[0]
11173 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11174 @value{GDBN} tells us the character sets it supports:
11177 (@value{GDBP}) set target-charset
11178 ASCII EBCDIC-US IBM1047 ISO-8859-1
11179 (@value{GDBP}) set target-charset
11182 We can select @sc{ibm1047} as our target character set, and examine the
11183 program's strings again. Now the @sc{ascii} string is wrong, but
11184 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11185 target character set, @sc{ibm1047}, to the host character set,
11186 @sc{ascii}, and they display correctly:
11189 (@value{GDBP}) set target-charset IBM1047
11190 (@value{GDBP}) show charset
11191 The current host character set is `ASCII'.
11192 The current target character set is `IBM1047'.
11193 (@value{GDBP}) print ascii_hello
11194 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11195 (@value{GDBP}) print ascii_hello[0]
11197 (@value{GDBP}) print ibm1047_hello
11198 $8 = 0x4016a8 "Hello, world!\n"
11199 (@value{GDBP}) print ibm1047_hello[0]
11204 As above, @value{GDBN} uses the target character set for character and
11205 string literals you use in expressions:
11208 (@value{GDBP}) print '+'
11213 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11216 @node Caching Target Data
11217 @section Caching Data of Targets
11218 @cindex caching data of targets
11220 @value{GDBN} caches data exchanged between the debugger and a target.
11221 Each cache is associated with the address space of the inferior.
11222 @xref{Inferiors and Programs}, about inferior and address space.
11223 Such caching generally improves performance in remote debugging
11224 (@pxref{Remote Debugging}), because it reduces the overhead of the
11225 remote protocol by bundling memory reads and writes into large chunks.
11226 Unfortunately, simply caching everything would lead to incorrect results,
11227 since @value{GDBN} does not necessarily know anything about volatile
11228 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11229 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11231 Therefore, by default, @value{GDBN} only caches data
11232 known to be on the stack@footnote{In non-stop mode, it is moderately
11233 rare for a running thread to modify the stack of a stopped thread
11234 in a way that would interfere with a backtrace, and caching of
11235 stack reads provides a significant speed up of remote backtraces.} or
11236 in the code segment.
11237 Other regions of memory can be explicitly marked as
11238 cacheable; @pxref{Memory Region Attributes}.
11241 @kindex set remotecache
11242 @item set remotecache on
11243 @itemx set remotecache off
11244 This option no longer does anything; it exists for compatibility
11247 @kindex show remotecache
11248 @item show remotecache
11249 Show the current state of the obsolete remotecache flag.
11251 @kindex set stack-cache
11252 @item set stack-cache on
11253 @itemx set stack-cache off
11254 Enable or disable caching of stack accesses. When @code{on}, use
11255 caching. By default, this option is @code{on}.
11257 @kindex show stack-cache
11258 @item show stack-cache
11259 Show the current state of data caching for memory accesses.
11261 @kindex set code-cache
11262 @item set code-cache on
11263 @itemx set code-cache off
11264 Enable or disable caching of code segment accesses. When @code{on},
11265 use caching. By default, this option is @code{on}. This improves
11266 performance of disassembly in remote debugging.
11268 @kindex show code-cache
11269 @item show code-cache
11270 Show the current state of target memory cache for code segment
11273 @kindex info dcache
11274 @item info dcache @r{[}line@r{]}
11275 Print the information about the performance of data cache of the
11276 current inferior's address space. The information displayed
11277 includes the dcache width and depth, and for each cache line, its
11278 number, address, and how many times it was referenced. This
11279 command is useful for debugging the data cache operation.
11281 If a line number is specified, the contents of that line will be
11284 @item set dcache size @var{size}
11285 @cindex dcache size
11286 @kindex set dcache size
11287 Set maximum number of entries in dcache (dcache depth above).
11289 @item set dcache line-size @var{line-size}
11290 @cindex dcache line-size
11291 @kindex set dcache line-size
11292 Set number of bytes each dcache entry caches (dcache width above).
11293 Must be a power of 2.
11295 @item show dcache size
11296 @kindex show dcache size
11297 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11299 @item show dcache line-size
11300 @kindex show dcache line-size
11301 Show default size of dcache lines.
11305 @node Searching Memory
11306 @section Search Memory
11307 @cindex searching memory
11309 Memory can be searched for a particular sequence of bytes with the
11310 @code{find} command.
11314 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11315 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11316 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11317 etc. The search begins at address @var{start_addr} and continues for either
11318 @var{len} bytes or through to @var{end_addr} inclusive.
11321 @var{s} and @var{n} are optional parameters.
11322 They may be specified in either order, apart or together.
11325 @item @var{s}, search query size
11326 The size of each search query value.
11332 halfwords (two bytes)
11336 giant words (eight bytes)
11339 All values are interpreted in the current language.
11340 This means, for example, that if the current source language is C/C@t{++}
11341 then searching for the string ``hello'' includes the trailing '\0'.
11343 If the value size is not specified, it is taken from the
11344 value's type in the current language.
11345 This is useful when one wants to specify the search
11346 pattern as a mixture of types.
11347 Note that this means, for example, that in the case of C-like languages
11348 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11349 which is typically four bytes.
11351 @item @var{n}, maximum number of finds
11352 The maximum number of matches to print. The default is to print all finds.
11355 You can use strings as search values. Quote them with double-quotes
11357 The string value is copied into the search pattern byte by byte,
11358 regardless of the endianness of the target and the size specification.
11360 The address of each match found is printed as well as a count of the
11361 number of matches found.
11363 The address of the last value found is stored in convenience variable
11365 A count of the number of matches is stored in @samp{$numfound}.
11367 For example, if stopped at the @code{printf} in this function:
11373 static char hello[] = "hello-hello";
11374 static struct @{ char c; short s; int i; @}
11375 __attribute__ ((packed)) mixed
11376 = @{ 'c', 0x1234, 0x87654321 @};
11377 printf ("%s\n", hello);
11382 you get during debugging:
11385 (gdb) find &hello[0], +sizeof(hello), "hello"
11386 0x804956d <hello.1620+6>
11388 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11389 0x8049567 <hello.1620>
11390 0x804956d <hello.1620+6>
11392 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11393 0x8049567 <hello.1620>
11395 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11396 0x8049560 <mixed.1625>
11398 (gdb) print $numfound
11401 $2 = (void *) 0x8049560
11404 @node Optimized Code
11405 @chapter Debugging Optimized Code
11406 @cindex optimized code, debugging
11407 @cindex debugging optimized code
11409 Almost all compilers support optimization. With optimization
11410 disabled, the compiler generates assembly code that corresponds
11411 directly to your source code, in a simplistic way. As the compiler
11412 applies more powerful optimizations, the generated assembly code
11413 diverges from your original source code. With help from debugging
11414 information generated by the compiler, @value{GDBN} can map from
11415 the running program back to constructs from your original source.
11417 @value{GDBN} is more accurate with optimization disabled. If you
11418 can recompile without optimization, it is easier to follow the
11419 progress of your program during debugging. But, there are many cases
11420 where you may need to debug an optimized version.
11422 When you debug a program compiled with @samp{-g -O}, remember that the
11423 optimizer has rearranged your code; the debugger shows you what is
11424 really there. Do not be too surprised when the execution path does not
11425 exactly match your source file! An extreme example: if you define a
11426 variable, but never use it, @value{GDBN} never sees that
11427 variable---because the compiler optimizes it out of existence.
11429 Some things do not work as well with @samp{-g -O} as with just
11430 @samp{-g}, particularly on machines with instruction scheduling. If in
11431 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11432 please report it to us as a bug (including a test case!).
11433 @xref{Variables}, for more information about debugging optimized code.
11436 * Inline Functions:: How @value{GDBN} presents inlining
11437 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11440 @node Inline Functions
11441 @section Inline Functions
11442 @cindex inline functions, debugging
11444 @dfn{Inlining} is an optimization that inserts a copy of the function
11445 body directly at each call site, instead of jumping to a shared
11446 routine. @value{GDBN} displays inlined functions just like
11447 non-inlined functions. They appear in backtraces. You can view their
11448 arguments and local variables, step into them with @code{step}, skip
11449 them with @code{next}, and escape from them with @code{finish}.
11450 You can check whether a function was inlined by using the
11451 @code{info frame} command.
11453 For @value{GDBN} to support inlined functions, the compiler must
11454 record information about inlining in the debug information ---
11455 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11456 other compilers do also. @value{GDBN} only supports inlined functions
11457 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11458 do not emit two required attributes (@samp{DW_AT_call_file} and
11459 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11460 function calls with earlier versions of @value{NGCC}. It instead
11461 displays the arguments and local variables of inlined functions as
11462 local variables in the caller.
11464 The body of an inlined function is directly included at its call site;
11465 unlike a non-inlined function, there are no instructions devoted to
11466 the call. @value{GDBN} still pretends that the call site and the
11467 start of the inlined function are different instructions. Stepping to
11468 the call site shows the call site, and then stepping again shows
11469 the first line of the inlined function, even though no additional
11470 instructions are executed.
11472 This makes source-level debugging much clearer; you can see both the
11473 context of the call and then the effect of the call. Only stepping by
11474 a single instruction using @code{stepi} or @code{nexti} does not do
11475 this; single instruction steps always show the inlined body.
11477 There are some ways that @value{GDBN} does not pretend that inlined
11478 function calls are the same as normal calls:
11482 Setting breakpoints at the call site of an inlined function may not
11483 work, because the call site does not contain any code. @value{GDBN}
11484 may incorrectly move the breakpoint to the next line of the enclosing
11485 function, after the call. This limitation will be removed in a future
11486 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11487 or inside the inlined function instead.
11490 @value{GDBN} cannot locate the return value of inlined calls after
11491 using the @code{finish} command. This is a limitation of compiler-generated
11492 debugging information; after @code{finish}, you can step to the next line
11493 and print a variable where your program stored the return value.
11497 @node Tail Call Frames
11498 @section Tail Call Frames
11499 @cindex tail call frames, debugging
11501 Function @code{B} can call function @code{C} in its very last statement. In
11502 unoptimized compilation the call of @code{C} is immediately followed by return
11503 instruction at the end of @code{B} code. Optimizing compiler may replace the
11504 call and return in function @code{B} into one jump to function @code{C}
11505 instead. Such use of a jump instruction is called @dfn{tail call}.
11507 During execution of function @code{C}, there will be no indication in the
11508 function call stack frames that it was tail-called from @code{B}. If function
11509 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11510 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11511 some cases @value{GDBN} can determine that @code{C} was tail-called from
11512 @code{B}, and it will then create fictitious call frame for that, with the
11513 return address set up as if @code{B} called @code{C} normally.
11515 This functionality is currently supported only by DWARF 2 debugging format and
11516 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11517 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11520 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11521 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11525 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11527 Stack level 1, frame at 0x7fffffffda30:
11528 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11529 tail call frame, caller of frame at 0x7fffffffda30
11530 source language c++.
11531 Arglist at unknown address.
11532 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11535 The detection of all the possible code path executions can find them ambiguous.
11536 There is no execution history stored (possible @ref{Reverse Execution} is never
11537 used for this purpose) and the last known caller could have reached the known
11538 callee by multiple different jump sequences. In such case @value{GDBN} still
11539 tries to show at least all the unambiguous top tail callers and all the
11540 unambiguous bottom tail calees, if any.
11543 @anchor{set debug entry-values}
11544 @item set debug entry-values
11545 @kindex set debug entry-values
11546 When set to on, enables printing of analysis messages for both frame argument
11547 values at function entry and tail calls. It will show all the possible valid
11548 tail calls code paths it has considered. It will also print the intersection
11549 of them with the final unambiguous (possibly partial or even empty) code path
11552 @item show debug entry-values
11553 @kindex show debug entry-values
11554 Show the current state of analysis messages printing for both frame argument
11555 values at function entry and tail calls.
11558 The analysis messages for tail calls can for example show why the virtual tail
11559 call frame for function @code{c} has not been recognized (due to the indirect
11560 reference by variable @code{x}):
11563 static void __attribute__((noinline, noclone)) c (void);
11564 void (*x) (void) = c;
11565 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11566 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11567 int main (void) @{ x (); return 0; @}
11569 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11570 DW_TAG_GNU_call_site 0x40039a in main
11572 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11575 #1 0x000000000040039a in main () at t.c:5
11578 Another possibility is an ambiguous virtual tail call frames resolution:
11582 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11583 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11584 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11585 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11586 static void __attribute__((noinline, noclone)) b (void)
11587 @{ if (i) c (); else e (); @}
11588 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11589 int main (void) @{ a (); return 0; @}
11591 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11592 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11593 tailcall: reduced: 0x4004d2(a) |
11596 #1 0x00000000004004d2 in a () at t.c:8
11597 #2 0x0000000000400395 in main () at t.c:9
11600 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11601 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11603 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11604 @ifset HAVE_MAKEINFO_CLICK
11605 @set ARROW @click{}
11606 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11607 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11609 @ifclear HAVE_MAKEINFO_CLICK
11611 @set CALLSEQ1B @value{CALLSEQ1A}
11612 @set CALLSEQ2B @value{CALLSEQ2A}
11615 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11616 The code can have possible execution paths @value{CALLSEQ1B} or
11617 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11619 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11620 has found. It then finds another possible calling sequcen - that one is
11621 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11622 printed as the @code{reduced:} calling sequence. That one could have many
11623 futher @code{compare:} and @code{reduced:} statements as long as there remain
11624 any non-ambiguous sequence entries.
11626 For the frame of function @code{b} in both cases there are different possible
11627 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11628 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11629 therefore this one is displayed to the user while the ambiguous frames are
11632 There can be also reasons why printing of frame argument values at function
11637 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11638 static void __attribute__((noinline, noclone)) a (int i);
11639 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11640 static void __attribute__((noinline, noclone)) a (int i)
11641 @{ if (i) b (i - 1); else c (0); @}
11642 int main (void) @{ a (5); return 0; @}
11645 #0 c (i=i@@entry=0) at t.c:2
11646 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11647 function "a" at 0x400420 can call itself via tail calls
11648 i=<optimized out>) at t.c:6
11649 #2 0x000000000040036e in main () at t.c:7
11652 @value{GDBN} cannot find out from the inferior state if and how many times did
11653 function @code{a} call itself (via function @code{b}) as these calls would be
11654 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11655 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11656 prints @code{<optimized out>} instead.
11659 @chapter C Preprocessor Macros
11661 Some languages, such as C and C@t{++}, provide a way to define and invoke
11662 ``preprocessor macros'' which expand into strings of tokens.
11663 @value{GDBN} can evaluate expressions containing macro invocations, show
11664 the result of macro expansion, and show a macro's definition, including
11665 where it was defined.
11667 You may need to compile your program specially to provide @value{GDBN}
11668 with information about preprocessor macros. Most compilers do not
11669 include macros in their debugging information, even when you compile
11670 with the @option{-g} flag. @xref{Compilation}.
11672 A program may define a macro at one point, remove that definition later,
11673 and then provide a different definition after that. Thus, at different
11674 points in the program, a macro may have different definitions, or have
11675 no definition at all. If there is a current stack frame, @value{GDBN}
11676 uses the macros in scope at that frame's source code line. Otherwise,
11677 @value{GDBN} uses the macros in scope at the current listing location;
11680 Whenever @value{GDBN} evaluates an expression, it always expands any
11681 macro invocations present in the expression. @value{GDBN} also provides
11682 the following commands for working with macros explicitly.
11686 @kindex macro expand
11687 @cindex macro expansion, showing the results of preprocessor
11688 @cindex preprocessor macro expansion, showing the results of
11689 @cindex expanding preprocessor macros
11690 @item macro expand @var{expression}
11691 @itemx macro exp @var{expression}
11692 Show the results of expanding all preprocessor macro invocations in
11693 @var{expression}. Since @value{GDBN} simply expands macros, but does
11694 not parse the result, @var{expression} need not be a valid expression;
11695 it can be any string of tokens.
11698 @item macro expand-once @var{expression}
11699 @itemx macro exp1 @var{expression}
11700 @cindex expand macro once
11701 @i{(This command is not yet implemented.)} Show the results of
11702 expanding those preprocessor macro invocations that appear explicitly in
11703 @var{expression}. Macro invocations appearing in that expansion are
11704 left unchanged. This command allows you to see the effect of a
11705 particular macro more clearly, without being confused by further
11706 expansions. Since @value{GDBN} simply expands macros, but does not
11707 parse the result, @var{expression} need not be a valid expression; it
11708 can be any string of tokens.
11711 @cindex macro definition, showing
11712 @cindex definition of a macro, showing
11713 @cindex macros, from debug info
11714 @item info macro [-a|-all] [--] @var{macro}
11715 Show the current definition or all definitions of the named @var{macro},
11716 and describe the source location or compiler command-line where that
11717 definition was established. The optional double dash is to signify the end of
11718 argument processing and the beginning of @var{macro} for non C-like macros where
11719 the macro may begin with a hyphen.
11721 @kindex info macros
11722 @item info macros @var{linespec}
11723 Show all macro definitions that are in effect at the location specified
11724 by @var{linespec}, and describe the source location or compiler
11725 command-line where those definitions were established.
11727 @kindex macro define
11728 @cindex user-defined macros
11729 @cindex defining macros interactively
11730 @cindex macros, user-defined
11731 @item macro define @var{macro} @var{replacement-list}
11732 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11733 Introduce a definition for a preprocessor macro named @var{macro},
11734 invocations of which are replaced by the tokens given in
11735 @var{replacement-list}. The first form of this command defines an
11736 ``object-like'' macro, which takes no arguments; the second form
11737 defines a ``function-like'' macro, which takes the arguments given in
11740 A definition introduced by this command is in scope in every
11741 expression evaluated in @value{GDBN}, until it is removed with the
11742 @code{macro undef} command, described below. The definition overrides
11743 all definitions for @var{macro} present in the program being debugged,
11744 as well as any previous user-supplied definition.
11746 @kindex macro undef
11747 @item macro undef @var{macro}
11748 Remove any user-supplied definition for the macro named @var{macro}.
11749 This command only affects definitions provided with the @code{macro
11750 define} command, described above; it cannot remove definitions present
11751 in the program being debugged.
11755 List all the macros defined using the @code{macro define} command.
11758 @cindex macros, example of debugging with
11759 Here is a transcript showing the above commands in action. First, we
11760 show our source files:
11765 #include "sample.h"
11768 #define ADD(x) (M + x)
11773 printf ("Hello, world!\n");
11775 printf ("We're so creative.\n");
11777 printf ("Goodbye, world!\n");
11784 Now, we compile the program using the @sc{gnu} C compiler,
11785 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11786 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11787 and @option{-gdwarf-4}; we recommend always choosing the most recent
11788 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11789 includes information about preprocessor macros in the debugging
11793 $ gcc -gdwarf-2 -g3 sample.c -o sample
11797 Now, we start @value{GDBN} on our sample program:
11801 GNU gdb 2002-05-06-cvs
11802 Copyright 2002 Free Software Foundation, Inc.
11803 GDB is free software, @dots{}
11807 We can expand macros and examine their definitions, even when the
11808 program is not running. @value{GDBN} uses the current listing position
11809 to decide which macro definitions are in scope:
11812 (@value{GDBP}) list main
11815 5 #define ADD(x) (M + x)
11820 10 printf ("Hello, world!\n");
11822 12 printf ("We're so creative.\n");
11823 (@value{GDBP}) info macro ADD
11824 Defined at /home/jimb/gdb/macros/play/sample.c:5
11825 #define ADD(x) (M + x)
11826 (@value{GDBP}) info macro Q
11827 Defined at /home/jimb/gdb/macros/play/sample.h:1
11828 included at /home/jimb/gdb/macros/play/sample.c:2
11830 (@value{GDBP}) macro expand ADD(1)
11831 expands to: (42 + 1)
11832 (@value{GDBP}) macro expand-once ADD(1)
11833 expands to: once (M + 1)
11837 In the example above, note that @code{macro expand-once} expands only
11838 the macro invocation explicit in the original text --- the invocation of
11839 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11840 which was introduced by @code{ADD}.
11842 Once the program is running, @value{GDBN} uses the macro definitions in
11843 force at the source line of the current stack frame:
11846 (@value{GDBP}) break main
11847 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11849 Starting program: /home/jimb/gdb/macros/play/sample
11851 Breakpoint 1, main () at sample.c:10
11852 10 printf ("Hello, world!\n");
11856 At line 10, the definition of the macro @code{N} at line 9 is in force:
11859 (@value{GDBP}) info macro N
11860 Defined at /home/jimb/gdb/macros/play/sample.c:9
11862 (@value{GDBP}) macro expand N Q M
11863 expands to: 28 < 42
11864 (@value{GDBP}) print N Q M
11869 As we step over directives that remove @code{N}'s definition, and then
11870 give it a new definition, @value{GDBN} finds the definition (or lack
11871 thereof) in force at each point:
11874 (@value{GDBP}) next
11876 12 printf ("We're so creative.\n");
11877 (@value{GDBP}) info macro N
11878 The symbol `N' has no definition as a C/C++ preprocessor macro
11879 at /home/jimb/gdb/macros/play/sample.c:12
11880 (@value{GDBP}) next
11882 14 printf ("Goodbye, world!\n");
11883 (@value{GDBP}) info macro N
11884 Defined at /home/jimb/gdb/macros/play/sample.c:13
11886 (@value{GDBP}) macro expand N Q M
11887 expands to: 1729 < 42
11888 (@value{GDBP}) print N Q M
11893 In addition to source files, macros can be defined on the compilation command
11894 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11895 such a way, @value{GDBN} displays the location of their definition as line zero
11896 of the source file submitted to the compiler.
11899 (@value{GDBP}) info macro __STDC__
11900 Defined at /home/jimb/gdb/macros/play/sample.c:0
11907 @chapter Tracepoints
11908 @c This chapter is based on the documentation written by Michael
11909 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11911 @cindex tracepoints
11912 In some applications, it is not feasible for the debugger to interrupt
11913 the program's execution long enough for the developer to learn
11914 anything helpful about its behavior. If the program's correctness
11915 depends on its real-time behavior, delays introduced by a debugger
11916 might cause the program to change its behavior drastically, or perhaps
11917 fail, even when the code itself is correct. It is useful to be able
11918 to observe the program's behavior without interrupting it.
11920 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11921 specify locations in the program, called @dfn{tracepoints}, and
11922 arbitrary expressions to evaluate when those tracepoints are reached.
11923 Later, using the @code{tfind} command, you can examine the values
11924 those expressions had when the program hit the tracepoints. The
11925 expressions may also denote objects in memory---structures or arrays,
11926 for example---whose values @value{GDBN} should record; while visiting
11927 a particular tracepoint, you may inspect those objects as if they were
11928 in memory at that moment. However, because @value{GDBN} records these
11929 values without interacting with you, it can do so quickly and
11930 unobtrusively, hopefully not disturbing the program's behavior.
11932 The tracepoint facility is currently available only for remote
11933 targets. @xref{Targets}. In addition, your remote target must know
11934 how to collect trace data. This functionality is implemented in the
11935 remote stub; however, none of the stubs distributed with @value{GDBN}
11936 support tracepoints as of this writing. The format of the remote
11937 packets used to implement tracepoints are described in @ref{Tracepoint
11940 It is also possible to get trace data from a file, in a manner reminiscent
11941 of corefiles; you specify the filename, and use @code{tfind} to search
11942 through the file. @xref{Trace Files}, for more details.
11944 This chapter describes the tracepoint commands and features.
11947 * Set Tracepoints::
11948 * Analyze Collected Data::
11949 * Tracepoint Variables::
11953 @node Set Tracepoints
11954 @section Commands to Set Tracepoints
11956 Before running such a @dfn{trace experiment}, an arbitrary number of
11957 tracepoints can be set. A tracepoint is actually a special type of
11958 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11959 standard breakpoint commands. For instance, as with breakpoints,
11960 tracepoint numbers are successive integers starting from one, and many
11961 of the commands associated with tracepoints take the tracepoint number
11962 as their argument, to identify which tracepoint to work on.
11964 For each tracepoint, you can specify, in advance, some arbitrary set
11965 of data that you want the target to collect in the trace buffer when
11966 it hits that tracepoint. The collected data can include registers,
11967 local variables, or global data. Later, you can use @value{GDBN}
11968 commands to examine the values these data had at the time the
11969 tracepoint was hit.
11971 Tracepoints do not support every breakpoint feature. Ignore counts on
11972 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11973 commands when they are hit. Tracepoints may not be thread-specific
11976 @cindex fast tracepoints
11977 Some targets may support @dfn{fast tracepoints}, which are inserted in
11978 a different way (such as with a jump instead of a trap), that is
11979 faster but possibly restricted in where they may be installed.
11981 @cindex static tracepoints
11982 @cindex markers, static tracepoints
11983 @cindex probing markers, static tracepoints
11984 Regular and fast tracepoints are dynamic tracing facilities, meaning
11985 that they can be used to insert tracepoints at (almost) any location
11986 in the target. Some targets may also support controlling @dfn{static
11987 tracepoints} from @value{GDBN}. With static tracing, a set of
11988 instrumentation points, also known as @dfn{markers}, are embedded in
11989 the target program, and can be activated or deactivated by name or
11990 address. These are usually placed at locations which facilitate
11991 investigating what the target is actually doing. @value{GDBN}'s
11992 support for static tracing includes being able to list instrumentation
11993 points, and attach them with @value{GDBN} defined high level
11994 tracepoints that expose the whole range of convenience of
11995 @value{GDBN}'s tracepoints support. Namely, support for collecting
11996 registers values and values of global or local (to the instrumentation
11997 point) variables; tracepoint conditions and trace state variables.
11998 The act of installing a @value{GDBN} static tracepoint on an
11999 instrumentation point, or marker, is referred to as @dfn{probing} a
12000 static tracepoint marker.
12002 @code{gdbserver} supports tracepoints on some target systems.
12003 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12005 This section describes commands to set tracepoints and associated
12006 conditions and actions.
12009 * Create and Delete Tracepoints::
12010 * Enable and Disable Tracepoints::
12011 * Tracepoint Passcounts::
12012 * Tracepoint Conditions::
12013 * Trace State Variables::
12014 * Tracepoint Actions::
12015 * Listing Tracepoints::
12016 * Listing Static Tracepoint Markers::
12017 * Starting and Stopping Trace Experiments::
12018 * Tracepoint Restrictions::
12021 @node Create and Delete Tracepoints
12022 @subsection Create and Delete Tracepoints
12025 @cindex set tracepoint
12027 @item trace @var{location}
12028 The @code{trace} command is very similar to the @code{break} command.
12029 Its argument @var{location} can be a source line, a function name, or
12030 an address in the target program. @xref{Specify Location}. The
12031 @code{trace} command defines a tracepoint, which is a point in the
12032 target program where the debugger will briefly stop, collect some
12033 data, and then allow the program to continue. Setting a tracepoint or
12034 changing its actions takes effect immediately if the remote stub
12035 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12037 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12038 these changes don't take effect until the next @code{tstart}
12039 command, and once a trace experiment is running, further changes will
12040 not have any effect until the next trace experiment starts. In addition,
12041 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12042 address is not yet resolved. (This is similar to pending breakpoints.)
12043 Pending tracepoints are not downloaded to the target and not installed
12044 until they are resolved. The resolution of pending tracepoints requires
12045 @value{GDBN} support---when debugging with the remote target, and
12046 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12047 tracing}), pending tracepoints can not be resolved (and downloaded to
12048 the remote stub) while @value{GDBN} is disconnected.
12050 Here are some examples of using the @code{trace} command:
12053 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12055 (@value{GDBP}) @b{trace +2} // 2 lines forward
12057 (@value{GDBP}) @b{trace my_function} // first source line of function
12059 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12061 (@value{GDBP}) @b{trace *0x2117c4} // an address
12065 You can abbreviate @code{trace} as @code{tr}.
12067 @item trace @var{location} if @var{cond}
12068 Set a tracepoint with condition @var{cond}; evaluate the expression
12069 @var{cond} each time the tracepoint is reached, and collect data only
12070 if the value is nonzero---that is, if @var{cond} evaluates as true.
12071 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12072 information on tracepoint conditions.
12074 @item ftrace @var{location} [ if @var{cond} ]
12075 @cindex set fast tracepoint
12076 @cindex fast tracepoints, setting
12078 The @code{ftrace} command sets a fast tracepoint. For targets that
12079 support them, fast tracepoints will use a more efficient but possibly
12080 less general technique to trigger data collection, such as a jump
12081 instruction instead of a trap, or some sort of hardware support. It
12082 may not be possible to create a fast tracepoint at the desired
12083 location, in which case the command will exit with an explanatory
12086 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12089 On 32-bit x86-architecture systems, fast tracepoints normally need to
12090 be placed at an instruction that is 5 bytes or longer, but can be
12091 placed at 4-byte instructions if the low 64K of memory of the target
12092 program is available to install trampolines. Some Unix-type systems,
12093 such as @sc{gnu}/Linux, exclude low addresses from the program's
12094 address space; but for instance with the Linux kernel it is possible
12095 to let @value{GDBN} use this area by doing a @command{sysctl} command
12096 to set the @code{mmap_min_addr} kernel parameter, as in
12099 sudo sysctl -w vm.mmap_min_addr=32768
12103 which sets the low address to 32K, which leaves plenty of room for
12104 trampolines. The minimum address should be set to a page boundary.
12106 @item strace @var{location} [ if @var{cond} ]
12107 @cindex set static tracepoint
12108 @cindex static tracepoints, setting
12109 @cindex probe static tracepoint marker
12111 The @code{strace} command sets a static tracepoint. For targets that
12112 support it, setting a static tracepoint probes a static
12113 instrumentation point, or marker, found at @var{location}. It may not
12114 be possible to set a static tracepoint at the desired location, in
12115 which case the command will exit with an explanatory message.
12117 @value{GDBN} handles arguments to @code{strace} exactly as for
12118 @code{trace}, with the addition that the user can also specify
12119 @code{-m @var{marker}} as @var{location}. This probes the marker
12120 identified by the @var{marker} string identifier. This identifier
12121 depends on the static tracepoint backend library your program is
12122 using. You can find all the marker identifiers in the @samp{ID} field
12123 of the @code{info static-tracepoint-markers} command output.
12124 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12125 Markers}. For example, in the following small program using the UST
12131 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12136 the marker id is composed of joining the first two arguments to the
12137 @code{trace_mark} call with a slash, which translates to:
12140 (@value{GDBP}) info static-tracepoint-markers
12141 Cnt Enb ID Address What
12142 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12148 so you may probe the marker above with:
12151 (@value{GDBP}) strace -m ust/bar33
12154 Static tracepoints accept an extra collect action --- @code{collect
12155 $_sdata}. This collects arbitrary user data passed in the probe point
12156 call to the tracing library. In the UST example above, you'll see
12157 that the third argument to @code{trace_mark} is a printf-like format
12158 string. The user data is then the result of running that formating
12159 string against the following arguments. Note that @code{info
12160 static-tracepoint-markers} command output lists that format string in
12161 the @samp{Data:} field.
12163 You can inspect this data when analyzing the trace buffer, by printing
12164 the $_sdata variable like any other variable available to
12165 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12168 @cindex last tracepoint number
12169 @cindex recent tracepoint number
12170 @cindex tracepoint number
12171 The convenience variable @code{$tpnum} records the tracepoint number
12172 of the most recently set tracepoint.
12174 @kindex delete tracepoint
12175 @cindex tracepoint deletion
12176 @item delete tracepoint @r{[}@var{num}@r{]}
12177 Permanently delete one or more tracepoints. With no argument, the
12178 default is to delete all tracepoints. Note that the regular
12179 @code{delete} command can remove tracepoints also.
12184 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12186 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12190 You can abbreviate this command as @code{del tr}.
12193 @node Enable and Disable Tracepoints
12194 @subsection Enable and Disable Tracepoints
12196 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12199 @kindex disable tracepoint
12200 @item disable tracepoint @r{[}@var{num}@r{]}
12201 Disable tracepoint @var{num}, or all tracepoints if no argument
12202 @var{num} is given. A disabled tracepoint will have no effect during
12203 a trace experiment, but it is not forgotten. You can re-enable
12204 a disabled tracepoint using the @code{enable tracepoint} command.
12205 If the command is issued during a trace experiment and the debug target
12206 has support for disabling tracepoints during a trace experiment, then the
12207 change will be effective immediately. Otherwise, it will be applied to the
12208 next trace experiment.
12210 @kindex enable tracepoint
12211 @item enable tracepoint @r{[}@var{num}@r{]}
12212 Enable tracepoint @var{num}, or all tracepoints. If this command is
12213 issued during a trace experiment and the debug target supports enabling
12214 tracepoints during a trace experiment, then the enabled tracepoints will
12215 become effective immediately. Otherwise, they will become effective the
12216 next time a trace experiment is run.
12219 @node Tracepoint Passcounts
12220 @subsection Tracepoint Passcounts
12224 @cindex tracepoint pass count
12225 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12226 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12227 automatically stop a trace experiment. If a tracepoint's passcount is
12228 @var{n}, then the trace experiment will be automatically stopped on
12229 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12230 @var{num} is not specified, the @code{passcount} command sets the
12231 passcount of the most recently defined tracepoint. If no passcount is
12232 given, the trace experiment will run until stopped explicitly by the
12238 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12239 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12241 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12242 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12243 (@value{GDBP}) @b{trace foo}
12244 (@value{GDBP}) @b{pass 3}
12245 (@value{GDBP}) @b{trace bar}
12246 (@value{GDBP}) @b{pass 2}
12247 (@value{GDBP}) @b{trace baz}
12248 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12249 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12250 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12251 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12255 @node Tracepoint Conditions
12256 @subsection Tracepoint Conditions
12257 @cindex conditional tracepoints
12258 @cindex tracepoint conditions
12260 The simplest sort of tracepoint collects data every time your program
12261 reaches a specified place. You can also specify a @dfn{condition} for
12262 a tracepoint. A condition is just a Boolean expression in your
12263 programming language (@pxref{Expressions, ,Expressions}). A
12264 tracepoint with a condition evaluates the expression each time your
12265 program reaches it, and data collection happens only if the condition
12268 Tracepoint conditions can be specified when a tracepoint is set, by
12269 using @samp{if} in the arguments to the @code{trace} command.
12270 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12271 also be set or changed at any time with the @code{condition} command,
12272 just as with breakpoints.
12274 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12275 the conditional expression itself. Instead, @value{GDBN} encodes the
12276 expression into an agent expression (@pxref{Agent Expressions})
12277 suitable for execution on the target, independently of @value{GDBN}.
12278 Global variables become raw memory locations, locals become stack
12279 accesses, and so forth.
12281 For instance, suppose you have a function that is usually called
12282 frequently, but should not be called after an error has occurred. You
12283 could use the following tracepoint command to collect data about calls
12284 of that function that happen while the error code is propagating
12285 through the program; an unconditional tracepoint could end up
12286 collecting thousands of useless trace frames that you would have to
12290 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12293 @node Trace State Variables
12294 @subsection Trace State Variables
12295 @cindex trace state variables
12297 A @dfn{trace state variable} is a special type of variable that is
12298 created and managed by target-side code. The syntax is the same as
12299 that for GDB's convenience variables (a string prefixed with ``$''),
12300 but they are stored on the target. They must be created explicitly,
12301 using a @code{tvariable} command. They are always 64-bit signed
12304 Trace state variables are remembered by @value{GDBN}, and downloaded
12305 to the target along with tracepoint information when the trace
12306 experiment starts. There are no intrinsic limits on the number of
12307 trace state variables, beyond memory limitations of the target.
12309 @cindex convenience variables, and trace state variables
12310 Although trace state variables are managed by the target, you can use
12311 them in print commands and expressions as if they were convenience
12312 variables; @value{GDBN} will get the current value from the target
12313 while the trace experiment is running. Trace state variables share
12314 the same namespace as other ``$'' variables, which means that you
12315 cannot have trace state variables with names like @code{$23} or
12316 @code{$pc}, nor can you have a trace state variable and a convenience
12317 variable with the same name.
12321 @item tvariable $@var{name} [ = @var{expression} ]
12323 The @code{tvariable} command creates a new trace state variable named
12324 @code{$@var{name}}, and optionally gives it an initial value of
12325 @var{expression}. The @var{expression} is evaluated when this command is
12326 entered; the result will be converted to an integer if possible,
12327 otherwise @value{GDBN} will report an error. A subsequent
12328 @code{tvariable} command specifying the same name does not create a
12329 variable, but instead assigns the supplied initial value to the
12330 existing variable of that name, overwriting any previous initial
12331 value. The default initial value is 0.
12333 @item info tvariables
12334 @kindex info tvariables
12335 List all the trace state variables along with their initial values.
12336 Their current values may also be displayed, if the trace experiment is
12339 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12340 @kindex delete tvariable
12341 Delete the given trace state variables, or all of them if no arguments
12346 @node Tracepoint Actions
12347 @subsection Tracepoint Action Lists
12351 @cindex tracepoint actions
12352 @item actions @r{[}@var{num}@r{]}
12353 This command will prompt for a list of actions to be taken when the
12354 tracepoint is hit. If the tracepoint number @var{num} is not
12355 specified, this command sets the actions for the one that was most
12356 recently defined (so that you can define a tracepoint and then say
12357 @code{actions} without bothering about its number). You specify the
12358 actions themselves on the following lines, one action at a time, and
12359 terminate the actions list with a line containing just @code{end}. So
12360 far, the only defined actions are @code{collect}, @code{teval}, and
12361 @code{while-stepping}.
12363 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12364 Commands, ,Breakpoint Command Lists}), except that only the defined
12365 actions are allowed; any other @value{GDBN} command is rejected.
12367 @cindex remove actions from a tracepoint
12368 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12369 and follow it immediately with @samp{end}.
12372 (@value{GDBP}) @b{collect @var{data}} // collect some data
12374 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12376 (@value{GDBP}) @b{end} // signals the end of actions.
12379 In the following example, the action list begins with @code{collect}
12380 commands indicating the things to be collected when the tracepoint is
12381 hit. Then, in order to single-step and collect additional data
12382 following the tracepoint, a @code{while-stepping} command is used,
12383 followed by the list of things to be collected after each step in a
12384 sequence of single steps. The @code{while-stepping} command is
12385 terminated by its own separate @code{end} command. Lastly, the action
12386 list is terminated by an @code{end} command.
12389 (@value{GDBP}) @b{trace foo}
12390 (@value{GDBP}) @b{actions}
12391 Enter actions for tracepoint 1, one per line:
12394 > while-stepping 12
12395 > collect $pc, arr[i]
12400 @kindex collect @r{(tracepoints)}
12401 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12402 Collect values of the given expressions when the tracepoint is hit.
12403 This command accepts a comma-separated list of any valid expressions.
12404 In addition to global, static, or local variables, the following
12405 special arguments are supported:
12409 Collect all registers.
12412 Collect all function arguments.
12415 Collect all local variables.
12418 Collect the return address. This is helpful if you want to see more
12422 Collects the number of arguments from the static probe at which the
12423 tracepoint is located.
12424 @xref{Static Probe Points}.
12426 @item $_probe_arg@var{n}
12427 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12428 from the static probe at which the tracepoint is located.
12429 @xref{Static Probe Points}.
12432 @vindex $_sdata@r{, collect}
12433 Collect static tracepoint marker specific data. Only available for
12434 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12435 Lists}. On the UST static tracepoints library backend, an
12436 instrumentation point resembles a @code{printf} function call. The
12437 tracing library is able to collect user specified data formatted to a
12438 character string using the format provided by the programmer that
12439 instrumented the program. Other backends have similar mechanisms.
12440 Here's an example of a UST marker call:
12443 const char master_name[] = "$your_name";
12444 trace_mark(channel1, marker1, "hello %s", master_name)
12447 In this case, collecting @code{$_sdata} collects the string
12448 @samp{hello $yourname}. When analyzing the trace buffer, you can
12449 inspect @samp{$_sdata} like any other variable available to
12453 You can give several consecutive @code{collect} commands, each one
12454 with a single argument, or one @code{collect} command with several
12455 arguments separated by commas; the effect is the same.
12457 The optional @var{mods} changes the usual handling of the arguments.
12458 @code{s} requests that pointers to chars be handled as strings, in
12459 particular collecting the contents of the memory being pointed at, up
12460 to the first zero. The upper bound is by default the value of the
12461 @code{print elements} variable; if @code{s} is followed by a decimal
12462 number, that is the upper bound instead. So for instance
12463 @samp{collect/s25 mystr} collects as many as 25 characters at
12466 The command @code{info scope} (@pxref{Symbols, info scope}) is
12467 particularly useful for figuring out what data to collect.
12469 @kindex teval @r{(tracepoints)}
12470 @item teval @var{expr1}, @var{expr2}, @dots{}
12471 Evaluate the given expressions when the tracepoint is hit. This
12472 command accepts a comma-separated list of expressions. The results
12473 are discarded, so this is mainly useful for assigning values to trace
12474 state variables (@pxref{Trace State Variables}) without adding those
12475 values to the trace buffer, as would be the case if the @code{collect}
12478 @kindex while-stepping @r{(tracepoints)}
12479 @item while-stepping @var{n}
12480 Perform @var{n} single-step instruction traces after the tracepoint,
12481 collecting new data after each step. The @code{while-stepping}
12482 command is followed by the list of what to collect while stepping
12483 (followed by its own @code{end} command):
12486 > while-stepping 12
12487 > collect $regs, myglobal
12493 Note that @code{$pc} is not automatically collected by
12494 @code{while-stepping}; you need to explicitly collect that register if
12495 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12498 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12499 @kindex set default-collect
12500 @cindex default collection action
12501 This variable is a list of expressions to collect at each tracepoint
12502 hit. It is effectively an additional @code{collect} action prepended
12503 to every tracepoint action list. The expressions are parsed
12504 individually for each tracepoint, so for instance a variable named
12505 @code{xyz} may be interpreted as a global for one tracepoint, and a
12506 local for another, as appropriate to the tracepoint's location.
12508 @item show default-collect
12509 @kindex show default-collect
12510 Show the list of expressions that are collected by default at each
12515 @node Listing Tracepoints
12516 @subsection Listing Tracepoints
12519 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12520 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12521 @cindex information about tracepoints
12522 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12523 Display information about the tracepoint @var{num}. If you don't
12524 specify a tracepoint number, displays information about all the
12525 tracepoints defined so far. The format is similar to that used for
12526 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12527 command, simply restricting itself to tracepoints.
12529 A tracepoint's listing may include additional information specific to
12534 its passcount as given by the @code{passcount @var{n}} command
12537 the state about installed on target of each location
12541 (@value{GDBP}) @b{info trace}
12542 Num Type Disp Enb Address What
12543 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12545 collect globfoo, $regs
12550 2 tracepoint keep y <MULTIPLE>
12552 2.1 y 0x0804859c in func4 at change-loc.h:35
12553 installed on target
12554 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12555 installed on target
12556 2.3 y <PENDING> set_tracepoint
12557 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12558 not installed on target
12563 This command can be abbreviated @code{info tp}.
12566 @node Listing Static Tracepoint Markers
12567 @subsection Listing Static Tracepoint Markers
12570 @kindex info static-tracepoint-markers
12571 @cindex information about static tracepoint markers
12572 @item info static-tracepoint-markers
12573 Display information about all static tracepoint markers defined in the
12576 For each marker, the following columns are printed:
12580 An incrementing counter, output to help readability. This is not a
12583 The marker ID, as reported by the target.
12584 @item Enabled or Disabled
12585 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12586 that are not enabled.
12588 Where the marker is in your program, as a memory address.
12590 Where the marker is in the source for your program, as a file and line
12591 number. If the debug information included in the program does not
12592 allow @value{GDBN} to locate the source of the marker, this column
12593 will be left blank.
12597 In addition, the following information may be printed for each marker:
12601 User data passed to the tracing library by the marker call. In the
12602 UST backend, this is the format string passed as argument to the
12604 @item Static tracepoints probing the marker
12605 The list of static tracepoints attached to the marker.
12609 (@value{GDBP}) info static-tracepoint-markers
12610 Cnt ID Enb Address What
12611 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12612 Data: number1 %d number2 %d
12613 Probed by static tracepoints: #2
12614 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12620 @node Starting and Stopping Trace Experiments
12621 @subsection Starting and Stopping Trace Experiments
12624 @kindex tstart [ @var{notes} ]
12625 @cindex start a new trace experiment
12626 @cindex collected data discarded
12628 This command starts the trace experiment, and begins collecting data.
12629 It has the side effect of discarding all the data collected in the
12630 trace buffer during the previous trace experiment. If any arguments
12631 are supplied, they are taken as a note and stored with the trace
12632 experiment's state. The notes may be arbitrary text, and are
12633 especially useful with disconnected tracing in a multi-user context;
12634 the notes can explain what the trace is doing, supply user contact
12635 information, and so forth.
12637 @kindex tstop [ @var{notes} ]
12638 @cindex stop a running trace experiment
12640 This command stops the trace experiment. If any arguments are
12641 supplied, they are recorded with the experiment as a note. This is
12642 useful if you are stopping a trace started by someone else, for
12643 instance if the trace is interfering with the system's behavior and
12644 needs to be stopped quickly.
12646 @strong{Note}: a trace experiment and data collection may stop
12647 automatically if any tracepoint's passcount is reached
12648 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12651 @cindex status of trace data collection
12652 @cindex trace experiment, status of
12654 This command displays the status of the current trace data
12658 Here is an example of the commands we described so far:
12661 (@value{GDBP}) @b{trace gdb_c_test}
12662 (@value{GDBP}) @b{actions}
12663 Enter actions for tracepoint #1, one per line.
12664 > collect $regs,$locals,$args
12665 > while-stepping 11
12669 (@value{GDBP}) @b{tstart}
12670 [time passes @dots{}]
12671 (@value{GDBP}) @b{tstop}
12674 @anchor{disconnected tracing}
12675 @cindex disconnected tracing
12676 You can choose to continue running the trace experiment even if
12677 @value{GDBN} disconnects from the target, voluntarily or
12678 involuntarily. For commands such as @code{detach}, the debugger will
12679 ask what you want to do with the trace. But for unexpected
12680 terminations (@value{GDBN} crash, network outage), it would be
12681 unfortunate to lose hard-won trace data, so the variable
12682 @code{disconnected-tracing} lets you decide whether the trace should
12683 continue running without @value{GDBN}.
12686 @item set disconnected-tracing on
12687 @itemx set disconnected-tracing off
12688 @kindex set disconnected-tracing
12689 Choose whether a tracing run should continue to run if @value{GDBN}
12690 has disconnected from the target. Note that @code{detach} or
12691 @code{quit} will ask you directly what to do about a running trace no
12692 matter what this variable's setting, so the variable is mainly useful
12693 for handling unexpected situations, such as loss of the network.
12695 @item show disconnected-tracing
12696 @kindex show disconnected-tracing
12697 Show the current choice for disconnected tracing.
12701 When you reconnect to the target, the trace experiment may or may not
12702 still be running; it might have filled the trace buffer in the
12703 meantime, or stopped for one of the other reasons. If it is running,
12704 it will continue after reconnection.
12706 Upon reconnection, the target will upload information about the
12707 tracepoints in effect. @value{GDBN} will then compare that
12708 information to the set of tracepoints currently defined, and attempt
12709 to match them up, allowing for the possibility that the numbers may
12710 have changed due to creation and deletion in the meantime. If one of
12711 the target's tracepoints does not match any in @value{GDBN}, the
12712 debugger will create a new tracepoint, so that you have a number with
12713 which to specify that tracepoint. This matching-up process is
12714 necessarily heuristic, and it may result in useless tracepoints being
12715 created; you may simply delete them if they are of no use.
12717 @cindex circular trace buffer
12718 If your target agent supports a @dfn{circular trace buffer}, then you
12719 can run a trace experiment indefinitely without filling the trace
12720 buffer; when space runs out, the agent deletes already-collected trace
12721 frames, oldest first, until there is enough room to continue
12722 collecting. This is especially useful if your tracepoints are being
12723 hit too often, and your trace gets terminated prematurely because the
12724 buffer is full. To ask for a circular trace buffer, simply set
12725 @samp{circular-trace-buffer} to on. You can set this at any time,
12726 including during tracing; if the agent can do it, it will change
12727 buffer handling on the fly, otherwise it will not take effect until
12731 @item set circular-trace-buffer on
12732 @itemx set circular-trace-buffer off
12733 @kindex set circular-trace-buffer
12734 Choose whether a tracing run should use a linear or circular buffer
12735 for trace data. A linear buffer will not lose any trace data, but may
12736 fill up prematurely, while a circular buffer will discard old trace
12737 data, but it will have always room for the latest tracepoint hits.
12739 @item show circular-trace-buffer
12740 @kindex show circular-trace-buffer
12741 Show the current choice for the trace buffer. Note that this may not
12742 match the agent's current buffer handling, nor is it guaranteed to
12743 match the setting that might have been in effect during a past run,
12744 for instance if you are looking at frames from a trace file.
12749 @item set trace-buffer-size @var{n}
12750 @itemx set trace-buffer-size unlimited
12751 @kindex set trace-buffer-size
12752 Request that the target use a trace buffer of @var{n} bytes. Not all
12753 targets will honor the request; they may have a compiled-in size for
12754 the trace buffer, or some other limitation. Set to a value of
12755 @code{unlimited} or @code{-1} to let the target use whatever size it
12756 likes. This is also the default.
12758 @item show trace-buffer-size
12759 @kindex show trace-buffer-size
12760 Show the current requested size for the trace buffer. Note that this
12761 will only match the actual size if the target supports size-setting,
12762 and was able to handle the requested size. For instance, if the
12763 target can only change buffer size between runs, this variable will
12764 not reflect the change until the next run starts. Use @code{tstatus}
12765 to get a report of the actual buffer size.
12769 @item set trace-user @var{text}
12770 @kindex set trace-user
12772 @item show trace-user
12773 @kindex show trace-user
12775 @item set trace-notes @var{text}
12776 @kindex set trace-notes
12777 Set the trace run's notes.
12779 @item show trace-notes
12780 @kindex show trace-notes
12781 Show the trace run's notes.
12783 @item set trace-stop-notes @var{text}
12784 @kindex set trace-stop-notes
12785 Set the trace run's stop notes. The handling of the note is as for
12786 @code{tstop} arguments; the set command is convenient way to fix a
12787 stop note that is mistaken or incomplete.
12789 @item show trace-stop-notes
12790 @kindex show trace-stop-notes
12791 Show the trace run's stop notes.
12795 @node Tracepoint Restrictions
12796 @subsection Tracepoint Restrictions
12798 @cindex tracepoint restrictions
12799 There are a number of restrictions on the use of tracepoints. As
12800 described above, tracepoint data gathering occurs on the target
12801 without interaction from @value{GDBN}. Thus the full capabilities of
12802 the debugger are not available during data gathering, and then at data
12803 examination time, you will be limited by only having what was
12804 collected. The following items describe some common problems, but it
12805 is not exhaustive, and you may run into additional difficulties not
12811 Tracepoint expressions are intended to gather objects (lvalues). Thus
12812 the full flexibility of GDB's expression evaluator is not available.
12813 You cannot call functions, cast objects to aggregate types, access
12814 convenience variables or modify values (except by assignment to trace
12815 state variables). Some language features may implicitly call
12816 functions (for instance Objective-C fields with accessors), and therefore
12817 cannot be collected either.
12820 Collection of local variables, either individually or in bulk with
12821 @code{$locals} or @code{$args}, during @code{while-stepping} may
12822 behave erratically. The stepping action may enter a new scope (for
12823 instance by stepping into a function), or the location of the variable
12824 may change (for instance it is loaded into a register). The
12825 tracepoint data recorded uses the location information for the
12826 variables that is correct for the tracepoint location. When the
12827 tracepoint is created, it is not possible, in general, to determine
12828 where the steps of a @code{while-stepping} sequence will advance the
12829 program---particularly if a conditional branch is stepped.
12832 Collection of an incompletely-initialized or partially-destroyed object
12833 may result in something that @value{GDBN} cannot display, or displays
12834 in a misleading way.
12837 When @value{GDBN} displays a pointer to character it automatically
12838 dereferences the pointer to also display characters of the string
12839 being pointed to. However, collecting the pointer during tracing does
12840 not automatically collect the string. You need to explicitly
12841 dereference the pointer and provide size information if you want to
12842 collect not only the pointer, but the memory pointed to. For example,
12843 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12847 It is not possible to collect a complete stack backtrace at a
12848 tracepoint. Instead, you may collect the registers and a few hundred
12849 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12850 (adjust to use the name of the actual stack pointer register on your
12851 target architecture, and the amount of stack you wish to capture).
12852 Then the @code{backtrace} command will show a partial backtrace when
12853 using a trace frame. The number of stack frames that can be examined
12854 depends on the sizes of the frames in the collected stack. Note that
12855 if you ask for a block so large that it goes past the bottom of the
12856 stack, the target agent may report an error trying to read from an
12860 If you do not collect registers at a tracepoint, @value{GDBN} can
12861 infer that the value of @code{$pc} must be the same as the address of
12862 the tracepoint and use that when you are looking at a trace frame
12863 for that tracepoint. However, this cannot work if the tracepoint has
12864 multiple locations (for instance if it was set in a function that was
12865 inlined), or if it has a @code{while-stepping} loop. In those cases
12866 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12871 @node Analyze Collected Data
12872 @section Using the Collected Data
12874 After the tracepoint experiment ends, you use @value{GDBN} commands
12875 for examining the trace data. The basic idea is that each tracepoint
12876 collects a trace @dfn{snapshot} every time it is hit and another
12877 snapshot every time it single-steps. All these snapshots are
12878 consecutively numbered from zero and go into a buffer, and you can
12879 examine them later. The way you examine them is to @dfn{focus} on a
12880 specific trace snapshot. When the remote stub is focused on a trace
12881 snapshot, it will respond to all @value{GDBN} requests for memory and
12882 registers by reading from the buffer which belongs to that snapshot,
12883 rather than from @emph{real} memory or registers of the program being
12884 debugged. This means that @strong{all} @value{GDBN} commands
12885 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12886 behave as if we were currently debugging the program state as it was
12887 when the tracepoint occurred. Any requests for data that are not in
12888 the buffer will fail.
12891 * tfind:: How to select a trace snapshot
12892 * tdump:: How to display all data for a snapshot
12893 * save tracepoints:: How to save tracepoints for a future run
12897 @subsection @code{tfind @var{n}}
12900 @cindex select trace snapshot
12901 @cindex find trace snapshot
12902 The basic command for selecting a trace snapshot from the buffer is
12903 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12904 counting from zero. If no argument @var{n} is given, the next
12905 snapshot is selected.
12907 Here are the various forms of using the @code{tfind} command.
12911 Find the first snapshot in the buffer. This is a synonym for
12912 @code{tfind 0} (since 0 is the number of the first snapshot).
12915 Stop debugging trace snapshots, resume @emph{live} debugging.
12918 Same as @samp{tfind none}.
12921 No argument means find the next trace snapshot.
12924 Find the previous trace snapshot before the current one. This permits
12925 retracing earlier steps.
12927 @item tfind tracepoint @var{num}
12928 Find the next snapshot associated with tracepoint @var{num}. Search
12929 proceeds forward from the last examined trace snapshot. If no
12930 argument @var{num} is given, it means find the next snapshot collected
12931 for the same tracepoint as the current snapshot.
12933 @item tfind pc @var{addr}
12934 Find the next snapshot associated with the value @var{addr} of the
12935 program counter. Search proceeds forward from the last examined trace
12936 snapshot. If no argument @var{addr} is given, it means find the next
12937 snapshot with the same value of PC as the current snapshot.
12939 @item tfind outside @var{addr1}, @var{addr2}
12940 Find the next snapshot whose PC is outside the given range of
12941 addresses (exclusive).
12943 @item tfind range @var{addr1}, @var{addr2}
12944 Find the next snapshot whose PC is between @var{addr1} and
12945 @var{addr2} (inclusive).
12947 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12948 Find the next snapshot associated with the source line @var{n}. If
12949 the optional argument @var{file} is given, refer to line @var{n} in
12950 that source file. Search proceeds forward from the last examined
12951 trace snapshot. If no argument @var{n} is given, it means find the
12952 next line other than the one currently being examined; thus saying
12953 @code{tfind line} repeatedly can appear to have the same effect as
12954 stepping from line to line in a @emph{live} debugging session.
12957 The default arguments for the @code{tfind} commands are specifically
12958 designed to make it easy to scan through the trace buffer. For
12959 instance, @code{tfind} with no argument selects the next trace
12960 snapshot, and @code{tfind -} with no argument selects the previous
12961 trace snapshot. So, by giving one @code{tfind} command, and then
12962 simply hitting @key{RET} repeatedly you can examine all the trace
12963 snapshots in order. Or, by saying @code{tfind -} and then hitting
12964 @key{RET} repeatedly you can examine the snapshots in reverse order.
12965 The @code{tfind line} command with no argument selects the snapshot
12966 for the next source line executed. The @code{tfind pc} command with
12967 no argument selects the next snapshot with the same program counter
12968 (PC) as the current frame. The @code{tfind tracepoint} command with
12969 no argument selects the next trace snapshot collected by the same
12970 tracepoint as the current one.
12972 In addition to letting you scan through the trace buffer manually,
12973 these commands make it easy to construct @value{GDBN} scripts that
12974 scan through the trace buffer and print out whatever collected data
12975 you are interested in. Thus, if we want to examine the PC, FP, and SP
12976 registers from each trace frame in the buffer, we can say this:
12979 (@value{GDBP}) @b{tfind start}
12980 (@value{GDBP}) @b{while ($trace_frame != -1)}
12981 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12982 $trace_frame, $pc, $sp, $fp
12986 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12987 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12988 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12989 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12990 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12991 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12992 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12993 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12994 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12995 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12996 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12999 Or, if we want to examine the variable @code{X} at each source line in
13003 (@value{GDBP}) @b{tfind start}
13004 (@value{GDBP}) @b{while ($trace_frame != -1)}
13005 > printf "Frame %d, X == %d\n", $trace_frame, X
13015 @subsection @code{tdump}
13017 @cindex dump all data collected at tracepoint
13018 @cindex tracepoint data, display
13020 This command takes no arguments. It prints all the data collected at
13021 the current trace snapshot.
13024 (@value{GDBP}) @b{trace 444}
13025 (@value{GDBP}) @b{actions}
13026 Enter actions for tracepoint #2, one per line:
13027 > collect $regs, $locals, $args, gdb_long_test
13030 (@value{GDBP}) @b{tstart}
13032 (@value{GDBP}) @b{tfind line 444}
13033 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13035 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13037 (@value{GDBP}) @b{tdump}
13038 Data collected at tracepoint 2, trace frame 1:
13039 d0 0xc4aa0085 -995491707
13043 d4 0x71aea3d 119204413
13046 d7 0x380035 3670069
13047 a0 0x19e24a 1696330
13048 a1 0x3000668 50333288
13050 a3 0x322000 3284992
13051 a4 0x3000698 50333336
13052 a5 0x1ad3cc 1758156
13053 fp 0x30bf3c 0x30bf3c
13054 sp 0x30bf34 0x30bf34
13056 pc 0x20b2c8 0x20b2c8
13060 p = 0x20e5b4 "gdb-test"
13067 gdb_long_test = 17 '\021'
13072 @code{tdump} works by scanning the tracepoint's current collection
13073 actions and printing the value of each expression listed. So
13074 @code{tdump} can fail, if after a run, you change the tracepoint's
13075 actions to mention variables that were not collected during the run.
13077 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13078 uses the collected value of @code{$pc} to distinguish between trace
13079 frames that were collected at the tracepoint hit, and frames that were
13080 collected while stepping. This allows it to correctly choose whether
13081 to display the basic list of collections, or the collections from the
13082 body of the while-stepping loop. However, if @code{$pc} was not collected,
13083 then @code{tdump} will always attempt to dump using the basic collection
13084 list, and may fail if a while-stepping frame does not include all the
13085 same data that is collected at the tracepoint hit.
13086 @c This is getting pretty arcane, example would be good.
13088 @node save tracepoints
13089 @subsection @code{save tracepoints @var{filename}}
13090 @kindex save tracepoints
13091 @kindex save-tracepoints
13092 @cindex save tracepoints for future sessions
13094 This command saves all current tracepoint definitions together with
13095 their actions and passcounts, into a file @file{@var{filename}}
13096 suitable for use in a later debugging session. To read the saved
13097 tracepoint definitions, use the @code{source} command (@pxref{Command
13098 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13099 alias for @w{@code{save tracepoints}}
13101 @node Tracepoint Variables
13102 @section Convenience Variables for Tracepoints
13103 @cindex tracepoint variables
13104 @cindex convenience variables for tracepoints
13107 @vindex $trace_frame
13108 @item (int) $trace_frame
13109 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13110 snapshot is selected.
13112 @vindex $tracepoint
13113 @item (int) $tracepoint
13114 The tracepoint for the current trace snapshot.
13116 @vindex $trace_line
13117 @item (int) $trace_line
13118 The line number for the current trace snapshot.
13120 @vindex $trace_file
13121 @item (char []) $trace_file
13122 The source file for the current trace snapshot.
13124 @vindex $trace_func
13125 @item (char []) $trace_func
13126 The name of the function containing @code{$tracepoint}.
13129 Note: @code{$trace_file} is not suitable for use in @code{printf},
13130 use @code{output} instead.
13132 Here's a simple example of using these convenience variables for
13133 stepping through all the trace snapshots and printing some of their
13134 data. Note that these are not the same as trace state variables,
13135 which are managed by the target.
13138 (@value{GDBP}) @b{tfind start}
13140 (@value{GDBP}) @b{while $trace_frame != -1}
13141 > output $trace_file
13142 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13148 @section Using Trace Files
13149 @cindex trace files
13151 In some situations, the target running a trace experiment may no
13152 longer be available; perhaps it crashed, or the hardware was needed
13153 for a different activity. To handle these cases, you can arrange to
13154 dump the trace data into a file, and later use that file as a source
13155 of trace data, via the @code{target tfile} command.
13160 @item tsave [ -r ] @var{filename}
13161 @itemx tsave [-ctf] @var{dirname}
13162 Save the trace data to @var{filename}. By default, this command
13163 assumes that @var{filename} refers to the host filesystem, so if
13164 necessary @value{GDBN} will copy raw trace data up from the target and
13165 then save it. If the target supports it, you can also supply the
13166 optional argument @code{-r} (``remote'') to direct the target to save
13167 the data directly into @var{filename} in its own filesystem, which may be
13168 more efficient if the trace buffer is very large. (Note, however, that
13169 @code{target tfile} can only read from files accessible to the host.)
13170 By default, this command will save trace frame in tfile format.
13171 You can supply the optional argument @code{-ctf} to save date in CTF
13172 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13173 that can be shared by multiple debugging and tracing tools. Please go to
13174 @indicateurl{http://www.efficios.com/ctf} to get more information.
13176 @kindex target tfile
13180 @item target tfile @var{filename}
13181 @itemx target ctf @var{dirname}
13182 Use the file named @var{filename} or directory named @var{dirname} as
13183 a source of trace data. Commands that examine data work as they do with
13184 a live target, but it is not possible to run any new trace experiments.
13185 @code{tstatus} will report the state of the trace run at the moment
13186 the data was saved, as well as the current trace frame you are examining.
13187 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13191 (@value{GDBP}) target ctf ctf.ctf
13192 (@value{GDBP}) tfind
13193 Found trace frame 0, tracepoint 2
13194 39 ++a; /* set tracepoint 1 here */
13195 (@value{GDBP}) tdump
13196 Data collected at tracepoint 2, trace frame 0:
13200 c = @{"123", "456", "789", "123", "456", "789"@}
13201 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13209 @chapter Debugging Programs That Use Overlays
13212 If your program is too large to fit completely in your target system's
13213 memory, you can sometimes use @dfn{overlays} to work around this
13214 problem. @value{GDBN} provides some support for debugging programs that
13218 * How Overlays Work:: A general explanation of overlays.
13219 * Overlay Commands:: Managing overlays in @value{GDBN}.
13220 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13221 mapped by asking the inferior.
13222 * Overlay Sample Program:: A sample program using overlays.
13225 @node How Overlays Work
13226 @section How Overlays Work
13227 @cindex mapped overlays
13228 @cindex unmapped overlays
13229 @cindex load address, overlay's
13230 @cindex mapped address
13231 @cindex overlay area
13233 Suppose you have a computer whose instruction address space is only 64
13234 kilobytes long, but which has much more memory which can be accessed by
13235 other means: special instructions, segment registers, or memory
13236 management hardware, for example. Suppose further that you want to
13237 adapt a program which is larger than 64 kilobytes to run on this system.
13239 One solution is to identify modules of your program which are relatively
13240 independent, and need not call each other directly; call these modules
13241 @dfn{overlays}. Separate the overlays from the main program, and place
13242 their machine code in the larger memory. Place your main program in
13243 instruction memory, but leave at least enough space there to hold the
13244 largest overlay as well.
13246 Now, to call a function located in an overlay, you must first copy that
13247 overlay's machine code from the large memory into the space set aside
13248 for it in the instruction memory, and then jump to its entry point
13251 @c NB: In the below the mapped area's size is greater or equal to the
13252 @c size of all overlays. This is intentional to remind the developer
13253 @c that overlays don't necessarily need to be the same size.
13257 Data Instruction Larger
13258 Address Space Address Space Address Space
13259 +-----------+ +-----------+ +-----------+
13261 +-----------+ +-----------+ +-----------+<-- overlay 1
13262 | program | | main | .----| overlay 1 | load address
13263 | variables | | program | | +-----------+
13264 | and heap | | | | | |
13265 +-----------+ | | | +-----------+<-- overlay 2
13266 | | +-----------+ | | | load address
13267 +-----------+ | | | .-| overlay 2 |
13269 mapped --->+-----------+ | | +-----------+
13270 address | | | | | |
13271 | overlay | <-' | | |
13272 | area | <---' +-----------+<-- overlay 3
13273 | | <---. | | load address
13274 +-----------+ `--| overlay 3 |
13281 @anchor{A code overlay}A code overlay
13285 The diagram (@pxref{A code overlay}) shows a system with separate data
13286 and instruction address spaces. To map an overlay, the program copies
13287 its code from the larger address space to the instruction address space.
13288 Since the overlays shown here all use the same mapped address, only one
13289 may be mapped at a time. For a system with a single address space for
13290 data and instructions, the diagram would be similar, except that the
13291 program variables and heap would share an address space with the main
13292 program and the overlay area.
13294 An overlay loaded into instruction memory and ready for use is called a
13295 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13296 instruction memory. An overlay not present (or only partially present)
13297 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13298 is its address in the larger memory. The mapped address is also called
13299 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13300 called the @dfn{load memory address}, or @dfn{LMA}.
13302 Unfortunately, overlays are not a completely transparent way to adapt a
13303 program to limited instruction memory. They introduce a new set of
13304 global constraints you must keep in mind as you design your program:
13309 Before calling or returning to a function in an overlay, your program
13310 must make sure that overlay is actually mapped. Otherwise, the call or
13311 return will transfer control to the right address, but in the wrong
13312 overlay, and your program will probably crash.
13315 If the process of mapping an overlay is expensive on your system, you
13316 will need to choose your overlays carefully to minimize their effect on
13317 your program's performance.
13320 The executable file you load onto your system must contain each
13321 overlay's instructions, appearing at the overlay's load address, not its
13322 mapped address. However, each overlay's instructions must be relocated
13323 and its symbols defined as if the overlay were at its mapped address.
13324 You can use GNU linker scripts to specify different load and relocation
13325 addresses for pieces of your program; see @ref{Overlay Description,,,
13326 ld.info, Using ld: the GNU linker}.
13329 The procedure for loading executable files onto your system must be able
13330 to load their contents into the larger address space as well as the
13331 instruction and data spaces.
13335 The overlay system described above is rather simple, and could be
13336 improved in many ways:
13341 If your system has suitable bank switch registers or memory management
13342 hardware, you could use those facilities to make an overlay's load area
13343 contents simply appear at their mapped address in instruction space.
13344 This would probably be faster than copying the overlay to its mapped
13345 area in the usual way.
13348 If your overlays are small enough, you could set aside more than one
13349 overlay area, and have more than one overlay mapped at a time.
13352 You can use overlays to manage data, as well as instructions. In
13353 general, data overlays are even less transparent to your design than
13354 code overlays: whereas code overlays only require care when you call or
13355 return to functions, data overlays require care every time you access
13356 the data. Also, if you change the contents of a data overlay, you
13357 must copy its contents back out to its load address before you can copy a
13358 different data overlay into the same mapped area.
13363 @node Overlay Commands
13364 @section Overlay Commands
13366 To use @value{GDBN}'s overlay support, each overlay in your program must
13367 correspond to a separate section of the executable file. The section's
13368 virtual memory address and load memory address must be the overlay's
13369 mapped and load addresses. Identifying overlays with sections allows
13370 @value{GDBN} to determine the appropriate address of a function or
13371 variable, depending on whether the overlay is mapped or not.
13373 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13374 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13379 Disable @value{GDBN}'s overlay support. When overlay support is
13380 disabled, @value{GDBN} assumes that all functions and variables are
13381 always present at their mapped addresses. By default, @value{GDBN}'s
13382 overlay support is disabled.
13384 @item overlay manual
13385 @cindex manual overlay debugging
13386 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13387 relies on you to tell it which overlays are mapped, and which are not,
13388 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13389 commands described below.
13391 @item overlay map-overlay @var{overlay}
13392 @itemx overlay map @var{overlay}
13393 @cindex map an overlay
13394 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13395 be the name of the object file section containing the overlay. When an
13396 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13397 functions and variables at their mapped addresses. @value{GDBN} assumes
13398 that any other overlays whose mapped ranges overlap that of
13399 @var{overlay} are now unmapped.
13401 @item overlay unmap-overlay @var{overlay}
13402 @itemx overlay unmap @var{overlay}
13403 @cindex unmap an overlay
13404 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13405 must be the name of the object file section containing the overlay.
13406 When an overlay is unmapped, @value{GDBN} assumes it can find the
13407 overlay's functions and variables at their load addresses.
13410 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13411 consults a data structure the overlay manager maintains in the inferior
13412 to see which overlays are mapped. For details, see @ref{Automatic
13413 Overlay Debugging}.
13415 @item overlay load-target
13416 @itemx overlay load
13417 @cindex reloading the overlay table
13418 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13419 re-reads the table @value{GDBN} automatically each time the inferior
13420 stops, so this command should only be necessary if you have changed the
13421 overlay mapping yourself using @value{GDBN}. This command is only
13422 useful when using automatic overlay debugging.
13424 @item overlay list-overlays
13425 @itemx overlay list
13426 @cindex listing mapped overlays
13427 Display a list of the overlays currently mapped, along with their mapped
13428 addresses, load addresses, and sizes.
13432 Normally, when @value{GDBN} prints a code address, it includes the name
13433 of the function the address falls in:
13436 (@value{GDBP}) print main
13437 $3 = @{int ()@} 0x11a0 <main>
13440 When overlay debugging is enabled, @value{GDBN} recognizes code in
13441 unmapped overlays, and prints the names of unmapped functions with
13442 asterisks around them. For example, if @code{foo} is a function in an
13443 unmapped overlay, @value{GDBN} prints it this way:
13446 (@value{GDBP}) overlay list
13447 No sections are mapped.
13448 (@value{GDBP}) print foo
13449 $5 = @{int (int)@} 0x100000 <*foo*>
13452 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13456 (@value{GDBP}) overlay list
13457 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13458 mapped at 0x1016 - 0x104a
13459 (@value{GDBP}) print foo
13460 $6 = @{int (int)@} 0x1016 <foo>
13463 When overlay debugging is enabled, @value{GDBN} can find the correct
13464 address for functions and variables in an overlay, whether or not the
13465 overlay is mapped. This allows most @value{GDBN} commands, like
13466 @code{break} and @code{disassemble}, to work normally, even on unmapped
13467 code. However, @value{GDBN}'s breakpoint support has some limitations:
13471 @cindex breakpoints in overlays
13472 @cindex overlays, setting breakpoints in
13473 You can set breakpoints in functions in unmapped overlays, as long as
13474 @value{GDBN} can write to the overlay at its load address.
13476 @value{GDBN} can not set hardware or simulator-based breakpoints in
13477 unmapped overlays. However, if you set a breakpoint at the end of your
13478 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13479 you are using manual overlay management), @value{GDBN} will re-set its
13480 breakpoints properly.
13484 @node Automatic Overlay Debugging
13485 @section Automatic Overlay Debugging
13486 @cindex automatic overlay debugging
13488 @value{GDBN} can automatically track which overlays are mapped and which
13489 are not, given some simple co-operation from the overlay manager in the
13490 inferior. If you enable automatic overlay debugging with the
13491 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13492 looks in the inferior's memory for certain variables describing the
13493 current state of the overlays.
13495 Here are the variables your overlay manager must define to support
13496 @value{GDBN}'s automatic overlay debugging:
13500 @item @code{_ovly_table}:
13501 This variable must be an array of the following structures:
13506 /* The overlay's mapped address. */
13509 /* The size of the overlay, in bytes. */
13510 unsigned long size;
13512 /* The overlay's load address. */
13515 /* Non-zero if the overlay is currently mapped;
13517 unsigned long mapped;
13521 @item @code{_novlys}:
13522 This variable must be a four-byte signed integer, holding the total
13523 number of elements in @code{_ovly_table}.
13527 To decide whether a particular overlay is mapped or not, @value{GDBN}
13528 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13529 @code{lma} members equal the VMA and LMA of the overlay's section in the
13530 executable file. When @value{GDBN} finds a matching entry, it consults
13531 the entry's @code{mapped} member to determine whether the overlay is
13534 In addition, your overlay manager may define a function called
13535 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13536 will silently set a breakpoint there. If the overlay manager then
13537 calls this function whenever it has changed the overlay table, this
13538 will enable @value{GDBN} to accurately keep track of which overlays
13539 are in program memory, and update any breakpoints that may be set
13540 in overlays. This will allow breakpoints to work even if the
13541 overlays are kept in ROM or other non-writable memory while they
13542 are not being executed.
13544 @node Overlay Sample Program
13545 @section Overlay Sample Program
13546 @cindex overlay example program
13548 When linking a program which uses overlays, you must place the overlays
13549 at their load addresses, while relocating them to run at their mapped
13550 addresses. To do this, you must write a linker script (@pxref{Overlay
13551 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13552 since linker scripts are specific to a particular host system, target
13553 architecture, and target memory layout, this manual cannot provide
13554 portable sample code demonstrating @value{GDBN}'s overlay support.
13556 However, the @value{GDBN} source distribution does contain an overlaid
13557 program, with linker scripts for a few systems, as part of its test
13558 suite. The program consists of the following files from
13559 @file{gdb/testsuite/gdb.base}:
13563 The main program file.
13565 A simple overlay manager, used by @file{overlays.c}.
13570 Overlay modules, loaded and used by @file{overlays.c}.
13573 Linker scripts for linking the test program on the @code{d10v-elf}
13574 and @code{m32r-elf} targets.
13577 You can build the test program using the @code{d10v-elf} GCC
13578 cross-compiler like this:
13581 $ d10v-elf-gcc -g -c overlays.c
13582 $ d10v-elf-gcc -g -c ovlymgr.c
13583 $ d10v-elf-gcc -g -c foo.c
13584 $ d10v-elf-gcc -g -c bar.c
13585 $ d10v-elf-gcc -g -c baz.c
13586 $ d10v-elf-gcc -g -c grbx.c
13587 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13588 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13591 The build process is identical for any other architecture, except that
13592 you must substitute the appropriate compiler and linker script for the
13593 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13597 @chapter Using @value{GDBN} with Different Languages
13600 Although programming languages generally have common aspects, they are
13601 rarely expressed in the same manner. For instance, in ANSI C,
13602 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13603 Modula-2, it is accomplished by @code{p^}. Values can also be
13604 represented (and displayed) differently. Hex numbers in C appear as
13605 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13607 @cindex working language
13608 Language-specific information is built into @value{GDBN} for some languages,
13609 allowing you to express operations like the above in your program's
13610 native language, and allowing @value{GDBN} to output values in a manner
13611 consistent with the syntax of your program's native language. The
13612 language you use to build expressions is called the @dfn{working
13616 * Setting:: Switching between source languages
13617 * Show:: Displaying the language
13618 * Checks:: Type and range checks
13619 * Supported Languages:: Supported languages
13620 * Unsupported Languages:: Unsupported languages
13624 @section Switching Between Source Languages
13626 There are two ways to control the working language---either have @value{GDBN}
13627 set it automatically, or select it manually yourself. You can use the
13628 @code{set language} command for either purpose. On startup, @value{GDBN}
13629 defaults to setting the language automatically. The working language is
13630 used to determine how expressions you type are interpreted, how values
13633 In addition to the working language, every source file that
13634 @value{GDBN} knows about has its own working language. For some object
13635 file formats, the compiler might indicate which language a particular
13636 source file is in. However, most of the time @value{GDBN} infers the
13637 language from the name of the file. The language of a source file
13638 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13639 show each frame appropriately for its own language. There is no way to
13640 set the language of a source file from within @value{GDBN}, but you can
13641 set the language associated with a filename extension. @xref{Show, ,
13642 Displaying the Language}.
13644 This is most commonly a problem when you use a program, such
13645 as @code{cfront} or @code{f2c}, that generates C but is written in
13646 another language. In that case, make the
13647 program use @code{#line} directives in its C output; that way
13648 @value{GDBN} will know the correct language of the source code of the original
13649 program, and will display that source code, not the generated C code.
13652 * Filenames:: Filename extensions and languages.
13653 * Manually:: Setting the working language manually
13654 * Automatically:: Having @value{GDBN} infer the source language
13658 @subsection List of Filename Extensions and Languages
13660 If a source file name ends in one of the following extensions, then
13661 @value{GDBN} infers that its language is the one indicated.
13679 C@t{++} source file
13685 Objective-C source file
13689 Fortran source file
13692 Modula-2 source file
13696 Assembler source file. This actually behaves almost like C, but
13697 @value{GDBN} does not skip over function prologues when stepping.
13700 In addition, you may set the language associated with a filename
13701 extension. @xref{Show, , Displaying the Language}.
13704 @subsection Setting the Working Language
13706 If you allow @value{GDBN} to set the language automatically,
13707 expressions are interpreted the same way in your debugging session and
13710 @kindex set language
13711 If you wish, you may set the language manually. To do this, issue the
13712 command @samp{set language @var{lang}}, where @var{lang} is the name of
13713 a language, such as
13714 @code{c} or @code{modula-2}.
13715 For a list of the supported languages, type @samp{set language}.
13717 Setting the language manually prevents @value{GDBN} from updating the working
13718 language automatically. This can lead to confusion if you try
13719 to debug a program when the working language is not the same as the
13720 source language, when an expression is acceptable to both
13721 languages---but means different things. For instance, if the current
13722 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13730 might not have the effect you intended. In C, this means to add
13731 @code{b} and @code{c} and place the result in @code{a}. The result
13732 printed would be the value of @code{a}. In Modula-2, this means to compare
13733 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13735 @node Automatically
13736 @subsection Having @value{GDBN} Infer the Source Language
13738 To have @value{GDBN} set the working language automatically, use
13739 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13740 then infers the working language. That is, when your program stops in a
13741 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13742 working language to the language recorded for the function in that
13743 frame. If the language for a frame is unknown (that is, if the function
13744 or block corresponding to the frame was defined in a source file that
13745 does not have a recognized extension), the current working language is
13746 not changed, and @value{GDBN} issues a warning.
13748 This may not seem necessary for most programs, which are written
13749 entirely in one source language. However, program modules and libraries
13750 written in one source language can be used by a main program written in
13751 a different source language. Using @samp{set language auto} in this
13752 case frees you from having to set the working language manually.
13755 @section Displaying the Language
13757 The following commands help you find out which language is the
13758 working language, and also what language source files were written in.
13761 @item show language
13762 @anchor{show language}
13763 @kindex show language
13764 Display the current working language. This is the
13765 language you can use with commands such as @code{print} to
13766 build and compute expressions that may involve variables in your program.
13769 @kindex info frame@r{, show the source language}
13770 Display the source language for this frame. This language becomes the
13771 working language if you use an identifier from this frame.
13772 @xref{Frame Info, ,Information about a Frame}, to identify the other
13773 information listed here.
13776 @kindex info source@r{, show the source language}
13777 Display the source language of this source file.
13778 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13779 information listed here.
13782 In unusual circumstances, you may have source files with extensions
13783 not in the standard list. You can then set the extension associated
13784 with a language explicitly:
13787 @item set extension-language @var{ext} @var{language}
13788 @kindex set extension-language
13789 Tell @value{GDBN} that source files with extension @var{ext} are to be
13790 assumed as written in the source language @var{language}.
13792 @item info extensions
13793 @kindex info extensions
13794 List all the filename extensions and the associated languages.
13798 @section Type and Range Checking
13800 Some languages are designed to guard you against making seemingly common
13801 errors through a series of compile- and run-time checks. These include
13802 checking the type of arguments to functions and operators and making
13803 sure mathematical overflows are caught at run time. Checks such as
13804 these help to ensure a program's correctness once it has been compiled
13805 by eliminating type mismatches and providing active checks for range
13806 errors when your program is running.
13808 By default @value{GDBN} checks for these errors according to the
13809 rules of the current source language. Although @value{GDBN} does not check
13810 the statements in your program, it can check expressions entered directly
13811 into @value{GDBN} for evaluation via the @code{print} command, for example.
13814 * Type Checking:: An overview of type checking
13815 * Range Checking:: An overview of range checking
13818 @cindex type checking
13819 @cindex checks, type
13820 @node Type Checking
13821 @subsection An Overview of Type Checking
13823 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13824 arguments to operators and functions have to be of the correct type,
13825 otherwise an error occurs. These checks prevent type mismatch
13826 errors from ever causing any run-time problems. For example,
13829 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13831 (@value{GDBP}) print obj.my_method (0)
13834 (@value{GDBP}) print obj.my_method (0x1234)
13835 Cannot resolve method klass::my_method to any overloaded instance
13838 The second example fails because in C@t{++} the integer constant
13839 @samp{0x1234} is not type-compatible with the pointer parameter type.
13841 For the expressions you use in @value{GDBN} commands, you can tell
13842 @value{GDBN} to not enforce strict type checking or
13843 to treat any mismatches as errors and abandon the expression;
13844 When type checking is disabled, @value{GDBN} successfully evaluates
13845 expressions like the second example above.
13847 Even if type checking is off, there may be other reasons
13848 related to type that prevent @value{GDBN} from evaluating an expression.
13849 For instance, @value{GDBN} does not know how to add an @code{int} and
13850 a @code{struct foo}. These particular type errors have nothing to do
13851 with the language in use and usually arise from expressions which make
13852 little sense to evaluate anyway.
13854 @value{GDBN} provides some additional commands for controlling type checking:
13856 @kindex set check type
13857 @kindex show check type
13859 @item set check type on
13860 @itemx set check type off
13861 Set strict type checking on or off. If any type mismatches occur in
13862 evaluating an expression while type checking is on, @value{GDBN} prints a
13863 message and aborts evaluation of the expression.
13865 @item show check type
13866 Show the current setting of type checking and whether @value{GDBN}
13867 is enforcing strict type checking rules.
13870 @cindex range checking
13871 @cindex checks, range
13872 @node Range Checking
13873 @subsection An Overview of Range Checking
13875 In some languages (such as Modula-2), it is an error to exceed the
13876 bounds of a type; this is enforced with run-time checks. Such range
13877 checking is meant to ensure program correctness by making sure
13878 computations do not overflow, or indices on an array element access do
13879 not exceed the bounds of the array.
13881 For expressions you use in @value{GDBN} commands, you can tell
13882 @value{GDBN} to treat range errors in one of three ways: ignore them,
13883 always treat them as errors and abandon the expression, or issue
13884 warnings but evaluate the expression anyway.
13886 A range error can result from numerical overflow, from exceeding an
13887 array index bound, or when you type a constant that is not a member
13888 of any type. Some languages, however, do not treat overflows as an
13889 error. In many implementations of C, mathematical overflow causes the
13890 result to ``wrap around'' to lower values---for example, if @var{m} is
13891 the largest integer value, and @var{s} is the smallest, then
13894 @var{m} + 1 @result{} @var{s}
13897 This, too, is specific to individual languages, and in some cases
13898 specific to individual compilers or machines. @xref{Supported Languages, ,
13899 Supported Languages}, for further details on specific languages.
13901 @value{GDBN} provides some additional commands for controlling the range checker:
13903 @kindex set check range
13904 @kindex show check range
13906 @item set check range auto
13907 Set range checking on or off based on the current working language.
13908 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13911 @item set check range on
13912 @itemx set check range off
13913 Set range checking on or off, overriding the default setting for the
13914 current working language. A warning is issued if the setting does not
13915 match the language default. If a range error occurs and range checking is on,
13916 then a message is printed and evaluation of the expression is aborted.
13918 @item set check range warn
13919 Output messages when the @value{GDBN} range checker detects a range error,
13920 but attempt to evaluate the expression anyway. Evaluating the
13921 expression may still be impossible for other reasons, such as accessing
13922 memory that the process does not own (a typical example from many Unix
13926 Show the current setting of the range checker, and whether or not it is
13927 being set automatically by @value{GDBN}.
13930 @node Supported Languages
13931 @section Supported Languages
13933 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13934 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13935 @c This is false ...
13936 Some @value{GDBN} features may be used in expressions regardless of the
13937 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13938 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13939 ,Expressions}) can be used with the constructs of any supported
13942 The following sections detail to what degree each source language is
13943 supported by @value{GDBN}. These sections are not meant to be language
13944 tutorials or references, but serve only as a reference guide to what the
13945 @value{GDBN} expression parser accepts, and what input and output
13946 formats should look like for different languages. There are many good
13947 books written on each of these languages; please look to these for a
13948 language reference or tutorial.
13951 * C:: C and C@t{++}
13954 * Objective-C:: Objective-C
13955 * OpenCL C:: OpenCL C
13956 * Fortran:: Fortran
13958 * Modula-2:: Modula-2
13963 @subsection C and C@t{++}
13965 @cindex C and C@t{++}
13966 @cindex expressions in C or C@t{++}
13968 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13969 to both languages. Whenever this is the case, we discuss those languages
13973 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13974 @cindex @sc{gnu} C@t{++}
13975 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13976 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13977 effectively, you must compile your C@t{++} programs with a supported
13978 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13979 compiler (@code{aCC}).
13982 * C Operators:: C and C@t{++} operators
13983 * C Constants:: C and C@t{++} constants
13984 * C Plus Plus Expressions:: C@t{++} expressions
13985 * C Defaults:: Default settings for C and C@t{++}
13986 * C Checks:: C and C@t{++} type and range checks
13987 * Debugging C:: @value{GDBN} and C
13988 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13989 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13993 @subsubsection C and C@t{++} Operators
13995 @cindex C and C@t{++} operators
13997 Operators must be defined on values of specific types. For instance,
13998 @code{+} is defined on numbers, but not on structures. Operators are
13999 often defined on groups of types.
14001 For the purposes of C and C@t{++}, the following definitions hold:
14006 @emph{Integral types} include @code{int} with any of its storage-class
14007 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14010 @emph{Floating-point types} include @code{float}, @code{double}, and
14011 @code{long double} (if supported by the target platform).
14014 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14017 @emph{Scalar types} include all of the above.
14022 The following operators are supported. They are listed here
14023 in order of increasing precedence:
14027 The comma or sequencing operator. Expressions in a comma-separated list
14028 are evaluated from left to right, with the result of the entire
14029 expression being the last expression evaluated.
14032 Assignment. The value of an assignment expression is the value
14033 assigned. Defined on scalar types.
14036 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14037 and translated to @w{@code{@var{a} = @var{a op b}}}.
14038 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14039 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14040 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14043 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14044 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14045 should be of an integral type.
14048 Logical @sc{or}. Defined on integral types.
14051 Logical @sc{and}. Defined on integral types.
14054 Bitwise @sc{or}. Defined on integral types.
14057 Bitwise exclusive-@sc{or}. Defined on integral types.
14060 Bitwise @sc{and}. Defined on integral types.
14063 Equality and inequality. Defined on scalar types. The value of these
14064 expressions is 0 for false and non-zero for true.
14066 @item <@r{, }>@r{, }<=@r{, }>=
14067 Less than, greater than, less than or equal, greater than or equal.
14068 Defined on scalar types. The value of these expressions is 0 for false
14069 and non-zero for true.
14072 left shift, and right shift. Defined on integral types.
14075 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14078 Addition and subtraction. Defined on integral types, floating-point types and
14081 @item *@r{, }/@r{, }%
14082 Multiplication, division, and modulus. Multiplication and division are
14083 defined on integral and floating-point types. Modulus is defined on
14087 Increment and decrement. When appearing before a variable, the
14088 operation is performed before the variable is used in an expression;
14089 when appearing after it, the variable's value is used before the
14090 operation takes place.
14093 Pointer dereferencing. Defined on pointer types. Same precedence as
14097 Address operator. Defined on variables. Same precedence as @code{++}.
14099 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14100 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14101 to examine the address
14102 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14106 Negative. Defined on integral and floating-point types. Same
14107 precedence as @code{++}.
14110 Logical negation. Defined on integral types. Same precedence as
14114 Bitwise complement operator. Defined on integral types. Same precedence as
14119 Structure member, and pointer-to-structure member. For convenience,
14120 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14121 pointer based on the stored type information.
14122 Defined on @code{struct} and @code{union} data.
14125 Dereferences of pointers to members.
14128 Array indexing. @code{@var{a}[@var{i}]} is defined as
14129 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14132 Function parameter list. Same precedence as @code{->}.
14135 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14136 and @code{class} types.
14139 Doubled colons also represent the @value{GDBN} scope operator
14140 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14144 If an operator is redefined in the user code, @value{GDBN} usually
14145 attempts to invoke the redefined version instead of using the operator's
14146 predefined meaning.
14149 @subsubsection C and C@t{++} Constants
14151 @cindex C and C@t{++} constants
14153 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14158 Integer constants are a sequence of digits. Octal constants are
14159 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14160 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14161 @samp{l}, specifying that the constant should be treated as a
14165 Floating point constants are a sequence of digits, followed by a decimal
14166 point, followed by a sequence of digits, and optionally followed by an
14167 exponent. An exponent is of the form:
14168 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14169 sequence of digits. The @samp{+} is optional for positive exponents.
14170 A floating-point constant may also end with a letter @samp{f} or
14171 @samp{F}, specifying that the constant should be treated as being of
14172 the @code{float} (as opposed to the default @code{double}) type; or with
14173 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14177 Enumerated constants consist of enumerated identifiers, or their
14178 integral equivalents.
14181 Character constants are a single character surrounded by single quotes
14182 (@code{'}), or a number---the ordinal value of the corresponding character
14183 (usually its @sc{ascii} value). Within quotes, the single character may
14184 be represented by a letter or by @dfn{escape sequences}, which are of
14185 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14186 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14187 @samp{@var{x}} is a predefined special character---for example,
14188 @samp{\n} for newline.
14190 Wide character constants can be written by prefixing a character
14191 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14192 form of @samp{x}. The target wide character set is used when
14193 computing the value of this constant (@pxref{Character Sets}).
14196 String constants are a sequence of character constants surrounded by
14197 double quotes (@code{"}). Any valid character constant (as described
14198 above) may appear. Double quotes within the string must be preceded by
14199 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14202 Wide string constants can be written by prefixing a string constant
14203 with @samp{L}, as in C. The target wide character set is used when
14204 computing the value of this constant (@pxref{Character Sets}).
14207 Pointer constants are an integral value. You can also write pointers
14208 to constants using the C operator @samp{&}.
14211 Array constants are comma-separated lists surrounded by braces @samp{@{}
14212 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14213 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14214 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14217 @node C Plus Plus Expressions
14218 @subsubsection C@t{++} Expressions
14220 @cindex expressions in C@t{++}
14221 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14223 @cindex debugging C@t{++} programs
14224 @cindex C@t{++} compilers
14225 @cindex debug formats and C@t{++}
14226 @cindex @value{NGCC} and C@t{++}
14228 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14229 the proper compiler and the proper debug format. Currently,
14230 @value{GDBN} works best when debugging C@t{++} code that is compiled
14231 with the most recent version of @value{NGCC} possible. The DWARF
14232 debugging format is preferred; @value{NGCC} defaults to this on most
14233 popular platforms. Other compilers and/or debug formats are likely to
14234 work badly or not at all when using @value{GDBN} to debug C@t{++}
14235 code. @xref{Compilation}.
14240 @cindex member functions
14242 Member function calls are allowed; you can use expressions like
14245 count = aml->GetOriginal(x, y)
14248 @vindex this@r{, inside C@t{++} member functions}
14249 @cindex namespace in C@t{++}
14251 While a member function is active (in the selected stack frame), your
14252 expressions have the same namespace available as the member function;
14253 that is, @value{GDBN} allows implicit references to the class instance
14254 pointer @code{this} following the same rules as C@t{++}. @code{using}
14255 declarations in the current scope are also respected by @value{GDBN}.
14257 @cindex call overloaded functions
14258 @cindex overloaded functions, calling
14259 @cindex type conversions in C@t{++}
14261 You can call overloaded functions; @value{GDBN} resolves the function
14262 call to the right definition, with some restrictions. @value{GDBN} does not
14263 perform overload resolution involving user-defined type conversions,
14264 calls to constructors, or instantiations of templates that do not exist
14265 in the program. It also cannot handle ellipsis argument lists or
14268 It does perform integral conversions and promotions, floating-point
14269 promotions, arithmetic conversions, pointer conversions, conversions of
14270 class objects to base classes, and standard conversions such as those of
14271 functions or arrays to pointers; it requires an exact match on the
14272 number of function arguments.
14274 Overload resolution is always performed, unless you have specified
14275 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14276 ,@value{GDBN} Features for C@t{++}}.
14278 You must specify @code{set overload-resolution off} in order to use an
14279 explicit function signature to call an overloaded function, as in
14281 p 'foo(char,int)'('x', 13)
14284 The @value{GDBN} command-completion facility can simplify this;
14285 see @ref{Completion, ,Command Completion}.
14287 @cindex reference declarations
14289 @value{GDBN} understands variables declared as C@t{++} references; you can use
14290 them in expressions just as you do in C@t{++} source---they are automatically
14293 In the parameter list shown when @value{GDBN} displays a frame, the values of
14294 reference variables are not displayed (unlike other variables); this
14295 avoids clutter, since references are often used for large structures.
14296 The @emph{address} of a reference variable is always shown, unless
14297 you have specified @samp{set print address off}.
14300 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14301 expressions can use it just as expressions in your program do. Since
14302 one scope may be defined in another, you can use @code{::} repeatedly if
14303 necessary, for example in an expression like
14304 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14305 resolving name scope by reference to source files, in both C and C@t{++}
14306 debugging (@pxref{Variables, ,Program Variables}).
14309 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14314 @subsubsection C and C@t{++} Defaults
14316 @cindex C and C@t{++} defaults
14318 If you allow @value{GDBN} to set range checking automatically, it
14319 defaults to @code{off} whenever the working language changes to
14320 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14321 selects the working language.
14323 If you allow @value{GDBN} to set the language automatically, it
14324 recognizes source files whose names end with @file{.c}, @file{.C}, or
14325 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14326 these files, it sets the working language to C or C@t{++}.
14327 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14328 for further details.
14331 @subsubsection C and C@t{++} Type and Range Checks
14333 @cindex C and C@t{++} checks
14335 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14336 checking is used. However, if you turn type checking off, @value{GDBN}
14337 will allow certain non-standard conversions, such as promoting integer
14338 constants to pointers.
14340 Range checking, if turned on, is done on mathematical operations. Array
14341 indices are not checked, since they are often used to index a pointer
14342 that is not itself an array.
14345 @subsubsection @value{GDBN} and C
14347 The @code{set print union} and @code{show print union} commands apply to
14348 the @code{union} type. When set to @samp{on}, any @code{union} that is
14349 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14350 appears as @samp{@{...@}}.
14352 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14353 with pointers and a memory allocation function. @xref{Expressions,
14356 @node Debugging C Plus Plus
14357 @subsubsection @value{GDBN} Features for C@t{++}
14359 @cindex commands for C@t{++}
14361 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14362 designed specifically for use with C@t{++}. Here is a summary:
14365 @cindex break in overloaded functions
14366 @item @r{breakpoint menus}
14367 When you want a breakpoint in a function whose name is overloaded,
14368 @value{GDBN} has the capability to display a menu of possible breakpoint
14369 locations to help you specify which function definition you want.
14370 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14372 @cindex overloading in C@t{++}
14373 @item rbreak @var{regex}
14374 Setting breakpoints using regular expressions is helpful for setting
14375 breakpoints on overloaded functions that are not members of any special
14377 @xref{Set Breaks, ,Setting Breakpoints}.
14379 @cindex C@t{++} exception handling
14381 @itemx catch rethrow
14383 Debug C@t{++} exception handling using these commands. @xref{Set
14384 Catchpoints, , Setting Catchpoints}.
14386 @cindex inheritance
14387 @item ptype @var{typename}
14388 Print inheritance relationships as well as other information for type
14390 @xref{Symbols, ,Examining the Symbol Table}.
14392 @item info vtbl @var{expression}.
14393 The @code{info vtbl} command can be used to display the virtual
14394 method tables of the object computed by @var{expression}. This shows
14395 one entry per virtual table; there may be multiple virtual tables when
14396 multiple inheritance is in use.
14398 @cindex C@t{++} demangling
14399 @item demangle @var{name}
14400 Demangle @var{name}.
14401 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14403 @cindex C@t{++} symbol display
14404 @item set print demangle
14405 @itemx show print demangle
14406 @itemx set print asm-demangle
14407 @itemx show print asm-demangle
14408 Control whether C@t{++} symbols display in their source form, both when
14409 displaying code as C@t{++} source and when displaying disassemblies.
14410 @xref{Print Settings, ,Print Settings}.
14412 @item set print object
14413 @itemx show print object
14414 Choose whether to print derived (actual) or declared types of objects.
14415 @xref{Print Settings, ,Print Settings}.
14417 @item set print vtbl
14418 @itemx show print vtbl
14419 Control the format for printing virtual function tables.
14420 @xref{Print Settings, ,Print Settings}.
14421 (The @code{vtbl} commands do not work on programs compiled with the HP
14422 ANSI C@t{++} compiler (@code{aCC}).)
14424 @kindex set overload-resolution
14425 @cindex overloaded functions, overload resolution
14426 @item set overload-resolution on
14427 Enable overload resolution for C@t{++} expression evaluation. The default
14428 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14429 and searches for a function whose signature matches the argument types,
14430 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14431 Expressions, ,C@t{++} Expressions}, for details).
14432 If it cannot find a match, it emits a message.
14434 @item set overload-resolution off
14435 Disable overload resolution for C@t{++} expression evaluation. For
14436 overloaded functions that are not class member functions, @value{GDBN}
14437 chooses the first function of the specified name that it finds in the
14438 symbol table, whether or not its arguments are of the correct type. For
14439 overloaded functions that are class member functions, @value{GDBN}
14440 searches for a function whose signature @emph{exactly} matches the
14443 @kindex show overload-resolution
14444 @item show overload-resolution
14445 Show the current setting of overload resolution.
14447 @item @r{Overloaded symbol names}
14448 You can specify a particular definition of an overloaded symbol, using
14449 the same notation that is used to declare such symbols in C@t{++}: type
14450 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14451 also use the @value{GDBN} command-line word completion facilities to list the
14452 available choices, or to finish the type list for you.
14453 @xref{Completion,, Command Completion}, for details on how to do this.
14456 @node Decimal Floating Point
14457 @subsubsection Decimal Floating Point format
14458 @cindex decimal floating point format
14460 @value{GDBN} can examine, set and perform computations with numbers in
14461 decimal floating point format, which in the C language correspond to the
14462 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14463 specified by the extension to support decimal floating-point arithmetic.
14465 There are two encodings in use, depending on the architecture: BID (Binary
14466 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14467 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14470 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14471 to manipulate decimal floating point numbers, it is not possible to convert
14472 (using a cast, for example) integers wider than 32-bit to decimal float.
14474 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14475 point computations, error checking in decimal float operations ignores
14476 underflow, overflow and divide by zero exceptions.
14478 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14479 to inspect @code{_Decimal128} values stored in floating point registers.
14480 See @ref{PowerPC,,PowerPC} for more details.
14486 @value{GDBN} can be used to debug programs written in D and compiled with
14487 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14488 specific feature --- dynamic arrays.
14493 @cindex Go (programming language)
14494 @value{GDBN} can be used to debug programs written in Go and compiled with
14495 @file{gccgo} or @file{6g} compilers.
14497 Here is a summary of the Go-specific features and restrictions:
14500 @cindex current Go package
14501 @item The current Go package
14502 The name of the current package does not need to be specified when
14503 specifying global variables and functions.
14505 For example, given the program:
14509 var myglob = "Shall we?"
14515 When stopped inside @code{main} either of these work:
14519 (gdb) p main.myglob
14522 @cindex builtin Go types
14523 @item Builtin Go types
14524 The @code{string} type is recognized by @value{GDBN} and is printed
14527 @cindex builtin Go functions
14528 @item Builtin Go functions
14529 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14530 function and handles it internally.
