1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. If it is @code{off}, then there is no
5840 locking and any thread may run at any time. If @code{on}, then only the
5841 current thread may run when the inferior is resumed. The @code{step}
5842 mode optimizes for single-stepping; it prevents other threads
5843 from preempting the current thread while you are stepping, so that
5844 the focus of debugging does not change unexpectedly.
5845 Other threads never get a chance to run when you step, and they are
5846 completely free to run when you use commands
5847 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5848 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5849 the current thread away from the thread that you are debugging.
5851 @item show scheduler-locking
5852 Display the current scheduler locking mode.
5855 @cindex resume threads of multiple processes simultaneously
5856 By default, when you issue one of the execution commands such as
5857 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5858 threads of the current inferior to run. For example, if @value{GDBN}
5859 is attached to two inferiors, each with two threads, the
5860 @code{continue} command resumes only the two threads of the current
5861 inferior. This is useful, for example, when you debug a program that
5862 forks and you want to hold the parent stopped (so that, for instance,
5863 it doesn't run to exit), while you debug the child. In other
5864 situations, you may not be interested in inspecting the current state
5865 of any of the processes @value{GDBN} is attached to, and you may want
5866 to resume them all until some breakpoint is hit. In the latter case,
5867 you can instruct @value{GDBN} to allow all threads of all the
5868 inferiors to run with the @w{@code{set schedule-multiple}} command.
5871 @kindex set schedule-multiple
5872 @item set schedule-multiple
5873 Set the mode for allowing threads of multiple processes to be resumed
5874 when an execution command is issued. When @code{on}, all threads of
5875 all processes are allowed to run. When @code{off}, only the threads
5876 of the current process are resumed. The default is @code{off}. The
5877 @code{scheduler-locking} mode takes precedence when set to @code{on},
5878 or while you are stepping and set to @code{step}.
5880 @item show schedule-multiple
5881 Display the current mode for resuming the execution of threads of
5886 @subsection Non-Stop Mode
5888 @cindex non-stop mode
5890 @c This section is really only a place-holder, and needs to be expanded
5891 @c with more details.
5893 For some multi-threaded targets, @value{GDBN} supports an optional
5894 mode of operation in which you can examine stopped program threads in
5895 the debugger while other threads continue to execute freely. This
5896 minimizes intrusion when debugging live systems, such as programs
5897 where some threads have real-time constraints or must continue to
5898 respond to external events. This is referred to as @dfn{non-stop} mode.
5900 In non-stop mode, when a thread stops to report a debugging event,
5901 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5902 threads as well, in contrast to the all-stop mode behavior. Additionally,
5903 execution commands such as @code{continue} and @code{step} apply by default
5904 only to the current thread in non-stop mode, rather than all threads as
5905 in all-stop mode. This allows you to control threads explicitly in
5906 ways that are not possible in all-stop mode --- for example, stepping
5907 one thread while allowing others to run freely, stepping
5908 one thread while holding all others stopped, or stepping several threads
5909 independently and simultaneously.
5911 To enter non-stop mode, use this sequence of commands before you run
5912 or attach to your program:
5915 # If using the CLI, pagination breaks non-stop.
5918 # Finally, turn it on!
5922 You can use these commands to manipulate the non-stop mode setting:
5925 @kindex set non-stop
5926 @item set non-stop on
5927 Enable selection of non-stop mode.
5928 @item set non-stop off
5929 Disable selection of non-stop mode.
5930 @kindex show non-stop
5932 Show the current non-stop enablement setting.
5935 Note these commands only reflect whether non-stop mode is enabled,
5936 not whether the currently-executing program is being run in non-stop mode.
5937 In particular, the @code{set non-stop} preference is only consulted when
5938 @value{GDBN} starts or connects to the target program, and it is generally
5939 not possible to switch modes once debugging has started. Furthermore,
5940 since not all targets support non-stop mode, even when you have enabled
5941 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5944 In non-stop mode, all execution commands apply only to the current thread
5945 by default. That is, @code{continue} only continues one thread.
5946 To continue all threads, issue @code{continue -a} or @code{c -a}.
5948 You can use @value{GDBN}'s background execution commands
5949 (@pxref{Background Execution}) to run some threads in the background
5950 while you continue to examine or step others from @value{GDBN}.
5951 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5952 always executed asynchronously in non-stop mode.
5954 Suspending execution is done with the @code{interrupt} command when
5955 running in the background, or @kbd{Ctrl-c} during foreground execution.
5956 In all-stop mode, this stops the whole process;
5957 but in non-stop mode the interrupt applies only to the current thread.
5958 To stop the whole program, use @code{interrupt -a}.
5960 Other execution commands do not currently support the @code{-a} option.
5962 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5963 that thread current, as it does in all-stop mode. This is because the
5964 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5965 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5966 changed to a different thread just as you entered a command to operate on the
5967 previously current thread.
5969 @node Background Execution
5970 @subsection Background Execution
5972 @cindex foreground execution
5973 @cindex background execution
5974 @cindex asynchronous execution
5975 @cindex execution, foreground, background and asynchronous
5977 @value{GDBN}'s execution commands have two variants: the normal
5978 foreground (synchronous) behavior, and a background
5979 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5980 the program to report that some thread has stopped before prompting for
5981 another command. In background execution, @value{GDBN} immediately gives
5982 a command prompt so that you can issue other commands while your program runs.
5984 If the target doesn't support async mode, @value{GDBN} issues an error
5985 message if you attempt to use the background execution commands.
5987 To specify background execution, add a @code{&} to the command. For example,
5988 the background form of the @code{continue} command is @code{continue&}, or
5989 just @code{c&}. The execution commands that accept background execution
5995 @xref{Starting, , Starting your Program}.
5999 @xref{Attach, , Debugging an Already-running Process}.
6003 @xref{Continuing and Stepping, step}.
6007 @xref{Continuing and Stepping, stepi}.
6011 @xref{Continuing and Stepping, next}.
6015 @xref{Continuing and Stepping, nexti}.
6019 @xref{Continuing and Stepping, continue}.
6023 @xref{Continuing and Stepping, finish}.
6027 @xref{Continuing and Stepping, until}.
6031 Background execution is especially useful in conjunction with non-stop
6032 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6033 However, you can also use these commands in the normal all-stop mode with
6034 the restriction that you cannot issue another execution command until the
6035 previous one finishes. Examples of commands that are valid in all-stop
6036 mode while the program is running include @code{help} and @code{info break}.
6038 You can interrupt your program while it is running in the background by
6039 using the @code{interrupt} command.
6046 Suspend execution of the running program. In all-stop mode,
6047 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6048 only the current thread. To stop the whole program in non-stop mode,
6049 use @code{interrupt -a}.
6052 @node Thread-Specific Breakpoints
6053 @subsection Thread-Specific Breakpoints
6055 When your program has multiple threads (@pxref{Threads,, Debugging
6056 Programs with Multiple Threads}), you can choose whether to set
6057 breakpoints on all threads, or on a particular thread.
6060 @cindex breakpoints and threads
6061 @cindex thread breakpoints
6062 @kindex break @dots{} thread @var{threadno}
6063 @item break @var{linespec} thread @var{threadno}
6064 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6065 @var{linespec} specifies source lines; there are several ways of
6066 writing them (@pxref{Specify Location}), but the effect is always to
6067 specify some source line.
6069 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6070 to specify that you only want @value{GDBN} to stop the program when a
6071 particular thread reaches this breakpoint. The @var{threadno} specifier
6072 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6073 in the first column of the @samp{info threads} display.
6075 If you do not specify @samp{thread @var{threadno}} when you set a
6076 breakpoint, the breakpoint applies to @emph{all} threads of your
6079 You can use the @code{thread} qualifier on conditional breakpoints as
6080 well; in this case, place @samp{thread @var{threadno}} before or
6081 after the breakpoint condition, like this:
6084 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6089 Thread-specific breakpoints are automatically deleted when
6090 @value{GDBN} detects the corresponding thread is no longer in the
6091 thread list. For example:
6095 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6098 There are several ways for a thread to disappear, such as a regular
6099 thread exit, but also when you detach from the process with the
6100 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6101 Process}), or if @value{GDBN} loses the remote connection
6102 (@pxref{Remote Debugging}), etc. Note that with some targets,
6103 @value{GDBN} is only able to detect a thread has exited when the user
6104 explictly asks for the thread list with the @code{info threads}
6107 @node Interrupted System Calls
6108 @subsection Interrupted System Calls
6110 @cindex thread breakpoints and system calls
6111 @cindex system calls and thread breakpoints
6112 @cindex premature return from system calls
6113 There is an unfortunate side effect when using @value{GDBN} to debug
6114 multi-threaded programs. If one thread stops for a
6115 breakpoint, or for some other reason, and another thread is blocked in a
6116 system call, then the system call may return prematurely. This is a
6117 consequence of the interaction between multiple threads and the signals
6118 that @value{GDBN} uses to implement breakpoints and other events that
6121 To handle this problem, your program should check the return value of
6122 each system call and react appropriately. This is good programming
6125 For example, do not write code like this:
6131 The call to @code{sleep} will return early if a different thread stops
6132 at a breakpoint or for some other reason.
6134 Instead, write this:
6139 unslept = sleep (unslept);
6142 A system call is allowed to return early, so the system is still
6143 conforming to its specification. But @value{GDBN} does cause your
6144 multi-threaded program to behave differently than it would without
6147 Also, @value{GDBN} uses internal breakpoints in the thread library to
6148 monitor certain events such as thread creation and thread destruction.
6149 When such an event happens, a system call in another thread may return
6150 prematurely, even though your program does not appear to stop.
6153 @subsection Observer Mode
6155 If you want to build on non-stop mode and observe program behavior
6156 without any chance of disruption by @value{GDBN}, you can set
6157 variables to disable all of the debugger's attempts to modify state,
6158 whether by writing memory, inserting breakpoints, etc. These operate
6159 at a low level, intercepting operations from all commands.
6161 When all of these are set to @code{off}, then @value{GDBN} is said to
6162 be @dfn{observer mode}. As a convenience, the variable
6163 @code{observer} can be set to disable these, plus enable non-stop
6166 Note that @value{GDBN} will not prevent you from making nonsensical
6167 combinations of these settings. For instance, if you have enabled
6168 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6169 then breakpoints that work by writing trap instructions into the code
6170 stream will still not be able to be placed.
6175 @item set observer on
6176 @itemx set observer off
6177 When set to @code{on}, this disables all the permission variables
6178 below (except for @code{insert-fast-tracepoints}), plus enables
6179 non-stop debugging. Setting this to @code{off} switches back to
6180 normal debugging, though remaining in non-stop mode.
6183 Show whether observer mode is on or off.
6185 @kindex may-write-registers
6186 @item set may-write-registers on
6187 @itemx set may-write-registers off
6188 This controls whether @value{GDBN} will attempt to alter the values of
6189 registers, such as with assignment expressions in @code{print}, or the
6190 @code{jump} command. It defaults to @code{on}.
6192 @item show may-write-registers
6193 Show the current permission to write registers.
6195 @kindex may-write-memory
6196 @item set may-write-memory on
6197 @itemx set may-write-memory off
6198 This controls whether @value{GDBN} will attempt to alter the contents
6199 of memory, such as with assignment expressions in @code{print}. It
6200 defaults to @code{on}.
6202 @item show may-write-memory
6203 Show the current permission to write memory.
6205 @kindex may-insert-breakpoints
6206 @item set may-insert-breakpoints on
6207 @itemx set may-insert-breakpoints off
6208 This controls whether @value{GDBN} will attempt to insert breakpoints.
6209 This affects all breakpoints, including internal breakpoints defined
6210 by @value{GDBN}. It defaults to @code{on}.
6212 @item show may-insert-breakpoints
6213 Show the current permission to insert breakpoints.
6215 @kindex may-insert-tracepoints
6216 @item set may-insert-tracepoints on
6217 @itemx set may-insert-tracepoints off
6218 This controls whether @value{GDBN} will attempt to insert (regular)
6219 tracepoints at the beginning of a tracing experiment. It affects only
6220 non-fast tracepoints, fast tracepoints being under the control of
6221 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6223 @item show may-insert-tracepoints
6224 Show the current permission to insert tracepoints.
6226 @kindex may-insert-fast-tracepoints
6227 @item set may-insert-fast-tracepoints on
6228 @itemx set may-insert-fast-tracepoints off
6229 This controls whether @value{GDBN} will attempt to insert fast
6230 tracepoints at the beginning of a tracing experiment. It affects only
6231 fast tracepoints, regular (non-fast) tracepoints being under the
6232 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6234 @item show may-insert-fast-tracepoints
6235 Show the current permission to insert fast tracepoints.
6237 @kindex may-interrupt
6238 @item set may-interrupt on
6239 @itemx set may-interrupt off
6240 This controls whether @value{GDBN} will attempt to interrupt or stop
6241 program execution. When this variable is @code{off}, the
6242 @code{interrupt} command will have no effect, nor will
6243 @kbd{Ctrl-c}. It defaults to @code{on}.
6245 @item show may-interrupt
6246 Show the current permission to interrupt or stop the program.
6250 @node Reverse Execution
6251 @chapter Running programs backward
6252 @cindex reverse execution
6253 @cindex running programs backward
6255 When you are debugging a program, it is not unusual to realize that
6256 you have gone too far, and some event of interest has already happened.
6257 If the target environment supports it, @value{GDBN} can allow you to
6258 ``rewind'' the program by running it backward.
6260 A target environment that supports reverse execution should be able
6261 to ``undo'' the changes in machine state that have taken place as the
6262 program was executing normally. Variables, registers etc.@: should
6263 revert to their previous values. Obviously this requires a great
6264 deal of sophistication on the part of the target environment; not
6265 all target environments can support reverse execution.
6267 When a program is executed in reverse, the instructions that
6268 have most recently been executed are ``un-executed'', in reverse
6269 order. The program counter runs backward, following the previous
6270 thread of execution in reverse. As each instruction is ``un-executed'',
6271 the values of memory and/or registers that were changed by that
6272 instruction are reverted to their previous states. After executing
6273 a piece of source code in reverse, all side effects of that code
6274 should be ``undone'', and all variables should be returned to their
6275 prior values@footnote{
6276 Note that some side effects are easier to undo than others. For instance,
6277 memory and registers are relatively easy, but device I/O is hard. Some
6278 targets may be able undo things like device I/O, and some may not.
6280 The contract between @value{GDBN} and the reverse executing target
6281 requires only that the target do something reasonable when
6282 @value{GDBN} tells it to execute backwards, and then report the
6283 results back to @value{GDBN}. Whatever the target reports back to
6284 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6285 assumes that the memory and registers that the target reports are in a
6286 consistant state, but @value{GDBN} accepts whatever it is given.
6289 If you are debugging in a target environment that supports
6290 reverse execution, @value{GDBN} provides the following commands.
6293 @kindex reverse-continue
6294 @kindex rc @r{(@code{reverse-continue})}
6295 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6296 @itemx rc @r{[}@var{ignore-count}@r{]}
6297 Beginning at the point where your program last stopped, start executing
6298 in reverse. Reverse execution will stop for breakpoints and synchronous
6299 exceptions (signals), just like normal execution. Behavior of
6300 asynchronous signals depends on the target environment.
6302 @kindex reverse-step
6303 @kindex rs @r{(@code{step})}
6304 @item reverse-step @r{[}@var{count}@r{]}
6305 Run the program backward until control reaches the start of a
6306 different source line; then stop it, and return control to @value{GDBN}.
6308 Like the @code{step} command, @code{reverse-step} will only stop
6309 at the beginning of a source line. It ``un-executes'' the previously
6310 executed source line. If the previous source line included calls to
6311 debuggable functions, @code{reverse-step} will step (backward) into
6312 the called function, stopping at the beginning of the @emph{last}
6313 statement in the called function (typically a return statement).
6315 Also, as with the @code{step} command, if non-debuggable functions are
6316 called, @code{reverse-step} will run thru them backward without stopping.
6318 @kindex reverse-stepi
6319 @kindex rsi @r{(@code{reverse-stepi})}
6320 @item reverse-stepi @r{[}@var{count}@r{]}
6321 Reverse-execute one machine instruction. Note that the instruction
6322 to be reverse-executed is @emph{not} the one pointed to by the program
6323 counter, but the instruction executed prior to that one. For instance,
6324 if the last instruction was a jump, @code{reverse-stepi} will take you
6325 back from the destination of the jump to the jump instruction itself.
6327 @kindex reverse-next
6328 @kindex rn @r{(@code{reverse-next})}
6329 @item reverse-next @r{[}@var{count}@r{]}
6330 Run backward to the beginning of the previous line executed in
6331 the current (innermost) stack frame. If the line contains function
6332 calls, they will be ``un-executed'' without stopping. Starting from
6333 the first line of a function, @code{reverse-next} will take you back
6334 to the caller of that function, @emph{before} the function was called,
6335 just as the normal @code{next} command would take you from the last
6336 line of a function back to its return to its caller
6337 @footnote{Unless the code is too heavily optimized.}.
6339 @kindex reverse-nexti
6340 @kindex rni @r{(@code{reverse-nexti})}
6341 @item reverse-nexti @r{[}@var{count}@r{]}
6342 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6343 in reverse, except that called functions are ``un-executed'' atomically.
6344 That is, if the previously executed instruction was a return from
6345 another function, @code{reverse-nexti} will continue to execute
6346 in reverse until the call to that function (from the current stack
6349 @kindex reverse-finish
6350 @item reverse-finish
6351 Just as the @code{finish} command takes you to the point where the
6352 current function returns, @code{reverse-finish} takes you to the point
6353 where it was called. Instead of ending up at the end of the current
6354 function invocation, you end up at the beginning.
6356 @kindex set exec-direction
6357 @item set exec-direction
6358 Set the direction of target execution.
6359 @item set exec-direction reverse
6360 @cindex execute forward or backward in time
6361 @value{GDBN} will perform all execution commands in reverse, until the
6362 exec-direction mode is changed to ``forward''. Affected commands include
6363 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6364 command cannot be used in reverse mode.
6365 @item set exec-direction forward
6366 @value{GDBN} will perform all execution commands in the normal fashion.
6367 This is the default.
6371 @node Process Record and Replay
6372 @chapter Recording Inferior's Execution and Replaying It
6373 @cindex process record and replay
6374 @cindex recording inferior's execution and replaying it
6376 On some platforms, @value{GDBN} provides a special @dfn{process record
6377 and replay} target that can record a log of the process execution, and
6378 replay it later with both forward and reverse execution commands.
6381 When this target is in use, if the execution log includes the record
6382 for the next instruction, @value{GDBN} will debug in @dfn{replay
6383 mode}. In the replay mode, the inferior does not really execute code
6384 instructions. Instead, all the events that normally happen during
6385 code execution are taken from the execution log. While code is not
6386 really executed in replay mode, the values of registers (including the
6387 program counter register) and the memory of the inferior are still
6388 changed as they normally would. Their contents are taken from the
6392 If the record for the next instruction is not in the execution log,
6393 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6394 inferior executes normally, and @value{GDBN} records the execution log
6397 The process record and replay target supports reverse execution
6398 (@pxref{Reverse Execution}), even if the platform on which the
6399 inferior runs does not. However, the reverse execution is limited in
6400 this case by the range of the instructions recorded in the execution
6401 log. In other words, reverse execution on platforms that don't
6402 support it directly can only be done in the replay mode.
6404 When debugging in the reverse direction, @value{GDBN} will work in
6405 replay mode as long as the execution log includes the record for the
6406 previous instruction; otherwise, it will work in record mode, if the
6407 platform supports reverse execution, or stop if not.
6409 For architecture environments that support process record and replay,
6410 @value{GDBN} provides the following commands:
6413 @kindex target record
6414 @kindex target record-full
6415 @kindex target record-btrace
6418 @kindex record btrace
6419 @kindex record btrace bts
6420 @kindex record btrace pt
6426 @kindex rec btrace bts
6427 @kindex rec btrace pt
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 reverse
6446 execution. Variables and registers are not available during reverse
6449 The recording format can be specified as parameter. Without a parameter
6450 the command chooses the recording format. The following recording
6451 formats are available:
6455 @cindex branch trace store
6456 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6457 this format, the processor stores a from/to record for each executed
6458 branch in the btrace ring buffer.
6461 @cindex Intel(R) Processor Trace
6462 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6463 format, the processor stores the execution trace in a compressed form
6464 that is afterwards decoded by @value{GDBN}.
6466 The trace can be recorded with very low overhead. The compressed
6467 trace format also allows small trace buffers to already contain a big
6468 number of instructions compared to @acronym{BTS}.
6470 Decoding the recorded execution trace, on the other hand, is more
6471 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6472 increased number of instructions to process. You should increase the
6473 buffer-size with care.
6476 Not all recording formats may be available on all processors.
6479 The process record and replay target can only debug a process that is
6480 already running. Therefore, you need first to start the process with
6481 the @kbd{run} or @kbd{start} commands, and then start the recording
6482 with the @kbd{record @var{method}} command.
6484 @cindex displaced stepping, and process record and replay
6485 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6486 will be automatically disabled when process record and replay target
6487 is started. That's because the process record and replay target
6488 doesn't support displaced stepping.
6490 @cindex non-stop mode, and process record and replay
6491 @cindex asynchronous execution, and process record and replay
6492 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6493 the asynchronous execution mode (@pxref{Background Execution}), not
6494 all recording methods are available. The @code{full} recording method
6495 does not support these two modes.
6500 Stop the process record and replay target. When process record and
6501 replay target stops, the entire execution log will be deleted and the
6502 inferior will either be terminated, or will remain in its final state.
6504 When you stop the process record and replay target in record mode (at
6505 the end of the execution log), the inferior will be stopped at the
6506 next instruction that would have been recorded. In other words, if
6507 you record for a while and then stop recording, the inferior process
6508 will be left in the same state as if the recording never happened.
6510 On the other hand, if the process record and replay target is stopped
6511 while in replay mode (that is, not at the end of the execution log,
6512 but at some earlier point), the inferior process will become ``live''
6513 at that earlier state, and it will then be possible to continue the
6514 usual ``live'' debugging of the process from that state.
6516 When the inferior process exits, or @value{GDBN} detaches from it,
6517 process record and replay target will automatically stop itself.
6521 Go to a specific location in the execution log. There are several
6522 ways to specify the location to go to:
6525 @item record goto begin
6526 @itemx record goto start
6527 Go to the beginning of the execution log.
6529 @item record goto end
6530 Go to the end of the execution log.
6532 @item record goto @var{n}
6533 Go to instruction number @var{n} in the execution log.
6537 @item record save @var{filename}
6538 Save the execution log to a file @file{@var{filename}}.
6539 Default filename is @file{gdb_record.@var{process_id}}, where
6540 @var{process_id} is the process ID of the inferior.
6542 This command may not be available for all recording methods.
6544 @kindex record restore
6545 @item record restore @var{filename}
6546 Restore the execution log from a file @file{@var{filename}}.
6547 File must have been created with @code{record save}.
6549 @kindex set record full
6550 @item set record full insn-number-max @var{limit}
6551 @itemx set record full insn-number-max unlimited
6552 Set the limit of instructions to be recorded for the @code{full}
6553 recording method. Default value is 200000.
6555 If @var{limit} is a positive number, then @value{GDBN} will start
6556 deleting instructions from the log once the number of the record
6557 instructions becomes greater than @var{limit}. For every new recorded
6558 instruction, @value{GDBN} will delete the earliest recorded
6559 instruction to keep the number of recorded instructions at the limit.
6560 (Since deleting recorded instructions loses information, @value{GDBN}
6561 lets you control what happens when the limit is reached, by means of
6562 the @code{stop-at-limit} option, described below.)
6564 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6565 delete recorded instructions from the execution log. The number of
6566 recorded instructions is limited only by the available memory.
6568 @kindex show record full
6569 @item show record full insn-number-max
6570 Show the limit of instructions to be recorded with the @code{full}
6573 @item set record full stop-at-limit
6574 Control the behavior of the @code{full} recording method when the
6575 number of recorded instructions reaches the limit. If ON (the
6576 default), @value{GDBN} will stop when the limit is reached for the
6577 first time and ask you whether you want to stop the inferior or
6578 continue running it and recording the execution log. If you decide
6579 to continue recording, each new recorded instruction will cause the
6580 oldest one to be deleted.
6582 If this option is OFF, @value{GDBN} will automatically delete the
6583 oldest record to make room for each new one, without asking.
6585 @item show record full stop-at-limit
6586 Show the current setting of @code{stop-at-limit}.
6588 @item set record full memory-query
6589 Control the behavior when @value{GDBN} is unable to record memory
6590 changes caused by an instruction for the @code{full} recording method.
6591 If ON, @value{GDBN} will query whether to stop the inferior in that
6594 If this option is OFF (the default), @value{GDBN} will automatically
6595 ignore the effect of such instructions on memory. Later, when
6596 @value{GDBN} replays this execution log, it will mark the log of this
6597 instruction as not accessible, and it will not affect the replay
6600 @item show record full memory-query
6601 Show the current setting of @code{memory-query}.
6603 @kindex set record btrace
6604 The @code{btrace} record target does not trace data. As a
6605 convenience, when replaying, @value{GDBN} reads read-only memory off
6606 the live program directly, assuming that the addresses of the
6607 read-only areas don't change. This for example makes it possible to
6608 disassemble code while replaying, but not to print variables.
6609 In some cases, being able to inspect variables might be useful.
6610 You can use the following command for that:
6612 @item set record btrace replay-memory-access
6613 Control the behavior of the @code{btrace} recording method when
6614 accessing memory during replay. If @code{read-only} (the default),
6615 @value{GDBN} will only allow accesses to read-only memory.
6616 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6617 and to read-write memory. Beware that the accessed memory corresponds
6618 to the live target and not necessarily to the current replay
6621 @kindex show record btrace
6622 @item show record btrace replay-memory-access
6623 Show the current setting of @code{replay-memory-access}.
6625 @kindex set record btrace bts
6626 @item set record btrace bts buffer-size @var{size}
6627 @itemx set record btrace bts buffer-size unlimited
6628 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6629 format. Default is 64KB.
6631 If @var{size} is a positive number, then @value{GDBN} will try to
6632 allocate a buffer of at least @var{size} bytes for each new thread
6633 that uses the btrace recording method and the @acronym{BTS} format.
6634 The actually obtained buffer size may differ from the requested
6635 @var{size}. Use the @code{info record} command to see the actual
6636 buffer size for each thread that uses the btrace recording method and
6637 the @acronym{BTS} format.
6639 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6640 allocate a buffer of 4MB.
6642 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6643 also need longer to process the branch trace data before it can be used.
6645 @item show record btrace bts buffer-size @var{size}
6646 Show the current setting of the requested ring buffer size for branch
6647 tracing in @acronym{BTS} format.
6649 @kindex set record btrace pt
6650 @item set record btrace pt buffer-size @var{size}
6651 @itemx set record btrace pt buffer-size unlimited
6652 Set the requested ring buffer size for branch tracing in Intel(R)
6653 Processor Trace format. Default is 16KB.
6655 If @var{size} is a positive number, then @value{GDBN} will try to
6656 allocate a buffer of at least @var{size} bytes for each new thread
6657 that uses the btrace recording method and the Intel(R) Processor Trace
6658 format. The actually obtained buffer size may differ from the
6659 requested @var{size}. Use the @code{info record} command to see the
6660 actual buffer size for each thread.
6662 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6663 allocate a buffer of 4MB.
6665 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6666 also need longer to process the branch trace data before it can be used.
6668 @item show record btrace pt buffer-size @var{size}
6669 Show the current setting of the requested ring buffer size for branch
6670 tracing in Intel(R) Processor Trace format.
6674 Show various statistics about the recording depending on the recording
6679 For the @code{full} recording method, it shows the state of process
6680 record and its in-memory execution log buffer, including:
6684 Whether in record mode or replay mode.
6686 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6688 Highest recorded instruction number.
6690 Current instruction about to be replayed (if in replay mode).
6692 Number of instructions contained in the execution log.
6694 Maximum number of instructions that may be contained in the execution log.
6698 For the @code{btrace} recording method, it shows:
6704 Number of instructions that have been recorded.
6706 Number of blocks of sequential control-flow formed by the recorded
6709 Whether in record mode or replay mode.
6712 For the @code{bts} recording format, it also shows:
6715 Size of the perf ring buffer.
6718 For the @code{pt} recording format, it also shows:
6721 Size of the perf ring buffer.
6725 @kindex record delete
6728 When record target runs in replay mode (``in the past''), delete the
6729 subsequent execution log and begin to record a new execution log starting
6730 from the current address. This means you will abandon the previously
6731 recorded ``future'' and begin recording a new ``future''.
6733 @kindex record instruction-history
6734 @kindex rec instruction-history
6735 @item record instruction-history
6736 Disassembles instructions from the recorded execution log. By
6737 default, ten instructions are disassembled. This can be changed using
6738 the @code{set record instruction-history-size} command. Instructions
6739 are printed in execution order. There are several ways to specify
6740 what part of the execution log to disassemble:
6743 @item record instruction-history @var{insn}
6744 Disassembles ten instructions starting from instruction number
6747 @item record instruction-history @var{insn}, +/-@var{n}
6748 Disassembles @var{n} instructions around instruction number
6749 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6750 @var{n} instructions after instruction number @var{insn}. If
6751 @var{n} is preceded with @code{-}, disassembles @var{n}
6752 instructions before instruction number @var{insn}.
6754 @item record instruction-history
6755 Disassembles ten more instructions after the last disassembly.
6757 @item record instruction-history -
6758 Disassembles ten more instructions before the last disassembly.
6760 @item record instruction-history @var{begin} @var{end}
6761 Disassembles instructions beginning with instruction number
6762 @var{begin} until instruction number @var{end}. The instruction
6763 number @var{end} is included.
6766 This command may not be available for all recording methods.
6769 @item set record instruction-history-size @var{size}
6770 @itemx set record instruction-history-size unlimited
6771 Define how many instructions to disassemble in the @code{record
6772 instruction-history} command. The default value is 10.
6773 A @var{size} of @code{unlimited} means unlimited instructions.
6776 @item show record instruction-history-size
6777 Show how many instructions to disassemble in the @code{record
6778 instruction-history} command.
6780 @kindex record function-call-history
6781 @kindex rec function-call-history
6782 @item record function-call-history
6783 Prints the execution history at function granularity. It prints one
6784 line for each sequence of instructions that belong to the same
6785 function giving the name of that function, the source lines
6786 for this instruction sequence (if the @code{/l} modifier is
6787 specified), and the instructions numbers that form the sequence (if
6788 the @code{/i} modifier is specified). The function names are indented
6789 to reflect the call stack depth if the @code{/c} modifier is
6790 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6794 (@value{GDBP}) @b{list 1, 10}
6805 (@value{GDBP}) @b{record function-call-history /ilc}
6806 1 bar inst 1,4 at foo.c:6,8
6807 2 foo inst 5,10 at foo.c:2,3
6808 3 bar inst 11,13 at foo.c:9,10
6811 By default, ten lines are printed. This can be changed using the
6812 @code{set record function-call-history-size} command. Functions are
6813 printed in execution order. There are several ways to specify what
6817 @item record function-call-history @var{func}
6818 Prints ten functions starting from function number @var{func}.
6820 @item record function-call-history @var{func}, +/-@var{n}
6821 Prints @var{n} functions around function number @var{func}. If
6822 @var{n} is preceded with @code{+}, prints @var{n} functions after
6823 function number @var{func}. If @var{n} is preceded with @code{-},
6824 prints @var{n} functions before function number @var{func}.
6826 @item record function-call-history
6827 Prints ten more functions after the last ten-line print.
6829 @item record function-call-history -
6830 Prints ten more functions before the last ten-line print.
6832 @item record function-call-history @var{begin} @var{end}
6833 Prints functions beginning with function number @var{begin} until
6834 function number @var{end}. The function number @var{end} is included.
6837 This command may not be available for all recording methods.
6839 @item set record function-call-history-size @var{size}
6840 @itemx set record function-call-history-size unlimited
6841 Define how many lines to print in the
6842 @code{record function-call-history} command. The default value is 10.
6843 A size of @code{unlimited} means unlimited lines.
6845 @item show record function-call-history-size
6846 Show how many lines to print in the
6847 @code{record function-call-history} command.
6852 @chapter Examining the Stack
6854 When your program has stopped, the first thing you need to know is where it
6855 stopped and how it got there.
6858 Each time your program performs a function call, information about the call
6860 That information includes the location of the call in your program,
6861 the arguments of the call,
6862 and the local variables of the function being called.
6863 The information is saved in a block of data called a @dfn{stack frame}.
6864 The stack frames are allocated in a region of memory called the @dfn{call
6867 When your program stops, the @value{GDBN} commands for examining the
6868 stack allow you to see all of this information.
6870 @cindex selected frame
6871 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6872 @value{GDBN} commands refer implicitly to the selected frame. In
6873 particular, whenever you ask @value{GDBN} for the value of a variable in
6874 your program, the value is found in the selected frame. There are
6875 special @value{GDBN} commands to select whichever frame you are
6876 interested in. @xref{Selection, ,Selecting a Frame}.
6878 When your program stops, @value{GDBN} automatically selects the
6879 currently executing frame and describes it briefly, similar to the
6880 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6883 * Frames:: Stack frames
6884 * Backtrace:: Backtraces
6885 * Frame Filter Management:: Managing frame filters
6886 * Selection:: Selecting a frame
6887 * Frame Info:: Information on a frame
6892 @section Stack Frames
6894 @cindex frame, definition
6896 The call stack is divided up into contiguous pieces called @dfn{stack
6897 frames}, or @dfn{frames} for short; each frame is the data associated
6898 with one call to one function. The frame contains the arguments given
6899 to the function, the function's local variables, and the address at
6900 which the function is executing.
6902 @cindex initial frame
6903 @cindex outermost frame
6904 @cindex innermost frame
6905 When your program is started, the stack has only one frame, that of the
6906 function @code{main}. This is called the @dfn{initial} frame or the
6907 @dfn{outermost} frame. Each time a function is called, a new frame is
6908 made. Each time a function returns, the frame for that function invocation
6909 is eliminated. If a function is recursive, there can be many frames for
6910 the same function. The frame for the function in which execution is
6911 actually occurring is called the @dfn{innermost} frame. This is the most
6912 recently created of all the stack frames that still exist.
6914 @cindex frame pointer
6915 Inside your program, stack frames are identified by their addresses. A
6916 stack frame consists of many bytes, each of which has its own address; each
6917 kind of computer has a convention for choosing one byte whose
6918 address serves as the address of the frame. Usually this address is kept
6919 in a register called the @dfn{frame pointer register}
6920 (@pxref{Registers, $fp}) while execution is going on in that frame.
6922 @cindex frame number
6923 @value{GDBN} assigns numbers to all existing stack frames, starting with
6924 zero for the innermost frame, one for the frame that called it,
6925 and so on upward. These numbers do not really exist in your program;
6926 they are assigned by @value{GDBN} to give you a way of designating stack
6927 frames in @value{GDBN} commands.
6929 @c The -fomit-frame-pointer below perennially causes hbox overflow
6930 @c underflow problems.
6931 @cindex frameless execution
6932 Some compilers provide a way to compile functions so that they operate
6933 without stack frames. (For example, the @value{NGCC} option
6935 @samp{-fomit-frame-pointer}
6937 generates functions without a frame.)
6938 This is occasionally done with heavily used library functions to save
6939 the frame setup time. @value{GDBN} has limited facilities for dealing
6940 with these function invocations. If the innermost function invocation
6941 has no stack frame, @value{GDBN} nevertheless regards it as though
6942 it had a separate frame, which is numbered zero as usual, allowing
6943 correct tracing of the function call chain. However, @value{GDBN} has
6944 no provision for frameless functions elsewhere in the stack.
6947 @kindex frame@r{, command}
6948 @cindex current stack frame
6949 @item frame @r{[}@var{framespec}@r{]}
6950 The @code{frame} command allows you to move from one stack frame to another,
6951 and to print the stack frame you select. The @var{framespec} may be either the
6952 address of the frame or the stack frame number. Without an argument,
6953 @code{frame} prints the current stack frame.
6955 @kindex select-frame
6956 @cindex selecting frame silently
6958 The @code{select-frame} command allows you to move from one stack frame
6959 to another without printing the frame. This is the silent version of
6967 @cindex call stack traces
6968 A backtrace is a summary of how your program got where it is. It shows one
6969 line per frame, for many frames, starting with the currently executing
6970 frame (frame zero), followed by its caller (frame one), and on up the
6973 @anchor{backtrace-command}
6976 @kindex bt @r{(@code{backtrace})}
6979 Print a backtrace of the entire stack: one line per frame for all
6980 frames in the stack.
6982 You can stop the backtrace at any time by typing the system interrupt
6983 character, normally @kbd{Ctrl-c}.
6985 @item backtrace @var{n}
6987 Similar, but print only the innermost @var{n} frames.
6989 @item backtrace -@var{n}
6991 Similar, but print only the outermost @var{n} frames.
6993 @item backtrace full
6995 @itemx bt full @var{n}
6996 @itemx bt full -@var{n}
6997 Print the values of the local variables also. As described above,
6998 @var{n} specifies the number of frames to print.
7000 @item backtrace no-filters
7001 @itemx bt no-filters
7002 @itemx bt no-filters @var{n}
7003 @itemx bt no-filters -@var{n}
7004 @itemx bt no-filters full
7005 @itemx bt no-filters full @var{n}
7006 @itemx bt no-filters full -@var{n}
7007 Do not run Python frame filters on this backtrace. @xref{Frame
7008 Filter API}, for more information. Additionally use @ref{disable
7009 frame-filter all} to turn off all frame filters. This is only
7010 relevant when @value{GDBN} has been configured with @code{Python}
7016 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7017 are additional aliases for @code{backtrace}.
7019 @cindex multiple threads, backtrace
7020 In a multi-threaded program, @value{GDBN} by default shows the
7021 backtrace only for the current thread. To display the backtrace for
7022 several or all of the threads, use the command @code{thread apply}
7023 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7024 apply all backtrace}, @value{GDBN} will display the backtrace for all
7025 the threads; this is handy when you debug a core dump of a
7026 multi-threaded program.
7028 Each line in the backtrace shows the frame number and the function name.
7029 The program counter value is also shown---unless you use @code{set
7030 print address off}. The backtrace also shows the source file name and
7031 line number, as well as the arguments to the function. The program
7032 counter value is omitted if it is at the beginning of the code for that
7035 Here is an example of a backtrace. It was made with the command
7036 @samp{bt 3}, so it shows the innermost three frames.
7040 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7042 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7043 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7045 (More stack frames follow...)
7050 The display for frame zero does not begin with a program counter
7051 value, indicating that your program has stopped at the beginning of the
7052 code for line @code{993} of @code{builtin.c}.
7055 The value of parameter @code{data} in frame 1 has been replaced by
7056 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7057 only if it is a scalar (integer, pointer, enumeration, etc). See command
7058 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7059 on how to configure the way function parameter values are printed.
7061 @cindex optimized out, in backtrace
7062 @cindex function call arguments, optimized out
7063 If your program was compiled with optimizations, some compilers will
7064 optimize away arguments passed to functions if those arguments are
7065 never used after the call. Such optimizations generate code that
7066 passes arguments through registers, but doesn't store those arguments
7067 in the stack frame. @value{GDBN} has no way of displaying such
7068 arguments in stack frames other than the innermost one. Here's what
7069 such a backtrace might look like:
7073 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7075 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7076 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7078 (More stack frames follow...)
7083 The values of arguments that were not saved in their stack frames are
7084 shown as @samp{<optimized out>}.
7086 If you need to display the values of such optimized-out arguments,
7087 either deduce that from other variables whose values depend on the one
7088 you are interested in, or recompile without optimizations.
7090 @cindex backtrace beyond @code{main} function
7091 @cindex program entry point
7092 @cindex startup code, and backtrace
7093 Most programs have a standard user entry point---a place where system
7094 libraries and startup code transition into user code. For C this is
7095 @code{main}@footnote{
7096 Note that embedded programs (the so-called ``free-standing''
7097 environment) are not required to have a @code{main} function as the
7098 entry point. They could even have multiple entry points.}.
7099 When @value{GDBN} finds the entry function in a backtrace
7100 it will terminate the backtrace, to avoid tracing into highly
7101 system-specific (and generally uninteresting) code.
7103 If you need to examine the startup code, or limit the number of levels
7104 in a backtrace, you can change this behavior:
7107 @item set backtrace past-main
7108 @itemx set backtrace past-main on
7109 @kindex set backtrace
7110 Backtraces will continue past the user entry point.
7112 @item set backtrace past-main off
7113 Backtraces will stop when they encounter the user entry point. This is the
7116 @item show backtrace past-main
7117 @kindex show backtrace
7118 Display the current user entry point backtrace policy.
7120 @item set backtrace past-entry
7121 @itemx set backtrace past-entry on
7122 Backtraces will continue past the internal entry point of an application.
7123 This entry point is encoded by the linker when the application is built,
7124 and is likely before the user entry point @code{main} (or equivalent) is called.
7126 @item set backtrace past-entry off
7127 Backtraces will stop when they encounter the internal entry point of an
7128 application. This is the default.
7130 @item show backtrace past-entry
7131 Display the current internal entry point backtrace policy.
7133 @item set backtrace limit @var{n}
7134 @itemx set backtrace limit 0
7135 @itemx set backtrace limit unlimited
7136 @cindex backtrace limit
7137 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7138 or zero means unlimited levels.
7140 @item show backtrace limit
7141 Display the current limit on backtrace levels.
7144 You can control how file names are displayed.
7147 @item set filename-display
7148 @itemx set filename-display relative
7149 @cindex filename-display
7150 Display file names relative to the compilation directory. This is the default.
7152 @item set filename-display basename
7153 Display only basename of a filename.
7155 @item set filename-display absolute
7156 Display an absolute filename.
7158 @item show filename-display
7159 Show the current way to display filenames.
7162 @node Frame Filter Management
7163 @section Management of Frame Filters.
7164 @cindex managing frame filters
7166 Frame filters are Python based utilities to manage and decorate the
7167 output of frames. @xref{Frame Filter API}, for further information.
7169 Managing frame filters is performed by several commands available
7170 within @value{GDBN}, detailed here.
7173 @kindex info frame-filter
7174 @item info frame-filter
7175 Print a list of installed frame filters from all dictionaries, showing
7176 their name, priority and enabled status.
7178 @kindex disable frame-filter
7179 @anchor{disable frame-filter all}
7180 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7181 Disable a frame filter in the dictionary matching
7182 @var{filter-dictionary} and @var{filter-name}. The
7183 @var{filter-dictionary} may be @code{all}, @code{global},
7184 @code{progspace}, or the name of the object file where the frame filter
7185 dictionary resides. When @code{all} is specified, all frame filters
7186 across all dictionaries are disabled. The @var{filter-name} is the name
7187 of the frame filter and is used when @code{all} is not the option for
7188 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7189 may be enabled again later.
7191 @kindex enable frame-filter
7192 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7193 Enable a frame filter in the dictionary matching
7194 @var{filter-dictionary} and @var{filter-name}. The
7195 @var{filter-dictionary} may be @code{all}, @code{global},
7196 @code{progspace} or the name of the object file where the frame filter
7197 dictionary resides. When @code{all} is specified, all frame filters across
7198 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7199 filter and is used when @code{all} is not the option for
7200 @var{filter-dictionary}.
7205 (gdb) info frame-filter
7207 global frame-filters:
7208 Priority Enabled Name
7209 1000 No PrimaryFunctionFilter
7212 progspace /build/test frame-filters:
7213 Priority Enabled Name
7214 100 Yes ProgspaceFilter
7216 objfile /build/test frame-filters:
7217 Priority Enabled Name
7218 999 Yes BuildProgra Filter
7220 (gdb) disable frame-filter /build/test BuildProgramFilter
7221 (gdb) info frame-filter
7223 global frame-filters:
7224 Priority Enabled Name
7225 1000 No PrimaryFunctionFilter
7228 progspace /build/test frame-filters:
7229 Priority Enabled Name
7230 100 Yes ProgspaceFilter
7232 objfile /build/test frame-filters:
7233 Priority Enabled Name
7234 999 No BuildProgramFilter
7236 (gdb) enable frame-filter global PrimaryFunctionFilter
7237 (gdb) info frame-filter
7239 global frame-filters:
7240 Priority Enabled Name
7241 1000 Yes PrimaryFunctionFilter
7244 progspace /build/test frame-filters:
7245 Priority Enabled Name
7246 100 Yes ProgspaceFilter
7248 objfile /build/test frame-filters:
7249 Priority Enabled Name
7250 999 No BuildProgramFilter
7253 @kindex set frame-filter priority
7254 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7255 Set the @var{priority} of a frame filter in the dictionary matching
7256 @var{filter-dictionary}, and the frame filter name matching
7257 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7258 @code{progspace} or the name of the object file where the frame filter
7259 dictionary resides. The @var{priority} is an integer.
7261 @kindex show frame-filter priority
7262 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7263 Show the @var{priority} of a frame filter in the dictionary matching
7264 @var{filter-dictionary}, and the frame filter name matching
7265 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7266 @code{progspace} or the name of the object file where the frame filter
7272 (gdb) info frame-filter
7274 global frame-filters:
7275 Priority Enabled Name
7276 1000 Yes PrimaryFunctionFilter
7279 progspace /build/test frame-filters:
7280 Priority Enabled Name
7281 100 Yes ProgspaceFilter
7283 objfile /build/test frame-filters:
7284 Priority Enabled Name
7285 999 No BuildProgramFilter
7287 (gdb) set frame-filter priority global Reverse 50
7288 (gdb) info frame-filter
7290 global frame-filters:
7291 Priority Enabled Name
7292 1000 Yes PrimaryFunctionFilter
7295 progspace /build/test frame-filters:
7296 Priority Enabled Name
7297 100 Yes ProgspaceFilter
7299 objfile /build/test frame-filters:
7300 Priority Enabled Name
7301 999 No BuildProgramFilter
7306 @section Selecting a Frame
7308 Most commands for examining the stack and other data in your program work on
7309 whichever stack frame is selected at the moment. Here are the commands for
7310 selecting a stack frame; all of them finish by printing a brief description
7311 of the stack frame just selected.
7314 @kindex frame@r{, selecting}
7315 @kindex f @r{(@code{frame})}
7318 Select frame number @var{n}. Recall that frame zero is the innermost
7319 (currently executing) frame, frame one is the frame that called the
7320 innermost one, and so on. The highest-numbered frame is the one for
7323 @item frame @var{stack-addr} [ @var{pc-addr} ]
7324 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7325 Select the frame at address @var{stack-addr}. This is useful mainly if the
7326 chaining of stack frames has been damaged by a bug, making it
7327 impossible for @value{GDBN} to assign numbers properly to all frames. In
7328 addition, this can be useful when your program has multiple stacks and
7329 switches between them. The optional @var{pc-addr} can also be given to
7330 specify the value of PC for the stack frame.
7334 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7335 numbers @var{n}, this advances toward the outermost frame, to higher
7336 frame numbers, to frames that have existed longer.
7339 @kindex do @r{(@code{down})}
7341 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7342 positive numbers @var{n}, this advances toward the innermost frame, to
7343 lower frame numbers, to frames that were created more recently.
7344 You may abbreviate @code{down} as @code{do}.
7347 All of these commands end by printing two lines of output describing the
7348 frame. The first line shows the frame number, the function name, the
7349 arguments, and the source file and line number of execution in that
7350 frame. The second line shows the text of that source line.
7358 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7360 10 read_input_file (argv[i]);
7364 After such a printout, the @code{list} command with no arguments
7365 prints ten lines centered on the point of execution in the frame.
7366 You can also edit the program at the point of execution with your favorite
7367 editing program by typing @code{edit}.
7368 @xref{List, ,Printing Source Lines},
7372 @kindex down-silently
7374 @item up-silently @var{n}
7375 @itemx down-silently @var{n}
7376 These two commands are variants of @code{up} and @code{down},
7377 respectively; they differ in that they do their work silently, without
7378 causing display of the new frame. They are intended primarily for use
7379 in @value{GDBN} command scripts, where the output might be unnecessary and
7384 @section Information About a Frame
7386 There are several other commands to print information about the selected
7392 When used without any argument, this command does not change which
7393 frame is selected, but prints a brief description of the currently
7394 selected stack frame. It can be abbreviated @code{f}. With an
7395 argument, this command is used to select a stack frame.
7396 @xref{Selection, ,Selecting a Frame}.
7399 @kindex info f @r{(@code{info frame})}
7402 This command prints a verbose description of the selected stack frame,
7407 the address of the frame
7409 the address of the next frame down (called by this frame)
7411 the address of the next frame up (caller of this frame)
7413 the language in which the source code corresponding to this frame is written
7415 the address of the frame's arguments
7417 the address of the frame's local variables
7419 the program counter saved in it (the address of execution in the caller frame)
7421 which registers were saved in the frame
7424 @noindent The verbose description is useful when
7425 something has gone wrong that has made the stack format fail to fit
7426 the usual conventions.
7428 @item info frame @var{addr}
7429 @itemx info f @var{addr}
7430 Print a verbose description of the frame at address @var{addr}, without
7431 selecting that frame. The selected frame remains unchanged by this
7432 command. This requires the same kind of address (more than one for some
7433 architectures) that you specify in the @code{frame} command.
7434 @xref{Selection, ,Selecting a Frame}.
7438 Print the arguments of the selected frame, each on a separate line.
7442 Print the local variables of the selected frame, each on a separate
7443 line. These are all variables (declared either static or automatic)
7444 accessible at the point of execution of the selected frame.
7450 @chapter Examining Source Files
7452 @value{GDBN} can print parts of your program's source, since the debugging
7453 information recorded in the program tells @value{GDBN} what source files were
7454 used to build it. When your program stops, @value{GDBN} spontaneously prints
7455 the line where it stopped. Likewise, when you select a stack frame
7456 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7457 execution in that frame has stopped. You can print other portions of
7458 source files by explicit command.
7460 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7461 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7462 @value{GDBN} under @sc{gnu} Emacs}.
7465 * List:: Printing source lines
7466 * Specify Location:: How to specify code locations
7467 * Edit:: Editing source files
7468 * Search:: Searching source files
7469 * Source Path:: Specifying source directories
7470 * Machine Code:: Source and machine code
7474 @section Printing Source Lines
7477 @kindex l @r{(@code{list})}
7478 To print lines from a source file, use the @code{list} command
7479 (abbreviated @code{l}). By default, ten lines are printed.
7480 There are several ways to specify what part of the file you want to
7481 print; see @ref{Specify Location}, for the full list.
7483 Here are the forms of the @code{list} command most commonly used:
7486 @item list @var{linenum}
7487 Print lines centered around line number @var{linenum} in the
7488 current source file.
7490 @item list @var{function}
7491 Print lines centered around the beginning of function
7495 Print more lines. If the last lines printed were printed with a
7496 @code{list} command, this prints lines following the last lines
7497 printed; however, if the last line printed was a solitary line printed
7498 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7499 Stack}), this prints lines centered around that line.
7502 Print lines just before the lines last printed.
7505 @cindex @code{list}, how many lines to display
7506 By default, @value{GDBN} prints ten source lines with any of these forms of
7507 the @code{list} command. You can change this using @code{set listsize}:
7510 @kindex set listsize
7511 @item set listsize @var{count}
7512 @itemx set listsize unlimited
7513 Make the @code{list} command display @var{count} source lines (unless
7514 the @code{list} argument explicitly specifies some other number).
7515 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7517 @kindex show listsize
7519 Display the number of lines that @code{list} prints.
7522 Repeating a @code{list} command with @key{RET} discards the argument,
7523 so it is equivalent to typing just @code{list}. This is more useful
7524 than listing the same lines again. An exception is made for an
7525 argument of @samp{-}; that argument is preserved in repetition so that
7526 each repetition moves up in the source file.
7528 In general, the @code{list} command expects you to supply zero, one or two
7529 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7530 of writing them (@pxref{Specify Location}), but the effect is always
7531 to specify some source line.
7533 Here is a complete description of the possible arguments for @code{list}:
7536 @item list @var{linespec}
7537 Print lines centered around the line specified by @var{linespec}.
7539 @item list @var{first},@var{last}
7540 Print lines from @var{first} to @var{last}. Both arguments are
7541 linespecs. When a @code{list} command has two linespecs, and the
7542 source file of the second linespec is omitted, this refers to
7543 the same source file as the first linespec.
7545 @item list ,@var{last}
7546 Print lines ending with @var{last}.
7548 @item list @var{first},
7549 Print lines starting with @var{first}.
7552 Print lines just after the lines last printed.
7555 Print lines just before the lines last printed.
7558 As described in the preceding table.
7561 @node Specify Location
7562 @section Specifying a Location
7563 @cindex specifying location
7566 Several @value{GDBN} commands accept arguments that specify a location
7567 of your program's code. Since @value{GDBN} is a source-level
7568 debugger, a location usually specifies some line in the source code;
7569 for that reason, locations are also known as @dfn{linespecs}.
7571 Here are all the different ways of specifying a code location that
7572 @value{GDBN} understands:
7576 Specifies the line number @var{linenum} of the current source file.
7579 @itemx +@var{offset}
7580 Specifies the line @var{offset} lines before or after the @dfn{current
7581 line}. For the @code{list} command, the current line is the last one
7582 printed; for the breakpoint commands, this is the line at which
7583 execution stopped in the currently selected @dfn{stack frame}
7584 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7585 used as the second of the two linespecs in a @code{list} command,
7586 this specifies the line @var{offset} lines up or down from the first
7589 @item @var{filename}:@var{linenum}
7590 Specifies the line @var{linenum} in the source file @var{filename}.
7591 If @var{filename} is a relative file name, then it will match any
7592 source file name with the same trailing components. For example, if
7593 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7594 name of @file{/build/trunk/gcc/expr.c}, but not
7595 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7597 @item @var{function}
7598 Specifies the line that begins the body of the function @var{function}.
7599 For example, in C, this is the line with the open brace.
7601 @item @var{function}:@var{label}
7602 Specifies the line where @var{label} appears in @var{function}.
7604 @item @var{filename}:@var{function}
7605 Specifies the line that begins the body of the function @var{function}
7606 in the file @var{filename}. You only need the file name with a
7607 function name to avoid ambiguity when there are identically named
7608 functions in different source files.
7611 Specifies the line at which the label named @var{label} appears.
7612 @value{GDBN} searches for the label in the function corresponding to
7613 the currently selected stack frame. If there is no current selected
7614 stack frame (for instance, if the inferior is not running), then
7615 @value{GDBN} will not search for a label.
7617 @item *@var{address}
7618 Specifies the program address @var{address}. For line-oriented
7619 commands, such as @code{list} and @code{edit}, this specifies a source
7620 line that contains @var{address}. For @code{break} and other
7621 breakpoint oriented commands, this can be used to set breakpoints in
7622 parts of your program which do not have debugging information or
7625 Here @var{address} may be any expression valid in the current working
7626 language (@pxref{Languages, working language}) that specifies a code
7627 address. In addition, as a convenience, @value{GDBN} extends the
7628 semantics of expressions used in locations to cover the situations
7629 that frequently happen during debugging. Here are the various forms
7633 @item @var{expression}
7634 Any expression valid in the current working language.
7636 @item @var{funcaddr}
7637 An address of a function or procedure derived from its name. In C,
7638 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7639 simply the function's name @var{function} (and actually a special case
7640 of a valid expression). In Pascal and Modula-2, this is
7641 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7642 (although the Pascal form also works).
7644 This form specifies the address of the function's first instruction,
7645 before the stack frame and arguments have been set up.
7647 @item '@var{filename}':@var{funcaddr}
7648 Like @var{funcaddr} above, but also specifies the name of the source
7649 file explicitly. This is useful if the name of the function does not
7650 specify the function unambiguously, e.g., if there are several
7651 functions with identical names in different source files.
7654 @cindex breakpoint at static probe point
7655 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7656 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7657 applications to embed static probes. @xref{Static Probe Points}, for more
7658 information on finding and using static probes. This form of linespec
7659 specifies the location of such a static probe.
7661 If @var{objfile} is given, only probes coming from that shared library
7662 or executable matching @var{objfile} as a regular expression are considered.
7663 If @var{provider} is given, then only probes from that provider are considered.
7664 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7665 each one of those probes.
7671 @section Editing Source Files
7672 @cindex editing source files
7675 @kindex e @r{(@code{edit})}
7676 To edit the lines in a source file, use the @code{edit} command.
7677 The editing program of your choice
7678 is invoked with the current line set to
7679 the active line in the program.
7680 Alternatively, there are several ways to specify what part of the file you
7681 want to print if you want to see other parts of the program:
7684 @item edit @var{location}
7685 Edit the source file specified by @code{location}. Editing starts at
7686 that @var{location}, e.g., at the specified source line of the
7687 specified file. @xref{Specify Location}, for all the possible forms
7688 of the @var{location} argument; here are the forms of the @code{edit}
7689 command most commonly used:
7692 @item edit @var{number}
7693 Edit the current source file with @var{number} as the active line number.
7695 @item edit @var{function}
7696 Edit the file containing @var{function} at the beginning of its definition.
7701 @subsection Choosing your Editor
7702 You can customize @value{GDBN} to use any editor you want
7704 The only restriction is that your editor (say @code{ex}), recognizes the
7705 following command-line syntax:
7707 ex +@var{number} file
7709 The optional numeric value +@var{number} specifies the number of the line in
7710 the file where to start editing.}.
7711 By default, it is @file{@value{EDITOR}}, but you can change this
7712 by setting the environment variable @code{EDITOR} before using
7713 @value{GDBN}. For example, to configure @value{GDBN} to use the
7714 @code{vi} editor, you could use these commands with the @code{sh} shell:
7720 or in the @code{csh} shell,
7722 setenv EDITOR /usr/bin/vi
7727 @section Searching Source Files
7728 @cindex searching source files
7730 There are two commands for searching through the current source file for a
7735 @kindex forward-search
7736 @kindex fo @r{(@code{forward-search})}
7737 @item forward-search @var{regexp}
7738 @itemx search @var{regexp}
7739 The command @samp{forward-search @var{regexp}} checks each line,
7740 starting with the one following the last line listed, for a match for
7741 @var{regexp}. It lists the line that is found. You can use the
7742 synonym @samp{search @var{regexp}} or abbreviate the command name as
7745 @kindex reverse-search
7746 @item reverse-search @var{regexp}
7747 The command @samp{reverse-search @var{regexp}} checks each line, starting
7748 with the one before the last line listed and going backward, for a match
7749 for @var{regexp}. It lists the line that is found. You can abbreviate
7750 this command as @code{rev}.
7754 @section Specifying Source Directories
7757 @cindex directories for source files
7758 Executable programs sometimes do not record the directories of the source
7759 files from which they were compiled, just the names. Even when they do,
7760 the directories could be moved between the compilation and your debugging
7761 session. @value{GDBN} has a list of directories to search for source files;
7762 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7763 it tries all the directories in the list, in the order they are present
7764 in the list, until it finds a file with the desired name.
7766 For example, suppose an executable references the file
7767 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7768 @file{/mnt/cross}. The file is first looked up literally; if this
7769 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7770 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7771 message is printed. @value{GDBN} does not look up the parts of the
7772 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7773 Likewise, the subdirectories of the source path are not searched: if
7774 the source path is @file{/mnt/cross}, and the binary refers to
7775 @file{foo.c}, @value{GDBN} would not find it under
7776 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7778 Plain file names, relative file names with leading directories, file
7779 names containing dots, etc.@: are all treated as described above; for
7780 instance, if the source path is @file{/mnt/cross}, and the source file
7781 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7782 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7783 that---@file{/mnt/cross/foo.c}.
7785 Note that the executable search path is @emph{not} used to locate the
7788 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7789 any information it has cached about where source files are found and where
7790 each line is in the file.
7794 When you start @value{GDBN}, its source path includes only @samp{cdir}
7795 and @samp{cwd}, in that order.
7796 To add other directories, use the @code{directory} command.
7798 The search path is used to find both program source files and @value{GDBN}
7799 script files (read using the @samp{-command} option and @samp{source} command).
7801 In addition to the source path, @value{GDBN} provides a set of commands
7802 that manage a list of source path substitution rules. A @dfn{substitution
7803 rule} specifies how to rewrite source directories stored in the program's
7804 debug information in case the sources were moved to a different
7805 directory between compilation and debugging. A rule is made of
7806 two strings, the first specifying what needs to be rewritten in
7807 the path, and the second specifying how it should be rewritten.
7808 In @ref{set substitute-path}, we name these two parts @var{from} and
7809 @var{to} respectively. @value{GDBN} does a simple string replacement
7810 of @var{from} with @var{to} at the start of the directory part of the
7811 source file name, and uses that result instead of the original file
7812 name to look up the sources.
7814 Using the previous example, suppose the @file{foo-1.0} tree has been
7815 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7816 @value{GDBN} to replace @file{/usr/src} in all source path names with
7817 @file{/mnt/cross}. The first lookup will then be
7818 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7819 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7820 substitution rule, use the @code{set substitute-path} command
7821 (@pxref{set substitute-path}).
7823 To avoid unexpected substitution results, a rule is applied only if the
7824 @var{from} part of the directory name ends at a directory separator.
7825 For instance, a rule substituting @file{/usr/source} into
7826 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7827 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7828 is applied only at the beginning of the directory name, this rule will
7829 not be applied to @file{/root/usr/source/baz.c} either.
7831 In many cases, you can achieve the same result using the @code{directory}
7832 command. However, @code{set substitute-path} can be more efficient in
7833 the case where the sources are organized in a complex tree with multiple
7834 subdirectories. With the @code{directory} command, you need to add each
7835 subdirectory of your project. If you moved the entire tree while
7836 preserving its internal organization, then @code{set substitute-path}
7837 allows you to direct the debugger to all the sources with one single
7840 @code{set substitute-path} is also more than just a shortcut command.
7841 The source path is only used if the file at the original location no
7842 longer exists. On the other hand, @code{set substitute-path} modifies
7843 the debugger behavior to look at the rewritten location instead. So, if
7844 for any reason a source file that is not relevant to your executable is
7845 located at the original location, a substitution rule is the only
7846 method available to point @value{GDBN} at the new location.
7848 @cindex @samp{--with-relocated-sources}
7849 @cindex default source path substitution
7850 You can configure a default source path substitution rule by
7851 configuring @value{GDBN} with the
7852 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7853 should be the name of a directory under @value{GDBN}'s configured
7854 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7855 directory names in debug information under @var{dir} will be adjusted
7856 automatically if the installed @value{GDBN} is moved to a new
7857 location. This is useful if @value{GDBN}, libraries or executables
7858 with debug information and corresponding source code are being moved
7862 @item directory @var{dirname} @dots{}
7863 @item dir @var{dirname} @dots{}
7864 Add directory @var{dirname} to the front of the source path. Several
7865 directory names may be given to this command, separated by @samp{:}
7866 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7867 part of absolute file names) or
7868 whitespace. You may specify a directory that is already in the source
7869 path; this moves it forward, so @value{GDBN} searches it sooner.
7873 @vindex $cdir@r{, convenience variable}
7874 @vindex $cwd@r{, convenience variable}
7875 @cindex compilation directory
7876 @cindex current directory
7877 @cindex working directory
7878 @cindex directory, current
7879 @cindex directory, compilation
7880 You can use the string @samp{$cdir} to refer to the compilation
7881 directory (if one is recorded), and @samp{$cwd} to refer to the current
7882 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7883 tracks the current working directory as it changes during your @value{GDBN}
7884 session, while the latter is immediately expanded to the current
7885 directory at the time you add an entry to the source path.
7888 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7890 @c RET-repeat for @code{directory} is explicitly disabled, but since
7891 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7893 @item set directories @var{path-list}
7894 @kindex set directories
7895 Set the source path to @var{path-list}.
7896 @samp{$cdir:$cwd} are added if missing.
7898 @item show directories
7899 @kindex show directories
7900 Print the source path: show which directories it contains.
7902 @anchor{set substitute-path}
7903 @item set substitute-path @var{from} @var{to}
7904 @kindex set substitute-path
7905 Define a source path substitution rule, and add it at the end of the
7906 current list of existing substitution rules. If a rule with the same
7907 @var{from} was already defined, then the old rule is also deleted.
7909 For example, if the file @file{/foo/bar/baz.c} was moved to
7910 @file{/mnt/cross/baz.c}, then the command
7913 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7917 will tell @value{GDBN} to replace @samp{/usr/src} with
7918 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7919 @file{baz.c} even though it was moved.
7921 In the case when more than one substitution rule have been defined,
7922 the rules are evaluated one by one in the order where they have been
7923 defined. The first one matching, if any, is selected to perform
7926 For instance, if we had entered the following commands:
7929 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7930 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7934 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7935 @file{/mnt/include/defs.h} by using the first rule. However, it would
7936 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7937 @file{/mnt/src/lib/foo.c}.
7940 @item unset substitute-path [path]
7941 @kindex unset substitute-path
7942 If a path is specified, search the current list of substitution rules
7943 for a rule that would rewrite that path. Delete that rule if found.
7944 A warning is emitted by the debugger if no rule could be found.
7946 If no path is specified, then all substitution rules are deleted.
7948 @item show substitute-path [path]
7949 @kindex show substitute-path
7950 If a path is specified, then print the source path substitution rule
7951 which would rewrite that path, if any.
7953 If no path is specified, then print all existing source path substitution
7958 If your source path is cluttered with directories that are no longer of
7959 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7960 versions of source. You can correct the situation as follows:
7964 Use @code{directory} with no argument to reset the source path to its default value.
7967 Use @code{directory} with suitable arguments to reinstall the
7968 directories you want in the source path. You can add all the
7969 directories in one command.
7973 @section Source and Machine Code
7974 @cindex source line and its code address
7976 You can use the command @code{info line} to map source lines to program
7977 addresses (and vice versa), and the command @code{disassemble} to display
7978 a range of addresses as machine instructions. You can use the command
7979 @code{set disassemble-next-line} to set whether to disassemble next
7980 source line when execution stops. When run under @sc{gnu} Emacs
7981 mode, the @code{info line} command causes the arrow to point to the
7982 line specified. Also, @code{info line} prints addresses in symbolic form as
7987 @item info line @var{linespec}
7988 Print the starting and ending addresses of the compiled code for
7989 source line @var{linespec}. You can specify source lines in any of
7990 the ways documented in @ref{Specify Location}.
7993 For example, we can use @code{info line} to discover the location of
7994 the object code for the first line of function
7995 @code{m4_changequote}:
7997 @c FIXME: I think this example should also show the addresses in
7998 @c symbolic form, as they usually would be displayed.
8000 (@value{GDBP}) info line m4_changequote
8001 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8005 @cindex code address and its source line
8006 We can also inquire (using @code{*@var{addr}} as the form for
8007 @var{linespec}) what source line covers a particular address:
8009 (@value{GDBP}) info line *0x63ff
8010 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8013 @cindex @code{$_} and @code{info line}
8014 @cindex @code{x} command, default address
8015 @kindex x@r{(examine), and} info line
8016 After @code{info line}, the default address for the @code{x} command
8017 is changed to the starting address of the line, so that @samp{x/i} is
8018 sufficient to begin examining the machine code (@pxref{Memory,
8019 ,Examining Memory}). Also, this address is saved as the value of the
8020 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8025 @cindex assembly instructions
8026 @cindex instructions, assembly
8027 @cindex machine instructions
8028 @cindex listing machine instructions
8030 @itemx disassemble /m
8031 @itemx disassemble /r
8032 This specialized command dumps a range of memory as machine
8033 instructions. It can also print mixed source+disassembly by specifying
8034 the @code{/m} modifier and print the raw instructions in hex as well as
8035 in symbolic form by specifying the @code{/r}.
8036 The default memory range is the function surrounding the
8037 program counter of the selected frame. A single argument to this
8038 command is a program counter value; @value{GDBN} dumps the function
8039 surrounding this value. When two arguments are given, they should
8040 be separated by a comma, possibly surrounded by whitespace. The
8041 arguments specify a range of addresses to dump, in one of two forms:
8044 @item @var{start},@var{end}
8045 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8046 @item @var{start},+@var{length}
8047 the addresses from @var{start} (inclusive) to
8048 @code{@var{start}+@var{length}} (exclusive).
8052 When 2 arguments are specified, the name of the function is also
8053 printed (since there could be several functions in the given range).
8055 The argument(s) can be any expression yielding a numeric value, such as
8056 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8058 If the range of memory being disassembled contains current program counter,
8059 the instruction at that location is shown with a @code{=>} marker.
8062 The following example shows the disassembly of a range of addresses of
8063 HP PA-RISC 2.0 code:
8066 (@value{GDBP}) disas 0x32c4, 0x32e4
8067 Dump of assembler code from 0x32c4 to 0x32e4:
8068 0x32c4 <main+204>: addil 0,dp
8069 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8070 0x32cc <main+212>: ldil 0x3000,r31
8071 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8072 0x32d4 <main+220>: ldo 0(r31),rp
8073 0x32d8 <main+224>: addil -0x800,dp
8074 0x32dc <main+228>: ldo 0x588(r1),r26
8075 0x32e0 <main+232>: ldil 0x3000,r31
8076 End of assembler dump.
8079 Here is an example showing mixed source+assembly for Intel x86, when the
8080 program is stopped just after function prologue:
8083 (@value{GDBP}) disas /m main
8084 Dump of assembler code for function main:
8086 0x08048330 <+0>: push %ebp
8087 0x08048331 <+1>: mov %esp,%ebp
8088 0x08048333 <+3>: sub $0x8,%esp
8089 0x08048336 <+6>: and $0xfffffff0,%esp
8090 0x08048339 <+9>: sub $0x10,%esp
8092 6 printf ("Hello.\n");
8093 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8094 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8098 0x08048348 <+24>: mov $0x0,%eax
8099 0x0804834d <+29>: leave
8100 0x0804834e <+30>: ret
8102 End of assembler dump.
8105 Here is another example showing raw instructions in hex for AMD x86-64,
8108 (gdb) disas /r 0x400281,+10
8109 Dump of assembler code from 0x400281 to 0x40028b:
8110 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8111 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8112 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8113 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8114 End of assembler dump.
8117 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8118 So, for example, if you want to disassemble function @code{bar}
8119 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8120 and not @samp{disassemble foo.c:bar}.
8122 Some architectures have more than one commonly-used set of instruction
8123 mnemonics or other syntax.
8125 For programs that were dynamically linked and use shared libraries,
8126 instructions that call functions or branch to locations in the shared
8127 libraries might show a seemingly bogus location---it's actually a
8128 location of the relocation table. On some architectures, @value{GDBN}
8129 might be able to resolve these to actual function names.
8132 @kindex set disassembly-flavor
8133 @cindex Intel disassembly flavor
8134 @cindex AT&T disassembly flavor
8135 @item set disassembly-flavor @var{instruction-set}
8136 Select the instruction set to use when disassembling the
8137 program via the @code{disassemble} or @code{x/i} commands.
8139 Currently this command is only defined for the Intel x86 family. You
8140 can set @var{instruction-set} to either @code{intel} or @code{att}.
8141 The default is @code{att}, the AT&T flavor used by default by Unix
8142 assemblers for x86-based targets.
8144 @kindex show disassembly-flavor
8145 @item show disassembly-flavor
8146 Show the current setting of the disassembly flavor.
8150 @kindex set disassemble-next-line
8151 @kindex show disassemble-next-line
8152 @item set disassemble-next-line
8153 @itemx show disassemble-next-line
8154 Control whether or not @value{GDBN} will disassemble the next source
8155 line or instruction when execution stops. If ON, @value{GDBN} will
8156 display disassembly of the next source line when execution of the
8157 program being debugged stops. This is @emph{in addition} to
8158 displaying the source line itself, which @value{GDBN} always does if
8159 possible. If the next source line cannot be displayed for some reason
8160 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8161 info in the debug info), @value{GDBN} will display disassembly of the
8162 next @emph{instruction} instead of showing the next source line. If
8163 AUTO, @value{GDBN} will display disassembly of next instruction only
8164 if the source line cannot be displayed. This setting causes
8165 @value{GDBN} to display some feedback when you step through a function
8166 with no line info or whose source file is unavailable. The default is
8167 OFF, which means never display the disassembly of the next line or
8173 @chapter Examining Data
8175 @cindex printing data
8176 @cindex examining data
8179 The usual way to examine data in your program is with the @code{print}
8180 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8181 evaluates and prints the value of an expression of the language your
8182 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8183 Different Languages}). It may also print the expression using a
8184 Python-based pretty-printer (@pxref{Pretty Printing}).
8187 @item print @var{expr}
8188 @itemx print /@var{f} @var{expr}
8189 @var{expr} is an expression (in the source language). By default the
8190 value of @var{expr} is printed in a format appropriate to its data type;
8191 you can choose a different format by specifying @samp{/@var{f}}, where
8192 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8196 @itemx print /@var{f}
8197 @cindex reprint the last value
8198 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8199 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8200 conveniently inspect the same value in an alternative format.
8203 A more low-level way of examining data is with the @code{x} command.
8204 It examines data in memory at a specified address and prints it in a
8205 specified format. @xref{Memory, ,Examining Memory}.
8207 If you are interested in information about types, or about how the
8208 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8209 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8212 @cindex exploring hierarchical data structures
8214 Another way of examining values of expressions and type information is
8215 through the Python extension command @code{explore} (available only if
8216 the @value{GDBN} build is configured with @code{--with-python}). It
8217 offers an interactive way to start at the highest level (or, the most
8218 abstract level) of the data type of an expression (or, the data type
8219 itself) and explore all the way down to leaf scalar values/fields
8220 embedded in the higher level data types.
8223 @item explore @var{arg}
8224 @var{arg} is either an expression (in the source language), or a type
8225 visible in the current context of the program being debugged.
8228 The working of the @code{explore} command can be illustrated with an
8229 example. If a data type @code{struct ComplexStruct} is defined in your
8239 struct ComplexStruct
8241 struct SimpleStruct *ss_p;
8247 followed by variable declarations as
8250 struct SimpleStruct ss = @{ 10, 1.11 @};
8251 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8255 then, the value of the variable @code{cs} can be explored using the
8256 @code{explore} command as follows.
8260 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8261 the following fields:
8263 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8264 arr = <Enter 1 to explore this field of type `int [10]'>
8266 Enter the field number of choice:
8270 Since the fields of @code{cs} are not scalar values, you are being
8271 prompted to chose the field you want to explore. Let's say you choose
8272 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8273 pointer, you will be asked if it is pointing to a single value. From
8274 the declaration of @code{cs} above, it is indeed pointing to a single
8275 value, hence you enter @code{y}. If you enter @code{n}, then you will
8276 be asked if it were pointing to an array of values, in which case this
8277 field will be explored as if it were an array.
8280 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8281 Continue exploring it as a pointer to a single value [y/n]: y
8282 The value of `*(cs.ss_p)' is a struct/class of type `struct
8283 SimpleStruct' with the following fields:
8285 i = 10 .. (Value of type `int')
8286 d = 1.1100000000000001 .. (Value of type `double')
8288 Press enter to return to parent value:
8292 If the field @code{arr} of @code{cs} was chosen for exploration by
8293 entering @code{1} earlier, then since it is as array, you will be
8294 prompted to enter the index of the element in the array that you want
8298 `cs.arr' is an array of `int'.
8299 Enter the index of the element you want to explore in `cs.arr': 5
8301 `(cs.arr)[5]' is a scalar value of type `int'.
8305 Press enter to return to parent value:
8308 In general, at any stage of exploration, you can go deeper towards the
8309 leaf values by responding to the prompts appropriately, or hit the
8310 return key to return to the enclosing data structure (the @i{higher}
8311 level data structure).
8313 Similar to exploring values, you can use the @code{explore} command to
8314 explore types. Instead of specifying a value (which is typically a
8315 variable name or an expression valid in the current context of the
8316 program being debugged), you specify a type name. If you consider the
8317 same example as above, your can explore the type
8318 @code{struct ComplexStruct} by passing the argument
8319 @code{struct ComplexStruct} to the @code{explore} command.
8322 (gdb) explore struct ComplexStruct
8326 By responding to the prompts appropriately in the subsequent interactive
8327 session, you can explore the type @code{struct ComplexStruct} in a
8328 manner similar to how the value @code{cs} was explored in the above
8331 The @code{explore} command also has two sub-commands,
8332 @code{explore value} and @code{explore type}. The former sub-command is
8333 a way to explicitly specify that value exploration of the argument is
8334 being invoked, while the latter is a way to explicitly specify that type
8335 exploration of the argument is being invoked.
8338 @item explore value @var{expr}
8339 @cindex explore value
8340 This sub-command of @code{explore} explores the value of the
8341 expression @var{expr} (if @var{expr} is an expression valid in the
8342 current context of the program being debugged). The behavior of this
8343 command is identical to that of the behavior of the @code{explore}
8344 command being passed the argument @var{expr}.
8346 @item explore type @var{arg}
8347 @cindex explore type
8348 This sub-command of @code{explore} explores the type of @var{arg} (if
8349 @var{arg} is a type visible in the current context of program being
8350 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8351 is an expression valid in the current context of the program being
8352 debugged). If @var{arg} is a type, then the behavior of this command is
8353 identical to that of the @code{explore} command being passed the
8354 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8355 this command will be identical to that of the @code{explore} command
8356 being passed the type of @var{arg} as the argument.
8360 * Expressions:: Expressions
8361 * Ambiguous Expressions:: Ambiguous Expressions
8362 * Variables:: Program variables
8363 * Arrays:: Artificial arrays
8364 * Output Formats:: Output formats
8365 * Memory:: Examining memory
8366 * Auto Display:: Automatic display
8367 * Print Settings:: Print settings
8368 * Pretty Printing:: Python pretty printing
8369 * Value History:: Value history
8370 * Convenience Vars:: Convenience variables
8371 * Convenience Funs:: Convenience functions
8372 * Registers:: Registers
8373 * Floating Point Hardware:: Floating point hardware
8374 * Vector Unit:: Vector Unit
8375 * OS Information:: Auxiliary data provided by operating system
8376 * Memory Region Attributes:: Memory region attributes
8377 * Dump/Restore Files:: Copy between memory and a file
8378 * Core File Generation:: Cause a program dump its core
8379 * Character Sets:: Debugging programs that use a different
8380 character set than GDB does
8381 * Caching Target Data:: Data caching for targets
8382 * Searching Memory:: Searching memory for a sequence of bytes
8386 @section Expressions
8389 @code{print} and many other @value{GDBN} commands accept an expression and
8390 compute its value. Any kind of constant, variable or operator defined
8391 by the programming language you are using is valid in an expression in
8392 @value{GDBN}. This includes conditional expressions, function calls,
8393 casts, and string constants. It also includes preprocessor macros, if
8394 you compiled your program to include this information; see
8397 @cindex arrays in expressions
8398 @value{GDBN} supports array constants in expressions input by
8399 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8400 you can use the command @code{print @{1, 2, 3@}} to create an array
8401 of three integers. If you pass an array to a function or assign it
8402 to a program variable, @value{GDBN} copies the array to memory that
8403 is @code{malloc}ed in the target program.
8405 Because C is so widespread, most of the expressions shown in examples in
8406 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8407 Languages}, for information on how to use expressions in other
8410 In this section, we discuss operators that you can use in @value{GDBN}
8411 expressions regardless of your programming language.
8413 @cindex casts, in expressions
8414 Casts are supported in all languages, not just in C, because it is so
8415 useful to cast a number into a pointer in order to examine a structure
8416 at that address in memory.
8417 @c FIXME: casts supported---Mod2 true?
8419 @value{GDBN} supports these operators, in addition to those common
8420 to programming languages:
8424 @samp{@@} is a binary operator for treating parts of memory as arrays.
8425 @xref{Arrays, ,Artificial Arrays}, for more information.
8428 @samp{::} allows you to specify a variable in terms of the file or
8429 function where it is defined. @xref{Variables, ,Program Variables}.
8431 @cindex @{@var{type}@}
8432 @cindex type casting memory
8433 @cindex memory, viewing as typed object
8434 @cindex casts, to view memory
8435 @item @{@var{type}@} @var{addr}
8436 Refers to an object of type @var{type} stored at address @var{addr} in
8437 memory. The address @var{addr} may be any expression whose value is
8438 an integer or pointer (but parentheses are required around binary
8439 operators, just as in a cast). This construct is allowed regardless
8440 of what kind of data is normally supposed to reside at @var{addr}.
8443 @node Ambiguous Expressions
8444 @section Ambiguous Expressions
8445 @cindex ambiguous expressions
8447 Expressions can sometimes contain some ambiguous elements. For instance,
8448 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8449 a single function name to be defined several times, for application in
8450 different contexts. This is called @dfn{overloading}. Another example
8451 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8452 templates and is typically instantiated several times, resulting in
8453 the same function name being defined in different contexts.
8455 In some cases and depending on the language, it is possible to adjust
8456 the expression to remove the ambiguity. For instance in C@t{++}, you
8457 can specify the signature of the function you want to break on, as in
8458 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8459 qualified name of your function often makes the expression unambiguous
8462 When an ambiguity that needs to be resolved is detected, the debugger
8463 has the capability to display a menu of numbered choices for each
8464 possibility, and then waits for the selection with the prompt @samp{>}.
8465 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8466 aborts the current command. If the command in which the expression was
8467 used allows more than one choice to be selected, the next option in the
8468 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8471 For example, the following session excerpt shows an attempt to set a
8472 breakpoint at the overloaded symbol @code{String::after}.
8473 We choose three particular definitions of that function name:
8475 @c FIXME! This is likely to change to show arg type lists, at least
8478 (@value{GDBP}) b String::after
8481 [2] file:String.cc; line number:867
8482 [3] file:String.cc; line number:860
8483 [4] file:String.cc; line number:875
8484 [5] file:String.cc; line number:853
8485 [6] file:String.cc; line number:846
8486 [7] file:String.cc; line number:735
8488 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8489 Breakpoint 2 at 0xb344: file String.cc, line 875.
8490 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8491 Multiple breakpoints were set.
8492 Use the "delete" command to delete unwanted
8499 @kindex set multiple-symbols
8500 @item set multiple-symbols @var{mode}
8501 @cindex multiple-symbols menu
8503 This option allows you to adjust the debugger behavior when an expression
8506 By default, @var{mode} is set to @code{all}. If the command with which
8507 the expression is used allows more than one choice, then @value{GDBN}
8508 automatically selects all possible choices. For instance, inserting
8509 a breakpoint on a function using an ambiguous name results in a breakpoint
8510 inserted on each possible match. However, if a unique choice must be made,
8511 then @value{GDBN} uses the menu to help you disambiguate the expression.
8512 For instance, printing the address of an overloaded function will result
8513 in the use of the menu.
8515 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8516 when an ambiguity is detected.
8518 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8519 an error due to the ambiguity and the command is aborted.
8521 @kindex show multiple-symbols
8522 @item show multiple-symbols
8523 Show the current value of the @code{multiple-symbols} setting.
8527 @section Program Variables
8529 The most common kind of expression to use is the name of a variable
8532 Variables in expressions are understood in the selected stack frame
8533 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8537 global (or file-static)
8544 visible according to the scope rules of the
8545 programming language from the point of execution in that frame
8548 @noindent This means that in the function
8563 you can examine and use the variable @code{a} whenever your program is
8564 executing within the function @code{foo}, but you can only use or
8565 examine the variable @code{b} while your program is executing inside
8566 the block where @code{b} is declared.
8568 @cindex variable name conflict
8569 There is an exception: you can refer to a variable or function whose
8570 scope is a single source file even if the current execution point is not
8571 in this file. But it is possible to have more than one such variable or
8572 function with the same name (in different source files). If that
8573 happens, referring to that name has unpredictable effects. If you wish,
8574 you can specify a static variable in a particular function or file by
8575 using the colon-colon (@code{::}) notation:
8577 @cindex colon-colon, context for variables/functions
8579 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8580 @cindex @code{::}, context for variables/functions
8583 @var{file}::@var{variable}
8584 @var{function}::@var{variable}
8588 Here @var{file} or @var{function} is the name of the context for the
8589 static @var{variable}. In the case of file names, you can use quotes to
8590 make sure @value{GDBN} parses the file name as a single word---for example,
8591 to print a global value of @code{x} defined in @file{f2.c}:
8594 (@value{GDBP}) p 'f2.c'::x
8597 The @code{::} notation is normally used for referring to
8598 static variables, since you typically disambiguate uses of local variables
8599 in functions by selecting the appropriate frame and using the
8600 simple name of the variable. However, you may also use this notation
8601 to refer to local variables in frames enclosing the selected frame:
8610 process (a); /* Stop here */
8621 For example, if there is a breakpoint at the commented line,
8622 here is what you might see
8623 when the program stops after executing the call @code{bar(0)}:
8628 (@value{GDBP}) p bar::a
8631 #2 0x080483d0 in foo (a=5) at foobar.c:12
8634 (@value{GDBP}) p bar::a
8638 @cindex C@t{++} scope resolution
8639 These uses of @samp{::} are very rarely in conflict with the very
8640 similar use of the same notation in C@t{++}. When they are in
8641 conflict, the C@t{++} meaning takes precedence; however, this can be
8642 overridden by quoting the file or function name with single quotes.
8644 For example, suppose the program is stopped in a method of a class
8645 that has a field named @code{includefile}, and there is also an
8646 include file named @file{includefile} that defines a variable,
8650 (@value{GDBP}) p includefile
8652 (@value{GDBP}) p includefile::some_global
8653 A syntax error in expression, near `'.
8654 (@value{GDBP}) p 'includefile'::some_global
8658 @cindex wrong values
8659 @cindex variable values, wrong
8660 @cindex function entry/exit, wrong values of variables
8661 @cindex optimized code, wrong values of variables
8663 @emph{Warning:} Occasionally, a local variable may appear to have the
8664 wrong value at certain points in a function---just after entry to a new
8665 scope, and just before exit.
8667 You may see this problem when you are stepping by machine instructions.
8668 This is because, on most machines, it takes more than one instruction to
8669 set up a stack frame (including local variable definitions); if you are
8670 stepping by machine instructions, variables may appear to have the wrong
8671 values until the stack frame is completely built. On exit, it usually
8672 also takes more than one machine instruction to destroy a stack frame;
8673 after you begin stepping through that group of instructions, local
8674 variable definitions may be gone.
8676 This may also happen when the compiler does significant optimizations.
8677 To be sure of always seeing accurate values, turn off all optimization
8680 @cindex ``No symbol "foo" in current context''
8681 Another possible effect of compiler optimizations is to optimize
8682 unused variables out of existence, or assign variables to registers (as
8683 opposed to memory addresses). Depending on the support for such cases
8684 offered by the debug info format used by the compiler, @value{GDBN}
8685 might not be able to display values for such local variables. If that
8686 happens, @value{GDBN} will print a message like this:
8689 No symbol "foo" in current context.
8692 To solve such problems, either recompile without optimizations, or use a
8693 different debug info format, if the compiler supports several such
8694 formats. @xref{Compilation}, for more information on choosing compiler
8695 options. @xref{C, ,C and C@t{++}}, for more information about debug
8696 info formats that are best suited to C@t{++} programs.
8698 If you ask to print an object whose contents are unknown to
8699 @value{GDBN}, e.g., because its data type is not completely specified
8700 by the debug information, @value{GDBN} will say @samp{<incomplete
8701 type>}. @xref{Symbols, incomplete type}, for more about this.
8703 If you append @kbd{@@entry} string to a function parameter name you get its
8704 value at the time the function got called. If the value is not available an
8705 error message is printed. Entry values are available only with some compilers.
8706 Entry values are normally also printed at the function parameter list according
8707 to @ref{set print entry-values}.
8710 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8716 (gdb) print i@@entry
8720 Strings are identified as arrays of @code{char} values without specified
8721 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8722 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8723 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8724 defines literal string type @code{"char"} as @code{char} without a sign.
8729 signed char var1[] = "A";
8732 You get during debugging
8737 $2 = @{65 'A', 0 '\0'@}
8741 @section Artificial Arrays
8743 @cindex artificial array
8745 @kindex @@@r{, referencing memory as an array}
8746 It is often useful to print out several successive objects of the
8747 same type in memory; a section of an array, or an array of
8748 dynamically determined size for which only a pointer exists in the
8751 You can do this by referring to a contiguous span of memory as an
8752 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8753 operand of @samp{@@} should be the first element of the desired array
8754 and be an individual object. The right operand should be the desired length
8755 of the array. The result is an array value whose elements are all of
8756 the type of the left argument. The first element is actually the left
8757 argument; the second element comes from bytes of memory immediately
8758 following those that hold the first element, and so on. Here is an
8759 example. If a program says
8762 int *array = (int *) malloc (len * sizeof (int));
8766 you can print the contents of @code{array} with
8772 The left operand of @samp{@@} must reside in memory. Array values made
8773 with @samp{@@} in this way behave just like other arrays in terms of
8774 subscripting, and are coerced to pointers when used in expressions.
8775 Artificial arrays most often appear in expressions via the value history
8776 (@pxref{Value History, ,Value History}), after printing one out.
8778 Another way to create an artificial array is to use a cast.
8779 This re-interprets a value as if it were an array.
8780 The value need not be in memory:
8782 (@value{GDBP}) p/x (short[2])0x12345678
8783 $1 = @{0x1234, 0x5678@}
8786 As a convenience, if you leave the array length out (as in
8787 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8788 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8790 (@value{GDBP}) p/x (short[])0x12345678
8791 $2 = @{0x1234, 0x5678@}
8794 Sometimes the artificial array mechanism is not quite enough; in
8795 moderately complex data structures, the elements of interest may not
8796 actually be adjacent---for example, if you are interested in the values
8797 of pointers in an array. One useful work-around in this situation is
8798 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8799 Variables}) as a counter in an expression that prints the first
8800 interesting value, and then repeat that expression via @key{RET}. For
8801 instance, suppose you have an array @code{dtab} of pointers to
8802 structures, and you are interested in the values of a field @code{fv}
8803 in each structure. Here is an example of what you might type:
8813 @node Output Formats
8814 @section Output Formats
8816 @cindex formatted output
8817 @cindex output formats
8818 By default, @value{GDBN} prints a value according to its data type. Sometimes
8819 this is not what you want. For example, you might want to print a number
8820 in hex, or a pointer in decimal. Or you might want to view data in memory
8821 at a certain address as a character string or as an instruction. To do
8822 these things, specify an @dfn{output format} when you print a value.
8824 The simplest use of output formats is to say how to print a value
8825 already computed. This is done by starting the arguments of the
8826 @code{print} command with a slash and a format letter. The format
8827 letters supported are:
8831 Regard the bits of the value as an integer, and print the integer in
8835 Print as integer in signed decimal.
8838 Print as integer in unsigned decimal.
8841 Print as integer in octal.
8844 Print as integer in binary. The letter @samp{t} stands for ``two''.
8845 @footnote{@samp{b} cannot be used because these format letters are also
8846 used with the @code{x} command, where @samp{b} stands for ``byte'';
8847 see @ref{Memory,,Examining Memory}.}
8850 @cindex unknown address, locating
8851 @cindex locate address
8852 Print as an address, both absolute in hexadecimal and as an offset from
8853 the nearest preceding symbol. You can use this format used to discover
8854 where (in what function) an unknown address is located:
8857 (@value{GDBP}) p/a 0x54320
8858 $3 = 0x54320 <_initialize_vx+396>
8862 The command @code{info symbol 0x54320} yields similar results.
8863 @xref{Symbols, info symbol}.
8866 Regard as an integer and print it as a character constant. This
8867 prints both the numerical value and its character representation. The
8868 character representation is replaced with the octal escape @samp{\nnn}
8869 for characters outside the 7-bit @sc{ascii} range.
8871 Without this format, @value{GDBN} displays @code{char},
8872 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8873 constants. Single-byte members of vectors are displayed as integer
8877 Regard the bits of the value as a floating point number and print
8878 using typical floating point syntax.
8881 @cindex printing strings
8882 @cindex printing byte arrays
8883 Regard as a string, if possible. With this format, pointers to single-byte
8884 data are displayed as null-terminated strings and arrays of single-byte data
8885 are displayed as fixed-length strings. Other values are displayed in their
8888 Without this format, @value{GDBN} displays pointers to and arrays of
8889 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8890 strings. Single-byte members of a vector are displayed as an integer
8894 Like @samp{x} formatting, the value is treated as an integer and
8895 printed as hexadecimal, but leading zeros are printed to pad the value
8896 to the size of the integer type.
8899 @cindex raw printing
8900 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8901 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8902 Printing}). This typically results in a higher-level display of the
8903 value's contents. The @samp{r} format bypasses any Python
8904 pretty-printer which might exist.
8907 For example, to print the program counter in hex (@pxref{Registers}), type
8914 Note that no space is required before the slash; this is because command
8915 names in @value{GDBN} cannot contain a slash.
8917 To reprint the last value in the value history with a different format,
8918 you can use the @code{print} command with just a format and no
8919 expression. For example, @samp{p/x} reprints the last value in hex.
8922 @section Examining Memory
8924 You can use the command @code{x} (for ``examine'') to examine memory in
8925 any of several formats, independently of your program's data types.
8927 @cindex examining memory
8929 @kindex x @r{(examine memory)}
8930 @item x/@var{nfu} @var{addr}
8933 Use the @code{x} command to examine memory.
8936 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8937 much memory to display and how to format it; @var{addr} is an
8938 expression giving the address where you want to start displaying memory.
8939 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8940 Several commands set convenient defaults for @var{addr}.
8943 @item @var{n}, the repeat count
8944 The repeat count is a decimal integer; the default is 1. It specifies
8945 how much memory (counting by units @var{u}) to display.
8946 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8949 @item @var{f}, the display format
8950 The display format is one of the formats used by @code{print}
8951 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8952 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8953 The default is @samp{x} (hexadecimal) initially. The default changes
8954 each time you use either @code{x} or @code{print}.
8956 @item @var{u}, the unit size
8957 The unit size is any of
8963 Halfwords (two bytes).
8965 Words (four bytes). This is the initial default.
8967 Giant words (eight bytes).
8970 Each time you specify a unit size with @code{x}, that size becomes the
8971 default unit the next time you use @code{x}. For the @samp{i} format,
8972 the unit size is ignored and is normally not written. For the @samp{s} format,
8973 the unit size defaults to @samp{b}, unless it is explicitly given.
8974 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8975 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8976 Note that the results depend on the programming language of the
8977 current compilation unit. If the language is C, the @samp{s}
8978 modifier will use the UTF-16 encoding while @samp{w} will use
8979 UTF-32. The encoding is set by the programming language and cannot
8982 @item @var{addr}, starting display address
8983 @var{addr} is the address where you want @value{GDBN} to begin displaying
8984 memory. The expression need not have a pointer value (though it may);
8985 it is always interpreted as an integer address of a byte of memory.
8986 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8987 @var{addr} is usually just after the last address examined---but several
8988 other commands also set the default address: @code{info breakpoints} (to
8989 the address of the last breakpoint listed), @code{info line} (to the
8990 starting address of a line), and @code{print} (if you use it to display
8991 a value from memory).
8994 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8995 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8996 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8997 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8998 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9000 Since the letters indicating unit sizes are all distinct from the
9001 letters specifying output formats, you do not have to remember whether
9002 unit size or format comes first; either order works. The output
9003 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9004 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9006 Even though the unit size @var{u} is ignored for the formats @samp{s}
9007 and @samp{i}, you might still want to use a count @var{n}; for example,
9008 @samp{3i} specifies that you want to see three machine instructions,
9009 including any operands. For convenience, especially when used with
9010 the @code{display} command, the @samp{i} format also prints branch delay
9011 slot instructions, if any, beyond the count specified, which immediately
9012 follow the last instruction that is within the count. The command
9013 @code{disassemble} gives an alternative way of inspecting machine
9014 instructions; see @ref{Machine Code,,Source and Machine Code}.
9016 All the defaults for the arguments to @code{x} are designed to make it
9017 easy to continue scanning memory with minimal specifications each time
9018 you use @code{x}. For example, after you have inspected three machine
9019 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9020 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9021 the repeat count @var{n} is used again; the other arguments default as
9022 for successive uses of @code{x}.
9024 When examining machine instructions, the instruction at current program
9025 counter is shown with a @code{=>} marker. For example:
9028 (@value{GDBP}) x/5i $pc-6
9029 0x804837f <main+11>: mov %esp,%ebp
9030 0x8048381 <main+13>: push %ecx
9031 0x8048382 <main+14>: sub $0x4,%esp
9032 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9033 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9036 @cindex @code{$_}, @code{$__}, and value history
9037 The addresses and contents printed by the @code{x} command are not saved
9038 in the value history because there is often too much of them and they
9039 would get in the way. Instead, @value{GDBN} makes these values available for
9040 subsequent use in expressions as values of the convenience variables
9041 @code{$_} and @code{$__}. After an @code{x} command, the last address
9042 examined is available for use in expressions in the convenience variable
9043 @code{$_}. The contents of that address, as examined, are available in
9044 the convenience variable @code{$__}.
9046 If the @code{x} command has a repeat count, the address and contents saved
9047 are from the last memory unit printed; this is not the same as the last
9048 address printed if several units were printed on the last line of output.
9050 @anchor{addressable memory unit}
9051 @cindex addressable memory unit
9052 Most targets have an addressable memory unit size of 8 bits. This means
9053 that to each memory address are associated 8 bits of data. Some
9054 targets, however, have other addressable memory unit sizes.
9055 Within @value{GDBN} and this document, the term
9056 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9057 when explicitly referring to a chunk of data of that size. The word
9058 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9059 the addressable memory unit size of the target. For most systems,
9060 addressable memory unit is a synonym of byte.
9062 @cindex remote memory comparison
9063 @cindex target memory comparison
9064 @cindex verify remote memory image
9065 @cindex verify target memory image
9066 When you are debugging a program running on a remote target machine
9067 (@pxref{Remote Debugging}), you may wish to verify the program's image
9068 in the remote machine's memory against the executable file you
9069 downloaded to the target. Or, on any target, you may want to check
9070 whether the program has corrupted its own read-only sections. The
9071 @code{compare-sections} command is provided for such situations.
9074 @kindex compare-sections
9075 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9076 Compare the data of a loadable section @var{section-name} in the
9077 executable file of the program being debugged with the same section in
9078 the target machine's memory, and report any mismatches. With no
9079 arguments, compares all loadable sections. With an argument of
9080 @code{-r}, compares all loadable read-only sections.
9082 Note: for remote targets, this command can be accelerated if the
9083 target supports computing the CRC checksum of a block of memory
9084 (@pxref{qCRC packet}).
9088 @section Automatic Display
9089 @cindex automatic display
9090 @cindex display of expressions
9092 If you find that you want to print the value of an expression frequently
9093 (to see how it changes), you might want to add it to the @dfn{automatic
9094 display list} so that @value{GDBN} prints its value each time your program stops.
9095 Each expression added to the list is given a number to identify it;
9096 to remove an expression from the list, you specify that number.
9097 The automatic display looks like this:
9101 3: bar[5] = (struct hack *) 0x3804
9105 This display shows item numbers, expressions and their current values. As with
9106 displays you request manually using @code{x} or @code{print}, you can
9107 specify the output format you prefer; in fact, @code{display} decides
9108 whether to use @code{print} or @code{x} depending your format
9109 specification---it uses @code{x} if you specify either the @samp{i}
9110 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9114 @item display @var{expr}
9115 Add the expression @var{expr} to the list of expressions to display
9116 each time your program stops. @xref{Expressions, ,Expressions}.
9118 @code{display} does not repeat if you press @key{RET} again after using it.
9120 @item display/@var{fmt} @var{expr}
9121 For @var{fmt} specifying only a display format and not a size or
9122 count, add the expression @var{expr} to the auto-display list but
9123 arrange to display it each time in the specified format @var{fmt}.
9124 @xref{Output Formats,,Output Formats}.
9126 @item display/@var{fmt} @var{addr}
9127 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9128 number of units, add the expression @var{addr} as a memory address to
9129 be examined each time your program stops. Examining means in effect
9130 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9133 For example, @samp{display/i $pc} can be helpful, to see the machine
9134 instruction about to be executed each time execution stops (@samp{$pc}
9135 is a common name for the program counter; @pxref{Registers, ,Registers}).
9138 @kindex delete display
9140 @item undisplay @var{dnums}@dots{}
9141 @itemx delete display @var{dnums}@dots{}
9142 Remove items from the list of expressions to display. Specify the
9143 numbers of the displays that you want affected with the command
9144 argument @var{dnums}. It can be a single display number, one of the
9145 numbers shown in the first field of the @samp{info display} display;
9146 or it could be a range of display numbers, as in @code{2-4}.
9148 @code{undisplay} does not repeat if you press @key{RET} after using it.
9149 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9151 @kindex disable display
9152 @item disable display @var{dnums}@dots{}
9153 Disable the display of item numbers @var{dnums}. A disabled display
9154 item is not printed automatically, but is not forgotten. It may be
9155 enabled again later. Specify the numbers of the displays that you
9156 want affected with the command argument @var{dnums}. It can be a
9157 single display number, one of the numbers shown in the first field of
9158 the @samp{info display} display; or it could be a range of display
9159 numbers, as in @code{2-4}.
9161 @kindex enable display
9162 @item enable display @var{dnums}@dots{}
9163 Enable display of item numbers @var{dnums}. It becomes effective once
9164 again in auto display of its expression, until you specify otherwise.
9165 Specify the numbers of the displays that you want affected with the
9166 command argument @var{dnums}. It can be a single display number, one
9167 of the numbers shown in the first field of the @samp{info display}
9168 display; or it could be a range of display numbers, as in @code{2-4}.
9171 Display the current values of the expressions on the list, just as is
9172 done when your program stops.
9174 @kindex info display
9176 Print the list of expressions previously set up to display
9177 automatically, each one with its item number, but without showing the
9178 values. This includes disabled expressions, which are marked as such.
9179 It also includes expressions which would not be displayed right now
9180 because they refer to automatic variables not currently available.
9183 @cindex display disabled out of scope
9184 If a display expression refers to local variables, then it does not make
9185 sense outside the lexical context for which it was set up. Such an
9186 expression is disabled when execution enters a context where one of its
9187 variables is not defined. For example, if you give the command
9188 @code{display last_char} while inside a function with an argument
9189 @code{last_char}, @value{GDBN} displays this argument while your program
9190 continues to stop inside that function. When it stops elsewhere---where
9191 there is no variable @code{last_char}---the display is disabled
9192 automatically. The next time your program stops where @code{last_char}
9193 is meaningful, you can enable the display expression once again.
9195 @node Print Settings
9196 @section Print Settings
9198 @cindex format options
9199 @cindex print settings
9200 @value{GDBN} provides the following ways to control how arrays, structures,
9201 and symbols are printed.
9204 These settings are useful for debugging programs in any language:
9208 @item set print address
9209 @itemx set print address on
9210 @cindex print/don't print memory addresses
9211 @value{GDBN} prints memory addresses showing the location of stack
9212 traces, structure values, pointer values, breakpoints, and so forth,
9213 even when it also displays the contents of those addresses. The default
9214 is @code{on}. For example, this is what a stack frame display looks like with
9215 @code{set print address on}:
9220 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9222 530 if (lquote != def_lquote)
9226 @item set print address off
9227 Do not print addresses when displaying their contents. For example,
9228 this is the same stack frame displayed with @code{set print address off}:
9232 (@value{GDBP}) set print addr off
9234 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9235 530 if (lquote != def_lquote)
9239 You can use @samp{set print address off} to eliminate all machine
9240 dependent displays from the @value{GDBN} interface. For example, with
9241 @code{print address off}, you should get the same text for backtraces on
9242 all machines---whether or not they involve pointer arguments.
9245 @item show print address
9246 Show whether or not addresses are to be printed.
9249 When @value{GDBN} prints a symbolic address, it normally prints the
9250 closest earlier symbol plus an offset. If that symbol does not uniquely
9251 identify the address (for example, it is a name whose scope is a single
9252 source file), you may need to clarify. One way to do this is with
9253 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9254 you can set @value{GDBN} to print the source file and line number when
9255 it prints a symbolic address:
9258 @item set print symbol-filename on
9259 @cindex source file and line of a symbol
9260 @cindex symbol, source file and line
9261 Tell @value{GDBN} to print the source file name and line number of a
9262 symbol in the symbolic form of an address.
9264 @item set print symbol-filename off
9265 Do not print source file name and line number of a symbol. This is the
9268 @item show print symbol-filename
9269 Show whether or not @value{GDBN} will print the source file name and
9270 line number of a symbol in the symbolic form of an address.
9273 Another situation where it is helpful to show symbol filenames and line
9274 numbers is when disassembling code; @value{GDBN} shows you the line
9275 number and source file that corresponds to each instruction.
9277 Also, you may wish to see the symbolic form only if the address being
9278 printed is reasonably close to the closest earlier symbol:
9281 @item set print max-symbolic-offset @var{max-offset}
9282 @itemx set print max-symbolic-offset unlimited
9283 @cindex maximum value for offset of closest symbol
9284 Tell @value{GDBN} to only display the symbolic form of an address if the
9285 offset between the closest earlier symbol and the address is less than
9286 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9287 to always print the symbolic form of an address if any symbol precedes
9288 it. Zero is equivalent to @code{unlimited}.
9290 @item show print max-symbolic-offset
9291 Ask how large the maximum offset is that @value{GDBN} prints in a
9295 @cindex wild pointer, interpreting
9296 @cindex pointer, finding referent
9297 If you have a pointer and you are not sure where it points, try
9298 @samp{set print symbol-filename on}. Then you can determine the name
9299 and source file location of the variable where it points, using
9300 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9301 For example, here @value{GDBN} shows that a variable @code{ptt} points
9302 at another variable @code{t}, defined in @file{hi2.c}:
9305 (@value{GDBP}) set print symbol-filename on
9306 (@value{GDBP}) p/a ptt
9307 $4 = 0xe008 <t in hi2.c>
9311 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9312 does not show the symbol name and filename of the referent, even with
9313 the appropriate @code{set print} options turned on.
9316 You can also enable @samp{/a}-like formatting all the time using
9317 @samp{set print symbol on}:
9320 @item set print symbol on
9321 Tell @value{GDBN} to print the symbol corresponding to an address, if
9324 @item set print symbol off
9325 Tell @value{GDBN} not to print the symbol corresponding to an
9326 address. In this mode, @value{GDBN} will still print the symbol
9327 corresponding to pointers to functions. This is the default.
9329 @item show print symbol
9330 Show whether @value{GDBN} will display the symbol corresponding to an
9334 Other settings control how different kinds of objects are printed:
9337 @item set print array
9338 @itemx set print array on
9339 @cindex pretty print arrays
9340 Pretty print arrays. This format is more convenient to read,
9341 but uses more space. The default is off.
9343 @item set print array off
9344 Return to compressed format for arrays.
9346 @item show print array
9347 Show whether compressed or pretty format is selected for displaying
9350 @cindex print array indexes
9351 @item set print array-indexes
9352 @itemx set print array-indexes on
9353 Print the index of each element when displaying arrays. May be more
9354 convenient to locate a given element in the array or quickly find the
9355 index of a given element in that printed array. The default is off.
9357 @item set print array-indexes off
9358 Stop printing element indexes when displaying arrays.
9360 @item show print array-indexes
9361 Show whether the index of each element is printed when displaying
9364 @item set print elements @var{number-of-elements}
9365 @itemx set print elements unlimited
9366 @cindex number of array elements to print
9367 @cindex limit on number of printed array elements
9368 Set a limit on how many elements of an array @value{GDBN} will print.
9369 If @value{GDBN} is printing a large array, it stops printing after it has
9370 printed the number of elements set by the @code{set print elements} command.
9371 This limit also applies to the display of strings.
9372 When @value{GDBN} starts, this limit is set to 200.
9373 Setting @var{number-of-elements} to @code{unlimited} or zero means
9374 that the number of elements to print is unlimited.
9376 @item show print elements
9377 Display the number of elements of a large array that @value{GDBN} will print.
9378 If the number is 0, then the printing is unlimited.
9380 @item set print frame-arguments @var{value}
9381 @kindex set print frame-arguments
9382 @cindex printing frame argument values
9383 @cindex print all frame argument values
9384 @cindex print frame argument values for scalars only
9385 @cindex do not print frame argument values
9386 This command allows to control how the values of arguments are printed
9387 when the debugger prints a frame (@pxref{Frames}). The possible
9392 The values of all arguments are printed.
9395 Print the value of an argument only if it is a scalar. The value of more
9396 complex arguments such as arrays, structures, unions, etc, is replaced
9397 by @code{@dots{}}. This is the default. Here is an example where
9398 only scalar arguments are shown:
9401 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9406 None of the argument values are printed. Instead, the value of each argument
9407 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9410 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9415 By default, only scalar arguments are printed. This command can be used
9416 to configure the debugger to print the value of all arguments, regardless
9417 of their type. However, it is often advantageous to not print the value
9418 of more complex parameters. For instance, it reduces the amount of
9419 information printed in each frame, making the backtrace more readable.
9420 Also, it improves performance when displaying Ada frames, because
9421 the computation of large arguments can sometimes be CPU-intensive,
9422 especially in large applications. Setting @code{print frame-arguments}
9423 to @code{scalars} (the default) or @code{none} avoids this computation,
9424 thus speeding up the display of each Ada frame.
9426 @item show print frame-arguments
9427 Show how the value of arguments should be displayed when printing a frame.
9429 @item set print raw frame-arguments on
9430 Print frame arguments in raw, non pretty-printed, form.
9432 @item set print raw frame-arguments off
9433 Print frame arguments in pretty-printed form, if there is a pretty-printer
9434 for the value (@pxref{Pretty Printing}),
9435 otherwise print the value in raw form.
9436 This is the default.
9438 @item show print raw frame-arguments
9439 Show whether to print frame arguments in raw form.
9441 @anchor{set print entry-values}
9442 @item set print entry-values @var{value}
9443 @kindex set print entry-values
9444 Set printing of frame argument values at function entry. In some cases
9445 @value{GDBN} can determine the value of function argument which was passed by
9446 the function caller, even if the value was modified inside the called function
9447 and therefore is different. With optimized code, the current value could be
9448 unavailable, but the entry value may still be known.
9450 The default value is @code{default} (see below for its description). Older
9451 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9452 this feature will behave in the @code{default} setting the same way as with the
9455 This functionality is currently supported only by DWARF 2 debugging format and
9456 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9457 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9460 The @var{value} parameter can be one of the following:
9464 Print only actual parameter values, never print values from function entry
9468 #0 different (val=6)
9469 #0 lost (val=<optimized out>)
9471 #0 invalid (val=<optimized out>)
9475 Print only parameter values from function entry point. The actual parameter
9476 values are never printed.
9478 #0 equal (val@@entry=5)
9479 #0 different (val@@entry=5)
9480 #0 lost (val@@entry=5)
9481 #0 born (val@@entry=<optimized out>)
9482 #0 invalid (val@@entry=<optimized out>)
9486 Print only parameter values from function entry point. If value from function
9487 entry point is not known while the actual value is known, print the actual
9488 value for such parameter.
9490 #0 equal (val@@entry=5)
9491 #0 different (val@@entry=5)
9492 #0 lost (val@@entry=5)
9494 #0 invalid (val@@entry=<optimized out>)
9498 Print actual parameter values. If actual parameter value is not known while
9499 value from function entry point is known, print the entry point value for such
9503 #0 different (val=6)
9504 #0 lost (val@@entry=5)
9506 #0 invalid (val=<optimized out>)
9510 Always print both the actual parameter value and its value from function entry
9511 point, even if values of one or both are not available due to compiler
9514 #0 equal (val=5, val@@entry=5)
9515 #0 different (val=6, val@@entry=5)
9516 #0 lost (val=<optimized out>, val@@entry=5)
9517 #0 born (val=10, val@@entry=<optimized out>)
9518 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9522 Print the actual parameter value if it is known and also its value from
9523 function entry point if it is known. If neither is known, print for the actual
9524 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9525 values are known and identical, print the shortened
9526 @code{param=param@@entry=VALUE} notation.
9528 #0 equal (val=val@@entry=5)
9529 #0 different (val=6, val@@entry=5)
9530 #0 lost (val@@entry=5)
9532 #0 invalid (val=<optimized out>)
9536 Always print the actual parameter value. Print also its value from function
9537 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9538 if both values are known and identical, print the shortened
9539 @code{param=param@@entry=VALUE} notation.
9541 #0 equal (val=val@@entry=5)
9542 #0 different (val=6, val@@entry=5)
9543 #0 lost (val=<optimized out>, val@@entry=5)
9545 #0 invalid (val=<optimized out>)
9549 For analysis messages on possible failures of frame argument values at function
9550 entry resolution see @ref{set debug entry-values}.
9552 @item show print entry-values
9553 Show the method being used for printing of frame argument values at function
9556 @item set print repeats @var{number-of-repeats}
9557 @itemx set print repeats unlimited
9558 @cindex repeated array elements
9559 Set the threshold for suppressing display of repeated array
9560 elements. When the number of consecutive identical elements of an
9561 array exceeds the threshold, @value{GDBN} prints the string
9562 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9563 identical repetitions, instead of displaying the identical elements
9564 themselves. Setting the threshold to @code{unlimited} or zero will
9565 cause all elements to be individually printed. The default threshold
9568 @item show print repeats
9569 Display the current threshold for printing repeated identical
9572 @item set print null-stop
9573 @cindex @sc{null} elements in arrays
9574 Cause @value{GDBN} to stop printing the characters of an array when the first
9575 @sc{null} is encountered. This is useful when large arrays actually
9576 contain only short strings.
9579 @item show print null-stop
9580 Show whether @value{GDBN} stops printing an array on the first
9581 @sc{null} character.
9583 @item set print pretty on
9584 @cindex print structures in indented form
9585 @cindex indentation in structure display
9586 Cause @value{GDBN} to print structures in an indented format with one member
9587 per line, like this:
9602 @item set print pretty off
9603 Cause @value{GDBN} to print structures in a compact format, like this:
9607 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9608 meat = 0x54 "Pork"@}
9613 This is the default format.
9615 @item show print pretty
9616 Show which format @value{GDBN} is using to print structures.
9618 @item set print sevenbit-strings on
9619 @cindex eight-bit characters in strings
9620 @cindex octal escapes in strings
9621 Print using only seven-bit characters; if this option is set,
9622 @value{GDBN} displays any eight-bit characters (in strings or
9623 character values) using the notation @code{\}@var{nnn}. This setting is
9624 best if you are working in English (@sc{ascii}) and you use the
9625 high-order bit of characters as a marker or ``meta'' bit.
9627 @item set print sevenbit-strings off
9628 Print full eight-bit characters. This allows the use of more
9629 international character sets, and is the default.
9631 @item show print sevenbit-strings
9632 Show whether or not @value{GDBN} is printing only seven-bit characters.
9634 @item set print union on
9635 @cindex unions in structures, printing
9636 Tell @value{GDBN} to print unions which are contained in structures
9637 and other unions. This is the default setting.
9639 @item set print union off
9640 Tell @value{GDBN} not to print unions which are contained in
9641 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9644 @item show print union
9645 Ask @value{GDBN} whether or not it will print unions which are contained in
9646 structures and other unions.
9648 For example, given the declarations
9651 typedef enum @{Tree, Bug@} Species;
9652 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9653 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9664 struct thing foo = @{Tree, @{Acorn@}@};
9668 with @code{set print union on} in effect @samp{p foo} would print
9671 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9675 and with @code{set print union off} in effect it would print
9678 $1 = @{it = Tree, form = @{...@}@}
9682 @code{set print union} affects programs written in C-like languages
9688 These settings are of interest when debugging C@t{++} programs:
9691 @cindex demangling C@t{++} names
9692 @item set print demangle
9693 @itemx set print demangle on
9694 Print C@t{++} names in their source form rather than in the encoded
9695 (``mangled'') form passed to the assembler and linker for type-safe
9696 linkage. The default is on.
9698 @item show print demangle
9699 Show whether C@t{++} names are printed in mangled or demangled form.
9701 @item set print asm-demangle
9702 @itemx set print asm-demangle on
9703 Print C@t{++} names in their source form rather than their mangled form, even
9704 in assembler code printouts such as instruction disassemblies.
9707 @item show print asm-demangle
9708 Show whether C@t{++} names in assembly listings are printed in mangled
9711 @cindex C@t{++} symbol decoding style
9712 @cindex symbol decoding style, C@t{++}
9713 @kindex set demangle-style
9714 @item set demangle-style @var{style}
9715 Choose among several encoding schemes used by different compilers to
9716 represent C@t{++} names. The choices for @var{style} are currently:
9720 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9721 This is the default.
9724 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9727 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9730 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9733 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9734 @strong{Warning:} this setting alone is not sufficient to allow
9735 debugging @code{cfront}-generated executables. @value{GDBN} would
9736 require further enhancement to permit that.
9739 If you omit @var{style}, you will see a list of possible formats.
9741 @item show demangle-style
9742 Display the encoding style currently in use for decoding C@t{++} symbols.
9744 @item set print object
9745 @itemx set print object on
9746 @cindex derived type of an object, printing
9747 @cindex display derived types
9748 When displaying a pointer to an object, identify the @emph{actual}
9749 (derived) type of the object rather than the @emph{declared} type, using
9750 the virtual function table. Note that the virtual function table is
9751 required---this feature can only work for objects that have run-time
9752 type identification; a single virtual method in the object's declared
9753 type is sufficient. Note that this setting is also taken into account when
9754 working with variable objects via MI (@pxref{GDB/MI}).
9756 @item set print object off
9757 Display only the declared type of objects, without reference to the
9758 virtual function table. This is the default setting.
9760 @item show print object
9761 Show whether actual, or declared, object types are displayed.
9763 @item set print static-members
9764 @itemx set print static-members on
9765 @cindex static members of C@t{++} objects
9766 Print static members when displaying a C@t{++} object. The default is on.
9768 @item set print static-members off
9769 Do not print static members when displaying a C@t{++} object.
9771 @item show print static-members
9772 Show whether C@t{++} static members are printed or not.
9774 @item set print pascal_static-members
9775 @itemx set print pascal_static-members on
9776 @cindex static members of Pascal objects
9777 @cindex Pascal objects, static members display
9778 Print static members when displaying a Pascal object. The default is on.
9780 @item set print pascal_static-members off
9781 Do not print static members when displaying a Pascal object.
9783 @item show print pascal_static-members
9784 Show whether Pascal static members are printed or not.
9786 @c These don't work with HP ANSI C++ yet.
9787 @item set print vtbl
9788 @itemx set print vtbl on
9789 @cindex pretty print C@t{++} virtual function tables
9790 @cindex virtual functions (C@t{++}) display
9791 @cindex VTBL display
9792 Pretty print C@t{++} virtual function tables. The default is off.
9793 (The @code{vtbl} commands do not work on programs compiled with the HP
9794 ANSI C@t{++} compiler (@code{aCC}).)
9796 @item set print vtbl off
9797 Do not pretty print C@t{++} virtual function tables.
9799 @item show print vtbl
9800 Show whether C@t{++} virtual function tables are pretty printed, or not.
9803 @node Pretty Printing
9804 @section Pretty Printing
9806 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9807 Python code. It greatly simplifies the display of complex objects. This
9808 mechanism works for both MI and the CLI.
9811 * Pretty-Printer Introduction:: Introduction to pretty-printers
9812 * Pretty-Printer Example:: An example pretty-printer
9813 * Pretty-Printer Commands:: Pretty-printer commands
9816 @node Pretty-Printer Introduction
9817 @subsection Pretty-Printer Introduction
9819 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9820 registered for the value. If there is then @value{GDBN} invokes the
9821 pretty-printer to print the value. Otherwise the value is printed normally.
9823 Pretty-printers are normally named. This makes them easy to manage.
9824 The @samp{info pretty-printer} command will list all the installed
9825 pretty-printers with their names.
9826 If a pretty-printer can handle multiple data types, then its
9827 @dfn{subprinters} are the printers for the individual data types.
9828 Each such subprinter has its own name.
9829 The format of the name is @var{printer-name};@var{subprinter-name}.
9831 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9832 Typically they are automatically loaded and registered when the corresponding
9833 debug information is loaded, thus making them available without having to
9834 do anything special.
9836 There are three places where a pretty-printer can be registered.
9840 Pretty-printers registered globally are available when debugging
9844 Pretty-printers registered with a program space are available only
9845 when debugging that program.
9846 @xref{Progspaces In Python}, for more details on program spaces in Python.
9849 Pretty-printers registered with an objfile are loaded and unloaded
9850 with the corresponding objfile (e.g., shared library).
9851 @xref{Objfiles In Python}, for more details on objfiles in Python.
9854 @xref{Selecting Pretty-Printers}, for further information on how
9855 pretty-printers are selected,
9857 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9860 @node Pretty-Printer Example
9861 @subsection Pretty-Printer Example
9863 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9866 (@value{GDBP}) print s
9868 static npos = 4294967295,
9870 <std::allocator<char>> = @{
9871 <__gnu_cxx::new_allocator<char>> = @{
9872 <No data fields>@}, <No data fields>
9874 members of std::basic_string<char, std::char_traits<char>,
9875 std::allocator<char> >::_Alloc_hider:
9876 _M_p = 0x804a014 "abcd"
9881 With a pretty-printer for @code{std::string} only the contents are printed:
9884 (@value{GDBP}) print s
9888 @node Pretty-Printer Commands
9889 @subsection Pretty-Printer Commands
9890 @cindex pretty-printer commands
9893 @kindex info pretty-printer
9894 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9895 Print the list of installed pretty-printers.
9896 This includes disabled pretty-printers, which are marked as such.
9898 @var{object-regexp} is a regular expression matching the objects
9899 whose pretty-printers to list.
9900 Objects can be @code{global}, the program space's file
9901 (@pxref{Progspaces In Python}),
9902 and the object files within that program space (@pxref{Objfiles In Python}).
9903 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9904 looks up a printer from these three objects.
9906 @var{name-regexp} is a regular expression matching the name of the printers
9909 @kindex disable pretty-printer
9910 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9911 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9912 A disabled pretty-printer is not forgotten, it may be enabled again later.
9914 @kindex enable pretty-printer
9915 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9916 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9921 Suppose we have three pretty-printers installed: one from library1.so
9922 named @code{foo} that prints objects of type @code{foo}, and
9923 another from library2.so named @code{bar} that prints two types of objects,
9924 @code{bar1} and @code{bar2}.
9927 (gdb) info pretty-printer
9934 (gdb) info pretty-printer library2
9939 (gdb) disable pretty-printer library1
9941 2 of 3 printers enabled
9942 (gdb) info pretty-printer
9949 (gdb) disable pretty-printer library2 bar:bar1
9951 1 of 3 printers enabled
9952 (gdb) info pretty-printer library2
9959 (gdb) disable pretty-printer library2 bar
9961 0 of 3 printers enabled
9962 (gdb) info pretty-printer library2
9971 Note that for @code{bar} the entire printer can be disabled,
9972 as can each individual subprinter.
