1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2016 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{} 1988-2016 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) 1988-2016 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.
2661 @vindex $_inferior@r{, convenience variable}
2662 The debugger convenience variable @samp{$_inferior} contains the
2663 number of the current inferior. You may find this useful in writing
2664 breakpoint conditional expressions, command scripts, and so forth.
2665 @xref{Convenience Vars,, Convenience Variables}, for general
2666 information on convenience variables.
2668 You can get multiple executables into a debugging session via the
2669 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2670 systems @value{GDBN} can add inferiors to the debug session
2671 automatically by following calls to @code{fork} and @code{exec}. To
2672 remove inferiors from the debugging session use the
2673 @w{@code{remove-inferiors}} command.
2676 @kindex add-inferior
2677 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2678 Adds @var{n} inferiors to be run using @var{executable} as the
2679 executable; @var{n} defaults to 1. If no executable is specified,
2680 the inferiors begins empty, with no program. You can still assign or
2681 change the program assigned to the inferior at any time by using the
2682 @code{file} command with the executable name as its argument.
2684 @kindex clone-inferior
2685 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2686 Adds @var{n} inferiors ready to execute the same program as inferior
2687 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2688 number of the current inferior. This is a convenient command when you
2689 want to run another instance of the inferior you are debugging.
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2694 * 1 process 29964 helloworld
2695 (@value{GDBP}) clone-inferior
2698 (@value{GDBP}) info inferiors
2699 Num Description Executable
2701 * 1 process 29964 helloworld
2704 You can now simply switch focus to inferior 2 and run it.
2706 @kindex remove-inferiors
2707 @item remove-inferiors @var{infno}@dots{}
2708 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2709 possible to remove an inferior that is running with this command. For
2710 those, use the @code{kill} or @code{detach} command first.
2714 To quit debugging one of the running inferiors that is not the current
2715 inferior, you can either detach from it by using the @w{@code{detach
2716 inferior}} command (allowing it to run independently), or kill it
2717 using the @w{@code{kill inferiors}} command:
2720 @kindex detach inferiors @var{infno}@dots{}
2721 @item detach inferior @var{infno}@dots{}
2722 Detach from the inferior or inferiors identified by @value{GDBN}
2723 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2724 still stays on the list of inferiors shown by @code{info inferiors},
2725 but its Description will show @samp{<null>}.
2727 @kindex kill inferiors @var{infno}@dots{}
2728 @item kill inferiors @var{infno}@dots{}
2729 Kill the inferior or inferiors identified by @value{GDBN} inferior
2730 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2731 stays on the list of inferiors shown by @code{info inferiors}, but its
2732 Description will show @samp{<null>}.
2735 After the successful completion of a command such as @code{detach},
2736 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2737 a normal process exit, the inferior is still valid and listed with
2738 @code{info inferiors}, ready to be restarted.
2741 To be notified when inferiors are started or exit under @value{GDBN}'s
2742 control use @w{@code{set print inferior-events}}:
2745 @kindex set print inferior-events
2746 @cindex print messages on inferior start and exit
2747 @item set print inferior-events
2748 @itemx set print inferior-events on
2749 @itemx set print inferior-events off
2750 The @code{set print inferior-events} command allows you to enable or
2751 disable printing of messages when @value{GDBN} notices that new
2752 inferiors have started or that inferiors have exited or have been
2753 detached. By default, these messages will not be printed.
2755 @kindex show print inferior-events
2756 @item show print inferior-events
2757 Show whether messages will be printed when @value{GDBN} detects that
2758 inferiors have started, exited or have been detached.
2761 Many commands will work the same with multiple programs as with a
2762 single program: e.g., @code{print myglobal} will simply display the
2763 value of @code{myglobal} in the current inferior.
2766 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2767 get more info about the relationship of inferiors, programs, address
2768 spaces in a debug session. You can do that with the @w{@code{maint
2769 info program-spaces}} command.
2772 @kindex maint info program-spaces
2773 @item maint info program-spaces
2774 Print a list of all program spaces currently being managed by
2777 @value{GDBN} displays for each program space (in this order):
2781 the program space number assigned by @value{GDBN}
2784 the name of the executable loaded into the program space, with e.g.,
2785 the @code{file} command.
2790 An asterisk @samp{*} preceding the @value{GDBN} program space number
2791 indicates the current program space.
2793 In addition, below each program space line, @value{GDBN} prints extra
2794 information that isn't suitable to display in tabular form. For
2795 example, the list of inferiors bound to the program space.
2798 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2805 Here we can see that no inferior is running the program @code{hello},
2806 while @code{process 21561} is running the program @code{goodbye}. On
2807 some targets, it is possible that multiple inferiors are bound to the
2808 same program space. The most common example is that of debugging both
2809 the parent and child processes of a @code{vfork} call. For example,
2812 (@value{GDBP}) maint info program-spaces
2815 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2818 Here, both inferior 2 and inferior 1 are running in the same program
2819 space as a result of inferior 1 having executed a @code{vfork} call.
2823 @section Debugging Programs with Multiple Threads
2825 @cindex threads of execution
2826 @cindex multiple threads
2827 @cindex switching threads
2828 In some operating systems, such as GNU/Linux and Solaris, a single program
2829 may have more than one @dfn{thread} of execution. The precise semantics
2830 of threads differ from one operating system to another, but in general
2831 the threads of a single program are akin to multiple processes---except
2832 that they share one address space (that is, they can all examine and
2833 modify the same variables). On the other hand, each thread has its own
2834 registers and execution stack, and perhaps private memory.
2836 @value{GDBN} provides these facilities for debugging multi-thread
2840 @item automatic notification of new threads
2841 @item @samp{thread @var{thread-id}}, a command to switch among threads
2842 @item @samp{info threads}, a command to inquire about existing threads
2843 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2844 a command to apply a command to a list of threads
2845 @item thread-specific breakpoints
2846 @item @samp{set print thread-events}, which controls printing of
2847 messages on thread start and exit.
2848 @item @samp{set libthread-db-search-path @var{path}}, which lets
2849 the user specify which @code{libthread_db} to use if the default choice
2850 isn't compatible with the program.
2853 @cindex focus of debugging
2854 @cindex current thread
2855 The @value{GDBN} thread debugging facility allows you to observe all
2856 threads while your program runs---but whenever @value{GDBN} takes
2857 control, one thread in particular is always the focus of debugging.
2858 This thread is called the @dfn{current thread}. Debugging commands show
2859 program information from the perspective of the current thread.
2861 @cindex @code{New} @var{systag} message
2862 @cindex thread identifier (system)
2863 @c FIXME-implementors!! It would be more helpful if the [New...] message
2864 @c included GDB's numeric thread handle, so you could just go to that
2865 @c thread without first checking `info threads'.
2866 Whenever @value{GDBN} detects a new thread in your program, it displays
2867 the target system's identification for the thread with a message in the
2868 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2869 whose form varies depending on the particular system. For example, on
2870 @sc{gnu}/Linux, you might see
2873 [New Thread 0x41e02940 (LWP 25582)]
2877 when @value{GDBN} notices a new thread. In contrast, on other systems,
2878 the @var{systag} is simply something like @samp{process 368}, with no
2881 @c FIXME!! (1) Does the [New...] message appear even for the very first
2882 @c thread of a program, or does it only appear for the
2883 @c second---i.e.@: when it becomes obvious we have a multithread
2885 @c (2) *Is* there necessarily a first thread always? Or do some
2886 @c multithread systems permit starting a program with multiple
2887 @c threads ab initio?
2889 @anchor{thread numbers}
2890 @cindex thread number, per inferior
2891 @cindex thread identifier (GDB)
2892 For debugging purposes, @value{GDBN} associates its own thread number
2893 ---always a single integer---with each thread of an inferior. This
2894 number is unique between all threads of an inferior, but not unique
2895 between threads of different inferiors.
2897 @cindex qualified thread ID
2898 You can refer to a given thread in an inferior using the qualified
2899 @var{inferior-num}.@var{thread-num} syntax, also known as
2900 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2901 number and @var{thread-num} being the thread number of the given
2902 inferior. For example, thread @code{2.3} refers to thread number 3 of
2903 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2904 then @value{GDBN} infers you're referring to a thread of the current
2907 Until you create a second inferior, @value{GDBN} does not show the
2908 @var{inferior-num} part of thread IDs, even though you can always use
2909 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2910 of inferior 1, the initial inferior.
2912 @anchor{thread ID lists}
2913 @cindex thread ID lists
2914 Some commands accept a space-separated @dfn{thread ID list} as
2915 argument. A list element can be a thread ID as shown in the first
2916 field of the @samp{info threads} display, with or without an inferior
2917 qualifier (e.g., @samp{2.1} or @samp{1}); or can be a range of thread
2918 numbers, again with or without an inferior qualifier, as in
2919 @var{inf1}.@var{thr1}-@var{thr2} or @var{thr1}-@var{thr2} (e.g.,
2920 @samp{1.2-4} or @samp{2-4}). For example, if the current inferior is
2921 1, the thread list @samp{1 2-3 4.5 6.7-9} includes threads 1 to 3 of
2922 inferior 1, thread 5 of inferior 4 and threads 7 to 9 of inferior 6.
2923 That is, in expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5
2926 @anchor{global thread numbers}
2927 @cindex global thread number
2928 @cindex global thread identifier (GDB)
2929 In addition to a @emph{per-inferior} number, each thread is also
2930 assigned a unique @emph{global} number, also known as @dfn{global
2931 thread ID}, a single integer. Unlike the thread number component of
2932 the thread ID, no two threads have the same global ID, even when
2933 you're debugging multiple inferiors.
2935 From @value{GDBN}'s perspective, a process always has at least one
2936 thread. In other words, @value{GDBN} assigns a thread number to the
2937 program's ``main thread'' even if the program is not multi-threaded.
2939 @vindex $_thread@r{, convenience variable}
2940 The debugger convenience variable @samp{$_thread} contains the
2941 per-inferior thread number of the current thread. You may find this
2942 useful in writing breakpoint conditional expressions, command scripts,
2943 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2944 general information on convenience variables.
2947 @kindex info threads
2948 @item info threads @r{[}@var{thread-id-list}@r{]}
2950 Display information about one or more threads. With no arguments
2951 displays information about all threads. You can specify the list of
2952 threads that you want to display using the thread ID list syntax
2953 (@pxref{thread ID lists}).
2955 @value{GDBN} displays for each thread (in this order):
2959 the per-inferior thread number assigned by @value{GDBN}
2962 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
2963 option was specified
2966 the target system's thread identifier (@var{systag})
2969 the thread's name, if one is known. A thread can either be named by
2970 the user (see @code{thread name}, below), or, in some cases, by the
2974 the current stack frame summary for that thread
2978 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2979 indicates the current thread.
2983 @c end table here to get a little more width for example
2986 (@value{GDBP}) info threads
2988 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2989 2 process 35 thread 23 0x34e5 in sigpause ()
2990 3 process 35 thread 27 0x34e5 in sigpause ()
2994 If you're debugging multiple inferiors, @value{GDBN} displays thread
2995 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
2996 Otherwise, only @var{thread-num} is shown.
2998 If you specify the @samp{-gid} option, @value{GDBN} displays a column
2999 indicating each thread's global thread ID:
3002 (@value{GDBP}) info threads
3003 Id GId Target Id Frame
3004 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3005 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3006 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3007 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3010 On Solaris, you can display more information about user threads with a
3011 Solaris-specific command:
3014 @item maint info sol-threads
3015 @kindex maint info sol-threads
3016 @cindex thread info (Solaris)
3017 Display info on Solaris user threads.
3021 @kindex thread @var{thread-id}
3022 @item thread @var{thread-id}
3023 Make thread ID @var{thread-id} the current thread. The command
3024 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3025 the first field of the @samp{info threads} display, with or without an
3026 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3028 @value{GDBN} responds by displaying the system identifier of the
3029 thread you selected, and its current stack frame summary:
3032 (@value{GDBP}) thread 2
3033 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3034 #0 some_function (ignore=0x0) at example.c:8
3035 8 printf ("hello\n");
3039 As with the @samp{[New @dots{}]} message, the form of the text after
3040 @samp{Switching to} depends on your system's conventions for identifying
3043 @kindex thread apply
3044 @cindex apply command to several threads
3045 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3046 The @code{thread apply} command allows you to apply the named
3047 @var{command} to one or more threads. Specify the threads that you
3048 want affected using the thread ID list syntax (@pxref{thread ID
3049 lists}), or specify @code{all} to apply to all threads. To apply a
3050 command to all threads in descending order, type @kbd{thread apply all
3051 @var{command}}. To apply a command to all threads in ascending order,
3052 type @kbd{thread apply all -ascending @var{command}}.
3056 @cindex name a thread
3057 @item thread name [@var{name}]
3058 This command assigns a name to the current thread. If no argument is
3059 given, any existing user-specified name is removed. The thread name
3060 appears in the @samp{info threads} display.
3062 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3063 determine the name of the thread as given by the OS. On these
3064 systems, a name specified with @samp{thread name} will override the
3065 system-give name, and removing the user-specified name will cause
3066 @value{GDBN} to once again display the system-specified name.
3069 @cindex search for a thread
3070 @item thread find [@var{regexp}]
3071 Search for and display thread ids whose name or @var{systag}
3072 matches the supplied regular expression.
3074 As well as being the complement to the @samp{thread name} command,
3075 this command also allows you to identify a thread by its target
3076 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3080 (@value{GDBN}) thread find 26688
3081 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3082 (@value{GDBN}) info thread 4
3084 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3087 @kindex set print thread-events
3088 @cindex print messages on thread start and exit
3089 @item set print thread-events
3090 @itemx set print thread-events on
3091 @itemx set print thread-events off
3092 The @code{set print thread-events} command allows you to enable or
3093 disable printing of messages when @value{GDBN} notices that new threads have
3094 started or that threads have exited. By default, these messages will
3095 be printed if detection of these events is supported by the target.
3096 Note that these messages cannot be disabled on all targets.
3098 @kindex show print thread-events
3099 @item show print thread-events
3100 Show whether messages will be printed when @value{GDBN} detects that threads
3101 have started and exited.
3104 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3105 more information about how @value{GDBN} behaves when you stop and start
3106 programs with multiple threads.
3108 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3109 watchpoints in programs with multiple threads.
3111 @anchor{set libthread-db-search-path}
3113 @kindex set libthread-db-search-path
3114 @cindex search path for @code{libthread_db}
3115 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3116 If this variable is set, @var{path} is a colon-separated list of
3117 directories @value{GDBN} will use to search for @code{libthread_db}.
3118 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3119 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3120 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3123 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3124 @code{libthread_db} library to obtain information about threads in the
3125 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3126 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3127 specific thread debugging library loading is enabled
3128 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3130 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3131 refers to the default system directories that are
3132 normally searched for loading shared libraries. The @samp{$sdir} entry
3133 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3134 (@pxref{libthread_db.so.1 file}).
3136 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3137 refers to the directory from which @code{libpthread}
3138 was loaded in the inferior process.
3140 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3141 @value{GDBN} attempts to initialize it with the current inferior process.
3142 If this initialization fails (which could happen because of a version
3143 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3144 will unload @code{libthread_db}, and continue with the next directory.
3145 If none of @code{libthread_db} libraries initialize successfully,
3146 @value{GDBN} will issue a warning and thread debugging will be disabled.
3148 Setting @code{libthread-db-search-path} is currently implemented
3149 only on some platforms.
3151 @kindex show libthread-db-search-path
3152 @item show libthread-db-search-path
3153 Display current libthread_db search path.
3155 @kindex set debug libthread-db
3156 @kindex show debug libthread-db
3157 @cindex debugging @code{libthread_db}
3158 @item set debug libthread-db
3159 @itemx show debug libthread-db
3160 Turns on or off display of @code{libthread_db}-related events.
3161 Use @code{1} to enable, @code{0} to disable.
3165 @section Debugging Forks
3167 @cindex fork, debugging programs which call
3168 @cindex multiple processes
3169 @cindex processes, multiple
3170 On most systems, @value{GDBN} has no special support for debugging
3171 programs which create additional processes using the @code{fork}
3172 function. When a program forks, @value{GDBN} will continue to debug the
3173 parent process and the child process will run unimpeded. If you have
3174 set a breakpoint in any code which the child then executes, the child
3175 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3176 will cause it to terminate.
3178 However, if you want to debug the child process there is a workaround
3179 which isn't too painful. Put a call to @code{sleep} in the code which
3180 the child process executes after the fork. It may be useful to sleep
3181 only if a certain environment variable is set, or a certain file exists,
3182 so that the delay need not occur when you don't want to run @value{GDBN}
3183 on the child. While the child is sleeping, use the @code{ps} program to
3184 get its process ID. Then tell @value{GDBN} (a new invocation of
3185 @value{GDBN} if you are also debugging the parent process) to attach to
3186 the child process (@pxref{Attach}). From that point on you can debug
3187 the child process just like any other process which you attached to.
3189 On some systems, @value{GDBN} provides support for debugging programs
3190 that create additional processes using the @code{fork} or @code{vfork}
3191 functions. On @sc{gnu}/Linux platforms, this feature is supported
3192 with kernel version 2.5.46 and later.
3194 The fork debugging commands are supported in native mode and when
3195 connected to @code{gdbserver} in either @code{target remote} mode or
3196 @code{target extended-remote} mode.
3198 By default, when a program forks, @value{GDBN} will continue to debug
3199 the parent process and the child process will run unimpeded.
3201 If you want to follow the child process instead of the parent process,
3202 use the command @w{@code{set follow-fork-mode}}.
3205 @kindex set follow-fork-mode
3206 @item set follow-fork-mode @var{mode}
3207 Set the debugger response to a program call of @code{fork} or
3208 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3209 process. The @var{mode} argument can be:
3213 The original process is debugged after a fork. The child process runs
3214 unimpeded. This is the default.
3217 The new process is debugged after a fork. The parent process runs
3222 @kindex show follow-fork-mode
3223 @item show follow-fork-mode
3224 Display the current debugger response to a @code{fork} or @code{vfork} call.
3227 @cindex debugging multiple processes
3228 On Linux, if you want to debug both the parent and child processes, use the
3229 command @w{@code{set detach-on-fork}}.
3232 @kindex set detach-on-fork
3233 @item set detach-on-fork @var{mode}
3234 Tells gdb whether to detach one of the processes after a fork, or
3235 retain debugger control over them both.
3239 The child process (or parent process, depending on the value of
3240 @code{follow-fork-mode}) will be detached and allowed to run
3241 independently. This is the default.
3244 Both processes will be held under the control of @value{GDBN}.
3245 One process (child or parent, depending on the value of
3246 @code{follow-fork-mode}) is debugged as usual, while the other
3251 @kindex show detach-on-fork
3252 @item show detach-on-fork
3253 Show whether detach-on-fork mode is on/off.
3256 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3257 will retain control of all forked processes (including nested forks).
3258 You can list the forked processes under the control of @value{GDBN} by
3259 using the @w{@code{info inferiors}} command, and switch from one fork
3260 to another by using the @code{inferior} command (@pxref{Inferiors and
3261 Programs, ,Debugging Multiple Inferiors and Programs}).
3263 To quit debugging one of the forked processes, you can either detach
3264 from it by using the @w{@code{detach inferiors}} command (allowing it
3265 to run independently), or kill it using the @w{@code{kill inferiors}}
3266 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3269 If you ask to debug a child process and a @code{vfork} is followed by an
3270 @code{exec}, @value{GDBN} executes the new target up to the first
3271 breakpoint in the new target. If you have a breakpoint set on
3272 @code{main} in your original program, the breakpoint will also be set on
3273 the child process's @code{main}.
3275 On some systems, when a child process is spawned by @code{vfork}, you
3276 cannot debug the child or parent until an @code{exec} call completes.
3278 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3279 call executes, the new target restarts. To restart the parent
3280 process, use the @code{file} command with the parent executable name
3281 as its argument. By default, after an @code{exec} call executes,
3282 @value{GDBN} discards the symbols of the previous executable image.
3283 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3287 @kindex set follow-exec-mode
3288 @item set follow-exec-mode @var{mode}
3290 Set debugger response to a program call of @code{exec}. An
3291 @code{exec} call replaces the program image of a process.
3293 @code{follow-exec-mode} can be:
3297 @value{GDBN} creates a new inferior and rebinds the process to this
3298 new inferior. The program the process was running before the
3299 @code{exec} call can be restarted afterwards by restarting the
3305 (@value{GDBP}) info inferiors
3307 Id Description Executable
3310 process 12020 is executing new program: prog2
3311 Program exited normally.
3312 (@value{GDBP}) info inferiors
3313 Id Description Executable
3319 @value{GDBN} keeps the process bound to the same inferior. The new
3320 executable image replaces the previous executable loaded in the
3321 inferior. Restarting the inferior after the @code{exec} call, with
3322 e.g., the @code{run} command, restarts the executable the process was
3323 running after the @code{exec} call. This is the default mode.
3328 (@value{GDBP}) info inferiors
3329 Id Description Executable
3332 process 12020 is executing new program: prog2
3333 Program exited normally.
3334 (@value{GDBP}) info inferiors
3335 Id Description Executable
3342 @code{follow-exec-mode} is supported in native mode and
3343 @code{target extended-remote} mode.
3345 You can use the @code{catch} command to make @value{GDBN} stop whenever
3346 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3347 Catchpoints, ,Setting Catchpoints}.
3349 @node Checkpoint/Restart
3350 @section Setting a @emph{Bookmark} to Return to Later
3355 @cindex snapshot of a process
3356 @cindex rewind program state
3358 On certain operating systems@footnote{Currently, only
3359 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3360 program's state, called a @dfn{checkpoint}, and come back to it
3363 Returning to a checkpoint effectively undoes everything that has
3364 happened in the program since the @code{checkpoint} was saved. This
3365 includes changes in memory, registers, and even (within some limits)
3366 system state. Effectively, it is like going back in time to the
3367 moment when the checkpoint was saved.
3369 Thus, if you're stepping thru a program and you think you're
3370 getting close to the point where things go wrong, you can save
3371 a checkpoint. Then, if you accidentally go too far and miss
3372 the critical statement, instead of having to restart your program
3373 from the beginning, you can just go back to the checkpoint and
3374 start again from there.
3376 This can be especially useful if it takes a lot of time or
3377 steps to reach the point where you think the bug occurs.
3379 To use the @code{checkpoint}/@code{restart} method of debugging:
3384 Save a snapshot of the debugged program's current execution state.
3385 The @code{checkpoint} command takes no arguments, but each checkpoint
3386 is assigned a small integer id, similar to a breakpoint id.
3388 @kindex info checkpoints
3389 @item info checkpoints
3390 List the checkpoints that have been saved in the current debugging
3391 session. For each checkpoint, the following information will be
3398 @item Source line, or label
3401 @kindex restart @var{checkpoint-id}
3402 @item restart @var{checkpoint-id}
3403 Restore the program state that was saved as checkpoint number
3404 @var{checkpoint-id}. All program variables, registers, stack frames
3405 etc.@: will be returned to the values that they had when the checkpoint
3406 was saved. In essence, gdb will ``wind back the clock'' to the point
3407 in time when the checkpoint was saved.
3409 Note that breakpoints, @value{GDBN} variables, command history etc.
3410 are not affected by restoring a checkpoint. In general, a checkpoint
3411 only restores things that reside in the program being debugged, not in
3414 @kindex delete checkpoint @var{checkpoint-id}
3415 @item delete checkpoint @var{checkpoint-id}
3416 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3420 Returning to a previously saved checkpoint will restore the user state
3421 of the program being debugged, plus a significant subset of the system
3422 (OS) state, including file pointers. It won't ``un-write'' data from
3423 a file, but it will rewind the file pointer to the previous location,
3424 so that the previously written data can be overwritten. For files
3425 opened in read mode, the pointer will also be restored so that the
3426 previously read data can be read again.
3428 Of course, characters that have been sent to a printer (or other
3429 external device) cannot be ``snatched back'', and characters received
3430 from eg.@: a serial device can be removed from internal program buffers,
3431 but they cannot be ``pushed back'' into the serial pipeline, ready to
3432 be received again. Similarly, the actual contents of files that have
3433 been changed cannot be restored (at this time).
3435 However, within those constraints, you actually can ``rewind'' your
3436 program to a previously saved point in time, and begin debugging it
3437 again --- and you can change the course of events so as to debug a
3438 different execution path this time.
3440 @cindex checkpoints and process id
3441 Finally, there is one bit of internal program state that will be
3442 different when you return to a checkpoint --- the program's process
3443 id. Each checkpoint will have a unique process id (or @var{pid}),
3444 and each will be different from the program's original @var{pid}.
3445 If your program has saved a local copy of its process id, this could
3446 potentially pose a problem.
3448 @subsection A Non-obvious Benefit of Using Checkpoints
3450 On some systems such as @sc{gnu}/Linux, address space randomization
3451 is performed on new processes for security reasons. This makes it
3452 difficult or impossible to set a breakpoint, or watchpoint, on an
3453 absolute address if you have to restart the program, since the
3454 absolute location of a symbol will change from one execution to the
3457 A checkpoint, however, is an @emph{identical} copy of a process.
3458 Therefore if you create a checkpoint at (eg.@:) the start of main,
3459 and simply return to that checkpoint instead of restarting the
3460 process, you can avoid the effects of address randomization and
3461 your symbols will all stay in the same place.
3464 @chapter Stopping and Continuing
3466 The principal purposes of using a debugger are so that you can stop your
3467 program before it terminates; or so that, if your program runs into
3468 trouble, you can investigate and find out why.
3470 Inside @value{GDBN}, your program may stop for any of several reasons,
3471 such as a signal, a breakpoint, or reaching a new line after a
3472 @value{GDBN} command such as @code{step}. You may then examine and
3473 change variables, set new breakpoints or remove old ones, and then
3474 continue execution. Usually, the messages shown by @value{GDBN} provide
3475 ample explanation of the status of your program---but you can also
3476 explicitly request this information at any time.
3479 @kindex info program
3481 Display information about the status of your program: whether it is
3482 running or not, what process it is, and why it stopped.
3486 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3487 * Continuing and Stepping:: Resuming execution
3488 * Skipping Over Functions and Files::
3489 Skipping over functions and files
3491 * Thread Stops:: Stopping and starting multi-thread programs
3495 @section Breakpoints, Watchpoints, and Catchpoints
3498 A @dfn{breakpoint} makes your program stop whenever a certain point in
3499 the program is reached. For each breakpoint, you can add conditions to
3500 control in finer detail whether your program stops. You can set
3501 breakpoints with the @code{break} command and its variants (@pxref{Set
3502 Breaks, ,Setting Breakpoints}), to specify the place where your program
3503 should stop by line number, function name or exact address in the
3506 On some systems, you can set breakpoints in shared libraries before
3507 the executable is run.
3510 @cindex data breakpoints
3511 @cindex memory tracing
3512 @cindex breakpoint on memory address
3513 @cindex breakpoint on variable modification
3514 A @dfn{watchpoint} is a special breakpoint that stops your program
3515 when the value of an expression changes. The expression may be a value
3516 of a variable, or it could involve values of one or more variables
3517 combined by operators, such as @samp{a + b}. This is sometimes called
3518 @dfn{data breakpoints}. You must use a different command to set
3519 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3520 from that, you can manage a watchpoint like any other breakpoint: you
3521 enable, disable, and delete both breakpoints and watchpoints using the
3524 You can arrange to have values from your program displayed automatically
3525 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3529 @cindex breakpoint on events
3530 A @dfn{catchpoint} is another special breakpoint that stops your program
3531 when a certain kind of event occurs, such as the throwing of a C@t{++}
3532 exception or the loading of a library. As with watchpoints, you use a
3533 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3534 Catchpoints}), but aside from that, you can manage a catchpoint like any
3535 other breakpoint. (To stop when your program receives a signal, use the
3536 @code{handle} command; see @ref{Signals, ,Signals}.)
3538 @cindex breakpoint numbers
3539 @cindex numbers for breakpoints
3540 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3541 catchpoint when you create it; these numbers are successive integers
3542 starting with one. In many of the commands for controlling various
3543 features of breakpoints you use the breakpoint number to say which
3544 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3545 @dfn{disabled}; if disabled, it has no effect on your program until you
3548 @cindex breakpoint ranges
3549 @cindex ranges of breakpoints
3550 Some @value{GDBN} commands accept a range of breakpoints on which to
3551 operate. A breakpoint range is either a single breakpoint number, like
3552 @samp{5}, or two such numbers, in increasing order, separated by a
3553 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3554 all breakpoints in that range are operated on.
3557 * Set Breaks:: Setting breakpoints
3558 * Set Watchpoints:: Setting watchpoints
3559 * Set Catchpoints:: Setting catchpoints
3560 * Delete Breaks:: Deleting breakpoints
3561 * Disabling:: Disabling breakpoints
3562 * Conditions:: Break conditions
3563 * Break Commands:: Breakpoint command lists
3564 * Dynamic Printf:: Dynamic printf
3565 * Save Breakpoints:: How to save breakpoints in a file
3566 * Static Probe Points:: Listing static probe points
3567 * Error in Breakpoints:: ``Cannot insert breakpoints''
3568 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3572 @subsection Setting Breakpoints
3574 @c FIXME LMB what does GDB do if no code on line of breakpt?
3575 @c consider in particular declaration with/without initialization.
3577 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3580 @kindex b @r{(@code{break})}
3581 @vindex $bpnum@r{, convenience variable}
3582 @cindex latest breakpoint
3583 Breakpoints are set with the @code{break} command (abbreviated
3584 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3585 number of the breakpoint you've set most recently; see @ref{Convenience
3586 Vars,, Convenience Variables}, for a discussion of what you can do with
3587 convenience variables.
3590 @item break @var{location}
3591 Set a breakpoint at the given @var{location}, which can specify a
3592 function name, a line number, or an address of an instruction.
3593 (@xref{Specify Location}, for a list of all the possible ways to
3594 specify a @var{location}.) The breakpoint will stop your program just
3595 before it executes any of the code in the specified @var{location}.
3597 When using source languages that permit overloading of symbols, such as
3598 C@t{++}, a function name may refer to more than one possible place to break.
3599 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3602 It is also possible to insert a breakpoint that will stop the program
3603 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3604 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3607 When called without any arguments, @code{break} sets a breakpoint at
3608 the next instruction to be executed in the selected stack frame
3609 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3610 innermost, this makes your program stop as soon as control
3611 returns to that frame. This is similar to the effect of a
3612 @code{finish} command in the frame inside the selected frame---except
3613 that @code{finish} does not leave an active breakpoint. If you use
3614 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3615 the next time it reaches the current location; this may be useful
3618 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3619 least one instruction has been executed. If it did not do this, you
3620 would be unable to proceed past a breakpoint without first disabling the
3621 breakpoint. This rule applies whether or not the breakpoint already
3622 existed when your program stopped.
3624 @item break @dots{} if @var{cond}
3625 Set a breakpoint with condition @var{cond}; evaluate the expression
3626 @var{cond} each time the breakpoint is reached, and stop only if the
3627 value is nonzero---that is, if @var{cond} evaluates as true.
3628 @samp{@dots{}} stands for one of the possible arguments described
3629 above (or no argument) specifying where to break. @xref{Conditions,
3630 ,Break Conditions}, for more information on breakpoint conditions.
3633 @item tbreak @var{args}
3634 Set a breakpoint enabled only for one stop. The @var{args} are the
3635 same as for the @code{break} command, and the breakpoint is set in the same
3636 way, but the breakpoint is automatically deleted after the first time your
3637 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3640 @cindex hardware breakpoints
3641 @item hbreak @var{args}
3642 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3643 @code{break} command and the breakpoint is set in the same way, but the
3644 breakpoint requires hardware support and some target hardware may not
3645 have this support. The main purpose of this is EPROM/ROM code
3646 debugging, so you can set a breakpoint at an instruction without
3647 changing the instruction. This can be used with the new trap-generation
3648 provided by SPARClite DSU and most x86-based targets. These targets
3649 will generate traps when a program accesses some data or instruction
3650 address that is assigned to the debug registers. However the hardware
3651 breakpoint registers can take a limited number of breakpoints. For
3652 example, on the DSU, only two data breakpoints can be set at a time, and
3653 @value{GDBN} will reject this command if more than two are used. Delete
3654 or disable unused hardware breakpoints before setting new ones
3655 (@pxref{Disabling, ,Disabling Breakpoints}).
3656 @xref{Conditions, ,Break Conditions}.
3657 For remote targets, you can restrict the number of hardware
3658 breakpoints @value{GDBN} will use, see @ref{set remote
3659 hardware-breakpoint-limit}.
3662 @item thbreak @var{args}
3663 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3664 are the same as for the @code{hbreak} command and the breakpoint is set in
3665 the same way. However, like the @code{tbreak} command,
3666 the breakpoint is automatically deleted after the
3667 first time your program stops there. Also, like the @code{hbreak}
3668 command, the breakpoint requires hardware support and some target hardware
3669 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3670 See also @ref{Conditions, ,Break Conditions}.
3673 @cindex regular expression
3674 @cindex breakpoints at functions matching a regexp
3675 @cindex set breakpoints in many functions
3676 @item rbreak @var{regex}
3677 Set breakpoints on all functions matching the regular expression
3678 @var{regex}. This command sets an unconditional breakpoint on all
3679 matches, printing a list of all breakpoints it set. Once these
3680 breakpoints are set, they are treated just like the breakpoints set with
3681 the @code{break} command. You can delete them, disable them, or make
3682 them conditional the same way as any other breakpoint.
3684 The syntax of the regular expression is the standard one used with tools
3685 like @file{grep}. Note that this is different from the syntax used by
3686 shells, so for instance @code{foo*} matches all functions that include
3687 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3688 @code{.*} leading and trailing the regular expression you supply, so to
3689 match only functions that begin with @code{foo}, use @code{^foo}.
3691 @cindex non-member C@t{++} functions, set breakpoint in
3692 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3693 breakpoints on overloaded functions that are not members of any special
3696 @cindex set breakpoints on all functions
3697 The @code{rbreak} command can be used to set breakpoints in
3698 @strong{all} the functions in a program, like this:
3701 (@value{GDBP}) rbreak .
3704 @item rbreak @var{file}:@var{regex}
3705 If @code{rbreak} is called with a filename qualification, it limits
3706 the search for functions matching the given regular expression to the
3707 specified @var{file}. This can be used, for example, to set breakpoints on
3708 every function in a given file:
3711 (@value{GDBP}) rbreak file.c:.
3714 The colon separating the filename qualifier from the regex may
3715 optionally be surrounded by spaces.
3717 @kindex info breakpoints
3718 @cindex @code{$_} and @code{info breakpoints}
3719 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3720 @itemx info break @r{[}@var{n}@dots{}@r{]}
3721 Print a table of all breakpoints, watchpoints, and catchpoints set and
3722 not deleted. Optional argument @var{n} means print information only
3723 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3724 For each breakpoint, following columns are printed:
3727 @item Breakpoint Numbers
3729 Breakpoint, watchpoint, or catchpoint.
3731 Whether the breakpoint is marked to be disabled or deleted when hit.
3732 @item Enabled or Disabled
3733 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3734 that are not enabled.
3736 Where the breakpoint is in your program, as a memory address. For a
3737 pending breakpoint whose address is not yet known, this field will
3738 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3739 library that has the symbol or line referred by breakpoint is loaded.
3740 See below for details. A breakpoint with several locations will
3741 have @samp{<MULTIPLE>} in this field---see below for details.
3743 Where the breakpoint is in the source for your program, as a file and
3744 line number. For a pending breakpoint, the original string passed to
3745 the breakpoint command will be listed as it cannot be resolved until
3746 the appropriate shared library is loaded in the future.
3750 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3751 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3752 @value{GDBN} on the host's side. If it is ``target'', then the condition
3753 is evaluated by the target. The @code{info break} command shows
3754 the condition on the line following the affected breakpoint, together with
3755 its condition evaluation mode in between parentheses.
3757 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3758 allowed to have a condition specified for it. The condition is not parsed for
3759 validity until a shared library is loaded that allows the pending
3760 breakpoint to resolve to a valid location.
3763 @code{info break} with a breakpoint
3764 number @var{n} as argument lists only that breakpoint. The
3765 convenience variable @code{$_} and the default examining-address for
3766 the @code{x} command are set to the address of the last breakpoint
3767 listed (@pxref{Memory, ,Examining Memory}).
3770 @code{info break} displays a count of the number of times the breakpoint
3771 has been hit. This is especially useful in conjunction with the
3772 @code{ignore} command. You can ignore a large number of breakpoint
3773 hits, look at the breakpoint info to see how many times the breakpoint
3774 was hit, and then run again, ignoring one less than that number. This
3775 will get you quickly to the last hit of that breakpoint.
3778 For a breakpoints with an enable count (xref) greater than 1,
3779 @code{info break} also displays that count.
3783 @value{GDBN} allows you to set any number of breakpoints at the same place in
3784 your program. There is nothing silly or meaningless about this. When
3785 the breakpoints are conditional, this is even useful
3786 (@pxref{Conditions, ,Break Conditions}).
3788 @cindex multiple locations, breakpoints
3789 @cindex breakpoints, multiple locations
3790 It is possible that a breakpoint corresponds to several locations
3791 in your program. Examples of this situation are:
3795 Multiple functions in the program may have the same name.
3798 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3799 instances of the function body, used in different cases.
3802 For a C@t{++} template function, a given line in the function can
3803 correspond to any number of instantiations.
3806 For an inlined function, a given source line can correspond to
3807 several places where that function is inlined.
3810 In all those cases, @value{GDBN} will insert a breakpoint at all
3811 the relevant locations.
3813 A breakpoint with multiple locations is displayed in the breakpoint
3814 table using several rows---one header row, followed by one row for
3815 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3816 address column. The rows for individual locations contain the actual
3817 addresses for locations, and show the functions to which those
3818 locations belong. The number column for a location is of the form
3819 @var{breakpoint-number}.@var{location-number}.
3824 Num Type Disp Enb Address What
3825 1 breakpoint keep y <MULTIPLE>
3827 breakpoint already hit 1 time
3828 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3829 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3832 Each location can be individually enabled or disabled by passing
3833 @var{breakpoint-number}.@var{location-number} as argument to the
3834 @code{enable} and @code{disable} commands. Note that you cannot
3835 delete the individual locations from the list, you can only delete the
3836 entire list of locations that belong to their parent breakpoint (with
3837 the @kbd{delete @var{num}} command, where @var{num} is the number of
3838 the parent breakpoint, 1 in the above example). Disabling or enabling
3839 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3840 that belong to that breakpoint.
3842 @cindex pending breakpoints
3843 It's quite common to have a breakpoint inside a shared library.
3844 Shared libraries can be loaded and unloaded explicitly,
3845 and possibly repeatedly, as the program is executed. To support
3846 this use case, @value{GDBN} updates breakpoint locations whenever
3847 any shared library is loaded or unloaded. Typically, you would
3848 set a breakpoint in a shared library at the beginning of your
3849 debugging session, when the library is not loaded, and when the
3850 symbols from the library are not available. When you try to set
3851 breakpoint, @value{GDBN} will ask you if you want to set
3852 a so called @dfn{pending breakpoint}---breakpoint whose address
3853 is not yet resolved.
3855 After the program is run, whenever a new shared library is loaded,
3856 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3857 shared library contains the symbol or line referred to by some
3858 pending breakpoint, that breakpoint is resolved and becomes an
3859 ordinary breakpoint. When a library is unloaded, all breakpoints
3860 that refer to its symbols or source lines become pending again.
3862 This logic works for breakpoints with multiple locations, too. For
3863 example, if you have a breakpoint in a C@t{++} template function, and
3864 a newly loaded shared library has an instantiation of that template,
3865 a new location is added to the list of locations for the breakpoint.
3867 Except for having unresolved address, pending breakpoints do not
3868 differ from regular breakpoints. You can set conditions or commands,
3869 enable and disable them and perform other breakpoint operations.
3871 @value{GDBN} provides some additional commands for controlling what
3872 happens when the @samp{break} command cannot resolve breakpoint
3873 address specification to an address:
3875 @kindex set breakpoint pending
3876 @kindex show breakpoint pending
3878 @item set breakpoint pending auto
3879 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3880 location, it queries you whether a pending breakpoint should be created.
3882 @item set breakpoint pending on
3883 This indicates that an unrecognized breakpoint location should automatically
3884 result in a pending breakpoint being created.
3886 @item set breakpoint pending off
3887 This indicates that pending breakpoints are not to be created. Any
3888 unrecognized breakpoint location results in an error. This setting does
3889 not affect any pending breakpoints previously created.
3891 @item show breakpoint pending
3892 Show the current behavior setting for creating pending breakpoints.
3895 The settings above only affect the @code{break} command and its
3896 variants. Once breakpoint is set, it will be automatically updated
3897 as shared libraries are loaded and unloaded.
3899 @cindex automatic hardware breakpoints
3900 For some targets, @value{GDBN} can automatically decide if hardware or
3901 software breakpoints should be used, depending on whether the
3902 breakpoint address is read-only or read-write. This applies to
3903 breakpoints set with the @code{break} command as well as to internal
3904 breakpoints set by commands like @code{next} and @code{finish}. For
3905 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3908 You can control this automatic behaviour with the following commands::
3910 @kindex set breakpoint auto-hw
3911 @kindex show breakpoint auto-hw
3913 @item set breakpoint auto-hw on
3914 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3915 will try to use the target memory map to decide if software or hardware
3916 breakpoint must be used.
3918 @item set breakpoint auto-hw off
3919 This indicates @value{GDBN} should not automatically select breakpoint
3920 type. If the target provides a memory map, @value{GDBN} will warn when
3921 trying to set software breakpoint at a read-only address.
3924 @value{GDBN} normally implements breakpoints by replacing the program code
3925 at the breakpoint address with a special instruction, which, when
3926 executed, given control to the debugger. By default, the program
3927 code is so modified only when the program is resumed. As soon as
3928 the program stops, @value{GDBN} restores the original instructions. This
3929 behaviour guards against leaving breakpoints inserted in the
3930 target should gdb abrubptly disconnect. However, with slow remote
3931 targets, inserting and removing breakpoint can reduce the performance.
3932 This behavior can be controlled with the following commands::
3934 @kindex set breakpoint always-inserted
3935 @kindex show breakpoint always-inserted
3937 @item set breakpoint always-inserted off
3938 All breakpoints, including newly added by the user, are inserted in
3939 the target only when the target is resumed. All breakpoints are
3940 removed from the target when it stops. This is the default mode.
3942 @item set breakpoint always-inserted on
3943 Causes all breakpoints to be inserted in the target at all times. If
3944 the user adds a new breakpoint, or changes an existing breakpoint, the
3945 breakpoints in the target are updated immediately. A breakpoint is
3946 removed from the target only when breakpoint itself is deleted.
3949 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3950 when a breakpoint breaks. If the condition is true, then the process being
3951 debugged stops, otherwise the process is resumed.
3953 If the target supports evaluating conditions on its end, @value{GDBN} may
3954 download the breakpoint, together with its conditions, to it.
3956 This feature can be controlled via the following commands:
3958 @kindex set breakpoint condition-evaluation
3959 @kindex show breakpoint condition-evaluation
3961 @item set breakpoint condition-evaluation host
3962 This option commands @value{GDBN} to evaluate the breakpoint
3963 conditions on the host's side. Unconditional breakpoints are sent to
3964 the target which in turn receives the triggers and reports them back to GDB
3965 for condition evaluation. This is the standard evaluation mode.
3967 @item set breakpoint condition-evaluation target
3968 This option commands @value{GDBN} to download breakpoint conditions
3969 to the target at the moment of their insertion. The target
3970 is responsible for evaluating the conditional expression and reporting
3971 breakpoint stop events back to @value{GDBN} whenever the condition
3972 is true. Due to limitations of target-side evaluation, some conditions
3973 cannot be evaluated there, e.g., conditions that depend on local data
3974 that is only known to the host. Examples include
3975 conditional expressions involving convenience variables, complex types
3976 that cannot be handled by the agent expression parser and expressions
3977 that are too long to be sent over to the target, specially when the
3978 target is a remote system. In these cases, the conditions will be
3979 evaluated by @value{GDBN}.
3981 @item set breakpoint condition-evaluation auto
3982 This is the default mode. If the target supports evaluating breakpoint
3983 conditions on its end, @value{GDBN} will download breakpoint conditions to
3984 the target (limitations mentioned previously apply). If the target does
3985 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3986 to evaluating all these conditions on the host's side.
3990 @cindex negative breakpoint numbers
3991 @cindex internal @value{GDBN} breakpoints
3992 @value{GDBN} itself sometimes sets breakpoints in your program for
3993 special purposes, such as proper handling of @code{longjmp} (in C
3994 programs). These internal breakpoints are assigned negative numbers,
3995 starting with @code{-1}; @samp{info breakpoints} does not display them.
3996 You can see these breakpoints with the @value{GDBN} maintenance command
3997 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4000 @node Set Watchpoints
4001 @subsection Setting Watchpoints
4003 @cindex setting watchpoints
4004 You can use a watchpoint to stop execution whenever the value of an
4005 expression changes, without having to predict a particular place where
4006 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4007 The expression may be as simple as the value of a single variable, or
4008 as complex as many variables combined by operators. Examples include:
4012 A reference to the value of a single variable.
4015 An address cast to an appropriate data type. For example,
4016 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4017 address (assuming an @code{int} occupies 4 bytes).
4020 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4021 expression can use any operators valid in the program's native
4022 language (@pxref{Languages}).
4025 You can set a watchpoint on an expression even if the expression can
4026 not be evaluated yet. For instance, you can set a watchpoint on
4027 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4028 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4029 the expression produces a valid value. If the expression becomes
4030 valid in some other way than changing a variable (e.g.@: if the memory
4031 pointed to by @samp{*global_ptr} becomes readable as the result of a
4032 @code{malloc} call), @value{GDBN} may not stop until the next time
4033 the expression changes.
4035 @cindex software watchpoints
4036 @cindex hardware watchpoints
4037 Depending on your system, watchpoints may be implemented in software or
4038 hardware. @value{GDBN} does software watchpointing by single-stepping your
4039 program and testing the variable's value each time, which is hundreds of
4040 times slower than normal execution. (But this may still be worth it, to
4041 catch errors where you have no clue what part of your program is the
4044 On some systems, such as most PowerPC or x86-based targets,
4045 @value{GDBN} includes support for hardware watchpoints, which do not
4046 slow down the running of your program.
4050 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4051 Set a watchpoint for an expression. @value{GDBN} will break when the
4052 expression @var{expr} is written into by the program and its value
4053 changes. The simplest (and the most popular) use of this command is
4054 to watch the value of a single variable:
4057 (@value{GDBP}) watch foo
4060 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4061 argument, @value{GDBN} breaks only when the thread identified by
4062 @var{thread-id} changes the value of @var{expr}. If any other threads
4063 change the value of @var{expr}, @value{GDBN} will not break. Note
4064 that watchpoints restricted to a single thread in this way only work
4065 with Hardware Watchpoints.
4067 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4068 (see below). The @code{-location} argument tells @value{GDBN} to
4069 instead watch the memory referred to by @var{expr}. In this case,
4070 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4071 and watch the memory at that address. The type of the result is used
4072 to determine the size of the watched memory. If the expression's
4073 result does not have an address, then @value{GDBN} will print an
4076 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4077 of masked watchpoints, if the current architecture supports this
4078 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4079 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4080 to an address to watch. The mask specifies that some bits of an address
4081 (the bits which are reset in the mask) should be ignored when matching
4082 the address accessed by the inferior against the watchpoint address.
4083 Thus, a masked watchpoint watches many addresses simultaneously---those
4084 addresses whose unmasked bits are identical to the unmasked bits in the
4085 watchpoint address. The @code{mask} argument implies @code{-location}.
4089 (@value{GDBP}) watch foo mask 0xffff00ff
4090 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4094 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4095 Set a watchpoint that will break when the value of @var{expr} is read
4099 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4100 Set a watchpoint that will break when @var{expr} is either read from
4101 or written into by the program.
4103 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4104 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4105 This command prints a list of watchpoints, using the same format as
4106 @code{info break} (@pxref{Set Breaks}).
4109 If you watch for a change in a numerically entered address you need to
4110 dereference it, as the address itself is just a constant number which will
4111 never change. @value{GDBN} refuses to create a watchpoint that watches
4112 a never-changing value:
4115 (@value{GDBP}) watch 0x600850
4116 Cannot watch constant value 0x600850.
4117 (@value{GDBP}) watch *(int *) 0x600850
4118 Watchpoint 1: *(int *) 6293584
4121 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4122 watchpoints execute very quickly, and the debugger reports a change in
4123 value at the exact instruction where the change occurs. If @value{GDBN}
4124 cannot set a hardware watchpoint, it sets a software watchpoint, which
4125 executes more slowly and reports the change in value at the next
4126 @emph{statement}, not the instruction, after the change occurs.
4128 @cindex use only software watchpoints
4129 You can force @value{GDBN} to use only software watchpoints with the
4130 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4131 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4132 the underlying system supports them. (Note that hardware-assisted
4133 watchpoints that were set @emph{before} setting
4134 @code{can-use-hw-watchpoints} to zero will still use the hardware
4135 mechanism of watching expression values.)
4138 @item set can-use-hw-watchpoints
4139 @kindex set can-use-hw-watchpoints
4140 Set whether or not to use hardware watchpoints.
4142 @item show can-use-hw-watchpoints
4143 @kindex show can-use-hw-watchpoints
4144 Show the current mode of using hardware watchpoints.
4147 For remote targets, you can restrict the number of hardware
4148 watchpoints @value{GDBN} will use, see @ref{set remote
4149 hardware-breakpoint-limit}.
4151 When you issue the @code{watch} command, @value{GDBN} reports
4154 Hardware watchpoint @var{num}: @var{expr}
4158 if it was able to set a hardware watchpoint.
4160 Currently, the @code{awatch} and @code{rwatch} commands can only set
4161 hardware watchpoints, because accesses to data that don't change the
4162 value of the watched expression cannot be detected without examining
4163 every instruction as it is being executed, and @value{GDBN} does not do
4164 that currently. If @value{GDBN} finds that it is unable to set a
4165 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4166 will print a message like this:
4169 Expression cannot be implemented with read/access watchpoint.
4172 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4173 data type of the watched expression is wider than what a hardware
4174 watchpoint on the target machine can handle. For example, some systems
4175 can only watch regions that are up to 4 bytes wide; on such systems you
4176 cannot set hardware watchpoints for an expression that yields a
4177 double-precision floating-point number (which is typically 8 bytes
4178 wide). As a work-around, it might be possible to break the large region
4179 into a series of smaller ones and watch them with separate watchpoints.
4181 If you set too many hardware watchpoints, @value{GDBN} might be unable
4182 to insert all of them when you resume the execution of your program.
4183 Since the precise number of active watchpoints is unknown until such
4184 time as the program is about to be resumed, @value{GDBN} might not be
4185 able to warn you about this when you set the watchpoints, and the
4186 warning will be printed only when the program is resumed:
4189 Hardware watchpoint @var{num}: Could not insert watchpoint
4193 If this happens, delete or disable some of the watchpoints.
4195 Watching complex expressions that reference many variables can also
4196 exhaust the resources available for hardware-assisted watchpoints.
4197 That's because @value{GDBN} needs to watch every variable in the
4198 expression with separately allocated resources.
4200 If you call a function interactively using @code{print} or @code{call},
4201 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4202 kind of breakpoint or the call completes.
4204 @value{GDBN} automatically deletes watchpoints that watch local
4205 (automatic) variables, or expressions that involve such variables, when
4206 they go out of scope, that is, when the execution leaves the block in
4207 which these variables were defined. In particular, when the program
4208 being debugged terminates, @emph{all} local variables go out of scope,
4209 and so only watchpoints that watch global variables remain set. If you
4210 rerun the program, you will need to set all such watchpoints again. One
4211 way of doing that would be to set a code breakpoint at the entry to the
4212 @code{main} function and when it breaks, set all the watchpoints.
4214 @cindex watchpoints and threads
4215 @cindex threads and watchpoints
4216 In multi-threaded programs, watchpoints will detect changes to the
4217 watched expression from every thread.
4220 @emph{Warning:} In multi-threaded programs, software watchpoints
4221 have only limited usefulness. If @value{GDBN} creates a software
4222 watchpoint, it can only watch the value of an expression @emph{in a
4223 single thread}. If you are confident that the expression can only
4224 change due to the current thread's activity (and if you are also
4225 confident that no other thread can become current), then you can use
4226 software watchpoints as usual. However, @value{GDBN} may not notice
4227 when a non-current thread's activity changes the expression. (Hardware
4228 watchpoints, in contrast, watch an expression in all threads.)
4231 @xref{set remote hardware-watchpoint-limit}.
4233 @node Set Catchpoints
4234 @subsection Setting Catchpoints
4235 @cindex catchpoints, setting
4236 @cindex exception handlers
4237 @cindex event handling
4239 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4240 kinds of program events, such as C@t{++} exceptions or the loading of a
4241 shared library. Use the @code{catch} command to set a catchpoint.
4245 @item catch @var{event}
4246 Stop when @var{event} occurs. The @var{event} can be any of the following:
4249 @item throw @r{[}@var{regexp}@r{]}
4250 @itemx rethrow @r{[}@var{regexp}@r{]}
4251 @itemx catch @r{[}@var{regexp}@r{]}
4253 @kindex catch rethrow
4255 @cindex stop on C@t{++} exceptions
4256 The throwing, re-throwing, or catching of a C@t{++} exception.
4258 If @var{regexp} is given, then only exceptions whose type matches the
4259 regular expression will be caught.
4261 @vindex $_exception@r{, convenience variable}
4262 The convenience variable @code{$_exception} is available at an
4263 exception-related catchpoint, on some systems. This holds the
4264 exception being thrown.
4266 There are currently some limitations to C@t{++} exception handling in
4271 The support for these commands is system-dependent. Currently, only
4272 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4276 The regular expression feature and the @code{$_exception} convenience
4277 variable rely on the presence of some SDT probes in @code{libstdc++}.
4278 If these probes are not present, then these features cannot be used.
4279 These probes were first available in the GCC 4.8 release, but whether
4280 or not they are available in your GCC also depends on how it was
4284 The @code{$_exception} convenience variable is only valid at the
4285 instruction at which an exception-related catchpoint is set.
4288 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4289 location in the system library which implements runtime exception
4290 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4291 (@pxref{Selection}) to get to your code.
4294 If you call a function interactively, @value{GDBN} normally returns
4295 control to you when the function has finished executing. If the call
4296 raises an exception, however, the call may bypass the mechanism that
4297 returns control to you and cause your program either to abort or to
4298 simply continue running until it hits a breakpoint, catches a signal
4299 that @value{GDBN} is listening for, or exits. This is the case even if
4300 you set a catchpoint for the exception; catchpoints on exceptions are
4301 disabled within interactive calls. @xref{Calling}, for information on
4302 controlling this with @code{set unwind-on-terminating-exception}.
4305 You cannot raise an exception interactively.
4308 You cannot install an exception handler interactively.
4312 @kindex catch exception
4313 @cindex Ada exception catching
4314 @cindex catch Ada exceptions
4315 An Ada exception being raised. If an exception name is specified
4316 at the end of the command (eg @code{catch exception Program_Error}),
4317 the debugger will stop only when this specific exception is raised.
4318 Otherwise, the debugger stops execution when any Ada exception is raised.
4320 When inserting an exception catchpoint on a user-defined exception whose
4321 name is identical to one of the exceptions defined by the language, the
4322 fully qualified name must be used as the exception name. Otherwise,
4323 @value{GDBN} will assume that it should stop on the pre-defined exception
4324 rather than the user-defined one. For instance, assuming an exception
4325 called @code{Constraint_Error} is defined in package @code{Pck}, then
4326 the command to use to catch such exceptions is @kbd{catch exception
4327 Pck.Constraint_Error}.
4329 @item exception unhandled
4330 @kindex catch exception unhandled
4331 An exception that was raised but is not handled by the program.
4334 @kindex catch assert
4335 A failed Ada assertion.
4339 @cindex break on fork/exec
4340 A call to @code{exec}.
4343 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4344 @kindex catch syscall
4345 @cindex break on a system call.
4346 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4347 syscall is a mechanism for application programs to request a service
4348 from the operating system (OS) or one of the OS system services.
4349 @value{GDBN} can catch some or all of the syscalls issued by the
4350 debuggee, and show the related information for each syscall. If no
4351 argument is specified, calls to and returns from all system calls
4354 @var{name} can be any system call name that is valid for the
4355 underlying OS. Just what syscalls are valid depends on the OS. On
4356 GNU and Unix systems, you can find the full list of valid syscall
4357 names on @file{/usr/include/asm/unistd.h}.
4359 @c For MS-Windows, the syscall names and the corresponding numbers
4360 @c can be found, e.g., on this URL:
4361 @c http://www.metasploit.com/users/opcode/syscalls.html
4362 @c but we don't support Windows syscalls yet.
4364 Normally, @value{GDBN} knows in advance which syscalls are valid for
4365 each OS, so you can use the @value{GDBN} command-line completion
4366 facilities (@pxref{Completion,, command completion}) to list the
4369 You may also specify the system call numerically. A syscall's
4370 number is the value passed to the OS's syscall dispatcher to
4371 identify the requested service. When you specify the syscall by its
4372 name, @value{GDBN} uses its database of syscalls to convert the name
4373 into the corresponding numeric code, but using the number directly
4374 may be useful if @value{GDBN}'s database does not have the complete
4375 list of syscalls on your system (e.g., because @value{GDBN} lags
4376 behind the OS upgrades).
4378 The example below illustrates how this command works if you don't provide
4382 (@value{GDBP}) catch syscall
4383 Catchpoint 1 (syscall)
4385 Starting program: /tmp/catch-syscall
4387 Catchpoint 1 (call to syscall 'close'), \
4388 0xffffe424 in __kernel_vsyscall ()
4392 Catchpoint 1 (returned from syscall 'close'), \
4393 0xffffe424 in __kernel_vsyscall ()
4397 Here is an example of catching a system call by name:
4400 (@value{GDBP}) catch syscall chroot
4401 Catchpoint 1 (syscall 'chroot' [61])
4403 Starting program: /tmp/catch-syscall
4405 Catchpoint 1 (call to syscall 'chroot'), \
4406 0xffffe424 in __kernel_vsyscall ()
4410 Catchpoint 1 (returned from syscall 'chroot'), \
4411 0xffffe424 in __kernel_vsyscall ()
4415 An example of specifying a system call numerically. In the case
4416 below, the syscall number has a corresponding entry in the XML
4417 file, so @value{GDBN} finds its name and prints it:
4420 (@value{GDBP}) catch syscall 252
4421 Catchpoint 1 (syscall(s) 'exit_group')
4423 Starting program: /tmp/catch-syscall
4425 Catchpoint 1 (call to syscall 'exit_group'), \
4426 0xffffe424 in __kernel_vsyscall ()
4430 Program exited normally.
4434 However, there can be situations when there is no corresponding name
4435 in XML file for that syscall number. In this case, @value{GDBN} prints
4436 a warning message saying that it was not able to find the syscall name,
4437 but the catchpoint will be set anyway. See the example below:
4440 (@value{GDBP}) catch syscall 764
4441 warning: The number '764' does not represent a known syscall.
4442 Catchpoint 2 (syscall 764)
4446 If you configure @value{GDBN} using the @samp{--without-expat} option,
4447 it will not be able to display syscall names. Also, if your
4448 architecture does not have an XML file describing its system calls,
4449 you will not be able to see the syscall names. It is important to
4450 notice that these two features are used for accessing the syscall
4451 name database. In either case, you will see a warning like this:
4454 (@value{GDBP}) catch syscall
4455 warning: Could not open "syscalls/i386-linux.xml"
4456 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4457 GDB will not be able to display syscall names.
4458 Catchpoint 1 (syscall)
4462 Of course, the file name will change depending on your architecture and system.
4464 Still using the example above, you can also try to catch a syscall by its
4465 number. In this case, you would see something like:
4468 (@value{GDBP}) catch syscall 252
4469 Catchpoint 1 (syscall(s) 252)
4472 Again, in this case @value{GDBN} would not be able to display syscall's names.
4476 A call to @code{fork}.
4480 A call to @code{vfork}.
4482 @item load @r{[}regexp@r{]}
4483 @itemx unload @r{[}regexp@r{]}
4485 @kindex catch unload
4486 The loading or unloading of a shared library. If @var{regexp} is
4487 given, then the catchpoint will stop only if the regular expression
4488 matches one of the affected libraries.
4490 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4491 @kindex catch signal
4492 The delivery of a signal.
4494 With no arguments, this catchpoint will catch any signal that is not
4495 used internally by @value{GDBN}, specifically, all signals except
4496 @samp{SIGTRAP} and @samp{SIGINT}.
4498 With the argument @samp{all}, all signals, including those used by
4499 @value{GDBN}, will be caught. This argument cannot be used with other
4502 Otherwise, the arguments are a list of signal names as given to
4503 @code{handle} (@pxref{Signals}). Only signals specified in this list
4506 One reason that @code{catch signal} can be more useful than
4507 @code{handle} is that you can attach commands and conditions to the
4510 When a signal is caught by a catchpoint, the signal's @code{stop} and
4511 @code{print} settings, as specified by @code{handle}, are ignored.
4512 However, whether the signal is still delivered to the inferior depends
4513 on the @code{pass} setting; this can be changed in the catchpoint's
4518 @item tcatch @var{event}
4520 Set a catchpoint that is enabled only for one stop. The catchpoint is
4521 automatically deleted after the first time the event is caught.
4525 Use the @code{info break} command to list the current catchpoints.
4529 @subsection Deleting Breakpoints
4531 @cindex clearing breakpoints, watchpoints, catchpoints
4532 @cindex deleting breakpoints, watchpoints, catchpoints
4533 It is often necessary to eliminate a breakpoint, watchpoint, or
4534 catchpoint once it has done its job and you no longer want your program
4535 to stop there. This is called @dfn{deleting} the breakpoint. A
4536 breakpoint that has been deleted no longer exists; it is forgotten.
4538 With the @code{clear} command you can delete breakpoints according to
4539 where they are in your program. With the @code{delete} command you can
4540 delete individual breakpoints, watchpoints, or catchpoints by specifying
4541 their breakpoint numbers.
4543 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4544 automatically ignores breakpoints on the first instruction to be executed
4545 when you continue execution without changing the execution address.
4550 Delete any breakpoints at the next instruction to be executed in the
4551 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4552 the innermost frame is selected, this is a good way to delete a
4553 breakpoint where your program just stopped.
4555 @item clear @var{location}
4556 Delete any breakpoints set at the specified @var{location}.
4557 @xref{Specify Location}, for the various forms of @var{location}; the
4558 most useful ones are listed below:
4561 @item clear @var{function}
4562 @itemx clear @var{filename}:@var{function}
4563 Delete any breakpoints set at entry to the named @var{function}.
4565 @item clear @var{linenum}
4566 @itemx clear @var{filename}:@var{linenum}
4567 Delete any breakpoints set at or within the code of the specified
4568 @var{linenum} of the specified @var{filename}.
4571 @cindex delete breakpoints
4573 @kindex d @r{(@code{delete})}
4574 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4575 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4576 ranges specified as arguments. If no argument is specified, delete all
4577 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4578 confirm off}). You can abbreviate this command as @code{d}.
4582 @subsection Disabling Breakpoints
4584 @cindex enable/disable a breakpoint
4585 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4586 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4587 it had been deleted, but remembers the information on the breakpoint so
4588 that you can @dfn{enable} it again later.
4590 You disable and enable breakpoints, watchpoints, and catchpoints with
4591 the @code{enable} and @code{disable} commands, optionally specifying
4592 one or more breakpoint numbers as arguments. Use @code{info break} to
4593 print a list of all breakpoints, watchpoints, and catchpoints if you
4594 do not know which numbers to use.
4596 Disabling and enabling a breakpoint that has multiple locations
4597 affects all of its locations.
4599 A breakpoint, watchpoint, or catchpoint can have any of several
4600 different states of enablement:
4604 Enabled. The breakpoint stops your program. A breakpoint set
4605 with the @code{break} command starts out in this state.
4607 Disabled. The breakpoint has no effect on your program.
4609 Enabled once. The breakpoint stops your program, but then becomes
4612 Enabled for a count. The breakpoint stops your program for the next
4613 N times, then becomes disabled.
4615 Enabled for deletion. The breakpoint stops your program, but
4616 immediately after it does so it is deleted permanently. A breakpoint
4617 set with the @code{tbreak} command starts out in this state.
4620 You can use the following commands to enable or disable breakpoints,
4621 watchpoints, and catchpoints:
4625 @kindex dis @r{(@code{disable})}
4626 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4627 Disable the specified breakpoints---or all breakpoints, if none are
4628 listed. A disabled breakpoint has no effect but is not forgotten. All
4629 options such as ignore-counts, conditions and commands are remembered in
4630 case the breakpoint is enabled again later. You may abbreviate
4631 @code{disable} as @code{dis}.
4634 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4635 Enable the specified breakpoints (or all defined breakpoints). They
4636 become effective once again in stopping your program.
4638 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4639 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4640 of these breakpoints immediately after stopping your program.
4642 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4643 Enable the specified breakpoints temporarily. @value{GDBN} records
4644 @var{count} with each of the specified breakpoints, and decrements a
4645 breakpoint's count when it is hit. When any count reaches 0,
4646 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4647 count (@pxref{Conditions, ,Break Conditions}), that will be
4648 decremented to 0 before @var{count} is affected.
4650 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4651 Enable the specified breakpoints to work once, then die. @value{GDBN}
4652 deletes any of these breakpoints as soon as your program stops there.
4653 Breakpoints set by the @code{tbreak} command start out in this state.
4656 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4657 @c confusing: tbreak is also initially enabled.
4658 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4659 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4660 subsequently, they become disabled or enabled only when you use one of
4661 the commands above. (The command @code{until} can set and delete a
4662 breakpoint of its own, but it does not change the state of your other
4663 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4667 @subsection Break Conditions
4668 @cindex conditional breakpoints
4669 @cindex breakpoint conditions
4671 @c FIXME what is scope of break condition expr? Context where wanted?
4672 @c in particular for a watchpoint?
4673 The simplest sort of breakpoint breaks every time your program reaches a
4674 specified place. You can also specify a @dfn{condition} for a
4675 breakpoint. A condition is just a Boolean expression in your
4676 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4677 a condition evaluates the expression each time your program reaches it,
4678 and your program stops only if the condition is @emph{true}.
4680 This is the converse of using assertions for program validation; in that
4681 situation, you want to stop when the assertion is violated---that is,
4682 when the condition is false. In C, if you want to test an assertion expressed
4683 by the condition @var{assert}, you should set the condition
4684 @samp{! @var{assert}} on the appropriate breakpoint.
4686 Conditions are also accepted for watchpoints; you may not need them,
4687 since a watchpoint is inspecting the value of an expression anyhow---but
4688 it might be simpler, say, to just set a watchpoint on a variable name,
4689 and specify a condition that tests whether the new value is an interesting
4692 Break conditions can have side effects, and may even call functions in
4693 your program. This can be useful, for example, to activate functions
4694 that log program progress, or to use your own print functions to
4695 format special data structures. The effects are completely predictable
4696 unless there is another enabled breakpoint at the same address. (In
4697 that case, @value{GDBN} might see the other breakpoint first and stop your
4698 program without checking the condition of this one.) Note that
4699 breakpoint commands are usually more convenient and flexible than break
4701 purpose of performing side effects when a breakpoint is reached
4702 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4704 Breakpoint conditions can also be evaluated on the target's side if
4705 the target supports it. Instead of evaluating the conditions locally,
4706 @value{GDBN} encodes the expression into an agent expression
4707 (@pxref{Agent Expressions}) suitable for execution on the target,
4708 independently of @value{GDBN}. Global variables become raw memory
4709 locations, locals become stack accesses, and so forth.
4711 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4712 when its condition evaluates to true. This mechanism may provide faster
4713 response times depending on the performance characteristics of the target
4714 since it does not need to keep @value{GDBN} informed about
4715 every breakpoint trigger, even those with false conditions.
4717 Break conditions can be specified when a breakpoint is set, by using
4718 @samp{if} in the arguments to the @code{break} command. @xref{Set
4719 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4720 with the @code{condition} command.
4722 You can also use the @code{if} keyword with the @code{watch} command.
4723 The @code{catch} command does not recognize the @code{if} keyword;
4724 @code{condition} is the only way to impose a further condition on a
4729 @item condition @var{bnum} @var{expression}
4730 Specify @var{expression} as the break condition for breakpoint,
4731 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4732 breakpoint @var{bnum} stops your program only if the value of
4733 @var{expression} is true (nonzero, in C). When you use
4734 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4735 syntactic correctness, and to determine whether symbols in it have
4736 referents in the context of your breakpoint. If @var{expression} uses
4737 symbols not referenced in the context of the breakpoint, @value{GDBN}
4738 prints an error message:
4741 No symbol "foo" in current context.
4746 not actually evaluate @var{expression} at the time the @code{condition}
4747 command (or a command that sets a breakpoint with a condition, like
4748 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4750 @item condition @var{bnum}
4751 Remove the condition from breakpoint number @var{bnum}. It becomes
4752 an ordinary unconditional breakpoint.
4755 @cindex ignore count (of breakpoint)
4756 A special case of a breakpoint condition is to stop only when the
4757 breakpoint has been reached a certain number of times. This is so
4758 useful that there is a special way to do it, using the @dfn{ignore
4759 count} of the breakpoint. Every breakpoint has an ignore count, which
4760 is an integer. Most of the time, the ignore count is zero, and
4761 therefore has no effect. But if your program reaches a breakpoint whose
4762 ignore count is positive, then instead of stopping, it just decrements
4763 the ignore count by one and continues. As a result, if the ignore count
4764 value is @var{n}, the breakpoint does not stop the next @var{n} times
4765 your program reaches it.
4769 @item ignore @var{bnum} @var{count}
4770 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4771 The next @var{count} times the breakpoint is reached, your program's
4772 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4775 To make the breakpoint stop the next time it is reached, specify
4778 When you use @code{continue} to resume execution of your program from a
4779 breakpoint, you can specify an ignore count directly as an argument to
4780 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4781 Stepping,,Continuing and Stepping}.
4783 If a breakpoint has a positive ignore count and a condition, the
4784 condition is not checked. Once the ignore count reaches zero,
4785 @value{GDBN} resumes checking the condition.
4787 You could achieve the effect of the ignore count with a condition such
4788 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4789 is decremented each time. @xref{Convenience Vars, ,Convenience
4793 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4796 @node Break Commands
4797 @subsection Breakpoint Command Lists
4799 @cindex breakpoint commands
4800 You can give any breakpoint (or watchpoint or catchpoint) a series of
4801 commands to execute when your program stops due to that breakpoint. For
4802 example, you might want to print the values of certain expressions, or
4803 enable other breakpoints.
4807 @kindex end@r{ (breakpoint commands)}
4808 @item commands @r{[}@var{range}@dots{}@r{]}
4809 @itemx @dots{} @var{command-list} @dots{}
4811 Specify a list of commands for the given breakpoints. The commands
4812 themselves appear on the following lines. Type a line containing just
4813 @code{end} to terminate the commands.
4815 To remove all commands from a breakpoint, type @code{commands} and
4816 follow it immediately with @code{end}; that is, give no commands.
4818 With no argument, @code{commands} refers to the last breakpoint,
4819 watchpoint, or catchpoint set (not to the breakpoint most recently
4820 encountered). If the most recent breakpoints were set with a single
4821 command, then the @code{commands} will apply to all the breakpoints
4822 set by that command. This applies to breakpoints set by
4823 @code{rbreak}, and also applies when a single @code{break} command
4824 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4828 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4829 disabled within a @var{command-list}.
4831 You can use breakpoint commands to start your program up again. Simply
4832 use the @code{continue} command, or @code{step}, or any other command
4833 that resumes execution.
4835 Any other commands in the command list, after a command that resumes
4836 execution, are ignored. This is because any time you resume execution
4837 (even with a simple @code{next} or @code{step}), you may encounter
4838 another breakpoint---which could have its own command list, leading to
4839 ambiguities about which list to execute.
4842 If the first command you specify in a command list is @code{silent}, the
4843 usual message about stopping at a breakpoint is not printed. This may
4844 be desirable for breakpoints that are to print a specific message and
4845 then continue. If none of the remaining commands print anything, you
4846 see no sign that the breakpoint was reached. @code{silent} is
4847 meaningful only at the beginning of a breakpoint command list.
4849 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4850 print precisely controlled output, and are often useful in silent
4851 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4853 For example, here is how you could use breakpoint commands to print the
4854 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4860 printf "x is %d\n",x
4865 One application for breakpoint commands is to compensate for one bug so
4866 you can test for another. Put a breakpoint just after the erroneous line
4867 of code, give it a condition to detect the case in which something
4868 erroneous has been done, and give it commands to assign correct values
4869 to any variables that need them. End with the @code{continue} command
4870 so that your program does not stop, and start with the @code{silent}
4871 command so that no output is produced. Here is an example:
4882 @node Dynamic Printf
4883 @subsection Dynamic Printf
4885 @cindex dynamic printf
4887 The dynamic printf command @code{dprintf} combines a breakpoint with
4888 formatted printing of your program's data to give you the effect of
4889 inserting @code{printf} calls into your program on-the-fly, without
4890 having to recompile it.
4892 In its most basic form, the output goes to the GDB console. However,
4893 you can set the variable @code{dprintf-style} for alternate handling.
4894 For instance, you can ask to format the output by calling your
4895 program's @code{printf} function. This has the advantage that the
4896 characters go to the program's output device, so they can recorded in
4897 redirects to files and so forth.
4899 If you are doing remote debugging with a stub or agent, you can also
4900 ask to have the printf handled by the remote agent. In addition to
4901 ensuring that the output goes to the remote program's device along
4902 with any other output the program might produce, you can also ask that
4903 the dprintf remain active even after disconnecting from the remote
4904 target. Using the stub/agent is also more efficient, as it can do
4905 everything without needing to communicate with @value{GDBN}.
4909 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4910 Whenever execution reaches @var{location}, print the values of one or
4911 more @var{expressions} under the control of the string @var{template}.
4912 To print several values, separate them with commas.
4914 @item set dprintf-style @var{style}
4915 Set the dprintf output to be handled in one of several different
4916 styles enumerated below. A change of style affects all existing
4917 dynamic printfs immediately. (If you need individual control over the
4918 print commands, simply define normal breakpoints with
4919 explicitly-supplied command lists.)
4922 @kindex dprintf-style gdb
4923 Handle the output using the @value{GDBN} @code{printf} command.
4926 @kindex dprintf-style call
4927 Handle the output by calling a function in your program (normally
4931 @kindex dprintf-style agent
4932 Have the remote debugging agent (such as @code{gdbserver}) handle
4933 the output itself. This style is only available for agents that
4934 support running commands on the target.
4936 @item set dprintf-function @var{function}
4937 Set the function to call if the dprintf style is @code{call}. By
4938 default its value is @code{printf}. You may set it to any expression.
4939 that @value{GDBN} can evaluate to a function, as per the @code{call}
4942 @item set dprintf-channel @var{channel}
4943 Set a ``channel'' for dprintf. If set to a non-empty value,
4944 @value{GDBN} will evaluate it as an expression and pass the result as
4945 a first argument to the @code{dprintf-function}, in the manner of
4946 @code{fprintf} and similar functions. Otherwise, the dprintf format
4947 string will be the first argument, in the manner of @code{printf}.
4949 As an example, if you wanted @code{dprintf} output to go to a logfile
4950 that is a standard I/O stream assigned to the variable @code{mylog},
4951 you could do the following:
4954 (gdb) set dprintf-style call
4955 (gdb) set dprintf-function fprintf
4956 (gdb) set dprintf-channel mylog
4957 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4958 Dprintf 1 at 0x123456: file main.c, line 25.
4960 1 dprintf keep y 0x00123456 in main at main.c:25
4961 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4966 Note that the @code{info break} displays the dynamic printf commands
4967 as normal breakpoint commands; you can thus easily see the effect of
4968 the variable settings.
4970 @item set disconnected-dprintf on
4971 @itemx set disconnected-dprintf off
4972 @kindex set disconnected-dprintf
4973 Choose whether @code{dprintf} commands should continue to run if
4974 @value{GDBN} has disconnected from the target. This only applies
4975 if the @code{dprintf-style} is @code{agent}.
4977 @item show disconnected-dprintf off
4978 @kindex show disconnected-dprintf
4979 Show the current choice for disconnected @code{dprintf}.
4983 @value{GDBN} does not check the validity of function and channel,
4984 relying on you to supply values that are meaningful for the contexts
4985 in which they are being used. For instance, the function and channel
4986 may be the values of local variables, but if that is the case, then
4987 all enabled dynamic prints must be at locations within the scope of
4988 those locals. If evaluation fails, @value{GDBN} will report an error.
4990 @node Save Breakpoints
4991 @subsection How to save breakpoints to a file
4993 To save breakpoint definitions to a file use the @w{@code{save
4994 breakpoints}} command.
4997 @kindex save breakpoints
4998 @cindex save breakpoints to a file for future sessions
4999 @item save breakpoints [@var{filename}]
5000 This command saves all current breakpoint definitions together with
5001 their commands and ignore counts, into a file @file{@var{filename}}
5002 suitable for use in a later debugging session. This includes all
5003 types of breakpoints (breakpoints, watchpoints, catchpoints,
5004 tracepoints). To read the saved breakpoint definitions, use the
5005 @code{source} command (@pxref{Command Files}). Note that watchpoints
5006 with expressions involving local variables may fail to be recreated
5007 because it may not be possible to access the context where the
5008 watchpoint is valid anymore. Because the saved breakpoint definitions
5009 are simply a sequence of @value{GDBN} commands that recreate the
5010 breakpoints, you can edit the file in your favorite editing program,
5011 and remove the breakpoint definitions you're not interested in, or
5012 that can no longer be recreated.
5015 @node Static Probe Points
5016 @subsection Static Probe Points
5018 @cindex static probe point, SystemTap
5019 @cindex static probe point, DTrace
5020 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5021 for Statically Defined Tracing, and the probes are designed to have a tiny
5022 runtime code and data footprint, and no dynamic relocations.
5024 Currently, the following types of probes are supported on
5025 ELF-compatible systems:
5029 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5030 @acronym{SDT} probes@footnote{See
5031 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5032 for more information on how to add @code{SystemTap} @acronym{SDT}
5033 probes in your applications.}. @code{SystemTap} probes are usable
5034 from assembly, C and C@t{++} languages@footnote{See
5035 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5036 for a good reference on how the @acronym{SDT} probes are implemented.}.
5038 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5039 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5043 @cindex semaphores on static probe points
5044 Some @code{SystemTap} probes have an associated semaphore variable;
5045 for instance, this happens automatically if you defined your probe
5046 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5047 @value{GDBN} will automatically enable it when you specify a
5048 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5049 breakpoint at a probe's location by some other method (e.g.,
5050 @code{break file:line}), then @value{GDBN} will not automatically set
5051 the semaphore. @code{DTrace} probes do not support semaphores.
5053 You can examine the available static static probes using @code{info
5054 probes}, with optional arguments:
5058 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5059 If given, @var{type} is either @code{stap} for listing
5060 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5061 probes. If omitted all probes are listed regardless of their types.
5063 If given, @var{provider} is a regular expression used to match against provider
5064 names when selecting which probes to list. If omitted, probes by all
5065 probes from all providers are listed.
5067 If given, @var{name} is a regular expression to match against probe names
5068 when selecting which probes to list. If omitted, probe names are not
5069 considered when deciding whether to display them.
5071 If given, @var{objfile} is a regular expression used to select which
5072 object files (executable or shared libraries) to examine. If not
5073 given, all object files are considered.
5075 @item info probes all
5076 List the available static probes, from all types.
5079 @cindex enabling and disabling probes
5080 Some probe points can be enabled and/or disabled. The effect of
5081 enabling or disabling a probe depends on the type of probe being
5082 handled. Some @code{DTrace} probes can be enabled or
5083 disabled, but @code{SystemTap} probes cannot be disabled.
5085 You can enable (or disable) one or more probes using the following
5086 commands, with optional arguments:
5089 @kindex enable probes
5090 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5091 If given, @var{provider} is a regular expression used to match against
5092 provider names when selecting which probes to enable. If omitted,
5093 all probes from all providers are enabled.
5095 If given, @var{name} is a regular expression to match against probe
5096 names when selecting which probes to enable. If omitted, probe names
5097 are not considered when deciding whether to enable them.
5099 If given, @var{objfile} is a regular expression used to select which
5100 object files (executable or shared libraries) to examine. If not
5101 given, all object files are considered.
5103 @kindex disable probes
5104 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5105 See the @code{enable probes} command above for a description of the
5106 optional arguments accepted by this command.
5109 @vindex $_probe_arg@r{, convenience variable}
5110 A probe may specify up to twelve arguments. These are available at the
5111 point at which the probe is defined---that is, when the current PC is
5112 at the probe's location. The arguments are available using the
5113 convenience variables (@pxref{Convenience Vars})
5114 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5115 probes each probe argument is an integer of the appropriate size;
5116 types are not preserved. In @code{DTrace} probes types are preserved
5117 provided that they are recognized as such by @value{GDBN}; otherwise
5118 the value of the probe argument will be a long integer. The
5119 convenience variable @code{$_probe_argc} holds the number of arguments
5120 at the current probe point.
5122 These variables are always available, but attempts to access them at
5123 any location other than a probe point will cause @value{GDBN} to give
5127 @c @ifclear BARETARGET
5128 @node Error in Breakpoints
5129 @subsection ``Cannot insert breakpoints''
5131 If you request too many active hardware-assisted breakpoints and
5132 watchpoints, you will see this error message:
5134 @c FIXME: the precise wording of this message may change; the relevant
5135 @c source change is not committed yet (Sep 3, 1999).
5137 Stopped; cannot insert breakpoints.
5138 You may have requested too many hardware breakpoints and watchpoints.
5142 This message is printed when you attempt to resume the program, since
5143 only then @value{GDBN} knows exactly how many hardware breakpoints and
5144 watchpoints it needs to insert.
5146 When this message is printed, you need to disable or remove some of the
5147 hardware-assisted breakpoints and watchpoints, and then continue.
5149 @node Breakpoint-related Warnings
5150 @subsection ``Breakpoint address adjusted...''
5151 @cindex breakpoint address adjusted
5153 Some processor architectures place constraints on the addresses at
5154 which breakpoints may be placed. For architectures thus constrained,
5155 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5156 with the constraints dictated by the architecture.
5158 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5159 a VLIW architecture in which a number of RISC-like instructions may be
5160 bundled together for parallel execution. The FR-V architecture
5161 constrains the location of a breakpoint instruction within such a
5162 bundle to the instruction with the lowest address. @value{GDBN}
5163 honors this constraint by adjusting a breakpoint's address to the
5164 first in the bundle.
5166 It is not uncommon for optimized code to have bundles which contain
5167 instructions from different source statements, thus it may happen that
5168 a breakpoint's address will be adjusted from one source statement to
5169 another. Since this adjustment may significantly alter @value{GDBN}'s
5170 breakpoint related behavior from what the user expects, a warning is
5171 printed when the breakpoint is first set and also when the breakpoint
5174 A warning like the one below is printed when setting a breakpoint
5175 that's been subject to address adjustment:
5178 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5181 Such warnings are printed both for user settable and @value{GDBN}'s
5182 internal breakpoints. If you see one of these warnings, you should
5183 verify that a breakpoint set at the adjusted address will have the
5184 desired affect. If not, the breakpoint in question may be removed and
5185 other breakpoints may be set which will have the desired behavior.
5186 E.g., it may be sufficient to place the breakpoint at a later
5187 instruction. A conditional breakpoint may also be useful in some
5188 cases to prevent the breakpoint from triggering too often.
5190 @value{GDBN} will also issue a warning when stopping at one of these
5191 adjusted breakpoints:
5194 warning: Breakpoint 1 address previously adjusted from 0x00010414
5198 When this warning is encountered, it may be too late to take remedial
5199 action except in cases where the breakpoint is hit earlier or more
5200 frequently than expected.
5202 @node Continuing and Stepping
5203 @section Continuing and Stepping
5207 @cindex resuming execution
5208 @dfn{Continuing} means resuming program execution until your program
5209 completes normally. In contrast, @dfn{stepping} means executing just
5210 one more ``step'' of your program, where ``step'' may mean either one
5211 line of source code, or one machine instruction (depending on what
5212 particular command you use). Either when continuing or when stepping,
5213 your program may stop even sooner, due to a breakpoint or a signal. (If
5214 it stops due to a signal, you may want to use @code{handle}, or use
5215 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5216 or you may step into the signal's handler (@pxref{stepping and signal
5221 @kindex c @r{(@code{continue})}
5222 @kindex fg @r{(resume foreground execution)}
5223 @item continue @r{[}@var{ignore-count}@r{]}
5224 @itemx c @r{[}@var{ignore-count}@r{]}
5225 @itemx fg @r{[}@var{ignore-count}@r{]}
5226 Resume program execution, at the address where your program last stopped;
5227 any breakpoints set at that address are bypassed. The optional argument
5228 @var{ignore-count} allows you to specify a further number of times to
5229 ignore a breakpoint at this location; its effect is like that of
5230 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5232 The argument @var{ignore-count} is meaningful only when your program
5233 stopped due to a breakpoint. At other times, the argument to
5234 @code{continue} is ignored.
5236 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5237 debugged program is deemed to be the foreground program) are provided
5238 purely for convenience, and have exactly the same behavior as
5242 To resume execution at a different place, you can use @code{return}
5243 (@pxref{Returning, ,Returning from a Function}) to go back to the
5244 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5245 Different Address}) to go to an arbitrary location in your program.
5247 A typical technique for using stepping is to set a breakpoint
5248 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5249 beginning of the function or the section of your program where a problem
5250 is believed to lie, run your program until it stops at that breakpoint,
5251 and then step through the suspect area, examining the variables that are
5252 interesting, until you see the problem happen.
5256 @kindex s @r{(@code{step})}
5258 Continue running your program until control reaches a different source
5259 line, then stop it and return control to @value{GDBN}. This command is
5260 abbreviated @code{s}.
5263 @c "without debugging information" is imprecise; actually "without line
5264 @c numbers in the debugging information". (gcc -g1 has debugging info but
5265 @c not line numbers). But it seems complex to try to make that
5266 @c distinction here.
5267 @emph{Warning:} If you use the @code{step} command while control is
5268 within a function that was compiled without debugging information,
5269 execution proceeds until control reaches a function that does have
5270 debugging information. Likewise, it will not step into a function which
5271 is compiled without debugging information. To step through functions
5272 without debugging information, use the @code{stepi} command, described
5276 The @code{step} command only stops at the first instruction of a source
5277 line. This prevents the multiple stops that could otherwise occur in
5278 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5279 to stop if a function that has debugging information is called within
5280 the line. In other words, @code{step} @emph{steps inside} any functions
5281 called within the line.
5283 Also, the @code{step} command only enters a function if there is line
5284 number information for the function. Otherwise it acts like the
5285 @code{next} command. This avoids problems when using @code{cc -gl}
5286 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5287 was any debugging information about the routine.
5289 @item step @var{count}
5290 Continue running as in @code{step}, but do so @var{count} times. If a
5291 breakpoint is reached, or a signal not related to stepping occurs before
5292 @var{count} steps, stepping stops right away.
5295 @kindex n @r{(@code{next})}
5296 @item next @r{[}@var{count}@r{]}
5297 Continue to the next source line in the current (innermost) stack frame.
5298 This is similar to @code{step}, but function calls that appear within
5299 the line of code are executed without stopping. Execution stops when
5300 control reaches a different line of code at the original stack level
5301 that was executing when you gave the @code{next} command. This command
5302 is abbreviated @code{n}.
5304 An argument @var{count} is a repeat count, as for @code{step}.
5307 @c FIX ME!! Do we delete this, or is there a way it fits in with
5308 @c the following paragraph? --- Vctoria
5310 @c @code{next} within a function that lacks debugging information acts like
5311 @c @code{step}, but any function calls appearing within the code of the
5312 @c function are executed without stopping.
5314 The @code{next} command only stops at the first instruction of a
5315 source line. This prevents multiple stops that could otherwise occur in
5316 @code{switch} statements, @code{for} loops, etc.
5318 @kindex set step-mode
5320 @cindex functions without line info, and stepping
5321 @cindex stepping into functions with no line info
5322 @itemx set step-mode on
5323 The @code{set step-mode on} command causes the @code{step} command to
5324 stop at the first instruction of a function which contains no debug line
5325 information rather than stepping over it.
5327 This is useful in cases where you may be interested in inspecting the
5328 machine instructions of a function which has no symbolic info and do not
5329 want @value{GDBN} to automatically skip over this function.
5331 @item set step-mode off
5332 Causes the @code{step} command to step over any functions which contains no
5333 debug information. This is the default.
5335 @item show step-mode
5336 Show whether @value{GDBN} will stop in or step over functions without
5337 source line debug information.
5340 @kindex fin @r{(@code{finish})}
5342 Continue running until just after function in the selected stack frame
5343 returns. Print the returned value (if any). This command can be
5344 abbreviated as @code{fin}.
5346 Contrast this with the @code{return} command (@pxref{Returning,
5347 ,Returning from a Function}).
5350 @kindex u @r{(@code{until})}
5351 @cindex run until specified location
5354 Continue running until a source line past the current line, in the
5355 current stack frame, is reached. This command is used to avoid single
5356 stepping through a loop more than once. It is like the @code{next}
5357 command, except that when @code{until} encounters a jump, it
5358 automatically continues execution until the program counter is greater
5359 than the address of the jump.
5361 This means that when you reach the end of a loop after single stepping
5362 though it, @code{until} makes your program continue execution until it
5363 exits the loop. In contrast, a @code{next} command at the end of a loop
5364 simply steps back to the beginning of the loop, which forces you to step
5365 through the next iteration.
5367 @code{until} always stops your program if it attempts to exit the current
5370 @code{until} may produce somewhat counterintuitive results if the order
5371 of machine code does not match the order of the source lines. For
5372 example, in the following excerpt from a debugging session, the @code{f}
5373 (@code{frame}) command shows that execution is stopped at line
5374 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5378 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5380 (@value{GDBP}) until
5381 195 for ( ; argc > 0; NEXTARG) @{
5384 This happened because, for execution efficiency, the compiler had
5385 generated code for the loop closure test at the end, rather than the
5386 start, of the loop---even though the test in a C @code{for}-loop is
5387 written before the body of the loop. The @code{until} command appeared
5388 to step back to the beginning of the loop when it advanced to this
5389 expression; however, it has not really gone to an earlier
5390 statement---not in terms of the actual machine code.
5392 @code{until} with no argument works by means of single
5393 instruction stepping, and hence is slower than @code{until} with an
5396 @item until @var{location}
5397 @itemx u @var{location}
5398 Continue running your program until either the specified @var{location} is
5399 reached, or the current stack frame returns. The location is any of
5400 the forms described in @ref{Specify Location}.
5401 This form of the command uses temporary breakpoints, and
5402 hence is quicker than @code{until} without an argument. The specified
5403 location is actually reached only if it is in the current frame. This
5404 implies that @code{until} can be used to skip over recursive function
5405 invocations. For instance in the code below, if the current location is
5406 line @code{96}, issuing @code{until 99} will execute the program up to
5407 line @code{99} in the same invocation of factorial, i.e., after the inner
5408 invocations have returned.
5411 94 int factorial (int value)
5413 96 if (value > 1) @{
5414 97 value *= factorial (value - 1);
5421 @kindex advance @var{location}
5422 @item advance @var{location}
5423 Continue running the program up to the given @var{location}. An argument is
5424 required, which should be of one of the forms described in
5425 @ref{Specify Location}.
5426 Execution will also stop upon exit from the current stack
5427 frame. This command is similar to @code{until}, but @code{advance} will
5428 not skip over recursive function calls, and the target location doesn't
5429 have to be in the same frame as the current one.
5433 @kindex si @r{(@code{stepi})}
5435 @itemx stepi @var{arg}
5437 Execute one machine instruction, then stop and return to the debugger.
5439 It is often useful to do @samp{display/i $pc} when stepping by machine
5440 instructions. This makes @value{GDBN} automatically display the next
5441 instruction to be executed, each time your program stops. @xref{Auto
5442 Display,, Automatic Display}.
5444 An argument is a repeat count, as in @code{step}.
5448 @kindex ni @r{(@code{nexti})}
5450 @itemx nexti @var{arg}
5452 Execute one machine instruction, but if it is a function call,
5453 proceed until the function returns.
5455 An argument is a repeat count, as in @code{next}.
5459 @anchor{range stepping}
5460 @cindex range stepping
5461 @cindex target-assisted range stepping
5462 By default, and if available, @value{GDBN} makes use of
5463 target-assisted @dfn{range stepping}. In other words, whenever you
5464 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5465 tells the target to step the corresponding range of instruction
5466 addresses instead of issuing multiple single-steps. This speeds up
5467 line stepping, particularly for remote targets. Ideally, there should
5468 be no reason you would want to turn range stepping off. However, it's
5469 possible that a bug in the debug info, a bug in the remote stub (for
5470 remote targets), or even a bug in @value{GDBN} could make line
5471 stepping behave incorrectly when target-assisted range stepping is
5472 enabled. You can use the following command to turn off range stepping
5476 @kindex set range-stepping
5477 @kindex show range-stepping
5478 @item set range-stepping
5479 @itemx show range-stepping
5480 Control whether range stepping is enabled.
5482 If @code{on}, and the target supports it, @value{GDBN} tells the
5483 target to step a range of addresses itself, instead of issuing
5484 multiple single-steps. If @code{off}, @value{GDBN} always issues
5485 single-steps, even if range stepping is supported by the target. The
5486 default is @code{on}.
5490 @node Skipping Over Functions and Files
5491 @section Skipping Over Functions and Files
5492 @cindex skipping over functions and files
5494 The program you are debugging may contain some functions which are
5495 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5496 skip a function or all functions in a file when stepping.
5498 For example, consider the following C function:
5509 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5510 are not interested in stepping through @code{boring}. If you run @code{step}
5511 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5512 step over both @code{foo} and @code{boring}!
5514 One solution is to @code{step} into @code{boring} and use the @code{finish}
5515 command to immediately exit it. But this can become tedious if @code{boring}
5516 is called from many places.
5518 A more flexible solution is to execute @kbd{skip boring}. This instructs
5519 @value{GDBN} never to step into @code{boring}. Now when you execute
5520 @code{step} at line 103, you'll step over @code{boring} and directly into
5523 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5524 example, @code{skip file boring.c}.
5527 @kindex skip function
5528 @item skip @r{[}@var{linespec}@r{]}
5529 @itemx skip function @r{[}@var{linespec}@r{]}
5530 After running this command, the function named by @var{linespec} or the
5531 function containing the line named by @var{linespec} will be skipped over when
5532 stepping. @xref{Specify Location}.
5534 If you do not specify @var{linespec}, the function you're currently debugging
5537 (If you have a function called @code{file} that you want to skip, use
5538 @kbd{skip function file}.)
5541 @item skip file @r{[}@var{filename}@r{]}
5542 After running this command, any function whose source lives in @var{filename}
5543 will be skipped over when stepping.
5545 If you do not specify @var{filename}, functions whose source lives in the file
5546 you're currently debugging will be skipped.
5549 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5550 These are the commands for managing your list of skips:
5554 @item info skip @r{[}@var{range}@r{]}
5555 Print details about the specified skip(s). If @var{range} is not specified,
5556 print a table with details about all functions and files marked for skipping.
5557 @code{info skip} prints the following information about each skip:
5561 A number identifying this skip.
5563 The type of this skip, either @samp{function} or @samp{file}.
5564 @item Enabled or Disabled
5565 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5567 For function skips, this column indicates the address in memory of the function
5568 being skipped. If you've set a function skip on a function which has not yet
5569 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5570 which has the function is loaded, @code{info skip} will show the function's
5573 For file skips, this field contains the filename being skipped. For functions
5574 skips, this field contains the function name and its line number in the file
5575 where it is defined.
5579 @item skip delete @r{[}@var{range}@r{]}
5580 Delete the specified skip(s). If @var{range} is not specified, delete all
5584 @item skip enable @r{[}@var{range}@r{]}
5585 Enable the specified skip(s). If @var{range} is not specified, enable all
5588 @kindex skip disable
5589 @item skip disable @r{[}@var{range}@r{]}
5590 Disable the specified skip(s). If @var{range} is not specified, disable all
5599 A signal is an asynchronous event that can happen in a program. The
5600 operating system defines the possible kinds of signals, and gives each
5601 kind a name and a number. For example, in Unix @code{SIGINT} is the
5602 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5603 @code{SIGSEGV} is the signal a program gets from referencing a place in
5604 memory far away from all the areas in use; @code{SIGALRM} occurs when
5605 the alarm clock timer goes off (which happens only if your program has
5606 requested an alarm).
5608 @cindex fatal signals
5609 Some signals, including @code{SIGALRM}, are a normal part of the
5610 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5611 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5612 program has not specified in advance some other way to handle the signal.
5613 @code{SIGINT} does not indicate an error in your program, but it is normally
5614 fatal so it can carry out the purpose of the interrupt: to kill the program.
5616 @value{GDBN} has the ability to detect any occurrence of a signal in your
5617 program. You can tell @value{GDBN} in advance what to do for each kind of
5620 @cindex handling signals
5621 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5622 @code{SIGALRM} be silently passed to your program
5623 (so as not to interfere with their role in the program's functioning)
5624 but to stop your program immediately whenever an error signal happens.
5625 You can change these settings with the @code{handle} command.
5628 @kindex info signals
5632 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5633 handle each one. You can use this to see the signal numbers of all
5634 the defined types of signals.
5636 @item info signals @var{sig}
5637 Similar, but print information only about the specified signal number.
5639 @code{info handle} is an alias for @code{info signals}.
5641 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5642 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5643 for details about this command.
5646 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5647 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5648 can be the number of a signal or its name (with or without the
5649 @samp{SIG} at the beginning); a list of signal numbers of the form
5650 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5651 known signals. Optional arguments @var{keywords}, described below,
5652 say what change to make.
5656 The keywords allowed by the @code{handle} command can be abbreviated.
5657 Their full names are:
5661 @value{GDBN} should not stop your program when this signal happens. It may
5662 still print a message telling you that the signal has come in.
5665 @value{GDBN} should stop your program when this signal happens. This implies
5666 the @code{print} keyword as well.
5669 @value{GDBN} should print a message when this signal happens.
5672 @value{GDBN} should not mention the occurrence of the signal at all. This
5673 implies the @code{nostop} keyword as well.
5677 @value{GDBN} should allow your program to see this signal; your program
5678 can handle the signal, or else it may terminate if the signal is fatal
5679 and not handled. @code{pass} and @code{noignore} are synonyms.
5683 @value{GDBN} should not allow your program to see this signal.
5684 @code{nopass} and @code{ignore} are synonyms.
5688 When a signal stops your program, the signal is not visible to the
5690 continue. Your program sees the signal then, if @code{pass} is in
5691 effect for the signal in question @emph{at that time}. In other words,
5692 after @value{GDBN} reports a signal, you can use the @code{handle}
5693 command with @code{pass} or @code{nopass} to control whether your
5694 program sees that signal when you continue.
5696 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5697 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5698 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5701 You can also use the @code{signal} command to prevent your program from
5702 seeing a signal, or cause it to see a signal it normally would not see,
5703 or to give it any signal at any time. For example, if your program stopped
5704 due to some sort of memory reference error, you might store correct
5705 values into the erroneous variables and continue, hoping to see more
5706 execution; but your program would probably terminate immediately as
5707 a result of the fatal signal once it saw the signal. To prevent this,
5708 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5711 @cindex stepping and signal handlers
5712 @anchor{stepping and signal handlers}
5714 @value{GDBN} optimizes for stepping the mainline code. If a signal
5715 that has @code{handle nostop} and @code{handle pass} set arrives while
5716 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5717 in progress, @value{GDBN} lets the signal handler run and then resumes
5718 stepping the mainline code once the signal handler returns. In other
5719 words, @value{GDBN} steps over the signal handler. This prevents
5720 signals that you've specified as not interesting (with @code{handle
5721 nostop}) from changing the focus of debugging unexpectedly. Note that
5722 the signal handler itself may still hit a breakpoint, stop for another
5723 signal that has @code{handle stop} in effect, or for any other event
5724 that normally results in stopping the stepping command sooner. Also
5725 note that @value{GDBN} still informs you that the program received a
5726 signal if @code{handle print} is set.
5728 @anchor{stepping into signal handlers}
5730 If you set @code{handle pass} for a signal, and your program sets up a
5731 handler for it, then issuing a stepping command, such as @code{step}
5732 or @code{stepi}, when your program is stopped due to the signal will
5733 step @emph{into} the signal handler (if the target supports that).
5735 Likewise, if you use the @code{queue-signal} command to queue a signal
5736 to be delivered to the current thread when execution of the thread
5737 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5738 stepping command will step into the signal handler.
5740 Here's an example, using @code{stepi} to step to the first instruction
5741 of @code{SIGUSR1}'s handler:
5744 (@value{GDBP}) handle SIGUSR1
5745 Signal Stop Print Pass to program Description
5746 SIGUSR1 Yes Yes Yes User defined signal 1
5750 Program received signal SIGUSR1, User defined signal 1.
5751 main () sigusr1.c:28
5754 sigusr1_handler () at sigusr1.c:9
5758 The same, but using @code{queue-signal} instead of waiting for the
5759 program to receive the signal first:
5764 (@value{GDBP}) queue-signal SIGUSR1
5766 sigusr1_handler () at sigusr1.c:9
5771 @cindex extra signal information
5772 @anchor{extra signal information}
5774 On some targets, @value{GDBN} can inspect extra signal information
5775 associated with the intercepted signal, before it is actually
5776 delivered to the program being debugged. This information is exported
5777 by the convenience variable @code{$_siginfo}, and consists of data
5778 that is passed by the kernel to the signal handler at the time of the
5779 receipt of a signal. The data type of the information itself is
5780 target dependent. You can see the data type using the @code{ptype
5781 $_siginfo} command. On Unix systems, it typically corresponds to the
5782 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5785 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5786 referenced address that raised a segmentation fault.
5790 (@value{GDBP}) continue
5791 Program received signal SIGSEGV, Segmentation fault.
5792 0x0000000000400766 in main ()
5794 (@value{GDBP}) ptype $_siginfo
5801 struct @{...@} _kill;
5802 struct @{...@} _timer;
5804 struct @{...@} _sigchld;
5805 struct @{...@} _sigfault;
5806 struct @{...@} _sigpoll;
5809 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5813 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5814 $1 = (void *) 0x7ffff7ff7000
5818 Depending on target support, @code{$_siginfo} may also be writable.
5821 @section Stopping and Starting Multi-thread Programs
5823 @cindex stopped threads
5824 @cindex threads, stopped
5826 @cindex continuing threads
5827 @cindex threads, continuing
5829 @value{GDBN} supports debugging programs with multiple threads
5830 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5831 are two modes of controlling execution of your program within the
5832 debugger. In the default mode, referred to as @dfn{all-stop mode},
5833 when any thread in your program stops (for example, at a breakpoint
5834 or while being stepped), all other threads in the program are also stopped by
5835 @value{GDBN}. On some targets, @value{GDBN} also supports
5836 @dfn{non-stop mode}, in which other threads can continue to run freely while
5837 you examine the stopped thread in the debugger.
5840 * All-Stop Mode:: All threads stop when GDB takes control
5841 * Non-Stop Mode:: Other threads continue to execute
5842 * Background Execution:: Running your program asynchronously
5843 * Thread-Specific Breakpoints:: Controlling breakpoints
5844 * Interrupted System Calls:: GDB may interfere with system calls
5845 * Observer Mode:: GDB does not alter program behavior
5849 @subsection All-Stop Mode
5851 @cindex all-stop mode
5853 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5854 @emph{all} threads of execution stop, not just the current thread. This
5855 allows you to examine the overall state of the program, including
5856 switching between threads, without worrying that things may change
5859 Conversely, whenever you restart the program, @emph{all} threads start
5860 executing. @emph{This is true even when single-stepping} with commands
5861 like @code{step} or @code{next}.
5863 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5864 Since thread scheduling is up to your debugging target's operating
5865 system (not controlled by @value{GDBN}), other threads may
5866 execute more than one statement while the current thread completes a
5867 single step. Moreover, in general other threads stop in the middle of a
5868 statement, rather than at a clean statement boundary, when the program
5871 You might even find your program stopped in another thread after
5872 continuing or even single-stepping. This happens whenever some other
5873 thread runs into a breakpoint, a signal, or an exception before the
5874 first thread completes whatever you requested.
5876 @cindex automatic thread selection
5877 @cindex switching threads automatically
5878 @cindex threads, automatic switching
5879 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5880 signal, it automatically selects the thread where that breakpoint or
5881 signal happened. @value{GDBN} alerts you to the context switch with a
5882 message such as @samp{[Switching to Thread @var{n}]} to identify the
5885 On some OSes, you can modify @value{GDBN}'s default behavior by
5886 locking the OS scheduler to allow only a single thread to run.
5889 @item set scheduler-locking @var{mode}
5890 @cindex scheduler locking mode
5891 @cindex lock scheduler
5892 Set the scheduler locking mode. It applies to normal execution,
5893 record mode, and replay mode. If it is @code{off}, then there is no
5894 locking and any thread may run at any time. If @code{on}, then only
5895 the current thread may run when the inferior is resumed. The
5896 @code{step} mode optimizes for single-stepping; it prevents other
5897 threads from preempting the current thread while you are stepping, so
5898 that the focus of debugging does not change unexpectedly. Other
5899 threads never get a chance to run when you step, and they are
5900 completely free to run when you use commands like @samp{continue},
5901 @samp{until}, or @samp{finish}. However, unless another thread hits a
5902 breakpoint during its timeslice, @value{GDBN} does not change the
5903 current thread away from the thread that you are debugging. The
5904 @code{replay} mode behaves like @code{off} in record mode and like
5905 @code{on} in replay mode.
5907 @item show scheduler-locking
5908 Display the current scheduler locking mode.
5911 @cindex resume threads of multiple processes simultaneously
5912 By default, when you issue one of the execution commands such as
5913 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5914 threads of the current inferior to run. For example, if @value{GDBN}
5915 is attached to two inferiors, each with two threads, the
5916 @code{continue} command resumes only the two threads of the current
5917 inferior. This is useful, for example, when you debug a program that
5918 forks and you want to hold the parent stopped (so that, for instance,
5919 it doesn't run to exit), while you debug the child. In other
5920 situations, you may not be interested in inspecting the current state
5921 of any of the processes @value{GDBN} is attached to, and you may want
5922 to resume them all until some breakpoint is hit. In the latter case,
5923 you can instruct @value{GDBN} to allow all threads of all the
5924 inferiors to run with the @w{@code{set schedule-multiple}} command.
5927 @kindex set schedule-multiple
5928 @item set schedule-multiple
5929 Set the mode for allowing threads of multiple processes to be resumed
5930 when an execution command is issued. When @code{on}, all threads of
5931 all processes are allowed to run. When @code{off}, only the threads
5932 of the current process are resumed. The default is @code{off}. The
5933 @code{scheduler-locking} mode takes precedence when set to @code{on},
5934 or while you are stepping and set to @code{step}.
5936 @item show schedule-multiple
5937 Display the current mode for resuming the execution of threads of
5942 @subsection Non-Stop Mode
5944 @cindex non-stop mode
5946 @c This section is really only a place-holder, and needs to be expanded
5947 @c with more details.
5949 For some multi-threaded targets, @value{GDBN} supports an optional
5950 mode of operation in which you can examine stopped program threads in
5951 the debugger while other threads continue to execute freely. This
5952 minimizes intrusion when debugging live systems, such as programs
5953 where some threads have real-time constraints or must continue to
5954 respond to external events. This is referred to as @dfn{non-stop} mode.
5956 In non-stop mode, when a thread stops to report a debugging event,
5957 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5958 threads as well, in contrast to the all-stop mode behavior. Additionally,
5959 execution commands such as @code{continue} and @code{step} apply by default
5960 only to the current thread in non-stop mode, rather than all threads as
5961 in all-stop mode. This allows you to control threads explicitly in
5962 ways that are not possible in all-stop mode --- for example, stepping
5963 one thread while allowing others to run freely, stepping
5964 one thread while holding all others stopped, or stepping several threads
5965 independently and simultaneously.
5967 To enter non-stop mode, use this sequence of commands before you run
5968 or attach to your program:
5971 # If using the CLI, pagination breaks non-stop.
5974 # Finally, turn it on!
5978 You can use these commands to manipulate the non-stop mode setting:
5981 @kindex set non-stop
5982 @item set non-stop on
5983 Enable selection of non-stop mode.
5984 @item set non-stop off
5985 Disable selection of non-stop mode.
5986 @kindex show non-stop
5988 Show the current non-stop enablement setting.
5991 Note these commands only reflect whether non-stop mode is enabled,
5992 not whether the currently-executing program is being run in non-stop mode.
5993 In particular, the @code{set non-stop} preference is only consulted when
5994 @value{GDBN} starts or connects to the target program, and it is generally
5995 not possible to switch modes once debugging has started. Furthermore,
5996 since not all targets support non-stop mode, even when you have enabled
5997 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6000 In non-stop mode, all execution commands apply only to the current thread
6001 by default. That is, @code{continue} only continues one thread.
6002 To continue all threads, issue @code{continue -a} or @code{c -a}.
6004 You can use @value{GDBN}'s background execution commands
6005 (@pxref{Background Execution}) to run some threads in the background
6006 while you continue to examine or step others from @value{GDBN}.
6007 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6008 always executed asynchronously in non-stop mode.
6010 Suspending execution is done with the @code{interrupt} command when
6011 running in the background, or @kbd{Ctrl-c} during foreground execution.
6012 In all-stop mode, this stops the whole process;
6013 but in non-stop mode the interrupt applies only to the current thread.
6014 To stop the whole program, use @code{interrupt -a}.
6016 Other execution commands do not currently support the @code{-a} option.
6018 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6019 that thread current, as it does in all-stop mode. This is because the
6020 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6021 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6022 changed to a different thread just as you entered a command to operate on the
6023 previously current thread.
6025 @node Background Execution
6026 @subsection Background Execution
6028 @cindex foreground execution
6029 @cindex background execution
6030 @cindex asynchronous execution
6031 @cindex execution, foreground, background and asynchronous
6033 @value{GDBN}'s execution commands have two variants: the normal
6034 foreground (synchronous) behavior, and a background
6035 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6036 the program to report that some thread has stopped before prompting for
6037 another command. In background execution, @value{GDBN} immediately gives
6038 a command prompt so that you can issue other commands while your program runs.
6040 If the target doesn't support async mode, @value{GDBN} issues an error
6041 message if you attempt to use the background execution commands.
6043 To specify background execution, add a @code{&} to the command. For example,
6044 the background form of the @code{continue} command is @code{continue&}, or
6045 just @code{c&}. The execution commands that accept background execution
6051 @xref{Starting, , Starting your Program}.
6055 @xref{Attach, , Debugging an Already-running Process}.
6059 @xref{Continuing and Stepping, step}.
6063 @xref{Continuing and Stepping, stepi}.
6067 @xref{Continuing and Stepping, next}.
6071 @xref{Continuing and Stepping, nexti}.
6075 @xref{Continuing and Stepping, continue}.
6079 @xref{Continuing and Stepping, finish}.
6083 @xref{Continuing and Stepping, until}.
6087 Background execution is especially useful in conjunction with non-stop
6088 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6089 However, you can also use these commands in the normal all-stop mode with
6090 the restriction that you cannot issue another execution command until the
6091 previous one finishes. Examples of commands that are valid in all-stop
6092 mode while the program is running include @code{help} and @code{info break}.
6094 You can interrupt your program while it is running in the background by
6095 using the @code{interrupt} command.
6102 Suspend execution of the running program. In all-stop mode,
6103 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6104 only the current thread. To stop the whole program in non-stop mode,
6105 use @code{interrupt -a}.
6108 @node Thread-Specific Breakpoints
6109 @subsection Thread-Specific Breakpoints
6111 When your program has multiple threads (@pxref{Threads,, Debugging
6112 Programs with Multiple Threads}), you can choose whether to set
6113 breakpoints on all threads, or on a particular thread.
6116 @cindex breakpoints and threads
6117 @cindex thread breakpoints
6118 @kindex break @dots{} thread @var{thread-id}
6119 @item break @var{location} thread @var{thread-id}
6120 @itemx break @var{location} thread @var{thread-id} if @dots{}
6121 @var{location} specifies source lines; there are several ways of
6122 writing them (@pxref{Specify Location}), but the effect is always to
6123 specify some source line.
6125 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6126 to specify that you only want @value{GDBN} to stop the program when a
6127 particular thread reaches this breakpoint. The @var{thread-id} specifier
6128 is one of the thread identifiers assigned by @value{GDBN}, shown
6129 in the first column of the @samp{info threads} display.
6131 If you do not specify @samp{thread @var{thread-id}} when you set a
6132 breakpoint, the breakpoint applies to @emph{all} threads of your
6135 You can use the @code{thread} qualifier on conditional breakpoints as
6136 well; in this case, place @samp{thread @var{thread-id}} before or
6137 after the breakpoint condition, like this:
6140 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6145 Thread-specific breakpoints are automatically deleted when
6146 @value{GDBN} detects the corresponding thread is no longer in the
6147 thread list. For example:
6151 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6154 There are several ways for a thread to disappear, such as a regular
6155 thread exit, but also when you detach from the process with the
6156 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6157 Process}), or if @value{GDBN} loses the remote connection
6158 (@pxref{Remote Debugging}), etc. Note that with some targets,
6159 @value{GDBN} is only able to detect a thread has exited when the user
6160 explictly asks for the thread list with the @code{info threads}
6163 @node Interrupted System Calls
6164 @subsection Interrupted System Calls
6166 @cindex thread breakpoints and system calls
6167 @cindex system calls and thread breakpoints
6168 @cindex premature return from system calls
6169 There is an unfortunate side effect when using @value{GDBN} to debug
6170 multi-threaded programs. If one thread stops for a
6171 breakpoint, or for some other reason, and another thread is blocked in a
6172 system call, then the system call may return prematurely. This is a
6173 consequence of the interaction between multiple threads and the signals
6174 that @value{GDBN} uses to implement breakpoints and other events that
6177 To handle this problem, your program should check the return value of
6178 each system call and react appropriately. This is good programming
6181 For example, do not write code like this:
6187 The call to @code{sleep} will return early if a different thread stops
6188 at a breakpoint or for some other reason.
6190 Instead, write this:
6195 unslept = sleep (unslept);
6198 A system call is allowed to return early, so the system is still
6199 conforming to its specification. But @value{GDBN} does cause your
6200 multi-threaded program to behave differently than it would without
6203 Also, @value{GDBN} uses internal breakpoints in the thread library to
6204 monitor certain events such as thread creation and thread destruction.
6205 When such an event happens, a system call in another thread may return
6206 prematurely, even though your program does not appear to stop.
6209 @subsection Observer Mode
6211 If you want to build on non-stop mode and observe program behavior
6212 without any chance of disruption by @value{GDBN}, you can set
6213 variables to disable all of the debugger's attempts to modify state,
6214 whether by writing memory, inserting breakpoints, etc. These operate
6215 at a low level, intercepting operations from all commands.
6217 When all of these are set to @code{off}, then @value{GDBN} is said to
6218 be @dfn{observer mode}. As a convenience, the variable
6219 @code{observer} can be set to disable these, plus enable non-stop
6222 Note that @value{GDBN} will not prevent you from making nonsensical
6223 combinations of these settings. For instance, if you have enabled
6224 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6225 then breakpoints that work by writing trap instructions into the code
6226 stream will still not be able to be placed.
6231 @item set observer on
6232 @itemx set observer off
6233 When set to @code{on}, this disables all the permission variables
6234 below (except for @code{insert-fast-tracepoints}), plus enables
6235 non-stop debugging. Setting this to @code{off} switches back to
6236 normal debugging, though remaining in non-stop mode.
6239 Show whether observer mode is on or off.
6241 @kindex may-write-registers
6242 @item set may-write-registers on
6243 @itemx set may-write-registers off
6244 This controls whether @value{GDBN} will attempt to alter the values of
6245 registers, such as with assignment expressions in @code{print}, or the
6246 @code{jump} command. It defaults to @code{on}.
6248 @item show may-write-registers
6249 Show the current permission to write registers.
6251 @kindex may-write-memory
6252 @item set may-write-memory on
6253 @itemx set may-write-memory off
6254 This controls whether @value{GDBN} will attempt to alter the contents
6255 of memory, such as with assignment expressions in @code{print}. It
6256 defaults to @code{on}.
6258 @item show may-write-memory
6259 Show the current permission to write memory.
6261 @kindex may-insert-breakpoints
6262 @item set may-insert-breakpoints on
6263 @itemx set may-insert-breakpoints off
6264 This controls whether @value{GDBN} will attempt to insert breakpoints.
6265 This affects all breakpoints, including internal breakpoints defined
6266 by @value{GDBN}. It defaults to @code{on}.
6268 @item show may-insert-breakpoints
6269 Show the current permission to insert breakpoints.
6271 @kindex may-insert-tracepoints
6272 @item set may-insert-tracepoints on
6273 @itemx set may-insert-tracepoints off
6274 This controls whether @value{GDBN} will attempt to insert (regular)
6275 tracepoints at the beginning of a tracing experiment. It affects only
6276 non-fast tracepoints, fast tracepoints being under the control of
6277 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6279 @item show may-insert-tracepoints
6280 Show the current permission to insert tracepoints.
6282 @kindex may-insert-fast-tracepoints
6283 @item set may-insert-fast-tracepoints on
6284 @itemx set may-insert-fast-tracepoints off
6285 This controls whether @value{GDBN} will attempt to insert fast
6286 tracepoints at the beginning of a tracing experiment. It affects only
6287 fast tracepoints, regular (non-fast) tracepoints being under the
6288 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6290 @item show may-insert-fast-tracepoints
6291 Show the current permission to insert fast tracepoints.
6293 @kindex may-interrupt
6294 @item set may-interrupt on
6295 @itemx set may-interrupt off
6296 This controls whether @value{GDBN} will attempt to interrupt or stop
6297 program execution. When this variable is @code{off}, the
6298 @code{interrupt} command will have no effect, nor will
6299 @kbd{Ctrl-c}. It defaults to @code{on}.
6301 @item show may-interrupt
6302 Show the current permission to interrupt or stop the program.
6306 @node Reverse Execution
6307 @chapter Running programs backward
6308 @cindex reverse execution
6309 @cindex running programs backward
6311 When you are debugging a program, it is not unusual to realize that
6312 you have gone too far, and some event of interest has already happened.
6313 If the target environment supports it, @value{GDBN} can allow you to
6314 ``rewind'' the program by running it backward.
6316 A target environment that supports reverse execution should be able
6317 to ``undo'' the changes in machine state that have taken place as the
6318 program was executing normally. Variables, registers etc.@: should
6319 revert to their previous values. Obviously this requires a great
6320 deal of sophistication on the part of the target environment; not
6321 all target environments can support reverse execution.
6323 When a program is executed in reverse, the instructions that
6324 have most recently been executed are ``un-executed'', in reverse
6325 order. The program counter runs backward, following the previous
6326 thread of execution in reverse. As each instruction is ``un-executed'',
6327 the values of memory and/or registers that were changed by that
6328 instruction are reverted to their previous states. After executing
6329 a piece of source code in reverse, all side effects of that code
6330 should be ``undone'', and all variables should be returned to their
6331 prior values@footnote{
6332 Note that some side effects are easier to undo than others. For instance,
6333 memory and registers are relatively easy, but device I/O is hard. Some
6334 targets may be able undo things like device I/O, and some may not.
6336 The contract between @value{GDBN} and the reverse executing target
6337 requires only that the target do something reasonable when
6338 @value{GDBN} tells it to execute backwards, and then report the
6339 results back to @value{GDBN}. Whatever the target reports back to
6340 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6341 assumes that the memory and registers that the target reports are in a
6342 consistant state, but @value{GDBN} accepts whatever it is given.
6345 If you are debugging in a target environment that supports
6346 reverse execution, @value{GDBN} provides the following commands.
6349 @kindex reverse-continue
6350 @kindex rc @r{(@code{reverse-continue})}
6351 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6352 @itemx rc @r{[}@var{ignore-count}@r{]}
6353 Beginning at the point where your program last stopped, start executing
6354 in reverse. Reverse execution will stop for breakpoints and synchronous
6355 exceptions (signals), just like normal execution. Behavior of
6356 asynchronous signals depends on the target environment.
6358 @kindex reverse-step
6359 @kindex rs @r{(@code{step})}
6360 @item reverse-step @r{[}@var{count}@r{]}
6361 Run the program backward until control reaches the start of a
6362 different source line; then stop it, and return control to @value{GDBN}.
6364 Like the @code{step} command, @code{reverse-step} will only stop
6365 at the beginning of a source line. It ``un-executes'' the previously
6366 executed source line. If the previous source line included calls to
6367 debuggable functions, @code{reverse-step} will step (backward) into
6368 the called function, stopping at the beginning of the @emph{last}
6369 statement in the called function (typically a return statement).
6371 Also, as with the @code{step} command, if non-debuggable functions are
6372 called, @code{reverse-step} will run thru them backward without stopping.
6374 @kindex reverse-stepi
6375 @kindex rsi @r{(@code{reverse-stepi})}
6376 @item reverse-stepi @r{[}@var{count}@r{]}
6377 Reverse-execute one machine instruction. Note that the instruction
6378 to be reverse-executed is @emph{not} the one pointed to by the program
6379 counter, but the instruction executed prior to that one. For instance,
6380 if the last instruction was a jump, @code{reverse-stepi} will take you
6381 back from the destination of the jump to the jump instruction itself.
6383 @kindex reverse-next
6384 @kindex rn @r{(@code{reverse-next})}
6385 @item reverse-next @r{[}@var{count}@r{]}
6386 Run backward to the beginning of the previous line executed in
6387 the current (innermost) stack frame. If the line contains function
6388 calls, they will be ``un-executed'' without stopping. Starting from
6389 the first line of a function, @code{reverse-next} will take you back
6390 to the caller of that function, @emph{before} the function was called,
6391 just as the normal @code{next} command would take you from the last
6392 line of a function back to its return to its caller
6393 @footnote{Unless the code is too heavily optimized.}.
6395 @kindex reverse-nexti
6396 @kindex rni @r{(@code{reverse-nexti})}
6397 @item reverse-nexti @r{[}@var{count}@r{]}
6398 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6399 in reverse, except that called functions are ``un-executed'' atomically.
6400 That is, if the previously executed instruction was a return from
6401 another function, @code{reverse-nexti} will continue to execute
6402 in reverse until the call to that function (from the current stack
6405 @kindex reverse-finish
6406 @item reverse-finish
6407 Just as the @code{finish} command takes you to the point where the
6408 current function returns, @code{reverse-finish} takes you to the point
6409 where it was called. Instead of ending up at the end of the current
6410 function invocation, you end up at the beginning.
6412 @kindex set exec-direction
6413 @item set exec-direction
6414 Set the direction of target execution.
6415 @item set exec-direction reverse
6416 @cindex execute forward or backward in time
6417 @value{GDBN} will perform all execution commands in reverse, until the
6418 exec-direction mode is changed to ``forward''. Affected commands include
6419 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6420 command cannot be used in reverse mode.
6421 @item set exec-direction forward
6422 @value{GDBN} will perform all execution commands in the normal fashion.
6423 This is the default.
6427 @node Process Record and Replay
6428 @chapter Recording Inferior's Execution and Replaying It
6429 @cindex process record and replay
6430 @cindex recording inferior's execution and replaying it
6432 On some platforms, @value{GDBN} provides a special @dfn{process record
6433 and replay} target that can record a log of the process execution, and
6434 replay it later with both forward and reverse execution commands.
6437 When this target is in use, if the execution log includes the record
6438 for the next instruction, @value{GDBN} will debug in @dfn{replay
6439 mode}. In the replay mode, the inferior does not really execute code
6440 instructions. Instead, all the events that normally happen during
6441 code execution are taken from the execution log. While code is not
6442 really executed in replay mode, the values of registers (including the
6443 program counter register) and the memory of the inferior are still
6444 changed as they normally would. Their contents are taken from the
6448 If the record for the next instruction is not in the execution log,
6449 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6450 inferior executes normally, and @value{GDBN} records the execution log
6453 The process record and replay target supports reverse execution
6454 (@pxref{Reverse Execution}), even if the platform on which the
6455 inferior runs does not. However, the reverse execution is limited in
6456 this case by the range of the instructions recorded in the execution
6457 log. In other words, reverse execution on platforms that don't
6458 support it directly can only be done in the replay mode.
6460 When debugging in the reverse direction, @value{GDBN} will work in
6461 replay mode as long as the execution log includes the record for the
6462 previous instruction; otherwise, it will work in record mode, if the
6463 platform supports reverse execution, or stop if not.
6465 For architecture environments that support process record and replay,
6466 @value{GDBN} provides the following commands:
6469 @kindex target record
6470 @kindex target record-full
6471 @kindex target record-btrace
6474 @kindex record btrace
6475 @kindex record btrace bts
6476 @kindex record btrace pt
6482 @kindex rec btrace bts
6483 @kindex rec btrace pt
6486 @item record @var{method}
6487 This command starts the process record and replay target. The
6488 recording method can be specified as parameter. Without a parameter
6489 the command uses the @code{full} recording method. The following
6490 recording methods are available:
6494 Full record/replay recording using @value{GDBN}'s software record and
6495 replay implementation. This method allows replaying and reverse
6498 @item btrace @var{format}
6499 Hardware-supported instruction recording. This method does not record
6500 data. Further, the data is collected in a ring buffer so old data will
6501 be overwritten when the buffer is full. It allows limited reverse
6502 execution. Variables and registers are not available during reverse
6505 The recording format can be specified as parameter. Without a parameter
6506 the command chooses the recording format. The following recording
6507 formats are available:
6511 @cindex branch trace store
6512 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6513 this format, the processor stores a from/to record for each executed
6514 branch in the btrace ring buffer.
6517 @cindex Intel Processor Trace
6518 Use the @dfn{Intel Processor Trace} recording format. In this
6519 format, the processor stores the execution trace in a compressed form
6520 that is afterwards decoded by @value{GDBN}.
6522 The trace can be recorded with very low overhead. The compressed
6523 trace format also allows small trace buffers to already contain a big
6524 number of instructions compared to @acronym{BTS}.
6526 Decoding the recorded execution trace, on the other hand, is more
6527 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6528 increased number of instructions to process. You should increase the
6529 buffer-size with care.
6532 Not all recording formats may be available on all processors.
6535 The process record and replay target can only debug a process that is
6536 already running. Therefore, you need first to start the process with
6537 the @kbd{run} or @kbd{start} commands, and then start the recording
6538 with the @kbd{record @var{method}} command.
6540 @cindex displaced stepping, and process record and replay
6541 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6542 will be automatically disabled when process record and replay target
6543 is started. That's because the process record and replay target
6544 doesn't support displaced stepping.
6546 @cindex non-stop mode, and process record and replay
6547 @cindex asynchronous execution, and process record and replay
6548 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6549 the asynchronous execution mode (@pxref{Background Execution}), not
6550 all recording methods are available. The @code{full} recording method
6551 does not support these two modes.
6556 Stop the process record and replay target. When process record and
6557 replay target stops, the entire execution log will be deleted and the
6558 inferior will either be terminated, or will remain in its final state.
6560 When you stop the process record and replay target in record mode (at
6561 the end of the execution log), the inferior will be stopped at the
6562 next instruction that would have been recorded. In other words, if
6563 you record for a while and then stop recording, the inferior process
6564 will be left in the same state as if the recording never happened.
6566 On the other hand, if the process record and replay target is stopped
6567 while in replay mode (that is, not at the end of the execution log,
6568 but at some earlier point), the inferior process will become ``live''
6569 at that earlier state, and it will then be possible to continue the
6570 usual ``live'' debugging of the process from that state.
6572 When the inferior process exits, or @value{GDBN} detaches from it,
6573 process record and replay target will automatically stop itself.
6577 Go to a specific location in the execution log. There are several
6578 ways to specify the location to go to:
6581 @item record goto begin
6582 @itemx record goto start
6583 Go to the beginning of the execution log.
6585 @item record goto end
6586 Go to the end of the execution log.
6588 @item record goto @var{n}
6589 Go to instruction number @var{n} in the execution log.
6593 @item record save @var{filename}
6594 Save the execution log to a file @file{@var{filename}}.
6595 Default filename is @file{gdb_record.@var{process_id}}, where
6596 @var{process_id} is the process ID of the inferior.
6598 This command may not be available for all recording methods.
6600 @kindex record restore
6601 @item record restore @var{filename}
6602 Restore the execution log from a file @file{@var{filename}}.
6603 File must have been created with @code{record save}.
6605 @kindex set record full
6606 @item set record full insn-number-max @var{limit}
6607 @itemx set record full insn-number-max unlimited
6608 Set the limit of instructions to be recorded for the @code{full}
6609 recording method. Default value is 200000.
6611 If @var{limit} is a positive number, then @value{GDBN} will start
6612 deleting instructions from the log once the number of the record
6613 instructions becomes greater than @var{limit}. For every new recorded
6614 instruction, @value{GDBN} will delete the earliest recorded
6615 instruction to keep the number of recorded instructions at the limit.
6616 (Since deleting recorded instructions loses information, @value{GDBN}
6617 lets you control what happens when the limit is reached, by means of
6618 the @code{stop-at-limit} option, described below.)
6620 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6621 delete recorded instructions from the execution log. The number of
6622 recorded instructions is limited only by the available memory.
6624 @kindex show record full
6625 @item show record full insn-number-max
6626 Show the limit of instructions to be recorded with the @code{full}
6629 @item set record full stop-at-limit
6630 Control the behavior of the @code{full} recording method when the
6631 number of recorded instructions reaches the limit. If ON (the
6632 default), @value{GDBN} will stop when the limit is reached for the
6633 first time and ask you whether you want to stop the inferior or
6634 continue running it and recording the execution log. If you decide
6635 to continue recording, each new recorded instruction will cause the
6636 oldest one to be deleted.
6638 If this option is OFF, @value{GDBN} will automatically delete the
6639 oldest record to make room for each new one, without asking.
6641 @item show record full stop-at-limit
6642 Show the current setting of @code{stop-at-limit}.
6644 @item set record full memory-query
6645 Control the behavior when @value{GDBN} is unable to record memory
6646 changes caused by an instruction for the @code{full} recording method.
6647 If ON, @value{GDBN} will query whether to stop the inferior in that
6650 If this option is OFF (the default), @value{GDBN} will automatically
6651 ignore the effect of such instructions on memory. Later, when
6652 @value{GDBN} replays this execution log, it will mark the log of this
6653 instruction as not accessible, and it will not affect the replay
6656 @item show record full memory-query
6657 Show the current setting of @code{memory-query}.
6659 @kindex set record btrace
6660 The @code{btrace} record target does not trace data. As a
6661 convenience, when replaying, @value{GDBN} reads read-only memory off
6662 the live program directly, assuming that the addresses of the
6663 read-only areas don't change. This for example makes it possible to
6664 disassemble code while replaying, but not to print variables.
6665 In some cases, being able to inspect variables might be useful.
6666 You can use the following command for that:
6668 @item set record btrace replay-memory-access
6669 Control the behavior of the @code{btrace} recording method when
6670 accessing memory during replay. If @code{read-only} (the default),
6671 @value{GDBN} will only allow accesses to read-only memory.
6672 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6673 and to read-write memory. Beware that the accessed memory corresponds
6674 to the live target and not necessarily to the current replay
6677 @kindex show record btrace
6678 @item show record btrace replay-memory-access
6679 Show the current setting of @code{replay-memory-access}.
6681 @kindex set record btrace bts
6682 @item set record btrace bts buffer-size @var{size}
6683 @itemx set record btrace bts buffer-size unlimited
6684 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6685 format. Default is 64KB.
6687 If @var{size} is a positive number, then @value{GDBN} will try to
6688 allocate a buffer of at least @var{size} bytes for each new thread
6689 that uses the btrace recording method and the @acronym{BTS} format.
6690 The actually obtained buffer size may differ from the requested
6691 @var{size}. Use the @code{info record} command to see the actual
6692 buffer size for each thread that uses the btrace recording method and
6693 the @acronym{BTS} format.
6695 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6696 allocate a buffer of 4MB.
6698 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6699 also need longer to process the branch trace data before it can be used.
6701 @item show record btrace bts buffer-size @var{size}
6702 Show the current setting of the requested ring buffer size for branch
6703 tracing in @acronym{BTS} format.
6705 @kindex set record btrace pt
6706 @item set record btrace pt buffer-size @var{size}
6707 @itemx set record btrace pt buffer-size unlimited
6708 Set the requested ring buffer size for branch tracing in Intel
6709 Processor Trace format. Default is 16KB.
6711 If @var{size} is a positive number, then @value{GDBN} will try to
6712 allocate a buffer of at least @var{size} bytes for each new thread
6713 that uses the btrace recording method and the Intel Processor Trace
6714 format. The actually obtained buffer size may differ from the
6715 requested @var{size}. Use the @code{info record} command to see the
6716 actual buffer size for each thread.
6718 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6719 allocate a buffer of 4MB.
6721 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6722 also need longer to process the branch trace data before it can be used.
6724 @item show record btrace pt buffer-size @var{size}
6725 Show the current setting of the requested ring buffer size for branch
6726 tracing in Intel Processor Trace format.
6730 Show various statistics about the recording depending on the recording
6735 For the @code{full} recording method, it shows the state of process
6736 record and its in-memory execution log buffer, including:
6740 Whether in record mode or replay mode.
6742 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6744 Highest recorded instruction number.
6746 Current instruction about to be replayed (if in replay mode).
6748 Number of instructions contained in the execution log.
6750 Maximum number of instructions that may be contained in the execution log.
6754 For the @code{btrace} recording method, it shows:
6760 Number of instructions that have been recorded.
6762 Number of blocks of sequential control-flow formed by the recorded
6765 Whether in record mode or replay mode.
6768 For the @code{bts} recording format, it also shows:
6771 Size of the perf ring buffer.
6774 For the @code{pt} recording format, it also shows:
6777 Size of the perf ring buffer.
6781 @kindex record delete
6784 When record target runs in replay mode (``in the past''), delete the
6785 subsequent execution log and begin to record a new execution log starting
6786 from the current address. This means you will abandon the previously
6787 recorded ``future'' and begin recording a new ``future''.
6789 @kindex record instruction-history
6790 @kindex rec instruction-history
6791 @item record instruction-history
6792 Disassembles instructions from the recorded execution log. By
6793 default, ten instructions are disassembled. This can be changed using
6794 the @code{set record instruction-history-size} command. Instructions
6795 are printed in execution order.
6797 It can also print mixed source+disassembly if you specify the the
6798 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6799 as well as in symbolic form by specifying the @code{/r} modifier.
6801 The current position marker is printed for the instruction at the
6802 current program counter value. This instruction can appear multiple
6803 times in the trace and the current position marker will be printed
6804 every time. To omit the current position marker, specify the
6807 To better align the printed instructions when the trace contains
6808 instructions from more than one function, the function name may be
6809 omitted by specifying the @code{/f} modifier.
6811 Speculatively executed instructions are prefixed with @samp{?}. This
6812 feature is not available for all recording formats.
6814 There are several ways to specify what part of the execution log to
6818 @item record instruction-history @var{insn}
6819 Disassembles ten instructions starting from instruction number
6822 @item record instruction-history @var{insn}, +/-@var{n}
6823 Disassembles @var{n} instructions around instruction number
6824 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6825 @var{n} instructions after instruction number @var{insn}. If
6826 @var{n} is preceded with @code{-}, disassembles @var{n}
6827 instructions before instruction number @var{insn}.
6829 @item record instruction-history
6830 Disassembles ten more instructions after the last disassembly.
6832 @item record instruction-history -
6833 Disassembles ten more instructions before the last disassembly.
6835 @item record instruction-history @var{begin}, @var{end}
6836 Disassembles instructions beginning with instruction number
6837 @var{begin} until instruction number @var{end}. The instruction
6838 number @var{end} is included.
6841 This command may not be available for all recording methods.
6844 @item set record instruction-history-size @var{size}
6845 @itemx set record instruction-history-size unlimited
6846 Define how many instructions to disassemble in the @code{record
6847 instruction-history} command. The default value is 10.
6848 A @var{size} of @code{unlimited} means unlimited instructions.
6851 @item show record instruction-history-size
6852 Show how many instructions to disassemble in the @code{record
6853 instruction-history} command.