14532 @cindex restrictions on Go expressions
14533 @item Restrictions on Go expressions
14534 All Go operators are supported except @code{&^}.
14535 The Go @code{_} ``blank identifier'' is not supported.
14536 Automatic dereferencing of pointers is not supported.
14540 @subsection Objective-C
14542 @cindex Objective-C
14543 This section provides information about some commands and command
14544 options that are useful for debugging Objective-C code. See also
14545 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14546 few more commands specific to Objective-C support.
14549 * Method Names in Commands::
14550 * The Print Command with Objective-C::
14553 @node Method Names in Commands
14554 @subsubsection Method Names in Commands
14556 The following commands have been extended to accept Objective-C method
14557 names as line specifications:
14559 @kindex clear@r{, and Objective-C}
14560 @kindex break@r{, and Objective-C}
14561 @kindex info line@r{, and Objective-C}
14562 @kindex jump@r{, and Objective-C}
14563 @kindex list@r{, and Objective-C}
14567 @item @code{info line}
14572 A fully qualified Objective-C method name is specified as
14575 -[@var{Class} @var{methodName}]
14578 where the minus sign is used to indicate an instance method and a
14579 plus sign (not shown) is used to indicate a class method. The class
14580 name @var{Class} and method name @var{methodName} are enclosed in
14581 brackets, similar to the way messages are specified in Objective-C
14582 source code. For example, to set a breakpoint at the @code{create}
14583 instance method of class @code{Fruit} in the program currently being
14587 break -[Fruit create]
14590 To list ten program lines around the @code{initialize} class method,
14594 list +[NSText initialize]
14597 In the current version of @value{GDBN}, the plus or minus sign is
14598 required. In future versions of @value{GDBN}, the plus or minus
14599 sign will be optional, but you can use it to narrow the search. It
14600 is also possible to specify just a method name:
14606 You must specify the complete method name, including any colons. If
14607 your program's source files contain more than one @code{create} method,
14608 you'll be presented with a numbered list of classes that implement that
14609 method. Indicate your choice by number, or type @samp{0} to exit if
14612 As another example, to clear a breakpoint established at the
14613 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14616 clear -[NSWindow makeKeyAndOrderFront:]
14619 @node The Print Command with Objective-C
14620 @subsubsection The Print Command With Objective-C
14621 @cindex Objective-C, print objects
14622 @kindex print-object
14623 @kindex po @r{(@code{print-object})}
14625 The print command has also been extended to accept methods. For example:
14628 print -[@var{object} hash]
14631 @cindex print an Objective-C object description
14632 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14634 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14635 and print the result. Also, an additional command has been added,
14636 @code{print-object} or @code{po} for short, which is meant to print
14637 the description of an object. However, this command may only work
14638 with certain Objective-C libraries that have a particular hook
14639 function, @code{_NSPrintForDebugger}, defined.
14642 @subsection OpenCL C
14645 This section provides information about @value{GDBN}s OpenCL C support.
14648 * OpenCL C Datatypes::
14649 * OpenCL C Expressions::
14650 * OpenCL C Operators::
14653 @node OpenCL C Datatypes
14654 @subsubsection OpenCL C Datatypes
14656 @cindex OpenCL C Datatypes
14657 @value{GDBN} supports the builtin scalar and vector datatypes specified
14658 by OpenCL 1.1. In addition the half- and double-precision floating point
14659 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14660 extensions are also known to @value{GDBN}.
14662 @node OpenCL C Expressions
14663 @subsubsection OpenCL C Expressions
14665 @cindex OpenCL C Expressions
14666 @value{GDBN} supports accesses to vector components including the access as
14667 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14668 supported by @value{GDBN} can be used as well.
14670 @node OpenCL C Operators
14671 @subsubsection OpenCL C Operators
14673 @cindex OpenCL C Operators
14674 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14678 @subsection Fortran
14679 @cindex Fortran-specific support in @value{GDBN}
14681 @value{GDBN} can be used to debug programs written in Fortran, but it
14682 currently supports only the features of Fortran 77 language.
14684 @cindex trailing underscore, in Fortran symbols
14685 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14686 among them) append an underscore to the names of variables and
14687 functions. When you debug programs compiled by those compilers, you
14688 will need to refer to variables and functions with a trailing
14692 * Fortran Operators:: Fortran operators and expressions
14693 * Fortran Defaults:: Default settings for Fortran
14694 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14697 @node Fortran Operators
14698 @subsubsection Fortran Operators and Expressions
14700 @cindex Fortran operators and expressions
14702 Operators must be defined on values of specific types. For instance,
14703 @code{+} is defined on numbers, but not on characters or other non-
14704 arithmetic types. Operators are often defined on groups of types.
14708 The exponentiation operator. It raises the first operand to the power
14712 The range operator. Normally used in the form of array(low:high) to
14713 represent a section of array.
14716 The access component operator. Normally used to access elements in derived
14717 types. Also suitable for unions. As unions aren't part of regular Fortran,
14718 this can only happen when accessing a register that uses a gdbarch-defined
14722 @node Fortran Defaults
14723 @subsubsection Fortran Defaults
14725 @cindex Fortran Defaults
14727 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14728 default uses case-insensitive matches for Fortran symbols. You can
14729 change that with the @samp{set case-insensitive} command, see
14730 @ref{Symbols}, for the details.
14732 @node Special Fortran Commands
14733 @subsubsection Special Fortran Commands
14735 @cindex Special Fortran commands
14737 @value{GDBN} has some commands to support Fortran-specific features,
14738 such as displaying common blocks.
14741 @cindex @code{COMMON} blocks, Fortran
14742 @kindex info common
14743 @item info common @r{[}@var{common-name}@r{]}
14744 This command prints the values contained in the Fortran @code{COMMON}
14745 block whose name is @var{common-name}. With no argument, the names of
14746 all @code{COMMON} blocks visible at the current program location are
14753 @cindex Pascal support in @value{GDBN}, limitations
14754 Debugging Pascal programs which use sets, subranges, file variables, or
14755 nested functions does not currently work. @value{GDBN} does not support
14756 entering expressions, printing values, or similar features using Pascal
14759 The Pascal-specific command @code{set print pascal_static-members}
14760 controls whether static members of Pascal objects are displayed.
14761 @xref{Print Settings, pascal_static-members}.
14764 @subsection Modula-2
14766 @cindex Modula-2, @value{GDBN} support
14768 The extensions made to @value{GDBN} to support Modula-2 only support
14769 output from the @sc{gnu} Modula-2 compiler (which is currently being
14770 developed). Other Modula-2 compilers are not currently supported, and
14771 attempting to debug executables produced by them is most likely
14772 to give an error as @value{GDBN} reads in the executable's symbol
14775 @cindex expressions in Modula-2
14777 * M2 Operators:: Built-in operators
14778 * Built-In Func/Proc:: Built-in functions and procedures
14779 * M2 Constants:: Modula-2 constants
14780 * M2 Types:: Modula-2 types
14781 * M2 Defaults:: Default settings for Modula-2
14782 * Deviations:: Deviations from standard Modula-2
14783 * M2 Checks:: Modula-2 type and range checks
14784 * M2 Scope:: The scope operators @code{::} and @code{.}
14785 * GDB/M2:: @value{GDBN} and Modula-2
14789 @subsubsection Operators
14790 @cindex Modula-2 operators
14792 Operators must be defined on values of specific types. For instance,
14793 @code{+} is defined on numbers, but not on structures. Operators are
14794 often defined on groups of types. For the purposes of Modula-2, the
14795 following definitions hold:
14800 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14804 @emph{Character types} consist of @code{CHAR} and its subranges.
14807 @emph{Floating-point types} consist of @code{REAL}.
14810 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14814 @emph{Scalar types} consist of all of the above.
14817 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14820 @emph{Boolean types} consist of @code{BOOLEAN}.
14824 The following operators are supported, and appear in order of
14825 increasing precedence:
14829 Function argument or array index separator.
14832 Assignment. The value of @var{var} @code{:=} @var{value} is
14836 Less than, greater than on integral, floating-point, or enumerated
14840 Less than or equal to, greater than or equal to
14841 on integral, floating-point and enumerated types, or set inclusion on
14842 set types. Same precedence as @code{<}.
14844 @item =@r{, }<>@r{, }#
14845 Equality and two ways of expressing inequality, valid on scalar types.
14846 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14847 available for inequality, since @code{#} conflicts with the script
14851 Set membership. Defined on set types and the types of their members.
14852 Same precedence as @code{<}.
14855 Boolean disjunction. Defined on boolean types.
14858 Boolean conjunction. Defined on boolean types.
14861 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14864 Addition and subtraction on integral and floating-point types, or union
14865 and difference on set types.
14868 Multiplication on integral and floating-point types, or set intersection
14872 Division on floating-point types, or symmetric set difference on set
14873 types. Same precedence as @code{*}.
14876 Integer division and remainder. Defined on integral types. Same
14877 precedence as @code{*}.
14880 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14883 Pointer dereferencing. Defined on pointer types.
14886 Boolean negation. Defined on boolean types. Same precedence as
14890 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14891 precedence as @code{^}.
14894 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14897 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14901 @value{GDBN} and Modula-2 scope operators.
14905 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14906 treats the use of the operator @code{IN}, or the use of operators
14907 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14908 @code{<=}, and @code{>=} on sets as an error.
14912 @node Built-In Func/Proc
14913 @subsubsection Built-in Functions and Procedures
14914 @cindex Modula-2 built-ins
14916 Modula-2 also makes available several built-in procedures and functions.
14917 In describing these, the following metavariables are used:
14922 represents an @code{ARRAY} variable.
14925 represents a @code{CHAR} constant or variable.
14928 represents a variable or constant of integral type.
14931 represents an identifier that belongs to a set. Generally used in the
14932 same function with the metavariable @var{s}. The type of @var{s} should
14933 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14936 represents a variable or constant of integral or floating-point type.
14939 represents a variable or constant of floating-point type.
14945 represents a variable.
14948 represents a variable or constant of one of many types. See the
14949 explanation of the function for details.
14952 All Modula-2 built-in procedures also return a result, described below.
14956 Returns the absolute value of @var{n}.
14959 If @var{c} is a lower case letter, it returns its upper case
14960 equivalent, otherwise it returns its argument.
14963 Returns the character whose ordinal value is @var{i}.
14966 Decrements the value in the variable @var{v} by one. Returns the new value.
14968 @item DEC(@var{v},@var{i})
14969 Decrements the value in the variable @var{v} by @var{i}. Returns the
14972 @item EXCL(@var{m},@var{s})
14973 Removes the element @var{m} from the set @var{s}. Returns the new
14976 @item FLOAT(@var{i})
14977 Returns the floating point equivalent of the integer @var{i}.
14979 @item HIGH(@var{a})
14980 Returns the index of the last member of @var{a}.
14983 Increments the value in the variable @var{v} by one. Returns the new value.
14985 @item INC(@var{v},@var{i})
14986 Increments the value in the variable @var{v} by @var{i}. Returns the
14989 @item INCL(@var{m},@var{s})
14990 Adds the element @var{m} to the set @var{s} if it is not already
14991 there. Returns the new set.
14994 Returns the maximum value of the type @var{t}.
14997 Returns the minimum value of the type @var{t}.
15000 Returns boolean TRUE if @var{i} is an odd number.
15003 Returns the ordinal value of its argument. For example, the ordinal
15004 value of a character is its @sc{ascii} value (on machines supporting
15005 the @sc{ascii} character set). The argument @var{x} must be of an
15006 ordered type, which include integral, character and enumerated types.
15008 @item SIZE(@var{x})
15009 Returns the size of its argument. The argument @var{x} can be a
15010 variable or a type.
15012 @item TRUNC(@var{r})
15013 Returns the integral part of @var{r}.
15015 @item TSIZE(@var{x})
15016 Returns the size of its argument. The argument @var{x} can be a
15017 variable or a type.
15019 @item VAL(@var{t},@var{i})
15020 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15024 @emph{Warning:} Sets and their operations are not yet supported, so
15025 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15029 @cindex Modula-2 constants
15031 @subsubsection Constants
15033 @value{GDBN} allows you to express the constants of Modula-2 in the following
15039 Integer constants are simply a sequence of digits. When used in an
15040 expression, a constant is interpreted to be type-compatible with the
15041 rest of the expression. Hexadecimal integers are specified by a
15042 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15045 Floating point constants appear as a sequence of digits, followed by a
15046 decimal point and another sequence of digits. An optional exponent can
15047 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15048 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15049 digits of the floating point constant must be valid decimal (base 10)
15053 Character constants consist of a single character enclosed by a pair of
15054 like quotes, either single (@code{'}) or double (@code{"}). They may
15055 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15056 followed by a @samp{C}.
15059 String constants consist of a sequence of characters enclosed by a
15060 pair of like quotes, either single (@code{'}) or double (@code{"}).
15061 Escape sequences in the style of C are also allowed. @xref{C
15062 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15066 Enumerated constants consist of an enumerated identifier.
15069 Boolean constants consist of the identifiers @code{TRUE} and
15073 Pointer constants consist of integral values only.
15076 Set constants are not yet supported.
15080 @subsubsection Modula-2 Types
15081 @cindex Modula-2 types
15083 Currently @value{GDBN} can print the following data types in Modula-2
15084 syntax: array types, record types, set types, pointer types, procedure
15085 types, enumerated types, subrange types and base types. You can also
15086 print the contents of variables declared using these type.
15087 This section gives a number of simple source code examples together with
15088 sample @value{GDBN} sessions.
15090 The first example contains the following section of code:
15099 and you can request @value{GDBN} to interrogate the type and value of
15100 @code{r} and @code{s}.
15103 (@value{GDBP}) print s
15105 (@value{GDBP}) ptype s
15107 (@value{GDBP}) print r
15109 (@value{GDBP}) ptype r
15114 Likewise if your source code declares @code{s} as:
15118 s: SET ['A'..'Z'] ;
15122 then you may query the type of @code{s} by:
15125 (@value{GDBP}) ptype s
15126 type = SET ['A'..'Z']
15130 Note that at present you cannot interactively manipulate set
15131 expressions using the debugger.
15133 The following example shows how you might declare an array in Modula-2
15134 and how you can interact with @value{GDBN} to print its type and contents:
15138 s: ARRAY [-10..10] OF CHAR ;
15142 (@value{GDBP}) ptype s
15143 ARRAY [-10..10] OF CHAR
15146 Note that the array handling is not yet complete and although the type
15147 is printed correctly, expression handling still assumes that all
15148 arrays have a lower bound of zero and not @code{-10} as in the example
15151 Here are some more type related Modula-2 examples:
15155 colour = (blue, red, yellow, green) ;
15156 t = [blue..yellow] ;
15164 The @value{GDBN} interaction shows how you can query the data type
15165 and value of a variable.
15168 (@value{GDBP}) print s
15170 (@value{GDBP}) ptype t
15171 type = [blue..yellow]
15175 In this example a Modula-2 array is declared and its contents
15176 displayed. Observe that the contents are written in the same way as
15177 their @code{C} counterparts.
15181 s: ARRAY [1..5] OF CARDINAL ;
15187 (@value{GDBP}) print s
15188 $1 = @{1, 0, 0, 0, 0@}
15189 (@value{GDBP}) ptype s
15190 type = ARRAY [1..5] OF CARDINAL
15193 The Modula-2 language interface to @value{GDBN} also understands
15194 pointer types as shown in this example:
15198 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15205 and you can request that @value{GDBN} describes the type of @code{s}.
15208 (@value{GDBP}) ptype s
15209 type = POINTER TO ARRAY [1..5] OF CARDINAL
15212 @value{GDBN} handles compound types as we can see in this example.
15213 Here we combine array types, record types, pointer types and subrange
15224 myarray = ARRAY myrange OF CARDINAL ;
15225 myrange = [-2..2] ;
15227 s: POINTER TO ARRAY myrange OF foo ;
15231 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15235 (@value{GDBP}) ptype s
15236 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15239 f3 : ARRAY [-2..2] OF CARDINAL;
15244 @subsubsection Modula-2 Defaults
15245 @cindex Modula-2 defaults
15247 If type and range checking are set automatically by @value{GDBN}, they
15248 both default to @code{on} whenever the working language changes to
15249 Modula-2. This happens regardless of whether you or @value{GDBN}
15250 selected the working language.
15252 If you allow @value{GDBN} to set the language automatically, then entering
15253 code compiled from a file whose name ends with @file{.mod} sets the
15254 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15255 Infer the Source Language}, for further details.
15258 @subsubsection Deviations from Standard Modula-2
15259 @cindex Modula-2, deviations from
15261 A few changes have been made to make Modula-2 programs easier to debug.
15262 This is done primarily via loosening its type strictness:
15266 Unlike in standard Modula-2, pointer constants can be formed by
15267 integers. This allows you to modify pointer variables during
15268 debugging. (In standard Modula-2, the actual address contained in a
15269 pointer variable is hidden from you; it can only be modified
15270 through direct assignment to another pointer variable or expression that
15271 returned a pointer.)
15274 C escape sequences can be used in strings and characters to represent
15275 non-printable characters. @value{GDBN} prints out strings with these
15276 escape sequences embedded. Single non-printable characters are
15277 printed using the @samp{CHR(@var{nnn})} format.
15280 The assignment operator (@code{:=}) returns the value of its right-hand
15284 All built-in procedures both modify @emph{and} return their argument.
15288 @subsubsection Modula-2 Type and Range Checks
15289 @cindex Modula-2 checks
15292 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15295 @c FIXME remove warning when type/range checks added
15297 @value{GDBN} considers two Modula-2 variables type equivalent if:
15301 They are of types that have been declared equivalent via a @code{TYPE
15302 @var{t1} = @var{t2}} statement
15305 They have been declared on the same line. (Note: This is true of the
15306 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15309 As long as type checking is enabled, any attempt to combine variables
15310 whose types are not equivalent is an error.
15312 Range checking is done on all mathematical operations, assignment, array
15313 index bounds, and all built-in functions and procedures.
15316 @subsubsection The Scope Operators @code{::} and @code{.}
15318 @cindex @code{.}, Modula-2 scope operator
15319 @cindex colon, doubled as scope operator
15321 @vindex colon-colon@r{, in Modula-2}
15322 @c Info cannot handle :: but TeX can.
15325 @vindex ::@r{, in Modula-2}
15328 There are a few subtle differences between the Modula-2 scope operator
15329 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15334 @var{module} . @var{id}
15335 @var{scope} :: @var{id}
15339 where @var{scope} is the name of a module or a procedure,
15340 @var{module} the name of a module, and @var{id} is any declared
15341 identifier within your program, except another module.
15343 Using the @code{::} operator makes @value{GDBN} search the scope
15344 specified by @var{scope} for the identifier @var{id}. If it is not
15345 found in the specified scope, then @value{GDBN} searches all scopes
15346 enclosing the one specified by @var{scope}.
15348 Using the @code{.} operator makes @value{GDBN} search the current scope for
15349 the identifier specified by @var{id} that was imported from the
15350 definition module specified by @var{module}. With this operator, it is
15351 an error if the identifier @var{id} was not imported from definition
15352 module @var{module}, or if @var{id} is not an identifier in
15356 @subsubsection @value{GDBN} and Modula-2
15358 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15359 Five subcommands of @code{set print} and @code{show print} apply
15360 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15361 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15362 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15363 analogue in Modula-2.
15365 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15366 with any language, is not useful with Modula-2. Its
15367 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15368 created in Modula-2 as they can in C or C@t{++}. However, because an
15369 address can be specified by an integral constant, the construct
15370 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15372 @cindex @code{#} in Modula-2
15373 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15374 interpreted as the beginning of a comment. Use @code{<>} instead.
15380 The extensions made to @value{GDBN} for Ada only support
15381 output from the @sc{gnu} Ada (GNAT) compiler.
15382 Other Ada compilers are not currently supported, and
15383 attempting to debug executables produced by them is most likely
15387 @cindex expressions in Ada
15389 * Ada Mode Intro:: General remarks on the Ada syntax
15390 and semantics supported by Ada mode
15392 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15393 * Additions to Ada:: Extensions of the Ada expression syntax.
15394 * Stopping Before Main Program:: Debugging the program during elaboration.
15395 * Ada Exceptions:: Ada Exceptions
15396 * Ada Tasks:: Listing and setting breakpoints in tasks.
15397 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15398 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15400 * Ada Glitches:: Known peculiarities of Ada mode.
15403 @node Ada Mode Intro
15404 @subsubsection Introduction
15405 @cindex Ada mode, general
15407 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15408 syntax, with some extensions.
15409 The philosophy behind the design of this subset is
15413 That @value{GDBN} should provide basic literals and access to operations for
15414 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15415 leaving more sophisticated computations to subprograms written into the
15416 program (which therefore may be called from @value{GDBN}).
15419 That type safety and strict adherence to Ada language restrictions
15420 are not particularly important to the @value{GDBN} user.
15423 That brevity is important to the @value{GDBN} user.
15426 Thus, for brevity, the debugger acts as if all names declared in
15427 user-written packages are directly visible, even if they are not visible
15428 according to Ada rules, thus making it unnecessary to fully qualify most
15429 names with their packages, regardless of context. Where this causes
15430 ambiguity, @value{GDBN} asks the user's intent.
15432 The debugger will start in Ada mode if it detects an Ada main program.
15433 As for other languages, it will enter Ada mode when stopped in a program that
15434 was translated from an Ada source file.
15436 While in Ada mode, you may use `@t{--}' for comments. This is useful
15437 mostly for documenting command files. The standard @value{GDBN} comment
15438 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15439 middle (to allow based literals).
15441 The debugger supports limited overloading. Given a subprogram call in which
15442 the function symbol has multiple definitions, it will use the number of
15443 actual parameters and some information about their types to attempt to narrow
15444 the set of definitions. It also makes very limited use of context, preferring
15445 procedures to functions in the context of the @code{call} command, and
15446 functions to procedures elsewhere.
15448 @node Omissions from Ada
15449 @subsubsection Omissions from Ada
15450 @cindex Ada, omissions from
15452 Here are the notable omissions from the subset:
15456 Only a subset of the attributes are supported:
15460 @t{'First}, @t{'Last}, and @t{'Length}
15461 on array objects (not on types and subtypes).
15464 @t{'Min} and @t{'Max}.
15467 @t{'Pos} and @t{'Val}.
15473 @t{'Range} on array objects (not subtypes), but only as the right
15474 operand of the membership (@code{in}) operator.
15477 @t{'Access}, @t{'Unchecked_Access}, and
15478 @t{'Unrestricted_Access} (a GNAT extension).
15486 @code{Characters.Latin_1} are not available and
15487 concatenation is not implemented. Thus, escape characters in strings are
15488 not currently available.
15491 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15492 equality of representations. They will generally work correctly
15493 for strings and arrays whose elements have integer or enumeration types.
15494 They may not work correctly for arrays whose element
15495 types have user-defined equality, for arrays of real values
15496 (in particular, IEEE-conformant floating point, because of negative
15497 zeroes and NaNs), and for arrays whose elements contain unused bits with
15498 indeterminate values.
15501 The other component-by-component array operations (@code{and}, @code{or},
15502 @code{xor}, @code{not}, and relational tests other than equality)
15503 are not implemented.
15506 @cindex array aggregates (Ada)
15507 @cindex record aggregates (Ada)
15508 @cindex aggregates (Ada)
15509 There is limited support for array and record aggregates. They are
15510 permitted only on the right sides of assignments, as in these examples:
15513 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15514 (@value{GDBP}) set An_Array := (1, others => 0)
15515 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15516 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15517 (@value{GDBP}) set A_Record := (1, "Peter", True);
15518 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15522 discriminant's value by assigning an aggregate has an
15523 undefined effect if that discriminant is used within the record.
15524 However, you can first modify discriminants by directly assigning to
15525 them (which normally would not be allowed in Ada), and then performing an
15526 aggregate assignment. For example, given a variable @code{A_Rec}
15527 declared to have a type such as:
15530 type Rec (Len : Small_Integer := 0) is record
15532 Vals : IntArray (1 .. Len);
15536 you can assign a value with a different size of @code{Vals} with two
15540 (@value{GDBP}) set A_Rec.Len := 4
15541 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15544 As this example also illustrates, @value{GDBN} is very loose about the usual
15545 rules concerning aggregates. You may leave out some of the
15546 components of an array or record aggregate (such as the @code{Len}
15547 component in the assignment to @code{A_Rec} above); they will retain their
15548 original values upon assignment. You may freely use dynamic values as
15549 indices in component associations. You may even use overlapping or
15550 redundant component associations, although which component values are
15551 assigned in such cases is not defined.
15554 Calls to dispatching subprograms are not implemented.
15557 The overloading algorithm is much more limited (i.e., less selective)
15558 than that of real Ada. It makes only limited use of the context in
15559 which a subexpression appears to resolve its meaning, and it is much
15560 looser in its rules for allowing type matches. As a result, some
15561 function calls will be ambiguous, and the user will be asked to choose
15562 the proper resolution.
15565 The @code{new} operator is not implemented.
15568 Entry calls are not implemented.
15571 Aside from printing, arithmetic operations on the native VAX floating-point
15572 formats are not supported.
15575 It is not possible to slice a packed array.
15578 The names @code{True} and @code{False}, when not part of a qualified name,
15579 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15581 Should your program
15582 redefine these names in a package or procedure (at best a dubious practice),
15583 you will have to use fully qualified names to access their new definitions.
15586 @node Additions to Ada
15587 @subsubsection Additions to Ada
15588 @cindex Ada, deviations from
15590 As it does for other languages, @value{GDBN} makes certain generic
15591 extensions to Ada (@pxref{Expressions}):
15595 If the expression @var{E} is a variable residing in memory (typically
15596 a local variable or array element) and @var{N} is a positive integer,
15597 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15598 @var{N}-1 adjacent variables following it in memory as an array. In
15599 Ada, this operator is generally not necessary, since its prime use is
15600 in displaying parts of an array, and slicing will usually do this in
15601 Ada. However, there are occasional uses when debugging programs in
15602 which certain debugging information has been optimized away.
15605 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15606 appears in function or file @var{B}.'' When @var{B} is a file name,
15607 you must typically surround it in single quotes.
15610 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15611 @var{type} that appears at address @var{addr}.''
15614 A name starting with @samp{$} is a convenience variable
15615 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15618 In addition, @value{GDBN} provides a few other shortcuts and outright
15619 additions specific to Ada:
15623 The assignment statement is allowed as an expression, returning
15624 its right-hand operand as its value. Thus, you may enter
15627 (@value{GDBP}) set x := y + 3
15628 (@value{GDBP}) print A(tmp := y + 1)
15632 The semicolon is allowed as an ``operator,'' returning as its value
15633 the value of its right-hand operand.
15634 This allows, for example,
15635 complex conditional breaks:
15638 (@value{GDBP}) break f
15639 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15643 Rather than use catenation and symbolic character names to introduce special
15644 characters into strings, one may instead use a special bracket notation,
15645 which is also used to print strings. A sequence of characters of the form
15646 @samp{["@var{XX}"]} within a string or character literal denotes the
15647 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15648 sequence of characters @samp{["""]} also denotes a single quotation mark
15649 in strings. For example,
15651 "One line.["0a"]Next line.["0a"]"
15654 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15658 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15659 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15663 (@value{GDBP}) print 'max(x, y)
15667 When printing arrays, @value{GDBN} uses positional notation when the
15668 array has a lower bound of 1, and uses a modified named notation otherwise.
15669 For example, a one-dimensional array of three integers with a lower bound
15670 of 3 might print as
15677 That is, in contrast to valid Ada, only the first component has a @code{=>}
15681 You may abbreviate attributes in expressions with any unique,
15682 multi-character subsequence of
15683 their names (an exact match gets preference).
15684 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15685 in place of @t{a'length}.
15688 @cindex quoting Ada internal identifiers
15689 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15690 to lower case. The GNAT compiler uses upper-case characters for
15691 some of its internal identifiers, which are normally of no interest to users.
15692 For the rare occasions when you actually have to look at them,
15693 enclose them in angle brackets to avoid the lower-case mapping.
15696 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15700 Printing an object of class-wide type or dereferencing an
15701 access-to-class-wide value will display all the components of the object's
15702 specific type (as indicated by its run-time tag). Likewise, component
15703 selection on such a value will operate on the specific type of the
15708 @node Stopping Before Main Program
15709 @subsubsection Stopping at the Very Beginning
15711 @cindex breakpointing Ada elaboration code
15712 It is sometimes necessary to debug the program during elaboration, and
15713 before reaching the main procedure.
15714 As defined in the Ada Reference
15715 Manual, the elaboration code is invoked from a procedure called
15716 @code{adainit}. To run your program up to the beginning of
15717 elaboration, simply use the following two commands:
15718 @code{tbreak adainit} and @code{run}.
15720 @node Ada Exceptions
15721 @subsubsection Ada Exceptions
15723 A command is provided to list all Ada exceptions:
15726 @kindex info exceptions
15727 @item info exceptions
15728 @itemx info exceptions @var{regexp}
15729 The @code{info exceptions} command allows you to list all Ada exceptions
15730 defined within the program being debugged, as well as their addresses.
15731 With a regular expression, @var{regexp}, as argument, only those exceptions
15732 whose names match @var{regexp} are listed.
15735 Below is a small example, showing how the command can be used, first
15736 without argument, and next with a regular expression passed as an
15740 (@value{GDBP}) info exceptions
15741 All defined Ada exceptions:
15742 constraint_error: 0x613da0
15743 program_error: 0x613d20
15744 storage_error: 0x613ce0
15745 tasking_error: 0x613ca0
15746 const.aint_global_e: 0x613b00
15747 (@value{GDBP}) info exceptions const.aint
15748 All Ada exceptions matching regular expression "const.aint":
15749 constraint_error: 0x613da0
15750 const.aint_global_e: 0x613b00
15753 It is also possible to ask @value{GDBN} to stop your program's execution
15754 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15757 @subsubsection Extensions for Ada Tasks
15758 @cindex Ada, tasking
15760 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15761 @value{GDBN} provides the following task-related commands:
15766 This command shows a list of current Ada tasks, as in the following example:
15773 (@value{GDBP}) info tasks
15774 ID TID P-ID Pri State Name
15775 1 8088000 0 15 Child Activation Wait main_task
15776 2 80a4000 1 15 Accept Statement b
15777 3 809a800 1 15 Child Activation Wait a
15778 * 4 80ae800 3 15 Runnable c
15783 In this listing, the asterisk before the last task indicates it to be the
15784 task currently being inspected.
15788 Represents @value{GDBN}'s internal task number.
15794 The parent's task ID (@value{GDBN}'s internal task number).
15797 The base priority of the task.
15800 Current state of the task.
15804 The task has been created but has not been activated. It cannot be
15808 The task is not blocked for any reason known to Ada. (It may be waiting
15809 for a mutex, though.) It is conceptually "executing" in normal mode.
15812 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15813 that were waiting on terminate alternatives have been awakened and have
15814 terminated themselves.
15816 @item Child Activation Wait
15817 The task is waiting for created tasks to complete activation.
15819 @item Accept Statement
15820 The task is waiting on an accept or selective wait statement.
15822 @item Waiting on entry call
15823 The task is waiting on an entry call.
15825 @item Async Select Wait
15826 The task is waiting to start the abortable part of an asynchronous
15830 The task is waiting on a select statement with only a delay
15833 @item Child Termination Wait
15834 The task is sleeping having completed a master within itself, and is
15835 waiting for the tasks dependent on that master to become terminated or
15836 waiting on a terminate Phase.
15838 @item Wait Child in Term Alt
15839 The task is sleeping waiting for tasks on terminate alternatives to
15840 finish terminating.
15842 @item Accepting RV with @var{taskno}
15843 The task is accepting a rendez-vous with the task @var{taskno}.
15847 Name of the task in the program.
15851 @kindex info task @var{taskno}
15852 @item info task @var{taskno}
15853 This command shows detailled informations on the specified task, as in
15854 the following example:
15859 (@value{GDBP}) info tasks
15860 ID TID P-ID Pri State Name
15861 1 8077880 0 15 Child Activation Wait main_task
15862 * 2 807c468 1 15 Runnable task_1
15863 (@value{GDBP}) info task 2
15864 Ada Task: 0x807c468
15867 Parent: 1 (main_task)
15873 @kindex task@r{ (Ada)}
15874 @cindex current Ada task ID
15875 This command prints the ID of the current task.
15881 (@value{GDBP}) info tasks
15882 ID TID P-ID Pri State Name
15883 1 8077870 0 15 Child Activation Wait main_task
15884 * 2 807c458 1 15 Runnable t
15885 (@value{GDBP}) task
15886 [Current task is 2]
15889 @item task @var{taskno}
15890 @cindex Ada task switching
15891 This command is like the @code{thread @var{threadno}}
15892 command (@pxref{Threads}). It switches the context of debugging
15893 from the current task to the given task.
15899 (@value{GDBP}) info tasks
15900 ID TID P-ID Pri State Name
15901 1 8077870 0 15 Child Activation Wait main_task
15902 * 2 807c458 1 15 Runnable t
15903 (@value{GDBP}) task 1
15904 [Switching to task 1]
15905 #0 0x8067726 in pthread_cond_wait ()
15907 #0 0x8067726 in pthread_cond_wait ()
15908 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15909 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15910 #3 0x806153e in system.tasking.stages.activate_tasks ()
15911 #4 0x804aacc in un () at un.adb:5
15914 @item break @var{linespec} task @var{taskno}
15915 @itemx break @var{linespec} task @var{taskno} if @dots{}
15916 @cindex breakpoints and tasks, in Ada
15917 @cindex task breakpoints, in Ada
15918 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15919 These commands are like the @code{break @dots{} thread @dots{}}
15920 command (@pxref{Thread Stops}). The
15921 @var{linespec} argument specifies source lines, as described
15922 in @ref{Specify Location}.
15924 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15925 to specify that you only want @value{GDBN} to stop the program when a
15926 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15927 numeric task identifiers assigned by @value{GDBN}, shown in the first
15928 column of the @samp{info tasks} display.
15930 If you do not specify @samp{task @var{taskno}} when you set a
15931 breakpoint, the breakpoint applies to @emph{all} tasks of your
15934 You can use the @code{task} qualifier on conditional breakpoints as
15935 well; in this case, place @samp{task @var{taskno}} before the
15936 breakpoint condition (before the @code{if}).
15944 (@value{GDBP}) info tasks
15945 ID TID P-ID Pri State Name
15946 1 140022020 0 15 Child Activation Wait main_task
15947 2 140045060 1 15 Accept/Select Wait t2
15948 3 140044840 1 15 Runnable t1
15949 * 4 140056040 1 15 Runnable t3
15950 (@value{GDBP}) b 15 task 2
15951 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15952 (@value{GDBP}) cont
15957 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15959 (@value{GDBP}) info tasks
15960 ID TID P-ID Pri State Name
15961 1 140022020 0 15 Child Activation Wait main_task
15962 * 2 140045060 1 15 Runnable t2
15963 3 140044840 1 15 Runnable t1
15964 4 140056040 1 15 Delay Sleep t3
15968 @node Ada Tasks and Core Files
15969 @subsubsection Tasking Support when Debugging Core Files
15970 @cindex Ada tasking and core file debugging
15972 When inspecting a core file, as opposed to debugging a live program,
15973 tasking support may be limited or even unavailable, depending on
15974 the platform being used.
15975 For instance, on x86-linux, the list of tasks is available, but task
15976 switching is not supported.
15978 On certain platforms, the debugger needs to perform some
15979 memory writes in order to provide Ada tasking support. When inspecting
15980 a core file, this means that the core file must be opened with read-write
15981 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15982 Under these circumstances, you should make a backup copy of the core
15983 file before inspecting it with @value{GDBN}.
15985 @node Ravenscar Profile
15986 @subsubsection Tasking Support when using the Ravenscar Profile
15987 @cindex Ravenscar Profile
15989 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15990 specifically designed for systems with safety-critical real-time
15994 @kindex set ravenscar task-switching on
15995 @cindex task switching with program using Ravenscar Profile
15996 @item set ravenscar task-switching on
15997 Allows task switching when debugging a program that uses the Ravenscar
15998 Profile. This is the default.
16000 @kindex set ravenscar task-switching off
16001 @item set ravenscar task-switching off
16002 Turn off task switching when debugging a program that uses the Ravenscar
16003 Profile. This is mostly intended to disable the code that adds support
16004 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16005 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16006 To be effective, this command should be run before the program is started.
16008 @kindex show ravenscar task-switching
16009 @item show ravenscar task-switching
16010 Show whether it is possible to switch from task to task in a program
16011 using the Ravenscar Profile.
16016 @subsubsection Known Peculiarities of Ada Mode
16017 @cindex Ada, problems
16019 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16020 we know of several problems with and limitations of Ada mode in
16022 some of which will be fixed with planned future releases of the debugger
16023 and the GNU Ada compiler.
16027 Static constants that the compiler chooses not to materialize as objects in
16028 storage are invisible to the debugger.
16031 Named parameter associations in function argument lists are ignored (the
16032 argument lists are treated as positional).
16035 Many useful library packages are currently invisible to the debugger.
16038 Fixed-point arithmetic, conversions, input, and output is carried out using
16039 floating-point arithmetic, and may give results that only approximate those on
16043 The GNAT compiler never generates the prefix @code{Standard} for any of
16044 the standard symbols defined by the Ada language. @value{GDBN} knows about
16045 this: it will strip the prefix from names when you use it, and will never
16046 look for a name you have so qualified among local symbols, nor match against
16047 symbols in other packages or subprograms. If you have
16048 defined entities anywhere in your program other than parameters and
16049 local variables whose simple names match names in @code{Standard},
16050 GNAT's lack of qualification here can cause confusion. When this happens,
16051 you can usually resolve the confusion
16052 by qualifying the problematic names with package
16053 @code{Standard} explicitly.
16056 Older versions of the compiler sometimes generate erroneous debugging
16057 information, resulting in the debugger incorrectly printing the value
16058 of affected entities. In some cases, the debugger is able to work
16059 around an issue automatically. In other cases, the debugger is able
16060 to work around the issue, but the work-around has to be specifically
16063 @kindex set ada trust-PAD-over-XVS
16064 @kindex show ada trust-PAD-over-XVS
16067 @item set ada trust-PAD-over-XVS on
16068 Configure GDB to strictly follow the GNAT encoding when computing the
16069 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16070 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16071 a complete description of the encoding used by the GNAT compiler).
16072 This is the default.
16074 @item set ada trust-PAD-over-XVS off
16075 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16076 sometimes prints the wrong value for certain entities, changing @code{ada
16077 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16078 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16079 @code{off}, but this incurs a slight performance penalty, so it is
16080 recommended to leave this setting to @code{on} unless necessary.
16084 @cindex GNAT descriptive types
16085 @cindex GNAT encoding
16086 Internally, the debugger also relies on the compiler following a number
16087 of conventions known as the @samp{GNAT Encoding}, all documented in
16088 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16089 how the debugging information should be generated for certain types.
16090 In particular, this convention makes use of @dfn{descriptive types},
16091 which are artificial types generated purely to help the debugger.
16093 These encodings were defined at a time when the debugging information
16094 format used was not powerful enough to describe some of the more complex
16095 types available in Ada. Since DWARF allows us to express nearly all
16096 Ada features, the long-term goal is to slowly replace these descriptive
16097 types by their pure DWARF equivalent. To facilitate that transition,
16098 a new maintenance option is available to force the debugger to ignore
16099 those descriptive types. It allows the user to quickly evaluate how
16100 well @value{GDBN} works without them.
16104 @kindex maint ada set ignore-descriptive-types
16105 @item maintenance ada set ignore-descriptive-types [on|off]
16106 Control whether the debugger should ignore descriptive types.
16107 The default is not to ignore descriptives types (@code{off}).
16109 @kindex maint ada show ignore-descriptive-types
16110 @item maintenance ada show ignore-descriptive-types
16111 Show if descriptive types are ignored by @value{GDBN}.
16115 @node Unsupported Languages
16116 @section Unsupported Languages
16118 @cindex unsupported languages
16119 @cindex minimal language
16120 In addition to the other fully-supported programming languages,
16121 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16122 It does not represent a real programming language, but provides a set
16123 of capabilities close to what the C or assembly languages provide.
16124 This should allow most simple operations to be performed while debugging
16125 an application that uses a language currently not supported by @value{GDBN}.
16127 If the language is set to @code{auto}, @value{GDBN} will automatically
16128 select this language if the current frame corresponds to an unsupported
16132 @chapter Examining the Symbol Table
16134 The commands described in this chapter allow you to inquire about the
16135 symbols (names of variables, functions and types) defined in your
16136 program. This information is inherent in the text of your program and
16137 does not change as your program executes. @value{GDBN} finds it in your
16138 program's symbol table, in the file indicated when you started @value{GDBN}
16139 (@pxref{File Options, ,Choosing Files}), or by one of the
16140 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16142 @cindex symbol names
16143 @cindex names of symbols
16144 @cindex quoting names
16145 Occasionally, you may need to refer to symbols that contain unusual
16146 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16147 most frequent case is in referring to static variables in other
16148 source files (@pxref{Variables,,Program Variables}). File names
16149 are recorded in object files as debugging symbols, but @value{GDBN} would
16150 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16151 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16152 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16159 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16162 @cindex case-insensitive symbol names
16163 @cindex case sensitivity in symbol names
16164 @kindex set case-sensitive
16165 @item set case-sensitive on
16166 @itemx set case-sensitive off
16167 @itemx set case-sensitive auto
16168 Normally, when @value{GDBN} looks up symbols, it matches their names
16169 with case sensitivity determined by the current source language.
16170 Occasionally, you may wish to control that. The command @code{set
16171 case-sensitive} lets you do that by specifying @code{on} for
16172 case-sensitive matches or @code{off} for case-insensitive ones. If
16173 you specify @code{auto}, case sensitivity is reset to the default
16174 suitable for the source language. The default is case-sensitive
16175 matches for all languages except for Fortran, for which the default is
16176 case-insensitive matches.
16178 @kindex show case-sensitive
16179 @item show case-sensitive
16180 This command shows the current setting of case sensitivity for symbols
16183 @kindex set print type methods
16184 @item set print type methods
16185 @itemx set print type methods on
16186 @itemx set print type methods off
16187 Normally, when @value{GDBN} prints a class, it displays any methods
16188 declared in that class. You can control this behavior either by
16189 passing the appropriate flag to @code{ptype}, or using @command{set
16190 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16191 display the methods; this is the default. Specifying @code{off} will
16192 cause @value{GDBN} to omit the methods.
16194 @kindex show print type methods
16195 @item show print type methods
16196 This command shows the current setting of method display when printing
16199 @kindex set print type typedefs
16200 @item set print type typedefs
16201 @itemx set print type typedefs on
16202 @itemx set print type typedefs off
16204 Normally, when @value{GDBN} prints a class, it displays any typedefs
16205 defined in that class. You can control this behavior either by
16206 passing the appropriate flag to @code{ptype}, or using @command{set
16207 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16208 display the typedef definitions; this is the default. Specifying
16209 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16210 Note that this controls whether the typedef definition itself is
16211 printed, not whether typedef names are substituted when printing other
16214 @kindex show print type typedefs
16215 @item show print type typedefs
16216 This command shows the current setting of typedef display when
16219 @kindex info address
16220 @cindex address of a symbol
16221 @item info address @var{symbol}
16222 Describe where the data for @var{symbol} is stored. For a register
16223 variable, this says which register it is kept in. For a non-register
16224 local variable, this prints the stack-frame offset at which the variable
16227 Note the contrast with @samp{print &@var{symbol}}, which does not work
16228 at all for a register variable, and for a stack local variable prints
16229 the exact address of the current instantiation of the variable.
16231 @kindex info symbol
16232 @cindex symbol from address
16233 @cindex closest symbol and offset for an address
16234 @item info symbol @var{addr}
16235 Print the name of a symbol which is stored at the address @var{addr}.
16236 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16237 nearest symbol and an offset from it:
16240 (@value{GDBP}) info symbol 0x54320
16241 _initialize_vx + 396 in section .text
16245 This is the opposite of the @code{info address} command. You can use
16246 it to find out the name of a variable or a function given its address.
16248 For dynamically linked executables, the name of executable or shared
16249 library containing the symbol is also printed:
16252 (@value{GDBP}) info symbol 0x400225
16253 _start + 5 in section .text of /tmp/a.out
16254 (@value{GDBP}) info symbol 0x2aaaac2811cf
16255 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16260 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16261 Demangle @var{name}.
16262 If @var{language} is provided it is the name of the language to demangle
16263 @var{name} in. Otherwise @var{name} is demangled in the current language.
16265 The @samp{--} option specifies the end of options,
16266 and is useful when @var{name} begins with a dash.
16268 The parameter @code{demangle-style} specifies how to interpret the kind
16269 of mangling used. @xref{Print Settings}.
16272 @item whatis[/@var{flags}] [@var{arg}]
16273 Print the data type of @var{arg}, which can be either an expression
16274 or a name of a data type. With no argument, print the data type of
16275 @code{$}, the last value in the value history.
16277 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16278 is not actually evaluated, and any side-effecting operations (such as
16279 assignments or function calls) inside it do not take place.
16281 If @var{arg} is a variable or an expression, @code{whatis} prints its
16282 literal type as it is used in the source code. If the type was
16283 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16284 the data type underlying the @code{typedef}. If the type of the
16285 variable or the expression is a compound data type, such as
16286 @code{struct} or @code{class}, @code{whatis} never prints their
16287 fields or methods. It just prints the @code{struct}/@code{class}
16288 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16289 such a compound data type, use @code{ptype}.
16291 If @var{arg} is a type name that was defined using @code{typedef},
16292 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16293 Unrolling means that @code{whatis} will show the underlying type used
16294 in the @code{typedef} declaration of @var{arg}. However, if that
16295 underlying type is also a @code{typedef}, @code{whatis} will not
16298 For C code, the type names may also have the form @samp{class
16299 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16300 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16302 @var{flags} can be used to modify how the type is displayed.
16303 Available flags are:
16307 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16308 parameters and typedefs defined in a class when printing the class'
16309 members. The @code{/r} flag disables this.
16312 Do not print methods defined in the class.
16315 Print methods defined in the class. This is the default, but the flag
16316 exists in case you change the default with @command{set print type methods}.
16319 Do not print typedefs defined in the class. Note that this controls
16320 whether the typedef definition itself is printed, not whether typedef
16321 names are substituted when printing other types.
16324 Print typedefs defined in the class. This is the default, but the flag
16325 exists in case you change the default with @command{set print type typedefs}.
16329 @item ptype[/@var{flags}] [@var{arg}]
16330 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16331 detailed description of the type, instead of just the name of the type.
16332 @xref{Expressions, ,Expressions}.
16334 Contrary to @code{whatis}, @code{ptype} always unrolls any
16335 @code{typedef}s in its argument declaration, whether the argument is
16336 a variable, expression, or a data type. This means that @code{ptype}
16337 of a variable or an expression will not print literally its type as
16338 present in the source code---use @code{whatis} for that. @code{typedef}s at
16339 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16340 fields, methods and inner @code{class typedef}s of @code{struct}s,
16341 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16343 For example, for this variable declaration:
16346 typedef double real_t;
16347 struct complex @{ real_t real; double imag; @};
16348 typedef struct complex complex_t;
16350 real_t *real_pointer_var;
16354 the two commands give this output:
16358 (@value{GDBP}) whatis var
16360 (@value{GDBP}) ptype var
16361 type = struct complex @{
16365 (@value{GDBP}) whatis complex_t
16366 type = struct complex
16367 (@value{GDBP}) whatis struct complex
16368 type = struct complex
16369 (@value{GDBP}) ptype struct complex
16370 type = struct complex @{
16374 (@value{GDBP}) whatis real_pointer_var
16376 (@value{GDBP}) ptype real_pointer_var
16382 As with @code{whatis}, using @code{ptype} without an argument refers to
16383 the type of @code{$}, the last value in the value history.
16385 @cindex incomplete type
16386 Sometimes, programs use opaque data types or incomplete specifications
16387 of complex data structure. If the debug information included in the
16388 program does not allow @value{GDBN} to display a full declaration of
16389 the data type, it will say @samp{<incomplete type>}. For example,
16390 given these declarations:
16394 struct foo *fooptr;
16398 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16401 (@value{GDBP}) ptype foo
16402 $1 = <incomplete type>
16406 ``Incomplete type'' is C terminology for data types that are not
16407 completely specified.
16410 @item info types @var{regexp}
16412 Print a brief description of all types whose names match the regular
16413 expression @var{regexp} (or all types in your program, if you supply
16414 no argument). Each complete typename is matched as though it were a
16415 complete line; thus, @samp{i type value} gives information on all
16416 types in your program whose names include the string @code{value}, but
16417 @samp{i type ^value$} gives information only on types whose complete
16418 name is @code{value}.
16420 This command differs from @code{ptype} in two ways: first, like
16421 @code{whatis}, it does not print a detailed description; second, it
16422 lists all source files where a type is defined.
16424 @kindex info type-printers
16425 @item info type-printers
16426 Versions of @value{GDBN} that ship with Python scripting enabled may
16427 have ``type printers'' available. When using @command{ptype} or
16428 @command{whatis}, these printers are consulted when the name of a type
16429 is needed. @xref{Type Printing API}, for more information on writing
16432 @code{info type-printers} displays all the available type printers.
16434 @kindex enable type-printer
16435 @kindex disable type-printer
16436 @item enable type-printer @var{name}@dots{}
16437 @item disable type-printer @var{name}@dots{}
16438 These commands can be used to enable or disable type printers.
16441 @cindex local variables
16442 @item info scope @var{location}
16443 List all the variables local to a particular scope. This command
16444 accepts a @var{location} argument---a function name, a source line, or
16445 an address preceded by a @samp{*}, and prints all the variables local
16446 to the scope defined by that location. (@xref{Specify Location}, for
16447 details about supported forms of @var{location}.) For example:
16450 (@value{GDBP}) @b{info scope command_line_handler}
16451 Scope for command_line_handler:
16452 Symbol rl is an argument at stack/frame offset 8, length 4.
16453 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16454 Symbol linelength is in static storage at address 0x150a1c, length 4.
16455 Symbol p is a local variable in register $esi, length 4.
16456 Symbol p1 is a local variable in register $ebx, length 4.
16457 Symbol nline is a local variable in register $edx, length 4.
16458 Symbol repeat is a local variable at frame offset -8, length 4.
16462 This command is especially useful for determining what data to collect
16463 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16466 @kindex info source
16468 Show information about the current source file---that is, the source file for
16469 the function containing the current point of execution:
16472 the name of the source file, and the directory containing it,
16474 the directory it was compiled in,
16476 its length, in lines,
16478 which programming language it is written in,
16480 if the debug information provides it, the program that compiled the file
16481 (which may include, e.g., the compiler version and command line arguments),
16483 whether the executable includes debugging information for that file, and
16484 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16486 whether the debugging information includes information about
16487 preprocessor macros.
16491 @kindex info sources
16493 Print the names of all source files in your program for which there is
16494 debugging information, organized into two lists: files whose symbols
16495 have already been read, and files whose symbols will be read when needed.
16497 @kindex info functions
16498 @item info functions
16499 Print the names and data types of all defined functions.
16501 @item info functions @var{regexp}
16502 Print the names and data types of all defined functions
16503 whose names contain a match for regular expression @var{regexp}.
16504 Thus, @samp{info fun step} finds all functions whose names
16505 include @code{step}; @samp{info fun ^step} finds those whose names
16506 start with @code{step}. If a function name contains characters
16507 that conflict with the regular expression language (e.g.@:
16508 @samp{operator*()}), they may be quoted with a backslash.
16510 @kindex info variables
16511 @item info variables
16512 Print the names and data types of all variables that are defined
16513 outside of functions (i.e.@: excluding local variables).
16515 @item info variables @var{regexp}
16516 Print the names and data types of all variables (except for local
16517 variables) whose names contain a match for regular expression
16520 @kindex info classes
16521 @cindex Objective-C, classes and selectors
16523 @itemx info classes @var{regexp}
16524 Display all Objective-C classes in your program, or
16525 (with the @var{regexp} argument) all those matching a particular regular
16528 @kindex info selectors
16529 @item info selectors
16530 @itemx info selectors @var{regexp}
16531 Display all Objective-C selectors in your program, or
16532 (with the @var{regexp} argument) all those matching a particular regular
16536 This was never implemented.
16537 @kindex info methods
16539 @itemx info methods @var{regexp}
16540 The @code{info methods} command permits the user to examine all defined
16541 methods within C@t{++} program, or (with the @var{regexp} argument) a
16542 specific set of methods found in the various C@t{++} classes. Many
16543 C@t{++} classes provide a large number of methods. Thus, the output
16544 from the @code{ptype} command can be overwhelming and hard to use. The
16545 @code{info-methods} command filters the methods, printing only those
16546 which match the regular-expression @var{regexp}.
16549 @cindex opaque data types
16550 @kindex set opaque-type-resolution
16551 @item set opaque-type-resolution on
16552 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16553 declared as a pointer to a @code{struct}, @code{class}, or
16554 @code{union}---for example, @code{struct MyType *}---that is used in one
16555 source file although the full declaration of @code{struct MyType} is in
16556 another source file. The default is on.
16558 A change in the setting of this subcommand will not take effect until
16559 the next time symbols for a file are loaded.
16561 @item set opaque-type-resolution off
16562 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16563 is printed as follows:
16565 @{<no data fields>@}
16568 @kindex show opaque-type-resolution
16569 @item show opaque-type-resolution
16570 Show whether opaque types are resolved or not.
16572 @kindex set print symbol-loading
16573 @cindex print messages when symbols are loaded
16574 @item set print symbol-loading
16575 @itemx set print symbol-loading full
16576 @itemx set print symbol-loading brief
16577 @itemx set print symbol-loading off
16578 The @code{set print symbol-loading} command allows you to control the
16579 printing of messages when @value{GDBN} loads symbol information.
16580 By default a message is printed for the executable and one for each
16581 shared library, and normally this is what you want. However, when
16582 debugging apps with large numbers of shared libraries these messages
16584 When set to @code{brief} a message is printed for each executable,
16585 and when @value{GDBN} loads a collection of shared libraries at once
16586 it will only print one message regardless of the number of shared
16587 libraries. When set to @code{off} no messages are printed.
16589 @kindex show print symbol-loading
16590 @item show print symbol-loading
16591 Show whether messages will be printed when a @value{GDBN} command
16592 entered from the keyboard causes symbol information to be loaded.
16594 @kindex maint print symbols
16595 @cindex symbol dump
16596 @kindex maint print psymbols
16597 @cindex partial symbol dump
16598 @kindex maint print msymbols
16599 @cindex minimal symbol dump
16600 @item maint print symbols @var{filename}
16601 @itemx maint print psymbols @var{filename}
16602 @itemx maint print msymbols @var{filename}
16603 Write a dump of debugging symbol data into the file @var{filename}.
16604 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16605 symbols with debugging data are included. If you use @samp{maint print
16606 symbols}, @value{GDBN} includes all the symbols for which it has already
16607 collected full details: that is, @var{filename} reflects symbols for
16608 only those files whose symbols @value{GDBN} has read. You can use the
16609 command @code{info sources} to find out which files these are. If you
16610 use @samp{maint print psymbols} instead, the dump shows information about
16611 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16612 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16613 @samp{maint print msymbols} dumps just the minimal symbol information
16614 required for each object file from which @value{GDBN} has read some symbols.
16615 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16616 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16618 @kindex maint info symtabs
16619 @kindex maint info psymtabs
16620 @cindex listing @value{GDBN}'s internal symbol tables
16621 @cindex symbol tables, listing @value{GDBN}'s internal
16622 @cindex full symbol tables, listing @value{GDBN}'s internal
16623 @cindex partial symbol tables, listing @value{GDBN}'s internal
16624 @item maint info symtabs @r{[} @var{regexp} @r{]}
16625 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16627 List the @code{struct symtab} or @code{struct partial_symtab}
16628 structures whose names match @var{regexp}. If @var{regexp} is not
16629 given, list them all. The output includes expressions which you can
16630 copy into a @value{GDBN} debugging this one to examine a particular
16631 structure in more detail. For example:
16634 (@value{GDBP}) maint info psymtabs dwarf2read
16635 @{ objfile /home/gnu/build/gdb/gdb
16636 ((struct objfile *) 0x82e69d0)
16637 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16638 ((struct partial_symtab *) 0x8474b10)
16641 text addresses 0x814d3c8 -- 0x8158074
16642 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16643 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16644 dependencies (none)
16647 (@value{GDBP}) maint info symtabs
16651 We see that there is one partial symbol table whose filename contains
16652 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16653 and we see that @value{GDBN} has not read in any symtabs yet at all.
16654 If we set a breakpoint on a function, that will cause @value{GDBN} to
16655 read the symtab for the compilation unit containing that function:
16658 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16659 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16661 (@value{GDBP}) maint info symtabs
16662 @{ objfile /home/gnu/build/gdb/gdb
16663 ((struct objfile *) 0x82e69d0)
16664 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16665 ((struct symtab *) 0x86c1f38)
16668 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16669 linetable ((struct linetable *) 0x8370fa0)
16670 debugformat DWARF 2
16676 @kindex maint set symbol-cache-size
16677 @cindex symbol cache size
16678 @item maint set symbol-cache-size @var{size}
16679 Set the size of the symbol cache to @var{size}.
16680 The default size is intended to be good enough for debugging
16681 most applications. This option exists to allow for experimenting
16682 with different sizes.
16684 @kindex maint show symbol-cache-size
16685 @item maint show symbol-cache-size
16686 Show the size of the symbol cache.
16688 @kindex maint print symbol-cache
16689 @cindex symbol cache, printing its contents
16690 @item maint print symbol-cache
16691 Print the contents of the symbol cache.
16692 This is useful when debugging symbol cache issues.
16694 @kindex maint print symbol-cache-statistics
16695 @cindex symbol cache, printing usage statistics
16696 @item maint print symbol-cache-statistics
16697 Print symbol cache usage statistics.
16698 This helps determine how well the cache is being utilized.
16700 @kindex maint flush-symbol-cache
16701 @cindex symbol cache, flushing
16702 @item maint flush-symbol-cache
16703 Flush the contents of the symbol cache, all entries are removed.
16704 This command is useful when debugging the symbol cache.
16705 It is also useful when collecting performance data.
16710 @chapter Altering Execution
16712 Once you think you have found an error in your program, you might want to
16713 find out for certain whether correcting the apparent error would lead to
16714 correct results in the rest of the run. You can find the answer by
16715 experiment, using the @value{GDBN} features for altering execution of the
16718 For example, you can store new values into variables or memory
16719 locations, give your program a signal, restart it at a different
16720 address, or even return prematurely from a function.
16723 * Assignment:: Assignment to variables
16724 * Jumping:: Continuing at a different address
16725 * Signaling:: Giving your program a signal
16726 * Returning:: Returning from a function
16727 * Calling:: Calling your program's functions
16728 * Patching:: Patching your program
16729 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16733 @section Assignment to Variables
16736 @cindex setting variables
16737 To alter the value of a variable, evaluate an assignment expression.
16738 @xref{Expressions, ,Expressions}. For example,
16745 stores the value 4 into the variable @code{x}, and then prints the
16746 value of the assignment expression (which is 4).
16747 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16748 information on operators in supported languages.
16750 @kindex set variable
16751 @cindex variables, setting
16752 If you are not interested in seeing the value of the assignment, use the
16753 @code{set} command instead of the @code{print} command. @code{set} is
16754 really the same as @code{print} except that the expression's value is
16755 not printed and is not put in the value history (@pxref{Value History,
16756 ,Value History}). The expression is evaluated only for its effects.
16758 If the beginning of the argument string of the @code{set} command
16759 appears identical to a @code{set} subcommand, use the @code{set
16760 variable} command instead of just @code{set}. This command is identical
16761 to @code{set} except for its lack of subcommands. For example, if your
16762 program has a variable @code{width}, you get an error if you try to set
16763 a new value with just @samp{set width=13}, because @value{GDBN} has the
16764 command @code{set width}:
16767 (@value{GDBP}) whatis width
16769 (@value{GDBP}) p width
16771 (@value{GDBP}) set width=47
16772 Invalid syntax in expression.
16776 The invalid expression, of course, is @samp{=47}. In
16777 order to actually set the program's variable @code{width}, use
16780 (@value{GDBP}) set var width=47
16783 Because the @code{set} command has many subcommands that can conflict
16784 with the names of program variables, it is a good idea to use the
16785 @code{set variable} command instead of just @code{set}. For example, if
16786 your program has a variable @code{g}, you run into problems if you try
16787 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16788 the command @code{set gnutarget}, abbreviated @code{set g}:
16792 (@value{GDBP}) whatis g
16796 (@value{GDBP}) set g=4
16800 The program being debugged has been started already.
16801 Start it from the beginning? (y or n) y
16802 Starting program: /home/smith/cc_progs/a.out
16803 "/home/smith/cc_progs/a.out": can't open to read symbols:
16804 Invalid bfd target.
16805 (@value{GDBP}) show g
16806 The current BFD target is "=4".
16811 The program variable @code{g} did not change, and you silently set the
16812 @code{gnutarget} to an invalid value. In order to set the variable
16816 (@value{GDBP}) set var g=4
16819 @value{GDBN} allows more implicit conversions in assignments than C; you can
16820 freely store an integer value into a pointer variable or vice versa,
16821 and you can convert any structure to any other structure that is the
16822 same length or shorter.
16823 @comment FIXME: how do structs align/pad in these conversions?
16824 @comment /doc@cygnus.com 18dec1990
16826 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16827 construct to generate a value of specified type at a specified address
16828 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16829 to memory location @code{0x83040} as an integer (which implies a certain size
16830 and representation in memory), and
16833 set @{int@}0x83040 = 4
16837 stores the value 4 into that memory location.
16840 @section Continuing at a Different Address
16842 Ordinarily, when you continue your program, you do so at the place where
16843 it stopped, with the @code{continue} command. You can instead continue at
16844 an address of your own choosing, with the following commands:
16848 @kindex j @r{(@code{jump})}
16849 @item jump @var{linespec}
16850 @itemx j @var{linespec}
16851 @itemx jump @var{location}
16852 @itemx j @var{location}
16853 Resume execution at line @var{linespec} or at address given by
16854 @var{location}. Execution stops again immediately if there is a
16855 breakpoint there. @xref{Specify Location}, for a description of the
16856 different forms of @var{linespec} and @var{location}. It is common
16857 practice to use the @code{tbreak} command in conjunction with
16858 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16860 The @code{jump} command does not change the current stack frame, or
16861 the stack pointer, or the contents of any memory location or any
16862 register other than the program counter. If line @var{linespec} is in
16863 a different function from the one currently executing, the results may
16864 be bizarre if the two functions expect different patterns of arguments or
16865 of local variables. For this reason, the @code{jump} command requests
16866 confirmation if the specified line is not in the function currently
16867 executing. However, even bizarre results are predictable if you are
16868 well acquainted with the machine-language code of your program.
16871 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16872 On many systems, you can get much the same effect as the @code{jump}
16873 command by storing a new value into the register @code{$pc}. The
16874 difference is that this does not start your program running; it only
16875 changes the address of where it @emph{will} run when you continue. For
16883 makes the next @code{continue} command or stepping command execute at
16884 address @code{0x485}, rather than at the address where your program stopped.
16885 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16887 The most common occasion to use the @code{jump} command is to back
16888 up---perhaps with more breakpoints set---over a portion of a program
16889 that has already executed, in order to examine its execution in more
16894 @section Giving your Program a Signal
16895 @cindex deliver a signal to a program
16899 @item signal @var{signal}
16900 Resume execution where your program is stopped, but immediately give it the
16901 signal @var{signal}. The @var{signal} can be the name or the number of a
16902 signal. For example, on many systems @code{signal 2} and @code{signal
16903 SIGINT} are both ways of sending an interrupt signal.
16905 Alternatively, if @var{signal} is zero, continue execution without
16906 giving a signal. This is useful when your program stopped on account of
16907 a signal and would ordinarily see the signal when resumed with the
16908 @code{continue} command; @samp{signal 0} causes it to resume without a
16911 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16912 delivered to the currently selected thread, not the thread that last
16913 reported a stop. This includes the situation where a thread was
16914 stopped due to a signal. So if you want to continue execution
16915 suppressing the signal that stopped a thread, you should select that
16916 same thread before issuing the @samp{signal 0} command. If you issue
16917 the @samp{signal 0} command with another thread as the selected one,
16918 @value{GDBN} detects that and asks for confirmation.
16920 Invoking the @code{signal} command is not the same as invoking the
16921 @code{kill} utility from the shell. Sending a signal with @code{kill}
16922 causes @value{GDBN} to decide what to do with the signal depending on
16923 the signal handling tables (@pxref{Signals}). The @code{signal} command
16924 passes the signal directly to your program.
16926 @code{signal} does not repeat when you press @key{RET} a second time
16927 after executing the command.
16929 @kindex queue-signal
16930 @item queue-signal @var{signal}
16931 Queue @var{signal} to be delivered immediately to the current thread
16932 when execution of the thread resumes. The @var{signal} can be the name or
16933 the number of a signal. For example, on many systems @code{signal 2} and
16934 @code{signal SIGINT} are both ways of sending an interrupt signal.
16935 The handling of the signal must be set to pass the signal to the program,
16936 otherwise @value{GDBN} will report an error.
16937 You can control the handling of signals from @value{GDBN} with the
16938 @code{handle} command (@pxref{Signals}).
16940 Alternatively, if @var{signal} is zero, any currently queued signal
16941 for the current thread is discarded and when execution resumes no signal
16942 will be delivered. This is useful when your program stopped on account
16943 of a signal and would ordinarily see the signal when resumed with the
16944 @code{continue} command.
16946 This command differs from the @code{signal} command in that the signal
16947 is just queued, execution is not resumed. And @code{queue-signal} cannot
16948 be used to pass a signal whose handling state has been set to @code{nopass}
16953 @xref{stepping into signal handlers}, for information on how stepping
16954 commands behave when the thread has a signal queued.
16957 @section Returning from a Function
16960 @cindex returning from a function
16963 @itemx return @var{expression}
16964 You can cancel execution of a function call with the @code{return}
16965 command. If you give an
16966 @var{expression} argument, its value is used as the function's return
16970 When you use @code{return}, @value{GDBN} discards the selected stack frame
16971 (and all frames within it). You can think of this as making the
16972 discarded frame return prematurely. If you wish to specify a value to
16973 be returned, give that value as the argument to @code{return}.
16975 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16976 Frame}), and any other frames inside of it, leaving its caller as the
16977 innermost remaining frame. That frame becomes selected. The
16978 specified value is stored in the registers used for returning values
16981 The @code{return} command does not resume execution; it leaves the
16982 program stopped in the state that would exist if the function had just
16983 returned. In contrast, the @code{finish} command (@pxref{Continuing
16984 and Stepping, ,Continuing and Stepping}) resumes execution until the
16985 selected stack frame returns naturally.
16987 @value{GDBN} needs to know how the @var{expression} argument should be set for
16988 the inferior. The concrete registers assignment depends on the OS ABI and the
16989 type being returned by the selected stack frame. For example it is common for
16990 OS ABI to return floating point values in FPU registers while integer values in
16991 CPU registers. Still some ABIs return even floating point values in CPU
16992 registers. Larger integer widths (such as @code{long long int}) also have
16993 specific placement rules. @value{GDBN} already knows the OS ABI from its
16994 current target so it needs to find out also the type being returned to make the
16995 assignment into the right register(s).
16997 Normally, the selected stack frame has debug info. @value{GDBN} will always
16998 use the debug info instead of the implicit type of @var{expression} when the
16999 debug info is available. For example, if you type @kbd{return -1}, and the
17000 function in the current stack frame is declared to return a @code{long long
17001 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17002 into a @code{long long int}:
17005 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17007 (@value{GDBP}) return -1
17008 Make func return now? (y or n) y
17009 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17010 43 printf ("result=%lld\n", func ());
17014 However, if the selected stack frame does not have a debug info, e.g., if the
17015 function was compiled without debug info, @value{GDBN} has to find out the type
17016 to return from user. Specifying a different type by mistake may set the value
17017 in different inferior registers than the caller code expects. For example,
17018 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17019 of a @code{long long int} result for a debug info less function (on 32-bit
17020 architectures). Therefore the user is required to specify the return type by
17021 an appropriate cast explicitly:
17024 Breakpoint 2, 0x0040050b in func ()
17025 (@value{GDBP}) return -1
17026 Return value type not available for selected stack frame.
17027 Please use an explicit cast of the value to return.
17028 (@value{GDBP}) return (long long int) -1
17029 Make selected stack frame return now? (y or n) y
17030 #0 0x00400526 in main ()
17035 @section Calling Program Functions
17038 @cindex calling functions
17039 @cindex inferior functions, calling
17040 @item print @var{expr}
17041 Evaluate the expression @var{expr} and display the resulting value.
17042 The expression may include calls to functions in the program being
17046 @item call @var{expr}
17047 Evaluate the expression @var{expr} without displaying @code{void}
17050 You can use this variant of the @code{print} command if you want to
17051 execute a function from your program that does not return anything
17052 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17053 with @code{void} returned values that @value{GDBN} will otherwise
17054 print. If the result is not void, it is printed and saved in the
17058 It is possible for the function you call via the @code{print} or
17059 @code{call} command to generate a signal (e.g., if there's a bug in
17060 the function, or if you passed it incorrect arguments). What happens
17061 in that case is controlled by the @code{set unwindonsignal} command.
17063 Similarly, with a C@t{++} program it is possible for the function you
17064 call via the @code{print} or @code{call} command to generate an
17065 exception that is not handled due to the constraints of the dummy
17066 frame. In this case, any exception that is raised in the frame, but has
17067 an out-of-frame exception handler will not be found. GDB builds a
17068 dummy-frame for the inferior function call, and the unwinder cannot
17069 seek for exception handlers outside of this dummy-frame. What happens
17070 in that case is controlled by the
17071 @code{set unwind-on-terminating-exception} command.
17074 @item set unwindonsignal
17075 @kindex set unwindonsignal
17076 @cindex unwind stack in called functions
17077 @cindex call dummy stack unwinding
17078 Set unwinding of the stack if a signal is received while in a function
17079 that @value{GDBN} called in the program being debugged. If set to on,
17080 @value{GDBN} unwinds the stack it created for the call and restores
17081 the context to what it was before the call. If set to off (the
17082 default), @value{GDBN} stops in the frame where the signal was
17085 @item show unwindonsignal
17086 @kindex show unwindonsignal
17087 Show the current setting of stack unwinding in the functions called by
17090 @item set unwind-on-terminating-exception
17091 @kindex set unwind-on-terminating-exception
17092 @cindex unwind stack in called functions with unhandled exceptions
17093 @cindex call dummy stack unwinding on unhandled exception.
17094 Set unwinding of the stack if a C@t{++} exception is raised, but left
17095 unhandled while in a function that @value{GDBN} called in the program being
17096 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17097 it created for the call and restores the context to what it was before
17098 the call. If set to off, @value{GDBN} the exception is delivered to
17099 the default C@t{++} exception handler and the inferior terminated.
17101 @item show unwind-on-terminating-exception
17102 @kindex show unwind-on-terminating-exception
17103 Show the current setting of stack unwinding in the functions called by
17108 @cindex weak alias functions
17109 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17110 for another function. In such case, @value{GDBN} might not pick up
17111 the type information, including the types of the function arguments,
17112 which causes @value{GDBN} to call the inferior function incorrectly.
17113 As a result, the called function will function erroneously and may
17114 even crash. A solution to that is to use the name of the aliased
17118 @section Patching Programs
17120 @cindex patching binaries
17121 @cindex writing into executables
17122 @cindex writing into corefiles
17124 By default, @value{GDBN} opens the file containing your program's
17125 executable code (or the corefile) read-only. This prevents accidental
17126 alterations to machine code; but it also prevents you from intentionally
17127 patching your program's binary.
17129 If you'd like to be able to patch the binary, you can specify that
17130 explicitly with the @code{set write} command. For example, you might
17131 want to turn on internal debugging flags, or even to make emergency
17137 @itemx set write off
17138 If you specify @samp{set write on}, @value{GDBN} opens executable and
17139 core files for both reading and writing; if you specify @kbd{set write
17140 off} (the default), @value{GDBN} opens them read-only.
17142 If you have already loaded a file, you must load it again (using the
17143 @code{exec-file} or @code{core-file} command) after changing @code{set
17144 write}, for your new setting to take effect.
17148 Display whether executable files and core files are opened for writing
17149 as well as reading.
17152 @node Compiling and Injecting Code
17153 @section Compiling and injecting code in @value{GDBN}
17154 @cindex injecting code
17155 @cindex writing into executables
17156 @cindex compiling code
17158 @value{GDBN} supports on-demand compilation and code injection into
17159 programs running under @value{GDBN}. GCC 5.0 or higher built with
17160 @file{libcc1.so} must be installed for this functionality to be enabled.
17161 This functionality is implemented with the following commands.
17164 @kindex compile code
17165 @item compile code @var{source-code}
17166 @itemx compile code -raw @var{--} @var{source-code}
17167 Compile @var{source-code} with the compiler language found as the current
17168 language in @value{GDBN} (@pxref{Languages}). If compilation and
17169 injection is not supported with the current language specified in
17170 @value{GDBN}, or the compiler does not support this feature, an error
17171 message will be printed. If @var{source-code} compiles and links
17172 successfully, @value{GDBN} will load the object-code emitted,
17173 and execute it within the context of the currently selected inferior.
17174 It is important to note that the compiled code is executed immediately.
17175 After execution, the compiled code is removed from @value{GDBN} and any
17176 new types or variables you have defined will be deleted.
17178 The command allows you to specify @var{source-code} in two ways.
17179 The simplest method is to provide a single line of code to the command.
17183 compile code printf ("hello world\n");
17186 If you specify options on the command line as well as source code, they
17187 may conflict. The @samp{--} delimiter can be used to separate options
17188 from actual source code. E.g.:
17191 compile code -r -- printf ("hello world\n");
17194 Alternatively you can enter source code as multiple lines of text. To
17195 enter this mode, invoke the @samp{compile code} command without any text
17196 following the command. This will start the multiple-line editor and
17197 allow you to type as many lines of source code as required. When you
17198 have completed typing, enter @samp{end} on its own line to exit the
17203 >printf ("hello\n");
17204 >printf ("world\n");
17208 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17209 provided @var{source-code} in a callable scope. In this case, you must
17210 specify the entry point of the code by defining a function named
17211 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17212 inferior. Using @samp{-raw} option may be needed for example when
17213 @var{source-code} requires @samp{#include} lines which may conflict with
17214 inferior symbols otherwise.
17216 @kindex compile file
17217 @item compile file @var{filename}
17218 @itemx compile file -raw @var{filename}
17219 Like @code{compile code}, but take the source code from @var{filename}.
17222 compile file /home/user/example.c
17226 @subsection Caveats when using the @code{compile} command
17228 There are a few caveats to keep in mind when using the @code{compile}
17229 command. As the caveats are different per language, the table below
17230 highlights specific issues on a per language basis.
17233 @item C code examples and caveats
17234 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17235 attempt to compile the source code with a @samp{C} compiler. The source
17236 code provided to the @code{compile} command will have much the same
17237 access to variables and types as it normally would if it were part of
17238 the program currently being debugged in @value{GDBN}.
17240 Below is a sample program that forms the basis of the examples that
17241 follow. This program has been compiled and loaded into @value{GDBN},
17242 much like any other normal debugging session.
17245 void function1 (void)
17248 printf ("function 1\n");
17251 void function2 (void)
17266 For the purposes of the examples in this section, the program above has
17267 been compiled, loaded into @value{GDBN}, stopped at the function
17268 @code{main}, and @value{GDBN} is awaiting input from the user.
17270 To access variables and types for any program in @value{GDBN}, the
17271 program must be compiled and packaged with debug information. The
17272 @code{compile} command is not an exception to this rule. Without debug
17273 information, you can still use the @code{compile} command, but you will
17274 be very limited in what variables and types you can access.
17276 So with that in mind, the example above has been compiled with debug
17277 information enabled. The @code{compile} command will have access to
17278 all variables and types (except those that may have been optimized
17279 out). Currently, as @value{GDBN} has stopped the program in the
17280 @code{main} function, the @code{compile} command would have access to
17281 the variable @code{k}. You could invoke the @code{compile} command
17282 and type some source code to set the value of @code{k}. You can also
17283 read it, or do anything with that variable you would normally do in
17284 @code{C}. Be aware that changes to inferior variables in the
17285 @code{compile} command are persistent. In the following example:
17288 compile code k = 3;
17292 the variable @code{k} is now 3. It will retain that value until
17293 something else in the example program changes it, or another
17294 @code{compile} command changes it.
17296 Normal scope and access rules apply to source code compiled and
17297 injected by the @code{compile} command. In the example, the variables
17298 @code{j} and @code{k} are not accessible yet, because the program is
17299 currently stopped in the @code{main} function, where these variables
17300 are not in scope. Therefore, the following command
17303 compile code j = 3;
17307 will result in a compilation error message.
17309 Once the program is continued, execution will bring these variables in
17310 scope, and they will become accessible; then the code you specify via
17311 the @code{compile} command will be able to access them.
17313 You can create variables and types with the @code{compile} command as
17314 part of your source code. Variables and types that are created as part
17315 of the @code{compile} command are not visible to the rest of the program for
17316 the duration of its run. This example is valid:
17319 compile code int ff = 5; printf ("ff is %d\n", ff);
17322 However, if you were to type the following into @value{GDBN} after that
17323 command has completed:
17326 compile code printf ("ff is %d\n'', ff);
17330 a compiler error would be raised as the variable @code{ff} no longer
17331 exists. Object code generated and injected by the @code{compile}
17332 command is removed when its execution ends. Caution is advised
17333 when assigning to program variables values of variables created by the
17334 code submitted to the @code{compile} command. This example is valid:
17337 compile code int ff = 5; k = ff;
17340 The value of the variable @code{ff} is assigned to @code{k}. The variable
17341 @code{k} does not require the existence of @code{ff} to maintain the value
17342 it has been assigned. However, pointers require particular care in
17343 assignment. If the source code compiled with the @code{compile} command
17344 changed the address of a pointer in the example program, perhaps to a
17345 variable created in the @code{compile} command, that pointer would point
17346 to an invalid location when the command exits. The following example
17347 would likely cause issues with your debugged program:
17350 compile code int ff = 5; p = &ff;
17353 In this example, @code{p} would point to @code{ff} when the
17354 @code{compile} command is executing the source code provided to it.
17355 However, as variables in the (example) program persist with their
17356 assigned values, the variable @code{p} would point to an invalid
17357 location when the command exists. A general rule should be followed
17358 in that you should either assign @code{NULL} to any assigned pointers,
17359 or restore a valid location to the pointer before the command exits.
17361 Similar caution must be exercised with any structs, unions, and typedefs
17362 defined in @code{compile} command. Types defined in the @code{compile}
17363 command will no longer be available in the next @code{compile} command.
17364 Therefore, if you cast a variable to a type defined in the
17365 @code{compile} command, care must be taken to ensure that any future
17366 need to resolve the type can be achieved.
17369 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17370 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17371 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17372 Compilation failed.
17373 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17377 Variables that have been optimized away by the compiler are not
17378 accessible to the code submitted to the @code{compile} command.
17379 Access to those variables will generate a compiler error which @value{GDBN}
17380 will print to the console.
17384 @chapter @value{GDBN} Files
17386 @value{GDBN} needs to know the file name of the program to be debugged,
17387 both in order to read its symbol table and in order to start your
17388 program. To debug a core dump of a previous run, you must also tell
17389 @value{GDBN} the name of the core dump file.
17392 * Files:: Commands to specify files
17393 * Separate Debug Files:: Debugging information in separate files
17394 * MiniDebugInfo:: Debugging information in a special section
17395 * Index Files:: Index files speed up GDB
17396 * Symbol Errors:: Errors reading symbol files
17397 * Data Files:: GDB data files
17401 @section Commands to Specify Files
17403 @cindex symbol table
17404 @cindex core dump file
17406 You may want to specify executable and core dump file names. The usual
17407 way to do this is at start-up time, using the arguments to
17408 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17409 Out of @value{GDBN}}).
17411 Occasionally it is necessary to change to a different file during a
17412 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17413 specify a file you want to use. Or you are debugging a remote target
17414 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17415 Program}). In these situations the @value{GDBN} commands to specify
17416 new files are useful.
17419 @cindex executable file
17421 @item file @var{filename}
17422 Use @var{filename} as the program to be debugged. It is read for its
17423 symbols and for the contents of pure memory. It is also the program
17424 executed when you use the @code{run} command. If you do not specify a
17425 directory and the file is not found in the @value{GDBN} working directory,
17426 @value{GDBN} uses the environment variable @code{PATH} as a list of
17427 directories to search, just as the shell does when looking for a program
17428 to run. You can change the value of this variable, for both @value{GDBN}
17429 and your program, using the @code{path} command.
17431 @cindex unlinked object files
17432 @cindex patching object files
17433 You can load unlinked object @file{.o} files into @value{GDBN} using
17434 the @code{file} command. You will not be able to ``run'' an object
17435 file, but you can disassemble functions and inspect variables. Also,
17436 if the underlying BFD functionality supports it, you could use
17437 @kbd{gdb -write} to patch object files using this technique. Note
17438 that @value{GDBN} can neither interpret nor modify relocations in this
17439 case, so branches and some initialized variables will appear to go to
17440 the wrong place. But this feature is still handy from time to time.
17443 @code{file} with no argument makes @value{GDBN} discard any information it
17444 has on both executable file and the symbol table.
17447 @item exec-file @r{[} @var{filename} @r{]}
17448 Specify that the program to be run (but not the symbol table) is found
17449 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17450 if necessary to locate your program. Omitting @var{filename} means to
17451 discard information on the executable file.
17453 @kindex symbol-file
17454 @item symbol-file @r{[} @var{filename} @r{]}
17455 Read symbol table information from file @var{filename}. @code{PATH} is
17456 searched when necessary. Use the @code{file} command to get both symbol
17457 table and program to run from the same file.
17459 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17460 program's symbol table.
17462 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17463 some breakpoints and auto-display expressions. This is because they may
17464 contain pointers to the internal data recording symbols and data types,
17465 which are part of the old symbol table data being discarded inside
17468 @code{symbol-file} does not repeat if you press @key{RET} again after
17471 When @value{GDBN} is configured for a particular environment, it
17472 understands debugging information in whatever format is the standard
17473 generated for that environment; you may use either a @sc{gnu} compiler, or
17474 other compilers that adhere to the local conventions.
17475 Best results are usually obtained from @sc{gnu} compilers; for example,
17476 using @code{@value{NGCC}} you can generate debugging information for
17479 For most kinds of object files, with the exception of old SVR3 systems
17480 using COFF, the @code{symbol-file} command does not normally read the
17481 symbol table in full right away. Instead, it scans the symbol table
17482 quickly to find which source files and which symbols are present. The
17483 details are read later, one source file at a time, as they are needed.
17485 The purpose of this two-stage reading strategy is to make @value{GDBN}
17486 start up faster. For the most part, it is invisible except for
17487 occasional pauses while the symbol table details for a particular source
17488 file are being read. (The @code{set verbose} command can turn these
17489 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17490 Warnings and Messages}.)
17492 We have not implemented the two-stage strategy for COFF yet. When the
17493 symbol table is stored in COFF format, @code{symbol-file} reads the
17494 symbol table data in full right away. Note that ``stabs-in-COFF''
17495 still does the two-stage strategy, since the debug info is actually
17499 @cindex reading symbols immediately
17500 @cindex symbols, reading immediately
17501 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17502 @itemx file @r{[} -readnow @r{]} @var{filename}
17503 You can override the @value{GDBN} two-stage strategy for reading symbol
17504 tables by using the @samp{-readnow} option with any of the commands that
17505 load symbol table information, if you want to be sure @value{GDBN} has the
17506 entire symbol table available.
17508 @c FIXME: for now no mention of directories, since this seems to be in
17509 @c flux. 13mar1992 status is that in theory GDB would look either in
17510 @c current dir or in same dir as myprog; but issues like competing
17511 @c GDB's, or clutter in system dirs, mean that in practice right now
17512 @c only current dir is used. FFish says maybe a special GDB hierarchy
17513 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17517 @item core-file @r{[}@var{filename}@r{]}
17519 Specify the whereabouts of a core dump file to be used as the ``contents
17520 of memory''. Traditionally, core files contain only some parts of the
17521 address space of the process that generated them; @value{GDBN} can access the
17522 executable file itself for other parts.
17524 @code{core-file} with no argument specifies that no core file is
17527 Note that the core file is ignored when your program is actually running
17528 under @value{GDBN}. So, if you have been running your program and you
17529 wish to debug a core file instead, you must kill the subprocess in which
17530 the program is running. To do this, use the @code{kill} command
17531 (@pxref{Kill Process, ,Killing the Child Process}).
17533 @kindex add-symbol-file
17534 @cindex dynamic linking
17535 @item add-symbol-file @var{filename} @var{address}
17536 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17537 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17538 The @code{add-symbol-file} command reads additional symbol table
17539 information from the file @var{filename}. You would use this command
17540 when @var{filename} has been dynamically loaded (by some other means)
17541 into the program that is running. The @var{address} should give the memory
17542 address at which the file has been loaded; @value{GDBN} cannot figure
17543 this out for itself. You can additionally specify an arbitrary number
17544 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17545 section name and base address for that section. You can specify any
17546 @var{address} as an expression.
17548 The symbol table of the file @var{filename} is added to the symbol table
17549 originally read with the @code{symbol-file} command. You can use the
17550 @code{add-symbol-file} command any number of times; the new symbol data
17551 thus read is kept in addition to the old.
17553 Changes can be reverted using the command @code{remove-symbol-file}.
17555 @cindex relocatable object files, reading symbols from
17556 @cindex object files, relocatable, reading symbols from
17557 @cindex reading symbols from relocatable object files
17558 @cindex symbols, reading from relocatable object files
17559 @cindex @file{.o} files, reading symbols from
17560 Although @var{filename} is typically a shared library file, an
17561 executable file, or some other object file which has been fully
17562 relocated for loading into a process, you can also load symbolic
17563 information from relocatable @file{.o} files, as long as:
17567 the file's symbolic information refers only to linker symbols defined in
17568 that file, not to symbols defined by other object files,
17570 every section the file's symbolic information refers to has actually
17571 been loaded into the inferior, as it appears in the file, and
17573 you can determine the address at which every section was loaded, and
17574 provide these to the @code{add-symbol-file} command.
17578 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17579 relocatable files into an already running program; such systems
17580 typically make the requirements above easy to meet. However, it's
17581 important to recognize that many native systems use complex link
17582 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17583 assembly, for example) that make the requirements difficult to meet. In
17584 general, one cannot assume that using @code{add-symbol-file} to read a
17585 relocatable object file's symbolic information will have the same effect
17586 as linking the relocatable object file into the program in the normal
17589 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17591 @kindex remove-symbol-file
17592 @item remove-symbol-file @var{filename}
17593 @item remove-symbol-file -a @var{address}
17594 Remove a symbol file added via the @code{add-symbol-file} command. The
17595 file to remove can be identified by its @var{filename} or by an @var{address}
17596 that lies within the boundaries of this symbol file in memory. Example:
17599 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17600 add symbol table from file "/home/user/gdb/mylib.so" at
17601 .text_addr = 0x7ffff7ff9480
17603 Reading symbols from /home/user/gdb/mylib.so...done.
17604 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17605 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17610 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17612 @kindex add-symbol-file-from-memory
17613 @cindex @code{syscall DSO}
17614 @cindex load symbols from memory
17615 @item add-symbol-file-from-memory @var{address}
17616 Load symbols from the given @var{address} in a dynamically loaded
17617 object file whose image is mapped directly into the inferior's memory.
17618 For example, the Linux kernel maps a @code{syscall DSO} into each
17619 process's address space; this DSO provides kernel-specific code for
17620 some system calls. The argument can be any expression whose
17621 evaluation yields the address of the file's shared object file header.
17622 For this command to work, you must have used @code{symbol-file} or
17623 @code{exec-file} commands in advance.
17626 @item section @var{section} @var{addr}
17627 The @code{section} command changes the base address of the named
17628 @var{section} of the exec file to @var{addr}. This can be used if the
17629 exec file does not contain section addresses, (such as in the
17630 @code{a.out} format), or when the addresses specified in the file
17631 itself are wrong. Each section must be changed separately. The
17632 @code{info files} command, described below, lists all the sections and
17636 @kindex info target
17639 @code{info files} and @code{info target} are synonymous; both print the
17640 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17641 including the names of the executable and core dump files currently in
17642 use by @value{GDBN}, and the files from which symbols were loaded. The
17643 command @code{help target} lists all possible targets rather than
17646 @kindex maint info sections
17647 @item maint info sections
17648 Another command that can give you extra information about program sections
17649 is @code{maint info sections}. In addition to the section information
17650 displayed by @code{info files}, this command displays the flags and file
17651 offset of each section in the executable and core dump files. In addition,
17652 @code{maint info sections} provides the following command options (which
17653 may be arbitrarily combined):
17657 Display sections for all loaded object files, including shared libraries.
17658 @item @var{sections}
17659 Display info only for named @var{sections}.
17660 @item @var{section-flags}
17661 Display info only for sections for which @var{section-flags} are true.
17662 The section flags that @value{GDBN} currently knows about are:
17665 Section will have space allocated in the process when loaded.
17666 Set for all sections except those containing debug information.
17668 Section will be loaded from the file into the child process memory.
17669 Set for pre-initialized code and data, clear for @code{.bss} sections.
17671 Section needs to be relocated before loading.
17673 Section cannot be modified by the child process.
17675 Section contains executable code only.
17677 Section contains data only (no executable code).
17679 Section will reside in ROM.
17681 Section contains data for constructor/destructor lists.
17683 Section is not empty.
17685 An instruction to the linker to not output the section.
17686 @item COFF_SHARED_LIBRARY
17687 A notification to the linker that the section contains
17688 COFF shared library information.
17690 Section contains common symbols.
17693 @kindex set trust-readonly-sections
17694 @cindex read-only sections
17695 @item set trust-readonly-sections on
17696 Tell @value{GDBN} that readonly sections in your object file
17697 really are read-only (i.e.@: that their contents will not change).
17698 In that case, @value{GDBN} can fetch values from these sections
17699 out of the object file, rather than from the target program.
17700 For some targets (notably embedded ones), this can be a significant
17701 enhancement to debugging performance.
17703 The default is off.
17705 @item set trust-readonly-sections off
17706 Tell @value{GDBN} not to trust readonly sections. This means that
17707 the contents of the section might change while the program is running,
17708 and must therefore be fetched from the target when needed.
17710 @item show trust-readonly-sections
17711 Show the current setting of trusting readonly sections.
17714 All file-specifying commands allow both absolute and relative file names
17715 as arguments. @value{GDBN} always converts the file name to an absolute file
17716 name and remembers it that way.
17718 @cindex shared libraries
17719 @anchor{Shared Libraries}
17720 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17721 and IBM RS/6000 AIX shared libraries.
17723 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17724 shared libraries. @xref{Expat}.
17726 @value{GDBN} automatically loads symbol definitions from shared libraries
17727 when you use the @code{run} command, or when you examine a core file.
17728 (Before you issue the @code{run} command, @value{GDBN} does not understand
17729 references to a function in a shared library, however---unless you are
17730 debugging a core file).
17732 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17733 automatically loads the symbols at the time of the @code{shl_load} call.
17735 @c FIXME: some @value{GDBN} release may permit some refs to undef
17736 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17737 @c FIXME...lib; check this from time to time when updating manual
17739 There are times, however, when you may wish to not automatically load
17740 symbol definitions from shared libraries, such as when they are
17741 particularly large or there are many of them.
17743 To control the automatic loading of shared library symbols, use the
17747 @kindex set auto-solib-add
17748 @item set auto-solib-add @var{mode}
17749 If @var{mode} is @code{on}, symbols from all shared object libraries
17750 will be loaded automatically when the inferior begins execution, you
17751 attach to an independently started inferior, or when the dynamic linker
17752 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17753 is @code{off}, symbols must be loaded manually, using the
17754 @code{sharedlibrary} command. The default value is @code{on}.
17756 @cindex memory used for symbol tables
17757 If your program uses lots of shared libraries with debug info that
17758 takes large amounts of memory, you can decrease the @value{GDBN}
17759 memory footprint by preventing it from automatically loading the
17760 symbols from shared libraries. To that end, type @kbd{set
17761 auto-solib-add off} before running the inferior, then load each
17762 library whose debug symbols you do need with @kbd{sharedlibrary
17763 @var{regexp}}, where @var{regexp} is a regular expression that matches
17764 the libraries whose symbols you want to be loaded.
17766 @kindex show auto-solib-add
17767 @item show auto-solib-add
17768 Display the current autoloading mode.
17771 @cindex load shared library
17772 To explicitly load shared library symbols, use the @code{sharedlibrary}
17776 @kindex info sharedlibrary
17778 @item info share @var{regex}
17779 @itemx info sharedlibrary @var{regex}
17780 Print the names of the shared libraries which are currently loaded
17781 that match @var{regex}. If @var{regex} is omitted then print
17782 all shared libraries that are loaded.
17784 @kindex sharedlibrary
17786 @item sharedlibrary @var{regex}
17787 @itemx share @var{regex}
17788 Load shared object library symbols for files matching a
17789 Unix regular expression.
17790 As with files loaded automatically, it only loads shared libraries
17791 required by your program for a core file or after typing @code{run}. If
17792 @var{regex} is omitted all shared libraries required by your program are
17795 @item nosharedlibrary
17796 @kindex nosharedlibrary
17797 @cindex unload symbols from shared libraries
17798 Unload all shared object library symbols. This discards all symbols
17799 that have been loaded from all shared libraries. Symbols from shared
17800 libraries that were loaded by explicit user requests are not
17804 Sometimes you may wish that @value{GDBN} stops and gives you control
17805 when any of shared library events happen. The best way to do this is
17806 to use @code{catch load} and @code{catch unload} (@pxref{Set
17809 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17810 command for this. This command exists for historical reasons. It is
17811 less useful than setting a catchpoint, because it does not allow for
17812 conditions or commands as a catchpoint does.
17815 @item set stop-on-solib-events
17816 @kindex set stop-on-solib-events
17817 This command controls whether @value{GDBN} should give you control
17818 when the dynamic linker notifies it about some shared library event.
17819 The most common event of interest is loading or unloading of a new
17822 @item show stop-on-solib-events
17823 @kindex show stop-on-solib-events
17824 Show whether @value{GDBN} stops and gives you control when shared
17825 library events happen.
17828 Shared libraries are also supported in many cross or remote debugging
17829 configurations. @value{GDBN} needs to have access to the target's libraries;
17830 this can be accomplished either by providing copies of the libraries
17831 on the host system, or by asking @value{GDBN} to automatically retrieve the
17832 libraries from the target. If copies of the target libraries are
17833 provided, they need to be the same as the target libraries, although the
17834 copies on the target can be stripped as long as the copies on the host are
17837 @cindex where to look for shared libraries
17838 For remote debugging, you need to tell @value{GDBN} where the target
17839 libraries are, so that it can load the correct copies---otherwise, it
17840 may try to load the host's libraries. @value{GDBN} has two variables
17841 to specify the search directories for target libraries.
17844 @cindex prefix for shared library file names
17845 @cindex system root, alternate
17846 @kindex set solib-absolute-prefix
17847 @kindex set sysroot
17848 @item set sysroot @var{path}
17849 Use @var{path} as the system root for the program being debugged. Any
17850 absolute shared library paths will be prefixed with @var{path}; many
17851 runtime loaders store the absolute paths to the shared library in the
17852 target program's memory. If you use @code{set sysroot} to find shared
17853 libraries, they need to be laid out in the same way that they are on
17854 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17857 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17858 retrieve the target libraries from the remote system. This is only
17859 supported when using a remote target that supports the @code{remote get}
17860 command (@pxref{File Transfer,,Sending files to a remote system}).
17861 The part of @var{path} following the initial @file{remote:}
17862 (if present) is used as system root prefix on the remote file system.
17863 @footnote{If you want to specify a local system root using a directory
17864 that happens to be named @file{remote:}, you need to use some equivalent
17865 variant of the name like @file{./remote:}.}
17867 For targets with an MS-DOS based filesystem, such as MS-Windows and
17868 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17869 absolute file name with @var{path}. But first, on Unix hosts,
17870 @value{GDBN} converts all backslash directory separators into forward
17871 slashes, because the backslash is not a directory separator on Unix:
17874 c:\foo\bar.dll @result{} c:/foo/bar.dll
17877 Then, @value{GDBN} attempts prefixing the target file name with
17878 @var{path}, and looks for the resulting file name in the host file
17882 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17885 If that does not find the shared library, @value{GDBN} tries removing
17886 the @samp{:} character from the drive spec, both for convenience, and,
17887 for the case of the host file system not supporting file names with
17891 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17894 This makes it possible to have a system root that mirrors a target
17895 with more than one drive. E.g., you may want to setup your local
17896 copies of the target system shared libraries like so (note @samp{c} vs
17900 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17901 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17902 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17906 and point the system root at @file{/path/to/sysroot}, so that
17907 @value{GDBN} can find the correct copies of both
17908 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17910 If that still does not find the shared library, @value{GDBN} tries
17911 removing the whole drive spec from the target file name:
17914 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17917 This last lookup makes it possible to not care about the drive name,
17918 if you don't want or need to.
17920 The @code{set solib-absolute-prefix} command is an alias for @code{set
17923 @cindex default system root
17924 @cindex @samp{--with-sysroot}
17925 You can set the default system root by using the configure-time
17926 @samp{--with-sysroot} option. If the system root is inside
17927 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17928 @samp{--exec-prefix}), then the default system root will be updated
17929 automatically if the installed @value{GDBN} is moved to a new
17932 @kindex show sysroot
17934 Display the current shared library prefix.
17936 @kindex set solib-search-path
17937 @item set solib-search-path @var{path}
17938 If this variable is set, @var{path} is a colon-separated list of
17939 directories to search for shared libraries. @samp{solib-search-path}
17940 is used after @samp{sysroot} fails to locate the library, or if the
17941 path to the library is relative instead of absolute. If you want to
17942 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17943 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17944 finding your host's libraries. @samp{sysroot} is preferred; setting
17945 it to a nonexistent directory may interfere with automatic loading
17946 of shared library symbols.
17948 @kindex show solib-search-path
17949 @item show solib-search-path
17950 Display the current shared library search path.
17952 @cindex DOS file-name semantics of file names.
17953 @kindex set target-file-system-kind (unix|dos-based|auto)
17954 @kindex show target-file-system-kind
17955 @item set target-file-system-kind @var{kind}
17956 Set assumed file system kind for target reported file names.
17958 Shared library file names as reported by the target system may not
17959 make sense as is on the system @value{GDBN} is running on. For
17960 example, when remote debugging a target that has MS-DOS based file
17961 system semantics, from a Unix host, the target may be reporting to
17962 @value{GDBN} a list of loaded shared libraries with file names such as
17963 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17964 drive letters, so the @samp{c:\} prefix is not normally understood as
17965 indicating an absolute file name, and neither is the backslash
17966 normally considered a directory separator character. In that case,
17967 the native file system would interpret this whole absolute file name
17968 as a relative file name with no directory components. This would make
17969 it impossible to point @value{GDBN} at a copy of the remote target's
17970 shared libraries on the host using @code{set sysroot}, and impractical
17971 with @code{set solib-search-path}. Setting
17972 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17973 to interpret such file names similarly to how the target would, and to
17974 map them to file names valid on @value{GDBN}'s native file system
17975 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17976 to one of the supported file system kinds. In that case, @value{GDBN}
17977 tries to determine the appropriate file system variant based on the
17978 current target's operating system (@pxref{ABI, ,Configuring the
17979 Current ABI}). The supported file system settings are:
17983 Instruct @value{GDBN} to assume the target file system is of Unix
17984 kind. Only file names starting the forward slash (@samp{/}) character
17985 are considered absolute, and the directory separator character is also
17989 Instruct @value{GDBN} to assume the target file system is DOS based.
17990 File names starting with either a forward slash, or a drive letter
17991 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17992 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17993 considered directory separators.
17996 Instruct @value{GDBN} to use the file system kind associated with the
17997 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17998 This is the default.
18002 @cindex file name canonicalization
18003 @cindex base name differences
18004 When processing file names provided by the user, @value{GDBN}
18005 frequently needs to compare them to the file names recorded in the
18006 program's debug info. Normally, @value{GDBN} compares just the
18007 @dfn{base names} of the files as strings, which is reasonably fast
18008 even for very large programs. (The base name of a file is the last
18009 portion of its name, after stripping all the leading directories.)
18010 This shortcut in comparison is based upon the assumption that files
18011 cannot have more than one base name. This is usually true, but
18012 references to files that use symlinks or similar filesystem
18013 facilities violate that assumption. If your program records files
18014 using such facilities, or if you provide file names to @value{GDBN}
18015 using symlinks etc., you can set @code{basenames-may-differ} to
18016 @code{true} to instruct @value{GDBN} to completely canonicalize each
18017 pair of file names it needs to compare. This will make file-name
18018 comparisons accurate, but at a price of a significant slowdown.