9975 @section Value History
9977 @cindex value history
9978 @cindex history of values printed by @value{GDBN}
9979 Values printed by the @code{print} command are saved in the @value{GDBN}
9980 @dfn{value history}. This allows you to refer to them in other expressions.
9981 Values are kept until the symbol table is re-read or discarded
9982 (for example with the @code{file} or @code{symbol-file} commands).
9983 When the symbol table changes, the value history is discarded,
9984 since the values may contain pointers back to the types defined in the
9989 @cindex history number
9990 The values printed are given @dfn{history numbers} by which you can
9991 refer to them. These are successive integers starting with one.
9992 @code{print} shows you the history number assigned to a value by
9993 printing @samp{$@var{num} = } before the value; here @var{num} is the
9996 To refer to any previous value, use @samp{$} followed by the value's
9997 history number. The way @code{print} labels its output is designed to
9998 remind you of this. Just @code{$} refers to the most recent value in
9999 the history, and @code{$$} refers to the value before that.
10000 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10001 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10002 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10004 For example, suppose you have just printed a pointer to a structure and
10005 want to see the contents of the structure. It suffices to type
10011 If you have a chain of structures where the component @code{next} points
10012 to the next one, you can print the contents of the next one with this:
10019 You can print successive links in the chain by repeating this
10020 command---which you can do by just typing @key{RET}.
10022 Note that the history records values, not expressions. If the value of
10023 @code{x} is 4 and you type these commands:
10031 then the value recorded in the value history by the @code{print} command
10032 remains 4 even though the value of @code{x} has changed.
10035 @kindex show values
10037 Print the last ten values in the value history, with their item numbers.
10038 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10039 values} does not change the history.
10041 @item show values @var{n}
10042 Print ten history values centered on history item number @var{n}.
10044 @item show values +
10045 Print ten history values just after the values last printed. If no more
10046 values are available, @code{show values +} produces no display.
10049 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10050 same effect as @samp{show values +}.
10052 @node Convenience Vars
10053 @section Convenience Variables
10055 @cindex convenience variables
10056 @cindex user-defined variables
10057 @value{GDBN} provides @dfn{convenience variables} that you can use within
10058 @value{GDBN} to hold on to a value and refer to it later. These variables
10059 exist entirely within @value{GDBN}; they are not part of your program, and
10060 setting a convenience variable has no direct effect on further execution
10061 of your program. That is why you can use them freely.
10063 Convenience variables are prefixed with @samp{$}. Any name preceded by
10064 @samp{$} can be used for a convenience variable, unless it is one of
10065 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10066 (Value history references, in contrast, are @emph{numbers} preceded
10067 by @samp{$}. @xref{Value History, ,Value History}.)
10069 You can save a value in a convenience variable with an assignment
10070 expression, just as you would set a variable in your program.
10074 set $foo = *object_ptr
10078 would save in @code{$foo} the value contained in the object pointed to by
10081 Using a convenience variable for the first time creates it, but its
10082 value is @code{void} until you assign a new value. You can alter the
10083 value with another assignment at any time.
10085 Convenience variables have no fixed types. You can assign a convenience
10086 variable any type of value, including structures and arrays, even if
10087 that variable already has a value of a different type. The convenience
10088 variable, when used as an expression, has the type of its current value.
10091 @kindex show convenience
10092 @cindex show all user variables and functions
10093 @item show convenience
10094 Print a list of convenience variables used so far, and their values,
10095 as well as a list of the convenience functions.
10096 Abbreviated @code{show conv}.
10098 @kindex init-if-undefined
10099 @cindex convenience variables, initializing
10100 @item init-if-undefined $@var{variable} = @var{expression}
10101 Set a convenience variable if it has not already been set. This is useful
10102 for user-defined commands that keep some state. It is similar, in concept,
10103 to using local static variables with initializers in C (except that
10104 convenience variables are global). It can also be used to allow users to
10105 override default values used in a command script.
10107 If the variable is already defined then the expression is not evaluated so
10108 any side-effects do not occur.
10111 One of the ways to use a convenience variable is as a counter to be
10112 incremented or a pointer to be advanced. For example, to print
10113 a field from successive elements of an array of structures:
10117 print bar[$i++]->contents
10121 Repeat that command by typing @key{RET}.
10123 Some convenience variables are created automatically by @value{GDBN} and given
10124 values likely to be useful.
10127 @vindex $_@r{, convenience variable}
10129 The variable @code{$_} is automatically set by the @code{x} command to
10130 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10131 commands which provide a default address for @code{x} to examine also
10132 set @code{$_} to that address; these commands include @code{info line}
10133 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10134 except when set by the @code{x} command, in which case it is a pointer
10135 to the type of @code{$__}.
10137 @vindex $__@r{, convenience variable}
10139 The variable @code{$__} is automatically set by the @code{x} command
10140 to the value found in the last address examined. Its type is chosen
10141 to match the format in which the data was printed.
10144 @vindex $_exitcode@r{, convenience variable}
10145 When the program being debugged terminates normally, @value{GDBN}
10146 automatically sets this variable to the exit code of the program, and
10147 resets @code{$_exitsignal} to @code{void}.
10150 @vindex $_exitsignal@r{, convenience variable}
10151 When the program being debugged dies due to an uncaught signal,
10152 @value{GDBN} automatically sets this variable to that signal's number,
10153 and resets @code{$_exitcode} to @code{void}.
10155 To distinguish between whether the program being debugged has exited
10156 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10157 @code{$_exitsignal} is not @code{void}), the convenience function
10158 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10159 Functions}). For example, considering the following source code:
10162 #include <signal.h>
10165 main (int argc, char *argv[])
10172 A valid way of telling whether the program being debugged has exited
10173 or signalled would be:
10176 (@value{GDBP}) define has_exited_or_signalled
10177 Type commands for definition of ``has_exited_or_signalled''.
10178 End with a line saying just ``end''.
10179 >if $_isvoid ($_exitsignal)
10180 >echo The program has exited\n
10182 >echo The program has signalled\n
10188 Program terminated with signal SIGALRM, Alarm clock.
10189 The program no longer exists.
10190 (@value{GDBP}) has_exited_or_signalled
10191 The program has signalled
10194 As can be seen, @value{GDBN} correctly informs that the program being
10195 debugged has signalled, since it calls @code{raise} and raises a
10196 @code{SIGALRM} signal. If the program being debugged had not called
10197 @code{raise}, then @value{GDBN} would report a normal exit:
10200 (@value{GDBP}) has_exited_or_signalled
10201 The program has exited
10205 The variable @code{$_exception} is set to the exception object being
10206 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10209 @itemx $_probe_arg0@dots{}$_probe_arg11
10210 Arguments to a static probe. @xref{Static Probe Points}.
10213 @vindex $_sdata@r{, inspect, convenience variable}
10214 The variable @code{$_sdata} contains extra collected static tracepoint
10215 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10216 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10217 if extra static tracepoint data has not been collected.
10220 @vindex $_siginfo@r{, convenience variable}
10221 The variable @code{$_siginfo} contains extra signal information
10222 (@pxref{extra signal information}). Note that @code{$_siginfo}
10223 could be empty, if the application has not yet received any signals.
10224 For example, it will be empty before you execute the @code{run} command.
10227 @vindex $_tlb@r{, convenience variable}
10228 The variable @code{$_tlb} is automatically set when debugging
10229 applications running on MS-Windows in native mode or connected to
10230 gdbserver that supports the @code{qGetTIBAddr} request.
10231 @xref{General Query Packets}.
10232 This variable contains the address of the thread information block.
10236 On HP-UX systems, if you refer to a function or variable name that
10237 begins with a dollar sign, @value{GDBN} searches for a user or system
10238 name first, before it searches for a convenience variable.
10240 @node Convenience Funs
10241 @section Convenience Functions
10243 @cindex convenience functions
10244 @value{GDBN} also supplies some @dfn{convenience functions}. These
10245 have a syntax similar to convenience variables. A convenience
10246 function can be used in an expression just like an ordinary function;
10247 however, a convenience function is implemented internally to
10250 These functions do not require @value{GDBN} to be configured with
10251 @code{Python} support, which means that they are always available.
10255 @item $_isvoid (@var{expr})
10256 @findex $_isvoid@r{, convenience function}
10257 Return one if the expression @var{expr} is @code{void}. Otherwise it
10260 A @code{void} expression is an expression where the type of the result
10261 is @code{void}. For example, you can examine a convenience variable
10262 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10266 (@value{GDBP}) print $_exitcode
10268 (@value{GDBP}) print $_isvoid ($_exitcode)
10271 Starting program: ./a.out
10272 [Inferior 1 (process 29572) exited normally]
10273 (@value{GDBP}) print $_exitcode
10275 (@value{GDBP}) print $_isvoid ($_exitcode)
10279 In the example above, we used @code{$_isvoid} to check whether
10280 @code{$_exitcode} is @code{void} before and after the execution of the
10281 program being debugged. Before the execution there is no exit code to
10282 be examined, therefore @code{$_exitcode} is @code{void}. After the
10283 execution the program being debugged returned zero, therefore
10284 @code{$_exitcode} is zero, which means that it is not @code{void}
10287 The @code{void} expression can also be a call of a function from the
10288 program being debugged. For example, given the following function:
10297 The result of calling it inside @value{GDBN} is @code{void}:
10300 (@value{GDBP}) print foo ()
10302 (@value{GDBP}) print $_isvoid (foo ())
10304 (@value{GDBP}) set $v = foo ()
10305 (@value{GDBP}) print $v
10307 (@value{GDBP}) print $_isvoid ($v)
10313 These functions require @value{GDBN} to be configured with
10314 @code{Python} support.
10318 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10319 @findex $_memeq@r{, convenience function}
10320 Returns one if the @var{length} bytes at the addresses given by
10321 @var{buf1} and @var{buf2} are equal.
10322 Otherwise it returns zero.
10324 @item $_regex(@var{str}, @var{regex})
10325 @findex $_regex@r{, convenience function}
10326 Returns one if the string @var{str} matches the regular expression
10327 @var{regex}. Otherwise it returns zero.
10328 The syntax of the regular expression is that specified by @code{Python}'s
10329 regular expression support.
10331 @item $_streq(@var{str1}, @var{str2})
10332 @findex $_streq@r{, convenience function}
10333 Returns one if the strings @var{str1} and @var{str2} are equal.
10334 Otherwise it returns zero.
10336 @item $_strlen(@var{str})
10337 @findex $_strlen@r{, convenience function}
10338 Returns the length of string @var{str}.
10340 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10341 @findex $_caller_is@r{, convenience function}
10342 Returns one if the calling function's name is equal to @var{name}.
10343 Otherwise it returns zero.
10345 If the optional argument @var{number_of_frames} is provided,
10346 it is the number of frames up in the stack to look.
10354 at testsuite/gdb.python/py-caller-is.c:21
10355 #1 0x00000000004005a0 in middle_func ()
10356 at testsuite/gdb.python/py-caller-is.c:27
10357 #2 0x00000000004005ab in top_func ()
10358 at testsuite/gdb.python/py-caller-is.c:33
10359 #3 0x00000000004005b6 in main ()
10360 at testsuite/gdb.python/py-caller-is.c:39
10361 (gdb) print $_caller_is ("middle_func")
10363 (gdb) print $_caller_is ("top_func", 2)
10367 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10368 @findex $_caller_matches@r{, convenience function}
10369 Returns one if the calling function's name matches the regular expression
10370 @var{regexp}. Otherwise it returns zero.
10372 If the optional argument @var{number_of_frames} is provided,
10373 it is the number of frames up in the stack to look.
10376 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10377 @findex $_any_caller_is@r{, convenience function}
10378 Returns one if any calling function's name is equal to @var{name}.
10379 Otherwise it returns zero.
10381 If the optional argument @var{number_of_frames} is provided,
10382 it is the number of frames up in the stack to look.
10385 This function differs from @code{$_caller_is} in that this function
10386 checks all stack frames from the immediate caller to the frame specified
10387 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10388 frame specified by @var{number_of_frames}.
10390 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10391 @findex $_any_caller_matches@r{, convenience function}
10392 Returns one if any calling function's name matches the regular expression
10393 @var{regexp}. Otherwise it returns zero.
10395 If the optional argument @var{number_of_frames} is provided,
10396 it is the number of frames up in the stack to look.
10399 This function differs from @code{$_caller_matches} in that this function
10400 checks all stack frames from the immediate caller to the frame specified
10401 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10402 frame specified by @var{number_of_frames}.
10406 @value{GDBN} provides the ability to list and get help on
10407 convenience functions.
10410 @item help function
10411 @kindex help function
10412 @cindex show all convenience functions
10413 Print a list of all convenience functions.
10420 You can refer to machine register contents, in expressions, as variables
10421 with names starting with @samp{$}. The names of registers are different
10422 for each machine; use @code{info registers} to see the names used on
10426 @kindex info registers
10427 @item info registers
10428 Print the names and values of all registers except floating-point
10429 and vector registers (in the selected stack frame).
10431 @kindex info all-registers
10432 @cindex floating point registers
10433 @item info all-registers
10434 Print the names and values of all registers, including floating-point
10435 and vector registers (in the selected stack frame).
10437 @item info registers @var{regname} @dots{}
10438 Print the @dfn{relativized} value of each specified register @var{regname}.
10439 As discussed in detail below, register values are normally relative to
10440 the selected stack frame. The @var{regname} may be any register name valid on
10441 the machine you are using, with or without the initial @samp{$}.
10444 @anchor{standard registers}
10445 @cindex stack pointer register
10446 @cindex program counter register
10447 @cindex process status register
10448 @cindex frame pointer register
10449 @cindex standard registers
10450 @value{GDBN} has four ``standard'' register names that are available (in
10451 expressions) on most machines---whenever they do not conflict with an
10452 architecture's canonical mnemonics for registers. The register names
10453 @code{$pc} and @code{$sp} are used for the program counter register and
10454 the stack pointer. @code{$fp} is used for a register that contains a
10455 pointer to the current stack frame, and @code{$ps} is used for a
10456 register that contains the processor status. For example,
10457 you could print the program counter in hex with
10464 or print the instruction to be executed next with
10471 or add four to the stack pointer@footnote{This is a way of removing
10472 one word from the stack, on machines where stacks grow downward in
10473 memory (most machines, nowadays). This assumes that the innermost
10474 stack frame is selected; setting @code{$sp} is not allowed when other
10475 stack frames are selected. To pop entire frames off the stack,
10476 regardless of machine architecture, use @code{return};
10477 see @ref{Returning, ,Returning from a Function}.} with
10483 Whenever possible, these four standard register names are available on
10484 your machine even though the machine has different canonical mnemonics,
10485 so long as there is no conflict. The @code{info registers} command
10486 shows the canonical names. For example, on the SPARC, @code{info
10487 registers} displays the processor status register as @code{$psr} but you
10488 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10489 is an alias for the @sc{eflags} register.
10491 @value{GDBN} always considers the contents of an ordinary register as an
10492 integer when the register is examined in this way. Some machines have
10493 special registers which can hold nothing but floating point; these
10494 registers are considered to have floating point values. There is no way
10495 to refer to the contents of an ordinary register as floating point value
10496 (although you can @emph{print} it as a floating point value with
10497 @samp{print/f $@var{regname}}).
10499 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10500 means that the data format in which the register contents are saved by
10501 the operating system is not the same one that your program normally
10502 sees. For example, the registers of the 68881 floating point
10503 coprocessor are always saved in ``extended'' (raw) format, but all C
10504 programs expect to work with ``double'' (virtual) format. In such
10505 cases, @value{GDBN} normally works with the virtual format only (the format
10506 that makes sense for your program), but the @code{info registers} command
10507 prints the data in both formats.
10509 @cindex SSE registers (x86)
10510 @cindex MMX registers (x86)
10511 Some machines have special registers whose contents can be interpreted
10512 in several different ways. For example, modern x86-based machines
10513 have SSE and MMX registers that can hold several values packed
10514 together in several different formats. @value{GDBN} refers to such
10515 registers in @code{struct} notation:
10518 (@value{GDBP}) print $xmm1
10520 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10521 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10522 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10523 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10524 v4_int32 = @{0, 20657912, 11, 13@},
10525 v2_int64 = @{88725056443645952, 55834574859@},
10526 uint128 = 0x0000000d0000000b013b36f800000000
10531 To set values of such registers, you need to tell @value{GDBN} which
10532 view of the register you wish to change, as if you were assigning
10533 value to a @code{struct} member:
10536 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10539 Normally, register values are relative to the selected stack frame
10540 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10541 value that the register would contain if all stack frames farther in
10542 were exited and their saved registers restored. In order to see the
10543 true contents of hardware registers, you must select the innermost
10544 frame (with @samp{frame 0}).
10546 @cindex caller-saved registers
10547 @cindex call-clobbered registers
10548 @cindex volatile registers
10549 @cindex <not saved> values
10550 Usually ABIs reserve some registers as not needed to be saved by the
10551 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10552 registers). It may therefore not be possible for @value{GDBN} to know
10553 the value a register had before the call (in other words, in the outer
10554 frame), if the register value has since been changed by the callee.
10555 @value{GDBN} tries to deduce where the inner frame saved
10556 (``callee-saved'') registers, from the debug info, unwind info, or the
10557 machine code generated by your compiler. If some register is not
10558 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10559 its own knowledge of the ABI, or because the debug/unwind info
10560 explicitly says the register's value is undefined), @value{GDBN}
10561 displays @w{@samp{<not saved>}} as the register's value. With targets
10562 that @value{GDBN} has no knowledge of the register saving convention,
10563 if a register was not saved by the callee, then its value and location
10564 in the outer frame are assumed to be the same of the inner frame.
10565 This is usually harmless, because if the register is call-clobbered,
10566 the caller either does not care what is in the register after the
10567 call, or has code to restore the value that it does care about. Note,
10568 however, that if you change such a register in the outer frame, you
10569 may also be affecting the inner frame. Also, the more ``outer'' the
10570 frame is you're looking at, the more likely a call-clobbered
10571 register's value is to be wrong, in the sense that it doesn't actually
10572 represent the value the register had just before the call.
10574 @node Floating Point Hardware
10575 @section Floating Point Hardware
10576 @cindex floating point
10578 Depending on the configuration, @value{GDBN} may be able to give
10579 you more information about the status of the floating point hardware.
10584 Display hardware-dependent information about the floating
10585 point unit. The exact contents and layout vary depending on the
10586 floating point chip. Currently, @samp{info float} is supported on
10587 the ARM and x86 machines.
10591 @section Vector Unit
10592 @cindex vector unit
10594 Depending on the configuration, @value{GDBN} may be able to give you
10595 more information about the status of the vector unit.
10598 @kindex info vector
10600 Display information about the vector unit. The exact contents and
10601 layout vary depending on the hardware.
10604 @node OS Information
10605 @section Operating System Auxiliary Information
10606 @cindex OS information
10608 @value{GDBN} provides interfaces to useful OS facilities that can help
10609 you debug your program.
10611 @cindex auxiliary vector
10612 @cindex vector, auxiliary
10613 Some operating systems supply an @dfn{auxiliary vector} to programs at
10614 startup. This is akin to the arguments and environment that you
10615 specify for a program, but contains a system-dependent variety of
10616 binary values that tell system libraries important details about the
10617 hardware, operating system, and process. Each value's purpose is
10618 identified by an integer tag; the meanings are well-known but system-specific.
10619 Depending on the configuration and operating system facilities,
10620 @value{GDBN} may be able to show you this information. For remote
10621 targets, this functionality may further depend on the remote stub's
10622 support of the @samp{qXfer:auxv:read} packet, see
10623 @ref{qXfer auxiliary vector read}.
10628 Display the auxiliary vector of the inferior, which can be either a
10629 live process or a core dump file. @value{GDBN} prints each tag value
10630 numerically, and also shows names and text descriptions for recognized
10631 tags. Some values in the vector are numbers, some bit masks, and some
10632 pointers to strings or other data. @value{GDBN} displays each value in the
10633 most appropriate form for a recognized tag, and in hexadecimal for
10634 an unrecognized tag.
10637 On some targets, @value{GDBN} can access operating system-specific
10638 information and show it to you. The types of information available
10639 will differ depending on the type of operating system running on the
10640 target. The mechanism used to fetch the data is described in
10641 @ref{Operating System Information}. For remote targets, this
10642 functionality depends on the remote stub's support of the
10643 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10647 @item info os @var{infotype}
10649 Display OS information of the requested type.
10651 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10653 @anchor{linux info os infotypes}
10655 @kindex info os cpus
10657 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10658 the available fields from /proc/cpuinfo. For each supported architecture
10659 different fields are available. Two common entries are processor which gives
10660 CPU number and bogomips; a system constant that is calculated during
10661 kernel initialization.
10663 @kindex info os files
10665 Display the list of open file descriptors on the target. For each
10666 file descriptor, @value{GDBN} prints the identifier of the process
10667 owning the descriptor, the command of the owning process, the value
10668 of the descriptor, and the target of the descriptor.
10670 @kindex info os modules
10672 Display the list of all loaded kernel modules on the target. For each
10673 module, @value{GDBN} prints the module name, the size of the module in
10674 bytes, the number of times the module is used, the dependencies of the
10675 module, the status of the module, and the address of the loaded module
10678 @kindex info os msg
10680 Display the list of all System V message queues on the target. For each
10681 message queue, @value{GDBN} prints the message queue key, the message
10682 queue identifier, the access permissions, the current number of bytes
10683 on the queue, the current number of messages on the queue, the processes
10684 that last sent and received a message on the queue, the user and group
10685 of the owner and creator of the message queue, the times at which a
10686 message was last sent and received on the queue, and the time at which
10687 the message queue was last changed.
10689 @kindex info os processes
10691 Display the list of processes on the target. For each process,
10692 @value{GDBN} prints the process identifier, the name of the user, the
10693 command corresponding to the process, and the list of processor cores
10694 that the process is currently running on. (To understand what these
10695 properties mean, for this and the following info types, please consult
10696 the general @sc{gnu}/Linux documentation.)
10698 @kindex info os procgroups
10700 Display the list of process groups on the target. For each process,
10701 @value{GDBN} prints the identifier of the process group that it belongs
10702 to, the command corresponding to the process group leader, the process
10703 identifier, and the command line of the process. The list is sorted
10704 first by the process group identifier, then by the process identifier,
10705 so that processes belonging to the same process group are grouped together
10706 and the process group leader is listed first.
10708 @kindex info os semaphores
10710 Display the list of all System V semaphore sets on the target. For each
10711 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10712 set identifier, the access permissions, the number of semaphores in the
10713 set, the user and group of the owner and creator of the semaphore set,
10714 and the times at which the semaphore set was operated upon and changed.
10716 @kindex info os shm
10718 Display the list of all System V shared-memory regions on the target.
10719 For each shared-memory region, @value{GDBN} prints the region key,
10720 the shared-memory identifier, the access permissions, the size of the
10721 region, the process that created the region, the process that last
10722 attached to or detached from the region, the current number of live
10723 attaches to the region, and the times at which the region was last
10724 attached to, detach from, and changed.
10726 @kindex info os sockets
10728 Display the list of Internet-domain sockets on the target. For each
10729 socket, @value{GDBN} prints the address and port of the local and
10730 remote endpoints, the current state of the connection, the creator of
10731 the socket, the IP address family of the socket, and the type of the
10734 @kindex info os threads
10736 Display the list of threads running on the target. For each thread,
10737 @value{GDBN} prints the identifier of the process that the thread
10738 belongs to, the command of the process, the thread identifier, and the
10739 processor core that it is currently running on. The main thread of a
10740 process is not listed.
10744 If @var{infotype} is omitted, then list the possible values for
10745 @var{infotype} and the kind of OS information available for each
10746 @var{infotype}. If the target does not return a list of possible
10747 types, this command will report an error.
10750 @node Memory Region Attributes
10751 @section Memory Region Attributes
10752 @cindex memory region attributes
10754 @dfn{Memory region attributes} allow you to describe special handling
10755 required by regions of your target's memory. @value{GDBN} uses
10756 attributes to determine whether to allow certain types of memory
10757 accesses; whether to use specific width accesses; and whether to cache
10758 target memory. By default the description of memory regions is
10759 fetched from the target (if the current target supports this), but the
10760 user can override the fetched regions.
10762 Defined memory regions can be individually enabled and disabled. When a
10763 memory region is disabled, @value{GDBN} uses the default attributes when
10764 accessing memory in that region. Similarly, if no memory regions have
10765 been defined, @value{GDBN} uses the default attributes when accessing
10768 When a memory region is defined, it is given a number to identify it;
10769 to enable, disable, or remove a memory region, you specify that number.
10773 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10774 Define a memory region bounded by @var{lower} and @var{upper} with
10775 attributes @var{attributes}@dots{}, and add it to the list of regions
10776 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10777 case: it is treated as the target's maximum memory address.
10778 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10781 Discard any user changes to the memory regions and use target-supplied
10782 regions, if available, or no regions if the target does not support.
10785 @item delete mem @var{nums}@dots{}
10786 Remove memory regions @var{nums}@dots{} from the list of regions
10787 monitored by @value{GDBN}.
10789 @kindex disable mem
10790 @item disable mem @var{nums}@dots{}
10791 Disable monitoring of memory regions @var{nums}@dots{}.
10792 A disabled memory region is not forgotten.
10793 It may be enabled again later.
10796 @item enable mem @var{nums}@dots{}
10797 Enable monitoring of memory regions @var{nums}@dots{}.
10801 Print a table of all defined memory regions, with the following columns
10805 @item Memory Region Number
10806 @item Enabled or Disabled.
10807 Enabled memory regions are marked with @samp{y}.
10808 Disabled memory regions are marked with @samp{n}.
10811 The address defining the inclusive lower bound of the memory region.
10814 The address defining the exclusive upper bound of the memory region.
10817 The list of attributes set for this memory region.
10822 @subsection Attributes
10824 @subsubsection Memory Access Mode
10825 The access mode attributes set whether @value{GDBN} may make read or
10826 write accesses to a memory region.
10828 While these attributes prevent @value{GDBN} from performing invalid
10829 memory accesses, they do nothing to prevent the target system, I/O DMA,
10830 etc.@: from accessing memory.
10834 Memory is read only.
10836 Memory is write only.
10838 Memory is read/write. This is the default.
10841 @subsubsection Memory Access Size
10842 The access size attribute tells @value{GDBN} to use specific sized
10843 accesses in the memory region. Often memory mapped device registers
10844 require specific sized accesses. If no access size attribute is
10845 specified, @value{GDBN} may use accesses of any size.
10849 Use 8 bit memory accesses.
10851 Use 16 bit memory accesses.
10853 Use 32 bit memory accesses.
10855 Use 64 bit memory accesses.
10858 @c @subsubsection Hardware/Software Breakpoints
10859 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10860 @c will use hardware or software breakpoints for the internal breakpoints
10861 @c used by the step, next, finish, until, etc. commands.
10865 @c Always use hardware breakpoints
10866 @c @item swbreak (default)
10869 @subsubsection Data Cache
10870 The data cache attributes set whether @value{GDBN} will cache target
10871 memory. While this generally improves performance by reducing debug
10872 protocol overhead, it can lead to incorrect results because @value{GDBN}
10873 does not know about volatile variables or memory mapped device
10878 Enable @value{GDBN} to cache target memory.
10880 Disable @value{GDBN} from caching target memory. This is the default.
10883 @subsection Memory Access Checking
10884 @value{GDBN} can be instructed to refuse accesses to memory that is
10885 not explicitly described. This can be useful if accessing such
10886 regions has undesired effects for a specific target, or to provide
10887 better error checking. The following commands control this behaviour.
10890 @kindex set mem inaccessible-by-default
10891 @item set mem inaccessible-by-default [on|off]
10892 If @code{on} is specified, make @value{GDBN} treat memory not
10893 explicitly described by the memory ranges as non-existent and refuse accesses
10894 to such memory. The checks are only performed if there's at least one
10895 memory range defined. If @code{off} is specified, make @value{GDBN}
10896 treat the memory not explicitly described by the memory ranges as RAM.
10897 The default value is @code{on}.
10898 @kindex show mem inaccessible-by-default
10899 @item show mem inaccessible-by-default
10900 Show the current handling of accesses to unknown memory.
10904 @c @subsubsection Memory Write Verification
10905 @c The memory write verification attributes set whether @value{GDBN}
10906 @c will re-reads data after each write to verify the write was successful.
10910 @c @item noverify (default)
10913 @node Dump/Restore Files
10914 @section Copy Between Memory and a File
10915 @cindex dump/restore files
10916 @cindex append data to a file
10917 @cindex dump data to a file
10918 @cindex restore data from a file
10920 You can use the commands @code{dump}, @code{append}, and
10921 @code{restore} to copy data between target memory and a file. The
10922 @code{dump} and @code{append} commands write data to a file, and the
10923 @code{restore} command reads data from a file back into the inferior's
10924 memory. Files may be in binary, Motorola S-record, Intel hex,
10925 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
10926 append to binary files, and cannot read from Verilog Hex files.
10931 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10932 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10933 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10934 or the value of @var{expr}, to @var{filename} in the given format.
10936 The @var{format} parameter may be any one of:
10943 Motorola S-record format.
10945 Tektronix Hex format.
10947 Verilog Hex format.
10950 @value{GDBN} uses the same definitions of these formats as the
10951 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10952 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10956 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10957 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10958 Append the contents of memory from @var{start_addr} to @var{end_addr},
10959 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10960 (@value{GDBN} can only append data to files in raw binary form.)
10963 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10964 Restore the contents of file @var{filename} into memory. The
10965 @code{restore} command can automatically recognize any known @sc{bfd}
10966 file format, except for raw binary. To restore a raw binary file you
10967 must specify the optional keyword @code{binary} after the filename.
10969 If @var{bias} is non-zero, its value will be added to the addresses
10970 contained in the file. Binary files always start at address zero, so
10971 they will be restored at address @var{bias}. Other bfd files have
10972 a built-in location; they will be restored at offset @var{bias}
10973 from that location.
10975 If @var{start} and/or @var{end} are non-zero, then only data between
10976 file offset @var{start} and file offset @var{end} will be restored.
10977 These offsets are relative to the addresses in the file, before
10978 the @var{bias} argument is applied.
10982 @node Core File Generation
10983 @section How to Produce a Core File from Your Program
10984 @cindex dump core from inferior
10986 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10987 image of a running process and its process status (register values
10988 etc.). Its primary use is post-mortem debugging of a program that
10989 crashed while it ran outside a debugger. A program that crashes
10990 automatically produces a core file, unless this feature is disabled by
10991 the user. @xref{Files}, for information on invoking @value{GDBN} in
10992 the post-mortem debugging mode.
10994 Occasionally, you may wish to produce a core file of the program you
10995 are debugging in order to preserve a snapshot of its state.
10996 @value{GDBN} has a special command for that.
11000 @kindex generate-core-file
11001 @item generate-core-file [@var{file}]
11002 @itemx gcore [@var{file}]
11003 Produce a core dump of the inferior process. The optional argument
11004 @var{file} specifies the file name where to put the core dump. If not
11005 specified, the file name defaults to @file{core.@var{pid}}, where
11006 @var{pid} is the inferior process ID.
11008 Note that this command is implemented only for some systems (as of
11009 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11011 On @sc{gnu}/Linux, this command can take into account the value of the
11012 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11013 dump (@pxref{set use-coredump-filter}).
11015 @kindex set use-coredump-filter
11016 @anchor{set use-coredump-filter}
11017 @item set use-coredump-filter on
11018 @itemx set use-coredump-filter off
11019 Enable or disable the use of the file
11020 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11021 files. This file is used by the Linux kernel to decide what types of
11022 memory mappings will be dumped or ignored when generating a core dump
11023 file. @var{pid} is the process ID of a currently running process.
11025 To make use of this feature, you have to write in the
11026 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11027 which is a bit mask representing the memory mapping types. If a bit
11028 is set in the bit mask, then the memory mappings of the corresponding
11029 types will be dumped; otherwise, they will be ignored. This
11030 configuration is inherited by child processes. For more information
11031 about the bits that can be set in the
11032 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11033 manpage of @code{core(5)}.
11035 By default, this option is @code{on}. If this option is turned
11036 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11037 and instead uses the same default value as the Linux kernel in order
11038 to decide which pages will be dumped in the core dump file. This
11039 value is currently @code{0x33}, which means that bits @code{0}
11040 (anonymous private mappings), @code{1} (anonymous shared mappings),
11041 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11042 This will cause these memory mappings to be dumped automatically.
11045 @node Character Sets
11046 @section Character Sets
11047 @cindex character sets
11049 @cindex translating between character sets
11050 @cindex host character set
11051 @cindex target character set
11053 If the program you are debugging uses a different character set to
11054 represent characters and strings than the one @value{GDBN} uses itself,
11055 @value{GDBN} can automatically translate between the character sets for
11056 you. The character set @value{GDBN} uses we call the @dfn{host
11057 character set}; the one the inferior program uses we call the
11058 @dfn{target character set}.
11060 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11061 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11062 remote protocol (@pxref{Remote Debugging}) to debug a program
11063 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11064 then the host character set is Latin-1, and the target character set is
11065 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11066 target-charset EBCDIC-US}, then @value{GDBN} translates between
11067 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11068 character and string literals in expressions.
11070 @value{GDBN} has no way to automatically recognize which character set
11071 the inferior program uses; you must tell it, using the @code{set
11072 target-charset} command, described below.
11074 Here are the commands for controlling @value{GDBN}'s character set
11078 @item set target-charset @var{charset}
11079 @kindex set target-charset
11080 Set the current target character set to @var{charset}. To display the
11081 list of supported target character sets, type
11082 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11084 @item set host-charset @var{charset}
11085 @kindex set host-charset
11086 Set the current host character set to @var{charset}.
11088 By default, @value{GDBN} uses a host character set appropriate to the
11089 system it is running on; you can override that default using the
11090 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11091 automatically determine the appropriate host character set. In this
11092 case, @value{GDBN} uses @samp{UTF-8}.
11094 @value{GDBN} can only use certain character sets as its host character
11095 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11096 @value{GDBN} will list the host character sets it supports.
11098 @item set charset @var{charset}
11099 @kindex set charset
11100 Set the current host and target character sets to @var{charset}. As
11101 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11102 @value{GDBN} will list the names of the character sets that can be used
11103 for both host and target.
11106 @kindex show charset
11107 Show the names of the current host and target character sets.
11109 @item show host-charset
11110 @kindex show host-charset
11111 Show the name of the current host character set.
11113 @item show target-charset
11114 @kindex show target-charset
11115 Show the name of the current target character set.
11117 @item set target-wide-charset @var{charset}
11118 @kindex set target-wide-charset
11119 Set the current target's wide character set to @var{charset}. This is
11120 the character set used by the target's @code{wchar_t} type. To
11121 display the list of supported wide character sets, type
11122 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11124 @item show target-wide-charset
11125 @kindex show target-wide-charset
11126 Show the name of the current target's wide character set.
11129 Here is an example of @value{GDBN}'s character set support in action.
11130 Assume that the following source code has been placed in the file
11131 @file{charset-test.c}:
11137 = @{72, 101, 108, 108, 111, 44, 32, 119,
11138 111, 114, 108, 100, 33, 10, 0@};
11139 char ibm1047_hello[]
11140 = @{200, 133, 147, 147, 150, 107, 64, 166,
11141 150, 153, 147, 132, 90, 37, 0@};
11145 printf ("Hello, world!\n");
11149 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11150 containing the string @samp{Hello, world!} followed by a newline,
11151 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11153 We compile the program, and invoke the debugger on it:
11156 $ gcc -g charset-test.c -o charset-test
11157 $ gdb -nw charset-test
11158 GNU gdb 2001-12-19-cvs
11159 Copyright 2001 Free Software Foundation, Inc.
11164 We can use the @code{show charset} command to see what character sets
11165 @value{GDBN} is currently using to interpret and display characters and
11169 (@value{GDBP}) show charset
11170 The current host and target character set is `ISO-8859-1'.
11174 For the sake of printing this manual, let's use @sc{ascii} as our
11175 initial character set:
11177 (@value{GDBP}) set charset ASCII
11178 (@value{GDBP}) show charset
11179 The current host and target character set is `ASCII'.
11183 Let's assume that @sc{ascii} is indeed the correct character set for our
11184 host system --- in other words, let's assume that if @value{GDBN} prints
11185 characters using the @sc{ascii} character set, our terminal will display
11186 them properly. Since our current target character set is also
11187 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11190 (@value{GDBP}) print ascii_hello
11191 $1 = 0x401698 "Hello, world!\n"
11192 (@value{GDBP}) print ascii_hello[0]
11197 @value{GDBN} uses the target character set for character and string
11198 literals you use in expressions:
11201 (@value{GDBP}) print '+'
11206 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11209 @value{GDBN} relies on the user to tell it which character set the
11210 target program uses. If we print @code{ibm1047_hello} while our target
11211 character set is still @sc{ascii}, we get jibberish:
11214 (@value{GDBP}) print ibm1047_hello
11215 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11216 (@value{GDBP}) print ibm1047_hello[0]
11221 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11222 @value{GDBN} tells us the character sets it supports:
11225 (@value{GDBP}) set target-charset
11226 ASCII EBCDIC-US IBM1047 ISO-8859-1
11227 (@value{GDBP}) set target-charset
11230 We can select @sc{ibm1047} as our target character set, and examine the
11231 program's strings again. Now the @sc{ascii} string is wrong, but
11232 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11233 target character set, @sc{ibm1047}, to the host character set,
11234 @sc{ascii}, and they display correctly:
11237 (@value{GDBP}) set target-charset IBM1047
11238 (@value{GDBP}) show charset
11239 The current host character set is `ASCII'.
11240 The current target character set is `IBM1047'.
11241 (@value{GDBP}) print ascii_hello
11242 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11243 (@value{GDBP}) print ascii_hello[0]
11245 (@value{GDBP}) print ibm1047_hello
11246 $8 = 0x4016a8 "Hello, world!\n"
11247 (@value{GDBP}) print ibm1047_hello[0]
11252 As above, @value{GDBN} uses the target character set for character and
11253 string literals you use in expressions:
11256 (@value{GDBP}) print '+'
11261 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11264 @node Caching Target Data
11265 @section Caching Data of Targets
11266 @cindex caching data of targets
11268 @value{GDBN} caches data exchanged between the debugger and a target.
11269 Each cache is associated with the address space of the inferior.
11270 @xref{Inferiors and Programs}, about inferior and address space.
11271 Such caching generally improves performance in remote debugging
11272 (@pxref{Remote Debugging}), because it reduces the overhead of the
11273 remote protocol by bundling memory reads and writes into large chunks.
11274 Unfortunately, simply caching everything would lead to incorrect results,
11275 since @value{GDBN} does not necessarily know anything about volatile
11276 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11277 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11279 Therefore, by default, @value{GDBN} only caches data
11280 known to be on the stack@footnote{In non-stop mode, it is moderately
11281 rare for a running thread to modify the stack of a stopped thread
11282 in a way that would interfere with a backtrace, and caching of
11283 stack reads provides a significant speed up of remote backtraces.} or
11284 in the code segment.
11285 Other regions of memory can be explicitly marked as
11286 cacheable; @pxref{Memory Region Attributes}.
11289 @kindex set remotecache
11290 @item set remotecache on
11291 @itemx set remotecache off
11292 This option no longer does anything; it exists for compatibility
11295 @kindex show remotecache
11296 @item show remotecache
11297 Show the current state of the obsolete remotecache flag.
11299 @kindex set stack-cache
11300 @item set stack-cache on
11301 @itemx set stack-cache off
11302 Enable or disable caching of stack accesses. When @code{on}, use
11303 caching. By default, this option is @code{on}.
11305 @kindex show stack-cache
11306 @item show stack-cache
11307 Show the current state of data caching for memory accesses.
11309 @kindex set code-cache
11310 @item set code-cache on
11311 @itemx set code-cache off
11312 Enable or disable caching of code segment accesses. When @code{on},
11313 use caching. By default, this option is @code{on}. This improves
11314 performance of disassembly in remote debugging.
11316 @kindex show code-cache
11317 @item show code-cache
11318 Show the current state of target memory cache for code segment
11321 @kindex info dcache
11322 @item info dcache @r{[}line@r{]}
11323 Print the information about the performance of data cache of the
11324 current inferior's address space. The information displayed
11325 includes the dcache width and depth, and for each cache line, its
11326 number, address, and how many times it was referenced. This
11327 command is useful for debugging the data cache operation.
11329 If a line number is specified, the contents of that line will be
11332 @item set dcache size @var{size}
11333 @cindex dcache size
11334 @kindex set dcache size
11335 Set maximum number of entries in dcache (dcache depth above).
11337 @item set dcache line-size @var{line-size}
11338 @cindex dcache line-size
11339 @kindex set dcache line-size
11340 Set number of bytes each dcache entry caches (dcache width above).
11341 Must be a power of 2.
11343 @item show dcache size
11344 @kindex show dcache size
11345 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11347 @item show dcache line-size
11348 @kindex show dcache line-size
11349 Show default size of dcache lines.
11353 @node Searching Memory
11354 @section Search Memory
11355 @cindex searching memory
11357 Memory can be searched for a particular sequence of bytes with the
11358 @code{find} command.
11362 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11363 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11364 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11365 etc. The search begins at address @var{start_addr} and continues for either
11366 @var{len} bytes or through to @var{end_addr} inclusive.
11369 @var{s} and @var{n} are optional parameters.
11370 They may be specified in either order, apart or together.
11373 @item @var{s}, search query size
11374 The size of each search query value.
11380 halfwords (two bytes)
11384 giant words (eight bytes)
11387 All values are interpreted in the current language.
11388 This means, for example, that if the current source language is C/C@t{++}
11389 then searching for the string ``hello'' includes the trailing '\0'.
11391 If the value size is not specified, it is taken from the
11392 value's type in the current language.
11393 This is useful when one wants to specify the search
11394 pattern as a mixture of types.
11395 Note that this means, for example, that in the case of C-like languages
11396 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11397 which is typically four bytes.
11399 @item @var{n}, maximum number of finds
11400 The maximum number of matches to print. The default is to print all finds.
11403 You can use strings as search values. Quote them with double-quotes
11405 The string value is copied into the search pattern byte by byte,
11406 regardless of the endianness of the target and the size specification.
11408 The address of each match found is printed as well as a count of the
11409 number of matches found.
11411 The address of the last value found is stored in convenience variable
11413 A count of the number of matches is stored in @samp{$numfound}.
11415 For example, if stopped at the @code{printf} in this function:
11421 static char hello[] = "hello-hello";
11422 static struct @{ char c; short s; int i; @}
11423 __attribute__ ((packed)) mixed
11424 = @{ 'c', 0x1234, 0x87654321 @};
11425 printf ("%s\n", hello);
11430 you get during debugging:
11433 (gdb) find &hello[0], +sizeof(hello), "hello"
11434 0x804956d <hello.1620+6>
11436 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11437 0x8049567 <hello.1620>
11438 0x804956d <hello.1620+6>
11440 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11441 0x8049567 <hello.1620>
11443 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11444 0x8049560 <mixed.1625>
11446 (gdb) print $numfound
11449 $2 = (void *) 0x8049560
11452 @node Optimized Code
11453 @chapter Debugging Optimized Code
11454 @cindex optimized code, debugging
11455 @cindex debugging optimized code
11457 Almost all compilers support optimization. With optimization
11458 disabled, the compiler generates assembly code that corresponds
11459 directly to your source code, in a simplistic way. As the compiler
11460 applies more powerful optimizations, the generated assembly code
11461 diverges from your original source code. With help from debugging
11462 information generated by the compiler, @value{GDBN} can map from
11463 the running program back to constructs from your original source.
11465 @value{GDBN} is more accurate with optimization disabled. If you
11466 can recompile without optimization, it is easier to follow the
11467 progress of your program during debugging. But, there are many cases
11468 where you may need to debug an optimized version.
11470 When you debug a program compiled with @samp{-g -O}, remember that the
11471 optimizer has rearranged your code; the debugger shows you what is
11472 really there. Do not be too surprised when the execution path does not
11473 exactly match your source file! An extreme example: if you define a
11474 variable, but never use it, @value{GDBN} never sees that
11475 variable---because the compiler optimizes it out of existence.
11477 Some things do not work as well with @samp{-g -O} as with just
11478 @samp{-g}, particularly on machines with instruction scheduling. If in
11479 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11480 please report it to us as a bug (including a test case!).
11481 @xref{Variables}, for more information about debugging optimized code.
11484 * Inline Functions:: How @value{GDBN} presents inlining
11485 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11488 @node Inline Functions
11489 @section Inline Functions
11490 @cindex inline functions, debugging
11492 @dfn{Inlining} is an optimization that inserts a copy of the function
11493 body directly at each call site, instead of jumping to a shared
11494 routine. @value{GDBN} displays inlined functions just like
11495 non-inlined functions. They appear in backtraces. You can view their
11496 arguments and local variables, step into them with @code{step}, skip
11497 them with @code{next}, and escape from them with @code{finish}.
11498 You can check whether a function was inlined by using the
11499 @code{info frame} command.
11501 For @value{GDBN} to support inlined functions, the compiler must
11502 record information about inlining in the debug information ---
11503 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11504 other compilers do also. @value{GDBN} only supports inlined functions
11505 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11506 do not emit two required attributes (@samp{DW_AT_call_file} and
11507 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11508 function calls with earlier versions of @value{NGCC}. It instead
11509 displays the arguments and local variables of inlined functions as
11510 local variables in the caller.
11512 The body of an inlined function is directly included at its call site;
11513 unlike a non-inlined function, there are no instructions devoted to
11514 the call. @value{GDBN} still pretends that the call site and the
11515 start of the inlined function are different instructions. Stepping to
11516 the call site shows the call site, and then stepping again shows
11517 the first line of the inlined function, even though no additional
11518 instructions are executed.
11520 This makes source-level debugging much clearer; you can see both the
11521 context of the call and then the effect of the call. Only stepping by
11522 a single instruction using @code{stepi} or @code{nexti} does not do
11523 this; single instruction steps always show the inlined body.
11525 There are some ways that @value{GDBN} does not pretend that inlined
11526 function calls are the same as normal calls:
11530 Setting breakpoints at the call site of an inlined function may not
11531 work, because the call site does not contain any code. @value{GDBN}
11532 may incorrectly move the breakpoint to the next line of the enclosing
11533 function, after the call. This limitation will be removed in a future
11534 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11535 or inside the inlined function instead.
11538 @value{GDBN} cannot locate the return value of inlined calls after
11539 using the @code{finish} command. This is a limitation of compiler-generated
11540 debugging information; after @code{finish}, you can step to the next line
11541 and print a variable where your program stored the return value.
11545 @node Tail Call Frames
11546 @section Tail Call Frames
11547 @cindex tail call frames, debugging
11549 Function @code{B} can call function @code{C} in its very last statement. In
11550 unoptimized compilation the call of @code{C} is immediately followed by return
11551 instruction at the end of @code{B} code. Optimizing compiler may replace the
11552 call and return in function @code{B} into one jump to function @code{C}
11553 instead. Such use of a jump instruction is called @dfn{tail call}.
11555 During execution of function @code{C}, there will be no indication in the
11556 function call stack frames that it was tail-called from @code{B}. If function
11557 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11558 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11559 some cases @value{GDBN} can determine that @code{C} was tail-called from
11560 @code{B}, and it will then create fictitious call frame for that, with the
11561 return address set up as if @code{B} called @code{C} normally.
11563 This functionality is currently supported only by DWARF 2 debugging format and
11564 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11565 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11568 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11569 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11573 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11575 Stack level 1, frame at 0x7fffffffda30:
11576 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11577 tail call frame, caller of frame at 0x7fffffffda30
11578 source language c++.
11579 Arglist at unknown address.
11580 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11583 The detection of all the possible code path executions can find them ambiguous.
11584 There is no execution history stored (possible @ref{Reverse Execution} is never
11585 used for this purpose) and the last known caller could have reached the known
11586 callee by multiple different jump sequences. In such case @value{GDBN} still
11587 tries to show at least all the unambiguous top tail callers and all the
11588 unambiguous bottom tail calees, if any.
11591 @anchor{set debug entry-values}
11592 @item set debug entry-values
11593 @kindex set debug entry-values
11594 When set to on, enables printing of analysis messages for both frame argument
11595 values at function entry and tail calls. It will show all the possible valid
11596 tail calls code paths it has considered. It will also print the intersection
11597 of them with the final unambiguous (possibly partial or even empty) code path
11600 @item show debug entry-values
11601 @kindex show debug entry-values
11602 Show the current state of analysis messages printing for both frame argument
11603 values at function entry and tail calls.
11606 The analysis messages for tail calls can for example show why the virtual tail
11607 call frame for function @code{c} has not been recognized (due to the indirect
11608 reference by variable @code{x}):
11611 static void __attribute__((noinline, noclone)) c (void);
11612 void (*x) (void) = c;
11613 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11614 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11615 int main (void) @{ x (); return 0; @}
11617 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11618 DW_TAG_GNU_call_site 0x40039a in main
11620 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11623 #1 0x000000000040039a in main () at t.c:5
11626 Another possibility is an ambiguous virtual tail call frames resolution:
11630 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11631 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11632 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11633 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11634 static void __attribute__((noinline, noclone)) b (void)
11635 @{ if (i) c (); else e (); @}
11636 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11637 int main (void) @{ a (); return 0; @}
11639 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11640 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11641 tailcall: reduced: 0x4004d2(a) |
11644 #1 0x00000000004004d2 in a () at t.c:8
11645 #2 0x0000000000400395 in main () at t.c:9
11648 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11649 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11651 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11652 @ifset HAVE_MAKEINFO_CLICK
11653 @set ARROW @click{}
11654 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11655 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11657 @ifclear HAVE_MAKEINFO_CLICK
11659 @set CALLSEQ1B @value{CALLSEQ1A}
11660 @set CALLSEQ2B @value{CALLSEQ2A}
11663 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11664 The code can have possible execution paths @value{CALLSEQ1B} or
11665 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11667 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11668 has found. It then finds another possible calling sequcen - that one is
11669 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11670 printed as the @code{reduced:} calling sequence. That one could have many
11671 futher @code{compare:} and @code{reduced:} statements as long as there remain
11672 any non-ambiguous sequence entries.
11674 For the frame of function @code{b} in both cases there are different possible
11675 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11676 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11677 therefore this one is displayed to the user while the ambiguous frames are
11680 There can be also reasons why printing of frame argument values at function
11685 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11686 static void __attribute__((noinline, noclone)) a (int i);
11687 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11688 static void __attribute__((noinline, noclone)) a (int i)
11689 @{ if (i) b (i - 1); else c (0); @}
11690 int main (void) @{ a (5); return 0; @}
11693 #0 c (i=i@@entry=0) at t.c:2
11694 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11695 function "a" at 0x400420 can call itself via tail calls
11696 i=<optimized out>) at t.c:6
11697 #2 0x000000000040036e in main () at t.c:7
11700 @value{GDBN} cannot find out from the inferior state if and how many times did
11701 function @code{a} call itself (via function @code{b}) as these calls would be
11702 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11703 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11704 prints @code{<optimized out>} instead.
11707 @chapter C Preprocessor Macros
11709 Some languages, such as C and C@t{++}, provide a way to define and invoke
11710 ``preprocessor macros'' which expand into strings of tokens.
11711 @value{GDBN} can evaluate expressions containing macro invocations, show
11712 the result of macro expansion, and show a macro's definition, including
11713 where it was defined.
11715 You may need to compile your program specially to provide @value{GDBN}
11716 with information about preprocessor macros. Most compilers do not
11717 include macros in their debugging information, even when you compile
11718 with the @option{-g} flag. @xref{Compilation}.
11720 A program may define a macro at one point, remove that definition later,
11721 and then provide a different definition after that. Thus, at different
11722 points in the program, a macro may have different definitions, or have
11723 no definition at all. If there is a current stack frame, @value{GDBN}
11724 uses the macros in scope at that frame's source code line. Otherwise,
11725 @value{GDBN} uses the macros in scope at the current listing location;
11728 Whenever @value{GDBN} evaluates an expression, it always expands any
11729 macro invocations present in the expression. @value{GDBN} also provides
11730 the following commands for working with macros explicitly.
11734 @kindex macro expand
11735 @cindex macro expansion, showing the results of preprocessor
11736 @cindex preprocessor macro expansion, showing the results of
11737 @cindex expanding preprocessor macros
11738 @item macro expand @var{expression}
11739 @itemx macro exp @var{expression}
11740 Show the results of expanding all preprocessor macro invocations in
11741 @var{expression}. Since @value{GDBN} simply expands macros, but does
11742 not parse the result, @var{expression} need not be a valid expression;
11743 it can be any string of tokens.
11746 @item macro expand-once @var{expression}
11747 @itemx macro exp1 @var{expression}
11748 @cindex expand macro once
11749 @i{(This command is not yet implemented.)} Show the results of
11750 expanding those preprocessor macro invocations that appear explicitly in
11751 @var{expression}. Macro invocations appearing in that expansion are
11752 left unchanged. This command allows you to see the effect of a
11753 particular macro more clearly, without being confused by further
11754 expansions. Since @value{GDBN} simply expands macros, but does not
11755 parse the result, @var{expression} need not be a valid expression; it
11756 can be any string of tokens.
11759 @cindex macro definition, showing
11760 @cindex definition of a macro, showing
11761 @cindex macros, from debug info
11762 @item info macro [-a|-all] [--] @var{macro}
11763 Show the current definition or all definitions of the named @var{macro},
11764 and describe the source location or compiler command-line where that
11765 definition was established. The optional double dash is to signify the end of
11766 argument processing and the beginning of @var{macro} for non C-like macros where
11767 the macro may begin with a hyphen.
11769 @kindex info macros
11770 @item info macros @var{linespec}
11771 Show all macro definitions that are in effect at the location specified
11772 by @var{linespec}, and describe the source location or compiler
11773 command-line where those definitions were established.
11775 @kindex macro define
11776 @cindex user-defined macros
11777 @cindex defining macros interactively
11778 @cindex macros, user-defined
11779 @item macro define @var{macro} @var{replacement-list}
11780 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11781 Introduce a definition for a preprocessor macro named @var{macro},
11782 invocations of which are replaced by the tokens given in
11783 @var{replacement-list}. The first form of this command defines an
11784 ``object-like'' macro, which takes no arguments; the second form
11785 defines a ``function-like'' macro, which takes the arguments given in
11788 A definition introduced by this command is in scope in every
11789 expression evaluated in @value{GDBN}, until it is removed with the
11790 @code{macro undef} command, described below. The definition overrides
11791 all definitions for @var{macro} present in the program being debugged,
11792 as well as any previous user-supplied definition.
11794 @kindex macro undef
11795 @item macro undef @var{macro}
11796 Remove any user-supplied definition for the macro named @var{macro}.
11797 This command only affects definitions provided with the @code{macro
11798 define} command, described above; it cannot remove definitions present
11799 in the program being debugged.
11803 List all the macros defined using the @code{macro define} command.
11806 @cindex macros, example of debugging with
11807 Here is a transcript showing the above commands in action. First, we
11808 show our source files:
11813 #include "sample.h"
11816 #define ADD(x) (M + x)
11821 printf ("Hello, world!\n");
11823 printf ("We're so creative.\n");
11825 printf ("Goodbye, world!\n");
11832 Now, we compile the program using the @sc{gnu} C compiler,
11833 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11834 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11835 and @option{-gdwarf-4}; we recommend always choosing the most recent
11836 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11837 includes information about preprocessor macros in the debugging
11841 $ gcc -gdwarf-2 -g3 sample.c -o sample
11845 Now, we start @value{GDBN} on our sample program:
11849 GNU gdb 2002-05-06-cvs
11850 Copyright 2002 Free Software Foundation, Inc.
11851 GDB is free software, @dots{}
11855 We can expand macros and examine their definitions, even when the
11856 program is not running. @value{GDBN} uses the current listing position
11857 to decide which macro definitions are in scope:
11860 (@value{GDBP}) list main
11863 5 #define ADD(x) (M + x)
11868 10 printf ("Hello, world!\n");
11870 12 printf ("We're so creative.\n");
11871 (@value{GDBP}) info macro ADD
11872 Defined at /home/jimb/gdb/macros/play/sample.c:5
11873 #define ADD(x) (M + x)
11874 (@value{GDBP}) info macro Q
11875 Defined at /home/jimb/gdb/macros/play/sample.h:1
11876 included at /home/jimb/gdb/macros/play/sample.c:2
11878 (@value{GDBP}) macro expand ADD(1)
11879 expands to: (42 + 1)
11880 (@value{GDBP}) macro expand-once ADD(1)
11881 expands to: once (M + 1)
11885 In the example above, note that @code{macro expand-once} expands only
11886 the macro invocation explicit in the original text --- the invocation of
11887 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11888 which was introduced by @code{ADD}.
11890 Once the program is running, @value{GDBN} uses the macro definitions in
11891 force at the source line of the current stack frame:
11894 (@value{GDBP}) break main
11895 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11897 Starting program: /home/jimb/gdb/macros/play/sample
11899 Breakpoint 1, main () at sample.c:10
11900 10 printf ("Hello, world!\n");
11904 At line 10, the definition of the macro @code{N} at line 9 is in force:
11907 (@value{GDBP}) info macro N
11908 Defined at /home/jimb/gdb/macros/play/sample.c:9
11910 (@value{GDBP}) macro expand N Q M
11911 expands to: 28 < 42
11912 (@value{GDBP}) print N Q M
11917 As we step over directives that remove @code{N}'s definition, and then
11918 give it a new definition, @value{GDBN} finds the definition (or lack
11919 thereof) in force at each point:
11922 (@value{GDBP}) next
11924 12 printf ("We're so creative.\n");
11925 (@value{GDBP}) info macro N
11926 The symbol `N' has no definition as a C/C++ preprocessor macro
11927 at /home/jimb/gdb/macros/play/sample.c:12
11928 (@value{GDBP}) next
11930 14 printf ("Goodbye, world!\n");
11931 (@value{GDBP}) info macro N
11932 Defined at /home/jimb/gdb/macros/play/sample.c:13
11934 (@value{GDBP}) macro expand N Q M
11935 expands to: 1729 < 42
11936 (@value{GDBP}) print N Q M
11941 In addition to source files, macros can be defined on the compilation command
11942 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11943 such a way, @value{GDBN} displays the location of their definition as line zero
11944 of the source file submitted to the compiler.
11947 (@value{GDBP}) info macro __STDC__
11948 Defined at /home/jimb/gdb/macros/play/sample.c:0
11955 @chapter Tracepoints
11956 @c This chapter is based on the documentation written by Michael
11957 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11959 @cindex tracepoints
11960 In some applications, it is not feasible for the debugger to interrupt
11961 the program's execution long enough for the developer to learn
11962 anything helpful about its behavior. If the program's correctness
11963 depends on its real-time behavior, delays introduced by a debugger
11964 might cause the program to change its behavior drastically, or perhaps
11965 fail, even when the code itself is correct. It is useful to be able
11966 to observe the program's behavior without interrupting it.
11968 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11969 specify locations in the program, called @dfn{tracepoints}, and
11970 arbitrary expressions to evaluate when those tracepoints are reached.
11971 Later, using the @code{tfind} command, you can examine the values
11972 those expressions had when the program hit the tracepoints. The
11973 expressions may also denote objects in memory---structures or arrays,
11974 for example---whose values @value{GDBN} should record; while visiting
11975 a particular tracepoint, you may inspect those objects as if they were
11976 in memory at that moment. However, because @value{GDBN} records these
11977 values without interacting with you, it can do so quickly and
11978 unobtrusively, hopefully not disturbing the program's behavior.
11980 The tracepoint facility is currently available only for remote
11981 targets. @xref{Targets}. In addition, your remote target must know
11982 how to collect trace data. This functionality is implemented in the
11983 remote stub; however, none of the stubs distributed with @value{GDBN}
11984 support tracepoints as of this writing. The format of the remote
11985 packets used to implement tracepoints are described in @ref{Tracepoint
11988 It is also possible to get trace data from a file, in a manner reminiscent
11989 of corefiles; you specify the filename, and use @code{tfind} to search
11990 through the file. @xref{Trace Files}, for more details.
11992 This chapter describes the tracepoint commands and features.
11995 * Set Tracepoints::
11996 * Analyze Collected Data::
11997 * Tracepoint Variables::
12001 @node Set Tracepoints
12002 @section Commands to Set Tracepoints
12004 Before running such a @dfn{trace experiment}, an arbitrary number of
12005 tracepoints can be set. A tracepoint is actually a special type of
12006 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12007 standard breakpoint commands. For instance, as with breakpoints,
12008 tracepoint numbers are successive integers starting from one, and many
12009 of the commands associated with tracepoints take the tracepoint number
12010 as their argument, to identify which tracepoint to work on.
12012 For each tracepoint, you can specify, in advance, some arbitrary set
12013 of data that you want the target to collect in the trace buffer when
12014 it hits that tracepoint. The collected data can include registers,
12015 local variables, or global data. Later, you can use @value{GDBN}
12016 commands to examine the values these data had at the time the
12017 tracepoint was hit.
12019 Tracepoints do not support every breakpoint feature. Ignore counts on
12020 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12021 commands when they are hit. Tracepoints may not be thread-specific
12024 @cindex fast tracepoints
12025 Some targets may support @dfn{fast tracepoints}, which are inserted in
12026 a different way (such as with a jump instead of a trap), that is
12027 faster but possibly restricted in where they may be installed.
12029 @cindex static tracepoints
12030 @cindex markers, static tracepoints
12031 @cindex probing markers, static tracepoints
12032 Regular and fast tracepoints are dynamic tracing facilities, meaning
12033 that they can be used to insert tracepoints at (almost) any location
12034 in the target. Some targets may also support controlling @dfn{static
12035 tracepoints} from @value{GDBN}. With static tracing, a set of
12036 instrumentation points, also known as @dfn{markers}, are embedded in
12037 the target program, and can be activated or deactivated by name or
12038 address. These are usually placed at locations which facilitate
12039 investigating what the target is actually doing. @value{GDBN}'s
12040 support for static tracing includes being able to list instrumentation
12041 points, and attach them with @value{GDBN} defined high level
12042 tracepoints that expose the whole range of convenience of
12043 @value{GDBN}'s tracepoints support. Namely, support for collecting
12044 registers values and values of global or local (to the instrumentation
12045 point) variables; tracepoint conditions and trace state variables.
12046 The act of installing a @value{GDBN} static tracepoint on an
12047 instrumentation point, or marker, is referred to as @dfn{probing} a
12048 static tracepoint marker.
12050 @code{gdbserver} supports tracepoints on some target systems.
12051 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12053 This section describes commands to set tracepoints and associated
12054 conditions and actions.
12057 * Create and Delete Tracepoints::
12058 * Enable and Disable Tracepoints::
12059 * Tracepoint Passcounts::
12060 * Tracepoint Conditions::
12061 * Trace State Variables::
12062 * Tracepoint Actions::
12063 * Listing Tracepoints::
12064 * Listing Static Tracepoint Markers::
12065 * Starting and Stopping Trace Experiments::
12066 * Tracepoint Restrictions::
12069 @node Create and Delete Tracepoints
12070 @subsection Create and Delete Tracepoints
12073 @cindex set tracepoint
12075 @item trace @var{location}
12076 The @code{trace} command is very similar to the @code{break} command.
12077 Its argument @var{location} can be a source line, a function name, or
12078 an address in the target program. @xref{Specify Location}. The
12079 @code{trace} command defines a tracepoint, which is a point in the
12080 target program where the debugger will briefly stop, collect some
12081 data, and then allow the program to continue. Setting a tracepoint or
12082 changing its actions takes effect immediately if the remote stub
12083 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12085 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12086 these changes don't take effect until the next @code{tstart}
12087 command, and once a trace experiment is running, further changes will
12088 not have any effect until the next trace experiment starts. In addition,
12089 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12090 address is not yet resolved. (This is similar to pending breakpoints.)
12091 Pending tracepoints are not downloaded to the target and not installed
12092 until they are resolved. The resolution of pending tracepoints requires
12093 @value{GDBN} support---when debugging with the remote target, and
12094 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12095 tracing}), pending tracepoints can not be resolved (and downloaded to
12096 the remote stub) while @value{GDBN} is disconnected.
12098 Here are some examples of using the @code{trace} command:
12101 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12103 (@value{GDBP}) @b{trace +2} // 2 lines forward
12105 (@value{GDBP}) @b{trace my_function} // first source line of function
12107 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12109 (@value{GDBP}) @b{trace *0x2117c4} // an address
12113 You can abbreviate @code{trace} as @code{tr}.
12115 @item trace @var{location} if @var{cond}
12116 Set a tracepoint with condition @var{cond}; evaluate the expression
12117 @var{cond} each time the tracepoint is reached, and collect data only
12118 if the value is nonzero---that is, if @var{cond} evaluates as true.
12119 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12120 information on tracepoint conditions.
12122 @item ftrace @var{location} [ if @var{cond} ]
12123 @cindex set fast tracepoint
12124 @cindex fast tracepoints, setting
12126 The @code{ftrace} command sets a fast tracepoint. For targets that
12127 support them, fast tracepoints will use a more efficient but possibly
12128 less general technique to trigger data collection, such as a jump
12129 instruction instead of a trap, or some sort of hardware support. It
12130 may not be possible to create a fast tracepoint at the desired
12131 location, in which case the command will exit with an explanatory
12134 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12137 On 32-bit x86-architecture systems, fast tracepoints normally need to
12138 be placed at an instruction that is 5 bytes or longer, but can be
12139 placed at 4-byte instructions if the low 64K of memory of the target
12140 program is available to install trampolines. Some Unix-type systems,
12141 such as @sc{gnu}/Linux, exclude low addresses from the program's
12142 address space; but for instance with the Linux kernel it is possible
12143 to let @value{GDBN} use this area by doing a @command{sysctl} command
12144 to set the @code{mmap_min_addr} kernel parameter, as in
12147 sudo sysctl -w vm.mmap_min_addr=32768
12151 which sets the low address to 32K, which leaves plenty of room for
12152 trampolines. The minimum address should be set to a page boundary.
12154 @item strace @var{location} [ if @var{cond} ]
12155 @cindex set static tracepoint
12156 @cindex static tracepoints, setting
12157 @cindex probe static tracepoint marker
12159 The @code{strace} command sets a static tracepoint. For targets that
12160 support it, setting a static tracepoint probes a static
12161 instrumentation point, or marker, found at @var{location}. It may not
12162 be possible to set a static tracepoint at the desired location, in
12163 which case the command will exit with an explanatory message.
12165 @value{GDBN} handles arguments to @code{strace} exactly as for
12166 @code{trace}, with the addition that the user can also specify
12167 @code{-m @var{marker}} as @var{location}. This probes the marker
12168 identified by the @var{marker} string identifier. This identifier
12169 depends on the static tracepoint backend library your program is
12170 using. You can find all the marker identifiers in the @samp{ID} field
12171 of the @code{info static-tracepoint-markers} command output.
12172 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12173 Markers}. For example, in the following small program using the UST
12179 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12184 the marker id is composed of joining the first two arguments to the
12185 @code{trace_mark} call with a slash, which translates to:
12188 (@value{GDBP}) info static-tracepoint-markers
12189 Cnt Enb ID Address What
12190 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12196 so you may probe the marker above with:
12199 (@value{GDBP}) strace -m ust/bar33
12202 Static tracepoints accept an extra collect action --- @code{collect
12203 $_sdata}. This collects arbitrary user data passed in the probe point
12204 call to the tracing library. In the UST example above, you'll see
12205 that the third argument to @code{trace_mark} is a printf-like format
12206 string. The user data is then the result of running that formating
12207 string against the following arguments. Note that @code{info
12208 static-tracepoint-markers} command output lists that format string in
12209 the @samp{Data:} field.
12211 You can inspect this data when analyzing the trace buffer, by printing
12212 the $_sdata variable like any other variable available to
12213 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12216 @cindex last tracepoint number
12217 @cindex recent tracepoint number
12218 @cindex tracepoint number
12219 The convenience variable @code{$tpnum} records the tracepoint number
12220 of the most recently set tracepoint.
12222 @kindex delete tracepoint
12223 @cindex tracepoint deletion
12224 @item delete tracepoint @r{[}@var{num}@r{]}
12225 Permanently delete one or more tracepoints. With no argument, the
12226 default is to delete all tracepoints. Note that the regular
12227 @code{delete} command can remove tracepoints also.
12232 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12234 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12238 You can abbreviate this command as @code{del tr}.
12241 @node Enable and Disable Tracepoints
12242 @subsection Enable and Disable Tracepoints
12244 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12247 @kindex disable tracepoint
12248 @item disable tracepoint @r{[}@var{num}@r{]}
12249 Disable tracepoint @var{num}, or all tracepoints if no argument
12250 @var{num} is given. A disabled tracepoint will have no effect during
12251 a trace experiment, but it is not forgotten. You can re-enable
12252 a disabled tracepoint using the @code{enable tracepoint} command.
12253 If the command is issued during a trace experiment and the debug target
12254 has support for disabling tracepoints during a trace experiment, then the
12255 change will be effective immediately. Otherwise, it will be applied to the
12256 next trace experiment.
12258 @kindex enable tracepoint
12259 @item enable tracepoint @r{[}@var{num}@r{]}
12260 Enable tracepoint @var{num}, or all tracepoints. If this command is
12261 issued during a trace experiment and the debug target supports enabling
12262 tracepoints during a trace experiment, then the enabled tracepoints will
12263 become effective immediately. Otherwise, they will become effective the
12264 next time a trace experiment is run.
12267 @node Tracepoint Passcounts
12268 @subsection Tracepoint Passcounts
12272 @cindex tracepoint pass count
12273 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12274 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12275 automatically stop a trace experiment. If a tracepoint's passcount is
12276 @var{n}, then the trace experiment will be automatically stopped on
12277 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12278 @var{num} is not specified, the @code{passcount} command sets the
12279 passcount of the most recently defined tracepoint. If no passcount is
12280 given, the trace experiment will run until stopped explicitly by the
12286 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12287 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12289 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12290 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12291 (@value{GDBP}) @b{trace foo}
12292 (@value{GDBP}) @b{pass 3}
12293 (@value{GDBP}) @b{trace bar}
12294 (@value{GDBP}) @b{pass 2}
12295 (@value{GDBP}) @b{trace baz}
12296 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12297 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12298 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12299 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12303 @node Tracepoint Conditions
12304 @subsection Tracepoint Conditions
12305 @cindex conditional tracepoints
12306 @cindex tracepoint conditions
12308 The simplest sort of tracepoint collects data every time your program
12309 reaches a specified place. You can also specify a @dfn{condition} for
12310 a tracepoint. A condition is just a Boolean expression in your
12311 programming language (@pxref{Expressions, ,Expressions}). A
12312 tracepoint with a condition evaluates the expression each time your
12313 program reaches it, and data collection happens only if the condition
12316 Tracepoint conditions can be specified when a tracepoint is set, by
12317 using @samp{if} in the arguments to the @code{trace} command.
12318 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12319 also be set or changed at any time with the @code{condition} command,
12320 just as with breakpoints.
12322 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12323 the conditional expression itself. Instead, @value{GDBN} encodes the
12324 expression into an agent expression (@pxref{Agent Expressions})
12325 suitable for execution on the target, independently of @value{GDBN}.
12326 Global variables become raw memory locations, locals become stack
12327 accesses, and so forth.
12329 For instance, suppose you have a function that is usually called
12330 frequently, but should not be called after an error has occurred. You
12331 could use the following tracepoint command to collect data about calls
12332 of that function that happen while the error code is propagating
12333 through the program; an unconditional tracepoint could end up
12334 collecting thousands of useless trace frames that you would have to
12338 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12341 @node Trace State Variables
12342 @subsection Trace State Variables
12343 @cindex trace state variables
12345 A @dfn{trace state variable} is a special type of variable that is
12346 created and managed by target-side code. The syntax is the same as
12347 that for GDB's convenience variables (a string prefixed with ``$''),
12348 but they are stored on the target. They must be created explicitly,
12349 using a @code{tvariable} command. They are always 64-bit signed
12352 Trace state variables are remembered by @value{GDBN}, and downloaded
12353 to the target along with tracepoint information when the trace
12354 experiment starts. There are no intrinsic limits on the number of
12355 trace state variables, beyond memory limitations of the target.
12357 @cindex convenience variables, and trace state variables
12358 Although trace state variables are managed by the target, you can use
12359 them in print commands and expressions as if they were convenience
12360 variables; @value{GDBN} will get the current value from the target
12361 while the trace experiment is running. Trace state variables share
12362 the same namespace as other ``$'' variables, which means that you
12363 cannot have trace state variables with names like @code{$23} or
12364 @code{$pc}, nor can you have a trace state variable and a convenience
12365 variable with the same name.
12369 @item tvariable $@var{name} [ = @var{expression} ]
12371 The @code{tvariable} command creates a new trace state variable named
12372 @code{$@var{name}}, and optionally gives it an initial value of
12373 @var{expression}. The @var{expression} is evaluated when this command is
12374 entered; the result will be converted to an integer if possible,
12375 otherwise @value{GDBN} will report an error. A subsequent
12376 @code{tvariable} command specifying the same name does not create a
12377 variable, but instead assigns the supplied initial value to the
12378 existing variable of that name, overwriting any previous initial
12379 value. The default initial value is 0.
12381 @item info tvariables
12382 @kindex info tvariables
12383 List all the trace state variables along with their initial values.
12384 Their current values may also be displayed, if the trace experiment is
12387 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12388 @kindex delete tvariable
12389 Delete the given trace state variables, or all of them if no arguments
12394 @node Tracepoint Actions
12395 @subsection Tracepoint Action Lists
12399 @cindex tracepoint actions
12400 @item actions @r{[}@var{num}@r{]}
12401 This command will prompt for a list of actions to be taken when the
12402 tracepoint is hit. If the tracepoint number @var{num} is not
12403 specified, this command sets the actions for the one that was most
12404 recently defined (so that you can define a tracepoint and then say
12405 @code{actions} without bothering about its number). You specify the
12406 actions themselves on the following lines, one action at a time, and
12407 terminate the actions list with a line containing just @code{end}. So
12408 far, the only defined actions are @code{collect}, @code{teval}, and
12409 @code{while-stepping}.
12411 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12412 Commands, ,Breakpoint Command Lists}), except that only the defined
12413 actions are allowed; any other @value{GDBN} command is rejected.
12415 @cindex remove actions from a tracepoint
12416 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12417 and follow it immediately with @samp{end}.
12420 (@value{GDBP}) @b{collect @var{data}} // collect some data
12422 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12424 (@value{GDBP}) @b{end} // signals the end of actions.
12427 In the following example, the action list begins with @code{collect}
12428 commands indicating the things to be collected when the tracepoint is
12429 hit. Then, in order to single-step and collect additional data
12430 following the tracepoint, a @code{while-stepping} command is used,
12431 followed by the list of things to be collected after each step in a
12432 sequence of single steps. The @code{while-stepping} command is
12433 terminated by its own separate @code{end} command. Lastly, the action
12434 list is terminated by an @code{end} command.
12437 (@value{GDBP}) @b{trace foo}
12438 (@value{GDBP}) @b{actions}
12439 Enter actions for tracepoint 1, one per line:
12442 > while-stepping 12
12443 > collect $pc, arr[i]
12448 @kindex collect @r{(tracepoints)}
12449 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12450 Collect values of the given expressions when the tracepoint is hit.
12451 This command accepts a comma-separated list of any valid expressions.
12452 In addition to global, static, or local variables, the following
12453 special arguments are supported:
12457 Collect all registers.
12460 Collect all function arguments.
12463 Collect all local variables.
12466 Collect the return address. This is helpful if you want to see more
12470 Collects the number of arguments from the static probe at which the
12471 tracepoint is located.
12472 @xref{Static Probe Points}.
12474 @item $_probe_arg@var{n}
12475 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12476 from the static probe at which the tracepoint is located.
12477 @xref{Static Probe Points}.
12480 @vindex $_sdata@r{, collect}
12481 Collect static tracepoint marker specific data. Only available for
12482 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12483 Lists}. On the UST static tracepoints library backend, an
12484 instrumentation point resembles a @code{printf} function call. The
12485 tracing library is able to collect user specified data formatted to a
12486 character string using the format provided by the programmer that
12487 instrumented the program. Other backends have similar mechanisms.
12488 Here's an example of a UST marker call:
12491 const char master_name[] = "$your_name";
12492 trace_mark(channel1, marker1, "hello %s", master_name)
12495 In this case, collecting @code{$_sdata} collects the string
12496 @samp{hello $yourname}. When analyzing the trace buffer, you can
12497 inspect @samp{$_sdata} like any other variable available to
12501 You can give several consecutive @code{collect} commands, each one
12502 with a single argument, or one @code{collect} command with several
12503 arguments separated by commas; the effect is the same.
12505 The optional @var{mods} changes the usual handling of the arguments.
12506 @code{s} requests that pointers to chars be handled as strings, in
12507 particular collecting the contents of the memory being pointed at, up
12508 to the first zero. The upper bound is by default the value of the
12509 @code{print elements} variable; if @code{s} is followed by a decimal
12510 number, that is the upper bound instead. So for instance
12511 @samp{collect/s25 mystr} collects as many as 25 characters at
12514 The command @code{info scope} (@pxref{Symbols, info scope}) is
12515 particularly useful for figuring out what data to collect.
12517 @kindex teval @r{(tracepoints)}
12518 @item teval @var{expr1}, @var{expr2}, @dots{}
12519 Evaluate the given expressions when the tracepoint is hit. This
12520 command accepts a comma-separated list of expressions. The results
12521 are discarded, so this is mainly useful for assigning values to trace
12522 state variables (@pxref{Trace State Variables}) without adding those
12523 values to the trace buffer, as would be the case if the @code{collect}
12526 @kindex while-stepping @r{(tracepoints)}
12527 @item while-stepping @var{n}
12528 Perform @var{n} single-step instruction traces after the tracepoint,
12529 collecting new data after each step. The @code{while-stepping}
12530 command is followed by the list of what to collect while stepping
12531 (followed by its own @code{end} command):
12534 > while-stepping 12
12535 > collect $regs, myglobal
12541 Note that @code{$pc} is not automatically collected by
12542 @code{while-stepping}; you need to explicitly collect that register if
12543 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12546 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12547 @kindex set default-collect
12548 @cindex default collection action
12549 This variable is a list of expressions to collect at each tracepoint
12550 hit. It is effectively an additional @code{collect} action prepended
12551 to every tracepoint action list. The expressions are parsed
12552 individually for each tracepoint, so for instance a variable named
12553 @code{xyz} may be interpreted as a global for one tracepoint, and a
12554 local for another, as appropriate to the tracepoint's location.
12556 @item show default-collect
12557 @kindex show default-collect
12558 Show the list of expressions that are collected by default at each
12563 @node Listing Tracepoints
12564 @subsection Listing Tracepoints
12567 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12568 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12569 @cindex information about tracepoints
12570 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12571 Display information about the tracepoint @var{num}. If you don't
12572 specify a tracepoint number, displays information about all the
12573 tracepoints defined so far. The format is similar to that used for
12574 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12575 command, simply restricting itself to tracepoints.
12577 A tracepoint's listing may include additional information specific to
12582 its passcount as given by the @code{passcount @var{n}} command
12585 the state about installed on target of each location
12589 (@value{GDBP}) @b{info trace}
12590 Num Type Disp Enb Address What
12591 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12593 collect globfoo, $regs
12598 2 tracepoint keep y <MULTIPLE>
12600 2.1 y 0x0804859c in func4 at change-loc.h:35
12601 installed on target
12602 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12603 installed on target
12604 2.3 y <PENDING> set_tracepoint
12605 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12606 not installed on target
12611 This command can be abbreviated @code{info tp}.
12614 @node Listing Static Tracepoint Markers
12615 @subsection Listing Static Tracepoint Markers
12618 @kindex info static-tracepoint-markers
12619 @cindex information about static tracepoint markers
12620 @item info static-tracepoint-markers
12621 Display information about all static tracepoint markers defined in the
12624 For each marker, the following columns are printed:
12628 An incrementing counter, output to help readability. This is not a
12631 The marker ID, as reported by the target.
12632 @item Enabled or Disabled
12633 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12634 that are not enabled.
12636 Where the marker is in your program, as a memory address.
12638 Where the marker is in the source for your program, as a file and line
12639 number. If the debug information included in the program does not
12640 allow @value{GDBN} to locate the source of the marker, this column
12641 will be left blank.
12645 In addition, the following information may be printed for each marker:
12649 User data passed to the tracing library by the marker call. In the
12650 UST backend, this is the format string passed as argument to the
12652 @item Static tracepoints probing the marker
12653 The list of static tracepoints attached to the marker.
12657 (@value{GDBP}) info static-tracepoint-markers
12658 Cnt ID Enb Address What
12659 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12660 Data: number1 %d number2 %d
12661 Probed by static tracepoints: #2
12662 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12668 @node Starting and Stopping Trace Experiments
12669 @subsection Starting and Stopping Trace Experiments
12672 @kindex tstart [ @var{notes} ]
12673 @cindex start a new trace experiment
12674 @cindex collected data discarded
12676 This command starts the trace experiment, and begins collecting data.
12677 It has the side effect of discarding all the data collected in the
12678 trace buffer during the previous trace experiment. If any arguments
12679 are supplied, they are taken as a note and stored with the trace
12680 experiment's state. The notes may be arbitrary text, and are
12681 especially useful with disconnected tracing in a multi-user context;
12682 the notes can explain what the trace is doing, supply user contact
12683 information, and so forth.
12685 @kindex tstop [ @var{notes} ]
12686 @cindex stop a running trace experiment
12688 This command stops the trace experiment. If any arguments are
12689 supplied, they are recorded with the experiment as a note. This is
12690 useful if you are stopping a trace started by someone else, for
12691 instance if the trace is interfering with the system's behavior and
12692 needs to be stopped quickly.
12694 @strong{Note}: a trace experiment and data collection may stop
12695 automatically if any tracepoint's passcount is reached
12696 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12699 @cindex status of trace data collection
12700 @cindex trace experiment, status of
12702 This command displays the status of the current trace data
12706 Here is an example of the commands we described so far:
12709 (@value{GDBP}) @b{trace gdb_c_test}
12710 (@value{GDBP}) @b{actions}
12711 Enter actions for tracepoint #1, one per line.
12712 > collect $regs,$locals,$args
12713 > while-stepping 11
12717 (@value{GDBP}) @b{tstart}
12718 [time passes @dots{}]
12719 (@value{GDBP}) @b{tstop}
12722 @anchor{disconnected tracing}
12723 @cindex disconnected tracing
12724 You can choose to continue running the trace experiment even if
12725 @value{GDBN} disconnects from the target, voluntarily or
12726 involuntarily. For commands such as @code{detach}, the debugger will
12727 ask what you want to do with the trace. But for unexpected
12728 terminations (@value{GDBN} crash, network outage), it would be
12729 unfortunate to lose hard-won trace data, so the variable
12730 @code{disconnected-tracing} lets you decide whether the trace should
12731 continue running without @value{GDBN}.
12734 @item set disconnected-tracing on
12735 @itemx set disconnected-tracing off
12736 @kindex set disconnected-tracing
12737 Choose whether a tracing run should continue to run if @value{GDBN}
12738 has disconnected from the target. Note that @code{detach} or
12739 @code{quit} will ask you directly what to do about a running trace no
12740 matter what this variable's setting, so the variable is mainly useful
12741 for handling unexpected situations, such as loss of the network.
12743 @item show disconnected-tracing
12744 @kindex show disconnected-tracing
12745 Show the current choice for disconnected tracing.
12749 When you reconnect to the target, the trace experiment may or may not
12750 still be running; it might have filled the trace buffer in the
12751 meantime, or stopped for one of the other reasons. If it is running,
12752 it will continue after reconnection.
12754 Upon reconnection, the target will upload information about the
12755 tracepoints in effect. @value{GDBN} will then compare that
12756 information to the set of tracepoints currently defined, and attempt
12757 to match them up, allowing for the possibility that the numbers may
12758 have changed due to creation and deletion in the meantime. If one of
12759 the target's tracepoints does not match any in @value{GDBN}, the
12760 debugger will create a new tracepoint, so that you have a number with
12761 which to specify that tracepoint. This matching-up process is
12762 necessarily heuristic, and it may result in useless tracepoints being
12763 created; you may simply delete them if they are of no use.
12765 @cindex circular trace buffer
12766 If your target agent supports a @dfn{circular trace buffer}, then you
12767 can run a trace experiment indefinitely without filling the trace
12768 buffer; when space runs out, the agent deletes already-collected trace
12769 frames, oldest first, until there is enough room to continue
12770 collecting. This is especially useful if your tracepoints are being
12771 hit too often, and your trace gets terminated prematurely because the
12772 buffer is full. To ask for a circular trace buffer, simply set
12773 @samp{circular-trace-buffer} to on. You can set this at any time,
12774 including during tracing; if the agent can do it, it will change
12775 buffer handling on the fly, otherwise it will not take effect until
12779 @item set circular-trace-buffer on
12780 @itemx set circular-trace-buffer off
12781 @kindex set circular-trace-buffer
12782 Choose whether a tracing run should use a linear or circular buffer
12783 for trace data. A linear buffer will not lose any trace data, but may
12784 fill up prematurely, while a circular buffer will discard old trace
12785 data, but it will have always room for the latest tracepoint hits.
12787 @item show circular-trace-buffer
12788 @kindex show circular-trace-buffer
12789 Show the current choice for the trace buffer. Note that this may not
12790 match the agent's current buffer handling, nor is it guaranteed to
12791 match the setting that might have been in effect during a past run,
12792 for instance if you are looking at frames from a trace file.
12797 @item set trace-buffer-size @var{n}
12798 @itemx set trace-buffer-size unlimited
12799 @kindex set trace-buffer-size
12800 Request that the target use a trace buffer of @var{n} bytes. Not all
12801 targets will honor the request; they may have a compiled-in size for
12802 the trace buffer, or some other limitation. Set to a value of
12803 @code{unlimited} or @code{-1} to let the target use whatever size it
12804 likes. This is also the default.
12806 @item show trace-buffer-size
12807 @kindex show trace-buffer-size
12808 Show the current requested size for the trace buffer. Note that this
12809 will only match the actual size if the target supports size-setting,
12810 and was able to handle the requested size. For instance, if the
12811 target can only change buffer size between runs, this variable will
12812 not reflect the change until the next run starts. Use @code{tstatus}
12813 to get a report of the actual buffer size.
12817 @item set trace-user @var{text}
12818 @kindex set trace-user
12820 @item show trace-user
12821 @kindex show trace-user
12823 @item set trace-notes @var{text}
12824 @kindex set trace-notes
12825 Set the trace run's notes.
12827 @item show trace-notes
12828 @kindex show trace-notes
12829 Show the trace run's notes.
12831 @item set trace-stop-notes @var{text}
12832 @kindex set trace-stop-notes
12833 Set the trace run's stop notes. The handling of the note is as for
12834 @code{tstop} arguments; the set command is convenient way to fix a
12835 stop note that is mistaken or incomplete.
12837 @item show trace-stop-notes
12838 @kindex show trace-stop-notes
12839 Show the trace run's stop notes.
12843 @node Tracepoint Restrictions
12844 @subsection Tracepoint Restrictions
12846 @cindex tracepoint restrictions
12847 There are a number of restrictions on the use of tracepoints. As
12848 described above, tracepoint data gathering occurs on the target
12849 without interaction from @value{GDBN}. Thus the full capabilities of
12850 the debugger are not available during data gathering, and then at data
12851 examination time, you will be limited by only having what was
12852 collected. The following items describe some common problems, but it
12853 is not exhaustive, and you may run into additional difficulties not
12859 Tracepoint expressions are intended to gather objects (lvalues). Thus
12860 the full flexibility of GDB's expression evaluator is not available.
12861 You cannot call functions, cast objects to aggregate types, access
12862 convenience variables or modify values (except by assignment to trace
12863 state variables). Some language features may implicitly call
12864 functions (for instance Objective-C fields with accessors), and therefore
12865 cannot be collected either.
12868 Collection of local variables, either individually or in bulk with
12869 @code{$locals} or @code{$args}, during @code{while-stepping} may
12870 behave erratically. The stepping action may enter a new scope (for
12871 instance by stepping into a function), or the location of the variable
12872 may change (for instance it is loaded into a register). The
12873 tracepoint data recorded uses the location information for the
12874 variables that is correct for the tracepoint location. When the
12875 tracepoint is created, it is not possible, in general, to determine
12876 where the steps of a @code{while-stepping} sequence will advance the
12877 program---particularly if a conditional branch is stepped.
12880 Collection of an incompletely-initialized or partially-destroyed object
12881 may result in something that @value{GDBN} cannot display, or displays
12882 in a misleading way.
12885 When @value{GDBN} displays a pointer to character it automatically
12886 dereferences the pointer to also display characters of the string
12887 being pointed to. However, collecting the pointer during tracing does
12888 not automatically collect the string. You need to explicitly
12889 dereference the pointer and provide size information if you want to
12890 collect not only the pointer, but the memory pointed to. For example,
12891 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12895 It is not possible to collect a complete stack backtrace at a
12896 tracepoint. Instead, you may collect the registers and a few hundred
12897 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12898 (adjust to use the name of the actual stack pointer register on your
12899 target architecture, and the amount of stack you wish to capture).
12900 Then the @code{backtrace} command will show a partial backtrace when
12901 using a trace frame. The number of stack frames that can be examined
12902 depends on the sizes of the frames in the collected stack. Note that
12903 if you ask for a block so large that it goes past the bottom of the
12904 stack, the target agent may report an error trying to read from an
12908 If you do not collect registers at a tracepoint, @value{GDBN} can
12909 infer that the value of @code{$pc} must be the same as the address of
12910 the tracepoint and use that when you are looking at a trace frame
12911 for that tracepoint. However, this cannot work if the tracepoint has
12912 multiple locations (for instance if it was set in a function that was
12913 inlined), or if it has a @code{while-stepping} loop. In those cases
12914 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12919 @node Analyze Collected Data
12920 @section Using the Collected Data
12922 After the tracepoint experiment ends, you use @value{GDBN} commands
12923 for examining the trace data. The basic idea is that each tracepoint
12924 collects a trace @dfn{snapshot} every time it is hit and another
12925 snapshot every time it single-steps. All these snapshots are
12926 consecutively numbered from zero and go into a buffer, and you can
12927 examine them later. The way you examine them is to @dfn{focus} on a
12928 specific trace snapshot. When the remote stub is focused on a trace
12929 snapshot, it will respond to all @value{GDBN} requests for memory and
12930 registers by reading from the buffer which belongs to that snapshot,
12931 rather than from @emph{real} memory or registers of the program being
12932 debugged. This means that @strong{all} @value{GDBN} commands
12933 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12934 behave as if we were currently debugging the program state as it was
12935 when the tracepoint occurred. Any requests for data that are not in
12936 the buffer will fail.
12939 * tfind:: How to select a trace snapshot
12940 * tdump:: How to display all data for a snapshot
12941 * save tracepoints:: How to save tracepoints for a future run
12945 @subsection @code{tfind @var{n}}
12948 @cindex select trace snapshot
12949 @cindex find trace snapshot
12950 The basic command for selecting a trace snapshot from the buffer is
12951 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12952 counting from zero. If no argument @var{n} is given, the next
12953 snapshot is selected.
12955 Here are the various forms of using the @code{tfind} command.
12959 Find the first snapshot in the buffer. This is a synonym for
12960 @code{tfind 0} (since 0 is the number of the first snapshot).
12963 Stop debugging trace snapshots, resume @emph{live} debugging.
12966 Same as @samp{tfind none}.
12969 No argument means find the next trace snapshot.
12972 Find the previous trace snapshot before the current one. This permits
12973 retracing earlier steps.
12975 @item tfind tracepoint @var{num}
12976 Find the next snapshot associated with tracepoint @var{num}. Search
12977 proceeds forward from the last examined trace snapshot. If no
12978 argument @var{num} is given, it means find the next snapshot collected
12979 for the same tracepoint as the current snapshot.
12981 @item tfind pc @var{addr}
12982 Find the next snapshot associated with the value @var{addr} of the
12983 program counter. Search proceeds forward from the last examined trace
12984 snapshot. If no argument @var{addr} is given, it means find the next
12985 snapshot with the same value of PC as the current snapshot.
12987 @item tfind outside @var{addr1}, @var{addr2}
12988 Find the next snapshot whose PC is outside the given range of
12989 addresses (exclusive).
12991 @item tfind range @var{addr1}, @var{addr2}
12992 Find the next snapshot whose PC is between @var{addr1} and
12993 @var{addr2} (inclusive).
12995 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12996 Find the next snapshot associated with the source line @var{n}. If
12997 the optional argument @var{file} is given, refer to line @var{n} in
12998 that source file. Search proceeds forward from the last examined
12999 trace snapshot. If no argument @var{n} is given, it means find the
13000 next line other than the one currently being examined; thus saying
13001 @code{tfind line} repeatedly can appear to have the same effect as
13002 stepping from line to line in a @emph{live} debugging session.
13005 The default arguments for the @code{tfind} commands are specifically
13006 designed to make it easy to scan through the trace buffer. For
13007 instance, @code{tfind} with no argument selects the next trace
13008 snapshot, and @code{tfind -} with no argument selects the previous
13009 trace snapshot. So, by giving one @code{tfind} command, and then
13010 simply hitting @key{RET} repeatedly you can examine all the trace
13011 snapshots in order. Or, by saying @code{tfind -} and then hitting
13012 @key{RET} repeatedly you can examine the snapshots in reverse order.
13013 The @code{tfind line} command with no argument selects the snapshot
13014 for the next source line executed. The @code{tfind pc} command with
13015 no argument selects the next snapshot with the same program counter
13016 (PC) as the current frame. The @code{tfind tracepoint} command with
13017 no argument selects the next trace snapshot collected by the same
13018 tracepoint as the current one.
13020 In addition to letting you scan through the trace buffer manually,
13021 these commands make it easy to construct @value{GDBN} scripts that
13022 scan through the trace buffer and print out whatever collected data
13023 you are interested in. Thus, if we want to examine the PC, FP, and SP
13024 registers from each trace frame in the buffer, we can say this:
13027 (@value{GDBP}) @b{tfind start}
13028 (@value{GDBP}) @b{while ($trace_frame != -1)}
13029 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13030 $trace_frame, $pc, $sp, $fp
13034 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13035 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13036 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13037 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13038 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13039 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13040 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13041 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13042 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13043 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13044 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13047 Or, if we want to examine the variable @code{X} at each source line in
13051 (@value{GDBP}) @b{tfind start}
13052 (@value{GDBP}) @b{while ($trace_frame != -1)}
13053 > printf "Frame %d, X == %d\n", $trace_frame, X
13063 @subsection @code{tdump}
13065 @cindex dump all data collected at tracepoint
13066 @cindex tracepoint data, display
13068 This command takes no arguments. It prints all the data collected at
13069 the current trace snapshot.
13072 (@value{GDBP}) @b{trace 444}
13073 (@value{GDBP}) @b{actions}
13074 Enter actions for tracepoint #2, one per line:
13075 > collect $regs, $locals, $args, gdb_long_test
13078 (@value{GDBP}) @b{tstart}
13080 (@value{GDBP}) @b{tfind line 444}
13081 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13083 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13085 (@value{GDBP}) @b{tdump}
13086 Data collected at tracepoint 2, trace frame 1:
13087 d0 0xc4aa0085 -995491707
13091 d4 0x71aea3d 119204413
13094 d7 0x380035 3670069
13095 a0 0x19e24a 1696330
13096 a1 0x3000668 50333288
13098 a3 0x322000 3284992
13099 a4 0x3000698 50333336
13100 a5 0x1ad3cc 1758156
13101 fp 0x30bf3c 0x30bf3c
13102 sp 0x30bf34 0x30bf34
13104 pc 0x20b2c8 0x20b2c8
13108 p = 0x20e5b4 "gdb-test"
13115 gdb_long_test = 17 '\021'
13120 @code{tdump} works by scanning the tracepoint's current collection
13121 actions and printing the value of each expression listed. So
13122 @code{tdump} can fail, if after a run, you change the tracepoint's
13123 actions to mention variables that were not collected during the run.
13125 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13126 uses the collected value of @code{$pc} to distinguish between trace
13127 frames that were collected at the tracepoint hit, and frames that were
13128 collected while stepping. This allows it to correctly choose whether
13129 to display the basic list of collections, or the collections from the
13130 body of the while-stepping loop. However, if @code{$pc} was not collected,
13131 then @code{tdump} will always attempt to dump using the basic collection
13132 list, and may fail if a while-stepping frame does not include all the
13133 same data that is collected at the tracepoint hit.
13134 @c This is getting pretty arcane, example would be good.
13136 @node save tracepoints
13137 @subsection @code{save tracepoints @var{filename}}
13138 @kindex save tracepoints
13139 @kindex save-tracepoints
13140 @cindex save tracepoints for future sessions
13142 This command saves all current tracepoint definitions together with
13143 their actions and passcounts, into a file @file{@var{filename}}
13144 suitable for use in a later debugging session. To read the saved
13145 tracepoint definitions, use the @code{source} command (@pxref{Command
13146 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13147 alias for @w{@code{save tracepoints}}
13149 @node Tracepoint Variables
13150 @section Convenience Variables for Tracepoints
13151 @cindex tracepoint variables
13152 @cindex convenience variables for tracepoints
13155 @vindex $trace_frame
13156 @item (int) $trace_frame
13157 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13158 snapshot is selected.
13160 @vindex $tracepoint
13161 @item (int) $tracepoint
13162 The tracepoint for the current trace snapshot.
13164 @vindex $trace_line
13165 @item (int) $trace_line
13166 The line number for the current trace snapshot.
13168 @vindex $trace_file
13169 @item (char []) $trace_file
13170 The source file for the current trace snapshot.
13172 @vindex $trace_func
13173 @item (char []) $trace_func
13174 The name of the function containing @code{$tracepoint}.
13177 Note: @code{$trace_file} is not suitable for use in @code{printf},
13178 use @code{output} instead.
13180 Here's a simple example of using these convenience variables for
13181 stepping through all the trace snapshots and printing some of their
13182 data. Note that these are not the same as trace state variables,
13183 which are managed by the target.
13186 (@value{GDBP}) @b{tfind start}
13188 (@value{GDBP}) @b{while $trace_frame != -1}
13189 > output $trace_file
13190 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13196 @section Using Trace Files
13197 @cindex trace files
13199 In some situations, the target running a trace experiment may no
13200 longer be available; perhaps it crashed, or the hardware was needed
13201 for a different activity. To handle these cases, you can arrange to
13202 dump the trace data into a file, and later use that file as a source
13203 of trace data, via the @code{target tfile} command.
13208 @item tsave [ -r ] @var{filename}
13209 @itemx tsave [-ctf] @var{dirname}
13210 Save the trace data to @var{filename}. By default, this command
13211 assumes that @var{filename} refers to the host filesystem, so if
13212 necessary @value{GDBN} will copy raw trace data up from the target and
13213 then save it. If the target supports it, you can also supply the
13214 optional argument @code{-r} (``remote'') to direct the target to save
13215 the data directly into @var{filename} in its own filesystem, which may be
13216 more efficient if the trace buffer is very large. (Note, however, that
13217 @code{target tfile} can only read from files accessible to the host.)
13218 By default, this command will save trace frame in tfile format.
13219 You can supply the optional argument @code{-ctf} to save date in CTF
13220 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13221 that can be shared by multiple debugging and tracing tools. Please go to
13222 @indicateurl{http://www.efficios.com/ctf} to get more information.
13224 @kindex target tfile
13228 @item target tfile @var{filename}
13229 @itemx target ctf @var{dirname}
13230 Use the file named @var{filename} or directory named @var{dirname} as
13231 a source of trace data. Commands that examine data work as they do with
13232 a live target, but it is not possible to run any new trace experiments.
13233 @code{tstatus} will report the state of the trace run at the moment
13234 the data was saved, as well as the current trace frame you are examining.
13235 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13239 (@value{GDBP}) target ctf ctf.ctf
13240 (@value{GDBP}) tfind
13241 Found trace frame 0, tracepoint 2
13242 39 ++a; /* set tracepoint 1 here */
13243 (@value{GDBP}) tdump
13244 Data collected at tracepoint 2, trace frame 0:
13248 c = @{"123", "456", "789", "123", "456", "789"@}
13249 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13257 @chapter Debugging Programs That Use Overlays
13260 If your program is too large to fit completely in your target system's
13261 memory, you can sometimes use @dfn{overlays} to work around this
13262 problem. @value{GDBN} provides some support for debugging programs that
13266 * How Overlays Work:: A general explanation of overlays.
13267 * Overlay Commands:: Managing overlays in @value{GDBN}.
13268 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13269 mapped by asking the inferior.
13270 * Overlay Sample Program:: A sample program using overlays.
13273 @node How Overlays Work
13274 @section How Overlays Work
13275 @cindex mapped overlays
13276 @cindex unmapped overlays
13277 @cindex load address, overlay's
13278 @cindex mapped address
13279 @cindex overlay area
13281 Suppose you have a computer whose instruction address space is only 64
13282 kilobytes long, but which has much more memory which can be accessed by
13283 other means: special instructions, segment registers, or memory
13284 management hardware, for example. Suppose further that you want to
13285 adapt a program which is larger than 64 kilobytes to run on this system.
13287 One solution is to identify modules of your program which are relatively
13288 independent, and need not call each other directly; call these modules
13289 @dfn{overlays}. Separate the overlays from the main program, and place
13290 their machine code in the larger memory. Place your main program in
13291 instruction memory, but leave at least enough space there to hold the
13292 largest overlay as well.
13294 Now, to call a function located in an overlay, you must first copy that
13295 overlay's machine code from the large memory into the space set aside
13296 for it in the instruction memory, and then jump to its entry point
13299 @c NB: In the below the mapped area's size is greater or equal to the
13300 @c size of all overlays. This is intentional to remind the developer
13301 @c that overlays don't necessarily need to be the same size.
13305 Data Instruction Larger
13306 Address Space Address Space Address Space
13307 +-----------+ +-----------+ +-----------+
13309 +-----------+ +-----------+ +-----------+<-- overlay 1
13310 | program | | main | .----| overlay 1 | load address
13311 | variables | | program | | +-----------+
13312 | and heap | | | | | |
13313 +-----------+ | | | +-----------+<-- overlay 2
13314 | | +-----------+ | | | load address
13315 +-----------+ | | | .-| overlay 2 |
13317 mapped --->+-----------+ | | +-----------+
13318 address | | | | | |
13319 | overlay | <-' | | |
13320 | area | <---' +-----------+<-- overlay 3
13321 | | <---. | | load address
13322 +-----------+ `--| overlay 3 |
13329 @anchor{A code overlay}A code overlay
13333 The diagram (@pxref{A code overlay}) shows a system with separate data
13334 and instruction address spaces. To map an overlay, the program copies
13335 its code from the larger address space to the instruction address space.
13336 Since the overlays shown here all use the same mapped address, only one
13337 may be mapped at a time. For a system with a single address space for
13338 data and instructions, the diagram would be similar, except that the
13339 program variables and heap would share an address space with the main
13340 program and the overlay area.
13342 An overlay loaded into instruction memory and ready for use is called a
13343 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13344 instruction memory. An overlay not present (or only partially present)
13345 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13346 is its address in the larger memory. The mapped address is also called
13347 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13348 called the @dfn{load memory address}, or @dfn{LMA}.
13350 Unfortunately, overlays are not a completely transparent way to adapt a
13351 program to limited instruction memory. They introduce a new set of
13352 global constraints you must keep in mind as you design your program:
13357 Before calling or returning to a function in an overlay, your program
13358 must make sure that overlay is actually mapped. Otherwise, the call or
13359 return will transfer control to the right address, but in the wrong
13360 overlay, and your program will probably crash.
13363 If the process of mapping an overlay is expensive on your system, you
13364 will need to choose your overlays carefully to minimize their effect on
13365 your program's performance.
13368 The executable file you load onto your system must contain each
13369 overlay's instructions, appearing at the overlay's load address, not its
13370 mapped address. However, each overlay's instructions must be relocated
13371 and its symbols defined as if the overlay were at its mapped address.
13372 You can use GNU linker scripts to specify different load and relocation
13373 addresses for pieces of your program; see @ref{Overlay Description,,,
13374 ld.info, Using ld: the GNU linker}.
13377 The procedure for loading executable files onto your system must be able
13378 to load their contents into the larger address space as well as the
13379 instruction and data spaces.
13383 The overlay system described above is rather simple, and could be
13384 improved in many ways:
13389 If your system has suitable bank switch registers or memory management
13390 hardware, you could use those facilities to make an overlay's load area
13391 contents simply appear at their mapped address in instruction space.
13392 This would probably be faster than copying the overlay to its mapped
13393 area in the usual way.
13396 If your overlays are small enough, you could set aside more than one
13397 overlay area, and have more than one overlay mapped at a time.
13400 You can use overlays to manage data, as well as instructions. In
13401 general, data overlays are even less transparent to your design than
13402 code overlays: whereas code overlays only require care when you call or
13403 return to functions, data overlays require care every time you access
13404 the data. Also, if you change the contents of a data overlay, you
13405 must copy its contents back out to its load address before you can copy a
13406 different data overlay into the same mapped area.
13411 @node Overlay Commands
13412 @section Overlay Commands
13414 To use @value{GDBN}'s overlay support, each overlay in your program must
13415 correspond to a separate section of the executable file. The section's
13416 virtual memory address and load memory address must be the overlay's
13417 mapped and load addresses. Identifying overlays with sections allows
13418 @value{GDBN} to determine the appropriate address of a function or
13419 variable, depending on whether the overlay is mapped or not.
13421 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13422 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13427 Disable @value{GDBN}'s overlay support. When overlay support is
13428 disabled, @value{GDBN} assumes that all functions and variables are
13429 always present at their mapped addresses. By default, @value{GDBN}'s
13430 overlay support is disabled.
13432 @item overlay manual
13433 @cindex manual overlay debugging
13434 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13435 relies on you to tell it which overlays are mapped, and which are not,
13436 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13437 commands described below.
13439 @item overlay map-overlay @var{overlay}
13440 @itemx overlay map @var{overlay}
13441 @cindex map an overlay
13442 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13443 be the name of the object file section containing the overlay. When an
13444 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13445 functions and variables at their mapped addresses. @value{GDBN} assumes
13446 that any other overlays whose mapped ranges overlap that of
13447 @var{overlay} are now unmapped.
13449 @item overlay unmap-overlay @var{overlay}
13450 @itemx overlay unmap @var{overlay}
13451 @cindex unmap an overlay
13452 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13453 must be the name of the object file section containing the overlay.
13454 When an overlay is unmapped, @value{GDBN} assumes it can find the
13455 overlay's functions and variables at their load addresses.
13458 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13459 consults a data structure the overlay manager maintains in the inferior
13460 to see which overlays are mapped. For details, see @ref{Automatic
13461 Overlay Debugging}.
13463 @item overlay load-target
13464 @itemx overlay load
13465 @cindex reloading the overlay table
13466 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13467 re-reads the table @value{GDBN} automatically each time the inferior
13468 stops, so this command should only be necessary if you have changed the
13469 overlay mapping yourself using @value{GDBN}. This command is only
13470 useful when using automatic overlay debugging.
13472 @item overlay list-overlays
13473 @itemx overlay list
13474 @cindex listing mapped overlays
13475 Display a list of the overlays currently mapped, along with their mapped
13476 addresses, load addresses, and sizes.
13480 Normally, when @value{GDBN} prints a code address, it includes the name
13481 of the function the address falls in:
13484 (@value{GDBP}) print main
13485 $3 = @{int ()@} 0x11a0 <main>
13488 When overlay debugging is enabled, @value{GDBN} recognizes code in
13489 unmapped overlays, and prints the names of unmapped functions with
13490 asterisks around them. For example, if @code{foo} is a function in an
13491 unmapped overlay, @value{GDBN} prints it this way:
13494 (@value{GDBP}) overlay list
13495 No sections are mapped.
13496 (@value{GDBP}) print foo
13497 $5 = @{int (int)@} 0x100000 <*foo*>
13500 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13504 (@value{GDBP}) overlay list
13505 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13506 mapped at 0x1016 - 0x104a
13507 (@value{GDBP}) print foo
13508 $6 = @{int (int)@} 0x1016 <foo>
13511 When overlay debugging is enabled, @value{GDBN} can find the correct
13512 address for functions and variables in an overlay, whether or not the
13513 overlay is mapped. This allows most @value{GDBN} commands, like
13514 @code{break} and @code{disassemble}, to work normally, even on unmapped
13515 code. However, @value{GDBN}'s breakpoint support has some limitations:
13519 @cindex breakpoints in overlays
13520 @cindex overlays, setting breakpoints in
13521 You can set breakpoints in functions in unmapped overlays, as long as
13522 @value{GDBN} can write to the overlay at its load address.
13524 @value{GDBN} can not set hardware or simulator-based breakpoints in
13525 unmapped overlays. However, if you set a breakpoint at the end of your
13526 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13527 you are using manual overlay management), @value{GDBN} will re-set its
13528 breakpoints properly.
13532 @node Automatic Overlay Debugging
13533 @section Automatic Overlay Debugging
13534 @cindex automatic overlay debugging
13536 @value{GDBN} can automatically track which overlays are mapped and which
13537 are not, given some simple co-operation from the overlay manager in the
13538 inferior. If you enable automatic overlay debugging with the
13539 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13540 looks in the inferior's memory for certain variables describing the
13541 current state of the overlays.
13543 Here are the variables your overlay manager must define to support
13544 @value{GDBN}'s automatic overlay debugging:
13548 @item @code{_ovly_table}:
13549 This variable must be an array of the following structures:
13554 /* The overlay's mapped address. */
13557 /* The size of the overlay, in bytes. */
13558 unsigned long size;
13560 /* The overlay's load address. */
13563 /* Non-zero if the overlay is currently mapped;
13565 unsigned long mapped;
13569 @item @code{_novlys}:
13570 This variable must be a four-byte signed integer, holding the total
13571 number of elements in @code{_ovly_table}.
13575 To decide whether a particular overlay is mapped or not, @value{GDBN}
13576 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13577 @code{lma} members equal the VMA and LMA of the overlay's section in the
13578 executable file. When @value{GDBN} finds a matching entry, it consults
13579 the entry's @code{mapped} member to determine whether the overlay is
13582 In addition, your overlay manager may define a function called
13583 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13584 will silently set a breakpoint there. If the overlay manager then
13585 calls this function whenever it has changed the overlay table, this
13586 will enable @value{GDBN} to accurately keep track of which overlays
13587 are in program memory, and update any breakpoints that may be set
13588 in overlays. This will allow breakpoints to work even if the
13589 overlays are kept in ROM or other non-writable memory while they
13590 are not being executed.
13592 @node Overlay Sample Program
13593 @section Overlay Sample Program
13594 @cindex overlay example program
13596 When linking a program which uses overlays, you must place the overlays
13597 at their load addresses, while relocating them to run at their mapped
13598 addresses. To do this, you must write a linker script (@pxref{Overlay
13599 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13600 since linker scripts are specific to a particular host system, target
13601 architecture, and target memory layout, this manual cannot provide
13602 portable sample code demonstrating @value{GDBN}'s overlay support.
13604 However, the @value{GDBN} source distribution does contain an overlaid
13605 program, with linker scripts for a few systems, as part of its test
13606 suite. The program consists of the following files from
13607 @file{gdb/testsuite/gdb.base}:
13611 The main program file.
13613 A simple overlay manager, used by @file{overlays.c}.
13618 Overlay modules, loaded and used by @file{overlays.c}.
13621 Linker scripts for linking the test program on the @code{d10v-elf}
13622 and @code{m32r-elf} targets.
13625 You can build the test program using the @code{d10v-elf} GCC
13626 cross-compiler like this:
13629 $ d10v-elf-gcc -g -c overlays.c
13630 $ d10v-elf-gcc -g -c ovlymgr.c
13631 $ d10v-elf-gcc -g -c foo.c
13632 $ d10v-elf-gcc -g -c bar.c
13633 $ d10v-elf-gcc -g -c baz.c
13634 $ d10v-elf-gcc -g -c grbx.c
13635 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13636 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13639 The build process is identical for any other architecture, except that
13640 you must substitute the appropriate compiler and linker script for the
13641 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13645 @chapter Using @value{GDBN} with Different Languages
13648 Although programming languages generally have common aspects, they are
13649 rarely expressed in the same manner. For instance, in ANSI C,
13650 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13651 Modula-2, it is accomplished by @code{p^}. Values can also be
13652 represented (and displayed) differently. Hex numbers in C appear as
13653 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13655 @cindex working language
13656 Language-specific information is built into @value{GDBN} for some languages,
13657 allowing you to express operations like the above in your program's
13658 native language, and allowing @value{GDBN} to output values in a manner
13659 consistent with the syntax of your program's native language. The
13660 language you use to build expressions is called the @dfn{working
13664 * Setting:: Switching between source languages
13665 * Show:: Displaying the language
13666 * Checks:: Type and range checks
13667 * Supported Languages:: Supported languages
13668 * Unsupported Languages:: Unsupported languages
13672 @section Switching Between Source Languages
13674 There are two ways to control the working language---either have @value{GDBN}
13675 set it automatically, or select it manually yourself. You can use the
13676 @code{set language} command for either purpose. On startup, @value{GDBN}
13677 defaults to setting the language automatically. The working language is
13678 used to determine how expressions you type are interpreted, how values
13681 In addition to the working language, every source file that
13682 @value{GDBN} knows about has its own working language. For some object
13683 file formats, the compiler might indicate which language a particular
13684 source file is in. However, most of the time @value{GDBN} infers the
13685 language from the name of the file. The language of a source file
13686 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13687 show each frame appropriately for its own language. There is no way to
13688 set the language of a source file from within @value{GDBN}, but you can
13689 set the language associated with a filename extension. @xref{Show, ,
13690 Displaying the Language}.
13692 This is most commonly a problem when you use a program, such
13693 as @code{cfront} or @code{f2c}, that generates C but is written in
13694 another language. In that case, make the
13695 program use @code{#line} directives in its C output; that way
13696 @value{GDBN} will know the correct language of the source code of the original
13697 program, and will display that source code, not the generated C code.
13700 * Filenames:: Filename extensions and languages.
13701 * Manually:: Setting the working language manually
13702 * Automatically:: Having @value{GDBN} infer the source language
13706 @subsection List of Filename Extensions and Languages
13708 If a source file name ends in one of the following extensions, then
13709 @value{GDBN} infers that its language is the one indicated.
13727 C@t{++} source file
13733 Objective-C source file
13737 Fortran source file
13740 Modula-2 source file
13744 Assembler source file. This actually behaves almost like C, but
13745 @value{GDBN} does not skip over function prologues when stepping.
13748 In addition, you may set the language associated with a filename
13749 extension. @xref{Show, , Displaying the Language}.
13752 @subsection Setting the Working Language
13754 If you allow @value{GDBN} to set the language automatically,
13755 expressions are interpreted the same way in your debugging session and
13758 @kindex set language
13759 If you wish, you may set the language manually. To do this, issue the
13760 command @samp{set language @var{lang}}, where @var{lang} is the name of
13761 a language, such as
13762 @code{c} or @code{modula-2}.
13763 For a list of the supported languages, type @samp{set language}.
13765 Setting the language manually prevents @value{GDBN} from updating the working
13766 language automatically. This can lead to confusion if you try
13767 to debug a program when the working language is not the same as the
13768 source language, when an expression is acceptable to both
13769 languages---but means different things. For instance, if the current
13770 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13778 might not have the effect you intended. In C, this means to add
13779 @code{b} and @code{c} and place the result in @code{a}. The result
13780 printed would be the value of @code{a}. In Modula-2, this means to compare
13781 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13783 @node Automatically
13784 @subsection Having @value{GDBN} Infer the Source Language
13786 To have @value{GDBN} set the working language automatically, use
13787 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13788 then infers the working language. That is, when your program stops in a
13789 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13790 working language to the language recorded for the function in that
13791 frame. If the language for a frame is unknown (that is, if the function
13792 or block corresponding to the frame was defined in a source file that
13793 does not have a recognized extension), the current working language is
13794 not changed, and @value{GDBN} issues a warning.
13796 This may not seem necessary for most programs, which are written
13797 entirely in one source language. However, program modules and libraries
13798 written in one source language can be used by a main program written in
13799 a different source language. Using @samp{set language auto} in this
13800 case frees you from having to set the working language manually.
13803 @section Displaying the Language
13805 The following commands help you find out which language is the
13806 working language, and also what language source files were written in.
13809 @item show language
13810 @anchor{show language}
13811 @kindex show language
13812 Display the current working language. This is the
13813 language you can use with commands such as @code{print} to
13814 build and compute expressions that may involve variables in your program.
13817 @kindex info frame@r{, show the source language}
13818 Display the source language for this frame. This language becomes the
13819 working language if you use an identifier from this frame.
13820 @xref{Frame Info, ,Information about a Frame}, to identify the other
13821 information listed here.
13824 @kindex info source@r{, show the source language}
13825 Display the source language of this source file.
13826 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13827 information listed here.
13830 In unusual circumstances, you may have source files with extensions
13831 not in the standard list. You can then set the extension associated
13832 with a language explicitly:
13835 @item set extension-language @var{ext} @var{language}
13836 @kindex set extension-language
13837 Tell @value{GDBN} that source files with extension @var{ext} are to be
13838 assumed as written in the source language @var{language}.
13840 @item info extensions
13841 @kindex info extensions
13842 List all the filename extensions and the associated languages.
13846 @section Type and Range Checking
13848 Some languages are designed to guard you against making seemingly common
13849 errors through a series of compile- and run-time checks. These include
13850 checking the type of arguments to functions and operators and making
13851 sure mathematical overflows are caught at run time. Checks such as
13852 these help to ensure a program's correctness once it has been compiled
13853 by eliminating type mismatches and providing active checks for range
13854 errors when your program is running.
13856 By default @value{GDBN} checks for these errors according to the
13857 rules of the current source language. Although @value{GDBN} does not check
13858 the statements in your program, it can check expressions entered directly
13859 into @value{GDBN} for evaluation via the @code{print} command, for example.
13862 * Type Checking:: An overview of type checking
13863 * Range Checking:: An overview of range checking
13866 @cindex type checking
13867 @cindex checks, type
13868 @node Type Checking
13869 @subsection An Overview of Type Checking
13871 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13872 arguments to operators and functions have to be of the correct type,
13873 otherwise an error occurs. These checks prevent type mismatch
13874 errors from ever causing any run-time problems. For example,
13877 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13879 (@value{GDBP}) print obj.my_method (0)
13882 (@value{GDBP}) print obj.my_method (0x1234)
13883 Cannot resolve method klass::my_method to any overloaded instance
13886 The second example fails because in C@t{++} the integer constant
13887 @samp{0x1234} is not type-compatible with the pointer parameter type.
13889 For the expressions you use in @value{GDBN} commands, you can tell
13890 @value{GDBN} to not enforce strict type checking or
13891 to treat any mismatches as errors and abandon the expression;
13892 When type checking is disabled, @value{GDBN} successfully evaluates
13893 expressions like the second example above.
13895 Even if type checking is off, there may be other reasons
13896 related to type that prevent @value{GDBN} from evaluating an expression.
13897 For instance, @value{GDBN} does not know how to add an @code{int} and
13898 a @code{struct foo}. These particular type errors have nothing to do
13899 with the language in use and usually arise from expressions which make
13900 little sense to evaluate anyway.
13902 @value{GDBN} provides some additional commands for controlling type checking:
13904 @kindex set check type
13905 @kindex show check type
13907 @item set check type on
13908 @itemx set check type off
13909 Set strict type checking on or off. If any type mismatches occur in
13910 evaluating an expression while type checking is on, @value{GDBN} prints a
13911 message and aborts evaluation of the expression.
13913 @item show check type
13914 Show the current setting of type checking and whether @value{GDBN}
13915 is enforcing strict type checking rules.
13918 @cindex range checking
13919 @cindex checks, range
13920 @node Range Checking
13921 @subsection An Overview of Range Checking
13923 In some languages (such as Modula-2), it is an error to exceed the
13924 bounds of a type; this is enforced with run-time checks. Such range
13925 checking is meant to ensure program correctness by making sure
13926 computations do not overflow, or indices on an array element access do
13927 not exceed the bounds of the array.
13929 For expressions you use in @value{GDBN} commands, you can tell
13930 @value{GDBN} to treat range errors in one of three ways: ignore them,
13931 always treat them as errors and abandon the expression, or issue
13932 warnings but evaluate the expression anyway.
13934 A range error can result from numerical overflow, from exceeding an
13935 array index bound, or when you type a constant that is not a member
13936 of any type. Some languages, however, do not treat overflows as an
13937 error. In many implementations of C, mathematical overflow causes the
13938 result to ``wrap around'' to lower values---for example, if @var{m} is
13939 the largest integer value, and @var{s} is the smallest, then
13942 @var{m} + 1 @result{} @var{s}
13945 This, too, is specific to individual languages, and in some cases
13946 specific to individual compilers or machines. @xref{Supported Languages, ,
13947 Supported Languages}, for further details on specific languages.
13949 @value{GDBN} provides some additional commands for controlling the range checker:
13951 @kindex set check range
13952 @kindex show check range
13954 @item set check range auto
13955 Set range checking on or off based on the current working language.
13956 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13959 @item set check range on
13960 @itemx set check range off
13961 Set range checking on or off, overriding the default setting for the
13962 current working language. A warning is issued if the setting does not
13963 match the language default. If a range error occurs and range checking is on,
13964 then a message is printed and evaluation of the expression is aborted.
13966 @item set check range warn
13967 Output messages when the @value{GDBN} range checker detects a range error,
13968 but attempt to evaluate the expression anyway. Evaluating the
13969 expression may still be impossible for other reasons, such as accessing
13970 memory that the process does not own (a typical example from many Unix
13974 Show the current setting of the range checker, and whether or not it is
13975 being set automatically by @value{GDBN}.
13978 @node Supported Languages
13979 @section Supported Languages
13981 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13982 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13983 @c This is false ...
13984 Some @value{GDBN} features may be used in expressions regardless of the
13985 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13986 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13987 ,Expressions}) can be used with the constructs of any supported
13990 The following sections detail to what degree each source language is
13991 supported by @value{GDBN}. These sections are not meant to be language
13992 tutorials or references, but serve only as a reference guide to what the
13993 @value{GDBN} expression parser accepts, and what input and output
13994 formats should look like for different languages. There are many good
13995 books written on each of these languages; please look to these for a
13996 language reference or tutorial.
13999 * C:: C and C@t{++}
14002 * Objective-C:: Objective-C
14003 * OpenCL C:: OpenCL C
14004 * Fortran:: Fortran
14006 * Modula-2:: Modula-2
14011 @subsection C and C@t{++}
14013 @cindex C and C@t{++}
14014 @cindex expressions in C or C@t{++}
14016 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14017 to both languages. Whenever this is the case, we discuss those languages
14021 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14022 @cindex @sc{gnu} C@t{++}
14023 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14024 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14025 effectively, you must compile your C@t{++} programs with a supported
14026 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14027 compiler (@code{aCC}).