6855 @kindex record function-call-history
6856 @kindex rec function-call-history
6857 @item record function-call-history
6858 Prints the execution history at function granularity. It prints one
6859 line for each sequence of instructions that belong to the same
6860 function giving the name of that function, the source lines
6861 for this instruction sequence (if the @code{/l} modifier is
6862 specified), and the instructions numbers that form the sequence (if
6863 the @code{/i} modifier is specified). The function names are indented
6864 to reflect the call stack depth if the @code{/c} modifier is
6865 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6869 (@value{GDBP}) @b{list 1, 10}
6880 (@value{GDBP}) @b{record function-call-history /ilc}
6881 1 bar inst 1,4 at foo.c:6,8
6882 2 foo inst 5,10 at foo.c:2,3
6883 3 bar inst 11,13 at foo.c:9,10
6886 By default, ten lines are printed. This can be changed using the
6887 @code{set record function-call-history-size} command. Functions are
6888 printed in execution order. There are several ways to specify what
6892 @item record function-call-history @var{func}
6893 Prints ten functions starting from function number @var{func}.
6895 @item record function-call-history @var{func}, +/-@var{n}
6896 Prints @var{n} functions around function number @var{func}. If
6897 @var{n} is preceded with @code{+}, prints @var{n} functions after
6898 function number @var{func}. If @var{n} is preceded with @code{-},
6899 prints @var{n} functions before function number @var{func}.
6901 @item record function-call-history
6902 Prints ten more functions after the last ten-line print.
6904 @item record function-call-history -
6905 Prints ten more functions before the last ten-line print.
6907 @item record function-call-history @var{begin}, @var{end}
6908 Prints functions beginning with function number @var{begin} until
6909 function number @var{end}. The function number @var{end} is included.
6912 This command may not be available for all recording methods.
6914 @item set record function-call-history-size @var{size}
6915 @itemx set record function-call-history-size unlimited
6916 Define how many lines to print in the
6917 @code{record function-call-history} command. The default value is 10.
6918 A size of @code{unlimited} means unlimited lines.
6920 @item show record function-call-history-size
6921 Show how many lines to print in the
6922 @code{record function-call-history} command.
6927 @chapter Examining the Stack
6929 When your program has stopped, the first thing you need to know is where it
6930 stopped and how it got there.
6933 Each time your program performs a function call, information about the call
6935 That information includes the location of the call in your program,
6936 the arguments of the call,
6937 and the local variables of the function being called.
6938 The information is saved in a block of data called a @dfn{stack frame}.
6939 The stack frames are allocated in a region of memory called the @dfn{call
6942 When your program stops, the @value{GDBN} commands for examining the
6943 stack allow you to see all of this information.
6945 @cindex selected frame
6946 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6947 @value{GDBN} commands refer implicitly to the selected frame. In
6948 particular, whenever you ask @value{GDBN} for the value of a variable in
6949 your program, the value is found in the selected frame. There are
6950 special @value{GDBN} commands to select whichever frame you are
6951 interested in. @xref{Selection, ,Selecting a Frame}.
6953 When your program stops, @value{GDBN} automatically selects the
6954 currently executing frame and describes it briefly, similar to the
6955 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6958 * Frames:: Stack frames
6959 * Backtrace:: Backtraces
6960 * Selection:: Selecting a frame
6961 * Frame Info:: Information on a frame
6962 * Frame Filter Management:: Managing frame filters
6967 @section Stack Frames
6969 @cindex frame, definition
6971 The call stack is divided up into contiguous pieces called @dfn{stack
6972 frames}, or @dfn{frames} for short; each frame is the data associated
6973 with one call to one function. The frame contains the arguments given
6974 to the function, the function's local variables, and the address at
6975 which the function is executing.
6977 @cindex initial frame
6978 @cindex outermost frame
6979 @cindex innermost frame
6980 When your program is started, the stack has only one frame, that of the
6981 function @code{main}. This is called the @dfn{initial} frame or the
6982 @dfn{outermost} frame. Each time a function is called, a new frame is
6983 made. Each time a function returns, the frame for that function invocation
6984 is eliminated. If a function is recursive, there can be many frames for
6985 the same function. The frame for the function in which execution is
6986 actually occurring is called the @dfn{innermost} frame. This is the most
6987 recently created of all the stack frames that still exist.
6989 @cindex frame pointer
6990 Inside your program, stack frames are identified by their addresses. A
6991 stack frame consists of many bytes, each of which has its own address; each
6992 kind of computer has a convention for choosing one byte whose
6993 address serves as the address of the frame. Usually this address is kept
6994 in a register called the @dfn{frame pointer register}
6995 (@pxref{Registers, $fp}) while execution is going on in that frame.
6997 @cindex frame number
6998 @value{GDBN} assigns numbers to all existing stack frames, starting with
6999 zero for the innermost frame, one for the frame that called it,
7000 and so on upward. These numbers do not really exist in your program;
7001 they are assigned by @value{GDBN} to give you a way of designating stack
7002 frames in @value{GDBN} commands.
7004 @c The -fomit-frame-pointer below perennially causes hbox overflow
7005 @c underflow problems.
7006 @cindex frameless execution
7007 Some compilers provide a way to compile functions so that they operate
7008 without stack frames. (For example, the @value{NGCC} option
7010 @samp{-fomit-frame-pointer}
7012 generates functions without a frame.)
7013 This is occasionally done with heavily used library functions to save
7014 the frame setup time. @value{GDBN} has limited facilities for dealing
7015 with these function invocations. If the innermost function invocation
7016 has no stack frame, @value{GDBN} nevertheless regards it as though
7017 it had a separate frame, which is numbered zero as usual, allowing
7018 correct tracing of the function call chain. However, @value{GDBN} has
7019 no provision for frameless functions elsewhere in the stack.
7025 @cindex call stack traces
7026 A backtrace is a summary of how your program got where it is. It shows one
7027 line per frame, for many frames, starting with the currently executing
7028 frame (frame zero), followed by its caller (frame one), and on up the
7031 @anchor{backtrace-command}
7034 @kindex bt @r{(@code{backtrace})}
7037 Print a backtrace of the entire stack: one line per frame for all
7038 frames in the stack.
7040 You can stop the backtrace at any time by typing the system interrupt
7041 character, normally @kbd{Ctrl-c}.
7043 @item backtrace @var{n}
7045 Similar, but print only the innermost @var{n} frames.
7047 @item backtrace -@var{n}
7049 Similar, but print only the outermost @var{n} frames.
7051 @item backtrace full
7053 @itemx bt full @var{n}
7054 @itemx bt full -@var{n}
7055 Print the values of the local variables also. As described above,
7056 @var{n} specifies the number of frames to print.
7058 @item backtrace no-filters
7059 @itemx bt no-filters
7060 @itemx bt no-filters @var{n}
7061 @itemx bt no-filters -@var{n}
7062 @itemx bt no-filters full
7063 @itemx bt no-filters full @var{n}
7064 @itemx bt no-filters full -@var{n}
7065 Do not run Python frame filters on this backtrace. @xref{Frame
7066 Filter API}, for more information. Additionally use @ref{disable
7067 frame-filter all} to turn off all frame filters. This is only
7068 relevant when @value{GDBN} has been configured with @code{Python}
7074 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7075 are additional aliases for @code{backtrace}.
7077 @cindex multiple threads, backtrace
7078 In a multi-threaded program, @value{GDBN} by default shows the
7079 backtrace only for the current thread. To display the backtrace for
7080 several or all of the threads, use the command @code{thread apply}
7081 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7082 apply all backtrace}, @value{GDBN} will display the backtrace for all
7083 the threads; this is handy when you debug a core dump of a
7084 multi-threaded program.
7086 Each line in the backtrace shows the frame number and the function name.
7087 The program counter value is also shown---unless you use @code{set
7088 print address off}. The backtrace also shows the source file name and
7089 line number, as well as the arguments to the function. The program
7090 counter value is omitted if it is at the beginning of the code for that
7093 Here is an example of a backtrace. It was made with the command
7094 @samp{bt 3}, so it shows the innermost three frames.
7098 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7100 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7101 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7103 (More stack frames follow...)
7108 The display for frame zero does not begin with a program counter
7109 value, indicating that your program has stopped at the beginning of the
7110 code for line @code{993} of @code{builtin.c}.
7113 The value of parameter @code{data} in frame 1 has been replaced by
7114 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7115 only if it is a scalar (integer, pointer, enumeration, etc). See command
7116 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7117 on how to configure the way function parameter values are printed.
7119 @cindex optimized out, in backtrace
7120 @cindex function call arguments, optimized out
7121 If your program was compiled with optimizations, some compilers will
7122 optimize away arguments passed to functions if those arguments are
7123 never used after the call. Such optimizations generate code that
7124 passes arguments through registers, but doesn't store those arguments
7125 in the stack frame. @value{GDBN} has no way of displaying such
7126 arguments in stack frames other than the innermost one. Here's what
7127 such a backtrace might look like:
7131 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7133 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7134 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7136 (More stack frames follow...)
7141 The values of arguments that were not saved in their stack frames are
7142 shown as @samp{<optimized out>}.
7144 If you need to display the values of such optimized-out arguments,
7145 either deduce that from other variables whose values depend on the one
7146 you are interested in, or recompile without optimizations.
7148 @cindex backtrace beyond @code{main} function
7149 @cindex program entry point
7150 @cindex startup code, and backtrace
7151 Most programs have a standard user entry point---a place where system
7152 libraries and startup code transition into user code. For C this is
7153 @code{main}@footnote{
7154 Note that embedded programs (the so-called ``free-standing''
7155 environment) are not required to have a @code{main} function as the
7156 entry point. They could even have multiple entry points.}.
7157 When @value{GDBN} finds the entry function in a backtrace
7158 it will terminate the backtrace, to avoid tracing into highly
7159 system-specific (and generally uninteresting) code.
7161 If you need to examine the startup code, or limit the number of levels
7162 in a backtrace, you can change this behavior:
7165 @item set backtrace past-main
7166 @itemx set backtrace past-main on
7167 @kindex set backtrace
7168 Backtraces will continue past the user entry point.
7170 @item set backtrace past-main off
7171 Backtraces will stop when they encounter the user entry point. This is the
7174 @item show backtrace past-main
7175 @kindex show backtrace
7176 Display the current user entry point backtrace policy.
7178 @item set backtrace past-entry
7179 @itemx set backtrace past-entry on
7180 Backtraces will continue past the internal entry point of an application.
7181 This entry point is encoded by the linker when the application is built,
7182 and is likely before the user entry point @code{main} (or equivalent) is called.
7184 @item set backtrace past-entry off
7185 Backtraces will stop when they encounter the internal entry point of an
7186 application. This is the default.
7188 @item show backtrace past-entry
7189 Display the current internal entry point backtrace policy.
7191 @item set backtrace limit @var{n}
7192 @itemx set backtrace limit 0
7193 @itemx set backtrace limit unlimited
7194 @cindex backtrace limit
7195 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7196 or zero means unlimited levels.
7198 @item show backtrace limit
7199 Display the current limit on backtrace levels.
7202 You can control how file names are displayed.
7205 @item set filename-display
7206 @itemx set filename-display relative
7207 @cindex filename-display
7208 Display file names relative to the compilation directory. This is the default.
7210 @item set filename-display basename
7211 Display only basename of a filename.
7213 @item set filename-display absolute
7214 Display an absolute filename.
7216 @item show filename-display
7217 Show the current way to display filenames.
7221 @section Selecting a Frame
7223 Most commands for examining the stack and other data in your program work on
7224 whichever stack frame is selected at the moment. Here are the commands for
7225 selecting a stack frame; all of them finish by printing a brief description
7226 of the stack frame just selected.
7229 @kindex frame@r{, selecting}
7230 @kindex f @r{(@code{frame})}
7233 Select frame number @var{n}. Recall that frame zero is the innermost
7234 (currently executing) frame, frame one is the frame that called the
7235 innermost one, and so on. The highest-numbered frame is the one for
7238 @item frame @var{stack-addr} [ @var{pc-addr} ]
7239 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7240 Select the frame at address @var{stack-addr}. This is useful mainly if the
7241 chaining of stack frames has been damaged by a bug, making it
7242 impossible for @value{GDBN} to assign numbers properly to all frames. In
7243 addition, this can be useful when your program has multiple stacks and
7244 switches between them. The optional @var{pc-addr} can also be given to
7245 specify the value of PC for the stack frame.
7249 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7250 numbers @var{n}, this advances toward the outermost frame, to higher
7251 frame numbers, to frames that have existed longer.
7254 @kindex do @r{(@code{down})}
7256 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7257 positive numbers @var{n}, this advances toward the innermost frame, to
7258 lower frame numbers, to frames that were created more recently.
7259 You may abbreviate @code{down} as @code{do}.
7262 All of these commands end by printing two lines of output describing the
7263 frame. The first line shows the frame number, the function name, the
7264 arguments, and the source file and line number of execution in that
7265 frame. The second line shows the text of that source line.
7273 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7275 10 read_input_file (argv[i]);
7279 After such a printout, the @code{list} command with no arguments
7280 prints ten lines centered on the point of execution in the frame.
7281 You can also edit the program at the point of execution with your favorite
7282 editing program by typing @code{edit}.
7283 @xref{List, ,Printing Source Lines},
7287 @kindex select-frame
7289 The @code{select-frame} command is a variant of @code{frame} that does
7290 not display the new frame after selecting it. This command is
7291 intended primarily for use in @value{GDBN} command scripts, where the
7292 output might be unnecessary and distracting.
7294 @kindex down-silently
7296 @item up-silently @var{n}
7297 @itemx down-silently @var{n}
7298 These two commands are variants of @code{up} and @code{down},
7299 respectively; they differ in that they do their work silently, without
7300 causing display of the new frame. They are intended primarily for use
7301 in @value{GDBN} command scripts, where the output might be unnecessary and
7306 @section Information About a Frame
7308 There are several other commands to print information about the selected
7314 When used without any argument, this command does not change which
7315 frame is selected, but prints a brief description of the currently
7316 selected stack frame. It can be abbreviated @code{f}. With an
7317 argument, this command is used to select a stack frame.
7318 @xref{Selection, ,Selecting a Frame}.
7321 @kindex info f @r{(@code{info frame})}
7324 This command prints a verbose description of the selected stack frame,
7329 the address of the frame
7331 the address of the next frame down (called by this frame)
7333 the address of the next frame up (caller of this frame)
7335 the language in which the source code corresponding to this frame is written
7337 the address of the frame's arguments
7339 the address of the frame's local variables
7341 the program counter saved in it (the address of execution in the caller frame)
7343 which registers were saved in the frame
7346 @noindent The verbose description is useful when
7347 something has gone wrong that has made the stack format fail to fit
7348 the usual conventions.
7350 @item info frame @var{addr}
7351 @itemx info f @var{addr}
7352 Print a verbose description of the frame at address @var{addr}, without
7353 selecting that frame. The selected frame remains unchanged by this
7354 command. This requires the same kind of address (more than one for some
7355 architectures) that you specify in the @code{frame} command.
7356 @xref{Selection, ,Selecting a Frame}.
7360 Print the arguments of the selected frame, each on a separate line.
7364 Print the local variables of the selected frame, each on a separate
7365 line. These are all variables (declared either static or automatic)
7366 accessible at the point of execution of the selected frame.
7370 @node Frame Filter Management
7371 @section Management of Frame Filters.
7372 @cindex managing frame filters
7374 Frame filters are Python based utilities to manage and decorate the
7375 output of frames. @xref{Frame Filter API}, for further information.
7377 Managing frame filters is performed by several commands available
7378 within @value{GDBN}, detailed here.
7381 @kindex info frame-filter
7382 @item info frame-filter
7383 Print a list of installed frame filters from all dictionaries, showing
7384 their name, priority and enabled status.
7386 @kindex disable frame-filter
7387 @anchor{disable frame-filter all}
7388 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7389 Disable a frame filter in the dictionary matching
7390 @var{filter-dictionary} and @var{filter-name}. The
7391 @var{filter-dictionary} may be @code{all}, @code{global},
7392 @code{progspace}, or the name of the object file where the frame filter
7393 dictionary resides. When @code{all} is specified, all frame filters
7394 across all dictionaries are disabled. The @var{filter-name} is the name
7395 of the frame filter and is used when @code{all} is not the option for
7396 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7397 may be enabled again later.
7399 @kindex enable frame-filter
7400 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7401 Enable a frame filter in the dictionary matching
7402 @var{filter-dictionary} and @var{filter-name}. The
7403 @var{filter-dictionary} may be @code{all}, @code{global},
7404 @code{progspace} or the name of the object file where the frame filter
7405 dictionary resides. When @code{all} is specified, all frame filters across
7406 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7407 filter and is used when @code{all} is not the option for
7408 @var{filter-dictionary}.
7413 (gdb) info frame-filter
7415 global frame-filters:
7416 Priority Enabled Name
7417 1000 No PrimaryFunctionFilter
7420 progspace /build/test frame-filters:
7421 Priority Enabled Name
7422 100 Yes ProgspaceFilter
7424 objfile /build/test frame-filters:
7425 Priority Enabled Name
7426 999 Yes BuildProgra Filter
7428 (gdb) disable frame-filter /build/test BuildProgramFilter
7429 (gdb) info frame-filter
7431 global frame-filters:
7432 Priority Enabled Name
7433 1000 No PrimaryFunctionFilter
7436 progspace /build/test frame-filters:
7437 Priority Enabled Name
7438 100 Yes ProgspaceFilter
7440 objfile /build/test frame-filters:
7441 Priority Enabled Name
7442 999 No BuildProgramFilter
7444 (gdb) enable frame-filter global PrimaryFunctionFilter
7445 (gdb) info frame-filter
7447 global frame-filters:
7448 Priority Enabled Name
7449 1000 Yes PrimaryFunctionFilter
7452 progspace /build/test frame-filters:
7453 Priority Enabled Name
7454 100 Yes ProgspaceFilter
7456 objfile /build/test frame-filters:
7457 Priority Enabled Name
7458 999 No BuildProgramFilter
7461 @kindex set frame-filter priority
7462 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7463 Set the @var{priority} of a frame filter in the dictionary matching
7464 @var{filter-dictionary}, and the frame filter name matching
7465 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7466 @code{progspace} or the name of the object file where the frame filter
7467 dictionary resides. The @var{priority} is an integer.
7469 @kindex show frame-filter priority
7470 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7471 Show the @var{priority} of a frame filter in the dictionary matching
7472 @var{filter-dictionary}, and the frame filter name matching
7473 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7474 @code{progspace} or the name of the object file where the frame filter
7480 (gdb) info frame-filter
7482 global frame-filters:
7483 Priority Enabled Name
7484 1000 Yes PrimaryFunctionFilter
7487 progspace /build/test frame-filters:
7488 Priority Enabled Name
7489 100 Yes ProgspaceFilter
7491 objfile /build/test frame-filters:
7492 Priority Enabled Name
7493 999 No BuildProgramFilter
7495 (gdb) set frame-filter priority global Reverse 50
7496 (gdb) info frame-filter
7498 global frame-filters:
7499 Priority Enabled Name
7500 1000 Yes PrimaryFunctionFilter
7503 progspace /build/test frame-filters:
7504 Priority Enabled Name
7505 100 Yes ProgspaceFilter
7507 objfile /build/test frame-filters:
7508 Priority Enabled Name
7509 999 No BuildProgramFilter
7514 @chapter Examining Source Files
7516 @value{GDBN} can print parts of your program's source, since the debugging
7517 information recorded in the program tells @value{GDBN} what source files were
7518 used to build it. When your program stops, @value{GDBN} spontaneously prints
7519 the line where it stopped. Likewise, when you select a stack frame
7520 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7521 execution in that frame has stopped. You can print other portions of
7522 source files by explicit command.
7524 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7525 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7526 @value{GDBN} under @sc{gnu} Emacs}.
7529 * List:: Printing source lines
7530 * Specify Location:: How to specify code locations
7531 * Edit:: Editing source files
7532 * Search:: Searching source files
7533 * Source Path:: Specifying source directories
7534 * Machine Code:: Source and machine code
7538 @section Printing Source Lines
7541 @kindex l @r{(@code{list})}
7542 To print lines from a source file, use the @code{list} command
7543 (abbreviated @code{l}). By default, ten lines are printed.
7544 There are several ways to specify what part of the file you want to
7545 print; see @ref{Specify Location}, for the full list.
7547 Here are the forms of the @code{list} command most commonly used:
7550 @item list @var{linenum}
7551 Print lines centered around line number @var{linenum} in the
7552 current source file.
7554 @item list @var{function}
7555 Print lines centered around the beginning of function
7559 Print more lines. If the last lines printed were printed with a
7560 @code{list} command, this prints lines following the last lines
7561 printed; however, if the last line printed was a solitary line printed
7562 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7563 Stack}), this prints lines centered around that line.
7566 Print lines just before the lines last printed.
7569 @cindex @code{list}, how many lines to display
7570 By default, @value{GDBN} prints ten source lines with any of these forms of
7571 the @code{list} command. You can change this using @code{set listsize}:
7574 @kindex set listsize
7575 @item set listsize @var{count}
7576 @itemx set listsize unlimited
7577 Make the @code{list} command display @var{count} source lines (unless
7578 the @code{list} argument explicitly specifies some other number).
7579 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7581 @kindex show listsize
7583 Display the number of lines that @code{list} prints.
7586 Repeating a @code{list} command with @key{RET} discards the argument,
7587 so it is equivalent to typing just @code{list}. This is more useful
7588 than listing the same lines again. An exception is made for an
7589 argument of @samp{-}; that argument is preserved in repetition so that
7590 each repetition moves up in the source file.
7592 In general, the @code{list} command expects you to supply zero, one or two
7593 @dfn{locations}. Locations specify source lines; there are several ways
7594 of writing them (@pxref{Specify Location}), but the effect is always
7595 to specify some source line.
7597 Here is a complete description of the possible arguments for @code{list}:
7600 @item list @var{location}
7601 Print lines centered around the line specified by @var{location}.
7603 @item list @var{first},@var{last}
7604 Print lines from @var{first} to @var{last}. Both arguments are
7605 locations. When a @code{list} command has two locations, and the
7606 source file of the second location is omitted, this refers to
7607 the same source file as the first location.
7609 @item list ,@var{last}
7610 Print lines ending with @var{last}.
7612 @item list @var{first},
7613 Print lines starting with @var{first}.
7616 Print lines just after the lines last printed.
7619 Print lines just before the lines last printed.
7622 As described in the preceding table.
7625 @node Specify Location
7626 @section Specifying a Location
7627 @cindex specifying location
7629 @cindex source location
7632 * Linespec Locations:: Linespec locations
7633 * Explicit Locations:: Explicit locations
7634 * Address Locations:: Address locations
7637 Several @value{GDBN} commands accept arguments that specify a location
7638 of your program's code. Since @value{GDBN} is a source-level
7639 debugger, a location usually specifies some line in the source code.
7640 Locations may be specified using three different formats:
7641 linespec locations, explicit locations, or address locations.
7643 @node Linespec Locations
7644 @subsection Linespec Locations
7645 @cindex linespec locations
7647 A @dfn{linespec} is a colon-separated list of source location parameters such
7648 as file name, function name, etc. Here are all the different ways of
7649 specifying a linespec:
7653 Specifies the line number @var{linenum} of the current source file.
7656 @itemx +@var{offset}
7657 Specifies the line @var{offset} lines before or after the @dfn{current
7658 line}. For the @code{list} command, the current line is the last one
7659 printed; for the breakpoint commands, this is the line at which
7660 execution stopped in the currently selected @dfn{stack frame}
7661 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7662 used as the second of the two linespecs in a @code{list} command,
7663 this specifies the line @var{offset} lines up or down from the first
7666 @item @var{filename}:@var{linenum}
7667 Specifies the line @var{linenum} in the source file @var{filename}.
7668 If @var{filename} is a relative file name, then it will match any
7669 source file name with the same trailing components. For example, if
7670 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7671 name of @file{/build/trunk/gcc/expr.c}, but not
7672 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7674 @item @var{function}
7675 Specifies the line that begins the body of the function @var{function}.
7676 For example, in C, this is the line with the open brace.
7678 @item @var{function}:@var{label}
7679 Specifies the line where @var{label} appears in @var{function}.
7681 @item @var{filename}:@var{function}
7682 Specifies the line that begins the body of the function @var{function}
7683 in the file @var{filename}. You only need the file name with a
7684 function name to avoid ambiguity when there are identically named
7685 functions in different source files.
7688 Specifies the line at which the label named @var{label} appears
7689 in the function corresponding to the currently selected stack frame.
7690 If there is no current selected stack frame (for instance, if the inferior
7691 is not running), then @value{GDBN} will not search for a label.
7693 @cindex breakpoint at static probe point
7694 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7695 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7696 applications to embed static probes. @xref{Static Probe Points}, for more
7697 information on finding and using static probes. This form of linespec
7698 specifies the location of such a static probe.
7700 If @var{objfile} is given, only probes coming from that shared library
7701 or executable matching @var{objfile} as a regular expression are considered.
7702 If @var{provider} is given, then only probes from that provider are considered.
7703 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7704 each one of those probes.
7707 @node Explicit Locations
7708 @subsection Explicit Locations
7709 @cindex explicit locations
7711 @dfn{Explicit locations} allow the user to directly specify the source
7712 location's parameters using option-value pairs.
7714 Explicit locations are useful when several functions, labels, or
7715 file names have the same name (base name for files) in the program's
7716 sources. In these cases, explicit locations point to the source
7717 line you meant more accurately and unambiguously. Also, using
7718 explicit locations might be faster in large programs.
7720 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7721 defined in the file named @file{foo} or the label @code{bar} in a function
7722 named @code{foo}. @value{GDBN} must search either the file system or
7723 the symbol table to know.
7725 The list of valid explicit location options is summarized in the
7729 @item -source @var{filename}
7730 The value specifies the source file name. To differentiate between
7731 files with the same base name, prepend as many directories as is necessary
7732 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7733 @value{GDBN} will use the first file it finds with the given base
7734 name. This option requires the use of either @code{-function} or @code{-line}.
7736 @item -function @var{function}
7737 The value specifies the name of a function. Operations
7738 on function locations unmodified by other options (such as @code{-label}
7739 or @code{-line}) refer to the line that begins the body of the function.
7740 In C, for example, this is the line with the open brace.
7742 @item -label @var{label}
7743 The value specifies the name of a label. When the function
7744 name is not specified, the label is searched in the function of the currently
7745 selected stack frame.
7747 @item -line @var{number}
7748 The value specifies a line offset for the location. The offset may either
7749 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7750 the command. When specified without any other options, the line offset is
7751 relative to the current line.
7754 Explicit location options may be abbreviated by omitting any non-unique
7755 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7757 @node Address Locations
7758 @subsection Address Locations
7759 @cindex address locations
7761 @dfn{Address locations} indicate a specific program address. They have
7762 the generalized form *@var{address}.
7764 For line-oriented commands, such as @code{list} and @code{edit}, this
7765 specifies a source line that contains @var{address}. For @code{break} and
7766 other breakpoint-oriented commands, this can be used to set breakpoints in
7767 parts of your program which do not have debugging information or
7770 Here @var{address} may be any expression valid in the current working
7771 language (@pxref{Languages, working language}) that specifies a code
7772 address. In addition, as a convenience, @value{GDBN} extends the
7773 semantics of expressions used in locations to cover several situations
7774 that frequently occur during debugging. Here are the various forms
7778 @item @var{expression}
7779 Any expression valid in the current working language.
7781 @item @var{funcaddr}
7782 An address of a function or procedure derived from its name. In C,
7783 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7784 simply the function's name @var{function} (and actually a special case
7785 of a valid expression). In Pascal and Modula-2, this is
7786 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7787 (although the Pascal form also works).
7789 This form specifies the address of the function's first instruction,
7790 before the stack frame and arguments have been set up.
7792 @item '@var{filename}':@var{funcaddr}
7793 Like @var{funcaddr} above, but also specifies the name of the source
7794 file explicitly. This is useful if the name of the function does not
7795 specify the function unambiguously, e.g., if there are several
7796 functions with identical names in different source files.
7800 @section Editing Source Files
7801 @cindex editing source files
7804 @kindex e @r{(@code{edit})}
7805 To edit the lines in a source file, use the @code{edit} command.
7806 The editing program of your choice
7807 is invoked with the current line set to
7808 the active line in the program.
7809 Alternatively, there are several ways to specify what part of the file you
7810 want to print if you want to see other parts of the program:
7813 @item edit @var{location}
7814 Edit the source file specified by @code{location}. Editing starts at
7815 that @var{location}, e.g., at the specified source line of the
7816 specified file. @xref{Specify Location}, for all the possible forms
7817 of the @var{location} argument; here are the forms of the @code{edit}
7818 command most commonly used:
7821 @item edit @var{number}
7822 Edit the current source file with @var{number} as the active line number.
7824 @item edit @var{function}
7825 Edit the file containing @var{function} at the beginning of its definition.
7830 @subsection Choosing your Editor
7831 You can customize @value{GDBN} to use any editor you want
7833 The only restriction is that your editor (say @code{ex}), recognizes the
7834 following command-line syntax:
7836 ex +@var{number} file
7838 The optional numeric value +@var{number} specifies the number of the line in
7839 the file where to start editing.}.
7840 By default, it is @file{@value{EDITOR}}, but you can change this
7841 by setting the environment variable @code{EDITOR} before using
7842 @value{GDBN}. For example, to configure @value{GDBN} to use the
7843 @code{vi} editor, you could use these commands with the @code{sh} shell:
7849 or in the @code{csh} shell,
7851 setenv EDITOR /usr/bin/vi
7856 @section Searching Source Files
7857 @cindex searching source files
7859 There are two commands for searching through the current source file for a
7864 @kindex forward-search
7865 @kindex fo @r{(@code{forward-search})}
7866 @item forward-search @var{regexp}
7867 @itemx search @var{regexp}
7868 The command @samp{forward-search @var{regexp}} checks each line,
7869 starting with the one following the last line listed, for a match for
7870 @var{regexp}. It lists the line that is found. You can use the
7871 synonym @samp{search @var{regexp}} or abbreviate the command name as
7874 @kindex reverse-search
7875 @item reverse-search @var{regexp}
7876 The command @samp{reverse-search @var{regexp}} checks each line, starting
7877 with the one before the last line listed and going backward, for a match
7878 for @var{regexp}. It lists the line that is found. You can abbreviate
7879 this command as @code{rev}.
7883 @section Specifying Source Directories
7886 @cindex directories for source files
7887 Executable programs sometimes do not record the directories of the source
7888 files from which they were compiled, just the names. Even when they do,
7889 the directories could be moved between the compilation and your debugging
7890 session. @value{GDBN} has a list of directories to search for source files;
7891 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7892 it tries all the directories in the list, in the order they are present
7893 in the list, until it finds a file with the desired name.
7895 For example, suppose an executable references the file
7896 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7897 @file{/mnt/cross}. The file is first looked up literally; if this
7898 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7899 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7900 message is printed. @value{GDBN} does not look up the parts of the
7901 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7902 Likewise, the subdirectories of the source path are not searched: if
7903 the source path is @file{/mnt/cross}, and the binary refers to
7904 @file{foo.c}, @value{GDBN} would not find it under
7905 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7907 Plain file names, relative file names with leading directories, file
7908 names containing dots, etc.@: are all treated as described above; for
7909 instance, if the source path is @file{/mnt/cross}, and the source file
7910 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7911 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7912 that---@file{/mnt/cross/foo.c}.
7914 Note that the executable search path is @emph{not} used to locate the
7917 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7918 any information it has cached about where source files are found and where
7919 each line is in the file.
7923 When you start @value{GDBN}, its source path includes only @samp{cdir}
7924 and @samp{cwd}, in that order.
7925 To add other directories, use the @code{directory} command.
7927 The search path is used to find both program source files and @value{GDBN}
7928 script files (read using the @samp{-command} option and @samp{source} command).
7930 In addition to the source path, @value{GDBN} provides a set of commands
7931 that manage a list of source path substitution rules. A @dfn{substitution
7932 rule} specifies how to rewrite source directories stored in the program's
7933 debug information in case the sources were moved to a different
7934 directory between compilation and debugging. A rule is made of
7935 two strings, the first specifying what needs to be rewritten in
7936 the path, and the second specifying how it should be rewritten.
7937 In @ref{set substitute-path}, we name these two parts @var{from} and
7938 @var{to} respectively. @value{GDBN} does a simple string replacement
7939 of @var{from} with @var{to} at the start of the directory part of the
7940 source file name, and uses that result instead of the original file
7941 name to look up the sources.
7943 Using the previous example, suppose the @file{foo-1.0} tree has been
7944 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7945 @value{GDBN} to replace @file{/usr/src} in all source path names with
7946 @file{/mnt/cross}. The first lookup will then be
7947 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7948 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7949 substitution rule, use the @code{set substitute-path} command
7950 (@pxref{set substitute-path}).
7952 To avoid unexpected substitution results, a rule is applied only if the
7953 @var{from} part of the directory name ends at a directory separator.
7954 For instance, a rule substituting @file{/usr/source} into
7955 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7956 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7957 is applied only at the beginning of the directory name, this rule will
7958 not be applied to @file{/root/usr/source/baz.c} either.
7960 In many cases, you can achieve the same result using the @code{directory}
7961 command. However, @code{set substitute-path} can be more efficient in
7962 the case where the sources are organized in a complex tree with multiple
7963 subdirectories. With the @code{directory} command, you need to add each
7964 subdirectory of your project. If you moved the entire tree while
7965 preserving its internal organization, then @code{set substitute-path}
7966 allows you to direct the debugger to all the sources with one single
7969 @code{set substitute-path} is also more than just a shortcut command.
7970 The source path is only used if the file at the original location no
7971 longer exists. On the other hand, @code{set substitute-path} modifies
7972 the debugger behavior to look at the rewritten location instead. So, if
7973 for any reason a source file that is not relevant to your executable is
7974 located at the original location, a substitution rule is the only
7975 method available to point @value{GDBN} at the new location.
7977 @cindex @samp{--with-relocated-sources}
7978 @cindex default source path substitution
7979 You can configure a default source path substitution rule by
7980 configuring @value{GDBN} with the
7981 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7982 should be the name of a directory under @value{GDBN}'s configured
7983 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7984 directory names in debug information under @var{dir} will be adjusted
7985 automatically if the installed @value{GDBN} is moved to a new
7986 location. This is useful if @value{GDBN}, libraries or executables
7987 with debug information and corresponding source code are being moved
7991 @item directory @var{dirname} @dots{}
7992 @item dir @var{dirname} @dots{}
7993 Add directory @var{dirname} to the front of the source path. Several
7994 directory names may be given to this command, separated by @samp{:}
7995 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7996 part of absolute file names) or
7997 whitespace. You may specify a directory that is already in the source
7998 path; this moves it forward, so @value{GDBN} searches it sooner.
8002 @vindex $cdir@r{, convenience variable}
8003 @vindex $cwd@r{, convenience variable}
8004 @cindex compilation directory
8005 @cindex current directory
8006 @cindex working directory
8007 @cindex directory, current
8008 @cindex directory, compilation
8009 You can use the string @samp{$cdir} to refer to the compilation
8010 directory (if one is recorded), and @samp{$cwd} to refer to the current
8011 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8012 tracks the current working directory as it changes during your @value{GDBN}
8013 session, while the latter is immediately expanded to the current
8014 directory at the time you add an entry to the source path.
8017 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8019 @c RET-repeat for @code{directory} is explicitly disabled, but since
8020 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8022 @item set directories @var{path-list}
8023 @kindex set directories
8024 Set the source path to @var{path-list}.
8025 @samp{$cdir:$cwd} are added if missing.
8027 @item show directories
8028 @kindex show directories
8029 Print the source path: show which directories it contains.
8031 @anchor{set substitute-path}
8032 @item set substitute-path @var{from} @var{to}
8033 @kindex set substitute-path
8034 Define a source path substitution rule, and add it at the end of the
8035 current list of existing substitution rules. If a rule with the same
8036 @var{from} was already defined, then the old rule is also deleted.
8038 For example, if the file @file{/foo/bar/baz.c} was moved to
8039 @file{/mnt/cross/baz.c}, then the command
8042 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8046 will tell @value{GDBN} to replace @samp{/foo/bar} with
8047 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8048 @file{baz.c} even though it was moved.
8050 In the case when more than one substitution rule have been defined,
8051 the rules are evaluated one by one in the order where they have been
8052 defined. The first one matching, if any, is selected to perform
8055 For instance, if we had entered the following commands:
8058 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8059 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8063 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8064 @file{/mnt/include/defs.h} by using the first rule. However, it would
8065 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8066 @file{/mnt/src/lib/foo.c}.
8069 @item unset substitute-path [path]
8070 @kindex unset substitute-path
8071 If a path is specified, search the current list of substitution rules
8072 for a rule that would rewrite that path. Delete that rule if found.
8073 A warning is emitted by the debugger if no rule could be found.
8075 If no path is specified, then all substitution rules are deleted.
8077 @item show substitute-path [path]
8078 @kindex show substitute-path
8079 If a path is specified, then print the source path substitution rule
8080 which would rewrite that path, if any.
8082 If no path is specified, then print all existing source path substitution
8087 If your source path is cluttered with directories that are no longer of
8088 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8089 versions of source. You can correct the situation as follows:
8093 Use @code{directory} with no argument to reset the source path to its default value.
8096 Use @code{directory} with suitable arguments to reinstall the
8097 directories you want in the source path. You can add all the
8098 directories in one command.
8102 @section Source and Machine Code
8103 @cindex source line and its code address
8105 You can use the command @code{info line} to map source lines to program
8106 addresses (and vice versa), and the command @code{disassemble} to display
8107 a range of addresses as machine instructions. You can use the command
8108 @code{set disassemble-next-line} to set whether to disassemble next
8109 source line when execution stops. When run under @sc{gnu} Emacs
8110 mode, the @code{info line} command causes the arrow to point to the
8111 line specified. Also, @code{info line} prints addresses in symbolic form as
8116 @item info line @var{location}
8117 Print the starting and ending addresses of the compiled code for
8118 source line @var{location}. You can specify source lines in any of
8119 the ways documented in @ref{Specify Location}.
8122 For example, we can use @code{info line} to discover the location of
8123 the object code for the first line of function
8124 @code{m4_changequote}:
8126 @c FIXME: I think this example should also show the addresses in
8127 @c symbolic form, as they usually would be displayed.
8129 (@value{GDBP}) info line m4_changequote
8130 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8134 @cindex code address and its source line
8135 We can also inquire (using @code{*@var{addr}} as the form for
8136 @var{location}) what source line covers a particular address:
8138 (@value{GDBP}) info line *0x63ff
8139 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8142 @cindex @code{$_} and @code{info line}
8143 @cindex @code{x} command, default address
8144 @kindex x@r{(examine), and} info line
8145 After @code{info line}, the default address for the @code{x} command
8146 is changed to the starting address of the line, so that @samp{x/i} is
8147 sufficient to begin examining the machine code (@pxref{Memory,
8148 ,Examining Memory}). Also, this address is saved as the value of the
8149 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8154 @cindex assembly instructions
8155 @cindex instructions, assembly
8156 @cindex machine instructions
8157 @cindex listing machine instructions
8159 @itemx disassemble /m
8160 @itemx disassemble /s
8161 @itemx disassemble /r
8162 This specialized command dumps a range of memory as machine
8163 instructions. It can also print mixed source+disassembly by specifying
8164 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8165 as well as in symbolic form by specifying the @code{/r} modifier.
8166 The default memory range is the function surrounding the
8167 program counter of the selected frame. A single argument to this
8168 command is a program counter value; @value{GDBN} dumps the function
8169 surrounding this value. When two arguments are given, they should
8170 be separated by a comma, possibly surrounded by whitespace. The
8171 arguments specify a range of addresses to dump, in one of two forms:
8174 @item @var{start},@var{end}
8175 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8176 @item @var{start},+@var{length}
8177 the addresses from @var{start} (inclusive) to
8178 @code{@var{start}+@var{length}} (exclusive).
8182 When 2 arguments are specified, the name of the function is also
8183 printed (since there could be several functions in the given range).
8185 The argument(s) can be any expression yielding a numeric value, such as
8186 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8188 If the range of memory being disassembled contains current program counter,
8189 the instruction at that location is shown with a @code{=>} marker.
8192 The following example shows the disassembly of a range of addresses of
8193 HP PA-RISC 2.0 code:
8196 (@value{GDBP}) disas 0x32c4, 0x32e4
8197 Dump of assembler code from 0x32c4 to 0x32e4:
8198 0x32c4 <main+204>: addil 0,dp
8199 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8200 0x32cc <main+212>: ldil 0x3000,r31
8201 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8202 0x32d4 <main+220>: ldo 0(r31),rp
8203 0x32d8 <main+224>: addil -0x800,dp
8204 0x32dc <main+228>: ldo 0x588(r1),r26
8205 0x32e0 <main+232>: ldil 0x3000,r31
8206 End of assembler dump.
8209 Here is an example showing mixed source+assembly for Intel x86
8210 with @code{/m} or @code{/s}, when the program is stopped just after
8211 function prologue in a non-optimized function with no inline code.
8214 (@value{GDBP}) disas /m main
8215 Dump of assembler code for function main:
8217 0x08048330 <+0>: push %ebp
8218 0x08048331 <+1>: mov %esp,%ebp
8219 0x08048333 <+3>: sub $0x8,%esp
8220 0x08048336 <+6>: and $0xfffffff0,%esp
8221 0x08048339 <+9>: sub $0x10,%esp
8223 6 printf ("Hello.\n");
8224 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8225 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8229 0x08048348 <+24>: mov $0x0,%eax
8230 0x0804834d <+29>: leave
8231 0x0804834e <+30>: ret
8233 End of assembler dump.
8236 The @code{/m} option is deprecated as its output is not useful when
8237 there is either inlined code or re-ordered code.
8238 The @code{/s} option is the preferred choice.
8239 Here is an example for AMD x86-64 showing the difference between
8240 @code{/m} output and @code{/s} output.
8241 This example has one inline function defined in a header file,
8242 and the code is compiled with @samp{-O2} optimization.
8243 Note how the @code{/m} output is missing the disassembly of
8244 several instructions that are present in the @code{/s} output.
8274 (@value{GDBP}) disas /m main
8275 Dump of assembler code for function main:
8279 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8280 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8284 0x000000000040041d <+29>: xor %eax,%eax
8285 0x000000000040041f <+31>: retq
8286 0x0000000000400420 <+32>: add %eax,%eax
8287 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8289 End of assembler dump.
8290 (@value{GDBP}) disas /s main
8291 Dump of assembler code for function main:
8295 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8299 0x0000000000400406 <+6>: test %eax,%eax
8300 0x0000000000400408 <+8>: js 0x400420 <main+32>
8305 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8306 0x000000000040040d <+13>: test %eax,%eax
8307 0x000000000040040f <+15>: mov $0x1,%eax
8308 0x0000000000400414 <+20>: cmovne %edx,%eax
8312 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8316 0x000000000040041d <+29>: xor %eax,%eax
8317 0x000000000040041f <+31>: retq
8321 0x0000000000400420 <+32>: add %eax,%eax
8322 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8323 End of assembler dump.
8326 Here is another example showing raw instructions in hex for AMD x86-64,
8329 (gdb) disas /r 0x400281,+10
8330 Dump of assembler code from 0x400281 to 0x40028b:
8331 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8332 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8333 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8334 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8335 End of assembler dump.
8338 Addresses cannot be specified as a location (@pxref{Specify Location}).
8339 So, for example, if you want to disassemble function @code{bar}
8340 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8341 and not @samp{disassemble foo.c:bar}.
8343 Some architectures have more than one commonly-used set of instruction
8344 mnemonics or other syntax.
8346 For programs that were dynamically linked and use shared libraries,
8347 instructions that call functions or branch to locations in the shared
8348 libraries might show a seemingly bogus location---it's actually a
8349 location of the relocation table. On some architectures, @value{GDBN}
8350 might be able to resolve these to actual function names.
8353 @kindex set disassembly-flavor
8354 @cindex Intel disassembly flavor
8355 @cindex AT&T disassembly flavor
8356 @item set disassembly-flavor @var{instruction-set}
8357 Select the instruction set to use when disassembling the
8358 program via the @code{disassemble} or @code{x/i} commands.
8360 Currently this command is only defined for the Intel x86 family. You
8361 can set @var{instruction-set} to either @code{intel} or @code{att}.
8362 The default is @code{att}, the AT&T flavor used by default by Unix
8363 assemblers for x86-based targets.
8365 @kindex show disassembly-flavor
8366 @item show disassembly-flavor
8367 Show the current setting of the disassembly flavor.
8371 @kindex set disassemble-next-line
8372 @kindex show disassemble-next-line
8373 @item set disassemble-next-line
8374 @itemx show disassemble-next-line
8375 Control whether or not @value{GDBN} will disassemble the next source
8376 line or instruction when execution stops. If ON, @value{GDBN} will
8377 display disassembly of the next source line when execution of the
8378 program being debugged stops. This is @emph{in addition} to
8379 displaying the source line itself, which @value{GDBN} always does if
8380 possible. If the next source line cannot be displayed for some reason
8381 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8382 info in the debug info), @value{GDBN} will display disassembly of the
8383 next @emph{instruction} instead of showing the next source line. If
8384 AUTO, @value{GDBN} will display disassembly of next instruction only
8385 if the source line cannot be displayed. This setting causes
8386 @value{GDBN} to display some feedback when you step through a function
8387 with no line info or whose source file is unavailable. The default is
8388 OFF, which means never display the disassembly of the next line or
8394 @chapter Examining Data
8396 @cindex printing data
8397 @cindex examining data
8400 The usual way to examine data in your program is with the @code{print}
8401 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8402 evaluates and prints the value of an expression of the language your
8403 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8404 Different Languages}). It may also print the expression using a
8405 Python-based pretty-printer (@pxref{Pretty Printing}).
8408 @item print @var{expr}
8409 @itemx print /@var{f} @var{expr}
8410 @var{expr} is an expression (in the source language). By default the
8411 value of @var{expr} is printed in a format appropriate to its data type;
8412 you can choose a different format by specifying @samp{/@var{f}}, where
8413 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8417 @itemx print /@var{f}
8418 @cindex reprint the last value
8419 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8420 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8421 conveniently inspect the same value in an alternative format.
8424 A more low-level way of examining data is with the @code{x} command.
8425 It examines data in memory at a specified address and prints it in a
8426 specified format. @xref{Memory, ,Examining Memory}.
8428 If you are interested in information about types, or about how the
8429 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8430 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8433 @cindex exploring hierarchical data structures
8435 Another way of examining values of expressions and type information is
8436 through the Python extension command @code{explore} (available only if
8437 the @value{GDBN} build is configured with @code{--with-python}). It
8438 offers an interactive way to start at the highest level (or, the most
8439 abstract level) of the data type of an expression (or, the data type
8440 itself) and explore all the way down to leaf scalar values/fields
8441 embedded in the higher level data types.
8444 @item explore @var{arg}
8445 @var{arg} is either an expression (in the source language), or a type
8446 visible in the current context of the program being debugged.
8449 The working of the @code{explore} command can be illustrated with an
8450 example. If a data type @code{struct ComplexStruct} is defined in your
8460 struct ComplexStruct
8462 struct SimpleStruct *ss_p;
8468 followed by variable declarations as
8471 struct SimpleStruct ss = @{ 10, 1.11 @};
8472 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8476 then, the value of the variable @code{cs} can be explored using the
8477 @code{explore} command as follows.
8481 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8482 the following fields:
8484 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8485 arr = <Enter 1 to explore this field of type `int [10]'>
8487 Enter the field number of choice:
8491 Since the fields of @code{cs} are not scalar values, you are being
8492 prompted to chose the field you want to explore. Let's say you choose
8493 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8494 pointer, you will be asked if it is pointing to a single value. From
8495 the declaration of @code{cs} above, it is indeed pointing to a single
8496 value, hence you enter @code{y}. If you enter @code{n}, then you will
8497 be asked if it were pointing to an array of values, in which case this
8498 field will be explored as if it were an array.
8501 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8502 Continue exploring it as a pointer to a single value [y/n]: y
8503 The value of `*(cs.ss_p)' is a struct/class of type `struct
8504 SimpleStruct' with the following fields:
8506 i = 10 .. (Value of type `int')
8507 d = 1.1100000000000001 .. (Value of type `double')
8509 Press enter to return to parent value:
8513 If the field @code{arr} of @code{cs} was chosen for exploration by
8514 entering @code{1} earlier, then since it is as array, you will be
8515 prompted to enter the index of the element in the array that you want
8519 `cs.arr' is an array of `int'.
8520 Enter the index of the element you want to explore in `cs.arr': 5
8522 `(cs.arr)[5]' is a scalar value of type `int'.
8526 Press enter to return to parent value:
8529 In general, at any stage of exploration, you can go deeper towards the
8530 leaf values by responding to the prompts appropriately, or hit the
8531 return key to return to the enclosing data structure (the @i{higher}
8532 level data structure).
8534 Similar to exploring values, you can use the @code{explore} command to
8535 explore types. Instead of specifying a value (which is typically a
8536 variable name or an expression valid in the current context of the
8537 program being debugged), you specify a type name. If you consider the
8538 same example as above, your can explore the type
8539 @code{struct ComplexStruct} by passing the argument
8540 @code{struct ComplexStruct} to the @code{explore} command.
8543 (gdb) explore struct ComplexStruct
8547 By responding to the prompts appropriately in the subsequent interactive
8548 session, you can explore the type @code{struct ComplexStruct} in a
8549 manner similar to how the value @code{cs} was explored in the above
8552 The @code{explore} command also has two sub-commands,
8553 @code{explore value} and @code{explore type}. The former sub-command is
8554 a way to explicitly specify that value exploration of the argument is
8555 being invoked, while the latter is a way to explicitly specify that type
8556 exploration of the argument is being invoked.
8559 @item explore value @var{expr}
8560 @cindex explore value
8561 This sub-command of @code{explore} explores the value of the
8562 expression @var{expr} (if @var{expr} is an expression valid in the
8563 current context of the program being debugged). The behavior of this
8564 command is identical to that of the behavior of the @code{explore}
8565 command being passed the argument @var{expr}.
8567 @item explore type @var{arg}
8568 @cindex explore type
8569 This sub-command of @code{explore} explores the type of @var{arg} (if
8570 @var{arg} is a type visible in the current context of program being
8571 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8572 is an expression valid in the current context of the program being
8573 debugged). If @var{arg} is a type, then the behavior of this command is
8574 identical to that of the @code{explore} command being passed the
8575 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8576 this command will be identical to that of the @code{explore} command
8577 being passed the type of @var{arg} as the argument.
8581 * Expressions:: Expressions
8582 * Ambiguous Expressions:: Ambiguous Expressions
8583 * Variables:: Program variables
8584 * Arrays:: Artificial arrays
8585 * Output Formats:: Output formats
8586 * Memory:: Examining memory
8587 * Auto Display:: Automatic display
8588 * Print Settings:: Print settings
8589 * Pretty Printing:: Python pretty printing
8590 * Value History:: Value history
8591 * Convenience Vars:: Convenience variables
8592 * Convenience Funs:: Convenience functions
8593 * Registers:: Registers
8594 * Floating Point Hardware:: Floating point hardware
8595 * Vector Unit:: Vector Unit
8596 * OS Information:: Auxiliary data provided by operating system
8597 * Memory Region Attributes:: Memory region attributes
8598 * Dump/Restore Files:: Copy between memory and a file
8599 * Core File Generation:: Cause a program dump its core
8600 * Character Sets:: Debugging programs that use a different
8601 character set than GDB does
8602 * Caching Target Data:: Data caching for targets
8603 * Searching Memory:: Searching memory for a sequence of bytes
8607 @section Expressions
8610 @code{print} and many other @value{GDBN} commands accept an expression and
8611 compute its value. Any kind of constant, variable or operator defined
8612 by the programming language you are using is valid in an expression in
8613 @value{GDBN}. This includes conditional expressions, function calls,
8614 casts, and string constants. It also includes preprocessor macros, if
8615 you compiled your program to include this information; see
8618 @cindex arrays in expressions
8619 @value{GDBN} supports array constants in expressions input by
8620 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8621 you can use the command @code{print @{1, 2, 3@}} to create an array
8622 of three integers. If you pass an array to a function or assign it
8623 to a program variable, @value{GDBN} copies the array to memory that
8624 is @code{malloc}ed in the target program.
8626 Because C is so widespread, most of the expressions shown in examples in
8627 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8628 Languages}, for information on how to use expressions in other
8631 In this section, we discuss operators that you can use in @value{GDBN}
8632 expressions regardless of your programming language.
8634 @cindex casts, in expressions
8635 Casts are supported in all languages, not just in C, because it is so
8636 useful to cast a number into a pointer in order to examine a structure
8637 at that address in memory.
8638 @c FIXME: casts supported---Mod2 true?
8640 @value{GDBN} supports these operators, in addition to those common
8641 to programming languages:
8645 @samp{@@} is a binary operator for treating parts of memory as arrays.
8646 @xref{Arrays, ,Artificial Arrays}, for more information.
8649 @samp{::} allows you to specify a variable in terms of the file or
8650 function where it is defined. @xref{Variables, ,Program Variables}.
8652 @cindex @{@var{type}@}
8653 @cindex type casting memory
8654 @cindex memory, viewing as typed object
8655 @cindex casts, to view memory
8656 @item @{@var{type}@} @var{addr}
8657 Refers to an object of type @var{type} stored at address @var{addr} in
8658 memory. The address @var{addr} may be any expression whose value is
8659 an integer or pointer (but parentheses are required around binary
8660 operators, just as in a cast). This construct is allowed regardless
8661 of what kind of data is normally supposed to reside at @var{addr}.
8664 @node Ambiguous Expressions
8665 @section Ambiguous Expressions
8666 @cindex ambiguous expressions
8668 Expressions can sometimes contain some ambiguous elements. For instance,
8669 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8670 a single function name to be defined several times, for application in
8671 different contexts. This is called @dfn{overloading}. Another example
8672 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8673 templates and is typically instantiated several times, resulting in
8674 the same function name being defined in different contexts.
8676 In some cases and depending on the language, it is possible to adjust
8677 the expression to remove the ambiguity. For instance in C@t{++}, you
8678 can specify the signature of the function you want to break on, as in
8679 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8680 qualified name of your function often makes the expression unambiguous
8683 When an ambiguity that needs to be resolved is detected, the debugger
8684 has the capability to display a menu of numbered choices for each
8685 possibility, and then waits for the selection with the prompt @samp{>}.
8686 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8687 aborts the current command. If the command in which the expression was
8688 used allows more than one choice to be selected, the next option in the
8689 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8692 For example, the following session excerpt shows an attempt to set a
8693 breakpoint at the overloaded symbol @code{String::after}.
8694 We choose three particular definitions of that function name:
8696 @c FIXME! This is likely to change to show arg type lists, at least
8699 (@value{GDBP}) b String::after
8702 [2] file:String.cc; line number:867
8703 [3] file:String.cc; line number:860
8704 [4] file:String.cc; line number:875
8705 [5] file:String.cc; line number:853
8706 [6] file:String.cc; line number:846
8707 [7] file:String.cc; line number:735
8709 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8710 Breakpoint 2 at 0xb344: file String.cc, line 875.
8711 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8712 Multiple breakpoints were set.
8713 Use the "delete" command to delete unwanted
8720 @kindex set multiple-symbols
8721 @item set multiple-symbols @var{mode}
8722 @cindex multiple-symbols menu
8724 This option allows you to adjust the debugger behavior when an expression
8727 By default, @var{mode} is set to @code{all}. If the command with which
8728 the expression is used allows more than one choice, then @value{GDBN}
8729 automatically selects all possible choices. For instance, inserting
8730 a breakpoint on a function using an ambiguous name results in a breakpoint
8731 inserted on each possible match. However, if a unique choice must be made,
8732 then @value{GDBN} uses the menu to help you disambiguate the expression.
8733 For instance, printing the address of an overloaded function will result
8734 in the use of the menu.
8736 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8737 when an ambiguity is detected.
8739 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8740 an error due to the ambiguity and the command is aborted.
8742 @kindex show multiple-symbols
8743 @item show multiple-symbols
8744 Show the current value of the @code{multiple-symbols} setting.
8748 @section Program Variables
8750 The most common kind of expression to use is the name of a variable
8753 Variables in expressions are understood in the selected stack frame
8754 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8758 global (or file-static)
8765 visible according to the scope rules of the
8766 programming language from the point of execution in that frame
8769 @noindent This means that in the function
8784 you can examine and use the variable @code{a} whenever your program is
8785 executing within the function @code{foo}, but you can only use or
8786 examine the variable @code{b} while your program is executing inside
8787 the block where @code{b} is declared.
8789 @cindex variable name conflict
8790 There is an exception: you can refer to a variable or function whose
8791 scope is a single source file even if the current execution point is not
8792 in this file. But it is possible to have more than one such variable or
8793 function with the same name (in different source files). If that
8794 happens, referring to that name has unpredictable effects. If you wish,
8795 you can specify a static variable in a particular function or file by
8796 using the colon-colon (@code{::}) notation:
8798 @cindex colon-colon, context for variables/functions
8800 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8801 @cindex @code{::}, context for variables/functions
8804 @var{file}::@var{variable}
8805 @var{function}::@var{variable}
8809 Here @var{file} or @var{function} is the name of the context for the
8810 static @var{variable}. In the case of file names, you can use quotes to
8811 make sure @value{GDBN} parses the file name as a single word---for example,
8812 to print a global value of @code{x} defined in @file{f2.c}:
8815 (@value{GDBP}) p 'f2.c'::x
8818 The @code{::} notation is normally used for referring to
8819 static variables, since you typically disambiguate uses of local variables
8820 in functions by selecting the appropriate frame and using the
8821 simple name of the variable. However, you may also use this notation
8822 to refer to local variables in frames enclosing the selected frame:
8831 process (a); /* Stop here */
8842 For example, if there is a breakpoint at the commented line,
8843 here is what you might see
8844 when the program stops after executing the call @code{bar(0)}:
8849 (@value{GDBP}) p bar::a
8852 #2 0x080483d0 in foo (a=5) at foobar.c:12
8855 (@value{GDBP}) p bar::a
8859 @cindex C@t{++} scope resolution
8860 These uses of @samp{::} are very rarely in conflict with the very
8861 similar use of the same notation in C@t{++}. When they are in
8862 conflict, the C@t{++} meaning takes precedence; however, this can be
8863 overridden by quoting the file or function name with single quotes.
8865 For example, suppose the program is stopped in a method of a class
8866 that has a field named @code{includefile}, and there is also an
8867 include file named @file{includefile} that defines a variable,
8871 (@value{GDBP}) p includefile
8873 (@value{GDBP}) p includefile::some_global
8874 A syntax error in expression, near `'.
8875 (@value{GDBP}) p 'includefile'::some_global
8879 @cindex wrong values
8880 @cindex variable values, wrong
8881 @cindex function entry/exit, wrong values of variables
8882 @cindex optimized code, wrong values of variables
8884 @emph{Warning:} Occasionally, a local variable may appear to have the
8885 wrong value at certain points in a function---just after entry to a new
8886 scope, and just before exit.
8888 You may see this problem when you are stepping by machine instructions.
8889 This is because, on most machines, it takes more than one instruction to
8890 set up a stack frame (including local variable definitions); if you are
8891 stepping by machine instructions, variables may appear to have the wrong
8892 values until the stack frame is completely built. On exit, it usually
8893 also takes more than one machine instruction to destroy a stack frame;
8894 after you begin stepping through that group of instructions, local
8895 variable definitions may be gone.
8897 This may also happen when the compiler does significant optimizations.
8898 To be sure of always seeing accurate values, turn off all optimization
8901 @cindex ``No symbol "foo" in current context''
8902 Another possible effect of compiler optimizations is to optimize
8903 unused variables out of existence, or assign variables to registers (as
8904 opposed to memory addresses). Depending on the support for such cases
8905 offered by the debug info format used by the compiler, @value{GDBN}
8906 might not be able to display values for such local variables. If that
8907 happens, @value{GDBN} will print a message like this:
8910 No symbol "foo" in current context.
8913 To solve such problems, either recompile without optimizations, or use a
8914 different debug info format, if the compiler supports several such
8915 formats. @xref{Compilation}, for more information on choosing compiler
8916 options. @xref{C, ,C and C@t{++}}, for more information about debug
8917 info formats that are best suited to C@t{++} programs.
8919 If you ask to print an object whose contents are unknown to
8920 @value{GDBN}, e.g., because its data type is not completely specified
8921 by the debug information, @value{GDBN} will say @samp{<incomplete
8922 type>}. @xref{Symbols, incomplete type}, for more about this.
8924 If you append @kbd{@@entry} string to a function parameter name you get its
8925 value at the time the function got called. If the value is not available an
8926 error message is printed. Entry values are available only with some compilers.
8927 Entry values are normally also printed at the function parameter list according
8928 to @ref{set print entry-values}.
8931 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8937 (gdb) print i@@entry
8941 Strings are identified as arrays of @code{char} values without specified
8942 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8943 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8944 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8945 defines literal string type @code{"char"} as @code{char} without a sign.
8950 signed char var1[] = "A";
8953 You get during debugging
8958 $2 = @{65 'A', 0 '\0'@}
8962 @section Artificial Arrays
8964 @cindex artificial array
8966 @kindex @@@r{, referencing memory as an array}
8967 It is often useful to print out several successive objects of the
8968 same type in memory; a section of an array, or an array of
8969 dynamically determined size for which only a pointer exists in the
8972 You can do this by referring to a contiguous span of memory as an
8973 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8974 operand of @samp{@@} should be the first element of the desired array
8975 and be an individual object. The right operand should be the desired length
8976 of the array. The result is an array value whose elements are all of
8977 the type of the left argument. The first element is actually the left
8978 argument; the second element comes from bytes of memory immediately
8979 following those that hold the first element, and so on. Here is an
8980 example. If a program says
8983 int *array = (int *) malloc (len * sizeof (int));
8987 you can print the contents of @code{array} with
8993 The left operand of @samp{@@} must reside in memory. Array values made
8994 with @samp{@@} in this way behave just like other arrays in terms of
8995 subscripting, and are coerced to pointers when used in expressions.
8996 Artificial arrays most often appear in expressions via the value history
8997 (@pxref{Value History, ,Value History}), after printing one out.
8999 Another way to create an artificial array is to use a cast.
9000 This re-interprets a value as if it were an array.
9001 The value need not be in memory:
9003 (@value{GDBP}) p/x (short[2])0x12345678
9004 $1 = @{0x1234, 0x5678@}
9007 As a convenience, if you leave the array length out (as in
9008 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9009 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9011 (@value{GDBP}) p/x (short[])0x12345678
9012 $2 = @{0x1234, 0x5678@}
9015 Sometimes the artificial array mechanism is not quite enough; in
9016 moderately complex data structures, the elements of interest may not
9017 actually be adjacent---for example, if you are interested in the values
9018 of pointers in an array. One useful work-around in this situation is
9019 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9020 Variables}) as a counter in an expression that prints the first
9021 interesting value, and then repeat that expression via @key{RET}. For
9022 instance, suppose you have an array @code{dtab} of pointers to
9023 structures, and you are interested in the values of a field @code{fv}
9024 in each structure. Here is an example of what you might type:
9034 @node Output Formats
9035 @section Output Formats
9037 @cindex formatted output
9038 @cindex output formats
9039 By default, @value{GDBN} prints a value according to its data type. Sometimes
9040 this is not what you want. For example, you might want to print a number
9041 in hex, or a pointer in decimal. Or you might want to view data in memory
9042 at a certain address as a character string or as an instruction. To do
9043 these things, specify an @dfn{output format} when you print a value.
9045 The simplest use of output formats is to say how to print a value
9046 already computed. This is done by starting the arguments of the
9047 @code{print} command with a slash and a format letter. The format
9048 letters supported are:
9052 Regard the bits of the value as an integer, and print the integer in
9056 Print as integer in signed decimal.
9059 Print as integer in unsigned decimal.
9062 Print as integer in octal.
9065 Print as integer in binary. The letter @samp{t} stands for ``two''.
9066 @footnote{@samp{b} cannot be used because these format letters are also
9067 used with the @code{x} command, where @samp{b} stands for ``byte'';
9068 see @ref{Memory,,Examining Memory}.}
9071 @cindex unknown address, locating
9072 @cindex locate address
9073 Print as an address, both absolute in hexadecimal and as an offset from
9074 the nearest preceding symbol. You can use this format used to discover
9075 where (in what function) an unknown address is located:
9078 (@value{GDBP}) p/a 0x54320
9079 $3 = 0x54320 <_initialize_vx+396>
9083 The command @code{info symbol 0x54320} yields similar results.
9084 @xref{Symbols, info symbol}.
9087 Regard as an integer and print it as a character constant. This
9088 prints both the numerical value and its character representation. The
9089 character representation is replaced with the octal escape @samp{\nnn}
9090 for characters outside the 7-bit @sc{ascii} range.
9092 Without this format, @value{GDBN} displays @code{char},
9093 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9094 constants. Single-byte members of vectors are displayed as integer
9098 Regard the bits of the value as a floating point number and print
9099 using typical floating point syntax.
9102 @cindex printing strings
9103 @cindex printing byte arrays
9104 Regard as a string, if possible. With this format, pointers to single-byte
9105 data are displayed as null-terminated strings and arrays of single-byte data
9106 are displayed as fixed-length strings. Other values are displayed in their
9109 Without this format, @value{GDBN} displays pointers to and arrays of
9110 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9111 strings. Single-byte members of a vector are displayed as an integer
9115 Like @samp{x} formatting, the value is treated as an integer and
9116 printed as hexadecimal, but leading zeros are printed to pad the value
9117 to the size of the integer type.
9120 @cindex raw printing
9121 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9122 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9123 Printing}). This typically results in a higher-level display of the
9124 value's contents. The @samp{r} format bypasses any Python
9125 pretty-printer which might exist.
9128 For example, to print the program counter in hex (@pxref{Registers}), type
9135 Note that no space is required before the slash; this is because command
9136 names in @value{GDBN} cannot contain a slash.
9138 To reprint the last value in the value history with a different format,
9139 you can use the @code{print} command with just a format and no
9140 expression. For example, @samp{p/x} reprints the last value in hex.
9143 @section Examining Memory
9145 You can use the command @code{x} (for ``examine'') to examine memory in
9146 any of several formats, independently of your program's data types.
9148 @cindex examining memory
9150 @kindex x @r{(examine memory)}
9151 @item x/@var{nfu} @var{addr}
9154 Use the @code{x} command to examine memory.
9157 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9158 much memory to display and how to format it; @var{addr} is an
9159 expression giving the address where you want to start displaying memory.
9160 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9161 Several commands set convenient defaults for @var{addr}.
9164 @item @var{n}, the repeat count
9165 The repeat count is a decimal integer; the default is 1. It specifies
9166 how much memory (counting by units @var{u}) to display.
9167 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9170 @item @var{f}, the display format
9171 The display format is one of the formats used by @code{print}
9172 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9173 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9174 The default is @samp{x} (hexadecimal) initially. The default changes
9175 each time you use either @code{x} or @code{print}.
9177 @item @var{u}, the unit size
9178 The unit size is any of
9184 Halfwords (two bytes).
9186 Words (four bytes). This is the initial default.
9188 Giant words (eight bytes).
9191 Each time you specify a unit size with @code{x}, that size becomes the
9192 default unit the next time you use @code{x}. For the @samp{i} format,
9193 the unit size is ignored and is normally not written. For the @samp{s} format,
9194 the unit size defaults to @samp{b}, unless it is explicitly given.
9195 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9196 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9197 Note that the results depend on the programming language of the
9198 current compilation unit. If the language is C, the @samp{s}
9199 modifier will use the UTF-16 encoding while @samp{w} will use
9200 UTF-32. The encoding is set by the programming language and cannot
9203 @item @var{addr}, starting display address
9204 @var{addr} is the address where you want @value{GDBN} to begin displaying
9205 memory. The expression need not have a pointer value (though it may);
9206 it is always interpreted as an integer address of a byte of memory.
9207 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9208 @var{addr} is usually just after the last address examined---but several
9209 other commands also set the default address: @code{info breakpoints} (to
9210 the address of the last breakpoint listed), @code{info line} (to the
9211 starting address of a line), and @code{print} (if you use it to display
9212 a value from memory).
9215 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9216 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9217 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9218 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9219 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9221 Since the letters indicating unit sizes are all distinct from the
9222 letters specifying output formats, you do not have to remember whether
9223 unit size or format comes first; either order works. The output
9224 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9225 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9227 Even though the unit size @var{u} is ignored for the formats @samp{s}
9228 and @samp{i}, you might still want to use a count @var{n}; for example,
9229 @samp{3i} specifies that you want to see three machine instructions,
9230 including any operands. For convenience, especially when used with
9231 the @code{display} command, the @samp{i} format also prints branch delay
9232 slot instructions, if any, beyond the count specified, which immediately
9233 follow the last instruction that is within the count. The command
9234 @code{disassemble} gives an alternative way of inspecting machine
9235 instructions; see @ref{Machine Code,,Source and Machine Code}.
9237 All the defaults for the arguments to @code{x} are designed to make it
9238 easy to continue scanning memory with minimal specifications each time
9239 you use @code{x}. For example, after you have inspected three machine
9240 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9241 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9242 the repeat count @var{n} is used again; the other arguments default as
9243 for successive uses of @code{x}.
9245 When examining machine instructions, the instruction at current program
9246 counter is shown with a @code{=>} marker. For example:
9249 (@value{GDBP}) x/5i $pc-6
9250 0x804837f <main+11>: mov %esp,%ebp
9251 0x8048381 <main+13>: push %ecx
9252 0x8048382 <main+14>: sub $0x4,%esp
9253 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9254 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9257 @cindex @code{$_}, @code{$__}, and value history
9258 The addresses and contents printed by the @code{x} command are not saved
9259 in the value history because there is often too much of them and they
9260 would get in the way. Instead, @value{GDBN} makes these values available for
9261 subsequent use in expressions as values of the convenience variables
9262 @code{$_} and @code{$__}. After an @code{x} command, the last address
9263 examined is available for use in expressions in the convenience variable
9264 @code{$_}. The contents of that address, as examined, are available in
9265 the convenience variable @code{$__}.
9267 If the @code{x} command has a repeat count, the address and contents saved
9268 are from the last memory unit printed; this is not the same as the last
9269 address printed if several units were printed on the last line of output.
9271 @anchor{addressable memory unit}
9272 @cindex addressable memory unit
9273 Most targets have an addressable memory unit size of 8 bits. This means
9274 that to each memory address are associated 8 bits of data. Some
9275 targets, however, have other addressable memory unit sizes.
9276 Within @value{GDBN} and this document, the term
9277 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9278 when explicitly referring to a chunk of data of that size. The word
9279 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9280 the addressable memory unit size of the target. For most systems,
9281 addressable memory unit is a synonym of byte.
9283 @cindex remote memory comparison
9284 @cindex target memory comparison
9285 @cindex verify remote memory image
9286 @cindex verify target memory image
9287 When you are debugging a program running on a remote target machine
9288 (@pxref{Remote Debugging}), you may wish to verify the program's image
9289 in the remote machine's memory against the executable file you
9290 downloaded to the target. Or, on any target, you may want to check
9291 whether the program has corrupted its own read-only sections. The
9292 @code{compare-sections} command is provided for such situations.
9295 @kindex compare-sections
9296 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9297 Compare the data of a loadable section @var{section-name} in the
9298 executable file of the program being debugged with the same section in
9299 the target machine's memory, and report any mismatches. With no
9300 arguments, compares all loadable sections. With an argument of
9301 @code{-r}, compares all loadable read-only sections.
9303 Note: for remote targets, this command can be accelerated if the
9304 target supports computing the CRC checksum of a block of memory
9305 (@pxref{qCRC packet}).
9309 @section Automatic Display
9310 @cindex automatic display
9311 @cindex display of expressions
9313 If you find that you want to print the value of an expression frequently
9314 (to see how it changes), you might want to add it to the @dfn{automatic
9315 display list} so that @value{GDBN} prints its value each time your program stops.
9316 Each expression added to the list is given a number to identify it;
9317 to remove an expression from the list, you specify that number.
9318 The automatic display looks like this:
9322 3: bar[5] = (struct hack *) 0x3804
9326 This display shows item numbers, expressions and their current values. As with
9327 displays you request manually using @code{x} or @code{print}, you can
9328 specify the output format you prefer; in fact, @code{display} decides
9329 whether to use @code{print} or @code{x} depending your format
9330 specification---it uses @code{x} if you specify either the @samp{i}
9331 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9335 @item display @var{expr}
9336 Add the expression @var{expr} to the list of expressions to display
9337 each time your program stops. @xref{Expressions, ,Expressions}.
9339 @code{display} does not repeat if you press @key{RET} again after using it.
9341 @item display/@var{fmt} @var{expr}
9342 For @var{fmt} specifying only a display format and not a size or
9343 count, add the expression @var{expr} to the auto-display list but
9344 arrange to display it each time in the specified format @var{fmt}.
9345 @xref{Output Formats,,Output Formats}.
9347 @item display/@var{fmt} @var{addr}
9348 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9349 number of units, add the expression @var{addr} as a memory address to
9350 be examined each time your program stops. Examining means in effect
9351 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9354 For example, @samp{display/i $pc} can be helpful, to see the machine
9355 instruction about to be executed each time execution stops (@samp{$pc}
9356 is a common name for the program counter; @pxref{Registers, ,Registers}).
9359 @kindex delete display
9361 @item undisplay @var{dnums}@dots{}
9362 @itemx delete display @var{dnums}@dots{}
9363 Remove items from the list of expressions to display. Specify the
9364 numbers of the displays that you want affected with the command
9365 argument @var{dnums}. It can be a single display number, one of the
9366 numbers shown in the first field of the @samp{info display} display;
9367 or it could be a range of display numbers, as in @code{2-4}.
9369 @code{undisplay} does not repeat if you press @key{RET} after using it.
9370 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9372 @kindex disable display
9373 @item disable display @var{dnums}@dots{}
9374 Disable the display of item numbers @var{dnums}. A disabled display
9375 item is not printed automatically, but is not forgotten. It may be
9376 enabled again later. Specify the numbers of the displays that you
9377 want affected with the command argument @var{dnums}. It can be a
9378 single display number, one of the numbers shown in the first field of
9379 the @samp{info display} display; or it could be a range of display
9380 numbers, as in @code{2-4}.
9382 @kindex enable display
9383 @item enable display @var{dnums}@dots{}
9384 Enable display of item numbers @var{dnums}. It becomes effective once
9385 again in auto display of its expression, until you specify otherwise.
9386 Specify the numbers of the displays that you want affected with the
9387 command argument @var{dnums}. It can be a single display number, one
9388 of the numbers shown in the first field of the @samp{info display}
9389 display; or it could be a range of display numbers, as in @code{2-4}.
9392 Display the current values of the expressions on the list, just as is
9393 done when your program stops.
9395 @kindex info display
9397 Print the list of expressions previously set up to display
9398 automatically, each one with its item number, but without showing the
9399 values. This includes disabled expressions, which are marked as such.
9400 It also includes expressions which would not be displayed right now
9401 because they refer to automatic variables not currently available.
9404 @cindex display disabled out of scope
9405 If a display expression refers to local variables, then it does not make
9406 sense outside the lexical context for which it was set up. Such an
9407 expression is disabled when execution enters a context where one of its
9408 variables is not defined. For example, if you give the command
9409 @code{display last_char} while inside a function with an argument
9410 @code{last_char}, @value{GDBN} displays this argument while your program
9411 continues to stop inside that function. When it stops elsewhere---where
9412 there is no variable @code{last_char}---the display is disabled
9413 automatically. The next time your program stops where @code{last_char}
9414 is meaningful, you can enable the display expression once again.
9416 @node Print Settings
9417 @section Print Settings
9419 @cindex format options
9420 @cindex print settings
9421 @value{GDBN} provides the following ways to control how arrays, structures,
9422 and symbols are printed.
9425 These settings are useful for debugging programs in any language:
9429 @item set print address
9430 @itemx set print address on
9431 @cindex print/don't print memory addresses
9432 @value{GDBN} prints memory addresses showing the location of stack
9433 traces, structure values, pointer values, breakpoints, and so forth,
9434 even when it also displays the contents of those addresses. The default
9435 is @code{on}. For example, this is what a stack frame display looks like with
9436 @code{set print address on}:
9441 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9443 530 if (lquote != def_lquote)
9447 @item set print address off
9448 Do not print addresses when displaying their contents. For example,
9449 this is the same stack frame displayed with @code{set print address off}:
9453 (@value{GDBP}) set print addr off
9455 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9456 530 if (lquote != def_lquote)
9460 You can use @samp{set print address off} to eliminate all machine
9461 dependent displays from the @value{GDBN} interface. For example, with
9462 @code{print address off}, you should get the same text for backtraces on
9463 all machines---whether or not they involve pointer arguments.
9466 @item show print address
9467 Show whether or not addresses are to be printed.
9470 When @value{GDBN} prints a symbolic address, it normally prints the
9471 closest earlier symbol plus an offset. If that symbol does not uniquely
9472 identify the address (for example, it is a name whose scope is a single
9473 source file), you may need to clarify. One way to do this is with
9474 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9475 you can set @value{GDBN} to print the source file and line number when
9476 it prints a symbolic address:
9479 @item set print symbol-filename on
9480 @cindex source file and line of a symbol
9481 @cindex symbol, source file and line
9482 Tell @value{GDBN} to print the source file name and line number of a
9483 symbol in the symbolic form of an address.
9485 @item set print symbol-filename off
9486 Do not print source file name and line number of a symbol. This is the
9489 @item show print symbol-filename
9490 Show whether or not @value{GDBN} will print the source file name and
9491 line number of a symbol in the symbolic form of an address.
9494 Another situation where it is helpful to show symbol filenames and line
9495 numbers is when disassembling code; @value{GDBN} shows you the line
9496 number and source file that corresponds to each instruction.
9498 Also, you may wish to see the symbolic form only if the address being
9499 printed is reasonably close to the closest earlier symbol:
9502 @item set print max-symbolic-offset @var{max-offset}
9503 @itemx set print max-symbolic-offset unlimited
9504 @cindex maximum value for offset of closest symbol
9505 Tell @value{GDBN} to only display the symbolic form of an address if the
9506 offset between the closest earlier symbol and the address is less than
9507 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9508 to always print the symbolic form of an address if any symbol precedes
9509 it. Zero is equivalent to @code{unlimited}.
9511 @item show print max-symbolic-offset
9512 Ask how large the maximum offset is that @value{GDBN} prints in a
9516 @cindex wild pointer, interpreting
9517 @cindex pointer, finding referent
9518 If you have a pointer and you are not sure where it points, try
9519 @samp{set print symbol-filename on}. Then you can determine the name
9520 and source file location of the variable where it points, using
9521 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9522 For example, here @value{GDBN} shows that a variable @code{ptt} points
9523 at another variable @code{t}, defined in @file{hi2.c}:
9526 (@value{GDBP}) set print symbol-filename on
9527 (@value{GDBP}) p/a ptt
9528 $4 = 0xe008 <t in hi2.c>
9532 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9533 does not show the symbol name and filename of the referent, even with
9534 the appropriate @code{set print} options turned on.
9537 You can also enable @samp{/a}-like formatting all the time using
9538 @samp{set print symbol on}:
9541 @item set print symbol on
9542 Tell @value{GDBN} to print the symbol corresponding to an address, if
9545 @item set print symbol off
9546 Tell @value{GDBN} not to print the symbol corresponding to an
9547 address. In this mode, @value{GDBN} will still print the symbol
9548 corresponding to pointers to functions. This is the default.
9550 @item show print symbol
9551 Show whether @value{GDBN} will display the symbol corresponding to an
9555 Other settings control how different kinds of objects are printed:
9558 @item set print array
9559 @itemx set print array on
9560 @cindex pretty print arrays
9561 Pretty print arrays. This format is more convenient to read,
9562 but uses more space. The default is off.
9564 @item set print array off
9565 Return to compressed format for arrays.
9567 @item show print array
9568 Show whether compressed or pretty format is selected for displaying
9571 @cindex print array indexes
9572 @item set print array-indexes
9573 @itemx set print array-indexes on
9574 Print the index of each element when displaying arrays. May be more
9575 convenient to locate a given element in the array or quickly find the
9576 index of a given element in that printed array. The default is off.
9578 @item set print array-indexes off
9579 Stop printing element indexes when displaying arrays.
9581 @item show print array-indexes
9582 Show whether the index of each element is printed when displaying
9585 @item set print elements @var{number-of-elements}
9586 @itemx set print elements unlimited
9587 @cindex number of array elements to print
9588 @cindex limit on number of printed array elements
9589 Set a limit on how many elements of an array @value{GDBN} will print.
9590 If @value{GDBN} is printing a large array, it stops printing after it has
9591 printed the number of elements set by the @code{set print elements} command.
9592 This limit also applies to the display of strings.
9593 When @value{GDBN} starts, this limit is set to 200.
9594 Setting @var{number-of-elements} to @code{unlimited} or zero means
9595 that the number of elements to print is unlimited.
9597 @item show print elements
9598 Display the number of elements of a large array that @value{GDBN} will print.
9599 If the number is 0, then the printing is unlimited.
9601 @item set print frame-arguments @var{value}
9602 @kindex set print frame-arguments
9603 @cindex printing frame argument values
9604 @cindex print all frame argument values
9605 @cindex print frame argument values for scalars only
9606 @cindex do not print frame argument values
9607 This command allows to control how the values of arguments are printed
9608 when the debugger prints a frame (@pxref{Frames}). The possible
9613 The values of all arguments are printed.
9616 Print the value of an argument only if it is a scalar. The value of more
9617 complex arguments such as arrays, structures, unions, etc, is replaced
9618 by @code{@dots{}}. This is the default. Here is an example where
9619 only scalar arguments are shown:
9622 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9627 None of the argument values are printed. Instead, the value of each argument
9628 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9631 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9636 By default, only scalar arguments are printed. This command can be used
9637 to configure the debugger to print the value of all arguments, regardless
9638 of their type. However, it is often advantageous to not print the value
9639 of more complex parameters. For instance, it reduces the amount of
9640 information printed in each frame, making the backtrace more readable.
9641 Also, it improves performance when displaying Ada frames, because
9642 the computation of large arguments can sometimes be CPU-intensive,
9643 especially in large applications. Setting @code{print frame-arguments}
9644 to @code{scalars} (the default) or @code{none} avoids this computation,
9645 thus speeding up the display of each Ada frame.
9647 @item show print frame-arguments
9648 Show how the value of arguments should be displayed when printing a frame.
9650 @item set print raw frame-arguments on
9651 Print frame arguments in raw, non pretty-printed, form.
9653 @item set print raw frame-arguments off
9654 Print frame arguments in pretty-printed form, if there is a pretty-printer
9655 for the value (@pxref{Pretty Printing}),
9656 otherwise print the value in raw form.
9657 This is the default.
9659 @item show print raw frame-arguments
9660 Show whether to print frame arguments in raw form.
9662 @anchor{set print entry-values}
9663 @item set print entry-values @var{value}
9664 @kindex set print entry-values
9665 Set printing of frame argument values at function entry. In some cases
9666 @value{GDBN} can determine the value of function argument which was passed by
9667 the function caller, even if the value was modified inside the called function
9668 and therefore is different. With optimized code, the current value could be
9669 unavailable, but the entry value may still be known.
9671 The default value is @code{default} (see below for its description). Older
9672 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9673 this feature will behave in the @code{default} setting the same way as with the
9676 This functionality is currently supported only by DWARF 2 debugging format and
9677 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9678 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9681 The @var{value} parameter can be one of the following:
9685 Print only actual parameter values, never print values from function entry
9689 #0 different (val=6)
9690 #0 lost (val=<optimized out>)
9692 #0 invalid (val=<optimized out>)
9696 Print only parameter values from function entry point. The actual parameter
9697 values are never printed.
9699 #0 equal (val@@entry=5)
9700 #0 different (val@@entry=5)
9701 #0 lost (val@@entry=5)
9702 #0 born (val@@entry=<optimized out>)
9703 #0 invalid (val@@entry=<optimized out>)
9707 Print only parameter values from function entry point. If value from function
9708 entry point is not known while the actual value is known, print the actual
9709 value for such parameter.
9711 #0 equal (val@@entry=5)
9712 #0 different (val@@entry=5)
9713 #0 lost (val@@entry=5)
9715 #0 invalid (val@@entry=<optimized out>)
9719 Print actual parameter values. If actual parameter value is not known while
9720 value from function entry point is known, print the entry point value for such
9724 #0 different (val=6)
9725 #0 lost (val@@entry=5)
9727 #0 invalid (val=<optimized out>)
9731 Always print both the actual parameter value and its value from function entry
9732 point, even if values of one or both are not available due to compiler
9735 #0 equal (val=5, val@@entry=5)
9736 #0 different (val=6, val@@entry=5)
9737 #0 lost (val=<optimized out>, val@@entry=5)
9738 #0 born (val=10, val@@entry=<optimized out>)
9739 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9743 Print the actual parameter value if it is known and also its value from
9744 function entry point if it is known. If neither is known, print for the actual
9745 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9746 values are known and identical, print the shortened
9747 @code{param=param@@entry=VALUE} notation.
9749 #0 equal (val=val@@entry=5)
9750 #0 different (val=6, val@@entry=5)
9751 #0 lost (val@@entry=5)
9753 #0 invalid (val=<optimized out>)
9757 Always print the actual parameter value. Print also its value from function
9758 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9759 if both values are known and identical, print the shortened
9760 @code{param=param@@entry=VALUE} notation.
9762 #0 equal (val=val@@entry=5)
9763 #0 different (val=6, val@@entry=5)
9764 #0 lost (val=<optimized out>, val@@entry=5)
9766 #0 invalid (val=<optimized out>)
9770 For analysis messages on possible failures of frame argument values at function
9771 entry resolution see @ref{set debug entry-values}.
9773 @item show print entry-values
9774 Show the method being used for printing of frame argument values at function
9777 @item set print repeats @var{number-of-repeats}
9778 @itemx set print repeats unlimited
9779 @cindex repeated array elements
9780 Set the threshold for suppressing display of repeated array
9781 elements. When the number of consecutive identical elements of an
9782 array exceeds the threshold, @value{GDBN} prints the string
9783 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9784 identical repetitions, instead of displaying the identical elements
9785 themselves. Setting the threshold to @code{unlimited} or zero will
9786 cause all elements to be individually printed. The default threshold
9789 @item show print repeats
9790 Display the current threshold for printing repeated identical
9793 @item set print null-stop
9794 @cindex @sc{null} elements in arrays
9795 Cause @value{GDBN} to stop printing the characters of an array when the first
9796 @sc{null} is encountered. This is useful when large arrays actually
9797 contain only short strings.
9800 @item show print null-stop
9801 Show whether @value{GDBN} stops printing an array on the first
9802 @sc{null} character.
9804 @item set print pretty on
9805 @cindex print structures in indented form
9806 @cindex indentation in structure display
9807 Cause @value{GDBN} to print structures in an indented format with one member
9808 per line, like this:
9823 @item set print pretty off
9824 Cause @value{GDBN} to print structures in a compact format, like this:
9828 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9829 meat = 0x54 "Pork"@}
9834 This is the default format.
9836 @item show print pretty
9837 Show which format @value{GDBN} is using to print structures.
9839 @item set print sevenbit-strings on
9840 @cindex eight-bit characters in strings
9841 @cindex octal escapes in strings
9842 Print using only seven-bit characters; if this option is set,
9843 @value{GDBN} displays any eight-bit characters (in strings or
9844 character values) using the notation @code{\}@var{nnn}. This setting is
9845 best if you are working in English (@sc{ascii}) and you use the
9846 high-order bit of characters as a marker or ``meta'' bit.
9848 @item set print sevenbit-strings off
9849 Print full eight-bit characters. This allows the use of more
9850 international character sets, and is the default.
9852 @item show print sevenbit-strings
9853 Show whether or not @value{GDBN} is printing only seven-bit characters.
9855 @item set print union on
9856 @cindex unions in structures, printing
9857 Tell @value{GDBN} to print unions which are contained in structures
9858 and other unions. This is the default setting.
9860 @item set print union off
9861 Tell @value{GDBN} not to print unions which are contained in
9862 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9865 @item show print union
9866 Ask @value{GDBN} whether or not it will print unions which are contained in
9867 structures and other unions.
9869 For example, given the declarations
9872 typedef enum @{Tree, Bug@} Species;
9873 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9874 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9885 struct thing foo = @{Tree, @{Acorn@}@};
9889 with @code{set print union on} in effect @samp{p foo} would print
9892 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9896 and with @code{set print union off} in effect it would print
9899 $1 = @{it = Tree, form = @{...@}@}
9903 @code{set print union} affects programs written in C-like languages
9909 These settings are of interest when debugging C@t{++} programs:
9912 @cindex demangling C@t{++} names
9913 @item set print demangle
9914 @itemx set print demangle on
9915 Print C@t{++} names in their source form rather than in the encoded
9916 (``mangled'') form passed to the assembler and linker for type-safe
9917 linkage. The default is on.
9919 @item show print demangle
9920 Show whether C@t{++} names are printed in mangled or demangled form.
9922 @item set print asm-demangle
9923 @itemx set print asm-demangle on
9924 Print C@t{++} names in their source form rather than their mangled form, even
9925 in assembler code printouts such as instruction disassemblies.
9928 @item show print asm-demangle
9929 Show whether C@t{++} names in assembly listings are printed in mangled
9932 @cindex C@t{++} symbol decoding style
9933 @cindex symbol decoding style, C@t{++}
9934 @kindex set demangle-style
9935 @item set demangle-style @var{style}
9936 Choose among several encoding schemes used by different compilers to
9937 represent C@t{++} names. The choices for @var{style} are currently:
9941 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9942 This is the default.
9945 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9948 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9951 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9954 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9955 @strong{Warning:} this setting alone is not sufficient to allow
9956 debugging @code{cfront}-generated executables. @value{GDBN} would
9957 require further enhancement to permit that.
9960 If you omit @var{style}, you will see a list of possible formats.
9962 @item show demangle-style
9963 Display the encoding style currently in use for decoding C@t{++} symbols.
9965 @item set print object
9966 @itemx set print object on
9967 @cindex derived type of an object, printing
9968 @cindex display derived types
9969 When displaying a pointer to an object, identify the @emph{actual}
9970 (derived) type of the object rather than the @emph{declared} type, using
9971 the virtual function table. Note that the virtual function table is
9972 required---this feature can only work for objects that have run-time
9973 type identification; a single virtual method in the object's declared
9974 type is sufficient. Note that this setting is also taken into account when
9975 working with variable objects via MI (@pxref{GDB/MI}).
9977 @item set print object off
9978 Display only the declared type of objects, without reference to the
9979 virtual function table. This is the default setting.
9981 @item show print object
9982 Show whether actual, or declared, object types are displayed.
9984 @item set print static-members
9985 @itemx set print static-members on
9986 @cindex static members of C@t{++} objects
9987 Print static members when displaying a C@t{++} object. The default is on.
9989 @item set print static-members off
9990 Do not print static members when displaying a C@t{++} object.
9992 @item show print static-members
9993 Show whether C@t{++} static members are printed or not.
9995 @item set print pascal_static-members
9996 @itemx set print pascal_static-members on
9997 @cindex static members of Pascal objects
9998 @cindex Pascal objects, static members display
9999 Print static members when displaying a Pascal object. The default is on.
10001 @item set print pascal_static-members off
10002 Do not print static members when displaying a Pascal object.
10004 @item show print pascal_static-members
10005 Show whether Pascal static members are printed or not.
10007 @c These don't work with HP ANSI C++ yet.
10008 @item set print vtbl
10009 @itemx set print vtbl on
10010 @cindex pretty print C@t{++} virtual function tables
10011 @cindex virtual functions (C@t{++}) display
10012 @cindex VTBL display
10013 Pretty print C@t{++} virtual function tables. The default is off.
10014 (The @code{vtbl} commands do not work on programs compiled with the HP
10015 ANSI C@t{++} compiler (@code{aCC}).)
10017 @item set print vtbl off
10018 Do not pretty print C@t{++} virtual function tables.
10020 @item show print vtbl
10021 Show whether C@t{++} virtual function tables are pretty printed, or not.
10024 @node Pretty Printing
10025 @section Pretty Printing
10027 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10028 Python code. It greatly simplifies the display of complex objects. This
10029 mechanism works for both MI and the CLI.
10032 * Pretty-Printer Introduction:: Introduction to pretty-printers
10033 * Pretty-Printer Example:: An example pretty-printer
10034 * Pretty-Printer Commands:: Pretty-printer commands
10037 @node Pretty-Printer Introduction
10038 @subsection Pretty-Printer Introduction
10040 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10041 registered for the value. If there is then @value{GDBN} invokes the
10042 pretty-printer to print the value. Otherwise the value is printed normally.
10044 Pretty-printers are normally named. This makes them easy to manage.
10045 The @samp{info pretty-printer} command will list all the installed
10046 pretty-printers with their names.
10047 If a pretty-printer can handle multiple data types, then its
10048 @dfn{subprinters} are the printers for the individual data types.
10049 Each such subprinter has its own name.
10050 The format of the name is @var{printer-name};@var{subprinter-name}.
10052 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10053 Typically they are automatically loaded and registered when the corresponding
10054 debug information is loaded, thus making them available without having to
10055 do anything special.
10057 There are three places where a pretty-printer can be registered.
10061 Pretty-printers registered globally are available when debugging
10065 Pretty-printers registered with a program space are available only
10066 when debugging that program.
10067 @xref{Progspaces In Python}, for more details on program spaces in Python.
10070 Pretty-printers registered with an objfile are loaded and unloaded
10071 with the corresponding objfile (e.g., shared library).
10072 @xref{Objfiles In Python}, for more details on objfiles in Python.
10075 @xref{Selecting Pretty-Printers}, for further information on how
10076 pretty-printers are selected,
10078 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10081 @node Pretty-Printer Example
10082 @subsection Pretty-Printer Example
10084 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10087 (@value{GDBP}) print s
10089 static npos = 4294967295,
10091 <std::allocator<char>> = @{
10092 <__gnu_cxx::new_allocator<char>> = @{
10093 <No data fields>@}, <No data fields>
10095 members of std::basic_string<char, std::char_traits<char>,
10096 std::allocator<char> >::_Alloc_hider:
10097 _M_p = 0x804a014 "abcd"
10102 With a pretty-printer for @code{std::string} only the contents are printed:
10105 (@value{GDBP}) print s
10109 @node Pretty-Printer Commands
10110 @subsection Pretty-Printer Commands
10111 @cindex pretty-printer commands
10114 @kindex info pretty-printer
10115 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10116 Print the list of installed pretty-printers.
10117 This includes disabled pretty-printers, which are marked as such.
10119 @var{object-regexp} is a regular expression matching the objects
10120 whose pretty-printers to list.
10121 Objects can be @code{global}, the program space's file
10122 (@pxref{Progspaces In Python}),
10123 and the object files within that program space (@pxref{Objfiles In Python}).
10124 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10125 looks up a printer from these three objects.
10127 @var{name-regexp} is a regular expression matching the name of the printers
10130 @kindex disable pretty-printer
10131 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10132 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10133 A disabled pretty-printer is not forgotten, it may be enabled again later.
10135 @kindex enable pretty-printer
10136 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10137 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10142 Suppose we have three pretty-printers installed: one from library1.so
10143 named @code{foo} that prints objects of type @code{foo}, and
10144 another from library2.so named @code{bar} that prints two types of objects,
10145 @code{bar1} and @code{bar2}.
10148 (gdb) info pretty-printer
10155 (gdb) info pretty-printer library2
10160 (gdb) disable pretty-printer library1
10162 2 of 3 printers enabled
10163 (gdb) info pretty-printer
10170 (gdb) disable pretty-printer library2 bar:bar1
10172 1 of 3 printers enabled
10173 (gdb) info pretty-printer library2
10180 (gdb) disable pretty-printer library2 bar
10182 0 of 3 printers enabled
10183 (gdb) info pretty-printer library2
10192 Note that for @code{bar} the entire printer can be disabled,
10193 as can each individual subprinter.
10195 @node Value History
10196 @section Value History
10198 @cindex value history
10199 @cindex history of values printed by @value{GDBN}
10200 Values printed by the @code{print} command are saved in the @value{GDBN}
10201 @dfn{value history}. This allows you to refer to them in other expressions.
10202 Values are kept until the symbol table is re-read or discarded
10203 (for example with the @code{file} or @code{symbol-file} commands).
10204 When the symbol table changes, the value history is discarded,
10205 since the values may contain pointers back to the types defined in the
10210 @cindex history number
10211 The values printed are given @dfn{history numbers} by which you can
10212 refer to them. These are successive integers starting with one.
10213 @code{print} shows you the history number assigned to a value by
10214 printing @samp{$@var{num} = } before the value; here @var{num} is the
10217 To refer to any previous value, use @samp{$} followed by the value's
10218 history number. The way @code{print} labels its output is designed to
10219 remind you of this. Just @code{$} refers to the most recent value in
10220 the history, and @code{$$} refers to the value before that.
10221 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10222 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10223 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10225 For example, suppose you have just printed a pointer to a structure and
10226 want to see the contents of the structure. It suffices to type
10232 If you have a chain of structures where the component @code{next} points
10233 to the next one, you can print the contents of the next one with this:
10240 You can print successive links in the chain by repeating this
10241 command---which you can do by just typing @key{RET}.
10243 Note that the history records values, not expressions. If the value of
10244 @code{x} is 4 and you type these commands:
10252 then the value recorded in the value history by the @code{print} command
10253 remains 4 even though the value of @code{x} has changed.
10256 @kindex show values
10258 Print the last ten values in the value history, with their item numbers.
10259 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10260 values} does not change the history.
10262 @item show values @var{n}
10263 Print ten history values centered on history item number @var{n}.
10265 @item show values +
10266 Print ten history values just after the values last printed. If no more
10267 values are available, @code{show values +} produces no display.
10270 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10271 same effect as @samp{show values +}.
10273 @node Convenience Vars
10274 @section Convenience Variables
10276 @cindex convenience variables
10277 @cindex user-defined variables
10278 @value{GDBN} provides @dfn{convenience variables} that you can use within
10279 @value{GDBN} to hold on to a value and refer to it later. These variables
10280 exist entirely within @value{GDBN}; they are not part of your program, and
10281 setting a convenience variable has no direct effect on further execution
10282 of your program. That is why you can use them freely.
10284 Convenience variables are prefixed with @samp{$}. Any name preceded by
10285 @samp{$} can be used for a convenience variable, unless it is one of
10286 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10287 (Value history references, in contrast, are @emph{numbers} preceded
10288 by @samp{$}. @xref{Value History, ,Value History}.)
10290 You can save a value in a convenience variable with an assignment
10291 expression, just as you would set a variable in your program.
10295 set $foo = *object_ptr
10299 would save in @code{$foo} the value contained in the object pointed to by
10302 Using a convenience variable for the first time creates it, but its
10303 value is @code{void} until you assign a new value. You can alter the
10304 value with another assignment at any time.
10306 Convenience variables have no fixed types. You can assign a convenience
10307 variable any type of value, including structures and arrays, even if
10308 that variable already has a value of a different type. The convenience
10309 variable, when used as an expression, has the type of its current value.
10312 @kindex show convenience
10313 @cindex show all user variables and functions
10314 @item show convenience
10315 Print a list of convenience variables used so far, and their values,
10316 as well as a list of the convenience functions.
10317 Abbreviated @code{show conv}.
10319 @kindex init-if-undefined
10320 @cindex convenience variables, initializing
10321 @item init-if-undefined $@var{variable} = @var{expression}
10322 Set a convenience variable if it has not already been set. This is useful
10323 for user-defined commands that keep some state. It is similar, in concept,
10324 to using local static variables with initializers in C (except that
10325 convenience variables are global). It can also be used to allow users to
10326 override default values used in a command script.
10328 If the variable is already defined then the expression is not evaluated so
10329 any side-effects do not occur.
10332 One of the ways to use a convenience variable is as a counter to be
10333 incremented or a pointer to be advanced. For example, to print
10334 a field from successive elements of an array of structures:
10338 print bar[$i++]->contents
10342 Repeat that command by typing @key{RET}.
10344 Some convenience variables are created automatically by @value{GDBN} and given
10345 values likely to be useful.
10348 @vindex $_@r{, convenience variable}
10350 The variable @code{$_} is automatically set by the @code{x} command to
10351 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10352 commands which provide a default address for @code{x} to examine also
10353 set @code{$_} to that address; these commands include @code{info line}
10354 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10355 except when set by the @code{x} command, in which case it is a pointer
10356 to the type of @code{$__}.
10358 @vindex $__@r{, convenience variable}
10360 The variable @code{$__} is automatically set by the @code{x} command
10361 to the value found in the last address examined. Its type is chosen
10362 to match the format in which the data was printed.
10365 @vindex $_exitcode@r{, convenience variable}
10366 When the program being debugged terminates normally, @value{GDBN}
10367 automatically sets this variable to the exit code of the program, and
10368 resets @code{$_exitsignal} to @code{void}.
10371 @vindex $_exitsignal@r{, convenience variable}
10372 When the program being debugged dies due to an uncaught signal,
10373 @value{GDBN} automatically sets this variable to that signal's number,
10374 and resets @code{$_exitcode} to @code{void}.
10376 To distinguish between whether the program being debugged has exited
10377 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10378 @code{$_exitsignal} is not @code{void}), the convenience function
10379 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10380 Functions}). For example, considering the following source code:
10383 #include <signal.h>
10386 main (int argc, char *argv[])
10393 A valid way of telling whether the program being debugged has exited
10394 or signalled would be:
10397 (@value{GDBP}) define has_exited_or_signalled
10398 Type commands for definition of ``has_exited_or_signalled''.
10399 End with a line saying just ``end''.
10400 >if $_isvoid ($_exitsignal)
10401 >echo The program has exited\n
10403 >echo The program has signalled\n
10409 Program terminated with signal SIGALRM, Alarm clock.
10410 The program no longer exists.
10411 (@value{GDBP}) has_exited_or_signalled
10412 The program has signalled
10415 As can be seen, @value{GDBN} correctly informs that the program being
10416 debugged has signalled, since it calls @code{raise} and raises a
10417 @code{SIGALRM} signal. If the program being debugged had not called
10418 @code{raise}, then @value{GDBN} would report a normal exit:
10421 (@value{GDBP}) has_exited_or_signalled
10422 The program has exited
10426 The variable @code{$_exception} is set to the exception object being
10427 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10430 @itemx $_probe_arg0@dots{}$_probe_arg11
10431 Arguments to a static probe. @xref{Static Probe Points}.
10434 @vindex $_sdata@r{, inspect, convenience variable}
10435 The variable @code{$_sdata} contains extra collected static tracepoint
10436 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10437 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10438 if extra static tracepoint data has not been collected.
10441 @vindex $_siginfo@r{, convenience variable}
10442 The variable @code{$_siginfo} contains extra signal information
10443 (@pxref{extra signal information}). Note that @code{$_siginfo}
10444 could be empty, if the application has not yet received any signals.
10445 For example, it will be empty before you execute the @code{run} command.
10448 @vindex $_tlb@r{, convenience variable}
10449 The variable @code{$_tlb} is automatically set when debugging
10450 applications running on MS-Windows in native mode or connected to
10451 gdbserver that supports the @code{qGetTIBAddr} request.
10452 @xref{General Query Packets}.
10453 This variable contains the address of the thread information block.
10456 The number of the current inferior. @xref{Inferiors and
10457 Programs, ,Debugging Multiple Inferiors and Programs}.
10460 The thread number of the current thread. @xref{thread numbers}.
10464 @node Convenience Funs
10465 @section Convenience Functions
10467 @cindex convenience functions
10468 @value{GDBN} also supplies some @dfn{convenience functions}. These
10469 have a syntax similar to convenience variables. A convenience
10470 function can be used in an expression just like an ordinary function;
10471 however, a convenience function is implemented internally to
10474 These functions do not require @value{GDBN} to be configured with
10475 @code{Python} support, which means that they are always available.
10479 @item $_isvoid (@var{expr})
10480 @findex $_isvoid@r{, convenience function}
10481 Return one if the expression @var{expr} is @code{void}. Otherwise it
10484 A @code{void} expression is an expression where the type of the result
10485 is @code{void}. For example, you can examine a convenience variable
10486 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10490 (@value{GDBP}) print $_exitcode
10492 (@value{GDBP}) print $_isvoid ($_exitcode)
10495 Starting program: ./a.out
10496 [Inferior 1 (process 29572) exited normally]
10497 (@value{GDBP}) print $_exitcode
10499 (@value{GDBP}) print $_isvoid ($_exitcode)
10503 In the example above, we used @code{$_isvoid} to check whether
10504 @code{$_exitcode} is @code{void} before and after the execution of the
10505 program being debugged. Before the execution there is no exit code to
10506 be examined, therefore @code{$_exitcode} is @code{void}. After the
10507 execution the program being debugged returned zero, therefore
10508 @code{$_exitcode} is zero, which means that it is not @code{void}
10511 The @code{void} expression can also be a call of a function from the
10512 program being debugged. For example, given the following function:
10521 The result of calling it inside @value{GDBN} is @code{void}:
10524 (@value{GDBP}) print foo ()
10526 (@value{GDBP}) print $_isvoid (foo ())
10528 (@value{GDBP}) set $v = foo ()
10529 (@value{GDBP}) print $v
10531 (@value{GDBP}) print $_isvoid ($v)
10537 These functions require @value{GDBN} to be configured with
10538 @code{Python} support.
10542 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10543 @findex $_memeq@r{, convenience function}
10544 Returns one if the @var{length} bytes at the addresses given by
10545 @var{buf1} and @var{buf2} are equal.
10546 Otherwise it returns zero.
10548 @item $_regex(@var{str}, @var{regex})
10549 @findex $_regex@r{, convenience function}
10550 Returns one if the string @var{str} matches the regular expression
10551 @var{regex}. Otherwise it returns zero.
10552 The syntax of the regular expression is that specified by @code{Python}'s
10553 regular expression support.
10555 @item $_streq(@var{str1}, @var{str2})
10556 @findex $_streq@r{, convenience function}
10557 Returns one if the strings @var{str1} and @var{str2} are equal.
10558 Otherwise it returns zero.
10560 @item $_strlen(@var{str})
10561 @findex $_strlen@r{, convenience function}
10562 Returns the length of string @var{str}.
10564 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10565 @findex $_caller_is@r{, convenience function}
10566 Returns one if the calling function's name is equal to @var{name}.
10567 Otherwise it returns zero.
10569 If the optional argument @var{number_of_frames} is provided,
10570 it is the number of frames up in the stack to look.
10578 at testsuite/gdb.python/py-caller-is.c:21
10579 #1 0x00000000004005a0 in middle_func ()
10580 at testsuite/gdb.python/py-caller-is.c:27
10581 #2 0x00000000004005ab in top_func ()
10582 at testsuite/gdb.python/py-caller-is.c:33
10583 #3 0x00000000004005b6 in main ()
10584 at testsuite/gdb.python/py-caller-is.c:39
10585 (gdb) print $_caller_is ("middle_func")
10587 (gdb) print $_caller_is ("top_func", 2)
10591 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10592 @findex $_caller_matches@r{, convenience function}
10593 Returns one if the calling function's name matches the regular expression
10594 @var{regexp}. Otherwise it returns zero.
10596 If the optional argument @var{number_of_frames} is provided,
10597 it is the number of frames up in the stack to look.
10600 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10601 @findex $_any_caller_is@r{, convenience function}
10602 Returns one if any calling function's name is equal to @var{name}.
10603 Otherwise it returns zero.
10605 If the optional argument @var{number_of_frames} is provided,
10606 it is the number of frames up in the stack to look.
10609 This function differs from @code{$_caller_is} in that this function
10610 checks all stack frames from the immediate caller to the frame specified
10611 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10612 frame specified by @var{number_of_frames}.
10614 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10615 @findex $_any_caller_matches@r{, convenience function}
10616 Returns one if any calling function's name matches the regular expression
10617 @var{regexp}. Otherwise it returns zero.
10619 If the optional argument @var{number_of_frames} is provided,
10620 it is the number of frames up in the stack to look.
10623 This function differs from @code{$_caller_matches} in that this function
10624 checks all stack frames from the immediate caller to the frame specified
10625 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10626 frame specified by @var{number_of_frames}.
10630 @value{GDBN} provides the ability to list and get help on
10631 convenience functions.
10634 @item help function
10635 @kindex help function
10636 @cindex show all convenience functions
10637 Print a list of all convenience functions.
10644 You can refer to machine register contents, in expressions, as variables
10645 with names starting with @samp{$}. The names of registers are different
10646 for each machine; use @code{info registers} to see the names used on
10650 @kindex info registers
10651 @item info registers
10652 Print the names and values of all registers except floating-point
10653 and vector registers (in the selected stack frame).
10655 @kindex info all-registers
10656 @cindex floating point registers
10657 @item info all-registers
10658 Print the names and values of all registers, including floating-point
10659 and vector registers (in the selected stack frame).
10661 @item info registers @var{regname} @dots{}
10662 Print the @dfn{relativized} value of each specified register @var{regname}.
10663 As discussed in detail below, register values are normally relative to
10664 the selected stack frame. The @var{regname} may be any register name valid on
10665 the machine you are using, with or without the initial @samp{$}.
10668 @anchor{standard registers}
10669 @cindex stack pointer register
10670 @cindex program counter register
10671 @cindex process status register
10672 @cindex frame pointer register
10673 @cindex standard registers
10674 @value{GDBN} has four ``standard'' register names that are available (in
10675 expressions) on most machines---whenever they do not conflict with an
10676 architecture's canonical mnemonics for registers. The register names
10677 @code{$pc} and @code{$sp} are used for the program counter register and
10678 the stack pointer. @code{$fp} is used for a register that contains a
10679 pointer to the current stack frame, and @code{$ps} is used for a
10680 register that contains the processor status. For example,
10681 you could print the program counter in hex with
10688 or print the instruction to be executed next with
10695 or add four to the stack pointer@footnote{This is a way of removing
10696 one word from the stack, on machines where stacks grow downward in
10697 memory (most machines, nowadays). This assumes that the innermost
10698 stack frame is selected; setting @code{$sp} is not allowed when other
10699 stack frames are selected. To pop entire frames off the stack,
10700 regardless of machine architecture, use @code{return};
10701 see @ref{Returning, ,Returning from a Function}.} with
10707 Whenever possible, these four standard register names are available on
10708 your machine even though the machine has different canonical mnemonics,
10709 so long as there is no conflict. The @code{info registers} command
10710 shows the canonical names. For example, on the SPARC, @code{info
10711 registers} displays the processor status register as @code{$psr} but you
10712 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10713 is an alias for the @sc{eflags} register.
10715 @value{GDBN} always considers the contents of an ordinary register as an
10716 integer when the register is examined in this way. Some machines have
10717 special registers which can hold nothing but floating point; these
10718 registers are considered to have floating point values. There is no way
10719 to refer to the contents of an ordinary register as floating point value
10720 (although you can @emph{print} it as a floating point value with
10721 @samp{print/f $@var{regname}}).
10723 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10724 means that the data format in which the register contents are saved by
10725 the operating system is not the same one that your program normally
10726 sees. For example, the registers of the 68881 floating point
10727 coprocessor are always saved in ``extended'' (raw) format, but all C
10728 programs expect to work with ``double'' (virtual) format. In such
10729 cases, @value{GDBN} normally works with the virtual format only (the format
10730 that makes sense for your program), but the @code{info registers} command
10731 prints the data in both formats.
10733 @cindex SSE registers (x86)
10734 @cindex MMX registers (x86)
10735 Some machines have special registers whose contents can be interpreted
10736 in several different ways. For example, modern x86-based machines
10737 have SSE and MMX registers that can hold several values packed
10738 together in several different formats. @value{GDBN} refers to such
10739 registers in @code{struct} notation:
10742 (@value{GDBP}) print $xmm1
10744 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10745 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10746 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10747 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10748 v4_int32 = @{0, 20657912, 11, 13@},
10749 v2_int64 = @{88725056443645952, 55834574859@},
10750 uint128 = 0x0000000d0000000b013b36f800000000
10755 To set values of such registers, you need to tell @value{GDBN} which
10756 view of the register you wish to change, as if you were assigning
10757 value to a @code{struct} member:
10760 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10763 Normally, register values are relative to the selected stack frame
10764 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10765 value that the register would contain if all stack frames farther in
10766 were exited and their saved registers restored. In order to see the
10767 true contents of hardware registers, you must select the innermost
10768 frame (with @samp{frame 0}).
10770 @cindex caller-saved registers
10771 @cindex call-clobbered registers
10772 @cindex volatile registers
10773 @cindex <not saved> values
10774 Usually ABIs reserve some registers as not needed to be saved by the
10775 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10776 registers). It may therefore not be possible for @value{GDBN} to know
10777 the value a register had before the call (in other words, in the outer
10778 frame), if the register value has since been changed by the callee.
10779 @value{GDBN} tries to deduce where the inner frame saved
10780 (``callee-saved'') registers, from the debug info, unwind info, or the
10781 machine code generated by your compiler. If some register is not
10782 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10783 its own knowledge of the ABI, or because the debug/unwind info
10784 explicitly says the register's value is undefined), @value{GDBN}
10785 displays @w{@samp{<not saved>}} as the register's value. With targets
10786 that @value{GDBN} has no knowledge of the register saving convention,
10787 if a register was not saved by the callee, then its value and location
10788 in the outer frame are assumed to be the same of the inner frame.
10789 This is usually harmless, because if the register is call-clobbered,
10790 the caller either does not care what is in the register after the
10791 call, or has code to restore the value that it does care about. Note,
10792 however, that if you change such a register in the outer frame, you
10793 may also be affecting the inner frame. Also, the more ``outer'' the
10794 frame is you're looking at, the more likely a call-clobbered
10795 register's value is to be wrong, in the sense that it doesn't actually
10796 represent the value the register had just before the call.
10798 @node Floating Point Hardware
10799 @section Floating Point Hardware
10800 @cindex floating point
10802 Depending on the configuration, @value{GDBN} may be able to give
10803 you more information about the status of the floating point hardware.
10808 Display hardware-dependent information about the floating
10809 point unit. The exact contents and layout vary depending on the
10810 floating point chip. Currently, @samp{info float} is supported on
10811 the ARM and x86 machines.
10815 @section Vector Unit
10816 @cindex vector unit
10818 Depending on the configuration, @value{GDBN} may be able to give you
10819 more information about the status of the vector unit.
10822 @kindex info vector
10824 Display information about the vector unit. The exact contents and
10825 layout vary depending on the hardware.
10828 @node OS Information
10829 @section Operating System Auxiliary Information
10830 @cindex OS information
10832 @value{GDBN} provides interfaces to useful OS facilities that can help
10833 you debug your program.
10835 @cindex auxiliary vector
10836 @cindex vector, auxiliary
10837 Some operating systems supply an @dfn{auxiliary vector} to programs at
10838 startup. This is akin to the arguments and environment that you
10839 specify for a program, but contains a system-dependent variety of
10840 binary values that tell system libraries important details about the
10841 hardware, operating system, and process. Each value's purpose is
10842 identified by an integer tag; the meanings are well-known but system-specific.
10843 Depending on the configuration and operating system facilities,
10844 @value{GDBN} may be able to show you this information. For remote
10845 targets, this functionality may further depend on the remote stub's
10846 support of the @samp{qXfer:auxv:read} packet, see
10847 @ref{qXfer auxiliary vector read}.
10852 Display the auxiliary vector of the inferior, which can be either a
10853 live process or a core dump file. @value{GDBN} prints each tag value
10854 numerically, and also shows names and text descriptions for recognized
10855 tags. Some values in the vector are numbers, some bit masks, and some
10856 pointers to strings or other data. @value{GDBN} displays each value in the
10857 most appropriate form for a recognized tag, and in hexadecimal for
10858 an unrecognized tag.
10861 On some targets, @value{GDBN} can access operating system-specific
10862 information and show it to you. The types of information available
10863 will differ depending on the type of operating system running on the
10864 target. The mechanism used to fetch the data is described in
10865 @ref{Operating System Information}. For remote targets, this
10866 functionality depends on the remote stub's support of the
10867 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10871 @item info os @var{infotype}
10873 Display OS information of the requested type.
10875 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10877 @anchor{linux info os infotypes}
10879 @kindex info os cpus
10881 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10882 the available fields from /proc/cpuinfo. For each supported architecture
10883 different fields are available. Two common entries are processor which gives
10884 CPU number and bogomips; a system constant that is calculated during
10885 kernel initialization.
10887 @kindex info os files
10889 Display the list of open file descriptors on the target. For each
10890 file descriptor, @value{GDBN} prints the identifier of the process
10891 owning the descriptor, the command of the owning process, the value
10892 of the descriptor, and the target of the descriptor.
10894 @kindex info os modules
10896 Display the list of all loaded kernel modules on the target. For each
10897 module, @value{GDBN} prints the module name, the size of the module in
10898 bytes, the number of times the module is used, the dependencies of the
10899 module, the status of the module, and the address of the loaded module
10902 @kindex info os msg
10904 Display the list of all System V message queues on the target. For each
10905 message queue, @value{GDBN} prints the message queue key, the message
10906 queue identifier, the access permissions, the current number of bytes
10907 on the queue, the current number of messages on the queue, the processes
10908 that last sent and received a message on the queue, the user and group
10909 of the owner and creator of the message queue, the times at which a
10910 message was last sent and received on the queue, and the time at which
10911 the message queue was last changed.
10913 @kindex info os processes
10915 Display the list of processes on the target. For each process,
10916 @value{GDBN} prints the process identifier, the name of the user, the
10917 command corresponding to the process, and the list of processor cores
10918 that the process is currently running on. (To understand what these
10919 properties mean, for this and the following info types, please consult
10920 the general @sc{gnu}/Linux documentation.)
10922 @kindex info os procgroups
10924 Display the list of process groups on the target. For each process,
10925 @value{GDBN} prints the identifier of the process group that it belongs
10926 to, the command corresponding to the process group leader, the process
10927 identifier, and the command line of the process. The list is sorted
10928 first by the process group identifier, then by the process identifier,
10929 so that processes belonging to the same process group are grouped together
10930 and the process group leader is listed first.
10932 @kindex info os semaphores
10934 Display the list of all System V semaphore sets on the target. For each
10935 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10936 set identifier, the access permissions, the number of semaphores in the
10937 set, the user and group of the owner and creator of the semaphore set,
10938 and the times at which the semaphore set was operated upon and changed.
10940 @kindex info os shm
10942 Display the list of all System V shared-memory regions on the target.
10943 For each shared-memory region, @value{GDBN} prints the region key,
10944 the shared-memory identifier, the access permissions, the size of the
10945 region, the process that created the region, the process that last
10946 attached to or detached from the region, the current number of live
10947 attaches to the region, and the times at which the region was last
10948 attached to, detach from, and changed.
10950 @kindex info os sockets
10952 Display the list of Internet-domain sockets on the target. For each
10953 socket, @value{GDBN} prints the address and port of the local and
10954 remote endpoints, the current state of the connection, the creator of
10955 the socket, the IP address family of the socket, and the type of the
10958 @kindex info os threads
10960 Display the list of threads running on the target. For each thread,
10961 @value{GDBN} prints the identifier of the process that the thread
10962 belongs to, the command of the process, the thread identifier, and the
10963 processor core that it is currently running on. The main thread of a
10964 process is not listed.
10968 If @var{infotype} is omitted, then list the possible values for
10969 @var{infotype} and the kind of OS information available for each
10970 @var{infotype}. If the target does not return a list of possible
10971 types, this command will report an error.
10974 @node Memory Region Attributes
10975 @section Memory Region Attributes
10976 @cindex memory region attributes
10978 @dfn{Memory region attributes} allow you to describe special handling
10979 required by regions of your target's memory. @value{GDBN} uses
10980 attributes to determine whether to allow certain types of memory
10981 accesses; whether to use specific width accesses; and whether to cache
10982 target memory. By default the description of memory regions is
10983 fetched from the target (if the current target supports this), but the
10984 user can override the fetched regions.
10986 Defined memory regions can be individually enabled and disabled. When a
10987 memory region is disabled, @value{GDBN} uses the default attributes when
10988 accessing memory in that region. Similarly, if no memory regions have
10989 been defined, @value{GDBN} uses the default attributes when accessing
10992 When a memory region is defined, it is given a number to identify it;
10993 to enable, disable, or remove a memory region, you specify that number.
10997 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10998 Define a memory region bounded by @var{lower} and @var{upper} with
10999 attributes @var{attributes}@dots{}, and add it to the list of regions
11000 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11001 case: it is treated as the target's maximum memory address.
11002 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11005 Discard any user changes to the memory regions and use target-supplied
11006 regions, if available, or no regions if the target does not support.
11009 @item delete mem @var{nums}@dots{}
11010 Remove memory regions @var{nums}@dots{} from the list of regions
11011 monitored by @value{GDBN}.
11013 @kindex disable mem
11014 @item disable mem @var{nums}@dots{}
11015 Disable monitoring of memory regions @var{nums}@dots{}.
11016 A disabled memory region is not forgotten.
11017 It may be enabled again later.
11020 @item enable mem @var{nums}@dots{}
11021 Enable monitoring of memory regions @var{nums}@dots{}.
11025 Print a table of all defined memory regions, with the following columns
11029 @item Memory Region Number
11030 @item Enabled or Disabled.
11031 Enabled memory regions are marked with @samp{y}.
11032 Disabled memory regions are marked with @samp{n}.
11035 The address defining the inclusive lower bound of the memory region.
11038 The address defining the exclusive upper bound of the memory region.
11041 The list of attributes set for this memory region.
11046 @subsection Attributes
11048 @subsubsection Memory Access Mode
11049 The access mode attributes set whether @value{GDBN} may make read or
11050 write accesses to a memory region.
11052 While these attributes prevent @value{GDBN} from performing invalid
11053 memory accesses, they do nothing to prevent the target system, I/O DMA,
11054 etc.@: from accessing memory.
11058 Memory is read only.
11060 Memory is write only.
11062 Memory is read/write. This is the default.
11065 @subsubsection Memory Access Size
11066 The access size attribute tells @value{GDBN} to use specific sized
11067 accesses in the memory region. Often memory mapped device registers
11068 require specific sized accesses. If no access size attribute is
11069 specified, @value{GDBN} may use accesses of any size.
11073 Use 8 bit memory accesses.
11075 Use 16 bit memory accesses.
11077 Use 32 bit memory accesses.
11079 Use 64 bit memory accesses.
11082 @c @subsubsection Hardware/Software Breakpoints
11083 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11084 @c will use hardware or software breakpoints for the internal breakpoints
11085 @c used by the step, next, finish, until, etc. commands.
11089 @c Always use hardware breakpoints
11090 @c @item swbreak (default)
11093 @subsubsection Data Cache
11094 The data cache attributes set whether @value{GDBN} will cache target
11095 memory. While this generally improves performance by reducing debug
11096 protocol overhead, it can lead to incorrect results because @value{GDBN}
11097 does not know about volatile variables or memory mapped device
11102 Enable @value{GDBN} to cache target memory.
11104 Disable @value{GDBN} from caching target memory. This is the default.
11107 @subsection Memory Access Checking
11108 @value{GDBN} can be instructed to refuse accesses to memory that is
11109 not explicitly described. This can be useful if accessing such
11110 regions has undesired effects for a specific target, or to provide
11111 better error checking. The following commands control this behaviour.
11114 @kindex set mem inaccessible-by-default
11115 @item set mem inaccessible-by-default [on|off]
11116 If @code{on} is specified, make @value{GDBN} treat memory not
11117 explicitly described by the memory ranges as non-existent and refuse accesses
11118 to such memory. The checks are only performed if there's at least one
11119 memory range defined. If @code{off} is specified, make @value{GDBN}
11120 treat the memory not explicitly described by the memory ranges as RAM.
11121 The default value is @code{on}.
11122 @kindex show mem inaccessible-by-default
11123 @item show mem inaccessible-by-default
11124 Show the current handling of accesses to unknown memory.
11128 @c @subsubsection Memory Write Verification
11129 @c The memory write verification attributes set whether @value{GDBN}
11130 @c will re-reads data after each write to verify the write was successful.
11134 @c @item noverify (default)
11137 @node Dump/Restore Files
11138 @section Copy Between Memory and a File
11139 @cindex dump/restore files
11140 @cindex append data to a file
11141 @cindex dump data to a file
11142 @cindex restore data from a file
11144 You can use the commands @code{dump}, @code{append}, and
11145 @code{restore} to copy data between target memory and a file. The
11146 @code{dump} and @code{append} commands write data to a file, and the
11147 @code{restore} command reads data from a file back into the inferior's
11148 memory. Files may be in binary, Motorola S-record, Intel hex,
11149 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11150 append to binary files, and cannot read from Verilog Hex files.
11155 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11156 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11157 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11158 or the value of @var{expr}, to @var{filename} in the given format.
11160 The @var{format} parameter may be any one of:
11167 Motorola S-record format.
11169 Tektronix Hex format.
11171 Verilog Hex format.
11174 @value{GDBN} uses the same definitions of these formats as the
11175 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11176 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11180 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11181 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11182 Append the contents of memory from @var{start_addr} to @var{end_addr},
11183 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11184 (@value{GDBN} can only append data to files in raw binary form.)
11187 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11188 Restore the contents of file @var{filename} into memory. The
11189 @code{restore} command can automatically recognize any known @sc{bfd}
11190 file format, except for raw binary. To restore a raw binary file you
11191 must specify the optional keyword @code{binary} after the filename.
11193 If @var{bias} is non-zero, its value will be added to the addresses
11194 contained in the file. Binary files always start at address zero, so
11195 they will be restored at address @var{bias}. Other bfd files have
11196 a built-in location; they will be restored at offset @var{bias}
11197 from that location.
11199 If @var{start} and/or @var{end} are non-zero, then only data between
11200 file offset @var{start} and file offset @var{end} will be restored.
11201 These offsets are relative to the addresses in the file, before
11202 the @var{bias} argument is applied.
11206 @node Core File Generation
11207 @section How to Produce a Core File from Your Program
11208 @cindex dump core from inferior
11210 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11211 image of a running process and its process status (register values
11212 etc.). Its primary use is post-mortem debugging of a program that
11213 crashed while it ran outside a debugger. A program that crashes
11214 automatically produces a core file, unless this feature is disabled by
11215 the user. @xref{Files}, for information on invoking @value{GDBN} in
11216 the post-mortem debugging mode.
11218 Occasionally, you may wish to produce a core file of the program you
11219 are debugging in order to preserve a snapshot of its state.
11220 @value{GDBN} has a special command for that.
11224 @kindex generate-core-file
11225 @item generate-core-file [@var{file}]
11226 @itemx gcore [@var{file}]
11227 Produce a core dump of the inferior process. The optional argument
11228 @var{file} specifies the file name where to put the core dump. If not
11229 specified, the file name defaults to @file{core.@var{pid}}, where
11230 @var{pid} is the inferior process ID.
11232 Note that this command is implemented only for some systems (as of
11233 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11235 On @sc{gnu}/Linux, this command can take into account the value of the
11236 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11237 dump (@pxref{set use-coredump-filter}).
11239 @kindex set use-coredump-filter
11240 @anchor{set use-coredump-filter}
11241 @item set use-coredump-filter on
11242 @itemx set use-coredump-filter off
11243 Enable or disable the use of the file
11244 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11245 files. This file is used by the Linux kernel to decide what types of
11246 memory mappings will be dumped or ignored when generating a core dump
11247 file. @var{pid} is the process ID of a currently running process.
11249 To make use of this feature, you have to write in the
11250 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11251 which is a bit mask representing the memory mapping types. If a bit
11252 is set in the bit mask, then the memory mappings of the corresponding
11253 types will be dumped; otherwise, they will be ignored. This
11254 configuration is inherited by child processes. For more information
11255 about the bits that can be set in the
11256 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11257 manpage of @code{core(5)}.
11259 By default, this option is @code{on}. If this option is turned
11260 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11261 and instead uses the same default value as the Linux kernel in order
11262 to decide which pages will be dumped in the core dump file. This
11263 value is currently @code{0x33}, which means that bits @code{0}
11264 (anonymous private mappings), @code{1} (anonymous shared mappings),
11265 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11266 This will cause these memory mappings to be dumped automatically.
11269 @node Character Sets
11270 @section Character Sets
11271 @cindex character sets
11273 @cindex translating between character sets
11274 @cindex host character set
11275 @cindex target character set
11277 If the program you are debugging uses a different character set to
11278 represent characters and strings than the one @value{GDBN} uses itself,
11279 @value{GDBN} can automatically translate between the character sets for
11280 you. The character set @value{GDBN} uses we call the @dfn{host
11281 character set}; the one the inferior program uses we call the
11282 @dfn{target character set}.
11284 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11285 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11286 remote protocol (@pxref{Remote Debugging}) to debug a program
11287 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11288 then the host character set is Latin-1, and the target character set is
11289 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11290 target-charset EBCDIC-US}, then @value{GDBN} translates between
11291 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11292 character and string literals in expressions.
11294 @value{GDBN} has no way to automatically recognize which character set
11295 the inferior program uses; you must tell it, using the @code{set
11296 target-charset} command, described below.
11298 Here are the commands for controlling @value{GDBN}'s character set
11302 @item set target-charset @var{charset}
11303 @kindex set target-charset
11304 Set the current target character set to @var{charset}. To display the
11305 list of supported target character sets, type
11306 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11308 @item set host-charset @var{charset}
11309 @kindex set host-charset
11310 Set the current host character set to @var{charset}.
11312 By default, @value{GDBN} uses a host character set appropriate to the
11313 system it is running on; you can override that default using the
11314 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11315 automatically determine the appropriate host character set. In this
11316 case, @value{GDBN} uses @samp{UTF-8}.
11318 @value{GDBN} can only use certain character sets as its host character
11319 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11320 @value{GDBN} will list the host character sets it supports.
11322 @item set charset @var{charset}
11323 @kindex set charset
11324 Set the current host and target character sets to @var{charset}. As
11325 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11326 @value{GDBN} will list the names of the character sets that can be used
11327 for both host and target.
11330 @kindex show charset
11331 Show the names of the current host and target character sets.
11333 @item show host-charset
11334 @kindex show host-charset
11335 Show the name of the current host character set.
11337 @item show target-charset
11338 @kindex show target-charset
11339 Show the name of the current target character set.
11341 @item set target-wide-charset @var{charset}
11342 @kindex set target-wide-charset
11343 Set the current target's wide character set to @var{charset}. This is
11344 the character set used by the target's @code{wchar_t} type. To
11345 display the list of supported wide character sets, type
11346 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11348 @item show target-wide-charset
11349 @kindex show target-wide-charset
11350 Show the name of the current target's wide character set.
11353 Here is an example of @value{GDBN}'s character set support in action.
11354 Assume that the following source code has been placed in the file
11355 @file{charset-test.c}:
11361 = @{72, 101, 108, 108, 111, 44, 32, 119,
11362 111, 114, 108, 100, 33, 10, 0@};
11363 char ibm1047_hello[]
11364 = @{200, 133, 147, 147, 150, 107, 64, 166,
11365 150, 153, 147, 132, 90, 37, 0@};
11369 printf ("Hello, world!\n");
11373 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11374 containing the string @samp{Hello, world!} followed by a newline,
11375 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11377 We compile the program, and invoke the debugger on it:
11380 $ gcc -g charset-test.c -o charset-test
11381 $ gdb -nw charset-test
11382 GNU gdb 2001-12-19-cvs
11383 Copyright 2001 Free Software Foundation, Inc.
11388 We can use the @code{show charset} command to see what character sets
11389 @value{GDBN} is currently using to interpret and display characters and
11393 (@value{GDBP}) show charset
11394 The current host and target character set is `ISO-8859-1'.
11398 For the sake of printing this manual, let's use @sc{ascii} as our
11399 initial character set:
11401 (@value{GDBP}) set charset ASCII
11402 (@value{GDBP}) show charset
11403 The current host and target character set is `ASCII'.
11407 Let's assume that @sc{ascii} is indeed the correct character set for our
11408 host system --- in other words, let's assume that if @value{GDBN} prints
11409 characters using the @sc{ascii} character set, our terminal will display
11410 them properly. Since our current target character set is also
11411 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11414 (@value{GDBP}) print ascii_hello
11415 $1 = 0x401698 "Hello, world!\n"
11416 (@value{GDBP}) print ascii_hello[0]
11421 @value{GDBN} uses the target character set for character and string
11422 literals you use in expressions:
11425 (@value{GDBP}) print '+'
11430 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11433 @value{GDBN} relies on the user to tell it which character set the
11434 target program uses. If we print @code{ibm1047_hello} while our target
11435 character set is still @sc{ascii}, we get jibberish:
11438 (@value{GDBP}) print ibm1047_hello
11439 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11440 (@value{GDBP}) print ibm1047_hello[0]
11445 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11446 @value{GDBN} tells us the character sets it supports:
11449 (@value{GDBP}) set target-charset
11450 ASCII EBCDIC-US IBM1047 ISO-8859-1
11451 (@value{GDBP}) set target-charset
11454 We can select @sc{ibm1047} as our target character set, and examine the
11455 program's strings again. Now the @sc{ascii} string is wrong, but
11456 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11457 target character set, @sc{ibm1047}, to the host character set,
11458 @sc{ascii}, and they display correctly:
11461 (@value{GDBP}) set target-charset IBM1047
11462 (@value{GDBP}) show charset
11463 The current host character set is `ASCII'.
11464 The current target character set is `IBM1047'.
11465 (@value{GDBP}) print ascii_hello
11466 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11467 (@value{GDBP}) print ascii_hello[0]
11469 (@value{GDBP}) print ibm1047_hello
11470 $8 = 0x4016a8 "Hello, world!\n"
11471 (@value{GDBP}) print ibm1047_hello[0]
11476 As above, @value{GDBN} uses the target character set for character and
11477 string literals you use in expressions:
11480 (@value{GDBP}) print '+'
11485 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11488 @node Caching Target Data
11489 @section Caching Data of Targets
11490 @cindex caching data of targets
11492 @value{GDBN} caches data exchanged between the debugger and a target.
11493 Each cache is associated with the address space of the inferior.
11494 @xref{Inferiors and Programs}, about inferior and address space.
11495 Such caching generally improves performance in remote debugging
11496 (@pxref{Remote Debugging}), because it reduces the overhead of the
11497 remote protocol by bundling memory reads and writes into large chunks.
11498 Unfortunately, simply caching everything would lead to incorrect results,
11499 since @value{GDBN} does not necessarily know anything about volatile
11500 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11501 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11503 Therefore, by default, @value{GDBN} only caches data
11504 known to be on the stack@footnote{In non-stop mode, it is moderately
11505 rare for a running thread to modify the stack of a stopped thread
11506 in a way that would interfere with a backtrace, and caching of
11507 stack reads provides a significant speed up of remote backtraces.} or
11508 in the code segment.
11509 Other regions of memory can be explicitly marked as
11510 cacheable; @pxref{Memory Region Attributes}.
11513 @kindex set remotecache
11514 @item set remotecache on
11515 @itemx set remotecache off
11516 This option no longer does anything; it exists for compatibility
11519 @kindex show remotecache
11520 @item show remotecache
11521 Show the current state of the obsolete remotecache flag.
11523 @kindex set stack-cache
11524 @item set stack-cache on
11525 @itemx set stack-cache off
11526 Enable or disable caching of stack accesses. When @code{on}, use
11527 caching. By default, this option is @code{on}.
11529 @kindex show stack-cache
11530 @item show stack-cache
11531 Show the current state of data caching for memory accesses.
11533 @kindex set code-cache
11534 @item set code-cache on
11535 @itemx set code-cache off
11536 Enable or disable caching of code segment accesses. When @code{on},
11537 use caching. By default, this option is @code{on}. This improves
11538 performance of disassembly in remote debugging.
11540 @kindex show code-cache
11541 @item show code-cache
11542 Show the current state of target memory cache for code segment
11545 @kindex info dcache
11546 @item info dcache @r{[}line@r{]}
11547 Print the information about the performance of data cache of the
11548 current inferior's address space. The information displayed
11549 includes the dcache width and depth, and for each cache line, its
11550 number, address, and how many times it was referenced. This
11551 command is useful for debugging the data cache operation.
11553 If a line number is specified, the contents of that line will be
11556 @item set dcache size @var{size}
11557 @cindex dcache size
11558 @kindex set dcache size
11559 Set maximum number of entries in dcache (dcache depth above).
11561 @item set dcache line-size @var{line-size}
11562 @cindex dcache line-size
11563 @kindex set dcache line-size
11564 Set number of bytes each dcache entry caches (dcache width above).
11565 Must be a power of 2.
11567 @item show dcache size
11568 @kindex show dcache size
11569 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11571 @item show dcache line-size
11572 @kindex show dcache line-size
11573 Show default size of dcache lines.
11577 @node Searching Memory
11578 @section Search Memory
11579 @cindex searching memory
11581 Memory can be searched for a particular sequence of bytes with the
11582 @code{find} command.
11586 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11587 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11588 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11589 etc. The search begins at address @var{start_addr} and continues for either
11590 @var{len} bytes or through to @var{end_addr} inclusive.
11593 @var{s} and @var{n} are optional parameters.