18021 @item set basenames-may-differ
18022 @kindex set basenames-may-differ
18023 Set whether a source file may have multiple base names.
18025 @item show basenames-may-differ
18026 @kindex show basenames-may-differ
18027 Show whether a source file may have multiple base names.
18030 @node Separate Debug Files
18031 @section Debugging Information in Separate Files
18032 @cindex separate debugging information files
18033 @cindex debugging information in separate files
18034 @cindex @file{.debug} subdirectories
18035 @cindex debugging information directory, global
18036 @cindex global debugging information directories
18037 @cindex build ID, and separate debugging files
18038 @cindex @file{.build-id} directory
18040 @value{GDBN} allows you to put a program's debugging information in a
18041 file separate from the executable itself, in a way that allows
18042 @value{GDBN} to find and load the debugging information automatically.
18043 Since debugging information can be very large---sometimes larger
18044 than the executable code itself---some systems distribute debugging
18045 information for their executables in separate files, which users can
18046 install only when they need to debug a problem.
18048 @value{GDBN} supports two ways of specifying the separate debug info
18053 The executable contains a @dfn{debug link} that specifies the name of
18054 the separate debug info file. The separate debug file's name is
18055 usually @file{@var{executable}.debug}, where @var{executable} is the
18056 name of the corresponding executable file without leading directories
18057 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18058 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18059 checksum for the debug file, which @value{GDBN} uses to validate that
18060 the executable and the debug file came from the same build.
18063 The executable contains a @dfn{build ID}, a unique bit string that is
18064 also present in the corresponding debug info file. (This is supported
18065 only on some operating systems, notably those which use the ELF format
18066 for binary files and the @sc{gnu} Binutils.) For more details about
18067 this feature, see the description of the @option{--build-id}
18068 command-line option in @ref{Options, , Command Line Options, ld.info,
18069 The GNU Linker}. The debug info file's name is not specified
18070 explicitly by the build ID, but can be computed from the build ID, see
18074 Depending on the way the debug info file is specified, @value{GDBN}
18075 uses two different methods of looking for the debug file:
18079 For the ``debug link'' method, @value{GDBN} looks up the named file in
18080 the directory of the executable file, then in a subdirectory of that
18081 directory named @file{.debug}, and finally under each one of the global debug
18082 directories, in a subdirectory whose name is identical to the leading
18083 directories of the executable's absolute file name.
18086 For the ``build ID'' method, @value{GDBN} looks in the
18087 @file{.build-id} subdirectory of each one of the global debug directories for
18088 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18089 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18090 are the rest of the bit string. (Real build ID strings are 32 or more
18091 hex characters, not 10.)
18094 So, for example, suppose you ask @value{GDBN} to debug
18095 @file{/usr/bin/ls}, which has a debug link that specifies the
18096 file @file{ls.debug}, and a build ID whose value in hex is
18097 @code{abcdef1234}. If the list of the global debug directories includes
18098 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18099 debug information files, in the indicated order:
18103 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18105 @file{/usr/bin/ls.debug}
18107 @file{/usr/bin/.debug/ls.debug}
18109 @file{/usr/lib/debug/usr/bin/ls.debug}.
18112 @anchor{debug-file-directory}
18113 Global debugging info directories default to what is set by @value{GDBN}
18114 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18115 you can also set the global debugging info directories, and view the list
18116 @value{GDBN} is currently using.
18120 @kindex set debug-file-directory
18121 @item set debug-file-directory @var{directories}
18122 Set the directories which @value{GDBN} searches for separate debugging
18123 information files to @var{directory}. Multiple path components can be set
18124 concatenating them by a path separator.
18126 @kindex show debug-file-directory
18127 @item show debug-file-directory
18128 Show the directories @value{GDBN} searches for separate debugging
18133 @cindex @code{.gnu_debuglink} sections
18134 @cindex debug link sections
18135 A debug link is a special section of the executable file named
18136 @code{.gnu_debuglink}. The section must contain:
18140 A filename, with any leading directory components removed, followed by
18143 zero to three bytes of padding, as needed to reach the next four-byte
18144 boundary within the section, and
18146 a four-byte CRC checksum, stored in the same endianness used for the
18147 executable file itself. The checksum is computed on the debugging
18148 information file's full contents by the function given below, passing
18149 zero as the @var{crc} argument.
18152 Any executable file format can carry a debug link, as long as it can
18153 contain a section named @code{.gnu_debuglink} with the contents
18156 @cindex @code{.note.gnu.build-id} sections
18157 @cindex build ID sections
18158 The build ID is a special section in the executable file (and in other
18159 ELF binary files that @value{GDBN} may consider). This section is
18160 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18161 It contains unique identification for the built files---the ID remains
18162 the same across multiple builds of the same build tree. The default
18163 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18164 content for the build ID string. The same section with an identical
18165 value is present in the original built binary with symbols, in its
18166 stripped variant, and in the separate debugging information file.
18168 The debugging information file itself should be an ordinary
18169 executable, containing a full set of linker symbols, sections, and
18170 debugging information. The sections of the debugging information file
18171 should have the same names, addresses, and sizes as the original file,
18172 but they need not contain any data---much like a @code{.bss} section
18173 in an ordinary executable.
18175 The @sc{gnu} binary utilities (Binutils) package includes the
18176 @samp{objcopy} utility that can produce
18177 the separated executable / debugging information file pairs using the
18178 following commands:
18181 @kbd{objcopy --only-keep-debug foo foo.debug}
18186 These commands remove the debugging
18187 information from the executable file @file{foo} and place it in the file
18188 @file{foo.debug}. You can use the first, second or both methods to link the
18193 The debug link method needs the following additional command to also leave
18194 behind a debug link in @file{foo}:
18197 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18200 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18201 a version of the @code{strip} command such that the command @kbd{strip foo -f
18202 foo.debug} has the same functionality as the two @code{objcopy} commands and
18203 the @code{ln -s} command above, together.
18206 Build ID gets embedded into the main executable using @code{ld --build-id} or
18207 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18208 compatibility fixes for debug files separation are present in @sc{gnu} binary
18209 utilities (Binutils) package since version 2.18.
18214 @cindex CRC algorithm definition
18215 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18216 IEEE 802.3 using the polynomial:
18218 @c TexInfo requires naked braces for multi-digit exponents for Tex
18219 @c output, but this causes HTML output to barf. HTML has to be set using
18220 @c raw commands. So we end up having to specify this equation in 2
18225 <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>
18226 + <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
18232 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18233 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18237 The function is computed byte at a time, taking the least
18238 significant bit of each byte first. The initial pattern
18239 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18240 the final result is inverted to ensure trailing zeros also affect the
18243 @emph{Note:} This is the same CRC polynomial as used in handling the
18244 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18245 However in the case of the Remote Serial Protocol, the CRC is computed
18246 @emph{most} significant bit first, and the result is not inverted, so
18247 trailing zeros have no effect on the CRC value.
18249 To complete the description, we show below the code of the function
18250 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18251 initially supplied @code{crc} argument means that an initial call to
18252 this function passing in zero will start computing the CRC using
18255 @kindex gnu_debuglink_crc32
18258 gnu_debuglink_crc32 (unsigned long crc,
18259 unsigned char *buf, size_t len)
18261 static const unsigned long crc32_table[256] =
18263 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18264 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18265 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18266 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18267 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18268 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18269 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18270 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18271 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18272 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18273 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18274 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18275 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18276 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18277 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18278 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18279 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18280 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18281 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18282 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18283 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18284 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18285 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18286 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18287 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18288 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18289 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18290 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18291 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18292 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18293 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18294 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18295 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18296 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18297 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18298 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18299 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18300 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18301 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18302 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18303 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18304 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18305 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18306 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18307 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18308 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18309 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18310 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18311 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18312 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18313 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18316 unsigned char *end;
18318 crc = ~crc & 0xffffffff;
18319 for (end = buf + len; buf < end; ++buf)
18320 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18321 return ~crc & 0xffffffff;
18326 This computation does not apply to the ``build ID'' method.
18328 @node MiniDebugInfo
18329 @section Debugging information in a special section
18330 @cindex separate debug sections
18331 @cindex @samp{.gnu_debugdata} section
18333 Some systems ship pre-built executables and libraries that have a
18334 special @samp{.gnu_debugdata} section. This feature is called
18335 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18336 is used to supply extra symbols for backtraces.
18338 The intent of this section is to provide extra minimal debugging
18339 information for use in simple backtraces. It is not intended to be a
18340 replacement for full separate debugging information (@pxref{Separate
18341 Debug Files}). The example below shows the intended use; however,
18342 @value{GDBN} does not currently put restrictions on what sort of
18343 debugging information might be included in the section.
18345 @value{GDBN} has support for this extension. If the section exists,
18346 then it is used provided that no other source of debugging information
18347 can be found, and that @value{GDBN} was configured with LZMA support.
18349 This section can be easily created using @command{objcopy} and other
18350 standard utilities:
18353 # Extract the dynamic symbols from the main binary, there is no need
18354 # to also have these in the normal symbol table.
18355 nm -D @var{binary} --format=posix --defined-only \
18356 | awk '@{ print $1 @}' | sort > dynsyms
18358 # Extract all the text (i.e. function) symbols from the debuginfo.
18359 # (Note that we actually also accept "D" symbols, for the benefit
18360 # of platforms like PowerPC64 that use function descriptors.)
18361 nm @var{binary} --format=posix --defined-only \
18362 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18365 # Keep all the function symbols not already in the dynamic symbol
18367 comm -13 dynsyms funcsyms > keep_symbols
18369 # Separate full debug info into debug binary.
18370 objcopy --only-keep-debug @var{binary} debug
18372 # Copy the full debuginfo, keeping only a minimal set of symbols and
18373 # removing some unnecessary sections.
18374 objcopy -S --remove-section .gdb_index --remove-section .comment \
18375 --keep-symbols=keep_symbols debug mini_debuginfo
18377 # Drop the full debug info from the original binary.
18378 strip --strip-all -R .comment @var{binary}
18380 # Inject the compressed data into the .gnu_debugdata section of the
18383 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18387 @section Index Files Speed Up @value{GDBN}
18388 @cindex index files
18389 @cindex @samp{.gdb_index} section
18391 When @value{GDBN} finds a symbol file, it scans the symbols in the
18392 file in order to construct an internal symbol table. This lets most
18393 @value{GDBN} operations work quickly---at the cost of a delay early
18394 on. For large programs, this delay can be quite lengthy, so
18395 @value{GDBN} provides a way to build an index, which speeds up
18398 The index is stored as a section in the symbol file. @value{GDBN} can
18399 write the index to a file, then you can put it into the symbol file
18400 using @command{objcopy}.
18402 To create an index file, use the @code{save gdb-index} command:
18405 @item save gdb-index @var{directory}
18406 @kindex save gdb-index
18407 Create an index file for each symbol file currently known by
18408 @value{GDBN}. Each file is named after its corresponding symbol file,
18409 with @samp{.gdb-index} appended, and is written into the given
18413 Once you have created an index file you can merge it into your symbol
18414 file, here named @file{symfile}, using @command{objcopy}:
18417 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18418 --set-section-flags .gdb_index=readonly symfile symfile
18421 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18422 sections that have been deprecated. Usually they are deprecated because
18423 they are missing a new feature or have performance issues.
18424 To tell @value{GDBN} to use a deprecated index section anyway
18425 specify @code{set use-deprecated-index-sections on}.
18426 The default is @code{off}.
18427 This can speed up startup, but may result in some functionality being lost.
18428 @xref{Index Section Format}.
18430 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18431 must be done before gdb reads the file. The following will not work:
18434 $ gdb -ex "set use-deprecated-index-sections on" <program>
18437 Instead you must do, for example,
18440 $ gdb -iex "set use-deprecated-index-sections on" <program>
18443 There are currently some limitation on indices. They only work when
18444 for DWARF debugging information, not stabs. And, they do not
18445 currently work for programs using Ada.
18447 @node Symbol Errors
18448 @section Errors Reading Symbol Files
18450 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18451 such as symbol types it does not recognize, or known bugs in compiler
18452 output. By default, @value{GDBN} does not notify you of such problems, since
18453 they are relatively common and primarily of interest to people
18454 debugging compilers. If you are interested in seeing information
18455 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18456 only one message about each such type of problem, no matter how many
18457 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18458 to see how many times the problems occur, with the @code{set
18459 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18462 The messages currently printed, and their meanings, include:
18465 @item inner block not inside outer block in @var{symbol}
18467 The symbol information shows where symbol scopes begin and end
18468 (such as at the start of a function or a block of statements). This
18469 error indicates that an inner scope block is not fully contained
18470 in its outer scope blocks.
18472 @value{GDBN} circumvents the problem by treating the inner block as if it had
18473 the same scope as the outer block. In the error message, @var{symbol}
18474 may be shown as ``@code{(don't know)}'' if the outer block is not a
18477 @item block at @var{address} out of order
18479 The symbol information for symbol scope blocks should occur in
18480 order of increasing addresses. This error indicates that it does not
18483 @value{GDBN} does not circumvent this problem, and has trouble
18484 locating symbols in the source file whose symbols it is reading. (You
18485 can often determine what source file is affected by specifying
18486 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18489 @item bad block start address patched
18491 The symbol information for a symbol scope block has a start address
18492 smaller than the address of the preceding source line. This is known
18493 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18495 @value{GDBN} circumvents the problem by treating the symbol scope block as
18496 starting on the previous source line.
18498 @item bad string table offset in symbol @var{n}
18501 Symbol number @var{n} contains a pointer into the string table which is
18502 larger than the size of the string table.
18504 @value{GDBN} circumvents the problem by considering the symbol to have the
18505 name @code{foo}, which may cause other problems if many symbols end up
18508 @item unknown symbol type @code{0x@var{nn}}
18510 The symbol information contains new data types that @value{GDBN} does
18511 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18512 uncomprehended information, in hexadecimal.
18514 @value{GDBN} circumvents the error by ignoring this symbol information.
18515 This usually allows you to debug your program, though certain symbols
18516 are not accessible. If you encounter such a problem and feel like
18517 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18518 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18519 and examine @code{*bufp} to see the symbol.
18521 @item stub type has NULL name
18523 @value{GDBN} could not find the full definition for a struct or class.
18525 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18526 The symbol information for a C@t{++} member function is missing some
18527 information that recent versions of the compiler should have output for
18530 @item info mismatch between compiler and debugger
18532 @value{GDBN} could not parse a type specification output by the compiler.
18537 @section GDB Data Files
18539 @cindex prefix for data files
18540 @value{GDBN} will sometimes read an auxiliary data file. These files
18541 are kept in a directory known as the @dfn{data directory}.
18543 You can set the data directory's name, and view the name @value{GDBN}
18544 is currently using.
18547 @kindex set data-directory
18548 @item set data-directory @var{directory}
18549 Set the directory which @value{GDBN} searches for auxiliary data files
18550 to @var{directory}.
18552 @kindex show data-directory
18553 @item show data-directory
18554 Show the directory @value{GDBN} searches for auxiliary data files.
18557 @cindex default data directory
18558 @cindex @samp{--with-gdb-datadir}
18559 You can set the default data directory by using the configure-time
18560 @samp{--with-gdb-datadir} option. If the data directory is inside
18561 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18562 @samp{--exec-prefix}), then the default data directory will be updated
18563 automatically if the installed @value{GDBN} is moved to a new
18566 The data directory may also be specified with the
18567 @code{--data-directory} command line option.
18568 @xref{Mode Options}.
18571 @chapter Specifying a Debugging Target
18573 @cindex debugging target
18574 A @dfn{target} is the execution environment occupied by your program.
18576 Often, @value{GDBN} runs in the same host environment as your program;
18577 in that case, the debugging target is specified as a side effect when
18578 you use the @code{file} or @code{core} commands. When you need more
18579 flexibility---for example, running @value{GDBN} on a physically separate
18580 host, or controlling a standalone system over a serial port or a
18581 realtime system over a TCP/IP connection---you can use the @code{target}
18582 command to specify one of the target types configured for @value{GDBN}
18583 (@pxref{Target Commands, ,Commands for Managing Targets}).
18585 @cindex target architecture
18586 It is possible to build @value{GDBN} for several different @dfn{target
18587 architectures}. When @value{GDBN} is built like that, you can choose
18588 one of the available architectures with the @kbd{set architecture}
18592 @kindex set architecture
18593 @kindex show architecture
18594 @item set architecture @var{arch}
18595 This command sets the current target architecture to @var{arch}. The
18596 value of @var{arch} can be @code{"auto"}, in addition to one of the
18597 supported architectures.
18599 @item show architecture
18600 Show the current target architecture.
18602 @item set processor
18604 @kindex set processor
18605 @kindex show processor
18606 These are alias commands for, respectively, @code{set architecture}
18607 and @code{show architecture}.
18611 * Active Targets:: Active targets
18612 * Target Commands:: Commands for managing targets
18613 * Byte Order:: Choosing target byte order
18616 @node Active Targets
18617 @section Active Targets
18619 @cindex stacking targets
18620 @cindex active targets
18621 @cindex multiple targets
18623 There are multiple classes of targets such as: processes, executable files or
18624 recording sessions. Core files belong to the process class, making core file
18625 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18626 on multiple active targets, one in each class. This allows you to (for
18627 example) start a process and inspect its activity, while still having access to
18628 the executable file after the process finishes. Or if you start process
18629 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18630 presented a virtual layer of the recording target, while the process target
18631 remains stopped at the chronologically last point of the process execution.
18633 Use the @code{core-file} and @code{exec-file} commands to select a new core
18634 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18635 specify as a target a process that is already running, use the @code{attach}
18636 command (@pxref{Attach, ,Debugging an Already-running Process}).
18638 @node Target Commands
18639 @section Commands for Managing Targets
18642 @item target @var{type} @var{parameters}
18643 Connects the @value{GDBN} host environment to a target machine or
18644 process. A target is typically a protocol for talking to debugging
18645 facilities. You use the argument @var{type} to specify the type or
18646 protocol of the target machine.
18648 Further @var{parameters} are interpreted by the target protocol, but
18649 typically include things like device names or host names to connect
18650 with, process numbers, and baud rates.
18652 The @code{target} command does not repeat if you press @key{RET} again
18653 after executing the command.
18655 @kindex help target
18657 Displays the names of all targets available. To display targets
18658 currently selected, use either @code{info target} or @code{info files}
18659 (@pxref{Files, ,Commands to Specify Files}).
18661 @item help target @var{name}
18662 Describe a particular target, including any parameters necessary to
18665 @kindex set gnutarget
18666 @item set gnutarget @var{args}
18667 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18668 knows whether it is reading an @dfn{executable},
18669 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18670 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18671 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18674 @emph{Warning:} To specify a file format with @code{set gnutarget},
18675 you must know the actual BFD name.
18679 @xref{Files, , Commands to Specify Files}.
18681 @kindex show gnutarget
18682 @item show gnutarget
18683 Use the @code{show gnutarget} command to display what file format
18684 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18685 @value{GDBN} will determine the file format for each file automatically,
18686 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18689 @cindex common targets
18690 Here are some common targets (available, or not, depending on the GDB
18695 @item target exec @var{program}
18696 @cindex executable file target
18697 An executable file. @samp{target exec @var{program}} is the same as
18698 @samp{exec-file @var{program}}.
18700 @item target core @var{filename}
18701 @cindex core dump file target
18702 A core dump file. @samp{target core @var{filename}} is the same as
18703 @samp{core-file @var{filename}}.
18705 @item target remote @var{medium}
18706 @cindex remote target
18707 A remote system connected to @value{GDBN} via a serial line or network
18708 connection. This command tells @value{GDBN} to use its own remote
18709 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18711 For example, if you have a board connected to @file{/dev/ttya} on the
18712 machine running @value{GDBN}, you could say:
18715 target remote /dev/ttya
18718 @code{target remote} supports the @code{load} command. This is only
18719 useful if you have some other way of getting the stub to the target
18720 system, and you can put it somewhere in memory where it won't get
18721 clobbered by the download.
18723 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18724 @cindex built-in simulator target
18725 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18733 works; however, you cannot assume that a specific memory map, device
18734 drivers, or even basic I/O is available, although some simulators do
18735 provide these. For info about any processor-specific simulator details,
18736 see the appropriate section in @ref{Embedded Processors, ,Embedded
18739 @item target native
18740 @cindex native target
18741 Setup for local/native process debugging. Useful to make the
18742 @code{run} command spawn native processes (likewise @code{attach},
18743 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18744 (@pxref{set auto-connect-native-target}).
18748 Different targets are available on different configurations of @value{GDBN};
18749 your configuration may have more or fewer targets.
18751 Many remote targets require you to download the executable's code once
18752 you've successfully established a connection. You may wish to control
18753 various aspects of this process.
18758 @kindex set hash@r{, for remote monitors}
18759 @cindex hash mark while downloading
18760 This command controls whether a hash mark @samp{#} is displayed while
18761 downloading a file to the remote monitor. If on, a hash mark is
18762 displayed after each S-record is successfully downloaded to the
18766 @kindex show hash@r{, for remote monitors}
18767 Show the current status of displaying the hash mark.
18769 @item set debug monitor
18770 @kindex set debug monitor
18771 @cindex display remote monitor communications
18772 Enable or disable display of communications messages between
18773 @value{GDBN} and the remote monitor.
18775 @item show debug monitor
18776 @kindex show debug monitor
18777 Show the current status of displaying communications between
18778 @value{GDBN} and the remote monitor.
18783 @kindex load @var{filename}
18784 @item load @var{filename}
18786 Depending on what remote debugging facilities are configured into
18787 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18788 is meant to make @var{filename} (an executable) available for debugging
18789 on the remote system---by downloading, or dynamic linking, for example.
18790 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18791 the @code{add-symbol-file} command.
18793 If your @value{GDBN} does not have a @code{load} command, attempting to
18794 execute it gets the error message ``@code{You can't do that when your
18795 target is @dots{}}''
18797 The file is loaded at whatever address is specified in the executable.
18798 For some object file formats, you can specify the load address when you
18799 link the program; for other formats, like a.out, the object file format
18800 specifies a fixed address.
18801 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18803 Depending on the remote side capabilities, @value{GDBN} may be able to
18804 load programs into flash memory.
18806 @code{load} does not repeat if you press @key{RET} again after using it.
18810 @section Choosing Target Byte Order
18812 @cindex choosing target byte order
18813 @cindex target byte order
18815 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18816 offer the ability to run either big-endian or little-endian byte
18817 orders. Usually the executable or symbol will include a bit to
18818 designate the endian-ness, and you will not need to worry about
18819 which to use. However, you may still find it useful to adjust
18820 @value{GDBN}'s idea of processor endian-ness manually.
18824 @item set endian big
18825 Instruct @value{GDBN} to assume the target is big-endian.
18827 @item set endian little
18828 Instruct @value{GDBN} to assume the target is little-endian.
18830 @item set endian auto
18831 Instruct @value{GDBN} to use the byte order associated with the
18835 Display @value{GDBN}'s current idea of the target byte order.
18839 Note that these commands merely adjust interpretation of symbolic
18840 data on the host, and that they have absolutely no effect on the
18844 @node Remote Debugging
18845 @chapter Debugging Remote Programs
18846 @cindex remote debugging
18848 If you are trying to debug a program running on a machine that cannot run
18849 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18850 For example, you might use remote debugging on an operating system kernel,
18851 or on a small system which does not have a general purpose operating system
18852 powerful enough to run a full-featured debugger.
18854 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18855 to make this work with particular debugging targets. In addition,
18856 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18857 but not specific to any particular target system) which you can use if you
18858 write the remote stubs---the code that runs on the remote system to
18859 communicate with @value{GDBN}.
18861 Other remote targets may be available in your
18862 configuration of @value{GDBN}; use @code{help target} to list them.
18865 * Connecting:: Connecting to a remote target
18866 * File Transfer:: Sending files to a remote system
18867 * Server:: Using the gdbserver program
18868 * Remote Configuration:: Remote configuration
18869 * Remote Stub:: Implementing a remote stub
18873 @section Connecting to a Remote Target
18875 On the @value{GDBN} host machine, you will need an unstripped copy of
18876 your program, since @value{GDBN} needs symbol and debugging information.
18877 Start up @value{GDBN} as usual, using the name of the local copy of your
18878 program as the first argument.
18880 @cindex @code{target remote}
18881 @value{GDBN} can communicate with the target over a serial line, or
18882 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18883 each case, @value{GDBN} uses the same protocol for debugging your
18884 program; only the medium carrying the debugging packets varies. The
18885 @code{target remote} command establishes a connection to the target.
18886 Its arguments indicate which medium to use:
18890 @item target remote @var{serial-device}
18891 @cindex serial line, @code{target remote}
18892 Use @var{serial-device} to communicate with the target. For example,
18893 to use a serial line connected to the device named @file{/dev/ttyb}:
18896 target remote /dev/ttyb
18899 If you're using a serial line, you may want to give @value{GDBN} the
18900 @samp{--baud} option, or use the @code{set serial baud} command
18901 (@pxref{Remote Configuration, set serial baud}) before the
18902 @code{target} command.
18904 @item target remote @code{@var{host}:@var{port}}
18905 @itemx target remote @code{tcp:@var{host}:@var{port}}
18906 @cindex @acronym{TCP} port, @code{target remote}
18907 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18908 The @var{host} may be either a host name or a numeric @acronym{IP}
18909 address; @var{port} must be a decimal number. The @var{host} could be
18910 the target machine itself, if it is directly connected to the net, or
18911 it might be a terminal server which in turn has a serial line to the
18914 For example, to connect to port 2828 on a terminal server named
18918 target remote manyfarms:2828
18921 If your remote target is actually running on the same machine as your
18922 debugger session (e.g.@: a simulator for your target running on the
18923 same host), you can omit the hostname. For example, to connect to
18924 port 1234 on your local machine:
18927 target remote :1234
18931 Note that the colon is still required here.
18933 @item target remote @code{udp:@var{host}:@var{port}}
18934 @cindex @acronym{UDP} port, @code{target remote}
18935 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18936 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18939 target remote udp:manyfarms:2828
18942 When using a @acronym{UDP} connection for remote debugging, you should
18943 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18944 can silently drop packets on busy or unreliable networks, which will
18945 cause havoc with your debugging session.
18947 @item target remote | @var{command}
18948 @cindex pipe, @code{target remote} to
18949 Run @var{command} in the background and communicate with it using a
18950 pipe. The @var{command} is a shell command, to be parsed and expanded
18951 by the system's command shell, @code{/bin/sh}; it should expect remote
18952 protocol packets on its standard input, and send replies on its
18953 standard output. You could use this to run a stand-alone simulator
18954 that speaks the remote debugging protocol, to make net connections
18955 using programs like @code{ssh}, or for other similar tricks.
18957 If @var{command} closes its standard output (perhaps by exiting),
18958 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18959 program has already exited, this will have no effect.)
18963 Once the connection has been established, you can use all the usual
18964 commands to examine and change data. The remote program is already
18965 running; you can use @kbd{step} and @kbd{continue}, and you do not
18966 need to use @kbd{run}.
18968 @cindex interrupting remote programs
18969 @cindex remote programs, interrupting
18970 Whenever @value{GDBN} is waiting for the remote program, if you type the
18971 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18972 program. This may or may not succeed, depending in part on the hardware
18973 and the serial drivers the remote system uses. If you type the
18974 interrupt character once again, @value{GDBN} displays this prompt:
18977 Interrupted while waiting for the program.
18978 Give up (and stop debugging it)? (y or n)
18981 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18982 (If you decide you want to try again later, you can use @samp{target
18983 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18984 goes back to waiting.
18987 @kindex detach (remote)
18989 When you have finished debugging the remote program, you can use the
18990 @code{detach} command to release it from @value{GDBN} control.
18991 Detaching from the target normally resumes its execution, but the results
18992 will depend on your particular remote stub. After the @code{detach}
18993 command, @value{GDBN} is free to connect to another target.
18997 The @code{disconnect} command behaves like @code{detach}, except that
18998 the target is generally not resumed. It will wait for @value{GDBN}
18999 (this instance or another one) to connect and continue debugging. After
19000 the @code{disconnect} command, @value{GDBN} is again free to connect to
19003 @cindex send command to remote monitor
19004 @cindex extend @value{GDBN} for remote targets
19005 @cindex add new commands for external monitor
19007 @item monitor @var{cmd}
19008 This command allows you to send arbitrary commands directly to the
19009 remote monitor. Since @value{GDBN} doesn't care about the commands it
19010 sends like this, this command is the way to extend @value{GDBN}---you
19011 can add new commands that only the external monitor will understand
19015 @node File Transfer
19016 @section Sending files to a remote system
19017 @cindex remote target, file transfer
19018 @cindex file transfer
19019 @cindex sending files to remote systems
19021 Some remote targets offer the ability to transfer files over the same
19022 connection used to communicate with @value{GDBN}. This is convenient
19023 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19024 running @code{gdbserver} over a network interface. For other targets,
19025 e.g.@: embedded devices with only a single serial port, this may be
19026 the only way to upload or download files.
19028 Not all remote targets support these commands.
19032 @item remote put @var{hostfile} @var{targetfile}
19033 Copy file @var{hostfile} from the host system (the machine running
19034 @value{GDBN}) to @var{targetfile} on the target system.
19037 @item remote get @var{targetfile} @var{hostfile}
19038 Copy file @var{targetfile} from the target system to @var{hostfile}
19039 on the host system.
19041 @kindex remote delete
19042 @item remote delete @var{targetfile}
19043 Delete @var{targetfile} from the target system.
19048 @section Using the @code{gdbserver} Program
19051 @cindex remote connection without stubs
19052 @code{gdbserver} is a control program for Unix-like systems, which
19053 allows you to connect your program with a remote @value{GDBN} via
19054 @code{target remote}---but without linking in the usual debugging stub.
19056 @code{gdbserver} is not a complete replacement for the debugging stubs,
19057 because it requires essentially the same operating-system facilities
19058 that @value{GDBN} itself does. In fact, a system that can run
19059 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19060 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19061 because it is a much smaller program than @value{GDBN} itself. It is
19062 also easier to port than all of @value{GDBN}, so you may be able to get
19063 started more quickly on a new system by using @code{gdbserver}.
19064 Finally, if you develop code for real-time systems, you may find that
19065 the tradeoffs involved in real-time operation make it more convenient to
19066 do as much development work as possible on another system, for example
19067 by cross-compiling. You can use @code{gdbserver} to make a similar
19068 choice for debugging.
19070 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19071 or a TCP connection, using the standard @value{GDBN} remote serial
19075 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19076 Do not run @code{gdbserver} connected to any public network; a
19077 @value{GDBN} connection to @code{gdbserver} provides access to the
19078 target system with the same privileges as the user running
19082 @subsection Running @code{gdbserver}
19083 @cindex arguments, to @code{gdbserver}
19084 @cindex @code{gdbserver}, command-line arguments
19086 Run @code{gdbserver} on the target system. You need a copy of the
19087 program you want to debug, including any libraries it requires.
19088 @code{gdbserver} does not need your program's symbol table, so you can
19089 strip the program if necessary to save space. @value{GDBN} on the host
19090 system does all the symbol handling.
19092 To use the server, you must tell it how to communicate with @value{GDBN};
19093 the name of your program; and the arguments for your program. The usual
19097 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19100 @var{comm} is either a device name (to use a serial line), or a TCP
19101 hostname and portnumber, or @code{-} or @code{stdio} to use
19102 stdin/stdout of @code{gdbserver}.
19103 For example, to debug Emacs with the argument
19104 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19108 target> gdbserver /dev/com1 emacs foo.txt
19111 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19114 To use a TCP connection instead of a serial line:
19117 target> gdbserver host:2345 emacs foo.txt
19120 The only difference from the previous example is the first argument,
19121 specifying that you are communicating with the host @value{GDBN} via
19122 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19123 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19124 (Currently, the @samp{host} part is ignored.) You can choose any number
19125 you want for the port number as long as it does not conflict with any
19126 TCP ports already in use on the target system (for example, @code{23} is
19127 reserved for @code{telnet}).@footnote{If you choose a port number that
19128 conflicts with another service, @code{gdbserver} prints an error message
19129 and exits.} You must use the same port number with the host @value{GDBN}
19130 @code{target remote} command.
19132 The @code{stdio} connection is useful when starting @code{gdbserver}
19136 (gdb) target remote | ssh -T hostname gdbserver - hello
19139 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19140 and we don't want escape-character handling. Ssh does this by default when
19141 a command is provided, the flag is provided to make it explicit.
19142 You could elide it if you want to.
19144 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19145 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19146 display through a pipe connected to gdbserver.
19147 Both @code{stdout} and @code{stderr} use the same pipe.
19149 @subsubsection Attaching to a Running Program
19150 @cindex attach to a program, @code{gdbserver}
19151 @cindex @option{--attach}, @code{gdbserver} option
19153 On some targets, @code{gdbserver} can also attach to running programs.
19154 This is accomplished via the @code{--attach} argument. The syntax is:
19157 target> gdbserver --attach @var{comm} @var{pid}
19160 @var{pid} is the process ID of a currently running process. It isn't necessary
19161 to point @code{gdbserver} at a binary for the running process.
19164 You can debug processes by name instead of process ID if your target has the
19165 @code{pidof} utility:
19168 target> gdbserver --attach @var{comm} `pidof @var{program}`
19171 In case more than one copy of @var{program} is running, or @var{program}
19172 has multiple threads, most versions of @code{pidof} support the
19173 @code{-s} option to only return the first process ID.
19175 @subsubsection Multi-Process Mode for @code{gdbserver}
19176 @cindex @code{gdbserver}, multiple processes
19177 @cindex multiple processes with @code{gdbserver}
19179 When you connect to @code{gdbserver} using @code{target remote},
19180 @code{gdbserver} debugs the specified program only once. When the
19181 program exits, or you detach from it, @value{GDBN} closes the connection
19182 and @code{gdbserver} exits.
19184 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19185 enters multi-process mode. When the debugged program exits, or you
19186 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19187 though no program is running. The @code{run} and @code{attach}
19188 commands instruct @code{gdbserver} to run or attach to a new program.
19189 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19190 remote exec-file}) to select the program to run. Command line
19191 arguments are supported, except for wildcard expansion and I/O
19192 redirection (@pxref{Arguments}).
19194 @cindex @option{--multi}, @code{gdbserver} option
19195 To start @code{gdbserver} without supplying an initial command to run
19196 or process ID to attach, use the @option{--multi} command line option.
19197 Then you can connect using @kbd{target extended-remote} and start
19198 the program you want to debug.
19200 In multi-process mode @code{gdbserver} does not automatically exit unless you
19201 use the option @option{--once}. You can terminate it by using
19202 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19203 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19204 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19205 @option{--multi} option to @code{gdbserver} has no influence on that.
19207 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19209 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19211 @code{gdbserver} normally terminates after all of its debugged processes have
19212 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19213 extended-remote}, @code{gdbserver} stays running even with no processes left.
19214 @value{GDBN} normally terminates the spawned debugged process on its exit,
19215 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19216 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19217 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19218 stays running even in the @kbd{target remote} mode.
19220 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19221 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19222 completeness, at most one @value{GDBN} can be connected at a time.
19224 @cindex @option{--once}, @code{gdbserver} option
19225 By default, @code{gdbserver} keeps the listening TCP port open, so that
19226 subsequent connections are possible. However, if you start @code{gdbserver}
19227 with the @option{--once} option, it will stop listening for any further
19228 connection attempts after connecting to the first @value{GDBN} session. This
19229 means no further connections to @code{gdbserver} will be possible after the
19230 first one. It also means @code{gdbserver} will terminate after the first
19231 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19232 connections and even in the @kbd{target extended-remote} mode. The
19233 @option{--once} option allows reusing the same port number for connecting to
19234 multiple instances of @code{gdbserver} running on the same host, since each
19235 instance closes its port after the first connection.
19237 @anchor{Other Command-Line Arguments for gdbserver}
19238 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19240 @cindex @option{--debug}, @code{gdbserver} option
19241 The @option{--debug} option tells @code{gdbserver} to display extra
19242 status information about the debugging process.
19243 @cindex @option{--remote-debug}, @code{gdbserver} option
19244 The @option{--remote-debug} option tells @code{gdbserver} to display
19245 remote protocol debug output. These options are intended for
19246 @code{gdbserver} development and for bug reports to the developers.
19248 @cindex @option{--debug-format}, @code{gdbserver} option
19249 The @option{--debug-format=option1[,option2,...]} option tells
19250 @code{gdbserver} to include additional information in each output.
19251 Possible options are:
19255 Turn off all extra information in debugging output.
19257 Turn on all extra information in debugging output.
19259 Include a timestamp in each line of debugging output.
19262 Options are processed in order. Thus, for example, if @option{none}
19263 appears last then no additional information is added to debugging output.
19265 @cindex @option{--wrapper}, @code{gdbserver} option
19266 The @option{--wrapper} option specifies a wrapper to launch programs
19267 for debugging. The option should be followed by the name of the
19268 wrapper, then any command-line arguments to pass to the wrapper, then
19269 @kbd{--} indicating the end of the wrapper arguments.
19271 @code{gdbserver} runs the specified wrapper program with a combined
19272 command line including the wrapper arguments, then the name of the
19273 program to debug, then any arguments to the program. The wrapper
19274 runs until it executes your program, and then @value{GDBN} gains control.
19276 You can use any program that eventually calls @code{execve} with
19277 its arguments as a wrapper. Several standard Unix utilities do
19278 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19279 with @code{exec "$@@"} will also work.
19281 For example, you can use @code{env} to pass an environment variable to
19282 the debugged program, without setting the variable in @code{gdbserver}'s
19286 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19289 @subsection Connecting to @code{gdbserver}
19291 Run @value{GDBN} on the host system.
19293 First make sure you have the necessary symbol files. Load symbols for
19294 your application using the @code{file} command before you connect. Use
19295 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19296 was compiled with the correct sysroot using @code{--with-sysroot}).
19298 The symbol file and target libraries must exactly match the executable
19299 and libraries on the target, with one exception: the files on the host
19300 system should not be stripped, even if the files on the target system
19301 are. Mismatched or missing files will lead to confusing results
19302 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19303 files may also prevent @code{gdbserver} from debugging multi-threaded
19306 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19307 For TCP connections, you must start up @code{gdbserver} prior to using
19308 the @code{target remote} command. Otherwise you may get an error whose
19309 text depends on the host system, but which usually looks something like
19310 @samp{Connection refused}. Don't use the @code{load}
19311 command in @value{GDBN} when using @code{gdbserver}, since the program is
19312 already on the target.
19314 @subsection Monitor Commands for @code{gdbserver}
19315 @cindex monitor commands, for @code{gdbserver}
19316 @anchor{Monitor Commands for gdbserver}
19318 During a @value{GDBN} session using @code{gdbserver}, you can use the
19319 @code{monitor} command to send special requests to @code{gdbserver}.
19320 Here are the available commands.
19324 List the available monitor commands.
19326 @item monitor set debug 0
19327 @itemx monitor set debug 1
19328 Disable or enable general debugging messages.
19330 @item monitor set remote-debug 0
19331 @itemx monitor set remote-debug 1
19332 Disable or enable specific debugging messages associated with the remote
19333 protocol (@pxref{Remote Protocol}).
19335 @item monitor set debug-format option1@r{[},option2,...@r{]}
19336 Specify additional text to add to debugging messages.
19337 Possible options are:
19341 Turn off all extra information in debugging output.
19343 Turn on all extra information in debugging output.
19345 Include a timestamp in each line of debugging output.
19348 Options are processed in order. Thus, for example, if @option{none}
19349 appears last then no additional information is added to debugging output.
19351 @item monitor set libthread-db-search-path [PATH]
19352 @cindex gdbserver, search path for @code{libthread_db}
19353 When this command is issued, @var{path} is a colon-separated list of
19354 directories to search for @code{libthread_db} (@pxref{Threads,,set
19355 libthread-db-search-path}). If you omit @var{path},
19356 @samp{libthread-db-search-path} will be reset to its default value.
19358 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19359 not supported in @code{gdbserver}.
19362 Tell gdbserver to exit immediately. This command should be followed by
19363 @code{disconnect} to close the debugging session. @code{gdbserver} will
19364 detach from any attached processes and kill any processes it created.
19365 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19366 of a multi-process mode debug session.
19370 @subsection Tracepoints support in @code{gdbserver}
19371 @cindex tracepoints support in @code{gdbserver}
19373 On some targets, @code{gdbserver} supports tracepoints, fast
19374 tracepoints and static tracepoints.
19376 For fast or static tracepoints to work, a special library called the
19377 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19378 This library is built and distributed as an integral part of
19379 @code{gdbserver}. In addition, support for static tracepoints
19380 requires building the in-process agent library with static tracepoints
19381 support. At present, the UST (LTTng Userspace Tracer,
19382 @url{http://lttng.org/ust}) tracing engine is supported. This support
19383 is automatically available if UST development headers are found in the
19384 standard include path when @code{gdbserver} is built, or if
19385 @code{gdbserver} was explicitly configured using @option{--with-ust}
19386 to point at such headers. You can explicitly disable the support
19387 using @option{--with-ust=no}.
19389 There are several ways to load the in-process agent in your program:
19392 @item Specifying it as dependency at link time
19394 You can link your program dynamically with the in-process agent
19395 library. On most systems, this is accomplished by adding
19396 @code{-linproctrace} to the link command.
19398 @item Using the system's preloading mechanisms
19400 You can force loading the in-process agent at startup time by using
19401 your system's support for preloading shared libraries. Many Unixes
19402 support the concept of preloading user defined libraries. In most
19403 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19404 in the environment. See also the description of @code{gdbserver}'s
19405 @option{--wrapper} command line option.
19407 @item Using @value{GDBN} to force loading the agent at run time
19409 On some systems, you can force the inferior to load a shared library,
19410 by calling a dynamic loader function in the inferior that takes care
19411 of dynamically looking up and loading a shared library. On most Unix
19412 systems, the function is @code{dlopen}. You'll use the @code{call}
19413 command for that. For example:
19416 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19419 Note that on most Unix systems, for the @code{dlopen} function to be
19420 available, the program needs to be linked with @code{-ldl}.
19423 On systems that have a userspace dynamic loader, like most Unix
19424 systems, when you connect to @code{gdbserver} using @code{target
19425 remote}, you'll find that the program is stopped at the dynamic
19426 loader's entry point, and no shared library has been loaded in the
19427 program's address space yet, including the in-process agent. In that
19428 case, before being able to use any of the fast or static tracepoints
19429 features, you need to let the loader run and load the shared
19430 libraries. The simplest way to do that is to run the program to the
19431 main procedure. E.g., if debugging a C or C@t{++} program, start
19432 @code{gdbserver} like so:
19435 $ gdbserver :9999 myprogram
19438 Start GDB and connect to @code{gdbserver} like so, and run to main:
19442 (@value{GDBP}) target remote myhost:9999
19443 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19444 (@value{GDBP}) b main
19445 (@value{GDBP}) continue
19448 The in-process tracing agent library should now be loaded into the
19449 process; you can confirm it with the @code{info sharedlibrary}
19450 command, which will list @file{libinproctrace.so} as loaded in the
19451 process. You are now ready to install fast tracepoints, list static
19452 tracepoint markers, probe static tracepoints markers, and start
19455 @node Remote Configuration
19456 @section Remote Configuration
19459 @kindex show remote
19460 This section documents the configuration options available when
19461 debugging remote programs. For the options related to the File I/O
19462 extensions of the remote protocol, see @ref{system,
19463 system-call-allowed}.
19466 @item set remoteaddresssize @var{bits}
19467 @cindex address size for remote targets
19468 @cindex bits in remote address
19469 Set the maximum size of address in a memory packet to the specified
19470 number of bits. @value{GDBN} will mask off the address bits above
19471 that number, when it passes addresses to the remote target. The
19472 default value is the number of bits in the target's address.
19474 @item show remoteaddresssize
19475 Show the current value of remote address size in bits.
19477 @item set serial baud @var{n}
19478 @cindex baud rate for remote targets
19479 Set the baud rate for the remote serial I/O to @var{n} baud. The
19480 value is used to set the speed of the serial port used for debugging
19483 @item show serial baud
19484 Show the current speed of the remote connection.
19486 @item set serial parity @var{parity}
19487 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19488 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19490 @item show serial parity
19491 Show the current parity of the serial port.
19493 @item set remotebreak
19494 @cindex interrupt remote programs
19495 @cindex BREAK signal instead of Ctrl-C
19496 @anchor{set remotebreak}
19497 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19498 when you type @kbd{Ctrl-c} to interrupt the program running
19499 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19500 character instead. The default is off, since most remote systems
19501 expect to see @samp{Ctrl-C} as the interrupt signal.
19503 @item show remotebreak
19504 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19505 interrupt the remote program.
19507 @item set remoteflow on
19508 @itemx set remoteflow off
19509 @kindex set remoteflow
19510 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19511 on the serial port used to communicate to the remote target.
19513 @item show remoteflow
19514 @kindex show remoteflow
19515 Show the current setting of hardware flow control.
19517 @item set remotelogbase @var{base}
19518 Set the base (a.k.a.@: radix) of logging serial protocol
19519 communications to @var{base}. Supported values of @var{base} are:
19520 @code{ascii}, @code{octal}, and @code{hex}. The default is
19523 @item show remotelogbase
19524 Show the current setting of the radix for logging remote serial
19527 @item set remotelogfile @var{file}
19528 @cindex record serial communications on file
19529 Record remote serial communications on the named @var{file}. The
19530 default is not to record at all.
19532 @item show remotelogfile.
19533 Show the current setting of the file name on which to record the
19534 serial communications.
19536 @item set remotetimeout @var{num}
19537 @cindex timeout for serial communications
19538 @cindex remote timeout
19539 Set the timeout limit to wait for the remote target to respond to
19540 @var{num} seconds. The default is 2 seconds.
19542 @item show remotetimeout
19543 Show the current number of seconds to wait for the remote target
19546 @cindex limit hardware breakpoints and watchpoints
19547 @cindex remote target, limit break- and watchpoints
19548 @anchor{set remote hardware-watchpoint-limit}
19549 @anchor{set remote hardware-breakpoint-limit}
19550 @item set remote hardware-watchpoint-limit @var{limit}
19551 @itemx set remote hardware-breakpoint-limit @var{limit}
19552 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19553 watchpoints. A limit of -1, the default, is treated as unlimited.
19555 @cindex limit hardware watchpoints length
19556 @cindex remote target, limit watchpoints length
19557 @anchor{set remote hardware-watchpoint-length-limit}
19558 @item set remote hardware-watchpoint-length-limit @var{limit}
19559 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19560 a remote hardware watchpoint. A limit of -1, the default, is treated
19563 @item show remote hardware-watchpoint-length-limit
19564 Show the current limit (in bytes) of the maximum length of
19565 a remote hardware watchpoint.
19567 @item set remote exec-file @var{filename}
19568 @itemx show remote exec-file
19569 @anchor{set remote exec-file}
19570 @cindex executable file, for remote target
19571 Select the file used for @code{run} with @code{target
19572 extended-remote}. This should be set to a filename valid on the
19573 target system. If it is not set, the target will use a default
19574 filename (e.g.@: the last program run).
19576 @item set remote interrupt-sequence
19577 @cindex interrupt remote programs
19578 @cindex select Ctrl-C, BREAK or BREAK-g
19579 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19580 @samp{BREAK-g} as the
19581 sequence to the remote target in order to interrupt the execution.
19582 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19583 is high level of serial line for some certain time.
19584 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19585 It is @code{BREAK} signal followed by character @code{g}.
19587 @item show interrupt-sequence
19588 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19589 is sent by @value{GDBN} to interrupt the remote program.
19590 @code{BREAK-g} is BREAK signal followed by @code{g} and
19591 also known as Magic SysRq g.
19593 @item set remote interrupt-on-connect
19594 @cindex send interrupt-sequence on start
19595 Specify whether interrupt-sequence is sent to remote target when
19596 @value{GDBN} connects to it. This is mostly needed when you debug
19597 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19598 which is known as Magic SysRq g in order to connect @value{GDBN}.
19600 @item show interrupt-on-connect
19601 Show whether interrupt-sequence is sent
19602 to remote target when @value{GDBN} connects to it.
19606 @item set tcp auto-retry on
19607 @cindex auto-retry, for remote TCP target
19608 Enable auto-retry for remote TCP connections. This is useful if the remote
19609 debugging agent is launched in parallel with @value{GDBN}; there is a race
19610 condition because the agent may not become ready to accept the connection
19611 before @value{GDBN} attempts to connect. When auto-retry is
19612 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19613 to establish the connection using the timeout specified by
19614 @code{set tcp connect-timeout}.
19616 @item set tcp auto-retry off
19617 Do not auto-retry failed TCP connections.
19619 @item show tcp auto-retry
19620 Show the current auto-retry setting.
19622 @item set tcp connect-timeout @var{seconds}
19623 @itemx set tcp connect-timeout unlimited
19624 @cindex connection timeout, for remote TCP target
19625 @cindex timeout, for remote target connection
19626 Set the timeout for establishing a TCP connection to the remote target to
19627 @var{seconds}. The timeout affects both polling to retry failed connections
19628 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19629 that are merely slow to complete, and represents an approximate cumulative
19630 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19631 @value{GDBN} will keep attempting to establish a connection forever,
19632 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19634 @item show tcp connect-timeout
19635 Show the current connection timeout setting.
19638 @cindex remote packets, enabling and disabling
19639 The @value{GDBN} remote protocol autodetects the packets supported by
19640 your debugging stub. If you need to override the autodetection, you
19641 can use these commands to enable or disable individual packets. Each
19642 packet can be set to @samp{on} (the remote target supports this
19643 packet), @samp{off} (the remote target does not support this packet),
19644 or @samp{auto} (detect remote target support for this packet). They
19645 all default to @samp{auto}. For more information about each packet,
19646 see @ref{Remote Protocol}.
19648 During normal use, you should not have to use any of these commands.
19649 If you do, that may be a bug in your remote debugging stub, or a bug
19650 in @value{GDBN}. You may want to report the problem to the
19651 @value{GDBN} developers.
19653 For each packet @var{name}, the command to enable or disable the
19654 packet is @code{set remote @var{name}-packet}. The available settings
19657 @multitable @columnfractions 0.28 0.32 0.25
19660 @tab Related Features
19662 @item @code{fetch-register}
19664 @tab @code{info registers}
19666 @item @code{set-register}
19670 @item @code{binary-download}
19672 @tab @code{load}, @code{set}
19674 @item @code{read-aux-vector}
19675 @tab @code{qXfer:auxv:read}
19676 @tab @code{info auxv}
19678 @item @code{symbol-lookup}
19679 @tab @code{qSymbol}
19680 @tab Detecting multiple threads
19682 @item @code{attach}
19683 @tab @code{vAttach}
19686 @item @code{verbose-resume}
19688 @tab Stepping or resuming multiple threads
19694 @item @code{software-breakpoint}
19698 @item @code{hardware-breakpoint}
19702 @item @code{write-watchpoint}
19706 @item @code{read-watchpoint}
19710 @item @code{access-watchpoint}
19714 @item @code{target-features}
19715 @tab @code{qXfer:features:read}
19716 @tab @code{set architecture}
19718 @item @code{library-info}
19719 @tab @code{qXfer:libraries:read}
19720 @tab @code{info sharedlibrary}
19722 @item @code{memory-map}
19723 @tab @code{qXfer:memory-map:read}
19724 @tab @code{info mem}
19726 @item @code{read-sdata-object}
19727 @tab @code{qXfer:sdata:read}
19728 @tab @code{print $_sdata}
19730 @item @code{read-spu-object}
19731 @tab @code{qXfer:spu:read}
19732 @tab @code{info spu}
19734 @item @code{write-spu-object}
19735 @tab @code{qXfer:spu:write}
19736 @tab @code{info spu}
19738 @item @code{read-siginfo-object}
19739 @tab @code{qXfer:siginfo:read}
19740 @tab @code{print $_siginfo}
19742 @item @code{write-siginfo-object}
19743 @tab @code{qXfer:siginfo:write}
19744 @tab @code{set $_siginfo}
19746 @item @code{threads}
19747 @tab @code{qXfer:threads:read}
19748 @tab @code{info threads}
19750 @item @code{get-thread-local-@*storage-address}
19751 @tab @code{qGetTLSAddr}
19752 @tab Displaying @code{__thread} variables
19754 @item @code{get-thread-information-block-address}
19755 @tab @code{qGetTIBAddr}
19756 @tab Display MS-Windows Thread Information Block.
19758 @item @code{search-memory}
19759 @tab @code{qSearch:memory}
19762 @item @code{supported-packets}
19763 @tab @code{qSupported}
19764 @tab Remote communications parameters
19766 @item @code{pass-signals}
19767 @tab @code{QPassSignals}
19768 @tab @code{handle @var{signal}}
19770 @item @code{program-signals}
19771 @tab @code{QProgramSignals}
19772 @tab @code{handle @var{signal}}
19774 @item @code{hostio-close-packet}
19775 @tab @code{vFile:close}
19776 @tab @code{remote get}, @code{remote put}
19778 @item @code{hostio-open-packet}
19779 @tab @code{vFile:open}
19780 @tab @code{remote get}, @code{remote put}
19782 @item @code{hostio-pread-packet}
19783 @tab @code{vFile:pread}
19784 @tab @code{remote get}, @code{remote put}
19786 @item @code{hostio-pwrite-packet}
19787 @tab @code{vFile:pwrite}
19788 @tab @code{remote get}, @code{remote put}
19790 @item @code{hostio-unlink-packet}
19791 @tab @code{vFile:unlink}
19792 @tab @code{remote delete}
19794 @item @code{hostio-readlink-packet}
19795 @tab @code{vFile:readlink}
19798 @item @code{hostio-fstat-packet}
19799 @tab @code{vFile:fstat}
19802 @item @code{noack-packet}
19803 @tab @code{QStartNoAckMode}
19804 @tab Packet acknowledgment
19806 @item @code{osdata}
19807 @tab @code{qXfer:osdata:read}
19808 @tab @code{info os}
19810 @item @code{query-attached}
19811 @tab @code{qAttached}
19812 @tab Querying remote process attach state.
19814 @item @code{trace-buffer-size}
19815 @tab @code{QTBuffer:size}
19816 @tab @code{set trace-buffer-size}
19818 @item @code{trace-status}
19819 @tab @code{qTStatus}
19820 @tab @code{tstatus}
19822 @item @code{traceframe-info}
19823 @tab @code{qXfer:traceframe-info:read}
19824 @tab Traceframe info
19826 @item @code{install-in-trace}
19827 @tab @code{InstallInTrace}
19828 @tab Install tracepoint in tracing
19830 @item @code{disable-randomization}
19831 @tab @code{QDisableRandomization}
19832 @tab @code{set disable-randomization}
19834 @item @code{conditional-breakpoints-packet}
19835 @tab @code{Z0 and Z1}
19836 @tab @code{Support for target-side breakpoint condition evaluation}
19838 @item @code{swbreak-feature}
19839 @tab @code{swbreak stop reason}
19842 @item @code{hwbreak-feature}
19843 @tab @code{hwbreak stop reason}
19849 @section Implementing a Remote Stub
19851 @cindex debugging stub, example
19852 @cindex remote stub, example
19853 @cindex stub example, remote debugging
19854 The stub files provided with @value{GDBN} implement the target side of the
19855 communication protocol, and the @value{GDBN} side is implemented in the
19856 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19857 these subroutines to communicate, and ignore the details. (If you're
19858 implementing your own stub file, you can still ignore the details: start
19859 with one of the existing stub files. @file{sparc-stub.c} is the best
19860 organized, and therefore the easiest to read.)
19862 @cindex remote serial debugging, overview
19863 To debug a program running on another machine (the debugging
19864 @dfn{target} machine), you must first arrange for all the usual
19865 prerequisites for the program to run by itself. For example, for a C
19870 A startup routine to set up the C runtime environment; these usually
19871 have a name like @file{crt0}. The startup routine may be supplied by
19872 your hardware supplier, or you may have to write your own.
19875 A C subroutine library to support your program's
19876 subroutine calls, notably managing input and output.
19879 A way of getting your program to the other machine---for example, a
19880 download program. These are often supplied by the hardware
19881 manufacturer, but you may have to write your own from hardware
19885 The next step is to arrange for your program to use a serial port to
19886 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19887 machine). In general terms, the scheme looks like this:
19891 @value{GDBN} already understands how to use this protocol; when everything
19892 else is set up, you can simply use the @samp{target remote} command
19893 (@pxref{Targets,,Specifying a Debugging Target}).
19895 @item On the target,
19896 you must link with your program a few special-purpose subroutines that
19897 implement the @value{GDBN} remote serial protocol. The file containing these
19898 subroutines is called a @dfn{debugging stub}.
19900 On certain remote targets, you can use an auxiliary program
19901 @code{gdbserver} instead of linking a stub into your program.
19902 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19905 The debugging stub is specific to the architecture of the remote
19906 machine; for example, use @file{sparc-stub.c} to debug programs on
19909 @cindex remote serial stub list
19910 These working remote stubs are distributed with @value{GDBN}:
19915 @cindex @file{i386-stub.c}
19918 For Intel 386 and compatible architectures.
19921 @cindex @file{m68k-stub.c}
19922 @cindex Motorola 680x0
19924 For Motorola 680x0 architectures.
19927 @cindex @file{sh-stub.c}
19930 For Renesas SH architectures.
19933 @cindex @file{sparc-stub.c}
19935 For @sc{sparc} architectures.
19937 @item sparcl-stub.c
19938 @cindex @file{sparcl-stub.c}
19941 For Fujitsu @sc{sparclite} architectures.
19945 The @file{README} file in the @value{GDBN} distribution may list other
19946 recently added stubs.
19949 * Stub Contents:: What the stub can do for you
19950 * Bootstrapping:: What you must do for the stub
19951 * Debug Session:: Putting it all together
19954 @node Stub Contents
19955 @subsection What the Stub Can Do for You
19957 @cindex remote serial stub
19958 The debugging stub for your architecture supplies these three
19962 @item set_debug_traps
19963 @findex set_debug_traps
19964 @cindex remote serial stub, initialization
19965 This routine arranges for @code{handle_exception} to run when your
19966 program stops. You must call this subroutine explicitly in your
19967 program's startup code.
19969 @item handle_exception
19970 @findex handle_exception
19971 @cindex remote serial stub, main routine
19972 This is the central workhorse, but your program never calls it
19973 explicitly---the setup code arranges for @code{handle_exception} to
19974 run when a trap is triggered.
19976 @code{handle_exception} takes control when your program stops during
19977 execution (for example, on a breakpoint), and mediates communications
19978 with @value{GDBN} on the host machine. This is where the communications
19979 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19980 representative on the target machine. It begins by sending summary
19981 information on the state of your program, then continues to execute,
19982 retrieving and transmitting any information @value{GDBN} needs, until you
19983 execute a @value{GDBN} command that makes your program resume; at that point,
19984 @code{handle_exception} returns control to your own code on the target
19988 @cindex @code{breakpoint} subroutine, remote
19989 Use this auxiliary subroutine to make your program contain a
19990 breakpoint. Depending on the particular situation, this may be the only
19991 way for @value{GDBN} to get control. For instance, if your target
19992 machine has some sort of interrupt button, you won't need to call this;
19993 pressing the interrupt button transfers control to
19994 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19995 simply receiving characters on the serial port may also trigger a trap;
19996 again, in that situation, you don't need to call @code{breakpoint} from
19997 your own program---simply running @samp{target remote} from the host
19998 @value{GDBN} session gets control.
20000 Call @code{breakpoint} if none of these is true, or if you simply want
20001 to make certain your program stops at a predetermined point for the
20002 start of your debugging session.
20005 @node Bootstrapping
20006 @subsection What You Must Do for the Stub
20008 @cindex remote stub, support routines
20009 The debugging stubs that come with @value{GDBN} are set up for a particular
20010 chip architecture, but they have no information about the rest of your
20011 debugging target machine.
20013 First of all you need to tell the stub how to communicate with the
20017 @item int getDebugChar()
20018 @findex getDebugChar
20019 Write this subroutine to read a single character from the serial port.
20020 It may be identical to @code{getchar} for your target system; a
20021 different name is used to allow you to distinguish the two if you wish.
20023 @item void putDebugChar(int)
20024 @findex putDebugChar
20025 Write this subroutine to write a single character to the serial port.
20026 It may be identical to @code{putchar} for your target system; a
20027 different name is used to allow you to distinguish the two if you wish.
20030 @cindex control C, and remote debugging
20031 @cindex interrupting remote targets
20032 If you want @value{GDBN} to be able to stop your program while it is
20033 running, you need to use an interrupt-driven serial driver, and arrange
20034 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20035 character). That is the character which @value{GDBN} uses to tell the
20036 remote system to stop.
20038 Getting the debugging target to return the proper status to @value{GDBN}
20039 probably requires changes to the standard stub; one quick and dirty way
20040 is to just execute a breakpoint instruction (the ``dirty'' part is that
20041 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20043 Other routines you need to supply are:
20046 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20047 @findex exceptionHandler
20048 Write this function to install @var{exception_address} in the exception
20049 handling tables. You need to do this because the stub does not have any
20050 way of knowing what the exception handling tables on your target system
20051 are like (for example, the processor's table might be in @sc{rom},
20052 containing entries which point to a table in @sc{ram}).
20053 The @var{exception_number} specifies the exception which should be changed;
20054 its meaning is architecture-dependent (for example, different numbers
20055 might represent divide by zero, misaligned access, etc). When this
20056 exception occurs, control should be transferred directly to
20057 @var{exception_address}, and the processor state (stack, registers,
20058 and so on) should be just as it is when a processor exception occurs. So if
20059 you want to use a jump instruction to reach @var{exception_address}, it
20060 should be a simple jump, not a jump to subroutine.
20062 For the 386, @var{exception_address} should be installed as an interrupt
20063 gate so that interrupts are masked while the handler runs. The gate
20064 should be at privilege level 0 (the most privileged level). The
20065 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20066 help from @code{exceptionHandler}.
20068 @item void flush_i_cache()
20069 @findex flush_i_cache
20070 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20071 instruction cache, if any, on your target machine. If there is no
20072 instruction cache, this subroutine may be a no-op.
20074 On target machines that have instruction caches, @value{GDBN} requires this
20075 function to make certain that the state of your program is stable.
20079 You must also make sure this library routine is available:
20082 @item void *memset(void *, int, int)
20084 This is the standard library function @code{memset} that sets an area of
20085 memory to a known value. If you have one of the free versions of
20086 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20087 either obtain it from your hardware manufacturer, or write your own.
20090 If you do not use the GNU C compiler, you may need other standard
20091 library subroutines as well; this varies from one stub to another,
20092 but in general the stubs are likely to use any of the common library
20093 subroutines which @code{@value{NGCC}} generates as inline code.
20096 @node Debug Session
20097 @subsection Putting it All Together
20099 @cindex remote serial debugging summary
20100 In summary, when your program is ready to debug, you must follow these
20105 Make sure you have defined the supporting low-level routines
20106 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20108 @code{getDebugChar}, @code{putDebugChar},
20109 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20113 Insert these lines in your program's startup code, before the main
20114 procedure is called:
20121 On some machines, when a breakpoint trap is raised, the hardware
20122 automatically makes the PC point to the instruction after the
20123 breakpoint. If your machine doesn't do that, you may need to adjust
20124 @code{handle_exception} to arrange for it to return to the instruction
20125 after the breakpoint on this first invocation, so that your program
20126 doesn't keep hitting the initial breakpoint instead of making
20130 For the 680x0 stub only, you need to provide a variable called
20131 @code{exceptionHook}. Normally you just use:
20134 void (*exceptionHook)() = 0;
20138 but if before calling @code{set_debug_traps}, you set it to point to a
20139 function in your program, that function is called when
20140 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20141 error). The function indicated by @code{exceptionHook} is called with
20142 one parameter: an @code{int} which is the exception number.
20145 Compile and link together: your program, the @value{GDBN} debugging stub for
20146 your target architecture, and the supporting subroutines.
20149 Make sure you have a serial connection between your target machine and
20150 the @value{GDBN} host, and identify the serial port on the host.
20153 @c The "remote" target now provides a `load' command, so we should
20154 @c document that. FIXME.
20155 Download your program to your target machine (or get it there by
20156 whatever means the manufacturer provides), and start it.
20159 Start @value{GDBN} on the host, and connect to the target
20160 (@pxref{Connecting,,Connecting to a Remote Target}).
20164 @node Configurations
20165 @chapter Configuration-Specific Information
20167 While nearly all @value{GDBN} commands are available for all native and
20168 cross versions of the debugger, there are some exceptions. This chapter
20169 describes things that are only available in certain configurations.
20171 There are three major categories of configurations: native
20172 configurations, where the host and target are the same, embedded
20173 operating system configurations, which are usually the same for several
20174 different processor architectures, and bare embedded processors, which
20175 are quite different from each other.
20180 * Embedded Processors::
20187 This section describes details specific to particular native
20192 * BSD libkvm Interface:: Debugging BSD kernel memory images
20193 * SVR4 Process Information:: SVR4 process information
20194 * DJGPP Native:: Features specific to the DJGPP port
20195 * Cygwin Native:: Features specific to the Cygwin port
20196 * Hurd Native:: Features specific to @sc{gnu} Hurd
20197 * Darwin:: Features specific to Darwin
20203 On HP-UX systems, if you refer to a function or variable name that
20204 begins with a dollar sign, @value{GDBN} searches for a user or system
20205 name first, before it searches for a convenience variable.
20208 @node BSD libkvm Interface
20209 @subsection BSD libkvm Interface
20212 @cindex kernel memory image
20213 @cindex kernel crash dump
20215 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20216 interface that provides a uniform interface for accessing kernel virtual
20217 memory images, including live systems and crash dumps. @value{GDBN}
20218 uses this interface to allow you to debug live kernels and kernel crash
20219 dumps on many native BSD configurations. This is implemented as a
20220 special @code{kvm} debugging target. For debugging a live system, load
20221 the currently running kernel into @value{GDBN} and connect to the
20225 (@value{GDBP}) @b{target kvm}
20228 For debugging crash dumps, provide the file name of the crash dump as an
20232 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20235 Once connected to the @code{kvm} target, the following commands are
20241 Set current context from the @dfn{Process Control Block} (PCB) address.
20244 Set current context from proc address. This command isn't available on
20245 modern FreeBSD systems.
20248 @node SVR4 Process Information
20249 @subsection SVR4 Process Information
20251 @cindex examine process image
20252 @cindex process info via @file{/proc}
20254 Many versions of SVR4 and compatible systems provide a facility called
20255 @samp{/proc} that can be used to examine the image of a running
20256 process using file-system subroutines.
20258 If @value{GDBN} is configured for an operating system with this
20259 facility, the command @code{info proc} is available to report
20260 information about the process running your program, or about any
20261 process running on your system. This includes, as of this writing,
20262 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20264 This command may also work on core files that were created on a system
20265 that has the @samp{/proc} facility.
20271 @itemx info proc @var{process-id}
20272 Summarize available information about any running process. If a
20273 process ID is specified by @var{process-id}, display information about
20274 that process; otherwise display information about the program being
20275 debugged. The summary includes the debugged process ID, the command
20276 line used to invoke it, its current working directory, and its
20277 executable file's absolute file name.
20279 On some systems, @var{process-id} can be of the form
20280 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20281 within a process. If the optional @var{pid} part is missing, it means
20282 a thread from the process being debugged (the leading @samp{/} still
20283 needs to be present, or else @value{GDBN} will interpret the number as
20284 a process ID rather than a thread ID).
20286 @item info proc cmdline
20287 @cindex info proc cmdline
20288 Show the original command line of the process. This command is
20289 specific to @sc{gnu}/Linux.
20291 @item info proc cwd
20292 @cindex info proc cwd
20293 Show the current working directory of the process. This command is
20294 specific to @sc{gnu}/Linux.
20296 @item info proc exe
20297 @cindex info proc exe
20298 Show the name of executable of the process. This command is specific
20301 @item info proc mappings
20302 @cindex memory address space mappings
20303 Report the memory address space ranges accessible in the program, with
20304 information on whether the process has read, write, or execute access
20305 rights to each range. On @sc{gnu}/Linux systems, each memory range
20306 includes the object file which is mapped to that range, instead of the
20307 memory access rights to that range.
20309 @item info proc stat
20310 @itemx info proc status
20311 @cindex process detailed status information
20312 These subcommands are specific to @sc{gnu}/Linux systems. They show
20313 the process-related information, including the user ID and group ID;
20314 how many threads are there in the process; its virtual memory usage;
20315 the signals that are pending, blocked, and ignored; its TTY; its
20316 consumption of system and user time; its stack size; its @samp{nice}
20317 value; etc. For more information, see the @samp{proc} man page
20318 (type @kbd{man 5 proc} from your shell prompt).
20320 @item info proc all
20321 Show all the information about the process described under all of the
20322 above @code{info proc} subcommands.
20325 @comment These sub-options of 'info proc' were not included when
20326 @comment procfs.c was re-written. Keep their descriptions around
20327 @comment against the day when someone finds the time to put them back in.
20328 @kindex info proc times
20329 @item info proc times
20330 Starting time, user CPU time, and system CPU time for your program and
20333 @kindex info proc id
20335 Report on the process IDs related to your program: its own process ID,
20336 the ID of its parent, the process group ID, and the session ID.
20339 @item set procfs-trace
20340 @kindex set procfs-trace
20341 @cindex @code{procfs} API calls
20342 This command enables and disables tracing of @code{procfs} API calls.
20344 @item show procfs-trace
20345 @kindex show procfs-trace
20346 Show the current state of @code{procfs} API call tracing.
20348 @item set procfs-file @var{file}
20349 @kindex set procfs-file
20350 Tell @value{GDBN} to write @code{procfs} API trace to the named
20351 @var{file}. @value{GDBN} appends the trace info to the previous
20352 contents of the file. The default is to display the trace on the
20355 @item show procfs-file
20356 @kindex show procfs-file
20357 Show the file to which @code{procfs} API trace is written.
20359 @item proc-trace-entry
20360 @itemx proc-trace-exit
20361 @itemx proc-untrace-entry
20362 @itemx proc-untrace-exit
20363 @kindex proc-trace-entry
20364 @kindex proc-trace-exit
20365 @kindex proc-untrace-entry
20366 @kindex proc-untrace-exit
20367 These commands enable and disable tracing of entries into and exits
20368 from the @code{syscall} interface.
20371 @kindex info pidlist
20372 @cindex process list, QNX Neutrino
20373 For QNX Neutrino only, this command displays the list of all the
20374 processes and all the threads within each process.
20377 @kindex info meminfo
20378 @cindex mapinfo list, QNX Neutrino
20379 For QNX Neutrino only, this command displays the list of all mapinfos.
20383 @subsection Features for Debugging @sc{djgpp} Programs
20384 @cindex @sc{djgpp} debugging
20385 @cindex native @sc{djgpp} debugging
20386 @cindex MS-DOS-specific commands
20389 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20390 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20391 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20392 top of real-mode DOS systems and their emulations.
20394 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20395 defines a few commands specific to the @sc{djgpp} port. This
20396 subsection describes those commands.
20401 This is a prefix of @sc{djgpp}-specific commands which print
20402 information about the target system and important OS structures.
20405 @cindex MS-DOS system info
20406 @cindex free memory information (MS-DOS)
20407 @item info dos sysinfo
20408 This command displays assorted information about the underlying
20409 platform: the CPU type and features, the OS version and flavor, the
20410 DPMI version, and the available conventional and DPMI memory.
20415 @cindex segment descriptor tables
20416 @cindex descriptor tables display
20418 @itemx info dos ldt
20419 @itemx info dos idt
20420 These 3 commands display entries from, respectively, Global, Local,
20421 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20422 tables are data structures which store a descriptor for each segment
20423 that is currently in use. The segment's selector is an index into a
20424 descriptor table; the table entry for that index holds the
20425 descriptor's base address and limit, and its attributes and access
20428 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20429 segment (used for both data and the stack), and a DOS segment (which
20430 allows access to DOS/BIOS data structures and absolute addresses in
20431 conventional memory). However, the DPMI host will usually define
20432 additional segments in order to support the DPMI environment.
20434 @cindex garbled pointers
20435 These commands allow to display entries from the descriptor tables.
20436 Without an argument, all entries from the specified table are
20437 displayed. An argument, which should be an integer expression, means
20438 display a single entry whose index is given by the argument. For
20439 example, here's a convenient way to display information about the
20440 debugged program's data segment:
20443 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20444 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20448 This comes in handy when you want to see whether a pointer is outside
20449 the data segment's limit (i.e.@: @dfn{garbled}).
20451 @cindex page tables display (MS-DOS)
20453 @itemx info dos pte
20454 These two commands display entries from, respectively, the Page
20455 Directory and the Page Tables. Page Directories and Page Tables are
20456 data structures which control how virtual memory addresses are mapped
20457 into physical addresses. A Page Table includes an entry for every
20458 page of memory that is mapped into the program's address space; there
20459 may be several Page Tables, each one holding up to 4096 entries. A
20460 Page Directory has up to 4096 entries, one each for every Page Table
20461 that is currently in use.
20463 Without an argument, @kbd{info dos pde} displays the entire Page
20464 Directory, and @kbd{info dos pte} displays all the entries in all of
20465 the Page Tables. An argument, an integer expression, given to the
20466 @kbd{info dos pde} command means display only that entry from the Page
20467 Directory table. An argument given to the @kbd{info dos pte} command
20468 means display entries from a single Page Table, the one pointed to by
20469 the specified entry in the Page Directory.
20471 @cindex direct memory access (DMA) on MS-DOS
20472 These commands are useful when your program uses @dfn{DMA} (Direct
20473 Memory Access), which needs physical addresses to program the DMA
20476 These commands are supported only with some DPMI servers.
20478 @cindex physical address from linear address
20479 @item info dos address-pte @var{addr}
20480 This command displays the Page Table entry for a specified linear
20481 address. The argument @var{addr} is a linear address which should
20482 already have the appropriate segment's base address added to it,
20483 because this command accepts addresses which may belong to @emph{any}
20484 segment. For example, here's how to display the Page Table entry for
20485 the page where a variable @code{i} is stored:
20488 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20489 @exdent @code{Page Table entry for address 0x11a00d30:}
20490 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20494 This says that @code{i} is stored at offset @code{0xd30} from the page
20495 whose physical base address is @code{0x02698000}, and shows all the
20496 attributes of that page.
20498 Note that you must cast the addresses of variables to a @code{char *},
20499 since otherwise the value of @code{__djgpp_base_address}, the base
20500 address of all variables and functions in a @sc{djgpp} program, will
20501 be added using the rules of C pointer arithmetics: if @code{i} is
20502 declared an @code{int}, @value{GDBN} will add 4 times the value of
20503 @code{__djgpp_base_address} to the address of @code{i}.
20505 Here's another example, it displays the Page Table entry for the
20509 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20510 @exdent @code{Page Table entry for address 0x29110:}
20511 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20515 (The @code{+ 3} offset is because the transfer buffer's address is the
20516 3rd member of the @code{_go32_info_block} structure.) The output
20517 clearly shows that this DPMI server maps the addresses in conventional
20518 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20519 linear (@code{0x29110}) addresses are identical.
20521 This command is supported only with some DPMI servers.
20524 @cindex DOS serial data link, remote debugging
20525 In addition to native debugging, the DJGPP port supports remote
20526 debugging via a serial data link. The following commands are specific
20527 to remote serial debugging in the DJGPP port of @value{GDBN}.
20530 @kindex set com1base
20531 @kindex set com1irq
20532 @kindex set com2base
20533 @kindex set com2irq
20534 @kindex set com3base
20535 @kindex set com3irq
20536 @kindex set com4base
20537 @kindex set com4irq
20538 @item set com1base @var{addr}
20539 This command sets the base I/O port address of the @file{COM1} serial
20542 @item set com1irq @var{irq}
20543 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20544 for the @file{COM1} serial port.
20546 There are similar commands @samp{set com2base}, @samp{set com3irq},
20547 etc.@: for setting the port address and the @code{IRQ} lines for the
20550 @kindex show com1base
20551 @kindex show com1irq
20552 @kindex show com2base
20553 @kindex show com2irq
20554 @kindex show com3base
20555 @kindex show com3irq
20556 @kindex show com4base
20557 @kindex show com4irq
20558 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20559 display the current settings of the base address and the @code{IRQ}
20560 lines used by the COM ports.
20563 @kindex info serial
20564 @cindex DOS serial port status
20565 This command prints the status of the 4 DOS serial ports. For each
20566 port, it prints whether it's active or not, its I/O base address and
20567 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20568 counts of various errors encountered so far.
20572 @node Cygwin Native
20573 @subsection Features for Debugging MS Windows PE Executables
20574 @cindex MS Windows debugging
20575 @cindex native Cygwin debugging
20576 @cindex Cygwin-specific commands
20578 @value{GDBN} supports native debugging of MS Windows programs, including
20579 DLLs with and without symbolic debugging information.
20581 @cindex Ctrl-BREAK, MS-Windows
20582 @cindex interrupt debuggee on MS-Windows
20583 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20584 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20585 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20586 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20587 sequence, which can be used to interrupt the debuggee even if it
20590 There are various additional Cygwin-specific commands, described in
20591 this section. Working with DLLs that have no debugging symbols is
20592 described in @ref{Non-debug DLL Symbols}.
20597 This is a prefix of MS Windows-specific commands which print
20598 information about the target system and important OS structures.
20600 @item info w32 selector
20601 This command displays information returned by
20602 the Win32 API @code{GetThreadSelectorEntry} function.
20603 It takes an optional argument that is evaluated to
20604 a long value to give the information about this given selector.
20605 Without argument, this command displays information
20606 about the six segment registers.
20608 @item info w32 thread-information-block
20609 This command displays thread specific information stored in the
20610 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20611 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20615 This is a Cygwin-specific alias of @code{info shared}.
20617 @kindex set cygwin-exceptions
20618 @cindex debugging the Cygwin DLL
20619 @cindex Cygwin DLL, debugging
20620 @item set cygwin-exceptions @var{mode}
20621 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20622 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20623 @value{GDBN} will delay recognition of exceptions, and may ignore some
20624 exceptions which seem to be caused by internal Cygwin DLL
20625 ``bookkeeping''. This option is meant primarily for debugging the
20626 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20627 @value{GDBN} users with false @code{SIGSEGV} signals.
20629 @kindex show cygwin-exceptions
20630 @item show cygwin-exceptions
20631 Displays whether @value{GDBN} will break on exceptions that happen
20632 inside the Cygwin DLL itself.
20634 @kindex set new-console
20635 @item set new-console @var{mode}
20636 If @var{mode} is @code{on} the debuggee will
20637 be started in a new console on next start.
20638 If @var{mode} is @code{off}, the debuggee will
20639 be started in the same console as the debugger.
20641 @kindex show new-console
20642 @item show new-console
20643 Displays whether a new console is used
20644 when the debuggee is started.
20646 @kindex set new-group
20647 @item set new-group @var{mode}
20648 This boolean value controls whether the debuggee should
20649 start a new group or stay in the same group as the debugger.
20650 This affects the way the Windows OS handles
20653 @kindex show new-group
20654 @item show new-group
20655 Displays current value of new-group boolean.
20657 @kindex set debugevents
20658 @item set debugevents
20659 This boolean value adds debug output concerning kernel events related
20660 to the debuggee seen by the debugger. This includes events that
20661 signal thread and process creation and exit, DLL loading and
20662 unloading, console interrupts, and debugging messages produced by the
20663 Windows @code{OutputDebugString} API call.
20665 @kindex set debugexec
20666 @item set debugexec
20667 This boolean value adds debug output concerning execute events
20668 (such as resume thread) seen by the debugger.
20670 @kindex set debugexceptions
20671 @item set debugexceptions
20672 This boolean value adds debug output concerning exceptions in the
20673 debuggee seen by the debugger.
20675 @kindex set debugmemory
20676 @item set debugmemory
20677 This boolean value adds debug output concerning debuggee memory reads
20678 and writes by the debugger.
20682 This boolean values specifies whether the debuggee is called
20683 via a shell or directly (default value is on).
20687 Displays if the debuggee will be started with a shell.
20692 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20695 @node Non-debug DLL Symbols
20696 @subsubsection Support for DLLs without Debugging Symbols
20697 @cindex DLLs with no debugging symbols
20698 @cindex Minimal symbols and DLLs
20700 Very often on windows, some of the DLLs that your program relies on do
20701 not include symbolic debugging information (for example,
20702 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20703 symbols in a DLL, it relies on the minimal amount of symbolic
20704 information contained in the DLL's export table. This section
20705 describes working with such symbols, known internally to @value{GDBN} as
20706 ``minimal symbols''.
20708 Note that before the debugged program has started execution, no DLLs
20709 will have been loaded. The easiest way around this problem is simply to
20710 start the program --- either by setting a breakpoint or letting the
20711 program run once to completion.
20713 @subsubsection DLL Name Prefixes
20715 In keeping with the naming conventions used by the Microsoft debugging
20716 tools, DLL export symbols are made available with a prefix based on the
20717 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20718 also entered into the symbol table, so @code{CreateFileA} is often
20719 sufficient. In some cases there will be name clashes within a program
20720 (particularly if the executable itself includes full debugging symbols)
20721 necessitating the use of the fully qualified name when referring to the
20722 contents of the DLL. Use single-quotes around the name to avoid the
20723 exclamation mark (``!'') being interpreted as a language operator.
20725 Note that the internal name of the DLL may be all upper-case, even
20726 though the file name of the DLL is lower-case, or vice-versa. Since
20727 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20728 some confusion. If in doubt, try the @code{info functions} and
20729 @code{info variables} commands or even @code{maint print msymbols}
20730 (@pxref{Symbols}). Here's an example:
20733 (@value{GDBP}) info function CreateFileA
20734 All functions matching regular expression "CreateFileA":
20736 Non-debugging symbols:
20737 0x77e885f4 CreateFileA
20738 0x77e885f4 KERNEL32!CreateFileA
20742 (@value{GDBP}) info function !
20743 All functions matching regular expression "!":
20745 Non-debugging symbols:
20746 0x6100114c cygwin1!__assert
20747 0x61004034 cygwin1!_dll_crt0@@0
20748 0x61004240 cygwin1!dll_crt0(per_process *)
20752 @subsubsection Working with Minimal Symbols
20754 Symbols extracted from a DLL's export table do not contain very much
20755 type information. All that @value{GDBN} can do is guess whether a symbol
20756 refers to a function or variable depending on the linker section that
20757 contains the symbol. Also note that the actual contents of the memory
20758 contained in a DLL are not available unless the program is running. This
20759 means that you cannot examine the contents of a variable or disassemble
20760 a function within a DLL without a running program.
20762 Variables are generally treated as pointers and dereferenced
20763 automatically. For this reason, it is often necessary to prefix a
20764 variable name with the address-of operator (``&'') and provide explicit
20765 type information in the command. Here's an example of the type of
20769 (@value{GDBP}) print 'cygwin1!__argv'
20774 (@value{GDBP}) x 'cygwin1!__argv'
20775 0x10021610: "\230y\""
20778 And two possible solutions:
20781 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20782 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20786 (@value{GDBP}) x/2x &'cygwin1!__argv'
20787 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20788 (@value{GDBP}) x/x 0x10021608
20789 0x10021608: 0x0022fd98
20790 (@value{GDBP}) x/s 0x0022fd98
20791 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20794 Setting a break point within a DLL is possible even before the program
20795 starts execution. However, under these circumstances, @value{GDBN} can't
20796 examine the initial instructions of the function in order to skip the
20797 function's frame set-up code. You can work around this by using ``*&''
20798 to set the breakpoint at a raw memory address:
20801 (@value{GDBP}) break *&'python22!PyOS_Readline'
20802 Breakpoint 1 at 0x1e04eff0
20805 The author of these extensions is not entirely convinced that setting a
20806 break point within a shared DLL like @file{kernel32.dll} is completely
20810 @subsection Commands Specific to @sc{gnu} Hurd Systems
20811 @cindex @sc{gnu} Hurd debugging
20813 This subsection describes @value{GDBN} commands specific to the
20814 @sc{gnu} Hurd native debugging.
20819 @kindex set signals@r{, Hurd command}
20820 @kindex set sigs@r{, Hurd command}
20821 This command toggles the state of inferior signal interception by
20822 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20823 affected by this command. @code{sigs} is a shorthand alias for
20828 @kindex show signals@r{, Hurd command}
20829 @kindex show sigs@r{, Hurd command}
20830 Show the current state of intercepting inferior's signals.
20832 @item set signal-thread
20833 @itemx set sigthread
20834 @kindex set signal-thread
20835 @kindex set sigthread
20836 This command tells @value{GDBN} which thread is the @code{libc} signal
20837 thread. That thread is run when a signal is delivered to a running
20838 process. @code{set sigthread} is the shorthand alias of @code{set
20841 @item show signal-thread
20842 @itemx show sigthread
20843 @kindex show signal-thread
20844 @kindex show sigthread
20845 These two commands show which thread will run when the inferior is
20846 delivered a signal.
20849 @kindex set stopped@r{, Hurd command}
20850 This commands tells @value{GDBN} that the inferior process is stopped,
20851 as with the @code{SIGSTOP} signal. The stopped process can be
20852 continued by delivering a signal to it.
20855 @kindex show stopped@r{, Hurd command}
20856 This command shows whether @value{GDBN} thinks the debuggee is
20859 @item set exceptions
20860 @kindex set exceptions@r{, Hurd command}
20861 Use this command to turn off trapping of exceptions in the inferior.
20862 When exception trapping is off, neither breakpoints nor
20863 single-stepping will work. To restore the default, set exception
20866 @item show exceptions
20867 @kindex show exceptions@r{, Hurd command}
20868 Show the current state of trapping exceptions in the inferior.
20870 @item set task pause
20871 @kindex set task@r{, Hurd commands}
20872 @cindex task attributes (@sc{gnu} Hurd)
20873 @cindex pause current task (@sc{gnu} Hurd)
20874 This command toggles task suspension when @value{GDBN} has control.
20875 Setting it to on takes effect immediately, and the task is suspended
20876 whenever @value{GDBN} gets control. Setting it to off will take
20877 effect the next time the inferior is continued. If this option is set
20878 to off, you can use @code{set thread default pause on} or @code{set
20879 thread pause on} (see below) to pause individual threads.
20881 @item show task pause
20882 @kindex show task@r{, Hurd commands}
20883 Show the current state of task suspension.
20885 @item set task detach-suspend-count
20886 @cindex task suspend count
20887 @cindex detach from task, @sc{gnu} Hurd
20888 This command sets the suspend count the task will be left with when
20889 @value{GDBN} detaches from it.
20891 @item show task detach-suspend-count
20892 Show the suspend count the task will be left with when detaching.
20894 @item set task exception-port
20895 @itemx set task excp
20896 @cindex task exception port, @sc{gnu} Hurd
20897 This command sets the task exception port to which @value{GDBN} will
20898 forward exceptions. The argument should be the value of the @dfn{send
20899 rights} of the task. @code{set task excp} is a shorthand alias.
20901 @item set noninvasive
20902 @cindex noninvasive task options
20903 This command switches @value{GDBN} to a mode that is the least
20904 invasive as far as interfering with the inferior is concerned. This
20905 is the same as using @code{set task pause}, @code{set exceptions}, and
20906 @code{set signals} to values opposite to the defaults.
20908 @item info send-rights
20909 @itemx info receive-rights
20910 @itemx info port-rights
20911 @itemx info port-sets
20912 @itemx info dead-names
20915 @cindex send rights, @sc{gnu} Hurd
20916 @cindex receive rights, @sc{gnu} Hurd
20917 @cindex port rights, @sc{gnu} Hurd
20918 @cindex port sets, @sc{gnu} Hurd
20919 @cindex dead names, @sc{gnu} Hurd
20920 These commands display information about, respectively, send rights,
20921 receive rights, port rights, port sets, and dead names of a task.
20922 There are also shorthand aliases: @code{info ports} for @code{info
20923 port-rights} and @code{info psets} for @code{info port-sets}.
20925 @item set thread pause
20926 @kindex set thread@r{, Hurd command}
20927 @cindex thread properties, @sc{gnu} Hurd
20928 @cindex pause current thread (@sc{gnu} Hurd)
20929 This command toggles current thread suspension when @value{GDBN} has
20930 control. Setting it to on takes effect immediately, and the current
20931 thread is suspended whenever @value{GDBN} gets control. Setting it to
20932 off will take effect the next time the inferior is continued.
20933 Normally, this command has no effect, since when @value{GDBN} has
20934 control, the whole task is suspended. However, if you used @code{set
20935 task pause off} (see above), this command comes in handy to suspend
20936 only the current thread.
20938 @item show thread pause
20939 @kindex show thread@r{, Hurd command}
20940 This command shows the state of current thread suspension.
20942 @item set thread run
20943 This command sets whether the current thread is allowed to run.
20945 @item show thread run
20946 Show whether the current thread is allowed to run.
20948 @item set thread detach-suspend-count
20949 @cindex thread suspend count, @sc{gnu} Hurd
20950 @cindex detach from thread, @sc{gnu} Hurd
20951 This command sets the suspend count @value{GDBN} will leave on a
20952 thread when detaching. This number is relative to the suspend count
20953 found by @value{GDBN} when it notices the thread; use @code{set thread
20954 takeover-suspend-count} to force it to an absolute value.
20956 @item show thread detach-suspend-count
20957 Show the suspend count @value{GDBN} will leave on the thread when
20960 @item set thread exception-port
20961 @itemx set thread excp
20962 Set the thread exception port to which to forward exceptions. This
20963 overrides the port set by @code{set task exception-port} (see above).
20964 @code{set thread excp} is the shorthand alias.
20966 @item set thread takeover-suspend-count
20967 Normally, @value{GDBN}'s thread suspend counts are relative to the
20968 value @value{GDBN} finds when it notices each thread. This command
20969 changes the suspend counts to be absolute instead.
20971 @item set thread default
20972 @itemx show thread default
20973 @cindex thread default settings, @sc{gnu} Hurd
20974 Each of the above @code{set thread} commands has a @code{set thread
20975 default} counterpart (e.g., @code{set thread default pause}, @code{set
20976 thread default exception-port}, etc.). The @code{thread default}
20977 variety of commands sets the default thread properties for all
20978 threads; you can then change the properties of individual threads with
20979 the non-default commands.
20986 @value{GDBN} provides the following commands specific to the Darwin target:
20989 @item set debug darwin @var{num}
20990 @kindex set debug darwin
20991 When set to a non zero value, enables debugging messages specific to
20992 the Darwin support. Higher values produce more verbose output.
20994 @item show debug darwin
20995 @kindex show debug darwin
20996 Show the current state of Darwin messages.
20998 @item set debug mach-o @var{num}
20999 @kindex set debug mach-o
21000 When set to a non zero value, enables debugging messages while
21001 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21002 file format used on Darwin for object and executable files.) Higher
21003 values produce more verbose output. This is a command to diagnose
21004 problems internal to @value{GDBN} and should not be needed in normal
21007 @item show debug mach-o
21008 @kindex show debug mach-o
21009 Show the current state of Mach-O file messages.
21011 @item set mach-exceptions on
21012 @itemx set mach-exceptions off
21013 @kindex set mach-exceptions
21014 On Darwin, faults are first reported as a Mach exception and are then
21015 mapped to a Posix signal. Use this command to turn on trapping of
21016 Mach exceptions in the inferior. This might be sometimes useful to
21017 better understand the cause of a fault. The default is off.
21019 @item show mach-exceptions
21020 @kindex show mach-exceptions
21021 Show the current state of exceptions trapping.
21026 @section Embedded Operating Systems
21028 This section describes configurations involving the debugging of
21029 embedded operating systems that are available for several different
21032 @value{GDBN} includes the ability to debug programs running on
21033 various real-time operating systems.
21035 @node Embedded Processors
21036 @section Embedded Processors
21038 This section goes into details specific to particular embedded
21041 @cindex send command to simulator
21042 Whenever a specific embedded processor has a simulator, @value{GDBN}
21043 allows to send an arbitrary command to the simulator.
21046 @item sim @var{command}
21047 @kindex sim@r{, a command}
21048 Send an arbitrary @var{command} string to the simulator. Consult the
21049 documentation for the specific simulator in use for information about
21050 acceptable commands.
21056 * M32R/D:: Renesas M32R/D
21057 * M68K:: Motorola M68K
21058 * MicroBlaze:: Xilinx MicroBlaze
21059 * MIPS Embedded:: MIPS Embedded
21060 * PowerPC Embedded:: PowerPC Embedded
21061 * PA:: HP PA Embedded
21062 * Sparclet:: Tsqware Sparclet
21063 * Sparclite:: Fujitsu Sparclite
21064 * Z8000:: Zilog Z8000
21067 * Super-H:: Renesas Super-H
21076 @item target rdi @var{dev}
21077 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21078 use this target to communicate with both boards running the Angel
21079 monitor, or with the EmbeddedICE JTAG debug device.
21082 @item target rdp @var{dev}
21087 @value{GDBN} provides the following ARM-specific commands:
21090 @item set arm disassembler
21092 This commands selects from a list of disassembly styles. The
21093 @code{"std"} style is the standard style.
21095 @item show arm disassembler
21097 Show the current disassembly style.
21099 @item set arm apcs32
21100 @cindex ARM 32-bit mode
21101 This command toggles ARM operation mode between 32-bit and 26-bit.
21103 @item show arm apcs32
21104 Display the current usage of the ARM 32-bit mode.
21106 @item set arm fpu @var{fputype}
21107 This command sets the ARM floating-point unit (FPU) type. The
21108 argument @var{fputype} can be one of these:
21112 Determine the FPU type by querying the OS ABI.
21114 Software FPU, with mixed-endian doubles on little-endian ARM
21117 GCC-compiled FPA co-processor.
21119 Software FPU with pure-endian doubles.
21125 Show the current type of the FPU.
21128 This command forces @value{GDBN} to use the specified ABI.
21131 Show the currently used ABI.
21133 @item set arm fallback-mode (arm|thumb|auto)
21134 @value{GDBN} uses the symbol table, when available, to determine
21135 whether instructions are ARM or Thumb. This command controls
21136 @value{GDBN}'s default behavior when the symbol table is not
21137 available. The default is @samp{auto}, which causes @value{GDBN} to
21138 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21141 @item show arm fallback-mode
21142 Show the current fallback instruction mode.
21144 @item set arm force-mode (arm|thumb|auto)
21145 This command overrides use of the symbol table to determine whether
21146 instructions are ARM or Thumb. The default is @samp{auto}, which
21147 causes @value{GDBN} to use the symbol table and then the setting
21148 of @samp{set arm fallback-mode}.
21150 @item show arm force-mode
21151 Show the current forced instruction mode.
21153 @item set debug arm
21154 Toggle whether to display ARM-specific debugging messages from the ARM
21155 target support subsystem.
21157 @item show debug arm
21158 Show whether ARM-specific debugging messages are enabled.
21161 The following commands are available when an ARM target is debugged
21162 using the RDI interface:
21165 @item rdilogfile @r{[}@var{file}@r{]}
21167 @cindex ADP (Angel Debugger Protocol) logging
21168 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21169 With an argument, sets the log file to the specified @var{file}. With
21170 no argument, show the current log file name. The default log file is
21173 @item rdilogenable @r{[}@var{arg}@r{]}
21174 @kindex rdilogenable
21175 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21176 enables logging, with an argument 0 or @code{"no"} disables it. With
21177 no arguments displays the current setting. When logging is enabled,
21178 ADP packets exchanged between @value{GDBN} and the RDI target device
21179 are logged to a file.
21181 @item set rdiromatzero
21182 @kindex set rdiromatzero
21183 @cindex ROM at zero address, RDI
21184 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21185 vector catching is disabled, so that zero address can be used. If off
21186 (the default), vector catching is enabled. For this command to take
21187 effect, it needs to be invoked prior to the @code{target rdi} command.
21189 @item show rdiromatzero
21190 @kindex show rdiromatzero
21191 Show the current setting of ROM at zero address.
21193 @item set rdiheartbeat
21194 @kindex set rdiheartbeat
21195 @cindex RDI heartbeat
21196 Enable or disable RDI heartbeat packets. It is not recommended to
21197 turn on this option, since it confuses ARM and EPI JTAG interface, as
21198 well as the Angel monitor.
21200 @item show rdiheartbeat
21201 @kindex show rdiheartbeat
21202 Show the setting of RDI heartbeat packets.
21206 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21207 The @value{GDBN} ARM simulator accepts the following optional arguments.
21210 @item --swi-support=@var{type}
21211 Tell the simulator which SWI interfaces to support. The argument
21212 @var{type} may be a comma separated list of the following values.
21213 The default value is @code{all}.
21226 @subsection Renesas M32R/D and M32R/SDI
21229 @kindex target m32r
21230 @item target m32r @var{dev}
21231 Renesas M32R/D ROM monitor.
21233 @kindex target m32rsdi
21234 @item target m32rsdi @var{dev}
21235 Renesas M32R SDI server, connected via parallel port to the board.
21238 The following @value{GDBN} commands are specific to the M32R monitor:
21241 @item set download-path @var{path}
21242 @kindex set download-path
21243 @cindex find downloadable @sc{srec} files (M32R)
21244 Set the default path for finding downloadable @sc{srec} files.
21246 @item show download-path
21247 @kindex show download-path
21248 Show the default path for downloadable @sc{srec} files.
21250 @item set board-address @var{addr}
21251 @kindex set board-address
21252 @cindex M32-EVA target board address
21253 Set the IP address for the M32R-EVA target board.
21255 @item show board-address
21256 @kindex show board-address
21257 Show the current IP address of the target board.
21259 @item set server-address @var{addr}
21260 @kindex set server-address
21261 @cindex download server address (M32R)
21262 Set the IP address for the download server, which is the @value{GDBN}'s
21265 @item show server-address
21266 @kindex show server-address
21267 Display the IP address of the download server.
21269 @item upload @r{[}@var{file}@r{]}
21270 @kindex upload@r{, M32R}
21271 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21272 upload capability. If no @var{file} argument is given, the current
21273 executable file is uploaded.
21275 @item tload @r{[}@var{file}@r{]}
21276 @kindex tload@r{, M32R}
21277 Test the @code{upload} command.
21280 The following commands are available for M32R/SDI:
21285 @cindex reset SDI connection, M32R
21286 This command resets the SDI connection.
21290 This command shows the SDI connection status.
21293 @kindex debug_chaos
21294 @cindex M32R/Chaos debugging
21295 Instructs the remote that M32R/Chaos debugging is to be used.
21297 @item use_debug_dma
21298 @kindex use_debug_dma
21299 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21302 @kindex use_mon_code
21303 Instructs the remote to use the MON_CODE method of accessing memory.
21306 @kindex use_ib_break
21307 Instructs the remote to set breakpoints by IB break.
21309 @item use_dbt_break
21310 @kindex use_dbt_break
21311 Instructs the remote to set breakpoints by DBT.
21317 The Motorola m68k configuration includes ColdFire support, and a
21318 target command for the following ROM monitor.
21322 @kindex target dbug
21323 @item target dbug @var{dev}
21324 dBUG ROM monitor for Motorola ColdFire.
21329 @subsection MicroBlaze
21330 @cindex Xilinx MicroBlaze
21331 @cindex XMD, Xilinx Microprocessor Debugger
21333 The MicroBlaze is a soft-core processor supported on various Xilinx
21334 FPGAs, such as Spartan or Virtex series. Boards with these processors
21335 usually have JTAG ports which connect to a host system running the Xilinx
21336 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21337 This host system is used to download the configuration bitstream to
21338 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21339 communicates with the target board using the JTAG interface and
21340 presents a @code{gdbserver} interface to the board. By default
21341 @code{xmd} uses port @code{1234}. (While it is possible to change
21342 this default port, it requires the use of undocumented @code{xmd}
21343 commands. Contact Xilinx support if you need to do this.)
21345 Use these GDB commands to connect to the MicroBlaze target processor.
21348 @item target remote :1234
21349 Use this command to connect to the target if you are running @value{GDBN}
21350 on the same system as @code{xmd}.
21352 @item target remote @var{xmd-host}:1234
21353 Use this command to connect to the target if it is connected to @code{xmd}
21354 running on a different system named @var{xmd-host}.
21357 Use this command to download a program to the MicroBlaze target.
21359 @item set debug microblaze @var{n}
21360 Enable MicroBlaze-specific debugging messages if non-zero.
21362 @item show debug microblaze @var{n}
21363 Show MicroBlaze-specific debugging level.
21366 @node MIPS Embedded
21367 @subsection @acronym{MIPS} Embedded
21369 @cindex @acronym{MIPS} boards
21370 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21371 @acronym{MIPS} board attached to a serial line. This is available when
21372 you configure @value{GDBN} with @samp{--target=mips-elf}.
21375 Use these @value{GDBN} commands to specify the connection to your target board:
21378 @item target mips @var{port}
21379 @kindex target mips @var{port}
21380 To run a program on the board, start up @code{@value{GDBP}} with the
21381 name of your program as the argument. To connect to the board, use the
21382 command @samp{target mips @var{port}}, where @var{port} is the name of
21383 the serial port connected to the board. If the program has not already
21384 been downloaded to the board, you may use the @code{load} command to
21385 download it. You can then use all the usual @value{GDBN} commands.
21387 For example, this sequence connects to the target board through a serial
21388 port, and loads and runs a program called @var{prog} through the
21392 host$ @value{GDBP} @var{prog}
21393 @value{GDBN} is free software and @dots{}
21394 (@value{GDBP}) target mips /dev/ttyb
21395 (@value{GDBP}) load @var{prog}
21399 @item target mips @var{hostname}:@var{portnumber}
21400 On some @value{GDBN} host configurations, you can specify a TCP
21401 connection (for instance, to a serial line managed by a terminal
21402 concentrator) instead of a serial port, using the syntax
21403 @samp{@var{hostname}:@var{portnumber}}.