14030 * C Operators:: C and C@t{++} operators
14031 * C Constants:: C and C@t{++} constants
14032 * C Plus Plus Expressions:: C@t{++} expressions
14033 * C Defaults:: Default settings for C and C@t{++}
14034 * C Checks:: C and C@t{++} type and range checks
14035 * Debugging C:: @value{GDBN} and C
14036 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14037 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14041 @subsubsection C and C@t{++} Operators
14043 @cindex C and C@t{++} operators
14045 Operators must be defined on values of specific types. For instance,
14046 @code{+} is defined on numbers, but not on structures. Operators are
14047 often defined on groups of types.
14049 For the purposes of C and C@t{++}, the following definitions hold:
14054 @emph{Integral types} include @code{int} with any of its storage-class
14055 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14058 @emph{Floating-point types} include @code{float}, @code{double}, and
14059 @code{long double} (if supported by the target platform).
14062 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14065 @emph{Scalar types} include all of the above.
14070 The following operators are supported. They are listed here
14071 in order of increasing precedence:
14075 The comma or sequencing operator. Expressions in a comma-separated list
14076 are evaluated from left to right, with the result of the entire
14077 expression being the last expression evaluated.
14080 Assignment. The value of an assignment expression is the value
14081 assigned. Defined on scalar types.
14084 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14085 and translated to @w{@code{@var{a} = @var{a op b}}}.
14086 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14087 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14088 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14091 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14092 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14093 should be of an integral type.
14096 Logical @sc{or}. Defined on integral types.
14099 Logical @sc{and}. Defined on integral types.
14102 Bitwise @sc{or}. Defined on integral types.
14105 Bitwise exclusive-@sc{or}. Defined on integral types.
14108 Bitwise @sc{and}. Defined on integral types.
14111 Equality and inequality. Defined on scalar types. The value of these
14112 expressions is 0 for false and non-zero for true.
14114 @item <@r{, }>@r{, }<=@r{, }>=
14115 Less than, greater than, less than or equal, greater than or equal.
14116 Defined on scalar types. The value of these expressions is 0 for false
14117 and non-zero for true.
14120 left shift, and right shift. Defined on integral types.
14123 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14126 Addition and subtraction. Defined on integral types, floating-point types and
14129 @item *@r{, }/@r{, }%
14130 Multiplication, division, and modulus. Multiplication and division are
14131 defined on integral and floating-point types. Modulus is defined on
14135 Increment and decrement. When appearing before a variable, the
14136 operation is performed before the variable is used in an expression;
14137 when appearing after it, the variable's value is used before the
14138 operation takes place.
14141 Pointer dereferencing. Defined on pointer types. Same precedence as
14145 Address operator. Defined on variables. Same precedence as @code{++}.
14147 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14148 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14149 to examine the address
14150 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14154 Negative. Defined on integral and floating-point types. Same
14155 precedence as @code{++}.
14158 Logical negation. Defined on integral types. Same precedence as
14162 Bitwise complement operator. Defined on integral types. Same precedence as
14167 Structure member, and pointer-to-structure member. For convenience,
14168 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14169 pointer based on the stored type information.
14170 Defined on @code{struct} and @code{union} data.
14173 Dereferences of pointers to members.
14176 Array indexing. @code{@var{a}[@var{i}]} is defined as
14177 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14180 Function parameter list. Same precedence as @code{->}.
14183 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14184 and @code{class} types.
14187 Doubled colons also represent the @value{GDBN} scope operator
14188 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14192 If an operator is redefined in the user code, @value{GDBN} usually
14193 attempts to invoke the redefined version instead of using the operator's
14194 predefined meaning.
14197 @subsubsection C and C@t{++} Constants
14199 @cindex C and C@t{++} constants
14201 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14206 Integer constants are a sequence of digits. Octal constants are
14207 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14208 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14209 @samp{l}, specifying that the constant should be treated as a
14213 Floating point constants are a sequence of digits, followed by a decimal
14214 point, followed by a sequence of digits, and optionally followed by an
14215 exponent. An exponent is of the form:
14216 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14217 sequence of digits. The @samp{+} is optional for positive exponents.
14218 A floating-point constant may also end with a letter @samp{f} or
14219 @samp{F}, specifying that the constant should be treated as being of
14220 the @code{float} (as opposed to the default @code{double}) type; or with
14221 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14225 Enumerated constants consist of enumerated identifiers, or their
14226 integral equivalents.
14229 Character constants are a single character surrounded by single quotes
14230 (@code{'}), or a number---the ordinal value of the corresponding character
14231 (usually its @sc{ascii} value). Within quotes, the single character may
14232 be represented by a letter or by @dfn{escape sequences}, which are of
14233 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14234 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14235 @samp{@var{x}} is a predefined special character---for example,
14236 @samp{\n} for newline.
14238 Wide character constants can be written by prefixing a character
14239 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14240 form of @samp{x}. The target wide character set is used when
14241 computing the value of this constant (@pxref{Character Sets}).
14244 String constants are a sequence of character constants surrounded by
14245 double quotes (@code{"}). Any valid character constant (as described
14246 above) may appear. Double quotes within the string must be preceded by
14247 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14250 Wide string constants can be written by prefixing a string constant
14251 with @samp{L}, as in C. The target wide character set is used when
14252 computing the value of this constant (@pxref{Character Sets}).
14255 Pointer constants are an integral value. You can also write pointers
14256 to constants using the C operator @samp{&}.
14259 Array constants are comma-separated lists surrounded by braces @samp{@{}
14260 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14261 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14262 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14265 @node C Plus Plus Expressions
14266 @subsubsection C@t{++} Expressions
14268 @cindex expressions in C@t{++}
14269 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14271 @cindex debugging C@t{++} programs
14272 @cindex C@t{++} compilers
14273 @cindex debug formats and C@t{++}
14274 @cindex @value{NGCC} and C@t{++}
14276 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14277 the proper compiler and the proper debug format. Currently,
14278 @value{GDBN} works best when debugging C@t{++} code that is compiled
14279 with the most recent version of @value{NGCC} possible. The DWARF
14280 debugging format is preferred; @value{NGCC} defaults to this on most
14281 popular platforms. Other compilers and/or debug formats are likely to
14282 work badly or not at all when using @value{GDBN} to debug C@t{++}
14283 code. @xref{Compilation}.
14288 @cindex member functions
14290 Member function calls are allowed; you can use expressions like
14293 count = aml->GetOriginal(x, y)
14296 @vindex this@r{, inside C@t{++} member functions}
14297 @cindex namespace in C@t{++}
14299 While a member function is active (in the selected stack frame), your
14300 expressions have the same namespace available as the member function;
14301 that is, @value{GDBN} allows implicit references to the class instance
14302 pointer @code{this} following the same rules as C@t{++}. @code{using}
14303 declarations in the current scope are also respected by @value{GDBN}.
14305 @cindex call overloaded functions
14306 @cindex overloaded functions, calling
14307 @cindex type conversions in C@t{++}
14309 You can call overloaded functions; @value{GDBN} resolves the function
14310 call to the right definition, with some restrictions. @value{GDBN} does not
14311 perform overload resolution involving user-defined type conversions,
14312 calls to constructors, or instantiations of templates that do not exist
14313 in the program. It also cannot handle ellipsis argument lists or
14316 It does perform integral conversions and promotions, floating-point
14317 promotions, arithmetic conversions, pointer conversions, conversions of
14318 class objects to base classes, and standard conversions such as those of
14319 functions or arrays to pointers; it requires an exact match on the
14320 number of function arguments.
14322 Overload resolution is always performed, unless you have specified
14323 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14324 ,@value{GDBN} Features for C@t{++}}.
14326 You must specify @code{set overload-resolution off} in order to use an
14327 explicit function signature to call an overloaded function, as in
14329 p 'foo(char,int)'('x', 13)
14332 The @value{GDBN} command-completion facility can simplify this;
14333 see @ref{Completion, ,Command Completion}.
14335 @cindex reference declarations
14337 @value{GDBN} understands variables declared as C@t{++} references; you can use
14338 them in expressions just as you do in C@t{++} source---they are automatically
14341 In the parameter list shown when @value{GDBN} displays a frame, the values of
14342 reference variables are not displayed (unlike other variables); this
14343 avoids clutter, since references are often used for large structures.
14344 The @emph{address} of a reference variable is always shown, unless
14345 you have specified @samp{set print address off}.
14348 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14349 expressions can use it just as expressions in your program do. Since
14350 one scope may be defined in another, you can use @code{::} repeatedly if
14351 necessary, for example in an expression like
14352 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14353 resolving name scope by reference to source files, in both C and C@t{++}
14354 debugging (@pxref{Variables, ,Program Variables}).
14357 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14362 @subsubsection C and C@t{++} Defaults
14364 @cindex C and C@t{++} defaults
14366 If you allow @value{GDBN} to set range checking automatically, it
14367 defaults to @code{off} whenever the working language changes to
14368 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14369 selects the working language.
14371 If you allow @value{GDBN} to set the language automatically, it
14372 recognizes source files whose names end with @file{.c}, @file{.C}, or
14373 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14374 these files, it sets the working language to C or C@t{++}.
14375 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14376 for further details.
14379 @subsubsection C and C@t{++} Type and Range Checks
14381 @cindex C and C@t{++} checks
14383 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14384 checking is used. However, if you turn type checking off, @value{GDBN}
14385 will allow certain non-standard conversions, such as promoting integer
14386 constants to pointers.
14388 Range checking, if turned on, is done on mathematical operations. Array
14389 indices are not checked, since they are often used to index a pointer
14390 that is not itself an array.
14393 @subsubsection @value{GDBN} and C
14395 The @code{set print union} and @code{show print union} commands apply to
14396 the @code{union} type. When set to @samp{on}, any @code{union} that is
14397 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14398 appears as @samp{@{...@}}.
14400 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14401 with pointers and a memory allocation function. @xref{Expressions,
14404 @node Debugging C Plus Plus
14405 @subsubsection @value{GDBN} Features for C@t{++}
14407 @cindex commands for C@t{++}
14409 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14410 designed specifically for use with C@t{++}. Here is a summary:
14413 @cindex break in overloaded functions
14414 @item @r{breakpoint menus}
14415 When you want a breakpoint in a function whose name is overloaded,
14416 @value{GDBN} has the capability to display a menu of possible breakpoint
14417 locations to help you specify which function definition you want.
14418 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14420 @cindex overloading in C@t{++}
14421 @item rbreak @var{regex}
14422 Setting breakpoints using regular expressions is helpful for setting
14423 breakpoints on overloaded functions that are not members of any special
14425 @xref{Set Breaks, ,Setting Breakpoints}.
14427 @cindex C@t{++} exception handling
14429 @itemx catch rethrow
14431 Debug C@t{++} exception handling using these commands. @xref{Set
14432 Catchpoints, , Setting Catchpoints}.
14434 @cindex inheritance
14435 @item ptype @var{typename}
14436 Print inheritance relationships as well as other information for type
14438 @xref{Symbols, ,Examining the Symbol Table}.
14440 @item info vtbl @var{expression}.
14441 The @code{info vtbl} command can be used to display the virtual
14442 method tables of the object computed by @var{expression}. This shows
14443 one entry per virtual table; there may be multiple virtual tables when
14444 multiple inheritance is in use.
14446 @cindex C@t{++} demangling
14447 @item demangle @var{name}
14448 Demangle @var{name}.
14449 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14451 @cindex C@t{++} symbol display
14452 @item set print demangle
14453 @itemx show print demangle
14454 @itemx set print asm-demangle
14455 @itemx show print asm-demangle
14456 Control whether C@t{++} symbols display in their source form, both when
14457 displaying code as C@t{++} source and when displaying disassemblies.
14458 @xref{Print Settings, ,Print Settings}.
14460 @item set print object
14461 @itemx show print object
14462 Choose whether to print derived (actual) or declared types of objects.
14463 @xref{Print Settings, ,Print Settings}.
14465 @item set print vtbl
14466 @itemx show print vtbl
14467 Control the format for printing virtual function tables.
14468 @xref{Print Settings, ,Print Settings}.
14469 (The @code{vtbl} commands do not work on programs compiled with the HP
14470 ANSI C@t{++} compiler (@code{aCC}).)
14472 @kindex set overload-resolution
14473 @cindex overloaded functions, overload resolution
14474 @item set overload-resolution on
14475 Enable overload resolution for C@t{++} expression evaluation. The default
14476 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14477 and searches for a function whose signature matches the argument types,
14478 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14479 Expressions, ,C@t{++} Expressions}, for details).
14480 If it cannot find a match, it emits a message.
14482 @item set overload-resolution off
14483 Disable overload resolution for C@t{++} expression evaluation. For
14484 overloaded functions that are not class member functions, @value{GDBN}
14485 chooses the first function of the specified name that it finds in the
14486 symbol table, whether or not its arguments are of the correct type. For
14487 overloaded functions that are class member functions, @value{GDBN}
14488 searches for a function whose signature @emph{exactly} matches the
14491 @kindex show overload-resolution
14492 @item show overload-resolution
14493 Show the current setting of overload resolution.
14495 @item @r{Overloaded symbol names}
14496 You can specify a particular definition of an overloaded symbol, using
14497 the same notation that is used to declare such symbols in C@t{++}: type
14498 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14499 also use the @value{GDBN} command-line word completion facilities to list the
14500 available choices, or to finish the type list for you.
14501 @xref{Completion,, Command Completion}, for details on how to do this.
14504 @node Decimal Floating Point
14505 @subsubsection Decimal Floating Point format
14506 @cindex decimal floating point format
14508 @value{GDBN} can examine, set and perform computations with numbers in
14509 decimal floating point format, which in the C language correspond to the
14510 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14511 specified by the extension to support decimal floating-point arithmetic.
14513 There are two encodings in use, depending on the architecture: BID (Binary
14514 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14515 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14518 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14519 to manipulate decimal floating point numbers, it is not possible to convert
14520 (using a cast, for example) integers wider than 32-bit to decimal float.
14522 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14523 point computations, error checking in decimal float operations ignores
14524 underflow, overflow and divide by zero exceptions.
14526 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14527 to inspect @code{_Decimal128} values stored in floating point registers.
14528 See @ref{PowerPC,,PowerPC} for more details.
14534 @value{GDBN} can be used to debug programs written in D and compiled with
14535 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14536 specific feature --- dynamic arrays.
14541 @cindex Go (programming language)
14542 @value{GDBN} can be used to debug programs written in Go and compiled with
14543 @file{gccgo} or @file{6g} compilers.
14545 Here is a summary of the Go-specific features and restrictions:
14548 @cindex current Go package
14549 @item The current Go package
14550 The name of the current package does not need to be specified when
14551 specifying global variables and functions.
14553 For example, given the program:
14557 var myglob = "Shall we?"
14563 When stopped inside @code{main} either of these work:
14567 (gdb) p main.myglob
14570 @cindex builtin Go types
14571 @item Builtin Go types
14572 The @code{string} type is recognized by @value{GDBN} and is printed
14575 @cindex builtin Go functions
14576 @item Builtin Go functions
14577 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14578 function and handles it internally.
14580 @cindex restrictions on Go expressions
14581 @item Restrictions on Go expressions
14582 All Go operators are supported except @code{&^}.
14583 The Go @code{_} ``blank identifier'' is not supported.
14584 Automatic dereferencing of pointers is not supported.
14588 @subsection Objective-C
14590 @cindex Objective-C
14591 This section provides information about some commands and command
14592 options that are useful for debugging Objective-C code. See also
14593 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14594 few more commands specific to Objective-C support.
14597 * Method Names in Commands::
14598 * The Print Command with Objective-C::
14601 @node Method Names in Commands
14602 @subsubsection Method Names in Commands
14604 The following commands have been extended to accept Objective-C method
14605 names as line specifications:
14607 @kindex clear@r{, and Objective-C}
14608 @kindex break@r{, and Objective-C}
14609 @kindex info line@r{, and Objective-C}
14610 @kindex jump@r{, and Objective-C}
14611 @kindex list@r{, and Objective-C}
14615 @item @code{info line}
14620 A fully qualified Objective-C method name is specified as
14623 -[@var{Class} @var{methodName}]
14626 where the minus sign is used to indicate an instance method and a
14627 plus sign (not shown) is used to indicate a class method. The class
14628 name @var{Class} and method name @var{methodName} are enclosed in
14629 brackets, similar to the way messages are specified in Objective-C
14630 source code. For example, to set a breakpoint at the @code{create}
14631 instance method of class @code{Fruit} in the program currently being
14635 break -[Fruit create]
14638 To list ten program lines around the @code{initialize} class method,
14642 list +[NSText initialize]
14645 In the current version of @value{GDBN}, the plus or minus sign is
14646 required. In future versions of @value{GDBN}, the plus or minus
14647 sign will be optional, but you can use it to narrow the search. It
14648 is also possible to specify just a method name:
14654 You must specify the complete method name, including any colons. If
14655 your program's source files contain more than one @code{create} method,
14656 you'll be presented with a numbered list of classes that implement that
14657 method. Indicate your choice by number, or type @samp{0} to exit if
14660 As another example, to clear a breakpoint established at the
14661 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14664 clear -[NSWindow makeKeyAndOrderFront:]
14667 @node The Print Command with Objective-C
14668 @subsubsection The Print Command With Objective-C
14669 @cindex Objective-C, print objects
14670 @kindex print-object
14671 @kindex po @r{(@code{print-object})}
14673 The print command has also been extended to accept methods. For example:
14676 print -[@var{object} hash]
14679 @cindex print an Objective-C object description
14680 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14682 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14683 and print the result. Also, an additional command has been added,
14684 @code{print-object} or @code{po} for short, which is meant to print
14685 the description of an object. However, this command may only work
14686 with certain Objective-C libraries that have a particular hook
14687 function, @code{_NSPrintForDebugger}, defined.
14690 @subsection OpenCL C
14693 This section provides information about @value{GDBN}s OpenCL C support.
14696 * OpenCL C Datatypes::
14697 * OpenCL C Expressions::
14698 * OpenCL C Operators::
14701 @node OpenCL C Datatypes
14702 @subsubsection OpenCL C Datatypes
14704 @cindex OpenCL C Datatypes
14705 @value{GDBN} supports the builtin scalar and vector datatypes specified
14706 by OpenCL 1.1. In addition the half- and double-precision floating point
14707 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14708 extensions are also known to @value{GDBN}.
14710 @node OpenCL C Expressions
14711 @subsubsection OpenCL C Expressions
14713 @cindex OpenCL C Expressions
14714 @value{GDBN} supports accesses to vector components including the access as
14715 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14716 supported by @value{GDBN} can be used as well.
14718 @node OpenCL C Operators
14719 @subsubsection OpenCL C Operators
14721 @cindex OpenCL C Operators
14722 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14726 @subsection Fortran
14727 @cindex Fortran-specific support in @value{GDBN}
14729 @value{GDBN} can be used to debug programs written in Fortran, but it
14730 currently supports only the features of Fortran 77 language.
14732 @cindex trailing underscore, in Fortran symbols
14733 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14734 among them) append an underscore to the names of variables and
14735 functions. When you debug programs compiled by those compilers, you
14736 will need to refer to variables and functions with a trailing
14740 * Fortran Operators:: Fortran operators and expressions
14741 * Fortran Defaults:: Default settings for Fortran
14742 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14745 @node Fortran Operators
14746 @subsubsection Fortran Operators and Expressions
14748 @cindex Fortran operators and expressions
14750 Operators must be defined on values of specific types. For instance,
14751 @code{+} is defined on numbers, but not on characters or other non-
14752 arithmetic types. Operators are often defined on groups of types.
14756 The exponentiation operator. It raises the first operand to the power
14760 The range operator. Normally used in the form of array(low:high) to
14761 represent a section of array.
14764 The access component operator. Normally used to access elements in derived
14765 types. Also suitable for unions. As unions aren't part of regular Fortran,
14766 this can only happen when accessing a register that uses a gdbarch-defined
14770 @node Fortran Defaults
14771 @subsubsection Fortran Defaults
14773 @cindex Fortran Defaults
14775 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14776 default uses case-insensitive matches for Fortran symbols. You can
14777 change that with the @samp{set case-insensitive} command, see
14778 @ref{Symbols}, for the details.
14780 @node Special Fortran Commands
14781 @subsubsection Special Fortran Commands
14783 @cindex Special Fortran commands
14785 @value{GDBN} has some commands to support Fortran-specific features,
14786 such as displaying common blocks.
14789 @cindex @code{COMMON} blocks, Fortran
14790 @kindex info common
14791 @item info common @r{[}@var{common-name}@r{]}
14792 This command prints the values contained in the Fortran @code{COMMON}
14793 block whose name is @var{common-name}. With no argument, the names of
14794 all @code{COMMON} blocks visible at the current program location are
14801 @cindex Pascal support in @value{GDBN}, limitations
14802 Debugging Pascal programs which use sets, subranges, file variables, or
14803 nested functions does not currently work. @value{GDBN} does not support
14804 entering expressions, printing values, or similar features using Pascal
14807 The Pascal-specific command @code{set print pascal_static-members}
14808 controls whether static members of Pascal objects are displayed.
14809 @xref{Print Settings, pascal_static-members}.
14812 @subsection Modula-2
14814 @cindex Modula-2, @value{GDBN} support
14816 The extensions made to @value{GDBN} to support Modula-2 only support
14817 output from the @sc{gnu} Modula-2 compiler (which is currently being
14818 developed). Other Modula-2 compilers are not currently supported, and
14819 attempting to debug executables produced by them is most likely
14820 to give an error as @value{GDBN} reads in the executable's symbol
14823 @cindex expressions in Modula-2
14825 * M2 Operators:: Built-in operators
14826 * Built-In Func/Proc:: Built-in functions and procedures
14827 * M2 Constants:: Modula-2 constants
14828 * M2 Types:: Modula-2 types
14829 * M2 Defaults:: Default settings for Modula-2
14830 * Deviations:: Deviations from standard Modula-2
14831 * M2 Checks:: Modula-2 type and range checks
14832 * M2 Scope:: The scope operators @code{::} and @code{.}
14833 * GDB/M2:: @value{GDBN} and Modula-2
14837 @subsubsection Operators
14838 @cindex Modula-2 operators
14840 Operators must be defined on values of specific types. For instance,
14841 @code{+} is defined on numbers, but not on structures. Operators are
14842 often defined on groups of types. For the purposes of Modula-2, the
14843 following definitions hold:
14848 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14852 @emph{Character types} consist of @code{CHAR} and its subranges.
14855 @emph{Floating-point types} consist of @code{REAL}.
14858 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14862 @emph{Scalar types} consist of all of the above.
14865 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14868 @emph{Boolean types} consist of @code{BOOLEAN}.
14872 The following operators are supported, and appear in order of
14873 increasing precedence:
14877 Function argument or array index separator.
14880 Assignment. The value of @var{var} @code{:=} @var{value} is
14884 Less than, greater than on integral, floating-point, or enumerated
14888 Less than or equal to, greater than or equal to
14889 on integral, floating-point and enumerated types, or set inclusion on
14890 set types. Same precedence as @code{<}.
14892 @item =@r{, }<>@r{, }#
14893 Equality and two ways of expressing inequality, valid on scalar types.
14894 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14895 available for inequality, since @code{#} conflicts with the script
14899 Set membership. Defined on set types and the types of their members.
14900 Same precedence as @code{<}.
14903 Boolean disjunction. Defined on boolean types.
14906 Boolean conjunction. Defined on boolean types.
14909 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14912 Addition and subtraction on integral and floating-point types, or union
14913 and difference on set types.
14916 Multiplication on integral and floating-point types, or set intersection
14920 Division on floating-point types, or symmetric set difference on set
14921 types. Same precedence as @code{*}.
14924 Integer division and remainder. Defined on integral types. Same
14925 precedence as @code{*}.
14928 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14931 Pointer dereferencing. Defined on pointer types.
14934 Boolean negation. Defined on boolean types. Same precedence as
14938 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14939 precedence as @code{^}.
14942 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14945 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14949 @value{GDBN} and Modula-2 scope operators.
14953 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14954 treats the use of the operator @code{IN}, or the use of operators
14955 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14956 @code{<=}, and @code{>=} on sets as an error.
14960 @node Built-In Func/Proc
14961 @subsubsection Built-in Functions and Procedures
14962 @cindex Modula-2 built-ins
14964 Modula-2 also makes available several built-in procedures and functions.
14965 In describing these, the following metavariables are used:
14970 represents an @code{ARRAY} variable.
14973 represents a @code{CHAR} constant or variable.
14976 represents a variable or constant of integral type.
14979 represents an identifier that belongs to a set. Generally used in the
14980 same function with the metavariable @var{s}. The type of @var{s} should
14981 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14984 represents a variable or constant of integral or floating-point type.
14987 represents a variable or constant of floating-point type.
14993 represents a variable.
14996 represents a variable or constant of one of many types. See the
14997 explanation of the function for details.
15000 All Modula-2 built-in procedures also return a result, described below.
15004 Returns the absolute value of @var{n}.
15007 If @var{c} is a lower case letter, it returns its upper case
15008 equivalent, otherwise it returns its argument.
15011 Returns the character whose ordinal value is @var{i}.
15014 Decrements the value in the variable @var{v} by one. Returns the new value.
15016 @item DEC(@var{v},@var{i})
15017 Decrements the value in the variable @var{v} by @var{i}. Returns the
15020 @item EXCL(@var{m},@var{s})
15021 Removes the element @var{m} from the set @var{s}. Returns the new
15024 @item FLOAT(@var{i})
15025 Returns the floating point equivalent of the integer @var{i}.
15027 @item HIGH(@var{a})
15028 Returns the index of the last member of @var{a}.
15031 Increments the value in the variable @var{v} by one. Returns the new value.
15033 @item INC(@var{v},@var{i})
15034 Increments the value in the variable @var{v} by @var{i}. Returns the
15037 @item INCL(@var{m},@var{s})
15038 Adds the element @var{m} to the set @var{s} if it is not already
15039 there. Returns the new set.
15042 Returns the maximum value of the type @var{t}.
15045 Returns the minimum value of the type @var{t}.
15048 Returns boolean TRUE if @var{i} is an odd number.
15051 Returns the ordinal value of its argument. For example, the ordinal
15052 value of a character is its @sc{ascii} value (on machines supporting
15053 the @sc{ascii} character set). The argument @var{x} must be of an
15054 ordered type, which include integral, character and enumerated types.
15056 @item SIZE(@var{x})
15057 Returns the size of its argument. The argument @var{x} can be a
15058 variable or a type.
15060 @item TRUNC(@var{r})
15061 Returns the integral part of @var{r}.
15063 @item TSIZE(@var{x})
15064 Returns the size of its argument. The argument @var{x} can be a
15065 variable or a type.
15067 @item VAL(@var{t},@var{i})
15068 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15072 @emph{Warning:} Sets and their operations are not yet supported, so
15073 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15077 @cindex Modula-2 constants
15079 @subsubsection Constants
15081 @value{GDBN} allows you to express the constants of Modula-2 in the following
15087 Integer constants are simply a sequence of digits. When used in an
15088 expression, a constant is interpreted to be type-compatible with the
15089 rest of the expression. Hexadecimal integers are specified by a
15090 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15093 Floating point constants appear as a sequence of digits, followed by a
15094 decimal point and another sequence of digits. An optional exponent can
15095 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15096 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15097 digits of the floating point constant must be valid decimal (base 10)
15101 Character constants consist of a single character enclosed by a pair of
15102 like quotes, either single (@code{'}) or double (@code{"}). They may
15103 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15104 followed by a @samp{C}.
15107 String constants consist of a sequence of characters enclosed by a
15108 pair of like quotes, either single (@code{'}) or double (@code{"}).
15109 Escape sequences in the style of C are also allowed. @xref{C
15110 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15114 Enumerated constants consist of an enumerated identifier.
15117 Boolean constants consist of the identifiers @code{TRUE} and
15121 Pointer constants consist of integral values only.
15124 Set constants are not yet supported.
15128 @subsubsection Modula-2 Types
15129 @cindex Modula-2 types
15131 Currently @value{GDBN} can print the following data types in Modula-2
15132 syntax: array types, record types, set types, pointer types, procedure
15133 types, enumerated types, subrange types and base types. You can also
15134 print the contents of variables declared using these type.
15135 This section gives a number of simple source code examples together with
15136 sample @value{GDBN} sessions.
15138 The first example contains the following section of code:
15147 and you can request @value{GDBN} to interrogate the type and value of
15148 @code{r} and @code{s}.
15151 (@value{GDBP}) print s
15153 (@value{GDBP}) ptype s
15155 (@value{GDBP}) print r
15157 (@value{GDBP}) ptype r
15162 Likewise if your source code declares @code{s} as:
15166 s: SET ['A'..'Z'] ;
15170 then you may query the type of @code{s} by:
15173 (@value{GDBP}) ptype s
15174 type = SET ['A'..'Z']
15178 Note that at present you cannot interactively manipulate set
15179 expressions using the debugger.
15181 The following example shows how you might declare an array in Modula-2
15182 and how you can interact with @value{GDBN} to print its type and contents:
15186 s: ARRAY [-10..10] OF CHAR ;
15190 (@value{GDBP}) ptype s
15191 ARRAY [-10..10] OF CHAR
15194 Note that the array handling is not yet complete and although the type
15195 is printed correctly, expression handling still assumes that all
15196 arrays have a lower bound of zero and not @code{-10} as in the example
15199 Here are some more type related Modula-2 examples:
15203 colour = (blue, red, yellow, green) ;
15204 t = [blue..yellow] ;
15212 The @value{GDBN} interaction shows how you can query the data type
15213 and value of a variable.
15216 (@value{GDBP}) print s
15218 (@value{GDBP}) ptype t
15219 type = [blue..yellow]
15223 In this example a Modula-2 array is declared and its contents
15224 displayed. Observe that the contents are written in the same way as
15225 their @code{C} counterparts.
15229 s: ARRAY [1..5] OF CARDINAL ;
15235 (@value{GDBP}) print s
15236 $1 = @{1, 0, 0, 0, 0@}
15237 (@value{GDBP}) ptype s
15238 type = ARRAY [1..5] OF CARDINAL
15241 The Modula-2 language interface to @value{GDBN} also understands
15242 pointer types as shown in this example:
15246 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15253 and you can request that @value{GDBN} describes the type of @code{s}.
15256 (@value{GDBP}) ptype s
15257 type = POINTER TO ARRAY [1..5] OF CARDINAL
15260 @value{GDBN} handles compound types as we can see in this example.
15261 Here we combine array types, record types, pointer types and subrange
15272 myarray = ARRAY myrange OF CARDINAL ;
15273 myrange = [-2..2] ;
15275 s: POINTER TO ARRAY myrange OF foo ;
15279 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15283 (@value{GDBP}) ptype s
15284 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15287 f3 : ARRAY [-2..2] OF CARDINAL;
15292 @subsubsection Modula-2 Defaults
15293 @cindex Modula-2 defaults
15295 If type and range checking are set automatically by @value{GDBN}, they
15296 both default to @code{on} whenever the working language changes to
15297 Modula-2. This happens regardless of whether you or @value{GDBN}
15298 selected the working language.
15300 If you allow @value{GDBN} to set the language automatically, then entering
15301 code compiled from a file whose name ends with @file{.mod} sets the
15302 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15303 Infer the Source Language}, for further details.
15306 @subsubsection Deviations from Standard Modula-2
15307 @cindex Modula-2, deviations from
15309 A few changes have been made to make Modula-2 programs easier to debug.
15310 This is done primarily via loosening its type strictness:
15314 Unlike in standard Modula-2, pointer constants can be formed by
15315 integers. This allows you to modify pointer variables during
15316 debugging. (In standard Modula-2, the actual address contained in a
15317 pointer variable is hidden from you; it can only be modified
15318 through direct assignment to another pointer variable or expression that
15319 returned a pointer.)
15322 C escape sequences can be used in strings and characters to represent
15323 non-printable characters. @value{GDBN} prints out strings with these
15324 escape sequences embedded. Single non-printable characters are
15325 printed using the @samp{CHR(@var{nnn})} format.
15328 The assignment operator (@code{:=}) returns the value of its right-hand
15332 All built-in procedures both modify @emph{and} return their argument.
15336 @subsubsection Modula-2 Type and Range Checks
15337 @cindex Modula-2 checks
15340 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15343 @c FIXME remove warning when type/range checks added
15345 @value{GDBN} considers two Modula-2 variables type equivalent if:
15349 They are of types that have been declared equivalent via a @code{TYPE
15350 @var{t1} = @var{t2}} statement
15353 They have been declared on the same line. (Note: This is true of the
15354 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15357 As long as type checking is enabled, any attempt to combine variables
15358 whose types are not equivalent is an error.
15360 Range checking is done on all mathematical operations, assignment, array
15361 index bounds, and all built-in functions and procedures.
15364 @subsubsection The Scope Operators @code{::} and @code{.}
15366 @cindex @code{.}, Modula-2 scope operator
15367 @cindex colon, doubled as scope operator
15369 @vindex colon-colon@r{, in Modula-2}
15370 @c Info cannot handle :: but TeX can.
15373 @vindex ::@r{, in Modula-2}
15376 There are a few subtle differences between the Modula-2 scope operator
15377 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15382 @var{module} . @var{id}
15383 @var{scope} :: @var{id}
15387 where @var{scope} is the name of a module or a procedure,
15388 @var{module} the name of a module, and @var{id} is any declared
15389 identifier within your program, except another module.
15391 Using the @code{::} operator makes @value{GDBN} search the scope
15392 specified by @var{scope} for the identifier @var{id}. If it is not
15393 found in the specified scope, then @value{GDBN} searches all scopes
15394 enclosing the one specified by @var{scope}.
15396 Using the @code{.} operator makes @value{GDBN} search the current scope for
15397 the identifier specified by @var{id} that was imported from the
15398 definition module specified by @var{module}. With this operator, it is
15399 an error if the identifier @var{id} was not imported from definition
15400 module @var{module}, or if @var{id} is not an identifier in
15404 @subsubsection @value{GDBN} and Modula-2
15406 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15407 Five subcommands of @code{set print} and @code{show print} apply
15408 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15409 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15410 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15411 analogue in Modula-2.
15413 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15414 with any language, is not useful with Modula-2. Its
15415 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15416 created in Modula-2 as they can in C or C@t{++}. However, because an
15417 address can be specified by an integral constant, the construct
15418 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15420 @cindex @code{#} in Modula-2
15421 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15422 interpreted as the beginning of a comment. Use @code{<>} instead.
15428 The extensions made to @value{GDBN} for Ada only support
15429 output from the @sc{gnu} Ada (GNAT) compiler.
15430 Other Ada compilers are not currently supported, and
15431 attempting to debug executables produced by them is most likely
15435 @cindex expressions in Ada
15437 * Ada Mode Intro:: General remarks on the Ada syntax
15438 and semantics supported by Ada mode
15440 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15441 * Additions to Ada:: Extensions of the Ada expression syntax.
15442 * Stopping Before Main Program:: Debugging the program during elaboration.
15443 * Ada Exceptions:: Ada Exceptions
15444 * Ada Tasks:: Listing and setting breakpoints in tasks.
15445 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15446 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15448 * Ada Glitches:: Known peculiarities of Ada mode.
15451 @node Ada Mode Intro
15452 @subsubsection Introduction
15453 @cindex Ada mode, general
15455 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15456 syntax, with some extensions.
15457 The philosophy behind the design of this subset is
15461 That @value{GDBN} should provide basic literals and access to operations for
15462 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15463 leaving more sophisticated computations to subprograms written into the
15464 program (which therefore may be called from @value{GDBN}).
15467 That type safety and strict adherence to Ada language restrictions
15468 are not particularly important to the @value{GDBN} user.
15471 That brevity is important to the @value{GDBN} user.
15474 Thus, for brevity, the debugger acts as if all names declared in
15475 user-written packages are directly visible, even if they are not visible
15476 according to Ada rules, thus making it unnecessary to fully qualify most
15477 names with their packages, regardless of context. Where this causes
15478 ambiguity, @value{GDBN} asks the user's intent.
15480 The debugger will start in Ada mode if it detects an Ada main program.
15481 As for other languages, it will enter Ada mode when stopped in a program that
15482 was translated from an Ada source file.
15484 While in Ada mode, you may use `@t{--}' for comments. This is useful
15485 mostly for documenting command files. The standard @value{GDBN} comment
15486 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15487 middle (to allow based literals).
15489 The debugger supports limited overloading. Given a subprogram call in which
15490 the function symbol has multiple definitions, it will use the number of
15491 actual parameters and some information about their types to attempt to narrow
15492 the set of definitions. It also makes very limited use of context, preferring
15493 procedures to functions in the context of the @code{call} command, and
15494 functions to procedures elsewhere.
15496 @node Omissions from Ada
15497 @subsubsection Omissions from Ada
15498 @cindex Ada, omissions from
15500 Here are the notable omissions from the subset:
15504 Only a subset of the attributes are supported:
15508 @t{'First}, @t{'Last}, and @t{'Length}
15509 on array objects (not on types and subtypes).
15512 @t{'Min} and @t{'Max}.
15515 @t{'Pos} and @t{'Val}.
15521 @t{'Range} on array objects (not subtypes), but only as the right
15522 operand of the membership (@code{in}) operator.
15525 @t{'Access}, @t{'Unchecked_Access}, and
15526 @t{'Unrestricted_Access} (a GNAT extension).
15534 @code{Characters.Latin_1} are not available and
15535 concatenation is not implemented. Thus, escape characters in strings are
15536 not currently available.
15539 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15540 equality of representations. They will generally work correctly
15541 for strings and arrays whose elements have integer or enumeration types.
15542 They may not work correctly for arrays whose element
15543 types have user-defined equality, for arrays of real values
15544 (in particular, IEEE-conformant floating point, because of negative
15545 zeroes and NaNs), and for arrays whose elements contain unused bits with
15546 indeterminate values.
15549 The other component-by-component array operations (@code{and}, @code{or},
15550 @code{xor}, @code{not}, and relational tests other than equality)
15551 are not implemented.
15554 @cindex array aggregates (Ada)
15555 @cindex record aggregates (Ada)
15556 @cindex aggregates (Ada)
15557 There is limited support for array and record aggregates. They are
15558 permitted only on the right sides of assignments, as in these examples:
15561 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15562 (@value{GDBP}) set An_Array := (1, others => 0)
15563 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15564 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15565 (@value{GDBP}) set A_Record := (1, "Peter", True);
15566 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15570 discriminant's value by assigning an aggregate has an
15571 undefined effect if that discriminant is used within the record.
15572 However, you can first modify discriminants by directly assigning to
15573 them (which normally would not be allowed in Ada), and then performing an
15574 aggregate assignment. For example, given a variable @code{A_Rec}
15575 declared to have a type such as:
15578 type Rec (Len : Small_Integer := 0) is record
15580 Vals : IntArray (1 .. Len);
15584 you can assign a value with a different size of @code{Vals} with two
15588 (@value{GDBP}) set A_Rec.Len := 4
15589 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15592 As this example also illustrates, @value{GDBN} is very loose about the usual
15593 rules concerning aggregates. You may leave out some of the
15594 components of an array or record aggregate (such as the @code{Len}
15595 component in the assignment to @code{A_Rec} above); they will retain their
15596 original values upon assignment. You may freely use dynamic values as
15597 indices in component associations. You may even use overlapping or
15598 redundant component associations, although which component values are
15599 assigned in such cases is not defined.
15602 Calls to dispatching subprograms are not implemented.
15605 The overloading algorithm is much more limited (i.e., less selective)
15606 than that of real Ada. It makes only limited use of the context in
15607 which a subexpression appears to resolve its meaning, and it is much
15608 looser in its rules for allowing type matches. As a result, some
15609 function calls will be ambiguous, and the user will be asked to choose
15610 the proper resolution.
15613 The @code{new} operator is not implemented.
15616 Entry calls are not implemented.
15619 Aside from printing, arithmetic operations on the native VAX floating-point
15620 formats are not supported.
15623 It is not possible to slice a packed array.
15626 The names @code{True} and @code{False}, when not part of a qualified name,
15627 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15629 Should your program
15630 redefine these names in a package or procedure (at best a dubious practice),
15631 you will have to use fully qualified names to access their new definitions.
15634 @node Additions to Ada
15635 @subsubsection Additions to Ada
15636 @cindex Ada, deviations from
15638 As it does for other languages, @value{GDBN} makes certain generic
15639 extensions to Ada (@pxref{Expressions}):
15643 If the expression @var{E} is a variable residing in memory (typically
15644 a local variable or array element) and @var{N} is a positive integer,
15645 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15646 @var{N}-1 adjacent variables following it in memory as an array. In
15647 Ada, this operator is generally not necessary, since its prime use is
15648 in displaying parts of an array, and slicing will usually do this in
15649 Ada. However, there are occasional uses when debugging programs in
15650 which certain debugging information has been optimized away.
15653 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15654 appears in function or file @var{B}.'' When @var{B} is a file name,
15655 you must typically surround it in single quotes.
15658 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15659 @var{type} that appears at address @var{addr}.''
15662 A name starting with @samp{$} is a convenience variable
15663 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15666 In addition, @value{GDBN} provides a few other shortcuts and outright
15667 additions specific to Ada:
15671 The assignment statement is allowed as an expression, returning
15672 its right-hand operand as its value. Thus, you may enter
15675 (@value{GDBP}) set x := y + 3
15676 (@value{GDBP}) print A(tmp := y + 1)
15680 The semicolon is allowed as an ``operator,'' returning as its value
15681 the value of its right-hand operand.
15682 This allows, for example,
15683 complex conditional breaks:
15686 (@value{GDBP}) break f
15687 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15691 Rather than use catenation and symbolic character names to introduce special
15692 characters into strings, one may instead use a special bracket notation,
15693 which is also used to print strings. A sequence of characters of the form
15694 @samp{["@var{XX}"]} within a string or character literal denotes the
15695 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15696 sequence of characters @samp{["""]} also denotes a single quotation mark
15697 in strings. For example,
15699 "One line.["0a"]Next line.["0a"]"
15702 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15706 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15707 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15711 (@value{GDBP}) print 'max(x, y)
15715 When printing arrays, @value{GDBN} uses positional notation when the
15716 array has a lower bound of 1, and uses a modified named notation otherwise.
15717 For example, a one-dimensional array of three integers with a lower bound
15718 of 3 might print as
15725 That is, in contrast to valid Ada, only the first component has a @code{=>}
15729 You may abbreviate attributes in expressions with any unique,
15730 multi-character subsequence of
15731 their names (an exact match gets preference).
15732 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15733 in place of @t{a'length}.
15736 @cindex quoting Ada internal identifiers
15737 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15738 to lower case. The GNAT compiler uses upper-case characters for
15739 some of its internal identifiers, which are normally of no interest to users.
15740 For the rare occasions when you actually have to look at them,
15741 enclose them in angle brackets to avoid the lower-case mapping.
15744 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15748 Printing an object of class-wide type or dereferencing an
15749 access-to-class-wide value will display all the components of the object's
15750 specific type (as indicated by its run-time tag). Likewise, component
15751 selection on such a value will operate on the specific type of the
15756 @node Stopping Before Main Program
15757 @subsubsection Stopping at the Very Beginning
15759 @cindex breakpointing Ada elaboration code
15760 It is sometimes necessary to debug the program during elaboration, and
15761 before reaching the main procedure.
15762 As defined in the Ada Reference
15763 Manual, the elaboration code is invoked from a procedure called
15764 @code{adainit}. To run your program up to the beginning of
15765 elaboration, simply use the following two commands:
15766 @code{tbreak adainit} and @code{run}.
15768 @node Ada Exceptions
15769 @subsubsection Ada Exceptions
15771 A command is provided to list all Ada exceptions:
15774 @kindex info exceptions
15775 @item info exceptions
15776 @itemx info exceptions @var{regexp}
15777 The @code{info exceptions} command allows you to list all Ada exceptions
15778 defined within the program being debugged, as well as their addresses.
15779 With a regular expression, @var{regexp}, as argument, only those exceptions
15780 whose names match @var{regexp} are listed.
15783 Below is a small example, showing how the command can be used, first
15784 without argument, and next with a regular expression passed as an
15788 (@value{GDBP}) info exceptions
15789 All defined Ada exceptions:
15790 constraint_error: 0x613da0
15791 program_error: 0x613d20
15792 storage_error: 0x613ce0
15793 tasking_error: 0x613ca0
15794 const.aint_global_e: 0x613b00
15795 (@value{GDBP}) info exceptions const.aint
15796 All Ada exceptions matching regular expression "const.aint":
15797 constraint_error: 0x613da0
15798 const.aint_global_e: 0x613b00
15801 It is also possible to ask @value{GDBN} to stop your program's execution
15802 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15805 @subsubsection Extensions for Ada Tasks
15806 @cindex Ada, tasking
15808 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15809 @value{GDBN} provides the following task-related commands:
15814 This command shows a list of current Ada tasks, as in the following example:
15821 (@value{GDBP}) info tasks
15822 ID TID P-ID Pri State Name
15823 1 8088000 0 15 Child Activation Wait main_task
15824 2 80a4000 1 15 Accept Statement b
15825 3 809a800 1 15 Child Activation Wait a
15826 * 4 80ae800 3 15 Runnable c
15831 In this listing, the asterisk before the last task indicates it to be the
15832 task currently being inspected.
15836 Represents @value{GDBN}'s internal task number.
15842 The parent's task ID (@value{GDBN}'s internal task number).
15845 The base priority of the task.
15848 Current state of the task.
15852 The task has been created but has not been activated. It cannot be
15856 The task is not blocked for any reason known to Ada. (It may be waiting
15857 for a mutex, though.) It is conceptually "executing" in normal mode.
15860 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15861 that were waiting on terminate alternatives have been awakened and have
15862 terminated themselves.
15864 @item Child Activation Wait
15865 The task is waiting for created tasks to complete activation.
15867 @item Accept Statement
15868 The task is waiting on an accept or selective wait statement.
15870 @item Waiting on entry call
15871 The task is waiting on an entry call.
15873 @item Async Select Wait
15874 The task is waiting to start the abortable part of an asynchronous
15878 The task is waiting on a select statement with only a delay
15881 @item Child Termination Wait
15882 The task is sleeping having completed a master within itself, and is
15883 waiting for the tasks dependent on that master to become terminated or
15884 waiting on a terminate Phase.
15886 @item Wait Child in Term Alt
15887 The task is sleeping waiting for tasks on terminate alternatives to
15888 finish terminating.
15890 @item Accepting RV with @var{taskno}
15891 The task is accepting a rendez-vous with the task @var{taskno}.
15895 Name of the task in the program.
15899 @kindex info task @var{taskno}
15900 @item info task @var{taskno}
15901 This command shows detailled informations on the specified task, as in
15902 the following example:
15907 (@value{GDBP}) info tasks
15908 ID TID P-ID Pri State Name
15909 1 8077880 0 15 Child Activation Wait main_task
15910 * 2 807c468 1 15 Runnable task_1
15911 (@value{GDBP}) info task 2
15912 Ada Task: 0x807c468
15915 Parent: 1 (main_task)
15921 @kindex task@r{ (Ada)}
15922 @cindex current Ada task ID
15923 This command prints the ID of the current task.
15929 (@value{GDBP}) info tasks
15930 ID TID P-ID Pri State Name
15931 1 8077870 0 15 Child Activation Wait main_task
15932 * 2 807c458 1 15 Runnable t
15933 (@value{GDBP}) task
15934 [Current task is 2]
15937 @item task @var{taskno}
15938 @cindex Ada task switching
15939 This command is like the @code{thread @var{threadno}}
15940 command (@pxref{Threads}). It switches the context of debugging
15941 from the current task to the given task.
15947 (@value{GDBP}) info tasks
15948 ID TID P-ID Pri State Name
15949 1 8077870 0 15 Child Activation Wait main_task
15950 * 2 807c458 1 15 Runnable t
15951 (@value{GDBP}) task 1
15952 [Switching to task 1]
15953 #0 0x8067726 in pthread_cond_wait ()
15955 #0 0x8067726 in pthread_cond_wait ()
15956 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15957 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15958 #3 0x806153e in system.tasking.stages.activate_tasks ()
15959 #4 0x804aacc in un () at un.adb:5
15962 @item break @var{linespec} task @var{taskno}
15963 @itemx break @var{linespec} task @var{taskno} if @dots{}
15964 @cindex breakpoints and tasks, in Ada
15965 @cindex task breakpoints, in Ada
15966 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15967 These commands are like the @code{break @dots{} thread @dots{}}
15968 command (@pxref{Thread Stops}). The
15969 @var{linespec} argument specifies source lines, as described
15970 in @ref{Specify Location}.
15972 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15973 to specify that you only want @value{GDBN} to stop the program when a
15974 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15975 numeric task identifiers assigned by @value{GDBN}, shown in the first
15976 column of the @samp{info tasks} display.
15978 If you do not specify @samp{task @var{taskno}} when you set a
15979 breakpoint, the breakpoint applies to @emph{all} tasks of your
15982 You can use the @code{task} qualifier on conditional breakpoints as
15983 well; in this case, place @samp{task @var{taskno}} before the
15984 breakpoint condition (before the @code{if}).
15992 (@value{GDBP}) info tasks
15993 ID TID P-ID Pri State Name
15994 1 140022020 0 15 Child Activation Wait main_task
15995 2 140045060 1 15 Accept/Select Wait t2
15996 3 140044840 1 15 Runnable t1
15997 * 4 140056040 1 15 Runnable t3
15998 (@value{GDBP}) b 15 task 2
15999 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16000 (@value{GDBP}) cont
16005 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16007 (@value{GDBP}) info tasks
16008 ID TID P-ID Pri State Name
16009 1 140022020 0 15 Child Activation Wait main_task
16010 * 2 140045060 1 15 Runnable t2
16011 3 140044840 1 15 Runnable t1
16012 4 140056040 1 15 Delay Sleep t3
16016 @node Ada Tasks and Core Files
16017 @subsubsection Tasking Support when Debugging Core Files
16018 @cindex Ada tasking and core file debugging
16020 When inspecting a core file, as opposed to debugging a live program,
16021 tasking support may be limited or even unavailable, depending on
16022 the platform being used.
16023 For instance, on x86-linux, the list of tasks is available, but task
16024 switching is not supported.
16026 On certain platforms, the debugger needs to perform some
16027 memory writes in order to provide Ada tasking support. When inspecting
16028 a core file, this means that the core file must be opened with read-write
16029 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16030 Under these circumstances, you should make a backup copy of the core
16031 file before inspecting it with @value{GDBN}.
16033 @node Ravenscar Profile
16034 @subsubsection Tasking Support when using the Ravenscar Profile
16035 @cindex Ravenscar Profile
16037 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16038 specifically designed for systems with safety-critical real-time
16042 @kindex set ravenscar task-switching on
16043 @cindex task switching with program using Ravenscar Profile
16044 @item set ravenscar task-switching on
16045 Allows task switching when debugging a program that uses the Ravenscar
16046 Profile. This is the default.
16048 @kindex set ravenscar task-switching off
16049 @item set ravenscar task-switching off
16050 Turn off task switching when debugging a program that uses the Ravenscar
16051 Profile. This is mostly intended to disable the code that adds support
16052 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16053 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16054 To be effective, this command should be run before the program is started.
16056 @kindex show ravenscar task-switching
16057 @item show ravenscar task-switching
16058 Show whether it is possible to switch from task to task in a program
16059 using the Ravenscar Profile.
16064 @subsubsection Known Peculiarities of Ada Mode
16065 @cindex Ada, problems
16067 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16068 we know of several problems with and limitations of Ada mode in
16070 some of which will be fixed with planned future releases of the debugger
16071 and the GNU Ada compiler.
16075 Static constants that the compiler chooses not to materialize as objects in
16076 storage are invisible to the debugger.
16079 Named parameter associations in function argument lists are ignored (the
16080 argument lists are treated as positional).
16083 Many useful library packages are currently invisible to the debugger.
16086 Fixed-point arithmetic, conversions, input, and output is carried out using
16087 floating-point arithmetic, and may give results that only approximate those on
16091 The GNAT compiler never generates the prefix @code{Standard} for any of
16092 the standard symbols defined by the Ada language. @value{GDBN} knows about
16093 this: it will strip the prefix from names when you use it, and will never
16094 look for a name you have so qualified among local symbols, nor match against
16095 symbols in other packages or subprograms. If you have
16096 defined entities anywhere in your program other than parameters and
16097 local variables whose simple names match names in @code{Standard},
16098 GNAT's lack of qualification here can cause confusion. When this happens,
16099 you can usually resolve the confusion
16100 by qualifying the problematic names with package
16101 @code{Standard} explicitly.
16104 Older versions of the compiler sometimes generate erroneous debugging
16105 information, resulting in the debugger incorrectly printing the value
16106 of affected entities. In some cases, the debugger is able to work
16107 around an issue automatically. In other cases, the debugger is able
16108 to work around the issue, but the work-around has to be specifically
16111 @kindex set ada trust-PAD-over-XVS
16112 @kindex show ada trust-PAD-over-XVS
16115 @item set ada trust-PAD-over-XVS on
16116 Configure GDB to strictly follow the GNAT encoding when computing the
16117 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16118 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16119 a complete description of the encoding used by the GNAT compiler).
16120 This is the default.
16122 @item set ada trust-PAD-over-XVS off
16123 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16124 sometimes prints the wrong value for certain entities, changing @code{ada
16125 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16126 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16127 @code{off}, but this incurs a slight performance penalty, so it is
16128 recommended to leave this setting to @code{on} unless necessary.
16132 @cindex GNAT descriptive types
16133 @cindex GNAT encoding
16134 Internally, the debugger also relies on the compiler following a number
16135 of conventions known as the @samp{GNAT Encoding}, all documented in
16136 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16137 how the debugging information should be generated for certain types.
16138 In particular, this convention makes use of @dfn{descriptive types},
16139 which are artificial types generated purely to help the debugger.
16141 These encodings were defined at a time when the debugging information
16142 format used was not powerful enough to describe some of the more complex
16143 types available in Ada. Since DWARF allows us to express nearly all
16144 Ada features, the long-term goal is to slowly replace these descriptive
16145 types by their pure DWARF equivalent. To facilitate that transition,
16146 a new maintenance option is available to force the debugger to ignore
16147 those descriptive types. It allows the user to quickly evaluate how
16148 well @value{GDBN} works without them.
16152 @kindex maint ada set ignore-descriptive-types
16153 @item maintenance ada set ignore-descriptive-types [on|off]
16154 Control whether the debugger should ignore descriptive types.
16155 The default is not to ignore descriptives types (@code{off}).
16157 @kindex maint ada show ignore-descriptive-types
16158 @item maintenance ada show ignore-descriptive-types
16159 Show if descriptive types are ignored by @value{GDBN}.
16163 @node Unsupported Languages
16164 @section Unsupported Languages
16166 @cindex unsupported languages
16167 @cindex minimal language
16168 In addition to the other fully-supported programming languages,
16169 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16170 It does not represent a real programming language, but provides a set
16171 of capabilities close to what the C or assembly languages provide.
16172 This should allow most simple operations to be performed while debugging
16173 an application that uses a language currently not supported by @value{GDBN}.
16175 If the language is set to @code{auto}, @value{GDBN} will automatically
16176 select this language if the current frame corresponds to an unsupported
16180 @chapter Examining the Symbol Table
16182 The commands described in this chapter allow you to inquire about the
16183 symbols (names of variables, functions and types) defined in your
16184 program. This information is inherent in the text of your program and
16185 does not change as your program executes. @value{GDBN} finds it in your
16186 program's symbol table, in the file indicated when you started @value{GDBN}
16187 (@pxref{File Options, ,Choosing Files}), or by one of the
16188 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16190 @cindex symbol names
16191 @cindex names of symbols
16192 @cindex quoting names
16193 Occasionally, you may need to refer to symbols that contain unusual
16194 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16195 most frequent case is in referring to static variables in other
16196 source files (@pxref{Variables,,Program Variables}). File names
16197 are recorded in object files as debugging symbols, but @value{GDBN} would
16198 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16199 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16200 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16207 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16210 @cindex case-insensitive symbol names
16211 @cindex case sensitivity in symbol names
16212 @kindex set case-sensitive
16213 @item set case-sensitive on
16214 @itemx set case-sensitive off
16215 @itemx set case-sensitive auto
16216 Normally, when @value{GDBN} looks up symbols, it matches their names
16217 with case sensitivity determined by the current source language.
16218 Occasionally, you may wish to control that. The command @code{set
16219 case-sensitive} lets you do that by specifying @code{on} for
16220 case-sensitive matches or @code{off} for case-insensitive ones. If
16221 you specify @code{auto}, case sensitivity is reset to the default
16222 suitable for the source language. The default is case-sensitive
16223 matches for all languages except for Fortran, for which the default is
16224 case-insensitive matches.
16226 @kindex show case-sensitive
16227 @item show case-sensitive
16228 This command shows the current setting of case sensitivity for symbols
16231 @kindex set print type methods
16232 @item set print type methods
16233 @itemx set print type methods on
16234 @itemx set print type methods off
16235 Normally, when @value{GDBN} prints a class, it displays any methods
16236 declared in that class. You can control this behavior either by
16237 passing the appropriate flag to @code{ptype}, or using @command{set
16238 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16239 display the methods; this is the default. Specifying @code{off} will
16240 cause @value{GDBN} to omit the methods.
16242 @kindex show print type methods
16243 @item show print type methods
16244 This command shows the current setting of method display when printing
16247 @kindex set print type typedefs
16248 @item set print type typedefs
16249 @itemx set print type typedefs on
16250 @itemx set print type typedefs off
16252 Normally, when @value{GDBN} prints a class, it displays any typedefs
16253 defined in that class. You can control this behavior either by
16254 passing the appropriate flag to @code{ptype}, or using @command{set
16255 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16256 display the typedef definitions; this is the default. Specifying
16257 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16258 Note that this controls whether the typedef definition itself is
16259 printed, not whether typedef names are substituted when printing other
16262 @kindex show print type typedefs
16263 @item show print type typedefs
16264 This command shows the current setting of typedef display when
16267 @kindex info address
16268 @cindex address of a symbol
16269 @item info address @var{symbol}
16270 Describe where the data for @var{symbol} is stored. For a register
16271 variable, this says which register it is kept in. For a non-register
16272 local variable, this prints the stack-frame offset at which the variable
16275 Note the contrast with @samp{print &@var{symbol}}, which does not work
16276 at all for a register variable, and for a stack local variable prints
16277 the exact address of the current instantiation of the variable.
16279 @kindex info symbol
16280 @cindex symbol from address
16281 @cindex closest symbol and offset for an address
16282 @item info symbol @var{addr}
16283 Print the name of a symbol which is stored at the address @var{addr}.
16284 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16285 nearest symbol and an offset from it:
16288 (@value{GDBP}) info symbol 0x54320
16289 _initialize_vx + 396 in section .text
16293 This is the opposite of the @code{info address} command. You can use
16294 it to find out the name of a variable or a function given its address.
16296 For dynamically linked executables, the name of executable or shared
16297 library containing the symbol is also printed:
16300 (@value{GDBP}) info symbol 0x400225
16301 _start + 5 in section .text of /tmp/a.out
16302 (@value{GDBP}) info symbol 0x2aaaac2811cf
16303 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16308 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16309 Demangle @var{name}.
16310 If @var{language} is provided it is the name of the language to demangle
16311 @var{name} in. Otherwise @var{name} is demangled in the current language.
16313 The @samp{--} option specifies the end of options,
16314 and is useful when @var{name} begins with a dash.
16316 The parameter @code{demangle-style} specifies how to interpret the kind
16317 of mangling used. @xref{Print Settings}.
16320 @item whatis[/@var{flags}] [@var{arg}]
16321 Print the data type of @var{arg}, which can be either an expression
16322 or a name of a data type. With no argument, print the data type of
16323 @code{$}, the last value in the value history.
16325 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16326 is not actually evaluated, and any side-effecting operations (such as
16327 assignments or function calls) inside it do not take place.
16329 If @var{arg} is a variable or an expression, @code{whatis} prints its
16330 literal type as it is used in the source code. If the type was
16331 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16332 the data type underlying the @code{typedef}. If the type of the
16333 variable or the expression is a compound data type, such as
16334 @code{struct} or @code{class}, @code{whatis} never prints their
16335 fields or methods. It just prints the @code{struct}/@code{class}
16336 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16337 such a compound data type, use @code{ptype}.
16339 If @var{arg} is a type name that was defined using @code{typedef},
16340 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16341 Unrolling means that @code{whatis} will show the underlying type used
16342 in the @code{typedef} declaration of @var{arg}. However, if that
16343 underlying type is also a @code{typedef}, @code{whatis} will not
16346 For C code, the type names may also have the form @samp{class
16347 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16348 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16350 @var{flags} can be used to modify how the type is displayed.
16351 Available flags are:
16355 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16356 parameters and typedefs defined in a class when printing the class'
16357 members. The @code{/r} flag disables this.
16360 Do not print methods defined in the class.
16363 Print methods defined in the class. This is the default, but the flag
16364 exists in case you change the default with @command{set print type methods}.
16367 Do not print typedefs defined in the class. Note that this controls
16368 whether the typedef definition itself is printed, not whether typedef
16369 names are substituted when printing other types.
16372 Print typedefs defined in the class. This is the default, but the flag
16373 exists in case you change the default with @command{set print type typedefs}.
16377 @item ptype[/@var{flags}] [@var{arg}]
16378 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16379 detailed description of the type, instead of just the name of the type.
16380 @xref{Expressions, ,Expressions}.
16382 Contrary to @code{whatis}, @code{ptype} always unrolls any
16383 @code{typedef}s in its argument declaration, whether the argument is
16384 a variable, expression, or a data type. This means that @code{ptype}
16385 of a variable or an expression will not print literally its type as
16386 present in the source code---use @code{whatis} for that. @code{typedef}s at
16387 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16388 fields, methods and inner @code{class typedef}s of @code{struct}s,
16389 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16391 For example, for this variable declaration:
16394 typedef double real_t;
16395 struct complex @{ real_t real; double imag; @};
16396 typedef struct complex complex_t;
16398 real_t *real_pointer_var;
16402 the two commands give this output:
16406 (@value{GDBP}) whatis var
16408 (@value{GDBP}) ptype var
16409 type = struct complex @{
16413 (@value{GDBP}) whatis complex_t
16414 type = struct complex
16415 (@value{GDBP}) whatis struct complex
16416 type = struct complex
16417 (@value{GDBP}) ptype struct complex
16418 type = struct complex @{
16422 (@value{GDBP}) whatis real_pointer_var
16424 (@value{GDBP}) ptype real_pointer_var
16430 As with @code{whatis}, using @code{ptype} without an argument refers to
16431 the type of @code{$}, the last value in the value history.
16433 @cindex incomplete type
16434 Sometimes, programs use opaque data types or incomplete specifications
16435 of complex data structure. If the debug information included in the
16436 program does not allow @value{GDBN} to display a full declaration of
16437 the data type, it will say @samp{<incomplete type>}. For example,
16438 given these declarations:
16442 struct foo *fooptr;
16446 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16449 (@value{GDBP}) ptype foo
16450 $1 = <incomplete type>
16454 ``Incomplete type'' is C terminology for data types that are not
16455 completely specified.
16458 @item info types @var{regexp}
16460 Print a brief description of all types whose names match the regular
16461 expression @var{regexp} (or all types in your program, if you supply
16462 no argument). Each complete typename is matched as though it were a
16463 complete line; thus, @samp{i type value} gives information on all
16464 types in your program whose names include the string @code{value}, but
16465 @samp{i type ^value$} gives information only on types whose complete
16466 name is @code{value}.
16468 This command differs from @code{ptype} in two ways: first, like
16469 @code{whatis}, it does not print a detailed description; second, it
16470 lists all source files where a type is defined.
16472 @kindex info type-printers
16473 @item info type-printers
16474 Versions of @value{GDBN} that ship with Python scripting enabled may
16475 have ``type printers'' available. When using @command{ptype} or
16476 @command{whatis}, these printers are consulted when the name of a type
16477 is needed. @xref{Type Printing API}, for more information on writing
16480 @code{info type-printers} displays all the available type printers.
16482 @kindex enable type-printer
16483 @kindex disable type-printer
16484 @item enable type-printer @var{name}@dots{}
16485 @item disable type-printer @var{name}@dots{}
16486 These commands can be used to enable or disable type printers.
16489 @cindex local variables
16490 @item info scope @var{location}
16491 List all the variables local to a particular scope. This command
16492 accepts a @var{location} argument---a function name, a source line, or
16493 an address preceded by a @samp{*}, and prints all the variables local
16494 to the scope defined by that location. (@xref{Specify Location}, for
16495 details about supported forms of @var{location}.) For example:
16498 (@value{GDBP}) @b{info scope command_line_handler}
16499 Scope for command_line_handler:
16500 Symbol rl is an argument at stack/frame offset 8, length 4.
16501 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16502 Symbol linelength is in static storage at address 0x150a1c, length 4.
16503 Symbol p is a local variable in register $esi, length 4.
16504 Symbol p1 is a local variable in register $ebx, length 4.
16505 Symbol nline is a local variable in register $edx, length 4.
16506 Symbol repeat is a local variable at frame offset -8, length 4.
16510 This command is especially useful for determining what data to collect
16511 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16514 @kindex info source
16516 Show information about the current source file---that is, the source file for
16517 the function containing the current point of execution:
16520 the name of the source file, and the directory containing it,
16522 the directory it was compiled in,
16524 its length, in lines,
16526 which programming language it is written in,
16528 if the debug information provides it, the program that compiled the file
16529 (which may include, e.g., the compiler version and command line arguments),
16531 whether the executable includes debugging information for that file, and
16532 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16534 whether the debugging information includes information about
16535 preprocessor macros.
16539 @kindex info sources
16541 Print the names of all source files in your program for which there is
16542 debugging information, organized into two lists: files whose symbols
16543 have already been read, and files whose symbols will be read when needed.
16545 @kindex info functions
16546 @item info functions
16547 Print the names and data types of all defined functions.
16549 @item info functions @var{regexp}
16550 Print the names and data types of all defined functions
16551 whose names contain a match for regular expression @var{regexp}.
16552 Thus, @samp{info fun step} finds all functions whose names
16553 include @code{step}; @samp{info fun ^step} finds those whose names
16554 start with @code{step}. If a function name contains characters
16555 that conflict with the regular expression language (e.g.@:
16556 @samp{operator*()}), they may be quoted with a backslash.
16558 @kindex info variables
16559 @item info variables
16560 Print the names and data types of all variables that are defined
16561 outside of functions (i.e.@: excluding local variables).
16563 @item info variables @var{regexp}
16564 Print the names and data types of all variables (except for local
16565 variables) whose names contain a match for regular expression
16568 @kindex info classes
16569 @cindex Objective-C, classes and selectors
16571 @itemx info classes @var{regexp}
16572 Display all Objective-C classes in your program, or
16573 (with the @var{regexp} argument) all those matching a particular regular
16576 @kindex info selectors
16577 @item info selectors
16578 @itemx info selectors @var{regexp}
16579 Display all Objective-C selectors in your program, or
16580 (with the @var{regexp} argument) all those matching a particular regular
16584 This was never implemented.
16585 @kindex info methods
16587 @itemx info methods @var{regexp}
16588 The @code{info methods} command permits the user to examine all defined
16589 methods within C@t{++} program, or (with the @var{regexp} argument) a
16590 specific set of methods found in the various C@t{++} classes. Many
16591 C@t{++} classes provide a large number of methods. Thus, the output
16592 from the @code{ptype} command can be overwhelming and hard to use. The
16593 @code{info-methods} command filters the methods, printing only those
16594 which match the regular-expression @var{regexp}.
16597 @cindex opaque data types
16598 @kindex set opaque-type-resolution
16599 @item set opaque-type-resolution on
16600 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16601 declared as a pointer to a @code{struct}, @code{class}, or
16602 @code{union}---for example, @code{struct MyType *}---that is used in one
16603 source file although the full declaration of @code{struct MyType} is in
16604 another source file. The default is on.
16606 A change in the setting of this subcommand will not take effect until
16607 the next time symbols for a file are loaded.
16609 @item set opaque-type-resolution off
16610 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16611 is printed as follows:
16613 @{<no data fields>@}
16616 @kindex show opaque-type-resolution
16617 @item show opaque-type-resolution
16618 Show whether opaque types are resolved or not.
16620 @kindex set print symbol-loading
16621 @cindex print messages when symbols are loaded
16622 @item set print symbol-loading
16623 @itemx set print symbol-loading full
16624 @itemx set print symbol-loading brief
16625 @itemx set print symbol-loading off
16626 The @code{set print symbol-loading} command allows you to control the
16627 printing of messages when @value{GDBN} loads symbol information.
16628 By default a message is printed for the executable and one for each
16629 shared library, and normally this is what you want. However, when
16630 debugging apps with large numbers of shared libraries these messages
16632 When set to @code{brief} a message is printed for each executable,
16633 and when @value{GDBN} loads a collection of shared libraries at once
16634 it will only print one message regardless of the number of shared
16635 libraries. When set to @code{off} no messages are printed.
16637 @kindex show print symbol-loading
16638 @item show print symbol-loading
16639 Show whether messages will be printed when a @value{GDBN} command
16640 entered from the keyboard causes symbol information to be loaded.
16642 @kindex maint print symbols
16643 @cindex symbol dump
16644 @kindex maint print psymbols
16645 @cindex partial symbol dump
16646 @kindex maint print msymbols
16647 @cindex minimal symbol dump
16648 @item maint print symbols @var{filename}
16649 @itemx maint print psymbols @var{filename}
16650 @itemx maint print msymbols @var{filename}
16651 Write a dump of debugging symbol data into the file @var{filename}.
16652 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16653 symbols with debugging data are included. If you use @samp{maint print
16654 symbols}, @value{GDBN} includes all the symbols for which it has already
16655 collected full details: that is, @var{filename} reflects symbols for
16656 only those files whose symbols @value{GDBN} has read. You can use the
16657 command @code{info sources} to find out which files these are. If you
16658 use @samp{maint print psymbols} instead, the dump shows information about
16659 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16660 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16661 @samp{maint print msymbols} dumps just the minimal symbol information
16662 required for each object file from which @value{GDBN} has read some symbols.
16663 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16664 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16666 @kindex maint info symtabs
16667 @kindex maint info psymtabs
16668 @cindex listing @value{GDBN}'s internal symbol tables
16669 @cindex symbol tables, listing @value{GDBN}'s internal
16670 @cindex full symbol tables, listing @value{GDBN}'s internal
16671 @cindex partial symbol tables, listing @value{GDBN}'s internal
16672 @item maint info symtabs @r{[} @var{regexp} @r{]}
16673 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16675 List the @code{struct symtab} or @code{struct partial_symtab}
16676 structures whose names match @var{regexp}. If @var{regexp} is not
16677 given, list them all. The output includes expressions which you can
16678 copy into a @value{GDBN} debugging this one to examine a particular
16679 structure in more detail. For example:
16682 (@value{GDBP}) maint info psymtabs dwarf2read
16683 @{ objfile /home/gnu/build/gdb/gdb
16684 ((struct objfile *) 0x82e69d0)
16685 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16686 ((struct partial_symtab *) 0x8474b10)
16689 text addresses 0x814d3c8 -- 0x8158074
16690 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16691 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16692 dependencies (none)
16695 (@value{GDBP}) maint info symtabs
16699 We see that there is one partial symbol table whose filename contains
16700 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16701 and we see that @value{GDBN} has not read in any symtabs yet at all.
16702 If we set a breakpoint on a function, that will cause @value{GDBN} to
16703 read the symtab for the compilation unit containing that function:
16706 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16707 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16709 (@value{GDBP}) maint info symtabs
16710 @{ objfile /home/gnu/build/gdb/gdb
16711 ((struct objfile *) 0x82e69d0)
16712 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16713 ((struct symtab *) 0x86c1f38)
16716 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16717 linetable ((struct linetable *) 0x8370fa0)
16718 debugformat DWARF 2
16724 @kindex maint set symbol-cache-size
16725 @cindex symbol cache size
16726 @item maint set symbol-cache-size @var{size}
16727 Set the size of the symbol cache to @var{size}.
16728 The default size is intended to be good enough for debugging
16729 most applications. This option exists to allow for experimenting
16730 with different sizes.
16732 @kindex maint show symbol-cache-size
16733 @item maint show symbol-cache-size
16734 Show the size of the symbol cache.
16736 @kindex maint print symbol-cache
16737 @cindex symbol cache, printing its contents
16738 @item maint print symbol-cache
16739 Print the contents of the symbol cache.
16740 This is useful when debugging symbol cache issues.
16742 @kindex maint print symbol-cache-statistics
16743 @cindex symbol cache, printing usage statistics
16744 @item maint print symbol-cache-statistics
16745 Print symbol cache usage statistics.
16746 This helps determine how well the cache is being utilized.
16748 @kindex maint flush-symbol-cache
16749 @cindex symbol cache, flushing
16750 @item maint flush-symbol-cache
16751 Flush the contents of the symbol cache, all entries are removed.
16752 This command is useful when debugging the symbol cache.
16753 It is also useful when collecting performance data.
16758 @chapter Altering Execution
16760 Once you think you have found an error in your program, you might want to
16761 find out for certain whether correcting the apparent error would lead to
16762 correct results in the rest of the run. You can find the answer by
16763 experiment, using the @value{GDBN} features for altering execution of the
16766 For example, you can store new values into variables or memory
16767 locations, give your program a signal, restart it at a different
16768 address, or even return prematurely from a function.
16771 * Assignment:: Assignment to variables
16772 * Jumping:: Continuing at a different address
16773 * Signaling:: Giving your program a signal
16774 * Returning:: Returning from a function
16775 * Calling:: Calling your program's functions
16776 * Patching:: Patching your program
16777 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16781 @section Assignment to Variables
16784 @cindex setting variables
16785 To alter the value of a variable, evaluate an assignment expression.
16786 @xref{Expressions, ,Expressions}. For example,
16793 stores the value 4 into the variable @code{x}, and then prints the
16794 value of the assignment expression (which is 4).
16795 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16796 information on operators in supported languages.
16798 @kindex set variable
16799 @cindex variables, setting
16800 If you are not interested in seeing the value of the assignment, use the
16801 @code{set} command instead of the @code{print} command. @code{set} is
16802 really the same as @code{print} except that the expression's value is
16803 not printed and is not put in the value history (@pxref{Value History,
16804 ,Value History}). The expression is evaluated only for its effects.
16806 If the beginning of the argument string of the @code{set} command
16807 appears identical to a @code{set} subcommand, use the @code{set
16808 variable} command instead of just @code{set}. This command is identical
16809 to @code{set} except for its lack of subcommands. For example, if your
16810 program has a variable @code{width}, you get an error if you try to set
16811 a new value with just @samp{set width=13}, because @value{GDBN} has the
16812 command @code{set width}:
16815 (@value{GDBP}) whatis width
16817 (@value{GDBP}) p width
16819 (@value{GDBP}) set width=47
16820 Invalid syntax in expression.
16824 The invalid expression, of course, is @samp{=47}. In
16825 order to actually set the program's variable @code{width}, use
16828 (@value{GDBP}) set var width=47
16831 Because the @code{set} command has many subcommands that can conflict
16832 with the names of program variables, it is a good idea to use the
16833 @code{set variable} command instead of just @code{set}. For example, if
16834 your program has a variable @code{g}, you run into problems if you try
16835 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16836 the command @code{set gnutarget}, abbreviated @code{set g}:
16840 (@value{GDBP}) whatis g
16844 (@value{GDBP}) set g=4
16848 The program being debugged has been started already.
16849 Start it from the beginning? (y or n) y
16850 Starting program: /home/smith/cc_progs/a.out
16851 "/home/smith/cc_progs/a.out": can't open to read symbols:
16852 Invalid bfd target.
16853 (@value{GDBP}) show g
16854 The current BFD target is "=4".
16859 The program variable @code{g} did not change, and you silently set the
16860 @code{gnutarget} to an invalid value. In order to set the variable
16864 (@value{GDBP}) set var g=4
16867 @value{GDBN} allows more implicit conversions in assignments than C; you can
16868 freely store an integer value into a pointer variable or vice versa,
16869 and you can convert any structure to any other structure that is the
16870 same length or shorter.
16871 @comment FIXME: how do structs align/pad in these conversions?
16872 @comment /doc@cygnus.com 18dec1990
16874 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16875 construct to generate a value of specified type at a specified address
16876 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16877 to memory location @code{0x83040} as an integer (which implies a certain size
16878 and representation in memory), and
16881 set @{int@}0x83040 = 4
16885 stores the value 4 into that memory location.
16888 @section Continuing at a Different Address
16890 Ordinarily, when you continue your program, you do so at the place where
16891 it stopped, with the @code{continue} command. You can instead continue at
16892 an address of your own choosing, with the following commands:
16896 @kindex j @r{(@code{jump})}
16897 @item jump @var{linespec}
16898 @itemx j @var{linespec}
16899 @itemx jump @var{location}
16900 @itemx j @var{location}
16901 Resume execution at line @var{linespec} or at address given by
16902 @var{location}. Execution stops again immediately if there is a
16903 breakpoint there. @xref{Specify Location}, for a description of the
16904 different forms of @var{linespec} and @var{location}. It is common
16905 practice to use the @code{tbreak} command in conjunction with
16906 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16908 The @code{jump} command does not change the current stack frame, or
16909 the stack pointer, or the contents of any memory location or any
16910 register other than the program counter. If line @var{linespec} is in
16911 a different function from the one currently executing, the results may
16912 be bizarre if the two functions expect different patterns of arguments or
16913 of local variables. For this reason, the @code{jump} command requests
16914 confirmation if the specified line is not in the function currently
16915 executing. However, even bizarre results are predictable if you are
16916 well acquainted with the machine-language code of your program.
16919 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16920 On many systems, you can get much the same effect as the @code{jump}
16921 command by storing a new value into the register @code{$pc}. The
16922 difference is that this does not start your program running; it only
16923 changes the address of where it @emph{will} run when you continue. For
16931 makes the next @code{continue} command or stepping command execute at
16932 address @code{0x485}, rather than at the address where your program stopped.
16933 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16935 The most common occasion to use the @code{jump} command is to back
16936 up---perhaps with more breakpoints set---over a portion of a program
16937 that has already executed, in order to examine its execution in more
16942 @section Giving your Program a Signal
16943 @cindex deliver a signal to a program
16947 @item signal @var{signal}
16948 Resume execution where your program is stopped, but immediately give it the
16949 signal @var{signal}. The @var{signal} can be the name or the number of a
16950 signal. For example, on many systems @code{signal 2} and @code{signal
16951 SIGINT} are both ways of sending an interrupt signal.
16953 Alternatively, if @var{signal} is zero, continue execution without
16954 giving a signal. This is useful when your program stopped on account of
16955 a signal and would ordinarily see the signal when resumed with the
16956 @code{continue} command; @samp{signal 0} causes it to resume without a
16959 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16960 delivered to the currently selected thread, not the thread that last
16961 reported a stop. This includes the situation where a thread was
16962 stopped due to a signal. So if you want to continue execution
16963 suppressing the signal that stopped a thread, you should select that
16964 same thread before issuing the @samp{signal 0} command. If you issue
16965 the @samp{signal 0} command with another thread as the selected one,
16966 @value{GDBN} detects that and asks for confirmation.
16968 Invoking the @code{signal} command is not the same as invoking the
16969 @code{kill} utility from the shell. Sending a signal with @code{kill}
16970 causes @value{GDBN} to decide what to do with the signal depending on
16971 the signal handling tables (@pxref{Signals}). The @code{signal} command
16972 passes the signal directly to your program.
16974 @code{signal} does not repeat when you press @key{RET} a second time
16975 after executing the command.
16977 @kindex queue-signal
16978 @item queue-signal @var{signal}
16979 Queue @var{signal} to be delivered immediately to the current thread
16980 when execution of the thread resumes. The @var{signal} can be the name or
16981 the number of a signal. For example, on many systems @code{signal 2} and
16982 @code{signal SIGINT} are both ways of sending an interrupt signal.
16983 The handling of the signal must be set to pass the signal to the program,
16984 otherwise @value{GDBN} will report an error.
16985 You can control the handling of signals from @value{GDBN} with the
16986 @code{handle} command (@pxref{Signals}).
16988 Alternatively, if @var{signal} is zero, any currently queued signal
16989 for the current thread is discarded and when execution resumes no signal
16990 will be delivered. This is useful when your program stopped on account
16991 of a signal and would ordinarily see the signal when resumed with the
16992 @code{continue} command.
16994 This command differs from the @code{signal} command in that the signal
16995 is just queued, execution is not resumed. And @code{queue-signal} cannot
16996 be used to pass a signal whose handling state has been set to @code{nopass}
17001 @xref{stepping into signal handlers}, for information on how stepping
17002 commands behave when the thread has a signal queued.
17005 @section Returning from a Function
17008 @cindex returning from a function
17011 @itemx return @var{expression}
17012 You can cancel execution of a function call with the @code{return}
17013 command. If you give an
17014 @var{expression} argument, its value is used as the function's return
17018 When you use @code{return}, @value{GDBN} discards the selected stack frame
17019 (and all frames within it). You can think of this as making the
17020 discarded frame return prematurely. If you wish to specify a value to
17021 be returned, give that value as the argument to @code{return}.
17023 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17024 Frame}), and any other frames inside of it, leaving its caller as the
17025 innermost remaining frame. That frame becomes selected. The
17026 specified value is stored in the registers used for returning values
17029 The @code{return} command does not resume execution; it leaves the
17030 program stopped in the state that would exist if the function had just
17031 returned. In contrast, the @code{finish} command (@pxref{Continuing
17032 and Stepping, ,Continuing and Stepping}) resumes execution until the
17033 selected stack frame returns naturally.
17035 @value{GDBN} needs to know how the @var{expression} argument should be set for
17036 the inferior. The concrete registers assignment depends on the OS ABI and the
17037 type being returned by the selected stack frame. For example it is common for
17038 OS ABI to return floating point values in FPU registers while integer values in
17039 CPU registers. Still some ABIs return even floating point values in CPU
17040 registers. Larger integer widths (such as @code{long long int}) also have
17041 specific placement rules. @value{GDBN} already knows the OS ABI from its
17042 current target so it needs to find out also the type being returned to make the
17043 assignment into the right register(s).
17045 Normally, the selected stack frame has debug info. @value{GDBN} will always
17046 use the debug info instead of the implicit type of @var{expression} when the
17047 debug info is available. For example, if you type @kbd{return -1}, and the
17048 function in the current stack frame is declared to return a @code{long long
17049 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17050 into a @code{long long int}:
17053 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17055 (@value{GDBP}) return -1
17056 Make func return now? (y or n) y
17057 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17058 43 printf ("result=%lld\n", func ());
17062 However, if the selected stack frame does not have a debug info, e.g., if the
17063 function was compiled without debug info, @value{GDBN} has to find out the type
17064 to return from user. Specifying a different type by mistake may set the value
17065 in different inferior registers than the caller code expects. For example,
17066 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17067 of a @code{long long int} result for a debug info less function (on 32-bit
17068 architectures). Therefore the user is required to specify the return type by
17069 an appropriate cast explicitly:
17072 Breakpoint 2, 0x0040050b in func ()
17073 (@value{GDBP}) return -1
17074 Return value type not available for selected stack frame.
17075 Please use an explicit cast of the value to return.
17076 (@value{GDBP}) return (long long int) -1
17077 Make selected stack frame return now? (y or n) y
17078 #0 0x00400526 in main ()
17083 @section Calling Program Functions
17086 @cindex calling functions
17087 @cindex inferior functions, calling
17088 @item print @var{expr}
17089 Evaluate the expression @var{expr} and display the resulting value.
17090 The expression may include calls to functions in the program being
17094 @item call @var{expr}
17095 Evaluate the expression @var{expr} without displaying @code{void}
17098 You can use this variant of the @code{print} command if you want to
17099 execute a function from your program that does not return anything
17100 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17101 with @code{void} returned values that @value{GDBN} will otherwise
17102 print. If the result is not void, it is printed and saved in the
17106 It is possible for the function you call via the @code{print} or
17107 @code{call} command to generate a signal (e.g., if there's a bug in
17108 the function, or if you passed it incorrect arguments). What happens
17109 in that case is controlled by the @code{set unwindonsignal} command.
17111 Similarly, with a C@t{++} program it is possible for the function you
17112 call via the @code{print} or @code{call} command to generate an
17113 exception that is not handled due to the constraints of the dummy
17114 frame. In this case, any exception that is raised in the frame, but has
17115 an out-of-frame exception handler will not be found. GDB builds a
17116 dummy-frame for the inferior function call, and the unwinder cannot
17117 seek for exception handlers outside of this dummy-frame. What happens
17118 in that case is controlled by the
17119 @code{set unwind-on-terminating-exception} command.
17122 @item set unwindonsignal
17123 @kindex set unwindonsignal
17124 @cindex unwind stack in called functions
17125 @cindex call dummy stack unwinding
17126 Set unwinding of the stack if a signal is received while in a function
17127 that @value{GDBN} called in the program being debugged. If set to on,
17128 @value{GDBN} unwinds the stack it created for the call and restores
17129 the context to what it was before the call. If set to off (the
17130 default), @value{GDBN} stops in the frame where the signal was
17133 @item show unwindonsignal
17134 @kindex show unwindonsignal
17135 Show the current setting of stack unwinding in the functions called by
17138 @item set unwind-on-terminating-exception
17139 @kindex set unwind-on-terminating-exception
17140 @cindex unwind stack in called functions with unhandled exceptions
17141 @cindex call dummy stack unwinding on unhandled exception.
17142 Set unwinding of the stack if a C@t{++} exception is raised, but left
17143 unhandled while in a function that @value{GDBN} called in the program being
17144 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17145 it created for the call and restores the context to what it was before
17146 the call. If set to off, @value{GDBN} the exception is delivered to
17147 the default C@t{++} exception handler and the inferior terminated.
17149 @item show unwind-on-terminating-exception
17150 @kindex show unwind-on-terminating-exception
17151 Show the current setting of stack unwinding in the functions called by
17156 @cindex weak alias functions
17157 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17158 for another function. In such case, @value{GDBN} might not pick up
17159 the type information, including the types of the function arguments,
17160 which causes @value{GDBN} to call the inferior function incorrectly.
17161 As a result, the called function will function erroneously and may
17162 even crash. A solution to that is to use the name of the aliased
17166 @section Patching Programs
17168 @cindex patching binaries
17169 @cindex writing into executables
17170 @cindex writing into corefiles
17172 By default, @value{GDBN} opens the file containing your program's
17173 executable code (or the corefile) read-only. This prevents accidental
17174 alterations to machine code; but it also prevents you from intentionally
17175 patching your program's binary.
17177 If you'd like to be able to patch the binary, you can specify that
17178 explicitly with the @code{set write} command. For example, you might
17179 want to turn on internal debugging flags, or even to make emergency
17185 @itemx set write off
17186 If you specify @samp{set write on}, @value{GDBN} opens executable and
17187 core files for both reading and writing; if you specify @kbd{set write
17188 off} (the default), @value{GDBN} opens them read-only.
17190 If you have already loaded a file, you must load it again (using the
17191 @code{exec-file} or @code{core-file} command) after changing @code{set
17192 write}, for your new setting to take effect.
17196 Display whether executable files and core files are opened for writing
17197 as well as reading.
17200 @node Compiling and Injecting Code
17201 @section Compiling and injecting code in @value{GDBN}
17202 @cindex injecting code
17203 @cindex writing into executables
17204 @cindex compiling code
17206 @value{GDBN} supports on-demand compilation and code injection into
17207 programs running under @value{GDBN}. GCC 5.0 or higher built with
17208 @file{libcc1.so} must be installed for this functionality to be enabled.
17209 This functionality is implemented with the following commands.
17212 @kindex compile code
17213 @item compile code @var{source-code}
17214 @itemx compile code -raw @var{--} @var{source-code}
17215 Compile @var{source-code} with the compiler language found as the current
17216 language in @value{GDBN} (@pxref{Languages}). If compilation and
17217 injection is not supported with the current language specified in
17218 @value{GDBN}, or the compiler does not support this feature, an error
17219 message will be printed. If @var{source-code} compiles and links
17220 successfully, @value{GDBN} will load the object-code emitted,
17221 and execute it within the context of the currently selected inferior.
17222 It is important to note that the compiled code is executed immediately.
17223 After execution, the compiled code is removed from @value{GDBN} and any
17224 new types or variables you have defined will be deleted.
17226 The command allows you to specify @var{source-code} in two ways.
17227 The simplest method is to provide a single line of code to the command.
17231 compile code printf ("hello world\n");
17234 If you specify options on the command line as well as source code, they
17235 may conflict. The @samp{--} delimiter can be used to separate options
17236 from actual source code. E.g.:
17239 compile code -r -- printf ("hello world\n");
17242 Alternatively you can enter source code as multiple lines of text. To
17243 enter this mode, invoke the @samp{compile code} command without any text
17244 following the command. This will start the multiple-line editor and
17245 allow you to type as many lines of source code as required. When you
17246 have completed typing, enter @samp{end} on its own line to exit the
17251 >printf ("hello\n");
17252 >printf ("world\n");
17256 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17257 provided @var{source-code} in a callable scope. In this case, you must
17258 specify the entry point of the code by defining a function named
17259 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17260 inferior. Using @samp{-raw} option may be needed for example when
17261 @var{source-code} requires @samp{#include} lines which may conflict with
17262 inferior symbols otherwise.
17264 @kindex compile file
17265 @item compile file @var{filename}
17266 @itemx compile file -raw @var{filename}
17267 Like @code{compile code}, but take the source code from @var{filename}.
17270 compile file /home/user/example.c
17275 @item compile print @var{expr}
17276 @itemx compile print /@var{f} @var{expr}
17277 Compile and execute @var{expr} with the compiler language found as the
17278 current language in @value{GDBN} (@pxref{Languages}). By default the
17279 value of @var{expr} is printed in a format appropriate to its data type;
17280 you can choose a different format by specifying @samp{/@var{f}}, where
17281 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17284 @item compile print
17285 @itemx compile print /@var{f}
17286 @cindex reprint the last value
17287 Alternatively you can enter the expression (source code producing it) as
17288 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17289 command without any text following the command. This will start the
17290 multiple-line editor.
17294 The process of compiling and injecting the code can be inspected using:
17297 @anchor{set debug compile}
17298 @item set debug compile
17299 @cindex compile command debugging info
17300 Turns on or off display of @value{GDBN} process of compiling and
17301 injecting the code. The default is off.
17303 @item show debug compile
17304 Displays the current state of displaying @value{GDBN} process of
17305 compiling and injecting the code.
17308 @subsection Compilation options for the @code{compile} command
17310 @value{GDBN} needs to specify the right compilation options for the code
17311 to be injected, in part to make its ABI compatible with the inferior
17312 and in part to make the injected code compatible with @value{GDBN}'s
17316 The options used, in increasing precedence:
17319 @item target architecture and OS options (@code{gdbarch})
17320 These options depend on target processor type and target operating
17321 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17322 (@code{-m64}) compilation option.
17324 @item compilation options recorded in the target
17325 @value{NGCC} (since version 4.7) stores the options used for compilation
17326 into @code{DW_AT_producer} part of DWARF debugging information according
17327 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17328 explicitly specify @code{-g} during inferior compilation otherwise
17329 @value{NGCC} produces no DWARF. This feature is only relevant for
17330 platforms where @code{-g} produces DWARF by default, otherwise one may
17331 try to enforce DWARF by using @code{-gdwarf-4}.
17333 @item compilation options set by @code{set compile-args}
17337 You can override compilation options using the following command:
17340 @item set compile-args
17341 @cindex compile command options override
17342 Set compilation options used for compiling and injecting code with the
17343 @code{compile} commands. These options override any conflicting ones
17344 from the target architecture and/or options stored during inferior
17347 @item show compile-args
17348 Displays the current state of compilation options override.
17349 This does not show all the options actually used during compilation,
17350 use @ref{set debug compile} for that.
17353 @subsection Caveats when using the @code{compile} command
17355 There are a few caveats to keep in mind when using the @code{compile}
17356 command. As the caveats are different per language, the table below
17357 highlights specific issues on a per language basis.
17360 @item C code examples and caveats
17361 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17362 attempt to compile the source code with a @samp{C} compiler. The source
17363 code provided to the @code{compile} command will have much the same
17364 access to variables and types as it normally would if it were part of
17365 the program currently being debugged in @value{GDBN}.
17367 Below is a sample program that forms the basis of the examples that
17368 follow. This program has been compiled and loaded into @value{GDBN},
17369 much like any other normal debugging session.
17372 void function1 (void)
17375 printf ("function 1\n");
17378 void function2 (void)
17393 For the purposes of the examples in this section, the program above has
17394 been compiled, loaded into @value{GDBN}, stopped at the function
17395 @code{main}, and @value{GDBN} is awaiting input from the user.
17397 To access variables and types for any program in @value{GDBN}, the
17398 program must be compiled and packaged with debug information. The
17399 @code{compile} command is not an exception to this rule. Without debug
17400 information, you can still use the @code{compile} command, but you will
17401 be very limited in what variables and types you can access.
17403 So with that in mind, the example above has been compiled with debug
17404 information enabled. The @code{compile} command will have access to
17405 all variables and types (except those that may have been optimized
17406 out). Currently, as @value{GDBN} has stopped the program in the
17407 @code{main} function, the @code{compile} command would have access to
17408 the variable @code{k}. You could invoke the @code{compile} command
17409 and type some source code to set the value of @code{k}. You can also
17410 read it, or do anything with that variable you would normally do in
17411 @code{C}. Be aware that changes to inferior variables in the
17412 @code{compile} command are persistent. In the following example:
17415 compile code k = 3;
17419 the variable @code{k} is now 3. It will retain that value until
17420 something else in the example program changes it, or another
17421 @code{compile} command changes it.
17423 Normal scope and access rules apply to source code compiled and
17424 injected by the @code{compile} command. In the example, the variables
17425 @code{j} and @code{k} are not accessible yet, because the program is
17426 currently stopped in the @code{main} function, where these variables
17427 are not in scope. Therefore, the following command
17430 compile code j = 3;
17434 will result in a compilation error message.
17436 Once the program is continued, execution will bring these variables in
17437 scope, and they will become accessible; then the code you specify via
17438 the @code{compile} command will be able to access them.
17440 You can create variables and types with the @code{compile} command as
17441 part of your source code. Variables and types that are created as part
17442 of the @code{compile} command are not visible to the rest of the program for
17443 the duration of its run. This example is valid:
17446 compile code int ff = 5; printf ("ff is %d\n", ff);
17449 However, if you were to type the following into @value{GDBN} after that
17450 command has completed:
17453 compile code printf ("ff is %d\n'', ff);
17457 a compiler error would be raised as the variable @code{ff} no longer
17458 exists. Object code generated and injected by the @code{compile}
17459 command is removed when its execution ends. Caution is advised
17460 when assigning to program variables values of variables created by the
17461 code submitted to the @code{compile} command. This example is valid:
17464 compile code int ff = 5; k = ff;
17467 The value of the variable @code{ff} is assigned to @code{k}. The variable
17468 @code{k} does not require the existence of @code{ff} to maintain the value
17469 it has been assigned. However, pointers require particular care in
17470 assignment. If the source code compiled with the @code{compile} command
17471 changed the address of a pointer in the example program, perhaps to a
17472 variable created in the @code{compile} command, that pointer would point
17473 to an invalid location when the command exits. The following example
17474 would likely cause issues with your debugged program:
17477 compile code int ff = 5; p = &ff;
17480 In this example, @code{p} would point to @code{ff} when the
17481 @code{compile} command is executing the source code provided to it.
17482 However, as variables in the (example) program persist with their
17483 assigned values, the variable @code{p} would point to an invalid
17484 location when the command exists. A general rule should be followed
17485 in that you should either assign @code{NULL} to any assigned pointers,
17486 or restore a valid location to the pointer before the command exits.
17488 Similar caution must be exercised with any structs, unions, and typedefs
17489 defined in @code{compile} command. Types defined in the @code{compile}
17490 command will no longer be available in the next @code{compile} command.
17491 Therefore, if you cast a variable to a type defined in the
17492 @code{compile} command, care must be taken to ensure that any future
17493 need to resolve the type can be achieved.
17496 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17497 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17498 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17499 Compilation failed.
17500 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17504 Variables that have been optimized away by the compiler are not
17505 accessible to the code submitted to the @code{compile} command.
17506 Access to those variables will generate a compiler error which @value{GDBN}
17507 will print to the console.
17510 @subsection Compiler search for the @code{compile} command
17512 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17513 may not be obvious for remote targets of different architecture than where
17514 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17515 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17516 command @code{set environment}). @xref{Environment}. @code{PATH} on
17517 @value{GDBN} host is searched for @value{NGCC} binary matching the
17518 target architecture and operating system.
17520 Specifically @code{PATH} is searched for binaries matching regular expression
17521 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17522 debugged. @var{arch} is processor name --- multiarch is supported, so for
17523 example both @code{i386} and @code{x86_64} targets look for pattern
17524 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17525 for pattern @code{s390x?}. @var{os} is currently supported only for
17526 pattern @code{linux(-gnu)?}.
17529 @chapter @value{GDBN} Files
17531 @value{GDBN} needs to know the file name of the program to be debugged,
17532 both in order to read its symbol table and in order to start your
17533 program. To debug a core dump of a previous run, you must also tell
17534 @value{GDBN} the name of the core dump file.
17537 * Files:: Commands to specify files
17538 * Separate Debug Files:: Debugging information in separate files
17539 * MiniDebugInfo:: Debugging information in a special section
17540 * Index Files:: Index files speed up GDB
17541 * Symbol Errors:: Errors reading symbol files
17542 * Data Files:: GDB data files
17546 @section Commands to Specify Files
17548 @cindex symbol table
17549 @cindex core dump file
17551 You may want to specify executable and core dump file names. The usual
17552 way to do this is at start-up time, using the arguments to
17553 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17554 Out of @value{GDBN}}).
17556 Occasionally it is necessary to change to a different file during a
17557 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17558 specify a file you want to use. Or you are debugging a remote target
17559 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17560 Program}). In these situations the @value{GDBN} commands to specify
17561 new files are useful.
17564 @cindex executable file
17566 @item file @var{filename}
17567 Use @var{filename} as the program to be debugged. It is read for its
17568 symbols and for the contents of pure memory. It is also the program
17569 executed when you use the @code{run} command. If you do not specify a
17570 directory and the file is not found in the @value{GDBN} working directory,
17571 @value{GDBN} uses the environment variable @code{PATH} as a list of
17572 directories to search, just as the shell does when looking for a program
17573 to run. You can change the value of this variable, for both @value{GDBN}
17574 and your program, using the @code{path} command.
17576 @cindex unlinked object files
17577 @cindex patching object files
17578 You can load unlinked object @file{.o} files into @value{GDBN} using
17579 the @code{file} command. You will not be able to ``run'' an object
17580 file, but you can disassemble functions and inspect variables. Also,
17581 if the underlying BFD functionality supports it, you could use
17582 @kbd{gdb -write} to patch object files using this technique. Note
17583 that @value{GDBN} can neither interpret nor modify relocations in this
17584 case, so branches and some initialized variables will appear to go to
17585 the wrong place. But this feature is still handy from time to time.
17588 @code{file} with no argument makes @value{GDBN} discard any information it
17589 has on both executable file and the symbol table.
17592 @item exec-file @r{[} @var{filename} @r{]}
17593 Specify that the program to be run (but not the symbol table) is found
17594 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17595 if necessary to locate your program. Omitting @var{filename} means to
17596 discard information on the executable file.
17598 @kindex symbol-file
17599 @item symbol-file @r{[} @var{filename} @r{]}
17600 Read symbol table information from file @var{filename}. @code{PATH} is
17601 searched when necessary. Use the @code{file} command to get both symbol
17602 table and program to run from the same file.
17604 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17605 program's symbol table.
17607 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17608 some breakpoints and auto-display expressions. This is because they may
17609 contain pointers to the internal data recording symbols and data types,
17610 which are part of the old symbol table data being discarded inside
17613 @code{symbol-file} does not repeat if you press @key{RET} again after
17616 When @value{GDBN} is configured for a particular environment, it
17617 understands debugging information in whatever format is the standard
17618 generated for that environment; you may use either a @sc{gnu} compiler, or
17619 other compilers that adhere to the local conventions.
17620 Best results are usually obtained from @sc{gnu} compilers; for example,
17621 using @code{@value{NGCC}} you can generate debugging information for
17624 For most kinds of object files, with the exception of old SVR3 systems
17625 using COFF, the @code{symbol-file} command does not normally read the
17626 symbol table in full right away. Instead, it scans the symbol table
17627 quickly to find which source files and which symbols are present. The
17628 details are read later, one source file at a time, as they are needed.
17630 The purpose of this two-stage reading strategy is to make @value{GDBN}
17631 start up faster. For the most part, it is invisible except for
17632 occasional pauses while the symbol table details for a particular source
17633 file are being read. (The @code{set verbose} command can turn these
17634 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17635 Warnings and Messages}.)
17637 We have not implemented the two-stage strategy for COFF yet. When the
17638 symbol table is stored in COFF format, @code{symbol-file} reads the
17639 symbol table data in full right away. Note that ``stabs-in-COFF''
17640 still does the two-stage strategy, since the debug info is actually
17644 @cindex reading symbols immediately
17645 @cindex symbols, reading immediately
17646 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17647 @itemx file @r{[} -readnow @r{]} @var{filename}
17648 You can override the @value{GDBN} two-stage strategy for reading symbol
17649 tables by using the @samp{-readnow} option with any of the commands that
17650 load symbol table information, if you want to be sure @value{GDBN} has the
17651 entire symbol table available.
17653 @c FIXME: for now no mention of directories, since this seems to be in
17654 @c flux. 13mar1992 status is that in theory GDB would look either in
17655 @c current dir or in same dir as myprog; but issues like competing
17656 @c GDB's, or clutter in system dirs, mean that in practice right now
17657 @c only current dir is used. FFish says maybe a special GDB hierarchy
17658 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17662 @item core-file @r{[}@var{filename}@r{]}
17664 Specify the whereabouts of a core dump file to be used as the ``contents
17665 of memory''. Traditionally, core files contain only some parts of the
17666 address space of the process that generated them; @value{GDBN} can access the
17667 executable file itself for other parts.
17669 @code{core-file} with no argument specifies that no core file is
17672 Note that the core file is ignored when your program is actually running
17673 under @value{GDBN}. So, if you have been running your program and you
17674 wish to debug a core file instead, you must kill the subprocess in which
17675 the program is running. To do this, use the @code{kill} command
17676 (@pxref{Kill Process, ,Killing the Child Process}).
17678 @kindex add-symbol-file
17679 @cindex dynamic linking
17680 @item add-symbol-file @var{filename} @var{address}
17681 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17682 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17683 The @code{add-symbol-file} command reads additional symbol table
17684 information from the file @var{filename}. You would use this command
17685 when @var{filename} has been dynamically loaded (by some other means)
17686 into the program that is running. The @var{address} should give the memory
17687 address at which the file has been loaded; @value{GDBN} cannot figure
17688 this out for itself. You can additionally specify an arbitrary number
17689 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17690 section name and base address for that section. You can specify any
17691 @var{address} as an expression.
17693 The symbol table of the file @var{filename} is added to the symbol table
17694 originally read with the @code{symbol-file} command. You can use the
17695 @code{add-symbol-file} command any number of times; the new symbol data
17696 thus read is kept in addition to the old.
17698 Changes can be reverted using the command @code{remove-symbol-file}.
17700 @cindex relocatable object files, reading symbols from
17701 @cindex object files, relocatable, reading symbols from
17702 @cindex reading symbols from relocatable object files
17703 @cindex symbols, reading from relocatable object files
17704 @cindex @file{.o} files, reading symbols from
17705 Although @var{filename} is typically a shared library file, an
17706 executable file, or some other object file which has been fully
17707 relocated for loading into a process, you can also load symbolic
17708 information from relocatable @file{.o} files, as long as:
17712 the file's symbolic information refers only to linker symbols defined in
17713 that file, not to symbols defined by other object files,
17715 every section the file's symbolic information refers to has actually
17716 been loaded into the inferior, as it appears in the file, and
17718 you can determine the address at which every section was loaded, and
17719 provide these to the @code{add-symbol-file} command.
17723 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17724 relocatable files into an already running program; such systems
17725 typically make the requirements above easy to meet. However, it's
17726 important to recognize that many native systems use complex link
17727 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17728 assembly, for example) that make the requirements difficult to meet. In
17729 general, one cannot assume that using @code{add-symbol-file} to read a
17730 relocatable object file's symbolic information will have the same effect
17731 as linking the relocatable object file into the program in the normal
17734 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17736 @kindex remove-symbol-file
17737 @item remove-symbol-file @var{filename}
17738 @item remove-symbol-file -a @var{address}
17739 Remove a symbol file added via the @code{add-symbol-file} command. The
17740 file to remove can be identified by its @var{filename} or by an @var{address}
17741 that lies within the boundaries of this symbol file in memory. Example:
17744 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17745 add symbol table from file "/home/user/gdb/mylib.so" at
17746 .text_addr = 0x7ffff7ff9480
17748 Reading symbols from /home/user/gdb/mylib.so...done.
17749 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17750 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17755 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17757 @kindex add-symbol-file-from-memory
17758 @cindex @code{syscall DSO}
17759 @cindex load symbols from memory
17760 @item add-symbol-file-from-memory @var{address}
17761 Load symbols from the given @var{address} in a dynamically loaded
17762 object file whose image is mapped directly into the inferior's memory.
17763 For example, the Linux kernel maps a @code{syscall DSO} into each
17764 process's address space; this DSO provides kernel-specific code for
17765 some system calls. The argument can be any expression whose
17766 evaluation yields the address of the file's shared object file header.
17767 For this command to work, you must have used @code{symbol-file} or
17768 @code{exec-file} commands in advance.
17771 @item section @var{section} @var{addr}
17772 The @code{section} command changes the base address of the named
17773 @var{section} of the exec file to @var{addr}. This can be used if the
17774 exec file does not contain section addresses, (such as in the
17775 @code{a.out} format), or when the addresses specified in the file
17776 itself are wrong. Each section must be changed separately. The
17777 @code{info files} command, described below, lists all the sections and
17781 @kindex info target
17784 @code{info files} and @code{info target} are synonymous; both print the
17785 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17786 including the names of the executable and core dump files currently in
17787 use by @value{GDBN}, and the files from which symbols were loaded. The
17788 command @code{help target} lists all possible targets rather than
17791 @kindex maint info sections
17792 @item maint info sections
17793 Another command that can give you extra information about program sections
17794 is @code{maint info sections}. In addition to the section information
17795 displayed by @code{info files}, this command displays the flags and file
17796 offset of each section in the executable and core dump files. In addition,
17797 @code{maint info sections} provides the following command options (which
17798 may be arbitrarily combined):
17802 Display sections for all loaded object files, including shared libraries.
17803 @item @var{sections}
17804 Display info only for named @var{sections}.
17805 @item @var{section-flags}
17806 Display info only for sections for which @var{section-flags} are true.
17807 The section flags that @value{GDBN} currently knows about are:
17810 Section will have space allocated in the process when loaded.
17811 Set for all sections except those containing debug information.
17813 Section will be loaded from the file into the child process memory.
17814 Set for pre-initialized code and data, clear for @code{.bss} sections.
17816 Section needs to be relocated before loading.
17818 Section cannot be modified by the child process.
17820 Section contains executable code only.
17822 Section contains data only (no executable code).
17824 Section will reside in ROM.
17826 Section contains data for constructor/destructor lists.
17828 Section is not empty.
17830 An instruction to the linker to not output the section.
17831 @item COFF_SHARED_LIBRARY
17832 A notification to the linker that the section contains
17833 COFF shared library information.
17835 Section contains common symbols.
17838 @kindex set trust-readonly-sections
17839 @cindex read-only sections
17840 @item set trust-readonly-sections on
17841 Tell @value{GDBN} that readonly sections in your object file
17842 really are read-only (i.e.@: that their contents will not change).
17843 In that case, @value{GDBN} can fetch values from these sections
17844 out of the object file, rather than from the target program.
17845 For some targets (notably embedded ones), this can be a significant
17846 enhancement to debugging performance.
17848 The default is off.
17850 @item set trust-readonly-sections off
17851 Tell @value{GDBN} not to trust readonly sections. This means that
17852 the contents of the section might change while the program is running,
17853 and must therefore be fetched from the target when needed.
17855 @item show trust-readonly-sections
17856 Show the current setting of trusting readonly sections.
17859 All file-specifying commands allow both absolute and relative file names
17860 as arguments. @value{GDBN} always converts the file name to an absolute file
17861 name and remembers it that way.
17863 @cindex shared libraries
17864 @anchor{Shared Libraries}
17865 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17866 and IBM RS/6000 AIX shared libraries.
17868 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17869 shared libraries. @xref{Expat}.
17871 @value{GDBN} automatically loads symbol definitions from shared libraries
17872 when you use the @code{run} command, or when you examine a core file.
17873 (Before you issue the @code{run} command, @value{GDBN} does not understand
17874 references to a function in a shared library, however---unless you are
17875 debugging a core file).
17877 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17878 automatically loads the symbols at the time of the @code{shl_load} call.
17880 @c FIXME: some @value{GDBN} release may permit some refs to undef
17881 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17882 @c FIXME...lib; check this from time to time when updating manual
17884 There are times, however, when you may wish to not automatically load
17885 symbol definitions from shared libraries, such as when they are
17886 particularly large or there are many of them.
17888 To control the automatic loading of shared library symbols, use the
17892 @kindex set auto-solib-add
17893 @item set auto-solib-add @var{mode}
17894 If @var{mode} is @code{on}, symbols from all shared object libraries
17895 will be loaded automatically when the inferior begins execution, you
17896 attach to an independently started inferior, or when the dynamic linker
17897 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17898 is @code{off}, symbols must be loaded manually, using the
17899 @code{sharedlibrary} command. The default value is @code{on}.
17901 @cindex memory used for symbol tables
17902 If your program uses lots of shared libraries with debug info that
17903 takes large amounts of memory, you can decrease the @value{GDBN}
17904 memory footprint by preventing it from automatically loading the
17905 symbols from shared libraries. To that end, type @kbd{set
17906 auto-solib-add off} before running the inferior, then load each
17907 library whose debug symbols you do need with @kbd{sharedlibrary
17908 @var{regexp}}, where @var{regexp} is a regular expression that matches
17909 the libraries whose symbols you want to be loaded.
17911 @kindex show auto-solib-add
17912 @item show auto-solib-add
17913 Display the current autoloading mode.
17916 @cindex load shared library
17917 To explicitly load shared library symbols, use the @code{sharedlibrary}
17921 @kindex info sharedlibrary
17923 @item info share @var{regex}
17924 @itemx info sharedlibrary @var{regex}
17925 Print the names of the shared libraries which are currently loaded
17926 that match @var{regex}. If @var{regex} is omitted then print
17927 all shared libraries that are loaded.
17930 @item info dll @var{regex}
17931 This is an alias of @code{info sharedlibrary}.
17933 @kindex sharedlibrary
17935 @item sharedlibrary @var{regex}
17936 @itemx share @var{regex}
17937 Load shared object library symbols for files matching a
17938 Unix regular expression.
17939 As with files loaded automatically, it only loads shared libraries
17940 required by your program for a core file or after typing @code{run}. If
17941 @var{regex} is omitted all shared libraries required by your program are
17944 @item nosharedlibrary
17945 @kindex nosharedlibrary
17946 @cindex unload symbols from shared libraries
17947 Unload all shared object library symbols. This discards all symbols
17948 that have been loaded from all shared libraries. Symbols from shared
17949 libraries that were loaded by explicit user requests are not
17953 Sometimes you may wish that @value{GDBN} stops and gives you control
17954 when any of shared library events happen. The best way to do this is
17955 to use @code{catch load} and @code{catch unload} (@pxref{Set
17958 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17959 command for this. This command exists for historical reasons. It is
17960 less useful than setting a catchpoint, because it does not allow for
17961 conditions or commands as a catchpoint does.
17964 @item set stop-on-solib-events
17965 @kindex set stop-on-solib-events
17966 This command controls whether @value{GDBN} should give you control
17967 when the dynamic linker notifies it about some shared library event.
17968 The most common event of interest is loading or unloading of a new
17971 @item show stop-on-solib-events
17972 @kindex show stop-on-solib-events
17973 Show whether @value{GDBN} stops and gives you control when shared
17974 library events happen.
17977 Shared libraries are also supported in many cross or remote debugging
17978 configurations. @value{GDBN} needs to have access to the target's libraries;
17979 this can be accomplished either by providing copies of the libraries
17980 on the host system, or by asking @value{GDBN} to automatically retrieve the
17981 libraries from the target. If copies of the target libraries are
17982 provided, they need to be the same as the target libraries, although the
17983 copies on the target can be stripped as long as the copies on the host are
17986 @cindex where to look for shared libraries
17987 For remote debugging, you need to tell @value{GDBN} where the target
17988 libraries are, so that it can load the correct copies---otherwise, it
17989 may try to load the host's libraries. @value{GDBN} has two variables
17990 to specify the search directories for target libraries.
17993 @cindex prefix for executable and shared library file names
17994 @cindex system root, alternate
17995 @kindex set solib-absolute-prefix
17996 @kindex set sysroot
17997 @item set sysroot @var{path}
17998 Use @var{path} as the system root for the program being debugged. Any
17999 absolute shared library paths will be prefixed with @var{path}; many
18000 runtime loaders store the absolute paths to the shared library in the
18001 target program's memory. When starting processes remotely, and when
18002 attaching to already-running processes (local or remote), their
18003 executable filenames will be prefixed with @var{path} if reported to
18004 @value{GDBN} as absolute by the operating system. If you use
18005 @code{set sysroot} to find executables and shared libraries, they need
18006 to be laid out in the same way that they are on the target, with
18007 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18010 If @var{path} starts with the sequence @file{target:} and the target
18011 system is remote then @value{GDBN} will retrieve the target binaries
18012 from the remote system. This is only supported when using a remote
18013 target that supports the @code{remote get} command (@pxref{File
18014 Transfer,,Sending files to a remote system}). The part of @var{path}
18015 following the initial @file{target:} (if present) is used as system
18016 root prefix on the remote file system. If @var{path} starts with the
18017 sequence @file{remote:} this is converted to the sequence
18018 @file{target:} by @code{set sysroot}@footnote{Historically the
18019 functionality to retrieve binaries from the remote system was
18020 provided by prefixing @var{path} with @file{remote:}}. If you want
18021 to specify a local system root using a directory that happens to be
18022 named @file{target:} or @file{remote:}, you need to use some
18023 equivalent variant of the name like @file{./target:}.
18025 For targets with an MS-DOS based filesystem, such as MS-Windows and
18026 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18027 absolute file name with @var{path}. But first, on Unix hosts,
18028 @value{GDBN} converts all backslash directory separators into forward
18029 slashes, because the backslash is not a directory separator on Unix:
18032 c:\foo\bar.dll @result{} c:/foo/bar.dll
18035 Then, @value{GDBN} attempts prefixing the target file name with
18036 @var{path}, and looks for the resulting file name in the host file
18040 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18043 If that does not find the binary, @value{GDBN} tries removing
18044 the @samp{:} character from the drive spec, both for convenience, and,
18045 for the case of the host file system not supporting file names with
18049 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18052 This makes it possible to have a system root that mirrors a target
18053 with more than one drive. E.g., you may want to setup your local
18054 copies of the target system shared libraries like so (note @samp{c} vs
18058 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18059 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18060 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18064 and point the system root at @file{/path/to/sysroot}, so that
18065 @value{GDBN} can find the correct copies of both
18066 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18068 If that still does not find the binary, @value{GDBN} tries
18069 removing the whole drive spec from the target file name:
18072 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18075 This last lookup makes it possible to not care about the drive name,
18076 if you don't want or need to.
18078 The @code{set solib-absolute-prefix} command is an alias for @code{set
18081 @cindex default system root
18082 @cindex @samp{--with-sysroot}
18083 You can set the default system root by using the configure-time
18084 @samp{--with-sysroot} option. If the system root is inside
18085 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18086 @samp{--exec-prefix}), then the default system root will be updated
18087 automatically if the installed @value{GDBN} is moved to a new
18090 @kindex show sysroot
18092 Display the current executable and shared library prefix.
18094 @kindex set solib-search-path
18095 @item set solib-search-path @var{path}
18096 If this variable is set, @var{path} is a colon-separated list of
18097 directories to search for shared libraries. @samp{solib-search-path}
18098 is used after @samp{sysroot} fails to locate the library, or if the
18099 path to the library is relative instead of absolute. If you want to
18100 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18101 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18102 finding your host's libraries. @samp{sysroot} is preferred; setting
18103 it to a nonexistent directory may interfere with automatic loading
18104 of shared library symbols.
18106 @kindex show solib-search-path
18107 @item show solib-search-path
18108 Display the current shared library search path.
18110 @cindex DOS file-name semantics of file names.
18111 @kindex set target-file-system-kind (unix|dos-based|auto)
18112 @kindex show target-file-system-kind
18113 @item set target-file-system-kind @var{kind}
18114 Set assumed file system kind for target reported file names.
18116 Shared library file names as reported by the target system may not
18117 make sense as is on the system @value{GDBN} is running on. For
18118 example, when remote debugging a target that has MS-DOS based file
18119 system semantics, from a Unix host, the target may be reporting to
18120 @value{GDBN} a list of loaded shared libraries with file names such as
18121 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18122 drive letters, so the @samp{c:\} prefix is not normally understood as
18123 indicating an absolute file name, and neither is the backslash
18124 normally considered a directory separator character. In that case,
18125 the native file system would interpret this whole absolute file name
18126 as a relative file name with no directory components. This would make
18127 it impossible to point @value{GDBN} at a copy of the remote target's
18128 shared libraries on the host using @code{set sysroot}, and impractical
18129 with @code{set solib-search-path}. Setting
18130 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18131 to interpret such file names similarly to how the target would, and to
18132 map them to file names valid on @value{GDBN}'s native file system
18133 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18134 to one of the supported file system kinds. In that case, @value{GDBN}
18135 tries to determine the appropriate file system variant based on the
18136 current target's operating system (@pxref{ABI, ,Configuring the
18137 Current ABI}). The supported file system settings are:
18141 Instruct @value{GDBN} to assume the target file system is of Unix
18142 kind. Only file names starting the forward slash (@samp{/}) character
18143 are considered absolute, and the directory separator character is also
18147 Instruct @value{GDBN} to assume the target file system is DOS based.
18148 File names starting with either a forward slash, or a drive letter
18149 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18150 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18151 considered directory separators.
18154 Instruct @value{GDBN} to use the file system kind associated with the
18155 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18156 This is the default.
18160 @cindex file name canonicalization
18161 @cindex base name differences
18162 When processing file names provided by the user, @value{GDBN}
18163 frequently needs to compare them to the file names recorded in the
18164 program's debug info. Normally, @value{GDBN} compares just the
18165 @dfn{base names} of the files as strings, which is reasonably fast
18166 even for very large programs. (The base name of a file is the last
18167 portion of its name, after stripping all the leading directories.)
18168 This shortcut in comparison is based upon the assumption that files
18169 cannot have more than one base name. This is usually true, but
18170 references to files that use symlinks or similar filesystem
18171 facilities violate that assumption. If your program records files
18172 using such facilities, or if you provide file names to @value{GDBN}
18173 using symlinks etc., you can set @code{basenames-may-differ} to
18174 @code{true} to instruct @value{GDBN} to completely canonicalize each
18175 pair of file names it needs to compare. This will make file-name
18176 comparisons accurate, but at a price of a significant slowdown.
18179 @item set basenames-may-differ
18180 @kindex set basenames-may-differ
18181 Set whether a source file may have multiple base names.
18183 @item show basenames-may-differ
18184 @kindex show basenames-may-differ
18185 Show whether a source file may have multiple base names.
18188 @node Separate Debug Files
18189 @section Debugging Information in Separate Files
18190 @cindex separate debugging information files
18191 @cindex debugging information in separate files
18192 @cindex @file{.debug} subdirectories
18193 @cindex debugging information directory, global
18194 @cindex global debugging information directories
18195 @cindex build ID, and separate debugging files
18196 @cindex @file{.build-id} directory
18198 @value{GDBN} allows you to put a program's debugging information in a
18199 file separate from the executable itself, in a way that allows
18200 @value{GDBN} to find and load the debugging information automatically.
18201 Since debugging information can be very large---sometimes larger
18202 than the executable code itself---some systems distribute debugging
18203 information for their executables in separate files, which users can
18204 install only when they need to debug a problem.
18206 @value{GDBN} supports two ways of specifying the separate debug info
18211 The executable contains a @dfn{debug link} that specifies the name of
18212 the separate debug info file. The separate debug file's name is
18213 usually @file{@var{executable}.debug}, where @var{executable} is the
18214 name of the corresponding executable file without leading directories
18215 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18216 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18217 checksum for the debug file, which @value{GDBN} uses to validate that
18218 the executable and the debug file came from the same build.
18221 The executable contains a @dfn{build ID}, a unique bit string that is
18222 also present in the corresponding debug info file. (This is supported
18223 only on some operating systems, when using the ELF or PE file formats
18224 for binary files and the @sc{gnu} Binutils.) For more details about
18225 this feature, see the description of the @option{--build-id}
18226 command-line option in @ref{Options, , Command Line Options, ld.info,
18227 The GNU Linker}. The debug info file's name is not specified
18228 explicitly by the build ID, but can be computed from the build ID, see
18232 Depending on the way the debug info file is specified, @value{GDBN}
18233 uses two different methods of looking for the debug file:
18237 For the ``debug link'' method, @value{GDBN} looks up the named file in
18238 the directory of the executable file, then in a subdirectory of that
18239 directory named @file{.debug}, and finally under each one of the global debug
18240 directories, in a subdirectory whose name is identical to the leading
18241 directories of the executable's absolute file name.
18244 For the ``build ID'' method, @value{GDBN} looks in the
18245 @file{.build-id} subdirectory of each one of the global debug directories for
18246 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18247 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18248 are the rest of the bit string. (Real build ID strings are 32 or more
18249 hex characters, not 10.)
18252 So, for example, suppose you ask @value{GDBN} to debug
18253 @file{/usr/bin/ls}, which has a debug link that specifies the
18254 file @file{ls.debug}, and a build ID whose value in hex is
18255 @code{abcdef1234}. If the list of the global debug directories includes
18256 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18257 debug information files, in the indicated order:
18261 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18263 @file{/usr/bin/ls.debug}
18265 @file{/usr/bin/.debug/ls.debug}
18267 @file{/usr/lib/debug/usr/bin/ls.debug}.
18270 @anchor{debug-file-directory}
18271 Global debugging info directories default to what is set by @value{GDBN}
18272 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18273 you can also set the global debugging info directories, and view the list
18274 @value{GDBN} is currently using.