11594 They may be specified in either order, apart or together.
11597 @item @var{s}, search query size
11598 The size of each search query value.
11604 halfwords (two bytes)
11608 giant words (eight bytes)
11611 All values are interpreted in the current language.
11612 This means, for example, that if the current source language is C/C@t{++}
11613 then searching for the string ``hello'' includes the trailing '\0'.
11615 If the value size is not specified, it is taken from the
11616 value's type in the current language.
11617 This is useful when one wants to specify the search
11618 pattern as a mixture of types.
11619 Note that this means, for example, that in the case of C-like languages
11620 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11621 which is typically four bytes.
11623 @item @var{n}, maximum number of finds
11624 The maximum number of matches to print. The default is to print all finds.
11627 You can use strings as search values. Quote them with double-quotes
11629 The string value is copied into the search pattern byte by byte,
11630 regardless of the endianness of the target and the size specification.
11632 The address of each match found is printed as well as a count of the
11633 number of matches found.
11635 The address of the last value found is stored in convenience variable
11637 A count of the number of matches is stored in @samp{$numfound}.
11639 For example, if stopped at the @code{printf} in this function:
11645 static char hello[] = "hello-hello";
11646 static struct @{ char c; short s; int i; @}
11647 __attribute__ ((packed)) mixed
11648 = @{ 'c', 0x1234, 0x87654321 @};
11649 printf ("%s\n", hello);
11654 you get during debugging:
11657 (gdb) find &hello[0], +sizeof(hello), "hello"
11658 0x804956d <hello.1620+6>
11660 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11661 0x8049567 <hello.1620>
11662 0x804956d <hello.1620+6>
11664 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11665 0x8049567 <hello.1620>
11667 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11668 0x8049560 <mixed.1625>
11670 (gdb) print $numfound
11673 $2 = (void *) 0x8049560
11676 @node Optimized Code
11677 @chapter Debugging Optimized Code
11678 @cindex optimized code, debugging
11679 @cindex debugging optimized code
11681 Almost all compilers support optimization. With optimization
11682 disabled, the compiler generates assembly code that corresponds
11683 directly to your source code, in a simplistic way. As the compiler
11684 applies more powerful optimizations, the generated assembly code
11685 diverges from your original source code. With help from debugging
11686 information generated by the compiler, @value{GDBN} can map from
11687 the running program back to constructs from your original source.
11689 @value{GDBN} is more accurate with optimization disabled. If you
11690 can recompile without optimization, it is easier to follow the
11691 progress of your program during debugging. But, there are many cases
11692 where you may need to debug an optimized version.
11694 When you debug a program compiled with @samp{-g -O}, remember that the
11695 optimizer has rearranged your code; the debugger shows you what is
11696 really there. Do not be too surprised when the execution path does not
11697 exactly match your source file! An extreme example: if you define a
11698 variable, but never use it, @value{GDBN} never sees that
11699 variable---because the compiler optimizes it out of existence.
11701 Some things do not work as well with @samp{-g -O} as with just
11702 @samp{-g}, particularly on machines with instruction scheduling. If in
11703 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11704 please report it to us as a bug (including a test case!).
11705 @xref{Variables}, for more information about debugging optimized code.
11708 * Inline Functions:: How @value{GDBN} presents inlining
11709 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11712 @node Inline Functions
11713 @section Inline Functions
11714 @cindex inline functions, debugging
11716 @dfn{Inlining} is an optimization that inserts a copy of the function
11717 body directly at each call site, instead of jumping to a shared
11718 routine. @value{GDBN} displays inlined functions just like
11719 non-inlined functions. They appear in backtraces. You can view their
11720 arguments and local variables, step into them with @code{step}, skip
11721 them with @code{next}, and escape from them with @code{finish}.
11722 You can check whether a function was inlined by using the
11723 @code{info frame} command.
11725 For @value{GDBN} to support inlined functions, the compiler must
11726 record information about inlining in the debug information ---
11727 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11728 other compilers do also. @value{GDBN} only supports inlined functions
11729 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11730 do not emit two required attributes (@samp{DW_AT_call_file} and
11731 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11732 function calls with earlier versions of @value{NGCC}. It instead
11733 displays the arguments and local variables of inlined functions as
11734 local variables in the caller.
11736 The body of an inlined function is directly included at its call site;
11737 unlike a non-inlined function, there are no instructions devoted to
11738 the call. @value{GDBN} still pretends that the call site and the
11739 start of the inlined function are different instructions. Stepping to
11740 the call site shows the call site, and then stepping again shows
11741 the first line of the inlined function, even though no additional
11742 instructions are executed.
11744 This makes source-level debugging much clearer; you can see both the
11745 context of the call and then the effect of the call. Only stepping by
11746 a single instruction using @code{stepi} or @code{nexti} does not do
11747 this; single instruction steps always show the inlined body.
11749 There are some ways that @value{GDBN} does not pretend that inlined
11750 function calls are the same as normal calls:
11754 Setting breakpoints at the call site of an inlined function may not
11755 work, because the call site does not contain any code. @value{GDBN}
11756 may incorrectly move the breakpoint to the next line of the enclosing
11757 function, after the call. This limitation will be removed in a future
11758 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11759 or inside the inlined function instead.
11762 @value{GDBN} cannot locate the return value of inlined calls after
11763 using the @code{finish} command. This is a limitation of compiler-generated
11764 debugging information; after @code{finish}, you can step to the next line
11765 and print a variable where your program stored the return value.
11769 @node Tail Call Frames
11770 @section Tail Call Frames
11771 @cindex tail call frames, debugging
11773 Function @code{B} can call function @code{C} in its very last statement. In
11774 unoptimized compilation the call of @code{C} is immediately followed by return
11775 instruction at the end of @code{B} code. Optimizing compiler may replace the
11776 call and return in function @code{B} into one jump to function @code{C}
11777 instead. Such use of a jump instruction is called @dfn{tail call}.
11779 During execution of function @code{C}, there will be no indication in the
11780 function call stack frames that it was tail-called from @code{B}. If function
11781 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11782 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11783 some cases @value{GDBN} can determine that @code{C} was tail-called from
11784 @code{B}, and it will then create fictitious call frame for that, with the
11785 return address set up as if @code{B} called @code{C} normally.
11787 This functionality is currently supported only by DWARF 2 debugging format and
11788 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11789 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11792 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11793 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11797 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11799 Stack level 1, frame at 0x7fffffffda30:
11800 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11801 tail call frame, caller of frame at 0x7fffffffda30
11802 source language c++.
11803 Arglist at unknown address.
11804 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11807 The detection of all the possible code path executions can find them ambiguous.
11808 There is no execution history stored (possible @ref{Reverse Execution} is never
11809 used for this purpose) and the last known caller could have reached the known
11810 callee by multiple different jump sequences. In such case @value{GDBN} still
11811 tries to show at least all the unambiguous top tail callers and all the
11812 unambiguous bottom tail calees, if any.
11815 @anchor{set debug entry-values}
11816 @item set debug entry-values
11817 @kindex set debug entry-values
11818 When set to on, enables printing of analysis messages for both frame argument
11819 values at function entry and tail calls. It will show all the possible valid
11820 tail calls code paths it has considered. It will also print the intersection
11821 of them with the final unambiguous (possibly partial or even empty) code path
11824 @item show debug entry-values
11825 @kindex show debug entry-values
11826 Show the current state of analysis messages printing for both frame argument
11827 values at function entry and tail calls.
11830 The analysis messages for tail calls can for example show why the virtual tail
11831 call frame for function @code{c} has not been recognized (due to the indirect
11832 reference by variable @code{x}):
11835 static void __attribute__((noinline, noclone)) c (void);
11836 void (*x) (void) = c;
11837 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11838 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11839 int main (void) @{ x (); return 0; @}
11841 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11842 DW_TAG_GNU_call_site 0x40039a in main
11844 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11847 #1 0x000000000040039a in main () at t.c:5
11850 Another possibility is an ambiguous virtual tail call frames resolution:
11854 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11855 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11856 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11857 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11858 static void __attribute__((noinline, noclone)) b (void)
11859 @{ if (i) c (); else e (); @}
11860 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11861 int main (void) @{ a (); return 0; @}
11863 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11864 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11865 tailcall: reduced: 0x4004d2(a) |
11868 #1 0x00000000004004d2 in a () at t.c:8
11869 #2 0x0000000000400395 in main () at t.c:9
11872 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11873 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11875 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11876 @ifset HAVE_MAKEINFO_CLICK
11877 @set ARROW @click{}
11878 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11879 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11881 @ifclear HAVE_MAKEINFO_CLICK
11883 @set CALLSEQ1B @value{CALLSEQ1A}
11884 @set CALLSEQ2B @value{CALLSEQ2A}
11887 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11888 The code can have possible execution paths @value{CALLSEQ1B} or
11889 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11891 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11892 has found. It then finds another possible calling sequcen - that one is
11893 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11894 printed as the @code{reduced:} calling sequence. That one could have many
11895 futher @code{compare:} and @code{reduced:} statements as long as there remain
11896 any non-ambiguous sequence entries.
11898 For the frame of function @code{b} in both cases there are different possible
11899 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11900 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11901 therefore this one is displayed to the user while the ambiguous frames are
11904 There can be also reasons why printing of frame argument values at function
11909 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11910 static void __attribute__((noinline, noclone)) a (int i);
11911 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11912 static void __attribute__((noinline, noclone)) a (int i)
11913 @{ if (i) b (i - 1); else c (0); @}
11914 int main (void) @{ a (5); return 0; @}
11917 #0 c (i=i@@entry=0) at t.c:2
11918 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11919 function "a" at 0x400420 can call itself via tail calls
11920 i=<optimized out>) at t.c:6
11921 #2 0x000000000040036e in main () at t.c:7
11924 @value{GDBN} cannot find out from the inferior state if and how many times did
11925 function @code{a} call itself (via function @code{b}) as these calls would be
11926 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11927 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11928 prints @code{<optimized out>} instead.
11931 @chapter C Preprocessor Macros
11933 Some languages, such as C and C@t{++}, provide a way to define and invoke
11934 ``preprocessor macros'' which expand into strings of tokens.
11935 @value{GDBN} can evaluate expressions containing macro invocations, show
11936 the result of macro expansion, and show a macro's definition, including
11937 where it was defined.
11939 You may need to compile your program specially to provide @value{GDBN}
11940 with information about preprocessor macros. Most compilers do not
11941 include macros in their debugging information, even when you compile
11942 with the @option{-g} flag. @xref{Compilation}.
11944 A program may define a macro at one point, remove that definition later,
11945 and then provide a different definition after that. Thus, at different
11946 points in the program, a macro may have different definitions, or have
11947 no definition at all. If there is a current stack frame, @value{GDBN}
11948 uses the macros in scope at that frame's source code line. Otherwise,
11949 @value{GDBN} uses the macros in scope at the current listing location;
11952 Whenever @value{GDBN} evaluates an expression, it always expands any
11953 macro invocations present in the expression. @value{GDBN} also provides
11954 the following commands for working with macros explicitly.
11958 @kindex macro expand
11959 @cindex macro expansion, showing the results of preprocessor
11960 @cindex preprocessor macro expansion, showing the results of
11961 @cindex expanding preprocessor macros
11962 @item macro expand @var{expression}
11963 @itemx macro exp @var{expression}
11964 Show the results of expanding all preprocessor macro invocations in
11965 @var{expression}. Since @value{GDBN} simply expands macros, but does
11966 not parse the result, @var{expression} need not be a valid expression;
11967 it can be any string of tokens.
11970 @item macro expand-once @var{expression}
11971 @itemx macro exp1 @var{expression}
11972 @cindex expand macro once
11973 @i{(This command is not yet implemented.)} Show the results of
11974 expanding those preprocessor macro invocations that appear explicitly in
11975 @var{expression}. Macro invocations appearing in that expansion are
11976 left unchanged. This command allows you to see the effect of a
11977 particular macro more clearly, without being confused by further
11978 expansions. Since @value{GDBN} simply expands macros, but does not
11979 parse the result, @var{expression} need not be a valid expression; it
11980 can be any string of tokens.
11983 @cindex macro definition, showing
11984 @cindex definition of a macro, showing
11985 @cindex macros, from debug info
11986 @item info macro [-a|-all] [--] @var{macro}
11987 Show the current definition or all definitions of the named @var{macro},
11988 and describe the source location or compiler command-line where that
11989 definition was established. The optional double dash is to signify the end of
11990 argument processing and the beginning of @var{macro} for non C-like macros where
11991 the macro may begin with a hyphen.
11993 @kindex info macros
11994 @item info macros @var{location}
11995 Show all macro definitions that are in effect at the location specified
11996 by @var{location}, and describe the source location or compiler
11997 command-line where those definitions were established.
11999 @kindex macro define
12000 @cindex user-defined macros
12001 @cindex defining macros interactively
12002 @cindex macros, user-defined
12003 @item macro define @var{macro} @var{replacement-list}
12004 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12005 Introduce a definition for a preprocessor macro named @var{macro},
12006 invocations of which are replaced by the tokens given in
12007 @var{replacement-list}. The first form of this command defines an
12008 ``object-like'' macro, which takes no arguments; the second form
12009 defines a ``function-like'' macro, which takes the arguments given in
12012 A definition introduced by this command is in scope in every
12013 expression evaluated in @value{GDBN}, until it is removed with the
12014 @code{macro undef} command, described below. The definition overrides
12015 all definitions for @var{macro} present in the program being debugged,
12016 as well as any previous user-supplied definition.
12018 @kindex macro undef
12019 @item macro undef @var{macro}
12020 Remove any user-supplied definition for the macro named @var{macro}.
12021 This command only affects definitions provided with the @code{macro
12022 define} command, described above; it cannot remove definitions present
12023 in the program being debugged.
12027 List all the macros defined using the @code{macro define} command.
12030 @cindex macros, example of debugging with
12031 Here is a transcript showing the above commands in action. First, we
12032 show our source files:
12037 #include "sample.h"
12040 #define ADD(x) (M + x)
12045 printf ("Hello, world!\n");
12047 printf ("We're so creative.\n");
12049 printf ("Goodbye, world!\n");
12056 Now, we compile the program using the @sc{gnu} C compiler,
12057 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12058 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12059 and @option{-gdwarf-4}; we recommend always choosing the most recent
12060 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12061 includes information about preprocessor macros in the debugging
12065 $ gcc -gdwarf-2 -g3 sample.c -o sample
12069 Now, we start @value{GDBN} on our sample program:
12073 GNU gdb 2002-05-06-cvs
12074 Copyright 2002 Free Software Foundation, Inc.
12075 GDB is free software, @dots{}
12079 We can expand macros and examine their definitions, even when the
12080 program is not running. @value{GDBN} uses the current listing position
12081 to decide which macro definitions are in scope:
12084 (@value{GDBP}) list main
12087 5 #define ADD(x) (M + x)
12092 10 printf ("Hello, world!\n");
12094 12 printf ("We're so creative.\n");
12095 (@value{GDBP}) info macro ADD
12096 Defined at /home/jimb/gdb/macros/play/sample.c:5
12097 #define ADD(x) (M + x)
12098 (@value{GDBP}) info macro Q
12099 Defined at /home/jimb/gdb/macros/play/sample.h:1
12100 included at /home/jimb/gdb/macros/play/sample.c:2
12102 (@value{GDBP}) macro expand ADD(1)
12103 expands to: (42 + 1)
12104 (@value{GDBP}) macro expand-once ADD(1)
12105 expands to: once (M + 1)
12109 In the example above, note that @code{macro expand-once} expands only
12110 the macro invocation explicit in the original text --- the invocation of
12111 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12112 which was introduced by @code{ADD}.
12114 Once the program is running, @value{GDBN} uses the macro definitions in
12115 force at the source line of the current stack frame:
12118 (@value{GDBP}) break main
12119 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12121 Starting program: /home/jimb/gdb/macros/play/sample
12123 Breakpoint 1, main () at sample.c:10
12124 10 printf ("Hello, world!\n");
12128 At line 10, the definition of the macro @code{N} at line 9 is in force:
12131 (@value{GDBP}) info macro N
12132 Defined at /home/jimb/gdb/macros/play/sample.c:9
12134 (@value{GDBP}) macro expand N Q M
12135 expands to: 28 < 42
12136 (@value{GDBP}) print N Q M
12141 As we step over directives that remove @code{N}'s definition, and then
12142 give it a new definition, @value{GDBN} finds the definition (or lack
12143 thereof) in force at each point:
12146 (@value{GDBP}) next
12148 12 printf ("We're so creative.\n");
12149 (@value{GDBP}) info macro N
12150 The symbol `N' has no definition as a C/C++ preprocessor macro
12151 at /home/jimb/gdb/macros/play/sample.c:12
12152 (@value{GDBP}) next
12154 14 printf ("Goodbye, world!\n");
12155 (@value{GDBP}) info macro N
12156 Defined at /home/jimb/gdb/macros/play/sample.c:13
12158 (@value{GDBP}) macro expand N Q M
12159 expands to: 1729 < 42
12160 (@value{GDBP}) print N Q M
12165 In addition to source files, macros can be defined on the compilation command
12166 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12167 such a way, @value{GDBN} displays the location of their definition as line zero
12168 of the source file submitted to the compiler.
12171 (@value{GDBP}) info macro __STDC__
12172 Defined at /home/jimb/gdb/macros/play/sample.c:0
12179 @chapter Tracepoints
12180 @c This chapter is based on the documentation written by Michael
12181 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12183 @cindex tracepoints
12184 In some applications, it is not feasible for the debugger to interrupt
12185 the program's execution long enough for the developer to learn
12186 anything helpful about its behavior. If the program's correctness
12187 depends on its real-time behavior, delays introduced by a debugger
12188 might cause the program to change its behavior drastically, or perhaps
12189 fail, even when the code itself is correct. It is useful to be able
12190 to observe the program's behavior without interrupting it.
12192 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12193 specify locations in the program, called @dfn{tracepoints}, and
12194 arbitrary expressions to evaluate when those tracepoints are reached.
12195 Later, using the @code{tfind} command, you can examine the values
12196 those expressions had when the program hit the tracepoints. The
12197 expressions may also denote objects in memory---structures or arrays,
12198 for example---whose values @value{GDBN} should record; while visiting
12199 a particular tracepoint, you may inspect those objects as if they were
12200 in memory at that moment. However, because @value{GDBN} records these
12201 values without interacting with you, it can do so quickly and
12202 unobtrusively, hopefully not disturbing the program's behavior.
12204 The tracepoint facility is currently available only for remote
12205 targets. @xref{Targets}. In addition, your remote target must know
12206 how to collect trace data. This functionality is implemented in the
12207 remote stub; however, none of the stubs distributed with @value{GDBN}
12208 support tracepoints as of this writing. The format of the remote
12209 packets used to implement tracepoints are described in @ref{Tracepoint
12212 It is also possible to get trace data from a file, in a manner reminiscent
12213 of corefiles; you specify the filename, and use @code{tfind} to search
12214 through the file. @xref{Trace Files}, for more details.
12216 This chapter describes the tracepoint commands and features.
12219 * Set Tracepoints::
12220 * Analyze Collected Data::
12221 * Tracepoint Variables::
12225 @node Set Tracepoints
12226 @section Commands to Set Tracepoints
12228 Before running such a @dfn{trace experiment}, an arbitrary number of
12229 tracepoints can be set. A tracepoint is actually a special type of
12230 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12231 standard breakpoint commands. For instance, as with breakpoints,
12232 tracepoint numbers are successive integers starting from one, and many
12233 of the commands associated with tracepoints take the tracepoint number
12234 as their argument, to identify which tracepoint to work on.
12236 For each tracepoint, you can specify, in advance, some arbitrary set
12237 of data that you want the target to collect in the trace buffer when
12238 it hits that tracepoint. The collected data can include registers,
12239 local variables, or global data. Later, you can use @value{GDBN}
12240 commands to examine the values these data had at the time the
12241 tracepoint was hit.
12243 Tracepoints do not support every breakpoint feature. Ignore counts on
12244 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12245 commands when they are hit. Tracepoints may not be thread-specific
12248 @cindex fast tracepoints
12249 Some targets may support @dfn{fast tracepoints}, which are inserted in
12250 a different way (such as with a jump instead of a trap), that is
12251 faster but possibly restricted in where they may be installed.
12253 @cindex static tracepoints
12254 @cindex markers, static tracepoints
12255 @cindex probing markers, static tracepoints
12256 Regular and fast tracepoints are dynamic tracing facilities, meaning
12257 that they can be used to insert tracepoints at (almost) any location
12258 in the target. Some targets may also support controlling @dfn{static
12259 tracepoints} from @value{GDBN}. With static tracing, a set of
12260 instrumentation points, also known as @dfn{markers}, are embedded in
12261 the target program, and can be activated or deactivated by name or
12262 address. These are usually placed at locations which facilitate
12263 investigating what the target is actually doing. @value{GDBN}'s
12264 support for static tracing includes being able to list instrumentation
12265 points, and attach them with @value{GDBN} defined high level
12266 tracepoints that expose the whole range of convenience of
12267 @value{GDBN}'s tracepoints support. Namely, support for collecting
12268 registers values and values of global or local (to the instrumentation
12269 point) variables; tracepoint conditions and trace state variables.
12270 The act of installing a @value{GDBN} static tracepoint on an
12271 instrumentation point, or marker, is referred to as @dfn{probing} a
12272 static tracepoint marker.
12274 @code{gdbserver} supports tracepoints on some target systems.
12275 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12277 This section describes commands to set tracepoints and associated
12278 conditions and actions.
12281 * Create and Delete Tracepoints::
12282 * Enable and Disable Tracepoints::
12283 * Tracepoint Passcounts::
12284 * Tracepoint Conditions::
12285 * Trace State Variables::
12286 * Tracepoint Actions::
12287 * Listing Tracepoints::
12288 * Listing Static Tracepoint Markers::
12289 * Starting and Stopping Trace Experiments::
12290 * Tracepoint Restrictions::
12293 @node Create and Delete Tracepoints
12294 @subsection Create and Delete Tracepoints
12297 @cindex set tracepoint
12299 @item trace @var{location}
12300 The @code{trace} command is very similar to the @code{break} command.
12301 Its argument @var{location} can be any valid location.
12302 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12303 which is a point in the target program where the debugger will briefly stop,
12304 collect some data, and then allow the program to continue. Setting a tracepoint
12305 or changing its actions takes effect immediately if the remote stub
12306 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12308 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12309 these changes don't take effect until the next @code{tstart}
12310 command, and once a trace experiment is running, further changes will
12311 not have any effect until the next trace experiment starts. In addition,
12312 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12313 address is not yet resolved. (This is similar to pending breakpoints.)
12314 Pending tracepoints are not downloaded to the target and not installed
12315 until they are resolved. The resolution of pending tracepoints requires
12316 @value{GDBN} support---when debugging with the remote target, and
12317 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12318 tracing}), pending tracepoints can not be resolved (and downloaded to
12319 the remote stub) while @value{GDBN} is disconnected.
12321 Here are some examples of using the @code{trace} command:
12324 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12326 (@value{GDBP}) @b{trace +2} // 2 lines forward
12328 (@value{GDBP}) @b{trace my_function} // first source line of function
12330 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12332 (@value{GDBP}) @b{trace *0x2117c4} // an address
12336 You can abbreviate @code{trace} as @code{tr}.
12338 @item trace @var{location} if @var{cond}
12339 Set a tracepoint with condition @var{cond}; evaluate the expression
12340 @var{cond} each time the tracepoint is reached, and collect data only
12341 if the value is nonzero---that is, if @var{cond} evaluates as true.
12342 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12343 information on tracepoint conditions.
12345 @item ftrace @var{location} [ if @var{cond} ]
12346 @cindex set fast tracepoint
12347 @cindex fast tracepoints, setting
12349 The @code{ftrace} command sets a fast tracepoint. For targets that
12350 support them, fast tracepoints will use a more efficient but possibly
12351 less general technique to trigger data collection, such as a jump
12352 instruction instead of a trap, or some sort of hardware support. It
12353 may not be possible to create a fast tracepoint at the desired
12354 location, in which case the command will exit with an explanatory
12357 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12360 On 32-bit x86-architecture systems, fast tracepoints normally need to
12361 be placed at an instruction that is 5 bytes or longer, but can be
12362 placed at 4-byte instructions if the low 64K of memory of the target
12363 program is available to install trampolines. Some Unix-type systems,
12364 such as @sc{gnu}/Linux, exclude low addresses from the program's
12365 address space; but for instance with the Linux kernel it is possible
12366 to let @value{GDBN} use this area by doing a @command{sysctl} command
12367 to set the @code{mmap_min_addr} kernel parameter, as in
12370 sudo sysctl -w vm.mmap_min_addr=32768
12374 which sets the low address to 32K, which leaves plenty of room for
12375 trampolines. The minimum address should be set to a page boundary.
12377 @item strace @var{location} [ if @var{cond} ]
12378 @cindex set static tracepoint
12379 @cindex static tracepoints, setting
12380 @cindex probe static tracepoint marker
12382 The @code{strace} command sets a static tracepoint. For targets that
12383 support it, setting a static tracepoint probes a static
12384 instrumentation point, or marker, found at @var{location}. It may not
12385 be possible to set a static tracepoint at the desired location, in
12386 which case the command will exit with an explanatory message.
12388 @value{GDBN} handles arguments to @code{strace} exactly as for
12389 @code{trace}, with the addition that the user can also specify
12390 @code{-m @var{marker}} as @var{location}. This probes the marker
12391 identified by the @var{marker} string identifier. This identifier
12392 depends on the static tracepoint backend library your program is
12393 using. You can find all the marker identifiers in the @samp{ID} field
12394 of the @code{info static-tracepoint-markers} command output.
12395 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12396 Markers}. For example, in the following small program using the UST
12402 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12407 the marker id is composed of joining the first two arguments to the
12408 @code{trace_mark} call with a slash, which translates to:
12411 (@value{GDBP}) info static-tracepoint-markers
12412 Cnt Enb ID Address What
12413 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12419 so you may probe the marker above with:
12422 (@value{GDBP}) strace -m ust/bar33
12425 Static tracepoints accept an extra collect action --- @code{collect
12426 $_sdata}. This collects arbitrary user data passed in the probe point
12427 call to the tracing library. In the UST example above, you'll see
12428 that the third argument to @code{trace_mark} is a printf-like format
12429 string. The user data is then the result of running that formating
12430 string against the following arguments. Note that @code{info
12431 static-tracepoint-markers} command output lists that format string in
12432 the @samp{Data:} field.
12434 You can inspect this data when analyzing the trace buffer, by printing
12435 the $_sdata variable like any other variable available to
12436 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12439 @cindex last tracepoint number
12440 @cindex recent tracepoint number
12441 @cindex tracepoint number
12442 The convenience variable @code{$tpnum} records the tracepoint number
12443 of the most recently set tracepoint.
12445 @kindex delete tracepoint
12446 @cindex tracepoint deletion
12447 @item delete tracepoint @r{[}@var{num}@r{]}
12448 Permanently delete one or more tracepoints. With no argument, the
12449 default is to delete all tracepoints. Note that the regular
12450 @code{delete} command can remove tracepoints also.
12455 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12457 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12461 You can abbreviate this command as @code{del tr}.
12464 @node Enable and Disable Tracepoints
12465 @subsection Enable and Disable Tracepoints
12467 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12470 @kindex disable tracepoint
12471 @item disable tracepoint @r{[}@var{num}@r{]}
12472 Disable tracepoint @var{num}, or all tracepoints if no argument
12473 @var{num} is given. A disabled tracepoint will have no effect during
12474 a trace experiment, but it is not forgotten. You can re-enable
12475 a disabled tracepoint using the @code{enable tracepoint} command.
12476 If the command is issued during a trace experiment and the debug target
12477 has support for disabling tracepoints during a trace experiment, then the
12478 change will be effective immediately. Otherwise, it will be applied to the
12479 next trace experiment.
12481 @kindex enable tracepoint
12482 @item enable tracepoint @r{[}@var{num}@r{]}
12483 Enable tracepoint @var{num}, or all tracepoints. If this command is
12484 issued during a trace experiment and the debug target supports enabling
12485 tracepoints during a trace experiment, then the enabled tracepoints will
12486 become effective immediately. Otherwise, they will become effective the
12487 next time a trace experiment is run.
12490 @node Tracepoint Passcounts
12491 @subsection Tracepoint Passcounts
12495 @cindex tracepoint pass count
12496 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12497 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12498 automatically stop a trace experiment. If a tracepoint's passcount is
12499 @var{n}, then the trace experiment will be automatically stopped on
12500 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12501 @var{num} is not specified, the @code{passcount} command sets the
12502 passcount of the most recently defined tracepoint. If no passcount is
12503 given, the trace experiment will run until stopped explicitly by the
12509 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12510 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12512 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12513 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12514 (@value{GDBP}) @b{trace foo}
12515 (@value{GDBP}) @b{pass 3}
12516 (@value{GDBP}) @b{trace bar}
12517 (@value{GDBP}) @b{pass 2}
12518 (@value{GDBP}) @b{trace baz}
12519 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12520 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12521 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12522 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12526 @node Tracepoint Conditions
12527 @subsection Tracepoint Conditions
12528 @cindex conditional tracepoints
12529 @cindex tracepoint conditions
12531 The simplest sort of tracepoint collects data every time your program
12532 reaches a specified place. You can also specify a @dfn{condition} for
12533 a tracepoint. A condition is just a Boolean expression in your
12534 programming language (@pxref{Expressions, ,Expressions}). A
12535 tracepoint with a condition evaluates the expression each time your
12536 program reaches it, and data collection happens only if the condition
12539 Tracepoint conditions can be specified when a tracepoint is set, by
12540 using @samp{if} in the arguments to the @code{trace} command.
12541 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12542 also be set or changed at any time with the @code{condition} command,
12543 just as with breakpoints.
12545 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12546 the conditional expression itself. Instead, @value{GDBN} encodes the
12547 expression into an agent expression (@pxref{Agent Expressions})
12548 suitable for execution on the target, independently of @value{GDBN}.
12549 Global variables become raw memory locations, locals become stack
12550 accesses, and so forth.
12552 For instance, suppose you have a function that is usually called
12553 frequently, but should not be called after an error has occurred. You
12554 could use the following tracepoint command to collect data about calls
12555 of that function that happen while the error code is propagating
12556 through the program; an unconditional tracepoint could end up
12557 collecting thousands of useless trace frames that you would have to
12561 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12564 @node Trace State Variables
12565 @subsection Trace State Variables
12566 @cindex trace state variables
12568 A @dfn{trace state variable} is a special type of variable that is
12569 created and managed by target-side code. The syntax is the same as
12570 that for GDB's convenience variables (a string prefixed with ``$''),
12571 but they are stored on the target. They must be created explicitly,
12572 using a @code{tvariable} command. They are always 64-bit signed
12575 Trace state variables are remembered by @value{GDBN}, and downloaded
12576 to the target along with tracepoint information when the trace
12577 experiment starts. There are no intrinsic limits on the number of
12578 trace state variables, beyond memory limitations of the target.
12580 @cindex convenience variables, and trace state variables
12581 Although trace state variables are managed by the target, you can use
12582 them in print commands and expressions as if they were convenience
12583 variables; @value{GDBN} will get the current value from the target
12584 while the trace experiment is running. Trace state variables share
12585 the same namespace as other ``$'' variables, which means that you
12586 cannot have trace state variables with names like @code{$23} or
12587 @code{$pc}, nor can you have a trace state variable and a convenience
12588 variable with the same name.
12592 @item tvariable $@var{name} [ = @var{expression} ]
12594 The @code{tvariable} command creates a new trace state variable named
12595 @code{$@var{name}}, and optionally gives it an initial value of
12596 @var{expression}. The @var{expression} is evaluated when this command is
12597 entered; the result will be converted to an integer if possible,
12598 otherwise @value{GDBN} will report an error. A subsequent
12599 @code{tvariable} command specifying the same name does not create a
12600 variable, but instead assigns the supplied initial value to the
12601 existing variable of that name, overwriting any previous initial
12602 value. The default initial value is 0.
12604 @item info tvariables
12605 @kindex info tvariables
12606 List all the trace state variables along with their initial values.
12607 Their current values may also be displayed, if the trace experiment is
12610 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12611 @kindex delete tvariable
12612 Delete the given trace state variables, or all of them if no arguments
12617 @node Tracepoint Actions
12618 @subsection Tracepoint Action Lists
12622 @cindex tracepoint actions
12623 @item actions @r{[}@var{num}@r{]}
12624 This command will prompt for a list of actions to be taken when the
12625 tracepoint is hit. If the tracepoint number @var{num} is not
12626 specified, this command sets the actions for the one that was most
12627 recently defined (so that you can define a tracepoint and then say
12628 @code{actions} without bothering about its number). You specify the
12629 actions themselves on the following lines, one action at a time, and
12630 terminate the actions list with a line containing just @code{end}. So
12631 far, the only defined actions are @code{collect}, @code{teval}, and
12632 @code{while-stepping}.
12634 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12635 Commands, ,Breakpoint Command Lists}), except that only the defined
12636 actions are allowed; any other @value{GDBN} command is rejected.
12638 @cindex remove actions from a tracepoint
12639 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12640 and follow it immediately with @samp{end}.
12643 (@value{GDBP}) @b{collect @var{data}} // collect some data
12645 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12647 (@value{GDBP}) @b{end} // signals the end of actions.
12650 In the following example, the action list begins with @code{collect}
12651 commands indicating the things to be collected when the tracepoint is
12652 hit. Then, in order to single-step and collect additional data
12653 following the tracepoint, a @code{while-stepping} command is used,
12654 followed by the list of things to be collected after each step in a
12655 sequence of single steps. The @code{while-stepping} command is
12656 terminated by its own separate @code{end} command. Lastly, the action
12657 list is terminated by an @code{end} command.
12660 (@value{GDBP}) @b{trace foo}
12661 (@value{GDBP}) @b{actions}
12662 Enter actions for tracepoint 1, one per line:
12665 > while-stepping 12
12666 > collect $pc, arr[i]
12671 @kindex collect @r{(tracepoints)}
12672 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12673 Collect values of the given expressions when the tracepoint is hit.
12674 This command accepts a comma-separated list of any valid expressions.
12675 In addition to global, static, or local variables, the following
12676 special arguments are supported:
12680 Collect all registers.
12683 Collect all function arguments.
12686 Collect all local variables.
12689 Collect the return address. This is helpful if you want to see more
12693 Collects the number of arguments from the static probe at which the
12694 tracepoint is located.
12695 @xref{Static Probe Points}.
12697 @item $_probe_arg@var{n}
12698 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12699 from the static probe at which the tracepoint is located.
12700 @xref{Static Probe Points}.
12703 @vindex $_sdata@r{, collect}
12704 Collect static tracepoint marker specific data. Only available for
12705 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12706 Lists}. On the UST static tracepoints library backend, an
12707 instrumentation point resembles a @code{printf} function call. The
12708 tracing library is able to collect user specified data formatted to a
12709 character string using the format provided by the programmer that
12710 instrumented the program. Other backends have similar mechanisms.
12711 Here's an example of a UST marker call:
12714 const char master_name[] = "$your_name";
12715 trace_mark(channel1, marker1, "hello %s", master_name)
12718 In this case, collecting @code{$_sdata} collects the string
12719 @samp{hello $yourname}. When analyzing the trace buffer, you can
12720 inspect @samp{$_sdata} like any other variable available to
12724 You can give several consecutive @code{collect} commands, each one
12725 with a single argument, or one @code{collect} command with several
12726 arguments separated by commas; the effect is the same.
12728 The optional @var{mods} changes the usual handling of the arguments.
12729 @code{s} requests that pointers to chars be handled as strings, in
12730 particular collecting the contents of the memory being pointed at, up
12731 to the first zero. The upper bound is by default the value of the
12732 @code{print elements} variable; if @code{s} is followed by a decimal
12733 number, that is the upper bound instead. So for instance
12734 @samp{collect/s25 mystr} collects as many as 25 characters at
12737 The command @code{info scope} (@pxref{Symbols, info scope}) is
12738 particularly useful for figuring out what data to collect.
12740 @kindex teval @r{(tracepoints)}
12741 @item teval @var{expr1}, @var{expr2}, @dots{}
12742 Evaluate the given expressions when the tracepoint is hit. This
12743 command accepts a comma-separated list of expressions. The results
12744 are discarded, so this is mainly useful for assigning values to trace
12745 state variables (@pxref{Trace State Variables}) without adding those
12746 values to the trace buffer, as would be the case if the @code{collect}
12749 @kindex while-stepping @r{(tracepoints)}
12750 @item while-stepping @var{n}
12751 Perform @var{n} single-step instruction traces after the tracepoint,
12752 collecting new data after each step. The @code{while-stepping}
12753 command is followed by the list of what to collect while stepping
12754 (followed by its own @code{end} command):
12757 > while-stepping 12
12758 > collect $regs, myglobal
12764 Note that @code{$pc} is not automatically collected by
12765 @code{while-stepping}; you need to explicitly collect that register if
12766 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12769 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12770 @kindex set default-collect
12771 @cindex default collection action
12772 This variable is a list of expressions to collect at each tracepoint
12773 hit. It is effectively an additional @code{collect} action prepended
12774 to every tracepoint action list. The expressions are parsed
12775 individually for each tracepoint, so for instance a variable named
12776 @code{xyz} may be interpreted as a global for one tracepoint, and a
12777 local for another, as appropriate to the tracepoint's location.
12779 @item show default-collect
12780 @kindex show default-collect
12781 Show the list of expressions that are collected by default at each
12786 @node Listing Tracepoints
12787 @subsection Listing Tracepoints
12790 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12791 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12792 @cindex information about tracepoints
12793 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12794 Display information about the tracepoint @var{num}. If you don't
12795 specify a tracepoint number, displays information about all the
12796 tracepoints defined so far. The format is similar to that used for
12797 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12798 command, simply restricting itself to tracepoints.
12800 A tracepoint's listing may include additional information specific to
12805 its passcount as given by the @code{passcount @var{n}} command
12808 the state about installed on target of each location
12812 (@value{GDBP}) @b{info trace}
12813 Num Type Disp Enb Address What
12814 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12816 collect globfoo, $regs
12821 2 tracepoint keep y <MULTIPLE>
12823 2.1 y 0x0804859c in func4 at change-loc.h:35
12824 installed on target
12825 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12826 installed on target
12827 2.3 y <PENDING> set_tracepoint
12828 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12829 not installed on target
12834 This command can be abbreviated @code{info tp}.
12837 @node Listing Static Tracepoint Markers
12838 @subsection Listing Static Tracepoint Markers
12841 @kindex info static-tracepoint-markers
12842 @cindex information about static tracepoint markers
12843 @item info static-tracepoint-markers
12844 Display information about all static tracepoint markers defined in the
12847 For each marker, the following columns are printed:
12851 An incrementing counter, output to help readability. This is not a
12854 The marker ID, as reported by the target.
12855 @item Enabled or Disabled
12856 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12857 that are not enabled.
12859 Where the marker is in your program, as a memory address.
12861 Where the marker is in the source for your program, as a file and line
12862 number. If the debug information included in the program does not
12863 allow @value{GDBN} to locate the source of the marker, this column
12864 will be left blank.
12868 In addition, the following information may be printed for each marker:
12872 User data passed to the tracing library by the marker call. In the
12873 UST backend, this is the format string passed as argument to the
12875 @item Static tracepoints probing the marker
12876 The list of static tracepoints attached to the marker.
12880 (@value{GDBP}) info static-tracepoint-markers
12881 Cnt ID Enb Address What
12882 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12883 Data: number1 %d number2 %d
12884 Probed by static tracepoints: #2
12885 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12891 @node Starting and Stopping Trace Experiments
12892 @subsection Starting and Stopping Trace Experiments
12895 @kindex tstart [ @var{notes} ]
12896 @cindex start a new trace experiment
12897 @cindex collected data discarded
12899 This command starts the trace experiment, and begins collecting data.
12900 It has the side effect of discarding all the data collected in the
12901 trace buffer during the previous trace experiment. If any arguments
12902 are supplied, they are taken as a note and stored with the trace
12903 experiment's state. The notes may be arbitrary text, and are
12904 especially useful with disconnected tracing in a multi-user context;
12905 the notes can explain what the trace is doing, supply user contact
12906 information, and so forth.
12908 @kindex tstop [ @var{notes} ]
12909 @cindex stop a running trace experiment
12911 This command stops the trace experiment. If any arguments are
12912 supplied, they are recorded with the experiment as a note. This is
12913 useful if you are stopping a trace started by someone else, for
12914 instance if the trace is interfering with the system's behavior and
12915 needs to be stopped quickly.
12917 @strong{Note}: a trace experiment and data collection may stop
12918 automatically if any tracepoint's passcount is reached
12919 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12922 @cindex status of trace data collection
12923 @cindex trace experiment, status of
12925 This command displays the status of the current trace data
12929 Here is an example of the commands we described so far:
12932 (@value{GDBP}) @b{trace gdb_c_test}
12933 (@value{GDBP}) @b{actions}
12934 Enter actions for tracepoint #1, one per line.
12935 > collect $regs,$locals,$args
12936 > while-stepping 11
12940 (@value{GDBP}) @b{tstart}
12941 [time passes @dots{}]
12942 (@value{GDBP}) @b{tstop}
12945 @anchor{disconnected tracing}
12946 @cindex disconnected tracing
12947 You can choose to continue running the trace experiment even if
12948 @value{GDBN} disconnects from the target, voluntarily or
12949 involuntarily. For commands such as @code{detach}, the debugger will
12950 ask what you want to do with the trace. But for unexpected
12951 terminations (@value{GDBN} crash, network outage), it would be
12952 unfortunate to lose hard-won trace data, so the variable
12953 @code{disconnected-tracing} lets you decide whether the trace should
12954 continue running without @value{GDBN}.
12957 @item set disconnected-tracing on
12958 @itemx set disconnected-tracing off
12959 @kindex set disconnected-tracing
12960 Choose whether a tracing run should continue to run if @value{GDBN}
12961 has disconnected from the target. Note that @code{detach} or
12962 @code{quit} will ask you directly what to do about a running trace no
12963 matter what this variable's setting, so the variable is mainly useful
12964 for handling unexpected situations, such as loss of the network.
12966 @item show disconnected-tracing
12967 @kindex show disconnected-tracing
12968 Show the current choice for disconnected tracing.
12972 When you reconnect to the target, the trace experiment may or may not
12973 still be running; it might have filled the trace buffer in the
12974 meantime, or stopped for one of the other reasons. If it is running,
12975 it will continue after reconnection.
12977 Upon reconnection, the target will upload information about the
12978 tracepoints in effect. @value{GDBN} will then compare that
12979 information to the set of tracepoints currently defined, and attempt
12980 to match them up, allowing for the possibility that the numbers may
12981 have changed due to creation and deletion in the meantime. If one of
12982 the target's tracepoints does not match any in @value{GDBN}, the
12983 debugger will create a new tracepoint, so that you have a number with
12984 which to specify that tracepoint. This matching-up process is
12985 necessarily heuristic, and it may result in useless tracepoints being
12986 created; you may simply delete them if they are of no use.
12988 @cindex circular trace buffer
12989 If your target agent supports a @dfn{circular trace buffer}, then you
12990 can run a trace experiment indefinitely without filling the trace
12991 buffer; when space runs out, the agent deletes already-collected trace
12992 frames, oldest first, until there is enough room to continue
12993 collecting. This is especially useful if your tracepoints are being
12994 hit too often, and your trace gets terminated prematurely because the
12995 buffer is full. To ask for a circular trace buffer, simply set
12996 @samp{circular-trace-buffer} to on. You can set this at any time,
12997 including during tracing; if the agent can do it, it will change
12998 buffer handling on the fly, otherwise it will not take effect until
13002 @item set circular-trace-buffer on
13003 @itemx set circular-trace-buffer off
13004 @kindex set circular-trace-buffer
13005 Choose whether a tracing run should use a linear or circular buffer
13006 for trace data. A linear buffer will not lose any trace data, but may
13007 fill up prematurely, while a circular buffer will discard old trace
13008 data, but it will have always room for the latest tracepoint hits.
13010 @item show circular-trace-buffer
13011 @kindex show circular-trace-buffer
13012 Show the current choice for the trace buffer. Note that this may not
13013 match the agent's current buffer handling, nor is it guaranteed to
13014 match the setting that might have been in effect during a past run,
13015 for instance if you are looking at frames from a trace file.
13020 @item set trace-buffer-size @var{n}
13021 @itemx set trace-buffer-size unlimited
13022 @kindex set trace-buffer-size
13023 Request that the target use a trace buffer of @var{n} bytes. Not all
13024 targets will honor the request; they may have a compiled-in size for
13025 the trace buffer, or some other limitation. Set to a value of
13026 @code{unlimited} or @code{-1} to let the target use whatever size it
13027 likes. This is also the default.
13029 @item show trace-buffer-size
13030 @kindex show trace-buffer-size
13031 Show the current requested size for the trace buffer. Note that this
13032 will only match the actual size if the target supports size-setting,
13033 and was able to handle the requested size. For instance, if the
13034 target can only change buffer size between runs, this variable will
13035 not reflect the change until the next run starts. Use @code{tstatus}
13036 to get a report of the actual buffer size.
13040 @item set trace-user @var{text}
13041 @kindex set trace-user
13043 @item show trace-user
13044 @kindex show trace-user
13046 @item set trace-notes @var{text}
13047 @kindex set trace-notes
13048 Set the trace run's notes.
13050 @item show trace-notes
13051 @kindex show trace-notes
13052 Show the trace run's notes.
13054 @item set trace-stop-notes @var{text}
13055 @kindex set trace-stop-notes
13056 Set the trace run's stop notes. The handling of the note is as for
13057 @code{tstop} arguments; the set command is convenient way to fix a
13058 stop note that is mistaken or incomplete.
13060 @item show trace-stop-notes
13061 @kindex show trace-stop-notes
13062 Show the trace run's stop notes.
13066 @node Tracepoint Restrictions
13067 @subsection Tracepoint Restrictions
13069 @cindex tracepoint restrictions
13070 There are a number of restrictions on the use of tracepoints. As
13071 described above, tracepoint data gathering occurs on the target
13072 without interaction from @value{GDBN}. Thus the full capabilities of
13073 the debugger are not available during data gathering, and then at data
13074 examination time, you will be limited by only having what was
13075 collected. The following items describe some common problems, but it
13076 is not exhaustive, and you may run into additional difficulties not
13082 Tracepoint expressions are intended to gather objects (lvalues). Thus
13083 the full flexibility of GDB's expression evaluator is not available.
13084 You cannot call functions, cast objects to aggregate types, access
13085 convenience variables or modify values (except by assignment to trace
13086 state variables). Some language features may implicitly call
13087 functions (for instance Objective-C fields with accessors), and therefore
13088 cannot be collected either.
13091 Collection of local variables, either individually or in bulk with
13092 @code{$locals} or @code{$args}, during @code{while-stepping} may
13093 behave erratically. The stepping action may enter a new scope (for
13094 instance by stepping into a function), or the location of the variable
13095 may change (for instance it is loaded into a register). The
13096 tracepoint data recorded uses the location information for the
13097 variables that is correct for the tracepoint location. When the
13098 tracepoint is created, it is not possible, in general, to determine
13099 where the steps of a @code{while-stepping} sequence will advance the
13100 program---particularly if a conditional branch is stepped.
13103 Collection of an incompletely-initialized or partially-destroyed object
13104 may result in something that @value{GDBN} cannot display, or displays
13105 in a misleading way.
13108 When @value{GDBN} displays a pointer to character it automatically
13109 dereferences the pointer to also display characters of the string
13110 being pointed to. However, collecting the pointer during tracing does
13111 not automatically collect the string. You need to explicitly
13112 dereference the pointer and provide size information if you want to
13113 collect not only the pointer, but the memory pointed to. For example,
13114 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13118 It is not possible to collect a complete stack backtrace at a
13119 tracepoint. Instead, you may collect the registers and a few hundred
13120 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13121 (adjust to use the name of the actual stack pointer register on your
13122 target architecture, and the amount of stack you wish to capture).
13123 Then the @code{backtrace} command will show a partial backtrace when
13124 using a trace frame. The number of stack frames that can be examined
13125 depends on the sizes of the frames in the collected stack. Note that
13126 if you ask for a block so large that it goes past the bottom of the
13127 stack, the target agent may report an error trying to read from an
13131 If you do not collect registers at a tracepoint, @value{GDBN} can
13132 infer that the value of @code{$pc} must be the same as the address of
13133 the tracepoint and use that when you are looking at a trace frame
13134 for that tracepoint. However, this cannot work if the tracepoint has
13135 multiple locations (for instance if it was set in a function that was
13136 inlined), or if it has a @code{while-stepping} loop. In those cases
13137 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13142 @node Analyze Collected Data
13143 @section Using the Collected Data
13145 After the tracepoint experiment ends, you use @value{GDBN} commands
13146 for examining the trace data. The basic idea is that each tracepoint
13147 collects a trace @dfn{snapshot} every time it is hit and another
13148 snapshot every time it single-steps. All these snapshots are
13149 consecutively numbered from zero and go into a buffer, and you can
13150 examine them later. The way you examine them is to @dfn{focus} on a
13151 specific trace snapshot. When the remote stub is focused on a trace
13152 snapshot, it will respond to all @value{GDBN} requests for memory and
13153 registers by reading from the buffer which belongs to that snapshot,
13154 rather than from @emph{real} memory or registers of the program being
13155 debugged. This means that @strong{all} @value{GDBN} commands
13156 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13157 behave as if we were currently debugging the program state as it was
13158 when the tracepoint occurred. Any requests for data that are not in
13159 the buffer will fail.
13162 * tfind:: How to select a trace snapshot
13163 * tdump:: How to display all data for a snapshot
13164 * save tracepoints:: How to save tracepoints for a future run
13168 @subsection @code{tfind @var{n}}
13171 @cindex select trace snapshot
13172 @cindex find trace snapshot
13173 The basic command for selecting a trace snapshot from the buffer is
13174 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13175 counting from zero. If no argument @var{n} is given, the next
13176 snapshot is selected.
13178 Here are the various forms of using the @code{tfind} command.
13182 Find the first snapshot in the buffer. This is a synonym for
13183 @code{tfind 0} (since 0 is the number of the first snapshot).
13186 Stop debugging trace snapshots, resume @emph{live} debugging.
13189 Same as @samp{tfind none}.
13192 No argument means find the next trace snapshot.
13195 Find the previous trace snapshot before the current one. This permits
13196 retracing earlier steps.
13198 @item tfind tracepoint @var{num}
13199 Find the next snapshot associated with tracepoint @var{num}. Search
13200 proceeds forward from the last examined trace snapshot. If no
13201 argument @var{num} is given, it means find the next snapshot collected
13202 for the same tracepoint as the current snapshot.
13204 @item tfind pc @var{addr}
13205 Find the next snapshot associated with the value @var{addr} of the
13206 program counter. Search proceeds forward from the last examined trace
13207 snapshot. If no argument @var{addr} is given, it means find the next
13208 snapshot with the same value of PC as the current snapshot.
13210 @item tfind outside @var{addr1}, @var{addr2}
13211 Find the next snapshot whose PC is outside the given range of
13212 addresses (exclusive).
13214 @item tfind range @var{addr1}, @var{addr2}
13215 Find the next snapshot whose PC is between @var{addr1} and
13216 @var{addr2} (inclusive).
13218 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13219 Find the next snapshot associated with the source line @var{n}. If
13220 the optional argument @var{file} is given, refer to line @var{n} in
13221 that source file. Search proceeds forward from the last examined
13222 trace snapshot. If no argument @var{n} is given, it means find the
13223 next line other than the one currently being examined; thus saying
13224 @code{tfind line} repeatedly can appear to have the same effect as
13225 stepping from line to line in a @emph{live} debugging session.
13228 The default arguments for the @code{tfind} commands are specifically
13229 designed to make it easy to scan through the trace buffer. For
13230 instance, @code{tfind} with no argument selects the next trace
13231 snapshot, and @code{tfind -} with no argument selects the previous
13232 trace snapshot. So, by giving one @code{tfind} command, and then
13233 simply hitting @key{RET} repeatedly you can examine all the trace
13234 snapshots in order. Or, by saying @code{tfind -} and then hitting
13235 @key{RET} repeatedly you can examine the snapshots in reverse order.
13236 The @code{tfind line} command with no argument selects the snapshot
13237 for the next source line executed. The @code{tfind pc} command with
13238 no argument selects the next snapshot with the same program counter
13239 (PC) as the current frame. The @code{tfind tracepoint} command with
13240 no argument selects the next trace snapshot collected by the same
13241 tracepoint as the current one.
13243 In addition to letting you scan through the trace buffer manually,
13244 these commands make it easy to construct @value{GDBN} scripts that
13245 scan through the trace buffer and print out whatever collected data
13246 you are interested in. Thus, if we want to examine the PC, FP, and SP
13247 registers from each trace frame in the buffer, we can say this:
13250 (@value{GDBP}) @b{tfind start}
13251 (@value{GDBP}) @b{while ($trace_frame != -1)}
13252 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13253 $trace_frame, $pc, $sp, $fp
13257 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13258 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13259 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13260 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13261 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13262 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13263 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13264 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13265 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13266 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13267 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13270 Or, if we want to examine the variable @code{X} at each source line in
13274 (@value{GDBP}) @b{tfind start}
13275 (@value{GDBP}) @b{while ($trace_frame != -1)}
13276 > printf "Frame %d, X == %d\n", $trace_frame, X
13286 @subsection @code{tdump}
13288 @cindex dump all data collected at tracepoint
13289 @cindex tracepoint data, display
13291 This command takes no arguments. It prints all the data collected at
13292 the current trace snapshot.
13295 (@value{GDBP}) @b{trace 444}
13296 (@value{GDBP}) @b{actions}
13297 Enter actions for tracepoint #2, one per line:
13298 > collect $regs, $locals, $args, gdb_long_test
13301 (@value{GDBP}) @b{tstart}
13303 (@value{GDBP}) @b{tfind line 444}
13304 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13306 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13308 (@value{GDBP}) @b{tdump}
13309 Data collected at tracepoint 2, trace frame 1:
13310 d0 0xc4aa0085 -995491707
13314 d4 0x71aea3d 119204413
13317 d7 0x380035 3670069
13318 a0 0x19e24a 1696330
13319 a1 0x3000668 50333288
13321 a3 0x322000 3284992
13322 a4 0x3000698 50333336
13323 a5 0x1ad3cc 1758156
13324 fp 0x30bf3c 0x30bf3c
13325 sp 0x30bf34 0x30bf34
13327 pc 0x20b2c8 0x20b2c8
13331 p = 0x20e5b4 "gdb-test"
13338 gdb_long_test = 17 '\021'
13343 @code{tdump} works by scanning the tracepoint's current collection
13344 actions and printing the value of each expression listed. So
13345 @code{tdump} can fail, if after a run, you change the tracepoint's
13346 actions to mention variables that were not collected during the run.
13348 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13349 uses the collected value of @code{$pc} to distinguish between trace
13350 frames that were collected at the tracepoint hit, and frames that were
13351 collected while stepping. This allows it to correctly choose whether
13352 to display the basic list of collections, or the collections from the
13353 body of the while-stepping loop. However, if @code{$pc} was not collected,
13354 then @code{tdump} will always attempt to dump using the basic collection
13355 list, and may fail if a while-stepping frame does not include all the
13356 same data that is collected at the tracepoint hit.
13357 @c This is getting pretty arcane, example would be good.
13359 @node save tracepoints
13360 @subsection @code{save tracepoints @var{filename}}
13361 @kindex save tracepoints
13362 @kindex save-tracepoints
13363 @cindex save tracepoints for future sessions
13365 This command saves all current tracepoint definitions together with
13366 their actions and passcounts, into a file @file{@var{filename}}
13367 suitable for use in a later debugging session. To read the saved
13368 tracepoint definitions, use the @code{source} command (@pxref{Command
13369 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13370 alias for @w{@code{save tracepoints}}
13372 @node Tracepoint Variables
13373 @section Convenience Variables for Tracepoints
13374 @cindex tracepoint variables
13375 @cindex convenience variables for tracepoints
13378 @vindex $trace_frame
13379 @item (int) $trace_frame
13380 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13381 snapshot is selected.
13383 @vindex $tracepoint
13384 @item (int) $tracepoint
13385 The tracepoint for the current trace snapshot.
13387 @vindex $trace_line
13388 @item (int) $trace_line
13389 The line number for the current trace snapshot.
13391 @vindex $trace_file
13392 @item (char []) $trace_file
13393 The source file for the current trace snapshot.
13395 @vindex $trace_func
13396 @item (char []) $trace_func
13397 The name of the function containing @code{$tracepoint}.
13400 Note: @code{$trace_file} is not suitable for use in @code{printf},
13401 use @code{output} instead.
13403 Here's a simple example of using these convenience variables for
13404 stepping through all the trace snapshots and printing some of their
13405 data. Note that these are not the same as trace state variables,
13406 which are managed by the target.
13409 (@value{GDBP}) @b{tfind start}
13411 (@value{GDBP}) @b{while $trace_frame != -1}
13412 > output $trace_file
13413 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13419 @section Using Trace Files
13420 @cindex trace files
13422 In some situations, the target running a trace experiment may no
13423 longer be available; perhaps it crashed, or the hardware was needed
13424 for a different activity. To handle these cases, you can arrange to
13425 dump the trace data into a file, and later use that file as a source
13426 of trace data, via the @code{target tfile} command.
13431 @item tsave [ -r ] @var{filename}
13432 @itemx tsave [-ctf] @var{dirname}
13433 Save the trace data to @var{filename}. By default, this command
13434 assumes that @var{filename} refers to the host filesystem, so if
13435 necessary @value{GDBN} will copy raw trace data up from the target and
13436 then save it. If the target supports it, you can also supply the
13437 optional argument @code{-r} (``remote'') to direct the target to save
13438 the data directly into @var{filename} in its own filesystem, which may be
13439 more efficient if the trace buffer is very large. (Note, however, that
13440 @code{target tfile} can only read from files accessible to the host.)
13441 By default, this command will save trace frame in tfile format.
13442 You can supply the optional argument @code{-ctf} to save date in CTF
13443 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13444 that can be shared by multiple debugging and tracing tools. Please go to
13445 @indicateurl{http://www.efficios.com/ctf} to get more information.
13447 @kindex target tfile
13451 @item target tfile @var{filename}
13452 @itemx target ctf @var{dirname}
13453 Use the file named @var{filename} or directory named @var{dirname} as
13454 a source of trace data. Commands that examine data work as they do with
13455 a live target, but it is not possible to run any new trace experiments.
13456 @code{tstatus} will report the state of the trace run at the moment
13457 the data was saved, as well as the current trace frame you are examining.
13458 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13462 (@value{GDBP}) target ctf ctf.ctf
13463 (@value{GDBP}) tfind
13464 Found trace frame 0, tracepoint 2
13465 39 ++a; /* set tracepoint 1 here */
13466 (@value{GDBP}) tdump
13467 Data collected at tracepoint 2, trace frame 0:
13471 c = @{"123", "456", "789", "123", "456", "789"@}
13472 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13480 @chapter Debugging Programs That Use Overlays
13483 If your program is too large to fit completely in your target system's
13484 memory, you can sometimes use @dfn{overlays} to work around this
13485 problem. @value{GDBN} provides some support for debugging programs that
13489 * How Overlays Work:: A general explanation of overlays.
13490 * Overlay Commands:: Managing overlays in @value{GDBN}.
13491 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13492 mapped by asking the inferior.
13493 * Overlay Sample Program:: A sample program using overlays.
13496 @node How Overlays Work
13497 @section How Overlays Work
13498 @cindex mapped overlays
13499 @cindex unmapped overlays
13500 @cindex load address, overlay's
13501 @cindex mapped address
13502 @cindex overlay area
13504 Suppose you have a computer whose instruction address space is only 64
13505 kilobytes long, but which has much more memory which can be accessed by
13506 other means: special instructions, segment registers, or memory
13507 management hardware, for example. Suppose further that you want to
13508 adapt a program which is larger than 64 kilobytes to run on this system.
13510 One solution is to identify modules of your program which are relatively
13511 independent, and need not call each other directly; call these modules
13512 @dfn{overlays}. Separate the overlays from the main program, and place
13513 their machine code in the larger memory. Place your main program in
13514 instruction memory, but leave at least enough space there to hold the
13515 largest overlay as well.
13517 Now, to call a function located in an overlay, you must first copy that
13518 overlay's machine code from the large memory into the space set aside
13519 for it in the instruction memory, and then jump to its entry point
13522 @c NB: In the below the mapped area's size is greater or equal to the
13523 @c size of all overlays. This is intentional to remind the developer
13524 @c that overlays don't necessarily need to be the same size.
13528 Data Instruction Larger
13529 Address Space Address Space Address Space
13530 +-----------+ +-----------+ +-----------+
13532 +-----------+ +-----------+ +-----------+<-- overlay 1
13533 | program | | main | .----| overlay 1 | load address
13534 | variables | | program | | +-----------+
13535 | and heap | | | | | |
13536 +-----------+ | | | +-----------+<-- overlay 2
13537 | | +-----------+ | | | load address
13538 +-----------+ | | | .-| overlay 2 |
13540 mapped --->+-----------+ | | +-----------+
13541 address | | | | | |
13542 | overlay | <-' | | |
13543 | area | <---' +-----------+<-- overlay 3
13544 | | <---. | | load address
13545 +-----------+ `--| overlay 3 |
13552 @anchor{A code overlay}A code overlay
13556 The diagram (@pxref{A code overlay}) shows a system with separate data
13557 and instruction address spaces. To map an overlay, the program copies
13558 its code from the larger address space to the instruction address space.
13559 Since the overlays shown here all use the same mapped address, only one
13560 may be mapped at a time. For a system with a single address space for
13561 data and instructions, the diagram would be similar, except that the
13562 program variables and heap would share an address space with the main
13563 program and the overlay area.
13565 An overlay loaded into instruction memory and ready for use is called a
13566 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13567 instruction memory. An overlay not present (or only partially present)
13568 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13569 is its address in the larger memory. The mapped address is also called
13570 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13571 called the @dfn{load memory address}, or @dfn{LMA}.
13573 Unfortunately, overlays are not a completely transparent way to adapt a
13574 program to limited instruction memory. They introduce a new set of
13575 global constraints you must keep in mind as you design your program:
13580 Before calling or returning to a function in an overlay, your program
13581 must make sure that overlay is actually mapped. Otherwise, the call or
13582 return will transfer control to the right address, but in the wrong
13583 overlay, and your program will probably crash.
13586 If the process of mapping an overlay is expensive on your system, you
13587 will need to choose your overlays carefully to minimize their effect on
13588 your program's performance.
13591 The executable file you load onto your system must contain each
13592 overlay's instructions, appearing at the overlay's load address, not its
13593 mapped address. However, each overlay's instructions must be relocated
13594 and its symbols defined as if the overlay were at its mapped address.
13595 You can use GNU linker scripts to specify different load and relocation
13596 addresses for pieces of your program; see @ref{Overlay Description,,,
13597 ld.info, Using ld: the GNU linker}.
13600 The procedure for loading executable files onto your system must be able
13601 to load their contents into the larger address space as well as the
13602 instruction and data spaces.
13606 The overlay system described above is rather simple, and could be
13607 improved in many ways:
13612 If your system has suitable bank switch registers or memory management
13613 hardware, you could use those facilities to make an overlay's load area
13614 contents simply appear at their mapped address in instruction space.
13615 This would probably be faster than copying the overlay to its mapped
13616 area in the usual way.
13619 If your overlays are small enough, you could set aside more than one
13620 overlay area, and have more than one overlay mapped at a time.
13623 You can use overlays to manage data, as well as instructions. In
13624 general, data overlays are even less transparent to your design than
13625 code overlays: whereas code overlays only require care when you call or
13626 return to functions, data overlays require care every time you access
13627 the data. Also, if you change the contents of a data overlay, you
13628 must copy its contents back out to its load address before you can copy a
13629 different data overlay into the same mapped area.
13634 @node Overlay Commands
13635 @section Overlay Commands
13637 To use @value{GDBN}'s overlay support, each overlay in your program must
13638 correspond to a separate section of the executable file. The section's
13639 virtual memory address and load memory address must be the overlay's
13640 mapped and load addresses. Identifying overlays with sections allows
13641 @value{GDBN} to determine the appropriate address of a function or
13642 variable, depending on whether the overlay is mapped or not.
13644 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13645 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13650 Disable @value{GDBN}'s overlay support. When overlay support is
13651 disabled, @value{GDBN} assumes that all functions and variables are
13652 always present at their mapped addresses. By default, @value{GDBN}'s
13653 overlay support is disabled.
13655 @item overlay manual
13656 @cindex manual overlay debugging
13657 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13658 relies on you to tell it which overlays are mapped, and which are not,
13659 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13660 commands described below.
13662 @item overlay map-overlay @var{overlay}
13663 @itemx overlay map @var{overlay}
13664 @cindex map an overlay
13665 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13666 be the name of the object file section containing the overlay. When an
13667 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13668 functions and variables at their mapped addresses. @value{GDBN} assumes
13669 that any other overlays whose mapped ranges overlap that of
13670 @var{overlay} are now unmapped.
13672 @item overlay unmap-overlay @var{overlay}
13673 @itemx overlay unmap @var{overlay}
13674 @cindex unmap an overlay
13675 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13676 must be the name of the object file section containing the overlay.
13677 When an overlay is unmapped, @value{GDBN} assumes it can find the
13678 overlay's functions and variables at their load addresses.
13681 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13682 consults a data structure the overlay manager maintains in the inferior
13683 to see which overlays are mapped. For details, see @ref{Automatic
13684 Overlay Debugging}.
13686 @item overlay load-target
13687 @itemx overlay load
13688 @cindex reloading the overlay table
13689 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13690 re-reads the table @value{GDBN} automatically each time the inferior
13691 stops, so this command should only be necessary if you have changed the
13692 overlay mapping yourself using @value{GDBN}. This command is only
13693 useful when using automatic overlay debugging.
13695 @item overlay list-overlays
13696 @itemx overlay list
13697 @cindex listing mapped overlays
13698 Display a list of the overlays currently mapped, along with their mapped
13699 addresses, load addresses, and sizes.
13703 Normally, when @value{GDBN} prints a code address, it includes the name
13704 of the function the address falls in:
13707 (@value{GDBP}) print main
13708 $3 = @{int ()@} 0x11a0 <main>
13711 When overlay debugging is enabled, @value{GDBN} recognizes code in
13712 unmapped overlays, and prints the names of unmapped functions with
13713 asterisks around them. For example, if @code{foo} is a function in an
13714 unmapped overlay, @value{GDBN} prints it this way:
13717 (@value{GDBP}) overlay list
13718 No sections are mapped.
13719 (@value{GDBP}) print foo
13720 $5 = @{int (int)@} 0x100000 <*foo*>
13723 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13727 (@value{GDBP}) overlay list
13728 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13729 mapped at 0x1016 - 0x104a
13730 (@value{GDBP}) print foo
13731 $6 = @{int (int)@} 0x1016 <foo>
13734 When overlay debugging is enabled, @value{GDBN} can find the correct
13735 address for functions and variables in an overlay, whether or not the
13736 overlay is mapped. This allows most @value{GDBN} commands, like
13737 @code{break} and @code{disassemble}, to work normally, even on unmapped
13738 code. However, @value{GDBN}'s breakpoint support has some limitations:
13742 @cindex breakpoints in overlays
13743 @cindex overlays, setting breakpoints in
13744 You can set breakpoints in functions in unmapped overlays, as long as
13745 @value{GDBN} can write to the overlay at its load address.
13747 @value{GDBN} can not set hardware or simulator-based breakpoints in
13748 unmapped overlays. However, if you set a breakpoint at the end of your
13749 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13750 you are using manual overlay management), @value{GDBN} will re-set its
13751 breakpoints properly.
13755 @node Automatic Overlay Debugging
13756 @section Automatic Overlay Debugging
13757 @cindex automatic overlay debugging
13759 @value{GDBN} can automatically track which overlays are mapped and which
13760 are not, given some simple co-operation from the overlay manager in the
13761 inferior. If you enable automatic overlay debugging with the
13762 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13763 looks in the inferior's memory for certain variables describing the
13764 current state of the overlays.
13766 Here are the variables your overlay manager must define to support
13767 @value{GDBN}'s automatic overlay debugging:
13771 @item @code{_ovly_table}:
13772 This variable must be an array of the following structures:
13777 /* The overlay's mapped address. */
13780 /* The size of the overlay, in bytes. */
13781 unsigned long size;
13783 /* The overlay's load address. */
13786 /* Non-zero if the overlay is currently mapped;
13788 unsigned long mapped;
13792 @item @code{_novlys}:
13793 This variable must be a four-byte signed integer, holding the total
13794 number of elements in @code{_ovly_table}.
13798 To decide whether a particular overlay is mapped or not, @value{GDBN}
13799 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13800 @code{lma} members equal the VMA and LMA of the overlay's section in the
13801 executable file. When @value{GDBN} finds a matching entry, it consults
13802 the entry's @code{mapped} member to determine whether the overlay is
13805 In addition, your overlay manager may define a function called
13806 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13807 will silently set a breakpoint there. If the overlay manager then
13808 calls this function whenever it has changed the overlay table, this
13809 will enable @value{GDBN} to accurately keep track of which overlays
13810 are in program memory, and update any breakpoints that may be set
13811 in overlays. This will allow breakpoints to work even if the
13812 overlays are kept in ROM or other non-writable memory while they
13813 are not being executed.
13815 @node Overlay Sample Program
13816 @section Overlay Sample Program
13817 @cindex overlay example program
13819 When linking a program which uses overlays, you must place the overlays
13820 at their load addresses, while relocating them to run at their mapped
13821 addresses. To do this, you must write a linker script (@pxref{Overlay
13822 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13823 since linker scripts are specific to a particular host system, target
13824 architecture, and target memory layout, this manual cannot provide
13825 portable sample code demonstrating @value{GDBN}'s overlay support.
13827 However, the @value{GDBN} source distribution does contain an overlaid
13828 program, with linker scripts for a few systems, as part of its test
13829 suite. The program consists of the following files from
13830 @file{gdb/testsuite/gdb.base}:
13834 The main program file.
13836 A simple overlay manager, used by @file{overlays.c}.
13841 Overlay modules, loaded and used by @file{overlays.c}.
13844 Linker scripts for linking the test program on the @code{d10v-elf}
13845 and @code{m32r-elf} targets.
13848 You can build the test program using the @code{d10v-elf} GCC
13849 cross-compiler like this:
13852 $ d10v-elf-gcc -g -c overlays.c
13853 $ d10v-elf-gcc -g -c ovlymgr.c
13854 $ d10v-elf-gcc -g -c foo.c
13855 $ d10v-elf-gcc -g -c bar.c
13856 $ d10v-elf-gcc -g -c baz.c
13857 $ d10v-elf-gcc -g -c grbx.c
13858 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13859 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13862 The build process is identical for any other architecture, except that
13863 you must substitute the appropriate compiler and linker script for the
13864 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13868 @chapter Using @value{GDBN} with Different Languages
13871 Although programming languages generally have common aspects, they are
13872 rarely expressed in the same manner. For instance, in ANSI C,
13873 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13874 Modula-2, it is accomplished by @code{p^}. Values can also be
13875 represented (and displayed) differently. Hex numbers in C appear as
13876 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13878 @cindex working language
13879 Language-specific information is built into @value{GDBN} for some languages,
13880 allowing you to express operations like the above in your program's
13881 native language, and allowing @value{GDBN} to output values in a manner
13882 consistent with the syntax of your program's native language. The
13883 language you use to build expressions is called the @dfn{working
13887 * Setting:: Switching between source languages
13888 * Show:: Displaying the language
13889 * Checks:: Type and range checks
13890 * Supported Languages:: Supported languages
13891 * Unsupported Languages:: Unsupported languages
13895 @section Switching Between Source Languages
13897 There are two ways to control the working language---either have @value{GDBN}
13898 set it automatically, or select it manually yourself. You can use the
13899 @code{set language} command for either purpose. On startup, @value{GDBN}
13900 defaults to setting the language automatically. The working language is
13901 used to determine how expressions you type are interpreted, how values
13904 In addition to the working language, every source file that
13905 @value{GDBN} knows about has its own working language. For some object
13906 file formats, the compiler might indicate which language a particular
13907 source file is in. However, most of the time @value{GDBN} infers the
13908 language from the name of the file. The language of a source file
13909 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13910 show each frame appropriately for its own language. There is no way to
13911 set the language of a source file from within @value{GDBN}, but you can
13912 set the language associated with a filename extension. @xref{Show, ,
13913 Displaying the Language}.
13915 This is most commonly a problem when you use a program, such
13916 as @code{cfront} or @code{f2c}, that generates C but is written in
13917 another language. In that case, make the
13918 program use @code{#line} directives in its C output; that way
13919 @value{GDBN} will know the correct language of the source code of the original
13920 program, and will display that source code, not the generated C code.
13923 * Filenames:: Filename extensions and languages.
13924 * Manually:: Setting the working language manually
13925 * Automatically:: Having @value{GDBN} infer the source language
13929 @subsection List of Filename Extensions and Languages
13931 If a source file name ends in one of the following extensions, then
13932 @value{GDBN} infers that its language is the one indicated.
13950 C@t{++} source file
13956 Objective-C source file
13960 Fortran source file
13963 Modula-2 source file
13967 Assembler source file. This actually behaves almost like C, but
13968 @value{GDBN} does not skip over function prologues when stepping.
13971 In addition, you may set the language associated with a filename
13972 extension. @xref{Show, , Displaying the Language}.
13975 @subsection Setting the Working Language
13977 If you allow @value{GDBN} to set the language automatically,
13978 expressions are interpreted the same way in your debugging session and
13981 @kindex set language
13982 If you wish, you may set the language manually. To do this, issue the
13983 command @samp{set language @var{lang}}, where @var{lang} is the name of
13984 a language, such as
13985 @code{c} or @code{modula-2}.
13986 For a list of the supported languages, type @samp{set language}.
13988 Setting the language manually prevents @value{GDBN} from updating the working
13989 language automatically. This can lead to confusion if you try
13990 to debug a program when the working language is not the same as the
13991 source language, when an expression is acceptable to both
13992 languages---but means different things. For instance, if the current
13993 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14001 might not have the effect you intended. In C, this means to add
14002 @code{b} and @code{c} and place the result in @code{a}. The result
14003 printed would be the value of @code{a}. In Modula-2, this means to compare
14004 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14006 @node Automatically
14007 @subsection Having @value{GDBN} Infer the Source Language
14009 To have @value{GDBN} set the working language automatically, use
14010 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14011 then infers the working language. That is, when your program stops in a
14012 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14013 working language to the language recorded for the function in that
14014 frame. If the language for a frame is unknown (that is, if the function
14015 or block corresponding to the frame was defined in a source file that
14016 does not have a recognized extension), the current working language is
14017 not changed, and @value{GDBN} issues a warning.
14019 This may not seem necessary for most programs, which are written
14020 entirely in one source language. However, program modules and libraries
14021 written in one source language can be used by a main program written in
14022 a different source language. Using @samp{set language auto} in this
14023 case frees you from having to set the working language manually.
14026 @section Displaying the Language
14028 The following commands help you find out which language is the
14029 working language, and also what language source files were written in.
14032 @item show language
14033 @anchor{show language}
14034 @kindex show language
14035 Display the current working language. This is the
14036 language you can use with commands such as @code{print} to
14037 build and compute expressions that may involve variables in your program.
14040 @kindex info frame@r{, show the source language}
14041 Display the source language for this frame. This language becomes the
14042 working language if you use an identifier from this frame.
14043 @xref{Frame Info, ,Information about a Frame}, to identify the other
14044 information listed here.
14047 @kindex info source@r{, show the source language}
14048 Display the source language of this source file.
14049 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14050 information listed here.
14053 In unusual circumstances, you may have source files with extensions
14054 not in the standard list. You can then set the extension associated
14055 with a language explicitly:
14058 @item set extension-language @var{ext} @var{language}
14059 @kindex set extension-language
14060 Tell @value{GDBN} that source files with extension @var{ext} are to be
14061 assumed as written in the source language @var{language}.
14063 @item info extensions
14064 @kindex info extensions
14065 List all the filename extensions and the associated languages.
14069 @section Type and Range Checking
14071 Some languages are designed to guard you against making seemingly common
14072 errors through a series of compile- and run-time checks. These include
14073 checking the type of arguments to functions and operators and making
14074 sure mathematical overflows are caught at run time. Checks such as
14075 these help to ensure a program's correctness once it has been compiled
14076 by eliminating type mismatches and providing active checks for range
14077 errors when your program is running.
14079 By default @value{GDBN} checks for these errors according to the
14080 rules of the current source language. Although @value{GDBN} does not check
14081 the statements in your program, it can check expressions entered directly
14082 into @value{GDBN} for evaluation via the @code{print} command, for example.
14085 * Type Checking:: An overview of type checking
14086 * Range Checking:: An overview of range checking
14089 @cindex type checking
14090 @cindex checks, type
14091 @node Type Checking
14092 @subsection An Overview of Type Checking
14094 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14095 arguments to operators and functions have to be of the correct type,
14096 otherwise an error occurs. These checks prevent type mismatch
14097 errors from ever causing any run-time problems. For example,
14100 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14102 (@value{GDBP}) print obj.my_method (0)
14105 (@value{GDBP}) print obj.my_method (0x1234)
14106 Cannot resolve method klass::my_method to any overloaded instance
14109 The second example fails because in C@t{++} the integer constant
14110 @samp{0x1234} is not type-compatible with the pointer parameter type.
14112 For the expressions you use in @value{GDBN} commands, you can tell
14113 @value{GDBN} to not enforce strict type checking or
14114 to treat any mismatches as errors and abandon the expression;
14115 When type checking is disabled, @value{GDBN} successfully evaluates
14116 expressions like the second example above.
14118 Even if type checking is off, there may be other reasons
14119 related to type that prevent @value{GDBN} from evaluating an expression.
14120 For instance, @value{GDBN} does not know how to add an @code{int} and
14121 a @code{struct foo}. These particular type errors have nothing to do
14122 with the language in use and usually arise from expressions which make
14123 little sense to evaluate anyway.
14125 @value{GDBN} provides some additional commands for controlling type checking:
14127 @kindex set check type
14128 @kindex show check type
14130 @item set check type on
14131 @itemx set check type off
14132 Set strict type checking on or off. If any type mismatches occur in
14133 evaluating an expression while type checking is on, @value{GDBN} prints a
14134 message and aborts evaluation of the expression.
14136 @item show check type
14137 Show the current setting of type checking and whether @value{GDBN}
14138 is enforcing strict type checking rules.
14141 @cindex range checking
14142 @cindex checks, range
14143 @node Range Checking
14144 @subsection An Overview of Range Checking
14146 In some languages (such as Modula-2), it is an error to exceed the
14147 bounds of a type; this is enforced with run-time checks. Such range
14148 checking is meant to ensure program correctness by making sure
14149 computations do not overflow, or indices on an array element access do
14150 not exceed the bounds of the array.
14152 For expressions you use in @value{GDBN} commands, you can tell
14153 @value{GDBN} to treat range errors in one of three ways: ignore them,
14154 always treat them as errors and abandon the expression, or issue
14155 warnings but evaluate the expression anyway.
14157 A range error can result from numerical overflow, from exceeding an
14158 array index bound, or when you type a constant that is not a member
14159 of any type. Some languages, however, do not treat overflows as an
14160 error. In many implementations of C, mathematical overflow causes the
14161 result to ``wrap around'' to lower values---for example, if @var{m} is
14162 the largest integer value, and @var{s} is the smallest, then
14165 @var{m} + 1 @result{} @var{s}
14168 This, too, is specific to individual languages, and in some cases
14169 specific to individual compilers or machines. @xref{Supported Languages, ,
14170 Supported Languages}, for further details on specific languages.
14172 @value{GDBN} provides some additional commands for controlling the range checker:
14174 @kindex set check range
14175 @kindex show check range
14177 @item set check range auto
14178 Set range checking on or off based on the current working language.
14179 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14182 @item set check range on
14183 @itemx set check range off
14184 Set range checking on or off, overriding the default setting for the
14185 current working language. A warning is issued if the setting does not
14186 match the language default. If a range error occurs and range checking is on,
14187 then a message is printed and evaluation of the expression is aborted.
14189 @item set check range warn
14190 Output messages when the @value{GDBN} range checker detects a range error,
14191 but attempt to evaluate the expression anyway. Evaluating the
14192 expression may still be impossible for other reasons, such as accessing
14193 memory that the process does not own (a typical example from many Unix
14197 Show the current setting of the range checker, and whether or not it is
14198 being set automatically by @value{GDBN}.
14201 @node Supported Languages
14202 @section Supported Languages
14204 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14205 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14206 @c This is false ...
14207 Some @value{GDBN} features may be used in expressions regardless of the
14208 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14209 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14210 ,Expressions}) can be used with the constructs of any supported
14213 The following sections detail to what degree each source language is
14214 supported by @value{GDBN}. These sections are not meant to be language
14215 tutorials or references, but serve only as a reference guide to what the
14216 @value{GDBN} expression parser accepts, and what input and output
14217 formats should look like for different languages. There are many good
14218 books written on each of these languages; please look to these for a
14219 language reference or tutorial.
14222 * C:: C and C@t{++}
14225 * Objective-C:: Objective-C
14226 * OpenCL C:: OpenCL C
14227 * Fortran:: Fortran
14229 * Modula-2:: Modula-2
14234 @subsection C and C@t{++}
14236 @cindex C and C@t{++}
14237 @cindex expressions in C or C@t{++}
14239 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14240 to both languages. Whenever this is the case, we discuss those languages
14244 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14245 @cindex @sc{gnu} C@t{++}
14246 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14247 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14248 effectively, you must compile your C@t{++} programs with a supported
14249 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14250 compiler (@code{aCC}).
14253 * C Operators:: C and C@t{++} operators
14254 * C Constants:: C and C@t{++} constants
14255 * C Plus Plus Expressions:: C@t{++} expressions
14256 * C Defaults:: Default settings for C and C@t{++}
14257 * C Checks:: C and C@t{++} type and range checks
14258 * Debugging C:: @value{GDBN} and C
14259 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14260 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14264 @subsubsection C and C@t{++} Operators
14266 @cindex C and C@t{++} operators
14268 Operators must be defined on values of specific types. For instance,
14269 @code{+} is defined on numbers, but not on structures. Operators are
14270 often defined on groups of types.
14272 For the purposes of C and C@t{++}, the following definitions hold:
14277 @emph{Integral types} include @code{int} with any of its storage-class
14278 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14281 @emph{Floating-point types} include @code{float}, @code{double}, and
14282 @code{long double} (if supported by the target platform).
14285 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14288 @emph{Scalar types} include all of the above.
14293 The following operators are supported. They are listed here
14294 in order of increasing precedence:
14298 The comma or sequencing operator. Expressions in a comma-separated list
14299 are evaluated from left to right, with the result of the entire
14300 expression being the last expression evaluated.
14303 Assignment. The value of an assignment expression is the value
14304 assigned. Defined on scalar types.
14307 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14308 and translated to @w{@code{@var{a} = @var{a op b}}}.
14309 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14310 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14311 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14314 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14315 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14316 should be of an integral type.
14319 Logical @sc{or}. Defined on integral types.
14322 Logical @sc{and}. Defined on integral types.
14325 Bitwise @sc{or}. Defined on integral types.
14328 Bitwise exclusive-@sc{or}. Defined on integral types.
14331 Bitwise @sc{and}. Defined on integral types.
14334 Equality and inequality. Defined on scalar types. The value of these
14335 expressions is 0 for false and non-zero for true.
14337 @item <@r{, }>@r{, }<=@r{, }>=
14338 Less than, greater than, less than or equal, greater than or equal.
14339 Defined on scalar types. The value of these expressions is 0 for false
14340 and non-zero for true.
14343 left shift, and right shift. Defined on integral types.
14346 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14349 Addition and subtraction. Defined on integral types, floating-point types and
14352 @item *@r{, }/@r{, }%
14353 Multiplication, division, and modulus. Multiplication and division are
14354 defined on integral and floating-point types. Modulus is defined on
14358 Increment and decrement. When appearing before a variable, the
14359 operation is performed before the variable is used in an expression;
14360 when appearing after it, the variable's value is used before the
14361 operation takes place.
14364 Pointer dereferencing. Defined on pointer types. Same precedence as
14368 Address operator. Defined on variables. Same precedence as @code{++}.
14370 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14371 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14372 to examine the address
14373 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14377 Negative. Defined on integral and floating-point types. Same
14378 precedence as @code{++}.
14381 Logical negation. Defined on integral types. Same precedence as
14385 Bitwise complement operator. Defined on integral types. Same precedence as
14390 Structure member, and pointer-to-structure member. For convenience,
14391 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14392 pointer based on the stored type information.
14393 Defined on @code{struct} and @code{union} data.
14396 Dereferences of pointers to members.
14399 Array indexing. @code{@var{a}[@var{i}]} is defined as
14400 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14403 Function parameter list. Same precedence as @code{->}.
14406 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14407 and @code{class} types.
14410 Doubled colons also represent the @value{GDBN} scope operator
14411 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14415 If an operator is redefined in the user code, @value{GDBN} usually
14416 attempts to invoke the redefined version instead of using the operator's
14417 predefined meaning.
14420 @subsubsection C and C@t{++} Constants
14422 @cindex C and C@t{++} constants
14424 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14429 Integer constants are a sequence of digits. Octal constants are
14430 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14431 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14432 @samp{l}, specifying that the constant should be treated as a
14436 Floating point constants are a sequence of digits, followed by a decimal
14437 point, followed by a sequence of digits, and optionally followed by an
14438 exponent. An exponent is of the form:
14439 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14440 sequence of digits. The @samp{+} is optional for positive exponents.
14441 A floating-point constant may also end with a letter @samp{f} or
14442 @samp{F}, specifying that the constant should be treated as being of
14443 the @code{float} (as opposed to the default @code{double}) type; or with
14444 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14448 Enumerated constants consist of enumerated identifiers, or their
14449 integral equivalents.
14452 Character constants are a single character surrounded by single quotes
14453 (@code{'}), or a number---the ordinal value of the corresponding character
14454 (usually its @sc{ascii} value). Within quotes, the single character may
14455 be represented by a letter or by @dfn{escape sequences}, which are of
14456 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14457 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14458 @samp{@var{x}} is a predefined special character---for example,
14459 @samp{\n} for newline.
14461 Wide character constants can be written by prefixing a character
14462 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14463 form of @samp{x}. The target wide character set is used when
14464 computing the value of this constant (@pxref{Character Sets}).
14467 String constants are a sequence of character constants surrounded by
14468 double quotes (@code{"}). Any valid character constant (as described
14469 above) may appear. Double quotes within the string must be preceded by
14470 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14473 Wide string constants can be written by prefixing a string constant
14474 with @samp{L}, as in C. The target wide character set is used when
14475 computing the value of this constant (@pxref{Character Sets}).
14478 Pointer constants are an integral value. You can also write pointers
14479 to constants using the C operator @samp{&}.
14482 Array constants are comma-separated lists surrounded by braces @samp{@{}
14483 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14484 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14485 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14488 @node C Plus Plus Expressions
14489 @subsubsection C@t{++} Expressions
14491 @cindex expressions in C@t{++}
14492 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14494 @cindex debugging C@t{++} programs
14495 @cindex C@t{++} compilers
14496 @cindex debug formats and C@t{++}
14497 @cindex @value{NGCC} and C@t{++}
14499 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14500 the proper compiler and the proper debug format. Currently,
14501 @value{GDBN} works best when debugging C@t{++} code that is compiled
14502 with the most recent version of @value{NGCC} possible. The DWARF
14503 debugging format is preferred; @value{NGCC} defaults to this on most
14504 popular platforms. Other compilers and/or debug formats are likely to
14505 work badly or not at all when using @value{GDBN} to debug C@t{++}
14506 code. @xref{Compilation}.
14511 @cindex member functions
14513 Member function calls are allowed; you can use expressions like
14516 count = aml->GetOriginal(x, y)
14519 @vindex this@r{, inside C@t{++} member functions}
14520 @cindex namespace in C@t{++}
14522 While a member function is active (in the selected stack frame), your
14523 expressions have the same namespace available as the member function;
14524 that is, @value{GDBN} allows implicit references to the class instance
14525 pointer @code{this} following the same rules as C@t{++}. @code{using}
14526 declarations in the current scope are also respected by @value{GDBN}.
14528 @cindex call overloaded functions
14529 @cindex overloaded functions, calling
14530 @cindex type conversions in C@t{++}
14532 You can call overloaded functions; @value{GDBN} resolves the function
14533 call to the right definition, with some restrictions. @value{GDBN} does not
14534 perform overload resolution involving user-defined type conversions,
14535 calls to constructors, or instantiations of templates that do not exist
14536 in the program. It also cannot handle ellipsis argument lists or
14539 It does perform integral conversions and promotions, floating-point
14540 promotions, arithmetic conversions, pointer conversions, conversions of
14541 class objects to base classes, and standard conversions such as those of
14542 functions or arrays to pointers; it requires an exact match on the
14543 number of function arguments.
14545 Overload resolution is always performed, unless you have specified
14546 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14547 ,@value{GDBN} Features for C@t{++}}.
14549 You must specify @code{set overload-resolution off} in order to use an
14550 explicit function signature to call an overloaded function, as in
14552 p 'foo(char,int)'('x', 13)
14555 The @value{GDBN} command-completion facility can simplify this;
14556 see @ref{Completion, ,Command Completion}.
14558 @cindex reference declarations
14560 @value{GDBN} understands variables declared as C@t{++} references; you can use
14561 them in expressions just as you do in C@t{++} source---they are automatically
14564 In the parameter list shown when @value{GDBN} displays a frame, the values of
14565 reference variables are not displayed (unlike other variables); this
14566 avoids clutter, since references are often used for large structures.
14567 The @emph{address} of a reference variable is always shown, unless
14568 you have specified @samp{set print address off}.
14571 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14572 expressions can use it just as expressions in your program do. Since
14573 one scope may be defined in another, you can use @code{::} repeatedly if
14574 necessary, for example in an expression like
14575 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14576 resolving name scope by reference to source files, in both C and C@t{++}
14577 debugging (@pxref{Variables, ,Program Variables}).
14580 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14585 @subsubsection C and C@t{++} Defaults
14587 @cindex C and C@t{++} defaults
14589 If you allow @value{GDBN} to set range checking automatically, it
14590 defaults to @code{off} whenever the working language changes to
14591 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14592 selects the working language.
14594 If you allow @value{GDBN} to set the language automatically, it
14595 recognizes source files whose names end with @file{.c}, @file{.C}, or
14596 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14597 these files, it sets the working language to C or C@t{++}.
14598 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14599 for further details.
14602 @subsubsection C and C@t{++} Type and Range Checks
14604 @cindex C and C@t{++} checks
14606 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14607 checking is used. However, if you turn type checking off, @value{GDBN}
14608 will allow certain non-standard conversions, such as promoting integer
14609 constants to pointers.
14611 Range checking, if turned on, is done on mathematical operations. Array
14612 indices are not checked, since they are often used to index a pointer
14613 that is not itself an array.
14616 @subsubsection @value{GDBN} and C
14618 The @code{set print union} and @code{show print union} commands apply to
14619 the @code{union} type. When set to @samp{on}, any @code{union} that is
14620 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14621 appears as @samp{@{...@}}.
14623 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14624 with pointers and a memory allocation function. @xref{Expressions,
14627 @node Debugging C Plus Plus
14628 @subsubsection @value{GDBN} Features for C@t{++}
14630 @cindex commands for C@t{++}
14632 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14633 designed specifically for use with C@t{++}. Here is a summary:
14636 @cindex break in overloaded functions
14637 @item @r{breakpoint menus}
14638 When you want a breakpoint in a function whose name is overloaded,
14639 @value{GDBN} has the capability to display a menu of possible breakpoint
14640 locations to help you specify which function definition you want.
14641 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14643 @cindex overloading in C@t{++}
14644 @item rbreak @var{regex}
14645 Setting breakpoints using regular expressions is helpful for setting
14646 breakpoints on overloaded functions that are not members of any special
14648 @xref{Set Breaks, ,Setting Breakpoints}.
14650 @cindex C@t{++} exception handling
14652 @itemx catch rethrow
14654 Debug C@t{++} exception handling using these commands. @xref{Set
14655 Catchpoints, , Setting Catchpoints}.
14657 @cindex inheritance
14658 @item ptype @var{typename}
14659 Print inheritance relationships as well as other information for type
14661 @xref{Symbols, ,Examining the Symbol Table}.
14663 @item info vtbl @var{expression}.
14664 The @code{info vtbl} command can be used to display the virtual
14665 method tables of the object computed by @var{expression}. This shows
14666 one entry per virtual table; there may be multiple virtual tables when
14667 multiple inheritance is in use.
14669 @cindex C@t{++} demangling
14670 @item demangle @var{name}
14671 Demangle @var{name}.
14672 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14674 @cindex C@t{++} symbol display
14675 @item set print demangle
14676 @itemx show print demangle
14677 @itemx set print asm-demangle
14678 @itemx show print asm-demangle
14679 Control whether C@t{++} symbols display in their source form, both when
14680 displaying code as C@t{++} source and when displaying disassemblies.
14681 @xref{Print Settings, ,Print Settings}.
14683 @item set print object
14684 @itemx show print object
14685 Choose whether to print derived (actual) or declared types of objects.
14686 @xref{Print Settings, ,Print Settings}.
14688 @item set print vtbl
14689 @itemx show print vtbl
14690 Control the format for printing virtual function tables.
14691 @xref{Print Settings, ,Print Settings}.
14692 (The @code{vtbl} commands do not work on programs compiled with the HP
14693 ANSI C@t{++} compiler (@code{aCC}).)
14695 @kindex set overload-resolution
14696 @cindex overloaded functions, overload resolution
14697 @item set overload-resolution on
14698 Enable overload resolution for C@t{++} expression evaluation. The default
14699 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14700 and searches for a function whose signature matches the argument types,
14701 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14702 Expressions, ,C@t{++} Expressions}, for details).
14703 If it cannot find a match, it emits a message.
14705 @item set overload-resolution off
14706 Disable overload resolution for C@t{++} expression evaluation. For
14707 overloaded functions that are not class member functions, @value{GDBN}
14708 chooses the first function of the specified name that it finds in the
14709 symbol table, whether or not its arguments are of the correct type. For
14710 overloaded functions that are class member functions, @value{GDBN}
14711 searches for a function whose signature @emph{exactly} matches the
14714 @kindex show overload-resolution
14715 @item show overload-resolution
14716 Show the current setting of overload resolution.
14718 @item @r{Overloaded symbol names}
14719 You can specify a particular definition of an overloaded symbol, using
14720 the same notation that is used to declare such symbols in C@t{++}: type
14721 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14722 also use the @value{GDBN} command-line word completion facilities to list the
14723 available choices, or to finish the type list for you.
14724 @xref{Completion,, Command Completion}, for details on how to do this.
14727 @node Decimal Floating Point
14728 @subsubsection Decimal Floating Point format
14729 @cindex decimal floating point format
14731 @value{GDBN} can examine, set and perform computations with numbers in
14732 decimal floating point format, which in the C language correspond to the
14733 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14734 specified by the extension to support decimal floating-point arithmetic.
14736 There are two encodings in use, depending on the architecture: BID (Binary
14737 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14738 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14741 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14742 to manipulate decimal floating point numbers, it is not possible to convert
14743 (using a cast, for example) integers wider than 32-bit to decimal float.
14745 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14746 point computations, error checking in decimal float operations ignores
14747 underflow, overflow and divide by zero exceptions.
14749 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14750 to inspect @code{_Decimal128} values stored in floating point registers.
14751 See @ref{PowerPC,,PowerPC} for more details.
14757 @value{GDBN} can be used to debug programs written in D and compiled with
14758 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14759 specific feature --- dynamic arrays.
14764 @cindex Go (programming language)
14765 @value{GDBN} can be used to debug programs written in Go and compiled with
14766 @file{gccgo} or @file{6g} compilers.
14768 Here is a summary of the Go-specific features and restrictions:
14771 @cindex current Go package
14772 @item The current Go package
14773 The name of the current package does not need to be specified when
14774 specifying global variables and functions.
14776 For example, given the program:
14780 var myglob = "Shall we?"
14786 When stopped inside @code{main} either of these work:
14790 (gdb) p main.myglob
14793 @cindex builtin Go types
14794 @item Builtin Go types
14795 The @code{string} type is recognized by @value{GDBN} and is printed
14798 @cindex builtin Go functions
14799 @item Builtin Go functions
14800 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14801 function and handles it internally.
14803 @cindex restrictions on Go expressions
14804 @item Restrictions on Go expressions
14805 All Go operators are supported except @code{&^}.
14806 The Go @code{_} ``blank identifier'' is not supported.
14807 Automatic dereferencing of pointers is not supported.
14811 @subsection Objective-C
14813 @cindex Objective-C
14814 This section provides information about some commands and command
14815 options that are useful for debugging Objective-C code. See also
14816 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14817 few more commands specific to Objective-C support.
14820 * Method Names in Commands::
14821 * The Print Command with Objective-C::
14824 @node Method Names in Commands
14825 @subsubsection Method Names in Commands
14827 The following commands have been extended to accept Objective-C method
14828 names as line specifications:
14830 @kindex clear@r{, and Objective-C}
14831 @kindex break@r{, and Objective-C}
14832 @kindex info line@r{, and Objective-C}
14833 @kindex jump@r{, and Objective-C}
14834 @kindex list@r{, and Objective-C}
14838 @item @code{info line}
14843 A fully qualified Objective-C method name is specified as
14846 -[@var{Class} @var{methodName}]
14849 where the minus sign is used to indicate an instance method and a
14850 plus sign (not shown) is used to indicate a class method. The class
14851 name @var{Class} and method name @var{methodName} are enclosed in
14852 brackets, similar to the way messages are specified in Objective-C
14853 source code. For example, to set a breakpoint at the @code{create}
14854 instance method of class @code{Fruit} in the program currently being
14858 break -[Fruit create]
14861 To list ten program lines around the @code{initialize} class method,
14865 list +[NSText initialize]
14868 In the current version of @value{GDBN}, the plus or minus sign is
14869 required. In future versions of @value{GDBN}, the plus or minus
14870 sign will be optional, but you can use it to narrow the search. It
14871 is also possible to specify just a method name:
14877 You must specify the complete method name, including any colons. If
14878 your program's source files contain more than one @code{create} method,
14879 you'll be presented with a numbered list of classes that implement that
14880 method. Indicate your choice by number, or type @samp{0} to exit if
14883 As another example, to clear a breakpoint established at the
14884 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14887 clear -[NSWindow makeKeyAndOrderFront:]
14890 @node The Print Command with Objective-C
14891 @subsubsection The Print Command With Objective-C
14892 @cindex Objective-C, print objects
14893 @kindex print-object
14894 @kindex po @r{(@code{print-object})}
14896 The print command has also been extended to accept methods. For example:
14899 print -[@var{object} hash]
14902 @cindex print an Objective-C object description
14903 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14905 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14906 and print the result. Also, an additional command has been added,
14907 @code{print-object} or @code{po} for short, which is meant to print
14908 the description of an object. However, this command may only work
14909 with certain Objective-C libraries that have a particular hook
14910 function, @code{_NSPrintForDebugger}, defined.
14913 @subsection OpenCL C
14916 This section provides information about @value{GDBN}s OpenCL C support.
14919 * OpenCL C Datatypes::
14920 * OpenCL C Expressions::
14921 * OpenCL C Operators::
14924 @node OpenCL C Datatypes
14925 @subsubsection OpenCL C Datatypes
14927 @cindex OpenCL C Datatypes
14928 @value{GDBN} supports the builtin scalar and vector datatypes specified
14929 by OpenCL 1.1. In addition the half- and double-precision floating point
14930 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14931 extensions are also known to @value{GDBN}.
14933 @node OpenCL C Expressions
14934 @subsubsection OpenCL C Expressions
14936 @cindex OpenCL C Expressions
14937 @value{GDBN} supports accesses to vector components including the access as
14938 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14939 supported by @value{GDBN} can be used as well.
14941 @node OpenCL C Operators
14942 @subsubsection OpenCL C Operators
14944 @cindex OpenCL C Operators
14945 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14949 @subsection Fortran
14950 @cindex Fortran-specific support in @value{GDBN}
14952 @value{GDBN} can be used to debug programs written in Fortran, but it
14953 currently supports only the features of Fortran 77 language.
14955 @cindex trailing underscore, in Fortran symbols
14956 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14957 among them) append an underscore to the names of variables and
14958 functions. When you debug programs compiled by those compilers, you
14959 will need to refer to variables and functions with a trailing
14963 * Fortran Operators:: Fortran operators and expressions
14964 * Fortran Defaults:: Default settings for Fortran
14965 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14968 @node Fortran Operators
14969 @subsubsection Fortran Operators and Expressions
14971 @cindex Fortran operators and expressions
14973 Operators must be defined on values of specific types. For instance,
14974 @code{+} is defined on numbers, but not on characters or other non-
14975 arithmetic types. Operators are often defined on groups of types.
14979 The exponentiation operator. It raises the first operand to the power
14983 The range operator. Normally used in the form of array(low:high) to
14984 represent a section of array.
14987 The access component operator. Normally used to access elements in derived
14988 types. Also suitable for unions. As unions aren't part of regular Fortran,
14989 this can only happen when accessing a register that uses a gdbarch-defined
14993 @node Fortran Defaults
14994 @subsubsection Fortran Defaults
14996 @cindex Fortran Defaults
14998 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14999 default uses case-insensitive matches for Fortran symbols. You can
15000 change that with the @samp{set case-insensitive} command, see
15001 @ref{Symbols}, for the details.
15003 @node Special Fortran Commands
15004 @subsubsection Special Fortran Commands
15006 @cindex Special Fortran commands
15008 @value{GDBN} has some commands to support Fortran-specific features,
15009 such as displaying common blocks.
15012 @cindex @code{COMMON} blocks, Fortran
15013 @kindex info common
15014 @item info common @r{[}@var{common-name}@r{]}
15015 This command prints the values contained in the Fortran @code{COMMON}
15016 block whose name is @var{common-name}. With no argument, the names of
15017 all @code{COMMON} blocks visible at the current program location are
15024 @cindex Pascal support in @value{GDBN}, limitations
15025 Debugging Pascal programs which use sets, subranges, file variables, or
15026 nested functions does not currently work. @value{GDBN} does not support
15027 entering expressions, printing values, or similar features using Pascal
15030 The Pascal-specific command @code{set print pascal_static-members}
15031 controls whether static members of Pascal objects are displayed.
15032 @xref{Print Settings, pascal_static-members}.
15035 @subsection Modula-2
15037 @cindex Modula-2, @value{GDBN} support
15039 The extensions made to @value{GDBN} to support Modula-2 only support
15040 output from the @sc{gnu} Modula-2 compiler (which is currently being
15041 developed). Other Modula-2 compilers are not currently supported, and
15042 attempting to debug executables produced by them is most likely
15043 to give an error as @value{GDBN} reads in the executable's symbol
15046 @cindex expressions in Modula-2
15048 * M2 Operators:: Built-in operators
15049 * Built-In Func/Proc:: Built-in functions and procedures
15050 * M2 Constants:: Modula-2 constants
15051 * M2 Types:: Modula-2 types
15052 * M2 Defaults:: Default settings for Modula-2
15053 * Deviations:: Deviations from standard Modula-2
15054 * M2 Checks:: Modula-2 type and range checks
15055 * M2 Scope:: The scope operators @code{::} and @code{.}
15056 * GDB/M2:: @value{GDBN} and Modula-2
15060 @subsubsection Operators
15061 @cindex Modula-2 operators
15063 Operators must be defined on values of specific types. For instance,
15064 @code{+} is defined on numbers, but not on structures. Operators are
15065 often defined on groups of types. For the purposes of Modula-2, the
15066 following definitions hold:
15071 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15075 @emph{Character types} consist of @code{CHAR} and its subranges.
15078 @emph{Floating-point types} consist of @code{REAL}.
15081 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15085 @emph{Scalar types} consist of all of the above.
15088 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15091 @emph{Boolean types} consist of @code{BOOLEAN}.
15095 The following operators are supported, and appear in order of
15096 increasing precedence:
15100 Function argument or array index separator.
15103 Assignment. The value of @var{var} @code{:=} @var{value} is
15107 Less than, greater than on integral, floating-point, or enumerated
15111 Less than or equal to, greater than or equal to
15112 on integral, floating-point and enumerated types, or set inclusion on
15113 set types. Same precedence as @code{<}.
15115 @item =@r{, }<>@r{, }#
15116 Equality and two ways of expressing inequality, valid on scalar types.
15117 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15118 available for inequality, since @code{#} conflicts with the script
15122 Set membership. Defined on set types and the types of their members.
15123 Same precedence as @code{<}.
15126 Boolean disjunction. Defined on boolean types.
15129 Boolean conjunction. Defined on boolean types.
15132 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15135 Addition and subtraction on integral and floating-point types, or union
15136 and difference on set types.
15139 Multiplication on integral and floating-point types, or set intersection
15143 Division on floating-point types, or symmetric set difference on set
15144 types. Same precedence as @code{*}.
15147 Integer division and remainder. Defined on integral types. Same
15148 precedence as @code{*}.
15151 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15154 Pointer dereferencing. Defined on pointer types.
15157 Boolean negation. Defined on boolean types. Same precedence as
15161 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15162 precedence as @code{^}.
15165 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15168 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15172 @value{GDBN} and Modula-2 scope operators.
15176 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15177 treats the use of the operator @code{IN}, or the use of operators
15178 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15179 @code{<=}, and @code{>=} on sets as an error.
15183 @node Built-In Func/Proc
15184 @subsubsection Built-in Functions and Procedures
15185 @cindex Modula-2 built-ins
15187 Modula-2 also makes available several built-in procedures and functions.
15188 In describing these, the following metavariables are used:
15193 represents an @code{ARRAY} variable.
15196 represents a @code{CHAR} constant or variable.
15199 represents a variable or constant of integral type.
15202 represents an identifier that belongs to a set. Generally used in the
15203 same function with the metavariable @var{s}. The type of @var{s} should
15204 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15207 represents a variable or constant of integral or floating-point type.
15210 represents a variable or constant of floating-point type.
15216 represents a variable.
15219 represents a variable or constant of one of many types. See the
15220 explanation of the function for details.
15223 All Modula-2 built-in procedures also return a result, described below.
15227 Returns the absolute value of @var{n}.
15230 If @var{c} is a lower case letter, it returns its upper case
15231 equivalent, otherwise it returns its argument.
15234 Returns the character whose ordinal value is @var{i}.
15237 Decrements the value in the variable @var{v} by one. Returns the new value.
15239 @item DEC(@var{v},@var{i})
15240 Decrements the value in the variable @var{v} by @var{i}. Returns the
15243 @item EXCL(@var{m},@var{s})
15244 Removes the element @var{m} from the set @var{s}. Returns the new
15247 @item FLOAT(@var{i})
15248 Returns the floating point equivalent of the integer @var{i}.
15250 @item HIGH(@var{a})
15251 Returns the index of the last member of @var{a}.
15254 Increments the value in the variable @var{v} by one. Returns the new value.
15256 @item INC(@var{v},@var{i})
15257 Increments the value in the variable @var{v} by @var{i}. Returns the
15260 @item INCL(@var{m},@var{s})
15261 Adds the element @var{m} to the set @var{s} if it is not already
15262 there. Returns the new set.
15265 Returns the maximum value of the type @var{t}.
15268 Returns the minimum value of the type @var{t}.
15271 Returns boolean TRUE if @var{i} is an odd number.
15274 Returns the ordinal value of its argument. For example, the ordinal
15275 value of a character is its @sc{ascii} value (on machines supporting
15276 the @sc{ascii} character set). The argument @var{x} must be of an
15277 ordered type, which include integral, character and enumerated types.
15279 @item SIZE(@var{x})
15280 Returns the size of its argument. The argument @var{x} can be a
15281 variable or a type.
15283 @item TRUNC(@var{r})
15284 Returns the integral part of @var{r}.
15286 @item TSIZE(@var{x})
15287 Returns the size of its argument. The argument @var{x} can be a
15288 variable or a type.
15290 @item VAL(@var{t},@var{i})
15291 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15295 @emph{Warning:} Sets and their operations are not yet supported, so
15296 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15300 @cindex Modula-2 constants
15302 @subsubsection Constants
15304 @value{GDBN} allows you to express the constants of Modula-2 in the following
15310 Integer constants are simply a sequence of digits. When used in an
15311 expression, a constant is interpreted to be type-compatible with the
15312 rest of the expression. Hexadecimal integers are specified by a
15313 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15316 Floating point constants appear as a sequence of digits, followed by a
15317 decimal point and another sequence of digits. An optional exponent can
15318 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15319 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15320 digits of the floating point constant must be valid decimal (base 10)
15324 Character constants consist of a single character enclosed by a pair of
15325 like quotes, either single (@code{'}) or double (@code{"}). They may
15326 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15327 followed by a @samp{C}.
15330 String constants consist of a sequence of characters enclosed by a
15331 pair of like quotes, either single (@code{'}) or double (@code{"}).
15332 Escape sequences in the style of C are also allowed. @xref{C
15333 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15337 Enumerated constants consist of an enumerated identifier.
15340 Boolean constants consist of the identifiers @code{TRUE} and
15344 Pointer constants consist of integral values only.
15347 Set constants are not yet supported.
15351 @subsubsection Modula-2 Types
15352 @cindex Modula-2 types
15354 Currently @value{GDBN} can print the following data types in Modula-2
15355 syntax: array types, record types, set types, pointer types, procedure
15356 types, enumerated types, subrange types and base types. You can also
15357 print the contents of variables declared using these type.
15358 This section gives a number of simple source code examples together with
15359 sample @value{GDBN} sessions.
15361 The first example contains the following section of code:
15370 and you can request @value{GDBN} to interrogate the type and value of
15371 @code{r} and @code{s}.
15374 (@value{GDBP}) print s
15376 (@value{GDBP}) ptype s
15378 (@value{GDBP}) print r
15380 (@value{GDBP}) ptype r
15385 Likewise if your source code declares @code{s} as:
15389 s: SET ['A'..'Z'] ;
15393 then you may query the type of @code{s} by:
15396 (@value{GDBP}) ptype s
15397 type = SET ['A'..'Z']
15401 Note that at present you cannot interactively manipulate set
15402 expressions using the debugger.
15404 The following example shows how you might declare an array in Modula-2
15405 and how you can interact with @value{GDBN} to print its type and contents:
15409 s: ARRAY [-10..10] OF CHAR ;
15413 (@value{GDBP}) ptype s
15414 ARRAY [-10..10] OF CHAR
15417 Note that the array handling is not yet complete and although the type
15418 is printed correctly, expression handling still assumes that all
15419 arrays have a lower bound of zero and not @code{-10} as in the example
15422 Here are some more type related Modula-2 examples:
15426 colour = (blue, red, yellow, green) ;
15427 t = [blue..yellow] ;
15435 The @value{GDBN} interaction shows how you can query the data type
15436 and value of a variable.
15439 (@value{GDBP}) print s
15441 (@value{GDBP}) ptype t
15442 type = [blue..yellow]
15446 In this example a Modula-2 array is declared and its contents
15447 displayed. Observe that the contents are written in the same way as
15448 their @code{C} counterparts.
15452 s: ARRAY [1..5] OF CARDINAL ;
15458 (@value{GDBP}) print s
15459 $1 = @{1, 0, 0, 0, 0@}
15460 (@value{GDBP}) ptype s
15461 type = ARRAY [1..5] OF CARDINAL
15464 The Modula-2 language interface to @value{GDBN} also understands
15465 pointer types as shown in this example:
15469 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15476 and you can request that @value{GDBN} describes the type of @code{s}.
15479 (@value{GDBP}) ptype s
15480 type = POINTER TO ARRAY [1..5] OF CARDINAL
15483 @value{GDBN} handles compound types as we can see in this example.
15484 Here we combine array types, record types, pointer types and subrange
15495 myarray = ARRAY myrange OF CARDINAL ;
15496 myrange = [-2..2] ;
15498 s: POINTER TO ARRAY myrange OF foo ;
15502 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15506 (@value{GDBP}) ptype s
15507 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15510 f3 : ARRAY [-2..2] OF CARDINAL;
15515 @subsubsection Modula-2 Defaults
15516 @cindex Modula-2 defaults
15518 If type and range checking are set automatically by @value{GDBN}, they
15519 both default to @code{on} whenever the working language changes to
15520 Modula-2. This happens regardless of whether you or @value{GDBN}
15521 selected the working language.
15523 If you allow @value{GDBN} to set the language automatically, then entering
15524 code compiled from a file whose name ends with @file{.mod} sets the
15525 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15526 Infer the Source Language}, for further details.
15529 @subsubsection Deviations from Standard Modula-2
15530 @cindex Modula-2, deviations from
15532 A few changes have been made to make Modula-2 programs easier to debug.
15533 This is done primarily via loosening its type strictness:
15537 Unlike in standard Modula-2, pointer constants can be formed by
15538 integers. This allows you to modify pointer variables during
15539 debugging. (In standard Modula-2, the actual address contained in a
15540 pointer variable is hidden from you; it can only be modified
15541 through direct assignment to another pointer variable or expression that
15542 returned a pointer.)
15545 C escape sequences can be used in strings and characters to represent
15546 non-printable characters. @value{GDBN} prints out strings with these
15547 escape sequences embedded. Single non-printable characters are
15548 printed using the @samp{CHR(@var{nnn})} format.
15551 The assignment operator (@code{:=}) returns the value of its right-hand
15555 All built-in procedures both modify @emph{and} return their argument.
15559 @subsubsection Modula-2 Type and Range Checks
15560 @cindex Modula-2 checks
15563 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15566 @c FIXME remove warning when type/range checks added
15568 @value{GDBN} considers two Modula-2 variables type equivalent if:
15572 They are of types that have been declared equivalent via a @code{TYPE
15573 @var{t1} = @var{t2}} statement
15576 They have been declared on the same line. (Note: This is true of the
15577 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15580 As long as type checking is enabled, any attempt to combine variables
15581 whose types are not equivalent is an error.
15583 Range checking is done on all mathematical operations, assignment, array
15584 index bounds, and all built-in functions and procedures.
15587 @subsubsection The Scope Operators @code{::} and @code{.}
15589 @cindex @code{.}, Modula-2 scope operator
15590 @cindex colon, doubled as scope operator
15592 @vindex colon-colon@r{, in Modula-2}
15593 @c Info cannot handle :: but TeX can.
15596 @vindex ::@r{, in Modula-2}
15599 There are a few subtle differences between the Modula-2 scope operator
15600 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15605 @var{module} . @var{id}
15606 @var{scope} :: @var{id}
15610 where @var{scope} is the name of a module or a procedure,
15611 @var{module} the name of a module, and @var{id} is any declared
15612 identifier within your program, except another module.
15614 Using the @code{::} operator makes @value{GDBN} search the scope
15615 specified by @var{scope} for the identifier @var{id}. If it is not
15616 found in the specified scope, then @value{GDBN} searches all scopes
15617 enclosing the one specified by @var{scope}.
15619 Using the @code{.} operator makes @value{GDBN} search the current scope for
15620 the identifier specified by @var{id} that was imported from the
15621 definition module specified by @var{module}. With this operator, it is
15622 an error if the identifier @var{id} was not imported from definition
15623 module @var{module}, or if @var{id} is not an identifier in
15627 @subsubsection @value{GDBN} and Modula-2
15629 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15630 Five subcommands of @code{set print} and @code{show print} apply
15631 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15632 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15633 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15634 analogue in Modula-2.
15636 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15637 with any language, is not useful with Modula-2. Its
15638 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15639 created in Modula-2 as they can in C or C@t{++}. However, because an
15640 address can be specified by an integral constant, the construct
15641 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15643 @cindex @code{#} in Modula-2
15644 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15645 interpreted as the beginning of a comment. Use @code{<>} instead.
15651 The extensions made to @value{GDBN} for Ada only support
15652 output from the @sc{gnu} Ada (GNAT) compiler.
15653 Other Ada compilers are not currently supported, and
15654 attempting to debug executables produced by them is most likely
15658 @cindex expressions in Ada
15660 * Ada Mode Intro:: General remarks on the Ada syntax
15661 and semantics supported by Ada mode
15663 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15664 * Additions to Ada:: Extensions of the Ada expression syntax.
15665 * Overloading support for Ada:: Support for expressions involving overloaded
15667 * Stopping Before Main Program:: Debugging the program during elaboration.
15668 * Ada Exceptions:: Ada Exceptions
15669 * Ada Tasks:: Listing and setting breakpoints in tasks.
15670 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15671 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15673 * Ada Glitches:: Known peculiarities of Ada mode.
15676 @node Ada Mode Intro
15677 @subsubsection Introduction
15678 @cindex Ada mode, general
15680 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15681 syntax, with some extensions.
15682 The philosophy behind the design of this subset is
15686 That @value{GDBN} should provide basic literals and access to operations for
15687 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15688 leaving more sophisticated computations to subprograms written into the
15689 program (which therefore may be called from @value{GDBN}).
15692 That type safety and strict adherence to Ada language restrictions
15693 are not particularly important to the @value{GDBN} user.
15696 That brevity is important to the @value{GDBN} user.
15699 Thus, for brevity, the debugger acts as if all names declared in
15700 user-written packages are directly visible, even if they are not visible
15701 according to Ada rules, thus making it unnecessary to fully qualify most
15702 names with their packages, regardless of context. Where this causes
15703 ambiguity, @value{GDBN} asks the user's intent.
15705 The debugger will start in Ada mode if it detects an Ada main program.
15706 As for other languages, it will enter Ada mode when stopped in a program that
15707 was translated from an Ada source file.
15709 While in Ada mode, you may use `@t{--}' for comments. This is useful
15710 mostly for documenting command files. The standard @value{GDBN} comment
15711 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15712 middle (to allow based literals).
15714 @node Omissions from Ada
15715 @subsubsection Omissions from Ada
15716 @cindex Ada, omissions from
15718 Here are the notable omissions from the subset:
15722 Only a subset of the attributes are supported:
15726 @t{'First}, @t{'Last}, and @t{'Length}
15727 on array objects (not on types and subtypes).
15730 @t{'Min} and @t{'Max}.
15733 @t{'Pos} and @t{'Val}.
15739 @t{'Range} on array objects (not subtypes), but only as the right
15740 operand of the membership (@code{in}) operator.
15743 @t{'Access}, @t{'Unchecked_Access}, and
15744 @t{'Unrestricted_Access} (a GNAT extension).
15752 @code{Characters.Latin_1} are not available and
15753 concatenation is not implemented. Thus, escape characters in strings are
15754 not currently available.
15757 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15758 equality of representations. They will generally work correctly
15759 for strings and arrays whose elements have integer or enumeration types.
15760 They may not work correctly for arrays whose element
15761 types have user-defined equality, for arrays of real values
15762 (in particular, IEEE-conformant floating point, because of negative
15763 zeroes and NaNs), and for arrays whose elements contain unused bits with
15764 indeterminate values.
15767 The other component-by-component array operations (@code{and}, @code{or},
15768 @code{xor}, @code{not}, and relational tests other than equality)
15769 are not implemented.
15772 @cindex array aggregates (Ada)
15773 @cindex record aggregates (Ada)
15774 @cindex aggregates (Ada)
15775 There is limited support for array and record aggregates. They are
15776 permitted only on the right sides of assignments, as in these examples:
15779 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15780 (@value{GDBP}) set An_Array := (1, others => 0)
15781 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15782 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15783 (@value{GDBP}) set A_Record := (1, "Peter", True);
15784 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15788 discriminant's value by assigning an aggregate has an
15789 undefined effect if that discriminant is used within the record.
15790 However, you can first modify discriminants by directly assigning to
15791 them (which normally would not be allowed in Ada), and then performing an
15792 aggregate assignment. For example, given a variable @code{A_Rec}
15793 declared to have a type such as:
15796 type Rec (Len : Small_Integer := 0) is record
15798 Vals : IntArray (1 .. Len);
15802 you can assign a value with a different size of @code{Vals} with two
15806 (@value{GDBP}) set A_Rec.Len := 4
15807 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15810 As this example also illustrates, @value{GDBN} is very loose about the usual
15811 rules concerning aggregates. You may leave out some of the
15812 components of an array or record aggregate (such as the @code{Len}
15813 component in the assignment to @code{A_Rec} above); they will retain their
15814 original values upon assignment. You may freely use dynamic values as
15815 indices in component associations. You may even use overlapping or
15816 redundant component associations, although which component values are
15817 assigned in such cases is not defined.
15820 Calls to dispatching subprograms are not implemented.
15823 The overloading algorithm is much more limited (i.e., less selective)
15824 than that of real Ada. It makes only limited use of the context in
15825 which a subexpression appears to resolve its meaning, and it is much
15826 looser in its rules for allowing type matches. As a result, some
15827 function calls will be ambiguous, and the user will be asked to choose
15828 the proper resolution.
15831 The @code{new} operator is not implemented.
15834 Entry calls are not implemented.
15837 Aside from printing, arithmetic operations on the native VAX floating-point
15838 formats are not supported.
15841 It is not possible to slice a packed array.
15844 The names @code{True} and @code{False}, when not part of a qualified name,
15845 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15847 Should your program
15848 redefine these names in a package or procedure (at best a dubious practice),
15849 you will have to use fully qualified names to access their new definitions.
15852 @node Additions to Ada
15853 @subsubsection Additions to Ada
15854 @cindex Ada, deviations from
15856 As it does for other languages, @value{GDBN} makes certain generic
15857 extensions to Ada (@pxref{Expressions}):
15861 If the expression @var{E} is a variable residing in memory (typically
15862 a local variable or array element) and @var{N} is a positive integer,
15863 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15864 @var{N}-1 adjacent variables following it in memory as an array. In
15865 Ada, this operator is generally not necessary, since its prime use is
15866 in displaying parts of an array, and slicing will usually do this in
15867 Ada. However, there are occasional uses when debugging programs in
15868 which certain debugging information has been optimized away.
15871 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15872 appears in function or file @var{B}.'' When @var{B} is a file name,
15873 you must typically surround it in single quotes.
15876 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15877 @var{type} that appears at address @var{addr}.''
15880 A name starting with @samp{$} is a convenience variable
15881 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15884 In addition, @value{GDBN} provides a few other shortcuts and outright
15885 additions specific to Ada:
15889 The assignment statement is allowed as an expression, returning
15890 its right-hand operand as its value. Thus, you may enter
15893 (@value{GDBP}) set x := y + 3
15894 (@value{GDBP}) print A(tmp := y + 1)
15898 The semicolon is allowed as an ``operator,'' returning as its value
15899 the value of its right-hand operand.
15900 This allows, for example,
15901 complex conditional breaks:
15904 (@value{GDBP}) break f
15905 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15909 Rather than use catenation and symbolic character names to introduce special
15910 characters into strings, one may instead use a special bracket notation,
15911 which is also used to print strings. A sequence of characters of the form
15912 @samp{["@var{XX}"]} within a string or character literal denotes the
15913 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15914 sequence of characters @samp{["""]} also denotes a single quotation mark
15915 in strings. For example,
15917 "One line.["0a"]Next line.["0a"]"
15920 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15924 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15925 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15929 (@value{GDBP}) print 'max(x, y)
15933 When printing arrays, @value{GDBN} uses positional notation when the
15934 array has a lower bound of 1, and uses a modified named notation otherwise.
15935 For example, a one-dimensional array of three integers with a lower bound
15936 of 3 might print as
15943 That is, in contrast to valid Ada, only the first component has a @code{=>}
15947 You may abbreviate attributes in expressions with any unique,
15948 multi-character subsequence of
15949 their names (an exact match gets preference).
15950 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15951 in place of @t{a'length}.
15954 @cindex quoting Ada internal identifiers
15955 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15956 to lower case. The GNAT compiler uses upper-case characters for
15957 some of its internal identifiers, which are normally of no interest to users.
15958 For the rare occasions when you actually have to look at them,
15959 enclose them in angle brackets to avoid the lower-case mapping.
15962 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15966 Printing an object of class-wide type or dereferencing an
15967 access-to-class-wide value will display all the components of the object's
15968 specific type (as indicated by its run-time tag). Likewise, component
15969 selection on such a value will operate on the specific type of the
15974 @node Overloading support for Ada
15975 @subsubsection Overloading support for Ada
15976 @cindex overloading, Ada
15978 The debugger supports limited overloading. Given a subprogram call in which
15979 the function symbol has multiple definitions, it will use the number of
15980 actual parameters and some information about their types to attempt to narrow
15981 the set of definitions. It also makes very limited use of context, preferring
15982 procedures to functions in the context of the @code{call} command, and
15983 functions to procedures elsewhere.
15985 If, after narrowing, the set of matching definitions still contains more than
15986 one definition, @value{GDBN} will display a menu to query which one it should
15990 (@value{GDBP}) print f(1)
15991 Multiple matches for f
15993 [1] foo.f (integer) return boolean at foo.adb:23
15994 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15998 In this case, just select one menu entry either to cancel expression evaluation
15999 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16000 instance (type the corresponding number and press @key{RET}).
16002 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16007 @kindex set ada print-signatures
16008 @item set ada print-signatures
16009 Control whether parameter types and return types are displayed in overloads
16010 selection menus. It is @code{on} by default.
16011 @xref{Overloading support for Ada}.
16013 @kindex show ada print-signatures
16014 @item show ada print-signatures
16015 Show the current setting for displaying parameter types and return types in
16016 overloads selection menu.
16017 @xref{Overloading support for Ada}.
16021 @node Stopping Before Main Program
16022 @subsubsection Stopping at the Very Beginning
16024 @cindex breakpointing Ada elaboration code
16025 It is sometimes necessary to debug the program during elaboration, and
16026 before reaching the main procedure.
16027 As defined in the Ada Reference
16028 Manual, the elaboration code is invoked from a procedure called
16029 @code{adainit}. To run your program up to the beginning of
16030 elaboration, simply use the following two commands:
16031 @code{tbreak adainit} and @code{run}.
16033 @node Ada Exceptions
16034 @subsubsection Ada Exceptions
16036 A command is provided to list all Ada exceptions:
16039 @kindex info exceptions
16040 @item info exceptions
16041 @itemx info exceptions @var{regexp}
16042 The @code{info exceptions} command allows you to list all Ada exceptions
16043 defined within the program being debugged, as well as their addresses.
16044 With a regular expression, @var{regexp}, as argument, only those exceptions
16045 whose names match @var{regexp} are listed.
16048 Below is a small example, showing how the command can be used, first
16049 without argument, and next with a regular expression passed as an
16053 (@value{GDBP}) info exceptions
16054 All defined Ada exceptions:
16055 constraint_error: 0x613da0
16056 program_error: 0x613d20
16057 storage_error: 0x613ce0
16058 tasking_error: 0x613ca0
16059 const.aint_global_e: 0x613b00
16060 (@value{GDBP}) info exceptions const.aint
16061 All Ada exceptions matching regular expression "const.aint":
16062 constraint_error: 0x613da0
16063 const.aint_global_e: 0x613b00
16066 It is also possible to ask @value{GDBN} to stop your program's execution
16067 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16070 @subsubsection Extensions for Ada Tasks
16071 @cindex Ada, tasking
16073 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16074 @value{GDBN} provides the following task-related commands:
16079 This command shows a list of current Ada tasks, as in the following example:
16086 (@value{GDBP}) info tasks
16087 ID TID P-ID Pri State Name
16088 1 8088000 0 15 Child Activation Wait main_task
16089 2 80a4000 1 15 Accept Statement b
16090 3 809a800 1 15 Child Activation Wait a
16091 * 4 80ae800 3 15 Runnable c
16096 In this listing, the asterisk before the last task indicates it to be the
16097 task currently being inspected.
16101 Represents @value{GDBN}'s internal task number.
16107 The parent's task ID (@value{GDBN}'s internal task number).
16110 The base priority of the task.
16113 Current state of the task.
16117 The task has been created but has not been activated. It cannot be
16121 The task is not blocked for any reason known to Ada. (It may be waiting
16122 for a mutex, though.) It is conceptually "executing" in normal mode.
16125 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16126 that were waiting on terminate alternatives have been awakened and have
16127 terminated themselves.
16129 @item Child Activation Wait
16130 The task is waiting for created tasks to complete activation.
16132 @item Accept Statement
16133 The task is waiting on an accept or selective wait statement.
16135 @item Waiting on entry call
16136 The task is waiting on an entry call.
16138 @item Async Select Wait
16139 The task is waiting to start the abortable part of an asynchronous
16143 The task is waiting on a select statement with only a delay
16146 @item Child Termination Wait
16147 The task is sleeping having completed a master within itself, and is
16148 waiting for the tasks dependent on that master to become terminated or
16149 waiting on a terminate Phase.
16151 @item Wait Child in Term Alt
16152 The task is sleeping waiting for tasks on terminate alternatives to
16153 finish terminating.
16155 @item Accepting RV with @var{taskno}
16156 The task is accepting a rendez-vous with the task @var{taskno}.
16160 Name of the task in the program.
16164 @kindex info task @var{taskno}
16165 @item info task @var{taskno}
16166 This command shows detailled informations on the specified task, as in
16167 the following example:
16172 (@value{GDBP}) info tasks
16173 ID TID P-ID Pri State Name
16174 1 8077880 0 15 Child Activation Wait main_task
16175 * 2 807c468 1 15 Runnable task_1
16176 (@value{GDBP}) info task 2
16177 Ada Task: 0x807c468
16180 Parent: 1 (main_task)
16186 @kindex task@r{ (Ada)}
16187 @cindex current Ada task ID
16188 This command prints the ID of the current task.
16194 (@value{GDBP}) info tasks
16195 ID TID P-ID Pri State Name
16196 1 8077870 0 15 Child Activation Wait main_task
16197 * 2 807c458 1 15 Runnable t
16198 (@value{GDBP}) task
16199 [Current task is 2]
16202 @item task @var{taskno}
16203 @cindex Ada task switching
16204 This command is like the @code{thread @var{thread-id}}
16205 command (@pxref{Threads}). It switches the context of debugging
16206 from the current task to the given task.
16212 (@value{GDBP}) info tasks
16213 ID TID P-ID Pri State Name
16214 1 8077870 0 15 Child Activation Wait main_task
16215 * 2 807c458 1 15 Runnable t
16216 (@value{GDBP}) task 1
16217 [Switching to task 1]
16218 #0 0x8067726 in pthread_cond_wait ()
16220 #0 0x8067726 in pthread_cond_wait ()
16221 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16222 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16223 #3 0x806153e in system.tasking.stages.activate_tasks ()
16224 #4 0x804aacc in un () at un.adb:5
16227 @item break @var{location} task @var{taskno}
16228 @itemx break @var{location} task @var{taskno} if @dots{}
16229 @cindex breakpoints and tasks, in Ada
16230 @cindex task breakpoints, in Ada
16231 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16232 These commands are like the @code{break @dots{} thread @dots{}}
16233 command (@pxref{Thread Stops}). The
16234 @var{location} argument specifies source lines, as described
16235 in @ref{Specify Location}.
16237 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16238 to specify that you only want @value{GDBN} to stop the program when a
16239 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16240 numeric task identifiers assigned by @value{GDBN}, shown in the first
16241 column of the @samp{info tasks} display.
16243 If you do not specify @samp{task @var{taskno}} when you set a
16244 breakpoint, the breakpoint applies to @emph{all} tasks of your
16247 You can use the @code{task} qualifier on conditional breakpoints as
16248 well; in this case, place @samp{task @var{taskno}} before the
16249 breakpoint condition (before the @code{if}).
16257 (@value{GDBP}) info tasks
16258 ID TID P-ID Pri State Name
16259 1 140022020 0 15 Child Activation Wait main_task
16260 2 140045060 1 15 Accept/Select Wait t2
16261 3 140044840 1 15 Runnable t1
16262 * 4 140056040 1 15 Runnable t3
16263 (@value{GDBP}) b 15 task 2
16264 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16265 (@value{GDBP}) cont
16270 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16272 (@value{GDBP}) info tasks
16273 ID TID P-ID Pri State Name
16274 1 140022020 0 15 Child Activation Wait main_task
16275 * 2 140045060 1 15 Runnable t2
16276 3 140044840 1 15 Runnable t1
16277 4 140056040 1 15 Delay Sleep t3
16281 @node Ada Tasks and Core Files
16282 @subsubsection Tasking Support when Debugging Core Files
16283 @cindex Ada tasking and core file debugging
16285 When inspecting a core file, as opposed to debugging a live program,
16286 tasking support may be limited or even unavailable, depending on
16287 the platform being used.
16288 For instance, on x86-linux, the list of tasks is available, but task
16289 switching is not supported.
16291 On certain platforms, the debugger needs to perform some
16292 memory writes in order to provide Ada tasking support. When inspecting
16293 a core file, this means that the core file must be opened with read-write
16294 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16295 Under these circumstances, you should make a backup copy of the core
16296 file before inspecting it with @value{GDBN}.
16298 @node Ravenscar Profile
16299 @subsubsection Tasking Support when using the Ravenscar Profile
16300 @cindex Ravenscar Profile
16302 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16303 specifically designed for systems with safety-critical real-time
16307 @kindex set ravenscar task-switching on
16308 @cindex task switching with program using Ravenscar Profile
16309 @item set ravenscar task-switching on
16310 Allows task switching when debugging a program that uses the Ravenscar
16311 Profile. This is the default.
16313 @kindex set ravenscar task-switching off
16314 @item set ravenscar task-switching off
16315 Turn off task switching when debugging a program that uses the Ravenscar
16316 Profile. This is mostly intended to disable the code that adds support
16317 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16318 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16319 To be effective, this command should be run before the program is started.
16321 @kindex show ravenscar task-switching
16322 @item show ravenscar task-switching
16323 Show whether it is possible to switch from task to task in a program
16324 using the Ravenscar Profile.
16329 @subsubsection Known Peculiarities of Ada Mode
16330 @cindex Ada, problems
16332 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16333 we know of several problems with and limitations of Ada mode in
16335 some of which will be fixed with planned future releases of the debugger
16336 and the GNU Ada compiler.
16340 Static constants that the compiler chooses not to materialize as objects in
16341 storage are invisible to the debugger.
16344 Named parameter associations in function argument lists are ignored (the
16345 argument lists are treated as positional).
16348 Many useful library packages are currently invisible to the debugger.
16351 Fixed-point arithmetic, conversions, input, and output is carried out using
16352 floating-point arithmetic, and may give results that only approximate those on
16356 The GNAT compiler never generates the prefix @code{Standard} for any of
16357 the standard symbols defined by the Ada language. @value{GDBN} knows about
16358 this: it will strip the prefix from names when you use it, and will never
16359 look for a name you have so qualified among local symbols, nor match against
16360 symbols in other packages or subprograms. If you have
16361 defined entities anywhere in your program other than parameters and
16362 local variables whose simple names match names in @code{Standard},
16363 GNAT's lack of qualification here can cause confusion. When this happens,
16364 you can usually resolve the confusion
16365 by qualifying the problematic names with package
16366 @code{Standard} explicitly.
16369 Older versions of the compiler sometimes generate erroneous debugging
16370 information, resulting in the debugger incorrectly printing the value
16371 of affected entities. In some cases, the debugger is able to work
16372 around an issue automatically. In other cases, the debugger is able
16373 to work around the issue, but the work-around has to be specifically
16376 @kindex set ada trust-PAD-over-XVS
16377 @kindex show ada trust-PAD-over-XVS
16380 @item set ada trust-PAD-over-XVS on
16381 Configure GDB to strictly follow the GNAT encoding when computing the
16382 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16383 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16384 a complete description of the encoding used by the GNAT compiler).
16385 This is the default.
16387 @item set ada trust-PAD-over-XVS off
16388 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16389 sometimes prints the wrong value for certain entities, changing @code{ada
16390 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16391 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16392 @code{off}, but this incurs a slight performance penalty, so it is
16393 recommended to leave this setting to @code{on} unless necessary.
16397 @cindex GNAT descriptive types
16398 @cindex GNAT encoding
16399 Internally, the debugger also relies on the compiler following a number
16400 of conventions known as the @samp{GNAT Encoding}, all documented in
16401 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16402 how the debugging information should be generated for certain types.
16403 In particular, this convention makes use of @dfn{descriptive types},
16404 which are artificial types generated purely to help the debugger.
16406 These encodings were defined at a time when the debugging information
16407 format used was not powerful enough to describe some of the more complex
16408 types available in Ada. Since DWARF allows us to express nearly all
16409 Ada features, the long-term goal is to slowly replace these descriptive
16410 types by their pure DWARF equivalent. To facilitate that transition,
16411 a new maintenance option is available to force the debugger to ignore
16412 those descriptive types. It allows the user to quickly evaluate how
16413 well @value{GDBN} works without them.