21405 @item target pmon @var{port}
21406 @kindex target pmon @var{port}
21409 @item target ddb @var{port}
21410 @kindex target ddb @var{port}
21411 NEC's DDB variant of PMON for Vr4300.
21413 @item target lsi @var{port}
21414 @kindex target lsi @var{port}
21415 LSI variant of PMON.
21417 @kindex target r3900
21418 @item target r3900 @var{dev}
21419 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21421 @kindex target array
21422 @item target array @var{dev}
21423 Array Tech LSI33K RAID controller board.
21429 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21432 @item set mipsfpu double
21433 @itemx set mipsfpu single
21434 @itemx set mipsfpu none
21435 @itemx set mipsfpu auto
21436 @itemx show mipsfpu
21437 @kindex set mipsfpu
21438 @kindex show mipsfpu
21439 @cindex @acronym{MIPS} remote floating point
21440 @cindex floating point, @acronym{MIPS} remote
21441 If your target board does not support the @acronym{MIPS} floating point
21442 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21443 need this, you may wish to put the command in your @value{GDBN} init
21444 file). This tells @value{GDBN} how to find the return value of
21445 functions which return floating point values. It also allows
21446 @value{GDBN} to avoid saving the floating point registers when calling
21447 functions on the board. If you are using a floating point coprocessor
21448 with only single precision floating point support, as on the @sc{r4650}
21449 processor, use the command @samp{set mipsfpu single}. The default
21450 double precision floating point coprocessor may be selected using
21451 @samp{set mipsfpu double}.
21453 In previous versions the only choices were double precision or no
21454 floating point, so @samp{set mipsfpu on} will select double precision
21455 and @samp{set mipsfpu off} will select no floating point.
21457 As usual, you can inquire about the @code{mipsfpu} variable with
21458 @samp{show mipsfpu}.
21460 @item set timeout @var{seconds}
21461 @itemx set retransmit-timeout @var{seconds}
21462 @itemx show timeout
21463 @itemx show retransmit-timeout
21464 @cindex @code{timeout}, @acronym{MIPS} protocol
21465 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21466 @kindex set timeout
21467 @kindex show timeout
21468 @kindex set retransmit-timeout
21469 @kindex show retransmit-timeout
21470 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21471 remote protocol, with the @code{set timeout @var{seconds}} command. The
21472 default is 5 seconds. Similarly, you can control the timeout used while
21473 waiting for an acknowledgment of a packet with the @code{set
21474 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21475 You can inspect both values with @code{show timeout} and @code{show
21476 retransmit-timeout}. (These commands are @emph{only} available when
21477 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21479 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21480 is waiting for your program to stop. In that case, @value{GDBN} waits
21481 forever because it has no way of knowing how long the program is going
21482 to run before stopping.
21484 @item set syn-garbage-limit @var{num}
21485 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21486 @cindex synchronize with remote @acronym{MIPS} target
21487 Limit the maximum number of characters @value{GDBN} should ignore when
21488 it tries to synchronize with the remote target. The default is 10
21489 characters. Setting the limit to -1 means there's no limit.
21491 @item show syn-garbage-limit
21492 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21493 Show the current limit on the number of characters to ignore when
21494 trying to synchronize with the remote system.
21496 @item set monitor-prompt @var{prompt}
21497 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21498 @cindex remote monitor prompt
21499 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21500 remote monitor. The default depends on the target:
21510 @item show monitor-prompt
21511 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21512 Show the current strings @value{GDBN} expects as the prompt from the
21515 @item set monitor-warnings
21516 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21517 Enable or disable monitor warnings about hardware breakpoints. This
21518 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21519 display warning messages whose codes are returned by the @code{lsi}
21520 PMON monitor for breakpoint commands.
21522 @item show monitor-warnings
21523 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21524 Show the current setting of printing monitor warnings.
21526 @item pmon @var{command}
21527 @kindex pmon@r{, @acronym{MIPS} remote}
21528 @cindex send PMON command
21529 This command allows sending an arbitrary @var{command} string to the
21530 monitor. The monitor must be in debug mode for this to work.
21533 @node PowerPC Embedded
21534 @subsection PowerPC Embedded
21536 @cindex DVC register
21537 @value{GDBN} supports using the DVC (Data Value Compare) register to
21538 implement in hardware simple hardware watchpoint conditions of the form:
21541 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21542 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21545 The DVC register will be automatically used when @value{GDBN} detects
21546 such pattern in a condition expression, and the created watchpoint uses one
21547 debug register (either the @code{exact-watchpoints} option is on and the
21548 variable is scalar, or the variable has a length of one byte). This feature
21549 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21552 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21553 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21554 in which case watchpoints using only one debug register are created when
21555 watching variables of scalar types.
21557 You can create an artificial array to watch an arbitrary memory
21558 region using one of the following commands (@pxref{Expressions}):
21561 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21562 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21565 PowerPC embedded processors support masked watchpoints. See the discussion
21566 about the @code{mask} argument in @ref{Set Watchpoints}.
21568 @cindex ranged breakpoint
21569 PowerPC embedded processors support hardware accelerated
21570 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21571 the inferior whenever it executes an instruction at any address within
21572 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21573 use the @code{break-range} command.
21575 @value{GDBN} provides the following PowerPC-specific commands:
21578 @kindex break-range
21579 @item break-range @var{start-location}, @var{end-location}
21580 Set a breakpoint for an address range given by
21581 @var{start-location} and @var{end-location}, which can specify a function name,
21582 a line number, an offset of lines from the current line or from the start
21583 location, or an address of an instruction (see @ref{Specify Location},
21584 for a list of all the possible ways to specify a @var{location}.)
21585 The breakpoint will stop execution of the inferior whenever it
21586 executes an instruction at any address within the specified range,
21587 (including @var{start-location} and @var{end-location}.)
21589 @kindex set powerpc
21590 @item set powerpc soft-float
21591 @itemx show powerpc soft-float
21592 Force @value{GDBN} to use (or not use) a software floating point calling
21593 convention. By default, @value{GDBN} selects the calling convention based
21594 on the selected architecture and the provided executable file.
21596 @item set powerpc vector-abi
21597 @itemx show powerpc vector-abi
21598 Force @value{GDBN} to use the specified calling convention for vector
21599 arguments and return values. The valid options are @samp{auto};
21600 @samp{generic}, to avoid vector registers even if they are present;
21601 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21602 registers. By default, @value{GDBN} selects the calling convention
21603 based on the selected architecture and the provided executable file.
21605 @item set powerpc exact-watchpoints
21606 @itemx show powerpc exact-watchpoints
21607 Allow @value{GDBN} to use only one debug register when watching a variable
21608 of scalar type, thus assuming that the variable is accessed through the
21609 address of its first byte.
21611 @kindex target dink32
21612 @item target dink32 @var{dev}
21613 DINK32 ROM monitor.
21615 @kindex target ppcbug
21616 @item target ppcbug @var{dev}
21617 @kindex target ppcbug1
21618 @item target ppcbug1 @var{dev}
21619 PPCBUG ROM monitor for PowerPC.
21622 @item target sds @var{dev}
21623 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21626 @cindex SDS protocol
21627 The following commands specific to the SDS protocol are supported
21631 @item set sdstimeout @var{nsec}
21632 @kindex set sdstimeout
21633 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21634 default is 2 seconds.
21636 @item show sdstimeout
21637 @kindex show sdstimeout
21638 Show the current value of the SDS timeout.
21640 @item sds @var{command}
21641 @kindex sds@r{, a command}
21642 Send the specified @var{command} string to the SDS monitor.
21647 @subsection HP PA Embedded
21651 @kindex target op50n
21652 @item target op50n @var{dev}
21653 OP50N monitor, running on an OKI HPPA board.
21655 @kindex target w89k
21656 @item target w89k @var{dev}
21657 W89K monitor, running on a Winbond HPPA board.
21662 @subsection Tsqware Sparclet
21666 @value{GDBN} enables developers to debug tasks running on
21667 Sparclet targets from a Unix host.
21668 @value{GDBN} uses code that runs on
21669 both the Unix host and on the Sparclet target. The program
21670 @code{@value{GDBP}} is installed and executed on the Unix host.
21673 @item remotetimeout @var{args}
21674 @kindex remotetimeout
21675 @value{GDBN} supports the option @code{remotetimeout}.
21676 This option is set by the user, and @var{args} represents the number of
21677 seconds @value{GDBN} waits for responses.
21680 @cindex compiling, on Sparclet
21681 When compiling for debugging, include the options @samp{-g} to get debug
21682 information and @samp{-Ttext} to relocate the program to where you wish to
21683 load it on the target. You may also want to add the options @samp{-n} or
21684 @samp{-N} in order to reduce the size of the sections. Example:
21687 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21690 You can use @code{objdump} to verify that the addresses are what you intended:
21693 sparclet-aout-objdump --headers --syms prog
21696 @cindex running, on Sparclet
21698 your Unix execution search path to find @value{GDBN}, you are ready to
21699 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21700 (or @code{sparclet-aout-gdb}, depending on your installation).
21702 @value{GDBN} comes up showing the prompt:
21709 * Sparclet File:: Setting the file to debug
21710 * Sparclet Connection:: Connecting to Sparclet
21711 * Sparclet Download:: Sparclet download
21712 * Sparclet Execution:: Running and debugging
21715 @node Sparclet File
21716 @subsubsection Setting File to Debug
21718 The @value{GDBN} command @code{file} lets you choose with program to debug.
21721 (gdbslet) file prog
21725 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21726 @value{GDBN} locates
21727 the file by searching the directories listed in the command search
21729 If the file was compiled with debug information (option @samp{-g}), source
21730 files will be searched as well.
21731 @value{GDBN} locates
21732 the source files by searching the directories listed in the directory search
21733 path (@pxref{Environment, ,Your Program's Environment}).
21735 to find a file, it displays a message such as:
21738 prog: No such file or directory.
21741 When this happens, add the appropriate directories to the search paths with
21742 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21743 @code{target} command again.
21745 @node Sparclet Connection
21746 @subsubsection Connecting to Sparclet
21748 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21749 To connect to a target on serial port ``@code{ttya}'', type:
21752 (gdbslet) target sparclet /dev/ttya
21753 Remote target sparclet connected to /dev/ttya
21754 main () at ../prog.c:3
21758 @value{GDBN} displays messages like these:
21764 @node Sparclet Download
21765 @subsubsection Sparclet Download
21767 @cindex download to Sparclet
21768 Once connected to the Sparclet target,
21769 you can use the @value{GDBN}
21770 @code{load} command to download the file from the host to the target.
21771 The file name and load offset should be given as arguments to the @code{load}
21773 Since the file format is aout, the program must be loaded to the starting
21774 address. You can use @code{objdump} to find out what this value is. The load
21775 offset is an offset which is added to the VMA (virtual memory address)
21776 of each of the file's sections.
21777 For instance, if the program
21778 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21779 and bss at 0x12010170, in @value{GDBN}, type:
21782 (gdbslet) load prog 0x12010000
21783 Loading section .text, size 0xdb0 vma 0x12010000
21786 If the code is loaded at a different address then what the program was linked
21787 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21788 to tell @value{GDBN} where to map the symbol table.
21790 @node Sparclet Execution
21791 @subsubsection Running and Debugging
21793 @cindex running and debugging Sparclet programs
21794 You can now begin debugging the task using @value{GDBN}'s execution control
21795 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21796 manual for the list of commands.
21800 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21802 Starting program: prog
21803 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21804 3 char *symarg = 0;
21806 4 char *execarg = "hello!";
21811 @subsection Fujitsu Sparclite
21815 @kindex target sparclite
21816 @item target sparclite @var{dev}
21817 Fujitsu sparclite boards, used only for the purpose of loading.
21818 You must use an additional command to debug the program.
21819 For example: target remote @var{dev} using @value{GDBN} standard
21825 @subsection Zilog Z8000
21828 @cindex simulator, Z8000
21829 @cindex Zilog Z8000 simulator
21831 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21834 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21835 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21836 segmented variant). The simulator recognizes which architecture is
21837 appropriate by inspecting the object code.
21840 @item target sim @var{args}
21842 @kindex target sim@r{, with Z8000}
21843 Debug programs on a simulated CPU. If the simulator supports setup
21844 options, specify them via @var{args}.
21848 After specifying this target, you can debug programs for the simulated
21849 CPU in the same style as programs for your host computer; use the
21850 @code{file} command to load a new program image, the @code{run} command
21851 to run your program, and so on.
21853 As well as making available all the usual machine registers
21854 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21855 additional items of information as specially named registers:
21860 Counts clock-ticks in the simulator.
21863 Counts instructions run in the simulator.
21866 Execution time in 60ths of a second.
21870 You can refer to these values in @value{GDBN} expressions with the usual
21871 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21872 conditional breakpoint that suspends only after at least 5000
21873 simulated clock ticks.
21876 @subsection Atmel AVR
21879 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21880 following AVR-specific commands:
21883 @item info io_registers
21884 @kindex info io_registers@r{, AVR}
21885 @cindex I/O registers (Atmel AVR)
21886 This command displays information about the AVR I/O registers. For
21887 each register, @value{GDBN} prints its number and value.
21894 When configured for debugging CRIS, @value{GDBN} provides the
21895 following CRIS-specific commands:
21898 @item set cris-version @var{ver}
21899 @cindex CRIS version
21900 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21901 The CRIS version affects register names and sizes. This command is useful in
21902 case autodetection of the CRIS version fails.
21904 @item show cris-version
21905 Show the current CRIS version.
21907 @item set cris-dwarf2-cfi
21908 @cindex DWARF-2 CFI and CRIS
21909 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21910 Change to @samp{off} when using @code{gcc-cris} whose version is below
21913 @item show cris-dwarf2-cfi
21914 Show the current state of using DWARF-2 CFI.
21916 @item set cris-mode @var{mode}
21918 Set the current CRIS mode to @var{mode}. It should only be changed when
21919 debugging in guru mode, in which case it should be set to
21920 @samp{guru} (the default is @samp{normal}).
21922 @item show cris-mode
21923 Show the current CRIS mode.
21927 @subsection Renesas Super-H
21930 For the Renesas Super-H processor, @value{GDBN} provides these
21934 @item set sh calling-convention @var{convention}
21935 @kindex set sh calling-convention
21936 Set the calling-convention used when calling functions from @value{GDBN}.
21937 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21938 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21939 convention. If the DWARF-2 information of the called function specifies
21940 that the function follows the Renesas calling convention, the function
21941 is called using the Renesas calling convention. If the calling convention
21942 is set to @samp{renesas}, the Renesas calling convention is always used,
21943 regardless of the DWARF-2 information. This can be used to override the
21944 default of @samp{gcc} if debug information is missing, or the compiler
21945 does not emit the DWARF-2 calling convention entry for a function.
21947 @item show sh calling-convention
21948 @kindex show sh calling-convention
21949 Show the current calling convention setting.
21954 @node Architectures
21955 @section Architectures
21957 This section describes characteristics of architectures that affect
21958 all uses of @value{GDBN} with the architecture, both native and cross.
21965 * HPPA:: HP PA architecture
21966 * SPU:: Cell Broadband Engine SPU architecture
21972 @subsection AArch64
21973 @cindex AArch64 support
21975 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21976 following special commands:
21979 @item set debug aarch64
21980 @kindex set debug aarch64
21981 This command determines whether AArch64 architecture-specific debugging
21982 messages are to be displayed.
21984 @item show debug aarch64
21985 Show whether AArch64 debugging messages are displayed.
21990 @subsection x86 Architecture-specific Issues
21993 @item set struct-convention @var{mode}
21994 @kindex set struct-convention
21995 @cindex struct return convention
21996 @cindex struct/union returned in registers
21997 Set the convention used by the inferior to return @code{struct}s and
21998 @code{union}s from functions to @var{mode}. Possible values of
21999 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22000 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22001 are returned on the stack, while @code{"reg"} means that a
22002 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22003 be returned in a register.
22005 @item show struct-convention
22006 @kindex show struct-convention
22007 Show the current setting of the convention to return @code{struct}s
22011 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22012 @cindex Intel(R) Memory Protection Extensions (MPX).
22014 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22015 @footnote{The register named with capital letters represent the architecture
22016 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22017 which are the lower bound and upper bound. Bounds are effective addresses or
22018 memory locations. The upper bounds are architecturally represented in 1's
22019 complement form. A bound having lower bound = 0, and upper bound = 0
22020 (1's complement of all bits set) will allow access to the entire address space.
22022 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22023 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22024 display the upper bound performing the complement of one operation on the
22025 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22026 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22027 can also be noted that the upper bounds are inclusive.
22029 As an example, assume that the register BND0 holds bounds for a pointer having
22030 access allowed for the range between 0x32 and 0x71. The values present on
22031 bnd0raw and bnd registers are presented as follows:
22034 bnd0raw = @{0x32, 0xffffffff8e@}
22035 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22038 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22039 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22040 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22041 Python, the display includes the memory size, in bits, accessible to
22047 See the following section.
22050 @subsection @acronym{MIPS}
22052 @cindex stack on Alpha
22053 @cindex stack on @acronym{MIPS}
22054 @cindex Alpha stack
22055 @cindex @acronym{MIPS} stack
22056 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22057 sometimes requires @value{GDBN} to search backward in the object code to
22058 find the beginning of a function.
22060 @cindex response time, @acronym{MIPS} debugging
22061 To improve response time (especially for embedded applications, where
22062 @value{GDBN} may be restricted to a slow serial line for this search)
22063 you may want to limit the size of this search, using one of these
22067 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22068 @item set heuristic-fence-post @var{limit}
22069 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22070 search for the beginning of a function. A value of @var{0} (the
22071 default) means there is no limit. However, except for @var{0}, the
22072 larger the limit the more bytes @code{heuristic-fence-post} must search
22073 and therefore the longer it takes to run. You should only need to use
22074 this command when debugging a stripped executable.
22076 @item show heuristic-fence-post
22077 Display the current limit.
22081 These commands are available @emph{only} when @value{GDBN} is configured
22082 for debugging programs on Alpha or @acronym{MIPS} processors.
22084 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22088 @item set mips abi @var{arg}
22089 @kindex set mips abi
22090 @cindex set ABI for @acronym{MIPS}
22091 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22092 values of @var{arg} are:
22096 The default ABI associated with the current binary (this is the
22106 @item show mips abi
22107 @kindex show mips abi
22108 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22110 @item set mips compression @var{arg}
22111 @kindex set mips compression
22112 @cindex code compression, @acronym{MIPS}
22113 Tell @value{GDBN} which @acronym{MIPS} compressed
22114 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22115 inferior. @value{GDBN} uses this for code disassembly and other
22116 internal interpretation purposes. This setting is only referred to
22117 when no executable has been associated with the debugging session or
22118 the executable does not provide information about the encoding it uses.
22119 Otherwise this setting is automatically updated from information
22120 provided by the executable.
22122 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22123 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22124 executables containing @acronym{MIPS16} code frequently are not
22125 identified as such.
22127 This setting is ``sticky''; that is, it retains its value across
22128 debugging sessions until reset either explicitly with this command or
22129 implicitly from an executable.
22131 The compiler and/or assembler typically add symbol table annotations to
22132 identify functions compiled for the @acronym{MIPS16} or
22133 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22134 are present, @value{GDBN} uses them in preference to the global
22135 compressed @acronym{ISA} encoding setting.
22137 @item show mips compression
22138 @kindex show mips compression
22139 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22140 @value{GDBN} to debug the inferior.
22143 @itemx show mipsfpu
22144 @xref{MIPS Embedded, set mipsfpu}.
22146 @item set mips mask-address @var{arg}
22147 @kindex set mips mask-address
22148 @cindex @acronym{MIPS} addresses, masking
22149 This command determines whether the most-significant 32 bits of 64-bit
22150 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22151 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22152 setting, which lets @value{GDBN} determine the correct value.
22154 @item show mips mask-address
22155 @kindex show mips mask-address
22156 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22159 @item set remote-mips64-transfers-32bit-regs
22160 @kindex set remote-mips64-transfers-32bit-regs
22161 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22162 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22163 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22164 and 64 bits for other registers, set this option to @samp{on}.
22166 @item show remote-mips64-transfers-32bit-regs
22167 @kindex show remote-mips64-transfers-32bit-regs
22168 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22170 @item set debug mips
22171 @kindex set debug mips
22172 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22173 target code in @value{GDBN}.
22175 @item show debug mips
22176 @kindex show debug mips
22177 Show the current setting of @acronym{MIPS} debugging messages.
22183 @cindex HPPA support
22185 When @value{GDBN} is debugging the HP PA architecture, it provides the
22186 following special commands:
22189 @item set debug hppa
22190 @kindex set debug hppa
22191 This command determines whether HPPA architecture-specific debugging
22192 messages are to be displayed.
22194 @item show debug hppa
22195 Show whether HPPA debugging messages are displayed.
22197 @item maint print unwind @var{address}
22198 @kindex maint print unwind@r{, HPPA}
22199 This command displays the contents of the unwind table entry at the
22200 given @var{address}.
22206 @subsection Cell Broadband Engine SPU architecture
22207 @cindex Cell Broadband Engine
22210 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22211 it provides the following special commands:
22214 @item info spu event
22216 Display SPU event facility status. Shows current event mask
22217 and pending event status.
22219 @item info spu signal
22220 Display SPU signal notification facility status. Shows pending
22221 signal-control word and signal notification mode of both signal
22222 notification channels.
22224 @item info spu mailbox
22225 Display SPU mailbox facility status. Shows all pending entries,
22226 in order of processing, in each of the SPU Write Outbound,
22227 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22230 Display MFC DMA status. Shows all pending commands in the MFC
22231 DMA queue. For each entry, opcode, tag, class IDs, effective
22232 and local store addresses and transfer size are shown.
22234 @item info spu proxydma
22235 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22236 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22237 and local store addresses and transfer size are shown.
22241 When @value{GDBN} is debugging a combined PowerPC/SPU application
22242 on the Cell Broadband Engine, it provides in addition the following
22246 @item set spu stop-on-load @var{arg}
22248 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22249 will give control to the user when a new SPE thread enters its @code{main}
22250 function. The default is @code{off}.
22252 @item show spu stop-on-load
22254 Show whether to stop for new SPE threads.
22256 @item set spu auto-flush-cache @var{arg}
22257 Set whether to automatically flush the software-managed cache. When set to
22258 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22259 cache to be flushed whenever SPE execution stops. This provides a consistent
22260 view of PowerPC memory that is accessed via the cache. If an application
22261 does not use the software-managed cache, this option has no effect.
22263 @item show spu auto-flush-cache
22264 Show whether to automatically flush the software-managed cache.
22269 @subsection PowerPC
22270 @cindex PowerPC architecture
22272 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22273 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22274 numbers stored in the floating point registers. These values must be stored
22275 in two consecutive registers, always starting at an even register like
22276 @code{f0} or @code{f2}.
22278 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22279 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22280 @code{f2} and @code{f3} for @code{$dl1} and so on.
22282 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22283 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22286 @subsection Nios II
22287 @cindex Nios II architecture
22289 When @value{GDBN} is debugging the Nios II architecture,
22290 it provides the following special commands:
22294 @item set debug nios2
22295 @kindex set debug nios2
22296 This command turns on and off debugging messages for the Nios II
22297 target code in @value{GDBN}.
22299 @item show debug nios2
22300 @kindex show debug nios2
22301 Show the current setting of Nios II debugging messages.
22304 @node Controlling GDB
22305 @chapter Controlling @value{GDBN}
22307 You can alter the way @value{GDBN} interacts with you by using the
22308 @code{set} command. For commands controlling how @value{GDBN} displays
22309 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22314 * Editing:: Command editing
22315 * Command History:: Command history
22316 * Screen Size:: Screen size
22317 * Numbers:: Numbers
22318 * ABI:: Configuring the current ABI
22319 * Auto-loading:: Automatically loading associated files
22320 * Messages/Warnings:: Optional warnings and messages
22321 * Debugging Output:: Optional messages about internal happenings
22322 * Other Misc Settings:: Other Miscellaneous Settings
22330 @value{GDBN} indicates its readiness to read a command by printing a string
22331 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22332 can change the prompt string with the @code{set prompt} command. For
22333 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22334 the prompt in one of the @value{GDBN} sessions so that you can always tell
22335 which one you are talking to.
22337 @emph{Note:} @code{set prompt} does not add a space for you after the
22338 prompt you set. This allows you to set a prompt which ends in a space
22339 or a prompt that does not.
22343 @item set prompt @var{newprompt}
22344 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22346 @kindex show prompt
22348 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22351 Versions of @value{GDBN} that ship with Python scripting enabled have
22352 prompt extensions. The commands for interacting with these extensions
22356 @kindex set extended-prompt
22357 @item set extended-prompt @var{prompt}
22358 Set an extended prompt that allows for substitutions.
22359 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22360 substitution. Any escape sequences specified as part of the prompt
22361 string are replaced with the corresponding strings each time the prompt
22367 set extended-prompt Current working directory: \w (gdb)
22370 Note that when an extended-prompt is set, it takes control of the
22371 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22373 @kindex show extended-prompt
22374 @item show extended-prompt
22375 Prints the extended prompt. Any escape sequences specified as part of
22376 the prompt string with @code{set extended-prompt}, are replaced with the
22377 corresponding strings each time the prompt is displayed.
22381 @section Command Editing
22383 @cindex command line editing
22385 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22386 @sc{gnu} library provides consistent behavior for programs which provide a
22387 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22388 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22389 substitution, and a storage and recall of command history across
22390 debugging sessions.
22392 You may control the behavior of command line editing in @value{GDBN} with the
22393 command @code{set}.
22396 @kindex set editing
22399 @itemx set editing on
22400 Enable command line editing (enabled by default).
22402 @item set editing off
22403 Disable command line editing.
22405 @kindex show editing
22407 Show whether command line editing is enabled.
22410 @ifset SYSTEM_READLINE
22411 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22413 @ifclear SYSTEM_READLINE
22414 @xref{Command Line Editing},
22416 for more details about the Readline
22417 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22418 encouraged to read that chapter.
22420 @node Command History
22421 @section Command History
22422 @cindex command history
22424 @value{GDBN} can keep track of the commands you type during your
22425 debugging sessions, so that you can be certain of precisely what
22426 happened. Use these commands to manage the @value{GDBN} command
22429 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22430 package, to provide the history facility.
22431 @ifset SYSTEM_READLINE
22432 @xref{Using History Interactively, , , history, GNU History Library},
22434 @ifclear SYSTEM_READLINE
22435 @xref{Using History Interactively},
22437 for the detailed description of the History library.
22439 To issue a command to @value{GDBN} without affecting certain aspects of
22440 the state which is seen by users, prefix it with @samp{server }
22441 (@pxref{Server Prefix}). This
22442 means that this command will not affect the command history, nor will it
22443 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22444 pressed on a line by itself.
22446 @cindex @code{server}, command prefix
22447 The server prefix does not affect the recording of values into the value
22448 history; to print a value without recording it into the value history,
22449 use the @code{output} command instead of the @code{print} command.
22451 Here is the description of @value{GDBN} commands related to command
22455 @cindex history substitution
22456 @cindex history file
22457 @kindex set history filename
22458 @cindex @env{GDBHISTFILE}, environment variable
22459 @item set history filename @var{fname}
22460 Set the name of the @value{GDBN} command history file to @var{fname}.
22461 This is the file where @value{GDBN} reads an initial command history
22462 list, and where it writes the command history from this session when it
22463 exits. You can access this list through history expansion or through
22464 the history command editing characters listed below. This file defaults
22465 to the value of the environment variable @code{GDBHISTFILE}, or to
22466 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22469 @cindex save command history
22470 @kindex set history save
22471 @item set history save
22472 @itemx set history save on
22473 Record command history in a file, whose name may be specified with the
22474 @code{set history filename} command. By default, this option is disabled.
22476 @item set history save off
22477 Stop recording command history in a file.
22479 @cindex history size
22480 @kindex set history size
22481 @cindex @env{HISTSIZE}, environment variable
22482 @item set history size @var{size}
22483 @itemx set history size unlimited
22484 Set the number of commands which @value{GDBN} keeps in its history list.
22485 This defaults to the value of the environment variable
22486 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22487 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22488 history list is unlimited.
22491 History expansion assigns special meaning to the character @kbd{!}.
22492 @ifset SYSTEM_READLINE
22493 @xref{Event Designators, , , history, GNU History Library},
22495 @ifclear SYSTEM_READLINE
22496 @xref{Event Designators},
22500 @cindex history expansion, turn on/off
22501 Since @kbd{!} is also the logical not operator in C, history expansion
22502 is off by default. If you decide to enable history expansion with the
22503 @code{set history expansion on} command, you may sometimes need to
22504 follow @kbd{!} (when it is used as logical not, in an expression) with
22505 a space or a tab to prevent it from being expanded. The readline
22506 history facilities do not attempt substitution on the strings
22507 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22509 The commands to control history expansion are:
22512 @item set history expansion on
22513 @itemx set history expansion
22514 @kindex set history expansion
22515 Enable history expansion. History expansion is off by default.
22517 @item set history expansion off
22518 Disable history expansion.
22521 @kindex show history
22523 @itemx show history filename
22524 @itemx show history save
22525 @itemx show history size
22526 @itemx show history expansion
22527 These commands display the state of the @value{GDBN} history parameters.
22528 @code{show history} by itself displays all four states.
22533 @kindex show commands
22534 @cindex show last commands
22535 @cindex display command history
22536 @item show commands
22537 Display the last ten commands in the command history.
22539 @item show commands @var{n}
22540 Print ten commands centered on command number @var{n}.
22542 @item show commands +
22543 Print ten commands just after the commands last printed.
22547 @section Screen Size
22548 @cindex size of screen
22549 @cindex screen size
22552 @cindex pauses in output
22554 Certain commands to @value{GDBN} may produce large amounts of
22555 information output to the screen. To help you read all of it,
22556 @value{GDBN} pauses and asks you for input at the end of each page of
22557 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22558 to discard the remaining output. Also, the screen width setting
22559 determines when to wrap lines of output. Depending on what is being
22560 printed, @value{GDBN} tries to break the line at a readable place,
22561 rather than simply letting it overflow onto the following line.
22563 Normally @value{GDBN} knows the size of the screen from the terminal
22564 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22565 together with the value of the @code{TERM} environment variable and the
22566 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22567 you can override it with the @code{set height} and @code{set
22574 @kindex show height
22575 @item set height @var{lpp}
22576 @itemx set height unlimited
22578 @itemx set width @var{cpl}
22579 @itemx set width unlimited
22581 These @code{set} commands specify a screen height of @var{lpp} lines and
22582 a screen width of @var{cpl} characters. The associated @code{show}
22583 commands display the current settings.
22585 If you specify a height of either @code{unlimited} or zero lines,
22586 @value{GDBN} does not pause during output no matter how long the
22587 output is. This is useful if output is to a file or to an editor
22590 Likewise, you can specify @samp{set width unlimited} or @samp{set
22591 width 0} to prevent @value{GDBN} from wrapping its output.
22593 @item set pagination on
22594 @itemx set pagination off
22595 @kindex set pagination
22596 Turn the output pagination on or off; the default is on. Turning
22597 pagination off is the alternative to @code{set height unlimited}. Note that
22598 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22599 Options, -batch}) also automatically disables pagination.
22601 @item show pagination
22602 @kindex show pagination
22603 Show the current pagination mode.
22608 @cindex number representation
22609 @cindex entering numbers
22611 You can always enter numbers in octal, decimal, or hexadecimal in
22612 @value{GDBN} by the usual conventions: octal numbers begin with
22613 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22614 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22615 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22616 10; likewise, the default display for numbers---when no particular
22617 format is specified---is base 10. You can change the default base for
22618 both input and output with the commands described below.
22621 @kindex set input-radix
22622 @item set input-radix @var{base}
22623 Set the default base for numeric input. Supported choices
22624 for @var{base} are decimal 8, 10, or 16. The base must itself be
22625 specified either unambiguously or using the current input radix; for
22629 set input-radix 012
22630 set input-radix 10.
22631 set input-radix 0xa
22635 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22636 leaves the input radix unchanged, no matter what it was, since
22637 @samp{10}, being without any leading or trailing signs of its base, is
22638 interpreted in the current radix. Thus, if the current radix is 16,
22639 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22642 @kindex set output-radix
22643 @item set output-radix @var{base}
22644 Set the default base for numeric display. Supported choices
22645 for @var{base} are decimal 8, 10, or 16. The base must itself be
22646 specified either unambiguously or using the current input radix.
22648 @kindex show input-radix
22649 @item show input-radix
22650 Display the current default base for numeric input.
22652 @kindex show output-radix
22653 @item show output-radix
22654 Display the current default base for numeric display.
22656 @item set radix @r{[}@var{base}@r{]}
22660 These commands set and show the default base for both input and output
22661 of numbers. @code{set radix} sets the radix of input and output to
22662 the same base; without an argument, it resets the radix back to its
22663 default value of 10.
22668 @section Configuring the Current ABI
22670 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22671 application automatically. However, sometimes you need to override its
22672 conclusions. Use these commands to manage @value{GDBN}'s view of the
22678 @cindex Newlib OS ABI and its influence on the longjmp handling
22680 One @value{GDBN} configuration can debug binaries for multiple operating
22681 system targets, either via remote debugging or native emulation.
22682 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22683 but you can override its conclusion using the @code{set osabi} command.
22684 One example where this is useful is in debugging of binaries which use
22685 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22686 not have the same identifying marks that the standard C library for your
22689 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22690 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22691 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22692 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22696 Show the OS ABI currently in use.
22699 With no argument, show the list of registered available OS ABI's.
22701 @item set osabi @var{abi}
22702 Set the current OS ABI to @var{abi}.
22705 @cindex float promotion
22707 Generally, the way that an argument of type @code{float} is passed to a
22708 function depends on whether the function is prototyped. For a prototyped
22709 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22710 according to the architecture's convention for @code{float}. For unprototyped
22711 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22712 @code{double} and then passed.
22714 Unfortunately, some forms of debug information do not reliably indicate whether
22715 a function is prototyped. If @value{GDBN} calls a function that is not marked
22716 as prototyped, it consults @kbd{set coerce-float-to-double}.
22719 @kindex set coerce-float-to-double
22720 @item set coerce-float-to-double
22721 @itemx set coerce-float-to-double on
22722 Arguments of type @code{float} will be promoted to @code{double} when passed
22723 to an unprototyped function. This is the default setting.
22725 @item set coerce-float-to-double off
22726 Arguments of type @code{float} will be passed directly to unprototyped
22729 @kindex show coerce-float-to-double
22730 @item show coerce-float-to-double
22731 Show the current setting of promoting @code{float} to @code{double}.
22735 @kindex show cp-abi
22736 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22737 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22738 used to build your application. @value{GDBN} only fully supports
22739 programs with a single C@t{++} ABI; if your program contains code using
22740 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22741 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22742 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22743 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22744 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22745 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22750 Show the C@t{++} ABI currently in use.
22753 With no argument, show the list of supported C@t{++} ABI's.
22755 @item set cp-abi @var{abi}
22756 @itemx set cp-abi auto
22757 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22761 @section Automatically loading associated files
22762 @cindex auto-loading
22764 @value{GDBN} sometimes reads files with commands and settings automatically,
22765 without being explicitly told so by the user. We call this feature
22766 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22767 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22768 results or introduce security risks (e.g., if the file comes from untrusted
22772 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22773 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22775 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22776 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22779 There are various kinds of files @value{GDBN} can automatically load.
22780 In addition to these files, @value{GDBN} supports auto-loading code written
22781 in various extension languages. @xref{Auto-loading extensions}.
22783 Note that loading of these associated files (including the local @file{.gdbinit}
22784 file) requires accordingly configured @code{auto-load safe-path}
22785 (@pxref{Auto-loading safe path}).
22787 For these reasons, @value{GDBN} includes commands and options to let you
22788 control when to auto-load files and which files should be auto-loaded.
22791 @anchor{set auto-load off}
22792 @kindex set auto-load off
22793 @item set auto-load off
22794 Globally disable loading of all auto-loaded files.
22795 You may want to use this command with the @samp{-iex} option
22796 (@pxref{Option -init-eval-command}) such as:
22798 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22801 Be aware that system init file (@pxref{System-wide configuration})
22802 and init files from your home directory (@pxref{Home Directory Init File})
22803 still get read (as they come from generally trusted directories).
22804 To prevent @value{GDBN} from auto-loading even those init files, use the
22805 @option{-nx} option (@pxref{Mode Options}), in addition to
22806 @code{set auto-load no}.
22808 @anchor{show auto-load}
22809 @kindex show auto-load
22810 @item show auto-load
22811 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22815 (gdb) show auto-load
22816 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22817 libthread-db: Auto-loading of inferior specific libthread_db is on.
22818 local-gdbinit: Auto-loading of .gdbinit script from current directory
22820 python-scripts: Auto-loading of Python scripts is on.
22821 safe-path: List of directories from which it is safe to auto-load files
22822 is $debugdir:$datadir/auto-load.
22823 scripts-directory: List of directories from which to load auto-loaded scripts
22824 is $debugdir:$datadir/auto-load.
22827 @anchor{info auto-load}
22828 @kindex info auto-load
22829 @item info auto-load
22830 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22834 (gdb) info auto-load
22837 Yes /home/user/gdb/gdb-gdb.gdb
22838 libthread-db: No auto-loaded libthread-db.
22839 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22843 Yes /home/user/gdb/gdb-gdb.py
22847 These are @value{GDBN} control commands for the auto-loading:
22849 @multitable @columnfractions .5 .5
22850 @item @xref{set auto-load off}.
22851 @tab Disable auto-loading globally.
22852 @item @xref{show auto-load}.
22853 @tab Show setting of all kinds of files.
22854 @item @xref{info auto-load}.
22855 @tab Show state of all kinds of files.
22856 @item @xref{set auto-load gdb-scripts}.
22857 @tab Control for @value{GDBN} command scripts.
22858 @item @xref{show auto-load gdb-scripts}.
22859 @tab Show setting of @value{GDBN} command scripts.
22860 @item @xref{info auto-load gdb-scripts}.
22861 @tab Show state of @value{GDBN} command scripts.
22862 @item @xref{set auto-load python-scripts}.
22863 @tab Control for @value{GDBN} Python scripts.
22864 @item @xref{show auto-load python-scripts}.
22865 @tab Show setting of @value{GDBN} Python scripts.
22866 @item @xref{info auto-load python-scripts}.
22867 @tab Show state of @value{GDBN} Python scripts.
22868 @item @xref{set auto-load guile-scripts}.
22869 @tab Control for @value{GDBN} Guile scripts.
22870 @item @xref{show auto-load guile-scripts}.
22871 @tab Show setting of @value{GDBN} Guile scripts.
22872 @item @xref{info auto-load guile-scripts}.
22873 @tab Show state of @value{GDBN} Guile scripts.
22874 @item @xref{set auto-load scripts-directory}.
22875 @tab Control for @value{GDBN} auto-loaded scripts location.
22876 @item @xref{show auto-load scripts-directory}.
22877 @tab Show @value{GDBN} auto-loaded scripts location.
22878 @item @xref{add-auto-load-scripts-directory}.
22879 @tab Add directory for auto-loaded scripts location list.
22880 @item @xref{set auto-load local-gdbinit}.
22881 @tab Control for init file in the current directory.
22882 @item @xref{show auto-load local-gdbinit}.
22883 @tab Show setting of init file in the current directory.
22884 @item @xref{info auto-load local-gdbinit}.
22885 @tab Show state of init file in the current directory.
22886 @item @xref{set auto-load libthread-db}.
22887 @tab Control for thread debugging library.
22888 @item @xref{show auto-load libthread-db}.
22889 @tab Show setting of thread debugging library.
22890 @item @xref{info auto-load libthread-db}.
22891 @tab Show state of thread debugging library.
22892 @item @xref{set auto-load safe-path}.
22893 @tab Control directories trusted for automatic loading.
22894 @item @xref{show auto-load safe-path}.
22895 @tab Show directories trusted for automatic loading.
22896 @item @xref{add-auto-load-safe-path}.
22897 @tab Add directory trusted for automatic loading.
22900 @node Init File in the Current Directory
22901 @subsection Automatically loading init file in the current directory
22902 @cindex auto-loading init file in the current directory
22904 By default, @value{GDBN} reads and executes the canned sequences of commands
22905 from init file (if any) in the current working directory,
22906 see @ref{Init File in the Current Directory during Startup}.
22908 Note that loading of this local @file{.gdbinit} file also requires accordingly
22909 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22912 @anchor{set auto-load local-gdbinit}
22913 @kindex set auto-load local-gdbinit
22914 @item set auto-load local-gdbinit [on|off]
22915 Enable or disable the auto-loading of canned sequences of commands
22916 (@pxref{Sequences}) found in init file in the current directory.
22918 @anchor{show auto-load local-gdbinit}
22919 @kindex show auto-load local-gdbinit
22920 @item show auto-load local-gdbinit
22921 Show whether auto-loading of canned sequences of commands from init file in the
22922 current directory is enabled or disabled.
22924 @anchor{info auto-load local-gdbinit}
22925 @kindex info auto-load local-gdbinit
22926 @item info auto-load local-gdbinit
22927 Print whether canned sequences of commands from init file in the
22928 current directory have been auto-loaded.
22931 @node libthread_db.so.1 file
22932 @subsection Automatically loading thread debugging library
22933 @cindex auto-loading libthread_db.so.1
22935 This feature is currently present only on @sc{gnu}/Linux native hosts.
22937 @value{GDBN} reads in some cases thread debugging library from places specific
22938 to the inferior (@pxref{set libthread-db-search-path}).
22940 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22941 without checking this @samp{set auto-load libthread-db} switch as system
22942 libraries have to be trusted in general. In all other cases of
22943 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22944 auto-load libthread-db} is enabled before trying to open such thread debugging
22947 Note that loading of this debugging library also requires accordingly configured
22948 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22951 @anchor{set auto-load libthread-db}
22952 @kindex set auto-load libthread-db
22953 @item set auto-load libthread-db [on|off]
22954 Enable or disable the auto-loading of inferior specific thread debugging library.
22956 @anchor{show auto-load libthread-db}
22957 @kindex show auto-load libthread-db
22958 @item show auto-load libthread-db
22959 Show whether auto-loading of inferior specific thread debugging library is
22960 enabled or disabled.
22962 @anchor{info auto-load libthread-db}
22963 @kindex info auto-load libthread-db
22964 @item info auto-load libthread-db
22965 Print the list of all loaded inferior specific thread debugging libraries and
22966 for each such library print list of inferior @var{pid}s using it.
22969 @node Auto-loading safe path
22970 @subsection Security restriction for auto-loading
22971 @cindex auto-loading safe-path
22973 As the files of inferior can come from untrusted source (such as submitted by
22974 an application user) @value{GDBN} does not always load any files automatically.
22975 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22976 directories trusted for loading files not explicitly requested by user.
22977 Each directory can also be a shell wildcard pattern.
22979 If the path is not set properly you will see a warning and the file will not
22984 Reading symbols from /home/user/gdb/gdb...done.
22985 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22986 declined by your `auto-load safe-path' set
22987 to "$debugdir:$datadir/auto-load".
22988 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22989 declined by your `auto-load safe-path' set
22990 to "$debugdir:$datadir/auto-load".
22994 To instruct @value{GDBN} to go ahead and use the init files anyway,
22995 invoke @value{GDBN} like this:
22998 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23001 The list of trusted directories is controlled by the following commands:
23004 @anchor{set auto-load safe-path}
23005 @kindex set auto-load safe-path
23006 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23007 Set the list of directories (and their subdirectories) trusted for automatic
23008 loading and execution of scripts. You can also enter a specific trusted file.
23009 Each directory can also be a shell wildcard pattern; wildcards do not match
23010 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23011 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23012 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23013 its default value as specified during @value{GDBN} compilation.
23015 The list of directories uses path separator (@samp{:} on GNU and Unix
23016 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23017 to the @env{PATH} environment variable.
23019 @anchor{show auto-load safe-path}
23020 @kindex show auto-load safe-path
23021 @item show auto-load safe-path
23022 Show the list of directories trusted for automatic loading and execution of
23025 @anchor{add-auto-load-safe-path}
23026 @kindex add-auto-load-safe-path
23027 @item add-auto-load-safe-path
23028 Add an entry (or list of entries) to the list of directories trusted for
23029 automatic loading and execution of scripts. Multiple entries may be delimited
23030 by the host platform path separator in use.
23033 This variable defaults to what @code{--with-auto-load-dir} has been configured
23034 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23035 substitution applies the same as for @ref{set auto-load scripts-directory}.
23036 The default @code{set auto-load safe-path} value can be also overriden by
23037 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23039 Setting this variable to @file{/} disables this security protection,
23040 corresponding @value{GDBN} configuration option is
23041 @option{--without-auto-load-safe-path}.
23042 This variable is supposed to be set to the system directories writable by the
23043 system superuser only. Users can add their source directories in init files in
23044 their home directories (@pxref{Home Directory Init File}). See also deprecated
23045 init file in the current directory
23046 (@pxref{Init File in the Current Directory during Startup}).
23048 To force @value{GDBN} to load the files it declined to load in the previous
23049 example, you could use one of the following ways:
23052 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23053 Specify this trusted directory (or a file) as additional component of the list.
23054 You have to specify also any existing directories displayed by
23055 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23057 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23058 Specify this directory as in the previous case but just for a single
23059 @value{GDBN} session.
23061 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23062 Disable auto-loading safety for a single @value{GDBN} session.
23063 This assumes all the files you debug during this @value{GDBN} session will come
23064 from trusted sources.
23066 @item @kbd{./configure --without-auto-load-safe-path}
23067 During compilation of @value{GDBN} you may disable any auto-loading safety.
23068 This assumes all the files you will ever debug with this @value{GDBN} come from
23072 On the other hand you can also explicitly forbid automatic files loading which
23073 also suppresses any such warning messages:
23076 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23077 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23079 @item @file{~/.gdbinit}: @samp{set auto-load no}
23080 Disable auto-loading globally for the user
23081 (@pxref{Home Directory Init File}). While it is improbable, you could also
23082 use system init file instead (@pxref{System-wide configuration}).
23085 This setting applies to the file names as entered by user. If no entry matches
23086 @value{GDBN} tries as a last resort to also resolve all the file names into
23087 their canonical form (typically resolving symbolic links) and compare the
23088 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23089 own before starting the comparison so a canonical form of directories is
23090 recommended to be entered.
23092 @node Auto-loading verbose mode
23093 @subsection Displaying files tried for auto-load
23094 @cindex auto-loading verbose mode
23096 For better visibility of all the file locations where you can place scripts to
23097 be auto-loaded with inferior --- or to protect yourself against accidental
23098 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23099 all the files attempted to be loaded. Both existing and non-existing files may
23102 For example the list of directories from which it is safe to auto-load files
23103 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23104 may not be too obvious while setting it up.
23107 (gdb) set debug auto-load on
23108 (gdb) file ~/src/t/true
23109 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23110 for objfile "/tmp/true".
23111 auto-load: Updating directories of "/usr:/opt".
23112 auto-load: Using directory "/usr".
23113 auto-load: Using directory "/opt".
23114 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23115 by your `auto-load safe-path' set to "/usr:/opt".
23119 @anchor{set debug auto-load}
23120 @kindex set debug auto-load
23121 @item set debug auto-load [on|off]
23122 Set whether to print the filenames attempted to be auto-loaded.
23124 @anchor{show debug auto-load}
23125 @kindex show debug auto-load
23126 @item show debug auto-load
23127 Show whether printing of the filenames attempted to be auto-loaded is turned
23131 @node Messages/Warnings
23132 @section Optional Warnings and Messages
23134 @cindex verbose operation
23135 @cindex optional warnings
23136 By default, @value{GDBN} is silent about its inner workings. If you are
23137 running on a slow machine, you may want to use the @code{set verbose}
23138 command. This makes @value{GDBN} tell you when it does a lengthy
23139 internal operation, so you will not think it has crashed.
23141 Currently, the messages controlled by @code{set verbose} are those
23142 which announce that the symbol table for a source file is being read;
23143 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23146 @kindex set verbose
23147 @item set verbose on
23148 Enables @value{GDBN} output of certain informational messages.
23150 @item set verbose off
23151 Disables @value{GDBN} output of certain informational messages.
23153 @kindex show verbose
23155 Displays whether @code{set verbose} is on or off.
23158 By default, if @value{GDBN} encounters bugs in the symbol table of an
23159 object file, it is silent; but if you are debugging a compiler, you may
23160 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23165 @kindex set complaints
23166 @item set complaints @var{limit}
23167 Permits @value{GDBN} to output @var{limit} complaints about each type of
23168 unusual symbols before becoming silent about the problem. Set
23169 @var{limit} to zero to suppress all complaints; set it to a large number
23170 to prevent complaints from being suppressed.
23172 @kindex show complaints
23173 @item show complaints
23174 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23178 @anchor{confirmation requests}
23179 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23180 lot of stupid questions to confirm certain commands. For example, if
23181 you try to run a program which is already running:
23185 The program being debugged has been started already.
23186 Start it from the beginning? (y or n)
23189 If you are willing to unflinchingly face the consequences of your own
23190 commands, you can disable this ``feature'':
23194 @kindex set confirm
23196 @cindex confirmation
23197 @cindex stupid questions
23198 @item set confirm off
23199 Disables confirmation requests. Note that running @value{GDBN} with
23200 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23201 automatically disables confirmation requests.
23203 @item set confirm on
23204 Enables confirmation requests (the default).
23206 @kindex show confirm
23208 Displays state of confirmation requests.
23212 @cindex command tracing
23213 If you need to debug user-defined commands or sourced files you may find it
23214 useful to enable @dfn{command tracing}. In this mode each command will be
23215 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23216 quantity denoting the call depth of each command.
23219 @kindex set trace-commands
23220 @cindex command scripts, debugging
23221 @item set trace-commands on
23222 Enable command tracing.
23223 @item set trace-commands off
23224 Disable command tracing.
23225 @item show trace-commands
23226 Display the current state of command tracing.
23229 @node Debugging Output
23230 @section Optional Messages about Internal Happenings
23231 @cindex optional debugging messages
23233 @value{GDBN} has commands that enable optional debugging messages from
23234 various @value{GDBN} subsystems; normally these commands are of
23235 interest to @value{GDBN} maintainers, or when reporting a bug. This
23236 section documents those commands.
23239 @kindex set exec-done-display
23240 @item set exec-done-display
23241 Turns on or off the notification of asynchronous commands'
23242 completion. When on, @value{GDBN} will print a message when an
23243 asynchronous command finishes its execution. The default is off.
23244 @kindex show exec-done-display
23245 @item show exec-done-display
23246 Displays the current setting of asynchronous command completion
23249 @cindex ARM AArch64
23250 @item set debug aarch64
23251 Turns on or off display of debugging messages related to ARM AArch64.
23252 The default is off.
23254 @item show debug aarch64
23255 Displays the current state of displaying debugging messages related to
23257 @cindex gdbarch debugging info
23258 @cindex architecture debugging info
23259 @item set debug arch
23260 Turns on or off display of gdbarch debugging info. The default is off
23261 @item show debug arch
23262 Displays the current state of displaying gdbarch debugging info.
23263 @item set debug aix-solib
23264 @cindex AIX shared library debugging
23265 Control display of debugging messages from the AIX shared library
23266 support module. The default is off.
23267 @item show debug aix-thread
23268 Show the current state of displaying AIX shared library debugging messages.
23269 @item set debug aix-thread
23270 @cindex AIX threads
23271 Display debugging messages about inner workings of the AIX thread
23273 @item show debug aix-thread
23274 Show the current state of AIX thread debugging info display.
23275 @item set debug check-physname
23277 Check the results of the ``physname'' computation. When reading DWARF
23278 debugging information for C@t{++}, @value{GDBN} attempts to compute
23279 each entity's name. @value{GDBN} can do this computation in two
23280 different ways, depending on exactly what information is present.
23281 When enabled, this setting causes @value{GDBN} to compute the names
23282 both ways and display any discrepancies.
23283 @item show debug check-physname
23284 Show the current state of ``physname'' checking.
23285 @item set debug coff-pe-read
23286 @cindex COFF/PE exported symbols
23287 Control display of debugging messages related to reading of COFF/PE
23288 exported symbols. The default is off.
23289 @item show debug coff-pe-read
23290 Displays the current state of displaying debugging messages related to
23291 reading of COFF/PE exported symbols.
23292 @item set debug dwarf2-die
23293 @cindex DWARF2 DIEs
23294 Dump DWARF2 DIEs after they are read in.
23295 The value is the number of nesting levels to print.
23296 A value of zero turns off the display.
23297 @item show debug dwarf2-die
23298 Show the current state of DWARF2 DIE debugging.
23299 @item set debug dwarf2-read
23300 @cindex DWARF2 Reading
23301 Turns on or off display of debugging messages related to reading
23302 DWARF debug info. The default is 0 (off).
23303 A value of 1 provides basic information.
23304 A value greater than 1 provides more verbose information.
23305 @item show debug dwarf2-read
23306 Show the current state of DWARF2 reader debugging.
23307 @item set debug displaced
23308 @cindex displaced stepping debugging info
23309 Turns on or off display of @value{GDBN} debugging info for the
23310 displaced stepping support. The default is off.
23311 @item show debug displaced
23312 Displays the current state of displaying @value{GDBN} debugging info
23313 related to displaced stepping.
23314 @item set debug event
23315 @cindex event debugging info
23316 Turns on or off display of @value{GDBN} event debugging info. The
23318 @item show debug event
23319 Displays the current state of displaying @value{GDBN} event debugging
23321 @item set debug expression
23322 @cindex expression debugging info
23323 Turns on or off display of debugging info about @value{GDBN}
23324 expression parsing. The default is off.
23325 @item show debug expression
23326 Displays the current state of displaying debugging info about
23327 @value{GDBN} expression parsing.
23328 @item set debug frame
23329 @cindex frame debugging info
23330 Turns on or off display of @value{GDBN} frame debugging info. The
23332 @item show debug frame
23333 Displays the current state of displaying @value{GDBN} frame debugging
23335 @item set debug gnu-nat
23336 @cindex @sc{gnu}/Hurd debug messages
23337 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23338 @item show debug gnu-nat
23339 Show the current state of @sc{gnu}/Hurd debugging messages.
23340 @item set debug infrun
23341 @cindex inferior debugging info
23342 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23343 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23344 for implementing operations such as single-stepping the inferior.
23345 @item show debug infrun
23346 Displays the current state of @value{GDBN} inferior debugging.
23347 @item set debug jit
23348 @cindex just-in-time compilation, debugging messages
23349 Turns on or off debugging messages from JIT debug support.
23350 @item show debug jit
23351 Displays the current state of @value{GDBN} JIT debugging.
23352 @item set debug lin-lwp
23353 @cindex @sc{gnu}/Linux LWP debug messages
23354 @cindex Linux lightweight processes
23355 Turns on or off debugging messages from the Linux LWP debug support.
23356 @item show debug lin-lwp
23357 Show the current state of Linux LWP debugging messages.
23358 @item set debug mach-o
23359 @cindex Mach-O symbols processing
23360 Control display of debugging messages related to Mach-O symbols
23361 processing. The default is off.
23362 @item show debug mach-o
23363 Displays the current state of displaying debugging messages related to
23364 reading of COFF/PE exported symbols.
23365 @item set debug notification
23366 @cindex remote async notification debugging info
23367 Turns on or off debugging messages about remote async notification.
23368 The default is off.
23369 @item show debug notification
23370 Displays the current state of remote async notification debugging messages.
23371 @item set debug observer
23372 @cindex observer debugging info
23373 Turns on or off display of @value{GDBN} observer debugging. This
23374 includes info such as the notification of observable events.
23375 @item show debug observer
23376 Displays the current state of observer debugging.
23377 @item set debug overload
23378 @cindex C@t{++} overload debugging info
23379 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23380 info. This includes info such as ranking of functions, etc. The default
23382 @item show debug overload
23383 Displays the current state of displaying @value{GDBN} C@t{++} overload
23385 @cindex expression parser, debugging info
23386 @cindex debug expression parser
23387 @item set debug parser
23388 Turns on or off the display of expression parser debugging output.
23389 Internally, this sets the @code{yydebug} variable in the expression
23390 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23391 details. The default is off.
23392 @item show debug parser
23393 Show the current state of expression parser debugging.
23394 @cindex packets, reporting on stdout
23395 @cindex serial connections, debugging
23396 @cindex debug remote protocol
23397 @cindex remote protocol debugging
23398 @cindex display remote packets
23399 @item set debug remote
23400 Turns on or off display of reports on all packets sent back and forth across
23401 the serial line to the remote machine. The info is printed on the
23402 @value{GDBN} standard output stream. The default is off.
23403 @item show debug remote
23404 Displays the state of display of remote packets.
23405 @item set debug serial
23406 Turns on or off display of @value{GDBN} serial debugging info. The
23408 @item show debug serial
23409 Displays the current state of displaying @value{GDBN} serial debugging
23411 @item set debug solib-frv
23412 @cindex FR-V shared-library debugging
23413 Turns on or off debugging messages for FR-V shared-library code.
23414 @item show debug solib-frv
23415 Display the current state of FR-V shared-library code debugging
23417 @item set debug symbol-lookup
23418 @cindex symbol lookup
23419 Turns on or off display of debugging messages related to symbol lookup.
23420 The default is 0 (off).
23421 A value of 1 provides basic information.
23422 A value greater than 1 provides more verbose information.
23423 @item show debug symbol-lookup
23424 Show the current state of symbol lookup debugging messages.
23425 @item set debug symfile
23426 @cindex symbol file functions
23427 Turns on or off display of debugging messages related to symbol file functions.
23428 The default is off. @xref{Files}.
23429 @item show debug symfile
23430 Show the current state of symbol file debugging messages.
23431 @item set debug symtab-create
23432 @cindex symbol table creation
23433 Turns on or off display of debugging messages related to symbol table creation.
23434 The default is 0 (off).
23435 A value of 1 provides basic information.
23436 A value greater than 1 provides more verbose information.
23437 @item show debug symtab-create
23438 Show the current state of symbol table creation debugging.
23439 @item set debug target
23440 @cindex target debugging info
23441 Turns on or off display of @value{GDBN} target debugging info. This info
23442 includes what is going on at the target level of GDB, as it happens. The
23443 default is 0. Set it to 1 to track events, and to 2 to also track the
23444 value of large memory transfers.
23445 @item show debug target
23446 Displays the current state of displaying @value{GDBN} target debugging
23448 @item set debug timestamp
23449 @cindex timestampping debugging info
23450 Turns on or off display of timestamps with @value{GDBN} debugging info.
23451 When enabled, seconds and microseconds are displayed before each debugging
23453 @item show debug timestamp
23454 Displays the current state of displaying timestamps with @value{GDBN}
23456 @item set debug varobj
23457 @cindex variable object debugging info
23458 Turns on or off display of @value{GDBN} variable object debugging
23459 info. The default is off.
23460 @item show debug varobj
23461 Displays the current state of displaying @value{GDBN} variable object
23463 @item set debug xml
23464 @cindex XML parser debugging
23465 Turns on or off debugging messages for built-in XML parsers.
23466 @item show debug xml
23467 Displays the current state of XML debugging messages.
23470 @node Other Misc Settings
23471 @section Other Miscellaneous Settings
23472 @cindex miscellaneous settings
23475 @kindex set interactive-mode
23476 @item set interactive-mode
23477 If @code{on}, forces @value{GDBN} to assume that GDB was started
23478 in a terminal. In practice, this means that @value{GDBN} should wait
23479 for the user to answer queries generated by commands entered at
23480 the command prompt. If @code{off}, forces @value{GDBN} to operate
23481 in the opposite mode, and it uses the default answers to all queries.
23482 If @code{auto} (the default), @value{GDBN} tries to determine whether
23483 its standard input is a terminal, and works in interactive-mode if it
23484 is, non-interactively otherwise.
23486 In the vast majority of cases, the debugger should be able to guess
23487 correctly which mode should be used. But this setting can be useful
23488 in certain specific cases, such as running a MinGW @value{GDBN}
23489 inside a cygwin window.
23491 @kindex show interactive-mode
23492 @item show interactive-mode
23493 Displays whether the debugger is operating in interactive mode or not.
23496 @node Extending GDB
23497 @chapter Extending @value{GDBN}
23498 @cindex extending GDB
23500 @value{GDBN} provides several mechanisms for extension.
23501 @value{GDBN} also provides the ability to automatically load
23502 extensions when it reads a file for debugging. This allows the
23503 user to automatically customize @value{GDBN} for the program
23507 * Sequences:: Canned Sequences of @value{GDBN} Commands
23508 * Python:: Extending @value{GDBN} using Python
23509 * Guile:: Extending @value{GDBN} using Guile
23510 * Auto-loading extensions:: Automatically loading extensions
23511 * Multiple Extension Languages:: Working with multiple extension languages
23512 * Aliases:: Creating new spellings of existing commands
23515 To facilitate the use of extension languages, @value{GDBN} is capable
23516 of evaluating the contents of a file. When doing so, @value{GDBN}
23517 can recognize which extension language is being used by looking at
23518 the filename extension. Files with an unrecognized filename extension
23519 are always treated as a @value{GDBN} Command Files.
23520 @xref{Command Files,, Command files}.
23522 You can control how @value{GDBN} evaluates these files with the following
23526 @kindex set script-extension
23527 @kindex show script-extension
23528 @item set script-extension off
23529 All scripts are always evaluated as @value{GDBN} Command Files.
23531 @item set script-extension soft
23532 The debugger determines the scripting language based on filename
23533 extension. If this scripting language is supported, @value{GDBN}
23534 evaluates the script using that language. Otherwise, it evaluates
23535 the file as a @value{GDBN} Command File.
23537 @item set script-extension strict
23538 The debugger determines the scripting language based on filename
23539 extension, and evaluates the script using that language. If the
23540 language is not supported, then the evaluation fails.
23542 @item show script-extension
23543 Display the current value of the @code{script-extension} option.
23548 @section Canned Sequences of Commands
23550 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23551 Command Lists}), @value{GDBN} provides two ways to store sequences of
23552 commands for execution as a unit: user-defined commands and command
23556 * Define:: How to define your own commands
23557 * Hooks:: Hooks for user-defined commands
23558 * Command Files:: How to write scripts of commands to be stored in a file
23559 * Output:: Commands for controlled output
23560 * Auto-loading sequences:: Controlling auto-loaded command files
23564 @subsection User-defined Commands
23566 @cindex user-defined command
23567 @cindex arguments, to user-defined commands
23568 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23569 which you assign a new name as a command. This is done with the
23570 @code{define} command. User commands may accept up to 10 arguments
23571 separated by whitespace. Arguments are accessed within the user command
23572 via @code{$arg0@dots{}$arg9}. A trivial example:
23576 print $arg0 + $arg1 + $arg2
23581 To execute the command use:
23588 This defines the command @code{adder}, which prints the sum of
23589 its three arguments. Note the arguments are text substitutions, so they may
23590 reference variables, use complex expressions, or even perform inferior
23593 @cindex argument count in user-defined commands
23594 @cindex how many arguments (user-defined commands)
23595 In addition, @code{$argc} may be used to find out how many arguments have
23596 been passed. This expands to a number in the range 0@dots{}10.
23601 print $arg0 + $arg1
23604 print $arg0 + $arg1 + $arg2
23612 @item define @var{commandname}
23613 Define a command named @var{commandname}. If there is already a command
23614 by that name, you are asked to confirm that you want to redefine it.
23615 The argument @var{commandname} may be a bare command name consisting of letters,
23616 numbers, dashes, and underscores. It may also start with any predefined
23617 prefix command. For example, @samp{define target my-target} creates
23618 a user-defined @samp{target my-target} command.
23620 The definition of the command is made up of other @value{GDBN} command lines,
23621 which are given following the @code{define} command. The end of these
23622 commands is marked by a line containing @code{end}.
23625 @kindex end@r{ (user-defined commands)}
23626 @item document @var{commandname}
23627 Document the user-defined command @var{commandname}, so that it can be
23628 accessed by @code{help}. The command @var{commandname} must already be
23629 defined. This command reads lines of documentation just as @code{define}
23630 reads the lines of the command definition, ending with @code{end}.
23631 After the @code{document} command is finished, @code{help} on command
23632 @var{commandname} displays the documentation you have written.
23634 You may use the @code{document} command again to change the
23635 documentation of a command. Redefining the command with @code{define}
23636 does not change the documentation.
23638 @kindex dont-repeat
23639 @cindex don't repeat command
23641 Used inside a user-defined command, this tells @value{GDBN} that this
23642 command should not be repeated when the user hits @key{RET}
23643 (@pxref{Command Syntax, repeat last command}).
23645 @kindex help user-defined
23646 @item help user-defined
23647 List all user-defined commands and all python commands defined in class
23648 COMAND_USER. The first line of the documentation or docstring is
23653 @itemx show user @var{commandname}
23654 Display the @value{GDBN} commands used to define @var{commandname} (but
23655 not its documentation). If no @var{commandname} is given, display the
23656 definitions for all user-defined commands.
23657 This does not work for user-defined python commands.
23659 @cindex infinite recursion in user-defined commands
23660 @kindex show max-user-call-depth
23661 @kindex set max-user-call-depth
23662 @item show max-user-call-depth
23663 @itemx set max-user-call-depth
23664 The value of @code{max-user-call-depth} controls how many recursion
23665 levels are allowed in user-defined commands before @value{GDBN} suspects an
23666 infinite recursion and aborts the command.
23667 This does not apply to user-defined python commands.
23670 In addition to the above commands, user-defined commands frequently
23671 use control flow commands, described in @ref{Command Files}.
23673 When user-defined commands are executed, the
23674 commands of the definition are not printed. An error in any command
23675 stops execution of the user-defined command.
23677 If used interactively, commands that would ask for confirmation proceed
23678 without asking when used inside a user-defined command. Many @value{GDBN}
23679 commands that normally print messages to say what they are doing omit the
23680 messages when used in a user-defined command.
23683 @subsection User-defined Command Hooks
23684 @cindex command hooks
23685 @cindex hooks, for commands
23686 @cindex hooks, pre-command
23689 You may define @dfn{hooks}, which are a special kind of user-defined
23690 command. Whenever you run the command @samp{foo}, if the user-defined
23691 command @samp{hook-foo} exists, it is executed (with no arguments)
23692 before that command.
23694 @cindex hooks, post-command
23696 A hook may also be defined which is run after the command you executed.
23697 Whenever you run the command @samp{foo}, if the user-defined command
23698 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23699 that command. Post-execution hooks may exist simultaneously with
23700 pre-execution hooks, for the same command.
23702 It is valid for a hook to call the command which it hooks. If this
23703 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23705 @c It would be nice if hookpost could be passed a parameter indicating
23706 @c if the command it hooks executed properly or not. FIXME!
23708 @kindex stop@r{, a pseudo-command}
23709 In addition, a pseudo-command, @samp{stop} exists. Defining
23710 (@samp{hook-stop}) makes the associated commands execute every time
23711 execution stops in your program: before breakpoint commands are run,
23712 displays are printed, or the stack frame is printed.
23714 For example, to ignore @code{SIGALRM} signals while
23715 single-stepping, but treat them normally during normal execution,
23720 handle SIGALRM nopass
23724 handle SIGALRM pass
23727 define hook-continue
23728 handle SIGALRM pass
23732 As a further example, to hook at the beginning and end of the @code{echo}
23733 command, and to add extra text to the beginning and end of the message,
23741 define hookpost-echo
23745 (@value{GDBP}) echo Hello World
23746 <<<---Hello World--->>>
23751 You can define a hook for any single-word command in @value{GDBN}, but
23752 not for command aliases; you should define a hook for the basic command
23753 name, e.g.@: @code{backtrace} rather than @code{bt}.
23754 @c FIXME! So how does Joe User discover whether a command is an alias
23756 You can hook a multi-word command by adding @code{hook-} or
23757 @code{hookpost-} to the last word of the command, e.g.@:
23758 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23760 If an error occurs during the execution of your hook, execution of
23761 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23762 (before the command that you actually typed had a chance to run).
23764 If you try to define a hook which does not match any known command, you
23765 get a warning from the @code{define} command.
23767 @node Command Files
23768 @subsection Command Files
23770 @cindex command files
23771 @cindex scripting commands
23772 A command file for @value{GDBN} is a text file made of lines that are
23773 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23774 also be included. An empty line in a command file does nothing; it
23775 does not mean to repeat the last command, as it would from the
23778 You can request the execution of a command file with the @code{source}
23779 command. Note that the @code{source} command is also used to evaluate
23780 scripts that are not Command Files. The exact behavior can be configured
23781 using the @code{script-extension} setting.
23782 @xref{Extending GDB,, Extending GDB}.
23786 @cindex execute commands from a file
23787 @item source [-s] [-v] @var{filename}
23788 Execute the command file @var{filename}.
23791 The lines in a command file are generally executed sequentially,
23792 unless the order of execution is changed by one of the
23793 @emph{flow-control commands} described below. The commands are not
23794 printed as they are executed. An error in any command terminates
23795 execution of the command file and control is returned to the console.
23797 @value{GDBN} first searches for @var{filename} in the current directory.
23798 If the file is not found there, and @var{filename} does not specify a
23799 directory, then @value{GDBN} also looks for the file on the source search path
23800 (specified with the @samp{directory} command);
23801 except that @file{$cdir} is not searched because the compilation directory
23802 is not relevant to scripts.
23804 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23805 on the search path even if @var{filename} specifies a directory.
23806 The search is done by appending @var{filename} to each element of the
23807 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23808 and the search path contains @file{/home/user} then @value{GDBN} will
23809 look for the script @file{/home/user/mylib/myscript}.
23810 The search is also done if @var{filename} is an absolute path.
23811 For example, if @var{filename} is @file{/tmp/myscript} and
23812 the search path contains @file{/home/user} then @value{GDBN} will
23813 look for the script @file{/home/user/tmp/myscript}.
23814 For DOS-like systems, if @var{filename} contains a drive specification,
23815 it is stripped before concatenation. For example, if @var{filename} is
23816 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23817 will look for the script @file{c:/tmp/myscript}.
23819 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23820 each command as it is executed. The option must be given before
23821 @var{filename}, and is interpreted as part of the filename anywhere else.
23823 Commands that would ask for confirmation if used interactively proceed
23824 without asking when used in a command file. Many @value{GDBN} commands that
23825 normally print messages to say what they are doing omit the messages
23826 when called from command files.
23828 @value{GDBN} also accepts command input from standard input. In this
23829 mode, normal output goes to standard output and error output goes to
23830 standard error. Errors in a command file supplied on standard input do
23831 not terminate execution of the command file---execution continues with
23835 gdb < cmds > log 2>&1
23838 (The syntax above will vary depending on the shell used.) This example
23839 will execute commands from the file @file{cmds}. All output and errors
23840 would be directed to @file{log}.
23842 Since commands stored on command files tend to be more general than
23843 commands typed interactively, they frequently need to deal with
23844 complicated situations, such as different or unexpected values of
23845 variables and symbols, changes in how the program being debugged is
23846 built, etc. @value{GDBN} provides a set of flow-control commands to
23847 deal with these complexities. Using these commands, you can write
23848 complex scripts that loop over data structures, execute commands
23849 conditionally, etc.
23856 This command allows to include in your script conditionally executed
23857 commands. The @code{if} command takes a single argument, which is an
23858 expression to evaluate. It is followed by a series of commands that
23859 are executed only if the expression is true (its value is nonzero).
23860 There can then optionally be an @code{else} line, followed by a series
23861 of commands that are only executed if the expression was false. The
23862 end of the list is marked by a line containing @code{end}.
23866 This command allows to write loops. Its syntax is similar to
23867 @code{if}: the command takes a single argument, which is an expression
23868 to evaluate, and must be followed by the commands to execute, one per
23869 line, terminated by an @code{end}. These commands are called the
23870 @dfn{body} of the loop. The commands in the body of @code{while} are
23871 executed repeatedly as long as the expression evaluates to true.
23875 This command exits the @code{while} loop in whose body it is included.
23876 Execution of the script continues after that @code{while}s @code{end}
23879 @kindex loop_continue
23880 @item loop_continue
23881 This command skips the execution of the rest of the body of commands
23882 in the @code{while} loop in whose body it is included. Execution
23883 branches to the beginning of the @code{while} loop, where it evaluates
23884 the controlling expression.
23886 @kindex end@r{ (if/else/while commands)}
23888 Terminate the block of commands that are the body of @code{if},
23889 @code{else}, or @code{while} flow-control commands.
23894 @subsection Commands for Controlled Output
23896 During the execution of a command file or a user-defined command, normal
23897 @value{GDBN} output is suppressed; the only output that appears is what is
23898 explicitly printed by the commands in the definition. This section
23899 describes three commands useful for generating exactly the output you
23904 @item echo @var{text}
23905 @c I do not consider backslash-space a standard C escape sequence
23906 @c because it is not in ANSI.
23907 Print @var{text}. Nonprinting characters can be included in
23908 @var{text} using C escape sequences, such as @samp{\n} to print a
23909 newline. @strong{No newline is printed unless you specify one.}
23910 In addition to the standard C escape sequences, a backslash followed
23911 by a space stands for a space. This is useful for displaying a
23912 string with spaces at the beginning or the end, since leading and
23913 trailing spaces are otherwise trimmed from all arguments.
23914 To print @samp{@w{ }and foo =@w{ }}, use the command
23915 @samp{echo \@w{ }and foo = \@w{ }}.
23917 A backslash at the end of @var{text} can be used, as in C, to continue
23918 the command onto subsequent lines. For example,
23921 echo This is some text\n\
23922 which is continued\n\
23923 onto several lines.\n
23926 produces the same output as
23929 echo This is some text\n
23930 echo which is continued\n
23931 echo onto several lines.\n
23935 @item output @var{expression}
23936 Print the value of @var{expression} and nothing but that value: no
23937 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23938 value history either. @xref{Expressions, ,Expressions}, for more information
23941 @item output/@var{fmt} @var{expression}
23942 Print the value of @var{expression} in format @var{fmt}. You can use
23943 the same formats as for @code{print}. @xref{Output Formats,,Output
23944 Formats}, for more information.
23947 @item printf @var{template}, @var{expressions}@dots{}
23948 Print the values of one or more @var{expressions} under the control of
23949 the string @var{template}. To print several values, make
23950 @var{expressions} be a comma-separated list of individual expressions,
23951 which may be either numbers or pointers. Their values are printed as
23952 specified by @var{template}, exactly as a C program would do by
23953 executing the code below:
23956 printf (@var{template}, @var{expressions}@dots{});
23959 As in @code{C} @code{printf}, ordinary characters in @var{template}
23960 are printed verbatim, while @dfn{conversion specification} introduced
23961 by the @samp{%} character cause subsequent @var{expressions} to be
23962 evaluated, their values converted and formatted according to type and
23963 style information encoded in the conversion specifications, and then
23966 For example, you can print two values in hex like this:
23969 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23972 @code{printf} supports all the standard @code{C} conversion
23973 specifications, including the flags and modifiers between the @samp{%}
23974 character and the conversion letter, with the following exceptions:
23978 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23981 The modifier @samp{*} is not supported for specifying precision or
23985 The @samp{'} flag (for separation of digits into groups according to
23986 @code{LC_NUMERIC'}) is not supported.
23989 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23993 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23996 The conversion letters @samp{a} and @samp{A} are not supported.
24000 Note that the @samp{ll} type modifier is supported only if the
24001 underlying @code{C} implementation used to build @value{GDBN} supports
24002 the @code{long long int} type, and the @samp{L} type modifier is
24003 supported only if @code{long double} type is available.
24005 As in @code{C}, @code{printf} supports simple backslash-escape
24006 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24007 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24008 single character. Octal and hexadecimal escape sequences are not
24011 Additionally, @code{printf} supports conversion specifications for DFP
24012 (@dfn{Decimal Floating Point}) types using the following length modifiers
24013 together with a floating point specifier.
24018 @samp{H} for printing @code{Decimal32} types.
24021 @samp{D} for printing @code{Decimal64} types.
24024 @samp{DD} for printing @code{Decimal128} types.
24027 If the underlying @code{C} implementation used to build @value{GDBN} has
24028 support for the three length modifiers for DFP types, other modifiers
24029 such as width and precision will also be available for @value{GDBN} to use.
24031 In case there is no such @code{C} support, no additional modifiers will be
24032 available and the value will be printed in the standard way.
24034 Here's an example of printing DFP types using the above conversion letters:
24036 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24040 @item eval @var{template}, @var{expressions}@dots{}
24041 Convert the values of one or more @var{expressions} under the control of
24042 the string @var{template} to a command line, and call it.
24046 @node Auto-loading sequences
24047 @subsection Controlling auto-loading native @value{GDBN} scripts
24048 @cindex native script auto-loading
24050 When a new object file is read (for example, due to the @code{file}
24051 command, or because the inferior has loaded a shared library),
24052 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24053 @xref{Auto-loading extensions}.
24055 Auto-loading can be enabled or disabled,
24056 and the list of auto-loaded scripts can be printed.
24059 @anchor{set auto-load gdb-scripts}
24060 @kindex set auto-load gdb-scripts
24061 @item set auto-load gdb-scripts [on|off]
24062 Enable or disable the auto-loading of canned sequences of commands scripts.
24064 @anchor{show auto-load gdb-scripts}
24065 @kindex show auto-load gdb-scripts
24066 @item show auto-load gdb-scripts
24067 Show whether auto-loading of canned sequences of commands scripts is enabled or
24070 @anchor{info auto-load gdb-scripts}
24071 @kindex info auto-load gdb-scripts
24072 @cindex print list of auto-loaded canned sequences of commands scripts
24073 @item info auto-load gdb-scripts [@var{regexp}]
24074 Print the list of all canned sequences of commands scripts that @value{GDBN}
24078 If @var{regexp} is supplied only canned sequences of commands scripts with
24079 matching names are printed.
24081 @c Python docs live in a separate file.
24082 @include python.texi
24084 @c Guile docs live in a separate file.
24085 @include guile.texi
24087 @node Auto-loading extensions
24088 @section Auto-loading extensions
24089 @cindex auto-loading extensions
24091 @value{GDBN} provides two mechanisms for automatically loading extensions
24092 when a new object file is read (for example, due to the @code{file}
24093 command, or because the inferior has loaded a shared library):
24094 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24095 section of modern file formats like ELF.
24098 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24099 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24100 * Which flavor to choose?::
24103 The auto-loading feature is useful for supplying application-specific
24104 debugging commands and features.
24106 Auto-loading can be enabled or disabled,
24107 and the list of auto-loaded scripts can be printed.
24108 See the @samp{auto-loading} section of each extension language
24109 for more information.
24110 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24111 For Python files see @ref{Python Auto-loading}.
24113 Note that loading of this script file also requires accordingly configured
24114 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24116 @node objfile-gdbdotext file
24117 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24118 @cindex @file{@var{objfile}-gdb.gdb}
24119 @cindex @file{@var{objfile}-gdb.py}
24120 @cindex @file{@var{objfile}-gdb.scm}
24122 When a new object file is read, @value{GDBN} looks for a file named
24123 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24124 where @var{objfile} is the object file's name and
24125 where @var{ext} is the file extension for the extension language:
24128 @item @file{@var{objfile}-gdb.gdb}
24129 GDB's own command language
24130 @item @file{@var{objfile}-gdb.py}
24132 @item @file{@var{objfile}-gdb.scm}
24136 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24137 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24138 components, and appending the @file{-gdb.@var{ext}} suffix.
24139 If this file exists and is readable, @value{GDBN} will evaluate it as a
24140 script in the specified extension language.
24142 If this file does not exist, then @value{GDBN} will look for
24143 @var{script-name} file in all of the directories as specified below.
24145 Note that loading of these files requires an accordingly configured
24146 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24148 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24149 scripts normally according to its @file{.exe} filename. But if no scripts are
24150 found @value{GDBN} also tries script filenames matching the object file without
24151 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24152 is attempted on any platform. This makes the script filenames compatible
24153 between Unix and MS-Windows hosts.
24156 @anchor{set auto-load scripts-directory}
24157 @kindex set auto-load scripts-directory
24158 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24159 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24160 may be delimited by the host platform path separator in use
24161 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24163 Each entry here needs to be covered also by the security setting
24164 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24166 @anchor{with-auto-load-dir}
24167 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24168 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24169 configuration option @option{--with-auto-load-dir}.
24171 Any reference to @file{$debugdir} will get replaced by
24172 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24173 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24174 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24175 @file{$datadir} must be placed as a directory component --- either alone or
24176 delimited by @file{/} or @file{\} directory separators, depending on the host
24179 The list of directories uses path separator (@samp{:} on GNU and Unix
24180 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24181 to the @env{PATH} environment variable.
24183 @anchor{show auto-load scripts-directory}
24184 @kindex show auto-load scripts-directory
24185 @item show auto-load scripts-directory
24186 Show @value{GDBN} auto-loaded scripts location.
24188 @anchor{add-auto-load-scripts-directory}
24189 @kindex add-auto-load-scripts-directory
24190 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24191 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24192 Multiple entries may be delimited by the host platform path separator in use.
24195 @value{GDBN} does not track which files it has already auto-loaded this way.
24196 @value{GDBN} will load the associated script every time the corresponding
24197 @var{objfile} is opened.
24198 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24199 is evaluated more than once.
24201 @node dotdebug_gdb_scripts section
24202 @subsection The @code{.debug_gdb_scripts} section
24203 @cindex @code{.debug_gdb_scripts} section
24205 For systems using file formats like ELF and COFF,
24206 when @value{GDBN} loads a new object file
24207 it will look for a special section named @code{.debug_gdb_scripts}.
24208 If this section exists, its contents is a list of null-terminated entries
24209 specifying scripts to load. Each entry begins with a non-null prefix byte that
24210 specifies the kind of entry, typically the extension language and whether the
24211 script is in a file or inlined in @code{.debug_gdb_scripts}.
24213 The following entries are supported:
24216 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24217 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24218 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24219 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24222 @subsubsection Script File Entries
24224 If the entry specifies a file, @value{GDBN} will look for the file first
24225 in the current directory and then along the source search path
24226 (@pxref{Source Path, ,Specifying Source Directories}),
24227 except that @file{$cdir} is not searched, since the compilation
24228 directory is not relevant to scripts.
24230 File entries can be placed in section @code{.debug_gdb_scripts} with,
24231 for example, this GCC macro for Python scripts.
24234 /* Note: The "MS" section flags are to remove duplicates. */
24235 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24237 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24238 .byte 1 /* Python */\n\
24239 .asciz \"" script_name "\"\n\
24245 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24246 Then one can reference the macro in a header or source file like this:
24249 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24252 The script name may include directories if desired.
24254 Note that loading of this script file also requires accordingly configured
24255 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24257 If the macro invocation is put in a header, any application or library
24258 using this header will get a reference to the specified script,
24259 and with the use of @code{"MS"} attributes on the section, the linker
24260 will remove duplicates.
24262 @subsubsection Script Text Entries
24264 Script text entries allow to put the executable script in the entry
24265 itself instead of loading it from a file.
24266 The first line of the entry, everything after the prefix byte and up to
24267 the first newline (@code{0xa}) character, is the script name, and must not
24268 contain any kind of space character, e.g., spaces or tabs.
24269 The rest of the entry, up to the trailing null byte, is the script to
24270 execute in the specified language. The name needs to be unique among
24271 all script names, as @value{GDBN} executes each script only once based
24274 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24278 #include "symcat.h"
24279 #include "gdb/section-scripts.h"
24281 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24282 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24283 ".ascii \"gdb.inlined-script\\n\"\n"
24284 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24285 ".ascii \" def __init__ (self):\\n\"\n"
24286 ".ascii \" super (test_cmd, self).__init__ ("
24287 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24288 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24289 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24290 ".ascii \"test_cmd ()\\n\"\n"
24296 Loading of inlined scripts requires a properly configured
24297 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24298 The path to specify in @code{auto-load safe-path} is the path of the file
24299 containing the @code{.debug_gdb_scripts} section.
24301 @node Which flavor to choose?
24302 @subsection Which flavor to choose?
24304 Given the multiple ways of auto-loading extensions, it might not always
24305 be clear which one to choose. This section provides some guidance.
24308 Benefits of the @file{-gdb.@var{ext}} way:
24312 Can be used with file formats that don't support multiple sections.
24315 Ease of finding scripts for public libraries.
24317 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24318 in the source search path.
24319 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24320 isn't a source directory in which to find the script.
24323 Doesn't require source code additions.
24327 Benefits of the @code{.debug_gdb_scripts} way:
24331 Works with static linking.
24333 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24334 trigger their loading. When an application is statically linked the only
24335 objfile available is the executable, and it is cumbersome to attach all the
24336 scripts from all the input libraries to the executable's
24337 @file{-gdb.@var{ext}} script.
24340 Works with classes that are entirely inlined.
24342 Some classes can be entirely inlined, and thus there may not be an associated
24343 shared library to attach a @file{-gdb.@var{ext}} script to.
24346 Scripts needn't be copied out of the source tree.
24348 In some circumstances, apps can be built out of large collections of internal
24349 libraries, and the build infrastructure necessary to install the
24350 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24351 cumbersome. It may be easier to specify the scripts in the
24352 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24353 top of the source tree to the source search path.
24356 @node Multiple Extension Languages
24357 @section Multiple Extension Languages
24359 The Guile and Python extension languages do not share any state,
24360 and generally do not interfere with each other.
24361 There are some things to be aware of, however.
24363 @subsection Python comes first
24365 Python was @value{GDBN}'s first extension language, and to avoid breaking
24366 existing behaviour Python comes first. This is generally solved by the
24367 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24368 extension languages, and when it makes a call to an extension language,
24369 (say to pretty-print a value), it tries each in turn until an extension
24370 language indicates it has performed the request (e.g., has returned the
24371 pretty-printed form of a value).
24372 This extends to errors while performing such requests: If an error happens
24373 while, for example, trying to pretty-print an object then the error is
24374 reported and any following extension languages are not tried.
24377 @section Creating new spellings of existing commands
24378 @cindex aliases for commands
24380 It is often useful to define alternate spellings of existing commands.
24381 For example, if a new @value{GDBN} command defined in Python has
24382 a long name to type, it is handy to have an abbreviated version of it
24383 that involves less typing.
24385 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24386 of the @samp{step} command even though it is otherwise an ambiguous
24387 abbreviation of other commands like @samp{set} and @samp{show}.
24389 Aliases are also used to provide shortened or more common versions
24390 of multi-word commands. For example, @value{GDBN} provides the
24391 @samp{tty} alias of the @samp{set inferior-tty} command.
24393 You can define a new alias with the @samp{alias} command.
24398 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24402 @var{ALIAS} specifies the name of the new alias.
24403 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24406 @var{COMMAND} specifies the name of an existing command
24407 that is being aliased.
24409 The @samp{-a} option specifies that the new alias is an abbreviation
24410 of the command. Abbreviations are not shown in command
24411 lists displayed by the @samp{help} command.
24413 The @samp{--} option specifies the end of options,
24414 and is useful when @var{ALIAS} begins with a dash.
24416 Here is a simple example showing how to make an abbreviation
24417 of a command so that there is less to type.
24418 Suppose you were tired of typing @samp{disas}, the current
24419 shortest unambiguous abbreviation of the @samp{disassemble} command
24420 and you wanted an even shorter version named @samp{di}.
24421 The following will accomplish this.
24424 (gdb) alias -a di = disas
24427 Note that aliases are different from user-defined commands.
24428 With a user-defined command, you also need to write documentation
24429 for it with the @samp{document} command.
24430 An alias automatically picks up the documentation of the existing command.
24432 Here is an example where we make @samp{elms} an abbreviation of
24433 @samp{elements} in the @samp{set print elements} command.
24434 This is to show that you can make an abbreviation of any part
24438 (gdb) alias -a set print elms = set print elements
24439 (gdb) alias -a show print elms = show print elements
24440 (gdb) set p elms 20
24442 Limit on string chars or array elements to print is 200.
24445 Note that if you are defining an alias of a @samp{set} command,
24446 and you want to have an alias for the corresponding @samp{show}
24447 command, then you need to define the latter separately.
24449 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24450 @var{ALIAS}, just as they are normally.
24453 (gdb) alias -a set pr elms = set p ele
24456 Finally, here is an example showing the creation of a one word
24457 alias for a more complex command.
24458 This creates alias @samp{spe} of the command @samp{set print elements}.
24461 (gdb) alias spe = set print elements
24466 @chapter Command Interpreters
24467 @cindex command interpreters
24469 @value{GDBN} supports multiple command interpreters, and some command
24470 infrastructure to allow users or user interface writers to switch
24471 between interpreters or run commands in other interpreters.
24473 @value{GDBN} currently supports two command interpreters, the console
24474 interpreter (sometimes called the command-line interpreter or @sc{cli})
24475 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24476 describes both of these interfaces in great detail.
24478 By default, @value{GDBN} will start with the console interpreter.
24479 However, the user may choose to start @value{GDBN} with another
24480 interpreter by specifying the @option{-i} or @option{--interpreter}
24481 startup options. Defined interpreters include:
24485 @cindex console interpreter
24486 The traditional console or command-line interpreter. This is the most often
24487 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24488 @value{GDBN} will use this interpreter.
24491 @cindex mi interpreter
24492 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24493 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24494 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24498 @cindex mi2 interpreter
24499 The current @sc{gdb/mi} interface.
24502 @cindex mi1 interpreter
24503 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24507 @cindex invoke another interpreter
24508 The interpreter being used by @value{GDBN} may not be dynamically
24509 switched at runtime. Although possible, this could lead to a very
24510 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24511 enters the command "interpreter-set console" in a console view,
24512 @value{GDBN} would switch to using the console interpreter, rendering
24513 the IDE inoperable!
24515 @kindex interpreter-exec
24516 Although you may only choose a single interpreter at startup, you may execute
24517 commands in any interpreter from the current interpreter using the appropriate
24518 command. If you are running the console interpreter, simply use the
24519 @code{interpreter-exec} command:
24522 interpreter-exec mi "-data-list-register-names"
24525 @sc{gdb/mi} has a similar command, although it is only available in versions of
24526 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24529 @chapter @value{GDBN} Text User Interface
24531 @cindex Text User Interface
24534 * TUI Overview:: TUI overview
24535 * TUI Keys:: TUI key bindings
24536 * TUI Single Key Mode:: TUI single key mode
24537 * TUI Commands:: TUI-specific commands
24538 * TUI Configuration:: TUI configuration variables
24541 The @value{GDBN} Text User Interface (TUI) is a terminal
24542 interface which uses the @code{curses} library to show the source
24543 file, the assembly output, the program registers and @value{GDBN}
24544 commands in separate text windows. The TUI mode is supported only
24545 on platforms where a suitable version of the @code{curses} library
24548 The TUI mode is enabled by default when you invoke @value{GDBN} as
24549 @samp{@value{GDBP} -tui}.
24550 You can also switch in and out of TUI mode while @value{GDBN} runs by
24551 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24552 @xref{TUI Keys, ,TUI Key Bindings}.
24555 @section TUI Overview
24557 In TUI mode, @value{GDBN} can display several text windows:
24561 This window is the @value{GDBN} command window with the @value{GDBN}
24562 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24563 managed using readline.
24566 The source window shows the source file of the program. The current
24567 line and active breakpoints are displayed in this window.
24570 The assembly window shows the disassembly output of the program.
24573 This window shows the processor registers. Registers are highlighted
24574 when their values change.
24577 The source and assembly windows show the current program position
24578 by highlighting the current line and marking it with a @samp{>} marker.
24579 Breakpoints are indicated with two markers. The first marker
24580 indicates the breakpoint type:
24584 Breakpoint which was hit at least once.
24587 Breakpoint which was never hit.
24590 Hardware breakpoint which was hit at least once.
24593 Hardware breakpoint which was never hit.
24596 The second marker indicates whether the breakpoint is enabled or not:
24600 Breakpoint is enabled.
24603 Breakpoint is disabled.
24606 The source, assembly and register windows are updated when the current
24607 thread changes, when the frame changes, or when the program counter
24610 These windows are not all visible at the same time. The command
24611 window is always visible. The others can be arranged in several
24622 source and assembly,
24625 source and registers, or
24628 assembly and registers.
24631 A status line above the command window shows the following information:
24635 Indicates the current @value{GDBN} target.
24636 (@pxref{Targets, ,Specifying a Debugging Target}).
24639 Gives the current process or thread number.
24640 When no process is being debugged, this field is set to @code{No process}.
24643 Gives the current function name for the selected frame.
24644 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24645 When there is no symbol corresponding to the current program counter,
24646 the string @code{??} is displayed.
24649 Indicates the current line number for the selected frame.
24650 When the current line number is not known, the string @code{??} is displayed.
24653 Indicates the current program counter address.
24657 @section TUI Key Bindings
24658 @cindex TUI key bindings
24660 The TUI installs several key bindings in the readline keymaps
24661 @ifset SYSTEM_READLINE
24662 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24664 @ifclear SYSTEM_READLINE
24665 (@pxref{Command Line Editing}).
24667 The following key bindings are installed for both TUI mode and the
24668 @value{GDBN} standard mode.
24677 Enter or leave the TUI mode. When leaving the TUI mode,
24678 the curses window management stops and @value{GDBN} operates using
24679 its standard mode, writing on the terminal directly. When reentering
24680 the TUI mode, control is given back to the curses windows.
24681 The screen is then refreshed.
24685 Use a TUI layout with only one window. The layout will
24686 either be @samp{source} or @samp{assembly}. When the TUI mode
24687 is not active, it will switch to the TUI mode.
24689 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24693 Use a TUI layout with at least two windows. When the current
24694 layout already has two windows, the next layout with two windows is used.
24695 When a new layout is chosen, one window will always be common to the
24696 previous layout and the new one.
24698 Think of it as the Emacs @kbd{C-x 2} binding.
24702 Change the active window. The TUI associates several key bindings
24703 (like scrolling and arrow keys) with the active window. This command
24704 gives the focus to the next TUI window.
24706 Think of it as the Emacs @kbd{C-x o} binding.
24710 Switch in and out of the TUI SingleKey mode that binds single
24711 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24714 The following key bindings only work in the TUI mode:
24719 Scroll the active window one page up.
24723 Scroll the active window one page down.
24727 Scroll the active window one line up.
24731 Scroll the active window one line down.
24735 Scroll the active window one column left.
24739 Scroll the active window one column right.
24743 Refresh the screen.
24746 Because the arrow keys scroll the active window in the TUI mode, they
24747 are not available for their normal use by readline unless the command
24748 window has the focus. When another window is active, you must use
24749 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24750 and @kbd{C-f} to control the command window.
24752 @node TUI Single Key Mode
24753 @section TUI Single Key Mode
24754 @cindex TUI single key mode
24756 The TUI also provides a @dfn{SingleKey} mode, which binds several
24757 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24758 switch into this mode, where the following key bindings are used:
24761 @kindex c @r{(SingleKey TUI key)}
24765 @kindex d @r{(SingleKey TUI key)}
24769 @kindex f @r{(SingleKey TUI key)}
24773 @kindex n @r{(SingleKey TUI key)}
24777 @kindex q @r{(SingleKey TUI key)}
24779 exit the SingleKey mode.
24781 @kindex r @r{(SingleKey TUI key)}
24785 @kindex s @r{(SingleKey TUI key)}
24789 @kindex u @r{(SingleKey TUI key)}
24793 @kindex v @r{(SingleKey TUI key)}
24797 @kindex w @r{(SingleKey TUI key)}
24802 Other keys temporarily switch to the @value{GDBN} command prompt.
24803 The key that was pressed is inserted in the editing buffer so that
24804 it is possible to type most @value{GDBN} commands without interaction
24805 with the TUI SingleKey mode. Once the command is entered the TUI
24806 SingleKey mode is restored. The only way to permanently leave
24807 this mode is by typing @kbd{q} or @kbd{C-x s}.
24811 @section TUI-specific Commands
24812 @cindex TUI commands
24814 The TUI has specific commands to control the text windows.
24815 These commands are always available, even when @value{GDBN} is not in
24816 the TUI mode. When @value{GDBN} is in the standard mode, most
24817 of these commands will automatically switch to the TUI mode.
24819 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24820 terminal, or @value{GDBN} has been started with the machine interface
24821 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24822 these commands will fail with an error, because it would not be
24823 possible or desirable to enable curses window management.
24828 List and give the size of all displayed windows.
24832 Display the next layout.
24835 Display the previous layout.
24838 Display the source window only.
24841 Display the assembly window only.
24844 Display the source and assembly window.
24847 Display the register window together with the source or assembly window.
24851 Make the next window active for scrolling.
24854 Make the previous window active for scrolling.
24857 Make the source window active for scrolling.
24860 Make the assembly window active for scrolling.
24863 Make the register window active for scrolling.
24866 Make the command window active for scrolling.
24870 Refresh the screen. This is similar to typing @kbd{C-L}.
24872 @item tui reg float
24874 Show the floating point registers in the register window.
24876 @item tui reg general
24877 Show the general registers in the register window.
24880 Show the next register group. The list of register groups as well as
24881 their order is target specific. The predefined register groups are the
24882 following: @code{general}, @code{float}, @code{system}, @code{vector},
24883 @code{all}, @code{save}, @code{restore}.
24885 @item tui reg system
24886 Show the system registers in the register window.
24890 Update the source window and the current execution point.
24892 @item winheight @var{name} +@var{count}
24893 @itemx winheight @var{name} -@var{count}
24895 Change the height of the window @var{name} by @var{count}
24896 lines. Positive counts increase the height, while negative counts
24897 decrease it. The @var{name} parameter can be one of @code{src} (the
24898 source window), @code{cmd} (the command window), @code{asm} (the
24899 disassembly window), or @code{regs} (the register display window).
24901 @item tabset @var{nchars}
24903 Set the width of tab stops to be @var{nchars} characters. This
24904 setting affects the display of TAB characters in the source and
24908 @node TUI Configuration
24909 @section TUI Configuration Variables
24910 @cindex TUI configuration variables
24912 Several configuration variables control the appearance of TUI windows.
24915 @item set tui border-kind @var{kind}
24916 @kindex set tui border-kind
24917 Select the border appearance for the source, assembly and register windows.
24918 The possible values are the following:
24921 Use a space character to draw the border.
24924 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24927 Use the Alternate Character Set to draw the border. The border is
24928 drawn using character line graphics if the terminal supports them.
24931 @item set tui border-mode @var{mode}
24932 @kindex set tui border-mode
24933 @itemx set tui active-border-mode @var{mode}
24934 @kindex set tui active-border-mode
24935 Select the display attributes for the borders of the inactive windows
24936 or the active window. The @var{mode} can be one of the following:
24939 Use normal attributes to display the border.
24945 Use reverse video mode.
24948 Use half bright mode.
24950 @item half-standout
24951 Use half bright and standout mode.
24954 Use extra bright or bold mode.
24956 @item bold-standout
24957 Use extra bright or bold and standout mode.
24962 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24965 @cindex @sc{gnu} Emacs
24966 A special interface allows you to use @sc{gnu} Emacs to view (and
24967 edit) the source files for the program you are debugging with
24970 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24971 executable file you want to debug as an argument. This command starts
24972 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24973 created Emacs buffer.
24974 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24976 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24981 All ``terminal'' input and output goes through an Emacs buffer, called
24984 This applies both to @value{GDBN} commands and their output, and to the input
24985 and output done by the program you are debugging.
24987 This is useful because it means that you can copy the text of previous
24988 commands and input them again; you can even use parts of the output
24991 All the facilities of Emacs' Shell mode are available for interacting
24992 with your program. In particular, you can send signals the usual
24993 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24997 @value{GDBN} displays source code through Emacs.
24999 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25000 source file for that frame and puts an arrow (@samp{=>}) at the
25001 left margin of the current line. Emacs uses a separate buffer for
25002 source display, and splits the screen to show both your @value{GDBN} session
25005 Explicit @value{GDBN} @code{list} or search commands still produce output as
25006 usual, but you probably have no reason to use them from Emacs.
25009 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25010 a graphical mode, enabled by default, which provides further buffers
25011 that can control the execution and describe the state of your program.
25012 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25014 If you specify an absolute file name when prompted for the @kbd{M-x
25015 gdb} argument, then Emacs sets your current working directory to where
25016 your program resides. If you only specify the file name, then Emacs
25017 sets your current working directory to the directory associated
25018 with the previous buffer. In this case, @value{GDBN} may find your
25019 program by searching your environment's @code{PATH} variable, but on
25020 some operating systems it might not find the source. So, although the
25021 @value{GDBN} input and output session proceeds normally, the auxiliary
25022 buffer does not display the current source and line of execution.
25024 The initial working directory of @value{GDBN} is printed on the top
25025 line of the GUD buffer and this serves as a default for the commands
25026 that specify files for @value{GDBN} to operate on. @xref{Files,
25027 ,Commands to Specify Files}.
25029 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25030 need to call @value{GDBN} by a different name (for example, if you
25031 keep several configurations around, with different names) you can
25032 customize the Emacs variable @code{gud-gdb-command-name} to run the
25035 In the GUD buffer, you can use these special Emacs commands in
25036 addition to the standard Shell mode commands:
25040 Describe the features of Emacs' GUD Mode.
25043 Execute to another source line, like the @value{GDBN} @code{step} command; also
25044 update the display window to show the current file and location.