18278 @kindex set debug-file-directory
18279 @item set debug-file-directory @var{directories}
18280 Set the directories which @value{GDBN} searches for separate debugging
18281 information files to @var{directory}. Multiple path components can be set
18282 concatenating them by a path separator.
18284 @kindex show debug-file-directory
18285 @item show debug-file-directory
18286 Show the directories @value{GDBN} searches for separate debugging
18291 @cindex @code{.gnu_debuglink} sections
18292 @cindex debug link sections
18293 A debug link is a special section of the executable file named
18294 @code{.gnu_debuglink}. The section must contain:
18298 A filename, with any leading directory components removed, followed by
18301 zero to three bytes of padding, as needed to reach the next four-byte
18302 boundary within the section, and
18304 a four-byte CRC checksum, stored in the same endianness used for the
18305 executable file itself. The checksum is computed on the debugging
18306 information file's full contents by the function given below, passing
18307 zero as the @var{crc} argument.
18310 Any executable file format can carry a debug link, as long as it can
18311 contain a section named @code{.gnu_debuglink} with the contents
18314 @cindex @code{.note.gnu.build-id} sections
18315 @cindex build ID sections
18316 The build ID is a special section in the executable file (and in other
18317 ELF binary files that @value{GDBN} may consider). This section is
18318 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18319 It contains unique identification for the built files---the ID remains
18320 the same across multiple builds of the same build tree. The default
18321 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18322 content for the build ID string. The same section with an identical
18323 value is present in the original built binary with symbols, in its
18324 stripped variant, and in the separate debugging information file.
18326 The debugging information file itself should be an ordinary
18327 executable, containing a full set of linker symbols, sections, and
18328 debugging information. The sections of the debugging information file
18329 should have the same names, addresses, and sizes as the original file,
18330 but they need not contain any data---much like a @code{.bss} section
18331 in an ordinary executable.
18333 The @sc{gnu} binary utilities (Binutils) package includes the
18334 @samp{objcopy} utility that can produce
18335 the separated executable / debugging information file pairs using the
18336 following commands:
18339 @kbd{objcopy --only-keep-debug foo foo.debug}
18344 These commands remove the debugging
18345 information from the executable file @file{foo} and place it in the file
18346 @file{foo.debug}. You can use the first, second or both methods to link the
18351 The debug link method needs the following additional command to also leave
18352 behind a debug link in @file{foo}:
18355 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18358 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18359 a version of the @code{strip} command such that the command @kbd{strip foo -f
18360 foo.debug} has the same functionality as the two @code{objcopy} commands and
18361 the @code{ln -s} command above, together.
18364 Build ID gets embedded into the main executable using @code{ld --build-id} or
18365 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18366 compatibility fixes for debug files separation are present in @sc{gnu} binary
18367 utilities (Binutils) package since version 2.18.
18372 @cindex CRC algorithm definition
18373 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18374 IEEE 802.3 using the polynomial:
18376 @c TexInfo requires naked braces for multi-digit exponents for Tex
18377 @c output, but this causes HTML output to barf. HTML has to be set using
18378 @c raw commands. So we end up having to specify this equation in 2
18383 <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>
18384 + <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
18390 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18391 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18395 The function is computed byte at a time, taking the least
18396 significant bit of each byte first. The initial pattern
18397 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18398 the final result is inverted to ensure trailing zeros also affect the
18401 @emph{Note:} This is the same CRC polynomial as used in handling the
18402 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18403 However in the case of the Remote Serial Protocol, the CRC is computed
18404 @emph{most} significant bit first, and the result is not inverted, so
18405 trailing zeros have no effect on the CRC value.
18407 To complete the description, we show below the code of the function
18408 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18409 initially supplied @code{crc} argument means that an initial call to
18410 this function passing in zero will start computing the CRC using
18413 @kindex gnu_debuglink_crc32
18416 gnu_debuglink_crc32 (unsigned long crc,
18417 unsigned char *buf, size_t len)
18419 static const unsigned long crc32_table[256] =
18421 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18422 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18423 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18424 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18425 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18426 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18427 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18428 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18429 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18430 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18431 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18432 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18433 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18434 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18435 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18436 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18437 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18438 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18439 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18440 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18441 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18442 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18443 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18444 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18445 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18446 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18447 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18448 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18449 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18450 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18451 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18452 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18453 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18454 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18455 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18456 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18457 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18458 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18459 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18460 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18461 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18462 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18463 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18464 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18465 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18466 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18467 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18468 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18469 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18470 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18471 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18474 unsigned char *end;
18476 crc = ~crc & 0xffffffff;
18477 for (end = buf + len; buf < end; ++buf)
18478 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18479 return ~crc & 0xffffffff;
18484 This computation does not apply to the ``build ID'' method.
18486 @node MiniDebugInfo
18487 @section Debugging information in a special section
18488 @cindex separate debug sections
18489 @cindex @samp{.gnu_debugdata} section
18491 Some systems ship pre-built executables and libraries that have a
18492 special @samp{.gnu_debugdata} section. This feature is called
18493 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18494 is used to supply extra symbols for backtraces.
18496 The intent of this section is to provide extra minimal debugging
18497 information for use in simple backtraces. It is not intended to be a
18498 replacement for full separate debugging information (@pxref{Separate
18499 Debug Files}). The example below shows the intended use; however,
18500 @value{GDBN} does not currently put restrictions on what sort of
18501 debugging information might be included in the section.
18503 @value{GDBN} has support for this extension. If the section exists,
18504 then it is used provided that no other source of debugging information
18505 can be found, and that @value{GDBN} was configured with LZMA support.
18507 This section can be easily created using @command{objcopy} and other
18508 standard utilities:
18511 # Extract the dynamic symbols from the main binary, there is no need
18512 # to also have these in the normal symbol table.
18513 nm -D @var{binary} --format=posix --defined-only \
18514 | awk '@{ print $1 @}' | sort > dynsyms
18516 # Extract all the text (i.e. function) symbols from the debuginfo.
18517 # (Note that we actually also accept "D" symbols, for the benefit
18518 # of platforms like PowerPC64 that use function descriptors.)
18519 nm @var{binary} --format=posix --defined-only \
18520 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18523 # Keep all the function symbols not already in the dynamic symbol
18525 comm -13 dynsyms funcsyms > keep_symbols
18527 # Separate full debug info into debug binary.
18528 objcopy --only-keep-debug @var{binary} debug
18530 # Copy the full debuginfo, keeping only a minimal set of symbols and
18531 # removing some unnecessary sections.
18532 objcopy -S --remove-section .gdb_index --remove-section .comment \
18533 --keep-symbols=keep_symbols debug mini_debuginfo
18535 # Drop the full debug info from the original binary.
18536 strip --strip-all -R .comment @var{binary}
18538 # Inject the compressed data into the .gnu_debugdata section of the
18541 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18545 @section Index Files Speed Up @value{GDBN}
18546 @cindex index files
18547 @cindex @samp{.gdb_index} section
18549 When @value{GDBN} finds a symbol file, it scans the symbols in the
18550 file in order to construct an internal symbol table. This lets most
18551 @value{GDBN} operations work quickly---at the cost of a delay early
18552 on. For large programs, this delay can be quite lengthy, so
18553 @value{GDBN} provides a way to build an index, which speeds up
18556 The index is stored as a section in the symbol file. @value{GDBN} can
18557 write the index to a file, then you can put it into the symbol file
18558 using @command{objcopy}.
18560 To create an index file, use the @code{save gdb-index} command:
18563 @item save gdb-index @var{directory}
18564 @kindex save gdb-index
18565 Create an index file for each symbol file currently known by
18566 @value{GDBN}. Each file is named after its corresponding symbol file,
18567 with @samp{.gdb-index} appended, and is written into the given
18571 Once you have created an index file you can merge it into your symbol
18572 file, here named @file{symfile}, using @command{objcopy}:
18575 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18576 --set-section-flags .gdb_index=readonly symfile symfile
18579 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18580 sections that have been deprecated. Usually they are deprecated because
18581 they are missing a new feature or have performance issues.
18582 To tell @value{GDBN} to use a deprecated index section anyway
18583 specify @code{set use-deprecated-index-sections on}.
18584 The default is @code{off}.
18585 This can speed up startup, but may result in some functionality being lost.
18586 @xref{Index Section Format}.
18588 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18589 must be done before gdb reads the file. The following will not work:
18592 $ gdb -ex "set use-deprecated-index-sections on" <program>
18595 Instead you must do, for example,
18598 $ gdb -iex "set use-deprecated-index-sections on" <program>
18601 There are currently some limitation on indices. They only work when
18602 for DWARF debugging information, not stabs. And, they do not
18603 currently work for programs using Ada.
18605 @node Symbol Errors
18606 @section Errors Reading Symbol Files
18608 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18609 such as symbol types it does not recognize, or known bugs in compiler
18610 output. By default, @value{GDBN} does not notify you of such problems, since
18611 they are relatively common and primarily of interest to people
18612 debugging compilers. If you are interested in seeing information
18613 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18614 only one message about each such type of problem, no matter how many
18615 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18616 to see how many times the problems occur, with the @code{set
18617 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18620 The messages currently printed, and their meanings, include:
18623 @item inner block not inside outer block in @var{symbol}
18625 The symbol information shows where symbol scopes begin and end
18626 (such as at the start of a function or a block of statements). This
18627 error indicates that an inner scope block is not fully contained
18628 in its outer scope blocks.
18630 @value{GDBN} circumvents the problem by treating the inner block as if it had
18631 the same scope as the outer block. In the error message, @var{symbol}
18632 may be shown as ``@code{(don't know)}'' if the outer block is not a
18635 @item block at @var{address} out of order
18637 The symbol information for symbol scope blocks should occur in
18638 order of increasing addresses. This error indicates that it does not
18641 @value{GDBN} does not circumvent this problem, and has trouble
18642 locating symbols in the source file whose symbols it is reading. (You
18643 can often determine what source file is affected by specifying
18644 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18647 @item bad block start address patched
18649 The symbol information for a symbol scope block has a start address
18650 smaller than the address of the preceding source line. This is known
18651 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18653 @value{GDBN} circumvents the problem by treating the symbol scope block as
18654 starting on the previous source line.
18656 @item bad string table offset in symbol @var{n}
18659 Symbol number @var{n} contains a pointer into the string table which is
18660 larger than the size of the string table.
18662 @value{GDBN} circumvents the problem by considering the symbol to have the
18663 name @code{foo}, which may cause other problems if many symbols end up
18666 @item unknown symbol type @code{0x@var{nn}}
18668 The symbol information contains new data types that @value{GDBN} does
18669 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18670 uncomprehended information, in hexadecimal.
18672 @value{GDBN} circumvents the error by ignoring this symbol information.
18673 This usually allows you to debug your program, though certain symbols
18674 are not accessible. If you encounter such a problem and feel like
18675 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18676 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18677 and examine @code{*bufp} to see the symbol.
18679 @item stub type has NULL name
18681 @value{GDBN} could not find the full definition for a struct or class.
18683 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18684 The symbol information for a C@t{++} member function is missing some
18685 information that recent versions of the compiler should have output for
18688 @item info mismatch between compiler and debugger
18690 @value{GDBN} could not parse a type specification output by the compiler.
18695 @section GDB Data Files
18697 @cindex prefix for data files
18698 @value{GDBN} will sometimes read an auxiliary data file. These files
18699 are kept in a directory known as the @dfn{data directory}.
18701 You can set the data directory's name, and view the name @value{GDBN}
18702 is currently using.
18705 @kindex set data-directory
18706 @item set data-directory @var{directory}
18707 Set the directory which @value{GDBN} searches for auxiliary data files
18708 to @var{directory}.
18710 @kindex show data-directory
18711 @item show data-directory
18712 Show the directory @value{GDBN} searches for auxiliary data files.
18715 @cindex default data directory
18716 @cindex @samp{--with-gdb-datadir}
18717 You can set the default data directory by using the configure-time
18718 @samp{--with-gdb-datadir} option. If the data directory is inside
18719 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18720 @samp{--exec-prefix}), then the default data directory will be updated
18721 automatically if the installed @value{GDBN} is moved to a new
18724 The data directory may also be specified with the
18725 @code{--data-directory} command line option.
18726 @xref{Mode Options}.
18729 @chapter Specifying a Debugging Target
18731 @cindex debugging target
18732 A @dfn{target} is the execution environment occupied by your program.
18734 Often, @value{GDBN} runs in the same host environment as your program;
18735 in that case, the debugging target is specified as a side effect when
18736 you use the @code{file} or @code{core} commands. When you need more
18737 flexibility---for example, running @value{GDBN} on a physically separate
18738 host, or controlling a standalone system over a serial port or a
18739 realtime system over a TCP/IP connection---you can use the @code{target}
18740 command to specify one of the target types configured for @value{GDBN}
18741 (@pxref{Target Commands, ,Commands for Managing Targets}).
18743 @cindex target architecture
18744 It is possible to build @value{GDBN} for several different @dfn{target
18745 architectures}. When @value{GDBN} is built like that, you can choose
18746 one of the available architectures with the @kbd{set architecture}
18750 @kindex set architecture
18751 @kindex show architecture
18752 @item set architecture @var{arch}
18753 This command sets the current target architecture to @var{arch}. The
18754 value of @var{arch} can be @code{"auto"}, in addition to one of the
18755 supported architectures.
18757 @item show architecture
18758 Show the current target architecture.
18760 @item set processor
18762 @kindex set processor
18763 @kindex show processor
18764 These are alias commands for, respectively, @code{set architecture}
18765 and @code{show architecture}.
18769 * Active Targets:: Active targets
18770 * Target Commands:: Commands for managing targets
18771 * Byte Order:: Choosing target byte order
18774 @node Active Targets
18775 @section Active Targets
18777 @cindex stacking targets
18778 @cindex active targets
18779 @cindex multiple targets
18781 There are multiple classes of targets such as: processes, executable files or
18782 recording sessions. Core files belong to the process class, making core file
18783 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18784 on multiple active targets, one in each class. This allows you to (for
18785 example) start a process and inspect its activity, while still having access to
18786 the executable file after the process finishes. Or if you start process
18787 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18788 presented a virtual layer of the recording target, while the process target
18789 remains stopped at the chronologically last point of the process execution.
18791 Use the @code{core-file} and @code{exec-file} commands to select a new core
18792 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18793 specify as a target a process that is already running, use the @code{attach}
18794 command (@pxref{Attach, ,Debugging an Already-running Process}).
18796 @node Target Commands
18797 @section Commands for Managing Targets
18800 @item target @var{type} @var{parameters}
18801 Connects the @value{GDBN} host environment to a target machine or
18802 process. A target is typically a protocol for talking to debugging
18803 facilities. You use the argument @var{type} to specify the type or
18804 protocol of the target machine.
18806 Further @var{parameters} are interpreted by the target protocol, but
18807 typically include things like device names or host names to connect
18808 with, process numbers, and baud rates.
18810 The @code{target} command does not repeat if you press @key{RET} again
18811 after executing the command.
18813 @kindex help target
18815 Displays the names of all targets available. To display targets
18816 currently selected, use either @code{info target} or @code{info files}
18817 (@pxref{Files, ,Commands to Specify Files}).
18819 @item help target @var{name}
18820 Describe a particular target, including any parameters necessary to
18823 @kindex set gnutarget
18824 @item set gnutarget @var{args}
18825 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18826 knows whether it is reading an @dfn{executable},
18827 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18828 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18829 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18832 @emph{Warning:} To specify a file format with @code{set gnutarget},
18833 you must know the actual BFD name.
18837 @xref{Files, , Commands to Specify Files}.
18839 @kindex show gnutarget
18840 @item show gnutarget
18841 Use the @code{show gnutarget} command to display what file format
18842 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18843 @value{GDBN} will determine the file format for each file automatically,
18844 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18847 @cindex common targets
18848 Here are some common targets (available, or not, depending on the GDB
18853 @item target exec @var{program}
18854 @cindex executable file target
18855 An executable file. @samp{target exec @var{program}} is the same as
18856 @samp{exec-file @var{program}}.
18858 @item target core @var{filename}
18859 @cindex core dump file target
18860 A core dump file. @samp{target core @var{filename}} is the same as
18861 @samp{core-file @var{filename}}.
18863 @item target remote @var{medium}
18864 @cindex remote target
18865 A remote system connected to @value{GDBN} via a serial line or network
18866 connection. This command tells @value{GDBN} to use its own remote
18867 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18869 For example, if you have a board connected to @file{/dev/ttya} on the
18870 machine running @value{GDBN}, you could say:
18873 target remote /dev/ttya
18876 @code{target remote} supports the @code{load} command. This is only
18877 useful if you have some other way of getting the stub to the target
18878 system, and you can put it somewhere in memory where it won't get
18879 clobbered by the download.
18881 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18882 @cindex built-in simulator target
18883 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18891 works; however, you cannot assume that a specific memory map, device
18892 drivers, or even basic I/O is available, although some simulators do
18893 provide these. For info about any processor-specific simulator details,
18894 see the appropriate section in @ref{Embedded Processors, ,Embedded
18897 @item target native
18898 @cindex native target
18899 Setup for local/native process debugging. Useful to make the
18900 @code{run} command spawn native processes (likewise @code{attach},
18901 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18902 (@pxref{set auto-connect-native-target}).
18906 Different targets are available on different configurations of @value{GDBN};
18907 your configuration may have more or fewer targets.
18909 Many remote targets require you to download the executable's code once
18910 you've successfully established a connection. You may wish to control
18911 various aspects of this process.
18916 @kindex set hash@r{, for remote monitors}
18917 @cindex hash mark while downloading
18918 This command controls whether a hash mark @samp{#} is displayed while
18919 downloading a file to the remote monitor. If on, a hash mark is
18920 displayed after each S-record is successfully downloaded to the
18924 @kindex show hash@r{, for remote monitors}
18925 Show the current status of displaying the hash mark.
18927 @item set debug monitor
18928 @kindex set debug monitor
18929 @cindex display remote monitor communications
18930 Enable or disable display of communications messages between
18931 @value{GDBN} and the remote monitor.
18933 @item show debug monitor
18934 @kindex show debug monitor
18935 Show the current status of displaying communications between
18936 @value{GDBN} and the remote monitor.
18941 @kindex load @var{filename}
18942 @item load @var{filename}
18944 Depending on what remote debugging facilities are configured into
18945 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18946 is meant to make @var{filename} (an executable) available for debugging
18947 on the remote system---by downloading, or dynamic linking, for example.
18948 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18949 the @code{add-symbol-file} command.
18951 If your @value{GDBN} does not have a @code{load} command, attempting to
18952 execute it gets the error message ``@code{You can't do that when your
18953 target is @dots{}}''
18955 The file is loaded at whatever address is specified in the executable.
18956 For some object file formats, you can specify the load address when you
18957 link the program; for other formats, like a.out, the object file format
18958 specifies a fixed address.
18959 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18961 Depending on the remote side capabilities, @value{GDBN} may be able to
18962 load programs into flash memory.
18964 @code{load} does not repeat if you press @key{RET} again after using it.
18968 @section Choosing Target Byte Order
18970 @cindex choosing target byte order
18971 @cindex target byte order
18973 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18974 offer the ability to run either big-endian or little-endian byte
18975 orders. Usually the executable or symbol will include a bit to
18976 designate the endian-ness, and you will not need to worry about
18977 which to use. However, you may still find it useful to adjust
18978 @value{GDBN}'s idea of processor endian-ness manually.
18982 @item set endian big
18983 Instruct @value{GDBN} to assume the target is big-endian.
18985 @item set endian little
18986 Instruct @value{GDBN} to assume the target is little-endian.
18988 @item set endian auto
18989 Instruct @value{GDBN} to use the byte order associated with the
18993 Display @value{GDBN}'s current idea of the target byte order.
18997 Note that these commands merely adjust interpretation of symbolic
18998 data on the host, and that they have absolutely no effect on the
19002 @node Remote Debugging
19003 @chapter Debugging Remote Programs
19004 @cindex remote debugging
19006 If you are trying to debug a program running on a machine that cannot run
19007 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19008 For example, you might use remote debugging on an operating system kernel,
19009 or on a small system which does not have a general purpose operating system
19010 powerful enough to run a full-featured debugger.
19012 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19013 to make this work with particular debugging targets. In addition,
19014 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19015 but not specific to any particular target system) which you can use if you
19016 write the remote stubs---the code that runs on the remote system to
19017 communicate with @value{GDBN}.
19019 Other remote targets may be available in your
19020 configuration of @value{GDBN}; use @code{help target} to list them.
19023 * Connecting:: Connecting to a remote target
19024 * File Transfer:: Sending files to a remote system
19025 * Server:: Using the gdbserver program
19026 * Remote Configuration:: Remote configuration
19027 * Remote Stub:: Implementing a remote stub
19031 @section Connecting to a Remote Target
19033 @value{GDBN} needs an unstripped copy of your program to access symbol
19034 and debugging information. Some remote targets (@pxref{qXfer
19035 executable filename read}, and @pxref{Host I/O Packets}) allow
19036 @value{GDBN} to access program files over the same connection used to
19037 communicate with @value{GDBN}. With such a target, if the remote
19038 program is unstripped, the only command you need is @code{target
19039 remote}. Otherwise, start up @value{GDBN} using the name of the local
19040 unstripped copy of your program as the first argument, or use the
19041 @code{file} command.
19043 @cindex @code{target remote}
19044 @value{GDBN} can communicate with the target over a serial line, or
19045 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19046 each case, @value{GDBN} uses the same protocol for debugging your
19047 program; only the medium carrying the debugging packets varies. The
19048 @code{target remote} command establishes a connection to the target.
19049 Its arguments indicate which medium to use:
19053 @item target remote @var{serial-device}
19054 @cindex serial line, @code{target remote}
19055 Use @var{serial-device} to communicate with the target. For example,
19056 to use a serial line connected to the device named @file{/dev/ttyb}:
19059 target remote /dev/ttyb
19062 If you're using a serial line, you may want to give @value{GDBN} the
19063 @samp{--baud} option, or use the @code{set serial baud} command
19064 (@pxref{Remote Configuration, set serial baud}) before the
19065 @code{target} command.
19067 @item target remote @code{@var{host}:@var{port}}
19068 @itemx target remote @code{tcp:@var{host}:@var{port}}
19069 @cindex @acronym{TCP} port, @code{target remote}
19070 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19071 The @var{host} may be either a host name or a numeric @acronym{IP}
19072 address; @var{port} must be a decimal number. The @var{host} could be
19073 the target machine itself, if it is directly connected to the net, or
19074 it might be a terminal server which in turn has a serial line to the
19077 For example, to connect to port 2828 on a terminal server named
19081 target remote manyfarms:2828
19084 If your remote target is actually running on the same machine as your
19085 debugger session (e.g.@: a simulator for your target running on the
19086 same host), you can omit the hostname. For example, to connect to
19087 port 1234 on your local machine:
19090 target remote :1234
19094 Note that the colon is still required here.
19096 @item target remote @code{udp:@var{host}:@var{port}}
19097 @cindex @acronym{UDP} port, @code{target remote}
19098 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19099 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19102 target remote udp:manyfarms:2828
19105 When using a @acronym{UDP} connection for remote debugging, you should
19106 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19107 can silently drop packets on busy or unreliable networks, which will
19108 cause havoc with your debugging session.
19110 @item target remote | @var{command}
19111 @cindex pipe, @code{target remote} to
19112 Run @var{command} in the background and communicate with it using a
19113 pipe. The @var{command} is a shell command, to be parsed and expanded
19114 by the system's command shell, @code{/bin/sh}; it should expect remote
19115 protocol packets on its standard input, and send replies on its
19116 standard output. You could use this to run a stand-alone simulator
19117 that speaks the remote debugging protocol, to make net connections
19118 using programs like @code{ssh}, or for other similar tricks.
19120 If @var{command} closes its standard output (perhaps by exiting),
19121 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19122 program has already exited, this will have no effect.)
19126 Once the connection has been established, you can use all the usual
19127 commands to examine and change data. The remote program is already
19128 running; you can use @kbd{step} and @kbd{continue}, and you do not
19129 need to use @kbd{run}.
19131 @cindex interrupting remote programs
19132 @cindex remote programs, interrupting
19133 Whenever @value{GDBN} is waiting for the remote program, if you type the
19134 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19135 program. This may or may not succeed, depending in part on the hardware
19136 and the serial drivers the remote system uses. If you type the
19137 interrupt character once again, @value{GDBN} displays this prompt:
19140 Interrupted while waiting for the program.
19141 Give up (and stop debugging it)? (y or n)
19144 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19145 (If you decide you want to try again later, you can use @samp{target
19146 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19147 goes back to waiting.
19150 @kindex detach (remote)
19152 When you have finished debugging the remote program, you can use the
19153 @code{detach} command to release it from @value{GDBN} control.
19154 Detaching from the target normally resumes its execution, but the results
19155 will depend on your particular remote stub. After the @code{detach}
19156 command, @value{GDBN} is free to connect to another target.
19160 The @code{disconnect} command behaves like @code{detach}, except that
19161 the target is generally not resumed. It will wait for @value{GDBN}
19162 (this instance or another one) to connect and continue debugging. After
19163 the @code{disconnect} command, @value{GDBN} is again free to connect to
19166 @cindex send command to remote monitor
19167 @cindex extend @value{GDBN} for remote targets
19168 @cindex add new commands for external monitor
19170 @item monitor @var{cmd}
19171 This command allows you to send arbitrary commands directly to the
19172 remote monitor. Since @value{GDBN} doesn't care about the commands it
19173 sends like this, this command is the way to extend @value{GDBN}---you
19174 can add new commands that only the external monitor will understand
19178 @node File Transfer
19179 @section Sending files to a remote system
19180 @cindex remote target, file transfer
19181 @cindex file transfer
19182 @cindex sending files to remote systems
19184 Some remote targets offer the ability to transfer files over the same
19185 connection used to communicate with @value{GDBN}. This is convenient
19186 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19187 running @code{gdbserver} over a network interface. For other targets,
19188 e.g.@: embedded devices with only a single serial port, this may be
19189 the only way to upload or download files.
19191 Not all remote targets support these commands.
19195 @item remote put @var{hostfile} @var{targetfile}
19196 Copy file @var{hostfile} from the host system (the machine running
19197 @value{GDBN}) to @var{targetfile} on the target system.
19200 @item remote get @var{targetfile} @var{hostfile}
19201 Copy file @var{targetfile} from the target system to @var{hostfile}
19202 on the host system.
19204 @kindex remote delete
19205 @item remote delete @var{targetfile}
19206 Delete @var{targetfile} from the target system.
19211 @section Using the @code{gdbserver} Program
19214 @cindex remote connection without stubs
19215 @code{gdbserver} is a control program for Unix-like systems, which
19216 allows you to connect your program with a remote @value{GDBN} via
19217 @code{target remote}---but without linking in the usual debugging stub.
19219 @code{gdbserver} is not a complete replacement for the debugging stubs,
19220 because it requires essentially the same operating-system facilities
19221 that @value{GDBN} itself does. In fact, a system that can run
19222 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19223 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19224 because it is a much smaller program than @value{GDBN} itself. It is
19225 also easier to port than all of @value{GDBN}, so you may be able to get
19226 started more quickly on a new system by using @code{gdbserver}.
19227 Finally, if you develop code for real-time systems, you may find that
19228 the tradeoffs involved in real-time operation make it more convenient to
19229 do as much development work as possible on another system, for example
19230 by cross-compiling. You can use @code{gdbserver} to make a similar
19231 choice for debugging.
19233 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19234 or a TCP connection, using the standard @value{GDBN} remote serial
19238 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19239 Do not run @code{gdbserver} connected to any public network; a
19240 @value{GDBN} connection to @code{gdbserver} provides access to the
19241 target system with the same privileges as the user running
19245 @subsection Running @code{gdbserver}
19246 @cindex arguments, to @code{gdbserver}
19247 @cindex @code{gdbserver}, command-line arguments
19249 Run @code{gdbserver} on the target system. You need a copy of the
19250 program you want to debug, including any libraries it requires.
19251 @code{gdbserver} does not need your program's symbol table, so you can
19252 strip the program if necessary to save space. @value{GDBN} on the host
19253 system does all the symbol handling.
19255 To use the server, you must tell it how to communicate with @value{GDBN};
19256 the name of your program; and the arguments for your program. The usual
19260 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19263 @var{comm} is either a device name (to use a serial line), or a TCP
19264 hostname and portnumber, or @code{-} or @code{stdio} to use
19265 stdin/stdout of @code{gdbserver}.
19266 For example, to debug Emacs with the argument
19267 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19271 target> gdbserver /dev/com1 emacs foo.txt
19274 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19277 To use a TCP connection instead of a serial line:
19280 target> gdbserver host:2345 emacs foo.txt
19283 The only difference from the previous example is the first argument,
19284 specifying that you are communicating with the host @value{GDBN} via
19285 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19286 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19287 (Currently, the @samp{host} part is ignored.) You can choose any number
19288 you want for the port number as long as it does not conflict with any
19289 TCP ports already in use on the target system (for example, @code{23} is
19290 reserved for @code{telnet}).@footnote{If you choose a port number that
19291 conflicts with another service, @code{gdbserver} prints an error message
19292 and exits.} You must use the same port number with the host @value{GDBN}
19293 @code{target remote} command.
19295 The @code{stdio} connection is useful when starting @code{gdbserver}
19299 (gdb) target remote | ssh -T hostname gdbserver - hello
19302 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19303 and we don't want escape-character handling. Ssh does this by default when
19304 a command is provided, the flag is provided to make it explicit.
19305 You could elide it if you want to.
19307 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19308 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19309 display through a pipe connected to gdbserver.
19310 Both @code{stdout} and @code{stderr} use the same pipe.
19312 @subsubsection Attaching to a Running Program
19313 @cindex attach to a program, @code{gdbserver}
19314 @cindex @option{--attach}, @code{gdbserver} option
19316 On some targets, @code{gdbserver} can also attach to running programs.
19317 This is accomplished via the @code{--attach} argument. The syntax is:
19320 target> gdbserver --attach @var{comm} @var{pid}
19323 @var{pid} is the process ID of a currently running process. It isn't necessary
19324 to point @code{gdbserver} at a binary for the running process.
19327 You can debug processes by name instead of process ID if your target has the
19328 @code{pidof} utility:
19331 target> gdbserver --attach @var{comm} `pidof @var{program}`
19334 In case more than one copy of @var{program} is running, or @var{program}
19335 has multiple threads, most versions of @code{pidof} support the
19336 @code{-s} option to only return the first process ID.
19338 @subsubsection Multi-Process Mode for @code{gdbserver}
19339 @cindex @code{gdbserver}, multiple processes
19340 @cindex multiple processes with @code{gdbserver}
19342 When you connect to @code{gdbserver} using @code{target remote},
19343 @code{gdbserver} debugs the specified program only once. When the
19344 program exits, or you detach from it, @value{GDBN} closes the connection
19345 and @code{gdbserver} exits.
19347 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19348 enters multi-process mode. When the debugged program exits, or you
19349 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19350 though no program is running. The @code{run} and @code{attach}
19351 commands instruct @code{gdbserver} to run or attach to a new program.
19352 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19353 remote exec-file}) to select the program to run. Command line
19354 arguments are supported, except for wildcard expansion and I/O
19355 redirection (@pxref{Arguments}).
19357 @cindex @option{--multi}, @code{gdbserver} option
19358 To start @code{gdbserver} without supplying an initial command to run
19359 or process ID to attach, use the @option{--multi} command line option.
19360 Then you can connect using @kbd{target extended-remote} and start
19361 the program you want to debug.
19363 In multi-process mode @code{gdbserver} does not automatically exit unless you
19364 use the option @option{--once}. You can terminate it by using
19365 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19366 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19367 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19368 @option{--multi} option to @code{gdbserver} has no influence on that.
19370 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19372 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19374 @code{gdbserver} normally terminates after all of its debugged processes have
19375 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19376 extended-remote}, @code{gdbserver} stays running even with no processes left.
19377 @value{GDBN} normally terminates the spawned debugged process on its exit,
19378 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19379 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19380 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19381 stays running even in the @kbd{target remote} mode.
19383 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19384 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19385 completeness, at most one @value{GDBN} can be connected at a time.
19387 @cindex @option{--once}, @code{gdbserver} option
19388 By default, @code{gdbserver} keeps the listening TCP port open, so that
19389 subsequent connections are possible. However, if you start @code{gdbserver}
19390 with the @option{--once} option, it will stop listening for any further
19391 connection attempts after connecting to the first @value{GDBN} session. This
19392 means no further connections to @code{gdbserver} will be possible after the
19393 first one. It also means @code{gdbserver} will terminate after the first
19394 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19395 connections and even in the @kbd{target extended-remote} mode. The
19396 @option{--once} option allows reusing the same port number for connecting to
19397 multiple instances of @code{gdbserver} running on the same host, since each
19398 instance closes its port after the first connection.
19400 @anchor{Other Command-Line Arguments for gdbserver}
19401 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19403 @cindex @option{--debug}, @code{gdbserver} option
19404 The @option{--debug} option tells @code{gdbserver} to display extra
19405 status information about the debugging process.
19406 @cindex @option{--remote-debug}, @code{gdbserver} option
19407 The @option{--remote-debug} option tells @code{gdbserver} to display
19408 remote protocol debug output. These options are intended for
19409 @code{gdbserver} development and for bug reports to the developers.
19411 @cindex @option{--debug-format}, @code{gdbserver} option
19412 The @option{--debug-format=option1[,option2,...]} option tells
19413 @code{gdbserver} to include additional information in each output.
19414 Possible options are:
19418 Turn off all extra information in debugging output.
19420 Turn on all extra information in debugging output.
19422 Include a timestamp in each line of debugging output.
19425 Options are processed in order. Thus, for example, if @option{none}
19426 appears last then no additional information is added to debugging output.
19428 @cindex @option{--wrapper}, @code{gdbserver} option
19429 The @option{--wrapper} option specifies a wrapper to launch programs
19430 for debugging. The option should be followed by the name of the
19431 wrapper, then any command-line arguments to pass to the wrapper, then
19432 @kbd{--} indicating the end of the wrapper arguments.
19434 @code{gdbserver} runs the specified wrapper program with a combined
19435 command line including the wrapper arguments, then the name of the
19436 program to debug, then any arguments to the program. The wrapper
19437 runs until it executes your program, and then @value{GDBN} gains control.
19439 You can use any program that eventually calls @code{execve} with
19440 its arguments as a wrapper. Several standard Unix utilities do
19441 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19442 with @code{exec "$@@"} will also work.
19444 For example, you can use @code{env} to pass an environment variable to
19445 the debugged program, without setting the variable in @code{gdbserver}'s
19449 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19452 @subsection Connecting to @code{gdbserver}
19454 Run @value{GDBN} on the host system.
19456 First make sure you have the necessary symbol files. Load symbols for
19457 your application using the @code{file} command before you connect. Use
19458 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19459 was compiled with the correct sysroot using @code{--with-sysroot}).
19461 The symbol file and target libraries must exactly match the executable
19462 and libraries on the target, with one exception: the files on the host
19463 system should not be stripped, even if the files on the target system
19464 are. Mismatched or missing files will lead to confusing results
19465 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19466 files may also prevent @code{gdbserver} from debugging multi-threaded
19469 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19470 For TCP connections, you must start up @code{gdbserver} prior to using
19471 the @code{target remote} command. Otherwise you may get an error whose
19472 text depends on the host system, but which usually looks something like
19473 @samp{Connection refused}. Don't use the @code{load}
19474 command in @value{GDBN} when using @code{gdbserver}, since the program is
19475 already on the target.
19477 @subsection Monitor Commands for @code{gdbserver}
19478 @cindex monitor commands, for @code{gdbserver}
19479 @anchor{Monitor Commands for gdbserver}
19481 During a @value{GDBN} session using @code{gdbserver}, you can use the
19482 @code{monitor} command to send special requests to @code{gdbserver}.
19483 Here are the available commands.
19487 List the available monitor commands.
19489 @item monitor set debug 0
19490 @itemx monitor set debug 1
19491 Disable or enable general debugging messages.
19493 @item monitor set remote-debug 0
19494 @itemx monitor set remote-debug 1
19495 Disable or enable specific debugging messages associated with the remote
19496 protocol (@pxref{Remote Protocol}).
19498 @item monitor set debug-format option1@r{[},option2,...@r{]}
19499 Specify additional text to add to debugging messages.
19500 Possible options are:
19504 Turn off all extra information in debugging output.
19506 Turn on all extra information in debugging output.
19508 Include a timestamp in each line of debugging output.
19511 Options are processed in order. Thus, for example, if @option{none}
19512 appears last then no additional information is added to debugging output.
19514 @item monitor set libthread-db-search-path [PATH]
19515 @cindex gdbserver, search path for @code{libthread_db}
19516 When this command is issued, @var{path} is a colon-separated list of
19517 directories to search for @code{libthread_db} (@pxref{Threads,,set
19518 libthread-db-search-path}). If you omit @var{path},
19519 @samp{libthread-db-search-path} will be reset to its default value.
19521 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19522 not supported in @code{gdbserver}.
19525 Tell gdbserver to exit immediately. This command should be followed by
19526 @code{disconnect} to close the debugging session. @code{gdbserver} will
19527 detach from any attached processes and kill any processes it created.
19528 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19529 of a multi-process mode debug session.
19533 @subsection Tracepoints support in @code{gdbserver}
19534 @cindex tracepoints support in @code{gdbserver}
19536 On some targets, @code{gdbserver} supports tracepoints, fast
19537 tracepoints and static tracepoints.
19539 For fast or static tracepoints to work, a special library called the
19540 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19541 This library is built and distributed as an integral part of
19542 @code{gdbserver}. In addition, support for static tracepoints
19543 requires building the in-process agent library with static tracepoints
19544 support. At present, the UST (LTTng Userspace Tracer,
19545 @url{http://lttng.org/ust}) tracing engine is supported. This support
19546 is automatically available if UST development headers are found in the
19547 standard include path when @code{gdbserver} is built, or if
19548 @code{gdbserver} was explicitly configured using @option{--with-ust}
19549 to point at such headers. You can explicitly disable the support
19550 using @option{--with-ust=no}.
19552 There are several ways to load the in-process agent in your program:
19555 @item Specifying it as dependency at link time
19557 You can link your program dynamically with the in-process agent
19558 library. On most systems, this is accomplished by adding
19559 @code{-linproctrace} to the link command.
19561 @item Using the system's preloading mechanisms
19563 You can force loading the in-process agent at startup time by using
19564 your system's support for preloading shared libraries. Many Unixes
19565 support the concept of preloading user defined libraries. In most
19566 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19567 in the environment. See also the description of @code{gdbserver}'s
19568 @option{--wrapper} command line option.
19570 @item Using @value{GDBN} to force loading the agent at run time
19572 On some systems, you can force the inferior to load a shared library,
19573 by calling a dynamic loader function in the inferior that takes care
19574 of dynamically looking up and loading a shared library. On most Unix
19575 systems, the function is @code{dlopen}. You'll use the @code{call}
19576 command for that. For example:
19579 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19582 Note that on most Unix systems, for the @code{dlopen} function to be
19583 available, the program needs to be linked with @code{-ldl}.
19586 On systems that have a userspace dynamic loader, like most Unix
19587 systems, when you connect to @code{gdbserver} using @code{target
19588 remote}, you'll find that the program is stopped at the dynamic
19589 loader's entry point, and no shared library has been loaded in the
19590 program's address space yet, including the in-process agent. In that
19591 case, before being able to use any of the fast or static tracepoints
19592 features, you need to let the loader run and load the shared
19593 libraries. The simplest way to do that is to run the program to the
19594 main procedure. E.g., if debugging a C or C@t{++} program, start
19595 @code{gdbserver} like so:
19598 $ gdbserver :9999 myprogram
19601 Start GDB and connect to @code{gdbserver} like so, and run to main:
19605 (@value{GDBP}) target remote myhost:9999
19606 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19607 (@value{GDBP}) b main
19608 (@value{GDBP}) continue
19611 The in-process tracing agent library should now be loaded into the
19612 process; you can confirm it with the @code{info sharedlibrary}
19613 command, which will list @file{libinproctrace.so} as loaded in the
19614 process. You are now ready to install fast tracepoints, list static
19615 tracepoint markers, probe static tracepoints markers, and start
19618 @node Remote Configuration
19619 @section Remote Configuration
19622 @kindex show remote
19623 This section documents the configuration options available when
19624 debugging remote programs. For the options related to the File I/O
19625 extensions of the remote protocol, see @ref{system,
19626 system-call-allowed}.
19629 @item set remoteaddresssize @var{bits}
19630 @cindex address size for remote targets
19631 @cindex bits in remote address
19632 Set the maximum size of address in a memory packet to the specified
19633 number of bits. @value{GDBN} will mask off the address bits above
19634 that number, when it passes addresses to the remote target. The
19635 default value is the number of bits in the target's address.
19637 @item show remoteaddresssize
19638 Show the current value of remote address size in bits.
19640 @item set serial baud @var{n}
19641 @cindex baud rate for remote targets
19642 Set the baud rate for the remote serial I/O to @var{n} baud. The
19643 value is used to set the speed of the serial port used for debugging
19646 @item show serial baud
19647 Show the current speed of the remote connection.
19649 @item set serial parity @var{parity}
19650 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19651 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19653 @item show serial parity
19654 Show the current parity of the serial port.
19656 @item set remotebreak
19657 @cindex interrupt remote programs
19658 @cindex BREAK signal instead of Ctrl-C
19659 @anchor{set remotebreak}
19660 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19661 when you type @kbd{Ctrl-c} to interrupt the program running
19662 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19663 character instead. The default is off, since most remote systems
19664 expect to see @samp{Ctrl-C} as the interrupt signal.
19666 @item show remotebreak
19667 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19668 interrupt the remote program.
19670 @item set remoteflow on
19671 @itemx set remoteflow off
19672 @kindex set remoteflow
19673 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19674 on the serial port used to communicate to the remote target.
19676 @item show remoteflow
19677 @kindex show remoteflow
19678 Show the current setting of hardware flow control.
19680 @item set remotelogbase @var{base}
19681 Set the base (a.k.a.@: radix) of logging serial protocol
19682 communications to @var{base}. Supported values of @var{base} are:
19683 @code{ascii}, @code{octal}, and @code{hex}. The default is
19686 @item show remotelogbase
19687 Show the current setting of the radix for logging remote serial
19690 @item set remotelogfile @var{file}
19691 @cindex record serial communications on file
19692 Record remote serial communications on the named @var{file}. The
19693 default is not to record at all.
19695 @item show remotelogfile.
19696 Show the current setting of the file name on which to record the
19697 serial communications.
19699 @item set remotetimeout @var{num}
19700 @cindex timeout for serial communications
19701 @cindex remote timeout
19702 Set the timeout limit to wait for the remote target to respond to
19703 @var{num} seconds. The default is 2 seconds.
19705 @item show remotetimeout
19706 Show the current number of seconds to wait for the remote target
19709 @cindex limit hardware breakpoints and watchpoints
19710 @cindex remote target, limit break- and watchpoints
19711 @anchor{set remote hardware-watchpoint-limit}
19712 @anchor{set remote hardware-breakpoint-limit}
19713 @item set remote hardware-watchpoint-limit @var{limit}
19714 @itemx set remote hardware-breakpoint-limit @var{limit}
19715 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19716 watchpoints. A limit of -1, the default, is treated as unlimited.
19718 @cindex limit hardware watchpoints length
19719 @cindex remote target, limit watchpoints length
19720 @anchor{set remote hardware-watchpoint-length-limit}
19721 @item set remote hardware-watchpoint-length-limit @var{limit}
19722 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19723 a remote hardware watchpoint. A limit of -1, the default, is treated
19726 @item show remote hardware-watchpoint-length-limit
19727 Show the current limit (in bytes) of the maximum length of
19728 a remote hardware watchpoint.
19730 @item set remote exec-file @var{filename}
19731 @itemx show remote exec-file
19732 @anchor{set remote exec-file}
19733 @cindex executable file, for remote target
19734 Select the file used for @code{run} with @code{target
19735 extended-remote}. This should be set to a filename valid on the
19736 target system. If it is not set, the target will use a default
19737 filename (e.g.@: the last program run).
19739 @item set remote interrupt-sequence
19740 @cindex interrupt remote programs
19741 @cindex select Ctrl-C, BREAK or BREAK-g
19742 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19743 @samp{BREAK-g} as the
19744 sequence to the remote target in order to interrupt the execution.
19745 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19746 is high level of serial line for some certain time.
19747 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19748 It is @code{BREAK} signal followed by character @code{g}.
19750 @item show interrupt-sequence
19751 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19752 is sent by @value{GDBN} to interrupt the remote program.
19753 @code{BREAK-g} is BREAK signal followed by @code{g} and
19754 also known as Magic SysRq g.
19756 @item set remote interrupt-on-connect
19757 @cindex send interrupt-sequence on start
19758 Specify whether interrupt-sequence is sent to remote target when
19759 @value{GDBN} connects to it. This is mostly needed when you debug
19760 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19761 which is known as Magic SysRq g in order to connect @value{GDBN}.
19763 @item show interrupt-on-connect
19764 Show whether interrupt-sequence is sent
19765 to remote target when @value{GDBN} connects to it.
19769 @item set tcp auto-retry on
19770 @cindex auto-retry, for remote TCP target
19771 Enable auto-retry for remote TCP connections. This is useful if the remote
19772 debugging agent is launched in parallel with @value{GDBN}; there is a race
19773 condition because the agent may not become ready to accept the connection
19774 before @value{GDBN} attempts to connect. When auto-retry is
19775 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19776 to establish the connection using the timeout specified by
19777 @code{set tcp connect-timeout}.
19779 @item set tcp auto-retry off
19780 Do not auto-retry failed TCP connections.
19782 @item show tcp auto-retry
19783 Show the current auto-retry setting.
19785 @item set tcp connect-timeout @var{seconds}
19786 @itemx set tcp connect-timeout unlimited
19787 @cindex connection timeout, for remote TCP target
19788 @cindex timeout, for remote target connection
19789 Set the timeout for establishing a TCP connection to the remote target to
19790 @var{seconds}. The timeout affects both polling to retry failed connections
19791 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19792 that are merely slow to complete, and represents an approximate cumulative
19793 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19794 @value{GDBN} will keep attempting to establish a connection forever,
19795 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19797 @item show tcp connect-timeout
19798 Show the current connection timeout setting.
19801 @cindex remote packets, enabling and disabling
19802 The @value{GDBN} remote protocol autodetects the packets supported by
19803 your debugging stub. If you need to override the autodetection, you
19804 can use these commands to enable or disable individual packets. Each
19805 packet can be set to @samp{on} (the remote target supports this
19806 packet), @samp{off} (the remote target does not support this packet),
19807 or @samp{auto} (detect remote target support for this packet). They
19808 all default to @samp{auto}. For more information about each packet,
19809 see @ref{Remote Protocol}.
19811 During normal use, you should not have to use any of these commands.
19812 If you do, that may be a bug in your remote debugging stub, or a bug
19813 in @value{GDBN}. You may want to report the problem to the
19814 @value{GDBN} developers.
19816 For each packet @var{name}, the command to enable or disable the
19817 packet is @code{set remote @var{name}-packet}. The available settings
19820 @multitable @columnfractions 0.28 0.32 0.25
19823 @tab Related Features
19825 @item @code{fetch-register}
19827 @tab @code{info registers}
19829 @item @code{set-register}
19833 @item @code{binary-download}
19835 @tab @code{load}, @code{set}
19837 @item @code{read-aux-vector}
19838 @tab @code{qXfer:auxv:read}
19839 @tab @code{info auxv}
19841 @item @code{symbol-lookup}
19842 @tab @code{qSymbol}
19843 @tab Detecting multiple threads
19845 @item @code{attach}
19846 @tab @code{vAttach}
19849 @item @code{verbose-resume}
19851 @tab Stepping or resuming multiple threads
19857 @item @code{software-breakpoint}
19861 @item @code{hardware-breakpoint}
19865 @item @code{write-watchpoint}
19869 @item @code{read-watchpoint}
19873 @item @code{access-watchpoint}
19877 @item @code{pid-to-exec-file}
19878 @tab @code{qXfer:exec-file:read}
19879 @tab @code{attach}, @code{run}
19881 @item @code{target-features}
19882 @tab @code{qXfer:features:read}
19883 @tab @code{set architecture}
19885 @item @code{library-info}
19886 @tab @code{qXfer:libraries:read}
19887 @tab @code{info sharedlibrary}
19889 @item @code{memory-map}
19890 @tab @code{qXfer:memory-map:read}
19891 @tab @code{info mem}
19893 @item @code{read-sdata-object}
19894 @tab @code{qXfer:sdata:read}
19895 @tab @code{print $_sdata}
19897 @item @code{read-spu-object}
19898 @tab @code{qXfer:spu:read}
19899 @tab @code{info spu}
19901 @item @code{write-spu-object}
19902 @tab @code{qXfer:spu:write}
19903 @tab @code{info spu}
19905 @item @code{read-siginfo-object}
19906 @tab @code{qXfer:siginfo:read}
19907 @tab @code{print $_siginfo}
19909 @item @code{write-siginfo-object}
19910 @tab @code{qXfer:siginfo:write}
19911 @tab @code{set $_siginfo}
19913 @item @code{threads}
19914 @tab @code{qXfer:threads:read}
19915 @tab @code{info threads}
19917 @item @code{get-thread-local-@*storage-address}
19918 @tab @code{qGetTLSAddr}
19919 @tab Displaying @code{__thread} variables
19921 @item @code{get-thread-information-block-address}
19922 @tab @code{qGetTIBAddr}
19923 @tab Display MS-Windows Thread Information Block.
19925 @item @code{search-memory}
19926 @tab @code{qSearch:memory}
19929 @item @code{supported-packets}
19930 @tab @code{qSupported}
19931 @tab Remote communications parameters
19933 @item @code{pass-signals}
19934 @tab @code{QPassSignals}
19935 @tab @code{handle @var{signal}}
19937 @item @code{program-signals}
19938 @tab @code{QProgramSignals}
19939 @tab @code{handle @var{signal}}
19941 @item @code{hostio-close-packet}
19942 @tab @code{vFile:close}
19943 @tab @code{remote get}, @code{remote put}
19945 @item @code{hostio-open-packet}
19946 @tab @code{vFile:open}
19947 @tab @code{remote get}, @code{remote put}
19949 @item @code{hostio-pread-packet}
19950 @tab @code{vFile:pread}
19951 @tab @code{remote get}, @code{remote put}
19953 @item @code{hostio-pwrite-packet}
19954 @tab @code{vFile:pwrite}
19955 @tab @code{remote get}, @code{remote put}
19957 @item @code{hostio-unlink-packet}
19958 @tab @code{vFile:unlink}
19959 @tab @code{remote delete}
19961 @item @code{hostio-readlink-packet}
19962 @tab @code{vFile:readlink}
19965 @item @code{hostio-fstat-packet}
19966 @tab @code{vFile:fstat}
19969 @item @code{hostio-setfs-packet}
19970 @tab @code{vFile:setfs}
19973 @item @code{noack-packet}
19974 @tab @code{QStartNoAckMode}
19975 @tab Packet acknowledgment
19977 @item @code{osdata}
19978 @tab @code{qXfer:osdata:read}
19979 @tab @code{info os}
19981 @item @code{query-attached}
19982 @tab @code{qAttached}
19983 @tab Querying remote process attach state.
19985 @item @code{trace-buffer-size}
19986 @tab @code{QTBuffer:size}
19987 @tab @code{set trace-buffer-size}
19989 @item @code{trace-status}
19990 @tab @code{qTStatus}
19991 @tab @code{tstatus}
19993 @item @code{traceframe-info}
19994 @tab @code{qXfer:traceframe-info:read}
19995 @tab Traceframe info
19997 @item @code{install-in-trace}
19998 @tab @code{InstallInTrace}
19999 @tab Install tracepoint in tracing
20001 @item @code{disable-randomization}
20002 @tab @code{QDisableRandomization}
20003 @tab @code{set disable-randomization}
20005 @item @code{conditional-breakpoints-packet}
20006 @tab @code{Z0 and Z1}
20007 @tab @code{Support for target-side breakpoint condition evaluation}
20009 @item @code{swbreak-feature}
20010 @tab @code{swbreak stop reason}
20013 @item @code{hwbreak-feature}
20014 @tab @code{hwbreak stop reason}
20017 @item @code{fork-event-feature}
20018 @tab @code{fork stop reason}
20021 @item @code{vfork-event-feature}
20022 @tab @code{vfork stop reason}
20028 @section Implementing a Remote Stub
20030 @cindex debugging stub, example
20031 @cindex remote stub, example
20032 @cindex stub example, remote debugging
20033 The stub files provided with @value{GDBN} implement the target side of the
20034 communication protocol, and the @value{GDBN} side is implemented in the
20035 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20036 these subroutines to communicate, and ignore the details. (If you're
20037 implementing your own stub file, you can still ignore the details: start
20038 with one of the existing stub files. @file{sparc-stub.c} is the best
20039 organized, and therefore the easiest to read.)
20041 @cindex remote serial debugging, overview
20042 To debug a program running on another machine (the debugging
20043 @dfn{target} machine), you must first arrange for all the usual
20044 prerequisites for the program to run by itself. For example, for a C
20049 A startup routine to set up the C runtime environment; these usually
20050 have a name like @file{crt0}. The startup routine may be supplied by
20051 your hardware supplier, or you may have to write your own.
20054 A C subroutine library to support your program's
20055 subroutine calls, notably managing input and output.
20058 A way of getting your program to the other machine---for example, a
20059 download program. These are often supplied by the hardware
20060 manufacturer, but you may have to write your own from hardware
20064 The next step is to arrange for your program to use a serial port to
20065 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20066 machine). In general terms, the scheme looks like this:
20070 @value{GDBN} already understands how to use this protocol; when everything
20071 else is set up, you can simply use the @samp{target remote} command
20072 (@pxref{Targets,,Specifying a Debugging Target}).
20074 @item On the target,
20075 you must link with your program a few special-purpose subroutines that
20076 implement the @value{GDBN} remote serial protocol. The file containing these
20077 subroutines is called a @dfn{debugging stub}.
20079 On certain remote targets, you can use an auxiliary program
20080 @code{gdbserver} instead of linking a stub into your program.
20081 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20084 The debugging stub is specific to the architecture of the remote
20085 machine; for example, use @file{sparc-stub.c} to debug programs on
20088 @cindex remote serial stub list
20089 These working remote stubs are distributed with @value{GDBN}:
20094 @cindex @file{i386-stub.c}
20097 For Intel 386 and compatible architectures.
20100 @cindex @file{m68k-stub.c}
20101 @cindex Motorola 680x0
20103 For Motorola 680x0 architectures.
20106 @cindex @file{sh-stub.c}
20109 For Renesas SH architectures.
20112 @cindex @file{sparc-stub.c}
20114 For @sc{sparc} architectures.
20116 @item sparcl-stub.c
20117 @cindex @file{sparcl-stub.c}
20120 For Fujitsu @sc{sparclite} architectures.
20124 The @file{README} file in the @value{GDBN} distribution may list other
20125 recently added stubs.
20128 * Stub Contents:: What the stub can do for you
20129 * Bootstrapping:: What you must do for the stub
20130 * Debug Session:: Putting it all together
20133 @node Stub Contents
20134 @subsection What the Stub Can Do for You
20136 @cindex remote serial stub
20137 The debugging stub for your architecture supplies these three
20141 @item set_debug_traps
20142 @findex set_debug_traps
20143 @cindex remote serial stub, initialization
20144 This routine arranges for @code{handle_exception} to run when your
20145 program stops. You must call this subroutine explicitly in your
20146 program's startup code.
20148 @item handle_exception
20149 @findex handle_exception
20150 @cindex remote serial stub, main routine
20151 This is the central workhorse, but your program never calls it
20152 explicitly---the setup code arranges for @code{handle_exception} to
20153 run when a trap is triggered.
20155 @code{handle_exception} takes control when your program stops during
20156 execution (for example, on a breakpoint), and mediates communications
20157 with @value{GDBN} on the host machine. This is where the communications
20158 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20159 representative on the target machine. It begins by sending summary
20160 information on the state of your program, then continues to execute,
20161 retrieving and transmitting any information @value{GDBN} needs, until you
20162 execute a @value{GDBN} command that makes your program resume; at that point,
20163 @code{handle_exception} returns control to your own code on the target
20167 @cindex @code{breakpoint} subroutine, remote
20168 Use this auxiliary subroutine to make your program contain a
20169 breakpoint. Depending on the particular situation, this may be the only
20170 way for @value{GDBN} to get control. For instance, if your target
20171 machine has some sort of interrupt button, you won't need to call this;
20172 pressing the interrupt button transfers control to
20173 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20174 simply receiving characters on the serial port may also trigger a trap;
20175 again, in that situation, you don't need to call @code{breakpoint} from
20176 your own program---simply running @samp{target remote} from the host
20177 @value{GDBN} session gets control.
20179 Call @code{breakpoint} if none of these is true, or if you simply want
20180 to make certain your program stops at a predetermined point for the
20181 start of your debugging session.
20184 @node Bootstrapping
20185 @subsection What You Must Do for the Stub
20187 @cindex remote stub, support routines
20188 The debugging stubs that come with @value{GDBN} are set up for a particular
20189 chip architecture, but they have no information about the rest of your
20190 debugging target machine.
20192 First of all you need to tell the stub how to communicate with the
20196 @item int getDebugChar()
20197 @findex getDebugChar
20198 Write this subroutine to read a single character from the serial port.
20199 It may be identical to @code{getchar} for your target system; a
20200 different name is used to allow you to distinguish the two if you wish.
20202 @item void putDebugChar(int)
20203 @findex putDebugChar
20204 Write this subroutine to write a single character to the serial port.
20205 It may be identical to @code{putchar} for your target system; a
20206 different name is used to allow you to distinguish the two if you wish.
20209 @cindex control C, and remote debugging
20210 @cindex interrupting remote targets
20211 If you want @value{GDBN} to be able to stop your program while it is
20212 running, you need to use an interrupt-driven serial driver, and arrange
20213 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20214 character). That is the character which @value{GDBN} uses to tell the
20215 remote system to stop.
20217 Getting the debugging target to return the proper status to @value{GDBN}
20218 probably requires changes to the standard stub; one quick and dirty way
20219 is to just execute a breakpoint instruction (the ``dirty'' part is that
20220 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20222 Other routines you need to supply are:
20225 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20226 @findex exceptionHandler
20227 Write this function to install @var{exception_address} in the exception
20228 handling tables. You need to do this because the stub does not have any
20229 way of knowing what the exception handling tables on your target system
20230 are like (for example, the processor's table might be in @sc{rom},
20231 containing entries which point to a table in @sc{ram}).
20232 The @var{exception_number} specifies the exception which should be changed;
20233 its meaning is architecture-dependent (for example, different numbers
20234 might represent divide by zero, misaligned access, etc). When this
20235 exception occurs, control should be transferred directly to
20236 @var{exception_address}, and the processor state (stack, registers,
20237 and so on) should be just as it is when a processor exception occurs. So if
20238 you want to use a jump instruction to reach @var{exception_address}, it
20239 should be a simple jump, not a jump to subroutine.
20241 For the 386, @var{exception_address} should be installed as an interrupt
20242 gate so that interrupts are masked while the handler runs. The gate
20243 should be at privilege level 0 (the most privileged level). The
20244 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20245 help from @code{exceptionHandler}.
20247 @item void flush_i_cache()
20248 @findex flush_i_cache
20249 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20250 instruction cache, if any, on your target machine. If there is no
20251 instruction cache, this subroutine may be a no-op.
20253 On target machines that have instruction caches, @value{GDBN} requires this
20254 function to make certain that the state of your program is stable.
20258 You must also make sure this library routine is available:
20261 @item void *memset(void *, int, int)
20263 This is the standard library function @code{memset} that sets an area of
20264 memory to a known value. If you have one of the free versions of
20265 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20266 either obtain it from your hardware manufacturer, or write your own.
20269 If you do not use the GNU C compiler, you may need other standard
20270 library subroutines as well; this varies from one stub to another,
20271 but in general the stubs are likely to use any of the common library
20272 subroutines which @code{@value{NGCC}} generates as inline code.
20275 @node Debug Session
20276 @subsection Putting it All Together
20278 @cindex remote serial debugging summary
20279 In summary, when your program is ready to debug, you must follow these
20284 Make sure you have defined the supporting low-level routines
20285 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20287 @code{getDebugChar}, @code{putDebugChar},
20288 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20292 Insert these lines in your program's startup code, before the main
20293 procedure is called:
20300 On some machines, when a breakpoint trap is raised, the hardware
20301 automatically makes the PC point to the instruction after the
20302 breakpoint. If your machine doesn't do that, you may need to adjust
20303 @code{handle_exception} to arrange for it to return to the instruction
20304 after the breakpoint on this first invocation, so that your program
20305 doesn't keep hitting the initial breakpoint instead of making
20309 For the 680x0 stub only, you need to provide a variable called
20310 @code{exceptionHook}. Normally you just use:
20313 void (*exceptionHook)() = 0;
20317 but if before calling @code{set_debug_traps}, you set it to point to a
20318 function in your program, that function is called when
20319 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20320 error). The function indicated by @code{exceptionHook} is called with
20321 one parameter: an @code{int} which is the exception number.
20324 Compile and link together: your program, the @value{GDBN} debugging stub for
20325 your target architecture, and the supporting subroutines.
20328 Make sure you have a serial connection between your target machine and
20329 the @value{GDBN} host, and identify the serial port on the host.
20332 @c The "remote" target now provides a `load' command, so we should
20333 @c document that. FIXME.
20334 Download your program to your target machine (or get it there by
20335 whatever means the manufacturer provides), and start it.
20338 Start @value{GDBN} on the host, and connect to the target
20339 (@pxref{Connecting,,Connecting to a Remote Target}).
20343 @node Configurations
20344 @chapter Configuration-Specific Information
20346 While nearly all @value{GDBN} commands are available for all native and
20347 cross versions of the debugger, there are some exceptions. This chapter
20348 describes things that are only available in certain configurations.
20350 There are three major categories of configurations: native
20351 configurations, where the host and target are the same, embedded
20352 operating system configurations, which are usually the same for several
20353 different processor architectures, and bare embedded processors, which
20354 are quite different from each other.
20359 * Embedded Processors::
20366 This section describes details specific to particular native
20371 * BSD libkvm Interface:: Debugging BSD kernel memory images
20372 * SVR4 Process Information:: SVR4 process information
20373 * DJGPP Native:: Features specific to the DJGPP port
20374 * Cygwin Native:: Features specific to the Cygwin port
20375 * Hurd Native:: Features specific to @sc{gnu} Hurd
20376 * Darwin:: Features specific to Darwin
20382 On HP-UX systems, if you refer to a function or variable name that
20383 begins with a dollar sign, @value{GDBN} searches for a user or system
20384 name first, before it searches for a convenience variable.
20387 @node BSD libkvm Interface
20388 @subsection BSD libkvm Interface
20391 @cindex kernel memory image
20392 @cindex kernel crash dump
20394 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20395 interface that provides a uniform interface for accessing kernel virtual
20396 memory images, including live systems and crash dumps. @value{GDBN}
20397 uses this interface to allow you to debug live kernels and kernel crash
20398 dumps on many native BSD configurations. This is implemented as a
20399 special @code{kvm} debugging target. For debugging a live system, load
20400 the currently running kernel into @value{GDBN} and connect to the
20404 (@value{GDBP}) @b{target kvm}
20407 For debugging crash dumps, provide the file name of the crash dump as an
20411 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20414 Once connected to the @code{kvm} target, the following commands are
20420 Set current context from the @dfn{Process Control Block} (PCB) address.
20423 Set current context from proc address. This command isn't available on
20424 modern FreeBSD systems.
20427 @node SVR4 Process Information
20428 @subsection SVR4 Process Information
20430 @cindex examine process image
20431 @cindex process info via @file{/proc}
20433 Many versions of SVR4 and compatible systems provide a facility called
20434 @samp{/proc} that can be used to examine the image of a running
20435 process using file-system subroutines.
20437 If @value{GDBN} is configured for an operating system with this
20438 facility, the command @code{info proc} is available to report
20439 information about the process running your program, or about any
20440 process running on your system. This includes, as of this writing,
20441 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20443 This command may also work on core files that were created on a system
20444 that has the @samp{/proc} facility.
20450 @itemx info proc @var{process-id}
20451 Summarize available information about any running process. If a
20452 process ID is specified by @var{process-id}, display information about
20453 that process; otherwise display information about the program being
20454 debugged. The summary includes the debugged process ID, the command
20455 line used to invoke it, its current working directory, and its
20456 executable file's absolute file name.
20458 On some systems, @var{process-id} can be of the form
20459 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20460 within a process. If the optional @var{pid} part is missing, it means
20461 a thread from the process being debugged (the leading @samp{/} still
20462 needs to be present, or else @value{GDBN} will interpret the number as
20463 a process ID rather than a thread ID).
20465 @item info proc cmdline
20466 @cindex info proc cmdline
20467 Show the original command line of the process. This command is
20468 specific to @sc{gnu}/Linux.
20470 @item info proc cwd
20471 @cindex info proc cwd
20472 Show the current working directory of the process. This command is
20473 specific to @sc{gnu}/Linux.
20475 @item info proc exe
20476 @cindex info proc exe
20477 Show the name of executable of the process. This command is specific
20480 @item info proc mappings
20481 @cindex memory address space mappings
20482 Report the memory address space ranges accessible in the program, with
20483 information on whether the process has read, write, or execute access
20484 rights to each range. On @sc{gnu}/Linux systems, each memory range
20485 includes the object file which is mapped to that range, instead of the
20486 memory access rights to that range.
20488 @item info proc stat
20489 @itemx info proc status
20490 @cindex process detailed status information
20491 These subcommands are specific to @sc{gnu}/Linux systems. They show
20492 the process-related information, including the user ID and group ID;
20493 how many threads are there in the process; its virtual memory usage;
20494 the signals that are pending, blocked, and ignored; its TTY; its
20495 consumption of system and user time; its stack size; its @samp{nice}
20496 value; etc. For more information, see the @samp{proc} man page
20497 (type @kbd{man 5 proc} from your shell prompt).
20499 @item info proc all
20500 Show all the information about the process described under all of the
20501 above @code{info proc} subcommands.
20504 @comment These sub-options of 'info proc' were not included when
20505 @comment procfs.c was re-written. Keep their descriptions around
20506 @comment against the day when someone finds the time to put them back in.
20507 @kindex info proc times
20508 @item info proc times
20509 Starting time, user CPU time, and system CPU time for your program and
20512 @kindex info proc id
20514 Report on the process IDs related to your program: its own process ID,
20515 the ID of its parent, the process group ID, and the session ID.
20518 @item set procfs-trace
20519 @kindex set procfs-trace
20520 @cindex @code{procfs} API calls
20521 This command enables and disables tracing of @code{procfs} API calls.
20523 @item show procfs-trace
20524 @kindex show procfs-trace
20525 Show the current state of @code{procfs} API call tracing.
20527 @item set procfs-file @var{file}
20528 @kindex set procfs-file
20529 Tell @value{GDBN} to write @code{procfs} API trace to the named
20530 @var{file}. @value{GDBN} appends the trace info to the previous
20531 contents of the file. The default is to display the trace on the
20534 @item show procfs-file
20535 @kindex show procfs-file
20536 Show the file to which @code{procfs} API trace is written.
20538 @item proc-trace-entry
20539 @itemx proc-trace-exit
20540 @itemx proc-untrace-entry
20541 @itemx proc-untrace-exit
20542 @kindex proc-trace-entry
20543 @kindex proc-trace-exit
20544 @kindex proc-untrace-entry
20545 @kindex proc-untrace-exit
20546 These commands enable and disable tracing of entries into and exits
20547 from the @code{syscall} interface.
20550 @kindex info pidlist
20551 @cindex process list, QNX Neutrino
20552 For QNX Neutrino only, this command displays the list of all the
20553 processes and all the threads within each process.
20556 @kindex info meminfo
20557 @cindex mapinfo list, QNX Neutrino
20558 For QNX Neutrino only, this command displays the list of all mapinfos.
20562 @subsection Features for Debugging @sc{djgpp} Programs
20563 @cindex @sc{djgpp} debugging
20564 @cindex native @sc{djgpp} debugging
20565 @cindex MS-DOS-specific commands
20568 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20569 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20570 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20571 top of real-mode DOS systems and their emulations.
20573 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20574 defines a few commands specific to the @sc{djgpp} port. This
20575 subsection describes those commands.
20580 This is a prefix of @sc{djgpp}-specific commands which print
20581 information about the target system and important OS structures.
20584 @cindex MS-DOS system info
20585 @cindex free memory information (MS-DOS)
20586 @item info dos sysinfo
20587 This command displays assorted information about the underlying
20588 platform: the CPU type and features, the OS version and flavor, the
20589 DPMI version, and the available conventional and DPMI memory.
20594 @cindex segment descriptor tables
20595 @cindex descriptor tables display
20597 @itemx info dos ldt
20598 @itemx info dos idt
20599 These 3 commands display entries from, respectively, Global, Local,
20600 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20601 tables are data structures which store a descriptor for each segment
20602 that is currently in use. The segment's selector is an index into a
20603 descriptor table; the table entry for that index holds the
20604 descriptor's base address and limit, and its attributes and access
20607 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20608 segment (used for both data and the stack), and a DOS segment (which
20609 allows access to DOS/BIOS data structures and absolute addresses in
20610 conventional memory). However, the DPMI host will usually define
20611 additional segments in order to support the DPMI environment.
20613 @cindex garbled pointers
20614 These commands allow to display entries from the descriptor tables.
20615 Without an argument, all entries from the specified table are
20616 displayed. An argument, which should be an integer expression, means
20617 display a single entry whose index is given by the argument. For
20618 example, here's a convenient way to display information about the
20619 debugged program's data segment:
20622 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20623 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20627 This comes in handy when you want to see whether a pointer is outside
20628 the data segment's limit (i.e.@: @dfn{garbled}).
20630 @cindex page tables display (MS-DOS)
20632 @itemx info dos pte
20633 These two commands display entries from, respectively, the Page
20634 Directory and the Page Tables. Page Directories and Page Tables are
20635 data structures which control how virtual memory addresses are mapped
20636 into physical addresses. A Page Table includes an entry for every
20637 page of memory that is mapped into the program's address space; there
20638 may be several Page Tables, each one holding up to 4096 entries. A
20639 Page Directory has up to 4096 entries, one each for every Page Table
20640 that is currently in use.
20642 Without an argument, @kbd{info dos pde} displays the entire Page
20643 Directory, and @kbd{info dos pte} displays all the entries in all of
20644 the Page Tables. An argument, an integer expression, given to the
20645 @kbd{info dos pde} command means display only that entry from the Page
20646 Directory table. An argument given to the @kbd{info dos pte} command
20647 means display entries from a single Page Table, the one pointed to by
20648 the specified entry in the Page Directory.
20650 @cindex direct memory access (DMA) on MS-DOS
20651 These commands are useful when your program uses @dfn{DMA} (Direct
20652 Memory Access), which needs physical addresses to program the DMA
20655 These commands are supported only with some DPMI servers.
20657 @cindex physical address from linear address
20658 @item info dos address-pte @var{addr}
20659 This command displays the Page Table entry for a specified linear
20660 address. The argument @var{addr} is a linear address which should
20661 already have the appropriate segment's base address added to it,
20662 because this command accepts addresses which may belong to @emph{any}
20663 segment. For example, here's how to display the Page Table entry for
20664 the page where a variable @code{i} is stored:
20667 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20668 @exdent @code{Page Table entry for address 0x11a00d30:}
20669 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20673 This says that @code{i} is stored at offset @code{0xd30} from the page
20674 whose physical base address is @code{0x02698000}, and shows all the
20675 attributes of that page.
20677 Note that you must cast the addresses of variables to a @code{char *},
20678 since otherwise the value of @code{__djgpp_base_address}, the base
20679 address of all variables and functions in a @sc{djgpp} program, will
20680 be added using the rules of C pointer arithmetics: if @code{i} is
20681 declared an @code{int}, @value{GDBN} will add 4 times the value of
20682 @code{__djgpp_base_address} to the address of @code{i}.
20684 Here's another example, it displays the Page Table entry for the
20688 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20689 @exdent @code{Page Table entry for address 0x29110:}
20690 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20694 (The @code{+ 3} offset is because the transfer buffer's address is the
20695 3rd member of the @code{_go32_info_block} structure.) The output
20696 clearly shows that this DPMI server maps the addresses in conventional
20697 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20698 linear (@code{0x29110}) addresses are identical.
20700 This command is supported only with some DPMI servers.
20703 @cindex DOS serial data link, remote debugging
20704 In addition to native debugging, the DJGPP port supports remote
20705 debugging via a serial data link. The following commands are specific
20706 to remote serial debugging in the DJGPP port of @value{GDBN}.
20709 @kindex set com1base
20710 @kindex set com1irq
20711 @kindex set com2base
20712 @kindex set com2irq
20713 @kindex set com3base
20714 @kindex set com3irq
20715 @kindex set com4base
20716 @kindex set com4irq
20717 @item set com1base @var{addr}
20718 This command sets the base I/O port address of the @file{COM1} serial
20721 @item set com1irq @var{irq}
20722 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20723 for the @file{COM1} serial port.
20725 There are similar commands @samp{set com2base}, @samp{set com3irq},
20726 etc.@: for setting the port address and the @code{IRQ} lines for the
20729 @kindex show com1base
20730 @kindex show com1irq
20731 @kindex show com2base
20732 @kindex show com2irq
20733 @kindex show com3base
20734 @kindex show com3irq
20735 @kindex show com4base
20736 @kindex show com4irq
20737 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20738 display the current settings of the base address and the @code{IRQ}
20739 lines used by the COM ports.
20742 @kindex info serial
20743 @cindex DOS serial port status
20744 This command prints the status of the 4 DOS serial ports. For each
20745 port, it prints whether it's active or not, its I/O base address and
20746 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20747 counts of various errors encountered so far.
20751 @node Cygwin Native
20752 @subsection Features for Debugging MS Windows PE Executables
20753 @cindex MS Windows debugging
20754 @cindex native Cygwin debugging
20755 @cindex Cygwin-specific commands
20757 @value{GDBN} supports native debugging of MS Windows programs, including
20758 DLLs with and without symbolic debugging information.
20760 @cindex Ctrl-BREAK, MS-Windows
20761 @cindex interrupt debuggee on MS-Windows
20762 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20763 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20764 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20765 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20766 sequence, which can be used to interrupt the debuggee even if it
20769 There are various additional Cygwin-specific commands, described in
20770 this section. Working with DLLs that have no debugging symbols is
20771 described in @ref{Non-debug DLL Symbols}.
20776 This is a prefix of MS Windows-specific commands which print
20777 information about the target system and important OS structures.
20779 @item info w32 selector
20780 This command displays information returned by
20781 the Win32 API @code{GetThreadSelectorEntry} function.
20782 It takes an optional argument that is evaluated to
20783 a long value to give the information about this given selector.
20784 Without argument, this command displays information
20785 about the six segment registers.
20787 @item info w32 thread-information-block
20788 This command displays thread specific information stored in the
20789 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20790 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20792 @kindex set cygwin-exceptions
20793 @cindex debugging the Cygwin DLL
20794 @cindex Cygwin DLL, debugging
20795 @item set cygwin-exceptions @var{mode}
20796 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20797 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20798 @value{GDBN} will delay recognition of exceptions, and may ignore some
20799 exceptions which seem to be caused by internal Cygwin DLL
20800 ``bookkeeping''. This option is meant primarily for debugging the
20801 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20802 @value{GDBN} users with false @code{SIGSEGV} signals.
20804 @kindex show cygwin-exceptions
20805 @item show cygwin-exceptions
20806 Displays whether @value{GDBN} will break on exceptions that happen
20807 inside the Cygwin DLL itself.
20809 @kindex set new-console
20810 @item set new-console @var{mode}
20811 If @var{mode} is @code{on} the debuggee will
20812 be started in a new console on next start.
20813 If @var{mode} is @code{off}, the debuggee will
20814 be started in the same console as the debugger.
20816 @kindex show new-console
20817 @item show new-console
20818 Displays whether a new console is used
20819 when the debuggee is started.
20821 @kindex set new-group
20822 @item set new-group @var{mode}
20823 This boolean value controls whether the debuggee should
20824 start a new group or stay in the same group as the debugger.
20825 This affects the way the Windows OS handles
20828 @kindex show new-group
20829 @item show new-group
20830 Displays current value of new-group boolean.
20832 @kindex set debugevents
20833 @item set debugevents
20834 This boolean value adds debug output concerning kernel events related
20835 to the debuggee seen by the debugger. This includes events that
20836 signal thread and process creation and exit, DLL loading and
20837 unloading, console interrupts, and debugging messages produced by the
20838 Windows @code{OutputDebugString} API call.
20840 @kindex set debugexec
20841 @item set debugexec
20842 This boolean value adds debug output concerning execute events
20843 (such as resume thread) seen by the debugger.
20845 @kindex set debugexceptions
20846 @item set debugexceptions
20847 This boolean value adds debug output concerning exceptions in the
20848 debuggee seen by the debugger.
20850 @kindex set debugmemory
20851 @item set debugmemory
20852 This boolean value adds debug output concerning debuggee memory reads
20853 and writes by the debugger.
20857 This boolean values specifies whether the debuggee is called
20858 via a shell or directly (default value is on).
20862 Displays if the debuggee will be started with a shell.
20867 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20870 @node Non-debug DLL Symbols
20871 @subsubsection Support for DLLs without Debugging Symbols
20872 @cindex DLLs with no debugging symbols
20873 @cindex Minimal symbols and DLLs
20875 Very often on windows, some of the DLLs that your program relies on do
20876 not include symbolic debugging information (for example,
20877 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20878 symbols in a DLL, it relies on the minimal amount of symbolic
20879 information contained in the DLL's export table. This section
20880 describes working with such symbols, known internally to @value{GDBN} as
20881 ``minimal symbols''.
20883 Note that before the debugged program has started execution, no DLLs
20884 will have been loaded. The easiest way around this problem is simply to
20885 start the program --- either by setting a breakpoint or letting the
20886 program run once to completion.
20888 @subsubsection DLL Name Prefixes
20890 In keeping with the naming conventions used by the Microsoft debugging
20891 tools, DLL export symbols are made available with a prefix based on the
20892 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20893 also entered into the symbol table, so @code{CreateFileA} is often
20894 sufficient. In some cases there will be name clashes within a program
20895 (particularly if the executable itself includes full debugging symbols)
20896 necessitating the use of the fully qualified name when referring to the
20897 contents of the DLL. Use single-quotes around the name to avoid the
20898 exclamation mark (``!'') being interpreted as a language operator.
20900 Note that the internal name of the DLL may be all upper-case, even
20901 though the file name of the DLL is lower-case, or vice-versa. Since
20902 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20903 some confusion. If in doubt, try the @code{info functions} and
20904 @code{info variables} commands or even @code{maint print msymbols}
20905 (@pxref{Symbols}). Here's an example:
20908 (@value{GDBP}) info function CreateFileA
20909 All functions matching regular expression "CreateFileA":
20911 Non-debugging symbols:
20912 0x77e885f4 CreateFileA
20913 0x77e885f4 KERNEL32!CreateFileA
20917 (@value{GDBP}) info function !
20918 All functions matching regular expression "!":
20920 Non-debugging symbols:
20921 0x6100114c cygwin1!__assert
20922 0x61004034 cygwin1!_dll_crt0@@0
20923 0x61004240 cygwin1!dll_crt0(per_process *)
20927 @subsubsection Working with Minimal Symbols
20929 Symbols extracted from a DLL's export table do not contain very much
20930 type information. All that @value{GDBN} can do is guess whether a symbol
20931 refers to a function or variable depending on the linker section that
20932 contains the symbol. Also note that the actual contents of the memory
20933 contained in a DLL are not available unless the program is running. This
20934 means that you cannot examine the contents of a variable or disassemble
20935 a function within a DLL without a running program.
20937 Variables are generally treated as pointers and dereferenced
20938 automatically. For this reason, it is often necessary to prefix a
20939 variable name with the address-of operator (``&'') and provide explicit
20940 type information in the command. Here's an example of the type of
20944 (@value{GDBP}) print 'cygwin1!__argv'
20949 (@value{GDBP}) x 'cygwin1!__argv'
20950 0x10021610: "\230y\""
20953 And two possible solutions:
20956 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20957 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20961 (@value{GDBP}) x/2x &'cygwin1!__argv'
20962 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20963 (@value{GDBP}) x/x 0x10021608
20964 0x10021608: 0x0022fd98
20965 (@value{GDBP}) x/s 0x0022fd98
20966 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20969 Setting a break point within a DLL is possible even before the program
20970 starts execution. However, under these circumstances, @value{GDBN} can't
20971 examine the initial instructions of the function in order to skip the
20972 function's frame set-up code. You can work around this by using ``*&''
20973 to set the breakpoint at a raw memory address:
20976 (@value{GDBP}) break *&'python22!PyOS_Readline'
20977 Breakpoint 1 at 0x1e04eff0
20980 The author of these extensions is not entirely convinced that setting a
20981 break point within a shared DLL like @file{kernel32.dll} is completely
20985 @subsection Commands Specific to @sc{gnu} Hurd Systems
20986 @cindex @sc{gnu} Hurd debugging
20988 This subsection describes @value{GDBN} commands specific to the
20989 @sc{gnu} Hurd native debugging.
20994 @kindex set signals@r{, Hurd command}
20995 @kindex set sigs@r{, Hurd command}
20996 This command toggles the state of inferior signal interception by
20997 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20998 affected by this command. @code{sigs} is a shorthand alias for
21003 @kindex show signals@r{, Hurd command}
21004 @kindex show sigs@r{, Hurd command}
21005 Show the current state of intercepting inferior's signals.
21007 @item set signal-thread
21008 @itemx set sigthread
21009 @kindex set signal-thread
21010 @kindex set sigthread
21011 This command tells @value{GDBN} which thread is the @code{libc} signal
21012 thread. That thread is run when a signal is delivered to a running
21013 process. @code{set sigthread} is the shorthand alias of @code{set
21016 @item show signal-thread
21017 @itemx show sigthread
21018 @kindex show signal-thread
21019 @kindex show sigthread
21020 These two commands show which thread will run when the inferior is
21021 delivered a signal.
21024 @kindex set stopped@r{, Hurd command}
21025 This commands tells @value{GDBN} that the inferior process is stopped,
21026 as with the @code{SIGSTOP} signal. The stopped process can be
21027 continued by delivering a signal to it.
21030 @kindex show stopped@r{, Hurd command}
21031 This command shows whether @value{GDBN} thinks the debuggee is
21034 @item set exceptions
21035 @kindex set exceptions@r{, Hurd command}
21036 Use this command to turn off trapping of exceptions in the inferior.
21037 When exception trapping is off, neither breakpoints nor
21038 single-stepping will work. To restore the default, set exception
21041 @item show exceptions
21042 @kindex show exceptions@r{, Hurd command}
21043 Show the current state of trapping exceptions in the inferior.
21045 @item set task pause
21046 @kindex set task@r{, Hurd commands}
21047 @cindex task attributes (@sc{gnu} Hurd)
21048 @cindex pause current task (@sc{gnu} Hurd)
21049 This command toggles task suspension when @value{GDBN} has control.
21050 Setting it to on takes effect immediately, and the task is suspended
21051 whenever @value{GDBN} gets control. Setting it to off will take
21052 effect the next time the inferior is continued. If this option is set
21053 to off, you can use @code{set thread default pause on} or @code{set
21054 thread pause on} (see below) to pause individual threads.
21056 @item show task pause
21057 @kindex show task@r{, Hurd commands}
21058 Show the current state of task suspension.
21060 @item set task detach-suspend-count
21061 @cindex task suspend count
21062 @cindex detach from task, @sc{gnu} Hurd
21063 This command sets the suspend count the task will be left with when
21064 @value{GDBN} detaches from it.
21066 @item show task detach-suspend-count
21067 Show the suspend count the task will be left with when detaching.
21069 @item set task exception-port
21070 @itemx set task excp
21071 @cindex task exception port, @sc{gnu} Hurd
21072 This command sets the task exception port to which @value{GDBN} will
21073 forward exceptions. The argument should be the value of the @dfn{send
21074 rights} of the task. @code{set task excp} is a shorthand alias.
21076 @item set noninvasive
21077 @cindex noninvasive task options
21078 This command switches @value{GDBN} to a mode that is the least
21079 invasive as far as interfering with the inferior is concerned. This
21080 is the same as using @code{set task pause}, @code{set exceptions}, and
21081 @code{set signals} to values opposite to the defaults.
21083 @item info send-rights
21084 @itemx info receive-rights
21085 @itemx info port-rights
21086 @itemx info port-sets
21087 @itemx info dead-names
21090 @cindex send rights, @sc{gnu} Hurd
21091 @cindex receive rights, @sc{gnu} Hurd
21092 @cindex port rights, @sc{gnu} Hurd
21093 @cindex port sets, @sc{gnu} Hurd
21094 @cindex dead names, @sc{gnu} Hurd
21095 These commands display information about, respectively, send rights,
21096 receive rights, port rights, port sets, and dead names of a task.
21097 There are also shorthand aliases: @code{info ports} for @code{info
21098 port-rights} and @code{info psets} for @code{info port-sets}.
21100 @item set thread pause
21101 @kindex set thread@r{, Hurd command}
21102 @cindex thread properties, @sc{gnu} Hurd
21103 @cindex pause current thread (@sc{gnu} Hurd)
21104 This command toggles current thread suspension when @value{GDBN} has
21105 control. Setting it to on takes effect immediately, and the current
21106 thread is suspended whenever @value{GDBN} gets control. Setting it to
21107 off will take effect the next time the inferior is continued.
21108 Normally, this command has no effect, since when @value{GDBN} has
21109 control, the whole task is suspended. However, if you used @code{set
21110 task pause off} (see above), this command comes in handy to suspend
21111 only the current thread.
21113 @item show thread pause
21114 @kindex show thread@r{, Hurd command}
21115 This command shows the state of current thread suspension.
21117 @item set thread run
21118 This command sets whether the current thread is allowed to run.
21120 @item show thread run
21121 Show whether the current thread is allowed to run.
21123 @item set thread detach-suspend-count
21124 @cindex thread suspend count, @sc{gnu} Hurd
21125 @cindex detach from thread, @sc{gnu} Hurd
21126 This command sets the suspend count @value{GDBN} will leave on a
21127 thread when detaching. This number is relative to the suspend count
21128 found by @value{GDBN} when it notices the thread; use @code{set thread
21129 takeover-suspend-count} to force it to an absolute value.
21131 @item show thread detach-suspend-count
21132 Show the suspend count @value{GDBN} will leave on the thread when
21135 @item set thread exception-port
21136 @itemx set thread excp
21137 Set the thread exception port to which to forward exceptions. This
21138 overrides the port set by @code{set task exception-port} (see above).
21139 @code{set thread excp} is the shorthand alias.
21141 @item set thread takeover-suspend-count
21142 Normally, @value{GDBN}'s thread suspend counts are relative to the
21143 value @value{GDBN} finds when it notices each thread. This command
21144 changes the suspend counts to be absolute instead.
21146 @item set thread default
21147 @itemx show thread default
21148 @cindex thread default settings, @sc{gnu} Hurd
21149 Each of the above @code{set thread} commands has a @code{set thread
21150 default} counterpart (e.g., @code{set thread default pause}, @code{set
21151 thread default exception-port}, etc.). The @code{thread default}
21152 variety of commands sets the default thread properties for all
21153 threads; you can then change the properties of individual threads with
21154 the non-default commands.
21161 @value{GDBN} provides the following commands specific to the Darwin target:
21164 @item set debug darwin @var{num}
21165 @kindex set debug darwin
21166 When set to a non zero value, enables debugging messages specific to
21167 the Darwin support. Higher values produce more verbose output.
21169 @item show debug darwin
21170 @kindex show debug darwin
21171 Show the current state of Darwin messages.
21173 @item set debug mach-o @var{num}
21174 @kindex set debug mach-o
21175 When set to a non zero value, enables debugging messages while
21176 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21177 file format used on Darwin for object and executable files.) Higher
21178 values produce more verbose output. This is a command to diagnose
21179 problems internal to @value{GDBN} and should not be needed in normal
21182 @item show debug mach-o
21183 @kindex show debug mach-o
21184 Show the current state of Mach-O file messages.
21186 @item set mach-exceptions on
21187 @itemx set mach-exceptions off
21188 @kindex set mach-exceptions
21189 On Darwin, faults are first reported as a Mach exception and are then
21190 mapped to a Posix signal. Use this command to turn on trapping of
21191 Mach exceptions in the inferior. This might be sometimes useful to
21192 better understand the cause of a fault. The default is off.
21194 @item show mach-exceptions
21195 @kindex show mach-exceptions
21196 Show the current state of exceptions trapping.
21201 @section Embedded Operating Systems
21203 This section describes configurations involving the debugging of
21204 embedded operating systems that are available for several different
21207 @value{GDBN} includes the ability to debug programs running on
21208 various real-time operating systems.
21210 @node Embedded Processors
21211 @section Embedded Processors
21213 This section goes into details specific to particular embedded
21216 @cindex send command to simulator
21217 Whenever a specific embedded processor has a simulator, @value{GDBN}
21218 allows to send an arbitrary command to the simulator.
21221 @item sim @var{command}
21222 @kindex sim@r{, a command}
21223 Send an arbitrary @var{command} string to the simulator. Consult the
21224 documentation for the specific simulator in use for information about
21225 acceptable commands.
21231 * M32R/D:: Renesas M32R/D
21232 * M68K:: Motorola M68K
21233 * MicroBlaze:: Xilinx MicroBlaze
21234 * MIPS Embedded:: MIPS Embedded
21235 * PowerPC Embedded:: PowerPC Embedded
21236 * PA:: HP PA Embedded
21237 * Sparclet:: Tsqware Sparclet
21238 * Sparclite:: Fujitsu Sparclite
21239 * Z8000:: Zilog Z8000
21242 * Super-H:: Renesas Super-H
21251 @item target rdi @var{dev}
21252 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21253 use this target to communicate with both boards running the Angel
21254 monitor, or with the EmbeddedICE JTAG debug device.
21257 @item target rdp @var{dev}
21262 @value{GDBN} provides the following ARM-specific commands:
21265 @item set arm disassembler
21267 This commands selects from a list of disassembly styles. The
21268 @code{"std"} style is the standard style.
21270 @item show arm disassembler
21272 Show the current disassembly style.
21274 @item set arm apcs32
21275 @cindex ARM 32-bit mode
21276 This command toggles ARM operation mode between 32-bit and 26-bit.
21278 @item show arm apcs32
21279 Display the current usage of the ARM 32-bit mode.
21281 @item set arm fpu @var{fputype}
21282 This command sets the ARM floating-point unit (FPU) type. The
21283 argument @var{fputype} can be one of these:
21287 Determine the FPU type by querying the OS ABI.
21289 Software FPU, with mixed-endian doubles on little-endian ARM
21292 GCC-compiled FPA co-processor.
21294 Software FPU with pure-endian doubles.
21300 Show the current type of the FPU.
21303 This command forces @value{GDBN} to use the specified ABI.
21306 Show the currently used ABI.
21308 @item set arm fallback-mode (arm|thumb|auto)
21309 @value{GDBN} uses the symbol table, when available, to determine
21310 whether instructions are ARM or Thumb. This command controls
21311 @value{GDBN}'s default behavior when the symbol table is not
21312 available. The default is @samp{auto}, which causes @value{GDBN} to
21313 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21316 @item show arm fallback-mode
21317 Show the current fallback instruction mode.
21319 @item set arm force-mode (arm|thumb|auto)
21320 This command overrides use of the symbol table to determine whether
21321 instructions are ARM or Thumb. The default is @samp{auto}, which
21322 causes @value{GDBN} to use the symbol table and then the setting
21323 of @samp{set arm fallback-mode}.
21325 @item show arm force-mode
21326 Show the current forced instruction mode.
21328 @item set debug arm
21329 Toggle whether to display ARM-specific debugging messages from the ARM
21330 target support subsystem.
21332 @item show debug arm
21333 Show whether ARM-specific debugging messages are enabled.
21336 The following commands are available when an ARM target is debugged
21337 using the RDI interface:
21340 @item rdilogfile @r{[}@var{file}@r{]}
21342 @cindex ADP (Angel Debugger Protocol) logging
21343 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21344 With an argument, sets the log file to the specified @var{file}. With
21345 no argument, show the current log file name. The default log file is
21348 @item rdilogenable @r{[}@var{arg}@r{]}
21349 @kindex rdilogenable
21350 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21351 enables logging, with an argument 0 or @code{"no"} disables it. With
21352 no arguments displays the current setting. When logging is enabled,
21353 ADP packets exchanged between @value{GDBN} and the RDI target device
21354 are logged to a file.
21356 @item set rdiromatzero
21357 @kindex set rdiromatzero
21358 @cindex ROM at zero address, RDI
21359 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21360 vector catching is disabled, so that zero address can be used. If off
21361 (the default), vector catching is enabled. For this command to take
21362 effect, it needs to be invoked prior to the @code{target rdi} command.
21364 @item show rdiromatzero
21365 @kindex show rdiromatzero
21366 Show the current setting of ROM at zero address.
21368 @item set rdiheartbeat
21369 @kindex set rdiheartbeat
21370 @cindex RDI heartbeat
21371 Enable or disable RDI heartbeat packets. It is not recommended to
21372 turn on this option, since it confuses ARM and EPI JTAG interface, as
21373 well as the Angel monitor.
21375 @item show rdiheartbeat
21376 @kindex show rdiheartbeat
21377 Show the setting of RDI heartbeat packets.
21381 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21382 The @value{GDBN} ARM simulator accepts the following optional arguments.
21385 @item --swi-support=@var{type}
21386 Tell the simulator which SWI interfaces to support. The argument
21387 @var{type} may be a comma separated list of the following values.
21388 The default value is @code{all}.
21401 @subsection Renesas M32R/D and M32R/SDI
21404 @kindex target m32r
21405 @item target m32r @var{dev}
21406 Renesas M32R/D ROM monitor.
21408 @kindex target m32rsdi
21409 @item target m32rsdi @var{dev}
21410 Renesas M32R SDI server, connected via parallel port to the board.
21413 The following @value{GDBN} commands are specific to the M32R monitor:
21416 @item set download-path @var{path}
21417 @kindex set download-path
21418 @cindex find downloadable @sc{srec} files (M32R)
21419 Set the default path for finding downloadable @sc{srec} files.
21421 @item show download-path
21422 @kindex show download-path
21423 Show the default path for downloadable @sc{srec} files.
21425 @item set board-address @var{addr}
21426 @kindex set board-address
21427 @cindex M32-EVA target board address
21428 Set the IP address for the M32R-EVA target board.
21430 @item show board-address
21431 @kindex show board-address
21432 Show the current IP address of the target board.
21434 @item set server-address @var{addr}
21435 @kindex set server-address
21436 @cindex download server address (M32R)
21437 Set the IP address for the download server, which is the @value{GDBN}'s
21440 @item show server-address
21441 @kindex show server-address
21442 Display the IP address of the download server.
21444 @item upload @r{[}@var{file}@r{]}
21445 @kindex upload@r{, M32R}
21446 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21447 upload capability. If no @var{file} argument is given, the current
21448 executable file is uploaded.
21450 @item tload @r{[}@var{file}@r{]}
21451 @kindex tload@r{, M32R}
21452 Test the @code{upload} command.
21455 The following commands are available for M32R/SDI:
21460 @cindex reset SDI connection, M32R
21461 This command resets the SDI connection.
21465 This command shows the SDI connection status.
21468 @kindex debug_chaos
21469 @cindex M32R/Chaos debugging
21470 Instructs the remote that M32R/Chaos debugging is to be used.
21472 @item use_debug_dma
21473 @kindex use_debug_dma
21474 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21477 @kindex use_mon_code
21478 Instructs the remote to use the MON_CODE method of accessing memory.
21481 @kindex use_ib_break
21482 Instructs the remote to set breakpoints by IB break.
21484 @item use_dbt_break
21485 @kindex use_dbt_break
21486 Instructs the remote to set breakpoints by DBT.
21492 The Motorola m68k configuration includes ColdFire support, and a
21493 target command for the following ROM monitor.
21497 @kindex target dbug
21498 @item target dbug @var{dev}
21499 dBUG ROM monitor for Motorola ColdFire.
21504 @subsection MicroBlaze
21505 @cindex Xilinx MicroBlaze
21506 @cindex XMD, Xilinx Microprocessor Debugger
21508 The MicroBlaze is a soft-core processor supported on various Xilinx
21509 FPGAs, such as Spartan or Virtex series. Boards with these processors
21510 usually have JTAG ports which connect to a host system running the Xilinx
21511 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21512 This host system is used to download the configuration bitstream to
21513 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21514 communicates with the target board using the JTAG interface and
21515 presents a @code{gdbserver} interface to the board. By default
21516 @code{xmd} uses port @code{1234}. (While it is possible to change
21517 this default port, it requires the use of undocumented @code{xmd}
21518 commands. Contact Xilinx support if you need to do this.)
21520 Use these GDB commands to connect to the MicroBlaze target processor.
21523 @item target remote :1234
21524 Use this command to connect to the target if you are running @value{GDBN}
21525 on the same system as @code{xmd}.
21527 @item target remote @var{xmd-host}:1234
21528 Use this command to connect to the target if it is connected to @code{xmd}
21529 running on a different system named @var{xmd-host}.
21532 Use this command to download a program to the MicroBlaze target.
21534 @item set debug microblaze @var{n}
21535 Enable MicroBlaze-specific debugging messages if non-zero.
21537 @item show debug microblaze @var{n}
21538 Show MicroBlaze-specific debugging level.
21541 @node MIPS Embedded
21542 @subsection @acronym{MIPS} Embedded
21544 @cindex @acronym{MIPS} boards
21545 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21546 @acronym{MIPS} board attached to a serial line. This is available when
21547 you configure @value{GDBN} with @samp{--target=mips-elf}.
21550 Use these @value{GDBN} commands to specify the connection to your target board:
21553 @item target mips @var{port}
21554 @kindex target mips @var{port}
21555 To run a program on the board, start up @code{@value{GDBP}} with the
21556 name of your program as the argument. To connect to the board, use the
21557 command @samp{target mips @var{port}}, where @var{port} is the name of
21558 the serial port connected to the board. If the program has not already
21559 been downloaded to the board, you may use the @code{load} command to
21560 download it. You can then use all the usual @value{GDBN} commands.
21562 For example, this sequence connects to the target board through a serial
21563 port, and loads and runs a program called @var{prog} through the
21567 host$ @value{GDBP} @var{prog}
21568 @value{GDBN} is free software and @dots{}
21569 (@value{GDBP}) target mips /dev/ttyb
21570 (@value{GDBP}) load @var{prog}
21574 @item target mips @var{hostname}:@var{portnumber}
21575 On some @value{GDBN} host configurations, you can specify a TCP
21576 connection (for instance, to a serial line managed by a terminal
21577 concentrator) instead of a serial port, using the syntax
21578 @samp{@var{hostname}:@var{portnumber}}.
21580 @item target pmon @var{port}
21581 @kindex target pmon @var{port}
21584 @item target ddb @var{port}
21585 @kindex target ddb @var{port}
21586 NEC's DDB variant of PMON for Vr4300.
21588 @item target lsi @var{port}
21589 @kindex target lsi @var{port}
21590 LSI variant of PMON.
21592 @kindex target r3900
21593 @item target r3900 @var{dev}
21594 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21596 @kindex target array
21597 @item target array @var{dev}
21598 Array Tech LSI33K RAID controller board.
21604 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21607 @item set mipsfpu double
21608 @itemx set mipsfpu single
21609 @itemx set mipsfpu none
21610 @itemx set mipsfpu auto
21611 @itemx show mipsfpu
21612 @kindex set mipsfpu
21613 @kindex show mipsfpu
21614 @cindex @acronym{MIPS} remote floating point
21615 @cindex floating point, @acronym{MIPS} remote
21616 If your target board does not support the @acronym{MIPS} floating point
21617 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21618 need this, you may wish to put the command in your @value{GDBN} init
21619 file). This tells @value{GDBN} how to find the return value of
21620 functions which return floating point values. It also allows
21621 @value{GDBN} to avoid saving the floating point registers when calling
21622 functions on the board. If you are using a floating point coprocessor
21623 with only single precision floating point support, as on the @sc{r4650}
21624 processor, use the command @samp{set mipsfpu single}. The default
21625 double precision floating point coprocessor may be selected using
21626 @samp{set mipsfpu double}.
21628 In previous versions the only choices were double precision or no
21629 floating point, so @samp{set mipsfpu on} will select double precision
21630 and @samp{set mipsfpu off} will select no floating point.
21632 As usual, you can inquire about the @code{mipsfpu} variable with
21633 @samp{show mipsfpu}.
21635 @item set timeout @var{seconds}
21636 @itemx set retransmit-timeout @var{seconds}
21637 @itemx show timeout
21638 @itemx show retransmit-timeout
21639 @cindex @code{timeout}, @acronym{MIPS} protocol
21640 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21641 @kindex set timeout
21642 @kindex show timeout
21643 @kindex set retransmit-timeout
21644 @kindex show retransmit-timeout
21645 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21646 remote protocol, with the @code{set timeout @var{seconds}} command. The
21647 default is 5 seconds. Similarly, you can control the timeout used while
21648 waiting for an acknowledgment of a packet with the @code{set
21649 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21650 You can inspect both values with @code{show timeout} and @code{show
21651 retransmit-timeout}. (These commands are @emph{only} available when
21652 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21654 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21655 is waiting for your program to stop. In that case, @value{GDBN} waits
21656 forever because it has no way of knowing how long the program is going
21657 to run before stopping.
21659 @item set syn-garbage-limit @var{num}
21660 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21661 @cindex synchronize with remote @acronym{MIPS} target
21662 Limit the maximum number of characters @value{GDBN} should ignore when
21663 it tries to synchronize with the remote target. The default is 10
21664 characters. Setting the limit to -1 means there's no limit.
21666 @item show syn-garbage-limit
21667 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21668 Show the current limit on the number of characters to ignore when
21669 trying to synchronize with the remote system.
21671 @item set monitor-prompt @var{prompt}
21672 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21673 @cindex remote monitor prompt
21674 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21675 remote monitor. The default depends on the target:
21685 @item show monitor-prompt
21686 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21687 Show the current strings @value{GDBN} expects as the prompt from the
21690 @item set monitor-warnings
21691 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21692 Enable or disable monitor warnings about hardware breakpoints. This
21693 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21694 display warning messages whose codes are returned by the @code{lsi}
21695 PMON monitor for breakpoint commands.
21697 @item show monitor-warnings
21698 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21699 Show the current setting of printing monitor warnings.
21701 @item pmon @var{command}
21702 @kindex pmon@r{, @acronym{MIPS} remote}
21703 @cindex send PMON command
21704 This command allows sending an arbitrary @var{command} string to the
21705 monitor. The monitor must be in debug mode for this to work.
21708 @node PowerPC Embedded
21709 @subsection PowerPC Embedded
21711 @cindex DVC register
21712 @value{GDBN} supports using the DVC (Data Value Compare) register to
21713 implement in hardware simple hardware watchpoint conditions of the form:
21716 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21717 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21720 The DVC register will be automatically used when @value{GDBN} detects
21721 such pattern in a condition expression, and the created watchpoint uses one
21722 debug register (either the @code{exact-watchpoints} option is on and the
21723 variable is scalar, or the variable has a length of one byte). This feature
21724 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21727 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21728 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21729 in which case watchpoints using only one debug register are created when
21730 watching variables of scalar types.
21732 You can create an artificial array to watch an arbitrary memory
21733 region using one of the following commands (@pxref{Expressions}):
21736 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21737 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21740 PowerPC embedded processors support masked watchpoints. See the discussion
21741 about the @code{mask} argument in @ref{Set Watchpoints}.
21743 @cindex ranged breakpoint
21744 PowerPC embedded processors support hardware accelerated
21745 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21746 the inferior whenever it executes an instruction at any address within
21747 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21748 use the @code{break-range} command.
21750 @value{GDBN} provides the following PowerPC-specific commands:
21753 @kindex break-range
21754 @item break-range @var{start-location}, @var{end-location}
21755 Set a breakpoint for an address range given by
21756 @var{start-location} and @var{end-location}, which can specify a function name,
21757 a line number, an offset of lines from the current line or from the start
21758 location, or an address of an instruction (see @ref{Specify Location},
21759 for a list of all the possible ways to specify a @var{location}.)
21760 The breakpoint will stop execution of the inferior whenever it
21761 executes an instruction at any address within the specified range,
21762 (including @var{start-location} and @var{end-location}.)
21764 @kindex set powerpc
21765 @item set powerpc soft-float
21766 @itemx show powerpc soft-float
21767 Force @value{GDBN} to use (or not use) a software floating point calling
21768 convention. By default, @value{GDBN} selects the calling convention based
21769 on the selected architecture and the provided executable file.
21771 @item set powerpc vector-abi
21772 @itemx show powerpc vector-abi
21773 Force @value{GDBN} to use the specified calling convention for vector
21774 arguments and return values. The valid options are @samp{auto};
21775 @samp{generic}, to avoid vector registers even if they are present;
21776 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21777 registers. By default, @value{GDBN} selects the calling convention
21778 based on the selected architecture and the provided executable file.
21780 @item set powerpc exact-watchpoints
21781 @itemx show powerpc exact-watchpoints
21782 Allow @value{GDBN} to use only one debug register when watching a variable
21783 of scalar type, thus assuming that the variable is accessed through the
21784 address of its first byte.
21786 @kindex target dink32
21787 @item target dink32 @var{dev}
21788 DINK32 ROM monitor.
21790 @kindex target ppcbug
21791 @item target ppcbug @var{dev}
21792 @kindex target ppcbug1
21793 @item target ppcbug1 @var{dev}
21794 PPCBUG ROM monitor for PowerPC.
21797 @item target sds @var{dev}
21798 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21801 @cindex SDS protocol
21802 The following commands specific to the SDS protocol are supported
21806 @item set sdstimeout @var{nsec}
21807 @kindex set sdstimeout
21808 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21809 default is 2 seconds.
21811 @item show sdstimeout
21812 @kindex show sdstimeout
21813 Show the current value of the SDS timeout.
21815 @item sds @var{command}
21816 @kindex sds@r{, a command}
21817 Send the specified @var{command} string to the SDS monitor.
21822 @subsection HP PA Embedded
21826 @kindex target op50n
21827 @item target op50n @var{dev}
21828 OP50N monitor, running on an OKI HPPA board.
21830 @kindex target w89k
21831 @item target w89k @var{dev}
21832 W89K monitor, running on a Winbond HPPA board.
21837 @subsection Tsqware Sparclet
21841 @value{GDBN} enables developers to debug tasks running on
21842 Sparclet targets from a Unix host.
21843 @value{GDBN} uses code that runs on
21844 both the Unix host and on the Sparclet target. The program
21845 @code{@value{GDBP}} is installed and executed on the Unix host.
21848 @item remotetimeout @var{args}
21849 @kindex remotetimeout
21850 @value{GDBN} supports the option @code{remotetimeout}.
21851 This option is set by the user, and @var{args} represents the number of
21852 seconds @value{GDBN} waits for responses.
21855 @cindex compiling, on Sparclet
21856 When compiling for debugging, include the options @samp{-g} to get debug
21857 information and @samp{-Ttext} to relocate the program to where you wish to
21858 load it on the target. You may also want to add the options @samp{-n} or
21859 @samp{-N} in order to reduce the size of the sections. Example:
21862 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21865 You can use @code{objdump} to verify that the addresses are what you intended:
21868 sparclet-aout-objdump --headers --syms prog
21871 @cindex running, on Sparclet
21873 your Unix execution search path to find @value{GDBN}, you are ready to
21874 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21875 (or @code{sparclet-aout-gdb}, depending on your installation).
21877 @value{GDBN} comes up showing the prompt:
21884 * Sparclet File:: Setting the file to debug
21885 * Sparclet Connection:: Connecting to Sparclet
21886 * Sparclet Download:: Sparclet download
21887 * Sparclet Execution:: Running and debugging
21890 @node Sparclet File
21891 @subsubsection Setting File to Debug
21893 The @value{GDBN} command @code{file} lets you choose with program to debug.
21896 (gdbslet) file prog
21900 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21901 @value{GDBN} locates
21902 the file by searching the directories listed in the command search
21904 If the file was compiled with debug information (option @samp{-g}), source
21905 files will be searched as well.
21906 @value{GDBN} locates
21907 the source files by searching the directories listed in the directory search
21908 path (@pxref{Environment, ,Your Program's Environment}).
21910 to find a file, it displays a message such as:
21913 prog: No such file or directory.
21916 When this happens, add the appropriate directories to the search paths with
21917 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21918 @code{target} command again.
21920 @node Sparclet Connection
21921 @subsubsection Connecting to Sparclet
21923 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21924 To connect to a target on serial port ``@code{ttya}'', type:
21927 (gdbslet) target sparclet /dev/ttya
21928 Remote target sparclet connected to /dev/ttya
21929 main () at ../prog.c:3
21933 @value{GDBN} displays messages like these:
21939 @node Sparclet Download
21940 @subsubsection Sparclet Download
21942 @cindex download to Sparclet
21943 Once connected to the Sparclet target,
21944 you can use the @value{GDBN}
21945 @code{load} command to download the file from the host to the target.
21946 The file name and load offset should be given as arguments to the @code{load}
21948 Since the file format is aout, the program must be loaded to the starting
21949 address. You can use @code{objdump} to find out what this value is. The load
21950 offset is an offset which is added to the VMA (virtual memory address)
21951 of each of the file's sections.
21952 For instance, if the program
21953 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21954 and bss at 0x12010170, in @value{GDBN}, type:
21957 (gdbslet) load prog 0x12010000
21958 Loading section .text, size 0xdb0 vma 0x12010000
21961 If the code is loaded at a different address then what the program was linked
21962 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21963 to tell @value{GDBN} where to map the symbol table.
21965 @node Sparclet Execution
21966 @subsubsection Running and Debugging
21968 @cindex running and debugging Sparclet programs
21969 You can now begin debugging the task using @value{GDBN}'s execution control
21970 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21971 manual for the list of commands.
21975 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21977 Starting program: prog
21978 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21979 3 char *symarg = 0;
21981 4 char *execarg = "hello!";
21986 @subsection Fujitsu Sparclite
21990 @kindex target sparclite
21991 @item target sparclite @var{dev}
21992 Fujitsu sparclite boards, used only for the purpose of loading.
21993 You must use an additional command to debug the program.
21994 For example: target remote @var{dev} using @value{GDBN} standard
22000 @subsection Zilog Z8000
22003 @cindex simulator, Z8000
22004 @cindex Zilog Z8000 simulator
22006 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
22009 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
22010 unsegmented variant of the Z8000 architecture) or the Z8001 (the
22011 segmented variant). The simulator recognizes which architecture is
22012 appropriate by inspecting the object code.
22015 @item target sim @var{args}
22017 @kindex target sim@r{, with Z8000}
22018 Debug programs on a simulated CPU. If the simulator supports setup
22019 options, specify them via @var{args}.
22023 After specifying this target, you can debug programs for the simulated
22024 CPU in the same style as programs for your host computer; use the
22025 @code{file} command to load a new program image, the @code{run} command
22026 to run your program, and so on.
22028 As well as making available all the usual machine registers
22029 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
22030 additional items of information as specially named registers:
22035 Counts clock-ticks in the simulator.
22038 Counts instructions run in the simulator.
22041 Execution time in 60ths of a second.
22045 You can refer to these values in @value{GDBN} expressions with the usual
22046 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
22047 conditional breakpoint that suspends only after at least 5000
22048 simulated clock ticks.
22051 @subsection Atmel AVR
22054 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22055 following AVR-specific commands:
22058 @item info io_registers
22059 @kindex info io_registers@r{, AVR}
22060 @cindex I/O registers (Atmel AVR)
22061 This command displays information about the AVR I/O registers. For
22062 each register, @value{GDBN} prints its number and value.
22069 When configured for debugging CRIS, @value{GDBN} provides the
22070 following CRIS-specific commands:
22073 @item set cris-version @var{ver}
22074 @cindex CRIS version
22075 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22076 The CRIS version affects register names and sizes. This command is useful in
22077 case autodetection of the CRIS version fails.
22079 @item show cris-version
22080 Show the current CRIS version.
22082 @item set cris-dwarf2-cfi
22083 @cindex DWARF-2 CFI and CRIS
22084 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22085 Change to @samp{off} when using @code{gcc-cris} whose version is below
22088 @item show cris-dwarf2-cfi
22089 Show the current state of using DWARF-2 CFI.
22091 @item set cris-mode @var{mode}
22093 Set the current CRIS mode to @var{mode}. It should only be changed when
22094 debugging in guru mode, in which case it should be set to
22095 @samp{guru} (the default is @samp{normal}).
22097 @item show cris-mode
22098 Show the current CRIS mode.
22102 @subsection Renesas Super-H
22105 For the Renesas Super-H processor, @value{GDBN} provides these
22109 @item set sh calling-convention @var{convention}
22110 @kindex set sh calling-convention
22111 Set the calling-convention used when calling functions from @value{GDBN}.
22112 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22113 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22114 convention. If the DWARF-2 information of the called function specifies
22115 that the function follows the Renesas calling convention, the function
22116 is called using the Renesas calling convention. If the calling convention
22117 is set to @samp{renesas}, the Renesas calling convention is always used,
22118 regardless of the DWARF-2 information. This can be used to override the
22119 default of @samp{gcc} if debug information is missing, or the compiler
22120 does not emit the DWARF-2 calling convention entry for a function.
22122 @item show sh calling-convention
22123 @kindex show sh calling-convention
22124 Show the current calling convention setting.
22129 @node Architectures
22130 @section Architectures
22132 This section describes characteristics of architectures that affect
22133 all uses of @value{GDBN} with the architecture, both native and cross.
22140 * HPPA:: HP PA architecture
22141 * SPU:: Cell Broadband Engine SPU architecture
22147 @subsection AArch64
22148 @cindex AArch64 support
22150 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22151 following special commands:
22154 @item set debug aarch64
22155 @kindex set debug aarch64
22156 This command determines whether AArch64 architecture-specific debugging
22157 messages are to be displayed.
22159 @item show debug aarch64
22160 Show whether AArch64 debugging messages are displayed.
22165 @subsection x86 Architecture-specific Issues
22168 @item set struct-convention @var{mode}
22169 @kindex set struct-convention
22170 @cindex struct return convention
22171 @cindex struct/union returned in registers
22172 Set the convention used by the inferior to return @code{struct}s and
22173 @code{union}s from functions to @var{mode}. Possible values of
22174 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22175 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22176 are returned on the stack, while @code{"reg"} means that a
22177 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22178 be returned in a register.
22180 @item show struct-convention
22181 @kindex show struct-convention
22182 Show the current setting of the convention to return @code{struct}s
22187 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22188 @cindex Intel(R) Memory Protection Extensions (MPX).
22190 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22191 @footnote{The register named with capital letters represent the architecture
22192 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22193 which are the lower bound and upper bound. Bounds are effective addresses or
22194 memory locations. The upper bounds are architecturally represented in 1's
22195 complement form. A bound having lower bound = 0, and upper bound = 0
22196 (1's complement of all bits set) will allow access to the entire address space.
22198 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22199 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22200 display the upper bound performing the complement of one operation on the
22201 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22202 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22203 can also be noted that the upper bounds are inclusive.
22205 As an example, assume that the register BND0 holds bounds for a pointer having
22206 access allowed for the range between 0x32 and 0x71. The values present on
22207 bnd0raw and bnd registers are presented as follows:
22210 bnd0raw = @{0x32, 0xffffffff8e@}
22211 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22214 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22215 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22216 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22217 Python, the display includes the memory size, in bits, accessible to
22220 Bounds can also be stored in bounds tables, which are stored in
22221 application memory. These tables store bounds for pointers by specifying
22222 the bounds pointer's value along with its bounds. Evaluating and changing
22223 bounds located in bound tables is therefore interesting while investigating
22224 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22227 @item show mpx bound @var{pointer}
22228 @kindex show mpx bound
22229 Display bounds of the given @var{pointer}.
22231 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22232 @kindex set mpx bound
22233 Set the bounds of a pointer in the bound table.
22234 This command takes three parameters: @var{pointer} is the pointers
22235 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22236 for lower and upper bounds respectively.
22242 See the following section.
22245 @subsection @acronym{MIPS}
22247 @cindex stack on Alpha
22248 @cindex stack on @acronym{MIPS}
22249 @cindex Alpha stack
22250 @cindex @acronym{MIPS} stack
22251 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22252 sometimes requires @value{GDBN} to search backward in the object code to
22253 find the beginning of a function.
22255 @cindex response time, @acronym{MIPS} debugging
22256 To improve response time (especially for embedded applications, where
22257 @value{GDBN} may be restricted to a slow serial line for this search)
22258 you may want to limit the size of this search, using one of these
22262 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22263 @item set heuristic-fence-post @var{limit}
22264 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22265 search for the beginning of a function. A value of @var{0} (the
22266 default) means there is no limit. However, except for @var{0}, the
22267 larger the limit the more bytes @code{heuristic-fence-post} must search
22268 and therefore the longer it takes to run. You should only need to use
22269 this command when debugging a stripped executable.
22271 @item show heuristic-fence-post
22272 Display the current limit.
22276 These commands are available @emph{only} when @value{GDBN} is configured
22277 for debugging programs on Alpha or @acronym{MIPS} processors.
22279 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22283 @item set mips abi @var{arg}
22284 @kindex set mips abi
22285 @cindex set ABI for @acronym{MIPS}
22286 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22287 values of @var{arg} are:
22291 The default ABI associated with the current binary (this is the
22301 @item show mips abi
22302 @kindex show mips abi
22303 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22305 @item set mips compression @var{arg}
22306 @kindex set mips compression
22307 @cindex code compression, @acronym{MIPS}
22308 Tell @value{GDBN} which @acronym{MIPS} compressed
22309 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22310 inferior. @value{GDBN} uses this for code disassembly and other
22311 internal interpretation purposes. This setting is only referred to
22312 when no executable has been associated with the debugging session or
22313 the executable does not provide information about the encoding it uses.
22314 Otherwise this setting is automatically updated from information
22315 provided by the executable.
22317 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22318 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22319 executables containing @acronym{MIPS16} code frequently are not
22320 identified as such.
22322 This setting is ``sticky''; that is, it retains its value across
22323 debugging sessions until reset either explicitly with this command or
22324 implicitly from an executable.
22326 The compiler and/or assembler typically add symbol table annotations to
22327 identify functions compiled for the @acronym{MIPS16} or
22328 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22329 are present, @value{GDBN} uses them in preference to the global
22330 compressed @acronym{ISA} encoding setting.
22332 @item show mips compression
22333 @kindex show mips compression
22334 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22335 @value{GDBN} to debug the inferior.
22338 @itemx show mipsfpu
22339 @xref{MIPS Embedded, set mipsfpu}.
22341 @item set mips mask-address @var{arg}
22342 @kindex set mips mask-address
22343 @cindex @acronym{MIPS} addresses, masking
22344 This command determines whether the most-significant 32 bits of 64-bit
22345 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22346 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22347 setting, which lets @value{GDBN} determine the correct value.
22349 @item show mips mask-address
22350 @kindex show mips mask-address
22351 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22354 @item set remote-mips64-transfers-32bit-regs
22355 @kindex set remote-mips64-transfers-32bit-regs
22356 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22357 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22358 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22359 and 64 bits for other registers, set this option to @samp{on}.
22361 @item show remote-mips64-transfers-32bit-regs
22362 @kindex show remote-mips64-transfers-32bit-regs
22363 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22365 @item set debug mips
22366 @kindex set debug mips
22367 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22368 target code in @value{GDBN}.
22370 @item show debug mips
22371 @kindex show debug mips
22372 Show the current setting of @acronym{MIPS} debugging messages.
22378 @cindex HPPA support
22380 When @value{GDBN} is debugging the HP PA architecture, it provides the
22381 following special commands:
22384 @item set debug hppa
22385 @kindex set debug hppa
22386 This command determines whether HPPA architecture-specific debugging
22387 messages are to be displayed.
22389 @item show debug hppa
22390 Show whether HPPA debugging messages are displayed.
22392 @item maint print unwind @var{address}
22393 @kindex maint print unwind@r{, HPPA}
22394 This command displays the contents of the unwind table entry at the
22395 given @var{address}.
22401 @subsection Cell Broadband Engine SPU architecture
22402 @cindex Cell Broadband Engine
22405 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22406 it provides the following special commands:
22409 @item info spu event
22411 Display SPU event facility status. Shows current event mask
22412 and pending event status.
22414 @item info spu signal
22415 Display SPU signal notification facility status. Shows pending
22416 signal-control word and signal notification mode of both signal
22417 notification channels.
22419 @item info spu mailbox
22420 Display SPU mailbox facility status. Shows all pending entries,
22421 in order of processing, in each of the SPU Write Outbound,
22422 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22425 Display MFC DMA status. Shows all pending commands in the MFC
22426 DMA queue. For each entry, opcode, tag, class IDs, effective
22427 and local store addresses and transfer size are shown.
22429 @item info spu proxydma
22430 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22431 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22432 and local store addresses and transfer size are shown.
22436 When @value{GDBN} is debugging a combined PowerPC/SPU application
22437 on the Cell Broadband Engine, it provides in addition the following
22441 @item set spu stop-on-load @var{arg}
22443 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22444 will give control to the user when a new SPE thread enters its @code{main}
22445 function. The default is @code{off}.
22447 @item show spu stop-on-load
22449 Show whether to stop for new SPE threads.
22451 @item set spu auto-flush-cache @var{arg}
22452 Set whether to automatically flush the software-managed cache. When set to
22453 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22454 cache to be flushed whenever SPE execution stops. This provides a consistent
22455 view of PowerPC memory that is accessed via the cache. If an application
22456 does not use the software-managed cache, this option has no effect.
22458 @item show spu auto-flush-cache
22459 Show whether to automatically flush the software-managed cache.
22464 @subsection PowerPC
22465 @cindex PowerPC architecture
22467 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22468 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22469 numbers stored in the floating point registers. These values must be stored
22470 in two consecutive registers, always starting at an even register like
22471 @code{f0} or @code{f2}.
22473 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22474 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22475 @code{f2} and @code{f3} for @code{$dl1} and so on.
22477 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22478 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22481 @subsection Nios II
22482 @cindex Nios II architecture
22484 When @value{GDBN} is debugging the Nios II architecture,
22485 it provides the following special commands:
22489 @item set debug nios2
22490 @kindex set debug nios2
22491 This command turns on and off debugging messages for the Nios II
22492 target code in @value{GDBN}.