16417 @kindex maint ada set ignore-descriptive-types
16418 @item maintenance ada set ignore-descriptive-types [on|off]
16419 Control whether the debugger should ignore descriptive types.
16420 The default is not to ignore descriptives types (@code{off}).
16422 @kindex maint ada show ignore-descriptive-types
16423 @item maintenance ada show ignore-descriptive-types
16424 Show if descriptive types are ignored by @value{GDBN}.
16428 @node Unsupported Languages
16429 @section Unsupported Languages
16431 @cindex unsupported languages
16432 @cindex minimal language
16433 In addition to the other fully-supported programming languages,
16434 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16435 It does not represent a real programming language, but provides a set
16436 of capabilities close to what the C or assembly languages provide.
16437 This should allow most simple operations to be performed while debugging
16438 an application that uses a language currently not supported by @value{GDBN}.
16440 If the language is set to @code{auto}, @value{GDBN} will automatically
16441 select this language if the current frame corresponds to an unsupported
16445 @chapter Examining the Symbol Table
16447 The commands described in this chapter allow you to inquire about the
16448 symbols (names of variables, functions and types) defined in your
16449 program. This information is inherent in the text of your program and
16450 does not change as your program executes. @value{GDBN} finds it in your
16451 program's symbol table, in the file indicated when you started @value{GDBN}
16452 (@pxref{File Options, ,Choosing Files}), or by one of the
16453 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16455 @cindex symbol names
16456 @cindex names of symbols
16457 @cindex quoting names
16458 Occasionally, you may need to refer to symbols that contain unusual
16459 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16460 most frequent case is in referring to static variables in other
16461 source files (@pxref{Variables,,Program Variables}). File names
16462 are recorded in object files as debugging symbols, but @value{GDBN} would
16463 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16464 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16465 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16472 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16475 @cindex case-insensitive symbol names
16476 @cindex case sensitivity in symbol names
16477 @kindex set case-sensitive
16478 @item set case-sensitive on
16479 @itemx set case-sensitive off
16480 @itemx set case-sensitive auto
16481 Normally, when @value{GDBN} looks up symbols, it matches their names
16482 with case sensitivity determined by the current source language.
16483 Occasionally, you may wish to control that. The command @code{set
16484 case-sensitive} lets you do that by specifying @code{on} for
16485 case-sensitive matches or @code{off} for case-insensitive ones. If
16486 you specify @code{auto}, case sensitivity is reset to the default
16487 suitable for the source language. The default is case-sensitive
16488 matches for all languages except for Fortran, for which the default is
16489 case-insensitive matches.
16491 @kindex show case-sensitive
16492 @item show case-sensitive
16493 This command shows the current setting of case sensitivity for symbols
16496 @kindex set print type methods
16497 @item set print type methods
16498 @itemx set print type methods on
16499 @itemx set print type methods off
16500 Normally, when @value{GDBN} prints a class, it displays any methods
16501 declared in that class. You can control this behavior either by
16502 passing the appropriate flag to @code{ptype}, or using @command{set
16503 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16504 display the methods; this is the default. Specifying @code{off} will
16505 cause @value{GDBN} to omit the methods.
16507 @kindex show print type methods
16508 @item show print type methods
16509 This command shows the current setting of method display when printing
16512 @kindex set print type typedefs
16513 @item set print type typedefs
16514 @itemx set print type typedefs on
16515 @itemx set print type typedefs off
16517 Normally, when @value{GDBN} prints a class, it displays any typedefs
16518 defined in that class. You can control this behavior either by
16519 passing the appropriate flag to @code{ptype}, or using @command{set
16520 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16521 display the typedef definitions; this is the default. Specifying
16522 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16523 Note that this controls whether the typedef definition itself is
16524 printed, not whether typedef names are substituted when printing other
16527 @kindex show print type typedefs
16528 @item show print type typedefs
16529 This command shows the current setting of typedef display when
16532 @kindex info address
16533 @cindex address of a symbol
16534 @item info address @var{symbol}
16535 Describe where the data for @var{symbol} is stored. For a register
16536 variable, this says which register it is kept in. For a non-register
16537 local variable, this prints the stack-frame offset at which the variable
16540 Note the contrast with @samp{print &@var{symbol}}, which does not work
16541 at all for a register variable, and for a stack local variable prints
16542 the exact address of the current instantiation of the variable.
16544 @kindex info symbol
16545 @cindex symbol from address
16546 @cindex closest symbol and offset for an address
16547 @item info symbol @var{addr}
16548 Print the name of a symbol which is stored at the address @var{addr}.
16549 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16550 nearest symbol and an offset from it:
16553 (@value{GDBP}) info symbol 0x54320
16554 _initialize_vx + 396 in section .text
16558 This is the opposite of the @code{info address} command. You can use
16559 it to find out the name of a variable or a function given its address.
16561 For dynamically linked executables, the name of executable or shared
16562 library containing the symbol is also printed:
16565 (@value{GDBP}) info symbol 0x400225
16566 _start + 5 in section .text of /tmp/a.out
16567 (@value{GDBP}) info symbol 0x2aaaac2811cf
16568 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16573 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16574 Demangle @var{name}.
16575 If @var{language} is provided it is the name of the language to demangle
16576 @var{name} in. Otherwise @var{name} is demangled in the current language.
16578 The @samp{--} option specifies the end of options,
16579 and is useful when @var{name} begins with a dash.
16581 The parameter @code{demangle-style} specifies how to interpret the kind
16582 of mangling used. @xref{Print Settings}.
16585 @item whatis[/@var{flags}] [@var{arg}]
16586 Print the data type of @var{arg}, which can be either an expression
16587 or a name of a data type. With no argument, print the data type of
16588 @code{$}, the last value in the value history.
16590 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16591 is not actually evaluated, and any side-effecting operations (such as
16592 assignments or function calls) inside it do not take place.
16594 If @var{arg} is a variable or an expression, @code{whatis} prints its
16595 literal type as it is used in the source code. If the type was
16596 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16597 the data type underlying the @code{typedef}. If the type of the
16598 variable or the expression is a compound data type, such as
16599 @code{struct} or @code{class}, @code{whatis} never prints their
16600 fields or methods. It just prints the @code{struct}/@code{class}
16601 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16602 such a compound data type, use @code{ptype}.
16604 If @var{arg} is a type name that was defined using @code{typedef},
16605 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16606 Unrolling means that @code{whatis} will show the underlying type used
16607 in the @code{typedef} declaration of @var{arg}. However, if that
16608 underlying type is also a @code{typedef}, @code{whatis} will not
16611 For C code, the type names may also have the form @samp{class
16612 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16613 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16615 @var{flags} can be used to modify how the type is displayed.
16616 Available flags are:
16620 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16621 parameters and typedefs defined in a class when printing the class'
16622 members. The @code{/r} flag disables this.
16625 Do not print methods defined in the class.
16628 Print methods defined in the class. This is the default, but the flag
16629 exists in case you change the default with @command{set print type methods}.
16632 Do not print typedefs defined in the class. Note that this controls
16633 whether the typedef definition itself is printed, not whether typedef
16634 names are substituted when printing other types.
16637 Print typedefs defined in the class. This is the default, but the flag
16638 exists in case you change the default with @command{set print type typedefs}.
16642 @item ptype[/@var{flags}] [@var{arg}]
16643 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16644 detailed description of the type, instead of just the name of the type.
16645 @xref{Expressions, ,Expressions}.
16647 Contrary to @code{whatis}, @code{ptype} always unrolls any
16648 @code{typedef}s in its argument declaration, whether the argument is
16649 a variable, expression, or a data type. This means that @code{ptype}
16650 of a variable or an expression will not print literally its type as
16651 present in the source code---use @code{whatis} for that. @code{typedef}s at
16652 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16653 fields, methods and inner @code{class typedef}s of @code{struct}s,
16654 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16656 For example, for this variable declaration:
16659 typedef double real_t;
16660 struct complex @{ real_t real; double imag; @};
16661 typedef struct complex complex_t;
16663 real_t *real_pointer_var;
16667 the two commands give this output:
16671 (@value{GDBP}) whatis var
16673 (@value{GDBP}) ptype var
16674 type = struct complex @{
16678 (@value{GDBP}) whatis complex_t
16679 type = struct complex
16680 (@value{GDBP}) whatis struct complex
16681 type = struct complex
16682 (@value{GDBP}) ptype struct complex
16683 type = struct complex @{
16687 (@value{GDBP}) whatis real_pointer_var
16689 (@value{GDBP}) ptype real_pointer_var
16695 As with @code{whatis}, using @code{ptype} without an argument refers to
16696 the type of @code{$}, the last value in the value history.
16698 @cindex incomplete type
16699 Sometimes, programs use opaque data types or incomplete specifications
16700 of complex data structure. If the debug information included in the
16701 program does not allow @value{GDBN} to display a full declaration of
16702 the data type, it will say @samp{<incomplete type>}. For example,
16703 given these declarations:
16707 struct foo *fooptr;
16711 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16714 (@value{GDBP}) ptype foo
16715 $1 = <incomplete type>
16719 ``Incomplete type'' is C terminology for data types that are not
16720 completely specified.
16723 @item info types @var{regexp}
16725 Print a brief description of all types whose names match the regular
16726 expression @var{regexp} (or all types in your program, if you supply
16727 no argument). Each complete typename is matched as though it were a
16728 complete line; thus, @samp{i type value} gives information on all
16729 types in your program whose names include the string @code{value}, but
16730 @samp{i type ^value$} gives information only on types whose complete
16731 name is @code{value}.
16733 This command differs from @code{ptype} in two ways: first, like
16734 @code{whatis}, it does not print a detailed description; second, it
16735 lists all source files where a type is defined.
16737 @kindex info type-printers
16738 @item info type-printers
16739 Versions of @value{GDBN} that ship with Python scripting enabled may
16740 have ``type printers'' available. When using @command{ptype} or
16741 @command{whatis}, these printers are consulted when the name of a type
16742 is needed. @xref{Type Printing API}, for more information on writing
16745 @code{info type-printers} displays all the available type printers.
16747 @kindex enable type-printer
16748 @kindex disable type-printer
16749 @item enable type-printer @var{name}@dots{}
16750 @item disable type-printer @var{name}@dots{}
16751 These commands can be used to enable or disable type printers.
16754 @cindex local variables
16755 @item info scope @var{location}
16756 List all the variables local to a particular scope. This command
16757 accepts a @var{location} argument---a function name, a source line, or
16758 an address preceded by a @samp{*}, and prints all the variables local
16759 to the scope defined by that location. (@xref{Specify Location}, for
16760 details about supported forms of @var{location}.) For example:
16763 (@value{GDBP}) @b{info scope command_line_handler}
16764 Scope for command_line_handler:
16765 Symbol rl is an argument at stack/frame offset 8, length 4.
16766 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16767 Symbol linelength is in static storage at address 0x150a1c, length 4.
16768 Symbol p is a local variable in register $esi, length 4.
16769 Symbol p1 is a local variable in register $ebx, length 4.
16770 Symbol nline is a local variable in register $edx, length 4.
16771 Symbol repeat is a local variable at frame offset -8, length 4.
16775 This command is especially useful for determining what data to collect
16776 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16779 @kindex info source
16781 Show information about the current source file---that is, the source file for
16782 the function containing the current point of execution:
16785 the name of the source file, and the directory containing it,
16787 the directory it was compiled in,
16789 its length, in lines,
16791 which programming language it is written in,
16793 if the debug information provides it, the program that compiled the file
16794 (which may include, e.g., the compiler version and command line arguments),
16796 whether the executable includes debugging information for that file, and
16797 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16799 whether the debugging information includes information about
16800 preprocessor macros.
16804 @kindex info sources
16806 Print the names of all source files in your program for which there is
16807 debugging information, organized into two lists: files whose symbols
16808 have already been read, and files whose symbols will be read when needed.
16810 @kindex info functions
16811 @item info functions
16812 Print the names and data types of all defined functions.
16814 @item info functions @var{regexp}
16815 Print the names and data types of all defined functions
16816 whose names contain a match for regular expression @var{regexp}.
16817 Thus, @samp{info fun step} finds all functions whose names
16818 include @code{step}; @samp{info fun ^step} finds those whose names
16819 start with @code{step}. If a function name contains characters
16820 that conflict with the regular expression language (e.g.@:
16821 @samp{operator*()}), they may be quoted with a backslash.
16823 @kindex info variables
16824 @item info variables
16825 Print the names and data types of all variables that are defined
16826 outside of functions (i.e.@: excluding local variables).
16828 @item info variables @var{regexp}
16829 Print the names and data types of all variables (except for local
16830 variables) whose names contain a match for regular expression
16833 @kindex info classes
16834 @cindex Objective-C, classes and selectors
16836 @itemx info classes @var{regexp}
16837 Display all Objective-C classes in your program, or
16838 (with the @var{regexp} argument) all those matching a particular regular
16841 @kindex info selectors
16842 @item info selectors
16843 @itemx info selectors @var{regexp}
16844 Display all Objective-C selectors in your program, or
16845 (with the @var{regexp} argument) all those matching a particular regular
16849 This was never implemented.
16850 @kindex info methods
16852 @itemx info methods @var{regexp}
16853 The @code{info methods} command permits the user to examine all defined
16854 methods within C@t{++} program, or (with the @var{regexp} argument) a
16855 specific set of methods found in the various C@t{++} classes. Many
16856 C@t{++} classes provide a large number of methods. Thus, the output
16857 from the @code{ptype} command can be overwhelming and hard to use. The
16858 @code{info-methods} command filters the methods, printing only those
16859 which match the regular-expression @var{regexp}.
16862 @cindex opaque data types
16863 @kindex set opaque-type-resolution
16864 @item set opaque-type-resolution on
16865 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16866 declared as a pointer to a @code{struct}, @code{class}, or
16867 @code{union}---for example, @code{struct MyType *}---that is used in one
16868 source file although the full declaration of @code{struct MyType} is in
16869 another source file. The default is on.
16871 A change in the setting of this subcommand will not take effect until
16872 the next time symbols for a file are loaded.
16874 @item set opaque-type-resolution off
16875 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16876 is printed as follows:
16878 @{<no data fields>@}
16881 @kindex show opaque-type-resolution
16882 @item show opaque-type-resolution
16883 Show whether opaque types are resolved or not.
16885 @kindex set print symbol-loading
16886 @cindex print messages when symbols are loaded
16887 @item set print symbol-loading
16888 @itemx set print symbol-loading full
16889 @itemx set print symbol-loading brief
16890 @itemx set print symbol-loading off
16891 The @code{set print symbol-loading} command allows you to control the
16892 printing of messages when @value{GDBN} loads symbol information.
16893 By default a message is printed for the executable and one for each
16894 shared library, and normally this is what you want. However, when
16895 debugging apps with large numbers of shared libraries these messages
16897 When set to @code{brief} a message is printed for each executable,
16898 and when @value{GDBN} loads a collection of shared libraries at once
16899 it will only print one message regardless of the number of shared
16900 libraries. When set to @code{off} no messages are printed.
16902 @kindex show print symbol-loading
16903 @item show print symbol-loading
16904 Show whether messages will be printed when a @value{GDBN} command
16905 entered from the keyboard causes symbol information to be loaded.
16907 @kindex maint print symbols
16908 @cindex symbol dump
16909 @kindex maint print psymbols
16910 @cindex partial symbol dump
16911 @kindex maint print msymbols
16912 @cindex minimal symbol dump
16913 @item maint print symbols @var{filename}
16914 @itemx maint print psymbols @var{filename}
16915 @itemx maint print msymbols @var{filename}
16916 Write a dump of debugging symbol data into the file @var{filename}.
16917 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16918 symbols with debugging data are included. If you use @samp{maint print
16919 symbols}, @value{GDBN} includes all the symbols for which it has already
16920 collected full details: that is, @var{filename} reflects symbols for
16921 only those files whose symbols @value{GDBN} has read. You can use the
16922 command @code{info sources} to find out which files these are. If you
16923 use @samp{maint print psymbols} instead, the dump shows information about
16924 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16925 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16926 @samp{maint print msymbols} dumps just the minimal symbol information
16927 required for each object file from which @value{GDBN} has read some symbols.
16928 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16929 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16931 @kindex maint info symtabs
16932 @kindex maint info psymtabs
16933 @cindex listing @value{GDBN}'s internal symbol tables
16934 @cindex symbol tables, listing @value{GDBN}'s internal
16935 @cindex full symbol tables, listing @value{GDBN}'s internal
16936 @cindex partial symbol tables, listing @value{GDBN}'s internal
16937 @item maint info symtabs @r{[} @var{regexp} @r{]}
16938 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16940 List the @code{struct symtab} or @code{struct partial_symtab}
16941 structures whose names match @var{regexp}. If @var{regexp} is not
16942 given, list them all. The output includes expressions which you can
16943 copy into a @value{GDBN} debugging this one to examine a particular
16944 structure in more detail. For example:
16947 (@value{GDBP}) maint info psymtabs dwarf2read
16948 @{ objfile /home/gnu/build/gdb/gdb
16949 ((struct objfile *) 0x82e69d0)
16950 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16951 ((struct partial_symtab *) 0x8474b10)
16954 text addresses 0x814d3c8 -- 0x8158074
16955 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16956 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16957 dependencies (none)
16960 (@value{GDBP}) maint info symtabs
16964 We see that there is one partial symbol table whose filename contains
16965 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16966 and we see that @value{GDBN} has not read in any symtabs yet at all.
16967 If we set a breakpoint on a function, that will cause @value{GDBN} to
16968 read the symtab for the compilation unit containing that function:
16971 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16972 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16974 (@value{GDBP}) maint info symtabs
16975 @{ objfile /home/gnu/build/gdb/gdb
16976 ((struct objfile *) 0x82e69d0)
16977 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16978 ((struct symtab *) 0x86c1f38)
16981 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16982 linetable ((struct linetable *) 0x8370fa0)
16983 debugformat DWARF 2
16989 @kindex maint set symbol-cache-size
16990 @cindex symbol cache size
16991 @item maint set symbol-cache-size @var{size}
16992 Set the size of the symbol cache to @var{size}.
16993 The default size is intended to be good enough for debugging
16994 most applications. This option exists to allow for experimenting
16995 with different sizes.
16997 @kindex maint show symbol-cache-size
16998 @item maint show symbol-cache-size
16999 Show the size of the symbol cache.
17001 @kindex maint print symbol-cache
17002 @cindex symbol cache, printing its contents
17003 @item maint print symbol-cache
17004 Print the contents of the symbol cache.
17005 This is useful when debugging symbol cache issues.
17007 @kindex maint print symbol-cache-statistics
17008 @cindex symbol cache, printing usage statistics
17009 @item maint print symbol-cache-statistics
17010 Print symbol cache usage statistics.
17011 This helps determine how well the cache is being utilized.
17013 @kindex maint flush-symbol-cache
17014 @cindex symbol cache, flushing
17015 @item maint flush-symbol-cache
17016 Flush the contents of the symbol cache, all entries are removed.
17017 This command is useful when debugging the symbol cache.
17018 It is also useful when collecting performance data.
17023 @chapter Altering Execution
17025 Once you think you have found an error in your program, you might want to
17026 find out for certain whether correcting the apparent error would lead to
17027 correct results in the rest of the run. You can find the answer by
17028 experiment, using the @value{GDBN} features for altering execution of the
17031 For example, you can store new values into variables or memory
17032 locations, give your program a signal, restart it at a different
17033 address, or even return prematurely from a function.
17036 * Assignment:: Assignment to variables
17037 * Jumping:: Continuing at a different address
17038 * Signaling:: Giving your program a signal
17039 * Returning:: Returning from a function
17040 * Calling:: Calling your program's functions
17041 * Patching:: Patching your program
17042 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17046 @section Assignment to Variables
17049 @cindex setting variables
17050 To alter the value of a variable, evaluate an assignment expression.
17051 @xref{Expressions, ,Expressions}. For example,
17058 stores the value 4 into the variable @code{x}, and then prints the
17059 value of the assignment expression (which is 4).
17060 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17061 information on operators in supported languages.
17063 @kindex set variable
17064 @cindex variables, setting
17065 If you are not interested in seeing the value of the assignment, use the
17066 @code{set} command instead of the @code{print} command. @code{set} is
17067 really the same as @code{print} except that the expression's value is
17068 not printed and is not put in the value history (@pxref{Value History,
17069 ,Value History}). The expression is evaluated only for its effects.
17071 If the beginning of the argument string of the @code{set} command
17072 appears identical to a @code{set} subcommand, use the @code{set
17073 variable} command instead of just @code{set}. This command is identical
17074 to @code{set} except for its lack of subcommands. For example, if your
17075 program has a variable @code{width}, you get an error if you try to set
17076 a new value with just @samp{set width=13}, because @value{GDBN} has the
17077 command @code{set width}:
17080 (@value{GDBP}) whatis width
17082 (@value{GDBP}) p width
17084 (@value{GDBP}) set width=47
17085 Invalid syntax in expression.
17089 The invalid expression, of course, is @samp{=47}. In
17090 order to actually set the program's variable @code{width}, use
17093 (@value{GDBP}) set var width=47
17096 Because the @code{set} command has many subcommands that can conflict
17097 with the names of program variables, it is a good idea to use the
17098 @code{set variable} command instead of just @code{set}. For example, if
17099 your program has a variable @code{g}, you run into problems if you try
17100 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17101 the command @code{set gnutarget}, abbreviated @code{set g}:
17105 (@value{GDBP}) whatis g
17109 (@value{GDBP}) set g=4
17113 The program being debugged has been started already.
17114 Start it from the beginning? (y or n) y
17115 Starting program: /home/smith/cc_progs/a.out
17116 "/home/smith/cc_progs/a.out": can't open to read symbols:
17117 Invalid bfd target.
17118 (@value{GDBP}) show g
17119 The current BFD target is "=4".
17124 The program variable @code{g} did not change, and you silently set the
17125 @code{gnutarget} to an invalid value. In order to set the variable
17129 (@value{GDBP}) set var g=4
17132 @value{GDBN} allows more implicit conversions in assignments than C; you can
17133 freely store an integer value into a pointer variable or vice versa,
17134 and you can convert any structure to any other structure that is the
17135 same length or shorter.
17136 @comment FIXME: how do structs align/pad in these conversions?
17137 @comment /doc@cygnus.com 18dec1990
17139 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17140 construct to generate a value of specified type at a specified address
17141 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17142 to memory location @code{0x83040} as an integer (which implies a certain size
17143 and representation in memory), and
17146 set @{int@}0x83040 = 4
17150 stores the value 4 into that memory location.
17153 @section Continuing at a Different Address
17155 Ordinarily, when you continue your program, you do so at the place where
17156 it stopped, with the @code{continue} command. You can instead continue at
17157 an address of your own choosing, with the following commands:
17161 @kindex j @r{(@code{jump})}
17162 @item jump @var{location}
17163 @itemx j @var{location}
17164 Resume execution at @var{location}. Execution stops again immediately
17165 if there is a breakpoint there. @xref{Specify Location}, for a description
17166 of the different forms of @var{location}. It is common
17167 practice to use the @code{tbreak} command in conjunction with
17168 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17170 The @code{jump} command does not change the current stack frame, or
17171 the stack pointer, or the contents of any memory location or any
17172 register other than the program counter. If @var{location} is in
17173 a different function from the one currently executing, the results may
17174 be bizarre if the two functions expect different patterns of arguments or
17175 of local variables. For this reason, the @code{jump} command requests
17176 confirmation if the specified line is not in the function currently
17177 executing. However, even bizarre results are predictable if you are
17178 well acquainted with the machine-language code of your program.
17181 On many systems, you can get much the same effect as the @code{jump}
17182 command by storing a new value into the register @code{$pc}. The
17183 difference is that this does not start your program running; it only
17184 changes the address of where it @emph{will} run when you continue. For
17192 makes the next @code{continue} command or stepping command execute at
17193 address @code{0x485}, rather than at the address where your program stopped.
17194 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17196 The most common occasion to use the @code{jump} command is to back
17197 up---perhaps with more breakpoints set---over a portion of a program
17198 that has already executed, in order to examine its execution in more
17203 @section Giving your Program a Signal
17204 @cindex deliver a signal to a program
17208 @item signal @var{signal}
17209 Resume execution where your program is stopped, but immediately give it the
17210 signal @var{signal}. The @var{signal} can be the name or the number of a
17211 signal. For example, on many systems @code{signal 2} and @code{signal
17212 SIGINT} are both ways of sending an interrupt signal.
17214 Alternatively, if @var{signal} is zero, continue execution without
17215 giving a signal. This is useful when your program stopped on account of
17216 a signal and would ordinarily see the signal when resumed with the
17217 @code{continue} command; @samp{signal 0} causes it to resume without a
17220 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17221 delivered to the currently selected thread, not the thread that last
17222 reported a stop. This includes the situation where a thread was
17223 stopped due to a signal. So if you want to continue execution
17224 suppressing the signal that stopped a thread, you should select that
17225 same thread before issuing the @samp{signal 0} command. If you issue
17226 the @samp{signal 0} command with another thread as the selected one,
17227 @value{GDBN} detects that and asks for confirmation.
17229 Invoking the @code{signal} command is not the same as invoking the
17230 @code{kill} utility from the shell. Sending a signal with @code{kill}
17231 causes @value{GDBN} to decide what to do with the signal depending on
17232 the signal handling tables (@pxref{Signals}). The @code{signal} command
17233 passes the signal directly to your program.
17235 @code{signal} does not repeat when you press @key{RET} a second time
17236 after executing the command.
17238 @kindex queue-signal
17239 @item queue-signal @var{signal}
17240 Queue @var{signal} to be delivered immediately to the current thread
17241 when execution of the thread resumes. The @var{signal} can be the name or
17242 the number of a signal. For example, on many systems @code{signal 2} and
17243 @code{signal SIGINT} are both ways of sending an interrupt signal.
17244 The handling of the signal must be set to pass the signal to the program,
17245 otherwise @value{GDBN} will report an error.
17246 You can control the handling of signals from @value{GDBN} with the
17247 @code{handle} command (@pxref{Signals}).
17249 Alternatively, if @var{signal} is zero, any currently queued signal
17250 for the current thread is discarded and when execution resumes no signal
17251 will be delivered. This is useful when your program stopped on account
17252 of a signal and would ordinarily see the signal when resumed with the
17253 @code{continue} command.
17255 This command differs from the @code{signal} command in that the signal
17256 is just queued, execution is not resumed. And @code{queue-signal} cannot
17257 be used to pass a signal whose handling state has been set to @code{nopass}
17262 @xref{stepping into signal handlers}, for information on how stepping
17263 commands behave when the thread has a signal queued.
17266 @section Returning from a Function
17269 @cindex returning from a function
17272 @itemx return @var{expression}
17273 You can cancel execution of a function call with the @code{return}
17274 command. If you give an
17275 @var{expression} argument, its value is used as the function's return
17279 When you use @code{return}, @value{GDBN} discards the selected stack frame
17280 (and all frames within it). You can think of this as making the
17281 discarded frame return prematurely. If you wish to specify a value to
17282 be returned, give that value as the argument to @code{return}.
17284 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17285 Frame}), and any other frames inside of it, leaving its caller as the
17286 innermost remaining frame. That frame becomes selected. The
17287 specified value is stored in the registers used for returning values
17290 The @code{return} command does not resume execution; it leaves the
17291 program stopped in the state that would exist if the function had just
17292 returned. In contrast, the @code{finish} command (@pxref{Continuing
17293 and Stepping, ,Continuing and Stepping}) resumes execution until the
17294 selected stack frame returns naturally.
17296 @value{GDBN} needs to know how the @var{expression} argument should be set for
17297 the inferior. The concrete registers assignment depends on the OS ABI and the
17298 type being returned by the selected stack frame. For example it is common for
17299 OS ABI to return floating point values in FPU registers while integer values in
17300 CPU registers. Still some ABIs return even floating point values in CPU
17301 registers. Larger integer widths (such as @code{long long int}) also have
17302 specific placement rules. @value{GDBN} already knows the OS ABI from its
17303 current target so it needs to find out also the type being returned to make the
17304 assignment into the right register(s).
17306 Normally, the selected stack frame has debug info. @value{GDBN} will always
17307 use the debug info instead of the implicit type of @var{expression} when the
17308 debug info is available. For example, if you type @kbd{return -1}, and the
17309 function in the current stack frame is declared to return a @code{long long
17310 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17311 into a @code{long long int}:
17314 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17316 (@value{GDBP}) return -1
17317 Make func return now? (y or n) y
17318 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17319 43 printf ("result=%lld\n", func ());
17323 However, if the selected stack frame does not have a debug info, e.g., if the
17324 function was compiled without debug info, @value{GDBN} has to find out the type
17325 to return from user. Specifying a different type by mistake may set the value
17326 in different inferior registers than the caller code expects. For example,
17327 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17328 of a @code{long long int} result for a debug info less function (on 32-bit
17329 architectures). Therefore the user is required to specify the return type by
17330 an appropriate cast explicitly:
17333 Breakpoint 2, 0x0040050b in func ()
17334 (@value{GDBP}) return -1
17335 Return value type not available for selected stack frame.
17336 Please use an explicit cast of the value to return.
17337 (@value{GDBP}) return (long long int) -1
17338 Make selected stack frame return now? (y or n) y
17339 #0 0x00400526 in main ()
17344 @section Calling Program Functions
17347 @cindex calling functions
17348 @cindex inferior functions, calling
17349 @item print @var{expr}
17350 Evaluate the expression @var{expr} and display the resulting value.
17351 The expression may include calls to functions in the program being
17355 @item call @var{expr}
17356 Evaluate the expression @var{expr} without displaying @code{void}
17359 You can use this variant of the @code{print} command if you want to
17360 execute a function from your program that does not return anything
17361 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17362 with @code{void} returned values that @value{GDBN} will otherwise
17363 print. If the result is not void, it is printed and saved in the
17367 It is possible for the function you call via the @code{print} or
17368 @code{call} command to generate a signal (e.g., if there's a bug in
17369 the function, or if you passed it incorrect arguments). What happens
17370 in that case is controlled by the @code{set unwindonsignal} command.
17372 Similarly, with a C@t{++} program it is possible for the function you
17373 call via the @code{print} or @code{call} command to generate an
17374 exception that is not handled due to the constraints of the dummy
17375 frame. In this case, any exception that is raised in the frame, but has
17376 an out-of-frame exception handler will not be found. GDB builds a
17377 dummy-frame for the inferior function call, and the unwinder cannot
17378 seek for exception handlers outside of this dummy-frame. What happens
17379 in that case is controlled by the
17380 @code{set unwind-on-terminating-exception} command.
17383 @item set unwindonsignal
17384 @kindex set unwindonsignal
17385 @cindex unwind stack in called functions
17386 @cindex call dummy stack unwinding
17387 Set unwinding of the stack if a signal is received while in a function
17388 that @value{GDBN} called in the program being debugged. If set to on,
17389 @value{GDBN} unwinds the stack it created for the call and restores
17390 the context to what it was before the call. If set to off (the
17391 default), @value{GDBN} stops in the frame where the signal was
17394 @item show unwindonsignal
17395 @kindex show unwindonsignal
17396 Show the current setting of stack unwinding in the functions called by
17399 @item set unwind-on-terminating-exception
17400 @kindex set unwind-on-terminating-exception
17401 @cindex unwind stack in called functions with unhandled exceptions
17402 @cindex call dummy stack unwinding on unhandled exception.
17403 Set unwinding of the stack if a C@t{++} exception is raised, but left
17404 unhandled while in a function that @value{GDBN} called in the program being
17405 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17406 it created for the call and restores the context to what it was before
17407 the call. If set to off, @value{GDBN} the exception is delivered to
17408 the default C@t{++} exception handler and the inferior terminated.
17410 @item show unwind-on-terminating-exception
17411 @kindex show unwind-on-terminating-exception
17412 Show the current setting of stack unwinding in the functions called by
17417 @cindex weak alias functions
17418 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17419 for another function. In such case, @value{GDBN} might not pick up
17420 the type information, including the types of the function arguments,
17421 which causes @value{GDBN} to call the inferior function incorrectly.
17422 As a result, the called function will function erroneously and may
17423 even crash. A solution to that is to use the name of the aliased
17427 @section Patching Programs
17429 @cindex patching binaries
17430 @cindex writing into executables
17431 @cindex writing into corefiles
17433 By default, @value{GDBN} opens the file containing your program's
17434 executable code (or the corefile) read-only. This prevents accidental
17435 alterations to machine code; but it also prevents you from intentionally
17436 patching your program's binary.
17438 If you'd like to be able to patch the binary, you can specify that
17439 explicitly with the @code{set write} command. For example, you might
17440 want to turn on internal debugging flags, or even to make emergency
17446 @itemx set write off
17447 If you specify @samp{set write on}, @value{GDBN} opens executable and
17448 core files for both reading and writing; if you specify @kbd{set write
17449 off} (the default), @value{GDBN} opens them read-only.
17451 If you have already loaded a file, you must load it again (using the
17452 @code{exec-file} or @code{core-file} command) after changing @code{set
17453 write}, for your new setting to take effect.
17457 Display whether executable files and core files are opened for writing
17458 as well as reading.
17461 @node Compiling and Injecting Code
17462 @section Compiling and injecting code in @value{GDBN}
17463 @cindex injecting code
17464 @cindex writing into executables
17465 @cindex compiling code
17467 @value{GDBN} supports on-demand compilation and code injection into
17468 programs running under @value{GDBN}. GCC 5.0 or higher built with
17469 @file{libcc1.so} must be installed for this functionality to be enabled.
17470 This functionality is implemented with the following commands.
17473 @kindex compile code
17474 @item compile code @var{source-code}
17475 @itemx compile code -raw @var{--} @var{source-code}
17476 Compile @var{source-code} with the compiler language found as the current
17477 language in @value{GDBN} (@pxref{Languages}). If compilation and
17478 injection is not supported with the current language specified in
17479 @value{GDBN}, or the compiler does not support this feature, an error
17480 message will be printed. If @var{source-code} compiles and links
17481 successfully, @value{GDBN} will load the object-code emitted,
17482 and execute it within the context of the currently selected inferior.
17483 It is important to note that the compiled code is executed immediately.
17484 After execution, the compiled code is removed from @value{GDBN} and any
17485 new types or variables you have defined will be deleted.
17487 The command allows you to specify @var{source-code} in two ways.
17488 The simplest method is to provide a single line of code to the command.
17492 compile code printf ("hello world\n");
17495 If you specify options on the command line as well as source code, they
17496 may conflict. The @samp{--} delimiter can be used to separate options
17497 from actual source code. E.g.:
17500 compile code -r -- printf ("hello world\n");
17503 Alternatively you can enter source code as multiple lines of text. To
17504 enter this mode, invoke the @samp{compile code} command without any text
17505 following the command. This will start the multiple-line editor and
17506 allow you to type as many lines of source code as required. When you
17507 have completed typing, enter @samp{end} on its own line to exit the
17512 >printf ("hello\n");
17513 >printf ("world\n");
17517 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17518 provided @var{source-code} in a callable scope. In this case, you must
17519 specify the entry point of the code by defining a function named
17520 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17521 inferior. Using @samp{-raw} option may be needed for example when
17522 @var{source-code} requires @samp{#include} lines which may conflict with
17523 inferior symbols otherwise.
17525 @kindex compile file
17526 @item compile file @var{filename}
17527 @itemx compile file -raw @var{filename}
17528 Like @code{compile code}, but take the source code from @var{filename}.
17531 compile file /home/user/example.c
17536 @item compile print @var{expr}
17537 @itemx compile print /@var{f} @var{expr}
17538 Compile and execute @var{expr} with the compiler language found as the
17539 current language in @value{GDBN} (@pxref{Languages}). By default the
17540 value of @var{expr} is printed in a format appropriate to its data type;
17541 you can choose a different format by specifying @samp{/@var{f}}, where
17542 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17545 @item compile print
17546 @itemx compile print /@var{f}
17547 @cindex reprint the last value
17548 Alternatively you can enter the expression (source code producing it) as
17549 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17550 command without any text following the command. This will start the
17551 multiple-line editor.
17555 The process of compiling and injecting the code can be inspected using:
17558 @anchor{set debug compile}
17559 @item set debug compile
17560 @cindex compile command debugging info
17561 Turns on or off display of @value{GDBN} process of compiling and
17562 injecting the code. The default is off.
17564 @item show debug compile
17565 Displays the current state of displaying @value{GDBN} process of
17566 compiling and injecting the code.
17569 @subsection Compilation options for the @code{compile} command
17571 @value{GDBN} needs to specify the right compilation options for the code
17572 to be injected, in part to make its ABI compatible with the inferior
17573 and in part to make the injected code compatible with @value{GDBN}'s
17577 The options used, in increasing precedence:
17580 @item target architecture and OS options (@code{gdbarch})
17581 These options depend on target processor type and target operating
17582 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17583 (@code{-m64}) compilation option.
17585 @item compilation options recorded in the target
17586 @value{NGCC} (since version 4.7) stores the options used for compilation
17587 into @code{DW_AT_producer} part of DWARF debugging information according
17588 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17589 explicitly specify @code{-g} during inferior compilation otherwise
17590 @value{NGCC} produces no DWARF. This feature is only relevant for
17591 platforms where @code{-g} produces DWARF by default, otherwise one may
17592 try to enforce DWARF by using @code{-gdwarf-4}.
17594 @item compilation options set by @code{set compile-args}
17598 You can override compilation options using the following command:
17601 @item set compile-args
17602 @cindex compile command options override
17603 Set compilation options used for compiling and injecting code with the
17604 @code{compile} commands. These options override any conflicting ones
17605 from the target architecture and/or options stored during inferior
17608 @item show compile-args
17609 Displays the current state of compilation options override.
17610 This does not show all the options actually used during compilation,
17611 use @ref{set debug compile} for that.
17614 @subsection Caveats when using the @code{compile} command
17616 There are a few caveats to keep in mind when using the @code{compile}
17617 command. As the caveats are different per language, the table below
17618 highlights specific issues on a per language basis.
17621 @item C code examples and caveats
17622 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17623 attempt to compile the source code with a @samp{C} compiler. The source
17624 code provided to the @code{compile} command will have much the same
17625 access to variables and types as it normally would if it were part of
17626 the program currently being debugged in @value{GDBN}.
17628 Below is a sample program that forms the basis of the examples that
17629 follow. This program has been compiled and loaded into @value{GDBN},
17630 much like any other normal debugging session.
17633 void function1 (void)
17636 printf ("function 1\n");
17639 void function2 (void)
17654 For the purposes of the examples in this section, the program above has
17655 been compiled, loaded into @value{GDBN}, stopped at the function
17656 @code{main}, and @value{GDBN} is awaiting input from the user.
17658 To access variables and types for any program in @value{GDBN}, the
17659 program must be compiled and packaged with debug information. The
17660 @code{compile} command is not an exception to this rule. Without debug
17661 information, you can still use the @code{compile} command, but you will
17662 be very limited in what variables and types you can access.
17664 So with that in mind, the example above has been compiled with debug
17665 information enabled. The @code{compile} command will have access to
17666 all variables and types (except those that may have been optimized
17667 out). Currently, as @value{GDBN} has stopped the program in the
17668 @code{main} function, the @code{compile} command would have access to
17669 the variable @code{k}. You could invoke the @code{compile} command
17670 and type some source code to set the value of @code{k}. You can also
17671 read it, or do anything with that variable you would normally do in
17672 @code{C}. Be aware that changes to inferior variables in the
17673 @code{compile} command are persistent. In the following example:
17676 compile code k = 3;
17680 the variable @code{k} is now 3. It will retain that value until
17681 something else in the example program changes it, or another
17682 @code{compile} command changes it.
17684 Normal scope and access rules apply to source code compiled and
17685 injected by the @code{compile} command. In the example, the variables
17686 @code{j} and @code{k} are not accessible yet, because the program is
17687 currently stopped in the @code{main} function, where these variables
17688 are not in scope. Therefore, the following command
17691 compile code j = 3;
17695 will result in a compilation error message.
17697 Once the program is continued, execution will bring these variables in
17698 scope, and they will become accessible; then the code you specify via
17699 the @code{compile} command will be able to access them.
17701 You can create variables and types with the @code{compile} command as
17702 part of your source code. Variables and types that are created as part
17703 of the @code{compile} command are not visible to the rest of the program for
17704 the duration of its run. This example is valid:
17707 compile code int ff = 5; printf ("ff is %d\n", ff);
17710 However, if you were to type the following into @value{GDBN} after that
17711 command has completed:
17714 compile code printf ("ff is %d\n'', ff);
17718 a compiler error would be raised as the variable @code{ff} no longer
17719 exists. Object code generated and injected by the @code{compile}
17720 command is removed when its execution ends. Caution is advised
17721 when assigning to program variables values of variables created by the
17722 code submitted to the @code{compile} command. This example is valid:
17725 compile code int ff = 5; k = ff;
17728 The value of the variable @code{ff} is assigned to @code{k}. The variable
17729 @code{k} does not require the existence of @code{ff} to maintain the value
17730 it has been assigned. However, pointers require particular care in
17731 assignment. If the source code compiled with the @code{compile} command
17732 changed the address of a pointer in the example program, perhaps to a
17733 variable created in the @code{compile} command, that pointer would point
17734 to an invalid location when the command exits. The following example
17735 would likely cause issues with your debugged program:
17738 compile code int ff = 5; p = &ff;
17741 In this example, @code{p} would point to @code{ff} when the
17742 @code{compile} command is executing the source code provided to it.
17743 However, as variables in the (example) program persist with their
17744 assigned values, the variable @code{p} would point to an invalid
17745 location when the command exists. A general rule should be followed
17746 in that you should either assign @code{NULL} to any assigned pointers,
17747 or restore a valid location to the pointer before the command exits.
17749 Similar caution must be exercised with any structs, unions, and typedefs
17750 defined in @code{compile} command. Types defined in the @code{compile}
17751 command will no longer be available in the next @code{compile} command.
17752 Therefore, if you cast a variable to a type defined in the
17753 @code{compile} command, care must be taken to ensure that any future
17754 need to resolve the type can be achieved.
17757 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17758 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17759 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17760 Compilation failed.
17761 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17765 Variables that have been optimized away by the compiler are not
17766 accessible to the code submitted to the @code{compile} command.
17767 Access to those variables will generate a compiler error which @value{GDBN}
17768 will print to the console.
17771 @subsection Compiler search for the @code{compile} command
17773 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17774 may not be obvious for remote targets of different architecture than where
17775 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17776 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17777 command @code{set environment}). @xref{Environment}. @code{PATH} on
17778 @value{GDBN} host is searched for @value{NGCC} binary matching the
17779 target architecture and operating system.
17781 Specifically @code{PATH} is searched for binaries matching regular expression
17782 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17783 debugged. @var{arch} is processor name --- multiarch is supported, so for
17784 example both @code{i386} and @code{x86_64} targets look for pattern
17785 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17786 for pattern @code{s390x?}. @var{os} is currently supported only for
17787 pattern @code{linux(-gnu)?}.
17790 @chapter @value{GDBN} Files
17792 @value{GDBN} needs to know the file name of the program to be debugged,
17793 both in order to read its symbol table and in order to start your
17794 program. To debug a core dump of a previous run, you must also tell
17795 @value{GDBN} the name of the core dump file.
17798 * Files:: Commands to specify files
17799 * File Caching:: Information about @value{GDBN}'s file caching
17800 * Separate Debug Files:: Debugging information in separate files
17801 * MiniDebugInfo:: Debugging information in a special section
17802 * Index Files:: Index files speed up GDB
17803 * Symbol Errors:: Errors reading symbol files
17804 * Data Files:: GDB data files
17808 @section Commands to Specify Files
17810 @cindex symbol table
17811 @cindex core dump file
17813 You may want to specify executable and core dump file names. The usual
17814 way to do this is at start-up time, using the arguments to
17815 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17816 Out of @value{GDBN}}).
17818 Occasionally it is necessary to change to a different file during a
17819 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17820 specify a file you want to use. Or you are debugging a remote target
17821 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17822 Program}). In these situations the @value{GDBN} commands to specify
17823 new files are useful.
17826 @cindex executable file
17828 @item file @var{filename}
17829 Use @var{filename} as the program to be debugged. It is read for its
17830 symbols and for the contents of pure memory. It is also the program
17831 executed when you use the @code{run} command. If you do not specify a
17832 directory and the file is not found in the @value{GDBN} working directory,
17833 @value{GDBN} uses the environment variable @code{PATH} as a list of
17834 directories to search, just as the shell does when looking for a program
17835 to run. You can change the value of this variable, for both @value{GDBN}
17836 and your program, using the @code{path} command.
17838 @cindex unlinked object files
17839 @cindex patching object files
17840 You can load unlinked object @file{.o} files into @value{GDBN} using
17841 the @code{file} command. You will not be able to ``run'' an object
17842 file, but you can disassemble functions and inspect variables. Also,
17843 if the underlying BFD functionality supports it, you could use
17844 @kbd{gdb -write} to patch object files using this technique. Note
17845 that @value{GDBN} can neither interpret nor modify relocations in this
17846 case, so branches and some initialized variables will appear to go to
17847 the wrong place. But this feature is still handy from time to time.
17850 @code{file} with no argument makes @value{GDBN} discard any information it
17851 has on both executable file and the symbol table.
17854 @item exec-file @r{[} @var{filename} @r{]}
17855 Specify that the program to be run (but not the symbol table) is found
17856 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17857 if necessary to locate your program. Omitting @var{filename} means to
17858 discard information on the executable file.
17860 @kindex symbol-file
17861 @item symbol-file @r{[} @var{filename} @r{]}
17862 Read symbol table information from file @var{filename}. @code{PATH} is
17863 searched when necessary. Use the @code{file} command to get both symbol
17864 table and program to run from the same file.
17866 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17867 program's symbol table.
17869 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17870 some breakpoints and auto-display expressions. This is because they may
17871 contain pointers to the internal data recording symbols and data types,
17872 which are part of the old symbol table data being discarded inside
17875 @code{symbol-file} does not repeat if you press @key{RET} again after
17878 When @value{GDBN} is configured for a particular environment, it
17879 understands debugging information in whatever format is the standard
17880 generated for that environment; you may use either a @sc{gnu} compiler, or
17881 other compilers that adhere to the local conventions.
17882 Best results are usually obtained from @sc{gnu} compilers; for example,
17883 using @code{@value{NGCC}} you can generate debugging information for
17886 For most kinds of object files, with the exception of old SVR3 systems
17887 using COFF, the @code{symbol-file} command does not normally read the
17888 symbol table in full right away. Instead, it scans the symbol table
17889 quickly to find which source files and which symbols are present. The
17890 details are read later, one source file at a time, as they are needed.
17892 The purpose of this two-stage reading strategy is to make @value{GDBN}
17893 start up faster. For the most part, it is invisible except for
17894 occasional pauses while the symbol table details for a particular source
17895 file are being read. (The @code{set verbose} command can turn these
17896 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17897 Warnings and Messages}.)
17899 We have not implemented the two-stage strategy for COFF yet. When the
17900 symbol table is stored in COFF format, @code{symbol-file} reads the
17901 symbol table data in full right away. Note that ``stabs-in-COFF''
17902 still does the two-stage strategy, since the debug info is actually
17906 @cindex reading symbols immediately
17907 @cindex symbols, reading immediately
17908 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17909 @itemx file @r{[} -readnow @r{]} @var{filename}
17910 You can override the @value{GDBN} two-stage strategy for reading symbol
17911 tables by using the @samp{-readnow} option with any of the commands that
17912 load symbol table information, if you want to be sure @value{GDBN} has the
17913 entire symbol table available.
17915 @c FIXME: for now no mention of directories, since this seems to be in
17916 @c flux. 13mar1992 status is that in theory GDB would look either in
17917 @c current dir or in same dir as myprog; but issues like competing
17918 @c GDB's, or clutter in system dirs, mean that in practice right now
17919 @c only current dir is used. FFish says maybe a special GDB hierarchy
17920 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17924 @item core-file @r{[}@var{filename}@r{]}
17926 Specify the whereabouts of a core dump file to be used as the ``contents
17927 of memory''. Traditionally, core files contain only some parts of the
17928 address space of the process that generated them; @value{GDBN} can access the
17929 executable file itself for other parts.
17931 @code{core-file} with no argument specifies that no core file is
17934 Note that the core file is ignored when your program is actually running
17935 under @value{GDBN}. So, if you have been running your program and you
17936 wish to debug a core file instead, you must kill the subprocess in which
17937 the program is running. To do this, use the @code{kill} command
17938 (@pxref{Kill Process, ,Killing the Child Process}).
17940 @kindex add-symbol-file
17941 @cindex dynamic linking
17942 @item add-symbol-file @var{filename} @var{address}
17943 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17944 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17945 The @code{add-symbol-file} command reads additional symbol table
17946 information from the file @var{filename}. You would use this command
17947 when @var{filename} has been dynamically loaded (by some other means)
17948 into the program that is running. The @var{address} should give the memory
17949 address at which the file has been loaded; @value{GDBN} cannot figure
17950 this out for itself. You can additionally specify an arbitrary number
17951 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17952 section name and base address for that section. You can specify any
17953 @var{address} as an expression.
17955 The symbol table of the file @var{filename} is added to the symbol table
17956 originally read with the @code{symbol-file} command. You can use the
17957 @code{add-symbol-file} command any number of times; the new symbol data
17958 thus read is kept in addition to the old.
17960 Changes can be reverted using the command @code{remove-symbol-file}.
17962 @cindex relocatable object files, reading symbols from
17963 @cindex object files, relocatable, reading symbols from
17964 @cindex reading symbols from relocatable object files
17965 @cindex symbols, reading from relocatable object files
17966 @cindex @file{.o} files, reading symbols from
17967 Although @var{filename} is typically a shared library file, an
17968 executable file, or some other object file which has been fully
17969 relocated for loading into a process, you can also load symbolic
17970 information from relocatable @file{.o} files, as long as:
17974 the file's symbolic information refers only to linker symbols defined in
17975 that file, not to symbols defined by other object files,
17977 every section the file's symbolic information refers to has actually
17978 been loaded into the inferior, as it appears in the file, and
17980 you can determine the address at which every section was loaded, and
17981 provide these to the @code{add-symbol-file} command.
17985 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17986 relocatable files into an already running program; such systems
17987 typically make the requirements above easy to meet. However, it's
17988 important to recognize that many native systems use complex link
17989 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17990 assembly, for example) that make the requirements difficult to meet. In
17991 general, one cannot assume that using @code{add-symbol-file} to read a
17992 relocatable object file's symbolic information will have the same effect
17993 as linking the relocatable object file into the program in the normal
17996 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17998 @kindex remove-symbol-file
17999 @item remove-symbol-file @var{filename}
18000 @item remove-symbol-file -a @var{address}
18001 Remove a symbol file added via the @code{add-symbol-file} command. The
18002 file to remove can be identified by its @var{filename} or by an @var{address}
18003 that lies within the boundaries of this symbol file in memory. Example:
18006 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18007 add symbol table from file "/home/user/gdb/mylib.so" at
18008 .text_addr = 0x7ffff7ff9480
18010 Reading symbols from /home/user/gdb/mylib.so...done.
18011 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18012 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18017 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18019 @kindex add-symbol-file-from-memory
18020 @cindex @code{syscall DSO}
18021 @cindex load symbols from memory
18022 @item add-symbol-file-from-memory @var{address}
18023 Load symbols from the given @var{address} in a dynamically loaded
18024 object file whose image is mapped directly into the inferior's memory.
18025 For example, the Linux kernel maps a @code{syscall DSO} into each
18026 process's address space; this DSO provides kernel-specific code for
18027 some system calls. The argument can be any expression whose
18028 evaluation yields the address of the file's shared object file header.
18029 For this command to work, you must have used @code{symbol-file} or
18030 @code{exec-file} commands in advance.
18033 @item section @var{section} @var{addr}
18034 The @code{section} command changes the base address of the named
18035 @var{section} of the exec file to @var{addr}. This can be used if the
18036 exec file does not contain section addresses, (such as in the
18037 @code{a.out} format), or when the addresses specified in the file
18038 itself are wrong. Each section must be changed separately. The
18039 @code{info files} command, described below, lists all the sections and
18043 @kindex info target
18046 @code{info files} and @code{info target} are synonymous; both print the
18047 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18048 including the names of the executable and core dump files currently in
18049 use by @value{GDBN}, and the files from which symbols were loaded. The
18050 command @code{help target} lists all possible targets rather than
18053 @kindex maint info sections
18054 @item maint info sections
18055 Another command that can give you extra information about program sections
18056 is @code{maint info sections}. In addition to the section information
18057 displayed by @code{info files}, this command displays the flags and file
18058 offset of each section in the executable and core dump files. In addition,
18059 @code{maint info sections} provides the following command options (which
18060 may be arbitrarily combined):
18064 Display sections for all loaded object files, including shared libraries.
18065 @item @var{sections}
18066 Display info only for named @var{sections}.
18067 @item @var{section-flags}
18068 Display info only for sections for which @var{section-flags} are true.
18069 The section flags that @value{GDBN} currently knows about are:
18072 Section will have space allocated in the process when loaded.
18073 Set for all sections except those containing debug information.
18075 Section will be loaded from the file into the child process memory.
18076 Set for pre-initialized code and data, clear for @code{.bss} sections.
18078 Section needs to be relocated before loading.
18080 Section cannot be modified by the child process.
18082 Section contains executable code only.
18084 Section contains data only (no executable code).
18086 Section will reside in ROM.
18088 Section contains data for constructor/destructor lists.
18090 Section is not empty.
18092 An instruction to the linker to not output the section.
18093 @item COFF_SHARED_LIBRARY
18094 A notification to the linker that the section contains
18095 COFF shared library information.
18097 Section contains common symbols.
18100 @kindex set trust-readonly-sections
18101 @cindex read-only sections
18102 @item set trust-readonly-sections on
18103 Tell @value{GDBN} that readonly sections in your object file
18104 really are read-only (i.e.@: that their contents will not change).
18105 In that case, @value{GDBN} can fetch values from these sections
18106 out of the object file, rather than from the target program.
18107 For some targets (notably embedded ones), this can be a significant
18108 enhancement to debugging performance.
18110 The default is off.
18112 @item set trust-readonly-sections off
18113 Tell @value{GDBN} not to trust readonly sections. This means that
18114 the contents of the section might change while the program is running,
18115 and must therefore be fetched from the target when needed.
18117 @item show trust-readonly-sections
18118 Show the current setting of trusting readonly sections.
18121 All file-specifying commands allow both absolute and relative file names
18122 as arguments. @value{GDBN} always converts the file name to an absolute file
18123 name and remembers it that way.
18125 @cindex shared libraries
18126 @anchor{Shared Libraries}
18127 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18128 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18129 DSBT (TIC6X) shared libraries.
18131 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18132 shared libraries. @xref{Expat}.
18134 @value{GDBN} automatically loads symbol definitions from shared libraries
18135 when you use the @code{run} command, or when you examine a core file.
18136 (Before you issue the @code{run} command, @value{GDBN} does not understand
18137 references to a function in a shared library, however---unless you are
18138 debugging a core file).
18140 @c FIXME: some @value{GDBN} release may permit some refs to undef
18141 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18142 @c FIXME...lib; check this from time to time when updating manual
18144 There are times, however, when you may wish to not automatically load
18145 symbol definitions from shared libraries, such as when they are
18146 particularly large or there are many of them.
18148 To control the automatic loading of shared library symbols, use the
18152 @kindex set auto-solib-add
18153 @item set auto-solib-add @var{mode}
18154 If @var{mode} is @code{on}, symbols from all shared object libraries
18155 will be loaded automatically when the inferior begins execution, you
18156 attach to an independently started inferior, or when the dynamic linker
18157 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18158 is @code{off}, symbols must be loaded manually, using the
18159 @code{sharedlibrary} command. The default value is @code{on}.
18161 @cindex memory used for symbol tables
18162 If your program uses lots of shared libraries with debug info that
18163 takes large amounts of memory, you can decrease the @value{GDBN}
18164 memory footprint by preventing it from automatically loading the
18165 symbols from shared libraries. To that end, type @kbd{set
18166 auto-solib-add off} before running the inferior, then load each
18167 library whose debug symbols you do need with @kbd{sharedlibrary
18168 @var{regexp}}, where @var{regexp} is a regular expression that matches
18169 the libraries whose symbols you want to be loaded.
18171 @kindex show auto-solib-add
18172 @item show auto-solib-add
18173 Display the current autoloading mode.
18176 @cindex load shared library
18177 To explicitly load shared library symbols, use the @code{sharedlibrary}
18181 @kindex info sharedlibrary
18183 @item info share @var{regex}
18184 @itemx info sharedlibrary @var{regex}
18185 Print the names of the shared libraries which are currently loaded
18186 that match @var{regex}. If @var{regex} is omitted then print
18187 all shared libraries that are loaded.
18190 @item info dll @var{regex}
18191 This is an alias of @code{info sharedlibrary}.
18193 @kindex sharedlibrary
18195 @item sharedlibrary @var{regex}
18196 @itemx share @var{regex}
18197 Load shared object library symbols for files matching a
18198 Unix regular expression.
18199 As with files loaded automatically, it only loads shared libraries
18200 required by your program for a core file or after typing @code{run}. If
18201 @var{regex} is omitted all shared libraries required by your program are
18204 @item nosharedlibrary
18205 @kindex nosharedlibrary
18206 @cindex unload symbols from shared libraries
18207 Unload all shared object library symbols. This discards all symbols
18208 that have been loaded from all shared libraries. Symbols from shared
18209 libraries that were loaded by explicit user requests are not
18213 Sometimes you may wish that @value{GDBN} stops and gives you control
18214 when any of shared library events happen. The best way to do this is
18215 to use @code{catch load} and @code{catch unload} (@pxref{Set
18218 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18219 command for this. This command exists for historical reasons. It is
18220 less useful than setting a catchpoint, because it does not allow for
18221 conditions or commands as a catchpoint does.
18224 @item set stop-on-solib-events
18225 @kindex set stop-on-solib-events
18226 This command controls whether @value{GDBN} should give you control
18227 when the dynamic linker notifies it about some shared library event.
18228 The most common event of interest is loading or unloading of a new
18231 @item show stop-on-solib-events
18232 @kindex show stop-on-solib-events
18233 Show whether @value{GDBN} stops and gives you control when shared
18234 library events happen.
18237 Shared libraries are also supported in many cross or remote debugging
18238 configurations. @value{GDBN} needs to have access to the target's libraries;
18239 this can be accomplished either by providing copies of the libraries
18240 on the host system, or by asking @value{GDBN} to automatically retrieve the
18241 libraries from the target. If copies of the target libraries are
18242 provided, they need to be the same as the target libraries, although the
18243 copies on the target can be stripped as long as the copies on the host are
18246 @cindex where to look for shared libraries
18247 For remote debugging, you need to tell @value{GDBN} where the target
18248 libraries are, so that it can load the correct copies---otherwise, it
18249 may try to load the host's libraries. @value{GDBN} has two variables
18250 to specify the search directories for target libraries.
18253 @cindex prefix for executable and shared library file names
18254 @cindex system root, alternate
18255 @kindex set solib-absolute-prefix
18256 @kindex set sysroot
18257 @item set sysroot @var{path}
18258 Use @var{path} as the system root for the program being debugged. Any
18259 absolute shared library paths will be prefixed with @var{path}; many
18260 runtime loaders store the absolute paths to the shared library in the
18261 target program's memory. When starting processes remotely, and when
18262 attaching to already-running processes (local or remote), their
18263 executable filenames will be prefixed with @var{path} if reported to
18264 @value{GDBN} as absolute by the operating system. If you use
18265 @code{set sysroot} to find executables and shared libraries, they need
18266 to be laid out in the same way that they are on the target, with
18267 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18270 If @var{path} starts with the sequence @file{target:} and the target
18271 system is remote then @value{GDBN} will retrieve the target binaries
18272 from the remote system. This is only supported when using a remote
18273 target that supports the @code{remote get} command (@pxref{File
18274 Transfer,,Sending files to a remote system}). The part of @var{path}
18275 following the initial @file{target:} (if present) is used as system
18276 root prefix on the remote file system. If @var{path} starts with the
18277 sequence @file{remote:} this is converted to the sequence
18278 @file{target:} by @code{set sysroot}@footnote{Historically the
18279 functionality to retrieve binaries from the remote system was
18280 provided by prefixing @var{path} with @file{remote:}}. If you want
18281 to specify a local system root using a directory that happens to be
18282 named @file{target:} or @file{remote:}, you need to use some
18283 equivalent variant of the name like @file{./target:}.
18285 For targets with an MS-DOS based filesystem, such as MS-Windows and
18286 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18287 absolute file name with @var{path}. But first, on Unix hosts,
18288 @value{GDBN} converts all backslash directory separators into forward
18289 slashes, because the backslash is not a directory separator on Unix:
18292 c:\foo\bar.dll @result{} c:/foo/bar.dll
18295 Then, @value{GDBN} attempts prefixing the target file name with
18296 @var{path}, and looks for the resulting file name in the host file
18300 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18303 If that does not find the binary, @value{GDBN} tries removing
18304 the @samp{:} character from the drive spec, both for convenience, and,
18305 for the case of the host file system not supporting file names with
18309 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18312 This makes it possible to have a system root that mirrors a target
18313 with more than one drive. E.g., you may want to setup your local
18314 copies of the target system shared libraries like so (note @samp{c} vs
18318 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18319 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18320 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18324 and point the system root at @file{/path/to/sysroot}, so that
18325 @value{GDBN} can find the correct copies of both
18326 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18328 If that still does not find the binary, @value{GDBN} tries
18329 removing the whole drive spec from the target file name:
18332 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18335 This last lookup makes it possible to not care about the drive name,
18336 if you don't want or need to.
18338 The @code{set solib-absolute-prefix} command is an alias for @code{set
18341 @cindex default system root
18342 @cindex @samp{--with-sysroot}
18343 You can set the default system root by using the configure-time
18344 @samp{--with-sysroot} option. If the system root is inside
18345 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18346 @samp{--exec-prefix}), then the default system root will be updated
18347 automatically if the installed @value{GDBN} is moved to a new
18350 @kindex show sysroot
18352 Display the current executable and shared library prefix.
18354 @kindex set solib-search-path
18355 @item set solib-search-path @var{path}
18356 If this variable is set, @var{path} is a colon-separated list of
18357 directories to search for shared libraries. @samp{solib-search-path}
18358 is used after @samp{sysroot} fails to locate the library, or if the
18359 path to the library is relative instead of absolute. If you want to
18360 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18361 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18362 finding your host's libraries. @samp{sysroot} is preferred; setting
18363 it to a nonexistent directory may interfere with automatic loading
18364 of shared library symbols.
18366 @kindex show solib-search-path
18367 @item show solib-search-path
18368 Display the current shared library search path.
18370 @cindex DOS file-name semantics of file names.
18371 @kindex set target-file-system-kind (unix|dos-based|auto)
18372 @kindex show target-file-system-kind
18373 @item set target-file-system-kind @var{kind}
18374 Set assumed file system kind for target reported file names.
18376 Shared library file names as reported by the target system may not
18377 make sense as is on the system @value{GDBN} is running on. For
18378 example, when remote debugging a target that has MS-DOS based file
18379 system semantics, from a Unix host, the target may be reporting to
18380 @value{GDBN} a list of loaded shared libraries with file names such as
18381 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18382 drive letters, so the @samp{c:\} prefix is not normally understood as
18383 indicating an absolute file name, and neither is the backslash
18384 normally considered a directory separator character. In that case,
18385 the native file system would interpret this whole absolute file name
18386 as a relative file name with no directory components. This would make
18387 it impossible to point @value{GDBN} at a copy of the remote target's
18388 shared libraries on the host using @code{set sysroot}, and impractical
18389 with @code{set solib-search-path}. Setting
18390 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18391 to interpret such file names similarly to how the target would, and to
18392 map them to file names valid on @value{GDBN}'s native file system
18393 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18394 to one of the supported file system kinds. In that case, @value{GDBN}
18395 tries to determine the appropriate file system variant based on the
18396 current target's operating system (@pxref{ABI, ,Configuring the
18397 Current ABI}). The supported file system settings are:
18401 Instruct @value{GDBN} to assume the target file system is of Unix
18402 kind. Only file names starting the forward slash (@samp{/}) character
18403 are considered absolute, and the directory separator character is also
18407 Instruct @value{GDBN} to assume the target file system is DOS based.
18408 File names starting with either a forward slash, or a drive letter
18409 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18410 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18411 considered directory separators.
18414 Instruct @value{GDBN} to use the file system kind associated with the
18415 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18416 This is the default.
18420 @cindex file name canonicalization
18421 @cindex base name differences
18422 When processing file names provided by the user, @value{GDBN}
18423 frequently needs to compare them to the file names recorded in the
18424 program's debug info. Normally, @value{GDBN} compares just the
18425 @dfn{base names} of the files as strings, which is reasonably fast
18426 even for very large programs. (The base name of a file is the last
18427 portion of its name, after stripping all the leading directories.)
18428 This shortcut in comparison is based upon the assumption that files
18429 cannot have more than one base name. This is usually true, but
18430 references to files that use symlinks or similar filesystem
18431 facilities violate that assumption. If your program records files
18432 using such facilities, or if you provide file names to @value{GDBN}
18433 using symlinks etc., you can set @code{basenames-may-differ} to
18434 @code{true} to instruct @value{GDBN} to completely canonicalize each
18435 pair of file names it needs to compare. This will make file-name
18436 comparisons accurate, but at a price of a significant slowdown.
18439 @item set basenames-may-differ
18440 @kindex set basenames-may-differ
18441 Set whether a source file may have multiple base names.
18443 @item show basenames-may-differ
18444 @kindex show basenames-may-differ
18445 Show whether a source file may have multiple base names.
18449 @section File Caching
18450 @cindex caching of opened files
18451 @cindex caching of bfd objects
18453 To speed up file loading, and reduce memory usage, @value{GDBN} will
18454 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18455 BFD, bfd, The Binary File Descriptor Library}. The following commands
18456 allow visibility and control of the caching behavior.
18459 @kindex maint info bfds
18460 @item maint info bfds
18461 This prints information about each @code{bfd} object that is known to
18464 @kindex maint set bfd-sharing
18465 @kindex maint show bfd-sharing
18466 @kindex bfd caching
18467 @item maint set bfd-sharing
18468 @item maint show bfd-sharing
18469 Control whether @code{bfd} objects can be shared. When sharing is
18470 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18471 than reopening the same file. Turning sharing off does not cause
18472 already shared @code{bfd} objects to be unshared, but all future files
18473 that are opened will create a new @code{bfd} object. Similarly,
18474 re-enabling sharing does not cause multiple existing @code{bfd}
18475 objects to be collapsed into a single shared @code{bfd} object.
18477 @kindex set debug bfd-cache @var{level}
18478 @kindex bfd caching
18479 @item set debug bfd-cache @var{level}
18480 Turns on debugging of the bfd cache, setting the level to @var{level}.
18482 @kindex show debug bfd-cache
18483 @kindex bfd caching
18484 @item show debug bfd-cache
18485 Show the current debugging level of the bfd cache.
18488 @node Separate Debug Files
18489 @section Debugging Information in Separate Files
18490 @cindex separate debugging information files
18491 @cindex debugging information in separate files
18492 @cindex @file{.debug} subdirectories
18493 @cindex debugging information directory, global
18494 @cindex global debugging information directories
18495 @cindex build ID, and separate debugging files
18496 @cindex @file{.build-id} directory
18498 @value{GDBN} allows you to put a program's debugging information in a
18499 file separate from the executable itself, in a way that allows
18500 @value{GDBN} to find and load the debugging information automatically.
18501 Since debugging information can be very large---sometimes larger
18502 than the executable code itself---some systems distribute debugging
18503 information for their executables in separate files, which users can
18504 install only when they need to debug a problem.
18506 @value{GDBN} supports two ways of specifying the separate debug info
18511 The executable contains a @dfn{debug link} that specifies the name of
18512 the separate debug info file. The separate debug file's name is
18513 usually @file{@var{executable}.debug}, where @var{executable} is the
18514 name of the corresponding executable file without leading directories
18515 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18516 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18517 checksum for the debug file, which @value{GDBN} uses to validate that
18518 the executable and the debug file came from the same build.
18521 The executable contains a @dfn{build ID}, a unique bit string that is
18522 also present in the corresponding debug info file. (This is supported
18523 only on some operating systems, when using the ELF or PE file formats
18524 for binary files and the @sc{gnu} Binutils.) For more details about
18525 this feature, see the description of the @option{--build-id}
18526 command-line option in @ref{Options, , Command Line Options, ld.info,
18527 The GNU Linker}. The debug info file's name is not specified
18528 explicitly by the build ID, but can be computed from the build ID, see
18532 Depending on the way the debug info file is specified, @value{GDBN}
18533 uses two different methods of looking for the debug file:
18537 For the ``debug link'' method, @value{GDBN} looks up the named file in
18538 the directory of the executable file, then in a subdirectory of that
18539 directory named @file{.debug}, and finally under each one of the global debug
18540 directories, in a subdirectory whose name is identical to the leading
18541 directories of the executable's absolute file name.
18544 For the ``build ID'' method, @value{GDBN} looks in the
18545 @file{.build-id} subdirectory of each one of the global debug directories for
18546 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18547 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18548 are the rest of the bit string. (Real build ID strings are 32 or more
18549 hex characters, not 10.)
18552 So, for example, suppose you ask @value{GDBN} to debug
18553 @file{/usr/bin/ls}, which has a debug link that specifies the
18554 file @file{ls.debug}, and a build ID whose value in hex is
18555 @code{abcdef1234}. If the list of the global debug directories includes
18556 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18557 debug information files, in the indicated order:
18561 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18563 @file{/usr/bin/ls.debug}
18565 @file{/usr/bin/.debug/ls.debug}
18567 @file{/usr/lib/debug/usr/bin/ls.debug}.
18570 @anchor{debug-file-directory}
18571 Global debugging info directories default to what is set by @value{GDBN}
18572 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18573 you can also set the global debugging info directories, and view the list
18574 @value{GDBN} is currently using.
18578 @kindex set debug-file-directory
18579 @item set debug-file-directory @var{directories}
18580 Set the directories which @value{GDBN} searches for separate debugging
18581 information files to @var{directory}. Multiple path components can be set
18582 concatenating them by a path separator.
18584 @kindex show debug-file-directory
18585 @item show debug-file-directory
18586 Show the directories @value{GDBN} searches for separate debugging
18591 @cindex @code{.gnu_debuglink} sections
18592 @cindex debug link sections
18593 A debug link is a special section of the executable file named
18594 @code{.gnu_debuglink}. The section must contain:
18598 A filename, with any leading directory components removed, followed by
18601 zero to three bytes of padding, as needed to reach the next four-byte
18602 boundary within the section, and
18604 a four-byte CRC checksum, stored in the same endianness used for the
18605 executable file itself. The checksum is computed on the debugging
18606 information file's full contents by the function given below, passing
18607 zero as the @var{crc} argument.
18610 Any executable file format can carry a debug link, as long as it can
18611 contain a section named @code{.gnu_debuglink} with the contents
18614 @cindex @code{.note.gnu.build-id} sections
18615 @cindex build ID sections
18616 The build ID is a special section in the executable file (and in other
18617 ELF binary files that @value{GDBN} may consider). This section is
18618 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18619 It contains unique identification for the built files---the ID remains
18620 the same across multiple builds of the same build tree. The default
18621 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18622 content for the build ID string. The same section with an identical
18623 value is present in the original built binary with symbols, in its
18624 stripped variant, and in the separate debugging information file.
18626 The debugging information file itself should be an ordinary
18627 executable, containing a full set of linker symbols, sections, and
18628 debugging information. The sections of the debugging information file
18629 should have the same names, addresses, and sizes as the original file,
18630 but they need not contain any data---much like a @code{.bss} section
18631 in an ordinary executable.
18633 The @sc{gnu} binary utilities (Binutils) package includes the
18634 @samp{objcopy} utility that can produce
18635 the separated executable / debugging information file pairs using the
18636 following commands:
18639 @kbd{objcopy --only-keep-debug foo foo.debug}
18644 These commands remove the debugging
18645 information from the executable file @file{foo} and place it in the file
18646 @file{foo.debug}. You can use the first, second or both methods to link the
18651 The debug link method needs the following additional command to also leave
18652 behind a debug link in @file{foo}:
18655 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18658 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18659 a version of the @code{strip} command such that the command @kbd{strip foo -f
18660 foo.debug} has the same functionality as the two @code{objcopy} commands and
18661 the @code{ln -s} command above, together.
18664 Build ID gets embedded into the main executable using @code{ld --build-id} or
18665 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18666 compatibility fixes for debug files separation are present in @sc{gnu} binary
18667 utilities (Binutils) package since version 2.18.
18672 @cindex CRC algorithm definition
18673 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18674 IEEE 802.3 using the polynomial:
18676 @c TexInfo requires naked braces for multi-digit exponents for Tex
18677 @c output, but this causes HTML output to barf. HTML has to be set using
18678 @c raw commands. So we end up having to specify this equation in 2
18683 <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>
18684 + <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
18690 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18691 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18695 The function is computed byte at a time, taking the least
18696 significant bit of each byte first. The initial pattern
18697 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18698 the final result is inverted to ensure trailing zeros also affect the
18701 @emph{Note:} This is the same CRC polynomial as used in handling the
18702 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18703 However in the case of the Remote Serial Protocol, the CRC is computed
18704 @emph{most} significant bit first, and the result is not inverted, so
18705 trailing zeros have no effect on the CRC value.
18707 To complete the description, we show below the code of the function
18708 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18709 initially supplied @code{crc} argument means that an initial call to
18710 this function passing in zero will start computing the CRC using
18713 @kindex gnu_debuglink_crc32
18716 gnu_debuglink_crc32 (unsigned long crc,
18717 unsigned char *buf, size_t len)
18719 static const unsigned long crc32_table[256] =
18721 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18722 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18723 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18724 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18725 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18726 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18727 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18728 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18729 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18730 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18731 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18732 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18733 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18734 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18735 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18736 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18737 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18738 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18739 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18740 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18741 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18742 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18743 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18744 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18745 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18746 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18747 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18748 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18749 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18750 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18751 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18752 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18753 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18754 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18755 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18756 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18757 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18758 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18759 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18760 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18761 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18762 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18763 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18764 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18765 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18766 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18767 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18768 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18769 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18770 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18771 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18774 unsigned char *end;
18776 crc = ~crc & 0xffffffff;
18777 for (end = buf + len; buf < end; ++buf)
18778 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18779 return ~crc & 0xffffffff;
18784 This computation does not apply to the ``build ID'' method.
18786 @node MiniDebugInfo
18787 @section Debugging information in a special section
18788 @cindex separate debug sections
18789 @cindex @samp{.gnu_debugdata} section
18791 Some systems ship pre-built executables and libraries that have a
18792 special @samp{.gnu_debugdata} section. This feature is called
18793 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18794 is used to supply extra symbols for backtraces.
18796 The intent of this section is to provide extra minimal debugging
18797 information for use in simple backtraces. It is not intended to be a
18798 replacement for full separate debugging information (@pxref{Separate
18799 Debug Files}). The example below shows the intended use; however,
18800 @value{GDBN} does not currently put restrictions on what sort of
18801 debugging information might be included in the section.
18803 @value{GDBN} has support for this extension. If the section exists,
18804 then it is used provided that no other source of debugging information
18805 can be found, and that @value{GDBN} was configured with LZMA support.
18807 This section can be easily created using @command{objcopy} and other
18808 standard utilities:
18811 # Extract the dynamic symbols from the main binary, there is no need
18812 # to also have these in the normal symbol table.
18813 nm -D @var{binary} --format=posix --defined-only \
18814 | awk '@{ print $1 @}' | sort > dynsyms
18816 # Extract all the text (i.e. function) symbols from the debuginfo.
18817 # (Note that we actually also accept "D" symbols, for the benefit
18818 # of platforms like PowerPC64 that use function descriptors.)
18819 nm @var{binary} --format=posix --defined-only \
18820 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18823 # Keep all the function symbols not already in the dynamic symbol
18825 comm -13 dynsyms funcsyms > keep_symbols
18827 # Separate full debug info into debug binary.
18828 objcopy --only-keep-debug @var{binary} debug
18830 # Copy the full debuginfo, keeping only a minimal set of symbols and
18831 # removing some unnecessary sections.
18832 objcopy -S --remove-section .gdb_index --remove-section .comment \
18833 --keep-symbols=keep_symbols debug mini_debuginfo
18835 # Drop the full debug info from the original binary.
18836 strip --strip-all -R .comment @var{binary}
18838 # Inject the compressed data into the .gnu_debugdata section of the
18841 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18845 @section Index Files Speed Up @value{GDBN}
18846 @cindex index files
18847 @cindex @samp{.gdb_index} section
18849 When @value{GDBN} finds a symbol file, it scans the symbols in the
18850 file in order to construct an internal symbol table. This lets most
18851 @value{GDBN} operations work quickly---at the cost of a delay early
18852 on. For large programs, this delay can be quite lengthy, so
18853 @value{GDBN} provides a way to build an index, which speeds up
18856 The index is stored as a section in the symbol file. @value{GDBN} can
18857 write the index to a file, then you can put it into the symbol file
18858 using @command{objcopy}.
18860 To create an index file, use the @code{save gdb-index} command:
18863 @item save gdb-index @var{directory}
18864 @kindex save gdb-index
18865 Create an index file for each symbol file currently known by
18866 @value{GDBN}. Each file is named after its corresponding symbol file,
18867 with @samp{.gdb-index} appended, and is written into the given
18871 Once you have created an index file you can merge it into your symbol
18872 file, here named @file{symfile}, using @command{objcopy}:
18875 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18876 --set-section-flags .gdb_index=readonly symfile symfile
18879 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18880 sections that have been deprecated. Usually they are deprecated because
18881 they are missing a new feature or have performance issues.
18882 To tell @value{GDBN} to use a deprecated index section anyway
18883 specify @code{set use-deprecated-index-sections on}.
18884 The default is @code{off}.
18885 This can speed up startup, but may result in some functionality being lost.
18886 @xref{Index Section Format}.
18888 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18889 must be done before gdb reads the file. The following will not work:
18892 $ gdb -ex "set use-deprecated-index-sections on" <program>
18895 Instead you must do, for example,
18898 $ gdb -iex "set use-deprecated-index-sections on" <program>
18901 There are currently some limitation on indices. They only work when
18902 for DWARF debugging information, not stabs. And, they do not
18903 currently work for programs using Ada.
18905 @node Symbol Errors
18906 @section Errors Reading Symbol Files
18908 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18909 such as symbol types it does not recognize, or known bugs in compiler
18910 output. By default, @value{GDBN} does not notify you of such problems, since
18911 they are relatively common and primarily of interest to people
18912 debugging compilers. If you are interested in seeing information
18913 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18914 only one message about each such type of problem, no matter how many
18915 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18916 to see how many times the problems occur, with the @code{set
18917 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18920 The messages currently printed, and their meanings, include:
18923 @item inner block not inside outer block in @var{symbol}
18925 The symbol information shows where symbol scopes begin and end
18926 (such as at the start of a function or a block of statements). This
18927 error indicates that an inner scope block is not fully contained
18928 in its outer scope blocks.
18930 @value{GDBN} circumvents the problem by treating the inner block as if it had
18931 the same scope as the outer block. In the error message, @var{symbol}
18932 may be shown as ``@code{(don't know)}'' if the outer block is not a
18935 @item block at @var{address} out of order
18937 The symbol information for symbol scope blocks should occur in
18938 order of increasing addresses. This error indicates that it does not
18941 @value{GDBN} does not circumvent this problem, and has trouble
18942 locating symbols in the source file whose symbols it is reading. (You
18943 can often determine what source file is affected by specifying
18944 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18947 @item bad block start address patched
18949 The symbol information for a symbol scope block has a start address
18950 smaller than the address of the preceding source line. This is known
18951 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18953 @value{GDBN} circumvents the problem by treating the symbol scope block as
18954 starting on the previous source line.
18956 @item bad string table offset in symbol @var{n}
18959 Symbol number @var{n} contains a pointer into the string table which is
18960 larger than the size of the string table.
18962 @value{GDBN} circumvents the problem by considering the symbol to have the
18963 name @code{foo}, which may cause other problems if many symbols end up
18966 @item unknown symbol type @code{0x@var{nn}}
18968 The symbol information contains new data types that @value{GDBN} does
18969 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18970 uncomprehended information, in hexadecimal.
18972 @value{GDBN} circumvents the error by ignoring this symbol information.
18973 This usually allows you to debug your program, though certain symbols
18974 are not accessible. If you encounter such a problem and feel like
18975 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18976 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18977 and examine @code{*bufp} to see the symbol.
18979 @item stub type has NULL name
18981 @value{GDBN} could not find the full definition for a struct or class.
18983 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18984 The symbol information for a C@t{++} member function is missing some
18985 information that recent versions of the compiler should have output for
18988 @item info mismatch between compiler and debugger
18990 @value{GDBN} could not parse a type specification output by the compiler.
18995 @section GDB Data Files
18997 @cindex prefix for data files
18998 @value{GDBN} will sometimes read an auxiliary data file. These files
18999 are kept in a directory known as the @dfn{data directory}.
19001 You can set the data directory's name, and view the name @value{GDBN}
19002 is currently using.
19005 @kindex set data-directory
19006 @item set data-directory @var{directory}
19007 Set the directory which @value{GDBN} searches for auxiliary data files
19008 to @var{directory}.
19010 @kindex show data-directory
19011 @item show data-directory
19012 Show the directory @value{GDBN} searches for auxiliary data files.
19015 @cindex default data directory
19016 @cindex @samp{--with-gdb-datadir}
19017 You can set the default data directory by using the configure-time
19018 @samp{--with-gdb-datadir} option. If the data directory is inside
19019 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19020 @samp{--exec-prefix}), then the default data directory will be updated
19021 automatically if the installed @value{GDBN} is moved to a new
19024 The data directory may also be specified with the
19025 @code{--data-directory} command line option.
19026 @xref{Mode Options}.
19029 @chapter Specifying a Debugging Target
19031 @cindex debugging target
19032 A @dfn{target} is the execution environment occupied by your program.
19034 Often, @value{GDBN} runs in the same host environment as your program;
19035 in that case, the debugging target is specified as a side effect when
19036 you use the @code{file} or @code{core} commands. When you need more
19037 flexibility---for example, running @value{GDBN} on a physically separate
19038 host, or controlling a standalone system over a serial port or a
19039 realtime system over a TCP/IP connection---you can use the @code{target}
19040 command to specify one of the target types configured for @value{GDBN}
19041 (@pxref{Target Commands, ,Commands for Managing Targets}).
19043 @cindex target architecture
19044 It is possible to build @value{GDBN} for several different @dfn{target
19045 architectures}. When @value{GDBN} is built like that, you can choose
19046 one of the available architectures with the @kbd{set architecture}
19050 @kindex set architecture
19051 @kindex show architecture
19052 @item set architecture @var{arch}
19053 This command sets the current target architecture to @var{arch}. The
19054 value of @var{arch} can be @code{"auto"}, in addition to one of the
19055 supported architectures.
19057 @item show architecture
19058 Show the current target architecture.
19060 @item set processor
19062 @kindex set processor
19063 @kindex show processor
19064 These are alias commands for, respectively, @code{set architecture}
19065 and @code{show architecture}.
19069 * Active Targets:: Active targets
19070 * Target Commands:: Commands for managing targets
19071 * Byte Order:: Choosing target byte order
19074 @node Active Targets
19075 @section Active Targets
19077 @cindex stacking targets
19078 @cindex active targets
19079 @cindex multiple targets
19081 There are multiple classes of targets such as: processes, executable files or
19082 recording sessions. Core files belong to the process class, making core file
19083 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19084 on multiple active targets, one in each class. This allows you to (for
19085 example) start a process and inspect its activity, while still having access to
19086 the executable file after the process finishes. Or if you start process
19087 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19088 presented a virtual layer of the recording target, while the process target
19089 remains stopped at the chronologically last point of the process execution.
19091 Use the @code{core-file} and @code{exec-file} commands to select a new core
19092 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19093 specify as a target a process that is already running, use the @code{attach}
19094 command (@pxref{Attach, ,Debugging an Already-running Process}).
19096 @node Target Commands
19097 @section Commands for Managing Targets
19100 @item target @var{type} @var{parameters}
19101 Connects the @value{GDBN} host environment to a target machine or
19102 process. A target is typically a protocol for talking to debugging
19103 facilities. You use the argument @var{type} to specify the type or
19104 protocol of the target machine.
19106 Further @var{parameters} are interpreted by the target protocol, but
19107 typically include things like device names or host names to connect
19108 with, process numbers, and baud rates.
19110 The @code{target} command does not repeat if you press @key{RET} again
19111 after executing the command.
19113 @kindex help target
19115 Displays the names of all targets available. To display targets
19116 currently selected, use either @code{info target} or @code{info files}
19117 (@pxref{Files, ,Commands to Specify Files}).
19119 @item help target @var{name}
19120 Describe a particular target, including any parameters necessary to
19123 @kindex set gnutarget
19124 @item set gnutarget @var{args}
19125 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19126 knows whether it is reading an @dfn{executable},
19127 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19128 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19129 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19132 @emph{Warning:} To specify a file format with @code{set gnutarget},
19133 you must know the actual BFD name.
19137 @xref{Files, , Commands to Specify Files}.
19139 @kindex show gnutarget
19140 @item show gnutarget
19141 Use the @code{show gnutarget} command to display what file format
19142 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19143 @value{GDBN} will determine the file format for each file automatically,
19144 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19147 @cindex common targets
19148 Here are some common targets (available, or not, depending on the GDB
19153 @item target exec @var{program}
19154 @cindex executable file target
19155 An executable file. @samp{target exec @var{program}} is the same as
19156 @samp{exec-file @var{program}}.
19158 @item target core @var{filename}
19159 @cindex core dump file target
19160 A core dump file. @samp{target core @var{filename}} is the same as
19161 @samp{core-file @var{filename}}.
19163 @item target remote @var{medium}
19164 @cindex remote target
19165 A remote system connected to @value{GDBN} via a serial line or network
19166 connection. This command tells @value{GDBN} to use its own remote
19167 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19169 For example, if you have a board connected to @file{/dev/ttya} on the
19170 machine running @value{GDBN}, you could say:
19173 target remote /dev/ttya
19176 @code{target remote} supports the @code{load} command. This is only
19177 useful if you have some other way of getting the stub to the target
19178 system, and you can put it somewhere in memory where it won't get
19179 clobbered by the download.
19181 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19182 @cindex built-in simulator target
19183 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19191 works; however, you cannot assume that a specific memory map, device
19192 drivers, or even basic I/O is available, although some simulators do
19193 provide these. For info about any processor-specific simulator details,
19194 see the appropriate section in @ref{Embedded Processors, ,Embedded
19197 @item target native
19198 @cindex native target
19199 Setup for local/native process debugging. Useful to make the
19200 @code{run} command spawn native processes (likewise @code{attach},
19201 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19202 (@pxref{set auto-connect-native-target}).
19206 Different targets are available on different configurations of @value{GDBN};
19207 your configuration may have more or fewer targets.
19209 Many remote targets require you to download the executable's code once
19210 you've successfully established a connection. You may wish to control
19211 various aspects of this process.
19216 @kindex set hash@r{, for remote monitors}
19217 @cindex hash mark while downloading
19218 This command controls whether a hash mark @samp{#} is displayed while
19219 downloading a file to the remote monitor. If on, a hash mark is
19220 displayed after each S-record is successfully downloaded to the
19224 @kindex show hash@r{, for remote monitors}
19225 Show the current status of displaying the hash mark.
19227 @item set debug monitor
19228 @kindex set debug monitor
19229 @cindex display remote monitor communications
19230 Enable or disable display of communications messages between
19231 @value{GDBN} and the remote monitor.
19233 @item show debug monitor
19234 @kindex show debug monitor
19235 Show the current status of displaying communications between
19236 @value{GDBN} and the remote monitor.
19241 @kindex load @var{filename}
19242 @item load @var{filename}
19244 Depending on what remote debugging facilities are configured into
19245 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19246 is meant to make @var{filename} (an executable) available for debugging
19247 on the remote system---by downloading, or dynamic linking, for example.
19248 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19249 the @code{add-symbol-file} command.
19251 If your @value{GDBN} does not have a @code{load} command, attempting to
19252 execute it gets the error message ``@code{You can't do that when your
19253 target is @dots{}}''
19255 The file is loaded at whatever address is specified in the executable.
19256 For some object file formats, you can specify the load address when you
19257 link the program; for other formats, like a.out, the object file format
19258 specifies a fixed address.
19259 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19261 Depending on the remote side capabilities, @value{GDBN} may be able to
19262 load programs into flash memory.
19264 @code{load} does not repeat if you press @key{RET} again after using it.
19268 @section Choosing Target Byte Order
19270 @cindex choosing target byte order
19271 @cindex target byte order
19273 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19274 offer the ability to run either big-endian or little-endian byte
19275 orders. Usually the executable or symbol will include a bit to
19276 designate the endian-ness, and you will not need to worry about
19277 which to use. However, you may still find it useful to adjust
19278 @value{GDBN}'s idea of processor endian-ness manually.
19282 @item set endian big
19283 Instruct @value{GDBN} to assume the target is big-endian.
19285 @item set endian little
19286 Instruct @value{GDBN} to assume the target is little-endian.
19288 @item set endian auto
19289 Instruct @value{GDBN} to use the byte order associated with the
19293 Display @value{GDBN}'s current idea of the target byte order.
19297 Note that these commands merely adjust interpretation of symbolic
19298 data on the host, and that they have absolutely no effect on the
19302 @node Remote Debugging
19303 @chapter Debugging Remote Programs
19304 @cindex remote debugging
19306 If you are trying to debug a program running on a machine that cannot run
19307 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19308 For example, you might use remote debugging on an operating system kernel,
19309 or on a small system which does not have a general purpose operating system
19310 powerful enough to run a full-featured debugger.
19312 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19313 to make this work with particular debugging targets. In addition,
19314 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19315 but not specific to any particular target system) which you can use if you
19316 write the remote stubs---the code that runs on the remote system to
19317 communicate with @value{GDBN}.
19319 Other remote targets may be available in your
19320 configuration of @value{GDBN}; use @code{help target} to list them.
19323 * Connecting:: Connecting to a remote target
19324 * File Transfer:: Sending files to a remote system
19325 * Server:: Using the gdbserver program
19326 * Remote Configuration:: Remote configuration
19327 * Remote Stub:: Implementing a remote stub
19331 @section Connecting to a Remote Target
19332 @cindex remote debugging, connecting
19333 @cindex @code{gdbserver}, connecting
19334 @cindex remote debugging, types of connections
19335 @cindex @code{gdbserver}, types of connections
19336 @cindex @code{gdbserver}, @code{target remote} mode
19337 @cindex @code{gdbserver}, @code{target extended-remote} mode
19339 This section describes how to connect to a remote target, including the
19340 types of connections and their differences, how to set up executable and
19341 symbol files on the host and target, and the commands used for
19342 connecting to and disconnecting from the remote target.
19344 @subsection Types of Remote Connections
19346 @value{GDBN} supports two types of remote connections, @code{target remote}
19347 mode and @code{target extended-remote} mode. Note that many remote targets
19348 support only @code{target remote} mode. There are several major
19349 differences between the two types of connections, enumerated here:
19353 @cindex remote debugging, detach and program exit
19354 @item Result of detach or program exit
19355 @strong{With target remote mode:} When the debugged program exits or you
19356 detach from it, @value{GDBN} disconnects from the target. When using
19357 @code{gdbserver}, @code{gdbserver} will exit.
19359 @strong{With target extended-remote mode:} When the debugged program exits or
19360 you detach from it, @value{GDBN} remains connected to the target, even
19361 though no program is running. You can rerun the program, attach to a
19362 running program, or use @code{monitor} commands specific to the target.
19364 When using @code{gdbserver} in this case, it does not exit unless it was
19365 invoked using the @option{--once} option. If the @option{--once} option
19366 was not used, you can ask @code{gdbserver} to exit using the
19367 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19369 @item Specifying the program to debug
19370 For both connection types you use the @code{file} command to specify the
19371 program on the host system. If you are using @code{gdbserver} there are
19372 some differences in how to specify the location of the program on the
19375 @strong{With target remote mode:} You must either specify the program to debug
19376 on the @code{gdbserver} command line or use the @option{--attach} option
19377 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19379 @cindex @option{--multi}, @code{gdbserver} option
19380 @strong{With target extended-remote mode:} You may specify the program to debug
19381 on the @code{gdbserver} command line, or you can load the program or attach
19382 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19384 @anchor{--multi Option in Types of Remote Connnections}
19385 You can start @code{gdbserver} without supplying an initial command to run
19386 or process ID to attach. To do this, use the @option{--multi} command line
19387 option. Then you can connect using @code{target extended-remote} and start
19388 the program you want to debug (see below for details on using the
19389 @code{run} command in this scenario). Note that the conditions under which
19390 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19391 (@code{target remote} or @code{target extended-remote}). The
19392 @option{--multi} option to @code{gdbserver} has no influence on that.
19394 @item The @code{run} command
19395 @strong{With target remote mode:} The @code{run} command is not
19396 supported. Once a connection has been established, you can use all
19397 the usual @value{GDBN} commands to examine and change data. The
19398 remote program is already running, so you can use commands like
19399 @kbd{step} and @kbd{continue}.
19401 @strong{With target extended-remote mode:} The @code{run} command is
19402 supported. The @code{run} command uses the value set by
19403 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19404 the program to run. Command line arguments are supported, except for
19405 wildcard expansion and I/O redirection (@pxref{Arguments}).
19407 If you specify the program to debug on the command line, then the
19408 @code{run} command is not required to start execution, and you can
19409 resume using commands like @kbd{step} and @kbd{continue} as with
19410 @code{target remote} mode.
19412 @anchor{Attaching in Types of Remote Connections}
19414 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19415 not supported. To attach to a running program using @code{gdbserver}, you
19416 must use the @option{--attach} option (@pxref{Running gdbserver}).
19418 @strong{With target extended-remote mode:} To attach to a running program,
19419 you may use the @code{attach} command after the connection has been
19420 established. If you are using @code{gdbserver}, you may also invoke
19421 @code{gdbserver} using the @option{--attach} option
19422 (@pxref{Running gdbserver}).
19426 @anchor{Host and target files}
19427 @subsection Host and Target Files
19428 @cindex remote debugging, symbol files
19429 @cindex symbol files, remote debugging
19431 @value{GDBN}, running on the host, needs access to symbol and debugging
19432 information for your program running on the target. This requires
19433 access to an unstripped copy of your program, and possibly any associated
19434 symbol files. Note that this section applies equally to both @code{target
19435 remote} mode and @code{target extended-remote} mode.
19437 Some remote targets (@pxref{qXfer executable filename read}, and
19438 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19439 the same connection used to communicate with @value{GDBN}. With such a
19440 target, if the remote program is unstripped, the only command you need is
19441 @code{target remote} (or @code{target extended-remote}).
19443 If the remote program is stripped, or the target does not support remote
19444 program file access, start up @value{GDBN} using the name of the local
19445 unstripped copy of your program as the first argument, or use the
19446 @code{file} command. Use @code{set sysroot} to specify the location (on
19447 the host) of target libraries (unless your @value{GDBN} was compiled with
19448 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19449 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19452 The symbol file and target libraries must exactly match the executable
19453 and libraries on the target, with one exception: the files on the host
19454 system should not be stripped, even if the files on the target system
19455 are. Mismatched or missing files will lead to confusing results
19456 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19457 files may also prevent @code{gdbserver} from debugging multi-threaded
19460 @subsection Remote Connection Commands
19461 @cindex remote connection commands
19462 @value{GDBN} can communicate with the target over a serial line, or
19463 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19464 each case, @value{GDBN} uses the same protocol for debugging your
19465 program; only the medium carrying the debugging packets varies. The
19466 @code{target remote} and @code{target extended-remote} commands
19467 establish a connection to the target. Both commands accept the same
19468 arguments, which indicate the medium to use:
19472 @item target remote @var{serial-device}
19473 @itemx target extended-remote @var{serial-device}
19474 @cindex serial line, @code{target remote}
19475 Use @var{serial-device} to communicate with the target. For example,
19476 to use a serial line connected to the device named @file{/dev/ttyb}:
19479 target remote /dev/ttyb
19482 If you're using a serial line, you may want to give @value{GDBN} the
19483 @samp{--baud} option, or use the @code{set serial baud} command
19484 (@pxref{Remote Configuration, set serial baud}) before the
19485 @code{target} command.
19487 @item target remote @code{@var{host}:@var{port}}
19488 @itemx target remote @code{tcp:@var{host}:@var{port}}
19489 @itemx target extended-remote @code{@var{host}:@var{port}}
19490 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19491 @cindex @acronym{TCP} port, @code{target remote}
19492 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19493 The @var{host} may be either a host name or a numeric @acronym{IP}
19494 address; @var{port} must be a decimal number. The @var{host} could be
19495 the target machine itself, if it is directly connected to the net, or
19496 it might be a terminal server which in turn has a serial line to the
19499 For example, to connect to port 2828 on a terminal server named
19503 target remote manyfarms:2828
19506 If your remote target is actually running on the same machine as your
19507 debugger session (e.g.@: a simulator for your target running on the
19508 same host), you can omit the hostname. For example, to connect to
19509 port 1234 on your local machine:
19512 target remote :1234
19516 Note that the colon is still required here.
19518 @item target remote @code{udp:@var{host}:@var{port}}
19519 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19520 @cindex @acronym{UDP} port, @code{target remote}
19521 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19522 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19525 target remote udp:manyfarms:2828
19528 When using a @acronym{UDP} connection for remote debugging, you should
19529 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19530 can silently drop packets on busy or unreliable networks, which will
19531 cause havoc with your debugging session.
19533 @item target remote | @var{command}
19534 @itemx target extended-remote | @var{command}
19535 @cindex pipe, @code{target remote} to
19536 Run @var{command} in the background and communicate with it using a
19537 pipe. The @var{command} is a shell command, to be parsed and expanded
19538 by the system's command shell, @code{/bin/sh}; it should expect remote
19539 protocol packets on its standard input, and send replies on its
19540 standard output. You could use this to run a stand-alone simulator
19541 that speaks the remote debugging protocol, to make net connections
19542 using programs like @code{ssh}, or for other similar tricks.
19544 If @var{command} closes its standard output (perhaps by exiting),
19545 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19546 program has already exited, this will have no effect.)
19550 @cindex interrupting remote programs
19551 @cindex remote programs, interrupting
19552 Whenever @value{GDBN} is waiting for the remote program, if you type the
19553 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19554 program. This may or may not succeed, depending in part on the hardware
19555 and the serial drivers the remote system uses. If you type the
19556 interrupt character once again, @value{GDBN} displays this prompt:
19559 Interrupted while waiting for the program.
19560 Give up (and stop debugging it)? (y or n)
19563 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19564 the remote debugging session. (If you decide you want to try again later,
19565 you can use @kbd{target remote} again to connect once more.) If you type
19566 @kbd{n}, @value{GDBN} goes back to waiting.
19568 In @code{target extended-remote} mode, typing @kbd{n} will leave
19569 @value{GDBN} connected to the target.
19572 @kindex detach (remote)
19574 When you have finished debugging the remote program, you can use the
19575 @code{detach} command to release it from @value{GDBN} control.
19576 Detaching from the target normally resumes its execution, but the results
19577 will depend on your particular remote stub. After the @code{detach}
19578 command in @code{target remote} mode, @value{GDBN} is free to connect to
19579 another target. In @code{target extended-remote} mode, @value{GDBN} is
19580 still connected to the target.
19584 The @code{disconnect} command closes the connection to the target, and
19585 the target is generally not resumed. It will wait for @value{GDBN}
19586 (this instance or another one) to connect and continue debugging. After
19587 the @code{disconnect} command, @value{GDBN} is again free to connect to
19590 @cindex send command to remote monitor
19591 @cindex extend @value{GDBN} for remote targets
19592 @cindex add new commands for external monitor
19594 @item monitor @var{cmd}
19595 This command allows you to send arbitrary commands directly to the
19596 remote monitor. Since @value{GDBN} doesn't care about the commands it
19597 sends like this, this command is the way to extend @value{GDBN}---you
19598 can add new commands that only the external monitor will understand
19602 @node File Transfer
19603 @section Sending files to a remote system
19604 @cindex remote target, file transfer
19605 @cindex file transfer
19606 @cindex sending files to remote systems
19608 Some remote targets offer the ability to transfer files over the same
19609 connection used to communicate with @value{GDBN}. This is convenient
19610 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19611 running @code{gdbserver} over a network interface. For other targets,
19612 e.g.@: embedded devices with only a single serial port, this may be
19613 the only way to upload or download files.
19615 Not all remote targets support these commands.
19619 @item remote put @var{hostfile} @var{targetfile}
19620 Copy file @var{hostfile} from the host system (the machine running
19621 @value{GDBN}) to @var{targetfile} on the target system.
19624 @item remote get @var{targetfile} @var{hostfile}
19625 Copy file @var{targetfile} from the target system to @var{hostfile}
19626 on the host system.
19628 @kindex remote delete
19629 @item remote delete @var{targetfile}
19630 Delete @var{targetfile} from the target system.
19635 @section Using the @code{gdbserver} Program
19638 @cindex remote connection without stubs
19639 @code{gdbserver} is a control program for Unix-like systems, which
19640 allows you to connect your program with a remote @value{GDBN} via
19641 @code{target remote} or @code{target extended-remote}---but without
19642 linking in the usual debugging stub.
19644 @code{gdbserver} is not a complete replacement for the debugging stubs,
19645 because it requires essentially the same operating-system facilities
19646 that @value{GDBN} itself does. In fact, a system that can run
19647 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19648 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19649 because it is a much smaller program than @value{GDBN} itself. It is
19650 also easier to port than all of @value{GDBN}, so you may be able to get
19651 started more quickly on a new system by using @code{gdbserver}.
19652 Finally, if you develop code for real-time systems, you may find that
19653 the tradeoffs involved in real-time operation make it more convenient to
19654 do as much development work as possible on another system, for example
19655 by cross-compiling. You can use @code{gdbserver} to make a similar
19656 choice for debugging.
19658 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19659 or a TCP connection, using the standard @value{GDBN} remote serial
19663 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19664 Do not run @code{gdbserver} connected to any public network; a
19665 @value{GDBN} connection to @code{gdbserver} provides access to the
19666 target system with the same privileges as the user running
19670 @anchor{Running gdbserver}
19671 @subsection Running @code{gdbserver}
19672 @cindex arguments, to @code{gdbserver}
19673 @cindex @code{gdbserver}, command-line arguments
19675 Run @code{gdbserver} on the target system. You need a copy of the
19676 program you want to debug, including any libraries it requires.
19677 @code{gdbserver} does not need your program's symbol table, so you can
19678 strip the program if necessary to save space. @value{GDBN} on the host
19679 system does all the symbol handling.
19681 To use the server, you must tell it how to communicate with @value{GDBN};
19682 the name of your program; and the arguments for your program. The usual
19686 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19689 @var{comm} is either a device name (to use a serial line), or a TCP
19690 hostname and portnumber, or @code{-} or @code{stdio} to use
19691 stdin/stdout of @code{gdbserver}.
19692 For example, to debug Emacs with the argument
19693 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19697 target> gdbserver /dev/com1 emacs foo.txt
19700 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19703 To use a TCP connection instead of a serial line:
19706 target> gdbserver host:2345 emacs foo.txt
19709 The only difference from the previous example is the first argument,
19710 specifying that you are communicating with the host @value{GDBN} via
19711 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19712 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19713 (Currently, the @samp{host} part is ignored.) You can choose any number
19714 you want for the port number as long as it does not conflict with any
19715 TCP ports already in use on the target system (for example, @code{23} is
19716 reserved for @code{telnet}).@footnote{If you choose a port number that
19717 conflicts with another service, @code{gdbserver} prints an error message
19718 and exits.} You must use the same port number with the host @value{GDBN}
19719 @code{target remote} command.
19721 The @code{stdio} connection is useful when starting @code{gdbserver}
19725 (gdb) target remote | ssh -T hostname gdbserver - hello
19728 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19729 and we don't want escape-character handling. Ssh does this by default when
19730 a command is provided, the flag is provided to make it explicit.
19731 You could elide it if you want to.
19733 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19734 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19735 display through a pipe connected to gdbserver.
19736 Both @code{stdout} and @code{stderr} use the same pipe.
19738 @anchor{Attaching to a program}
19739 @subsubsection Attaching to a Running Program
19740 @cindex attach to a program, @code{gdbserver}
19741 @cindex @option{--attach}, @code{gdbserver} option
19743 On some targets, @code{gdbserver} can also attach to running programs.
19744 This is accomplished via the @code{--attach} argument. The syntax is:
19747 target> gdbserver --attach @var{comm} @var{pid}
19750 @var{pid} is the process ID of a currently running process. It isn't
19751 necessary to point @code{gdbserver} at a binary for the running process.
19753 In @code{target extended-remote} mode, you can also attach using the
19754 @value{GDBN} attach command
19755 (@pxref{Attaching in Types of Remote Connections}).
19758 You can debug processes by name instead of process ID if your target has the
19759 @code{pidof} utility:
19762 target> gdbserver --attach @var{comm} `pidof @var{program}`
19765 In case more than one copy of @var{program} is running, or @var{program}
19766 has multiple threads, most versions of @code{pidof} support the
19767 @code{-s} option to only return the first process ID.
19769 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19771 This section applies only when @code{gdbserver} is run to listen on a TCP
19774 @code{gdbserver} normally terminates after all of its debugged processes have
19775 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19776 extended-remote}, @code{gdbserver} stays running even with no processes left.
19777 @value{GDBN} normally terminates the spawned debugged process on its exit,
19778 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19779 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19780 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19781 stays running even in the @kbd{target remote} mode.
19783 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19784 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19785 completeness, at most one @value{GDBN} can be connected at a time.
19787 @cindex @option{--once}, @code{gdbserver} option
19788 By default, @code{gdbserver} keeps the listening TCP port open, so that
19789 subsequent connections are possible. However, if you start @code{gdbserver}
19790 with the @option{--once} option, it will stop listening for any further
19791 connection attempts after connecting to the first @value{GDBN} session. This
19792 means no further connections to @code{gdbserver} will be possible after the
19793 first one. It also means @code{gdbserver} will terminate after the first
19794 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19795 connections and even in the @kbd{target extended-remote} mode. The
19796 @option{--once} option allows reusing the same port number for connecting to
19797 multiple instances of @code{gdbserver} running on the same host, since each
19798 instance closes its port after the first connection.
19800 @anchor{Other Command-Line Arguments for gdbserver}
19801 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19803 You can use the @option{--multi} option to start @code{gdbserver} without
19804 specifying a program to debug or a process to attach to. Then you can
19805 attach in @code{target extended-remote} mode and run or attach to a
19806 program. For more information,
19807 @pxref{--multi Option in Types of Remote Connnections}.
19809 @cindex @option{--debug}, @code{gdbserver} option
19810 The @option{--debug} option tells @code{gdbserver} to display extra
19811 status information about the debugging process.
19812 @cindex @option{--remote-debug}, @code{gdbserver} option
19813 The @option{--remote-debug} option tells @code{gdbserver} to display
19814 remote protocol debug output. These options are intended for
19815 @code{gdbserver} development and for bug reports to the developers.
19817 @cindex @option{--debug-format}, @code{gdbserver} option
19818 The @option{--debug-format=option1[,option2,...]} option tells
19819 @code{gdbserver} to include additional information in each output.
19820 Possible options are:
19824 Turn off all extra information in debugging output.
19826 Turn on all extra information in debugging output.
19828 Include a timestamp in each line of debugging output.
19831 Options are processed in order. Thus, for example, if @option{none}
19832 appears last then no additional information is added to debugging output.
19834 @cindex @option{--wrapper}, @code{gdbserver} option
19835 The @option{--wrapper} option specifies a wrapper to launch programs
19836 for debugging. The option should be followed by the name of the
19837 wrapper, then any command-line arguments to pass to the wrapper, then
19838 @kbd{--} indicating the end of the wrapper arguments.
19840 @code{gdbserver} runs the specified wrapper program with a combined
19841 command line including the wrapper arguments, then the name of the
19842 program to debug, then any arguments to the program. The wrapper
19843 runs until it executes your program, and then @value{GDBN} gains control.
19845 You can use any program that eventually calls @code{execve} with
19846 its arguments as a wrapper. Several standard Unix utilities do
19847 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19848 with @code{exec "$@@"} will also work.
19850 For example, you can use @code{env} to pass an environment variable to
19851 the debugged program, without setting the variable in @code{gdbserver}'s
19855 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19858 @subsection Connecting to @code{gdbserver}
19860 The basic procedure for connecting to the remote target is:
19864 Run @value{GDBN} on the host system.
19867 Make sure you have the necessary symbol files
19868 (@pxref{Host and target files}).
19869 Load symbols for your application using the @code{file} command before you
19870 connect. Use @code{set sysroot} to locate target libraries (unless your
19871 @value{GDBN} was compiled with the correct sysroot using
19872 @code{--with-sysroot}).
19875 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19876 For TCP connections, you must start up @code{gdbserver} prior to using
19877 the @code{target} command. Otherwise you may get an error whose
19878 text depends on the host system, but which usually looks something like
19879 @samp{Connection refused}. Don't use the @code{load}
19880 command in @value{GDBN} when using @code{target remote} mode, since the
19881 program is already on the target.
19885 @anchor{Monitor Commands for gdbserver}
19886 @subsection Monitor Commands for @code{gdbserver}
19887 @cindex monitor commands, for @code{gdbserver}
19889 During a @value{GDBN} session using @code{gdbserver}, you can use the
19890 @code{monitor} command to send special requests to @code{gdbserver}.
19891 Here are the available commands.
19895 List the available monitor commands.
19897 @item monitor set debug 0
19898 @itemx monitor set debug 1
19899 Disable or enable general debugging messages.
19901 @item monitor set remote-debug 0
19902 @itemx monitor set remote-debug 1
19903 Disable or enable specific debugging messages associated with the remote
19904 protocol (@pxref{Remote Protocol}).
19906 @item monitor set debug-format option1@r{[},option2,...@r{]}
19907 Specify additional text to add to debugging messages.
19908 Possible options are:
19912 Turn off all extra information in debugging output.
19914 Turn on all extra information in debugging output.
19916 Include a timestamp in each line of debugging output.
19919 Options are processed in order. Thus, for example, if @option{none}
19920 appears last then no additional information is added to debugging output.
19922 @item monitor set libthread-db-search-path [PATH]
19923 @cindex gdbserver, search path for @code{libthread_db}
19924 When this command is issued, @var{path} is a colon-separated list of
19925 directories to search for @code{libthread_db} (@pxref{Threads,,set
19926 libthread-db-search-path}). If you omit @var{path},
19927 @samp{libthread-db-search-path} will be reset to its default value.
19929 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19930 not supported in @code{gdbserver}.
19933 Tell gdbserver to exit immediately. This command should be followed by
19934 @code{disconnect} to close the debugging session. @code{gdbserver} will
19935 detach from any attached processes and kill any processes it created.
19936 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19937 of a multi-process mode debug session.
19941 @subsection Tracepoints support in @code{gdbserver}
19942 @cindex tracepoints support in @code{gdbserver}
19944 On some targets, @code{gdbserver} supports tracepoints, fast
19945 tracepoints and static tracepoints.
19947 For fast or static tracepoints to work, a special library called the
19948 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19949 This library is built and distributed as an integral part of
19950 @code{gdbserver}. In addition, support for static tracepoints
19951 requires building the in-process agent library with static tracepoints
19952 support. At present, the UST (LTTng Userspace Tracer,
19953 @url{http://lttng.org/ust}) tracing engine is supported. This support
19954 is automatically available if UST development headers are found in the
19955 standard include path when @code{gdbserver} is built, or if
19956 @code{gdbserver} was explicitly configured using @option{--with-ust}
19957 to point at such headers. You can explicitly disable the support
19958 using @option{--with-ust=no}.
19960 There are several ways to load the in-process agent in your program:
19963 @item Specifying it as dependency at link time
19965 You can link your program dynamically with the in-process agent
19966 library. On most systems, this is accomplished by adding
19967 @code{-linproctrace} to the link command.
19969 @item Using the system's preloading mechanisms
19971 You can force loading the in-process agent at startup time by using
19972 your system's support for preloading shared libraries. Many Unixes
19973 support the concept of preloading user defined libraries. In most
19974 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19975 in the environment. See also the description of @code{gdbserver}'s
19976 @option{--wrapper} command line option.
19978 @item Using @value{GDBN} to force loading the agent at run time
19980 On some systems, you can force the inferior to load a shared library,
19981 by calling a dynamic loader function in the inferior that takes care
19982 of dynamically looking up and loading a shared library. On most Unix
19983 systems, the function is @code{dlopen}. You'll use the @code{call}
19984 command for that. For example:
19987 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19990 Note that on most Unix systems, for the @code{dlopen} function to be
19991 available, the program needs to be linked with @code{-ldl}.
19994 On systems that have a userspace dynamic loader, like most Unix
19995 systems, when you connect to @code{gdbserver} using @code{target
19996 remote}, you'll find that the program is stopped at the dynamic
19997 loader's entry point, and no shared library has been loaded in the
19998 program's address space yet, including the in-process agent. In that
19999 case, before being able to use any of the fast or static tracepoints
20000 features, you need to let the loader run and load the shared
20001 libraries. The simplest way to do that is to run the program to the
20002 main procedure. E.g., if debugging a C or C@t{++} program, start
20003 @code{gdbserver} like so:
20006 $ gdbserver :9999 myprogram
20009 Start GDB and connect to @code{gdbserver} like so, and run to main:
20013 (@value{GDBP}) target remote myhost:9999
20014 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20015 (@value{GDBP}) b main
20016 (@value{GDBP}) continue
20019 The in-process tracing agent library should now be loaded into the
20020 process; you can confirm it with the @code{info sharedlibrary}
20021 command, which will list @file{libinproctrace.so} as loaded in the
20022 process. You are now ready to install fast tracepoints, list static
20023 tracepoint markers, probe static tracepoints markers, and start
20026 @node Remote Configuration
20027 @section Remote Configuration
20030 @kindex show remote
20031 This section documents the configuration options available when
20032 debugging remote programs. For the options related to the File I/O
20033 extensions of the remote protocol, see @ref{system,
20034 system-call-allowed}.
20037 @item set remoteaddresssize @var{bits}
20038 @cindex address size for remote targets
20039 @cindex bits in remote address
20040 Set the maximum size of address in a memory packet to the specified
20041 number of bits. @value{GDBN} will mask off the address bits above
20042 that number, when it passes addresses to the remote target. The
20043 default value is the number of bits in the target's address.
20045 @item show remoteaddresssize
20046 Show the current value of remote address size in bits.
20048 @item set serial baud @var{n}
20049 @cindex baud rate for remote targets
20050 Set the baud rate for the remote serial I/O to @var{n} baud. The
20051 value is used to set the speed of the serial port used for debugging
20054 @item show serial baud
20055 Show the current speed of the remote connection.
20057 @item set serial parity @var{parity}
20058 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20059 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20061 @item show serial parity
20062 Show the current parity of the serial port.
20064 @item set remotebreak
20065 @cindex interrupt remote programs
20066 @cindex BREAK signal instead of Ctrl-C
20067 @anchor{set remotebreak}
20068 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20069 when you type @kbd{Ctrl-c} to interrupt the program running
20070 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20071 character instead. The default is off, since most remote systems
20072 expect to see @samp{Ctrl-C} as the interrupt signal.
20074 @item show remotebreak
20075 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20076 interrupt the remote program.
20078 @item set remoteflow on
20079 @itemx set remoteflow off
20080 @kindex set remoteflow
20081 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20082 on the serial port used to communicate to the remote target.
20084 @item show remoteflow
20085 @kindex show remoteflow
20086 Show the current setting of hardware flow control.
20088 @item set remotelogbase @var{base}
20089 Set the base (a.k.a.@: radix) of logging serial protocol
20090 communications to @var{base}. Supported values of @var{base} are:
20091 @code{ascii}, @code{octal}, and @code{hex}. The default is
20094 @item show remotelogbase
20095 Show the current setting of the radix for logging remote serial
20098 @item set remotelogfile @var{file}
20099 @cindex record serial communications on file
20100 Record remote serial communications on the named @var{file}. The
20101 default is not to record at all.
20103 @item show remotelogfile.
20104 Show the current setting of the file name on which to record the
20105 serial communications.
20107 @item set remotetimeout @var{num}
20108 @cindex timeout for serial communications
20109 @cindex remote timeout
20110 Set the timeout limit to wait for the remote target to respond to
20111 @var{num} seconds. The default is 2 seconds.
20113 @item show remotetimeout
20114 Show the current number of seconds to wait for the remote target
20117 @cindex limit hardware breakpoints and watchpoints
20118 @cindex remote target, limit break- and watchpoints
20119 @anchor{set remote hardware-watchpoint-limit}
20120 @anchor{set remote hardware-breakpoint-limit}
20121 @item set remote hardware-watchpoint-limit @var{limit}
20122 @itemx set remote hardware-breakpoint-limit @var{limit}
20123 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20124 watchpoints. A limit of -1, the default, is treated as unlimited.
20126 @cindex limit hardware watchpoints length
20127 @cindex remote target, limit watchpoints length
20128 @anchor{set remote hardware-watchpoint-length-limit}
20129 @item set remote hardware-watchpoint-length-limit @var{limit}
20130 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20131 a remote hardware watchpoint. A limit of -1, the default, is treated
20134 @item show remote hardware-watchpoint-length-limit
20135 Show the current limit (in bytes) of the maximum length of
20136 a remote hardware watchpoint.
20138 @item set remote exec-file @var{filename}
20139 @itemx show remote exec-file
20140 @anchor{set remote exec-file}
20141 @cindex executable file, for remote target
20142 Select the file used for @code{run} with @code{target
20143 extended-remote}. This should be set to a filename valid on the
20144 target system. If it is not set, the target will use a default
20145 filename (e.g.@: the last program run).
20147 @item set remote interrupt-sequence
20148 @cindex interrupt remote programs
20149 @cindex select Ctrl-C, BREAK or BREAK-g
20150 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20151 @samp{BREAK-g} as the
20152 sequence to the remote target in order to interrupt the execution.
20153 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20154 is high level of serial line for some certain time.
20155 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20156 It is @code{BREAK} signal followed by character @code{g}.
20158 @item show interrupt-sequence
20159 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20160 is sent by @value{GDBN} to interrupt the remote program.
20161 @code{BREAK-g} is BREAK signal followed by @code{g} and
20162 also known as Magic SysRq g.
20164 @item set remote interrupt-on-connect
20165 @cindex send interrupt-sequence on start
20166 Specify whether interrupt-sequence is sent to remote target when
20167 @value{GDBN} connects to it. This is mostly needed when you debug
20168 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20169 which is known as Magic SysRq g in order to connect @value{GDBN}.
20171 @item show interrupt-on-connect
20172 Show whether interrupt-sequence is sent
20173 to remote target when @value{GDBN} connects to it.
20177 @item set tcp auto-retry on
20178 @cindex auto-retry, for remote TCP target
20179 Enable auto-retry for remote TCP connections. This is useful if the remote
20180 debugging agent is launched in parallel with @value{GDBN}; there is a race
20181 condition because the agent may not become ready to accept the connection
20182 before @value{GDBN} attempts to connect. When auto-retry is
20183 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20184 to establish the connection using the timeout specified by
20185 @code{set tcp connect-timeout}.
20187 @item set tcp auto-retry off
20188 Do not auto-retry failed TCP connections.
20190 @item show tcp auto-retry
20191 Show the current auto-retry setting.
20193 @item set tcp connect-timeout @var{seconds}
20194 @itemx set tcp connect-timeout unlimited
20195 @cindex connection timeout, for remote TCP target
20196 @cindex timeout, for remote target connection
20197 Set the timeout for establishing a TCP connection to the remote target to
20198 @var{seconds}. The timeout affects both polling to retry failed connections
20199 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20200 that are merely slow to complete, and represents an approximate cumulative
20201 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20202 @value{GDBN} will keep attempting to establish a connection forever,
20203 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20205 @item show tcp connect-timeout
20206 Show the current connection timeout setting.
20209 @cindex remote packets, enabling and disabling
20210 The @value{GDBN} remote protocol autodetects the packets supported by
20211 your debugging stub. If you need to override the autodetection, you
20212 can use these commands to enable or disable individual packets. Each
20213 packet can be set to @samp{on} (the remote target supports this
20214 packet), @samp{off} (the remote target does not support this packet),
20215 or @samp{auto} (detect remote target support for this packet). They
20216 all default to @samp{auto}. For more information about each packet,
20217 see @ref{Remote Protocol}.
20219 During normal use, you should not have to use any of these commands.
20220 If you do, that may be a bug in your remote debugging stub, or a bug
20221 in @value{GDBN}. You may want to report the problem to the
20222 @value{GDBN} developers.
20224 For each packet @var{name}, the command to enable or disable the
20225 packet is @code{set remote @var{name}-packet}. The available settings
20228 @multitable @columnfractions 0.28 0.32 0.25
20231 @tab Related Features
20233 @item @code{fetch-register}
20235 @tab @code{info registers}
20237 @item @code{set-register}
20241 @item @code{binary-download}
20243 @tab @code{load}, @code{set}
20245 @item @code{read-aux-vector}
20246 @tab @code{qXfer:auxv:read}
20247 @tab @code{info auxv}
20249 @item @code{symbol-lookup}
20250 @tab @code{qSymbol}
20251 @tab Detecting multiple threads
20253 @item @code{attach}
20254 @tab @code{vAttach}
20257 @item @code{verbose-resume}
20259 @tab Stepping or resuming multiple threads
20265 @item @code{software-breakpoint}
20269 @item @code{hardware-breakpoint}
20273 @item @code{write-watchpoint}
20277 @item @code{read-watchpoint}
20281 @item @code{access-watchpoint}
20285 @item @code{pid-to-exec-file}
20286 @tab @code{qXfer:exec-file:read}
20287 @tab @code{attach}, @code{run}
20289 @item @code{target-features}
20290 @tab @code{qXfer:features:read}
20291 @tab @code{set architecture}
20293 @item @code{library-info}
20294 @tab @code{qXfer:libraries:read}
20295 @tab @code{info sharedlibrary}
20297 @item @code{memory-map}
20298 @tab @code{qXfer:memory-map:read}
20299 @tab @code{info mem}
20301 @item @code{read-sdata-object}
20302 @tab @code{qXfer:sdata:read}
20303 @tab @code{print $_sdata}
20305 @item @code{read-spu-object}
20306 @tab @code{qXfer:spu:read}
20307 @tab @code{info spu}
20309 @item @code{write-spu-object}
20310 @tab @code{qXfer:spu:write}
20311 @tab @code{info spu}
20313 @item @code{read-siginfo-object}
20314 @tab @code{qXfer:siginfo:read}
20315 @tab @code{print $_siginfo}
20317 @item @code{write-siginfo-object}
20318 @tab @code{qXfer:siginfo:write}
20319 @tab @code{set $_siginfo}
20321 @item @code{threads}
20322 @tab @code{qXfer:threads:read}
20323 @tab @code{info threads}
20325 @item @code{get-thread-local-@*storage-address}
20326 @tab @code{qGetTLSAddr}
20327 @tab Displaying @code{__thread} variables
20329 @item @code{get-thread-information-block-address}
20330 @tab @code{qGetTIBAddr}
20331 @tab Display MS-Windows Thread Information Block.
20333 @item @code{search-memory}
20334 @tab @code{qSearch:memory}
20337 @item @code{supported-packets}
20338 @tab @code{qSupported}
20339 @tab Remote communications parameters
20341 @item @code{catch-syscalls}
20342 @tab @code{QCatchSyscalls}
20343 @tab @code{catch syscall}
20345 @item @code{pass-signals}
20346 @tab @code{QPassSignals}
20347 @tab @code{handle @var{signal}}
20349 @item @code{program-signals}
20350 @tab @code{QProgramSignals}
20351 @tab @code{handle @var{signal}}
20353 @item @code{hostio-close-packet}
20354 @tab @code{vFile:close}
20355 @tab @code{remote get}, @code{remote put}
20357 @item @code{hostio-open-packet}
20358 @tab @code{vFile:open}
20359 @tab @code{remote get}, @code{remote put}
20361 @item @code{hostio-pread-packet}
20362 @tab @code{vFile:pread}
20363 @tab @code{remote get}, @code{remote put}
20365 @item @code{hostio-pwrite-packet}
20366 @tab @code{vFile:pwrite}
20367 @tab @code{remote get}, @code{remote put}
20369 @item @code{hostio-unlink-packet}
20370 @tab @code{vFile:unlink}
20371 @tab @code{remote delete}
20373 @item @code{hostio-readlink-packet}
20374 @tab @code{vFile:readlink}
20377 @item @code{hostio-fstat-packet}
20378 @tab @code{vFile:fstat}
20381 @item @code{hostio-setfs-packet}
20382 @tab @code{vFile:setfs}
20385 @item @code{noack-packet}
20386 @tab @code{QStartNoAckMode}
20387 @tab Packet acknowledgment
20389 @item @code{osdata}
20390 @tab @code{qXfer:osdata:read}
20391 @tab @code{info os}
20393 @item @code{query-attached}
20394 @tab @code{qAttached}
20395 @tab Querying remote process attach state.
20397 @item @code{trace-buffer-size}
20398 @tab @code{QTBuffer:size}
20399 @tab @code{set trace-buffer-size}
20401 @item @code{trace-status}
20402 @tab @code{qTStatus}
20403 @tab @code{tstatus}
20405 @item @code{traceframe-info}
20406 @tab @code{qXfer:traceframe-info:read}
20407 @tab Traceframe info
20409 @item @code{install-in-trace}
20410 @tab @code{InstallInTrace}
20411 @tab Install tracepoint in tracing
20413 @item @code{disable-randomization}
20414 @tab @code{QDisableRandomization}
20415 @tab @code{set disable-randomization}
20417 @item @code{conditional-breakpoints-packet}
20418 @tab @code{Z0 and Z1}
20419 @tab @code{Support for target-side breakpoint condition evaluation}
20421 @item @code{multiprocess-extensions}
20422 @tab @code{multiprocess extensions}
20423 @tab Debug multiple processes and remote process PID awareness
20425 @item @code{swbreak-feature}
20426 @tab @code{swbreak stop reason}
20429 @item @code{hwbreak-feature}
20430 @tab @code{hwbreak stop reason}
20433 @item @code{fork-event-feature}
20434 @tab @code{fork stop reason}
20437 @item @code{vfork-event-feature}
20438 @tab @code{vfork stop reason}
20441 @item @code{exec-event-feature}
20442 @tab @code{exec stop reason}
20445 @item @code{thread-events}
20446 @tab @code{QThreadEvents}
20447 @tab Tracking thread lifetime.
20449 @item @code{no-resumed-stop-reply}
20450 @tab @code{no resumed thread left stop reply}
20451 @tab Tracking thread lifetime.
20456 @section Implementing a Remote Stub
20458 @cindex debugging stub, example
20459 @cindex remote stub, example
20460 @cindex stub example, remote debugging
20461 The stub files provided with @value{GDBN} implement the target side of the
20462 communication protocol, and the @value{GDBN} side is implemented in the
20463 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20464 these subroutines to communicate, and ignore the details. (If you're
20465 implementing your own stub file, you can still ignore the details: start
20466 with one of the existing stub files. @file{sparc-stub.c} is the best
20467 organized, and therefore the easiest to read.)
20469 @cindex remote serial debugging, overview
20470 To debug a program running on another machine (the debugging
20471 @dfn{target} machine), you must first arrange for all the usual
20472 prerequisites for the program to run by itself. For example, for a C
20477 A startup routine to set up the C runtime environment; these usually
20478 have a name like @file{crt0}. The startup routine may be supplied by
20479 your hardware supplier, or you may have to write your own.
20482 A C subroutine library to support your program's
20483 subroutine calls, notably managing input and output.
20486 A way of getting your program to the other machine---for example, a
20487 download program. These are often supplied by the hardware
20488 manufacturer, but you may have to write your own from hardware
20492 The next step is to arrange for your program to use a serial port to
20493 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20494 machine). In general terms, the scheme looks like this:
20498 @value{GDBN} already understands how to use this protocol; when everything
20499 else is set up, you can simply use the @samp{target remote} command
20500 (@pxref{Targets,,Specifying a Debugging Target}).
20502 @item On the target,
20503 you must link with your program a few special-purpose subroutines that
20504 implement the @value{GDBN} remote serial protocol. The file containing these
20505 subroutines is called a @dfn{debugging stub}.
20507 On certain remote targets, you can use an auxiliary program
20508 @code{gdbserver} instead of linking a stub into your program.
20509 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20512 The debugging stub is specific to the architecture of the remote
20513 machine; for example, use @file{sparc-stub.c} to debug programs on
20516 @cindex remote serial stub list
20517 These working remote stubs are distributed with @value{GDBN}:
20522 @cindex @file{i386-stub.c}
20525 For Intel 386 and compatible architectures.
20528 @cindex @file{m68k-stub.c}
20529 @cindex Motorola 680x0
20531 For Motorola 680x0 architectures.
20534 @cindex @file{sh-stub.c}
20537 For Renesas SH architectures.
20540 @cindex @file{sparc-stub.c}
20542 For @sc{sparc} architectures.
20544 @item sparcl-stub.c
20545 @cindex @file{sparcl-stub.c}
20548 For Fujitsu @sc{sparclite} architectures.
20552 The @file{README} file in the @value{GDBN} distribution may list other
20553 recently added stubs.
20556 * Stub Contents:: What the stub can do for you
20557 * Bootstrapping:: What you must do for the stub
20558 * Debug Session:: Putting it all together
20561 @node Stub Contents
20562 @subsection What the Stub Can Do for You
20564 @cindex remote serial stub
20565 The debugging stub for your architecture supplies these three
20569 @item set_debug_traps
20570 @findex set_debug_traps
20571 @cindex remote serial stub, initialization
20572 This routine arranges for @code{handle_exception} to run when your
20573 program stops. You must call this subroutine explicitly in your
20574 program's startup code.
20576 @item handle_exception
20577 @findex handle_exception
20578 @cindex remote serial stub, main routine
20579 This is the central workhorse, but your program never calls it
20580 explicitly---the setup code arranges for @code{handle_exception} to
20581 run when a trap is triggered.
20583 @code{handle_exception} takes control when your program stops during
20584 execution (for example, on a breakpoint), and mediates communications
20585 with @value{GDBN} on the host machine. This is where the communications
20586 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20587 representative on the target machine. It begins by sending summary
20588 information on the state of your program, then continues to execute,
20589 retrieving and transmitting any information @value{GDBN} needs, until you
20590 execute a @value{GDBN} command that makes your program resume; at that point,
20591 @code{handle_exception} returns control to your own code on the target
20595 @cindex @code{breakpoint} subroutine, remote
20596 Use this auxiliary subroutine to make your program contain a
20597 breakpoint. Depending on the particular situation, this may be the only
20598 way for @value{GDBN} to get control. For instance, if your target
20599 machine has some sort of interrupt button, you won't need to call this;
20600 pressing the interrupt button transfers control to
20601 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20602 simply receiving characters on the serial port may also trigger a trap;
20603 again, in that situation, you don't need to call @code{breakpoint} from
20604 your own program---simply running @samp{target remote} from the host
20605 @value{GDBN} session gets control.
20607 Call @code{breakpoint} if none of these is true, or if you simply want
20608 to make certain your program stops at a predetermined point for the
20609 start of your debugging session.
20612 @node Bootstrapping
20613 @subsection What You Must Do for the Stub
20615 @cindex remote stub, support routines
20616 The debugging stubs that come with @value{GDBN} are set up for a particular
20617 chip architecture, but they have no information about the rest of your
20618 debugging target machine.
20620 First of all you need to tell the stub how to communicate with the
20624 @item int getDebugChar()
20625 @findex getDebugChar
20626 Write this subroutine to read a single character from the serial port.
20627 It may be identical to @code{getchar} for your target system; a
20628 different name is used to allow you to distinguish the two if you wish.
20630 @item void putDebugChar(int)
20631 @findex putDebugChar
20632 Write this subroutine to write a single character to the serial port.
20633 It may be identical to @code{putchar} for your target system; a
20634 different name is used to allow you to distinguish the two if you wish.
20637 @cindex control C, and remote debugging
20638 @cindex interrupting remote targets
20639 If you want @value{GDBN} to be able to stop your program while it is
20640 running, you need to use an interrupt-driven serial driver, and arrange
20641 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20642 character). That is the character which @value{GDBN} uses to tell the
20643 remote system to stop.
20645 Getting the debugging target to return the proper status to @value{GDBN}
20646 probably requires changes to the standard stub; one quick and dirty way
20647 is to just execute a breakpoint instruction (the ``dirty'' part is that
20648 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20650 Other routines you need to supply are:
20653 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20654 @findex exceptionHandler
20655 Write this function to install @var{exception_address} in the exception
20656 handling tables. You need to do this because the stub does not have any
20657 way of knowing what the exception handling tables on your target system
20658 are like (for example, the processor's table might be in @sc{rom},
20659 containing entries which point to a table in @sc{ram}).
20660 The @var{exception_number} specifies the exception which should be changed;
20661 its meaning is architecture-dependent (for example, different numbers
20662 might represent divide by zero, misaligned access, etc). When this
20663 exception occurs, control should be transferred directly to
20664 @var{exception_address}, and the processor state (stack, registers,
20665 and so on) should be just as it is when a processor exception occurs. So if
20666 you want to use a jump instruction to reach @var{exception_address}, it
20667 should be a simple jump, not a jump to subroutine.
20669 For the 386, @var{exception_address} should be installed as an interrupt
20670 gate so that interrupts are masked while the handler runs. The gate
20671 should be at privilege level 0 (the most privileged level). The
20672 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20673 help from @code{exceptionHandler}.
20675 @item void flush_i_cache()
20676 @findex flush_i_cache
20677 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20678 instruction cache, if any, on your target machine. If there is no
20679 instruction cache, this subroutine may be a no-op.
20681 On target machines that have instruction caches, @value{GDBN} requires this
20682 function to make certain that the state of your program is stable.
20686 You must also make sure this library routine is available:
20689 @item void *memset(void *, int, int)
20691 This is the standard library function @code{memset} that sets an area of
20692 memory to a known value. If you have one of the free versions of
20693 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20694 either obtain it from your hardware manufacturer, or write your own.
20697 If you do not use the GNU C compiler, you may need other standard
20698 library subroutines as well; this varies from one stub to another,
20699 but in general the stubs are likely to use any of the common library
20700 subroutines which @code{@value{NGCC}} generates as inline code.
20703 @node Debug Session
20704 @subsection Putting it All Together
20706 @cindex remote serial debugging summary
20707 In summary, when your program is ready to debug, you must follow these
20712 Make sure you have defined the supporting low-level routines
20713 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20715 @code{getDebugChar}, @code{putDebugChar},
20716 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20720 Insert these lines in your program's startup code, before the main
20721 procedure is called:
20728 On some machines, when a breakpoint trap is raised, the hardware
20729 automatically makes the PC point to the instruction after the
20730 breakpoint. If your machine doesn't do that, you may need to adjust
20731 @code{handle_exception} to arrange for it to return to the instruction
20732 after the breakpoint on this first invocation, so that your program
20733 doesn't keep hitting the initial breakpoint instead of making
20737 For the 680x0 stub only, you need to provide a variable called
20738 @code{exceptionHook}. Normally you just use:
20741 void (*exceptionHook)() = 0;
20745 but if before calling @code{set_debug_traps}, you set it to point to a
20746 function in your program, that function is called when
20747 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20748 error). The function indicated by @code{exceptionHook} is called with
20749 one parameter: an @code{int} which is the exception number.
20752 Compile and link together: your program, the @value{GDBN} debugging stub for
20753 your target architecture, and the supporting subroutines.
20756 Make sure you have a serial connection between your target machine and
20757 the @value{GDBN} host, and identify the serial port on the host.
20760 @c The "remote" target now provides a `load' command, so we should
20761 @c document that. FIXME.
20762 Download your program to your target machine (or get it there by
20763 whatever means the manufacturer provides), and start it.
20766 Start @value{GDBN} on the host, and connect to the target
20767 (@pxref{Connecting,,Connecting to a Remote Target}).
20771 @node Configurations
20772 @chapter Configuration-Specific Information
20774 While nearly all @value{GDBN} commands are available for all native and
20775 cross versions of the debugger, there are some exceptions. This chapter
20776 describes things that are only available in certain configurations.
20778 There are three major categories of configurations: native
20779 configurations, where the host and target are the same, embedded
20780 operating system configurations, which are usually the same for several
20781 different processor architectures, and bare embedded processors, which
20782 are quite different from each other.