25047 Execute to next source line in this function, skipping all function
25048 calls, like the @value{GDBN} @code{next} command. Then update the display window
25049 to show the current file and location.
25052 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25053 display window accordingly.
25056 Execute until exit from the selected stack frame, like the @value{GDBN}
25057 @code{finish} command.
25060 Continue execution of your program, like the @value{GDBN} @code{continue}
25064 Go up the number of frames indicated by the numeric argument
25065 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25066 like the @value{GDBN} @code{up} command.
25069 Go down the number of frames indicated by the numeric argument, like the
25070 @value{GDBN} @code{down} command.
25073 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25074 tells @value{GDBN} to set a breakpoint on the source line point is on.
25076 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25077 separate frame which shows a backtrace when the GUD buffer is current.
25078 Move point to any frame in the stack and type @key{RET} to make it
25079 become the current frame and display the associated source in the
25080 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25081 selected frame become the current one. In graphical mode, the
25082 speedbar displays watch expressions.
25084 If you accidentally delete the source-display buffer, an easy way to get
25085 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25086 request a frame display; when you run under Emacs, this recreates
25087 the source buffer if necessary to show you the context of the current
25090 The source files displayed in Emacs are in ordinary Emacs buffers
25091 which are visiting the source files in the usual way. You can edit
25092 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25093 communicates with Emacs in terms of line numbers. If you add or
25094 delete lines from the text, the line numbers that @value{GDBN} knows cease
25095 to correspond properly with the code.
25097 A more detailed description of Emacs' interaction with @value{GDBN} is
25098 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25102 @chapter The @sc{gdb/mi} Interface
25104 @unnumberedsec Function and Purpose
25106 @cindex @sc{gdb/mi}, its purpose
25107 @sc{gdb/mi} is a line based machine oriented text interface to
25108 @value{GDBN} and is activated by specifying using the
25109 @option{--interpreter} command line option (@pxref{Mode Options}). It
25110 is specifically intended to support the development of systems which
25111 use the debugger as just one small component of a larger system.
25113 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25114 in the form of a reference manual.
25116 Note that @sc{gdb/mi} is still under construction, so some of the
25117 features described below are incomplete and subject to change
25118 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25120 @unnumberedsec Notation and Terminology
25122 @cindex notational conventions, for @sc{gdb/mi}
25123 This chapter uses the following notation:
25127 @code{|} separates two alternatives.
25130 @code{[ @var{something} ]} indicates that @var{something} is optional:
25131 it may or may not be given.
25134 @code{( @var{group} )*} means that @var{group} inside the parentheses
25135 may repeat zero or more times.
25138 @code{( @var{group} )+} means that @var{group} inside the parentheses
25139 may repeat one or more times.
25142 @code{"@var{string}"} means a literal @var{string}.
25146 @heading Dependencies
25150 * GDB/MI General Design::
25151 * GDB/MI Command Syntax::
25152 * GDB/MI Compatibility with CLI::
25153 * GDB/MI Development and Front Ends::
25154 * GDB/MI Output Records::
25155 * GDB/MI Simple Examples::
25156 * GDB/MI Command Description Format::
25157 * GDB/MI Breakpoint Commands::
25158 * GDB/MI Catchpoint Commands::
25159 * GDB/MI Program Context::
25160 * GDB/MI Thread Commands::
25161 * GDB/MI Ada Tasking Commands::
25162 * GDB/MI Program Execution::
25163 * GDB/MI Stack Manipulation::
25164 * GDB/MI Variable Objects::
25165 * GDB/MI Data Manipulation::
25166 * GDB/MI Tracepoint Commands::
25167 * GDB/MI Symbol Query::
25168 * GDB/MI File Commands::
25170 * GDB/MI Kod Commands::
25171 * GDB/MI Memory Overlay Commands::
25172 * GDB/MI Signal Handling Commands::
25174 * GDB/MI Target Manipulation::
25175 * GDB/MI File Transfer Commands::
25176 * GDB/MI Ada Exceptions Commands::
25177 * GDB/MI Support Commands::
25178 * GDB/MI Miscellaneous Commands::
25181 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25182 @node GDB/MI General Design
25183 @section @sc{gdb/mi} General Design
25184 @cindex GDB/MI General Design
25186 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25187 parts---commands sent to @value{GDBN}, responses to those commands
25188 and notifications. Each command results in exactly one response,
25189 indicating either successful completion of the command, or an error.
25190 For the commands that do not resume the target, the response contains the
25191 requested information. For the commands that resume the target, the
25192 response only indicates whether the target was successfully resumed.
25193 Notifications is the mechanism for reporting changes in the state of the
25194 target, or in @value{GDBN} state, that cannot conveniently be associated with
25195 a command and reported as part of that command response.
25197 The important examples of notifications are:
25201 Exec notifications. These are used to report changes in
25202 target state---when a target is resumed, or stopped. It would not
25203 be feasible to include this information in response of resuming
25204 commands, because one resume commands can result in multiple events in
25205 different threads. Also, quite some time may pass before any event
25206 happens in the target, while a frontend needs to know whether the resuming
25207 command itself was successfully executed.
25210 Console output, and status notifications. Console output
25211 notifications are used to report output of CLI commands, as well as
25212 diagnostics for other commands. Status notifications are used to
25213 report the progress of a long-running operation. Naturally, including
25214 this information in command response would mean no output is produced
25215 until the command is finished, which is undesirable.
25218 General notifications. Commands may have various side effects on
25219 the @value{GDBN} or target state beyond their official purpose. For example,
25220 a command may change the selected thread. Although such changes can
25221 be included in command response, using notification allows for more
25222 orthogonal frontend design.
25226 There's no guarantee that whenever an MI command reports an error,
25227 @value{GDBN} or the target are in any specific state, and especially,
25228 the state is not reverted to the state before the MI command was
25229 processed. Therefore, whenever an MI command results in an error,
25230 we recommend that the frontend refreshes all the information shown in
25231 the user interface.
25235 * Context management::
25236 * Asynchronous and non-stop modes::
25240 @node Context management
25241 @subsection Context management
25243 @subsubsection Threads and Frames
25245 In most cases when @value{GDBN} accesses the target, this access is
25246 done in context of a specific thread and frame (@pxref{Frames}).
25247 Often, even when accessing global data, the target requires that a thread
25248 be specified. The CLI interface maintains the selected thread and frame,
25249 and supplies them to target on each command. This is convenient,
25250 because a command line user would not want to specify that information
25251 explicitly on each command, and because user interacts with
25252 @value{GDBN} via a single terminal, so no confusion is possible as
25253 to what thread and frame are the current ones.
25255 In the case of MI, the concept of selected thread and frame is less
25256 useful. First, a frontend can easily remember this information
25257 itself. Second, a graphical frontend can have more than one window,
25258 each one used for debugging a different thread, and the frontend might
25259 want to access additional threads for internal purposes. This
25260 increases the risk that by relying on implicitly selected thread, the
25261 frontend may be operating on a wrong one. Therefore, each MI command
25262 should explicitly specify which thread and frame to operate on. To
25263 make it possible, each MI command accepts the @samp{--thread} and
25264 @samp{--frame} options, the value to each is @value{GDBN} identifier
25265 for thread and frame to operate on.
25267 Usually, each top-level window in a frontend allows the user to select
25268 a thread and a frame, and remembers the user selection for further
25269 operations. However, in some cases @value{GDBN} may suggest that the
25270 current thread be changed. For example, when stopping on a breakpoint
25271 it is reasonable to switch to the thread where breakpoint is hit. For
25272 another example, if the user issues the CLI @samp{thread} command via
25273 the frontend, it is desirable to change the frontend's selected thread to the
25274 one specified by user. @value{GDBN} communicates the suggestion to
25275 change current thread using the @samp{=thread-selected} notification.
25276 No such notification is available for the selected frame at the moment.
25278 Note that historically, MI shares the selected thread with CLI, so
25279 frontends used the @code{-thread-select} to execute commands in the
25280 right context. However, getting this to work right is cumbersome. The
25281 simplest way is for frontend to emit @code{-thread-select} command
25282 before every command. This doubles the number of commands that need
25283 to be sent. The alternative approach is to suppress @code{-thread-select}
25284 if the selected thread in @value{GDBN} is supposed to be identical to the
25285 thread the frontend wants to operate on. However, getting this
25286 optimization right can be tricky. In particular, if the frontend
25287 sends several commands to @value{GDBN}, and one of the commands changes the
25288 selected thread, then the behaviour of subsequent commands will
25289 change. So, a frontend should either wait for response from such
25290 problematic commands, or explicitly add @code{-thread-select} for
25291 all subsequent commands. No frontend is known to do this exactly
25292 right, so it is suggested to just always pass the @samp{--thread} and
25293 @samp{--frame} options.
25295 @subsubsection Language
25297 The execution of several commands depends on which language is selected.
25298 By default, the current language (@pxref{show language}) is used.
25299 But for commands known to be language-sensitive, it is recommended
25300 to use the @samp{--language} option. This option takes one argument,
25301 which is the name of the language to use while executing the command.
25305 -data-evaluate-expression --language c "sizeof (void*)"
25310 The valid language names are the same names accepted by the
25311 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25312 @samp{local} or @samp{unknown}.
25314 @node Asynchronous and non-stop modes
25315 @subsection Asynchronous command execution and non-stop mode
25317 On some targets, @value{GDBN} is capable of processing MI commands
25318 even while the target is running. This is called @dfn{asynchronous
25319 command execution} (@pxref{Background Execution}). The frontend may
25320 specify a preferrence for asynchronous execution using the
25321 @code{-gdb-set mi-async 1} command, which should be emitted before
25322 either running the executable or attaching to the target. After the
25323 frontend has started the executable or attached to the target, it can
25324 find if asynchronous execution is enabled using the
25325 @code{-list-target-features} command.
25328 @item -gdb-set mi-async on
25329 @item -gdb-set mi-async off
25330 Set whether MI is in asynchronous mode.
25332 When @code{off}, which is the default, MI execution commands (e.g.,
25333 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25334 for the program to stop before processing further commands.
25336 When @code{on}, MI execution commands are background execution
25337 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25338 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25339 MI commands even while the target is running.
25341 @item -gdb-show mi-async
25342 Show whether MI asynchronous mode is enabled.
25345 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25346 @code{target-async} instead of @code{mi-async}, and it had the effect
25347 of both putting MI in asynchronous mode and making CLI background
25348 commands possible. CLI background commands are now always possible
25349 ``out of the box'' if the target supports them. The old spelling is
25350 kept as a deprecated alias for backwards compatibility.
25352 Even if @value{GDBN} can accept a command while target is running,
25353 many commands that access the target do not work when the target is
25354 running. Therefore, asynchronous command execution is most useful
25355 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25356 it is possible to examine the state of one thread, while other threads
25359 When a given thread is running, MI commands that try to access the
25360 target in the context of that thread may not work, or may work only on
25361 some targets. In particular, commands that try to operate on thread's
25362 stack will not work, on any target. Commands that read memory, or
25363 modify breakpoints, may work or not work, depending on the target. Note
25364 that even commands that operate on global state, such as @code{print},
25365 @code{set}, and breakpoint commands, still access the target in the
25366 context of a specific thread, so frontend should try to find a
25367 stopped thread and perform the operation on that thread (using the
25368 @samp{--thread} option).
25370 Which commands will work in the context of a running thread is
25371 highly target dependent. However, the two commands
25372 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25373 to find the state of a thread, will always work.
25375 @node Thread groups
25376 @subsection Thread groups
25377 @value{GDBN} may be used to debug several processes at the same time.
25378 On some platfroms, @value{GDBN} may support debugging of several
25379 hardware systems, each one having several cores with several different
25380 processes running on each core. This section describes the MI
25381 mechanism to support such debugging scenarios.
25383 The key observation is that regardless of the structure of the
25384 target, MI can have a global list of threads, because most commands that
25385 accept the @samp{--thread} option do not need to know what process that
25386 thread belongs to. Therefore, it is not necessary to introduce
25387 neither additional @samp{--process} option, nor an notion of the
25388 current process in the MI interface. The only strictly new feature
25389 that is required is the ability to find how the threads are grouped
25392 To allow the user to discover such grouping, and to support arbitrary
25393 hierarchy of machines/cores/processes, MI introduces the concept of a
25394 @dfn{thread group}. Thread group is a collection of threads and other
25395 thread groups. A thread group always has a string identifier, a type,
25396 and may have additional attributes specific to the type. A new
25397 command, @code{-list-thread-groups}, returns the list of top-level
25398 thread groups, which correspond to processes that @value{GDBN} is
25399 debugging at the moment. By passing an identifier of a thread group
25400 to the @code{-list-thread-groups} command, it is possible to obtain
25401 the members of specific thread group.
25403 To allow the user to easily discover processes, and other objects, he
25404 wishes to debug, a concept of @dfn{available thread group} is
25405 introduced. Available thread group is an thread group that
25406 @value{GDBN} is not debugging, but that can be attached to, using the
25407 @code{-target-attach} command. The list of available top-level thread
25408 groups can be obtained using @samp{-list-thread-groups --available}.
25409 In general, the content of a thread group may be only retrieved only
25410 after attaching to that thread group.
25412 Thread groups are related to inferiors (@pxref{Inferiors and
25413 Programs}). Each inferior corresponds to a thread group of a special
25414 type @samp{process}, and some additional operations are permitted on
25415 such thread groups.
25417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25418 @node GDB/MI Command Syntax
25419 @section @sc{gdb/mi} Command Syntax
25422 * GDB/MI Input Syntax::
25423 * GDB/MI Output Syntax::
25426 @node GDB/MI Input Syntax
25427 @subsection @sc{gdb/mi} Input Syntax
25429 @cindex input syntax for @sc{gdb/mi}
25430 @cindex @sc{gdb/mi}, input syntax
25432 @item @var{command} @expansion{}
25433 @code{@var{cli-command} | @var{mi-command}}
25435 @item @var{cli-command} @expansion{}
25436 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25437 @var{cli-command} is any existing @value{GDBN} CLI command.
25439 @item @var{mi-command} @expansion{}
25440 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25441 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25443 @item @var{token} @expansion{}
25444 "any sequence of digits"
25446 @item @var{option} @expansion{}
25447 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25449 @item @var{parameter} @expansion{}
25450 @code{@var{non-blank-sequence} | @var{c-string}}
25452 @item @var{operation} @expansion{}
25453 @emph{any of the operations described in this chapter}
25455 @item @var{non-blank-sequence} @expansion{}
25456 @emph{anything, provided it doesn't contain special characters such as
25457 "-", @var{nl}, """ and of course " "}
25459 @item @var{c-string} @expansion{}
25460 @code{""" @var{seven-bit-iso-c-string-content} """}
25462 @item @var{nl} @expansion{}
25471 The CLI commands are still handled by the @sc{mi} interpreter; their
25472 output is described below.
25475 The @code{@var{token}}, when present, is passed back when the command
25479 Some @sc{mi} commands accept optional arguments as part of the parameter
25480 list. Each option is identified by a leading @samp{-} (dash) and may be
25481 followed by an optional argument parameter. Options occur first in the
25482 parameter list and can be delimited from normal parameters using
25483 @samp{--} (this is useful when some parameters begin with a dash).
25490 We want easy access to the existing CLI syntax (for debugging).
25493 We want it to be easy to spot a @sc{mi} operation.
25496 @node GDB/MI Output Syntax
25497 @subsection @sc{gdb/mi} Output Syntax
25499 @cindex output syntax of @sc{gdb/mi}
25500 @cindex @sc{gdb/mi}, output syntax
25501 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25502 followed, optionally, by a single result record. This result record
25503 is for the most recent command. The sequence of output records is
25504 terminated by @samp{(gdb)}.
25506 If an input command was prefixed with a @code{@var{token}} then the
25507 corresponding output for that command will also be prefixed by that same
25511 @item @var{output} @expansion{}
25512 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25514 @item @var{result-record} @expansion{}
25515 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25517 @item @var{out-of-band-record} @expansion{}
25518 @code{@var{async-record} | @var{stream-record}}
25520 @item @var{async-record} @expansion{}
25521 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25523 @item @var{exec-async-output} @expansion{}
25524 @code{[ @var{token} ] "*" @var{async-output nl}}
25526 @item @var{status-async-output} @expansion{}
25527 @code{[ @var{token} ] "+" @var{async-output nl}}
25529 @item @var{notify-async-output} @expansion{}
25530 @code{[ @var{token} ] "=" @var{async-output nl}}
25532 @item @var{async-output} @expansion{}
25533 @code{@var{async-class} ( "," @var{result} )*}
25535 @item @var{result-class} @expansion{}
25536 @code{"done" | "running" | "connected" | "error" | "exit"}
25538 @item @var{async-class} @expansion{}
25539 @code{"stopped" | @var{others}} (where @var{others} will be added
25540 depending on the needs---this is still in development).
25542 @item @var{result} @expansion{}
25543 @code{ @var{variable} "=" @var{value}}
25545 @item @var{variable} @expansion{}
25546 @code{ @var{string} }
25548 @item @var{value} @expansion{}
25549 @code{ @var{const} | @var{tuple} | @var{list} }
25551 @item @var{const} @expansion{}
25552 @code{@var{c-string}}
25554 @item @var{tuple} @expansion{}
25555 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25557 @item @var{list} @expansion{}
25558 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25559 @var{result} ( "," @var{result} )* "]" }
25561 @item @var{stream-record} @expansion{}
25562 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25564 @item @var{console-stream-output} @expansion{}
25565 @code{"~" @var{c-string nl}}
25567 @item @var{target-stream-output} @expansion{}
25568 @code{"@@" @var{c-string nl}}
25570 @item @var{log-stream-output} @expansion{}
25571 @code{"&" @var{c-string nl}}
25573 @item @var{nl} @expansion{}
25576 @item @var{token} @expansion{}
25577 @emph{any sequence of digits}.
25585 All output sequences end in a single line containing a period.
25588 The @code{@var{token}} is from the corresponding request. Note that
25589 for all async output, while the token is allowed by the grammar and
25590 may be output by future versions of @value{GDBN} for select async
25591 output messages, it is generally omitted. Frontends should treat
25592 all async output as reporting general changes in the state of the
25593 target and there should be no need to associate async output to any
25597 @cindex status output in @sc{gdb/mi}
25598 @var{status-async-output} contains on-going status information about the
25599 progress of a slow operation. It can be discarded. All status output is
25600 prefixed by @samp{+}.
25603 @cindex async output in @sc{gdb/mi}
25604 @var{exec-async-output} contains asynchronous state change on the target
25605 (stopped, started, disappeared). All async output is prefixed by
25609 @cindex notify output in @sc{gdb/mi}
25610 @var{notify-async-output} contains supplementary information that the
25611 client should handle (e.g., a new breakpoint information). All notify
25612 output is prefixed by @samp{=}.
25615 @cindex console output in @sc{gdb/mi}
25616 @var{console-stream-output} is output that should be displayed as is in the
25617 console. It is the textual response to a CLI command. All the console
25618 output is prefixed by @samp{~}.
25621 @cindex target output in @sc{gdb/mi}
25622 @var{target-stream-output} is the output produced by the target program.
25623 All the target output is prefixed by @samp{@@}.
25626 @cindex log output in @sc{gdb/mi}
25627 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25628 instance messages that should be displayed as part of an error log. All
25629 the log output is prefixed by @samp{&}.
25632 @cindex list output in @sc{gdb/mi}
25633 New @sc{gdb/mi} commands should only output @var{lists} containing
25639 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25640 details about the various output records.
25642 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25643 @node GDB/MI Compatibility with CLI
25644 @section @sc{gdb/mi} Compatibility with CLI
25646 @cindex compatibility, @sc{gdb/mi} and CLI
25647 @cindex @sc{gdb/mi}, compatibility with CLI
25649 For the developers convenience CLI commands can be entered directly,
25650 but there may be some unexpected behaviour. For example, commands
25651 that query the user will behave as if the user replied yes, breakpoint
25652 command lists are not executed and some CLI commands, such as
25653 @code{if}, @code{when} and @code{define}, prompt for further input with
25654 @samp{>}, which is not valid MI output.
25656 This feature may be removed at some stage in the future and it is
25657 recommended that front ends use the @code{-interpreter-exec} command
25658 (@pxref{-interpreter-exec}).
25660 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25661 @node GDB/MI Development and Front Ends
25662 @section @sc{gdb/mi} Development and Front Ends
25663 @cindex @sc{gdb/mi} development
25665 The application which takes the MI output and presents the state of the
25666 program being debugged to the user is called a @dfn{front end}.
25668 Although @sc{gdb/mi} is still incomplete, it is currently being used
25669 by a variety of front ends to @value{GDBN}. This makes it difficult
25670 to introduce new functionality without breaking existing usage. This
25671 section tries to minimize the problems by describing how the protocol
25674 Some changes in MI need not break a carefully designed front end, and
25675 for these the MI version will remain unchanged. The following is a
25676 list of changes that may occur within one level, so front ends should
25677 parse MI output in a way that can handle them:
25681 New MI commands may be added.
25684 New fields may be added to the output of any MI command.
25687 The range of values for fields with specified values, e.g.,
25688 @code{in_scope} (@pxref{-var-update}) may be extended.
25690 @c The format of field's content e.g type prefix, may change so parse it
25691 @c at your own risk. Yes, in general?
25693 @c The order of fields may change? Shouldn't really matter but it might
25694 @c resolve inconsistencies.
25697 If the changes are likely to break front ends, the MI version level
25698 will be increased by one. This will allow the front end to parse the
25699 output according to the MI version. Apart from mi0, new versions of
25700 @value{GDBN} will not support old versions of MI and it will be the
25701 responsibility of the front end to work with the new one.
25703 @c Starting with mi3, add a new command -mi-version that prints the MI
25706 The best way to avoid unexpected changes in MI that might break your front
25707 end is to make your project known to @value{GDBN} developers and
25708 follow development on @email{gdb@@sourceware.org} and
25709 @email{gdb-patches@@sourceware.org}.
25710 @cindex mailing lists
25712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25713 @node GDB/MI Output Records
25714 @section @sc{gdb/mi} Output Records
25717 * GDB/MI Result Records::
25718 * GDB/MI Stream Records::
25719 * GDB/MI Async Records::
25720 * GDB/MI Breakpoint Information::
25721 * GDB/MI Frame Information::
25722 * GDB/MI Thread Information::
25723 * GDB/MI Ada Exception Information::
25726 @node GDB/MI Result Records
25727 @subsection @sc{gdb/mi} Result Records
25729 @cindex result records in @sc{gdb/mi}
25730 @cindex @sc{gdb/mi}, result records
25731 In addition to a number of out-of-band notifications, the response to a
25732 @sc{gdb/mi} command includes one of the following result indications:
25736 @item "^done" [ "," @var{results} ]
25737 The synchronous operation was successful, @code{@var{results}} are the return
25742 This result record is equivalent to @samp{^done}. Historically, it
25743 was output instead of @samp{^done} if the command has resumed the
25744 target. This behaviour is maintained for backward compatibility, but
25745 all frontends should treat @samp{^done} and @samp{^running}
25746 identically and rely on the @samp{*running} output record to determine
25747 which threads are resumed.
25751 @value{GDBN} has connected to a remote target.
25753 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25755 The operation failed. The @code{msg=@var{c-string}} variable contains
25756 the corresponding error message.
25758 If present, the @code{code=@var{c-string}} variable provides an error
25759 code on which consumers can rely on to detect the corresponding
25760 error condition. At present, only one error code is defined:
25763 @item "undefined-command"
25764 Indicates that the command causing the error does not exist.
25769 @value{GDBN} has terminated.
25773 @node GDB/MI Stream Records
25774 @subsection @sc{gdb/mi} Stream Records
25776 @cindex @sc{gdb/mi}, stream records
25777 @cindex stream records in @sc{gdb/mi}
25778 @value{GDBN} internally maintains a number of output streams: the console, the
25779 target, and the log. The output intended for each of these streams is
25780 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25782 Each stream record begins with a unique @dfn{prefix character} which
25783 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25784 Syntax}). In addition to the prefix, each stream record contains a
25785 @code{@var{string-output}}. This is either raw text (with an implicit new
25786 line) or a quoted C string (which does not contain an implicit newline).
25789 @item "~" @var{string-output}
25790 The console output stream contains text that should be displayed in the
25791 CLI console window. It contains the textual responses to CLI commands.
25793 @item "@@" @var{string-output}
25794 The target output stream contains any textual output from the running
25795 target. This is only present when GDB's event loop is truly
25796 asynchronous, which is currently only the case for remote targets.
25798 @item "&" @var{string-output}
25799 The log stream contains debugging messages being produced by @value{GDBN}'s
25803 @node GDB/MI Async Records
25804 @subsection @sc{gdb/mi} Async Records
25806 @cindex async records in @sc{gdb/mi}
25807 @cindex @sc{gdb/mi}, async records
25808 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25809 additional changes that have occurred. Those changes can either be a
25810 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25811 target activity (e.g., target stopped).
25813 The following is the list of possible async records:
25817 @item *running,thread-id="@var{thread}"
25818 The target is now running. The @var{thread} field tells which
25819 specific thread is now running, and can be @samp{all} if all threads
25820 are running. The frontend should assume that no interaction with a
25821 running thread is possible after this notification is produced.
25822 The frontend should not assume that this notification is output
25823 only once for any command. @value{GDBN} may emit this notification
25824 several times, either for different threads, because it cannot resume
25825 all threads together, or even for a single thread, if the thread must
25826 be stepped though some code before letting it run freely.
25828 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25829 The target has stopped. The @var{reason} field can have one of the
25833 @item breakpoint-hit
25834 A breakpoint was reached.
25835 @item watchpoint-trigger
25836 A watchpoint was triggered.
25837 @item read-watchpoint-trigger
25838 A read watchpoint was triggered.
25839 @item access-watchpoint-trigger
25840 An access watchpoint was triggered.
25841 @item function-finished
25842 An -exec-finish or similar CLI command was accomplished.
25843 @item location-reached
25844 An -exec-until or similar CLI command was accomplished.
25845 @item watchpoint-scope
25846 A watchpoint has gone out of scope.
25847 @item end-stepping-range
25848 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25849 similar CLI command was accomplished.
25850 @item exited-signalled
25851 The inferior exited because of a signal.
25853 The inferior exited.
25854 @item exited-normally
25855 The inferior exited normally.
25856 @item signal-received
25857 A signal was received by the inferior.
25859 The inferior has stopped due to a library being loaded or unloaded.
25860 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25861 set or when a @code{catch load} or @code{catch unload} catchpoint is
25862 in use (@pxref{Set Catchpoints}).
25864 The inferior has forked. This is reported when @code{catch fork}
25865 (@pxref{Set Catchpoints}) has been used.
25867 The inferior has vforked. This is reported in when @code{catch vfork}
25868 (@pxref{Set Catchpoints}) has been used.
25869 @item syscall-entry
25870 The inferior entered a system call. This is reported when @code{catch
25871 syscall} (@pxref{Set Catchpoints}) has been used.
25872 @item syscall-return
25873 The inferior returned from a system call. This is reported when
25874 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25876 The inferior called @code{exec}. This is reported when @code{catch exec}
25877 (@pxref{Set Catchpoints}) has been used.
25880 The @var{id} field identifies the thread that directly caused the stop
25881 -- for example by hitting a breakpoint. Depending on whether all-stop
25882 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25883 stop all threads, or only the thread that directly triggered the stop.
25884 If all threads are stopped, the @var{stopped} field will have the
25885 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25886 field will be a list of thread identifiers. Presently, this list will
25887 always include a single thread, but frontend should be prepared to see
25888 several threads in the list. The @var{core} field reports the
25889 processor core on which the stop event has happened. This field may be absent
25890 if such information is not available.
25892 @item =thread-group-added,id="@var{id}"
25893 @itemx =thread-group-removed,id="@var{id}"
25894 A thread group was either added or removed. The @var{id} field
25895 contains the @value{GDBN} identifier of the thread group. When a thread
25896 group is added, it generally might not be associated with a running
25897 process. When a thread group is removed, its id becomes invalid and
25898 cannot be used in any way.
25900 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25901 A thread group became associated with a running program,
25902 either because the program was just started or the thread group
25903 was attached to a program. The @var{id} field contains the
25904 @value{GDBN} identifier of the thread group. The @var{pid} field
25905 contains process identifier, specific to the operating system.
25907 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25908 A thread group is no longer associated with a running program,
25909 either because the program has exited, or because it was detached
25910 from. The @var{id} field contains the @value{GDBN} identifier of the
25911 thread group. The @var{code} field is the exit code of the inferior; it exists
25912 only when the inferior exited with some code.
25914 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25915 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25916 A thread either was created, or has exited. The @var{id} field
25917 contains the @value{GDBN} identifier of the thread. The @var{gid}
25918 field identifies the thread group this thread belongs to.
25920 @item =thread-selected,id="@var{id}"
25921 Informs that the selected thread was changed as result of the last
25922 command. This notification is not emitted as result of @code{-thread-select}
25923 command but is emitted whenever an MI command that is not documented
25924 to change the selected thread actually changes it. In particular,
25925 invoking, directly or indirectly (via user-defined command), the CLI
25926 @code{thread} command, will generate this notification.
25928 We suggest that in response to this notification, front ends
25929 highlight the selected thread and cause subsequent commands to apply to
25932 @item =library-loaded,...
25933 Reports that a new library file was loaded by the program. This
25934 notification has 4 fields---@var{id}, @var{target-name},
25935 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25936 opaque identifier of the library. For remote debugging case,
25937 @var{target-name} and @var{host-name} fields give the name of the
25938 library file on the target, and on the host respectively. For native
25939 debugging, both those fields have the same value. The
25940 @var{symbols-loaded} field is emitted only for backward compatibility
25941 and should not be relied on to convey any useful information. The
25942 @var{thread-group} field, if present, specifies the id of the thread
25943 group in whose context the library was loaded. If the field is
25944 absent, it means the library was loaded in the context of all present
25947 @item =library-unloaded,...
25948 Reports that a library was unloaded by the program. This notification
25949 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25950 the same meaning as for the @code{=library-loaded} notification.
25951 The @var{thread-group} field, if present, specifies the id of the
25952 thread group in whose context the library was unloaded. If the field is
25953 absent, it means the library was unloaded in the context of all present
25956 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25957 @itemx =traceframe-changed,end
25958 Reports that the trace frame was changed and its new number is
25959 @var{tfnum}. The number of the tracepoint associated with this trace
25960 frame is @var{tpnum}.
25962 @item =tsv-created,name=@var{name},initial=@var{initial}
25963 Reports that the new trace state variable @var{name} is created with
25964 initial value @var{initial}.
25966 @item =tsv-deleted,name=@var{name}
25967 @itemx =tsv-deleted
25968 Reports that the trace state variable @var{name} is deleted or all
25969 trace state variables are deleted.
25971 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25972 Reports that the trace state variable @var{name} is modified with
25973 the initial value @var{initial}. The current value @var{current} of
25974 trace state variable is optional and is reported if the current
25975 value of trace state variable is known.
25977 @item =breakpoint-created,bkpt=@{...@}
25978 @itemx =breakpoint-modified,bkpt=@{...@}
25979 @itemx =breakpoint-deleted,id=@var{number}
25980 Reports that a breakpoint was created, modified, or deleted,
25981 respectively. Only user-visible breakpoints are reported to the MI
25984 The @var{bkpt} argument is of the same form as returned by the various
25985 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25986 @var{number} is the ordinal number of the breakpoint.
25988 Note that if a breakpoint is emitted in the result record of a
25989 command, then it will not also be emitted in an async record.
25991 @item =record-started,thread-group="@var{id}"
25992 @itemx =record-stopped,thread-group="@var{id}"
25993 Execution log recording was either started or stopped on an
25994 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25995 group corresponding to the affected inferior.
25997 @item =cmd-param-changed,param=@var{param},value=@var{value}
25998 Reports that a parameter of the command @code{set @var{param}} is
25999 changed to @var{value}. In the multi-word @code{set} command,
26000 the @var{param} is the whole parameter list to @code{set} command.
26001 For example, In command @code{set check type on}, @var{param}
26002 is @code{check type} and @var{value} is @code{on}.
26004 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26005 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26006 written in an inferior. The @var{id} is the identifier of the
26007 thread group corresponding to the affected inferior. The optional
26008 @code{type="code"} part is reported if the memory written to holds
26012 @node GDB/MI Breakpoint Information
26013 @subsection @sc{gdb/mi} Breakpoint Information
26015 When @value{GDBN} reports information about a breakpoint, a
26016 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26021 The breakpoint number. For a breakpoint that represents one location
26022 of a multi-location breakpoint, this will be a dotted pair, like
26026 The type of the breakpoint. For ordinary breakpoints this will be
26027 @samp{breakpoint}, but many values are possible.
26030 If the type of the breakpoint is @samp{catchpoint}, then this
26031 indicates the exact type of catchpoint.
26034 This is the breakpoint disposition---either @samp{del}, meaning that
26035 the breakpoint will be deleted at the next stop, or @samp{keep},
26036 meaning that the breakpoint will not be deleted.
26039 This indicates whether the breakpoint is enabled, in which case the
26040 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26041 Note that this is not the same as the field @code{enable}.
26044 The address of the breakpoint. This may be a hexidecimal number,
26045 giving the address; or the string @samp{<PENDING>}, for a pending
26046 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26047 multiple locations. This field will not be present if no address can
26048 be determined. For example, a watchpoint does not have an address.
26051 If known, the function in which the breakpoint appears.
26052 If not known, this field is not present.
26055 The name of the source file which contains this function, if known.
26056 If not known, this field is not present.
26059 The full file name of the source file which contains this function, if
26060 known. If not known, this field is not present.
26063 The line number at which this breakpoint appears, if known.
26064 If not known, this field is not present.
26067 If the source file is not known, this field may be provided. If
26068 provided, this holds the address of the breakpoint, possibly followed
26072 If this breakpoint is pending, this field is present and holds the
26073 text used to set the breakpoint, as entered by the user.
26076 Where this breakpoint's condition is evaluated, either @samp{host} or
26080 If this is a thread-specific breakpoint, then this identifies the
26081 thread in which the breakpoint can trigger.
26084 If this breakpoint is restricted to a particular Ada task, then this
26085 field will hold the task identifier.
26088 If the breakpoint is conditional, this is the condition expression.
26091 The ignore count of the breakpoint.
26094 The enable count of the breakpoint.
26096 @item traceframe-usage
26099 @item static-tracepoint-marker-string-id
26100 For a static tracepoint, the name of the static tracepoint marker.
26103 For a masked watchpoint, this is the mask.
26106 A tracepoint's pass count.
26108 @item original-location
26109 The location of the breakpoint as originally specified by the user.
26110 This field is optional.
26113 The number of times the breakpoint has been hit.
26116 This field is only given for tracepoints. This is either @samp{y},
26117 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26121 Some extra data, the exact contents of which are type-dependent.
26125 For example, here is what the output of @code{-break-insert}
26126 (@pxref{GDB/MI Breakpoint Commands}) might be:
26129 -> -break-insert main
26130 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26131 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26132 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26137 @node GDB/MI Frame Information
26138 @subsection @sc{gdb/mi} Frame Information
26140 Response from many MI commands includes an information about stack
26141 frame. This information is a tuple that may have the following
26146 The level of the stack frame. The innermost frame has the level of
26147 zero. This field is always present.
26150 The name of the function corresponding to the frame. This field may
26151 be absent if @value{GDBN} is unable to determine the function name.
26154 The code address for the frame. This field is always present.
26157 The name of the source files that correspond to the frame's code
26158 address. This field may be absent.
26161 The source line corresponding to the frames' code address. This field
26165 The name of the binary file (either executable or shared library) the
26166 corresponds to the frame's code address. This field may be absent.
26170 @node GDB/MI Thread Information
26171 @subsection @sc{gdb/mi} Thread Information
26173 Whenever @value{GDBN} has to report an information about a thread, it
26174 uses a tuple with the following fields:
26178 The numeric id assigned to the thread by @value{GDBN}. This field is
26182 Target-specific string identifying the thread. This field is always present.
26185 Additional information about the thread provided by the target.
26186 It is supposed to be human-readable and not interpreted by the
26187 frontend. This field is optional.
26190 Either @samp{stopped} or @samp{running}, depending on whether the
26191 thread is presently running. This field is always present.
26194 The value of this field is an integer number of the processor core the
26195 thread was last seen on. This field is optional.
26198 @node GDB/MI Ada Exception Information
26199 @subsection @sc{gdb/mi} Ada Exception Information
26201 Whenever a @code{*stopped} record is emitted because the program
26202 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26203 @value{GDBN} provides the name of the exception that was raised via
26204 the @code{exception-name} field.
26206 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26207 @node GDB/MI Simple Examples
26208 @section Simple Examples of @sc{gdb/mi} Interaction
26209 @cindex @sc{gdb/mi}, simple examples
26211 This subsection presents several simple examples of interaction using
26212 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26213 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26214 the output received from @sc{gdb/mi}.
26216 Note the line breaks shown in the examples are here only for
26217 readability, they don't appear in the real output.
26219 @subheading Setting a Breakpoint
26221 Setting a breakpoint generates synchronous output which contains detailed
26222 information of the breakpoint.
26225 -> -break-insert main
26226 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26227 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26228 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26233 @subheading Program Execution
26235 Program execution generates asynchronous records and MI gives the
26236 reason that execution stopped.
26242 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26243 frame=@{addr="0x08048564",func="main",
26244 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26245 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26250 <- *stopped,reason="exited-normally"
26254 @subheading Quitting @value{GDBN}
26256 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26264 Please note that @samp{^exit} is printed immediately, but it might
26265 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26266 performs necessary cleanups, including killing programs being debugged
26267 or disconnecting from debug hardware, so the frontend should wait till
26268 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26269 fails to exit in reasonable time.
26271 @subheading A Bad Command
26273 Here's what happens if you pass a non-existent command:
26277 <- ^error,msg="Undefined MI command: rubbish"
26282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26283 @node GDB/MI Command Description Format
26284 @section @sc{gdb/mi} Command Description Format
26286 The remaining sections describe blocks of commands. Each block of
26287 commands is laid out in a fashion similar to this section.
26289 @subheading Motivation
26291 The motivation for this collection of commands.
26293 @subheading Introduction
26295 A brief introduction to this collection of commands as a whole.
26297 @subheading Commands
26299 For each command in the block, the following is described:
26301 @subsubheading Synopsis
26304 -command @var{args}@dots{}
26307 @subsubheading Result
26309 @subsubheading @value{GDBN} Command
26311 The corresponding @value{GDBN} CLI command(s), if any.
26313 @subsubheading Example
26315 Example(s) formatted for readability. Some of the described commands have
26316 not been implemented yet and these are labeled N.A.@: (not available).
26319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26320 @node GDB/MI Breakpoint Commands
26321 @section @sc{gdb/mi} Breakpoint Commands
26323 @cindex breakpoint commands for @sc{gdb/mi}
26324 @cindex @sc{gdb/mi}, breakpoint commands
26325 This section documents @sc{gdb/mi} commands for manipulating
26328 @subheading The @code{-break-after} Command
26329 @findex -break-after
26331 @subsubheading Synopsis
26334 -break-after @var{number} @var{count}
26337 The breakpoint number @var{number} is not in effect until it has been
26338 hit @var{count} times. To see how this is reflected in the output of
26339 the @samp{-break-list} command, see the description of the
26340 @samp{-break-list} command below.
26342 @subsubheading @value{GDBN} Command
26344 The corresponding @value{GDBN} command is @samp{ignore}.
26346 @subsubheading Example
26351 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26352 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26353 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26361 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26362 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26363 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26364 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26365 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26366 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26367 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26368 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26369 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26370 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26375 @subheading The @code{-break-catch} Command
26376 @findex -break-catch
26379 @subheading The @code{-break-commands} Command
26380 @findex -break-commands
26382 @subsubheading Synopsis
26385 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26388 Specifies the CLI commands that should be executed when breakpoint
26389 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26390 are the commands. If no command is specified, any previously-set
26391 commands are cleared. @xref{Break Commands}. Typical use of this
26392 functionality is tracing a program, that is, printing of values of
26393 some variables whenever breakpoint is hit and then continuing.
26395 @subsubheading @value{GDBN} Command
26397 The corresponding @value{GDBN} command is @samp{commands}.
26399 @subsubheading Example
26404 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26405 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26406 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26409 -break-commands 1 "print v" "continue"
26414 @subheading The @code{-break-condition} Command
26415 @findex -break-condition
26417 @subsubheading Synopsis
26420 -break-condition @var{number} @var{expr}
26423 Breakpoint @var{number} will stop the program only if the condition in
26424 @var{expr} is true. The condition becomes part of the
26425 @samp{-break-list} output (see the description of the @samp{-break-list}
26428 @subsubheading @value{GDBN} Command
26430 The corresponding @value{GDBN} command is @samp{condition}.
26432 @subsubheading Example
26436 -break-condition 1 1
26440 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26441 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26442 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26443 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26444 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26445 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26446 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26447 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26448 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26449 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26453 @subheading The @code{-break-delete} Command
26454 @findex -break-delete
26456 @subsubheading Synopsis
26459 -break-delete ( @var{breakpoint} )+
26462 Delete the breakpoint(s) whose number(s) are specified in the argument
26463 list. This is obviously reflected in the breakpoint list.
26465 @subsubheading @value{GDBN} Command
26467 The corresponding @value{GDBN} command is @samp{delete}.
26469 @subsubheading Example
26477 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26478 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26479 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26480 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26481 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26482 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26483 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26488 @subheading The @code{-break-disable} Command
26489 @findex -break-disable
26491 @subsubheading Synopsis
26494 -break-disable ( @var{breakpoint} )+
26497 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26498 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26500 @subsubheading @value{GDBN} Command
26502 The corresponding @value{GDBN} command is @samp{disable}.
26504 @subsubheading Example
26512 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26519 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26520 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26521 line="5",thread-groups=["i1"],times="0"@}]@}
26525 @subheading The @code{-break-enable} Command
26526 @findex -break-enable
26528 @subsubheading Synopsis
26531 -break-enable ( @var{breakpoint} )+
26534 Enable (previously disabled) @var{breakpoint}(s).
26536 @subsubheading @value{GDBN} Command
26538 The corresponding @value{GDBN} command is @samp{enable}.
26540 @subsubheading Example
26548 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26549 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26550 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26551 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26552 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26553 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26554 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26555 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26556 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26557 line="5",thread-groups=["i1"],times="0"@}]@}
26561 @subheading The @code{-break-info} Command
26562 @findex -break-info
26564 @subsubheading Synopsis
26567 -break-info @var{breakpoint}
26571 Get information about a single breakpoint.
26573 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26574 Information}, for details on the format of each breakpoint in the
26577 @subsubheading @value{GDBN} Command
26579 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26581 @subsubheading Example
26584 @subheading The @code{-break-insert} Command
26585 @findex -break-insert
26587 @subsubheading Synopsis
26590 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26591 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26592 [ -p @var{thread-id} ] [ @var{location} ]
26596 If specified, @var{location}, can be one of:
26603 @item filename:linenum
26604 @item filename:function
26608 The possible optional parameters of this command are:
26612 Insert a temporary breakpoint.
26614 Insert a hardware breakpoint.
26616 If @var{location} cannot be parsed (for example if it
26617 refers to unknown files or functions), create a pending
26618 breakpoint. Without this flag, @value{GDBN} will report
26619 an error, and won't create a breakpoint, if @var{location}
26622 Create a disabled breakpoint.
26624 Create a tracepoint. @xref{Tracepoints}. When this parameter
26625 is used together with @samp{-h}, a fast tracepoint is created.
26626 @item -c @var{condition}
26627 Make the breakpoint conditional on @var{condition}.
26628 @item -i @var{ignore-count}
26629 Initialize the @var{ignore-count}.
26630 @item -p @var{thread-id}
26631 Restrict the breakpoint to the specified @var{thread-id}.
26634 @subsubheading Result
26636 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26637 resulting breakpoint.
26639 Note: this format is open to change.
26640 @c An out-of-band breakpoint instead of part of the result?
26642 @subsubheading @value{GDBN} Command
26644 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26645 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26647 @subsubheading Example
26652 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26653 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26656 -break-insert -t foo
26657 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26658 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26662 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26663 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26664 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26665 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26666 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26667 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26668 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26669 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26670 addr="0x0001072c", func="main",file="recursive2.c",
26671 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26673 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26674 addr="0x00010774",func="foo",file="recursive2.c",
26675 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26678 @c -break-insert -r foo.*
26679 @c ~int foo(int, int);
26680 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26681 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26686 @subheading The @code{-dprintf-insert} Command
26687 @findex -dprintf-insert
26689 @subsubheading Synopsis
26692 -dprintf-insert [ -t ] [ -f ] [ -d ]
26693 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26694 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26699 If specified, @var{location}, can be one of:
26702 @item @var{function}
26705 @c @item @var{linenum}
26706 @item @var{filename}:@var{linenum}
26707 @item @var{filename}:function
26708 @item *@var{address}
26711 The possible optional parameters of this command are:
26715 Insert a temporary breakpoint.
26717 If @var{location} cannot be parsed (for example, if it
26718 refers to unknown files or functions), create a pending
26719 breakpoint. Without this flag, @value{GDBN} will report
26720 an error, and won't create a breakpoint, if @var{location}
26723 Create a disabled breakpoint.
26724 @item -c @var{condition}
26725 Make the breakpoint conditional on @var{condition}.
26726 @item -i @var{ignore-count}
26727 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26728 to @var{ignore-count}.
26729 @item -p @var{thread-id}
26730 Restrict the breakpoint to the specified @var{thread-id}.
26733 @subsubheading Result
26735 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26736 resulting breakpoint.
26738 @c An out-of-band breakpoint instead of part of the result?
26740 @subsubheading @value{GDBN} Command
26742 The corresponding @value{GDBN} command is @samp{dprintf}.
26744 @subsubheading Example
26748 4-dprintf-insert foo "At foo entry\n"
26749 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26750 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26751 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26752 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26753 original-location="foo"@}
26755 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26756 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26757 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26758 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26759 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26760 original-location="mi-dprintf.c:26"@}
26764 @subheading The @code{-break-list} Command
26765 @findex -break-list
26767 @subsubheading Synopsis
26773 Displays the list of inserted breakpoints, showing the following fields:
26777 number of the breakpoint
26779 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26781 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26784 is the breakpoint enabled or no: @samp{y} or @samp{n}
26786 memory location at which the breakpoint is set
26788 logical location of the breakpoint, expressed by function name, file
26790 @item Thread-groups
26791 list of thread groups to which this breakpoint applies
26793 number of times the breakpoint has been hit
26796 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26797 @code{body} field is an empty list.
26799 @subsubheading @value{GDBN} Command
26801 The corresponding @value{GDBN} command is @samp{info break}.
26803 @subsubheading Example
26808 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26815 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26816 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26818 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26819 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26820 line="13",thread-groups=["i1"],times="0"@}]@}
26824 Here's an example of the result when there are no breakpoints:
26829 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26830 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26831 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26832 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26833 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26834 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26835 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26840 @subheading The @code{-break-passcount} Command
26841 @findex -break-passcount
26843 @subsubheading Synopsis
26846 -break-passcount @var{tracepoint-number} @var{passcount}
26849 Set the passcount for tracepoint @var{tracepoint-number} to
26850 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26851 is not a tracepoint, error is emitted. This corresponds to CLI
26852 command @samp{passcount}.
26854 @subheading The @code{-break-watch} Command
26855 @findex -break-watch
26857 @subsubheading Synopsis
26860 -break-watch [ -a | -r ]
26863 Create a watchpoint. With the @samp{-a} option it will create an
26864 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26865 read from or on a write to the memory location. With the @samp{-r}
26866 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26867 trigger only when the memory location is accessed for reading. Without
26868 either of the options, the watchpoint created is a regular watchpoint,
26869 i.e., it will trigger when the memory location is accessed for writing.
26870 @xref{Set Watchpoints, , Setting Watchpoints}.
26872 Note that @samp{-break-list} will report a single list of watchpoints and
26873 breakpoints inserted.
26875 @subsubheading @value{GDBN} Command
26877 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26880 @subsubheading Example
26882 Setting a watchpoint on a variable in the @code{main} function:
26887 ^done,wpt=@{number="2",exp="x"@}
26892 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26893 value=@{old="-268439212",new="55"@},
26894 frame=@{func="main",args=[],file="recursive2.c",
26895 fullname="/home/foo/bar/recursive2.c",line="5"@}
26899 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26900 the program execution twice: first for the variable changing value, then
26901 for the watchpoint going out of scope.
26906 ^done,wpt=@{number="5",exp="C"@}
26911 *stopped,reason="watchpoint-trigger",
26912 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26913 frame=@{func="callee4",args=[],
26914 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26915 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26920 *stopped,reason="watchpoint-scope",wpnum="5",
26921 frame=@{func="callee3",args=[@{name="strarg",
26922 value="0x11940 \"A string argument.\""@}],
26923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26924 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26928 Listing breakpoints and watchpoints, at different points in the program
26929 execution. Note that once the watchpoint goes out of scope, it is
26935 ^done,wpt=@{number="2",exp="C"@}
26938 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26939 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26940 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26941 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26942 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26943 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26944 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26945 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26946 addr="0x00010734",func="callee4",
26947 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26948 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26950 bkpt=@{number="2",type="watchpoint",disp="keep",
26951 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26956 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26957 value=@{old="-276895068",new="3"@},
26958 frame=@{func="callee4",args=[],
26959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26960 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26963 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26964 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26965 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26966 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26967 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26968 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26969 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26970 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26971 addr="0x00010734",func="callee4",
26972 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26973 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26975 bkpt=@{number="2",type="watchpoint",disp="keep",
26976 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26980 ^done,reason="watchpoint-scope",wpnum="2",
26981 frame=@{func="callee3",args=[@{name="strarg",
26982 value="0x11940 \"A string argument.\""@}],
26983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26984 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26987 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26988 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26989 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26990 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26991 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26992 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26993 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26994 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26995 addr="0x00010734",func="callee4",
26996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26997 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26998 thread-groups=["i1"],times="1"@}]@}
27003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27004 @node GDB/MI Catchpoint Commands
27005 @section @sc{gdb/mi} Catchpoint Commands
27007 This section documents @sc{gdb/mi} commands for manipulating
27011 * Shared Library GDB/MI Catchpoint Commands::
27012 * Ada Exception GDB/MI Catchpoint Commands::
27015 @node Shared Library GDB/MI Catchpoint Commands
27016 @subsection Shared Library @sc{gdb/mi} Catchpoints
27018 @subheading The @code{-catch-load} Command
27019 @findex -catch-load
27021 @subsubheading Synopsis
27024 -catch-load [ -t ] [ -d ] @var{regexp}
27027 Add a catchpoint for library load events. If the @samp{-t} option is used,
27028 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27029 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27030 in a disabled state. The @samp{regexp} argument is a regular
27031 expression used to match the name of the loaded library.
27034 @subsubheading @value{GDBN} Command
27036 The corresponding @value{GDBN} command is @samp{catch load}.
27038 @subsubheading Example
27041 -catch-load -t foo.so
27042 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27043 what="load of library matching foo.so",catch-type="load",times="0"@}
27048 @subheading The @code{-catch-unload} Command
27049 @findex -catch-unload
27051 @subsubheading Synopsis
27054 -catch-unload [ -t ] [ -d ] @var{regexp}
27057 Add a catchpoint for library unload events. If the @samp{-t} option is
27058 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27059 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27060 created in a disabled state. The @samp{regexp} argument is a regular
27061 expression used to match the name of the unloaded library.
27063 @subsubheading @value{GDBN} Command
27065 The corresponding @value{GDBN} command is @samp{catch unload}.
27067 @subsubheading Example
27070 -catch-unload -d bar.so
27071 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27072 what="load of library matching bar.so",catch-type="unload",times="0"@}
27076 @node Ada Exception GDB/MI Catchpoint Commands
27077 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27079 The following @sc{gdb/mi} commands can be used to create catchpoints
27080 that stop the execution when Ada exceptions are being raised.
27082 @subheading The @code{-catch-assert} Command
27083 @findex -catch-assert
27085 @subsubheading Synopsis
27088 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27091 Add a catchpoint for failed Ada assertions.
27093 The possible optional parameters for this command are:
27096 @item -c @var{condition}
27097 Make the catchpoint conditional on @var{condition}.
27099 Create a disabled catchpoint.
27101 Create a temporary catchpoint.
27104 @subsubheading @value{GDBN} Command
27106 The corresponding @value{GDBN} command is @samp{catch assert}.
27108 @subsubheading Example
27112 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27113 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27114 thread-groups=["i1"],times="0",
27115 original-location="__gnat_debug_raise_assert_failure"@}
27119 @subheading The @code{-catch-exception} Command
27120 @findex -catch-exception
27122 @subsubheading Synopsis
27125 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27129 Add a catchpoint stopping when Ada exceptions are raised.
27130 By default, the command stops the program when any Ada exception
27131 gets raised. But it is also possible, by using some of the
27132 optional parameters described below, to create more selective
27135 The possible optional parameters for this command are:
27138 @item -c @var{condition}
27139 Make the catchpoint conditional on @var{condition}.
27141 Create a disabled catchpoint.
27142 @item -e @var{exception-name}
27143 Only stop when @var{exception-name} is raised. This option cannot
27144 be used combined with @samp{-u}.
27146 Create a temporary catchpoint.
27148 Stop only when an unhandled exception gets raised. This option
27149 cannot be used combined with @samp{-e}.
27152 @subsubheading @value{GDBN} Command
27154 The corresponding @value{GDBN} commands are @samp{catch exception}
27155 and @samp{catch exception unhandled}.
27157 @subsubheading Example
27160 -catch-exception -e Program_Error
27161 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27162 enabled="y",addr="0x0000000000404874",
27163 what="`Program_Error' Ada exception", thread-groups=["i1"],
27164 times="0",original-location="__gnat_debug_raise_exception"@}
27168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27169 @node GDB/MI Program Context
27170 @section @sc{gdb/mi} Program Context
27172 @subheading The @code{-exec-arguments} Command
27173 @findex -exec-arguments
27176 @subsubheading Synopsis
27179 -exec-arguments @var{args}
27182 Set the inferior program arguments, to be used in the next
27185 @subsubheading @value{GDBN} Command
27187 The corresponding @value{GDBN} command is @samp{set args}.
27189 @subsubheading Example
27193 -exec-arguments -v word
27200 @subheading The @code{-exec-show-arguments} Command
27201 @findex -exec-show-arguments
27203 @subsubheading Synopsis
27206 -exec-show-arguments
27209 Print the arguments of the program.
27211 @subsubheading @value{GDBN} Command
27213 The corresponding @value{GDBN} command is @samp{show args}.
27215 @subsubheading Example
27220 @subheading The @code{-environment-cd} Command
27221 @findex -environment-cd
27223 @subsubheading Synopsis
27226 -environment-cd @var{pathdir}
27229 Set @value{GDBN}'s working directory.
27231 @subsubheading @value{GDBN} Command
27233 The corresponding @value{GDBN} command is @samp{cd}.
27235 @subsubheading Example
27239 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27245 @subheading The @code{-environment-directory} Command
27246 @findex -environment-directory
27248 @subsubheading Synopsis
27251 -environment-directory [ -r ] [ @var{pathdir} ]+
27254 Add directories @var{pathdir} to beginning of search path for source files.
27255 If the @samp{-r} option is used, the search path is reset to the default
27256 search path. If directories @var{pathdir} are supplied in addition to the
27257 @samp{-r} option, the search path is first reset and then addition
27259 Multiple directories may be specified, separated by blanks. Specifying
27260 multiple directories in a single command
27261 results in the directories added to the beginning of the
27262 search path in the same order they were presented in the command.
27263 If blanks are needed as
27264 part of a directory name, double-quotes should be used around
27265 the name. In the command output, the path will show up separated
27266 by the system directory-separator character. The directory-separator
27267 character must not be used
27268 in any directory name.
27269 If no directories are specified, the current search path is displayed.
27271 @subsubheading @value{GDBN} Command
27273 The corresponding @value{GDBN} command is @samp{dir}.
27275 @subsubheading Example
27279 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27280 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27282 -environment-directory ""
27283 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27285 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27286 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27288 -environment-directory -r
27289 ^done,source-path="$cdir:$cwd"
27294 @subheading The @code{-environment-path} Command
27295 @findex -environment-path
27297 @subsubheading Synopsis
27300 -environment-path [ -r ] [ @var{pathdir} ]+
27303 Add directories @var{pathdir} to beginning of search path for object files.
27304 If the @samp{-r} option is used, the search path is reset to the original
27305 search path that existed at gdb start-up. If directories @var{pathdir} are
27306 supplied in addition to the
27307 @samp{-r} option, the search path is first reset and then addition
27309 Multiple directories may be specified, separated by blanks. Specifying
27310 multiple directories in a single command
27311 results in the directories added to the beginning of the
27312 search path in the same order they were presented in the command.
27313 If blanks are needed as
27314 part of a directory name, double-quotes should be used around
27315 the name. In the command output, the path will show up separated
27316 by the system directory-separator character. The directory-separator
27317 character must not be used
27318 in any directory name.
27319 If no directories are specified, the current path is displayed.
27322 @subsubheading @value{GDBN} Command
27324 The corresponding @value{GDBN} command is @samp{path}.
27326 @subsubheading Example
27331 ^done,path="/usr/bin"
27333 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27334 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27336 -environment-path -r /usr/local/bin
27337 ^done,path="/usr/local/bin:/usr/bin"
27342 @subheading The @code{-environment-pwd} Command
27343 @findex -environment-pwd
27345 @subsubheading Synopsis
27351 Show the current working directory.
27353 @subsubheading @value{GDBN} Command
27355 The corresponding @value{GDBN} command is @samp{pwd}.
27357 @subsubheading Example
27362 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27367 @node GDB/MI Thread Commands
27368 @section @sc{gdb/mi} Thread Commands
27371 @subheading The @code{-thread-info} Command
27372 @findex -thread-info
27374 @subsubheading Synopsis
27377 -thread-info [ @var{thread-id} ]
27380 Reports information about either a specific thread, if
27381 the @var{thread-id} parameter is present, or about all
27382 threads. When printing information about all threads,
27383 also reports the current thread.
27385 @subsubheading @value{GDBN} Command
27387 The @samp{info thread} command prints the same information
27390 @subsubheading Result
27392 The result is a list of threads. The following attributes are
27393 defined for a given thread:
27397 This field exists only for the current thread. It has the value @samp{*}.
27400 The identifier that @value{GDBN} uses to refer to the thread.
27403 The identifier that the target uses to refer to the thread.
27406 Extra information about the thread, in a target-specific format. This
27410 The name of the thread. If the user specified a name using the
27411 @code{thread name} command, then this name is given. Otherwise, if
27412 @value{GDBN} can extract the thread name from the target, then that
27413 name is given. If @value{GDBN} cannot find the thread name, then this
27417 The stack frame currently executing in the thread.
27420 The thread's state. The @samp{state} field may have the following
27425 The thread is stopped. Frame information is available for stopped
27429 The thread is running. There's no frame information for running
27435 If @value{GDBN} can find the CPU core on which this thread is running,
27436 then this field is the core identifier. This field is optional.
27440 @subsubheading Example
27445 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27446 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27447 args=[]@},state="running"@},
27448 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27449 frame=@{level="0",addr="0x0804891f",func="foo",
27450 args=[@{name="i",value="10"@}],
27451 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27452 state="running"@}],
27453 current-thread-id="1"
27457 @subheading The @code{-thread-list-ids} Command
27458 @findex -thread-list-ids
27460 @subsubheading Synopsis
27466 Produces a list of the currently known @value{GDBN} thread ids. At the
27467 end of the list it also prints the total number of such threads.
27469 This command is retained for historical reasons, the
27470 @code{-thread-info} command should be used instead.
27472 @subsubheading @value{GDBN} Command
27474 Part of @samp{info threads} supplies the same information.
27476 @subsubheading Example
27481 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27482 current-thread-id="1",number-of-threads="3"
27487 @subheading The @code{-thread-select} Command
27488 @findex -thread-select
27490 @subsubheading Synopsis
27493 -thread-select @var{threadnum}
27496 Make @var{threadnum} the current thread. It prints the number of the new
27497 current thread, and the topmost frame for that thread.
27499 This command is deprecated in favor of explicitly using the
27500 @samp{--thread} option to each command.
27502 @subsubheading @value{GDBN} Command
27504 The corresponding @value{GDBN} command is @samp{thread}.
27506 @subsubheading Example
27513 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27514 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27518 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27519 number-of-threads="3"
27522 ^done,new-thread-id="3",
27523 frame=@{level="0",func="vprintf",
27524 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27525 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27530 @node GDB/MI Ada Tasking Commands
27531 @section @sc{gdb/mi} Ada Tasking Commands
27533 @subheading The @code{-ada-task-info} Command
27534 @findex -ada-task-info
27536 @subsubheading Synopsis
27539 -ada-task-info [ @var{task-id} ]
27542 Reports information about either a specific Ada task, if the
27543 @var{task-id} parameter is present, or about all Ada tasks.
27545 @subsubheading @value{GDBN} Command
27547 The @samp{info tasks} command prints the same information
27548 about all Ada tasks (@pxref{Ada Tasks}).
27550 @subsubheading Result
27552 The result is a table of Ada tasks. The following columns are
27553 defined for each Ada task:
27557 This field exists only for the current thread. It has the value @samp{*}.
27560 The identifier that @value{GDBN} uses to refer to the Ada task.
27563 The identifier that the target uses to refer to the Ada task.
27566 The identifier of the thread corresponding to the Ada task.
27568 This field should always exist, as Ada tasks are always implemented
27569 on top of a thread. But if @value{GDBN} cannot find this corresponding
27570 thread for any reason, the field is omitted.
27573 This field exists only when the task was created by another task.
27574 In this case, it provides the ID of the parent task.
27577 The base priority of the task.
27580 The current state of the task. For a detailed description of the
27581 possible states, see @ref{Ada Tasks}.
27584 The name of the task.
27588 @subsubheading Example
27592 ^done,tasks=@{nr_rows="3",nr_cols="8",
27593 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27594 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27595 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27596 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27597 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27598 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27599 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27600 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27601 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27602 state="Child Termination Wait",name="main_task"@}]@}
27606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27607 @node GDB/MI Program Execution
27608 @section @sc{gdb/mi} Program Execution
27610 These are the asynchronous commands which generate the out-of-band
27611 record @samp{*stopped}. Currently @value{GDBN} only really executes
27612 asynchronously with remote targets and this interaction is mimicked in
27615 @subheading The @code{-exec-continue} Command
27616 @findex -exec-continue
27618 @subsubheading Synopsis
27621 -exec-continue [--reverse] [--all|--thread-group N]
27624 Resumes the execution of the inferior program, which will continue
27625 to execute until it reaches a debugger stop event. If the
27626 @samp{--reverse} option is specified, execution resumes in reverse until
27627 it reaches a stop event. Stop events may include
27630 breakpoints or watchpoints
27632 signals or exceptions
27634 the end of the process (or its beginning under @samp{--reverse})
27636 the end or beginning of a replay log if one is being used.
27638 In all-stop mode (@pxref{All-Stop
27639 Mode}), may resume only one thread, or all threads, depending on the
27640 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27641 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27642 ignored in all-stop mode. If the @samp{--thread-group} options is
27643 specified, then all threads in that thread group are resumed.
27645 @subsubheading @value{GDBN} Command
27647 The corresponding @value{GDBN} corresponding is @samp{continue}.
27649 @subsubheading Example
27656 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27657 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27663 @subheading The @code{-exec-finish} Command
27664 @findex -exec-finish
27666 @subsubheading Synopsis
27669 -exec-finish [--reverse]
27672 Resumes the execution of the inferior program until the current
27673 function is exited. Displays the results returned by the function.
27674 If the @samp{--reverse} option is specified, resumes the reverse
27675 execution of the inferior program until the point where current
27676 function was called.
27678 @subsubheading @value{GDBN} Command
27680 The corresponding @value{GDBN} command is @samp{finish}.
27682 @subsubheading Example
27684 Function returning @code{void}.
27691 *stopped,reason="function-finished",frame=@{func="main",args=[],
27692 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27696 Function returning other than @code{void}. The name of the internal
27697 @value{GDBN} variable storing the result is printed, together with the
27704 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27705 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27706 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27707 gdb-result-var="$1",return-value="0"
27712 @subheading The @code{-exec-interrupt} Command
27713 @findex -exec-interrupt
27715 @subsubheading Synopsis
27718 -exec-interrupt [--all|--thread-group N]
27721 Interrupts the background execution of the target. Note how the token
27722 associated with the stop message is the one for the execution command
27723 that has been interrupted. The token for the interrupt itself only
27724 appears in the @samp{^done} output. If the user is trying to
27725 interrupt a non-running program, an error message will be printed.
27727 Note that when asynchronous execution is enabled, this command is
27728 asynchronous just like other execution commands. That is, first the
27729 @samp{^done} response will be printed, and the target stop will be
27730 reported after that using the @samp{*stopped} notification.
27732 In non-stop mode, only the context thread is interrupted by default.
27733 All threads (in all inferiors) will be interrupted if the
27734 @samp{--all} option is specified. If the @samp{--thread-group}
27735 option is specified, all threads in that group will be interrupted.
27737 @subsubheading @value{GDBN} Command
27739 The corresponding @value{GDBN} command is @samp{interrupt}.
27741 @subsubheading Example
27752 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27753 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27754 fullname="/home/foo/bar/try.c",line="13"@}
27759 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27763 @subheading The @code{-exec-jump} Command
27766 @subsubheading Synopsis
27769 -exec-jump @var{location}
27772 Resumes execution of the inferior program at the location specified by
27773 parameter. @xref{Specify Location}, for a description of the
27774 different forms of @var{location}.
27776 @subsubheading @value{GDBN} Command
27778 The corresponding @value{GDBN} command is @samp{jump}.
27780 @subsubheading Example
27783 -exec-jump foo.c:10
27784 *running,thread-id="all"
27789 @subheading The @code{-exec-next} Command
27792 @subsubheading Synopsis
27795 -exec-next [--reverse]
27798 Resumes execution of the inferior program, stopping when the beginning
27799 of the next source line is reached.
27801 If the @samp{--reverse} option is specified, resumes reverse execution
27802 of the inferior program, stopping at the beginning of the previous
27803 source line. If you issue this command on the first line of a
27804 function, it will take you back to the caller of that function, to the
27805 source line where the function was called.
27808 @subsubheading @value{GDBN} Command
27810 The corresponding @value{GDBN} command is @samp{next}.
27812 @subsubheading Example
27818 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27823 @subheading The @code{-exec-next-instruction} Command
27824 @findex -exec-next-instruction
27826 @subsubheading Synopsis
27829 -exec-next-instruction [--reverse]
27832 Executes one machine instruction. If the instruction is a function
27833 call, continues until the function returns. If the program stops at an
27834 instruction in the middle of a source line, the address will be
27837 If the @samp{--reverse} option is specified, resumes reverse execution
27838 of the inferior program, stopping at the previous instruction. If the
27839 previously executed instruction was a return from another function,
27840 it will continue to execute in reverse until the call to that function
27841 (from the current stack frame) is reached.
27843 @subsubheading @value{GDBN} Command
27845 The corresponding @value{GDBN} command is @samp{nexti}.
27847 @subsubheading Example
27851 -exec-next-instruction
27855 *stopped,reason="end-stepping-range",
27856 addr="0x000100d4",line="5",file="hello.c"
27861 @subheading The @code{-exec-return} Command
27862 @findex -exec-return
27864 @subsubheading Synopsis
27870 Makes current function return immediately. Doesn't execute the inferior.
27871 Displays the new current frame.
27873 @subsubheading @value{GDBN} Command
27875 The corresponding @value{GDBN} command is @samp{return}.
27877 @subsubheading Example
27881 200-break-insert callee4
27882 200^done,bkpt=@{number="1",addr="0x00010734",
27883 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27888 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27889 frame=@{func="callee4",args=[],
27890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27891 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27897 111^done,frame=@{level="0",func="callee3",
27898 args=[@{name="strarg",
27899 value="0x11940 \"A string argument.\""@}],
27900 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27901 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27906 @subheading The @code{-exec-run} Command
27909 @subsubheading Synopsis
27912 -exec-run [ --all | --thread-group N ] [ --start ]
27915 Starts execution of the inferior from the beginning. The inferior
27916 executes until either a breakpoint is encountered or the program
27917 exits. In the latter case the output will include an exit code, if
27918 the program has exited exceptionally.
27920 When neither the @samp{--all} nor the @samp{--thread-group} option
27921 is specified, the current inferior is started. If the
27922 @samp{--thread-group} option is specified, it should refer to a thread
27923 group of type @samp{process}, and that thread group will be started.
27924 If the @samp{--all} option is specified, then all inferiors will be started.
27926 Using the @samp{--start} option instructs the debugger to stop
27927 the execution at the start of the inferior's main subprogram,
27928 following the same behavior as the @code{start} command
27929 (@pxref{Starting}).
27931 @subsubheading @value{GDBN} Command
27933 The corresponding @value{GDBN} command is @samp{run}.
27935 @subsubheading Examples
27940 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27945 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27946 frame=@{func="main",args=[],file="recursive2.c",
27947 fullname="/home/foo/bar/recursive2.c",line="4"@}
27952 Program exited normally:
27960 *stopped,reason="exited-normally"
27965 Program exited exceptionally:
27973 *stopped,reason="exited",exit-code="01"
27977 Another way the program can terminate is if it receives a signal such as
27978 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27982 *stopped,reason="exited-signalled",signal-name="SIGINT",
27983 signal-meaning="Interrupt"
27987 @c @subheading -exec-signal
27990 @subheading The @code{-exec-step} Command
27993 @subsubheading Synopsis
27996 -exec-step [--reverse]
27999 Resumes execution of the inferior program, stopping when the beginning
28000 of the next source line is reached, if the next source line is not a
28001 function call. If it is, stop at the first instruction of the called
28002 function. If the @samp{--reverse} option is specified, resumes reverse
28003 execution of the inferior program, stopping at the beginning of the
28004 previously executed source line.
28006 @subsubheading @value{GDBN} Command
28008 The corresponding @value{GDBN} command is @samp{step}.
28010 @subsubheading Example
28012 Stepping into a function:
28018 *stopped,reason="end-stepping-range",
28019 frame=@{func="foo",args=[@{name="a",value="10"@},
28020 @{name="b",value="0"@}],file="recursive2.c",
28021 fullname="/home/foo/bar/recursive2.c",line="11"@}
28031 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28036 @subheading The @code{-exec-step-instruction} Command
28037 @findex -exec-step-instruction
28039 @subsubheading Synopsis
28042 -exec-step-instruction [--reverse]
28045 Resumes the inferior which executes one machine instruction. If the
28046 @samp{--reverse} option is specified, resumes reverse execution of the
28047 inferior program, stopping at the previously executed instruction.
28048 The output, once @value{GDBN} has stopped, will vary depending on
28049 whether we have stopped in the middle of a source line or not. In the
28050 former case, the address at which the program stopped will be printed
28053 @subsubheading @value{GDBN} Command
28055 The corresponding @value{GDBN} command is @samp{stepi}.
28057 @subsubheading Example
28061 -exec-step-instruction
28065 *stopped,reason="end-stepping-range",
28066 frame=@{func="foo",args=[],file="try.c",
28067 fullname="/home/foo/bar/try.c",line="10"@}
28069 -exec-step-instruction
28073 *stopped,reason="end-stepping-range",
28074 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28075 fullname="/home/foo/bar/try.c",line="10"@}
28080 @subheading The @code{-exec-until} Command
28081 @findex -exec-until
28083 @subsubheading Synopsis
28086 -exec-until [ @var{location} ]
28089 Executes the inferior until the @var{location} specified in the
28090 argument is reached. If there is no argument, the inferior executes
28091 until a source line greater than the current one is reached. The
28092 reason for stopping in this case will be @samp{location-reached}.
28094 @subsubheading @value{GDBN} Command
28096 The corresponding @value{GDBN} command is @samp{until}.
28098 @subsubheading Example
28102 -exec-until recursive2.c:6
28106 *stopped,reason="location-reached",frame=@{func="main",args=[],
28107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28112 @subheading -file-clear
28113 Is this going away????
28116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28117 @node GDB/MI Stack Manipulation
28118 @section @sc{gdb/mi} Stack Manipulation Commands
28120 @subheading The @code{-enable-frame-filters} Command
28121 @findex -enable-frame-filters
28124 -enable-frame-filters
28127 @value{GDBN} allows Python-based frame filters to affect the output of
28128 the MI commands relating to stack traces. As there is no way to
28129 implement this in a fully backward-compatible way, a front end must
28130 request that this functionality be enabled.
28132 Once enabled, this feature cannot be disabled.
28134 Note that if Python support has not been compiled into @value{GDBN},
28135 this command will still succeed (and do nothing).
28137 @subheading The @code{-stack-info-frame} Command
28138 @findex -stack-info-frame
28140 @subsubheading Synopsis
28146 Get info on the selected frame.
28148 @subsubheading @value{GDBN} Command
28150 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28151 (without arguments).
28153 @subsubheading Example
28158 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28159 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28160 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28164 @subheading The @code{-stack-info-depth} Command
28165 @findex -stack-info-depth
28167 @subsubheading Synopsis
28170 -stack-info-depth [ @var{max-depth} ]
28173 Return the depth of the stack. If the integer argument @var{max-depth}
28174 is specified, do not count beyond @var{max-depth} frames.
28176 @subsubheading @value{GDBN} Command
28178 There's no equivalent @value{GDBN} command.
28180 @subsubheading Example
28182 For a stack with frame levels 0 through 11:
28189 -stack-info-depth 4
28192 -stack-info-depth 12
28195 -stack-info-depth 11
28198 -stack-info-depth 13
28203 @anchor{-stack-list-arguments}
28204 @subheading The @code{-stack-list-arguments} Command
28205 @findex -stack-list-arguments
28207 @subsubheading Synopsis
28210 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28211 [ @var{low-frame} @var{high-frame} ]
28214 Display a list of the arguments for the frames between @var{low-frame}
28215 and @var{high-frame} (inclusive). If @var{low-frame} and
28216 @var{high-frame} are not provided, list the arguments for the whole
28217 call stack. If the two arguments are equal, show the single frame
28218 at the corresponding level. It is an error if @var{low-frame} is
28219 larger than the actual number of frames. On the other hand,
28220 @var{high-frame} may be larger than the actual number of frames, in
28221 which case only existing frames will be returned.
28223 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28224 the variables; if it is 1 or @code{--all-values}, print also their
28225 values; and if it is 2 or @code{--simple-values}, print the name,
28226 type and value for simple data types, and the name and type for arrays,
28227 structures and unions. If the option @code{--no-frame-filters} is
28228 supplied, then Python frame filters will not be executed.
28230 If the @code{--skip-unavailable} option is specified, arguments that
28231 are not available are not listed. Partially available arguments
28232 are still displayed, however.
28234 Use of this command to obtain arguments in a single frame is
28235 deprecated in favor of the @samp{-stack-list-variables} command.
28237 @subsubheading @value{GDBN} Command
28239 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28240 @samp{gdb_get_args} command which partially overlaps with the
28241 functionality of @samp{-stack-list-arguments}.
28243 @subsubheading Example
28250 frame=@{level="0",addr="0x00010734",func="callee4",
28251 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28252 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28253 frame=@{level="1",addr="0x0001076c",func="callee3",
28254 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28255 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28256 frame=@{level="2",addr="0x0001078c",func="callee2",
28257 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28258 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28259 frame=@{level="3",addr="0x000107b4",func="callee1",
28260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28262 frame=@{level="4",addr="0x000107e0",func="main",
28263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28266 -stack-list-arguments 0
28269 frame=@{level="0",args=[]@},
28270 frame=@{level="1",args=[name="strarg"]@},
28271 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28272 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28273 frame=@{level="4",args=[]@}]
28275 -stack-list-arguments 1
28278 frame=@{level="0",args=[]@},
28280 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28281 frame=@{level="2",args=[
28282 @{name="intarg",value="2"@},
28283 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28284 @{frame=@{level="3",args=[
28285 @{name="intarg",value="2"@},
28286 @{name="strarg",value="0x11940 \"A string argument.\""@},
28287 @{name="fltarg",value="3.5"@}]@},
28288 frame=@{level="4",args=[]@}]
28290 -stack-list-arguments 0 2 2
28291 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28293 -stack-list-arguments 1 2 2
28294 ^done,stack-args=[frame=@{level="2",
28295 args=[@{name="intarg",value="2"@},
28296 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28300 @c @subheading -stack-list-exception-handlers
28303 @anchor{-stack-list-frames}
28304 @subheading The @code{-stack-list-frames} Command
28305 @findex -stack-list-frames
28307 @subsubheading Synopsis
28310 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28313 List the frames currently on the stack. For each frame it displays the
28318 The frame number, 0 being the topmost frame, i.e., the innermost function.
28320 The @code{$pc} value for that frame.
28324 File name of the source file where the function lives.
28325 @item @var{fullname}
28326 The full file name of the source file where the function lives.
28328 Line number corresponding to the @code{$pc}.
28330 The shared library where this function is defined. This is only given
28331 if the frame's function is not known.
28334 If invoked without arguments, this command prints a backtrace for the
28335 whole stack. If given two integer arguments, it shows the frames whose
28336 levels are between the two arguments (inclusive). If the two arguments
28337 are equal, it shows the single frame at the corresponding level. It is
28338 an error if @var{low-frame} is larger than the actual number of
28339 frames. On the other hand, @var{high-frame} may be larger than the
28340 actual number of frames, in which case only existing frames will be
28341 returned. If the option @code{--no-frame-filters} is supplied, then
28342 Python frame filters will not be executed.
28344 @subsubheading @value{GDBN} Command
28346 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28348 @subsubheading Example
28350 Full stack backtrace:
28356 [frame=@{level="0",addr="0x0001076c",func="foo",
28357 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28358 frame=@{level="1",addr="0x000107a4",func="foo",
28359 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28360 frame=@{level="2",addr="0x000107a4",func="foo",
28361 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28362 frame=@{level="3",addr="0x000107a4",func="foo",
28363 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28364 frame=@{level="4",addr="0x000107a4",func="foo",
28365 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28366 frame=@{level="5",addr="0x000107a4",func="foo",
28367 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28368 frame=@{level="6",addr="0x000107a4",func="foo",
28369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28370 frame=@{level="7",addr="0x000107a4",func="foo",
28371 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28372 frame=@{level="8",addr="0x000107a4",func="foo",
28373 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28374 frame=@{level="9",addr="0x000107a4",func="foo",
28375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28376 frame=@{level="10",addr="0x000107a4",func="foo",
28377 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28378 frame=@{level="11",addr="0x00010738",func="main",
28379 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28383 Show frames between @var{low_frame} and @var{high_frame}:
28387 -stack-list-frames 3 5
28389 [frame=@{level="3",addr="0x000107a4",func="foo",
28390 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28391 frame=@{level="4",addr="0x000107a4",func="foo",
28392 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28393 frame=@{level="5",addr="0x000107a4",func="foo",
28394 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28398 Show a single frame:
28402 -stack-list-frames 3 3
28404 [frame=@{level="3",addr="0x000107a4",func="foo",
28405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28410 @subheading The @code{-stack-list-locals} Command
28411 @findex -stack-list-locals
28412 @anchor{-stack-list-locals}
28414 @subsubheading Synopsis
28417 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28420 Display the local variable names for the selected frame. If
28421 @var{print-values} is 0 or @code{--no-values}, print only the names of
28422 the variables; if it is 1 or @code{--all-values}, print also their
28423 values; and if it is 2 or @code{--simple-values}, print the name,
28424 type and value for simple data types, and the name and type for arrays,
28425 structures and unions. In this last case, a frontend can immediately
28426 display the value of simple data types and create variable objects for
28427 other data types when the user wishes to explore their values in
28428 more detail. If the option @code{--no-frame-filters} is supplied, then
28429 Python frame filters will not be executed.
28431 If the @code{--skip-unavailable} option is specified, local variables
28432 that are not available are not listed. Partially available local
28433 variables are still displayed, however.
28435 This command is deprecated in favor of the
28436 @samp{-stack-list-variables} command.
28438 @subsubheading @value{GDBN} Command
28440 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28442 @subsubheading Example
28446 -stack-list-locals 0
28447 ^done,locals=[name="A",name="B",name="C"]
28449 -stack-list-locals --all-values
28450 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28451 @{name="C",value="@{1, 2, 3@}"@}]
28452 -stack-list-locals --simple-values
28453 ^done,locals=[@{name="A",type="int",value="1"@},
28454 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28458 @anchor{-stack-list-variables}
28459 @subheading The @code{-stack-list-variables} Command
28460 @findex -stack-list-variables
28462 @subsubheading Synopsis
28465 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28468 Display the names of local variables and function arguments for the selected frame. If
28469 @var{print-values} is 0 or @code{--no-values}, print only the names of
28470 the variables; if it is 1 or @code{--all-values}, print also their
28471 values; and if it is 2 or @code{--simple-values}, print the name,
28472 type and value for simple data types, and the name and type for arrays,
28473 structures and unions. If the option @code{--no-frame-filters} is
28474 supplied, then Python frame filters will not be executed.
28476 If the @code{--skip-unavailable} option is specified, local variables
28477 and arguments that are not available are not listed. Partially
28478 available arguments and local variables are still displayed, however.
28480 @subsubheading Example
28484 -stack-list-variables --thread 1 --frame 0 --all-values
28485 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28490 @subheading The @code{-stack-select-frame} Command
28491 @findex -stack-select-frame
28493 @subsubheading Synopsis
28496 -stack-select-frame @var{framenum}
28499 Change the selected frame. Select a different frame @var{framenum} on
28502 This command in deprecated in favor of passing the @samp{--frame}
28503 option to every command.
28505 @subsubheading @value{GDBN} Command
28507 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28508 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28510 @subsubheading Example
28514 -stack-select-frame 2
28519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28520 @node GDB/MI Variable Objects
28521 @section @sc{gdb/mi} Variable Objects
28525 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28527 For the implementation of a variable debugger window (locals, watched
28528 expressions, etc.), we are proposing the adaptation of the existing code
28529 used by @code{Insight}.
28531 The two main reasons for that are:
28535 It has been proven in practice (it is already on its second generation).
28538 It will shorten development time (needless to say how important it is
28542 The original interface was designed to be used by Tcl code, so it was
28543 slightly changed so it could be used through @sc{gdb/mi}. This section
28544 describes the @sc{gdb/mi} operations that will be available and gives some
28545 hints about their use.
28547 @emph{Note}: In addition to the set of operations described here, we
28548 expect the @sc{gui} implementation of a variable window to require, at
28549 least, the following operations:
28552 @item @code{-gdb-show} @code{output-radix}
28553 @item @code{-stack-list-arguments}
28554 @item @code{-stack-list-locals}
28555 @item @code{-stack-select-frame}
28560 @subheading Introduction to Variable Objects
28562 @cindex variable objects in @sc{gdb/mi}
28564 Variable objects are "object-oriented" MI interface for examining and
28565 changing values of expressions. Unlike some other MI interfaces that
28566 work with expressions, variable objects are specifically designed for
28567 simple and efficient presentation in the frontend. A variable object
28568 is identified by string name. When a variable object is created, the
28569 frontend specifies the expression for that variable object. The
28570 expression can be a simple variable, or it can be an arbitrary complex
28571 expression, and can even involve CPU registers. After creating a
28572 variable object, the frontend can invoke other variable object
28573 operations---for example to obtain or change the value of a variable
28574 object, or to change display format.
28576 Variable objects have hierarchical tree structure. Any variable object
28577 that corresponds to a composite type, such as structure in C, has
28578 a number of child variable objects, for example corresponding to each
28579 element of a structure. A child variable object can itself have
28580 children, recursively. Recursion ends when we reach
28581 leaf variable objects, which always have built-in types. Child variable
28582 objects are created only by explicit request, so if a frontend
28583 is not interested in the children of a particular variable object, no
28584 child will be created.
28586 For a leaf variable object it is possible to obtain its value as a
28587 string, or set the value from a string. String value can be also
28588 obtained for a non-leaf variable object, but it's generally a string
28589 that only indicates the type of the object, and does not list its
28590 contents. Assignment to a non-leaf variable object is not allowed.
28592 A frontend does not need to read the values of all variable objects each time
28593 the program stops. Instead, MI provides an update command that lists all
28594 variable objects whose values has changed since the last update
28595 operation. This considerably reduces the amount of data that must
28596 be transferred to the frontend. As noted above, children variable
28597 objects are created on demand, and only leaf variable objects have a
28598 real value. As result, gdb will read target memory only for leaf
28599 variables that frontend has created.
28601 The automatic update is not always desirable. For example, a frontend
28602 might want to keep a value of some expression for future reference,
28603 and never update it. For another example, fetching memory is
28604 relatively slow for embedded targets, so a frontend might want
28605 to disable automatic update for the variables that are either not
28606 visible on the screen, or ``closed''. This is possible using so
28607 called ``frozen variable objects''. Such variable objects are never
28608 implicitly updated.
28610 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28611 fixed variable object, the expression is parsed when the variable
28612 object is created, including associating identifiers to specific
28613 variables. The meaning of expression never changes. For a floating
28614 variable object the values of variables whose names appear in the
28615 expressions are re-evaluated every time in the context of the current
28616 frame. Consider this example:
28621 struct work_state state;
28628 If a fixed variable object for the @code{state} variable is created in
28629 this function, and we enter the recursive call, the variable
28630 object will report the value of @code{state} in the top-level
28631 @code{do_work} invocation. On the other hand, a floating variable
28632 object will report the value of @code{state} in the current frame.
28634 If an expression specified when creating a fixed variable object
28635 refers to a local variable, the variable object becomes bound to the
28636 thread and frame in which the variable object is created. When such
28637 variable object is updated, @value{GDBN} makes sure that the
28638 thread/frame combination the variable object is bound to still exists,
28639 and re-evaluates the variable object in context of that thread/frame.
28641 The following is the complete set of @sc{gdb/mi} operations defined to
28642 access this functionality:
28644 @multitable @columnfractions .4 .6
28645 @item @strong{Operation}
28646 @tab @strong{Description}
28648 @item @code{-enable-pretty-printing}
28649 @tab enable Python-based pretty-printing
28650 @item @code{-var-create}
28651 @tab create a variable object
28652 @item @code{-var-delete}
28653 @tab delete the variable object and/or its children
28654 @item @code{-var-set-format}
28655 @tab set the display format of this variable
28656 @item @code{-var-show-format}
28657 @tab show the display format of this variable
28658 @item @code{-var-info-num-children}
28659 @tab tells how many children this object has
28660 @item @code{-var-list-children}
28661 @tab return a list of the object's children
28662 @item @code{-var-info-type}
28663 @tab show the type of this variable object
28664 @item @code{-var-info-expression}
28665 @tab print parent-relative expression that this variable object represents
28666 @item @code{-var-info-path-expression}
28667 @tab print full expression that this variable object represents
28668 @item @code{-var-show-attributes}
28669 @tab is this variable editable? does it exist here?
28670 @item @code{-var-evaluate-expression}
28671 @tab get the value of this variable
28672 @item @code{-var-assign}
28673 @tab set the value of this variable
28674 @item @code{-var-update}
28675 @tab update the variable and its children
28676 @item @code{-var-set-frozen}
28677 @tab set frozeness attribute
28678 @item @code{-var-set-update-range}
28679 @tab set range of children to display on update
28682 In the next subsection we describe each operation in detail and suggest
28683 how it can be used.
28685 @subheading Description And Use of Operations on Variable Objects
28687 @subheading The @code{-enable-pretty-printing} Command
28688 @findex -enable-pretty-printing
28691 -enable-pretty-printing
28694 @value{GDBN} allows Python-based visualizers to affect the output of the
28695 MI variable object commands. However, because there was no way to
28696 implement this in a fully backward-compatible way, a front end must
28697 request that this functionality be enabled.
28699 Once enabled, this feature cannot be disabled.
28701 Note that if Python support has not been compiled into @value{GDBN},
28702 this command will still succeed (and do nothing).
28704 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28705 may work differently in future versions of @value{GDBN}.
28707 @subheading The @code{-var-create} Command
28708 @findex -var-create
28710 @subsubheading Synopsis
28713 -var-create @{@var{name} | "-"@}
28714 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28717 This operation creates a variable object, which allows the monitoring of
28718 a variable, the result of an expression, a memory cell or a CPU
28721 The @var{name} parameter is the string by which the object can be
28722 referenced. It must be unique. If @samp{-} is specified, the varobj
28723 system will generate a string ``varNNNNNN'' automatically. It will be
28724 unique provided that one does not specify @var{name} of that format.
28725 The command fails if a duplicate name is found.
28727 The frame under which the expression should be evaluated can be
28728 specified by @var{frame-addr}. A @samp{*} indicates that the current
28729 frame should be used. A @samp{@@} indicates that a floating variable
28730 object must be created.
28732 @var{expression} is any expression valid on the current language set (must not
28733 begin with a @samp{*}), or one of the following:
28737 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28740 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28743 @samp{$@var{regname}} --- a CPU register name
28746 @cindex dynamic varobj
28747 A varobj's contents may be provided by a Python-based pretty-printer. In this
28748 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28749 have slightly different semantics in some cases. If the
28750 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28751 will never create a dynamic varobj. This ensures backward
28752 compatibility for existing clients.
28754 @subsubheading Result
28756 This operation returns attributes of the newly-created varobj. These
28761 The name of the varobj.
28764 The number of children of the varobj. This number is not necessarily
28765 reliable for a dynamic varobj. Instead, you must examine the
28766 @samp{has_more} attribute.
28769 The varobj's scalar value. For a varobj whose type is some sort of
28770 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28771 will not be interesting.
28774 The varobj's type. This is a string representation of the type, as
28775 would be printed by the @value{GDBN} CLI. If @samp{print object}
28776 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28777 @emph{actual} (derived) type of the object is shown rather than the
28778 @emph{declared} one.
28781 If a variable object is bound to a specific thread, then this is the
28782 thread's identifier.
28785 For a dynamic varobj, this indicates whether there appear to be any
28786 children available. For a non-dynamic varobj, this will be 0.
28789 This attribute will be present and have the value @samp{1} if the
28790 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28791 then this attribute will not be present.
28794 A dynamic varobj can supply a display hint to the front end. The
28795 value comes directly from the Python pretty-printer object's
28796 @code{display_hint} method. @xref{Pretty Printing API}.
28799 Typical output will look like this:
28802 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28803 has_more="@var{has_more}"
28807 @subheading The @code{-var-delete} Command
28808 @findex -var-delete
28810 @subsubheading Synopsis
28813 -var-delete [ -c ] @var{name}
28816 Deletes a previously created variable object and all of its children.
28817 With the @samp{-c} option, just deletes the children.
28819 Returns an error if the object @var{name} is not found.
28822 @subheading The @code{-var-set-format} Command
28823 @findex -var-set-format
28825 @subsubheading Synopsis
28828 -var-set-format @var{name} @var{format-spec}
28831 Sets the output format for the value of the object @var{name} to be
28834 @anchor{-var-set-format}
28835 The syntax for the @var{format-spec} is as follows:
28838 @var{format-spec} @expansion{}
28839 @{binary | decimal | hexadecimal | octal | natural@}
28842 The natural format is the default format choosen automatically
28843 based on the variable type (like decimal for an @code{int}, hex
28844 for pointers, etc.).
28846 For a variable with children, the format is set only on the
28847 variable itself, and the children are not affected.
28849 @subheading The @code{-var-show-format} Command
28850 @findex -var-show-format
28852 @subsubheading Synopsis
28855 -var-show-format @var{name}
28858 Returns the format used to display the value of the object @var{name}.
28861 @var{format} @expansion{}
28866 @subheading The @code{-var-info-num-children} Command
28867 @findex -var-info-num-children
28869 @subsubheading Synopsis
28872 -var-info-num-children @var{name}
28875 Returns the number of children of a variable object @var{name}:
28881 Note that this number is not completely reliable for a dynamic varobj.
28882 It will return the current number of children, but more children may
28886 @subheading The @code{-var-list-children} Command
28887 @findex -var-list-children
28889 @subsubheading Synopsis
28892 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28894 @anchor{-var-list-children}
28896 Return a list of the children of the specified variable object and
28897 create variable objects for them, if they do not already exist. With
28898 a single argument or if @var{print-values} has a value of 0 or
28899 @code{--no-values}, print only the names of the variables; if
28900 @var{print-values} is 1 or @code{--all-values}, also print their
28901 values; and if it is 2 or @code{--simple-values} print the name and
28902 value for simple data types and just the name for arrays, structures
28905 @var{from} and @var{to}, if specified, indicate the range of children
28906 to report. If @var{from} or @var{to} is less than zero, the range is
28907 reset and all children will be reported. Otherwise, children starting
28908 at @var{from} (zero-based) and up to and excluding @var{to} will be
28911 If a child range is requested, it will only affect the current call to
28912 @code{-var-list-children}, but not future calls to @code{-var-update}.
28913 For this, you must instead use @code{-var-set-update-range}. The
28914 intent of this approach is to enable a front end to implement any
28915 update approach it likes; for example, scrolling a view may cause the
28916 front end to request more children with @code{-var-list-children}, and
28917 then the front end could call @code{-var-set-update-range} with a
28918 different range to ensure that future updates are restricted to just
28921 For each child the following results are returned:
28926 Name of the variable object created for this child.
28929 The expression to be shown to the user by the front end to designate this child.
28930 For example this may be the name of a structure member.
28932 For a dynamic varobj, this value cannot be used to form an
28933 expression. There is no way to do this at all with a dynamic varobj.
28935 For C/C@t{++} structures there are several pseudo children returned to
28936 designate access qualifiers. For these pseudo children @var{exp} is
28937 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28938 type and value are not present.
28940 A dynamic varobj will not report the access qualifying
28941 pseudo-children, regardless of the language. This information is not
28942 available at all with a dynamic varobj.
28945 Number of children this child has. For a dynamic varobj, this will be
28949 The type of the child. If @samp{print object}
28950 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28951 @emph{actual} (derived) type of the object is shown rather than the
28952 @emph{declared} one.
28955 If values were requested, this is the value.
28958 If this variable object is associated with a thread, this is the thread id.
28959 Otherwise this result is not present.
28962 If the variable object is frozen, this variable will be present with a value of 1.
28965 A dynamic varobj can supply a display hint to the front end. The
28966 value comes directly from the Python pretty-printer object's
28967 @code{display_hint} method. @xref{Pretty Printing API}.
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.
28976 The result may have its own attributes:
28980 A dynamic varobj can supply a display hint to the front end. The
28981 value comes directly from the Python pretty-printer object's
28982 @code{display_hint} method. @xref{Pretty Printing API}.
28985 This is an integer attribute which is nonzero if there are children
28986 remaining after the end of the selected range.
28989 @subsubheading Example
28993 -var-list-children n
28994 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28995 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28997 -var-list-children --all-values n
28998 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28999 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29003 @subheading The @code{-var-info-type} Command
29004 @findex -var-info-type
29006 @subsubheading Synopsis
29009 -var-info-type @var{name}
29012 Returns the type of the specified variable @var{name}. The type is
29013 returned as a string in the same format as it is output by the
29017 type=@var{typename}
29021 @subheading The @code{-var-info-expression} Command
29022 @findex -var-info-expression
29024 @subsubheading Synopsis
29027 -var-info-expression @var{name}
29030 Returns a string that is suitable for presenting this
29031 variable object in user interface. The string is generally
29032 not valid expression in the current language, and cannot be evaluated.
29034 For example, if @code{a} is an array, and variable object
29035 @code{A} was created for @code{a}, then we'll get this output:
29038 (gdb) -var-info-expression A.1
29039 ^done,lang="C",exp="1"
29043 Here, the value of @code{lang} is the language name, which can be
29044 found in @ref{Supported Languages}.
29046 Note that the output of the @code{-var-list-children} command also
29047 includes those expressions, so the @code{-var-info-expression} command
29050 @subheading The @code{-var-info-path-expression} Command
29051 @findex -var-info-path-expression
29053 @subsubheading Synopsis
29056 -var-info-path-expression @var{name}
29059 Returns an expression that can be evaluated in the current
29060 context and will yield the same value that a variable object has.
29061 Compare this with the @code{-var-info-expression} command, which
29062 result can be used only for UI presentation. Typical use of
29063 the @code{-var-info-path-expression} command is creating a
29064 watchpoint from a variable object.
29066 This command is currently not valid for children of a dynamic varobj,
29067 and will give an error when invoked on one.
29069 For example, suppose @code{C} is a C@t{++} class, derived from class
29070 @code{Base}, and that the @code{Base} class has a member called
29071 @code{m_size}. Assume a variable @code{c} is has the type of
29072 @code{C} and a variable object @code{C} was created for variable
29073 @code{c}. Then, we'll get this output:
29075 (gdb) -var-info-path-expression C.Base.public.m_size
29076 ^done,path_expr=((Base)c).m_size)
29079 @subheading The @code{-var-show-attributes} Command
29080 @findex -var-show-attributes
29082 @subsubheading Synopsis
29085 -var-show-attributes @var{name}
29088 List attributes of the specified variable object @var{name}:
29091 status=@var{attr} [ ( ,@var{attr} )* ]
29095 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29097 @subheading The @code{-var-evaluate-expression} Command
29098 @findex -var-evaluate-expression
29100 @subsubheading Synopsis
29103 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29106 Evaluates the expression that is represented by the specified variable
29107 object and returns its value as a string. The format of the string
29108 can be specified with the @samp{-f} option. The possible values of
29109 this option are the same as for @code{-var-set-format}
29110 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29111 the current display format will be used. The current display format
29112 can be changed using the @code{-var-set-format} command.
29118 Note that one must invoke @code{-var-list-children} for a variable
29119 before the value of a child variable can be evaluated.
29121 @subheading The @code{-var-assign} Command
29122 @findex -var-assign
29124 @subsubheading Synopsis
29127 -var-assign @var{name} @var{expression}
29130 Assigns the value of @var{expression} to the variable object specified
29131 by @var{name}. The object must be @samp{editable}. If the variable's
29132 value is altered by the assign, the variable will show up in any
29133 subsequent @code{-var-update} list.
29135 @subsubheading Example
29143 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29147 @subheading The @code{-var-update} Command
29148 @findex -var-update
29150 @subsubheading Synopsis
29153 -var-update [@var{print-values}] @{@var{name} | "*"@}
29156 Reevaluate the expressions corresponding to the variable object
29157 @var{name} and all its direct and indirect children, and return the
29158 list of variable objects whose values have changed; @var{name} must
29159 be a root variable object. Here, ``changed'' means that the result of
29160 @code{-var-evaluate-expression} before and after the
29161 @code{-var-update} is different. If @samp{*} is used as the variable
29162 object names, all existing variable objects are updated, except
29163 for frozen ones (@pxref{-var-set-frozen}). The option
29164 @var{print-values} determines whether both names and values, or just
29165 names are printed. The possible values of this option are the same
29166 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29167 recommended to use the @samp{--all-values} option, to reduce the
29168 number of MI commands needed on each program stop.
29170 With the @samp{*} parameter, if a variable object is bound to a
29171 currently running thread, it will not be updated, without any
29174 If @code{-var-set-update-range} was previously used on a varobj, then
29175 only the selected range of children will be reported.
29177 @code{-var-update} reports all the changed varobjs in a tuple named
29180 Each item in the change list is itself a tuple holding:
29184 The name of the varobj.
29187 If values were requested for this update, then this field will be
29188 present and will hold the value of the varobj.
29191 @anchor{-var-update}
29192 This field is a string which may take one of three values:
29196 The variable object's current value is valid.
29199 The variable object does not currently hold a valid value but it may
29200 hold one in the future if its associated expression comes back into
29204 The variable object no longer holds a valid value.
29205 This can occur when the executable file being debugged has changed,
29206 either through recompilation or by using the @value{GDBN} @code{file}
29207 command. The front end should normally choose to delete these variable
29211 In the future new values may be added to this list so the front should
29212 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29215 This is only present if the varobj is still valid. If the type
29216 changed, then this will be the string @samp{true}; otherwise it will
29219 When a varobj's type changes, its children are also likely to have
29220 become incorrect. Therefore, the varobj's children are automatically
29221 deleted when this attribute is @samp{true}. Also, the varobj's update
29222 range, when set using the @code{-var-set-update-range} command, is
29226 If the varobj's type changed, then this field will be present and will
29229 @item new_num_children
29230 For a dynamic varobj, if the number of children changed, or if the
29231 type changed, this will be the new number of children.
29233 The @samp{numchild} field in other varobj responses is generally not
29234 valid for a dynamic varobj -- it will show the number of children that
29235 @value{GDBN} knows about, but because dynamic varobjs lazily
29236 instantiate their children, this will not reflect the number of
29237 children which may be available.
29239 The @samp{new_num_children} attribute only reports changes to the
29240 number of children known by @value{GDBN}. This is the only way to
29241 detect whether an update has removed children (which necessarily can
29242 only happen at the end of the update range).
29245 The display hint, if any.
29248 This is an integer value, which will be 1 if there are more children
29249 available outside the varobj's update range.