22494 @item show debug nios2
22495 @kindex show debug nios2
22496 Show the current setting of Nios II debugging messages.
22499 @node Controlling GDB
22500 @chapter Controlling @value{GDBN}
22502 You can alter the way @value{GDBN} interacts with you by using the
22503 @code{set} command. For commands controlling how @value{GDBN} displays
22504 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22509 * Editing:: Command editing
22510 * Command History:: Command history
22511 * Screen Size:: Screen size
22512 * Numbers:: Numbers
22513 * ABI:: Configuring the current ABI
22514 * Auto-loading:: Automatically loading associated files
22515 * Messages/Warnings:: Optional warnings and messages
22516 * Debugging Output:: Optional messages about internal happenings
22517 * Other Misc Settings:: Other Miscellaneous Settings
22525 @value{GDBN} indicates its readiness to read a command by printing a string
22526 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22527 can change the prompt string with the @code{set prompt} command. For
22528 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22529 the prompt in one of the @value{GDBN} sessions so that you can always tell
22530 which one you are talking to.
22532 @emph{Note:} @code{set prompt} does not add a space for you after the
22533 prompt you set. This allows you to set a prompt which ends in a space
22534 or a prompt that does not.
22538 @item set prompt @var{newprompt}
22539 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22541 @kindex show prompt
22543 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22546 Versions of @value{GDBN} that ship with Python scripting enabled have
22547 prompt extensions. The commands for interacting with these extensions
22551 @kindex set extended-prompt
22552 @item set extended-prompt @var{prompt}
22553 Set an extended prompt that allows for substitutions.
22554 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22555 substitution. Any escape sequences specified as part of the prompt
22556 string are replaced with the corresponding strings each time the prompt
22562 set extended-prompt Current working directory: \w (gdb)
22565 Note that when an extended-prompt is set, it takes control of the
22566 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22568 @kindex show extended-prompt
22569 @item show extended-prompt
22570 Prints the extended prompt. Any escape sequences specified as part of
22571 the prompt string with @code{set extended-prompt}, are replaced with the
22572 corresponding strings each time the prompt is displayed.
22576 @section Command Editing
22578 @cindex command line editing
22580 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22581 @sc{gnu} library provides consistent behavior for programs which provide a
22582 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22583 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22584 substitution, and a storage and recall of command history across
22585 debugging sessions.
22587 You may control the behavior of command line editing in @value{GDBN} with the
22588 command @code{set}.
22591 @kindex set editing
22594 @itemx set editing on
22595 Enable command line editing (enabled by default).
22597 @item set editing off
22598 Disable command line editing.
22600 @kindex show editing
22602 Show whether command line editing is enabled.
22605 @ifset SYSTEM_READLINE
22606 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22608 @ifclear SYSTEM_READLINE
22609 @xref{Command Line Editing},
22611 for more details about the Readline
22612 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22613 encouraged to read that chapter.
22615 @node Command History
22616 @section Command History
22617 @cindex command history
22619 @value{GDBN} can keep track of the commands you type during your
22620 debugging sessions, so that you can be certain of precisely what
22621 happened. Use these commands to manage the @value{GDBN} command
22624 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22625 package, to provide the history facility.
22626 @ifset SYSTEM_READLINE
22627 @xref{Using History Interactively, , , history, GNU History Library},
22629 @ifclear SYSTEM_READLINE
22630 @xref{Using History Interactively},
22632 for the detailed description of the History library.
22634 To issue a command to @value{GDBN} without affecting certain aspects of
22635 the state which is seen by users, prefix it with @samp{server }
22636 (@pxref{Server Prefix}). This
22637 means that this command will not affect the command history, nor will it
22638 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22639 pressed on a line by itself.
22641 @cindex @code{server}, command prefix
22642 The server prefix does not affect the recording of values into the value
22643 history; to print a value without recording it into the value history,
22644 use the @code{output} command instead of the @code{print} command.
22646 Here is the description of @value{GDBN} commands related to command
22650 @cindex history substitution
22651 @cindex history file
22652 @kindex set history filename
22653 @cindex @env{GDBHISTFILE}, environment variable
22654 @item set history filename @var{fname}
22655 Set the name of the @value{GDBN} command history file to @var{fname}.
22656 This is the file where @value{GDBN} reads an initial command history
22657 list, and where it writes the command history from this session when it
22658 exits. You can access this list through history expansion or through
22659 the history command editing characters listed below. This file defaults
22660 to the value of the environment variable @code{GDBHISTFILE}, or to
22661 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22664 @cindex save command history
22665 @kindex set history save
22666 @item set history save
22667 @itemx set history save on
22668 Record command history in a file, whose name may be specified with the
22669 @code{set history filename} command. By default, this option is disabled.
22671 @item set history save off
22672 Stop recording command history in a file.
22674 @cindex history size
22675 @kindex set history size
22676 @cindex @env{GDBHISTSIZE}, environment variable
22677 @item set history size @var{size}
22678 @itemx set history size unlimited
22679 Set the number of commands which @value{GDBN} keeps in its history list.
22680 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22681 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22682 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22683 either a negative number or the empty string, then the number of commands
22684 @value{GDBN} keeps in the history list is unlimited.
22686 @cindex remove duplicate history
22687 @kindex set history remove-duplicates
22688 @item set history remove-duplicates @var{count}
22689 @itemx set history remove-duplicates unlimited
22690 Control the removal of duplicate history entries in the command history list.
22691 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22692 history entries and remove the first entry that is a duplicate of the current
22693 entry being added to the command history list. If @var{count} is
22694 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22695 removal of duplicate history entries is disabled.
22697 Only history entries added during the current session are considered for
22698 removal. This option is set to 0 by default.
22702 History expansion assigns special meaning to the character @kbd{!}.
22703 @ifset SYSTEM_READLINE
22704 @xref{Event Designators, , , history, GNU History Library},
22706 @ifclear SYSTEM_READLINE
22707 @xref{Event Designators},
22711 @cindex history expansion, turn on/off
22712 Since @kbd{!} is also the logical not operator in C, history expansion
22713 is off by default. If you decide to enable history expansion with the
22714 @code{set history expansion on} command, you may sometimes need to
22715 follow @kbd{!} (when it is used as logical not, in an expression) with
22716 a space or a tab to prevent it from being expanded. The readline
22717 history facilities do not attempt substitution on the strings
22718 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22720 The commands to control history expansion are:
22723 @item set history expansion on
22724 @itemx set history expansion
22725 @kindex set history expansion
22726 Enable history expansion. History expansion is off by default.
22728 @item set history expansion off
22729 Disable history expansion.
22732 @kindex show history
22734 @itemx show history filename
22735 @itemx show history save
22736 @itemx show history size
22737 @itemx show history expansion
22738 These commands display the state of the @value{GDBN} history parameters.
22739 @code{show history} by itself displays all four states.
22744 @kindex show commands
22745 @cindex show last commands
22746 @cindex display command history
22747 @item show commands
22748 Display the last ten commands in the command history.
22750 @item show commands @var{n}
22751 Print ten commands centered on command number @var{n}.
22753 @item show commands +
22754 Print ten commands just after the commands last printed.
22758 @section Screen Size
22759 @cindex size of screen
22760 @cindex screen size
22763 @cindex pauses in output
22765 Certain commands to @value{GDBN} may produce large amounts of
22766 information output to the screen. To help you read all of it,
22767 @value{GDBN} pauses and asks you for input at the end of each page of
22768 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22769 to discard the remaining output. Also, the screen width setting
22770 determines when to wrap lines of output. Depending on what is being
22771 printed, @value{GDBN} tries to break the line at a readable place,
22772 rather than simply letting it overflow onto the following line.
22774 Normally @value{GDBN} knows the size of the screen from the terminal
22775 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22776 together with the value of the @code{TERM} environment variable and the
22777 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22778 you can override it with the @code{set height} and @code{set
22785 @kindex show height
22786 @item set height @var{lpp}
22787 @itemx set height unlimited
22789 @itemx set width @var{cpl}
22790 @itemx set width unlimited
22792 These @code{set} commands specify a screen height of @var{lpp} lines and
22793 a screen width of @var{cpl} characters. The associated @code{show}
22794 commands display the current settings.
22796 If you specify a height of either @code{unlimited} or zero lines,
22797 @value{GDBN} does not pause during output no matter how long the
22798 output is. This is useful if output is to a file or to an editor
22801 Likewise, you can specify @samp{set width unlimited} or @samp{set
22802 width 0} to prevent @value{GDBN} from wrapping its output.
22804 @item set pagination on
22805 @itemx set pagination off
22806 @kindex set pagination
22807 Turn the output pagination on or off; the default is on. Turning
22808 pagination off is the alternative to @code{set height unlimited}. Note that
22809 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22810 Options, -batch}) also automatically disables pagination.
22812 @item show pagination
22813 @kindex show pagination
22814 Show the current pagination mode.
22819 @cindex number representation
22820 @cindex entering numbers
22822 You can always enter numbers in octal, decimal, or hexadecimal in
22823 @value{GDBN} by the usual conventions: octal numbers begin with
22824 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22825 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22826 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22827 10; likewise, the default display for numbers---when no particular
22828 format is specified---is base 10. You can change the default base for
22829 both input and output with the commands described below.
22832 @kindex set input-radix
22833 @item set input-radix @var{base}
22834 Set the default base for numeric input. Supported choices
22835 for @var{base} are decimal 8, 10, or 16. The base must itself be
22836 specified either unambiguously or using the current input radix; for
22840 set input-radix 012
22841 set input-radix 10.
22842 set input-radix 0xa
22846 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22847 leaves the input radix unchanged, no matter what it was, since
22848 @samp{10}, being without any leading or trailing signs of its base, is
22849 interpreted in the current radix. Thus, if the current radix is 16,
22850 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22853 @kindex set output-radix
22854 @item set output-radix @var{base}
22855 Set the default base for numeric display. Supported choices
22856 for @var{base} are decimal 8, 10, or 16. The base must itself be
22857 specified either unambiguously or using the current input radix.
22859 @kindex show input-radix
22860 @item show input-radix
22861 Display the current default base for numeric input.
22863 @kindex show output-radix
22864 @item show output-radix
22865 Display the current default base for numeric display.
22867 @item set radix @r{[}@var{base}@r{]}
22871 These commands set and show the default base for both input and output
22872 of numbers. @code{set radix} sets the radix of input and output to
22873 the same base; without an argument, it resets the radix back to its
22874 default value of 10.
22879 @section Configuring the Current ABI
22881 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22882 application automatically. However, sometimes you need to override its
22883 conclusions. Use these commands to manage @value{GDBN}'s view of the
22889 @cindex Newlib OS ABI and its influence on the longjmp handling
22891 One @value{GDBN} configuration can debug binaries for multiple operating
22892 system targets, either via remote debugging or native emulation.
22893 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22894 but you can override its conclusion using the @code{set osabi} command.
22895 One example where this is useful is in debugging of binaries which use
22896 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22897 not have the same identifying marks that the standard C library for your
22900 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22901 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22902 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22903 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22907 Show the OS ABI currently in use.
22910 With no argument, show the list of registered available OS ABI's.
22912 @item set osabi @var{abi}
22913 Set the current OS ABI to @var{abi}.
22916 @cindex float promotion
22918 Generally, the way that an argument of type @code{float} is passed to a
22919 function depends on whether the function is prototyped. For a prototyped
22920 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22921 according to the architecture's convention for @code{float}. For unprototyped
22922 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22923 @code{double} and then passed.
22925 Unfortunately, some forms of debug information do not reliably indicate whether
22926 a function is prototyped. If @value{GDBN} calls a function that is not marked
22927 as prototyped, it consults @kbd{set coerce-float-to-double}.
22930 @kindex set coerce-float-to-double
22931 @item set coerce-float-to-double
22932 @itemx set coerce-float-to-double on
22933 Arguments of type @code{float} will be promoted to @code{double} when passed
22934 to an unprototyped function. This is the default setting.
22936 @item set coerce-float-to-double off
22937 Arguments of type @code{float} will be passed directly to unprototyped
22940 @kindex show coerce-float-to-double
22941 @item show coerce-float-to-double
22942 Show the current setting of promoting @code{float} to @code{double}.
22946 @kindex show cp-abi
22947 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22948 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22949 used to build your application. @value{GDBN} only fully supports
22950 programs with a single C@t{++} ABI; if your program contains code using
22951 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22952 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22953 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22954 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22955 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22956 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22961 Show the C@t{++} ABI currently in use.
22964 With no argument, show the list of supported C@t{++} ABI's.
22966 @item set cp-abi @var{abi}
22967 @itemx set cp-abi auto
22968 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22972 @section Automatically loading associated files
22973 @cindex auto-loading
22975 @value{GDBN} sometimes reads files with commands and settings automatically,
22976 without being explicitly told so by the user. We call this feature
22977 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22978 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22979 results or introduce security risks (e.g., if the file comes from untrusted
22983 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22984 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22986 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22987 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22990 There are various kinds of files @value{GDBN} can automatically load.
22991 In addition to these files, @value{GDBN} supports auto-loading code written
22992 in various extension languages. @xref{Auto-loading extensions}.
22994 Note that loading of these associated files (including the local @file{.gdbinit}
22995 file) requires accordingly configured @code{auto-load safe-path}
22996 (@pxref{Auto-loading safe path}).
22998 For these reasons, @value{GDBN} includes commands and options to let you
22999 control when to auto-load files and which files should be auto-loaded.
23002 @anchor{set auto-load off}
23003 @kindex set auto-load off
23004 @item set auto-load off
23005 Globally disable loading of all auto-loaded files.
23006 You may want to use this command with the @samp{-iex} option
23007 (@pxref{Option -init-eval-command}) such as:
23009 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23012 Be aware that system init file (@pxref{System-wide configuration})
23013 and init files from your home directory (@pxref{Home Directory Init File})
23014 still get read (as they come from generally trusted directories).
23015 To prevent @value{GDBN} from auto-loading even those init files, use the
23016 @option{-nx} option (@pxref{Mode Options}), in addition to
23017 @code{set auto-load no}.
23019 @anchor{show auto-load}
23020 @kindex show auto-load
23021 @item show auto-load
23022 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23026 (gdb) show auto-load
23027 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23028 libthread-db: Auto-loading of inferior specific libthread_db is on.
23029 local-gdbinit: Auto-loading of .gdbinit script from current directory
23031 python-scripts: Auto-loading of Python scripts is on.
23032 safe-path: List of directories from which it is safe to auto-load files
23033 is $debugdir:$datadir/auto-load.
23034 scripts-directory: List of directories from which to load auto-loaded scripts
23035 is $debugdir:$datadir/auto-load.
23038 @anchor{info auto-load}
23039 @kindex info auto-load
23040 @item info auto-load
23041 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23045 (gdb) info auto-load
23048 Yes /home/user/gdb/gdb-gdb.gdb
23049 libthread-db: No auto-loaded libthread-db.
23050 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23054 Yes /home/user/gdb/gdb-gdb.py
23058 These are @value{GDBN} control commands for the auto-loading:
23060 @multitable @columnfractions .5 .5
23061 @item @xref{set auto-load off}.
23062 @tab Disable auto-loading globally.
23063 @item @xref{show auto-load}.
23064 @tab Show setting of all kinds of files.
23065 @item @xref{info auto-load}.
23066 @tab Show state of all kinds of files.
23067 @item @xref{set auto-load gdb-scripts}.
23068 @tab Control for @value{GDBN} command scripts.
23069 @item @xref{show auto-load gdb-scripts}.
23070 @tab Show setting of @value{GDBN} command scripts.
23071 @item @xref{info auto-load gdb-scripts}.
23072 @tab Show state of @value{GDBN} command scripts.
23073 @item @xref{set auto-load python-scripts}.
23074 @tab Control for @value{GDBN} Python scripts.
23075 @item @xref{show auto-load python-scripts}.
23076 @tab Show setting of @value{GDBN} Python scripts.
23077 @item @xref{info auto-load python-scripts}.
23078 @tab Show state of @value{GDBN} Python scripts.
23079 @item @xref{set auto-load guile-scripts}.
23080 @tab Control for @value{GDBN} Guile scripts.
23081 @item @xref{show auto-load guile-scripts}.
23082 @tab Show setting of @value{GDBN} Guile scripts.
23083 @item @xref{info auto-load guile-scripts}.
23084 @tab Show state of @value{GDBN} Guile scripts.
23085 @item @xref{set auto-load scripts-directory}.
23086 @tab Control for @value{GDBN} auto-loaded scripts location.
23087 @item @xref{show auto-load scripts-directory}.
23088 @tab Show @value{GDBN} auto-loaded scripts location.
23089 @item @xref{add-auto-load-scripts-directory}.
23090 @tab Add directory for auto-loaded scripts location list.
23091 @item @xref{set auto-load local-gdbinit}.
23092 @tab Control for init file in the current directory.
23093 @item @xref{show auto-load local-gdbinit}.
23094 @tab Show setting of init file in the current directory.
23095 @item @xref{info auto-load local-gdbinit}.
23096 @tab Show state of init file in the current directory.
23097 @item @xref{set auto-load libthread-db}.
23098 @tab Control for thread debugging library.
23099 @item @xref{show auto-load libthread-db}.
23100 @tab Show setting of thread debugging library.
23101 @item @xref{info auto-load libthread-db}.
23102 @tab Show state of thread debugging library.
23103 @item @xref{set auto-load safe-path}.
23104 @tab Control directories trusted for automatic loading.
23105 @item @xref{show auto-load safe-path}.
23106 @tab Show directories trusted for automatic loading.
23107 @item @xref{add-auto-load-safe-path}.
23108 @tab Add directory trusted for automatic loading.
23111 @node Init File in the Current Directory
23112 @subsection Automatically loading init file in the current directory
23113 @cindex auto-loading init file in the current directory
23115 By default, @value{GDBN} reads and executes the canned sequences of commands
23116 from init file (if any) in the current working directory,
23117 see @ref{Init File in the Current Directory during Startup}.
23119 Note that loading of this local @file{.gdbinit} file also requires accordingly
23120 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23123 @anchor{set auto-load local-gdbinit}
23124 @kindex set auto-load local-gdbinit
23125 @item set auto-load local-gdbinit [on|off]
23126 Enable or disable the auto-loading of canned sequences of commands
23127 (@pxref{Sequences}) found in init file in the current directory.
23129 @anchor{show auto-load local-gdbinit}
23130 @kindex show auto-load local-gdbinit
23131 @item show auto-load local-gdbinit
23132 Show whether auto-loading of canned sequences of commands from init file in the
23133 current directory is enabled or disabled.
23135 @anchor{info auto-load local-gdbinit}
23136 @kindex info auto-load local-gdbinit
23137 @item info auto-load local-gdbinit
23138 Print whether canned sequences of commands from init file in the
23139 current directory have been auto-loaded.
23142 @node libthread_db.so.1 file
23143 @subsection Automatically loading thread debugging library
23144 @cindex auto-loading libthread_db.so.1
23146 This feature is currently present only on @sc{gnu}/Linux native hosts.
23148 @value{GDBN} reads in some cases thread debugging library from places specific
23149 to the inferior (@pxref{set libthread-db-search-path}).
23151 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23152 without checking this @samp{set auto-load libthread-db} switch as system
23153 libraries have to be trusted in general. In all other cases of
23154 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23155 auto-load libthread-db} is enabled before trying to open such thread debugging
23158 Note that loading of this debugging library also requires accordingly configured
23159 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23162 @anchor{set auto-load libthread-db}
23163 @kindex set auto-load libthread-db
23164 @item set auto-load libthread-db [on|off]
23165 Enable or disable the auto-loading of inferior specific thread debugging library.
23167 @anchor{show auto-load libthread-db}
23168 @kindex show auto-load libthread-db
23169 @item show auto-load libthread-db
23170 Show whether auto-loading of inferior specific thread debugging library is
23171 enabled or disabled.
23173 @anchor{info auto-load libthread-db}
23174 @kindex info auto-load libthread-db
23175 @item info auto-load libthread-db
23176 Print the list of all loaded inferior specific thread debugging libraries and
23177 for each such library print list of inferior @var{pid}s using it.
23180 @node Auto-loading safe path
23181 @subsection Security restriction for auto-loading
23182 @cindex auto-loading safe-path
23184 As the files of inferior can come from untrusted source (such as submitted by
23185 an application user) @value{GDBN} does not always load any files automatically.
23186 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23187 directories trusted for loading files not explicitly requested by user.
23188 Each directory can also be a shell wildcard pattern.
23190 If the path is not set properly you will see a warning and the file will not
23195 Reading symbols from /home/user/gdb/gdb...done.
23196 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23197 declined by your `auto-load safe-path' set
23198 to "$debugdir:$datadir/auto-load".
23199 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23200 declined by your `auto-load safe-path' set
23201 to "$debugdir:$datadir/auto-load".
23205 To instruct @value{GDBN} to go ahead and use the init files anyway,
23206 invoke @value{GDBN} like this:
23209 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23212 The list of trusted directories is controlled by the following commands:
23215 @anchor{set auto-load safe-path}
23216 @kindex set auto-load safe-path
23217 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23218 Set the list of directories (and their subdirectories) trusted for automatic
23219 loading and execution of scripts. You can also enter a specific trusted file.
23220 Each directory can also be a shell wildcard pattern; wildcards do not match
23221 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23222 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23223 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23224 its default value as specified during @value{GDBN} compilation.
23226 The list of directories uses path separator (@samp{:} on GNU and Unix
23227 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23228 to the @env{PATH} environment variable.
23230 @anchor{show auto-load safe-path}
23231 @kindex show auto-load safe-path
23232 @item show auto-load safe-path
23233 Show the list of directories trusted for automatic loading and execution of
23236 @anchor{add-auto-load-safe-path}
23237 @kindex add-auto-load-safe-path
23238 @item add-auto-load-safe-path
23239 Add an entry (or list of entries) to the list of directories trusted for
23240 automatic loading and execution of scripts. Multiple entries may be delimited
23241 by the host platform path separator in use.
23244 This variable defaults to what @code{--with-auto-load-dir} has been configured
23245 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23246 substitution applies the same as for @ref{set auto-load scripts-directory}.
23247 The default @code{set auto-load safe-path} value can be also overriden by
23248 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23250 Setting this variable to @file{/} disables this security protection,
23251 corresponding @value{GDBN} configuration option is
23252 @option{--without-auto-load-safe-path}.
23253 This variable is supposed to be set to the system directories writable by the
23254 system superuser only. Users can add their source directories in init files in
23255 their home directories (@pxref{Home Directory Init File}). See also deprecated
23256 init file in the current directory
23257 (@pxref{Init File in the Current Directory during Startup}).
23259 To force @value{GDBN} to load the files it declined to load in the previous
23260 example, you could use one of the following ways:
23263 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23264 Specify this trusted directory (or a file) as additional component of the list.
23265 You have to specify also any existing directories displayed by
23266 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23268 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23269 Specify this directory as in the previous case but just for a single
23270 @value{GDBN} session.
23272 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23273 Disable auto-loading safety for a single @value{GDBN} session.
23274 This assumes all the files you debug during this @value{GDBN} session will come
23275 from trusted sources.
23277 @item @kbd{./configure --without-auto-load-safe-path}
23278 During compilation of @value{GDBN} you may disable any auto-loading safety.
23279 This assumes all the files you will ever debug with this @value{GDBN} come from
23283 On the other hand you can also explicitly forbid automatic files loading which
23284 also suppresses any such warning messages:
23287 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23288 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23290 @item @file{~/.gdbinit}: @samp{set auto-load no}
23291 Disable auto-loading globally for the user
23292 (@pxref{Home Directory Init File}). While it is improbable, you could also
23293 use system init file instead (@pxref{System-wide configuration}).
23296 This setting applies to the file names as entered by user. If no entry matches
23297 @value{GDBN} tries as a last resort to also resolve all the file names into
23298 their canonical form (typically resolving symbolic links) and compare the
23299 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23300 own before starting the comparison so a canonical form of directories is
23301 recommended to be entered.
23303 @node Auto-loading verbose mode
23304 @subsection Displaying files tried for auto-load
23305 @cindex auto-loading verbose mode
23307 For better visibility of all the file locations where you can place scripts to
23308 be auto-loaded with inferior --- or to protect yourself against accidental
23309 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23310 all the files attempted to be loaded. Both existing and non-existing files may
23313 For example the list of directories from which it is safe to auto-load files
23314 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23315 may not be too obvious while setting it up.
23318 (gdb) set debug auto-load on
23319 (gdb) file ~/src/t/true
23320 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23321 for objfile "/tmp/true".
23322 auto-load: Updating directories of "/usr:/opt".
23323 auto-load: Using directory "/usr".
23324 auto-load: Using directory "/opt".
23325 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23326 by your `auto-load safe-path' set to "/usr:/opt".
23330 @anchor{set debug auto-load}
23331 @kindex set debug auto-load
23332 @item set debug auto-load [on|off]
23333 Set whether to print the filenames attempted to be auto-loaded.
23335 @anchor{show debug auto-load}
23336 @kindex show debug auto-load
23337 @item show debug auto-load
23338 Show whether printing of the filenames attempted to be auto-loaded is turned
23342 @node Messages/Warnings
23343 @section Optional Warnings and Messages
23345 @cindex verbose operation
23346 @cindex optional warnings
23347 By default, @value{GDBN} is silent about its inner workings. If you are
23348 running on a slow machine, you may want to use the @code{set verbose}
23349 command. This makes @value{GDBN} tell you when it does a lengthy
23350 internal operation, so you will not think it has crashed.
23352 Currently, the messages controlled by @code{set verbose} are those
23353 which announce that the symbol table for a source file is being read;
23354 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23357 @kindex set verbose
23358 @item set verbose on
23359 Enables @value{GDBN} output of certain informational messages.
23361 @item set verbose off
23362 Disables @value{GDBN} output of certain informational messages.
23364 @kindex show verbose
23366 Displays whether @code{set verbose} is on or off.
23369 By default, if @value{GDBN} encounters bugs in the symbol table of an
23370 object file, it is silent; but if you are debugging a compiler, you may
23371 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23376 @kindex set complaints
23377 @item set complaints @var{limit}
23378 Permits @value{GDBN} to output @var{limit} complaints about each type of
23379 unusual symbols before becoming silent about the problem. Set
23380 @var{limit} to zero to suppress all complaints; set it to a large number
23381 to prevent complaints from being suppressed.
23383 @kindex show complaints
23384 @item show complaints
23385 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23389 @anchor{confirmation requests}
23390 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23391 lot of stupid questions to confirm certain commands. For example, if
23392 you try to run a program which is already running:
23396 The program being debugged has been started already.
23397 Start it from the beginning? (y or n)
23400 If you are willing to unflinchingly face the consequences of your own
23401 commands, you can disable this ``feature'':
23405 @kindex set confirm
23407 @cindex confirmation
23408 @cindex stupid questions
23409 @item set confirm off
23410 Disables confirmation requests. Note that running @value{GDBN} with
23411 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23412 automatically disables confirmation requests.
23414 @item set confirm on
23415 Enables confirmation requests (the default).
23417 @kindex show confirm
23419 Displays state of confirmation requests.
23423 @cindex command tracing
23424 If you need to debug user-defined commands or sourced files you may find it
23425 useful to enable @dfn{command tracing}. In this mode each command will be
23426 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23427 quantity denoting the call depth of each command.
23430 @kindex set trace-commands
23431 @cindex command scripts, debugging
23432 @item set trace-commands on
23433 Enable command tracing.
23434 @item set trace-commands off
23435 Disable command tracing.
23436 @item show trace-commands
23437 Display the current state of command tracing.
23440 @node Debugging Output
23441 @section Optional Messages about Internal Happenings
23442 @cindex optional debugging messages
23444 @value{GDBN} has commands that enable optional debugging messages from
23445 various @value{GDBN} subsystems; normally these commands are of
23446 interest to @value{GDBN} maintainers, or when reporting a bug. This
23447 section documents those commands.
23450 @kindex set exec-done-display
23451 @item set exec-done-display
23452 Turns on or off the notification of asynchronous commands'
23453 completion. When on, @value{GDBN} will print a message when an
23454 asynchronous command finishes its execution. The default is off.
23455 @kindex show exec-done-display
23456 @item show exec-done-display
23457 Displays the current setting of asynchronous command completion
23460 @cindex ARM AArch64
23461 @item set debug aarch64
23462 Turns on or off display of debugging messages related to ARM AArch64.
23463 The default is off.
23465 @item show debug aarch64
23466 Displays the current state of displaying debugging messages related to
23468 @cindex gdbarch debugging info
23469 @cindex architecture debugging info
23470 @item set debug arch
23471 Turns on or off display of gdbarch debugging info. The default is off
23472 @item show debug arch
23473 Displays the current state of displaying gdbarch debugging info.
23474 @item set debug aix-solib
23475 @cindex AIX shared library debugging
23476 Control display of debugging messages from the AIX shared library
23477 support module. The default is off.
23478 @item show debug aix-thread
23479 Show the current state of displaying AIX shared library debugging messages.
23480 @item set debug aix-thread
23481 @cindex AIX threads
23482 Display debugging messages about inner workings of the AIX thread
23484 @item show debug aix-thread
23485 Show the current state of AIX thread debugging info display.
23486 @item set debug check-physname
23488 Check the results of the ``physname'' computation. When reading DWARF
23489 debugging information for C@t{++}, @value{GDBN} attempts to compute
23490 each entity's name. @value{GDBN} can do this computation in two
23491 different ways, depending on exactly what information is present.
23492 When enabled, this setting causes @value{GDBN} to compute the names
23493 both ways and display any discrepancies.
23494 @item show debug check-physname
23495 Show the current state of ``physname'' checking.
23496 @item set debug coff-pe-read
23497 @cindex COFF/PE exported symbols
23498 Control display of debugging messages related to reading of COFF/PE
23499 exported symbols. The default is off.
23500 @item show debug coff-pe-read
23501 Displays the current state of displaying debugging messages related to
23502 reading of COFF/PE exported symbols.
23503 @item set debug dwarf-die
23505 Dump DWARF DIEs after they are read in.
23506 The value is the number of nesting levels to print.
23507 A value of zero turns off the display.
23508 @item show debug dwarf-die
23509 Show the current state of DWARF DIE debugging.
23510 @item set debug dwarf-line
23511 @cindex DWARF Line Tables
23512 Turns on or off display of debugging messages related to reading
23513 DWARF line tables. The default is 0 (off).
23514 A value of 1 provides basic information.
23515 A value greater than 1 provides more verbose information.
23516 @item show debug dwarf-line
23517 Show the current state of DWARF line table debugging.
23518 @item set debug dwarf-read
23519 @cindex DWARF Reading
23520 Turns on or off display of debugging messages related to reading
23521 DWARF debug info. The default is 0 (off).
23522 A value of 1 provides basic information.
23523 A value greater than 1 provides more verbose information.
23524 @item show debug dwarf-read
23525 Show the current state of DWARF reader debugging.
23526 @item set debug displaced
23527 @cindex displaced stepping debugging info
23528 Turns on or off display of @value{GDBN} debugging info for the
23529 displaced stepping support. The default is off.
23530 @item show debug displaced
23531 Displays the current state of displaying @value{GDBN} debugging info
23532 related to displaced stepping.
23533 @item set debug event
23534 @cindex event debugging info
23535 Turns on or off display of @value{GDBN} event debugging info. The
23537 @item show debug event
23538 Displays the current state of displaying @value{GDBN} event debugging
23540 @item set debug expression
23541 @cindex expression debugging info
23542 Turns on or off display of debugging info about @value{GDBN}
23543 expression parsing. The default is off.
23544 @item show debug expression
23545 Displays the current state of displaying debugging info about
23546 @value{GDBN} expression parsing.
23547 @item set debug frame
23548 @cindex frame debugging info
23549 Turns on or off display of @value{GDBN} frame debugging info. The
23551 @item show debug frame
23552 Displays the current state of displaying @value{GDBN} frame debugging
23554 @item set debug gnu-nat
23555 @cindex @sc{gnu}/Hurd debug messages
23556 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23557 @item show debug gnu-nat
23558 Show the current state of @sc{gnu}/Hurd debugging messages.
23559 @item set debug infrun
23560 @cindex inferior debugging info
23561 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23562 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23563 for implementing operations such as single-stepping the inferior.
23564 @item show debug infrun
23565 Displays the current state of @value{GDBN} inferior debugging.
23566 @item set debug jit
23567 @cindex just-in-time compilation, debugging messages
23568 Turns on or off debugging messages from JIT debug support.
23569 @item show debug jit
23570 Displays the current state of @value{GDBN} JIT debugging.
23571 @item set debug lin-lwp
23572 @cindex @sc{gnu}/Linux LWP debug messages
23573 @cindex Linux lightweight processes
23574 Turns on or off debugging messages from the Linux LWP debug support.
23575 @item show debug lin-lwp
23576 Show the current state of Linux LWP debugging messages.
23577 @item set debug linux-namespaces
23578 @cindex @sc{gnu}/Linux namespaces debug messages
23579 Turns on or off debugging messages from the Linux namespaces debug support.
23580 @item show debug linux-namespaces
23581 Show the current state of Linux namespaces debugging messages.
23582 @item set debug mach-o
23583 @cindex Mach-O symbols processing
23584 Control display of debugging messages related to Mach-O symbols
23585 processing. The default is off.
23586 @item show debug mach-o
23587 Displays the current state of displaying debugging messages related to
23588 reading of COFF/PE exported symbols.
23589 @item set debug notification
23590 @cindex remote async notification debugging info
23591 Turns on or off debugging messages about remote async notification.
23592 The default is off.
23593 @item show debug notification
23594 Displays the current state of remote async notification debugging messages.
23595 @item set debug observer
23596 @cindex observer debugging info
23597 Turns on or off display of @value{GDBN} observer debugging. This
23598 includes info such as the notification of observable events.
23599 @item show debug observer
23600 Displays the current state of observer debugging.
23601 @item set debug overload
23602 @cindex C@t{++} overload debugging info
23603 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23604 info. This includes info such as ranking of functions, etc. The default
23606 @item show debug overload
23607 Displays the current state of displaying @value{GDBN} C@t{++} overload
23609 @cindex expression parser, debugging info
23610 @cindex debug expression parser
23611 @item set debug parser
23612 Turns on or off the display of expression parser debugging output.
23613 Internally, this sets the @code{yydebug} variable in the expression
23614 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23615 details. The default is off.
23616 @item show debug parser
23617 Show the current state of expression parser debugging.
23618 @cindex packets, reporting on stdout
23619 @cindex serial connections, debugging
23620 @cindex debug remote protocol
23621 @cindex remote protocol debugging
23622 @cindex display remote packets
23623 @item set debug remote
23624 Turns on or off display of reports on all packets sent back and forth across
23625 the serial line to the remote machine. The info is printed on the
23626 @value{GDBN} standard output stream. The default is off.
23627 @item show debug remote
23628 Displays the state of display of remote packets.
23629 @item set debug serial
23630 Turns on or off display of @value{GDBN} serial debugging info. The
23632 @item show debug serial
23633 Displays the current state of displaying @value{GDBN} serial debugging
23635 @item set debug solib-frv
23636 @cindex FR-V shared-library debugging
23637 Turns on or off debugging messages for FR-V shared-library code.
23638 @item show debug solib-frv
23639 Display the current state of FR-V shared-library code debugging
23641 @item set debug symbol-lookup
23642 @cindex symbol lookup
23643 Turns on or off display of debugging messages related to symbol lookup.
23644 The default is 0 (off).
23645 A value of 1 provides basic information.
23646 A value greater than 1 provides more verbose information.
23647 @item show debug symbol-lookup
23648 Show the current state of symbol lookup debugging messages.
23649 @item set debug symfile
23650 @cindex symbol file functions
23651 Turns on or off display of debugging messages related to symbol file functions.
23652 The default is off. @xref{Files}.
23653 @item show debug symfile
23654 Show the current state of symbol file debugging messages.
23655 @item set debug symtab-create
23656 @cindex symbol table creation
23657 Turns on or off display of debugging messages related to symbol table creation.
23658 The default is 0 (off).
23659 A value of 1 provides basic information.
23660 A value greater than 1 provides more verbose information.
23661 @item show debug symtab-create
23662 Show the current state of symbol table creation debugging.
23663 @item set debug target
23664 @cindex target debugging info
23665 Turns on or off display of @value{GDBN} target debugging info. This info
23666 includes what is going on at the target level of GDB, as it happens. The
23667 default is 0. Set it to 1 to track events, and to 2 to also track the
23668 value of large memory transfers.
23669 @item show debug target
23670 Displays the current state of displaying @value{GDBN} target debugging
23672 @item set debug timestamp
23673 @cindex timestampping debugging info
23674 Turns on or off display of timestamps with @value{GDBN} debugging info.
23675 When enabled, seconds and microseconds are displayed before each debugging
23677 @item show debug timestamp
23678 Displays the current state of displaying timestamps with @value{GDBN}
23680 @item set debug varobj
23681 @cindex variable object debugging info
23682 Turns on or off display of @value{GDBN} variable object debugging
23683 info. The default is off.
23684 @item show debug varobj
23685 Displays the current state of displaying @value{GDBN} variable object
23687 @item set debug xml
23688 @cindex XML parser debugging
23689 Turns on or off debugging messages for built-in XML parsers.
23690 @item show debug xml
23691 Displays the current state of XML debugging messages.
23694 @node Other Misc Settings
23695 @section Other Miscellaneous Settings
23696 @cindex miscellaneous settings
23699 @kindex set interactive-mode
23700 @item set interactive-mode
23701 If @code{on}, forces @value{GDBN} to assume that GDB was started
23702 in a terminal. In practice, this means that @value{GDBN} should wait
23703 for the user to answer queries generated by commands entered at
23704 the command prompt. If @code{off}, forces @value{GDBN} to operate
23705 in the opposite mode, and it uses the default answers to all queries.
23706 If @code{auto} (the default), @value{GDBN} tries to determine whether
23707 its standard input is a terminal, and works in interactive-mode if it
23708 is, non-interactively otherwise.
23710 In the vast majority of cases, the debugger should be able to guess
23711 correctly which mode should be used. But this setting can be useful
23712 in certain specific cases, such as running a MinGW @value{GDBN}
23713 inside a cygwin window.
23715 @kindex show interactive-mode
23716 @item show interactive-mode
23717 Displays whether the debugger is operating in interactive mode or not.
23720 @node Extending GDB
23721 @chapter Extending @value{GDBN}
23722 @cindex extending GDB
23724 @value{GDBN} provides several mechanisms for extension.
23725 @value{GDBN} also provides the ability to automatically load
23726 extensions when it reads a file for debugging. This allows the
23727 user to automatically customize @value{GDBN} for the program
23731 * Sequences:: Canned Sequences of @value{GDBN} Commands
23732 * Python:: Extending @value{GDBN} using Python
23733 * Guile:: Extending @value{GDBN} using Guile
23734 * Auto-loading extensions:: Automatically loading extensions
23735 * Multiple Extension Languages:: Working with multiple extension languages
23736 * Aliases:: Creating new spellings of existing commands
23739 To facilitate the use of extension languages, @value{GDBN} is capable
23740 of evaluating the contents of a file. When doing so, @value{GDBN}
23741 can recognize which extension language is being used by looking at
23742 the filename extension. Files with an unrecognized filename extension
23743 are always treated as a @value{GDBN} Command Files.
23744 @xref{Command Files,, Command files}.
23746 You can control how @value{GDBN} evaluates these files with the following
23750 @kindex set script-extension
23751 @kindex show script-extension
23752 @item set script-extension off
23753 All scripts are always evaluated as @value{GDBN} Command Files.
23755 @item set script-extension soft
23756 The debugger determines the scripting language based on filename
23757 extension. If this scripting language is supported, @value{GDBN}
23758 evaluates the script using that language. Otherwise, it evaluates
23759 the file as a @value{GDBN} Command File.
23761 @item set script-extension strict
23762 The debugger determines the scripting language based on filename
23763 extension, and evaluates the script using that language. If the
23764 language is not supported, then the evaluation fails.
23766 @item show script-extension
23767 Display the current value of the @code{script-extension} option.
23772 @section Canned Sequences of Commands
23774 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23775 Command Lists}), @value{GDBN} provides two ways to store sequences of
23776 commands for execution as a unit: user-defined commands and command
23780 * Define:: How to define your own commands
23781 * Hooks:: Hooks for user-defined commands
23782 * Command Files:: How to write scripts of commands to be stored in a file
23783 * Output:: Commands for controlled output
23784 * Auto-loading sequences:: Controlling auto-loaded command files
23788 @subsection User-defined Commands
23790 @cindex user-defined command
23791 @cindex arguments, to user-defined commands
23792 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23793 which you assign a new name as a command. This is done with the
23794 @code{define} command. User commands may accept up to 10 arguments
23795 separated by whitespace. Arguments are accessed within the user command
23796 via @code{$arg0@dots{}$arg9}. A trivial example:
23800 print $arg0 + $arg1 + $arg2
23805 To execute the command use:
23812 This defines the command @code{adder}, which prints the sum of
23813 its three arguments. Note the arguments are text substitutions, so they may
23814 reference variables, use complex expressions, or even perform inferior
23817 @cindex argument count in user-defined commands
23818 @cindex how many arguments (user-defined commands)
23819 In addition, @code{$argc} may be used to find out how many arguments have
23820 been passed. This expands to a number in the range 0@dots{}10.
23825 print $arg0 + $arg1
23828 print $arg0 + $arg1 + $arg2
23836 @item define @var{commandname}
23837 Define a command named @var{commandname}. If there is already a command
23838 by that name, you are asked to confirm that you want to redefine it.
23839 The argument @var{commandname} may be a bare command name consisting of letters,
23840 numbers, dashes, and underscores. It may also start with any predefined
23841 prefix command. For example, @samp{define target my-target} creates
23842 a user-defined @samp{target my-target} command.
23844 The definition of the command is made up of other @value{GDBN} command lines,
23845 which are given following the @code{define} command. The end of these
23846 commands is marked by a line containing @code{end}.
23849 @kindex end@r{ (user-defined commands)}
23850 @item document @var{commandname}
23851 Document the user-defined command @var{commandname}, so that it can be
23852 accessed by @code{help}. The command @var{commandname} must already be
23853 defined. This command reads lines of documentation just as @code{define}
23854 reads the lines of the command definition, ending with @code{end}.
23855 After the @code{document} command is finished, @code{help} on command
23856 @var{commandname} displays the documentation you have written.
23858 You may use the @code{document} command again to change the
23859 documentation of a command. Redefining the command with @code{define}
23860 does not change the documentation.
23862 @kindex dont-repeat
23863 @cindex don't repeat command
23865 Used inside a user-defined command, this tells @value{GDBN} that this
23866 command should not be repeated when the user hits @key{RET}
23867 (@pxref{Command Syntax, repeat last command}).
23869 @kindex help user-defined
23870 @item help user-defined
23871 List all user-defined commands and all python commands defined in class
23872 COMAND_USER. The first line of the documentation or docstring is
23877 @itemx show user @var{commandname}
23878 Display the @value{GDBN} commands used to define @var{commandname} (but
23879 not its documentation). If no @var{commandname} is given, display the
23880 definitions for all user-defined commands.
23881 This does not work for user-defined python commands.
23883 @cindex infinite recursion in user-defined commands
23884 @kindex show max-user-call-depth
23885 @kindex set max-user-call-depth
23886 @item show max-user-call-depth
23887 @itemx set max-user-call-depth
23888 The value of @code{max-user-call-depth} controls how many recursion
23889 levels are allowed in user-defined commands before @value{GDBN} suspects an
23890 infinite recursion and aborts the command.
23891 This does not apply to user-defined python commands.
23894 In addition to the above commands, user-defined commands frequently
23895 use control flow commands, described in @ref{Command Files}.
23897 When user-defined commands are executed, the
23898 commands of the definition are not printed. An error in any command
23899 stops execution of the user-defined command.
23901 If used interactively, commands that would ask for confirmation proceed
23902 without asking when used inside a user-defined command. Many @value{GDBN}
23903 commands that normally print messages to say what they are doing omit the
23904 messages when used in a user-defined command.
23907 @subsection User-defined Command Hooks
23908 @cindex command hooks
23909 @cindex hooks, for commands
23910 @cindex hooks, pre-command
23913 You may define @dfn{hooks}, which are a special kind of user-defined
23914 command. Whenever you run the command @samp{foo}, if the user-defined
23915 command @samp{hook-foo} exists, it is executed (with no arguments)
23916 before that command.
23918 @cindex hooks, post-command
23920 A hook may also be defined which is run after the command you executed.
23921 Whenever you run the command @samp{foo}, if the user-defined command
23922 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23923 that command. Post-execution hooks may exist simultaneously with
23924 pre-execution hooks, for the same command.
23926 It is valid for a hook to call the command which it hooks. If this
23927 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23929 @c It would be nice if hookpost could be passed a parameter indicating
23930 @c if the command it hooks executed properly or not. FIXME!
23932 @kindex stop@r{, a pseudo-command}
23933 In addition, a pseudo-command, @samp{stop} exists. Defining
23934 (@samp{hook-stop}) makes the associated commands execute every time
23935 execution stops in your program: before breakpoint commands are run,
23936 displays are printed, or the stack frame is printed.
23938 For example, to ignore @code{SIGALRM} signals while
23939 single-stepping, but treat them normally during normal execution,
23944 handle SIGALRM nopass
23948 handle SIGALRM pass
23951 define hook-continue
23952 handle SIGALRM pass
23956 As a further example, to hook at the beginning and end of the @code{echo}
23957 command, and to add extra text to the beginning and end of the message,
23965 define hookpost-echo
23969 (@value{GDBP}) echo Hello World
23970 <<<---Hello World--->>>
23975 You can define a hook for any single-word command in @value{GDBN}, but
23976 not for command aliases; you should define a hook for the basic command
23977 name, e.g.@: @code{backtrace} rather than @code{bt}.
23978 @c FIXME! So how does Joe User discover whether a command is an alias
23980 You can hook a multi-word command by adding @code{hook-} or
23981 @code{hookpost-} to the last word of the command, e.g.@:
23982 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23984 If an error occurs during the execution of your hook, execution of
23985 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23986 (before the command that you actually typed had a chance to run).
23988 If you try to define a hook which does not match any known command, you
23989 get a warning from the @code{define} command.
23991 @node Command Files
23992 @subsection Command Files
23994 @cindex command files
23995 @cindex scripting commands
23996 A command file for @value{GDBN} is a text file made of lines that are
23997 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23998 also be included. An empty line in a command file does nothing; it
23999 does not mean to repeat the last command, as it would from the
24002 You can request the execution of a command file with the @code{source}
24003 command. Note that the @code{source} command is also used to evaluate
24004 scripts that are not Command Files. The exact behavior can be configured
24005 using the @code{script-extension} setting.
24006 @xref{Extending GDB,, Extending GDB}.
24010 @cindex execute commands from a file
24011 @item source [-s] [-v] @var{filename}
24012 Execute the command file @var{filename}.
24015 The lines in a command file are generally executed sequentially,
24016 unless the order of execution is changed by one of the
24017 @emph{flow-control commands} described below. The commands are not
24018 printed as they are executed. An error in any command terminates
24019 execution of the command file and control is returned to the console.
24021 @value{GDBN} first searches for @var{filename} in the current directory.
24022 If the file is not found there, and @var{filename} does not specify a
24023 directory, then @value{GDBN} also looks for the file on the source search path
24024 (specified with the @samp{directory} command);
24025 except that @file{$cdir} is not searched because the compilation directory
24026 is not relevant to scripts.
24028 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24029 on the search path even if @var{filename} specifies a directory.
24030 The search is done by appending @var{filename} to each element of the
24031 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24032 and the search path contains @file{/home/user} then @value{GDBN} will
24033 look for the script @file{/home/user/mylib/myscript}.
24034 The search is also done if @var{filename} is an absolute path.
24035 For example, if @var{filename} is @file{/tmp/myscript} and
24036 the search path contains @file{/home/user} then @value{GDBN} will
24037 look for the script @file{/home/user/tmp/myscript}.
24038 For DOS-like systems, if @var{filename} contains a drive specification,
24039 it is stripped before concatenation. For example, if @var{filename} is
24040 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24041 will look for the script @file{c:/tmp/myscript}.
24043 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24044 each command as it is executed. The option must be given before
24045 @var{filename}, and is interpreted as part of the filename anywhere else.
24047 Commands that would ask for confirmation if used interactively proceed
24048 without asking when used in a command file. Many @value{GDBN} commands that
24049 normally print messages to say what they are doing omit the messages
24050 when called from command files.
24052 @value{GDBN} also accepts command input from standard input. In this
24053 mode, normal output goes to standard output and error output goes to
24054 standard error. Errors in a command file supplied on standard input do
24055 not terminate execution of the command file---execution continues with
24059 gdb < cmds > log 2>&1
24062 (The syntax above will vary depending on the shell used.) This example
24063 will execute commands from the file @file{cmds}. All output and errors
24064 would be directed to @file{log}.
24066 Since commands stored on command files tend to be more general than
24067 commands typed interactively, they frequently need to deal with
24068 complicated situations, such as different or unexpected values of
24069 variables and symbols, changes in how the program being debugged is
24070 built, etc. @value{GDBN} provides a set of flow-control commands to
24071 deal with these complexities. Using these commands, you can write
24072 complex scripts that loop over data structures, execute commands
24073 conditionally, etc.
24080 This command allows to include in your script conditionally executed
24081 commands. The @code{if} command takes a single argument, which is an
24082 expression to evaluate. It is followed by a series of commands that
24083 are executed only if the expression is true (its value is nonzero).
24084 There can then optionally be an @code{else} line, followed by a series
24085 of commands that are only executed if the expression was false. The
24086 end of the list is marked by a line containing @code{end}.
24090 This command allows to write loops. Its syntax is similar to
24091 @code{if}: the command takes a single argument, which is an expression
24092 to evaluate, and must be followed by the commands to execute, one per
24093 line, terminated by an @code{end}. These commands are called the
24094 @dfn{body} of the loop. The commands in the body of @code{while} are
24095 executed repeatedly as long as the expression evaluates to true.
24099 This command exits the @code{while} loop in whose body it is included.
24100 Execution of the script continues after that @code{while}s @code{end}
24103 @kindex loop_continue
24104 @item loop_continue
24105 This command skips the execution of the rest of the body of commands
24106 in the @code{while} loop in whose body it is included. Execution
24107 branches to the beginning of the @code{while} loop, where it evaluates
24108 the controlling expression.
24110 @kindex end@r{ (if/else/while commands)}
24112 Terminate the block of commands that are the body of @code{if},
24113 @code{else}, or @code{while} flow-control commands.
24118 @subsection Commands for Controlled Output
24120 During the execution of a command file or a user-defined command, normal
24121 @value{GDBN} output is suppressed; the only output that appears is what is
24122 explicitly printed by the commands in the definition. This section
24123 describes three commands useful for generating exactly the output you
24128 @item echo @var{text}
24129 @c I do not consider backslash-space a standard C escape sequence
24130 @c because it is not in ANSI.
24131 Print @var{text}. Nonprinting characters can be included in
24132 @var{text} using C escape sequences, such as @samp{\n} to print a
24133 newline. @strong{No newline is printed unless you specify one.}
24134 In addition to the standard C escape sequences, a backslash followed
24135 by a space stands for a space. This is useful for displaying a
24136 string with spaces at the beginning or the end, since leading and
24137 trailing spaces are otherwise trimmed from all arguments.
24138 To print @samp{@w{ }and foo =@w{ }}, use the command
24139 @samp{echo \@w{ }and foo = \@w{ }}.
24141 A backslash at the end of @var{text} can be used, as in C, to continue
24142 the command onto subsequent lines. For example,
24145 echo This is some text\n\
24146 which is continued\n\
24147 onto several lines.\n
24150 produces the same output as
24153 echo This is some text\n
24154 echo which is continued\n
24155 echo onto several lines.\n
24159 @item output @var{expression}
24160 Print the value of @var{expression} and nothing but that value: no
24161 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24162 value history either. @xref{Expressions, ,Expressions}, for more information
24165 @item output/@var{fmt} @var{expression}
24166 Print the value of @var{expression} in format @var{fmt}. You can use
24167 the same formats as for @code{print}. @xref{Output Formats,,Output
24168 Formats}, for more information.
24171 @item printf @var{template}, @var{expressions}@dots{}
24172 Print the values of one or more @var{expressions} under the control of
24173 the string @var{template}. To print several values, make
24174 @var{expressions} be a comma-separated list of individual expressions,
24175 which may be either numbers or pointers. Their values are printed as
24176 specified by @var{template}, exactly as a C program would do by
24177 executing the code below:
24180 printf (@var{template}, @var{expressions}@dots{});
24183 As in @code{C} @code{printf}, ordinary characters in @var{template}
24184 are printed verbatim, while @dfn{conversion specification} introduced
24185 by the @samp{%} character cause subsequent @var{expressions} to be
24186 evaluated, their values converted and formatted according to type and
24187 style information encoded in the conversion specifications, and then
24190 For example, you can print two values in hex like this:
24193 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24196 @code{printf} supports all the standard @code{C} conversion
24197 specifications, including the flags and modifiers between the @samp{%}
24198 character and the conversion letter, with the following exceptions:
24202 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24205 The modifier @samp{*} is not supported for specifying precision or
24209 The @samp{'} flag (for separation of digits into groups according to
24210 @code{LC_NUMERIC'}) is not supported.
24213 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24217 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24220 The conversion letters @samp{a} and @samp{A} are not supported.
24224 Note that the @samp{ll} type modifier is supported only if the
24225 underlying @code{C} implementation used to build @value{GDBN} supports
24226 the @code{long long int} type, and the @samp{L} type modifier is
24227 supported only if @code{long double} type is available.
24229 As in @code{C}, @code{printf} supports simple backslash-escape
24230 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24231 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24232 single character. Octal and hexadecimal escape sequences are not
24235 Additionally, @code{printf} supports conversion specifications for DFP
24236 (@dfn{Decimal Floating Point}) types using the following length modifiers
24237 together with a floating point specifier.
24242 @samp{H} for printing @code{Decimal32} types.
24245 @samp{D} for printing @code{Decimal64} types.
24248 @samp{DD} for printing @code{Decimal128} types.
24251 If the underlying @code{C} implementation used to build @value{GDBN} has
24252 support for the three length modifiers for DFP types, other modifiers
24253 such as width and precision will also be available for @value{GDBN} to use.
24255 In case there is no such @code{C} support, no additional modifiers will be
24256 available and the value will be printed in the standard way.
24258 Here's an example of printing DFP types using the above conversion letters:
24260 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24264 @item eval @var{template}, @var{expressions}@dots{}
24265 Convert the values of one or more @var{expressions} under the control of
24266 the string @var{template} to a command line, and call it.
24270 @node Auto-loading sequences
24271 @subsection Controlling auto-loading native @value{GDBN} scripts
24272 @cindex native script auto-loading
24274 When a new object file is read (for example, due to the @code{file}
24275 command, or because the inferior has loaded a shared library),
24276 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24277 @xref{Auto-loading extensions}.
24279 Auto-loading can be enabled or disabled,
24280 and the list of auto-loaded scripts can be printed.
24283 @anchor{set auto-load gdb-scripts}
24284 @kindex set auto-load gdb-scripts
24285 @item set auto-load gdb-scripts [on|off]
24286 Enable or disable the auto-loading of canned sequences of commands scripts.
24288 @anchor{show auto-load gdb-scripts}
24289 @kindex show auto-load gdb-scripts
24290 @item show auto-load gdb-scripts
24291 Show whether auto-loading of canned sequences of commands scripts is enabled or
24294 @anchor{info auto-load gdb-scripts}
24295 @kindex info auto-load gdb-scripts
24296 @cindex print list of auto-loaded canned sequences of commands scripts
24297 @item info auto-load gdb-scripts [@var{regexp}]
24298 Print the list of all canned sequences of commands scripts that @value{GDBN}
24302 If @var{regexp} is supplied only canned sequences of commands scripts with
24303 matching names are printed.
24305 @c Python docs live in a separate file.
24306 @include python.texi
24308 @c Guile docs live in a separate file.
24309 @include guile.texi
24311 @node Auto-loading extensions
24312 @section Auto-loading extensions
24313 @cindex auto-loading extensions
24315 @value{GDBN} provides two mechanisms for automatically loading extensions
24316 when a new object file is read (for example, due to the @code{file}
24317 command, or because the inferior has loaded a shared library):
24318 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24319 section of modern file formats like ELF.
24322 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24323 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24324 * Which flavor to choose?::
24327 The auto-loading feature is useful for supplying application-specific
24328 debugging commands and features.
24330 Auto-loading can be enabled or disabled,
24331 and the list of auto-loaded scripts can be printed.
24332 See the @samp{auto-loading} section of each extension language
24333 for more information.
24334 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24335 For Python files see @ref{Python Auto-loading}.
24337 Note that loading of this script file also requires accordingly configured
24338 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24340 @node objfile-gdbdotext file
24341 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24342 @cindex @file{@var{objfile}-gdb.gdb}
24343 @cindex @file{@var{objfile}-gdb.py}
24344 @cindex @file{@var{objfile}-gdb.scm}
24346 When a new object file is read, @value{GDBN} looks for a file named
24347 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24348 where @var{objfile} is the object file's name and
24349 where @var{ext} is the file extension for the extension language:
24352 @item @file{@var{objfile}-gdb.gdb}
24353 GDB's own command language
24354 @item @file{@var{objfile}-gdb.py}
24356 @item @file{@var{objfile}-gdb.scm}
24360 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24361 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24362 components, and appending the @file{-gdb.@var{ext}} suffix.
24363 If this file exists and is readable, @value{GDBN} will evaluate it as a
24364 script in the specified extension language.
24366 If this file does not exist, then @value{GDBN} will look for
24367 @var{script-name} file in all of the directories as specified below.
24369 Note that loading of these files requires an accordingly configured
24370 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24372 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24373 scripts normally according to its @file{.exe} filename. But if no scripts are
24374 found @value{GDBN} also tries script filenames matching the object file without
24375 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24376 is attempted on any platform. This makes the script filenames compatible
24377 between Unix and MS-Windows hosts.
24380 @anchor{set auto-load scripts-directory}
24381 @kindex set auto-load scripts-directory
24382 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24383 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24384 may be delimited by the host platform path separator in use
24385 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24387 Each entry here needs to be covered also by the security setting
24388 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24390 @anchor{with-auto-load-dir}
24391 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24392 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24393 configuration option @option{--with-auto-load-dir}.
24395 Any reference to @file{$debugdir} will get replaced by
24396 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24397 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24398 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24399 @file{$datadir} must be placed as a directory component --- either alone or
24400 delimited by @file{/} or @file{\} directory separators, depending on the host
24403 The list of directories uses path separator (@samp{:} on GNU and Unix
24404 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24405 to the @env{PATH} environment variable.
24407 @anchor{show auto-load scripts-directory}
24408 @kindex show auto-load scripts-directory
24409 @item show auto-load scripts-directory
24410 Show @value{GDBN} auto-loaded scripts location.
24412 @anchor{add-auto-load-scripts-directory}
24413 @kindex add-auto-load-scripts-directory
24414 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24415 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24416 Multiple entries may be delimited by the host platform path separator in use.
24419 @value{GDBN} does not track which files it has already auto-loaded this way.
24420 @value{GDBN} will load the associated script every time the corresponding
24421 @var{objfile} is opened.
24422 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24423 is evaluated more than once.
24425 @node dotdebug_gdb_scripts section
24426 @subsection The @code{.debug_gdb_scripts} section
24427 @cindex @code{.debug_gdb_scripts} section
24429 For systems using file formats like ELF and COFF,
24430 when @value{GDBN} loads a new object file
24431 it will look for a special section named @code{.debug_gdb_scripts}.
24432 If this section exists, its contents is a list of null-terminated entries
24433 specifying scripts to load. Each entry begins with a non-null prefix byte that
24434 specifies the kind of entry, typically the extension language and whether the
24435 script is in a file or inlined in @code{.debug_gdb_scripts}.
24437 The following entries are supported:
24440 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24441 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24442 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24443 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24446 @subsubsection Script File Entries
24448 If the entry specifies a file, @value{GDBN} will look for the file first
24449 in the current directory and then along the source search path
24450 (@pxref{Source Path, ,Specifying Source Directories}),
24451 except that @file{$cdir} is not searched, since the compilation
24452 directory is not relevant to scripts.
24454 File entries can be placed in section @code{.debug_gdb_scripts} with,
24455 for example, this GCC macro for Python scripts.
24458 /* Note: The "MS" section flags are to remove duplicates. */
24459 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24461 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24462 .byte 1 /* Python */\n\
24463 .asciz \"" script_name "\"\n\
24469 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24470 Then one can reference the macro in a header or source file like this:
24473 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24476 The script name may include directories if desired.
24478 Note that loading of this script file also requires accordingly configured
24479 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24481 If the macro invocation is put in a header, any application or library
24482 using this header will get a reference to the specified script,
24483 and with the use of @code{"MS"} attributes on the section, the linker
24484 will remove duplicates.
24486 @subsubsection Script Text Entries
24488 Script text entries allow to put the executable script in the entry
24489 itself instead of loading it from a file.
24490 The first line of the entry, everything after the prefix byte and up to
24491 the first newline (@code{0xa}) character, is the script name, and must not
24492 contain any kind of space character, e.g., spaces or tabs.
24493 The rest of the entry, up to the trailing null byte, is the script to
24494 execute in the specified language. The name needs to be unique among
24495 all script names, as @value{GDBN} executes each script only once based
24498 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24502 #include "symcat.h"
24503 #include "gdb/section-scripts.h"
24505 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24506 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24507 ".ascii \"gdb.inlined-script\\n\"\n"
24508 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24509 ".ascii \" def __init__ (self):\\n\"\n"
24510 ".ascii \" super (test_cmd, self).__init__ ("
24511 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24512 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24513 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24514 ".ascii \"test_cmd ()\\n\"\n"
24520 Loading of inlined scripts requires a properly configured
24521 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24522 The path to specify in @code{auto-load safe-path} is the path of the file
24523 containing the @code{.debug_gdb_scripts} section.
24525 @node Which flavor to choose?
24526 @subsection Which flavor to choose?
24528 Given the multiple ways of auto-loading extensions, it might not always
24529 be clear which one to choose. This section provides some guidance.
24532 Benefits of the @file{-gdb.@var{ext}} way:
24536 Can be used with file formats that don't support multiple sections.
24539 Ease of finding scripts for public libraries.
24541 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24542 in the source search path.
24543 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24544 isn't a source directory in which to find the script.
24547 Doesn't require source code additions.
24551 Benefits of the @code{.debug_gdb_scripts} way:
24555 Works with static linking.
24557 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24558 trigger their loading. When an application is statically linked the only
24559 objfile available is the executable, and it is cumbersome to attach all the
24560 scripts from all the input libraries to the executable's
24561 @file{-gdb.@var{ext}} script.
24564 Works with classes that are entirely inlined.
24566 Some classes can be entirely inlined, and thus there may not be an associated
24567 shared library to attach a @file{-gdb.@var{ext}} script to.
24570 Scripts needn't be copied out of the source tree.
24572 In some circumstances, apps can be built out of large collections of internal
24573 libraries, and the build infrastructure necessary to install the
24574 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24575 cumbersome. It may be easier to specify the scripts in the
24576 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24577 top of the source tree to the source search path.
24580 @node Multiple Extension Languages
24581 @section Multiple Extension Languages
24583 The Guile and Python extension languages do not share any state,
24584 and generally do not interfere with each other.
24585 There are some things to be aware of, however.
24587 @subsection Python comes first
24589 Python was @value{GDBN}'s first extension language, and to avoid breaking
24590 existing behaviour Python comes first. This is generally solved by the
24591 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24592 extension languages, and when it makes a call to an extension language,
24593 (say to pretty-print a value), it tries each in turn until an extension
24594 language indicates it has performed the request (e.g., has returned the
24595 pretty-printed form of a value).
24596 This extends to errors while performing such requests: If an error happens
24597 while, for example, trying to pretty-print an object then the error is
24598 reported and any following extension languages are not tried.
24601 @section Creating new spellings of existing commands
24602 @cindex aliases for commands
24604 It is often useful to define alternate spellings of existing commands.
24605 For example, if a new @value{GDBN} command defined in Python has
24606 a long name to type, it is handy to have an abbreviated version of it
24607 that involves less typing.
24609 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24610 of the @samp{step} command even though it is otherwise an ambiguous
24611 abbreviation of other commands like @samp{set} and @samp{show}.
24613 Aliases are also used to provide shortened or more common versions
24614 of multi-word commands. For example, @value{GDBN} provides the
24615 @samp{tty} alias of the @samp{set inferior-tty} command.
24617 You can define a new alias with the @samp{alias} command.
24622 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24626 @var{ALIAS} specifies the name of the new alias.
24627 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24630 @var{COMMAND} specifies the name of an existing command
24631 that is being aliased.
24633 The @samp{-a} option specifies that the new alias is an abbreviation
24634 of the command. Abbreviations are not shown in command
24635 lists displayed by the @samp{help} command.
24637 The @samp{--} option specifies the end of options,
24638 and is useful when @var{ALIAS} begins with a dash.
24640 Here is a simple example showing how to make an abbreviation
24641 of a command so that there is less to type.
24642 Suppose you were tired of typing @samp{disas}, the current
24643 shortest unambiguous abbreviation of the @samp{disassemble} command
24644 and you wanted an even shorter version named @samp{di}.
24645 The following will accomplish this.
24648 (gdb) alias -a di = disas
24651 Note that aliases are different from user-defined commands.
24652 With a user-defined command, you also need to write documentation
24653 for it with the @samp{document} command.
24654 An alias automatically picks up the documentation of the existing command.
24656 Here is an example where we make @samp{elms} an abbreviation of
24657 @samp{elements} in the @samp{set print elements} command.
24658 This is to show that you can make an abbreviation of any part
24662 (gdb) alias -a set print elms = set print elements
24663 (gdb) alias -a show print elms = show print elements
24664 (gdb) set p elms 20
24666 Limit on string chars or array elements to print is 200.
24669 Note that if you are defining an alias of a @samp{set} command,
24670 and you want to have an alias for the corresponding @samp{show}
24671 command, then you need to define the latter separately.
24673 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24674 @var{ALIAS}, just as they are normally.
24677 (gdb) alias -a set pr elms = set p ele
24680 Finally, here is an example showing the creation of a one word
24681 alias for a more complex command.
24682 This creates alias @samp{spe} of the command @samp{set print elements}.
24685 (gdb) alias spe = set print elements
24690 @chapter Command Interpreters
24691 @cindex command interpreters
24693 @value{GDBN} supports multiple command interpreters, and some command
24694 infrastructure to allow users or user interface writers to switch
24695 between interpreters or run commands in other interpreters.
24697 @value{GDBN} currently supports two command interpreters, the console
24698 interpreter (sometimes called the command-line interpreter or @sc{cli})
24699 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24700 describes both of these interfaces in great detail.
24702 By default, @value{GDBN} will start with the console interpreter.
24703 However, the user may choose to start @value{GDBN} with another
24704 interpreter by specifying the @option{-i} or @option{--interpreter}
24705 startup options. Defined interpreters include:
24709 @cindex console interpreter
24710 The traditional console or command-line interpreter. This is the most often
24711 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24712 @value{GDBN} will use this interpreter.
24715 @cindex mi interpreter
24716 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24717 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24718 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24722 @cindex mi2 interpreter
24723 The current @sc{gdb/mi} interface.
24726 @cindex mi1 interpreter
24727 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24731 @cindex invoke another interpreter
24732 The interpreter being used by @value{GDBN} may not be dynamically
24733 switched at runtime. Although possible, this could lead to a very
24734 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24735 enters the command "interpreter-set console" in a console view,
24736 @value{GDBN} would switch to using the console interpreter, rendering
24737 the IDE inoperable!
24739 @kindex interpreter-exec
24740 Although you may only choose a single interpreter at startup, you may execute
24741 commands in any interpreter from the current interpreter using the appropriate
24742 command. If you are running the console interpreter, simply use the
24743 @code{interpreter-exec} command:
24746 interpreter-exec mi "-data-list-register-names"
24749 @sc{gdb/mi} has a similar command, although it is only available in versions of
24750 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24753 @chapter @value{GDBN} Text User Interface
24755 @cindex Text User Interface
24758 * TUI Overview:: TUI overview
24759 * TUI Keys:: TUI key bindings
24760 * TUI Single Key Mode:: TUI single key mode
24761 * TUI Commands:: TUI-specific commands
24762 * TUI Configuration:: TUI configuration variables
24765 The @value{GDBN} Text User Interface (TUI) is a terminal
24766 interface which uses the @code{curses} library to show the source
24767 file, the assembly output, the program registers and @value{GDBN}
24768 commands in separate text windows. The TUI mode is supported only
24769 on platforms where a suitable version of the @code{curses} library
24772 The TUI mode is enabled by default when you invoke @value{GDBN} as
24773 @samp{@value{GDBP} -tui}.
24774 You can also switch in and out of TUI mode while @value{GDBN} runs by
24775 using various TUI commands and key bindings, such as @command{tui
24776 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24777 @ref{TUI Keys, ,TUI Key Bindings}.
24780 @section TUI Overview
24782 In TUI mode, @value{GDBN} can display several text windows:
24786 This window is the @value{GDBN} command window with the @value{GDBN}
24787 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24788 managed using readline.
24791 The source window shows the source file of the program. The current
24792 line and active breakpoints are displayed in this window.
24795 The assembly window shows the disassembly output of the program.
24798 This window shows the processor registers. Registers are highlighted
24799 when their values change.
24802 The source and assembly windows show the current program position
24803 by highlighting the current line and marking it with a @samp{>} marker.
24804 Breakpoints are indicated with two markers. The first marker
24805 indicates the breakpoint type:
24809 Breakpoint which was hit at least once.
24812 Breakpoint which was never hit.
24815 Hardware breakpoint which was hit at least once.
24818 Hardware breakpoint which was never hit.
24821 The second marker indicates whether the breakpoint is enabled or not:
24825 Breakpoint is enabled.
24828 Breakpoint is disabled.
24831 The source, assembly and register windows are updated when the current
24832 thread changes, when the frame changes, or when the program counter
24835 These windows are not all visible at the same time. The command
24836 window is always visible. The others can be arranged in several
24847 source and assembly,
24850 source and registers, or
24853 assembly and registers.
24856 A status line above the command window shows the following information:
24860 Indicates the current @value{GDBN} target.
24861 (@pxref{Targets, ,Specifying a Debugging Target}).
24864 Gives the current process or thread number.
24865 When no process is being debugged, this field is set to @code{No process}.
24868 Gives the current function name for the selected frame.
24869 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24870 When there is no symbol corresponding to the current program counter,
24871 the string @code{??} is displayed.
24874 Indicates the current line number for the selected frame.
24875 When the current line number is not known, the string @code{??} is displayed.
24878 Indicates the current program counter address.
24882 @section TUI Key Bindings
24883 @cindex TUI key bindings
24885 The TUI installs several key bindings in the readline keymaps
24886 @ifset SYSTEM_READLINE
24887 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24889 @ifclear SYSTEM_READLINE
24890 (@pxref{Command Line Editing}).
24892 The following key bindings are installed for both TUI mode and the
24893 @value{GDBN} standard mode.
24902 Enter or leave the TUI mode. When leaving the TUI mode,
24903 the curses window management stops and @value{GDBN} operates using
24904 its standard mode, writing on the terminal directly. When reentering
24905 the TUI mode, control is given back to the curses windows.
24906 The screen is then refreshed.
24910 Use a TUI layout with only one window. The layout will
24911 either be @samp{source} or @samp{assembly}. When the TUI mode
24912 is not active, it will switch to the TUI mode.
24914 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24918 Use a TUI layout with at least two windows. When the current
24919 layout already has two windows, the next layout with two windows is used.
24920 When a new layout is chosen, one window will always be common to the
24921 previous layout and the new one.
24923 Think of it as the Emacs @kbd{C-x 2} binding.
24927 Change the active window. The TUI associates several key bindings
24928 (like scrolling and arrow keys) with the active window. This command
24929 gives the focus to the next TUI window.
24931 Think of it as the Emacs @kbd{C-x o} binding.
24935 Switch in and out of the TUI SingleKey mode that binds single
24936 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24939 The following key bindings only work in the TUI mode:
24944 Scroll the active window one page up.
24948 Scroll the active window one page down.
24952 Scroll the active window one line up.
24956 Scroll the active window one line down.
24960 Scroll the active window one column left.
24964 Scroll the active window one column right.
24968 Refresh the screen.
24971 Because the arrow keys scroll the active window in the TUI mode, they
24972 are not available for their normal use by readline unless the command
24973 window has the focus. When another window is active, you must use
24974 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24975 and @kbd{C-f} to control the command window.
24977 @node TUI Single Key Mode
24978 @section TUI Single Key Mode
24979 @cindex TUI single key mode
24981 The TUI also provides a @dfn{SingleKey} mode, which binds several
24982 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24983 switch into this mode, where the following key bindings are used:
24986 @kindex c @r{(SingleKey TUI key)}
24990 @kindex d @r{(SingleKey TUI key)}
24994 @kindex f @r{(SingleKey TUI key)}
24998 @kindex n @r{(SingleKey TUI key)}
25002 @kindex q @r{(SingleKey TUI key)}
25004 exit the SingleKey mode.
25006 @kindex r @r{(SingleKey TUI key)}
25010 @kindex s @r{(SingleKey TUI key)}
25014 @kindex u @r{(SingleKey TUI key)}
25018 @kindex v @r{(SingleKey TUI key)}
25022 @kindex w @r{(SingleKey TUI key)}
25027 Other keys temporarily switch to the @value{GDBN} command prompt.
25028 The key that was pressed is inserted in the editing buffer so that
25029 it is possible to type most @value{GDBN} commands without interaction
25030 with the TUI SingleKey mode. Once the command is entered the TUI
25031 SingleKey mode is restored. The only way to permanently leave
25032 this mode is by typing @kbd{q} or @kbd{C-x s}.
25036 @section TUI-specific Commands
25037 @cindex TUI commands
25039 The TUI has specific commands to control the text windows.
25040 These commands are always available, even when @value{GDBN} is not in
25041 the TUI mode. When @value{GDBN} is in the standard mode, most
25042 of these commands will automatically switch to the TUI mode.
25044 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25045 terminal, or @value{GDBN} has been started with the machine interface
25046 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25047 these commands will fail with an error, because it would not be
25048 possible or desirable to enable curses window management.
25053 Activate TUI mode. The last active TUI window layout will be used if
25054 TUI mode has prevsiouly been used in the current debugging session,
25055 otherwise a default layout is used.
25058 @kindex tui disable
25059 Disable TUI mode, returning to the console interpreter.
25063 List and give the size of all displayed windows.
25065 @item layout @var{name}
25067 Changes which TUI windows are displayed. In each layout the command
25068 window is always displayed, the @var{name} parameter controls which
25069 additional windows are displayed, and can be any of the following:
25073 Display the next layout.
25076 Display the previous layout.
25079 Display the source and command windows.
25082 Display the assembly and command windows.
25085 Display the source, assembly, and command windows.
25088 When in @code{src} layout display the register, source, and command
25089 windows. When in @code{asm} or @code{split} layout display the
25090 register, assembler, and command windows.
25093 @item focus @var{name}
25095 Changes which TUI window is currently active for scrolling. The
25096 @var{name} parameter can be any of the following:
25100 Make the next window active for scrolling.
25103 Make the previous window active for scrolling.
25106 Make the source window active for scrolling.
25109 Make the assembly window active for scrolling.
25112 Make the register window active for scrolling.
25115 Make the command window active for scrolling.
25120 Refresh the screen. This is similar to typing @kbd{C-L}.
25122 @item tui reg @var{group}
25124 Changes the register group displayed in the tui register window to
25125 @var{group}. If the register window is not currently displayed this
25126 command will cause the register window to be displayed. The list of
25127 register groups, as well as their order is target specific. The
25128 following groups are available on most targets:
25131 Repeatedly selecting this group will cause the display to cycle
25132 through all of the available register groups.
25135 Repeatedly selecting this group will cause the display to cycle
25136 through all of the available register groups in the reverse order to
25140 Display the general registers.
25142 Display the floating point registers.
25144 Display the system registers.
25146 Display the vector registers.
25148 Display all registers.
25153 Update the source window and the current execution point.
25155 @item winheight @var{name} +@var{count}
25156 @itemx winheight @var{name} -@var{count}
25158 Change the height of the window @var{name} by @var{count}
25159 lines. Positive counts increase the height, while negative counts
25160 decrease it. The @var{name} parameter can be one of @code{src} (the
25161 source window), @code{cmd} (the command window), @code{asm} (the
25162 disassembly window), or @code{regs} (the register display window).
25164 @item tabset @var{nchars}
25166 Set the width of tab stops to be @var{nchars} characters. This
25167 setting affects the display of TAB characters in the source and
25171 @node TUI Configuration
25172 @section TUI Configuration Variables
25173 @cindex TUI configuration variables
25175 Several configuration variables control the appearance of TUI windows.
25178 @item set tui border-kind @var{kind}
25179 @kindex set tui border-kind
25180 Select the border appearance for the source, assembly and register windows.
25181 The possible values are the following:
25184 Use a space character to draw the border.
25187 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25190 Use the Alternate Character Set to draw the border. The border is
25191 drawn using character line graphics if the terminal supports them.
25194 @item set tui border-mode @var{mode}
25195 @kindex set tui border-mode
25196 @itemx set tui active-border-mode @var{mode}
25197 @kindex set tui active-border-mode
25198 Select the display attributes for the borders of the inactive windows
25199 or the active window. The @var{mode} can be one of the following:
25202 Use normal attributes to display the border.
25208 Use reverse video mode.
25211 Use half bright mode.
25213 @item half-standout
25214 Use half bright and standout mode.
25217 Use extra bright or bold mode.
25219 @item bold-standout
25220 Use extra bright or bold and standout mode.
25225 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25228 @cindex @sc{gnu} Emacs
25229 A special interface allows you to use @sc{gnu} Emacs to view (and
25230 edit) the source files for the program you are debugging with
25233 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25234 executable file you want to debug as an argument. This command starts
25235 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25236 created Emacs buffer.
25237 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25239 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25244 All ``terminal'' input and output goes through an Emacs buffer, called
25247 This applies both to @value{GDBN} commands and their output, and to the input
25248 and output done by the program you are debugging.
25250 This is useful because it means that you can copy the text of previous
25251 commands and input them again; you can even use parts of the output
25254 All the facilities of Emacs' Shell mode are available for interacting
25255 with your program. In particular, you can send signals the usual
25256 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25260 @value{GDBN} displays source code through Emacs.
25262 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25263 source file for that frame and puts an arrow (@samp{=>}) at the
25264 left margin of the current line. Emacs uses a separate buffer for
25265 source display, and splits the screen to show both your @value{GDBN} session
25268 Explicit @value{GDBN} @code{list} or search commands still produce output as
25269 usual, but you probably have no reason to use them from Emacs.
25272 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25273 a graphical mode, enabled by default, which provides further buffers
25274 that can control the execution and describe the state of your program.
25275 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25277 If you specify an absolute file name when prompted for the @kbd{M-x
25278 gdb} argument, then Emacs sets your current working directory to where
25279 your program resides. If you only specify the file name, then Emacs
25280 sets your current working directory to the directory associated
25281 with the previous buffer. In this case, @value{GDBN} may find your
25282 program by searching your environment's @code{PATH} variable, but on
25283 some operating systems it might not find the source. So, although the
25284 @value{GDBN} input and output session proceeds normally, the auxiliary
25285 buffer does not display the current source and line of execution.
25287 The initial working directory of @value{GDBN} is printed on the top
25288 line of the GUD buffer and this serves as a default for the commands
25289 that specify files for @value{GDBN} to operate on. @xref{Files,
25290 ,Commands to Specify Files}.
25292 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25293 need to call @value{GDBN} by a different name (for example, if you
25294 keep several configurations around, with different names) you can
25295 customize the Emacs variable @code{gud-gdb-command-name} to run the
25298 In the GUD buffer, you can use these special Emacs commands in
25299 addition to the standard Shell mode commands:
25303 Describe the features of Emacs' GUD Mode.
25306 Execute to another source line, like the @value{GDBN} @code{step} command; also
25307 update the display window to show the current file and location.
25310 Execute to next source line in this function, skipping all function
25311 calls, like the @value{GDBN} @code{next} command. Then update the display window
25312 to show the current file and location.
25315 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25316 display window accordingly.
25319 Execute until exit from the selected stack frame, like the @value{GDBN}
25320 @code{finish} command.
25323 Continue execution of your program, like the @value{GDBN} @code{continue}
25327 Go up the number of frames indicated by the numeric argument
25328 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25329 like the @value{GDBN} @code{up} command.
25332 Go down the number of frames indicated by the numeric argument, like the
25333 @value{GDBN} @code{down} command.
25336 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25337 tells @value{GDBN} to set a breakpoint on the source line point is on.
25339 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25340 separate frame which shows a backtrace when the GUD buffer is current.
25341 Move point to any frame in the stack and type @key{RET} to make it
25342 become the current frame and display the associated source in the
25343 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25344 selected frame become the current one. In graphical mode, the
25345 speedbar displays watch expressions.
25347 If you accidentally delete the source-display buffer, an easy way to get
25348 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25349 request a frame display; when you run under Emacs, this recreates
25350 the source buffer if necessary to show you the context of the current
25353 The source files displayed in Emacs are in ordinary Emacs buffers
25354 which are visiting the source files in the usual way. You can edit
25355 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25356 communicates with Emacs in terms of line numbers. If you add or
25357 delete lines from the text, the line numbers that @value{GDBN} knows cease
25358 to correspond properly with the code.
25360 A more detailed description of Emacs' interaction with @value{GDBN} is
25361 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25365 @chapter The @sc{gdb/mi} Interface
25367 @unnumberedsec Function and Purpose
25369 @cindex @sc{gdb/mi}, its purpose
25370 @sc{gdb/mi} is a line based machine oriented text interface to
25371 @value{GDBN} and is activated by specifying using the
25372 @option{--interpreter} command line option (@pxref{Mode Options}). It
25373 is specifically intended to support the development of systems which
25374 use the debugger as just one small component of a larger system.
25376 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25377 in the form of a reference manual.
25379 Note that @sc{gdb/mi} is still under construction, so some of the
25380 features described below are incomplete and subject to change
25381 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25383 @unnumberedsec Notation and Terminology
25385 @cindex notational conventions, for @sc{gdb/mi}
25386 This chapter uses the following notation:
25390 @code{|} separates two alternatives.
25393 @code{[ @var{something} ]} indicates that @var{something} is optional:
25394 it may or may not be given.
25397 @code{( @var{group} )*} means that @var{group} inside the parentheses
25398 may repeat zero or more times.
25401 @code{( @var{group} )+} means that @var{group} inside the parentheses
25402 may repeat one or more times.
25405 @code{"@var{string}"} means a literal @var{string}.
25409 @heading Dependencies
25413 * GDB/MI General Design::
25414 * GDB/MI Command Syntax::
25415 * GDB/MI Compatibility with CLI::
25416 * GDB/MI Development and Front Ends::
25417 * GDB/MI Output Records::
25418 * GDB/MI Simple Examples::
25419 * GDB/MI Command Description Format::
25420 * GDB/MI Breakpoint Commands::
25421 * GDB/MI Catchpoint Commands::
25422 * GDB/MI Program Context::
25423 * GDB/MI Thread Commands::
25424 * GDB/MI Ada Tasking Commands::
25425 * GDB/MI Program Execution::
25426 * GDB/MI Stack Manipulation::
25427 * GDB/MI Variable Objects::
25428 * GDB/MI Data Manipulation::
25429 * GDB/MI Tracepoint Commands::
25430 * GDB/MI Symbol Query::
25431 * GDB/MI File Commands::
25433 * GDB/MI Kod Commands::
25434 * GDB/MI Memory Overlay Commands::
25435 * GDB/MI Signal Handling Commands::
25437 * GDB/MI Target Manipulation::
25438 * GDB/MI File Transfer Commands::
25439 * GDB/MI Ada Exceptions Commands::
25440 * GDB/MI Support Commands::
25441 * GDB/MI Miscellaneous Commands::
25444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25445 @node GDB/MI General Design
25446 @section @sc{gdb/mi} General Design
25447 @cindex GDB/MI General Design
25449 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25450 parts---commands sent to @value{GDBN}, responses to those commands
25451 and notifications. Each command results in exactly one response,
25452 indicating either successful completion of the command, or an error.
25453 For the commands that do not resume the target, the response contains the
25454 requested information. For the commands that resume the target, the
25455 response only indicates whether the target was successfully resumed.
25456 Notifications is the mechanism for reporting changes in the state of the
25457 target, or in @value{GDBN} state, that cannot conveniently be associated with
25458 a command and reported as part of that command response.
25460 The important examples of notifications are:
25464 Exec notifications. These are used to report changes in
25465 target state---when a target is resumed, or stopped. It would not
25466 be feasible to include this information in response of resuming
25467 commands, because one resume commands can result in multiple events in
25468 different threads. Also, quite some time may pass before any event
25469 happens in the target, while a frontend needs to know whether the resuming
25470 command itself was successfully executed.
25473 Console output, and status notifications. Console output
25474 notifications are used to report output of CLI commands, as well as
25475 diagnostics for other commands. Status notifications are used to
25476 report the progress of a long-running operation. Naturally, including
25477 this information in command response would mean no output is produced
25478 until the command is finished, which is undesirable.
25481 General notifications. Commands may have various side effects on
25482 the @value{GDBN} or target state beyond their official purpose. For example,
25483 a command may change the selected thread. Although such changes can
25484 be included in command response, using notification allows for more
25485 orthogonal frontend design.
25489 There's no guarantee that whenever an MI command reports an error,
25490 @value{GDBN} or the target are in any specific state, and especially,
25491 the state is not reverted to the state before the MI command was
25492 processed. Therefore, whenever an MI command results in an error,
25493 we recommend that the frontend refreshes all the information shown in
25494 the user interface.
25498 * Context management::
25499 * Asynchronous and non-stop modes::
25503 @node Context management
25504 @subsection Context management
25506 @subsubsection Threads and Frames
25508 In most cases when @value{GDBN} accesses the target, this access is
25509 done in context of a specific thread and frame (@pxref{Frames}).
25510 Often, even when accessing global data, the target requires that a thread
25511 be specified. The CLI interface maintains the selected thread and frame,
25512 and supplies them to target on each command. This is convenient,
25513 because a command line user would not want to specify that information
25514 explicitly on each command, and because user interacts with
25515 @value{GDBN} via a single terminal, so no confusion is possible as
25516 to what thread and frame are the current ones.
25518 In the case of MI, the concept of selected thread and frame is less
25519 useful. First, a frontend can easily remember this information
25520 itself. Second, a graphical frontend can have more than one window,
25521 each one used for debugging a different thread, and the frontend might
25522 want to access additional threads for internal purposes. This
25523 increases the risk that by relying on implicitly selected thread, the
25524 frontend may be operating on a wrong one. Therefore, each MI command
25525 should explicitly specify which thread and frame to operate on. To
25526 make it possible, each MI command accepts the @samp{--thread} and
25527 @samp{--frame} options, the value to each is @value{GDBN} identifier
25528 for thread and frame to operate on.
25530 Usually, each top-level window in a frontend allows the user to select
25531 a thread and a frame, and remembers the user selection for further
25532 operations. However, in some cases @value{GDBN} may suggest that the
25533 current thread be changed. For example, when stopping on a breakpoint
25534 it is reasonable to switch to the thread where breakpoint is hit. For
25535 another example, if the user issues the CLI @samp{thread} command via
25536 the frontend, it is desirable to change the frontend's selected thread to the
25537 one specified by user. @value{GDBN} communicates the suggestion to
25538 change current thread using the @samp{=thread-selected} notification.
25539 No such notification is available for the selected frame at the moment.
25541 Note that historically, MI shares the selected thread with CLI, so
25542 frontends used the @code{-thread-select} to execute commands in the
25543 right context. However, getting this to work right is cumbersome. The
25544 simplest way is for frontend to emit @code{-thread-select} command
25545 before every command. This doubles the number of commands that need
25546 to be sent. The alternative approach is to suppress @code{-thread-select}
25547 if the selected thread in @value{GDBN} is supposed to be identical to the
25548 thread the frontend wants to operate on. However, getting this
25549 optimization right can be tricky. In particular, if the frontend
25550 sends several commands to @value{GDBN}, and one of the commands changes the
25551 selected thread, then the behaviour of subsequent commands will
25552 change. So, a frontend should either wait for response from such
25553 problematic commands, or explicitly add @code{-thread-select} for
25554 all subsequent commands. No frontend is known to do this exactly
25555 right, so it is suggested to just always pass the @samp{--thread} and
25556 @samp{--frame} options.
25558 @subsubsection Language
25560 The execution of several commands depends on which language is selected.
25561 By default, the current language (@pxref{show language}) is used.
25562 But for commands known to be language-sensitive, it is recommended
25563 to use the @samp{--language} option. This option takes one argument,
25564 which is the name of the language to use while executing the command.
25568 -data-evaluate-expression --language c "sizeof (void*)"
25573 The valid language names are the same names accepted by the
25574 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25575 @samp{local} or @samp{unknown}.
25577 @node Asynchronous and non-stop modes
25578 @subsection Asynchronous command execution and non-stop mode
25580 On some targets, @value{GDBN} is capable of processing MI commands
25581 even while the target is running. This is called @dfn{asynchronous
25582 command execution} (@pxref{Background Execution}). The frontend may
25583 specify a preferrence for asynchronous execution using the
25584 @code{-gdb-set mi-async 1} command, which should be emitted before
25585 either running the executable or attaching to the target. After the
25586 frontend has started the executable or attached to the target, it can
25587 find if asynchronous execution is enabled using the
25588 @code{-list-target-features} command.
25591 @item -gdb-set mi-async on
25592 @item -gdb-set mi-async off
25593 Set whether MI is in asynchronous mode.
25595 When @code{off}, which is the default, MI execution commands (e.g.,
25596 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25597 for the program to stop before processing further commands.
25599 When @code{on}, MI execution commands are background execution
25600 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25601 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25602 MI commands even while the target is running.
25604 @item -gdb-show mi-async
25605 Show whether MI asynchronous mode is enabled.
25608 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25609 @code{target-async} instead of @code{mi-async}, and it had the effect
25610 of both putting MI in asynchronous mode and making CLI background
25611 commands possible. CLI background commands are now always possible
25612 ``out of the box'' if the target supports them. The old spelling is
25613 kept as a deprecated alias for backwards compatibility.
25615 Even if @value{GDBN} can accept a command while target is running,
25616 many commands that access the target do not work when the target is
25617 running. Therefore, asynchronous command execution is most useful
25618 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25619 it is possible to examine the state of one thread, while other threads
25622 When a given thread is running, MI commands that try to access the
25623 target in the context of that thread may not work, or may work only on
25624 some targets. In particular, commands that try to operate on thread's
25625 stack will not work, on any target. Commands that read memory, or
25626 modify breakpoints, may work or not work, depending on the target. Note
25627 that even commands that operate on global state, such as @code{print},
25628 @code{set}, and breakpoint commands, still access the target in the
25629 context of a specific thread, so frontend should try to find a
25630 stopped thread and perform the operation on that thread (using the
25631 @samp{--thread} option).
25633 Which commands will work in the context of a running thread is
25634 highly target dependent. However, the two commands
25635 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25636 to find the state of a thread, will always work.
25638 @node Thread groups
25639 @subsection Thread groups
25640 @value{GDBN} may be used to debug several processes at the same time.
25641 On some platfroms, @value{GDBN} may support debugging of several
25642 hardware systems, each one having several cores with several different
25643 processes running on each core. This section describes the MI
25644 mechanism to support such debugging scenarios.
25646 The key observation is that regardless of the structure of the
25647 target, MI can have a global list of threads, because most commands that
25648 accept the @samp{--thread} option do not need to know what process that
25649 thread belongs to. Therefore, it is not necessary to introduce
25650 neither additional @samp{--process} option, nor an notion of the
25651 current process in the MI interface. The only strictly new feature
25652 that is required is the ability to find how the threads are grouped
25655 To allow the user to discover such grouping, and to support arbitrary
25656 hierarchy of machines/cores/processes, MI introduces the concept of a
25657 @dfn{thread group}. Thread group is a collection of threads and other
25658 thread groups. A thread group always has a string identifier, a type,
25659 and may have additional attributes specific to the type. A new
25660 command, @code{-list-thread-groups}, returns the list of top-level
25661 thread groups, which correspond to processes that @value{GDBN} is
25662 debugging at the moment. By passing an identifier of a thread group
25663 to the @code{-list-thread-groups} command, it is possible to obtain
25664 the members of specific thread group.
25666 To allow the user to easily discover processes, and other objects, he
25667 wishes to debug, a concept of @dfn{available thread group} is
25668 introduced. Available thread group is an thread group that
25669 @value{GDBN} is not debugging, but that can be attached to, using the
25670 @code{-target-attach} command. The list of available top-level thread
25671 groups can be obtained using @samp{-list-thread-groups --available}.
25672 In general, the content of a thread group may be only retrieved only
25673 after attaching to that thread group.
25675 Thread groups are related to inferiors (@pxref{Inferiors and
25676 Programs}). Each inferior corresponds to a thread group of a special
25677 type @samp{process}, and some additional operations are permitted on
25678 such thread groups.
25680 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25681 @node GDB/MI Command Syntax
25682 @section @sc{gdb/mi} Command Syntax
25685 * GDB/MI Input Syntax::
25686 * GDB/MI Output Syntax::
25689 @node GDB/MI Input Syntax
25690 @subsection @sc{gdb/mi} Input Syntax
25692 @cindex input syntax for @sc{gdb/mi}
25693 @cindex @sc{gdb/mi}, input syntax
25695 @item @var{command} @expansion{}
25696 @code{@var{cli-command} | @var{mi-command}}
25698 @item @var{cli-command} @expansion{}
25699 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25700 @var{cli-command} is any existing @value{GDBN} CLI command.
25702 @item @var{mi-command} @expansion{}
25703 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25704 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25706 @item @var{token} @expansion{}
25707 "any sequence of digits"
25709 @item @var{option} @expansion{}
25710 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25712 @item @var{parameter} @expansion{}
25713 @code{@var{non-blank-sequence} | @var{c-string}}
25715 @item @var{operation} @expansion{}
25716 @emph{any of the operations described in this chapter}
25718 @item @var{non-blank-sequence} @expansion{}
25719 @emph{anything, provided it doesn't contain special characters such as
25720 "-", @var{nl}, """ and of course " "}
25722 @item @var{c-string} @expansion{}
25723 @code{""" @var{seven-bit-iso-c-string-content} """}
25725 @item @var{nl} @expansion{}
25734 The CLI commands are still handled by the @sc{mi} interpreter; their
25735 output is described below.
25738 The @code{@var{token}}, when present, is passed back when the command
25742 Some @sc{mi} commands accept optional arguments as part of the parameter
25743 list. Each option is identified by a leading @samp{-} (dash) and may be
25744 followed by an optional argument parameter. Options occur first in the
25745 parameter list and can be delimited from normal parameters using
25746 @samp{--} (this is useful when some parameters begin with a dash).
25753 We want easy access to the existing CLI syntax (for debugging).
25756 We want it to be easy to spot a @sc{mi} operation.
25759 @node GDB/MI Output Syntax
25760 @subsection @sc{gdb/mi} Output Syntax
25762 @cindex output syntax of @sc{gdb/mi}
25763 @cindex @sc{gdb/mi}, output syntax
25764 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25765 followed, optionally, by a single result record. This result record
25766 is for the most recent command. The sequence of output records is
25767 terminated by @samp{(gdb)}.
25769 If an input command was prefixed with a @code{@var{token}} then the
25770 corresponding output for that command will also be prefixed by that same
25774 @item @var{output} @expansion{}
25775 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25777 @item @var{result-record} @expansion{}
25778 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25780 @item @var{out-of-band-record} @expansion{}
25781 @code{@var{async-record} | @var{stream-record}}
25783 @item @var{async-record} @expansion{}
25784 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25786 @item @var{exec-async-output} @expansion{}
25787 @code{[ @var{token} ] "*" @var{async-output nl}}
25789 @item @var{status-async-output} @expansion{}
25790 @code{[ @var{token} ] "+" @var{async-output nl}}
25792 @item @var{notify-async-output} @expansion{}
25793 @code{[ @var{token} ] "=" @var{async-output nl}}
25795 @item @var{async-output} @expansion{}
25796 @code{@var{async-class} ( "," @var{result} )*}
25798 @item @var{result-class} @expansion{}
25799 @code{"done" | "running" | "connected" | "error" | "exit"}
25801 @item @var{async-class} @expansion{}
25802 @code{"stopped" | @var{others}} (where @var{others} will be added
25803 depending on the needs---this is still in development).
25805 @item @var{result} @expansion{}
25806 @code{ @var{variable} "=" @var{value}}
25808 @item @var{variable} @expansion{}
25809 @code{ @var{string} }
25811 @item @var{value} @expansion{}
25812 @code{ @var{const} | @var{tuple} | @var{list} }
25814 @item @var{const} @expansion{}
25815 @code{@var{c-string}}
25817 @item @var{tuple} @expansion{}
25818 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25820 @item @var{list} @expansion{}
25821 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25822 @var{result} ( "," @var{result} )* "]" }
25824 @item @var{stream-record} @expansion{}
25825 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25827 @item @var{console-stream-output} @expansion{}
25828 @code{"~" @var{c-string nl}}
25830 @item @var{target-stream-output} @expansion{}
25831 @code{"@@" @var{c-string nl}}
25833 @item @var{log-stream-output} @expansion{}
25834 @code{"&" @var{c-string nl}}
25836 @item @var{nl} @expansion{}
25839 @item @var{token} @expansion{}
25840 @emph{any sequence of digits}.
25848 All output sequences end in a single line containing a period.
25851 The @code{@var{token}} is from the corresponding request. Note that
25852 for all async output, while the token is allowed by the grammar and
25853 may be output by future versions of @value{GDBN} for select async
25854 output messages, it is generally omitted. Frontends should treat
25855 all async output as reporting general changes in the state of the
25856 target and there should be no need to associate async output to any
25860 @cindex status output in @sc{gdb/mi}
25861 @var{status-async-output} contains on-going status information about the
25862 progress of a slow operation. It can be discarded. All status output is
25863 prefixed by @samp{+}.
25866 @cindex async output in @sc{gdb/mi}
25867 @var{exec-async-output} contains asynchronous state change on the target
25868 (stopped, started, disappeared). All async output is prefixed by
25872 @cindex notify output in @sc{gdb/mi}
25873 @var{notify-async-output} contains supplementary information that the
25874 client should handle (e.g., a new breakpoint information). All notify
25875 output is prefixed by @samp{=}.
25878 @cindex console output in @sc{gdb/mi}
25879 @var{console-stream-output} is output that should be displayed as is in the
25880 console. It is the textual response to a CLI command. All the console
25881 output is prefixed by @samp{~}.
25884 @cindex target output in @sc{gdb/mi}
25885 @var{target-stream-output} is the output produced by the target program.
25886 All the target output is prefixed by @samp{@@}.
25889 @cindex log output in @sc{gdb/mi}
25890 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25891 instance messages that should be displayed as part of an error log. All
25892 the log output is prefixed by @samp{&}.
25895 @cindex list output in @sc{gdb/mi}
25896 New @sc{gdb/mi} commands should only output @var{lists} containing
25902 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25903 details about the various output records.
25905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25906 @node GDB/MI Compatibility with CLI
25907 @section @sc{gdb/mi} Compatibility with CLI
25909 @cindex compatibility, @sc{gdb/mi} and CLI
25910 @cindex @sc{gdb/mi}, compatibility with CLI
25912 For the developers convenience CLI commands can be entered directly,
25913 but there may be some unexpected behaviour. For example, commands
25914 that query the user will behave as if the user replied yes, breakpoint
25915 command lists are not executed and some CLI commands, such as
25916 @code{if}, @code{when} and @code{define}, prompt for further input with
25917 @samp{>}, which is not valid MI output.
25919 This feature may be removed at some stage in the future and it is
25920 recommended that front ends use the @code{-interpreter-exec} command
25921 (@pxref{-interpreter-exec}).
25923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25924 @node GDB/MI Development and Front Ends
25925 @section @sc{gdb/mi} Development and Front Ends
25926 @cindex @sc{gdb/mi} development
25928 The application which takes the MI output and presents the state of the
25929 program being debugged to the user is called a @dfn{front end}.
25931 Although @sc{gdb/mi} is still incomplete, it is currently being used
25932 by a variety of front ends to @value{GDBN}. This makes it difficult
25933 to introduce new functionality without breaking existing usage. This
25934 section tries to minimize the problems by describing how the protocol
25937 Some changes in MI need not break a carefully designed front end, and
25938 for these the MI version will remain unchanged. The following is a
25939 list of changes that may occur within one level, so front ends should
25940 parse MI output in a way that can handle them:
25944 New MI commands may be added.
25947 New fields may be added to the output of any MI command.
25950 The range of values for fields with specified values, e.g.,
25951 @code{in_scope} (@pxref{-var-update}) may be extended.
25953 @c The format of field's content e.g type prefix, may change so parse it
25954 @c at your own risk. Yes, in general?
25956 @c The order of fields may change? Shouldn't really matter but it might
25957 @c resolve inconsistencies.
25960 If the changes are likely to break front ends, the MI version level
25961 will be increased by one. This will allow the front end to parse the
25962 output according to the MI version. Apart from mi0, new versions of
25963 @value{GDBN} will not support old versions of MI and it will be the
25964 responsibility of the front end to work with the new one.
25966 @c Starting with mi3, add a new command -mi-version that prints the MI
25969 The best way to avoid unexpected changes in MI that might break your front
25970 end is to make your project known to @value{GDBN} developers and
25971 follow development on @email{gdb@@sourceware.org} and
25972 @email{gdb-patches@@sourceware.org}.
25973 @cindex mailing lists
25975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25976 @node GDB/MI Output Records
25977 @section @sc{gdb/mi} Output Records
25980 * GDB/MI Result Records::
25981 * GDB/MI Stream Records::
25982 * GDB/MI Async Records::
25983 * GDB/MI Breakpoint Information::
25984 * GDB/MI Frame Information::
25985 * GDB/MI Thread Information::
25986 * GDB/MI Ada Exception Information::
25989 @node GDB/MI Result Records
25990 @subsection @sc{gdb/mi} Result Records
25992 @cindex result records in @sc{gdb/mi}
25993 @cindex @sc{gdb/mi}, result records
25994 In addition to a number of out-of-band notifications, the response to a
25995 @sc{gdb/mi} command includes one of the following result indications:
25999 @item "^done" [ "," @var{results} ]
26000 The synchronous operation was successful, @code{@var{results}} are the return
26005 This result record is equivalent to @samp{^done}. Historically, it
26006 was output instead of @samp{^done} if the command has resumed the
26007 target. This behaviour is maintained for backward compatibility, but
26008 all frontends should treat @samp{^done} and @samp{^running}
26009 identically and rely on the @samp{*running} output record to determine
26010 which threads are resumed.
26014 @value{GDBN} has connected to a remote target.
26016 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26018 The operation failed. The @code{msg=@var{c-string}} variable contains
26019 the corresponding error message.
26021 If present, the @code{code=@var{c-string}} variable provides an error
26022 code on which consumers can rely on to detect the corresponding
26023 error condition. At present, only one error code is defined:
26026 @item "undefined-command"
26027 Indicates that the command causing the error does not exist.
26032 @value{GDBN} has terminated.
26036 @node GDB/MI Stream Records
26037 @subsection @sc{gdb/mi} Stream Records
26039 @cindex @sc{gdb/mi}, stream records
26040 @cindex stream records in @sc{gdb/mi}
26041 @value{GDBN} internally maintains a number of output streams: the console, the
26042 target, and the log. The output intended for each of these streams is
26043 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26045 Each stream record begins with a unique @dfn{prefix character} which
26046 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26047 Syntax}). In addition to the prefix, each stream record contains a
26048 @code{@var{string-output}}. This is either raw text (with an implicit new
26049 line) or a quoted C string (which does not contain an implicit newline).
26052 @item "~" @var{string-output}
26053 The console output stream contains text that should be displayed in the
26054 CLI console window. It contains the textual responses to CLI commands.
26056 @item "@@" @var{string-output}
26057 The target output stream contains any textual output from the running
26058 target. This is only present when GDB's event loop is truly
26059 asynchronous, which is currently only the case for remote targets.
26061 @item "&" @var{string-output}
26062 The log stream contains debugging messages being produced by @value{GDBN}'s
26066 @node GDB/MI Async Records
26067 @subsection @sc{gdb/mi} Async Records
26069 @cindex async records in @sc{gdb/mi}
26070 @cindex @sc{gdb/mi}, async records
26071 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26072 additional changes that have occurred. Those changes can either be a
26073 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26074 target activity (e.g., target stopped).
26076 The following is the list of possible async records:
26080 @item *running,thread-id="@var{thread}"
26081 The target is now running. The @var{thread} field tells which
26082 specific thread is now running, and can be @samp{all} if all threads
26083 are running. The frontend should assume that no interaction with a
26084 running thread is possible after this notification is produced.
26085 The frontend should not assume that this notification is output
26086 only once for any command. @value{GDBN} may emit this notification
26087 several times, either for different threads, because it cannot resume
26088 all threads together, or even for a single thread, if the thread must
26089 be stepped though some code before letting it run freely.
26091 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26092 The target has stopped. The @var{reason} field can have one of the
26096 @item breakpoint-hit
26097 A breakpoint was reached.
26098 @item watchpoint-trigger
26099 A watchpoint was triggered.
26100 @item read-watchpoint-trigger
26101 A read watchpoint was triggered.
26102 @item access-watchpoint-trigger
26103 An access watchpoint was triggered.
26104 @item function-finished
26105 An -exec-finish or similar CLI command was accomplished.
26106 @item location-reached
26107 An -exec-until or similar CLI command was accomplished.
26108 @item watchpoint-scope
26109 A watchpoint has gone out of scope.
26110 @item end-stepping-range
26111 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26112 similar CLI command was accomplished.
26113 @item exited-signalled
26114 The inferior exited because of a signal.
26116 The inferior exited.
26117 @item exited-normally
26118 The inferior exited normally.
26119 @item signal-received
26120 A signal was received by the inferior.
26122 The inferior has stopped due to a library being loaded or unloaded.
26123 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26124 set or when a @code{catch load} or @code{catch unload} catchpoint is
26125 in use (@pxref{Set Catchpoints}).
26127 The inferior has forked. This is reported when @code{catch fork}
26128 (@pxref{Set Catchpoints}) has been used.
26130 The inferior has vforked. This is reported in when @code{catch vfork}
26131 (@pxref{Set Catchpoints}) has been used.
26132 @item syscall-entry
26133 The inferior entered a system call. This is reported when @code{catch
26134 syscall} (@pxref{Set Catchpoints}) has been used.
26135 @item syscall-return
26136 The inferior returned from a system call. This is reported when
26137 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26139 The inferior called @code{exec}. This is reported when @code{catch exec}
26140 (@pxref{Set Catchpoints}) has been used.
26143 The @var{id} field identifies the thread that directly caused the stop
26144 -- for example by hitting a breakpoint. Depending on whether all-stop
26145 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26146 stop all threads, or only the thread that directly triggered the stop.
26147 If all threads are stopped, the @var{stopped} field will have the
26148 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26149 field will be a list of thread identifiers. Presently, this list will
26150 always include a single thread, but frontend should be prepared to see
26151 several threads in the list. The @var{core} field reports the
26152 processor core on which the stop event has happened. This field may be absent
26153 if such information is not available.
26155 @item =thread-group-added,id="@var{id}"
26156 @itemx =thread-group-removed,id="@var{id}"
26157 A thread group was either added or removed. The @var{id} field
26158 contains the @value{GDBN} identifier of the thread group. When a thread
26159 group is added, it generally might not be associated with a running
26160 process. When a thread group is removed, its id becomes invalid and
26161 cannot be used in any way.
26163 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26164 A thread group became associated with a running program,
26165 either because the program was just started or the thread group
26166 was attached to a program. The @var{id} field contains the
26167 @value{GDBN} identifier of the thread group. The @var{pid} field
26168 contains process identifier, specific to the operating system.
26170 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26171 A thread group is no longer associated with a running program,
26172 either because the program has exited, or because it was detached
26173 from. The @var{id} field contains the @value{GDBN} identifier of the
26174 thread group. The @var{code} field is the exit code of the inferior; it exists
26175 only when the inferior exited with some code.
26177 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26178 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26179 A thread either was created, or has exited. The @var{id} field
26180 contains the @value{GDBN} identifier of the thread. The @var{gid}
26181 field identifies the thread group this thread belongs to.
26183 @item =thread-selected,id="@var{id}"
26184 Informs that the selected thread was changed as result of the last
26185 command. This notification is not emitted as result of @code{-thread-select}
26186 command but is emitted whenever an MI command that is not documented
26187 to change the selected thread actually changes it. In particular,
26188 invoking, directly or indirectly (via user-defined command), the CLI
26189 @code{thread} command, will generate this notification.
26191 We suggest that in response to this notification, front ends
26192 highlight the selected thread and cause subsequent commands to apply to
26195 @item =library-loaded,...
26196 Reports that a new library file was loaded by the program. This
26197 notification has 4 fields---@var{id}, @var{target-name},
26198 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26199 opaque identifier of the library. For remote debugging case,
26200 @var{target-name} and @var{host-name} fields give the name of the
26201 library file on the target, and on the host respectively. For native
26202 debugging, both those fields have the same value. The
26203 @var{symbols-loaded} field is emitted only for backward compatibility
26204 and should not be relied on to convey any useful information. The
26205 @var{thread-group} field, if present, specifies the id of the thread
26206 group in whose context the library was loaded. If the field is
26207 absent, it means the library was loaded in the context of all present
26210 @item =library-unloaded,...
26211 Reports that a library was unloaded by the program. This notification
26212 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26213 the same meaning as for the @code{=library-loaded} notification.
26214 The @var{thread-group} field, if present, specifies the id of the
26215 thread group in whose context the library was unloaded. If the field is
26216 absent, it means the library was unloaded in the context of all present
26219 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26220 @itemx =traceframe-changed,end
26221 Reports that the trace frame was changed and its new number is
26222 @var{tfnum}. The number of the tracepoint associated with this trace
26223 frame is @var{tpnum}.
26225 @item =tsv-created,name=@var{name},initial=@var{initial}
26226 Reports that the new trace state variable @var{name} is created with
26227 initial value @var{initial}.
26229 @item =tsv-deleted,name=@var{name}
26230 @itemx =tsv-deleted
26231 Reports that the trace state variable @var{name} is deleted or all
26232 trace state variables are deleted.
26234 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26235 Reports that the trace state variable @var{name} is modified with
26236 the initial value @var{initial}. The current value @var{current} of
26237 trace state variable is optional and is reported if the current
26238 value of trace state variable is known.
26240 @item =breakpoint-created,bkpt=@{...@}
26241 @itemx =breakpoint-modified,bkpt=@{...@}
26242 @itemx =breakpoint-deleted,id=@var{number}
26243 Reports that a breakpoint was created, modified, or deleted,
26244 respectively. Only user-visible breakpoints are reported to the MI
26247 The @var{bkpt} argument is of the same form as returned by the various
26248 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26249 @var{number} is the ordinal number of the breakpoint.
26251 Note that if a breakpoint is emitted in the result record of a
26252 command, then it will not also be emitted in an async record.
26254 @item =record-started,thread-group="@var{id}"
26255 @itemx =record-stopped,thread-group="@var{id}"
26256 Execution log recording was either started or stopped on an
26257 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26258 group corresponding to the affected inferior.
26260 @item =cmd-param-changed,param=@var{param},value=@var{value}
26261 Reports that a parameter of the command @code{set @var{param}} is
26262 changed to @var{value}. In the multi-word @code{set} command,
26263 the @var{param} is the whole parameter list to @code{set} command.
26264 For example, In command @code{set check type on}, @var{param}
26265 is @code{check type} and @var{value} is @code{on}.
26267 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26268 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26269 written in an inferior. The @var{id} is the identifier of the
26270 thread group corresponding to the affected inferior. The optional
26271 @code{type="code"} part is reported if the memory written to holds
26275 @node GDB/MI Breakpoint Information
26276 @subsection @sc{gdb/mi} Breakpoint Information
26278 When @value{GDBN} reports information about a breakpoint, a
26279 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26284 The breakpoint number. For a breakpoint that represents one location
26285 of a multi-location breakpoint, this will be a dotted pair, like
26289 The type of the breakpoint. For ordinary breakpoints this will be
26290 @samp{breakpoint}, but many values are possible.
26293 If the type of the breakpoint is @samp{catchpoint}, then this
26294 indicates the exact type of catchpoint.
26297 This is the breakpoint disposition---either @samp{del}, meaning that
26298 the breakpoint will be deleted at the next stop, or @samp{keep},
26299 meaning that the breakpoint will not be deleted.
26302 This indicates whether the breakpoint is enabled, in which case the
26303 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26304 Note that this is not the same as the field @code{enable}.
26307 The address of the breakpoint. This may be a hexidecimal number,
26308 giving the address; or the string @samp{<PENDING>}, for a pending
26309 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26310 multiple locations. This field will not be present if no address can
26311 be determined. For example, a watchpoint does not have an address.
26314 If known, the function in which the breakpoint appears.
26315 If not known, this field is not present.
26318 The name of the source file which contains this function, if known.
26319 If not known, this field is not present.
26322 The full file name of the source file which contains this function, if
26323 known. If not known, this field is not present.
26326 The line number at which this breakpoint appears, if known.
26327 If not known, this field is not present.
26330 If the source file is not known, this field may be provided. If
26331 provided, this holds the address of the breakpoint, possibly followed
26335 If this breakpoint is pending, this field is present and holds the
26336 text used to set the breakpoint, as entered by the user.
26339 Where this breakpoint's condition is evaluated, either @samp{host} or
26343 If this is a thread-specific breakpoint, then this identifies the
26344 thread in which the breakpoint can trigger.
26347 If this breakpoint is restricted to a particular Ada task, then this
26348 field will hold the task identifier.
26351 If the breakpoint is conditional, this is the condition expression.
26354 The ignore count of the breakpoint.
26357 The enable count of the breakpoint.
26359 @item traceframe-usage
26362 @item static-tracepoint-marker-string-id
26363 For a static tracepoint, the name of the static tracepoint marker.
26366 For a masked watchpoint, this is the mask.
26369 A tracepoint's pass count.
26371 @item original-location
26372 The location of the breakpoint as originally specified by the user.
26373 This field is optional.
26376 The number of times the breakpoint has been hit.
26379 This field is only given for tracepoints. This is either @samp{y},
26380 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26384 Some extra data, the exact contents of which are type-dependent.
26388 For example, here is what the output of @code{-break-insert}
26389 (@pxref{GDB/MI Breakpoint Commands}) might be:
26392 -> -break-insert main
26393 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26394 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26395 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26400 @node GDB/MI Frame Information
26401 @subsection @sc{gdb/mi} Frame Information
26403 Response from many MI commands includes an information about stack
26404 frame. This information is a tuple that may have the following
26409 The level of the stack frame. The innermost frame has the level of
26410 zero. This field is always present.
26413 The name of the function corresponding to the frame. This field may
26414 be absent if @value{GDBN} is unable to determine the function name.
26417 The code address for the frame. This field is always present.
26420 The name of the source files that correspond to the frame's code
26421 address. This field may be absent.
26424 The source line corresponding to the frames' code address. This field
26428 The name of the binary file (either executable or shared library) the
26429 corresponds to the frame's code address. This field may be absent.
26433 @node GDB/MI Thread Information
26434 @subsection @sc{gdb/mi} Thread Information
26436 Whenever @value{GDBN} has to report an information about a thread, it
26437 uses a tuple with the following fields:
26441 The numeric id assigned to the thread by @value{GDBN}. This field is
26445 Target-specific string identifying the thread. This field is always present.
26448 Additional information about the thread provided by the target.
26449 It is supposed to be human-readable and not interpreted by the
26450 frontend. This field is optional.
26453 Either @samp{stopped} or @samp{running}, depending on whether the
26454 thread is presently running. This field is always present.
26457 The value of this field is an integer number of the processor core the
26458 thread was last seen on. This field is optional.
26461 @node GDB/MI Ada Exception Information
26462 @subsection @sc{gdb/mi} Ada Exception Information
26464 Whenever a @code{*stopped} record is emitted because the program
26465 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26466 @value{GDBN} provides the name of the exception that was raised via
26467 the @code{exception-name} field.
26469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26470 @node GDB/MI Simple Examples
26471 @section Simple Examples of @sc{gdb/mi} Interaction
26472 @cindex @sc{gdb/mi}, simple examples
26474 This subsection presents several simple examples of interaction using
26475 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26476 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26477 the output received from @sc{gdb/mi}.
26479 Note the line breaks shown in the examples are here only for
26480 readability, they don't appear in the real output.
26482 @subheading Setting a Breakpoint
26484 Setting a breakpoint generates synchronous output which contains detailed
26485 information of the breakpoint.
26488 -> -break-insert main
26489 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26490 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26491 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26496 @subheading Program Execution
26498 Program execution generates asynchronous records and MI gives the
26499 reason that execution stopped.
26505 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26506 frame=@{addr="0x08048564",func="main",
26507 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26508 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26513 <- *stopped,reason="exited-normally"
26517 @subheading Quitting @value{GDBN}
26519 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26527 Please note that @samp{^exit} is printed immediately, but it might
26528 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26529 performs necessary cleanups, including killing programs being debugged
26530 or disconnecting from debug hardware, so the frontend should wait till
26531 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26532 fails to exit in reasonable time.
26534 @subheading A Bad Command
26536 Here's what happens if you pass a non-existent command:
26540 <- ^error,msg="Undefined MI command: rubbish"
26545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26546 @node GDB/MI Command Description Format
26547 @section @sc{gdb/mi} Command Description Format
26549 The remaining sections describe blocks of commands. Each block of
26550 commands is laid out in a fashion similar to this section.
26552 @subheading Motivation
26554 The motivation for this collection of commands.
26556 @subheading Introduction
26558 A brief introduction to this collection of commands as a whole.
26560 @subheading Commands
26562 For each command in the block, the following is described:
26564 @subsubheading Synopsis
26567 -command @var{args}@dots{}
26570 @subsubheading Result
26572 @subsubheading @value{GDBN} Command
26574 The corresponding @value{GDBN} CLI command(s), if any.
26576 @subsubheading Example
26578 Example(s) formatted for readability. Some of the described commands have
26579 not been implemented yet and these are labeled N.A.@: (not available).
26582 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26583 @node GDB/MI Breakpoint Commands
26584 @section @sc{gdb/mi} Breakpoint Commands
26586 @cindex breakpoint commands for @sc{gdb/mi}
26587 @cindex @sc{gdb/mi}, breakpoint commands
26588 This section documents @sc{gdb/mi} commands for manipulating
26591 @subheading The @code{-break-after} Command
26592 @findex -break-after
26594 @subsubheading Synopsis
26597 -break-after @var{number} @var{count}
26600 The breakpoint number @var{number} is not in effect until it has been
26601 hit @var{count} times. To see how this is reflected in the output of
26602 the @samp{-break-list} command, see the description of the
26603 @samp{-break-list} command below.
26605 @subsubheading @value{GDBN} Command
26607 The corresponding @value{GDBN} command is @samp{ignore}.
26609 @subsubheading Example
26614 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26615 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26616 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26624 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26625 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26626 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26627 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26628 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26629 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26630 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26631 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26632 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26633 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26638 @subheading The @code{-break-catch} Command
26639 @findex -break-catch
26642 @subheading The @code{-break-commands} Command
26643 @findex -break-commands
26645 @subsubheading Synopsis
26648 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26651 Specifies the CLI commands that should be executed when breakpoint
26652 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26653 are the commands. If no command is specified, any previously-set
26654 commands are cleared. @xref{Break Commands}. Typical use of this
26655 functionality is tracing a program, that is, printing of values of
26656 some variables whenever breakpoint is hit and then continuing.
26658 @subsubheading @value{GDBN} Command
26660 The corresponding @value{GDBN} command is @samp{commands}.
26662 @subsubheading Example
26667 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26668 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26669 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26672 -break-commands 1 "print v" "continue"
26677 @subheading The @code{-break-condition} Command
26678 @findex -break-condition
26680 @subsubheading Synopsis
26683 -break-condition @var{number} @var{expr}
26686 Breakpoint @var{number} will stop the program only if the condition in
26687 @var{expr} is true. The condition becomes part of the
26688 @samp{-break-list} output (see the description of the @samp{-break-list}
26691 @subsubheading @value{GDBN} Command
26693 The corresponding @value{GDBN} command is @samp{condition}.
26695 @subsubheading Example
26699 -break-condition 1 1
26703 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26704 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26705 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26706 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26707 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26708 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26709 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26710 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26711 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26712 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26716 @subheading The @code{-break-delete} Command
26717 @findex -break-delete
26719 @subsubheading Synopsis
26722 -break-delete ( @var{breakpoint} )+
26725 Delete the breakpoint(s) whose number(s) are specified in the argument
26726 list. This is obviously reflected in the breakpoint list.
26728 @subsubheading @value{GDBN} Command
26730 The corresponding @value{GDBN} command is @samp{delete}.
26732 @subsubheading Example
26740 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26751 @subheading The @code{-break-disable} Command
26752 @findex -break-disable
26754 @subsubheading Synopsis
26757 -break-disable ( @var{breakpoint} )+
26760 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26761 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26763 @subsubheading @value{GDBN} Command
26765 The corresponding @value{GDBN} command is @samp{disable}.
26767 @subsubheading Example
26775 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26776 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26777 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26778 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26779 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26780 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26781 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26782 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26783 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26784 line="5",thread-groups=["i1"],times="0"@}]@}
26788 @subheading The @code{-break-enable} Command
26789 @findex -break-enable
26791 @subsubheading Synopsis
26794 -break-enable ( @var{breakpoint} )+
26797 Enable (previously disabled) @var{breakpoint}(s).
26799 @subsubheading @value{GDBN} Command
26801 The corresponding @value{GDBN} command is @samp{enable}.
26803 @subsubheading Example
26811 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26818 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26819 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26820 line="5",thread-groups=["i1"],times="0"@}]@}
26824 @subheading The @code{-break-info} Command
26825 @findex -break-info
26827 @subsubheading Synopsis
26830 -break-info @var{breakpoint}
26834 Get information about a single breakpoint.
26836 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26837 Information}, for details on the format of each breakpoint in the
26840 @subsubheading @value{GDBN} Command
26842 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26844 @subsubheading Example
26847 @subheading The @code{-break-insert} Command
26848 @findex -break-insert
26850 @subsubheading Synopsis
26853 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26854 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26855 [ -p @var{thread-id} ] [ @var{location} ]
26859 If specified, @var{location}, can be one of:
26866 @item filename:linenum
26867 @item filename:function
26871 The possible optional parameters of this command are:
26875 Insert a temporary breakpoint.
26877 Insert a hardware breakpoint.
26879 If @var{location} cannot be parsed (for example if it
26880 refers to unknown files or functions), create a pending
26881 breakpoint. Without this flag, @value{GDBN} will report
26882 an error, and won't create a breakpoint, if @var{location}
26885 Create a disabled breakpoint.
26887 Create a tracepoint. @xref{Tracepoints}. When this parameter
26888 is used together with @samp{-h}, a fast tracepoint is created.