20787 * Embedded Processors::
20794 This section describes details specific to particular native
20798 * BSD libkvm Interface:: Debugging BSD kernel memory images
20799 * SVR4 Process Information:: SVR4 process information
20800 * DJGPP Native:: Features specific to the DJGPP port
20801 * Cygwin Native:: Features specific to the Cygwin port
20802 * Hurd Native:: Features specific to @sc{gnu} Hurd
20803 * Darwin:: Features specific to Darwin
20806 @node BSD libkvm Interface
20807 @subsection BSD libkvm Interface
20810 @cindex kernel memory image
20811 @cindex kernel crash dump
20813 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20814 interface that provides a uniform interface for accessing kernel virtual
20815 memory images, including live systems and crash dumps. @value{GDBN}
20816 uses this interface to allow you to debug live kernels and kernel crash
20817 dumps on many native BSD configurations. This is implemented as a
20818 special @code{kvm} debugging target. For debugging a live system, load
20819 the currently running kernel into @value{GDBN} and connect to the
20823 (@value{GDBP}) @b{target kvm}
20826 For debugging crash dumps, provide the file name of the crash dump as an
20830 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20833 Once connected to the @code{kvm} target, the following commands are
20839 Set current context from the @dfn{Process Control Block} (PCB) address.
20842 Set current context from proc address. This command isn't available on
20843 modern FreeBSD systems.
20846 @node SVR4 Process Information
20847 @subsection SVR4 Process Information
20849 @cindex examine process image
20850 @cindex process info via @file{/proc}
20852 Many versions of SVR4 and compatible systems provide a facility called
20853 @samp{/proc} that can be used to examine the image of a running
20854 process using file-system subroutines.
20856 If @value{GDBN} is configured for an operating system with this
20857 facility, the command @code{info proc} is available to report
20858 information about the process running your program, or about any
20859 process running on your system. This includes, as of this writing,
20860 @sc{gnu}/Linux and Solaris, for example.
20862 This command may also work on core files that were created on a system
20863 that has the @samp{/proc} facility.
20869 @itemx info proc @var{process-id}
20870 Summarize available information about any running process. If a
20871 process ID is specified by @var{process-id}, display information about
20872 that process; otherwise display information about the program being
20873 debugged. The summary includes the debugged process ID, the command
20874 line used to invoke it, its current working directory, and its
20875 executable file's absolute file name.
20877 On some systems, @var{process-id} can be of the form
20878 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20879 within a process. If the optional @var{pid} part is missing, it means
20880 a thread from the process being debugged (the leading @samp{/} still
20881 needs to be present, or else @value{GDBN} will interpret the number as
20882 a process ID rather than a thread ID).
20884 @item info proc cmdline
20885 @cindex info proc cmdline
20886 Show the original command line of the process. This command is
20887 specific to @sc{gnu}/Linux.
20889 @item info proc cwd
20890 @cindex info proc cwd
20891 Show the current working directory of the process. This command is
20892 specific to @sc{gnu}/Linux.
20894 @item info proc exe
20895 @cindex info proc exe
20896 Show the name of executable of the process. This command is specific
20899 @item info proc mappings
20900 @cindex memory address space mappings
20901 Report the memory address space ranges accessible in the program, with
20902 information on whether the process has read, write, or execute access
20903 rights to each range. On @sc{gnu}/Linux systems, each memory range
20904 includes the object file which is mapped to that range, instead of the
20905 memory access rights to that range.
20907 @item info proc stat
20908 @itemx info proc status
20909 @cindex process detailed status information
20910 These subcommands are specific to @sc{gnu}/Linux systems. They show
20911 the process-related information, including the user ID and group ID;
20912 how many threads are there in the process; its virtual memory usage;
20913 the signals that are pending, blocked, and ignored; its TTY; its
20914 consumption of system and user time; its stack size; its @samp{nice}
20915 value; etc. For more information, see the @samp{proc} man page
20916 (type @kbd{man 5 proc} from your shell prompt).
20918 @item info proc all
20919 Show all the information about the process described under all of the
20920 above @code{info proc} subcommands.
20923 @comment These sub-options of 'info proc' were not included when
20924 @comment procfs.c was re-written. Keep their descriptions around
20925 @comment against the day when someone finds the time to put them back in.
20926 @kindex info proc times
20927 @item info proc times
20928 Starting time, user CPU time, and system CPU time for your program and
20931 @kindex info proc id
20933 Report on the process IDs related to your program: its own process ID,
20934 the ID of its parent, the process group ID, and the session ID.
20937 @item set procfs-trace
20938 @kindex set procfs-trace
20939 @cindex @code{procfs} API calls
20940 This command enables and disables tracing of @code{procfs} API calls.
20942 @item show procfs-trace
20943 @kindex show procfs-trace
20944 Show the current state of @code{procfs} API call tracing.
20946 @item set procfs-file @var{file}
20947 @kindex set procfs-file
20948 Tell @value{GDBN} to write @code{procfs} API trace to the named
20949 @var{file}. @value{GDBN} appends the trace info to the previous
20950 contents of the file. The default is to display the trace on the
20953 @item show procfs-file
20954 @kindex show procfs-file
20955 Show the file to which @code{procfs} API trace is written.
20957 @item proc-trace-entry
20958 @itemx proc-trace-exit
20959 @itemx proc-untrace-entry
20960 @itemx proc-untrace-exit
20961 @kindex proc-trace-entry
20962 @kindex proc-trace-exit
20963 @kindex proc-untrace-entry
20964 @kindex proc-untrace-exit
20965 These commands enable and disable tracing of entries into and exits
20966 from the @code{syscall} interface.
20969 @kindex info pidlist
20970 @cindex process list, QNX Neutrino
20971 For QNX Neutrino only, this command displays the list of all the
20972 processes and all the threads within each process.
20975 @kindex info meminfo
20976 @cindex mapinfo list, QNX Neutrino
20977 For QNX Neutrino only, this command displays the list of all mapinfos.
20981 @subsection Features for Debugging @sc{djgpp} Programs
20982 @cindex @sc{djgpp} debugging
20983 @cindex native @sc{djgpp} debugging
20984 @cindex MS-DOS-specific commands
20987 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20988 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20989 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20990 top of real-mode DOS systems and their emulations.
20992 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20993 defines a few commands specific to the @sc{djgpp} port. This
20994 subsection describes those commands.
20999 This is a prefix of @sc{djgpp}-specific commands which print
21000 information about the target system and important OS structures.
21003 @cindex MS-DOS system info
21004 @cindex free memory information (MS-DOS)
21005 @item info dos sysinfo
21006 This command displays assorted information about the underlying
21007 platform: the CPU type and features, the OS version and flavor, the
21008 DPMI version, and the available conventional and DPMI memory.
21013 @cindex segment descriptor tables
21014 @cindex descriptor tables display
21016 @itemx info dos ldt
21017 @itemx info dos idt
21018 These 3 commands display entries from, respectively, Global, Local,
21019 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21020 tables are data structures which store a descriptor for each segment
21021 that is currently in use. The segment's selector is an index into a
21022 descriptor table; the table entry for that index holds the
21023 descriptor's base address and limit, and its attributes and access
21026 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21027 segment (used for both data and the stack), and a DOS segment (which
21028 allows access to DOS/BIOS data structures and absolute addresses in
21029 conventional memory). However, the DPMI host will usually define
21030 additional segments in order to support the DPMI environment.
21032 @cindex garbled pointers
21033 These commands allow to display entries from the descriptor tables.
21034 Without an argument, all entries from the specified table are
21035 displayed. An argument, which should be an integer expression, means
21036 display a single entry whose index is given by the argument. For
21037 example, here's a convenient way to display information about the
21038 debugged program's data segment:
21041 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21042 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21046 This comes in handy when you want to see whether a pointer is outside
21047 the data segment's limit (i.e.@: @dfn{garbled}).
21049 @cindex page tables display (MS-DOS)
21051 @itemx info dos pte
21052 These two commands display entries from, respectively, the Page
21053 Directory and the Page Tables. Page Directories and Page Tables are
21054 data structures which control how virtual memory addresses are mapped
21055 into physical addresses. A Page Table includes an entry for every
21056 page of memory that is mapped into the program's address space; there
21057 may be several Page Tables, each one holding up to 4096 entries. A
21058 Page Directory has up to 4096 entries, one each for every Page Table
21059 that is currently in use.
21061 Without an argument, @kbd{info dos pde} displays the entire Page
21062 Directory, and @kbd{info dos pte} displays all the entries in all of
21063 the Page Tables. An argument, an integer expression, given to the
21064 @kbd{info dos pde} command means display only that entry from the Page
21065 Directory table. An argument given to the @kbd{info dos pte} command
21066 means display entries from a single Page Table, the one pointed to by
21067 the specified entry in the Page Directory.
21069 @cindex direct memory access (DMA) on MS-DOS
21070 These commands are useful when your program uses @dfn{DMA} (Direct
21071 Memory Access), which needs physical addresses to program the DMA
21074 These commands are supported only with some DPMI servers.
21076 @cindex physical address from linear address
21077 @item info dos address-pte @var{addr}
21078 This command displays the Page Table entry for a specified linear
21079 address. The argument @var{addr} is a linear address which should
21080 already have the appropriate segment's base address added to it,
21081 because this command accepts addresses which may belong to @emph{any}
21082 segment. For example, here's how to display the Page Table entry for
21083 the page where a variable @code{i} is stored:
21086 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21087 @exdent @code{Page Table entry for address 0x11a00d30:}
21088 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21092 This says that @code{i} is stored at offset @code{0xd30} from the page
21093 whose physical base address is @code{0x02698000}, and shows all the
21094 attributes of that page.
21096 Note that you must cast the addresses of variables to a @code{char *},
21097 since otherwise the value of @code{__djgpp_base_address}, the base
21098 address of all variables and functions in a @sc{djgpp} program, will
21099 be added using the rules of C pointer arithmetics: if @code{i} is
21100 declared an @code{int}, @value{GDBN} will add 4 times the value of
21101 @code{__djgpp_base_address} to the address of @code{i}.
21103 Here's another example, it displays the Page Table entry for the
21107 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21108 @exdent @code{Page Table entry for address 0x29110:}
21109 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21113 (The @code{+ 3} offset is because the transfer buffer's address is the
21114 3rd member of the @code{_go32_info_block} structure.) The output
21115 clearly shows that this DPMI server maps the addresses in conventional
21116 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21117 linear (@code{0x29110}) addresses are identical.
21119 This command is supported only with some DPMI servers.
21122 @cindex DOS serial data link, remote debugging
21123 In addition to native debugging, the DJGPP port supports remote
21124 debugging via a serial data link. The following commands are specific
21125 to remote serial debugging in the DJGPP port of @value{GDBN}.
21128 @kindex set com1base
21129 @kindex set com1irq
21130 @kindex set com2base
21131 @kindex set com2irq
21132 @kindex set com3base
21133 @kindex set com3irq
21134 @kindex set com4base
21135 @kindex set com4irq
21136 @item set com1base @var{addr}
21137 This command sets the base I/O port address of the @file{COM1} serial
21140 @item set com1irq @var{irq}
21141 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21142 for the @file{COM1} serial port.
21144 There are similar commands @samp{set com2base}, @samp{set com3irq},
21145 etc.@: for setting the port address and the @code{IRQ} lines for the
21148 @kindex show com1base
21149 @kindex show com1irq
21150 @kindex show com2base
21151 @kindex show com2irq
21152 @kindex show com3base
21153 @kindex show com3irq
21154 @kindex show com4base
21155 @kindex show com4irq
21156 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21157 display the current settings of the base address and the @code{IRQ}
21158 lines used by the COM ports.
21161 @kindex info serial
21162 @cindex DOS serial port status
21163 This command prints the status of the 4 DOS serial ports. For each
21164 port, it prints whether it's active or not, its I/O base address and
21165 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21166 counts of various errors encountered so far.
21170 @node Cygwin Native
21171 @subsection Features for Debugging MS Windows PE Executables
21172 @cindex MS Windows debugging
21173 @cindex native Cygwin debugging
21174 @cindex Cygwin-specific commands
21176 @value{GDBN} supports native debugging of MS Windows programs, including
21177 DLLs with and without symbolic debugging information.
21179 @cindex Ctrl-BREAK, MS-Windows
21180 @cindex interrupt debuggee on MS-Windows
21181 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21182 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21183 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21184 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21185 sequence, which can be used to interrupt the debuggee even if it
21188 There are various additional Cygwin-specific commands, described in
21189 this section. Working with DLLs that have no debugging symbols is
21190 described in @ref{Non-debug DLL Symbols}.
21195 This is a prefix of MS Windows-specific commands which print
21196 information about the target system and important OS structures.
21198 @item info w32 selector
21199 This command displays information returned by
21200 the Win32 API @code{GetThreadSelectorEntry} function.
21201 It takes an optional argument that is evaluated to
21202 a long value to give the information about this given selector.
21203 Without argument, this command displays information
21204 about the six segment registers.
21206 @item info w32 thread-information-block
21207 This command displays thread specific information stored in the
21208 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21209 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21211 @kindex set cygwin-exceptions
21212 @cindex debugging the Cygwin DLL
21213 @cindex Cygwin DLL, debugging
21214 @item set cygwin-exceptions @var{mode}
21215 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21216 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21217 @value{GDBN} will delay recognition of exceptions, and may ignore some
21218 exceptions which seem to be caused by internal Cygwin DLL
21219 ``bookkeeping''. This option is meant primarily for debugging the
21220 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21221 @value{GDBN} users with false @code{SIGSEGV} signals.
21223 @kindex show cygwin-exceptions
21224 @item show cygwin-exceptions
21225 Displays whether @value{GDBN} will break on exceptions that happen
21226 inside the Cygwin DLL itself.
21228 @kindex set new-console
21229 @item set new-console @var{mode}
21230 If @var{mode} is @code{on} the debuggee will
21231 be started in a new console on next start.
21232 If @var{mode} is @code{off}, the debuggee will
21233 be started in the same console as the debugger.
21235 @kindex show new-console
21236 @item show new-console
21237 Displays whether a new console is used
21238 when the debuggee is started.
21240 @kindex set new-group
21241 @item set new-group @var{mode}
21242 This boolean value controls whether the debuggee should
21243 start a new group or stay in the same group as the debugger.
21244 This affects the way the Windows OS handles
21247 @kindex show new-group
21248 @item show new-group
21249 Displays current value of new-group boolean.
21251 @kindex set debugevents
21252 @item set debugevents
21253 This boolean value adds debug output concerning kernel events related
21254 to the debuggee seen by the debugger. This includes events that
21255 signal thread and process creation and exit, DLL loading and
21256 unloading, console interrupts, and debugging messages produced by the
21257 Windows @code{OutputDebugString} API call.
21259 @kindex set debugexec
21260 @item set debugexec
21261 This boolean value adds debug output concerning execute events
21262 (such as resume thread) seen by the debugger.
21264 @kindex set debugexceptions
21265 @item set debugexceptions
21266 This boolean value adds debug output concerning exceptions in the
21267 debuggee seen by the debugger.
21269 @kindex set debugmemory
21270 @item set debugmemory
21271 This boolean value adds debug output concerning debuggee memory reads
21272 and writes by the debugger.
21276 This boolean values specifies whether the debuggee is called
21277 via a shell or directly (default value is on).
21281 Displays if the debuggee will be started with a shell.
21286 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21289 @node Non-debug DLL Symbols
21290 @subsubsection Support for DLLs without Debugging Symbols
21291 @cindex DLLs with no debugging symbols
21292 @cindex Minimal symbols and DLLs
21294 Very often on windows, some of the DLLs that your program relies on do
21295 not include symbolic debugging information (for example,
21296 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21297 symbols in a DLL, it relies on the minimal amount of symbolic
21298 information contained in the DLL's export table. This section
21299 describes working with such symbols, known internally to @value{GDBN} as
21300 ``minimal symbols''.
21302 Note that before the debugged program has started execution, no DLLs
21303 will have been loaded. The easiest way around this problem is simply to
21304 start the program --- either by setting a breakpoint or letting the
21305 program run once to completion.
21307 @subsubsection DLL Name Prefixes
21309 In keeping with the naming conventions used by the Microsoft debugging
21310 tools, DLL export symbols are made available with a prefix based on the
21311 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21312 also entered into the symbol table, so @code{CreateFileA} is often
21313 sufficient. In some cases there will be name clashes within a program
21314 (particularly if the executable itself includes full debugging symbols)
21315 necessitating the use of the fully qualified name when referring to the
21316 contents of the DLL. Use single-quotes around the name to avoid the
21317 exclamation mark (``!'') being interpreted as a language operator.
21319 Note that the internal name of the DLL may be all upper-case, even
21320 though the file name of the DLL is lower-case, or vice-versa. Since
21321 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21322 some confusion. If in doubt, try the @code{info functions} and
21323 @code{info variables} commands or even @code{maint print msymbols}
21324 (@pxref{Symbols}). Here's an example:
21327 (@value{GDBP}) info function CreateFileA
21328 All functions matching regular expression "CreateFileA":
21330 Non-debugging symbols:
21331 0x77e885f4 CreateFileA
21332 0x77e885f4 KERNEL32!CreateFileA
21336 (@value{GDBP}) info function !
21337 All functions matching regular expression "!":
21339 Non-debugging symbols:
21340 0x6100114c cygwin1!__assert
21341 0x61004034 cygwin1!_dll_crt0@@0
21342 0x61004240 cygwin1!dll_crt0(per_process *)
21346 @subsubsection Working with Minimal Symbols
21348 Symbols extracted from a DLL's export table do not contain very much
21349 type information. All that @value{GDBN} can do is guess whether a symbol
21350 refers to a function or variable depending on the linker section that
21351 contains the symbol. Also note that the actual contents of the memory
21352 contained in a DLL are not available unless the program is running. This
21353 means that you cannot examine the contents of a variable or disassemble
21354 a function within a DLL without a running program.
21356 Variables are generally treated as pointers and dereferenced
21357 automatically. For this reason, it is often necessary to prefix a
21358 variable name with the address-of operator (``&'') and provide explicit
21359 type information in the command. Here's an example of the type of
21363 (@value{GDBP}) print 'cygwin1!__argv'
21368 (@value{GDBP}) x 'cygwin1!__argv'
21369 0x10021610: "\230y\""
21372 And two possible solutions:
21375 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21376 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21380 (@value{GDBP}) x/2x &'cygwin1!__argv'
21381 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21382 (@value{GDBP}) x/x 0x10021608
21383 0x10021608: 0x0022fd98
21384 (@value{GDBP}) x/s 0x0022fd98
21385 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21388 Setting a break point within a DLL is possible even before the program
21389 starts execution. However, under these circumstances, @value{GDBN} can't
21390 examine the initial instructions of the function in order to skip the
21391 function's frame set-up code. You can work around this by using ``*&''
21392 to set the breakpoint at a raw memory address:
21395 (@value{GDBP}) break *&'python22!PyOS_Readline'
21396 Breakpoint 1 at 0x1e04eff0
21399 The author of these extensions is not entirely convinced that setting a
21400 break point within a shared DLL like @file{kernel32.dll} is completely
21404 @subsection Commands Specific to @sc{gnu} Hurd Systems
21405 @cindex @sc{gnu} Hurd debugging
21407 This subsection describes @value{GDBN} commands specific to the
21408 @sc{gnu} Hurd native debugging.
21413 @kindex set signals@r{, Hurd command}
21414 @kindex set sigs@r{, Hurd command}
21415 This command toggles the state of inferior signal interception by
21416 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21417 affected by this command. @code{sigs} is a shorthand alias for
21422 @kindex show signals@r{, Hurd command}
21423 @kindex show sigs@r{, Hurd command}
21424 Show the current state of intercepting inferior's signals.
21426 @item set signal-thread
21427 @itemx set sigthread
21428 @kindex set signal-thread
21429 @kindex set sigthread
21430 This command tells @value{GDBN} which thread is the @code{libc} signal
21431 thread. That thread is run when a signal is delivered to a running
21432 process. @code{set sigthread} is the shorthand alias of @code{set
21435 @item show signal-thread
21436 @itemx show sigthread
21437 @kindex show signal-thread
21438 @kindex show sigthread
21439 These two commands show which thread will run when the inferior is
21440 delivered a signal.
21443 @kindex set stopped@r{, Hurd command}
21444 This commands tells @value{GDBN} that the inferior process is stopped,
21445 as with the @code{SIGSTOP} signal. The stopped process can be
21446 continued by delivering a signal to it.
21449 @kindex show stopped@r{, Hurd command}
21450 This command shows whether @value{GDBN} thinks the debuggee is
21453 @item set exceptions
21454 @kindex set exceptions@r{, Hurd command}
21455 Use this command to turn off trapping of exceptions in the inferior.
21456 When exception trapping is off, neither breakpoints nor
21457 single-stepping will work. To restore the default, set exception
21460 @item show exceptions
21461 @kindex show exceptions@r{, Hurd command}
21462 Show the current state of trapping exceptions in the inferior.
21464 @item set task pause
21465 @kindex set task@r{, Hurd commands}
21466 @cindex task attributes (@sc{gnu} Hurd)
21467 @cindex pause current task (@sc{gnu} Hurd)
21468 This command toggles task suspension when @value{GDBN} has control.
21469 Setting it to on takes effect immediately, and the task is suspended
21470 whenever @value{GDBN} gets control. Setting it to off will take
21471 effect the next time the inferior is continued. If this option is set
21472 to off, you can use @code{set thread default pause on} or @code{set
21473 thread pause on} (see below) to pause individual threads.
21475 @item show task pause
21476 @kindex show task@r{, Hurd commands}
21477 Show the current state of task suspension.
21479 @item set task detach-suspend-count
21480 @cindex task suspend count
21481 @cindex detach from task, @sc{gnu} Hurd
21482 This command sets the suspend count the task will be left with when
21483 @value{GDBN} detaches from it.
21485 @item show task detach-suspend-count
21486 Show the suspend count the task will be left with when detaching.
21488 @item set task exception-port
21489 @itemx set task excp
21490 @cindex task exception port, @sc{gnu} Hurd
21491 This command sets the task exception port to which @value{GDBN} will
21492 forward exceptions. The argument should be the value of the @dfn{send
21493 rights} of the task. @code{set task excp} is a shorthand alias.
21495 @item set noninvasive
21496 @cindex noninvasive task options
21497 This command switches @value{GDBN} to a mode that is the least
21498 invasive as far as interfering with the inferior is concerned. This
21499 is the same as using @code{set task pause}, @code{set exceptions}, and
21500 @code{set signals} to values opposite to the defaults.
21502 @item info send-rights
21503 @itemx info receive-rights
21504 @itemx info port-rights
21505 @itemx info port-sets
21506 @itemx info dead-names
21509 @cindex send rights, @sc{gnu} Hurd
21510 @cindex receive rights, @sc{gnu} Hurd
21511 @cindex port rights, @sc{gnu} Hurd
21512 @cindex port sets, @sc{gnu} Hurd
21513 @cindex dead names, @sc{gnu} Hurd
21514 These commands display information about, respectively, send rights,
21515 receive rights, port rights, port sets, and dead names of a task.
21516 There are also shorthand aliases: @code{info ports} for @code{info
21517 port-rights} and @code{info psets} for @code{info port-sets}.
21519 @item set thread pause
21520 @kindex set thread@r{, Hurd command}
21521 @cindex thread properties, @sc{gnu} Hurd
21522 @cindex pause current thread (@sc{gnu} Hurd)
21523 This command toggles current thread suspension when @value{GDBN} has
21524 control. Setting it to on takes effect immediately, and the current
21525 thread is suspended whenever @value{GDBN} gets control. Setting it to
21526 off will take effect the next time the inferior is continued.
21527 Normally, this command has no effect, since when @value{GDBN} has
21528 control, the whole task is suspended. However, if you used @code{set
21529 task pause off} (see above), this command comes in handy to suspend
21530 only the current thread.
21532 @item show thread pause
21533 @kindex show thread@r{, Hurd command}
21534 This command shows the state of current thread suspension.
21536 @item set thread run
21537 This command sets whether the current thread is allowed to run.
21539 @item show thread run
21540 Show whether the current thread is allowed to run.
21542 @item set thread detach-suspend-count
21543 @cindex thread suspend count, @sc{gnu} Hurd
21544 @cindex detach from thread, @sc{gnu} Hurd
21545 This command sets the suspend count @value{GDBN} will leave on a
21546 thread when detaching. This number is relative to the suspend count
21547 found by @value{GDBN} when it notices the thread; use @code{set thread
21548 takeover-suspend-count} to force it to an absolute value.
21550 @item show thread detach-suspend-count
21551 Show the suspend count @value{GDBN} will leave on the thread when
21554 @item set thread exception-port
21555 @itemx set thread excp
21556 Set the thread exception port to which to forward exceptions. This
21557 overrides the port set by @code{set task exception-port} (see above).
21558 @code{set thread excp} is the shorthand alias.
21560 @item set thread takeover-suspend-count
21561 Normally, @value{GDBN}'s thread suspend counts are relative to the
21562 value @value{GDBN} finds when it notices each thread. This command
21563 changes the suspend counts to be absolute instead.
21565 @item set thread default
21566 @itemx show thread default
21567 @cindex thread default settings, @sc{gnu} Hurd
21568 Each of the above @code{set thread} commands has a @code{set thread
21569 default} counterpart (e.g., @code{set thread default pause}, @code{set
21570 thread default exception-port}, etc.). The @code{thread default}
21571 variety of commands sets the default thread properties for all
21572 threads; you can then change the properties of individual threads with
21573 the non-default commands.
21580 @value{GDBN} provides the following commands specific to the Darwin target:
21583 @item set debug darwin @var{num}
21584 @kindex set debug darwin
21585 When set to a non zero value, enables debugging messages specific to
21586 the Darwin support. Higher values produce more verbose output.
21588 @item show debug darwin
21589 @kindex show debug darwin
21590 Show the current state of Darwin messages.
21592 @item set debug mach-o @var{num}
21593 @kindex set debug mach-o
21594 When set to a non zero value, enables debugging messages while
21595 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21596 file format used on Darwin for object and executable files.) Higher
21597 values produce more verbose output. This is a command to diagnose
21598 problems internal to @value{GDBN} and should not be needed in normal
21601 @item show debug mach-o
21602 @kindex show debug mach-o
21603 Show the current state of Mach-O file messages.
21605 @item set mach-exceptions on
21606 @itemx set mach-exceptions off
21607 @kindex set mach-exceptions
21608 On Darwin, faults are first reported as a Mach exception and are then
21609 mapped to a Posix signal. Use this command to turn on trapping of
21610 Mach exceptions in the inferior. This might be sometimes useful to
21611 better understand the cause of a fault. The default is off.
21613 @item show mach-exceptions
21614 @kindex show mach-exceptions
21615 Show the current state of exceptions trapping.
21620 @section Embedded Operating Systems
21622 This section describes configurations involving the debugging of
21623 embedded operating systems that are available for several different
21626 @value{GDBN} includes the ability to debug programs running on
21627 various real-time operating systems.
21629 @node Embedded Processors
21630 @section Embedded Processors
21632 This section goes into details specific to particular embedded
21635 @cindex send command to simulator
21636 Whenever a specific embedded processor has a simulator, @value{GDBN}
21637 allows to send an arbitrary command to the simulator.
21640 @item sim @var{command}
21641 @kindex sim@r{, a command}
21642 Send an arbitrary @var{command} string to the simulator. Consult the
21643 documentation for the specific simulator in use for information about
21644 acceptable commands.
21650 * M32R/SDI:: Renesas M32R/SDI
21651 * M68K:: Motorola M68K
21652 * MicroBlaze:: Xilinx MicroBlaze
21653 * MIPS Embedded:: MIPS Embedded
21654 * PowerPC Embedded:: PowerPC Embedded
21657 * Super-H:: Renesas Super-H
21663 @value{GDBN} provides the following ARM-specific commands:
21666 @item set arm disassembler
21668 This commands selects from a list of disassembly styles. The
21669 @code{"std"} style is the standard style.
21671 @item show arm disassembler
21673 Show the current disassembly style.
21675 @item set arm apcs32
21676 @cindex ARM 32-bit mode
21677 This command toggles ARM operation mode between 32-bit and 26-bit.
21679 @item show arm apcs32
21680 Display the current usage of the ARM 32-bit mode.
21682 @item set arm fpu @var{fputype}
21683 This command sets the ARM floating-point unit (FPU) type. The
21684 argument @var{fputype} can be one of these:
21688 Determine the FPU type by querying the OS ABI.
21690 Software FPU, with mixed-endian doubles on little-endian ARM
21693 GCC-compiled FPA co-processor.
21695 Software FPU with pure-endian doubles.
21701 Show the current type of the FPU.
21704 This command forces @value{GDBN} to use the specified ABI.
21707 Show the currently used ABI.
21709 @item set arm fallback-mode (arm|thumb|auto)
21710 @value{GDBN} uses the symbol table, when available, to determine
21711 whether instructions are ARM or Thumb. This command controls
21712 @value{GDBN}'s default behavior when the symbol table is not
21713 available. The default is @samp{auto}, which causes @value{GDBN} to
21714 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21717 @item show arm fallback-mode
21718 Show the current fallback instruction mode.
21720 @item set arm force-mode (arm|thumb|auto)
21721 This command overrides use of the symbol table to determine whether
21722 instructions are ARM or Thumb. The default is @samp{auto}, which
21723 causes @value{GDBN} to use the symbol table and then the setting
21724 of @samp{set arm fallback-mode}.
21726 @item show arm force-mode
21727 Show the current forced instruction mode.
21729 @item set debug arm
21730 Toggle whether to display ARM-specific debugging messages from the ARM
21731 target support subsystem.
21733 @item show debug arm
21734 Show whether ARM-specific debugging messages are enabled.
21738 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21739 The @value{GDBN} ARM simulator accepts the following optional arguments.
21742 @item --swi-support=@var{type}
21743 Tell the simulator which SWI interfaces to support. The argument
21744 @var{type} may be a comma separated list of the following values.
21745 The default value is @code{all}.
21758 @subsection Renesas M32R/SDI
21760 The following commands are available for M32R/SDI:
21765 @cindex reset SDI connection, M32R
21766 This command resets the SDI connection.
21770 This command shows the SDI connection status.
21773 @kindex debug_chaos
21774 @cindex M32R/Chaos debugging
21775 Instructs the remote that M32R/Chaos debugging is to be used.
21777 @item use_debug_dma
21778 @kindex use_debug_dma
21779 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21782 @kindex use_mon_code
21783 Instructs the remote to use the MON_CODE method of accessing memory.
21786 @kindex use_ib_break
21787 Instructs the remote to set breakpoints by IB break.
21789 @item use_dbt_break
21790 @kindex use_dbt_break
21791 Instructs the remote to set breakpoints by DBT.
21797 The Motorola m68k configuration includes ColdFire support.
21800 @subsection MicroBlaze
21801 @cindex Xilinx MicroBlaze
21802 @cindex XMD, Xilinx Microprocessor Debugger
21804 The MicroBlaze is a soft-core processor supported on various Xilinx
21805 FPGAs, such as Spartan or Virtex series. Boards with these processors
21806 usually have JTAG ports which connect to a host system running the Xilinx
21807 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21808 This host system is used to download the configuration bitstream to
21809 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21810 communicates with the target board using the JTAG interface and
21811 presents a @code{gdbserver} interface to the board. By default
21812 @code{xmd} uses port @code{1234}. (While it is possible to change
21813 this default port, it requires the use of undocumented @code{xmd}
21814 commands. Contact Xilinx support if you need to do this.)
21816 Use these GDB commands to connect to the MicroBlaze target processor.
21819 @item target remote :1234
21820 Use this command to connect to the target if you are running @value{GDBN}
21821 on the same system as @code{xmd}.
21823 @item target remote @var{xmd-host}:1234
21824 Use this command to connect to the target if it is connected to @code{xmd}
21825 running on a different system named @var{xmd-host}.
21828 Use this command to download a program to the MicroBlaze target.
21830 @item set debug microblaze @var{n}
21831 Enable MicroBlaze-specific debugging messages if non-zero.
21833 @item show debug microblaze @var{n}
21834 Show MicroBlaze-specific debugging level.
21837 @node MIPS Embedded
21838 @subsection @acronym{MIPS} Embedded
21840 @cindex @acronym{MIPS} boards
21841 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21842 @acronym{MIPS} board attached to a serial line. This is available when
21843 you configure @value{GDBN} with @samp{--target=mips-elf}.
21846 Use these @value{GDBN} commands to specify the connection to your target board:
21849 @item target mips @var{port}
21850 @kindex target mips @var{port}
21851 To run a program on the board, start up @code{@value{GDBP}} with the
21852 name of your program as the argument. To connect to the board, use the
21853 command @samp{target mips @var{port}}, where @var{port} is the name of
21854 the serial port connected to the board. If the program has not already
21855 been downloaded to the board, you may use the @code{load} command to
21856 download it. You can then use all the usual @value{GDBN} commands.
21858 For example, this sequence connects to the target board through a serial
21859 port, and loads and runs a program called @var{prog} through the
21863 host$ @value{GDBP} @var{prog}
21864 @value{GDBN} is free software and @dots{}
21865 (@value{GDBP}) target mips /dev/ttyb
21866 (@value{GDBP}) load @var{prog}
21870 @item target mips @var{hostname}:@var{portnumber}
21871 On some @value{GDBN} host configurations, you can specify a TCP
21872 connection (for instance, to a serial line managed by a terminal
21873 concentrator) instead of a serial port, using the syntax
21874 @samp{@var{hostname}:@var{portnumber}}.
21876 @item target pmon @var{port}
21877 @kindex target pmon @var{port}
21880 @item target ddb @var{port}
21881 @kindex target ddb @var{port}
21882 NEC's DDB variant of PMON for Vr4300.
21884 @item target lsi @var{port}
21885 @kindex target lsi @var{port}
21886 LSI variant of PMON.
21892 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21895 @item set mipsfpu double
21896 @itemx set mipsfpu single
21897 @itemx set mipsfpu none
21898 @itemx set mipsfpu auto
21899 @itemx show mipsfpu
21900 @kindex set mipsfpu
21901 @kindex show mipsfpu
21902 @cindex @acronym{MIPS} remote floating point
21903 @cindex floating point, @acronym{MIPS} remote
21904 If your target board does not support the @acronym{MIPS} floating point
21905 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21906 need this, you may wish to put the command in your @value{GDBN} init
21907 file). This tells @value{GDBN} how to find the return value of
21908 functions which return floating point values. It also allows
21909 @value{GDBN} to avoid saving the floating point registers when calling
21910 functions on the board. If you are using a floating point coprocessor
21911 with only single precision floating point support, as on the @sc{r4650}
21912 processor, use the command @samp{set mipsfpu single}. The default
21913 double precision floating point coprocessor may be selected using
21914 @samp{set mipsfpu double}.
21916 In previous versions the only choices were double precision or no
21917 floating point, so @samp{set mipsfpu on} will select double precision
21918 and @samp{set mipsfpu off} will select no floating point.
21920 As usual, you can inquire about the @code{mipsfpu} variable with
21921 @samp{show mipsfpu}.
21923 @item set timeout @var{seconds}
21924 @itemx set retransmit-timeout @var{seconds}
21925 @itemx show timeout
21926 @itemx show retransmit-timeout
21927 @cindex @code{timeout}, @acronym{MIPS} protocol
21928 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21929 @kindex set timeout
21930 @kindex show timeout
21931 @kindex set retransmit-timeout
21932 @kindex show retransmit-timeout
21933 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21934 remote protocol, with the @code{set timeout @var{seconds}} command. The
21935 default is 5 seconds. Similarly, you can control the timeout used while
21936 waiting for an acknowledgment of a packet with the @code{set
21937 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21938 You can inspect both values with @code{show timeout} and @code{show
21939 retransmit-timeout}. (These commands are @emph{only} available when
21940 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21942 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21943 is waiting for your program to stop. In that case, @value{GDBN} waits
21944 forever because it has no way of knowing how long the program is going
21945 to run before stopping.
21947 @item set syn-garbage-limit @var{num}
21948 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21949 @cindex synchronize with remote @acronym{MIPS} target
21950 Limit the maximum number of characters @value{GDBN} should ignore when
21951 it tries to synchronize with the remote target. The default is 10
21952 characters. Setting the limit to -1 means there's no limit.
21954 @item show syn-garbage-limit
21955 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21956 Show the current limit on the number of characters to ignore when
21957 trying to synchronize with the remote system.
21959 @item set monitor-prompt @var{prompt}
21960 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21961 @cindex remote monitor prompt
21962 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21963 remote monitor. The default depends on the target:
21973 @item show monitor-prompt
21974 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21975 Show the current strings @value{GDBN} expects as the prompt from the
21978 @item set monitor-warnings
21979 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21980 Enable or disable monitor warnings about hardware breakpoints. This
21981 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21982 display warning messages whose codes are returned by the @code{lsi}
21983 PMON monitor for breakpoint commands.
21985 @item show monitor-warnings
21986 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21987 Show the current setting of printing monitor warnings.
21989 @item pmon @var{command}
21990 @kindex pmon@r{, @acronym{MIPS} remote}
21991 @cindex send PMON command
21992 This command allows sending an arbitrary @var{command} string to the
21993 monitor. The monitor must be in debug mode for this to work.
21996 @node PowerPC Embedded
21997 @subsection PowerPC Embedded
21999 @cindex DVC register
22000 @value{GDBN} supports using the DVC (Data Value Compare) register to
22001 implement in hardware simple hardware watchpoint conditions of the form:
22004 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22005 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22008 The DVC register will be automatically used when @value{GDBN} detects
22009 such pattern in a condition expression, and the created watchpoint uses one
22010 debug register (either the @code{exact-watchpoints} option is on and the
22011 variable is scalar, or the variable has a length of one byte). This feature
22012 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22015 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22016 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22017 in which case watchpoints using only one debug register are created when
22018 watching variables of scalar types.
22020 You can create an artificial array to watch an arbitrary memory
22021 region using one of the following commands (@pxref{Expressions}):
22024 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22025 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22028 PowerPC embedded processors support masked watchpoints. See the discussion
22029 about the @code{mask} argument in @ref{Set Watchpoints}.
22031 @cindex ranged breakpoint
22032 PowerPC embedded processors support hardware accelerated
22033 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22034 the inferior whenever it executes an instruction at any address within
22035 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22036 use the @code{break-range} command.
22038 @value{GDBN} provides the following PowerPC-specific commands:
22041 @kindex break-range
22042 @item break-range @var{start-location}, @var{end-location}
22043 Set a breakpoint for an address range given by
22044 @var{start-location} and @var{end-location}, which can specify a function name,
22045 a line number, an offset of lines from the current line or from the start
22046 location, or an address of an instruction (see @ref{Specify Location},
22047 for a list of all the possible ways to specify a @var{location}.)
22048 The breakpoint will stop execution of the inferior whenever it
22049 executes an instruction at any address within the specified range,
22050 (including @var{start-location} and @var{end-location}.)
22052 @kindex set powerpc
22053 @item set powerpc soft-float
22054 @itemx show powerpc soft-float
22055 Force @value{GDBN} to use (or not use) a software floating point calling
22056 convention. By default, @value{GDBN} selects the calling convention based
22057 on the selected architecture and the provided executable file.
22059 @item set powerpc vector-abi
22060 @itemx show powerpc vector-abi
22061 Force @value{GDBN} to use the specified calling convention for vector
22062 arguments and return values. The valid options are @samp{auto};
22063 @samp{generic}, to avoid vector registers even if they are present;
22064 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22065 registers. By default, @value{GDBN} selects the calling convention
22066 based on the selected architecture and the provided executable file.
22068 @item set powerpc exact-watchpoints
22069 @itemx show powerpc exact-watchpoints
22070 Allow @value{GDBN} to use only one debug register when watching a variable
22071 of scalar type, thus assuming that the variable is accessed through the
22072 address of its first byte.
22077 @subsection Atmel AVR
22080 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22081 following AVR-specific commands:
22084 @item info io_registers
22085 @kindex info io_registers@r{, AVR}
22086 @cindex I/O registers (Atmel AVR)
22087 This command displays information about the AVR I/O registers. For
22088 each register, @value{GDBN} prints its number and value.
22095 When configured for debugging CRIS, @value{GDBN} provides the
22096 following CRIS-specific commands:
22099 @item set cris-version @var{ver}
22100 @cindex CRIS version
22101 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22102 The CRIS version affects register names and sizes. This command is useful in
22103 case autodetection of the CRIS version fails.
22105 @item show cris-version
22106 Show the current CRIS version.
22108 @item set cris-dwarf2-cfi
22109 @cindex DWARF-2 CFI and CRIS
22110 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22111 Change to @samp{off} when using @code{gcc-cris} whose version is below
22114 @item show cris-dwarf2-cfi
22115 Show the current state of using DWARF-2 CFI.
22117 @item set cris-mode @var{mode}
22119 Set the current CRIS mode to @var{mode}. It should only be changed when
22120 debugging in guru mode, in which case it should be set to
22121 @samp{guru} (the default is @samp{normal}).
22123 @item show cris-mode
22124 Show the current CRIS mode.
22128 @subsection Renesas Super-H
22131 For the Renesas Super-H processor, @value{GDBN} provides these
22135 @item set sh calling-convention @var{convention}
22136 @kindex set sh calling-convention
22137 Set the calling-convention used when calling functions from @value{GDBN}.
22138 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22139 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22140 convention. If the DWARF-2 information of the called function specifies
22141 that the function follows the Renesas calling convention, the function
22142 is called using the Renesas calling convention. If the calling convention
22143 is set to @samp{renesas}, the Renesas calling convention is always used,
22144 regardless of the DWARF-2 information. This can be used to override the
22145 default of @samp{gcc} if debug information is missing, or the compiler
22146 does not emit the DWARF-2 calling convention entry for a function.
22148 @item show sh calling-convention
22149 @kindex show sh calling-convention
22150 Show the current calling convention setting.
22155 @node Architectures
22156 @section Architectures
22158 This section describes characteristics of architectures that affect
22159 all uses of @value{GDBN} with the architecture, both native and cross.
22166 * HPPA:: HP PA architecture
22167 * SPU:: Cell Broadband Engine SPU architecture
22173 @subsection AArch64
22174 @cindex AArch64 support
22176 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22177 following special commands:
22180 @item set debug aarch64
22181 @kindex set debug aarch64
22182 This command determines whether AArch64 architecture-specific debugging
22183 messages are to be displayed.
22185 @item show debug aarch64
22186 Show whether AArch64 debugging messages are displayed.
22191 @subsection x86 Architecture-specific Issues
22194 @item set struct-convention @var{mode}
22195 @kindex set struct-convention
22196 @cindex struct return convention
22197 @cindex struct/union returned in registers
22198 Set the convention used by the inferior to return @code{struct}s and
22199 @code{union}s from functions to @var{mode}. Possible values of
22200 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22201 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22202 are returned on the stack, while @code{"reg"} means that a
22203 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22204 be returned in a register.
22206 @item show struct-convention
22207 @kindex show struct-convention
22208 Show the current setting of the convention to return @code{struct}s
22213 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22214 @cindex Intel Memory Protection Extensions (MPX).
22216 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22217 @footnote{The register named with capital letters represent the architecture
22218 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22219 which are the lower bound and upper bound. Bounds are effective addresses or
22220 memory locations. The upper bounds are architecturally represented in 1's
22221 complement form. A bound having lower bound = 0, and upper bound = 0
22222 (1's complement of all bits set) will allow access to the entire address space.
22224 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22225 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22226 display the upper bound performing the complement of one operation on the
22227 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22228 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22229 can also be noted that the upper bounds are inclusive.
22231 As an example, assume that the register BND0 holds bounds for a pointer having
22232 access allowed for the range between 0x32 and 0x71. The values present on
22233 bnd0raw and bnd registers are presented as follows:
22236 bnd0raw = @{0x32, 0xffffffff8e@}
22237 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22240 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22241 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22242 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22243 Python, the display includes the memory size, in bits, accessible to
22246 Bounds can also be stored in bounds tables, which are stored in
22247 application memory. These tables store bounds for pointers by specifying
22248 the bounds pointer's value along with its bounds. Evaluating and changing
22249 bounds located in bound tables is therefore interesting while investigating
22250 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22253 @item show mpx bound @var{pointer}
22254 @kindex show mpx bound
22255 Display bounds of the given @var{pointer}.
22257 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22258 @kindex set mpx bound
22259 Set the bounds of a pointer in the bound table.
22260 This command takes three parameters: @var{pointer} is the pointers
22261 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22262 for lower and upper bounds respectively.
22268 See the following section.
22271 @subsection @acronym{MIPS}
22273 @cindex stack on Alpha
22274 @cindex stack on @acronym{MIPS}
22275 @cindex Alpha stack
22276 @cindex @acronym{MIPS} stack
22277 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22278 sometimes requires @value{GDBN} to search backward in the object code to
22279 find the beginning of a function.
22281 @cindex response time, @acronym{MIPS} debugging
22282 To improve response time (especially for embedded applications, where
22283 @value{GDBN} may be restricted to a slow serial line for this search)
22284 you may want to limit the size of this search, using one of these
22288 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22289 @item set heuristic-fence-post @var{limit}
22290 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22291 search for the beginning of a function. A value of @var{0} (the
22292 default) means there is no limit. However, except for @var{0}, the
22293 larger the limit the more bytes @code{heuristic-fence-post} must search
22294 and therefore the longer it takes to run. You should only need to use
22295 this command when debugging a stripped executable.
22297 @item show heuristic-fence-post
22298 Display the current limit.
22302 These commands are available @emph{only} when @value{GDBN} is configured
22303 for debugging programs on Alpha or @acronym{MIPS} processors.
22305 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22309 @item set mips abi @var{arg}
22310 @kindex set mips abi
22311 @cindex set ABI for @acronym{MIPS}
22312 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22313 values of @var{arg} are:
22317 The default ABI associated with the current binary (this is the
22327 @item show mips abi
22328 @kindex show mips abi
22329 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22331 @item set mips compression @var{arg}
22332 @kindex set mips compression
22333 @cindex code compression, @acronym{MIPS}
22334 Tell @value{GDBN} which @acronym{MIPS} compressed
22335 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22336 inferior. @value{GDBN} uses this for code disassembly and other
22337 internal interpretation purposes. This setting is only referred to
22338 when no executable has been associated with the debugging session or
22339 the executable does not provide information about the encoding it uses.
22340 Otherwise this setting is automatically updated from information
22341 provided by the executable.
22343 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22344 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22345 executables containing @acronym{MIPS16} code frequently are not
22346 identified as such.
22348 This setting is ``sticky''; that is, it retains its value across
22349 debugging sessions until reset either explicitly with this command or
22350 implicitly from an executable.
22352 The compiler and/or assembler typically add symbol table annotations to
22353 identify functions compiled for the @acronym{MIPS16} or
22354 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22355 are present, @value{GDBN} uses them in preference to the global
22356 compressed @acronym{ISA} encoding setting.
22358 @item show mips compression
22359 @kindex show mips compression
22360 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22361 @value{GDBN} to debug the inferior.
22364 @itemx show mipsfpu
22365 @xref{MIPS Embedded, set mipsfpu}.
22367 @item set mips mask-address @var{arg}
22368 @kindex set mips mask-address
22369 @cindex @acronym{MIPS} addresses, masking
22370 This command determines whether the most-significant 32 bits of 64-bit
22371 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22372 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22373 setting, which lets @value{GDBN} determine the correct value.
22375 @item show mips mask-address
22376 @kindex show mips mask-address
22377 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22380 @item set remote-mips64-transfers-32bit-regs
22381 @kindex set remote-mips64-transfers-32bit-regs
22382 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22383 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22384 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22385 and 64 bits for other registers, set this option to @samp{on}.
22387 @item show remote-mips64-transfers-32bit-regs
22388 @kindex show remote-mips64-transfers-32bit-regs
22389 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22391 @item set debug mips
22392 @kindex set debug mips
22393 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22394 target code in @value{GDBN}.
22396 @item show debug mips
22397 @kindex show debug mips
22398 Show the current setting of @acronym{MIPS} debugging messages.
22404 @cindex HPPA support
22406 When @value{GDBN} is debugging the HP PA architecture, it provides the
22407 following special commands:
22410 @item set debug hppa
22411 @kindex set debug hppa
22412 This command determines whether HPPA architecture-specific debugging
22413 messages are to be displayed.
22415 @item show debug hppa
22416 Show whether HPPA debugging messages are displayed.
22418 @item maint print unwind @var{address}
22419 @kindex maint print unwind@r{, HPPA}
22420 This command displays the contents of the unwind table entry at the
22421 given @var{address}.
22427 @subsection Cell Broadband Engine SPU architecture
22428 @cindex Cell Broadband Engine
22431 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22432 it provides the following special commands:
22435 @item info spu event
22437 Display SPU event facility status. Shows current event mask
22438 and pending event status.
22440 @item info spu signal
22441 Display SPU signal notification facility status. Shows pending
22442 signal-control word and signal notification mode of both signal
22443 notification channels.
22445 @item info spu mailbox
22446 Display SPU mailbox facility status. Shows all pending entries,
22447 in order of processing, in each of the SPU Write Outbound,
22448 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22451 Display MFC DMA status. Shows all pending commands in the MFC
22452 DMA queue. For each entry, opcode, tag, class IDs, effective
22453 and local store addresses and transfer size are shown.
22455 @item info spu proxydma
22456 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22457 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22458 and local store addresses and transfer size are shown.
22462 When @value{GDBN} is debugging a combined PowerPC/SPU application
22463 on the Cell Broadband Engine, it provides in addition the following
22467 @item set spu stop-on-load @var{arg}
22469 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22470 will give control to the user when a new SPE thread enters its @code{main}
22471 function. The default is @code{off}.
22473 @item show spu stop-on-load
22475 Show whether to stop for new SPE threads.
22477 @item set spu auto-flush-cache @var{arg}
22478 Set whether to automatically flush the software-managed cache. When set to
22479 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22480 cache to be flushed whenever SPE execution stops. This provides a consistent
22481 view of PowerPC memory that is accessed via the cache. If an application
22482 does not use the software-managed cache, this option has no effect.
22484 @item show spu auto-flush-cache
22485 Show whether to automatically flush the software-managed cache.
22490 @subsection PowerPC
22491 @cindex PowerPC architecture
22493 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22494 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22495 numbers stored in the floating point registers. These values must be stored
22496 in two consecutive registers, always starting at an even register like
22497 @code{f0} or @code{f2}.
22499 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22500 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22501 @code{f2} and @code{f3} for @code{$dl1} and so on.
22503 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22504 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22507 @subsection Nios II
22508 @cindex Nios II architecture
22510 When @value{GDBN} is debugging the Nios II architecture,
22511 it provides the following special commands:
22515 @item set debug nios2
22516 @kindex set debug nios2
22517 This command turns on and off debugging messages for the Nios II
22518 target code in @value{GDBN}.
22520 @item show debug nios2
22521 @kindex show debug nios2
22522 Show the current setting of Nios II debugging messages.
22525 @node Controlling GDB
22526 @chapter Controlling @value{GDBN}
22528 You can alter the way @value{GDBN} interacts with you by using the
22529 @code{set} command. For commands controlling how @value{GDBN} displays
22530 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22535 * Editing:: Command editing
22536 * Command History:: Command history
22537 * Screen Size:: Screen size
22538 * Numbers:: Numbers
22539 * ABI:: Configuring the current ABI
22540 * Auto-loading:: Automatically loading associated files
22541 * Messages/Warnings:: Optional warnings and messages
22542 * Debugging Output:: Optional messages about internal happenings
22543 * Other Misc Settings:: Other Miscellaneous Settings
22551 @value{GDBN} indicates its readiness to read a command by printing a string
22552 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22553 can change the prompt string with the @code{set prompt} command. For
22554 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22555 the prompt in one of the @value{GDBN} sessions so that you can always tell
22556 which one you are talking to.
22558 @emph{Note:} @code{set prompt} does not add a space for you after the
22559 prompt you set. This allows you to set a prompt which ends in a space
22560 or a prompt that does not.
22564 @item set prompt @var{newprompt}
22565 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22567 @kindex show prompt
22569 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22572 Versions of @value{GDBN} that ship with Python scripting enabled have
22573 prompt extensions. The commands for interacting with these extensions
22577 @kindex set extended-prompt
22578 @item set extended-prompt @var{prompt}
22579 Set an extended prompt that allows for substitutions.
22580 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22581 substitution. Any escape sequences specified as part of the prompt
22582 string are replaced with the corresponding strings each time the prompt
22588 set extended-prompt Current working directory: \w (gdb)
22591 Note that when an extended-prompt is set, it takes control of the
22592 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22594 @kindex show extended-prompt
22595 @item show extended-prompt
22596 Prints the extended prompt. Any escape sequences specified as part of
22597 the prompt string with @code{set extended-prompt}, are replaced with the
22598 corresponding strings each time the prompt is displayed.
22602 @section Command Editing
22604 @cindex command line editing
22606 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22607 @sc{gnu} library provides consistent behavior for programs which provide a
22608 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22609 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22610 substitution, and a storage and recall of command history across
22611 debugging sessions.
22613 You may control the behavior of command line editing in @value{GDBN} with the
22614 command @code{set}.
22617 @kindex set editing
22620 @itemx set editing on
22621 Enable command line editing (enabled by default).
22623 @item set editing off
22624 Disable command line editing.
22626 @kindex show editing
22628 Show whether command line editing is enabled.
22631 @ifset SYSTEM_READLINE
22632 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22634 @ifclear SYSTEM_READLINE
22635 @xref{Command Line Editing},
22637 for more details about the Readline
22638 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22639 encouraged to read that chapter.
22641 @node Command History
22642 @section Command History
22643 @cindex command history
22645 @value{GDBN} can keep track of the commands you type during your
22646 debugging sessions, so that you can be certain of precisely what
22647 happened. Use these commands to manage the @value{GDBN} command
22650 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22651 package, to provide the history facility.
22652 @ifset SYSTEM_READLINE
22653 @xref{Using History Interactively, , , history, GNU History Library},
22655 @ifclear SYSTEM_READLINE
22656 @xref{Using History Interactively},
22658 for the detailed description of the History library.
22660 To issue a command to @value{GDBN} without affecting certain aspects of
22661 the state which is seen by users, prefix it with @samp{server }
22662 (@pxref{Server Prefix}). This
22663 means that this command will not affect the command history, nor will it
22664 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22665 pressed on a line by itself.
22667 @cindex @code{server}, command prefix
22668 The server prefix does not affect the recording of values into the value
22669 history; to print a value without recording it into the value history,
22670 use the @code{output} command instead of the @code{print} command.
22672 Here is the description of @value{GDBN} commands related to command
22676 @cindex history substitution
22677 @cindex history file
22678 @kindex set history filename
22679 @cindex @env{GDBHISTFILE}, environment variable
22680 @item set history filename @var{fname}
22681 Set the name of the @value{GDBN} command history file to @var{fname}.
22682 This is the file where @value{GDBN} reads an initial command history
22683 list, and where it writes the command history from this session when it
22684 exits. You can access this list through history expansion or through
22685 the history command editing characters listed below. This file defaults
22686 to the value of the environment variable @code{GDBHISTFILE}, or to
22687 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22690 @cindex save command history
22691 @kindex set history save
22692 @item set history save
22693 @itemx set history save on
22694 Record command history in a file, whose name may be specified with the
22695 @code{set history filename} command. By default, this option is disabled.
22697 @item set history save off
22698 Stop recording command history in a file.
22700 @cindex history size
22701 @kindex set history size
22702 @cindex @env{GDBHISTSIZE}, environment variable
22703 @item set history size @var{size}
22704 @itemx set history size unlimited
22705 Set the number of commands which @value{GDBN} keeps in its history list.
22706 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22707 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22708 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22709 either a negative number or the empty string, then the number of commands
22710 @value{GDBN} keeps in the history list is unlimited.
22712 @cindex remove duplicate history
22713 @kindex set history remove-duplicates
22714 @item set history remove-duplicates @var{count}
22715 @itemx set history remove-duplicates unlimited
22716 Control the removal of duplicate history entries in the command history list.
22717 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22718 history entries and remove the first entry that is a duplicate of the current
22719 entry being added to the command history list. If @var{count} is
22720 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22721 removal of duplicate history entries is disabled.
22723 Only history entries added during the current session are considered for
22724 removal. This option is set to 0 by default.
22728 History expansion assigns special meaning to the character @kbd{!}.
22729 @ifset SYSTEM_READLINE
22730 @xref{Event Designators, , , history, GNU History Library},
22732 @ifclear SYSTEM_READLINE
22733 @xref{Event Designators},
22737 @cindex history expansion, turn on/off
22738 Since @kbd{!} is also the logical not operator in C, history expansion
22739 is off by default. If you decide to enable history expansion with the
22740 @code{set history expansion on} command, you may sometimes need to
22741 follow @kbd{!} (when it is used as logical not, in an expression) with
22742 a space or a tab to prevent it from being expanded. The readline
22743 history facilities do not attempt substitution on the strings
22744 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22746 The commands to control history expansion are:
22749 @item set history expansion on
22750 @itemx set history expansion
22751 @kindex set history expansion
22752 Enable history expansion. History expansion is off by default.
22754 @item set history expansion off
22755 Disable history expansion.
22758 @kindex show history
22760 @itemx show history filename
22761 @itemx show history save
22762 @itemx show history size
22763 @itemx show history expansion
22764 These commands display the state of the @value{GDBN} history parameters.
22765 @code{show history} by itself displays all four states.
22770 @kindex show commands
22771 @cindex show last commands
22772 @cindex display command history
22773 @item show commands
22774 Display the last ten commands in the command history.
22776 @item show commands @var{n}
22777 Print ten commands centered on command number @var{n}.
22779 @item show commands +
22780 Print ten commands just after the commands last printed.
22784 @section Screen Size
22785 @cindex size of screen
22786 @cindex screen size
22789 @cindex pauses in output
22791 Certain commands to @value{GDBN} may produce large amounts of
22792 information output to the screen. To help you read all of it,
22793 @value{GDBN} pauses and asks you for input at the end of each page of
22794 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22795 to discard the remaining output. Also, the screen width setting
22796 determines when to wrap lines of output. Depending on what is being
22797 printed, @value{GDBN} tries to break the line at a readable place,
22798 rather than simply letting it overflow onto the following line.
22800 Normally @value{GDBN} knows the size of the screen from the terminal
22801 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22802 together with the value of the @code{TERM} environment variable and the
22803 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22804 you can override it with the @code{set height} and @code{set
22811 @kindex show height
22812 @item set height @var{lpp}
22813 @itemx set height unlimited
22815 @itemx set width @var{cpl}
22816 @itemx set width unlimited
22818 These @code{set} commands specify a screen height of @var{lpp} lines and
22819 a screen width of @var{cpl} characters. The associated @code{show}
22820 commands display the current settings.
22822 If you specify a height of either @code{unlimited} or zero lines,
22823 @value{GDBN} does not pause during output no matter how long the
22824 output is. This is useful if output is to a file or to an editor
22827 Likewise, you can specify @samp{set width unlimited} or @samp{set
22828 width 0} to prevent @value{GDBN} from wrapping its output.
22830 @item set pagination on
22831 @itemx set pagination off
22832 @kindex set pagination
22833 Turn the output pagination on or off; the default is on. Turning
22834 pagination off is the alternative to @code{set height unlimited}. Note that
22835 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22836 Options, -batch}) also automatically disables pagination.
22838 @item show pagination
22839 @kindex show pagination
22840 Show the current pagination mode.
22845 @cindex number representation
22846 @cindex entering numbers
22848 You can always enter numbers in octal, decimal, or hexadecimal in
22849 @value{GDBN} by the usual conventions: octal numbers begin with
22850 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22851 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22852 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22853 10; likewise, the default display for numbers---when no particular
22854 format is specified---is base 10. You can change the default base for
22855 both input and output with the commands described below.
22858 @kindex set input-radix
22859 @item set input-radix @var{base}
22860 Set the default base for numeric input. Supported choices
22861 for @var{base} are decimal 8, 10, or 16. The base must itself be
22862 specified either unambiguously or using the current input radix; for
22866 set input-radix 012
22867 set input-radix 10.
22868 set input-radix 0xa
22872 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22873 leaves the input radix unchanged, no matter what it was, since
22874 @samp{10}, being without any leading or trailing signs of its base, is
22875 interpreted in the current radix. Thus, if the current radix is 16,
22876 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22879 @kindex set output-radix
22880 @item set output-radix @var{base}
22881 Set the default base for numeric display. Supported choices
22882 for @var{base} are decimal 8, 10, or 16. The base must itself be
22883 specified either unambiguously or using the current input radix.
22885 @kindex show input-radix
22886 @item show input-radix
22887 Display the current default base for numeric input.
22889 @kindex show output-radix
22890 @item show output-radix
22891 Display the current default base for numeric display.
22893 @item set radix @r{[}@var{base}@r{]}
22897 These commands set and show the default base for both input and output
22898 of numbers. @code{set radix} sets the radix of input and output to
22899 the same base; without an argument, it resets the radix back to its
22900 default value of 10.
22905 @section Configuring the Current ABI
22907 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22908 application automatically. However, sometimes you need to override its
22909 conclusions. Use these commands to manage @value{GDBN}'s view of the
22915 @cindex Newlib OS ABI and its influence on the longjmp handling
22917 One @value{GDBN} configuration can debug binaries for multiple operating
22918 system targets, either via remote debugging or native emulation.
22919 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22920 but you can override its conclusion using the @code{set osabi} command.
22921 One example where this is useful is in debugging of binaries which use
22922 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22923 not have the same identifying marks that the standard C library for your
22926 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22927 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22928 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22929 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22933 Show the OS ABI currently in use.
22936 With no argument, show the list of registered available OS ABI's.
22938 @item set osabi @var{abi}
22939 Set the current OS ABI to @var{abi}.
22942 @cindex float promotion
22944 Generally, the way that an argument of type @code{float} is passed to a
22945 function depends on whether the function is prototyped. For a prototyped
22946 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22947 according to the architecture's convention for @code{float}. For unprototyped
22948 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22949 @code{double} and then passed.
22951 Unfortunately, some forms of debug information do not reliably indicate whether
22952 a function is prototyped. If @value{GDBN} calls a function that is not marked
22953 as prototyped, it consults @kbd{set coerce-float-to-double}.
22956 @kindex set coerce-float-to-double
22957 @item set coerce-float-to-double
22958 @itemx set coerce-float-to-double on
22959 Arguments of type @code{float} will be promoted to @code{double} when passed
22960 to an unprototyped function. This is the default setting.
22962 @item set coerce-float-to-double off
22963 Arguments of type @code{float} will be passed directly to unprototyped
22966 @kindex show coerce-float-to-double
22967 @item show coerce-float-to-double
22968 Show the current setting of promoting @code{float} to @code{double}.
22972 @kindex show cp-abi
22973 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22974 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22975 used to build your application. @value{GDBN} only fully supports
22976 programs with a single C@t{++} ABI; if your program contains code using
22977 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22978 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22979 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22980 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22981 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22982 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22987 Show the C@t{++} ABI currently in use.
22990 With no argument, show the list of supported C@t{++} ABI's.
22992 @item set cp-abi @var{abi}
22993 @itemx set cp-abi auto
22994 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22998 @section Automatically loading associated files
22999 @cindex auto-loading
23001 @value{GDBN} sometimes reads files with commands and settings automatically,
23002 without being explicitly told so by the user. We call this feature
23003 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23004 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23005 results or introduce security risks (e.g., if the file comes from untrusted
23009 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23010 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23012 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23013 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23016 There are various kinds of files @value{GDBN} can automatically load.
23017 In addition to these files, @value{GDBN} supports auto-loading code written
23018 in various extension languages. @xref{Auto-loading extensions}.
23020 Note that loading of these associated files (including the local @file{.gdbinit}
23021 file) requires accordingly configured @code{auto-load safe-path}
23022 (@pxref{Auto-loading safe path}).
23024 For these reasons, @value{GDBN} includes commands and options to let you
23025 control when to auto-load files and which files should be auto-loaded.
23028 @anchor{set auto-load off}
23029 @kindex set auto-load off
23030 @item set auto-load off
23031 Globally disable loading of all auto-loaded files.
23032 You may want to use this command with the @samp{-iex} option
23033 (@pxref{Option -init-eval-command}) such as:
23035 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23038 Be aware that system init file (@pxref{System-wide configuration})
23039 and init files from your home directory (@pxref{Home Directory Init File})
23040 still get read (as they come from generally trusted directories).
23041 To prevent @value{GDBN} from auto-loading even those init files, use the
23042 @option{-nx} option (@pxref{Mode Options}), in addition to
23043 @code{set auto-load no}.
23045 @anchor{show auto-load}
23046 @kindex show auto-load
23047 @item show auto-load
23048 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23052 (gdb) show auto-load
23053 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23054 libthread-db: Auto-loading of inferior specific libthread_db is on.
23055 local-gdbinit: Auto-loading of .gdbinit script from current directory
23057 python-scripts: Auto-loading of Python scripts is on.
23058 safe-path: List of directories from which it is safe to auto-load files
23059 is $debugdir:$datadir/auto-load.
23060 scripts-directory: List of directories from which to load auto-loaded scripts
23061 is $debugdir:$datadir/auto-load.
23064 @anchor{info auto-load}
23065 @kindex info auto-load
23066 @item info auto-load
23067 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23071 (gdb) info auto-load
23074 Yes /home/user/gdb/gdb-gdb.gdb
23075 libthread-db: No auto-loaded libthread-db.
23076 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23080 Yes /home/user/gdb/gdb-gdb.py
23084 These are @value{GDBN} control commands for the auto-loading:
23086 @multitable @columnfractions .5 .5
23087 @item @xref{set auto-load off}.
23088 @tab Disable auto-loading globally.
23089 @item @xref{show auto-load}.
23090 @tab Show setting of all kinds of files.
23091 @item @xref{info auto-load}.
23092 @tab Show state of all kinds of files.
23093 @item @xref{set auto-load gdb-scripts}.
23094 @tab Control for @value{GDBN} command scripts.
23095 @item @xref{show auto-load gdb-scripts}.
23096 @tab Show setting of @value{GDBN} command scripts.
23097 @item @xref{info auto-load gdb-scripts}.
23098 @tab Show state of @value{GDBN} command scripts.
23099 @item @xref{set auto-load python-scripts}.
23100 @tab Control for @value{GDBN} Python scripts.
23101 @item @xref{show auto-load python-scripts}.
23102 @tab Show setting of @value{GDBN} Python scripts.
23103 @item @xref{info auto-load python-scripts}.
23104 @tab Show state of @value{GDBN} Python scripts.
23105 @item @xref{set auto-load guile-scripts}.
23106 @tab Control for @value{GDBN} Guile scripts.
23107 @item @xref{show auto-load guile-scripts}.
23108 @tab Show setting of @value{GDBN} Guile scripts.
23109 @item @xref{info auto-load guile-scripts}.
23110 @tab Show state of @value{GDBN} Guile scripts.
23111 @item @xref{set auto-load scripts-directory}.
23112 @tab Control for @value{GDBN} auto-loaded scripts location.
23113 @item @xref{show auto-load scripts-directory}.
23114 @tab Show @value{GDBN} auto-loaded scripts location.
23115 @item @xref{add-auto-load-scripts-directory}.
23116 @tab Add directory for auto-loaded scripts location list.
23117 @item @xref{set auto-load local-gdbinit}.
23118 @tab Control for init file in the current directory.
23119 @item @xref{show auto-load local-gdbinit}.
23120 @tab Show setting of init file in the current directory.
23121 @item @xref{info auto-load local-gdbinit}.
23122 @tab Show state of init file in the current directory.
23123 @item @xref{set auto-load libthread-db}.
23124 @tab Control for thread debugging library.
23125 @item @xref{show auto-load libthread-db}.
23126 @tab Show setting of thread debugging library.
23127 @item @xref{info auto-load libthread-db}.
23128 @tab Show state of thread debugging library.
23129 @item @xref{set auto-load safe-path}.
23130 @tab Control directories trusted for automatic loading.
23131 @item @xref{show auto-load safe-path}.
23132 @tab Show directories trusted for automatic loading.
23133 @item @xref{add-auto-load-safe-path}.
23134 @tab Add directory trusted for automatic loading.
23137 @node Init File in the Current Directory
23138 @subsection Automatically loading init file in the current directory
23139 @cindex auto-loading init file in the current directory
23141 By default, @value{GDBN} reads and executes the canned sequences of commands
23142 from init file (if any) in the current working directory,
23143 see @ref{Init File in the Current Directory during Startup}.
23145 Note that loading of this local @file{.gdbinit} file also requires accordingly
23146 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23149 @anchor{set auto-load local-gdbinit}
23150 @kindex set auto-load local-gdbinit
23151 @item set auto-load local-gdbinit [on|off]
23152 Enable or disable the auto-loading of canned sequences of commands
23153 (@pxref{Sequences}) found in init file in the current directory.
23155 @anchor{show auto-load local-gdbinit}
23156 @kindex show auto-load local-gdbinit
23157 @item show auto-load local-gdbinit
23158 Show whether auto-loading of canned sequences of commands from init file in the
23159 current directory is enabled or disabled.
23161 @anchor{info auto-load local-gdbinit}
23162 @kindex info auto-load local-gdbinit
23163 @item info auto-load local-gdbinit
23164 Print whether canned sequences of commands from init file in the
23165 current directory have been auto-loaded.
23168 @node libthread_db.so.1 file
23169 @subsection Automatically loading thread debugging library
23170 @cindex auto-loading libthread_db.so.1
23172 This feature is currently present only on @sc{gnu}/Linux native hosts.
23174 @value{GDBN} reads in some cases thread debugging library from places specific
23175 to the inferior (@pxref{set libthread-db-search-path}).
23177 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23178 without checking this @samp{set auto-load libthread-db} switch as system
23179 libraries have to be trusted in general. In all other cases of
23180 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23181 auto-load libthread-db} is enabled before trying to open such thread debugging
23184 Note that loading of this debugging library also requires accordingly configured
23185 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23188 @anchor{set auto-load libthread-db}
23189 @kindex set auto-load libthread-db
23190 @item set auto-load libthread-db [on|off]
23191 Enable or disable the auto-loading of inferior specific thread debugging library.
23193 @anchor{show auto-load libthread-db}
23194 @kindex show auto-load libthread-db
23195 @item show auto-load libthread-db
23196 Show whether auto-loading of inferior specific thread debugging library is
23197 enabled or disabled.
23199 @anchor{info auto-load libthread-db}
23200 @kindex info auto-load libthread-db
23201 @item info auto-load libthread-db
23202 Print the list of all loaded inferior specific thread debugging libraries and
23203 for each such library print list of inferior @var{pid}s using it.
23206 @node Auto-loading safe path
23207 @subsection Security restriction for auto-loading
23208 @cindex auto-loading safe-path
23210 As the files of inferior can come from untrusted source (such as submitted by
23211 an application user) @value{GDBN} does not always load any files automatically.
23212 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23213 directories trusted for loading files not explicitly requested by user.
23214 Each directory can also be a shell wildcard pattern.
23216 If the path is not set properly you will see a warning and the file will not
23221 Reading symbols from /home/user/gdb/gdb...done.
23222 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23223 declined by your `auto-load safe-path' set
23224 to "$debugdir:$datadir/auto-load".
23225 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23226 declined by your `auto-load safe-path' set
23227 to "$debugdir:$datadir/auto-load".
23231 To instruct @value{GDBN} to go ahead and use the init files anyway,
23232 invoke @value{GDBN} like this:
23235 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23238 The list of trusted directories is controlled by the following commands:
23241 @anchor{set auto-load safe-path}
23242 @kindex set auto-load safe-path
23243 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23244 Set the list of directories (and their subdirectories) trusted for automatic
23245 loading and execution of scripts. You can also enter a specific trusted file.
23246 Each directory can also be a shell wildcard pattern; wildcards do not match
23247 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23248 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23249 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23250 its default value as specified during @value{GDBN} compilation.
23252 The list of directories uses path separator (@samp{:} on GNU and Unix
23253 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23254 to the @env{PATH} environment variable.
23256 @anchor{show auto-load safe-path}
23257 @kindex show auto-load safe-path
23258 @item show auto-load safe-path
23259 Show the list of directories trusted for automatic loading and execution of
23262 @anchor{add-auto-load-safe-path}
23263 @kindex add-auto-load-safe-path
23264 @item add-auto-load-safe-path
23265 Add an entry (or list of entries) to the list of directories trusted for
23266 automatic loading and execution of scripts. Multiple entries may be delimited
23267 by the host platform path separator in use.
23270 This variable defaults to what @code{--with-auto-load-dir} has been configured
23271 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23272 substitution applies the same as for @ref{set auto-load scripts-directory}.
23273 The default @code{set auto-load safe-path} value can be also overriden by
23274 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23276 Setting this variable to @file{/} disables this security protection,
23277 corresponding @value{GDBN} configuration option is
23278 @option{--without-auto-load-safe-path}.
23279 This variable is supposed to be set to the system directories writable by the
23280 system superuser only. Users can add their source directories in init files in
23281 their home directories (@pxref{Home Directory Init File}). See also deprecated
23282 init file in the current directory
23283 (@pxref{Init File in the Current Directory during Startup}).
23285 To force @value{GDBN} to load the files it declined to load in the previous
23286 example, you could use one of the following ways:
23289 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23290 Specify this trusted directory (or a file) as additional component of the list.
23291 You have to specify also any existing directories displayed by
23292 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23294 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23295 Specify this directory as in the previous case but just for a single
23296 @value{GDBN} session.
23298 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23299 Disable auto-loading safety for a single @value{GDBN} session.
23300 This assumes all the files you debug during this @value{GDBN} session will come
23301 from trusted sources.
23303 @item @kbd{./configure --without-auto-load-safe-path}
23304 During compilation of @value{GDBN} you may disable any auto-loading safety.
23305 This assumes all the files you will ever debug with this @value{GDBN} come from
23309 On the other hand you can also explicitly forbid automatic files loading which
23310 also suppresses any such warning messages:
23313 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23314 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23316 @item @file{~/.gdbinit}: @samp{set auto-load no}
23317 Disable auto-loading globally for the user
23318 (@pxref{Home Directory Init File}). While it is improbable, you could also
23319 use system init file instead (@pxref{System-wide configuration}).
23322 This setting applies to the file names as entered by user. If no entry matches
23323 @value{GDBN} tries as a last resort to also resolve all the file names into
23324 their canonical form (typically resolving symbolic links) and compare the
23325 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23326 own before starting the comparison so a canonical form of directories is
23327 recommended to be entered.
23329 @node Auto-loading verbose mode
23330 @subsection Displaying files tried for auto-load
23331 @cindex auto-loading verbose mode
23333 For better visibility of all the file locations where you can place scripts to
23334 be auto-loaded with inferior --- or to protect yourself against accidental
23335 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23336 all the files attempted to be loaded. Both existing and non-existing files may
23339 For example the list of directories from which it is safe to auto-load files
23340 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23341 may not be too obvious while setting it up.
23344 (gdb) set debug auto-load on
23345 (gdb) file ~/src/t/true
23346 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23347 for objfile "/tmp/true".
23348 auto-load: Updating directories of "/usr:/opt".
23349 auto-load: Using directory "/usr".
23350 auto-load: Using directory "/opt".
23351 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23352 by your `auto-load safe-path' set to "/usr:/opt".
23356 @anchor{set debug auto-load}
23357 @kindex set debug auto-load
23358 @item set debug auto-load [on|off]
23359 Set whether to print the filenames attempted to be auto-loaded.
23361 @anchor{show debug auto-load}
23362 @kindex show debug auto-load
23363 @item show debug auto-load
23364 Show whether printing of the filenames attempted to be auto-loaded is turned
23368 @node Messages/Warnings
23369 @section Optional Warnings and Messages
23371 @cindex verbose operation
23372 @cindex optional warnings
23373 By default, @value{GDBN} is silent about its inner workings. If you are
23374 running on a slow machine, you may want to use the @code{set verbose}
23375 command. This makes @value{GDBN} tell you when it does a lengthy
23376 internal operation, so you will not think it has crashed.
23378 Currently, the messages controlled by @code{set verbose} are those
23379 which announce that the symbol table for a source file is being read;
23380 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23383 @kindex set verbose
23384 @item set verbose on
23385 Enables @value{GDBN} output of certain informational messages.
23387 @item set verbose off
23388 Disables @value{GDBN} output of certain informational messages.
23390 @kindex show verbose
23392 Displays whether @code{set verbose} is on or off.
23395 By default, if @value{GDBN} encounters bugs in the symbol table of an
23396 object file, it is silent; but if you are debugging a compiler, you may
23397 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23402 @kindex set complaints
23403 @item set complaints @var{limit}
23404 Permits @value{GDBN} to output @var{limit} complaints about each type of
23405 unusual symbols before becoming silent about the problem. Set
23406 @var{limit} to zero to suppress all complaints; set it to a large number
23407 to prevent complaints from being suppressed.
23409 @kindex show complaints
23410 @item show complaints
23411 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23415 @anchor{confirmation requests}
23416 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23417 lot of stupid questions to confirm certain commands. For example, if
23418 you try to run a program which is already running:
23422 The program being debugged has been started already.
23423 Start it from the beginning? (y or n)
23426 If you are willing to unflinchingly face the consequences of your own
23427 commands, you can disable this ``feature'':
23431 @kindex set confirm
23433 @cindex confirmation
23434 @cindex stupid questions
23435 @item set confirm off
23436 Disables confirmation requests. Note that running @value{GDBN} with
23437 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23438 automatically disables confirmation requests.
23440 @item set confirm on
23441 Enables confirmation requests (the default).
23443 @kindex show confirm
23445 Displays state of confirmation requests.
23449 @cindex command tracing
23450 If you need to debug user-defined commands or sourced files you may find it
23451 useful to enable @dfn{command tracing}. In this mode each command will be
23452 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23453 quantity denoting the call depth of each command.
23456 @kindex set trace-commands
23457 @cindex command scripts, debugging
23458 @item set trace-commands on
23459 Enable command tracing.
23460 @item set trace-commands off
23461 Disable command tracing.
23462 @item show trace-commands
23463 Display the current state of command tracing.
23466 @node Debugging Output
23467 @section Optional Messages about Internal Happenings
23468 @cindex optional debugging messages
23470 @value{GDBN} has commands that enable optional debugging messages from
23471 various @value{GDBN} subsystems; normally these commands are of
23472 interest to @value{GDBN} maintainers, or when reporting a bug. This
23473 section documents those commands.
23476 @kindex set exec-done-display
23477 @item set exec-done-display
23478 Turns on or off the notification of asynchronous commands'
23479 completion. When on, @value{GDBN} will print a message when an
23480 asynchronous command finishes its execution. The default is off.
23481 @kindex show exec-done-display
23482 @item show exec-done-display
23483 Displays the current setting of asynchronous command completion
23486 @cindex ARM AArch64
23487 @item set debug aarch64
23488 Turns on or off display of debugging messages related to ARM AArch64.
23489 The default is off.
23491 @item show debug aarch64
23492 Displays the current state of displaying debugging messages related to
23494 @cindex gdbarch debugging info
23495 @cindex architecture debugging info
23496 @item set debug arch
23497 Turns on or off display of gdbarch debugging info. The default is off
23498 @item show debug arch
23499 Displays the current state of displaying gdbarch debugging info.
23500 @item set debug aix-solib
23501 @cindex AIX shared library debugging
23502 Control display of debugging messages from the AIX shared library
23503 support module. The default is off.
23504 @item show debug aix-thread
23505 Show the current state of displaying AIX shared library debugging messages.
23506 @item set debug aix-thread
23507 @cindex AIX threads
23508 Display debugging messages about inner workings of the AIX thread
23510 @item show debug aix-thread
23511 Show the current state of AIX thread debugging info display.
23512 @item set debug check-physname
23514 Check the results of the ``physname'' computation. When reading DWARF
23515 debugging information for C@t{++}, @value{GDBN} attempts to compute
23516 each entity's name. @value{GDBN} can do this computation in two
23517 different ways, depending on exactly what information is present.
23518 When enabled, this setting causes @value{GDBN} to compute the names
23519 both ways and display any discrepancies.
23520 @item show debug check-physname
23521 Show the current state of ``physname'' checking.
23522 @item set debug coff-pe-read
23523 @cindex COFF/PE exported symbols
23524 Control display of debugging messages related to reading of COFF/PE
23525 exported symbols. The default is off.
23526 @item show debug coff-pe-read
23527 Displays the current state of displaying debugging messages related to
23528 reading of COFF/PE exported symbols.
23529 @item set debug dwarf-die
23531 Dump DWARF DIEs after they are read in.
23532 The value is the number of nesting levels to print.
23533 A value of zero turns off the display.
23534 @item show debug dwarf-die
23535 Show the current state of DWARF DIE debugging.
23536 @item set debug dwarf-line
23537 @cindex DWARF Line Tables
23538 Turns on or off display of debugging messages related to reading
23539 DWARF line tables. The default is 0 (off).
23540 A value of 1 provides basic information.
23541 A value greater than 1 provides more verbose information.
23542 @item show debug dwarf-line
23543 Show the current state of DWARF line table debugging.
23544 @item set debug dwarf-read
23545 @cindex DWARF Reading
23546 Turns on or off display of debugging messages related to reading
23547 DWARF debug info. The default is 0 (off).
23548 A value of 1 provides basic information.
23549 A value greater than 1 provides more verbose information.
23550 @item show debug dwarf-read
23551 Show the current state of DWARF reader debugging.
23552 @item set debug displaced
23553 @cindex displaced stepping debugging info
23554 Turns on or off display of @value{GDBN} debugging info for the
23555 displaced stepping support. The default is off.
23556 @item show debug displaced
23557 Displays the current state of displaying @value{GDBN} debugging info
23558 related to displaced stepping.
23559 @item set debug event
23560 @cindex event debugging info
23561 Turns on or off display of @value{GDBN} event debugging info. The
23563 @item show debug event
23564 Displays the current state of displaying @value{GDBN} event debugging
23566 @item set debug expression
23567 @cindex expression debugging info
23568 Turns on or off display of debugging info about @value{GDBN}
23569 expression parsing. The default is off.
23570 @item show debug expression
23571 Displays the current state of displaying debugging info about
23572 @value{GDBN} expression parsing.
23573 @item set debug frame
23574 @cindex frame debugging info
23575 Turns on or off display of @value{GDBN} frame debugging info. The
23577 @item show debug frame
23578 Displays the current state of displaying @value{GDBN} frame debugging
23580 @item set debug gnu-nat
23581 @cindex @sc{gnu}/Hurd debug messages
23582 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23583 @item show debug gnu-nat
23584 Show the current state of @sc{gnu}/Hurd debugging messages.
23585 @item set debug infrun
23586 @cindex inferior debugging info
23587 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23588 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23589 for implementing operations such as single-stepping the inferior.
23590 @item show debug infrun
23591 Displays the current state of @value{GDBN} inferior debugging.
23592 @item set debug jit
23593 @cindex just-in-time compilation, debugging messages
23594 Turns on or off debugging messages from JIT debug support.
23595 @item show debug jit
23596 Displays the current state of @value{GDBN} JIT debugging.
23597 @item set debug lin-lwp
23598 @cindex @sc{gnu}/Linux LWP debug messages
23599 @cindex Linux lightweight processes
23600 Turns on or off debugging messages from the Linux LWP debug support.
23601 @item show debug lin-lwp
23602 Show the current state of Linux LWP debugging messages.
23603 @item set debug linux-namespaces
23604 @cindex @sc{gnu}/Linux namespaces debug messages
23605 Turns on or off debugging messages from the Linux namespaces debug support.
23606 @item show debug linux-namespaces
23607 Show the current state of Linux namespaces debugging messages.
23608 @item set debug mach-o
23609 @cindex Mach-O symbols processing
23610 Control display of debugging messages related to Mach-O symbols
23611 processing. The default is off.
23612 @item show debug mach-o
23613 Displays the current state of displaying debugging messages related to
23614 reading of COFF/PE exported symbols.
23615 @item set debug notification
23616 @cindex remote async notification debugging info
23617 Turns on or off debugging messages about remote async notification.
23618 The default is off.
23619 @item show debug notification
23620 Displays the current state of remote async notification debugging messages.
23621 @item set debug observer
23622 @cindex observer debugging info
23623 Turns on or off display of @value{GDBN} observer debugging. This
23624 includes info such as the notification of observable events.
23625 @item show debug observer
23626 Displays the current state of observer debugging.
23627 @item set debug overload
23628 @cindex C@t{++} overload debugging info
23629 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23630 info. This includes info such as ranking of functions, etc. The default
23632 @item show debug overload
23633 Displays the current state of displaying @value{GDBN} C@t{++} overload
23635 @cindex expression parser, debugging info
23636 @cindex debug expression parser
23637 @item set debug parser
23638 Turns on or off the display of expression parser debugging output.
23639 Internally, this sets the @code{yydebug} variable in the expression
23640 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23641 details. The default is off.
23642 @item show debug parser
23643 Show the current state of expression parser debugging.
23644 @cindex packets, reporting on stdout
23645 @cindex serial connections, debugging
23646 @cindex debug remote protocol
23647 @cindex remote protocol debugging
23648 @cindex display remote packets
23649 @item set debug remote
23650 Turns on or off display of reports on all packets sent back and forth across
23651 the serial line to the remote machine. The info is printed on the
23652 @value{GDBN} standard output stream. The default is off.
23653 @item show debug remote
23654 Displays the state of display of remote packets.
23655 @item set debug serial
23656 Turns on or off display of @value{GDBN} serial debugging info. The
23658 @item show debug serial
23659 Displays the current state of displaying @value{GDBN} serial debugging
23661 @item set debug solib-frv
23662 @cindex FR-V shared-library debugging
23663 Turns on or off debugging messages for FR-V shared-library code.
23664 @item show debug solib-frv
23665 Display the current state of FR-V shared-library code debugging
23667 @item set debug symbol-lookup
23668 @cindex symbol lookup
23669 Turns on or off display of debugging messages related to symbol lookup.
23670 The default is 0 (off).
23671 A value of 1 provides basic information.
23672 A value greater than 1 provides more verbose information.
23673 @item show debug symbol-lookup
23674 Show the current state of symbol lookup debugging messages.
23675 @item set debug symfile
23676 @cindex symbol file functions
23677 Turns on or off display of debugging messages related to symbol file functions.
23678 The default is off. @xref{Files}.
23679 @item show debug symfile
23680 Show the current state of symbol file debugging messages.
23681 @item set debug symtab-create
23682 @cindex symbol table creation
23683 Turns on or off display of debugging messages related to symbol table creation.
23684 The default is 0 (off).
23685 A value of 1 provides basic information.
23686 A value greater than 1 provides more verbose information.
23687 @item show debug symtab-create
23688 Show the current state of symbol table creation debugging.
23689 @item set debug target
23690 @cindex target debugging info
23691 Turns on or off display of @value{GDBN} target debugging info. This info
23692 includes what is going on at the target level of GDB, as it happens. The
23693 default is 0. Set it to 1 to track events, and to 2 to also track the
23694 value of large memory transfers.
23695 @item show debug target
23696 Displays the current state of displaying @value{GDBN} target debugging
23698 @item set debug timestamp
23699 @cindex timestampping debugging info
23700 Turns on or off display of timestamps with @value{GDBN} debugging info.
23701 When enabled, seconds and microseconds are displayed before each debugging
23703 @item show debug timestamp
23704 Displays the current state of displaying timestamps with @value{GDBN}
23706 @item set debug varobj
23707 @cindex variable object debugging info
23708 Turns on or off display of @value{GDBN} variable object debugging
23709 info. The default is off.
23710 @item show debug varobj
23711 Displays the current state of displaying @value{GDBN} variable object
23713 @item set debug xml
23714 @cindex XML parser debugging
23715 Turns on or off debugging messages for built-in XML parsers.
23716 @item show debug xml
23717 Displays the current state of XML debugging messages.
23720 @node Other Misc Settings
23721 @section Other Miscellaneous Settings
23722 @cindex miscellaneous settings
23725 @kindex set interactive-mode
23726 @item set interactive-mode
23727 If @code{on}, forces @value{GDBN} to assume that GDB was started
23728 in a terminal. In practice, this means that @value{GDBN} should wait
23729 for the user to answer queries generated by commands entered at
23730 the command prompt. If @code{off}, forces @value{GDBN} to operate
23731 in the opposite mode, and it uses the default answers to all queries.
23732 If @code{auto} (the default), @value{GDBN} tries to determine whether
23733 its standard input is a terminal, and works in interactive-mode if it
23734 is, non-interactively otherwise.
23736 In the vast majority of cases, the debugger should be able to guess
23737 correctly which mode should be used. But this setting can be useful
23738 in certain specific cases, such as running a MinGW @value{GDBN}
23739 inside a cygwin window.
23741 @kindex show interactive-mode
23742 @item show interactive-mode
23743 Displays whether the debugger is operating in interactive mode or not.
23746 @node Extending GDB
23747 @chapter Extending @value{GDBN}
23748 @cindex extending GDB
23750 @value{GDBN} provides several mechanisms for extension.
23751 @value{GDBN} also provides the ability to automatically load
23752 extensions when it reads a file for debugging. This allows the
23753 user to automatically customize @value{GDBN} for the program
23757 * Sequences:: Canned Sequences of @value{GDBN} Commands
23758 * Python:: Extending @value{GDBN} using Python
23759 * Guile:: Extending @value{GDBN} using Guile
23760 * Auto-loading extensions:: Automatically loading extensions
23761 * Multiple Extension Languages:: Working with multiple extension languages
23762 * Aliases:: Creating new spellings of existing commands
23765 To facilitate the use of extension languages, @value{GDBN} is capable
23766 of evaluating the contents of a file. When doing so, @value{GDBN}
23767 can recognize which extension language is being used by looking at
23768 the filename extension. Files with an unrecognized filename extension
23769 are always treated as a @value{GDBN} Command Files.
23770 @xref{Command Files,, Command files}.
23772 You can control how @value{GDBN} evaluates these files with the following
23776 @kindex set script-extension
23777 @kindex show script-extension
23778 @item set script-extension off
23779 All scripts are always evaluated as @value{GDBN} Command Files.
23781 @item set script-extension soft
23782 The debugger determines the scripting language based on filename
23783 extension. If this scripting language is supported, @value{GDBN}
23784 evaluates the script using that language. Otherwise, it evaluates
23785 the file as a @value{GDBN} Command File.
23787 @item set script-extension strict
23788 The debugger determines the scripting language based on filename
23789 extension, and evaluates the script using that language. If the
23790 language is not supported, then the evaluation fails.
23792 @item show script-extension
23793 Display the current value of the @code{script-extension} option.
23798 @section Canned Sequences of Commands
23800 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23801 Command Lists}), @value{GDBN} provides two ways to store sequences of
23802 commands for execution as a unit: user-defined commands and command
23806 * Define:: How to define your own commands
23807 * Hooks:: Hooks for user-defined commands
23808 * Command Files:: How to write scripts of commands to be stored in a file
23809 * Output:: Commands for controlled output
23810 * Auto-loading sequences:: Controlling auto-loaded command files
23814 @subsection User-defined Commands
23816 @cindex user-defined command
23817 @cindex arguments, to user-defined commands
23818 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23819 which you assign a new name as a command. This is done with the
23820 @code{define} command. User commands may accept up to 10 arguments
23821 separated by whitespace. Arguments are accessed within the user command
23822 via @code{$arg0@dots{}$arg9}. A trivial example:
23826 print $arg0 + $arg1 + $arg2
23831 To execute the command use:
23838 This defines the command @code{adder}, which prints the sum of
23839 its three arguments. Note the arguments are text substitutions, so they may
23840 reference variables, use complex expressions, or even perform inferior
23843 @cindex argument count in user-defined commands
23844 @cindex how many arguments (user-defined commands)
23845 In addition, @code{$argc} may be used to find out how many arguments have
23846 been passed. This expands to a number in the range 0@dots{}10.
23851 print $arg0 + $arg1
23854 print $arg0 + $arg1 + $arg2
23862 @item define @var{commandname}
23863 Define a command named @var{commandname}. If there is already a command
23864 by that name, you are asked to confirm that you want to redefine it.
23865 The argument @var{commandname} may be a bare command name consisting of letters,
23866 numbers, dashes, and underscores. It may also start with any predefined
23867 prefix command. For example, @samp{define target my-target} creates
23868 a user-defined @samp{target my-target} command.
23870 The definition of the command is made up of other @value{GDBN} command lines,
23871 which are given following the @code{define} command. The end of these
23872 commands is marked by a line containing @code{end}.
23875 @kindex end@r{ (user-defined commands)}
23876 @item document @var{commandname}
23877 Document the user-defined command @var{commandname}, so that it can be
23878 accessed by @code{help}. The command @var{commandname} must already be
23879 defined. This command reads lines of documentation just as @code{define}
23880 reads the lines of the command definition, ending with @code{end}.
23881 After the @code{document} command is finished, @code{help} on command
23882 @var{commandname} displays the documentation you have written.
23884 You may use the @code{document} command again to change the
23885 documentation of a command. Redefining the command with @code{define}
23886 does not change the documentation.
23888 @kindex dont-repeat
23889 @cindex don't repeat command
23891 Used inside a user-defined command, this tells @value{GDBN} that this
23892 command should not be repeated when the user hits @key{RET}
23893 (@pxref{Command Syntax, repeat last command}).
23895 @kindex help user-defined
23896 @item help user-defined
23897 List all user-defined commands and all python commands defined in class
23898 COMAND_USER. The first line of the documentation or docstring is
23903 @itemx show user @var{commandname}
23904 Display the @value{GDBN} commands used to define @var{commandname} (but
23905 not its documentation). If no @var{commandname} is given, display the
23906 definitions for all user-defined commands.
23907 This does not work for user-defined python commands.
23909 @cindex infinite recursion in user-defined commands
23910 @kindex show max-user-call-depth
23911 @kindex set max-user-call-depth
23912 @item show max-user-call-depth
23913 @itemx set max-user-call-depth
23914 The value of @code{max-user-call-depth} controls how many recursion
23915 levels are allowed in user-defined commands before @value{GDBN} suspects an
23916 infinite recursion and aborts the command.
23917 This does not apply to user-defined python commands.
23920 In addition to the above commands, user-defined commands frequently
23921 use control flow commands, described in @ref{Command Files}.
23923 When user-defined commands are executed, the
23924 commands of the definition are not printed. An error in any command
23925 stops execution of the user-defined command.
23927 If used interactively, commands that would ask for confirmation proceed
23928 without asking when used inside a user-defined command. Many @value{GDBN}
23929 commands that normally print messages to say what they are doing omit the
23930 messages when used in a user-defined command.
23933 @subsection User-defined Command Hooks
23934 @cindex command hooks
23935 @cindex hooks, for commands
23936 @cindex hooks, pre-command
23939 You may define @dfn{hooks}, which are a special kind of user-defined
23940 command. Whenever you run the command @samp{foo}, if the user-defined
23941 command @samp{hook-foo} exists, it is executed (with no arguments)
23942 before that command.
23944 @cindex hooks, post-command
23946 A hook may also be defined which is run after the command you executed.
23947 Whenever you run the command @samp{foo}, if the user-defined command
23948 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23949 that command. Post-execution hooks may exist simultaneously with
23950 pre-execution hooks, for the same command.
23952 It is valid for a hook to call the command which it hooks. If this
23953 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23955 @c It would be nice if hookpost could be passed a parameter indicating
23956 @c if the command it hooks executed properly or not. FIXME!
23958 @kindex stop@r{, a pseudo-command}
23959 In addition, a pseudo-command, @samp{stop} exists. Defining
23960 (@samp{hook-stop}) makes the associated commands execute every time
23961 execution stops in your program: before breakpoint commands are run,
23962 displays are printed, or the stack frame is printed.
23964 For example, to ignore @code{SIGALRM} signals while
23965 single-stepping, but treat them normally during normal execution,
23970 handle SIGALRM nopass
23974 handle SIGALRM pass
23977 define hook-continue
23978 handle SIGALRM pass
23982 As a further example, to hook at the beginning and end of the @code{echo}
23983 command, and to add extra text to the beginning and end of the message,
23991 define hookpost-echo
23995 (@value{GDBP}) echo Hello World
23996 <<<---Hello World--->>>
24001 You can define a hook for any single-word command in @value{GDBN}, but
24002 not for command aliases; you should define a hook for the basic command
24003 name, e.g.@: @code{backtrace} rather than @code{bt}.
24004 @c FIXME! So how does Joe User discover whether a command is an alias
24006 You can hook a multi-word command by adding @code{hook-} or
24007 @code{hookpost-} to the last word of the command, e.g.@:
24008 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24010 If an error occurs during the execution of your hook, execution of
24011 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24012 (before the command that you actually typed had a chance to run).
24014 If you try to define a hook which does not match any known command, you
24015 get a warning from the @code{define} command.
24017 @node Command Files
24018 @subsection Command Files
24020 @cindex command files
24021 @cindex scripting commands
24022 A command file for @value{GDBN} is a text file made of lines that are
24023 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24024 also be included. An empty line in a command file does nothing; it
24025 does not mean to repeat the last command, as it would from the
24028 You can request the execution of a command file with the @code{source}
24029 command. Note that the @code{source} command is also used to evaluate
24030 scripts that are not Command Files. The exact behavior can be configured
24031 using the @code{script-extension} setting.
24032 @xref{Extending GDB,, Extending GDB}.
24036 @cindex execute commands from a file
24037 @item source [-s] [-v] @var{filename}
24038 Execute the command file @var{filename}.
24041 The lines in a command file are generally executed sequentially,
24042 unless the order of execution is changed by one of the
24043 @emph{flow-control commands} described below. The commands are not
24044 printed as they are executed. An error in any command terminates
24045 execution of the command file and control is returned to the console.
24047 @value{GDBN} first searches for @var{filename} in the current directory.
24048 If the file is not found there, and @var{filename} does not specify a
24049 directory, then @value{GDBN} also looks for the file on the source search path
24050 (specified with the @samp{directory} command);
24051 except that @file{$cdir} is not searched because the compilation directory
24052 is not relevant to scripts.
24054 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24055 on the search path even if @var{filename} specifies a directory.
24056 The search is done by appending @var{filename} to each element of the
24057 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24058 and the search path contains @file{/home/user} then @value{GDBN} will
24059 look for the script @file{/home/user/mylib/myscript}.
24060 The search is also done if @var{filename} is an absolute path.
24061 For example, if @var{filename} is @file{/tmp/myscript} and
24062 the search path contains @file{/home/user} then @value{GDBN} will
24063 look for the script @file{/home/user/tmp/myscript}.
24064 For DOS-like systems, if @var{filename} contains a drive specification,
24065 it is stripped before concatenation. For example, if @var{filename} is
24066 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24067 will look for the script @file{c:/tmp/myscript}.
24069 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24070 each command as it is executed. The option must be given before
24071 @var{filename}, and is interpreted as part of the filename anywhere else.
24073 Commands that would ask for confirmation if used interactively proceed
24074 without asking when used in a command file. Many @value{GDBN} commands that
24075 normally print messages to say what they are doing omit the messages
24076 when called from command files.
24078 @value{GDBN} also accepts command input from standard input. In this
24079 mode, normal output goes to standard output and error output goes to
24080 standard error. Errors in a command file supplied on standard input do
24081 not terminate execution of the command file---execution continues with
24085 gdb < cmds > log 2>&1
24088 (The syntax above will vary depending on the shell used.) This example
24089 will execute commands from the file @file{cmds}. All output and errors
24090 would be directed to @file{log}.
24092 Since commands stored on command files tend to be more general than
24093 commands typed interactively, they frequently need to deal with
24094 complicated situations, such as different or unexpected values of
24095 variables and symbols, changes in how the program being debugged is
24096 built, etc. @value{GDBN} provides a set of flow-control commands to
24097 deal with these complexities. Using these commands, you can write
24098 complex scripts that loop over data structures, execute commands
24099 conditionally, etc.
24106 This command allows to include in your script conditionally executed
24107 commands. The @code{if} command takes a single argument, which is an
24108 expression to evaluate. It is followed by a series of commands that
24109 are executed only if the expression is true (its value is nonzero).
24110 There can then optionally be an @code{else} line, followed by a series
24111 of commands that are only executed if the expression was false. The
24112 end of the list is marked by a line containing @code{end}.
24116 This command allows to write loops. Its syntax is similar to
24117 @code{if}: the command takes a single argument, which is an expression
24118 to evaluate, and must be followed by the commands to execute, one per
24119 line, terminated by an @code{end}. These commands are called the
24120 @dfn{body} of the loop. The commands in the body of @code{while} are
24121 executed repeatedly as long as the expression evaluates to true.
24125 This command exits the @code{while} loop in whose body it is included.
24126 Execution of the script continues after that @code{while}s @code{end}
24129 @kindex loop_continue
24130 @item loop_continue
24131 This command skips the execution of the rest of the body of commands
24132 in the @code{while} loop in whose body it is included. Execution
24133 branches to the beginning of the @code{while} loop, where it evaluates
24134 the controlling expression.
24136 @kindex end@r{ (if/else/while commands)}
24138 Terminate the block of commands that are the body of @code{if},
24139 @code{else}, or @code{while} flow-control commands.
24144 @subsection Commands for Controlled Output
24146 During the execution of a command file or a user-defined command, normal
24147 @value{GDBN} output is suppressed; the only output that appears is what is
24148 explicitly printed by the commands in the definition. This section
24149 describes three commands useful for generating exactly the output you
24154 @item echo @var{text}
24155 @c I do not consider backslash-space a standard C escape sequence
24156 @c because it is not in ANSI.
24157 Print @var{text}. Nonprinting characters can be included in
24158 @var{text} using C escape sequences, such as @samp{\n} to print a
24159 newline. @strong{No newline is printed unless you specify one.}
24160 In addition to the standard C escape sequences, a backslash followed
24161 by a space stands for a space. This is useful for displaying a
24162 string with spaces at the beginning or the end, since leading and
24163 trailing spaces are otherwise trimmed from all arguments.
24164 To print @samp{@w{ }and foo =@w{ }}, use the command
24165 @samp{echo \@w{ }and foo = \@w{ }}.
24167 A backslash at the end of @var{text} can be used, as in C, to continue
24168 the command onto subsequent lines. For example,
24171 echo This is some text\n\
24172 which is continued\n\
24173 onto several lines.\n
24176 produces the same output as
24179 echo This is some text\n
24180 echo which is continued\n
24181 echo onto several lines.\n
24185 @item output @var{expression}
24186 Print the value of @var{expression} and nothing but that value: no
24187 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24188 value history either. @xref{Expressions, ,Expressions}, for more information
24191 @item output/@var{fmt} @var{expression}
24192 Print the value of @var{expression} in format @var{fmt}. You can use
24193 the same formats as for @code{print}. @xref{Output Formats,,Output
24194 Formats}, for more information.
24197 @item printf @var{template}, @var{expressions}@dots{}
24198 Print the values of one or more @var{expressions} under the control of
24199 the string @var{template}. To print several values, make
24200 @var{expressions} be a comma-separated list of individual expressions,
24201 which may be either numbers or pointers. Their values are printed as
24202 specified by @var{template}, exactly as a C program would do by
24203 executing the code below:
24206 printf (@var{template}, @var{expressions}@dots{});
24209 As in @code{C} @code{printf}, ordinary characters in @var{template}
24210 are printed verbatim, while @dfn{conversion specification} introduced
24211 by the @samp{%} character cause subsequent @var{expressions} to be
24212 evaluated, their values converted and formatted according to type and
24213 style information encoded in the conversion specifications, and then
24216 For example, you can print two values in hex like this:
24219 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24222 @code{printf} supports all the standard @code{C} conversion
24223 specifications, including the flags and modifiers between the @samp{%}
24224 character and the conversion letter, with the following exceptions:
24228 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24231 The modifier @samp{*} is not supported for specifying precision or
24235 The @samp{'} flag (for separation of digits into groups according to
24236 @code{LC_NUMERIC'}) is not supported.
24239 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24243 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24246 The conversion letters @samp{a} and @samp{A} are not supported.
24250 Note that the @samp{ll} type modifier is supported only if the
24251 underlying @code{C} implementation used to build @value{GDBN} supports
24252 the @code{long long int} type, and the @samp{L} type modifier is
24253 supported only if @code{long double} type is available.
24255 As in @code{C}, @code{printf} supports simple backslash-escape
24256 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24257 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24258 single character. Octal and hexadecimal escape sequences are not
24261 Additionally, @code{printf} supports conversion specifications for DFP
24262 (@dfn{Decimal Floating Point}) types using the following length modifiers
24263 together with a floating point specifier.
24268 @samp{H} for printing @code{Decimal32} types.
24271 @samp{D} for printing @code{Decimal64} types.
24274 @samp{DD} for printing @code{Decimal128} types.
24277 If the underlying @code{C} implementation used to build @value{GDBN} has
24278 support for the three length modifiers for DFP types, other modifiers
24279 such as width and precision will also be available for @value{GDBN} to use.
24281 In case there is no such @code{C} support, no additional modifiers will be
24282 available and the value will be printed in the standard way.
24284 Here's an example of printing DFP types using the above conversion letters:
24286 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24290 @item eval @var{template}, @var{expressions}@dots{}
24291 Convert the values of one or more @var{expressions} under the control of
24292 the string @var{template} to a command line, and call it.
24296 @node Auto-loading sequences
24297 @subsection Controlling auto-loading native @value{GDBN} scripts
24298 @cindex native script auto-loading
24300 When a new object file is read (for example, due to the @code{file}
24301 command, or because the inferior has loaded a shared library),
24302 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24303 @xref{Auto-loading extensions}.
24305 Auto-loading can be enabled or disabled,
24306 and the list of auto-loaded scripts can be printed.
24309 @anchor{set auto-load gdb-scripts}
24310 @kindex set auto-load gdb-scripts
24311 @item set auto-load gdb-scripts [on|off]
24312 Enable or disable the auto-loading of canned sequences of commands scripts.
24314 @anchor{show auto-load gdb-scripts}
24315 @kindex show auto-load gdb-scripts
24316 @item show auto-load gdb-scripts
24317 Show whether auto-loading of canned sequences of commands scripts is enabled or
24320 @anchor{info auto-load gdb-scripts}
24321 @kindex info auto-load gdb-scripts
24322 @cindex print list of auto-loaded canned sequences of commands scripts
24323 @item info auto-load gdb-scripts [@var{regexp}]
24324 Print the list of all canned sequences of commands scripts that @value{GDBN}
24328 If @var{regexp} is supplied only canned sequences of commands scripts with
24329 matching names are printed.
24331 @c Python docs live in a separate file.
24332 @include python.texi
24334 @c Guile docs live in a separate file.
24335 @include guile.texi
24337 @node Auto-loading extensions
24338 @section Auto-loading extensions
24339 @cindex auto-loading extensions
24341 @value{GDBN} provides two mechanisms for automatically loading extensions
24342 when a new object file is read (for example, due to the @code{file}
24343 command, or because the inferior has loaded a shared library):
24344 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24345 section of modern file formats like ELF.
24348 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24349 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24350 * Which flavor to choose?::
24353 The auto-loading feature is useful for supplying application-specific
24354 debugging commands and features.
24356 Auto-loading can be enabled or disabled,
24357 and the list of auto-loaded scripts can be printed.
24358 See the @samp{auto-loading} section of each extension language
24359 for more information.
24360 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24361 For Python files see @ref{Python Auto-loading}.
24363 Note that loading of this script file also requires accordingly configured
24364 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24366 @node objfile-gdbdotext file
24367 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24368 @cindex @file{@var{objfile}-gdb.gdb}
24369 @cindex @file{@var{objfile}-gdb.py}
24370 @cindex @file{@var{objfile}-gdb.scm}
24372 When a new object file is read, @value{GDBN} looks for a file named
24373 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24374 where @var{objfile} is the object file's name and
24375 where @var{ext} is the file extension for the extension language:
24378 @item @file{@var{objfile}-gdb.gdb}
24379 GDB's own command language
24380 @item @file{@var{objfile}-gdb.py}
24382 @item @file{@var{objfile}-gdb.scm}
24386 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24387 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24388 components, and appending the @file{-gdb.@var{ext}} suffix.
24389 If this file exists and is readable, @value{GDBN} will evaluate it as a
24390 script in the specified extension language.
24392 If this file does not exist, then @value{GDBN} will look for
24393 @var{script-name} file in all of the directories as specified below.
24395 Note that loading of these files requires an accordingly configured
24396 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24398 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24399 scripts normally according to its @file{.exe} filename. But if no scripts are
24400 found @value{GDBN} also tries script filenames matching the object file without
24401 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24402 is attempted on any platform. This makes the script filenames compatible
24403 between Unix and MS-Windows hosts.
24406 @anchor{set auto-load scripts-directory}
24407 @kindex set auto-load scripts-directory
24408 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24409 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24410 may be delimited by the host platform path separator in use
24411 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24413 Each entry here needs to be covered also by the security setting
24414 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24416 @anchor{with-auto-load-dir}
24417 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24418 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24419 configuration option @option{--with-auto-load-dir}.
24421 Any reference to @file{$debugdir} will get replaced by
24422 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24423 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24424 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24425 @file{$datadir} must be placed as a directory component --- either alone or
24426 delimited by @file{/} or @file{\} directory separators, depending on the host
24429 The list of directories uses path separator (@samp{:} on GNU and Unix
24430 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24431 to the @env{PATH} environment variable.
24433 @anchor{show auto-load scripts-directory}
24434 @kindex show auto-load scripts-directory
24435 @item show auto-load scripts-directory
24436 Show @value{GDBN} auto-loaded scripts location.
24438 @anchor{add-auto-load-scripts-directory}
24439 @kindex add-auto-load-scripts-directory
24440 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24441 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24442 Multiple entries may be delimited by the host platform path separator in use.
24445 @value{GDBN} does not track which files it has already auto-loaded this way.
24446 @value{GDBN} will load the associated script every time the corresponding
24447 @var{objfile} is opened.
24448 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24449 is evaluated more than once.
24451 @node dotdebug_gdb_scripts section
24452 @subsection The @code{.debug_gdb_scripts} section
24453 @cindex @code{.debug_gdb_scripts} section
24455 For systems using file formats like ELF and COFF,
24456 when @value{GDBN} loads a new object file
24457 it will look for a special section named @code{.debug_gdb_scripts}.
24458 If this section exists, its contents is a list of null-terminated entries
24459 specifying scripts to load. Each entry begins with a non-null prefix byte that
24460 specifies the kind of entry, typically the extension language and whether the
24461 script is in a file or inlined in @code{.debug_gdb_scripts}.
24463 The following entries are supported:
24466 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24467 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24468 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24469 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24472 @subsubsection Script File Entries
24474 If the entry specifies a file, @value{GDBN} will look for the file first
24475 in the current directory and then along the source search path
24476 (@pxref{Source Path, ,Specifying Source Directories}),
24477 except that @file{$cdir} is not searched, since the compilation
24478 directory is not relevant to scripts.
24480 File entries can be placed in section @code{.debug_gdb_scripts} with,
24481 for example, this GCC macro for Python scripts.
24484 /* Note: The "MS" section flags are to remove duplicates. */
24485 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24487 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24488 .byte 1 /* Python */\n\
24489 .asciz \"" script_name "\"\n\
24495 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24496 Then one can reference the macro in a header or source file like this:
24499 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24502 The script name may include directories if desired.
24504 Note that loading of this script file also requires accordingly configured
24505 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24507 If the macro invocation is put in a header, any application or library
24508 using this header will get a reference to the specified script,
24509 and with the use of @code{"MS"} attributes on the section, the linker
24510 will remove duplicates.
24512 @subsubsection Script Text Entries
24514 Script text entries allow to put the executable script in the entry
24515 itself instead of loading it from a file.
24516 The first line of the entry, everything after the prefix byte and up to
24517 the first newline (@code{0xa}) character, is the script name, and must not
24518 contain any kind of space character, e.g., spaces or tabs.
24519 The rest of the entry, up to the trailing null byte, is the script to
24520 execute in the specified language. The name needs to be unique among
24521 all script names, as @value{GDBN} executes each script only once based
24524 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24528 #include "symcat.h"
24529 #include "gdb/section-scripts.h"
24531 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24532 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24533 ".ascii \"gdb.inlined-script\\n\"\n"
24534 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24535 ".ascii \" def __init__ (self):\\n\"\n"
24536 ".ascii \" super (test_cmd, self).__init__ ("
24537 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24538 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24539 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24540 ".ascii \"test_cmd ()\\n\"\n"
24546 Loading of inlined scripts requires a properly configured
24547 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24548 The path to specify in @code{auto-load safe-path} is the path of the file
24549 containing the @code{.debug_gdb_scripts} section.
24551 @node Which flavor to choose?
24552 @subsection Which flavor to choose?
24554 Given the multiple ways of auto-loading extensions, it might not always
24555 be clear which one to choose. This section provides some guidance.
24558 Benefits of the @file{-gdb.@var{ext}} way:
24562 Can be used with file formats that don't support multiple sections.
24565 Ease of finding scripts for public libraries.
24567 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24568 in the source search path.
24569 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24570 isn't a source directory in which to find the script.
24573 Doesn't require source code additions.
24577 Benefits of the @code{.debug_gdb_scripts} way:
24581 Works with static linking.
24583 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24584 trigger their loading. When an application is statically linked the only
24585 objfile available is the executable, and it is cumbersome to attach all the
24586 scripts from all the input libraries to the executable's
24587 @file{-gdb.@var{ext}} script.
24590 Works with classes that are entirely inlined.
24592 Some classes can be entirely inlined, and thus there may not be an associated
24593 shared library to attach a @file{-gdb.@var{ext}} script to.
24596 Scripts needn't be copied out of the source tree.
24598 In some circumstances, apps can be built out of large collections of internal
24599 libraries, and the build infrastructure necessary to install the
24600 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24601 cumbersome. It may be easier to specify the scripts in the
24602 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24603 top of the source tree to the source search path.
24606 @node Multiple Extension Languages
24607 @section Multiple Extension Languages
24609 The Guile and Python extension languages do not share any state,
24610 and generally do not interfere with each other.
24611 There are some things to be aware of, however.
24613 @subsection Python comes first
24615 Python was @value{GDBN}'s first extension language, and to avoid breaking
24616 existing behaviour Python comes first. This is generally solved by the
24617 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24618 extension languages, and when it makes a call to an extension language,
24619 (say to pretty-print a value), it tries each in turn until an extension
24620 language indicates it has performed the request (e.g., has returned the
24621 pretty-printed form of a value).
24622 This extends to errors while performing such requests: If an error happens
24623 while, for example, trying to pretty-print an object then the error is
24624 reported and any following extension languages are not tried.
24627 @section Creating new spellings of existing commands
24628 @cindex aliases for commands
24630 It is often useful to define alternate spellings of existing commands.
24631 For example, if a new @value{GDBN} command defined in Python has
24632 a long name to type, it is handy to have an abbreviated version of it
24633 that involves less typing.
24635 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24636 of the @samp{step} command even though it is otherwise an ambiguous
24637 abbreviation of other commands like @samp{set} and @samp{show}.
24639 Aliases are also used to provide shortened or more common versions
24640 of multi-word commands. For example, @value{GDBN} provides the
24641 @samp{tty} alias of the @samp{set inferior-tty} command.
24643 You can define a new alias with the @samp{alias} command.
24648 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24652 @var{ALIAS} specifies the name of the new alias.
24653 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24656 @var{COMMAND} specifies the name of an existing command
24657 that is being aliased.
24659 The @samp{-a} option specifies that the new alias is an abbreviation
24660 of the command. Abbreviations are not shown in command
24661 lists displayed by the @samp{help} command.
24663 The @samp{--} option specifies the end of options,
24664 and is useful when @var{ALIAS} begins with a dash.
24666 Here is a simple example showing how to make an abbreviation
24667 of a command so that there is less to type.
24668 Suppose you were tired of typing @samp{disas}, the current
24669 shortest unambiguous abbreviation of the @samp{disassemble} command
24670 and you wanted an even shorter version named @samp{di}.
24671 The following will accomplish this.
24674 (gdb) alias -a di = disas
24677 Note that aliases are different from user-defined commands.
24678 With a user-defined command, you also need to write documentation
24679 for it with the @samp{document} command.
24680 An alias automatically picks up the documentation of the existing command.
24682 Here is an example where we make @samp{elms} an abbreviation of
24683 @samp{elements} in the @samp{set print elements} command.
24684 This is to show that you can make an abbreviation of any part
24688 (gdb) alias -a set print elms = set print elements
24689 (gdb) alias -a show print elms = show print elements
24690 (gdb) set p elms 20
24692 Limit on string chars or array elements to print is 200.
24695 Note that if you are defining an alias of a @samp{set} command,
24696 and you want to have an alias for the corresponding @samp{show}
24697 command, then you need to define the latter separately.
24699 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24700 @var{ALIAS}, just as they are normally.
24703 (gdb) alias -a set pr elms = set p ele
24706 Finally, here is an example showing the creation of a one word
24707 alias for a more complex command.
24708 This creates alias @samp{spe} of the command @samp{set print elements}.
24711 (gdb) alias spe = set print elements
24716 @chapter Command Interpreters
24717 @cindex command interpreters
24719 @value{GDBN} supports multiple command interpreters, and some command
24720 infrastructure to allow users or user interface writers to switch
24721 between interpreters or run commands in other interpreters.
24723 @value{GDBN} currently supports two command interpreters, the console
24724 interpreter (sometimes called the command-line interpreter or @sc{cli})
24725 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24726 describes both of these interfaces in great detail.
24728 By default, @value{GDBN} will start with the console interpreter.
24729 However, the user may choose to start @value{GDBN} with another
24730 interpreter by specifying the @option{-i} or @option{--interpreter}
24731 startup options. Defined interpreters include:
24735 @cindex console interpreter
24736 The traditional console or command-line interpreter. This is the most often
24737 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24738 @value{GDBN} will use this interpreter.
24741 @cindex mi interpreter
24742 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24743 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24744 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24748 @cindex mi2 interpreter
24749 The current @sc{gdb/mi} interface.
24752 @cindex mi1 interpreter
24753 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24757 @cindex invoke another interpreter
24758 The interpreter being used by @value{GDBN} may not be dynamically
24759 switched at runtime. Although possible, this could lead to a very
24760 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24761 enters the command "interpreter-set console" in a console view,
24762 @value{GDBN} would switch to using the console interpreter, rendering
24763 the IDE inoperable!
24765 @kindex interpreter-exec
24766 Although you may only choose a single interpreter at startup, you may execute
24767 commands in any interpreter from the current interpreter using the appropriate
24768 command. If you are running the console interpreter, simply use the
24769 @code{interpreter-exec} command:
24772 interpreter-exec mi "-data-list-register-names"
24775 @sc{gdb/mi} has a similar command, although it is only available in versions of
24776 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24779 @chapter @value{GDBN} Text User Interface
24781 @cindex Text User Interface
24784 * TUI Overview:: TUI overview
24785 * TUI Keys:: TUI key bindings
24786 * TUI Single Key Mode:: TUI single key mode
24787 * TUI Commands:: TUI-specific commands
24788 * TUI Configuration:: TUI configuration variables
24791 The @value{GDBN} Text User Interface (TUI) is a terminal
24792 interface which uses the @code{curses} library to show the source
24793 file, the assembly output, the program registers and @value{GDBN}
24794 commands in separate text windows. The TUI mode is supported only
24795 on platforms where a suitable version of the @code{curses} library
24798 The TUI mode is enabled by default when you invoke @value{GDBN} as
24799 @samp{@value{GDBP} -tui}.
24800 You can also switch in and out of TUI mode while @value{GDBN} runs by
24801 using various TUI commands and key bindings, such as @command{tui
24802 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24803 @ref{TUI Keys, ,TUI Key Bindings}.
24806 @section TUI Overview
24808 In TUI mode, @value{GDBN} can display several text windows:
24812 This window is the @value{GDBN} command window with the @value{GDBN}
24813 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24814 managed using readline.
24817 The source window shows the source file of the program. The current
24818 line and active breakpoints are displayed in this window.
24821 The assembly window shows the disassembly output of the program.
24824 This window shows the processor registers. Registers are highlighted
24825 when their values change.
24828 The source and assembly windows show the current program position
24829 by highlighting the current line and marking it with a @samp{>} marker.
24830 Breakpoints are indicated with two markers. The first marker
24831 indicates the breakpoint type:
24835 Breakpoint which was hit at least once.
24838 Breakpoint which was never hit.
24841 Hardware breakpoint which was hit at least once.
24844 Hardware breakpoint which was never hit.
24847 The second marker indicates whether the breakpoint is enabled or not:
24851 Breakpoint is enabled.
24854 Breakpoint is disabled.
24857 The source, assembly and register windows are updated when the current
24858 thread changes, when the frame changes, or when the program counter
24861 These windows are not all visible at the same time. The command
24862 window is always visible. The others can be arranged in several
24873 source and assembly,
24876 source and registers, or
24879 assembly and registers.
24882 A status line above the command window shows the following information:
24886 Indicates the current @value{GDBN} target.
24887 (@pxref{Targets, ,Specifying a Debugging Target}).
24890 Gives the current process or thread number.
24891 When no process is being debugged, this field is set to @code{No process}.
24894 Gives the current function name for the selected frame.
24895 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24896 When there is no symbol corresponding to the current program counter,
24897 the string @code{??} is displayed.
24900 Indicates the current line number for the selected frame.
24901 When the current line number is not known, the string @code{??} is displayed.
24904 Indicates the current program counter address.
24908 @section TUI Key Bindings
24909 @cindex TUI key bindings
24911 The TUI installs several key bindings in the readline keymaps
24912 @ifset SYSTEM_READLINE
24913 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24915 @ifclear SYSTEM_READLINE
24916 (@pxref{Command Line Editing}).
24918 The following key bindings are installed for both TUI mode and the
24919 @value{GDBN} standard mode.
24928 Enter or leave the TUI mode. When leaving the TUI mode,
24929 the curses window management stops and @value{GDBN} operates using
24930 its standard mode, writing on the terminal directly. When reentering
24931 the TUI mode, control is given back to the curses windows.
24932 The screen is then refreshed.
24936 Use a TUI layout with only one window. The layout will
24937 either be @samp{source} or @samp{assembly}. When the TUI mode
24938 is not active, it will switch to the TUI mode.
24940 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24944 Use a TUI layout with at least two windows. When the current
24945 layout already has two windows, the next layout with two windows is used.
24946 When a new layout is chosen, one window will always be common to the
24947 previous layout and the new one.
24949 Think of it as the Emacs @kbd{C-x 2} binding.
24953 Change the active window. The TUI associates several key bindings
24954 (like scrolling and arrow keys) with the active window. This command
24955 gives the focus to the next TUI window.
24957 Think of it as the Emacs @kbd{C-x o} binding.
24961 Switch in and out of the TUI SingleKey mode that binds single
24962 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24965 The following key bindings only work in the TUI mode:
24970 Scroll the active window one page up.
24974 Scroll the active window one page down.
24978 Scroll the active window one line up.
24982 Scroll the active window one line down.
24986 Scroll the active window one column left.
24990 Scroll the active window one column right.
24994 Refresh the screen.
24997 Because the arrow keys scroll the active window in the TUI mode, they
24998 are not available for their normal use by readline unless the command
24999 window has the focus. When another window is active, you must use
25000 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25001 and @kbd{C-f} to control the command window.
25003 @node TUI Single Key Mode
25004 @section TUI Single Key Mode
25005 @cindex TUI single key mode
25007 The TUI also provides a @dfn{SingleKey} mode, which binds several
25008 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25009 switch into this mode, where the following key bindings are used:
25012 @kindex c @r{(SingleKey TUI key)}
25016 @kindex d @r{(SingleKey TUI key)}
25020 @kindex f @r{(SingleKey TUI key)}
25024 @kindex n @r{(SingleKey TUI key)}
25028 @kindex q @r{(SingleKey TUI key)}
25030 exit the SingleKey mode.
25032 @kindex r @r{(SingleKey TUI key)}
25036 @kindex s @r{(SingleKey TUI key)}
25040 @kindex u @r{(SingleKey TUI key)}
25044 @kindex v @r{(SingleKey TUI key)}
25048 @kindex w @r{(SingleKey TUI key)}
25053 Other keys temporarily switch to the @value{GDBN} command prompt.
25054 The key that was pressed is inserted in the editing buffer so that
25055 it is possible to type most @value{GDBN} commands without interaction
25056 with the TUI SingleKey mode. Once the command is entered the TUI
25057 SingleKey mode is restored. The only way to permanently leave
25058 this mode is by typing @kbd{q} or @kbd{C-x s}.
25062 @section TUI-specific Commands
25063 @cindex TUI commands
25065 The TUI has specific commands to control the text windows.
25066 These commands are always available, even when @value{GDBN} is not in
25067 the TUI mode. When @value{GDBN} is in the standard mode, most
25068 of these commands will automatically switch to the TUI mode.
25070 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25071 terminal, or @value{GDBN} has been started with the machine interface
25072 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25073 these commands will fail with an error, because it would not be
25074 possible or desirable to enable curses window management.
25079 Activate TUI mode. The last active TUI window layout will be used if
25080 TUI mode has prevsiouly been used in the current debugging session,
25081 otherwise a default layout is used.
25084 @kindex tui disable
25085 Disable TUI mode, returning to the console interpreter.
25089 List and give the size of all displayed windows.
25091 @item layout @var{name}
25093 Changes which TUI windows are displayed. In each layout the command
25094 window is always displayed, the @var{name} parameter controls which
25095 additional windows are displayed, and can be any of the following:
25099 Display the next layout.
25102 Display the previous layout.
25105 Display the source and command windows.
25108 Display the assembly and command windows.
25111 Display the source, assembly, and command windows.
25114 When in @code{src} layout display the register, source, and command
25115 windows. When in @code{asm} or @code{split} layout display the
25116 register, assembler, and command windows.
25119 @item focus @var{name}
25121 Changes which TUI window is currently active for scrolling. The
25122 @var{name} parameter can be any of the following:
25126 Make the next window active for scrolling.
25129 Make the previous window active for scrolling.
25132 Make the source window active for scrolling.
25135 Make the assembly window active for scrolling.
25138 Make the register window active for scrolling.
25141 Make the command window active for scrolling.
25146 Refresh the screen. This is similar to typing @kbd{C-L}.
25148 @item tui reg @var{group}
25150 Changes the register group displayed in the tui register window to
25151 @var{group}. If the register window is not currently displayed this
25152 command will cause the register window to be displayed. The list of
25153 register groups, as well as their order is target specific. The
25154 following groups are available on most targets:
25157 Repeatedly selecting this group will cause the display to cycle
25158 through all of the available register groups.
25161 Repeatedly selecting this group will cause the display to cycle
25162 through all of the available register groups in the reverse order to
25166 Display the general registers.
25168 Display the floating point registers.
25170 Display the system registers.
25172 Display the vector registers.
25174 Display all registers.
25179 Update the source window and the current execution point.
25181 @item winheight @var{name} +@var{count}
25182 @itemx winheight @var{name} -@var{count}
25184 Change the height of the window @var{name} by @var{count}
25185 lines. Positive counts increase the height, while negative counts
25186 decrease it. The @var{name} parameter can be one of @code{src} (the
25187 source window), @code{cmd} (the command window), @code{asm} (the
25188 disassembly window), or @code{regs} (the register display window).
25190 @item tabset @var{nchars}
25192 Set the width of tab stops to be @var{nchars} characters. This
25193 setting affects the display of TAB characters in the source and
25197 @node TUI Configuration
25198 @section TUI Configuration Variables
25199 @cindex TUI configuration variables
25201 Several configuration variables control the appearance of TUI windows.
25204 @item set tui border-kind @var{kind}
25205 @kindex set tui border-kind
25206 Select the border appearance for the source, assembly and register windows.
25207 The possible values are the following:
25210 Use a space character to draw the border.
25213 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25216 Use the Alternate Character Set to draw the border. The border is
25217 drawn using character line graphics if the terminal supports them.
25220 @item set tui border-mode @var{mode}
25221 @kindex set tui border-mode
25222 @itemx set tui active-border-mode @var{mode}
25223 @kindex set tui active-border-mode
25224 Select the display attributes for the borders of the inactive windows
25225 or the active window. The @var{mode} can be one of the following:
25228 Use normal attributes to display the border.
25234 Use reverse video mode.
25237 Use half bright mode.
25239 @item half-standout
25240 Use half bright and standout mode.
25243 Use extra bright or bold mode.
25245 @item bold-standout
25246 Use extra bright or bold and standout mode.
25251 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25254 @cindex @sc{gnu} Emacs
25255 A special interface allows you to use @sc{gnu} Emacs to view (and
25256 edit) the source files for the program you are debugging with
25259 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25260 executable file you want to debug as an argument. This command starts
25261 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25262 created Emacs buffer.
25263 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25265 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25270 All ``terminal'' input and output goes through an Emacs buffer, called
25273 This applies both to @value{GDBN} commands and their output, and to the input
25274 and output done by the program you are debugging.
25276 This is useful because it means that you can copy the text of previous
25277 commands and input them again; you can even use parts of the output
25280 All the facilities of Emacs' Shell mode are available for interacting
25281 with your program. In particular, you can send signals the usual
25282 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25286 @value{GDBN} displays source code through Emacs.
25288 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25289 source file for that frame and puts an arrow (@samp{=>}) at the
25290 left margin of the current line. Emacs uses a separate buffer for
25291 source display, and splits the screen to show both your @value{GDBN} session
25294 Explicit @value{GDBN} @code{list} or search commands still produce output as
25295 usual, but you probably have no reason to use them from Emacs.
25298 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25299 a graphical mode, enabled by default, which provides further buffers
25300 that can control the execution and describe the state of your program.
25301 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25303 If you specify an absolute file name when prompted for the @kbd{M-x
25304 gdb} argument, then Emacs sets your current working directory to where
25305 your program resides. If you only specify the file name, then Emacs
25306 sets your current working directory to the directory associated
25307 with the previous buffer. In this case, @value{GDBN} may find your
25308 program by searching your environment's @code{PATH} variable, but on
25309 some operating systems it might not find the source. So, although the
25310 @value{GDBN} input and output session proceeds normally, the auxiliary
25311 buffer does not display the current source and line of execution.
25313 The initial working directory of @value{GDBN} is printed on the top
25314 line of the GUD buffer and this serves as a default for the commands
25315 that specify files for @value{GDBN} to operate on. @xref{Files,
25316 ,Commands to Specify Files}.
25318 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25319 need to call @value{GDBN} by a different name (for example, if you
25320 keep several configurations around, with different names) you can
25321 customize the Emacs variable @code{gud-gdb-command-name} to run the
25324 In the GUD buffer, you can use these special Emacs commands in
25325 addition to the standard Shell mode commands:
25329 Describe the features of Emacs' GUD Mode.
25332 Execute to another source line, like the @value{GDBN} @code{step} command; also
25333 update the display window to show the current file and location.
25336 Execute to next source line in this function, skipping all function
25337 calls, like the @value{GDBN} @code{next} command. Then update the display window
25338 to show the current file and location.
25341 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25342 display window accordingly.
25345 Execute until exit from the selected stack frame, like the @value{GDBN}
25346 @code{finish} command.
25349 Continue execution of your program, like the @value{GDBN} @code{continue}
25353 Go up the number of frames indicated by the numeric argument
25354 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25355 like the @value{GDBN} @code{up} command.
25358 Go down the number of frames indicated by the numeric argument, like the
25359 @value{GDBN} @code{down} command.
25362 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25363 tells @value{GDBN} to set a breakpoint on the source line point is on.
25365 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25366 separate frame which shows a backtrace when the GUD buffer is current.
25367 Move point to any frame in the stack and type @key{RET} to make it
25368 become the current frame and display the associated source in the
25369 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25370 selected frame become the current one. In graphical mode, the
25371 speedbar displays watch expressions.
25373 If you accidentally delete the source-display buffer, an easy way to get
25374 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25375 request a frame display; when you run under Emacs, this recreates
25376 the source buffer if necessary to show you the context of the current
25379 The source files displayed in Emacs are in ordinary Emacs buffers
25380 which are visiting the source files in the usual way. You can edit
25381 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25382 communicates with Emacs in terms of line numbers. If you add or
25383 delete lines from the text, the line numbers that @value{GDBN} knows cease
25384 to correspond properly with the code.
25386 A more detailed description of Emacs' interaction with @value{GDBN} is
25387 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25391 @chapter The @sc{gdb/mi} Interface
25393 @unnumberedsec Function and Purpose
25395 @cindex @sc{gdb/mi}, its purpose
25396 @sc{gdb/mi} is a line based machine oriented text interface to
25397 @value{GDBN} and is activated by specifying using the
25398 @option{--interpreter} command line option (@pxref{Mode Options}). It
25399 is specifically intended to support the development of systems which
25400 use the debugger as just one small component of a larger system.
25402 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25403 in the form of a reference manual.
25405 Note that @sc{gdb/mi} is still under construction, so some of the
25406 features described below are incomplete and subject to change
25407 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25409 @unnumberedsec Notation and Terminology
25411 @cindex notational conventions, for @sc{gdb/mi}
25412 This chapter uses the following notation:
25416 @code{|} separates two alternatives.
25419 @code{[ @var{something} ]} indicates that @var{something} is optional:
25420 it may or may not be given.
25423 @code{( @var{group} )*} means that @var{group} inside the parentheses
25424 may repeat zero or more times.
25427 @code{( @var{group} )+} means that @var{group} inside the parentheses
25428 may repeat one or more times.
25431 @code{"@var{string}"} means a literal @var{string}.
25435 @heading Dependencies
25439 * GDB/MI General Design::
25440 * GDB/MI Command Syntax::
25441 * GDB/MI Compatibility with CLI::
25442 * GDB/MI Development and Front Ends::
25443 * GDB/MI Output Records::
25444 * GDB/MI Simple Examples::
25445 * GDB/MI Command Description Format::
25446 * GDB/MI Breakpoint Commands::
25447 * GDB/MI Catchpoint Commands::
25448 * GDB/MI Program Context::
25449 * GDB/MI Thread Commands::
25450 * GDB/MI Ada Tasking Commands::
25451 * GDB/MI Program Execution::
25452 * GDB/MI Stack Manipulation::
25453 * GDB/MI Variable Objects::
25454 * GDB/MI Data Manipulation::
25455 * GDB/MI Tracepoint Commands::
25456 * GDB/MI Symbol Query::
25457 * GDB/MI File Commands::
25459 * GDB/MI Kod Commands::
25460 * GDB/MI Memory Overlay Commands::
25461 * GDB/MI Signal Handling Commands::
25463 * GDB/MI Target Manipulation::
25464 * GDB/MI File Transfer Commands::
25465 * GDB/MI Ada Exceptions Commands::
25466 * GDB/MI Support Commands::
25467 * GDB/MI Miscellaneous Commands::
25470 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25471 @node GDB/MI General Design
25472 @section @sc{gdb/mi} General Design
25473 @cindex GDB/MI General Design
25475 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25476 parts---commands sent to @value{GDBN}, responses to those commands
25477 and notifications. Each command results in exactly one response,
25478 indicating either successful completion of the command, or an error.
25479 For the commands that do not resume the target, the response contains the
25480 requested information. For the commands that resume the target, the
25481 response only indicates whether the target was successfully resumed.
25482 Notifications is the mechanism for reporting changes in the state of the
25483 target, or in @value{GDBN} state, that cannot conveniently be associated with
25484 a command and reported as part of that command response.
25486 The important examples of notifications are:
25490 Exec notifications. These are used to report changes in
25491 target state---when a target is resumed, or stopped. It would not
25492 be feasible to include this information in response of resuming
25493 commands, because one resume commands can result in multiple events in
25494 different threads. Also, quite some time may pass before any event
25495 happens in the target, while a frontend needs to know whether the resuming
25496 command itself was successfully executed.
25499 Console output, and status notifications. Console output
25500 notifications are used to report output of CLI commands, as well as
25501 diagnostics for other commands. Status notifications are used to
25502 report the progress of a long-running operation. Naturally, including
25503 this information in command response would mean no output is produced
25504 until the command is finished, which is undesirable.
25507 General notifications. Commands may have various side effects on
25508 the @value{GDBN} or target state beyond their official purpose. For example,
25509 a command may change the selected thread. Although such changes can
25510 be included in command response, using notification allows for more
25511 orthogonal frontend design.
25515 There's no guarantee that whenever an MI command reports an error,
25516 @value{GDBN} or the target are in any specific state, and especially,
25517 the state is not reverted to the state before the MI command was
25518 processed. Therefore, whenever an MI command results in an error,
25519 we recommend that the frontend refreshes all the information shown in
25520 the user interface.
25524 * Context management::
25525 * Asynchronous and non-stop modes::
25529 @node Context management
25530 @subsection Context management
25532 @subsubsection Threads and Frames
25534 In most cases when @value{GDBN} accesses the target, this access is
25535 done in context of a specific thread and frame (@pxref{Frames}).
25536 Often, even when accessing global data, the target requires that a thread
25537 be specified. The CLI interface maintains the selected thread and frame,
25538 and supplies them to target on each command. This is convenient,
25539 because a command line user would not want to specify that information
25540 explicitly on each command, and because user interacts with
25541 @value{GDBN} via a single terminal, so no confusion is possible as
25542 to what thread and frame are the current ones.
25544 In the case of MI, the concept of selected thread and frame is less
25545 useful. First, a frontend can easily remember this information
25546 itself. Second, a graphical frontend can have more than one window,
25547 each one used for debugging a different thread, and the frontend might
25548 want to access additional threads for internal purposes. This
25549 increases the risk that by relying on implicitly selected thread, the
25550 frontend may be operating on a wrong one. Therefore, each MI command
25551 should explicitly specify which thread and frame to operate on. To
25552 make it possible, each MI command accepts the @samp{--thread} and
25553 @samp{--frame} options, the value to each is @value{GDBN} global
25554 identifier for thread and frame to operate on.