29252 This attribute will be present and have the value @samp{1} if the
29253 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29254 then this attribute will not be present.
29257 If new children were added to a dynamic varobj within the selected
29258 update range (as set by @code{-var-set-update-range}), then they will
29259 be listed in this attribute.
29262 @subsubheading Example
29269 -var-update --all-values var1
29270 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29271 type_changed="false"@}]
29275 @subheading The @code{-var-set-frozen} Command
29276 @findex -var-set-frozen
29277 @anchor{-var-set-frozen}
29279 @subsubheading Synopsis
29282 -var-set-frozen @var{name} @var{flag}
29285 Set the frozenness flag on the variable object @var{name}. The
29286 @var{flag} parameter should be either @samp{1} to make the variable
29287 frozen or @samp{0} to make it unfrozen. If a variable object is
29288 frozen, then neither itself, nor any of its children, are
29289 implicitly updated by @code{-var-update} of
29290 a parent variable or by @code{-var-update *}. Only
29291 @code{-var-update} of the variable itself will update its value and
29292 values of its children. After a variable object is unfrozen, it is
29293 implicitly updated by all subsequent @code{-var-update} operations.
29294 Unfreezing a variable does not update it, only subsequent
29295 @code{-var-update} does.
29297 @subsubheading Example
29301 -var-set-frozen V 1
29306 @subheading The @code{-var-set-update-range} command
29307 @findex -var-set-update-range
29308 @anchor{-var-set-update-range}
29310 @subsubheading Synopsis
29313 -var-set-update-range @var{name} @var{from} @var{to}
29316 Set the range of children to be returned by future invocations of
29317 @code{-var-update}.
29319 @var{from} and @var{to} indicate the range of children to report. If
29320 @var{from} or @var{to} is less than zero, the range is reset and all
29321 children will be reported. Otherwise, children starting at @var{from}
29322 (zero-based) and up to and excluding @var{to} will be reported.
29324 @subsubheading Example
29328 -var-set-update-range V 1 2
29332 @subheading The @code{-var-set-visualizer} command
29333 @findex -var-set-visualizer
29334 @anchor{-var-set-visualizer}
29336 @subsubheading Synopsis
29339 -var-set-visualizer @var{name} @var{visualizer}
29342 Set a visualizer for the variable object @var{name}.
29344 @var{visualizer} is the visualizer to use. The special value
29345 @samp{None} means to disable any visualizer in use.
29347 If not @samp{None}, @var{visualizer} must be a Python expression.
29348 This expression must evaluate to a callable object which accepts a
29349 single argument. @value{GDBN} will call this object with the value of
29350 the varobj @var{name} as an argument (this is done so that the same
29351 Python pretty-printing code can be used for both the CLI and MI).
29352 When called, this object must return an object which conforms to the
29353 pretty-printing interface (@pxref{Pretty Printing API}).
29355 The pre-defined function @code{gdb.default_visualizer} may be used to
29356 select a visualizer by following the built-in process
29357 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29358 a varobj is created, and so ordinarily is not needed.
29360 This feature is only available if Python support is enabled. The MI
29361 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29362 can be used to check this.
29364 @subsubheading Example
29366 Resetting the visualizer:
29370 -var-set-visualizer V None
29374 Reselecting the default (type-based) visualizer:
29378 -var-set-visualizer V gdb.default_visualizer
29382 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29383 can be used to instantiate this class for a varobj:
29387 -var-set-visualizer V "lambda val: SomeClass()"
29391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29392 @node GDB/MI Data Manipulation
29393 @section @sc{gdb/mi} Data Manipulation
29395 @cindex data manipulation, in @sc{gdb/mi}
29396 @cindex @sc{gdb/mi}, data manipulation
29397 This section describes the @sc{gdb/mi} commands that manipulate data:
29398 examine memory and registers, evaluate expressions, etc.
29400 @c REMOVED FROM THE INTERFACE.
29401 @c @subheading -data-assign
29402 @c Change the value of a program variable. Plenty of side effects.
29403 @c @subsubheading GDB Command
29405 @c @subsubheading Example
29408 @subheading The @code{-data-disassemble} Command
29409 @findex -data-disassemble
29411 @subsubheading Synopsis
29415 [ -s @var{start-addr} -e @var{end-addr} ]
29416 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29424 @item @var{start-addr}
29425 is the beginning address (or @code{$pc})
29426 @item @var{end-addr}
29428 @item @var{filename}
29429 is the name of the file to disassemble
29430 @item @var{linenum}
29431 is the line number to disassemble around
29433 is the number of disassembly lines to be produced. If it is -1,
29434 the whole function will be disassembled, in case no @var{end-addr} is
29435 specified. If @var{end-addr} is specified as a non-zero value, and
29436 @var{lines} is lower than the number of disassembly lines between
29437 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29438 displayed; if @var{lines} is higher than the number of lines between
29439 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29442 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29443 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29444 mixed source and disassembly with raw opcodes).
29447 @subsubheading Result
29449 The result of the @code{-data-disassemble} command will be a list named
29450 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29451 used with the @code{-data-disassemble} command.
29453 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29458 The address at which this instruction was disassembled.
29461 The name of the function this instruction is within.
29464 The decimal offset in bytes from the start of @samp{func-name}.
29467 The text disassembly for this @samp{address}.
29470 This field is only present for mode 2. This contains the raw opcode
29471 bytes for the @samp{inst} field.
29475 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29476 @samp{src_and_asm_line}, each of which has the following fields:
29480 The line number within @samp{file}.
29483 The file name from the compilation unit. This might be an absolute
29484 file name or a relative file name depending on the compile command
29488 Absolute file name of @samp{file}. It is converted to a canonical form
29489 using the source file search path
29490 (@pxref{Source Path, ,Specifying Source Directories})
29491 and after resolving all the symbolic links.
29493 If the source file is not found this field will contain the path as
29494 present in the debug information.
29496 @item line_asm_insn
29497 This is a list of tuples containing the disassembly for @samp{line} in
29498 @samp{file}. The fields of each tuple are the same as for
29499 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29500 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29505 Note that whatever included in the @samp{inst} field, is not
29506 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29509 @subsubheading @value{GDBN} Command
29511 The corresponding @value{GDBN} command is @samp{disassemble}.
29513 @subsubheading Example
29515 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29519 -data-disassemble -s $pc -e "$pc + 20" -- 0
29522 @{address="0x000107c0",func-name="main",offset="4",
29523 inst="mov 2, %o0"@},
29524 @{address="0x000107c4",func-name="main",offset="8",
29525 inst="sethi %hi(0x11800), %o2"@},
29526 @{address="0x000107c8",func-name="main",offset="12",
29527 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29528 @{address="0x000107cc",func-name="main",offset="16",
29529 inst="sethi %hi(0x11800), %o2"@},
29530 @{address="0x000107d0",func-name="main",offset="20",
29531 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29535 Disassemble the whole @code{main} function. Line 32 is part of
29539 -data-disassemble -f basics.c -l 32 -- 0
29541 @{address="0x000107bc",func-name="main",offset="0",
29542 inst="save %sp, -112, %sp"@},
29543 @{address="0x000107c0",func-name="main",offset="4",
29544 inst="mov 2, %o0"@},
29545 @{address="0x000107c4",func-name="main",offset="8",
29546 inst="sethi %hi(0x11800), %o2"@},
29548 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29549 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29553 Disassemble 3 instructions from the start of @code{main}:
29557 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29559 @{address="0x000107bc",func-name="main",offset="0",
29560 inst="save %sp, -112, %sp"@},
29561 @{address="0x000107c0",func-name="main",offset="4",
29562 inst="mov 2, %o0"@},
29563 @{address="0x000107c4",func-name="main",offset="8",
29564 inst="sethi %hi(0x11800), %o2"@}]
29568 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29572 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29574 src_and_asm_line=@{line="31",
29575 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29576 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29577 line_asm_insn=[@{address="0x000107bc",
29578 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29579 src_and_asm_line=@{line="32",
29580 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29581 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29582 line_asm_insn=[@{address="0x000107c0",
29583 func-name="main",offset="4",inst="mov 2, %o0"@},
29584 @{address="0x000107c4",func-name="main",offset="8",
29585 inst="sethi %hi(0x11800), %o2"@}]@}]
29590 @subheading The @code{-data-evaluate-expression} Command
29591 @findex -data-evaluate-expression
29593 @subsubheading Synopsis
29596 -data-evaluate-expression @var{expr}
29599 Evaluate @var{expr} as an expression. The expression could contain an
29600 inferior function call. The function call will execute synchronously.
29601 If the expression contains spaces, it must be enclosed in double quotes.
29603 @subsubheading @value{GDBN} Command
29605 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29606 @samp{call}. In @code{gdbtk} only, there's a corresponding
29607 @samp{gdb_eval} command.
29609 @subsubheading Example
29611 In the following example, the numbers that precede the commands are the
29612 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29613 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29617 211-data-evaluate-expression A
29620 311-data-evaluate-expression &A
29621 311^done,value="0xefffeb7c"
29623 411-data-evaluate-expression A+3
29626 511-data-evaluate-expression "A + 3"
29632 @subheading The @code{-data-list-changed-registers} Command
29633 @findex -data-list-changed-registers
29635 @subsubheading Synopsis
29638 -data-list-changed-registers
29641 Display a list of the registers that have changed.
29643 @subsubheading @value{GDBN} Command
29645 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29646 has the corresponding command @samp{gdb_changed_register_list}.
29648 @subsubheading Example
29650 On a PPC MBX board:
29658 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29659 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29662 -data-list-changed-registers
29663 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29664 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29665 "24","25","26","27","28","30","31","64","65","66","67","69"]
29670 @subheading The @code{-data-list-register-names} Command
29671 @findex -data-list-register-names
29673 @subsubheading Synopsis
29676 -data-list-register-names [ ( @var{regno} )+ ]
29679 Show a list of register names for the current target. If no arguments
29680 are given, it shows a list of the names of all the registers. If
29681 integer numbers are given as arguments, it will print a list of the
29682 names of the registers corresponding to the arguments. To ensure
29683 consistency between a register name and its number, the output list may
29684 include empty register names.
29686 @subsubheading @value{GDBN} Command
29688 @value{GDBN} does not have a command which corresponds to
29689 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29690 corresponding command @samp{gdb_regnames}.
29692 @subsubheading Example
29694 For the PPC MBX board:
29697 -data-list-register-names
29698 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29699 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29700 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29701 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29702 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29703 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29704 "", "pc","ps","cr","lr","ctr","xer"]
29706 -data-list-register-names 1 2 3
29707 ^done,register-names=["r1","r2","r3"]
29711 @subheading The @code{-data-list-register-values} Command
29712 @findex -data-list-register-values
29714 @subsubheading Synopsis
29717 -data-list-register-values
29718 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29721 Display the registers' contents. The format according to which the
29722 registers' contents are to be returned is given by @var{fmt}, followed
29723 by an optional list of numbers specifying the registers to display. A
29724 missing list of numbers indicates that the contents of all the
29725 registers must be returned. The @code{--skip-unavailable} option
29726 indicates that only the available registers are to be returned.
29728 Allowed formats for @var{fmt} are:
29745 @subsubheading @value{GDBN} Command
29747 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29748 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29750 @subsubheading Example
29752 For a PPC MBX board (note: line breaks are for readability only, they
29753 don't appear in the actual output):
29757 -data-list-register-values r 64 65
29758 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29759 @{number="65",value="0x00029002"@}]
29761 -data-list-register-values x
29762 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29763 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29764 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29765 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29766 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29767 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29768 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29769 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29770 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29771 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29772 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29773 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29774 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29775 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29776 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29777 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29778 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29779 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29780 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29781 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29782 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29783 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29784 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29785 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29786 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29787 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29788 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29789 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29790 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29791 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29792 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29793 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29794 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29795 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29796 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29797 @{number="69",value="0x20002b03"@}]
29802 @subheading The @code{-data-read-memory} Command
29803 @findex -data-read-memory
29805 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29807 @subsubheading Synopsis
29810 -data-read-memory [ -o @var{byte-offset} ]
29811 @var{address} @var{word-format} @var{word-size}
29812 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29819 @item @var{address}
29820 An expression specifying the address of the first memory word to be
29821 read. Complex expressions containing embedded white space should be
29822 quoted using the C convention.
29824 @item @var{word-format}
29825 The format to be used to print the memory words. The notation is the
29826 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29829 @item @var{word-size}
29830 The size of each memory word in bytes.
29832 @item @var{nr-rows}
29833 The number of rows in the output table.
29835 @item @var{nr-cols}
29836 The number of columns in the output table.
29839 If present, indicates that each row should include an @sc{ascii} dump. The
29840 value of @var{aschar} is used as a padding character when a byte is not a
29841 member of the printable @sc{ascii} character set (printable @sc{ascii}
29842 characters are those whose code is between 32 and 126, inclusively).
29844 @item @var{byte-offset}
29845 An offset to add to the @var{address} before fetching memory.
29848 This command displays memory contents as a table of @var{nr-rows} by
29849 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29850 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29851 (returned as @samp{total-bytes}). Should less than the requested number
29852 of bytes be returned by the target, the missing words are identified
29853 using @samp{N/A}. The number of bytes read from the target is returned
29854 in @samp{nr-bytes} and the starting address used to read memory in
29857 The address of the next/previous row or page is available in
29858 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29861 @subsubheading @value{GDBN} Command
29863 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29864 @samp{gdb_get_mem} memory read command.
29866 @subsubheading Example
29868 Read six bytes of memory starting at @code{bytes+6} but then offset by
29869 @code{-6} bytes. Format as three rows of two columns. One byte per
29870 word. Display each word in hex.
29874 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29875 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29876 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29877 prev-page="0x0000138a",memory=[
29878 @{addr="0x00001390",data=["0x00","0x01"]@},
29879 @{addr="0x00001392",data=["0x02","0x03"]@},
29880 @{addr="0x00001394",data=["0x04","0x05"]@}]
29884 Read two bytes of memory starting at address @code{shorts + 64} and
29885 display as a single word formatted in decimal.
29889 5-data-read-memory shorts+64 d 2 1 1
29890 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29891 next-row="0x00001512",prev-row="0x0000150e",
29892 next-page="0x00001512",prev-page="0x0000150e",memory=[
29893 @{addr="0x00001510",data=["128"]@}]
29897 Read thirty two bytes of memory starting at @code{bytes+16} and format
29898 as eight rows of four columns. Include a string encoding with @samp{x}
29899 used as the non-printable character.
29903 4-data-read-memory bytes+16 x 1 8 4 x
29904 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29905 next-row="0x000013c0",prev-row="0x0000139c",
29906 next-page="0x000013c0",prev-page="0x00001380",memory=[
29907 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29908 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29909 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29910 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29911 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29912 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29913 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29914 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29918 @subheading The @code{-data-read-memory-bytes} Command
29919 @findex -data-read-memory-bytes
29921 @subsubheading Synopsis
29924 -data-read-memory-bytes [ -o @var{byte-offset} ]
29925 @var{address} @var{count}
29932 @item @var{address}
29933 An expression specifying the address of the first memory word to be
29934 read. Complex expressions containing embedded white space should be
29935 quoted using the C convention.
29938 The number of bytes to read. This should be an integer literal.
29940 @item @var{byte-offset}
29941 The offsets in bytes relative to @var{address} at which to start
29942 reading. This should be an integer literal. This option is provided
29943 so that a frontend is not required to first evaluate address and then
29944 perform address arithmetics itself.
29948 This command attempts to read all accessible memory regions in the
29949 specified range. First, all regions marked as unreadable in the memory
29950 map (if one is defined) will be skipped. @xref{Memory Region
29951 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29952 regions. For each one, if reading full region results in an errors,
29953 @value{GDBN} will try to read a subset of the region.
29955 In general, every single byte in the region may be readable or not,
29956 and the only way to read every readable byte is to try a read at
29957 every address, which is not practical. Therefore, @value{GDBN} will
29958 attempt to read all accessible bytes at either beginning or the end
29959 of the region, using a binary division scheme. This heuristic works
29960 well for reading accross a memory map boundary. Note that if a region
29961 has a readable range that is neither at the beginning or the end,
29962 @value{GDBN} will not read it.
29964 The result record (@pxref{GDB/MI Result Records}) that is output of
29965 the command includes a field named @samp{memory} whose content is a
29966 list of tuples. Each tuple represent a successfully read memory block
29967 and has the following fields:
29971 The start address of the memory block, as hexadecimal literal.
29974 The end address of the memory block, as hexadecimal literal.
29977 The offset of the memory block, as hexadecimal literal, relative to
29978 the start address passed to @code{-data-read-memory-bytes}.
29981 The contents of the memory block, in hex.
29987 @subsubheading @value{GDBN} Command
29989 The corresponding @value{GDBN} command is @samp{x}.
29991 @subsubheading Example
29995 -data-read-memory-bytes &a 10
29996 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29998 contents="01000000020000000300"@}]
30003 @subheading The @code{-data-write-memory-bytes} Command
30004 @findex -data-write-memory-bytes
30006 @subsubheading Synopsis
30009 -data-write-memory-bytes @var{address} @var{contents}
30010 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30017 @item @var{address}
30018 An expression specifying the address of the first memory word to be
30019 written. Complex expressions containing embedded white space should be
30020 quoted using the C convention.
30022 @item @var{contents}
30023 The hex-encoded bytes to write.
30026 Optional argument indicating the number of bytes to be written. If @var{count}
30027 is greater than @var{contents}' length, @value{GDBN} will repeatedly
30028 write @var{contents} until it fills @var{count} bytes.
30032 @subsubheading @value{GDBN} Command
30034 There's no corresponding @value{GDBN} command.
30036 @subsubheading Example
30040 -data-write-memory-bytes &a "aabbccdd"
30047 -data-write-memory-bytes &a "aabbccdd" 16e
30052 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30053 @node GDB/MI Tracepoint Commands
30054 @section @sc{gdb/mi} Tracepoint Commands
30056 The commands defined in this section implement MI support for
30057 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30059 @subheading The @code{-trace-find} Command
30060 @findex -trace-find
30062 @subsubheading Synopsis
30065 -trace-find @var{mode} [@var{parameters}@dots{}]
30068 Find a trace frame using criteria defined by @var{mode} and
30069 @var{parameters}. The following table lists permissible
30070 modes and their parameters. For details of operation, see @ref{tfind}.
30075 No parameters are required. Stops examining trace frames.
30078 An integer is required as parameter. Selects tracepoint frame with
30081 @item tracepoint-number
30082 An integer is required as parameter. Finds next
30083 trace frame that corresponds to tracepoint with the specified number.
30086 An address is required as parameter. Finds
30087 next trace frame that corresponds to any tracepoint at the specified
30090 @item pc-inside-range
30091 Two addresses are required as parameters. Finds next trace
30092 frame that corresponds to a tracepoint at an address inside the
30093 specified range. Both bounds are considered to be inside the range.
30095 @item pc-outside-range
30096 Two addresses are required as parameters. Finds
30097 next trace frame that corresponds to a tracepoint at an address outside
30098 the specified range. Both bounds are considered to be inside the range.
30101 Line specification is required as parameter. @xref{Specify Location}.
30102 Finds next trace frame that corresponds to a tracepoint at
30103 the specified location.
30107 If @samp{none} was passed as @var{mode}, the response does not
30108 have fields. Otherwise, the response may have the following fields:
30112 This field has either @samp{0} or @samp{1} as the value, depending
30113 on whether a matching tracepoint was found.
30116 The index of the found traceframe. This field is present iff
30117 the @samp{found} field has value of @samp{1}.
30120 The index of the found tracepoint. This field is present iff
30121 the @samp{found} field has value of @samp{1}.
30124 The information about the frame corresponding to the found trace
30125 frame. This field is present only if a trace frame was found.
30126 @xref{GDB/MI Frame Information}, for description of this field.
30130 @subsubheading @value{GDBN} Command
30132 The corresponding @value{GDBN} command is @samp{tfind}.
30134 @subheading -trace-define-variable
30135 @findex -trace-define-variable
30137 @subsubheading Synopsis
30140 -trace-define-variable @var{name} [ @var{value} ]
30143 Create trace variable @var{name} if it does not exist. If
30144 @var{value} is specified, sets the initial value of the specified
30145 trace variable to that value. Note that the @var{name} should start
30146 with the @samp{$} character.
30148 @subsubheading @value{GDBN} Command
30150 The corresponding @value{GDBN} command is @samp{tvariable}.
30152 @subheading The @code{-trace-frame-collected} Command
30153 @findex -trace-frame-collected
30155 @subsubheading Synopsis
30158 -trace-frame-collected
30159 [--var-print-values @var{var_pval}]
30160 [--comp-print-values @var{comp_pval}]
30161 [--registers-format @var{regformat}]
30162 [--memory-contents]
30165 This command returns the set of collected objects, register names,
30166 trace state variable names, memory ranges and computed expressions
30167 that have been collected at a particular trace frame. The optional
30168 parameters to the command affect the output format in different ways.
30169 See the output description table below for more details.
30171 The reported names can be used in the normal manner to create
30172 varobjs and inspect the objects themselves. The items returned by
30173 this command are categorized so that it is clear which is a variable,
30174 which is a register, which is a trace state variable, which is a
30175 memory range and which is a computed expression.
30177 For instance, if the actions were
30179 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30180 collect *(int*)0xaf02bef0@@40
30184 the object collected in its entirety would be @code{myVar}. The
30185 object @code{myArray} would be partially collected, because only the
30186 element at index @code{myIndex} would be collected. The remaining
30187 objects would be computed expressions.
30189 An example output would be:
30193 -trace-frame-collected
30195 explicit-variables=[@{name="myVar",value="1"@}],
30196 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30197 @{name="myObj.field",value="0"@},
30198 @{name="myPtr->field",value="1"@},
30199 @{name="myCount + 2",value="3"@},
30200 @{name="$tvar1 + 1",value="43970027"@}],
30201 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30202 @{number="1",value="0x0"@},
30203 @{number="2",value="0x4"@},
30205 @{number="125",value="0x0"@}],
30206 tvars=[@{name="$tvar1",current="43970026"@}],
30207 memory=[@{address="0x0000000000602264",length="4"@},
30208 @{address="0x0000000000615bc0",length="4"@}]
30215 @item explicit-variables
30216 The set of objects that have been collected in their entirety (as
30217 opposed to collecting just a few elements of an array or a few struct
30218 members). For each object, its name and value are printed.
30219 The @code{--var-print-values} option affects how or whether the value
30220 field is output. If @var{var_pval} is 0, then print only the names;
30221 if it is 1, print also their values; and if it is 2, print the name,
30222 type and value for simple data types, and the name and type for
30223 arrays, structures and unions.
30225 @item computed-expressions
30226 The set of computed expressions that have been collected at the
30227 current trace frame. The @code{--comp-print-values} option affects
30228 this set like the @code{--var-print-values} option affects the
30229 @code{explicit-variables} set. See above.
30232 The registers that have been collected at the current trace frame.
30233 For each register collected, the name and current value are returned.
30234 The value is formatted according to the @code{--registers-format}
30235 option. See the @command{-data-list-register-values} command for a
30236 list of the allowed formats. The default is @samp{x}.
30239 The trace state variables that have been collected at the current
30240 trace frame. For each trace state variable collected, the name and
30241 current value are returned.
30244 The set of memory ranges that have been collected at the current trace
30245 frame. Its content is a list of tuples. Each tuple represents a
30246 collected memory range and has the following fields:
30250 The start address of the memory range, as hexadecimal literal.
30253 The length of the memory range, as decimal literal.
30256 The contents of the memory block, in hex. This field is only present
30257 if the @code{--memory-contents} option is specified.
30263 @subsubheading @value{GDBN} Command
30265 There is no corresponding @value{GDBN} command.
30267 @subsubheading Example
30269 @subheading -trace-list-variables
30270 @findex -trace-list-variables
30272 @subsubheading Synopsis
30275 -trace-list-variables
30278 Return a table of all defined trace variables. Each element of the
30279 table has the following fields:
30283 The name of the trace variable. This field is always present.
30286 The initial value. This is a 64-bit signed integer. This
30287 field is always present.
30290 The value the trace variable has at the moment. This is a 64-bit
30291 signed integer. This field is absent iff current value is
30292 not defined, for example if the trace was never run, or is
30297 @subsubheading @value{GDBN} Command
30299 The corresponding @value{GDBN} command is @samp{tvariables}.
30301 @subsubheading Example
30305 -trace-list-variables
30306 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30307 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30308 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30309 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30310 body=[variable=@{name="$trace_timestamp",initial="0"@}
30311 variable=@{name="$foo",initial="10",current="15"@}]@}
30315 @subheading -trace-save
30316 @findex -trace-save
30318 @subsubheading Synopsis
30321 -trace-save [-r ] @var{filename}
30324 Saves the collected trace data to @var{filename}. Without the
30325 @samp{-r} option, the data is downloaded from the target and saved
30326 in a local file. With the @samp{-r} option the target is asked
30327 to perform the save.
30329 @subsubheading @value{GDBN} Command
30331 The corresponding @value{GDBN} command is @samp{tsave}.
30334 @subheading -trace-start
30335 @findex -trace-start
30337 @subsubheading Synopsis
30343 Starts a tracing experiments. The result of this command does not
30346 @subsubheading @value{GDBN} Command
30348 The corresponding @value{GDBN} command is @samp{tstart}.
30350 @subheading -trace-status
30351 @findex -trace-status
30353 @subsubheading Synopsis
30359 Obtains the status of a tracing experiment. The result may include
30360 the following fields:
30365 May have a value of either @samp{0}, when no tracing operations are
30366 supported, @samp{1}, when all tracing operations are supported, or
30367 @samp{file} when examining trace file. In the latter case, examining
30368 of trace frame is possible but new tracing experiement cannot be
30369 started. This field is always present.
30372 May have a value of either @samp{0} or @samp{1} depending on whether
30373 tracing experiement is in progress on target. This field is present
30374 if @samp{supported} field is not @samp{0}.
30377 Report the reason why the tracing was stopped last time. This field
30378 may be absent iff tracing was never stopped on target yet. The
30379 value of @samp{request} means the tracing was stopped as result of
30380 the @code{-trace-stop} command. The value of @samp{overflow} means
30381 the tracing buffer is full. The value of @samp{disconnection} means
30382 tracing was automatically stopped when @value{GDBN} has disconnected.
30383 The value of @samp{passcount} means tracing was stopped when a
30384 tracepoint was passed a maximal number of times for that tracepoint.
30385 This field is present if @samp{supported} field is not @samp{0}.
30387 @item stopping-tracepoint
30388 The number of tracepoint whose passcount as exceeded. This field is
30389 present iff the @samp{stop-reason} field has the value of
30393 @itemx frames-created
30394 The @samp{frames} field is a count of the total number of trace frames
30395 in the trace buffer, while @samp{frames-created} is the total created
30396 during the run, including ones that were discarded, such as when a
30397 circular trace buffer filled up. Both fields are optional.
30401 These fields tell the current size of the tracing buffer and the
30402 remaining space. These fields are optional.
30405 The value of the circular trace buffer flag. @code{1} means that the
30406 trace buffer is circular and old trace frames will be discarded if
30407 necessary to make room, @code{0} means that the trace buffer is linear
30411 The value of the disconnected tracing flag. @code{1} means that
30412 tracing will continue after @value{GDBN} disconnects, @code{0} means
30413 that the trace run will stop.
30416 The filename of the trace file being examined. This field is
30417 optional, and only present when examining a trace file.
30421 @subsubheading @value{GDBN} Command
30423 The corresponding @value{GDBN} command is @samp{tstatus}.
30425 @subheading -trace-stop
30426 @findex -trace-stop
30428 @subsubheading Synopsis
30434 Stops a tracing experiment. The result of this command has the same
30435 fields as @code{-trace-status}, except that the @samp{supported} and
30436 @samp{running} fields are not output.
30438 @subsubheading @value{GDBN} Command
30440 The corresponding @value{GDBN} command is @samp{tstop}.
30443 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30444 @node GDB/MI Symbol Query
30445 @section @sc{gdb/mi} Symbol Query Commands
30449 @subheading The @code{-symbol-info-address} Command
30450 @findex -symbol-info-address
30452 @subsubheading Synopsis
30455 -symbol-info-address @var{symbol}
30458 Describe where @var{symbol} is stored.
30460 @subsubheading @value{GDBN} Command
30462 The corresponding @value{GDBN} command is @samp{info address}.
30464 @subsubheading Example
30468 @subheading The @code{-symbol-info-file} Command
30469 @findex -symbol-info-file
30471 @subsubheading Synopsis
30477 Show the file for the symbol.
30479 @subsubheading @value{GDBN} Command
30481 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30482 @samp{gdb_find_file}.
30484 @subsubheading Example
30488 @subheading The @code{-symbol-info-function} Command
30489 @findex -symbol-info-function
30491 @subsubheading Synopsis
30494 -symbol-info-function
30497 Show which function the symbol lives in.
30499 @subsubheading @value{GDBN} Command
30501 @samp{gdb_get_function} in @code{gdbtk}.
30503 @subsubheading Example
30507 @subheading The @code{-symbol-info-line} Command
30508 @findex -symbol-info-line
30510 @subsubheading Synopsis
30516 Show the core addresses of the code for a source line.
30518 @subsubheading @value{GDBN} Command
30520 The corresponding @value{GDBN} command is @samp{info line}.
30521 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30523 @subsubheading Example
30527 @subheading The @code{-symbol-info-symbol} Command
30528 @findex -symbol-info-symbol
30530 @subsubheading Synopsis
30533 -symbol-info-symbol @var{addr}
30536 Describe what symbol is at location @var{addr}.
30538 @subsubheading @value{GDBN} Command
30540 The corresponding @value{GDBN} command is @samp{info symbol}.
30542 @subsubheading Example
30546 @subheading The @code{-symbol-list-functions} Command
30547 @findex -symbol-list-functions
30549 @subsubheading Synopsis
30552 -symbol-list-functions
30555 List the functions in the executable.
30557 @subsubheading @value{GDBN} Command
30559 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30560 @samp{gdb_search} in @code{gdbtk}.
30562 @subsubheading Example
30567 @subheading The @code{-symbol-list-lines} Command
30568 @findex -symbol-list-lines
30570 @subsubheading Synopsis
30573 -symbol-list-lines @var{filename}
30576 Print the list of lines that contain code and their associated program
30577 addresses for the given source filename. The entries are sorted in
30578 ascending PC order.
30580 @subsubheading @value{GDBN} Command
30582 There is no corresponding @value{GDBN} command.
30584 @subsubheading Example
30587 -symbol-list-lines basics.c
30588 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30594 @subheading The @code{-symbol-list-types} Command
30595 @findex -symbol-list-types
30597 @subsubheading Synopsis
30603 List all the type names.
30605 @subsubheading @value{GDBN} Command
30607 The corresponding commands are @samp{info types} in @value{GDBN},
30608 @samp{gdb_search} in @code{gdbtk}.
30610 @subsubheading Example
30614 @subheading The @code{-symbol-list-variables} Command
30615 @findex -symbol-list-variables
30617 @subsubheading Synopsis
30620 -symbol-list-variables
30623 List all the global and static variable names.
30625 @subsubheading @value{GDBN} Command
30627 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30629 @subsubheading Example
30633 @subheading The @code{-symbol-locate} Command
30634 @findex -symbol-locate
30636 @subsubheading Synopsis
30642 @subsubheading @value{GDBN} Command
30644 @samp{gdb_loc} in @code{gdbtk}.
30646 @subsubheading Example
30650 @subheading The @code{-symbol-type} Command
30651 @findex -symbol-type
30653 @subsubheading Synopsis
30656 -symbol-type @var{variable}
30659 Show type of @var{variable}.
30661 @subsubheading @value{GDBN} Command
30663 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30664 @samp{gdb_obj_variable}.
30666 @subsubheading Example
30671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30672 @node GDB/MI File Commands
30673 @section @sc{gdb/mi} File Commands
30675 This section describes the GDB/MI commands to specify executable file names
30676 and to read in and obtain symbol table information.
30678 @subheading The @code{-file-exec-and-symbols} Command
30679 @findex -file-exec-and-symbols
30681 @subsubheading Synopsis
30684 -file-exec-and-symbols @var{file}
30687 Specify the executable file to be debugged. This file is the one from
30688 which the symbol table is also read. If no file is specified, the
30689 command clears the executable and symbol information. If breakpoints
30690 are set when using this command with no arguments, @value{GDBN} will produce
30691 error messages. Otherwise, no output is produced, except a completion
30694 @subsubheading @value{GDBN} Command
30696 The corresponding @value{GDBN} command is @samp{file}.
30698 @subsubheading Example
30702 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30708 @subheading The @code{-file-exec-file} Command
30709 @findex -file-exec-file
30711 @subsubheading Synopsis
30714 -file-exec-file @var{file}
30717 Specify the executable file to be debugged. Unlike
30718 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30719 from this file. If used without argument, @value{GDBN} clears the information
30720 about the executable file. No output is produced, except a completion
30723 @subsubheading @value{GDBN} Command
30725 The corresponding @value{GDBN} command is @samp{exec-file}.
30727 @subsubheading Example
30731 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30738 @subheading The @code{-file-list-exec-sections} Command
30739 @findex -file-list-exec-sections
30741 @subsubheading Synopsis
30744 -file-list-exec-sections
30747 List the sections of the current executable file.
30749 @subsubheading @value{GDBN} Command
30751 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30752 information as this command. @code{gdbtk} has a corresponding command
30753 @samp{gdb_load_info}.
30755 @subsubheading Example
30760 @subheading The @code{-file-list-exec-source-file} Command
30761 @findex -file-list-exec-source-file
30763 @subsubheading Synopsis
30766 -file-list-exec-source-file
30769 List the line number, the current source file, and the absolute path
30770 to the current source file for the current executable. The macro
30771 information field has a value of @samp{1} or @samp{0} depending on
30772 whether or not the file includes preprocessor macro information.
30774 @subsubheading @value{GDBN} Command
30776 The @value{GDBN} equivalent is @samp{info source}
30778 @subsubheading Example
30782 123-file-list-exec-source-file
30783 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30788 @subheading The @code{-file-list-exec-source-files} Command
30789 @findex -file-list-exec-source-files
30791 @subsubheading Synopsis
30794 -file-list-exec-source-files
30797 List the source files for the current executable.
30799 It will always output both the filename and fullname (absolute file
30800 name) of a source file.
30802 @subsubheading @value{GDBN} Command
30804 The @value{GDBN} equivalent is @samp{info sources}.
30805 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30807 @subsubheading Example
30810 -file-list-exec-source-files
30812 @{file=foo.c,fullname=/home/foo.c@},
30813 @{file=/home/bar.c,fullname=/home/bar.c@},
30814 @{file=gdb_could_not_find_fullpath.c@}]
30819 @subheading The @code{-file-list-shared-libraries} Command
30820 @findex -file-list-shared-libraries
30822 @subsubheading Synopsis
30825 -file-list-shared-libraries
30828 List the shared libraries in the program.
30830 @subsubheading @value{GDBN} Command
30832 The corresponding @value{GDBN} command is @samp{info shared}.
30834 @subsubheading Example
30838 @subheading The @code{-file-list-symbol-files} Command
30839 @findex -file-list-symbol-files
30841 @subsubheading Synopsis
30844 -file-list-symbol-files
30849 @subsubheading @value{GDBN} Command
30851 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30853 @subsubheading Example
30858 @subheading The @code{-file-symbol-file} Command
30859 @findex -file-symbol-file
30861 @subsubheading Synopsis
30864 -file-symbol-file @var{file}
30867 Read symbol table info from the specified @var{file} argument. When
30868 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30869 produced, except for a completion notification.
30871 @subsubheading @value{GDBN} Command
30873 The corresponding @value{GDBN} command is @samp{symbol-file}.
30875 @subsubheading Example
30879 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30886 @node GDB/MI Memory Overlay Commands
30887 @section @sc{gdb/mi} Memory Overlay Commands
30889 The memory overlay commands are not implemented.
30891 @c @subheading -overlay-auto
30893 @c @subheading -overlay-list-mapping-state
30895 @c @subheading -overlay-list-overlays
30897 @c @subheading -overlay-map
30899 @c @subheading -overlay-off
30901 @c @subheading -overlay-on
30903 @c @subheading -overlay-unmap
30905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30906 @node GDB/MI Signal Handling Commands
30907 @section @sc{gdb/mi} Signal Handling Commands
30909 Signal handling commands are not implemented.
30911 @c @subheading -signal-handle
30913 @c @subheading -signal-list-handle-actions
30915 @c @subheading -signal-list-signal-types
30919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30920 @node GDB/MI Target Manipulation
30921 @section @sc{gdb/mi} Target Manipulation Commands
30924 @subheading The @code{-target-attach} Command
30925 @findex -target-attach
30927 @subsubheading Synopsis
30930 -target-attach @var{pid} | @var{gid} | @var{file}
30933 Attach to a process @var{pid} or a file @var{file} outside of
30934 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30935 group, the id previously returned by
30936 @samp{-list-thread-groups --available} must be used.
30938 @subsubheading @value{GDBN} Command
30940 The corresponding @value{GDBN} command is @samp{attach}.
30942 @subsubheading Example
30946 =thread-created,id="1"
30947 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30953 @subheading The @code{-target-compare-sections} Command
30954 @findex -target-compare-sections
30956 @subsubheading Synopsis
30959 -target-compare-sections [ @var{section} ]
30962 Compare data of section @var{section} on target to the exec file.
30963 Without the argument, all sections are compared.
30965 @subsubheading @value{GDBN} Command
30967 The @value{GDBN} equivalent is @samp{compare-sections}.
30969 @subsubheading Example
30974 @subheading The @code{-target-detach} Command
30975 @findex -target-detach
30977 @subsubheading Synopsis
30980 -target-detach [ @var{pid} | @var{gid} ]
30983 Detach from the remote target which normally resumes its execution.
30984 If either @var{pid} or @var{gid} is specified, detaches from either
30985 the specified process, or specified thread group. There's no output.
30987 @subsubheading @value{GDBN} Command
30989 The corresponding @value{GDBN} command is @samp{detach}.
30991 @subsubheading Example
31001 @subheading The @code{-target-disconnect} Command
31002 @findex -target-disconnect
31004 @subsubheading Synopsis
31010 Disconnect from the remote target. There's no output and the target is
31011 generally not resumed.
31013 @subsubheading @value{GDBN} Command
31015 The corresponding @value{GDBN} command is @samp{disconnect}.
31017 @subsubheading Example
31027 @subheading The @code{-target-download} Command
31028 @findex -target-download
31030 @subsubheading Synopsis
31036 Loads the executable onto the remote target.
31037 It prints out an update message every half second, which includes the fields:
31041 The name of the section.
31043 The size of what has been sent so far for that section.
31045 The size of the section.
31047 The total size of what was sent so far (the current and the previous sections).
31049 The size of the overall executable to download.
31053 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31054 @sc{gdb/mi} Output Syntax}).
31056 In addition, it prints the name and size of the sections, as they are
31057 downloaded. These messages include the following fields:
31061 The name of the section.
31063 The size of the section.
31065 The size of the overall executable to download.
31069 At the end, a summary is printed.
31071 @subsubheading @value{GDBN} Command
31073 The corresponding @value{GDBN} command is @samp{load}.
31075 @subsubheading Example
31077 Note: each status message appears on a single line. Here the messages
31078 have been broken down so that they can fit onto a page.
31083 +download,@{section=".text",section-size="6668",total-size="9880"@}
31084 +download,@{section=".text",section-sent="512",section-size="6668",
31085 total-sent="512",total-size="9880"@}
31086 +download,@{section=".text",section-sent="1024",section-size="6668",
31087 total-sent="1024",total-size="9880"@}
31088 +download,@{section=".text",section-sent="1536",section-size="6668",
31089 total-sent="1536",total-size="9880"@}
31090 +download,@{section=".text",section-sent="2048",section-size="6668",
31091 total-sent="2048",total-size="9880"@}
31092 +download,@{section=".text",section-sent="2560",section-size="6668",
31093 total-sent="2560",total-size="9880"@}
31094 +download,@{section=".text",section-sent="3072",section-size="6668",
31095 total-sent="3072",total-size="9880"@}
31096 +download,@{section=".text",section-sent="3584",section-size="6668",
31097 total-sent="3584",total-size="9880"@}
31098 +download,@{section=".text",section-sent="4096",section-size="6668",
31099 total-sent="4096",total-size="9880"@}
31100 +download,@{section=".text",section-sent="4608",section-size="6668",
31101 total-sent="4608",total-size="9880"@}
31102 +download,@{section=".text",section-sent="5120",section-size="6668",
31103 total-sent="5120",total-size="9880"@}
31104 +download,@{section=".text",section-sent="5632",section-size="6668",
31105 total-sent="5632",total-size="9880"@}
31106 +download,@{section=".text",section-sent="6144",section-size="6668",
31107 total-sent="6144",total-size="9880"@}
31108 +download,@{section=".text",section-sent="6656",section-size="6668",
31109 total-sent="6656",total-size="9880"@}
31110 +download,@{section=".init",section-size="28",total-size="9880"@}
31111 +download,@{section=".fini",section-size="28",total-size="9880"@}
31112 +download,@{section=".data",section-size="3156",total-size="9880"@}
31113 +download,@{section=".data",section-sent="512",section-size="3156",
31114 total-sent="7236",total-size="9880"@}
31115 +download,@{section=".data",section-sent="1024",section-size="3156",
31116 total-sent="7748",total-size="9880"@}
31117 +download,@{section=".data",section-sent="1536",section-size="3156",
31118 total-sent="8260",total-size="9880"@}
31119 +download,@{section=".data",section-sent="2048",section-size="3156",
31120 total-sent="8772",total-size="9880"@}
31121 +download,@{section=".data",section-sent="2560",section-size="3156",
31122 total-sent="9284",total-size="9880"@}
31123 +download,@{section=".data",section-sent="3072",section-size="3156",
31124 total-sent="9796",total-size="9880"@}
31125 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31132 @subheading The @code{-target-exec-status} Command
31133 @findex -target-exec-status
31135 @subsubheading Synopsis
31138 -target-exec-status
31141 Provide information on the state of the target (whether it is running or
31142 not, for instance).
31144 @subsubheading @value{GDBN} Command
31146 There's no equivalent @value{GDBN} command.
31148 @subsubheading Example
31152 @subheading The @code{-target-list-available-targets} Command
31153 @findex -target-list-available-targets
31155 @subsubheading Synopsis
31158 -target-list-available-targets
31161 List the possible targets to connect to.
31163 @subsubheading @value{GDBN} Command
31165 The corresponding @value{GDBN} command is @samp{help target}.
31167 @subsubheading Example
31171 @subheading The @code{-target-list-current-targets} Command
31172 @findex -target-list-current-targets
31174 @subsubheading Synopsis
31177 -target-list-current-targets
31180 Describe the current target.
31182 @subsubheading @value{GDBN} Command
31184 The corresponding information is printed by @samp{info file} (among
31187 @subsubheading Example
31191 @subheading The @code{-target-list-parameters} Command
31192 @findex -target-list-parameters
31194 @subsubheading Synopsis
31197 -target-list-parameters
31203 @subsubheading @value{GDBN} Command
31207 @subsubheading Example
31211 @subheading The @code{-target-select} Command
31212 @findex -target-select
31214 @subsubheading Synopsis
31217 -target-select @var{type} @var{parameters @dots{}}
31220 Connect @value{GDBN} to the remote target. This command takes two args:
31224 The type of target, for instance @samp{remote}, etc.
31225 @item @var{parameters}
31226 Device names, host names and the like. @xref{Target Commands, ,
31227 Commands for Managing Targets}, for more details.
31230 The output is a connection notification, followed by the address at
31231 which the target program is, in the following form:
31234 ^connected,addr="@var{address}",func="@var{function name}",
31235 args=[@var{arg list}]
31238 @subsubheading @value{GDBN} Command
31240 The corresponding @value{GDBN} command is @samp{target}.
31242 @subsubheading Example
31246 -target-select remote /dev/ttya
31247 ^connected,addr="0xfe00a300",func="??",args=[]
31251 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31252 @node GDB/MI File Transfer Commands
31253 @section @sc{gdb/mi} File Transfer Commands
31256 @subheading The @code{-target-file-put} Command
31257 @findex -target-file-put
31259 @subsubheading Synopsis
31262 -target-file-put @var{hostfile} @var{targetfile}
31265 Copy file @var{hostfile} from the host system (the machine running
31266 @value{GDBN}) to @var{targetfile} on the target system.
31268 @subsubheading @value{GDBN} Command
31270 The corresponding @value{GDBN} command is @samp{remote put}.
31272 @subsubheading Example
31276 -target-file-put localfile remotefile
31282 @subheading The @code{-target-file-get} Command
31283 @findex -target-file-get
31285 @subsubheading Synopsis
31288 -target-file-get @var{targetfile} @var{hostfile}
31291 Copy file @var{targetfile} from the target system to @var{hostfile}
31292 on the host system.
31294 @subsubheading @value{GDBN} Command
31296 The corresponding @value{GDBN} command is @samp{remote get}.
31298 @subsubheading Example
31302 -target-file-get remotefile localfile
31308 @subheading The @code{-target-file-delete} Command
31309 @findex -target-file-delete
31311 @subsubheading Synopsis
31314 -target-file-delete @var{targetfile}
31317 Delete @var{targetfile} from the target system.
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} command is @samp{remote delete}.
31323 @subsubheading Example
31327 -target-file-delete remotefile
31333 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31334 @node GDB/MI Ada Exceptions Commands
31335 @section Ada Exceptions @sc{gdb/mi} Commands
31337 @subheading The @code{-info-ada-exceptions} Command
31338 @findex -info-ada-exceptions
31340 @subsubheading Synopsis
31343 -info-ada-exceptions [ @var{regexp}]
31346 List all Ada exceptions defined within the program being debugged.
31347 With a regular expression @var{regexp}, only those exceptions whose
31348 names match @var{regexp} are listed.
31350 @subsubheading @value{GDBN} Command
31352 The corresponding @value{GDBN} command is @samp{info exceptions}.
31354 @subsubheading Result
31356 The result is a table of Ada exceptions. The following columns are
31357 defined for each exception:
31361 The name of the exception.
31364 The address of the exception.
31368 @subsubheading Example
31371 -info-ada-exceptions aint
31372 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31373 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31374 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31375 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31376 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31379 @subheading Catching Ada Exceptions
31381 The commands describing how to ask @value{GDBN} to stop when a program
31382 raises an exception are described at @ref{Ada Exception GDB/MI
31383 Catchpoint Commands}.
31386 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31387 @node GDB/MI Support Commands
31388 @section @sc{gdb/mi} Support Commands
31390 Since new commands and features get regularly added to @sc{gdb/mi},
31391 some commands are available to help front-ends query the debugger
31392 about support for these capabilities. Similarly, it is also possible
31393 to query @value{GDBN} about target support of certain features.
31395 @subheading The @code{-info-gdb-mi-command} Command
31396 @cindex @code{-info-gdb-mi-command}
31397 @findex -info-gdb-mi-command
31399 @subsubheading Synopsis
31402 -info-gdb-mi-command @var{cmd_name}
31405 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31407 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31408 is technically not part of the command name (@pxref{GDB/MI Input
31409 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31410 for ease of use, this command also accepts the form with the leading
31413 @subsubheading @value{GDBN} Command
31415 There is no corresponding @value{GDBN} command.
31417 @subsubheading Result
31419 The result is a tuple. There is currently only one field:
31423 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31424 @code{"false"} otherwise.
31428 @subsubheading Example
31430 Here is an example where the @sc{gdb/mi} command does not exist:
31433 -info-gdb-mi-command unsupported-command
31434 ^done,command=@{exists="false"@}
31438 And here is an example where the @sc{gdb/mi} command is known
31442 -info-gdb-mi-command symbol-list-lines
31443 ^done,command=@{exists="true"@}
31446 @subheading The @code{-list-features} Command
31447 @findex -list-features
31448 @cindex supported @sc{gdb/mi} features, list
31450 Returns a list of particular features of the MI protocol that
31451 this version of gdb implements. A feature can be a command,
31452 or a new field in an output of some command, or even an
31453 important bugfix. While a frontend can sometimes detect presence
31454 of a feature at runtime, it is easier to perform detection at debugger
31457 The command returns a list of strings, with each string naming an
31458 available feature. Each returned string is just a name, it does not
31459 have any internal structure. The list of possible feature names
31465 (gdb) -list-features
31466 ^done,result=["feature1","feature2"]
31469 The current list of features is:
31472 @item frozen-varobjs
31473 Indicates support for the @code{-var-set-frozen} command, as well
31474 as possible presense of the @code{frozen} field in the output
31475 of @code{-varobj-create}.
31476 @item pending-breakpoints
31477 Indicates support for the @option{-f} option to the @code{-break-insert}
31480 Indicates Python scripting support, Python-based
31481 pretty-printing commands, and possible presence of the
31482 @samp{display_hint} field in the output of @code{-var-list-children}
31484 Indicates support for the @code{-thread-info} command.
31485 @item data-read-memory-bytes
31486 Indicates support for the @code{-data-read-memory-bytes} and the
31487 @code{-data-write-memory-bytes} commands.
31488 @item breakpoint-notifications
31489 Indicates that changes to breakpoints and breakpoints created via the
31490 CLI will be announced via async records.
31491 @item ada-task-info
31492 Indicates support for the @code{-ada-task-info} command.
31493 @item language-option
31494 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31495 option (@pxref{Context management}).
31496 @item info-gdb-mi-command
31497 Indicates support for the @code{-info-gdb-mi-command} command.
31498 @item undefined-command-error-code
31499 Indicates support for the "undefined-command" error code in error result
31500 records, produced when trying to execute an undefined @sc{gdb/mi} command
31501 (@pxref{GDB/MI Result Records}).
31502 @item exec-run-start-option
31503 Indicates that the @code{-exec-run} command supports the @option{--start}
31504 option (@pxref{GDB/MI Program Execution}).
31507 @subheading The @code{-list-target-features} Command
31508 @findex -list-target-features
31510 Returns a list of particular features that are supported by the
31511 target. Those features affect the permitted MI commands, but
31512 unlike the features reported by the @code{-list-features} command, the
31513 features depend on which target GDB is using at the moment. Whenever
31514 a target can change, due to commands such as @code{-target-select},
31515 @code{-target-attach} or @code{-exec-run}, the list of target features
31516 may change, and the frontend should obtain it again.
31520 (gdb) -list-target-features
31521 ^done,result=["async"]
31524 The current list of features is:
31528 Indicates that the target is capable of asynchronous command
31529 execution, which means that @value{GDBN} will accept further commands
31530 while the target is running.
31533 Indicates that the target is capable of reverse execution.
31534 @xref{Reverse Execution}, for more information.
31538 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31539 @node GDB/MI Miscellaneous Commands
31540 @section Miscellaneous @sc{gdb/mi} Commands
31542 @c @subheading -gdb-complete
31544 @subheading The @code{-gdb-exit} Command
31547 @subsubheading Synopsis
31553 Exit @value{GDBN} immediately.
31555 @subsubheading @value{GDBN} Command
31557 Approximately corresponds to @samp{quit}.
31559 @subsubheading Example
31569 @subheading The @code{-exec-abort} Command
31570 @findex -exec-abort
31572 @subsubheading Synopsis
31578 Kill the inferior running program.
31580 @subsubheading @value{GDBN} Command
31582 The corresponding @value{GDBN} command is @samp{kill}.
31584 @subsubheading Example
31589 @subheading The @code{-gdb-set} Command
31592 @subsubheading Synopsis
31598 Set an internal @value{GDBN} variable.
31599 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31601 @subsubheading @value{GDBN} Command
31603 The corresponding @value{GDBN} command is @samp{set}.
31605 @subsubheading Example
31615 @subheading The @code{-gdb-show} Command
31618 @subsubheading Synopsis
31624 Show the current value of a @value{GDBN} variable.
31626 @subsubheading @value{GDBN} Command
31628 The corresponding @value{GDBN} command is @samp{show}.
31630 @subsubheading Example
31639 @c @subheading -gdb-source
31642 @subheading The @code{-gdb-version} Command
31643 @findex -gdb-version
31645 @subsubheading Synopsis
31651 Show version information for @value{GDBN}. Used mostly in testing.
31653 @subsubheading @value{GDBN} Command
31655 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31656 default shows this information when you start an interactive session.
31658 @subsubheading Example
31660 @c This example modifies the actual output from GDB to avoid overfull
31666 ~Copyright 2000 Free Software Foundation, Inc.
31667 ~GDB is free software, covered by the GNU General Public License, and
31668 ~you are welcome to change it and/or distribute copies of it under
31669 ~ certain conditions.
31670 ~Type "show copying" to see the conditions.
31671 ~There is absolutely no warranty for GDB. Type "show warranty" for
31673 ~This GDB was configured as
31674 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31679 @subheading The @code{-list-thread-groups} Command
31680 @findex -list-thread-groups
31682 @subheading Synopsis
31685 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31688 Lists thread groups (@pxref{Thread groups}). When a single thread
31689 group is passed as the argument, lists the children of that group.
31690 When several thread group are passed, lists information about those
31691 thread groups. Without any parameters, lists information about all
31692 top-level thread groups.
31694 Normally, thread groups that are being debugged are reported.
31695 With the @samp{--available} option, @value{GDBN} reports thread groups
31696 available on the target.
31698 The output of this command may have either a @samp{threads} result or
31699 a @samp{groups} result. The @samp{thread} result has a list of tuples
31700 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31701 Information}). The @samp{groups} result has a list of tuples as value,
31702 each tuple describing a thread group. If top-level groups are
31703 requested (that is, no parameter is passed), or when several groups
31704 are passed, the output always has a @samp{groups} result. The format
31705 of the @samp{group} result is described below.
31707 To reduce the number of roundtrips it's possible to list thread groups
31708 together with their children, by passing the @samp{--recurse} option
31709 and the recursion depth. Presently, only recursion depth of 1 is
31710 permitted. If this option is present, then every reported thread group
31711 will also include its children, either as @samp{group} or
31712 @samp{threads} field.
31714 In general, any combination of option and parameters is permitted, with
31715 the following caveats:
31719 When a single thread group is passed, the output will typically
31720 be the @samp{threads} result. Because threads may not contain
31721 anything, the @samp{recurse} option will be ignored.
31724 When the @samp{--available} option is passed, limited information may
31725 be available. In particular, the list of threads of a process might
31726 be inaccessible. Further, specifying specific thread groups might
31727 not give any performance advantage over listing all thread groups.
31728 The frontend should assume that @samp{-list-thread-groups --available}
31729 is always an expensive operation and cache the results.
31733 The @samp{groups} result is a list of tuples, where each tuple may
31734 have the following fields:
31738 Identifier of the thread group. This field is always present.
31739 The identifier is an opaque string; frontends should not try to
31740 convert it to an integer, even though it might look like one.
31743 The type of the thread group. At present, only @samp{process} is a
31747 The target-specific process identifier. This field is only present
31748 for thread groups of type @samp{process} and only if the process exists.
31751 The exit code of this group's last exited thread, formatted in octal.
31752 This field is only present for thread groups of type @samp{process} and
31753 only if the process is not running.
31756 The number of children this thread group has. This field may be
31757 absent for an available thread group.
31760 This field has a list of tuples as value, each tuple describing a
31761 thread. It may be present if the @samp{--recurse} option is
31762 specified, and it's actually possible to obtain the threads.
31765 This field is a list of integers, each identifying a core that one
31766 thread of the group is running on. This field may be absent if
31767 such information is not available.
31770 The name of the executable file that corresponds to this thread group.
31771 The field is only present for thread groups of type @samp{process},
31772 and only if there is a corresponding executable file.
31776 @subheading Example
31780 -list-thread-groups
31781 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31782 -list-thread-groups 17
31783 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31784 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31785 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31786 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31787 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31788 -list-thread-groups --available
31789 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31790 -list-thread-groups --available --recurse 1
31791 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31792 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31793 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31794 -list-thread-groups --available --recurse 1 17 18
31795 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31796 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31797 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31800 @subheading The @code{-info-os} Command
31803 @subsubheading Synopsis
31806 -info-os [ @var{type} ]
31809 If no argument is supplied, the command returns a table of available
31810 operating-system-specific information types. If one of these types is
31811 supplied as an argument @var{type}, then the command returns a table
31812 of data of that type.
31814 The types of information available depend on the target operating
31817 @subsubheading @value{GDBN} Command
31819 The corresponding @value{GDBN} command is @samp{info os}.
31821 @subsubheading Example
31823 When run on a @sc{gnu}/Linux system, the output will look something
31829 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31830 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31831 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31832 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31833 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31835 item=@{col0="files",col1="Listing of all file descriptors",
31836 col2="File descriptors"@},
31837 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31838 col2="Kernel modules"@},
31839 item=@{col0="msg",col1="Listing of all message queues",
31840 col2="Message queues"@},
31841 item=@{col0="processes",col1="Listing of all processes",
31842 col2="Processes"@},
31843 item=@{col0="procgroups",col1="Listing of all process groups",
31844 col2="Process groups"@},
31845 item=@{col0="semaphores",col1="Listing of all semaphores",
31846 col2="Semaphores"@},
31847 item=@{col0="shm",col1="Listing of all shared-memory regions",
31848 col2="Shared-memory regions"@},
31849 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31851 item=@{col0="threads",col1="Listing of all threads",
31855 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31856 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31857 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31858 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31859 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31860 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31861 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31862 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31864 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31865 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31869 (Note that the MI output here includes a @code{"Title"} column that
31870 does not appear in command-line @code{info os}; this column is useful
31871 for MI clients that want to enumerate the types of data, such as in a
31872 popup menu, but is needless clutter on the command line, and
31873 @code{info os} omits it.)
31875 @subheading The @code{-add-inferior} Command
31876 @findex -add-inferior
31878 @subheading Synopsis
31884 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31885 inferior is not associated with any executable. Such association may
31886 be established with the @samp{-file-exec-and-symbols} command
31887 (@pxref{GDB/MI File Commands}). The command response has a single
31888 field, @samp{inferior}, whose value is the identifier of the
31889 thread group corresponding to the new inferior.
31891 @subheading Example
31896 ^done,inferior="i3"
31899 @subheading The @code{-interpreter-exec} Command
31900 @findex -interpreter-exec
31902 @subheading Synopsis
31905 -interpreter-exec @var{interpreter} @var{command}
31907 @anchor{-interpreter-exec}
31909 Execute the specified @var{command} in the given @var{interpreter}.
31911 @subheading @value{GDBN} Command
31913 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31915 @subheading Example
31919 -interpreter-exec console "break main"
31920 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31921 &"During symbol reading, bad structure-type format.\n"
31922 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31927 @subheading The @code{-inferior-tty-set} Command
31928 @findex -inferior-tty-set
31930 @subheading Synopsis
31933 -inferior-tty-set /dev/pts/1
31936 Set terminal for future runs of the program being debugged.
31938 @subheading @value{GDBN} Command
31940 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31942 @subheading Example
31946 -inferior-tty-set /dev/pts/1
31951 @subheading The @code{-inferior-tty-show} Command
31952 @findex -inferior-tty-show
31954 @subheading Synopsis
31960 Show terminal for future runs of program being debugged.
31962 @subheading @value{GDBN} Command
31964 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31966 @subheading Example
31970 -inferior-tty-set /dev/pts/1
31974 ^done,inferior_tty_terminal="/dev/pts/1"
31978 @subheading The @code{-enable-timings} Command
31979 @findex -enable-timings
31981 @subheading Synopsis
31984 -enable-timings [yes | no]
31987 Toggle the printing of the wallclock, user and system times for an MI
31988 command as a field in its output. This command is to help frontend
31989 developers optimize the performance of their code. No argument is
31990 equivalent to @samp{yes}.
31992 @subheading @value{GDBN} Command
31996 @subheading Example
32004 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32005 addr="0x080484ed",func="main",file="myprog.c",
32006 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32008 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32016 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32017 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32018 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32019 fullname="/home/nickrob/myprog.c",line="73"@}
32024 @chapter @value{GDBN} Annotations
32026 This chapter describes annotations in @value{GDBN}. Annotations were
32027 designed to interface @value{GDBN} to graphical user interfaces or other
32028 similar programs which want to interact with @value{GDBN} at a
32029 relatively high level.
32031 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32035 This is Edition @value{EDITION}, @value{DATE}.
32039 * Annotations Overview:: What annotations are; the general syntax.
32040 * Server Prefix:: Issuing a command without affecting user state.
32041 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32042 * Errors:: Annotations for error messages.
32043 * Invalidation:: Some annotations describe things now invalid.
32044 * Annotations for Running::
32045 Whether the program is running, how it stopped, etc.
32046 * Source Annotations:: Annotations describing source code.
32049 @node Annotations Overview
32050 @section What is an Annotation?
32051 @cindex annotations
32053 Annotations start with a newline character, two @samp{control-z}
32054 characters, and the name of the annotation. If there is no additional
32055 information associated with this annotation, the name of the annotation
32056 is followed immediately by a newline. If there is additional
32057 information, the name of the annotation is followed by a space, the
32058 additional information, and a newline. The additional information
32059 cannot contain newline characters.
32061 Any output not beginning with a newline and two @samp{control-z}
32062 characters denotes literal output from @value{GDBN}. Currently there is
32063 no need for @value{GDBN} to output a newline followed by two
32064 @samp{control-z} characters, but if there was such a need, the
32065 annotations could be extended with an @samp{escape} annotation which
32066 means those three characters as output.
32068 The annotation @var{level}, which is specified using the
32069 @option{--annotate} command line option (@pxref{Mode Options}), controls
32070 how much information @value{GDBN} prints together with its prompt,
32071 values of expressions, source lines, and other types of output. Level 0
32072 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32073 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32074 for programs that control @value{GDBN}, and level 2 annotations have
32075 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32076 Interface, annotate, GDB's Obsolete Annotations}).
32079 @kindex set annotate
32080 @item set annotate @var{level}
32081 The @value{GDBN} command @code{set annotate} sets the level of
32082 annotations to the specified @var{level}.
32084 @item show annotate
32085 @kindex show annotate
32086 Show the current annotation level.
32089 This chapter describes level 3 annotations.
32091 A simple example of starting up @value{GDBN} with annotations is:
32094 $ @kbd{gdb --annotate=3}
32096 Copyright 2003 Free Software Foundation, Inc.
32097 GDB is free software, covered by the GNU General Public License,
32098 and you are welcome to change it and/or distribute copies of it
32099 under certain conditions.
32100 Type "show copying" to see the conditions.
32101 There is absolutely no warranty for GDB. Type "show warranty"
32103 This GDB was configured as "i386-pc-linux-gnu"
32114 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32115 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32116 denotes a @samp{control-z} character) are annotations; the rest is
32117 output from @value{GDBN}.
32119 @node Server Prefix
32120 @section The Server Prefix
32121 @cindex server prefix
32123 If you prefix a command with @samp{server } then it will not affect
32124 the command history, nor will it affect @value{GDBN}'s notion of which
32125 command to repeat if @key{RET} is pressed on a line by itself. This
32126 means that commands can be run behind a user's back by a front-end in
32127 a transparent manner.
32129 The @code{server } prefix does not affect the recording of values into
32130 the value history; to print a value without recording it into the
32131 value history, use the @code{output} command instead of the
32132 @code{print} command.
32134 Using this prefix also disables confirmation requests
32135 (@pxref{confirmation requests}).
32138 @section Annotation for @value{GDBN} Input
32140 @cindex annotations for prompts
32141 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32142 to know when to send output, when the output from a given command is
32145 Different kinds of input each have a different @dfn{input type}. Each
32146 input type has three annotations: a @code{pre-} annotation, which
32147 denotes the beginning of any prompt which is being output, a plain
32148 annotation, which denotes the end of the prompt, and then a @code{post-}
32149 annotation which denotes the end of any echo which may (or may not) be
32150 associated with the input. For example, the @code{prompt} input type
32151 features the following annotations:
32159 The input types are
32162 @findex pre-prompt annotation
32163 @findex prompt annotation
32164 @findex post-prompt annotation
32166 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32168 @findex pre-commands annotation
32169 @findex commands annotation
32170 @findex post-commands annotation
32172 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32173 command. The annotations are repeated for each command which is input.
32175 @findex pre-overload-choice annotation
32176 @findex overload-choice annotation
32177 @findex post-overload-choice annotation
32178 @item overload-choice
32179 When @value{GDBN} wants the user to select between various overloaded functions.
32181 @findex pre-query annotation
32182 @findex query annotation
32183 @findex post-query annotation
32185 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32187 @findex pre-prompt-for-continue annotation
32188 @findex prompt-for-continue annotation
32189 @findex post-prompt-for-continue annotation
32190 @item prompt-for-continue
32191 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32192 expect this to work well; instead use @code{set height 0} to disable
32193 prompting. This is because the counting of lines is buggy in the
32194 presence of annotations.
32199 @cindex annotations for errors, warnings and interrupts
32201 @findex quit annotation
32206 This annotation occurs right before @value{GDBN} responds to an interrupt.
32208 @findex error annotation
32213 This annotation occurs right before @value{GDBN} responds to an error.
32215 Quit and error annotations indicate that any annotations which @value{GDBN} was
32216 in the middle of may end abruptly. For example, if a
32217 @code{value-history-begin} annotation is followed by a @code{error}, one
32218 cannot expect to receive the matching @code{value-history-end}. One
32219 cannot expect not to receive it either, however; an error annotation
32220 does not necessarily mean that @value{GDBN} is immediately returning all the way
32223 @findex error-begin annotation
32224 A quit or error annotation may be preceded by
32230 Any output between that and the quit or error annotation is the error
32233 Warning messages are not yet annotated.
32234 @c If we want to change that, need to fix warning(), type_error(),
32235 @c range_error(), and possibly other places.
32238 @section Invalidation Notices
32240 @cindex annotations for invalidation messages
32241 The following annotations say that certain pieces of state may have
32245 @findex frames-invalid annotation
32246 @item ^Z^Zframes-invalid
32248 The frames (for example, output from the @code{backtrace} command) may
32251 @findex breakpoints-invalid annotation
32252 @item ^Z^Zbreakpoints-invalid
32254 The breakpoints may have changed. For example, the user just added or
32255 deleted a breakpoint.
32258 @node Annotations for Running
32259 @section Running the Program
32260 @cindex annotations for running programs
32262 @findex starting annotation
32263 @findex stopping annotation
32264 When the program starts executing due to a @value{GDBN} command such as
32265 @code{step} or @code{continue},
32271 is output. When the program stops,
32277 is output. Before the @code{stopped} annotation, a variety of
32278 annotations describe how the program stopped.
32281 @findex exited annotation
32282 @item ^Z^Zexited @var{exit-status}
32283 The program exited, and @var{exit-status} is the exit status (zero for
32284 successful exit, otherwise nonzero).
32286 @findex signalled annotation
32287 @findex signal-name annotation
32288 @findex signal-name-end annotation
32289 @findex signal-string annotation
32290 @findex signal-string-end annotation
32291 @item ^Z^Zsignalled
32292 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32293 annotation continues:
32299 ^Z^Zsignal-name-end
32303 ^Z^Zsignal-string-end
32308 where @var{name} is the name of the signal, such as @code{SIGILL} or
32309 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32310 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32311 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32312 user's benefit and have no particular format.
32314 @findex signal annotation
32316 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32317 just saying that the program received the signal, not that it was
32318 terminated with it.
32320 @findex breakpoint annotation
32321 @item ^Z^Zbreakpoint @var{number}
32322 The program hit breakpoint number @var{number}.
32324 @findex watchpoint annotation
32325 @item ^Z^Zwatchpoint @var{number}
32326 The program hit watchpoint number @var{number}.
32329 @node Source Annotations
32330 @section Displaying Source
32331 @cindex annotations for source display
32333 @findex source annotation
32334 The following annotation is used instead of displaying source code:
32337 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32340 where @var{filename} is an absolute file name indicating which source
32341 file, @var{line} is the line number within that file (where 1 is the
32342 first line in the file), @var{character} is the character position
32343 within the file (where 0 is the first character in the file) (for most
32344 debug formats this will necessarily point to the beginning of a line),
32345 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32346 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32347 @var{addr} is the address in the target program associated with the
32348 source which is being displayed. The @var{addr} is in the form @samp{0x}
32349 followed by one or more lowercase hex digits (note that this does not
32350 depend on the language).
32352 @node JIT Interface
32353 @chapter JIT Compilation Interface
32354 @cindex just-in-time compilation
32355 @cindex JIT compilation interface
32357 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32358 interface. A JIT compiler is a program or library that generates native
32359 executable code at runtime and executes it, usually in order to achieve good
32360 performance while maintaining platform independence.
32362 Programs that use JIT compilation are normally difficult to debug because
32363 portions of their code are generated at runtime, instead of being loaded from
32364 object files, which is where @value{GDBN} normally finds the program's symbols
32365 and debug information. In order to debug programs that use JIT compilation,
32366 @value{GDBN} has an interface that allows the program to register in-memory
32367 symbol files with @value{GDBN} at runtime.
32369 If you are using @value{GDBN} to debug a program that uses this interface, then
32370 it should work transparently so long as you have not stripped the binary. If
32371 you are developing a JIT compiler, then the interface is documented in the rest
32372 of this chapter. At this time, the only known client of this interface is the
32375 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32376 JIT compiler communicates with @value{GDBN} by writing data into a global
32377 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32378 attaches, it reads a linked list of symbol files from the global variable to
32379 find existing code, and puts a breakpoint in the function so that it can find
32380 out about additional code.
32383 * Declarations:: Relevant C struct declarations
32384 * Registering Code:: Steps to register code
32385 * Unregistering Code:: Steps to unregister code
32386 * Custom Debug Info:: Emit debug information in a custom format
32390 @section JIT Declarations
32392 These are the relevant struct declarations that a C program should include to
32393 implement the interface:
32403 struct jit_code_entry
32405 struct jit_code_entry *next_entry;
32406 struct jit_code_entry *prev_entry;
32407 const char *symfile_addr;
32408 uint64_t symfile_size;
32411 struct jit_descriptor
32414 /* This type should be jit_actions_t, but we use uint32_t
32415 to be explicit about the bitwidth. */
32416 uint32_t action_flag;
32417 struct jit_code_entry *relevant_entry;
32418 struct jit_code_entry *first_entry;
32421 /* GDB puts a breakpoint in this function. */
32422 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32424 /* Make sure to specify the version statically, because the
32425 debugger may check the version before we can set it. */
32426 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32429 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32430 modifications to this global data properly, which can easily be done by putting
32431 a global mutex around modifications to these structures.
32433 @node Registering Code
32434 @section Registering Code
32436 To register code with @value{GDBN}, the JIT should follow this protocol:
32440 Generate an object file in memory with symbols and other desired debug
32441 information. The file must include the virtual addresses of the sections.
32444 Create a code entry for the file, which gives the start and size of the symbol
32448 Add it to the linked list in the JIT descriptor.
32451 Point the relevant_entry field of the descriptor at the entry.
32454 Set @code{action_flag} to @code{JIT_REGISTER} and call
32455 @code{__jit_debug_register_code}.
32458 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32459 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32460 new code. However, the linked list must still be maintained in order to allow
32461 @value{GDBN} to attach to a running process and still find the symbol files.
32463 @node Unregistering Code
32464 @section Unregistering Code
32466 If code is freed, then the JIT should use the following protocol:
32470 Remove the code entry corresponding to the code from the linked list.
32473 Point the @code{relevant_entry} field of the descriptor at the code entry.
32476 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32477 @code{__jit_debug_register_code}.
32480 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32481 and the JIT will leak the memory used for the associated symbol files.
32483 @node Custom Debug Info
32484 @section Custom Debug Info
32485 @cindex custom JIT debug info
32486 @cindex JIT debug info reader
32488 Generating debug information in platform-native file formats (like ELF
32489 or COFF) may be an overkill for JIT compilers; especially if all the
32490 debug info is used for is displaying a meaningful backtrace. The
32491 issue can be resolved by having the JIT writers decide on a debug info
32492 format and also provide a reader that parses the debug info generated
32493 by the JIT compiler. This section gives a brief overview on writing
32494 such a parser. More specific details can be found in the source file
32495 @file{gdb/jit-reader.in}, which is also installed as a header at
32496 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32498 The reader is implemented as a shared object (so this functionality is
32499 not available on platforms which don't allow loading shared objects at
32500 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32501 @code{jit-reader-unload} are provided, to be used to load and unload
32502 the readers from a preconfigured directory. Once loaded, the shared
32503 object is used the parse the debug information emitted by the JIT
32507 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32508 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32511 @node Using JIT Debug Info Readers
32512 @subsection Using JIT Debug Info Readers
32513 @kindex jit-reader-load
32514 @kindex jit-reader-unload
32516 Readers can be loaded and unloaded using the @code{jit-reader-load}
32517 and @code{jit-reader-unload} commands.
32520 @item jit-reader-load @var{reader}
32521 Load the JIT reader named @var{reader}, which is a shared
32522 object specified as either an absolute or a relative file name. In
32523 the latter case, @value{GDBN} will try to load the reader from a
32524 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32525 system (here @var{libdir} is the system library directory, often
32526 @file{/usr/local/lib}).
32528 Only one reader can be active at a time; trying to load a second
32529 reader when one is already loaded will result in @value{GDBN}
32530 reporting an error. A new JIT reader can be loaded by first unloading
32531 the current one using @code{jit-reader-unload} and then invoking
32532 @code{jit-reader-load}.
32534 @item jit-reader-unload
32535 Unload the currently loaded JIT reader.
32539 @node Writing JIT Debug Info Readers
32540 @subsection Writing JIT Debug Info Readers
32541 @cindex writing JIT debug info readers
32543 As mentioned, a reader is essentially a shared object conforming to a
32544 certain ABI. This ABI is described in @file{jit-reader.h}.
32546 @file{jit-reader.h} defines the structures, macros and functions
32547 required to write a reader. It is installed (along with
32548 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32549 the system include directory.
32551 Readers need to be released under a GPL compatible license. A reader
32552 can be declared as released under such a license by placing the macro
32553 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32555 The entry point for readers is the symbol @code{gdb_init_reader},
32556 which is expected to be a function with the prototype
32558 @findex gdb_init_reader
32560 extern struct gdb_reader_funcs *gdb_init_reader (void);
32563 @cindex @code{struct gdb_reader_funcs}
32565 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32566 functions. These functions are executed to read the debug info
32567 generated by the JIT compiler (@code{read}), to unwind stack frames
32568 (@code{unwind}) and to create canonical frame IDs
32569 (@code{get_Frame_id}). It also has a callback that is called when the
32570 reader is being unloaded (@code{destroy}). The struct looks like this
32573 struct gdb_reader_funcs
32575 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32576 int reader_version;
32578 /* For use by the reader. */
32581 gdb_read_debug_info *read;
32582 gdb_unwind_frame *unwind;
32583 gdb_get_frame_id *get_frame_id;
32584 gdb_destroy_reader *destroy;
32588 @cindex @code{struct gdb_symbol_callbacks}
32589 @cindex @code{struct gdb_unwind_callbacks}
32591 The callbacks are provided with another set of callbacks by
32592 @value{GDBN} to do their job. For @code{read}, these callbacks are
32593 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32594 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32595 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32596 files and new symbol tables inside those object files. @code{struct
32597 gdb_unwind_callbacks} has callbacks to read registers off the current
32598 frame and to write out the values of the registers in the previous
32599 frame. Both have a callback (@code{target_read}) to read bytes off the
32600 target's address space.
32602 @node In-Process Agent
32603 @chapter In-Process Agent
32604 @cindex debugging agent
32605 The traditional debugging model is conceptually low-speed, but works fine,
32606 because most bugs can be reproduced in debugging-mode execution. However,
32607 as multi-core or many-core processors are becoming mainstream, and
32608 multi-threaded programs become more and more popular, there should be more
32609 and more bugs that only manifest themselves at normal-mode execution, for
32610 example, thread races, because debugger's interference with the program's
32611 timing may conceal the bugs. On the other hand, in some applications,
32612 it is not feasible for the debugger to interrupt the program's execution
32613 long enough for the developer to learn anything helpful about its behavior.
32614 If the program's correctness depends on its real-time behavior, delays
32615 introduced by a debugger might cause the program to fail, even when the
32616 code itself is correct. It is useful to be able to observe the program's
32617 behavior without interrupting it.
32619 Therefore, traditional debugging model is too intrusive to reproduce
32620 some bugs. In order to reduce the interference with the program, we can
32621 reduce the number of operations performed by debugger. The
32622 @dfn{In-Process Agent}, a shared library, is running within the same
32623 process with inferior, and is able to perform some debugging operations
32624 itself. As a result, debugger is only involved when necessary, and
32625 performance of debugging can be improved accordingly. Note that
32626 interference with program can be reduced but can't be removed completely,
32627 because the in-process agent will still stop or slow down the program.
32629 The in-process agent can interpret and execute Agent Expressions
32630 (@pxref{Agent Expressions}) during performing debugging operations. The
32631 agent expressions can be used for different purposes, such as collecting
32632 data in tracepoints, and condition evaluation in breakpoints.
32634 @anchor{Control Agent}
32635 You can control whether the in-process agent is used as an aid for
32636 debugging with the following commands:
32639 @kindex set agent on
32641 Causes the in-process agent to perform some operations on behalf of the
32642 debugger. Just which operations requested by the user will be done
32643 by the in-process agent depends on the its capabilities. For example,
32644 if you request to evaluate breakpoint conditions in the in-process agent,
32645 and the in-process agent has such capability as well, then breakpoint
32646 conditions will be evaluated in the in-process agent.
32648 @kindex set agent off
32649 @item set agent off
32650 Disables execution of debugging operations by the in-process agent. All
32651 of the operations will be performed by @value{GDBN}.
32655 Display the current setting of execution of debugging operations by
32656 the in-process agent.
32660 * In-Process Agent Protocol::
32663 @node In-Process Agent Protocol
32664 @section In-Process Agent Protocol
32665 @cindex in-process agent protocol
32667 The in-process agent is able to communicate with both @value{GDBN} and
32668 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32669 used for communications between @value{GDBN} or GDBserver and the IPA.
32670 In general, @value{GDBN} or GDBserver sends commands
32671 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32672 in-process agent replies back with the return result of the command, or
32673 some other information. The data sent to in-process agent is composed
32674 of primitive data types, such as 4-byte or 8-byte type, and composite
32675 types, which are called objects (@pxref{IPA Protocol Objects}).
32678 * IPA Protocol Objects::
32679 * IPA Protocol Commands::
32682 @node IPA Protocol Objects
32683 @subsection IPA Protocol Objects
32684 @cindex ipa protocol objects
32686 The commands sent to and results received from agent may contain some
32687 complex data types called @dfn{objects}.
32689 The in-process agent is running on the same machine with @value{GDBN}
32690 or GDBserver, so it doesn't have to handle as much differences between
32691 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32692 However, there are still some differences of two ends in two processes:
32696 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32697 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32699 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32700 GDBserver is compiled with one, and in-process agent is compiled with
32704 Here are the IPA Protocol Objects:
32708 agent expression object. It represents an agent expression
32709 (@pxref{Agent Expressions}).
32710 @anchor{agent expression object}
32712 tracepoint action object. It represents a tracepoint action
32713 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32714 memory, static trace data and to evaluate expression.
32715 @anchor{tracepoint action object}
32717 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32718 @anchor{tracepoint object}
32722 The following table describes important attributes of each IPA protocol
32725 @multitable @columnfractions .30 .20 .50
32726 @headitem Name @tab Size @tab Description
32727 @item @emph{agent expression object} @tab @tab
32728 @item length @tab 4 @tab length of bytes code
32729 @item byte code @tab @var{length} @tab contents of byte code
32730 @item @emph{tracepoint action for collecting memory} @tab @tab
32731 @item 'M' @tab 1 @tab type of tracepoint action
32732 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32733 address of the lowest byte to collect, otherwise @var{addr} is the offset
32734 of @var{basereg} for memory collecting.
32735 @item len @tab 8 @tab length of memory for collecting
32736 @item basereg @tab 4 @tab the register number containing the starting
32737 memory address for collecting.
32738 @item @emph{tracepoint action for collecting registers} @tab @tab
32739 @item 'R' @tab 1 @tab type of tracepoint action
32740 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32741 @item 'L' @tab 1 @tab type of tracepoint action
32742 @item @emph{tracepoint action for expression evaluation} @tab @tab
32743 @item 'X' @tab 1 @tab type of tracepoint action
32744 @item agent expression @tab length of @tab @ref{agent expression object}
32745 @item @emph{tracepoint object} @tab @tab
32746 @item number @tab 4 @tab number of tracepoint
32747 @item address @tab 8 @tab address of tracepoint inserted on
32748 @item type @tab 4 @tab type of tracepoint
32749 @item enabled @tab 1 @tab enable or disable of tracepoint
32750 @item step_count @tab 8 @tab step
32751 @item pass_count @tab 8 @tab pass
32752 @item numactions @tab 4 @tab number of tracepoint actions
32753 @item hit count @tab 8 @tab hit count
32754 @item trace frame usage @tab 8 @tab trace frame usage
32755 @item compiled_cond @tab 8 @tab compiled condition
32756 @item orig_size @tab 8 @tab orig size
32757 @item condition @tab 4 if condition is NULL otherwise length of
32758 @ref{agent expression object}
32759 @tab zero if condition is NULL, otherwise is
32760 @ref{agent expression object}
32761 @item actions @tab variable
32762 @tab numactions number of @ref{tracepoint action object}
32765 @node IPA Protocol Commands
32766 @subsection IPA Protocol Commands
32767 @cindex ipa protocol commands
32769 The spaces in each command are delimiters to ease reading this commands
32770 specification. They don't exist in real commands.
32774 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32775 Installs a new fast tracepoint described by @var{tracepoint_object}
32776 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32777 head of @dfn{jumppad}, which is used to jump to data collection routine
32782 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32783 @var{target_address} is address of tracepoint in the inferior.
32784 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32785 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32786 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32787 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32794 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32795 is about to kill inferiors.
32803 @item probe_marker_at:@var{address}
32804 Asks in-process agent to probe the marker at @var{address}.
32811 @item unprobe_marker_at:@var{address}
32812 Asks in-process agent to unprobe the marker at @var{address}.
32816 @chapter Reporting Bugs in @value{GDBN}
32817 @cindex bugs in @value{GDBN}
32818 @cindex reporting bugs in @value{GDBN}
32820 Your bug reports play an essential role in making @value{GDBN} reliable.
32822 Reporting a bug may help you by bringing a solution to your problem, or it
32823 may not. But in any case the principal function of a bug report is to help
32824 the entire community by making the next version of @value{GDBN} work better. Bug
32825 reports are your contribution to the maintenance of @value{GDBN}.
32827 In order for a bug report to serve its purpose, you must include the
32828 information that enables us to fix the bug.
32831 * Bug Criteria:: Have you found a bug?
32832 * Bug Reporting:: How to report bugs
32836 @section Have You Found a Bug?
32837 @cindex bug criteria
32839 If you are not sure whether you have found a bug, here are some guidelines:
32842 @cindex fatal signal
32843 @cindex debugger crash
32844 @cindex crash of debugger
32846 If the debugger gets a fatal signal, for any input whatever, that is a
32847 @value{GDBN} bug. Reliable debuggers never crash.
32849 @cindex error on valid input
32851 If @value{GDBN} produces an error message for valid input, that is a
32852 bug. (Note that if you're cross debugging, the problem may also be
32853 somewhere in the connection to the target.)
32855 @cindex invalid input
32857 If @value{GDBN} does not produce an error message for invalid input,
32858 that is a bug. However, you should note that your idea of
32859 ``invalid input'' might be our idea of ``an extension'' or ``support
32860 for traditional practice''.
32863 If you are an experienced user of debugging tools, your suggestions
32864 for improvement of @value{GDBN} are welcome in any case.
32867 @node Bug Reporting
32868 @section How to Report Bugs
32869 @cindex bug reports
32870 @cindex @value{GDBN} bugs, reporting
32872 A number of companies and individuals offer support for @sc{gnu} products.
32873 If you obtained @value{GDBN} from a support organization, we recommend you
32874 contact that organization first.
32876 You can find contact information for many support companies and
32877 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32879 @c should add a web page ref...
32882 @ifset BUGURL_DEFAULT
32883 In any event, we also recommend that you submit bug reports for
32884 @value{GDBN}. The preferred method is to submit them directly using
32885 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32886 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32889 @strong{Do not send bug reports to @samp{info-gdb}, or to
32890 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32891 not want to receive bug reports. Those that do have arranged to receive
32894 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32895 serves as a repeater. The mailing list and the newsgroup carry exactly
32896 the same messages. Often people think of posting bug reports to the
32897 newsgroup instead of mailing them. This appears to work, but it has one
32898 problem which can be crucial: a newsgroup posting often lacks a mail
32899 path back to the sender. Thus, if we need to ask for more information,
32900 we may be unable to reach you. For this reason, it is better to send
32901 bug reports to the mailing list.
32903 @ifclear BUGURL_DEFAULT
32904 In any event, we also recommend that you submit bug reports for
32905 @value{GDBN} to @value{BUGURL}.
32909 The fundamental principle of reporting bugs usefully is this:
32910 @strong{report all the facts}. If you are not sure whether to state a
32911 fact or leave it out, state it!
32913 Often people omit facts because they think they know what causes the
32914 problem and assume that some details do not matter. Thus, you might
32915 assume that the name of the variable you use in an example does not matter.
32916 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32917 stray memory reference which happens to fetch from the location where that
32918 name is stored in memory; perhaps, if the name were different, the contents
32919 of that location would fool the debugger into doing the right thing despite
32920 the bug. Play it safe and give a specific, complete example. That is the
32921 easiest thing for you to do, and the most helpful.
32923 Keep in mind that the purpose of a bug report is to enable us to fix the
32924 bug. It may be that the bug has been reported previously, but neither
32925 you nor we can know that unless your bug report is complete and
32928 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32929 bell?'' Those bug reports are useless, and we urge everyone to
32930 @emph{refuse to respond to them} except to chide the sender to report
32933 To enable us to fix the bug, you should include all these things:
32937 The version of @value{GDBN}. @value{GDBN} announces it if you start
32938 with no arguments; you can also print it at any time using @code{show
32941 Without this, we will not know whether there is any point in looking for
32942 the bug in the current version of @value{GDBN}.
32945 The type of machine you are using, and the operating system name and
32949 The details of the @value{GDBN} build-time configuration.
32950 @value{GDBN} shows these details if you invoke it with the
32951 @option{--configuration} command-line option, or if you type
32952 @code{show configuration} at @value{GDBN}'s prompt.
32955 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32956 ``@value{GCC}--2.8.1''.
32959 What compiler (and its version) was used to compile the program you are
32960 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32961 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32962 to get this information; for other compilers, see the documentation for
32966 The command arguments you gave the compiler to compile your example and
32967 observe the bug. For example, did you use @samp{-O}? To guarantee
32968 you will not omit something important, list them all. A copy of the
32969 Makefile (or the output from make) is sufficient.
32971 If we were to try to guess the arguments, we would probably guess wrong
32972 and then we might not encounter the bug.
32975 A complete input script, and all necessary source files, that will
32979 A description of what behavior you observe that you believe is
32980 incorrect. For example, ``It gets a fatal signal.''
32982 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32983 will certainly notice it. But if the bug is incorrect output, we might
32984 not notice unless it is glaringly wrong. You might as well not give us
32985 a chance to make a mistake.
32987 Even if the problem you experience is a fatal signal, you should still
32988 say so explicitly. Suppose something strange is going on, such as, your
32989 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32990 the C library on your system. (This has happened!) Your copy might
32991 crash and ours would not. If you told us to expect a crash, then when
32992 ours fails to crash, we would know that the bug was not happening for
32993 us. If you had not told us to expect a crash, then we would not be able
32994 to draw any conclusion from our observations.
32997 @cindex recording a session script
32998 To collect all this information, you can use a session recording program
32999 such as @command{script}, which is available on many Unix systems.
33000 Just run your @value{GDBN} session inside @command{script} and then
33001 include the @file{typescript} file with your bug report.
33003 Another way to record a @value{GDBN} session is to run @value{GDBN}
33004 inside Emacs and then save the entire buffer to a file.
33007 If you wish to suggest changes to the @value{GDBN} source, send us context
33008 diffs. If you even discuss something in the @value{GDBN} source, refer to
33009 it by context, not by line number.
33011 The line numbers in our development sources will not match those in your
33012 sources. Your line numbers would convey no useful information to us.
33016 Here are some things that are not necessary:
33020 A description of the envelope of the bug.
33022 Often people who encounter a bug spend a lot of time investigating
33023 which changes to the input file will make the bug go away and which
33024 changes will not affect it.
33026 This is often time consuming and not very useful, because the way we
33027 will find the bug is by running a single example under the debugger
33028 with breakpoints, not by pure deduction from a series of examples.
33029 We recommend that you save your time for something else.
33031 Of course, if you can find a simpler example to report @emph{instead}
33032 of the original one, that is a convenience for us. Errors in the
33033 output will be easier to spot, running under the debugger will take
33034 less time, and so on.
33036 However, simplification is not vital; if you do not want to do this,
33037 report the bug anyway and send us the entire test case you used.
33040 A patch for the bug.
33042 A patch for the bug does help us if it is a good one. But do not omit
33043 the necessary information, such as the test case, on the assumption that
33044 a patch is all we need. We might see problems with your patch and decide
33045 to fix the problem another way, or we might not understand it at all.
33047 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33048 construct an example that will make the program follow a certain path
33049 through the code. If you do not send us the example, we will not be able
33050 to construct one, so we will not be able to verify that the bug is fixed.
33052 And if we cannot understand what bug you are trying to fix, or why your
33053 patch should be an improvement, we will not install it. A test case will
33054 help us to understand.
33057 A guess about what the bug is or what it depends on.
33059 Such guesses are usually wrong. Even we cannot guess right about such
33060 things without first using the debugger to find the facts.
33063 @c The readline documentation is distributed with the readline code
33064 @c and consists of the two following files:
33067 @c Use -I with makeinfo to point to the appropriate directory,
33068 @c environment var TEXINPUTS with TeX.
33069 @ifclear SYSTEM_READLINE
33070 @include rluser.texi
33071 @include hsuser.texi
33075 @appendix In Memoriam
33077 The @value{GDBN} project mourns the loss of the following long-time
33082 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33083 to Free Software in general. Outside of @value{GDBN}, he was known in
33084 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33086 @item Michael Snyder
33087 Michael was one of the Global Maintainers of the @value{GDBN} project,
33088 with contributions recorded as early as 1996, until 2011. In addition
33089 to his day to day participation, he was a large driving force behind
33090 adding Reverse Debugging to @value{GDBN}.
33093 Beyond their technical contributions to the project, they were also
33094 enjoyable members of the Free Software Community. We will miss them.
33096 @node Formatting Documentation
33097 @appendix Formatting Documentation
33099 @cindex @value{GDBN} reference card
33100 @cindex reference card
33101 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33102 for printing with PostScript or Ghostscript, in the @file{gdb}
33103 subdirectory of the main source directory@footnote{In
33104 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33105 release.}. If you can use PostScript or Ghostscript with your printer,
33106 you can print the reference card immediately with @file{refcard.ps}.
33108 The release also includes the source for the reference card. You
33109 can format it, using @TeX{}, by typing:
33115 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33116 mode on US ``letter'' size paper;
33117 that is, on a sheet 11 inches wide by 8.5 inches
33118 high. You will need to specify this form of printing as an option to
33119 your @sc{dvi} output program.
33121 @cindex documentation
33123 All the documentation for @value{GDBN} comes as part of the machine-readable
33124 distribution. The documentation is written in Texinfo format, which is
33125 a documentation system that uses a single source file to produce both
33126 on-line information and a printed manual. You can use one of the Info
33127 formatting commands to create the on-line version of the documentation
33128 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33130 @value{GDBN} includes an already formatted copy of the on-line Info
33131 version of this manual in the @file{gdb} subdirectory. The main Info
33132 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33133 subordinate files matching @samp{gdb.info*} in the same directory. If
33134 necessary, you can print out these files, or read them with any editor;
33135 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33136 Emacs or the standalone @code{info} program, available as part of the
33137 @sc{gnu} Texinfo distribution.
33139 If you want to format these Info files yourself, you need one of the
33140 Info formatting programs, such as @code{texinfo-format-buffer} or
33143 If you have @code{makeinfo} installed, and are in the top level
33144 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33145 version @value{GDBVN}), you can make the Info file by typing:
33152 If you want to typeset and print copies of this manual, you need @TeX{},
33153 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33154 Texinfo definitions file.
33156 @TeX{} is a typesetting program; it does not print files directly, but
33157 produces output files called @sc{dvi} files. To print a typeset
33158 document, you need a program to print @sc{dvi} files. If your system
33159 has @TeX{} installed, chances are it has such a program. The precise
33160 command to use depends on your system; @kbd{lpr -d} is common; another
33161 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33162 require a file name without any extension or a @samp{.dvi} extension.
33164 @TeX{} also requires a macro definitions file called
33165 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33166 written in Texinfo format. On its own, @TeX{} cannot either read or
33167 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33168 and is located in the @file{gdb-@var{version-number}/texinfo}
33171 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33172 typeset and print this manual. First switch to the @file{gdb}
33173 subdirectory of the main source directory (for example, to
33174 @file{gdb-@value{GDBVN}/gdb}) and type:
33180 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33182 @node Installing GDB
33183 @appendix Installing @value{GDBN}
33184 @cindex installation
33187 * Requirements:: Requirements for building @value{GDBN}
33188 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33189 * Separate Objdir:: Compiling @value{GDBN} in another directory
33190 * Config Names:: Specifying names for hosts and targets
33191 * Configure Options:: Summary of options for configure
33192 * System-wide configuration:: Having a system-wide init file
33196 @section Requirements for Building @value{GDBN}
33197 @cindex building @value{GDBN}, requirements for
33199 Building @value{GDBN} requires various tools and packages to be available.
33200 Other packages will be used only if they are found.
33202 @heading Tools/Packages Necessary for Building @value{GDBN}
33204 @item ISO C90 compiler
33205 @value{GDBN} is written in ISO C90. It should be buildable with any
33206 working C90 compiler, e.g.@: GCC.
33210 @heading Tools/Packages Optional for Building @value{GDBN}
33214 @value{GDBN} can use the Expat XML parsing library. This library may be
33215 included with your operating system distribution; if it is not, you
33216 can get the latest version from @url{http://expat.sourceforge.net}.
33217 The @file{configure} script will search for this library in several
33218 standard locations; if it is installed in an unusual path, you can
33219 use the @option{--with-libexpat-prefix} option to specify its location.
33225 Remote protocol memory maps (@pxref{Memory Map Format})
33227 Target descriptions (@pxref{Target Descriptions})
33229 Remote shared library lists (@xref{Library List Format},
33230 or alternatively @pxref{Library List Format for SVR4 Targets})
33232 MS-Windows shared libraries (@pxref{Shared Libraries})
33234 Traceframe info (@pxref{Traceframe Info Format})
33236 Branch trace (@pxref{Branch Trace Format},
33237 @pxref{Branch Trace Configuration Format})
33241 @cindex compressed debug sections
33242 @value{GDBN} will use the @samp{zlib} library, if available, to read
33243 compressed debug sections. Some linkers, such as GNU gold, are capable
33244 of producing binaries with compressed debug sections. If @value{GDBN}
33245 is compiled with @samp{zlib}, it will be able to read the debug
33246 information in such binaries.
33248 The @samp{zlib} library is likely included with your operating system
33249 distribution; if it is not, you can get the latest version from
33250 @url{http://zlib.net}.
33253 @value{GDBN}'s features related to character sets (@pxref{Character
33254 Sets}) require a functioning @code{iconv} implementation. If you are
33255 on a GNU system, then this is provided by the GNU C Library. Some
33256 other systems also provide a working @code{iconv}.
33258 If @value{GDBN} is using the @code{iconv} program which is installed
33259 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33260 This is done with @option{--with-iconv-bin} which specifies the
33261 directory that contains the @code{iconv} program.
33263 On systems without @code{iconv}, you can install GNU Libiconv. If you
33264 have previously installed Libiconv, you can use the
33265 @option{--with-libiconv-prefix} option to configure.
33267 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33268 arrange to build Libiconv if a directory named @file{libiconv} appears
33269 in the top-most source directory. If Libiconv is built this way, and
33270 if the operating system does not provide a suitable @code{iconv}
33271 implementation, then the just-built library will automatically be used
33272 by @value{GDBN}. One easy way to set this up is to download GNU
33273 Libiconv, unpack it, and then rename the directory holding the
33274 Libiconv source code to @samp{libiconv}.
33277 @node Running Configure
33278 @section Invoking the @value{GDBN} @file{configure} Script
33279 @cindex configuring @value{GDBN}
33280 @value{GDBN} comes with a @file{configure} script that automates the process
33281 of preparing @value{GDBN} for installation; you can then use @code{make} to
33282 build the @code{gdb} program.
33284 @c irrelevant in info file; it's as current as the code it lives with.
33285 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33286 look at the @file{README} file in the sources; we may have improved the
33287 installation procedures since publishing this manual.}
33290 The @value{GDBN} distribution includes all the source code you need for
33291 @value{GDBN} in a single directory, whose name is usually composed by
33292 appending the version number to @samp{gdb}.
33294 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33295 @file{gdb-@value{GDBVN}} directory. That directory contains:
33298 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33299 script for configuring @value{GDBN} and all its supporting libraries
33301 @item gdb-@value{GDBVN}/gdb
33302 the source specific to @value{GDBN} itself
33304 @item gdb-@value{GDBVN}/bfd
33305 source for the Binary File Descriptor library
33307 @item gdb-@value{GDBVN}/include
33308 @sc{gnu} include files
33310 @item gdb-@value{GDBVN}/libiberty
33311 source for the @samp{-liberty} free software library
33313 @item gdb-@value{GDBVN}/opcodes
33314 source for the library of opcode tables and disassemblers
33316 @item gdb-@value{GDBVN}/readline
33317 source for the @sc{gnu} command-line interface
33319 @item gdb-@value{GDBVN}/glob
33320 source for the @sc{gnu} filename pattern-matching subroutine
33322 @item gdb-@value{GDBVN}/mmalloc
33323 source for the @sc{gnu} memory-mapped malloc package
33326 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33327 from the @file{gdb-@var{version-number}} source directory, which in
33328 this example is the @file{gdb-@value{GDBVN}} directory.
33330 First switch to the @file{gdb-@var{version-number}} source directory
33331 if you are not already in it; then run @file{configure}. Pass the
33332 identifier for the platform on which @value{GDBN} will run as an
33338 cd gdb-@value{GDBVN}
33339 ./configure @var{host}
33344 where @var{host} is an identifier such as @samp{sun4} or
33345 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33346 (You can often leave off @var{host}; @file{configure} tries to guess the
33347 correct value by examining your system.)
33349 Running @samp{configure @var{host}} and then running @code{make} builds the
33350 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33351 libraries, then @code{gdb} itself. The configured source files, and the
33352 binaries, are left in the corresponding source directories.
33355 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33356 system does not recognize this automatically when you run a different
33357 shell, you may need to run @code{sh} on it explicitly:
33360 sh configure @var{host}
33363 If you run @file{configure} from a directory that contains source
33364 directories for multiple libraries or programs, such as the
33365 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33367 creates configuration files for every directory level underneath (unless
33368 you tell it not to, with the @samp{--norecursion} option).
33370 You should run the @file{configure} script from the top directory in the
33371 source tree, the @file{gdb-@var{version-number}} directory. If you run
33372 @file{configure} from one of the subdirectories, you will configure only
33373 that subdirectory. That is usually not what you want. In particular,
33374 if you run the first @file{configure} from the @file{gdb} subdirectory
33375 of the @file{gdb-@var{version-number}} directory, you will omit the
33376 configuration of @file{bfd}, @file{readline}, and other sibling
33377 directories of the @file{gdb} subdirectory. This leads to build errors
33378 about missing include files such as @file{bfd/bfd.h}.
33380 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33381 However, you should make sure that the shell on your path (named by
33382 the @samp{SHELL} environment variable) is publicly readable. Remember
33383 that @value{GDBN} uses the shell to start your program---some systems refuse to
33384 let @value{GDBN} debug child processes whose programs are not readable.
33386 @node Separate Objdir
33387 @section Compiling @value{GDBN} in Another Directory
33389 If you want to run @value{GDBN} versions for several host or target machines,
33390 you need a different @code{gdb} compiled for each combination of
33391 host and target. @file{configure} is designed to make this easy by
33392 allowing you to generate each configuration in a separate subdirectory,
33393 rather than in the source directory. If your @code{make} program
33394 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33395 @code{make} in each of these directories builds the @code{gdb}
33396 program specified there.
33398 To build @code{gdb} in a separate directory, run @file{configure}
33399 with the @samp{--srcdir} option to specify where to find the source.
33400 (You also need to specify a path to find @file{configure}
33401 itself from your working directory. If the path to @file{configure}
33402 would be the same as the argument to @samp{--srcdir}, you can leave out
33403 the @samp{--srcdir} option; it is assumed.)
33405 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33406 separate directory for a Sun 4 like this:
33410 cd gdb-@value{GDBVN}
33413 ../gdb-@value{GDBVN}/configure sun4
33418 When @file{configure} builds a configuration using a remote source
33419 directory, it creates a tree for the binaries with the same structure
33420 (and using the same names) as the tree under the source directory. In
33421 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33422 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33423 @file{gdb-sun4/gdb}.