26889 @item -c @var{condition}
26890 Make the breakpoint conditional on @var{condition}.
26891 @item -i @var{ignore-count}
26892 Initialize the @var{ignore-count}.
26893 @item -p @var{thread-id}
26894 Restrict the breakpoint to the specified @var{thread-id}.
26897 @subsubheading Result
26899 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26900 resulting breakpoint.
26902 Note: this format is open to change.
26903 @c An out-of-band breakpoint instead of part of the result?
26905 @subsubheading @value{GDBN} Command
26907 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26908 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26910 @subsubheading Example
26915 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26916 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26919 -break-insert -t foo
26920 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26921 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26925 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26926 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26927 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26928 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26929 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26930 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26931 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26932 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26933 addr="0x0001072c", func="main",file="recursive2.c",
26934 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26936 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26937 addr="0x00010774",func="foo",file="recursive2.c",
26938 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26941 @c -break-insert -r foo.*
26942 @c ~int foo(int, int);
26943 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26944 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26949 @subheading The @code{-dprintf-insert} Command
26950 @findex -dprintf-insert
26952 @subsubheading Synopsis
26955 -dprintf-insert [ -t ] [ -f ] [ -d ]
26956 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26957 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26962 If specified, @var{location}, can be one of:
26965 @item @var{function}
26968 @c @item @var{linenum}
26969 @item @var{filename}:@var{linenum}
26970 @item @var{filename}:function
26971 @item *@var{address}
26974 The possible optional parameters of this command are:
26978 Insert a temporary breakpoint.
26980 If @var{location} cannot be parsed (for example, if it
26981 refers to unknown files or functions), create a pending
26982 breakpoint. Without this flag, @value{GDBN} will report
26983 an error, and won't create a breakpoint, if @var{location}
26986 Create a disabled breakpoint.
26987 @item -c @var{condition}
26988 Make the breakpoint conditional on @var{condition}.
26989 @item -i @var{ignore-count}
26990 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26991 to @var{ignore-count}.
26992 @item -p @var{thread-id}
26993 Restrict the breakpoint to the specified @var{thread-id}.
26996 @subsubheading Result
26998 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26999 resulting breakpoint.
27001 @c An out-of-band breakpoint instead of part of the result?
27003 @subsubheading @value{GDBN} Command
27005 The corresponding @value{GDBN} command is @samp{dprintf}.
27007 @subsubheading Example
27011 4-dprintf-insert foo "At foo entry\n"
27012 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27013 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27014 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27015 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27016 original-location="foo"@}
27018 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27019 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27020 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27021 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27022 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27023 original-location="mi-dprintf.c:26"@}
27027 @subheading The @code{-break-list} Command
27028 @findex -break-list
27030 @subsubheading Synopsis
27036 Displays the list of inserted breakpoints, showing the following fields:
27040 number of the breakpoint
27042 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27044 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27047 is the breakpoint enabled or no: @samp{y} or @samp{n}
27049 memory location at which the breakpoint is set
27051 logical location of the breakpoint, expressed by function name, file
27053 @item Thread-groups
27054 list of thread groups to which this breakpoint applies
27056 number of times the breakpoint has been hit
27059 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27060 @code{body} field is an empty list.
27062 @subsubheading @value{GDBN} Command
27064 The corresponding @value{GDBN} command is @samp{info break}.
27066 @subsubheading Example
27071 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27072 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27073 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27074 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27075 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27076 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27077 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27078 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27079 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27081 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27082 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27083 line="13",thread-groups=["i1"],times="0"@}]@}
27087 Here's an example of the result when there are no breakpoints:
27092 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27093 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27094 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27095 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27096 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27097 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27098 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27103 @subheading The @code{-break-passcount} Command
27104 @findex -break-passcount
27106 @subsubheading Synopsis
27109 -break-passcount @var{tracepoint-number} @var{passcount}
27112 Set the passcount for tracepoint @var{tracepoint-number} to
27113 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27114 is not a tracepoint, error is emitted. This corresponds to CLI
27115 command @samp{passcount}.
27117 @subheading The @code{-break-watch} Command
27118 @findex -break-watch
27120 @subsubheading Synopsis
27123 -break-watch [ -a | -r ]
27126 Create a watchpoint. With the @samp{-a} option it will create an
27127 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27128 read from or on a write to the memory location. With the @samp{-r}
27129 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27130 trigger only when the memory location is accessed for reading. Without
27131 either of the options, the watchpoint created is a regular watchpoint,
27132 i.e., it will trigger when the memory location is accessed for writing.
27133 @xref{Set Watchpoints, , Setting Watchpoints}.
27135 Note that @samp{-break-list} will report a single list of watchpoints and
27136 breakpoints inserted.
27138 @subsubheading @value{GDBN} Command
27140 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27143 @subsubheading Example
27145 Setting a watchpoint on a variable in the @code{main} function:
27150 ^done,wpt=@{number="2",exp="x"@}
27155 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27156 value=@{old="-268439212",new="55"@},
27157 frame=@{func="main",args=[],file="recursive2.c",
27158 fullname="/home/foo/bar/recursive2.c",line="5"@}
27162 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27163 the program execution twice: first for the variable changing value, then
27164 for the watchpoint going out of scope.
27169 ^done,wpt=@{number="5",exp="C"@}
27174 *stopped,reason="watchpoint-trigger",
27175 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27176 frame=@{func="callee4",args=[],
27177 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27178 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27183 *stopped,reason="watchpoint-scope",wpnum="5",
27184 frame=@{func="callee3",args=[@{name="strarg",
27185 value="0x11940 \"A string argument.\""@}],
27186 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27187 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27191 Listing breakpoints and watchpoints, at different points in the program
27192 execution. Note that once the watchpoint goes out of scope, it is
27198 ^done,wpt=@{number="2",exp="C"@}
27201 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27202 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27203 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27204 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27205 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27206 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27207 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27208 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27209 addr="0x00010734",func="callee4",
27210 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27211 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27213 bkpt=@{number="2",type="watchpoint",disp="keep",
27214 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27219 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27220 value=@{old="-276895068",new="3"@},
27221 frame=@{func="callee4",args=[],
27222 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27223 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27226 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27227 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27228 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27229 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27230 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27231 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27232 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27233 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27234 addr="0x00010734",func="callee4",
27235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27236 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27238 bkpt=@{number="2",type="watchpoint",disp="keep",
27239 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27243 ^done,reason="watchpoint-scope",wpnum="2",
27244 frame=@{func="callee3",args=[@{name="strarg",
27245 value="0x11940 \"A string argument.\""@}],
27246 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27247 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27250 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27251 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27252 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27253 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27254 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27255 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27256 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27257 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27258 addr="0x00010734",func="callee4",
27259 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27260 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27261 thread-groups=["i1"],times="1"@}]@}
27266 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27267 @node GDB/MI Catchpoint Commands
27268 @section @sc{gdb/mi} Catchpoint Commands
27270 This section documents @sc{gdb/mi} commands for manipulating
27274 * Shared Library GDB/MI Catchpoint Commands::
27275 * Ada Exception GDB/MI Catchpoint Commands::
27278 @node Shared Library GDB/MI Catchpoint Commands
27279 @subsection Shared Library @sc{gdb/mi} Catchpoints
27281 @subheading The @code{-catch-load} Command
27282 @findex -catch-load
27284 @subsubheading Synopsis
27287 -catch-load [ -t ] [ -d ] @var{regexp}
27290 Add a catchpoint for library load events. If the @samp{-t} option is used,
27291 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27292 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27293 in a disabled state. The @samp{regexp} argument is a regular
27294 expression used to match the name of the loaded library.
27297 @subsubheading @value{GDBN} Command
27299 The corresponding @value{GDBN} command is @samp{catch load}.
27301 @subsubheading Example
27304 -catch-load -t foo.so
27305 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27306 what="load of library matching foo.so",catch-type="load",times="0"@}
27311 @subheading The @code{-catch-unload} Command
27312 @findex -catch-unload
27314 @subsubheading Synopsis
27317 -catch-unload [ -t ] [ -d ] @var{regexp}
27320 Add a catchpoint for library unload events. If the @samp{-t} option is
27321 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27322 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27323 created in a disabled state. The @samp{regexp} argument is a regular
27324 expression used to match the name of the unloaded library.
27326 @subsubheading @value{GDBN} Command
27328 The corresponding @value{GDBN} command is @samp{catch unload}.
27330 @subsubheading Example
27333 -catch-unload -d bar.so
27334 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27335 what="load of library matching bar.so",catch-type="unload",times="0"@}
27339 @node Ada Exception GDB/MI Catchpoint Commands
27340 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27342 The following @sc{gdb/mi} commands can be used to create catchpoints
27343 that stop the execution when Ada exceptions are being raised.
27345 @subheading The @code{-catch-assert} Command
27346 @findex -catch-assert
27348 @subsubheading Synopsis
27351 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27354 Add a catchpoint for failed Ada assertions.
27356 The possible optional parameters for this command are:
27359 @item -c @var{condition}
27360 Make the catchpoint conditional on @var{condition}.
27362 Create a disabled catchpoint.
27364 Create a temporary catchpoint.
27367 @subsubheading @value{GDBN} Command
27369 The corresponding @value{GDBN} command is @samp{catch assert}.
27371 @subsubheading Example
27375 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27376 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27377 thread-groups=["i1"],times="0",
27378 original-location="__gnat_debug_raise_assert_failure"@}
27382 @subheading The @code{-catch-exception} Command
27383 @findex -catch-exception
27385 @subsubheading Synopsis
27388 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27392 Add a catchpoint stopping when Ada exceptions are raised.
27393 By default, the command stops the program when any Ada exception
27394 gets raised. But it is also possible, by using some of the
27395 optional parameters described below, to create more selective
27398 The possible optional parameters for this command are:
27401 @item -c @var{condition}
27402 Make the catchpoint conditional on @var{condition}.
27404 Create a disabled catchpoint.
27405 @item -e @var{exception-name}
27406 Only stop when @var{exception-name} is raised. This option cannot
27407 be used combined with @samp{-u}.
27409 Create a temporary catchpoint.
27411 Stop only when an unhandled exception gets raised. This option
27412 cannot be used combined with @samp{-e}.
27415 @subsubheading @value{GDBN} Command
27417 The corresponding @value{GDBN} commands are @samp{catch exception}
27418 and @samp{catch exception unhandled}.
27420 @subsubheading Example
27423 -catch-exception -e Program_Error
27424 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27425 enabled="y",addr="0x0000000000404874",
27426 what="`Program_Error' Ada exception", thread-groups=["i1"],
27427 times="0",original-location="__gnat_debug_raise_exception"@}
27431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27432 @node GDB/MI Program Context
27433 @section @sc{gdb/mi} Program Context
27435 @subheading The @code{-exec-arguments} Command
27436 @findex -exec-arguments
27439 @subsubheading Synopsis
27442 -exec-arguments @var{args}
27445 Set the inferior program arguments, to be used in the next
27448 @subsubheading @value{GDBN} Command
27450 The corresponding @value{GDBN} command is @samp{set args}.
27452 @subsubheading Example
27456 -exec-arguments -v word
27463 @subheading The @code{-exec-show-arguments} Command
27464 @findex -exec-show-arguments
27466 @subsubheading Synopsis
27469 -exec-show-arguments
27472 Print the arguments of the program.
27474 @subsubheading @value{GDBN} Command
27476 The corresponding @value{GDBN} command is @samp{show args}.
27478 @subsubheading Example
27483 @subheading The @code{-environment-cd} Command
27484 @findex -environment-cd
27486 @subsubheading Synopsis
27489 -environment-cd @var{pathdir}
27492 Set @value{GDBN}'s working directory.
27494 @subsubheading @value{GDBN} Command
27496 The corresponding @value{GDBN} command is @samp{cd}.
27498 @subsubheading Example
27502 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27508 @subheading The @code{-environment-directory} Command
27509 @findex -environment-directory
27511 @subsubheading Synopsis
27514 -environment-directory [ -r ] [ @var{pathdir} ]+
27517 Add directories @var{pathdir} to beginning of search path for source files.
27518 If the @samp{-r} option is used, the search path is reset to the default
27519 search path. If directories @var{pathdir} are supplied in addition to the
27520 @samp{-r} option, the search path is first reset and then addition
27522 Multiple directories may be specified, separated by blanks. Specifying
27523 multiple directories in a single command
27524 results in the directories added to the beginning of the
27525 search path in the same order they were presented in the command.
27526 If blanks are needed as
27527 part of a directory name, double-quotes should be used around
27528 the name. In the command output, the path will show up separated
27529 by the system directory-separator character. The directory-separator
27530 character must not be used
27531 in any directory name.
27532 If no directories are specified, the current search path is displayed.
27534 @subsubheading @value{GDBN} Command
27536 The corresponding @value{GDBN} command is @samp{dir}.
27538 @subsubheading Example
27542 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27543 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27545 -environment-directory ""
27546 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27548 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27549 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27551 -environment-directory -r
27552 ^done,source-path="$cdir:$cwd"
27557 @subheading The @code{-environment-path} Command
27558 @findex -environment-path
27560 @subsubheading Synopsis
27563 -environment-path [ -r ] [ @var{pathdir} ]+
27566 Add directories @var{pathdir} to beginning of search path for object files.
27567 If the @samp{-r} option is used, the search path is reset to the original
27568 search path that existed at gdb start-up. If directories @var{pathdir} are
27569 supplied in addition to the
27570 @samp{-r} option, the search path is first reset and then addition
27572 Multiple directories may be specified, separated by blanks. Specifying
27573 multiple directories in a single command
27574 results in the directories added to the beginning of the
27575 search path in the same order they were presented in the command.
27576 If blanks are needed as
27577 part of a directory name, double-quotes should be used around
27578 the name. In the command output, the path will show up separated
27579 by the system directory-separator character. The directory-separator
27580 character must not be used
27581 in any directory name.
27582 If no directories are specified, the current path is displayed.
27585 @subsubheading @value{GDBN} Command
27587 The corresponding @value{GDBN} command is @samp{path}.
27589 @subsubheading Example
27594 ^done,path="/usr/bin"
27596 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27597 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27599 -environment-path -r /usr/local/bin
27600 ^done,path="/usr/local/bin:/usr/bin"
27605 @subheading The @code{-environment-pwd} Command
27606 @findex -environment-pwd
27608 @subsubheading Synopsis
27614 Show the current working directory.
27616 @subsubheading @value{GDBN} Command
27618 The corresponding @value{GDBN} command is @samp{pwd}.
27620 @subsubheading Example
27625 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27629 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27630 @node GDB/MI Thread Commands
27631 @section @sc{gdb/mi} Thread Commands
27634 @subheading The @code{-thread-info} Command
27635 @findex -thread-info
27637 @subsubheading Synopsis
27640 -thread-info [ @var{thread-id} ]
27643 Reports information about either a specific thread, if
27644 the @var{thread-id} parameter is present, or about all
27645 threads. When printing information about all threads,
27646 also reports the current thread.
27648 @subsubheading @value{GDBN} Command
27650 The @samp{info thread} command prints the same information
27653 @subsubheading Result
27655 The result is a list of threads. The following attributes are
27656 defined for a given thread:
27660 This field exists only for the current thread. It has the value @samp{*}.
27663 The identifier that @value{GDBN} uses to refer to the thread.
27666 The identifier that the target uses to refer to the thread.
27669 Extra information about the thread, in a target-specific format. This
27673 The name of the thread. If the user specified a name using the
27674 @code{thread name} command, then this name is given. Otherwise, if
27675 @value{GDBN} can extract the thread name from the target, then that
27676 name is given. If @value{GDBN} cannot find the thread name, then this
27680 The stack frame currently executing in the thread.
27683 The thread's state. The @samp{state} field may have the following
27688 The thread is stopped. Frame information is available for stopped
27692 The thread is running. There's no frame information for running
27698 If @value{GDBN} can find the CPU core on which this thread is running,
27699 then this field is the core identifier. This field is optional.
27703 @subsubheading Example
27708 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27709 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27710 args=[]@},state="running"@},
27711 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27712 frame=@{level="0",addr="0x0804891f",func="foo",
27713 args=[@{name="i",value="10"@}],
27714 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27715 state="running"@}],
27716 current-thread-id="1"
27720 @subheading The @code{-thread-list-ids} Command
27721 @findex -thread-list-ids
27723 @subsubheading Synopsis
27729 Produces a list of the currently known @value{GDBN} thread ids. At the
27730 end of the list it also prints the total number of such threads.
27732 This command is retained for historical reasons, the
27733 @code{-thread-info} command should be used instead.
27735 @subsubheading @value{GDBN} Command
27737 Part of @samp{info threads} supplies the same information.
27739 @subsubheading Example
27744 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27745 current-thread-id="1",number-of-threads="3"
27750 @subheading The @code{-thread-select} Command
27751 @findex -thread-select
27753 @subsubheading Synopsis
27756 -thread-select @var{threadnum}
27759 Make @var{threadnum} the current thread. It prints the number of the new
27760 current thread, and the topmost frame for that thread.
27762 This command is deprecated in favor of explicitly using the
27763 @samp{--thread} option to each command.
27765 @subsubheading @value{GDBN} Command
27767 The corresponding @value{GDBN} command is @samp{thread}.
27769 @subsubheading Example
27776 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27777 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27781 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27782 number-of-threads="3"
27785 ^done,new-thread-id="3",
27786 frame=@{level="0",func="vprintf",
27787 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27788 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27793 @node GDB/MI Ada Tasking Commands
27794 @section @sc{gdb/mi} Ada Tasking Commands
27796 @subheading The @code{-ada-task-info} Command
27797 @findex -ada-task-info
27799 @subsubheading Synopsis
27802 -ada-task-info [ @var{task-id} ]
27805 Reports information about either a specific Ada task, if the
27806 @var{task-id} parameter is present, or about all Ada tasks.
27808 @subsubheading @value{GDBN} Command
27810 The @samp{info tasks} command prints the same information
27811 about all Ada tasks (@pxref{Ada Tasks}).
27813 @subsubheading Result
27815 The result is a table of Ada tasks. The following columns are
27816 defined for each Ada task:
27820 This field exists only for the current thread. It has the value @samp{*}.
27823 The identifier that @value{GDBN} uses to refer to the Ada task.
27826 The identifier that the target uses to refer to the Ada task.
27829 The identifier of the thread corresponding to the Ada task.
27831 This field should always exist, as Ada tasks are always implemented
27832 on top of a thread. But if @value{GDBN} cannot find this corresponding
27833 thread for any reason, the field is omitted.
27836 This field exists only when the task was created by another task.
27837 In this case, it provides the ID of the parent task.
27840 The base priority of the task.
27843 The current state of the task. For a detailed description of the
27844 possible states, see @ref{Ada Tasks}.
27847 The name of the task.
27851 @subsubheading Example
27855 ^done,tasks=@{nr_rows="3",nr_cols="8",
27856 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27857 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27858 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27859 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27860 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27861 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27862 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27863 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27864 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27865 state="Child Termination Wait",name="main_task"@}]@}
27869 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27870 @node GDB/MI Program Execution
27871 @section @sc{gdb/mi} Program Execution
27873 These are the asynchronous commands which generate the out-of-band
27874 record @samp{*stopped}. Currently @value{GDBN} only really executes
27875 asynchronously with remote targets and this interaction is mimicked in
27878 @subheading The @code{-exec-continue} Command
27879 @findex -exec-continue
27881 @subsubheading Synopsis
27884 -exec-continue [--reverse] [--all|--thread-group N]
27887 Resumes the execution of the inferior program, which will continue
27888 to execute until it reaches a debugger stop event. If the
27889 @samp{--reverse} option is specified, execution resumes in reverse until
27890 it reaches a stop event. Stop events may include
27893 breakpoints or watchpoints
27895 signals or exceptions
27897 the end of the process (or its beginning under @samp{--reverse})
27899 the end or beginning of a replay log if one is being used.
27901 In all-stop mode (@pxref{All-Stop
27902 Mode}), may resume only one thread, or all threads, depending on the
27903 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27904 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27905 ignored in all-stop mode. If the @samp{--thread-group} options is
27906 specified, then all threads in that thread group are resumed.
27908 @subsubheading @value{GDBN} Command
27910 The corresponding @value{GDBN} corresponding is @samp{continue}.
27912 @subsubheading Example
27919 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27920 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27926 @subheading The @code{-exec-finish} Command
27927 @findex -exec-finish
27929 @subsubheading Synopsis
27932 -exec-finish [--reverse]
27935 Resumes the execution of the inferior program until the current
27936 function is exited. Displays the results returned by the function.
27937 If the @samp{--reverse} option is specified, resumes the reverse
27938 execution of the inferior program until the point where current
27939 function was called.
27941 @subsubheading @value{GDBN} Command
27943 The corresponding @value{GDBN} command is @samp{finish}.
27945 @subsubheading Example
27947 Function returning @code{void}.
27954 *stopped,reason="function-finished",frame=@{func="main",args=[],
27955 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27959 Function returning other than @code{void}. The name of the internal
27960 @value{GDBN} variable storing the result is printed, together with the
27967 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27968 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27970 gdb-result-var="$1",return-value="0"
27975 @subheading The @code{-exec-interrupt} Command
27976 @findex -exec-interrupt
27978 @subsubheading Synopsis
27981 -exec-interrupt [--all|--thread-group N]
27984 Interrupts the background execution of the target. Note how the token
27985 associated with the stop message is the one for the execution command
27986 that has been interrupted. The token for the interrupt itself only
27987 appears in the @samp{^done} output. If the user is trying to
27988 interrupt a non-running program, an error message will be printed.
27990 Note that when asynchronous execution is enabled, this command is
27991 asynchronous just like other execution commands. That is, first the
27992 @samp{^done} response will be printed, and the target stop will be
27993 reported after that using the @samp{*stopped} notification.
27995 In non-stop mode, only the context thread is interrupted by default.
27996 All threads (in all inferiors) will be interrupted if the
27997 @samp{--all} option is specified. If the @samp{--thread-group}
27998 option is specified, all threads in that group will be interrupted.
28000 @subsubheading @value{GDBN} Command
28002 The corresponding @value{GDBN} command is @samp{interrupt}.
28004 @subsubheading Example
28015 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28016 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28017 fullname="/home/foo/bar/try.c",line="13"@}
28022 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28026 @subheading The @code{-exec-jump} Command
28029 @subsubheading Synopsis
28032 -exec-jump @var{location}
28035 Resumes execution of the inferior program at the location specified by
28036 parameter. @xref{Specify Location}, for a description of the
28037 different forms of @var{location}.
28039 @subsubheading @value{GDBN} Command
28041 The corresponding @value{GDBN} command is @samp{jump}.
28043 @subsubheading Example
28046 -exec-jump foo.c:10
28047 *running,thread-id="all"
28052 @subheading The @code{-exec-next} Command
28055 @subsubheading Synopsis
28058 -exec-next [--reverse]
28061 Resumes execution of the inferior program, stopping when the beginning
28062 of the next source line is reached.
28064 If the @samp{--reverse} option is specified, resumes reverse execution
28065 of the inferior program, stopping at the beginning of the previous
28066 source line. If you issue this command on the first line of a
28067 function, it will take you back to the caller of that function, to the
28068 source line where the function was called.
28071 @subsubheading @value{GDBN} Command
28073 The corresponding @value{GDBN} command is @samp{next}.
28075 @subsubheading Example
28081 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28086 @subheading The @code{-exec-next-instruction} Command
28087 @findex -exec-next-instruction
28089 @subsubheading Synopsis
28092 -exec-next-instruction [--reverse]
28095 Executes one machine instruction. If the instruction is a function
28096 call, continues until the function returns. If the program stops at an
28097 instruction in the middle of a source line, the address will be
28100 If the @samp{--reverse} option is specified, resumes reverse execution
28101 of the inferior program, stopping at the previous instruction. If the
28102 previously executed instruction was a return from another function,
28103 it will continue to execute in reverse until the call to that function
28104 (from the current stack frame) is reached.
28106 @subsubheading @value{GDBN} Command
28108 The corresponding @value{GDBN} command is @samp{nexti}.
28110 @subsubheading Example
28114 -exec-next-instruction
28118 *stopped,reason="end-stepping-range",
28119 addr="0x000100d4",line="5",file="hello.c"
28124 @subheading The @code{-exec-return} Command
28125 @findex -exec-return
28127 @subsubheading Synopsis
28133 Makes current function return immediately. Doesn't execute the inferior.
28134 Displays the new current frame.
28136 @subsubheading @value{GDBN} Command
28138 The corresponding @value{GDBN} command is @samp{return}.
28140 @subsubheading Example
28144 200-break-insert callee4
28145 200^done,bkpt=@{number="1",addr="0x00010734",
28146 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28151 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28152 frame=@{func="callee4",args=[],
28153 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28154 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28160 111^done,frame=@{level="0",func="callee3",
28161 args=[@{name="strarg",
28162 value="0x11940 \"A string argument.\""@}],
28163 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28164 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28169 @subheading The @code{-exec-run} Command
28172 @subsubheading Synopsis
28175 -exec-run [ --all | --thread-group N ] [ --start ]
28178 Starts execution of the inferior from the beginning. The inferior
28179 executes until either a breakpoint is encountered or the program
28180 exits. In the latter case the output will include an exit code, if
28181 the program has exited exceptionally.
28183 When neither the @samp{--all} nor the @samp{--thread-group} option
28184 is specified, the current inferior is started. If the
28185 @samp{--thread-group} option is specified, it should refer to a thread
28186 group of type @samp{process}, and that thread group will be started.
28187 If the @samp{--all} option is specified, then all inferiors will be started.
28189 Using the @samp{--start} option instructs the debugger to stop
28190 the execution at the start of the inferior's main subprogram,
28191 following the same behavior as the @code{start} command
28192 (@pxref{Starting}).
28194 @subsubheading @value{GDBN} Command
28196 The corresponding @value{GDBN} command is @samp{run}.
28198 @subsubheading Examples
28203 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28208 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28209 frame=@{func="main",args=[],file="recursive2.c",
28210 fullname="/home/foo/bar/recursive2.c",line="4"@}
28215 Program exited normally:
28223 *stopped,reason="exited-normally"
28228 Program exited exceptionally:
28236 *stopped,reason="exited",exit-code="01"
28240 Another way the program can terminate is if it receives a signal such as
28241 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28245 *stopped,reason="exited-signalled",signal-name="SIGINT",
28246 signal-meaning="Interrupt"
28250 @c @subheading -exec-signal
28253 @subheading The @code{-exec-step} Command
28256 @subsubheading Synopsis
28259 -exec-step [--reverse]
28262 Resumes execution of the inferior program, stopping when the beginning
28263 of the next source line is reached, if the next source line is not a
28264 function call. If it is, stop at the first instruction of the called
28265 function. If the @samp{--reverse} option is specified, resumes reverse
28266 execution of the inferior program, stopping at the beginning of the
28267 previously executed source line.
28269 @subsubheading @value{GDBN} Command
28271 The corresponding @value{GDBN} command is @samp{step}.
28273 @subsubheading Example
28275 Stepping into a function:
28281 *stopped,reason="end-stepping-range",
28282 frame=@{func="foo",args=[@{name="a",value="10"@},
28283 @{name="b",value="0"@}],file="recursive2.c",
28284 fullname="/home/foo/bar/recursive2.c",line="11"@}
28294 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28299 @subheading The @code{-exec-step-instruction} Command
28300 @findex -exec-step-instruction
28302 @subsubheading Synopsis
28305 -exec-step-instruction [--reverse]
28308 Resumes the inferior which executes one machine instruction. If the
28309 @samp{--reverse} option is specified, resumes reverse execution of the
28310 inferior program, stopping at the previously executed instruction.
28311 The output, once @value{GDBN} has stopped, will vary depending on
28312 whether we have stopped in the middle of a source line or not. In the
28313 former case, the address at which the program stopped will be printed
28316 @subsubheading @value{GDBN} Command
28318 The corresponding @value{GDBN} command is @samp{stepi}.
28320 @subsubheading Example
28324 -exec-step-instruction
28328 *stopped,reason="end-stepping-range",
28329 frame=@{func="foo",args=[],file="try.c",
28330 fullname="/home/foo/bar/try.c",line="10"@}
28332 -exec-step-instruction
28336 *stopped,reason="end-stepping-range",
28337 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28338 fullname="/home/foo/bar/try.c",line="10"@}
28343 @subheading The @code{-exec-until} Command
28344 @findex -exec-until
28346 @subsubheading Synopsis
28349 -exec-until [ @var{location} ]
28352 Executes the inferior until the @var{location} specified in the
28353 argument is reached. If there is no argument, the inferior executes
28354 until a source line greater than the current one is reached. The
28355 reason for stopping in this case will be @samp{location-reached}.
28357 @subsubheading @value{GDBN} Command
28359 The corresponding @value{GDBN} command is @samp{until}.
28361 @subsubheading Example
28365 -exec-until recursive2.c:6
28369 *stopped,reason="location-reached",frame=@{func="main",args=[],
28370 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28375 @subheading -file-clear
28376 Is this going away????
28379 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28380 @node GDB/MI Stack Manipulation
28381 @section @sc{gdb/mi} Stack Manipulation Commands
28383 @subheading The @code{-enable-frame-filters} Command
28384 @findex -enable-frame-filters
28387 -enable-frame-filters
28390 @value{GDBN} allows Python-based frame filters to affect the output of
28391 the MI commands relating to stack traces. As there is no way to
28392 implement this in a fully backward-compatible way, a front end must
28393 request that this functionality be enabled.
28395 Once enabled, this feature cannot be disabled.
28397 Note that if Python support has not been compiled into @value{GDBN},
28398 this command will still succeed (and do nothing).
28400 @subheading The @code{-stack-info-frame} Command
28401 @findex -stack-info-frame
28403 @subsubheading Synopsis
28409 Get info on the selected frame.
28411 @subsubheading @value{GDBN} Command
28413 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28414 (without arguments).
28416 @subsubheading Example
28421 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28422 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28423 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28427 @subheading The @code{-stack-info-depth} Command
28428 @findex -stack-info-depth
28430 @subsubheading Synopsis
28433 -stack-info-depth [ @var{max-depth} ]
28436 Return the depth of the stack. If the integer argument @var{max-depth}
28437 is specified, do not count beyond @var{max-depth} frames.
28439 @subsubheading @value{GDBN} Command
28441 There's no equivalent @value{GDBN} command.
28443 @subsubheading Example
28445 For a stack with frame levels 0 through 11:
28452 -stack-info-depth 4
28455 -stack-info-depth 12
28458 -stack-info-depth 11
28461 -stack-info-depth 13
28466 @anchor{-stack-list-arguments}
28467 @subheading The @code{-stack-list-arguments} Command
28468 @findex -stack-list-arguments
28470 @subsubheading Synopsis
28473 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28474 [ @var{low-frame} @var{high-frame} ]
28477 Display a list of the arguments for the frames between @var{low-frame}
28478 and @var{high-frame} (inclusive). If @var{low-frame} and
28479 @var{high-frame} are not provided, list the arguments for the whole
28480 call stack. If the two arguments are equal, show the single frame
28481 at the corresponding level. It is an error if @var{low-frame} is
28482 larger than the actual number of frames. On the other hand,
28483 @var{high-frame} may be larger than the actual number of frames, in
28484 which case only existing frames will be returned.
28486 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28487 the variables; if it is 1 or @code{--all-values}, print also their
28488 values; and if it is 2 or @code{--simple-values}, print the name,
28489 type and value for simple data types, and the name and type for arrays,
28490 structures and unions. If the option @code{--no-frame-filters} is
28491 supplied, then Python frame filters will not be executed.
28493 If the @code{--skip-unavailable} option is specified, arguments that
28494 are not available are not listed. Partially available arguments
28495 are still displayed, however.
28497 Use of this command to obtain arguments in a single frame is
28498 deprecated in favor of the @samp{-stack-list-variables} command.
28500 @subsubheading @value{GDBN} Command
28502 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28503 @samp{gdb_get_args} command which partially overlaps with the
28504 functionality of @samp{-stack-list-arguments}.
28506 @subsubheading Example
28513 frame=@{level="0",addr="0x00010734",func="callee4",
28514 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28515 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28516 frame=@{level="1",addr="0x0001076c",func="callee3",
28517 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28518 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28519 frame=@{level="2",addr="0x0001078c",func="callee2",
28520 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28521 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28522 frame=@{level="3",addr="0x000107b4",func="callee1",
28523 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28524 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28525 frame=@{level="4",addr="0x000107e0",func="main",
28526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28529 -stack-list-arguments 0
28532 frame=@{level="0",args=[]@},
28533 frame=@{level="1",args=[name="strarg"]@},
28534 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28535 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28536 frame=@{level="4",args=[]@}]
28538 -stack-list-arguments 1
28541 frame=@{level="0",args=[]@},
28543 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28544 frame=@{level="2",args=[
28545 @{name="intarg",value="2"@},
28546 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28547 @{frame=@{level="3",args=[
28548 @{name="intarg",value="2"@},
28549 @{name="strarg",value="0x11940 \"A string argument.\""@},
28550 @{name="fltarg",value="3.5"@}]@},
28551 frame=@{level="4",args=[]@}]
28553 -stack-list-arguments 0 2 2
28554 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28556 -stack-list-arguments 1 2 2
28557 ^done,stack-args=[frame=@{level="2",
28558 args=[@{name="intarg",value="2"@},
28559 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28563 @c @subheading -stack-list-exception-handlers
28566 @anchor{-stack-list-frames}
28567 @subheading The @code{-stack-list-frames} Command
28568 @findex -stack-list-frames
28570 @subsubheading Synopsis
28573 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28576 List the frames currently on the stack. For each frame it displays the
28581 The frame number, 0 being the topmost frame, i.e., the innermost function.
28583 The @code{$pc} value for that frame.
28587 File name of the source file where the function lives.
28588 @item @var{fullname}
28589 The full file name of the source file where the function lives.
28591 Line number corresponding to the @code{$pc}.
28593 The shared library where this function is defined. This is only given
28594 if the frame's function is not known.
28597 If invoked without arguments, this command prints a backtrace for the
28598 whole stack. If given two integer arguments, it shows the frames whose
28599 levels are between the two arguments (inclusive). If the two arguments
28600 are equal, it shows the single frame at the corresponding level. It is
28601 an error if @var{low-frame} is larger than the actual number of
28602 frames. On the other hand, @var{high-frame} may be larger than the
28603 actual number of frames, in which case only existing frames will be
28604 returned. If the option @code{--no-frame-filters} is supplied, then
28605 Python frame filters will not be executed.
28607 @subsubheading @value{GDBN} Command
28609 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28611 @subsubheading Example
28613 Full stack backtrace:
28619 [frame=@{level="0",addr="0x0001076c",func="foo",
28620 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28621 frame=@{level="1",addr="0x000107a4",func="foo",
28622 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28623 frame=@{level="2",addr="0x000107a4",func="foo",
28624 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28625 frame=@{level="3",addr="0x000107a4",func="foo",
28626 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28627 frame=@{level="4",addr="0x000107a4",func="foo",
28628 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28629 frame=@{level="5",addr="0x000107a4",func="foo",
28630 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28631 frame=@{level="6",addr="0x000107a4",func="foo",
28632 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28633 frame=@{level="7",addr="0x000107a4",func="foo",
28634 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28635 frame=@{level="8",addr="0x000107a4",func="foo",
28636 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28637 frame=@{level="9",addr="0x000107a4",func="foo",
28638 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28639 frame=@{level="10",addr="0x000107a4",func="foo",
28640 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28641 frame=@{level="11",addr="0x00010738",func="main",
28642 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28646 Show frames between @var{low_frame} and @var{high_frame}:
28650 -stack-list-frames 3 5
28652 [frame=@{level="3",addr="0x000107a4",func="foo",
28653 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28654 frame=@{level="4",addr="0x000107a4",func="foo",
28655 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28656 frame=@{level="5",addr="0x000107a4",func="foo",
28657 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28661 Show a single frame:
28665 -stack-list-frames 3 3
28667 [frame=@{level="3",addr="0x000107a4",func="foo",
28668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28673 @subheading The @code{-stack-list-locals} Command
28674 @findex -stack-list-locals
28675 @anchor{-stack-list-locals}
28677 @subsubheading Synopsis
28680 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28683 Display the local variable names for the selected frame. If
28684 @var{print-values} is 0 or @code{--no-values}, print only the names of
28685 the variables; if it is 1 or @code{--all-values}, print also their
28686 values; and if it is 2 or @code{--simple-values}, print the name,
28687 type and value for simple data types, and the name and type for arrays,
28688 structures and unions. In this last case, a frontend can immediately
28689 display the value of simple data types and create variable objects for
28690 other data types when the user wishes to explore their values in
28691 more detail. If the option @code{--no-frame-filters} is supplied, then
28692 Python frame filters will not be executed.
28694 If the @code{--skip-unavailable} option is specified, local variables
28695 that are not available are not listed. Partially available local
28696 variables are still displayed, however.
28698 This command is deprecated in favor of the
28699 @samp{-stack-list-variables} command.
28701 @subsubheading @value{GDBN} Command
28703 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28705 @subsubheading Example
28709 -stack-list-locals 0
28710 ^done,locals=[name="A",name="B",name="C"]
28712 -stack-list-locals --all-values
28713 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28714 @{name="C",value="@{1, 2, 3@}"@}]
28715 -stack-list-locals --simple-values
28716 ^done,locals=[@{name="A",type="int",value="1"@},
28717 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28721 @anchor{-stack-list-variables}
28722 @subheading The @code{-stack-list-variables} Command
28723 @findex -stack-list-variables
28725 @subsubheading Synopsis
28728 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28731 Display the names of local variables and function arguments for the selected frame. If
28732 @var{print-values} is 0 or @code{--no-values}, print only the names of
28733 the variables; if it is 1 or @code{--all-values}, print also their
28734 values; and if it is 2 or @code{--simple-values}, print the name,
28735 type and value for simple data types, and the name and type for arrays,
28736 structures and unions. If the option @code{--no-frame-filters} is
28737 supplied, then Python frame filters will not be executed.
28739 If the @code{--skip-unavailable} option is specified, local variables
28740 and arguments that are not available are not listed. Partially
28741 available arguments and local variables are still displayed, however.
28743 @subsubheading Example
28747 -stack-list-variables --thread 1 --frame 0 --all-values
28748 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28753 @subheading The @code{-stack-select-frame} Command
28754 @findex -stack-select-frame
28756 @subsubheading Synopsis
28759 -stack-select-frame @var{framenum}
28762 Change the selected frame. Select a different frame @var{framenum} on
28765 This command in deprecated in favor of passing the @samp{--frame}
28766 option to every command.
28768 @subsubheading @value{GDBN} Command
28770 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28771 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28773 @subsubheading Example
28777 -stack-select-frame 2
28782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28783 @node GDB/MI Variable Objects
28784 @section @sc{gdb/mi} Variable Objects
28788 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28790 For the implementation of a variable debugger window (locals, watched
28791 expressions, etc.), we are proposing the adaptation of the existing code
28792 used by @code{Insight}.
28794 The two main reasons for that are:
28798 It has been proven in practice (it is already on its second generation).
28801 It will shorten development time (needless to say how important it is
28805 The original interface was designed to be used by Tcl code, so it was
28806 slightly changed so it could be used through @sc{gdb/mi}. This section
28807 describes the @sc{gdb/mi} operations that will be available and gives some
28808 hints about their use.
28810 @emph{Note}: In addition to the set of operations described here, we
28811 expect the @sc{gui} implementation of a variable window to require, at
28812 least, the following operations:
28815 @item @code{-gdb-show} @code{output-radix}
28816 @item @code{-stack-list-arguments}
28817 @item @code{-stack-list-locals}
28818 @item @code{-stack-select-frame}
28823 @subheading Introduction to Variable Objects
28825 @cindex variable objects in @sc{gdb/mi}
28827 Variable objects are "object-oriented" MI interface for examining and
28828 changing values of expressions. Unlike some other MI interfaces that
28829 work with expressions, variable objects are specifically designed for
28830 simple and efficient presentation in the frontend. A variable object
28831 is identified by string name. When a variable object is created, the
28832 frontend specifies the expression for that variable object. The
28833 expression can be a simple variable, or it can be an arbitrary complex
28834 expression, and can even involve CPU registers. After creating a
28835 variable object, the frontend can invoke other variable object
28836 operations---for example to obtain or change the value of a variable
28837 object, or to change display format.
28839 Variable objects have hierarchical tree structure. Any variable object
28840 that corresponds to a composite type, such as structure in C, has
28841 a number of child variable objects, for example corresponding to each
28842 element of a structure. A child variable object can itself have
28843 children, recursively. Recursion ends when we reach
28844 leaf variable objects, which always have built-in types. Child variable
28845 objects are created only by explicit request, so if a frontend
28846 is not interested in the children of a particular variable object, no
28847 child will be created.
28849 For a leaf variable object it is possible to obtain its value as a
28850 string, or set the value from a string. String value can be also
28851 obtained for a non-leaf variable object, but it's generally a string
28852 that only indicates the type of the object, and does not list its
28853 contents. Assignment to a non-leaf variable object is not allowed.
28855 A frontend does not need to read the values of all variable objects each time
28856 the program stops. Instead, MI provides an update command that lists all
28857 variable objects whose values has changed since the last update
28858 operation. This considerably reduces the amount of data that must
28859 be transferred to the frontend. As noted above, children variable
28860 objects are created on demand, and only leaf variable objects have a
28861 real value. As result, gdb will read target memory only for leaf
28862 variables that frontend has created.
28864 The automatic update is not always desirable. For example, a frontend
28865 might want to keep a value of some expression for future reference,
28866 and never update it. For another example, fetching memory is
28867 relatively slow for embedded targets, so a frontend might want
28868 to disable automatic update for the variables that are either not
28869 visible on the screen, or ``closed''. This is possible using so
28870 called ``frozen variable objects''. Such variable objects are never
28871 implicitly updated.
28873 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28874 fixed variable object, the expression is parsed when the variable
28875 object is created, including associating identifiers to specific
28876 variables. The meaning of expression never changes. For a floating
28877 variable object the values of variables whose names appear in the
28878 expressions are re-evaluated every time in the context of the current
28879 frame. Consider this example:
28884 struct work_state state;
28891 If a fixed variable object for the @code{state} variable is created in
28892 this function, and we enter the recursive call, the variable
28893 object will report the value of @code{state} in the top-level
28894 @code{do_work} invocation. On the other hand, a floating variable
28895 object will report the value of @code{state} in the current frame.
28897 If an expression specified when creating a fixed variable object
28898 refers to a local variable, the variable object becomes bound to the
28899 thread and frame in which the variable object is created. When such
28900 variable object is updated, @value{GDBN} makes sure that the
28901 thread/frame combination the variable object is bound to still exists,
28902 and re-evaluates the variable object in context of that thread/frame.
28904 The following is the complete set of @sc{gdb/mi} operations defined to
28905 access this functionality:
28907 @multitable @columnfractions .4 .6
28908 @item @strong{Operation}
28909 @tab @strong{Description}
28911 @item @code{-enable-pretty-printing}
28912 @tab enable Python-based pretty-printing
28913 @item @code{-var-create}
28914 @tab create a variable object
28915 @item @code{-var-delete}
28916 @tab delete the variable object and/or its children
28917 @item @code{-var-set-format}
28918 @tab set the display format of this variable
28919 @item @code{-var-show-format}
28920 @tab show the display format of this variable
28921 @item @code{-var-info-num-children}
28922 @tab tells how many children this object has
28923 @item @code{-var-list-children}
28924 @tab return a list of the object's children
28925 @item @code{-var-info-type}
28926 @tab show the type of this variable object
28927 @item @code{-var-info-expression}
28928 @tab print parent-relative expression that this variable object represents
28929 @item @code{-var-info-path-expression}
28930 @tab print full expression that this variable object represents
28931 @item @code{-var-show-attributes}
28932 @tab is this variable editable? does it exist here?
28933 @item @code{-var-evaluate-expression}
28934 @tab get the value of this variable
28935 @item @code{-var-assign}
28936 @tab set the value of this variable
28937 @item @code{-var-update}
28938 @tab update the variable and its children
28939 @item @code{-var-set-frozen}
28940 @tab set frozeness attribute
28941 @item @code{-var-set-update-range}
28942 @tab set range of children to display on update
28945 In the next subsection we describe each operation in detail and suggest
28946 how it can be used.
28948 @subheading Description And Use of Operations on Variable Objects
28950 @subheading The @code{-enable-pretty-printing} Command
28951 @findex -enable-pretty-printing
28954 -enable-pretty-printing
28957 @value{GDBN} allows Python-based visualizers to affect the output of the
28958 MI variable object commands. However, because there was no way to
28959 implement this in a fully backward-compatible way, a front end must
28960 request that this functionality be enabled.
28962 Once enabled, this feature cannot be disabled.
28964 Note that if Python support has not been compiled into @value{GDBN},
28965 this command will still succeed (and do nothing).
28967 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28968 may work differently in future versions of @value{GDBN}.
28970 @subheading The @code{-var-create} Command
28971 @findex -var-create
28973 @subsubheading Synopsis
28976 -var-create @{@var{name} | "-"@}
28977 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28980 This operation creates a variable object, which allows the monitoring of
28981 a variable, the result of an expression, a memory cell or a CPU
28984 The @var{name} parameter is the string by which the object can be
28985 referenced. It must be unique. If @samp{-} is specified, the varobj
28986 system will generate a string ``varNNNNNN'' automatically. It will be
28987 unique provided that one does not specify @var{name} of that format.
28988 The command fails if a duplicate name is found.
28990 The frame under which the expression should be evaluated can be
28991 specified by @var{frame-addr}. A @samp{*} indicates that the current
28992 frame should be used. A @samp{@@} indicates that a floating variable
28993 object must be created.
28995 @var{expression} is any expression valid on the current language set (must not
28996 begin with a @samp{*}), or one of the following:
29000 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29003 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29006 @samp{$@var{regname}} --- a CPU register name
29009 @cindex dynamic varobj
29010 A varobj's contents may be provided by a Python-based pretty-printer. In this
29011 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29012 have slightly different semantics in some cases. If the
29013 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29014 will never create a dynamic varobj. This ensures backward
29015 compatibility for existing clients.
29017 @subsubheading Result
29019 This operation returns attributes of the newly-created varobj. These
29024 The name of the varobj.
29027 The number of children of the varobj. This number is not necessarily
29028 reliable for a dynamic varobj. Instead, you must examine the
29029 @samp{has_more} attribute.
29032 The varobj's scalar value. For a varobj whose type is some sort of
29033 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29034 will not be interesting.
29037 The varobj's type. This is a string representation of the type, as
29038 would be printed by the @value{GDBN} CLI. If @samp{print object}
29039 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29040 @emph{actual} (derived) type of the object is shown rather than the
29041 @emph{declared} one.
29044 If a variable object is bound to a specific thread, then this is the
29045 thread's identifier.
29048 For a dynamic varobj, this indicates whether there appear to be any
29049 children available. For a non-dynamic varobj, this will be 0.
29052 This attribute will be present and have the value @samp{1} if the
29053 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29054 then this attribute will not be present.
29057 A dynamic varobj can supply a display hint to the front end. The
29058 value comes directly from the Python pretty-printer object's
29059 @code{display_hint} method. @xref{Pretty Printing API}.
29062 Typical output will look like this:
29065 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29066 has_more="@var{has_more}"
29070 @subheading The @code{-var-delete} Command
29071 @findex -var-delete
29073 @subsubheading Synopsis
29076 -var-delete [ -c ] @var{name}
29079 Deletes a previously created variable object and all of its children.
29080 With the @samp{-c} option, just deletes the children.
29082 Returns an error if the object @var{name} is not found.
29085 @subheading The @code{-var-set-format} Command
29086 @findex -var-set-format
29088 @subsubheading Synopsis
29091 -var-set-format @var{name} @var{format-spec}
29094 Sets the output format for the value of the object @var{name} to be
29097 @anchor{-var-set-format}
29098 The syntax for the @var{format-spec} is as follows:
29101 @var{format-spec} @expansion{}
29102 @{binary | decimal | hexadecimal | octal | natural@}
29105 The natural format is the default format choosen automatically
29106 based on the variable type (like decimal for an @code{int}, hex
29107 for pointers, etc.).
29109 For a variable with children, the format is set only on the
29110 variable itself, and the children are not affected.
29112 @subheading The @code{-var-show-format} Command
29113 @findex -var-show-format
29115 @subsubheading Synopsis
29118 -var-show-format @var{name}
29121 Returns the format used to display the value of the object @var{name}.
29124 @var{format} @expansion{}
29129 @subheading The @code{-var-info-num-children} Command
29130 @findex -var-info-num-children
29132 @subsubheading Synopsis
29135 -var-info-num-children @var{name}
29138 Returns the number of children of a variable object @var{name}:
29144 Note that this number is not completely reliable for a dynamic varobj.
29145 It will return the current number of children, but more children may
29149 @subheading The @code{-var-list-children} Command
29150 @findex -var-list-children
29152 @subsubheading Synopsis
29155 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29157 @anchor{-var-list-children}
29159 Return a list of the children of the specified variable object and
29160 create variable objects for them, if they do not already exist. With
29161 a single argument or if @var{print-values} has a value of 0 or
29162 @code{--no-values}, print only the names of the variables; if
29163 @var{print-values} is 1 or @code{--all-values}, also print their
29164 values; and if it is 2 or @code{--simple-values} print the name and
29165 value for simple data types and just the name for arrays, structures
29168 @var{from} and @var{to}, if specified, indicate the range of children
29169 to report. If @var{from} or @var{to} is less than zero, the range is
29170 reset and all children will be reported. Otherwise, children starting
29171 at @var{from} (zero-based) and up to and excluding @var{to} will be
29174 If a child range is requested, it will only affect the current call to
29175 @code{-var-list-children}, but not future calls to @code{-var-update}.
29176 For this, you must instead use @code{-var-set-update-range}. The
29177 intent of this approach is to enable a front end to implement any
29178 update approach it likes; for example, scrolling a view may cause the
29179 front end to request more children with @code{-var-list-children}, and
29180 then the front end could call @code{-var-set-update-range} with a
29181 different range to ensure that future updates are restricted to just
29184 For each child the following results are returned:
29189 Name of the variable object created for this child.
29192 The expression to be shown to the user by the front end to designate this child.
29193 For example this may be the name of a structure member.
29195 For a dynamic varobj, this value cannot be used to form an
29196 expression. There is no way to do this at all with a dynamic varobj.
29198 For C/C@t{++} structures there are several pseudo children returned to
29199 designate access qualifiers. For these pseudo children @var{exp} is
29200 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29201 type and value are not present.
29203 A dynamic varobj will not report the access qualifying
29204 pseudo-children, regardless of the language. This information is not
29205 available at all with a dynamic varobj.
29208 Number of children this child has. For a dynamic varobj, this will be
29212 The type of the child. If @samp{print object}
29213 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29214 @emph{actual} (derived) type of the object is shown rather than the
29215 @emph{declared} one.
29218 If values were requested, this is the value.
29221 If this variable object is associated with a thread, this is the thread id.
29222 Otherwise this result is not present.
29225 If the variable object is frozen, this variable will be present with a value of 1.
29228 A dynamic varobj can supply a display hint to the front end. The
29229 value comes directly from the Python pretty-printer object's
29230 @code{display_hint} method. @xref{Pretty Printing API}.
29233 This attribute will be present and have the value @samp{1} if the
29234 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29235 then this attribute will not be present.
29239 The result may have its own attributes:
29243 A dynamic varobj can supply a display hint to the front end. The
29244 value comes directly from the Python pretty-printer object's
29245 @code{display_hint} method. @xref{Pretty Printing API}.
29248 This is an integer attribute which is nonzero if there are children
29249 remaining after the end of the selected range.
29252 @subsubheading Example
29256 -var-list-children n
29257 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29258 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29260 -var-list-children --all-values n
29261 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29262 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29266 @subheading The @code{-var-info-type} Command
29267 @findex -var-info-type
29269 @subsubheading Synopsis
29272 -var-info-type @var{name}
29275 Returns the type of the specified variable @var{name}. The type is
29276 returned as a string in the same format as it is output by the
29280 type=@var{typename}
29284 @subheading The @code{-var-info-expression} Command
29285 @findex -var-info-expression
29287 @subsubheading Synopsis
29290 -var-info-expression @var{name}
29293 Returns a string that is suitable for presenting this
29294 variable object in user interface. The string is generally
29295 not valid expression in the current language, and cannot be evaluated.
29297 For example, if @code{a} is an array, and variable object
29298 @code{A} was created for @code{a}, then we'll get this output:
29301 (gdb) -var-info-expression A.1
29302 ^done,lang="C",exp="1"
29306 Here, the value of @code{lang} is the language name, which can be
29307 found in @ref{Supported Languages}.
29309 Note that the output of the @code{-var-list-children} command also
29310 includes those expressions, so the @code{-var-info-expression} command
29313 @subheading The @code{-var-info-path-expression} Command
29314 @findex -var-info-path-expression
29316 @subsubheading Synopsis
29319 -var-info-path-expression @var{name}
29322 Returns an expression that can be evaluated in the current
29323 context and will yield the same value that a variable object has.
29324 Compare this with the @code{-var-info-expression} command, which
29325 result can be used only for UI presentation. Typical use of
29326 the @code{-var-info-path-expression} command is creating a
29327 watchpoint from a variable object.
29329 This command is currently not valid for children of a dynamic varobj,
29330 and will give an error when invoked on one.
29332 For example, suppose @code{C} is a C@t{++} class, derived from class
29333 @code{Base}, and that the @code{Base} class has a member called
29334 @code{m_size}. Assume a variable @code{c} is has the type of
29335 @code{C} and a variable object @code{C} was created for variable
29336 @code{c}. Then, we'll get this output:
29338 (gdb) -var-info-path-expression C.Base.public.m_size
29339 ^done,path_expr=((Base)c).m_size)
29342 @subheading The @code{-var-show-attributes} Command
29343 @findex -var-show-attributes
29345 @subsubheading Synopsis
29348 -var-show-attributes @var{name}
29351 List attributes of the specified variable object @var{name}:
29354 status=@var{attr} [ ( ,@var{attr} )* ]
29358 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29360 @subheading The @code{-var-evaluate-expression} Command
29361 @findex -var-evaluate-expression
29363 @subsubheading Synopsis
29366 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29369 Evaluates the expression that is represented by the specified variable
29370 object and returns its value as a string. The format of the string
29371 can be specified with the @samp{-f} option. The possible values of
29372 this option are the same as for @code{-var-set-format}
29373 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29374 the current display format will be used. The current display format
29375 can be changed using the @code{-var-set-format} command.
29381 Note that one must invoke @code{-var-list-children} for a variable
29382 before the value of a child variable can be evaluated.
29384 @subheading The @code{-var-assign} Command
29385 @findex -var-assign
29387 @subsubheading Synopsis
29390 -var-assign @var{name} @var{expression}
29393 Assigns the value of @var{expression} to the variable object specified
29394 by @var{name}. The object must be @samp{editable}. If the variable's
29395 value is altered by the assign, the variable will show up in any
29396 subsequent @code{-var-update} list.
29398 @subsubheading Example
29406 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29410 @subheading The @code{-var-update} Command
29411 @findex -var-update
29413 @subsubheading Synopsis
29416 -var-update [@var{print-values}] @{@var{name} | "*"@}
29419 Reevaluate the expressions corresponding to the variable object
29420 @var{name} and all its direct and indirect children, and return the
29421 list of variable objects whose values have changed; @var{name} must
29422 be a root variable object. Here, ``changed'' means that the result of
29423 @code{-var-evaluate-expression} before and after the
29424 @code{-var-update} is different. If @samp{*} is used as the variable
29425 object names, all existing variable objects are updated, except
29426 for frozen ones (@pxref{-var-set-frozen}). The option
29427 @var{print-values} determines whether both names and values, or just
29428 names are printed. The possible values of this option are the same
29429 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29430 recommended to use the @samp{--all-values} option, to reduce the
29431 number of MI commands needed on each program stop.
29433 With the @samp{*} parameter, if a variable object is bound to a
29434 currently running thread, it will not be updated, without any
29437 If @code{-var-set-update-range} was previously used on a varobj, then
29438 only the selected range of children will be reported.
29440 @code{-var-update} reports all the changed varobjs in a tuple named
29443 Each item in the change list is itself a tuple holding:
29447 The name of the varobj.
29450 If values were requested for this update, then this field will be
29451 present and will hold the value of the varobj.
29454 @anchor{-var-update}
29455 This field is a string which may take one of three values:
29459 The variable object's current value is valid.
29462 The variable object does not currently hold a valid value but it may
29463 hold one in the future if its associated expression comes back into
29467 The variable object no longer holds a valid value.
29468 This can occur when the executable file being debugged has changed,
29469 either through recompilation or by using the @value{GDBN} @code{file}
29470 command. The front end should normally choose to delete these variable
29474 In the future new values may be added to this list so the front should
29475 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29478 This is only present if the varobj is still valid. If the type
29479 changed, then this will be the string @samp{true}; otherwise it will
29482 When a varobj's type changes, its children are also likely to have
29483 become incorrect. Therefore, the varobj's children are automatically
29484 deleted when this attribute is @samp{true}. Also, the varobj's update
29485 range, when set using the @code{-var-set-update-range} command, is
29489 If the varobj's type changed, then this field will be present and will
29492 @item new_num_children
29493 For a dynamic varobj, if the number of children changed, or if the
29494 type changed, this will be the new number of children.
29496 The @samp{numchild} field in other varobj responses is generally not
29497 valid for a dynamic varobj -- it will show the number of children that
29498 @value{GDBN} knows about, but because dynamic varobjs lazily
29499 instantiate their children, this will not reflect the number of
29500 children which may be available.
29502 The @samp{new_num_children} attribute only reports changes to the
29503 number of children known by @value{GDBN}. This is the only way to
29504 detect whether an update has removed children (which necessarily can
29505 only happen at the end of the update range).
29508 The display hint, if any.
29511 This is an integer value, which will be 1 if there are more children
29512 available outside the varobj's update range.
29515 This attribute will be present and have the value @samp{1} if the
29516 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29517 then this attribute will not be present.
29520 If new children were added to a dynamic varobj within the selected
29521 update range (as set by @code{-var-set-update-range}), then they will
29522 be listed in this attribute.
29525 @subsubheading Example
29532 -var-update --all-values var1
29533 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29534 type_changed="false"@}]
29538 @subheading The @code{-var-set-frozen} Command
29539 @findex -var-set-frozen
29540 @anchor{-var-set-frozen}
29542 @subsubheading Synopsis
29545 -var-set-frozen @var{name} @var{flag}
29548 Set the frozenness flag on the variable object @var{name}. The
29549 @var{flag} parameter should be either @samp{1} to make the variable
29550 frozen or @samp{0} to make it unfrozen. If a variable object is
29551 frozen, then neither itself, nor any of its children, are
29552 implicitly updated by @code{-var-update} of
29553 a parent variable or by @code{-var-update *}. Only
29554 @code{-var-update} of the variable itself will update its value and
29555 values of its children. After a variable object is unfrozen, it is
29556 implicitly updated by all subsequent @code{-var-update} operations.
29557 Unfreezing a variable does not update it, only subsequent
29558 @code{-var-update} does.
29560 @subsubheading Example
29564 -var-set-frozen V 1
29569 @subheading The @code{-var-set-update-range} command
29570 @findex -var-set-update-range
29571 @anchor{-var-set-update-range}
29573 @subsubheading Synopsis
29576 -var-set-update-range @var{name} @var{from} @var{to}
29579 Set the range of children to be returned by future invocations of
29580 @code{-var-update}.
29582 @var{from} and @var{to} indicate the range of children to report. If
29583 @var{from} or @var{to} is less than zero, the range is reset and all
29584 children will be reported. Otherwise, children starting at @var{from}
29585 (zero-based) and up to and excluding @var{to} will be reported.
29587 @subsubheading Example
29591 -var-set-update-range V 1 2
29595 @subheading The @code{-var-set-visualizer} command
29596 @findex -var-set-visualizer
29597 @anchor{-var-set-visualizer}
29599 @subsubheading Synopsis
29602 -var-set-visualizer @var{name} @var{visualizer}
29605 Set a visualizer for the variable object @var{name}.
29607 @var{visualizer} is the visualizer to use. The special value
29608 @samp{None} means to disable any visualizer in use.
29610 If not @samp{None}, @var{visualizer} must be a Python expression.
29611 This expression must evaluate to a callable object which accepts a
29612 single argument. @value{GDBN} will call this object with the value of
29613 the varobj @var{name} as an argument (this is done so that the same
29614 Python pretty-printing code can be used for both the CLI and MI).
29615 When called, this object must return an object which conforms to the
29616 pretty-printing interface (@pxref{Pretty Printing API}).
29618 The pre-defined function @code{gdb.default_visualizer} may be used to
29619 select a visualizer by following the built-in process
29620 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29621 a varobj is created, and so ordinarily is not needed.
29623 This feature is only available if Python support is enabled. The MI
29624 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29625 can be used to check this.
29627 @subsubheading Example
29629 Resetting the visualizer:
29633 -var-set-visualizer V None
29637 Reselecting the default (type-based) visualizer:
29641 -var-set-visualizer V gdb.default_visualizer
29645 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29646 can be used to instantiate this class for a varobj:
29650 -var-set-visualizer V "lambda val: SomeClass()"
29654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29655 @node GDB/MI Data Manipulation
29656 @section @sc{gdb/mi} Data Manipulation
29658 @cindex data manipulation, in @sc{gdb/mi}
29659 @cindex @sc{gdb/mi}, data manipulation
29660 This section describes the @sc{gdb/mi} commands that manipulate data:
29661 examine memory and registers, evaluate expressions, etc.
29663 For details about what an addressable memory unit is,
29664 @pxref{addressable memory unit}.
29666 @c REMOVED FROM THE INTERFACE.
29667 @c @subheading -data-assign
29668 @c Change the value of a program variable. Plenty of side effects.
29669 @c @subsubheading GDB Command
29671 @c @subsubheading Example
29674 @subheading The @code{-data-disassemble} Command
29675 @findex -data-disassemble
29677 @subsubheading Synopsis
29681 [ -s @var{start-addr} -e @var{end-addr} ]
29682 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29690 @item @var{start-addr}
29691 is the beginning address (or @code{$pc})
29692 @item @var{end-addr}
29694 @item @var{filename}
29695 is the name of the file to disassemble
29696 @item @var{linenum}
29697 is the line number to disassemble around
29699 is the number of disassembly lines to be produced. If it is -1,
29700 the whole function will be disassembled, in case no @var{end-addr} is
29701 specified. If @var{end-addr} is specified as a non-zero value, and
29702 @var{lines} is lower than the number of disassembly lines between
29703 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29704 displayed; if @var{lines} is higher than the number of lines between
29705 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29708 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29709 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29710 mixed source and disassembly with raw opcodes).
29713 @subsubheading Result
29715 The result of the @code{-data-disassemble} command will be a list named
29716 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29717 used with the @code{-data-disassemble} command.
29719 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29724 The address at which this instruction was disassembled.
29727 The name of the function this instruction is within.
29730 The decimal offset in bytes from the start of @samp{func-name}.
29733 The text disassembly for this @samp{address}.
29736 This field is only present for mode 2. This contains the raw opcode
29737 bytes for the @samp{inst} field.
29741 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29742 @samp{src_and_asm_line}, each of which has the following fields:
29746 The line number within @samp{file}.
29749 The file name from the compilation unit. This might be an absolute
29750 file name or a relative file name depending on the compile command
29754 Absolute file name of @samp{file}. It is converted to a canonical form
29755 using the source file search path
29756 (@pxref{Source Path, ,Specifying Source Directories})
29757 and after resolving all the symbolic links.
29759 If the source file is not found this field will contain the path as
29760 present in the debug information.
29762 @item line_asm_insn
29763 This is a list of tuples containing the disassembly for @samp{line} in
29764 @samp{file}. The fields of each tuple are the same as for
29765 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29766 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29771 Note that whatever included in the @samp{inst} field, is not
29772 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29775 @subsubheading @value{GDBN} Command
29777 The corresponding @value{GDBN} command is @samp{disassemble}.
29779 @subsubheading Example
29781 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29785 -data-disassemble -s $pc -e "$pc + 20" -- 0
29788 @{address="0x000107c0",func-name="main",offset="4",
29789 inst="mov 2, %o0"@},
29790 @{address="0x000107c4",func-name="main",offset="8",
29791 inst="sethi %hi(0x11800), %o2"@},
29792 @{address="0x000107c8",func-name="main",offset="12",
29793 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29794 @{address="0x000107cc",func-name="main",offset="16",
29795 inst="sethi %hi(0x11800), %o2"@},
29796 @{address="0x000107d0",func-name="main",offset="20",
29797 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29801 Disassemble the whole @code{main} function. Line 32 is part of
29805 -data-disassemble -f basics.c -l 32 -- 0
29807 @{address="0x000107bc",func-name="main",offset="0",
29808 inst="save %sp, -112, %sp"@},
29809 @{address="0x000107c0",func-name="main",offset="4",
29810 inst="mov 2, %o0"@},
29811 @{address="0x000107c4",func-name="main",offset="8",
29812 inst="sethi %hi(0x11800), %o2"@},
29814 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29815 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29819 Disassemble 3 instructions from the start of @code{main}:
29823 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29825 @{address="0x000107bc",func-name="main",offset="0",
29826 inst="save %sp, -112, %sp"@},
29827 @{address="0x000107c0",func-name="main",offset="4",
29828 inst="mov 2, %o0"@},
29829 @{address="0x000107c4",func-name="main",offset="8",
29830 inst="sethi %hi(0x11800), %o2"@}]
29834 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29838 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29840 src_and_asm_line=@{line="31",
29841 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29842 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29843 line_asm_insn=[@{address="0x000107bc",
29844 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29845 src_and_asm_line=@{line="32",
29846 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29847 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29848 line_asm_insn=[@{address="0x000107c0",
29849 func-name="main",offset="4",inst="mov 2, %o0"@},
29850 @{address="0x000107c4",func-name="main",offset="8",
29851 inst="sethi %hi(0x11800), %o2"@}]@}]
29856 @subheading The @code{-data-evaluate-expression} Command
29857 @findex -data-evaluate-expression
29859 @subsubheading Synopsis
29862 -data-evaluate-expression @var{expr}
29865 Evaluate @var{expr} as an expression. The expression could contain an
29866 inferior function call. The function call will execute synchronously.
29867 If the expression contains spaces, it must be enclosed in double quotes.
29869 @subsubheading @value{GDBN} Command
29871 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29872 @samp{call}. In @code{gdbtk} only, there's a corresponding
29873 @samp{gdb_eval} command.
29875 @subsubheading Example
29877 In the following example, the numbers that precede the commands are the
29878 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29879 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29883 211-data-evaluate-expression A
29886 311-data-evaluate-expression &A
29887 311^done,value="0xefffeb7c"
29889 411-data-evaluate-expression A+3
29892 511-data-evaluate-expression "A + 3"
29898 @subheading The @code{-data-list-changed-registers} Command
29899 @findex -data-list-changed-registers
29901 @subsubheading Synopsis
29904 -data-list-changed-registers
29907 Display a list of the registers that have changed.
29909 @subsubheading @value{GDBN} Command
29911 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29912 has the corresponding command @samp{gdb_changed_register_list}.
29914 @subsubheading Example
29916 On a PPC MBX board:
29924 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29925 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29928 -data-list-changed-registers
29929 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29930 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29931 "24","25","26","27","28","30","31","64","65","66","67","69"]
29936 @subheading The @code{-data-list-register-names} Command
29937 @findex -data-list-register-names
29939 @subsubheading Synopsis
29942 -data-list-register-names [ ( @var{regno} )+ ]
29945 Show a list of register names for the current target. If no arguments
29946 are given, it shows a list of the names of all the registers. If
29947 integer numbers are given as arguments, it will print a list of the
29948 names of the registers corresponding to the arguments. To ensure
29949 consistency between a register name and its number, the output list may
29950 include empty register names.
29952 @subsubheading @value{GDBN} Command
29954 @value{GDBN} does not have a command which corresponds to
29955 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29956 corresponding command @samp{gdb_regnames}.
29958 @subsubheading Example
29960 For the PPC MBX board:
29963 -data-list-register-names
29964 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29965 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29966 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29967 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29968 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29969 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29970 "", "pc","ps","cr","lr","ctr","xer"]
29972 -data-list-register-names 1 2 3
29973 ^done,register-names=["r1","r2","r3"]
29977 @subheading The @code{-data-list-register-values} Command
29978 @findex -data-list-register-values
29980 @subsubheading Synopsis
29983 -data-list-register-values
29984 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29987 Display the registers' contents. The format according to which the
29988 registers' contents are to be returned is given by @var{fmt}, followed
29989 by an optional list of numbers specifying the registers to display. A
29990 missing list of numbers indicates that the contents of all the
29991 registers must be returned. The @code{--skip-unavailable} option
29992 indicates that only the available registers are to be returned.
29994 Allowed formats for @var{fmt} are:
30011 @subsubheading @value{GDBN} Command
30013 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30014 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30016 @subsubheading Example
30018 For a PPC MBX board (note: line breaks are for readability only, they
30019 don't appear in the actual output):
30023 -data-list-register-values r 64 65
30024 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30025 @{number="65",value="0x00029002"@}]
30027 -data-list-register-values x
30028 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30029 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30030 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30031 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30032 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30033 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30034 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30035 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30036 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30037 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30038 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30039 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30040 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30041 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30042 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30043 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30044 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30045 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30046 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30047 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30048 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30049 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30050 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30051 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30052 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30053 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30054 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30055 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30056 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30057 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30058 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30059 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30060 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30061 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30062 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30063 @{number="69",value="0x20002b03"@}]
30068 @subheading The @code{-data-read-memory} Command
30069 @findex -data-read-memory
30071 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30073 @subsubheading Synopsis
30076 -data-read-memory [ -o @var{byte-offset} ]
30077 @var{address} @var{word-format} @var{word-size}
30078 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30085 @item @var{address}
30086 An expression specifying the address of the first memory word to be
30087 read. Complex expressions containing embedded white space should be
30088 quoted using the C convention.
30090 @item @var{word-format}
30091 The format to be used to print the memory words. The notation is the
30092 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30095 @item @var{word-size}
30096 The size of each memory word in bytes.
30098 @item @var{nr-rows}
30099 The number of rows in the output table.
30101 @item @var{nr-cols}
30102 The number of columns in the output table.
30105 If present, indicates that each row should include an @sc{ascii} dump. The
30106 value of @var{aschar} is used as a padding character when a byte is not a
30107 member of the printable @sc{ascii} character set (printable @sc{ascii}
30108 characters are those whose code is between 32 and 126, inclusively).
30110 @item @var{byte-offset}
30111 An offset to add to the @var{address} before fetching memory.
30114 This command displays memory contents as a table of @var{nr-rows} by
30115 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30116 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30117 (returned as @samp{total-bytes}). Should less than the requested number
30118 of bytes be returned by the target, the missing words are identified
30119 using @samp{N/A}. The number of bytes read from the target is returned
30120 in @samp{nr-bytes} and the starting address used to read memory in
30123 The address of the next/previous row or page is available in
30124 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30127 @subsubheading @value{GDBN} Command
30129 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30130 @samp{gdb_get_mem} memory read command.
30132 @subsubheading Example
30134 Read six bytes of memory starting at @code{bytes+6} but then offset by
30135 @code{-6} bytes. Format as three rows of two columns. One byte per
30136 word. Display each word in hex.
30140 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30141 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30142 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30143 prev-page="0x0000138a",memory=[
30144 @{addr="0x00001390",data=["0x00","0x01"]@},
30145 @{addr="0x00001392",data=["0x02","0x03"]@},
30146 @{addr="0x00001394",data=["0x04","0x05"]@}]
30150 Read two bytes of memory starting at address @code{shorts + 64} and
30151 display as a single word formatted in decimal.
30155 5-data-read-memory shorts+64 d 2 1 1
30156 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30157 next-row="0x00001512",prev-row="0x0000150e",
30158 next-page="0x00001512",prev-page="0x0000150e",memory=[
30159 @{addr="0x00001510",data=["128"]@}]
30163 Read thirty two bytes of memory starting at @code{bytes+16} and format
30164 as eight rows of four columns. Include a string encoding with @samp{x}
30165 used as the non-printable character.
30169 4-data-read-memory bytes+16 x 1 8 4 x
30170 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30171 next-row="0x000013c0",prev-row="0x0000139c",
30172 next-page="0x000013c0",prev-page="0x00001380",memory=[
30173 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30174 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30175 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30176 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30177 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30178 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30179 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30180 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30184 @subheading The @code{-data-read-memory-bytes} Command
30185 @findex -data-read-memory-bytes
30187 @subsubheading Synopsis
30190 -data-read-memory-bytes [ -o @var{offset} ]
30191 @var{address} @var{count}
30198 @item @var{address}
30199 An expression specifying the address of the first addressable memory unit
30200 to be read. Complex expressions containing embedded white space should be
30201 quoted using the C convention.
30204 The number of addressable memory units to read. This should be an integer
30208 The offset relative to @var{address} at which to start reading. This
30209 should be an integer literal. This option is provided so that a frontend
30210 is not required to first evaluate address and then perform address
30211 arithmetics itself.
30215 This command attempts to read all accessible memory regions in the
30216 specified range. First, all regions marked as unreadable in the memory
30217 map (if one is defined) will be skipped. @xref{Memory Region
30218 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30219 regions. For each one, if reading full region results in an errors,
30220 @value{GDBN} will try to read a subset of the region.
30222 In general, every single memory unit in the region may be readable or not,
30223 and the only way to read every readable unit is to try a read at
30224 every address, which is not practical. Therefore, @value{GDBN} will
30225 attempt to read all accessible memory units at either beginning or the end
30226 of the region, using a binary division scheme. This heuristic works
30227 well for reading accross a memory map boundary. Note that if a region
30228 has a readable range that is neither at the beginning or the end,
30229 @value{GDBN} will not read it.
30231 The result record (@pxref{GDB/MI Result Records}) that is output of
30232 the command includes a field named @samp{memory} whose content is a
30233 list of tuples. Each tuple represent a successfully read memory block
30234 and has the following fields:
30238 The start address of the memory block, as hexadecimal literal.
30241 The end address of the memory block, as hexadecimal literal.
30244 The offset of the memory block, as hexadecimal literal, relative to
30245 the start address passed to @code{-data-read-memory-bytes}.
30248 The contents of the memory block, in hex.
30254 @subsubheading @value{GDBN} Command
30256 The corresponding @value{GDBN} command is @samp{x}.
30258 @subsubheading Example
30262 -data-read-memory-bytes &a 10
30263 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30265 contents="01000000020000000300"@}]
30270 @subheading The @code{-data-write-memory-bytes} Command
30271 @findex -data-write-memory-bytes
30273 @subsubheading Synopsis
30276 -data-write-memory-bytes @var{address} @var{contents}
30277 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30284 @item @var{address}
30285 An expression specifying the address of the first addressable memory unit
30286 to be written. Complex expressions containing embedded white space should
30287 be quoted using the C convention.
30289 @item @var{contents}
30290 The hex-encoded data to write. It is an error if @var{contents} does
30291 not represent an integral number of addressable memory units.
30294 Optional argument indicating the number of addressable memory units to be
30295 written. If @var{count} is greater than @var{contents}' length,
30296 @value{GDBN} will repeatedly write @var{contents} until it fills
30297 @var{count} memory units.
30301 @subsubheading @value{GDBN} Command
30303 There's no corresponding @value{GDBN} command.
30305 @subsubheading Example
30309 -data-write-memory-bytes &a "aabbccdd"
30316 -data-write-memory-bytes &a "aabbccdd" 16e
30321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30322 @node GDB/MI Tracepoint Commands
30323 @section @sc{gdb/mi} Tracepoint Commands
30325 The commands defined in this section implement MI support for
30326 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30328 @subheading The @code{-trace-find} Command
30329 @findex -trace-find
30331 @subsubheading Synopsis
30334 -trace-find @var{mode} [@var{parameters}@dots{}]
30337 Find a trace frame using criteria defined by @var{mode} and
30338 @var{parameters}. The following table lists permissible
30339 modes and their parameters. For details of operation, see @ref{tfind}.
30344 No parameters are required. Stops examining trace frames.
30347 An integer is required as parameter. Selects tracepoint frame with
30350 @item tracepoint-number
30351 An integer is required as parameter. Finds next
30352 trace frame that corresponds to tracepoint with the specified number.
30355 An address is required as parameter. Finds
30356 next trace frame that corresponds to any tracepoint at the specified
30359 @item pc-inside-range
30360 Two addresses are required as parameters. Finds next trace
30361 frame that corresponds to a tracepoint at an address inside the
30362 specified range. Both bounds are considered to be inside the range.
30364 @item pc-outside-range
30365 Two addresses are required as parameters. Finds
30366 next trace frame that corresponds to a tracepoint at an address outside
30367 the specified range. Both bounds are considered to be inside the range.
30370 Line specification is required as parameter. @xref{Specify Location}.
30371 Finds next trace frame that corresponds to a tracepoint at
30372 the specified location.
30376 If @samp{none} was passed as @var{mode}, the response does not
30377 have fields. Otherwise, the response may have the following fields:
30381 This field has either @samp{0} or @samp{1} as the value, depending
30382 on whether a matching tracepoint was found.
30385 The index of the found traceframe. This field is present iff
30386 the @samp{found} field has value of @samp{1}.
30389 The index of the found tracepoint. This field is present iff
30390 the @samp{found} field has value of @samp{1}.
30393 The information about the frame corresponding to the found trace
30394 frame. This field is present only if a trace frame was found.
30395 @xref{GDB/MI Frame Information}, for description of this field.
30399 @subsubheading @value{GDBN} Command
30401 The corresponding @value{GDBN} command is @samp{tfind}.
30403 @subheading -trace-define-variable
30404 @findex -trace-define-variable
30406 @subsubheading Synopsis
30409 -trace-define-variable @var{name} [ @var{value} ]
30412 Create trace variable @var{name} if it does not exist. If
30413 @var{value} is specified, sets the initial value of the specified
30414 trace variable to that value. Note that the @var{name} should start
30415 with the @samp{$} character.
30417 @subsubheading @value{GDBN} Command
30419 The corresponding @value{GDBN} command is @samp{tvariable}.
30421 @subheading The @code{-trace-frame-collected} Command
30422 @findex -trace-frame-collected
30424 @subsubheading Synopsis
30427 -trace-frame-collected
30428 [--var-print-values @var{var_pval}]
30429 [--comp-print-values @var{comp_pval}]
30430 [--registers-format @var{regformat}]
30431 [--memory-contents]
30434 This command returns the set of collected objects, register names,
30435 trace state variable names, memory ranges and computed expressions
30436 that have been collected at a particular trace frame. The optional
30437 parameters to the command affect the output format in different ways.
30438 See the output description table below for more details.
30440 The reported names can be used in the normal manner to create
30441 varobjs and inspect the objects themselves. The items returned by
30442 this command are categorized so that it is clear which is a variable,
30443 which is a register, which is a trace state variable, which is a
30444 memory range and which is a computed expression.
30446 For instance, if the actions were
30448 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30449 collect *(int*)0xaf02bef0@@40
30453 the object collected in its entirety would be @code{myVar}. The
30454 object @code{myArray} would be partially collected, because only the
30455 element at index @code{myIndex} would be collected. The remaining
30456 objects would be computed expressions.
30458 An example output would be:
30462 -trace-frame-collected
30464 explicit-variables=[@{name="myVar",value="1"@}],
30465 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30466 @{name="myObj.field",value="0"@},
30467 @{name="myPtr->field",value="1"@},
30468 @{name="myCount + 2",value="3"@},
30469 @{name="$tvar1 + 1",value="43970027"@}],
30470 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30471 @{number="1",value="0x0"@},
30472 @{number="2",value="0x4"@},
30474 @{number="125",value="0x0"@}],
30475 tvars=[@{name="$tvar1",current="43970026"@}],
30476 memory=[@{address="0x0000000000602264",length="4"@},
30477 @{address="0x0000000000615bc0",length="4"@}]
30484 @item explicit-variables
30485 The set of objects that have been collected in their entirety (as
30486 opposed to collecting just a few elements of an array or a few struct
30487 members). For each object, its name and value are printed.
30488 The @code{--var-print-values} option affects how or whether the value
30489 field is output. If @var{var_pval} is 0, then print only the names;
30490 if it is 1, print also their values; and if it is 2, print the name,
30491 type and value for simple data types, and the name and type for
30492 arrays, structures and unions.
30494 @item computed-expressions
30495 The set of computed expressions that have been collected at the
30496 current trace frame. The @code{--comp-print-values} option affects
30497 this set like the @code{--var-print-values} option affects the
30498 @code{explicit-variables} set. See above.
30501 The registers that have been collected at the current trace frame.
30502 For each register collected, the name and current value are returned.
30503 The value is formatted according to the @code{--registers-format}
30504 option. See the @command{-data-list-register-values} command for a
30505 list of the allowed formats. The default is @samp{x}.
30508 The trace state variables that have been collected at the current
30509 trace frame. For each trace state variable collected, the name and
30510 current value are returned.
30513 The set of memory ranges that have been collected at the current trace
30514 frame. Its content is a list of tuples. Each tuple represents a
30515 collected memory range and has the following fields:
30519 The start address of the memory range, as hexadecimal literal.
30522 The length of the memory range, as decimal literal.
30525 The contents of the memory block, in hex. This field is only present
30526 if the @code{--memory-contents} option is specified.
30532 @subsubheading @value{GDBN} Command
30534 There is no corresponding @value{GDBN} command.
30536 @subsubheading Example
30538 @subheading -trace-list-variables
30539 @findex -trace-list-variables
30541 @subsubheading Synopsis
30544 -trace-list-variables
30547 Return a table of all defined trace variables. Each element of the
30548 table has the following fields:
30552 The name of the trace variable. This field is always present.
30555 The initial value. This is a 64-bit signed integer. This
30556 field is always present.
30559 The value the trace variable has at the moment. This is a 64-bit
30560 signed integer. This field is absent iff current value is
30561 not defined, for example if the trace was never run, or is
30566 @subsubheading @value{GDBN} Command
30568 The corresponding @value{GDBN} command is @samp{tvariables}.
30570 @subsubheading Example
30574 -trace-list-variables
30575 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30576 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30577 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30578 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30579 body=[variable=@{name="$trace_timestamp",initial="0"@}
30580 variable=@{name="$foo",initial="10",current="15"@}]@}
30584 @subheading -trace-save
30585 @findex -trace-save
30587 @subsubheading Synopsis
30590 -trace-save [-r ] @var{filename}
30593 Saves the collected trace data to @var{filename}. Without the
30594 @samp{-r} option, the data is downloaded from the target and saved
30595 in a local file. With the @samp{-r} option the target is asked
30596 to perform the save.
30598 @subsubheading @value{GDBN} Command
30600 The corresponding @value{GDBN} command is @samp{tsave}.
30603 @subheading -trace-start
30604 @findex -trace-start
30606 @subsubheading Synopsis
30612 Starts a tracing experiments. The result of this command does not
30615 @subsubheading @value{GDBN} Command
30617 The corresponding @value{GDBN} command is @samp{tstart}.
30619 @subheading -trace-status
30620 @findex -trace-status
30622 @subsubheading Synopsis
30628 Obtains the status of a tracing experiment. The result may include
30629 the following fields:
30634 May have a value of either @samp{0}, when no tracing operations are
30635 supported, @samp{1}, when all tracing operations are supported, or
30636 @samp{file} when examining trace file. In the latter case, examining
30637 of trace frame is possible but new tracing experiement cannot be
30638 started. This field is always present.
30641 May have a value of either @samp{0} or @samp{1} depending on whether
30642 tracing experiement is in progress on target. This field is present
30643 if @samp{supported} field is not @samp{0}.
30646 Report the reason why the tracing was stopped last time. This field
30647 may be absent iff tracing was never stopped on target yet. The
30648 value of @samp{request} means the tracing was stopped as result of
30649 the @code{-trace-stop} command. The value of @samp{overflow} means
30650 the tracing buffer is full. The value of @samp{disconnection} means
30651 tracing was automatically stopped when @value{GDBN} has disconnected.
30652 The value of @samp{passcount} means tracing was stopped when a
30653 tracepoint was passed a maximal number of times for that tracepoint.
30654 This field is present if @samp{supported} field is not @samp{0}.
30656 @item stopping-tracepoint
30657 The number of tracepoint whose passcount as exceeded. This field is
30658 present iff the @samp{stop-reason} field has the value of
30662 @itemx frames-created
30663 The @samp{frames} field is a count of the total number of trace frames
30664 in the trace buffer, while @samp{frames-created} is the total created
30665 during the run, including ones that were discarded, such as when a
30666 circular trace buffer filled up. Both fields are optional.
30670 These fields tell the current size of the tracing buffer and the
30671 remaining space. These fields are optional.
30674 The value of the circular trace buffer flag. @code{1} means that the
30675 trace buffer is circular and old trace frames will be discarded if
30676 necessary to make room, @code{0} means that the trace buffer is linear
30680 The value of the disconnected tracing flag. @code{1} means that
30681 tracing will continue after @value{GDBN} disconnects, @code{0} means
30682 that the trace run will stop.
30685 The filename of the trace file being examined. This field is
30686 optional, and only present when examining a trace file.
30690 @subsubheading @value{GDBN} Command
30692 The corresponding @value{GDBN} command is @samp{tstatus}.
30694 @subheading -trace-stop
30695 @findex -trace-stop
30697 @subsubheading Synopsis
30703 Stops a tracing experiment. The result of this command has the same
30704 fields as @code{-trace-status}, except that the @samp{supported} and
30705 @samp{running} fields are not output.
30707 @subsubheading @value{GDBN} Command
30709 The corresponding @value{GDBN} command is @samp{tstop}.
30712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30713 @node GDB/MI Symbol Query
30714 @section @sc{gdb/mi} Symbol Query Commands
30718 @subheading The @code{-symbol-info-address} Command
30719 @findex -symbol-info-address
30721 @subsubheading Synopsis
30724 -symbol-info-address @var{symbol}
30727 Describe where @var{symbol} is stored.
30729 @subsubheading @value{GDBN} Command
30731 The corresponding @value{GDBN} command is @samp{info address}.
30733 @subsubheading Example
30737 @subheading The @code{-symbol-info-file} Command
30738 @findex -symbol-info-file
30740 @subsubheading Synopsis
30746 Show the file for the symbol.
30748 @subsubheading @value{GDBN} Command
30750 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30751 @samp{gdb_find_file}.
30753 @subsubheading Example
30757 @subheading The @code{-symbol-info-function} Command
30758 @findex -symbol-info-function
30760 @subsubheading Synopsis
30763 -symbol-info-function
30766 Show which function the symbol lives in.
30768 @subsubheading @value{GDBN} Command
30770 @samp{gdb_get_function} in @code{gdbtk}.
30772 @subsubheading Example
30776 @subheading The @code{-symbol-info-line} Command
30777 @findex -symbol-info-line
30779 @subsubheading Synopsis
30785 Show the core addresses of the code for a source line.
30787 @subsubheading @value{GDBN} Command
30789 The corresponding @value{GDBN} command is @samp{info line}.
30790 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30792 @subsubheading Example
30796 @subheading The @code{-symbol-info-symbol} Command
30797 @findex -symbol-info-symbol
30799 @subsubheading Synopsis
30802 -symbol-info-symbol @var{addr}
30805 Describe what symbol is at location @var{addr}.
30807 @subsubheading @value{GDBN} Command
30809 The corresponding @value{GDBN} command is @samp{info symbol}.
30811 @subsubheading Example
30815 @subheading The @code{-symbol-list-functions} Command
30816 @findex -symbol-list-functions
30818 @subsubheading Synopsis
30821 -symbol-list-functions
30824 List the functions in the executable.
30826 @subsubheading @value{GDBN} Command
30828 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30829 @samp{gdb_search} in @code{gdbtk}.
30831 @subsubheading Example
30836 @subheading The @code{-symbol-list-lines} Command
30837 @findex -symbol-list-lines
30839 @subsubheading Synopsis
30842 -symbol-list-lines @var{filename}
30845 Print the list of lines that contain code and their associated program
30846 addresses for the given source filename. The entries are sorted in
30847 ascending PC order.
30849 @subsubheading @value{GDBN} Command
30851 There is no corresponding @value{GDBN} command.
30853 @subsubheading Example
30856 -symbol-list-lines basics.c
30857 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30863 @subheading The @code{-symbol-list-types} Command
30864 @findex -symbol-list-types
30866 @subsubheading Synopsis
30872 List all the type names.
30874 @subsubheading @value{GDBN} Command
30876 The corresponding commands are @samp{info types} in @value{GDBN},
30877 @samp{gdb_search} in @code{gdbtk}.
30879 @subsubheading Example
30883 @subheading The @code{-symbol-list-variables} Command
30884 @findex -symbol-list-variables
30886 @subsubheading Synopsis
30889 -symbol-list-variables
30892 List all the global and static variable names.
30894 @subsubheading @value{GDBN} Command
30896 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30898 @subsubheading Example
30902 @subheading The @code{-symbol-locate} Command
30903 @findex -symbol-locate
30905 @subsubheading Synopsis
30911 @subsubheading @value{GDBN} Command
30913 @samp{gdb_loc} in @code{gdbtk}.
30915 @subsubheading Example
30919 @subheading The @code{-symbol-type} Command
30920 @findex -symbol-type
30922 @subsubheading Synopsis
30925 -symbol-type @var{variable}
30928 Show type of @var{variable}.
30930 @subsubheading @value{GDBN} Command
30932 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30933 @samp{gdb_obj_variable}.
30935 @subsubheading Example
30940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30941 @node GDB/MI File Commands
30942 @section @sc{gdb/mi} File Commands
30944 This section describes the GDB/MI commands to specify executable file names
30945 and to read in and obtain symbol table information.
30947 @subheading The @code{-file-exec-and-symbols} Command
30948 @findex -file-exec-and-symbols
30950 @subsubheading Synopsis
30953 -file-exec-and-symbols @var{file}
30956 Specify the executable file to be debugged. This file is the one from
30957 which the symbol table is also read. If no file is specified, the
30958 command clears the executable and symbol information. If breakpoints
30959 are set when using this command with no arguments, @value{GDBN} will produce
30960 error messages. Otherwise, no output is produced, except a completion
30963 @subsubheading @value{GDBN} Command
30965 The corresponding @value{GDBN} command is @samp{file}.
30967 @subsubheading Example
30971 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30977 @subheading The @code{-file-exec-file} Command
30978 @findex -file-exec-file
30980 @subsubheading Synopsis
30983 -file-exec-file @var{file}
30986 Specify the executable file to be debugged. Unlike
30987 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30988 from this file. If used without argument, @value{GDBN} clears the information
30989 about the executable file. No output is produced, except a completion
30992 @subsubheading @value{GDBN} Command
30994 The corresponding @value{GDBN} command is @samp{exec-file}.
30996 @subsubheading Example
31000 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31007 @subheading The @code{-file-list-exec-sections} Command
31008 @findex -file-list-exec-sections
31010 @subsubheading Synopsis
31013 -file-list-exec-sections
31016 List the sections of the current executable file.
31018 @subsubheading @value{GDBN} Command
31020 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31021 information as this command. @code{gdbtk} has a corresponding command
31022 @samp{gdb_load_info}.
31024 @subsubheading Example
31029 @subheading The @code{-file-list-exec-source-file} Command
31030 @findex -file-list-exec-source-file
31032 @subsubheading Synopsis
31035 -file-list-exec-source-file
31038 List the line number, the current source file, and the absolute path
31039 to the current source file for the current executable. The macro
31040 information field has a value of @samp{1} or @samp{0} depending on
31041 whether or not the file includes preprocessor macro information.
31043 @subsubheading @value{GDBN} Command
31045 The @value{GDBN} equivalent is @samp{info source}
31047 @subsubheading Example
31051 123-file-list-exec-source-file
31052 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31057 @subheading The @code{-file-list-exec-source-files} Command
31058 @findex -file-list-exec-source-files
31060 @subsubheading Synopsis
31063 -file-list-exec-source-files
31066 List the source files for the current executable.
31068 It will always output both the filename and fullname (absolute file
31069 name) of a source file.
31071 @subsubheading @value{GDBN} Command
31073 The @value{GDBN} equivalent is @samp{info sources}.
31074 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31076 @subsubheading Example
31079 -file-list-exec-source-files
31081 @{file=foo.c,fullname=/home/foo.c@},
31082 @{file=/home/bar.c,fullname=/home/bar.c@},
31083 @{file=gdb_could_not_find_fullpath.c@}]
31088 @subheading The @code{-file-list-shared-libraries} Command
31089 @findex -file-list-shared-libraries
31091 @subsubheading Synopsis
31094 -file-list-shared-libraries
31097 List the shared libraries in the program.
31099 @subsubheading @value{GDBN} Command
31101 The corresponding @value{GDBN} command is @samp{info shared}.
31103 @subsubheading Example
31107 @subheading The @code{-file-list-symbol-files} Command
31108 @findex -file-list-symbol-files
31110 @subsubheading Synopsis
31113 -file-list-symbol-files
31118 @subsubheading @value{GDBN} Command
31120 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31122 @subsubheading Example
31127 @subheading The @code{-file-symbol-file} Command
31128 @findex -file-symbol-file
31130 @subsubheading Synopsis
31133 -file-symbol-file @var{file}
31136 Read symbol table info from the specified @var{file} argument. When
31137 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31138 produced, except for a completion notification.
31140 @subsubheading @value{GDBN} Command
31142 The corresponding @value{GDBN} command is @samp{symbol-file}.
31144 @subsubheading Example
31148 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31154 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31155 @node GDB/MI Memory Overlay Commands
31156 @section @sc{gdb/mi} Memory Overlay Commands
31158 The memory overlay commands are not implemented.
31160 @c @subheading -overlay-auto
31162 @c @subheading -overlay-list-mapping-state
31164 @c @subheading -overlay-list-overlays
31166 @c @subheading -overlay-map
31168 @c @subheading -overlay-off
31170 @c @subheading -overlay-on
31172 @c @subheading -overlay-unmap
31174 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31175 @node GDB/MI Signal Handling Commands
31176 @section @sc{gdb/mi} Signal Handling Commands
31178 Signal handling commands are not implemented.
31180 @c @subheading -signal-handle
31182 @c @subheading -signal-list-handle-actions
31184 @c @subheading -signal-list-signal-types
31188 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31189 @node GDB/MI Target Manipulation
31190 @section @sc{gdb/mi} Target Manipulation Commands
31193 @subheading The @code{-target-attach} Command
31194 @findex -target-attach
31196 @subsubheading Synopsis
31199 -target-attach @var{pid} | @var{gid} | @var{file}
31202 Attach to a process @var{pid} or a file @var{file} outside of
31203 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31204 group, the id previously returned by
31205 @samp{-list-thread-groups --available} must be used.
31207 @subsubheading @value{GDBN} Command
31209 The corresponding @value{GDBN} command is @samp{attach}.
31211 @subsubheading Example
31215 =thread-created,id="1"
31216 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31222 @subheading The @code{-target-compare-sections} Command
31223 @findex -target-compare-sections
31225 @subsubheading Synopsis
31228 -target-compare-sections [ @var{section} ]
31231 Compare data of section @var{section} on target to the exec file.
31232 Without the argument, all sections are compared.
31234 @subsubheading @value{GDBN} Command
31236 The @value{GDBN} equivalent is @samp{compare-sections}.
31238 @subsubheading Example
31243 @subheading The @code{-target-detach} Command
31244 @findex -target-detach
31246 @subsubheading Synopsis
31249 -target-detach [ @var{pid} | @var{gid} ]
31252 Detach from the remote target which normally resumes its execution.
31253 If either @var{pid} or @var{gid} is specified, detaches from either
31254 the specified process, or specified thread group. There's no output.
31256 @subsubheading @value{GDBN} Command
31258 The corresponding @value{GDBN} command is @samp{detach}.
31260 @subsubheading Example
31270 @subheading The @code{-target-disconnect} Command
31271 @findex -target-disconnect
31273 @subsubheading Synopsis
31279 Disconnect from the remote target. There's no output and the target is
31280 generally not resumed.
31282 @subsubheading @value{GDBN} Command
31284 The corresponding @value{GDBN} command is @samp{disconnect}.
31286 @subsubheading Example
31296 @subheading The @code{-target-download} Command
31297 @findex -target-download
31299 @subsubheading Synopsis
31305 Loads the executable onto the remote target.
31306 It prints out an update message every half second, which includes the fields:
31310 The name of the section.
31312 The size of what has been sent so far for that section.
31314 The size of the section.
31316 The total size of what was sent so far (the current and the previous sections).
31318 The size of the overall executable to download.
31322 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31323 @sc{gdb/mi} Output Syntax}).
31325 In addition, it prints the name and size of the sections, as they are
31326 downloaded. These messages include the following fields:
31330 The name of the section.
31332 The size of the section.
31334 The size of the overall executable to download.
31338 At the end, a summary is printed.
31340 @subsubheading @value{GDBN} Command
31342 The corresponding @value{GDBN} command is @samp{load}.
31344 @subsubheading Example
31346 Note: each status message appears on a single line. Here the messages
31347 have been broken down so that they can fit onto a page.
31352 +download,@{section=".text",section-size="6668",total-size="9880"@}
31353 +download,@{section=".text",section-sent="512",section-size="6668",
31354 total-sent="512",total-size="9880"@}
31355 +download,@{section=".text",section-sent="1024",section-size="6668",
31356 total-sent="1024",total-size="9880"@}
31357 +download,@{section=".text",section-sent="1536",section-size="6668",
31358 total-sent="1536",total-size="9880"@}
31359 +download,@{section=".text",section-sent="2048",section-size="6668",
31360 total-sent="2048",total-size="9880"@}
31361 +download,@{section=".text",section-sent="2560",section-size="6668",
31362 total-sent="2560",total-size="9880"@}
31363 +download,@{section=".text",section-sent="3072",section-size="6668",
31364 total-sent="3072",total-size="9880"@}
31365 +download,@{section=".text",section-sent="3584",section-size="6668",
31366 total-sent="3584",total-size="9880"@}
31367 +download,@{section=".text",section-sent="4096",section-size="6668",
31368 total-sent="4096",total-size="9880"@}
31369 +download,@{section=".text",section-sent="4608",section-size="6668",
31370 total-sent="4608",total-size="9880"@}
31371 +download,@{section=".text",section-sent="5120",section-size="6668",
31372 total-sent="5120",total-size="9880"@}
31373 +download,@{section=".text",section-sent="5632",section-size="6668",
31374 total-sent="5632",total-size="9880"@}
31375 +download,@{section=".text",section-sent="6144",section-size="6668",
31376 total-sent="6144",total-size="9880"@}
31377 +download,@{section=".text",section-sent="6656",section-size="6668",
31378 total-sent="6656",total-size="9880"@}
31379 +download,@{section=".init",section-size="28",total-size="9880"@}
31380 +download,@{section=".fini",section-size="28",total-size="9880"@}
31381 +download,@{section=".data",section-size="3156",total-size="9880"@}
31382 +download,@{section=".data",section-sent="512",section-size="3156",
31383 total-sent="7236",total-size="9880"@}
31384 +download,@{section=".data",section-sent="1024",section-size="3156",
31385 total-sent="7748",total-size="9880"@}
31386 +download,@{section=".data",section-sent="1536",section-size="3156",
31387 total-sent="8260",total-size="9880"@}
31388 +download,@{section=".data",section-sent="2048",section-size="3156",
31389 total-sent="8772",total-size="9880"@}
31390 +download,@{section=".data",section-sent="2560",section-size="3156",
31391 total-sent="9284",total-size="9880"@}
31392 +download,@{section=".data",section-sent="3072",section-size="3156",
31393 total-sent="9796",total-size="9880"@}
31394 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31401 @subheading The @code{-target-exec-status} Command
31402 @findex -target-exec-status
31404 @subsubheading Synopsis
31407 -target-exec-status
31410 Provide information on the state of the target (whether it is running or
31411 not, for instance).
31413 @subsubheading @value{GDBN} Command
31415 There's no equivalent @value{GDBN} command.
31417 @subsubheading Example
31421 @subheading The @code{-target-list-available-targets} Command
31422 @findex -target-list-available-targets
31424 @subsubheading Synopsis
31427 -target-list-available-targets
31430 List the possible targets to connect to.
31432 @subsubheading @value{GDBN} Command
31434 The corresponding @value{GDBN} command is @samp{help target}.
31436 @subsubheading Example
31440 @subheading The @code{-target-list-current-targets} Command
31441 @findex -target-list-current-targets
31443 @subsubheading Synopsis
31446 -target-list-current-targets
31449 Describe the current target.
31451 @subsubheading @value{GDBN} Command
31453 The corresponding information is printed by @samp{info file} (among
31456 @subsubheading Example
31460 @subheading The @code{-target-list-parameters} Command
31461 @findex -target-list-parameters
31463 @subsubheading Synopsis
31466 -target-list-parameters
31472 @subsubheading @value{GDBN} Command
31476 @subsubheading Example
31480 @subheading The @code{-target-select} Command
31481 @findex -target-select
31483 @subsubheading Synopsis
31486 -target-select @var{type} @var{parameters @dots{}}
31489 Connect @value{GDBN} to the remote target. This command takes two args:
31493 The type of target, for instance @samp{remote}, etc.
31494 @item @var{parameters}
31495 Device names, host names and the like. @xref{Target Commands, ,
31496 Commands for Managing Targets}, for more details.
31499 The output is a connection notification, followed by the address at
31500 which the target program is, in the following form:
31503 ^connected,addr="@var{address}",func="@var{function name}",
31504 args=[@var{arg list}]
31507 @subsubheading @value{GDBN} Command
31509 The corresponding @value{GDBN} command is @samp{target}.
31511 @subsubheading Example
31515 -target-select remote /dev/ttya
31516 ^connected,addr="0xfe00a300",func="??",args=[]
31520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31521 @node GDB/MI File Transfer Commands
31522 @section @sc{gdb/mi} File Transfer Commands
31525 @subheading The @code{-target-file-put} Command
31526 @findex -target-file-put
31528 @subsubheading Synopsis
31531 -target-file-put @var{hostfile} @var{targetfile}
31534 Copy file @var{hostfile} from the host system (the machine running
31535 @value{GDBN}) to @var{targetfile} on the target system.
31537 @subsubheading @value{GDBN} Command
31539 The corresponding @value{GDBN} command is @samp{remote put}.
31541 @subsubheading Example
31545 -target-file-put localfile remotefile
31551 @subheading The @code{-target-file-get} Command
31552 @findex -target-file-get
31554 @subsubheading Synopsis
31557 -target-file-get @var{targetfile} @var{hostfile}
31560 Copy file @var{targetfile} from the target system to @var{hostfile}
31561 on the host system.
31563 @subsubheading @value{GDBN} Command
31565 The corresponding @value{GDBN} command is @samp{remote get}.
31567 @subsubheading Example
31571 -target-file-get remotefile localfile
31577 @subheading The @code{-target-file-delete} Command
31578 @findex -target-file-delete
31580 @subsubheading Synopsis
31583 -target-file-delete @var{targetfile}
31586 Delete @var{targetfile} from the target system.
31588 @subsubheading @value{GDBN} Command
31590 The corresponding @value{GDBN} command is @samp{remote delete}.
31592 @subsubheading Example
31596 -target-file-delete remotefile
31602 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31603 @node GDB/MI Ada Exceptions Commands
31604 @section Ada Exceptions @sc{gdb/mi} Commands
31606 @subheading The @code{-info-ada-exceptions} Command
31607 @findex -info-ada-exceptions
31609 @subsubheading Synopsis
31612 -info-ada-exceptions [ @var{regexp}]
31615 List all Ada exceptions defined within the program being debugged.
31616 With a regular expression @var{regexp}, only those exceptions whose
31617 names match @var{regexp} are listed.
31619 @subsubheading @value{GDBN} Command
31621 The corresponding @value{GDBN} command is @samp{info exceptions}.
31623 @subsubheading Result
31625 The result is a table of Ada exceptions. The following columns are
31626 defined for each exception:
31630 The name of the exception.
31633 The address of the exception.
31637 @subsubheading Example
31640 -info-ada-exceptions aint
31641 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31642 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31643 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31644 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31645 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31648 @subheading Catching Ada Exceptions
31650 The commands describing how to ask @value{GDBN} to stop when a program
31651 raises an exception are described at @ref{Ada Exception GDB/MI
31652 Catchpoint Commands}.
31655 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31656 @node GDB/MI Support Commands
31657 @section @sc{gdb/mi} Support Commands
31659 Since new commands and features get regularly added to @sc{gdb/mi},
31660 some commands are available to help front-ends query the debugger
31661 about support for these capabilities. Similarly, it is also possible
31662 to query @value{GDBN} about target support of certain features.
31664 @subheading The @code{-info-gdb-mi-command} Command
31665 @cindex @code{-info-gdb-mi-command}
31666 @findex -info-gdb-mi-command
31668 @subsubheading Synopsis
31671 -info-gdb-mi-command @var{cmd_name}
31674 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31676 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31677 is technically not part of the command name (@pxref{GDB/MI Input
31678 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31679 for ease of use, this command also accepts the form with the leading
31682 @subsubheading @value{GDBN} Command
31684 There is no corresponding @value{GDBN} command.
31686 @subsubheading Result
31688 The result is a tuple. There is currently only one field:
31692 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31693 @code{"false"} otherwise.
31697 @subsubheading Example
31699 Here is an example where the @sc{gdb/mi} command does not exist:
31702 -info-gdb-mi-command unsupported-command
31703 ^done,command=@{exists="false"@}
31707 And here is an example where the @sc{gdb/mi} command is known
31711 -info-gdb-mi-command symbol-list-lines
31712 ^done,command=@{exists="true"@}
31715 @subheading The @code{-list-features} Command
31716 @findex -list-features
31717 @cindex supported @sc{gdb/mi} features, list
31719 Returns a list of particular features of the MI protocol that
31720 this version of gdb implements. A feature can be a command,
31721 or a new field in an output of some command, or even an
31722 important bugfix. While a frontend can sometimes detect presence
31723 of a feature at runtime, it is easier to perform detection at debugger
31726 The command returns a list of strings, with each string naming an
31727 available feature. Each returned string is just a name, it does not
31728 have any internal structure. The list of possible feature names
31734 (gdb) -list-features
31735 ^done,result=["feature1","feature2"]
31738 The current list of features is:
31741 @item frozen-varobjs
31742 Indicates support for the @code{-var-set-frozen} command, as well
31743 as possible presense of the @code{frozen} field in the output
31744 of @code{-varobj-create}.
31745 @item pending-breakpoints
31746 Indicates support for the @option{-f} option to the @code{-break-insert}
31749 Indicates Python scripting support, Python-based
31750 pretty-printing commands, and possible presence of the
31751 @samp{display_hint} field in the output of @code{-var-list-children}
31753 Indicates support for the @code{-thread-info} command.
31754 @item data-read-memory-bytes
31755 Indicates support for the @code{-data-read-memory-bytes} and the
31756 @code{-data-write-memory-bytes} commands.
31757 @item breakpoint-notifications
31758 Indicates that changes to breakpoints and breakpoints created via the
31759 CLI will be announced via async records.
31760 @item ada-task-info
31761 Indicates support for the @code{-ada-task-info} command.
31762 @item language-option
31763 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31764 option (@pxref{Context management}).
31765 @item info-gdb-mi-command
31766 Indicates support for the @code{-info-gdb-mi-command} command.
31767 @item undefined-command-error-code
31768 Indicates support for the "undefined-command" error code in error result
31769 records, produced when trying to execute an undefined @sc{gdb/mi} command
31770 (@pxref{GDB/MI Result Records}).
31771 @item exec-run-start-option
31772 Indicates that the @code{-exec-run} command supports the @option{--start}
31773 option (@pxref{GDB/MI Program Execution}).
31776 @subheading The @code{-list-target-features} Command
31777 @findex -list-target-features
31779 Returns a list of particular features that are supported by the
31780 target. Those features affect the permitted MI commands, but
31781 unlike the features reported by the @code{-list-features} command, the
31782 features depend on which target GDB is using at the moment. Whenever
31783 a target can change, due to commands such as @code{-target-select},
31784 @code{-target-attach} or @code{-exec-run}, the list of target features
31785 may change, and the frontend should obtain it again.
31789 (gdb) -list-target-features
31790 ^done,result=["async"]
31793 The current list of features is:
31797 Indicates that the target is capable of asynchronous command
31798 execution, which means that @value{GDBN} will accept further commands
31799 while the target is running.
31802 Indicates that the target is capable of reverse execution.
31803 @xref{Reverse Execution}, for more information.
31807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31808 @node GDB/MI Miscellaneous Commands
31809 @section Miscellaneous @sc{gdb/mi} Commands
31811 @c @subheading -gdb-complete
31813 @subheading The @code{-gdb-exit} Command
31816 @subsubheading Synopsis
31822 Exit @value{GDBN} immediately.
31824 @subsubheading @value{GDBN} Command
31826 Approximately corresponds to @samp{quit}.
31828 @subsubheading Example
31838 @subheading The @code{-exec-abort} Command
31839 @findex -exec-abort
31841 @subsubheading Synopsis
31847 Kill the inferior running program.
31849 @subsubheading @value{GDBN} Command
31851 The corresponding @value{GDBN} command is @samp{kill}.
31853 @subsubheading Example
31858 @subheading The @code{-gdb-set} Command
31861 @subsubheading Synopsis
31867 Set an internal @value{GDBN} variable.
31868 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31870 @subsubheading @value{GDBN} Command
31872 The corresponding @value{GDBN} command is @samp{set}.
31874 @subsubheading Example
31884 @subheading The @code{-gdb-show} Command
31887 @subsubheading Synopsis
31893 Show the current value of a @value{GDBN} variable.
31895 @subsubheading @value{GDBN} Command
31897 The corresponding @value{GDBN} command is @samp{show}.
31899 @subsubheading Example
31908 @c @subheading -gdb-source
31911 @subheading The @code{-gdb-version} Command
31912 @findex -gdb-version
31914 @subsubheading Synopsis
31920 Show version information for @value{GDBN}. Used mostly in testing.
31922 @subsubheading @value{GDBN} Command
31924 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31925 default shows this information when you start an interactive session.
31927 @subsubheading Example
31929 @c This example modifies the actual output from GDB to avoid overfull
31935 ~Copyright 2000 Free Software Foundation, Inc.
31936 ~GDB is free software, covered by the GNU General Public License, and
31937 ~you are welcome to change it and/or distribute copies of it under
31938 ~ certain conditions.
31939 ~Type "show copying" to see the conditions.
31940 ~There is absolutely no warranty for GDB. Type "show warranty" for
31942 ~This GDB was configured as
31943 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31948 @subheading The @code{-list-thread-groups} Command
31949 @findex -list-thread-groups
31951 @subheading Synopsis
31954 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31957 Lists thread groups (@pxref{Thread groups}). When a single thread
31958 group is passed as the argument, lists the children of that group.
31959 When several thread group are passed, lists information about those
31960 thread groups. Without any parameters, lists information about all
31961 top-level thread groups.
31963 Normally, thread groups that are being debugged are reported.
31964 With the @samp{--available} option, @value{GDBN} reports thread groups
31965 available on the target.
31967 The output of this command may have either a @samp{threads} result or
31968 a @samp{groups} result. The @samp{thread} result has a list of tuples
31969 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31970 Information}). The @samp{groups} result has a list of tuples as value,
31971 each tuple describing a thread group. If top-level groups are
31972 requested (that is, no parameter is passed), or when several groups
31973 are passed, the output always has a @samp{groups} result. The format
31974 of the @samp{group} result is described below.
31976 To reduce the number of roundtrips it's possible to list thread groups
31977 together with their children, by passing the @samp{--recurse} option
31978 and the recursion depth. Presently, only recursion depth of 1 is
31979 permitted. If this option is present, then every reported thread group
31980 will also include its children, either as @samp{group} or
31981 @samp{threads} field.
31983 In general, any combination of option and parameters is permitted, with
31984 the following caveats:
31988 When a single thread group is passed, the output will typically
31989 be the @samp{threads} result. Because threads may not contain
31990 anything, the @samp{recurse} option will be ignored.
31993 When the @samp{--available} option is passed, limited information may
31994 be available. In particular, the list of threads of a process might
31995 be inaccessible. Further, specifying specific thread groups might
31996 not give any performance advantage over listing all thread groups.
31997 The frontend should assume that @samp{-list-thread-groups --available}
31998 is always an expensive operation and cache the results.
32002 The @samp{groups} result is a list of tuples, where each tuple may
32003 have the following fields:
32007 Identifier of the thread group. This field is always present.
32008 The identifier is an opaque string; frontends should not try to
32009 convert it to an integer, even though it might look like one.
32012 The type of the thread group. At present, only @samp{process} is a
32016 The target-specific process identifier. This field is only present
32017 for thread groups of type @samp{process} and only if the process exists.
32020 The exit code of this group's last exited thread, formatted in octal.
32021 This field is only present for thread groups of type @samp{process} and
32022 only if the process is not running.
32025 The number of children this thread group has. This field may be
32026 absent for an available thread group.
32029 This field has a list of tuples as value, each tuple describing a
32030 thread. It may be present if the @samp{--recurse} option is
32031 specified, and it's actually possible to obtain the threads.
32034 This field is a list of integers, each identifying a core that one
32035 thread of the group is running on. This field may be absent if
32036 such information is not available.
32039 The name of the executable file that corresponds to this thread group.
32040 The field is only present for thread groups of type @samp{process},
32041 and only if there is a corresponding executable file.
32045 @subheading Example
32049 -list-thread-groups
32050 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32051 -list-thread-groups 17
32052 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32053 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32054 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32055 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32056 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32057 -list-thread-groups --available
32058 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32059 -list-thread-groups --available --recurse 1
32060 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32061 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32062 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32063 -list-thread-groups --available --recurse 1 17 18
32064 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32065 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32066 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32069 @subheading The @code{-info-os} Command
32072 @subsubheading Synopsis
32075 -info-os [ @var{type} ]
32078 If no argument is supplied, the command returns a table of available
32079 operating-system-specific information types. If one of these types is
32080 supplied as an argument @var{type}, then the command returns a table
32081 of data of that type.
32083 The types of information available depend on the target operating
32086 @subsubheading @value{GDBN} Command
32088 The corresponding @value{GDBN} command is @samp{info os}.
32090 @subsubheading Example
32092 When run on a @sc{gnu}/Linux system, the output will look something
32098 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32099 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32100 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32101 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32102 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32104 item=@{col0="files",col1="Listing of all file descriptors",
32105 col2="File descriptors"@},
32106 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32107 col2="Kernel modules"@},
32108 item=@{col0="msg",col1="Listing of all message queues",
32109 col2="Message queues"@},
32110 item=@{col0="processes",col1="Listing of all processes",
32111 col2="Processes"@},
32112 item=@{col0="procgroups",col1="Listing of all process groups",
32113 col2="Process groups"@},
32114 item=@{col0="semaphores",col1="Listing of all semaphores",
32115 col2="Semaphores"@},
32116 item=@{col0="shm",col1="Listing of all shared-memory regions",
32117 col2="Shared-memory regions"@},
32118 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32120 item=@{col0="threads",col1="Listing of all threads",
32124 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32125 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32126 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32127 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32128 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32129 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32130 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32131 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32133 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32134 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32138 (Note that the MI output here includes a @code{"Title"} column that
32139 does not appear in command-line @code{info os}; this column is useful
32140 for MI clients that want to enumerate the types of data, such as in a
32141 popup menu, but is needless clutter on the command line, and
32142 @code{info os} omits it.)
32144 @subheading The @code{-add-inferior} Command
32145 @findex -add-inferior
32147 @subheading Synopsis
32153 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32154 inferior is not associated with any executable. Such association may
32155 be established with the @samp{-file-exec-and-symbols} command
32156 (@pxref{GDB/MI File Commands}). The command response has a single
32157 field, @samp{inferior}, whose value is the identifier of the
32158 thread group corresponding to the new inferior.
32160 @subheading Example
32165 ^done,inferior="i3"
32168 @subheading The @code{-interpreter-exec} Command
32169 @findex -interpreter-exec
32171 @subheading Synopsis
32174 -interpreter-exec @var{interpreter} @var{command}
32176 @anchor{-interpreter-exec}
32178 Execute the specified @var{command} in the given @var{interpreter}.
32180 @subheading @value{GDBN} Command
32182 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32184 @subheading Example
32188 -interpreter-exec console "break main"
32189 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32190 &"During symbol reading, bad structure-type format.\n"
32191 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32196 @subheading The @code{-inferior-tty-set} Command
32197 @findex -inferior-tty-set
32199 @subheading Synopsis
32202 -inferior-tty-set /dev/pts/1
32205 Set terminal for future runs of the program being debugged.
32207 @subheading @value{GDBN} Command
32209 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32211 @subheading Example
32215 -inferior-tty-set /dev/pts/1
32220 @subheading The @code{-inferior-tty-show} Command
32221 @findex -inferior-tty-show
32223 @subheading Synopsis
32229 Show terminal for future runs of program being debugged.
32231 @subheading @value{GDBN} Command
32233 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32235 @subheading Example
32239 -inferior-tty-set /dev/pts/1
32243 ^done,inferior_tty_terminal="/dev/pts/1"
32247 @subheading The @code{-enable-timings} Command
32248 @findex -enable-timings
32250 @subheading Synopsis
32253 -enable-timings [yes | no]
32256 Toggle the printing of the wallclock, user and system times for an MI
32257 command as a field in its output. This command is to help frontend
32258 developers optimize the performance of their code. No argument is
32259 equivalent to @samp{yes}.
32261 @subheading @value{GDBN} Command
32265 @subheading Example
32273 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32274 addr="0x080484ed",func="main",file="myprog.c",
32275 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32277 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32285 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32286 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32287 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32288 fullname="/home/nickrob/myprog.c",line="73"@}
32293 @chapter @value{GDBN} Annotations
32295 This chapter describes annotations in @value{GDBN}. Annotations were
32296 designed to interface @value{GDBN} to graphical user interfaces or other
32297 similar programs which want to interact with @value{GDBN} at a
32298 relatively high level.
32300 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32304 This is Edition @value{EDITION}, @value{DATE}.
32308 * Annotations Overview:: What annotations are; the general syntax.
32309 * Server Prefix:: Issuing a command without affecting user state.
32310 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32311 * Errors:: Annotations for error messages.
32312 * Invalidation:: Some annotations describe things now invalid.
32313 * Annotations for Running::
32314 Whether the program is running, how it stopped, etc.
32315 * Source Annotations:: Annotations describing source code.
32318 @node Annotations Overview
32319 @section What is an Annotation?
32320 @cindex annotations
32322 Annotations start with a newline character, two @samp{control-z}
32323 characters, and the name of the annotation. If there is no additional
32324 information associated with this annotation, the name of the annotation
32325 is followed immediately by a newline. If there is additional
32326 information, the name of the annotation is followed by a space, the
32327 additional information, and a newline. The additional information
32328 cannot contain newline characters.
32330 Any output not beginning with a newline and two @samp{control-z}
32331 characters denotes literal output from @value{GDBN}. Currently there is
32332 no need for @value{GDBN} to output a newline followed by two
32333 @samp{control-z} characters, but if there was such a need, the
32334 annotations could be extended with an @samp{escape} annotation which
32335 means those three characters as output.
32337 The annotation @var{level}, which is specified using the
32338 @option{--annotate} command line option (@pxref{Mode Options}), controls
32339 how much information @value{GDBN} prints together with its prompt,
32340 values of expressions, source lines, and other types of output. Level 0
32341 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32342 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32343 for programs that control @value{GDBN}, and level 2 annotations have
32344 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32345 Interface, annotate, GDB's Obsolete Annotations}).
32348 @kindex set annotate
32349 @item set annotate @var{level}
32350 The @value{GDBN} command @code{set annotate} sets the level of
32351 annotations to the specified @var{level}.
32353 @item show annotate
32354 @kindex show annotate
32355 Show the current annotation level.
32358 This chapter describes level 3 annotations.
32360 A simple example of starting up @value{GDBN} with annotations is:
32363 $ @kbd{gdb --annotate=3}
32365 Copyright 2003 Free Software Foundation, Inc.
32366 GDB is free software, covered by the GNU General Public License,
32367 and you are welcome to change it and/or distribute copies of it
32368 under certain conditions.
32369 Type "show copying" to see the conditions.
32370 There is absolutely no warranty for GDB. Type "show warranty"
32372 This GDB was configured as "i386-pc-linux-gnu"
32383 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32384 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32385 denotes a @samp{control-z} character) are annotations; the rest is
32386 output from @value{GDBN}.
32388 @node Server Prefix
32389 @section The Server Prefix
32390 @cindex server prefix
32392 If you prefix a command with @samp{server } then it will not affect
32393 the command history, nor will it affect @value{GDBN}'s notion of which
32394 command to repeat if @key{RET} is pressed on a line by itself. This
32395 means that commands can be run behind a user's back by a front-end in
32396 a transparent manner.
32398 The @code{server } prefix does not affect the recording of values into
32399 the value history; to print a value without recording it into the
32400 value history, use the @code{output} command instead of the
32401 @code{print} command.
32403 Using this prefix also disables confirmation requests
32404 (@pxref{confirmation requests}).
32407 @section Annotation for @value{GDBN} Input
32409 @cindex annotations for prompts
32410 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32411 to know when to send output, when the output from a given command is
32414 Different kinds of input each have a different @dfn{input type}. Each
32415 input type has three annotations: a @code{pre-} annotation, which
32416 denotes the beginning of any prompt which is being output, a plain
32417 annotation, which denotes the end of the prompt, and then a @code{post-}
32418 annotation which denotes the end of any echo which may (or may not) be
32419 associated with the input. For example, the @code{prompt} input type
32420 features the following annotations:
32428 The input types are
32431 @findex pre-prompt annotation
32432 @findex prompt annotation
32433 @findex post-prompt annotation
32435 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32437 @findex pre-commands annotation
32438 @findex commands annotation
32439 @findex post-commands annotation
32441 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32442 command. The annotations are repeated for each command which is input.