25556 Usually, each top-level window in a frontend allows the user to select
25557 a thread and a frame, and remembers the user selection for further
25558 operations. However, in some cases @value{GDBN} may suggest that the
25559 current thread be changed. For example, when stopping on a breakpoint
25560 it is reasonable to switch to the thread where breakpoint is hit. For
25561 another example, if the user issues the CLI @samp{thread} command via
25562 the frontend, it is desirable to change the frontend's selected thread to the
25563 one specified by user. @value{GDBN} communicates the suggestion to
25564 change current thread using the @samp{=thread-selected} notification.
25565 No such notification is available for the selected frame at the moment.
25567 Note that historically, MI shares the selected thread with CLI, so
25568 frontends used the @code{-thread-select} to execute commands in the
25569 right context. However, getting this to work right is cumbersome. The
25570 simplest way is for frontend to emit @code{-thread-select} command
25571 before every command. This doubles the number of commands that need
25572 to be sent. The alternative approach is to suppress @code{-thread-select}
25573 if the selected thread in @value{GDBN} is supposed to be identical to the
25574 thread the frontend wants to operate on. However, getting this
25575 optimization right can be tricky. In particular, if the frontend
25576 sends several commands to @value{GDBN}, and one of the commands changes the
25577 selected thread, then the behaviour of subsequent commands will
25578 change. So, a frontend should either wait for response from such
25579 problematic commands, or explicitly add @code{-thread-select} for
25580 all subsequent commands. No frontend is known to do this exactly
25581 right, so it is suggested to just always pass the @samp{--thread} and
25582 @samp{--frame} options.
25584 @subsubsection Language
25586 The execution of several commands depends on which language is selected.
25587 By default, the current language (@pxref{show language}) is used.
25588 But for commands known to be language-sensitive, it is recommended
25589 to use the @samp{--language} option. This option takes one argument,
25590 which is the name of the language to use while executing the command.
25594 -data-evaluate-expression --language c "sizeof (void*)"
25599 The valid language names are the same names accepted by the
25600 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25601 @samp{local} or @samp{unknown}.
25603 @node Asynchronous and non-stop modes
25604 @subsection Asynchronous command execution and non-stop mode
25606 On some targets, @value{GDBN} is capable of processing MI commands
25607 even while the target is running. This is called @dfn{asynchronous
25608 command execution} (@pxref{Background Execution}). The frontend may
25609 specify a preferrence for asynchronous execution using the
25610 @code{-gdb-set mi-async 1} command, which should be emitted before
25611 either running the executable or attaching to the target. After the
25612 frontend has started the executable or attached to the target, it can
25613 find if asynchronous execution is enabled using the
25614 @code{-list-target-features} command.
25617 @item -gdb-set mi-async on
25618 @item -gdb-set mi-async off
25619 Set whether MI is in asynchronous mode.
25621 When @code{off}, which is the default, MI execution commands (e.g.,
25622 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25623 for the program to stop before processing further commands.
25625 When @code{on}, MI execution commands are background execution
25626 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25627 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25628 MI commands even while the target is running.
25630 @item -gdb-show mi-async
25631 Show whether MI asynchronous mode is enabled.
25634 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25635 @code{target-async} instead of @code{mi-async}, and it had the effect
25636 of both putting MI in asynchronous mode and making CLI background
25637 commands possible. CLI background commands are now always possible
25638 ``out of the box'' if the target supports them. The old spelling is
25639 kept as a deprecated alias for backwards compatibility.
25641 Even if @value{GDBN} can accept a command while target is running,
25642 many commands that access the target do not work when the target is
25643 running. Therefore, asynchronous command execution is most useful
25644 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25645 it is possible to examine the state of one thread, while other threads
25648 When a given thread is running, MI commands that try to access the
25649 target in the context of that thread may not work, or may work only on
25650 some targets. In particular, commands that try to operate on thread's
25651 stack will not work, on any target. Commands that read memory, or
25652 modify breakpoints, may work or not work, depending on the target. Note
25653 that even commands that operate on global state, such as @code{print},
25654 @code{set}, and breakpoint commands, still access the target in the
25655 context of a specific thread, so frontend should try to find a
25656 stopped thread and perform the operation on that thread (using the
25657 @samp{--thread} option).
25659 Which commands will work in the context of a running thread is
25660 highly target dependent. However, the two commands
25661 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25662 to find the state of a thread, will always work.
25664 @node Thread groups
25665 @subsection Thread groups
25666 @value{GDBN} may be used to debug several processes at the same time.
25667 On some platfroms, @value{GDBN} may support debugging of several
25668 hardware systems, each one having several cores with several different
25669 processes running on each core. This section describes the MI
25670 mechanism to support such debugging scenarios.
25672 The key observation is that regardless of the structure of the
25673 target, MI can have a global list of threads, because most commands that
25674 accept the @samp{--thread} option do not need to know what process that
25675 thread belongs to. Therefore, it is not necessary to introduce
25676 neither additional @samp{--process} option, nor an notion of the
25677 current process in the MI interface. The only strictly new feature
25678 that is required is the ability to find how the threads are grouped
25681 To allow the user to discover such grouping, and to support arbitrary
25682 hierarchy of machines/cores/processes, MI introduces the concept of a
25683 @dfn{thread group}. Thread group is a collection of threads and other
25684 thread groups. A thread group always has a string identifier, a type,
25685 and may have additional attributes specific to the type. A new
25686 command, @code{-list-thread-groups}, returns the list of top-level
25687 thread groups, which correspond to processes that @value{GDBN} is
25688 debugging at the moment. By passing an identifier of a thread group
25689 to the @code{-list-thread-groups} command, it is possible to obtain
25690 the members of specific thread group.
25692 To allow the user to easily discover processes, and other objects, he
25693 wishes to debug, a concept of @dfn{available thread group} is
25694 introduced. Available thread group is an thread group that
25695 @value{GDBN} is not debugging, but that can be attached to, using the
25696 @code{-target-attach} command. The list of available top-level thread
25697 groups can be obtained using @samp{-list-thread-groups --available}.
25698 In general, the content of a thread group may be only retrieved only
25699 after attaching to that thread group.
25701 Thread groups are related to inferiors (@pxref{Inferiors and
25702 Programs}). Each inferior corresponds to a thread group of a special
25703 type @samp{process}, and some additional operations are permitted on
25704 such thread groups.
25706 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25707 @node GDB/MI Command Syntax
25708 @section @sc{gdb/mi} Command Syntax
25711 * GDB/MI Input Syntax::
25712 * GDB/MI Output Syntax::
25715 @node GDB/MI Input Syntax
25716 @subsection @sc{gdb/mi} Input Syntax
25718 @cindex input syntax for @sc{gdb/mi}
25719 @cindex @sc{gdb/mi}, input syntax
25721 @item @var{command} @expansion{}
25722 @code{@var{cli-command} | @var{mi-command}}
25724 @item @var{cli-command} @expansion{}
25725 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25726 @var{cli-command} is any existing @value{GDBN} CLI command.
25728 @item @var{mi-command} @expansion{}
25729 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25730 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25732 @item @var{token} @expansion{}
25733 "any sequence of digits"
25735 @item @var{option} @expansion{}
25736 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25738 @item @var{parameter} @expansion{}
25739 @code{@var{non-blank-sequence} | @var{c-string}}
25741 @item @var{operation} @expansion{}
25742 @emph{any of the operations described in this chapter}
25744 @item @var{non-blank-sequence} @expansion{}
25745 @emph{anything, provided it doesn't contain special characters such as
25746 "-", @var{nl}, """ and of course " "}
25748 @item @var{c-string} @expansion{}
25749 @code{""" @var{seven-bit-iso-c-string-content} """}
25751 @item @var{nl} @expansion{}
25760 The CLI commands are still handled by the @sc{mi} interpreter; their
25761 output is described below.
25764 The @code{@var{token}}, when present, is passed back when the command
25768 Some @sc{mi} commands accept optional arguments as part of the parameter
25769 list. Each option is identified by a leading @samp{-} (dash) and may be
25770 followed by an optional argument parameter. Options occur first in the
25771 parameter list and can be delimited from normal parameters using
25772 @samp{--} (this is useful when some parameters begin with a dash).
25779 We want easy access to the existing CLI syntax (for debugging).
25782 We want it to be easy to spot a @sc{mi} operation.
25785 @node GDB/MI Output Syntax
25786 @subsection @sc{gdb/mi} Output Syntax
25788 @cindex output syntax of @sc{gdb/mi}
25789 @cindex @sc{gdb/mi}, output syntax
25790 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25791 followed, optionally, by a single result record. This result record
25792 is for the most recent command. The sequence of output records is
25793 terminated by @samp{(gdb)}.
25795 If an input command was prefixed with a @code{@var{token}} then the
25796 corresponding output for that command will also be prefixed by that same
25800 @item @var{output} @expansion{}
25801 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25803 @item @var{result-record} @expansion{}
25804 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25806 @item @var{out-of-band-record} @expansion{}
25807 @code{@var{async-record} | @var{stream-record}}
25809 @item @var{async-record} @expansion{}
25810 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25812 @item @var{exec-async-output} @expansion{}
25813 @code{[ @var{token} ] "*" @var{async-output nl}}
25815 @item @var{status-async-output} @expansion{}
25816 @code{[ @var{token} ] "+" @var{async-output nl}}
25818 @item @var{notify-async-output} @expansion{}
25819 @code{[ @var{token} ] "=" @var{async-output nl}}
25821 @item @var{async-output} @expansion{}
25822 @code{@var{async-class} ( "," @var{result} )*}
25824 @item @var{result-class} @expansion{}
25825 @code{"done" | "running" | "connected" | "error" | "exit"}
25827 @item @var{async-class} @expansion{}
25828 @code{"stopped" | @var{others}} (where @var{others} will be added
25829 depending on the needs---this is still in development).
25831 @item @var{result} @expansion{}
25832 @code{ @var{variable} "=" @var{value}}
25834 @item @var{variable} @expansion{}
25835 @code{ @var{string} }
25837 @item @var{value} @expansion{}
25838 @code{ @var{const} | @var{tuple} | @var{list} }
25840 @item @var{const} @expansion{}
25841 @code{@var{c-string}}
25843 @item @var{tuple} @expansion{}
25844 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25846 @item @var{list} @expansion{}
25847 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25848 @var{result} ( "," @var{result} )* "]" }
25850 @item @var{stream-record} @expansion{}
25851 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25853 @item @var{console-stream-output} @expansion{}
25854 @code{"~" @var{c-string nl}}
25856 @item @var{target-stream-output} @expansion{}
25857 @code{"@@" @var{c-string nl}}
25859 @item @var{log-stream-output} @expansion{}
25860 @code{"&" @var{c-string nl}}
25862 @item @var{nl} @expansion{}
25865 @item @var{token} @expansion{}
25866 @emph{any sequence of digits}.
25874 All output sequences end in a single line containing a period.
25877 The @code{@var{token}} is from the corresponding request. Note that
25878 for all async output, while the token is allowed by the grammar and
25879 may be output by future versions of @value{GDBN} for select async
25880 output messages, it is generally omitted. Frontends should treat
25881 all async output as reporting general changes in the state of the
25882 target and there should be no need to associate async output to any
25886 @cindex status output in @sc{gdb/mi}
25887 @var{status-async-output} contains on-going status information about the
25888 progress of a slow operation. It can be discarded. All status output is
25889 prefixed by @samp{+}.
25892 @cindex async output in @sc{gdb/mi}
25893 @var{exec-async-output} contains asynchronous state change on the target
25894 (stopped, started, disappeared). All async output is prefixed by
25898 @cindex notify output in @sc{gdb/mi}
25899 @var{notify-async-output} contains supplementary information that the
25900 client should handle (e.g., a new breakpoint information). All notify
25901 output is prefixed by @samp{=}.
25904 @cindex console output in @sc{gdb/mi}
25905 @var{console-stream-output} is output that should be displayed as is in the
25906 console. It is the textual response to a CLI command. All the console
25907 output is prefixed by @samp{~}.
25910 @cindex target output in @sc{gdb/mi}
25911 @var{target-stream-output} is the output produced by the target program.
25912 All the target output is prefixed by @samp{@@}.
25915 @cindex log output in @sc{gdb/mi}
25916 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25917 instance messages that should be displayed as part of an error log. All
25918 the log output is prefixed by @samp{&}.
25921 @cindex list output in @sc{gdb/mi}
25922 New @sc{gdb/mi} commands should only output @var{lists} containing
25928 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25929 details about the various output records.
25931 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25932 @node GDB/MI Compatibility with CLI
25933 @section @sc{gdb/mi} Compatibility with CLI
25935 @cindex compatibility, @sc{gdb/mi} and CLI
25936 @cindex @sc{gdb/mi}, compatibility with CLI
25938 For the developers convenience CLI commands can be entered directly,
25939 but there may be some unexpected behaviour. For example, commands
25940 that query the user will behave as if the user replied yes, breakpoint
25941 command lists are not executed and some CLI commands, such as
25942 @code{if}, @code{when} and @code{define}, prompt for further input with
25943 @samp{>}, which is not valid MI output.
25945 This feature may be removed at some stage in the future and it is
25946 recommended that front ends use the @code{-interpreter-exec} command
25947 (@pxref{-interpreter-exec}).
25949 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25950 @node GDB/MI Development and Front Ends
25951 @section @sc{gdb/mi} Development and Front Ends
25952 @cindex @sc{gdb/mi} development
25954 The application which takes the MI output and presents the state of the
25955 program being debugged to the user is called a @dfn{front end}.
25957 Although @sc{gdb/mi} is still incomplete, it is currently being used
25958 by a variety of front ends to @value{GDBN}. This makes it difficult
25959 to introduce new functionality without breaking existing usage. This
25960 section tries to minimize the problems by describing how the protocol
25963 Some changes in MI need not break a carefully designed front end, and
25964 for these the MI version will remain unchanged. The following is a
25965 list of changes that may occur within one level, so front ends should
25966 parse MI output in a way that can handle them:
25970 New MI commands may be added.
25973 New fields may be added to the output of any MI command.
25976 The range of values for fields with specified values, e.g.,
25977 @code{in_scope} (@pxref{-var-update}) may be extended.
25979 @c The format of field's content e.g type prefix, may change so parse it
25980 @c at your own risk. Yes, in general?
25982 @c The order of fields may change? Shouldn't really matter but it might
25983 @c resolve inconsistencies.
25986 If the changes are likely to break front ends, the MI version level
25987 will be increased by one. This will allow the front end to parse the
25988 output according to the MI version. Apart from mi0, new versions of
25989 @value{GDBN} will not support old versions of MI and it will be the
25990 responsibility of the front end to work with the new one.
25992 @c Starting with mi3, add a new command -mi-version that prints the MI
25995 The best way to avoid unexpected changes in MI that might break your front
25996 end is to make your project known to @value{GDBN} developers and
25997 follow development on @email{gdb@@sourceware.org} and
25998 @email{gdb-patches@@sourceware.org}.
25999 @cindex mailing lists
26001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26002 @node GDB/MI Output Records
26003 @section @sc{gdb/mi} Output Records
26006 * GDB/MI Result Records::
26007 * GDB/MI Stream Records::
26008 * GDB/MI Async Records::
26009 * GDB/MI Breakpoint Information::
26010 * GDB/MI Frame Information::
26011 * GDB/MI Thread Information::
26012 * GDB/MI Ada Exception Information::
26015 @node GDB/MI Result Records
26016 @subsection @sc{gdb/mi} Result Records
26018 @cindex result records in @sc{gdb/mi}
26019 @cindex @sc{gdb/mi}, result records
26020 In addition to a number of out-of-band notifications, the response to a
26021 @sc{gdb/mi} command includes one of the following result indications:
26025 @item "^done" [ "," @var{results} ]
26026 The synchronous operation was successful, @code{@var{results}} are the return
26031 This result record is equivalent to @samp{^done}. Historically, it
26032 was output instead of @samp{^done} if the command has resumed the
26033 target. This behaviour is maintained for backward compatibility, but
26034 all frontends should treat @samp{^done} and @samp{^running}
26035 identically and rely on the @samp{*running} output record to determine
26036 which threads are resumed.
26040 @value{GDBN} has connected to a remote target.
26042 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26044 The operation failed. The @code{msg=@var{c-string}} variable contains
26045 the corresponding error message.
26047 If present, the @code{code=@var{c-string}} variable provides an error
26048 code on which consumers can rely on to detect the corresponding
26049 error condition. At present, only one error code is defined:
26052 @item "undefined-command"
26053 Indicates that the command causing the error does not exist.
26058 @value{GDBN} has terminated.
26062 @node GDB/MI Stream Records
26063 @subsection @sc{gdb/mi} Stream Records
26065 @cindex @sc{gdb/mi}, stream records
26066 @cindex stream records in @sc{gdb/mi}
26067 @value{GDBN} internally maintains a number of output streams: the console, the
26068 target, and the log. The output intended for each of these streams is
26069 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26071 Each stream record begins with a unique @dfn{prefix character} which
26072 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26073 Syntax}). In addition to the prefix, each stream record contains a
26074 @code{@var{string-output}}. This is either raw text (with an implicit new
26075 line) or a quoted C string (which does not contain an implicit newline).
26078 @item "~" @var{string-output}
26079 The console output stream contains text that should be displayed in the
26080 CLI console window. It contains the textual responses to CLI commands.
26082 @item "@@" @var{string-output}
26083 The target output stream contains any textual output from the running
26084 target. This is only present when GDB's event loop is truly
26085 asynchronous, which is currently only the case for remote targets.
26087 @item "&" @var{string-output}
26088 The log stream contains debugging messages being produced by @value{GDBN}'s
26092 @node GDB/MI Async Records
26093 @subsection @sc{gdb/mi} Async Records
26095 @cindex async records in @sc{gdb/mi}
26096 @cindex @sc{gdb/mi}, async records
26097 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26098 additional changes that have occurred. Those changes can either be a
26099 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26100 target activity (e.g., target stopped).
26102 The following is the list of possible async records:
26106 @item *running,thread-id="@var{thread}"
26107 The target is now running. The @var{thread} field can be the global
26108 thread ID of the the thread that is now running, and it can be
26109 @samp{all} if all threads are running. The frontend should assume
26110 that no interaction with a running thread is possible after this
26111 notification is produced. The frontend should not assume that this
26112 notification is output only once for any command. @value{GDBN} may
26113 emit this notification several times, either for different threads,
26114 because it cannot resume all threads together, or even for a single
26115 thread, if the thread must be stepped though some code before letting
26118 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26119 The target has stopped. The @var{reason} field can have one of the
26123 @item breakpoint-hit
26124 A breakpoint was reached.
26125 @item watchpoint-trigger
26126 A watchpoint was triggered.
26127 @item read-watchpoint-trigger
26128 A read watchpoint was triggered.
26129 @item access-watchpoint-trigger
26130 An access watchpoint was triggered.
26131 @item function-finished
26132 An -exec-finish or similar CLI command was accomplished.
26133 @item location-reached
26134 An -exec-until or similar CLI command was accomplished.
26135 @item watchpoint-scope
26136 A watchpoint has gone out of scope.
26137 @item end-stepping-range
26138 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26139 similar CLI command was accomplished.
26140 @item exited-signalled
26141 The inferior exited because of a signal.
26143 The inferior exited.
26144 @item exited-normally
26145 The inferior exited normally.
26146 @item signal-received
26147 A signal was received by the inferior.
26149 The inferior has stopped due to a library being loaded or unloaded.
26150 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26151 set or when a @code{catch load} or @code{catch unload} catchpoint is
26152 in use (@pxref{Set Catchpoints}).
26154 The inferior has forked. This is reported when @code{catch fork}
26155 (@pxref{Set Catchpoints}) has been used.
26157 The inferior has vforked. This is reported in when @code{catch vfork}
26158 (@pxref{Set Catchpoints}) has been used.
26159 @item syscall-entry
26160 The inferior entered a system call. This is reported when @code{catch
26161 syscall} (@pxref{Set Catchpoints}) has been used.
26162 @item syscall-return
26163 The inferior returned from a system call. This is reported when
26164 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26166 The inferior called @code{exec}. This is reported when @code{catch exec}
26167 (@pxref{Set Catchpoints}) has been used.
26170 The @var{id} field identifies the global thread ID of the thread
26171 that directly caused the stop -- for example by hitting a breakpoint.
26172 Depending on whether all-stop
26173 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26174 stop all threads, or only the thread that directly triggered the stop.
26175 If all threads are stopped, the @var{stopped} field will have the
26176 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26177 field will be a list of thread identifiers. Presently, this list will
26178 always include a single thread, but frontend should be prepared to see
26179 several threads in the list. The @var{core} field reports the
26180 processor core on which the stop event has happened. This field may be absent
26181 if such information is not available.
26183 @item =thread-group-added,id="@var{id}"
26184 @itemx =thread-group-removed,id="@var{id}"
26185 A thread group was either added or removed. The @var{id} field
26186 contains the @value{GDBN} identifier of the thread group. When a thread
26187 group is added, it generally might not be associated with a running
26188 process. When a thread group is removed, its id becomes invalid and
26189 cannot be used in any way.
26191 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26192 A thread group became associated with a running program,
26193 either because the program was just started or the thread group
26194 was attached to a program. The @var{id} field contains the
26195 @value{GDBN} identifier of the thread group. The @var{pid} field
26196 contains process identifier, specific to the operating system.
26198 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26199 A thread group is no longer associated with a running program,
26200 either because the program has exited, or because it was detached
26201 from. The @var{id} field contains the @value{GDBN} identifier of the
26202 thread group. The @var{code} field is the exit code of the inferior; it exists
26203 only when the inferior exited with some code.
26205 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26206 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26207 A thread either was created, or has exited. The @var{id} field
26208 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26209 field identifies the thread group this thread belongs to.
26211 @item =thread-selected,id="@var{id}"
26212 Informs that the selected thread was changed as result of the last
26213 command. This notification is not emitted as result of @code{-thread-select}
26214 command but is emitted whenever an MI command that is not documented
26215 to change the selected thread actually changes it. In particular,
26216 invoking, directly or indirectly (via user-defined command), the CLI
26217 @code{thread} command, will generate this notification.
26219 We suggest that in response to this notification, front ends
26220 highlight the selected thread and cause subsequent commands to apply to
26223 @item =library-loaded,...
26224 Reports that a new library file was loaded by the program. This
26225 notification has 4 fields---@var{id}, @var{target-name},
26226 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26227 opaque identifier of the library. For remote debugging case,
26228 @var{target-name} and @var{host-name} fields give the name of the
26229 library file on the target, and on the host respectively. For native
26230 debugging, both those fields have the same value. The
26231 @var{symbols-loaded} field is emitted only for backward compatibility
26232 and should not be relied on to convey any useful information. The
26233 @var{thread-group} field, if present, specifies the id of the thread
26234 group in whose context the library was loaded. If the field is
26235 absent, it means the library was loaded in the context of all present
26238 @item =library-unloaded,...
26239 Reports that a library was unloaded by the program. This notification
26240 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26241 the same meaning as for the @code{=library-loaded} notification.
26242 The @var{thread-group} field, if present, specifies the id of the
26243 thread group in whose context the library was unloaded. If the field is
26244 absent, it means the library was unloaded in the context of all present
26247 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26248 @itemx =traceframe-changed,end
26249 Reports that the trace frame was changed and its new number is
26250 @var{tfnum}. The number of the tracepoint associated with this trace
26251 frame is @var{tpnum}.
26253 @item =tsv-created,name=@var{name},initial=@var{initial}
26254 Reports that the new trace state variable @var{name} is created with
26255 initial value @var{initial}.
26257 @item =tsv-deleted,name=@var{name}
26258 @itemx =tsv-deleted
26259 Reports that the trace state variable @var{name} is deleted or all
26260 trace state variables are deleted.
26262 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26263 Reports that the trace state variable @var{name} is modified with
26264 the initial value @var{initial}. The current value @var{current} of
26265 trace state variable is optional and is reported if the current
26266 value of trace state variable is known.
26268 @item =breakpoint-created,bkpt=@{...@}
26269 @itemx =breakpoint-modified,bkpt=@{...@}
26270 @itemx =breakpoint-deleted,id=@var{number}
26271 Reports that a breakpoint was created, modified, or deleted,
26272 respectively. Only user-visible breakpoints are reported to the MI
26275 The @var{bkpt} argument is of the same form as returned by the various
26276 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26277 @var{number} is the ordinal number of the breakpoint.
26279 Note that if a breakpoint is emitted in the result record of a
26280 command, then it will not also be emitted in an async record.
26282 @item =record-started,thread-group="@var{id}"
26283 @itemx =record-stopped,thread-group="@var{id}"
26284 Execution log recording was either started or stopped on an
26285 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26286 group corresponding to the affected inferior.
26288 @item =cmd-param-changed,param=@var{param},value=@var{value}
26289 Reports that a parameter of the command @code{set @var{param}} is
26290 changed to @var{value}. In the multi-word @code{set} command,
26291 the @var{param} is the whole parameter list to @code{set} command.
26292 For example, In command @code{set check type on}, @var{param}
26293 is @code{check type} and @var{value} is @code{on}.
26295 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26296 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26297 written in an inferior. The @var{id} is the identifier of the
26298 thread group corresponding to the affected inferior. The optional
26299 @code{type="code"} part is reported if the memory written to holds
26303 @node GDB/MI Breakpoint Information
26304 @subsection @sc{gdb/mi} Breakpoint Information
26306 When @value{GDBN} reports information about a breakpoint, a
26307 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26312 The breakpoint number. For a breakpoint that represents one location
26313 of a multi-location breakpoint, this will be a dotted pair, like
26317 The type of the breakpoint. For ordinary breakpoints this will be
26318 @samp{breakpoint}, but many values are possible.
26321 If the type of the breakpoint is @samp{catchpoint}, then this
26322 indicates the exact type of catchpoint.
26325 This is the breakpoint disposition---either @samp{del}, meaning that
26326 the breakpoint will be deleted at the next stop, or @samp{keep},
26327 meaning that the breakpoint will not be deleted.
26330 This indicates whether the breakpoint is enabled, in which case the
26331 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26332 Note that this is not the same as the field @code{enable}.
26335 The address of the breakpoint. This may be a hexidecimal number,
26336 giving the address; or the string @samp{<PENDING>}, for a pending
26337 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26338 multiple locations. This field will not be present if no address can
26339 be determined. For example, a watchpoint does not have an address.
26342 If known, the function in which the breakpoint appears.
26343 If not known, this field is not present.
26346 The name of the source file which contains this function, if known.
26347 If not known, this field is not present.
26350 The full file name of the source file which contains this function, if
26351 known. If not known, this field is not present.
26354 The line number at which this breakpoint appears, if known.
26355 If not known, this field is not present.
26358 If the source file is not known, this field may be provided. If
26359 provided, this holds the address of the breakpoint, possibly followed
26363 If this breakpoint is pending, this field is present and holds the
26364 text used to set the breakpoint, as entered by the user.
26367 Where this breakpoint's condition is evaluated, either @samp{host} or
26371 If this is a thread-specific breakpoint, then this identifies the
26372 thread in which the breakpoint can trigger.
26375 If this breakpoint is restricted to a particular Ada task, then this
26376 field will hold the task identifier.
26379 If the breakpoint is conditional, this is the condition expression.
26382 The ignore count of the breakpoint.
26385 The enable count of the breakpoint.
26387 @item traceframe-usage
26390 @item static-tracepoint-marker-string-id
26391 For a static tracepoint, the name of the static tracepoint marker.
26394 For a masked watchpoint, this is the mask.
26397 A tracepoint's pass count.
26399 @item original-location
26400 The location of the breakpoint as originally specified by the user.
26401 This field is optional.
26404 The number of times the breakpoint has been hit.
26407 This field is only given for tracepoints. This is either @samp{y},
26408 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26412 Some extra data, the exact contents of which are type-dependent.
26416 For example, here is what the output of @code{-break-insert}
26417 (@pxref{GDB/MI Breakpoint Commands}) might be:
26420 -> -break-insert main
26421 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26422 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26423 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26428 @node GDB/MI Frame Information
26429 @subsection @sc{gdb/mi} Frame Information
26431 Response from many MI commands includes an information about stack
26432 frame. This information is a tuple that may have the following
26437 The level of the stack frame. The innermost frame has the level of
26438 zero. This field is always present.
26441 The name of the function corresponding to the frame. This field may
26442 be absent if @value{GDBN} is unable to determine the function name.
26445 The code address for the frame. This field is always present.
26448 The name of the source files that correspond to the frame's code
26449 address. This field may be absent.
26452 The source line corresponding to the frames' code address. This field
26456 The name of the binary file (either executable or shared library) the
26457 corresponds to the frame's code address. This field may be absent.
26461 @node GDB/MI Thread Information
26462 @subsection @sc{gdb/mi} Thread Information
26464 Whenever @value{GDBN} has to report an information about a thread, it
26465 uses a tuple with the following fields:
26469 The global numeric id assigned to the thread by @value{GDBN}. This field is
26473 Target-specific string identifying the thread. This field is always present.
26476 Additional information about the thread provided by the target.
26477 It is supposed to be human-readable and not interpreted by the
26478 frontend. This field is optional.
26481 Either @samp{stopped} or @samp{running}, depending on whether the
26482 thread is presently running. This field is always present.
26485 The value of this field is an integer number of the processor core the
26486 thread was last seen on. This field is optional.
26489 @node GDB/MI Ada Exception Information
26490 @subsection @sc{gdb/mi} Ada Exception Information
26492 Whenever a @code{*stopped} record is emitted because the program
26493 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26494 @value{GDBN} provides the name of the exception that was raised via
26495 the @code{exception-name} field.
26497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26498 @node GDB/MI Simple Examples
26499 @section Simple Examples of @sc{gdb/mi} Interaction
26500 @cindex @sc{gdb/mi}, simple examples
26502 This subsection presents several simple examples of interaction using
26503 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26504 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26505 the output received from @sc{gdb/mi}.
26507 Note the line breaks shown in the examples are here only for
26508 readability, they don't appear in the real output.
26510 @subheading Setting a Breakpoint
26512 Setting a breakpoint generates synchronous output which contains detailed
26513 information of the breakpoint.
26516 -> -break-insert main
26517 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26518 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26519 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26524 @subheading Program Execution
26526 Program execution generates asynchronous records and MI gives the
26527 reason that execution stopped.
26533 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26534 frame=@{addr="0x08048564",func="main",
26535 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26536 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26541 <- *stopped,reason="exited-normally"
26545 @subheading Quitting @value{GDBN}
26547 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26555 Please note that @samp{^exit} is printed immediately, but it might
26556 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26557 performs necessary cleanups, including killing programs being debugged
26558 or disconnecting from debug hardware, so the frontend should wait till
26559 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26560 fails to exit in reasonable time.
26562 @subheading A Bad Command
26564 Here's what happens if you pass a non-existent command:
26568 <- ^error,msg="Undefined MI command: rubbish"
26573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26574 @node GDB/MI Command Description Format
26575 @section @sc{gdb/mi} Command Description Format
26577 The remaining sections describe blocks of commands. Each block of
26578 commands is laid out in a fashion similar to this section.
26580 @subheading Motivation
26582 The motivation for this collection of commands.
26584 @subheading Introduction
26586 A brief introduction to this collection of commands as a whole.
26588 @subheading Commands
26590 For each command in the block, the following is described:
26592 @subsubheading Synopsis
26595 -command @var{args}@dots{}
26598 @subsubheading Result
26600 @subsubheading @value{GDBN} Command
26602 The corresponding @value{GDBN} CLI command(s), if any.
26604 @subsubheading Example
26606 Example(s) formatted for readability. Some of the described commands have
26607 not been implemented yet and these are labeled N.A.@: (not available).
26610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26611 @node GDB/MI Breakpoint Commands
26612 @section @sc{gdb/mi} Breakpoint Commands
26614 @cindex breakpoint commands for @sc{gdb/mi}
26615 @cindex @sc{gdb/mi}, breakpoint commands
26616 This section documents @sc{gdb/mi} commands for manipulating
26619 @subheading The @code{-break-after} Command
26620 @findex -break-after
26622 @subsubheading Synopsis
26625 -break-after @var{number} @var{count}
26628 The breakpoint number @var{number} is not in effect until it has been
26629 hit @var{count} times. To see how this is reflected in the output of
26630 the @samp{-break-list} command, see the description of the
26631 @samp{-break-list} command below.
26633 @subsubheading @value{GDBN} Command
26635 The corresponding @value{GDBN} command is @samp{ignore}.
26637 @subsubheading Example
26642 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26643 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26644 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26652 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26653 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26654 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26655 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26656 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26657 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26658 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26659 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26660 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26661 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26666 @subheading The @code{-break-catch} Command
26667 @findex -break-catch
26670 @subheading The @code{-break-commands} Command
26671 @findex -break-commands
26673 @subsubheading Synopsis
26676 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26679 Specifies the CLI commands that should be executed when breakpoint
26680 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26681 are the commands. If no command is specified, any previously-set
26682 commands are cleared. @xref{Break Commands}. Typical use of this
26683 functionality is tracing a program, that is, printing of values of
26684 some variables whenever breakpoint is hit and then continuing.
26686 @subsubheading @value{GDBN} Command
26688 The corresponding @value{GDBN} command is @samp{commands}.
26690 @subsubheading Example
26695 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26696 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26697 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26700 -break-commands 1 "print v" "continue"
26705 @subheading The @code{-break-condition} Command
26706 @findex -break-condition
26708 @subsubheading Synopsis
26711 -break-condition @var{number} @var{expr}
26714 Breakpoint @var{number} will stop the program only if the condition in
26715 @var{expr} is true. The condition becomes part of the
26716 @samp{-break-list} output (see the description of the @samp{-break-list}
26719 @subsubheading @value{GDBN} Command
26721 The corresponding @value{GDBN} command is @samp{condition}.
26723 @subsubheading Example
26727 -break-condition 1 1
26731 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26732 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26733 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26734 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26735 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26736 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26737 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26738 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26739 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26740 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26744 @subheading The @code{-break-delete} Command
26745 @findex -break-delete
26747 @subsubheading Synopsis
26750 -break-delete ( @var{breakpoint} )+
26753 Delete the breakpoint(s) whose number(s) are specified in the argument
26754 list. This is obviously reflected in the breakpoint list.
26756 @subsubheading @value{GDBN} Command
26758 The corresponding @value{GDBN} command is @samp{delete}.
26760 @subsubheading Example
26768 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26769 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26770 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26771 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26772 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26773 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26774 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26779 @subheading The @code{-break-disable} Command
26780 @findex -break-disable
26782 @subsubheading Synopsis
26785 -break-disable ( @var{breakpoint} )+
26788 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26789 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26791 @subsubheading @value{GDBN} Command
26793 The corresponding @value{GDBN} command is @samp{disable}.
26795 @subsubheading Example
26803 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26804 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26805 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26806 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26807 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26808 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26809 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26810 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26811 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26812 line="5",thread-groups=["i1"],times="0"@}]@}
26816 @subheading The @code{-break-enable} Command
26817 @findex -break-enable
26819 @subsubheading Synopsis
26822 -break-enable ( @var{breakpoint} )+
26825 Enable (previously disabled) @var{breakpoint}(s).
26827 @subsubheading @value{GDBN} Command
26829 The corresponding @value{GDBN} command is @samp{enable}.
26831 @subsubheading Example
26839 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26840 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26841 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26842 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26843 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26844 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26845 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26846 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26847 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26848 line="5",thread-groups=["i1"],times="0"@}]@}
26852 @subheading The @code{-break-info} Command
26853 @findex -break-info
26855 @subsubheading Synopsis
26858 -break-info @var{breakpoint}
26862 Get information about a single breakpoint.
26864 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26865 Information}, for details on the format of each breakpoint in the
26868 @subsubheading @value{GDBN} Command
26870 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26872 @subsubheading Example
26875 @subheading The @code{-break-insert} Command
26876 @findex -break-insert
26877 @anchor{-break-insert}
26879 @subsubheading Synopsis
26882 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26883 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26884 [ -p @var{thread-id} ] [ @var{location} ]
26888 If specified, @var{location}, can be one of:
26891 @item linespec location
26892 A linespec location. @xref{Linespec Locations}.
26894 @item explicit location
26895 An explicit location. @sc{gdb/mi} explicit locations are
26896 analogous to the CLI's explicit locations using the option names
26897 listed below. @xref{Explicit Locations}.
26900 @item --source @var{filename}
26901 The source file name of the location. This option requires the use
26902 of either @samp{--function} or @samp{--line}.
26904 @item --function @var{function}
26905 The name of a function or method.
26907 @item --label @var{label}
26908 The name of a label.
26910 @item --line @var{lineoffset}
26911 An absolute or relative line offset from the start of the location.
26914 @item address location
26915 An address location, *@var{address}. @xref{Address Locations}.
26919 The possible optional parameters of this command are:
26923 Insert a temporary breakpoint.
26925 Insert a hardware breakpoint.
26927 If @var{location} cannot be parsed (for example if it
26928 refers to unknown files or functions), create a pending
26929 breakpoint. Without this flag, @value{GDBN} will report
26930 an error, and won't create a breakpoint, if @var{location}
26933 Create a disabled breakpoint.
26935 Create a tracepoint. @xref{Tracepoints}. When this parameter
26936 is used together with @samp{-h}, a fast tracepoint is created.
26937 @item -c @var{condition}
26938 Make the breakpoint conditional on @var{condition}.
26939 @item -i @var{ignore-count}
26940 Initialize the @var{ignore-count}.
26941 @item -p @var{thread-id}
26942 Restrict the breakpoint to the thread with the specified global
26946 @subsubheading Result
26948 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26949 resulting breakpoint.
26951 Note: this format is open to change.
26952 @c An out-of-band breakpoint instead of part of the result?
26954 @subsubheading @value{GDBN} Command
26956 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26957 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26959 @subsubheading Example
26964 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26965 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26968 -break-insert -t foo
26969 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26970 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26974 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26982 addr="0x0001072c", func="main",file="recursive2.c",
26983 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26985 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26986 addr="0x00010774",func="foo",file="recursive2.c",
26987 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26990 @c -break-insert -r foo.*
26991 @c ~int foo(int, int);
26992 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26993 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26998 @subheading The @code{-dprintf-insert} Command
26999 @findex -dprintf-insert
27001 @subsubheading Synopsis
27004 -dprintf-insert [ -t ] [ -f ] [ -d ]
27005 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27006 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27011 If supplied, @var{location} may be specified the same way as for
27012 the @code{-break-insert} command. @xref{-break-insert}.
27014 The possible optional parameters of this command are:
27018 Insert a temporary breakpoint.
27020 If @var{location} cannot be parsed (for example, if it
27021 refers to unknown files or functions), create a pending
27022 breakpoint. Without this flag, @value{GDBN} will report
27023 an error, and won't create a breakpoint, if @var{location}
27026 Create a disabled breakpoint.
27027 @item -c @var{condition}
27028 Make the breakpoint conditional on @var{condition}.
27029 @item -i @var{ignore-count}
27030 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27031 to @var{ignore-count}.
27032 @item -p @var{thread-id}
27033 Restrict the breakpoint to the thread with the specified global
27037 @subsubheading Result
27039 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27040 resulting breakpoint.
27042 @c An out-of-band breakpoint instead of part of the result?
27044 @subsubheading @value{GDBN} Command
27046 The corresponding @value{GDBN} command is @samp{dprintf}.
27048 @subsubheading Example
27052 4-dprintf-insert foo "At foo entry\n"
27053 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27054 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27055 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27056 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27057 original-location="foo"@}
27059 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27060 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27061 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27062 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27063 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27064 original-location="mi-dprintf.c:26"@}
27068 @subheading The @code{-break-list} Command
27069 @findex -break-list
27071 @subsubheading Synopsis
27077 Displays the list of inserted breakpoints, showing the following fields:
27081 number of the breakpoint
27083 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27085 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27088 is the breakpoint enabled or no: @samp{y} or @samp{n}
27090 memory location at which the breakpoint is set
27092 logical location of the breakpoint, expressed by function name, file
27094 @item Thread-groups
27095 list of thread groups to which this breakpoint applies
27097 number of times the breakpoint has been hit
27100 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27101 @code{body} field is an empty list.
27103 @subsubheading @value{GDBN} Command
27105 The corresponding @value{GDBN} command is @samp{info break}.
27107 @subsubheading Example
27112 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27113 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27114 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27115 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27116 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27117 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27118 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27119 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27120 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27122 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27123 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27124 line="13",thread-groups=["i1"],times="0"@}]@}
27128 Here's an example of the result when there are no breakpoints:
27133 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27134 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27135 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27136 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27137 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27138 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27139 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27144 @subheading The @code{-break-passcount} Command
27145 @findex -break-passcount
27147 @subsubheading Synopsis
27150 -break-passcount @var{tracepoint-number} @var{passcount}
27153 Set the passcount for tracepoint @var{tracepoint-number} to
27154 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27155 is not a tracepoint, error is emitted. This corresponds to CLI
27156 command @samp{passcount}.
27158 @subheading The @code{-break-watch} Command
27159 @findex -break-watch
27161 @subsubheading Synopsis
27164 -break-watch [ -a | -r ]
27167 Create a watchpoint. With the @samp{-a} option it will create an
27168 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27169 read from or on a write to the memory location. With the @samp{-r}
27170 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27171 trigger only when the memory location is accessed for reading. Without
27172 either of the options, the watchpoint created is a regular watchpoint,
27173 i.e., it will trigger when the memory location is accessed for writing.
27174 @xref{Set Watchpoints, , Setting Watchpoints}.
27176 Note that @samp{-break-list} will report a single list of watchpoints and
27177 breakpoints inserted.
27179 @subsubheading @value{GDBN} Command
27181 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27184 @subsubheading Example
27186 Setting a watchpoint on a variable in the @code{main} function:
27191 ^done,wpt=@{number="2",exp="x"@}
27196 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27197 value=@{old="-268439212",new="55"@},
27198 frame=@{func="main",args=[],file="recursive2.c",
27199 fullname="/home/foo/bar/recursive2.c",line="5"@}
27203 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27204 the program execution twice: first for the variable changing value, then
27205 for the watchpoint going out of scope.
27210 ^done,wpt=@{number="5",exp="C"@}
27215 *stopped,reason="watchpoint-trigger",
27216 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27217 frame=@{func="callee4",args=[],
27218 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27219 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27224 *stopped,reason="watchpoint-scope",wpnum="5",
27225 frame=@{func="callee3",args=[@{name="strarg",
27226 value="0x11940 \"A string argument.\""@}],
27227 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27228 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27232 Listing breakpoints and watchpoints, at different points in the program
27233 execution. Note that once the watchpoint goes out of scope, it is
27239 ^done,wpt=@{number="2",exp="C"@}
27242 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27243 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27244 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27245 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27246 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27247 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27248 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27249 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27250 addr="0x00010734",func="callee4",
27251 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27252 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27254 bkpt=@{number="2",type="watchpoint",disp="keep",
27255 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27260 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27261 value=@{old="-276895068",new="3"@},
27262 frame=@{func="callee4",args=[],
27263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27267 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27268 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27269 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27270 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27271 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27272 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27273 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27274 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27275 addr="0x00010734",func="callee4",
27276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27277 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27279 bkpt=@{number="2",type="watchpoint",disp="keep",
27280 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27284 ^done,reason="watchpoint-scope",wpnum="2",
27285 frame=@{func="callee3",args=[@{name="strarg",
27286 value="0x11940 \"A string argument.\""@}],
27287 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27288 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27291 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27292 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27293 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27294 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27295 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27296 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27297 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27298 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27299 addr="0x00010734",func="callee4",
27300 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27301 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27302 thread-groups=["i1"],times="1"@}]@}
27307 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27308 @node GDB/MI Catchpoint Commands
27309 @section @sc{gdb/mi} Catchpoint Commands
27311 This section documents @sc{gdb/mi} commands for manipulating
27315 * Shared Library GDB/MI Catchpoint Commands::
27316 * Ada Exception GDB/MI Catchpoint Commands::
27319 @node Shared Library GDB/MI Catchpoint Commands
27320 @subsection Shared Library @sc{gdb/mi} Catchpoints
27322 @subheading The @code{-catch-load} Command
27323 @findex -catch-load
27325 @subsubheading Synopsis
27328 -catch-load [ -t ] [ -d ] @var{regexp}
27331 Add a catchpoint for library load events. If the @samp{-t} option is used,
27332 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27333 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27334 in a disabled state. The @samp{regexp} argument is a regular
27335 expression used to match the name of the loaded library.
27338 @subsubheading @value{GDBN} Command
27340 The corresponding @value{GDBN} command is @samp{catch load}.
27342 @subsubheading Example
27345 -catch-load -t foo.so
27346 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27347 what="load of library matching foo.so",catch-type="load",times="0"@}
27352 @subheading The @code{-catch-unload} Command
27353 @findex -catch-unload
27355 @subsubheading Synopsis
27358 -catch-unload [ -t ] [ -d ] @var{regexp}
27361 Add a catchpoint for library unload events. If the @samp{-t} option is
27362 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27363 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27364 created in a disabled state. The @samp{regexp} argument is a regular
27365 expression used to match the name of the unloaded library.
27367 @subsubheading @value{GDBN} Command
27369 The corresponding @value{GDBN} command is @samp{catch unload}.
27371 @subsubheading Example
27374 -catch-unload -d bar.so
27375 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27376 what="load of library matching bar.so",catch-type="unload",times="0"@}
27380 @node Ada Exception GDB/MI Catchpoint Commands
27381 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27383 The following @sc{gdb/mi} commands can be used to create catchpoints
27384 that stop the execution when Ada exceptions are being raised.
27386 @subheading The @code{-catch-assert} Command
27387 @findex -catch-assert
27389 @subsubheading Synopsis
27392 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27395 Add a catchpoint for failed Ada assertions.
27397 The possible optional parameters for this command are:
27400 @item -c @var{condition}
27401 Make the catchpoint conditional on @var{condition}.
27403 Create a disabled catchpoint.
27405 Create a temporary catchpoint.
27408 @subsubheading @value{GDBN} Command
27410 The corresponding @value{GDBN} command is @samp{catch assert}.
27412 @subsubheading Example
27416 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27417 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27418 thread-groups=["i1"],times="0",
27419 original-location="__gnat_debug_raise_assert_failure"@}
27423 @subheading The @code{-catch-exception} Command
27424 @findex -catch-exception
27426 @subsubheading Synopsis
27429 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27433 Add a catchpoint stopping when Ada exceptions are raised.
27434 By default, the command stops the program when any Ada exception
27435 gets raised. But it is also possible, by using some of the
27436 optional parameters described below, to create more selective
27439 The possible optional parameters for this command are:
27442 @item -c @var{condition}
27443 Make the catchpoint conditional on @var{condition}.
27445 Create a disabled catchpoint.
27446 @item -e @var{exception-name}
27447 Only stop when @var{exception-name} is raised. This option cannot
27448 be used combined with @samp{-u}.
27450 Create a temporary catchpoint.
27452 Stop only when an unhandled exception gets raised. This option
27453 cannot be used combined with @samp{-e}.
27456 @subsubheading @value{GDBN} Command
27458 The corresponding @value{GDBN} commands are @samp{catch exception}
27459 and @samp{catch exception unhandled}.
27461 @subsubheading Example
27464 -catch-exception -e Program_Error
27465 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27466 enabled="y",addr="0x0000000000404874",
27467 what="`Program_Error' Ada exception", thread-groups=["i1"],
27468 times="0",original-location="__gnat_debug_raise_exception"@}
27472 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27473 @node GDB/MI Program Context
27474 @section @sc{gdb/mi} Program Context
27476 @subheading The @code{-exec-arguments} Command
27477 @findex -exec-arguments
27480 @subsubheading Synopsis
27483 -exec-arguments @var{args}
27486 Set the inferior program arguments, to be used in the next
27489 @subsubheading @value{GDBN} Command
27491 The corresponding @value{GDBN} command is @samp{set args}.
27493 @subsubheading Example
27497 -exec-arguments -v word
27504 @subheading The @code{-exec-show-arguments} Command
27505 @findex -exec-show-arguments
27507 @subsubheading Synopsis
27510 -exec-show-arguments
27513 Print the arguments of the program.
27515 @subsubheading @value{GDBN} Command
27517 The corresponding @value{GDBN} command is @samp{show args}.
27519 @subsubheading Example
27524 @subheading The @code{-environment-cd} Command
27525 @findex -environment-cd
27527 @subsubheading Synopsis
27530 -environment-cd @var{pathdir}
27533 Set @value{GDBN}'s working directory.
27535 @subsubheading @value{GDBN} Command
27537 The corresponding @value{GDBN} command is @samp{cd}.
27539 @subsubheading Example
27543 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27549 @subheading The @code{-environment-directory} Command
27550 @findex -environment-directory
27552 @subsubheading Synopsis
27555 -environment-directory [ -r ] [ @var{pathdir} ]+
27558 Add directories @var{pathdir} to beginning of search path for source files.
27559 If the @samp{-r} option is used, the search path is reset to the default
27560 search path. If directories @var{pathdir} are supplied in addition to the
27561 @samp{-r} option, the search path is first reset and then addition
27563 Multiple directories may be specified, separated by blanks. Specifying
27564 multiple directories in a single command
27565 results in the directories added to the beginning of the
27566 search path in the same order they were presented in the command.
27567 If blanks are needed as
27568 part of a directory name, double-quotes should be used around
27569 the name. In the command output, the path will show up separated
27570 by the system directory-separator character. The directory-separator
27571 character must not be used
27572 in any directory name.
27573 If no directories are specified, the current search path is displayed.
27575 @subsubheading @value{GDBN} Command
27577 The corresponding @value{GDBN} command is @samp{dir}.
27579 @subsubheading Example
27583 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27584 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27586 -environment-directory ""
27587 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27589 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27590 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27592 -environment-directory -r
27593 ^done,source-path="$cdir:$cwd"
27598 @subheading The @code{-environment-path} Command
27599 @findex -environment-path
27601 @subsubheading Synopsis
27604 -environment-path [ -r ] [ @var{pathdir} ]+
27607 Add directories @var{pathdir} to beginning of search path for object files.
27608 If the @samp{-r} option is used, the search path is reset to the original
27609 search path that existed at gdb start-up. If directories @var{pathdir} are
27610 supplied in addition to the
27611 @samp{-r} option, the search path is first reset and then addition
27613 Multiple directories may be specified, separated by blanks. Specifying
27614 multiple directories in a single command
27615 results in the directories added to the beginning of the
27616 search path in the same order they were presented in the command.
27617 If blanks are needed as
27618 part of a directory name, double-quotes should be used around
27619 the name. In the command output, the path will show up separated
27620 by the system directory-separator character. The directory-separator
27621 character must not be used
27622 in any directory name.
27623 If no directories are specified, the current path is displayed.
27626 @subsubheading @value{GDBN} Command
27628 The corresponding @value{GDBN} command is @samp{path}.
27630 @subsubheading Example
27635 ^done,path="/usr/bin"
27637 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27638 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27640 -environment-path -r /usr/local/bin
27641 ^done,path="/usr/local/bin:/usr/bin"
27646 @subheading The @code{-environment-pwd} Command
27647 @findex -environment-pwd
27649 @subsubheading Synopsis
27655 Show the current working directory.
27657 @subsubheading @value{GDBN} Command
27659 The corresponding @value{GDBN} command is @samp{pwd}.
27661 @subsubheading Example
27666 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27670 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27671 @node GDB/MI Thread Commands
27672 @section @sc{gdb/mi} Thread Commands
27675 @subheading The @code{-thread-info} Command
27676 @findex -thread-info
27678 @subsubheading Synopsis
27681 -thread-info [ @var{thread-id} ]
27684 Reports information about either a specific thread, if the
27685 @var{thread-id} parameter is present, or about all threads.
27686 @var{thread-id} is the thread's global thread ID. When printing
27687 information about all threads, also reports the global ID of the
27690 @subsubheading @value{GDBN} Command
27692 The @samp{info thread} command prints the same information
27695 @subsubheading Result
27697 The result is a list of threads. The following attributes are
27698 defined for a given thread:
27702 This field exists only for the current thread. It has the value @samp{*}.
27705 The global identifier that @value{GDBN} uses to refer to the thread.
27708 The identifier that the target uses to refer to the thread.
27711 Extra information about the thread, in a target-specific format. This
27715 The name of the thread. If the user specified a name using the
27716 @code{thread name} command, then this name is given. Otherwise, if
27717 @value{GDBN} can extract the thread name from the target, then that
27718 name is given. If @value{GDBN} cannot find the thread name, then this
27722 The stack frame currently executing in the thread.
27725 The thread's state. The @samp{state} field may have the following
27730 The thread is stopped. Frame information is available for stopped
27734 The thread is running. There's no frame information for running
27740 If @value{GDBN} can find the CPU core on which this thread is running,
27741 then this field is the core identifier. This field is optional.
27745 @subsubheading Example
27750 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27751 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27752 args=[]@},state="running"@},
27753 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27754 frame=@{level="0",addr="0x0804891f",func="foo",
27755 args=[@{name="i",value="10"@}],
27756 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27757 state="running"@}],
27758 current-thread-id="1"
27762 @subheading The @code{-thread-list-ids} Command
27763 @findex -thread-list-ids
27765 @subsubheading Synopsis
27771 Produces a list of the currently known global @value{GDBN} thread ids.
27772 At the end of the list it also prints the total number of such
27775 This command is retained for historical reasons, the
27776 @code{-thread-info} command should be used instead.
27778 @subsubheading @value{GDBN} Command
27780 Part of @samp{info threads} supplies the same information.
27782 @subsubheading Example
27787 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27788 current-thread-id="1",number-of-threads="3"
27793 @subheading The @code{-thread-select} Command
27794 @findex -thread-select
27796 @subsubheading Synopsis
27799 -thread-select @var{thread-id}
27802 Make thread with global thread number @var{thread-id} the current
27803 thread. It prints the number of the new current thread, and the
27804 topmost frame for that thread.
27806 This command is deprecated in favor of explicitly using the
27807 @samp{--thread} option to each command.
27809 @subsubheading @value{GDBN} Command
27811 The corresponding @value{GDBN} command is @samp{thread}.
27813 @subsubheading Example
27820 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27821 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27825 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27826 number-of-threads="3"
27829 ^done,new-thread-id="3",
27830 frame=@{level="0",func="vprintf",
27831 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27832 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27836 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27837 @node GDB/MI Ada Tasking Commands
27838 @section @sc{gdb/mi} Ada Tasking Commands
27840 @subheading The @code{-ada-task-info} Command
27841 @findex -ada-task-info
27843 @subsubheading Synopsis
27846 -ada-task-info [ @var{task-id} ]
27849 Reports information about either a specific Ada task, if the
27850 @var{task-id} parameter is present, or about all Ada tasks.
27852 @subsubheading @value{GDBN} Command
27854 The @samp{info tasks} command prints the same information
27855 about all Ada tasks (@pxref{Ada Tasks}).
27857 @subsubheading Result
27859 The result is a table of Ada tasks. The following columns are
27860 defined for each Ada task:
27864 This field exists only for the current thread. It has the value @samp{*}.
27867 The identifier that @value{GDBN} uses to refer to the Ada task.
27870 The identifier that the target uses to refer to the Ada task.
27873 The global thread identifier of the thread corresponding to the Ada
27876 This field should always exist, as Ada tasks are always implemented
27877 on top of a thread. But if @value{GDBN} cannot find this corresponding
27878 thread for any reason, the field is omitted.
27881 This field exists only when the task was created by another task.
27882 In this case, it provides the ID of the parent task.
27885 The base priority of the task.
27888 The current state of the task. For a detailed description of the
27889 possible states, see @ref{Ada Tasks}.
27892 The name of the task.
27896 @subsubheading Example
27900 ^done,tasks=@{nr_rows="3",nr_cols="8",
27901 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27902 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27903 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27904 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27905 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27906 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27907 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27908 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27909 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27910 state="Child Termination Wait",name="main_task"@}]@}
27914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27915 @node GDB/MI Program Execution
27916 @section @sc{gdb/mi} Program Execution
27918 These are the asynchronous commands which generate the out-of-band
27919 record @samp{*stopped}. Currently @value{GDBN} only really executes
27920 asynchronously with remote targets and this interaction is mimicked in
27923 @subheading The @code{-exec-continue} Command
27924 @findex -exec-continue
27926 @subsubheading Synopsis
27929 -exec-continue [--reverse] [--all|--thread-group N]
27932 Resumes the execution of the inferior program, which will continue
27933 to execute until it reaches a debugger stop event. If the
27934 @samp{--reverse} option is specified, execution resumes in reverse until
27935 it reaches a stop event. Stop events may include
27938 breakpoints or watchpoints
27940 signals or exceptions
27942 the end of the process (or its beginning under @samp{--reverse})
27944 the end or beginning of a replay log if one is being used.
27946 In all-stop mode (@pxref{All-Stop
27947 Mode}), may resume only one thread, or all threads, depending on the
27948 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27949 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27950 ignored in all-stop mode. If the @samp{--thread-group} options is
27951 specified, then all threads in that thread group are resumed.
27953 @subsubheading @value{GDBN} Command
27955 The corresponding @value{GDBN} corresponding is @samp{continue}.
27957 @subsubheading Example
27964 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27965 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27971 @subheading The @code{-exec-finish} Command
27972 @findex -exec-finish
27974 @subsubheading Synopsis
27977 -exec-finish [--reverse]
27980 Resumes the execution of the inferior program until the current
27981 function is exited. Displays the results returned by the function.
27982 If the @samp{--reverse} option is specified, resumes the reverse
27983 execution of the inferior program until the point where current
27984 function was called.
27986 @subsubheading @value{GDBN} Command
27988 The corresponding @value{GDBN} command is @samp{finish}.
27990 @subsubheading Example
27992 Function returning @code{void}.
27999 *stopped,reason="function-finished",frame=@{func="main",args=[],
28000 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28004 Function returning other than @code{void}. The name of the internal
28005 @value{GDBN} variable storing the result is printed, together with the
28012 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28013 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28014 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28015 gdb-result-var="$1",return-value="0"
28020 @subheading The @code{-exec-interrupt} Command
28021 @findex -exec-interrupt
28023 @subsubheading Synopsis
28026 -exec-interrupt [--all|--thread-group N]
28029 Interrupts the background execution of the target. Note how the token
28030 associated with the stop message is the one for the execution command
28031 that has been interrupted. The token for the interrupt itself only
28032 appears in the @samp{^done} output. If the user is trying to
28033 interrupt a non-running program, an error message will be printed.
28035 Note that when asynchronous execution is enabled, this command is
28036 asynchronous just like other execution commands. That is, first the
28037 @samp{^done} response will be printed, and the target stop will be
28038 reported after that using the @samp{*stopped} notification.
28040 In non-stop mode, only the context thread is interrupted by default.
28041 All threads (in all inferiors) will be interrupted if the
28042 @samp{--all} option is specified. If the @samp{--thread-group}
28043 option is specified, all threads in that group will be interrupted.
28045 @subsubheading @value{GDBN} Command
28047 The corresponding @value{GDBN} command is @samp{interrupt}.
28049 @subsubheading Example
28060 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28061 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28062 fullname="/home/foo/bar/try.c",line="13"@}
28067 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28071 @subheading The @code{-exec-jump} Command
28074 @subsubheading Synopsis
28077 -exec-jump @var{location}
28080 Resumes execution of the inferior program at the location specified by
28081 parameter. @xref{Specify Location}, for a description of the
28082 different forms of @var{location}.
28084 @subsubheading @value{GDBN} Command
28086 The corresponding @value{GDBN} command is @samp{jump}.
28088 @subsubheading Example
28091 -exec-jump foo.c:10
28092 *running,thread-id="all"
28097 @subheading The @code{-exec-next} Command
28100 @subsubheading Synopsis
28103 -exec-next [--reverse]
28106 Resumes execution of the inferior program, stopping when the beginning
28107 of the next source line is reached.
28109 If the @samp{--reverse} option is specified, resumes reverse execution
28110 of the inferior program, stopping at the beginning of the previous
28111 source line. If you issue this command on the first line of a
28112 function, it will take you back to the caller of that function, to the
28113 source line where the function was called.
28116 @subsubheading @value{GDBN} Command
28118 The corresponding @value{GDBN} command is @samp{next}.
28120 @subsubheading Example
28126 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28131 @subheading The @code{-exec-next-instruction} Command
28132 @findex -exec-next-instruction
28134 @subsubheading Synopsis
28137 -exec-next-instruction [--reverse]
28140 Executes one machine instruction. If the instruction is a function
28141 call, continues until the function returns. If the program stops at an
28142 instruction in the middle of a source line, the address will be
28145 If the @samp{--reverse} option is specified, resumes reverse execution
28146 of the inferior program, stopping at the previous instruction. If the
28147 previously executed instruction was a return from another function,
28148 it will continue to execute in reverse until the call to that function
28149 (from the current stack frame) is reached.
28151 @subsubheading @value{GDBN} Command
28153 The corresponding @value{GDBN} command is @samp{nexti}.
28155 @subsubheading Example
28159 -exec-next-instruction
28163 *stopped,reason="end-stepping-range",
28164 addr="0x000100d4",line="5",file="hello.c"
28169 @subheading The @code{-exec-return} Command
28170 @findex -exec-return
28172 @subsubheading Synopsis
28178 Makes current function return immediately. Doesn't execute the inferior.
28179 Displays the new current frame.
28181 @subsubheading @value{GDBN} Command
28183 The corresponding @value{GDBN} command is @samp{return}.
28185 @subsubheading Example
28189 200-break-insert callee4
28190 200^done,bkpt=@{number="1",addr="0x00010734",
28191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28196 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28197 frame=@{func="callee4",args=[],
28198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28205 111^done,frame=@{level="0",func="callee3",
28206 args=[@{name="strarg",
28207 value="0x11940 \"A string argument.\""@}],
28208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28214 @subheading The @code{-exec-run} Command
28217 @subsubheading Synopsis
28220 -exec-run [ --all | --thread-group N ] [ --start ]
28223 Starts execution of the inferior from the beginning. The inferior
28224 executes until either a breakpoint is encountered or the program
28225 exits. In the latter case the output will include an exit code, if
28226 the program has exited exceptionally.
28228 When neither the @samp{--all} nor the @samp{--thread-group} option
28229 is specified, the current inferior is started. If the
28230 @samp{--thread-group} option is specified, it should refer to a thread
28231 group of type @samp{process}, and that thread group will be started.
28232 If the @samp{--all} option is specified, then all inferiors will be started.
28234 Using the @samp{--start} option instructs the debugger to stop
28235 the execution at the start of the inferior's main subprogram,
28236 following the same behavior as the @code{start} command
28237 (@pxref{Starting}).
28239 @subsubheading @value{GDBN} Command
28241 The corresponding @value{GDBN} command is @samp{run}.
28243 @subsubheading Examples
28248 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28253 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28254 frame=@{func="main",args=[],file="recursive2.c",
28255 fullname="/home/foo/bar/recursive2.c",line="4"@}
28260 Program exited normally:
28268 *stopped,reason="exited-normally"
28273 Program exited exceptionally:
28281 *stopped,reason="exited",exit-code="01"
28285 Another way the program can terminate is if it receives a signal such as
28286 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28290 *stopped,reason="exited-signalled",signal-name="SIGINT",
28291 signal-meaning="Interrupt"
28295 @c @subheading -exec-signal
28298 @subheading The @code{-exec-step} Command
28301 @subsubheading Synopsis
28304 -exec-step [--reverse]
28307 Resumes execution of the inferior program, stopping when the beginning
28308 of the next source line is reached, if the next source line is not a
28309 function call. If it is, stop at the first instruction of the called
28310 function. If the @samp{--reverse} option is specified, resumes reverse
28311 execution of the inferior program, stopping at the beginning of the
28312 previously executed source line.
28314 @subsubheading @value{GDBN} Command
28316 The corresponding @value{GDBN} command is @samp{step}.
28318 @subsubheading Example
28320 Stepping into a function:
28326 *stopped,reason="end-stepping-range",
28327 frame=@{func="foo",args=[@{name="a",value="10"@},
28328 @{name="b",value="0"@}],file="recursive2.c",
28329 fullname="/home/foo/bar/recursive2.c",line="11"@}
28339 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28344 @subheading The @code{-exec-step-instruction} Command
28345 @findex -exec-step-instruction
28347 @subsubheading Synopsis
28350 -exec-step-instruction [--reverse]
28353 Resumes the inferior which executes one machine instruction. If the
28354 @samp{--reverse} option is specified, resumes reverse execution of the
28355 inferior program, stopping at the previously executed instruction.
28356 The output, once @value{GDBN} has stopped, will vary depending on
28357 whether we have stopped in the middle of a source line or not. In the
28358 former case, the address at which the program stopped will be printed
28361 @subsubheading @value{GDBN} Command
28363 The corresponding @value{GDBN} command is @samp{stepi}.
28365 @subsubheading Example
28369 -exec-step-instruction
28373 *stopped,reason="end-stepping-range",
28374 frame=@{func="foo",args=[],file="try.c",
28375 fullname="/home/foo/bar/try.c",line="10"@}
28377 -exec-step-instruction
28381 *stopped,reason="end-stepping-range",
28382 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28383 fullname="/home/foo/bar/try.c",line="10"@}
28388 @subheading The @code{-exec-until} Command
28389 @findex -exec-until
28391 @subsubheading Synopsis
28394 -exec-until [ @var{location} ]
28397 Executes the inferior until the @var{location} specified in the
28398 argument is reached. If there is no argument, the inferior executes
28399 until a source line greater than the current one is reached. The
28400 reason for stopping in this case will be @samp{location-reached}.
28402 @subsubheading @value{GDBN} Command
28404 The corresponding @value{GDBN} command is @samp{until}.
28406 @subsubheading Example
28410 -exec-until recursive2.c:6
28414 *stopped,reason="location-reached",frame=@{func="main",args=[],
28415 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28420 @subheading -file-clear
28421 Is this going away????
28424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28425 @node GDB/MI Stack Manipulation
28426 @section @sc{gdb/mi} Stack Manipulation Commands
28428 @subheading The @code{-enable-frame-filters} Command
28429 @findex -enable-frame-filters
28432 -enable-frame-filters
28435 @value{GDBN} allows Python-based frame filters to affect the output of
28436 the MI commands relating to stack traces. As there is no way to
28437 implement this in a fully backward-compatible way, a front end must
28438 request that this functionality be enabled.
28440 Once enabled, this feature cannot be disabled.
28442 Note that if Python support has not been compiled into @value{GDBN},
28443 this command will still succeed (and do nothing).
28445 @subheading The @code{-stack-info-frame} Command
28446 @findex -stack-info-frame
28448 @subsubheading Synopsis
28454 Get info on the selected frame.
28456 @subsubheading @value{GDBN} Command
28458 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28459 (without arguments).
28461 @subsubheading Example
28466 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28468 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28472 @subheading The @code{-stack-info-depth} Command
28473 @findex -stack-info-depth
28475 @subsubheading Synopsis
28478 -stack-info-depth [ @var{max-depth} ]
28481 Return the depth of the stack. If the integer argument @var{max-depth}
28482 is specified, do not count beyond @var{max-depth} frames.
28484 @subsubheading @value{GDBN} Command
28486 There's no equivalent @value{GDBN} command.
28488 @subsubheading Example
28490 For a stack with frame levels 0 through 11:
28497 -stack-info-depth 4
28500 -stack-info-depth 12
28503 -stack-info-depth 11
28506 -stack-info-depth 13
28511 @anchor{-stack-list-arguments}
28512 @subheading The @code{-stack-list-arguments} Command
28513 @findex -stack-list-arguments
28515 @subsubheading Synopsis
28518 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28519 [ @var{low-frame} @var{high-frame} ]
28522 Display a list of the arguments for the frames between @var{low-frame}
28523 and @var{high-frame} (inclusive). If @var{low-frame} and
28524 @var{high-frame} are not provided, list the arguments for the whole
28525 call stack. If the two arguments are equal, show the single frame
28526 at the corresponding level. It is an error if @var{low-frame} is
28527 larger than the actual number of frames. On the other hand,
28528 @var{high-frame} may be larger than the actual number of frames, in
28529 which case only existing frames will be returned.
28531 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28532 the variables; if it is 1 or @code{--all-values}, print also their
28533 values; and if it is 2 or @code{--simple-values}, print the name,
28534 type and value for simple data types, and the name and type for arrays,
28535 structures and unions. If the option @code{--no-frame-filters} is
28536 supplied, then Python frame filters will not be executed.
28538 If the @code{--skip-unavailable} option is specified, arguments that
28539 are not available are not listed. Partially available arguments
28540 are still displayed, however.
28542 Use of this command to obtain arguments in a single frame is
28543 deprecated in favor of the @samp{-stack-list-variables} command.
28545 @subsubheading @value{GDBN} Command
28547 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28548 @samp{gdb_get_args} command which partially overlaps with the
28549 functionality of @samp{-stack-list-arguments}.
28551 @subsubheading Example
28558 frame=@{level="0",addr="0x00010734",func="callee4",
28559 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28560 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28561 frame=@{level="1",addr="0x0001076c",func="callee3",
28562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28563 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28564 frame=@{level="2",addr="0x0001078c",func="callee2",
28565 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28566 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28567 frame=@{level="3",addr="0x000107b4",func="callee1",
28568 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28569 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28570 frame=@{level="4",addr="0x000107e0",func="main",
28571 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28572 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28574 -stack-list-arguments 0
28577 frame=@{level="0",args=[]@},
28578 frame=@{level="1",args=[name="strarg"]@},
28579 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28580 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28581 frame=@{level="4",args=[]@}]
28583 -stack-list-arguments 1
28586 frame=@{level="0",args=[]@},
28588 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28589 frame=@{level="2",args=[
28590 @{name="intarg",value="2"@},
28591 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28592 @{frame=@{level="3",args=[
28593 @{name="intarg",value="2"@},
28594 @{name="strarg",value="0x11940 \"A string argument.\""@},
28595 @{name="fltarg",value="3.5"@}]@},
28596 frame=@{level="4",args=[]@}]
28598 -stack-list-arguments 0 2 2
28599 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28601 -stack-list-arguments 1 2 2
28602 ^done,stack-args=[frame=@{level="2",
28603 args=[@{name="intarg",value="2"@},
28604 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28608 @c @subheading -stack-list-exception-handlers
28611 @anchor{-stack-list-frames}
28612 @subheading The @code{-stack-list-frames} Command
28613 @findex -stack-list-frames
28615 @subsubheading Synopsis
28618 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28621 List the frames currently on the stack. For each frame it displays the
28626 The frame number, 0 being the topmost frame, i.e., the innermost function.
28628 The @code{$pc} value for that frame.
28632 File name of the source file where the function lives.
28633 @item @var{fullname}
28634 The full file name of the source file where the function lives.
28636 Line number corresponding to the @code{$pc}.
28638 The shared library where this function is defined. This is only given
28639 if the frame's function is not known.
28642 If invoked without arguments, this command prints a backtrace for the
28643 whole stack. If given two integer arguments, it shows the frames whose
28644 levels are between the two arguments (inclusive). If the two arguments
28645 are equal, it shows the single frame at the corresponding level. It is
28646 an error if @var{low-frame} is larger than the actual number of
28647 frames. On the other hand, @var{high-frame} may be larger than the
28648 actual number of frames, in which case only existing frames will be
28649 returned. If the option @code{--no-frame-filters} is supplied, then
28650 Python frame filters will not be executed.
28652 @subsubheading @value{GDBN} Command
28654 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28656 @subsubheading Example
28658 Full stack backtrace:
28664 [frame=@{level="0",addr="0x0001076c",func="foo",
28665 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28666 frame=@{level="1",addr="0x000107a4",func="foo",
28667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28668 frame=@{level="2",addr="0x000107a4",func="foo",
28669 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28670 frame=@{level="3",addr="0x000107a4",func="foo",
28671 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28672 frame=@{level="4",addr="0x000107a4",func="foo",
28673 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28674 frame=@{level="5",addr="0x000107a4",func="foo",
28675 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28676 frame=@{level="6",addr="0x000107a4",func="foo",
28677 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28678 frame=@{level="7",addr="0x000107a4",func="foo",
28679 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28680 frame=@{level="8",addr="0x000107a4",func="foo",
28681 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28682 frame=@{level="9",addr="0x000107a4",func="foo",
28683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28684 frame=@{level="10",addr="0x000107a4",func="foo",
28685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28686 frame=@{level="11",addr="0x00010738",func="main",
28687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28691 Show frames between @var{low_frame} and @var{high_frame}:
28695 -stack-list-frames 3 5
28697 [frame=@{level="3",addr="0x000107a4",func="foo",
28698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28699 frame=@{level="4",addr="0x000107a4",func="foo",
28700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28701 frame=@{level="5",addr="0x000107a4",func="foo",
28702 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28706 Show a single frame:
28710 -stack-list-frames 3 3
28712 [frame=@{level="3",addr="0x000107a4",func="foo",
28713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28718 @subheading The @code{-stack-list-locals} Command
28719 @findex -stack-list-locals
28720 @anchor{-stack-list-locals}
28722 @subsubheading Synopsis
28725 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28728 Display the local variable names for the selected frame. If
28729 @var{print-values} is 0 or @code{--no-values}, print only the names of
28730 the variables; if it is 1 or @code{--all-values}, print also their
28731 values; and if it is 2 or @code{--simple-values}, print the name,
28732 type and value for simple data types, and the name and type for arrays,
28733 structures and unions. In this last case, a frontend can immediately
28734 display the value of simple data types and create variable objects for
28735 other data types when the user wishes to explore their values in
28736 more detail. If the option @code{--no-frame-filters} is supplied, then
28737 Python frame filters will not be executed.
28739 If the @code{--skip-unavailable} option is specified, local variables
28740 that are not available are not listed. Partially available local
28741 variables are still displayed, however.
28743 This command is deprecated in favor of the
28744 @samp{-stack-list-variables} command.
28746 @subsubheading @value{GDBN} Command
28748 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28750 @subsubheading Example
28754 -stack-list-locals 0
28755 ^done,locals=[name="A",name="B",name="C"]
28757 -stack-list-locals --all-values
28758 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28759 @{name="C",value="@{1, 2, 3@}"@}]
28760 -stack-list-locals --simple-values
28761 ^done,locals=[@{name="A",type="int",value="1"@},
28762 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28766 @anchor{-stack-list-variables}
28767 @subheading The @code{-stack-list-variables} Command
28768 @findex -stack-list-variables
28770 @subsubheading Synopsis
28773 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28776 Display the names of local variables and function arguments for the selected frame. If
28777 @var{print-values} is 0 or @code{--no-values}, print only the names of
28778 the variables; if it is 1 or @code{--all-values}, print also their
28779 values; and if it is 2 or @code{--simple-values}, print the name,
28780 type and value for simple data types, and the name and type for arrays,
28781 structures and unions. If the option @code{--no-frame-filters} is
28782 supplied, then Python frame filters will not be executed.
28784 If the @code{--skip-unavailable} option is specified, local variables
28785 and arguments that are not available are not listed. Partially
28786 available arguments and local variables are still displayed, however.
28788 @subsubheading Example
28792 -stack-list-variables --thread 1 --frame 0 --all-values
28793 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28798 @subheading The @code{-stack-select-frame} Command
28799 @findex -stack-select-frame
28801 @subsubheading Synopsis
28804 -stack-select-frame @var{framenum}
28807 Change the selected frame. Select a different frame @var{framenum} on
28810 This command in deprecated in favor of passing the @samp{--frame}
28811 option to every command.
28813 @subsubheading @value{GDBN} Command
28815 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28816 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28818 @subsubheading Example
28822 -stack-select-frame 2
28827 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28828 @node GDB/MI Variable Objects
28829 @section @sc{gdb/mi} Variable Objects
28833 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28835 For the implementation of a variable debugger window (locals, watched
28836 expressions, etc.), we are proposing the adaptation of the existing code
28837 used by @code{Insight}.
28839 The two main reasons for that are:
28843 It has been proven in practice (it is already on its second generation).
28846 It will shorten development time (needless to say how important it is
28850 The original interface was designed to be used by Tcl code, so it was
28851 slightly changed so it could be used through @sc{gdb/mi}. This section
28852 describes the @sc{gdb/mi} operations that will be available and gives some
28853 hints about their use.
28855 @emph{Note}: In addition to the set of operations described here, we
28856 expect the @sc{gui} implementation of a variable window to require, at
28857 least, the following operations:
28860 @item @code{-gdb-show} @code{output-radix}
28861 @item @code{-stack-list-arguments}
28862 @item @code{-stack-list-locals}
28863 @item @code{-stack-select-frame}
28868 @subheading Introduction to Variable Objects
28870 @cindex variable objects in @sc{gdb/mi}
28872 Variable objects are "object-oriented" MI interface for examining and
28873 changing values of expressions. Unlike some other MI interfaces that
28874 work with expressions, variable objects are specifically designed for
28875 simple and efficient presentation in the frontend. A variable object
28876 is identified by string name. When a variable object is created, the
28877 frontend specifies the expression for that variable object. The
28878 expression can be a simple variable, or it can be an arbitrary complex
28879 expression, and can even involve CPU registers. After creating a
28880 variable object, the frontend can invoke other variable object
28881 operations---for example to obtain or change the value of a variable
28882 object, or to change display format.
28884 Variable objects have hierarchical tree structure. Any variable object
28885 that corresponds to a composite type, such as structure in C, has
28886 a number of child variable objects, for example corresponding to each
28887 element of a structure. A child variable object can itself have
28888 children, recursively. Recursion ends when we reach
28889 leaf variable objects, which always have built-in types. Child variable
28890 objects are created only by explicit request, so if a frontend
28891 is not interested in the children of a particular variable object, no
28892 child will be created.
28894 For a leaf variable object it is possible to obtain its value as a
28895 string, or set the value from a string. String value can be also
28896 obtained for a non-leaf variable object, but it's generally a string
28897 that only indicates the type of the object, and does not list its
28898 contents. Assignment to a non-leaf variable object is not allowed.
28900 A frontend does not need to read the values of all variable objects each time
28901 the program stops. Instead, MI provides an update command that lists all
28902 variable objects whose values has changed since the last update
28903 operation. This considerably reduces the amount of data that must
28904 be transferred to the frontend. As noted above, children variable
28905 objects are created on demand, and only leaf variable objects have a
28906 real value. As result, gdb will read target memory only for leaf
28907 variables that frontend has created.
28909 The automatic update is not always desirable. For example, a frontend
28910 might want to keep a value of some expression for future reference,
28911 and never update it. For another example, fetching memory is
28912 relatively slow for embedded targets, so a frontend might want
28913 to disable automatic update for the variables that are either not
28914 visible on the screen, or ``closed''. This is possible using so
28915 called ``frozen variable objects''. Such variable objects are never
28916 implicitly updated.
28918 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28919 fixed variable object, the expression is parsed when the variable
28920 object is created, including associating identifiers to specific
28921 variables. The meaning of expression never changes. For a floating
28922 variable object the values of variables whose names appear in the
28923 expressions are re-evaluated every time in the context of the current
28924 frame. Consider this example:
28929 struct work_state state;
28936 If a fixed variable object for the @code{state} variable is created in
28937 this function, and we enter the recursive call, the variable
28938 object will report the value of @code{state} in the top-level
28939 @code{do_work} invocation. On the other hand, a floating variable
28940 object will report the value of @code{state} in the current frame.
28942 If an expression specified when creating a fixed variable object
28943 refers to a local variable, the variable object becomes bound to the
28944 thread and frame in which the variable object is created. When such
28945 variable object is updated, @value{GDBN} makes sure that the
28946 thread/frame combination the variable object is bound to still exists,
28947 and re-evaluates the variable object in context of that thread/frame.
28949 The following is the complete set of @sc{gdb/mi} operations defined to
28950 access this functionality:
28952 @multitable @columnfractions .4 .6
28953 @item @strong{Operation}
28954 @tab @strong{Description}
28956 @item @code{-enable-pretty-printing}
28957 @tab enable Python-based pretty-printing
28958 @item @code{-var-create}
28959 @tab create a variable object
28960 @item @code{-var-delete}
28961 @tab delete the variable object and/or its children
28962 @item @code{-var-set-format}
28963 @tab set the display format of this variable
28964 @item @code{-var-show-format}
28965 @tab show the display format of this variable
28966 @item @code{-var-info-num-children}
28967 @tab tells how many children this object has
28968 @item @code{-var-list-children}
28969 @tab return a list of the object's children
28970 @item @code{-var-info-type}
28971 @tab show the type of this variable object
28972 @item @code{-var-info-expression}
28973 @tab print parent-relative expression that this variable object represents
28974 @item @code{-var-info-path-expression}
28975 @tab print full expression that this variable object represents
28976 @item @code{-var-show-attributes}
28977 @tab is this variable editable? does it exist here?
28978 @item @code{-var-evaluate-expression}
28979 @tab get the value of this variable
28980 @item @code{-var-assign}
28981 @tab set the value of this variable
28982 @item @code{-var-update}
28983 @tab update the variable and its children
28984 @item @code{-var-set-frozen}
28985 @tab set frozeness attribute
28986 @item @code{-var-set-update-range}
28987 @tab set range of children to display on update
28990 In the next subsection we describe each operation in detail and suggest
28991 how it can be used.
28993 @subheading Description And Use of Operations on Variable Objects
28995 @subheading The @code{-enable-pretty-printing} Command
28996 @findex -enable-pretty-printing
28999 -enable-pretty-printing
29002 @value{GDBN} allows Python-based visualizers to affect the output of the
29003 MI variable object commands. However, because there was no way to
29004 implement this in a fully backward-compatible way, a front end must
29005 request that this functionality be enabled.
29007 Once enabled, this feature cannot be disabled.
29009 Note that if Python support has not been compiled into @value{GDBN},
29010 this command will still succeed (and do nothing).
29012 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29013 may work differently in future versions of @value{GDBN}.
29015 @subheading The @code{-var-create} Command
29016 @findex -var-create
29018 @subsubheading Synopsis
29021 -var-create @{@var{name} | "-"@}
29022 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29025 This operation creates a variable object, which allows the monitoring of
29026 a variable, the result of an expression, a memory cell or a CPU
29029 The @var{name} parameter is the string by which the object can be
29030 referenced. It must be unique. If @samp{-} is specified, the varobj
29031 system will generate a string ``varNNNNNN'' automatically. It will be
29032 unique provided that one does not specify @var{name} of that format.
29033 The command fails if a duplicate name is found.
29035 The frame under which the expression should be evaluated can be
29036 specified by @var{frame-addr}. A @samp{*} indicates that the current
29037 frame should be used. A @samp{@@} indicates that a floating variable
29038 object must be created.
29040 @var{expression} is any expression valid on the current language set (must not
29041 begin with a @samp{*}), or one of the following:
29045 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29048 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29051 @samp{$@var{regname}} --- a CPU register name
29054 @cindex dynamic varobj
29055 A varobj's contents may be provided by a Python-based pretty-printer. In this
29056 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29057 have slightly different semantics in some cases. If the
29058 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29059 will never create a dynamic varobj. This ensures backward
29060 compatibility for existing clients.
29062 @subsubheading Result
29064 This operation returns attributes of the newly-created varobj. These
29069 The name of the varobj.
29072 The number of children of the varobj. This number is not necessarily
29073 reliable for a dynamic varobj. Instead, you must examine the
29074 @samp{has_more} attribute.
29077 The varobj's scalar value. For a varobj whose type is some sort of
29078 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29079 will not be interesting.
29082 The varobj's type. This is a string representation of the type, as
29083 would be printed by the @value{GDBN} CLI. If @samp{print object}
29084 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29085 @emph{actual} (derived) type of the object is shown rather than the
29086 @emph{declared} one.
29089 If a variable object is bound to a specific thread, then this is the
29090 thread's global identifier.
29093 For a dynamic varobj, this indicates whether there appear to be any
29094 children available. For a non-dynamic varobj, this will be 0.
29097 This attribute will be present and have the value @samp{1} if the
29098 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29099 then this attribute will not be present.
29102 A dynamic varobj can supply a display hint to the front end. The
29103 value comes directly from the Python pretty-printer object's
29104 @code{display_hint} method. @xref{Pretty Printing API}.
29107 Typical output will look like this:
29110 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29111 has_more="@var{has_more}"
29115 @subheading The @code{-var-delete} Command
29116 @findex -var-delete
29118 @subsubheading Synopsis
29121 -var-delete [ -c ] @var{name}
29124 Deletes a previously created variable object and all of its children.
29125 With the @samp{-c} option, just deletes the children.
29127 Returns an error if the object @var{name} is not found.
29130 @subheading The @code{-var-set-format} Command
29131 @findex -var-set-format
29133 @subsubheading Synopsis
29136 -var-set-format @var{name} @var{format-spec}
29139 Sets the output format for the value of the object @var{name} to be
29142 @anchor{-var-set-format}
29143 The syntax for the @var{format-spec} is as follows:
29146 @var{format-spec} @expansion{}
29147 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29150 The natural format is the default format choosen automatically
29151 based on the variable type (like decimal for an @code{int}, hex
29152 for pointers, etc.).
29154 The zero-hexadecimal format has a representation similar to hexadecimal
29155 but with padding zeroes to the left of the value. For example, a 32-bit
29156 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29157 zero-hexadecimal format.
29159 For a variable with children, the format is set only on the
29160 variable itself, and the children are not affected.
29162 @subheading The @code{-var-show-format} Command
29163 @findex -var-show-format
29165 @subsubheading Synopsis
29168 -var-show-format @var{name}
29171 Returns the format used to display the value of the object @var{name}.
29174 @var{format} @expansion{}
29179 @subheading The @code{-var-info-num-children} Command
29180 @findex -var-info-num-children
29182 @subsubheading Synopsis
29185 -var-info-num-children @var{name}
29188 Returns the number of children of a variable object @var{name}:
29194 Note that this number is not completely reliable for a dynamic varobj.
29195 It will return the current number of children, but more children may
29199 @subheading The @code{-var-list-children} Command
29200 @findex -var-list-children
29202 @subsubheading Synopsis
29205 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29207 @anchor{-var-list-children}
29209 Return a list of the children of the specified variable object and
29210 create variable objects for them, if they do not already exist. With
29211 a single argument or if @var{print-values} has a value of 0 or
29212 @code{--no-values}, print only the names of the variables; if
29213 @var{print-values} is 1 or @code{--all-values}, also print their
29214 values; and if it is 2 or @code{--simple-values} print the name and
29215 value for simple data types and just the name for arrays, structures
29218 @var{from} and @var{to}, if specified, indicate the range of children
29219 to report. If @var{from} or @var{to} is less than zero, the range is
29220 reset and all children will be reported. Otherwise, children starting
29221 at @var{from} (zero-based) and up to and excluding @var{to} will be
29224 If a child range is requested, it will only affect the current call to
29225 @code{-var-list-children}, but not future calls to @code{-var-update}.
29226 For this, you must instead use @code{-var-set-update-range}. The
29227 intent of this approach is to enable a front end to implement any
29228 update approach it likes; for example, scrolling a view may cause the
29229 front end to request more children with @code{-var-list-children}, and
29230 then the front end could call @code{-var-set-update-range} with a
29231 different range to ensure that future updates are restricted to just
29234 For each child the following results are returned:
29239 Name of the variable object created for this child.
29242 The expression to be shown to the user by the front end to designate this child.
29243 For example this may be the name of a structure member.
29245 For a dynamic varobj, this value cannot be used to form an
29246 expression. There is no way to do this at all with a dynamic varobj.
29248 For C/C@t{++} structures there are several pseudo children returned to
29249 designate access qualifiers. For these pseudo children @var{exp} is
29250 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29251 type and value are not present.
29253 A dynamic varobj will not report the access qualifying
29254 pseudo-children, regardless of the language. This information is not
29255 available at all with a dynamic varobj.
29258 Number of children this child has. For a dynamic varobj, this will be
29262 The type of the child. If @samp{print object}
29263 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29264 @emph{actual} (derived) type of the object is shown rather than the
29265 @emph{declared} one.
29268 If values were requested, this is the value.
29271 If this variable object is associated with a thread, this is the
29272 thread's global thread id. Otherwise this result is not present.
29275 If the variable object is frozen, this variable will be present with a value of 1.
29278 A dynamic varobj can supply a display hint to the front end. The
29279 value comes directly from the Python pretty-printer object's
29280 @code{display_hint} method. @xref{Pretty Printing API}.
29283 This attribute will be present and have the value @samp{1} if the
29284 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29285 then this attribute will not be present.
29289 The result may have its own attributes:
29293 A dynamic varobj can supply a display hint to the front end. The
29294 value comes directly from the Python pretty-printer object's
29295 @code{display_hint} method. @xref{Pretty Printing API}.
29298 This is an integer attribute which is nonzero if there are children
29299 remaining after the end of the selected range.
29302 @subsubheading Example
29306 -var-list-children n
29307 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29308 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29310 -var-list-children --all-values n
29311 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29312 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29316 @subheading The @code{-var-info-type} Command
29317 @findex -var-info-type
29319 @subsubheading Synopsis
29322 -var-info-type @var{name}
29325 Returns the type of the specified variable @var{name}. The type is
29326 returned as a string in the same format as it is output by the
29330 type=@var{typename}
29334 @subheading The @code{-var-info-expression} Command
29335 @findex -var-info-expression
29337 @subsubheading Synopsis
29340 -var-info-expression @var{name}
29343 Returns a string that is suitable for presenting this
29344 variable object in user interface. The string is generally
29345 not valid expression in the current language, and cannot be evaluated.
29347 For example, if @code{a} is an array, and variable object
29348 @code{A} was created for @code{a}, then we'll get this output:
29351 (gdb) -var-info-expression A.1
29352 ^done,lang="C",exp="1"
29356 Here, the value of @code{lang} is the language name, which can be
29357 found in @ref{Supported Languages}.
29359 Note that the output of the @code{-var-list-children} command also
29360 includes those expressions, so the @code{-var-info-expression} command
29363 @subheading The @code{-var-info-path-expression} Command
29364 @findex -var-info-path-expression
29366 @subsubheading Synopsis
29369 -var-info-path-expression @var{name}
29372 Returns an expression that can be evaluated in the current
29373 context and will yield the same value that a variable object has.
29374 Compare this with the @code{-var-info-expression} command, which
29375 result can be used only for UI presentation. Typical use of
29376 the @code{-var-info-path-expression} command is creating a
29377 watchpoint from a variable object.
29379 This command is currently not valid for children of a dynamic varobj,
29380 and will give an error when invoked on one.
29382 For example, suppose @code{C} is a C@t{++} class, derived from class
29383 @code{Base}, and that the @code{Base} class has a member called
29384 @code{m_size}. Assume a variable @code{c} is has the type of
29385 @code{C} and a variable object @code{C} was created for variable
29386 @code{c}. Then, we'll get this output:
29388 (gdb) -var-info-path-expression C.Base.public.m_size
29389 ^done,path_expr=((Base)c).m_size)
29392 @subheading The @code{-var-show-attributes} Command
29393 @findex -var-show-attributes
29395 @subsubheading Synopsis
29398 -var-show-attributes @var{name}
29401 List attributes of the specified variable object @var{name}:
29404 status=@var{attr} [ ( ,@var{attr} )* ]
29408 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29410 @subheading The @code{-var-evaluate-expression} Command
29411 @findex -var-evaluate-expression
29413 @subsubheading Synopsis
29416 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29419 Evaluates the expression that is represented by the specified variable
29420 object and returns its value as a string. The format of the string
29421 can be specified with the @samp{-f} option. The possible values of
29422 this option are the same as for @code{-var-set-format}
29423 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29424 the current display format will be used. The current display format
29425 can be changed using the @code{-var-set-format} command.
29431 Note that one must invoke @code{-var-list-children} for a variable
29432 before the value of a child variable can be evaluated.
29434 @subheading The @code{-var-assign} Command
29435 @findex -var-assign
29437 @subsubheading Synopsis
29440 -var-assign @var{name} @var{expression}
29443 Assigns the value of @var{expression} to the variable object specified
29444 by @var{name}. The object must be @samp{editable}. If the variable's
29445 value is altered by the assign, the variable will show up in any
29446 subsequent @code{-var-update} list.
29448 @subsubheading Example
29456 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29460 @subheading The @code{-var-update} Command
29461 @findex -var-update
29463 @subsubheading Synopsis
29466 -var-update [@var{print-values}] @{@var{name} | "*"@}
29469 Reevaluate the expressions corresponding to the variable object
29470 @var{name} and all its direct and indirect children, and return the
29471 list of variable objects whose values have changed; @var{name} must
29472 be a root variable object. Here, ``changed'' means that the result of
29473 @code{-var-evaluate-expression} before and after the
29474 @code{-var-update} is different. If @samp{*} is used as the variable
29475 object names, all existing variable objects are updated, except
29476 for frozen ones (@pxref{-var-set-frozen}). The option
29477 @var{print-values} determines whether both names and values, or just
29478 names are printed. The possible values of this option are the same
29479 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29480 recommended to use the @samp{--all-values} option, to reduce the
29481 number of MI commands needed on each program stop.
29483 With the @samp{*} parameter, if a variable object is bound to a
29484 currently running thread, it will not be updated, without any
29487 If @code{-var-set-update-range} was previously used on a varobj, then
29488 only the selected range of children will be reported.
29490 @code{-var-update} reports all the changed varobjs in a tuple named
29493 Each item in the change list is itself a tuple holding:
29497 The name of the varobj.
29500 If values were requested for this update, then this field will be
29501 present and will hold the value of the varobj.
29504 @anchor{-var-update}
29505 This field is a string which may take one of three values:
29509 The variable object's current value is valid.
29512 The variable object does not currently hold a valid value but it may
29513 hold one in the future if its associated expression comes back into
29517 The variable object no longer holds a valid value.
29518 This can occur when the executable file being debugged has changed,
29519 either through recompilation or by using the @value{GDBN} @code{file}
29520 command. The front end should normally choose to delete these variable
29524 In the future new values may be added to this list so the front should
29525 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29528 This is only present if the varobj is still valid. If the type
29529 changed, then this will be the string @samp{true}; otherwise it will
29532 When a varobj's type changes, its children are also likely to have
29533 become incorrect. Therefore, the varobj's children are automatically
29534 deleted when this attribute is @samp{true}. Also, the varobj's update
29535 range, when set using the @code{-var-set-update-range} command, is
29539 If the varobj's type changed, then this field will be present and will
29542 @item new_num_children
29543 For a dynamic varobj, if the number of children changed, or if the
29544 type changed, this will be the new number of children.
29546 The @samp{numchild} field in other varobj responses is generally not
29547 valid for a dynamic varobj -- it will show the number of children that
29548 @value{GDBN} knows about, but because dynamic varobjs lazily
29549 instantiate their children, this will not reflect the number of
29550 children which may be available.
29552 The @samp{new_num_children} attribute only reports changes to the
29553 number of children known by @value{GDBN}. This is the only way to
29554 detect whether an update has removed children (which necessarily can
29555 only happen at the end of the update range).
29558 The display hint, if any.
29561 This is an integer value, which will be 1 if there are more children
29562 available outside the varobj's update range.
29565 This attribute will be present and have the value @samp{1} if the
29566 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29567 then this attribute will not be present.
29570 If new children were added to a dynamic varobj within the selected
29571 update range (as set by @code{-var-set-update-range}), then they will
29572 be listed in this attribute.
29575 @subsubheading Example
29582 -var-update --all-values var1
29583 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29584 type_changed="false"@}]
29588 @subheading The @code{-var-set-frozen} Command
29589 @findex -var-set-frozen
29590 @anchor{-var-set-frozen}
29592 @subsubheading Synopsis
29595 -var-set-frozen @var{name} @var{flag}
29598 Set the frozenness flag on the variable object @var{name}. The
29599 @var{flag} parameter should be either @samp{1} to make the variable
29600 frozen or @samp{0} to make it unfrozen. If a variable object is
29601 frozen, then neither itself, nor any of its children, are
29602 implicitly updated by @code{-var-update} of
29603 a parent variable or by @code{-var-update *}. Only
29604 @code{-var-update} of the variable itself will update its value and
29605 values of its children. After a variable object is unfrozen, it is
29606 implicitly updated by all subsequent @code{-var-update} operations.
29607 Unfreezing a variable does not update it, only subsequent
29608 @code{-var-update} does.
29610 @subsubheading Example
29614 -var-set-frozen V 1
29619 @subheading The @code{-var-set-update-range} command
29620 @findex -var-set-update-range
29621 @anchor{-var-set-update-range}
29623 @subsubheading Synopsis
29626 -var-set-update-range @var{name} @var{from} @var{to}
29629 Set the range of children to be returned by future invocations of
29630 @code{-var-update}.
29632 @var{from} and @var{to} indicate the range of children to report. If
29633 @var{from} or @var{to} is less than zero, the range is reset and all
29634 children will be reported. Otherwise, children starting at @var{from}
29635 (zero-based) and up to and excluding @var{to} will be reported.
29637 @subsubheading Example
29641 -var-set-update-range V 1 2
29645 @subheading The @code{-var-set-visualizer} command
29646 @findex -var-set-visualizer
29647 @anchor{-var-set-visualizer}
29649 @subsubheading Synopsis
29652 -var-set-visualizer @var{name} @var{visualizer}
29655 Set a visualizer for the variable object @var{name}.
29657 @var{visualizer} is the visualizer to use. The special value
29658 @samp{None} means to disable any visualizer in use.
29660 If not @samp{None}, @var{visualizer} must be a Python expression.
29661 This expression must evaluate to a callable object which accepts a
29662 single argument. @value{GDBN} will call this object with the value of
29663 the varobj @var{name} as an argument (this is done so that the same
29664 Python pretty-printing code can be used for both the CLI and MI).
29665 When called, this object must return an object which conforms to the
29666 pretty-printing interface (@pxref{Pretty Printing API}).
29668 The pre-defined function @code{gdb.default_visualizer} may be used to
29669 select a visualizer by following the built-in process
29670 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29671 a varobj is created, and so ordinarily is not needed.
29673 This feature is only available if Python support is enabled. The MI
29674 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29675 can be used to check this.
29677 @subsubheading Example
29679 Resetting the visualizer:
29683 -var-set-visualizer V None
29687 Reselecting the default (type-based) visualizer:
29691 -var-set-visualizer V gdb.default_visualizer
29695 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29696 can be used to instantiate this class for a varobj:
29700 -var-set-visualizer V "lambda val: SomeClass()"
29704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29705 @node GDB/MI Data Manipulation
29706 @section @sc{gdb/mi} Data Manipulation
29708 @cindex data manipulation, in @sc{gdb/mi}
29709 @cindex @sc{gdb/mi}, data manipulation
29710 This section describes the @sc{gdb/mi} commands that manipulate data:
29711 examine memory and registers, evaluate expressions, etc.
29713 For details about what an addressable memory unit is,
29714 @pxref{addressable memory unit}.
29716 @c REMOVED FROM THE INTERFACE.
29717 @c @subheading -data-assign
29718 @c Change the value of a program variable. Plenty of side effects.
29719 @c @subsubheading GDB Command
29721 @c @subsubheading Example
29724 @subheading The @code{-data-disassemble} Command
29725 @findex -data-disassemble
29727 @subsubheading Synopsis
29731 [ -s @var{start-addr} -e @var{end-addr} ]
29732 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29740 @item @var{start-addr}
29741 is the beginning address (or @code{$pc})
29742 @item @var{end-addr}
29744 @item @var{filename}
29745 is the name of the file to disassemble
29746 @item @var{linenum}
29747 is the line number to disassemble around
29749 is the number of disassembly lines to be produced. If it is -1,
29750 the whole function will be disassembled, in case no @var{end-addr} is
29751 specified. If @var{end-addr} is specified as a non-zero value, and
29752 @var{lines} is lower than the number of disassembly lines between
29753 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29754 displayed; if @var{lines} is higher than the number of lines between
29755 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29760 @item 0 disassembly only
29761 @item 1 mixed source and disassembly (deprecated)
29762 @item 2 disassembly with raw opcodes
29763 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29764 @item 4 mixed source and disassembly
29765 @item 5 mixed source and disassembly with raw opcodes
29768 Modes 1 and 3 are deprecated. The output is ``source centric''
29769 which hasn't proved useful in practice.
29770 @xref{Machine Code}, for a discussion of the difference between
29771 @code{/m} and @code{/s} output of the @code{disassemble} command.
29774 @subsubheading Result
29776 The result of the @code{-data-disassemble} command will be a list named
29777 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29778 used with the @code{-data-disassemble} command.
29780 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29785 The address at which this instruction was disassembled.
29788 The name of the function this instruction is within.
29791 The decimal offset in bytes from the start of @samp{func-name}.
29794 The text disassembly for this @samp{address}.
29797 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29798 bytes for the @samp{inst} field.
29802 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29803 @samp{src_and_asm_line}, each of which has the following fields:
29807 The line number within @samp{file}.
29810 The file name from the compilation unit. This might be an absolute
29811 file name or a relative file name depending on the compile command
29815 Absolute file name of @samp{file}. It is converted to a canonical form
29816 using the source file search path
29817 (@pxref{Source Path, ,Specifying Source Directories})
29818 and after resolving all the symbolic links.
29820 If the source file is not found this field will contain the path as
29821 present in the debug information.
29823 @item line_asm_insn
29824 This is a list of tuples containing the disassembly for @samp{line} in
29825 @samp{file}. The fields of each tuple are the same as for
29826 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29827 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29832 Note that whatever included in the @samp{inst} field, is not
29833 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29836 @subsubheading @value{GDBN} Command
29838 The corresponding @value{GDBN} command is @samp{disassemble}.
29840 @subsubheading Example
29842 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29846 -data-disassemble -s $pc -e "$pc + 20" -- 0
29849 @{address="0x000107c0",func-name="main",offset="4",
29850 inst="mov 2, %o0"@},
29851 @{address="0x000107c4",func-name="main",offset="8",
29852 inst="sethi %hi(0x11800), %o2"@},
29853 @{address="0x000107c8",func-name="main",offset="12",
29854 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29855 @{address="0x000107cc",func-name="main",offset="16",
29856 inst="sethi %hi(0x11800), %o2"@},
29857 @{address="0x000107d0",func-name="main",offset="20",
29858 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29862 Disassemble the whole @code{main} function. Line 32 is part of
29866 -data-disassemble -f basics.c -l 32 -- 0
29868 @{address="0x000107bc",func-name="main",offset="0",
29869 inst="save %sp, -112, %sp"@},
29870 @{address="0x000107c0",func-name="main",offset="4",
29871 inst="mov 2, %o0"@},
29872 @{address="0x000107c4",func-name="main",offset="8",
29873 inst="sethi %hi(0x11800), %o2"@},
29875 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29876 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29880 Disassemble 3 instructions from the start of @code{main}:
29884 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29886 @{address="0x000107bc",func-name="main",offset="0",
29887 inst="save %sp, -112, %sp"@},
29888 @{address="0x000107c0",func-name="main",offset="4",
29889 inst="mov 2, %o0"@},
29890 @{address="0x000107c4",func-name="main",offset="8",
29891 inst="sethi %hi(0x11800), %o2"@}]
29895 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29899 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29901 src_and_asm_line=@{line="31",
29902 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29903 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29904 line_asm_insn=[@{address="0x000107bc",
29905 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29906 src_and_asm_line=@{line="32",
29907 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29908 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29909 line_asm_insn=[@{address="0x000107c0",
29910 func-name="main",offset="4",inst="mov 2, %o0"@},
29911 @{address="0x000107c4",func-name="main",offset="8",
29912 inst="sethi %hi(0x11800), %o2"@}]@}]
29917 @subheading The @code{-data-evaluate-expression} Command
29918 @findex -data-evaluate-expression
29920 @subsubheading Synopsis
29923 -data-evaluate-expression @var{expr}
29926 Evaluate @var{expr} as an expression. The expression could contain an
29927 inferior function call. The function call will execute synchronously.
29928 If the expression contains spaces, it must be enclosed in double quotes.
29930 @subsubheading @value{GDBN} Command
29932 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29933 @samp{call}. In @code{gdbtk} only, there's a corresponding
29934 @samp{gdb_eval} command.
29936 @subsubheading Example
29938 In the following example, the numbers that precede the commands are the
29939 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29940 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29944 211-data-evaluate-expression A
29947 311-data-evaluate-expression &A
29948 311^done,value="0xefffeb7c"
29950 411-data-evaluate-expression A+3
29953 511-data-evaluate-expression "A + 3"
29959 @subheading The @code{-data-list-changed-registers} Command
29960 @findex -data-list-changed-registers
29962 @subsubheading Synopsis
29965 -data-list-changed-registers
29968 Display a list of the registers that have changed.
29970 @subsubheading @value{GDBN} Command
29972 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29973 has the corresponding command @samp{gdb_changed_register_list}.
29975 @subsubheading Example
29977 On a PPC MBX board:
29985 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29986 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29989 -data-list-changed-registers
29990 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29991 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29992 "24","25","26","27","28","30","31","64","65","66","67","69"]
29997 @subheading The @code{-data-list-register-names} Command
29998 @findex -data-list-register-names
30000 @subsubheading Synopsis
30003 -data-list-register-names [ ( @var{regno} )+ ]
30006 Show a list of register names for the current target. If no arguments
30007 are given, it shows a list of the names of all the registers. If
30008 integer numbers are given as arguments, it will print a list of the
30009 names of the registers corresponding to the arguments. To ensure
30010 consistency between a register name and its number, the output list may
30011 include empty register names.
30013 @subsubheading @value{GDBN} Command
30015 @value{GDBN} does not have a command which corresponds to
30016 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30017 corresponding command @samp{gdb_regnames}.
30019 @subsubheading Example
30021 For the PPC MBX board:
30024 -data-list-register-names
30025 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30026 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30027 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30028 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30029 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30030 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30031 "", "pc","ps","cr","lr","ctr","xer"]
30033 -data-list-register-names 1 2 3
30034 ^done,register-names=["r1","r2","r3"]
30038 @subheading The @code{-data-list-register-values} Command
30039 @findex -data-list-register-values
30041 @subsubheading Synopsis
30044 -data-list-register-values
30045 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30048 Display the registers' contents. The format according to which the
30049 registers' contents are to be returned is given by @var{fmt}, followed
30050 by an optional list of numbers specifying the registers to display. A
30051 missing list of numbers indicates that the contents of all the
30052 registers must be returned. The @code{--skip-unavailable} option
30053 indicates that only the available registers are to be returned.
30055 Allowed formats for @var{fmt} are:
30072 @subsubheading @value{GDBN} Command
30074 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30075 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30077 @subsubheading Example
30079 For a PPC MBX board (note: line breaks are for readability only, they
30080 don't appear in the actual output):
30084 -data-list-register-values r 64 65
30085 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30086 @{number="65",value="0x00029002"@}]
30088 -data-list-register-values x
30089 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30090 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30091 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30092 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30093 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30094 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30095 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30096 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30097 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30098 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30099 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30100 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30101 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30102 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30103 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30104 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30105 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30106 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30107 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30108 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30109 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30110 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30111 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30112 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30113 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30114 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30115 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30116 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30117 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30118 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30119 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30120 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30121 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30122 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30123 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30124 @{number="69",value="0x20002b03"@}]
30129 @subheading The @code{-data-read-memory} Command
30130 @findex -data-read-memory
30132 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30134 @subsubheading Synopsis
30137 -data-read-memory [ -o @var{byte-offset} ]
30138 @var{address} @var{word-format} @var{word-size}
30139 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30146 @item @var{address}
30147 An expression specifying the address of the first memory word to be
30148 read. Complex expressions containing embedded white space should be
30149 quoted using the C convention.
30151 @item @var{word-format}
30152 The format to be used to print the memory words. The notation is the
30153 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30156 @item @var{word-size}
30157 The size of each memory word in bytes.
30159 @item @var{nr-rows}
30160 The number of rows in the output table.
30162 @item @var{nr-cols}
30163 The number of columns in the output table.
30166 If present, indicates that each row should include an @sc{ascii} dump. The
30167 value of @var{aschar} is used as a padding character when a byte is not a
30168 member of the printable @sc{ascii} character set (printable @sc{ascii}
30169 characters are those whose code is between 32 and 126, inclusively).
30171 @item @var{byte-offset}
30172 An offset to add to the @var{address} before fetching memory.
30175 This command displays memory contents as a table of @var{nr-rows} by
30176 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30177 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30178 (returned as @samp{total-bytes}). Should less than the requested number
30179 of bytes be returned by the target, the missing words are identified
30180 using @samp{N/A}. The number of bytes read from the target is returned
30181 in @samp{nr-bytes} and the starting address used to read memory in
30184 The address of the next/previous row or page is available in
30185 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30188 @subsubheading @value{GDBN} Command
30190 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30191 @samp{gdb_get_mem} memory read command.
30193 @subsubheading Example
30195 Read six bytes of memory starting at @code{bytes+6} but then offset by
30196 @code{-6} bytes. Format as three rows of two columns. One byte per
30197 word. Display each word in hex.
30201 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30202 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30203 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30204 prev-page="0x0000138a",memory=[
30205 @{addr="0x00001390",data=["0x00","0x01"]@},
30206 @{addr="0x00001392",data=["0x02","0x03"]@},
30207 @{addr="0x00001394",data=["0x04","0x05"]@}]
30211 Read two bytes of memory starting at address @code{shorts + 64} and
30212 display as a single word formatted in decimal.
30216 5-data-read-memory shorts+64 d 2 1 1
30217 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30218 next-row="0x00001512",prev-row="0x0000150e",
30219 next-page="0x00001512",prev-page="0x0000150e",memory=[
30220 @{addr="0x00001510",data=["128"]@}]
30224 Read thirty two bytes of memory starting at @code{bytes+16} and format
30225 as eight rows of four columns. Include a string encoding with @samp{x}
30226 used as the non-printable character.
30230 4-data-read-memory bytes+16 x 1 8 4 x
30231 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30232 next-row="0x000013c0",prev-row="0x0000139c",
30233 next-page="0x000013c0",prev-page="0x00001380",memory=[
30234 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30235 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30236 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30237 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30238 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30239 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30240 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30241 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30245 @subheading The @code{-data-read-memory-bytes} Command
30246 @findex -data-read-memory-bytes
30248 @subsubheading Synopsis
30251 -data-read-memory-bytes [ -o @var{offset} ]
30252 @var{address} @var{count}
30259 @item @var{address}
30260 An expression specifying the address of the first addressable memory unit
30261 to be read. Complex expressions containing embedded white space should be
30262 quoted using the C convention.
30265 The number of addressable memory units to read. This should be an integer
30269 The offset relative to @var{address} at which to start reading. This
30270 should be an integer literal. This option is provided so that a frontend
30271 is not required to first evaluate address and then perform address
30272 arithmetics itself.
30276 This command attempts to read all accessible memory regions in the
30277 specified range. First, all regions marked as unreadable in the memory
30278 map (if one is defined) will be skipped. @xref{Memory Region
30279 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30280 regions. For each one, if reading full region results in an errors,
30281 @value{GDBN} will try to read a subset of the region.
30283 In general, every single memory unit in the region may be readable or not,
30284 and the only way to read every readable unit is to try a read at
30285 every address, which is not practical. Therefore, @value{GDBN} will
30286 attempt to read all accessible memory units at either beginning or the end
30287 of the region, using a binary division scheme. This heuristic works
30288 well for reading accross a memory map boundary. Note that if a region
30289 has a readable range that is neither at the beginning or the end,
30290 @value{GDBN} will not read it.
30292 The result record (@pxref{GDB/MI Result Records}) that is output of
30293 the command includes a field named @samp{memory} whose content is a
30294 list of tuples. Each tuple represent a successfully read memory block
30295 and has the following fields:
30299 The start address of the memory block, as hexadecimal literal.
30302 The end address of the memory block, as hexadecimal literal.
30305 The offset of the memory block, as hexadecimal literal, relative to
30306 the start address passed to @code{-data-read-memory-bytes}.
30309 The contents of the memory block, in hex.
30315 @subsubheading @value{GDBN} Command
30317 The corresponding @value{GDBN} command is @samp{x}.
30319 @subsubheading Example
30323 -data-read-memory-bytes &a 10
30324 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30326 contents="01000000020000000300"@}]
30331 @subheading The @code{-data-write-memory-bytes} Command
30332 @findex -data-write-memory-bytes
30334 @subsubheading Synopsis
30337 -data-write-memory-bytes @var{address} @var{contents}
30338 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30345 @item @var{address}
30346 An expression specifying the address of the first addressable memory unit
30347 to be written. Complex expressions containing embedded white space should
30348 be quoted using the C convention.
30350 @item @var{contents}
30351 The hex-encoded data to write. It is an error if @var{contents} does
30352 not represent an integral number of addressable memory units.
30355 Optional argument indicating the number of addressable memory units to be
30356 written. If @var{count} is greater than @var{contents}' length,
30357 @value{GDBN} will repeatedly write @var{contents} until it fills
30358 @var{count} memory units.
30362 @subsubheading @value{GDBN} Command
30364 There's no corresponding @value{GDBN} command.
30366 @subsubheading Example
30370 -data-write-memory-bytes &a "aabbccdd"
30377 -data-write-memory-bytes &a "aabbccdd" 16e
30382 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30383 @node GDB/MI Tracepoint Commands
30384 @section @sc{gdb/mi} Tracepoint Commands
30386 The commands defined in this section implement MI support for
30387 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30389 @subheading The @code{-trace-find} Command
30390 @findex -trace-find
30392 @subsubheading Synopsis
30395 -trace-find @var{mode} [@var{parameters}@dots{}]
30398 Find a trace frame using criteria defined by @var{mode} and
30399 @var{parameters}. The following table lists permissible
30400 modes and their parameters. For details of operation, see @ref{tfind}.
30405 No parameters are required. Stops examining trace frames.
30408 An integer is required as parameter. Selects tracepoint frame with
30411 @item tracepoint-number
30412 An integer is required as parameter. Finds next
30413 trace frame that corresponds to tracepoint with the specified number.
30416 An address is required as parameter. Finds
30417 next trace frame that corresponds to any tracepoint at the specified
30420 @item pc-inside-range
30421 Two addresses are required as parameters. Finds next trace
30422 frame that corresponds to a tracepoint at an address inside the
30423 specified range. Both bounds are considered to be inside the range.
30425 @item pc-outside-range
30426 Two addresses are required as parameters. Finds
30427 next trace frame that corresponds to a tracepoint at an address outside
30428 the specified range. Both bounds are considered to be inside the range.
30431 Line specification is required as parameter. @xref{Specify Location}.
30432 Finds next trace frame that corresponds to a tracepoint at
30433 the specified location.
30437 If @samp{none} was passed as @var{mode}, the response does not
30438 have fields. Otherwise, the response may have the following fields:
30442 This field has either @samp{0} or @samp{1} as the value, depending
30443 on whether a matching tracepoint was found.
30446 The index of the found traceframe. This field is present iff
30447 the @samp{found} field has value of @samp{1}.
30450 The index of the found tracepoint. This field is present iff
30451 the @samp{found} field has value of @samp{1}.
30454 The information about the frame corresponding to the found trace
30455 frame. This field is present only if a trace frame was found.
30456 @xref{GDB/MI Frame Information}, for description of this field.
30460 @subsubheading @value{GDBN} Command
30462 The corresponding @value{GDBN} command is @samp{tfind}.
30464 @subheading -trace-define-variable
30465 @findex -trace-define-variable
30467 @subsubheading Synopsis
30470 -trace-define-variable @var{name} [ @var{value} ]
30473 Create trace variable @var{name} if it does not exist. If
30474 @var{value} is specified, sets the initial value of the specified
30475 trace variable to that value. Note that the @var{name} should start
30476 with the @samp{$} character.
30478 @subsubheading @value{GDBN} Command
30480 The corresponding @value{GDBN} command is @samp{tvariable}.
30482 @subheading The @code{-trace-frame-collected} Command
30483 @findex -trace-frame-collected
30485 @subsubheading Synopsis
30488 -trace-frame-collected
30489 [--var-print-values @var{var_pval}]
30490 [--comp-print-values @var{comp_pval}]
30491 [--registers-format @var{regformat}]
30492 [--memory-contents]
30495 This command returns the set of collected objects, register names,
30496 trace state variable names, memory ranges and computed expressions
30497 that have been collected at a particular trace frame. The optional
30498 parameters to the command affect the output format in different ways.
30499 See the output description table below for more details.
30501 The reported names can be used in the normal manner to create
30502 varobjs and inspect the objects themselves. The items returned by
30503 this command are categorized so that it is clear which is a variable,
30504 which is a register, which is a trace state variable, which is a
30505 memory range and which is a computed expression.
30507 For instance, if the actions were
30509 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30510 collect *(int*)0xaf02bef0@@40
30514 the object collected in its entirety would be @code{myVar}. The
30515 object @code{myArray} would be partially collected, because only the
30516 element at index @code{myIndex} would be collected. The remaining
30517 objects would be computed expressions.
30519 An example output would be:
30523 -trace-frame-collected
30525 explicit-variables=[@{name="myVar",value="1"@}],
30526 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30527 @{name="myObj.field",value="0"@},
30528 @{name="myPtr->field",value="1"@},
30529 @{name="myCount + 2",value="3"@},
30530 @{name="$tvar1 + 1",value="43970027"@}],
30531 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30532 @{number="1",value="0x0"@},
30533 @{number="2",value="0x4"@},
30535 @{number="125",value="0x0"@}],
30536 tvars=[@{name="$tvar1",current="43970026"@}],
30537 memory=[@{address="0x0000000000602264",length="4"@},
30538 @{address="0x0000000000615bc0",length="4"@}]
30545 @item explicit-variables
30546 The set of objects that have been collected in their entirety (as
30547 opposed to collecting just a few elements of an array or a few struct
30548 members). For each object, its name and value are printed.
30549 The @code{--var-print-values} option affects how or whether the value
30550 field is output. If @var{var_pval} is 0, then print only the names;
30551 if it is 1, print also their values; and if it is 2, print the name,
30552 type and value for simple data types, and the name and type for
30553 arrays, structures and unions.
30555 @item computed-expressions
30556 The set of computed expressions that have been collected at the
30557 current trace frame. The @code{--comp-print-values} option affects
30558 this set like the @code{--var-print-values} option affects the
30559 @code{explicit-variables} set. See above.
30562 The registers that have been collected at the current trace frame.
30563 For each register collected, the name and current value are returned.
30564 The value is formatted according to the @code{--registers-format}
30565 option. See the @command{-data-list-register-values} command for a
30566 list of the allowed formats. The default is @samp{x}.
30569 The trace state variables that have been collected at the current
30570 trace frame. For each trace state variable collected, the name and
30571 current value are returned.
30574 The set of memory ranges that have been collected at the current trace
30575 frame. Its content is a list of tuples. Each tuple represents a
30576 collected memory range and has the following fields:
30580 The start address of the memory range, as hexadecimal literal.
30583 The length of the memory range, as decimal literal.
30586 The contents of the memory block, in hex. This field is only present
30587 if the @code{--memory-contents} option is specified.
30593 @subsubheading @value{GDBN} Command
30595 There is no corresponding @value{GDBN} command.
30597 @subsubheading Example
30599 @subheading -trace-list-variables
30600 @findex -trace-list-variables
30602 @subsubheading Synopsis
30605 -trace-list-variables
30608 Return a table of all defined trace variables. Each element of the
30609 table has the following fields:
30613 The name of the trace variable. This field is always present.
30616 The initial value. This is a 64-bit signed integer. This
30617 field is always present.
30620 The value the trace variable has at the moment. This is a 64-bit
30621 signed integer. This field is absent iff current value is
30622 not defined, for example if the trace was never run, or is
30627 @subsubheading @value{GDBN} Command
30629 The corresponding @value{GDBN} command is @samp{tvariables}.
30631 @subsubheading Example
30635 -trace-list-variables
30636 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30637 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30638 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30639 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30640 body=[variable=@{name="$trace_timestamp",initial="0"@}
30641 variable=@{name="$foo",initial="10",current="15"@}]@}
30645 @subheading -trace-save
30646 @findex -trace-save
30648 @subsubheading Synopsis
30651 -trace-save [-r ] @var{filename}
30654 Saves the collected trace data to @var{filename}. Without the
30655 @samp{-r} option, the data is downloaded from the target and saved
30656 in a local file. With the @samp{-r} option the target is asked
30657 to perform the save.
30659 @subsubheading @value{GDBN} Command
30661 The corresponding @value{GDBN} command is @samp{tsave}.
30664 @subheading -trace-start
30665 @findex -trace-start
30667 @subsubheading Synopsis
30673 Starts a tracing experiments. The result of this command does not
30676 @subsubheading @value{GDBN} Command
30678 The corresponding @value{GDBN} command is @samp{tstart}.
30680 @subheading -trace-status
30681 @findex -trace-status
30683 @subsubheading Synopsis
30689 Obtains the status of a tracing experiment. The result may include
30690 the following fields:
30695 May have a value of either @samp{0}, when no tracing operations are
30696 supported, @samp{1}, when all tracing operations are supported, or
30697 @samp{file} when examining trace file. In the latter case, examining
30698 of trace frame is possible but new tracing experiement cannot be
30699 started. This field is always present.
30702 May have a value of either @samp{0} or @samp{1} depending on whether
30703 tracing experiement is in progress on target. This field is present
30704 if @samp{supported} field is not @samp{0}.
30707 Report the reason why the tracing was stopped last time. This field
30708 may be absent iff tracing was never stopped on target yet. The
30709 value of @samp{request} means the tracing was stopped as result of
30710 the @code{-trace-stop} command. The value of @samp{overflow} means
30711 the tracing buffer is full. The value of @samp{disconnection} means
30712 tracing was automatically stopped when @value{GDBN} has disconnected.
30713 The value of @samp{passcount} means tracing was stopped when a
30714 tracepoint was passed a maximal number of times for that tracepoint.
30715 This field is present if @samp{supported} field is not @samp{0}.
30717 @item stopping-tracepoint
30718 The number of tracepoint whose passcount as exceeded. This field is
30719 present iff the @samp{stop-reason} field has the value of
30723 @itemx frames-created
30724 The @samp{frames} field is a count of the total number of trace frames
30725 in the trace buffer, while @samp{frames-created} is the total created
30726 during the run, including ones that were discarded, such as when a
30727 circular trace buffer filled up. Both fields are optional.
30731 These fields tell the current size of the tracing buffer and the
30732 remaining space. These fields are optional.
30735 The value of the circular trace buffer flag. @code{1} means that the
30736 trace buffer is circular and old trace frames will be discarded if
30737 necessary to make room, @code{0} means that the trace buffer is linear
30741 The value of the disconnected tracing flag. @code{1} means that
30742 tracing will continue after @value{GDBN} disconnects, @code{0} means
30743 that the trace run will stop.
30746 The filename of the trace file being examined. This field is
30747 optional, and only present when examining a trace file.
30751 @subsubheading @value{GDBN} Command
30753 The corresponding @value{GDBN} command is @samp{tstatus}.
30755 @subheading -trace-stop
30756 @findex -trace-stop
30758 @subsubheading Synopsis
30764 Stops a tracing experiment. The result of this command has the same
30765 fields as @code{-trace-status}, except that the @samp{supported} and
30766 @samp{running} fields are not output.
30768 @subsubheading @value{GDBN} Command
30770 The corresponding @value{GDBN} command is @samp{tstop}.
30773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30774 @node GDB/MI Symbol Query
30775 @section @sc{gdb/mi} Symbol Query Commands
30779 @subheading The @code{-symbol-info-address} Command
30780 @findex -symbol-info-address
30782 @subsubheading Synopsis
30785 -symbol-info-address @var{symbol}
30788 Describe where @var{symbol} is stored.
30790 @subsubheading @value{GDBN} Command
30792 The corresponding @value{GDBN} command is @samp{info address}.
30794 @subsubheading Example
30798 @subheading The @code{-symbol-info-file} Command
30799 @findex -symbol-info-file
30801 @subsubheading Synopsis
30807 Show the file for the symbol.
30809 @subsubheading @value{GDBN} Command
30811 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30812 @samp{gdb_find_file}.
30814 @subsubheading Example
30818 @subheading The @code{-symbol-info-function} Command
30819 @findex -symbol-info-function
30821 @subsubheading Synopsis
30824 -symbol-info-function
30827 Show which function the symbol lives in.
30829 @subsubheading @value{GDBN} Command
30831 @samp{gdb_get_function} in @code{gdbtk}.
30833 @subsubheading Example
30837 @subheading The @code{-symbol-info-line} Command
30838 @findex -symbol-info-line
30840 @subsubheading Synopsis
30846 Show the core addresses of the code for a source line.
30848 @subsubheading @value{GDBN} Command
30850 The corresponding @value{GDBN} command is @samp{info line}.
30851 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30853 @subsubheading Example
30857 @subheading The @code{-symbol-info-symbol} Command
30858 @findex -symbol-info-symbol
30860 @subsubheading Synopsis
30863 -symbol-info-symbol @var{addr}
30866 Describe what symbol is at location @var{addr}.
30868 @subsubheading @value{GDBN} Command
30870 The corresponding @value{GDBN} command is @samp{info symbol}.
30872 @subsubheading Example
30876 @subheading The @code{-symbol-list-functions} Command
30877 @findex -symbol-list-functions
30879 @subsubheading Synopsis
30882 -symbol-list-functions
30885 List the functions in the executable.
30887 @subsubheading @value{GDBN} Command
30889 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30890 @samp{gdb_search} in @code{gdbtk}.
30892 @subsubheading Example
30897 @subheading The @code{-symbol-list-lines} Command
30898 @findex -symbol-list-lines
30900 @subsubheading Synopsis
30903 -symbol-list-lines @var{filename}
30906 Print the list of lines that contain code and their associated program
30907 addresses for the given source filename. The entries are sorted in
30908 ascending PC order.
30910 @subsubheading @value{GDBN} Command
30912 There is no corresponding @value{GDBN} command.
30914 @subsubheading Example
30917 -symbol-list-lines basics.c
30918 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30924 @subheading The @code{-symbol-list-types} Command
30925 @findex -symbol-list-types
30927 @subsubheading Synopsis
30933 List all the type names.
30935 @subsubheading @value{GDBN} Command
30937 The corresponding commands are @samp{info types} in @value{GDBN},
30938 @samp{gdb_search} in @code{gdbtk}.
30940 @subsubheading Example
30944 @subheading The @code{-symbol-list-variables} Command
30945 @findex -symbol-list-variables
30947 @subsubheading Synopsis
30950 -symbol-list-variables
30953 List all the global and static variable names.
30955 @subsubheading @value{GDBN} Command
30957 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30959 @subsubheading Example
30963 @subheading The @code{-symbol-locate} Command
30964 @findex -symbol-locate
30966 @subsubheading Synopsis
30972 @subsubheading @value{GDBN} Command
30974 @samp{gdb_loc} in @code{gdbtk}.
30976 @subsubheading Example
30980 @subheading The @code{-symbol-type} Command
30981 @findex -symbol-type
30983 @subsubheading Synopsis
30986 -symbol-type @var{variable}
30989 Show type of @var{variable}.
30991 @subsubheading @value{GDBN} Command
30993 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30994 @samp{gdb_obj_variable}.
30996 @subsubheading Example
31001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31002 @node GDB/MI File Commands
31003 @section @sc{gdb/mi} File Commands
31005 This section describes the GDB/MI commands to specify executable file names
31006 and to read in and obtain symbol table information.
31008 @subheading The @code{-file-exec-and-symbols} Command
31009 @findex -file-exec-and-symbols
31011 @subsubheading Synopsis
31014 -file-exec-and-symbols @var{file}
31017 Specify the executable file to be debugged. This file is the one from
31018 which the symbol table is also read. If no file is specified, the
31019 command clears the executable and symbol information. If breakpoints
31020 are set when using this command with no arguments, @value{GDBN} will produce
31021 error messages. Otherwise, no output is produced, except a completion
31024 @subsubheading @value{GDBN} Command
31026 The corresponding @value{GDBN} command is @samp{file}.
31028 @subsubheading Example
31032 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31038 @subheading The @code{-file-exec-file} Command
31039 @findex -file-exec-file
31041 @subsubheading Synopsis
31044 -file-exec-file @var{file}
31047 Specify the executable file to be debugged. Unlike
31048 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31049 from this file. If used without argument, @value{GDBN} clears the information
31050 about the executable file. No output is produced, except a completion
31053 @subsubheading @value{GDBN} Command
31055 The corresponding @value{GDBN} command is @samp{exec-file}.
31057 @subsubheading Example
31061 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31068 @subheading The @code{-file-list-exec-sections} Command
31069 @findex -file-list-exec-sections
31071 @subsubheading Synopsis
31074 -file-list-exec-sections
31077 List the sections of the current executable file.
31079 @subsubheading @value{GDBN} Command
31081 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31082 information as this command. @code{gdbtk} has a corresponding command
31083 @samp{gdb_load_info}.
31085 @subsubheading Example
31090 @subheading The @code{-file-list-exec-source-file} Command
31091 @findex -file-list-exec-source-file
31093 @subsubheading Synopsis
31096 -file-list-exec-source-file
31099 List the line number, the current source file, and the absolute path
31100 to the current source file for the current executable. The macro
31101 information field has a value of @samp{1} or @samp{0} depending on
31102 whether or not the file includes preprocessor macro information.
31104 @subsubheading @value{GDBN} Command
31106 The @value{GDBN} equivalent is @samp{info source}
31108 @subsubheading Example
31112 123-file-list-exec-source-file
31113 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31118 @subheading The @code{-file-list-exec-source-files} Command
31119 @findex -file-list-exec-source-files
31121 @subsubheading Synopsis
31124 -file-list-exec-source-files
31127 List the source files for the current executable.
31129 It will always output both the filename and fullname (absolute file
31130 name) of a source file.
31132 @subsubheading @value{GDBN} Command
31134 The @value{GDBN} equivalent is @samp{info sources}.
31135 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31137 @subsubheading Example
31140 -file-list-exec-source-files
31142 @{file=foo.c,fullname=/home/foo.c@},
31143 @{file=/home/bar.c,fullname=/home/bar.c@},
31144 @{file=gdb_could_not_find_fullpath.c@}]
31149 @subheading The @code{-file-list-shared-libraries} Command
31150 @findex -file-list-shared-libraries
31152 @subsubheading Synopsis
31155 -file-list-shared-libraries
31158 List the shared libraries in the program.
31160 @subsubheading @value{GDBN} Command
31162 The corresponding @value{GDBN} command is @samp{info shared}.
31164 @subsubheading Example
31168 @subheading The @code{-file-list-symbol-files} Command
31169 @findex -file-list-symbol-files
31171 @subsubheading Synopsis
31174 -file-list-symbol-files
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31183 @subsubheading Example
31188 @subheading The @code{-file-symbol-file} Command
31189 @findex -file-symbol-file
31191 @subsubheading Synopsis
31194 -file-symbol-file @var{file}
31197 Read symbol table info from the specified @var{file} argument. When
31198 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31199 produced, except for a completion notification.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{symbol-file}.
31205 @subsubheading Example
31209 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31215 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31216 @node GDB/MI Memory Overlay Commands
31217 @section @sc{gdb/mi} Memory Overlay Commands
31219 The memory overlay commands are not implemented.
31221 @c @subheading -overlay-auto
31223 @c @subheading -overlay-list-mapping-state
31225 @c @subheading -overlay-list-overlays
31227 @c @subheading -overlay-map
31229 @c @subheading -overlay-off
31231 @c @subheading -overlay-on
31233 @c @subheading -overlay-unmap
31235 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31236 @node GDB/MI Signal Handling Commands
31237 @section @sc{gdb/mi} Signal Handling Commands
31239 Signal handling commands are not implemented.
31241 @c @subheading -signal-handle
31243 @c @subheading -signal-list-handle-actions
31245 @c @subheading -signal-list-signal-types
31249 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31250 @node GDB/MI Target Manipulation
31251 @section @sc{gdb/mi} Target Manipulation Commands
31254 @subheading The @code{-target-attach} Command
31255 @findex -target-attach
31257 @subsubheading Synopsis
31260 -target-attach @var{pid} | @var{gid} | @var{file}
31263 Attach to a process @var{pid} or a file @var{file} outside of
31264 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31265 group, the id previously returned by
31266 @samp{-list-thread-groups --available} must be used.
31268 @subsubheading @value{GDBN} Command
31270 The corresponding @value{GDBN} command is @samp{attach}.
31272 @subsubheading Example
31276 =thread-created,id="1"
31277 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31283 @subheading The @code{-target-compare-sections} Command
31284 @findex -target-compare-sections
31286 @subsubheading Synopsis
31289 -target-compare-sections [ @var{section} ]
31292 Compare data of section @var{section} on target to the exec file.
31293 Without the argument, all sections are compared.
31295 @subsubheading @value{GDBN} Command
31297 The @value{GDBN} equivalent is @samp{compare-sections}.
31299 @subsubheading Example
31304 @subheading The @code{-target-detach} Command
31305 @findex -target-detach
31307 @subsubheading Synopsis
31310 -target-detach [ @var{pid} | @var{gid} ]
31313 Detach from the remote target which normally resumes its execution.
31314 If either @var{pid} or @var{gid} is specified, detaches from either
31315 the specified process, or specified thread group. There's no output.
31317 @subsubheading @value{GDBN} Command
31319 The corresponding @value{GDBN} command is @samp{detach}.
31321 @subsubheading Example
31331 @subheading The @code{-target-disconnect} Command
31332 @findex -target-disconnect
31334 @subsubheading Synopsis
31340 Disconnect from the remote target. There's no output and the target is
31341 generally not resumed.
31343 @subsubheading @value{GDBN} Command
31345 The corresponding @value{GDBN} command is @samp{disconnect}.
31347 @subsubheading Example
31357 @subheading The @code{-target-download} Command
31358 @findex -target-download
31360 @subsubheading Synopsis
31366 Loads the executable onto the remote target.
31367 It prints out an update message every half second, which includes the fields:
31371 The name of the section.
31373 The size of what has been sent so far for that section.
31375 The size of the section.
31377 The total size of what was sent so far (the current and the previous sections).
31379 The size of the overall executable to download.
31383 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31384 @sc{gdb/mi} Output Syntax}).
31386 In addition, it prints the name and size of the sections, as they are
31387 downloaded. These messages include the following fields:
31391 The name of the section.
31393 The size of the section.
31395 The size of the overall executable to download.
31399 At the end, a summary is printed.
31401 @subsubheading @value{GDBN} Command
31403 The corresponding @value{GDBN} command is @samp{load}.
31405 @subsubheading Example
31407 Note: each status message appears on a single line. Here the messages
31408 have been broken down so that they can fit onto a page.
31413 +download,@{section=".text",section-size="6668",total-size="9880"@}
31414 +download,@{section=".text",section-sent="512",section-size="6668",
31415 total-sent="512",total-size="9880"@}
31416 +download,@{section=".text",section-sent="1024",section-size="6668",
31417 total-sent="1024",total-size="9880"@}
31418 +download,@{section=".text",section-sent="1536",section-size="6668",
31419 total-sent="1536",total-size="9880"@}
31420 +download,@{section=".text",section-sent="2048",section-size="6668",
31421 total-sent="2048",total-size="9880"@}
31422 +download,@{section=".text",section-sent="2560",section-size="6668",
31423 total-sent="2560",total-size="9880"@}
31424 +download,@{section=".text",section-sent="3072",section-size="6668",
31425 total-sent="3072",total-size="9880"@}
31426 +download,@{section=".text",section-sent="3584",section-size="6668",
31427 total-sent="3584",total-size="9880"@}
31428 +download,@{section=".text",section-sent="4096",section-size="6668",
31429 total-sent="4096",total-size="9880"@}
31430 +download,@{section=".text",section-sent="4608",section-size="6668",
31431 total-sent="4608",total-size="9880"@}
31432 +download,@{section=".text",section-sent="5120",section-size="6668",
31433 total-sent="5120",total-size="9880"@}
31434 +download,@{section=".text",section-sent="5632",section-size="6668",
31435 total-sent="5632",total-size="9880"@}
31436 +download,@{section=".text",section-sent="6144",section-size="6668",
31437 total-sent="6144",total-size="9880"@}
31438 +download,@{section=".text",section-sent="6656",section-size="6668",
31439 total-sent="6656",total-size="9880"@}
31440 +download,@{section=".init",section-size="28",total-size="9880"@}
31441 +download,@{section=".fini",section-size="28",total-size="9880"@}
31442 +download,@{section=".data",section-size="3156",total-size="9880"@}
31443 +download,@{section=".data",section-sent="512",section-size="3156",
31444 total-sent="7236",total-size="9880"@}
31445 +download,@{section=".data",section-sent="1024",section-size="3156",
31446 total-sent="7748",total-size="9880"@}
31447 +download,@{section=".data",section-sent="1536",section-size="3156",
31448 total-sent="8260",total-size="9880"@}
31449 +download,@{section=".data",section-sent="2048",section-size="3156",
31450 total-sent="8772",total-size="9880"@}
31451 +download,@{section=".data",section-sent="2560",section-size="3156",
31452 total-sent="9284",total-size="9880"@}
31453 +download,@{section=".data",section-sent="3072",section-size="3156",
31454 total-sent="9796",total-size="9880"@}
31455 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31462 @subheading The @code{-target-exec-status} Command
31463 @findex -target-exec-status
31465 @subsubheading Synopsis
31468 -target-exec-status
31471 Provide information on the state of the target (whether it is running or
31472 not, for instance).