33425 Make sure that your path to the @file{configure} script has just one
33426 instance of @file{gdb} in it. If your path to @file{configure} looks
33427 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33428 one subdirectory of @value{GDBN}, not the whole package. This leads to
33429 build errors about missing include files such as @file{bfd/bfd.h}.
33431 One popular reason to build several @value{GDBN} configurations in separate
33432 directories is to configure @value{GDBN} for cross-compiling (where
33433 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33434 programs that run on another machine---the @dfn{target}).
33435 You specify a cross-debugging target by
33436 giving the @samp{--target=@var{target}} option to @file{configure}.
33438 When you run @code{make} to build a program or library, you must run
33439 it in a configured directory---whatever directory you were in when you
33440 called @file{configure} (or one of its subdirectories).
33442 The @code{Makefile} that @file{configure} generates in each source
33443 directory also runs recursively. If you type @code{make} in a source
33444 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33445 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33446 will build all the required libraries, and then build GDB.
33448 When you have multiple hosts or targets configured in separate
33449 directories, you can run @code{make} on them in parallel (for example,
33450 if they are NFS-mounted on each of the hosts); they will not interfere
33454 @section Specifying Names for Hosts and Targets
33456 The specifications used for hosts and targets in the @file{configure}
33457 script are based on a three-part naming scheme, but some short predefined
33458 aliases are also supported. The full naming scheme encodes three pieces
33459 of information in the following pattern:
33462 @var{architecture}-@var{vendor}-@var{os}
33465 For example, you can use the alias @code{sun4} as a @var{host} argument,
33466 or as the value for @var{target} in a @code{--target=@var{target}}
33467 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33469 The @file{configure} script accompanying @value{GDBN} does not provide
33470 any query facility to list all supported host and target names or
33471 aliases. @file{configure} calls the Bourne shell script
33472 @code{config.sub} to map abbreviations to full names; you can read the
33473 script, if you wish, or you can use it to test your guesses on
33474 abbreviations---for example:
33477 % sh config.sub i386-linux
33479 % sh config.sub alpha-linux
33480 alpha-unknown-linux-gnu
33481 % sh config.sub hp9k700
33483 % sh config.sub sun4
33484 sparc-sun-sunos4.1.1
33485 % sh config.sub sun3
33486 m68k-sun-sunos4.1.1
33487 % sh config.sub i986v
33488 Invalid configuration `i986v': machine `i986v' not recognized
33492 @code{config.sub} is also distributed in the @value{GDBN} source
33493 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33495 @node Configure Options
33496 @section @file{configure} Options
33498 Here is a summary of the @file{configure} options and arguments that
33499 are most often useful for building @value{GDBN}. @file{configure} also has
33500 several other options not listed here. @inforef{What Configure
33501 Does,,configure.info}, for a full explanation of @file{configure}.
33504 configure @r{[}--help@r{]}
33505 @r{[}--prefix=@var{dir}@r{]}
33506 @r{[}--exec-prefix=@var{dir}@r{]}
33507 @r{[}--srcdir=@var{dirname}@r{]}
33508 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33509 @r{[}--target=@var{target}@r{]}
33514 You may introduce options with a single @samp{-} rather than
33515 @samp{--} if you prefer; but you may abbreviate option names if you use
33520 Display a quick summary of how to invoke @file{configure}.
33522 @item --prefix=@var{dir}
33523 Configure the source to install programs and files under directory
33526 @item --exec-prefix=@var{dir}
33527 Configure the source to install programs under directory
33530 @c avoid splitting the warning from the explanation:
33532 @item --srcdir=@var{dirname}
33533 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33534 @code{make} that implements the @code{VPATH} feature.}@*
33535 Use this option to make configurations in directories separate from the
33536 @value{GDBN} source directories. Among other things, you can use this to
33537 build (or maintain) several configurations simultaneously, in separate
33538 directories. @file{configure} writes configuration-specific files in
33539 the current directory, but arranges for them to use the source in the
33540 directory @var{dirname}. @file{configure} creates directories under
33541 the working directory in parallel to the source directories below
33544 @item --norecursion
33545 Configure only the directory level where @file{configure} is executed; do not
33546 propagate configuration to subdirectories.
33548 @item --target=@var{target}
33549 Configure @value{GDBN} for cross-debugging programs running on the specified
33550 @var{target}. Without this option, @value{GDBN} is configured to debug
33551 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33553 There is no convenient way to generate a list of all available targets.
33555 @item @var{host} @dots{}
33556 Configure @value{GDBN} to run on the specified @var{host}.
33558 There is no convenient way to generate a list of all available hosts.
33561 There are many other options available as well, but they are generally
33562 needed for special purposes only.
33564 @node System-wide configuration
33565 @section System-wide configuration and settings
33566 @cindex system-wide init file
33568 @value{GDBN} can be configured to have a system-wide init file;
33569 this file will be read and executed at startup (@pxref{Startup, , What
33570 @value{GDBN} does during startup}).
33572 Here is the corresponding configure option:
33575 @item --with-system-gdbinit=@var{file}
33576 Specify that the default location of the system-wide init file is
33580 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33581 it may be subject to relocation. Two possible cases:
33585 If the default location of this init file contains @file{$prefix},
33586 it will be subject to relocation. Suppose that the configure options
33587 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33588 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33589 init file is looked for as @file{$install/etc/gdbinit} instead of
33590 @file{$prefix/etc/gdbinit}.
33593 By contrast, if the default location does not contain the prefix,
33594 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33595 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33596 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33597 wherever @value{GDBN} is installed.
33600 If the configured location of the system-wide init file (as given by the
33601 @option{--with-system-gdbinit} option at configure time) is in the
33602 data-directory (as specified by @option{--with-gdb-datadir} at configure
33603 time) or in one of its subdirectories, then @value{GDBN} will look for the
33604 system-wide init file in the directory specified by the
33605 @option{--data-directory} command-line option.
33606 Note that the system-wide init file is only read once, during @value{GDBN}
33607 initialization. If the data-directory is changed after @value{GDBN} has
33608 started with the @code{set data-directory} command, the file will not be
33612 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33615 @node System-wide Configuration Scripts
33616 @subsection Installed System-wide Configuration Scripts
33617 @cindex system-wide configuration scripts
33619 The @file{system-gdbinit} directory, located inside the data-directory
33620 (as specified by @option{--with-gdb-datadir} at configure time) contains
33621 a number of scripts which can be used as system-wide init files. To
33622 automatically source those scripts at startup, @value{GDBN} should be
33623 configured with @option{--with-system-gdbinit}. Otherwise, any user
33624 should be able to source them by hand as needed.
33626 The following scripts are currently available:
33629 @item @file{elinos.py}
33631 @cindex ELinOS system-wide configuration script
33632 This script is useful when debugging a program on an ELinOS target.
33633 It takes advantage of the environment variables defined in a standard
33634 ELinOS environment in order to determine the location of the system
33635 shared libraries, and then sets the @samp{solib-absolute-prefix}
33636 and @samp{solib-search-path} variables appropriately.
33638 @item @file{wrs-linux.py}
33639 @pindex wrs-linux.py
33640 @cindex Wind River Linux system-wide configuration script
33641 This script is useful when debugging a program on a target running
33642 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33643 the host-side sysroot used by the target system.
33647 @node Maintenance Commands
33648 @appendix Maintenance Commands
33649 @cindex maintenance commands
33650 @cindex internal commands
33652 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33653 includes a number of commands intended for @value{GDBN} developers,
33654 that are not documented elsewhere in this manual. These commands are
33655 provided here for reference. (For commands that turn on debugging
33656 messages, see @ref{Debugging Output}.)
33659 @kindex maint agent
33660 @kindex maint agent-eval
33661 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33662 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33663 Translate the given @var{expression} into remote agent bytecodes.
33664 This command is useful for debugging the Agent Expression mechanism
33665 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33666 expression useful for data collection, such as by tracepoints, while
33667 @samp{maint agent-eval} produces an expression that evaluates directly
33668 to a result. For instance, a collection expression for @code{globa +
33669 globb} will include bytecodes to record four bytes of memory at each
33670 of the addresses of @code{globa} and @code{globb}, while discarding
33671 the result of the addition, while an evaluation expression will do the
33672 addition and return the sum.
33673 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33674 If not, generate remote agent bytecode for current frame PC address.
33676 @kindex maint agent-printf
33677 @item maint agent-printf @var{format},@var{expr},...
33678 Translate the given format string and list of argument expressions
33679 into remote agent bytecodes and display them as a disassembled list.
33680 This command is useful for debugging the agent version of dynamic
33681 printf (@pxref{Dynamic Printf}).
33683 @kindex maint info breakpoints
33684 @item @anchor{maint info breakpoints}maint info breakpoints
33685 Using the same format as @samp{info breakpoints}, display both the
33686 breakpoints you've set explicitly, and those @value{GDBN} is using for
33687 internal purposes. Internal breakpoints are shown with negative
33688 breakpoint numbers. The type column identifies what kind of breakpoint
33693 Normal, explicitly set breakpoint.
33696 Normal, explicitly set watchpoint.
33699 Internal breakpoint, used to handle correctly stepping through
33700 @code{longjmp} calls.
33702 @item longjmp resume
33703 Internal breakpoint at the target of a @code{longjmp}.
33706 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33709 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33712 Shared library events.
33716 @kindex maint info bfds
33717 @item maint info bfds
33718 This prints information about each @code{bfd} object that is known to
33719 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33721 @kindex set displaced-stepping
33722 @kindex show displaced-stepping
33723 @cindex displaced stepping support
33724 @cindex out-of-line single-stepping
33725 @item set displaced-stepping
33726 @itemx show displaced-stepping
33727 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33728 if the target supports it. Displaced stepping is a way to single-step
33729 over breakpoints without removing them from the inferior, by executing
33730 an out-of-line copy of the instruction that was originally at the
33731 breakpoint location. It is also known as out-of-line single-stepping.
33734 @item set displaced-stepping on
33735 If the target architecture supports it, @value{GDBN} will use
33736 displaced stepping to step over breakpoints.
33738 @item set displaced-stepping off
33739 @value{GDBN} will not use displaced stepping to step over breakpoints,
33740 even if such is supported by the target architecture.
33742 @cindex non-stop mode, and @samp{set displaced-stepping}
33743 @item set displaced-stepping auto
33744 This is the default mode. @value{GDBN} will use displaced stepping
33745 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33746 architecture supports displaced stepping.
33749 @kindex maint check-psymtabs
33750 @item maint check-psymtabs
33751 Check the consistency of currently expanded psymtabs versus symtabs.
33752 Use this to check, for example, whether a symbol is in one but not the other.
33754 @kindex maint check-symtabs
33755 @item maint check-symtabs
33756 Check the consistency of currently expanded symtabs.
33758 @kindex maint expand-symtabs
33759 @item maint expand-symtabs [@var{regexp}]
33760 Expand symbol tables.
33761 If @var{regexp} is specified, only expand symbol tables for file
33762 names matching @var{regexp}.
33764 @kindex maint set catch-demangler-crashes
33765 @kindex maint show catch-demangler-crashes
33766 @cindex demangler crashes
33767 @item maint set catch-demangler-crashes [on|off]
33768 @itemx maint show catch-demangler-crashes
33769 Control whether @value{GDBN} should attempt to catch crashes in the
33770 symbol name demangler. The default is to attempt to catch crashes.
33771 If enabled, the first time a crash is caught, a core file is created,
33772 the offending symbol is displayed and the user is presented with the
33773 option to terminate the current session.
33775 @kindex maint cplus first_component
33776 @item maint cplus first_component @var{name}
33777 Print the first C@t{++} class/namespace component of @var{name}.
33779 @kindex maint cplus namespace
33780 @item maint cplus namespace
33781 Print the list of possible C@t{++} namespaces.
33783 @kindex maint deprecate
33784 @kindex maint undeprecate
33785 @cindex deprecated commands
33786 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33787 @itemx maint undeprecate @var{command}
33788 Deprecate or undeprecate the named @var{command}. Deprecated commands
33789 cause @value{GDBN} to issue a warning when you use them. The optional
33790 argument @var{replacement} says which newer command should be used in
33791 favor of the deprecated one; if it is given, @value{GDBN} will mention
33792 the replacement as part of the warning.
33794 @kindex maint dump-me
33795 @item maint dump-me
33796 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33797 Cause a fatal signal in the debugger and force it to dump its core.
33798 This is supported only on systems which support aborting a program
33799 with the @code{SIGQUIT} signal.
33801 @kindex maint internal-error
33802 @kindex maint internal-warning
33803 @kindex maint demangler-warning
33804 @cindex demangler crashes
33805 @item maint internal-error @r{[}@var{message-text}@r{]}
33806 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33807 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33809 Cause @value{GDBN} to call the internal function @code{internal_error},
33810 @code{internal_warning} or @code{demangler_warning} and hence behave
33811 as though an internal problem has been detected. In addition to
33812 reporting the internal problem, these functions give the user the
33813 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33814 and @code{internal_warning}) create a core file of the current
33815 @value{GDBN} session.
33817 These commands take an optional parameter @var{message-text} that is
33818 used as the text of the error or warning message.
33820 Here's an example of using @code{internal-error}:
33823 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33824 @dots{}/maint.c:121: internal-error: testing, 1, 2
33825 A problem internal to GDB has been detected. Further
33826 debugging may prove unreliable.
33827 Quit this debugging session? (y or n) @kbd{n}
33828 Create a core file? (y or n) @kbd{n}
33832 @cindex @value{GDBN} internal error
33833 @cindex internal errors, control of @value{GDBN} behavior
33834 @cindex demangler crashes
33836 @kindex maint set internal-error
33837 @kindex maint show internal-error
33838 @kindex maint set internal-warning
33839 @kindex maint show internal-warning
33840 @kindex maint set demangler-warning
33841 @kindex maint show demangler-warning
33842 @item maint set internal-error @var{action} [ask|yes|no]
33843 @itemx maint show internal-error @var{action}
33844 @itemx maint set internal-warning @var{action} [ask|yes|no]
33845 @itemx maint show internal-warning @var{action}
33846 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33847 @itemx maint show demangler-warning @var{action}
33848 When @value{GDBN} reports an internal problem (error or warning) it
33849 gives the user the opportunity to both quit @value{GDBN} and create a
33850 core file of the current @value{GDBN} session. These commands let you
33851 override the default behaviour for each particular @var{action},
33852 described in the table below.
33856 You can specify that @value{GDBN} should always (yes) or never (no)
33857 quit. The default is to ask the user what to do.
33860 You can specify that @value{GDBN} should always (yes) or never (no)
33861 create a core file. The default is to ask the user what to do. Note
33862 that there is no @code{corefile} option for @code{demangler-warning}:
33863 demangler warnings always create a core file and this cannot be
33867 @kindex maint packet
33868 @item maint packet @var{text}
33869 If @value{GDBN} is talking to an inferior via the serial protocol,
33870 then this command sends the string @var{text} to the inferior, and
33871 displays the response packet. @value{GDBN} supplies the initial
33872 @samp{$} character, the terminating @samp{#} character, and the
33875 @kindex maint print architecture
33876 @item maint print architecture @r{[}@var{file}@r{]}
33877 Print the entire architecture configuration. The optional argument
33878 @var{file} names the file where the output goes.
33880 @kindex maint print c-tdesc
33881 @item maint print c-tdesc
33882 Print the current target description (@pxref{Target Descriptions}) as
33883 a C source file. The created source file can be used in @value{GDBN}
33884 when an XML parser is not available to parse the description.
33886 @kindex maint print dummy-frames
33887 @item maint print dummy-frames
33888 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33891 (@value{GDBP}) @kbd{b add}
33893 (@value{GDBP}) @kbd{print add(2,3)}
33894 Breakpoint 2, add (a=2, b=3) at @dots{}
33896 The program being debugged stopped while in a function called from GDB.
33898 (@value{GDBP}) @kbd{maint print dummy-frames}
33899 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33903 Takes an optional file parameter.
33905 @kindex maint print registers
33906 @kindex maint print raw-registers
33907 @kindex maint print cooked-registers
33908 @kindex maint print register-groups
33909 @kindex maint print remote-registers
33910 @item maint print registers @r{[}@var{file}@r{]}
33911 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33912 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33913 @itemx maint print register-groups @r{[}@var{file}@r{]}
33914 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33915 Print @value{GDBN}'s internal register data structures.
33917 The command @code{maint print raw-registers} includes the contents of
33918 the raw register cache; the command @code{maint print
33919 cooked-registers} includes the (cooked) value of all registers,
33920 including registers which aren't available on the target nor visible
33921 to user; the command @code{maint print register-groups} includes the
33922 groups that each register is a member of; and the command @code{maint
33923 print remote-registers} includes the remote target's register numbers
33924 and offsets in the `G' packets.
33926 These commands take an optional parameter, a file name to which to
33927 write the information.
33929 @kindex maint print reggroups
33930 @item maint print reggroups @r{[}@var{file}@r{]}
33931 Print @value{GDBN}'s internal register group data structures. The
33932 optional argument @var{file} tells to what file to write the
33935 The register groups info looks like this:
33938 (@value{GDBP}) @kbd{maint print reggroups}
33951 This command forces @value{GDBN} to flush its internal register cache.
33953 @kindex maint print objfiles
33954 @cindex info for known object files
33955 @item maint print objfiles @r{[}@var{regexp}@r{]}
33956 Print a dump of all known object files.
33957 If @var{regexp} is specified, only print object files whose names
33958 match @var{regexp}. For each object file, this command prints its name,
33959 address in memory, and all of its psymtabs and symtabs.
33961 @kindex maint print user-registers
33962 @cindex user registers
33963 @item maint print user-registers
33964 List all currently available @dfn{user registers}. User registers
33965 typically provide alternate names for actual hardware registers. They
33966 include the four ``standard'' registers @code{$fp}, @code{$pc},
33967 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
33968 registers can be used in expressions in the same way as the canonical
33969 register names, but only the latter are listed by the @code{info
33970 registers} and @code{maint print registers} commands.
33972 @kindex maint print section-scripts
33973 @cindex info for known .debug_gdb_scripts-loaded scripts
33974 @item maint print section-scripts [@var{regexp}]
33975 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33976 If @var{regexp} is specified, only print scripts loaded by object files
33977 matching @var{regexp}.
33978 For each script, this command prints its name as specified in the objfile,
33979 and the full path if known.
33980 @xref{dotdebug_gdb_scripts section}.
33982 @kindex maint print statistics
33983 @cindex bcache statistics
33984 @item maint print statistics
33985 This command prints, for each object file in the program, various data
33986 about that object file followed by the byte cache (@dfn{bcache})
33987 statistics for the object file. The objfile data includes the number
33988 of minimal, partial, full, and stabs symbols, the number of types
33989 defined by the objfile, the number of as yet unexpanded psym tables,
33990 the number of line tables and string tables, and the amount of memory
33991 used by the various tables. The bcache statistics include the counts,
33992 sizes, and counts of duplicates of all and unique objects, max,
33993 average, and median entry size, total memory used and its overhead and
33994 savings, and various measures of the hash table size and chain
33997 @kindex maint print target-stack
33998 @cindex target stack description
33999 @item maint print target-stack
34000 A @dfn{target} is an interface between the debugger and a particular
34001 kind of file or process. Targets can be stacked in @dfn{strata},
34002 so that more than one target can potentially respond to a request.
34003 In particular, memory accesses will walk down the stack of targets
34004 until they find a target that is interested in handling that particular
34007 This command prints a short description of each layer that was pushed on
34008 the @dfn{target stack}, starting from the top layer down to the bottom one.
34010 @kindex maint print type
34011 @cindex type chain of a data type
34012 @item maint print type @var{expr}
34013 Print the type chain for a type specified by @var{expr}. The argument
34014 can be either a type name or a symbol. If it is a symbol, the type of
34015 that symbol is described. The type chain produced by this command is
34016 a recursive definition of the data type as stored in @value{GDBN}'s
34017 data structures, including its flags and contained types.
34019 @kindex maint set dwarf2 always-disassemble
34020 @kindex maint show dwarf2 always-disassemble
34021 @item maint set dwarf2 always-disassemble
34022 @item maint show dwarf2 always-disassemble
34023 Control the behavior of @code{info address} when using DWARF debugging
34026 The default is @code{off}, which means that @value{GDBN} should try to
34027 describe a variable's location in an easily readable format. When
34028 @code{on}, @value{GDBN} will instead display the DWARF location
34029 expression in an assembly-like format. Note that some locations are
34030 too complex for @value{GDBN} to describe simply; in this case you will
34031 always see the disassembly form.
34033 Here is an example of the resulting disassembly:
34036 (gdb) info addr argc
34037 Symbol "argc" is a complex DWARF expression:
34041 For more information on these expressions, see
34042 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34044 @kindex maint set dwarf2 max-cache-age
34045 @kindex maint show dwarf2 max-cache-age
34046 @item maint set dwarf2 max-cache-age
34047 @itemx maint show dwarf2 max-cache-age
34048 Control the DWARF 2 compilation unit cache.
34050 @cindex DWARF 2 compilation units cache
34051 In object files with inter-compilation-unit references, such as those
34052 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34053 reader needs to frequently refer to previously read compilation units.
34054 This setting controls how long a compilation unit will remain in the
34055 cache if it is not referenced. A higher limit means that cached
34056 compilation units will be stored in memory longer, and more total
34057 memory will be used. Setting it to zero disables caching, which will
34058 slow down @value{GDBN} startup, but reduce memory consumption.
34060 @kindex maint set profile
34061 @kindex maint show profile
34062 @cindex profiling GDB
34063 @item maint set profile
34064 @itemx maint show profile
34065 Control profiling of @value{GDBN}.
34067 Profiling will be disabled until you use the @samp{maint set profile}
34068 command to enable it. When you enable profiling, the system will begin
34069 collecting timing and execution count data; when you disable profiling or
34070 exit @value{GDBN}, the results will be written to a log file. Remember that
34071 if you use profiling, @value{GDBN} will overwrite the profiling log file
34072 (often called @file{gmon.out}). If you have a record of important profiling
34073 data in a @file{gmon.out} file, be sure to move it to a safe location.
34075 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34076 compiled with the @samp{-pg} compiler option.
34078 @kindex maint set show-debug-regs
34079 @kindex maint show show-debug-regs
34080 @cindex hardware debug registers
34081 @item maint set show-debug-regs
34082 @itemx maint show show-debug-regs
34083 Control whether to show variables that mirror the hardware debug
34084 registers. Use @code{on} to enable, @code{off} to disable. If
34085 enabled, the debug registers values are shown when @value{GDBN} inserts or
34086 removes a hardware breakpoint or watchpoint, and when the inferior
34087 triggers a hardware-assisted breakpoint or watchpoint.
34089 @kindex maint set show-all-tib
34090 @kindex maint show show-all-tib
34091 @item maint set show-all-tib
34092 @itemx maint show show-all-tib
34093 Control whether to show all non zero areas within a 1k block starting
34094 at thread local base, when using the @samp{info w32 thread-information-block}
34097 @kindex maint set target-async
34098 @kindex maint show target-async
34099 @item maint set target-async
34100 @itemx maint show target-async
34101 This controls whether @value{GDBN} targets operate in synchronous or
34102 asynchronous mode (@pxref{Background Execution}). Normally the
34103 default is asynchronous, if it is available; but this can be changed
34104 to more easily debug problems occurring only in synchronous mode.
34106 @kindex maint set per-command
34107 @kindex maint show per-command
34108 @item maint set per-command
34109 @itemx maint show per-command
34110 @cindex resources used by commands
34112 @value{GDBN} can display the resources used by each command.
34113 This is useful in debugging performance problems.
34116 @item maint set per-command space [on|off]
34117 @itemx maint show per-command space
34118 Enable or disable the printing of the memory used by GDB for each command.
34119 If enabled, @value{GDBN} will display how much memory each command
34120 took, following the command's own output.
34121 This can also be requested by invoking @value{GDBN} with the
34122 @option{--statistics} command-line switch (@pxref{Mode Options}).
34124 @item maint set per-command time [on|off]
34125 @itemx maint show per-command time
34126 Enable or disable the printing of the execution time of @value{GDBN}
34128 If enabled, @value{GDBN} will display how much time it
34129 took to execute each command, following the command's own output.
34130 Both CPU time and wallclock time are printed.
34131 Printing both is useful when trying to determine whether the cost is
34132 CPU or, e.g., disk/network latency.
34133 Note that the CPU time printed is for @value{GDBN} only, it does not include
34134 the execution time of the inferior because there's no mechanism currently
34135 to compute how much time was spent by @value{GDBN} and how much time was
34136 spent by the program been debugged.
34137 This can also be requested by invoking @value{GDBN} with the
34138 @option{--statistics} command-line switch (@pxref{Mode Options}).
34140 @item maint set per-command symtab [on|off]
34141 @itemx maint show per-command symtab
34142 Enable or disable the printing of basic symbol table statistics
34144 If enabled, @value{GDBN} will display the following information:
34148 number of symbol tables
34150 number of primary symbol tables
34152 number of blocks in the blockvector
34156 @kindex maint space
34157 @cindex memory used by commands
34158 @item maint space @var{value}
34159 An alias for @code{maint set per-command space}.
34160 A non-zero value enables it, zero disables it.
34163 @cindex time of command execution
34164 @item maint time @var{value}
34165 An alias for @code{maint set per-command time}.
34166 A non-zero value enables it, zero disables it.
34168 @kindex maint translate-address
34169 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34170 Find the symbol stored at the location specified by the address
34171 @var{addr} and an optional section name @var{section}. If found,
34172 @value{GDBN} prints the name of the closest symbol and an offset from
34173 the symbol's location to the specified address. This is similar to
34174 the @code{info address} command (@pxref{Symbols}), except that this
34175 command also allows to find symbols in other sections.
34177 If section was not specified, the section in which the symbol was found
34178 is also printed. For dynamically linked executables, the name of
34179 executable or shared library containing the symbol is printed as well.
34183 The following command is useful for non-interactive invocations of
34184 @value{GDBN}, such as in the test suite.
34187 @item set watchdog @var{nsec}
34188 @kindex set watchdog
34189 @cindex watchdog timer
34190 @cindex timeout for commands
34191 Set the maximum number of seconds @value{GDBN} will wait for the
34192 target operation to finish. If this time expires, @value{GDBN}
34193 reports and error and the command is aborted.
34195 @item show watchdog
34196 Show the current setting of the target wait timeout.
34199 @node Remote Protocol
34200 @appendix @value{GDBN} Remote Serial Protocol
34205 * Stop Reply Packets::
34206 * General Query Packets::
34207 * Architecture-Specific Protocol Details::
34208 * Tracepoint Packets::
34209 * Host I/O Packets::
34211 * Notification Packets::
34212 * Remote Non-Stop::
34213 * Packet Acknowledgment::
34215 * File-I/O Remote Protocol Extension::
34216 * Library List Format::
34217 * Library List Format for SVR4 Targets::
34218 * Memory Map Format::
34219 * Thread List Format::
34220 * Traceframe Info Format::
34221 * Branch Trace Format::
34222 * Branch Trace Configuration Format::
34228 There may be occasions when you need to know something about the
34229 protocol---for example, if there is only one serial port to your target
34230 machine, you might want your program to do something special if it
34231 recognizes a packet meant for @value{GDBN}.
34233 In the examples below, @samp{->} and @samp{<-} are used to indicate
34234 transmitted and received data, respectively.
34236 @cindex protocol, @value{GDBN} remote serial
34237 @cindex serial protocol, @value{GDBN} remote
34238 @cindex remote serial protocol
34239 All @value{GDBN} commands and responses (other than acknowledgments
34240 and notifications, see @ref{Notification Packets}) are sent as a
34241 @var{packet}. A @var{packet} is introduced with the character
34242 @samp{$}, the actual @var{packet-data}, and the terminating character
34243 @samp{#} followed by a two-digit @var{checksum}:
34246 @code{$}@var{packet-data}@code{#}@var{checksum}
34250 @cindex checksum, for @value{GDBN} remote
34252 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34253 characters between the leading @samp{$} and the trailing @samp{#} (an
34254 eight bit unsigned checksum).
34256 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34257 specification also included an optional two-digit @var{sequence-id}:
34260 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34263 @cindex sequence-id, for @value{GDBN} remote
34265 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34266 has never output @var{sequence-id}s. Stubs that handle packets added
34267 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34269 When either the host or the target machine receives a packet, the first
34270 response expected is an acknowledgment: either @samp{+} (to indicate
34271 the package was received correctly) or @samp{-} (to request
34275 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34280 The @samp{+}/@samp{-} acknowledgments can be disabled
34281 once a connection is established.
34282 @xref{Packet Acknowledgment}, for details.
34284 The host (@value{GDBN}) sends @var{command}s, and the target (the
34285 debugging stub incorporated in your program) sends a @var{response}. In
34286 the case of step and continue @var{command}s, the response is only sent
34287 when the operation has completed, and the target has again stopped all
34288 threads in all attached processes. This is the default all-stop mode
34289 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34290 execution mode; see @ref{Remote Non-Stop}, for details.
34292 @var{packet-data} consists of a sequence of characters with the
34293 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34296 @cindex remote protocol, field separator
34297 Fields within the packet should be separated using @samp{,} @samp{;} or
34298 @samp{:}. Except where otherwise noted all numbers are represented in
34299 @sc{hex} with leading zeros suppressed.
34301 Implementors should note that prior to @value{GDBN} 5.0, the character
34302 @samp{:} could not appear as the third character in a packet (as it
34303 would potentially conflict with the @var{sequence-id}).
34305 @cindex remote protocol, binary data
34306 @anchor{Binary Data}
34307 Binary data in most packets is encoded either as two hexadecimal
34308 digits per byte of binary data. This allowed the traditional remote
34309 protocol to work over connections which were only seven-bit clean.
34310 Some packets designed more recently assume an eight-bit clean
34311 connection, and use a more efficient encoding to send and receive
34314 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34315 as an escape character. Any escaped byte is transmitted as the escape
34316 character followed by the original character XORed with @code{0x20}.
34317 For example, the byte @code{0x7d} would be transmitted as the two
34318 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34319 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34320 @samp{@}}) must always be escaped. Responses sent by the stub
34321 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34322 is not interpreted as the start of a run-length encoded sequence
34325 Response @var{data} can be run-length encoded to save space.
34326 Run-length encoding replaces runs of identical characters with one
34327 instance of the repeated character, followed by a @samp{*} and a
34328 repeat count. The repeat count is itself sent encoded, to avoid
34329 binary characters in @var{data}: a value of @var{n} is sent as
34330 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34331 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34332 code 32) for a repeat count of 3. (This is because run-length
34333 encoding starts to win for counts 3 or more.) Thus, for example,
34334 @samp{0* } is a run-length encoding of ``0000'': the space character
34335 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34338 The printable characters @samp{#} and @samp{$} or with a numeric value
34339 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34340 seven repeats (@samp{$}) can be expanded using a repeat count of only
34341 five (@samp{"}). For example, @samp{00000000} can be encoded as
34344 The error response returned for some packets includes a two character
34345 error number. That number is not well defined.
34347 @cindex empty response, for unsupported packets
34348 For any @var{command} not supported by the stub, an empty response
34349 (@samp{$#00}) should be returned. That way it is possible to extend the
34350 protocol. A newer @value{GDBN} can tell if a packet is supported based
34353 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34354 commands for register access, and the @samp{m} and @samp{M} commands
34355 for memory access. Stubs that only control single-threaded targets
34356 can implement run control with the @samp{c} (continue), and @samp{s}
34357 (step) commands. Stubs that support multi-threading targets should
34358 support the @samp{vCont} command. All other commands are optional.
34363 The following table provides a complete list of all currently defined
34364 @var{command}s and their corresponding response @var{data}.
34365 @xref{File-I/O Remote Protocol Extension}, for details about the File
34366 I/O extension of the remote protocol.
34368 Each packet's description has a template showing the packet's overall
34369 syntax, followed by an explanation of the packet's meaning. We
34370 include spaces in some of the templates for clarity; these are not
34371 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34372 separate its components. For example, a template like @samp{foo
34373 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34374 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34375 @var{baz}. @value{GDBN} does not transmit a space character between the
34376 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34379 @cindex @var{thread-id}, in remote protocol
34380 @anchor{thread-id syntax}
34381 Several packets and replies include a @var{thread-id} field to identify
34382 a thread. Normally these are positive numbers with a target-specific
34383 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34384 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34387 In addition, the remote protocol supports a multiprocess feature in
34388 which the @var{thread-id} syntax is extended to optionally include both
34389 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34390 The @var{pid} (process) and @var{tid} (thread) components each have the
34391 format described above: a positive number with target-specific
34392 interpretation formatted as a big-endian hex string, literal @samp{-1}
34393 to indicate all processes or threads (respectively), or @samp{0} to
34394 indicate an arbitrary process or thread. Specifying just a process, as
34395 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34396 error to specify all processes but a specific thread, such as
34397 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34398 for those packets and replies explicitly documented to include a process
34399 ID, rather than a @var{thread-id}.
34401 The multiprocess @var{thread-id} syntax extensions are only used if both
34402 @value{GDBN} and the stub report support for the @samp{multiprocess}
34403 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34406 Note that all packet forms beginning with an upper- or lower-case
34407 letter, other than those described here, are reserved for future use.
34409 Here are the packet descriptions.
34414 @cindex @samp{!} packet
34415 @anchor{extended mode}
34416 Enable extended mode. In extended mode, the remote server is made
34417 persistent. The @samp{R} packet is used to restart the program being
34423 The remote target both supports and has enabled extended mode.
34427 @cindex @samp{?} packet
34429 Indicate the reason the target halted. The reply is the same as for
34430 step and continue. This packet has a special interpretation when the
34431 target is in non-stop mode; see @ref{Remote Non-Stop}.
34434 @xref{Stop Reply Packets}, for the reply specifications.
34436 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34437 @cindex @samp{A} packet
34438 Initialized @code{argv[]} array passed into program. @var{arglen}
34439 specifies the number of bytes in the hex encoded byte stream
34440 @var{arg}. See @code{gdbserver} for more details.
34445 The arguments were set.
34451 @cindex @samp{b} packet
34452 (Don't use this packet; its behavior is not well-defined.)
34453 Change the serial line speed to @var{baud}.
34455 JTC: @emph{When does the transport layer state change? When it's
34456 received, or after the ACK is transmitted. In either case, there are
34457 problems if the command or the acknowledgment packet is dropped.}
34459 Stan: @emph{If people really wanted to add something like this, and get
34460 it working for the first time, they ought to modify ser-unix.c to send
34461 some kind of out-of-band message to a specially-setup stub and have the
34462 switch happen "in between" packets, so that from remote protocol's point
34463 of view, nothing actually happened.}
34465 @item B @var{addr},@var{mode}
34466 @cindex @samp{B} packet
34467 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34468 breakpoint at @var{addr}.
34470 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34471 (@pxref{insert breakpoint or watchpoint packet}).
34473 @cindex @samp{bc} packet
34476 Backward continue. Execute the target system in reverse. No parameter.
34477 @xref{Reverse Execution}, for more information.
34480 @xref{Stop Reply Packets}, for the reply specifications.
34482 @cindex @samp{bs} packet
34485 Backward single step. Execute one instruction in reverse. No parameter.
34486 @xref{Reverse Execution}, for more information.
34489 @xref{Stop Reply Packets}, for the reply specifications.
34491 @item c @r{[}@var{addr}@r{]}
34492 @cindex @samp{c} packet
34493 Continue at @var{addr}, which is the address to resume. If @var{addr}
34494 is omitted, resume at current address.
34496 This packet is deprecated for multi-threading support. @xref{vCont
34500 @xref{Stop Reply Packets}, for the reply specifications.
34502 @item C @var{sig}@r{[};@var{addr}@r{]}
34503 @cindex @samp{C} packet
34504 Continue with signal @var{sig} (hex signal number). If
34505 @samp{;@var{addr}} is omitted, resume at same address.
34507 This packet is deprecated for multi-threading support. @xref{vCont
34511 @xref{Stop Reply Packets}, for the reply specifications.
34514 @cindex @samp{d} packet
34517 Don't use this packet; instead, define a general set packet
34518 (@pxref{General Query Packets}).
34522 @cindex @samp{D} packet
34523 The first form of the packet is used to detach @value{GDBN} from the
34524 remote system. It is sent to the remote target
34525 before @value{GDBN} disconnects via the @code{detach} command.
34527 The second form, including a process ID, is used when multiprocess
34528 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34529 detach only a specific process. The @var{pid} is specified as a
34530 big-endian hex string.
34540 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34541 @cindex @samp{F} packet
34542 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34543 This is part of the File-I/O protocol extension. @xref{File-I/O
34544 Remote Protocol Extension}, for the specification.
34547 @anchor{read registers packet}
34548 @cindex @samp{g} packet
34549 Read general registers.
34553 @item @var{XX@dots{}}
34554 Each byte of register data is described by two hex digits. The bytes
34555 with the register are transmitted in target byte order. The size of
34556 each register and their position within the @samp{g} packet are
34557 determined by the @value{GDBN} internal gdbarch functions
34558 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34559 specification of several standard @samp{g} packets is specified below.
34561 When reading registers from a trace frame (@pxref{Analyze Collected
34562 Data,,Using the Collected Data}), the stub may also return a string of
34563 literal @samp{x}'s in place of the register data digits, to indicate
34564 that the corresponding register has not been collected, thus its value
34565 is unavailable. For example, for an architecture with 4 registers of
34566 4 bytes each, the following reply indicates to @value{GDBN} that
34567 registers 0 and 2 have not been collected, while registers 1 and 3
34568 have been collected, and both have zero value:
34572 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34579 @item G @var{XX@dots{}}
34580 @cindex @samp{G} packet
34581 Write general registers. @xref{read registers packet}, for a
34582 description of the @var{XX@dots{}} data.
34592 @item H @var{op} @var{thread-id}
34593 @cindex @samp{H} packet
34594 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34595 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34596 should be @samp{c} for step and continue operations (note that this
34597 is deprecated, supporting the @samp{vCont} command is a better
34598 option), and @samp{g} for other operations. The thread designator
34599 @var{thread-id} has the format and interpretation described in
34600 @ref{thread-id syntax}.
34611 @c 'H': How restrictive (or permissive) is the thread model. If a
34612 @c thread is selected and stopped, are other threads allowed
34613 @c to continue to execute? As I mentioned above, I think the
34614 @c semantics of each command when a thread is selected must be
34615 @c described. For example:
34617 @c 'g': If the stub supports threads and a specific thread is
34618 @c selected, returns the register block from that thread;
34619 @c otherwise returns current registers.
34621 @c 'G' If the stub supports threads and a specific thread is
34622 @c selected, sets the registers of the register block of
34623 @c that thread; otherwise sets current registers.
34625 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34626 @anchor{cycle step packet}
34627 @cindex @samp{i} packet
34628 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34629 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34630 step starting at that address.
34633 @cindex @samp{I} packet
34634 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34638 @cindex @samp{k} packet
34641 The exact effect of this packet is not specified.
34643 For a bare-metal target, it may power cycle or reset the target
34644 system. For that reason, the @samp{k} packet has no reply.
34646 For a single-process target, it may kill that process if possible.
34648 A multiple-process target may choose to kill just one process, or all
34649 that are under @value{GDBN}'s control. For more precise control, use
34650 the vKill packet (@pxref{vKill packet}).
34652 If the target system immediately closes the connection in response to
34653 @samp{k}, @value{GDBN} does not consider the lack of packet
34654 acknowledgment to be an error, and assumes the kill was successful.
34656 If connected using @kbd{target extended-remote}, and the target does
34657 not close the connection in response to a kill request, @value{GDBN}
34658 probes the target state as if a new connection was opened
34659 (@pxref{? packet}).
34661 @item m @var{addr},@var{length}
34662 @cindex @samp{m} packet
34663 Read @var{length} bytes of memory starting at address @var{addr}.
34664 Note that @var{addr} may not be aligned to any particular boundary.
34666 The stub need not use any particular size or alignment when gathering
34667 data from memory for the response; even if @var{addr} is word-aligned
34668 and @var{length} is a multiple of the word size, the stub is free to
34669 use byte accesses, or not. For this reason, this packet may not be
34670 suitable for accessing memory-mapped I/O devices.
34671 @cindex alignment of remote memory accesses
34672 @cindex size of remote memory accesses
34673 @cindex memory, alignment and size of remote accesses
34677 @item @var{XX@dots{}}
34678 Memory contents; each byte is transmitted as a two-digit hexadecimal
34679 number. The reply may contain fewer bytes than requested if the
34680 server was able to read only part of the region of memory.
34685 @item M @var{addr},@var{length}:@var{XX@dots{}}
34686 @cindex @samp{M} packet
34687 Write @var{length} bytes of memory starting at address @var{addr}.
34688 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34689 hexadecimal number.
34696 for an error (this includes the case where only part of the data was
34701 @cindex @samp{p} packet
34702 Read the value of register @var{n}; @var{n} is in hex.
34703 @xref{read registers packet}, for a description of how the returned
34704 register value is encoded.
34708 @item @var{XX@dots{}}
34709 the register's value
34713 Indicating an unrecognized @var{query}.
34716 @item P @var{n@dots{}}=@var{r@dots{}}
34717 @anchor{write register packet}
34718 @cindex @samp{P} packet
34719 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34720 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34721 digits for each byte in the register (target byte order).
34731 @item q @var{name} @var{params}@dots{}
34732 @itemx Q @var{name} @var{params}@dots{}
34733 @cindex @samp{q} packet
34734 @cindex @samp{Q} packet
34735 General query (@samp{q}) and set (@samp{Q}). These packets are
34736 described fully in @ref{General Query Packets}.
34739 @cindex @samp{r} packet
34740 Reset the entire system.
34742 Don't use this packet; use the @samp{R} packet instead.
34745 @cindex @samp{R} packet
34746 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34747 This packet is only available in extended mode (@pxref{extended mode}).
34749 The @samp{R} packet has no reply.
34751 @item s @r{[}@var{addr}@r{]}
34752 @cindex @samp{s} packet
34753 Single step, resuming at @var{addr}. If
34754 @var{addr} is omitted, resume at same address.
34756 This packet is deprecated for multi-threading support. @xref{vCont
34760 @xref{Stop Reply Packets}, for the reply specifications.
34762 @item S @var{sig}@r{[};@var{addr}@r{]}
34763 @anchor{step with signal packet}
34764 @cindex @samp{S} packet
34765 Step with signal. This is analogous to the @samp{C} packet, but
34766 requests a single-step, rather than a normal resumption of execution.
34768 This packet is deprecated for multi-threading support. @xref{vCont
34772 @xref{Stop Reply Packets}, for the reply specifications.
34774 @item t @var{addr}:@var{PP},@var{MM}
34775 @cindex @samp{t} packet
34776 Search backwards starting at address @var{addr} for a match with pattern
34777 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34778 There must be at least 3 digits in @var{addr}.
34780 @item T @var{thread-id}
34781 @cindex @samp{T} packet
34782 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34787 thread is still alive
34793 Packets starting with @samp{v} are identified by a multi-letter name,
34794 up to the first @samp{;} or @samp{?} (or the end of the packet).
34796 @item vAttach;@var{pid}
34797 @cindex @samp{vAttach} packet
34798 Attach to a new process with the specified process ID @var{pid}.
34799 The process ID is a
34800 hexadecimal integer identifying the process. In all-stop mode, all
34801 threads in the attached process are stopped; in non-stop mode, it may be
34802 attached without being stopped if that is supported by the target.
34804 @c In non-stop mode, on a successful vAttach, the stub should set the
34805 @c current thread to a thread of the newly-attached process. After
34806 @c attaching, GDB queries for the attached process's thread ID with qC.
34807 @c Also note that, from a user perspective, whether or not the
34808 @c target is stopped on attach in non-stop mode depends on whether you
34809 @c use the foreground or background version of the attach command, not
34810 @c on what vAttach does; GDB does the right thing with respect to either
34811 @c stopping or restarting threads.
34813 This packet is only available in extended mode (@pxref{extended mode}).
34819 @item @r{Any stop packet}
34820 for success in all-stop mode (@pxref{Stop Reply Packets})
34822 for success in non-stop mode (@pxref{Remote Non-Stop})
34825 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34826 @cindex @samp{vCont} packet
34827 @anchor{vCont packet}
34828 Resume the inferior, specifying different actions for each thread.
34829 If an action is specified with no @var{thread-id}, then it is applied to any
34830 threads that don't have a specific action specified; if no default action is
34831 specified then other threads should remain stopped in all-stop mode and
34832 in their current state in non-stop mode.
34833 Specifying multiple
34834 default actions is an error; specifying no actions is also an error.
34835 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34837 Currently supported actions are:
34843 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34847 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34850 @item r @var{start},@var{end}
34851 Step once, and then keep stepping as long as the thread stops at
34852 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34853 The remote stub reports a stop reply when either the thread goes out
34854 of the range or is stopped due to an unrelated reason, such as hitting
34855 a breakpoint. @xref{range stepping}.
34857 If the range is empty (@var{start} == @var{end}), then the action
34858 becomes equivalent to the @samp{s} action. In other words,
34859 single-step once, and report the stop (even if the stepped instruction
34860 jumps to @var{start}).
34862 (A stop reply may be sent at any point even if the PC is still within
34863 the stepping range; for example, it is valid to implement this packet
34864 in a degenerate way as a single instruction step operation.)
34868 The optional argument @var{addr} normally associated with the
34869 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34870 not supported in @samp{vCont}.
34872 The @samp{t} action is only relevant in non-stop mode
34873 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34874 A stop reply should be generated for any affected thread not already stopped.
34875 When a thread is stopped by means of a @samp{t} action,
34876 the corresponding stop reply should indicate that the thread has stopped with
34877 signal @samp{0}, regardless of whether the target uses some other signal
34878 as an implementation detail.
34880 The stub must support @samp{vCont} if it reports support for
34881 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34882 this case @samp{vCont} actions can be specified to apply to all threads
34883 in a process by using the @samp{p@var{pid}.-1} form of the
34887 @xref{Stop Reply Packets}, for the reply specifications.
34890 @cindex @samp{vCont?} packet
34891 Request a list of actions supported by the @samp{vCont} packet.
34895 @item vCont@r{[};@var{action}@dots{}@r{]}
34896 The @samp{vCont} packet is supported. Each @var{action} is a supported
34897 command in the @samp{vCont} packet.
34899 The @samp{vCont} packet is not supported.
34902 @item vFile:@var{operation}:@var{parameter}@dots{}
34903 @cindex @samp{vFile} packet
34904 Perform a file operation on the target system. For details,
34905 see @ref{Host I/O Packets}.
34907 @item vFlashErase:@var{addr},@var{length}
34908 @cindex @samp{vFlashErase} packet
34909 Direct the stub to erase @var{length} bytes of flash starting at
34910 @var{addr}. The region may enclose any number of flash blocks, but
34911 its start and end must fall on block boundaries, as indicated by the
34912 flash block size appearing in the memory map (@pxref{Memory Map
34913 Format}). @value{GDBN} groups flash memory programming operations
34914 together, and sends a @samp{vFlashDone} request after each group; the
34915 stub is allowed to delay erase operation until the @samp{vFlashDone}
34916 packet is received.
34926 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34927 @cindex @samp{vFlashWrite} packet
34928 Direct the stub to write data to flash address @var{addr}. The data
34929 is passed in binary form using the same encoding as for the @samp{X}
34930 packet (@pxref{Binary Data}). The memory ranges specified by
34931 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34932 not overlap, and must appear in order of increasing addresses
34933 (although @samp{vFlashErase} packets for higher addresses may already
34934 have been received; the ordering is guaranteed only between
34935 @samp{vFlashWrite} packets). If a packet writes to an address that was
34936 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34937 target-specific method, the results are unpredictable.
34945 for vFlashWrite addressing non-flash memory
34951 @cindex @samp{vFlashDone} packet
34952 Indicate to the stub that flash programming operation is finished.
34953 The stub is permitted to delay or batch the effects of a group of
34954 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34955 @samp{vFlashDone} packet is received. The contents of the affected
34956 regions of flash memory are unpredictable until the @samp{vFlashDone}
34957 request is completed.
34959 @item vKill;@var{pid}
34960 @cindex @samp{vKill} packet
34961 @anchor{vKill packet}
34962 Kill the process with the specified process ID @var{pid}, which is a
34963 hexadecimal integer identifying the process. This packet is used in
34964 preference to @samp{k} when multiprocess protocol extensions are
34965 supported; see @ref{multiprocess extensions}.
34975 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34976 @cindex @samp{vRun} packet
34977 Run the program @var{filename}, passing it each @var{argument} on its
34978 command line. The file and arguments are hex-encoded strings. If
34979 @var{filename} is an empty string, the stub may use a default program
34980 (e.g.@: the last program run). The program is created in the stopped
34983 @c FIXME: What about non-stop mode?
34985 This packet is only available in extended mode (@pxref{extended mode}).
34991 @item @r{Any stop packet}
34992 for success (@pxref{Stop Reply Packets})
34996 @cindex @samp{vStopped} packet
34997 @xref{Notification Packets}.
34999 @item X @var{addr},@var{length}:@var{XX@dots{}}
35001 @cindex @samp{X} packet
35002 Write data to memory, where the data is transmitted in binary.
35003 Memory is specified by its address @var{addr} and number of bytes @var{length};
35004 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35014 @item z @var{type},@var{addr},@var{kind}
35015 @itemx Z @var{type},@var{addr},@var{kind}
35016 @anchor{insert breakpoint or watchpoint packet}
35017 @cindex @samp{z} packet
35018 @cindex @samp{Z} packets
35019 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35020 watchpoint starting at address @var{address} of kind @var{kind}.
35022 Each breakpoint and watchpoint packet @var{type} is documented
35025 @emph{Implementation notes: A remote target shall return an empty string
35026 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35027 remote target shall support either both or neither of a given
35028 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35029 avoid potential problems with duplicate packets, the operations should
35030 be implemented in an idempotent way.}
35032 @item z0,@var{addr},@var{kind}
35033 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35034 @cindex @samp{z0} packet
35035 @cindex @samp{Z0} packet
35036 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35037 @var{addr} of type @var{kind}.
35039 A memory breakpoint is implemented by replacing the instruction at
35040 @var{addr} with a software breakpoint or trap instruction. The
35041 @var{kind} is target-specific and typically indicates the size of
35042 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35043 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35044 architectures have additional meanings for @var{kind};
35045 @var{cond_list} is an optional list of conditional expressions in bytecode
35046 form that should be evaluated on the target's side. These are the
35047 conditions that should be taken into consideration when deciding if
35048 the breakpoint trigger should be reported back to @var{GDBN}.
35050 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35051 for how to best report a memory breakpoint event to @value{GDBN}.
35053 The @var{cond_list} parameter is comprised of a series of expressions,
35054 concatenated without separators. Each expression has the following form:
35058 @item X @var{len},@var{expr}
35059 @var{len} is the length of the bytecode expression and @var{expr} is the
35060 actual conditional expression in bytecode form.
35064 The optional @var{cmd_list} parameter introduces commands that may be
35065 run on the target, rather than being reported back to @value{GDBN}.
35066 The parameter starts with a numeric flag @var{persist}; if the flag is
35067 nonzero, then the breakpoint may remain active and the commands
35068 continue to be run even when @value{GDBN} disconnects from the target.
35069 Following this flag is a series of expressions concatenated with no
35070 separators. Each expression has the following form:
35074 @item X @var{len},@var{expr}
35075 @var{len} is the length of the bytecode expression and @var{expr} is the
35076 actual conditional expression in bytecode form.
35080 see @ref{Architecture-Specific Protocol Details}.
35082 @emph{Implementation note: It is possible for a target to copy or move
35083 code that contains memory breakpoints (e.g., when implementing
35084 overlays). The behavior of this packet, in the presence of such a
35085 target, is not defined.}
35097 @item z1,@var{addr},@var{kind}
35098 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35099 @cindex @samp{z1} packet
35100 @cindex @samp{Z1} packet
35101 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35102 address @var{addr}.
35104 A hardware breakpoint is implemented using a mechanism that is not
35105 dependant on being able to modify the target's memory. The @var{kind}
35106 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35108 @emph{Implementation note: A hardware breakpoint is not affected by code
35121 @item z2,@var{addr},@var{kind}
35122 @itemx Z2,@var{addr},@var{kind}
35123 @cindex @samp{z2} packet
35124 @cindex @samp{Z2} packet
35125 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35126 The number of bytes to watch is specified by @var{kind}.
35138 @item z3,@var{addr},@var{kind}
35139 @itemx Z3,@var{addr},@var{kind}
35140 @cindex @samp{z3} packet
35141 @cindex @samp{Z3} packet
35142 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35143 The number of bytes to watch is specified by @var{kind}.
35155 @item z4,@var{addr},@var{kind}
35156 @itemx Z4,@var{addr},@var{kind}
35157 @cindex @samp{z4} packet
35158 @cindex @samp{Z4} packet
35159 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35160 The number of bytes to watch is specified by @var{kind}.
35174 @node Stop Reply Packets
35175 @section Stop Reply Packets
35176 @cindex stop reply packets
35178 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35179 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35180 receive any of the below as a reply. Except for @samp{?}
35181 and @samp{vStopped}, that reply is only returned
35182 when the target halts. In the below the exact meaning of @dfn{signal
35183 number} is defined by the header @file{include/gdb/signals.h} in the
35184 @value{GDBN} source code.
35186 As in the description of request packets, we include spaces in the
35187 reply templates for clarity; these are not part of the reply packet's
35188 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35194 The program received signal number @var{AA} (a two-digit hexadecimal
35195 number). This is equivalent to a @samp{T} response with no
35196 @var{n}:@var{r} pairs.
35198 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35199 @cindex @samp{T} packet reply
35200 The program received signal number @var{AA} (a two-digit hexadecimal
35201 number). This is equivalent to an @samp{S} response, except that the
35202 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35203 and other information directly in the stop reply packet, reducing
35204 round-trip latency. Single-step and breakpoint traps are reported
35205 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35209 If @var{n} is a hexadecimal number, it is a register number, and the
35210 corresponding @var{r} gives that register's value. The data @var{r} is a
35211 series of bytes in target byte order, with each byte given by a
35212 two-digit hex number.
35215 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35216 the stopped thread, as specified in @ref{thread-id syntax}.
35219 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35220 the core on which the stop event was detected.
35223 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35224 specific event that stopped the target. The currently defined stop
35225 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35226 signal. At most one stop reason should be present.
35229 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35230 and go on to the next; this allows us to extend the protocol in the
35234 The currently defined stop reasons are:
35240 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35243 @cindex shared library events, remote reply
35245 The packet indicates that the loaded libraries have changed.
35246 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35247 list of loaded libraries. The @var{r} part is ignored.
35249 @cindex replay log events, remote reply
35251 The packet indicates that the target cannot continue replaying
35252 logged execution events, because it has reached the end (or the
35253 beginning when executing backward) of the log. The value of @var{r}
35254 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35255 for more information.
35258 @anchor{swbreak stop reason}
35259 The packet indicates a memory breakpoint instruction was executed,
35260 irrespective of whether it was @value{GDBN} that planted the
35261 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35262 part must be left empty.
35264 On some architectures, such as x86, at the architecture level, when a
35265 breakpoint instruction executes the program counter points at the
35266 breakpoint address plus an offset. On such targets, the stub is
35267 responsible for adjusting the PC to point back at the breakpoint
35270 This packet should not be sent by default; older @value{GDBN} versions
35271 did not support it. @value{GDBN} requests it, by supplying an
35272 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35273 remote stub must also supply the appropriate @samp{qSupported} feature
35274 indicating support.
35276 This packet is required for correct non-stop mode operation.
35279 The packet indicates the target stopped for a hardware breakpoint.
35280 The @var{r} part must be left empty.
35282 The same remarks about @samp{qSupported} and non-stop mode above
35287 @itemx W @var{AA} ; process:@var{pid}
35288 The process exited, and @var{AA} is the exit status. This is only
35289 applicable to certain targets.
35291 The second form of the response, including the process ID of the exited
35292 process, can be used only when @value{GDBN} has reported support for
35293 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35294 The @var{pid} is formatted as a big-endian hex string.
35297 @itemx X @var{AA} ; process:@var{pid}
35298 The process terminated with signal @var{AA}.
35300 The second form of the response, including the process ID of the
35301 terminated process, can be used only when @value{GDBN} has reported
35302 support for multiprocess protocol extensions; see @ref{multiprocess
35303 extensions}. The @var{pid} is formatted as a big-endian hex string.
35305 @item O @var{XX}@dots{}
35306 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35307 written as the program's console output. This can happen at any time
35308 while the program is running and the debugger should continue to wait
35309 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35311 @item F @var{call-id},@var{parameter}@dots{}
35312 @var{call-id} is the identifier which says which host system call should
35313 be called. This is just the name of the function. Translation into the
35314 correct system call is only applicable as it's defined in @value{GDBN}.
35315 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35318 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35319 this very system call.
35321 The target replies with this packet when it expects @value{GDBN} to
35322 call a host system call on behalf of the target. @value{GDBN} replies
35323 with an appropriate @samp{F} packet and keeps up waiting for the next
35324 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35325 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35326 Protocol Extension}, for more details.
35330 @node General Query Packets
35331 @section General Query Packets
35332 @cindex remote query requests
35334 Packets starting with @samp{q} are @dfn{general query packets};
35335 packets starting with @samp{Q} are @dfn{general set packets}. General
35336 query and set packets are a semi-unified form for retrieving and
35337 sending information to and from the stub.
35339 The initial letter of a query or set packet is followed by a name
35340 indicating what sort of thing the packet applies to. For example,
35341 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35342 definitions with the stub. These packet names follow some
35347 The name must not contain commas, colons or semicolons.
35349 Most @value{GDBN} query and set packets have a leading upper case
35352 The names of custom vendor packets should use a company prefix, in
35353 lower case, followed by a period. For example, packets designed at
35354 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35355 foos) or @samp{Qacme.bar} (for setting bars).
35358 The name of a query or set packet should be separated from any
35359 parameters by a @samp{:}; the parameters themselves should be
35360 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35361 full packet name, and check for a separator or the end of the packet,
35362 in case two packet names share a common prefix. New packets should not begin
35363 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35364 packets predate these conventions, and have arguments without any terminator
35365 for the packet name; we suspect they are in widespread use in places that
35366 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35367 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35370 Like the descriptions of the other packets, each description here
35371 has a template showing the packet's overall syntax, followed by an
35372 explanation of the packet's meaning. We include spaces in some of the
35373 templates for clarity; these are not part of the packet's syntax. No
35374 @value{GDBN} packet uses spaces to separate its components.
35376 Here are the currently defined query and set packets:
35382 Turn on or off the agent as a helper to perform some debugging operations
35383 delegated from @value{GDBN} (@pxref{Control Agent}).
35385 @item QAllow:@var{op}:@var{val}@dots{}
35386 @cindex @samp{QAllow} packet
35387 Specify which operations @value{GDBN} expects to request of the
35388 target, as a semicolon-separated list of operation name and value
35389 pairs. Possible values for @var{op} include @samp{WriteReg},
35390 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35391 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35392 indicating that @value{GDBN} will not request the operation, or 1,
35393 indicating that it may. (The target can then use this to set up its
35394 own internals optimally, for instance if the debugger never expects to
35395 insert breakpoints, it may not need to install its own trap handler.)
35398 @cindex current thread, remote request
35399 @cindex @samp{qC} packet
35400 Return the current thread ID.
35404 @item QC @var{thread-id}
35405 Where @var{thread-id} is a thread ID as documented in
35406 @ref{thread-id syntax}.
35407 @item @r{(anything else)}
35408 Any other reply implies the old thread ID.
35411 @item qCRC:@var{addr},@var{length}
35412 @cindex CRC of memory block, remote request
35413 @cindex @samp{qCRC} packet
35414 @anchor{qCRC packet}
35415 Compute the CRC checksum of a block of memory using CRC-32 defined in
35416 IEEE 802.3. The CRC is computed byte at a time, taking the most
35417 significant bit of each byte first. The initial pattern code
35418 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35420 @emph{Note:} This is the same CRC used in validating separate debug
35421 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35422 Files}). However the algorithm is slightly different. When validating
35423 separate debug files, the CRC is computed taking the @emph{least}
35424 significant bit of each byte first, and the final result is inverted to
35425 detect trailing zeros.
35430 An error (such as memory fault)
35431 @item C @var{crc32}
35432 The specified memory region's checksum is @var{crc32}.
35435 @item QDisableRandomization:@var{value}
35436 @cindex disable address space randomization, remote request
35437 @cindex @samp{QDisableRandomization} packet
35438 Some target operating systems will randomize the virtual address space
35439 of the inferior process as a security feature, but provide a feature
35440 to disable such randomization, e.g.@: to allow for a more deterministic
35441 debugging experience. On such systems, this packet with a @var{value}
35442 of 1 directs the target to disable address space randomization for
35443 processes subsequently started via @samp{vRun} packets, while a packet
35444 with a @var{value} of 0 tells the target to enable address space
35447 This packet is only available in extended mode (@pxref{extended mode}).
35452 The request succeeded.
35455 An error occurred. The error number @var{nn} is given as hex digits.
35458 An empty reply indicates that @samp{QDisableRandomization} is not supported
35462 This packet is not probed by default; the remote stub must request it,
35463 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35464 This should only be done on targets that actually support disabling
35465 address space randomization.
35468 @itemx qsThreadInfo
35469 @cindex list active threads, remote request
35470 @cindex @samp{qfThreadInfo} packet
35471 @cindex @samp{qsThreadInfo} packet
35472 Obtain a list of all active thread IDs from the target (OS). Since there
35473 may be too many active threads to fit into one reply packet, this query
35474 works iteratively: it may require more than one query/reply sequence to
35475 obtain the entire list of threads. The first query of the sequence will
35476 be the @samp{qfThreadInfo} query; subsequent queries in the
35477 sequence will be the @samp{qsThreadInfo} query.
35479 NOTE: This packet replaces the @samp{qL} query (see below).
35483 @item m @var{thread-id}
35485 @item m @var{thread-id},@var{thread-id}@dots{}
35486 a comma-separated list of thread IDs
35488 (lower case letter @samp{L}) denotes end of list.
35491 In response to each query, the target will reply with a list of one or
35492 more thread IDs, separated by commas.
35493 @value{GDBN} will respond to each reply with a request for more thread
35494 ids (using the @samp{qs} form of the query), until the target responds
35495 with @samp{l} (lower-case ell, for @dfn{last}).
35496 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35499 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35500 initial connection with the remote target, and the very first thread ID
35501 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35502 message. Therefore, the stub should ensure that the first thread ID in
35503 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35505 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35506 @cindex get thread-local storage address, remote request
35507 @cindex @samp{qGetTLSAddr} packet
35508 Fetch the address associated with thread local storage specified
35509 by @var{thread-id}, @var{offset}, and @var{lm}.
35511 @var{thread-id} is the thread ID associated with the
35512 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35514 @var{offset} is the (big endian, hex encoded) offset associated with the
35515 thread local variable. (This offset is obtained from the debug
35516 information associated with the variable.)
35518 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35519 load module associated with the thread local storage. For example,
35520 a @sc{gnu}/Linux system will pass the link map address of the shared
35521 object associated with the thread local storage under consideration.
35522 Other operating environments may choose to represent the load module
35523 differently, so the precise meaning of this parameter will vary.
35527 @item @var{XX}@dots{}
35528 Hex encoded (big endian) bytes representing the address of the thread
35529 local storage requested.
35532 An error occurred. The error number @var{nn} is given as hex digits.
35535 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35538 @item qGetTIBAddr:@var{thread-id}
35539 @cindex get thread information block address
35540 @cindex @samp{qGetTIBAddr} packet
35541 Fetch address of the Windows OS specific Thread Information Block.
35543 @var{thread-id} is the thread ID associated with the thread.
35547 @item @var{XX}@dots{}
35548 Hex encoded (big endian) bytes representing the linear address of the
35549 thread information block.
35552 An error occured. This means that either the thread was not found, or the
35553 address could not be retrieved.
35556 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35559 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35560 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35561 digit) is one to indicate the first query and zero to indicate a
35562 subsequent query; @var{threadcount} (two hex digits) is the maximum
35563 number of threads the response packet can contain; and @var{nextthread}
35564 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35565 returned in the response as @var{argthread}.
35567 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35571 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35572 Where: @var{count} (two hex digits) is the number of threads being
35573 returned; @var{done} (one hex digit) is zero to indicate more threads
35574 and one indicates no further threads; @var{argthreadid} (eight hex
35575 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35576 is a sequence of thread IDs, @var{threadid} (eight hex
35577 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35581 @cindex section offsets, remote request
35582 @cindex @samp{qOffsets} packet
35583 Get section offsets that the target used when relocating the downloaded
35588 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35589 Relocate the @code{Text} section by @var{xxx} from its original address.
35590 Relocate the @code{Data} section by @var{yyy} from its original address.
35591 If the object file format provides segment information (e.g.@: @sc{elf}
35592 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35593 segments by the supplied offsets.
35595 @emph{Note: while a @code{Bss} offset may be included in the response,
35596 @value{GDBN} ignores this and instead applies the @code{Data} offset
35597 to the @code{Bss} section.}
35599 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35600 Relocate the first segment of the object file, which conventionally
35601 contains program code, to a starting address of @var{xxx}. If
35602 @samp{DataSeg} is specified, relocate the second segment, which
35603 conventionally contains modifiable data, to a starting address of
35604 @var{yyy}. @value{GDBN} will report an error if the object file
35605 does not contain segment information, or does not contain at least
35606 as many segments as mentioned in the reply. Extra segments are
35607 kept at fixed offsets relative to the last relocated segment.
35610 @item qP @var{mode} @var{thread-id}
35611 @cindex thread information, remote request
35612 @cindex @samp{qP} packet
35613 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35614 encoded 32 bit mode; @var{thread-id} is a thread ID
35615 (@pxref{thread-id syntax}).
35617 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35620 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35624 @cindex non-stop mode, remote request
35625 @cindex @samp{QNonStop} packet
35627 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35628 @xref{Remote Non-Stop}, for more information.
35633 The request succeeded.
35636 An error occurred. The error number @var{nn} is given as hex digits.
35639 An empty reply indicates that @samp{QNonStop} is not supported by
35643 This packet is not probed by default; the remote stub must request it,
35644 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35645 Use of this packet is controlled by the @code{set non-stop} command;
35646 @pxref{Non-Stop Mode}.
35648 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35649 @cindex pass signals to inferior, remote request
35650 @cindex @samp{QPassSignals} packet
35651 @anchor{QPassSignals}
35652 Each listed @var{signal} should be passed directly to the inferior process.
35653 Signals are numbered identically to continue packets and stop replies
35654 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35655 strictly greater than the previous item. These signals do not need to stop
35656 the inferior, or be reported to @value{GDBN}. All other signals should be
35657 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35658 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35659 new list. This packet improves performance when using @samp{handle
35660 @var{signal} nostop noprint pass}.
35665 The request succeeded.
35668 An error occurred. The error number @var{nn} is given as hex digits.
35671 An empty reply indicates that @samp{QPassSignals} is not supported by
35675 Use of this packet is controlled by the @code{set remote pass-signals}
35676 command (@pxref{Remote Configuration, set remote pass-signals}).
35677 This packet is not probed by default; the remote stub must request it,
35678 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35680 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35681 @cindex signals the inferior may see, remote request
35682 @cindex @samp{QProgramSignals} packet
35683 @anchor{QProgramSignals}
35684 Each listed @var{signal} may be delivered to the inferior process.
35685 Others should be silently discarded.
35687 In some cases, the remote stub may need to decide whether to deliver a
35688 signal to the program or not without @value{GDBN} involvement. One
35689 example of that is while detaching --- the program's threads may have
35690 stopped for signals that haven't yet had a chance of being reported to
35691 @value{GDBN}, and so the remote stub can use the signal list specified
35692 by this packet to know whether to deliver or ignore those pending
35695 This does not influence whether to deliver a signal as requested by a
35696 resumption packet (@pxref{vCont packet}).
35698 Signals are numbered identically to continue packets and stop replies
35699 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35700 strictly greater than the previous item. Multiple
35701 @samp{QProgramSignals} packets do not combine; any earlier
35702 @samp{QProgramSignals} list is completely replaced by the new list.
35707 The request succeeded.
35710 An error occurred. The error number @var{nn} is given as hex digits.
35713 An empty reply indicates that @samp{QProgramSignals} is not supported
35717 Use of this packet is controlled by the @code{set remote program-signals}
35718 command (@pxref{Remote Configuration, set remote program-signals}).
35719 This packet is not probed by default; the remote stub must request it,
35720 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35722 @item qRcmd,@var{command}
35723 @cindex execute remote command, remote request
35724 @cindex @samp{qRcmd} packet
35725 @var{command} (hex encoded) is passed to the local interpreter for
35726 execution. Invalid commands should be reported using the output
35727 string. Before the final result packet, the target may also respond
35728 with a number of intermediate @samp{O@var{output}} console output
35729 packets. @emph{Implementors should note that providing access to a
35730 stubs's interpreter may have security implications}.
35735 A command response with no output.
35737 A command response with the hex encoded output string @var{OUTPUT}.
35739 Indicate a badly formed request.
35741 An empty reply indicates that @samp{qRcmd} is not recognized.
35744 (Note that the @code{qRcmd} packet's name is separated from the
35745 command by a @samp{,}, not a @samp{:}, contrary to the naming
35746 conventions above. Please don't use this packet as a model for new
35749 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35750 @cindex searching memory, in remote debugging
35752 @cindex @samp{qSearch:memory} packet
35754 @cindex @samp{qSearch memory} packet
35755 @anchor{qSearch memory}
35756 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35757 Both @var{address} and @var{length} are encoded in hex;
35758 @var{search-pattern} is a sequence of bytes, also hex encoded.
35763 The pattern was not found.
35765 The pattern was found at @var{address}.
35767 A badly formed request or an error was encountered while searching memory.
35769 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35772 @item QStartNoAckMode
35773 @cindex @samp{QStartNoAckMode} packet
35774 @anchor{QStartNoAckMode}
35775 Request that the remote stub disable the normal @samp{+}/@samp{-}
35776 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35781 The stub has switched to no-acknowledgment mode.
35782 @value{GDBN} acknowledges this reponse,
35783 but neither the stub nor @value{GDBN} shall send or expect further
35784 @samp{+}/@samp{-} acknowledgments in the current connection.
35786 An empty reply indicates that the stub does not support no-acknowledgment mode.
35789 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35790 @cindex supported packets, remote query
35791 @cindex features of the remote protocol
35792 @cindex @samp{qSupported} packet
35793 @anchor{qSupported}
35794 Tell the remote stub about features supported by @value{GDBN}, and
35795 query the stub for features it supports. This packet allows
35796 @value{GDBN} and the remote stub to take advantage of each others'
35797 features. @samp{qSupported} also consolidates multiple feature probes
35798 at startup, to improve @value{GDBN} performance---a single larger
35799 packet performs better than multiple smaller probe packets on
35800 high-latency links. Some features may enable behavior which must not
35801 be on by default, e.g.@: because it would confuse older clients or
35802 stubs. Other features may describe packets which could be
35803 automatically probed for, but are not. These features must be
35804 reported before @value{GDBN} will use them. This ``default
35805 unsupported'' behavior is not appropriate for all packets, but it
35806 helps to keep the initial connection time under control with new
35807 versions of @value{GDBN} which support increasing numbers of packets.
35811 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35812 The stub supports or does not support each returned @var{stubfeature},
35813 depending on the form of each @var{stubfeature} (see below for the
35816 An empty reply indicates that @samp{qSupported} is not recognized,
35817 or that no features needed to be reported to @value{GDBN}.
35820 The allowed forms for each feature (either a @var{gdbfeature} in the
35821 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35825 @item @var{name}=@var{value}
35826 The remote protocol feature @var{name} is supported, and associated
35827 with the specified @var{value}. The format of @var{value} depends
35828 on the feature, but it must not include a semicolon.
35830 The remote protocol feature @var{name} is supported, and does not
35831 need an associated value.
35833 The remote protocol feature @var{name} is not supported.
35835 The remote protocol feature @var{name} may be supported, and
35836 @value{GDBN} should auto-detect support in some other way when it is
35837 needed. This form will not be used for @var{gdbfeature} notifications,
35838 but may be used for @var{stubfeature} responses.
35841 Whenever the stub receives a @samp{qSupported} request, the
35842 supplied set of @value{GDBN} features should override any previous
35843 request. This allows @value{GDBN} to put the stub in a known
35844 state, even if the stub had previously been communicating with
35845 a different version of @value{GDBN}.
35847 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35852 This feature indicates whether @value{GDBN} supports multiprocess
35853 extensions to the remote protocol. @value{GDBN} does not use such
35854 extensions unless the stub also reports that it supports them by
35855 including @samp{multiprocess+} in its @samp{qSupported} reply.
35856 @xref{multiprocess extensions}, for details.
35859 This feature indicates that @value{GDBN} supports the XML target
35860 description. If the stub sees @samp{xmlRegisters=} with target
35861 specific strings separated by a comma, it will report register
35865 This feature indicates whether @value{GDBN} supports the
35866 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35867 instruction reply packet}).
35870 This feature indicates whether @value{GDBN} supports the swbreak stop
35871 reason in stop replies. @xref{swbreak stop reason}, for details.
35874 This feature indicates whether @value{GDBN} supports the hwbreak stop
35875 reason in stop replies. @xref{swbreak stop reason}, for details.
35878 Stubs should ignore any unknown values for
35879 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35880 packet supports receiving packets of unlimited length (earlier
35881 versions of @value{GDBN} may reject overly long responses). Additional values
35882 for @var{gdbfeature} may be defined in the future to let the stub take
35883 advantage of new features in @value{GDBN}, e.g.@: incompatible
35884 improvements in the remote protocol---the @samp{multiprocess} feature is
35885 an example of such a feature. The stub's reply should be independent
35886 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35887 describes all the features it supports, and then the stub replies with
35888 all the features it supports.
35890 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35891 responses, as long as each response uses one of the standard forms.
35893 Some features are flags. A stub which supports a flag feature
35894 should respond with a @samp{+} form response. Other features
35895 require values, and the stub should respond with an @samp{=}
35898 Each feature has a default value, which @value{GDBN} will use if
35899 @samp{qSupported} is not available or if the feature is not mentioned
35900 in the @samp{qSupported} response. The default values are fixed; a
35901 stub is free to omit any feature responses that match the defaults.
35903 Not all features can be probed, but for those which can, the probing
35904 mechanism is useful: in some cases, a stub's internal
35905 architecture may not allow the protocol layer to know some information
35906 about the underlying target in advance. This is especially common in
35907 stubs which may be configured for multiple targets.
35909 These are the currently defined stub features and their properties:
35911 @multitable @columnfractions 0.35 0.2 0.12 0.2
35912 @c NOTE: The first row should be @headitem, but we do not yet require
35913 @c a new enough version of Texinfo (4.7) to use @headitem.
35915 @tab Value Required
35919 @item @samp{PacketSize}
35924 @item @samp{qXfer:auxv:read}
35929 @item @samp{qXfer:btrace:read}
35934 @item @samp{qXfer:btrace-conf:read}
35939 @item @samp{qXfer:features:read}
35944 @item @samp{qXfer:libraries:read}
35949 @item @samp{qXfer:libraries-svr4:read}
35954 @item @samp{augmented-libraries-svr4-read}
35959 @item @samp{qXfer:memory-map:read}
35964 @item @samp{qXfer:sdata:read}
35969 @item @samp{qXfer:spu:read}
35974 @item @samp{qXfer:spu:write}
35979 @item @samp{qXfer:siginfo:read}
35984 @item @samp{qXfer:siginfo:write}
35989 @item @samp{qXfer:threads:read}
35994 @item @samp{qXfer:traceframe-info:read}
35999 @item @samp{qXfer:uib:read}
36004 @item @samp{qXfer:fdpic:read}
36009 @item @samp{Qbtrace:off}
36014 @item @samp{Qbtrace:bts}
36019 @item @samp{Qbtrace-conf:bts:size}
36024 @item @samp{QNonStop}
36029 @item @samp{QPassSignals}
36034 @item @samp{QStartNoAckMode}
36039 @item @samp{multiprocess}
36044 @item @samp{ConditionalBreakpoints}
36049 @item @samp{ConditionalTracepoints}
36054 @item @samp{ReverseContinue}
36059 @item @samp{ReverseStep}
36064 @item @samp{TracepointSource}
36069 @item @samp{QAgent}
36074 @item @samp{QAllow}
36079 @item @samp{QDisableRandomization}
36084 @item @samp{EnableDisableTracepoints}
36089 @item @samp{QTBuffer:size}
36094 @item @samp{tracenz}
36099 @item @samp{BreakpointCommands}
36104 @item @samp{swbreak}
36109 @item @samp{hwbreak}
36116 These are the currently defined stub features, in more detail:
36119 @cindex packet size, remote protocol
36120 @item PacketSize=@var{bytes}
36121 The remote stub can accept packets up to at least @var{bytes} in
36122 length. @value{GDBN} will send packets up to this size for bulk
36123 transfers, and will never send larger packets. This is a limit on the
36124 data characters in the packet, including the frame and checksum.
36125 There is no trailing NUL byte in a remote protocol packet; if the stub
36126 stores packets in a NUL-terminated format, it should allow an extra
36127 byte in its buffer for the NUL. If this stub feature is not supported,
36128 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36130 @item qXfer:auxv:read
36131 The remote stub understands the @samp{qXfer:auxv:read} packet
36132 (@pxref{qXfer auxiliary vector read}).
36134 @item qXfer:btrace:read
36135 The remote stub understands the @samp{qXfer:btrace:read}
36136 packet (@pxref{qXfer btrace read}).
36138 @item qXfer:btrace-conf:read
36139 The remote stub understands the @samp{qXfer:btrace-conf:read}
36140 packet (@pxref{qXfer btrace-conf read}).
36142 @item qXfer:features:read
36143 The remote stub understands the @samp{qXfer:features:read} packet
36144 (@pxref{qXfer target description read}).
36146 @item qXfer:libraries:read
36147 The remote stub understands the @samp{qXfer:libraries:read} packet
36148 (@pxref{qXfer library list read}).
36150 @item qXfer:libraries-svr4:read
36151 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36152 (@pxref{qXfer svr4 library list read}).
36154 @item augmented-libraries-svr4-read
36155 The remote stub understands the augmented form of the
36156 @samp{qXfer:libraries-svr4:read} packet
36157 (@pxref{qXfer svr4 library list read}).
36159 @item qXfer:memory-map:read
36160 The remote stub understands the @samp{qXfer:memory-map:read} packet
36161 (@pxref{qXfer memory map read}).
36163 @item qXfer:sdata:read
36164 The remote stub understands the @samp{qXfer:sdata:read} packet
36165 (@pxref{qXfer sdata read}).
36167 @item qXfer:spu:read
36168 The remote stub understands the @samp{qXfer:spu:read} packet
36169 (@pxref{qXfer spu read}).
36171 @item qXfer:spu:write
36172 The remote stub understands the @samp{qXfer:spu:write} packet
36173 (@pxref{qXfer spu write}).
36175 @item qXfer:siginfo:read
36176 The remote stub understands the @samp{qXfer:siginfo:read} packet
36177 (@pxref{qXfer siginfo read}).
36179 @item qXfer:siginfo:write
36180 The remote stub understands the @samp{qXfer:siginfo:write} packet
36181 (@pxref{qXfer siginfo write}).
36183 @item qXfer:threads:read
36184 The remote stub understands the @samp{qXfer:threads:read} packet
36185 (@pxref{qXfer threads read}).
36187 @item qXfer:traceframe-info:read
36188 The remote stub understands the @samp{qXfer:traceframe-info:read}
36189 packet (@pxref{qXfer traceframe info read}).
36191 @item qXfer:uib:read
36192 The remote stub understands the @samp{qXfer:uib:read}
36193 packet (@pxref{qXfer unwind info block}).
36195 @item qXfer:fdpic:read
36196 The remote stub understands the @samp{qXfer:fdpic:read}
36197 packet (@pxref{qXfer fdpic loadmap read}).
36200 The remote stub understands the @samp{QNonStop} packet
36201 (@pxref{QNonStop}).
36204 The remote stub understands the @samp{QPassSignals} packet
36205 (@pxref{QPassSignals}).
36207 @item QStartNoAckMode
36208 The remote stub understands the @samp{QStartNoAckMode} packet and
36209 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36212 @anchor{multiprocess extensions}
36213 @cindex multiprocess extensions, in remote protocol
36214 The remote stub understands the multiprocess extensions to the remote
36215 protocol syntax. The multiprocess extensions affect the syntax of
36216 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36217 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36218 replies. Note that reporting this feature indicates support for the
36219 syntactic extensions only, not that the stub necessarily supports
36220 debugging of more than one process at a time. The stub must not use
36221 multiprocess extensions in packet replies unless @value{GDBN} has also
36222 indicated it supports them in its @samp{qSupported} request.
36224 @item qXfer:osdata:read
36225 The remote stub understands the @samp{qXfer:osdata:read} packet
36226 ((@pxref{qXfer osdata read}).
36228 @item ConditionalBreakpoints
36229 The target accepts and implements evaluation of conditional expressions
36230 defined for breakpoints. The target will only report breakpoint triggers
36231 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36233 @item ConditionalTracepoints
36234 The remote stub accepts and implements conditional expressions defined
36235 for tracepoints (@pxref{Tracepoint Conditions}).
36237 @item ReverseContinue
36238 The remote stub accepts and implements the reverse continue packet
36242 The remote stub accepts and implements the reverse step packet
36245 @item TracepointSource
36246 The remote stub understands the @samp{QTDPsrc} packet that supplies
36247 the source form of tracepoint definitions.
36250 The remote stub understands the @samp{QAgent} packet.
36253 The remote stub understands the @samp{QAllow} packet.
36255 @item QDisableRandomization
36256 The remote stub understands the @samp{QDisableRandomization} packet.
36258 @item StaticTracepoint
36259 @cindex static tracepoints, in remote protocol
36260 The remote stub supports static tracepoints.
36262 @item InstallInTrace
36263 @anchor{install tracepoint in tracing}
36264 The remote stub supports installing tracepoint in tracing.
36266 @item EnableDisableTracepoints
36267 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36268 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36269 to be enabled and disabled while a trace experiment is running.
36271 @item QTBuffer:size
36272 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36273 packet that allows to change the size of the trace buffer.
36276 @cindex string tracing, in remote protocol
36277 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36278 See @ref{Bytecode Descriptions} for details about the bytecode.
36280 @item BreakpointCommands
36281 @cindex breakpoint commands, in remote protocol
36282 The remote stub supports running a breakpoint's command list itself,
36283 rather than reporting the hit to @value{GDBN}.
36286 The remote stub understands the @samp{Qbtrace:off} packet.
36289 The remote stub understands the @samp{Qbtrace:bts} packet.
36291 @item Qbtrace-conf:bts:size
36292 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36295 The remote stub reports the @samp{swbreak} stop reason for memory
36299 The remote stub reports the @samp{hwbreak} stop reason for hardware
36305 @cindex symbol lookup, remote request
36306 @cindex @samp{qSymbol} packet
36307 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36308 requests. Accept requests from the target for the values of symbols.
36313 The target does not need to look up any (more) symbols.
36314 @item qSymbol:@var{sym_name}
36315 The target requests the value of symbol @var{sym_name} (hex encoded).
36316 @value{GDBN} may provide the value by using the
36317 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36321 @item qSymbol:@var{sym_value}:@var{sym_name}
36322 Set the value of @var{sym_name} to @var{sym_value}.
36324 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36325 target has previously requested.
36327 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36328 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36334 The target does not need to look up any (more) symbols.
36335 @item qSymbol:@var{sym_name}
36336 The target requests the value of a new symbol @var{sym_name} (hex
36337 encoded). @value{GDBN} will continue to supply the values of symbols
36338 (if available), until the target ceases to request them.
36343 @itemx QTDisconnected
36350 @itemx qTMinFTPILen
36352 @xref{Tracepoint Packets}.
36354 @item qThreadExtraInfo,@var{thread-id}
36355 @cindex thread attributes info, remote request
36356 @cindex @samp{qThreadExtraInfo} packet
36357 Obtain from the target OS a printable string description of thread
36358 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36359 for the forms of @var{thread-id}. This
36360 string may contain anything that the target OS thinks is interesting
36361 for @value{GDBN} to tell the user about the thread. The string is
36362 displayed in @value{GDBN}'s @code{info threads} display. Some
36363 examples of possible thread extra info strings are @samp{Runnable}, or
36364 @samp{Blocked on Mutex}.
36368 @item @var{XX}@dots{}
36369 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36370 comprising the printable string containing the extra information about
36371 the thread's attributes.
36374 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36375 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36376 conventions above. Please don't use this packet as a model for new
36395 @xref{Tracepoint Packets}.
36397 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36398 @cindex read special object, remote request
36399 @cindex @samp{qXfer} packet
36400 @anchor{qXfer read}
36401 Read uninterpreted bytes from the target's special data area
36402 identified by the keyword @var{object}. Request @var{length} bytes
36403 starting at @var{offset} bytes into the data. The content and
36404 encoding of @var{annex} is specific to @var{object}; it can supply
36405 additional details about what data to access.
36407 Here are the specific requests of this form defined so far. All
36408 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36409 formats, listed below.
36412 @item qXfer:auxv:read::@var{offset},@var{length}
36413 @anchor{qXfer auxiliary vector read}
36414 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36415 auxiliary vector}. Note @var{annex} must be empty.
36417 This packet is not probed by default; the remote stub must request it,
36418 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36420 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36421 @anchor{qXfer btrace read}
36423 Return a description of the current branch trace.
36424 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36425 packet may have one of the following values:
36429 Returns all available branch trace.
36432 Returns all available branch trace if the branch trace changed since
36433 the last read request.
36436 Returns the new branch trace since the last read request. Adds a new
36437 block to the end of the trace that begins at zero and ends at the source
36438 location of the first branch in the trace buffer. This extra block is
36439 used to stitch traces together.
36441 If the trace buffer overflowed, returns an error indicating the overflow.
36444 This packet is not probed by default; the remote stub must request it
36445 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36447 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36448 @anchor{qXfer btrace-conf read}
36450 Return a description of the current branch trace configuration.
36451 @xref{Branch Trace Configuration Format}.
36453 This packet is not probed by default; the remote stub must request it
36454 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36456 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36457 @anchor{qXfer target description read}
36458 Access the @dfn{target description}. @xref{Target Descriptions}. The
36459 annex specifies which XML document to access. The main description is
36460 always loaded from the @samp{target.xml} annex.
36462 This packet is not probed by default; the remote stub must request it,
36463 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36465 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36466 @anchor{qXfer library list read}
36467 Access the target's list of loaded libraries. @xref{Library List Format}.
36468 The annex part of the generic @samp{qXfer} packet must be empty
36469 (@pxref{qXfer read}).
36471 Targets which maintain a list of libraries in the program's memory do
36472 not need to implement this packet; it is designed for platforms where
36473 the operating system manages the list of loaded libraries.
36475 This packet is not probed by default; the remote stub must request it,
36476 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36478 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36479 @anchor{qXfer svr4 library list read}
36480 Access the target's list of loaded libraries when the target is an SVR4
36481 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36482 of the generic @samp{qXfer} packet must be empty unless the remote
36483 stub indicated it supports the augmented form of this packet
36484 by supplying an appropriate @samp{qSupported} response
36485 (@pxref{qXfer read}, @ref{qSupported}).
36487 This packet is optional for better performance on SVR4 targets.
36488 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36490 This packet is not probed by default; the remote stub must request it,
36491 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36493 If the remote stub indicates it supports the augmented form of this
36494 packet then the annex part of the generic @samp{qXfer} packet may
36495 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36496 arguments. The currently supported arguments are:
36499 @item start=@var{address}
36500 A hexadecimal number specifying the address of the @samp{struct
36501 link_map} to start reading the library list from. If unset or zero
36502 then the first @samp{struct link_map} in the library list will be
36503 chosen as the starting point.
36505 @item prev=@var{address}
36506 A hexadecimal number specifying the address of the @samp{struct
36507 link_map} immediately preceding the @samp{struct link_map}
36508 specified by the @samp{start} argument. If unset or zero then
36509 the remote stub will expect that no @samp{struct link_map}
36510 exists prior to the starting point.
36514 Arguments that are not understood by the remote stub will be silently
36517 @item qXfer:memory-map:read::@var{offset},@var{length}
36518 @anchor{qXfer memory map read}
36519 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36520 annex part of the generic @samp{qXfer} packet must be empty
36521 (@pxref{qXfer read}).
36523 This packet is not probed by default; the remote stub must request it,
36524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36526 @item qXfer:sdata:read::@var{offset},@var{length}
36527 @anchor{qXfer sdata read}
36529 Read contents of the extra collected static tracepoint marker
36530 information. The annex part of the generic @samp{qXfer} packet must
36531 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36534 This packet is not probed by default; the remote stub must request it,
36535 by supplying an appropriate @samp{qSupported} response
36536 (@pxref{qSupported}).
36538 @item qXfer:siginfo:read::@var{offset},@var{length}
36539 @anchor{qXfer siginfo read}
36540 Read contents of the extra signal information on the target
36541 system. The annex part of the generic @samp{qXfer} packet must be
36542 empty (@pxref{qXfer read}).
36544 This packet is not probed by default; the remote stub must request it,
36545 by supplying an appropriate @samp{qSupported} response
36546 (@pxref{qSupported}).
36548 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36549 @anchor{qXfer spu read}
36550 Read contents of an @code{spufs} file on the target system. The
36551 annex specifies which file to read; it must be of the form
36552 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36553 in the target process, and @var{name} identifes the @code{spufs} file
36554 in that context to be accessed.
36556 This packet is not probed by default; the remote stub must request it,
36557 by supplying an appropriate @samp{qSupported} response
36558 (@pxref{qSupported}).
36560 @item qXfer:threads:read::@var{offset},@var{length}
36561 @anchor{qXfer threads read}
36562 Access the list of threads on target. @xref{Thread List Format}. The
36563 annex part of the generic @samp{qXfer} packet must be empty
36564 (@pxref{qXfer read}).
36566 This packet is not probed by default; the remote stub must request it,
36567 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36569 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36570 @anchor{qXfer traceframe info read}
36572 Return a description of the current traceframe's contents.
36573 @xref{Traceframe Info Format}. The annex part of the generic
36574 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36576 This packet is not probed by default; the remote stub must request it,
36577 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36579 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36580 @anchor{qXfer unwind info block}
36582 Return the unwind information block for @var{pc}. This packet is used
36583 on OpenVMS/ia64 to ask the kernel unwind information.
36585 This packet is not probed by default.
36587 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36588 @anchor{qXfer fdpic loadmap read}
36589 Read contents of @code{loadmap}s on the target system. The
36590 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36591 executable @code{loadmap} or interpreter @code{loadmap} to read.
36593 This packet is not probed by default; the remote stub must request it,
36594 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36596 @item qXfer:osdata:read::@var{offset},@var{length}
36597 @anchor{qXfer osdata read}
36598 Access the target's @dfn{operating system information}.
36599 @xref{Operating System Information}.
36606 Data @var{data} (@pxref{Binary Data}) has been read from the
36607 target. There may be more data at a higher address (although
36608 it is permitted to return @samp{m} even for the last valid
36609 block of data, as long as at least one byte of data was read).
36610 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36614 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36615 There is no more data to be read. It is possible for @var{data} to
36616 have fewer bytes than the @var{length} in the request.
36619 The @var{offset} in the request is at the end of the data.
36620 There is no more data to be read.
36623 The request was malformed, or @var{annex} was invalid.
36626 The offset was invalid, or there was an error encountered reading the data.
36627 The @var{nn} part is a hex-encoded @code{errno} value.
36630 An empty reply indicates the @var{object} string was not recognized by
36631 the stub, or that the object does not support reading.
36634 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36635 @cindex write data into object, remote request
36636 @anchor{qXfer write}
36637 Write uninterpreted bytes into the target's special data area
36638 identified by the keyword @var{object}, starting at @var{offset} bytes
36639 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36640 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36641 is specific to @var{object}; it can supply additional details about what data
36644 Here are the specific requests of this form defined so far. All
36645 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36646 formats, listed below.
36649 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36650 @anchor{qXfer siginfo write}
36651 Write @var{data} to the extra signal information on the target system.
36652 The annex part of the generic @samp{qXfer} packet must be
36653 empty (@pxref{qXfer write}).
36655 This packet is not probed by default; the remote stub must request it,
36656 by supplying an appropriate @samp{qSupported} response
36657 (@pxref{qSupported}).
36659 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36660 @anchor{qXfer spu write}
36661 Write @var{data} to an @code{spufs} file on the target system. The
36662 annex specifies which file to write; it must be of the form
36663 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36664 in the target process, and @var{name} identifes the @code{spufs} file
36665 in that context to be accessed.
36667 This packet is not probed by default; the remote stub must request it,
36668 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36674 @var{nn} (hex encoded) is the number of bytes written.
36675 This may be fewer bytes than supplied in the request.
36678 The request was malformed, or @var{annex} was invalid.
36681 The offset was invalid, or there was an error encountered writing the data.
36682 The @var{nn} part is a hex-encoded @code{errno} value.
36685 An empty reply indicates the @var{object} string was not
36686 recognized by the stub, or that the object does not support writing.
36689 @item qXfer:@var{object}:@var{operation}:@dots{}
36690 Requests of this form may be added in the future. When a stub does
36691 not recognize the @var{object} keyword, or its support for
36692 @var{object} does not recognize the @var{operation} keyword, the stub
36693 must respond with an empty packet.
36695 @item qAttached:@var{pid}
36696 @cindex query attached, remote request
36697 @cindex @samp{qAttached} packet
36698 Return an indication of whether the remote server attached to an
36699 existing process or created a new process. When the multiprocess
36700 protocol extensions are supported (@pxref{multiprocess extensions}),
36701 @var{pid} is an integer in hexadecimal format identifying the target
36702 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36703 the query packet will be simplified as @samp{qAttached}.
36705 This query is used, for example, to know whether the remote process
36706 should be detached or killed when a @value{GDBN} session is ended with
36707 the @code{quit} command.
36712 The remote server attached to an existing process.
36714 The remote server created a new process.
36716 A badly formed request or an error was encountered.
36720 Enable branch tracing for the current thread using bts tracing.
36725 Branch tracing has been enabled.
36727 A badly formed request or an error was encountered.
36731 Disable branch tracing for the current thread.
36736 Branch tracing has been disabled.
36738 A badly formed request or an error was encountered.
36741 @item Qbtrace-conf:bts:size=@var{value}
36742 Set the requested ring buffer size for new threads that use the
36743 btrace recording method in bts format.
36748 The ring buffer size has been set.
36750 A badly formed request or an error was encountered.
36755 @node Architecture-Specific Protocol Details
36756 @section Architecture-Specific Protocol Details
36758 This section describes how the remote protocol is applied to specific
36759 target architectures. Also see @ref{Standard Target Features}, for
36760 details of XML target descriptions for each architecture.
36763 * ARM-Specific Protocol Details::
36764 * MIPS-Specific Protocol Details::
36767 @node ARM-Specific Protocol Details
36768 @subsection @acronym{ARM}-specific Protocol Details
36771 * ARM Breakpoint Kinds::
36774 @node ARM Breakpoint Kinds
36775 @subsubsection @acronym{ARM} Breakpoint Kinds
36776 @cindex breakpoint kinds, @acronym{ARM}
36778 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36783 16-bit Thumb mode breakpoint.
36786 32-bit Thumb mode (Thumb-2) breakpoint.
36789 32-bit @acronym{ARM} mode breakpoint.
36793 @node MIPS-Specific Protocol Details
36794 @subsection @acronym{MIPS}-specific Protocol Details
36797 * MIPS Register packet Format::
36798 * MIPS Breakpoint Kinds::
36801 @node MIPS Register packet Format
36802 @subsubsection @acronym{MIPS} Register Packet Format
36803 @cindex register packet format, @acronym{MIPS}
36805 The following @code{g}/@code{G} packets have previously been defined.
36806 In the below, some thirty-two bit registers are transferred as
36807 sixty-four bits. Those registers should be zero/sign extended (which?)
36808 to fill the space allocated. Register bytes are transferred in target
36809 byte order. The two nibbles within a register byte are transferred
36810 most-significant -- least-significant.
36815 All registers are transferred as thirty-two bit quantities in the order:
36816 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36817 registers; fsr; fir; fp.
36820 All registers are transferred as sixty-four bit quantities (including
36821 thirty-two bit registers such as @code{sr}). The ordering is the same
36826 @node MIPS Breakpoint Kinds
36827 @subsubsection @acronym{MIPS} Breakpoint Kinds
36828 @cindex breakpoint kinds, @acronym{MIPS}
36830 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36835 16-bit @acronym{MIPS16} mode breakpoint.
36838 16-bit @acronym{microMIPS} mode breakpoint.
36841 32-bit standard @acronym{MIPS} mode breakpoint.
36844 32-bit @acronym{microMIPS} mode breakpoint.
36848 @node Tracepoint Packets
36849 @section Tracepoint Packets
36850 @cindex tracepoint packets
36851 @cindex packets, tracepoint
36853 Here we describe the packets @value{GDBN} uses to implement
36854 tracepoints (@pxref{Tracepoints}).
36858 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36859 @cindex @samp{QTDP} packet
36860 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36861 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36862 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36863 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36864 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36865 the number of bytes that the target should copy elsewhere to make room
36866 for the tracepoint. If an @samp{X} is present, it introduces a
36867 tracepoint condition, which consists of a hexadecimal length, followed
36868 by a comma and hex-encoded bytes, in a manner similar to action
36869 encodings as described below. If the trailing @samp{-} is present,
36870 further @samp{QTDP} packets will follow to specify this tracepoint's
36876 The packet was understood and carried out.
36878 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36880 The packet was not recognized.
36883 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36884 Define actions to be taken when a tracepoint is hit. The @var{n} and
36885 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36886 this tracepoint. This packet may only be sent immediately after
36887 another @samp{QTDP} packet that ended with a @samp{-}. If the
36888 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36889 specifying more actions for this tracepoint.
36891 In the series of action packets for a given tracepoint, at most one
36892 can have an @samp{S} before its first @var{action}. If such a packet
36893 is sent, it and the following packets define ``while-stepping''
36894 actions. Any prior packets define ordinary actions --- that is, those
36895 taken when the tracepoint is first hit. If no action packet has an
36896 @samp{S}, then all the packets in the series specify ordinary
36897 tracepoint actions.
36899 The @samp{@var{action}@dots{}} portion of the packet is a series of
36900 actions, concatenated without separators. Each action has one of the
36906 Collect the registers whose bits are set in @var{mask},
36907 a hexadecimal number whose @var{i}'th bit is set if register number
36908 @var{i} should be collected. (The least significant bit is numbered
36909 zero.) Note that @var{mask} may be any number of digits long; it may
36910 not fit in a 32-bit word.
36912 @item M @var{basereg},@var{offset},@var{len}
36913 Collect @var{len} bytes of memory starting at the address in register
36914 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36915 @samp{-1}, then the range has a fixed address: @var{offset} is the
36916 address of the lowest byte to collect. The @var{basereg},
36917 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36918 values (the @samp{-1} value for @var{basereg} is a special case).
36920 @item X @var{len},@var{expr}
36921 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36922 it directs. The agent expression @var{expr} is as described in
36923 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36924 two-digit hex number in the packet; @var{len} is the number of bytes
36925 in the expression (and thus one-half the number of hex digits in the
36930 Any number of actions may be packed together in a single @samp{QTDP}
36931 packet, as long as the packet does not exceed the maximum packet
36932 length (400 bytes, for many stubs). There may be only one @samp{R}
36933 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36934 actions. Any registers referred to by @samp{M} and @samp{X} actions
36935 must be collected by a preceding @samp{R} action. (The
36936 ``while-stepping'' actions are treated as if they were attached to a
36937 separate tracepoint, as far as these restrictions are concerned.)
36942 The packet was understood and carried out.
36944 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36946 The packet was not recognized.
36949 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36950 @cindex @samp{QTDPsrc} packet
36951 Specify a source string of tracepoint @var{n} at address @var{addr}.
36952 This is useful to get accurate reproduction of the tracepoints
36953 originally downloaded at the beginning of the trace run. The @var{type}
36954 is the name of the tracepoint part, such as @samp{cond} for the
36955 tracepoint's conditional expression (see below for a list of types), while
36956 @var{bytes} is the string, encoded in hexadecimal.
36958 @var{start} is the offset of the @var{bytes} within the overall source
36959 string, while @var{slen} is the total length of the source string.
36960 This is intended for handling source strings that are longer than will
36961 fit in a single packet.
36962 @c Add detailed example when this info is moved into a dedicated
36963 @c tracepoint descriptions section.
36965 The available string types are @samp{at} for the location,
36966 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36967 @value{GDBN} sends a separate packet for each command in the action
36968 list, in the same order in which the commands are stored in the list.