32444 @findex pre-overload-choice annotation
32445 @findex overload-choice annotation
32446 @findex post-overload-choice annotation
32447 @item overload-choice
32448 When @value{GDBN} wants the user to select between various overloaded functions.
32450 @findex pre-query annotation
32451 @findex query annotation
32452 @findex post-query annotation
32454 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32456 @findex pre-prompt-for-continue annotation
32457 @findex prompt-for-continue annotation
32458 @findex post-prompt-for-continue annotation
32459 @item prompt-for-continue
32460 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32461 expect this to work well; instead use @code{set height 0} to disable
32462 prompting. This is because the counting of lines is buggy in the
32463 presence of annotations.
32468 @cindex annotations for errors, warnings and interrupts
32470 @findex quit annotation
32475 This annotation occurs right before @value{GDBN} responds to an interrupt.
32477 @findex error annotation
32482 This annotation occurs right before @value{GDBN} responds to an error.
32484 Quit and error annotations indicate that any annotations which @value{GDBN} was
32485 in the middle of may end abruptly. For example, if a
32486 @code{value-history-begin} annotation is followed by a @code{error}, one
32487 cannot expect to receive the matching @code{value-history-end}. One
32488 cannot expect not to receive it either, however; an error annotation
32489 does not necessarily mean that @value{GDBN} is immediately returning all the way
32492 @findex error-begin annotation
32493 A quit or error annotation may be preceded by
32499 Any output between that and the quit or error annotation is the error
32502 Warning messages are not yet annotated.
32503 @c If we want to change that, need to fix warning(), type_error(),
32504 @c range_error(), and possibly other places.
32507 @section Invalidation Notices
32509 @cindex annotations for invalidation messages
32510 The following annotations say that certain pieces of state may have
32514 @findex frames-invalid annotation
32515 @item ^Z^Zframes-invalid
32517 The frames (for example, output from the @code{backtrace} command) may
32520 @findex breakpoints-invalid annotation
32521 @item ^Z^Zbreakpoints-invalid
32523 The breakpoints may have changed. For example, the user just added or
32524 deleted a breakpoint.
32527 @node Annotations for Running
32528 @section Running the Program
32529 @cindex annotations for running programs
32531 @findex starting annotation
32532 @findex stopping annotation
32533 When the program starts executing due to a @value{GDBN} command such as
32534 @code{step} or @code{continue},
32540 is output. When the program stops,
32546 is output. Before the @code{stopped} annotation, a variety of
32547 annotations describe how the program stopped.
32550 @findex exited annotation
32551 @item ^Z^Zexited @var{exit-status}
32552 The program exited, and @var{exit-status} is the exit status (zero for
32553 successful exit, otherwise nonzero).
32555 @findex signalled annotation
32556 @findex signal-name annotation
32557 @findex signal-name-end annotation
32558 @findex signal-string annotation
32559 @findex signal-string-end annotation
32560 @item ^Z^Zsignalled
32561 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32562 annotation continues:
32568 ^Z^Zsignal-name-end
32572 ^Z^Zsignal-string-end
32577 where @var{name} is the name of the signal, such as @code{SIGILL} or
32578 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32579 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32580 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32581 user's benefit and have no particular format.
32583 @findex signal annotation
32585 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32586 just saying that the program received the signal, not that it was
32587 terminated with it.
32589 @findex breakpoint annotation
32590 @item ^Z^Zbreakpoint @var{number}
32591 The program hit breakpoint number @var{number}.
32593 @findex watchpoint annotation
32594 @item ^Z^Zwatchpoint @var{number}
32595 The program hit watchpoint number @var{number}.
32598 @node Source Annotations
32599 @section Displaying Source
32600 @cindex annotations for source display
32602 @findex source annotation
32603 The following annotation is used instead of displaying source code:
32606 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32609 where @var{filename} is an absolute file name indicating which source
32610 file, @var{line} is the line number within that file (where 1 is the
32611 first line in the file), @var{character} is the character position
32612 within the file (where 0 is the first character in the file) (for most
32613 debug formats this will necessarily point to the beginning of a line),
32614 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32615 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32616 @var{addr} is the address in the target program associated with the
32617 source which is being displayed. The @var{addr} is in the form @samp{0x}
32618 followed by one or more lowercase hex digits (note that this does not
32619 depend on the language).
32621 @node JIT Interface
32622 @chapter JIT Compilation Interface
32623 @cindex just-in-time compilation
32624 @cindex JIT compilation interface
32626 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32627 interface. A JIT compiler is a program or library that generates native
32628 executable code at runtime and executes it, usually in order to achieve good
32629 performance while maintaining platform independence.
32631 Programs that use JIT compilation are normally difficult to debug because
32632 portions of their code are generated at runtime, instead of being loaded from
32633 object files, which is where @value{GDBN} normally finds the program's symbols
32634 and debug information. In order to debug programs that use JIT compilation,
32635 @value{GDBN} has an interface that allows the program to register in-memory
32636 symbol files with @value{GDBN} at runtime.
32638 If you are using @value{GDBN} to debug a program that uses this interface, then
32639 it should work transparently so long as you have not stripped the binary. If
32640 you are developing a JIT compiler, then the interface is documented in the rest
32641 of this chapter. At this time, the only known client of this interface is the
32644 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32645 JIT compiler communicates with @value{GDBN} by writing data into a global
32646 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32647 attaches, it reads a linked list of symbol files from the global variable to
32648 find existing code, and puts a breakpoint in the function so that it can find
32649 out about additional code.
32652 * Declarations:: Relevant C struct declarations
32653 * Registering Code:: Steps to register code
32654 * Unregistering Code:: Steps to unregister code
32655 * Custom Debug Info:: Emit debug information in a custom format
32659 @section JIT Declarations
32661 These are the relevant struct declarations that a C program should include to
32662 implement the interface:
32672 struct jit_code_entry
32674 struct jit_code_entry *next_entry;
32675 struct jit_code_entry *prev_entry;
32676 const char *symfile_addr;
32677 uint64_t symfile_size;
32680 struct jit_descriptor
32683 /* This type should be jit_actions_t, but we use uint32_t
32684 to be explicit about the bitwidth. */
32685 uint32_t action_flag;
32686 struct jit_code_entry *relevant_entry;
32687 struct jit_code_entry *first_entry;
32690 /* GDB puts a breakpoint in this function. */
32691 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32693 /* Make sure to specify the version statically, because the
32694 debugger may check the version before we can set it. */
32695 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32698 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32699 modifications to this global data properly, which can easily be done by putting
32700 a global mutex around modifications to these structures.
32702 @node Registering Code
32703 @section Registering Code
32705 To register code with @value{GDBN}, the JIT should follow this protocol:
32709 Generate an object file in memory with symbols and other desired debug
32710 information. The file must include the virtual addresses of the sections.
32713 Create a code entry for the file, which gives the start and size of the symbol
32717 Add it to the linked list in the JIT descriptor.
32720 Point the relevant_entry field of the descriptor at the entry.
32723 Set @code{action_flag} to @code{JIT_REGISTER} and call
32724 @code{__jit_debug_register_code}.
32727 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32728 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32729 new code. However, the linked list must still be maintained in order to allow
32730 @value{GDBN} to attach to a running process and still find the symbol files.
32732 @node Unregistering Code
32733 @section Unregistering Code
32735 If code is freed, then the JIT should use the following protocol:
32739 Remove the code entry corresponding to the code from the linked list.
32742 Point the @code{relevant_entry} field of the descriptor at the code entry.
32745 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32746 @code{__jit_debug_register_code}.
32749 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32750 and the JIT will leak the memory used for the associated symbol files.
32752 @node Custom Debug Info
32753 @section Custom Debug Info
32754 @cindex custom JIT debug info
32755 @cindex JIT debug info reader
32757 Generating debug information in platform-native file formats (like ELF
32758 or COFF) may be an overkill for JIT compilers; especially if all the
32759 debug info is used for is displaying a meaningful backtrace. The
32760 issue can be resolved by having the JIT writers decide on a debug info
32761 format and also provide a reader that parses the debug info generated
32762 by the JIT compiler. This section gives a brief overview on writing
32763 such a parser. More specific details can be found in the source file
32764 @file{gdb/jit-reader.in}, which is also installed as a header at
32765 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32767 The reader is implemented as a shared object (so this functionality is
32768 not available on platforms which don't allow loading shared objects at
32769 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32770 @code{jit-reader-unload} are provided, to be used to load and unload
32771 the readers from a preconfigured directory. Once loaded, the shared
32772 object is used the parse the debug information emitted by the JIT
32776 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32777 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32780 @node Using JIT Debug Info Readers
32781 @subsection Using JIT Debug Info Readers
32782 @kindex jit-reader-load
32783 @kindex jit-reader-unload
32785 Readers can be loaded and unloaded using the @code{jit-reader-load}
32786 and @code{jit-reader-unload} commands.
32789 @item jit-reader-load @var{reader}
32790 Load the JIT reader named @var{reader}, which is a shared
32791 object specified as either an absolute or a relative file name. In
32792 the latter case, @value{GDBN} will try to load the reader from a
32793 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32794 system (here @var{libdir} is the system library directory, often
32795 @file{/usr/local/lib}).
32797 Only one reader can be active at a time; trying to load a second
32798 reader when one is already loaded will result in @value{GDBN}
32799 reporting an error. A new JIT reader can be loaded by first unloading
32800 the current one using @code{jit-reader-unload} and then invoking
32801 @code{jit-reader-load}.
32803 @item jit-reader-unload
32804 Unload the currently loaded JIT reader.
32808 @node Writing JIT Debug Info Readers
32809 @subsection Writing JIT Debug Info Readers
32810 @cindex writing JIT debug info readers
32812 As mentioned, a reader is essentially a shared object conforming to a
32813 certain ABI. This ABI is described in @file{jit-reader.h}.
32815 @file{jit-reader.h} defines the structures, macros and functions
32816 required to write a reader. It is installed (along with
32817 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32818 the system include directory.
32820 Readers need to be released under a GPL compatible license. A reader
32821 can be declared as released under such a license by placing the macro
32822 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32824 The entry point for readers is the symbol @code{gdb_init_reader},
32825 which is expected to be a function with the prototype
32827 @findex gdb_init_reader
32829 extern struct gdb_reader_funcs *gdb_init_reader (void);
32832 @cindex @code{struct gdb_reader_funcs}
32834 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32835 functions. These functions are executed to read the debug info
32836 generated by the JIT compiler (@code{read}), to unwind stack frames
32837 (@code{unwind}) and to create canonical frame IDs
32838 (@code{get_Frame_id}). It also has a callback that is called when the
32839 reader is being unloaded (@code{destroy}). The struct looks like this
32842 struct gdb_reader_funcs
32844 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32845 int reader_version;
32847 /* For use by the reader. */
32850 gdb_read_debug_info *read;
32851 gdb_unwind_frame *unwind;
32852 gdb_get_frame_id *get_frame_id;
32853 gdb_destroy_reader *destroy;
32857 @cindex @code{struct gdb_symbol_callbacks}
32858 @cindex @code{struct gdb_unwind_callbacks}
32860 The callbacks are provided with another set of callbacks by
32861 @value{GDBN} to do their job. For @code{read}, these callbacks are
32862 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32863 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32864 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32865 files and new symbol tables inside those object files. @code{struct
32866 gdb_unwind_callbacks} has callbacks to read registers off the current
32867 frame and to write out the values of the registers in the previous
32868 frame. Both have a callback (@code{target_read}) to read bytes off the
32869 target's address space.
32871 @node In-Process Agent
32872 @chapter In-Process Agent
32873 @cindex debugging agent
32874 The traditional debugging model is conceptually low-speed, but works fine,
32875 because most bugs can be reproduced in debugging-mode execution. However,
32876 as multi-core or many-core processors are becoming mainstream, and
32877 multi-threaded programs become more and more popular, there should be more
32878 and more bugs that only manifest themselves at normal-mode execution, for
32879 example, thread races, because debugger's interference with the program's
32880 timing may conceal the bugs. On the other hand, in some applications,
32881 it is not feasible for the debugger to interrupt the program's execution
32882 long enough for the developer to learn anything helpful about its behavior.
32883 If the program's correctness depends on its real-time behavior, delays
32884 introduced by a debugger might cause the program to fail, even when the
32885 code itself is correct. It is useful to be able to observe the program's
32886 behavior without interrupting it.
32888 Therefore, traditional debugging model is too intrusive to reproduce
32889 some bugs. In order to reduce the interference with the program, we can
32890 reduce the number of operations performed by debugger. The
32891 @dfn{In-Process Agent}, a shared library, is running within the same
32892 process with inferior, and is able to perform some debugging operations
32893 itself. As a result, debugger is only involved when necessary, and
32894 performance of debugging can be improved accordingly. Note that
32895 interference with program can be reduced but can't be removed completely,
32896 because the in-process agent will still stop or slow down the program.
32898 The in-process agent can interpret and execute Agent Expressions
32899 (@pxref{Agent Expressions}) during performing debugging operations. The
32900 agent expressions can be used for different purposes, such as collecting
32901 data in tracepoints, and condition evaluation in breakpoints.
32903 @anchor{Control Agent}
32904 You can control whether the in-process agent is used as an aid for
32905 debugging with the following commands:
32908 @kindex set agent on
32910 Causes the in-process agent to perform some operations on behalf of the
32911 debugger. Just which operations requested by the user will be done
32912 by the in-process agent depends on the its capabilities. For example,
32913 if you request to evaluate breakpoint conditions in the in-process agent,
32914 and the in-process agent has such capability as well, then breakpoint
32915 conditions will be evaluated in the in-process agent.
32917 @kindex set agent off
32918 @item set agent off
32919 Disables execution of debugging operations by the in-process agent. All
32920 of the operations will be performed by @value{GDBN}.
32924 Display the current setting of execution of debugging operations by
32925 the in-process agent.
32929 * In-Process Agent Protocol::
32932 @node In-Process Agent Protocol
32933 @section In-Process Agent Protocol
32934 @cindex in-process agent protocol
32936 The in-process agent is able to communicate with both @value{GDBN} and
32937 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32938 used for communications between @value{GDBN} or GDBserver and the IPA.
32939 In general, @value{GDBN} or GDBserver sends commands
32940 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32941 in-process agent replies back with the return result of the command, or
32942 some other information. The data sent to in-process agent is composed
32943 of primitive data types, such as 4-byte or 8-byte type, and composite
32944 types, which are called objects (@pxref{IPA Protocol Objects}).
32947 * IPA Protocol Objects::
32948 * IPA Protocol Commands::
32951 @node IPA Protocol Objects
32952 @subsection IPA Protocol Objects
32953 @cindex ipa protocol objects
32955 The commands sent to and results received from agent may contain some
32956 complex data types called @dfn{objects}.
32958 The in-process agent is running on the same machine with @value{GDBN}
32959 or GDBserver, so it doesn't have to handle as much differences between
32960 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32961 However, there are still some differences of two ends in two processes:
32965 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32966 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32968 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32969 GDBserver is compiled with one, and in-process agent is compiled with
32973 Here are the IPA Protocol Objects:
32977 agent expression object. It represents an agent expression
32978 (@pxref{Agent Expressions}).
32979 @anchor{agent expression object}
32981 tracepoint action object. It represents a tracepoint action
32982 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32983 memory, static trace data and to evaluate expression.
32984 @anchor{tracepoint action object}
32986 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32987 @anchor{tracepoint object}
32991 The following table describes important attributes of each IPA protocol
32994 @multitable @columnfractions .30 .20 .50
32995 @headitem Name @tab Size @tab Description
32996 @item @emph{agent expression object} @tab @tab
32997 @item length @tab 4 @tab length of bytes code
32998 @item byte code @tab @var{length} @tab contents of byte code
32999 @item @emph{tracepoint action for collecting memory} @tab @tab
33000 @item 'M' @tab 1 @tab type of tracepoint action
33001 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33002 address of the lowest byte to collect, otherwise @var{addr} is the offset
33003 of @var{basereg} for memory collecting.
33004 @item len @tab 8 @tab length of memory for collecting
33005 @item basereg @tab 4 @tab the register number containing the starting
33006 memory address for collecting.
33007 @item @emph{tracepoint action for collecting registers} @tab @tab
33008 @item 'R' @tab 1 @tab type of tracepoint action
33009 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33010 @item 'L' @tab 1 @tab type of tracepoint action
33011 @item @emph{tracepoint action for expression evaluation} @tab @tab
33012 @item 'X' @tab 1 @tab type of tracepoint action
33013 @item agent expression @tab length of @tab @ref{agent expression object}
33014 @item @emph{tracepoint object} @tab @tab
33015 @item number @tab 4 @tab number of tracepoint
33016 @item address @tab 8 @tab address of tracepoint inserted on
33017 @item type @tab 4 @tab type of tracepoint
33018 @item enabled @tab 1 @tab enable or disable of tracepoint
33019 @item step_count @tab 8 @tab step
33020 @item pass_count @tab 8 @tab pass
33021 @item numactions @tab 4 @tab number of tracepoint actions
33022 @item hit count @tab 8 @tab hit count
33023 @item trace frame usage @tab 8 @tab trace frame usage
33024 @item compiled_cond @tab 8 @tab compiled condition
33025 @item orig_size @tab 8 @tab orig size
33026 @item condition @tab 4 if condition is NULL otherwise length of
33027 @ref{agent expression object}
33028 @tab zero if condition is NULL, otherwise is
33029 @ref{agent expression object}
33030 @item actions @tab variable
33031 @tab numactions number of @ref{tracepoint action object}
33034 @node IPA Protocol Commands
33035 @subsection IPA Protocol Commands
33036 @cindex ipa protocol commands
33038 The spaces in each command are delimiters to ease reading this commands
33039 specification. They don't exist in real commands.
33043 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33044 Installs a new fast tracepoint described by @var{tracepoint_object}
33045 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33046 head of @dfn{jumppad}, which is used to jump to data collection routine
33051 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33052 @var{target_address} is address of tracepoint in the inferior.
33053 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33054 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33055 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33056 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33063 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33064 is about to kill inferiors.
33072 @item probe_marker_at:@var{address}
33073 Asks in-process agent to probe the marker at @var{address}.
33080 @item unprobe_marker_at:@var{address}
33081 Asks in-process agent to unprobe the marker at @var{address}.
33085 @chapter Reporting Bugs in @value{GDBN}
33086 @cindex bugs in @value{GDBN}
33087 @cindex reporting bugs in @value{GDBN}
33089 Your bug reports play an essential role in making @value{GDBN} reliable.
33091 Reporting a bug may help you by bringing a solution to your problem, or it
33092 may not. But in any case the principal function of a bug report is to help
33093 the entire community by making the next version of @value{GDBN} work better. Bug
33094 reports are your contribution to the maintenance of @value{GDBN}.
33096 In order for a bug report to serve its purpose, you must include the
33097 information that enables us to fix the bug.
33100 * Bug Criteria:: Have you found a bug?
33101 * Bug Reporting:: How to report bugs
33105 @section Have You Found a Bug?
33106 @cindex bug criteria
33108 If you are not sure whether you have found a bug, here are some guidelines:
33111 @cindex fatal signal
33112 @cindex debugger crash
33113 @cindex crash of debugger
33115 If the debugger gets a fatal signal, for any input whatever, that is a
33116 @value{GDBN} bug. Reliable debuggers never crash.
33118 @cindex error on valid input
33120 If @value{GDBN} produces an error message for valid input, that is a
33121 bug. (Note that if you're cross debugging, the problem may also be
33122 somewhere in the connection to the target.)
33124 @cindex invalid input
33126 If @value{GDBN} does not produce an error message for invalid input,
33127 that is a bug. However, you should note that your idea of
33128 ``invalid input'' might be our idea of ``an extension'' or ``support
33129 for traditional practice''.
33132 If you are an experienced user of debugging tools, your suggestions
33133 for improvement of @value{GDBN} are welcome in any case.
33136 @node Bug Reporting
33137 @section How to Report Bugs
33138 @cindex bug reports
33139 @cindex @value{GDBN} bugs, reporting
33141 A number of companies and individuals offer support for @sc{gnu} products.
33142 If you obtained @value{GDBN} from a support organization, we recommend you
33143 contact that organization first.
33145 You can find contact information for many support companies and
33146 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33148 @c should add a web page ref...
33151 @ifset BUGURL_DEFAULT
33152 In any event, we also recommend that you submit bug reports for
33153 @value{GDBN}. The preferred method is to submit them directly using
33154 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33155 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33158 @strong{Do not send bug reports to @samp{info-gdb}, or to
33159 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33160 not want to receive bug reports. Those that do have arranged to receive
33163 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33164 serves as a repeater. The mailing list and the newsgroup carry exactly
33165 the same messages. Often people think of posting bug reports to the
33166 newsgroup instead of mailing them. This appears to work, but it has one
33167 problem which can be crucial: a newsgroup posting often lacks a mail
33168 path back to the sender. Thus, if we need to ask for more information,
33169 we may be unable to reach you. For this reason, it is better to send
33170 bug reports to the mailing list.
33172 @ifclear BUGURL_DEFAULT
33173 In any event, we also recommend that you submit bug reports for
33174 @value{GDBN} to @value{BUGURL}.
33178 The fundamental principle of reporting bugs usefully is this:
33179 @strong{report all the facts}. If you are not sure whether to state a
33180 fact or leave it out, state it!
33182 Often people omit facts because they think they know what causes the
33183 problem and assume that some details do not matter. Thus, you might
33184 assume that the name of the variable you use in an example does not matter.
33185 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33186 stray memory reference which happens to fetch from the location where that
33187 name is stored in memory; perhaps, if the name were different, the contents
33188 of that location would fool the debugger into doing the right thing despite
33189 the bug. Play it safe and give a specific, complete example. That is the
33190 easiest thing for you to do, and the most helpful.
33192 Keep in mind that the purpose of a bug report is to enable us to fix the
33193 bug. It may be that the bug has been reported previously, but neither
33194 you nor we can know that unless your bug report is complete and
33197 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33198 bell?'' Those bug reports are useless, and we urge everyone to
33199 @emph{refuse to respond to them} except to chide the sender to report
33202 To enable us to fix the bug, you should include all these things:
33206 The version of @value{GDBN}. @value{GDBN} announces it if you start
33207 with no arguments; you can also print it at any time using @code{show
33210 Without this, we will not know whether there is any point in looking for
33211 the bug in the current version of @value{GDBN}.
33214 The type of machine you are using, and the operating system name and
33218 The details of the @value{GDBN} build-time configuration.
33219 @value{GDBN} shows these details if you invoke it with the
33220 @option{--configuration} command-line option, or if you type
33221 @code{show configuration} at @value{GDBN}'s prompt.
33224 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33225 ``@value{GCC}--2.8.1''.
33228 What compiler (and its version) was used to compile the program you are
33229 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33230 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33231 to get this information; for other compilers, see the documentation for
33235 The command arguments you gave the compiler to compile your example and
33236 observe the bug. For example, did you use @samp{-O}? To guarantee
33237 you will not omit something important, list them all. A copy of the
33238 Makefile (or the output from make) is sufficient.
33240 If we were to try to guess the arguments, we would probably guess wrong
33241 and then we might not encounter the bug.
33244 A complete input script, and all necessary source files, that will
33248 A description of what behavior you observe that you believe is
33249 incorrect. For example, ``It gets a fatal signal.''
33251 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33252 will certainly notice it. But if the bug is incorrect output, we might
33253 not notice unless it is glaringly wrong. You might as well not give us
33254 a chance to make a mistake.
33256 Even if the problem you experience is a fatal signal, you should still
33257 say so explicitly. Suppose something strange is going on, such as, your
33258 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33259 the C library on your system. (This has happened!) Your copy might
33260 crash and ours would not. If you told us to expect a crash, then when
33261 ours fails to crash, we would know that the bug was not happening for
33262 us. If you had not told us to expect a crash, then we would not be able
33263 to draw any conclusion from our observations.
33266 @cindex recording a session script
33267 To collect all this information, you can use a session recording program
33268 such as @command{script}, which is available on many Unix systems.
33269 Just run your @value{GDBN} session inside @command{script} and then
33270 include the @file{typescript} file with your bug report.
33272 Another way to record a @value{GDBN} session is to run @value{GDBN}
33273 inside Emacs and then save the entire buffer to a file.
33276 If you wish to suggest changes to the @value{GDBN} source, send us context
33277 diffs. If you even discuss something in the @value{GDBN} source, refer to
33278 it by context, not by line number.
33280 The line numbers in our development sources will not match those in your
33281 sources. Your line numbers would convey no useful information to us.
33285 Here are some things that are not necessary:
33289 A description of the envelope of the bug.
33291 Often people who encounter a bug spend a lot of time investigating
33292 which changes to the input file will make the bug go away and which
33293 changes will not affect it.
33295 This is often time consuming and not very useful, because the way we
33296 will find the bug is by running a single example under the debugger
33297 with breakpoints, not by pure deduction from a series of examples.
33298 We recommend that you save your time for something else.
33300 Of course, if you can find a simpler example to report @emph{instead}
33301 of the original one, that is a convenience for us. Errors in the
33302 output will be easier to spot, running under the debugger will take
33303 less time, and so on.
33305 However, simplification is not vital; if you do not want to do this,
33306 report the bug anyway and send us the entire test case you used.
33309 A patch for the bug.
33311 A patch for the bug does help us if it is a good one. But do not omit
33312 the necessary information, such as the test case, on the assumption that
33313 a patch is all we need. We might see problems with your patch and decide
33314 to fix the problem another way, or we might not understand it at all.
33316 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33317 construct an example that will make the program follow a certain path
33318 through the code. If you do not send us the example, we will not be able
33319 to construct one, so we will not be able to verify that the bug is fixed.
33321 And if we cannot understand what bug you are trying to fix, or why your
33322 patch should be an improvement, we will not install it. A test case will
33323 help us to understand.
33326 A guess about what the bug is or what it depends on.
33328 Such guesses are usually wrong. Even we cannot guess right about such
33329 things without first using the debugger to find the facts.
33332 @c The readline documentation is distributed with the readline code
33333 @c and consists of the two following files:
33336 @c Use -I with makeinfo to point to the appropriate directory,
33337 @c environment var TEXINPUTS with TeX.
33338 @ifclear SYSTEM_READLINE
33339 @include rluser.texi
33340 @include hsuser.texi
33344 @appendix In Memoriam
33346 The @value{GDBN} project mourns the loss of the following long-time
33351 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33352 to Free Software in general. Outside of @value{GDBN}, he was known in
33353 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33355 @item Michael Snyder
33356 Michael was one of the Global Maintainers of the @value{GDBN} project,
33357 with contributions recorded as early as 1996, until 2011. In addition
33358 to his day to day participation, he was a large driving force behind
33359 adding Reverse Debugging to @value{GDBN}.
33362 Beyond their technical contributions to the project, they were also
33363 enjoyable members of the Free Software Community. We will miss them.
33365 @node Formatting Documentation
33366 @appendix Formatting Documentation
33368 @cindex @value{GDBN} reference card
33369 @cindex reference card
33370 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33371 for printing with PostScript or Ghostscript, in the @file{gdb}
33372 subdirectory of the main source directory@footnote{In
33373 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33374 release.}. If you can use PostScript or Ghostscript with your printer,
33375 you can print the reference card immediately with @file{refcard.ps}.
33377 The release also includes the source for the reference card. You
33378 can format it, using @TeX{}, by typing:
33384 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33385 mode on US ``letter'' size paper;
33386 that is, on a sheet 11 inches wide by 8.5 inches
33387 high. You will need to specify this form of printing as an option to
33388 your @sc{dvi} output program.
33390 @cindex documentation
33392 All the documentation for @value{GDBN} comes as part of the machine-readable
33393 distribution. The documentation is written in Texinfo format, which is
33394 a documentation system that uses a single source file to produce both
33395 on-line information and a printed manual. You can use one of the Info
33396 formatting commands to create the on-line version of the documentation
33397 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33399 @value{GDBN} includes an already formatted copy of the on-line Info
33400 version of this manual in the @file{gdb} subdirectory. The main Info
33401 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33402 subordinate files matching @samp{gdb.info*} in the same directory. If
33403 necessary, you can print out these files, or read them with any editor;
33404 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33405 Emacs or the standalone @code{info} program, available as part of the
33406 @sc{gnu} Texinfo distribution.
33408 If you want to format these Info files yourself, you need one of the
33409 Info formatting programs, such as @code{texinfo-format-buffer} or
33412 If you have @code{makeinfo} installed, and are in the top level
33413 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33414 version @value{GDBVN}), you can make the Info file by typing:
33421 If you want to typeset and print copies of this manual, you need @TeX{},
33422 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33423 Texinfo definitions file.
33425 @TeX{} is a typesetting program; it does not print files directly, but
33426 produces output files called @sc{dvi} files. To print a typeset
33427 document, you need a program to print @sc{dvi} files. If your system
33428 has @TeX{} installed, chances are it has such a program. The precise
33429 command to use depends on your system; @kbd{lpr -d} is common; another
33430 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33431 require a file name without any extension or a @samp{.dvi} extension.
33433 @TeX{} also requires a macro definitions file called
33434 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33435 written in Texinfo format. On its own, @TeX{} cannot either read or
33436 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33437 and is located in the @file{gdb-@var{version-number}/texinfo}
33440 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33441 typeset and print this manual. First switch to the @file{gdb}
33442 subdirectory of the main source directory (for example, to
33443 @file{gdb-@value{GDBVN}/gdb}) and type:
33449 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33451 @node Installing GDB
33452 @appendix Installing @value{GDBN}
33453 @cindex installation
33456 * Requirements:: Requirements for building @value{GDBN}
33457 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33458 * Separate Objdir:: Compiling @value{GDBN} in another directory
33459 * Config Names:: Specifying names for hosts and targets
33460 * Configure Options:: Summary of options for configure
33461 * System-wide configuration:: Having a system-wide init file
33465 @section Requirements for Building @value{GDBN}
33466 @cindex building @value{GDBN}, requirements for
33468 Building @value{GDBN} requires various tools and packages to be available.
33469 Other packages will be used only if they are found.
33471 @heading Tools/Packages Necessary for Building @value{GDBN}
33473 @item ISO C90 compiler
33474 @value{GDBN} is written in ISO C90. It should be buildable with any
33475 working C90 compiler, e.g.@: GCC.
33479 @heading Tools/Packages Optional for Building @value{GDBN}
33483 @value{GDBN} can use the Expat XML parsing library. This library may be
33484 included with your operating system distribution; if it is not, you
33485 can get the latest version from @url{http://expat.sourceforge.net}.
33486 The @file{configure} script will search for this library in several
33487 standard locations; if it is installed in an unusual path, you can
33488 use the @option{--with-libexpat-prefix} option to specify its location.
33494 Remote protocol memory maps (@pxref{Memory Map Format})
33496 Target descriptions (@pxref{Target Descriptions})
33498 Remote shared library lists (@xref{Library List Format},
33499 or alternatively @pxref{Library List Format for SVR4 Targets})
33501 MS-Windows shared libraries (@pxref{Shared Libraries})
33503 Traceframe info (@pxref{Traceframe Info Format})
33505 Branch trace (@pxref{Branch Trace Format},
33506 @pxref{Branch Trace Configuration Format})
33510 @cindex compressed debug sections
33511 @value{GDBN} will use the @samp{zlib} library, if available, to read
33512 compressed debug sections. Some linkers, such as GNU gold, are capable
33513 of producing binaries with compressed debug sections. If @value{GDBN}
33514 is compiled with @samp{zlib}, it will be able to read the debug
33515 information in such binaries.
33517 The @samp{zlib} library is likely included with your operating system
33518 distribution; if it is not, you can get the latest version from
33519 @url{http://zlib.net}.
33522 @value{GDBN}'s features related to character sets (@pxref{Character
33523 Sets}) require a functioning @code{iconv} implementation. If you are
33524 on a GNU system, then this is provided by the GNU C Library. Some
33525 other systems also provide a working @code{iconv}.
33527 If @value{GDBN} is using the @code{iconv} program which is installed
33528 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33529 This is done with @option{--with-iconv-bin} which specifies the
33530 directory that contains the @code{iconv} program.
33532 On systems without @code{iconv}, you can install GNU Libiconv. If you
33533 have previously installed Libiconv, you can use the
33534 @option{--with-libiconv-prefix} option to configure.
33536 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33537 arrange to build Libiconv if a directory named @file{libiconv} appears
33538 in the top-most source directory. If Libiconv is built this way, and
33539 if the operating system does not provide a suitable @code{iconv}
33540 implementation, then the just-built library will automatically be used
33541 by @value{GDBN}. One easy way to set this up is to download GNU
33542 Libiconv, unpack it, and then rename the directory holding the
33543 Libiconv source code to @samp{libiconv}.
33546 @node Running Configure
33547 @section Invoking the @value{GDBN} @file{configure} Script
33548 @cindex configuring @value{GDBN}
33549 @value{GDBN} comes with a @file{configure} script that automates the process
33550 of preparing @value{GDBN} for installation; you can then use @code{make} to
33551 build the @code{gdb} program.
33553 @c irrelevant in info file; it's as current as the code it lives with.
33554 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33555 look at the @file{README} file in the sources; we may have improved the
33556 installation procedures since publishing this manual.}
33559 The @value{GDBN} distribution includes all the source code you need for
33560 @value{GDBN} in a single directory, whose name is usually composed by
33561 appending the version number to @samp{gdb}.
33563 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33564 @file{gdb-@value{GDBVN}} directory. That directory contains:
33567 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33568 script for configuring @value{GDBN} and all its supporting libraries
33570 @item gdb-@value{GDBVN}/gdb
33571 the source specific to @value{GDBN} itself
33573 @item gdb-@value{GDBVN}/bfd
33574 source for the Binary File Descriptor library
33576 @item gdb-@value{GDBVN}/include
33577 @sc{gnu} include files
33579 @item gdb-@value{GDBVN}/libiberty
33580 source for the @samp{-liberty} free software library
33582 @item gdb-@value{GDBVN}/opcodes
33583 source for the library of opcode tables and disassemblers
33585 @item gdb-@value{GDBVN}/readline
33586 source for the @sc{gnu} command-line interface
33588 @item gdb-@value{GDBVN}/glob
33589 source for the @sc{gnu} filename pattern-matching subroutine
33591 @item gdb-@value{GDBVN}/mmalloc
33592 source for the @sc{gnu} memory-mapped malloc package
33595 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33596 from the @file{gdb-@var{version-number}} source directory, which in
33597 this example is the @file{gdb-@value{GDBVN}} directory.
33599 First switch to the @file{gdb-@var{version-number}} source directory
33600 if you are not already in it; then run @file{configure}. Pass the
33601 identifier for the platform on which @value{GDBN} will run as an
33607 cd gdb-@value{GDBVN}
33608 ./configure @var{host}
33613 where @var{host} is an identifier such as @samp{sun4} or
33614 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33615 (You can often leave off @var{host}; @file{configure} tries to guess the
33616 correct value by examining your system.)
33618 Running @samp{configure @var{host}} and then running @code{make} builds the
33619 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33620 libraries, then @code{gdb} itself. The configured source files, and the
33621 binaries, are left in the corresponding source directories.
33624 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33625 system does not recognize this automatically when you run a different
33626 shell, you may need to run @code{sh} on it explicitly:
33629 sh configure @var{host}
33632 If you run @file{configure} from a directory that contains source
33633 directories for multiple libraries or programs, such as the
33634 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33636 creates configuration files for every directory level underneath (unless
33637 you tell it not to, with the @samp{--norecursion} option).
33639 You should run the @file{configure} script from the top directory in the
33640 source tree, the @file{gdb-@var{version-number}} directory. If you run
33641 @file{configure} from one of the subdirectories, you will configure only
33642 that subdirectory. That is usually not what you want. In particular,
33643 if you run the first @file{configure} from the @file{gdb} subdirectory
33644 of the @file{gdb-@var{version-number}} directory, you will omit the
33645 configuration of @file{bfd}, @file{readline}, and other sibling
33646 directories of the @file{gdb} subdirectory. This leads to build errors
33647 about missing include files such as @file{bfd/bfd.h}.
33649 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33650 However, you should make sure that the shell on your path (named by
33651 the @samp{SHELL} environment variable) is publicly readable. Remember
33652 that @value{GDBN} uses the shell to start your program---some systems refuse to
33653 let @value{GDBN} debug child processes whose programs are not readable.
33655 @node Separate Objdir
33656 @section Compiling @value{GDBN} in Another Directory
33658 If you want to run @value{GDBN} versions for several host or target machines,
33659 you need a different @code{gdb} compiled for each combination of
33660 host and target. @file{configure} is designed to make this easy by
33661 allowing you to generate each configuration in a separate subdirectory,
33662 rather than in the source directory. If your @code{make} program
33663 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33664 @code{make} in each of these directories builds the @code{gdb}
33665 program specified there.
33667 To build @code{gdb} in a separate directory, run @file{configure}
33668 with the @samp{--srcdir} option to specify where to find the source.
33669 (You also need to specify a path to find @file{configure}
33670 itself from your working directory. If the path to @file{configure}
33671 would be the same as the argument to @samp{--srcdir}, you can leave out
33672 the @samp{--srcdir} option; it is assumed.)
33674 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33675 separate directory for a Sun 4 like this:
33679 cd gdb-@value{GDBVN}
33682 ../gdb-@value{GDBVN}/configure sun4
33687 When @file{configure} builds a configuration using a remote source
33688 directory, it creates a tree for the binaries with the same structure
33689 (and using the same names) as the tree under the source directory. In
33690 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33691 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33692 @file{gdb-sun4/gdb}.
33694 Make sure that your path to the @file{configure} script has just one
33695 instance of @file{gdb} in it. If your path to @file{configure} looks
33696 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33697 one subdirectory of @value{GDBN}, not the whole package. This leads to
33698 build errors about missing include files such as @file{bfd/bfd.h}.
33700 One popular reason to build several @value{GDBN} configurations in separate
33701 directories is to configure @value{GDBN} for cross-compiling (where
33702 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33703 programs that run on another machine---the @dfn{target}).
33704 You specify a cross-debugging target by
33705 giving the @samp{--target=@var{target}} option to @file{configure}.
33707 When you run @code{make} to build a program or library, you must run
33708 it in a configured directory---whatever directory you were in when you
33709 called @file{configure} (or one of its subdirectories).
33711 The @code{Makefile} that @file{configure} generates in each source
33712 directory also runs recursively. If you type @code{make} in a source
33713 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33714 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33715 will build all the required libraries, and then build GDB.
33717 When you have multiple hosts or targets configured in separate
33718 directories, you can run @code{make} on them in parallel (for example,
33719 if they are NFS-mounted on each of the hosts); they will not interfere
33723 @section Specifying Names for Hosts and Targets
33725 The specifications used for hosts and targets in the @file{configure}
33726 script are based on a three-part naming scheme, but some short predefined
33727 aliases are also supported. The full naming scheme encodes three pieces
33728 of information in the following pattern:
33731 @var{architecture}-@var{vendor}-@var{os}
33734 For example, you can use the alias @code{sun4} as a @var{host} argument,
33735 or as the value for @var{target} in a @code{--target=@var{target}}
33736 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33738 The @file{configure} script accompanying @value{GDBN} does not provide
33739 any query facility to list all supported host and target names or
33740 aliases. @file{configure} calls the Bourne shell script
33741 @code{config.sub} to map abbreviations to full names; you can read the
33742 script, if you wish, or you can use it to test your guesses on
33743 abbreviations---for example:
33746 % sh config.sub i386-linux
33748 % sh config.sub alpha-linux
33749 alpha-unknown-linux-gnu
33750 % sh config.sub hp9k700
33752 % sh config.sub sun4
33753 sparc-sun-sunos4.1.1
33754 % sh config.sub sun3
33755 m68k-sun-sunos4.1.1
33756 % sh config.sub i986v
33757 Invalid configuration `i986v': machine `i986v' not recognized
33761 @code{config.sub} is also distributed in the @value{GDBN} source
33762 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33764 @node Configure Options
33765 @section @file{configure} Options
33767 Here is a summary of the @file{configure} options and arguments that
33768 are most often useful for building @value{GDBN}. @file{configure} also has
33769 several other options not listed here. @inforef{What Configure
33770 Does,,configure.info}, for a full explanation of @file{configure}.
33773 configure @r{[}--help@r{]}
33774 @r{[}--prefix=@var{dir}@r{]}
33775 @r{[}--exec-prefix=@var{dir}@r{]}
33776 @r{[}--srcdir=@var{dirname}@r{]}
33777 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33778 @r{[}--target=@var{target}@r{]}
33783 You may introduce options with a single @samp{-} rather than
33784 @samp{--} if you prefer; but you may abbreviate option names if you use
33789 Display a quick summary of how to invoke @file{configure}.
33791 @item --prefix=@var{dir}
33792 Configure the source to install programs and files under directory
33795 @item --exec-prefix=@var{dir}
33796 Configure the source to install programs under directory
33799 @c avoid splitting the warning from the explanation:
33801 @item --srcdir=@var{dirname}
33802 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33803 @code{make} that implements the @code{VPATH} feature.}@*
33804 Use this option to make configurations in directories separate from the
33805 @value{GDBN} source directories. Among other things, you can use this to
33806 build (or maintain) several configurations simultaneously, in separate
33807 directories. @file{configure} writes configuration-specific files in
33808 the current directory, but arranges for them to use the source in the
33809 directory @var{dirname}. @file{configure} creates directories under
33810 the working directory in parallel to the source directories below
33813 @item --norecursion
33814 Configure only the directory level where @file{configure} is executed; do not
33815 propagate configuration to subdirectories.
33817 @item --target=@var{target}
33818 Configure @value{GDBN} for cross-debugging programs running on the specified
33819 @var{target}. Without this option, @value{GDBN} is configured to debug
33820 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33822 There is no convenient way to generate a list of all available targets.
33824 @item @var{host} @dots{}
33825 Configure @value{GDBN} to run on the specified @var{host}.
33827 There is no convenient way to generate a list of all available hosts.
33830 There are many other options available as well, but they are generally
33831 needed for special purposes only.
33833 @node System-wide configuration
33834 @section System-wide configuration and settings
33835 @cindex system-wide init file
33837 @value{GDBN} can be configured to have a system-wide init file;
33838 this file will be read and executed at startup (@pxref{Startup, , What
33839 @value{GDBN} does during startup}).
33841 Here is the corresponding configure option:
33844 @item --with-system-gdbinit=@var{file}
33845 Specify that the default location of the system-wide init file is
33849 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33850 it may be subject to relocation. Two possible cases:
33854 If the default location of this init file contains @file{$prefix},
33855 it will be subject to relocation. Suppose that the configure options
33856 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33857 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33858 init file is looked for as @file{$install/etc/gdbinit} instead of
33859 @file{$prefix/etc/gdbinit}.
33862 By contrast, if the default location does not contain the prefix,
33863 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33864 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33865 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33866 wherever @value{GDBN} is installed.
33869 If the configured location of the system-wide init file (as given by the
33870 @option{--with-system-gdbinit} option at configure time) is in the
33871 data-directory (as specified by @option{--with-gdb-datadir} at configure
33872 time) or in one of its subdirectories, then @value{GDBN} will look for the
33873 system-wide init file in the directory specified by the
33874 @option{--data-directory} command-line option.
33875 Note that the system-wide init file is only read once, during @value{GDBN}
33876 initialization. If the data-directory is changed after @value{GDBN} has
33877 started with the @code{set data-directory} command, the file will not be
33881 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33884 @node System-wide Configuration Scripts
33885 @subsection Installed System-wide Configuration Scripts
33886 @cindex system-wide configuration scripts
33888 The @file{system-gdbinit} directory, located inside the data-directory
33889 (as specified by @option{--with-gdb-datadir} at configure time) contains
33890 a number of scripts which can be used as system-wide init files. To
33891 automatically source those scripts at startup, @value{GDBN} should be
33892 configured with @option{--with-system-gdbinit}. Otherwise, any user
33893 should be able to source them by hand as needed.
33895 The following scripts are currently available:
33898 @item @file{elinos.py}
33900 @cindex ELinOS system-wide configuration script
33901 This script is useful when debugging a program on an ELinOS target.
33902 It takes advantage of the environment variables defined in a standard
33903 ELinOS environment in order to determine the location of the system
33904 shared libraries, and then sets the @samp{solib-absolute-prefix}
33905 and @samp{solib-search-path} variables appropriately.
33907 @item @file{wrs-linux.py}
33908 @pindex wrs-linux.py
33909 @cindex Wind River Linux system-wide configuration script
33910 This script is useful when debugging a program on a target running
33911 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33912 the host-side sysroot used by the target system.
33916 @node Maintenance Commands
33917 @appendix Maintenance Commands
33918 @cindex maintenance commands
33919 @cindex internal commands
33921 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33922 includes a number of commands intended for @value{GDBN} developers,
33923 that are not documented elsewhere in this manual. These commands are
33924 provided here for reference. (For commands that turn on debugging
33925 messages, see @ref{Debugging Output}.)
33928 @kindex maint agent
33929 @kindex maint agent-eval
33930 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33931 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33932 Translate the given @var{expression} into remote agent bytecodes.
33933 This command is useful for debugging the Agent Expression mechanism
33934 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33935 expression useful for data collection, such as by tracepoints, while
33936 @samp{maint agent-eval} produces an expression that evaluates directly
33937 to a result. For instance, a collection expression for @code{globa +
33938 globb} will include bytecodes to record four bytes of memory at each
33939 of the addresses of @code{globa} and @code{globb}, while discarding
33940 the result of the addition, while an evaluation expression will do the
33941 addition and return the sum.
33942 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33943 If not, generate remote agent bytecode for current frame PC address.
33945 @kindex maint agent-printf
33946 @item maint agent-printf @var{format},@var{expr},...
33947 Translate the given format string and list of argument expressions
33948 into remote agent bytecodes and display them as a disassembled list.
33949 This command is useful for debugging the agent version of dynamic
33950 printf (@pxref{Dynamic Printf}).
33952 @kindex maint info breakpoints
33953 @item @anchor{maint info breakpoints}maint info breakpoints
33954 Using the same format as @samp{info breakpoints}, display both the
33955 breakpoints you've set explicitly, and those @value{GDBN} is using for
33956 internal purposes. Internal breakpoints are shown with negative
33957 breakpoint numbers. The type column identifies what kind of breakpoint
33962 Normal, explicitly set breakpoint.
33965 Normal, explicitly set watchpoint.
33968 Internal breakpoint, used to handle correctly stepping through
33969 @code{longjmp} calls.
33971 @item longjmp resume
33972 Internal breakpoint at the target of a @code{longjmp}.
33975 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33978 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33981 Shared library events.
33985 @kindex maint info bfds
33986 @item maint info bfds
33987 This prints information about each @code{bfd} object that is known to
33988 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33990 @kindex maint info btrace
33991 @item maint info btrace
33992 Pint information about raw branch tracing data.
33994 @kindex maint btrace packet-history
33995 @item maint btrace packet-history
33996 Print the raw branch trace packets that are used to compute the
33997 execution history for the @samp{record btrace} command. Both the
33998 information and the format in which it is printed depend on the btrace
34003 For the BTS recording format, print a list of blocks of sequential
34004 code. For each block, the following information is printed:
34008 Newer blocks have higher numbers. The oldest block has number zero.
34009 @item Lowest @samp{PC}
34010 @item Highest @samp{PC}
34014 For the Intel(R) Processor Trace recording format, print a list of
34015 Intel(R) Processor Trace packets. For each packet, the following
34016 information is printed:
34019 @item Packet number
34020 Newer packets have higher numbers. The oldest packet has number zero.
34022 The packet's offset in the trace stream.
34023 @item Packet opcode and payload
34027 @kindex maint btrace clear-packet-history
34028 @item maint btrace clear-packet-history
34029 Discards the cached packet history printed by the @samp{maint btrace
34030 packet-history} command. The history will be computed again when
34033 @kindex maint btrace clear
34034 @item maint btrace clear
34035 Discard the branch trace data. The data will be fetched anew and the
34036 branch trace will be recomputed when needed.
34038 This implicitly truncates the branch trace to a single branch trace
34039 buffer. When updating branch trace incrementally, the branch trace
34040 available to @value{GDBN} may be bigger than a single branch trace
34043 @kindex maint set btrace pt skip-pad
34044 @item maint set btrace pt skip-pad
34045 @kindex maint show btrace pt skip-pad
34046 @item maint show btrace pt skip-pad
34047 Control whether @value{GDBN} will skip PAD packets when computing the
34050 @kindex set displaced-stepping
34051 @kindex show displaced-stepping
34052 @cindex displaced stepping support
34053 @cindex out-of-line single-stepping
34054 @item set displaced-stepping
34055 @itemx show displaced-stepping
34056 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34057 if the target supports it. Displaced stepping is a way to single-step
34058 over breakpoints without removing them from the inferior, by executing
34059 an out-of-line copy of the instruction that was originally at the
34060 breakpoint location. It is also known as out-of-line single-stepping.
34063 @item set displaced-stepping on
34064 If the target architecture supports it, @value{GDBN} will use
34065 displaced stepping to step over breakpoints.
34067 @item set displaced-stepping off
34068 @value{GDBN} will not use displaced stepping to step over breakpoints,
34069 even if such is supported by the target architecture.
34071 @cindex non-stop mode, and @samp{set displaced-stepping}
34072 @item set displaced-stepping auto
34073 This is the default mode. @value{GDBN} will use displaced stepping
34074 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34075 architecture supports displaced stepping.
34078 @kindex maint check-psymtabs
34079 @item maint check-psymtabs
34080 Check the consistency of currently expanded psymtabs versus symtabs.
34081 Use this to check, for example, whether a symbol is in one but not the other.
34083 @kindex maint check-symtabs
34084 @item maint check-symtabs
34085 Check the consistency of currently expanded symtabs.
34087 @kindex maint expand-symtabs
34088 @item maint expand-symtabs [@var{regexp}]
34089 Expand symbol tables.
34090 If @var{regexp} is specified, only expand symbol tables for file
34091 names matching @var{regexp}.
34093 @kindex maint set catch-demangler-crashes
34094 @kindex maint show catch-demangler-crashes
34095 @cindex demangler crashes
34096 @item maint set catch-demangler-crashes [on|off]
34097 @itemx maint show catch-demangler-crashes
34098 Control whether @value{GDBN} should attempt to catch crashes in the
34099 symbol name demangler. The default is to attempt to catch crashes.
34100 If enabled, the first time a crash is caught, a core file is created,
34101 the offending symbol is displayed and the user is presented with the
34102 option to terminate the current session.
34104 @kindex maint cplus first_component
34105 @item maint cplus first_component @var{name}
34106 Print the first C@t{++} class/namespace component of @var{name}.
34108 @kindex maint cplus namespace
34109 @item maint cplus namespace
34110 Print the list of possible C@t{++} namespaces.
34112 @kindex maint deprecate
34113 @kindex maint undeprecate
34114 @cindex deprecated commands
34115 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34116 @itemx maint undeprecate @var{command}
34117 Deprecate or undeprecate the named @var{command}. Deprecated commands
34118 cause @value{GDBN} to issue a warning when you use them. The optional
34119 argument @var{replacement} says which newer command should be used in
34120 favor of the deprecated one; if it is given, @value{GDBN} will mention
34121 the replacement as part of the warning.
34123 @kindex maint dump-me
34124 @item maint dump-me
34125 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34126 Cause a fatal signal in the debugger and force it to dump its core.
34127 This is supported only on systems which support aborting a program
34128 with the @code{SIGQUIT} signal.
34130 @kindex maint internal-error
34131 @kindex maint internal-warning
34132 @kindex maint demangler-warning
34133 @cindex demangler crashes
34134 @item maint internal-error @r{[}@var{message-text}@r{]}
34135 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34136 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34138 Cause @value{GDBN} to call the internal function @code{internal_error},
34139 @code{internal_warning} or @code{demangler_warning} and hence behave
34140 as though an internal problem has been detected. In addition to
34141 reporting the internal problem, these functions give the user the
34142 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34143 and @code{internal_warning}) create a core file of the current
34144 @value{GDBN} session.
34146 These commands take an optional parameter @var{message-text} that is
34147 used as the text of the error or warning message.
34149 Here's an example of using @code{internal-error}:
34152 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34153 @dots{}/maint.c:121: internal-error: testing, 1, 2
34154 A problem internal to GDB has been detected. Further
34155 debugging may prove unreliable.
34156 Quit this debugging session? (y or n) @kbd{n}
34157 Create a core file? (y or n) @kbd{n}
34161 @cindex @value{GDBN} internal error
34162 @cindex internal errors, control of @value{GDBN} behavior
34163 @cindex demangler crashes
34165 @kindex maint set internal-error
34166 @kindex maint show internal-error
34167 @kindex maint set internal-warning
34168 @kindex maint show internal-warning
34169 @kindex maint set demangler-warning
34170 @kindex maint show demangler-warning
34171 @item maint set internal-error @var{action} [ask|yes|no]
34172 @itemx maint show internal-error @var{action}
34173 @itemx maint set internal-warning @var{action} [ask|yes|no]
34174 @itemx maint show internal-warning @var{action}
34175 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34176 @itemx maint show demangler-warning @var{action}
34177 When @value{GDBN} reports an internal problem (error or warning) it
34178 gives the user the opportunity to both quit @value{GDBN} and create a
34179 core file of the current @value{GDBN} session. These commands let you
34180 override the default behaviour for each particular @var{action},
34181 described in the table below.
34185 You can specify that @value{GDBN} should always (yes) or never (no)
34186 quit. The default is to ask the user what to do.
34189 You can specify that @value{GDBN} should always (yes) or never (no)
34190 create a core file. The default is to ask the user what to do. Note
34191 that there is no @code{corefile} option for @code{demangler-warning}:
34192 demangler warnings always create a core file and this cannot be
34196 @kindex maint packet
34197 @item maint packet @var{text}
34198 If @value{GDBN} is talking to an inferior via the serial protocol,
34199 then this command sends the string @var{text} to the inferior, and
34200 displays the response packet. @value{GDBN} supplies the initial
34201 @samp{$} character, the terminating @samp{#} character, and the
34204 @kindex maint print architecture
34205 @item maint print architecture @r{[}@var{file}@r{]}
34206 Print the entire architecture configuration. The optional argument
34207 @var{file} names the file where the output goes.
34209 @kindex maint print c-tdesc
34210 @item maint print c-tdesc
34211 Print the current target description (@pxref{Target Descriptions}) as
34212 a C source file. The created source file can be used in @value{GDBN}
34213 when an XML parser is not available to parse the description.
34215 @kindex maint print dummy-frames
34216 @item maint print dummy-frames
34217 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34220 (@value{GDBP}) @kbd{b add}
34222 (@value{GDBP}) @kbd{print add(2,3)}
34223 Breakpoint 2, add (a=2, b=3) at @dots{}
34225 The program being debugged stopped while in a function called from GDB.
34227 (@value{GDBP}) @kbd{maint print dummy-frames}
34228 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34232 Takes an optional file parameter.
34234 @kindex maint print registers
34235 @kindex maint print raw-registers
34236 @kindex maint print cooked-registers
34237 @kindex maint print register-groups
34238 @kindex maint print remote-registers
34239 @item maint print registers @r{[}@var{file}@r{]}
34240 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34241 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34242 @itemx maint print register-groups @r{[}@var{file}@r{]}
34243 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34244 Print @value{GDBN}'s internal register data structures.
34246 The command @code{maint print raw-registers} includes the contents of
34247 the raw register cache; the command @code{maint print
34248 cooked-registers} includes the (cooked) value of all registers,
34249 including registers which aren't available on the target nor visible
34250 to user; the command @code{maint print register-groups} includes the
34251 groups that each register is a member of; and the command @code{maint
34252 print remote-registers} includes the remote target's register numbers
34253 and offsets in the `G' packets.
34255 These commands take an optional parameter, a file name to which to
34256 write the information.
34258 @kindex maint print reggroups
34259 @item maint print reggroups @r{[}@var{file}@r{]}
34260 Print @value{GDBN}'s internal register group data structures. The
34261 optional argument @var{file} tells to what file to write the
34264 The register groups info looks like this:
34267 (@value{GDBP}) @kbd{maint print reggroups}
34280 This command forces @value{GDBN} to flush its internal register cache.
34282 @kindex maint print objfiles
34283 @cindex info for known object files
34284 @item maint print objfiles @r{[}@var{regexp}@r{]}
34285 Print a dump of all known object files.
34286 If @var{regexp} is specified, only print object files whose names
34287 match @var{regexp}. For each object file, this command prints its name,
34288 address in memory, and all of its psymtabs and symtabs.
34290 @kindex maint print user-registers
34291 @cindex user registers
34292 @item maint print user-registers
34293 List all currently available @dfn{user registers}. User registers
34294 typically provide alternate names for actual hardware registers. They
34295 include the four ``standard'' registers @code{$fp}, @code{$pc},
34296 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34297 registers can be used in expressions in the same way as the canonical
34298 register names, but only the latter are listed by the @code{info
34299 registers} and @code{maint print registers} commands.
34301 @kindex maint print section-scripts
34302 @cindex info for known .debug_gdb_scripts-loaded scripts
34303 @item maint print section-scripts [@var{regexp}]
34304 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34305 If @var{regexp} is specified, only print scripts loaded by object files
34306 matching @var{regexp}.
34307 For each script, this command prints its name as specified in the objfile,
34308 and the full path if known.
34309 @xref{dotdebug_gdb_scripts section}.
34311 @kindex maint print statistics
34312 @cindex bcache statistics
34313 @item maint print statistics
34314 This command prints, for each object file in the program, various data
34315 about that object file followed by the byte cache (@dfn{bcache})
34316 statistics for the object file. The objfile data includes the number
34317 of minimal, partial, full, and stabs symbols, the number of types
34318 defined by the objfile, the number of as yet unexpanded psym tables,
34319 the number of line tables and string tables, and the amount of memory
34320 used by the various tables. The bcache statistics include the counts,
34321 sizes, and counts of duplicates of all and unique objects, max,
34322 average, and median entry size, total memory used and its overhead and
34323 savings, and various measures of the hash table size and chain
34326 @kindex maint print target-stack
34327 @cindex target stack description
34328 @item maint print target-stack
34329 A @dfn{target} is an interface between the debugger and a particular
34330 kind of file or process. Targets can be stacked in @dfn{strata},
34331 so that more than one target can potentially respond to a request.
34332 In particular, memory accesses will walk down the stack of targets
34333 until they find a target that is interested in handling that particular
34336 This command prints a short description of each layer that was pushed on
34337 the @dfn{target stack}, starting from the top layer down to the bottom one.
34339 @kindex maint print type
34340 @cindex type chain of a data type
34341 @item maint print type @var{expr}
34342 Print the type chain for a type specified by @var{expr}. The argument
34343 can be either a type name or a symbol. If it is a symbol, the type of
34344 that symbol is described. The type chain produced by this command is
34345 a recursive definition of the data type as stored in @value{GDBN}'s
34346 data structures, including its flags and contained types.
34348 @kindex maint set dwarf always-disassemble
34349 @kindex maint show dwarf always-disassemble
34350 @item maint set dwarf always-disassemble
34351 @item maint show dwarf always-disassemble
34352 Control the behavior of @code{info address} when using DWARF debugging
34355 The default is @code{off}, which means that @value{GDBN} should try to
34356 describe a variable's location in an easily readable format. When
34357 @code{on}, @value{GDBN} will instead display the DWARF location
34358 expression in an assembly-like format. Note that some locations are
34359 too complex for @value{GDBN} to describe simply; in this case you will
34360 always see the disassembly form.
34362 Here is an example of the resulting disassembly:
34365 (gdb) info addr argc
34366 Symbol "argc" is a complex DWARF expression:
34370 For more information on these expressions, see
34371 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34373 @kindex maint set dwarf max-cache-age
34374 @kindex maint show dwarf max-cache-age
34375 @item maint set dwarf max-cache-age
34376 @itemx maint show dwarf max-cache-age
34377 Control the DWARF compilation unit cache.
34379 @cindex DWARF compilation units cache
34380 In object files with inter-compilation-unit references, such as those
34381 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34382 reader needs to frequently refer to previously read compilation units.
34383 This setting controls how long a compilation unit will remain in the
34384 cache if it is not referenced. A higher limit means that cached
34385 compilation units will be stored in memory longer, and more total
34386 memory will be used. Setting it to zero disables caching, which will
34387 slow down @value{GDBN} startup, but reduce memory consumption.
34389 @kindex maint set profile
34390 @kindex maint show profile
34391 @cindex profiling GDB
34392 @item maint set profile
34393 @itemx maint show profile
34394 Control profiling of @value{GDBN}.
34396 Profiling will be disabled until you use the @samp{maint set profile}
34397 command to enable it. When you enable profiling, the system will begin
34398 collecting timing and execution count data; when you disable profiling or
34399 exit @value{GDBN}, the results will be written to a log file. Remember that
34400 if you use profiling, @value{GDBN} will overwrite the profiling log file
34401 (often called @file{gmon.out}). If you have a record of important profiling
34402 data in a @file{gmon.out} file, be sure to move it to a safe location.
34404 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34405 compiled with the @samp{-pg} compiler option.
34407 @kindex maint set show-debug-regs
34408 @kindex maint show show-debug-regs
34409 @cindex hardware debug registers
34410 @item maint set show-debug-regs
34411 @itemx maint show show-debug-regs
34412 Control whether to show variables that mirror the hardware debug
34413 registers. Use @code{on} to enable, @code{off} to disable. If
34414 enabled, the debug registers values are shown when @value{GDBN} inserts or
34415 removes a hardware breakpoint or watchpoint, and when the inferior
34416 triggers a hardware-assisted breakpoint or watchpoint.
34418 @kindex maint set show-all-tib
34419 @kindex maint show show-all-tib
34420 @item maint set show-all-tib
34421 @itemx maint show show-all-tib
34422 Control whether to show all non zero areas within a 1k block starting
34423 at thread local base, when using the @samp{info w32 thread-information-block}
34426 @kindex maint set target-async
34427 @kindex maint show target-async
34428 @item maint set target-async
34429 @itemx maint show target-async
34430 This controls whether @value{GDBN} targets operate in synchronous or
34431 asynchronous mode (@pxref{Background Execution}). Normally the
34432 default is asynchronous, if it is available; but this can be changed
34433 to more easily debug problems occurring only in synchronous mode.
34435 @kindex maint set per-command
34436 @kindex maint show per-command
34437 @item maint set per-command
34438 @itemx maint show per-command
34439 @cindex resources used by commands
34441 @value{GDBN} can display the resources used by each command.
34442 This is useful in debugging performance problems.
34445 @item maint set per-command space [on|off]
34446 @itemx maint show per-command space
34447 Enable or disable the printing of the memory used by GDB for each command.
34448 If enabled, @value{GDBN} will display how much memory each command
34449 took, following the command's own output.
34450 This can also be requested by invoking @value{GDBN} with the
34451 @option{--statistics} command-line switch (@pxref{Mode Options}).
34453 @item maint set per-command time [on|off]
34454 @itemx maint show per-command time
34455 Enable or disable the printing of the execution time of @value{GDBN}
34457 If enabled, @value{GDBN} will display how much time it
34458 took to execute each command, following the command's own output.
34459 Both CPU time and wallclock time are printed.
34460 Printing both is useful when trying to determine whether the cost is
34461 CPU or, e.g., disk/network latency.
34462 Note that the CPU time printed is for @value{GDBN} only, it does not include
34463 the execution time of the inferior because there's no mechanism currently
34464 to compute how much time was spent by @value{GDBN} and how much time was
34465 spent by the program been debugged.
34466 This can also be requested by invoking @value{GDBN} with the
34467 @option{--statistics} command-line switch (@pxref{Mode Options}).
34469 @item maint set per-command symtab [on|off]
34470 @itemx maint show per-command symtab
34471 Enable or disable the printing of basic symbol table statistics
34473 If enabled, @value{GDBN} will display the following information:
34477 number of symbol tables
34479 number of primary symbol tables
34481 number of blocks in the blockvector
34485 @kindex maint space
34486 @cindex memory used by commands
34487 @item maint space @var{value}
34488 An alias for @code{maint set per-command space}.
34489 A non-zero value enables it, zero disables it.
34492 @cindex time of command execution
34493 @item maint time @var{value}
34494 An alias for @code{maint set per-command time}.
34495 A non-zero value enables it, zero disables it.
34497 @kindex maint translate-address
34498 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34499 Find the symbol stored at the location specified by the address
34500 @var{addr} and an optional section name @var{section}. If found,
34501 @value{GDBN} prints the name of the closest symbol and an offset from
34502 the symbol's location to the specified address. This is similar to
34503 the @code{info address} command (@pxref{Symbols}), except that this
34504 command also allows to find symbols in other sections.
34506 If section was not specified, the section in which the symbol was found
34507 is also printed. For dynamically linked executables, the name of
34508 executable or shared library containing the symbol is printed as well.
34512 The following command is useful for non-interactive invocations of
34513 @value{GDBN}, such as in the test suite.
34516 @item set watchdog @var{nsec}
34517 @kindex set watchdog
34518 @cindex watchdog timer
34519 @cindex timeout for commands
34520 Set the maximum number of seconds @value{GDBN} will wait for the
34521 target operation to finish. If this time expires, @value{GDBN}
34522 reports and error and the command is aborted.
34524 @item show watchdog
34525 Show the current setting of the target wait timeout.
34528 @node Remote Protocol
34529 @appendix @value{GDBN} Remote Serial Protocol
34534 * Stop Reply Packets::
34535 * General Query Packets::
34536 * Architecture-Specific Protocol Details::
34537 * Tracepoint Packets::
34538 * Host I/O Packets::
34540 * Notification Packets::
34541 * Remote Non-Stop::
34542 * Packet Acknowledgment::
34544 * File-I/O Remote Protocol Extension::
34545 * Library List Format::
34546 * Library List Format for SVR4 Targets::
34547 * Memory Map Format::
34548 * Thread List Format::
34549 * Traceframe Info Format::
34550 * Branch Trace Format::
34551 * Branch Trace Configuration Format::
34557 There may be occasions when you need to know something about the
34558 protocol---for example, if there is only one serial port to your target
34559 machine, you might want your program to do something special if it
34560 recognizes a packet meant for @value{GDBN}.
34562 In the examples below, @samp{->} and @samp{<-} are used to indicate
34563 transmitted and received data, respectively.
34565 @cindex protocol, @value{GDBN} remote serial
34566 @cindex serial protocol, @value{GDBN} remote
34567 @cindex remote serial protocol
34568 All @value{GDBN} commands and responses (other than acknowledgments
34569 and notifications, see @ref{Notification Packets}) are sent as a
34570 @var{packet}. A @var{packet} is introduced with the character
34571 @samp{$}, the actual @var{packet-data}, and the terminating character
34572 @samp{#} followed by a two-digit @var{checksum}:
34575 @code{$}@var{packet-data}@code{#}@var{checksum}
34579 @cindex checksum, for @value{GDBN} remote
34581 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34582 characters between the leading @samp{$} and the trailing @samp{#} (an
34583 eight bit unsigned checksum).
34585 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34586 specification also included an optional two-digit @var{sequence-id}:
34589 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34592 @cindex sequence-id, for @value{GDBN} remote
34594 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34595 has never output @var{sequence-id}s. Stubs that handle packets added
34596 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34598 When either the host or the target machine receives a packet, the first
34599 response expected is an acknowledgment: either @samp{+} (to indicate
34600 the package was received correctly) or @samp{-} (to request
34604 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34609 The @samp{+}/@samp{-} acknowledgments can be disabled
34610 once a connection is established.
34611 @xref{Packet Acknowledgment}, for details.
34613 The host (@value{GDBN}) sends @var{command}s, and the target (the
34614 debugging stub incorporated in your program) sends a @var{response}. In
34615 the case of step and continue @var{command}s, the response is only sent
34616 when the operation has completed, and the target has again stopped all
34617 threads in all attached processes. This is the default all-stop mode
34618 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34619 execution mode; see @ref{Remote Non-Stop}, for details.
34621 @var{packet-data} consists of a sequence of characters with the
34622 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34625 @cindex remote protocol, field separator
34626 Fields within the packet should be separated using @samp{,} @samp{;} or
34627 @samp{:}. Except where otherwise noted all numbers are represented in
34628 @sc{hex} with leading zeros suppressed.
34630 Implementors should note that prior to @value{GDBN} 5.0, the character
34631 @samp{:} could not appear as the third character in a packet (as it
34632 would potentially conflict with the @var{sequence-id}).
34634 @cindex remote protocol, binary data
34635 @anchor{Binary Data}
34636 Binary data in most packets is encoded either as two hexadecimal
34637 digits per byte of binary data. This allowed the traditional remote
34638 protocol to work over connections which were only seven-bit clean.
34639 Some packets designed more recently assume an eight-bit clean
34640 connection, and use a more efficient encoding to send and receive
34643 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34644 as an escape character. Any escaped byte is transmitted as the escape
34645 character followed by the original character XORed with @code{0x20}.
34646 For example, the byte @code{0x7d} would be transmitted as the two
34647 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34648 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34649 @samp{@}}) must always be escaped. Responses sent by the stub
34650 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34651 is not interpreted as the start of a run-length encoded sequence
34654 Response @var{data} can be run-length encoded to save space.
34655 Run-length encoding replaces runs of identical characters with one
34656 instance of the repeated character, followed by a @samp{*} and a
34657 repeat count. The repeat count is itself sent encoded, to avoid
34658 binary characters in @var{data}: a value of @var{n} is sent as
34659 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34660 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34661 code 32) for a repeat count of 3. (This is because run-length
34662 encoding starts to win for counts 3 or more.) Thus, for example,
34663 @samp{0* } is a run-length encoding of ``0000'': the space character
34664 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34667 The printable characters @samp{#} and @samp{$} or with a numeric value
34668 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34669 seven repeats (@samp{$}) can be expanded using a repeat count of only
34670 five (@samp{"}). For example, @samp{00000000} can be encoded as
34673 The error response returned for some packets includes a two character
34674 error number. That number is not well defined.
34676 @cindex empty response, for unsupported packets
34677 For any @var{command} not supported by the stub, an empty response
34678 (@samp{$#00}) should be returned. That way it is possible to extend the
34679 protocol. A newer @value{GDBN} can tell if a packet is supported based
34682 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34683 commands for register access, and the @samp{m} and @samp{M} commands
34684 for memory access. Stubs that only control single-threaded targets
34685 can implement run control with the @samp{c} (continue), and @samp{s}
34686 (step) commands. Stubs that support multi-threading targets should
34687 support the @samp{vCont} command. All other commands are optional.
34692 The following table provides a complete list of all currently defined
34693 @var{command}s and their corresponding response @var{data}.
34694 @xref{File-I/O Remote Protocol Extension}, for details about the File
34695 I/O extension of the remote protocol.
34697 Each packet's description has a template showing the packet's overall
34698 syntax, followed by an explanation of the packet's meaning. We
34699 include spaces in some of the templates for clarity; these are not
34700 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34701 separate its components. For example, a template like @samp{foo
34702 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34703 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34704 @var{baz}. @value{GDBN} does not transmit a space character between the
34705 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34708 @cindex @var{thread-id}, in remote protocol
34709 @anchor{thread-id syntax}
34710 Several packets and replies include a @var{thread-id} field to identify
34711 a thread. Normally these are positive numbers with a target-specific
34712 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34713 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34716 In addition, the remote protocol supports a multiprocess feature in
34717 which the @var{thread-id} syntax is extended to optionally include both
34718 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34719 The @var{pid} (process) and @var{tid} (thread) components each have the
34720 format described above: a positive number with target-specific
34721 interpretation formatted as a big-endian hex string, literal @samp{-1}
34722 to indicate all processes or threads (respectively), or @samp{0} to
34723 indicate an arbitrary process or thread. Specifying just a process, as
34724 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34725 error to specify all processes but a specific thread, such as
34726 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34727 for those packets and replies explicitly documented to include a process
34728 ID, rather than a @var{thread-id}.
34730 The multiprocess @var{thread-id} syntax extensions are only used if both
34731 @value{GDBN} and the stub report support for the @samp{multiprocess}
34732 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34735 Note that all packet forms beginning with an upper- or lower-case
34736 letter, other than those described here, are reserved for future use.
34738 Here are the packet descriptions.
34743 @cindex @samp{!} packet
34744 @anchor{extended mode}
34745 Enable extended mode. In extended mode, the remote server is made
34746 persistent. The @samp{R} packet is used to restart the program being
34752 The remote target both supports and has enabled extended mode.
34756 @cindex @samp{?} packet
34758 Indicate the reason the target halted. The reply is the same as for
34759 step and continue. This packet has a special interpretation when the
34760 target is in non-stop mode; see @ref{Remote Non-Stop}.
34763 @xref{Stop Reply Packets}, for the reply specifications.
34765 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34766 @cindex @samp{A} packet
34767 Initialized @code{argv[]} array passed into program. @var{arglen}
34768 specifies the number of bytes in the hex encoded byte stream
34769 @var{arg}. See @code{gdbserver} for more details.
34774 The arguments were set.
34780 @cindex @samp{b} packet
34781 (Don't use this packet; its behavior is not well-defined.)
34782 Change the serial line speed to @var{baud}.
34784 JTC: @emph{When does the transport layer state change? When it's
34785 received, or after the ACK is transmitted. In either case, there are
34786 problems if the command or the acknowledgment packet is dropped.}
34788 Stan: @emph{If people really wanted to add something like this, and get
34789 it working for the first time, they ought to modify ser-unix.c to send
34790 some kind of out-of-band message to a specially-setup stub and have the
34791 switch happen "in between" packets, so that from remote protocol's point
34792 of view, nothing actually happened.}
34794 @item B @var{addr},@var{mode}
34795 @cindex @samp{B} packet
34796 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34797 breakpoint at @var{addr}.
34799 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34800 (@pxref{insert breakpoint or watchpoint packet}).
34802 @cindex @samp{bc} packet
34805 Backward continue. Execute the target system in reverse. No parameter.
34806 @xref{Reverse Execution}, for more information.
34809 @xref{Stop Reply Packets}, for the reply specifications.
34811 @cindex @samp{bs} packet
34814 Backward single step. Execute one instruction in reverse. No parameter.
34815 @xref{Reverse Execution}, for more information.
34818 @xref{Stop Reply Packets}, for the reply specifications.
34820 @item c @r{[}@var{addr}@r{]}
34821 @cindex @samp{c} packet
34822 Continue at @var{addr}, which is the address to resume. If @var{addr}
34823 is omitted, resume at current address.
34825 This packet is deprecated for multi-threading support. @xref{vCont
34829 @xref{Stop Reply Packets}, for the reply specifications.
34831 @item C @var{sig}@r{[};@var{addr}@r{]}
34832 @cindex @samp{C} packet
34833 Continue with signal @var{sig} (hex signal number). If
34834 @samp{;@var{addr}} is omitted, resume at same address.
34836 This packet is deprecated for multi-threading support. @xref{vCont
34840 @xref{Stop Reply Packets}, for the reply specifications.
34843 @cindex @samp{d} packet
34846 Don't use this packet; instead, define a general set packet
34847 (@pxref{General Query Packets}).
34851 @cindex @samp{D} packet
34852 The first form of the packet is used to detach @value{GDBN} from the
34853 remote system. It is sent to the remote target
34854 before @value{GDBN} disconnects via the @code{detach} command.
34856 The second form, including a process ID, is used when multiprocess
34857 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34858 detach only a specific process. The @var{pid} is specified as a
34859 big-endian hex string.
34869 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34870 @cindex @samp{F} packet
34871 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34872 This is part of the File-I/O protocol extension. @xref{File-I/O
34873 Remote Protocol Extension}, for the specification.
34876 @anchor{read registers packet}
34877 @cindex @samp{g} packet
34878 Read general registers.
34882 @item @var{XX@dots{}}
34883 Each byte of register data is described by two hex digits. The bytes
34884 with the register are transmitted in target byte order. The size of
34885 each register and their position within the @samp{g} packet are
34886 determined by the @value{GDBN} internal gdbarch functions
34887 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34888 specification of several standard @samp{g} packets is specified below.
34890 When reading registers from a trace frame (@pxref{Analyze Collected
34891 Data,,Using the Collected Data}), the stub may also return a string of
34892 literal @samp{x}'s in place of the register data digits, to indicate
34893 that the corresponding register has not been collected, thus its value
34894 is unavailable. For example, for an architecture with 4 registers of
34895 4 bytes each, the following reply indicates to @value{GDBN} that
34896 registers 0 and 2 have not been collected, while registers 1 and 3
34897 have been collected, and both have zero value:
34901 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34908 @item G @var{XX@dots{}}
34909 @cindex @samp{G} packet
34910 Write general registers. @xref{read registers packet}, for a
34911 description of the @var{XX@dots{}} data.
34921 @item H @var{op} @var{thread-id}
34922 @cindex @samp{H} packet
34923 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34924 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34925 should be @samp{c} for step and continue operations (note that this
34926 is deprecated, supporting the @samp{vCont} command is a better
34927 option), and @samp{g} for other operations. The thread designator
34928 @var{thread-id} has the format and interpretation described in
34929 @ref{thread-id syntax}.
34940 @c 'H': How restrictive (or permissive) is the thread model. If a
34941 @c thread is selected and stopped, are other threads allowed
34942 @c to continue to execute? As I mentioned above, I think the
34943 @c semantics of each command when a thread is selected must be
34944 @c described. For example:
34946 @c 'g': If the stub supports threads and a specific thread is
34947 @c selected, returns the register block from that thread;
34948 @c otherwise returns current registers.
34950 @c 'G' If the stub supports threads and a specific thread is
34951 @c selected, sets the registers of the register block of
34952 @c that thread; otherwise sets current registers.
34954 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34955 @anchor{cycle step packet}
34956 @cindex @samp{i} packet
34957 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34958 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34959 step starting at that address.
34962 @cindex @samp{I} packet
34963 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34967 @cindex @samp{k} packet
34970 The exact effect of this packet is not specified.
34972 For a bare-metal target, it may power cycle or reset the target
34973 system. For that reason, the @samp{k} packet has no reply.
34975 For a single-process target, it may kill that process if possible.
34977 A multiple-process target may choose to kill just one process, or all
34978 that are under @value{GDBN}'s control. For more precise control, use
34979 the vKill packet (@pxref{vKill packet}).
34981 If the target system immediately closes the connection in response to
34982 @samp{k}, @value{GDBN} does not consider the lack of packet
34983 acknowledgment to be an error, and assumes the kill was successful.
34985 If connected using @kbd{target extended-remote}, and the target does
34986 not close the connection in response to a kill request, @value{GDBN}
34987 probes the target state as if a new connection was opened
34988 (@pxref{? packet}).
34990 @item m @var{addr},@var{length}
34991 @cindex @samp{m} packet
34992 Read @var{length} addressable memory units starting at address @var{addr}
34993 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34994 any particular boundary.
34996 The stub need not use any particular size or alignment when gathering
34997 data from memory for the response; even if @var{addr} is word-aligned
34998 and @var{length} is a multiple of the word size, the stub is free to
34999 use byte accesses, or not. For this reason, this packet may not be
35000 suitable for accessing memory-mapped I/O devices.
35001 @cindex alignment of remote memory accesses
35002 @cindex size of remote memory accesses
35003 @cindex memory, alignment and size of remote accesses
35007 @item @var{XX@dots{}}
35008 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35009 The reply may contain fewer addressable memory units than requested if the
35010 server was able to read only part of the region of memory.
35015 @item M @var{addr},@var{length}:@var{XX@dots{}}
35016 @cindex @samp{M} packet
35017 Write @var{length} addressable memory units starting at address @var{addr}
35018 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35019 byte is transmitted as a two-digit hexadecimal number.
35026 for an error (this includes the case where only part of the data was
35031 @cindex @samp{p} packet
35032 Read the value of register @var{n}; @var{n} is in hex.
35033 @xref{read registers packet}, for a description of how the returned
35034 register value is encoded.
35038 @item @var{XX@dots{}}
35039 the register's value
35043 Indicating an unrecognized @var{query}.
35046 @item P @var{n@dots{}}=@var{r@dots{}}
35047 @anchor{write register packet}
35048 @cindex @samp{P} packet
35049 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35050 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35051 digits for each byte in the register (target byte order).
35061 @item q @var{name} @var{params}@dots{}
35062 @itemx Q @var{name} @var{params}@dots{}
35063 @cindex @samp{q} packet
35064 @cindex @samp{Q} packet
35065 General query (@samp{q}) and set (@samp{Q}). These packets are
35066 described fully in @ref{General Query Packets}.
35069 @cindex @samp{r} packet
35070 Reset the entire system.
35072 Don't use this packet; use the @samp{R} packet instead.
35075 @cindex @samp{R} packet
35076 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35077 This packet is only available in extended mode (@pxref{extended mode}).
35079 The @samp{R} packet has no reply.
35081 @item s @r{[}@var{addr}@r{]}
35082 @cindex @samp{s} packet
35083 Single step, resuming at @var{addr}. If
35084 @var{addr} is omitted, resume at same address.
35086 This packet is deprecated for multi-threading support. @xref{vCont
35090 @xref{Stop Reply Packets}, for the reply specifications.
35092 @item S @var{sig}@r{[};@var{addr}@r{]}
35093 @anchor{step with signal packet}
35094 @cindex @samp{S} packet
35095 Step with signal. This is analogous to the @samp{C} packet, but
35096 requests a single-step, rather than a normal resumption of execution.
35098 This packet is deprecated for multi-threading support. @xref{vCont
35102 @xref{Stop Reply Packets}, for the reply specifications.
35104 @item t @var{addr}:@var{PP},@var{MM}
35105 @cindex @samp{t} packet
35106 Search backwards starting at address @var{addr} for a match with pattern
35107 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35108 There must be at least 3 digits in @var{addr}.
35110 @item T @var{thread-id}
35111 @cindex @samp{T} packet
35112 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35117 thread is still alive
35123 Packets starting with @samp{v} are identified by a multi-letter name,
35124 up to the first @samp{;} or @samp{?} (or the end of the packet).
35126 @item vAttach;@var{pid}
35127 @cindex @samp{vAttach} packet
35128 Attach to a new process with the specified process ID @var{pid}.
35129 The process ID is a
35130 hexadecimal integer identifying the process. In all-stop mode, all
35131 threads in the attached process are stopped; in non-stop mode, it may be
35132 attached without being stopped if that is supported by the target.
35134 @c In non-stop mode, on a successful vAttach, the stub should set the
35135 @c current thread to a thread of the newly-attached process. After
35136 @c attaching, GDB queries for the attached process's thread ID with qC.
35137 @c Also note that, from a user perspective, whether or not the
35138 @c target is stopped on attach in non-stop mode depends on whether you
35139 @c use the foreground or background version of the attach command, not
35140 @c on what vAttach does; GDB does the right thing with respect to either
35141 @c stopping or restarting threads.
35143 This packet is only available in extended mode (@pxref{extended mode}).
35149 @item @r{Any stop packet}
35150 for success in all-stop mode (@pxref{Stop Reply Packets})
35152 for success in non-stop mode (@pxref{Remote Non-Stop})
35155 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35156 @cindex @samp{vCont} packet
35157 @anchor{vCont packet}
35158 Resume the inferior, specifying different actions for each thread.
35159 If an action is specified with no @var{thread-id}, then it is applied to any
35160 threads that don't have a specific action specified; if no default action is
35161 specified then other threads should remain stopped in all-stop mode and
35162 in their current state in non-stop mode.
35163 Specifying multiple
35164 default actions is an error; specifying no actions is also an error.
35165 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35167 Currently supported actions are:
35173 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35177 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35180 @item r @var{start},@var{end}
35181 Step once, and then keep stepping as long as the thread stops at
35182 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35183 The remote stub reports a stop reply when either the thread goes out
35184 of the range or is stopped due to an unrelated reason, such as hitting
35185 a breakpoint. @xref{range stepping}.
35187 If the range is empty (@var{start} == @var{end}), then the action
35188 becomes equivalent to the @samp{s} action. In other words,
35189 single-step once, and report the stop (even if the stepped instruction
35190 jumps to @var{start}).
35192 (A stop reply may be sent at any point even if the PC is still within
35193 the stepping range; for example, it is valid to implement this packet
35194 in a degenerate way as a single instruction step operation.)
35198 The optional argument @var{addr} normally associated with the
35199 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35200 not supported in @samp{vCont}.
35202 The @samp{t} action is only relevant in non-stop mode
35203 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35204 A stop reply should be generated for any affected thread not already stopped.
35205 When a thread is stopped by means of a @samp{t} action,
35206 the corresponding stop reply should indicate that the thread has stopped with
35207 signal @samp{0}, regardless of whether the target uses some other signal
35208 as an implementation detail.
35210 The stub must support @samp{vCont} if it reports support for
35211 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35212 this case @samp{vCont} actions can be specified to apply to all threads
35213 in a process by using the @samp{p@var{pid}.-1} form of the
35217 @xref{Stop Reply Packets}, for the reply specifications.
35220 @cindex @samp{vCont?} packet
35221 Request a list of actions supported by the @samp{vCont} packet.
35225 @item vCont@r{[};@var{action}@dots{}@r{]}
35226 The @samp{vCont} packet is supported. Each @var{action} is a supported
35227 command in the @samp{vCont} packet.
35229 The @samp{vCont} packet is not supported.
35232 @item vFile:@var{operation}:@var{parameter}@dots{}
35233 @cindex @samp{vFile} packet
35234 Perform a file operation on the target system. For details,
35235 see @ref{Host I/O Packets}.
35237 @item vFlashErase:@var{addr},@var{length}
35238 @cindex @samp{vFlashErase} packet
35239 Direct the stub to erase @var{length} bytes of flash starting at
35240 @var{addr}. The region may enclose any number of flash blocks, but
35241 its start and end must fall on block boundaries, as indicated by the
35242 flash block size appearing in the memory map (@pxref{Memory Map
35243 Format}). @value{GDBN} groups flash memory programming operations
35244 together, and sends a @samp{vFlashDone} request after each group; the
35245 stub is allowed to delay erase operation until the @samp{vFlashDone}
35246 packet is received.
35256 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35257 @cindex @samp{vFlashWrite} packet
35258 Direct the stub to write data to flash address @var{addr}. The data
35259 is passed in binary form using the same encoding as for the @samp{X}
35260 packet (@pxref{Binary Data}). The memory ranges specified by
35261 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35262 not overlap, and must appear in order of increasing addresses
35263 (although @samp{vFlashErase} packets for higher addresses may already
35264 have been received; the ordering is guaranteed only between
35265 @samp{vFlashWrite} packets). If a packet writes to an address that was
35266 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35267 target-specific method, the results are unpredictable.
35275 for vFlashWrite addressing non-flash memory
35281 @cindex @samp{vFlashDone} packet
35282 Indicate to the stub that flash programming operation is finished.
35283 The stub is permitted to delay or batch the effects of a group of
35284 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35285 @samp{vFlashDone} packet is received. The contents of the affected
35286 regions of flash memory are unpredictable until the @samp{vFlashDone}
35287 request is completed.
35289 @item vKill;@var{pid}
35290 @cindex @samp{vKill} packet
35291 @anchor{vKill packet}
35292 Kill the process with the specified process ID @var{pid}, which is a
35293 hexadecimal integer identifying the process. This packet is used in
35294 preference to @samp{k} when multiprocess protocol extensions are
35295 supported; see @ref{multiprocess extensions}.
35305 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35306 @cindex @samp{vRun} packet
35307 Run the program @var{filename}, passing it each @var{argument} on its
35308 command line. The file and arguments are hex-encoded strings. If
35309 @var{filename} is an empty string, the stub may use a default program
35310 (e.g.@: the last program run). The program is created in the stopped
35313 @c FIXME: What about non-stop mode?
35315 This packet is only available in extended mode (@pxref{extended mode}).
35321 @item @r{Any stop packet}
35322 for success (@pxref{Stop Reply Packets})
35326 @cindex @samp{vStopped} packet
35327 @xref{Notification Packets}.
35329 @item X @var{addr},@var{length}:@var{XX@dots{}}
35331 @cindex @samp{X} packet
35332 Write data to memory, where the data is transmitted in binary.
35333 Memory is specified by its address @var{addr} and number of addressable memory
35334 units @var{length} (@pxref{addressable memory unit});
35335 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35345 @item z @var{type},@var{addr},@var{kind}
35346 @itemx Z @var{type},@var{addr},@var{kind}
35347 @anchor{insert breakpoint or watchpoint packet}
35348 @cindex @samp{z} packet
35349 @cindex @samp{Z} packets
35350 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35351 watchpoint starting at address @var{address} of kind @var{kind}.
35353 Each breakpoint and watchpoint packet @var{type} is documented
35356 @emph{Implementation notes: A remote target shall return an empty string
35357 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35358 remote target shall support either both or neither of a given
35359 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35360 avoid potential problems with duplicate packets, the operations should
35361 be implemented in an idempotent way.}
35363 @item z0,@var{addr},@var{kind}
35364 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35365 @cindex @samp{z0} packet
35366 @cindex @samp{Z0} packet
35367 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35368 @var{addr} of type @var{kind}.
35370 A memory breakpoint is implemented by replacing the instruction at
35371 @var{addr} with a software breakpoint or trap instruction. The
35372 @var{kind} is target-specific and typically indicates the size of
35373 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35374 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35375 architectures have additional meanings for @var{kind};
35376 @var{cond_list} is an optional list of conditional expressions in bytecode
35377 form that should be evaluated on the target's side. These are the
35378 conditions that should be taken into consideration when deciding if
35379 the breakpoint trigger should be reported back to @var{GDBN}.
35381 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35382 for how to best report a memory breakpoint event to @value{GDBN}.
35384 The @var{cond_list} parameter is comprised of a series of expressions,
35385 concatenated without separators. Each expression has the following form:
35389 @item X @var{len},@var{expr}
35390 @var{len} is the length of the bytecode expression and @var{expr} is the
35391 actual conditional expression in bytecode form.
35395 The optional @var{cmd_list} parameter introduces commands that may be
35396 run on the target, rather than being reported back to @value{GDBN}.
35397 The parameter starts with a numeric flag @var{persist}; if the flag is
35398 nonzero, then the breakpoint may remain active and the commands
35399 continue to be run even when @value{GDBN} disconnects from the target.
35400 Following this flag is a series of expressions concatenated with no
35401 separators. Each expression has the following form:
35405 @item X @var{len},@var{expr}
35406 @var{len} is the length of the bytecode expression and @var{expr} is the
35407 actual conditional expression in bytecode form.
35411 see @ref{Architecture-Specific Protocol Details}.
35413 @emph{Implementation note: It is possible for a target to copy or move
35414 code that contains memory breakpoints (e.g., when implementing
35415 overlays). The behavior of this packet, in the presence of such a
35416 target, is not defined.}
35428 @item z1,@var{addr},@var{kind}
35429 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35430 @cindex @samp{z1} packet
35431 @cindex @samp{Z1} packet
35432 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35433 address @var{addr}.
35435 A hardware breakpoint is implemented using a mechanism that is not
35436 dependant on being able to modify the target's memory. The @var{kind}
35437 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35439 @emph{Implementation note: A hardware breakpoint is not affected by code
35452 @item z2,@var{addr},@var{kind}
35453 @itemx Z2,@var{addr},@var{kind}
35454 @cindex @samp{z2} packet
35455 @cindex @samp{Z2} packet
35456 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35457 The number of bytes to watch is specified by @var{kind}.
35469 @item z3,@var{addr},@var{kind}
35470 @itemx Z3,@var{addr},@var{kind}
35471 @cindex @samp{z3} packet
35472 @cindex @samp{Z3} packet
35473 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35474 The number of bytes to watch is specified by @var{kind}.
35486 @item z4,@var{addr},@var{kind}
35487 @itemx Z4,@var{addr},@var{kind}
35488 @cindex @samp{z4} packet
35489 @cindex @samp{Z4} packet
35490 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35491 The number of bytes to watch is specified by @var{kind}.
35505 @node Stop Reply Packets
35506 @section Stop Reply Packets
35507 @cindex stop reply packets
35509 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35510 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35511 receive any of the below as a reply. Except for @samp{?}
35512 and @samp{vStopped}, that reply is only returned
35513 when the target halts. In the below the exact meaning of @dfn{signal
35514 number} is defined by the header @file{include/gdb/signals.h} in the
35515 @value{GDBN} source code.
35517 As in the description of request packets, we include spaces in the
35518 reply templates for clarity; these are not part of the reply packet's
35519 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35525 The program received signal number @var{AA} (a two-digit hexadecimal
35526 number). This is equivalent to a @samp{T} response with no
35527 @var{n}:@var{r} pairs.
35529 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35530 @cindex @samp{T} packet reply
35531 The program received signal number @var{AA} (a two-digit hexadecimal
35532 number). This is equivalent to an @samp{S} response, except that the
35533 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35534 and other information directly in the stop reply packet, reducing
35535 round-trip latency. Single-step and breakpoint traps are reported
35536 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35540 If @var{n} is a hexadecimal number, it is a register number, and the
35541 corresponding @var{r} gives that register's value. The data @var{r} is a
35542 series of bytes in target byte order, with each byte given by a
35543 two-digit hex number.
35546 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35547 the stopped thread, as specified in @ref{thread-id syntax}.
35550 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35551 the core on which the stop event was detected.
35554 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35555 specific event that stopped the target. The currently defined stop
35556 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35557 signal. At most one stop reason should be present.
35560 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35561 and go on to the next; this allows us to extend the protocol in the
35565 The currently defined stop reasons are:
35571 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35574 @cindex shared library events, remote reply
35576 The packet indicates that the loaded libraries have changed.
35577 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35578 list of loaded libraries. The @var{r} part is ignored.
35580 @cindex replay log events, remote reply
35582 The packet indicates that the target cannot continue replaying
35583 logged execution events, because it has reached the end (or the
35584 beginning when executing backward) of the log. The value of @var{r}
35585 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35586 for more information.
35589 @anchor{swbreak stop reason}
35590 The packet indicates a memory breakpoint instruction was executed,
35591 irrespective of whether it was @value{GDBN} that planted the
35592 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35593 part must be left empty.
35595 On some architectures, such as x86, at the architecture level, when a
35596 breakpoint instruction executes the program counter points at the
35597 breakpoint address plus an offset. On such targets, the stub is
35598 responsible for adjusting the PC to point back at the breakpoint
35601 This packet should not be sent by default; older @value{GDBN} versions
35602 did not support it. @value{GDBN} requests it, by supplying an
35603 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35604 remote stub must also supply the appropriate @samp{qSupported} feature
35605 indicating support.
35607 This packet is required for correct non-stop mode operation.
35610 The packet indicates the target stopped for a hardware breakpoint.
35611 The @var{r} part must be left empty.
35613 The same remarks about @samp{qSupported} and non-stop mode above
35616 @cindex fork events, remote reply
35618 The packet indicates that @code{fork} was called, and @var{r}
35619 is the thread ID of the new child process. Refer to
35620 @ref{thread-id syntax} for the format of the @var{thread-id}
35621 field. This packet is only applicable to targets that support
35624 This packet should not be sent by default; older @value{GDBN} versions
35625 did not support it. @value{GDBN} requests it, by supplying an
35626 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35627 remote stub must also supply the appropriate @samp{qSupported} feature
35628 indicating support.
35630 @cindex vfork events, remote reply
35632 The packet indicates that @code{vfork} was called, and @var{r}
35633 is the thread ID of the new child process. Refer to
35634 @ref{thread-id syntax} for the format of the @var{thread-id}
35635 field. This packet is only applicable to targets that support
35638 This packet should not be sent by default; older @value{GDBN} versions
35639 did not support it. @value{GDBN} requests it, by supplying an
35640 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35641 remote stub must also supply the appropriate @samp{qSupported} feature
35642 indicating support.
35644 @cindex vforkdone events, remote reply
35646 The packet indicates that a child process created by a vfork
35647 has either called @code{exec} or terminated, so that the
35648 address spaces of the parent and child process are no longer
35649 shared. The @var{r} part is ignored. This packet is only
35650 applicable to targets that support vforkdone events.
35652 This packet should not be sent by default; older @value{GDBN} versions
35653 did not support it. @value{GDBN} requests it, by supplying an
35654 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35655 remote stub must also supply the appropriate @samp{qSupported} feature
35656 indicating support.
35661 @itemx W @var{AA} ; process:@var{pid}
35662 The process exited, and @var{AA} is the exit status. This is only
35663 applicable to certain targets.
35665 The second form of the response, including the process ID of the exited
35666 process, can be used only when @value{GDBN} has reported support for
35667 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35668 The @var{pid} is formatted as a big-endian hex string.
35671 @itemx X @var{AA} ; process:@var{pid}
35672 The process terminated with signal @var{AA}.
35674 The second form of the response, including the process ID of the
35675 terminated process, can be used only when @value{GDBN} has reported
35676 support for multiprocess protocol extensions; see @ref{multiprocess
35677 extensions}. The @var{pid} is formatted as a big-endian hex string.
35679 @item O @var{XX}@dots{}
35680 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35681 written as the program's console output. This can happen at any time
35682 while the program is running and the debugger should continue to wait
35683 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35685 @item F @var{call-id},@var{parameter}@dots{}
35686 @var{call-id} is the identifier which says which host system call should
35687 be called. This is just the name of the function. Translation into the
35688 correct system call is only applicable as it's defined in @value{GDBN}.
35689 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35692 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35693 this very system call.
35695 The target replies with this packet when it expects @value{GDBN} to
35696 call a host system call on behalf of the target. @value{GDBN} replies
35697 with an appropriate @samp{F} packet and keeps up waiting for the next
35698 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35699 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35700 Protocol Extension}, for more details.
35704 @node General Query Packets
35705 @section General Query Packets
35706 @cindex remote query requests
35708 Packets starting with @samp{q} are @dfn{general query packets};
35709 packets starting with @samp{Q} are @dfn{general set packets}. General
35710 query and set packets are a semi-unified form for retrieving and
35711 sending information to and from the stub.
35713 The initial letter of a query or set packet is followed by a name
35714 indicating what sort of thing the packet applies to. For example,
35715 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35716 definitions with the stub. These packet names follow some
35721 The name must not contain commas, colons or semicolons.
35723 Most @value{GDBN} query and set packets have a leading upper case
35726 The names of custom vendor packets should use a company prefix, in
35727 lower case, followed by a period. For example, packets designed at
35728 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35729 foos) or @samp{Qacme.bar} (for setting bars).
35732 The name of a query or set packet should be separated from any
35733 parameters by a @samp{:}; the parameters themselves should be
35734 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35735 full packet name, and check for a separator or the end of the packet,
35736 in case two packet names share a common prefix. New packets should not begin
35737 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35738 packets predate these conventions, and have arguments without any terminator
35739 for the packet name; we suspect they are in widespread use in places that
35740 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35741 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35744 Like the descriptions of the other packets, each description here
35745 has a template showing the packet's overall syntax, followed by an
35746 explanation of the packet's meaning. We include spaces in some of the
35747 templates for clarity; these are not part of the packet's syntax. No
35748 @value{GDBN} packet uses spaces to separate its components.
35750 Here are the currently defined query and set packets:
35756 Turn on or off the agent as a helper to perform some debugging operations
35757 delegated from @value{GDBN} (@pxref{Control Agent}).
35759 @item QAllow:@var{op}:@var{val}@dots{}
35760 @cindex @samp{QAllow} packet
35761 Specify which operations @value{GDBN} expects to request of the
35762 target, as a semicolon-separated list of operation name and value
35763 pairs. Possible values for @var{op} include @samp{WriteReg},
35764 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35765 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35766 indicating that @value{GDBN} will not request the operation, or 1,
35767 indicating that it may. (The target can then use this to set up its
35768 own internals optimally, for instance if the debugger never expects to
35769 insert breakpoints, it may not need to install its own trap handler.)
35772 @cindex current thread, remote request
35773 @cindex @samp{qC} packet
35774 Return the current thread ID.
35778 @item QC @var{thread-id}
35779 Where @var{thread-id} is a thread ID as documented in
35780 @ref{thread-id syntax}.
35781 @item @r{(anything else)}
35782 Any other reply implies the old thread ID.
35785 @item qCRC:@var{addr},@var{length}
35786 @cindex CRC of memory block, remote request
35787 @cindex @samp{qCRC} packet
35788 @anchor{qCRC packet}
35789 Compute the CRC checksum of a block of memory using CRC-32 defined in
35790 IEEE 802.3. The CRC is computed byte at a time, taking the most
35791 significant bit of each byte first. The initial pattern code
35792 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35794 @emph{Note:} This is the same CRC used in validating separate debug
35795 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35796 Files}). However the algorithm is slightly different. When validating
35797 separate debug files, the CRC is computed taking the @emph{least}
35798 significant bit of each byte first, and the final result is inverted to
35799 detect trailing zeros.
35804 An error (such as memory fault)
35805 @item C @var{crc32}
35806 The specified memory region's checksum is @var{crc32}.
35809 @item QDisableRandomization:@var{value}
35810 @cindex disable address space randomization, remote request
35811 @cindex @samp{QDisableRandomization} packet
35812 Some target operating systems will randomize the virtual address space
35813 of the inferior process as a security feature, but provide a feature
35814 to disable such randomization, e.g.@: to allow for a more deterministic
35815 debugging experience. On such systems, this packet with a @var{value}
35816 of 1 directs the target to disable address space randomization for
35817 processes subsequently started via @samp{vRun} packets, while a packet
35818 with a @var{value} of 0 tells the target to enable address space
35821 This packet is only available in extended mode (@pxref{extended mode}).
35826 The request succeeded.
35829 An error occurred. The error number @var{nn} is given as hex digits.
35832 An empty reply indicates that @samp{QDisableRandomization} is not supported
35836 This packet is not probed by default; the remote stub must request it,
35837 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35838 This should only be done on targets that actually support disabling
35839 address space randomization.
35842 @itemx qsThreadInfo
35843 @cindex list active threads, remote request
35844 @cindex @samp{qfThreadInfo} packet
35845 @cindex @samp{qsThreadInfo} packet
35846 Obtain a list of all active thread IDs from the target (OS). Since there
35847 may be too many active threads to fit into one reply packet, this query
35848 works iteratively: it may require more than one query/reply sequence to
35849 obtain the entire list of threads. The first query of the sequence will
35850 be the @samp{qfThreadInfo} query; subsequent queries in the
35851 sequence will be the @samp{qsThreadInfo} query.
35853 NOTE: This packet replaces the @samp{qL} query (see below).
35857 @item m @var{thread-id}
35859 @item m @var{thread-id},@var{thread-id}@dots{}
35860 a comma-separated list of thread IDs
35862 (lower case letter @samp{L}) denotes end of list.
35865 In response to each query, the target will reply with a list of one or
35866 more thread IDs, separated by commas.
35867 @value{GDBN} will respond to each reply with a request for more thread
35868 ids (using the @samp{qs} form of the query), until the target responds
35869 with @samp{l} (lower-case ell, for @dfn{last}).
35870 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35873 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35874 initial connection with the remote target, and the very first thread ID
35875 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35876 message. Therefore, the stub should ensure that the first thread ID in
35877 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35879 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35880 @cindex get thread-local storage address, remote request
35881 @cindex @samp{qGetTLSAddr} packet
35882 Fetch the address associated with thread local storage specified
35883 by @var{thread-id}, @var{offset}, and @var{lm}.
35885 @var{thread-id} is the thread ID associated with the
35886 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35888 @var{offset} is the (big endian, hex encoded) offset associated with the
35889 thread local variable. (This offset is obtained from the debug
35890 information associated with the variable.)
35892 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35893 load module associated with the thread local storage. For example,
35894 a @sc{gnu}/Linux system will pass the link map address of the shared
35895 object associated with the thread local storage under consideration.
35896 Other operating environments may choose to represent the load module
35897 differently, so the precise meaning of this parameter will vary.
35901 @item @var{XX}@dots{}
35902 Hex encoded (big endian) bytes representing the address of the thread
35903 local storage requested.
35906 An error occurred. The error number @var{nn} is given as hex digits.
35909 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35912 @item qGetTIBAddr:@var{thread-id}
35913 @cindex get thread information block address
35914 @cindex @samp{qGetTIBAddr} packet
35915 Fetch address of the Windows OS specific Thread Information Block.
35917 @var{thread-id} is the thread ID associated with the thread.
35921 @item @var{XX}@dots{}
35922 Hex encoded (big endian) bytes representing the linear address of the
35923 thread information block.
35926 An error occured. This means that either the thread was not found, or the
35927 address could not be retrieved.
35930 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35933 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35934 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35935 digit) is one to indicate the first query and zero to indicate a
35936 subsequent query; @var{threadcount} (two hex digits) is the maximum
35937 number of threads the response packet can contain; and @var{nextthread}
35938 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35939 returned in the response as @var{argthread}.
35941 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35945 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35946 Where: @var{count} (two hex digits) is the number of threads being
35947 returned; @var{done} (one hex digit) is zero to indicate more threads
35948 and one indicates no further threads; @var{argthreadid} (eight hex
35949 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35950 is a sequence of thread IDs, @var{threadid} (eight hex
35951 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35955 @cindex section offsets, remote request
35956 @cindex @samp{qOffsets} packet
35957 Get section offsets that the target used when relocating the downloaded
35962 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35963 Relocate the @code{Text} section by @var{xxx} from its original address.
35964 Relocate the @code{Data} section by @var{yyy} from its original address.
35965 If the object file format provides segment information (e.g.@: @sc{elf}
35966 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35967 segments by the supplied offsets.
35969 @emph{Note: while a @code{Bss} offset may be included in the response,
35970 @value{GDBN} ignores this and instead applies the @code{Data} offset
35971 to the @code{Bss} section.}
35973 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35974 Relocate the first segment of the object file, which conventionally
35975 contains program code, to a starting address of @var{xxx}. If
35976 @samp{DataSeg} is specified, relocate the second segment, which
35977 conventionally contains modifiable data, to a starting address of
35978 @var{yyy}. @value{GDBN} will report an error if the object file
35979 does not contain segment information, or does not contain at least
35980 as many segments as mentioned in the reply. Extra segments are
35981 kept at fixed offsets relative to the last relocated segment.
35984 @item qP @var{mode} @var{thread-id}
35985 @cindex thread information, remote request
35986 @cindex @samp{qP} packet
35987 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35988 encoded 32 bit mode; @var{thread-id} is a thread ID
35989 (@pxref{thread-id syntax}).
35991 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35994 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35998 @cindex non-stop mode, remote request
35999 @cindex @samp{QNonStop} packet
36001 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36002 @xref{Remote Non-Stop}, for more information.
36007 The request succeeded.
36010 An error occurred. The error number @var{nn} is given as hex digits.
36013 An empty reply indicates that @samp{QNonStop} is not supported by
36017 This packet is not probed by default; the remote stub must request it,
36018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36019 Use of this packet is controlled by the @code{set non-stop} command;
36020 @pxref{Non-Stop Mode}.
36022 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36023 @cindex pass signals to inferior, remote request
36024 @cindex @samp{QPassSignals} packet
36025 @anchor{QPassSignals}
36026 Each listed @var{signal} should be passed directly to the inferior process.
36027 Signals are numbered identically to continue packets and stop replies
36028 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36029 strictly greater than the previous item. These signals do not need to stop
36030 the inferior, or be reported to @value{GDBN}. All other signals should be
36031 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36032 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36033 new list. This packet improves performance when using @samp{handle
36034 @var{signal} nostop noprint pass}.
36039 The request succeeded.
36042 An error occurred. The error number @var{nn} is given as hex digits.
36045 An empty reply indicates that @samp{QPassSignals} is not supported by
36049 Use of this packet is controlled by the @code{set remote pass-signals}
36050 command (@pxref{Remote Configuration, set remote pass-signals}).
36051 This packet is not probed by default; the remote stub must request it,
36052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36054 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36055 @cindex signals the inferior may see, remote request
36056 @cindex @samp{QProgramSignals} packet
36057 @anchor{QProgramSignals}
36058 Each listed @var{signal} may be delivered to the inferior process.
36059 Others should be silently discarded.
36061 In some cases, the remote stub may need to decide whether to deliver a
36062 signal to the program or not without @value{GDBN} involvement. One
36063 example of that is while detaching --- the program's threads may have
36064 stopped for signals that haven't yet had a chance of being reported to
36065 @value{GDBN}, and so the remote stub can use the signal list specified
36066 by this packet to know whether to deliver or ignore those pending
36069 This does not influence whether to deliver a signal as requested by a
36070 resumption packet (@pxref{vCont packet}).
36072 Signals are numbered identically to continue packets and stop replies
36073 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36074 strictly greater than the previous item. Multiple
36075 @samp{QProgramSignals} packets do not combine; any earlier
36076 @samp{QProgramSignals} list is completely replaced by the new list.
36081 The request succeeded.
36084 An error occurred. The error number @var{nn} is given as hex digits.
36087 An empty reply indicates that @samp{QProgramSignals} is not supported
36091 Use of this packet is controlled by the @code{set remote program-signals}
36092 command (@pxref{Remote Configuration, set remote program-signals}).
36093 This packet is not probed by default; the remote stub must request it,
36094 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36096 @item qRcmd,@var{command}
36097 @cindex execute remote command, remote request
36098 @cindex @samp{qRcmd} packet
36099 @var{command} (hex encoded) is passed to the local interpreter for
36100 execution. Invalid commands should be reported using the output
36101 string. Before the final result packet, the target may also respond
36102 with a number of intermediate @samp{O@var{output}} console output
36103 packets. @emph{Implementors should note that providing access to a
36104 stubs's interpreter may have security implications}.
36109 A command response with no output.
36111 A command response with the hex encoded output string @var{OUTPUT}.
36113 Indicate a badly formed request.
36115 An empty reply indicates that @samp{qRcmd} is not recognized.
36118 (Note that the @code{qRcmd} packet's name is separated from the
36119 command by a @samp{,}, not a @samp{:}, contrary to the naming
36120 conventions above. Please don't use this packet as a model for new
36123 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36124 @cindex searching memory, in remote debugging
36126 @cindex @samp{qSearch:memory} packet
36128 @cindex @samp{qSearch memory} packet
36129 @anchor{qSearch memory}
36130 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36131 Both @var{address} and @var{length} are encoded in hex;
36132 @var{search-pattern} is a sequence of bytes, also hex encoded.
36137 The pattern was not found.
36139 The pattern was found at @var{address}.
36141 A badly formed request or an error was encountered while searching memory.
36143 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36146 @item QStartNoAckMode
36147 @cindex @samp{QStartNoAckMode} packet
36148 @anchor{QStartNoAckMode}
36149 Request that the remote stub disable the normal @samp{+}/@samp{-}
36150 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36155 The stub has switched to no-acknowledgment mode.
36156 @value{GDBN} acknowledges this reponse,
36157 but neither the stub nor @value{GDBN} shall send or expect further
36158 @samp{+}/@samp{-} acknowledgments in the current connection.
36160 An empty reply indicates that the stub does not support no-acknowledgment mode.
36163 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36164 @cindex supported packets, remote query
36165 @cindex features of the remote protocol
36166 @cindex @samp{qSupported} packet
36167 @anchor{qSupported}
36168 Tell the remote stub about features supported by @value{GDBN}, and
36169 query the stub for features it supports. This packet allows
36170 @value{GDBN} and the remote stub to take advantage of each others'
36171 features. @samp{qSupported} also consolidates multiple feature probes
36172 at startup, to improve @value{GDBN} performance---a single larger
36173 packet performs better than multiple smaller probe packets on
36174 high-latency links. Some features may enable behavior which must not
36175 be on by default, e.g.@: because it would confuse older clients or
36176 stubs. Other features may describe packets which could be
36177 automatically probed for, but are not. These features must be
36178 reported before @value{GDBN} will use them. This ``default
36179 unsupported'' behavior is not appropriate for all packets, but it
36180 helps to keep the initial connection time under control with new
36181 versions of @value{GDBN} which support increasing numbers of packets.
36185 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36186 The stub supports or does not support each returned @var{stubfeature},
36187 depending on the form of each @var{stubfeature} (see below for the
36190 An empty reply indicates that @samp{qSupported} is not recognized,
36191 or that no features needed to be reported to @value{GDBN}.
36194 The allowed forms for each feature (either a @var{gdbfeature} in the
36195 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36199 @item @var{name}=@var{value}
36200 The remote protocol feature @var{name} is supported, and associated
36201 with the specified @var{value}. The format of @var{value} depends
36202 on the feature, but it must not include a semicolon.
36204 The remote protocol feature @var{name} is supported, and does not
36205 need an associated value.
36207 The remote protocol feature @var{name} is not supported.
36209 The remote protocol feature @var{name} may be supported, and
36210 @value{GDBN} should auto-detect support in some other way when it is
36211 needed. This form will not be used for @var{gdbfeature} notifications,
36212 but may be used for @var{stubfeature} responses.
36215 Whenever the stub receives a @samp{qSupported} request, the
36216 supplied set of @value{GDBN} features should override any previous
36217 request. This allows @value{GDBN} to put the stub in a known
36218 state, even if the stub had previously been communicating with
36219 a different version of @value{GDBN}.
36221 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36226 This feature indicates whether @value{GDBN} supports multiprocess
36227 extensions to the remote protocol. @value{GDBN} does not use such
36228 extensions unless the stub also reports that it supports them by
36229 including @samp{multiprocess+} in its @samp{qSupported} reply.
36230 @xref{multiprocess extensions}, for details.
36233 This feature indicates that @value{GDBN} supports the XML target
36234 description. If the stub sees @samp{xmlRegisters=} with target
36235 specific strings separated by a comma, it will report register
36239 This feature indicates whether @value{GDBN} supports the
36240 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36241 instruction reply packet}).
36244 This feature indicates whether @value{GDBN} supports the swbreak stop
36245 reason in stop replies. @xref{swbreak stop reason}, for details.
36248 This feature indicates whether @value{GDBN} supports the hwbreak stop
36249 reason in stop replies. @xref{swbreak stop reason}, for details.
36252 This feature indicates whether @value{GDBN} supports fork event
36253 extensions to the remote protocol. @value{GDBN} does not use such
36254 extensions unless the stub also reports that it supports them by
36255 including @samp{fork-events+} in its @samp{qSupported} reply.
36258 This feature indicates whether @value{GDBN} supports vfork event
36259 extensions to the remote protocol. @value{GDBN} does not use such
36260 extensions unless the stub also reports that it supports them by
36261 including @samp{vfork-events+} in its @samp{qSupported} reply.
36264 Stubs should ignore any unknown values for
36265 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36266 packet supports receiving packets of unlimited length (earlier
36267 versions of @value{GDBN} may reject overly long responses). Additional values
36268 for @var{gdbfeature} may be defined in the future to let the stub take
36269 advantage of new features in @value{GDBN}, e.g.@: incompatible
36270 improvements in the remote protocol---the @samp{multiprocess} feature is
36271 an example of such a feature. The stub's reply should be independent
36272 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36273 describes all the features it supports, and then the stub replies with
36274 all the features it supports.
36276 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36277 responses, as long as each response uses one of the standard forms.
36279 Some features are flags. A stub which supports a flag feature
36280 should respond with a @samp{+} form response. Other features
36281 require values, and the stub should respond with an @samp{=}
36284 Each feature has a default value, which @value{GDBN} will use if
36285 @samp{qSupported} is not available or if the feature is not mentioned
36286 in the @samp{qSupported} response. The default values are fixed; a
36287 stub is free to omit any feature responses that match the defaults.
36289 Not all features can be probed, but for those which can, the probing
36290 mechanism is useful: in some cases, a stub's internal
36291 architecture may not allow the protocol layer to know some information
36292 about the underlying target in advance. This is especially common in
36293 stubs which may be configured for multiple targets.
36295 These are the currently defined stub features and their properties:
36297 @multitable @columnfractions 0.35 0.2 0.12 0.2
36298 @c NOTE: The first row should be @headitem, but we do not yet require
36299 @c a new enough version of Texinfo (4.7) to use @headitem.
36301 @tab Value Required
36305 @item @samp{PacketSize}
36310 @item @samp{qXfer:auxv:read}
36315 @item @samp{qXfer:btrace:read}
36320 @item @samp{qXfer:btrace-conf:read}
36325 @item @samp{qXfer:exec-file:read}
36330 @item @samp{qXfer:features:read}
36335 @item @samp{qXfer:libraries:read}
36340 @item @samp{qXfer:libraries-svr4:read}
36345 @item @samp{augmented-libraries-svr4-read}
36350 @item @samp{qXfer:memory-map:read}
36355 @item @samp{qXfer:sdata:read}
36360 @item @samp{qXfer:spu:read}
36365 @item @samp{qXfer:spu:write}
36370 @item @samp{qXfer:siginfo:read}
36375 @item @samp{qXfer:siginfo:write}
36380 @item @samp{qXfer:threads:read}
36385 @item @samp{qXfer:traceframe-info:read}
36390 @item @samp{qXfer:uib:read}
36395 @item @samp{qXfer:fdpic:read}
36400 @item @samp{Qbtrace:off}
36405 @item @samp{Qbtrace:bts}
36410 @item @samp{Qbtrace:pt}
36415 @item @samp{Qbtrace-conf:bts:size}
36420 @item @samp{Qbtrace-conf:pt:size}
36425 @item @samp{QNonStop}
36430 @item @samp{QPassSignals}
36435 @item @samp{QStartNoAckMode}
36440 @item @samp{multiprocess}
36445 @item @samp{ConditionalBreakpoints}
36450 @item @samp{ConditionalTracepoints}
36455 @item @samp{ReverseContinue}
36460 @item @samp{ReverseStep}
36465 @item @samp{TracepointSource}
36470 @item @samp{QAgent}
36475 @item @samp{QAllow}
36480 @item @samp{QDisableRandomization}
36485 @item @samp{EnableDisableTracepoints}
36490 @item @samp{QTBuffer:size}
36495 @item @samp{tracenz}
36500 @item @samp{BreakpointCommands}
36505 @item @samp{swbreak}
36510 @item @samp{hwbreak}
36515 @item @samp{fork-events}
36520 @item @samp{vfork-events}
36527 These are the currently defined stub features, in more detail:
36530 @cindex packet size, remote protocol
36531 @item PacketSize=@var{bytes}
36532 The remote stub can accept packets up to at least @var{bytes} in
36533 length. @value{GDBN} will send packets up to this size for bulk
36534 transfers, and will never send larger packets. This is a limit on the
36535 data characters in the packet, including the frame and checksum.
36536 There is no trailing NUL byte in a remote protocol packet; if the stub
36537 stores packets in a NUL-terminated format, it should allow an extra
36538 byte in its buffer for the NUL. If this stub feature is not supported,
36539 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36541 @item qXfer:auxv:read
36542 The remote stub understands the @samp{qXfer:auxv:read} packet
36543 (@pxref{qXfer auxiliary vector read}).
36545 @item qXfer:btrace:read
36546 The remote stub understands the @samp{qXfer:btrace:read}
36547 packet (@pxref{qXfer btrace read}).
36549 @item qXfer:btrace-conf:read
36550 The remote stub understands the @samp{qXfer:btrace-conf:read}
36551 packet (@pxref{qXfer btrace-conf read}).
36553 @item qXfer:exec-file:read
36554 The remote stub understands the @samp{qXfer:exec-file:read} packet
36555 (@pxref{qXfer executable filename read}).
36557 @item qXfer:features:read
36558 The remote stub understands the @samp{qXfer:features:read} packet
36559 (@pxref{qXfer target description read}).
36561 @item qXfer:libraries:read
36562 The remote stub understands the @samp{qXfer:libraries:read} packet
36563 (@pxref{qXfer library list read}).
36565 @item qXfer:libraries-svr4:read
36566 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36567 (@pxref{qXfer svr4 library list read}).
36569 @item augmented-libraries-svr4-read
36570 The remote stub understands the augmented form of the
36571 @samp{qXfer:libraries-svr4:read} packet
36572 (@pxref{qXfer svr4 library list read}).
36574 @item qXfer:memory-map:read
36575 The remote stub understands the @samp{qXfer:memory-map:read} packet
36576 (@pxref{qXfer memory map read}).
36578 @item qXfer:sdata:read
36579 The remote stub understands the @samp{qXfer:sdata:read} packet
36580 (@pxref{qXfer sdata read}).
36582 @item qXfer:spu:read
36583 The remote stub understands the @samp{qXfer:spu:read} packet
36584 (@pxref{qXfer spu read}).
36586 @item qXfer:spu:write
36587 The remote stub understands the @samp{qXfer:spu:write} packet
36588 (@pxref{qXfer spu write}).
36590 @item qXfer:siginfo:read
36591 The remote stub understands the @samp{qXfer:siginfo:read} packet
36592 (@pxref{qXfer siginfo read}).
36594 @item qXfer:siginfo:write
36595 The remote stub understands the @samp{qXfer:siginfo:write} packet
36596 (@pxref{qXfer siginfo write}).
36598 @item qXfer:threads:read
36599 The remote stub understands the @samp{qXfer:threads:read} packet
36600 (@pxref{qXfer threads read}).
36602 @item qXfer:traceframe-info:read
36603 The remote stub understands the @samp{qXfer:traceframe-info:read}
36604 packet (@pxref{qXfer traceframe info read}).
36606 @item qXfer:uib:read
36607 The remote stub understands the @samp{qXfer:uib:read}
36608 packet (@pxref{qXfer unwind info block}).
36610 @item qXfer:fdpic:read
36611 The remote stub understands the @samp{qXfer:fdpic:read}
36612 packet (@pxref{qXfer fdpic loadmap read}).
36615 The remote stub understands the @samp{QNonStop} packet
36616 (@pxref{QNonStop}).
36619 The remote stub understands the @samp{QPassSignals} packet
36620 (@pxref{QPassSignals}).
36622 @item QStartNoAckMode
36623 The remote stub understands the @samp{QStartNoAckMode} packet and
36624 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36627 @anchor{multiprocess extensions}
36628 @cindex multiprocess extensions, in remote protocol
36629 The remote stub understands the multiprocess extensions to the remote
36630 protocol syntax. The multiprocess extensions affect the syntax of
36631 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36632 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36633 replies. Note that reporting this feature indicates support for the
36634 syntactic extensions only, not that the stub necessarily supports
36635 debugging of more than one process at a time. The stub must not use
36636 multiprocess extensions in packet replies unless @value{GDBN} has also
36637 indicated it supports them in its @samp{qSupported} request.
36639 @item qXfer:osdata:read
36640 The remote stub understands the @samp{qXfer:osdata:read} packet
36641 ((@pxref{qXfer osdata read}).
36643 @item ConditionalBreakpoints
36644 The target accepts and implements evaluation of conditional expressions
36645 defined for breakpoints. The target will only report breakpoint triggers
36646 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36648 @item ConditionalTracepoints
36649 The remote stub accepts and implements conditional expressions defined
36650 for tracepoints (@pxref{Tracepoint Conditions}).
36652 @item ReverseContinue
36653 The remote stub accepts and implements the reverse continue packet
36657 The remote stub accepts and implements the reverse step packet
36660 @item TracepointSource
36661 The remote stub understands the @samp{QTDPsrc} packet that supplies
36662 the source form of tracepoint definitions.