31474 @subsubheading @value{GDBN} Command
31476 There's no equivalent @value{GDBN} command.
31478 @subsubheading Example
31482 @subheading The @code{-target-list-available-targets} Command
31483 @findex -target-list-available-targets
31485 @subsubheading Synopsis
31488 -target-list-available-targets
31491 List the possible targets to connect to.
31493 @subsubheading @value{GDBN} Command
31495 The corresponding @value{GDBN} command is @samp{help target}.
31497 @subsubheading Example
31501 @subheading The @code{-target-list-current-targets} Command
31502 @findex -target-list-current-targets
31504 @subsubheading Synopsis
31507 -target-list-current-targets
31510 Describe the current target.
31512 @subsubheading @value{GDBN} Command
31514 The corresponding information is printed by @samp{info file} (among
31517 @subsubheading Example
31521 @subheading The @code{-target-list-parameters} Command
31522 @findex -target-list-parameters
31524 @subsubheading Synopsis
31527 -target-list-parameters
31533 @subsubheading @value{GDBN} Command
31537 @subsubheading Example
31541 @subheading The @code{-target-select} Command
31542 @findex -target-select
31544 @subsubheading Synopsis
31547 -target-select @var{type} @var{parameters @dots{}}
31550 Connect @value{GDBN} to the remote target. This command takes two args:
31554 The type of target, for instance @samp{remote}, etc.
31555 @item @var{parameters}
31556 Device names, host names and the like. @xref{Target Commands, ,
31557 Commands for Managing Targets}, for more details.
31560 The output is a connection notification, followed by the address at
31561 which the target program is, in the following form:
31564 ^connected,addr="@var{address}",func="@var{function name}",
31565 args=[@var{arg list}]
31568 @subsubheading @value{GDBN} Command
31570 The corresponding @value{GDBN} command is @samp{target}.
31572 @subsubheading Example
31576 -target-select remote /dev/ttya
31577 ^connected,addr="0xfe00a300",func="??",args=[]
31581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31582 @node GDB/MI File Transfer Commands
31583 @section @sc{gdb/mi} File Transfer Commands
31586 @subheading The @code{-target-file-put} Command
31587 @findex -target-file-put
31589 @subsubheading Synopsis
31592 -target-file-put @var{hostfile} @var{targetfile}
31595 Copy file @var{hostfile} from the host system (the machine running
31596 @value{GDBN}) to @var{targetfile} on the target system.
31598 @subsubheading @value{GDBN} Command
31600 The corresponding @value{GDBN} command is @samp{remote put}.
31602 @subsubheading Example
31606 -target-file-put localfile remotefile
31612 @subheading The @code{-target-file-get} Command
31613 @findex -target-file-get
31615 @subsubheading Synopsis
31618 -target-file-get @var{targetfile} @var{hostfile}
31621 Copy file @var{targetfile} from the target system to @var{hostfile}
31622 on the host system.
31624 @subsubheading @value{GDBN} Command
31626 The corresponding @value{GDBN} command is @samp{remote get}.
31628 @subsubheading Example
31632 -target-file-get remotefile localfile
31638 @subheading The @code{-target-file-delete} Command
31639 @findex -target-file-delete
31641 @subsubheading Synopsis
31644 -target-file-delete @var{targetfile}
31647 Delete @var{targetfile} from the target system.
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{remote delete}.
31653 @subsubheading Example
31657 -target-file-delete remotefile
31663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31664 @node GDB/MI Ada Exceptions Commands
31665 @section Ada Exceptions @sc{gdb/mi} Commands
31667 @subheading The @code{-info-ada-exceptions} Command
31668 @findex -info-ada-exceptions
31670 @subsubheading Synopsis
31673 -info-ada-exceptions [ @var{regexp}]
31676 List all Ada exceptions defined within the program being debugged.
31677 With a regular expression @var{regexp}, only those exceptions whose
31678 names match @var{regexp} are listed.
31680 @subsubheading @value{GDBN} Command
31682 The corresponding @value{GDBN} command is @samp{info exceptions}.
31684 @subsubheading Result
31686 The result is a table of Ada exceptions. The following columns are
31687 defined for each exception:
31691 The name of the exception.
31694 The address of the exception.
31698 @subsubheading Example
31701 -info-ada-exceptions aint
31702 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31703 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31704 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31705 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31706 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31709 @subheading Catching Ada Exceptions
31711 The commands describing how to ask @value{GDBN} to stop when a program
31712 raises an exception are described at @ref{Ada Exception GDB/MI
31713 Catchpoint Commands}.
31716 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31717 @node GDB/MI Support Commands
31718 @section @sc{gdb/mi} Support Commands
31720 Since new commands and features get regularly added to @sc{gdb/mi},
31721 some commands are available to help front-ends query the debugger
31722 about support for these capabilities. Similarly, it is also possible
31723 to query @value{GDBN} about target support of certain features.
31725 @subheading The @code{-info-gdb-mi-command} Command
31726 @cindex @code{-info-gdb-mi-command}
31727 @findex -info-gdb-mi-command
31729 @subsubheading Synopsis
31732 -info-gdb-mi-command @var{cmd_name}
31735 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31737 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31738 is technically not part of the command name (@pxref{GDB/MI Input
31739 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31740 for ease of use, this command also accepts the form with the leading
31743 @subsubheading @value{GDBN} Command
31745 There is no corresponding @value{GDBN} command.
31747 @subsubheading Result
31749 The result is a tuple. There is currently only one field:
31753 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31754 @code{"false"} otherwise.
31758 @subsubheading Example
31760 Here is an example where the @sc{gdb/mi} command does not exist:
31763 -info-gdb-mi-command unsupported-command
31764 ^done,command=@{exists="false"@}
31768 And here is an example where the @sc{gdb/mi} command is known
31772 -info-gdb-mi-command symbol-list-lines
31773 ^done,command=@{exists="true"@}
31776 @subheading The @code{-list-features} Command
31777 @findex -list-features
31778 @cindex supported @sc{gdb/mi} features, list
31780 Returns a list of particular features of the MI protocol that
31781 this version of gdb implements. A feature can be a command,
31782 or a new field in an output of some command, or even an
31783 important bugfix. While a frontend can sometimes detect presence
31784 of a feature at runtime, it is easier to perform detection at debugger
31787 The command returns a list of strings, with each string naming an
31788 available feature. Each returned string is just a name, it does not
31789 have any internal structure. The list of possible feature names
31795 (gdb) -list-features
31796 ^done,result=["feature1","feature2"]
31799 The current list of features is:
31802 @item frozen-varobjs
31803 Indicates support for the @code{-var-set-frozen} command, as well
31804 as possible presense of the @code{frozen} field in the output
31805 of @code{-varobj-create}.
31806 @item pending-breakpoints
31807 Indicates support for the @option{-f} option to the @code{-break-insert}
31810 Indicates Python scripting support, Python-based
31811 pretty-printing commands, and possible presence of the
31812 @samp{display_hint} field in the output of @code{-var-list-children}
31814 Indicates support for the @code{-thread-info} command.
31815 @item data-read-memory-bytes
31816 Indicates support for the @code{-data-read-memory-bytes} and the
31817 @code{-data-write-memory-bytes} commands.
31818 @item breakpoint-notifications
31819 Indicates that changes to breakpoints and breakpoints created via the
31820 CLI will be announced via async records.
31821 @item ada-task-info
31822 Indicates support for the @code{-ada-task-info} command.
31823 @item language-option
31824 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31825 option (@pxref{Context management}).
31826 @item info-gdb-mi-command
31827 Indicates support for the @code{-info-gdb-mi-command} command.
31828 @item undefined-command-error-code
31829 Indicates support for the "undefined-command" error code in error result
31830 records, produced when trying to execute an undefined @sc{gdb/mi} command
31831 (@pxref{GDB/MI Result Records}).
31832 @item exec-run-start-option
31833 Indicates that the @code{-exec-run} command supports the @option{--start}
31834 option (@pxref{GDB/MI Program Execution}).
31837 @subheading The @code{-list-target-features} Command
31838 @findex -list-target-features
31840 Returns a list of particular features that are supported by the
31841 target. Those features affect the permitted MI commands, but
31842 unlike the features reported by the @code{-list-features} command, the
31843 features depend on which target GDB is using at the moment. Whenever
31844 a target can change, due to commands such as @code{-target-select},
31845 @code{-target-attach} or @code{-exec-run}, the list of target features
31846 may change, and the frontend should obtain it again.
31850 (gdb) -list-target-features
31851 ^done,result=["async"]
31854 The current list of features is:
31858 Indicates that the target is capable of asynchronous command
31859 execution, which means that @value{GDBN} will accept further commands
31860 while the target is running.
31863 Indicates that the target is capable of reverse execution.
31864 @xref{Reverse Execution}, for more information.
31868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31869 @node GDB/MI Miscellaneous Commands
31870 @section Miscellaneous @sc{gdb/mi} Commands
31872 @c @subheading -gdb-complete
31874 @subheading The @code{-gdb-exit} Command
31877 @subsubheading Synopsis
31883 Exit @value{GDBN} immediately.
31885 @subsubheading @value{GDBN} Command
31887 Approximately corresponds to @samp{quit}.
31889 @subsubheading Example
31899 @subheading The @code{-exec-abort} Command
31900 @findex -exec-abort
31902 @subsubheading Synopsis
31908 Kill the inferior running program.
31910 @subsubheading @value{GDBN} Command
31912 The corresponding @value{GDBN} command is @samp{kill}.
31914 @subsubheading Example
31919 @subheading The @code{-gdb-set} Command
31922 @subsubheading Synopsis
31928 Set an internal @value{GDBN} variable.
31929 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31931 @subsubheading @value{GDBN} Command
31933 The corresponding @value{GDBN} command is @samp{set}.
31935 @subsubheading Example
31945 @subheading The @code{-gdb-show} Command
31948 @subsubheading Synopsis
31954 Show the current value of a @value{GDBN} variable.
31956 @subsubheading @value{GDBN} Command
31958 The corresponding @value{GDBN} command is @samp{show}.
31960 @subsubheading Example
31969 @c @subheading -gdb-source
31972 @subheading The @code{-gdb-version} Command
31973 @findex -gdb-version
31975 @subsubheading Synopsis
31981 Show version information for @value{GDBN}. Used mostly in testing.
31983 @subsubheading @value{GDBN} Command
31985 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31986 default shows this information when you start an interactive session.
31988 @subsubheading Example
31990 @c This example modifies the actual output from GDB to avoid overfull
31996 ~Copyright 2000 Free Software Foundation, Inc.
31997 ~GDB is free software, covered by the GNU General Public License, and
31998 ~you are welcome to change it and/or distribute copies of it under
31999 ~ certain conditions.
32000 ~Type "show copying" to see the conditions.
32001 ~There is absolutely no warranty for GDB. Type "show warranty" for
32003 ~This GDB was configured as
32004 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32009 @subheading The @code{-list-thread-groups} Command
32010 @findex -list-thread-groups
32012 @subheading Synopsis
32015 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32018 Lists thread groups (@pxref{Thread groups}). When a single thread
32019 group is passed as the argument, lists the children of that group.
32020 When several thread group are passed, lists information about those
32021 thread groups. Without any parameters, lists information about all
32022 top-level thread groups.
32024 Normally, thread groups that are being debugged are reported.
32025 With the @samp{--available} option, @value{GDBN} reports thread groups
32026 available on the target.
32028 The output of this command may have either a @samp{threads} result or
32029 a @samp{groups} result. The @samp{thread} result has a list of tuples
32030 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32031 Information}). The @samp{groups} result has a list of tuples as value,
32032 each tuple describing a thread group. If top-level groups are
32033 requested (that is, no parameter is passed), or when several groups
32034 are passed, the output always has a @samp{groups} result. The format
32035 of the @samp{group} result is described below.
32037 To reduce the number of roundtrips it's possible to list thread groups
32038 together with their children, by passing the @samp{--recurse} option
32039 and the recursion depth. Presently, only recursion depth of 1 is
32040 permitted. If this option is present, then every reported thread group
32041 will also include its children, either as @samp{group} or
32042 @samp{threads} field.
32044 In general, any combination of option and parameters is permitted, with
32045 the following caveats:
32049 When a single thread group is passed, the output will typically
32050 be the @samp{threads} result. Because threads may not contain
32051 anything, the @samp{recurse} option will be ignored.
32054 When the @samp{--available} option is passed, limited information may
32055 be available. In particular, the list of threads of a process might
32056 be inaccessible. Further, specifying specific thread groups might
32057 not give any performance advantage over listing all thread groups.
32058 The frontend should assume that @samp{-list-thread-groups --available}
32059 is always an expensive operation and cache the results.
32063 The @samp{groups} result is a list of tuples, where each tuple may
32064 have the following fields:
32068 Identifier of the thread group. This field is always present.
32069 The identifier is an opaque string; frontends should not try to
32070 convert it to an integer, even though it might look like one.
32073 The type of the thread group. At present, only @samp{process} is a
32077 The target-specific process identifier. This field is only present
32078 for thread groups of type @samp{process} and only if the process exists.
32081 The exit code of this group's last exited thread, formatted in octal.
32082 This field is only present for thread groups of type @samp{process} and
32083 only if the process is not running.
32086 The number of children this thread group has. This field may be
32087 absent for an available thread group.
32090 This field has a list of tuples as value, each tuple describing a
32091 thread. It may be present if the @samp{--recurse} option is
32092 specified, and it's actually possible to obtain the threads.
32095 This field is a list of integers, each identifying a core that one
32096 thread of the group is running on. This field may be absent if
32097 such information is not available.
32100 The name of the executable file that corresponds to this thread group.
32101 The field is only present for thread groups of type @samp{process},
32102 and only if there is a corresponding executable file.
32106 @subheading Example
32110 -list-thread-groups
32111 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32112 -list-thread-groups 17
32113 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32114 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32115 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32116 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32117 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32118 -list-thread-groups --available
32119 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32120 -list-thread-groups --available --recurse 1
32121 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32122 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32123 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32124 -list-thread-groups --available --recurse 1 17 18
32125 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32126 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32127 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32130 @subheading The @code{-info-os} Command
32133 @subsubheading Synopsis
32136 -info-os [ @var{type} ]
32139 If no argument is supplied, the command returns a table of available
32140 operating-system-specific information types. If one of these types is
32141 supplied as an argument @var{type}, then the command returns a table
32142 of data of that type.
32144 The types of information available depend on the target operating
32147 @subsubheading @value{GDBN} Command
32149 The corresponding @value{GDBN} command is @samp{info os}.
32151 @subsubheading Example
32153 When run on a @sc{gnu}/Linux system, the output will look something
32159 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32160 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32161 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32162 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32163 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32165 item=@{col0="files",col1="Listing of all file descriptors",
32166 col2="File descriptors"@},
32167 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32168 col2="Kernel modules"@},
32169 item=@{col0="msg",col1="Listing of all message queues",
32170 col2="Message queues"@},
32171 item=@{col0="processes",col1="Listing of all processes",
32172 col2="Processes"@},
32173 item=@{col0="procgroups",col1="Listing of all process groups",
32174 col2="Process groups"@},
32175 item=@{col0="semaphores",col1="Listing of all semaphores",
32176 col2="Semaphores"@},
32177 item=@{col0="shm",col1="Listing of all shared-memory regions",
32178 col2="Shared-memory regions"@},
32179 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32181 item=@{col0="threads",col1="Listing of all threads",
32185 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32186 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32187 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32188 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32189 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32190 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32191 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32192 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32194 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32195 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32199 (Note that the MI output here includes a @code{"Title"} column that
32200 does not appear in command-line @code{info os}; this column is useful
32201 for MI clients that want to enumerate the types of data, such as in a
32202 popup menu, but is needless clutter on the command line, and
32203 @code{info os} omits it.)
32205 @subheading The @code{-add-inferior} Command
32206 @findex -add-inferior
32208 @subheading Synopsis
32214 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32215 inferior is not associated with any executable. Such association may
32216 be established with the @samp{-file-exec-and-symbols} command
32217 (@pxref{GDB/MI File Commands}). The command response has a single
32218 field, @samp{inferior}, whose value is the identifier of the
32219 thread group corresponding to the new inferior.
32221 @subheading Example
32226 ^done,inferior="i3"
32229 @subheading The @code{-interpreter-exec} Command
32230 @findex -interpreter-exec
32232 @subheading Synopsis
32235 -interpreter-exec @var{interpreter} @var{command}
32237 @anchor{-interpreter-exec}
32239 Execute the specified @var{command} in the given @var{interpreter}.
32241 @subheading @value{GDBN} Command
32243 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32245 @subheading Example
32249 -interpreter-exec console "break main"
32250 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32251 &"During symbol reading, bad structure-type format.\n"
32252 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32257 @subheading The @code{-inferior-tty-set} Command
32258 @findex -inferior-tty-set
32260 @subheading Synopsis
32263 -inferior-tty-set /dev/pts/1
32266 Set terminal for future runs of the program being debugged.
32268 @subheading @value{GDBN} Command
32270 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32272 @subheading Example
32276 -inferior-tty-set /dev/pts/1
32281 @subheading The @code{-inferior-tty-show} Command
32282 @findex -inferior-tty-show
32284 @subheading Synopsis
32290 Show terminal for future runs of program being debugged.
32292 @subheading @value{GDBN} Command
32294 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32296 @subheading Example
32300 -inferior-tty-set /dev/pts/1
32304 ^done,inferior_tty_terminal="/dev/pts/1"
32308 @subheading The @code{-enable-timings} Command
32309 @findex -enable-timings
32311 @subheading Synopsis
32314 -enable-timings [yes | no]
32317 Toggle the printing of the wallclock, user and system times for an MI
32318 command as a field in its output. This command is to help frontend
32319 developers optimize the performance of their code. No argument is
32320 equivalent to @samp{yes}.
32322 @subheading @value{GDBN} Command
32326 @subheading Example
32334 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32335 addr="0x080484ed",func="main",file="myprog.c",
32336 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32338 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32346 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32347 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32348 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32349 fullname="/home/nickrob/myprog.c",line="73"@}
32354 @chapter @value{GDBN} Annotations
32356 This chapter describes annotations in @value{GDBN}. Annotations were
32357 designed to interface @value{GDBN} to graphical user interfaces or other
32358 similar programs which want to interact with @value{GDBN} at a
32359 relatively high level.
32361 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32365 This is Edition @value{EDITION}, @value{DATE}.
32369 * Annotations Overview:: What annotations are; the general syntax.
32370 * Server Prefix:: Issuing a command without affecting user state.
32371 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32372 * Errors:: Annotations for error messages.
32373 * Invalidation:: Some annotations describe things now invalid.
32374 * Annotations for Running::
32375 Whether the program is running, how it stopped, etc.
32376 * Source Annotations:: Annotations describing source code.
32379 @node Annotations Overview
32380 @section What is an Annotation?
32381 @cindex annotations
32383 Annotations start with a newline character, two @samp{control-z}
32384 characters, and the name of the annotation. If there is no additional
32385 information associated with this annotation, the name of the annotation
32386 is followed immediately by a newline. If there is additional
32387 information, the name of the annotation is followed by a space, the
32388 additional information, and a newline. The additional information
32389 cannot contain newline characters.
32391 Any output not beginning with a newline and two @samp{control-z}
32392 characters denotes literal output from @value{GDBN}. Currently there is
32393 no need for @value{GDBN} to output a newline followed by two
32394 @samp{control-z} characters, but if there was such a need, the
32395 annotations could be extended with an @samp{escape} annotation which
32396 means those three characters as output.
32398 The annotation @var{level}, which is specified using the
32399 @option{--annotate} command line option (@pxref{Mode Options}), controls
32400 how much information @value{GDBN} prints together with its prompt,
32401 values of expressions, source lines, and other types of output. Level 0
32402 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32403 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32404 for programs that control @value{GDBN}, and level 2 annotations have
32405 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32406 Interface, annotate, GDB's Obsolete Annotations}).
32409 @kindex set annotate
32410 @item set annotate @var{level}
32411 The @value{GDBN} command @code{set annotate} sets the level of
32412 annotations to the specified @var{level}.
32414 @item show annotate
32415 @kindex show annotate
32416 Show the current annotation level.
32419 This chapter describes level 3 annotations.
32421 A simple example of starting up @value{GDBN} with annotations is:
32424 $ @kbd{gdb --annotate=3}
32426 Copyright 2003 Free Software Foundation, Inc.
32427 GDB is free software, covered by the GNU General Public License,
32428 and you are welcome to change it and/or distribute copies of it
32429 under certain conditions.
32430 Type "show copying" to see the conditions.
32431 There is absolutely no warranty for GDB. Type "show warranty"
32433 This GDB was configured as "i386-pc-linux-gnu"
32444 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32445 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32446 denotes a @samp{control-z} character) are annotations; the rest is
32447 output from @value{GDBN}.
32449 @node Server Prefix
32450 @section The Server Prefix
32451 @cindex server prefix
32453 If you prefix a command with @samp{server } then it will not affect
32454 the command history, nor will it affect @value{GDBN}'s notion of which
32455 command to repeat if @key{RET} is pressed on a line by itself. This
32456 means that commands can be run behind a user's back by a front-end in
32457 a transparent manner.
32459 The @code{server } prefix does not affect the recording of values into
32460 the value history; to print a value without recording it into the
32461 value history, use the @code{output} command instead of the
32462 @code{print} command.
32464 Using this prefix also disables confirmation requests
32465 (@pxref{confirmation requests}).
32468 @section Annotation for @value{GDBN} Input
32470 @cindex annotations for prompts
32471 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32472 to know when to send output, when the output from a given command is
32475 Different kinds of input each have a different @dfn{input type}. Each
32476 input type has three annotations: a @code{pre-} annotation, which
32477 denotes the beginning of any prompt which is being output, a plain
32478 annotation, which denotes the end of the prompt, and then a @code{post-}
32479 annotation which denotes the end of any echo which may (or may not) be
32480 associated with the input. For example, the @code{prompt} input type
32481 features the following annotations:
32489 The input types are
32492 @findex pre-prompt annotation
32493 @findex prompt annotation
32494 @findex post-prompt annotation
32496 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32498 @findex pre-commands annotation
32499 @findex commands annotation
32500 @findex post-commands annotation
32502 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32503 command. The annotations are repeated for each command which is input.
32505 @findex pre-overload-choice annotation
32506 @findex overload-choice annotation
32507 @findex post-overload-choice annotation
32508 @item overload-choice
32509 When @value{GDBN} wants the user to select between various overloaded functions.
32511 @findex pre-query annotation
32512 @findex query annotation
32513 @findex post-query annotation
32515 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32517 @findex pre-prompt-for-continue annotation
32518 @findex prompt-for-continue annotation
32519 @findex post-prompt-for-continue annotation
32520 @item prompt-for-continue
32521 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32522 expect this to work well; instead use @code{set height 0} to disable
32523 prompting. This is because the counting of lines is buggy in the
32524 presence of annotations.
32529 @cindex annotations for errors, warnings and interrupts
32531 @findex quit annotation
32536 This annotation occurs right before @value{GDBN} responds to an interrupt.
32538 @findex error annotation
32543 This annotation occurs right before @value{GDBN} responds to an error.
32545 Quit and error annotations indicate that any annotations which @value{GDBN} was
32546 in the middle of may end abruptly. For example, if a
32547 @code{value-history-begin} annotation is followed by a @code{error}, one
32548 cannot expect to receive the matching @code{value-history-end}. One
32549 cannot expect not to receive it either, however; an error annotation
32550 does not necessarily mean that @value{GDBN} is immediately returning all the way
32553 @findex error-begin annotation
32554 A quit or error annotation may be preceded by
32560 Any output between that and the quit or error annotation is the error
32563 Warning messages are not yet annotated.
32564 @c If we want to change that, need to fix warning(), type_error(),
32565 @c range_error(), and possibly other places.
32568 @section Invalidation Notices
32570 @cindex annotations for invalidation messages
32571 The following annotations say that certain pieces of state may have
32575 @findex frames-invalid annotation
32576 @item ^Z^Zframes-invalid
32578 The frames (for example, output from the @code{backtrace} command) may
32581 @findex breakpoints-invalid annotation
32582 @item ^Z^Zbreakpoints-invalid
32584 The breakpoints may have changed. For example, the user just added or
32585 deleted a breakpoint.
32588 @node Annotations for Running
32589 @section Running the Program
32590 @cindex annotations for running programs
32592 @findex starting annotation
32593 @findex stopping annotation
32594 When the program starts executing due to a @value{GDBN} command such as
32595 @code{step} or @code{continue},
32601 is output. When the program stops,
32607 is output. Before the @code{stopped} annotation, a variety of
32608 annotations describe how the program stopped.
32611 @findex exited annotation
32612 @item ^Z^Zexited @var{exit-status}
32613 The program exited, and @var{exit-status} is the exit status (zero for
32614 successful exit, otherwise nonzero).
32616 @findex signalled annotation
32617 @findex signal-name annotation
32618 @findex signal-name-end annotation
32619 @findex signal-string annotation
32620 @findex signal-string-end annotation
32621 @item ^Z^Zsignalled
32622 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32623 annotation continues:
32629 ^Z^Zsignal-name-end
32633 ^Z^Zsignal-string-end
32638 where @var{name} is the name of the signal, such as @code{SIGILL} or
32639 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32640 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32641 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32642 user's benefit and have no particular format.
32644 @findex signal annotation
32646 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32647 just saying that the program received the signal, not that it was
32648 terminated with it.
32650 @findex breakpoint annotation
32651 @item ^Z^Zbreakpoint @var{number}
32652 The program hit breakpoint number @var{number}.
32654 @findex watchpoint annotation
32655 @item ^Z^Zwatchpoint @var{number}
32656 The program hit watchpoint number @var{number}.
32659 @node Source Annotations
32660 @section Displaying Source
32661 @cindex annotations for source display
32663 @findex source annotation
32664 The following annotation is used instead of displaying source code:
32667 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32670 where @var{filename} is an absolute file name indicating which source
32671 file, @var{line} is the line number within that file (where 1 is the
32672 first line in the file), @var{character} is the character position
32673 within the file (where 0 is the first character in the file) (for most
32674 debug formats this will necessarily point to the beginning of a line),
32675 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32676 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32677 @var{addr} is the address in the target program associated with the
32678 source which is being displayed. The @var{addr} is in the form @samp{0x}
32679 followed by one or more lowercase hex digits (note that this does not
32680 depend on the language).
32682 @node JIT Interface
32683 @chapter JIT Compilation Interface
32684 @cindex just-in-time compilation
32685 @cindex JIT compilation interface
32687 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32688 interface. A JIT compiler is a program or library that generates native
32689 executable code at runtime and executes it, usually in order to achieve good
32690 performance while maintaining platform independence.
32692 Programs that use JIT compilation are normally difficult to debug because
32693 portions of their code are generated at runtime, instead of being loaded from
32694 object files, which is where @value{GDBN} normally finds the program's symbols
32695 and debug information. In order to debug programs that use JIT compilation,
32696 @value{GDBN} has an interface that allows the program to register in-memory
32697 symbol files with @value{GDBN} at runtime.
32699 If you are using @value{GDBN} to debug a program that uses this interface, then
32700 it should work transparently so long as you have not stripped the binary. If
32701 you are developing a JIT compiler, then the interface is documented in the rest
32702 of this chapter. At this time, the only known client of this interface is the
32705 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32706 JIT compiler communicates with @value{GDBN} by writing data into a global
32707 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32708 attaches, it reads a linked list of symbol files from the global variable to
32709 find existing code, and puts a breakpoint in the function so that it can find
32710 out about additional code.
32713 * Declarations:: Relevant C struct declarations
32714 * Registering Code:: Steps to register code
32715 * Unregistering Code:: Steps to unregister code
32716 * Custom Debug Info:: Emit debug information in a custom format
32720 @section JIT Declarations
32722 These are the relevant struct declarations that a C program should include to
32723 implement the interface:
32733 struct jit_code_entry
32735 struct jit_code_entry *next_entry;
32736 struct jit_code_entry *prev_entry;
32737 const char *symfile_addr;
32738 uint64_t symfile_size;
32741 struct jit_descriptor
32744 /* This type should be jit_actions_t, but we use uint32_t
32745 to be explicit about the bitwidth. */
32746 uint32_t action_flag;
32747 struct jit_code_entry *relevant_entry;
32748 struct jit_code_entry *first_entry;
32751 /* GDB puts a breakpoint in this function. */
32752 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32754 /* Make sure to specify the version statically, because the
32755 debugger may check the version before we can set it. */
32756 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32759 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32760 modifications to this global data properly, which can easily be done by putting
32761 a global mutex around modifications to these structures.
32763 @node Registering Code
32764 @section Registering Code
32766 To register code with @value{GDBN}, the JIT should follow this protocol:
32770 Generate an object file in memory with symbols and other desired debug
32771 information. The file must include the virtual addresses of the sections.
32774 Create a code entry for the file, which gives the start and size of the symbol
32778 Add it to the linked list in the JIT descriptor.
32781 Point the relevant_entry field of the descriptor at the entry.
32784 Set @code{action_flag} to @code{JIT_REGISTER} and call
32785 @code{__jit_debug_register_code}.
32788 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32789 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32790 new code. However, the linked list must still be maintained in order to allow
32791 @value{GDBN} to attach to a running process and still find the symbol files.
32793 @node Unregistering Code
32794 @section Unregistering Code
32796 If code is freed, then the JIT should use the following protocol:
32800 Remove the code entry corresponding to the code from the linked list.
32803 Point the @code{relevant_entry} field of the descriptor at the code entry.
32806 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32807 @code{__jit_debug_register_code}.
32810 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32811 and the JIT will leak the memory used for the associated symbol files.
32813 @node Custom Debug Info
32814 @section Custom Debug Info
32815 @cindex custom JIT debug info
32816 @cindex JIT debug info reader
32818 Generating debug information in platform-native file formats (like ELF
32819 or COFF) may be an overkill for JIT compilers; especially if all the
32820 debug info is used for is displaying a meaningful backtrace. The
32821 issue can be resolved by having the JIT writers decide on a debug info
32822 format and also provide a reader that parses the debug info generated
32823 by the JIT compiler. This section gives a brief overview on writing
32824 such a parser. More specific details can be found in the source file
32825 @file{gdb/jit-reader.in}, which is also installed as a header at
32826 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32828 The reader is implemented as a shared object (so this functionality is
32829 not available on platforms which don't allow loading shared objects at
32830 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32831 @code{jit-reader-unload} are provided, to be used to load and unload
32832 the readers from a preconfigured directory. Once loaded, the shared
32833 object is used the parse the debug information emitted by the JIT
32837 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32838 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32841 @node Using JIT Debug Info Readers
32842 @subsection Using JIT Debug Info Readers
32843 @kindex jit-reader-load
32844 @kindex jit-reader-unload
32846 Readers can be loaded and unloaded using the @code{jit-reader-load}
32847 and @code{jit-reader-unload} commands.
32850 @item jit-reader-load @var{reader}
32851 Load the JIT reader named @var{reader}, which is a shared
32852 object specified as either an absolute or a relative file name. In
32853 the latter case, @value{GDBN} will try to load the reader from a
32854 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32855 system (here @var{libdir} is the system library directory, often
32856 @file{/usr/local/lib}).
32858 Only one reader can be active at a time; trying to load a second
32859 reader when one is already loaded will result in @value{GDBN}
32860 reporting an error. A new JIT reader can be loaded by first unloading
32861 the current one using @code{jit-reader-unload} and then invoking
32862 @code{jit-reader-load}.
32864 @item jit-reader-unload
32865 Unload the currently loaded JIT reader.
32869 @node Writing JIT Debug Info Readers
32870 @subsection Writing JIT Debug Info Readers
32871 @cindex writing JIT debug info readers
32873 As mentioned, a reader is essentially a shared object conforming to a
32874 certain ABI. This ABI is described in @file{jit-reader.h}.
32876 @file{jit-reader.h} defines the structures, macros and functions
32877 required to write a reader. It is installed (along with
32878 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32879 the system include directory.
32881 Readers need to be released under a GPL compatible license. A reader
32882 can be declared as released under such a license by placing the macro
32883 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32885 The entry point for readers is the symbol @code{gdb_init_reader},
32886 which is expected to be a function with the prototype
32888 @findex gdb_init_reader
32890 extern struct gdb_reader_funcs *gdb_init_reader (void);
32893 @cindex @code{struct gdb_reader_funcs}
32895 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32896 functions. These functions are executed to read the debug info
32897 generated by the JIT compiler (@code{read}), to unwind stack frames
32898 (@code{unwind}) and to create canonical frame IDs
32899 (@code{get_Frame_id}). It also has a callback that is called when the
32900 reader is being unloaded (@code{destroy}). The struct looks like this
32903 struct gdb_reader_funcs
32905 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32906 int reader_version;
32908 /* For use by the reader. */
32911 gdb_read_debug_info *read;
32912 gdb_unwind_frame *unwind;
32913 gdb_get_frame_id *get_frame_id;
32914 gdb_destroy_reader *destroy;
32918 @cindex @code{struct gdb_symbol_callbacks}
32919 @cindex @code{struct gdb_unwind_callbacks}
32921 The callbacks are provided with another set of callbacks by
32922 @value{GDBN} to do their job. For @code{read}, these callbacks are
32923 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32924 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32925 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32926 files and new symbol tables inside those object files. @code{struct
32927 gdb_unwind_callbacks} has callbacks to read registers off the current
32928 frame and to write out the values of the registers in the previous
32929 frame. Both have a callback (@code{target_read}) to read bytes off the
32930 target's address space.
32932 @node In-Process Agent
32933 @chapter In-Process Agent
32934 @cindex debugging agent
32935 The traditional debugging model is conceptually low-speed, but works fine,
32936 because most bugs can be reproduced in debugging-mode execution. However,
32937 as multi-core or many-core processors are becoming mainstream, and
32938 multi-threaded programs become more and more popular, there should be more
32939 and more bugs that only manifest themselves at normal-mode execution, for
32940 example, thread races, because debugger's interference with the program's
32941 timing may conceal the bugs. On the other hand, in some applications,
32942 it is not feasible for the debugger to interrupt the program's execution
32943 long enough for the developer to learn anything helpful about its behavior.
32944 If the program's correctness depends on its real-time behavior, delays
32945 introduced by a debugger might cause the program to fail, even when the
32946 code itself is correct. It is useful to be able to observe the program's
32947 behavior without interrupting it.
32949 Therefore, traditional debugging model is too intrusive to reproduce
32950 some bugs. In order to reduce the interference with the program, we can
32951 reduce the number of operations performed by debugger. The
32952 @dfn{In-Process Agent}, a shared library, is running within the same
32953 process with inferior, and is able to perform some debugging operations
32954 itself. As a result, debugger is only involved when necessary, and
32955 performance of debugging can be improved accordingly. Note that
32956 interference with program can be reduced but can't be removed completely,
32957 because the in-process agent will still stop or slow down the program.
32959 The in-process agent can interpret and execute Agent Expressions
32960 (@pxref{Agent Expressions}) during performing debugging operations. The
32961 agent expressions can be used for different purposes, such as collecting
32962 data in tracepoints, and condition evaluation in breakpoints.
32964 @anchor{Control Agent}
32965 You can control whether the in-process agent is used as an aid for
32966 debugging with the following commands:
32969 @kindex set agent on
32971 Causes the in-process agent to perform some operations on behalf of the
32972 debugger. Just which operations requested by the user will be done
32973 by the in-process agent depends on the its capabilities. For example,
32974 if you request to evaluate breakpoint conditions in the in-process agent,
32975 and the in-process agent has such capability as well, then breakpoint
32976 conditions will be evaluated in the in-process agent.
32978 @kindex set agent off
32979 @item set agent off
32980 Disables execution of debugging operations by the in-process agent. All
32981 of the operations will be performed by @value{GDBN}.
32985 Display the current setting of execution of debugging operations by
32986 the in-process agent.
32990 * In-Process Agent Protocol::
32993 @node In-Process Agent Protocol
32994 @section In-Process Agent Protocol
32995 @cindex in-process agent protocol
32997 The in-process agent is able to communicate with both @value{GDBN} and
32998 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32999 used for communications between @value{GDBN} or GDBserver and the IPA.
33000 In general, @value{GDBN} or GDBserver sends commands
33001 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33002 in-process agent replies back with the return result of the command, or
33003 some other information. The data sent to in-process agent is composed
33004 of primitive data types, such as 4-byte or 8-byte type, and composite
33005 types, which are called objects (@pxref{IPA Protocol Objects}).
33008 * IPA Protocol Objects::
33009 * IPA Protocol Commands::
33012 @node IPA Protocol Objects
33013 @subsection IPA Protocol Objects
33014 @cindex ipa protocol objects
33016 The commands sent to and results received from agent may contain some
33017 complex data types called @dfn{objects}.
33019 The in-process agent is running on the same machine with @value{GDBN}
33020 or GDBserver, so it doesn't have to handle as much differences between
33021 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33022 However, there are still some differences of two ends in two processes:
33026 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33027 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33029 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33030 GDBserver is compiled with one, and in-process agent is compiled with
33034 Here are the IPA Protocol Objects:
33038 agent expression object. It represents an agent expression
33039 (@pxref{Agent Expressions}).
33040 @anchor{agent expression object}
33042 tracepoint action object. It represents a tracepoint action
33043 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33044 memory, static trace data and to evaluate expression.
33045 @anchor{tracepoint action object}
33047 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33048 @anchor{tracepoint object}
33052 The following table describes important attributes of each IPA protocol
33055 @multitable @columnfractions .30 .20 .50
33056 @headitem Name @tab Size @tab Description
33057 @item @emph{agent expression object} @tab @tab
33058 @item length @tab 4 @tab length of bytes code
33059 @item byte code @tab @var{length} @tab contents of byte code
33060 @item @emph{tracepoint action for collecting memory} @tab @tab
33061 @item 'M' @tab 1 @tab type of tracepoint action
33062 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33063 address of the lowest byte to collect, otherwise @var{addr} is the offset
33064 of @var{basereg} for memory collecting.
33065 @item len @tab 8 @tab length of memory for collecting
33066 @item basereg @tab 4 @tab the register number containing the starting
33067 memory address for collecting.
33068 @item @emph{tracepoint action for collecting registers} @tab @tab
33069 @item 'R' @tab 1 @tab type of tracepoint action
33070 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33071 @item 'L' @tab 1 @tab type of tracepoint action
33072 @item @emph{tracepoint action for expression evaluation} @tab @tab
33073 @item 'X' @tab 1 @tab type of tracepoint action
33074 @item agent expression @tab length of @tab @ref{agent expression object}
33075 @item @emph{tracepoint object} @tab @tab
33076 @item number @tab 4 @tab number of tracepoint
33077 @item address @tab 8 @tab address of tracepoint inserted on
33078 @item type @tab 4 @tab type of tracepoint
33079 @item enabled @tab 1 @tab enable or disable of tracepoint
33080 @item step_count @tab 8 @tab step
33081 @item pass_count @tab 8 @tab pass
33082 @item numactions @tab 4 @tab number of tracepoint actions
33083 @item hit count @tab 8 @tab hit count
33084 @item trace frame usage @tab 8 @tab trace frame usage
33085 @item compiled_cond @tab 8 @tab compiled condition
33086 @item orig_size @tab 8 @tab orig size
33087 @item condition @tab 4 if condition is NULL otherwise length of
33088 @ref{agent expression object}
33089 @tab zero if condition is NULL, otherwise is
33090 @ref{agent expression object}
33091 @item actions @tab variable
33092 @tab numactions number of @ref{tracepoint action object}
33095 @node IPA Protocol Commands
33096 @subsection IPA Protocol Commands
33097 @cindex ipa protocol commands
33099 The spaces in each command are delimiters to ease reading this commands
33100 specification. They don't exist in real commands.
33104 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33105 Installs a new fast tracepoint described by @var{tracepoint_object}
33106 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33107 head of @dfn{jumppad}, which is used to jump to data collection routine
33112 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33113 @var{target_address} is address of tracepoint in the inferior.
33114 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33115 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33116 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33117 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33124 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33125 is about to kill inferiors.
33133 @item probe_marker_at:@var{address}
33134 Asks in-process agent to probe the marker at @var{address}.
33141 @item unprobe_marker_at:@var{address}
33142 Asks in-process agent to unprobe the marker at @var{address}.
33146 @chapter Reporting Bugs in @value{GDBN}
33147 @cindex bugs in @value{GDBN}
33148 @cindex reporting bugs in @value{GDBN}
33150 Your bug reports play an essential role in making @value{GDBN} reliable.
33152 Reporting a bug may help you by bringing a solution to your problem, or it
33153 may not. But in any case the principal function of a bug report is to help
33154 the entire community by making the next version of @value{GDBN} work better. Bug
33155 reports are your contribution to the maintenance of @value{GDBN}.
33157 In order for a bug report to serve its purpose, you must include the
33158 information that enables us to fix the bug.
33161 * Bug Criteria:: Have you found a bug?
33162 * Bug Reporting:: How to report bugs
33166 @section Have You Found a Bug?
33167 @cindex bug criteria
33169 If you are not sure whether you have found a bug, here are some guidelines:
33172 @cindex fatal signal
33173 @cindex debugger crash
33174 @cindex crash of debugger
33176 If the debugger gets a fatal signal, for any input whatever, that is a
33177 @value{GDBN} bug. Reliable debuggers never crash.
33179 @cindex error on valid input
33181 If @value{GDBN} produces an error message for valid input, that is a
33182 bug. (Note that if you're cross debugging, the problem may also be
33183 somewhere in the connection to the target.)
33185 @cindex invalid input
33187 If @value{GDBN} does not produce an error message for invalid input,
33188 that is a bug. However, you should note that your idea of
33189 ``invalid input'' might be our idea of ``an extension'' or ``support
33190 for traditional practice''.
33193 If you are an experienced user of debugging tools, your suggestions
33194 for improvement of @value{GDBN} are welcome in any case.
33197 @node Bug Reporting
33198 @section How to Report Bugs
33199 @cindex bug reports
33200 @cindex @value{GDBN} bugs, reporting
33202 A number of companies and individuals offer support for @sc{gnu} products.
33203 If you obtained @value{GDBN} from a support organization, we recommend you
33204 contact that organization first.
33206 You can find contact information for many support companies and
33207 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33209 @c should add a web page ref...
33212 @ifset BUGURL_DEFAULT
33213 In any event, we also recommend that you submit bug reports for
33214 @value{GDBN}. The preferred method is to submit them directly using
33215 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33216 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33219 @strong{Do not send bug reports to @samp{info-gdb}, or to
33220 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33221 not want to receive bug reports. Those that do have arranged to receive
33224 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33225 serves as a repeater. The mailing list and the newsgroup carry exactly
33226 the same messages. Often people think of posting bug reports to the
33227 newsgroup instead of mailing them. This appears to work, but it has one
33228 problem which can be crucial: a newsgroup posting often lacks a mail
33229 path back to the sender. Thus, if we need to ask for more information,
33230 we may be unable to reach you. For this reason, it is better to send
33231 bug reports to the mailing list.
33233 @ifclear BUGURL_DEFAULT
33234 In any event, we also recommend that you submit bug reports for
33235 @value{GDBN} to @value{BUGURL}.
33239 The fundamental principle of reporting bugs usefully is this:
33240 @strong{report all the facts}. If you are not sure whether to state a
33241 fact or leave it out, state it!
33243 Often people omit facts because they think they know what causes the
33244 problem and assume that some details do not matter. Thus, you might
33245 assume that the name of the variable you use in an example does not matter.
33246 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33247 stray memory reference which happens to fetch from the location where that
33248 name is stored in memory; perhaps, if the name were different, the contents
33249 of that location would fool the debugger into doing the right thing despite
33250 the bug. Play it safe and give a specific, complete example. That is the
33251 easiest thing for you to do, and the most helpful.
33253 Keep in mind that the purpose of a bug report is to enable us to fix the
33254 bug. It may be that the bug has been reported previously, but neither
33255 you nor we can know that unless your bug report is complete and
33258 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33259 bell?'' Those bug reports are useless, and we urge everyone to
33260 @emph{refuse to respond to them} except to chide the sender to report
33263 To enable us to fix the bug, you should include all these things:
33267 The version of @value{GDBN}. @value{GDBN} announces it if you start
33268 with no arguments; you can also print it at any time using @code{show
33271 Without this, we will not know whether there is any point in looking for
33272 the bug in the current version of @value{GDBN}.
33275 The type of machine you are using, and the operating system name and
33279 The details of the @value{GDBN} build-time configuration.
33280 @value{GDBN} shows these details if you invoke it with the
33281 @option{--configuration} command-line option, or if you type
33282 @code{show configuration} at @value{GDBN}'s prompt.
33285 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33286 ``@value{GCC}--2.8.1''.
33289 What compiler (and its version) was used to compile the program you are
33290 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33291 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33292 to get this information; for other compilers, see the documentation for
33296 The command arguments you gave the compiler to compile your example and
33297 observe the bug. For example, did you use @samp{-O}? To guarantee
33298 you will not omit something important, list them all. A copy of the
33299 Makefile (or the output from make) is sufficient.
33301 If we were to try to guess the arguments, we would probably guess wrong
33302 and then we might not encounter the bug.
33305 A complete input script, and all necessary source files, that will
33309 A description of what behavior you observe that you believe is
33310 incorrect. For example, ``It gets a fatal signal.''
33312 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33313 will certainly notice it. But if the bug is incorrect output, we might
33314 not notice unless it is glaringly wrong. You might as well not give us
33315 a chance to make a mistake.
33317 Even if the problem you experience is a fatal signal, you should still
33318 say so explicitly. Suppose something strange is going on, such as, your
33319 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33320 the C library on your system. (This has happened!) Your copy might
33321 crash and ours would not. If you told us to expect a crash, then when
33322 ours fails to crash, we would know that the bug was not happening for
33323 us. If you had not told us to expect a crash, then we would not be able
33324 to draw any conclusion from our observations.
33327 @cindex recording a session script
33328 To collect all this information, you can use a session recording program
33329 such as @command{script}, which is available on many Unix systems.
33330 Just run your @value{GDBN} session inside @command{script} and then
33331 include the @file{typescript} file with your bug report.
33333 Another way to record a @value{GDBN} session is to run @value{GDBN}
33334 inside Emacs and then save the entire buffer to a file.
33337 If you wish to suggest changes to the @value{GDBN} source, send us context
33338 diffs. If you even discuss something in the @value{GDBN} source, refer to
33339 it by context, not by line number.
33341 The line numbers in our development sources will not match those in your
33342 sources. Your line numbers would convey no useful information to us.
33346 Here are some things that are not necessary:
33350 A description of the envelope of the bug.
33352 Often people who encounter a bug spend a lot of time investigating
33353 which changes to the input file will make the bug go away and which
33354 changes will not affect it.
33356 This is often time consuming and not very useful, because the way we
33357 will find the bug is by running a single example under the debugger
33358 with breakpoints, not by pure deduction from a series of examples.
33359 We recommend that you save your time for something else.
33361 Of course, if you can find a simpler example to report @emph{instead}
33362 of the original one, that is a convenience for us. Errors in the
33363 output will be easier to spot, running under the debugger will take
33364 less time, and so on.
33366 However, simplification is not vital; if you do not want to do this,
33367 report the bug anyway and send us the entire test case you used.
33370 A patch for the bug.
33372 A patch for the bug does help us if it is a good one. But do not omit
33373 the necessary information, such as the test case, on the assumption that
33374 a patch is all we need. We might see problems with your patch and decide
33375 to fix the problem another way, or we might not understand it at all.
33377 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33378 construct an example that will make the program follow a certain path
33379 through the code. If you do not send us the example, we will not be able
33380 to construct one, so we will not be able to verify that the bug is fixed.
33382 And if we cannot understand what bug you are trying to fix, or why your
33383 patch should be an improvement, we will not install it. A test case will
33384 help us to understand.
33387 A guess about what the bug is or what it depends on.
33389 Such guesses are usually wrong. Even we cannot guess right about such
33390 things without first using the debugger to find the facts.
33393 @c The readline documentation is distributed with the readline code
33394 @c and consists of the two following files:
33397 @c Use -I with makeinfo to point to the appropriate directory,
33398 @c environment var TEXINPUTS with TeX.
33399 @ifclear SYSTEM_READLINE
33400 @include rluser.texi
33401 @include hsuser.texi
33405 @appendix In Memoriam
33407 The @value{GDBN} project mourns the loss of the following long-time
33412 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33413 to Free Software in general. Outside of @value{GDBN}, he was known in
33414 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33416 @item Michael Snyder
33417 Michael was one of the Global Maintainers of the @value{GDBN} project,
33418 with contributions recorded as early as 1996, until 2011. In addition
33419 to his day to day participation, he was a large driving force behind
33420 adding Reverse Debugging to @value{GDBN}.
33423 Beyond their technical contributions to the project, they were also
33424 enjoyable members of the Free Software Community. We will miss them.
33426 @node Formatting Documentation
33427 @appendix Formatting Documentation
33429 @cindex @value{GDBN} reference card
33430 @cindex reference card
33431 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33432 for printing with PostScript or Ghostscript, in the @file{gdb}
33433 subdirectory of the main source directory@footnote{In
33434 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33435 release.}. If you can use PostScript or Ghostscript with your printer,
33436 you can print the reference card immediately with @file{refcard.ps}.
33438 The release also includes the source for the reference card. You
33439 can format it, using @TeX{}, by typing:
33445 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33446 mode on US ``letter'' size paper;
33447 that is, on a sheet 11 inches wide by 8.5 inches
33448 high. You will need to specify this form of printing as an option to
33449 your @sc{dvi} output program.
33451 @cindex documentation
33453 All the documentation for @value{GDBN} comes as part of the machine-readable
33454 distribution. The documentation is written in Texinfo format, which is
33455 a documentation system that uses a single source file to produce both
33456 on-line information and a printed manual. You can use one of the Info
33457 formatting commands to create the on-line version of the documentation
33458 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33460 @value{GDBN} includes an already formatted copy of the on-line Info
33461 version of this manual in the @file{gdb} subdirectory. The main Info
33462 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33463 subordinate files matching @samp{gdb.info*} in the same directory. If
33464 necessary, you can print out these files, or read them with any editor;
33465 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33466 Emacs or the standalone @code{info} program, available as part of the
33467 @sc{gnu} Texinfo distribution.
33469 If you want to format these Info files yourself, you need one of the
33470 Info formatting programs, such as @code{texinfo-format-buffer} or
33473 If you have @code{makeinfo} installed, and are in the top level
33474 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33475 version @value{GDBVN}), you can make the Info file by typing:
33482 If you want to typeset and print copies of this manual, you need @TeX{},
33483 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33484 Texinfo definitions file.
33486 @TeX{} is a typesetting program; it does not print files directly, but
33487 produces output files called @sc{dvi} files. To print a typeset
33488 document, you need a program to print @sc{dvi} files. If your system
33489 has @TeX{} installed, chances are it has such a program. The precise
33490 command to use depends on your system; @kbd{lpr -d} is common; another
33491 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33492 require a file name without any extension or a @samp{.dvi} extension.
33494 @TeX{} also requires a macro definitions file called
33495 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33496 written in Texinfo format. On its own, @TeX{} cannot either read or
33497 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33498 and is located in the @file{gdb-@var{version-number}/texinfo}
33501 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33502 typeset and print this manual. First switch to the @file{gdb}
33503 subdirectory of the main source directory (for example, to
33504 @file{gdb-@value{GDBVN}/gdb}) and type:
33510 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33512 @node Installing GDB
33513 @appendix Installing @value{GDBN}
33514 @cindex installation
33517 * Requirements:: Requirements for building @value{GDBN}
33518 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33519 * Separate Objdir:: Compiling @value{GDBN} in another directory
33520 * Config Names:: Specifying names for hosts and targets
33521 * Configure Options:: Summary of options for configure
33522 * System-wide configuration:: Having a system-wide init file
33526 @section Requirements for Building @value{GDBN}
33527 @cindex building @value{GDBN}, requirements for
33529 Building @value{GDBN} requires various tools and packages to be available.
33530 Other packages will be used only if they are found.
33532 @heading Tools/Packages Necessary for Building @value{GDBN}
33534 @item ISO C90 compiler
33535 @value{GDBN} is written in ISO C90. It should be buildable with any
33536 working C90 compiler, e.g.@: GCC.
33540 @heading Tools/Packages Optional for Building @value{GDBN}
33544 @value{GDBN} can use the Expat XML parsing library. This library may be
33545 included with your operating system distribution; if it is not, you
33546 can get the latest version from @url{http://expat.sourceforge.net}.
33547 The @file{configure} script will search for this library in several
33548 standard locations; if it is installed in an unusual path, you can
33549 use the @option{--with-libexpat-prefix} option to specify its location.
33555 Remote protocol memory maps (@pxref{Memory Map Format})
33557 Target descriptions (@pxref{Target Descriptions})
33559 Remote shared library lists (@xref{Library List Format},
33560 or alternatively @pxref{Library List Format for SVR4 Targets})
33562 MS-Windows shared libraries (@pxref{Shared Libraries})
33564 Traceframe info (@pxref{Traceframe Info Format})
33566 Branch trace (@pxref{Branch Trace Format},
33567 @pxref{Branch Trace Configuration Format})
33571 @cindex compressed debug sections
33572 @value{GDBN} will use the @samp{zlib} library, if available, to read
33573 compressed debug sections. Some linkers, such as GNU gold, are capable
33574 of producing binaries with compressed debug sections. If @value{GDBN}
33575 is compiled with @samp{zlib}, it will be able to read the debug
33576 information in such binaries.
33578 The @samp{zlib} library is likely included with your operating system
33579 distribution; if it is not, you can get the latest version from
33580 @url{http://zlib.net}.
33583 @value{GDBN}'s features related to character sets (@pxref{Character
33584 Sets}) require a functioning @code{iconv} implementation. If you are
33585 on a GNU system, then this is provided by the GNU C Library. Some
33586 other systems also provide a working @code{iconv}.
33588 If @value{GDBN} is using the @code{iconv} program which is installed
33589 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33590 This is done with @option{--with-iconv-bin} which specifies the
33591 directory that contains the @code{iconv} program.
33593 On systems without @code{iconv}, you can install GNU Libiconv. If you
33594 have previously installed Libiconv, you can use the
33595 @option{--with-libiconv-prefix} option to configure.
33597 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33598 arrange to build Libiconv if a directory named @file{libiconv} appears
33599 in the top-most source directory. If Libiconv is built this way, and
33600 if the operating system does not provide a suitable @code{iconv}
33601 implementation, then the just-built library will automatically be used
33602 by @value{GDBN}. One easy way to set this up is to download GNU
33603 Libiconv, unpack it, and then rename the directory holding the
33604 Libiconv source code to @samp{libiconv}.
33607 @node Running Configure
33608 @section Invoking the @value{GDBN} @file{configure} Script
33609 @cindex configuring @value{GDBN}
33610 @value{GDBN} comes with a @file{configure} script that automates the process
33611 of preparing @value{GDBN} for installation; you can then use @code{make} to
33612 build the @code{gdb} program.
33614 @c irrelevant in info file; it's as current as the code it lives with.
33615 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33616 look at the @file{README} file in the sources; we may have improved the
33617 installation procedures since publishing this manual.}
33620 The @value{GDBN} distribution includes all the source code you need for
33621 @value{GDBN} in a single directory, whose name is usually composed by
33622 appending the version number to @samp{gdb}.
33624 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33625 @file{gdb-@value{GDBVN}} directory. That directory contains:
33628 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33629 script for configuring @value{GDBN} and all its supporting libraries
33631 @item gdb-@value{GDBVN}/gdb
33632 the source specific to @value{GDBN} itself
33634 @item gdb-@value{GDBVN}/bfd
33635 source for the Binary File Descriptor library
33637 @item gdb-@value{GDBVN}/include
33638 @sc{gnu} include files
33640 @item gdb-@value{GDBVN}/libiberty
33641 source for the @samp{-liberty} free software library
33643 @item gdb-@value{GDBVN}/opcodes
33644 source for the library of opcode tables and disassemblers
33646 @item gdb-@value{GDBVN}/readline
33647 source for the @sc{gnu} command-line interface
33649 @item gdb-@value{GDBVN}/glob
33650 source for the @sc{gnu} filename pattern-matching subroutine
33652 @item gdb-@value{GDBVN}/mmalloc
33653 source for the @sc{gnu} memory-mapped malloc package
33656 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33657 from the @file{gdb-@var{version-number}} source directory, which in
33658 this example is the @file{gdb-@value{GDBVN}} directory.
33660 First switch to the @file{gdb-@var{version-number}} source directory
33661 if you are not already in it; then run @file{configure}. Pass the
33662 identifier for the platform on which @value{GDBN} will run as an
33668 cd gdb-@value{GDBVN}
33669 ./configure @var{host}
33674 where @var{host} is an identifier such as @samp{sun4} or
33675 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33676 (You can often leave off @var{host}; @file{configure} tries to guess the
33677 correct value by examining your system.)
33679 Running @samp{configure @var{host}} and then running @code{make} builds the
33680 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33681 libraries, then @code{gdb} itself. The configured source files, and the
33682 binaries, are left in the corresponding source directories.
33685 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33686 system does not recognize this automatically when you run a different
33687 shell, you may need to run @code{sh} on it explicitly:
33690 sh configure @var{host}
33693 If you run @file{configure} from a directory that contains source
33694 directories for multiple libraries or programs, such as the
33695 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33697 creates configuration files for every directory level underneath (unless
33698 you tell it not to, with the @samp{--norecursion} option).
33700 You should run the @file{configure} script from the top directory in the
33701 source tree, the @file{gdb-@var{version-number}} directory. If you run
33702 @file{configure} from one of the subdirectories, you will configure only
33703 that subdirectory. That is usually not what you want. In particular,
33704 if you run the first @file{configure} from the @file{gdb} subdirectory
33705 of the @file{gdb-@var{version-number}} directory, you will omit the
33706 configuration of @file{bfd}, @file{readline}, and other sibling
33707 directories of the @file{gdb} subdirectory. This leads to build errors
33708 about missing include files such as @file{bfd/bfd.h}.
33710 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33711 However, you should make sure that the shell on your path (named by
33712 the @samp{SHELL} environment variable) is publicly readable. Remember
33713 that @value{GDBN} uses the shell to start your program---some systems refuse to
33714 let @value{GDBN} debug child processes whose programs are not readable.
33716 @node Separate Objdir
33717 @section Compiling @value{GDBN} in Another Directory
33719 If you want to run @value{GDBN} versions for several host or target machines,
33720 you need a different @code{gdb} compiled for each combination of
33721 host and target. @file{configure} is designed to make this easy by
33722 allowing you to generate each configuration in a separate subdirectory,
33723 rather than in the source directory. If your @code{make} program
33724 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33725 @code{make} in each of these directories builds the @code{gdb}
33726 program specified there.
33728 To build @code{gdb} in a separate directory, run @file{configure}
33729 with the @samp{--srcdir} option to specify where to find the source.
33730 (You also need to specify a path to find @file{configure}
33731 itself from your working directory. If the path to @file{configure}
33732 would be the same as the argument to @samp{--srcdir}, you can leave out
33733 the @samp{--srcdir} option; it is assumed.)
33735 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33736 separate directory for a Sun 4 like this:
33740 cd gdb-@value{GDBVN}
33743 ../gdb-@value{GDBVN}/configure sun4
33748 When @file{configure} builds a configuration using a remote source
33749 directory, it creates a tree for the binaries with the same structure
33750 (and using the same names) as the tree under the source directory. In
33751 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33752 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33753 @file{gdb-sun4/gdb}.
33755 Make sure that your path to the @file{configure} script has just one
33756 instance of @file{gdb} in it. If your path to @file{configure} looks
33757 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33758 one subdirectory of @value{GDBN}, not the whole package. This leads to
33759 build errors about missing include files such as @file{bfd/bfd.h}.
33761 One popular reason to build several @value{GDBN} configurations in separate
33762 directories is to configure @value{GDBN} for cross-compiling (where
33763 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33764 programs that run on another machine---the @dfn{target}).
33765 You specify a cross-debugging target by
33766 giving the @samp{--target=@var{target}} option to @file{configure}.
33768 When you run @code{make} to build a program or library, you must run
33769 it in a configured directory---whatever directory you were in when you
33770 called @file{configure} (or one of its subdirectories).
33772 The @code{Makefile} that @file{configure} generates in each source
33773 directory also runs recursively. If you type @code{make} in a source
33774 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33775 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33776 will build all the required libraries, and then build GDB.
33778 When you have multiple hosts or targets configured in separate
33779 directories, you can run @code{make} on them in parallel (for example,
33780 if they are NFS-mounted on each of the hosts); they will not interfere
33784 @section Specifying Names for Hosts and Targets
33786 The specifications used for hosts and targets in the @file{configure}
33787 script are based on a three-part naming scheme, but some short predefined
33788 aliases are also supported. The full naming scheme encodes three pieces
33789 of information in the following pattern:
33792 @var{architecture}-@var{vendor}-@var{os}
33795 For example, you can use the alias @code{sun4} as a @var{host} argument,
33796 or as the value for @var{target} in a @code{--target=@var{target}}
33797 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33799 The @file{configure} script accompanying @value{GDBN} does not provide
33800 any query facility to list all supported host and target names or
33801 aliases. @file{configure} calls the Bourne shell script
33802 @code{config.sub} to map abbreviations to full names; you can read the
33803 script, if you wish, or you can use it to test your guesses on
33804 abbreviations---for example:
33807 % sh config.sub i386-linux
33809 % sh config.sub alpha-linux
33810 alpha-unknown-linux-gnu
33811 % sh config.sub hp9k700
33813 % sh config.sub sun4
33814 sparc-sun-sunos4.1.1
33815 % sh config.sub sun3
33816 m68k-sun-sunos4.1.1
33817 % sh config.sub i986v
33818 Invalid configuration `i986v': machine `i986v' not recognized
33822 @code{config.sub} is also distributed in the @value{GDBN} source
33823 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33825 @node Configure Options
33826 @section @file{configure} Options
33828 Here is a summary of the @file{configure} options and arguments that
33829 are most often useful for building @value{GDBN}. @file{configure} also has
33830 several other options not listed here. @inforef{What Configure
33831 Does,,configure.info}, for a full explanation of @file{configure}.
33834 configure @r{[}--help@r{]}
33835 @r{[}--prefix=@var{dir}@r{]}
33836 @r{[}--exec-prefix=@var{dir}@r{]}
33837 @r{[}--srcdir=@var{dirname}@r{]}
33838 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33839 @r{[}--target=@var{target}@r{]}
33844 You may introduce options with a single @samp{-} rather than
33845 @samp{--} if you prefer; but you may abbreviate option names if you use
33850 Display a quick summary of how to invoke @file{configure}.
33852 @item --prefix=@var{dir}
33853 Configure the source to install programs and files under directory
33856 @item --exec-prefix=@var{dir}
33857 Configure the source to install programs under directory
33860 @c avoid splitting the warning from the explanation:
33862 @item --srcdir=@var{dirname}
33863 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33864 @code{make} that implements the @code{VPATH} feature.}@*
33865 Use this option to make configurations in directories separate from the
33866 @value{GDBN} source directories. Among other things, you can use this to
33867 build (or maintain) several configurations simultaneously, in separate
33868 directories. @file{configure} writes configuration-specific files in
33869 the current directory, but arranges for them to use the source in the
33870 directory @var{dirname}. @file{configure} creates directories under
33871 the working directory in parallel to the source directories below
33874 @item --norecursion
33875 Configure only the directory level where @file{configure} is executed; do not
33876 propagate configuration to subdirectories.
33878 @item --target=@var{target}
33879 Configure @value{GDBN} for cross-debugging programs running on the specified
33880 @var{target}. Without this option, @value{GDBN} is configured to debug
33881 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33883 There is no convenient way to generate a list of all available targets.
33885 @item @var{host} @dots{}
33886 Configure @value{GDBN} to run on the specified @var{host}.
33888 There is no convenient way to generate a list of all available hosts.
33891 There are many other options available as well, but they are generally
33892 needed for special purposes only.
33894 @node System-wide configuration
33895 @section System-wide configuration and settings
33896 @cindex system-wide init file
33898 @value{GDBN} can be configured to have a system-wide init file;
33899 this file will be read and executed at startup (@pxref{Startup, , What
33900 @value{GDBN} does during startup}).
33902 Here is the corresponding configure option:
33905 @item --with-system-gdbinit=@var{file}
33906 Specify that the default location of the system-wide init file is
33910 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33911 it may be subject to relocation. Two possible cases:
33915 If the default location of this init file contains @file{$prefix},
33916 it will be subject to relocation. Suppose that the configure options
33917 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33918 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33919 init file is looked for as @file{$install/etc/gdbinit} instead of
33920 @file{$prefix/etc/gdbinit}.
33923 By contrast, if the default location does not contain the prefix,
33924 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33925 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33926 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33927 wherever @value{GDBN} is installed.
33930 If the configured location of the system-wide init file (as given by the
33931 @option{--with-system-gdbinit} option at configure time) is in the
33932 data-directory (as specified by @option{--with-gdb-datadir} at configure
33933 time) or in one of its subdirectories, then @value{GDBN} will look for the
33934 system-wide init file in the directory specified by the
33935 @option{--data-directory} command-line option.
33936 Note that the system-wide init file is only read once, during @value{GDBN}
33937 initialization. If the data-directory is changed after @value{GDBN} has
33938 started with the @code{set data-directory} command, the file will not be
33942 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33945 @node System-wide Configuration Scripts
33946 @subsection Installed System-wide Configuration Scripts
33947 @cindex system-wide configuration scripts
33949 The @file{system-gdbinit} directory, located inside the data-directory
33950 (as specified by @option{--with-gdb-datadir} at configure time) contains
33951 a number of scripts which can be used as system-wide init files. To
33952 automatically source those scripts at startup, @value{GDBN} should be
33953 configured with @option{--with-system-gdbinit}. Otherwise, any user
33954 should be able to source them by hand as needed.
33956 The following scripts are currently available:
33959 @item @file{elinos.py}
33961 @cindex ELinOS system-wide configuration script
33962 This script is useful when debugging a program on an ELinOS target.
33963 It takes advantage of the environment variables defined in a standard
33964 ELinOS environment in order to determine the location of the system
33965 shared libraries, and then sets the @samp{solib-absolute-prefix}
33966 and @samp{solib-search-path} variables appropriately.
33968 @item @file{wrs-linux.py}
33969 @pindex wrs-linux.py
33970 @cindex Wind River Linux system-wide configuration script
33971 This script is useful when debugging a program on a target running
33972 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33973 the host-side sysroot used by the target system.
33977 @node Maintenance Commands
33978 @appendix Maintenance Commands
33979 @cindex maintenance commands
33980 @cindex internal commands
33982 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33983 includes a number of commands intended for @value{GDBN} developers,
33984 that are not documented elsewhere in this manual. These commands are
33985 provided here for reference. (For commands that turn on debugging
33986 messages, see @ref{Debugging Output}.)
33989 @kindex maint agent
33990 @kindex maint agent-eval
33991 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33992 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33993 Translate the given @var{expression} into remote agent bytecodes.
33994 This command is useful for debugging the Agent Expression mechanism
33995 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33996 expression useful for data collection, such as by tracepoints, while
33997 @samp{maint agent-eval} produces an expression that evaluates directly
33998 to a result. For instance, a collection expression for @code{globa +
33999 globb} will include bytecodes to record four bytes of memory at each
34000 of the addresses of @code{globa} and @code{globb}, while discarding
34001 the result of the addition, while an evaluation expression will do the
34002 addition and return the sum.
34003 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34004 If not, generate remote agent bytecode for current frame PC address.
34006 @kindex maint agent-printf
34007 @item maint agent-printf @var{format},@var{expr},...
34008 Translate the given format string and list of argument expressions
34009 into remote agent bytecodes and display them as a disassembled list.
34010 This command is useful for debugging the agent version of dynamic
34011 printf (@pxref{Dynamic Printf}).
34013 @kindex maint info breakpoints
34014 @item @anchor{maint info breakpoints}maint info breakpoints
34015 Using the same format as @samp{info breakpoints}, display both the
34016 breakpoints you've set explicitly, and those @value{GDBN} is using for
34017 internal purposes. Internal breakpoints are shown with negative
34018 breakpoint numbers. The type column identifies what kind of breakpoint
34023 Normal, explicitly set breakpoint.
34026 Normal, explicitly set watchpoint.
34029 Internal breakpoint, used to handle correctly stepping through
34030 @code{longjmp} calls.
34032 @item longjmp resume
34033 Internal breakpoint at the target of a @code{longjmp}.
34036 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34039 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34042 Shared library events.
34046 @kindex maint info btrace
34047 @item maint info btrace
34048 Pint information about raw branch tracing data.
34050 @kindex maint btrace packet-history
34051 @item maint btrace packet-history
34052 Print the raw branch trace packets that are used to compute the
34053 execution history for the @samp{record btrace} command. Both the
34054 information and the format in which it is printed depend on the btrace
34059 For the BTS recording format, print a list of blocks of sequential
34060 code. For each block, the following information is printed:
34064 Newer blocks have higher numbers. The oldest block has number zero.
34065 @item Lowest @samp{PC}
34066 @item Highest @samp{PC}
34070 For the Intel Processor Trace recording format, print a list of
34071 Intel Processor Trace packets. For each packet, the following
34072 information is printed:
34075 @item Packet number
34076 Newer packets have higher numbers. The oldest packet has number zero.
34078 The packet's offset in the trace stream.
34079 @item Packet opcode and payload
34083 @kindex maint btrace clear-packet-history
34084 @item maint btrace clear-packet-history
34085 Discards the cached packet history printed by the @samp{maint btrace
34086 packet-history} command. The history will be computed again when
34089 @kindex maint btrace clear
34090 @item maint btrace clear
34091 Discard the branch trace data. The data will be fetched anew and the
34092 branch trace will be recomputed when needed.
34094 This implicitly truncates the branch trace to a single branch trace
34095 buffer. When updating branch trace incrementally, the branch trace
34096 available to @value{GDBN} may be bigger than a single branch trace
34099 @kindex maint set btrace pt skip-pad
34100 @item maint set btrace pt skip-pad
34101 @kindex maint show btrace pt skip-pad
34102 @item maint show btrace pt skip-pad
34103 Control whether @value{GDBN} will skip PAD packets when computing the
34106 @kindex set displaced-stepping
34107 @kindex show displaced-stepping
34108 @cindex displaced stepping support
34109 @cindex out-of-line single-stepping
34110 @item set displaced-stepping
34111 @itemx show displaced-stepping
34112 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34113 if the target supports it. Displaced stepping is a way to single-step
34114 over breakpoints without removing them from the inferior, by executing
34115 an out-of-line copy of the instruction that was originally at the
34116 breakpoint location. It is also known as out-of-line single-stepping.
34119 @item set displaced-stepping on
34120 If the target architecture supports it, @value{GDBN} will use
34121 displaced stepping to step over breakpoints.
34123 @item set displaced-stepping off
34124 @value{GDBN} will not use displaced stepping to step over breakpoints,
34125 even if such is supported by the target architecture.
34127 @cindex non-stop mode, and @samp{set displaced-stepping}
34128 @item set displaced-stepping auto
34129 This is the default mode. @value{GDBN} will use displaced stepping
34130 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34131 architecture supports displaced stepping.
34134 @kindex maint check-psymtabs
34135 @item maint check-psymtabs
34136 Check the consistency of currently expanded psymtabs versus symtabs.
34137 Use this to check, for example, whether a symbol is in one but not the other.
34139 @kindex maint check-symtabs
34140 @item maint check-symtabs
34141 Check the consistency of currently expanded symtabs.
34143 @kindex maint expand-symtabs
34144 @item maint expand-symtabs [@var{regexp}]
34145 Expand symbol tables.
34146 If @var{regexp} is specified, only expand symbol tables for file
34147 names matching @var{regexp}.
34149 @kindex maint set catch-demangler-crashes
34150 @kindex maint show catch-demangler-crashes
34151 @cindex demangler crashes
34152 @item maint set catch-demangler-crashes [on|off]
34153 @itemx maint show catch-demangler-crashes
34154 Control whether @value{GDBN} should attempt to catch crashes in the
34155 symbol name demangler. The default is to attempt to catch crashes.
34156 If enabled, the first time a crash is caught, a core file is created,
34157 the offending symbol is displayed and the user is presented with the
34158 option to terminate the current session.
34160 @kindex maint cplus first_component
34161 @item maint cplus first_component @var{name}
34162 Print the first C@t{++} class/namespace component of @var{name}.
34164 @kindex maint cplus namespace
34165 @item maint cplus namespace
34166 Print the list of possible C@t{++} namespaces.
34168 @kindex maint deprecate
34169 @kindex maint undeprecate
34170 @cindex deprecated commands
34171 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34172 @itemx maint undeprecate @var{command}
34173 Deprecate or undeprecate the named @var{command}. Deprecated commands
34174 cause @value{GDBN} to issue a warning when you use them. The optional
34175 argument @var{replacement} says which newer command should be used in
34176 favor of the deprecated one; if it is given, @value{GDBN} will mention
34177 the replacement as part of the warning.
34179 @kindex maint dump-me
34180 @item maint dump-me
34181 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34182 Cause a fatal signal in the debugger and force it to dump its core.
34183 This is supported only on systems which support aborting a program
34184 with the @code{SIGQUIT} signal.
34186 @kindex maint internal-error
34187 @kindex maint internal-warning
34188 @kindex maint demangler-warning
34189 @cindex demangler crashes
34190 @item maint internal-error @r{[}@var{message-text}@r{]}
34191 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34192 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34194 Cause @value{GDBN} to call the internal function @code{internal_error},
34195 @code{internal_warning} or @code{demangler_warning} and hence behave
34196 as though an internal problem has been detected. In addition to
34197 reporting the internal problem, these functions give the user the
34198 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34199 and @code{internal_warning}) create a core file of the current
34200 @value{GDBN} session.
34202 These commands take an optional parameter @var{message-text} that is
34203 used as the text of the error or warning message.
34205 Here's an example of using @code{internal-error}:
34208 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34209 @dots{}/maint.c:121: internal-error: testing, 1, 2
34210 A problem internal to GDB has been detected. Further
34211 debugging may prove unreliable.
34212 Quit this debugging session? (y or n) @kbd{n}
34213 Create a core file? (y or n) @kbd{n}
34217 @cindex @value{GDBN} internal error
34218 @cindex internal errors, control of @value{GDBN} behavior
34219 @cindex demangler crashes
34221 @kindex maint set internal-error
34222 @kindex maint show internal-error
34223 @kindex maint set internal-warning
34224 @kindex maint show internal-warning
34225 @kindex maint set demangler-warning
34226 @kindex maint show demangler-warning
34227 @item maint set internal-error @var{action} [ask|yes|no]
34228 @itemx maint show internal-error @var{action}
34229 @itemx maint set internal-warning @var{action} [ask|yes|no]
34230 @itemx maint show internal-warning @var{action}
34231 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34232 @itemx maint show demangler-warning @var{action}
34233 When @value{GDBN} reports an internal problem (error or warning) it
34234 gives the user the opportunity to both quit @value{GDBN} and create a
34235 core file of the current @value{GDBN} session. These commands let you
34236 override the default behaviour for each particular @var{action},
34237 described in the table below.
34241 You can specify that @value{GDBN} should always (yes) or never (no)
34242 quit. The default is to ask the user what to do.
34245 You can specify that @value{GDBN} should always (yes) or never (no)
34246 create a core file. The default is to ask the user what to do. Note
34247 that there is no @code{corefile} option for @code{demangler-warning}:
34248 demangler warnings always create a core file and this cannot be
34252 @kindex maint packet
34253 @item maint packet @var{text}
34254 If @value{GDBN} is talking to an inferior via the serial protocol,
34255 then this command sends the string @var{text} to the inferior, and
34256 displays the response packet. @value{GDBN} supplies the initial
34257 @samp{$} character, the terminating @samp{#} character, and the
34260 @kindex maint print architecture
34261 @item maint print architecture @r{[}@var{file}@r{]}
34262 Print the entire architecture configuration. The optional argument
34263 @var{file} names the file where the output goes.
34265 @kindex maint print c-tdesc
34266 @item maint print c-tdesc
34267 Print the current target description (@pxref{Target Descriptions}) as
34268 a C source file. The created source file can be used in @value{GDBN}
34269 when an XML parser is not available to parse the description.
34271 @kindex maint print dummy-frames
34272 @item maint print dummy-frames
34273 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34276 (@value{GDBP}) @kbd{b add}
34278 (@value{GDBP}) @kbd{print add(2,3)}
34279 Breakpoint 2, add (a=2, b=3) at @dots{}
34281 The program being debugged stopped while in a function called from GDB.
34283 (@value{GDBP}) @kbd{maint print dummy-frames}
34284 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34288 Takes an optional file parameter.
34290 @kindex maint print registers
34291 @kindex maint print raw-registers
34292 @kindex maint print cooked-registers
34293 @kindex maint print register-groups
34294 @kindex maint print remote-registers
34295 @item maint print registers @r{[}@var{file}@r{]}
34296 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34297 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34298 @itemx maint print register-groups @r{[}@var{file}@r{]}
34299 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34300 Print @value{GDBN}'s internal register data structures.
34302 The command @code{maint print raw-registers} includes the contents of
34303 the raw register cache; the command @code{maint print
34304 cooked-registers} includes the (cooked) value of all registers,
34305 including registers which aren't available on the target nor visible
34306 to user; the command @code{maint print register-groups} includes the
34307 groups that each register is a member of; and the command @code{maint
34308 print remote-registers} includes the remote target's register numbers
34309 and offsets in the `G' packets.
34311 These commands take an optional parameter, a file name to which to
34312 write the information.
34314 @kindex maint print reggroups
34315 @item maint print reggroups @r{[}@var{file}@r{]}
34316 Print @value{GDBN}'s internal register group data structures. The
34317 optional argument @var{file} tells to what file to write the
34320 The register groups info looks like this:
34323 (@value{GDBP}) @kbd{maint print reggroups}
34336 This command forces @value{GDBN} to flush its internal register cache.
34338 @kindex maint print objfiles
34339 @cindex info for known object files
34340 @item maint print objfiles @r{[}@var{regexp}@r{]}
34341 Print a dump of all known object files.
34342 If @var{regexp} is specified, only print object files whose names
34343 match @var{regexp}. For each object file, this command prints its name,
34344 address in memory, and all of its psymtabs and symtabs.
34346 @kindex maint print user-registers
34347 @cindex user registers
34348 @item maint print user-registers
34349 List all currently available @dfn{user registers}. User registers
34350 typically provide alternate names for actual hardware registers. They
34351 include the four ``standard'' registers @code{$fp}, @code{$pc},
34352 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34353 registers can be used in expressions in the same way as the canonical
34354 register names, but only the latter are listed by the @code{info
34355 registers} and @code{maint print registers} commands.
34357 @kindex maint print section-scripts
34358 @cindex info for known .debug_gdb_scripts-loaded scripts
34359 @item maint print section-scripts [@var{regexp}]
34360 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34361 If @var{regexp} is specified, only print scripts loaded by object files
34362 matching @var{regexp}.
34363 For each script, this command prints its name as specified in the objfile,
34364 and the full path if known.
34365 @xref{dotdebug_gdb_scripts section}.
34367 @kindex maint print statistics
34368 @cindex bcache statistics
34369 @item maint print statistics
34370 This command prints, for each object file in the program, various data
34371 about that object file followed by the byte cache (@dfn{bcache})
34372 statistics for the object file. The objfile data includes the number
34373 of minimal, partial, full, and stabs symbols, the number of types
34374 defined by the objfile, the number of as yet unexpanded psym tables,
34375 the number of line tables and string tables, and the amount of memory
34376 used by the various tables. The bcache statistics include the counts,
34377 sizes, and counts of duplicates of all and unique objects, max,
34378 average, and median entry size, total memory used and its overhead and
34379 savings, and various measures of the hash table size and chain
34382 @kindex maint print target-stack
34383 @cindex target stack description
34384 @item maint print target-stack
34385 A @dfn{target} is an interface between the debugger and a particular
34386 kind of file or process. Targets can be stacked in @dfn{strata},
34387 so that more than one target can potentially respond to a request.
34388 In particular, memory accesses will walk down the stack of targets
34389 until they find a target that is interested in handling that particular
34392 This command prints a short description of each layer that was pushed on
34393 the @dfn{target stack}, starting from the top layer down to the bottom one.
34395 @kindex maint print type
34396 @cindex type chain of a data type
34397 @item maint print type @var{expr}
34398 Print the type chain for a type specified by @var{expr}. The argument
34399 can be either a type name or a symbol. If it is a symbol, the type of
34400 that symbol is described. The type chain produced by this command is
34401 a recursive definition of the data type as stored in @value{GDBN}'s
34402 data structures, including its flags and contained types.
34404 @kindex maint set dwarf always-disassemble
34405 @kindex maint show dwarf always-disassemble
34406 @item maint set dwarf always-disassemble
34407 @item maint show dwarf always-disassemble
34408 Control the behavior of @code{info address} when using DWARF debugging
34411 The default is @code{off}, which means that @value{GDBN} should try to
34412 describe a variable's location in an easily readable format. When
34413 @code{on}, @value{GDBN} will instead display the DWARF location
34414 expression in an assembly-like format. Note that some locations are
34415 too complex for @value{GDBN} to describe simply; in this case you will
34416 always see the disassembly form.
34418 Here is an example of the resulting disassembly:
34421 (gdb) info addr argc
34422 Symbol "argc" is a complex DWARF expression:
34426 For more information on these expressions, see
34427 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34429 @kindex maint set dwarf max-cache-age
34430 @kindex maint show dwarf max-cache-age
34431 @item maint set dwarf max-cache-age
34432 @itemx maint show dwarf max-cache-age
34433 Control the DWARF compilation unit cache.
34435 @cindex DWARF compilation units cache
34436 In object files with inter-compilation-unit references, such as those
34437 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34438 reader needs to frequently refer to previously read compilation units.
34439 This setting controls how long a compilation unit will remain in the
34440 cache if it is not referenced. A higher limit means that cached
34441 compilation units will be stored in memory longer, and more total
34442 memory will be used. Setting it to zero disables caching, which will
34443 slow down @value{GDBN} startup, but reduce memory consumption.
34445 @kindex maint set profile
34446 @kindex maint show profile
34447 @cindex profiling GDB
34448 @item maint set profile
34449 @itemx maint show profile
34450 Control profiling of @value{GDBN}.
34452 Profiling will be disabled until you use the @samp{maint set profile}
34453 command to enable it. When you enable profiling, the system will begin
34454 collecting timing and execution count data; when you disable profiling or
34455 exit @value{GDBN}, the results will be written to a log file. Remember that
34456 if you use profiling, @value{GDBN} will overwrite the profiling log file
34457 (often called @file{gmon.out}). If you have a record of important profiling
34458 data in a @file{gmon.out} file, be sure to move it to a safe location.
34460 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34461 compiled with the @samp{-pg} compiler option.
34463 @kindex maint set show-debug-regs
34464 @kindex maint show show-debug-regs
34465 @cindex hardware debug registers
34466 @item maint set show-debug-regs
34467 @itemx maint show show-debug-regs
34468 Control whether to show variables that mirror the hardware debug
34469 registers. Use @code{on} to enable, @code{off} to disable. If
34470 enabled, the debug registers values are shown when @value{GDBN} inserts or
34471 removes a hardware breakpoint or watchpoint, and when the inferior
34472 triggers a hardware-assisted breakpoint or watchpoint.
34474 @kindex maint set show-all-tib
34475 @kindex maint show show-all-tib
34476 @item maint set show-all-tib
34477 @itemx maint show show-all-tib
34478 Control whether to show all non zero areas within a 1k block starting
34479 at thread local base, when using the @samp{info w32 thread-information-block}
34482 @kindex maint set target-async
34483 @kindex maint show target-async
34484 @item maint set target-async
34485 @itemx maint show target-async
34486 This controls whether @value{GDBN} targets operate in synchronous or
34487 asynchronous mode (@pxref{Background Execution}). Normally the
34488 default is asynchronous, if it is available; but this can be changed
34489 to more easily debug problems occurring only in synchronous mode.
34491 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34492 @kindex maint show target-non-stop
34493 @item maint set target-non-stop
34494 @itemx maint show target-non-stop
34496 This controls whether @value{GDBN} targets always operate in non-stop
34497 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34498 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34499 if supported by the target.
34502 @item maint set target-non-stop auto
34503 This is the default mode. @value{GDBN} controls the target in
34504 non-stop mode if the target supports it.
34506 @item maint set target-non-stop on
34507 @value{GDBN} controls the target in non-stop mode even if the target
34508 does not indicate support.
34510 @item maint set target-non-stop off
34511 @value{GDBN} does not control the target in non-stop mode even if the
34512 target supports it.
34515 @kindex maint set per-command
34516 @kindex maint show per-command
34517 @item maint set per-command
34518 @itemx maint show per-command
34519 @cindex resources used by commands
34521 @value{GDBN} can display the resources used by each command.
34522 This is useful in debugging performance problems.
34525 @item maint set per-command space [on|off]
34526 @itemx maint show per-command space
34527 Enable or disable the printing of the memory used by GDB for each command.
34528 If enabled, @value{GDBN} will display how much memory each command
34529 took, following the command's own output.
34530 This can also be requested by invoking @value{GDBN} with the
34531 @option{--statistics} command-line switch (@pxref{Mode Options}).
34533 @item maint set per-command time [on|off]
34534 @itemx maint show per-command time
34535 Enable or disable the printing of the execution time of @value{GDBN}
34537 If enabled, @value{GDBN} will display how much time it
34538 took to execute each command, following the command's own output.
34539 Both CPU time and wallclock time are printed.
34540 Printing both is useful when trying to determine whether the cost is
34541 CPU or, e.g., disk/network latency.
34542 Note that the CPU time printed is for @value{GDBN} only, it does not include
34543 the execution time of the inferior because there's no mechanism currently
34544 to compute how much time was spent by @value{GDBN} and how much time was
34545 spent by the program been debugged.
34546 This can also be requested by invoking @value{GDBN} with the
34547 @option{--statistics} command-line switch (@pxref{Mode Options}).
34549 @item maint set per-command symtab [on|off]
34550 @itemx maint show per-command symtab
34551 Enable or disable the printing of basic symbol table statistics
34553 If enabled, @value{GDBN} will display the following information:
34557 number of symbol tables
34559 number of primary symbol tables
34561 number of blocks in the blockvector
34565 @kindex maint space
34566 @cindex memory used by commands
34567 @item maint space @var{value}
34568 An alias for @code{maint set per-command space}.
34569 A non-zero value enables it, zero disables it.
34572 @cindex time of command execution
34573 @item maint time @var{value}
34574 An alias for @code{maint set per-command time}.
34575 A non-zero value enables it, zero disables it.
34577 @kindex maint translate-address
34578 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34579 Find the symbol stored at the location specified by the address
34580 @var{addr} and an optional section name @var{section}. If found,
34581 @value{GDBN} prints the name of the closest symbol and an offset from
34582 the symbol's location to the specified address. This is similar to
34583 the @code{info address} command (@pxref{Symbols}), except that this
34584 command also allows to find symbols in other sections.
34586 If section was not specified, the section in which the symbol was found
34587 is also printed. For dynamically linked executables, the name of
34588 executable or shared library containing the symbol is printed as well.
34592 The following command is useful for non-interactive invocations of
34593 @value{GDBN}, such as in the test suite.
34596 @item set watchdog @var{nsec}
34597 @kindex set watchdog
34598 @cindex watchdog timer
34599 @cindex timeout for commands
34600 Set the maximum number of seconds @value{GDBN} will wait for the
34601 target operation to finish. If this time expires, @value{GDBN}
34602 reports and error and the command is aborted.
34604 @item show watchdog
34605 Show the current setting of the target wait timeout.
34608 @node Remote Protocol
34609 @appendix @value{GDBN} Remote Serial Protocol
34614 * Stop Reply Packets::
34615 * General Query Packets::
34616 * Architecture-Specific Protocol Details::
34617 * Tracepoint Packets::
34618 * Host I/O Packets::
34620 * Notification Packets::
34621 * Remote Non-Stop::
34622 * Packet Acknowledgment::
34624 * File-I/O Remote Protocol Extension::
34625 * Library List Format::
34626 * Library List Format for SVR4 Targets::
34627 * Memory Map Format::
34628 * Thread List Format::
34629 * Traceframe Info Format::
34630 * Branch Trace Format::
34631 * Branch Trace Configuration Format::
34637 There may be occasions when you need to know something about the
34638 protocol---for example, if there is only one serial port to your target
34639 machine, you might want your program to do something special if it
34640 recognizes a packet meant for @value{GDBN}.
34642 In the examples below, @samp{->} and @samp{<-} are used to indicate
34643 transmitted and received data, respectively.
34645 @cindex protocol, @value{GDBN} remote serial
34646 @cindex serial protocol, @value{GDBN} remote
34647 @cindex remote serial protocol
34648 All @value{GDBN} commands and responses (other than acknowledgments
34649 and notifications, see @ref{Notification Packets}) are sent as a
34650 @var{packet}. A @var{packet} is introduced with the character
34651 @samp{$}, the actual @var{packet-data}, and the terminating character
34652 @samp{#} followed by a two-digit @var{checksum}:
34655 @code{$}@var{packet-data}@code{#}@var{checksum}
34659 @cindex checksum, for @value{GDBN} remote
34661 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34662 characters between the leading @samp{$} and the trailing @samp{#} (an
34663 eight bit unsigned checksum).
34665 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34666 specification also included an optional two-digit @var{sequence-id}:
34669 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34672 @cindex sequence-id, for @value{GDBN} remote
34674 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34675 has never output @var{sequence-id}s. Stubs that handle packets added
34676 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34678 When either the host or the target machine receives a packet, the first
34679 response expected is an acknowledgment: either @samp{+} (to indicate
34680 the package was received correctly) or @samp{-} (to request
34684 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34689 The @samp{+}/@samp{-} acknowledgments can be disabled
34690 once a connection is established.
34691 @xref{Packet Acknowledgment}, for details.
34693 The host (@value{GDBN}) sends @var{command}s, and the target (the
34694 debugging stub incorporated in your program) sends a @var{response}. In
34695 the case of step and continue @var{command}s, the response is only sent
34696 when the operation has completed, and the target has again stopped all
34697 threads in all attached processes. This is the default all-stop mode
34698 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34699 execution mode; see @ref{Remote Non-Stop}, for details.
34701 @var{packet-data} consists of a sequence of characters with the
34702 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34705 @cindex remote protocol, field separator
34706 Fields within the packet should be separated using @samp{,} @samp{;} or
34707 @samp{:}. Except where otherwise noted all numbers are represented in
34708 @sc{hex} with leading zeros suppressed.
34710 Implementors should note that prior to @value{GDBN} 5.0, the character
34711 @samp{:} could not appear as the third character in a packet (as it
34712 would potentially conflict with the @var{sequence-id}).
34714 @cindex remote protocol, binary data
34715 @anchor{Binary Data}
34716 Binary data in most packets is encoded either as two hexadecimal
34717 digits per byte of binary data. This allowed the traditional remote
34718 protocol to work over connections which were only seven-bit clean.
34719 Some packets designed more recently assume an eight-bit clean
34720 connection, and use a more efficient encoding to send and receive
34723 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34724 as an escape character. Any escaped byte is transmitted as the escape
34725 character followed by the original character XORed with @code{0x20}.
34726 For example, the byte @code{0x7d} would be transmitted as the two
34727 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34728 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34729 @samp{@}}) must always be escaped. Responses sent by the stub
34730 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34731 is not interpreted as the start of a run-length encoded sequence
34734 Response @var{data} can be run-length encoded to save space.
34735 Run-length encoding replaces runs of identical characters with one
34736 instance of the repeated character, followed by a @samp{*} and a
34737 repeat count. The repeat count is itself sent encoded, to avoid
34738 binary characters in @var{data}: a value of @var{n} is sent as
34739 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34740 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34741 code 32) for a repeat count of 3. (This is because run-length
34742 encoding starts to win for counts 3 or more.) Thus, for example,
34743 @samp{0* } is a run-length encoding of ``0000'': the space character
34744 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34747 The printable characters @samp{#} and @samp{$} or with a numeric value
34748 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34749 seven repeats (@samp{$}) can be expanded using a repeat count of only
34750 five (@samp{"}). For example, @samp{00000000} can be encoded as
34753 The error response returned for some packets includes a two character
34754 error number. That number is not well defined.
34756 @cindex empty response, for unsupported packets
34757 For any @var{command} not supported by the stub, an empty response
34758 (@samp{$#00}) should be returned. That way it is possible to extend the
34759 protocol. A newer @value{GDBN} can tell if a packet is supported based
34762 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34763 commands for register access, and the @samp{m} and @samp{M} commands
34764 for memory access. Stubs that only control single-threaded targets
34765 can implement run control with the @samp{c} (continue), and @samp{s}
34766 (step) commands. Stubs that support multi-threading targets should
34767 support the @samp{vCont} command. All other commands are optional.
34772 The following table provides a complete list of all currently defined
34773 @var{command}s and their corresponding response @var{data}.
34774 @xref{File-I/O Remote Protocol Extension}, for details about the File
34775 I/O extension of the remote protocol.
34777 Each packet's description has a template showing the packet's overall
34778 syntax, followed by an explanation of the packet's meaning. We
34779 include spaces in some of the templates for clarity; these are not
34780 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34781 separate its components. For example, a template like @samp{foo
34782 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34783 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34784 @var{baz}. @value{GDBN} does not transmit a space character between the
34785 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34788 @cindex @var{thread-id}, in remote protocol
34789 @anchor{thread-id syntax}
34790 Several packets and replies include a @var{thread-id} field to identify
34791 a thread. Normally these are positive numbers with a target-specific
34792 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34793 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34796 In addition, the remote protocol supports a multiprocess feature in
34797 which the @var{thread-id} syntax is extended to optionally include both
34798 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34799 The @var{pid} (process) and @var{tid} (thread) components each have the
34800 format described above: a positive number with target-specific
34801 interpretation formatted as a big-endian hex string, literal @samp{-1}
34802 to indicate all processes or threads (respectively), or @samp{0} to
34803 indicate an arbitrary process or thread. Specifying just a process, as
34804 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34805 error to specify all processes but a specific thread, such as
34806 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34807 for those packets and replies explicitly documented to include a process
34808 ID, rather than a @var{thread-id}.
34810 The multiprocess @var{thread-id} syntax extensions are only used if both
34811 @value{GDBN} and the stub report support for the @samp{multiprocess}
34812 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34815 Note that all packet forms beginning with an upper- or lower-case
34816 letter, other than those described here, are reserved for future use.
34818 Here are the packet descriptions.
34823 @cindex @samp{!} packet
34824 @anchor{extended mode}
34825 Enable extended mode. In extended mode, the remote server is made
34826 persistent. The @samp{R} packet is used to restart the program being
34832 The remote target both supports and has enabled extended mode.
34836 @cindex @samp{?} packet
34838 Indicate the reason the target halted. The reply is the same as for
34839 step and continue. This packet has a special interpretation when the
34840 target is in non-stop mode; see @ref{Remote Non-Stop}.
34843 @xref{Stop Reply Packets}, for the reply specifications.
34845 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34846 @cindex @samp{A} packet
34847 Initialized @code{argv[]} array passed into program. @var{arglen}
34848 specifies the number of bytes in the hex encoded byte stream
34849 @var{arg}. See @code{gdbserver} for more details.
34854 The arguments were set.
34860 @cindex @samp{b} packet
34861 (Don't use this packet; its behavior is not well-defined.)
34862 Change the serial line speed to @var{baud}.
34864 JTC: @emph{When does the transport layer state change? When it's
34865 received, or after the ACK is transmitted. In either case, there are
34866 problems if the command or the acknowledgment packet is dropped.}
34868 Stan: @emph{If people really wanted to add something like this, and get
34869 it working for the first time, they ought to modify ser-unix.c to send
34870 some kind of out-of-band message to a specially-setup stub and have the
34871 switch happen "in between" packets, so that from remote protocol's point
34872 of view, nothing actually happened.}
34874 @item B @var{addr},@var{mode}
34875 @cindex @samp{B} packet
34876 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34877 breakpoint at @var{addr}.
34879 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34880 (@pxref{insert breakpoint or watchpoint packet}).
34882 @cindex @samp{bc} packet
34885 Backward continue. Execute the target system in reverse. No parameter.
34886 @xref{Reverse Execution}, for more information.
34889 @xref{Stop Reply Packets}, for the reply specifications.
34891 @cindex @samp{bs} packet
34894 Backward single step. Execute one instruction in reverse. No parameter.
34895 @xref{Reverse Execution}, for more information.
34898 @xref{Stop Reply Packets}, for the reply specifications.
34900 @item c @r{[}@var{addr}@r{]}
34901 @cindex @samp{c} packet
34902 Continue at @var{addr}, which is the address to resume. If @var{addr}
34903 is omitted, resume at current address.
34905 This packet is deprecated for multi-threading support. @xref{vCont
34909 @xref{Stop Reply Packets}, for the reply specifications.
34911 @item C @var{sig}@r{[};@var{addr}@r{]}
34912 @cindex @samp{C} packet
34913 Continue with signal @var{sig} (hex signal number). If
34914 @samp{;@var{addr}} is omitted, resume at same address.
34916 This packet is deprecated for multi-threading support. @xref{vCont
34920 @xref{Stop Reply Packets}, for the reply specifications.
34923 @cindex @samp{d} packet
34926 Don't use this packet; instead, define a general set packet
34927 (@pxref{General Query Packets}).
34931 @cindex @samp{D} packet
34932 The first form of the packet is used to detach @value{GDBN} from the
34933 remote system. It is sent to the remote target
34934 before @value{GDBN} disconnects via the @code{detach} command.
34936 The second form, including a process ID, is used when multiprocess
34937 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34938 detach only a specific process. The @var{pid} is specified as a
34939 big-endian hex string.
34949 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34950 @cindex @samp{F} packet
34951 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34952 This is part of the File-I/O protocol extension. @xref{File-I/O
34953 Remote Protocol Extension}, for the specification.
34956 @anchor{read registers packet}
34957 @cindex @samp{g} packet
34958 Read general registers.
34962 @item @var{XX@dots{}}
34963 Each byte of register data is described by two hex digits. The bytes
34964 with the register are transmitted in target byte order. The size of
34965 each register and their position within the @samp{g} packet are
34966 determined by the @value{GDBN} internal gdbarch functions
34967 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34968 specification of several standard @samp{g} packets is specified below.
34970 When reading registers from a trace frame (@pxref{Analyze Collected
34971 Data,,Using the Collected Data}), the stub may also return a string of
34972 literal @samp{x}'s in place of the register data digits, to indicate
34973 that the corresponding register has not been collected, thus its value
34974 is unavailable. For example, for an architecture with 4 registers of
34975 4 bytes each, the following reply indicates to @value{GDBN} that
34976 registers 0 and 2 have not been collected, while registers 1 and 3
34977 have been collected, and both have zero value:
34981 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34988 @item G @var{XX@dots{}}
34989 @cindex @samp{G} packet
34990 Write general registers. @xref{read registers packet}, for a
34991 description of the @var{XX@dots{}} data.
35001 @item H @var{op} @var{thread-id}
35002 @cindex @samp{H} packet
35003 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35004 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35005 should be @samp{c} for step and continue operations (note that this
35006 is deprecated, supporting the @samp{vCont} command is a better
35007 option), and @samp{g} for other operations. The thread designator
35008 @var{thread-id} has the format and interpretation described in
35009 @ref{thread-id syntax}.
35020 @c 'H': How restrictive (or permissive) is the thread model. If a
35021 @c thread is selected and stopped, are other threads allowed
35022 @c to continue to execute? As I mentioned above, I think the
35023 @c semantics of each command when a thread is selected must be
35024 @c described. For example:
35026 @c 'g': If the stub supports threads and a specific thread is
35027 @c selected, returns the register block from that thread;
35028 @c otherwise returns current registers.
35030 @c 'G' If the stub supports threads and a specific thread is
35031 @c selected, sets the registers of the register block of
35032 @c that thread; otherwise sets current registers.
35034 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35035 @anchor{cycle step packet}
35036 @cindex @samp{i} packet
35037 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35038 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35039 step starting at that address.
35042 @cindex @samp{I} packet
35043 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35047 @cindex @samp{k} packet
35050 The exact effect of this packet is not specified.
35052 For a bare-metal target, it may power cycle or reset the target
35053 system. For that reason, the @samp{k} packet has no reply.
35055 For a single-process target, it may kill that process if possible.
35057 A multiple-process target may choose to kill just one process, or all
35058 that are under @value{GDBN}'s control. For more precise control, use
35059 the vKill packet (@pxref{vKill packet}).
35061 If the target system immediately closes the connection in response to
35062 @samp{k}, @value{GDBN} does not consider the lack of packet
35063 acknowledgment to be an error, and assumes the kill was successful.
35065 If connected using @kbd{target extended-remote}, and the target does
35066 not close the connection in response to a kill request, @value{GDBN}
35067 probes the target state as if a new connection was opened
35068 (@pxref{? packet}).
35070 @item m @var{addr},@var{length}
35071 @cindex @samp{m} packet
35072 Read @var{length} addressable memory units starting at address @var{addr}
35073 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35074 any particular boundary.
35076 The stub need not use any particular size or alignment when gathering
35077 data from memory for the response; even if @var{addr} is word-aligned
35078 and @var{length} is a multiple of the word size, the stub is free to
35079 use byte accesses, or not. For this reason, this packet may not be
35080 suitable for accessing memory-mapped I/O devices.
35081 @cindex alignment of remote memory accesses
35082 @cindex size of remote memory accesses
35083 @cindex memory, alignment and size of remote accesses
35087 @item @var{XX@dots{}}
35088 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35089 The reply may contain fewer addressable memory units than requested if the
35090 server was able to read only part of the region of memory.
35095 @item M @var{addr},@var{length}:@var{XX@dots{}}
35096 @cindex @samp{M} packet
35097 Write @var{length} addressable memory units starting at address @var{addr}
35098 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35099 byte is transmitted as a two-digit hexadecimal number.
35106 for an error (this includes the case where only part of the data was
35111 @cindex @samp{p} packet
35112 Read the value of register @var{n}; @var{n} is in hex.
35113 @xref{read registers packet}, for a description of how the returned
35114 register value is encoded.
35118 @item @var{XX@dots{}}
35119 the register's value
35123 Indicating an unrecognized @var{query}.
35126 @item P @var{n@dots{}}=@var{r@dots{}}
35127 @anchor{write register packet}
35128 @cindex @samp{P} packet
35129 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35130 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35131 digits for each byte in the register (target byte order).
35141 @item q @var{name} @var{params}@dots{}
35142 @itemx Q @var{name} @var{params}@dots{}
35143 @cindex @samp{q} packet
35144 @cindex @samp{Q} packet
35145 General query (@samp{q}) and set (@samp{Q}). These packets are
35146 described fully in @ref{General Query Packets}.
35149 @cindex @samp{r} packet
35150 Reset the entire system.
35152 Don't use this packet; use the @samp{R} packet instead.
35155 @cindex @samp{R} packet
35156 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35157 This packet is only available in extended mode (@pxref{extended mode}).
35159 The @samp{R} packet has no reply.
35161 @item s @r{[}@var{addr}@r{]}
35162 @cindex @samp{s} packet
35163 Single step, resuming at @var{addr}. If
35164 @var{addr} is omitted, resume at same address.
35166 This packet is deprecated for multi-threading support. @xref{vCont
35170 @xref{Stop Reply Packets}, for the reply specifications.
35172 @item S @var{sig}@r{[};@var{addr}@r{]}
35173 @anchor{step with signal packet}
35174 @cindex @samp{S} packet
35175 Step with signal. This is analogous to the @samp{C} packet, but
35176 requests a single-step, rather than a normal resumption of execution.
35178 This packet is deprecated for multi-threading support. @xref{vCont
35182 @xref{Stop Reply Packets}, for the reply specifications.
35184 @item t @var{addr}:@var{PP},@var{MM}
35185 @cindex @samp{t} packet
35186 Search backwards starting at address @var{addr} for a match with pattern
35187 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35188 There must be at least 3 digits in @var{addr}.
35190 @item T @var{thread-id}
35191 @cindex @samp{T} packet
35192 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35197 thread is still alive
35203 Packets starting with @samp{v} are identified by a multi-letter name,
35204 up to the first @samp{;} or @samp{?} (or the end of the packet).
35206 @item vAttach;@var{pid}
35207 @cindex @samp{vAttach} packet
35208 Attach to a new process with the specified process ID @var{pid}.
35209 The process ID is a
35210 hexadecimal integer identifying the process. In all-stop mode, all
35211 threads in the attached process are stopped; in non-stop mode, it may be
35212 attached without being stopped if that is supported by the target.
35214 @c In non-stop mode, on a successful vAttach, the stub should set the
35215 @c current thread to a thread of the newly-attached process. After
35216 @c attaching, GDB queries for the attached process's thread ID with qC.
35217 @c Also note that, from a user perspective, whether or not the
35218 @c target is stopped on attach in non-stop mode depends on whether you
35219 @c use the foreground or background version of the attach command, not
35220 @c on what vAttach does; GDB does the right thing with respect to either
35221 @c stopping or restarting threads.
35223 This packet is only available in extended mode (@pxref{extended mode}).
35229 @item @r{Any stop packet}
35230 for success in all-stop mode (@pxref{Stop Reply Packets})
35232 for success in non-stop mode (@pxref{Remote Non-Stop})
35235 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35236 @cindex @samp{vCont} packet
35237 @anchor{vCont packet}
35238 Resume the inferior, specifying different actions for each thread.
35239 If an action is specified with no @var{thread-id}, then it is applied to any
35240 threads that don't have a specific action specified; if no default action is
35241 specified then other threads should remain stopped in all-stop mode and
35242 in their current state in non-stop mode.
35243 Specifying multiple
35244 default actions is an error; specifying no actions is also an error.
35245 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35247 Currently supported actions are:
35253 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35257 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35260 @item r @var{start},@var{end}
35261 Step once, and then keep stepping as long as the thread stops at
35262 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35263 The remote stub reports a stop reply when either the thread goes out
35264 of the range or is stopped due to an unrelated reason, such as hitting
35265 a breakpoint. @xref{range stepping}.
35267 If the range is empty (@var{start} == @var{end}), then the action
35268 becomes equivalent to the @samp{s} action. In other words,
35269 single-step once, and report the stop (even if the stepped instruction
35270 jumps to @var{start}).
35272 (A stop reply may be sent at any point even if the PC is still within
35273 the stepping range; for example, it is valid to implement this packet
35274 in a degenerate way as a single instruction step operation.)
35278 The optional argument @var{addr} normally associated with the
35279 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35280 not supported in @samp{vCont}.
35282 The @samp{t} action is only relevant in non-stop mode
35283 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35284 A stop reply should be generated for any affected thread not already stopped.
35285 When a thread is stopped by means of a @samp{t} action,
35286 the corresponding stop reply should indicate that the thread has stopped with
35287 signal @samp{0}, regardless of whether the target uses some other signal
35288 as an implementation detail.
35290 The stub must support @samp{vCont} if it reports support for
35291 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35292 this case @samp{vCont} actions can be specified to apply to all threads
35293 in a process by using the @samp{p@var{pid}.-1} form of the
35297 @xref{Stop Reply Packets}, for the reply specifications.
35300 @cindex @samp{vCont?} packet
35301 Request a list of actions supported by the @samp{vCont} packet.
35305 @item vCont@r{[};@var{action}@dots{}@r{]}
35306 The @samp{vCont} packet is supported. Each @var{action} is a supported
35307 command in the @samp{vCont} packet.
35309 The @samp{vCont} packet is not supported.
35312 @anchor{vCtrlC packet}
35314 @cindex @samp{vCtrlC} packet
35315 Interrupt remote target as if a control-C was pressed on the remote
35316 terminal. This is the equivalent to reacting to the @code{^C}
35317 (@samp{\003}, the control-C character) character in all-stop mode
35318 while the target is running, except this works in non-stop mode.
35319 @xref{interrupting remote targets}, for more info on the all-stop
35330 @item vFile:@var{operation}:@var{parameter}@dots{}
35331 @cindex @samp{vFile} packet
35332 Perform a file operation on the target system. For details,
35333 see @ref{Host I/O Packets}.
35335 @item vFlashErase:@var{addr},@var{length}
35336 @cindex @samp{vFlashErase} packet
35337 Direct the stub to erase @var{length} bytes of flash starting at
35338 @var{addr}. The region may enclose any number of flash blocks, but
35339 its start and end must fall on block boundaries, as indicated by the
35340 flash block size appearing in the memory map (@pxref{Memory Map
35341 Format}). @value{GDBN} groups flash memory programming operations
35342 together, and sends a @samp{vFlashDone} request after each group; the
35343 stub is allowed to delay erase operation until the @samp{vFlashDone}
35344 packet is received.
35354 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35355 @cindex @samp{vFlashWrite} packet
35356 Direct the stub to write data to flash address @var{addr}. The data
35357 is passed in binary form using the same encoding as for the @samp{X}
35358 packet (@pxref{Binary Data}). The memory ranges specified by
35359 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35360 not overlap, and must appear in order of increasing addresses
35361 (although @samp{vFlashErase} packets for higher addresses may already
35362 have been received; the ordering is guaranteed only between
35363 @samp{vFlashWrite} packets). If a packet writes to an address that was
35364 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35365 target-specific method, the results are unpredictable.
35373 for vFlashWrite addressing non-flash memory
35379 @cindex @samp{vFlashDone} packet
35380 Indicate to the stub that flash programming operation is finished.
35381 The stub is permitted to delay or batch the effects of a group of
35382 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35383 @samp{vFlashDone} packet is received. The contents of the affected
35384 regions of flash memory are unpredictable until the @samp{vFlashDone}
35385 request is completed.
35387 @item vKill;@var{pid}
35388 @cindex @samp{vKill} packet
35389 @anchor{vKill packet}
35390 Kill the process with the specified process ID @var{pid}, which is a
35391 hexadecimal integer identifying the process. This packet is used in
35392 preference to @samp{k} when multiprocess protocol extensions are
35393 supported; see @ref{multiprocess extensions}.
35403 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35404 @cindex @samp{vRun} packet
35405 Run the program @var{filename}, passing it each @var{argument} on its
35406 command line. The file and arguments are hex-encoded strings. If
35407 @var{filename} is an empty string, the stub may use a default program
35408 (e.g.@: the last program run). The program is created in the stopped
35411 @c FIXME: What about non-stop mode?
35413 This packet is only available in extended mode (@pxref{extended mode}).
35419 @item @r{Any stop packet}
35420 for success (@pxref{Stop Reply Packets})
35424 @cindex @samp{vStopped} packet
35425 @xref{Notification Packets}.
35427 @item X @var{addr},@var{length}:@var{XX@dots{}}
35429 @cindex @samp{X} packet
35430 Write data to memory, where the data is transmitted in binary.
35431 Memory is specified by its address @var{addr} and number of addressable memory
35432 units @var{length} (@pxref{addressable memory unit});
35433 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35443 @item z @var{type},@var{addr},@var{kind}
35444 @itemx Z @var{type},@var{addr},@var{kind}
35445 @anchor{insert breakpoint or watchpoint packet}
35446 @cindex @samp{z} packet
35447 @cindex @samp{Z} packets
35448 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35449 watchpoint starting at address @var{address} of kind @var{kind}.
35451 Each breakpoint and watchpoint packet @var{type} is documented
35454 @emph{Implementation notes: A remote target shall return an empty string
35455 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35456 remote target shall support either both or neither of a given
35457 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35458 avoid potential problems with duplicate packets, the operations should
35459 be implemented in an idempotent way.}
35461 @item z0,@var{addr},@var{kind}
35462 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35463 @cindex @samp{z0} packet
35464 @cindex @samp{Z0} packet
35465 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35466 @var{addr} of type @var{kind}.
35468 A memory breakpoint is implemented by replacing the instruction at
35469 @var{addr} with a software breakpoint or trap instruction. The
35470 @var{kind} is target-specific and typically indicates the size of
35471 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35472 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35473 architectures have additional meanings for @var{kind};
35474 @var{cond_list} is an optional list of conditional expressions in bytecode
35475 form that should be evaluated on the target's side. These are the
35476 conditions that should be taken into consideration when deciding if
35477 the breakpoint trigger should be reported back to @var{GDBN}.
35479 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35480 for how to best report a memory breakpoint event to @value{GDBN}.
35482 The @var{cond_list} parameter is comprised of a series of expressions,
35483 concatenated without separators. Each expression has the following form:
35487 @item X @var{len},@var{expr}
35488 @var{len} is the length of the bytecode expression and @var{expr} is the
35489 actual conditional expression in bytecode form.
35493 The optional @var{cmd_list} parameter introduces commands that may be
35494 run on the target, rather than being reported back to @value{GDBN}.
35495 The parameter starts with a numeric flag @var{persist}; if the flag is
35496 nonzero, then the breakpoint may remain active and the commands
35497 continue to be run even when @value{GDBN} disconnects from the target.
35498 Following this flag is a series of expressions concatenated with no
35499 separators. Each expression has the following form:
35503 @item X @var{len},@var{expr}
35504 @var{len} is the length of the bytecode expression and @var{expr} is the
35505 actual conditional expression in bytecode form.
35509 see @ref{Architecture-Specific Protocol Details}.
35511 @emph{Implementation note: It is possible for a target to copy or move
35512 code that contains memory breakpoints (e.g., when implementing
35513 overlays). The behavior of this packet, in the presence of such a
35514 target, is not defined.}
35526 @item z1,@var{addr},@var{kind}
35527 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35528 @cindex @samp{z1} packet
35529 @cindex @samp{Z1} packet
35530 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35531 address @var{addr}.
35533 A hardware breakpoint is implemented using a mechanism that is not
35534 dependant on being able to modify the target's memory. The @var{kind}
35535 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35537 @emph{Implementation note: A hardware breakpoint is not affected by code
35550 @item z2,@var{addr},@var{kind}
35551 @itemx Z2,@var{addr},@var{kind}
35552 @cindex @samp{z2} packet
35553 @cindex @samp{Z2} packet
35554 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35555 The number of bytes to watch is specified by @var{kind}.
35567 @item z3,@var{addr},@var{kind}
35568 @itemx Z3,@var{addr},@var{kind}
35569 @cindex @samp{z3} packet
35570 @cindex @samp{Z3} packet
35571 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35572 The number of bytes to watch is specified by @var{kind}.
35584 @item z4,@var{addr},@var{kind}
35585 @itemx Z4,@var{addr},@var{kind}
35586 @cindex @samp{z4} packet
35587 @cindex @samp{Z4} packet
35588 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35589 The number of bytes to watch is specified by @var{kind}.
35603 @node Stop Reply Packets
35604 @section Stop Reply Packets
35605 @cindex stop reply packets
35607 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35608 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35609 receive any of the below as a reply. Except for @samp{?}
35610 and @samp{vStopped}, that reply is only returned
35611 when the target halts. In the below the exact meaning of @dfn{signal
35612 number} is defined by the header @file{include/gdb/signals.h} in the
35613 @value{GDBN} source code.
35615 As in the description of request packets, we include spaces in the
35616 reply templates for clarity; these are not part of the reply packet's
35617 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35623 The program received signal number @var{AA} (a two-digit hexadecimal
35624 number). This is equivalent to a @samp{T} response with no
35625 @var{n}:@var{r} pairs.
35627 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35628 @cindex @samp{T} packet reply
35629 The program received signal number @var{AA} (a two-digit hexadecimal
35630 number). This is equivalent to an @samp{S} response, except that the
35631 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35632 and other information directly in the stop reply packet, reducing
35633 round-trip latency. Single-step and breakpoint traps are reported
35634 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35638 If @var{n} is a hexadecimal number, it is a register number, and the
35639 corresponding @var{r} gives that register's value. The data @var{r} is a
35640 series of bytes in target byte order, with each byte given by a
35641 two-digit hex number.
35644 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35645 the stopped thread, as specified in @ref{thread-id syntax}.
35648 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35649 the core on which the stop event was detected.
35652 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35653 specific event that stopped the target. The currently defined stop
35654 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35655 signal. At most one stop reason should be present.
35658 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35659 and go on to the next; this allows us to extend the protocol in the
35663 The currently defined stop reasons are:
35669 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35672 @item syscall_entry
35673 @itemx syscall_return
35674 The packet indicates a syscall entry or return, and @var{r} is the
35675 syscall number, in hex.
35677 @cindex shared library events, remote reply
35679 The packet indicates that the loaded libraries have changed.
35680 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35681 list of loaded libraries. The @var{r} part is ignored.
35683 @cindex replay log events, remote reply
35685 The packet indicates that the target cannot continue replaying
35686 logged execution events, because it has reached the end (or the
35687 beginning when executing backward) of the log. The value of @var{r}
35688 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35689 for more information.
35692 @anchor{swbreak stop reason}
35693 The packet indicates a memory breakpoint instruction was executed,
35694 irrespective of whether it was @value{GDBN} that planted the
35695 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35696 part must be left empty.
35698 On some architectures, such as x86, at the architecture level, when a
35699 breakpoint instruction executes the program counter points at the
35700 breakpoint address plus an offset. On such targets, the stub is
35701 responsible for adjusting the PC to point back at the breakpoint
35704 This packet should not be sent by default; older @value{GDBN} versions
35705 did not support it. @value{GDBN} requests it, by supplying an
35706 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35707 remote stub must also supply the appropriate @samp{qSupported} feature
35708 indicating support.
35710 This packet is required for correct non-stop mode operation.
35713 The packet indicates the target stopped for a hardware breakpoint.
35714 The @var{r} part must be left empty.
35716 The same remarks about @samp{qSupported} and non-stop mode above
35719 @cindex fork events, remote reply
35721 The packet indicates that @code{fork} was called, and @var{r}
35722 is the thread ID of the new child process. Refer to
35723 @ref{thread-id syntax} for the format of the @var{thread-id}
35724 field. This packet is only applicable to targets that support
35727 This packet should not be sent by default; older @value{GDBN} versions
35728 did not support it. @value{GDBN} requests it, by supplying an
35729 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35730 remote stub must also supply the appropriate @samp{qSupported} feature
35731 indicating support.
35733 @cindex vfork events, remote reply
35735 The packet indicates that @code{vfork} was called, and @var{r}
35736 is the thread ID of the new child process. Refer to
35737 @ref{thread-id syntax} for the format of the @var{thread-id}
35738 field. This packet is only applicable to targets that support
35741 This packet should not be sent by default; older @value{GDBN} versions
35742 did not support it. @value{GDBN} requests it, by supplying an
35743 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35744 remote stub must also supply the appropriate @samp{qSupported} feature
35745 indicating support.
35747 @cindex vforkdone events, remote reply
35749 The packet indicates that a child process created by a vfork
35750 has either called @code{exec} or terminated, so that the
35751 address spaces of the parent and child process are no longer
35752 shared. The @var{r} part is ignored. This packet is only
35753 applicable to targets that support vforkdone events.
35755 This packet should not be sent by default; older @value{GDBN} versions
35756 did not support it. @value{GDBN} requests it, by supplying an
35757 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35758 remote stub must also supply the appropriate @samp{qSupported} feature
35759 indicating support.
35761 @cindex exec events, remote reply
35763 The packet indicates that @code{execve} was called, and @var{r}
35764 is the absolute pathname of the file that was executed, in hex.
35765 This packet is only applicable to targets that support exec events.
35767 This packet should not be sent by default; older @value{GDBN} versions
35768 did not support it. @value{GDBN} requests it, by supplying an
35769 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35770 remote stub must also supply the appropriate @samp{qSupported} feature
35771 indicating support.
35773 @cindex thread create event, remote reply
35774 @anchor{thread create event}
35776 The packet indicates that the thread was just created. The new thread
35777 is stopped until @value{GDBN} sets it running with a resumption packet
35778 (@pxref{vCont packet}). This packet should not be sent by default;
35779 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35780 also the @samp{w} (@ref{thread exit event}) remote reply below.
35785 @itemx W @var{AA} ; process:@var{pid}
35786 The process exited, and @var{AA} is the exit status. This is only
35787 applicable to certain targets.
35789 The second form of the response, including the process ID of the exited
35790 process, can be used only when @value{GDBN} has reported support for
35791 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35792 The @var{pid} is formatted as a big-endian hex string.
35795 @itemx X @var{AA} ; process:@var{pid}
35796 The process terminated with signal @var{AA}.
35798 The second form of the response, including the process ID of the
35799 terminated process, can be used only when @value{GDBN} has reported
35800 support for multiprocess protocol extensions; see @ref{multiprocess
35801 extensions}. The @var{pid} is formatted as a big-endian hex string.
35803 @anchor{thread exit event}
35804 @cindex thread exit event, remote reply
35805 @item w @var{AA} ; @var{tid}
35807 The thread exited, and @var{AA} is the exit status. This response
35808 should not be sent by default; @value{GDBN} requests it with the
35809 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35812 There are no resumed threads left in the target. In other words, even
35813 though the process is alive, the last resumed thread has exited. For
35814 example, say the target process has two threads: thread 1 and thread
35815 2. The client leaves thread 1 stopped, and resumes thread 2, which
35816 subsequently exits. At this point, even though the process is still
35817 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35818 executing either. The @samp{N} stop reply thus informs the client
35819 that it can stop waiting for stop replies. This packet should not be
35820 sent by default; older @value{GDBN} versions did not support it.
35821 @value{GDBN} requests it, by supplying an appropriate
35822 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35823 also supply the appropriate @samp{qSupported} feature indicating
35826 @item O @var{XX}@dots{}
35827 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35828 written as the program's console output. This can happen at any time
35829 while the program is running and the debugger should continue to wait
35830 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35832 @item F @var{call-id},@var{parameter}@dots{}
35833 @var{call-id} is the identifier which says which host system call should
35834 be called. This is just the name of the function. Translation into the
35835 correct system call is only applicable as it's defined in @value{GDBN}.
35836 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35839 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35840 this very system call.
35842 The target replies with this packet when it expects @value{GDBN} to
35843 call a host system call on behalf of the target. @value{GDBN} replies
35844 with an appropriate @samp{F} packet and keeps up waiting for the next
35845 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35846 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35847 Protocol Extension}, for more details.
35851 @node General Query Packets
35852 @section General Query Packets
35853 @cindex remote query requests
35855 Packets starting with @samp{q} are @dfn{general query packets};
35856 packets starting with @samp{Q} are @dfn{general set packets}. General
35857 query and set packets are a semi-unified form for retrieving and
35858 sending information to and from the stub.
35860 The initial letter of a query or set packet is followed by a name
35861 indicating what sort of thing the packet applies to. For example,
35862 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35863 definitions with the stub. These packet names follow some
35868 The name must not contain commas, colons or semicolons.
35870 Most @value{GDBN} query and set packets have a leading upper case
35873 The names of custom vendor packets should use a company prefix, in
35874 lower case, followed by a period. For example, packets designed at
35875 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35876 foos) or @samp{Qacme.bar} (for setting bars).
35879 The name of a query or set packet should be separated from any
35880 parameters by a @samp{:}; the parameters themselves should be
35881 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35882 full packet name, and check for a separator or the end of the packet,
35883 in case two packet names share a common prefix. New packets should not begin
35884 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35885 packets predate these conventions, and have arguments without any terminator
35886 for the packet name; we suspect they are in widespread use in places that
35887 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35888 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35891 Like the descriptions of the other packets, each description here
35892 has a template showing the packet's overall syntax, followed by an
35893 explanation of the packet's meaning. We include spaces in some of the
35894 templates for clarity; these are not part of the packet's syntax. No
35895 @value{GDBN} packet uses spaces to separate its components.
35897 Here are the currently defined query and set packets:
35903 Turn on or off the agent as a helper to perform some debugging operations
35904 delegated from @value{GDBN} (@pxref{Control Agent}).
35906 @item QAllow:@var{op}:@var{val}@dots{}
35907 @cindex @samp{QAllow} packet
35908 Specify which operations @value{GDBN} expects to request of the
35909 target, as a semicolon-separated list of operation name and value
35910 pairs. Possible values for @var{op} include @samp{WriteReg},
35911 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35912 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35913 indicating that @value{GDBN} will not request the operation, or 1,
35914 indicating that it may. (The target can then use this to set up its
35915 own internals optimally, for instance if the debugger never expects to
35916 insert breakpoints, it may not need to install its own trap handler.)
35919 @cindex current thread, remote request
35920 @cindex @samp{qC} packet
35921 Return the current thread ID.
35925 @item QC @var{thread-id}
35926 Where @var{thread-id} is a thread ID as documented in
35927 @ref{thread-id syntax}.
35928 @item @r{(anything else)}
35929 Any other reply implies the old thread ID.
35932 @item qCRC:@var{addr},@var{length}
35933 @cindex CRC of memory block, remote request
35934 @cindex @samp{qCRC} packet
35935 @anchor{qCRC packet}
35936 Compute the CRC checksum of a block of memory using CRC-32 defined in
35937 IEEE 802.3. The CRC is computed byte at a time, taking the most
35938 significant bit of each byte first. The initial pattern code
35939 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35941 @emph{Note:} This is the same CRC used in validating separate debug
35942 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35943 Files}). However the algorithm is slightly different. When validating
35944 separate debug files, the CRC is computed taking the @emph{least}
35945 significant bit of each byte first, and the final result is inverted to
35946 detect trailing zeros.
35951 An error (such as memory fault)
35952 @item C @var{crc32}
35953 The specified memory region's checksum is @var{crc32}.
35956 @item QDisableRandomization:@var{value}
35957 @cindex disable address space randomization, remote request
35958 @cindex @samp{QDisableRandomization} packet
35959 Some target operating systems will randomize the virtual address space
35960 of the inferior process as a security feature, but provide a feature
35961 to disable such randomization, e.g.@: to allow for a more deterministic
35962 debugging experience. On such systems, this packet with a @var{value}
35963 of 1 directs the target to disable address space randomization for
35964 processes subsequently started via @samp{vRun} packets, while a packet
35965 with a @var{value} of 0 tells the target to enable address space
35968 This packet is only available in extended mode (@pxref{extended mode}).
35973 The request succeeded.
35976 An error occurred. The error number @var{nn} is given as hex digits.
35979 An empty reply indicates that @samp{QDisableRandomization} is not supported
35983 This packet is not probed by default; the remote stub must request it,
35984 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35985 This should only be done on targets that actually support disabling
35986 address space randomization.
35989 @itemx qsThreadInfo
35990 @cindex list active threads, remote request
35991 @cindex @samp{qfThreadInfo} packet
35992 @cindex @samp{qsThreadInfo} packet
35993 Obtain a list of all active thread IDs from the target (OS). Since there
35994 may be too many active threads to fit into one reply packet, this query
35995 works iteratively: it may require more than one query/reply sequence to
35996 obtain the entire list of threads. The first query of the sequence will
35997 be the @samp{qfThreadInfo} query; subsequent queries in the
35998 sequence will be the @samp{qsThreadInfo} query.
36000 NOTE: This packet replaces the @samp{qL} query (see below).
36004 @item m @var{thread-id}
36006 @item m @var{thread-id},@var{thread-id}@dots{}
36007 a comma-separated list of thread IDs
36009 (lower case letter @samp{L}) denotes end of list.
36012 In response to each query, the target will reply with a list of one or
36013 more thread IDs, separated by commas.
36014 @value{GDBN} will respond to each reply with a request for more thread
36015 ids (using the @samp{qs} form of the query), until the target responds
36016 with @samp{l} (lower-case ell, for @dfn{last}).
36017 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36020 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36021 initial connection with the remote target, and the very first thread ID
36022 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36023 message. Therefore, the stub should ensure that the first thread ID in
36024 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36026 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36027 @cindex get thread-local storage address, remote request
36028 @cindex @samp{qGetTLSAddr} packet
36029 Fetch the address associated with thread local storage specified
36030 by @var{thread-id}, @var{offset}, and @var{lm}.
36032 @var{thread-id} is the thread ID associated with the
36033 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36035 @var{offset} is the (big endian, hex encoded) offset associated with the
36036 thread local variable. (This offset is obtained from the debug
36037 information associated with the variable.)
36039 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36040 load module associated with the thread local storage. For example,
36041 a @sc{gnu}/Linux system will pass the link map address of the shared
36042 object associated with the thread local storage under consideration.
36043 Other operating environments may choose to represent the load module
36044 differently, so the precise meaning of this parameter will vary.
36048 @item @var{XX}@dots{}
36049 Hex encoded (big endian) bytes representing the address of the thread
36050 local storage requested.
36053 An error occurred. The error number @var{nn} is given as hex digits.
36056 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36059 @item qGetTIBAddr:@var{thread-id}
36060 @cindex get thread information block address
36061 @cindex @samp{qGetTIBAddr} packet
36062 Fetch address of the Windows OS specific Thread Information Block.
36064 @var{thread-id} is the thread ID associated with the thread.
36068 @item @var{XX}@dots{}
36069 Hex encoded (big endian) bytes representing the linear address of the
36070 thread information block.
36073 An error occured. This means that either the thread was not found, or the
36074 address could not be retrieved.
36077 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36080 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36081 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36082 digit) is one to indicate the first query and zero to indicate a
36083 subsequent query; @var{threadcount} (two hex digits) is the maximum
36084 number of threads the response packet can contain; and @var{nextthread}
36085 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36086 returned in the response as @var{argthread}.
36088 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36092 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36093 Where: @var{count} (two hex digits) is the number of threads being
36094 returned; @var{done} (one hex digit) is zero to indicate more threads
36095 and one indicates no further threads; @var{argthreadid} (eight hex
36096 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36097 is a sequence of thread IDs, @var{threadid} (eight hex
36098 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36102 @cindex section offsets, remote request
36103 @cindex @samp{qOffsets} packet
36104 Get section offsets that the target used when relocating the downloaded
36109 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36110 Relocate the @code{Text} section by @var{xxx} from its original address.
36111 Relocate the @code{Data} section by @var{yyy} from its original address.
36112 If the object file format provides segment information (e.g.@: @sc{elf}
36113 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36114 segments by the supplied offsets.
36116 @emph{Note: while a @code{Bss} offset may be included in the response,
36117 @value{GDBN} ignores this and instead applies the @code{Data} offset
36118 to the @code{Bss} section.}
36120 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36121 Relocate the first segment of the object file, which conventionally
36122 contains program code, to a starting address of @var{xxx}. If
36123 @samp{DataSeg} is specified, relocate the second segment, which
36124 conventionally contains modifiable data, to a starting address of
36125 @var{yyy}. @value{GDBN} will report an error if the object file
36126 does not contain segment information, or does not contain at least
36127 as many segments as mentioned in the reply. Extra segments are
36128 kept at fixed offsets relative to the last relocated segment.
36131 @item qP @var{mode} @var{thread-id}
36132 @cindex thread information, remote request
36133 @cindex @samp{qP} packet
36134 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36135 encoded 32 bit mode; @var{thread-id} is a thread ID
36136 (@pxref{thread-id syntax}).
36138 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36141 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36145 @cindex non-stop mode, remote request
36146 @cindex @samp{QNonStop} packet
36148 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36149 @xref{Remote Non-Stop}, for more information.
36154 The request succeeded.
36157 An error occurred. The error number @var{nn} is given as hex digits.
36160 An empty reply indicates that @samp{QNonStop} is not supported by
36164 This packet is not probed by default; the remote stub must request it,
36165 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36166 Use of this packet is controlled by the @code{set non-stop} command;
36167 @pxref{Non-Stop Mode}.
36169 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36170 @itemx QCatchSyscalls:0
36171 @cindex catch syscalls from inferior, remote request
36172 @cindex @samp{QCatchSyscalls} packet
36173 @anchor{QCatchSyscalls}
36174 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36175 catching syscalls from the inferior process.
36177 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36178 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36179 is listed, every system call should be reported.
36181 Note that if a syscall not in the list is reported, @value{GDBN} will
36182 still filter the event according to its own list from all corresponding
36183 @code{catch syscall} commands. However, it is more efficient to only
36184 report the requested syscalls.
36186 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36187 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36189 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36190 kept for the new process too. On targets where exec may affect syscall
36191 numbers, for example with exec between 32 and 64-bit processes, the
36192 client should send a new packet with the new syscall list.
36197 The request succeeded.
36200 An error occurred. @var{nn} are hex digits.
36203 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36207 Use of this packet is controlled by the @code{set remote catch-syscalls}
36208 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36209 This packet is not probed by default; the remote stub must request it,
36210 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36212 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36213 @cindex pass signals to inferior, remote request
36214 @cindex @samp{QPassSignals} packet
36215 @anchor{QPassSignals}
36216 Each listed @var{signal} should be passed directly to the inferior process.
36217 Signals are numbered identically to continue packets and stop replies
36218 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36219 strictly greater than the previous item. These signals do not need to stop
36220 the inferior, or be reported to @value{GDBN}. All other signals should be
36221 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36222 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36223 new list. This packet improves performance when using @samp{handle
36224 @var{signal} nostop noprint pass}.
36229 The request succeeded.
36232 An error occurred. The error number @var{nn} is given as hex digits.
36235 An empty reply indicates that @samp{QPassSignals} is not supported by
36239 Use of this packet is controlled by the @code{set remote pass-signals}
36240 command (@pxref{Remote Configuration, set remote pass-signals}).
36241 This packet is not probed by default; the remote stub must request it,
36242 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36244 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36245 @cindex signals the inferior may see, remote request
36246 @cindex @samp{QProgramSignals} packet
36247 @anchor{QProgramSignals}
36248 Each listed @var{signal} may be delivered to the inferior process.
36249 Others should be silently discarded.
36251 In some cases, the remote stub may need to decide whether to deliver a
36252 signal to the program or not without @value{GDBN} involvement. One
36253 example of that is while detaching --- the program's threads may have
36254 stopped for signals that haven't yet had a chance of being reported to
36255 @value{GDBN}, and so the remote stub can use the signal list specified
36256 by this packet to know whether to deliver or ignore those pending
36259 This does not influence whether to deliver a signal as requested by a
36260 resumption packet (@pxref{vCont packet}).
36262 Signals are numbered identically to continue packets and stop replies
36263 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36264 strictly greater than the previous item. Multiple
36265 @samp{QProgramSignals} packets do not combine; any earlier
36266 @samp{QProgramSignals} list is completely replaced by the new list.
36271 The request succeeded.
36274 An error occurred. The error number @var{nn} is given as hex digits.
36277 An empty reply indicates that @samp{QProgramSignals} is not supported
36281 Use of this packet is controlled by the @code{set remote program-signals}
36282 command (@pxref{Remote Configuration, set remote program-signals}).
36283 This packet is not probed by default; the remote stub must request it,
36284 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36286 @anchor{QThreadEvents}
36287 @item QThreadEvents:1
36288 @itemx QThreadEvents:0
36289 @cindex thread create/exit events, remote request
36290 @cindex @samp{QThreadEvents} packet
36292 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36293 reporting of thread create and exit events. @xref{thread create
36294 event}, for the reply specifications. For example, this is used in
36295 non-stop mode when @value{GDBN} stops a set of threads and
36296 synchronously waits for the their corresponding stop replies. Without
36297 exit events, if one of the threads exits, @value{GDBN} would hang
36298 forever not knowing that it should no longer expect a stop for that
36299 same thread. @value{GDBN} does not enable this feature unless the
36300 stub reports that it supports it by including @samp{QThreadEvents+} in
36301 its @samp{qSupported} reply.
36306 The request succeeded.
36309 An error occurred. The error number @var{nn} is given as hex digits.
36312 An empty reply indicates that @samp{QThreadEvents} is not supported by
36316 Use of this packet is controlled by the @code{set remote thread-events}
36317 command (@pxref{Remote Configuration, set remote thread-events}).
36319 @item qRcmd,@var{command}
36320 @cindex execute remote command, remote request
36321 @cindex @samp{qRcmd} packet
36322 @var{command} (hex encoded) is passed to the local interpreter for
36323 execution. Invalid commands should be reported using the output
36324 string. Before the final result packet, the target may also respond
36325 with a number of intermediate @samp{O@var{output}} console output
36326 packets. @emph{Implementors should note that providing access to a
36327 stubs's interpreter may have security implications}.
36332 A command response with no output.
36334 A command response with the hex encoded output string @var{OUTPUT}.
36336 Indicate a badly formed request.
36338 An empty reply indicates that @samp{qRcmd} is not recognized.
36341 (Note that the @code{qRcmd} packet's name is separated from the
36342 command by a @samp{,}, not a @samp{:}, contrary to the naming
36343 conventions above. Please don't use this packet as a model for new
36346 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36347 @cindex searching memory, in remote debugging
36349 @cindex @samp{qSearch:memory} packet
36351 @cindex @samp{qSearch memory} packet
36352 @anchor{qSearch memory}
36353 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36354 Both @var{address} and @var{length} are encoded in hex;
36355 @var{search-pattern} is a sequence of bytes, also hex encoded.