36970 The target does not need to do anything with source strings except
36971 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36974 Although this packet is optional, and @value{GDBN} will only send it
36975 if the target replies with @samp{TracepointSource} @xref{General
36976 Query Packets}, it makes both disconnected tracing and trace files
36977 much easier to use. Otherwise the user must be careful that the
36978 tracepoints in effect while looking at trace frames are identical to
36979 the ones in effect during the trace run; even a small discrepancy
36980 could cause @samp{tdump} not to work, or a particular trace frame not
36983 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
36984 @cindex define trace state variable, remote request
36985 @cindex @samp{QTDV} packet
36986 Create a new trace state variable, number @var{n}, with an initial
36987 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36988 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36989 the option of not using this packet for initial values of zero; the
36990 target should simply create the trace state variables as they are
36991 mentioned in expressions. The value @var{builtin} should be 1 (one)
36992 if the trace state variable is builtin and 0 (zero) if it is not builtin.
36993 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
36994 @samp{qTsV} packet had it set. The contents of @var{name} is the
36995 hex-encoded name (without the leading @samp{$}) of the trace state
36998 @item QTFrame:@var{n}
36999 @cindex @samp{QTFrame} packet
37000 Select the @var{n}'th tracepoint frame from the buffer, and use the
37001 register and memory contents recorded there to answer subsequent
37002 request packets from @value{GDBN}.
37004 A successful reply from the stub indicates that the stub has found the
37005 requested frame. The response is a series of parts, concatenated
37006 without separators, describing the frame we selected. Each part has
37007 one of the following forms:
37011 The selected frame is number @var{n} in the trace frame buffer;
37012 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37013 was no frame matching the criteria in the request packet.
37016 The selected trace frame records a hit of tracepoint number @var{t};
37017 @var{t} is a hexadecimal number.
37021 @item QTFrame:pc:@var{addr}
37022 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37023 currently selected frame whose PC is @var{addr};
37024 @var{addr} is a hexadecimal number.
37026 @item QTFrame:tdp:@var{t}
37027 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37028 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37029 is a hexadecimal number.
37031 @item QTFrame:range:@var{start}:@var{end}
37032 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37033 currently selected frame whose PC is between @var{start} (inclusive)
37034 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37037 @item QTFrame:outside:@var{start}:@var{end}
37038 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37039 frame @emph{outside} the given range of addresses (exclusive).
37042 @cindex @samp{qTMinFTPILen} packet
37043 This packet requests the minimum length of instruction at which a fast
37044 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37045 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37046 it depends on the target system being able to create trampolines in
37047 the first 64K of memory, which might or might not be possible for that
37048 system. So the reply to this packet will be 4 if it is able to
37055 The minimum instruction length is currently unknown.
37057 The minimum instruction length is @var{length}, where @var{length}
37058 is a hexadecimal number greater or equal to 1. A reply
37059 of 1 means that a fast tracepoint may be placed on any instruction
37060 regardless of size.
37062 An error has occurred.
37064 An empty reply indicates that the request is not supported by the stub.
37068 @cindex @samp{QTStart} packet
37069 Begin the tracepoint experiment. Begin collecting data from
37070 tracepoint hits in the trace frame buffer. This packet supports the
37071 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37072 instruction reply packet}).
37075 @cindex @samp{QTStop} packet
37076 End the tracepoint experiment. Stop collecting trace frames.
37078 @item QTEnable:@var{n}:@var{addr}
37080 @cindex @samp{QTEnable} packet
37081 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37082 experiment. If the tracepoint was previously disabled, then collection
37083 of data from it will resume.
37085 @item QTDisable:@var{n}:@var{addr}
37087 @cindex @samp{QTDisable} packet
37088 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37089 experiment. No more data will be collected from the tracepoint unless
37090 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37093 @cindex @samp{QTinit} packet
37094 Clear the table of tracepoints, and empty the trace frame buffer.
37096 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37097 @cindex @samp{QTro} packet
37098 Establish the given ranges of memory as ``transparent''. The stub
37099 will answer requests for these ranges from memory's current contents,
37100 if they were not collected as part of the tracepoint hit.
37102 @value{GDBN} uses this to mark read-only regions of memory, like those
37103 containing program code. Since these areas never change, they should
37104 still have the same contents they did when the tracepoint was hit, so
37105 there's no reason for the stub to refuse to provide their contents.
37107 @item QTDisconnected:@var{value}
37108 @cindex @samp{QTDisconnected} packet
37109 Set the choice to what to do with the tracing run when @value{GDBN}
37110 disconnects from the target. A @var{value} of 1 directs the target to
37111 continue the tracing run, while 0 tells the target to stop tracing if
37112 @value{GDBN} is no longer in the picture.
37115 @cindex @samp{qTStatus} packet
37116 Ask the stub if there is a trace experiment running right now.
37118 The reply has the form:
37122 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37123 @var{running} is a single digit @code{1} if the trace is presently
37124 running, or @code{0} if not. It is followed by semicolon-separated
37125 optional fields that an agent may use to report additional status.
37129 If the trace is not running, the agent may report any of several
37130 explanations as one of the optional fields:
37135 No trace has been run yet.
37137 @item tstop[:@var{text}]:0
37138 The trace was stopped by a user-originated stop command. The optional
37139 @var{text} field is a user-supplied string supplied as part of the
37140 stop command (for instance, an explanation of why the trace was
37141 stopped manually). It is hex-encoded.
37144 The trace stopped because the trace buffer filled up.
37146 @item tdisconnected:0
37147 The trace stopped because @value{GDBN} disconnected from the target.
37149 @item tpasscount:@var{tpnum}
37150 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37152 @item terror:@var{text}:@var{tpnum}
37153 The trace stopped because tracepoint @var{tpnum} had an error. The
37154 string @var{text} is available to describe the nature of the error
37155 (for instance, a divide by zero in the condition expression); it
37159 The trace stopped for some other reason.
37163 Additional optional fields supply statistical and other information.
37164 Although not required, they are extremely useful for users monitoring
37165 the progress of a trace run. If a trace has stopped, and these
37166 numbers are reported, they must reflect the state of the just-stopped
37171 @item tframes:@var{n}
37172 The number of trace frames in the buffer.
37174 @item tcreated:@var{n}
37175 The total number of trace frames created during the run. This may
37176 be larger than the trace frame count, if the buffer is circular.
37178 @item tsize:@var{n}
37179 The total size of the trace buffer, in bytes.
37181 @item tfree:@var{n}
37182 The number of bytes still unused in the buffer.
37184 @item circular:@var{n}
37185 The value of the circular trace buffer flag. @code{1} means that the
37186 trace buffer is circular and old trace frames will be discarded if
37187 necessary to make room, @code{0} means that the trace buffer is linear
37190 @item disconn:@var{n}
37191 The value of the disconnected tracing flag. @code{1} means that
37192 tracing will continue after @value{GDBN} disconnects, @code{0} means
37193 that the trace run will stop.
37197 @item qTP:@var{tp}:@var{addr}
37198 @cindex tracepoint status, remote request
37199 @cindex @samp{qTP} packet
37200 Ask the stub for the current state of tracepoint number @var{tp} at
37201 address @var{addr}.
37205 @item V@var{hits}:@var{usage}
37206 The tracepoint has been hit @var{hits} times so far during the trace
37207 run, and accounts for @var{usage} in the trace buffer. Note that
37208 @code{while-stepping} steps are not counted as separate hits, but the
37209 steps' space consumption is added into the usage number.
37213 @item qTV:@var{var}
37214 @cindex trace state variable value, remote request
37215 @cindex @samp{qTV} packet
37216 Ask the stub for the value of the trace state variable number @var{var}.
37221 The value of the variable is @var{value}. This will be the current
37222 value of the variable if the user is examining a running target, or a
37223 saved value if the variable was collected in the trace frame that the
37224 user is looking at. Note that multiple requests may result in
37225 different reply values, such as when requesting values while the
37226 program is running.
37229 The value of the variable is unknown. This would occur, for example,
37230 if the user is examining a trace frame in which the requested variable
37235 @cindex @samp{qTfP} packet
37237 @cindex @samp{qTsP} packet
37238 These packets request data about tracepoints that are being used by
37239 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37240 of data, and multiple @code{qTsP} to get additional pieces. Replies
37241 to these packets generally take the form of the @code{QTDP} packets
37242 that define tracepoints. (FIXME add detailed syntax)
37245 @cindex @samp{qTfV} packet
37247 @cindex @samp{qTsV} packet
37248 These packets request data about trace state variables that are on the
37249 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37250 and multiple @code{qTsV} to get additional variables. Replies to
37251 these packets follow the syntax of the @code{QTDV} packets that define
37252 trace state variables.
37258 @cindex @samp{qTfSTM} packet
37259 @cindex @samp{qTsSTM} packet
37260 These packets request data about static tracepoint markers that exist
37261 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37262 first piece of data, and multiple @code{qTsSTM} to get additional
37263 pieces. Replies to these packets take the following form:
37267 @item m @var{address}:@var{id}:@var{extra}
37269 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37270 a comma-separated list of markers
37272 (lower case letter @samp{L}) denotes end of list.
37274 An error occurred. The error number @var{nn} is given as hex digits.
37276 An empty reply indicates that the request is not supported by the
37280 The @var{address} is encoded in hex;
37281 @var{id} and @var{extra} are strings encoded in hex.
37283 In response to each query, the target will reply with a list of one or
37284 more markers, separated by commas. @value{GDBN} will respond to each
37285 reply with a request for more markers (using the @samp{qs} form of the
37286 query), until the target responds with @samp{l} (lower-case ell, for
37289 @item qTSTMat:@var{address}
37291 @cindex @samp{qTSTMat} packet
37292 This packets requests data about static tracepoint markers in the
37293 target program at @var{address}. Replies to this packet follow the
37294 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37295 tracepoint markers.
37297 @item QTSave:@var{filename}
37298 @cindex @samp{QTSave} packet
37299 This packet directs the target to save trace data to the file name
37300 @var{filename} in the target's filesystem. The @var{filename} is encoded
37301 as a hex string; the interpretation of the file name (relative vs
37302 absolute, wild cards, etc) is up to the target.
37304 @item qTBuffer:@var{offset},@var{len}
37305 @cindex @samp{qTBuffer} packet
37306 Return up to @var{len} bytes of the current contents of trace buffer,
37307 starting at @var{offset}. The trace buffer is treated as if it were
37308 a contiguous collection of traceframes, as per the trace file format.
37309 The reply consists as many hex-encoded bytes as the target can deliver
37310 in a packet; it is not an error to return fewer than were asked for.
37311 A reply consisting of just @code{l} indicates that no bytes are
37314 @item QTBuffer:circular:@var{value}
37315 This packet directs the target to use a circular trace buffer if
37316 @var{value} is 1, or a linear buffer if the value is 0.
37318 @item QTBuffer:size:@var{size}
37319 @anchor{QTBuffer-size}
37320 @cindex @samp{QTBuffer size} packet
37321 This packet directs the target to make the trace buffer be of size
37322 @var{size} if possible. A value of @code{-1} tells the target to
37323 use whatever size it prefers.
37325 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37326 @cindex @samp{QTNotes} packet
37327 This packet adds optional textual notes to the trace run. Allowable
37328 types include @code{user}, @code{notes}, and @code{tstop}, the
37329 @var{text} fields are arbitrary strings, hex-encoded.
37333 @subsection Relocate instruction reply packet
37334 When installing fast tracepoints in memory, the target may need to
37335 relocate the instruction currently at the tracepoint address to a
37336 different address in memory. For most instructions, a simple copy is
37337 enough, but, for example, call instructions that implicitly push the
37338 return address on the stack, and relative branches or other
37339 PC-relative instructions require offset adjustment, so that the effect
37340 of executing the instruction at a different address is the same as if
37341 it had executed in the original location.
37343 In response to several of the tracepoint packets, the target may also
37344 respond with a number of intermediate @samp{qRelocInsn} request
37345 packets before the final result packet, to have @value{GDBN} handle
37346 this relocation operation. If a packet supports this mechanism, its
37347 documentation will explicitly say so. See for example the above
37348 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37349 format of the request is:
37352 @item qRelocInsn:@var{from};@var{to}
37354 This requests @value{GDBN} to copy instruction at address @var{from}
37355 to address @var{to}, possibly adjusted so that executing the
37356 instruction at @var{to} has the same effect as executing it at
37357 @var{from}. @value{GDBN} writes the adjusted instruction to target
37358 memory starting at @var{to}.
37363 @item qRelocInsn:@var{adjusted_size}
37364 Informs the stub the relocation is complete. The @var{adjusted_size} is
37365 the length in bytes of resulting relocated instruction sequence.
37367 A badly formed request was detected, or an error was encountered while
37368 relocating the instruction.
37371 @node Host I/O Packets
37372 @section Host I/O Packets
37373 @cindex Host I/O, remote protocol
37374 @cindex file transfer, remote protocol
37376 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37377 operations on the far side of a remote link. For example, Host I/O is
37378 used to upload and download files to a remote target with its own
37379 filesystem. Host I/O uses the same constant values and data structure
37380 layout as the target-initiated File-I/O protocol. However, the
37381 Host I/O packets are structured differently. The target-initiated
37382 protocol relies on target memory to store parameters and buffers.
37383 Host I/O requests are initiated by @value{GDBN}, and the
37384 target's memory is not involved. @xref{File-I/O Remote Protocol
37385 Extension}, for more details on the target-initiated protocol.
37387 The Host I/O request packets all encode a single operation along with
37388 its arguments. They have this format:
37392 @item vFile:@var{operation}: @var{parameter}@dots{}
37393 @var{operation} is the name of the particular request; the target
37394 should compare the entire packet name up to the second colon when checking
37395 for a supported operation. The format of @var{parameter} depends on
37396 the operation. Numbers are always passed in hexadecimal. Negative
37397 numbers have an explicit minus sign (i.e.@: two's complement is not
37398 used). Strings (e.g.@: filenames) are encoded as a series of
37399 hexadecimal bytes. The last argument to a system call may be a
37400 buffer of escaped binary data (@pxref{Binary Data}).
37404 The valid responses to Host I/O packets are:
37408 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37409 @var{result} is the integer value returned by this operation, usually
37410 non-negative for success and -1 for errors. If an error has occured,
37411 @var{errno} will be included in the result specifying a
37412 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37413 operations which return data, @var{attachment} supplies the data as a
37414 binary buffer. Binary buffers in response packets are escaped in the
37415 normal way (@pxref{Binary Data}). See the individual packet
37416 documentation for the interpretation of @var{result} and
37420 An empty response indicates that this operation is not recognized.
37424 These are the supported Host I/O operations:
37427 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37428 Open a file at @var{filename} and return a file descriptor for it, or
37429 return -1 if an error occurs. The @var{filename} is a string,
37430 @var{flags} is an integer indicating a mask of open flags
37431 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37432 of mode bits to use if the file is created (@pxref{mode_t Values}).
37433 @xref{open}, for details of the open flags and mode values.
37435 @item vFile:close: @var{fd}
37436 Close the open file corresponding to @var{fd} and return 0, or
37437 -1 if an error occurs.
37439 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37440 Read data from the open file corresponding to @var{fd}. Up to
37441 @var{count} bytes will be read from the file, starting at @var{offset}
37442 relative to the start of the file. The target may read fewer bytes;
37443 common reasons include packet size limits and an end-of-file
37444 condition. The number of bytes read is returned. Zero should only be
37445 returned for a successful read at the end of the file, or if
37446 @var{count} was zero.
37448 The data read should be returned as a binary attachment on success.
37449 If zero bytes were read, the response should include an empty binary
37450 attachment (i.e.@: a trailing semicolon). The return value is the
37451 number of target bytes read; the binary attachment may be longer if
37452 some characters were escaped.
37454 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37455 Write @var{data} (a binary buffer) to the open file corresponding
37456 to @var{fd}. Start the write at @var{offset} from the start of the
37457 file. Unlike many @code{write} system calls, there is no
37458 separate @var{count} argument; the length of @var{data} in the
37459 packet is used. @samp{vFile:write} returns the number of bytes written,
37460 which may be shorter than the length of @var{data}, or -1 if an
37463 @item vFile:fstat: @var{fd}
37464 Get information about the open file corresponding to @var{fd}.
37465 On success the information is returned as a binary attachment
37466 and the return value is the size of this attachment in bytes.
37467 If an error occurs the return value is -1. The format of the
37468 returned binary attachment is as described in @ref{struct stat}.
37470 @item vFile:unlink: @var{filename}
37471 Delete the file at @var{filename} on the target. Return 0,
37472 or -1 if an error occurs. The @var{filename} is a string.
37474 @item vFile:readlink: @var{filename}
37475 Read value of symbolic link @var{filename} on the target. Return
37476 the number of bytes read, or -1 if an error occurs.
37478 The data read should be returned as a binary attachment on success.
37479 If zero bytes were read, the response should include an empty binary
37480 attachment (i.e.@: a trailing semicolon). The return value is the
37481 number of target bytes read; the binary attachment may be longer if
37482 some characters were escaped.
37487 @section Interrupts
37488 @cindex interrupts (remote protocol)
37490 When a program on the remote target is running, @value{GDBN} may
37491 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37492 a @code{BREAK} followed by @code{g},
37493 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37495 The precise meaning of @code{BREAK} is defined by the transport
37496 mechanism and may, in fact, be undefined. @value{GDBN} does not
37497 currently define a @code{BREAK} mechanism for any of the network
37498 interfaces except for TCP, in which case @value{GDBN} sends the
37499 @code{telnet} BREAK sequence.
37501 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37502 transport mechanisms. It is represented by sending the single byte
37503 @code{0x03} without any of the usual packet overhead described in
37504 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37505 transmitted as part of a packet, it is considered to be packet data
37506 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37507 (@pxref{X packet}), used for binary downloads, may include an unescaped
37508 @code{0x03} as part of its packet.
37510 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37511 When Linux kernel receives this sequence from serial port,
37512 it stops execution and connects to gdb.
37514 Stubs are not required to recognize these interrupt mechanisms and the
37515 precise meaning associated with receipt of the interrupt is
37516 implementation defined. If the target supports debugging of multiple
37517 threads and/or processes, it should attempt to interrupt all
37518 currently-executing threads and processes.
37519 If the stub is successful at interrupting the
37520 running program, it should send one of the stop
37521 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37522 of successfully stopping the program in all-stop mode, and a stop reply
37523 for each stopped thread in non-stop mode.
37524 Interrupts received while the
37525 program is stopped are discarded.
37527 @node Notification Packets
37528 @section Notification Packets
37529 @cindex notification packets
37530 @cindex packets, notification
37532 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37533 packets that require no acknowledgment. Both the GDB and the stub
37534 may send notifications (although the only notifications defined at
37535 present are sent by the stub). Notifications carry information
37536 without incurring the round-trip latency of an acknowledgment, and so
37537 are useful for low-impact communications where occasional packet loss
37540 A notification packet has the form @samp{% @var{data} #
37541 @var{checksum}}, where @var{data} is the content of the notification,
37542 and @var{checksum} is a checksum of @var{data}, computed and formatted
37543 as for ordinary @value{GDBN} packets. A notification's @var{data}
37544 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37545 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37546 to acknowledge the notification's receipt or to report its corruption.
37548 Every notification's @var{data} begins with a name, which contains no
37549 colon characters, followed by a colon character.
37551 Recipients should silently ignore corrupted notifications and
37552 notifications they do not understand. Recipients should restart
37553 timeout periods on receipt of a well-formed notification, whether or
37554 not they understand it.
37556 Senders should only send the notifications described here when this
37557 protocol description specifies that they are permitted. In the
37558 future, we may extend the protocol to permit existing notifications in
37559 new contexts; this rule helps older senders avoid confusing newer
37562 (Older versions of @value{GDBN} ignore bytes received until they see
37563 the @samp{$} byte that begins an ordinary packet, so new stubs may
37564 transmit notifications without fear of confusing older clients. There
37565 are no notifications defined for @value{GDBN} to send at the moment, but we
37566 assume that most older stubs would ignore them, as well.)
37568 Each notification is comprised of three parts:
37570 @item @var{name}:@var{event}
37571 The notification packet is sent by the side that initiates the
37572 exchange (currently, only the stub does that), with @var{event}
37573 carrying the specific information about the notification, and
37574 @var{name} specifying the name of the notification.
37576 The acknowledge sent by the other side, usually @value{GDBN}, to
37577 acknowledge the exchange and request the event.
37580 The purpose of an asynchronous notification mechanism is to report to
37581 @value{GDBN} that something interesting happened in the remote stub.
37583 The remote stub may send notification @var{name}:@var{event}
37584 at any time, but @value{GDBN} acknowledges the notification when
37585 appropriate. The notification event is pending before @value{GDBN}
37586 acknowledges. Only one notification at a time may be pending; if
37587 additional events occur before @value{GDBN} has acknowledged the
37588 previous notification, they must be queued by the stub for later
37589 synchronous transmission in response to @var{ack} packets from
37590 @value{GDBN}. Because the notification mechanism is unreliable,
37591 the stub is permitted to resend a notification if it believes
37592 @value{GDBN} may not have received it.
37594 Specifically, notifications may appear when @value{GDBN} is not
37595 otherwise reading input from the stub, or when @value{GDBN} is
37596 expecting to read a normal synchronous response or a
37597 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37598 Notification packets are distinct from any other communication from
37599 the stub so there is no ambiguity.
37601 After receiving a notification, @value{GDBN} shall acknowledge it by
37602 sending a @var{ack} packet as a regular, synchronous request to the
37603 stub. Such acknowledgment is not required to happen immediately, as
37604 @value{GDBN} is permitted to send other, unrelated packets to the
37605 stub first, which the stub should process normally.
37607 Upon receiving a @var{ack} packet, if the stub has other queued
37608 events to report to @value{GDBN}, it shall respond by sending a
37609 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37610 packet to solicit further responses; again, it is permitted to send
37611 other, unrelated packets as well which the stub should process
37614 If the stub receives a @var{ack} packet and there are no additional
37615 @var{event} to report, the stub shall return an @samp{OK} response.
37616 At this point, @value{GDBN} has finished processing a notification
37617 and the stub has completed sending any queued events. @value{GDBN}
37618 won't accept any new notifications until the final @samp{OK} is
37619 received . If further notification events occur, the stub shall send
37620 a new notification, @value{GDBN} shall accept the notification, and
37621 the process shall be repeated.
37623 The process of asynchronous notification can be illustrated by the
37626 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37629 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37631 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37636 The following notifications are defined:
37637 @multitable @columnfractions 0.12 0.12 0.38 0.38
37646 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37647 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37648 for information on how these notifications are acknowledged by
37650 @tab Report an asynchronous stop event in non-stop mode.
37654 @node Remote Non-Stop
37655 @section Remote Protocol Support for Non-Stop Mode
37657 @value{GDBN}'s remote protocol supports non-stop debugging of
37658 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37659 supports non-stop mode, it should report that to @value{GDBN} by including
37660 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37662 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37663 establishing a new connection with the stub. Entering non-stop mode
37664 does not alter the state of any currently-running threads, but targets
37665 must stop all threads in any already-attached processes when entering
37666 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37667 probe the target state after a mode change.
37669 In non-stop mode, when an attached process encounters an event that
37670 would otherwise be reported with a stop reply, it uses the
37671 asynchronous notification mechanism (@pxref{Notification Packets}) to
37672 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37673 in all processes are stopped when a stop reply is sent, in non-stop
37674 mode only the thread reporting the stop event is stopped. That is,
37675 when reporting a @samp{S} or @samp{T} response to indicate completion
37676 of a step operation, hitting a breakpoint, or a fault, only the
37677 affected thread is stopped; any other still-running threads continue
37678 to run. When reporting a @samp{W} or @samp{X} response, all running
37679 threads belonging to other attached processes continue to run.
37681 In non-stop mode, the target shall respond to the @samp{?} packet as
37682 follows. First, any incomplete stop reply notification/@samp{vStopped}
37683 sequence in progress is abandoned. The target must begin a new
37684 sequence reporting stop events for all stopped threads, whether or not
37685 it has previously reported those events to @value{GDBN}. The first
37686 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37687 subsequent stop replies are sent as responses to @samp{vStopped} packets
37688 using the mechanism described above. The target must not send
37689 asynchronous stop reply notifications until the sequence is complete.
37690 If all threads are running when the target receives the @samp{?} packet,
37691 or if the target is not attached to any process, it shall respond
37694 If the stub supports non-stop mode, it should also support the
37695 @samp{swbreak} stop reason if software breakpoints are supported, and
37696 the @samp{hwbreak} stop reason if hardware breakpoints are supported
37697 (@pxref{swbreak stop reason}). This is because given the asynchronous
37698 nature of non-stop mode, between the time a thread hits a breakpoint
37699 and the time the event is finally processed by @value{GDBN}, the
37700 breakpoint may have already been removed from the target. Due to
37701 this, @value{GDBN} needs to be able to tell whether a trap stop was
37702 caused by a delayed breakpoint event, which should be ignored, as
37703 opposed to a random trap signal, which should be reported to the user.
37704 Note the @samp{swbreak} feature implies that the target is responsible
37705 for adjusting the PC when a software breakpoint triggers, if
37706 necessary, such as on the x86 architecture.
37708 @node Packet Acknowledgment
37709 @section Packet Acknowledgment
37711 @cindex acknowledgment, for @value{GDBN} remote
37712 @cindex packet acknowledgment, for @value{GDBN} remote
37713 By default, when either the host or the target machine receives a packet,
37714 the first response expected is an acknowledgment: either @samp{+} (to indicate
37715 the package was received correctly) or @samp{-} (to request retransmission).
37716 This mechanism allows the @value{GDBN} remote protocol to operate over
37717 unreliable transport mechanisms, such as a serial line.
37719 In cases where the transport mechanism is itself reliable (such as a pipe or
37720 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37721 It may be desirable to disable them in that case to reduce communication
37722 overhead, or for other reasons. This can be accomplished by means of the
37723 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37725 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37726 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37727 and response format still includes the normal checksum, as described in
37728 @ref{Overview}, but the checksum may be ignored by the receiver.
37730 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37731 no-acknowledgment mode, it should report that to @value{GDBN}
37732 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37733 @pxref{qSupported}.
37734 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37735 disabled via the @code{set remote noack-packet off} command
37736 (@pxref{Remote Configuration}),
37737 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37738 Only then may the stub actually turn off packet acknowledgments.
37739 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37740 response, which can be safely ignored by the stub.
37742 Note that @code{set remote noack-packet} command only affects negotiation
37743 between @value{GDBN} and the stub when subsequent connections are made;
37744 it does not affect the protocol acknowledgment state for any current
37746 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37747 new connection is established,
37748 there is also no protocol request to re-enable the acknowledgments
37749 for the current connection, once disabled.
37754 Example sequence of a target being re-started. Notice how the restart
37755 does not get any direct output:
37760 @emph{target restarts}
37763 <- @code{T001:1234123412341234}
37767 Example sequence of a target being stepped by a single instruction:
37770 -> @code{G1445@dots{}}
37775 <- @code{T001:1234123412341234}
37779 <- @code{1455@dots{}}
37783 @node File-I/O Remote Protocol Extension
37784 @section File-I/O Remote Protocol Extension
37785 @cindex File-I/O remote protocol extension
37788 * File-I/O Overview::
37789 * Protocol Basics::
37790 * The F Request Packet::
37791 * The F Reply Packet::
37792 * The Ctrl-C Message::
37794 * List of Supported Calls::
37795 * Protocol-specific Representation of Datatypes::
37797 * File-I/O Examples::
37800 @node File-I/O Overview
37801 @subsection File-I/O Overview
37802 @cindex file-i/o overview
37804 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37805 target to use the host's file system and console I/O to perform various
37806 system calls. System calls on the target system are translated into a
37807 remote protocol packet to the host system, which then performs the needed
37808 actions and returns a response packet to the target system.
37809 This simulates file system operations even on targets that lack file systems.
37811 The protocol is defined to be independent of both the host and target systems.
37812 It uses its own internal representation of datatypes and values. Both
37813 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37814 translating the system-dependent value representations into the internal
37815 protocol representations when data is transmitted.
37817 The communication is synchronous. A system call is possible only when
37818 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37819 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37820 the target is stopped to allow deterministic access to the target's
37821 memory. Therefore File-I/O is not interruptible by target signals. On
37822 the other hand, it is possible to interrupt File-I/O by a user interrupt
37823 (@samp{Ctrl-C}) within @value{GDBN}.
37825 The target's request to perform a host system call does not finish
37826 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37827 after finishing the system call, the target returns to continuing the
37828 previous activity (continue, step). No additional continue or step
37829 request from @value{GDBN} is required.
37832 (@value{GDBP}) continue
37833 <- target requests 'system call X'
37834 target is stopped, @value{GDBN} executes system call
37835 -> @value{GDBN} returns result
37836 ... target continues, @value{GDBN} returns to wait for the target
37837 <- target hits breakpoint and sends a Txx packet
37840 The protocol only supports I/O on the console and to regular files on
37841 the host file system. Character or block special devices, pipes,
37842 named pipes, sockets or any other communication method on the host
37843 system are not supported by this protocol.
37845 File I/O is not supported in non-stop mode.
37847 @node Protocol Basics
37848 @subsection Protocol Basics
37849 @cindex protocol basics, file-i/o
37851 The File-I/O protocol uses the @code{F} packet as the request as well
37852 as reply packet. Since a File-I/O system call can only occur when
37853 @value{GDBN} is waiting for a response from the continuing or stepping target,
37854 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37855 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37856 This @code{F} packet contains all information needed to allow @value{GDBN}
37857 to call the appropriate host system call:
37861 A unique identifier for the requested system call.
37864 All parameters to the system call. Pointers are given as addresses
37865 in the target memory address space. Pointers to strings are given as
37866 pointer/length pair. Numerical values are given as they are.
37867 Numerical control flags are given in a protocol-specific representation.
37871 At this point, @value{GDBN} has to perform the following actions.
37875 If the parameters include pointer values to data needed as input to a
37876 system call, @value{GDBN} requests this data from the target with a
37877 standard @code{m} packet request. This additional communication has to be
37878 expected by the target implementation and is handled as any other @code{m}
37882 @value{GDBN} translates all value from protocol representation to host
37883 representation as needed. Datatypes are coerced into the host types.
37886 @value{GDBN} calls the system call.
37889 It then coerces datatypes back to protocol representation.
37892 If the system call is expected to return data in buffer space specified
37893 by pointer parameters to the call, the data is transmitted to the
37894 target using a @code{M} or @code{X} packet. This packet has to be expected
37895 by the target implementation and is handled as any other @code{M} or @code{X}
37900 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37901 necessary information for the target to continue. This at least contains
37908 @code{errno}, if has been changed by the system call.
37915 After having done the needed type and value coercion, the target continues
37916 the latest continue or step action.
37918 @node The F Request Packet
37919 @subsection The @code{F} Request Packet
37920 @cindex file-i/o request packet
37921 @cindex @code{F} request packet
37923 The @code{F} request packet has the following format:
37926 @item F@var{call-id},@var{parameter@dots{}}
37928 @var{call-id} is the identifier to indicate the host system call to be called.
37929 This is just the name of the function.
37931 @var{parameter@dots{}} are the parameters to the system call.
37932 Parameters are hexadecimal integer values, either the actual values in case
37933 of scalar datatypes, pointers to target buffer space in case of compound
37934 datatypes and unspecified memory areas, or pointer/length pairs in case
37935 of string parameters. These are appended to the @var{call-id} as a
37936 comma-delimited list. All values are transmitted in ASCII
37937 string representation, pointer/length pairs separated by a slash.
37943 @node The F Reply Packet
37944 @subsection The @code{F} Reply Packet
37945 @cindex file-i/o reply packet
37946 @cindex @code{F} reply packet
37948 The @code{F} reply packet has the following format:
37952 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37954 @var{retcode} is the return code of the system call as hexadecimal value.
37956 @var{errno} is the @code{errno} set by the call, in protocol-specific
37958 This parameter can be omitted if the call was successful.
37960 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37961 case, @var{errno} must be sent as well, even if the call was successful.
37962 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37969 or, if the call was interrupted before the host call has been performed:
37976 assuming 4 is the protocol-specific representation of @code{EINTR}.
37981 @node The Ctrl-C Message
37982 @subsection The @samp{Ctrl-C} Message
37983 @cindex ctrl-c message, in file-i/o protocol
37985 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37986 reply packet (@pxref{The F Reply Packet}),
37987 the target should behave as if it had
37988 gotten a break message. The meaning for the target is ``system call
37989 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37990 (as with a break message) and return to @value{GDBN} with a @code{T02}
37993 It's important for the target to know in which
37994 state the system call was interrupted. There are two possible cases:
37998 The system call hasn't been performed on the host yet.
38001 The system call on the host has been finished.
38005 These two states can be distinguished by the target by the value of the
38006 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38007 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38008 on POSIX systems. In any other case, the target may presume that the
38009 system call has been finished --- successfully or not --- and should behave
38010 as if the break message arrived right after the system call.
38012 @value{GDBN} must behave reliably. If the system call has not been called
38013 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38014 @code{errno} in the packet. If the system call on the host has been finished
38015 before the user requests a break, the full action must be finished by
38016 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38017 The @code{F} packet may only be sent when either nothing has happened
38018 or the full action has been completed.
38021 @subsection Console I/O
38022 @cindex console i/o as part of file-i/o
38024 By default and if not explicitly closed by the target system, the file
38025 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38026 on the @value{GDBN} console is handled as any other file output operation
38027 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38028 by @value{GDBN} so that after the target read request from file descriptor
38029 0 all following typing is buffered until either one of the following
38034 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38036 system call is treated as finished.
38039 The user presses @key{RET}. This is treated as end of input with a trailing
38043 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38044 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38048 If the user has typed more characters than fit in the buffer given to
38049 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38050 either another @code{read(0, @dots{})} is requested by the target, or debugging
38051 is stopped at the user's request.
38054 @node List of Supported Calls
38055 @subsection List of Supported Calls
38056 @cindex list of supported file-i/o calls
38073 @unnumberedsubsubsec open
38074 @cindex open, file-i/o system call
38079 int open(const char *pathname, int flags);
38080 int open(const char *pathname, int flags, mode_t mode);
38084 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38087 @var{flags} is the bitwise @code{OR} of the following values:
38091 If the file does not exist it will be created. The host
38092 rules apply as far as file ownership and time stamps
38096 When used with @code{O_CREAT}, if the file already exists it is
38097 an error and open() fails.
38100 If the file already exists and the open mode allows
38101 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38102 truncated to zero length.
38105 The file is opened in append mode.
38108 The file is opened for reading only.
38111 The file is opened for writing only.
38114 The file is opened for reading and writing.
38118 Other bits are silently ignored.
38122 @var{mode} is the bitwise @code{OR} of the following values:
38126 User has read permission.
38129 User has write permission.
38132 Group has read permission.
38135 Group has write permission.
38138 Others have read permission.
38141 Others have write permission.
38145 Other bits are silently ignored.
38148 @item Return value:
38149 @code{open} returns the new file descriptor or -1 if an error
38156 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38159 @var{pathname} refers to a directory.
38162 The requested access is not allowed.
38165 @var{pathname} was too long.
38168 A directory component in @var{pathname} does not exist.
38171 @var{pathname} refers to a device, pipe, named pipe or socket.
38174 @var{pathname} refers to a file on a read-only filesystem and
38175 write access was requested.
38178 @var{pathname} is an invalid pointer value.
38181 No space on device to create the file.
38184 The process already has the maximum number of files open.
38187 The limit on the total number of files open on the system
38191 The call was interrupted by the user.
38197 @unnumberedsubsubsec close
38198 @cindex close, file-i/o system call
38207 @samp{Fclose,@var{fd}}
38209 @item Return value:
38210 @code{close} returns zero on success, or -1 if an error occurred.
38216 @var{fd} isn't a valid open file descriptor.
38219 The call was interrupted by the user.
38225 @unnumberedsubsubsec read
38226 @cindex read, file-i/o system call
38231 int read(int fd, void *buf, unsigned int count);
38235 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38237 @item Return value:
38238 On success, the number of bytes read is returned.
38239 Zero indicates end of file. If count is zero, read
38240 returns zero as well. On error, -1 is returned.
38246 @var{fd} is not a valid file descriptor or is not open for
38250 @var{bufptr} is an invalid pointer value.
38253 The call was interrupted by the user.
38259 @unnumberedsubsubsec write
38260 @cindex write, file-i/o system call
38265 int write(int fd, const void *buf, unsigned int count);
38269 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38271 @item Return value:
38272 On success, the number of bytes written are returned.
38273 Zero indicates nothing was written. On error, -1
38280 @var{fd} is not a valid file descriptor or is not open for
38284 @var{bufptr} is an invalid pointer value.
38287 An attempt was made to write a file that exceeds the
38288 host-specific maximum file size allowed.
38291 No space on device to write the data.
38294 The call was interrupted by the user.
38300 @unnumberedsubsubsec lseek
38301 @cindex lseek, file-i/o system call
38306 long lseek (int fd, long offset, int flag);
38310 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38312 @var{flag} is one of:
38316 The offset is set to @var{offset} bytes.
38319 The offset is set to its current location plus @var{offset}
38323 The offset is set to the size of the file plus @var{offset}
38327 @item Return value:
38328 On success, the resulting unsigned offset in bytes from
38329 the beginning of the file is returned. Otherwise, a
38330 value of -1 is returned.
38336 @var{fd} is not a valid open file descriptor.
38339 @var{fd} is associated with the @value{GDBN} console.
38342 @var{flag} is not a proper value.
38345 The call was interrupted by the user.
38351 @unnumberedsubsubsec rename
38352 @cindex rename, file-i/o system call
38357 int rename(const char *oldpath, const char *newpath);
38361 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38363 @item Return value:
38364 On success, zero is returned. On error, -1 is returned.
38370 @var{newpath} is an existing directory, but @var{oldpath} is not a
38374 @var{newpath} is a non-empty directory.
38377 @var{oldpath} or @var{newpath} is a directory that is in use by some
38381 An attempt was made to make a directory a subdirectory
38385 A component used as a directory in @var{oldpath} or new
38386 path is not a directory. Or @var{oldpath} is a directory
38387 and @var{newpath} exists but is not a directory.
38390 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38393 No access to the file or the path of the file.
38397 @var{oldpath} or @var{newpath} was too long.
38400 A directory component in @var{oldpath} or @var{newpath} does not exist.
38403 The file is on a read-only filesystem.
38406 The device containing the file has no room for the new
38410 The call was interrupted by the user.
38416 @unnumberedsubsubsec unlink
38417 @cindex unlink, file-i/o system call
38422 int unlink(const char *pathname);
38426 @samp{Funlink,@var{pathnameptr}/@var{len}}
38428 @item Return value:
38429 On success, zero is returned. On error, -1 is returned.
38435 No access to the file or the path of the file.
38438 The system does not allow unlinking of directories.
38441 The file @var{pathname} cannot be unlinked because it's
38442 being used by another process.
38445 @var{pathnameptr} is an invalid pointer value.
38448 @var{pathname} was too long.
38451 A directory component in @var{pathname} does not exist.
38454 A component of the path is not a directory.
38457 The file is on a read-only filesystem.
38460 The call was interrupted by the user.
38466 @unnumberedsubsubsec stat/fstat
38467 @cindex fstat, file-i/o system call
38468 @cindex stat, file-i/o system call
38473 int stat(const char *pathname, struct stat *buf);
38474 int fstat(int fd, struct stat *buf);
38478 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38479 @samp{Ffstat,@var{fd},@var{bufptr}}
38481 @item Return value:
38482 On success, zero is returned. On error, -1 is returned.
38488 @var{fd} is not a valid open file.
38491 A directory component in @var{pathname} does not exist or the
38492 path is an empty string.
38495 A component of the path is not a directory.
38498 @var{pathnameptr} is an invalid pointer value.
38501 No access to the file or the path of the file.
38504 @var{pathname} was too long.
38507 The call was interrupted by the user.
38513 @unnumberedsubsubsec gettimeofday
38514 @cindex gettimeofday, file-i/o system call
38519 int gettimeofday(struct timeval *tv, void *tz);
38523 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38525 @item Return value:
38526 On success, 0 is returned, -1 otherwise.
38532 @var{tz} is a non-NULL pointer.
38535 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38541 @unnumberedsubsubsec isatty
38542 @cindex isatty, file-i/o system call
38547 int isatty(int fd);
38551 @samp{Fisatty,@var{fd}}
38553 @item Return value:
38554 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38560 The call was interrupted by the user.
38565 Note that the @code{isatty} call is treated as a special case: it returns
38566 1 to the target if the file descriptor is attached
38567 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38568 would require implementing @code{ioctl} and would be more complex than
38573 @unnumberedsubsubsec system
38574 @cindex system, file-i/o system call
38579 int system(const char *command);
38583 @samp{Fsystem,@var{commandptr}/@var{len}}
38585 @item Return value:
38586 If @var{len} is zero, the return value indicates whether a shell is
38587 available. A zero return value indicates a shell is not available.
38588 For non-zero @var{len}, the value returned is -1 on error and the
38589 return status of the command otherwise. Only the exit status of the
38590 command is returned, which is extracted from the host's @code{system}
38591 return value by calling @code{WEXITSTATUS(retval)}. In case
38592 @file{/bin/sh} could not be executed, 127 is returned.
38598 The call was interrupted by the user.
38603 @value{GDBN} takes over the full task of calling the necessary host calls
38604 to perform the @code{system} call. The return value of @code{system} on
38605 the host is simplified before it's returned
38606 to the target. Any termination signal information from the child process
38607 is discarded, and the return value consists
38608 entirely of the exit status of the called command.
38610 Due to security concerns, the @code{system} call is by default refused
38611 by @value{GDBN}. The user has to allow this call explicitly with the
38612 @code{set remote system-call-allowed 1} command.
38615 @item set remote system-call-allowed
38616 @kindex set remote system-call-allowed
38617 Control whether to allow the @code{system} calls in the File I/O
38618 protocol for the remote target. The default is zero (disabled).
38620 @item show remote system-call-allowed
38621 @kindex show remote system-call-allowed
38622 Show whether the @code{system} calls are allowed in the File I/O
38626 @node Protocol-specific Representation of Datatypes
38627 @subsection Protocol-specific Representation of Datatypes
38628 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38631 * Integral Datatypes::
38633 * Memory Transfer::
38638 @node Integral Datatypes
38639 @unnumberedsubsubsec Integral Datatypes
38640 @cindex integral datatypes, in file-i/o protocol
38642 The integral datatypes used in the system calls are @code{int},
38643 @code{unsigned int}, @code{long}, @code{unsigned long},
38644 @code{mode_t}, and @code{time_t}.
38646 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38647 implemented as 32 bit values in this protocol.
38649 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38651 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38652 in @file{limits.h}) to allow range checking on host and target.
38654 @code{time_t} datatypes are defined as seconds since the Epoch.
38656 All integral datatypes transferred as part of a memory read or write of a
38657 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38660 @node Pointer Values
38661 @unnumberedsubsubsec Pointer Values
38662 @cindex pointer values, in file-i/o protocol
38664 Pointers to target data are transmitted as they are. An exception
38665 is made for pointers to buffers for which the length isn't
38666 transmitted as part of the function call, namely strings. Strings
38667 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38674 which is a pointer to data of length 18 bytes at position 0x1aaf.
38675 The length is defined as the full string length in bytes, including
38676 the trailing null byte. For example, the string @code{"hello world"}
38677 at address 0x123456 is transmitted as
38683 @node Memory Transfer
38684 @unnumberedsubsubsec Memory Transfer
38685 @cindex memory transfer, in file-i/o protocol
38687 Structured data which is transferred using a memory read or write (for
38688 example, a @code{struct stat}) is expected to be in a protocol-specific format
38689 with all scalar multibyte datatypes being big endian. Translation to
38690 this representation needs to be done both by the target before the @code{F}
38691 packet is sent, and by @value{GDBN} before
38692 it transfers memory to the target. Transferred pointers to structured
38693 data should point to the already-coerced data at any time.
38697 @unnumberedsubsubsec struct stat
38698 @cindex struct stat, in file-i/o protocol
38700 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38701 is defined as follows:
38705 unsigned int st_dev; /* device */
38706 unsigned int st_ino; /* inode */
38707 mode_t st_mode; /* protection */
38708 unsigned int st_nlink; /* number of hard links */
38709 unsigned int st_uid; /* user ID of owner */
38710 unsigned int st_gid; /* group ID of owner */
38711 unsigned int st_rdev; /* device type (if inode device) */
38712 unsigned long st_size; /* total size, in bytes */
38713 unsigned long st_blksize; /* blocksize for filesystem I/O */
38714 unsigned long st_blocks; /* number of blocks allocated */
38715 time_t st_atime; /* time of last access */
38716 time_t st_mtime; /* time of last modification */
38717 time_t st_ctime; /* time of last change */
38721 The integral datatypes conform to the definitions given in the
38722 appropriate section (see @ref{Integral Datatypes}, for details) so this
38723 structure is of size 64 bytes.
38725 The values of several fields have a restricted meaning and/or
38731 A value of 0 represents a file, 1 the console.
38734 No valid meaning for the target. Transmitted unchanged.
38737 Valid mode bits are described in @ref{Constants}. Any other
38738 bits have currently no meaning for the target.
38743 No valid meaning for the target. Transmitted unchanged.
38748 These values have a host and file system dependent
38749 accuracy. Especially on Windows hosts, the file system may not
38750 support exact timing values.
38753 The target gets a @code{struct stat} of the above representation and is
38754 responsible for coercing it to the target representation before
38757 Note that due to size differences between the host, target, and protocol
38758 representations of @code{struct stat} members, these members could eventually
38759 get truncated on the target.
38761 @node struct timeval
38762 @unnumberedsubsubsec struct timeval
38763 @cindex struct timeval, in file-i/o protocol
38765 The buffer of type @code{struct timeval} used by the File-I/O protocol
38766 is defined as follows:
38770 time_t tv_sec; /* second */
38771 long tv_usec; /* microsecond */
38775 The integral datatypes conform to the definitions given in the
38776 appropriate section (see @ref{Integral Datatypes}, for details) so this
38777 structure is of size 8 bytes.
38780 @subsection Constants
38781 @cindex constants, in file-i/o protocol
38783 The following values are used for the constants inside of the
38784 protocol. @value{GDBN} and target are responsible for translating these
38785 values before and after the call as needed.
38796 @unnumberedsubsubsec Open Flags
38797 @cindex open flags, in file-i/o protocol
38799 All values are given in hexadecimal representation.
38811 @node mode_t Values
38812 @unnumberedsubsubsec mode_t Values
38813 @cindex mode_t values, in file-i/o protocol
38815 All values are given in octal representation.
38832 @unnumberedsubsubsec Errno Values
38833 @cindex errno values, in file-i/o protocol
38835 All values are given in decimal representation.
38860 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38861 any error value not in the list of supported error numbers.
38864 @unnumberedsubsubsec Lseek Flags
38865 @cindex lseek flags, in file-i/o protocol
38874 @unnumberedsubsubsec Limits
38875 @cindex limits, in file-i/o protocol
38877 All values are given in decimal representation.
38880 INT_MIN -2147483648
38882 UINT_MAX 4294967295
38883 LONG_MIN -9223372036854775808
38884 LONG_MAX 9223372036854775807
38885 ULONG_MAX 18446744073709551615
38888 @node File-I/O Examples
38889 @subsection File-I/O Examples
38890 @cindex file-i/o examples
38892 Example sequence of a write call, file descriptor 3, buffer is at target
38893 address 0x1234, 6 bytes should be written:
38896 <- @code{Fwrite,3,1234,6}
38897 @emph{request memory read from target}
38900 @emph{return "6 bytes written"}
38904 Example sequence of a read call, file descriptor 3, buffer is at target
38905 address 0x1234, 6 bytes should be read:
38908 <- @code{Fread,3,1234,6}
38909 @emph{request memory write to target}
38910 -> @code{X1234,6:XXXXXX}
38911 @emph{return "6 bytes read"}
38915 Example sequence of a read call, call fails on the host due to invalid
38916 file descriptor (@code{EBADF}):
38919 <- @code{Fread,3,1234,6}
38923 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38927 <- @code{Fread,3,1234,6}
38932 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38936 <- @code{Fread,3,1234,6}
38937 -> @code{X1234,6:XXXXXX}
38941 @node Library List Format
38942 @section Library List Format
38943 @cindex library list format, remote protocol
38945 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38946 same process as your application to manage libraries. In this case,
38947 @value{GDBN} can use the loader's symbol table and normal memory
38948 operations to maintain a list of shared libraries. On other
38949 platforms, the operating system manages loaded libraries.
38950 @value{GDBN} can not retrieve the list of currently loaded libraries
38951 through memory operations, so it uses the @samp{qXfer:libraries:read}
38952 packet (@pxref{qXfer library list read}) instead. The remote stub
38953 queries the target's operating system and reports which libraries
38956 The @samp{qXfer:libraries:read} packet returns an XML document which
38957 lists loaded libraries and their offsets. Each library has an
38958 associated name and one or more segment or section base addresses,
38959 which report where the library was loaded in memory.
38961 For the common case of libraries that are fully linked binaries, the
38962 library should have a list of segments. If the target supports
38963 dynamic linking of a relocatable object file, its library XML element
38964 should instead include a list of allocated sections. The segment or
38965 section bases are start addresses, not relocation offsets; they do not
38966 depend on the library's link-time base addresses.
38968 @value{GDBN} must be linked with the Expat library to support XML
38969 library lists. @xref{Expat}.
38971 A simple memory map, with one loaded library relocated by a single
38972 offset, looks like this:
38976 <library name="/lib/libc.so.6">
38977 <segment address="0x10000000"/>
38982 Another simple memory map, with one loaded library with three
38983 allocated sections (.text, .data, .bss), looks like this:
38987 <library name="sharedlib.o">
38988 <section address="0x10000000"/>
38989 <section address="0x20000000"/>
38990 <section address="0x30000000"/>
38995 The format of a library list is described by this DTD:
38998 <!-- library-list: Root element with versioning -->
38999 <!ELEMENT library-list (library)*>
39000 <!ATTLIST library-list version CDATA #FIXED "1.0">
39001 <!ELEMENT library (segment*, section*)>
39002 <!ATTLIST library name CDATA #REQUIRED>
39003 <!ELEMENT segment EMPTY>
39004 <!ATTLIST segment address CDATA #REQUIRED>
39005 <!ELEMENT section EMPTY>
39006 <!ATTLIST section address CDATA #REQUIRED>
39009 In addition, segments and section descriptors cannot be mixed within a
39010 single library element, and you must supply at least one segment or
39011 section for each library.
39013 @node Library List Format for SVR4 Targets
39014 @section Library List Format for SVR4 Targets
39015 @cindex library list format, remote protocol
39017 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39018 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39019 shared libraries. Still a special library list provided by this packet is
39020 more efficient for the @value{GDBN} remote protocol.
39022 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39023 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39024 target, the following parameters are reported:
39028 @code{name}, the absolute file name from the @code{l_name} field of
39029 @code{struct link_map}.
39031 @code{lm} with address of @code{struct link_map} used for TLS
39032 (Thread Local Storage) access.
39034 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39035 @code{struct link_map}. For prelinked libraries this is not an absolute
39036 memory address. It is a displacement of absolute memory address against
39037 address the file was prelinked to during the library load.
39039 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39042 Additionally the single @code{main-lm} attribute specifies address of
39043 @code{struct link_map} used for the main executable. This parameter is used
39044 for TLS access and its presence is optional.
39046 @value{GDBN} must be linked with the Expat library to support XML
39047 SVR4 library lists. @xref{Expat}.
39049 A simple memory map, with two loaded libraries (which do not use prelink),
39053 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39054 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39056 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39058 </library-list-svr>
39061 The format of an SVR4 library list is described by this DTD:
39064 <!-- library-list-svr4: Root element with versioning -->
39065 <!ELEMENT library-list-svr4 (library)*>
39066 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39067 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39068 <!ELEMENT library EMPTY>
39069 <!ATTLIST library name CDATA #REQUIRED>
39070 <!ATTLIST library lm CDATA #REQUIRED>
39071 <!ATTLIST library l_addr CDATA #REQUIRED>
39072 <!ATTLIST library l_ld CDATA #REQUIRED>
39075 @node Memory Map Format
39076 @section Memory Map Format
39077 @cindex memory map format
39079 To be able to write into flash memory, @value{GDBN} needs to obtain a
39080 memory map from the target. This section describes the format of the
39083 The memory map is obtained using the @samp{qXfer:memory-map:read}
39084 (@pxref{qXfer memory map read}) packet and is an XML document that
39085 lists memory regions.
39087 @value{GDBN} must be linked with the Expat library to support XML
39088 memory maps. @xref{Expat}.
39090 The top-level structure of the document is shown below:
39093 <?xml version="1.0"?>
39094 <!DOCTYPE memory-map
39095 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39096 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39102 Each region can be either:
39107 A region of RAM starting at @var{addr} and extending for @var{length}
39111 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39116 A region of read-only memory:
39119 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39124 A region of flash memory, with erasure blocks @var{blocksize}
39128 <memory type="flash" start="@var{addr}" length="@var{length}">
39129 <property name="blocksize">@var{blocksize}</property>
39135 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39136 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39137 packets to write to addresses in such ranges.
39139 The formal DTD for memory map format is given below:
39142 <!-- ................................................... -->
39143 <!-- Memory Map XML DTD ................................ -->
39144 <!-- File: memory-map.dtd .............................. -->
39145 <!-- .................................... .............. -->
39146 <!-- memory-map.dtd -->
39147 <!-- memory-map: Root element with versioning -->
39148 <!ELEMENT memory-map (memory | property)>
39149 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39150 <!ELEMENT memory (property)>
39151 <!-- memory: Specifies a memory region,
39152 and its type, or device. -->
39153 <!ATTLIST memory type CDATA #REQUIRED
39154 start CDATA #REQUIRED
39155 length CDATA #REQUIRED
39156 device CDATA #IMPLIED>
39157 <!-- property: Generic attribute tag -->
39158 <!ELEMENT property (#PCDATA | property)*>
39159 <!ATTLIST property name CDATA #REQUIRED>
39162 @node Thread List Format
39163 @section Thread List Format
39164 @cindex thread list format
39166 To efficiently update the list of threads and their attributes,
39167 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39168 (@pxref{qXfer threads read}) and obtains the XML document with
39169 the following structure:
39172 <?xml version="1.0"?>
39174 <thread id="id" core="0">
39175 ... description ...
39180 Each @samp{thread} element must have the @samp{id} attribute that
39181 identifies the thread (@pxref{thread-id syntax}). The
39182 @samp{core} attribute, if present, specifies which processor core
39183 the thread was last executing on. The content of the of @samp{thread}
39184 element is interpreted as human-readable auxilliary information.
39186 @node Traceframe Info Format
39187 @section Traceframe Info Format
39188 @cindex traceframe info format
39190 To be able to know which objects in the inferior can be examined when
39191 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39192 memory ranges, registers and trace state variables that have been
39193 collected in a traceframe.
39195 This list is obtained using the @samp{qXfer:traceframe-info:read}
39196 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39198 @value{GDBN} must be linked with the Expat library to support XML
39199 traceframe info discovery. @xref{Expat}.
39201 The top-level structure of the document is shown below:
39204 <?xml version="1.0"?>
39205 <!DOCTYPE traceframe-info
39206 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39207 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39213 Each traceframe block can be either:
39218 A region of collected memory starting at @var{addr} and extending for
39219 @var{length} bytes from there:
39222 <memory start="@var{addr}" length="@var{length}"/>
39226 A block indicating trace state variable numbered @var{number} has been
39230 <tvar id="@var{number}"/>
39235 The formal DTD for the traceframe info format is given below:
39238 <!ELEMENT traceframe-info (memory | tvar)* >
39239 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39241 <!ELEMENT memory EMPTY>
39242 <!ATTLIST memory start CDATA #REQUIRED
39243 length CDATA #REQUIRED>
39245 <!ATTLIST tvar id CDATA #REQUIRED>
39248 @node Branch Trace Format
39249 @section Branch Trace Format
39250 @cindex branch trace format
39252 In order to display the branch trace of an inferior thread,
39253 @value{GDBN} needs to obtain the list of branches. This list is
39254 represented as list of sequential code blocks that are connected via
39255 branches. The code in each block has been executed sequentially.
39257 This list is obtained using the @samp{qXfer:btrace:read}
39258 (@pxref{qXfer btrace read}) packet and is an XML document.
39260 @value{GDBN} must be linked with the Expat library to support XML
39261 traceframe info discovery. @xref{Expat}.
39263 The top-level structure of the document is shown below:
39266 <?xml version="1.0"?>
39268 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39269 "http://sourceware.org/gdb/gdb-btrace.dtd">
39278 A block of sequentially executed instructions starting at @var{begin}
39279 and ending at @var{end}:
39282 <block begin="@var{begin}" end="@var{end}"/>
39287 The formal DTD for the branch trace format is given below:
39290 <!ELEMENT btrace (block)* >
39291 <!ATTLIST btrace version CDATA #FIXED "1.0">
39293 <!ELEMENT block EMPTY>
39294 <!ATTLIST block begin CDATA #REQUIRED
39295 end CDATA #REQUIRED>
39298 @node Branch Trace Configuration Format
39299 @section Branch Trace Configuration Format
39300 @cindex branch trace configuration format
39302 For each inferior thread, @value{GDBN} can obtain the branch trace
39303 configuration using the @samp{qXfer:btrace-conf:read}
39304 (@pxref{qXfer btrace-conf read}) packet.
39306 The configuration describes the branch trace format and configuration
39307 settings for that format. The following information is described:
39311 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39314 The size of the @acronym{BTS} ring buffer in bytes.
39318 @value{GDBN} must be linked with the Expat library to support XML
39319 branch trace configuration discovery. @xref{Expat}.
39321 The formal DTD for the branch trace configuration format is given below:
39324 <!ELEMENT btrace-conf (bts?)>
39325 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39327 <!ELEMENT bts EMPTY>
39328 <!ATTLIST bts size CDATA #IMPLIED>
39331 @include agentexpr.texi
39333 @node Target Descriptions
39334 @appendix Target Descriptions
39335 @cindex target descriptions
39337 One of the challenges of using @value{GDBN} to debug embedded systems
39338 is that there are so many minor variants of each processor
39339 architecture in use. It is common practice for vendors to start with
39340 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39341 and then make changes to adapt it to a particular market niche. Some
39342 architectures have hundreds of variants, available from dozens of
39343 vendors. This leads to a number of problems:
39347 With so many different customized processors, it is difficult for
39348 the @value{GDBN} maintainers to keep up with the changes.
39350 Since individual variants may have short lifetimes or limited
39351 audiences, it may not be worthwhile to carry information about every
39352 variant in the @value{GDBN} source tree.
39354 When @value{GDBN} does support the architecture of the embedded system
39355 at hand, the task of finding the correct architecture name to give the
39356 @command{set architecture} command can be error-prone.
39359 To address these problems, the @value{GDBN} remote protocol allows a
39360 target system to not only identify itself to @value{GDBN}, but to
39361 actually describe its own features. This lets @value{GDBN} support
39362 processor variants it has never seen before --- to the extent that the
39363 descriptions are accurate, and that @value{GDBN} understands them.
39365 @value{GDBN} must be linked with the Expat library to support XML
39366 target descriptions. @xref{Expat}.
39369 * Retrieving Descriptions:: How descriptions are fetched from a target.
39370 * Target Description Format:: The contents of a target description.
39371 * Predefined Target Types:: Standard types available for target
39373 * Standard Target Features:: Features @value{GDBN} knows about.
39376 @node Retrieving Descriptions
39377 @section Retrieving Descriptions
39379 Target descriptions can be read from the target automatically, or
39380 specified by the user manually. The default behavior is to read the
39381 description from the target. @value{GDBN} retrieves it via the remote
39382 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39383 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39384 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39385 XML document, of the form described in @ref{Target Description
39388 Alternatively, you can specify a file to read for the target description.
39389 If a file is set, the target will not be queried. The commands to
39390 specify a file are:
39393 @cindex set tdesc filename
39394 @item set tdesc filename @var{path}
39395 Read the target description from @var{path}.
39397 @cindex unset tdesc filename
39398 @item unset tdesc filename
39399 Do not read the XML target description from a file. @value{GDBN}
39400 will use the description supplied by the current target.
39402 @cindex show tdesc filename
39403 @item show tdesc filename
39404 Show the filename to read for a target description, if any.
39408 @node Target Description Format
39409 @section Target Description Format
39410 @cindex target descriptions, XML format
39412 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39413 document which complies with the Document Type Definition provided in
39414 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39415 means you can use generally available tools like @command{xmllint} to
39416 check that your feature descriptions are well-formed and valid.
39417 However, to help people unfamiliar with XML write descriptions for
39418 their targets, we also describe the grammar here.
39420 Target descriptions can identify the architecture of the remote target
39421 and (for some architectures) provide information about custom register
39422 sets. They can also identify the OS ABI of the remote target.
39423 @value{GDBN} can use this information to autoconfigure for your
39424 target, or to warn you if you connect to an unsupported target.
39426 Here is a simple target description:
39429 <target version="1.0">
39430 <architecture>i386:x86-64</architecture>
39435 This minimal description only says that the target uses
39436 the x86-64 architecture.
39438 A target description has the following overall form, with [ ] marking
39439 optional elements and @dots{} marking repeatable elements. The elements
39440 are explained further below.
39443 <?xml version="1.0"?>
39444 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39445 <target version="1.0">
39446 @r{[}@var{architecture}@r{]}
39447 @r{[}@var{osabi}@r{]}
39448 @r{[}@var{compatible}@r{]}
39449 @r{[}@var{feature}@dots{}@r{]}
39454 The description is generally insensitive to whitespace and line
39455 breaks, under the usual common-sense rules. The XML version
39456 declaration and document type declaration can generally be omitted
39457 (@value{GDBN} does not require them), but specifying them may be
39458 useful for XML validation tools. The @samp{version} attribute for
39459 @samp{<target>} may also be omitted, but we recommend
39460 including it; if future versions of @value{GDBN} use an incompatible
39461 revision of @file{gdb-target.dtd}, they will detect and report
39462 the version mismatch.
39464 @subsection Inclusion
39465 @cindex target descriptions, inclusion
39468 @cindex <xi:include>
39471 It can sometimes be valuable to split a target description up into
39472 several different annexes, either for organizational purposes, or to
39473 share files between different possible target descriptions. You can
39474 divide a description into multiple files by replacing any element of
39475 the target description with an inclusion directive of the form:
39478 <xi:include href="@var{document}"/>
39482 When @value{GDBN} encounters an element of this form, it will retrieve
39483 the named XML @var{document}, and replace the inclusion directive with
39484 the contents of that document. If the current description was read
39485 using @samp{qXfer}, then so will be the included document;
39486 @var{document} will be interpreted as the name of an annex. If the
39487 current description was read from a file, @value{GDBN} will look for
39488 @var{document} as a file in the same directory where it found the
39489 original description.
39491 @subsection Architecture
39492 @cindex <architecture>
39494 An @samp{<architecture>} element has this form:
39497 <architecture>@var{arch}</architecture>
39500 @var{arch} is one of the architectures from the set accepted by
39501 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39504 @cindex @code{<osabi>}
39506 This optional field was introduced in @value{GDBN} version 7.0.
39507 Previous versions of @value{GDBN} ignore it.
39509 An @samp{<osabi>} element has this form:
39512 <osabi>@var{abi-name}</osabi>
39515 @var{abi-name} is an OS ABI name from the same selection accepted by
39516 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39518 @subsection Compatible Architecture
39519 @cindex @code{<compatible>}
39521 This optional field was introduced in @value{GDBN} version 7.0.
39522 Previous versions of @value{GDBN} ignore it.
39524 A @samp{<compatible>} element has this form:
39527 <compatible>@var{arch}</compatible>
39530 @var{arch} is one of the architectures from the set accepted by
39531 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39533 A @samp{<compatible>} element is used to specify that the target
39534 is able to run binaries in some other than the main target architecture
39535 given by the @samp{<architecture>} element. For example, on the
39536 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39537 or @code{powerpc:common64}, but the system is able to run binaries
39538 in the @code{spu} architecture as well. The way to describe this
39539 capability with @samp{<compatible>} is as follows:
39542 <architecture>powerpc:common</architecture>
39543 <compatible>spu</compatible>
39546 @subsection Features
39549 Each @samp{<feature>} describes some logical portion of the target
39550 system. Features are currently used to describe available CPU
39551 registers and the types of their contents. A @samp{<feature>} element
39555 <feature name="@var{name}">
39556 @r{[}@var{type}@dots{}@r{]}
39562 Each feature's name should be unique within the description. The name
39563 of a feature does not matter unless @value{GDBN} has some special
39564 knowledge of the contents of that feature; if it does, the feature
39565 should have its standard name. @xref{Standard Target Features}.
39569 Any register's value is a collection of bits which @value{GDBN} must
39570 interpret. The default interpretation is a two's complement integer,
39571 but other types can be requested by name in the register description.
39572 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39573 Target Types}), and the description can define additional composite types.
39575 Each type element must have an @samp{id} attribute, which gives
39576 a unique (within the containing @samp{<feature>}) name to the type.
39577 Types must be defined before they are used.
39580 Some targets offer vector registers, which can be treated as arrays
39581 of scalar elements. These types are written as @samp{<vector>} elements,
39582 specifying the array element type, @var{type}, and the number of elements,
39586 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39590 If a register's value is usefully viewed in multiple ways, define it
39591 with a union type containing the useful representations. The
39592 @samp{<union>} element contains one or more @samp{<field>} elements,
39593 each of which has a @var{name} and a @var{type}:
39596 <union id="@var{id}">
39597 <field name="@var{name}" type="@var{type}"/>
39603 If a register's value is composed from several separate values, define
39604 it with a structure type. There are two forms of the @samp{<struct>}
39605 element; a @samp{<struct>} element must either contain only bitfields
39606 or contain no bitfields. If the structure contains only bitfields,
39607 its total size in bytes must be specified, each bitfield must have an
39608 explicit start and end, and bitfields are automatically assigned an
39609 integer type. The field's @var{start} should be less than or
39610 equal to its @var{end}, and zero represents the least significant bit.
39613 <struct id="@var{id}" size="@var{size}">
39614 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39619 If the structure contains no bitfields, then each field has an
39620 explicit type, and no implicit padding is added.
39623 <struct id="@var{id}">
39624 <field name="@var{name}" type="@var{type}"/>
39630 If a register's value is a series of single-bit flags, define it with
39631 a flags type. The @samp{<flags>} element has an explicit @var{size}
39632 and contains one or more @samp{<field>} elements. Each field has a
39633 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39637 <flags id="@var{id}" size="@var{size}">
39638 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39643 @subsection Registers
39646 Each register is represented as an element with this form:
39649 <reg name="@var{name}"
39650 bitsize="@var{size}"
39651 @r{[}regnum="@var{num}"@r{]}
39652 @r{[}save-restore="@var{save-restore}"@r{]}
39653 @r{[}type="@var{type}"@r{]}
39654 @r{[}group="@var{group}"@r{]}/>
39658 The components are as follows:
39663 The register's name; it must be unique within the target description.
39666 The register's size, in bits.
39669 The register's number. If omitted, a register's number is one greater
39670 than that of the previous register (either in the current feature or in
39671 a preceding feature); the first register in the target description
39672 defaults to zero. This register number is used to read or write
39673 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39674 packets, and registers appear in the @code{g} and @code{G} packets
39675 in order of increasing register number.
39678 Whether the register should be preserved across inferior function
39679 calls; this must be either @code{yes} or @code{no}. The default is
39680 @code{yes}, which is appropriate for most registers except for
39681 some system control registers; this is not related to the target's
39685 The type of the register. It may be a predefined type, a type
39686 defined in the current feature, or one of the special types @code{int}
39687 and @code{float}. @code{int} is an integer type of the correct size
39688 for @var{bitsize}, and @code{float} is a floating point type (in the
39689 architecture's normal floating point format) of the correct size for
39690 @var{bitsize}. The default is @code{int}.
39693 The register group to which this register belongs. It must
39694 be either @code{general}, @code{float}, or @code{vector}. If no
39695 @var{group} is specified, @value{GDBN} will not display the register
39696 in @code{info registers}.
39700 @node Predefined Target Types
39701 @section Predefined Target Types
39702 @cindex target descriptions, predefined types
39704 Type definitions in the self-description can build up composite types
39705 from basic building blocks, but can not define fundamental types. Instead,
39706 standard identifiers are provided by @value{GDBN} for the fundamental
39707 types. The currently supported types are:
39716 Signed integer types holding the specified number of bits.
39723 Unsigned integer types holding the specified number of bits.
39727 Pointers to unspecified code and data. The program counter and
39728 any dedicated return address register may be marked as code
39729 pointers; printing a code pointer converts it into a symbolic
39730 address. The stack pointer and any dedicated address registers
39731 may be marked as data pointers.
39734 Single precision IEEE floating point.
39737 Double precision IEEE floating point.
39740 The 12-byte extended precision format used by ARM FPA registers.
39743 The 10-byte extended precision format used by x87 registers.
39746 32bit @sc{eflags} register used by x86.
39749 32bit @sc{mxcsr} register used by x86.
39753 @node Standard Target Features
39754 @section Standard Target Features
39755 @cindex target descriptions, standard features
39757 A target description must contain either no registers or all the
39758 target's registers. If the description contains no registers, then
39759 @value{GDBN} will assume a default register layout, selected based on
39760 the architecture. If the description contains any registers, the
39761 default layout will not be used; the standard registers must be
39762 described in the target description, in such a way that @value{GDBN}
39763 can recognize them.
39765 This is accomplished by giving specific names to feature elements
39766 which contain standard registers. @value{GDBN} will look for features
39767 with those names and verify that they contain the expected registers;
39768 if any known feature is missing required registers, or if any required
39769 feature is missing, @value{GDBN} will reject the target
39770 description. You can add additional registers to any of the
39771 standard features --- @value{GDBN} will display them just as if
39772 they were added to an unrecognized feature.
39774 This section lists the known features and their expected contents.
39775 Sample XML documents for these features are included in the
39776 @value{GDBN} source tree, in the directory @file{gdb/features}.
39778 Names recognized by @value{GDBN} should include the name of the
39779 company or organization which selected the name, and the overall
39780 architecture to which the feature applies; so e.g.@: the feature
39781 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39783 The names of registers are not case sensitive for the purpose
39784 of recognizing standard features, but @value{GDBN} will only display
39785 registers using the capitalization used in the description.
39788 * AArch64 Features::
39791 * MicroBlaze Features::
39794 * Nios II Features::
39795 * PowerPC Features::
39796 * S/390 and System z Features::
39801 @node AArch64 Features
39802 @subsection AArch64 Features
39803 @cindex target descriptions, AArch64 features
39805 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39806 targets. It should contain registers @samp{x0} through @samp{x30},
39807 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39809 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39810 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39814 @subsection ARM Features
39815 @cindex target descriptions, ARM features
39817 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39819 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39820 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39822 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39823 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39824 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39827 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39828 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39830 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39831 it should contain at least registers @samp{wR0} through @samp{wR15} and
39832 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39833 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39835 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39836 should contain at least registers @samp{d0} through @samp{d15}. If
39837 they are present, @samp{d16} through @samp{d31} should also be included.
39838 @value{GDBN} will synthesize the single-precision registers from
39839 halves of the double-precision registers.
39841 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39842 need to contain registers; it instructs @value{GDBN} to display the
39843 VFP double-precision registers as vectors and to synthesize the
39844 quad-precision registers from pairs of double-precision registers.
39845 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39846 be present and include 32 double-precision registers.
39848 @node i386 Features
39849 @subsection i386 Features
39850 @cindex target descriptions, i386 features
39852 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39853 targets. It should describe the following registers:
39857 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39859 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39861 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39862 @samp{fs}, @samp{gs}
39864 @samp{st0} through @samp{st7}
39866 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39867 @samp{foseg}, @samp{fooff} and @samp{fop}
39870 The register sets may be different, depending on the target.
39872 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39873 describe registers:
39877 @samp{xmm0} through @samp{xmm7} for i386
39879 @samp{xmm0} through @samp{xmm15} for amd64
39884 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39885 @samp{org.gnu.gdb.i386.sse} feature. It should
39886 describe the upper 128 bits of @sc{ymm} registers:
39890 @samp{ymm0h} through @samp{ymm7h} for i386
39892 @samp{ymm0h} through @samp{ymm15h} for amd64
39895 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39896 Memory Protection Extension (MPX). It should describe the following registers:
39900 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39902 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39905 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39906 describe a single register, @samp{orig_eax}.
39908 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39909 @samp{org.gnu.gdb.i386.avx} feature. It should
39910 describe additional @sc{xmm} registers:
39914 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39917 It should describe the upper 128 bits of additional @sc{ymm} registers:
39921 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39925 describe the upper 256 bits of @sc{zmm} registers:
39929 @samp{zmm0h} through @samp{zmm7h} for i386.
39931 @samp{zmm0h} through @samp{zmm15h} for amd64.
39935 describe the additional @sc{zmm} registers:
39939 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39942 @node MicroBlaze Features
39943 @subsection MicroBlaze Features
39944 @cindex target descriptions, MicroBlaze features
39946 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
39947 targets. It should contain registers @samp{r0} through @samp{r31},
39948 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
39949 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
39950 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
39952 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
39953 If present, it should contain registers @samp{rshr} and @samp{rslr}
39955 @node MIPS Features
39956 @subsection @acronym{MIPS} Features
39957 @cindex target descriptions, @acronym{MIPS} features
39959 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39960 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39961 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39964 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39965 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39966 registers. They may be 32-bit or 64-bit depending on the target.
39968 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39969 it may be optional in a future version of @value{GDBN}. It should
39970 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39971 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39973 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39974 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39975 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39976 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39978 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39979 contain a single register, @samp{restart}, which is used by the
39980 Linux kernel to control restartable syscalls.
39982 @node M68K Features
39983 @subsection M68K Features
39984 @cindex target descriptions, M68K features
39987 @item @samp{org.gnu.gdb.m68k.core}
39988 @itemx @samp{org.gnu.gdb.coldfire.core}
39989 @itemx @samp{org.gnu.gdb.fido.core}
39990 One of those features must be always present.
39991 The feature that is present determines which flavor of m68k is
39992 used. The feature that is present should contain registers
39993 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39994 @samp{sp}, @samp{ps} and @samp{pc}.
39996 @item @samp{org.gnu.gdb.coldfire.fp}
39997 This feature is optional. If present, it should contain registers
39998 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40002 @node Nios II Features
40003 @subsection Nios II Features
40004 @cindex target descriptions, Nios II features
40006 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40007 targets. It should contain the 32 core registers (@samp{zero},
40008 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40009 @samp{pc}, and the 16 control registers (@samp{status} through
40012 @node PowerPC Features
40013 @subsection PowerPC Features
40014 @cindex target descriptions, PowerPC features
40016 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40017 targets. It should contain registers @samp{r0} through @samp{r31},
40018 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40019 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40021 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40022 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40024 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40025 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40028 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40029 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40030 will combine these registers with the floating point registers
40031 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40032 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40033 through @samp{vs63}, the set of vector registers for POWER7.
40035 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40036 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40037 @samp{spefscr}. SPE targets should provide 32-bit registers in
40038 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40039 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40040 these to present registers @samp{ev0} through @samp{ev31} to the
40043 @node S/390 and System z Features
40044 @subsection S/390 and System z Features
40045 @cindex target descriptions, S/390 features
40046 @cindex target descriptions, System z features
40048 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40049 System z targets. It should contain the PSW and the 16 general
40050 registers. In particular, System z targets should provide the 64-bit
40051 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40052 S/390 targets should provide the 32-bit versions of these registers.
40053 A System z target that runs in 31-bit addressing mode should provide
40054 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40055 register's upper halves @samp{r0h} through @samp{r15h}, and their
40056 lower halves @samp{r0l} through @samp{r15l}.
40058 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40059 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40062 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40063 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40065 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40066 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40067 targets and 32-bit otherwise. In addition, the feature may contain
40068 the @samp{last_break} register, whose width depends on the addressing
40069 mode, as well as the @samp{system_call} register, which is always
40072 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40073 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40074 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40076 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40077 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40078 combined by @value{GDBN} with the floating point registers @samp{f0}
40079 through @samp{f15} to present the 128-bit wide vector registers
40080 @samp{v0} through @samp{v15}. In addition, this feature should
40081 contain the 128-bit wide vector registers @samp{v16} through
40084 @node TIC6x Features
40085 @subsection TMS320C6x Features
40086 @cindex target descriptions, TIC6x features
40087 @cindex target descriptions, TMS320C6x features
40088 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40089 targets. It should contain registers @samp{A0} through @samp{A15},
40090 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40092 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40093 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40094 through @samp{B31}.
40096 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40097 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40099 @node Operating System Information
40100 @appendix Operating System Information
40101 @cindex operating system information
40107 Users of @value{GDBN} often wish to obtain information about the state of
40108 the operating system running on the target---for example the list of
40109 processes, or the list of open files. This section describes the
40110 mechanism that makes it possible. This mechanism is similar to the
40111 target features mechanism (@pxref{Target Descriptions}), but focuses
40112 on a different aspect of target.
40114 Operating system information is retrived from the target via the
40115 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40116 read}). The object name in the request should be @samp{osdata}, and
40117 the @var{annex} identifies the data to be fetched.
40120 @appendixsection Process list
40121 @cindex operating system information, process list
40123 When requesting the process list, the @var{annex} field in the
40124 @samp{qXfer} request should be @samp{processes}. The returned data is
40125 an XML document. The formal syntax of this document is defined in
40126 @file{gdb/features/osdata.dtd}.
40128 An example document is:
40131 <?xml version="1.0"?>
40132 <!DOCTYPE target SYSTEM "osdata.dtd">
40133 <osdata type="processes">
40135 <column name="pid">1</column>
40136 <column name="user">root</column>
40137 <column name="command">/sbin/init</column>
40138 <column name="cores">1,2,3</column>
40143 Each item should include a column whose name is @samp{pid}. The value
40144 of that column should identify the process on the target. The
40145 @samp{user} and @samp{command} columns are optional, and will be
40146 displayed by @value{GDBN}. The @samp{cores} column, if present,
40147 should contain a comma-separated list of cores that this process
40148 is running on. Target may provide additional columns,
40149 which @value{GDBN} currently ignores.
40151 @node Trace File Format
40152 @appendix Trace File Format
40153 @cindex trace file format
40155 The trace file comes in three parts: a header, a textual description
40156 section, and a trace frame section with binary data.
40158 The header has the form @code{\x7fTRACE0\n}. The first byte is
40159 @code{0x7f} so as to indicate that the file contains binary data,
40160 while the @code{0} is a version number that may have different values
40163 The description section consists of multiple lines of @sc{ascii} text
40164 separated by newline characters (@code{0xa}). The lines may include a
40165 variety of optional descriptive or context-setting information, such
40166 as tracepoint definitions or register set size. @value{GDBN} will
40167 ignore any line that it does not recognize. An empty line marks the end
40170 @c FIXME add some specific types of data
40172 The trace frame section consists of a number of consecutive frames.
40173 Each frame begins with a two-byte tracepoint number, followed by a
40174 four-byte size giving the amount of data in the frame. The data in
40175 the frame consists of a number of blocks, each introduced by a
40176 character indicating its type (at least register, memory, and trace
40177 state variable). The data in this section is raw binary, not a
40178 hexadecimal or other encoding; its endianness matches the target's
40181 @c FIXME bi-arch may require endianness/arch info in description section
40184 @item R @var{bytes}
40185 Register block. The number and ordering of bytes matches that of a
40186 @code{g} packet in the remote protocol. Note that these are the
40187 actual bytes, in target order and @value{GDBN} register order, not a
40188 hexadecimal encoding.
40190 @item M @var{address} @var{length} @var{bytes}...
40191 Memory block. This is a contiguous block of memory, at the 8-byte
40192 address @var{address}, with a 2-byte length @var{length}, followed by
40193 @var{length} bytes.
40195 @item V @var{number} @var{value}
40196 Trace state variable block. This records the 8-byte signed value
40197 @var{value} of trace state variable numbered @var{number}.
40201 Future enhancements of the trace file format may include additional types
40204 @node Index Section Format
40205 @appendix @code{.gdb_index} section format
40206 @cindex .gdb_index section format
40207 @cindex index section format
40209 This section documents the index section that is created by @code{save
40210 gdb-index} (@pxref{Index Files}). The index section is
40211 DWARF-specific; some knowledge of DWARF is assumed in this
40214 The mapped index file format is designed to be directly
40215 @code{mmap}able on any architecture. In most cases, a datum is
40216 represented using a little-endian 32-bit integer value, called an
40217 @code{offset_type}. Big endian machines must byte-swap the values
40218 before using them. Exceptions to this rule are noted. The data is
40219 laid out such that alignment is always respected.
40221 A mapped index consists of several areas, laid out in order.
40225 The file header. This is a sequence of values, of @code{offset_type}
40226 unless otherwise noted:
40230 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40231 Version 4 uses a different hashing function from versions 5 and 6.
40232 Version 6 includes symbols for inlined functions, whereas versions 4
40233 and 5 do not. Version 7 adds attributes to the CU indices in the
40234 symbol table. Version 8 specifies that symbols from DWARF type units
40235 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40236 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40238 @value{GDBN} will only read version 4, 5, or 6 indices
40239 by specifying @code{set use-deprecated-index-sections on}.
40240 GDB has a workaround for potentially broken version 7 indices so it is
40241 currently not flagged as deprecated.
40244 The offset, from the start of the file, of the CU list.
40247 The offset, from the start of the file, of the types CU list. Note
40248 that this area can be empty, in which case this offset will be equal
40249 to the next offset.
40252 The offset, from the start of the file, of the address area.
40255 The offset, from the start of the file, of the symbol table.
40258 The offset, from the start of the file, of the constant pool.
40262 The CU list. This is a sequence of pairs of 64-bit little-endian
40263 values, sorted by the CU offset. The first element in each pair is
40264 the offset of a CU in the @code{.debug_info} section. The second
40265 element in each pair is the length of that CU. References to a CU
40266 elsewhere in the map are done using a CU index, which is just the
40267 0-based index into this table. Note that if there are type CUs, then
40268 conceptually CUs and type CUs form a single list for the purposes of
40272 The types CU list. This is a sequence of triplets of 64-bit
40273 little-endian values. In a triplet, the first value is the CU offset,
40274 the second value is the type offset in the CU, and the third value is
40275 the type signature. The types CU list is not sorted.
40278 The address area. The address area consists of a sequence of address
40279 entries. Each address entry has three elements:
40283 The low address. This is a 64-bit little-endian value.
40286 The high address. This is a 64-bit little-endian value. Like
40287 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40290 The CU index. This is an @code{offset_type} value.
40294 The symbol table. This is an open-addressed hash table. The size of
40295 the hash table is always a power of 2.
40297 Each slot in the hash table consists of a pair of @code{offset_type}
40298 values. The first value is the offset of the symbol's name in the
40299 constant pool. The second value is the offset of the CU vector in the
40302 If both values are 0, then this slot in the hash table is empty. This
40303 is ok because while 0 is a valid constant pool index, it cannot be a
40304 valid index for both a string and a CU vector.
40306 The hash value for a table entry is computed by applying an
40307 iterative hash function to the symbol's name. Starting with an
40308 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40309 the string is incorporated into the hash using the formula depending on the
40314 The formula is @code{r = r * 67 + c - 113}.
40316 @item Versions 5 to 7
40317 The formula is @code{r = r * 67 + tolower (c) - 113}.
40320 The terminating @samp{\0} is not incorporated into the hash.
40322 The step size used in the hash table is computed via
40323 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40324 value, and @samp{size} is the size of the hash table. The step size
40325 is used to find the next candidate slot when handling a hash
40328 The names of C@t{++} symbols in the hash table are canonicalized. We
40329 don't currently have a simple description of the canonicalization
40330 algorithm; if you intend to create new index sections, you must read
40334 The constant pool. This is simply a bunch of bytes. It is organized
40335 so that alignment is correct: CU vectors are stored first, followed by
40338 A CU vector in the constant pool is a sequence of @code{offset_type}
40339 values. The first value is the number of CU indices in the vector.
40340 Each subsequent value is the index and symbol attributes of a CU in
40341 the CU list. This element in the hash table is used to indicate which
40342 CUs define the symbol and how the symbol is used.
40343 See below for the format of each CU index+attributes entry.
40345 A string in the constant pool is zero-terminated.
40348 Attributes were added to CU index values in @code{.gdb_index} version 7.
40349 If a symbol has multiple uses within a CU then there is one
40350 CU index+attributes value for each use.
40352 The format of each CU index+attributes entry is as follows
40358 This is the index of the CU in the CU list.
40360 These bits are reserved for future purposes and must be zero.
40362 The kind of the symbol in the CU.
40366 This value is reserved and should not be used.
40367 By reserving zero the full @code{offset_type} value is backwards compatible
40368 with previous versions of the index.
40370 The symbol is a type.
40372 The symbol is a variable or an enum value.
40374 The symbol is a function.
40376 Any other kind of symbol.
40378 These values are reserved.
40382 This bit is zero if the value is global and one if it is static.
40384 The determination of whether a symbol is global or static is complicated.
40385 The authorative reference is the file @file{dwarf2read.c} in
40386 @value{GDBN} sources.
40390 This pseudo-code describes the computation of a symbol's kind and
40391 global/static attributes in the index.
40394 is_external = get_attribute (die, DW_AT_external);
40395 language = get_attribute (cu_die, DW_AT_language);
40398 case DW_TAG_typedef:
40399 case DW_TAG_base_type:
40400 case DW_TAG_subrange_type:
40404 case DW_TAG_enumerator:
40406 is_static = (language != CPLUS && language != JAVA);
40408 case DW_TAG_subprogram:
40410 is_static = ! (is_external || language == ADA);
40412 case DW_TAG_constant:
40414 is_static = ! is_external;
40416 case DW_TAG_variable:
40418 is_static = ! is_external;
40420 case DW_TAG_namespace:
40424 case DW_TAG_class_type:
40425 case DW_TAG_interface_type:
40426 case DW_TAG_structure_type:
40427 case DW_TAG_union_type:
40428 case DW_TAG_enumeration_type:
40430 is_static = (language != CPLUS && language != JAVA);
40438 @appendix Manual pages
40442 * gdb man:: The GNU Debugger man page
40443 * gdbserver man:: Remote Server for the GNU Debugger man page
40444 * gcore man:: Generate a core file of a running program
40445 * gdbinit man:: gdbinit scripts
40451 @c man title gdb The GNU Debugger
40453 @c man begin SYNOPSIS gdb
40454 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40455 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40456 [@option{-b}@w{ }@var{bps}]
40457 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40458 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40459 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40460 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40461 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40464 @c man begin DESCRIPTION gdb
40465 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40466 going on ``inside'' another program while it executes -- or what another
40467 program was doing at the moment it crashed.
40469 @value{GDBN} can do four main kinds of things (plus other things in support of
40470 these) to help you catch bugs in the act:
40474 Start your program, specifying anything that might affect its behavior.
40477 Make your program stop on specified conditions.
40480 Examine what has happened, when your program has stopped.
40483 Change things in your program, so you can experiment with correcting the
40484 effects of one bug and go on to learn about another.
40487 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40490 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40491 commands from the terminal until you tell it to exit with the @value{GDBN}
40492 command @code{quit}. You can get online help from @value{GDBN} itself
40493 by using the command @code{help}.
40495 You can run @code{gdb} with no arguments or options; but the most
40496 usual way to start @value{GDBN} is with one argument or two, specifying an
40497 executable program as the argument:
40503 You can also start with both an executable program and a core file specified:
40509 You can, instead, specify a process ID as a second argument, if you want
40510 to debug a running process:
40518 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40519 named @file{1234}; @value{GDBN} does check for a core file first).
40520 With option @option{-p} you can omit the @var{program} filename.
40522 Here are some of the most frequently needed @value{GDBN} commands:
40524 @c pod2man highlights the right hand side of the @item lines.
40526 @item break [@var{file}:]@var{functiop}
40527 Set a breakpoint at @var{function} (in @var{file}).
40529 @item run [@var{arglist}]
40530 Start your program (with @var{arglist}, if specified).
40533 Backtrace: display the program stack.
40535 @item print @var{expr}
40536 Display the value of an expression.
40539 Continue running your program (after stopping, e.g. at a breakpoint).
40542 Execute next program line (after stopping); step @emph{over} any
40543 function calls in the line.
40545 @item edit [@var{file}:]@var{function}
40546 look at the program line where it is presently stopped.
40548 @item list [@var{file}:]@var{function}
40549 type the text of the program in the vicinity of where it is presently stopped.
40552 Execute next program line (after stopping); step @emph{into} any
40553 function calls in the line.
40555 @item help [@var{name}]
40556 Show information about @value{GDBN} command @var{name}, or general information
40557 about using @value{GDBN}.
40560 Exit from @value{GDBN}.
40564 For full details on @value{GDBN},
40565 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40566 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40567 as the @code{gdb} entry in the @code{info} program.
40571 @c man begin OPTIONS gdb
40572 Any arguments other than options specify an executable
40573 file and core file (or process ID); that is, the first argument
40574 encountered with no
40575 associated option flag is equivalent to a @option{-se} option, and the second,
40576 if any, is equivalent to a @option{-c} option if it's the name of a file.
40578 both long and short forms; both are shown here. The long forms are also
40579 recognized if you truncate them, so long as enough of the option is
40580 present to be unambiguous. (If you prefer, you can flag option
40581 arguments with @option{+} rather than @option{-}, though we illustrate the
40582 more usual convention.)
40584 All the options and command line arguments you give are processed
40585 in sequential order. The order makes a difference when the @option{-x}
40591 List all options, with brief explanations.
40593 @item -symbols=@var{file}
40594 @itemx -s @var{file}
40595 Read symbol table from file @var{file}.
40598 Enable writing into executable and core files.
40600 @item -exec=@var{file}
40601 @itemx -e @var{file}
40602 Use file @var{file} as the executable file to execute when
40603 appropriate, and for examining pure data in conjunction with a core
40606 @item -se=@var{file}
40607 Read symbol table from file @var{file} and use it as the executable
40610 @item -core=@var{file}
40611 @itemx -c @var{file}
40612 Use file @var{file} as a core dump to examine.
40614 @item -command=@var{file}
40615 @itemx -x @var{file}
40616 Execute @value{GDBN} commands from file @var{file}.
40618 @item -ex @var{command}
40619 Execute given @value{GDBN} @var{command}.
40621 @item -directory=@var{directory}
40622 @itemx -d @var{directory}
40623 Add @var{directory} to the path to search for source files.
40626 Do not execute commands from @file{~/.gdbinit}.
40630 Do not execute commands from any @file{.gdbinit} initialization files.
40634 ``Quiet''. Do not print the introductory and copyright messages. These
40635 messages are also suppressed in batch mode.
40638 Run in batch mode. Exit with status @code{0} after processing all the command
40639 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40640 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40641 commands in the command files.
40643 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40644 download and run a program on another computer; in order to make this
40645 more useful, the message
40648 Program exited normally.
40652 (which is ordinarily issued whenever a program running under @value{GDBN} control
40653 terminates) is not issued when running in batch mode.
40655 @item -cd=@var{directory}
40656 Run @value{GDBN} using @var{directory} as its working directory,
40657 instead of the current directory.
40661 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40662 @value{GDBN} to output the full file name and line number in a standard,
40663 recognizable fashion each time a stack frame is displayed (which
40664 includes each time the program stops). This recognizable format looks
40665 like two @samp{\032} characters, followed by the file name, line number
40666 and character position separated by colons, and a newline. The
40667 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40668 characters as a signal to display the source code for the frame.
40671 Set the line speed (baud rate or bits per second) of any serial
40672 interface used by @value{GDBN} for remote debugging.
40674 @item -tty=@var{device}
40675 Run using @var{device} for your program's standard input and output.
40679 @c man begin SEEALSO gdb
40681 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40682 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40683 documentation are properly installed at your site, the command
40690 should give you access to the complete manual.
40692 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40693 Richard M. Stallman and Roland H. Pesch, July 1991.
40697 @node gdbserver man
40698 @heading gdbserver man
40700 @c man title gdbserver Remote Server for the GNU Debugger
40702 @c man begin SYNOPSIS gdbserver
40703 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40705 gdbserver --attach @var{comm} @var{pid}
40707 gdbserver --multi @var{comm}
40711 @c man begin DESCRIPTION gdbserver
40712 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40713 than the one which is running the program being debugged.
40716 @subheading Usage (server (target) side)
40719 Usage (server (target) side):
40722 First, you need to have a copy of the program you want to debug put onto
40723 the target system. The program can be stripped to save space if needed, as
40724 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40725 the @value{GDBN} running on the host system.
40727 To use the server, you log on to the target system, and run the @command{gdbserver}
40728 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40729 your program, and (c) its arguments. The general syntax is:
40732 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40735 For example, using a serial port, you might say:
40739 @c @file would wrap it as F</dev/com1>.
40740 target> gdbserver /dev/com1 emacs foo.txt
40743 target> gdbserver @file{/dev/com1} emacs foo.txt
40747 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40748 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40749 waits patiently for the host @value{GDBN} to communicate with it.
40751 To use a TCP connection, you could say:
40754 target> gdbserver host:2345 emacs foo.txt
40757 This says pretty much the same thing as the last example, except that we are
40758 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40759 that we are expecting to see a TCP connection from @code{host} to local TCP port
40760 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40761 want for the port number as long as it does not conflict with any existing TCP
40762 ports on the target system. This same port number must be used in the host
40763 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40764 you chose a port number that conflicts with another service, @command{gdbserver} will
40765 print an error message and exit.
40767 @command{gdbserver} can also attach to running programs.
40768 This is accomplished via the @option{--attach} argument. The syntax is:
40771 target> gdbserver --attach @var{comm} @var{pid}
40774 @var{pid} is the process ID of a currently running process. It isn't
40775 necessary to point @command{gdbserver} at a binary for the running process.
40777 To start @code{gdbserver} without supplying an initial command to run
40778 or process ID to attach, use the @option{--multi} command line option.
40779 In such case you should connect using @kbd{target extended-remote} to start
40780 the program you want to debug.
40783 target> gdbserver --multi @var{comm}
40787 @subheading Usage (host side)
40793 You need an unstripped copy of the target program on your host system, since
40794 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40795 would, with the target program as the first argument. (You may need to use the
40796 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40797 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40798 new command you need to know about is @code{target remote}
40799 (or @code{target extended-remote}). Its argument is either
40800 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40801 descriptor. For example:
40805 @c @file would wrap it as F</dev/ttyb>.
40806 (gdb) target remote /dev/ttyb
40809 (gdb) target remote @file{/dev/ttyb}
40814 communicates with the server via serial line @file{/dev/ttyb}, and:
40817 (gdb) target remote the-target:2345
40821 communicates via a TCP connection to port 2345 on host `the-target', where
40822 you previously started up @command{gdbserver} with the same port number. Note that for
40823 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40824 command, otherwise you may get an error that looks something like
40825 `Connection refused'.
40827 @command{gdbserver} can also debug multiple inferiors at once,
40830 the @value{GDBN} manual in node @code{Inferiors and Programs}
40831 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40834 @ref{Inferiors and Programs}.
40836 In such case use the @code{extended-remote} @value{GDBN} command variant:
40839 (gdb) target extended-remote the-target:2345
40842 The @command{gdbserver} option @option{--multi} may or may not be used in such
40846 @c man begin OPTIONS gdbserver
40847 There are three different modes for invoking @command{gdbserver}:
40852 Debug a specific program specified by its program name:
40855 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40858 The @var{comm} parameter specifies how should the server communicate
40859 with @value{GDBN}; it is either a device name (to use a serial line),
40860 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40861 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40862 debug in @var{prog}. Any remaining arguments will be passed to the
40863 program verbatim. When the program exits, @value{GDBN} will close the
40864 connection, and @code{gdbserver} will exit.
40867 Debug a specific program by specifying the process ID of a running
40871 gdbserver --attach @var{comm} @var{pid}
40874 The @var{comm} parameter is as described above. Supply the process ID
40875 of a running program in @var{pid}; @value{GDBN} will do everything
40876 else. Like with the previous mode, when the process @var{pid} exits,
40877 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40880 Multi-process mode -- debug more than one program/process:
40883 gdbserver --multi @var{comm}
40886 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40887 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40888 close the connection when a process being debugged exits, so you can
40889 debug several processes in the same session.
40892 In each of the modes you may specify these options:
40897 List all options, with brief explanations.
40900 This option causes @command{gdbserver} to print its version number and exit.
40903 @command{gdbserver} will attach to a running program. The syntax is:
40906 target> gdbserver --attach @var{comm} @var{pid}
40909 @var{pid} is the process ID of a currently running process. It isn't
40910 necessary to point @command{gdbserver} at a binary for the running process.
40913 To start @code{gdbserver} without supplying an initial command to run
40914 or process ID to attach, use this command line option.
40915 Then you can connect using @kbd{target extended-remote} and start
40916 the program you want to debug. The syntax is:
40919 target> gdbserver --multi @var{comm}
40923 Instruct @code{gdbserver} to display extra status information about the debugging
40925 This option is intended for @code{gdbserver} development and for bug reports to
40928 @item --remote-debug
40929 Instruct @code{gdbserver} to display remote protocol debug output.
40930 This option is intended for @code{gdbserver} development and for bug reports to
40933 @item --debug-format=option1@r{[},option2,...@r{]}
40934 Instruct @code{gdbserver} to include extra information in each line
40935 of debugging output.
40936 @xref{Other Command-Line Arguments for gdbserver}.
40939 Specify a wrapper to launch programs
40940 for debugging. The option should be followed by the name of the
40941 wrapper, then any command-line arguments to pass to the wrapper, then
40942 @kbd{--} indicating the end of the wrapper arguments.
40945 By default, @command{gdbserver} keeps the listening TCP port open, so that
40946 additional connections are possible. However, if you start @code{gdbserver}
40947 with the @option{--once} option, it will stop listening for any further
40948 connection attempts after connecting to the first @value{GDBN} session.
40950 @c --disable-packet is not documented for users.
40952 @c --disable-randomization and --no-disable-randomization are superseded by
40953 @c QDisableRandomization.
40958 @c man begin SEEALSO gdbserver
40960 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40961 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40962 documentation are properly installed at your site, the command
40968 should give you access to the complete manual.
40970 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40971 Richard M. Stallman and Roland H. Pesch, July 1991.
40978 @c man title gcore Generate a core file of a running program
40981 @c man begin SYNOPSIS gcore
40982 gcore [-o @var{filename}] @var{pid}
40986 @c man begin DESCRIPTION gcore
40987 Generate a core dump of a running program with process ID @var{pid}.
40988 Produced file is equivalent to a kernel produced core file as if the process
40989 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40990 limit). Unlike after a crash, after @command{gcore} the program remains
40991 running without any change.
40994 @c man begin OPTIONS gcore
40996 @item -o @var{filename}
40997 The optional argument
40998 @var{filename} specifies the file name where to put the core dump.
40999 If not specified, the file name defaults to @file{core.@var{pid}},
41000 where @var{pid} is the running program process ID.
41004 @c man begin SEEALSO gcore
41006 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41007 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41008 documentation are properly installed at your site, the command
41015 should give you access to the complete manual.
41017 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41018 Richard M. Stallman and Roland H. Pesch, July 1991.
41025 @c man title gdbinit GDB initialization scripts
41028 @c man begin SYNOPSIS gdbinit
41029 @ifset SYSTEM_GDBINIT
41030 @value{SYSTEM_GDBINIT}
41039 @c man begin DESCRIPTION gdbinit
41040 These files contain @value{GDBN} commands to automatically execute during
41041 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41044 the @value{GDBN} manual in node @code{Sequences}
41045 -- shell command @code{info -f gdb -n Sequences}.
41051 Please read more in
41053 the @value{GDBN} manual in node @code{Startup}
41054 -- shell command @code{info -f gdb -n Startup}.
41061 @ifset SYSTEM_GDBINIT
41062 @item @value{SYSTEM_GDBINIT}
41064 @ifclear SYSTEM_GDBINIT
41065 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41067 System-wide initialization file. It is executed unless user specified
41068 @value{GDBN} option @code{-nx} or @code{-n}.
41071 the @value{GDBN} manual in node @code{System-wide configuration}
41072 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41075 @ref{System-wide configuration}.
41079 User initialization file. It is executed unless user specified
41080 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41083 Initialization file for current directory. It may need to be enabled with
41084 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41087 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41088 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41091 @ref{Init File in the Current Directory}.
41096 @c man begin SEEALSO gdbinit
41098 gdb(1), @code{info -f gdb -n Startup}
41100 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41101 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41102 documentation are properly installed at your site, the command
41108 should give you access to the complete manual.
41110 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41111 Richard M. Stallman and Roland H. Pesch, July 1991.
41117 @node GNU Free Documentation License
41118 @appendix GNU Free Documentation License
41121 @node Concept Index
41122 @unnumbered Concept Index
41126 @node Command and Variable Index
41127 @unnumbered Command, Variable, and Function Index
41132 % I think something like @@colophon should be in texinfo. In the
41134 \long\def\colophon{\hbox to0pt{}\vfill
41135 \centerline{The body of this manual is set in}
41136 \centerline{\fontname\tenrm,}
41137 \centerline{with headings in {\bf\fontname\tenbf}}
41138 \centerline{and examples in {\tt\fontname\tentt}.}
41139 \centerline{{\it\fontname\tenit\/},}
41140 \centerline{{\bf\fontname\tenbf}, and}
41141 \centerline{{\sl\fontname\tensl\/}}
41142 \centerline{are used for emphasis.}\vfill}
41144 % Blame: doc@@cygnus.com, 1991.