36665 The remote stub understands the @samp{QAgent} packet.
36668 The remote stub understands the @samp{QAllow} packet.
36670 @item QDisableRandomization
36671 The remote stub understands the @samp{QDisableRandomization} packet.
36673 @item StaticTracepoint
36674 @cindex static tracepoints, in remote protocol
36675 The remote stub supports static tracepoints.
36677 @item InstallInTrace
36678 @anchor{install tracepoint in tracing}
36679 The remote stub supports installing tracepoint in tracing.
36681 @item EnableDisableTracepoints
36682 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36683 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36684 to be enabled and disabled while a trace experiment is running.
36686 @item QTBuffer:size
36687 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36688 packet that allows to change the size of the trace buffer.
36691 @cindex string tracing, in remote protocol
36692 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36693 See @ref{Bytecode Descriptions} for details about the bytecode.
36695 @item BreakpointCommands
36696 @cindex breakpoint commands, in remote protocol
36697 The remote stub supports running a breakpoint's command list itself,
36698 rather than reporting the hit to @value{GDBN}.
36701 The remote stub understands the @samp{Qbtrace:off} packet.
36704 The remote stub understands the @samp{Qbtrace:bts} packet.
36707 The remote stub understands the @samp{Qbtrace:pt} packet.
36709 @item Qbtrace-conf:bts:size
36710 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36712 @item Qbtrace-conf:pt:size
36713 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36716 The remote stub reports the @samp{swbreak} stop reason for memory
36720 The remote stub reports the @samp{hwbreak} stop reason for hardware
36724 The remote stub reports the @samp{fork} stop reason for fork events.
36727 The remote stub reports the @samp{vfork} stop reason for vfork events
36728 and vforkdone events.
36733 @cindex symbol lookup, remote request
36734 @cindex @samp{qSymbol} packet
36735 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36736 requests. Accept requests from the target for the values of symbols.
36741 The target does not need to look up any (more) symbols.
36742 @item qSymbol:@var{sym_name}
36743 The target requests the value of symbol @var{sym_name} (hex encoded).
36744 @value{GDBN} may provide the value by using the
36745 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36749 @item qSymbol:@var{sym_value}:@var{sym_name}
36750 Set the value of @var{sym_name} to @var{sym_value}.
36752 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36753 target has previously requested.
36755 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36756 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36762 The target does not need to look up any (more) symbols.
36763 @item qSymbol:@var{sym_name}
36764 The target requests the value of a new symbol @var{sym_name} (hex
36765 encoded). @value{GDBN} will continue to supply the values of symbols
36766 (if available), until the target ceases to request them.
36771 @itemx QTDisconnected
36778 @itemx qTMinFTPILen
36780 @xref{Tracepoint Packets}.
36782 @item qThreadExtraInfo,@var{thread-id}
36783 @cindex thread attributes info, remote request
36784 @cindex @samp{qThreadExtraInfo} packet
36785 Obtain from the target OS a printable string description of thread
36786 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36787 for the forms of @var{thread-id}. This
36788 string may contain anything that the target OS thinks is interesting
36789 for @value{GDBN} to tell the user about the thread. The string is
36790 displayed in @value{GDBN}'s @code{info threads} display. Some
36791 examples of possible thread extra info strings are @samp{Runnable}, or
36792 @samp{Blocked on Mutex}.
36796 @item @var{XX}@dots{}
36797 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36798 comprising the printable string containing the extra information about
36799 the thread's attributes.
36802 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36803 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36804 conventions above. Please don't use this packet as a model for new
36823 @xref{Tracepoint Packets}.
36825 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36826 @cindex read special object, remote request
36827 @cindex @samp{qXfer} packet
36828 @anchor{qXfer read}
36829 Read uninterpreted bytes from the target's special data area
36830 identified by the keyword @var{object}. Request @var{length} bytes
36831 starting at @var{offset} bytes into the data. The content and
36832 encoding of @var{annex} is specific to @var{object}; it can supply
36833 additional details about what data to access.
36835 Here are the specific requests of this form defined so far. All
36836 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36837 formats, listed below.
36840 @item qXfer:auxv:read::@var{offset},@var{length}
36841 @anchor{qXfer auxiliary vector read}
36842 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36843 auxiliary vector}. Note @var{annex} must be empty.
36845 This packet is not probed by default; the remote stub must request it,
36846 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36848 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36849 @anchor{qXfer btrace read}
36851 Return a description of the current branch trace.
36852 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36853 packet may have one of the following values:
36857 Returns all available branch trace.
36860 Returns all available branch trace if the branch trace changed since
36861 the last read request.
36864 Returns the new branch trace since the last read request. Adds a new
36865 block to the end of the trace that begins at zero and ends at the source
36866 location of the first branch in the trace buffer. This extra block is
36867 used to stitch traces together.
36869 If the trace buffer overflowed, returns an error indicating the overflow.
36872 This packet is not probed by default; the remote stub must request it
36873 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36875 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36876 @anchor{qXfer btrace-conf read}
36878 Return a description of the current branch trace configuration.
36879 @xref{Branch Trace Configuration Format}.
36881 This packet is not probed by default; the remote stub must request it
36882 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36884 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36885 @anchor{qXfer executable filename read}
36886 Return the full absolute name of the file that was executed to create
36887 a process running on the remote system. The annex specifies the
36888 numeric process ID of the process to query, encoded as a hexadecimal
36889 number. If the annex part is empty the remote stub should return the
36890 filename corresponding to the currently executing process.
36892 This packet is not probed by default; the remote stub must request it,
36893 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36895 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36896 @anchor{qXfer target description read}
36897 Access the @dfn{target description}. @xref{Target Descriptions}. The
36898 annex specifies which XML document to access. The main description is
36899 always loaded from the @samp{target.xml} annex.
36901 This packet is not probed by default; the remote stub must request it,
36902 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36904 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36905 @anchor{qXfer library list read}
36906 Access the target's list of loaded libraries. @xref{Library List Format}.
36907 The annex part of the generic @samp{qXfer} packet must be empty
36908 (@pxref{qXfer read}).
36910 Targets which maintain a list of libraries in the program's memory do
36911 not need to implement this packet; it is designed for platforms where
36912 the operating system manages the list of loaded libraries.
36914 This packet is not probed by default; the remote stub must request it,
36915 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36917 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36918 @anchor{qXfer svr4 library list read}
36919 Access the target's list of loaded libraries when the target is an SVR4
36920 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36921 of the generic @samp{qXfer} packet must be empty unless the remote
36922 stub indicated it supports the augmented form of this packet
36923 by supplying an appropriate @samp{qSupported} response
36924 (@pxref{qXfer read}, @ref{qSupported}).
36926 This packet is optional for better performance on SVR4 targets.
36927 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36929 This packet is not probed by default; the remote stub must request it,
36930 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36932 If the remote stub indicates it supports the augmented form of this
36933 packet then the annex part of the generic @samp{qXfer} packet may
36934 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36935 arguments. The currently supported arguments are:
36938 @item start=@var{address}
36939 A hexadecimal number specifying the address of the @samp{struct
36940 link_map} to start reading the library list from. If unset or zero
36941 then the first @samp{struct link_map} in the library list will be
36942 chosen as the starting point.
36944 @item prev=@var{address}
36945 A hexadecimal number specifying the address of the @samp{struct
36946 link_map} immediately preceding the @samp{struct link_map}
36947 specified by the @samp{start} argument. If unset or zero then
36948 the remote stub will expect that no @samp{struct link_map}
36949 exists prior to the starting point.
36953 Arguments that are not understood by the remote stub will be silently
36956 @item qXfer:memory-map:read::@var{offset},@var{length}
36957 @anchor{qXfer memory map read}
36958 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36959 annex part of the generic @samp{qXfer} packet must be empty
36960 (@pxref{qXfer read}).
36962 This packet is not probed by default; the remote stub must request it,
36963 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36965 @item qXfer:sdata:read::@var{offset},@var{length}
36966 @anchor{qXfer sdata read}
36968 Read contents of the extra collected static tracepoint marker
36969 information. The annex part of the generic @samp{qXfer} packet must
36970 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36973 This packet is not probed by default; the remote stub must request it,
36974 by supplying an appropriate @samp{qSupported} response
36975 (@pxref{qSupported}).
36977 @item qXfer:siginfo:read::@var{offset},@var{length}
36978 @anchor{qXfer siginfo read}
36979 Read contents of the extra signal information on the target
36980 system. The annex part of the generic @samp{qXfer} packet must be
36981 empty (@pxref{qXfer read}).
36983 This packet is not probed by default; the remote stub must request it,
36984 by supplying an appropriate @samp{qSupported} response
36985 (@pxref{qSupported}).
36987 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36988 @anchor{qXfer spu read}
36989 Read contents of an @code{spufs} file on the target system. The
36990 annex specifies which file to read; it must be of the form
36991 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36992 in the target process, and @var{name} identifes the @code{spufs} file
36993 in that context to be accessed.
36995 This packet is not probed by default; the remote stub must request it,
36996 by supplying an appropriate @samp{qSupported} response
36997 (@pxref{qSupported}).
36999 @item qXfer:threads:read::@var{offset},@var{length}
37000 @anchor{qXfer threads read}
37001 Access the list of threads on target. @xref{Thread List Format}. The
37002 annex part of the generic @samp{qXfer} packet must be empty
37003 (@pxref{qXfer read}).
37005 This packet is not probed by default; the remote stub must request it,
37006 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37008 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37009 @anchor{qXfer traceframe info read}
37011 Return a description of the current traceframe's contents.
37012 @xref{Traceframe Info Format}. The annex part of the generic
37013 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37015 This packet is not probed by default; the remote stub must request it,
37016 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37018 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37019 @anchor{qXfer unwind info block}
37021 Return the unwind information block for @var{pc}. This packet is used
37022 on OpenVMS/ia64 to ask the kernel unwind information.
37024 This packet is not probed by default.
37026 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37027 @anchor{qXfer fdpic loadmap read}
37028 Read contents of @code{loadmap}s on the target system. The
37029 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37030 executable @code{loadmap} or interpreter @code{loadmap} to read.
37032 This packet is not probed by default; the remote stub must request it,
37033 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37035 @item qXfer:osdata:read::@var{offset},@var{length}
37036 @anchor{qXfer osdata read}
37037 Access the target's @dfn{operating system information}.
37038 @xref{Operating System Information}.
37045 Data @var{data} (@pxref{Binary Data}) has been read from the
37046 target. There may be more data at a higher address (although
37047 it is permitted to return @samp{m} even for the last valid
37048 block of data, as long as at least one byte of data was read).
37049 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37053 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37054 There is no more data to be read. It is possible for @var{data} to
37055 have fewer bytes than the @var{length} in the request.
37058 The @var{offset} in the request is at the end of the data.
37059 There is no more data to be read.
37062 The request was malformed, or @var{annex} was invalid.
37065 The offset was invalid, or there was an error encountered reading the data.
37066 The @var{nn} part is a hex-encoded @code{errno} value.
37069 An empty reply indicates the @var{object} string was not recognized by
37070 the stub, or that the object does not support reading.
37073 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37074 @cindex write data into object, remote request
37075 @anchor{qXfer write}
37076 Write uninterpreted bytes into the target's special data area
37077 identified by the keyword @var{object}, starting at @var{offset} bytes
37078 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37079 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37080 is specific to @var{object}; it can supply additional details about what data
37083 Here are the specific requests of this form defined so far. All
37084 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37085 formats, listed below.
37088 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37089 @anchor{qXfer siginfo write}
37090 Write @var{data} to the extra signal information on the target system.
37091 The annex part of the generic @samp{qXfer} packet must be
37092 empty (@pxref{qXfer write}).
37094 This packet is not probed by default; the remote stub must request it,
37095 by supplying an appropriate @samp{qSupported} response
37096 (@pxref{qSupported}).
37098 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37099 @anchor{qXfer spu write}
37100 Write @var{data} to an @code{spufs} file on the target system. The
37101 annex specifies which file to write; it must be of the form
37102 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37103 in the target process, and @var{name} identifes the @code{spufs} file
37104 in that context to be accessed.
37106 This packet is not probed by default; the remote stub must request it,
37107 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37113 @var{nn} (hex encoded) is the number of bytes written.
37114 This may be fewer bytes than supplied in the request.
37117 The request was malformed, or @var{annex} was invalid.
37120 The offset was invalid, or there was an error encountered writing the data.
37121 The @var{nn} part is a hex-encoded @code{errno} value.
37124 An empty reply indicates the @var{object} string was not
37125 recognized by the stub, or that the object does not support writing.
37128 @item qXfer:@var{object}:@var{operation}:@dots{}
37129 Requests of this form may be added in the future. When a stub does
37130 not recognize the @var{object} keyword, or its support for
37131 @var{object} does not recognize the @var{operation} keyword, the stub
37132 must respond with an empty packet.
37134 @item qAttached:@var{pid}
37135 @cindex query attached, remote request
37136 @cindex @samp{qAttached} packet
37137 Return an indication of whether the remote server attached to an
37138 existing process or created a new process. When the multiprocess
37139 protocol extensions are supported (@pxref{multiprocess extensions}),
37140 @var{pid} is an integer in hexadecimal format identifying the target
37141 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37142 the query packet will be simplified as @samp{qAttached}.
37144 This query is used, for example, to know whether the remote process
37145 should be detached or killed when a @value{GDBN} session is ended with
37146 the @code{quit} command.
37151 The remote server attached to an existing process.
37153 The remote server created a new process.
37155 A badly formed request or an error was encountered.
37159 Enable branch tracing for the current thread using Branch Trace Store.
37164 Branch tracing has been enabled.
37166 A badly formed request or an error was encountered.
37170 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37175 Branch tracing has been enabled.
37177 A badly formed request or an error was encountered.
37181 Disable branch tracing for the current thread.
37186 Branch tracing has been disabled.
37188 A badly formed request or an error was encountered.
37191 @item Qbtrace-conf:bts:size=@var{value}
37192 Set the requested ring buffer size for new threads that use the
37193 btrace recording method in bts format.
37198 The ring buffer size has been set.
37200 A badly formed request or an error was encountered.
37203 @item Qbtrace-conf:pt:size=@var{value}
37204 Set the requested ring buffer size for new threads that use the
37205 btrace recording method in pt format.
37210 The ring buffer size has been set.
37212 A badly formed request or an error was encountered.
37217 @node Architecture-Specific Protocol Details
37218 @section Architecture-Specific Protocol Details
37220 This section describes how the remote protocol is applied to specific
37221 target architectures. Also see @ref{Standard Target Features}, for
37222 details of XML target descriptions for each architecture.
37225 * ARM-Specific Protocol Details::
37226 * MIPS-Specific Protocol Details::
37229 @node ARM-Specific Protocol Details
37230 @subsection @acronym{ARM}-specific Protocol Details
37233 * ARM Breakpoint Kinds::
37236 @node ARM Breakpoint Kinds
37237 @subsubsection @acronym{ARM} Breakpoint Kinds
37238 @cindex breakpoint kinds, @acronym{ARM}
37240 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37245 16-bit Thumb mode breakpoint.
37248 32-bit Thumb mode (Thumb-2) breakpoint.
37251 32-bit @acronym{ARM} mode breakpoint.
37255 @node MIPS-Specific Protocol Details
37256 @subsection @acronym{MIPS}-specific Protocol Details
37259 * MIPS Register packet Format::
37260 * MIPS Breakpoint Kinds::
37263 @node MIPS Register packet Format
37264 @subsubsection @acronym{MIPS} Register Packet Format
37265 @cindex register packet format, @acronym{MIPS}
37267 The following @code{g}/@code{G} packets have previously been defined.
37268 In the below, some thirty-two bit registers are transferred as
37269 sixty-four bits. Those registers should be zero/sign extended (which?)
37270 to fill the space allocated. Register bytes are transferred in target
37271 byte order. The two nibbles within a register byte are transferred
37272 most-significant -- least-significant.
37277 All registers are transferred as thirty-two bit quantities in the order:
37278 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37279 registers; fsr; fir; fp.
37282 All registers are transferred as sixty-four bit quantities (including
37283 thirty-two bit registers such as @code{sr}). The ordering is the same
37288 @node MIPS Breakpoint Kinds
37289 @subsubsection @acronym{MIPS} Breakpoint Kinds
37290 @cindex breakpoint kinds, @acronym{MIPS}
37292 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37297 16-bit @acronym{MIPS16} mode breakpoint.
37300 16-bit @acronym{microMIPS} mode breakpoint.
37303 32-bit standard @acronym{MIPS} mode breakpoint.
37306 32-bit @acronym{microMIPS} mode breakpoint.
37310 @node Tracepoint Packets
37311 @section Tracepoint Packets
37312 @cindex tracepoint packets
37313 @cindex packets, tracepoint
37315 Here we describe the packets @value{GDBN} uses to implement
37316 tracepoints (@pxref{Tracepoints}).
37320 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37321 @cindex @samp{QTDP} packet
37322 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37323 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37324 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37325 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37326 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37327 the number of bytes that the target should copy elsewhere to make room
37328 for the tracepoint. If an @samp{X} is present, it introduces a
37329 tracepoint condition, which consists of a hexadecimal length, followed
37330 by a comma and hex-encoded bytes, in a manner similar to action
37331 encodings as described below. If the trailing @samp{-} is present,
37332 further @samp{QTDP} packets will follow to specify this tracepoint's
37338 The packet was understood and carried out.
37340 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37342 The packet was not recognized.
37345 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37346 Define actions to be taken when a tracepoint is hit. The @var{n} and
37347 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37348 this tracepoint. This packet may only be sent immediately after
37349 another @samp{QTDP} packet that ended with a @samp{-}. If the
37350 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37351 specifying more actions for this tracepoint.
37353 In the series of action packets for a given tracepoint, at most one
37354 can have an @samp{S} before its first @var{action}. If such a packet
37355 is sent, it and the following packets define ``while-stepping''
37356 actions. Any prior packets define ordinary actions --- that is, those
37357 taken when the tracepoint is first hit. If no action packet has an
37358 @samp{S}, then all the packets in the series specify ordinary
37359 tracepoint actions.
37361 The @samp{@var{action}@dots{}} portion of the packet is a series of
37362 actions, concatenated without separators. Each action has one of the
37368 Collect the registers whose bits are set in @var{mask},
37369 a hexadecimal number whose @var{i}'th bit is set if register number
37370 @var{i} should be collected. (The least significant bit is numbered
37371 zero.) Note that @var{mask} may be any number of digits long; it may
37372 not fit in a 32-bit word.
37374 @item M @var{basereg},@var{offset},@var{len}
37375 Collect @var{len} bytes of memory starting at the address in register
37376 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37377 @samp{-1}, then the range has a fixed address: @var{offset} is the
37378 address of the lowest byte to collect. The @var{basereg},
37379 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37380 values (the @samp{-1} value for @var{basereg} is a special case).
37382 @item X @var{len},@var{expr}
37383 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37384 it directs. The agent expression @var{expr} is as described in
37385 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37386 two-digit hex number in the packet; @var{len} is the number of bytes
37387 in the expression (and thus one-half the number of hex digits in the
37392 Any number of actions may be packed together in a single @samp{QTDP}
37393 packet, as long as the packet does not exceed the maximum packet
37394 length (400 bytes, for many stubs). There may be only one @samp{R}
37395 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37396 actions. Any registers referred to by @samp{M} and @samp{X} actions
37397 must be collected by a preceding @samp{R} action. (The
37398 ``while-stepping'' actions are treated as if they were attached to a
37399 separate tracepoint, as far as these restrictions are concerned.)
37404 The packet was understood and carried out.
37406 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37408 The packet was not recognized.
37411 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37412 @cindex @samp{QTDPsrc} packet
37413 Specify a source string of tracepoint @var{n} at address @var{addr}.
37414 This is useful to get accurate reproduction of the tracepoints
37415 originally downloaded at the beginning of the trace run. The @var{type}
37416 is the name of the tracepoint part, such as @samp{cond} for the
37417 tracepoint's conditional expression (see below for a list of types), while
37418 @var{bytes} is the string, encoded in hexadecimal.
37420 @var{start} is the offset of the @var{bytes} within the overall source
37421 string, while @var{slen} is the total length of the source string.
37422 This is intended for handling source strings that are longer than will
37423 fit in a single packet.
37424 @c Add detailed example when this info is moved into a dedicated
37425 @c tracepoint descriptions section.
37427 The available string types are @samp{at} for the location,
37428 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37429 @value{GDBN} sends a separate packet for each command in the action
37430 list, in the same order in which the commands are stored in the list.
37432 The target does not need to do anything with source strings except
37433 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37436 Although this packet is optional, and @value{GDBN} will only send it
37437 if the target replies with @samp{TracepointSource} @xref{General
37438 Query Packets}, it makes both disconnected tracing and trace files
37439 much easier to use. Otherwise the user must be careful that the
37440 tracepoints in effect while looking at trace frames are identical to
37441 the ones in effect during the trace run; even a small discrepancy
37442 could cause @samp{tdump} not to work, or a particular trace frame not
37445 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37446 @cindex define trace state variable, remote request
37447 @cindex @samp{QTDV} packet
37448 Create a new trace state variable, number @var{n}, with an initial
37449 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37450 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37451 the option of not using this packet for initial values of zero; the
37452 target should simply create the trace state variables as they are
37453 mentioned in expressions. The value @var{builtin} should be 1 (one)
37454 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37455 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37456 @samp{qTsV} packet had it set. The contents of @var{name} is the
37457 hex-encoded name (without the leading @samp{$}) of the trace state
37460 @item QTFrame:@var{n}
37461 @cindex @samp{QTFrame} packet
37462 Select the @var{n}'th tracepoint frame from the buffer, and use the
37463 register and memory contents recorded there to answer subsequent
37464 request packets from @value{GDBN}.
37466 A successful reply from the stub indicates that the stub has found the
37467 requested frame. The response is a series of parts, concatenated
37468 without separators, describing the frame we selected. Each part has
37469 one of the following forms:
37473 The selected frame is number @var{n} in the trace frame buffer;
37474 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37475 was no frame matching the criteria in the request packet.
37478 The selected trace frame records a hit of tracepoint number @var{t};
37479 @var{t} is a hexadecimal number.
37483 @item QTFrame:pc:@var{addr}
37484 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37485 currently selected frame whose PC is @var{addr};
37486 @var{addr} is a hexadecimal number.
37488 @item QTFrame:tdp:@var{t}
37489 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37490 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37491 is a hexadecimal number.
37493 @item QTFrame:range:@var{start}:@var{end}
37494 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37495 currently selected frame whose PC is between @var{start} (inclusive)
37496 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37499 @item QTFrame:outside:@var{start}:@var{end}
37500 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37501 frame @emph{outside} the given range of addresses (exclusive).
37504 @cindex @samp{qTMinFTPILen} packet
37505 This packet requests the minimum length of instruction at which a fast
37506 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37507 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37508 it depends on the target system being able to create trampolines in
37509 the first 64K of memory, which might or might not be possible for that
37510 system. So the reply to this packet will be 4 if it is able to
37517 The minimum instruction length is currently unknown.
37519 The minimum instruction length is @var{length}, where @var{length}
37520 is a hexadecimal number greater or equal to 1. A reply
37521 of 1 means that a fast tracepoint may be placed on any instruction
37522 regardless of size.
37524 An error has occurred.
37526 An empty reply indicates that the request is not supported by the stub.
37530 @cindex @samp{QTStart} packet
37531 Begin the tracepoint experiment. Begin collecting data from
37532 tracepoint hits in the trace frame buffer. This packet supports the
37533 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37534 instruction reply packet}).
37537 @cindex @samp{QTStop} packet
37538 End the tracepoint experiment. Stop collecting trace frames.
37540 @item QTEnable:@var{n}:@var{addr}
37542 @cindex @samp{QTEnable} packet
37543 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37544 experiment. If the tracepoint was previously disabled, then collection
37545 of data from it will resume.
37547 @item QTDisable:@var{n}:@var{addr}
37549 @cindex @samp{QTDisable} packet
37550 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37551 experiment. No more data will be collected from the tracepoint unless
37552 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37555 @cindex @samp{QTinit} packet
37556 Clear the table of tracepoints, and empty the trace frame buffer.
37558 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37559 @cindex @samp{QTro} packet
37560 Establish the given ranges of memory as ``transparent''. The stub
37561 will answer requests for these ranges from memory's current contents,
37562 if they were not collected as part of the tracepoint hit.
37564 @value{GDBN} uses this to mark read-only regions of memory, like those
37565 containing program code. Since these areas never change, they should
37566 still have the same contents they did when the tracepoint was hit, so
37567 there's no reason for the stub to refuse to provide their contents.
37569 @item QTDisconnected:@var{value}
37570 @cindex @samp{QTDisconnected} packet
37571 Set the choice to what to do with the tracing run when @value{GDBN}
37572 disconnects from the target. A @var{value} of 1 directs the target to
37573 continue the tracing run, while 0 tells the target to stop tracing if
37574 @value{GDBN} is no longer in the picture.
37577 @cindex @samp{qTStatus} packet
37578 Ask the stub if there is a trace experiment running right now.
37580 The reply has the form:
37584 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37585 @var{running} is a single digit @code{1} if the trace is presently
37586 running, or @code{0} if not. It is followed by semicolon-separated
37587 optional fields that an agent may use to report additional status.
37591 If the trace is not running, the agent may report any of several
37592 explanations as one of the optional fields:
37597 No trace has been run yet.
37599 @item tstop[:@var{text}]:0
37600 The trace was stopped by a user-originated stop command. The optional
37601 @var{text} field is a user-supplied string supplied as part of the
37602 stop command (for instance, an explanation of why the trace was
37603 stopped manually). It is hex-encoded.
37606 The trace stopped because the trace buffer filled up.
37608 @item tdisconnected:0
37609 The trace stopped because @value{GDBN} disconnected from the target.
37611 @item tpasscount:@var{tpnum}
37612 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37614 @item terror:@var{text}:@var{tpnum}
37615 The trace stopped because tracepoint @var{tpnum} had an error. The
37616 string @var{text} is available to describe the nature of the error
37617 (for instance, a divide by zero in the condition expression); it
37621 The trace stopped for some other reason.
37625 Additional optional fields supply statistical and other information.
37626 Although not required, they are extremely useful for users monitoring
37627 the progress of a trace run. If a trace has stopped, and these
37628 numbers are reported, they must reflect the state of the just-stopped
37633 @item tframes:@var{n}
37634 The number of trace frames in the buffer.
37636 @item tcreated:@var{n}
37637 The total number of trace frames created during the run. This may
37638 be larger than the trace frame count, if the buffer is circular.
37640 @item tsize:@var{n}
37641 The total size of the trace buffer, in bytes.
37643 @item tfree:@var{n}
37644 The number of bytes still unused in the buffer.
37646 @item circular:@var{n}
37647 The value of the circular trace buffer flag. @code{1} means that the
37648 trace buffer is circular and old trace frames will be discarded if
37649 necessary to make room, @code{0} means that the trace buffer is linear
37652 @item disconn:@var{n}
37653 The value of the disconnected tracing flag. @code{1} means that
37654 tracing will continue after @value{GDBN} disconnects, @code{0} means
37655 that the trace run will stop.
37659 @item qTP:@var{tp}:@var{addr}
37660 @cindex tracepoint status, remote request
37661 @cindex @samp{qTP} packet
37662 Ask the stub for the current state of tracepoint number @var{tp} at
37663 address @var{addr}.
37667 @item V@var{hits}:@var{usage}
37668 The tracepoint has been hit @var{hits} times so far during the trace
37669 run, and accounts for @var{usage} in the trace buffer. Note that
37670 @code{while-stepping} steps are not counted as separate hits, but the
37671 steps' space consumption is added into the usage number.
37675 @item qTV:@var{var}
37676 @cindex trace state variable value, remote request
37677 @cindex @samp{qTV} packet
37678 Ask the stub for the value of the trace state variable number @var{var}.
37683 The value of the variable is @var{value}. This will be the current
37684 value of the variable if the user is examining a running target, or a
37685 saved value if the variable was collected in the trace frame that the
37686 user is looking at. Note that multiple requests may result in
37687 different reply values, such as when requesting values while the
37688 program is running.
37691 The value of the variable is unknown. This would occur, for example,
37692 if the user is examining a trace frame in which the requested variable
37697 @cindex @samp{qTfP} packet
37699 @cindex @samp{qTsP} packet
37700 These packets request data about tracepoints that are being used by
37701 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37702 of data, and multiple @code{qTsP} to get additional pieces. Replies
37703 to these packets generally take the form of the @code{QTDP} packets
37704 that define tracepoints. (FIXME add detailed syntax)
37707 @cindex @samp{qTfV} packet
37709 @cindex @samp{qTsV} packet
37710 These packets request data about trace state variables that are on the
37711 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37712 and multiple @code{qTsV} to get additional variables. Replies to
37713 these packets follow the syntax of the @code{QTDV} packets that define
37714 trace state variables.
37720 @cindex @samp{qTfSTM} packet
37721 @cindex @samp{qTsSTM} packet
37722 These packets request data about static tracepoint markers that exist
37723 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37724 first piece of data, and multiple @code{qTsSTM} to get additional
37725 pieces. Replies to these packets take the following form:
37729 @item m @var{address}:@var{id}:@var{extra}
37731 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37732 a comma-separated list of markers
37734 (lower case letter @samp{L}) denotes end of list.
37736 An error occurred. The error number @var{nn} is given as hex digits.
37738 An empty reply indicates that the request is not supported by the
37742 The @var{address} is encoded in hex;
37743 @var{id} and @var{extra} are strings encoded in hex.
37745 In response to each query, the target will reply with a list of one or
37746 more markers, separated by commas. @value{GDBN} will respond to each
37747 reply with a request for more markers (using the @samp{qs} form of the
37748 query), until the target responds with @samp{l} (lower-case ell, for
37751 @item qTSTMat:@var{address}
37753 @cindex @samp{qTSTMat} packet
37754 This packets requests data about static tracepoint markers in the
37755 target program at @var{address}. Replies to this packet follow the
37756 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37757 tracepoint markers.
37759 @item QTSave:@var{filename}
37760 @cindex @samp{QTSave} packet
37761 This packet directs the target to save trace data to the file name
37762 @var{filename} in the target's filesystem. The @var{filename} is encoded
37763 as a hex string; the interpretation of the file name (relative vs
37764 absolute, wild cards, etc) is up to the target.
37766 @item qTBuffer:@var{offset},@var{len}
37767 @cindex @samp{qTBuffer} packet
37768 Return up to @var{len} bytes of the current contents of trace buffer,
37769 starting at @var{offset}. The trace buffer is treated as if it were
37770 a contiguous collection of traceframes, as per the trace file format.
37771 The reply consists as many hex-encoded bytes as the target can deliver
37772 in a packet; it is not an error to return fewer than were asked for.
37773 A reply consisting of just @code{l} indicates that no bytes are
37776 @item QTBuffer:circular:@var{value}
37777 This packet directs the target to use a circular trace buffer if
37778 @var{value} is 1, or a linear buffer if the value is 0.
37780 @item QTBuffer:size:@var{size}
37781 @anchor{QTBuffer-size}
37782 @cindex @samp{QTBuffer size} packet
37783 This packet directs the target to make the trace buffer be of size
37784 @var{size} if possible. A value of @code{-1} tells the target to
37785 use whatever size it prefers.
37787 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37788 @cindex @samp{QTNotes} packet
37789 This packet adds optional textual notes to the trace run. Allowable
37790 types include @code{user}, @code{notes}, and @code{tstop}, the
37791 @var{text} fields are arbitrary strings, hex-encoded.
37795 @subsection Relocate instruction reply packet
37796 When installing fast tracepoints in memory, the target may need to
37797 relocate the instruction currently at the tracepoint address to a
37798 different address in memory. For most instructions, a simple copy is
37799 enough, but, for example, call instructions that implicitly push the
37800 return address on the stack, and relative branches or other
37801 PC-relative instructions require offset adjustment, so that the effect
37802 of executing the instruction at a different address is the same as if
37803 it had executed in the original location.
37805 In response to several of the tracepoint packets, the target may also
37806 respond with a number of intermediate @samp{qRelocInsn} request
37807 packets before the final result packet, to have @value{GDBN} handle
37808 this relocation operation. If a packet supports this mechanism, its
37809 documentation will explicitly say so. See for example the above
37810 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37811 format of the request is:
37814 @item qRelocInsn:@var{from};@var{to}
37816 This requests @value{GDBN} to copy instruction at address @var{from}
37817 to address @var{to}, possibly adjusted so that executing the
37818 instruction at @var{to} has the same effect as executing it at
37819 @var{from}. @value{GDBN} writes the adjusted instruction to target
37820 memory starting at @var{to}.
37825 @item qRelocInsn:@var{adjusted_size}
37826 Informs the stub the relocation is complete. The @var{adjusted_size} is
37827 the length in bytes of resulting relocated instruction sequence.
37829 A badly formed request was detected, or an error was encountered while
37830 relocating the instruction.
37833 @node Host I/O Packets
37834 @section Host I/O Packets
37835 @cindex Host I/O, remote protocol
37836 @cindex file transfer, remote protocol
37838 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37839 operations on the far side of a remote link. For example, Host I/O is
37840 used to upload and download files to a remote target with its own
37841 filesystem. Host I/O uses the same constant values and data structure
37842 layout as the target-initiated File-I/O protocol. However, the
37843 Host I/O packets are structured differently. The target-initiated
37844 protocol relies on target memory to store parameters and buffers.
37845 Host I/O requests are initiated by @value{GDBN}, and the
37846 target's memory is not involved. @xref{File-I/O Remote Protocol
37847 Extension}, for more details on the target-initiated protocol.
37849 The Host I/O request packets all encode a single operation along with
37850 its arguments. They have this format:
37854 @item vFile:@var{operation}: @var{parameter}@dots{}
37855 @var{operation} is the name of the particular request; the target
37856 should compare the entire packet name up to the second colon when checking
37857 for a supported operation. The format of @var{parameter} depends on
37858 the operation. Numbers are always passed in hexadecimal. Negative
37859 numbers have an explicit minus sign (i.e.@: two's complement is not
37860 used). Strings (e.g.@: filenames) are encoded as a series of
37861 hexadecimal bytes. The last argument to a system call may be a
37862 buffer of escaped binary data (@pxref{Binary Data}).
37866 The valid responses to Host I/O packets are:
37870 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37871 @var{result} is the integer value returned by this operation, usually
37872 non-negative for success and -1 for errors. If an error has occured,
37873 @var{errno} will be included in the result specifying a
37874 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37875 operations which return data, @var{attachment} supplies the data as a
37876 binary buffer. Binary buffers in response packets are escaped in the
37877 normal way (@pxref{Binary Data}). See the individual packet
37878 documentation for the interpretation of @var{result} and
37882 An empty response indicates that this operation is not recognized.
37886 These are the supported Host I/O operations:
37889 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37890 Open a file at @var{filename} and return a file descriptor for it, or
37891 return -1 if an error occurs. The @var{filename} is a string,
37892 @var{flags} is an integer indicating a mask of open flags
37893 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37894 of mode bits to use if the file is created (@pxref{mode_t Values}).
37895 @xref{open}, for details of the open flags and mode values.
37897 @item vFile:close: @var{fd}
37898 Close the open file corresponding to @var{fd} and return 0, or
37899 -1 if an error occurs.
37901 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37902 Read data from the open file corresponding to @var{fd}. Up to
37903 @var{count} bytes will be read from the file, starting at @var{offset}
37904 relative to the start of the file. The target may read fewer bytes;
37905 common reasons include packet size limits and an end-of-file
37906 condition. The number of bytes read is returned. Zero should only be
37907 returned for a successful read at the end of the file, or if
37908 @var{count} was zero.
37910 The data read should be returned as a binary attachment on success.
37911 If zero bytes were read, the response should include an empty binary
37912 attachment (i.e.@: a trailing semicolon). The return value is the
37913 number of target bytes read; the binary attachment may be longer if
37914 some characters were escaped.
37916 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37917 Write @var{data} (a binary buffer) to the open file corresponding
37918 to @var{fd}. Start the write at @var{offset} from the start of the
37919 file. Unlike many @code{write} system calls, there is no
37920 separate @var{count} argument; the length of @var{data} in the
37921 packet is used. @samp{vFile:write} returns the number of bytes written,
37922 which may be shorter than the length of @var{data}, or -1 if an
37925 @item vFile:fstat: @var{fd}
37926 Get information about the open file corresponding to @var{fd}.
37927 On success the information is returned as a binary attachment
37928 and the return value is the size of this attachment in bytes.
37929 If an error occurs the return value is -1. The format of the
37930 returned binary attachment is as described in @ref{struct stat}.
37932 @item vFile:unlink: @var{filename}
37933 Delete the file at @var{filename} on the target. Return 0,
37934 or -1 if an error occurs. The @var{filename} is a string.
37936 @item vFile:readlink: @var{filename}
37937 Read value of symbolic link @var{filename} on the target. Return
37938 the number of bytes read, or -1 if an error occurs.
37940 The data read should be returned as a binary attachment on success.
37941 If zero bytes were read, the response should include an empty binary
37942 attachment (i.e.@: a trailing semicolon). The return value is the
37943 number of target bytes read; the binary attachment may be longer if
37944 some characters were escaped.
37946 @item vFile:setfs: @var{pid}
37947 Select the filesystem on which @code{vFile} operations with
37948 @var{filename} arguments will operate. This is required for
37949 @value{GDBN} to be able to access files on remote targets where
37950 the remote stub does not share a common filesystem with the
37953 If @var{pid} is nonzero, select the filesystem as seen by process
37954 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37955 the remote stub. Return 0 on success, or -1 if an error occurs.
37956 If @code{vFile:setfs:} indicates success, the selected filesystem
37957 remains selected until the next successful @code{vFile:setfs:}
37963 @section Interrupts
37964 @cindex interrupts (remote protocol)
37966 When a program on the remote target is running, @value{GDBN} may
37967 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37968 a @code{BREAK} followed by @code{g},
37969 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37971 The precise meaning of @code{BREAK} is defined by the transport
37972 mechanism and may, in fact, be undefined. @value{GDBN} does not
37973 currently define a @code{BREAK} mechanism for any of the network
37974 interfaces except for TCP, in which case @value{GDBN} sends the
37975 @code{telnet} BREAK sequence.
37977 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37978 transport mechanisms. It is represented by sending the single byte
37979 @code{0x03} without any of the usual packet overhead described in
37980 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37981 transmitted as part of a packet, it is considered to be packet data
37982 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37983 (@pxref{X packet}), used for binary downloads, may include an unescaped
37984 @code{0x03} as part of its packet.
37986 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37987 When Linux kernel receives this sequence from serial port,
37988 it stops execution and connects to gdb.
37990 Stubs are not required to recognize these interrupt mechanisms and the
37991 precise meaning associated with receipt of the interrupt is
37992 implementation defined. If the target supports debugging of multiple
37993 threads and/or processes, it should attempt to interrupt all
37994 currently-executing threads and processes.
37995 If the stub is successful at interrupting the
37996 running program, it should send one of the stop
37997 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37998 of successfully stopping the program in all-stop mode, and a stop reply
37999 for each stopped thread in non-stop mode.
38000 Interrupts received while the
38001 program is stopped are discarded.
38003 @node Notification Packets
38004 @section Notification Packets
38005 @cindex notification packets
38006 @cindex packets, notification
38008 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38009 packets that require no acknowledgment. Both the GDB and the stub
38010 may send notifications (although the only notifications defined at
38011 present are sent by the stub). Notifications carry information
38012 without incurring the round-trip latency of an acknowledgment, and so
38013 are useful for low-impact communications where occasional packet loss
38016 A notification packet has the form @samp{% @var{data} #
38017 @var{checksum}}, where @var{data} is the content of the notification,
38018 and @var{checksum} is a checksum of @var{data}, computed and formatted
38019 as for ordinary @value{GDBN} packets. A notification's @var{data}
38020 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38021 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38022 to acknowledge the notification's receipt or to report its corruption.
38024 Every notification's @var{data} begins with a name, which contains no
38025 colon characters, followed by a colon character.
38027 Recipients should silently ignore corrupted notifications and
38028 notifications they do not understand. Recipients should restart
38029 timeout periods on receipt of a well-formed notification, whether or
38030 not they understand it.
38032 Senders should only send the notifications described here when this
38033 protocol description specifies that they are permitted. In the
38034 future, we may extend the protocol to permit existing notifications in
38035 new contexts; this rule helps older senders avoid confusing newer
38038 (Older versions of @value{GDBN} ignore bytes received until they see
38039 the @samp{$} byte that begins an ordinary packet, so new stubs may
38040 transmit notifications without fear of confusing older clients. There
38041 are no notifications defined for @value{GDBN} to send at the moment, but we
38042 assume that most older stubs would ignore them, as well.)
38044 Each notification is comprised of three parts:
38046 @item @var{name}:@var{event}
38047 The notification packet is sent by the side that initiates the
38048 exchange (currently, only the stub does that), with @var{event}
38049 carrying the specific information about the notification, and
38050 @var{name} specifying the name of the notification.
38052 The acknowledge sent by the other side, usually @value{GDBN}, to
38053 acknowledge the exchange and request the event.
38056 The purpose of an asynchronous notification mechanism is to report to
38057 @value{GDBN} that something interesting happened in the remote stub.
38059 The remote stub may send notification @var{name}:@var{event}
38060 at any time, but @value{GDBN} acknowledges the notification when
38061 appropriate. The notification event is pending before @value{GDBN}
38062 acknowledges. Only one notification at a time may be pending; if
38063 additional events occur before @value{GDBN} has acknowledged the
38064 previous notification, they must be queued by the stub for later
38065 synchronous transmission in response to @var{ack} packets from
38066 @value{GDBN}. Because the notification mechanism is unreliable,
38067 the stub is permitted to resend a notification if it believes
38068 @value{GDBN} may not have received it.
38070 Specifically, notifications may appear when @value{GDBN} is not
38071 otherwise reading input from the stub, or when @value{GDBN} is
38072 expecting to read a normal synchronous response or a
38073 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38074 Notification packets are distinct from any other communication from
38075 the stub so there is no ambiguity.
38077 After receiving a notification, @value{GDBN} shall acknowledge it by
38078 sending a @var{ack} packet as a regular, synchronous request to the
38079 stub. Such acknowledgment is not required to happen immediately, as
38080 @value{GDBN} is permitted to send other, unrelated packets to the
38081 stub first, which the stub should process normally.
38083 Upon receiving a @var{ack} packet, if the stub has other queued
38084 events to report to @value{GDBN}, it shall respond by sending a
38085 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38086 packet to solicit further responses; again, it is permitted to send
38087 other, unrelated packets as well which the stub should process
38090 If the stub receives a @var{ack} packet and there are no additional
38091 @var{event} to report, the stub shall return an @samp{OK} response.
38092 At this point, @value{GDBN} has finished processing a notification
38093 and the stub has completed sending any queued events. @value{GDBN}
38094 won't accept any new notifications until the final @samp{OK} is
38095 received . If further notification events occur, the stub shall send
38096 a new notification, @value{GDBN} shall accept the notification, and
38097 the process shall be repeated.
38099 The process of asynchronous notification can be illustrated by the
38102 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38105 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38107 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38112 The following notifications are defined:
38113 @multitable @columnfractions 0.12 0.12 0.38 0.38
38122 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38123 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38124 for information on how these notifications are acknowledged by
38126 @tab Report an asynchronous stop event in non-stop mode.
38130 @node Remote Non-Stop
38131 @section Remote Protocol Support for Non-Stop Mode
38133 @value{GDBN}'s remote protocol supports non-stop debugging of
38134 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38135 supports non-stop mode, it should report that to @value{GDBN} by including
38136 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38138 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38139 establishing a new connection with the stub. Entering non-stop mode
38140 does not alter the state of any currently-running threads, but targets
38141 must stop all threads in any already-attached processes when entering
38142 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38143 probe the target state after a mode change.
38145 In non-stop mode, when an attached process encounters an event that
38146 would otherwise be reported with a stop reply, it uses the
38147 asynchronous notification mechanism (@pxref{Notification Packets}) to
38148 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38149 in all processes are stopped when a stop reply is sent, in non-stop
38150 mode only the thread reporting the stop event is stopped. That is,
38151 when reporting a @samp{S} or @samp{T} response to indicate completion
38152 of a step operation, hitting a breakpoint, or a fault, only the
38153 affected thread is stopped; any other still-running threads continue
38154 to run. When reporting a @samp{W} or @samp{X} response, all running
38155 threads belonging to other attached processes continue to run.
38157 In non-stop mode, the target shall respond to the @samp{?} packet as
38158 follows. First, any incomplete stop reply notification/@samp{vStopped}
38159 sequence in progress is abandoned. The target must begin a new
38160 sequence reporting stop events for all stopped threads, whether or not
38161 it has previously reported those events to @value{GDBN}. The first
38162 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38163 subsequent stop replies are sent as responses to @samp{vStopped} packets
38164 using the mechanism described above. The target must not send
38165 asynchronous stop reply notifications until the sequence is complete.
38166 If all threads are running when the target receives the @samp{?} packet,
38167 or if the target is not attached to any process, it shall respond
38170 If the stub supports non-stop mode, it should also support the
38171 @samp{swbreak} stop reason if software breakpoints are supported, and
38172 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38173 (@pxref{swbreak stop reason}). This is because given the asynchronous
38174 nature of non-stop mode, between the time a thread hits a breakpoint
38175 and the time the event is finally processed by @value{GDBN}, the
38176 breakpoint may have already been removed from the target. Due to
38177 this, @value{GDBN} needs to be able to tell whether a trap stop was
38178 caused by a delayed breakpoint event, which should be ignored, as
38179 opposed to a random trap signal, which should be reported to the user.
38180 Note the @samp{swbreak} feature implies that the target is responsible
38181 for adjusting the PC when a software breakpoint triggers, if
38182 necessary, such as on the x86 architecture.
38184 @node Packet Acknowledgment
38185 @section Packet Acknowledgment
38187 @cindex acknowledgment, for @value{GDBN} remote
38188 @cindex packet acknowledgment, for @value{GDBN} remote
38189 By default, when either the host or the target machine receives a packet,
38190 the first response expected is an acknowledgment: either @samp{+} (to indicate
38191 the package was received correctly) or @samp{-} (to request retransmission).
38192 This mechanism allows the @value{GDBN} remote protocol to operate over
38193 unreliable transport mechanisms, such as a serial line.
38195 In cases where the transport mechanism is itself reliable (such as a pipe or
38196 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38197 It may be desirable to disable them in that case to reduce communication
38198 overhead, or for other reasons. This can be accomplished by means of the
38199 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38201 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38202 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38203 and response format still includes the normal checksum, as described in
38204 @ref{Overview}, but the checksum may be ignored by the receiver.
38206 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38207 no-acknowledgment mode, it should report that to @value{GDBN}
38208 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38209 @pxref{qSupported}.
38210 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38211 disabled via the @code{set remote noack-packet off} command
38212 (@pxref{Remote Configuration}),
38213 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38214 Only then may the stub actually turn off packet acknowledgments.
38215 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38216 response, which can be safely ignored by the stub.
38218 Note that @code{set remote noack-packet} command only affects negotiation
38219 between @value{GDBN} and the stub when subsequent connections are made;
38220 it does not affect the protocol acknowledgment state for any current
38222 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38223 new connection is established,
38224 there is also no protocol request to re-enable the acknowledgments
38225 for the current connection, once disabled.
38230 Example sequence of a target being re-started. Notice how the restart
38231 does not get any direct output:
38236 @emph{target restarts}
38239 <- @code{T001:1234123412341234}
38243 Example sequence of a target being stepped by a single instruction:
38246 -> @code{G1445@dots{}}
38251 <- @code{T001:1234123412341234}
38255 <- @code{1455@dots{}}
38259 @node File-I/O Remote Protocol Extension
38260 @section File-I/O Remote Protocol Extension
38261 @cindex File-I/O remote protocol extension
38264 * File-I/O Overview::
38265 * Protocol Basics::
38266 * The F Request Packet::
38267 * The F Reply Packet::
38268 * The Ctrl-C Message::
38270 * List of Supported Calls::
38271 * Protocol-specific Representation of Datatypes::
38273 * File-I/O Examples::
38276 @node File-I/O Overview
38277 @subsection File-I/O Overview
38278 @cindex file-i/o overview
38280 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38281 target to use the host's file system and console I/O to perform various
38282 system calls. System calls on the target system are translated into a
38283 remote protocol packet to the host system, which then performs the needed
38284 actions and returns a response packet to the target system.
38285 This simulates file system operations even on targets that lack file systems.
38287 The protocol is defined to be independent of both the host and target systems.
38288 It uses its own internal representation of datatypes and values. Both
38289 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38290 translating the system-dependent value representations into the internal
38291 protocol representations when data is transmitted.
38293 The communication is synchronous. A system call is possible only when
38294 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38295 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38296 the target is stopped to allow deterministic access to the target's
38297 memory. Therefore File-I/O is not interruptible by target signals. On
38298 the other hand, it is possible to interrupt File-I/O by a user interrupt
38299 (@samp{Ctrl-C}) within @value{GDBN}.
38301 The target's request to perform a host system call does not finish
38302 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38303 after finishing the system call, the target returns to continuing the
38304 previous activity (continue, step). No additional continue or step
38305 request from @value{GDBN} is required.
38308 (@value{GDBP}) continue
38309 <- target requests 'system call X'
38310 target is stopped, @value{GDBN} executes system call
38311 -> @value{GDBN} returns result
38312 ... target continues, @value{GDBN} returns to wait for the target
38313 <- target hits breakpoint and sends a Txx packet
38316 The protocol only supports I/O on the console and to regular files on
38317 the host file system. Character or block special devices, pipes,
38318 named pipes, sockets or any other communication method on the host
38319 system are not supported by this protocol.
38321 File I/O is not supported in non-stop mode.
38323 @node Protocol Basics
38324 @subsection Protocol Basics
38325 @cindex protocol basics, file-i/o
38327 The File-I/O protocol uses the @code{F} packet as the request as well
38328 as reply packet. Since a File-I/O system call can only occur when
38329 @value{GDBN} is waiting for a response from the continuing or stepping target,
38330 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38331 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38332 This @code{F} packet contains all information needed to allow @value{GDBN}
38333 to call the appropriate host system call:
38337 A unique identifier for the requested system call.
38340 All parameters to the system call. Pointers are given as addresses
38341 in the target memory address space. Pointers to strings are given as
38342 pointer/length pair. Numerical values are given as they are.
38343 Numerical control flags are given in a protocol-specific representation.
38347 At this point, @value{GDBN} has to perform the following actions.
38351 If the parameters include pointer values to data needed as input to a
38352 system call, @value{GDBN} requests this data from the target with a
38353 standard @code{m} packet request. This additional communication has to be
38354 expected by the target implementation and is handled as any other @code{m}
38358 @value{GDBN} translates all value from protocol representation to host
38359 representation as needed. Datatypes are coerced into the host types.
38362 @value{GDBN} calls the system call.
38365 It then coerces datatypes back to protocol representation.
38368 If the system call is expected to return data in buffer space specified
38369 by pointer parameters to the call, the data is transmitted to the
38370 target using a @code{M} or @code{X} packet. This packet has to be expected
38371 by the target implementation and is handled as any other @code{M} or @code{X}
38376 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38377 necessary information for the target to continue. This at least contains
38384 @code{errno}, if has been changed by the system call.
38391 After having done the needed type and value coercion, the target continues
38392 the latest continue or step action.
38394 @node The F Request Packet
38395 @subsection The @code{F} Request Packet
38396 @cindex file-i/o request packet
38397 @cindex @code{F} request packet
38399 The @code{F} request packet has the following format:
38402 @item F@var{call-id},@var{parameter@dots{}}
38404 @var{call-id} is the identifier to indicate the host system call to be called.
38405 This is just the name of the function.
38407 @var{parameter@dots{}} are the parameters to the system call.
38408 Parameters are hexadecimal integer values, either the actual values in case
38409 of scalar datatypes, pointers to target buffer space in case of compound
38410 datatypes and unspecified memory areas, or pointer/length pairs in case
38411 of string parameters. These are appended to the @var{call-id} as a
38412 comma-delimited list. All values are transmitted in ASCII
38413 string representation, pointer/length pairs separated by a slash.
38419 @node The F Reply Packet
38420 @subsection The @code{F} Reply Packet
38421 @cindex file-i/o reply packet
38422 @cindex @code{F} reply packet
38424 The @code{F} reply packet has the following format:
38428 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38430 @var{retcode} is the return code of the system call as hexadecimal value.
38432 @var{errno} is the @code{errno} set by the call, in protocol-specific
38434 This parameter can be omitted if the call was successful.
38436 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38437 case, @var{errno} must be sent as well, even if the call was successful.
38438 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38445 or, if the call was interrupted before the host call has been performed:
38452 assuming 4 is the protocol-specific representation of @code{EINTR}.
38457 @node The Ctrl-C Message
38458 @subsection The @samp{Ctrl-C} Message
38459 @cindex ctrl-c message, in file-i/o protocol
38461 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38462 reply packet (@pxref{The F Reply Packet}),
38463 the target should behave as if it had
38464 gotten a break message. The meaning for the target is ``system call
38465 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38466 (as with a break message) and return to @value{GDBN} with a @code{T02}
38469 It's important for the target to know in which
38470 state the system call was interrupted. There are two possible cases:
38474 The system call hasn't been performed on the host yet.
38477 The system call on the host has been finished.
38481 These two states can be distinguished by the target by the value of the
38482 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38483 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38484 on POSIX systems. In any other case, the target may presume that the
38485 system call has been finished --- successfully or not --- and should behave
38486 as if the break message arrived right after the system call.
38488 @value{GDBN} must behave reliably. If the system call has not been called
38489 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38490 @code{errno} in the packet. If the system call on the host has been finished
38491 before the user requests a break, the full action must be finished by
38492 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38493 The @code{F} packet may only be sent when either nothing has happened
38494 or the full action has been completed.
38497 @subsection Console I/O
38498 @cindex console i/o as part of file-i/o
38500 By default and if not explicitly closed by the target system, the file
38501 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38502 on the @value{GDBN} console is handled as any other file output operation
38503 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38504 by @value{GDBN} so that after the target read request from file descriptor
38505 0 all following typing is buffered until either one of the following
38510 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38512 system call is treated as finished.
38515 The user presses @key{RET}. This is treated as end of input with a trailing
38519 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38520 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38524 If the user has typed more characters than fit in the buffer given to
38525 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38526 either another @code{read(0, @dots{})} is requested by the target, or debugging
38527 is stopped at the user's request.
38530 @node List of Supported Calls
38531 @subsection List of Supported Calls
38532 @cindex list of supported file-i/o calls
38549 @unnumberedsubsubsec open
38550 @cindex open, file-i/o system call
38555 int open(const char *pathname, int flags);
38556 int open(const char *pathname, int flags, mode_t mode);
38560 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38563 @var{flags} is the bitwise @code{OR} of the following values:
38567 If the file does not exist it will be created. The host
38568 rules apply as far as file ownership and time stamps
38572 When used with @code{O_CREAT}, if the file already exists it is
38573 an error and open() fails.
38576 If the file already exists and the open mode allows
38577 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38578 truncated to zero length.
38581 The file is opened in append mode.
38584 The file is opened for reading only.
38587 The file is opened for writing only.
38590 The file is opened for reading and writing.
38594 Other bits are silently ignored.
38598 @var{mode} is the bitwise @code{OR} of the following values:
38602 User has read permission.
38605 User has write permission.
38608 Group has read permission.
38611 Group has write permission.
38614 Others have read permission.
38617 Others have write permission.
38621 Other bits are silently ignored.
38624 @item Return value:
38625 @code{open} returns the new file descriptor or -1 if an error
38632 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38635 @var{pathname} refers to a directory.
38638 The requested access is not allowed.
38641 @var{pathname} was too long.
38644 A directory component in @var{pathname} does not exist.
38647 @var{pathname} refers to a device, pipe, named pipe or socket.
38650 @var{pathname} refers to a file on a read-only filesystem and
38651 write access was requested.
38654 @var{pathname} is an invalid pointer value.
38657 No space on device to create the file.
38660 The process already has the maximum number of files open.
38663 The limit on the total number of files open on the system
38667 The call was interrupted by the user.
38673 @unnumberedsubsubsec close
38674 @cindex close, file-i/o system call
38683 @samp{Fclose,@var{fd}}
38685 @item Return value:
38686 @code{close} returns zero on success, or -1 if an error occurred.
38692 @var{fd} isn't a valid open file descriptor.
38695 The call was interrupted by the user.
38701 @unnumberedsubsubsec read
38702 @cindex read, file-i/o system call
38707 int read(int fd, void *buf, unsigned int count);
38711 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38713 @item Return value:
38714 On success, the number of bytes read is returned.
38715 Zero indicates end of file. If count is zero, read
38716 returns zero as well. On error, -1 is returned.
38722 @var{fd} is not a valid file descriptor or is not open for
38726 @var{bufptr} is an invalid pointer value.
38729 The call was interrupted by the user.
38735 @unnumberedsubsubsec write
38736 @cindex write, file-i/o system call
38741 int write(int fd, const void *buf, unsigned int count);
38745 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38747 @item Return value:
38748 On success, the number of bytes written are returned.
38749 Zero indicates nothing was written. On error, -1
38756 @var{fd} is not a valid file descriptor or is not open for
38760 @var{bufptr} is an invalid pointer value.
38763 An attempt was made to write a file that exceeds the
38764 host-specific maximum file size allowed.
38767 No space on device to write the data.
38770 The call was interrupted by the user.
38776 @unnumberedsubsubsec lseek
38777 @cindex lseek, file-i/o system call
38782 long lseek (int fd, long offset, int flag);
38786 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38788 @var{flag} is one of:
38792 The offset is set to @var{offset} bytes.
38795 The offset is set to its current location plus @var{offset}
38799 The offset is set to the size of the file plus @var{offset}
38803 @item Return value:
38804 On success, the resulting unsigned offset in bytes from
38805 the beginning of the file is returned. Otherwise, a
38806 value of -1 is returned.
38812 @var{fd} is not a valid open file descriptor.
38815 @var{fd} is associated with the @value{GDBN} console.
38818 @var{flag} is not a proper value.
38821 The call was interrupted by the user.
38827 @unnumberedsubsubsec rename
38828 @cindex rename, file-i/o system call
38833 int rename(const char *oldpath, const char *newpath);
38837 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38839 @item Return value:
38840 On success, zero is returned. On error, -1 is returned.
38846 @var{newpath} is an existing directory, but @var{oldpath} is not a
38850 @var{newpath} is a non-empty directory.
38853 @var{oldpath} or @var{newpath} is a directory that is in use by some
38857 An attempt was made to make a directory a subdirectory
38861 A component used as a directory in @var{oldpath} or new
38862 path is not a directory. Or @var{oldpath} is a directory
38863 and @var{newpath} exists but is not a directory.
38866 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38869 No access to the file or the path of the file.
38873 @var{oldpath} or @var{newpath} was too long.
38876 A directory component in @var{oldpath} or @var{newpath} does not exist.
38879 The file is on a read-only filesystem.
38882 The device containing the file has no room for the new
38886 The call was interrupted by the user.
38892 @unnumberedsubsubsec unlink
38893 @cindex unlink, file-i/o system call
38898 int unlink(const char *pathname);
38902 @samp{Funlink,@var{pathnameptr}/@var{len}}
38904 @item Return value:
38905 On success, zero is returned. On error, -1 is returned.
38911 No access to the file or the path of the file.
38914 The system does not allow unlinking of directories.
38917 The file @var{pathname} cannot be unlinked because it's
38918 being used by another process.
38921 @var{pathnameptr} is an invalid pointer value.
38924 @var{pathname} was too long.
38927 A directory component in @var{pathname} does not exist.
38930 A component of the path is not a directory.
38933 The file is on a read-only filesystem.
38936 The call was interrupted by the user.
38942 @unnumberedsubsubsec stat/fstat
38943 @cindex fstat, file-i/o system call
38944 @cindex stat, file-i/o system call
38949 int stat(const char *pathname, struct stat *buf);
38950 int fstat(int fd, struct stat *buf);
38954 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38955 @samp{Ffstat,@var{fd},@var{bufptr}}
38957 @item Return value:
38958 On success, zero is returned. On error, -1 is returned.
38964 @var{fd} is not a valid open file.
38967 A directory component in @var{pathname} does not exist or the
38968 path is an empty string.
38971 A component of the path is not a directory.
38974 @var{pathnameptr} is an invalid pointer value.
38977 No access to the file or the path of the file.
38980 @var{pathname} was too long.
38983 The call was interrupted by the user.
38989 @unnumberedsubsubsec gettimeofday
38990 @cindex gettimeofday, file-i/o system call
38995 int gettimeofday(struct timeval *tv, void *tz);
38999 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39001 @item Return value:
39002 On success, 0 is returned, -1 otherwise.
39008 @var{tz} is a non-NULL pointer.
39011 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39017 @unnumberedsubsubsec isatty
39018 @cindex isatty, file-i/o system call
39023 int isatty(int fd);
39027 @samp{Fisatty,@var{fd}}
39029 @item Return value:
39030 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39036 The call was interrupted by the user.
39041 Note that the @code{isatty} call is treated as a special case: it returns
39042 1 to the target if the file descriptor is attached
39043 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39044 would require implementing @code{ioctl} and would be more complex than
39049 @unnumberedsubsubsec system
39050 @cindex system, file-i/o system call
39055 int system(const char *command);
39059 @samp{Fsystem,@var{commandptr}/@var{len}}
39061 @item Return value:
39062 If @var{len} is zero, the return value indicates whether a shell is
39063 available. A zero return value indicates a shell is not available.
39064 For non-zero @var{len}, the value returned is -1 on error and the
39065 return status of the command otherwise. Only the exit status of the
39066 command is returned, which is extracted from the host's @code{system}
39067 return value by calling @code{WEXITSTATUS(retval)}. In case
39068 @file{/bin/sh} could not be executed, 127 is returned.
39074 The call was interrupted by the user.
39079 @value{GDBN} takes over the full task of calling the necessary host calls
39080 to perform the @code{system} call. The return value of @code{system} on
39081 the host is simplified before it's returned
39082 to the target. Any termination signal information from the child process
39083 is discarded, and the return value consists
39084 entirely of the exit status of the called command.
39086 Due to security concerns, the @code{system} call is by default refused
39087 by @value{GDBN}. The user has to allow this call explicitly with the
39088 @code{set remote system-call-allowed 1} command.
39091 @item set remote system-call-allowed
39092 @kindex set remote system-call-allowed
39093 Control whether to allow the @code{system} calls in the File I/O
39094 protocol for the remote target. The default is zero (disabled).
39096 @item show remote system-call-allowed
39097 @kindex show remote system-call-allowed
39098 Show whether the @code{system} calls are allowed in the File I/O
39102 @node Protocol-specific Representation of Datatypes
39103 @subsection Protocol-specific Representation of Datatypes
39104 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39107 * Integral Datatypes::
39109 * Memory Transfer::
39114 @node Integral Datatypes
39115 @unnumberedsubsubsec Integral Datatypes
39116 @cindex integral datatypes, in file-i/o protocol
39118 The integral datatypes used in the system calls are @code{int},
39119 @code{unsigned int}, @code{long}, @code{unsigned long},
39120 @code{mode_t}, and @code{time_t}.
39122 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39123 implemented as 32 bit values in this protocol.
39125 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39127 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39128 in @file{limits.h}) to allow range checking on host and target.
39130 @code{time_t} datatypes are defined as seconds since the Epoch.
39132 All integral datatypes transferred as part of a memory read or write of a
39133 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39136 @node Pointer Values
39137 @unnumberedsubsubsec Pointer Values
39138 @cindex pointer values, in file-i/o protocol
39140 Pointers to target data are transmitted as they are. An exception
39141 is made for pointers to buffers for which the length isn't
39142 transmitted as part of the function call, namely strings. Strings
39143 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39150 which is a pointer to data of length 18 bytes at position 0x1aaf.
39151 The length is defined as the full string length in bytes, including
39152 the trailing null byte. For example, the string @code{"hello world"}
39153 at address 0x123456 is transmitted as
39159 @node Memory Transfer
39160 @unnumberedsubsubsec Memory Transfer
39161 @cindex memory transfer, in file-i/o protocol
39163 Structured data which is transferred using a memory read or write (for
39164 example, a @code{struct stat}) is expected to be in a protocol-specific format
39165 with all scalar multibyte datatypes being big endian. Translation to
39166 this representation needs to be done both by the target before the @code{F}
39167 packet is sent, and by @value{GDBN} before
39168 it transfers memory to the target. Transferred pointers to structured
39169 data should point to the already-coerced data at any time.
39173 @unnumberedsubsubsec struct stat
39174 @cindex struct stat, in file-i/o protocol
39176 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39177 is defined as follows:
39181 unsigned int st_dev; /* device */
39182 unsigned int st_ino; /* inode */
39183 mode_t st_mode; /* protection */
39184 unsigned int st_nlink; /* number of hard links */
39185 unsigned int st_uid; /* user ID of owner */
39186 unsigned int st_gid; /* group ID of owner */
39187 unsigned int st_rdev; /* device type (if inode device) */
39188 unsigned long st_size; /* total size, in bytes */
39189 unsigned long st_blksize; /* blocksize for filesystem I/O */
39190 unsigned long st_blocks; /* number of blocks allocated */
39191 time_t st_atime; /* time of last access */
39192 time_t st_mtime; /* time of last modification */
39193 time_t st_ctime; /* time of last change */
39197 The integral datatypes conform to the definitions given in the
39198 appropriate section (see @ref{Integral Datatypes}, for details) so this
39199 structure is of size 64 bytes.
39201 The values of several fields have a restricted meaning and/or
39207 A value of 0 represents a file, 1 the console.
39210 No valid meaning for the target. Transmitted unchanged.
39213 Valid mode bits are described in @ref{Constants}. Any other
39214 bits have currently no meaning for the target.
39219 No valid meaning for the target. Transmitted unchanged.
39224 These values have a host and file system dependent
39225 accuracy. Especially on Windows hosts, the file system may not
39226 support exact timing values.
39229 The target gets a @code{struct stat} of the above representation and is
39230 responsible for coercing it to the target representation before
39233 Note that due to size differences between the host, target, and protocol
39234 representations of @code{struct stat} members, these members could eventually
39235 get truncated on the target.
39237 @node struct timeval
39238 @unnumberedsubsubsec struct timeval
39239 @cindex struct timeval, in file-i/o protocol
39241 The buffer of type @code{struct timeval} used by the File-I/O protocol
39242 is defined as follows:
39246 time_t tv_sec; /* second */
39247 long tv_usec; /* microsecond */
39251 The integral datatypes conform to the definitions given in the
39252 appropriate section (see @ref{Integral Datatypes}, for details) so this
39253 structure is of size 8 bytes.
39256 @subsection Constants
39257 @cindex constants, in file-i/o protocol
39259 The following values are used for the constants inside of the
39260 protocol. @value{GDBN} and target are responsible for translating these
39261 values before and after the call as needed.
39272 @unnumberedsubsubsec Open Flags
39273 @cindex open flags, in file-i/o protocol
39275 All values are given in hexadecimal representation.
39287 @node mode_t Values
39288 @unnumberedsubsubsec mode_t Values
39289 @cindex mode_t values, in file-i/o protocol
39291 All values are given in octal representation.
39308 @unnumberedsubsubsec Errno Values
39309 @cindex errno values, in file-i/o protocol
39311 All values are given in decimal representation.
39336 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39337 any error value not in the list of supported error numbers.
39340 @unnumberedsubsubsec Lseek Flags
39341 @cindex lseek flags, in file-i/o protocol
39350 @unnumberedsubsubsec Limits
39351 @cindex limits, in file-i/o protocol
39353 All values are given in decimal representation.
39356 INT_MIN -2147483648
39358 UINT_MAX 4294967295
39359 LONG_MIN -9223372036854775808
39360 LONG_MAX 9223372036854775807
39361 ULONG_MAX 18446744073709551615
39364 @node File-I/O Examples
39365 @subsection File-I/O Examples
39366 @cindex file-i/o examples
39368 Example sequence of a write call, file descriptor 3, buffer is at target
39369 address 0x1234, 6 bytes should be written:
39372 <- @code{Fwrite,3,1234,6}
39373 @emph{request memory read from target}
39376 @emph{return "6 bytes written"}
39380 Example sequence of a read call, file descriptor 3, buffer is at target
39381 address 0x1234, 6 bytes should be read:
39384 <- @code{Fread,3,1234,6}
39385 @emph{request memory write to target}
39386 -> @code{X1234,6:XXXXXX}
39387 @emph{return "6 bytes read"}
39391 Example sequence of a read call, call fails on the host due to invalid
39392 file descriptor (@code{EBADF}):
39395 <- @code{Fread,3,1234,6}
39399 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39403 <- @code{Fread,3,1234,6}
39408 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39412 <- @code{Fread,3,1234,6}
39413 -> @code{X1234,6:XXXXXX}
39417 @node Library List Format
39418 @section Library List Format
39419 @cindex library list format, remote protocol
39421 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39422 same process as your application to manage libraries. In this case,
39423 @value{GDBN} can use the loader's symbol table and normal memory
39424 operations to maintain a list of shared libraries. On other
39425 platforms, the operating system manages loaded libraries.
39426 @value{GDBN} can not retrieve the list of currently loaded libraries
39427 through memory operations, so it uses the @samp{qXfer:libraries:read}
39428 packet (@pxref{qXfer library list read}) instead. The remote stub
39429 queries the target's operating system and reports which libraries
39432 The @samp{qXfer:libraries:read} packet returns an XML document which
39433 lists loaded libraries and their offsets. Each library has an
39434 associated name and one or more segment or section base addresses,
39435 which report where the library was loaded in memory.
39437 For the common case of libraries that are fully linked binaries, the
39438 library should have a list of segments. If the target supports
39439 dynamic linking of a relocatable object file, its library XML element
39440 should instead include a list of allocated sections. The segment or
39441 section bases are start addresses, not relocation offsets; they do not
39442 depend on the library's link-time base addresses.
39444 @value{GDBN} must be linked with the Expat library to support XML
39445 library lists. @xref{Expat}.
39447 A simple memory map, with one loaded library relocated by a single
39448 offset, looks like this:
39452 <library name="/lib/libc.so.6">
39453 <segment address="0x10000000"/>
39458 Another simple memory map, with one loaded library with three
39459 allocated sections (.text, .data, .bss), looks like this:
39463 <library name="sharedlib.o">
39464 <section address="0x10000000"/>
39465 <section address="0x20000000"/>
39466 <section address="0x30000000"/>
39471 The format of a library list is described by this DTD:
39474 <!-- library-list: Root element with versioning -->
39475 <!ELEMENT library-list (library)*>
39476 <!ATTLIST library-list version CDATA #FIXED "1.0">
39477 <!ELEMENT library (segment*, section*)>
39478 <!ATTLIST library name CDATA #REQUIRED>
39479 <!ELEMENT segment EMPTY>
39480 <!ATTLIST segment address CDATA #REQUIRED>
39481 <!ELEMENT section EMPTY>
39482 <!ATTLIST section address CDATA #REQUIRED>
39485 In addition, segments and section descriptors cannot be mixed within a
39486 single library element, and you must supply at least one segment or
39487 section for each library.
39489 @node Library List Format for SVR4 Targets
39490 @section Library List Format for SVR4 Targets
39491 @cindex library list format, remote protocol
39493 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39494 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39495 shared libraries. Still a special library list provided by this packet is
39496 more efficient for the @value{GDBN} remote protocol.
39498 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39499 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39500 target, the following parameters are reported:
39504 @code{name}, the absolute file name from the @code{l_name} field of
39505 @code{struct link_map}.
39507 @code{lm} with address of @code{struct link_map} used for TLS
39508 (Thread Local Storage) access.
39510 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39511 @code{struct link_map}. For prelinked libraries this is not an absolute
39512 memory address. It is a displacement of absolute memory address against
39513 address the file was prelinked to during the library load.
39515 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39517 @code{build-id}, hex encoded @code{NT_GNU_BUILD_ID} note, if it exists.
39520 Additionally the single @code{main-lm} attribute specifies address of
39521 @code{struct link_map} used for the main executable. This parameter is used
39522 for TLS access and its presence is optional.
39524 @value{GDBN} must be linked with the Expat library to support XML
39525 SVR4 library lists. @xref{Expat}.
39527 A simple memory map, with two loaded libraries (which do not use prelink),
39531 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39532 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39534 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39535 l_ld="0x152350" build-id="9afccf7cc41e6293476223fe72480854"/>
39536 </library-list-svr>
39539 The format of an SVR4 library list is described by this DTD:
39542 <!-- library-list-svr4: Root element with versioning -->
39543 <!ELEMENT library-list-svr4 (library)*>
39544 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39545 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39546 <!ELEMENT library EMPTY>
39547 <!ATTLIST library name CDATA #REQUIRED>
39548 <!ATTLIST library lm CDATA #REQUIRED>
39549 <!ATTLIST library l_addr CDATA #REQUIRED>
39550 <!ATTLIST library l_ld CDATA #REQUIRED>
39551 <!ATTLIST library build-id CDATA #IMPLIED>
39554 @node Memory Map Format
39555 @section Memory Map Format
39556 @cindex memory map format
39558 To be able to write into flash memory, @value{GDBN} needs to obtain a
39559 memory map from the target. This section describes the format of the
39562 The memory map is obtained using the @samp{qXfer:memory-map:read}
39563 (@pxref{qXfer memory map read}) packet and is an XML document that
39564 lists memory regions.
39566 @value{GDBN} must be linked with the Expat library to support XML
39567 memory maps. @xref{Expat}.
39569 The top-level structure of the document is shown below:
39572 <?xml version="1.0"?>
39573 <!DOCTYPE memory-map
39574 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39575 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39581 Each region can be either:
39586 A region of RAM starting at @var{addr} and extending for @var{length}
39590 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39595 A region of read-only memory:
39598 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39603 A region of flash memory, with erasure blocks @var{blocksize}
39607 <memory type="flash" start="@var{addr}" length="@var{length}">
39608 <property name="blocksize">@var{blocksize}</property>
39614 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39615 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39616 packets to write to addresses in such ranges.
39618 The formal DTD for memory map format is given below:
39621 <!-- ................................................... -->
39622 <!-- Memory Map XML DTD ................................ -->
39623 <!-- File: memory-map.dtd .............................. -->
39624 <!-- .................................... .............. -->
39625 <!-- memory-map.dtd -->
39626 <!-- memory-map: Root element with versioning -->
39627 <!ELEMENT memory-map (memory | property)>
39628 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39629 <!ELEMENT memory (property)>
39630 <!-- memory: Specifies a memory region,
39631 and its type, or device. -->
39632 <!ATTLIST memory type CDATA #REQUIRED
39633 start CDATA #REQUIRED
39634 length CDATA #REQUIRED
39635 device CDATA #IMPLIED>
39636 <!-- property: Generic attribute tag -->
39637 <!ELEMENT property (#PCDATA | property)*>
39638 <!ATTLIST property name CDATA #REQUIRED>
39641 @node Thread List Format
39642 @section Thread List Format
39643 @cindex thread list format
39645 To efficiently update the list of threads and their attributes,
39646 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39647 (@pxref{qXfer threads read}) and obtains the XML document with
39648 the following structure:
39651 <?xml version="1.0"?>
39653 <thread id="id" core="0">
39654 ... description ...
39659 Each @samp{thread} element must have the @samp{id} attribute that
39660 identifies the thread (@pxref{thread-id syntax}). The
39661 @samp{core} attribute, if present, specifies which processor core
39662 the thread was last executing on. The content of the of @samp{thread}
39663 element is interpreted as human-readable auxilliary information.
39665 @node Traceframe Info Format
39666 @section Traceframe Info Format
39667 @cindex traceframe info format
39669 To be able to know which objects in the inferior can be examined when
39670 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39671 memory ranges, registers and trace state variables that have been
39672 collected in a traceframe.
39674 This list is obtained using the @samp{qXfer:traceframe-info:read}
39675 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39677 @value{GDBN} must be linked with the Expat library to support XML
39678 traceframe info discovery. @xref{Expat}.
39680 The top-level structure of the document is shown below:
39683 <?xml version="1.0"?>
39684 <!DOCTYPE traceframe-info
39685 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39686 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39692 Each traceframe block can be either:
39697 A region of collected memory starting at @var{addr} and extending for
39698 @var{length} bytes from there:
39701 <memory start="@var{addr}" length="@var{length}"/>
39705 A block indicating trace state variable numbered @var{number} has been
39709 <tvar id="@var{number}"/>
39714 The formal DTD for the traceframe info format is given below:
39717 <!ELEMENT traceframe-info (memory | tvar)* >
39718 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39720 <!ELEMENT memory EMPTY>
39721 <!ATTLIST memory start CDATA #REQUIRED
39722 length CDATA #REQUIRED>
39724 <!ATTLIST tvar id CDATA #REQUIRED>
39727 @node Branch Trace Format
39728 @section Branch Trace Format
39729 @cindex branch trace format
39731 In order to display the branch trace of an inferior thread,
39732 @value{GDBN} needs to obtain the list of branches. This list is
39733 represented as list of sequential code blocks that are connected via
39734 branches. The code in each block has been executed sequentially.
39736 This list is obtained using the @samp{qXfer:btrace:read}
39737 (@pxref{qXfer btrace read}) packet and is an XML document.
39739 @value{GDBN} must be linked with the Expat library to support XML
39740 traceframe info discovery. @xref{Expat}.
39742 The top-level structure of the document is shown below:
39745 <?xml version="1.0"?>
39747 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39748 "http://sourceware.org/gdb/gdb-btrace.dtd">
39757 A block of sequentially executed instructions starting at @var{begin}
39758 and ending at @var{end}:
39761 <block begin="@var{begin}" end="@var{end}"/>
39766 The formal DTD for the branch trace format is given below:
39769 <!ELEMENT btrace (block* | pt) >
39770 <!ATTLIST btrace version CDATA #FIXED "1.0">
39772 <!ELEMENT block EMPTY>
39773 <!ATTLIST block begin CDATA #REQUIRED
39774 end CDATA #REQUIRED>
39776 <!ELEMENT pt (pt-config?, raw?)>
39778 <!ELEMENT pt-config (cpu?)>
39780 <!ELEMENT cpu EMPTY>
39781 <!ATTLIST cpu vendor CDATA #REQUIRED
39782 family CDATA #REQUIRED
39783 model CDATA #REQUIRED
39784 stepping CDATA #REQUIRED>
39786 <!ELEMENT raw (#PCDATA)>
39789 @node Branch Trace Configuration Format
39790 @section Branch Trace Configuration Format
39791 @cindex branch trace configuration format
39793 For each inferior thread, @value{GDBN} can obtain the branch trace
39794 configuration using the @samp{qXfer:btrace-conf:read}
39795 (@pxref{qXfer btrace-conf read}) packet.
39797 The configuration describes the branch trace format and configuration
39798 settings for that format. The following information is described:
39802 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39805 The size of the @acronym{BTS} ring buffer in bytes.
39808 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39812 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39816 @value{GDBN} must be linked with the Expat library to support XML
39817 branch trace configuration discovery. @xref{Expat}.
39819 The formal DTD for the branch trace configuration format is given below:
39822 <!ELEMENT btrace-conf (bts?, pt?)>
39823 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39825 <!ELEMENT bts EMPTY>
39826 <!ATTLIST bts size CDATA #IMPLIED>
39828 <!ELEMENT pt EMPTY>
39829 <!ATTLIST pt size CDATA #IMPLIED>
39832 @include agentexpr.texi
39834 @node Target Descriptions
39835 @appendix Target Descriptions
39836 @cindex target descriptions
39838 One of the challenges of using @value{GDBN} to debug embedded systems
39839 is that there are so many minor variants of each processor
39840 architecture in use. It is common practice for vendors to start with
39841 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39842 and then make changes to adapt it to a particular market niche. Some
39843 architectures have hundreds of variants, available from dozens of
39844 vendors. This leads to a number of problems:
39848 With so many different customized processors, it is difficult for
39849 the @value{GDBN} maintainers to keep up with the changes.
39851 Since individual variants may have short lifetimes or limited
39852 audiences, it may not be worthwhile to carry information about every
39853 variant in the @value{GDBN} source tree.
39855 When @value{GDBN} does support the architecture of the embedded system
39856 at hand, the task of finding the correct architecture name to give the
39857 @command{set architecture} command can be error-prone.
39860 To address these problems, the @value{GDBN} remote protocol allows a
39861 target system to not only identify itself to @value{GDBN}, but to
39862 actually describe its own features. This lets @value{GDBN} support
39863 processor variants it has never seen before --- to the extent that the
39864 descriptions are accurate, and that @value{GDBN} understands them.
39866 @value{GDBN} must be linked with the Expat library to support XML
39867 target descriptions. @xref{Expat}.
39870 * Retrieving Descriptions:: How descriptions are fetched from a target.
39871 * Target Description Format:: The contents of a target description.
39872 * Predefined Target Types:: Standard types available for target
39874 * Standard Target Features:: Features @value{GDBN} knows about.
39877 @node Retrieving Descriptions
39878 @section Retrieving Descriptions
39880 Target descriptions can be read from the target automatically, or
39881 specified by the user manually. The default behavior is to read the
39882 description from the target. @value{GDBN} retrieves it via the remote
39883 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39884 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39885 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39886 XML document, of the form described in @ref{Target Description
39889 Alternatively, you can specify a file to read for the target description.
39890 If a file is set, the target will not be queried. The commands to
39891 specify a file are:
39894 @cindex set tdesc filename
39895 @item set tdesc filename @var{path}
39896 Read the target description from @var{path}.
39898 @cindex unset tdesc filename
39899 @item unset tdesc filename
39900 Do not read the XML target description from a file. @value{GDBN}
39901 will use the description supplied by the current target.
39903 @cindex show tdesc filename
39904 @item show tdesc filename
39905 Show the filename to read for a target description, if any.
39909 @node Target Description Format
39910 @section Target Description Format
39911 @cindex target descriptions, XML format
39913 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39914 document which complies with the Document Type Definition provided in
39915 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39916 means you can use generally available tools like @command{xmllint} to
39917 check that your feature descriptions are well-formed and valid.
39918 However, to help people unfamiliar with XML write descriptions for
39919 their targets, we also describe the grammar here.
39921 Target descriptions can identify the architecture of the remote target
39922 and (for some architectures) provide information about custom register
39923 sets. They can also identify the OS ABI of the remote target.
39924 @value{GDBN} can use this information to autoconfigure for your
39925 target, or to warn you if you connect to an unsupported target.
39927 Here is a simple target description:
39930 <target version="1.0">
39931 <architecture>i386:x86-64</architecture>
39936 This minimal description only says that the target uses
39937 the x86-64 architecture.
39939 A target description has the following overall form, with [ ] marking
39940 optional elements and @dots{} marking repeatable elements. The elements
39941 are explained further below.
39944 <?xml version="1.0"?>
39945 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39946 <target version="1.0">
39947 @r{[}@var{architecture}@r{]}
39948 @r{[}@var{osabi}@r{]}
39949 @r{[}@var{compatible}@r{]}
39950 @r{[}@var{feature}@dots{}@r{]}
39955 The description is generally insensitive to whitespace and line
39956 breaks, under the usual common-sense rules. The XML version
39957 declaration and document type declaration can generally be omitted
39958 (@value{GDBN} does not require them), but specifying them may be
39959 useful for XML validation tools. The @samp{version} attribute for
39960 @samp{<target>} may also be omitted, but we recommend
39961 including it; if future versions of @value{GDBN} use an incompatible
39962 revision of @file{gdb-target.dtd}, they will detect and report
39963 the version mismatch.
39965 @subsection Inclusion
39966 @cindex target descriptions, inclusion
39969 @cindex <xi:include>
39972 It can sometimes be valuable to split a target description up into
39973 several different annexes, either for organizational purposes, or to
39974 share files between different possible target descriptions. You can
39975 divide a description into multiple files by replacing any element of
39976 the target description with an inclusion directive of the form:
39979 <xi:include href="@var{document}"/>
39983 When @value{GDBN} encounters an element of this form, it will retrieve
39984 the named XML @var{document}, and replace the inclusion directive with
39985 the contents of that document. If the current description was read
39986 using @samp{qXfer}, then so will be the included document;
39987 @var{document} will be interpreted as the name of an annex. If the
39988 current description was read from a file, @value{GDBN} will look for
39989 @var{document} as a file in the same directory where it found the
39990 original description.
39992 @subsection Architecture
39993 @cindex <architecture>
39995 An @samp{<architecture>} element has this form:
39998 <architecture>@var{arch}</architecture>
40001 @var{arch} is one of the architectures from the set accepted by
40002 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40005 @cindex @code{<osabi>}
40007 This optional field was introduced in @value{GDBN} version 7.0.
40008 Previous versions of @value{GDBN} ignore it.
40010 An @samp{<osabi>} element has this form:
40013 <osabi>@var{abi-name}</osabi>
40016 @var{abi-name} is an OS ABI name from the same selection accepted by
40017 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40019 @subsection Compatible Architecture
40020 @cindex @code{<compatible>}
40022 This optional field was introduced in @value{GDBN} version 7.0.
40023 Previous versions of @value{GDBN} ignore it.
40025 A @samp{<compatible>} element has this form:
40028 <compatible>@var{arch}</compatible>
40031 @var{arch} is one of the architectures from the set accepted by
40032 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40034 A @samp{<compatible>} element is used to specify that the target
40035 is able to run binaries in some other than the main target architecture
40036 given by the @samp{<architecture>} element. For example, on the
40037 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40038 or @code{powerpc:common64}, but the system is able to run binaries
40039 in the @code{spu} architecture as well. The way to describe this
40040 capability with @samp{<compatible>} is as follows:
40043 <architecture>powerpc:common</architecture>
40044 <compatible>spu</compatible>
40047 @subsection Features
40050 Each @samp{<feature>} describes some logical portion of the target
40051 system. Features are currently used to describe available CPU
40052 registers and the types of their contents. A @samp{<feature>} element
40056 <feature name="@var{name}">
40057 @r{[}@var{type}@dots{}@r{]}
40063 Each feature's name should be unique within the description. The name
40064 of a feature does not matter unless @value{GDBN} has some special
40065 knowledge of the contents of that feature; if it does, the feature
40066 should have its standard name. @xref{Standard Target Features}.
40070 Any register's value is a collection of bits which @value{GDBN} must
40071 interpret. The default interpretation is a two's complement integer,
40072 but other types can be requested by name in the register description.
40073 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40074 Target Types}), and the description can define additional composite types.
40076 Each type element must have an @samp{id} attribute, which gives
40077 a unique (within the containing @samp{<feature>}) name to the type.
40078 Types must be defined before they are used.
40081 Some targets offer vector registers, which can be treated as arrays
40082 of scalar elements. These types are written as @samp{<vector>} elements,
40083 specifying the array element type, @var{type}, and the number of elements,
40087 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40091 If a register's value is usefully viewed in multiple ways, define it
40092 with a union type containing the useful representations. The
40093 @samp{<union>} element contains one or more @samp{<field>} elements,
40094 each of which has a @var{name} and a @var{type}:
40097 <union id="@var{id}">
40098 <field name="@var{name}" type="@var{type}"/>
40104 If a register's value is composed from several separate values, define
40105 it with a structure type. There are two forms of the @samp{<struct>}
40106 element; a @samp{<struct>} element must either contain only bitfields
40107 or contain no bitfields. If the structure contains only bitfields,
40108 its total size in bytes must be specified, each bitfield must have an
40109 explicit start and end, and bitfields are automatically assigned an
40110 integer type. The field's @var{start} should be less than or
40111 equal to its @var{end}, and zero represents the least significant bit.
40114 <struct id="@var{id}" size="@var{size}">
40115 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40120 If the structure contains no bitfields, then each field has an
40121 explicit type, and no implicit padding is added.
40124 <struct id="@var{id}">
40125 <field name="@var{name}" type="@var{type}"/>
40131 If a register's value is a series of single-bit flags, define it with
40132 a flags type. The @samp{<flags>} element has an explicit @var{size}
40133 and contains one or more @samp{<field>} elements. Each field has a
40134 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40138 <flags id="@var{id}" size="@var{size}">
40139 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40144 @subsection Registers
40147 Each register is represented as an element with this form:
40150 <reg name="@var{name}"
40151 bitsize="@var{size}"
40152 @r{[}regnum="@var{num}"@r{]}
40153 @r{[}save-restore="@var{save-restore}"@r{]}
40154 @r{[}type="@var{type}"@r{]}
40155 @r{[}group="@var{group}"@r{]}/>
40159 The components are as follows:
40164 The register's name; it must be unique within the target description.
40167 The register's size, in bits.
40170 The register's number. If omitted, a register's number is one greater
40171 than that of the previous register (either in the current feature or in
40172 a preceding feature); the first register in the target description
40173 defaults to zero. This register number is used to read or write
40174 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40175 packets, and registers appear in the @code{g} and @code{G} packets
40176 in order of increasing register number.
40179 Whether the register should be preserved across inferior function
40180 calls; this must be either @code{yes} or @code{no}. The default is
40181 @code{yes}, which is appropriate for most registers except for
40182 some system control registers; this is not related to the target's
40186 The type of the register. It may be a predefined type, a type
40187 defined in the current feature, or one of the special types @code{int}
40188 and @code{float}. @code{int} is an integer type of the correct size
40189 for @var{bitsize}, and @code{float} is a floating point type (in the
40190 architecture's normal floating point format) of the correct size for
40191 @var{bitsize}. The default is @code{int}.
40194 The register group to which this register belongs. It must
40195 be either @code{general}, @code{float}, or @code{vector}. If no
40196 @var{group} is specified, @value{GDBN} will not display the register
40197 in @code{info registers}.
40201 @node Predefined Target Types
40202 @section Predefined Target Types
40203 @cindex target descriptions, predefined types
40205 Type definitions in the self-description can build up composite types
40206 from basic building blocks, but can not define fundamental types. Instead,
40207 standard identifiers are provided by @value{GDBN} for the fundamental
40208 types. The currently supported types are:
40217 Signed integer types holding the specified number of bits.
40224 Unsigned integer types holding the specified number of bits.
40228 Pointers to unspecified code and data. The program counter and
40229 any dedicated return address register may be marked as code
40230 pointers; printing a code pointer converts it into a symbolic
40231 address. The stack pointer and any dedicated address registers
40232 may be marked as data pointers.
40235 Single precision IEEE floating point.
40238 Double precision IEEE floating point.
40241 The 12-byte extended precision format used by ARM FPA registers.
40244 The 10-byte extended precision format used by x87 registers.
40247 32bit @sc{eflags} register used by x86.
40250 32bit @sc{mxcsr} register used by x86.
40254 @node Standard Target Features
40255 @section Standard Target Features
40256 @cindex target descriptions, standard features
40258 A target description must contain either no registers or all the
40259 target's registers. If the description contains no registers, then
40260 @value{GDBN} will assume a default register layout, selected based on
40261 the architecture. If the description contains any registers, the
40262 default layout will not be used; the standard registers must be
40263 described in the target description, in such a way that @value{GDBN}
40264 can recognize them.
40266 This is accomplished by giving specific names to feature elements
40267 which contain standard registers. @value{GDBN} will look for features
40268 with those names and verify that they contain the expected registers;
40269 if any known feature is missing required registers, or if any required
40270 feature is missing, @value{GDBN} will reject the target
40271 description. You can add additional registers to any of the
40272 standard features --- @value{GDBN} will display them just as if
40273 they were added to an unrecognized feature.
40275 This section lists the known features and their expected contents.
40276 Sample XML documents for these features are included in the
40277 @value{GDBN} source tree, in the directory @file{gdb/features}.
40279 Names recognized by @value{GDBN} should include the name of the
40280 company or organization which selected the name, and the overall
40281 architecture to which the feature applies; so e.g.@: the feature
40282 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40284 The names of registers are not case sensitive for the purpose
40285 of recognizing standard features, but @value{GDBN} will only display
40286 registers using the capitalization used in the description.
40289 * AArch64 Features::
40292 * MicroBlaze Features::
40295 * Nios II Features::
40296 * PowerPC Features::
40297 * S/390 and System z Features::
40302 @node AArch64 Features
40303 @subsection AArch64 Features
40304 @cindex target descriptions, AArch64 features
40306 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40307 targets. It should contain registers @samp{x0} through @samp{x30},
40308 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40310 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40311 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40315 @subsection ARM Features
40316 @cindex target descriptions, ARM features
40318 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40320 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40321 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40323 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40324 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40325 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40328 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40329 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40331 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40332 it should contain at least registers @samp{wR0} through @samp{wR15} and
40333 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40334 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40336 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40337 should contain at least registers @samp{d0} through @samp{d15}. If
40338 they are present, @samp{d16} through @samp{d31} should also be included.
40339 @value{GDBN} will synthesize the single-precision registers from
40340 halves of the double-precision registers.
40342 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40343 need to contain registers; it instructs @value{GDBN} to display the
40344 VFP double-precision registers as vectors and to synthesize the
40345 quad-precision registers from pairs of double-precision registers.
40346 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40347 be present and include 32 double-precision registers.
40349 @node i386 Features
40350 @subsection i386 Features
40351 @cindex target descriptions, i386 features
40353 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40354 targets. It should describe the following registers:
40358 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40360 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40362 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40363 @samp{fs}, @samp{gs}
40365 @samp{st0} through @samp{st7}
40367 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40368 @samp{foseg}, @samp{fooff} and @samp{fop}
40371 The register sets may be different, depending on the target.
40373 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40374 describe registers:
40378 @samp{xmm0} through @samp{xmm7} for i386
40380 @samp{xmm0} through @samp{xmm15} for amd64
40385 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40386 @samp{org.gnu.gdb.i386.sse} feature. It should
40387 describe the upper 128 bits of @sc{ymm} registers:
40391 @samp{ymm0h} through @samp{ymm7h} for i386
40393 @samp{ymm0h} through @samp{ymm15h} for amd64
40396 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40397 Memory Protection Extension (MPX). It should describe the following registers:
40401 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40403 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40406 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40407 describe a single register, @samp{orig_eax}.
40409 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40410 @samp{org.gnu.gdb.i386.avx} feature. It should
40411 describe additional @sc{xmm} registers:
40415 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40418 It should describe the upper 128 bits of additional @sc{ymm} registers:
40422 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40426 describe the upper 256 bits of @sc{zmm} registers:
40430 @samp{zmm0h} through @samp{zmm7h} for i386.
40432 @samp{zmm0h} through @samp{zmm15h} for amd64.
40436 describe the additional @sc{zmm} registers:
40440 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40443 @node MicroBlaze Features
40444 @subsection MicroBlaze Features
40445 @cindex target descriptions, MicroBlaze features
40447 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40448 targets. It should contain registers @samp{r0} through @samp{r31},
40449 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40450 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40451 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40453 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40454 If present, it should contain registers @samp{rshr} and @samp{rslr}
40456 @node MIPS Features
40457 @subsection @acronym{MIPS} Features
40458 @cindex target descriptions, @acronym{MIPS} features
40460 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40461 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40462 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40465 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40466 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40467 registers. They may be 32-bit or 64-bit depending on the target.
40469 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40470 it may be optional in a future version of @value{GDBN}. It should
40471 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40472 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40474 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40475 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40476 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40477 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40479 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40480 contain a single register, @samp{restart}, which is used by the
40481 Linux kernel to control restartable syscalls.
40483 @node M68K Features
40484 @subsection M68K Features
40485 @cindex target descriptions, M68K features
40488 @item @samp{org.gnu.gdb.m68k.core}
40489 @itemx @samp{org.gnu.gdb.coldfire.core}
40490 @itemx @samp{org.gnu.gdb.fido.core}
40491 One of those features must be always present.
40492 The feature that is present determines which flavor of m68k is
40493 used. The feature that is present should contain registers
40494 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40495 @samp{sp}, @samp{ps} and @samp{pc}.
40497 @item @samp{org.gnu.gdb.coldfire.fp}
40498 This feature is optional. If present, it should contain registers
40499 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40503 @node Nios II Features
40504 @subsection Nios II Features
40505 @cindex target descriptions, Nios II features
40507 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40508 targets. It should contain the 32 core registers (@samp{zero},
40509 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40510 @samp{pc}, and the 16 control registers (@samp{status} through
40513 @node PowerPC Features
40514 @subsection PowerPC Features
40515 @cindex target descriptions, PowerPC features
40517 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40518 targets. It should contain registers @samp{r0} through @samp{r31},
40519 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40520 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40522 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40523 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40525 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40526 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40529 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40530 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40531 will combine these registers with the floating point registers
40532 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40533 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40534 through @samp{vs63}, the set of vector registers for POWER7.
40536 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40537 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40538 @samp{spefscr}. SPE targets should provide 32-bit registers in
40539 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40540 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40541 these to present registers @samp{ev0} through @samp{ev31} to the
40544 @node S/390 and System z Features
40545 @subsection S/390 and System z Features
40546 @cindex target descriptions, S/390 features
40547 @cindex target descriptions, System z features
40549 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40550 System z targets. It should contain the PSW and the 16 general
40551 registers. In particular, System z targets should provide the 64-bit
40552 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40553 S/390 targets should provide the 32-bit versions of these registers.
40554 A System z target that runs in 31-bit addressing mode should provide
40555 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40556 register's upper halves @samp{r0h} through @samp{r15h}, and their
40557 lower halves @samp{r0l} through @samp{r15l}.
40559 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40560 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40563 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40564 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40566 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40567 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40568 targets and 32-bit otherwise. In addition, the feature may contain
40569 the @samp{last_break} register, whose width depends on the addressing
40570 mode, as well as the @samp{system_call} register, which is always
40573 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40574 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40575 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40577 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40578 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40579 combined by @value{GDBN} with the floating point registers @samp{f0}
40580 through @samp{f15} to present the 128-bit wide vector registers
40581 @samp{v0} through @samp{v15}. In addition, this feature should
40582 contain the 128-bit wide vector registers @samp{v16} through
40585 @node TIC6x Features
40586 @subsection TMS320C6x Features
40587 @cindex target descriptions, TIC6x features
40588 @cindex target descriptions, TMS320C6x features
40589 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40590 targets. It should contain registers @samp{A0} through @samp{A15},
40591 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40593 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40594 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40595 through @samp{B31}.
40597 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40598 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40600 @node Operating System Information
40601 @appendix Operating System Information
40602 @cindex operating system information
40608 Users of @value{GDBN} often wish to obtain information about the state of
40609 the operating system running on the target---for example the list of
40610 processes, or the list of open files. This section describes the
40611 mechanism that makes it possible. This mechanism is similar to the
40612 target features mechanism (@pxref{Target Descriptions}), but focuses
40613 on a different aspect of target.
40615 Operating system information is retrived from the target via the
40616 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40617 read}). The object name in the request should be @samp{osdata}, and
40618 the @var{annex} identifies the data to be fetched.
40621 @appendixsection Process list
40622 @cindex operating system information, process list
40624 When requesting the process list, the @var{annex} field in the
40625 @samp{qXfer} request should be @samp{processes}. The returned data is
40626 an XML document. The formal syntax of this document is defined in
40627 @file{gdb/features/osdata.dtd}.
40629 An example document is:
40632 <?xml version="1.0"?>
40633 <!DOCTYPE target SYSTEM "osdata.dtd">
40634 <osdata type="processes">
40636 <column name="pid">1</column>
40637 <column name="user">root</column>
40638 <column name="command">/sbin/init</column>
40639 <column name="cores">1,2,3</column>
40644 Each item should include a column whose name is @samp{pid}. The value
40645 of that column should identify the process on the target. The
40646 @samp{user} and @samp{command} columns are optional, and will be
40647 displayed by @value{GDBN}. The @samp{cores} column, if present,
40648 should contain a comma-separated list of cores that this process
40649 is running on. Target may provide additional columns,
40650 which @value{GDBN} currently ignores.
40652 @node Trace File Format
40653 @appendix Trace File Format
40654 @cindex trace file format
40656 The trace file comes in three parts: a header, a textual description
40657 section, and a trace frame section with binary data.
40659 The header has the form @code{\x7fTRACE0\n}. The first byte is
40660 @code{0x7f} so as to indicate that the file contains binary data,
40661 while the @code{0} is a version number that may have different values
40664 The description section consists of multiple lines of @sc{ascii} text
40665 separated by newline characters (@code{0xa}). The lines may include a
40666 variety of optional descriptive or context-setting information, such
40667 as tracepoint definitions or register set size. @value{GDBN} will
40668 ignore any line that it does not recognize. An empty line marks the end
40671 @c FIXME add some specific types of data
40673 The trace frame section consists of a number of consecutive frames.
40674 Each frame begins with a two-byte tracepoint number, followed by a
40675 four-byte size giving the amount of data in the frame. The data in
40676 the frame consists of a number of blocks, each introduced by a
40677 character indicating its type (at least register, memory, and trace
40678 state variable). The data in this section is raw binary, not a
40679 hexadecimal or other encoding; its endianness matches the target's
40682 @c FIXME bi-arch may require endianness/arch info in description section
40685 @item R @var{bytes}
40686 Register block. The number and ordering of bytes matches that of a
40687 @code{g} packet in the remote protocol. Note that these are the
40688 actual bytes, in target order and @value{GDBN} register order, not a
40689 hexadecimal encoding.
40691 @item M @var{address} @var{length} @var{bytes}...
40692 Memory block. This is a contiguous block of memory, at the 8-byte
40693 address @var{address}, with a 2-byte length @var{length}, followed by
40694 @var{length} bytes.
40696 @item V @var{number} @var{value}
40697 Trace state variable block. This records the 8-byte signed value
40698 @var{value} of trace state variable numbered @var{number}.
40702 Future enhancements of the trace file format may include additional types
40705 @node Index Section Format
40706 @appendix @code{.gdb_index} section format
40707 @cindex .gdb_index section format
40708 @cindex index section format
40710 This section documents the index section that is created by @code{save
40711 gdb-index} (@pxref{Index Files}). The index section is
40712 DWARF-specific; some knowledge of DWARF is assumed in this
40715 The mapped index file format is designed to be directly
40716 @code{mmap}able on any architecture. In most cases, a datum is
40717 represented using a little-endian 32-bit integer value, called an
40718 @code{offset_type}. Big endian machines must byte-swap the values
40719 before using them. Exceptions to this rule are noted. The data is
40720 laid out such that alignment is always respected.
40722 A mapped index consists of several areas, laid out in order.
40726 The file header. This is a sequence of values, of @code{offset_type}
40727 unless otherwise noted:
40731 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40732 Version 4 uses a different hashing function from versions 5 and 6.
40733 Version 6 includes symbols for inlined functions, whereas versions 4
40734 and 5 do not. Version 7 adds attributes to the CU indices in the
40735 symbol table. Version 8 specifies that symbols from DWARF type units
40736 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40737 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40739 @value{GDBN} will only read version 4, 5, or 6 indices
40740 by specifying @code{set use-deprecated-index-sections on}.
40741 GDB has a workaround for potentially broken version 7 indices so it is
40742 currently not flagged as deprecated.
40745 The offset, from the start of the file, of the CU list.
40748 The offset, from the start of the file, of the types CU list. Note
40749 that this area can be empty, in which case this offset will be equal
40750 to the next offset.
40753 The offset, from the start of the file, of the address area.
40756 The offset, from the start of the file, of the symbol table.
40759 The offset, from the start of the file, of the constant pool.
40763 The CU list. This is a sequence of pairs of 64-bit little-endian
40764 values, sorted by the CU offset. The first element in each pair is
40765 the offset of a CU in the @code{.debug_info} section. The second
40766 element in each pair is the length of that CU. References to a CU
40767 elsewhere in the map are done using a CU index, which is just the
40768 0-based index into this table. Note that if there are type CUs, then
40769 conceptually CUs and type CUs form a single list for the purposes of
40773 The types CU list. This is a sequence of triplets of 64-bit
40774 little-endian values. In a triplet, the first value is the CU offset,
40775 the second value is the type offset in the CU, and the third value is
40776 the type signature. The types CU list is not sorted.
40779 The address area. The address area consists of a sequence of address
40780 entries. Each address entry has three elements:
40784 The low address. This is a 64-bit little-endian value.
40787 The high address. This is a 64-bit little-endian value. Like
40788 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40791 The CU index. This is an @code{offset_type} value.
40795 The symbol table. This is an open-addressed hash table. The size of
40796 the hash table is always a power of 2.
40798 Each slot in the hash table consists of a pair of @code{offset_type}
40799 values. The first value is the offset of the symbol's name in the
40800 constant pool. The second value is the offset of the CU vector in the
40803 If both values are 0, then this slot in the hash table is empty. This
40804 is ok because while 0 is a valid constant pool index, it cannot be a
40805 valid index for both a string and a CU vector.
40807 The hash value for a table entry is computed by applying an
40808 iterative hash function to the symbol's name. Starting with an
40809 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40810 the string is incorporated into the hash using the formula depending on the
40815 The formula is @code{r = r * 67 + c - 113}.
40817 @item Versions 5 to 7
40818 The formula is @code{r = r * 67 + tolower (c) - 113}.
40821 The terminating @samp{\0} is not incorporated into the hash.
40823 The step size used in the hash table is computed via
40824 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40825 value, and @samp{size} is the size of the hash table. The step size
40826 is used to find the next candidate slot when handling a hash
40829 The names of C@t{++} symbols in the hash table are canonicalized. We
40830 don't currently have a simple description of the canonicalization
40831 algorithm; if you intend to create new index sections, you must read
40835 The constant pool. This is simply a bunch of bytes. It is organized
40836 so that alignment is correct: CU vectors are stored first, followed by
40839 A CU vector in the constant pool is a sequence of @code{offset_type}
40840 values. The first value is the number of CU indices in the vector.
40841 Each subsequent value is the index and symbol attributes of a CU in
40842 the CU list. This element in the hash table is used to indicate which
40843 CUs define the symbol and how the symbol is used.
40844 See below for the format of each CU index+attributes entry.
40846 A string in the constant pool is zero-terminated.
40849 Attributes were added to CU index values in @code{.gdb_index} version 7.
40850 If a symbol has multiple uses within a CU then there is one
40851 CU index+attributes value for each use.
40853 The format of each CU index+attributes entry is as follows
40859 This is the index of the CU in the CU list.
40861 These bits are reserved for future purposes and must be zero.
40863 The kind of the symbol in the CU.
40867 This value is reserved and should not be used.
40868 By reserving zero the full @code{offset_type} value is backwards compatible
40869 with previous versions of the index.
40871 The symbol is a type.
40873 The symbol is a variable or an enum value.
40875 The symbol is a function.
40877 Any other kind of symbol.
40879 These values are reserved.
40883 This bit is zero if the value is global and one if it is static.
40885 The determination of whether a symbol is global or static is complicated.
40886 The authorative reference is the file @file{dwarf2read.c} in
40887 @value{GDBN} sources.
40891 This pseudo-code describes the computation of a symbol's kind and
40892 global/static attributes in the index.
40895 is_external = get_attribute (die, DW_AT_external);
40896 language = get_attribute (cu_die, DW_AT_language);
40899 case DW_TAG_typedef:
40900 case DW_TAG_base_type:
40901 case DW_TAG_subrange_type:
40905 case DW_TAG_enumerator:
40907 is_static = (language != CPLUS && language != JAVA);
40909 case DW_TAG_subprogram:
40911 is_static = ! (is_external || language == ADA);
40913 case DW_TAG_constant:
40915 is_static = ! is_external;
40917 case DW_TAG_variable:
40919 is_static = ! is_external;
40921 case DW_TAG_namespace:
40925 case DW_TAG_class_type:
40926 case DW_TAG_interface_type:
40927 case DW_TAG_structure_type:
40928 case DW_TAG_union_type:
40929 case DW_TAG_enumeration_type:
40931 is_static = (language != CPLUS && language != JAVA);
40939 @appendix Manual pages
40943 * gdb man:: The GNU Debugger man page
40944 * gdbserver man:: Remote Server for the GNU Debugger man page
40945 * gcore man:: Generate a core file of a running program
40946 * gdbinit man:: gdbinit scripts
40952 @c man title gdb The GNU Debugger
40954 @c man begin SYNOPSIS gdb
40955 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40956 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40957 [@option{-b}@w{ }@var{bps}]
40958 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40959 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40960 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40961 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40962 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40965 @c man begin DESCRIPTION gdb
40966 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40967 going on ``inside'' another program while it executes -- or what another
40968 program was doing at the moment it crashed.
40970 @value{GDBN} can do four main kinds of things (plus other things in support of
40971 these) to help you catch bugs in the act:
40975 Start your program, specifying anything that might affect its behavior.
40978 Make your program stop on specified conditions.
40981 Examine what has happened, when your program has stopped.
40984 Change things in your program, so you can experiment with correcting the
40985 effects of one bug and go on to learn about another.
40988 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40991 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40992 commands from the terminal until you tell it to exit with the @value{GDBN}
40993 command @code{quit}. You can get online help from @value{GDBN} itself
40994 by using the command @code{help}.
40996 You can run @code{gdb} with no arguments or options; but the most
40997 usual way to start @value{GDBN} is with one argument or two, specifying an
40998 executable program as the argument:
41004 You can also start with both an executable program and a core file specified:
41010 You can, instead, specify a process ID as a second argument, if you want
41011 to debug a running process:
41019 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41020 named @file{1234}; @value{GDBN} does check for a core file first).
41021 With option @option{-p} you can omit the @var{program} filename.
41023 Here are some of the most frequently needed @value{GDBN} commands:
41025 @c pod2man highlights the right hand side of the @item lines.
41027 @item break [@var{file}:]@var{functiop}
41028 Set a breakpoint at @var{function} (in @var{file}).
41030 @item run [@var{arglist}]
41031 Start your program (with @var{arglist}, if specified).
41034 Backtrace: display the program stack.
41036 @item print @var{expr}
41037 Display the value of an expression.
41040 Continue running your program (after stopping, e.g. at a breakpoint).
41043 Execute next program line (after stopping); step @emph{over} any
41044 function calls in the line.
41046 @item edit [@var{file}:]@var{function}
41047 look at the program line where it is presently stopped.
41049 @item list [@var{file}:]@var{function}
41050 type the text of the program in the vicinity of where it is presently stopped.
41053 Execute next program line (after stopping); step @emph{into} any
41054 function calls in the line.
41056 @item help [@var{name}]
41057 Show information about @value{GDBN} command @var{name}, or general information
41058 about using @value{GDBN}.
41061 Exit from @value{GDBN}.
41065 For full details on @value{GDBN},
41066 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41067 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41068 as the @code{gdb} entry in the @code{info} program.
41072 @c man begin OPTIONS gdb
41073 Any arguments other than options specify an executable
41074 file and core file (or process ID); that is, the first argument
41075 encountered with no
41076 associated option flag is equivalent to a @option{-se} option, and the second,
41077 if any, is equivalent to a @option{-c} option if it's the name of a file.
41079 both long and short forms; both are shown here. The long forms are also
41080 recognized if you truncate them, so long as enough of the option is
41081 present to be unambiguous. (If you prefer, you can flag option
41082 arguments with @option{+} rather than @option{-}, though we illustrate the
41083 more usual convention.)
41085 All the options and command line arguments you give are processed
41086 in sequential order. The order makes a difference when the @option{-x}
41092 List all options, with brief explanations.
41094 @item -symbols=@var{file}
41095 @itemx -s @var{file}
41096 Read symbol table from file @var{file}.
41099 Enable writing into executable and core files.
41101 @item -exec=@var{file}
41102 @itemx -e @var{file}
41103 Use file @var{file} as the executable file to execute when
41104 appropriate, and for examining pure data in conjunction with a core
41107 @item -se=@var{file}
41108 Read symbol table from file @var{file} and use it as the executable
41111 @item -core=@var{file}
41112 @itemx -c @var{file}
41113 Use file @var{file} as a core dump to examine.
41115 @item -command=@var{file}
41116 @itemx -x @var{file}
41117 Execute @value{GDBN} commands from file @var{file}.
41119 @item -ex @var{command}
41120 Execute given @value{GDBN} @var{command}.
41122 @item -directory=@var{directory}
41123 @itemx -d @var{directory}
41124 Add @var{directory} to the path to search for source files.
41127 Do not execute commands from @file{~/.gdbinit}.
41131 Do not execute commands from any @file{.gdbinit} initialization files.
41135 ``Quiet''. Do not print the introductory and copyright messages. These
41136 messages are also suppressed in batch mode.
41139 Run in batch mode. Exit with status @code{0} after processing all the command
41140 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41141 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41142 commands in the command files.
41144 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41145 download and run a program on another computer; in order to make this
41146 more useful, the message
41149 Program exited normally.
41153 (which is ordinarily issued whenever a program running under @value{GDBN} control
41154 terminates) is not issued when running in batch mode.
41156 @item -cd=@var{directory}
41157 Run @value{GDBN} using @var{directory} as its working directory,
41158 instead of the current directory.
41162 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41163 @value{GDBN} to output the full file name and line number in a standard,
41164 recognizable fashion each time a stack frame is displayed (which
41165 includes each time the program stops). This recognizable format looks
41166 like two @samp{\032} characters, followed by the file name, line number
41167 and character position separated by colons, and a newline. The
41168 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41169 characters as a signal to display the source code for the frame.
41172 Set the line speed (baud rate or bits per second) of any serial
41173 interface used by @value{GDBN} for remote debugging.
41175 @item -tty=@var{device}
41176 Run using @var{device} for your program's standard input and output.
41180 @c man begin SEEALSO gdb
41182 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41183 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41184 documentation are properly installed at your site, the command
41191 should give you access to the complete manual.
41193 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41194 Richard M. Stallman and Roland H. Pesch, July 1991.
41198 @node gdbserver man
41199 @heading gdbserver man
41201 @c man title gdbserver Remote Server for the GNU Debugger
41203 @c man begin SYNOPSIS gdbserver
41204 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41206 gdbserver --attach @var{comm} @var{pid}
41208 gdbserver --multi @var{comm}
41212 @c man begin DESCRIPTION gdbserver
41213 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41214 than the one which is running the program being debugged.
41217 @subheading Usage (server (target) side)
41220 Usage (server (target) side):
41223 First, you need to have a copy of the program you want to debug put onto
41224 the target system. The program can be stripped to save space if needed, as
41225 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41226 the @value{GDBN} running on the host system.
41228 To use the server, you log on to the target system, and run the @command{gdbserver}
41229 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41230 your program, and (c) its arguments. The general syntax is:
41233 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41236 For example, using a serial port, you might say:
41240 @c @file would wrap it as F</dev/com1>.
41241 target> gdbserver /dev/com1 emacs foo.txt
41244 target> gdbserver @file{/dev/com1} emacs foo.txt
41248 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41249 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41250 waits patiently for the host @value{GDBN} to communicate with it.
41252 To use a TCP connection, you could say:
41255 target> gdbserver host:2345 emacs foo.txt
41258 This says pretty much the same thing as the last example, except that we are
41259 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41260 that we are expecting to see a TCP connection from @code{host} to local TCP port
41261 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41262 want for the port number as long as it does not conflict with any existing TCP
41263 ports on the target system. This same port number must be used in the host
41264 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41265 you chose a port number that conflicts with another service, @command{gdbserver} will
41266 print an error message and exit.
41268 @command{gdbserver} can also attach to running programs.
41269 This is accomplished via the @option{--attach} argument. The syntax is:
41272 target> gdbserver --attach @var{comm} @var{pid}
41275 @var{pid} is the process ID of a currently running process. It isn't
41276 necessary to point @command{gdbserver} at a binary for the running process.
41278 To start @code{gdbserver} without supplying an initial command to run
41279 or process ID to attach, use the @option{--multi} command line option.
41280 In such case you should connect using @kbd{target extended-remote} to start
41281 the program you want to debug.
41284 target> gdbserver --multi @var{comm}
41288 @subheading Usage (host side)
41294 You need an unstripped copy of the target program on your host system, since
41295 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41296 would, with the target program as the first argument. (You may need to use the
41297 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41298 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41299 new command you need to know about is @code{target remote}
41300 (or @code{target extended-remote}). Its argument is either
41301 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41302 descriptor. For example:
41306 @c @file would wrap it as F</dev/ttyb>.
41307 (gdb) target remote /dev/ttyb
41310 (gdb) target remote @file{/dev/ttyb}
41315 communicates with the server via serial line @file{/dev/ttyb}, and:
41318 (gdb) target remote the-target:2345
41322 communicates via a TCP connection to port 2345 on host `the-target', where
41323 you previously started up @command{gdbserver} with the same port number. Note that for
41324 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41325 command, otherwise you may get an error that looks something like
41326 `Connection refused'.
41328 @command{gdbserver} can also debug multiple inferiors at once,
41331 the @value{GDBN} manual in node @code{Inferiors and Programs}
41332 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41335 @ref{Inferiors and Programs}.
41337 In such case use the @code{extended-remote} @value{GDBN} command variant:
41340 (gdb) target extended-remote the-target:2345
41343 The @command{gdbserver} option @option{--multi} may or may not be used in such
41347 @c man begin OPTIONS gdbserver
41348 There are three different modes for invoking @command{gdbserver}:
41353 Debug a specific program specified by its program name:
41356 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41359 The @var{comm} parameter specifies how should the server communicate
41360 with @value{GDBN}; it is either a device name (to use a serial line),
41361 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41362 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41363 debug in @var{prog}. Any remaining arguments will be passed to the
41364 program verbatim. When the program exits, @value{GDBN} will close the
41365 connection, and @code{gdbserver} will exit.
41368 Debug a specific program by specifying the process ID of a running
41372 gdbserver --attach @var{comm} @var{pid}
41375 The @var{comm} parameter is as described above. Supply the process ID
41376 of a running program in @var{pid}; @value{GDBN} will do everything
41377 else. Like with the previous mode, when the process @var{pid} exits,
41378 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41381 Multi-process mode -- debug more than one program/process:
41384 gdbserver --multi @var{comm}
41387 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41388 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41389 close the connection when a process being debugged exits, so you can
41390 debug several processes in the same session.
41393 In each of the modes you may specify these options:
41398 List all options, with brief explanations.
41401 This option causes @command{gdbserver} to print its version number and exit.
41404 @command{gdbserver} will attach to a running program. The syntax is:
41407 target> gdbserver --attach @var{comm} @var{pid}
41410 @var{pid} is the process ID of a currently running process. It isn't
41411 necessary to point @command{gdbserver} at a binary for the running process.
41414 To start @code{gdbserver} without supplying an initial command to run
41415 or process ID to attach, use this command line option.
41416 Then you can connect using @kbd{target extended-remote} and start
41417 the program you want to debug. The syntax is:
41420 target> gdbserver --multi @var{comm}
41424 Instruct @code{gdbserver} to display extra status information about the debugging
41426 This option is intended for @code{gdbserver} development and for bug reports to
41429 @item --remote-debug
41430 Instruct @code{gdbserver} to display remote protocol debug output.
41431 This option is intended for @code{gdbserver} development and for bug reports to
41434 @item --debug-format=option1@r{[},option2,...@r{]}
41435 Instruct @code{gdbserver} to include extra information in each line
41436 of debugging output.
41437 @xref{Other Command-Line Arguments for gdbserver}.
41440 Specify a wrapper to launch programs
41441 for debugging. The option should be followed by the name of the
41442 wrapper, then any command-line arguments to pass to the wrapper, then
41443 @kbd{--} indicating the end of the wrapper arguments.
41446 By default, @command{gdbserver} keeps the listening TCP port open, so that
41447 additional connections are possible. However, if you start @code{gdbserver}
41448 with the @option{--once} option, it will stop listening for any further
41449 connection attempts after connecting to the first @value{GDBN} session.
41451 @c --disable-packet is not documented for users.
41453 @c --disable-randomization and --no-disable-randomization are superseded by
41454 @c QDisableRandomization.
41459 @c man begin SEEALSO gdbserver
41461 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41462 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41463 documentation are properly installed at your site, the command
41469 should give you access to the complete manual.
41471 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41472 Richard M. Stallman and Roland H. Pesch, July 1991.
41479 @c man title gcore Generate a core file of a running program
41482 @c man begin SYNOPSIS gcore
41483 gcore [-o @var{filename}] @var{pid}
41487 @c man begin DESCRIPTION gcore
41488 Generate a core dump of a running program with process ID @var{pid}.
41489 Produced file is equivalent to a kernel produced core file as if the process
41490 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41491 limit). Unlike after a crash, after @command{gcore} the program remains
41492 running without any change.
41495 @c man begin OPTIONS gcore
41497 @item -o @var{filename}
41498 The optional argument
41499 @var{filename} specifies the file name where to put the core dump.
41500 If not specified, the file name defaults to @file{core.@var{pid}},
41501 where @var{pid} is the running program process ID.
41505 @c man begin SEEALSO gcore
41507 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41508 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41509 documentation are properly installed at your site, the command
41516 should give you access to the complete manual.
41518 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41519 Richard M. Stallman and Roland H. Pesch, July 1991.
41526 @c man title gdbinit GDB initialization scripts
41529 @c man begin SYNOPSIS gdbinit
41530 @ifset SYSTEM_GDBINIT
41531 @value{SYSTEM_GDBINIT}
41540 @c man begin DESCRIPTION gdbinit
41541 These files contain @value{GDBN} commands to automatically execute during
41542 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41545 the @value{GDBN} manual in node @code{Sequences}
41546 -- shell command @code{info -f gdb -n Sequences}.
41552 Please read more in
41554 the @value{GDBN} manual in node @code{Startup}
41555 -- shell command @code{info -f gdb -n Startup}.
41562 @ifset SYSTEM_GDBINIT
41563 @item @value{SYSTEM_GDBINIT}
41565 @ifclear SYSTEM_GDBINIT
41566 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41568 System-wide initialization file. It is executed unless user specified
41569 @value{GDBN} option @code{-nx} or @code{-n}.
41572 the @value{GDBN} manual in node @code{System-wide configuration}
41573 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41576 @ref{System-wide configuration}.
41580 User initialization file. It is executed unless user specified
41581 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41584 Initialization file for current directory. It may need to be enabled with
41585 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41588 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41589 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41592 @ref{Init File in the Current Directory}.
41597 @c man begin SEEALSO gdbinit
41599 gdb(1), @code{info -f gdb -n Startup}
41601 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41602 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41603 documentation are properly installed at your site, the command
41609 should give you access to the complete manual.
41611 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41612 Richard M. Stallman and Roland H. Pesch, July 1991.
41618 @node GNU Free Documentation License
41619 @appendix GNU Free Documentation License
41622 @node Concept Index
41623 @unnumbered Concept Index
41627 @node Command and Variable Index
41628 @unnumbered Command, Variable, and Function Index
41633 % I think something like @@colophon should be in texinfo. In the
41635 \long\def\colophon{\hbox to0pt{}\vfill
41636 \centerline{The body of this manual is set in}
41637 \centerline{\fontname\tenrm,}
41638 \centerline{with headings in {\bf\fontname\tenbf}}
41639 \centerline{and examples in {\tt\fontname\tentt}.}
41640 \centerline{{\it\fontname\tenit\/},}
41641 \centerline{{\bf\fontname\tenbf}, and}
41642 \centerline{{\sl\fontname\tensl\/}}
41643 \centerline{are used for emphasis.}\vfill}
41645 % Blame: doc@@cygnus.com, 1991.