36360 The pattern was not found.
36362 The pattern was found at @var{address}.
36364 A badly formed request or an error was encountered while searching memory.
36366 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36369 @item QStartNoAckMode
36370 @cindex @samp{QStartNoAckMode} packet
36371 @anchor{QStartNoAckMode}
36372 Request that the remote stub disable the normal @samp{+}/@samp{-}
36373 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36378 The stub has switched to no-acknowledgment mode.
36379 @value{GDBN} acknowledges this reponse,
36380 but neither the stub nor @value{GDBN} shall send or expect further
36381 @samp{+}/@samp{-} acknowledgments in the current connection.
36383 An empty reply indicates that the stub does not support no-acknowledgment mode.
36386 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36387 @cindex supported packets, remote query
36388 @cindex features of the remote protocol
36389 @cindex @samp{qSupported} packet
36390 @anchor{qSupported}
36391 Tell the remote stub about features supported by @value{GDBN}, and
36392 query the stub for features it supports. This packet allows
36393 @value{GDBN} and the remote stub to take advantage of each others'
36394 features. @samp{qSupported} also consolidates multiple feature probes
36395 at startup, to improve @value{GDBN} performance---a single larger
36396 packet performs better than multiple smaller probe packets on
36397 high-latency links. Some features may enable behavior which must not
36398 be on by default, e.g.@: because it would confuse older clients or
36399 stubs. Other features may describe packets which could be
36400 automatically probed for, but are not. These features must be
36401 reported before @value{GDBN} will use them. This ``default
36402 unsupported'' behavior is not appropriate for all packets, but it
36403 helps to keep the initial connection time under control with new
36404 versions of @value{GDBN} which support increasing numbers of packets.
36408 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36409 The stub supports or does not support each returned @var{stubfeature},
36410 depending on the form of each @var{stubfeature} (see below for the
36413 An empty reply indicates that @samp{qSupported} is not recognized,
36414 or that no features needed to be reported to @value{GDBN}.
36417 The allowed forms for each feature (either a @var{gdbfeature} in the
36418 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36422 @item @var{name}=@var{value}
36423 The remote protocol feature @var{name} is supported, and associated
36424 with the specified @var{value}. The format of @var{value} depends
36425 on the feature, but it must not include a semicolon.
36427 The remote protocol feature @var{name} is supported, and does not
36428 need an associated value.
36430 The remote protocol feature @var{name} is not supported.
36432 The remote protocol feature @var{name} may be supported, and
36433 @value{GDBN} should auto-detect support in some other way when it is
36434 needed. This form will not be used for @var{gdbfeature} notifications,
36435 but may be used for @var{stubfeature} responses.
36438 Whenever the stub receives a @samp{qSupported} request, the
36439 supplied set of @value{GDBN} features should override any previous
36440 request. This allows @value{GDBN} to put the stub in a known
36441 state, even if the stub had previously been communicating with
36442 a different version of @value{GDBN}.
36444 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36449 This feature indicates whether @value{GDBN} supports multiprocess
36450 extensions to the remote protocol. @value{GDBN} does not use such
36451 extensions unless the stub also reports that it supports them by
36452 including @samp{multiprocess+} in its @samp{qSupported} reply.
36453 @xref{multiprocess extensions}, for details.
36456 This feature indicates that @value{GDBN} supports the XML target
36457 description. If the stub sees @samp{xmlRegisters=} with target
36458 specific strings separated by a comma, it will report register
36462 This feature indicates whether @value{GDBN} supports the
36463 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36464 instruction reply packet}).
36467 This feature indicates whether @value{GDBN} supports the swbreak stop
36468 reason in stop replies. @xref{swbreak stop reason}, for details.
36471 This feature indicates whether @value{GDBN} supports the hwbreak stop
36472 reason in stop replies. @xref{swbreak stop reason}, for details.
36475 This feature indicates whether @value{GDBN} supports fork event
36476 extensions to the remote protocol. @value{GDBN} does not use such
36477 extensions unless the stub also reports that it supports them by
36478 including @samp{fork-events+} in its @samp{qSupported} reply.
36481 This feature indicates whether @value{GDBN} supports vfork event
36482 extensions to the remote protocol. @value{GDBN} does not use such
36483 extensions unless the stub also reports that it supports them by
36484 including @samp{vfork-events+} in its @samp{qSupported} reply.
36487 This feature indicates whether @value{GDBN} supports exec event
36488 extensions to the remote protocol. @value{GDBN} does not use such
36489 extensions unless the stub also reports that it supports them by
36490 including @samp{exec-events+} in its @samp{qSupported} reply.
36492 @item vContSupported
36493 This feature indicates whether @value{GDBN} wants to know the
36494 supported actions in the reply to @samp{vCont?} packet.
36497 Stubs should ignore any unknown values for
36498 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36499 packet supports receiving packets of unlimited length (earlier
36500 versions of @value{GDBN} may reject overly long responses). Additional values
36501 for @var{gdbfeature} may be defined in the future to let the stub take
36502 advantage of new features in @value{GDBN}, e.g.@: incompatible
36503 improvements in the remote protocol---the @samp{multiprocess} feature is
36504 an example of such a feature. The stub's reply should be independent
36505 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36506 describes all the features it supports, and then the stub replies with
36507 all the features it supports.
36509 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36510 responses, as long as each response uses one of the standard forms.
36512 Some features are flags. A stub which supports a flag feature
36513 should respond with a @samp{+} form response. Other features
36514 require values, and the stub should respond with an @samp{=}
36517 Each feature has a default value, which @value{GDBN} will use if
36518 @samp{qSupported} is not available or if the feature is not mentioned
36519 in the @samp{qSupported} response. The default values are fixed; a
36520 stub is free to omit any feature responses that match the defaults.
36522 Not all features can be probed, but for those which can, the probing
36523 mechanism is useful: in some cases, a stub's internal
36524 architecture may not allow the protocol layer to know some information
36525 about the underlying target in advance. This is especially common in
36526 stubs which may be configured for multiple targets.
36528 These are the currently defined stub features and their properties:
36530 @multitable @columnfractions 0.35 0.2 0.12 0.2
36531 @c NOTE: The first row should be @headitem, but we do not yet require
36532 @c a new enough version of Texinfo (4.7) to use @headitem.
36534 @tab Value Required
36538 @item @samp{PacketSize}
36543 @item @samp{qXfer:auxv:read}
36548 @item @samp{qXfer:btrace:read}
36553 @item @samp{qXfer:btrace-conf:read}
36558 @item @samp{qXfer:exec-file:read}
36563 @item @samp{qXfer:features:read}
36568 @item @samp{qXfer:libraries:read}
36573 @item @samp{qXfer:libraries-svr4:read}
36578 @item @samp{augmented-libraries-svr4-read}
36583 @item @samp{qXfer:memory-map:read}
36588 @item @samp{qXfer:sdata:read}
36593 @item @samp{qXfer:spu:read}
36598 @item @samp{qXfer:spu:write}
36603 @item @samp{qXfer:siginfo:read}
36608 @item @samp{qXfer:siginfo:write}
36613 @item @samp{qXfer:threads:read}
36618 @item @samp{qXfer:traceframe-info:read}
36623 @item @samp{qXfer:uib:read}
36628 @item @samp{qXfer:fdpic:read}
36633 @item @samp{Qbtrace:off}
36638 @item @samp{Qbtrace:bts}
36643 @item @samp{Qbtrace:pt}
36648 @item @samp{Qbtrace-conf:bts:size}
36653 @item @samp{Qbtrace-conf:pt:size}
36658 @item @samp{QNonStop}
36663 @item @samp{QCatchSyscalls}
36668 @item @samp{QPassSignals}
36673 @item @samp{QStartNoAckMode}
36678 @item @samp{multiprocess}
36683 @item @samp{ConditionalBreakpoints}
36688 @item @samp{ConditionalTracepoints}
36693 @item @samp{ReverseContinue}
36698 @item @samp{ReverseStep}
36703 @item @samp{TracepointSource}
36708 @item @samp{QAgent}
36713 @item @samp{QAllow}
36718 @item @samp{QDisableRandomization}
36723 @item @samp{EnableDisableTracepoints}
36728 @item @samp{QTBuffer:size}
36733 @item @samp{tracenz}
36738 @item @samp{BreakpointCommands}
36743 @item @samp{swbreak}
36748 @item @samp{hwbreak}
36753 @item @samp{fork-events}
36758 @item @samp{vfork-events}
36763 @item @samp{exec-events}
36768 @item @samp{QThreadEvents}
36773 @item @samp{no-resumed}
36780 These are the currently defined stub features, in more detail:
36783 @cindex packet size, remote protocol
36784 @item PacketSize=@var{bytes}
36785 The remote stub can accept packets up to at least @var{bytes} in
36786 length. @value{GDBN} will send packets up to this size for bulk
36787 transfers, and will never send larger packets. This is a limit on the
36788 data characters in the packet, including the frame and checksum.
36789 There is no trailing NUL byte in a remote protocol packet; if the stub
36790 stores packets in a NUL-terminated format, it should allow an extra
36791 byte in its buffer for the NUL. If this stub feature is not supported,
36792 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36794 @item qXfer:auxv:read
36795 The remote stub understands the @samp{qXfer:auxv:read} packet
36796 (@pxref{qXfer auxiliary vector read}).
36798 @item qXfer:btrace:read
36799 The remote stub understands the @samp{qXfer:btrace:read}
36800 packet (@pxref{qXfer btrace read}).
36802 @item qXfer:btrace-conf:read
36803 The remote stub understands the @samp{qXfer:btrace-conf:read}
36804 packet (@pxref{qXfer btrace-conf read}).
36806 @item qXfer:exec-file:read
36807 The remote stub understands the @samp{qXfer:exec-file:read} packet
36808 (@pxref{qXfer executable filename read}).
36810 @item qXfer:features:read
36811 The remote stub understands the @samp{qXfer:features:read} packet
36812 (@pxref{qXfer target description read}).
36814 @item qXfer:libraries:read
36815 The remote stub understands the @samp{qXfer:libraries:read} packet
36816 (@pxref{qXfer library list read}).
36818 @item qXfer:libraries-svr4:read
36819 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36820 (@pxref{qXfer svr4 library list read}).
36822 @item augmented-libraries-svr4-read
36823 The remote stub understands the augmented form of the
36824 @samp{qXfer:libraries-svr4:read} packet
36825 (@pxref{qXfer svr4 library list read}).
36827 @item qXfer:memory-map:read
36828 The remote stub understands the @samp{qXfer:memory-map:read} packet
36829 (@pxref{qXfer memory map read}).
36831 @item qXfer:sdata:read
36832 The remote stub understands the @samp{qXfer:sdata:read} packet
36833 (@pxref{qXfer sdata read}).
36835 @item qXfer:spu:read
36836 The remote stub understands the @samp{qXfer:spu:read} packet
36837 (@pxref{qXfer spu read}).
36839 @item qXfer:spu:write
36840 The remote stub understands the @samp{qXfer:spu:write} packet
36841 (@pxref{qXfer spu write}).
36843 @item qXfer:siginfo:read
36844 The remote stub understands the @samp{qXfer:siginfo:read} packet
36845 (@pxref{qXfer siginfo read}).
36847 @item qXfer:siginfo:write
36848 The remote stub understands the @samp{qXfer:siginfo:write} packet
36849 (@pxref{qXfer siginfo write}).
36851 @item qXfer:threads:read
36852 The remote stub understands the @samp{qXfer:threads:read} packet
36853 (@pxref{qXfer threads read}).
36855 @item qXfer:traceframe-info:read
36856 The remote stub understands the @samp{qXfer:traceframe-info:read}
36857 packet (@pxref{qXfer traceframe info read}).
36859 @item qXfer:uib:read
36860 The remote stub understands the @samp{qXfer:uib:read}
36861 packet (@pxref{qXfer unwind info block}).
36863 @item qXfer:fdpic:read
36864 The remote stub understands the @samp{qXfer:fdpic:read}
36865 packet (@pxref{qXfer fdpic loadmap read}).
36868 The remote stub understands the @samp{QNonStop} packet
36869 (@pxref{QNonStop}).
36871 @item QCatchSyscalls
36872 The remote stub understands the @samp{QCatchSyscalls} packet
36873 (@pxref{QCatchSyscalls}).
36876 The remote stub understands the @samp{QPassSignals} packet
36877 (@pxref{QPassSignals}).
36879 @item QStartNoAckMode
36880 The remote stub understands the @samp{QStartNoAckMode} packet and
36881 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36884 @anchor{multiprocess extensions}
36885 @cindex multiprocess extensions, in remote protocol
36886 The remote stub understands the multiprocess extensions to the remote
36887 protocol syntax. The multiprocess extensions affect the syntax of
36888 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36889 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36890 replies. Note that reporting this feature indicates support for the
36891 syntactic extensions only, not that the stub necessarily supports
36892 debugging of more than one process at a time. The stub must not use
36893 multiprocess extensions in packet replies unless @value{GDBN} has also
36894 indicated it supports them in its @samp{qSupported} request.
36896 @item qXfer:osdata:read
36897 The remote stub understands the @samp{qXfer:osdata:read} packet
36898 ((@pxref{qXfer osdata read}).
36900 @item ConditionalBreakpoints
36901 The target accepts and implements evaluation of conditional expressions
36902 defined for breakpoints. The target will only report breakpoint triggers
36903 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36905 @item ConditionalTracepoints
36906 The remote stub accepts and implements conditional expressions defined
36907 for tracepoints (@pxref{Tracepoint Conditions}).
36909 @item ReverseContinue
36910 The remote stub accepts and implements the reverse continue packet
36914 The remote stub accepts and implements the reverse step packet
36917 @item TracepointSource
36918 The remote stub understands the @samp{QTDPsrc} packet that supplies
36919 the source form of tracepoint definitions.
36922 The remote stub understands the @samp{QAgent} packet.
36925 The remote stub understands the @samp{QAllow} packet.
36927 @item QDisableRandomization
36928 The remote stub understands the @samp{QDisableRandomization} packet.
36930 @item StaticTracepoint
36931 @cindex static tracepoints, in remote protocol
36932 The remote stub supports static tracepoints.
36934 @item InstallInTrace
36935 @anchor{install tracepoint in tracing}
36936 The remote stub supports installing tracepoint in tracing.
36938 @item EnableDisableTracepoints
36939 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36940 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36941 to be enabled and disabled while a trace experiment is running.
36943 @item QTBuffer:size
36944 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36945 packet that allows to change the size of the trace buffer.
36948 @cindex string tracing, in remote protocol
36949 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36950 See @ref{Bytecode Descriptions} for details about the bytecode.
36952 @item BreakpointCommands
36953 @cindex breakpoint commands, in remote protocol
36954 The remote stub supports running a breakpoint's command list itself,
36955 rather than reporting the hit to @value{GDBN}.
36958 The remote stub understands the @samp{Qbtrace:off} packet.
36961 The remote stub understands the @samp{Qbtrace:bts} packet.
36964 The remote stub understands the @samp{Qbtrace:pt} packet.
36966 @item Qbtrace-conf:bts:size
36967 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36969 @item Qbtrace-conf:pt:size
36970 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36973 The remote stub reports the @samp{swbreak} stop reason for memory
36977 The remote stub reports the @samp{hwbreak} stop reason for hardware
36981 The remote stub reports the @samp{fork} stop reason for fork events.
36984 The remote stub reports the @samp{vfork} stop reason for vfork events
36985 and vforkdone events.
36988 The remote stub reports the @samp{exec} stop reason for exec events.
36990 @item vContSupported
36991 The remote stub reports the supported actions in the reply to
36992 @samp{vCont?} packet.
36994 @item QThreadEvents
36995 The remote stub understands the @samp{QThreadEvents} packet.
36998 The remote stub reports the @samp{N} stop reply.
37003 @cindex symbol lookup, remote request
37004 @cindex @samp{qSymbol} packet
37005 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37006 requests. Accept requests from the target for the values of symbols.
37011 The target does not need to look up any (more) symbols.
37012 @item qSymbol:@var{sym_name}
37013 The target requests the value of symbol @var{sym_name} (hex encoded).
37014 @value{GDBN} may provide the value by using the
37015 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37019 @item qSymbol:@var{sym_value}:@var{sym_name}
37020 Set the value of @var{sym_name} to @var{sym_value}.
37022 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37023 target has previously requested.
37025 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37026 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37032 The target does not need to look up any (more) symbols.
37033 @item qSymbol:@var{sym_name}
37034 The target requests the value of a new symbol @var{sym_name} (hex
37035 encoded). @value{GDBN} will continue to supply the values of symbols
37036 (if available), until the target ceases to request them.
37041 @itemx QTDisconnected
37048 @itemx qTMinFTPILen
37050 @xref{Tracepoint Packets}.
37052 @item qThreadExtraInfo,@var{thread-id}
37053 @cindex thread attributes info, remote request
37054 @cindex @samp{qThreadExtraInfo} packet
37055 Obtain from the target OS a printable string description of thread
37056 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37057 for the forms of @var{thread-id}. This
37058 string may contain anything that the target OS thinks is interesting
37059 for @value{GDBN} to tell the user about the thread. The string is
37060 displayed in @value{GDBN}'s @code{info threads} display. Some
37061 examples of possible thread extra info strings are @samp{Runnable}, or
37062 @samp{Blocked on Mutex}.
37066 @item @var{XX}@dots{}
37067 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37068 comprising the printable string containing the extra information about
37069 the thread's attributes.
37072 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37073 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37074 conventions above. Please don't use this packet as a model for new
37093 @xref{Tracepoint Packets}.
37095 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37096 @cindex read special object, remote request
37097 @cindex @samp{qXfer} packet
37098 @anchor{qXfer read}
37099 Read uninterpreted bytes from the target's special data area
37100 identified by the keyword @var{object}. Request @var{length} bytes
37101 starting at @var{offset} bytes into the data. The content and
37102 encoding of @var{annex} is specific to @var{object}; it can supply
37103 additional details about what data to access.
37105 Here are the specific requests of this form defined so far. All
37106 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37107 formats, listed below.
37110 @item qXfer:auxv:read::@var{offset},@var{length}
37111 @anchor{qXfer auxiliary vector read}
37112 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37113 auxiliary vector}. Note @var{annex} must be empty.
37115 This packet is not probed by default; the remote stub must request it,
37116 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37118 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37119 @anchor{qXfer btrace read}
37121 Return a description of the current branch trace.
37122 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37123 packet may have one of the following values:
37127 Returns all available branch trace.
37130 Returns all available branch trace if the branch trace changed since
37131 the last read request.
37134 Returns the new branch trace since the last read request. Adds a new
37135 block to the end of the trace that begins at zero and ends at the source
37136 location of the first branch in the trace buffer. This extra block is
37137 used to stitch traces together.
37139 If the trace buffer overflowed, returns an error indicating the overflow.
37142 This packet is not probed by default; the remote stub must request it
37143 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37145 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37146 @anchor{qXfer btrace-conf read}
37148 Return a description of the current branch trace configuration.
37149 @xref{Branch Trace Configuration Format}.
37151 This packet is not probed by default; the remote stub must request it
37152 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37154 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37155 @anchor{qXfer executable filename read}
37156 Return the full absolute name of the file that was executed to create
37157 a process running on the remote system. The annex specifies the
37158 numeric process ID of the process to query, encoded as a hexadecimal
37159 number. If the annex part is empty the remote stub should return the
37160 filename corresponding to the currently executing process.
37162 This packet is not probed by default; the remote stub must request it,
37163 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37165 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37166 @anchor{qXfer target description read}
37167 Access the @dfn{target description}. @xref{Target Descriptions}. The
37168 annex specifies which XML document to access. The main description is
37169 always loaded from the @samp{target.xml} annex.
37171 This packet is not probed by default; the remote stub must request it,
37172 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37174 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37175 @anchor{qXfer library list read}
37176 Access the target's list of loaded libraries. @xref{Library List Format}.
37177 The annex part of the generic @samp{qXfer} packet must be empty
37178 (@pxref{qXfer read}).
37180 Targets which maintain a list of libraries in the program's memory do
37181 not need to implement this packet; it is designed for platforms where
37182 the operating system manages the list of loaded libraries.
37184 This packet is not probed by default; the remote stub must request it,
37185 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37187 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37188 @anchor{qXfer svr4 library list read}
37189 Access the target's list of loaded libraries when the target is an SVR4
37190 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37191 of the generic @samp{qXfer} packet must be empty unless the remote
37192 stub indicated it supports the augmented form of this packet
37193 by supplying an appropriate @samp{qSupported} response
37194 (@pxref{qXfer read}, @ref{qSupported}).
37196 This packet is optional for better performance on SVR4 targets.
37197 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37199 This packet is not probed by default; the remote stub must request it,
37200 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37202 If the remote stub indicates it supports the augmented form of this
37203 packet then the annex part of the generic @samp{qXfer} packet may
37204 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37205 arguments. The currently supported arguments are:
37208 @item start=@var{address}
37209 A hexadecimal number specifying the address of the @samp{struct
37210 link_map} to start reading the library list from. If unset or zero
37211 then the first @samp{struct link_map} in the library list will be
37212 chosen as the starting point.
37214 @item prev=@var{address}
37215 A hexadecimal number specifying the address of the @samp{struct
37216 link_map} immediately preceding the @samp{struct link_map}
37217 specified by the @samp{start} argument. If unset or zero then
37218 the remote stub will expect that no @samp{struct link_map}
37219 exists prior to the starting point.
37223 Arguments that are not understood by the remote stub will be silently
37226 @item qXfer:memory-map:read::@var{offset},@var{length}
37227 @anchor{qXfer memory map read}
37228 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37229 annex part of the generic @samp{qXfer} packet must be empty
37230 (@pxref{qXfer read}).
37232 This packet is not probed by default; the remote stub must request it,
37233 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37235 @item qXfer:sdata:read::@var{offset},@var{length}
37236 @anchor{qXfer sdata read}
37238 Read contents of the extra collected static tracepoint marker
37239 information. The annex part of the generic @samp{qXfer} packet must
37240 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37243 This packet is not probed by default; the remote stub must request it,
37244 by supplying an appropriate @samp{qSupported} response
37245 (@pxref{qSupported}).
37247 @item qXfer:siginfo:read::@var{offset},@var{length}
37248 @anchor{qXfer siginfo read}
37249 Read contents of the extra signal information on the target
37250 system. The annex part of the generic @samp{qXfer} packet must be
37251 empty (@pxref{qXfer read}).
37253 This packet is not probed by default; the remote stub must request it,
37254 by supplying an appropriate @samp{qSupported} response
37255 (@pxref{qSupported}).
37257 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37258 @anchor{qXfer spu read}
37259 Read contents of an @code{spufs} file on the target system. The
37260 annex specifies which file to read; it must be of the form
37261 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37262 in the target process, and @var{name} identifes the @code{spufs} file
37263 in that context to be accessed.
37265 This packet is not probed by default; the remote stub must request it,
37266 by supplying an appropriate @samp{qSupported} response
37267 (@pxref{qSupported}).
37269 @item qXfer:threads:read::@var{offset},@var{length}
37270 @anchor{qXfer threads read}
37271 Access the list of threads on target. @xref{Thread List Format}. The
37272 annex part of the generic @samp{qXfer} packet must be empty
37273 (@pxref{qXfer read}).
37275 This packet is not probed by default; the remote stub must request it,
37276 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37278 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37279 @anchor{qXfer traceframe info read}
37281 Return a description of the current traceframe's contents.
37282 @xref{Traceframe Info Format}. The annex part of the generic
37283 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37285 This packet is not probed by default; the remote stub must request it,
37286 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37288 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37289 @anchor{qXfer unwind info block}
37291 Return the unwind information block for @var{pc}. This packet is used
37292 on OpenVMS/ia64 to ask the kernel unwind information.
37294 This packet is not probed by default.
37296 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37297 @anchor{qXfer fdpic loadmap read}
37298 Read contents of @code{loadmap}s on the target system. The
37299 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37300 executable @code{loadmap} or interpreter @code{loadmap} to read.
37302 This packet is not probed by default; the remote stub must request it,
37303 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37305 @item qXfer:osdata:read::@var{offset},@var{length}
37306 @anchor{qXfer osdata read}
37307 Access the target's @dfn{operating system information}.
37308 @xref{Operating System Information}.
37315 Data @var{data} (@pxref{Binary Data}) has been read from the
37316 target. There may be more data at a higher address (although
37317 it is permitted to return @samp{m} even for the last valid
37318 block of data, as long as at least one byte of data was read).
37319 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37323 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37324 There is no more data to be read. It is possible for @var{data} to
37325 have fewer bytes than the @var{length} in the request.
37328 The @var{offset} in the request is at the end of the data.
37329 There is no more data to be read.
37332 The request was malformed, or @var{annex} was invalid.
37335 The offset was invalid, or there was an error encountered reading the data.
37336 The @var{nn} part is a hex-encoded @code{errno} value.
37339 An empty reply indicates the @var{object} string was not recognized by
37340 the stub, or that the object does not support reading.
37343 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37344 @cindex write data into object, remote request
37345 @anchor{qXfer write}
37346 Write uninterpreted bytes into the target's special data area
37347 identified by the keyword @var{object}, starting at @var{offset} bytes
37348 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37349 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37350 is specific to @var{object}; it can supply additional details about what data
37353 Here are the specific requests of this form defined so far. All
37354 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37355 formats, listed below.
37358 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37359 @anchor{qXfer siginfo write}
37360 Write @var{data} to the extra signal information on the target system.
37361 The annex part of the generic @samp{qXfer} packet must be
37362 empty (@pxref{qXfer write}).
37364 This packet is not probed by default; the remote stub must request it,
37365 by supplying an appropriate @samp{qSupported} response
37366 (@pxref{qSupported}).
37368 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37369 @anchor{qXfer spu write}
37370 Write @var{data} to an @code{spufs} file on the target system. The
37371 annex specifies which file to write; it must be of the form
37372 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37373 in the target process, and @var{name} identifes the @code{spufs} file
37374 in that context to be accessed.
37376 This packet is not probed by default; the remote stub must request it,
37377 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37383 @var{nn} (hex encoded) is the number of bytes written.
37384 This may be fewer bytes than supplied in the request.
37387 The request was malformed, or @var{annex} was invalid.
37390 The offset was invalid, or there was an error encountered writing the data.
37391 The @var{nn} part is a hex-encoded @code{errno} value.
37394 An empty reply indicates the @var{object} string was not
37395 recognized by the stub, or that the object does not support writing.
37398 @item qXfer:@var{object}:@var{operation}:@dots{}
37399 Requests of this form may be added in the future. When a stub does
37400 not recognize the @var{object} keyword, or its support for
37401 @var{object} does not recognize the @var{operation} keyword, the stub
37402 must respond with an empty packet.
37404 @item qAttached:@var{pid}
37405 @cindex query attached, remote request
37406 @cindex @samp{qAttached} packet
37407 Return an indication of whether the remote server attached to an
37408 existing process or created a new process. When the multiprocess
37409 protocol extensions are supported (@pxref{multiprocess extensions}),
37410 @var{pid} is an integer in hexadecimal format identifying the target
37411 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37412 the query packet will be simplified as @samp{qAttached}.
37414 This query is used, for example, to know whether the remote process
37415 should be detached or killed when a @value{GDBN} session is ended with
37416 the @code{quit} command.
37421 The remote server attached to an existing process.
37423 The remote server created a new process.
37425 A badly formed request or an error was encountered.
37429 Enable branch tracing for the current thread using Branch Trace Store.
37434 Branch tracing has been enabled.
37436 A badly formed request or an error was encountered.
37440 Enable branch tracing for the current thread using Intel Processor Trace.
37445 Branch tracing has been enabled.
37447 A badly formed request or an error was encountered.
37451 Disable branch tracing for the current thread.
37456 Branch tracing has been disabled.
37458 A badly formed request or an error was encountered.
37461 @item Qbtrace-conf:bts:size=@var{value}
37462 Set the requested ring buffer size for new threads that use the
37463 btrace recording method in bts format.
37468 The ring buffer size has been set.
37470 A badly formed request or an error was encountered.
37473 @item Qbtrace-conf:pt:size=@var{value}
37474 Set the requested ring buffer size for new threads that use the
37475 btrace recording method in pt format.
37480 The ring buffer size has been set.
37482 A badly formed request or an error was encountered.
37487 @node Architecture-Specific Protocol Details
37488 @section Architecture-Specific Protocol Details
37490 This section describes how the remote protocol is applied to specific
37491 target architectures. Also see @ref{Standard Target Features}, for
37492 details of XML target descriptions for each architecture.
37495 * ARM-Specific Protocol Details::
37496 * MIPS-Specific Protocol Details::
37499 @node ARM-Specific Protocol Details
37500 @subsection @acronym{ARM}-specific Protocol Details
37503 * ARM Breakpoint Kinds::
37506 @node ARM Breakpoint Kinds
37507 @subsubsection @acronym{ARM} Breakpoint Kinds
37508 @cindex breakpoint kinds, @acronym{ARM}
37510 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37515 16-bit Thumb mode breakpoint.
37518 32-bit Thumb mode (Thumb-2) breakpoint.
37521 32-bit @acronym{ARM} mode breakpoint.
37525 @node MIPS-Specific Protocol Details
37526 @subsection @acronym{MIPS}-specific Protocol Details
37529 * MIPS Register packet Format::
37530 * MIPS Breakpoint Kinds::
37533 @node MIPS Register packet Format
37534 @subsubsection @acronym{MIPS} Register Packet Format
37535 @cindex register packet format, @acronym{MIPS}
37537 The following @code{g}/@code{G} packets have previously been defined.
37538 In the below, some thirty-two bit registers are transferred as
37539 sixty-four bits. Those registers should be zero/sign extended (which?)
37540 to fill the space allocated. Register bytes are transferred in target
37541 byte order. The two nibbles within a register byte are transferred
37542 most-significant -- least-significant.
37547 All registers are transferred as thirty-two bit quantities in the order:
37548 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37549 registers; fsr; fir; fp.
37552 All registers are transferred as sixty-four bit quantities (including
37553 thirty-two bit registers such as @code{sr}). The ordering is the same
37558 @node MIPS Breakpoint Kinds
37559 @subsubsection @acronym{MIPS} Breakpoint Kinds
37560 @cindex breakpoint kinds, @acronym{MIPS}
37562 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37567 16-bit @acronym{MIPS16} mode breakpoint.
37570 16-bit @acronym{microMIPS} mode breakpoint.
37573 32-bit standard @acronym{MIPS} mode breakpoint.
37576 32-bit @acronym{microMIPS} mode breakpoint.
37580 @node Tracepoint Packets
37581 @section Tracepoint Packets
37582 @cindex tracepoint packets
37583 @cindex packets, tracepoint
37585 Here we describe the packets @value{GDBN} uses to implement
37586 tracepoints (@pxref{Tracepoints}).
37590 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37591 @cindex @samp{QTDP} packet
37592 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37593 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37594 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37595 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37596 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37597 the number of bytes that the target should copy elsewhere to make room
37598 for the tracepoint. If an @samp{X} is present, it introduces a
37599 tracepoint condition, which consists of a hexadecimal length, followed
37600 by a comma and hex-encoded bytes, in a manner similar to action
37601 encodings as described below. If the trailing @samp{-} is present,
37602 further @samp{QTDP} packets will follow to specify this tracepoint's
37608 The packet was understood and carried out.
37610 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37612 The packet was not recognized.
37615 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37616 Define actions to be taken when a tracepoint is hit. The @var{n} and
37617 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37618 this tracepoint. This packet may only be sent immediately after
37619 another @samp{QTDP} packet that ended with a @samp{-}. If the
37620 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37621 specifying more actions for this tracepoint.
37623 In the series of action packets for a given tracepoint, at most one
37624 can have an @samp{S} before its first @var{action}. If such a packet
37625 is sent, it and the following packets define ``while-stepping''
37626 actions. Any prior packets define ordinary actions --- that is, those
37627 taken when the tracepoint is first hit. If no action packet has an
37628 @samp{S}, then all the packets in the series specify ordinary
37629 tracepoint actions.
37631 The @samp{@var{action}@dots{}} portion of the packet is a series of
37632 actions, concatenated without separators. Each action has one of the
37638 Collect the registers whose bits are set in @var{mask},
37639 a hexadecimal number whose @var{i}'th bit is set if register number
37640 @var{i} should be collected. (The least significant bit is numbered
37641 zero.) Note that @var{mask} may be any number of digits long; it may
37642 not fit in a 32-bit word.
37644 @item M @var{basereg},@var{offset},@var{len}
37645 Collect @var{len} bytes of memory starting at the address in register
37646 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37647 @samp{-1}, then the range has a fixed address: @var{offset} is the
37648 address of the lowest byte to collect. The @var{basereg},
37649 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37650 values (the @samp{-1} value for @var{basereg} is a special case).
37652 @item X @var{len},@var{expr}
37653 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37654 it directs. The agent expression @var{expr} is as described in
37655 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37656 two-digit hex number in the packet; @var{len} is the number of bytes
37657 in the expression (and thus one-half the number of hex digits in the
37662 Any number of actions may be packed together in a single @samp{QTDP}
37663 packet, as long as the packet does not exceed the maximum packet
37664 length (400 bytes, for many stubs). There may be only one @samp{R}
37665 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37666 actions. Any registers referred to by @samp{M} and @samp{X} actions
37667 must be collected by a preceding @samp{R} action. (The
37668 ``while-stepping'' actions are treated as if they were attached to a
37669 separate tracepoint, as far as these restrictions are concerned.)
37674 The packet was understood and carried out.
37676 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37678 The packet was not recognized.
37681 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37682 @cindex @samp{QTDPsrc} packet
37683 Specify a source string of tracepoint @var{n} at address @var{addr}.
37684 This is useful to get accurate reproduction of the tracepoints
37685 originally downloaded at the beginning of the trace run. The @var{type}
37686 is the name of the tracepoint part, such as @samp{cond} for the
37687 tracepoint's conditional expression (see below for a list of types), while
37688 @var{bytes} is the string, encoded in hexadecimal.
37690 @var{start} is the offset of the @var{bytes} within the overall source
37691 string, while @var{slen} is the total length of the source string.
37692 This is intended for handling source strings that are longer than will
37693 fit in a single packet.
37694 @c Add detailed example when this info is moved into a dedicated
37695 @c tracepoint descriptions section.
37697 The available string types are @samp{at} for the location,
37698 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37699 @value{GDBN} sends a separate packet for each command in the action
37700 list, in the same order in which the commands are stored in the list.
37702 The target does not need to do anything with source strings except
37703 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37706 Although this packet is optional, and @value{GDBN} will only send it
37707 if the target replies with @samp{TracepointSource} @xref{General
37708 Query Packets}, it makes both disconnected tracing and trace files
37709 much easier to use. Otherwise the user must be careful that the
37710 tracepoints in effect while looking at trace frames are identical to
37711 the ones in effect during the trace run; even a small discrepancy
37712 could cause @samp{tdump} not to work, or a particular trace frame not
37715 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37716 @cindex define trace state variable, remote request
37717 @cindex @samp{QTDV} packet
37718 Create a new trace state variable, number @var{n}, with an initial
37719 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37720 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37721 the option of not using this packet for initial values of zero; the
37722 target should simply create the trace state variables as they are
37723 mentioned in expressions. The value @var{builtin} should be 1 (one)
37724 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37725 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37726 @samp{qTsV} packet had it set. The contents of @var{name} is the
37727 hex-encoded name (without the leading @samp{$}) of the trace state
37730 @item QTFrame:@var{n}
37731 @cindex @samp{QTFrame} packet
37732 Select the @var{n}'th tracepoint frame from the buffer, and use the
37733 register and memory contents recorded there to answer subsequent
37734 request packets from @value{GDBN}.
37736 A successful reply from the stub indicates that the stub has found the
37737 requested frame. The response is a series of parts, concatenated
37738 without separators, describing the frame we selected. Each part has
37739 one of the following forms:
37743 The selected frame is number @var{n} in the trace frame buffer;
37744 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37745 was no frame matching the criteria in the request packet.
37748 The selected trace frame records a hit of tracepoint number @var{t};
37749 @var{t} is a hexadecimal number.
37753 @item QTFrame:pc:@var{addr}
37754 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37755 currently selected frame whose PC is @var{addr};
37756 @var{addr} is a hexadecimal number.
37758 @item QTFrame:tdp:@var{t}
37759 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37760 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37761 is a hexadecimal number.
37763 @item QTFrame:range:@var{start}:@var{end}
37764 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37765 currently selected frame whose PC is between @var{start} (inclusive)
37766 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37769 @item QTFrame:outside:@var{start}:@var{end}
37770 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37771 frame @emph{outside} the given range of addresses (exclusive).
37774 @cindex @samp{qTMinFTPILen} packet
37775 This packet requests the minimum length of instruction at which a fast
37776 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37777 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37778 it depends on the target system being able to create trampolines in
37779 the first 64K of memory, which might or might not be possible for that
37780 system. So the reply to this packet will be 4 if it is able to
37787 The minimum instruction length is currently unknown.
37789 The minimum instruction length is @var{length}, where @var{length}
37790 is a hexadecimal number greater or equal to 1. A reply
37791 of 1 means that a fast tracepoint may be placed on any instruction
37792 regardless of size.
37794 An error has occurred.
37796 An empty reply indicates that the request is not supported by the stub.
37800 @cindex @samp{QTStart} packet
37801 Begin the tracepoint experiment. Begin collecting data from
37802 tracepoint hits in the trace frame buffer. This packet supports the
37803 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37804 instruction reply packet}).
37807 @cindex @samp{QTStop} packet
37808 End the tracepoint experiment. Stop collecting trace frames.
37810 @item QTEnable:@var{n}:@var{addr}
37812 @cindex @samp{QTEnable} packet
37813 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37814 experiment. If the tracepoint was previously disabled, then collection
37815 of data from it will resume.
37817 @item QTDisable:@var{n}:@var{addr}
37819 @cindex @samp{QTDisable} packet
37820 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37821 experiment. No more data will be collected from the tracepoint unless
37822 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37825 @cindex @samp{QTinit} packet
37826 Clear the table of tracepoints, and empty the trace frame buffer.
37828 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37829 @cindex @samp{QTro} packet
37830 Establish the given ranges of memory as ``transparent''. The stub
37831 will answer requests for these ranges from memory's current contents,
37832 if they were not collected as part of the tracepoint hit.
37834 @value{GDBN} uses this to mark read-only regions of memory, like those
37835 containing program code. Since these areas never change, they should
37836 still have the same contents they did when the tracepoint was hit, so
37837 there's no reason for the stub to refuse to provide their contents.
37839 @item QTDisconnected:@var{value}
37840 @cindex @samp{QTDisconnected} packet
37841 Set the choice to what to do with the tracing run when @value{GDBN}
37842 disconnects from the target. A @var{value} of 1 directs the target to
37843 continue the tracing run, while 0 tells the target to stop tracing if
37844 @value{GDBN} is no longer in the picture.
37847 @cindex @samp{qTStatus} packet
37848 Ask the stub if there is a trace experiment running right now.
37850 The reply has the form:
37854 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37855 @var{running} is a single digit @code{1} if the trace is presently
37856 running, or @code{0} if not. It is followed by semicolon-separated
37857 optional fields that an agent may use to report additional status.
37861 If the trace is not running, the agent may report any of several
37862 explanations as one of the optional fields:
37867 No trace has been run yet.
37869 @item tstop[:@var{text}]:0
37870 The trace was stopped by a user-originated stop command. The optional
37871 @var{text} field is a user-supplied string supplied as part of the
37872 stop command (for instance, an explanation of why the trace was
37873 stopped manually). It is hex-encoded.
37876 The trace stopped because the trace buffer filled up.
37878 @item tdisconnected:0
37879 The trace stopped because @value{GDBN} disconnected from the target.
37881 @item tpasscount:@var{tpnum}
37882 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37884 @item terror:@var{text}:@var{tpnum}
37885 The trace stopped because tracepoint @var{tpnum} had an error. The
37886 string @var{text} is available to describe the nature of the error
37887 (for instance, a divide by zero in the condition expression); it
37891 The trace stopped for some other reason.
37895 Additional optional fields supply statistical and other information.
37896 Although not required, they are extremely useful for users monitoring
37897 the progress of a trace run. If a trace has stopped, and these
37898 numbers are reported, they must reflect the state of the just-stopped
37903 @item tframes:@var{n}
37904 The number of trace frames in the buffer.
37906 @item tcreated:@var{n}
37907 The total number of trace frames created during the run. This may
37908 be larger than the trace frame count, if the buffer is circular.
37910 @item tsize:@var{n}
37911 The total size of the trace buffer, in bytes.
37913 @item tfree:@var{n}
37914 The number of bytes still unused in the buffer.
37916 @item circular:@var{n}
37917 The value of the circular trace buffer flag. @code{1} means that the
37918 trace buffer is circular and old trace frames will be discarded if
37919 necessary to make room, @code{0} means that the trace buffer is linear
37922 @item disconn:@var{n}
37923 The value of the disconnected tracing flag. @code{1} means that
37924 tracing will continue after @value{GDBN} disconnects, @code{0} means
37925 that the trace run will stop.
37929 @item qTP:@var{tp}:@var{addr}
37930 @cindex tracepoint status, remote request
37931 @cindex @samp{qTP} packet
37932 Ask the stub for the current state of tracepoint number @var{tp} at
37933 address @var{addr}.
37937 @item V@var{hits}:@var{usage}
37938 The tracepoint has been hit @var{hits} times so far during the trace
37939 run, and accounts for @var{usage} in the trace buffer. Note that
37940 @code{while-stepping} steps are not counted as separate hits, but the
37941 steps' space consumption is added into the usage number.
37945 @item qTV:@var{var}
37946 @cindex trace state variable value, remote request
37947 @cindex @samp{qTV} packet
37948 Ask the stub for the value of the trace state variable number @var{var}.
37953 The value of the variable is @var{value}. This will be the current
37954 value of the variable if the user is examining a running target, or a
37955 saved value if the variable was collected in the trace frame that the
37956 user is looking at. Note that multiple requests may result in
37957 different reply values, such as when requesting values while the
37958 program is running.
37961 The value of the variable is unknown. This would occur, for example,
37962 if the user is examining a trace frame in which the requested variable
37967 @cindex @samp{qTfP} packet
37969 @cindex @samp{qTsP} packet
37970 These packets request data about tracepoints that are being used by
37971 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37972 of data, and multiple @code{qTsP} to get additional pieces. Replies
37973 to these packets generally take the form of the @code{QTDP} packets
37974 that define tracepoints. (FIXME add detailed syntax)
37977 @cindex @samp{qTfV} packet
37979 @cindex @samp{qTsV} packet
37980 These packets request data about trace state variables that are on the
37981 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37982 and multiple @code{qTsV} to get additional variables. Replies to
37983 these packets follow the syntax of the @code{QTDV} packets that define
37984 trace state variables.
37990 @cindex @samp{qTfSTM} packet
37991 @cindex @samp{qTsSTM} packet
37992 These packets request data about static tracepoint markers that exist
37993 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37994 first piece of data, and multiple @code{qTsSTM} to get additional
37995 pieces. Replies to these packets take the following form:
37999 @item m @var{address}:@var{id}:@var{extra}
38001 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38002 a comma-separated list of markers
38004 (lower case letter @samp{L}) denotes end of list.
38006 An error occurred. The error number @var{nn} is given as hex digits.
38008 An empty reply indicates that the request is not supported by the
38012 The @var{address} is encoded in hex;
38013 @var{id} and @var{extra} are strings encoded in hex.
38015 In response to each query, the target will reply with a list of one or
38016 more markers, separated by commas. @value{GDBN} will respond to each
38017 reply with a request for more markers (using the @samp{qs} form of the
38018 query), until the target responds with @samp{l} (lower-case ell, for
38021 @item qTSTMat:@var{address}
38023 @cindex @samp{qTSTMat} packet
38024 This packets requests data about static tracepoint markers in the
38025 target program at @var{address}. Replies to this packet follow the
38026 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38027 tracepoint markers.
38029 @item QTSave:@var{filename}
38030 @cindex @samp{QTSave} packet
38031 This packet directs the target to save trace data to the file name
38032 @var{filename} in the target's filesystem. The @var{filename} is encoded
38033 as a hex string; the interpretation of the file name (relative vs
38034 absolute, wild cards, etc) is up to the target.
38036 @item qTBuffer:@var{offset},@var{len}
38037 @cindex @samp{qTBuffer} packet
38038 Return up to @var{len} bytes of the current contents of trace buffer,
38039 starting at @var{offset}. The trace buffer is treated as if it were
38040 a contiguous collection of traceframes, as per the trace file format.
38041 The reply consists as many hex-encoded bytes as the target can deliver
38042 in a packet; it is not an error to return fewer than were asked for.
38043 A reply consisting of just @code{l} indicates that no bytes are
38046 @item QTBuffer:circular:@var{value}
38047 This packet directs the target to use a circular trace buffer if
38048 @var{value} is 1, or a linear buffer if the value is 0.
38050 @item QTBuffer:size:@var{size}
38051 @anchor{QTBuffer-size}
38052 @cindex @samp{QTBuffer size} packet
38053 This packet directs the target to make the trace buffer be of size
38054 @var{size} if possible. A value of @code{-1} tells the target to
38055 use whatever size it prefers.
38057 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38058 @cindex @samp{QTNotes} packet
38059 This packet adds optional textual notes to the trace run. Allowable
38060 types include @code{user}, @code{notes}, and @code{tstop}, the
38061 @var{text} fields are arbitrary strings, hex-encoded.
38065 @subsection Relocate instruction reply packet
38066 When installing fast tracepoints in memory, the target may need to
38067 relocate the instruction currently at the tracepoint address to a
38068 different address in memory. For most instructions, a simple copy is
38069 enough, but, for example, call instructions that implicitly push the
38070 return address on the stack, and relative branches or other
38071 PC-relative instructions require offset adjustment, so that the effect
38072 of executing the instruction at a different address is the same as if
38073 it had executed in the original location.
38075 In response to several of the tracepoint packets, the target may also
38076 respond with a number of intermediate @samp{qRelocInsn} request
38077 packets before the final result packet, to have @value{GDBN} handle
38078 this relocation operation. If a packet supports this mechanism, its
38079 documentation will explicitly say so. See for example the above
38080 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38081 format of the request is:
38084 @item qRelocInsn:@var{from};@var{to}
38086 This requests @value{GDBN} to copy instruction at address @var{from}
38087 to address @var{to}, possibly adjusted so that executing the
38088 instruction at @var{to} has the same effect as executing it at
38089 @var{from}. @value{GDBN} writes the adjusted instruction to target
38090 memory starting at @var{to}.
38095 @item qRelocInsn:@var{adjusted_size}
38096 Informs the stub the relocation is complete. The @var{adjusted_size} is
38097 the length in bytes of resulting relocated instruction sequence.
38099 A badly formed request was detected, or an error was encountered while
38100 relocating the instruction.
38103 @node Host I/O Packets
38104 @section Host I/O Packets
38105 @cindex Host I/O, remote protocol
38106 @cindex file transfer, remote protocol
38108 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38109 operations on the far side of a remote link. For example, Host I/O is
38110 used to upload and download files to a remote target with its own
38111 filesystem. Host I/O uses the same constant values and data structure
38112 layout as the target-initiated File-I/O protocol. However, the
38113 Host I/O packets are structured differently. The target-initiated
38114 protocol relies on target memory to store parameters and buffers.
38115 Host I/O requests are initiated by @value{GDBN}, and the
38116 target's memory is not involved. @xref{File-I/O Remote Protocol
38117 Extension}, for more details on the target-initiated protocol.
38119 The Host I/O request packets all encode a single operation along with
38120 its arguments. They have this format:
38124 @item vFile:@var{operation}: @var{parameter}@dots{}
38125 @var{operation} is the name of the particular request; the target
38126 should compare the entire packet name up to the second colon when checking
38127 for a supported operation. The format of @var{parameter} depends on
38128 the operation. Numbers are always passed in hexadecimal. Negative
38129 numbers have an explicit minus sign (i.e.@: two's complement is not
38130 used). Strings (e.g.@: filenames) are encoded as a series of
38131 hexadecimal bytes. The last argument to a system call may be a
38132 buffer of escaped binary data (@pxref{Binary Data}).
38136 The valid responses to Host I/O packets are:
38140 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38141 @var{result} is the integer value returned by this operation, usually
38142 non-negative for success and -1 for errors. If an error has occured,
38143 @var{errno} will be included in the result specifying a
38144 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38145 operations which return data, @var{attachment} supplies the data as a
38146 binary buffer. Binary buffers in response packets are escaped in the
38147 normal way (@pxref{Binary Data}). See the individual packet
38148 documentation for the interpretation of @var{result} and
38152 An empty response indicates that this operation is not recognized.
38156 These are the supported Host I/O operations:
38159 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38160 Open a file at @var{filename} and return a file descriptor for it, or
38161 return -1 if an error occurs. The @var{filename} is a string,
38162 @var{flags} is an integer indicating a mask of open flags
38163 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38164 of mode bits to use if the file is created (@pxref{mode_t Values}).
38165 @xref{open}, for details of the open flags and mode values.
38167 @item vFile:close: @var{fd}
38168 Close the open file corresponding to @var{fd} and return 0, or
38169 -1 if an error occurs.
38171 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38172 Read data from the open file corresponding to @var{fd}. Up to
38173 @var{count} bytes will be read from the file, starting at @var{offset}
38174 relative to the start of the file. The target may read fewer bytes;
38175 common reasons include packet size limits and an end-of-file
38176 condition. The number of bytes read is returned. Zero should only be
38177 returned for a successful read at the end of the file, or if
38178 @var{count} was zero.
38180 The data read should be returned as a binary attachment on success.
38181 If zero bytes were read, the response should include an empty binary
38182 attachment (i.e.@: a trailing semicolon). The return value is the
38183 number of target bytes read; the binary attachment may be longer if
38184 some characters were escaped.
38186 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38187 Write @var{data} (a binary buffer) to the open file corresponding
38188 to @var{fd}. Start the write at @var{offset} from the start of the
38189 file. Unlike many @code{write} system calls, there is no
38190 separate @var{count} argument; the length of @var{data} in the
38191 packet is used. @samp{vFile:write} returns the number of bytes written,
38192 which may be shorter than the length of @var{data}, or -1 if an
38195 @item vFile:fstat: @var{fd}
38196 Get information about the open file corresponding to @var{fd}.
38197 On success the information is returned as a binary attachment
38198 and the return value is the size of this attachment in bytes.
38199 If an error occurs the return value is -1. The format of the
38200 returned binary attachment is as described in @ref{struct stat}.
38202 @item vFile:unlink: @var{filename}
38203 Delete the file at @var{filename} on the target. Return 0,
38204 or -1 if an error occurs. The @var{filename} is a string.
38206 @item vFile:readlink: @var{filename}
38207 Read value of symbolic link @var{filename} on the target. Return
38208 the number of bytes read, or -1 if an error occurs.
38210 The data read should be returned as a binary attachment on success.
38211 If zero bytes were read, the response should include an empty binary
38212 attachment (i.e.@: a trailing semicolon). The return value is the
38213 number of target bytes read; the binary attachment may be longer if
38214 some characters were escaped.
38216 @item vFile:setfs: @var{pid}
38217 Select the filesystem on which @code{vFile} operations with
38218 @var{filename} arguments will operate. This is required for
38219 @value{GDBN} to be able to access files on remote targets where
38220 the remote stub does not share a common filesystem with the
38223 If @var{pid} is nonzero, select the filesystem as seen by process
38224 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38225 the remote stub. Return 0 on success, or -1 if an error occurs.
38226 If @code{vFile:setfs:} indicates success, the selected filesystem
38227 remains selected until the next successful @code{vFile:setfs:}
38233 @section Interrupts
38234 @cindex interrupts (remote protocol)
38235 @anchor{interrupting remote targets}
38237 In all-stop mode, when a program on the remote target is running,
38238 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38239 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38240 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38242 The precise meaning of @code{BREAK} is defined by the transport
38243 mechanism and may, in fact, be undefined. @value{GDBN} does not
38244 currently define a @code{BREAK} mechanism for any of the network
38245 interfaces except for TCP, in which case @value{GDBN} sends the
38246 @code{telnet} BREAK sequence.
38248 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38249 transport mechanisms. It is represented by sending the single byte
38250 @code{0x03} without any of the usual packet overhead described in
38251 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38252 transmitted as part of a packet, it is considered to be packet data
38253 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38254 (@pxref{X packet}), used for binary downloads, may include an unescaped
38255 @code{0x03} as part of its packet.
38257 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38258 When Linux kernel receives this sequence from serial port,
38259 it stops execution and connects to gdb.
38261 In non-stop mode, because packet resumptions are asynchronous
38262 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38263 command to the remote stub, even when the target is running. For that
38264 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38265 packet}) with the usual packet framing instead of the single byte
38268 Stubs are not required to recognize these interrupt mechanisms and the
38269 precise meaning associated with receipt of the interrupt is
38270 implementation defined. If the target supports debugging of multiple
38271 threads and/or processes, it should attempt to interrupt all
38272 currently-executing threads and processes.
38273 If the stub is successful at interrupting the
38274 running program, it should send one of the stop
38275 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38276 of successfully stopping the program in all-stop mode, and a stop reply
38277 for each stopped thread in non-stop mode.
38278 Interrupts received while the
38279 program is stopped are queued and the program will be interrupted when
38280 it is resumed next time.
38282 @node Notification Packets
38283 @section Notification Packets
38284 @cindex notification packets
38285 @cindex packets, notification
38287 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38288 packets that require no acknowledgment. Both the GDB and the stub
38289 may send notifications (although the only notifications defined at
38290 present are sent by the stub). Notifications carry information
38291 without incurring the round-trip latency of an acknowledgment, and so
38292 are useful for low-impact communications where occasional packet loss
38295 A notification packet has the form @samp{% @var{data} #
38296 @var{checksum}}, where @var{data} is the content of the notification,
38297 and @var{checksum} is a checksum of @var{data}, computed and formatted
38298 as for ordinary @value{GDBN} packets. A notification's @var{data}
38299 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38300 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38301 to acknowledge the notification's receipt or to report its corruption.
38303 Every notification's @var{data} begins with a name, which contains no
38304 colon characters, followed by a colon character.
38306 Recipients should silently ignore corrupted notifications and
38307 notifications they do not understand. Recipients should restart
38308 timeout periods on receipt of a well-formed notification, whether or
38309 not they understand it.
38311 Senders should only send the notifications described here when this
38312 protocol description specifies that they are permitted. In the
38313 future, we may extend the protocol to permit existing notifications in
38314 new contexts; this rule helps older senders avoid confusing newer
38317 (Older versions of @value{GDBN} ignore bytes received until they see
38318 the @samp{$} byte that begins an ordinary packet, so new stubs may
38319 transmit notifications without fear of confusing older clients. There
38320 are no notifications defined for @value{GDBN} to send at the moment, but we
38321 assume that most older stubs would ignore them, as well.)
38323 Each notification is comprised of three parts:
38325 @item @var{name}:@var{event}
38326 The notification packet is sent by the side that initiates the
38327 exchange (currently, only the stub does that), with @var{event}
38328 carrying the specific information about the notification, and
38329 @var{name} specifying the name of the notification.
38331 The acknowledge sent by the other side, usually @value{GDBN}, to
38332 acknowledge the exchange and request the event.
38335 The purpose of an asynchronous notification mechanism is to report to
38336 @value{GDBN} that something interesting happened in the remote stub.
38338 The remote stub may send notification @var{name}:@var{event}
38339 at any time, but @value{GDBN} acknowledges the notification when
38340 appropriate. The notification event is pending before @value{GDBN}
38341 acknowledges. Only one notification at a time may be pending; if
38342 additional events occur before @value{GDBN} has acknowledged the
38343 previous notification, they must be queued by the stub for later
38344 synchronous transmission in response to @var{ack} packets from
38345 @value{GDBN}. Because the notification mechanism is unreliable,
38346 the stub is permitted to resend a notification if it believes
38347 @value{GDBN} may not have received it.
38349 Specifically, notifications may appear when @value{GDBN} is not
38350 otherwise reading input from the stub, or when @value{GDBN} is
38351 expecting to read a normal synchronous response or a
38352 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38353 Notification packets are distinct from any other communication from
38354 the stub so there is no ambiguity.
38356 After receiving a notification, @value{GDBN} shall acknowledge it by
38357 sending a @var{ack} packet as a regular, synchronous request to the
38358 stub. Such acknowledgment is not required to happen immediately, as
38359 @value{GDBN} is permitted to send other, unrelated packets to the
38360 stub first, which the stub should process normally.
38362 Upon receiving a @var{ack} packet, if the stub has other queued
38363 events to report to @value{GDBN}, it shall respond by sending a
38364 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38365 packet to solicit further responses; again, it is permitted to send
38366 other, unrelated packets as well which the stub should process
38369 If the stub receives a @var{ack} packet and there are no additional
38370 @var{event} to report, the stub shall return an @samp{OK} response.
38371 At this point, @value{GDBN} has finished processing a notification
38372 and the stub has completed sending any queued events. @value{GDBN}
38373 won't accept any new notifications until the final @samp{OK} is
38374 received . If further notification events occur, the stub shall send
38375 a new notification, @value{GDBN} shall accept the notification, and
38376 the process shall be repeated.
38378 The process of asynchronous notification can be illustrated by the
38381 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38384 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38386 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38391 The following notifications are defined:
38392 @multitable @columnfractions 0.12 0.12 0.38 0.38
38401 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38402 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38403 for information on how these notifications are acknowledged by
38405 @tab Report an asynchronous stop event in non-stop mode.
38409 @node Remote Non-Stop
38410 @section Remote Protocol Support for Non-Stop Mode
38412 @value{GDBN}'s remote protocol supports non-stop debugging of
38413 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38414 supports non-stop mode, it should report that to @value{GDBN} by including
38415 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38417 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38418 establishing a new connection with the stub. Entering non-stop mode
38419 does not alter the state of any currently-running threads, but targets
38420 must stop all threads in any already-attached processes when entering
38421 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38422 probe the target state after a mode change.
38424 In non-stop mode, when an attached process encounters an event that
38425 would otherwise be reported with a stop reply, it uses the
38426 asynchronous notification mechanism (@pxref{Notification Packets}) to
38427 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38428 in all processes are stopped when a stop reply is sent, in non-stop
38429 mode only the thread reporting the stop event is stopped. That is,
38430 when reporting a @samp{S} or @samp{T} response to indicate completion
38431 of a step operation, hitting a breakpoint, or a fault, only the
38432 affected thread is stopped; any other still-running threads continue
38433 to run. When reporting a @samp{W} or @samp{X} response, all running
38434 threads belonging to other attached processes continue to run.
38436 In non-stop mode, the target shall respond to the @samp{?} packet as
38437 follows. First, any incomplete stop reply notification/@samp{vStopped}
38438 sequence in progress is abandoned. The target must begin a new
38439 sequence reporting stop events for all stopped threads, whether or not
38440 it has previously reported those events to @value{GDBN}. The first
38441 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38442 subsequent stop replies are sent as responses to @samp{vStopped} packets
38443 using the mechanism described above. The target must not send
38444 asynchronous stop reply notifications until the sequence is complete.
38445 If all threads are running when the target receives the @samp{?} packet,
38446 or if the target is not attached to any process, it shall respond
38449 If the stub supports non-stop mode, it should also support the
38450 @samp{swbreak} stop reason if software breakpoints are supported, and
38451 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38452 (@pxref{swbreak stop reason}). This is because given the asynchronous
38453 nature of non-stop mode, between the time a thread hits a breakpoint
38454 and the time the event is finally processed by @value{GDBN}, the
38455 breakpoint may have already been removed from the target. Due to
38456 this, @value{GDBN} needs to be able to tell whether a trap stop was
38457 caused by a delayed breakpoint event, which should be ignored, as
38458 opposed to a random trap signal, which should be reported to the user.
38459 Note the @samp{swbreak} feature implies that the target is responsible
38460 for adjusting the PC when a software breakpoint triggers, if
38461 necessary, such as on the x86 architecture.
38463 @node Packet Acknowledgment
38464 @section Packet Acknowledgment
38466 @cindex acknowledgment, for @value{GDBN} remote
38467 @cindex packet acknowledgment, for @value{GDBN} remote
38468 By default, when either the host or the target machine receives a packet,
38469 the first response expected is an acknowledgment: either @samp{+} (to indicate
38470 the package was received correctly) or @samp{-} (to request retransmission).
38471 This mechanism allows the @value{GDBN} remote protocol to operate over
38472 unreliable transport mechanisms, such as a serial line.
38474 In cases where the transport mechanism is itself reliable (such as a pipe or
38475 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38476 It may be desirable to disable them in that case to reduce communication
38477 overhead, or for other reasons. This can be accomplished by means of the
38478 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38480 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38481 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38482 and response format still includes the normal checksum, as described in
38483 @ref{Overview}, but the checksum may be ignored by the receiver.
38485 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38486 no-acknowledgment mode, it should report that to @value{GDBN}
38487 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38488 @pxref{qSupported}.
38489 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38490 disabled via the @code{set remote noack-packet off} command
38491 (@pxref{Remote Configuration}),
38492 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38493 Only then may the stub actually turn off packet acknowledgments.
38494 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38495 response, which can be safely ignored by the stub.
38497 Note that @code{set remote noack-packet} command only affects negotiation
38498 between @value{GDBN} and the stub when subsequent connections are made;
38499 it does not affect the protocol acknowledgment state for any current
38501 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38502 new connection is established,
38503 there is also no protocol request to re-enable the acknowledgments
38504 for the current connection, once disabled.
38509 Example sequence of a target being re-started. Notice how the restart
38510 does not get any direct output:
38515 @emph{target restarts}
38518 <- @code{T001:1234123412341234}
38522 Example sequence of a target being stepped by a single instruction:
38525 -> @code{G1445@dots{}}
38530 <- @code{T001:1234123412341234}
38534 <- @code{1455@dots{}}
38538 @node File-I/O Remote Protocol Extension
38539 @section File-I/O Remote Protocol Extension
38540 @cindex File-I/O remote protocol extension
38543 * File-I/O Overview::
38544 * Protocol Basics::
38545 * The F Request Packet::
38546 * The F Reply Packet::
38547 * The Ctrl-C Message::
38549 * List of Supported Calls::
38550 * Protocol-specific Representation of Datatypes::
38552 * File-I/O Examples::
38555 @node File-I/O Overview
38556 @subsection File-I/O Overview
38557 @cindex file-i/o overview
38559 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38560 target to use the host's file system and console I/O to perform various
38561 system calls. System calls on the target system are translated into a
38562 remote protocol packet to the host system, which then performs the needed
38563 actions and returns a response packet to the target system.
38564 This simulates file system operations even on targets that lack file systems.
38566 The protocol is defined to be independent of both the host and target systems.
38567 It uses its own internal representation of datatypes and values. Both
38568 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38569 translating the system-dependent value representations into the internal
38570 protocol representations when data is transmitted.
38572 The communication is synchronous. A system call is possible only when
38573 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38574 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38575 the target is stopped to allow deterministic access to the target's
38576 memory. Therefore File-I/O is not interruptible by target signals. On
38577 the other hand, it is possible to interrupt File-I/O by a user interrupt
38578 (@samp{Ctrl-C}) within @value{GDBN}.
38580 The target's request to perform a host system call does not finish
38581 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38582 after finishing the system call, the target returns to continuing the
38583 previous activity (continue, step). No additional continue or step
38584 request from @value{GDBN} is required.
38587 (@value{GDBP}) continue
38588 <- target requests 'system call X'
38589 target is stopped, @value{GDBN} executes system call
38590 -> @value{GDBN} returns result
38591 ... target continues, @value{GDBN} returns to wait for the target
38592 <- target hits breakpoint and sends a Txx packet
38595 The protocol only supports I/O on the console and to regular files on
38596 the host file system. Character or block special devices, pipes,
38597 named pipes, sockets or any other communication method on the host
38598 system are not supported by this protocol.
38600 File I/O is not supported in non-stop mode.
38602 @node Protocol Basics
38603 @subsection Protocol Basics
38604 @cindex protocol basics, file-i/o
38606 The File-I/O protocol uses the @code{F} packet as the request as well
38607 as reply packet. Since a File-I/O system call can only occur when
38608 @value{GDBN} is waiting for a response from the continuing or stepping target,
38609 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38610 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38611 This @code{F} packet contains all information needed to allow @value{GDBN}
38612 to call the appropriate host system call:
38616 A unique identifier for the requested system call.
38619 All parameters to the system call. Pointers are given as addresses
38620 in the target memory address space. Pointers to strings are given as
38621 pointer/length pair. Numerical values are given as they are.
38622 Numerical control flags are given in a protocol-specific representation.
38626 At this point, @value{GDBN} has to perform the following actions.
38630 If the parameters include pointer values to data needed as input to a
38631 system call, @value{GDBN} requests this data from the target with a
38632 standard @code{m} packet request. This additional communication has to be
38633 expected by the target implementation and is handled as any other @code{m}
38637 @value{GDBN} translates all value from protocol representation to host
38638 representation as needed. Datatypes are coerced into the host types.
38641 @value{GDBN} calls the system call.
38644 It then coerces datatypes back to protocol representation.
38647 If the system call is expected to return data in buffer space specified
38648 by pointer parameters to the call, the data is transmitted to the
38649 target using a @code{M} or @code{X} packet. This packet has to be expected
38650 by the target implementation and is handled as any other @code{M} or @code{X}
38655 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38656 necessary information for the target to continue. This at least contains
38663 @code{errno}, if has been changed by the system call.
38670 After having done the needed type and value coercion, the target continues
38671 the latest continue or step action.
38673 @node The F Request Packet
38674 @subsection The @code{F} Request Packet
38675 @cindex file-i/o request packet
38676 @cindex @code{F} request packet
38678 The @code{F} request packet has the following format:
38681 @item F@var{call-id},@var{parameter@dots{}}
38683 @var{call-id} is the identifier to indicate the host system call to be called.
38684 This is just the name of the function.
38686 @var{parameter@dots{}} are the parameters to the system call.
38687 Parameters are hexadecimal integer values, either the actual values in case
38688 of scalar datatypes, pointers to target buffer space in case of compound
38689 datatypes and unspecified memory areas, or pointer/length pairs in case
38690 of string parameters. These are appended to the @var{call-id} as a
38691 comma-delimited list. All values are transmitted in ASCII
38692 string representation, pointer/length pairs separated by a slash.
38698 @node The F Reply Packet
38699 @subsection The @code{F} Reply Packet
38700 @cindex file-i/o reply packet
38701 @cindex @code{F} reply packet
38703 The @code{F} reply packet has the following format:
38707 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38709 @var{retcode} is the return code of the system call as hexadecimal value.
38711 @var{errno} is the @code{errno} set by the call, in protocol-specific
38713 This parameter can be omitted if the call was successful.
38715 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38716 case, @var{errno} must be sent as well, even if the call was successful.
38717 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38724 or, if the call was interrupted before the host call has been performed:
38731 assuming 4 is the protocol-specific representation of @code{EINTR}.
38736 @node The Ctrl-C Message
38737 @subsection The @samp{Ctrl-C} Message
38738 @cindex ctrl-c message, in file-i/o protocol
38740 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38741 reply packet (@pxref{The F Reply Packet}),
38742 the target should behave as if it had
38743 gotten a break message. The meaning for the target is ``system call
38744 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38745 (as with a break message) and return to @value{GDBN} with a @code{T02}
38748 It's important for the target to know in which
38749 state the system call was interrupted. There are two possible cases:
38753 The system call hasn't been performed on the host yet.
38756 The system call on the host has been finished.
38760 These two states can be distinguished by the target by the value of the
38761 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38762 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38763 on POSIX systems. In any other case, the target may presume that the
38764 system call has been finished --- successfully or not --- and should behave
38765 as if the break message arrived right after the system call.
38767 @value{GDBN} must behave reliably. If the system call has not been called
38768 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38769 @code{errno} in the packet. If the system call on the host has been finished
38770 before the user requests a break, the full action must be finished by
38771 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38772 The @code{F} packet may only be sent when either nothing has happened
38773 or the full action has been completed.
38776 @subsection Console I/O
38777 @cindex console i/o as part of file-i/o
38779 By default and if not explicitly closed by the target system, the file
38780 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38781 on the @value{GDBN} console is handled as any other file output operation
38782 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38783 by @value{GDBN} so that after the target read request from file descriptor
38784 0 all following typing is buffered until either one of the following
38789 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38791 system call is treated as finished.
38794 The user presses @key{RET}. This is treated as end of input with a trailing
38798 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38799 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38803 If the user has typed more characters than fit in the buffer given to
38804 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38805 either another @code{read(0, @dots{})} is requested by the target, or debugging
38806 is stopped at the user's request.
38809 @node List of Supported Calls
38810 @subsection List of Supported Calls
38811 @cindex list of supported file-i/o calls
38828 @unnumberedsubsubsec open
38829 @cindex open, file-i/o system call
38834 int open(const char *pathname, int flags);
38835 int open(const char *pathname, int flags, mode_t mode);
38839 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38842 @var{flags} is the bitwise @code{OR} of the following values:
38846 If the file does not exist it will be created. The host
38847 rules apply as far as file ownership and time stamps
38851 When used with @code{O_CREAT}, if the file already exists it is
38852 an error and open() fails.
38855 If the file already exists and the open mode allows
38856 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38857 truncated to zero length.
38860 The file is opened in append mode.
38863 The file is opened for reading only.
38866 The file is opened for writing only.
38869 The file is opened for reading and writing.
38873 Other bits are silently ignored.
38877 @var{mode} is the bitwise @code{OR} of the following values:
38881 User has read permission.
38884 User has write permission.
38887 Group has read permission.
38890 Group has write permission.
38893 Others have read permission.
38896 Others have write permission.
38900 Other bits are silently ignored.
38903 @item Return value:
38904 @code{open} returns the new file descriptor or -1 if an error
38911 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38914 @var{pathname} refers to a directory.
38917 The requested access is not allowed.
38920 @var{pathname} was too long.
38923 A directory component in @var{pathname} does not exist.
38926 @var{pathname} refers to a device, pipe, named pipe or socket.
38929 @var{pathname} refers to a file on a read-only filesystem and
38930 write access was requested.
38933 @var{pathname} is an invalid pointer value.
38936 No space on device to create the file.
38939 The process already has the maximum number of files open.
38942 The limit on the total number of files open on the system
38946 The call was interrupted by the user.
38952 @unnumberedsubsubsec close
38953 @cindex close, file-i/o system call
38962 @samp{Fclose,@var{fd}}
38964 @item Return value:
38965 @code{close} returns zero on success, or -1 if an error occurred.
38971 @var{fd} isn't a valid open file descriptor.
38974 The call was interrupted by the user.
38980 @unnumberedsubsubsec read
38981 @cindex read, file-i/o system call
38986 int read(int fd, void *buf, unsigned int count);
38990 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38992 @item Return value:
38993 On success, the number of bytes read is returned.
38994 Zero indicates end of file. If count is zero, read
38995 returns zero as well. On error, -1 is returned.
39001 @var{fd} is not a valid file descriptor or is not open for
39005 @var{bufptr} is an invalid pointer value.
39008 The call was interrupted by the user.
39014 @unnumberedsubsubsec write
39015 @cindex write, file-i/o system call
39020 int write(int fd, const void *buf, unsigned int count);
39024 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39026 @item Return value:
39027 On success, the number of bytes written are returned.
39028 Zero indicates nothing was written. On error, -1
39035 @var{fd} is not a valid file descriptor or is not open for
39039 @var{bufptr} is an invalid pointer value.
39042 An attempt was made to write a file that exceeds the
39043 host-specific maximum file size allowed.
39046 No space on device to write the data.
39049 The call was interrupted by the user.
39055 @unnumberedsubsubsec lseek
39056 @cindex lseek, file-i/o system call
39061 long lseek (int fd, long offset, int flag);
39065 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39067 @var{flag} is one of:
39071 The offset is set to @var{offset} bytes.
39074 The offset is set to its current location plus @var{offset}
39078 The offset is set to the size of the file plus @var{offset}
39082 @item Return value:
39083 On success, the resulting unsigned offset in bytes from
39084 the beginning of the file is returned. Otherwise, a
39085 value of -1 is returned.
39091 @var{fd} is not a valid open file descriptor.
39094 @var{fd} is associated with the @value{GDBN} console.
39097 @var{flag} is not a proper value.
39100 The call was interrupted by the user.
39106 @unnumberedsubsubsec rename
39107 @cindex rename, file-i/o system call
39112 int rename(const char *oldpath, const char *newpath);
39116 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39118 @item Return value:
39119 On success, zero is returned. On error, -1 is returned.
39125 @var{newpath} is an existing directory, but @var{oldpath} is not a
39129 @var{newpath} is a non-empty directory.
39132 @var{oldpath} or @var{newpath} is a directory that is in use by some
39136 An attempt was made to make a directory a subdirectory
39140 A component used as a directory in @var{oldpath} or new
39141 path is not a directory. Or @var{oldpath} is a directory
39142 and @var{newpath} exists but is not a directory.
39145 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39148 No access to the file or the path of the file.
39152 @var{oldpath} or @var{newpath} was too long.
39155 A directory component in @var{oldpath} or @var{newpath} does not exist.
39158 The file is on a read-only filesystem.
39161 The device containing the file has no room for the new
39165 The call was interrupted by the user.
39171 @unnumberedsubsubsec unlink
39172 @cindex unlink, file-i/o system call
39177 int unlink(const char *pathname);
39181 @samp{Funlink,@var{pathnameptr}/@var{len}}
39183 @item Return value:
39184 On success, zero is returned. On error, -1 is returned.
39190 No access to the file or the path of the file.
39193 The system does not allow unlinking of directories.
39196 The file @var{pathname} cannot be unlinked because it's
39197 being used by another process.
39200 @var{pathnameptr} is an invalid pointer value.
39203 @var{pathname} was too long.
39206 A directory component in @var{pathname} does not exist.
39209 A component of the path is not a directory.
39212 The file is on a read-only filesystem.
39215 The call was interrupted by the user.
39221 @unnumberedsubsubsec stat/fstat
39222 @cindex fstat, file-i/o system call
39223 @cindex stat, file-i/o system call
39228 int stat(const char *pathname, struct stat *buf);
39229 int fstat(int fd, struct stat *buf);
39233 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39234 @samp{Ffstat,@var{fd},@var{bufptr}}
39236 @item Return value:
39237 On success, zero is returned. On error, -1 is returned.
39243 @var{fd} is not a valid open file.
39246 A directory component in @var{pathname} does not exist or the
39247 path is an empty string.
39250 A component of the path is not a directory.
39253 @var{pathnameptr} is an invalid pointer value.
39256 No access to the file or the path of the file.
39259 @var{pathname} was too long.
39262 The call was interrupted by the user.
39268 @unnumberedsubsubsec gettimeofday
39269 @cindex gettimeofday, file-i/o system call
39274 int gettimeofday(struct timeval *tv, void *tz);
39278 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39280 @item Return value:
39281 On success, 0 is returned, -1 otherwise.
39287 @var{tz} is a non-NULL pointer.
39290 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39296 @unnumberedsubsubsec isatty
39297 @cindex isatty, file-i/o system call
39302 int isatty(int fd);
39306 @samp{Fisatty,@var{fd}}
39308 @item Return value:
39309 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39315 The call was interrupted by the user.
39320 Note that the @code{isatty} call is treated as a special case: it returns
39321 1 to the target if the file descriptor is attached
39322 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39323 would require implementing @code{ioctl} and would be more complex than
39328 @unnumberedsubsubsec system
39329 @cindex system, file-i/o system call
39334 int system(const char *command);
39338 @samp{Fsystem,@var{commandptr}/@var{len}}
39340 @item Return value:
39341 If @var{len} is zero, the return value indicates whether a shell is
39342 available. A zero return value indicates a shell is not available.
39343 For non-zero @var{len}, the value returned is -1 on error and the
39344 return status of the command otherwise. Only the exit status of the
39345 command is returned, which is extracted from the host's @code{system}
39346 return value by calling @code{WEXITSTATUS(retval)}. In case
39347 @file{/bin/sh} could not be executed, 127 is returned.
39353 The call was interrupted by the user.
39358 @value{GDBN} takes over the full task of calling the necessary host calls
39359 to perform the @code{system} call. The return value of @code{system} on
39360 the host is simplified before it's returned
39361 to the target. Any termination signal information from the child process
39362 is discarded, and the return value consists
39363 entirely of the exit status of the called command.
39365 Due to security concerns, the @code{system} call is by default refused
39366 by @value{GDBN}. The user has to allow this call explicitly with the
39367 @code{set remote system-call-allowed 1} command.
39370 @item set remote system-call-allowed
39371 @kindex set remote system-call-allowed
39372 Control whether to allow the @code{system} calls in the File I/O
39373 protocol for the remote target. The default is zero (disabled).
39375 @item show remote system-call-allowed
39376 @kindex show remote system-call-allowed
39377 Show whether the @code{system} calls are allowed in the File I/O
39381 @node Protocol-specific Representation of Datatypes
39382 @subsection Protocol-specific Representation of Datatypes
39383 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39386 * Integral Datatypes::
39388 * Memory Transfer::
39393 @node Integral Datatypes
39394 @unnumberedsubsubsec Integral Datatypes
39395 @cindex integral datatypes, in file-i/o protocol
39397 The integral datatypes used in the system calls are @code{int},
39398 @code{unsigned int}, @code{long}, @code{unsigned long},
39399 @code{mode_t}, and @code{time_t}.
39401 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39402 implemented as 32 bit values in this protocol.
39404 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39406 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39407 in @file{limits.h}) to allow range checking on host and target.
39409 @code{time_t} datatypes are defined as seconds since the Epoch.
39411 All integral datatypes transferred as part of a memory read or write of a
39412 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39415 @node Pointer Values
39416 @unnumberedsubsubsec Pointer Values
39417 @cindex pointer values, in file-i/o protocol
39419 Pointers to target data are transmitted as they are. An exception
39420 is made for pointers to buffers for which the length isn't
39421 transmitted as part of the function call, namely strings. Strings
39422 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39429 which is a pointer to data of length 18 bytes at position 0x1aaf.
39430 The length is defined as the full string length in bytes, including
39431 the trailing null byte. For example, the string @code{"hello world"}
39432 at address 0x123456 is transmitted as
39438 @node Memory Transfer
39439 @unnumberedsubsubsec Memory Transfer
39440 @cindex memory transfer, in file-i/o protocol
39442 Structured data which is transferred using a memory read or write (for
39443 example, a @code{struct stat}) is expected to be in a protocol-specific format
39444 with all scalar multibyte datatypes being big endian. Translation to
39445 this representation needs to be done both by the target before the @code{F}
39446 packet is sent, and by @value{GDBN} before
39447 it transfers memory to the target. Transferred pointers to structured
39448 data should point to the already-coerced data at any time.
39452 @unnumberedsubsubsec struct stat
39453 @cindex struct stat, in file-i/o protocol
39455 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39456 is defined as follows:
39460 unsigned int st_dev; /* device */
39461 unsigned int st_ino; /* inode */
39462 mode_t st_mode; /* protection */
39463 unsigned int st_nlink; /* number of hard links */
39464 unsigned int st_uid; /* user ID of owner */
39465 unsigned int st_gid; /* group ID of owner */
39466 unsigned int st_rdev; /* device type (if inode device) */
39467 unsigned long st_size; /* total size, in bytes */
39468 unsigned long st_blksize; /* blocksize for filesystem I/O */
39469 unsigned long st_blocks; /* number of blocks allocated */
39470 time_t st_atime; /* time of last access */
39471 time_t st_mtime; /* time of last modification */
39472 time_t st_ctime; /* time of last change */
39476 The integral datatypes conform to the definitions given in the
39477 appropriate section (see @ref{Integral Datatypes}, for details) so this
39478 structure is of size 64 bytes.
39480 The values of several fields have a restricted meaning and/or
39486 A value of 0 represents a file, 1 the console.
39489 No valid meaning for the target. Transmitted unchanged.
39492 Valid mode bits are described in @ref{Constants}. Any other
39493 bits have currently no meaning for the target.
39498 No valid meaning for the target. Transmitted unchanged.
39503 These values have a host and file system dependent
39504 accuracy. Especially on Windows hosts, the file system may not
39505 support exact timing values.
39508 The target gets a @code{struct stat} of the above representation and is
39509 responsible for coercing it to the target representation before
39512 Note that due to size differences between the host, target, and protocol
39513 representations of @code{struct stat} members, these members could eventually
39514 get truncated on the target.
39516 @node struct timeval
39517 @unnumberedsubsubsec struct timeval
39518 @cindex struct timeval, in file-i/o protocol
39520 The buffer of type @code{struct timeval} used by the File-I/O protocol
39521 is defined as follows:
39525 time_t tv_sec; /* second */
39526 long tv_usec; /* microsecond */
39530 The integral datatypes conform to the definitions given in the
39531 appropriate section (see @ref{Integral Datatypes}, for details) so this
39532 structure is of size 8 bytes.
39535 @subsection Constants
39536 @cindex constants, in file-i/o protocol
39538 The following values are used for the constants inside of the
39539 protocol. @value{GDBN} and target are responsible for translating these
39540 values before and after the call as needed.
39551 @unnumberedsubsubsec Open Flags
39552 @cindex open flags, in file-i/o protocol
39554 All values are given in hexadecimal representation.
39566 @node mode_t Values
39567 @unnumberedsubsubsec mode_t Values
39568 @cindex mode_t values, in file-i/o protocol
39570 All values are given in octal representation.
39587 @unnumberedsubsubsec Errno Values
39588 @cindex errno values, in file-i/o protocol
39590 All values are given in decimal representation.
39615 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39616 any error value not in the list of supported error numbers.
39619 @unnumberedsubsubsec Lseek Flags
39620 @cindex lseek flags, in file-i/o protocol
39629 @unnumberedsubsubsec Limits
39630 @cindex limits, in file-i/o protocol
39632 All values are given in decimal representation.
39635 INT_MIN -2147483648
39637 UINT_MAX 4294967295
39638 LONG_MIN -9223372036854775808
39639 LONG_MAX 9223372036854775807
39640 ULONG_MAX 18446744073709551615
39643 @node File-I/O Examples
39644 @subsection File-I/O Examples
39645 @cindex file-i/o examples
39647 Example sequence of a write call, file descriptor 3, buffer is at target
39648 address 0x1234, 6 bytes should be written:
39651 <- @code{Fwrite,3,1234,6}
39652 @emph{request memory read from target}
39655 @emph{return "6 bytes written"}
39659 Example sequence of a read call, file descriptor 3, buffer is at target
39660 address 0x1234, 6 bytes should be read:
39663 <- @code{Fread,3,1234,6}
39664 @emph{request memory write to target}
39665 -> @code{X1234,6:XXXXXX}
39666 @emph{return "6 bytes read"}
39670 Example sequence of a read call, call fails on the host due to invalid
39671 file descriptor (@code{EBADF}):
39674 <- @code{Fread,3,1234,6}
39678 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39682 <- @code{Fread,3,1234,6}
39687 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39691 <- @code{Fread,3,1234,6}
39692 -> @code{X1234,6:XXXXXX}
39696 @node Library List Format
39697 @section Library List Format
39698 @cindex library list format, remote protocol
39700 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39701 same process as your application to manage libraries. In this case,
39702 @value{GDBN} can use the loader's symbol table and normal memory
39703 operations to maintain a list of shared libraries. On other
39704 platforms, the operating system manages loaded libraries.
39705 @value{GDBN} can not retrieve the list of currently loaded libraries
39706 through memory operations, so it uses the @samp{qXfer:libraries:read}
39707 packet (@pxref{qXfer library list read}) instead. The remote stub
39708 queries the target's operating system and reports which libraries
39711 The @samp{qXfer:libraries:read} packet returns an XML document which
39712 lists loaded libraries and their offsets. Each library has an
39713 associated name and one or more segment or section base addresses,
39714 which report where the library was loaded in memory.
39716 For the common case of libraries that are fully linked binaries, the
39717 library should have a list of segments. If the target supports
39718 dynamic linking of a relocatable object file, its library XML element
39719 should instead include a list of allocated sections. The segment or
39720 section bases are start addresses, not relocation offsets; they do not
39721 depend on the library's link-time base addresses.
39723 @value{GDBN} must be linked with the Expat library to support XML
39724 library lists. @xref{Expat}.
39726 A simple memory map, with one loaded library relocated by a single
39727 offset, looks like this:
39731 <library name="/lib/libc.so.6">
39732 <segment address="0x10000000"/>
39737 Another simple memory map, with one loaded library with three
39738 allocated sections (.text, .data, .bss), looks like this:
39742 <library name="sharedlib.o">
39743 <section address="0x10000000"/>
39744 <section address="0x20000000"/>
39745 <section address="0x30000000"/>
39750 The format of a library list is described by this DTD:
39753 <!-- library-list: Root element with versioning -->
39754 <!ELEMENT library-list (library)*>
39755 <!ATTLIST library-list version CDATA #FIXED "1.0">
39756 <!ELEMENT library (segment*, section*)>
39757 <!ATTLIST library name CDATA #REQUIRED>
39758 <!ELEMENT segment EMPTY>
39759 <!ATTLIST segment address CDATA #REQUIRED>
39760 <!ELEMENT section EMPTY>
39761 <!ATTLIST section address CDATA #REQUIRED>
39764 In addition, segments and section descriptors cannot be mixed within a
39765 single library element, and you must supply at least one segment or
39766 section for each library.
39768 @node Library List Format for SVR4 Targets
39769 @section Library List Format for SVR4 Targets
39770 @cindex library list format, remote protocol
39772 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39773 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39774 shared libraries. Still a special library list provided by this packet is
39775 more efficient for the @value{GDBN} remote protocol.
39777 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39778 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39779 target, the following parameters are reported:
39783 @code{name}, the absolute file name from the @code{l_name} field of
39784 @code{struct link_map}.
39786 @code{lm} with address of @code{struct link_map} used for TLS
39787 (Thread Local Storage) access.
39789 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39790 @code{struct link_map}. For prelinked libraries this is not an absolute
39791 memory address. It is a displacement of absolute memory address against
39792 address the file was prelinked to during the library load.
39794 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39797 Additionally the single @code{main-lm} attribute specifies address of
39798 @code{struct link_map} used for the main executable. This parameter is used
39799 for TLS access and its presence is optional.
39801 @value{GDBN} must be linked with the Expat library to support XML
39802 SVR4 library lists. @xref{Expat}.
39804 A simple memory map, with two loaded libraries (which do not use prelink),
39808 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39809 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39811 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39813 </library-list-svr>
39816 The format of an SVR4 library list is described by this DTD:
39819 <!-- library-list-svr4: Root element with versioning -->
39820 <!ELEMENT library-list-svr4 (library)*>
39821 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39822 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39823 <!ELEMENT library EMPTY>
39824 <!ATTLIST library name CDATA #REQUIRED>
39825 <!ATTLIST library lm CDATA #REQUIRED>
39826 <!ATTLIST library l_addr CDATA #REQUIRED>
39827 <!ATTLIST library l_ld CDATA #REQUIRED>
39830 @node Memory Map Format
39831 @section Memory Map Format
39832 @cindex memory map format
39834 To be able to write into flash memory, @value{GDBN} needs to obtain a
39835 memory map from the target. This section describes the format of the
39838 The memory map is obtained using the @samp{qXfer:memory-map:read}
39839 (@pxref{qXfer memory map read}) packet and is an XML document that
39840 lists memory regions.
39842 @value{GDBN} must be linked with the Expat library to support XML
39843 memory maps. @xref{Expat}.
39845 The top-level structure of the document is shown below:
39848 <?xml version="1.0"?>
39849 <!DOCTYPE memory-map
39850 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39851 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39857 Each region can be either:
39862 A region of RAM starting at @var{addr} and extending for @var{length}
39866 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39871 A region of read-only memory:
39874 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39879 A region of flash memory, with erasure blocks @var{blocksize}
39883 <memory type="flash" start="@var{addr}" length="@var{length}">
39884 <property name="blocksize">@var{blocksize}</property>
39890 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39891 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39892 packets to write to addresses in such ranges.
39894 The formal DTD for memory map format is given below:
39897 <!-- ................................................... -->
39898 <!-- Memory Map XML DTD ................................ -->
39899 <!-- File: memory-map.dtd .............................. -->
39900 <!-- .................................... .............. -->
39901 <!-- memory-map.dtd -->
39902 <!-- memory-map: Root element with versioning -->
39903 <!ELEMENT memory-map (memory | property)>
39904 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39905 <!ELEMENT memory (property)>
39906 <!-- memory: Specifies a memory region,
39907 and its type, or device. -->
39908 <!ATTLIST memory type CDATA #REQUIRED
39909 start CDATA #REQUIRED
39910 length CDATA #REQUIRED
39911 device CDATA #IMPLIED>
39912 <!-- property: Generic attribute tag -->
39913 <!ELEMENT property (#PCDATA | property)*>
39914 <!ATTLIST property name CDATA #REQUIRED>
39917 @node Thread List Format
39918 @section Thread List Format
39919 @cindex thread list format
39921 To efficiently update the list of threads and their attributes,
39922 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39923 (@pxref{qXfer threads read}) and obtains the XML document with
39924 the following structure:
39927 <?xml version="1.0"?>
39929 <thread id="id" core="0" name="name">
39930 ... description ...
39935 Each @samp{thread} element must have the @samp{id} attribute that
39936 identifies the thread (@pxref{thread-id syntax}). The
39937 @samp{core} attribute, if present, specifies which processor core
39938 the thread was last executing on. The @samp{name} attribute, if
39939 present, specifies the human-readable name of the thread. The content
39940 of the of @samp{thread} element is interpreted as human-readable
39941 auxiliary information.
39943 @node Traceframe Info Format
39944 @section Traceframe Info Format
39945 @cindex traceframe info format
39947 To be able to know which objects in the inferior can be examined when
39948 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39949 memory ranges, registers and trace state variables that have been
39950 collected in a traceframe.
39952 This list is obtained using the @samp{qXfer:traceframe-info:read}
39953 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39955 @value{GDBN} must be linked with the Expat library to support XML
39956 traceframe info discovery. @xref{Expat}.
39958 The top-level structure of the document is shown below:
39961 <?xml version="1.0"?>
39962 <!DOCTYPE traceframe-info
39963 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39964 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39970 Each traceframe block can be either:
39975 A region of collected memory starting at @var{addr} and extending for
39976 @var{length} bytes from there:
39979 <memory start="@var{addr}" length="@var{length}"/>
39983 A block indicating trace state variable numbered @var{number} has been
39987 <tvar id="@var{number}"/>
39992 The formal DTD for the traceframe info format is given below:
39995 <!ELEMENT traceframe-info (memory | tvar)* >
39996 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39998 <!ELEMENT memory EMPTY>
39999 <!ATTLIST memory start CDATA #REQUIRED
40000 length CDATA #REQUIRED>
40002 <!ATTLIST tvar id CDATA #REQUIRED>
40005 @node Branch Trace Format
40006 @section Branch Trace Format
40007 @cindex branch trace format
40009 In order to display the branch trace of an inferior thread,
40010 @value{GDBN} needs to obtain the list of branches. This list is
40011 represented as list of sequential code blocks that are connected via
40012 branches. The code in each block has been executed sequentially.
40014 This list is obtained using the @samp{qXfer:btrace:read}
40015 (@pxref{qXfer btrace read}) packet and is an XML document.
40017 @value{GDBN} must be linked with the Expat library to support XML
40018 traceframe info discovery. @xref{Expat}.
40020 The top-level structure of the document is shown below:
40023 <?xml version="1.0"?>
40025 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40026 "http://sourceware.org/gdb/gdb-btrace.dtd">
40035 A block of sequentially executed instructions starting at @var{begin}
40036 and ending at @var{end}:
40039 <block begin="@var{begin}" end="@var{end}"/>
40044 The formal DTD for the branch trace format is given below:
40047 <!ELEMENT btrace (block* | pt) >
40048 <!ATTLIST btrace version CDATA #FIXED "1.0">
40050 <!ELEMENT block EMPTY>
40051 <!ATTLIST block begin CDATA #REQUIRED
40052 end CDATA #REQUIRED>
40054 <!ELEMENT pt (pt-config?, raw?)>
40056 <!ELEMENT pt-config (cpu?)>
40058 <!ELEMENT cpu EMPTY>
40059 <!ATTLIST cpu vendor CDATA #REQUIRED
40060 family CDATA #REQUIRED
40061 model CDATA #REQUIRED
40062 stepping CDATA #REQUIRED>
40064 <!ELEMENT raw (#PCDATA)>
40067 @node Branch Trace Configuration Format
40068 @section Branch Trace Configuration Format
40069 @cindex branch trace configuration format
40071 For each inferior thread, @value{GDBN} can obtain the branch trace
40072 configuration using the @samp{qXfer:btrace-conf:read}
40073 (@pxref{qXfer btrace-conf read}) packet.
40075 The configuration describes the branch trace format and configuration
40076 settings for that format. The following information is described:
40080 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40083 The size of the @acronym{BTS} ring buffer in bytes.
40086 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40090 The size of the @acronym{Intel PT} ring buffer in bytes.
40094 @value{GDBN} must be linked with the Expat library to support XML
40095 branch trace configuration discovery. @xref{Expat}.
40097 The formal DTD for the branch trace configuration format is given below:
40100 <!ELEMENT btrace-conf (bts?, pt?)>
40101 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40103 <!ELEMENT bts EMPTY>
40104 <!ATTLIST bts size CDATA #IMPLIED>
40106 <!ELEMENT pt EMPTY>
40107 <!ATTLIST pt size CDATA #IMPLIED>
40110 @include agentexpr.texi
40112 @node Target Descriptions
40113 @appendix Target Descriptions
40114 @cindex target descriptions
40116 One of the challenges of using @value{GDBN} to debug embedded systems
40117 is that there are so many minor variants of each processor
40118 architecture in use. It is common practice for vendors to start with
40119 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40120 and then make changes to adapt it to a particular market niche. Some
40121 architectures have hundreds of variants, available from dozens of
40122 vendors. This leads to a number of problems:
40126 With so many different customized processors, it is difficult for
40127 the @value{GDBN} maintainers to keep up with the changes.
40129 Since individual variants may have short lifetimes or limited
40130 audiences, it may not be worthwhile to carry information about every
40131 variant in the @value{GDBN} source tree.
40133 When @value{GDBN} does support the architecture of the embedded system
40134 at hand, the task of finding the correct architecture name to give the
40135 @command{set architecture} command can be error-prone.
40138 To address these problems, the @value{GDBN} remote protocol allows a
40139 target system to not only identify itself to @value{GDBN}, but to
40140 actually describe its own features. This lets @value{GDBN} support
40141 processor variants it has never seen before --- to the extent that the
40142 descriptions are accurate, and that @value{GDBN} understands them.
40144 @value{GDBN} must be linked with the Expat library to support XML
40145 target descriptions. @xref{Expat}.
40148 * Retrieving Descriptions:: How descriptions are fetched from a target.
40149 * Target Description Format:: The contents of a target description.
40150 * Predefined Target Types:: Standard types available for target
40152 * Standard Target Features:: Features @value{GDBN} knows about.
40155 @node Retrieving Descriptions
40156 @section Retrieving Descriptions
40158 Target descriptions can be read from the target automatically, or
40159 specified by the user manually. The default behavior is to read the
40160 description from the target. @value{GDBN} retrieves it via the remote
40161 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40162 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40163 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40164 XML document, of the form described in @ref{Target Description
40167 Alternatively, you can specify a file to read for the target description.
40168 If a file is set, the target will not be queried. The commands to
40169 specify a file are:
40172 @cindex set tdesc filename
40173 @item set tdesc filename @var{path}
40174 Read the target description from @var{path}.
40176 @cindex unset tdesc filename
40177 @item unset tdesc filename
40178 Do not read the XML target description from a file. @value{GDBN}
40179 will use the description supplied by the current target.
40181 @cindex show tdesc filename
40182 @item show tdesc filename
40183 Show the filename to read for a target description, if any.
40187 @node Target Description Format
40188 @section Target Description Format
40189 @cindex target descriptions, XML format
40191 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40192 document which complies with the Document Type Definition provided in
40193 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40194 means you can use generally available tools like @command{xmllint} to
40195 check that your feature descriptions are well-formed and valid.
40196 However, to help people unfamiliar with XML write descriptions for
40197 their targets, we also describe the grammar here.
40199 Target descriptions can identify the architecture of the remote target
40200 and (for some architectures) provide information about custom register
40201 sets. They can also identify the OS ABI of the remote target.
40202 @value{GDBN} can use this information to autoconfigure for your
40203 target, or to warn you if you connect to an unsupported target.
40205 Here is a simple target description:
40208 <target version="1.0">
40209 <architecture>i386:x86-64</architecture>
40214 This minimal description only says that the target uses
40215 the x86-64 architecture.
40217 A target description has the following overall form, with [ ] marking
40218 optional elements and @dots{} marking repeatable elements. The elements
40219 are explained further below.
40222 <?xml version="1.0"?>
40223 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40224 <target version="1.0">
40225 @r{[}@var{architecture}@r{]}
40226 @r{[}@var{osabi}@r{]}
40227 @r{[}@var{compatible}@r{]}
40228 @r{[}@var{feature}@dots{}@r{]}
40233 The description is generally insensitive to whitespace and line
40234 breaks, under the usual common-sense rules. The XML version
40235 declaration and document type declaration can generally be omitted
40236 (@value{GDBN} does not require them), but specifying them may be
40237 useful for XML validation tools. The @samp{version} attribute for
40238 @samp{<target>} may also be omitted, but we recommend
40239 including it; if future versions of @value{GDBN} use an incompatible
40240 revision of @file{gdb-target.dtd}, they will detect and report
40241 the version mismatch.
40243 @subsection Inclusion
40244 @cindex target descriptions, inclusion
40247 @cindex <xi:include>
40250 It can sometimes be valuable to split a target description up into
40251 several different annexes, either for organizational purposes, or to
40252 share files between different possible target descriptions. You can
40253 divide a description into multiple files by replacing any element of
40254 the target description with an inclusion directive of the form:
40257 <xi:include href="@var{document}"/>
40261 When @value{GDBN} encounters an element of this form, it will retrieve
40262 the named XML @var{document}, and replace the inclusion directive with
40263 the contents of that document. If the current description was read
40264 using @samp{qXfer}, then so will be the included document;
40265 @var{document} will be interpreted as the name of an annex. If the
40266 current description was read from a file, @value{GDBN} will look for
40267 @var{document} as a file in the same directory where it found the
40268 original description.
40270 @subsection Architecture
40271 @cindex <architecture>
40273 An @samp{<architecture>} element has this form:
40276 <architecture>@var{arch}</architecture>
40279 @var{arch} is one of the architectures from the set accepted by
40280 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40283 @cindex @code{<osabi>}
40285 This optional field was introduced in @value{GDBN} version 7.0.
40286 Previous versions of @value{GDBN} ignore it.
40288 An @samp{<osabi>} element has this form:
40291 <osabi>@var{abi-name}</osabi>
40294 @var{abi-name} is an OS ABI name from the same selection accepted by
40295 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40297 @subsection Compatible Architecture
40298 @cindex @code{<compatible>}
40300 This optional field was introduced in @value{GDBN} version 7.0.
40301 Previous versions of @value{GDBN} ignore it.
40303 A @samp{<compatible>} element has this form:
40306 <compatible>@var{arch}</compatible>
40309 @var{arch} is one of the architectures from the set accepted by
40310 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40312 A @samp{<compatible>} element is used to specify that the target
40313 is able to run binaries in some other than the main target architecture
40314 given by the @samp{<architecture>} element. For example, on the
40315 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40316 or @code{powerpc:common64}, but the system is able to run binaries
40317 in the @code{spu} architecture as well. The way to describe this
40318 capability with @samp{<compatible>} is as follows:
40321 <architecture>powerpc:common</architecture>
40322 <compatible>spu</compatible>
40325 @subsection Features
40328 Each @samp{<feature>} describes some logical portion of the target
40329 system. Features are currently used to describe available CPU
40330 registers and the types of their contents. A @samp{<feature>} element
40334 <feature name="@var{name}">
40335 @r{[}@var{type}@dots{}@r{]}
40341 Each feature's name should be unique within the description. The name
40342 of a feature does not matter unless @value{GDBN} has some special
40343 knowledge of the contents of that feature; if it does, the feature
40344 should have its standard name. @xref{Standard Target Features}.
40348 Any register's value is a collection of bits which @value{GDBN} must
40349 interpret. The default interpretation is a two's complement integer,
40350 but other types can be requested by name in the register description.
40351 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40352 Target Types}), and the description can define additional composite types.
40354 Each type element must have an @samp{id} attribute, which gives
40355 a unique (within the containing @samp{<feature>}) name to the type.
40356 Types must be defined before they are used.
40359 Some targets offer vector registers, which can be treated as arrays
40360 of scalar elements. These types are written as @samp{<vector>} elements,
40361 specifying the array element type, @var{type}, and the number of elements,
40365 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40369 If a register's value is usefully viewed in multiple ways, define it
40370 with a union type containing the useful representations. The
40371 @samp{<union>} element contains one or more @samp{<field>} elements,
40372 each of which has a @var{name} and a @var{type}:
40375 <union id="@var{id}">
40376 <field name="@var{name}" type="@var{type}"/>
40382 If a register's value is composed from several separate values, define
40383 it with a structure type. There are two forms of the @samp{<struct>}
40384 element; a @samp{<struct>} element must either contain only bitfields
40385 or contain no bitfields. If the structure contains only bitfields,
40386 its total size in bytes must be specified, each bitfield must have an
40387 explicit start and end, and bitfields are automatically assigned an
40388 integer type. The field's @var{start} should be less than or
40389 equal to its @var{end}, and zero represents the least significant bit.
40392 <struct id="@var{id}" size="@var{size}">
40393 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40398 If the structure contains no bitfields, then each field has an
40399 explicit type, and no implicit padding is added.
40402 <struct id="@var{id}">
40403 <field name="@var{name}" type="@var{type}"/>
40409 If a register's value is a series of single-bit flags, define it with
40410 a flags type. The @samp{<flags>} element has an explicit @var{size}
40411 and contains one or more @samp{<field>} elements. Each field has a
40412 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40416 <flags id="@var{id}" size="@var{size}">
40417 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40422 @subsection Registers
40425 Each register is represented as an element with this form:
40428 <reg name="@var{name}"
40429 bitsize="@var{size}"
40430 @r{[}regnum="@var{num}"@r{]}
40431 @r{[}save-restore="@var{save-restore}"@r{]}
40432 @r{[}type="@var{type}"@r{]}
40433 @r{[}group="@var{group}"@r{]}/>
40437 The components are as follows:
40442 The register's name; it must be unique within the target description.
40445 The register's size, in bits.
40448 The register's number. If omitted, a register's number is one greater
40449 than that of the previous register (either in the current feature or in
40450 a preceding feature); the first register in the target description
40451 defaults to zero. This register number is used to read or write
40452 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40453 packets, and registers appear in the @code{g} and @code{G} packets
40454 in order of increasing register number.
40457 Whether the register should be preserved across inferior function
40458 calls; this must be either @code{yes} or @code{no}. The default is
40459 @code{yes}, which is appropriate for most registers except for
40460 some system control registers; this is not related to the target's
40464 The type of the register. It may be a predefined type, a type
40465 defined in the current feature, or one of the special types @code{int}
40466 and @code{float}. @code{int} is an integer type of the correct size
40467 for @var{bitsize}, and @code{float} is a floating point type (in the
40468 architecture's normal floating point format) of the correct size for
40469 @var{bitsize}. The default is @code{int}.
40472 The register group to which this register belongs. It must
40473 be either @code{general}, @code{float}, or @code{vector}. If no
40474 @var{group} is specified, @value{GDBN} will not display the register
40475 in @code{info registers}.
40479 @node Predefined Target Types
40480 @section Predefined Target Types
40481 @cindex target descriptions, predefined types
40483 Type definitions in the self-description can build up composite types
40484 from basic building blocks, but can not define fundamental types. Instead,
40485 standard identifiers are provided by @value{GDBN} for the fundamental
40486 types. The currently supported types are:
40495 Signed integer types holding the specified number of bits.
40502 Unsigned integer types holding the specified number of bits.
40506 Pointers to unspecified code and data. The program counter and
40507 any dedicated return address register may be marked as code
40508 pointers; printing a code pointer converts it into a symbolic
40509 address. The stack pointer and any dedicated address registers
40510 may be marked as data pointers.
40513 Single precision IEEE floating point.
40516 Double precision IEEE floating point.
40519 The 12-byte extended precision format used by ARM FPA registers.
40522 The 10-byte extended precision format used by x87 registers.
40525 32bit @sc{eflags} register used by x86.
40528 32bit @sc{mxcsr} register used by x86.
40532 @node Standard Target Features
40533 @section Standard Target Features
40534 @cindex target descriptions, standard features
40536 A target description must contain either no registers or all the
40537 target's registers. If the description contains no registers, then
40538 @value{GDBN} will assume a default register layout, selected based on
40539 the architecture. If the description contains any registers, the
40540 default layout will not be used; the standard registers must be
40541 described in the target description, in such a way that @value{GDBN}
40542 can recognize them.
40544 This is accomplished by giving specific names to feature elements
40545 which contain standard registers. @value{GDBN} will look for features
40546 with those names and verify that they contain the expected registers;
40547 if any known feature is missing required registers, or if any required
40548 feature is missing, @value{GDBN} will reject the target
40549 description. You can add additional registers to any of the
40550 standard features --- @value{GDBN} will display them just as if
40551 they were added to an unrecognized feature.
40553 This section lists the known features and their expected contents.
40554 Sample XML documents for these features are included in the
40555 @value{GDBN} source tree, in the directory @file{gdb/features}.
40557 Names recognized by @value{GDBN} should include the name of the
40558 company or organization which selected the name, and the overall
40559 architecture to which the feature applies; so e.g.@: the feature
40560 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40562 The names of registers are not case sensitive for the purpose
40563 of recognizing standard features, but @value{GDBN} will only display
40564 registers using the capitalization used in the description.
40567 * AArch64 Features::
40570 * MicroBlaze Features::
40573 * Nios II Features::
40574 * PowerPC Features::
40575 * S/390 and System z Features::
40580 @node AArch64 Features
40581 @subsection AArch64 Features
40582 @cindex target descriptions, AArch64 features
40584 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40585 targets. It should contain registers @samp{x0} through @samp{x30},
40586 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40588 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40589 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40593 @subsection ARM Features
40594 @cindex target descriptions, ARM features
40596 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40598 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40599 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40601 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40602 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40603 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40606 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40607 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40609 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40610 it should contain at least registers @samp{wR0} through @samp{wR15} and
40611 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40612 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40614 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40615 should contain at least registers @samp{d0} through @samp{d15}. If
40616 they are present, @samp{d16} through @samp{d31} should also be included.
40617 @value{GDBN} will synthesize the single-precision registers from
40618 halves of the double-precision registers.
40620 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40621 need to contain registers; it instructs @value{GDBN} to display the
40622 VFP double-precision registers as vectors and to synthesize the
40623 quad-precision registers from pairs of double-precision registers.
40624 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40625 be present and include 32 double-precision registers.
40627 @node i386 Features
40628 @subsection i386 Features
40629 @cindex target descriptions, i386 features
40631 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40632 targets. It should describe the following registers:
40636 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40638 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40640 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40641 @samp{fs}, @samp{gs}
40643 @samp{st0} through @samp{st7}
40645 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40646 @samp{foseg}, @samp{fooff} and @samp{fop}
40649 The register sets may be different, depending on the target.
40651 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40652 describe registers:
40656 @samp{xmm0} through @samp{xmm7} for i386
40658 @samp{xmm0} through @samp{xmm15} for amd64
40663 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40664 @samp{org.gnu.gdb.i386.sse} feature. It should
40665 describe the upper 128 bits of @sc{ymm} registers:
40669 @samp{ymm0h} through @samp{ymm7h} for i386
40671 @samp{ymm0h} through @samp{ymm15h} for amd64
40674 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
40675 Memory Protection Extension (MPX). It should describe the following registers:
40679 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40681 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40684 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40685 describe a single register, @samp{orig_eax}.
40687 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40688 @samp{org.gnu.gdb.i386.avx} feature. It should
40689 describe additional @sc{xmm} registers:
40693 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40696 It should describe the upper 128 bits of additional @sc{ymm} registers:
40700 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40704 describe the upper 256 bits of @sc{zmm} registers:
40708 @samp{zmm0h} through @samp{zmm7h} for i386.
40710 @samp{zmm0h} through @samp{zmm15h} for amd64.
40714 describe the additional @sc{zmm} registers:
40718 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40721 @node MicroBlaze Features
40722 @subsection MicroBlaze Features
40723 @cindex target descriptions, MicroBlaze features
40725 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40726 targets. It should contain registers @samp{r0} through @samp{r31},
40727 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40728 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40729 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40731 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40732 If present, it should contain registers @samp{rshr} and @samp{rslr}
40734 @node MIPS Features
40735 @subsection @acronym{MIPS} Features
40736 @cindex target descriptions, @acronym{MIPS} features
40738 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40739 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40740 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40743 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40744 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40745 registers. They may be 32-bit or 64-bit depending on the target.
40747 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40748 it may be optional in a future version of @value{GDBN}. It should
40749 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40750 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40752 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40753 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40754 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40755 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40757 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40758 contain a single register, @samp{restart}, which is used by the
40759 Linux kernel to control restartable syscalls.
40761 @node M68K Features
40762 @subsection M68K Features
40763 @cindex target descriptions, M68K features
40766 @item @samp{org.gnu.gdb.m68k.core}
40767 @itemx @samp{org.gnu.gdb.coldfire.core}
40768 @itemx @samp{org.gnu.gdb.fido.core}
40769 One of those features must be always present.
40770 The feature that is present determines which flavor of m68k is
40771 used. The feature that is present should contain registers
40772 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40773 @samp{sp}, @samp{ps} and @samp{pc}.
40775 @item @samp{org.gnu.gdb.coldfire.fp}
40776 This feature is optional. If present, it should contain registers
40777 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40781 @node Nios II Features
40782 @subsection Nios II Features
40783 @cindex target descriptions, Nios II features
40785 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40786 targets. It should contain the 32 core registers (@samp{zero},
40787 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40788 @samp{pc}, and the 16 control registers (@samp{status} through
40791 @node PowerPC Features
40792 @subsection PowerPC Features
40793 @cindex target descriptions, PowerPC features
40795 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40796 targets. It should contain registers @samp{r0} through @samp{r31},
40797 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40798 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40800 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40801 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40803 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40804 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40807 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40808 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40809 will combine these registers with the floating point registers
40810 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40811 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40812 through @samp{vs63}, the set of vector registers for POWER7.
40814 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40815 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40816 @samp{spefscr}. SPE targets should provide 32-bit registers in
40817 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40818 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40819 these to present registers @samp{ev0} through @samp{ev31} to the
40822 @node S/390 and System z Features
40823 @subsection S/390 and System z Features
40824 @cindex target descriptions, S/390 features
40825 @cindex target descriptions, System z features
40827 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40828 System z targets. It should contain the PSW and the 16 general
40829 registers. In particular, System z targets should provide the 64-bit
40830 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40831 S/390 targets should provide the 32-bit versions of these registers.
40832 A System z target that runs in 31-bit addressing mode should provide
40833 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40834 register's upper halves @samp{r0h} through @samp{r15h}, and their
40835 lower halves @samp{r0l} through @samp{r15l}.
40837 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40838 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40841 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40842 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40844 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40845 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40846 targets and 32-bit otherwise. In addition, the feature may contain
40847 the @samp{last_break} register, whose width depends on the addressing
40848 mode, as well as the @samp{system_call} register, which is always
40851 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40852 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40853 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40855 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40856 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40857 combined by @value{GDBN} with the floating point registers @samp{f0}
40858 through @samp{f15} to present the 128-bit wide vector registers
40859 @samp{v0} through @samp{v15}. In addition, this feature should
40860 contain the 128-bit wide vector registers @samp{v16} through
40863 @node TIC6x Features
40864 @subsection TMS320C6x Features
40865 @cindex target descriptions, TIC6x features
40866 @cindex target descriptions, TMS320C6x features
40867 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40868 targets. It should contain registers @samp{A0} through @samp{A15},
40869 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40871 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40872 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40873 through @samp{B31}.
40875 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40876 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40878 @node Operating System Information
40879 @appendix Operating System Information
40880 @cindex operating system information
40886 Users of @value{GDBN} often wish to obtain information about the state of
40887 the operating system running on the target---for example the list of
40888 processes, or the list of open files. This section describes the
40889 mechanism that makes it possible. This mechanism is similar to the
40890 target features mechanism (@pxref{Target Descriptions}), but focuses
40891 on a different aspect of target.
40893 Operating system information is retrived from the target via the
40894 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40895 read}). The object name in the request should be @samp{osdata}, and
40896 the @var{annex} identifies the data to be fetched.
40899 @appendixsection Process list
40900 @cindex operating system information, process list
40902 When requesting the process list, the @var{annex} field in the
40903 @samp{qXfer} request should be @samp{processes}. The returned data is
40904 an XML document. The formal syntax of this document is defined in
40905 @file{gdb/features/osdata.dtd}.
40907 An example document is:
40910 <?xml version="1.0"?>
40911 <!DOCTYPE target SYSTEM "osdata.dtd">
40912 <osdata type="processes">
40914 <column name="pid">1</column>
40915 <column name="user">root</column>
40916 <column name="command">/sbin/init</column>
40917 <column name="cores">1,2,3</column>
40922 Each item should include a column whose name is @samp{pid}. The value
40923 of that column should identify the process on the target. The
40924 @samp{user} and @samp{command} columns are optional, and will be
40925 displayed by @value{GDBN}. The @samp{cores} column, if present,
40926 should contain a comma-separated list of cores that this process
40927 is running on. Target may provide additional columns,
40928 which @value{GDBN} currently ignores.
40930 @node Trace File Format
40931 @appendix Trace File Format
40932 @cindex trace file format
40934 The trace file comes in three parts: a header, a textual description
40935 section, and a trace frame section with binary data.
40937 The header has the form @code{\x7fTRACE0\n}. The first byte is
40938 @code{0x7f} so as to indicate that the file contains binary data,
40939 while the @code{0} is a version number that may have different values
40942 The description section consists of multiple lines of @sc{ascii} text
40943 separated by newline characters (@code{0xa}). The lines may include a
40944 variety of optional descriptive or context-setting information, such
40945 as tracepoint definitions or register set size. @value{GDBN} will
40946 ignore any line that it does not recognize. An empty line marks the end
40949 @c FIXME add some specific types of data
40951 The trace frame section consists of a number of consecutive frames.
40952 Each frame begins with a two-byte tracepoint number, followed by a
40953 four-byte size giving the amount of data in the frame. The data in
40954 the frame consists of a number of blocks, each introduced by a
40955 character indicating its type (at least register, memory, and trace
40956 state variable). The data in this section is raw binary, not a
40957 hexadecimal or other encoding; its endianness matches the target's
40960 @c FIXME bi-arch may require endianness/arch info in description section
40963 @item R @var{bytes}
40964 Register block. The number and ordering of bytes matches that of a
40965 @code{g} packet in the remote protocol. Note that these are the
40966 actual bytes, in target order and @value{GDBN} register order, not a
40967 hexadecimal encoding.
40969 @item M @var{address} @var{length} @var{bytes}...
40970 Memory block. This is a contiguous block of memory, at the 8-byte
40971 address @var{address}, with a 2-byte length @var{length}, followed by
40972 @var{length} bytes.
40974 @item V @var{number} @var{value}
40975 Trace state variable block. This records the 8-byte signed value
40976 @var{value} of trace state variable numbered @var{number}.
40980 Future enhancements of the trace file format may include additional types
40983 @node Index Section Format
40984 @appendix @code{.gdb_index} section format
40985 @cindex .gdb_index section format
40986 @cindex index section format
40988 This section documents the index section that is created by @code{save
40989 gdb-index} (@pxref{Index Files}). The index section is
40990 DWARF-specific; some knowledge of DWARF is assumed in this
40993 The mapped index file format is designed to be directly
40994 @code{mmap}able on any architecture. In most cases, a datum is
40995 represented using a little-endian 32-bit integer value, called an
40996 @code{offset_type}. Big endian machines must byte-swap the values
40997 before using them. Exceptions to this rule are noted. The data is
40998 laid out such that alignment is always respected.
41000 A mapped index consists of several areas, laid out in order.
41004 The file header. This is a sequence of values, of @code{offset_type}
41005 unless otherwise noted:
41009 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41010 Version 4 uses a different hashing function from versions 5 and 6.
41011 Version 6 includes symbols for inlined functions, whereas versions 4
41012 and 5 do not. Version 7 adds attributes to the CU indices in the
41013 symbol table. Version 8 specifies that symbols from DWARF type units
41014 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41015 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41017 @value{GDBN} will only read version 4, 5, or 6 indices
41018 by specifying @code{set use-deprecated-index-sections on}.
41019 GDB has a workaround for potentially broken version 7 indices so it is
41020 currently not flagged as deprecated.
41023 The offset, from the start of the file, of the CU list.
41026 The offset, from the start of the file, of the types CU list. Note
41027 that this area can be empty, in which case this offset will be equal
41028 to the next offset.
41031 The offset, from the start of the file, of the address area.
41034 The offset, from the start of the file, of the symbol table.
41037 The offset, from the start of the file, of the constant pool.
41041 The CU list. This is a sequence of pairs of 64-bit little-endian
41042 values, sorted by the CU offset. The first element in each pair is
41043 the offset of a CU in the @code{.debug_info} section. The second
41044 element in each pair is the length of that CU. References to a CU
41045 elsewhere in the map are done using a CU index, which is just the
41046 0-based index into this table. Note that if there are type CUs, then
41047 conceptually CUs and type CUs form a single list for the purposes of
41051 The types CU list. This is a sequence of triplets of 64-bit
41052 little-endian values. In a triplet, the first value is the CU offset,
41053 the second value is the type offset in the CU, and the third value is
41054 the type signature. The types CU list is not sorted.
41057 The address area. The address area consists of a sequence of address
41058 entries. Each address entry has three elements:
41062 The low address. This is a 64-bit little-endian value.
41065 The high address. This is a 64-bit little-endian value. Like
41066 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41069 The CU index. This is an @code{offset_type} value.
41073 The symbol table. This is an open-addressed hash table. The size of
41074 the hash table is always a power of 2.
41076 Each slot in the hash table consists of a pair of @code{offset_type}
41077 values. The first value is the offset of the symbol's name in the
41078 constant pool. The second value is the offset of the CU vector in the
41081 If both values are 0, then this slot in the hash table is empty. This
41082 is ok because while 0 is a valid constant pool index, it cannot be a
41083 valid index for both a string and a CU vector.
41085 The hash value for a table entry is computed by applying an
41086 iterative hash function to the symbol's name. Starting with an
41087 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41088 the string is incorporated into the hash using the formula depending on the
41093 The formula is @code{r = r * 67 + c - 113}.
41095 @item Versions 5 to 7
41096 The formula is @code{r = r * 67 + tolower (c) - 113}.
41099 The terminating @samp{\0} is not incorporated into the hash.
41101 The step size used in the hash table is computed via
41102 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41103 value, and @samp{size} is the size of the hash table. The step size
41104 is used to find the next candidate slot when handling a hash
41107 The names of C@t{++} symbols in the hash table are canonicalized. We
41108 don't currently have a simple description of the canonicalization
41109 algorithm; if you intend to create new index sections, you must read
41113 The constant pool. This is simply a bunch of bytes. It is organized
41114 so that alignment is correct: CU vectors are stored first, followed by
41117 A CU vector in the constant pool is a sequence of @code{offset_type}
41118 values. The first value is the number of CU indices in the vector.
41119 Each subsequent value is the index and symbol attributes of a CU in
41120 the CU list. This element in the hash table is used to indicate which
41121 CUs define the symbol and how the symbol is used.
41122 See below for the format of each CU index+attributes entry.
41124 A string in the constant pool is zero-terminated.
41127 Attributes were added to CU index values in @code{.gdb_index} version 7.
41128 If a symbol has multiple uses within a CU then there is one
41129 CU index+attributes value for each use.
41131 The format of each CU index+attributes entry is as follows
41137 This is the index of the CU in the CU list.
41139 These bits are reserved for future purposes and must be zero.
41141 The kind of the symbol in the CU.
41145 This value is reserved and should not be used.
41146 By reserving zero the full @code{offset_type} value is backwards compatible
41147 with previous versions of the index.
41149 The symbol is a type.
41151 The symbol is a variable or an enum value.
41153 The symbol is a function.
41155 Any other kind of symbol.
41157 These values are reserved.
41161 This bit is zero if the value is global and one if it is static.
41163 The determination of whether a symbol is global or static is complicated.
41164 The authorative reference is the file @file{dwarf2read.c} in
41165 @value{GDBN} sources.
41169 This pseudo-code describes the computation of a symbol's kind and
41170 global/static attributes in the index.
41173 is_external = get_attribute (die, DW_AT_external);
41174 language = get_attribute (cu_die, DW_AT_language);
41177 case DW_TAG_typedef:
41178 case DW_TAG_base_type:
41179 case DW_TAG_subrange_type:
41183 case DW_TAG_enumerator:
41185 is_static = (language != CPLUS && language != JAVA);
41187 case DW_TAG_subprogram:
41189 is_static = ! (is_external || language == ADA);
41191 case DW_TAG_constant:
41193 is_static = ! is_external;
41195 case DW_TAG_variable:
41197 is_static = ! is_external;
41199 case DW_TAG_namespace:
41203 case DW_TAG_class_type:
41204 case DW_TAG_interface_type:
41205 case DW_TAG_structure_type:
41206 case DW_TAG_union_type:
41207 case DW_TAG_enumeration_type:
41209 is_static = (language != CPLUS && language != JAVA);
41217 @appendix Manual pages
41221 * gdb man:: The GNU Debugger man page
41222 * gdbserver man:: Remote Server for the GNU Debugger man page
41223 * gcore man:: Generate a core file of a running program
41224 * gdbinit man:: gdbinit scripts
41230 @c man title gdb The GNU Debugger
41232 @c man begin SYNOPSIS gdb
41233 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41234 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41235 [@option{-b}@w{ }@var{bps}]
41236 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41237 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41238 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41239 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41240 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41243 @c man begin DESCRIPTION gdb
41244 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41245 going on ``inside'' another program while it executes -- or what another
41246 program was doing at the moment it crashed.
41248 @value{GDBN} can do four main kinds of things (plus other things in support of
41249 these) to help you catch bugs in the act:
41253 Start your program, specifying anything that might affect its behavior.
41256 Make your program stop on specified conditions.
41259 Examine what has happened, when your program has stopped.
41262 Change things in your program, so you can experiment with correcting the
41263 effects of one bug and go on to learn about another.
41266 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41269 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41270 commands from the terminal until you tell it to exit with the @value{GDBN}
41271 command @code{quit}. You can get online help from @value{GDBN} itself
41272 by using the command @code{help}.
41274 You can run @code{gdb} with no arguments or options; but the most
41275 usual way to start @value{GDBN} is with one argument or two, specifying an
41276 executable program as the argument:
41282 You can also start with both an executable program and a core file specified:
41288 You can, instead, specify a process ID as a second argument, if you want
41289 to debug a running process:
41297 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41298 named @file{1234}; @value{GDBN} does check for a core file first).
41299 With option @option{-p} you can omit the @var{program} filename.
41301 Here are some of the most frequently needed @value{GDBN} commands:
41303 @c pod2man highlights the right hand side of the @item lines.
41305 @item break [@var{file}:]@var{functiop}
41306 Set a breakpoint at @var{function} (in @var{file}).
41308 @item run [@var{arglist}]
41309 Start your program (with @var{arglist}, if specified).
41312 Backtrace: display the program stack.
41314 @item print @var{expr}
41315 Display the value of an expression.
41318 Continue running your program (after stopping, e.g. at a breakpoint).
41321 Execute next program line (after stopping); step @emph{over} any
41322 function calls in the line.
41324 @item edit [@var{file}:]@var{function}
41325 look at the program line where it is presently stopped.
41327 @item list [@var{file}:]@var{function}
41328 type the text of the program in the vicinity of where it is presently stopped.
41331 Execute next program line (after stopping); step @emph{into} any
41332 function calls in the line.
41334 @item help [@var{name}]
41335 Show information about @value{GDBN} command @var{name}, or general information
41336 about using @value{GDBN}.
41339 Exit from @value{GDBN}.
41343 For full details on @value{GDBN},
41344 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41345 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41346 as the @code{gdb} entry in the @code{info} program.
41350 @c man begin OPTIONS gdb
41351 Any arguments other than options specify an executable
41352 file and core file (or process ID); that is, the first argument
41353 encountered with no
41354 associated option flag is equivalent to a @option{-se} option, and the second,
41355 if any, is equivalent to a @option{-c} option if it's the name of a file.
41357 both long and short forms; both are shown here. The long forms are also
41358 recognized if you truncate them, so long as enough of the option is
41359 present to be unambiguous. (If you prefer, you can flag option
41360 arguments with @option{+} rather than @option{-}, though we illustrate the
41361 more usual convention.)
41363 All the options and command line arguments you give are processed
41364 in sequential order. The order makes a difference when the @option{-x}
41370 List all options, with brief explanations.
41372 @item -symbols=@var{file}
41373 @itemx -s @var{file}
41374 Read symbol table from file @var{file}.
41377 Enable writing into executable and core files.
41379 @item -exec=@var{file}
41380 @itemx -e @var{file}
41381 Use file @var{file} as the executable file to execute when
41382 appropriate, and for examining pure data in conjunction with a core
41385 @item -se=@var{file}
41386 Read symbol table from file @var{file} and use it as the executable
41389 @item -core=@var{file}
41390 @itemx -c @var{file}
41391 Use file @var{file} as a core dump to examine.
41393 @item -command=@var{file}
41394 @itemx -x @var{file}
41395 Execute @value{GDBN} commands from file @var{file}.
41397 @item -ex @var{command}
41398 Execute given @value{GDBN} @var{command}.
41400 @item -directory=@var{directory}
41401 @itemx -d @var{directory}
41402 Add @var{directory} to the path to search for source files.
41405 Do not execute commands from @file{~/.gdbinit}.
41409 Do not execute commands from any @file{.gdbinit} initialization files.
41413 ``Quiet''. Do not print the introductory and copyright messages. These
41414 messages are also suppressed in batch mode.
41417 Run in batch mode. Exit with status @code{0} after processing all the command
41418 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41419 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41420 commands in the command files.
41422 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41423 download and run a program on another computer; in order to make this
41424 more useful, the message
41427 Program exited normally.
41431 (which is ordinarily issued whenever a program running under @value{GDBN} control
41432 terminates) is not issued when running in batch mode.
41434 @item -cd=@var{directory}
41435 Run @value{GDBN} using @var{directory} as its working directory,
41436 instead of the current directory.
41440 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41441 @value{GDBN} to output the full file name and line number in a standard,
41442 recognizable fashion each time a stack frame is displayed (which
41443 includes each time the program stops). This recognizable format looks
41444 like two @samp{\032} characters, followed by the file name, line number
41445 and character position separated by colons, and a newline. The
41446 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41447 characters as a signal to display the source code for the frame.
41450 Set the line speed (baud rate or bits per second) of any serial
41451 interface used by @value{GDBN} for remote debugging.
41453 @item -tty=@var{device}
41454 Run using @var{device} for your program's standard input and output.
41458 @c man begin SEEALSO gdb
41460 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41461 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41462 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.
41476 @node gdbserver man
41477 @heading gdbserver man
41479 @c man title gdbserver Remote Server for the GNU Debugger
41481 @c man begin SYNOPSIS gdbserver
41482 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41484 gdbserver --attach @var{comm} @var{pid}
41486 gdbserver --multi @var{comm}
41490 @c man begin DESCRIPTION gdbserver
41491 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41492 than the one which is running the program being debugged.
41495 @subheading Usage (server (target) side)
41498 Usage (server (target) side):
41501 First, you need to have a copy of the program you want to debug put onto
41502 the target system. The program can be stripped to save space if needed, as
41503 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41504 the @value{GDBN} running on the host system.
41506 To use the server, you log on to the target system, and run the @command{gdbserver}
41507 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41508 your program, and (c) its arguments. The general syntax is:
41511 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41514 For example, using a serial port, you might say:
41518 @c @file would wrap it as F</dev/com1>.
41519 target> gdbserver /dev/com1 emacs foo.txt
41522 target> gdbserver @file{/dev/com1} emacs foo.txt
41526 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41527 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41528 waits patiently for the host @value{GDBN} to communicate with it.
41530 To use a TCP connection, you could say:
41533 target> gdbserver host:2345 emacs foo.txt
41536 This says pretty much the same thing as the last example, except that we are
41537 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41538 that we are expecting to see a TCP connection from @code{host} to local TCP port
41539 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41540 want for the port number as long as it does not conflict with any existing TCP
41541 ports on the target system. This same port number must be used in the host
41542 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41543 you chose a port number that conflicts with another service, @command{gdbserver} will
41544 print an error message and exit.
41546 @command{gdbserver} can also attach to running programs.
41547 This is accomplished via the @option{--attach} argument. The syntax is:
41550 target> gdbserver --attach @var{comm} @var{pid}
41553 @var{pid} is the process ID of a currently running process. It isn't
41554 necessary to point @command{gdbserver} at a binary for the running process.
41556 To start @code{gdbserver} without supplying an initial command to run
41557 or process ID to attach, use the @option{--multi} command line option.
41558 In such case you should connect using @kbd{target extended-remote} to start
41559 the program you want to debug.
41562 target> gdbserver --multi @var{comm}
41566 @subheading Usage (host side)
41572 You need an unstripped copy of the target program on your host system, since
41573 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41574 would, with the target program as the first argument. (You may need to use the
41575 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41576 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41577 new command you need to know about is @code{target remote}
41578 (or @code{target extended-remote}). Its argument is either
41579 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41580 descriptor. For example:
41584 @c @file would wrap it as F</dev/ttyb>.
41585 (gdb) target remote /dev/ttyb
41588 (gdb) target remote @file{/dev/ttyb}
41593 communicates with the server via serial line @file{/dev/ttyb}, and:
41596 (gdb) target remote the-target:2345
41600 communicates via a TCP connection to port 2345 on host `the-target', where
41601 you previously started up @command{gdbserver} with the same port number. Note that for
41602 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41603 command, otherwise you may get an error that looks something like
41604 `Connection refused'.
41606 @command{gdbserver} can also debug multiple inferiors at once,
41609 the @value{GDBN} manual in node @code{Inferiors and Programs}
41610 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41613 @ref{Inferiors and Programs}.
41615 In such case use the @code{extended-remote} @value{GDBN} command variant:
41618 (gdb) target extended-remote the-target:2345
41621 The @command{gdbserver} option @option{--multi} may or may not be used in such
41625 @c man begin OPTIONS gdbserver
41626 There are three different modes for invoking @command{gdbserver}:
41631 Debug a specific program specified by its program name:
41634 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41637 The @var{comm} parameter specifies how should the server communicate
41638 with @value{GDBN}; it is either a device name (to use a serial line),
41639 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41640 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41641 debug in @var{prog}. Any remaining arguments will be passed to the
41642 program verbatim. When the program exits, @value{GDBN} will close the
41643 connection, and @code{gdbserver} will exit.
41646 Debug a specific program by specifying the process ID of a running
41650 gdbserver --attach @var{comm} @var{pid}
41653 The @var{comm} parameter is as described above. Supply the process ID
41654 of a running program in @var{pid}; @value{GDBN} will do everything
41655 else. Like with the previous mode, when the process @var{pid} exits,
41656 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41659 Multi-process mode -- debug more than one program/process:
41662 gdbserver --multi @var{comm}
41665 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41666 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41667 close the connection when a process being debugged exits, so you can
41668 debug several processes in the same session.
41671 In each of the modes you may specify these options:
41676 List all options, with brief explanations.
41679 This option causes @command{gdbserver} to print its version number and exit.
41682 @command{gdbserver} will attach to a running program. The syntax is:
41685 target> gdbserver --attach @var{comm} @var{pid}
41688 @var{pid} is the process ID of a currently running process. It isn't
41689 necessary to point @command{gdbserver} at a binary for the running process.
41692 To start @code{gdbserver} without supplying an initial command to run
41693 or process ID to attach, use this command line option.
41694 Then you can connect using @kbd{target extended-remote} and start
41695 the program you want to debug. The syntax is:
41698 target> gdbserver --multi @var{comm}
41702 Instruct @code{gdbserver} to display extra status information about the debugging
41704 This option is intended for @code{gdbserver} development and for bug reports to
41707 @item --remote-debug
41708 Instruct @code{gdbserver} to display remote protocol debug output.
41709 This option is intended for @code{gdbserver} development and for bug reports to
41712 @item --debug-format=option1@r{[},option2,...@r{]}
41713 Instruct @code{gdbserver} to include extra information in each line
41714 of debugging output.
41715 @xref{Other Command-Line Arguments for gdbserver}.
41718 Specify a wrapper to launch programs
41719 for debugging. The option should be followed by the name of the
41720 wrapper, then any command-line arguments to pass to the wrapper, then
41721 @kbd{--} indicating the end of the wrapper arguments.
41724 By default, @command{gdbserver} keeps the listening TCP port open, so that
41725 additional connections are possible. However, if you start @code{gdbserver}
41726 with the @option{--once} option, it will stop listening for any further
41727 connection attempts after connecting to the first @value{GDBN} session.
41729 @c --disable-packet is not documented for users.
41731 @c --disable-randomization and --no-disable-randomization are superseded by
41732 @c QDisableRandomization.
41737 @c man begin SEEALSO gdbserver
41739 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41740 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41741 documentation are properly installed at your site, the command
41747 should give you access to the complete manual.
41749 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41750 Richard M. Stallman and Roland H. Pesch, July 1991.
41757 @c man title gcore Generate a core file of a running program
41760 @c man begin SYNOPSIS gcore
41761 gcore [-o @var{filename}] @var{pid}
41765 @c man begin DESCRIPTION gcore
41766 Generate a core dump of a running program with process ID @var{pid}.
41767 Produced file is equivalent to a kernel produced core file as if the process
41768 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41769 limit). Unlike after a crash, after @command{gcore} the program remains
41770 running without any change.
41773 @c man begin OPTIONS gcore
41775 @item -o @var{filename}
41776 The optional argument
41777 @var{filename} specifies the file name where to put the core dump.
41778 If not specified, the file name defaults to @file{core.@var{pid}},
41779 where @var{pid} is the running program process ID.
41783 @c man begin SEEALSO gcore
41785 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41786 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41787 documentation are properly installed at your site, the command
41794 should give you access to the complete manual.
41796 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41797 Richard M. Stallman and Roland H. Pesch, July 1991.
41804 @c man title gdbinit GDB initialization scripts
41807 @c man begin SYNOPSIS gdbinit
41808 @ifset SYSTEM_GDBINIT
41809 @value{SYSTEM_GDBINIT}
41818 @c man begin DESCRIPTION gdbinit
41819 These files contain @value{GDBN} commands to automatically execute during
41820 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41823 the @value{GDBN} manual in node @code{Sequences}
41824 -- shell command @code{info -f gdb -n Sequences}.
41830 Please read more in
41832 the @value{GDBN} manual in node @code{Startup}
41833 -- shell command @code{info -f gdb -n Startup}.
41840 @ifset SYSTEM_GDBINIT
41841 @item @value{SYSTEM_GDBINIT}
41843 @ifclear SYSTEM_GDBINIT
41844 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41846 System-wide initialization file. It is executed unless user specified
41847 @value{GDBN} option @code{-nx} or @code{-n}.
41850 the @value{GDBN} manual in node @code{System-wide configuration}
41851 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41854 @ref{System-wide configuration}.
41858 User initialization file. It is executed unless user specified
41859 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41862 Initialization file for current directory. It may need to be enabled with
41863 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41866 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41867 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41870 @ref{Init File in the Current Directory}.
41875 @c man begin SEEALSO gdbinit
41877 gdb(1), @code{info -f gdb -n Startup}
41879 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41880 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41881 documentation are properly installed at your site, the command
41887 should give you access to the complete manual.
41889 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41890 Richard M. Stallman and Roland H. Pesch, July 1991.
41896 @node GNU Free Documentation License
41897 @appendix GNU Free Documentation License
41900 @node Concept Index
41901 @unnumbered Concept Index
41905 @node Command and Variable Index
41906 @unnumbered Command, Variable, and Function Index
41911 % I think something like @@colophon should be in texinfo. In the
41913 \long\def\colophon{\hbox to0pt{}\vfill
41914 \centerline{The body of this manual is set in}
41915 \centerline{\fontname\tenrm,}
41916 \centerline{with headings in {\bf\fontname\tenbf}}
41917 \centerline{and examples in {\tt\fontname\tentt}.}
41918 \centerline{{\it\fontname\tenit\/},}
41919 \centerline{{\bf\fontname\tenbf}, and}
41920 \centerline{{\sl\fontname\tensl\/}}
41921 \centerline{are used for emphasis.}\vfill}
41923 % Blame: doc@@cygnus.com, 1991.